Leukemic cell apoptosis may be enhanced by appropriate oxidative stress. We report here the mechanism of Jurkat cell apoptosis by monochloramine (NH(2)Cl), a neutrophil-derived oxidant. NH(2)Cl induced caspase-dependent apoptosis, which was preceded by cytochrome c and Smac/Diablo release from mitochondria. Within 10min of NH(2)Cl treatment, c-Jun N-terminal kinase (JNK) activation and elevation of cytosolic Ca(2+) were observed. JNK inhibitors (SP600125 or JNK inhibitor VIII) significantly suppressed the apoptosis as well as caspase cleavage and cytochrome c release. In contrast, Ca(2+) chelation by EGTA+acetoxymethyl-EGTA had no effects on apoptosis. Our results indicated that JNK activation contributed most importantly to the NH(2)Cl-induced apoptosis.
"Spermine-mediated apoptosis triggered by oxidative stress has also been demonstrated in a variety of cell systems, including ischaemia-induced apoptosis of cardiac myoblasts (Maccarrone et al., 2001; Takano et al., 2005; Tantini et al., 2006). Emerging evidence now suggests that oxidative stress can promote JNK activation (Osto et al., 2008; Wei et al., 2008; Ogino et al., 2009), which constitutes a critical component of apoptotic signalling in various cells, including muscle cells (Tamagno et al., 2003; Sinha- Hikim et al., 2007; Braga et al., 2008; Philpott and Facci, 2008; Nadeau et al., 2009). Thus, the signal for JNK activation most likely emanates from spermine-induced generation of oxidative stress. "
[Show abstract][Hide abstract] ABSTRACT: CKD (chronic kidney disease) is a public health problem, mediated by haemodynamic and non-haemodynamic events including oxidative stress. We investigated the effect of two GSH (glutathione) precursors, NAC (N-acetylcysteine) and cystine as the physiological carrier of cysteine in GSH with added selenomethionine (F1) in preventing spermine (uraemic toxin)-induced apoptosis in cultured human aortic VSMC (vascular smooth muscle cells). VSMCs exposed to spermine (15 microM) with or without antioxidants (doses 50, 100, 200 and 500 microg/ml) were assessed for apoptosis, JNK (c-Jun-NH2-terminal kinase) activation and iNOS (inducible nitric oxide synthase) induction and activation of intrinsic pathway signalling. Spermine exposure resulted in activation of JNK and iNOS induction and apoptosis. NAC and F1 (dose range 50-500 microg/ml) attenuated spermine-induced acceleration of VSMC apoptosis but only F1 (at 200 and 500 microg/ml) maintained spermine-induced apoptosis at control levels. Spermine-induced JNK activation was prevented by 200 microg/ml of both NAC and F1, while iNOS induction was blocked only by F1. Notably, the adverse effects of spermine on BAX/BCL-2 ratio, cytochrome c release and caspase activation was fully attenuated by F1. In conclusion, F1 was more effective than NAC in preventing spermine-induced apoptosis and downstream changes in related signal transduction pathways in VSMCs. Further studies are needed to examine the effect of these compounds in preventing CKD-associated vascular disease.
Cell Biology International 05/2010; 34(5):503-11. DOI:10.1042/CBI20090349 · 1.93 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: It has been well established that amino acid availability can control gene expression. Previous studies have shown that amino
acid depletion induces transcription of the ATF3 (activation transcription factor 3) gene through an amino acid response element (AARE) located in its promoter. This event
requires phosphorylation of activating transcription factor 2 (ATF2), a constitutive AARE-bound factor. To identify the signaling
cascade leading to phosphorylation of ATF2 in response to amino acid starvation, we used an individual gene knockdown approach
by small interfering RNA transfection. We identified the mitogen-activated protein kinase (MAPK) module MEKK1/MKK7/JNK2 as
the pathway responsible for ATF2 phosphorylation on the threonine 69 (Thr69) and Thr71 residues. Then, we progressed backwards
up the signal transduction pathway and showed that the GTPase Rac1/Cdc42 and the protein Gα12 control the MAPK module, ATF2
phosphorylation, and AARE-dependent transcription. Taken together, our data reveal a new signaling pathway activated by amino
acid starvation leading to ATF2 phosphorylation and subsequently positively affecting the transcription of amino acid-regulated
[Show abstract][Hide abstract] ABSTRACT: This paper studied the effects of physiologically available oxidants on HL 60 differentiation induced by all-trans retinoic acid (ATRA) or dimethyl sulfoxide (DMSO). Hydrogen peroxide (15 μM) and taurine chloramine (200 μM) induced HL 60 differentiation, which was detected by CD11b expression and superoxide production. Cd11b and p67phox mRNA expression was also augmented by these oxidants. In contrast, reducing chemicals, such as dithiothreitol, 2,3-dimercapto-1-propanol and N-acetylcysteine inhibited CD11b expression. Notably, DMSO inhibited methionine sulfoxide reductase activity, induced heme oxygenase-1 (ho-1) mRNA and enhanced oxidant-induced cell death, which indicated that DMSO intensified oxidative stress. After the addition of oxidants, ho-1 expression preceded the cd11b expression. Vicinal dithiol-reactive phenylarsine oxide (50 nM) also increased CD11b expression induced by DMSO or ATRA. These observations suggested that oxidative stress enhanced granulocytic differentiation of HL 60 cells and that leukaemic cell differentiation was affected by cellular redox status.
Free Radical Research 11/2010; 44(11):1328-37. DOI:10.3109/10715762.2010.503757 · 2.98 Impact Factor
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