SIRT7-Mediated H2BK120 Succinylation Drives Aberrant Mitophagy in Sepsis-Associated Cognitive Dysfunction.

Summary

This study identifies a SIRT7–H2BK120 succinylation–PD-1/PD-L1–PINK1/Parkin pathway linking metabolic accumulation to aberrant neuronal mitophagy in sepsis-associated encephalopathy (SAE). Reduction of succinylation or inhibition of PD-1/PD-L1 signaling reduced neuronal injury and improved cognition, whereas neuron-specific Sirt7 deletion worsened the phenotype. SIRT7 overexpression reversed these pathological changes, supporting succinylation control as a therapeutic strategy.

Key Findings

• Septic mice showed hippocampal succinate and succinyl-CoA accumulation with increased neuronal H2BK120 succinylation.
• H2BK120 succinylation at the Pdcd1 promoter activated the PD-1/PD-L1 axis and promoted PINK1/Parkin-dependent mitophagy, mitochondrial dysfunction, and neuronal apoptosis.
• SIRT7 overexpression reduced succinylation-associated pathology and improved cognitive dysfunction, whereas neuron-specific Sirt7 deletion exacerbated it.

Clinical Implications

The findings support investigation of succinylation-modulating or PD-1/PD-L1-directed strategies for SAE, but they do not justify clinical use. Because these pathways regulate host immunity and neuronal metabolism, safety, timing, cell specificity, and effects on infection control must be established before translation.

Limitations

• The evidence is primarily derived from experimental mouse models and does not demonstrate that the pathway operates in human SAE.
• The safety and feasibility of manipulating SIRT7, histone succinylation, or PD-1/PD-L1 signaling during active infection remain unresolved.

Future Directions

Future work should validate the pathway in human brain or cerebrospinal-fluid samples, define the therapeutic window and cell specificity, and test whether pathway modulation preserves antimicrobial immunity while improving long-term neurological outcomes.