Interleukin 8 and monocyte chemoattractant protein 1 production by cultured human airway smooth muscle cells.

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.

A novel inhibitory prostanoid receptor in piglet saphenous vein.

A range of prostanoid agonists were tested for activity on isolated ring preparations of piglet saphenous vein. The selective TxA2-mimetic (TP-receptor agonist), U-46619, contracted the preparation in a concentration-related fashion. These contractions were inhibited by the TP-receptor blocking drug, GR32191B, producing a pA2 of 7.8 (slope = 1.6). Prostanoid-induced relaxant responses were studied on preparations which had been pre-contracted using an EC60 concentration of phenylephrine (mean EC60 = 0.97 microM), in the presence of GR32191B (1 microM), to block contractile TP-receptors. Under these conditions, PGD2, PGE2, PGF2 alpha, PGI2, and U-46619, all caused concentration-related relaxation. PGE2 was the most potent agonist (EC50 = 0.23nM), whereas, all of the other agonists were at least 1,000-fold weaker, providing strong evidence for the presence of inhibitory EP-receptors. The selective synthetic EP-agonists, sulprostone (EP1/EP3) and AH13205X (EP2), were next tested for relaxant activity. While both compounds caused concentration-related relaxant activity, they were respectively 6,000 and 11,000-fold less potent than PGE2. The potent TP-receptor blocking drugs, AH22921X and AH23848B, were both weak antagonists of PGE2 but not isoproterenol-induced relaxant responses of piglet saphenous vein in a concentration-related fashion. These two compounds had pA2 values against PGE2 of 5.3 and 5.4 respectively, with regression slopes not significantly different from unity. In contrast, neither compound at a concentration of 30 microM had any antagonist activity against prostanoid-induced effects on guinea-pig fundus (EP1), rabbit ear artery (EP2) or guinea-pig vas deferens (EP3). In conclusion, the piglet saphenous vein contains TP-receptors mediating smooth muscle contraction, and a PGE2-specific (EP) receptor mediating relaxation. The inhibitory EP-receptor does not appear to be of the EP1, EP2 or EP3-subtypes, and appears therefore to be a novel subtype which we tentatively term EP4, and the potent TP-receptor blocking drugs, AH22921X and AH23848B, appear to be weak, but specific EP4-receptor blocking drugs.