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

Treatment of vascular tissue with lipopolysaccharide (LPS) in vitro in duces hyporesponsiveness to contractile agonists. We investigated whet her protein kinase C (PKC) transduces the LPS signal into contractile dysfunction. Rat aortic tissue was incubated .5-18 h with LPS (10 or 3 0 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-m ethyl piperazine, 25 mu M), and HA1004 (N-(2-guanidinoethyl)-5-isoquin olinesulfonamide, 25 mu M). LPS and beta-PDB induced a sustained trans location of PKC activity from the cytosol to the membrane, an increase d protein synthesis-dependent expression of nitric oxide synthase (NOS ) activity, and an impaired contractility that could be partially reve rsed by treatment with the NOS inhibitor N omega-nitro-L-arginine meth yl ester. Incubation with alpha-PDB, an inactive isomer of beta-PDB, d id not alter any of the tissue functions. Sphingosine blocked LPS- and beta-PDB-induced NOS activity and LPS-induced impairments in tissue c ontractility and PKC translocation. Incubation with H7 also protected against LPS-induced vasoplegia, while HA1004, used as a negative contr ol 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.