RESUMEN
Chronic cyclosporine (CsA) nephrotoxicity is a relevant factor in the pathogenesis of chronic allograft nephropathy. Pioglitazone is an agonist of PPARgamma, capable of reducing chronic inflammation. We investigated the capacity of pioglitazone in preventing renal dysfunction. Adult male Wistar rats were assigned to: Vehicle (olive oil 1 ml/kg/day), CsA (10 mg/kg/day) alone and with pioglitazone (5 or 10 mg/kg/day). The animals were sacrificed at 28 days, where blood (serum creatinine ratio, CR) and kidney samples (arteriolopathy analyses) were collected. The mRNA transcripts of TGF-beta1, PAI-1, Smad3 and 7 were evaluated by real-time PCR. As expected, CsA treatment significantly decreased renal function that peaked at day 28, compared with vehicle (CR=1.29+/-0.03 vs. 0.95+/-0.14, p<0.05). In contrast, the administration of pioglitazone 5 or 10 mg/kg combined with CsA resulted in better renal function (CR=1.09+/-0.05 and 1.14+/-0.14, respectively, p<0.05). Animals treated with CSA showed relevant arteriolopathy (49.5+/-2.86%) and pioglitazone administration significantly limited it (37.0+/-3.59% and 36.6+/-1.72%, respectively, 5 or 10 mg/kg, p<0.05). In CsA-treated animals (alone and with pioglitazone), TGF-beta1 and Smad3 increased significantly. In animals treated with CsA and pioglitazone (5 mg/kg), PAI-1 was significantly lower than CsA alone (3.96+/-0.92 vs. 7.53+/-1.38, p<0.05). Interestingly, the administration of pioglitazone 5 or 10 mg/kg was associated with an increase in Smad7 (1.79+/-0.25 and 1.75+/-0.19, respectively), compared to vehicle and to CsA-treated groups (1.08+/-0.17 and 1.17+/-0.19, respectively, p<0.05). These data provide evidence that pioglitazone acts through down regulation of pro-fibrotic cytokine PAI-1 and overexpression of the regulatory Smad7.