Endocrine Abstracts

Background: Polycystic ovary syndrome (PCOS) is characterized by hyperandrogenism and polycystic ovaries. Renal injury is prevalent in PCOS, yet the molecular mechanisms are poorly understood. The JAK/STAT3 signaling pathway, activated by the inflammatory cytokine interleukin-6 (IL-6), negatively impacts renal mitochondrial function to induce oxidative stress and renal injury. Despite its chronic activation by excess androgen in extra-renal tissues in PCOS, its role in PCOS associated renal injury is unknown. We aimed to test the hypothesis that excess androgen activates the JAK/STAT3 pathway, leading to renal injury by inducing mitochondrial dysfunction in PCOS.

Methods: PCOS was induced in 3-week-old female mice by dihydrotestosterone Silastic tubes implantation (DHT, 8 mg, 12 weeks). Eight weeks later, the mice were given the JAK/STAT3 inhibitor Stattic (10 mg/kg, SC, 3x/week) or vehicle for 4 weeks. Kidney weight, serum IL-6 (Bioplex), glomerular filtration rate (GFR, transcutaneous fluorescence), and urinary albumin to creatinine ratio (UACR, clinical chemistry analyzer) were assessed. Renal JAK1, JAK2, active STAT3 [phosphorylated-STAT3 (Tyr705)], total STAT3, and mitochondrial markers (cytochrome C, succinate dehydrogenase A, and stress protein HSP60) were assessed by Western blot. IL-6 mRNA was quantified by RT-qPCR. Histopathological analysis was done in H&E-stained renal sections. Mitochondrial reactive oxygen species (mtROS, Amplex Red assay), complexes I and II-driven respiration, and complex IV activity (Oroboros Fluorespirometer) were measured in freshly-isolated kidney mitochondria. Oxidative stress measurement (DCF fluorescence) was performed in DHT (10nM)/Stattic (100nM) or vehicle-co-treated mouse proximal tubule (MCT) cells.

Results: DHT significantly increased kidney weight, UACR, and both systemic and renal IL-6 levels (1.4-3.2-fold) while decreasing GFR (1067.2 ± 59.9 vs 1335.6 ± 60.3 uL/min/100g body weight). PCOS mice have more active STAT3 signaling (higher JAK1, JAK2, and active STAT3). Renal mtROS was higher (2-fold) and complexes I, II, III, and IV respiration was lower (43-71%) in PCOS mice, along with lower cytochrome c (32%), and higher HSP60 (4-fold) levels. These changes were associated with worsen renal histological structure with congested glomeruli and luminal epithelial lining exfoliation. Stattic didn’t affect kidney weight but normalized UACR and GFR while decreasing both glomerular and tubular injury. Stattic decreased renal HSP60 and mtROS generation while increasing complexes I, II, and IV derived respiration. Stattic co-treatment abolished DHT-mediated oxidative stress in MCT cells.

Conclusion and significance: Our findings suggest that STAT3 activation plays a significant role in renal outcomes in PCOS, and its targeting could be a novel therapeutic approach to ameliorate renal injury in PCOS.