Suppressive Effects of Iron on TGF-β1 Production by Renal Proximal Tubular Epithelial Cells

Mesenchymal Stem Cells Alleviate Renal Fibrosis and Inhibit Autophagy via Exosome Transfer of miRNA-122a

Exosomes derived from mesenchymal stem cell (MSC) alleviate kidney damage through autophagy. This study determined whether MSCs relieve renal fibrosis and inhibit autophagy by exosome transfer of miRNA-122a. The gene expression involved in the mTOR signaling pathway and autophagy was assessed in TGF-β1-treated human renal tubular epithelial cells (HK-2) and unilateral ureteral obstruction (UUO) mice before and after MSC-derived exosomes and miRNA-122a mimic treatment. Small RNA (sRNA) next-generation sequencing was also performed on TGF-β1-treated HK-2 cells. MSC-derived exosomes relieve fibrosis caused by TGFβ in HK-2 via regulation of the mTOR signaling pathway and downstream autophagy. Furthermore, we found that MSC-derived exosomes mediate miRNA-122a to relieve renal fibrosis in HK-2 cells in response to TGF-β1 through the regulation of mTOR signaling and autophagy. In the UUO mouse model, miRNA-122a mimic-transfected MSC treatment and its combination with 3-MA both recapitulated the same results as the in vitro experiments, along with reduced expansion of renal tubule, interstitial expansion, and preservation of kidney architecture. The antifibrotic activity of MSC-derived exosomes after renal fibrosis occurs partially by autophagy suppression via excreted exosomes containing mainly miRNA-122a. These findings indicate that the export of miRNA-122a via MSC-derived exosomes represents a novel strategy to alleviate renal fibrosis.

Kaempferol attenuates diabetic nephropathy by inhibiting RhoA/Rho-kinase mediated inflammatory signalling

RhoA/Rho-associated coiled-coil forming protein serine/threonine kinase (ROCK) has appeared as a potential therapeutic target in numerous diseases, because of its preventing action on various enzymes providing antioxidant and cytoprotective action. Progression and pathophysiology of diabetic nephropathy have also shown potential involvement of oxidative stress and inflammatory pathways. In the present study, we investigated the effect of kaempferol on hyperglycemia-induced activation of RhoA kinase and associated inflammatory signaling cascade. Currently there is only small literature available on the mechanism of anti-diabetic and nephroprotective action of this compound, which creates a void. Therefore, we focused here on the investigation of molecular mechanisms for kaempferol by means of in vitro testing, using rat (NRK-52E) and human renal tubular epithelial cells (RPTEC). Our findings suggest that kaempferol inhibits hyperglycemia-induced activation of RhoA and decreased oxidative stress, pro-inflammatory cytokines (TNF-α and IL-1β) and fibrosis (TGF-β1 expression, extracellular matrix protein expression) in NRK-52E and RPTEC cells. Therefore, kaempferol can be used as a potential therapeutic for the treatment of diabetic nephropathy.

Iron sucrose induced morphological and functional changes in the rat kidney

Treatment of anemia in uremic patients requires simultaneous supplementation of erythropoietin and iron. Because of the impaired iron absorption from the gastrointestinal tract in conditions of renal insufficiency, intravenous supplementation is a treatment of choice in such conditions. Iron compounds used for intravenous supplementation induce several systemic side effects, and therefore, we studied the effect of chronic exposure to iron sucrose in rats on renal function. Experiments were performed on male Wistar rats, which were infused intraperitoneally every 4 days, for 28 days with iron sucrose in a dose 1 mg/kg bw or 10 mg/kg bw diluted in 20 mL of the dialysis fluid. Control animals were infused with plain dialysis fluid. Renal function was evaluated at the beginning and at the end of the study. Additionally morphology of the kidneys was evaluated in all animals after 28 days of the study. Chronic exposure of rats to iron sucrose resulted in increased accumulation of PAS-positive material in their glomeruli: + 38% at Fe 1 mg/kg bw P < 0.05 and + 42% at Fe 10 mg/kg/bw P < 0.01 and collagen in the peritubular area: + 40% at Fe 1 mg/kg bw P < 0.005 and + 77% at Fe 10 mg/kg/bw P < 0.001. Only renal clearance of urea was decreased by 53%, P < 0.01 in rats exposed to iron sucrose at a dose of 10 mg/kg bw. Chronic exposure of rats to iron sucrose results in morphologic changes of the kidney; however, mild impairment in renal function was observed only at the highest (10 mg Fe/kg bw) concentration of iron sucrose.