Attenuation of permeability lung injury after phorbol myristate acetate by verapamil and OKY-046

Effect of PKC isozyme inhibition on forskolin-induced activation of BKCa channels in rat pulmonary arterial smooth muscle

Signaling mechanisms that elevate cyclic AMP (cAMP) activate large-conductance, calcium- and voltage-activated potassium (BKCa) channels in vascular smooth muscle and cause vasodilatation. In pulmonary vascular smooth muscle (PVSM), BKCa channel modulation is important in the regulation of pulmonary arterial pressure, and inhibition (closing) of the BKCa channel causes pulmonary vasoconstriction. Protein kinase C (PKC) modulates BKCa channels in systemic vascular smooth muscle, but little is known about the effect of PKC on BKCa channel activity in PVSM. A novel finding from our laboratory showed that PKC activates BKCa channels in rat pulmonary arterial smooth muscle and, having observed that cAMP-elevating agents also open BKCa channels, we hypothesized that PKC may open BKCa channels via a cAMP-dependent mechanism. Forskolin (10 microM), an activator of adenylyl cyclase, which increases cAMP concentration, opened BKCa channels in single pulmonary arterial smooth muscle cells (PASMC) of the Sprague-Dawley rat. The effect of forskolin was completely blocked by the PKC inhibitor Go 6983, which selectively blocks the alpha, beta, delta, gamma, and zeta PKC isozymes, and, by rottlerin, which selectively inhibits PKCdelta, and partially blocked by Go 6976, which selectively inhibits PKCalpha PKCbeta, and PKCmu. These results indicate that specific PKC isozymes mediate forskolin-induced activation of BKCa channels in PASMC, which suggests that a signaling pathway involving PKC activation and cAMP exists in pulmonary arterial smooth muscle to open BKCa channels.

Effects of polycations on pulmonary vascular permeability in conscious sheep

The role of charged sites on the permeability characteristics of the pulmonary microvascular barrier were investigated using chronically instrumented unanesthetized sheep. In one series of experiments we studied the effects of the cationic amphiphile, dodecyl trimethylamine (DTA; 297 mol wt), and the anionic amphiphile, SDS (288 mol wt), on lung lymph flow rates (Ql), lung lymph to plasma protein ratios (L/P), pulmonary hemodynamics, and systemic hemodynamics. DTA significantly increased both Ql and L/P, whereas SDS had a more modest and transient effect on these variables. In a second series of experiments the polycations polybrene and poly-l-lysine were found to have very similar effects as those of DTA. In another series of experiments we tested the pretreatment inhibition potential of chlorpheniramine (an H1 receptor antagonist), dibutyryl-cyclic AMP (db-cAMP), and the calcium channel antagonists verapamil and nifedipine on polybrene-induced lung injury. We found that only verapamil and db-cAMP significantly attenuated the permeability effects of polybrene. We conclude that both cationic amphiphiles and polycations cause hemodynamic and permeability alterations in the pulmonary circulation of unanesthetized sheep. In addition, the permeability alterations induced by polybrene can be modulated by intracellular calcium and/or cAMP levels.