Estimation of hydroxyl radical generation by salicylate hydroxylation method in kidney of mice exposed to ferric nitrilotriacetate and potassium bromate

Norepinephrine-induced apoptotic and hypertrophic responses in H9c2 cardiac myoblasts are characterized by different repertoire of reactive oxygen species generation

Despite recent advances, the role of ROS in mediating hypertrophic and apoptotic responses in cardiac myocytes elicited by norepinephrine (NE) is rather poorly understood. We demonstrate through our experiments that H9c2 cardiac myoblasts treated with 2 µM NE (hypertrophic dose) generate DCFH-DA positive ROS only for 2 h; while those treated with 100 µM NE (apoptotic dose) sustains generation for 48 h, followed by apoptosis. Though the levels of DCFH fluorescence were comparable at early time points in the two treatment sets, its quenching by DPI, catalase and MnTmPyP suggested the existence of a different repertoire of ROS. Both doses of NE also induced moderate levels of H₂O₂ but with different kinetics. Sustained but intermittent generation of highly reactive species detectable by HPF was seen in both treatment sets but no peroxynitrite was generated in either conditions. Sustained generation of hydroxyl radicals with no appreciable differences were noticed in both treatment sets. Nevertheless, despite similar profile of ROS generation between the two conditions, extensive DNA damage as evident from the increase in 8-OH-dG content, formation of γ-H2AX and PARP cleavage was seen only in cells treated with the higher dose of NE. We therefore conclude that hypertrophic and apoptotic doses of NE generate distinct but comparable repertoire of ROS/RNS leading to two very distinct downstream responses.

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H9c2 myoblasts upon treatment with 2 and 100 µM NE induces hypertrophy and apoptosis.

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Both treatments show comparable levels of DCFH fluorescence with different kinetics.

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Both treatments show comparable levels of HPF fluorescence in an oscillating manner.

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More hydroxyl radical was generated in 100 µM NE treated set.

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DNA damage and apoptosis occurs only in 100 µM NE treated sets.

Smoking induces bimodal DNA damage in mouse lung

To clarify the relationship between DNA damage and free radical generation caused by smoking in vivo, DNA damage was investigated in the mouse lung by single-cell gel electrophoresis assay after exposure to cigarette smoke (CS) or gas phase cigarette smoke (GPCS). Although GPCS did not induce DNA lesions, bimodal peaks of DNA damage were detected in mouse lung exposed to CS, one immediately after exposure and another 15 min later. Pretreatment with a specific hydroxyl radical (•OH) scavenger completely prevented both types of DNA damage induced by CS. Electron spin resonance (ESR) study of the kinetics of free radical generation in CS or GPCS revealed that •OH could be detected immediately after the spin trapping of CS without chelators (first •OH generation), whereas •OH was also generated gradually with a time lag when the spin trapping was performed with chelators (second •OH generation). Our ESR study also indicated that the first •OH peak was probably generated from H(2)O(2) via a metal-independent pathway, whereas the second •OH peak might have been generated from H(2)O(2) and other sources via at least two different metal-masked pathways. The bimodal DNA damage induced in lung by smoking appears to be the result of a time lag between the first •OH generation and second •OH generation after exposure to the tar in CS.