Protein kinase C (PKC) phosphorylation of leukocyte NADPH oxidase is essential to generatesuperoxide (SO) release. Inhibition of leukocyte SO release attenuates inflammation mediated vascular injury. However, the role of PKC isoforms mediating this response has not been fully elucidated. We hypothesize that PKC beta II (βII) isoform positively regulates leukocyte NADPH oxidase, and that a cell-permeable (myr)-PKC βII peptide inhibitor (N-myr-SLNPEWNET) would dose-dependently attenuate fMLP induced leukocyte SO release. fMLP is a leukocyte chemoattractant cell membrane receptor agonist. We isolated leukocytes by peritoneal lavage from male Sprague-Dawley rats using standard methods. fMLP (1 M)-induced leukocyte SO release was measured for 120 sec spectrophotometrically by reduction of ferricytochrome c in the presence/absence of myr-PKC βII peptide inhibitor (0.2 to 20 M) in 5 x 106 leukocytes. After each assay, cell viability was determined by 0.3% trypan blue exclusion. fMLP-induced leukocyte SO release increased peak absorbance to 0.18±0.03 in controls (n=20). This response was dose-dependently inhibited by myr-PKC βII peptide inhibitor at 0.17±0.05 (0.2 M; n=9), 0.14±0.05 (0.5 M; n=11), 0.1±0.05 (1 M; n=9), 0.05±0.03 (5 M; n=9), 0.04±0.03 (10 M; n=8) and 0.05±0.03 (20 µM; n=7) and was significantly attenuated in the 5 to 20 M range compared to controls (p<0.05). Moreover, cell viability was > 94±1% in all study groups. These results suggest that myr-PKC βII peptide inhibitor dose-dependently inhibits fMLP-induced leukocyte SO release in the 0.2 to 5 M dose-range and these effects are attributed to inhibition of PKC βII isoform.
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