Nitric oxide (NO·) produced by inducible nitric oxide synthase (iNOS) mediates a number of important physiological and pathophysiological processes. The objective of this investigation was to examine the role of mitogen-activated protein kinases (MAPKs) in the regulation of iNOS and NO· by interferon-γ (IFN-γ) + lipopolysaccharide (LPS) in macrophages using specific inhibitors and dominant inhibitory mutant proteins of the MAPK pathways. The signaling pathway utilized by IFN-γ in iNOS induction is well elucidated. To study signaling pathways that are restricted to the LPS-signaling arm, we used a subclone of the parental RAW 264.7 cell line that is unresponsive to IFN-γ alone with respect to iNOS induction. In this RAW 264.7γNO(−) subclone, IFN-γ and LPS are nevertheless required for synergistic activation of the iNOS promoter. We found that extracellular signal-regulated kinase (ERK) augmented and p38 mapk inhibited IFN-γ + LPS induction of iNOS. Dominant-negative MAPK kinase-4 inhibited iNOS promoter activation by IFN-γ + LPS, also implicating the c-Jun NH2-terminal kinase (JNK) pathway in mediating iNOS induction. Inhibition of the ERK pathway markedly reduced IFN-γ + LPS-induced tumor necrosis factor-α protein expression, providing a possible mechanism by which ERK augments iNOS expression. The inhibitory effect of p38 mapk appears more complex and may be due to the ability of p38 mapk to inhibit LPS-induced JNK activation. These results indicate that the MAPKs are important regulators of iNOS-NO· expression by IFN-γ + LPS.
Inhibitory effect of Isothiocyanate on Apoptosis Caused by iNOS Induction in Heart Left Ventricle infected by LP‐BM5 retrovirus a Murine AIDS Model
