Lyn- and ERK-mediated vs. Ca -mediated neutrophil O2 responses with thermal injury

Fazal, Nadeem, Walid M. Al-Ghoul, Megan J. Schmidt, Mashkoor A. Choudhry, and Mohammed M. Sayeed. Lynand ERK-mediated vs. Ca2 -mediated neutrophil O2 responses with thermal injury. Am J Physiol Cell Physiol 283: C1469–C1479, 2002. First published June 20, 2002; 10.1152/ajpcell.00114.2002.—We evaluated the dependency of neutrophil O2 production on PTK-Lyn and MAPKERK1/2 in rats after thermal injury. Activation of PTK-Lyn was assessed by immunoprecipitation. Phosphorylation of ERK1/2 was assessed by Western blot analysis. O2 production was measured by isoluminol-enhanced luminometry. Imaging technique was employed to measure neutrophil [Ca2 ]i in individual cells. Thermal injury caused marked upregulation of Lyn and ERK1/2 accompanying enhanced neutrophil O2 production. Treatment of rats with PTK blocker (AG556) or MAPK blocker (AG1478) before burn injury caused complete inhibition of the respective kinase activation. Both AG556 and AG1478 produced an 66% inhibition in O2 production. Treatment with diltiazem (DZ) produced an 37% inhibition of O2 production without affecting Lyn or ERK1/2 activation with burn injury. Ca2 mobilization was upregulated with burn injury but not affected by treatment of burn rats with AG556. Unlike the partial inhibition of burn-induced O2 production by AG556, AG1478, or DZ, platelet-activating factor antagonist (PAFa) treatment of burn rats produced near complete inhibition of O2 production. PAFa treatment also blocked activation of Lyn. The findings suggest that the near complete inhibition of O2 production by PAFa was a result of blockade of PTK as well as Ca2 signaling. Overall, our studies show that enhanced neutrophil O2 production after thermal injury is a result of potentiation of Ca2 -linked and -independent signaling triggered by inflammatory agents such as PAF.