396 - Chorioamnionitis-induced sequential changes in brain inflammatory-immune signatures correlate with sustained increase in Hemeoxygenase1(HO-1)/TransferrinR1(TfR1) during a critical developmental window

Poster Number: 396
Publication Number: 396.236

Maide Ozen, Johns Hopkins University School of Medicine, Baltimore, MD, United States; Alexander R. Gall, Johns Hopkins University School of Medicine, Baltimore, MD, United States; Shenandoah Robinson, Johns Hopkins University, Baltimore, MD, United States; Lauren L. Jantzie, Johns Hopkins University School of Medicine, Baltimore, MD, United States

Background: We previously showed that elevation in HO-1 mRNA expression in utero and in the early perinatal period resulted in sustained increase in HO-1/TfR1, increased neuroinflammation (CD45+CD11b/c+ mononuclear cells (M)) at term equivalent age and increase in peripheral double negative T cells at P21. Dysregulation of HO-1 favors pro-inflammatory signals while TfR1 regulates anti-inflammatory signal transduction. Here, we hypothesized that altered HO-1/TfR1 timeline would correlate with inflammatory/immune signal changes in brain. 

Objective: To define chorioamnionitis (CHORIO)-induced inflammatory signatures in brain mononuclear and T cell subsets, during a critical developmental window and its correlation with sustained increase in HO-1/TfR1 timeline.

Design/Methods: Pregnant Sprague-Dawley rats were stratified to Sham or CHORIO groups and underwent laparotomy on embryonic day 18 (E18). CHORIO was induced by transient occlusion of the uterine arteries followed by intra-amniotic injection of lipopolysaccharide. Shams received laparotomy with equivalent duration of anesthesia. Brains from male and female pups were collected at E18.5, E19, P2 and P7 for TNFα, CD86 (M1, inflammatory) and Arg1 (M2, anti-inflammatory) mRNA expression. Brain T cell subsets were studied at P21 by flow cytometry. n=7, E18.5-P2, n=3-6, P7-21. Data are represented as mean±SEM. For statistical comparisons t-test, Mann-Whitney U, ANOVA were used with p< 0.05 considered significant.

Results: Our results show that Arg1 is significantly decreased at E18.5, in CHORIO cortex compared to Sham (p=0.007) consistent with decreased M2 macrophages. At P2, there is a significant increase in CD86 in CHORIO compared to Sham (p=0.042) which suggests an increased M1. Importantly, CHORIO has a significant injury effect on cortical Arg1 expression. We did not see a significant timepoint effect on TNFα, CD86 and Arg1 expression between E18.5 and P7. At P21, CD3+CD4+ T helper (Th) cells are significantly increased in CHORIO brains compared to Sham (p=0.019) concomitant with an increase in peripheral double negative T cells.Conclusion(s): An acute decrease in anti-inflammatory M2 mononuclear signature in cortex at E18.5 precedes the increased proinflammatory signature at P2. The timing of M2 and M1 changes correlate with our previously reported sustained HO-1/TfR1 dysregulation at E18.5-P2, leading to neuroinflammation. Prominence of Th cells at P21 may suggest evidence of emerging chronic neuroinflammation and neural injury. Further studies will define how these inflammatory/immune signatures contribute to white matter injury in CHORIO.