Inhibition of rat liver fibrogenesis through noradrenergic antagonism

The effect of adrenergic innervation and/or circulating catecholamines on the function of liver fibrogenic cells is poorly understood. Our aim was to investigate the effects of noradrenergic antagonism on carbon tetrachloride (CCl₄)-induced liver fibrosis in rats. Two weeks of CCl₄ induced a ∼5-fold increase in the area of fibrosis as compared with controls. The addition of 6-hydroxydopamine (OHDA), a toxin that destroys noradrenergic fibers, decreased fibrosis by 60%. After 6 weeks of CCl₄, the area of fibrosis increased about 30-fold in CCl₄-treated animals and was decreased by 36% with OHDA. At 2 weeks, OHDA abrogated the CCl₄-induced increase in mRNA level of tissue inhibitor of matrix metalloproteinases-1 (TIMP-1), an inhibitor of extracellular matrix degradation, and it greatly reduced it at 6 weeks. Finally, when rats treated with CCl₄ for 2 weeks also received prazosin, an antagonist of α₁-adrenergic receptors, fibrosis was decreased by 83%. In conclusion, destruction of noradrenergic fibers or antagonism of noradrenergic signaling through α₁ receptors inhibited the development of liver fibrosis. Because adrenoreceptor antagonists have a very sound safety profile, they appear as attractive drugs to reduce liver fibrogenesis.