JAK2/STAT3 pathway regulates microglia polarization involved in hippocampal inflammatory damage due to acute paraquat exposure

Zhuo Fan; Wendi Zhang; Qi Cao; Lingyun Zou; Xiaobei Fan; Changcun Qi; Yuandong Yan; Bo Song; Bailin Wu

doi:10.1016/j.ecoenv.2022.113372

JAK2/STAT3 pathway regulates microglia polarization involved in hippocampal inflammatory damage due to acute paraquat exposure

Ecotoxicol Environ Saf. 2022 Apr 1:234:113372. doi: 10.1016/j.ecoenv.2022.113372. Epub 2022 Mar 3.

Authors

Zhuo Fan¹, Wendi Zhang¹, Qi Cao¹, Lingyun Zou¹, Xiaobei Fan¹, Changcun Qi¹, Yuandong Yan¹, Bo Song², Bailin Wu³

Affiliations

¹ Department of Occupational Health and Environmental Health, School of Public Health, Hebei Medical University, Shijiazhuang, Hebei 050000, China; Hebei Province Key Laboratory of Environment and Human Health, Shijiazhuang, Hebei 050000, China.
² Department of Occupational Health and Environmental Health, School of Public Health, Hebei Medical University, Shijiazhuang, Hebei 050000, China; Hebei Province Key Laboratory of Environment and Human Health, Shijiazhuang, Hebei 050000, China. Electronic address: songbootc@163.com.
³ Department of Radiology, The Second Hospital of Hebei Medical University, Shijiazhuang, Hebei 050000, China. Electronic address: wubailins@163.com.

PMID: 35248926
DOI: 10.1016/j.ecoenv.2022.113372

Abstract

Objective: To explore the effects of acute paraquat (PQ) exposure on the phenotypic polarization of hippocampal microglia and its mechanism.

Methods: An acute PQ exposure rat model was established. Male SD rats were exposed to 0, 5, 25, and 50 mg/kg PQ, and brain hippocampal tissue was collected after 1, 3, and 7 days of exposure, respectively. Hippocampal pathological changes were examined by H&E staining, and immunohistochemistry (IHC) was used to detect changes in the number of Iba-1-positive cells, the average number of endpoints, and the average process length. The protein expression of Iba-1 was detected by western blotting. BV-2 microglia were treated with 0, 0.01, 0.025, 0.05, or 0.1 μmol/L PQ for 24 h. ELISA and western blotting assays were performed to detect the expression of TNF-α and IL-1β in vivo and in vitro. The M1 microglia marker iNOS, the M2 microglia marker Arg-1, and the p-JAK2 and p-STAT3 protein were detected by western blotting. JAK2/STAT3 pathway activation role in regulating microglia phenotypic polarization was further validated in vivo and in vitro by JAK2-specific inhibitor AG490 administration.

Results: After acute PQ exposure, hippocampal neurons showed pathological changes such as loose arrangement and nuclear pyknosis, the number of Iba-1 positive cells and the expression of Iba-1 protein increased, and the average number of endpoints and average process length of microglia decreased. Histological examination revealed that compared with the control group, in the 50 mg/kg PQ group on the 3rd and 7th day, the expression of TNF-α, IL-1β, and iNOS significantly increased, while that of Arg-1 significantly decreased. p-JAK2 and p-STAT3 expression significantly increased in the 50 mg/kg PQ group on the 1st, 3rd, and 7th day. In vitro, compared with the control group, the expression of TNF-α, IL-1β, iNOS, p-JAK2, and p-STAT3 significantly increased, while Arg-1 expression was significantly reduced in the 0.025, 0.05, and 0.1 μmol/L PQ groups. After AG490 administration, the expression levels of p-JAK2, p-STAT3, iNOS, TNF-α, and IL-1β in the AG490 +PQ group were significantly inhibited in vivo and in vitro compared with the PQ-only group. On the contrary, Arg-1 expression was significantly increased.

Conclusion: Our results suggest that acute PQ exposure may induce M1-type polarization of hippocampal microglia by activating the JAK2/STAT3 pathway, which in turn releases pro-inflammatory factors such as TNF-α and IL-1β, leading to hippocampal inflammatory damage.

Keywords: Acute exposure; JAK2/STAT3; Microglia; Paraquat; Phenotypic polarization.