Intra-amniotic LPS causes acute neuroinflammation in preterm rhesus macaques

Abstract

BackgroundChorioamnionitis is associated with an increased risk of brain injury in preterm neonates. Inflammatory changes in brain could underlie this injury. Here, we evaluated whether neuroinflammation is induced by chorioamnionitis in a clinically relevant model.MethodsRhesus macaque fetuses were exposed to either intra-amniotic (IA) saline, or IA lipopolysaccharide (LPS) (1 mg) 16 or 48 h prior to delivery at 130 days (85 % of gestation) (n = 4–5 animals/group). We measured cytokines in the cerebrospinal fluid (CSF), froze samples from the left brain for molecular analysis, and immersion fixed the right brain hemisphere for immunohistology. We analyzed the messenger RNA (mRNA) levels of the pro-inflammatory cytokines IL-1β, CCL2, TNF-α, IL-6, IL-8, IL-10, and COX-2 in the periventricular white matter (PVWM), cortex, thalamus, hippocampus, and cerebellum by RT-qPCR. Brain injury was assessed by immunohistology for myelin basic protein (MBP), IBA1 (microglial marker), GFAP (astrocyte marker), OLIG2 (oligodendrocyte marker), NeuN (neuronal marker), CD3 (T cells), and CD14 (monocytes). Microglial proliferation was assessed by co-immunostaining for IBA1 and Ki67. Data were analyzed by ANOVA with Tukey’s post-test.ResultsIA LPS increased mRNA expression of pro-inflammatory cytokines in the PVWM, thalamus, and cerebellum, increased IL-6 concentration in the CSF, and increased apoptosis in the periventricular area after 16 h. Microglial proliferation in the white matter was increased 48 h after IA LPS.ConclusionsLPS-induced chorioamnionitis caused neuroinflammation, microglial proliferation, and periventricular apoptosis in a clinically relevant model of chorioamnionitis in fetal rhesus macaques. These findings identify specific responses in the fetal brain and support the hypothesis that neuroinflammatory changes may mediate the adverse neurodevelopmental outcomes associated with chorioamnionitis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0706-4) contains supplementary material, which is available to authorized users.

Prenatal Intra-Amniotic Endotoxin Induces Fetal Gut and Lung Immune Responses and Postnatal Systemic Inflammation in Preterm Pigs

“…13,14 Most of these injection routes (except IA) induce strong maternal and fetal systemic inflammation, whereas human chorioamnionitis often shows more moderate fetal inflammatory responses. 15,16 Most likely, animal models using IA injection to expose the fetus to inflammatory factors best reflect the conditions in human chorioamnionitis. Inflammatory agents and cytokines in the amniotic fluid are thought to initially interact with fetal epithelial surfaces, including the gut, lung, and skin, to elicit local tissue inflammation before spreading inflammatory signals to the circulation and internal organs.…”

The trophic effect of nerve growth factor in primary cultures of rat hippocampal neurons is associated to an anti‐inflammatory and immunosuppressive transcriptional program

“…Chemokines, such as CCL2 , and cytokines, such as IL‐1α , IL‐1β , TNF α , TGF beta 1, Tnfsf13 , were significantly down‐regulated in Ngf treated‐HNs. They are key apoptotic and pro‐inflammatory molecules as demonstrated by previous studies in different cell types (Grubic Kezele, Blagojevic Zagorac, Jakovac, Domitrovic, & Radosevic‐Stasic, ; Lage et al, ; Lee, Kang, Homer, Chupp, & Elias, ; Liu, Zhang, Wu, Wu, & Wang, ; Martinez, Ramesh, Jacobs, & Philipp, ; Roth et al, ; Schmidt et al, ; Syeda, Patel, Lee, & Hackam, ; Zhang, Huang, & Chen, ). In Ngf treated HNs, we observed the down‐regulation of Nlrp3/Nalp3 and Ctss , two genes implicated in apoptosis (Hsieh et al, ; Wu et al, ; Ye et al, ).…”

Umbilical cord blood stem cell therapy in premature brain injury: Opportunities and challenges

“…Inflammation is another main cause of WMI by increasing the influx of chemokines, cytokines, and other inflammatory factors across the blood–brain barrier, inducing microglia activation, and interfering with oligodendrocyte maturation (Albertsson et al, ; Schmidt et al, ). Lipopolysaccharide (LPS) can trigger a severe inflammatory response, and thus LPS is commonly used to mimic infection and induce WMI in animal models (Wang, Rousset, Hagberg, & Mallard, ).…”