Mast cell deficient W/Wv mice have lower serum IL-6 and less cardiac tissue necrosis than their normal littermates following myocardial ischemia-reperfusion

Myocardial ischemia-reperfusion (IR) injury complicates all forms of coronary artery revascularization. Circulating interleukin-6 (IL-6) has been implicated in cell death following a variety of stimuli. Macrophages, platelets, neutrophils and the endothelium have been shown to release IL-6 after IR injury. Cardiac mast cells have been implicated in IR; however, their involvement has never been quantified. In this randomized, prospective study, we compared cardiac tissue susceptibility and serum IL-6 changes between mast cell deficient (W/W-v) mice and their normal littermates (+/+). Twentyeight male W/W-v mice (n=14) and their +/+ littermates (n=14) were anaesthetized with 2.5% isofluorane. The left coronary artery (LCA) was ligated for 30 minutes or a sham procedure was performed. After 6 hours of reperfusion, the animals were sacrificed. The muscle viability was assessed on fresh wholemount slices by nitroblue tetrazolium (NBT) histochemical assay and serum IL-6 concentrations measured by ELISA. Cardiac muscle viability was significantly higher in W/W-v mice than the +/+ mice. Serum IL-6 levels were higher in the +/+ sham mice (465 +/- 32 pg/ml, n=6) than the W/W-v mice (185 +/- 31 pg/ml, n=6), p < 0.001. The IL-6 levels increased significantly after reperfusion only in the +/+ mice (698 +/- 41 pg/ml, n=8, p=0.001), while it remained similar in the W/W-v mice (202 +/- 48 pg/ml, n=8, p=0.783). These results show that the absence of mast cells reduces the myocardial damage associated with IR injury. Furthermore, there is an attenuation in the inflammatory response, as measured by serum IL-6 levels, following this local insult. This finding entertains the prospect of developing prophylactic therapy -targeting selective inhibition of cardiac mast cell activation, in clinical situations involving medical or surgical myocardial revascularization.