Role of Protein Kinase C Isoforms in the Regulation of Interleukin-13-induced 15-Lipoxygenase Gene Expression in Human Monocytes

Abstract

We reported previously that interleukin-13 (IL-13) induces tyrosine phosphorylation/activation of Jak2 and Tyk2 kinases and Stats 1, 3, 5, and 6 in primary human monocytes. We recently revealed that p38 MAPK-mediated serine phosphorylation of both Stat1 and Stat3 is required for the induction of 15-lipoxygenase (15-LO) expression by IL-13. In this study, we present data indicating that another serine/threonine kinase, PKC␦, is also required for IL-13-induced 15-LO expression. PKC␦, a member of the novel protein kinase C (PKC) subclass, was rapidly phosphorylated and activated upon exposure to IL-13. Treatment of cells with rottlerin, a PKC␦ inhibitor, blocked IL-13-induced 15-LO mRNA and protein expression, whereas Go6976, an inhibitor of the conventional PKC subclass, had no inhibitory effects. Down-regulation of cellular PKC␦ protein levels by PKC␦-specific antisense oligodeoxyribonucleotides also inhibited 15-LO expression markedly. IL-13-induced 15-LO expression resulted in significant inhibition of synthesis of the potent chemotactic factor leukotriene B 4 , and that process was reversed by rottlerin, presumably through the blockage of PKC␦-dependent 15-LO expression. Furthermore, our data demonstrate that IL-13-mediated activation of PKC␦ and p38 MAPK are independent pathways, because inhibition of one kinase activity had no effect on the other, suggesting that the two pathways act in parallel to regulate the downstream targets necessary for 15-LO expression. Inhibition of PKC␦ activation by rottlerin also markedly attenuated IL-13-induced Stat3 DNA binding activity. Our findings indicate that PKC␦ plays an important role in regulating IL-13-induced 15-LO expression in human monocytes and subsequently modulates the inflammatory responses mediated by 15-LO products.Th2 lymphocytes secrete IL-4 1 and IL-13, which have the unique ability to induce the expression of the lipid-oxidizing enzyme 15-LO in primary human monocytes (1-3). To date, no monocytic cell lines have been shown to respond in a similar fashion. 15-LO dioxygenates polyenoic fatty acids to their corresponding hydroperoxide derivatives. These molecules are potent mediators of inflammatory responses and are found in atherosclerotic lesions. It is believed that 15-LO products play an important role in the pathogenesis of atherosclerosis and other inflammatory diseases (4 -7). In addition to its pro-inflammatory actions, 15-LO has also been shown to suppress the inflammatory responses by inhibiting the production of the potent chemotactic factor LTB 4 . This process has been observed in several cell types, including human monocytes (8 -10).Previously, we demonstrated that Jak2 and Tyk2 are upstream tyrosine kinases involved in regulating IL-13-induced expression of 15-LO (3). We have further defined the functional IL-13 receptor complex, the association of Jaks with the receptor constituents, and the tyrosine phosphorylation and activation of Stats in response to IL-13 (11). Tyrosine phosphorylation of Stat molecules facilitates the formation of di...

Protein kinase C-δ is involved in the inflammatory effect of IL-6 in mouse adipose cells

“…In HepG2 cells, Schuringa et al [18] found no inhibition of IL-6-induced STAT3 Tyr-705 phosphorylation while Xu et al [33] found that pretreatment with rottlerin totally blocked IL-13-induced STAT3-DNA binding in monocytes. Another report showed that prolactin-or rat placental lactogen 1-induced Tyr-705 phosphorylation of STAT3 is reduced in response to rottlerin in granulosa cells and, thus, also STAT3-DNA binding [34].…”

Monocyte 15-Lipoxygenase Expression Is Regulated by a Novel Cytosolic Signaling Complex with Protein Kinase C δ and Tyrosine-Phosphorylated Stat3

“…First, we have shown that PKC␦ is activated by IL-13 and is required for IL-13-induced 15-LO expression in human monocytes (33). PKC␦ activation by a variety of stimuli has been shown to activate various transcription factors including Stats (28,29,34,35).…”

Rôles de PPAR et de p21WAF1/CIP1dans la différenciation monocyte/macrophage

“…Nous avons montré récemment que l'IL-13 augmente l'expression de p21 WAF1/CIP1 par un mécanisme transcriptionnel [22] et inhibe la production des IRO induite par le TPA (12-O-tetradecanoylphorbol-13-acetate) dans les monocytes humains [33]. Il est également établi que cette cytokine déclenche une augmentation du signal calcium dans la cellule via une phosphorylation sur tyrosine de la PLC (phospholipase C) et d'IRS 2 (insulin receptor substrate 2) [34] et que ce processus est impliqué dans l'inhibition de l'hyperactivité oxydative des monocytes. Nous avons également établi que l'IL-13 et l'IL-4 déclenchent très précocement une mobilisation de l'acide arachidonique des phospholipides membranaires [22,[33][34][35].…”

“…Il est également établi que cette cytokine déclenche une augmentation du signal calcium dans la cellule via une phosphorylation sur tyrosine de la PLC (phospholipase C) et d'IRS 2 (insulin receptor substrate 2) [34] et que ce processus est impliqué dans l'inhibition de l'hyperactivité oxydative des monocytes. Nous avons également établi que l'IL-13 et l'IL-4 déclenchent très précocement une mobilisation de l'acide arachidonique des phospholipides membranaires [22,[33][34][35]. Le [12,14].…”