OP07 Neuroprotective effect of hydrogen sulfide: Regulation of amyloidosis and inflammation in SH-SY5Y neuroblastoma and BV-2 microglia cells

Abstract

The excessive accumulation of amyloid peptide and chronic neuroinflammation have been shown to play indisputable roles in pathogenesis of Alzheimer’s disease (AD). In the process of ongoing neurological damage in AD, increased extracellular levels of ATP and its metabolites (e.g. adenosine) in brain worsen the scenario by evoking the cascade of harmful events. The goal of this project was to investigate anti-amyloidogenic and anti-inflammatory effects of hydrogen sulfide (H 2 S) in various in vitro experimental models used for studying AD pathology. We found that NaHS attenuated HENECA (selective A2A adenosinergic receptor agonist) induced amyloid β -42 (A β 42) production in SH-SY5Y cells. NaHS interfered with the production and post-translational modification of amyloid precursor protein (APP) by inhibiting APP maturation. While NaHS did not affect β -secretase activity, it significantly inhibited γ -secretase activity. NaHS induced-reductions were accompanied by similar decreases in intracellular cAMP levels and phosphorylation of cAMP responsive element binding protein (CREB). Moreover, studies using forskolin (adenylyl cyclase agonist) and IBMX (phosphodiesterase inhibitor) suggested that NaHS may preferentially suppress adenylyl cyclase activity when it is stimulated. Therefore, H 2 S protects SH-SY5Y cells against HENECA induced amyloidogenesis by inhibiting γ -secretase via cAMP dependent pathway. Consistent with its effect in SH-SY5Y cells, NaHS significantly reduced ATP induced APP holoprotein production and A β 42 levels in murine microglial BV-2 cells. We found that NaHS suppressed ATP induced production of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF- α ) and interleukin - 1 beta (IL-1 β ). NaHS reversed the upregulation of oxidative stress markers like nitric oxide (NO) and reactive oxygen species (ROS) accompanied by decreases in the protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Furthermore, NaHS suppressed ATP augmentation of extracellular signal-regulated protein kinases 1 and 2 (ERK 1/2) expression as P2 purinergic receptor couple to the ERK signaling pathway. We also found that inhibition of ERK pathway by NaHS blocked specific serine phosphorylation of signal transducer and activator of transcription 3 (STAT3) transcription factor which regulates genes participating in inflammation and amyloidogenesis. To this end, we found that H 2 S inhibits ATP induced inflammation and amyloidogenesis in BV-2 cells via regulating ERK1/2 and STAT3 signaling pathway. Overall, our results demonstrate that by combination of anti-amyloidogenic and anti-inflammatory properties, H 2 S can be of immense therapeutic value in treatment of AD.