【Abstract】
Ghrelin, a brain-gut peptide, has been proven to exert neuroprotection in different kinds of neurological diseases; however, its role and the potential molecular mechanisms in secondary brain injury (SBI) after intracerebral hemorrhage (ICH) are still unknown. In this study, we investigate whether treatment with ghrelin may attenuate SBI in a murine ICH model, and if so, whether the neuroprotective effects are due to the inhibition of nucleotidebinding oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3) inflammasome activation and promotion of nuclear factor-E2-related factor 2 (Nrf2)/antioxidative response element (ARE) signaling pathway. Stereotactically intrastriatal infusion of autologous blood was performed to mimic ICH. Ghrelin was given intraperitoneally immediately following ICH and again 1 h later. Results showed that ghrelin attenuated neurobehavioral deficits, brain edema, hematoma volume, and perihematomal cell death post-ICH. Ghrelin inhibited the NLRP3 inflammasome activation and subsequently suppressed the neuroinflammatory response as evidenced by reduced microglia activation, neutrophil infiltration, and pro-inflammatory mediators release after ICH. Additionally, ghrelin alleviated ICH-induced oxidative stress according to the chemiluminescence of luminol and lucigenin, malondialdehyde (MDA) content, and total superoxide dismutase (SOD) activity assays. These changes were accompanied by upregulation of Nrf2 expression, Nrf2 nuclear accumulation, and enhanced Nrf2 DNA binding activity, as well as by increased expressions of Nrf2 downstream target antioxidative genes, including NAD(P)H quinine oxidoreductase-1 (NQO1), glutathione cysteine ligase regulatory subunit (GCLC), and glutathione cysteine ligase modulatory subunit (GCLM). Together, our data suggested that ghrelin protected against ICH-induced SBI by inhibiting NLRP3 inflammasome activation and promoting Nrf2/ARE signaling pathway.
【中文摘要】
腦腸肽ghrelin已被發現在數種中樞神經疾病中發揮神經保護作用；然而，其在腦出血後繼發性腦損傷中作用仍不清楚。本研究旨在探究ghrelin對腦出血後繼發性腦損傷的抑制作用，及其作用機制是否與NLRP3炎症小體活化及Nrf2/ARE信號通路的調控相關。本研究採用自體血立體定位下二次注射法構建小鼠腦出血模型。模型構建成功後即刻及一小時後腹腔給藥ghrelin。結果顯示ghrelin可以明顯減輕腦出血後小鼠神經功能損傷，腦水腫，血腫大小及血腫周圍神經元死亡情況。此外，ghrelin有效抑制腦出血後NLRP3炎性小體活化及其介導的神經炎症。同時，ghrelin能夠明顯降低腦出血後氧化應激水平，具體表現為給藥後腦組織魯米那和光澤精光度值，丙二醇含量降低及超氧化物歧化酶活性升高。值得注意的是，這些改變伴隨著Nrf2/ARE抗氧化信號通路的激活，反映為ghrelin可以增加腦組織Nrf2表達，促進Nrf2核轉錄，增強Nrf2與DNA結合能力及促進Nrf2下遊靶基因NQO1，GCLC和GCLM等表達。綜上所述，腦腸肽ghrelin可通過抑制NLRP3炎症小體活化及激活Nrf2/ARE信號通路進而減輕腦出血後繼發性腦損傷。