Green tea polyphenol (-)-epigallocatechin gallate attenuates the neuronal NADPH-d/nNOS expression in the nodose ganglion of acute hypoxic rats

Recent studies have shown that (-)-epigallocatechin gallate (EGCG), one of the green tea polyphenols, has a potent antioxidant property. Nitric oxide (NO) plays an important role in the neuropathogenesis induced by brain ischemia/reperfusion and hypoxia. This study aimed to explore the potential neuroprotective effect of EGCG on the ganglionic neurons of the nodose ganglion (NG) in acute hypoxic rats. Thus, the young adult rats were pretreated with EGCG (10, 25, or 50 mg/kg, i.p.) 30 min before they were exposed to the altitude chamber at 10,000 m with the partial pressure of oxygen set at the level of 0.27 atm (pO2=43 Torr) for 4 h. All the animals examined were allowed to survive for 3, 7, and 14 successive days, respectively, except for those animals sacrificed immediately following hypoxic exposure. Nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry and neuronal nitric oxide synthase (nNOS) immunohistochemistry were carried out to detect the neuronal NADPH-d/nNOS expression in the NG. The present results show a significant increase in the expression of NADPH-d/nNOS reactivity in neurons of the NG at various time intervals following hypoxia. However, the hypoxia-induced increase in NADPH-d/nNOS expression was significantly depressed only in the hypoxic rats treated with high dosages of EGCG (25 or 50 mg/kg). These data suggest that EGCG may attenuate the oxidative stress following acute hypoxia.