Neuroprotection by Nrf2 via modulating microglial phenotype and phagocytosis after intracerebral hemorrhage

Chuntian Liang; Lirong Liu; Shuangjin Bao; Zhenjia Yao; Qinqin Bai; Pengcheng Fu; Xiangyu Liu; John H Zhang; Gaiqing Wang

doi:10.1016/j.heliyon.2023.e13777

Neuroprotection by Nrf2 via modulating microglial phenotype and phagocytosis after intracerebral hemorrhage

Heliyon. 2023 Feb 16;9(2):e13777. doi: 10.1016/j.heliyon.2023.e13777. eCollection 2023 Feb.

Authors

Chuntian Liang¹, Lirong Liu^{1

2}, Shuangjin Bao³, Zhenjia Yao¹, Qinqin Bai¹, Pengcheng Fu⁴, Xiangyu Liu⁴, John H Zhang^{5

6}, Gaiqing Wang^{1

7}

Affiliations

¹ Department of Neurology, Shanxi Medical University, Taiyuan 030000, China.
² People's Hospital of Yaodu District, Linfen 041000, China.
³ Department of Pathology and Pathophysiology, Basic Medical College, Shanxi Medical University, Taiyuan 030000, China.
⁴ Department of Neurology, Shenzhen Longhua District Central Hospital, Shenzhen 518000, China.
⁵ Department of Physiology and Pharmacology, Loma Linda University School of Medicine, Loma Linda, CA, USA.
⁶ Department of Anesthesiology, Loma Linda University School of Medicine, Loma Linda, CA, USA.
⁷ Department of Neurology, Sanya Central Hospital (Haian Third People's Hospital), Hainan Medical University, Sanya 572000, China.

Abstract

Activated microglia are divided into pro-inflammatory and anti-inflammatory functional states. In anti-inflammatory state, activated microglia contribute to phagocytosis, neural repair and anti-inflammation. Nrf2 as a major endogenous regulator in hematoma clearance after intracerebral hemorrhage (ICH) has received much attention. This study aims to investigate the mechanism underlying Nrf2-mediated regulation of microglial phenotype and phagocytosis in hematoma clearance after ICH. In vitro experiments, BV-2 cells were assigned to normal group and administration group (Nrf2-siRNA, Nrf2 agonists Monascin and Xuezhikang). In vivo experiments, mice were divided into 5 groups: sham, ICH + vehicle, ICH + Nrf2-/-, ICH + Monascin and ICH + Xuezhikang. In vitro and in vivo, 72 h after administration of Monascin and Xuezhikang, the expression of Nrf2, inflammatory-associated factors such as Trem1, TNF-α and CD80, anti-inflammatory, neural repair and phagocytic associated factors such as Trem2, CD206 and BDNF were analyzed by the Western blot method. In vitro, fluorescent latex beads or erythrocytes were uptaken by BV-2 cells in order to study microglial phagocytic ability. In vivo, hemoglobin levels reflect the hematoma volume. In this study, Nrf2 agonists (Monascin and Xuezhikang) upregulated the expression of Trem2, CD206 and BDNF while decreased the expression of Trem1, TNF-α and CD80 both in vivo and in vitro. At the same time, after Monascin and Xuezhikang treatment, the phagocytic capacity of microglia increased in vitro, neurological deficits improved and hematoma volume lessened in vivo. These results were reversed in the Nrf2-siRNA or the Nrf2-/- mice. All these results indicated that Nrf2 enhanced hematoma clearance and neural repair, improved neurological outcomes through enhancing microglial phagocytosis and alleviating neuroinflammation.

Keywords: BDNF, Brain-derived neurotrophic factor; CNS, Central nervous system; DAMPs, Danger-associated molecular patterns; HO-1,Heme oxygenase-1, Hp,Haptoglobin; Hematoma clearance; ICH, Intracerebral hemorrhage; IFNγ,Interferon-gamma, IL-1β,Interleukin 1β; Intracerebral hemorrhage; MMP, Matrix metalloproteasesNF-κB,Nuclear factor-kappa light chain enhancer of activated B cells; Microglial phenotype; NO, Nitric oxide; Nrf2; Nrf2, Nuclear factor erythroid 2-related factor 2; PPAR-ɤ, Peroxidase proliferator-activated receptor gamma; Phagocytosis; TLR4, Toll-like receptor 4; TNFα, Tumor necrosis factor-α; Trem1, Triggering receptors I expressed on myeloid cells; Trem2, Triggering receptors II expressed on myeloid cells.