The pro-inflammatory oxidant hypochlorous acid induces Bax-dependent mitochondrial permeabilisation and cell death through AIF-/EndoG-dependent pathways

University of Reading, Reading, England, United Kingdom
Cellular Signalling (Impact Factor: 4.32). 05/2007; 19(4):705-14. DOI: 10.1016/j.cellsig.2006.08.019
Source: PubMed


At sites of chronic inflammation, such as in the inflamed rheumatoid joint, activated neutrophils release hydrogen peroxide (H(2)O(2)) and the enzyme myeloperoxidase to catalyse the formation of hypochlorous acid (HOCl). 3-chlorotyrosine, a marker of HOCl in vivo, has been observed in synovial fluid proteins from rheumatoid arthritis patients. However the mechanisms of HOCl-induced cytotxicity are unknown. We determined the molecular mechanisms by which HOCl induced cell death in human mesenchymal progenitor cells (MPCs) differentiated into a chondrocytic phenotype as a model of human cartilage cells and show that HOCl induced rapid Bax conformational change, mitochondrial permeability and release of intra-mitochondrial pro-apoptotic proteins which resulted in nuclear translocation of AIF and EndoG. siRNA-mediated knockdown of Bax substantially prevented mitochondrial permeability, release of intra-mitochondrial pro-apoptotic proteins. Cell death was inhibited by siRNA-mediated knockdown of Bax, AIF or EndoG. Although we observed several biochemical markers of apoptosis, caspase activation was not detected either by western blotting, fluorescence activity assays or by using caspase inhibitors to inhibit cell death. This was further supported by findings that (1) in vitro exposure of recombinant human caspases to HOCl caused significant inhibition of caspase activity and (2) the addition of HOCl to staurosporine-treated MPCs inhibited the activity of cellular caspases. Our results show for the first time that HOCl induced Bax-dependent mitochondrial permeability which led to cell death without caspase activity by processes involving AIF/EndoG-dependent pathways. Our study provides a novel insight into the potential mechanisms of cell death in the inflamed human joint.

10 Reads
  • Source
    • "We saw increases in the activity of caspase-3 in each cell line treated with LCA, and cell death induced by LCA was only partially dependent on this main effector caspase. Previous studies have shown that the cleaved form of Bax can significantly sensitize cells to stress-induced apoptosis by releasing cytochrome c, apoptosis-inducing factor and endonuclease G from the mitochondria (Cao, Deng & May, 2003; Gao & Dou, 2000; Toyota et al., 2003; Wood & Newcomb, 2000; Cabon et al., 2012; Moubarak et al., 2007; Whiteman et al., 2007). Paired with our observation that inhibition of caspase-8 did not completely abrogate LCA-induced cell death, it is likely that LCA induces both caspase-dependent and -independent modes of apoptosis in prostate cancer cells. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Prostate cancer is a prevalent age-related disease in North America, accounting for about 15% of all diagnosed cancers. We have previously identified lithocholic acid (LCA) as a potential chemotherapeutic compound that selectively kills neuroblastoma cells while sparing normal human neurons. Now, we report that LCA inhibits the proliferation of androgen-dependent (AD) LNCaP prostate cancer cells and that LCA is the most potent bile acid with respect to inducing apoptosis in LNCaP as well as androgen-independent (AI) PC-3 cells, without killing RWPE-1 immortalized normal prostate epithelial cells. In LNCaP and PC-3 cells, LCA triggered the extrinsic pathway of apoptosis and cell death induced by LCA was partially dependent on the activation of caspase-8 and -3. Moreover, LCA increased cleavage of Bid and Bax, down-regulation of Bcl-2, permeabilization of the mitochondrial outer membrane and activation of caspase-9. The cytotoxic actions of LCA occurred despite the inability of this bile acid to enter the prostate cancer cells with about 98% of the nominal test concentrations present in the extracellular culture medium. With our findings, we provide evidence to support a mechanism of action underlying the broad anticancer activity of LCA in various human tissues.
    PeerJ 08/2013; 1(21):e122. DOI:10.7717/peerj.122 · 2.11 Impact Factor
  • Source
    • "Alterations of the mitochondrial membrane potential (« m ) were determined by fluorescence microscopy using 1 ␮g/mL rhodamine 123 (Rhod123; Sigma–Aldrich), a fluorescent molecule that is commonly used for detecting mitochondrial membrane potential (Whiteman et al., 2007). Spores of P. expansum (1 × 10 6 spores/mL) were cultured at 23 • C in PDB medium. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Boron in the form of potassium tetraborate was effective for control of blue mold rot caused by Penicillium expansum in jujube fruit. The control activity was positively correlated with the concentration of boron solution. Boron at 0.5% enhanced the biocontrol efficacy of the antagonistic yeast Cryptococcus laurentii against P. expansum. Analysis of population dynamics demonstrated that growth of C. laurentii was not significantly influenced by boron in the fruit wounds. C. laurentii multiplied quickly, regardless of whether the yeast was used alone or combined with boron. An in vitro study showed that boron at 0.25% even stimulated the growth of C. laurentii at the end of incubation period. By comparison, mycelial spread of P. expansum in the culture medium was completely inhibited by boron at 0.25%. Using the fluorescent probe rhodamine 123, we found that the mitochondrial membrane potential collapsed significantly after boron treatment. This indicated that boron inhibited the growth of P. expansum by targeting the mitochondria of the fungal pathogen. Taken together, our data suggest that the enhancement in biocontrol efficacy of C. laurentii may be related to the differential influence of boron on the antagonistic yeast and the fungal pathogen.
    Postharvest Biology and Technology 06/2012; 68:16–21. DOI:10.1016/j.postharvbio.2012.01.008 · 2.22 Impact Factor
  • Source
    • "During apoptotic stimulation, alteration of the Bcl-2/Bax protein ratio may affect mitochondrial cytochrome c release (Hildeman et al., 2003). The ratio of these two protein levels can be predictive of whether or not a cell undergoes apoptosis (Gross et al., 1999); a decrease in Bcl-2/Bax ratio is a decisive correlated in apoptosis or cell death (Whiteman et al., 2007; Kim et al., 2010; Wiebe et al., 2010). Once released into the cytoplasm, cytochrome c catalyzes the oligomerization of apoptotic protease activating factor-1 (Apaf1), thereby promoting the activation of caspase (Zimmermann et al., 2001). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Cypermethrin (CYP), a widely used Type II pyrethroid pesticide, is one of the most common contaminants in the freshwater aquatic system. We studied the effects of CYP exposure on the induction of hepatic oxidative stress, DNA damage and the alteration of gene expression related to apoptosis in adult zebrafish. Hepatic mRNA levels for the genes encoding antioxidant proteins, such as Cu/Zn-Sod, Mn-Sod, Cat, and Gpx, were significantly upregulated when zebrafish were exposed to various concentrations of CYP for 4 or 8 days. In addition, the main genes related to fatty acid β-oxidation and the mitochondrial genes related to respiration and ATP synthesis were also significantly upregulated after exposure to high concentrations (1 and 3 μg L(-1)) of CYP for 4 or 8 days. Moreover, in a comet assay of zebrafish hepatocytes, tail DNA, tail length, tail moment and Olive tail moment increased in a concentration-dependent manner. The significant induction (p<0.01) of all four parameters observed with CYP concentrations of 0.3 μg L(-1) or higher suggests that heavy DNA damage was induced even at low levels. Furthermore, several apoptosis- related genes, such as p53, Apaf1 and Cas3, were significantly upregulated after CYP exposure, and Bcl2/Bax expression ratio decreased, especially in groups treated with 1 and 3 μg L(-1) CYP for 8 days. Taken together, our results suggested that CYP has the potential to induce hepatic oxidative stress, DNA damage and apoptosis in zebrafish. This information will be helpful in fully understanding the mechanism of aquatic toxicology induced by CYP in fish.
    Chemosphere 10/2010; 82(3):398-404. DOI:10.1016/j.chemosphere.2010.09.072 · 3.34 Impact Factor
Show more