Neuro-regulator role of H2S in astrocyte activation and its effects on neurological damage and behavior of VPA-exposed rats.

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder increasingly associated with aberrant astrocyte activation. Hydrogen sulfide (H2S) has recently emerged as a key regulator of astrocyte function, yet its role in ASD remains largely unexplored. Here, we investigated the association between H₂S modulation, ASD-like phenotypes, and astrocyte activation. In valproic acid (VPA)-exposed rats, H₂S were modulated using α-lipoic acid (LA) or aminooxyacetic acid (AOAA), a cystathionine β-synthase (CBS) inhibitor. Behavioral performance, neuronal injury, astrocyte phenotypes, H₂S levels, CBS expression and the homocysteine/cystathionine ratio were evaluated in vivo and in primary astrocytes. VPA-exposed rats exhibited reduced H₂S levels and CBS expression, an increased homocysteine/cystathionine ratio, ASD-like behavioral deficits and neuronal injury, and astrocyte activation toward a neurotoxic A1 phenotype. Elevation of H2S by LA was associated with improvements in ASD behavioral performance, reduced neuronal damage, reduced inflammatory cytokines and suppressed astrocyte activation, with changes in astrocyte marker expression towards a more A2-like, neuroprotective profile. Conversely, AOAA reversed these beneficial effects. Collectively, these findings suggested enhanced H₂S signaling is linked to improvements in ASD-like behavioral and neuropathological abnormalities, alongside modulation of astrocyte activation involving the CBS/H₂S pathway. These findings highlight the potential involvement of the CBS/H₂S axis in ASD-related pathology.