Depletion of B1 and B2 lymphocytes in placental ischemia‐induced hypertension in the rat

Abstract

Preeclampsia is a pregnancy specific disease characterized by new‐onset maternal hypertension and increased systemic inflammation, including increased complement activation. Although the exact pathophysiology is unknown, abnormal arterial remodeling and placental insufficiency have been implicated as initiating events. Studies of others have provided evidence for the importance of the B cell in placental ischemia‐induced hypertension, but contribution of the B1 lineage of innate B lymphocytes vs. the traditional B2 cell is unknown. Our previous studies showed increased peritoneal B1 cells following placental ischemia. Thus, we hypothesized that IgM producing B1 cells are the important B cell responsible for complement activation and hypertension following chronic placental ischemia in the reduced uterine placental perfusion (RUPP) rat model. The effect of anti‐CD20 antibody treatment on placental ischemia‐induced hypertension and B cell subpopulations in peritoneal cavity, spleen and blood was determined. Anti‐murine CD20 mAb (5 mg/kg, Clone 5D2, Genentech) or corresponding mu IgG2a isotype control were administered IP to timed pregnant Sprague Dawley rats (Charles River) on gestation day (GD)10 and 13. On GD14, rats underwent either Sham surgery or clip placement on ovarian arteries and abdominal aorta to reduce uterine perfusion pressure (RUPP) resulting in increased maternal blood pressure on GD19 (n=4–14 animals/group). Mean arterial pressure was measured from a carotid catheter in unanesthetized, restrained animals and increased from 91 ± 4 to 104 ± 4 mm Hg with RUPP in isotype treated animals and was not significantly attenuated in RUPP anti‐CD20 treated animals (100 ± 3 mm Hg). On GD19, peritoneal cavity was lavaged with PBS, spleen removed and mechanically disrupted, blood obtained from abdominal aorta, and B1 (IgM+ CD11b+) and B2 (IgM+ CD11b‐) lymphocytes enumerated by flow cytometry. Data is expressed as % of total lymphocytes. Both peritoneal B1 and B2 cells increased following placental ischemia (**) with no change in blood or spleen. When evaluated at GD19, anti‐CD20 treatment significantly depleted B2 cells in all compartments and B1 cells in peritoneum and blood (*) with no effect on RUPP‐induced hypertension. A separate group of rats was used to determine if anti‐CD20 treatment effectively depleted B cells at time of RUPP surgery (GD14). On GD14, anti‐CD20 treatment reduced B1 cells in peritoneal cavity and blood and B2 cells in all compartments compared to isotype treated GD14 animals (*). However, comparing anti‐CD20 treatment at GD14 to GD19, B1 and B2 cells in peritoneal cavity were significantly greater at GD14 (#), indicating incomplete peritoneal B cell depletion at time of RUPP surgery. These data suggest that sufficient B1 and B2 cells may be present in the peritoneal cavity at time of induction of placental ischemia to contribute to hypertension, and that placental ischemia induced hypertension occurs despite significant depletion of splenic B2 cells and peripheral B1/B2 cells.Support or Funding InformationNIH HL109843 and American Heart Association Grant in Aid %B1 %B2 Peritoneal Spleen Blood Peritoneal Spleen Blood GD19 Sham Isotype 3.0 ± 0.6 19.9 ± 1.1 4.6 ± 0.8 1.4 ± 0.4 35.7 ± 2.6 21.4 ± 7.0 GD19 Sham AntiCD20 1.6 ± 0.7* 17.2 ± 2.0 0.7 ± 0.3* 0.2 ± 0.04* 7.5 ± 1.7* 1.5 ± 0.5* GD19 RUPP Isotype 4.9 ± 1.2** 20.8 ± 1.9 7.8 ± 1.5 2.4 ± 0.6** 37.2 ± 2.1 21.9 ± 1.6 GD19 RUPP AntiCD20 1.4 ± 0.6* 17.8 ± 1.2 1.1 ± 0.3* 0.3 ± 0.1* 7.0 ± 0.9* 1.5 ± 0.2* GD14 Isotype 18.1 ± 3.1 14.7 ± 2.6 6.4 ± 2.2 7.7 ± 1.6 47.9 ± 5.6 33.4 ± 2.2 GD14 AntiCD20 5.9 ± 2.6*# 11.0 ± 4.0 2.0 ± 0.6* 3.3 ± 0.9*# 6.6 ± 1.1* 2.7 ± 0.8* p<0.05: vs Isotype; RUPP > Sham Isotype; GD14 AntiCD20 > GD19 AntiCD20 This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.