Expression and regulation of HIF-1alpha in macrophages under inflammatory conditions; significant reduction of VEGF by CaMKII inhibitor

<p>Abstract</p> <p>Background</p> <p>Macrophages expressing the pro-angiogenic transcription factor hypoxia-inducible factor (HIF)-1alpha have been demonstrated in rheumatoid arthritis (RA) in the synovial tissue. Aim of the present study was to investigate intracellular signal transduction regulation of pro-inflammatory HIF-1 alpha expression in macrophages to identify possible new intervention strategies. We investigated the effects of CaMKII-inhibitors amongst other kinase inhibitors, on HIF-1 alpha expression and downstream production of pro-angiogenic factors in macrophages.</p> <p>Methods</p> <p>Differentiated THP-1 cells and synovial fluid (SF) macrophages were stimulated with 1 μg/ml LPS with or without pretreatment with specific inhibitors of the ERK pathway (PD98059), the PI3K pathway (LY294002), and the CaMKII pathway (KN93 and SMP-114). mRNA and protein expression of HIF-1 alpha, VEGF, MMP-9, and IL-8 was measured in cell lysates and cell supernatants.</p> <p>Results</p> <p>HIF-1 alpha protein expression in LPS-stimulated THP-1 macrophages could be blocked by ERK- and PI3K-inhibitors, but also by the CaMKII inhibitor KN93. THP-1 and SF macrophages produced high levels of VEGF, IL-8, and MMP-9, and VEGF protein production was significantly inhibited by PI3K-inhibitor, and by both CaMKII inhibitors. LPS stimulation in an hypoxic environment did not change VEGF levels, suggesting that LPS induced VEGF production in macrophages is more important than the hypoxic induction.</p> <p>Conclusions</p> <p>Expression of HIF-1 alpha and downstream effects in macrophages are regulated by ERK-, PI3K, but also by CaMKII pathways. Inhibition of HIF-1α protein expression and significant inhibition of VEGF production in macrophages was found using CaMKII inhibitors. This is an unknown but very interesting effect of the CaMKII inhibitor SMP-114, which has been in clinical trial as DMARD for the treatment of RA. This effect may contribute to the anti-arthritic effects of SMP-114.</p

MAPK p38 and JNK have opposing activities on TRAIL-induced apoptosis activation in NSCLC H460 cells that involves RIP1 and caspase-8 and is mediated by Mcl-1

<p>Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) can induce both caspase-dependent apoptosis and kinase activation in tumor cells. Here, we examined the consequences and mechanisms of TRAIL-induced MAPKs p38 and JNK in non-small cell lung cancer (NSCLC) cells. In apoptosis sensitive H460 cells, these kinases were phosphorylated, but not in resistant A549 cells. Time course experiments in H460 cells showed that induction of p38 phosphorylation preceded that of JNK. To explore the function of these kinases in apoptosis activation by TRAIL, chemical inhibitors or siRNAs were employed to impair JNK or p38 functioning. JNK activation counteracted TRAIL-induced apoptosis whereas activation of p38 stimulated apoptosis. Notably, the serine/threonine kinase RIP1 was cleaved following TRAIL treatment, concomitant with detectable JNK phosphorylation. Further examination of the role of RIP1 by short hairpin (sh)RNA-dependent knockdown or inhibition by necrostatin-1 showed that p38 can be phosphorylated in both RIP1-dependent and -independent manner, whereas JNK phosphorylation occurred independent of RIP1. On the other hand JNK appeared to suppress RIP1 cleavage via an unknown mechanism. In addition, only the activation of JNK by TRAIL was caspase-8-dependent. Finally, we identified Mcl-1, a known substrate for p38 and JNK, as a downstream modulator of JNK or p38 activity. Collectively, our data suggest in a subset of NSCLC cells a model in which TRAIL-induced activation of p38 and JNK have counteracting effects on Mcl-1 expression leading to pro- or anti-apoptotic effects, respectively. Strategies aiming to stimulate p38 and inhibit JNK may have benefit for TRAIL-based therapies in NSCLC.</p>