# Enriched Environment Ameliorates Cerebral Ischemia–Reperfusion Injury via Dopamine–H2S Axis-Mediated Dual Mitophagy Activation

## TL;DR

An enriched environment helps protect the brain after stroke by boosting H2S and activating two pathways to clear damaged mitochondria.

## Contribution

Reveals a novel dopamine–H2S axis mechanism linking enriched environments to dual mitophagy activation in cerebral ischemia–reperfusion injury.

## Key findings

- EE improved neurological outcomes and reduced oxidative damage in ischemic models.
- EE activates both PINK1/parkin and HIF-1α/BNIP3L mitophagy pathways via H2S.
- H2S synthesis is upregulated by dopamine-induced calcium influx through calmodulin signaling.

## Abstract

Cerebral ischemia–reperfusion injury triggers mitochondrial dysfunction and oxidative stress, exacerbating neuronal apoptosis. Emerging evidence highlights hydrogen sulfide (H2S) as a gasotransmitter modulating redox balance, autophagy, and apoptosis. This study investigates the neuroprotective mechanisms of Enriched Environment (EE) against ischemic injury, focusing on mitochondrial dynamics and H2S-mediated pathways. Using MCAO mice and OGD/R-treated SH-SY5Y neurons, interventions targeting H2S synthesis, hypoxia-inducible factor 1-alpha (HIF-1α), and mitophagy were implemented. Behavioral, histological, and molecular analyses demonstrated EE significantly improved neurological outcomes, suppressed apoptosis, and attenuated oxidative damage (reduced MDA, elevated MnSOD/glutathione). Mechanistically, EE enhanced mitophagy via dual pathways: canonical PINK1/parkin-mediated mitochondrial clearance, corroborated by transmission electron microscope and LC3B/parkin colocalization, and non-canonical HIF-1α/BNIP3L axis activation. Transcriptomic and Co-immunoprecipitation (Co-IP) data revealed EE upregulated endogenous H2S biosynthesis post-injury by promoting dopamine-induced calcium influx, which activated calmodulin-dependent signaling to stimulate cystathionine β-synthase/γ-lyase expression. Pharmacological blockade of H2S synthesis or HIF-1α abolished mitochondrial protection, confirming H2S as a central mediator. Notably, H2S exerted antiapoptotic effects by restoring mitochondrial integrity through synergistic mitophagy activation and oxidative stress mitigation. These findings propose a novel neuroprotective cascade: EE-induced dopaminergic signaling potentiates H2S production, which coordinates PINK1/parkin and HIF-1α/BNIP3L pathways to eliminate dysfunctional mitochondria, thereby preserving neuronal homeostasis. This study elucidates therapeutic potential of EE via H2S-driven mitochondrial quality control, offering insights for ischemic brain injury intervention.