Role of protein kinase A in LPS-induced activation of NF-kappa B proteins of a mouse macrophage-like cell line, J774.

The electrophoretic mobility shift assays (EMSA) with the use of the synthetic HIV-1 NF-kappa B motif as a probe, showed that LPS-treatment of J774 cells (a mouse macrophage cell line) leads to the activation of the fast-moving (denoted as B1) and the slow-moving NF-kappa B (denoted as B2). The binding of both B1 and B2 to the NF-kappa B probe was inhibited specifically by either unlabelled NF-kappa B, or competitor probes, but not by unrelated probes. LPS-induced activation of NF-kappa B was inhibited by a protein kinase A (PKA) inhibitor (H-89), but not by a protein kinase C (PKC) inhibitor (H-7). PMA itself failed to activate NF-kappa B and the depletion of PKC did not prevent LPS-induced activation of NF-kappa B. The pre-treatment of J774 cells with dibutyric cAMP, forskolin, prostaglandin E2 or cholera toxin resulted in NF-kappa B activation. Thus, these data suggested a probable involvement of PKA in LPS-induced NF-kappa B activation in macrophages.