IL-6/STAT3 Induced Neuron Apoptosis in Hypoxia by Downregulating ATF6 Expression

Abstract

Background: Neuron apoptosis, regulated by endoplasmic reticulum (ER) stress in the hippocampus, is an essential factor influencing the cognitive impairment induced by hypobaric hypoxia. Hypoxia mainly changes the activating transcription factor (ATF6) pathway of ER stress. However, the role of ATF6 in neuron survival, apoptosis, and upstream regulation is still controversial.Methods: We established a hypobaric hypoxia-induced C57BL/6 murine model and cell lines exposed to 1% hypoxia, including PC12 and HT22. First, we tested the expressions of interleukin 6 (IL-6), IL-1β, and IL-10 in C57BL/6 mice’s hippocampus under hypoxia using enzyme-linked immunosorbent assay (ELISA). We determined the signal transducer and activator of transcription 3 (STAT3) phosphorylation at tyrosine (Tyr)705 by western blot and the expression of ATF6, 78-kDa glucose-regulated protein (GRP78), and C/-EBP homologous protein (CHOP) related to ER stress by immunofluorescence (IF), western blot, and qRT-PCR; they were then verified on the cell model. Additionally, IL-6 (40 ng/mL) and STAT3 siRNA were used to treat the PC12 cells for 48 and 4 h to activate or silence STAT3, respectively. Subsequently, the cells of siRNA group were exposed to 1% hypoxia for 48 h. Furthermore, the ATF6 and CHOP expressions were detected with western blot and qRT-PCR. Finally, we examined the binding of STAT3 to the ATF6 promoter by chromatin immunoprecipitation (ChIP)-seq.Results: The results showed that IL-6 increased, IL-10 decreased in the hypoxia group, and IL-1β showed no difference between the hypoxia and the normoxia groups. Neuron apoptosis was significantly elevated by exposure to hypoxia for 48h in PC12 cells. The hypobaric hypoxia-induced ER stress proteins, ATF6, GRP78, and CHOP, and the p-STAT3 (Tyr705) expressions increased both in in vivo and in vitro. Besides, STAT3 silencing significantly promoted the ATF6 expression and inhibited CHOP, while STAT3 activation downregulated the expression of ATF6 and upregulated CHOP in PC12 cells. The ChIP-seq assay demonstrated that p-STAT3 (Tyr705) protein could bind to the ATF6 promoter region in HT22 cells.Conclusion: Phosphorylation of STAT3 at the Tyr705 site contributes to hypoxia-induced neuron apoptosis by downregulating ATF6, which might explain the inflammatory reaction and apoptosis of the hippocampal neurons induced by ER stress.

Mechanisms of mRNA processing defects in inherited THOC6 intellectual disability syndrome

“…HIF1 , NRSF , SMAD3 , and STAT3 target genes were enriched in Thoc6 fs/fs E9.5 forebrain (Figure S6G). HIF-1 and STAT3 can induce apoptosis in response to hypoxia (Greijer and van der Wall, 2004; Zhou et al, 2021), which is consistent the observed elevation of apoptosis in Thoc6 fs/fs E9.5 neuroepithelium (Figures 3E and 3F). SMAD3 signaling is activated by TGF-β to promote cortical differentiation (Vogel et al , 2010), suggesting shared disruption of TGF-β signaling in both human and mouse model systems.…”

LGALS3BP in Microglia Promotes Retinal Angiogenesis Through PI3K/AKT Pathway During Hypoxia

“…Pathological neovascularization is a major feature of OIR, 34 , 35 which is mainly manifested by the rapid and massive proliferation of endothelial cells to form vascular clusters. 21 , 36 In our study, we found a significantly elevated LGALS3BP in the retinas of OIR mice that was positively correlated with angiogenesis, suggesting that LGALS3BP may play a proangiogenic role in the OIR model. Given these results, we knocked down LGALS3BP in HMC3 cells for relative functional and phenotypic analysis in vitro, and we further found that LGALS3BP in HMC3 cells regulates the proliferation, migration, and tube formation of HUVECs.…”

Curcumin affects apoptosis of colorectal cancer cells through ATF6‐mediated endoplasmic reticulum stress

“…Accumulating reports have revealed that the expression patterns of CHOP and Grp78, two target genes of ATF6, are dampened subsequent to ATF6 knockdown (Dadey et al., 2016; Zhou, Zhong, et al., 2021). In the study, we discovered the reduction of CHOP and Grp78 protein levels and Ca 2+ concentration and the rise of SW620 cell proliferation, which demonstrated that knockdown of ATF6 partially negated the proapoptotic effect of curcumin on CRC cells.…”