1,25-Dihydroxyvitamin D3 ameliorates podocytopenia in rats with adriamycin-induced nephropathy.

OBJECTIVE: To investigate the role of α3ß1 integrin and α/ß-dystroglycan in protective effects of 1,25(OH)2D3 on podocytes in rats with adriamycin-induced nephropathy. METHODS: Sprague-Dawley rats were randomly divided into three groups: control group (NC), nephropathy group (NE), and nephropathy+1,25(OH)2D3 group (ND). Rats in NE and ND group were injected intravenously with adriamycin (0.1 mg/10 g body weight) to induce nephropathy, and those in ND group were then subcutaneously treated with 1,25(OH)2D3 for 8 weeks. Urinary protein level, number of urine podocytes, foot process width and glomerulosclerotic index were determined. Nephrin and podocin mRNA and protein expressions were determined by RT-PCR and western blot, respectively. Podocyte density and expressions of α3ß1 integrin and α/ß-dystroglycan (DG) were analyzed by immunohistochemistry and western blot, respectively. RESULTS: The increase in proteinuria, podocyturia and width of foot process in NE group were ameliorated after treatment with 1,25(OH)2D3 for 8 weeks. The glomerulosclerotic index was significantly decreased in ND group when compared with NE group. The podocyte density in ND group (10.3±1.64 cells/glomerulus) was significantly higher than that in NE group (8.43±1.75 cells/glomerulus) (p=0.008). 1,25(OH)2D3 treatment could significantly up-regulate the mRNA and protein expressions of nephrin and podocin, and the protein expressions of α3ß1 integrin and α/ß-DG. CONCLUSION: The expressions of nephrin, podocin, α3ß1 integrin and α/ß-DG were decreased in rats with nephropathy. However, 1,25(OH)2D3 treatment could significantly up-regulate the expressions of nephrin, podocin, α3ß1 integrin and α/ß-DG proteins which might suppress podocyte detachment and podocytopenia.

1, 25-dihydroxyvitamin D3 decreases adriamycin-induced podocyte apoptosis and loss.

BACKGROUND: Selective proteinuria is frequently observed in glomerular diseases characterized by podocyte injury. Although, 1,25-dihydroxyvitamin D3 [1,25(OH)(2)D(3)] has potential therapeutic effects on chronic kidney diseases through decreasing podocyte loss, the mechanism underlying the beneficial effects of 1,25(OH)(2)D(3) on podocytes remains still unknown. The present study tested the hypothesis that 1,25(OH)(2)D(3) directly reduced podocyte apoptosis and loss. METHODS: Sprague-Dawley (SD) rats were randomly assigned into three groups: Adriamycin (ADR) group (n=15), ADR+1,25-(OH)(2)D(3) group (n=16), and control group (n=16). Rats in ADR+1,25-(OH)(2)D(3) group were treated with 1,25(OH)(2)D(3) for 8 weeks. The number of podocytes and foot process width (FPW) were detected by transmission electron microscopy. The number of apoptotic podocytes per glomerulus and that of apoptotic nuclei and caspase-3 activity in cultured podocytes were determined by TUNEL staining. The average number of podocytes per glomerulus was quantified by immunohistochemistry. Expressions of p-Smad2/3, p-Smad1/5/8, Fas, Fas-Associated protein with Death Domain (FADD), Bax, and Bcl-2 proteins were examined by Western blot assay. RESULTS: Compared with control group, proteinuria, FPW, apoptotic podocytes, caspase-3 activity, the protein expressions of p-Smad2/3, Fas, FADD, and Bax were significantly increased, podocyte density, p-Smad1/5/8 and Bcl-2 expression were decreased in ADR group. 1,25(OH)(2)D(3) significantly reduced proteinuria, FPW, caspase-3 activity, expressions of p-Smad2/3, Fas, FADD, and Bax and apoptosis of podocytes, but increased serum albumin, number of viable podocytes , p-Smad1/5/8 and Bcl-2 expression in ADR treated rats. CONCLUSION: ADR-induced podocyte apoptosis was associated with the imbalance of p-Smad2/3, p-Smad1/5/8 the activity of caspase-3 and aberrant expressions of, Fas, FADD, Bax and Bcl-2. The beneficial effects of 1,25(OH)(2)D(3 )on podocytes may be attributable to inhibit podocyte apoptosis and the amelioration of podocytopenia.