enalaprilat-anhydrous and Fibrosis

The limited antifibrotic effect of therapeutic angiotensin blockade, the fact that angiotensin blockade dramatically elevates renin levels, and recent evidence that renin has an angiotensin-independent, receptor-mediated profibrotic action led us to hypothesize that combining renin receptor inhibition and ANG II blockade would increase the antifibrotic effect of angiotensin blockade alone. Using cultured nephritic glomeruli from rats with anti-Thy-1-induced glomerulonephritis, the maximally effective dose of enalaprilate was determined to be 10(-4) M, which reduced mRNAs for transforming growth factor (TGF)-β1, fibronectin (FN), and plasminogen activator inhibitor-1 (PAI-1) by 49, 65, and 56% and production of TGF-β1 and FN proteins by 60 and 49%, respectively. Disease alone caused 6.8-fold increases in ANG II levels that were reduced 64% with enalaprilate. In contrast, two- and threefold disease-induced increases in renin mRNA and activity were further increased 2- and 3.7-fold with 10(-4) M enalaprilate treatment. Depressing the renin receptor by 80% with small interfering (si) RNA alone reduced fibrotic markers in a manner remarkably similar to enalaprilate alone but had no effect on glomerular renin expression. Enalaprilate and siRNA combination therapy further reduced disease markers. Notably, elevated TGF-β1 and FN production was reduced by 73 and 81%, respectively. These results support the notion of a receptor-mediated profibrotic action of renin, suggest that the limited effectiveness of ANG II blockade may be due, at least in part, to the elevated renin they induce, and support our hypothesis that adding renin receptor inhibitor to ANG II blockade in patients may have therapeutic potential.

Topics: Angiotensin II; Angiotensin-Converting Enzyme Inhibitors; Animals; Cells, Cultured; Drug Therapy, Combination; Enalaprilat; Fibronectins; Fibrosis; Glomerulonephritis; Isoantibodies; Male; Plasminogen Activator Inhibitor 1; Prorenin Receptor; Rats; Rats, Sprague-Dawley; Receptors, Cell Surface; RNA, Small Interfering; Transforming Growth Factor beta1

We have previously shown that angiotensin converting enzyme-inhibitor (ACE-I) improved colonic inflammation and apoptosis in a dextran sodium sulfate (DSS)-induced colitis model. This study attempted to determine whether ACE-I could prevent the development of colonic fibrosis.. Colitis was induced in C57BL/6 mice with 2.5% DSS water for 7 days, followed by 7 days without DSS (fibrosis development). Study groups: Control (naive or non-treated), DSS+Placebo (polyethylene glycol (PEG), and DSS+ACE-I (using enalaprilat and PEG which are not absorbed through intact mucosa). Placebo and ACE-I were delivered daily via transanal route. Colonic mucosal fibrosis and inflammation were evaluated based on histological findings and cytokine expression.. Transanal administration of ACE-I/PEG dose-dependently decreased the severity of fibrosis and pro-inflammatory cytokine expression. We next investigated if ACE-I acted on the TGF-beta/Smad signaling pathway as a mechanism of this anti-fibrosis action. Results showed a significant down-regulation of TGF-beta1 expression; as well, downstream signaling of the Smad family, known to mediate fibrosis, showed a decline in Smad 3 and 4 expression with ACE-I/PEG.. ACE-I/PEG is effective in preventing colonic fibrosis and pro-inflammatory cytokine expression in a DSS colitis model, most likely by down-regulating the TGF-beta signaling pathway. ACE-I/PEG may be a potential new option for treating inflammatory bowel disease.

Topics: Administration, Rectal; Angiotensin-Converting Enzyme Inhibitors; Animals; Colitis; Collagen; Colon; Dextran Sulfate; Dose-Response Relationship, Drug; Enalaprilat; Fibrosis; Interleukin-1beta; Intestinal Mucosa; Male; Mice; Mice, Inbred C57BL; Smad Proteins; Tumor Necrosis Factor-alpha