p38 MAPK and MSK1 mediate caspase-8 activation in manganese-induced mitochondria-dependent cell death

Abstract

Heavy metals are important regulators of cell apoptosis. Manganese (Mn 2 þ ) is a potent inducer of apoptosis in different cell types, but the precise mechanisms that mediate such effects are not well defined. We previously reported that Mn 2 þ was a potent apoptotic agent in human B cells, including lymphoma B cell lines. We show here that Mn 2 þ -induced cell death in human B cells is associated with caspase-8-dependent mitochondrial activation leading to caspase-3 activity and apoptosis. We used specific caspase-8 interfering shRNAs to reduce caspase-8 expression, and this also reduced Mn 2 þ -induced caspase-3 activation and apoptosis. Mn 2 þ -triggered caspase-8 activation is associated with a specific pathway, which is independent of Fas-associated death domain protein, and dependent on the sequential activation of p38-mitogen-activated protein kinase (p38 MAPK) and mitogen-and stress-response kinase 1 (MSK1). Inhibition of p38 activity using either pharmacological inhibitors or dominant-negative mutant forms of p38 blocked Mn 2 þ -mediated phosphorylation of MSK1 and blocked subsequent caspase-8 activation. However, specific inhibitors and the expression of a dominant-interfering mutant of MSK1 only inhibited caspase-8 activation, but not p38 activity. These findings suggest a novel model for the regulation of caspase-8 during Mn 2 þ -induced apoptosis based on the sequential activation of p38 MAPK, MSK1, caspase-8 and mitochondria, respectively.

Mitochondrial-dependent manganese neurotoxicity in rat primary astrocyte cultures

“…Other authors have also reported that Mn exerts oxidative stress and increases free radical production in experimental models of Mn neurotoxicity (Brenneman et al, 1999;HaMai and Bondy 2004). Mn also causes mitochondriadependent cell death in human B cells, including lymphoma B cell lines (El McHichi et al, 2007;Schrantz et al, 1999). In an in vivo study, researchers reported that weekly injections of Mn over a 3-month period in the striatum and globus pallidus of monkeys (0, 2.25, 4.5 and 9 gm), produce dose-related clinical signs, which are more severe in the higher dose ranges.…”

TGFβ-mediated apoptosis of Burkitt's lymphoma BL41 cells is associated with the relocation of mitochondrial BimEL

“…For instance, p38 activation is involved in TGFb-mediated activation of GADD45b (Yoo et al, 2003) and p38 may also be responsible for Bim phosphorylation (Ley et al, 2004). In BL41 cells, a major role for p38 is to activate caspase-8 as also reported in various models (Park et al, 2003;Alvarado-Kristensson et al, 2004;Choi et al, 2004;El Mchichi et al, 2007). In our experimental conditions, one of the possible roles for p38 might reside in its involvement in caspase-8 activation leading to Mcl-1 cleavage and delocalization of Bim from the mitochondria surface.…”

“…Western blotting, immunoprecipitation and subcellular fractionation Western blot For drastic lyses condition (SDS buffer), cells were lysed as described (El Mchichi et al, 2007). Cells were also lysed by RIPA buffer for 30 min at 4 1C.…”

NF-κB-Mediated Modulation of Inducible Nitric Oxide Synthase Activity Controls Induction of the Epstein-Barr Virus Productive Cycle by Transforming Growth Factor Beta 1

“…In Sav-I cells, 2 M BAY11-7082 severely reduced ZEBRA expression, and total inhibition was observed with a 10 M concentration of the inhibitor. No (10,20,50, or 100 nM) (B) for 1 h prior to incubation with TGF-␤1 (2 ng/ml). Seventeen hours later, cells were harvested and lysed.…”

“…Staining and analysis were performed as recommended by the manufacturer. The ability of this kit to detect cell death was controlled using a treatment with 0.4 mM MnCl 2 (10). Cell number was determined with a Kova counting chamber (Hycor, Edinburgh, United Kingdom).…”