Hydrogen supplemented air inhalation reduces changes of prooxidant enzyme and gap junction protein levels after transient global cerebral ischemia in the rat hippocampus

Transient global cerebral ischemia (TGCI) occurs during acute severe hypotension depriving the brain of oxygen and glucose for a short period of time. During reperfusion, several mechanisms can induce secondary neuronal damage, including the increased production of reactive oxygen species (ROS). Hydrogen gas-enriched air inhalation is a neuroprotective approach with proven antioxidant potential, which has not yet been examined in TGCI. Accordingly, we set out to describe the effect of inhalation of 2.1% hydrogen supplemented room air (H2-RA) in comparison with a well studied neuroprotective agent, rosiglitazone (RSG) in a TGCI rat model.Male Wistar rats were exposed to TGCI (n = 26) or sham operation (n = 26), while a third group served as intact control (naive, n = 5). The operated groups were further divided into non-treated, H2-RA, RSG (6 mg/kg i.v.) and vehicle treated animals. Tissue samples from the hippocampus and frontal cortex were taken 3 days following surgery. Western blot analysis was applied to determine the expressions of cyclooxygenase-2 (COX-2), neuronal and endothelial nitric oxide synthase (nNOS and eNOS, respectively), manganese superoxide dismutase (MnSOD) and glial connexin proteins: connexin 30 and connexin 43. The expressions of COX-2, and connexin proteins were upregulated, while nNOS was downregulated 3 days after TGCI. Both RSG and H2-RA prevented the changes of enzyme and connexin levels. Considering the lack of harmful side effects, inhalation of H2-RA can be a promising approach to reduce neuronal damage after TGCI.

► TGCI elevates COX-2 and glial connexin levels and decreases nNOS expression.
► H2-RA prevents TGCI-induced changes of enzyme and protein expressions.
► RSG treatment prevents TGCI-induced changes of enzyme and connexin levels.
► RSG downregulates the basal COX-2 expression.