Secretion of IL‐17 is localized to inflammatory cells from the brainstem among hypertensive pregnant rats

Hypertension is associated with neuroinflammation and vascular damage, which when it occurs during pregnancy can have long‐lasting effects on maternal cognition and mood. During pregnancy, the maternal vasculature becomes more susceptible to injury which is especially true in pregnancies complicated with high blood pressure such as HELLP syndrome (hemolysis, elevated liver enzymes, low platelets) and preeclampsia (PreE). Several studies have suggested that neuroinflammation in response to hypertension occurs in women with HELLP syndrome or PreE, however the cell types and brain regions that may be affected have not been fully identified. The objective of the current study was to determine if certain brain regions were more susceptible to neuroinflammation animal models with hypertensive pregnancies. METHODS On gestational day (GD) 12 mini‐osmotic pumps infusing sFlt‐1 (4ug) and sEng (7ug) were placed into rats to induce HELLP or with sFlt‐1 (PreE model) to increase blood pressure and systemic inflammation. On GD18 carotid catheters were inserted, followed by mean arterial pressure (MAP) measurement, plasma, tissue and maternal brain collection on GD19. At the time of euthanization brains were collected, sectioned into the frontal and posterior cortices, brainstem and cerebellum. T cells, astrocytes and microglia were isolated from each region through a series of enzymatic and microbead isolations. Cell populations were cultured overnight, followed by media collection for inflammation assays and cell collection for flow cytometry. Cell populations were verified for purity via flow cytometry. Neuroinflammation was assessed via secretion of tumor necrosis factor alpha (TNFα) and interleukin‐17 (IL‐17) in the cell culture media via ELISA. IL‐17 secretion within the media was normalized to total protein level before individual normalization to 1x10 5 cells. Results MAP was increased in HELLP (p<0.01) and PreE (p=0.03) compared to NP rats. T cell secretion of IL‐17 was significantly increased among hypertensive pregnancies vs. NP in the brainstem (p=0.007). Microglia secretion of IL‐17 was significantly increased among hypertensive pregnancies vs NP in the brainstem (p=0.02). IL‐17 secretion was not increased in response to hypertension in other regions or cell types when compared to NP rats (p>0.05). Preliminary studies with TNFα are inconclusive as the levels have been undetectable via Quantikine ELISA. There were not any regional differences between groups in regards to cell types, except for NP and HELLP rats where the amount of CD11+ T cells was increased in the brainstem (2.54% vs. 4.37% gated). Similar results were seen with microglia in the brainstem where NP rats 0.71% vs. 1.77% gated cells. Conclusion These data indicate that there are regional differences among neuroinflammatory cells during pregnancy. These preliminary results suggest that the brainstem is more susceptible to T cell and microglia infiltration or activation compared to the frontal and posterior cortex and the cerebellum. Current studies are being conducted to increase n's among the groups, brain regions and cell types and to find a more sensitive assay to detect TNFα secretion.