RESUMO
Osteopontin is a proinflammatory cytokine and monocyte chemoattractant implicated in the pathogenesis of diabetic nephropathy. Synthetic agonists for liver X receptors (LXRs) suppress the expression of proinflammatory genes, including osteopontin, but whether LXR activation modulates diabetic nephropathy is unknown. We administered the LXR agonist T0901317 to mice with streptozotocin-induced diabetes and evaluated its effects on diabetic nephropathy. The LXR agonist decreased urinary albumin excretion without altering blood glucose levels and substantially attenuated macrophage infiltration, mesangial matrix accumulation, and interstitial fibrosis. LXR activation suppressed the gene expression of inflammatory mediators, including osteopontin, in the kidney cortex. In vitro, LXR activation suppressed osteopontin expression in proximal tubular epithelial cells by inhibiting AP-1-dependent transcriptional activation of the osteopontin promoter. Taken together, these results suggest that inhibition of renal osteopontin by LXR agonists may have therapeutic potential for diabetic nephropathy.
Assuntos
Nefropatias Diabéticas/tratamento farmacológico , Nefropatias Diabéticas/metabolismo , Hidrocarbonetos Fluorados/farmacologia , Receptores Nucleares Órfãos/agonistas , Osteopontina/antagonistas & inibidores , Sulfonamidas/farmacologia , Animais , Linhagem Celular , Diabetes Mellitus Experimental/tratamento farmacológico , Diabetes Mellitus Experimental/genética , Diabetes Mellitus Experimental/metabolismo , Nefropatias Diabéticas/genética , Nefropatias Diabéticas/patologia , Expressão Gênica/efeitos dos fármacos , Mediadores da Inflamação/metabolismo , Rim/efeitos dos fármacos , Rim/metabolismo , Rim/patologia , Ligantes , Receptores X do Fígado , Macrófagos/efeitos dos fármacos , Macrófagos/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Osteopontina/genética , Osteopontina/metabolismo , Regiões Promotoras Genéticas , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Fator de Transcrição AP-1/metabolismoRESUMO
BACKGROUND/AIMS: Telmisartan, an angiotensin II type 1 receptor blocker, is widely used to treat hypertension and kidney diseases, including diabetic nephropathy, because of its renoprotective effects. However, the mechanism by which telmisartan prevents proteinuria and renal dysfunction in diabetic nephropathy is still unclear. In this study, we examined the effects of telmisartan against diabetic nephropathy in db/db mice. METHODS: Telmisartan was administered at a dose of 5 mg/kg/day for 3 weeks to db/db (diabetic) and db/m (control) mice. Urinary albumin excretion, renal histology, and the gene expression of oxidative stress and inflammatory markers in renal tissue were determined. To evaluate the effects of telmisartan on reactive oxygen species (ROS) production, superoxide was detected by dihydroethidium (DHE) staining in vivo and in vitro. RESULTS: Telmisartan reduced albuminuria, mesangial matrix expansion, macrophage infiltration, and the expression of ROS markers (NADPH oxidase 4- and 8-hydroxydeoxyguanosine) and inflammatory cytokines (monocyte chemoattractant protein-1, osteopontin, and transforming growth factor-ß) in the kidney. DHE staining showed that telmisartan decreased ROS generation in the kidney and in cultured mesangial and proximal tubular epithelial cells. CONCLUSIONS: Taken together, these findings indicate that telmisartan protects against diabetic nephropathy by reducing diabetes-induced oxidative stress.