The antioxidant N-acetylcysteine induces mesangial cells to create three-dimensional cytoarchitecture that underlies cellular differentiation

Eviprostat activates cAMP signaling pathway and suppresses bladder smooth muscle cell proliferation

Eviprostat is a popular phytotherapeutic agent for the treatment of lower urinary tract symptoms (LUTS). At present, the signaling mechanisms underlying its therapeutic effects are still poorly understood. Given that cAMP has been reported to suppress cell hyperplasia and hypertrophy in various pathological situations, we asked whether the effect of Eviprostat could be ascribed to the activation of the cAMP signaling pathway. In the study, exposure of cAMP response element (CRE)-secreted alkaline phosphatase (SEAP) (CRE-SEAP)-reporter cells to Eviprostat elevated SEAP secretion, which was associated with an increased phosphorylation of vasodilator-stimulated phosphoprotein (VASP) and cAMP-response element-binding protein (CREB), as well as enhanced expression of CRE-regulated protein connexin43, indicating an activation of the cAMP signaling pathway. Consistent with these observations, Eviprostat-induced expression of Cx43 was abolished in the presence of adenylyl cyclase inhibitor SQ22536 or PKA inhibitor H89, whereas it was mimicked by adenylyl cyclase activator, forskolin. Further analysis demonstrated that Eviprostat significantly potentiated the effect of phosphodiesterase 3 (PDE3) inhibitor, but not that of PDE4 inhibitor, on CRE activation. Moreover, Eviprostat suppressed PDGF-induced activation of ERK and Akt and inhibited cell proliferation and hillock formation in both mesangial cells and bladder smooth muscle cells. Collectively, activation of the cAMP signaling pathway could be an important mechanism by which Eviprostat exerts its therapeutic effects for LUTS.

Initiation of caspase-independent death in mouse mesangial cells by Cd2+: involvement of p38 kinase and CaMK-II

Cadmium (Cd) is a toxic metal with multiple effects on cell signaling and cell death. We studied the effects of Cd(2+) on quiescent mouse mesangial cells in serum-free conditions. Cadmium induces cell death over 6 h through annexin V+ states without or with causing uptake of propidium iodide, termed apoptotic and apoptosis-like death, respectively. Little or no necrosis is observed, and cell death is caspase-independent and associated with nuclear translocation of the apoptosis-inducing factor, AIF. We previously showed that Cd(2+) increased phosphorylation of Erk and CaMK-II, and CaMK-II activation increased cell death in an Erk-independent manner. Here we demonstrate that Cd(2+) increases Jnk and p38 kinase phosphorylation, and inhibition of p38-but not of Jnk-increases cell viability by suppressing apoptosis in preference to apoptosis-like death. Neither p38 kinase nor CaMK-II inhibition protects against a decrease in mitochondrial membrane potential, psi, indicating that kinase-mediated death is either independent of, or involves events downstream of a mitochondrial pathway. However, both the antioxidant N-acetyl cysteine (NAC) and the mitochondrial membrane-stabilizing agent cyclosporine A (CsA) partially preserve psi, suppress activation of p38 kinase, and partially protect the cells from Cd(2+)-induced death. Whereas the effect of CsA is on apoptosis, NAC acts on apoptosis-like death. Inhibition of glutathione synthesis exacerbates a Cd(2+)-dependent increase in cellular peroxides and favors apoptosis-like death over apoptosis. The caspase-independence of these modes of cell death is not due to an absence of this machinery in the mesangial cells: when they are exposed to Cd(2+) for longer periods in the presence of serum, procaspase-3 and PARP are cleaved and caspase inhibition is protective. We conclude that Cd(2+) can kill mesangial cells by multiple pathways, including caspase-dependent and -independent apoptotic and apoptosis-like death. Necrosis is not prominent. Activation of p38 kinase and of CaMK-II by Cd(2+) are associated with caspase-independent apoptosis that is not dependent on mitochondrial destabilization.

Oxidative stress in the pathogenesis of experimental mesangial proliferative glomerulonephritis

Reactive oxygen species (ROS) are increasingly believed to be important intracellular signaling molecules in mitogenic pathways involved in the pathogenesis of glomerulonephritis (GN). We explored the effects of the antioxidants α-lipoic acid and N-acetyl-l-cysteine on ERK activation in cultured mesangial cells and the role of ERK activation in the severity of glomerular injury in a rat model of anti-Thy 1 GN. In cultured mesangial cells, growth factors stimulated ERK phosphorylation by 150–450%. Antioxidants reduced this increase by 50–60%. Induction of anti-Thy 1 nephritis in rats led to a 210% increase in glomerular ERK phosphorylation. This increase in phosphorylated ERK was reduced by 50% in animals treated with α-lipoic acid. Treatment with α-lipoic acid resulted in significant improvement of glomerular injury. Cellular proliferation was reduced by 100%, and the number of proliferating cell nuclear antigen-positive cells was reduced by 64%. The increased expression of glomerular transforming growth factor-β1 protein and mRNA in rats with anti-Thy 1 nephritis was significantly attenuated and mesangial cell transformation into myofibroblasts was completely prevented by treatment with α-lipoic acid. The effects of α-lipoic acid were at least partially due to inhibition of oxidative stress. In rats with anti-Thy 1 nephritis, ROS production was increased 400–500%, and this increase was inhibited by 55% by treatment with α-lipoic acid. We suggest that ROS may mediate glomerular injury by inducing ERK phosphorylation. α-Lipoic acid should be considered a potential therapeutic agent in certain types of human GN.

Enhancement of TNF-alpha-induced apoptosis by immobilized arginine-glycine-aspartate: involvement of a tyrosine kinase-dependent, MAP kinase-independent mechanism

Extracellular matrix facilitates anchorage-dependent cell survival via interaction of its arginine-glycine-aspartate (RGD) motif with integrins. In this report, we describe an unexpected, apoptosis-promoting the effect of immobilized RGD (iRGD) on tumor necrosis factor-alpha (TNF-alpha)-induced apoptosis. Mesangial cells cultured on RGD-coated plates showed enhanced susceptibility to TNF-alpha-induced apoptosis. iRGD alone did not affect cell survival. In contrast, iRGD did not facilitate but inhibited apoptosis induced by H(2)O(2). Mitogen-activated protein (MAP) kinases and tyrosine kinases are important mediators for the RGD-integrin signaling. Pretreatment with MAP kinase kinase inhibitor PD098059, c-Jun N-terminal kinase (JNK)-c-Jun/AP-1 inhibitor curcumin or p38 MAP kinase inhibitor SB203580 did not attenuate the apoptosis-promoting effect of iRGD. Consistently, transfection with dominant-negative mutants of extracellular signal-regulated kinases, JNK or p38 MAP kinase did not inhibit the effect of iRGD. In contrast, protein tyrosine kinase inhibitors, genistein, and herbimycin A, abrogated the apoptosis-promoting effect of iRGD. Of note, TNF-alpha-induced apoptosis on uncoated plates was not attenuated by tyrosine kinase inhibitors. These data provide the first evidence that iRGD accelerates certain apoptosis. We identified that the effect was mediated by the tyrosine kinase-dependent, MAP kinase-independent mechanism.