SOCS1/JAK2/STAT3 axis regulates early brain injury induced by subarachnoid hemorrhage via inflammatory responses

The SOCS1/JAK2/STAT3 axis is strongly associated with tumor growth and progression,and participates in cytokine secretion in many diseases.However,the effects of the SOCS1/JAK2/STAT3 axis in experimental subarachnoid hemorrhage remain to be studied.A subarachnoid hemorrhage model was established in rats by infusing autologous blood into the optic chiasm pool.Some rats were first treated with JAK2/STAT3 small interfering RNA(Si-JAK2/Si-STAT3)or overexpression plasmids of JAK2/STAT3.In the brains of subarachnoid hemorrhage model rats,the expression levels of both JAK2 and STAT3 were upregulated and the expression of SOCS1 was downregulated,reaching a peak at 48 hours after injury.Simultaneously,the interactions between JAK2 and SOCS1 were reduced.In contrast,the interactions between JAK2 and STAT3 were markedly enhanced.Si-JAK2 and Si-STAT3 treatment alleviated cortical neuronal cell apoptosis and necrosis,destruction of the blood-brain barrier,brain edema,and cognitive functional impairment after subarachnoid hemorrhage.This was accompanied by decreased phosphorylation of JAK2 and STAT3 protein,decreased total levels of JAK2 and STAT3 protein,and increased SOCS1 protein expression.However,overexpression of JAK2 and STAT3 exerted opposite effects,aggravating subarachnoid hemorrhage-induced early brain injury.Si-JAK2 and Si-STAT3 inhibited M1-type microglial conversion and the release of pro-inflammatory factors(inducible nitric oxide synthase,interleukin-1β,and tumor necrosis factor-α)and increased the release of anti-inflammatory factors(arginase-1,interleukin-10,and interleukin-4).Furthermore,primary neurons stimulated with oxyhemoglobin were used to simulate subarachnoid hemorrhage in vitro,and the JAK2 inhibitor AG490 was used as an intervention.The in vitro results also suggested that neuronal protection is mediated by the inhibition of JAK2 and STAT3 expression.Together,our findings indicate that the SOCS1/JAK2/STAT3 axis contributes to early brain injury after subarachnoid hemorrhage both in vitro and in vivo by inducing inflammatory responses.This study was approved by the Animal Ethics Committee of Anhui Medical University and the First Affiliated Hospital of University of Science and Technology of China(approval No.LLSC-20180202)on March 1,2018.

Neuroprotection mediated by the Wnt/Frizzled signaling pathway in early brain injury induced by subarachnoid hemorrhage

The Wnt/Frizzled signaling pathway participates in many inflammation-linked diseases. However, the inflammatory response mediated by the Wnt/Frizzled signaling pathway in experimental subarachnoid hemorrhage has not been thoroughly investigated. Consequently, in this study, we examined the potential role of the Wnt/Frizzled signaling pathway in early brain injury in rat models of subarachnoid hemorrhage.Simultaneously, possible neuroprotective mechanisms were also investigated. Experimental subarachnoid hemorrhage rat models were induced by injecting autologous blood into the prechiasmatic cistern. Experiment 1 was designed to examine expression of the Wnt/Frizzled signaling pathway in early brain injury induced by subarachnoid hemorrhage. In total, 42 adult rats were divided into sham(injection of equivalent volume of saline), 6-, 12-, 24-, 48-, 72-hour, and 1-week subarachnoid hemorrhage groups. Experiment 2 was designed to examine neuroprotective mechanisms of the Wnt/Frizzled signaling pathway in early brain injury induced by subarachnoid hemorrhage. Rats were treated with recombinant human Wnt1(rhwnt1), small interfering Wnt1(siwnt1) RNA, and monoclonal antibody of Frizzled1(anti-Frizzled1) at 48 hours after subarachnoid hemorrhage. Expression levels of Wnt1, Frizzled1, β-catenin, peroxisome proliferator-activated receptor-γ, CD36, and active nuclear factor-κB were examined by western blot assay and immunofluorescence staining. Microglia type conversion and inflammatory cytokine levels in brain tissue were examined by immunofluorescence staining and enzyme-linked immunosorbent assay. Our results show that compared with the sham group, expression levels of Wnt1, Frizzled1, and β-catenin were low and reduced to a minimum at 48 hours, gradually returning to baseline at 1 week after subarachnoid hemorrhage. rhwnt1 treatment markedly increased Wnt1 expression and alleviated subarachnoid hemorrhage-induced early brain injury(within 72 hours), including cortical cell apoptosis, brain edema, and neurobehavioral deficits, accompanied by increasing protein levels of β-catenin, CD36, and peroxisome proliferator-activated receptor-γ and decreasing protein levels of nuclear factor-κB. Of note, rhwnt1 promoted M2-type microglia conversion and inhibited release of inflammatory cytokines(interleukin-1β, interleukin-6, and tumor necrosis factor-α). In contrast, siwnt1 RNA and anti-Frizzled1 treatment both resulted in an opposite effect. In conclusion, the Wnt/Frizzled1 signaling pathway may participate in subarachnoid hemorrhage-induced early brain injury via inhibiting the inflammatory response, including regulating microglia type conversion and decreasing inflammatory cytokine release. The study was approved by the Animal Ethics Committee of Anhui Medical University and First Affiliated Hospital of USTC,Division of Life Sciences and Medicine, University of Science and Technology of China(approval No. LLSC-20180202) in May 2017.