Blue LED light exposure develops intracellular reactive oxygen species, lipid peroxidation, and subsequent cellular injuries in cultured bovine retinal pigment epithelial cells.

The effects of blue light emitter diode (LED) light exposure on retinal pigment epithelial cells (RPE cells) were examined to detect cellular damage or change and to clarify its mechanisms. The RPE cells were cultured and exposed by blue (470 nm) LED at 4.8 mW/cm(2). The cellular viability was determined by XTT assay and cellular injury was determined by the lactate dehydrogenase activity in medium. Intracellular reactive oxygen species (ROS) generation was determined by confocal laser microscope image analysis using dihydrorhodamine 123 and lipid peroxidation was determined by 4-hydroxy-2-nonenal protein-adducts immunofluorescent staining (HNE). At 24 h after 50 J/cm(2) exposures, cellular viability was significantly decreased to 74% and cellular injury was significantly increased to 365% of control. Immediately after the light exposure, ROS generation was significantly increased to 154%, 177%, and 395% of control and HNE intensity was increased to 211%, 359%, and 746% of control by 1, 10, and 50 J/cm(2), respectively. These results suggest, at least in part, that oxidative stress is an early step leading to cellular damage by blue LED exposure and cellular oxidative damage would be caused by the blue light exposure at even lower dose (1, 10 J/cm(2)).

Salt is an oxidative stressor for gastric epithelial cells.

Salt/NaCl has been reported to induce necrosis in gastric mucosal cells, however, the mechanisms for gastric injury by salt are not clarified. In this study, we elucidated whether salt is an oxidative stress inducer via mitochondrial injury on rat gastric epithelial cells (RGM-1) in 300, 450, 650 and 1000 mM of NaCl-contained medium. To clarify whether salt-induced reactive oxygen species (ROS) is derived from mitochondria, we also investigated a salt-induced ROS production in manganese superoxide dismutase overexpressing cells (RGM-MnSOD). MnSOD is a specific scavenger for superoxide anion produced from mitochondria. The results showed that cellular injuries in RGM-MnSOD were significantly less severe than that in normal RGM-1. The electron paramagnetic resonance (EPR) studies also provided an evidence that the salt-derived superoxide production in RGM-MnSOD was less than that in normal RGM-1. These results indicated that salt is not merely a necrotizing factor for gastric epithelial cells, but also an oxidative stress inducer.

Rebamipide attenuates nonsteroidal anti-inflammatory drugs (NSAID) induced lipid peroxidation by the manganese superoxide dismutase (MnSOD) overexpression in gastrointestinal epithelial cells.

Nonsteroidal anti-inflammatory drugs (NSAIDs) often cause gastrointestinal complications such as gastric ulcers and erosions. Recent studies on the pathogenesis have revealed that NSAIDs induce lipid peroxidation in gastric epithelial cells by generating superoxide anion in mitochondria, independently with cyclooxygenase-inhibition and the subsequent prostaglandin deficiency. Although not clearly elucidated, the impairment of mitochondrial oxidative phosphorylation, or uncoupling, by NSAIDs is associated with the generation of superoxide anion. Physiologically, superoxide is immediately transformed into hydrogen peroxide and diatomic oxygen with manganese superoxide dismutase (MnSOD). Rebamipide is an antiulcer agent that showed protective effects against NSAID-induced lipid peroxidation in gastrointestinal tracts. We hypothesized that rebamipide may attenuate lipid peroxidation by increasing the expression of MnSOD protein in mitochondria and decreasing the leakage of superoxide anion in NSAID-treated gastric and small intestinal epithelial cells. Firstly, to examine rebamipide increases the expression of MnSOD proteins in mitochondria of gastrointestinal epithelial cells, we underwent Western blotting analysis against anti-MnSOD antibody in gastric RGM1 cells and small intestinal IEC6 cells. Secondly, to examine whether the pretreatment of rebamipide decreases NSAID-induced mitochondrial impairment and lipid peroxidation, we treated these cells with NSAIDs with or without rebamipide pretreatment, and examined with specific fluorescent indicators. Finally, to examine whether pretreatment of rebamipide attenuates NSAID-induced superoxide anion leakage from mitochondria, we examined the mitochondria from indomethacin-treated RGM1 cells with electron spin resonance (ESR) spectroscopy using a specific spin-trapping reagent, CYPMPO. Rebamipide increased the expression of MnSOD protein, and attenuated NSAID-induced mitochondrial impairment and lipid peroxidation in RGM1 and IEC6 cells. The pretreatment of rebamipide significantly decreased the signal intensity of superoxide anion from the mitochondria. We conclude that rebamipide attenuates lipid peroxidation by increasing the expression of MnSOD protein and decreasing superoxide anion leakage from mitochondria in both gastric and small intestinal epithelial cells.