Inflammation is a key mediator of renal ischemia-reperfusion (IR) injury. Gender disparities have been reported in acute and chronic kidney disease. In particular, males are considered to be more susceptible to renal ischemic injury compared with females according to animal studies. The purpose of the present study was to investigate the effect of gender on the renal inflammatory response following acute renal IR injury in mice. Experiments were performed in male and female C57BL/6 mice. Two weeks prior to the study, castration or ovariectomy were performed and testosterone propionate (100 μg/kg) or 17β-estradiol (100 μg/kg) was injected. Acute kidney injury (AKI) was induced by bilateral clamping of the renal pedicle for 23 min. Histological examination, western blot analysis and quantitative polymerase chain reaction were performed. In the acute renal IR injury model, the female mice were more resistant to kidney injury compared with the male mice. However, castration of the male mice reduced the levels of IR-induced tubular injury and macrophage infiltration compared with those in the injured male mice. Supplementation of testosterone reversed this protective effect in the male AKI model. Depletion of estrogen in the female mice increased the levels of IR-induced tubular injury and macrophage infiltration compared with those in the injured female mice. However, supplementation of estrogen in the ovariectomized female mice attenuated the IR-induced tubular injury and reduced the levels of macrophage infiltration. The expression levels of inflammatory cytokines, including tumor necrosis factor-α, monocyte chemotactic protein-1, interferon-γ and chemokine (C-C motif) ligand 17, were elevated in the male AKI mice compared with those in the control male mice, and were attenuated by castration. Estrogen depletion in the female mice significantly increased the expression levels of the renal inflammatory cytokines compared with those in the injured female mice, and were attenuated by estrogen supplementation in the ovariectomized female mice. These results suggested that the male gender confers greater susceptibility to IR renal injury due to an enhanced inflammatory response.

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Adipose tissue inflammation is a reproducible feature of obesity and obesity-linked insulin resistance. Although sirtuin 6 (Sirt6) deficiency has previously been implicated in diet-induced obesity and systemic insulin resistance, the adipocyte-specific role of Sirt6 in the regulation of adipose tissue inflammation and systemic metabolic dysfunction in mice fed normal chow and in humans remains elusive. Here, using Adipoq-Cre -mediated adipocyte-specific Sirt6 knockout (aS6KO) mice, we explored whether adipocyte Sirt6 inhibits adipose tissue inflammation and its underlying mechanism. aS6KO mice fed normal chow gained more body weight and fat mass than wild-type mice and exhibited glucose intolerance and systemic insulin resistance. Measurement of plasma and tissue cytokines and flow cytometric analysis of adipose stromal vascular cells indicated a decrease in alternatively activated M2 macrophages in the adipose tissue of aS6KO mice. Mechanistically, Sirt6 regulated the expression of the canonical type 2 cytokine IL-4 by adipocytes in a cell autonomous manner, which in turn affects M2 macrophage polarization. Consistent with animal experimental data, the degree of obesity and insulin resistance demonstrated by the body mass index, fasting blood glucose and HbA1c correlated negatively with the expression of Sirt6 in human visceral fat tissues. Collectively, these results suggest that adipocyte Sirt6 regulates body weight gain and insulin sensitivity independent of diet, and the increased IL-4 production by Sirt6 and resultant M2 polarization of adipose tissue macrophages may attenuate proinflammatory responses in adipose tissue.

Protein kinase 2 (CK2) activation was reported to enhance reactive oxygen species production and activate the nuclear factor κB (NF-κB) pathway. Because oxidative stress and inflammation are critical events for tissue destruction during ischemia reperfusion (I/R), we sought to determine whether CK2 was important in the renal response to I/R. Mice underwent 25 min of renal ischemia and were then reperfused. We confirmed an increased expression of CK2α during the reperfusion period, while expression of CK2β remained consistent. We administered tetrabromobenzotriazole (TBBt), a selective CK2α inhibitor before inducing I/R injury. Mice subjected to I/R injury showed typical patterns of acute kidney injury; blood urea nitrogen and serum creatinine levels, tubular necrosis and apoptosis, inflammatory cell infiltration and proinflammatory cytokine production, and oxidative stress were markedly increased when compared to sham mice. However, pretreatment with TBBt abolished these changes and improved renal function and architecture. Similar renoprotective effects of CK2α inhibition were observed for emodin. Renoprotective effects of CK2α inhibition were associated with suppression of NF-κB and mitogen activated protein kinase (MAPK) pathways. Taken together, these results suggest that CK2α mediates proapoptotic and proinflammatory signaling, thus the CK2α inhibitor may be used to prevent renal I/R injuries observed in clinical settings.