Dataset Information

Microglial PGC-1α protects against ischemic brain injury by suppressing neuroinflammation.

ABSTRACT:

Background

Neuroinflammation and immune responses occurring minutes to hours after stroke are associated with brain injury after acute ischemic stroke (AIS). PPARγ coactivator-1α (PGC-1α), as a master coregulator of gene expression in mitochondrial biogenesis, was found to be transiently upregulated in microglia after AIS. However, the role of microglial PGC-1α in poststroke immune modulation remains unknown.

Methods

PGC-1α expression in microglia from human and mouse brain samples following ischemic stroke was first determined. Subsequently, we employed transgenic mice with microglia-specific overexpression of PGC-1α for middle cerebral artery occlusion (MCAO). The morphology and gene expression profile of microglia with PGC-1α overexpression were evaluated. Downstream inflammatory cytokine production and NLRP3 activation were also determined. ChIP-Seq analysis was performed to detect PGC-1α-binding sites in microglia. Autophagic and mitophagic activity was further monitored by immunofluorescence staining. Unc-51-like autophagy activating kinase 1 (ULK1) expression was evaluated under the PGC-1α interaction with ERRα. Finally, pharmacological inhibition and genomic knockdown of ULK1 were performed to estimate the role of ULK1 in mediating mitophagic activity after ischemic stroke.

Results

PGC-1α expression was shortly increased after ischemic stroke, not only in human brain samples but also in mouse brain samples. Microglia-specific PGC-1α overexpressing mice exhibited significantly decreased neurologic deficits after ischemic injury, with reduced NLRP3 activation and proinflammatory cytokine production. ChIP-Seq analysis and KEGG pathway analysis revealed that mitophagy was significantly enhanced. PGC-1α significantly promoted autophagic flux and induced autolysosome formation. More specifically, the autophagic clearance of mitochondria was enhanced by PGC-1α regulation, indicating the important role of mitophagy. Pharmacological inhibition or knockdown of ULK1 expression impaired autophagic/mitophagic activity, thus abolishing the neuroprotective effects of PGC-1α.

Conclusions

Mechanistically, in AIS, PGC-1α promotes autophagy and mitophagy through ULK1 and reduces NLRP3 activation. Our findings indicate that microglial PGC-1α may be a promising therapeutic target for AIS.

SUBMITTER: Han B

PROVIDER: S-EPMC8004413 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description:Hypoxic-ischemia (HI) is a major cause of acquired visual impairment in children from developed countries. Previous studies have shown that systemic administration of 7,8-dihydroxyavone (DHF), a selective tropomyosin receptor kinase B (TrkB) agonist, provides long-term neuroprotection against HI injury in an immature retina. However, the target genes and the mechanisms of the neuroprotective effects of TrkB signaling are not known. In the present study, we induced an HI retinal injury through unilateral common carotid artery ligation followed by 8% oxygen for 2 h in P7 rat pups. DHF was administered intraperitoneally 2 h before and 18 h after the HI injury. A polymerase chain reaction (PCR) array was used to identify the target genes upregulated after the DHF treatment, which was then confirmed with quantitative real-time reverse transcriptase PCR and a western blot. Effects of the downstream mediator of DHF were assessed using an intravitreal injection of neutralizing antibody 4 h after DHF administration (24 h after HI). Meanwhile, the target protein was injected into the vitreous 24 h after HI to validate its protective effect when exogenously supplemented. We found that systemic DHF treatment after HI significantly increased the expression of the artemin (ARTN) gene and protein at P8 and P10, respectively. The neuroprotective effects of DHF were inhibited after the ARTN protein blockade, with an increase in neuroinflammation and astrogliosis. ARTN treatment showed long-term protection against HI injury at both the histopathological and functional levels. The neuroprotective effects of ARTN were related to a decrease in microglial activation at P17 and attenuation of astrogliosis at P29. ARTN enhances phosphorylation of RET, ERK, and JNK, but not AKT or p38 in the immature retina. Altogether, these results suggest that the neuroprotective effect of a TrkB agonist is partially exerted through a mechanism that involves ARTN because the protective effect is ameliorated by ARTN sequestration. ARTN treatment after HI injury protects the immature retina by attenuating late neuroinflammation and astrogliosis in the immature retina relating to the ARTN/RET/JNK/ERK signaling pathway. ARTN may be a strategy by which to provide long-term protection in the immature retina against HI injury.

Project description:Background/Aims:Increasing evidence have associated mitochondrial dysfunction and reactive oxygen species (ROS) generation to neuron loss in multiple sclerosis (MS). PGC-1α regulates mitochondrial biogenesis and respiration and plays a pivotal role in modulating ROS levels. Here, we investigated the potential function of peroxisome proliferator-activated receptor-γ co-activator-1α (PGC-1α) in the mammalian MS disease model, EAE experimental autoimmune encephalomyelitis (EAE). Methods:We used WT mice to evaluate the change of PGC during the course of EAE. The transgenic mice with neuron-specific overexpression of PGC-1α was applied to explore how PGC1 in neuron affects EAE outcome. A neuronal cell line of lentivirus transfection leading to PGC-1α markedly increased was applied to verify the protective effects of PGC1 in neurons. RNA-seq was employed to explore the potential target genes and signaling pathways. Results: We observed that PGC-1α were decreased at 13d, continuously decreased at 20d, then mildly increased at 30d in wild-type (WT) EAE mice, which is accompanied with alterations of mitochondrial antioxidants SOD2, Prx3, Trx2 and UCP4,5. Our study revealed that PGC-1αf/f Eno2-Cre mice improved EAE clinical symptoms, ameliorated inflammation and demyelination in spinal cords, increased mitochondrial antioxidants SOD2, Prx3, Trx2 and UCPs, reduced the production of ROS and inhibited the apoptotic pathways. In addition, PGC-1αf/f Eno2-Cre mice showed decreased apoptotic neurons compared with the WT EAE mice. In vitro, overexpressing PGC-1α by lentivirus transfection revealed similar results with that of in vivo by using NSC-34 cells treated with 1mg/ml lipopolysaccharide (LPS). Furthermore, RNA-seq analysis showed that apoptotic processes were significantly enriched in the top 10 significant GO terms of differentially expressed (DE) gene and apotosis pathway was significantly enriched in KEGG pathway analysis. Conclusion: Taken together, our findings indicate that upregulation of neuronal PGC-1α protected neuron apotosis in EAE and in vitro.