Free radical biology & medicine
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Free Radic. Biol. Med. · Nov 2012
Poly(ADP-ribosyl)ation is a survival mechanism in cigarette smoke-induced and hydrogen peroxide-mediated cell death.
Cigarette smoking can contribute to the development of many human diseases such as cardiovascular disease, lung cancer, asthma, and chronic obstructive pulmonary disease. Thousands of compounds are present in cigarette smoke, including a large number of reactive oxygen species that can cause DNA damage, leading to the activation of poly(ADP-ribose) polymerase (PARP) enzymes. The PAR polymer is degraded by poly(ADP-ribose) glycohydrolase (PARG). ⋯ Addition of superoxide dismutase increased, whereas catalase abolished, CSE-induced PAR formation. In summary, our data show that the superoxide-hydrogen peroxide-DNA breakage pathway activates the PAR cycle by PARP-1 and PARG, which serves as a survival mechanism in CSE-exposed cells. Our data also raise the possibility that the PARP-1/PARG status of smokers may be an important determinant of the efficiency of DNA repair in their lungs and of their susceptibility to CS-induced carcinogenesis.
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Free Radic. Biol. Med. · Oct 2012
Hydrogen peroxide-induced poly(ADP-ribosyl)ation regulates osteogenic differentiation-associated cell death.
We set out to investigate the role of poly(ADP-ribosylation), the attachment of NAD(+)-derived (ADP-ribose)(n) polymers to proteins, in the regulation of osteogenic differentiation of SAOS-2 cells and mesenchymal stem cells. In osteogenic differentiation medium, SAOS-2 cells showed mineralization and expressed alkaline phosphatase and osteoblastic marker genes such as Runx2, osterix, BMP2, and osteopontin. The cells also released hydrogen peroxide, displayed poly(ADP-ribose) polymerase (PARP) activation, and showed commitment to cell death (apoptosis and necrosis). ⋯ PARP-1 silencing suppressed both apoptotic and necrotic cell death, but the PARP inhibitor PJ34 sensitized cells to cell death, indicating that the effects of PARP-1 silencing are not related to the activity of the enzyme. PARG silencing resulted in more apoptosis and, in the last days of differentiation, a shift from apoptosis toward necrosis. In conclusion our data prove that hydrogen peroxide-induced poly(ADP-ribose) signaling regulates cell death and osteodifferentiation.
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Free Radic. Biol. Med. · Oct 2012
Nrf2 promotes alveolar mitochondrial biogenesis and resolution of lung injury in Staphylococcus aureus pneumonia in mice.
Acute lung injury (ALI) initiates protective responses involving genes downstream of the Nrf2 (Nfe2l2) transcription factor, including heme oxygenase-1 (HO-1), which stimulates mitochondrial biogenesis and related anti-inflammatory processes. We examined mitochondrial biogenesis during Staphylococcus aureus pneumonia in mice and the effect of Nrf2 deficiency on lung mitochondrial biogenesis and resolution of lung inflammation. S. aureus pneumonia established by nasal insufflation of live bacteria was studied in mitochondrial reporter (mt-COX8-GFP) mice, wild-type (WT) mice, and Nrf2⁻/⁻ mice. ⋯ These findings indicate that S. aureus pneumonia induces Nrf2-dependent mitochondrial biogenesis in the alveolar region, mainly in AT2 cells. Absence of Nrf2 suppresses the alveolar transcriptional network for mitochondrial biogenesis and anti-inflammation, which worsens ALI. The findings link redox activation of mitochondrial biogenesis to ALI resolution.
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Free Radic. Biol. Med. · Oct 2012
Reactive oxygen species contribute to the promotion of the ATP-mediated proliferation of mouse skeletal myoblasts.
Reactive oxygen species (ROS) and extracellular adenosine 5'-triphosphate (ATP) participate in autocrine and paracrine regulation in skeletal muscle. However, the link between these two signaling systems is not well established. Here, we studied cell proliferation as a possible consequence of the trophic effect of ATP in cultured skeletal mouse myoblasts and we tested the possibility that low concentrations of ROS represent the intermediate signaling molecule mediating this effect. ⋯ Low-micromolar concentrations of exogenous H(2)O(2) mimicked the stimulatory effect of ATP on myoblast growth. DCF imaging revealed ATP-induced catalase and DPI-sensitive ROS production in myoblasts. In conclusion, our results indicate that extracellular ATP controls mouse myoblast proliferation via induction of ROS generation.
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Free Radic. Biol. Med. · Aug 2012
Functional dissection of Nrf2-dependent phase II genes in vascular inflammation and endotoxic injury using Keap1 siRNA.
Keap1 is a cytoplasmic repressor of the transcription factor Nrf2, and its degradation induces Nrf2 activation, leading to upregulation of antioxidant phase II genes. We investigated the roles of phase II genes in vascular inflammation and septic injury using Keap1 siRNA and elucidated its underlying mechanism. Selective knockdown of Keap1 with siRNA promoted Nrf2-dependent expression of phase II genes in endothelial cells, such as heme oxygenase-1 (HO-1), glutamate-cysteine ligase (GCL), and peroxiredoxin-1 (Prx1), resulting in the elevation of cellular glutathione levels and suppression of tumor necrosis factor (TNF)-α-induced intracellular H(2)O(2) accumulation. ⋯ Moreover, in vivo Keap1 knockdown increased the expression of phase II genes and suppressed the expression of ICAM-1, VCAM-1, iNOS, and TNF-α in an endotoxemic mouse model, resulting in significant protection against liver and lung injuries and lethality. Our results indicate that Keap1 knockdown prevents NF-κB-mediated vascular inflammation and endotoxic shock by suppressing NF-κB-mediated inflammatory gene expression via upregulation of Nrf2-mediated antioxidant genes. Thus, siRNA targeting Keap1 may provide a new therapeutic approach for inflammation-associated vascular diseases and sepsis.