C2-ceramide as a cell death inducer in HC11 mouse mammary epithelial cells

Involvement of oxidative stress-mediated ERK1/2 and p38 activation regulated mitochondria-dependent apoptotic signals in methylmercury-induced neuronal cell injury

Methylmercury (MeHg) is well-known for causing irreversible damage in the central nervous system as well as a risk factor for inducing neuronal degeneration. However, the molecular mechanisms of MeHg-induced neurotoxicity remain unclear. Here, we investigated the effects and possible mechanisms of MeHg in the mouse cerebrum (in vivo) and in cultured Neuro-2a cells (in vitro). In vivo study showed that the levels of LPO in the plasma and cerebral cortex significantly increased after administration of MeHg (50μg/kg/day) for 7 consecutive weeks. MeHg could also decrease glutathione level and increase the expressions of caspase-3, -7, and -9, accompanied by Bcl-2 down-regulation and up-regulation of Bax, Bak, and p53. Moreover, treatment of Neuro-2a cells with MeHg significantly reduced cell viability, increased oxidative stress damage, and induced several features of mitochondria-dependent apoptotic signals, including increased sub-G1 hypodiploids, mitochondrial dysfunctions, and the activation of PARP, and caspase cascades. These MeHg-induced apoptotic-related signals could be remarkably reversed by antioxidant NAC. MeHg also increased the phosphorylation of ERK1/2 and p38, but not JNK. Pharmacological inhibitors NAC, PD98059, and SB203580 attenuated MeHg-induced cytotoxicity, ERK1/2 and p38 activation, MMP loss, and caspase-3 activation in Neuro-2a cells. Taken together, these results suggest that the signals of ROS-mediated ERK1/2 and p38 activation regulated mitochondria-dependent apoptotic pathways that are involved in MeHg-induced neurotoxicity.

The role of NF-κB in mediating the anti-inflammatory effects of IL-10 in intestinal epithelial cells

In inflammatory bowel disease, cells that infiltrate the mucosa regulate intestinal epithelial cell function partly through release of pro- and anti-inflammatory cytokines. The aim of this study is to evaluate the role of the anti-inflammatory cytokine, IL-10, on normal mouse intestinal epithelial cells (Mode-K) in the absence or presence of IL-1. Western blotting assays and immunocytochemistry were used to identify the presence of IL-1 and IL-10 receptors on Mode-K cells; and electrophoretic mobility shift assays were used to study the activation of NF-kappaB transcription factor. Stimulation of Mode-K cells with IL-1 or IL-10 did not modify IL-1 and IL-10 receptor expression levels. IL-1 induced the synthesis of the enzyme cyclooxygenase-2 (COX-2) through the activation and translocation of p65 subunit of NF-kappaB. Inhibition of translocated p65 binding to DNA, inhibited COX-2 production and induced apoptosis. IL-10 inhibited IL-1-induced effects on IKB-alpha and IKB-beta proteins through stabilizing these proteins; subsequently causing inhibition of NF-kappaB translocation to the nucleus and any subsequent induction of COX-2. These data support a role for IL-10 in the regulation of IEC function under inflammatory conditions and the involvement of COX-2 in inhibiting apoptosis in mouse intestinal epithelial cells.

Ceramide triggers an NF-kappaB-dependent survival pathway through calpain

We have shown that C2 ceramide, a cell-permeable analog of this lipid second messenger, triggers an NF-kappaB dependent survival pathway that counteracts cell death. Activation of NF-kappaB and subsequent induction of prosurvival genes relies on calpain activity and is prevented on silencing of the calpain small subunit (Capn4) that is required for the function of ubiquitous calpains. We have demonstrated that p105 (NF-kappaB1) and its proteolytic product p50 can be targets of micro- and milli-calpain in vitro and that a p50 deletion mutant, lacking both the N- and the C-terminal ends, is resistant to calpain-mediated degradation. Capn4 silencing results in stabilization of endogenous p105 and p50 in diverse human cell lines. Furthermore, p105 processing and activation of NF-kappaB survival genes in response to C2 ceramide is impaired in Capn4-/- mouse embryonic fibroblasts defective in calpain activity. Altogether, these data argue for the existence of a ceramide-calpain-NF-kappaB axis with prosurvival functions.