PROTEIN-KINASE-C IS A MEDIATOR OF LIPOPOLYSACCHARIDE-INDUCED VASCULAR SUPPRESSION IN THE RAT AORTA

Treatment of vascular tissue with lipopolysaccharide (LPS) in vitro induces hyporesponsiveness to contractile agonists. We investigated whether protein kinase C (PKC) transduces the LPS signal into contractile dysfunction. Rat aortic tissue was incubated .5-18 h with LPS (10 or 30 ng/mL) or alpha- and beta-phorbol 12,13-dibutyrate (PDB,.1 or 1 mu M), either alone or combined with cycloheximide (50 mu M) or the kinase inhibitors sphingosine (20 mu M), H7 (1-(5-isoquinolinylsulfonyl)-2-methyl piperazine, 25 mu M), and HA1004 (N-(2-guanidinoethyl)-5-isoquinolinesulfonamide, 25 mu M). LPS and beta-PDB induced a sustained translocation of PKC activity from the cytosol to the membrane, an increased protein synthesis-dependent expression of nitric oxide synthase (NOS) activity, and an impaired contractility that could be partially reversed by treatment with the NOS inhibitor N omega-nitro-L-arginine methyl ester. Incubation with alpha-PDB, an inactive isomer of beta-PDB, did not alter any of the tissue functions. Sphingosine blocked LPS- and beta-PDB-induced NOS activity and LPS-induced impairments in tissue contractility and PKC translocation. Incubation with H7 also protected against LPS-induced vasoplegia, while HA1004, used as a negative control for H7, provided little protection against LPS. These data indicate that PKC plays a role as an intracellular mediator of LPS-induced NOS activity and vascular suppression.