Protein kinase C (PKC) delta activation negatively regulates phorbol 12-myristate 13-acetate (PMA) induced superoxide (SO) release in polymorphonuclear leukocytes (PMNs)

It’s known that PMA is a broad-spectrum PKC activator that augments SO release in PMNs viaNADPH oxidase activation. It was shown that PKC delta (δ) negatively regulates PMN elastase release which suggests that PKC δ may also negatively regulate PMN NADPH oxidase SO release. To test the hypothesis, we altered PKC δ activity using selective cell permeable PKC δ activator, inhibitor peptides, and rottlerin, another type of PKC δ inhibitor. We predict that PKC δ activation would attenuate PMA-induced PMN SO release, whereas PKC δ inhibition would augment the response. Isolated PMNs (5x106) from male Sprague-Dawley rats were incubated in the presence/absence of PKC δ activator (Myr-MRAAEDPM, MW=1130 g/mol, 2.5-20 µM, n=6-8), PKC δ inhibitor (Myr-SFNSYELGSL, MW=1326 g/mol, 1-20 µM, n=6-10) or rottlerin (MW=516 g/mol, 2.5-20 µM, n=8-9) prior to PMA (MW=616 g/mol, 15 or 30 nM, n=11-16) stimulation. SO release was measured spectrophotometrically by the reduction of ferricytochrome C. At the end of the assay, cell viability was determined by 0.3% trypan blue exclusion. As expected, PKC δ peptide activator attenuated PMN SO release up to 56%, whereas, rottlerin augmented the PMA response up to 90% compared to untreated controls (p92±5% in all study groups. The data suggest that PKC δ negatively regulates PMN NADPH oxidase SO release. PKC δ peptide inhibitor is relatively ineffective regulating PMN SO release compared to rottlerin.