The effect of hypoxia on Hydrogen Sulfide concentration of brain tissue in AD transgenic mice and its mechanism.

OBJECTIVE: Research has shown that hydrogen sulfide (H2S) plays a protective role in many diseases of the nervous system. The aim of this study is to investigate the effect of hypoxia on endogenous H2S concentration in the cerebral cortex of Alzheimer's disease (AD) transgenic mice and its mechanism. METHODS: AD transgenic mice were raised in closed boxes and pure nitrogen was introduced to reduce the oxygen concentration to 8%-10%, establishing an animal model of hypoxia. Oxygen partial pressure was measured with an oxygen meter. The expression of cystathionine-ß-synthase (CBS) in cerebral cortex tissue was determined by Western blot, and H2S concentration was measured by a modified methylene blue method. RESULTS: (1) Hypoxia down-regulated CBS expression in cerebral cortex tissue of AD transgenic mice (p < 0.05). (2) The concentration of H2S in the cerebral cortex tissue of the hypoxic transgenic group was significantly lower than that of the Control group (p < 0.01). (3) Overexpression of CBS reversed the hypoxia-induced decrease of H2S concentration in the cerebral cortex tissue of AD transgenic mice (p < 0.01). CONCLUSIONS: Hypoxia decreased the concentration of endogenous H2S in the cerebral cortex tissue of AD transgenic mice by down-regulating the expression of CBS.

Calcium sensing receptor mediated the excessive generation of ß-amyloid peptide induced by hypoxia in vivo and in vitro.

Hypoxia played an important role in the pathogenesis of AD. Hypoxia increased Aß formation, then caused Alzheimer's disease. Calcium sensing receptor (CaSR) was involved in the regulation of cell growth, differentiation, hormonal secretion and other physiological function. Increasing evidence supported CaSR might play a more prominent role in susceptibility to AD, but the role of CaSR in Aß overproduction induced by hypoxia and its mechanisms remain unclear. To investigate whether CaSR mediated the overproduction of Aß induced by hypoxia, immunoblot and immunochemistry were employed to determine the expression of CaSR and BACE1 in hippocampal neurons and tissue and Ca(2+) image system was used to measure [Ca(2+)]i in hippocampal neurons. The content of Aß was detected with ELISA kits. Our research found that hypoxia increased the expression of CaSR in hippocampal neurons and tissue and [Ca(2+)]i in hippocampal neurons. Calhex 231, a selective blocher of CaSR, inhibited the increase in [Ca(2+)]i induced by hypoxia. Hypoxia or GdCl3, an agonist of CaSR, increased the expression of BACE1 in hippocampal neurons and tissue, but Calhex 231 or Xesto C (a selective inhibitor of IP3 receptor) partly prevented hypoxia-induced BACE1 overexpression. Hypoxia or GdCl3 increased the content of Aß42 and Aß40 in hippocampal tissue, however Calhex 231 or Xesto C prevented hypoxia-induced the overproduction of Aß42 and Aß40 partly. Based on the above data, we suggested that hypoxia increased [Ca(2+)]i by elevated CaSR expression to promote BACE1 expression, thereby resulting in the overproduction of Aß42 and Aß40.

Hydrogen sulfide prevents OGD/R-induced apoptosis via improving mitochondrial dysfunction and suppressing an ROS-mediated caspase-3 pathway in cortical neurons.

Hydrogen sulfide (H2S), an endogenous gaseous mediator, has been shown to have protective effects against neuronal damage caused by brain ischemia. In this study, we explored the potential effects of H2S on oxygen-glucose deprivation/reoxygenation (OGD/R)-induced neuronal apoptosis and the possible mechanisms. We find that sodium hydrosulfide (NaHS, a donator of H2S) prevents OGD/R-induced intracellular reactive oxygen species (ROS) elevation and activation of caspase-3 in cultured mouse cortical neurons. The pretreatment of N-acetyl-l-cysteine (NAC, an ROS scavenger) also prevents OGD/R-induced activation of caspase-3. Both NaHS and NAC counteract OGD/R-induced decline in mitochondria membrane potential (MMP). Additionally, NaHS, NAC or N-Acetyl-Asp-Glu-Val-Asp-CHO (DEVD-CHO, a caspase-3 inhibitor), is shown to significantly inhibit OGD/R-induced neuronal apoptosis. These data suggest that H2S can protect against OGD/R-induced neuronal apoptosis through improving mitochondria dysfunction and suppressing an ROS-activated caspase-3 signaling pathway.