Loss of TSPOAP1 exacerbates mitochondrial dysfunction and neuronal apoptosis after intracerebral hemorrhage

Abstract

Intracerebral hemorrhage (ICH) induces severe secondary neuronal injury, in which mitochondrial dysfunction and apoptosis play central roles. Accumulating evidence suggests that mitochondrial failure represents a critical convergence point linking diverse injurious stimuli to neuronal apoptosis after ICH. However, the molecular mechanisms that connect mitochondrial dysfunction to irreversible apoptotic commitment remain incompletely understood. In particular, the upstream regulators governing mitochondrial permeability transition pore (mPTP) opening during ICH have yet to be fully defined. Transcriptomic analyses of perihematomal tissue from patients with ICH and mouse models were integrated with functional studies using an HT22 neuronal cell line deficient in 18-kDa translocator protein (TSPO)-associated protein 1 (TSPOAP1), together with pharmacological intervention using FG-7142. Mitochondrial integrity, mPTP opening, apoptotic signaling, and protein–protein interactions were evaluated in vitro and in vivo. The mitochondria-associated protein TSPOAP1 was markedly downregulated after ICH in both human and mouse brains and was predominantly expressed in neurons. TSPOAP1 deficiency was associated with substantial mitochondrial impairment, evidenced by membrane depolarization, ultrastructural abnormalities, elevated mPTP opening, and increased neuronal apoptosis, along with disruption of the Bax/Bcl-2 balance and cytochrome c leakage. Loss of TSPOAP1 sensitized mPTP opening and was accompanied by increased mitochondrial oxidative stress, while remaining relatively insensitive to cyclophilin D (CypD) inhibition. Mechanistically, TSPOAP1 was associated with adenine nucleotide translocator 2 (ANT2). FG-7142 increased TSPOAP1 expression, maintained mitochondrial homeostasis, suppressed neuronal apoptosis in vitro, and promoted functional recovery after ICH in vivo. Notably, these beneficial effects were markedly attenuated in the absence of TSPOAP1. This study identifies TSPOAP1 as a previously unrecognized mitochondrial protective factor that influences neuronal apoptosis after ICH by regulating ANT2-associated, CypD-independent mPTP opening. Enhancing TSPOAP1 function represents a promising therapeutic strategy for mitigating mitochondrial dysfunction and secondary brain injury following ICH.