5′-AMP-activated protein kinase activation prevents postischemic leukocyteendothelial cell adhesive interactions

Preconditioning ( PC) with nitric oxide ( NO) donors or agents that increase endothelial NO synthase ( eNOS) activity 24 h before ischemia- reperfusion ( I/R) prevents postischemic leukocyte rolling ( LR) and stationary leukocyte adhesion ( LA). Since 5'-AMP-activated protein kinase ( AMPK) phosphorylates eNOS at Ser1177, resulting in activation, we postulated that AMPK activation may trigger the development of a preconditioned anti-inflammatory phenotype similar to that induced by NO donors. Wild- type ( WT) C57BL/ 6J and eNOS (-/) mice were treated with the AMPK agonist 5- aminoimidazole- 4- carboxamide 1-beta- D- furanoside ( AICAR) 30 min ( early AICAR PC) or 24 h ( late AICAR PC) before I/R; LR and LA were quantified in single postcapillary venules in the jejunum using intravital microscopy. I/ R induced comparable marked increases in LR and LA in WT and eNOS (-/-) mice relative to sham- operated ( no ischemia) animals. Late AICAR PC prevented postischemic LR and LA, whereas early AICAR PC prevented LA in WT mice. Late AICAR PC was ineffective in preventing I/ R-induced LR but not LA in the eNOS (-/-) mice, and the same pattern was seen in WT animals treated with the NOS inhibitor N-omega- nitro- L- arginine. Early AICAR PC remained effective in preventing LA in eNOS (-/-) mice. Our results indicate that both early and late PC with an AMPK agonist produces an anti-inflammatory phenotype in postcapillary venules. Since the protection afforded by late AICAR PC on postischemic LR was prevented by NOS inhibition in WT mice and absent in eNOS-deficient mice, it appears that eNOS triggers this protective effect. In stark contrast, antecedent AMPK activation prevented I/R-induced LA by an eNOS- independent mechanism.