Antifibrotic, nephroprotective potential of ACE inhibitor vs AT1 antagonist in a murine model of renal fibrosis.
BACKGROUND
Several studies have shown antifibrotic effects of angiotensin converting enzyme (ACE) inhibitors as well as of angiotensin receptor 1 (AT1) antagonists, however, prospective trials with clinical end points comparing these effects do not exist. COL4A3-/- mice develop a non-hypertensive progressive renal fibrosis. We used this animal model to compare the potential of ACE inhibitor vs AT1 antagonist to prevent renal fibrosis irrespective of blood pressure-dependent involvement by the renin system.


METHODS
COL4A3-/- mice were treated with placebo, ramipril or candesartan. Blood pressure, proteinuria, serum urea and lifespan were monitored. Renal matrix was characterized by immuno-histochemistry, light and electron microscopy. Further biochemical analysis was provided using cDNA microarray and western blot techniques.


RESULTS
Untreated mice died of renal failure after 71+/-6 days. Ramipril and candesartan both delayed onset and reduced the extent of proteinuria. Both had minor effects on blood pressure and postponed onset of uraemia. Ramipril increased lifespan by 111% to 150+/-21 days (P<0.01), whereas candesartan resulted in only a 38% prolongation to 98+/-16 days (P<0.01). Ramipril reduced glomerular and tubulo-interstitial fibrosis and numbers of activated fibroblasts to a greater extent than candesartan. Microarray and western blot analysis revealed a higher antifibrotic potential of ramipril in terms of downregulation of TGFbeta, connective tissue growth factor, metalloproteinases and extracellular matrix proteins.


CONCLUSIONS
The results indicate an antifibrotic, nephroprotective effect of ACE inhibitors and AT1 antagonists in an animal model of progressive renal fibrosis. The greater antifibrotic effect of ramipril at the maximal therapeutic doses employed may not be explained by different antiproteinuric or blood pressure lowering properties, but by-in contrast to candesartan-its ability to hinder the proinflammatory, profibrotic activation of the angiotensin receptor 2.
Gross
Oliver
O
Medical Faculty University of Cologne, Department of Internal Medicine I, Cologne General Hospital, Merheim Medical Center, Cologne, Germany. oliver.gross@uni-koeln.de
Schulze-Lohoff
Eckhard
E
Koepke
Marie-Louise
ML
Beirowski
Bogdan
B
Addicks
Klaus
K
Bloch
Wilhelm
W
Smyth
Neil
N
Weber
Manfred
M
D047228:Angiotensin II Type 1 Receptor Blockers / Q000627:therapeutic use*; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000627:therapeutic use*; D000818:Animals; D001562:Benzimidazoles / Q000627:therapeutic use*; D001713:Biphenyl Compounds; D004195:Disease Models, Animal; D005355:Fibrosis / Q000517:prevention & control; D006977:Hypertension, Renal / Q000517:prevention & control*; D007668:Kidney / Q000187:drug effects* / Q000473:pathology*; D051379:Mice; D017257:Ramipril / Q000627:therapeutic use*; D013777:Tetrazoles / Q000627:therapeutic use*; D013997:Time Factors
D047228:Angiotensin II Type 1 Receptor Blockers; D000806:Angiotensin-Converting Enzyme Inhibitors; D001562:Benzimidazoles; D001713:Biphenyl Compounds; D013777:Tetrazoles; D017257:Ramipril; C081643:candesartan