Inhibition of rat renal fibroblast proliferation by halofuginone

Interstitial fibrosis is the final common pathway of renal damage and represents an important therapeutic target. Halofuginone is a nontoxic alkaloid, used as a coccidiostat, and is a potent inhibitor of collagen alpha(1)(I) and matrix metalloproteinase-2 (MMP-2) expression. We thus studied the effects of halofuginone on proliferation, collagen I synthesis, and MMP-2 activity of rat renal papillary fibroblasts in culture.

Fibroblasts were isolated from rat renal papillae and studied during passages 3-4. The cell proliferation was studied in the presence of varying concentrations of halofuginone. The collagen synthesis was studied by [3H]proline uptake, before and after collagenase digestion, at varying concentrations of halofuginone. The MMP-2 activity was determined by zymography. The gelatinolytic activity was determined on gelatin-impregnated polyacrylamide gels containing samples of cell medium after incubation for 24 h with different halofuginone doses.

We studied a phenotype of papillary fibroblasts which stained positive for alpha smooth muscle actin. These cells are phenotypically myofibroblasts. Halufuginone inhibited the proliferation of these cells in a dose-related and reversible manner. Platelet-derived growth factor is known to stimulate fibroblast proliferation. Halofuginone at a concentration of 250 ng/ml almost completely abolished the effect of platelet-derived growth factor. It also almost completely inhibited the MMP-2 activity at doses of 250-350 ng/ml, as shown by zymography.

Halofuginone exhibits antifibrotic effects in rat renal papillary fibroblasts in culture, in terms of inhibition of proliferation and inhibition of MMP-2. These findings could have therapeutic potential.