Involvement of YC-1 in extracellular signal-regulated kinase action in rat cremasteric muscle

Objectives The nitric oxide (NO)–soluble guanylate cyclase (sGC) signalling pathway is attributed to the prevention of ischaemia–reperfusion (I/R)‐induced leucocyte–endothelium adhesive interactions. YC‐1 (3‐(5′‐hydroxymethyl‐2′‐furyl)‐1‐benzylindazole), a NO‐independent sGC activator, has been shown to exert cardiovascular benefits, but its action on leucocyte–endothelium interactions remains unknown. In this study, the direct effect and the underlying mechanism of the anti‐adhesive action of YC‐1 have been examined in cremasteric microcirculation. Methods Rat cremaster muscle was subjected to 4 h pudic‐epigastric artery ischaemia followed by 2 h reperfusion and intravital microscopy was used to observe leucocyte–endothelium interaction and to quantify functional capillaries in rat cremaster muscle flaps. Key findings The values for leucocyte rolling, adhering and transmigrating were 5.5‐, 6.9‐ and 8.8‐fold greater, respectively, in I/R than in sham‐control animals. YC‐1 treatment rescued functional capillary density and reduced leucocyte rolling, adhering and transmigrating in I/R injured cremaster muscles to levels observed in sham‐controls. Interestingly, these effects were completely blocked by the MEK (extracellular signal‐regulated kinase (ERK) kinase) inhibitor (PD98059) but not by sGC or protein kinase C inhibitors. Cotreatment of PD98059 with YC‐1 caused a 3.3‐, 7.5‐ and 8.3‐fold increase in the values for leucocyte rolling, adhering and transmigrating, respectively, in postcapillary venules of I/R‐injured cremaster muscle. Conclusions This study has indicated that the anti‐adhesive and functional capillary density rescue properties of YC‐1 were mediated predominantly by the activation of ERK but not sGC, although YC‐1 was identified to be a sGC activator. A better understanding of the action of YC‐1 on the microvasculature may help shed light on its therapeutic potential for cardiovascular disease.