Role of Mitogen-Activated Protein Kinases inS-Nitrosoglutathione-Induced Macrophage Apoptosis

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Abstract
The inflammatory mediator nitric oxide (NO•) promotes apoptotic cell death based on morphological evidence, accumulation of the tumor suppressor p53, caspase-3 activation, and DNA fragmentation in RAW 264.7 macrophages. Since nitrosothiols may actually be the predominant form of biologically active NO• in vivo, we used S-nitrosoglutathione (GSNO) to study activation of extracellular signal-regulated protein kinases1/2 (ERK1/2), c-Jun N-terminal kinases/stress-activated protein kinases (JNK1/2), and p38 kinases. Moreover, we determined the role of mitogen-activated protein kinase signaling in the apoptotic transducing ability of GSNO. ERK1/2 became activated in response to GSNO after 4 h and remained active for the next 20 h. Blocking the ERK1/2 pathway by the mitogen-activated protein kinase kinase inhibitor PD 98059 enhanced GSNO-elicited apoptosis. p38 was activated as well, but inhibition of p38 with SB 203580 left apoptosis unaltered. Activation of JNK1/2 by GSNO showed maximal kinase activities between 2 and 8 h. Attenuating JNK1/2 by antisense-depletion eliminated the pro-apoptotic action of low GSNO concentrations (250 μM), whereas apoptosis proceeded independently of JNK1/2 at higher doses of the NO donor (500 μM). Decreased apoptosis by JNK1/2 depletion prevented p53 accumulation after the addition of GSNO, which positions JNK1/2 upstream of the p53 response at low agonist concentrations. In line, JNK1/2 activation proceeded unaltered in p53-antisense transfected macrophages. However, with higher GSNO concentrations apoptotic transducing pathways, including p53 accumulation, were JNK1/2 unrelated. The regulation of mitogen-activated protein kinases by GSNO may help to define cell protective and destructive actions of reactive nitrogen species.