miR-146b Protects the Perinatal Brain against Microglia-Induced Hypomyelination.

OBJECTIVES: In the premature newborn, perinatal inflammation mediated by microglia contributes significantly to neurodevelopmental injuries including white matter injury (WMI). Brain inflammation alters development through neuroinflammatory processes mediated by activation of homeostatic microglia toward a pro-inflammatory and neurotoxic phenotype. Investigating immune regulators of microglial activation is crucial to find effective strategies to prevent and treat WMI. METHODS: Ex vivo microglial cultures and a mouse model of WMI induced by perinatal inflammation (interleukin-1-beta [IL-1ß] and postnatal days 1-5) were used to uncover and elucidate the role of microRNA-146b-5p in microglial activation and WMI. RESULTS: A specific reduction in vivo in microglia of Dicer, a protein required for microRNAs maturation, reduces pro-inflammatory activation of microglia and prevents hypomyelination in our model of WMI. Microglial miRNome analysis in the WMI model identified miRNA-146b-5p as a candidate modulator of microglial activation. Ex vivo microglial cell culture treated with the pro-inflammatory stimulus lipopolysaccharide (LPS) led to overexpression of immunomodulatory miRNA-146b-5p but its drastic reduction in the microglial extracellular vesicles (EVs). To increase miRNA-146b-5p expression, we used a 3DNA nanocarrier to deliver synthetic miRNA-146b-5p specifically to microglia. Enhancing microglial miRNA-146b-5p overexpression significantly decreased LPS-induced activation, downregulated IRAK1, and restored miRNA-146b-5p levels in EVs. In our WMI model, 3DNA miRNA-146b-5p treatment significantly prevented microglial activation, hypomyelination, and cognitive defect induced by perinatal inflammation. INTERPRETATIONS: These findings support that miRNA-146b-5p is a major regulator of microglia phenotype and could be targeted to reduce the incidence and the severity of perinatal brain injuries and their long-term consequences. ANN NEUROL 2022;91:48-65.

Targeting the brain 5-HT7 receptor to prevent hypomyelination in a rodent model of perinatal white matter injuries.

Approximately 15 million babies are born prematurely every year and many will face lifetime motor and/or cognitive deficits. Children born prematurely are at higher risk of developing perinatal brain lesions, especially white matter injuries (WMI). Evidence in humans and rodents demonstrates that systemic inflammation-induced neuroinflammation, including microglial and astrocyte reactivity, is the prominent processes of WMI associated with preterm birth. Thus, a new challenge in the field of perinatal brain injuries is to develop new neuroprotective strategies to target neuroinflammation to prevent WMI. Serotonin (5-HT) and its receptors play an important role in inflammation, and emerging evidence indicates that 5-HT may regulate brain inflammation by the modulation of microglial reactivity and astrocyte functions. The present study is based on a mouse model of WMI induced by intraperitoneal (i.p.) injections of IL-1ß during the first 5 days of life. In this model, certain key lesions of preterm brain injuries can be summarized by (i) systemic inflammation, (ii) pro-inflammatory microglial and astrocyte activation, and (iii) inhibition of oligodendrocyte maturation, leading to hypomyelination. We demonstrate that Htr7 mRNA (coding for the HTR7/5-HT7 receptor) is significantly overexpressed in the anterior cortex of IL-1ß-exposed animals, suggesting it as a potential therapeutic target. LP-211 is a specific high-affinity HTR7 agonist that crosses the blood-brain barrier (BBB). When co-injected with IL-1ß, LP-211 treatment prevented glial reactivity, the down-regulation of myelin-associated proteins, and the apparition of anxiety-like phenotypes. Thus, HTR7 may represent an innovative therapeutic target to protect the developing brain from preterm brain injuries.

Effects of opioid-reduced anesthesia during scoliosis surgery in children: a prospective observational study.

Aims: Opioid-reduced anesthesia (ORA) was suggested to decrease morphine consumption after adolescent idiopathic scoliosis (AIS) surgery and incidence of chronic pain. Materials & methods: A prospective analysis using the ORA in AIS surgery was performed. Two cohorts were compared: a control group (opioid-based anesthesia) and the ORA group. The main outcome was morphine consumption at day 1. Results: 33 patients operated for AIS using ORA were compared with 36 with opioid-based anesthesia. Morphine consumption was decreased in the ORA group (1.1 mg.kg-1 [0.2-2] vs 0.8 mg.kg-1 [0.3-2]; p = 0.02) at day 1. Persistent neuropathic pain at 1 year was decreased in the ORA group (p = 0.02). Conclusion: The ORA protocol is efficient to reduce postoperative morphine consumption in AIS surgery and preventing neuropathic pain.