HIRI is an important clinical challenge that occurs when blood supply to the liver is temporarily interrupted and then restored, as commonly seen in liver resection and liver transplantation. Current research indicates that the injury includes oxidative stress, mitochondrial dysfunction, metabolic imbalance, and excessive inflammation. Although strategies such as reducing ischemic time, ischemic preconditioning, antioxidants, and mitochondrial protectors have been investigated, their protective effects remain limited. A key unresolved problem is how mitochondrial lipid metabolism, mtDNA-centered oxidative stress, and inflammatory signaling interact to enhance liver injury.
A study (DOI: 10.48130/targetome-0026-0011) published in Target March 31, 2026 By Xiaojiaoyang Li’s group, Peking University of Chinese Medicine, ACT protects against HIRI by suppressing CMPK2-mediated mitochondrial redox dysregulation and blocking the lipotoxicity-oxidative stress-inflammation cycle.
To determine the role of CMPK2 and the protective mechanism of ACT, the researchers combined animal models, cell models, sequence analysis, and molecular biology experiments. In mice, they established a model of 70% hepatic ischemia followed by reperfusion and treated animals with different doses of ACT, using N-acetylcysteine as a positive control. They also constructed a hepatocyte-specific CMPK2 overexpression model to test whether CMPK2 was necessary for ACT-mediated protection. In vitro, AML12 hepatocytes were exposed to hypoxia/reoxygenation to mimic ischemia-reperfusion stress, followed by ACT treatment, gene silencing, recombinant protein stimulation, and mtDNA transfection. RNA sequencing of whole liver tissue and isolated hepatocytes showed that HIRI strongly altered pathways related to ATP synthesis, lipid metabolism, mitochondrial electron transport, apoptosis, and inflammation. ACT reversed many of these transcriptional changes. Further analysis identified CMPK2 and MYD88 as common critical targets. The team found that HIRI increased acyl-CoA thioesterase 2 (ACOT2), promoting the accumulation of free fatty acids in the mitochondria. This lipid overload enhanced ROS production and impaired mitochondrial oxidative metabolism. ACT decreased ACOT2 expression, reduced free fatty acid levels, restored genes related to fatty acid β-oxidation, increased ATP production, and improved mitochondrial complex I and IV activities. The researchers then examined oxidative damage associated with mtDNA. HIRI and hypoxia/reoxygenation increased CMPK2 expression, mtDNA synthesis, oxidized mtDNA accumulation, mitochondrial permeability transition pore opening, and mtDNA release. Released mtDNA activated TLR9-MYD88-NF-MrPathway B, which promoted nuclear translocation of interferon regulatory factor 1 (IRF1). IRF1 further stimulated the transcription of Cmpk2 and Duox2, creating a detrimental feedback loop that enhanced ROS generation and inflammatory signaling. ACT interrupted this cycle by inhibiting IRF1 nuclear translocation, reducing Cmpk2 and Duox2 transcription, and limiting mtDNA leakage. Binding assays, including DARTS, CETSA, SPR, and MST, further suggested that ACT may directly interact with CMPK2 and promote its mitophagy-dependent degradation. Importantly, hepatocyte-specific CMPK2 overexpression attenuated the protective effects of ACT, confirming CMPK2 as a central therapeutic target.
Taken together, the study establishes CMPK2 as a key regulator linking mitochondrial lipid metabolism, redox imbalance, mtDNA release and inflammasome activation in HIRI. By targeting CMPK2 and the TLR9-IRF1-CMPK2/DUOX2-mtDNA axis, ACT provides a mechanistic basis for the development of new interventions to reduce liver injury associated with transplantation and major liver surgery.
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