5-Aminoimidazole-4-carboxamide riboside suppresses lipopolysaccharide-induced TNF-α production through inhibition of phosphatidylinositol 3-kinase/Akt activation in RAW 264.7 murine macrophages

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5-Aminoimidazole-4-carboxamide riboside (AICAR) is an adenosine analog and a widely used activator of AMP-activated protein kinase (AMPK). We examined the effect of AICAR on LPS-induced TNF-α production in RAW 264.7 and peritoneal macrophages and its molecular mechanism in RAW 264.7 macrophages. Treatment with AICAR inhibited LPS-induced increases in TNF-α mRNA and protein levels in these cells. AICAR or LPS did not alter the AMPK activity as well as the phosphorylations of AMPK α (Thr172) and ACC (Ser79). Moreover, an adenosine kinase inhibitor 5 ′-iodotubercidin enhanced the suppressive effect of AICAR on TNF-α levels. These results suggest that the effect of AICAR on TNF-α suppression in RAW 264.7 cells is independent of AMPK activation. In addition, an adenosine receptor antagonist 8-SPT had no effect on AICAR-induced suppression of TNF-α levels. Finally, we observed that AICAR inhibited LPS-induced activation of PI 3-kinase and Akt, whereas it had no effect on the activation of p38 and ERK1/2. Taken together, these results suggest that the anti-inflammatory action of AICAR in RAW 264.7 macrophages is independent of AMPK activation and is associated with inhibition of LPS-induced activation of PI 3-kinase/Akt pathway.