SELECTIVE ACTIVATION OF PROTEIN KINASE C DELTA IN HUMAN NEUTROPHILS FOLLOWING ISCHEMIA REPERFUSION OF SKELETAL MUSCLE

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Abstract

ABSTRACT—

Circulatory neutrophils are known to be critical mediators of inflammation and oxidative stress during ischemia reperfusion (I/R) injury. Recent studies have shown an important role for protein kinase C (PKC) in neutrophil survival and function. Activation of specific isotypes of PKC are known to be involved in membrane alteration and motility, oxidative phosphorylation, and apoptosis modulation of neutrophils. However, the role of PKC in neutrophil responses to I/R in the clinical setting has not been studied. In this study, we examined the neutrophil activation of PKC induced by tourniquet-controlled I/R of skeletal muscle in humans. We found that I/R rapidly activates and translocates PKCδ, but not any of the classical forms of PKC (α or β) from cytosol to the particulate fraction of neutrophils. Particulate translocation of PKCδ is sustained up to 4 h after reperfusion and is associated with kinase activity. Postreperfusion activation of PKCδ in neutrophils signals proapoptosis, but does not cause immediate cell death (as revealed by neutrophil morphology study and DNA-laddering assay). This study indicates that calcium-independent novel PKCδ (nPKCδ) might be predominantly involved in regulating membrane functions and survival of neutrophils associated with post-I/R-induced inflammatory oxidative stress.

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