, Volume 14, Issue 6, pp 681-689

Endotoxin-mediated bovine alveolar macrophage procoagulant induction is dependent on protein kinase C activation

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Abstract

The induction of pulmonary alveolar macrophage (PAM) tissue factor-dependent procoagulant activity is central to the deposition of inflammatory fibrin in the pulmonary alveolus. The presence of enhanced tissue factor activity is often associated with pulmonary fibrin deposition, an important pathogenetic event that can delay resolution of pulmonary inflammation and promote the induction of pulmonary fibrosis. Since tissue factor synthesis induction and activation pathways are potential therapeutic targets for modulation of alveolar macrophage tissue factor (procoagulant) activity, we examined the pathways through which endotoxin lipopolysaccharide (LPS) induces bovine PAM tissue factor-dependent procoagulant activity. PAM procoagulant activity was markedly enhanced to 10 times the levels of freshly isolated PAM after 8 h of culture in the presence of either the protein kinase C (PKC) agonist phorbol 12-myristate 13-acetate (PMA) or LPS. Both LPS-(P < 0.002) and PMA-induced activity (P < 0.007) was completely ablated by the PKC inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H 7,100μM but was unaffected by the cyclic nucleotide-dependent protein kinase inhibitorN-(2-guanidinoethyl)-5-isoquinolinesulfonamide (HA-1004, 100μM). The arachidonate cyclooxygenase pathway inhibitor phenylbutazone (10−4 M) had modest effects that were not statistically significant. The unstimulated increase of procoagulant activity in 8-h cultures was unaffected by the same inhibitory modulations. These results indicate that PKC-dependent signal transduction pathways are involved in the stimulation of PAM procoagulant activity and that inhibition of this protein kinase prevents LPS-induction of new activity. The results also suggest that the transduction pathways leading to either PMA- or LPS-induced procoagulant activity are similar to the extent that both appear to require an intact PKC system.