Peripherally expressed misfolded proteins remotely disrupt brain function and aggravate stroke-induced brain injury

Impaired proteostasis has been linked to various diseases, whereas little is known about the impact of peripherally misfolded proteins on the brain. We here studied the brain of mice with cardiomyocyte-restricted overexpression of a missense (R120G) mutant small heat shock protein, αB-crystallin (CryAB). At baseline, the CryAB mice showed impaired cognitive and motor functions, aberrant protein aggregates, neuroinflammation, impaired blood-brain barrier, and reduced proteasome activity in the brain compared with their non-transgenic (Ntg) littermates. Ischemic stroke dramatically exacerbated these pathological alterations and caused more severe brain dysfunction in CryAB mice than in the Ntg mice. Intravenously injecting the exosomes isolated from CryAB mouse blood into wild-type mice caused the similar phenotypes seen from CryAB mice. Importantly, the CryAB protein showed the prion-like properties. These results suggest that peripherally misfolded proteins in the heart remotely disrupt brain function through prion-like neuropathology, which may represent an underappreciated mechanism underlying heart-brain crosstalk.