# SS-31 improves post-cardiac arrest brain injury by inhibiting microglial ferroptosis and polarization

## TL;DR

SS-31, a mitochondria-targeting peptide, reduces brain injury after cardiac arrest by inhibiting microglial ferroptosis and shifting microglia to an anti-inflammatory state.

## Contribution

This study demonstrates that SS-31 improves post-cardiac arrest brain injury through inhibition of microglial ferroptosis and regulation of the Sesn2 signaling pathway.

## Key findings

- SS-31 improved survival rates and neurological outcomes in post-cardiac arrest rats.
- SS-31 reduced microglial ferroptosis and shifted microglia from pro-inflammatory M1 to anti-inflammatory M2 phenotype.
- The protective effects of SS-31 were mediated through the Sesn2 signaling pathway.

## Abstract

Accumulating evidence suggests that ferroptosis and mitochondrial dysfunction contribute significantly to brain injury following cardiac arrest (CA) and resuscitation. SS-31, a novel mitochondria-targeting peptide, has demonstrated protective effects against mitochondrial dysfunction induced by ischemia/reperfusion injury. This study aimed to investigate the neuroprotective effects of SS-31 in post-CA brain injury and clarify the underlying signaling mechanisms. An in vivo rat model of CA and resuscitation was established. Following resuscitation, animals were randomly divided into three groups: a saline-treated control group, an SS-31-treated group, and a sham-operated control group. Survival rates, neurological deficit scores, serum neuronal injury markers (NSE and S100B), and histopathological changes were evaluated for up to 72 ​h post-resuscitation. Mechanistically, ferroptosis-related signaling pathways were examined, including glutathione peroxidase 4 (GPX4) expression, iron accumulation, oxidative stress markers, and pro-inflammatory cytokine levels, utilizing microglia-specific Sesn2 knockdown via adeno-associated virus vectors. In vitro experiments were performed on BV2 cells subjected to oxygen-glucose deprivation/reoxygenation, assessing cell viability, lipid peroxidation, ferroptosis-associated protein expression, and cytokine secretion following SS-31 intervention. Brain injury post-CA and resuscitation is significantly accompanied by ferroptosis of microglia. Treatment with SS-31 substantially improved survival rates, reduced neurological deficits, and lowered serum NSE and S100B levels. Mechanistically, SS-31 attenuated ferroptosis and promoted an anti-inflammatory shift in microglial polarization by enhancing GPX4 expression and decreasing iron content, oxidative stress, and pro-inflammatory cytokines. These effects were primarily mediated via the Sesn2 signaling pathway. SS-31 could effectively improve post-CA brain injury, in which the mechanism was potentially related to the inhibition of microglial ferroptosis and polarization through the regulation of Sesn2 signaling pathway.

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•SS-31 enhances survival and neurological outcomes after cardiac arrest.•SS-31 reduces microglial ferroptosis and promotes a shift from the pro-inflammatory M1 phenotype toward the anti-inflammatory M2 phenotype.•SS-31 exerts neuroprotection against post-cardiac arrest brain injury by regulating Sesn2-mediated signaling.

SS-31 enhances survival and neurological outcomes after cardiac arrest.

SS-31 reduces microglial ferroptosis and promotes a shift from the pro-inflammatory M1 phenotype toward the anti-inflammatory M2 phenotype.

SS-31 exerts neuroprotection against post-cardiac arrest brain injury by regulating Sesn2-mediated signaling.