SP1-mediated SYN1 promotes hemin-induced damage in PC12 cells in vitro and exacerbates blood-barrier disruption and brain injury after intracerebral hemorrhage in vivo

Background

Intracerebral hemorrhage (ICH) is one deadly subtype of stroke with high morbidity and mortality. Oxidative stress and inflammation are major factors contributing to blood-brain barrier (BBB) dysfunction, which induces perihematoma edema and exacerbates ICH-induced secondary brain injury. SYN1 is a crucial neuronal phosphoprotein that plays a pivotal role in neuronal development. Our study was devised to clarify the function of SYN1 in hemin-induced cell injury in PC12 cells and brain injury in ICH rat models.

Methods

For in vitro assay, PC12 cells were first stimulated by 150 µM hemin for 4 h and then transfected with si-SYN1 and pcDNA3.1-SP1. Cell viability was tested through lactate dehydrogenase (LDH) release and CCK-8 assays. Cell apoptosis was observed through TUNEL staining. Inflammatory factors (IL-1β, IL-6, and TNF-α) were evaluated through western blotting. Oxidative markers (GSH, MDA, and SOD) were detected by adopting commercial kits. The binding sites of SP1 on the SYN1 promoter were predicted by using the JASPAR database and were validated through performing CHIP and luciferase reporter assays. SP1 and SYN1 expression in PC12 cells was investigated by RT-qPCR. For in vivo assay, rats were administrated intracerebroventricularly with si-SYN1 at 72 h before ICH induction. SYN1 and SP1 expression in ICH rats was assessed by RT-qPCR. Neurological deficits, brain edema, and BBB disruption at 24 h following ICH were assessed by conducting neurobehavioral tests, brain water content examination, and Evans blue extravasation assay.

Results

In vitro, hemin stimulation elevated SYN1 expression, attenuated cell viability, enhanced apoptosis, and induced inflammation and oxidative stress in PC12 cells, which were offset by SYN1 knockdown. SP1 bound to the SYN1 promoter region and positively regulated SYN1 expression. Overexpressing SP1 antagonized the impacts of SYN1 downregulation on hemin-induced damage in PC12 cells. In vivo, SYN1 and SP1 expression was upregulated in ICH rat models. Administration of si-SYN1 effectually improved neurological function, attenuated brain edema, and ameliorated BBB disruption following ICH.

Conclusion

SP1-mediated SYN1 probably participates in the process of neuronal damage, BBB disruption, and brain injury following ICH.