Dataset Information

Peripherally misfolded proteins exacerbate ischemic stroke-induced neuroinflammation and brain injury.

ABSTRACT:

Background

Protein aggregates can be found in peripheral organs, such as the heart, kidney, and pancreas, but little is known about the impact of peripherally misfolded proteins on neuroinflammation and brain functional recovery following ischemic stroke.

Methods

Here, we studied the ischemia/reperfusion (I/R) induced brain injury in mice with cardiomyocyte-restricted overexpression of a missense (R120G) mutant small heat shock protein, ?B-crystallin (CryAB^R120G), by examining neuroinflammation and brain functional recovery following I/R in comparison to their non-transgenic (Ntg) littermates. To understand how peripherally misfolded proteins influence brain functionality, exosomes were isolated from CryAB^R120G and Ntg mouse blood and were used to treat wild-type (WT) mice and primary cortical neuron-glia mix cultures. Additionally, isolated protein aggregates from the brain following I/R were isolated and subjected to mass-spectrometric analysis to assess whether the aggregates contained the mutant protein, CryAB^R120G. To determine whether the CryAB^R120G misfolding can self-propagate, a misfolded protein seeding assay was performed in cell cultures.

Results

Our results showed that CryAB^R120G mice exhibited dramatically increased infarct volume, delayed brain functional recovery, and enhanced neuroinflammation and protein aggregation in the brain following I/R when compared to the Ntg mice. Intriguingly, mass-spectrometric analysis of the protein aggregates isolated from CryAB^R120G mouse brains confirmed presence of the mutant CryAB^R120G protein in the brain. Importantly, intravenous administration of WT mice with the exosomes isolated from CryAB^R120G mouse blood exacerbated I/R-induced cerebral injury in WT mice. Moreover, incubation of the CryAB^R120G mouse exosomes with primary neuronal cultures induced pronounced protein aggregation. Transduction of CryAB^R120G aggregate seeds into cell cultures caused normal CryAB proteins to undergo dramatic aggregation and form large aggregates, suggesting self-propagation of CryAB^R120G misfolding in cells.

Conclusions

These results suggest that peripherally misfolded proteins in the heart remotely enhance neuroinflammation and exacerbate brain injury following I/R likely through exosomes, which may represent an underappreciated mechanism underlying heart-brain crosstalk.

SUBMITTER: Liu Y

PROVIDER: S-EPMC7818745 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Publications

Peripherally misfolded proteins exacerbate ischemic stroke-induced neuroinflammation and brain injury.

Liu Yanying Y Subedi Kalpana K Baride Aravind A Romanova Svetlana S Callegari Eduardo E Huber Christa C CC Wang Xuejun X Wang Hongmin H

Journal of neuroinflammation 20210120 1

<h4>Background</h4>Protein aggregates can be found in peripheral organs, such as the heart, kidney, and pancreas, but little is known about the impact of peripherally misfolded proteins on neuroinflammation and brain functional recovery following ischemic stroke.<h4>Methods</h4>Here, we studied the ischemia/reperfusion (I/R) induced brain injury in mice with cardiomyocyte-restricted overexpression of a missense (R120G) mutant small heat shock protein, αB-crystallin (CryAB<sup>R120G</sup>), by ex ...[more]

PMID: 33472658

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Project description:BackgroundNeuroinflammation 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.MethodsPGC-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.ResultsPGC-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.ConclusionsMechanistically, 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.

Dataset Information

Peripherally misfolded proteins exacerbate ischemic stroke-induced neuroinflammation and brain injury.

Background

Methods

Results

Conclusions

Publications

Peripherally misfolded proteins exacerbate ischemic stroke-induced neuroinflammation and brain injury.

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