{"paper_id":"ffb138b3-1b0d-4443-85de-2d915f20b39c","body_text":"Volume 10 • Number 4 • December 2019 • em00729 \nwww.jceionline.org  Copyright © 2019 by Authors. Licensee Modestum Ltd., UK. OPEN ACCESS for all. | 1 / 8 \nJOURNAL OF CLINICAL AND \nEXPERIMENTAL INVESTIGATIONS RESEARCH  ARTICLE \n \nThe Importance of Serum Prolidase Activity in \nEndometriosis \nMukaddes Demir Dural 1, Fatma Devran Bıldırcın 1, Pervin Karlı 2*, Ayse Zehra Özdemir 1 \n \n \n1 Ondokuz Mayis University, \nSamsun, Turkey \n2 Amasya University, Amasya, \nTurkey \n \nABSTRACT \nObjective: In this study, our objective was to evaluate the abnormal collagen destruction and \nturnover and the prolidase activity in the etiopathogenesis of endometriosis, which may \ndeteriorate the collagenous structure of exracellular matrix (ECM). \nMaterials and Methods: For the assessment of the prolidase activity, venous blood samples \nwere obtained from 37 patients, who had applied to the outpatient department of the Medical \nFaculty at Ondokuz Mayıs University with complaints of pelvic pain, dysmenorrhea and \ninfertility between October 1st, 2011 and February 15th, 2012, underwent clinical and \nultrasonographic examination, prediagnosed with endometriosis, and scheduled for \nlaparoscopy or laparotomy. A total of 22 patients, who were diagnosed with endometriosis via \nintraoperative exploration and/or pathological examination, constituted the study group and \nthe remaining 15 patients, who did not have any pathological finding or were diagnosed with \na benign disease except for endometriosis, constituted the control group. \nSerum samples obtained from all patients were first centrifuged and then stored in a freezer \nat -70 C until the time of analysis. During the analysis, the prolidase activity was measured \nfollowing the necessary biochemical enzymatic processing. \nResults: We found a statistically significant difference between stage 4 and stage 1,2,3 patients \nin the study group regarding the CA 125 levels (p=0.018). On the other hand, there was no \nstatistically significant difference between stage 1,2,3 patients in the study group and the \ncontrol group for serum prolidase levels (p=0.778). There was a statistically significant \ndifference between stage 4 endometriosis patients in the study group and the control group \nconsidering the serum prolidase levels (p=0.026). \nConclusion: We conclude that serum prolidase activity has a critical function in the \ndevelopment of the endometriotic lesions. In endometriosis patients, the increase in the serum \nprolidase activity may play an important role in the progress to more advanced stages and in \nthe development of infertility. \nKeywords: serum prolidase activity, endometriosis, CA 125 \n \n \nCorrespondence:  \nPervin Karlı \nAddress: Amasya University, \nAmasya, Turkey \nEmail: parpi2300@hotmail.com  \n \n \nINTRODUCTION \nEndometriosis is defined as the presence \nof endometrial gland and stroma outside the \nuterus cavity and muscular layer [1]. The \nprevalence of endometriosis in the general \npopulation is unknown [1-3]. The \ndetermination of the prevalence is rather \ndifficult because of the asymptomatic \npatients and nonspecific and diverse \nsymptomatology in symptomatic patients. \nApproximately 12%-32% of patients, who \nunderwent laparoscopy due to the pelvic \npain, 9%-50% of patients, who underwent \nlaparoscopy due to infertility and 50% of \npatients, who underwent laparoscopy due to \nthe chronic pelvic pain or dysmenorrhea, \nwere diagnosed with endometriosis [1-3]. \nThe pathological process in endometriosis is \nnot fully elucidated yet. Although the \npathogenesis is not known, several theories \nbased on certain evidence were proposed [1]. \nRetrograde menstruation – transplantation, \ncoelomic metaplasia – induction, vascular \ndissemination and theories related to the \nimmune system are among them. As \nendometriosis is usually encountered in \nwomen of reproductive age, the symptoms \nReceived: 29.05.2019, \nAccepted: 06.08.2019 \nhttps://doi.org/10.5799/jcei/5903  \n\n \n \nSerum Prolidase Activity and Endometriosis \n2 / 8 | Copyright © 2019 by Authors. Licensee Modestum Ltd., UK. OPEN ACCESS for all. www.jceionline.org \nregress with the onset of menopause [4]. Reoccurrence of \nsymptoms in postmenopausal women treated with estrogen \nreplacement therapy indicates that endometriosis is an \nestrogen-dependent disease. The immune system hypothesis \nexplains the secretion of different cytokines, which initiate \nthe proliferation of implants, lead to the capillary support \nand to leukocyte chemotaxis due to the peritoneal \ninflammation following the access of the endometrial \nimplant and inflammatory cells to the peritoneal cavity [4]. \nOxidative stress might be one of the components of the \ninflammatory process [5]. Therefore, the immune system \nmay play an important role in the characteristics and the \nseverity of the clinical findings and in whom they will emerge \n[6,7]. For a long time, it is widely accepted that there is a \nfamilial disposition in endometriosis. Pain is the most \ncommon symptom of endometriosis. Approximately 75% of \nthe symptomatic patients complain of pelvic pain and/or \ndysmenorrhea [8]. Chronic pelvic pain, dysmenorrhea, \ndyspareunia, subfertility, abnormal menstrual bleeding, and \nback pain are other symptoms. The stage of endometriosis \ndoes not correlate with the presence and the severity of the \nsymptoms. Laparoscopy and visual detection of the lesion \nare the gold standards in the diagnosis of endometriosis [8-\n10]. Endometriosis is a chronic disease, which requires \nlifelong optimal treatment and avoidance from the re-\noperation. In spite of intensive research, the optimal \ntreatment of endometriosis is still not clear. The treatment of \nendometriosis should be based on the specific symptoms, the \nseverity of the symptoms, the localization of the \nendometriotic lesions, the goals of the treatment, the age of \nthe patient and the desire to preserve the fertility in the \nfuture. Observation and the medical treatments consisting of \nhormonal suppression and analgesia and surgical \ninterventions are the main therapeutic alternatives. \nUnder normal physiological conditions, the \nendometrium tissue is formed by the extracellular matrix \n(ECM). The matrix metalloproteinase  (MMP) consists of \nproteolytic enzymes, which regulate and change ECM. \nStudies demonstrated that endometriosis may develop as a \nresult of the impairment of the regulatory control in MMP \n[11,12]. Regarding the collagen remodeling in ECM, which \nis started by MMPs, collagen degradation stimulated by \nprolidase is the final step. The abnormal collagen \ndegradation and turnover and increased prolidase activity, \nwhich may deteriorate the collagenous structure of ECM, \nmay be responsible for the etiopathogenesis of endometriosis \n[13]. \nIt was demonstrated that MMP-9 increased in the ectopic \nendometrium of women with endometriosis [14]. The MMP \nactivity is controlled by oxidative stress activity. It was \nreported that the reactive oxygen species had an important \nrole in the invasion and growth of the endometrial cells in \nthe peritoneal cavity in women with endometriosis [15,16]. \nIt was also determined that MMPs had a critical function in \nthe early development of the endometriotic lesions and \nMMP inhibitors prevented the endometriotic lesions \n[17,18]. \nThe activity of matrix metalloproteinases and prolidases \nwas investigated in various obstetric and gynecological \ndiseases. It was observed that MMP-9, MMP-2, MMP-3, and \ncollagenases increased in the fetal membrane and amniotic \nfluid close to the delivery. It was suggested that the MMP \nactivation in the specific areas of the fetal membrane may \ncause membrane rupture at term or preterm [19-22]. MMPs \nparticipate in the placenta invasion. The increase in MMP \nlevels is one of the factors blamed for the placental abruption \n[23,24]. The increase in the extracellular matrix turnover is \none of the pathological mechanisms responsible for the \nvascular resistance and emergence of the endothelial \ndysfunction in the intrauterine growth retardation. \nTherefore the serum prolidase level, which is a marker for \nthe extracellular matrix and collagen turnover, was \ninvestigated in the intrauterine growth retardation and it was \ndemonstrated that it increased in these cases [25]. \nThe objective of our study was to evaluate the abnormal \ncollagen degradation and turnover in the etiopathogenesis of \nendometriosis and the prolidase activity, which may \ndeteriorate the collagenous structure in ECM. Furthermore, \nthe elucidation of the etiology may facilitate the development \nof new therapeutic approaches in endometriosis. \nMATERIALS AND METHODS \nThis article was approved by the Ethics Committee of the \nFaculty of Medicine of Ondokuz Mayıs University (OMU \nTAEK 2010-153). Study type is “prospective study”. For the \nassessment of the prolidase activity, venous blood samples \nwere obtained from 37 patients, who had applied to the \noutpatient department of the Medical Faculty at Ondokuz \nMayıs University with complaints of pelvic pain, \ndysmenorrhea and infertility between October 1st, 2011 and \nFebruary 15th, 2012, underwent clinical and \nultrasonographic examination, prediagnosed with \nendometriosis, and scheduled for laparoscopy or \nlaparotomy. Written patient consent was obtained from all \npatients in the study and control groups. A total of 22 \npatients, who were diagnosed with endometriosis via \nintraoperative exploration and/or pathological examination, \nconstituted the study group and the remaining 15 patients, \nwho did not have any pathological finding or were diagnosed \nwith a benign disease except for endometriosis, constituted \nthe control group. All patients in the study and control \ngroups were Caucasians and were Turkish nationality. The \neducational background was not taken into consideration. \nAll patients in the study and control group fulfilled the \npatient information form and the following patient \ncharacteristics were recorded: Age, presence and duration \ninfertility, pre-operative CA 125 values, presence of \ndysmenorrhea and dyspareunia symptoms, previous \nendometriosis operations, presence of concomitant \ngynecological diseases, stage of the disease, operation \n\n \n \nSerum Prolidase Activity and Endometriosis \nwww.jceionline.org  Copyright © 2019 by Authors. Licensee Modestum Ltd., UK. OPEN ACCESS for all. | 3 / 8 \nreports, primary complaints, information about \npreoperative TVS, gravida, parity, number of abortion and \nliving children, drug therapy, presence of chronic diseases \nwas recorded. Patients with endometriosis, who were \ndiagnosed with laparoscopy or laparotomy and included in \nthe study, were classified according to the endometriosis \nclassification of ASRM (American Society for Reproductive \nMedicine): Stage 1 (minimal), stage 2 (mild), stage 3 \n(moderate), and stage 4 (severe). In the study group, 2 \npatients were at stage 1 (minimal), one patient at stage 2 \n(mild), 4 patients at stage 3 (moderate), and 15 patients at \nstage 4 (severe). Five and 17 of the patients underwent \nlaparotomy and laparoscopy respectively. \nInclusion Criteria \na) 18-47 years of age \nb) preoperative examination and suspected unilateral \nor bilateral ovarian endometrioma by ultrasound and \ndiagnosed as endometrioma in the pathology after \nlaparoscopic surgery \nExclusion Criteria \na) ovarian surgery, hysterectomy or determined \nasprevious surgery \nb) postoperative non-endometrioma pathology \nc) hormonal preoperative get treatment or have any \nhormonal disease \nd) inflammatory bowel disease or irritable colon \nsyndrome \nObtainment of Serum Samples \nSerum samples were taken from the left or right \nantecubital veins of patients while they were sitting at room \ntemperature (24°C) after the related region was cleaned with \nalcohol and cotton. A 10cc syringe was used and approx. 7-8 \ncc blood was drawn. The samples were taken approx. one \nhour before the intervention. The blood samples were \ntransferred in vacuumed and red-capped biochemistry \ntubes, which did not contain an anticoagulant agent. After \nthe centrifuge process, samples were stored at -70°C until the \nanalysis. \nSerum Prolidase Enzyme Activity \nThe prolidase enzyme activity was calculated with the \nmeasurement of the L-proline complex, which forms as a \nresult of the degradation of the glycine-L-proline substrate \nwith enzymes, and ninhydrin at 90°C (pH: 7.8). The analysis \nwas performed according to the modified Chinard method \nwith the reagents produced in the Research Laboratory of the \nBiochemistry Department in the Ondokuz Mayıs University \nMedical Faculty [26]. The serum prolidase enzyme activity \nwas assessed by a specialist, who was blinded to the study and \ncontrol groups. \nThe Preparation of the Solutions \n1. 50 mM Tris-HCl tamponade (pH: 7.8): After 6.057 \ng Tris was completely solved in approx. 60 ml distilled water \nin the magnetic mixer, pH was adjusted to 7.8 with 1 N HCl \nand the volume was adjusted to 1 liter with distilled water.  \n2. 5 mM MgCl2-4H2O, 0.1% Triton X-100, 1 mM \nGSH: In a dark-colored bottle containing approx. 60 mL 50 \nmM Tris-HCl tamponade (pH:7.8), 100 mg MnCl2-4H2O, \n100 µl Triton X-100 and 30.7 mg GSH were dissolved in this \norder in a magnetic mixer. The final volume was adjusted to \n100 mL with 50 mM Tris-HCl tamponade (pH: 7.8). \n3. 144 mM glycine-L-proline (substrate): First 5 mg \nMnCl2-4H2O and then 124 mg glycine-L-proline were \ndissolved completely in a dark-colored bottle containing \napprox. 3 ml 50 mM Tris-HCl tamponade (pH: 7.8). Final \nvolume was adjusted to 5 ml with 50 mM Tris-HCl buffer \n(pH: 7.8). \n4. 0.45 M TCA: After 73.52 g trichloroacetic acid \n(TCA) was completely dissolved in 600 ml distilled water in \nthe magnetic mixer, the final volume was adjusted to 1000 ml \nwith distilled water. \n5. L-proline standard: After 7.5 mg L-proline was \ncompletely dissolved in approx. 60 ml 0.45 M TCA in a \nmagnetic mixer, the final volume was adjusted to 100 ml with \ndistilled water. \n6. Modified Chinard reagent: 550 ml glacial acetic acid \n(GAA) and 450 ml 6M orthophosphoric acid (OFA) were \nmixed in a vortex mixer until the mixture became completely \nhomogeneous. 60 ml of this mixture was transferred into a \ndark-colored bottle and 30 g ninhydrin was added. After it \nwas completely dissolved in the magnetic mixer at 70°C, the \nfinal volume was adjusted to 100 ml with the GAA-OFA \nmixture. \nImplementation of the Method \nSerum samples, which were kept in the deep freezer, were \nbrought to room temperature. Then they were diluted with \nTris-HCl tamponade containing 5 mM MnCl2–4 H2O, 0.1% \nTriton X-100 and 1 mM GSH in a ratio of 1:6 and stored at \n37°C to incubate for 3 hours. Then, 100 µl from each sample \nwere transferred to tubes, which were labeled as sample and \nblind sample. 100 µl substrate (glycine-L-proline) was added \nto the sample tube and the sample and blind sample tubes let \nto incubate at 37°C for 30 minutes. After the incubation, 1 \nml 0.45M TCA was added to both tubes and the prolidase \nenzyme was inhibited with mixing in the vortex mixer. Then, \n100 µl substrate was added and mixed to the blind sample \ntube, the sample was centrifuged at 4000 rpm for 10 minutes. \nAfter the centrifuge, 0.5 ml supernatant from sample and \nblind sample was transferred to new tubes. 0.5 ml standard \n(7.5% mg L-proline) and 0.5 ml TCA were added to separate \ntubes and labeled as standard and reagent blind respectively. \n1 mL GAA added to all tubes and mixed in the vortex mixer \nand then 1 ml modified Chinard reagent added to the tubes \nand mixed again. All tubes let to incubate at 90°C for 20 \nminutes. After the incubation period, all tubes brought to \nroom temperature and the absorbance at 515 nm wavelength \n\n \n \nSerum Prolidase Activity and Endometriosis \n4 / 8 | Copyright © 2019 by Authors. Licensee Modestum Ltd., UK. OPEN ACCESS for all. www.jceionline.org \nwas measured with the spectrophotometer. The obtained \ndata were inserted to the below-mentioned formula and the \nserum prolidase enzyme activities were calculated in U/l \n(Figure 1). \nStatistical Analysis \nAll analyses were done with SPSS for Windows v15.0. \nThe intergroup comparisons were performed with the \nStudent’s t-test, Mann-Whitney U test, and Chi-square test. \nRESULTS \nThe preoperative CA 125 values were between 5 and 150 \nIU/ml in the study group. The duration of infertility was \nbetween 2 and 11 years among patients, who were diagnosed \nwith infertility. Eighteen of the patients had symptoms \nrelated to dysmenorrhea and 10 patients had symptoms \nrelated to dyspareunia. Eight patients had previous \nendometriosis operation. Five patients had myoma uteri as a \nconcomitant gynecological pelvic disease. 10 of the patients, \nwho were diagnosed with endometriosis via laparoscopy and \nlaparotomy, were operated due to the pre-diagnosis of pelvic \npain, a pelvic mass. Twelve patients were operated due to the \nprediagnosis of infertility (8 patients had primary infertility, \n4 patients had secondary infertility). \nTotal abdominal hysterectomy and bilateral salpingo-\noophorectomy were performed in one of 15 stage 4 patients. \ntotal abdominal hysterectomy and unilateral salpingo-\noophorectomy were performed one of these patients. Eight \npatients underwent endometrioma cyst excision and \nadhesiolysis. Five patients underwent endometrioma cyst \naspiration, cyst capsule ablation, and adhesiolysis.  \nFour stage 3 patients underwent adhesiolysis and \nendometrioma cyst excision. We did not perform any \nadditional intervention during laparoscopy in patients with \nstage 1 or stage 2. Drug treatment with a GnRH agonist was \ninitiated in one of stage 4 patients in the postoperative \nperiod. \nThere was no statistically significant difference between \nthe study and control groups regarding the age of the \nparticipants. The age of the patients was between 18 and 47 \nyears in the study group and between 18 and 45 years in the \ncontrol group. The mean age was 31±9.1 and 28±2.4 years in \nthe study and control groups respectively.  \nSixteen patients in the study group had infertility and 6 \nhad no infertility. The comparison of the patients in the \nstudy group for infertility revealed a statistically significant \ndifference (p<0.05). In the study group, 17 patients had \ndysmenorrhea and 5 patients had no dysmenorrhea. The \ncomparison of the patients in the study group for \ndysmenorrhea showed a statistically significant difference \n(p=0.011). Again in the study group, 10 patients had \ndyspareunia and 12 had no dyspareunia. The comparison of \nthe patients in the study group for dyspareunia showed no \nstatistically significant difference (p>0.05). In the study \ngroup, the main symptom was infertility in 14 patients and \nabdominal pain in 8 patients. The comparison of the patients \nin the study group for abdominal pain and infertility \ndisplayed no statistically significant difference (p<0.05) \n(Table 2). In the study group, pelvic masses (size: 2-9 cm) \nwere determined in 19 patients during TVS. Eight of these \npelvic masses were unilateral and 11 were bilateral. Twenty-\ntwo patients underwent laparoscopy/laparotomy and were \ndiagnosed with endometriosis according to the ASRM \n(American Society for Reproductive Medicine) \nendometriosis classification and were included in the study \ngroup. Ten of the endometriosis patients (45.4%), who were \nprediagnosed during laparoscopy/laparotomy, were \noperated due to the chronic pelvic pain and pelvic mass, 12 \nof them (54.6%) were operated due to the prediagnosis of \ninfertility (8 patients had primary infertility and 4 had \nsecondary infertility). 15 of these 22 patients (68.1%) had \nstage 4 endometriosis. Two of the cases (9.3%) had stage 1 \n(minimal), one (4.5%) had stage 2 (mild), and four (18.1%) \nhad stage 3 (moderate) endometriosis (Table 1). \nStage 4 and stage 1, 2, 3 patients in the study groups were \ncompared for serum CA 125 levels with a statistically \nsignificant difference (p=0.018) (Table 3). \n𝐀𝐀𝐨𝐨S − 𝐀𝐀𝐨𝐨BS − 𝐀𝐀𝐨𝐨BR\n𝐀𝐀𝐨𝐨S − 𝐀𝐀𝐨𝐨BR × 1560 \n𝐀𝐀𝐨𝐨S = Absorbance of Sample \n𝐀𝐀𝐨𝐨BS = Absorbance of Blind Sample \n𝐀𝐀𝐨𝐨BR = Absorbance of Blind Reagent  \n𝐀𝐀𝐨𝐨S = Absorbance of Standard \n \nFigure 1. Calculation of Serum Prolidase Enzyme Activity \nTable 1. Distribution of the cases according to the stage of \nendometriosis \nStage Number of patients % \n1 2 9.3 \n2 1 4.5 \n3 4 18.1 \n4 15 68.1 \n \nTable 2. Comparison in the study group according to the \nsymptom and fertility characteristics \nSymptom Number of \npatients (%) P \nInfertility (No) 6 (17.2) \n0.033 \nInfertility (Yes) 16 (72.8) \nDysmenorrhea (No) 5 (22.7) \n0.011 \nDysmenorrhea (Yes) 17 (77.3) \nDyspareunia (No) 12 (54.5) \n0.670 \nDyspareunia (Yes) 10 (45.5) \nInfertility 14 (63.6) \n0.201 \nAbdominal pain 8 (36.4) \n \n\n \n \nSerum Prolidase Activity and Endometriosis \nwww.jceionline.org  Copyright © 2019 by Authors. Licensee Modestum Ltd., UK. OPEN ACCESS for all. | 5 / 8 \nThe comparison of stage 1,2,3 patients in the study with \nthe control group for serum prolidase levels did not display \nany statistically significant difference (p=0.778). There was \nalso no statistically significant difference between stage 4 and \nstage 1,2,3 patients regarding the serum prolidase levels \n(p=0.259). However, we found a statistically significant \ndifference between stage 4 endometriosis patients in the \nstudy group and the control group in respect of the serum \nprolidase levels (p=0.026) (Table 4). \nAlthough the serum prolidase levels were higher in the \nstudy group compared to the control group, the difference \nwas not statistically significant (p=0.086). However, there \nwas a statistically significant difference between stage 4 \nendometriosis patients in the study group and the control \ngroup for the serum prolidase levels (p=0.026). We could not \ndetect any statistically significant difference between stage 4 \nand stage 1,2,3 endometriosis patients in the study group \nregarding the serum prolidase levels (Figure 2). \nThe comparison of the study and control groups for the \nserum prolidase levels showed that the stage 4 patients were \nresponsible for the high prolidase levels and the difference \nwas not statistically significant because of the low prolidase \nlevels in stage 1,2,3 patients. In the study group, the \ncomparison of the patients with and without infertility \ndisplayed a statistically significant difference for the serum \nprolidase level (p=0.021). However, there was no statistically \nsignificant difference between the patients with and without \nabdominal pain for the serum prolidase level (p=0.183). \nSimilarly, there was also no statistically significant difference \nbetween the patients with and without dyspareunia and \ndysmenorrhea symptoms for the serum prolidase level \n(p=0.821 and p=0.594 respectively) (Table 5). \nIn the study group, 16 patients had infertility and 6 \npatients did not have infertility. The comparison of the \npatients with and without infertility for serum prolidase level \nshowed a significant difference (p=0.012) (Figure 3). \nDISCUSSION \nMatrix metalloproteinase (MMP) family is an important \nmember of the extracellular proteinases [17,18]. The most \nimportant function of MMPs is the degradation of the \nextracellular matrix (ECM). Studies showed that MMPs took \npart in various physiological and pathological processes \n[17,18]. These enzymes are rather essential regarding ECM \nturnover, tissue remodeling, angiogenesis, morphogenesis, \nand development. MMPs also play an important role in \nseveral physiological processes such as embryonic \ndevelopment, ovulation, bone remodeling and wound \nhealing [17,18,27]. Furthermore, it is well known that MMPs \ntake part in cell migration, invasion, proliferation, and \nTable 3. Comparison of stage 4 and stage 1,2,3 endometriosis patients for serum CA 125 level \n Stage Patient Mean Min./Max. P \nPreoperative CA 125 \nStage (1, 2, 3) 7 29.4±21.5 5-66 \n0.018 Stage 4 15 61.7±32.3 29-50 \nTotal 22 51,432.6 5-150 \n \nTable 4. Comparison of stage 1,2,3 and stage 4 endometriosis patients in the study group for the serum prolidase levels \nGroup Number of \npatients \nMean±SD \nProlidase Median Max./Min. \nProlidase \nStage 4 endometriosis 15 915±297 938 1428-457 \nStage 1,2,3 endometriosis 7 720±268 672 1079-287 \nControl Group 15 697±203 669 1023-208 \n  P \n Between stage 4 and the control group 0.026 \n Between stage 1,2,3 and the control group 0.778 \n Between stage 1,2,3 and stage 4 0.259 \n \n \nFigure 2. The distribution of the serum prolidase levels between \nthe stage 1,2,3 and stage 4 endometriosis patients in the study \ngroup and the control group \n\n\n \n \nSerum Prolidase Activity and Endometriosis \n6 / 8 | Copyright © 2019 by Authors. Licensee Modestum Ltd., UK. OPEN ACCESS for all. www.jceionline.org \napoptosis. It is believed that the uncontrolled increases in the \nMMP activity take part in the pathogenesis of acute and \nchronic diseases depending on the ECM degradation [27]. \nThe proteolytic activity of MMPs may be prevented with \ntissue metalloproteinase inhibitors (TIMP), which inhibit \nthe degradation of collagen and other matrix \nmacromolecules. The existing proportion between MMPs \nand TIMPs may change during various physiological and \npathological processes and thus the balance between them \nmay play an important role in the pathogenesis of several \npathological events. Numerous processes including \novulation, implantation, gestation, lactation, and involution, \nwhich are components of the reproduction process, require \nTIMP and/or MMP activation [27]. \nIn a study, it was determined that serum prolidase \nactivity was increased and placental prolidase activity was \ndecreased depending on the possible placental use in patients \nwith early pregnancy loss. In this study, the authors \nconcluded that the decreased placental activity of prolidase \nmight be an etiopathological factor in women with early \npregnancy loss [28]. In a study conducted by Camuzcuoğlu \net al., it was found out that serum prolidase activity and total \noxidative stress increased and total antioxidant capacity \ndecreased in women with epithelial ovarian cancer. They also \ndetermined that there was a strong correlation between the \nserum prolidase activity and stage and the grade of the tumor \nand the preoperative CA 125 levels. This study indicated that \nserum prolidase activity might be a prognostic factor in \nepithelial ovarian cancer [29]. \nEndometriosis was detected in 80% of women with \ncomplaints of pelvic pain or infertility [1-3]. Factors like the \nimmune, hormonal, genetic, and environmental factors of \nthe peritoneal fluid and content and invasive potential of the \nendometriotic cells are determinative in the development of \nendometriosis [30]. Oxidative stress might be one of the \ncomponents of the inflammatory process [5]. \nRegarding the etiology of endometriosis, which is not \nclear yet, various agents were blamed. One of the most \npopular opinions is that the matrix metalloproteinases \n(MMP) play an important role in the etiology of \nendometriosis [11,12]. During the normal physiological \nprocesses, endometrium tissue is formed by the extracellular \nmatrix (ECM). MMPs are proteolytic enzymes that regulate \nand modify ECM [11,12]. Studies had shown that the \nimpairment in the regulatory control of MMPs might lead to \nendometriosis [11,12]. Abnormal collagen degradation and \nturnover and increased prolidase activity, which may \ndeteriorate the collagenous structure of ECM may be \nresponsible for the etiopathogenesis of endometriosis [13]. \nIn our study, significant outcomes of serum prolidase \nactivity in stage 4 endometriosis may be related to abnormal \ncollagen degradation and turnover and increased prolidase \nactivity. \nOxidative stress is one of the factors blamed in the \netiology of endometriosis [15,16]. Macrophages, iron ions \nand the presence of the environmental waste, which cause \noxidative stress and endometriosis due to the disturbance of \nthe balance between the radical oxygen species and \nantioxidants in the peritoneal fluid of some women, are \nconsidered [15,16]. In several studies, it was demonstrated \nTable 5. Comparison of patients in the study group classified according to the symptoms and fertility characteristics for the serum \nprolidase levels \nGroup Number of \npatients \nMean±SD \nProlidase \nMedian \nProlidase \nMin./Max. \nProlidase P (significance) \nInfertility – No 6 648±128 613 528-815 \n0.021 \nInfertility (Yes) 16 930±308 969 287-1428  \nAbdominal pain – No 14 902±312 961 287-1428 \n0.183 \n \nAbdominal pain – Yes 8 768±264 727 528-1305  \nDyspareunia – No 12 811±234 844 287-1079 \n.821 \n \nDyspareunia – Yes 10 904±365 868 457-1428  \nDysmenorrhea – No 5 781±439 651 287-1428 \n0.594 \n \nDysmenorrhea – Yes 17 874±255 874 457-1355  \n \n \nFigure 3. The distribution of serum prolidase levels between the \npatients with and without infertility in the study group \n\n\n \n \nSerum Prolidase Activity and Endometriosis \nwww.jceionline.org  Copyright © 2019 by Authors. Licensee Modestum Ltd., UK. OPEN ACCESS for all. | 7 / 8 \nthat the reactive oxygen species had an important role in the \nadhesion and growth of the endometrial cells in the \nperitoneal cavity of women with endometriosis [15,16]. \nMMP-9 levels, which is a specific enzyme found in the \nectopic endometrium of the women with endometriosis, was \nincreased according to the results of some studies [14]. \nMMPs may be controlled with oxidative stress. Radical \noxygen species (ROS) are responsible for the conversion of \nMMP-9 and MMP-2 from latent form to the active form. \nAnimal studies had shown that the use of the antioxidant \nenzyme might be a protective factor against the development \nof endometriosis. Melatonin has antioxidant activity. In an \nanimal study, it was demonstrated that melatonin had a \nprotective role in the prevention of the peritoneal \nendometriosis. It was observed that melatonin suppressed \nthe activation and release of MMPs after MMP activity was \nincreased by oxidative stress. Further studies are needed for \nthe demonstration of the role of melatonin in the regression \nof the endometriotic lesions through the MMP regulation \n[15,16]. Nap et al. conducted an animal study and found out \nthat MMPs had a critical function in the early development \nof the endometriotic lesions and MMP inhibitors prevented \nthe endometriosis lesions [17,18]. Further studies are needed \nfor the definition of the role of the release and regulation of \nMMPs in the development of endometriosis.  \nVural M et al. claimed that serum prolidase activity is \nhigher in women with fibriods and Hilali et al. found that \nprolidase activity is different in women with PCOS. It was \nproven that prolidase enzyme activity may play a role in pre-\neclampsia in 2017 [31,32]. \nIn our study, prolidase level was higher in women with \nendometriosis compared to the control group. However, the \ndifference was not statistically significant. The comparison \nof stage 4 endometriosis patients with the control group \nshowed a statistically significant difference for the serum \nprolidase level. In addition, there was also a statistically \nsignificant difference between the women with and without \ninfertility for the serum prolidase level. \nCONCLUSION \nIn light of the data obtained in our study, we conclude \nthat serum prolidase activity has a critical function in the \ndevelopment of the endometriotic lesions. The elevation of \nthe serum prolidase activity may play an important role in \nthe progress to more advanced stages and in the \ndevelopment of infertility in patients with endometriosis. \nThese results confirmed that increased prolidase activity, \nwhich might cause abnormal collagen degradation and \nturnover and disturbance in the collagenous structure of \nECM, might be responsible for the etiopathogenesis of \nendometriosis. \nDeclaration of interest: The authors report no conflicts of interest. \nFinancial Disclosure: No financial support was received. \n \nREFERENCES \n1. Sangi-Haghpeykar H, Poindexter AN 3rd. Epidemiology \nof endometriosis among parous women. Obstet Gynecol \n1995;85:983. \n2. Chatman DL, Ward AB. Endometriosis in adolescents. J \nReprod Med 1982;27:156. \n3. Missmer SA, Hankinson SE, Spiegelman D, et al. \nIncidence of laparoscopically confirmed endometriosis \nby demographic, anthropometric, and lifestyle factors. \nAm J Epidemiol 2004;160:784. \n4. 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