Extracellular αB-crystallin modulates the inflammatory responses.

Abstract Neuroinflammation is considered a challenging clinical problem. Chronic inflammatory responses play important roles in the onset and progression of various neurodegenerative diseases, including multiple sclerosis (MS). Previous studies have shown that astrocytes express small heat shock protein αB-crystallin (CRYAB) which is capable of inhibiting inflammatory responses in astrocytes per se. However, the underlying mechanisms of CRYAB-induced modulation of neuroinflammation are still not fully understood. In the present study, we investigated the role of extracellular CRYAB in the interaction between microglia and astrocytes in the context of MS-associated neuroinflammation. We found that the expression of CRYAB was profoundly increased in EAE mice. CRYAB was preferentially expressed in astrocytes and could be secreted via exosomes. Levels of exosomal CRYAB secreted from astrocytes were markedly increased under stress conditions. Furthermore, incubation of immortalized astrocytes or microglia cell lines with CRYAB remarkably suppressed astrocytes and microglia-mediated inflammatory responses in both autocrine and paracrine manners. Our results reveal a novel function for extracellular CRYAB in the regulation of neuroinflammation. Targeting extracellular CRYAB-modulated neuroinflammation is a potential therapeutic intervention for MS. Highlights • In EAE mice, expression of CRYAB along with pro-inflammatory mediators are markedly increased. • CRYAB is preferentially expressed in astrocytes, but not in microglia. • CRYAB is secreted via exosomes. Pro-inflammatory stimulation of U251 cells increases levels of CRYAB in secreted exosomes. • Extracellular CRYAB protein markedly suppresses LPS-induced neuroinflammation. [ABSTRACT FROM AUTHOR]