BDNF-TrkB Pathway Mediates The Protection Of Hydrogen Sulfide Against FA-induced Neurotoxicity By Downregulation Of ALDH2in PC12Cells

[Backgroud and Objective]Formaldehyde (FA) can induce neurotoxicity. We have previously found thatHydrogen sulfide (H2S) protects against the neurotoxicity of FA. However, theunderlying mechanism is poor. Brain derived neurophic factor (BDNF) is animportant endogenous neuroprotectant. Aldehyde-dehydrogenase2(ALDH2) plays amajor role in detoxification of reactive aldehyde in rang of organs and cell types.Therefore, we guessed that the H2S can antagonize the formaldehyde-generatedneurotoxicity by modulating BDNF and/or ALDH2.To confirm the hypothesis, we use FA-treated PC12cell as the cell model of FAneurotoxicity to explore the mechanism underlying H2S-caused protection against FA-induced neurotoxicity from the modulation of BDNF and/or ALDH2.[Methods]The cell viability was detected by Cell Counting Kit-8; The cell apoptosis wasmeasured by flow cytometry (FCM) after PI staining; The level of intracellular ROSwas measured by NBT reduction assay; The intracellular level of MDA, and4-HNEand the activity of Caspase-3were determined by Elisa assay; The activity of ALDH2was measured by ALDH2activity Kit; The expressions of BDNF, ALDH2, Bcl-2, andBax were detected by Western Blot.[Results]1. BDNF-TrkB pathway mediates the protection of H2S against neurotoxicityinduced by formaldehyde (FA) in PC12cells. 1.1H2S upregulates the expression of BDNF in PC12cells.After PC12cells were treated with H2S (100,200, or400μmol/L) for24h, theexpression of BDNF was increased in a concentration-dependent manner. Afterpretreated with200μM of H2S for30min, PC12cells were exposed to FA (120μM)for24h. H2S attenuated the inhibitory effects of FA on BDNF expression. These dataindicate that the protective role of H2S in FA-induced neurotoxicity is involved inupregulation of BDNF.1.2blocking the BDNF-TrkB pathway by K252a reverses the protective effect ofH2S on FA-induced neurotoxicity in PC12cells.After pretreated with200μM of H2S for30min, PC12cells were exposed to FA (120μM) for24h, and K252a was added into the culture medium30min before H2Sapplication. K252a, the blocker of BDNF-TrkB pathway, reversed the protection ofH2S against FA-induced cytotoxicity, apoptosis, accumulation of cellular reactivealdehydes (4-HNE and MDA) and reactive oxygen species (ROS), activation ofCaspase-3, downregulation of Bcl-2expression and upregulation of Bax expression,which suggested that K5252a, blocking BDNF receptor TrkB, eliminates the effect ofH2S anti-formaldehyde-induced neurotoxicity.These results imply that BDNF-TrkB pathway mediates the protective role of H2S inFA-induced neurotoxicity.2. The protection of H2S against FA-induced neurotoxicity to PC12cells isinvolved in downregulation of ALDH2.2.1FA upregulates the expression and activity of ALDH2in PC12cells.After PC12cells were exposed to formaldehyde (60,120, or240μM) for24h, theexpression and activity of ALDH2was increased in a concentration-dependentmanner.2.2Inhibition of ALDH2activity by Dadzin antagonizes FA-inducedneurotoxicity to PC12cells. Pre-treatment of PC12cells with Dadzin (10μM) for30min significantly inhibitedthe reduction of cell viability and apoptosis and the accumulation of intracellularMDA,4-HNE and ROS induced by FA (120μΜ,24h), which indicated thatupregulation of ALDH2mediates the neurotoxicity of formaldehyde and thatinhibitiing the expression and activity ALDH2could lead to the reduction of FA-induced neurotoxicity.2.3H2S inhibits the expression of ALDH2in PC12cells.Treatment of PC12cells with H2S (100,200, or400μmol/L) for24h decreased theexpression of ALDH2in a concentration-dependent manner.2.4H2S inhibits formaldehyde-induced upregulation of ALDH2in PC12cells.Pretreatment of PC12cells with200μM of H2S for30min before24h exposure toformaldehyde (FA,120μM) attenuated FA-induced upregulation of ALDH2,indicating that the protective action of H2S is mediated by the inhibition of ALDH2.3. BDNF-TrkB pathway is involved in the down-regulation of ALDH2mediatedby H2S in PC12cells.Pretreatment of PC12cells with K252a (10nM), the blocker of BDNF-TrkB pathway,reversed H2S-induced the downregulation of ALDH2expression, which implied thatBDNF-TrkB pathway mediates the down-regulation of ALDH2caused by H2S.[Conclusions]BDNF-TrkB pathway mediates the protective role of H2S in formaldehyde-inducedneurotoxicity through down-regulation of ALDH2.