Interleukin-6/Glycoprotein130 Signaling Inhibition Ameliorates Renal Mitochondrial Dysfunction And Associated Renal Injury In Polycystic Ovary Syndrome

Abstract

Background: Polycystic ovary syndrome (PCOS) is characterized by hyperandrogenism and polycystic ovaries. Renal injury, increased central adiposity, and chronic low-grade systemic inflammation are common characteristics of PCOS. Renal inflammation can induce mitochondrial dysfunction, which plays a pivotal role in renal pathophysiology and chronic kidney disease progression. Interleukin-6 (IL-6) is a key inflammatory cytokine that is involved in renal injury progression by activating its soluble receptor (sIL-6R) and a membrane-bound glycoprotein130 (gp130). Serum IL-6 levels are elevated in women with PCOS; however, its role in inducing renal mitochondrial dysfunction and consequently PCOS-mediated renal injury is unknown. Therefore, we aimed to test the hypothesis that hyperandrogenemia increases systemic and renal IL-6 levels, leading to the activation of IL-6/gp130 signaling, which in turn triggers intrarenal mitochondrial dysfunction and renal injury in a well-characterized mouse model of PCOS. Methods: Three-week-old peripubertal female mice were implanted with Silastic tubes filled with the non-aromatizable androgen dihydrotestosterone (DHT, 8 mg) or vehicle for 12 weeks. Eight weeks post-Silastic tubes implantation, the animals were treated with the IL-6/gp130 signaling inhibitor SC144 (10 mg/kg, SC, 3x/week) or its vehicle for 4 weeks. Body weight (gravimetry), fat mass (EchoMRI), kidney weight (gravimetry), serum IL-6 (Bioplex), glomerular filtration rate (GFR, transcutaneous fluorescence), as well as the renal injury markers urinary albumin to creatinine ratio (UACR, clinical chemistry analyzer), and NGAL (ELISA) were assessed. Renal gp130 protein and IL-6 mRNA expression were quantified by Western blot and RT-qPCR, respectively. The mitochondrial markers cytochrome C, succinate dehydrogenase A (SDHA), the mitochondrial stress protein HSP60, and voltage-dependent anion channel (VDAC) were assessed in the renal tissue by Western blot. H&E stained renal sections were used for histopathological analysis. Freshly isolated kidney mitochondria were used to measure mitochondrial reactive oxygen species (mtROS) by Amplex Red assay. Moreover, mitochondrial complex I and complex II-driven respiration along with complex IV activity were assessed using Oroboros Fluorespirometer. Results: DHT significantly (p<0.05) increased body weight (26.2±0.9 vs. 22.23±0.4 g), fat mass (3.2±0.4 vs. 1.9±0.4 g), kidney weight (365.6 ± 13.1 vs. 257.1 ± 3.7 mg), UACR (1,227±420 vs. 404±169 μg albumin/mg creatinine), urinary NGAL (2-fold), and serum IL-6 levels (2.2-fold). Additionally, DHT increased the expression of renal gp130 and IL-6 (1.5-fold) and decreased GFR (1067.2 ± 59.9 vs. 1335.6 ± 60.3 uL/min/100g body weight). Moreover, cytochrome c levels in PCOS mice were significantly lower (32%), while HSP60 levels were higher (4-fold). The latter changes were associated with higher mtROS generation (2-fold), as well as lower complexes I, II, III, and IV respiration (43-71%). PCOS mice also showed a worsen renal histological structure with congested glomeruli, exfoliation of luminal epithelial lining, and interstitial hemorrhage. SC144 therapy had no effect on kidney weight or GFR; however, it abolished DHT-induced increases in body weight and fat mass. Excitingly, SC144 treatment normalized the levels of UACR, and decreased both glomerular and tubular injury in PCOS mice. It also decreased renal HSP60 levels and mtROS generation and increased complex IV derived respiration. Conclusion and significance: Our findings suggest that IL-6/gp130 activation plays a significant role in renal outcomes in PCOS. Targeting IL-6 signaling could be a novel therapeutic approach to ameliorate renal injury in PCOS women. Supported by NIH grants NIGMS P20GM121334 to KSE, LLYC, and DGR; NIH-NIGMS P30GM149404 to SR. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.