The mechanism of MAP kinase activation under acidic condition in feline esophageal smooth muscle cells

Cytoprotective effect of eupatilin against indomethacin-induced damage in feline esophageal epithelial cells: relevance of HSP27 and HSP70

Indomethacin is a non-steroidal anti-inflammatory drug with clearly known side effects on the gastrointestinal tract. The purpose of the present study was to investigate whether eupatilin inhibit cell injury induced by indomethacin in cultured feline esophageal epithelial cells (EECs). EECs were used to investigate the ability of eupatilin to induce the expression of heat shock proteins (HSP27 and HSP70) and analyze its cytoprotective effect against indomethacin-induced damage. The treatment of EECs with indomethacin for 8 h decreased cell viability. Western blot analysis showed that the levels of HSPs gradually decreased in cells treated with indomethacin, while eupatilin treatment increased the levels of HSPs. When treated with both indomethacin and eupatilin, the levels of HSPs increased rapidly, and were maintained at 130-140%. In addition, treatment with the specific inhibitors of PTK, PKC, PLC, p38 MAPK, JNKs, and PI3K attenuated the eupatilin-induced expression of HSPs. Pretreatment of EECs with the inhibitors of protein synthesis, actinomycin D or cycloheximide, attenuated the cytoprotective effect of eupatilin on indomethacin-induced cell damage. Reactive oxygen species production was upregulated by indomethacin, but downregulated by eupatilin. Taken together, it was suggested that HSPs were partly responsible for the eupatilin-mediated cytoprotective activity against the indomethacin-induced damage in EECs.

Novel effects of FTY720 on perinuclear reorganization of keratin network induced by sphingosylphosphorylcholine: Involvement of protein phosphatase 2A and G-protein-coupled receptor-12

Sphingosylphosphorylcholine (SPC) evokes perinuclear reorganization of keratin 8 (K8) filaments and regulates the viscoelasticity of metastatic cancer cells leading to enhanced migration. Few studies have addressed the compounds modulating the viscoelasticity of metastatic cancer cells. We studied the effects of sphingosine (SPH), sphingosine 1-phosphate (S1P), FTY720 and FTY720-phosphate (FTY720P) on SPC-induced K8 phosphorylation and reorganization using Western blot and confocal microscopy, and also evaluated the elasticity of PANC-1 cells by atomic force microscopy. FTY720, FTY720P, SPH, and S1P concentration-dependently inhibited SPC-evoked phosphorylation and reorganization of K8, and migration of PANC-1 cells. SPC triggered reduction and narrow distribution of elastic constant K and conversely, FTY720 blocked them. A common upstream regulator of JNK and ERK, protein phosphatase 2A (PP2A) expression was reduced by SPC, but was restored by FTY720 and FTY72P. Butyryl forskolin, a PP2A activator, suppressed SPC-induced K8 phosphorylation and okadaic acid, a PP2A inhibitor, induced K8 phosphorylation. Gene silencing of PP2A also led to K8 phosphorylation, reorganization and migration. We also investigated the involvement of GPR12, a high-affinity SPC receptor, in SPC-evoked keratin phosphorylation and reorganization. GPR12 siRNA suppressed the SPC-triggered phosphorylation and reorganization of K8. GPR12 overexpression stimulated keratin phosphorylation and reorganization even without SPC. FTY720 and FTY720P suppressed the GPR12-induced phosphorylation and reorganization of K8. The collective data indicates that FTY720 and FTY720P suppress SPC-induced phosphorylation and reorganization of K8 in PANC-1 cells by restoring the expression of PP2A via GPR12. These findings might be helpful in the development of compounds that modulate the viscoelasticity of metastatic cancer cells and various SPC actions.

Nuclear phosphoinositide-specific phospholipase C β1 controls cytoplasmic CCL2 mRNA levels in HIV-1 gp120-stimulated primary human macrophages

HIV-1 envelope glycoprotein gp120 induces, independently of infection, the release of CCL2 from macrophages. In turn, this chemokine acts as an autocrine factor enhancing viral replication. In this study, we show for the first time that phosphoinositide-specific phospholipase C (PI-PLC) is required for the production of CCL2 triggered by gp120 in macrophages. Using a combination of confocal laser-scanner microscopy, pharmacologic inhibition, western blotting and fluorescence-activated cell sorter analysis, we demonstrate that gp120 interaction with CCR5 leads to nuclear localization of the PI-PLC β1 isozyme mediated by mitogen-activated protein kinase ERK-1/2. Notably, phosphatidylcholine-specific phospholipase C (PC-PLC), previously reported to be required for NF-kB-mediated CCL2 production induced by gp120 in macrophages, drives both ERK1/2 activation and PI-PLC β1 nuclear localization induced by gp120. PI-PLC β1 activation through CCR5 is also triggered by the natural chemokine ligand CCL4, but independently of ERK1/2. Finally, PI-PLC inhibition neither blocks gp120-mediated NF-kB activation nor overall accumulation of CCL2 mRNA, whereas it decreases CCL2 transcript level in the cytoplasm. These results identify nuclear PI-PLC β1 as a new intermediate in the gp120-triggered PC-PLC-driven signal transduction pathway leading to CCL2 secretion in macrophages. The finding that a concerted gp120-mediated signaling involving both PC- and PI-specific PLCs is required for the expression of CCL2 in macrophages suggests that this signal transduction pathway may also be relevant for the modulation of viral replication in these cells. Thus, this study may contribute to identify novel targets for therapeutic intervention in HIV-1 infection.