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The oncometabolite 2-hydroxyglutarate inhibits microglial activation via the AMPK/mTOR/NF-?B pathway.

ABSTRACT: Microglia, the brain-resident macrophage, is known as the innate immune cell type in the central nervous system. Microglia is also the major cellular component of tumor mass of gliomas that plays a key role in glioma development. Mutations of isocitrate dehydrogenases 1 and 2 (IDH1/2) frequently occur in gliomas, which leads to accumulation of oncometabolic product 2-hydroxyglutarate (2HG). Moreover, IDH1/2 mutations were found to correlate with better prognosis in glioma patients. In the present study, we investigated the effects of the 2HG on microglial inflammatory activation. We showed that the conditioned media (CM) from GL261 glioma cells stimulated the activation of BV-2 microglia cells, evidenced by markedly increased expression of interleukin-6 (IL-6), IL-1?, tumor necrosis factor-? (TNF-?), CCL2 (C-C motif chemokine ligand 2) and CXCL10 (C-X-C motif chemokine 10). CM-induced expression of proinflammatory genes was significantly suppressed by pretreatment with a synthetic cell-permeable 2HG (1?mM) or a nuclear factor-?B (NF-?B) inhibitor BAY11-7082 (10??M). In lipopolysaccharide (LPS)- or TNF-?-stimulated BV-2 microglia cells and primary microglia, pretreatment with 2HG (0.25-1?mM) dose-dependently suppressed the expression of proinflammatory genes. We further demonstrated that 2HG significantly suppressed LPS-induced phosphorylation of I?B kinase ?/? (IKK?/?), I?B? and p65, I?B degradation, and nuclear translocation of p65 subunit of NF-?B, as well as NF-?B transcriptional activity. Similarly, ectopic expression of mutant isocitrate dehydrogenase 1 (IDH1) (R132H) significantly decreased TNF-?-induced activation of NF-?B signaling pathway. Finally, we revealed that activation of adenosine 5'-monophosphate-activated protein kinase (AMPK) and subsequent inhibition of mammalian target of rapamycin (mTOR) signaling contributed to the inhibitory effect of 2HG on NF-?B signaling pathway in BV-2 cells. Taken together, these results, for the first time, show that oncometabolite 2HG inhibits microglial activation through affecting AMPK/mTOR/NF-?B signaling pathway and provide evidence that oncometabolite 2HG may regulate glioma development via modulating microglial activation in tumor microenvironment.

SUBMITTER: Han CJ

PROVIDER: S-EPMC6786375 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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Project description:BackgroundAMP-activated Protein Kinase (AMPK) is a stress-activated kinase that protects against cardiomyocyte injury during ischemia and reperfusion. c-Jun N-terminal kinase (JNK), a mitogen activated protein kinase, is activated by ischemia and reperfusion. NF-κB is an important transcription factor involved in ischemia and reperfusion injury.Methods and resultsThe intrinsic activation of AMPK attenuates the inflammation which occurred during ischemia/reperfusion through the modulation of the JNK mediated NF-κB signaling pathway. Rat cardiac myoblast H9c2 cells were subjected to hypoxia and/or reoxygenation to investigate the signal transduction that occurred during myocardial ischemia/reperfusion. Mitochondrial function was measured by the Seahorse XF24 V7 PS system. Hypoxia treatment triggered AMPK activation in H9c2 cells in a time dependent manner. The inhibition of hypoxic AMPK activation through a pharmacological approach (Compound C) or siRNA knockdown of AMPK α catalytic subunits caused dramatic augmentation in JNK activation, inflammatory NF-κB phosphorylation, and apoptosis during hypoxia and reoxygenation. Inhibition of AMPK activation significantly impaired mitochondrial function and increased the generation of reactive oxygen species (ROS) during hypoxia and reoxygenation. In contrast, pharmacological activation of AMPK by metformin significantly inhibited mitochondrial permeability transition pore (mPTP) opening and ROS generation. Moreover, AMPK activation significantly attenuated the JNK-NF-κB signaling cascade and inhibited mRNA and protein levels of pro-inflammatory cytokines, such as TNF-α and IL-6, during hyopoxia/reoxygenation in H9c2 cells. Intriguingly, both pharmacologic inhibition of JNK by JNK-IN-8 and siRNA knockdown of JNK signaling pathway attenuated NF-κB phosphorylation and apoptosis but did not affect AMPK activation in response to hypoxia and reoxygenation.ConclusionsAMPK activation modulates JNK-NF-κB signaling cascade during hypoxia and reoxygenation stress conditions. Cardiac AMPK activation plays a critical role in maintaining mitochondrial function and inhibiting the inflammatory response caused by ischemic insults.

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The oncometabolite 2-hydroxyglutarate inhibits microglial activation via the AMPK/mTOR/NF-?B pathway.

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