Effect of melatonin on attenuating the isoflurane-induced oxidative damage is related to PKCα/Nrf2 signaling pathway in developing rats.

Isoflurane, an inhalational anesthesia, has frequently been used in pediatric anesthesia. However, research indicates that isoflurane can induce oxidative stress and affect neural and cognitive development. Melatonin, an endogenous hormone that exhibits antioxidant functions, can play a neuroprotective role by activating the PKCα/Nrf2 signaling pathway in response to oxidative stress. This study aims to determine whether the effect of melatonin on isoflurane-induced oxidative stress is related to activation of the PKCα/Nrf2 signaling pathway. Rat pups at postnatal day 7 were treated with control or 1.5% isoflurane for 4 h after pretreatment for 15 min with either melatonin (10 mg/kg i.p.) or 1% ethanol. The hematoxylin and eosin staining and transmission electron microscopic examination were used for observation of histopathology. The oxidative stress-related indicators were detected by using assay kits. The western blotting, immunohistochemistry and immunofluorescence were used to detect the activation of PKCα/Nrf2 signaling pathway. Results showed that isoflurane induced nerve damage in the hippocampus, and melatonin could reduce this injury. Oxidative stress-related indicators suggested that isoflurane can significantly increase reactive oxygen species and malondialdehyde levels, and decrease superoxide dismutase and glutathione activity compared with the control group, whereas melatonin ameliorated these indices. Expression of proteins associated with the PKCα/Nrf2 signaling pathway indicated that the neuroprotective effect of melatonin is related to activation of the PKCα/Nrf2 signaling pathway. These results suggest that the attenuating effect of melatonin on isoflurane-induced oxidative stress is related to activation of the PKCα/Nrf2 signaling pathway. These findings promote further research into underlying mechanisms and effective treatments to attenuate anesthesia neurotoxicity.

R-stereopreference analysis of lipase Novozym 435 in kinetic resolution of flurbiprofen.

Immobilized lipase from Candida antarctica (Novozym 435) was employed in the kinetic resolution of racemic flurbiprofen by enantioselective esterification with methanol. It was found that the lipase has the R-stereopreference and the reaction matches Bi Bi Ping Pong mechanism with dead-end inhibition of methanol. Furthermore, the R-stereopreference was analyzed in details from the aspects of enzymatic kinetic mechanism and reaction activation energy of both enantiomers. The R-enantiomer shows lower activation energy and higher maximum reaction rate than the S-enantiomer, which implies the R-stereopreference of the lipase and makes the kinetic resolution of flurbiprofen via enzymatic reaction feasible.

Experimental optimization of enzymic kinetic resolution of racemic flurbiprofen.

Immobilized lipase from Candida antarctica (Novozym 435) was employed for the kinetic resolution of racemic flurbiprofen by the method of enantioselective esterification with alcohols. However, the presence of accumulated water from the esterification influenced the enantiomeric ratio and reaction rate, due to increased rate of hydrolysis of the esterified enantiomer. In the present study, the procedure for optimizing the experimental resolution of the racemate was tested, with a focus on solvent and alcohol types, inhibition of alcohol substrates and the nature of the reversible reaction. The optimal concentration of feed flurbiprofen (180 mM or 44 mg/ml) was determined on basis of the maximum water content favourable for esterification, in single resolution, with the use of methanol in the solvent of cyclohexane.