Experimental necrotizing enterocolitis induces neuroinflammation in the neonatal brain

Abstract

Background Necrotizing enterocolitis (NEC) is an inflammatory gastrointestinal disease primarily affecting preterm neonates. Neonates with NEC suffer from a degree of neurodevelopmental delay that is not explained by prematurity alone. There is a need to understand the pathogenesis of neurodevelopmental delay in NEC. In this study, we assessed the macroscopic and microscopic changes that occur to brain cell populations in specific brain regions in a neonatal mouse model of NEC. Moreover, we investigated the role of intestinal inflammation as part of the mechanism responsible for the changes observed in the brain of pups with NEC. Methods Brains of mice were assessed for gross morphology and cerebral cortex thickness (using histology). Markers for mature neurons, oligodendrocytes, neural progenitor cells, microglia, and astrocytes were used to quantify their cell populations in different regions of the brain. Levels of cell apoptosis in the brain were measured by Western blotting and immunohistochemistry. Endoplasmic reticulum (ER) stress markers and levels of pro-inflammatory cytokines (in the ileum and brain) were measured by RT-qPCR and Western blotting. A Pearson test was used to correlate the levels of cytokines (ELISA) in the brain and ileum and to correlate activated microglia and astrocyte populations to the severity of NEC. Results NEC pups had smaller brain weights, higher brain-to-body weight ratios, and thinner cortices compared to control pups. NEC pups had increased levels of apoptosis and ER stress. In addition, NEC was associated with a reduction in the number of neurons, oligodendrocytes, and neural progenitors in specific regions of the brain. Levels of pro-inflammatory cytokines and the density of activated microglia and astrocytes were increased in the brain and positively correlated with the increase in the levels pro-inflammatory cytokines in the gut and the severity of NEC damage respectively. Conclusions NEC is associated with severe changes in brain morphology, a pro-inflammatory response in the brain that alters cell homeostasis and density of brain cell populations in specific cerebral regions. We show that the severity of neuroinflammation is associated with the severity of NEC. Our findings suggest that early intervention during NEC may reduce the chance of acute neuroinflammation and cerebral damage. Electronic supplementary material The online version of this article (10.1186/s12974-019-1481-9) contains supplementary material, which is available to authorized users.

COVID‐19 in pregnancy: Placental and neonatal involvement

“…Necrotizing enterocolitis (NEC) is one of the many risks of preterm birth. This inflammatory disease of the gastrointestinal tract is a significant cause of neonatal morbidity and mortality 95‐97 . Both neonatal and maternal inflammation appear to contribute to NEC pathogenesis.…”

“…This inflammatory disease of the gastrointestinal tract is a significant cause of neonatal morbidity and mortality. [95][96][97] Both neonatal and maternal inflammation appear to contribute to transcription factor that upregulates production of cytokines and immunological mediators. [98][99][100] In animal models, fetal exposure to maternal inflammation induced by chorioamnionitis has been shown to generate higher levels of inflammatory markers, like IL-6, and reduced intestinal innate immune cells.…”

Neurodevelopmental impairment in necrotising enterocolitis survivors: systematic review and meta-analysis

“…These results were confirmed by Niño et al , who demonstrated that, in a mouse model of NEC, activation of intestinal TLR4 signalling resulted in the release of high-mobility group Box 1 protein in the intestine, which activated the brain microglia and caused neurological dysfunction 74. More recently, our group reported that the levels of pro-inflammatory cytokines and the density of activated microglia and astrocytes were increased in the brains of mice with NEC and were positively correlated with the increase in the levels of pro-inflammatory cytokines in the gut and the severity of NEC damage, respectively 75. These laboratory findings are useful because they provide an explanation for the development of NEC-associated brain injury by suggesting the activation of the gut–brain axis is implicated in the pathogenesis and are also relevant for their clinical implications.…”

Blockage of NLRP3 inflammasome activation ameliorates acute inflammatory injury and long-term cognitive impairment induced by necrotizing enterocolitis in mice

“…Experimental NEC mouse model was established as described previously with a little modification [ 13 ]. In brief, 7-day-old mice were fed by gavage with hyperosmolar formula [Similac Advance infant formula (Abbott Nutrition) and Esbilac canine milk replacer (PetAg) at a ratio of 2:1] every 3 h, meanwhile, exposed to transient hypoxia (5% O 2 , 10 min) and hypothermia twice daily for 4 days.…”