A THIOL BASED TOOL TO EXPLORE PERITONEAL MEMBRANE PROTECTIVE DRUG CANDIDATES

Abstract

Introduction: Peritoneal dialysis (PD) is a renal replacement therapy that offers several advantages, including greater patient autonomy. However, peritoneal membrane fibrosis and loss of membrane integrity remain the main limiting factors for the long-term success of PD [1]. At SPF 2024, our group reported an association between peritoneal membrane fibrosis and aminothiol levels, namely cysteine, in PD effluent. Based on these findings, we hypothesized that pharmacological targeting endogenous thiols—the thiolome—may represent a strategy to preserve peritoneal membrane integrity. Our objective was to compare the thiolome of PD patients chronically treated with a specific drug class with known antioxidant effects with those whose therapeutic regimen did not include this drug class. Materials & Methods: Cysteine (Cys), homocysteine (HCys), cysteinylglycine (CysGly), glutathione (GSH), and urinary N-Acetyl cystine (NAC) were quantified in plasma and in PD effluent by high-performance liquid chromatography with fluorescence detection [2]. PD effluent was obtained during the peritoneal equilibration test (PET), a 4-hour standardized clinical test in which a supraphysiological glucose-based solution is used as a stimulus to assess the peritoneal membrane’s transport characteristics collected at 0, 2, and 4 hours. PET is performed in the morning at the hospital. Thiols were also quantified in the bag obtained in the night before PET (overnight PD effluent). Ethical approvals: NMS 120/2023/CEFCM; ULSLO 2024-63. Statistical analyses included principal component analysis (PCA), between- group comparisons using Student’s t-test or Mann–Whitney U test as appropriate, and chi- square test for categorical variables. Results: A total of 41 PD patients were included; 59% were treated with drug class X. Patients from X-treated group were older (63±11 vs 51±13 years, p=0.0003), while the proportion of women was comparable between groups (21% vs 24%, p=ns), as it was the proportion of patients with more than 1 year on PD; 75% vs 53%, p=ns). Integrated PCA did not reveal a clear separation between groups treated vs. non-treated in each fluid, nor when all fluids were included. However, treatment with drug X was associated with significantly higher GSH levels in overnight PDE (p=0.010), 2-h and 4-h PET effluents (p=0.026 and p=0.006, respectively), while plasma GSH levels remained unchanged. The CysGly/GSH ratio was used as a proxy for γ-glutamyltransferase activity, a marker of chronic oxidative stress and fibrosis [3]; this ratio was decreased in patients with drug X across overnight PDE (p=0.024) and 2h-PET effluent (p=0.025), suggesting membrane protective activity. Conclusion: Since PD effluent reflects the peritoneal membrane microenvironment, the observed changes in GSH levels and the CysGly/GSH ratio in PD effluent, but not in plasma, appear to be informative indicators of membrane status, supporting a mechanistic involvement of thiol pathways in the pathophysiology of membrane fibrosis. These pilot results demonstrate the potential of our approach in drug repurposing studies aimed at peritoneal membrane protection.