USP4 modulates ZBP1 ubiquitination to regulate microglial PANoptosis and functional outcomes following traumatic brain injury.

Secondary damage in traumatic brain injury (TBI) is characterized by the abnormal release of damage-associated molecular patterns and excessive production of pro-inflammatory cytokines. Neuroinflammation is a hallmark of TBI. However, the mechanisms through which immune cells contribute to cognitive deficits and secondary inflammatory pathology remain poorly understood. In this study, we found that ZBP1-mediated microglial PANoptosis, which is a distinct form of innate immune-driven inflammatory cell death, is triggered following TBI. We further determined that microglial PANoptosis is induced by the synergistic action of heme and TNF-α. Mechanistically, we identified USP4 as a critical deubiquitinase for ZBP1 in microglia. USP4 was found to interact with, deubiquitinate, and stabilize ZBP1. Notably, AKT-mediated phosphorylation was found to be essential for maintaining USP4 protein stability. Pharmacological inhibition of USP4 using Vialinin A led to ZBP1 degradation, reduced microglial PANoptosis, and the amelioration of TBI-related functional deficits. Moreover, USP4 expression levels were found to be negatively correlated with prognosis patients with severe TBI. Collectively, our findings highlight a crucial role for USP4 in facilitating ZBP1-mediated inflammasome activation, microglial death, and cognitive impairment post-TBI, underscoring its potential as a therapeutic target.