Endogenous sulfur dioxide alleviates septic lung injury by suppressing Bax-mediated apoptosis of alveolar epithelial cells

Endogenous sulfur dioxide alleviates septic lung injury by suppressing Bax-mediated apoptosis of alveolar epithelial cells | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Endogenous sulfur dioxide alleviates septic lung injury by suppressing Bax-mediated apoptosis of alveolar epithelial cells Zhiwei Liu, Bin Zhao, Zhaoxing Tian This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8739206/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Objective: To investigate the regulatory effect of endogenous sulfur dioxide (SO₂) on alveolar epithelial cell apoptosis in rats with sepsis-induced lung injury. Methods: Male Sprague Dawley rats were randomly divided into four groups: normal control group, sepsis group, sepsis + SO₂ group, and SO₂ control group. Each group was observed for 12 hours. Lung tissues from each group were subjected to HE pathological staining and semi-quantitative lung injury scoring. The BAX content in lung tissues was measured using ELISA, and apoptosis was assessed via TUNEL staining. Results: In rats with lung injury, the semi-quantitative lung injury score, BAX content, and TUNEL staining were significantly increased. After SO₂ intervention, these indicators (semi-quantitative lung injury score, BAX content, and TUNEL staining) were significantly reduced. Conclusion: Endogenous sulfur dioxide can exert a protective effect in sepsis-induced lung injury by inhibiting BAX-mediated apoptosis of alveolar epithelial cells. Biological sciences/Cell biology Health sciences/Diseases Health sciences/Medical research Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Sepsis is a common and life-threatening critical condition in clinical practice [ 1 ]. Lung injury is the most frequent and fatal complication of sepsis, with alveolar epithelial cell apoptosis being a key pathogenic mechanism in sepsis-induced lung injury. Endogenous sulfur dioxide (SO₂) has been shown to exert a protective effect in lung injury models induced by limb ischemia-reperfusion [ 2 , 3 ]. Additionally, endogenous SO₂ protects against oleic acid-induced acute lung injury in rat models by inhibiting alveolar epithelial cell apoptosis [ 4 ]. However, whether endogenous SO₂ can alleviate sepsis-induced lung injury in rats by suppressing alveolar epithelial cell apoptosis remains unexplored. Therefore, this study investigates the regulatory role of endogenous SO₂ on oxidative stress in sepsis-induced lung injury using a cecal ligation and puncture (CLP)-induced septic rat model. Materials and Methods Experimental Animals and Grouping Twenty-four male Sprague-Dawley (SD) rats (weight: 200–250 g) were provided by the Experimental Animal Center of Peking University First Hospital. The rats were randomly divided into four groups (n = 6 per group): Control group: Rats underwent laparotomy with only intestinal manipulation before abdominal closure. SO₂ group: Rats received an intraperitoneal injection of an SO₂ donor (Na₂SO₃/NaHSO₃, 0.5 mL/kg) 30 minutes before laparotomy. The Na₂SO₃/NaHSO₃ solution (3:1 ratio, 0.54 mmol/kg:0.18 mmol/kg) was freshly prepared in saline and served as an endogenous SO₂ donor. Sepsis group: Rats underwent cecal ligation and puncture (CLP) after laparotomy [ 4 ]. Sepsis + SO₂ group: Rats received an intraperitoneal injection of the SO₂ donor (0.5 mL/kg) 30 minutes before CLP. CLP Surgical Procedure: Animals were housed in an SPF environment and fasted for 12 hours (with free access to water) before surgery. Anesthesia was induced via intraperitoneal injection of 13% pentobarbital sodium (1 mL/kg). After fixation, hair removal, and alcohol disinfection, a 1 cm midline abdominal incision was made to expose the cecum. The cecum was ligated below the ileocecal valve at the midpoint, then punctured twice with a 21-gauge needle. A 3 mm-wide rubber drainage strip was left in place to prevent puncture closure. The cecum was repositioned, and the abdomen was closed layer by layer under strict aseptic conditions. Immediately after surgery, 50 mL/kg saline was administered for shock prevention, and rats were allowed free access to food and water. Experimental Termination: After 12 hours of observation, rats were anesthetized with 12% urethane (1 mL/kg, intraperitoneal), followed by euthanasia via abdominal aortic exsanguination. Morphological Observation of Lung Tissue Under Light Microscopy and Semi-Quantitative Lung Injury Scoring (IQA) The middle lobe of the right lung was fixed in 10% formalin, embedded in paraffin, sectioned, and stained with hematoxylin and eosin (H&E) for observation under a light microscope (400× magnification). For each section, 10 fields of view were selected for semi-quantitative lung injury scoring. The evaluation criteria included alveolar edema, inflammatory cell infiltration, and hyaline membrane formation. Each parameter was graded as normal (0), mild (1), moderate (2), or severe (3), with corresponding scores recorded. Detection of Bax in Lung Tissue Lung tissues from rats in each group were weighed, homogenized, and the Bax content was measured using an enzyme-linked immunosorbent assay (ELISA). Apoptosis of alveolar epithelial cells by Tunel staining The paraffin sections of the lung tissues were used for terminal deoxynucleotidyl transferase (TdT) mediated dUTP nick end labelling analysis. After that the paraffin was removed, hydrated and blocked with 3% H 2 O 2 , and incubated with 100 µ g/ml proteinase K for 10 min at room temperature. The sections were incubated with labeling buffer for 30 min, and then 2.5 µ l of TdT, 2.5 µ l of digoxigenin (DIG)-dUTP, and 2.5 µ l of TdT buffer. The sections were incubated with the reaction system overnight at 4°C and then washed in the reaction fluid. The sections were incubated with horse serum (1:100) for 20 min at room temperature. And the sections were incubated with Anti-DIG-biotin (diluted 1:100 with blocking red) for 30 min at 37°C. After that, the sections were incubated with streptavidin-biotin-enzyme complex (diluted 1:100 with Tris buffer solution) for 30 min at 37°C. Then, the sections were rinsed for (4×5 min). The sections were colourated with 3, 3-diaminobenzidin, without light for 3 min at room temperature. The nuclear brown-colored cells were defined as apoptotic cells. The surface marker expression was quantified as Mean Fluorescence Intensity (MFI) . Statistical Analysis Statistical analysis was performed using SPSS 22.0 software. Data were expressed as mean ± standard error (mean ± SE). One-way analysis of variance (One-Way ANOVA) was used for comparisons among multiple groups. When homogeneity of variance was satisfied, the Least-Significant Difference (LSD) method was applied for intergroup comparisons. For data with unequal variances, Tamhane's T2 test was employed. A P-value < 0.05 was considered statistically significant. Results Morphological Observation of Lung Tissues Under Light Microscopy Under light microscopy, the control group exhibited normal pulmonary histoarchitecture with intact alveolar walls, clear alveolar spaces devoid of significant exudate, and absence of inflammatory cell infiltration or erythrocyte extravasation. The SO₂ group demonstrated comparable morphological features to the control group.In contrast, the sepsis group showed marked pathological alterations, including: Disrupted pulmonary microstructure, Significantly thickened alveolar septa, Pronounced interstitial and alveolar edema. Notably, the sepsis + SO₂ group displayed improved histological preservation compared to the sepsis group, characterized by: More intact alveolar structure, Reduced septal thickening, Attenuated interstitial edema (Fig. 1 ). Semi-quantitative Assessment of Lung Injury in Experimental Groups The semi-quantitative lung injury scores demonstrated significant variations among the experimental groups (Fig. 2 ). The control group exhibited a baseline score of 5.50 ± 1.09, while the sepsis group showed markedly elevated scores (7.67 ± 2.16, p < 0.05 vs control). Notably, SO₂ administration in the sepsis + SO₂ group significantly attenuated lung injury scores to 4.67 ± 1.21 (p 0.05), indicating that SO₂ treatment specifically ameliorated sepsis-induced lung injury without affecting normal pulmonary histology. Pulmonary Bax Protein Expression Levels Across Experimental Groups Quantitative analysis revealed significant alterations in Bax protein content (ng/ml) among the treatment groups (Fig. 3 ). The control group demonstrated basal Bax levels of 1.66 ± 0.34 ng/ml. In contrast, the sepsis group exhibited a substantial 3.7-fold increase in Bax expression (6.13 ± 1.28 ng/ml, p < 0.05 vs control). Importantly, SO₂ co-administration in the sepsis + SO₂ group significantly suppressed sepsis-induced Bax upregulation, reducing levels to 2.11 ± 0.30 ng/ml (p 0.05), suggesting that SO₂ specifically modulates Bax expression in the context of sepsis-induced lung injury rather than under physiological conditions. The relative fluorescence ratio of TUNEL in each groups The quantification of alveolar epithelial cell apoptosis revealed significant differences among treatment groups (Figs. 4 , 5 ). The control group showed a baseline apoptotic rate of 40.34% ± 16.28%. In the sepsis group, we observed a dramatic 3-fold increase in apoptosis (121.42% ± 12.02%, p < 0.05 vs control). Notably, SO₂ treatment in the sepsis + SO₂ group significantly attenuated this apoptotic response to 57.73% ± 17.94% (p 0.05), indicating that the anti-apoptotic effect of SO₂ was specifically manifested in the pathological context of sepsis-induced lung injury. Discussion Sepsis, defined as a systemic inflammatory response syndrome induced by infection, represents a common complication following severe trauma, burns, shock, and major surgical procedures. Without timely intervention, it may progress to septic shock and multiple organ dysfunction syndrome. Despite advancements in medical care, sepsis remains a critical clinical challenge due to its high incidence and mortality rates [ 6 , 7 ]. Sepsis-associated acute lung injury (ALI) [ 8 , 9 ] poses a significant clinical dilemma in critical care medicine, with its core pathological mechanisms involving an imbalance between uncontrolled inflammatory responses [ 10 ] and cellular apoptosis [ 11 ]. Recent studies have gradually unveiled the organ-protective roles of gaseous signaling molecules, particularly endogenous sulfur dioxide (SO₂) [ 12 ]. Our study provides the first evidence that endogenous SO₂ alleviates programmed cell death in alveolar epithelial cells during sepsis-induced lung injury by specifically inhibiting the Bax-mediated mitochondrial apoptotic pathway, thereby offering novel theoretical foundations for clinical intervention. The discussion will proceed in three aspects: Cytoprotective Effects of Endogenous SO₂ in Sepsis-Induced Lung Injury Previous research has established that SO₂, as an endogenous gaseous signaling molecule, exerts organ-protective effects by modulating oxidative stress [ 13 , 14 ] and inflammatory responses [ 15 ]. The lungs are particularly vulnerable to sepsis, often resulting in sepsis-induced lung injury, which is the most frequent and fatal complication of sepsis and a leading cause of sepsis-related mortality. In our study, cecal ligation and puncture (CLP) in male rats [ 16 ] induced characteristic pathological changes, including disrupted pulmonary architecture, increased capillary permeability, markedly thickened alveolar septa, and interstitial/alveolar edema, accompanied by significantly elevated lung injury scores. These alterations are consistent with the pathological progression of ALI [ 17 ], reaffirming that sepsis can indeed lead to acute lung injury. Endogenous SO₂ has been previously reported to protect against lung injury [ 18 ]. In our experiments, administration of the SO₂ donor Na₂SO₃/NaHSO₃ ameliorated these pathological features, demonstrating improved pulmonary structure, reduced capillary permeability, and decreased alveolar septal thickening, along with significantly lower histological lung injury scores (IQA). These findings further confirm the protective role of SO₂ in sepsis-induced lung injury. SO₂ Attenuates Alveolar Epithelial Cell Apoptosis in Sepsis-Induced Lung Injury Cellular apoptosis plays a pivotal role in the pathogenesis of sepsis-induced lung injury [ 19 ]. Our study revealed a substantial increase in alveolar epithelial cell apoptosis during sepsis, while SO₂ intervention significantly reduced both lung injury and apoptotic rates. This suggests that SO₂ confers protection by suppressing alveolar epithelial cell apoptosis. SO₂ Inhibits Bax-Mediated Mitochondrial Apoptotic Pathway Aberrant activation of the mitochondrial apoptotic pathway is central to alveolar epithelial cell apoptosis in sepsis-induced lung injury. Bax is a key regulator of this pathway. Our results demonstrated markedly elevated Bax levels in lung tissue during sepsis, correlating with increased alveolar epithelial cell apoptosis. SO₂ intervention effectively downregulated Bax expression and concurrently reduced apoptosis, indicating that SO₂ protects against lung injury by inhibiting the Bax-mediated apoptotic pathway. Conclusion In summary, our study demonstrates that endogenous SO₂ mitigates sepsis-induced lung injury by suppressing the Bax pathway and subsequent alveolar epithelial cell apoptosis. However, the precise molecular mechanisms warrant further investigation in future studies. These findings highlight the therapeutic potential of SO₂ in managing sepsis-associated ALI and provide a foundation for developing novel treatment strategies. Declarations Acknowledgements None. Funding This project is funded by Beijing Jishuitan Hospital Elite Young Scholar Programme (NO. XKGG202204). Data Availability Data is provided within the manuscript files. Ethics Approval This study was approved by the Ethics Committee of Beijing Jishuitan Hospital (Approval No. Jilunke 2024-03-S32). All methods were performed in accordance with the relevant guidelines and regulations Consent to Participate Not applicable. Consent for publication All the results/data/figures in this manuscript have not been published elsewhere, nor are they under consideration (from you or one of your Contributing Authors) by another publisher. Conflicts of Interest The authors declare that they have no conflicts of interest. References Rhodes, A. et al. Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock: 2016. Intensive Care Med. 43 (3), 304–377 (2017). Huang, X. L. et al. Role of sulfur dioxide in acute lung injury following limb ischemia/reperfusion in rats[J]. J. Biochem. Mol. Toxicol. 2013 (7/ 8):389–397 . Zhao, Y. R. et al. The PI3K/Akt, p38MAPK, and JAK2/STAT3 signaling pathways mediate the protection of SO2 against acute lung injury induced by limb ischemia/reperfusion in rats. J. Physiol. Sci. 66 (3), 229–239 (2016). Chen, S. Y. et al. ndogeous sulfur dioxide protects against oleic acid-induced acute lung injury in association with inhibition of oxidative stress in rats[J].Laboratory investigation, (2): 142–156. (2015). Toscano, M. G., Ganea, D. & Gamero, A. M. Cecal ligation puncture procedure. J. Vis. Exp. ;(51):2860. doi (2011). : 10.3791/2860. PMID: 21587163; PMCID: PMC3339843. Chiu, C. & Legrand, M. Epidemiology of sepsis and septic shock. Curr Opin Anaesthesiol. ;34(2):71–76. (2021). 10.1097/ACO.0000000000000958 . PMID: 33492864. Arina, P. & Singer, M. Pathophysiology of sepsis. Curr Opin Anaesthesiol. ;34(2):77–84. (2021). 10.1097/ACO.0000000000000963 . PMID: 33652454. Krutsinger, D. C., Yadav, K. N., Harhay, M. O., Bartels, K. & Courtright, K. R. A systematic review and meta-analysis of enrollment into ARDS and sepsis trials published between 2009 and 2019 in major journals. Crit. Care . 25 (1), 392. 10.1186/s13054-021-03804-1 (2021). PMID: 34781998; PMCID: PMC8591428. Weiss, S. L. et al. Surviving sepsis campaign international guidelines for the management of septic shock and sepsis-associated organ dysfunction in children. Intensive Care Med. 46 (Suppl 1), 10–67. 10.1007/s00134-019-05878-6 (2020). PMID: 32030529; PMCID: PMC7095013. Guo, Y. et al. Xueqin Dou; IL-37 Alleviates Sepsis-Induced Lung Injury by Inhibiting Inflammatory Response Through the TGF-β/Smad3 Pathway Immunological investigations ;:1–15 (2025). 10.1080/08820139.2025.2495958 Zou, J., Guo, J. & Hu, G. Yiming Qian; Curcumin Attenuates PD-L1-Positive Neutrophil-Induced T-Lymphocyte Apoptosis and Alleviates Lung Injury During Sepsis in Rats Discovery medicine 2025; 37 (195):772–782 10.24976/Discov.Med.202537195.67 Yu Zhai, X. L., Huang, H. J., Ma, X. H., Zhou, J. L. & Zhou, Y. M. Sulfur dioxide reduces lipopolysaccharide-induced acute lung injury in rats Central-European. J. Immunol. 44 (3), 226–236. 10.5114/ceji.2019.89593 (2019). Zhiwei Liu, J., Gao, X., Ye, C. & Wang Bin Zhao; Endogenous Sulfur Dioxide Improves the Survival Rate of Sepsis by Improving the Oxidative Stress Response during Lung Injury Oxidative medicine and cellular longevity 2022;2022:6339355 10.1155/2022/6339355 Zhao, Y. R., Liu, Y., Wang, D. & Lv, W. R. Zhou; [Effects of sulfur dioxide on alveolar macrophage apoptosis in acute lung injury induced by limb ischemia/reperfusion in rats] Beijing da xue xue bao. Yi xue ban = Journal of Peking University. Health Sci. 51 (2), 239–244 (2019). Elisabeth Wigenstam, L., Elfsmark, L., Ågren, C., Akfur, A. & Bucht, S. Jonasson; Anti-inflammatory and anti-fibrotic treatment in a rodent model of acute lung injury induced by sulfur dioxide Clinical toxicology (Philadelphia, Pa.) 12 ;56(12):1185–1194 (2018). 10.1080/15563650.2018.1479527 Lien Dejager, I., Pinheiro, E. & Dejonckheere, C. Cecal ligation and puncture: the gold standard model for polymicrobial sepsis? Trends Microbiol. 19 (4), 198–208. 10.1016/j.tim.2011.01.001 (2011). Chen, S. et al. Hongfang Jin; Endogeous sulfur dioxide protects against oleic acid-induced acute lung injury in association with inhibition of oxidative stress in rats Laboratory investigation. J. Tech. methods Pathol. 95 (2), 142–156. 10.1038/labinvest.2014.147 (2015). Huang, X. L. et al. Hua Cao; Role of sulfur dioxide in acute lung injury following limb ischemia/reperfusion in rats. J. Biochem. Mol. Toxicol. 27 (8), 389–397. 10.1002/jbt.21492 (2013). Zhang, H. et al. Changhong Miao; Neutrophil extracellular traps mediate m6A modification and regulates sepsis-associated acute lung injury by activating ferroptosis in alveolar epithelial cells. Int. J. Biol. Sci. 18 (8), 3337–3357. 10.7150/ijbs.69141 (2022). Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8739206","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":610130854,"identity":"8664a360-0dd8-4341-b5e7-3d87283e56ca","order_by":0,"name":"Zhiwei Liu","email":"","orcid":"","institution":"Beijing Jishuitan Hospital, Capital Medical University","correspondingAuthor":false,"prefix":"","firstName":"Zhiwei","middleName":"","lastName":"Liu","suffix":""},{"id":610130855,"identity":"e2a83e7e-22e9-4ba3-80bd-6ecc6d9b173a","order_by":1,"name":"Bin Zhao","email":"","orcid":"","institution":"Beijing Jishuitan Hospital, Capital Medical University","correspondingAuthor":false,"prefix":"","firstName":"Bin","middleName":"","lastName":"Zhao","suffix":""},{"id":610130856,"identity":"e5a97355-5595-402b-b1b2-c3532dafc1fd","order_by":2,"name":"Zhaoxing Tian","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAo0lEQVRIiWNgGAWjYFCCA0BcISHHT7QGHobDQPKMhbFkA/FamBkYGNsqEjcQrcWe8fzhz7zzJBg3MDA/fHSDWIcZztwmwWzOwGZsnEOsloSP2yTYLBt42KSJ1nIgcY4Ej8EBErQwNnxskJAgQcuBw8aMM45JGEg2E+sX9hkHH3/mqamr72dvfviYKC0MEgegDGailIMAfwPRSkfBKBgFo2CkAgAvxCxQz5xV5gAAAABJRU5ErkJggg==","orcid":"","institution":"Beijing Jishuitan Hospital, Capital Medical University","correspondingAuthor":true,"prefix":"","firstName":"Zhaoxing","middleName":"","lastName":"Tian","suffix":""}],"badges":[],"createdAt":"2026-01-30 08:53:34","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8739206/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8739206/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":105564439,"identity":"5ac3eaa2-a143-47f5-97f5-23827761dbb5","added_by":"auto","created_at":"2026-03-27 12:49:33","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":326075,"visible":true,"origin":"","legend":"\u003cp\u003eMicrophotographs of morphological changes of lung tissues (×40). Hematoxylin and eosin staining: (A) control group, (B) Sepsis group, (C) Sepsis+SO\u003csub\u003e2 \u003c/sub\u003egroup,(D) SO\u003csub\u003e2 \u003c/sub\u003egroup.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8739206/v1/5a7fe99d622b4eb824c1509b.png"},{"id":105230054,"identity":"142341ed-daea-4071-9af8-fc6c44b69407","added_by":"auto","created_at":"2026-03-23 17:41:59","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":22078,"visible":true,"origin":"","legend":"\u003cp\u003eIndex of quantitative assessment (IQA) scores of lung tissue in each group. \u003csup\u003e#\u003c/sup\u003e\u003cem\u003eP\u0026lt;\u003c/em\u003e0.05 compared with Sepsis group.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8739206/v1/acd2a6476c53acbab2639efb.png"},{"id":105230050,"identity":"b7de6c9a-af09-47e8-b3ee-5d6ed23b51cd","added_by":"auto","created_at":"2026-03-23 17:41:59","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":26407,"visible":true,"origin":"","legend":"\u003cp\u003eBAX of lung tissue in each group (ng/ml). \u003csup\u003e#\u003c/sup\u003e\u003cem\u003eP\u0026lt;\u003c/em\u003e0.05 compared with Sepsis group.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8739206/v1/050d4c1d3581d7adb7263363.png"},{"id":105563975,"identity":"5ae42770-27e1-4891-8d4f-441c7312fd43","added_by":"auto","created_at":"2026-03-27 12:48:20","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":31315,"visible":true,"origin":"","legend":"\u003cp\u003eTUNEL Fluorescence Ratio of lung tissue in each group.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8739206/v1/68d5ceb298ef4f7330e87700.png"},{"id":105230052,"identity":"b2c3fa0e-900d-4a66-b431-13c494b1e67b","added_by":"auto","created_at":"2026-03-23 17:41:59","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":356001,"visible":true,"origin":"","legend":"\u003cp\u003eThe relative fluorescence ratio of TUNEL in each groups.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8739206/v1/a3894ce943b5cefd1507e407.png"},{"id":106747924,"identity":"9c7f6976-ca3d-4898-81db-8685846919b6","added_by":"auto","created_at":"2026-04-13 06:12:02","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1366040,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8739206/v1/6100b8b4-7bcd-409d-877c-2fde9167d5f5.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eEndogenous sulfur dioxide alleviates septic lung injury by suppressing Bax-mediated apoptosis of alveolar epithelial cells\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSepsis is a common and life-threatening critical condition in clinical practice [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Lung injury is the most frequent and fatal complication of sepsis, with alveolar epithelial cell apoptosis being a key pathogenic mechanism in sepsis-induced lung injury. Endogenous sulfur dioxide (SO₂) has been shown to exert a protective effect in lung injury models induced by limb ischemia-reperfusion [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Additionally, endogenous SO₂ protects against oleic acid-induced acute lung injury in rat models by inhibiting alveolar epithelial cell apoptosis [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. However, whether endogenous SO₂ can alleviate sepsis-induced lung injury in rats by suppressing alveolar epithelial cell apoptosis remains unexplored. Therefore, this study investigates the regulatory role of endogenous SO₂ on oxidative stress in sepsis-induced lung injury using a cecal ligation and puncture (CLP)-induced septic rat model.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eExperimental Animals and Grouping\u003c/h2\u003e \u003cp\u003eTwenty-four male Sprague-Dawley (SD) rats (weight: 200\u0026ndash;250 g) were provided by the Experimental Animal Center of Peking University First Hospital. The rats were randomly divided into four groups (n\u0026thinsp;=\u0026thinsp;6 per group): Control group: Rats underwent laparotomy with only intestinal manipulation before abdominal closure. SO₂ group: Rats received an intraperitoneal injection of an SO₂ donor (Na₂SO₃/NaHSO₃, 0.5 mL/kg) 30 minutes before laparotomy. The Na₂SO₃/NaHSO₃ solution (3:1 ratio, 0.54 mmol/kg:0.18 mmol/kg) was freshly prepared in saline and served as an endogenous SO₂ donor. Sepsis group: Rats underwent cecal ligation and puncture (CLP) after laparotomy [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Sepsis\u0026thinsp;+\u0026thinsp;SO₂ group: Rats received an intraperitoneal injection of the SO₂ donor (0.5 mL/kg) 30 minutes before CLP. CLP Surgical Procedure: Animals were housed in an SPF environment and fasted for 12 hours (with free access to water) before surgery. Anesthesia was induced via intraperitoneal injection of 13% pentobarbital sodium (1 mL/kg). After fixation, hair removal, and alcohol disinfection, a 1 cm midline abdominal incision was made to expose the cecum. The cecum was ligated below the ileocecal valve at the midpoint, then punctured twice with a 21-gauge needle. A 3 mm-wide rubber drainage strip was left in place to prevent puncture closure. The cecum was repositioned, and the abdomen was closed layer by layer under strict aseptic conditions. Immediately after surgery, 50 mL/kg saline was administered for shock prevention, and rats were allowed free access to food and water. Experimental Termination: After 12 hours of observation, rats were anesthetized with 12% urethane (1 mL/kg, intraperitoneal), followed by euthanasia via abdominal aortic exsanguination.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eMorphological Observation of Lung Tissue Under Light Microscopy and Semi-Quantitative Lung Injury Scoring (IQA)\u003c/h3\u003e\n\u003cp\u003eThe middle lobe of the right lung was fixed in 10% formalin, embedded in paraffin, sectioned, and stained with hematoxylin and eosin (H\u0026amp;E) for observation under a light microscope (400\u0026times; magnification). For each section, 10 fields of view were selected for semi-quantitative lung injury scoring. The evaluation criteria included alveolar edema, inflammatory cell infiltration, and hyaline membrane formation. Each parameter was graded as normal (0), mild (1), moderate (2), or severe (3), with corresponding scores recorded.\u003c/p\u003e\n\u003ch3\u003eDetection of Bax in Lung Tissue\u003c/h3\u003e\n\u003cp\u003eLung tissues from rats in each group were weighed, homogenized, and the Bax content was measured using an enzyme-linked immunosorbent assay (ELISA).\u003c/p\u003e\n\u003ch3\u003eApoptosis of alveolar epithelial cells by Tunel staining\u003c/h3\u003e\n\u003cp\u003eThe paraffin sections of the lung tissues were used for terminal deoxynucleotidyl transferase (TdT) mediated dUTP nick end labelling analysis. After that the paraffin was removed, hydrated and blocked with 3% H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, and incubated with 100 \u0026micro; g/ml proteinase K for 10 min at room temperature. The sections were incubated with labeling buffer for 30 min, and then 2.5 \u0026micro; l of TdT, 2.5 \u0026micro; l of digoxigenin (DIG)-dUTP, and 2.5 \u0026micro; l of TdT buffer. The sections were incubated with the reaction system overnight at 4\u0026deg;C and then washed in the reaction fluid. The sections were incubated with horse serum (1:100) for 20 min at room temperature. And the sections were incubated with Anti-DIG-biotin (diluted 1:100 with blocking red) for 30 min at 37\u0026deg;C. After that, the sections were incubated with streptavidin-biotin-enzyme complex (diluted 1:100 with Tris buffer solution) for 30 min at 37\u0026deg;C. Then, the sections were rinsed for (4\u0026times;5 min). The sections were colourated with 3, 3-diaminobenzidin, without light for 3 min at room temperature. The nuclear brown-colored cells were defined as apoptotic cells. The surface marker expression was quantified as Mean Fluorescence Intensity (MFI) .\u003c/p\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eStatistical analysis was performed using SPSS 22.0 software. Data were expressed as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard error (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SE). One-way analysis of variance (One-Way ANOVA) was used for comparisons among multiple groups. When homogeneity of variance was satisfied, the Least-Significant Difference (LSD) method was applied for intergroup comparisons. For data with unequal variances, Tamhane's T2 test was employed. A P-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eMorphological Observation of Lung Tissues Under Light Microscopy\u003c/h2\u003e \u003cp\u003eUnder light microscopy, the control group exhibited normal pulmonary histoarchitecture with intact alveolar walls, clear alveolar spaces devoid of significant exudate, and absence of inflammatory cell infiltration or erythrocyte extravasation. The SO₂ group demonstrated comparable morphological features to the control group.In contrast, the sepsis group showed marked pathological alterations, including: Disrupted pulmonary microstructure, Significantly thickened alveolar septa, Pronounced interstitial and alveolar edema. Notably, the sepsis\u0026thinsp;+\u0026thinsp;SO₂ group displayed improved histological preservation compared to the sepsis group, characterized by: More intact alveolar structure, Reduced septal thickening, Attenuated interstitial edema (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSemi-quantitative Assessment of Lung Injury in Experimental Groups\u003c/h3\u003e\n\u003cp\u003eThe semi-quantitative lung injury scores demonstrated significant variations among the experimental groups (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The control group exhibited a baseline score of 5.50\u0026thinsp;\u0026plusmn;\u0026thinsp;1.09, while the sepsis group showed markedly elevated scores (7.67\u0026thinsp;\u0026plusmn;\u0026thinsp;2.16, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 vs control). Notably, SO₂ administration in the sepsis\u0026thinsp;+\u0026thinsp;SO₂ group significantly attenuated lung injury scores to 4.67\u0026thinsp;\u0026plusmn;\u0026thinsp;1.21 (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 vs sepsis group). The SO₂-alone group (5.33\u0026thinsp;\u0026plusmn;\u0026thinsp;1.03) did not show significant differences compared to the control group (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05), indicating that SO₂ treatment specifically ameliorated sepsis-induced lung injury without affecting normal pulmonary histology.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003ePulmonary Bax Protein Expression Levels Across Experimental Groups\u003c/h2\u003e \u003cp\u003eQuantitative analysis revealed significant alterations in Bax protein content (ng/ml) among the treatment groups (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The control group demonstrated basal Bax levels of 1.66\u0026thinsp;\u0026plusmn;\u0026thinsp;0.34 ng/ml. In contrast, the sepsis group exhibited a substantial 3.7-fold increase in Bax expression (6.13\u0026thinsp;\u0026plusmn;\u0026thinsp;1.28 ng/ml, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 vs control). Importantly, SO₂ co-administration in the sepsis\u0026thinsp;+\u0026thinsp;SO₂ group significantly suppressed sepsis-induced Bax upregulation, reducing levels to 2.11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.30 ng/ml (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 vs sepsis group). The SO₂-alone group (2.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.42 ng/ml) showed no statistically significant difference compared to controls (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05), suggesting that SO₂ specifically modulates Bax expression in the context of sepsis-induced lung injury rather than under physiological conditions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eThe relative fluorescence ratio of TUNEL in each groups\u003c/h2\u003e \u003cp\u003eThe quantification of alveolar epithelial cell apoptosis revealed significant differences among treatment groups (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e,\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The control group showed a baseline apoptotic rate of 40.34% \u0026plusmn; 16.28%. In the sepsis group, we observed a dramatic 3-fold increase in apoptosis (121.42% \u0026plusmn; 12.02%, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 vs control). Notably, SO₂ treatment in the sepsis\u0026thinsp;+\u0026thinsp;SO₂ group significantly attenuated this apoptotic response to 57.73% \u0026plusmn; 17.94% (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 vs sepsis group), representing a 52.5% reduction compared to untreated septic animals. The SO₂-alone group (59.41% \u0026plusmn; 17.50%) demonstrated no significant difference from controls (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05), indicating that the anti-apoptotic effect of SO₂ was specifically manifested in the pathological context of sepsis-induced lung injury.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eSepsis, defined as a systemic inflammatory response syndrome induced by infection, represents a common complication following severe trauma, burns, shock, and major surgical procedures. Without timely intervention, it may progress to septic shock and multiple organ dysfunction syndrome. Despite advancements in medical care, sepsis remains a critical clinical challenge due to its high incidence and mortality rates [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Sepsis-associated acute lung injury (ALI) [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] poses a significant clinical dilemma in critical care medicine, with its core pathological mechanisms involving an imbalance between uncontrolled inflammatory responses [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] and cellular apoptosis [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Recent studies have gradually unveiled the organ-protective roles of gaseous signaling molecules, particularly endogenous sulfur dioxide (SO₂) [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Our study provides the first evidence that endogenous SO₂ alleviates programmed cell death in alveolar epithelial cells during sepsis-induced lung injury by specifically inhibiting the Bax-mediated mitochondrial apoptotic pathway, thereby offering novel theoretical foundations for clinical intervention. The discussion will proceed in three aspects:\u003c/p\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eCytoprotective Effects of Endogenous SO₂ in Sepsis-Induced Lung Injury\u003c/h2\u003e \u003cp\u003ePrevious research has established that SO₂, as an endogenous gaseous signaling molecule, exerts organ-protective effects by modulating oxidative stress [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] and inflammatory responses [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The lungs are particularly vulnerable to sepsis, often resulting in sepsis-induced lung injury, which is the most frequent and fatal complication of sepsis and a leading cause of sepsis-related mortality. In our study, cecal ligation and puncture (CLP) in male rats [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] induced characteristic pathological changes, including disrupted pulmonary architecture, increased capillary permeability, markedly thickened alveolar septa, and interstitial/alveolar edema, accompanied by significantly elevated lung injury scores. These alterations are consistent with the pathological progression of ALI [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], reaffirming that sepsis can indeed lead to acute lung injury.\u003c/p\u003e \u003cp\u003eEndogenous SO₂ has been previously reported to protect against lung injury [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. In our experiments, administration of the SO₂ donor Na₂SO₃/NaHSO₃ ameliorated these pathological features, demonstrating improved pulmonary structure, reduced capillary permeability, and decreased alveolar septal thickening, along with significantly lower histological lung injury scores (IQA). These findings further confirm the protective role of SO₂ in sepsis-induced lung injury.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eSO₂ Attenuates Alveolar Epithelial Cell Apoptosis in Sepsis-Induced Lung Injury\u003c/h2\u003e \u003cp\u003eCellular apoptosis plays a pivotal role in the pathogenesis of sepsis-induced lung injury [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Our study revealed a substantial increase in alveolar epithelial cell apoptosis during sepsis, while SO₂ intervention significantly reduced both lung injury and apoptotic rates. This suggests that SO₂ confers protection by suppressing alveolar epithelial cell apoptosis.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eSO₂ Inhibits Bax-Mediated Mitochondrial Apoptotic Pathway\u003c/h2\u003e \u003cp\u003eAberrant activation of the mitochondrial apoptotic pathway is central to alveolar epithelial cell apoptosis in sepsis-induced lung injury. Bax is a key regulator of this pathway. Our results demonstrated markedly elevated Bax levels in lung tissue during sepsis, correlating with increased alveolar epithelial cell apoptosis. SO₂ intervention effectively downregulated Bax expression and concurrently reduced apoptosis, indicating that SO₂ protects against lung injury by inhibiting the Bax-mediated apoptotic pathway.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn summary, our study demonstrates that endogenous SO₂ mitigates sepsis-induced lung injury by suppressing the Bax pathway and subsequent alveolar epithelial cell apoptosis. However, the precise molecular mechanisms warrant further investigation in future studies. These findings highlight the therapeutic potential of SO₂ in managing sepsis-associated ALI and provide a foundation for developing novel treatment strategies.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis project is funded by Beijing Jishuitan Hospital Elite Young Scholar Programme (NO. XKGG202204).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData is provided within the manuscript files.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics Approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Ethics Committee of Beijing Jishuitan Hospital (Approval No. Jilunke 2024-03-S32). All methods were performed in accordance with the relevant guidelines and regulations\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll the results/data/figures in this manuscript have not been published elsewhere, nor are they under consideration (from you or one of your Contributing Authors) by another publisher.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no conflicts of interest.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eRhodes, A. et al. 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Changhong Miao; Neutrophil extracellular traps mediate m6A modification and regulates sepsis-associated acute lung injury by activating ferroptosis in alveolar epithelial cells. \u003cem\u003eInt. J. Biol. Sci.\u003c/em\u003e \u003cb\u003e18\u003c/b\u003e (8), 3337\u0026ndash;3357. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.7150/ijbs.69141\u003c/span\u003e\u003cspan address=\"10.7150/ijbs.69141\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (2022).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-8739206/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8739206/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eObjective: To investigate the regulatory effect of endogenous sulfur dioxide (SO₂) on alveolar epithelial cell apoptosis in rats with sepsis-induced lung injury.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eMethods: Male Sprague Dawley rats were randomly divided into four groups: normal control group, sepsis group, sepsis + SO₂ group, and SO₂ control group. Each group was observed for 12 hours. Lung tissues from each group were subjected to HE pathological staining and semi-quantitative lung injury scoring. The BAX content in lung tissues was measured using ELISA, and apoptosis was assessed via TUNEL staining.\u003c/p\u003e\n\u003cp\u003eResults: In rats with lung injury, the semi-quantitative lung injury score, BAX content, and TUNEL staining were significantly increased. After SO₂ intervention, these indicators (semi-quantitative lung injury score, BAX content, and TUNEL staining) were significantly reduced.\u003c/p\u003e\n\u003cp\u003eConclusion: Endogenous sulfur dioxide can exert a protective effect in sepsis-induced lung injury by inhibiting BAX-mediated apoptosis of alveolar epithelial cells.\u003c/p\u003e","manuscriptTitle":"Endogenous sulfur dioxide alleviates septic lung injury by suppressing Bax-mediated apoptosis of alveolar epithelial cells","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-23 17:41:54","doi":"10.21203/rs.3.rs-8739206/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e4fb8e7b-bf66-4ee8-ba9e-b694a1541908","owner":[],"postedDate":"March 23rd, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":64998848,"name":"Biological sciences/Cell biology"},{"id":64998849,"name":"Health sciences/Diseases"},{"id":64998850,"name":"Health sciences/Medical research"}],"tags":[],"updatedAt":"2026-04-13T06:10:33+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-23 17:41:54","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8739206","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8739206","identity":"rs-8739206","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}