Subject(s)
Endocarditis , Heart Valve Prosthesis Implantation , Heart Valve Prosthesis , Pulmonary Valve , Transcatheter Aortic Valve Replacement , Humans , Pulmonary Valve/diagnostic imaging , Pulmonary Valve/surgery , Endocarditis/diagnostic imaging , Endocarditis/etiology , Heart Valve Prosthesis Implantation/adverse effects , Transcatheter Aortic Valve Replacement/adverse effects , Treatment Outcome , Aortic ValveABSTRACT
BACKGROUND: Following birth asphyxia there is a robust inflammatory response. NLRP3 is a receptor of the innate immune system. Upon activation, NLRP3 forms an inflammasome together with ASC and procaspase-1 to mediate release of IL-1ß and IL-18. NLRP3 has previously been shown to be upregulated following neonatal hypoxic-ischemic (HI) brain injury in mice, but with no early effect on brain injury. OBJECTIVE: We aimed to evaluate if deficiency of NLRP3 or ASC protects against neonatal HI brain damage 7 days after hypoxia-ischemia. METHODS: C57BL/6J, NLRP3-/-, and ASC-/- mice were subjected to unilateral common carotid artery ligation followed by hypoxia at P9. Brain infarction, apoptosis, and microglial response were evaluated, as well as total RNA sequencing and examination of plasma levels of systemic proinflammatory cytokines. RESULTS: NLRP3-/- mice showed significantly increased brain infarction volumes compared to wild-type (Wt) mice, while ASC-/- mice showed reduced brain infarction volumes after neonatal hypoxia-ischemia. The amount of activated microglia was increased in NLRP3-/- mice, while decreased in ASC-/- mice compared to Wt mice. Total RNA sequencing showed an impaired inflammatory transcriptional response in the hippocampus of NLRP3-/- mice. Plasma levels of IL-1ß and IL-18 were not affected, but TNF was lower in NLRP3-/- and ASC-/- mice compared to Wt mice. CONCLUSION: ASC deficiency is neuroprotective in neonatal HI brain damage in mice, while NLRP3 deficiency increases brain damage.
Subject(s)
Brain Infarction/pathology , Brain/pathology , CARD Signaling Adaptor Proteins/genetics , Hypoxia-Ischemia, Brain/pathology , NLR Family, Pyrin Domain-Containing 3 Protein/genetics , Tumor Necrosis Factors/blood , Animals , Animals, Newborn , Apoptosis , Brain Infarction/genetics , Down-Regulation , Hypoxia-Ischemia, Brain/genetics , Interleukin-18/blood , Interleukin-1beta/blood , Mice , Mice, Inbred C57BL , Mice, Knockout , Microglia/pathology , Sequence Analysis, RNA , Up-RegulationABSTRACT
BACKGROUND: The NLRP3 inflammasome acts as an early mediator of inflammation by cleaving and releasing IL-1ß and IL-18 from their proforms. OBJECTIVE: The aim of this study was to describe NLRP3 activation and evaluate whether deficiency of NLRP3 protects against neonatal hypoxic ischemic brain damage. METHODS: C57BL/6 and NLRP3-/- mice at P9 were subjected to unilateral common carotid ligation followed by hypoxia. RT-PCR was used on mRNA in five different subregions of the brain. Brain infarction was evaluated by histopathology and 2,3,5-triphenyltetrazolium chloride staining. Plasma levels of IL-18 were measured by ELISA. Double labeling immunohistochemistry was used to examine cell-specific NLRP3 expression. RESULTS: NLRP3 was upregulated 24 h after hypoxia-ischemia (HI) in the hippocampus (2.6-fold), striatum (2.2-fold) and thalamus (2.3-fold). Brain infarction volumes were not statistically significantly different in NLRP3-/- mice compared to WT mice 24 h after HI, accompanied by no significant changes in plasma IL-18 levels. Three hours after HI, NLRP3 expression occurred in astrocytes located in the hippocampus and habenular nucleus of the thalamus. Microglia only showed scarce expression at this time point, but prominent NLRP3 expression 72 h after HI. CONCLUSION: Astrocytes are early mediators of NLRP3 activity. No early neuroprotective effect of NLRP3 deficiency in neonatal HI brain damage was shown.
