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Abstract

The steady-state levels of extracellular matrix proteins are regulated by the rates of their synthesis and degradation. Metalloproteinases and their specific inhibitors, tissue inhibitor of metalloproteinases-1 and -2 are believed to play a crucial role in extracellular matrix protein degradation. Here we show that the tissue inhibitor of metalloproteinases-1 is expressed in rat hepatocytes in primary culture and regulated by inflammatory cytokines. Rat hepatocytes constitutively express mRNA of tissue inhibitors of metalloproteinases-1 at a low level. Incubation with conditioned medium from lipopolysaccharide-stimulated human monocytes led to a dramatic induction of mRNA of tissue inhibitors of metalloproteinases-1. The inflammatory cytokines interleukin-1β, interleukin-6, interleukin-11, leukemia inhibitory factor and ciliary neurotrophic factor were also capable of stimulating expression of mRNA of tissue inhibitors of metalloproteinases-1. Among these cytokines interleukin-6 was the most potent stimulator. The combination of interleukin-1β, interleukin-6 and interleukin-11 synergistically up-regulated mRNA of tissue inhibitors of metalloproteinases-1. The synthetic glucocorticoid dexamethasone dose dependently inhibited constitutive and interleukin-6-induced expression of tissue inhibitors of metalloproteinases-1. A possible involvement of tissue inhibitor of metalloproteinases-1 in the pathogenesis of liver fibrosis and cirrhosis is discussed. (HEPATOLOGY 1993;18:1437–1442.)