Background: Although angiotensin II (Ang II) blockade is rapidly becoming standard antifibrotic therapy in renal diseases, current data suggest that Ang II blockade alone cannot stop fibrotic disease. New therapies, such as antibodies to transforming growth factor-beta (TGF-beta), or drug combinations will be required to further slow or halt disease progression. Here, using the anti-Thy1 model of glomerulonephritis, the maximally therapeutic dose of the TGF-beta neutralizing mouse monoclonal antibody (1D11) was determined and compared with the maximally effective dose of enalapril. Then, the effect of combining both treatments at maximal doses was determined.
Methods: After disease induction with the anti-Thy1 antibody, OX-7, increasing doses of 1D11 were given intraperitoneally (IP) on days 1, 3, and 5. Enalapril was administered in drinking water from day 1. The fibrotic response was assessed at day 6.
Results: 1D11 dose-dependently reduced fibrosis, with the 0.5 and 5 mg/kg doses showing maximal therapeutic effects, reducing period-acid Schiff (PAS) staining by 56% and 45%, respectively. Fibronectin and collagen I staining was reduced by 32% to 36%, respectively. Glomerular mRNA and production of fibronectin, plasminogen activator inhibitor-1 (PAI-1), TGF-beta1, and p-Smad2 protein were also reduced. The maximal therapeutic effects of 1D11 and enalapril alone were very similar. However, combination therapy led to further reduction in disease. Notably, matrix deposition was reduced by 80%.
Conclusion: While 1D11 or enalapril at maximal doses reduce fibrosis equally, simultaneous blockade of Ang II and TGF-beta reduces fibrotic disease considerably more, offering hope that such drug combinations may confer a therapeutic advantage over angiotensin blockade alone.