IRE1α inhibition decreased TXNIP/NLRP3 inflammasome activation through miR-17-5p after neonatal hypoxic–ischemic brain injury in rats

Abstract

BackgroundThe endoplasmic reticulum (ER) is responsible for the control of correct protein folding and protein function which is crucial for cell survival. However, under pathological conditions, such as hypoxia–ischemia (HI), there is an accumulation of unfolded proteins thereby triggering the unfolded protein response (UPR) and causing ER stress which is associated with activation of several stress sensor signaling pathways, one of them being the inositol requiring enzyme-1 alpha (IRE1α) signaling pathway. The UPR is regarded as a potential contributor to neuronal cell death and inflammation after HI. In the present study, we sought to investigate whether microRNA-17 (miR-17), a potential IRE1α ribonuclease (RNase) substrate, arbitrates downregulation of thioredoxin-interacting protein (TXNIP) and consequent NLRP3 inflammasome activation in the immature brain after HI injury and whether inhibition of IRE1α may attenuate inflammation via miR-17/TXNIP regulation.MethodsPostnatal day 10 rat pups (n = 287) were subjected to unilateral carotid artery ligation followed by 2.5 h of hypoxia (8% O2). STF-083010, an IRE1α RNase inhibitor, was intranasally delivered at 1 h post-HI or followed by an additional one administration per day for 2 days. MiR-17-5p mimic or anti-miR-17-5p inhibitor was injected intracerebroventricularly at 48 h before HI. Infarct volume and body weight were used to evaluate the short-term effects while brain weight, gross and microscopic brain tissue morphologies, and neurobehavioral tests were conducted for the long-term evaluation. Western blots, immunofluorescence staining, reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR), and co-immunoprecipitation (Co-IP) were used for mechanism studies.ResultsEndogenous phosphorylated IRE1α expression was significantly increased after HI. Intranasal administration of STF-083010 alleviated brain injury and improved neurological behavior. MiR-17-5p expression was reduced after HI, and this decrease was attenuated by STF-083010 treatment. MiR-17-5p mimic administration ameliorated TXNIP expression, NLRP3 inflammasome activation, caspase-1 cleavage, and IL-1β production, as well as brain infarct volume. Conversely, anti-miR-17-5p inhibitor reversed IRE1α inhibition-induced decrease in TXNIP expression and inflammasome activation, as well as exacerbated brain injury after HI.ConclusionsIRE1a-induced UPR pathway may contribute to inflammatory activation and brain injury following neonatal HI. IRE1a activation, through decay of miR-17-5p, elevated TXNIP expression to activate NLRP3 inflammasome and aggravated brain damage.Electronic supplementary materialThe online version of this article (10.1186/s12974-018-1077-9) contains supplementary material, which is available to authorized users.

Ginkgolide B ameliorates NLRP3 inflammasome activation after hypoxic‐ischemic brain injury in the neonatal male rat

“…As previously described (Chen et al, 2018), hypoxic‐ischemic brain injury was induced in P7 pups. Briefly, pups were anesthetized with 3% isoflurane and maintained with at 2.5% isoflurane in air during surgery.…”

“…In particular, the secretion of IL‐1β and IL‐18 requires the NOD (nucleotide‐binding oligomerization domain)‐like receptor (NLR) Pyrin domain containing 3 (NLRP3) inflammasome (Singh and Jha, 2018; Song et al, 2017). NLRP3 activation has been reported to mediate injury in various CNS disorders including HIE (Ystgaard et al, 2015; Chen et al, 2018). The up‐regulation of NLRP3 was found in several regions of the brain at 24 h after neonatal HI (Ystgaard et al, 2015; Chen et al, 2018).…”

“…NLRP3 activation has been reported to mediate injury in various CNS disorders including HIE (Ystgaard et al, 2015; Chen et al, 2018). The up‐regulation of NLRP3 was found in several regions of the brain at 24 h after neonatal HI (Ystgaard et al, 2015; Chen et al, 2018). Thus, the pharmacological targeting of NLRP3‐mediated inflammatory response may help design a new approach to develop therapeutic strategies for the treatment of HIE.…”

Microglia-derived FGF21 as a modulator of astrocytic phenotype and cerebral ischemia injury

“…Accumulating evidence suggests that circulating factors released by glia subjected to ischemia play important roles in the pathogenesis of stroke [6]. Microglia, the brain-resident phagocytes, can be activated in response to brain injury and diseases and are involved in neuroinflammation in ischemic brains [7,8].…”

Long noncoding MIAT acting as a ceRNA to sponge microRNA‐204‐5p to participate in cerebral microvascular endothelial cell injury after cerebral ischemia through regulating HMGB1

“…ischemia, an important risk element in perinatal brain injuries worldwide, results in chronic disability and acute mortality (D. Chen et al, 2018). Cerebral microvascular endothelial cells (CMECs), astrocytes as well as the extracellular matrix comprise the microenvironment of cerebral ischemia, which plays a role in the survival and function of neurons (J.…”