Comparative study of the antifibrotic effect of halofuginone with that of some potentially antifibrotic drugs on rat liver fibrosis induced by CCL4

ABSTRACT

Abnormal deposition of the extracellular matrix is the hallmark of liver fibrosis and cirrhosis. In fibrosis, the quantity of most extracellular matrix molecules, the fibrillar collagen, increase dramatically with types I and III representing between 80 and 90 per cent of collagens, both in normal and fibrotic liver. Halofuginone [HAL] is a coccidiostat, which has recently evidenced to inhibit collagen synthesis by fibrogenic cells in vivo and in vitro. In this study, we have investigated the antifibrotic effect of HAL on liver fibrogenesis in two separate experiment. The first experiment was conducted in vivo where liver fibrosis was induced in rats by oral administration of carbon tetrachloride [CCl4], The second experiment was conducted in vitro where the drugs were examined on its ability to inhibit collagen type I or III alpha-chains synthesis by the principle four types of liver cells; hepatocytes [HCs], liver endothelial cells [LECs], Kupffer cells [KCs], and hepatic stellate cells [HSCs]. Measurement of collagen alpha-chains was done by SDS-PAGE and computer-assisted densitometry. The anticipated antifibrogenic effect of HAL was matched to that of some other drugs evidenced in recent work to have antifibrogenic effects in some models of liver fibrosis namely, colchicine [COL], silymarin [SIL], pentoxifylline [PTX], and prednisolone [PDN]. Validation of the in vivo results was based on four reliable parameters included [i] scoring the histopathological lesions in the livers; [ii] digital image analysis of liver fibrosis in the stained liver sections through the recent digital image analysis technique; [iii] measurement of the aminoterminal propeptide of type III procollagen [PIIINP] in serum, and [iv] measurement of serum alanine aminotransferase enzyme [ALT]. It was shown that all the five drugs have considerably reduced liver necroinflammatory reaction and fibrosis with variable degree of success, while they differed markedly in their effect on two serological markers; one for active hepatic fibrogenesis, the PIIINP, and the other for parenchymal cell integrity, the ALT. In vitro, HAL reduced only synthesis of collagen type I constituent chains, alpha1[I] and alpha2[I], while did not affect - 1 [III] chain synthesis by cultured HCs, LECs and HSCs. It could not be examined on collagen synthesis by KCs because we were not able to detect any collagen synthesized by it in vitro. However, an extensive work has to be conducted to find out drugs that are capable of preventing or treating liver fibrosis and to elucidate its exact mechanism of action in each type of liver pathology