Leukocyte accumulation and activation are key events in the pathogenesis of inflammatory lung disease. The ability of human airway smooth muscle cells (HASM) to contribute to the inflammatory process by its ability to produce the chemokines interleukin (IL) 8, monocyte chemotactic protein (MCP-1) and regulated on activation, normal T cell expressed and secreted (RANTES) was investigated. Cultured HASM, when stimulated with the pro-inflammatory cytokines IL-1 alpha (0.01-1 ng/ml) or tumour necrosis factor alpha (TNF-alpha, 0.3-30 ng/ml), synthesize and release substantial amounts of IL-8, as assessed by specific immunoassay, bioasssay (elevation of intracellular free calcium in human neutrophils), and upregulation of mRNA. These stimuli also increased MCP-1 production and mRNA expression, but RANTES mRNA expression was not detected at 24 h. The smooth muscle spasmogen endothelin 1 (1 microM) was unable to stimulate IL-8 or MCP-1 release or mRNA expression. These data indicate that HASM may constitute an important source of leukocyte attractants in the inflamed lung, where the inducing stimuli, IL-1 alpha and TNF-alpha, are also likely to be present.