P-353 The role of endoplasmic reticulum aminopeptidases 1/2 (ERAP1/ERAP2) and cysteinyl aminopeptidase (LNPEP) in the pathomechanism of endometriosis - a study of genetic and proteomic determinants

Abstract Study question How might ERAP1, ERAP2 and LNPEP polymorphisms and levels of these aminopeptidases tested in plasma and peritoneal fluid be related to endometriosis susceptibility and severity? Summary answer ERAP1 rs7063 A/T polymorphism is correlated with enzymatic activity and expression of the ERAP1 protein and could influence susceptibility and severity to endometriosis. What is known already Endometriosis is a serious gynecological disease characterized by endometrial cells in abnormal or ectopic locations, outside the uterine cavity. The range of symptoms of endometriosis includes bleeding and pain between periods, pain during urination, heavy bleeding, severe pelvic ramping or infertility. The inability to form proper HLA class I – antigen complexes may influence disease development, as proteins associated with antigen processing machinery can affect the immune response of CD8+ and NK cells, contributing to the development of endometriosis. Study design, size, duration We used 387 DNA samples from patients with endometriosis and 390 healthy controls, plasma from 89 healthy controls and 75 patients with endometriosis, peritoneal fluid from 9 controls and 64 patients with endometriosis. This project is supported by a grant from the National Science Centre, Poland, no. 2021/43/B/NZ5/00328, entitled: ‘’Elements of the HLA class I antigen processing machinery as factors involved in the pathomechanism and progression of endometriosis’’ since 2022. Participants/materials, setting, methods Genotyping for 21 single nucleotide polymorphisms of ERAP1, ERAP2 and LNPEP genes was performed by Real-Time PCR using TaqMan probes. Concentrations of ERAP1, ERAP2 and LNPEP proteins in plasma and peritoneal fluid were tested using Enzyme-Linked Immunosorbent Assay (ELISA) kits. Statistical analysis was carried out using GraphPad Prism 10. Main results and the role of chance Our results indicate that the ERAP1 rs7063 AA genotype increases the risk of endometriosis (p = 0.0225, OR = 1.176) while the AT genotype protects from disease (p = 0.0112, OR = 0.8291). The significance became stronger in stage III disease for AT (p = 0.0274, OR = 0.6427), in IV disease for AA (p = 0.0026, OR = 1.631) and AT (p = 0.0002, OR = 0.5213) genotypes. ERAP1 protein was mostly undetectable in plasma and the peritoneal fluid of patients and controls. ERAP2 protein levels in plasma were significantly higher in the III and IV stages of endometriosis than in the I and II stages (Median 1.825 vs. 0.880, p = 0.0053). Moreover, concentrations of ERAP2 were significantly different in plasma and peritoneal fluid (Median 1.660 vs. 2.090, p = 0.0084) in patients. In the case of LNPEP, we detected higher protein levels in the plasma of endometriosis patients in comparison to control women (Median 2.040 vs. 0.0570, p < 0.0001). In addition in patients, the concentration of this protein was increased in plasma than in peritoneal fluid (Median 2.040 vs. 0.960, p < 0.0001). Limitations, reasons for caution A limitation of our study is the small number of peritoneal fluids tested in healthy women. The project is still ongoing and research is continuing. Wider implications of the findings Aminopeptidases ERAP2 and LNPEP are released into plasma and peritoneal fluid. ERAP1 protein was detected only in some samples. Women with endometriosis differ in concentrations of ERAP2 and LNPEP protein. However, their function is unknown in endometriosis. Trial registration number No