S100A9 and subarachnoid hemorrhage: For example, in models of subarachnoid hemorrhage, increased lactate and lactylation of β-arrestin1 (ARRB1) in neurons led to mitochondrial respiratory dysfunction, reduced ATP synthesis, and enhanced neuronal apoptosis, effects that were mediated through the upregulation of S100A9 and could be mitigated by targeting the lactylation process (Mi et al., 2025).