IL-33 Exacerbates Endometriotic Lesions via Polarizing Peritoneal Macrophages to M2 Subtype

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Interleukin-33, elevated in endometriosis lesions, polarizes peritoneal macrophages to an M2 subtype, driving a pro-inflammatory cycle that exacerbates lesion development.

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The study examined interleukin-33 (IL-33) expression in endometriosis lesions and tested its effects on peritoneal macrophage polarization and IL-1β production using immunohistochemistry, measurement of IL-33 in ovarian cystic fluid, and in vitro experiments with endometriotic stromal cells (ESC) and patient-derived macrophages. IL-33 was detected in the epithelium and stromal cells of endometriotic lesions, and mean IL-33 levels in endometrioma cystic fluid were higher than in non-endometriomas (2.2 ng/ml vs. 0.02 ng/ml), while IL-1β induced IL-33 mRNA in ESC via p38 MAPK. IL-33 stimulation polarized peritoneal macrophages to an M2 subtype and increased IL-1β mRNA, an effect that was negated by soluble ST2 (a decoy receptor of IL-33), and the authors describe a reinforcing loop where lesion-derived IL-33 increases ESC IL-33 through macrophage IL-1β. This paper is centrally about endometriosis — specifically IL-33’s role in exacerbating endometriotic lesions via M2 polarization of peritoneal macrophages and an IL-33/IL-1β feedback cycle.

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Abstract

In endometriosis, M2 macrophages (MΦ) are dominant and promote the development of endometriosis lesions. However, the factor(s) which induces M2 MΦ are unknown. In the present study, we focused on interleukin (IL)-33, known as an alarmin and investigated its expression and its role in endometriosis, especially from the point of the relevance with MΦ. The expression of IL-33 in endometriosis lesions was examined by immunohistochemistry. The cystic fluid of ovarian cysts/tumors was obtained and used to measure IL-33 concentration. Endometriotic stromal cells (ESC) and MΦ derived from patients were used for in vitro experiments. IL-33 was detected in the epithelium and stromal cells of endometriotic lesions. The mean IL-33 concentration in the cystic fluid of endometriomas was significantly higher than that in non-endometriomas (2.2 ng/ml vs. 0.02 ng/ml, P < 0.01). IL-1β induced IL-33 mRNA expression in ESC via p38 MAPK activation. With IL-33 stimulation, peritoneal MΦ polarized to M2 MΦ and produced IL-1β mRNA with a 2.2-fold increase, which was negated with soluble ST2, a decoy receptor of IL-33. IL-33, derived from endometriotic lesions, stimulated MΦ to produce IL-1β, which results in increasing IL-33 production in ESC. This cycle may continue to exacerbate the endometriotic lesions.
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Abstract

In endometriosis, M2 macrophages (MΦ) are dominant and promote the development of endometriosis lesions. However, the factor(s) which induces M2 MΦ are unknown. In the present study, we focused on interleukin (IL)-33, known as an alarmin and investigated its expression and its role in endometriosis, especially from the point of the relevance with MΦ. The expression of IL-33 in endometriosis lesions was examined by immunohistochemistry. The cystic fluid of ovarian cysts/tumors was obtained and used to measure IL-33 concentration. Endometriotic stromal cells (ESC) and MΦ derived from patients were used for in vitro experiments. IL-33 was detected in the epithelium and stromal cells of endometriotic lesions. The mean IL-33 concentration in the cystic fluid of endometriomas was significantly higher than that in non-endometriomas (2.2 ng/ml vs. 0.02 ng/ml, P < 0.01). IL-1β induced IL-33 mRNA expression in ESC via p38 MAPK activation. With IL-33 stimulation, peritoneal MΦ polarized to M2 MΦ and produced IL-1β mRNA with a 2.2-fold increase, which was negated with soluble ST2, a decoy receptor of IL-33. IL-33, derived from endometriotic lesions, stimulated MΦ to produce IL-1β, which results in increasing IL-33 production in ESC. This cycle may continue to exacerbate the endometriotic lesions. Similar content being viewed by others

References

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Condition tags

mesh:D004716endometriosis

MeSH descriptors

Endometriosis Endometriosis Endometritis Interleukin-33 Macrophages, Peritoneal Peritoneum Adult Endometriosis Endometriosis Endometritis Endometritis Female Humans Interleukin-33 Macrophages, Peritoneal Peritoneum Peritoneum Signal Transduction

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