Effect of angiotensin-converting enzyme inhibition on growth factor mRNA in chronic renal allograft rejection in the rat

Abstract

Background: Despite considerable progress in immunosuppression, the incidence of chronic renal allograft rejection has not decreased. Recent studies have revealed that angiotensin-converting enzyme (ACE) inhibition ameliorates graft arteriosclerosis, glomerulosclerosis, and tubular atrophy. Moreover, it decreases systemic and glomerular capillary hydrostatic pressure in a rat kidney allograft model. We evaluated the effects of the ACE inhibitor enalapril on cytokine and growth factor expression in chronically rejecting rat kidney allografts.

Methods: Kidneys of Fisher (F344) rats were orthotopically transplanted into Lewis (Lew) rats. To prevent acute rejection, cyclosporine A (1.5 mg/kg/day) was given to all recipients during the first 10 days after transplantation. Enalapril (60 mg/L) or vehicle was added to the drinking water 10 days after transplantation. Animals were harvested 20 weeks after transplantation for histologic and immunohistologic studies, as well as for evaluation of cytokine and growth factor mRNA by semiquantitative polymerase chain reaction.

Results: Controls developed severe signs of chronic rejection, such as glomerular and vascular lesions, associated with a large number of infiltrating leukocytes. Enalapril-treated animals developed less proteinuria and other signs of chronic rejection. The mRNA levels of transforming growth factor-beta 1 (TGF-beta 1), platelet-derived growth factor A and B chain (PDGF A and B), insulin-like growth factor-I (IGF-I), interleukin-1 (IL-1), and monocyte chemoattractant protein-1 (MCP-1) were significantly reduced in the enalapril group and were most pronounced for IL-1 and PDGF A. In addition, we found an increased level of renal angiotensinogen mRNA after treatment with enalapril.

Conclusions: Treatment with enalapril attenuated the development of proteinuria, ameliorated morphological damage, decreased leukocyte infiltration, and prevented a rise in renal mRNA levels of growth factors and cytokines in kidney grafts in a rat model of chronic renal allograft rejection.