Differential Brain and Cerebrospinal Fluid Proteomic Responses To Acute Prenatal Endotoxin Exposure

Background Chorioamnionitis (CA) is a risk factor for preterm birth and is associated with neurodevelopmental delay and cognitive disorders. Prenatal inflammation-induced brain injury may resolve during the immediate postnatal period, which is a time of rapid metabolic and brain remodeling. Cerebrospinal fluid (CSF) collected at birth may be a critical source of predictive biomarkers. Using pigs as a model of preterm infants exposed to CA, we hypothesized that prenatal lipopolysaccharide (LPS) exposure induces proteome changes in the CSF and brain both at birth and later. Methods Fetal piglets (103 days gestation of the full-term 117 days) were administered intra-amniotic (IA) lipopolysaccharide (LPS) 3 days before preterm delivery by caesarian section. CSF and brain tissue were collected on postnatal Days 1 and 5 (P1 and P5). CSF and hippocampal proteins were profiled by LC–MS-based quantitative proteomics. Neuroinflammatory responses in the cerebral cortex, periventricular white matter and hippocampus were evaluated by immunohistochemistry, and gene expression was evaluated by qPCR. Results Pigs exposed to LPS in utero showed changes in CSF protein levels at birth but not at P5. Complement protein C3, hemopexin, vasointestinal peptide, carboxypeptidase N subunit 2, ITIH1 and plasminogen expression was upregulated in the CSF, while the expression of proteins associated with axon growth and synaptic functions (FGFR1, BASP1, HSPD1, UBER2N, and RCN2), adhesion (Talin1), and neuronal survival (Atox1) was downregulated. Microglia, but not astrocytes, were activated by LPS at P5 in the hippocampus but not in other brain regions. At this time, marginal increases in complement protein C3, LBP, Hif1a, Basp1, Minpp1 and FGFR1 transcription indicated hippocampal proinflammatory responses. Conclusion A brief period of prenatal endotoxin exposure induces proteome changes in the CSF and brain at birth, but most changes resolve a few days later. The developing hippocampus has high neuronal plasticity in response to perinatal inflammation. Changes in CSF protein expression at birth may help to predict later structural brain damage in preterm infants exposed to variable types and durations of CA-related inflammation in utero.

PSX-B-23 Immune tolerance of dairy heifers in response to repeated bacterial endotoxin exposure

Lipopolysaccharide (LPS) endotoxin from the membrane of Gram-negative bacteria is often used to simulate bacterial infection in mammals. Repeated exposure to LPS over a short period of time, however, is reported to result in an attenuated acute-phase response. This “LPS tolerance” is an essential immune-homeostatic response that can protect against over-activation of the inflammatory response during chronic exposure to LPS. In the present study, Holstein calves (n=20) were initially intramuscularly challenged with either saline, or 100, 200 or 400 ng/kg of LPS and then all animals were re-challenged with 200 ng/kg of LPS 2-weeks later to assess potential LPS tolerance in ruminants. Serum was collected every 2 hrs for 6 hrs to profile changes in circulatory stress biomarkers. In comparison to the first challenge and saline control animals that received LPS for the first time, heifers re-challenged with LPS demonstrated significantly attenuated cortisol responses in the second LPS challenge (p < 0.05). Blood cell populations were also attenuated in animals receiving their second LPS challenge, in that re-challenged animals showed significantly less severe thrombocytopenic (p < 0.05), and leukopenic responses to their second LPS challenge as compared to their first (p < 0.05); this trend was also apparent when comparing newly LPS-challenged animals to the LPS re-challenged animals. MicroRNA expression profiles were determined to assess a potential epigenetic response to repeated LPS exposure, which may help identify therapeutic targets to protect against LPS-associated diseases including clinical mastitis and sepsis. The present study demonstrated that LPS tolerance occurs in dairy cattle, and understanding the roles of various miRNAs in the context of innate immune cell tolerance is essential for evaluating their impact on immune system homeostasis.

Pregnancy-specific transcriptional changes upon endotoxin exposure in mice

Objectives Pregnant women are more susceptible to certain infections; however, this increased susceptibility is not fully understood. Herein, systems biology approaches were utilized to elucidate how pregnancy modulates tissue-specific host responses to a bacterial product, endotoxin. Methods Pregnant and non-pregnant mice were injected with endotoxin or saline on 16.5 days post coitum (n=8–11 per group). The uterus, cervix, liver, adrenal gland, kidney, lung, and brain were collected 12 h after injection and transcriptomes were measured using microarrays. Heatmaps and principal component analysis were used for visualization. Differentially expressed genes between groups were assessed using linear models that included interaction terms to determine whether the effect of infection differed with pregnancy status. Pathway analysis was conducted to interpret gene expression changes. Results We report herein a multi-organ atlas of the transcript perturbations in pregnant and non-pregnant mice in response to endotoxin. Pregnancy strongly modified the host responses to endotoxin in the uterus, cervix, and liver. In contrast, pregnancy had a milder effect on the host response to endotoxin in the adrenal gland, lung, and kidney. However, pregnancy did not drastically affect the host response to endotoxin in the brain. Conclusions Pregnancy imprints organ-specific host immune responses upon endotoxin exposure. These findings provide insight into the host-response against microbes during pregnancy.