Studies on the effect of 3,4-dehydroproline on collagen metabolism in carbon tetrachloride-induced hepatic fibrosis

Decreased collagen accumulation by a prolyl hydroxylase inhibitor in pig serum-induced fibrotic rat liver

Hepatic fibrosis was induced in rats by repeated i.p. injections of pig serum. The hepatic hydroxyproline content increased to 2.1 times the normal control level at 6 weeks and to 3.2 times at 10 weeks. When P-1894B, an inhibitor of prolyl hydroxylase, was administered, there was a dose-dependent inhibition of the increase to nearly normal control levels at 6 and 10 weeks. There was also by histology a dose-dependent reduction in the degree of hepatic fibrosis. Hepatocellular damage was minimal and its extent did not vary with the degree of fibrosis or the treatment. P-1894B dose dependently reduced the hydroxylation of peptidyl proline in the fibrotic liver. These data suggest that P-1894B inhibited hepatic fibrogenesis by direct action on collagen but not by protection against hepatocellular damage leading to collagen formation. A prolyl hydroxylase inhibitor may be a candidate for use in treatment of hepatic fibrosis.

Effects of bleomycin on 14C-proline uptake, its incorporation into proteins and hydroxylation in collagenous proteins of hamster lung slices

The uptake of 14C-proline by lung slices and its incorporation into trichloroacetic-acid (TCA)-insoluble proteins and hydroxylation in collagenous proteins were studied. They were found to be linearly increased with the incubation time for as long as 8 h. The effects of different concentrations of bleomycin on these parameters were subsequently investigated. Bleomycin at 10(-3) M significantly reduced the uptake of 14C-proline to 75% of the control value. The incorporation of 14C-proline into TCA-insoluble proteins was reduced to 84%, 78% and 75% of the control at 2.5 X 10(-4) M, 5 X 10(-4) M and 10(-3) M concentrations of bleomycin, respectively. Bleomycin failed to alter the proline pool size of the lung slices at any of these concentrations. In addition, bleomycin also inhibited the hydroxylation of 14C-proline into collagen to 72% and 69% of the control at 5 X 10(-4) M and 10(-3) M, respectively. These findings show that bleomycin-induced increases in collagen synthesis in vivo is probably secondary to inflammatory reactions of the lung and bleomycin per se has little effect on increased collagen synthesis responsible for lung fibrosis.