Lactulose ameliorates cerebral ischemia-reperfusion injury in rats by inducing hydrogen by activating Nrf2 expression

Abstract

Molecular hydrogen has been proven effective in ameliorating cerebral ischemia/reperfusion (I/R) injury by selectively neutralizing reactive oxygen species. Lactulose can produce a considerable amount of hydrogen through fermentation by the bacteria in the gastrointestinal tract. To determine the neuroprotective effects of lactulose against cerebral I/R injury in rats and explore the probable mechanisms, we carried out this study. The stroke model was produced in Sprague-Dawley rats through middle cerebral artery occlusion. Intragastric administration of lactulose substantially increased breath hydrogen concentration. Behavioral and histopathological verifications matched biochemical findings. Behaviorally, rats in the lactulose administration group won higher neurological scores and showed shorter escape latency time in the Morris test. Morphologically, 2,3,5-triphenyltetrazolium chloride showed smaller infarction volume; Nissl staining manifested relatively clear and intact neurons and TUNEL staining showed fewer apoptotic neurons. Biochemically, lactulose decreased brain malondialdehyde content, caspase-3 activity, and 3-nitrotyrosine and 8-hydroxy-2-deoxyguanosine concentration and increased superoxide dismutase activity. The effects of lactulose were superior to those of edaravone. Lactulose orally administered activated the expression of NF-E2-related factor 2 (Nrf2) in the brain as verified by RT-PCR and Western blot. The antibiotics suppressed the neuroprotective effects of lactulose by reducing hydrogen production. Our study for the first time demonstrates a novel therapeutic effect of lactulose on cerebral ischemia/reperfusion injury and the probable underlying mechanisms. Lactulose intragastrically administered possessed neuroprotective effects on cerebral I/R injury in rats, which could be attributed to hydrogen production by the fermentation of lactulose through intestinal bacteria and Nrf2 activation.

Keywords: 2,3,5-triphenyltetrazolium chloride; 3-NT; 3-nitrotyrosine; 8-OHdG; 8-hydroxy-2-deoxyguanosine; ANTI; Antioxidant; ECA; Ed; Free radicals; Hydrogen; I/R; ICA; Ischemia/reperfusion; LAC; Lactulose; MCAO; MDA; NF-E2-related factor 2; Nrf2; PBS; PD; Parkinson disease; ROS; SOD; TTC; TUNEL; antibiotics; edaravone; external carotid artery; internal carotid artery; ischemia/reperfusion; lactulose; malondialdehyde; middle cerebral artery occlusion; phosphate-buffered saline; qRT-PCR; quantitative reverse transcription–PCR; reactive oxygen species; superoxide dismutase; terminal deoxynucleotidyl transferase dUTP nick-end labeling.