GRP78 alleviates secondary brain injury by regulating phenotype polarization in astrocytes via JAK2-STAT3 pathway after intracerebral hemorrhage.

BACKGROUND

Astrocytes, exhibiting dual phenotypes (A1 neurotoxic and A2 neuroprotective), play a pivotal role in secondary brain injury (SBI) subsequent to intracerebral hemorrhage (ICH). However, the underlying mechanisms remain elusive. This study sought to explore whether Glucose-regulated protein 78 (GRP78), an essential chaperone involved in endoplasmic reticulum stress, alleviates SBI by influencing astrocytic polarization and to elucidate the underlying mechanisms.

METHODS

An autologous blood intracerebral hemorrhage model was established in C57BL/6 mice (8-10 weeks old, 25-30 g), and mouse astrocyte cell line CRL-2541 was exposed to hemin to mimic ICH in vitro. GRP78 small interfering RNAs(siRNAs) were utilized to knock down GRP78, and plasmids were constructed to effectively overexpress GRP78 in CRL-2541 cells. Immunofluorescence, Western blot, immunoprecipitation, CCK-8 assays, and quantitative real-time RT-PCR (qRT-PCR) were evaluated.

RESULTS

It was shown that GRP78 was increased after ICH, peaking at 72 h in vivo and 24 h in vitro. GRP78 knockdown promoted A1 astrocyte expression and suppressed A2 astrocyte expression. Inhibition of GRP78 aggravated hemin-induced cell damage. While GRP78 overexpression significantly promoted astrocytic polarization toward the A2 phenotype, reduced pro-inflammatory cytokine release, and activated the JAK2-STAT3 pathway. Inhibition of the JAK2-STAT3 pathway attenuated the influence of GRP78 on the phenotypic transformation from A1 to A2.

CONCLUSIONS

GRP78 alleviates SBI after ICH by promoting astrocytic polarization via JAK2-STAT3 signaling. These findings highlight GRP78 as a potential therapeutic target for SBI caused by ICH.