ABSTRACT
BACKGROUND: Endogenous hydrogen sulfide (H2S) may have multiple physiological functions in brain. Our previous study showed that H2S improved spatial memory impairment and decreased the production of Aß in APP/PS1 transgenic mice. However, many of the underlying mechanisms are not still being elucidated. The aim of the present study is to investigate the neuroprotective mechanisms of H2S involving in the activity of ß-secretase (BACE1), γ-secretase (PS1) and α-secretase (ADAM17). METHODS: Morris water maze was used to measure the behavior change. The levels of Aß40 and Aß42 were quantified using colorimetric ELISA kits and immunohistochemical analysis. The levels of BACE1, PS1, ADAM17, pAkt, pp38MAPK, pERK and pJNK were tested by Western blot analysis in normal mice, APP/PS1 transgenic mice and 50µmol/kg-NaHS-treated transgenic mice. On the basis of exogenous H2S treatment, LY294002 (inhibitors of PI3K/Akt) or PD98059 (inhibitors of MAPK/ERK) was injected into lateral cerebral ventricle. RESULTS: The levels of BACE1, PS1 and pp38MAPK were increased and ADAM17 were decreased in the APP/PS1 transgenic mice. After intraperitoneal administration of an H2S donor (NaHS) into APP/PS1 mice, the levels of BACE1, PS1 and pp38MAPK were reduced and ADAM17 increased. The level of pp38 MAPKs, pAkt and pERK1/2 was increased in APP/PS1 transgenic mice compared with normal mice (p<0.05). There was no difference in the expression of pJNK between AD transgenic mice and normal mice (p>0.05). These results demonstrated that LY294002 inhibited the effect of H2S on decreasing the BACE1 and PS1, reducing the level of Aß and improving memory impairment in APP/PS1 transgenic mice. PD98059 had no influence on the expression of BACE1 and PS1. CONCLUSIONS: H2S inhibits the expression of BACE1 and PS1 by activating PI3K/Akt pathway in AD.
Subject(s)
Amyloid Precursor Protein Secretases/metabolism , Aspartic Acid Endopeptidases/metabolism , Down-Regulation/drug effects , Hydrogen Sulfide/pharmacology , Phosphatidylinositol 3-Kinases/metabolism , Proto-Oncogene Proteins c-akt/metabolism , ADAM17 Protein/metabolism , Alzheimer Disease/drug therapy , Alzheimer Disease/metabolism , Amyloid beta-Peptides/metabolism , Animals , Brain/drug effects , Brain/metabolism , Disease Models, Animal , Memory Disorders/drug therapy , Memory Disorders/metabolism , Mice , Mice, Transgenic/metabolism , p38 Mitogen-Activated Protein Kinases/metabolismABSTRACT
Alzheimer's disease (AD) is defined both by its progressive cognitive deterioration and hallmark increase in neuronal Aß plaque formation. However, many of the underlying neurobiological facets of this disease are still being elucidated. Previous research has demonstrated that production of neuronal hydrogen sulfide (H2S) is significantly decreased in patients with AD. Moreover, systemic plasma H2S levels are negatively correlated with its severity. However, how a decrease in H2S production might be correlated with either the etiology or pathophysiology of AD remains unknown. To better understand the role of H2S in AD, we examined both levels of H2S and the expression and activity H2S-synthesizing enzyme (cystathionine beta synthase or CBS) in an APP/PS1 transgenic mouse line at 3, 6, 9 and 12 months. After intraperitoneal (i.p.) administration of an H2S donor (NaHS) into APP/PS1 mice, application of exogenous H2S resulted in improved spatial learning and memory acquisition in APP/PS1 mice. H2S administration also led to significant decrease in extracellular levels of Aß40 and Aß42, the expression of BACE1 and PS1, and a significant increase of ADAM17 expression. Similarly, an increase in non-amyloidogenic C83 fragment generation and a decrease in amyloidogenic C99 fragment generation were also observed. Thus, NaHS application resulted in a shift from the plaque-forming beta pathway to the non-plaque forming alpha pathway of APP cleavage in 6 and 12 month APP/PS1 mice. These results indicate the importance of H2S to AD severity and that administration of exogenous H2S can promote a non-amyloidogenic processing of APP.
