NOD1/RIP2 signalling enhances the microglia-driven inflammatory response and undergoes crosstalk with inflammatory cytokines to exacerbate brain damage following intracerebral haemorrhage in mice

Abstract

Background Secondary brain damage caused by the innate immune response and subsequent proinflammatory factor production is a major factor contributing to the high mortality of intracerebral haemorrhage (ICH). Nucleotide-binding oligomerization domain 1 (NOD1)/receptor-interacting protein 2 (RIP2) signalling has been reported to participate in the innate immune response and inflammatory response. Therefore, we investigated the role of NOD1/RIP2 signalling in mice with collagenase-induced ICH and in cultured primary microglia challenged with hemin. Methods Adult male C57BL/6 mice were subjected to collagenase for induction of ICH model in vivo. Cultured primary microglia and BV2 microglial cells (microglial cell line) challenged with hemin aimed to simulate the ICH model in vitro. We first defined the expression of NOD1 and RIP2 in vivo and in vitro using an ICH model by western blotting. The effect of NOD1/RIP2 signalling on ICH-induced brain injury volume, neurological deficits, brain oedema, and microglial activation were assessed following intraventricular injection of either ML130 (a NOD1 inhibitor) or GSK583 (a RIP2 inhibitor). In addition, levels of JNK/P38 MAPK, IκBα, and inflammatory factors, including tumour necrosis factor-α (TNF-α), interleukin (IL)-1β, and inducible nitric oxide synthase (iNOS) expression, were analysed in ICH-challenged brain and hemin-exposed cultured primary microglia by western blotting. Finally, we investigated whether the inflammatory factors could undergo crosstalk with NOD1 and RIP2. Results The levels of NOD1 and its adaptor RIP2 were significantly elevated in the brains of mice in response to ICH and in cultured primary microglia, BV2 cells challenged with hemin. Administration of either a NOD1 or RIP2 inhibitor in mice with ICH prevented microglial activation and neuroinflammation, followed by alleviation of ICH-induced brain damage. Interestingly, the inflammatory factors interleukin (IL)-1β and tumour necrosis factor-α (TNF-α), which were enhanced by NOD1/RIP2 signalling, were found to contribute to the NOD1 and RIP2 upregulation in our study. Conclusion NOD1/RIP2 signalling played an important role in the regulation of the inflammatory response during ICH. In addition, a vicious feedback cycle was observed between NOD1/RIP2 and IL-1β/TNF-α, which could to some extent result in sustained brain damage during ICH. Hence, our study highlights NOD1/RIP2 signalling as a potential therapeutic target to protect the brain against secondary brain damage during ICH.

Perampanel, an AMPAR antagonist, alleviates experimental intracerebral hemorrhage‑induced brain injury via necroptosis and neuroinflammation

“…The neuroinflammatory mechanisms include activation of microglia, the resident macrophages in the brain, and other blood-derived immune cells ( 9 ). Activated microglia/macrophages and peripheral blood-derived immune cells release proinflammatory cytokines, including tumor necrosis factor (TNF-) α, interleukin (IL-) 1β, chemokines, free radicals, and other toxic chemicals, which ultimately leads to brain edema and neuronal death ( 17 , 18 ). ICH-induced neuronal death was initially divided into two different categories, necrosis and apoptosis.…”

MiR-200c-3p inhibits LPS-induced M1 polarization of BV2 cells by targeting RIP2

“…RIP2 plays an important role in innate and adaptive immunity (Jaafar et al 2018). In primary microglia, RIP2 inhibition partially alleviated intracerebral haemorrhage-induced brain injury by reducing microglia activation (Wang et al 2020a).…”

Cannabidiol prevents lipopolysaccharide-induced sickness behavior and alters cytokine and neurotrophic factor levels in the brain

“…In the hippocampus, these cells are an important source of neurotrophic factors that contribute to neurogenesis [ 78 ]. Interestingly, it has been shown that LPS activates microglia and induces neurotrophic factors release [ 62 , 79 – 82 ]. However, in our model, CBD pretreatment might have prevented LPS-induced microglia activation, which could explain why the cannabinoid prevented the increase of the evaluated neurotrophic factors and cytokines levels in the hippocampus.…”