GABPA

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPDQ) has raised significant concerns due to its widespread distribution and high toxicity to aquatic organisms. However, the cardiac developmental toxicity of 6PPDQ and the underlying mechanisms remain unclear. In this study, we observed no notable alterations in heart morphology or embryo survival in zebrafish embryos exposed to 6PPDQ (0.2-2000 μg/L) up to 3 days post-fertilization (dpf). However, concentrations at 2 μg/L or higher induced cardiac dysfunctions, leading to lethal effects at later stages (6-8 dpf). We further found that the aryl hydrocarbon receptor (AHR) inhibitor CH22351 attenuated 6PPDQ-induced cardiac dysfunctions, implicating the involvement of AHR signal pathway. Moreover, 6PPDQ exposure led to an overproduction of reactive oxygen species (ROS) and an upregulation of genes associated with oxidative stress (sod1, sod2, and nrf2a). This was accompanied by an increase in oxidative DNA damage and the induction of p53-dependent extrinsic apoptosis. Co-exposure to the ROS scavenger N-acetylcysteine effectively counteracted the DNA damage and apoptosis induced by 6PPDQ. Importantly, inhibition of AHR or its downstream target cyp1b1 attenuated 6PPDQ-induced oxidative stress, DNA damage, and apoptosis. In conclusion, our results provide evidence that 6PPDQ induces oxidative stress through the AHR/cyp1b1 signaling pathway, leading to DNA damage and extrinsic apoptosis, ultimately resulting in cardiac dysfunction.

Tebuconazole exposure has been described as an increasing hazard to human health. An increasing number of recent studies have shown a positive association between tebuconazole exposure and cardiovascular disease risk, which is characterized by the reduction of adenosine triphosphate (ATP) synthesis. However, researches on the damage of tebuconazole exposure to energy metabolism and the related molecular mechanisms are limited. In the present study, male C57BL/6 mice were treated with tebuconazole at different low concentrations for 4 weeks. The results indicated that tebuconazole could accumulate in the heart and further induce the decrease of ATP content in the mouse heart. Importantly, tebuconazole induced an obvious shift in substrate utilization of fatty acid and glucose by disrupting their corresponding transporters (GLUT1, GLUT4, CD36, FABP3 and FATP1) expression, and significantly repressed the expression of mitochondrial biogenesis (Gabpa and Tfam) and oxidative phosphorylation (CS, Ndufa4, Sdhb, Cox5a and Atp5b) related genes in a dose-dependent manner. Further investigation revealed that these alterations were related to the IRS1/AKT and PPARγ/RXRα pathways. These findings contribute to a better understanding of triazole fungicide-induced cardiovascular disease by revealing the key indicators associated with this phenomenon.

Fat infiltration in muscle, called 'myosteatosis', precedes muscle atrophy, which subsequently results in sarcopenia. Myosteatosis is frequently observed in patients with nonalcoholic fatty liver disease (NAFLD). We have previously reported that retinoic acid receptor-related orphan receptor-α (RORα) regulates mitochondrial dynamics and mitophagy in hepatocytes, resulting in an alleviation of NAFLD. In this study, we aimed to investigate the role of RORα in skeletal muscle and to understand molecular mechanisms by which RORα controls mitochondrial capacity, using an NAFLD-associated myosteatosis mouse model.

To establish a myosteatosis model, 7-week-old C57BL/6N mice were fed with high-fat diet (HFD). After 15 weeks of diet feeding, an adeno-associated virus vector encoding RORα (AAV-RORα) was injected to gastrocnemius (GA) muscles, or after 7 weeks of HFD feeding, JC1-40, an RORα agonistic ligand, was administered daily at a dose of 5 mg/kg/day by oral gavage for 5 weeks. Histological, biochemical and molecular analyses in various in vivo and in vitro experiments were performed.

First, the number of oxidative MyHC2a fibres with intensive lipid infiltration increased by 3.8-fold in the red region of the GA of mice with myosteatosis (P < 0.001). RORα was expressed around MyHC2a fibres, and its level increased by 2.7-fold after HFD feeding (P < 0.01). Second, treatment of RORα ligands in C2C12 myoblasts, such as cholesterol sulfate and JC1-40, enhanced the number of oxidative fibres stained for MyHC1 and MyHC2a by two-fold to four-fold (P < 0.01), while it reduced the lipid levels in MyHC2a fibres by 20-50% (P < 0.001) in the presence of palmitic acids. Third, mitochondrial membrane potential (P < 0.01) and total area of mitochondria (P < 0.01) were enhanced by treatment of these ligands. Chromatin immunoprecipitation analysis showed that RORα bound the promoter of GA-binding protein α subunit gene that led to activation of mitochondrial transcription factor A (TFAM) in C2C12 myoblasts (P < 0.05). Finally, intramuscular transduction of AAV-RORα alleviated the HFD-induced myosteatosis with fatty atrophy; lipid contents in MyHC2a fibres decreased by 48% (P < 0.001), whereas the number of MyHC2b fibre increased by 22% (P < 0.001). Also, administration of JC1-40 improved the signs of myosteatosis in that it decreased the level of adipose differentiation-related protein (P < 0.01) but increased mitochondrial proteins such as cytochrome c oxidase 4 and TFAM in GA muscle (P < 0.01).

RORα plays a versatile role in regulating the quantity of mitochondria and the oxidative capacity, ultimately leading to an improvement in myosteatosis symptoms.