Role of B1 and B2 lymphocytes in placental ischemia-induced hypertension.

Preeclampsia is a prevalent pregnancy complication characterized by new-onset maternal hypertension and inflammation, with placental ischemia as the initiating event. Studies of others have provided evidence for the importance of lymphocytes in placental ischemia-induced hypertension; however, the contributions of B1 versus B2 lymphocytes are unknown. We hypothesized that peritoneal B1 lymphocytes are important for placental ischemia-induced hypertension. As an initial test of this hypothesis, the effect of anti-CD20 depletion on both B-cell populations was determined in a reduced utero-placental perfusion pressure (RUPP) model of preeclampsia. Anti-murine CD20 monoclonal antibody (5 mg/kg, Clone 5D2) or corresponding mu IgG2a isotype control was administered intraperitoneally to timed pregnant Sprague-Dawley rats on gestation day (GD)10 and 13. RUPP or sham control surgeries were performed on GD14, and mean arterial pressure (MAP) was measured on GD19 from a carotid catheter. As anticipated, RUPP surgery increased MAP and heart rate and decreased mean fetal and placental weight. However, anti-CD20 treatment did not affect these responses. On GD19, B-cell populations were enumerated in the blood, peritoneal cavity, spleen, and placenta with flow cytometry. B1 and B2 cells were not significantly increased following RUPP. Anti-CD20 depleted B1 and B2 cells in peritoneum and circulation but depleted only B2 lymphocytes in spleen and placenta, with no effect on circulating or peritoneal IgM. Overall, these data do not exclude a role for antibodies produced by B cells before depletion but indicate the presence of B lymphocytes in the last trimester of pregnancy is not critical for placental ischemia-induced hypertension.NEW & NOTEWORTHY The adaptive and innate immune systems are implicated in hypertension, including the pregnancy-specific hypertensive condition preeclampsia. However, the mechanism of immune system dysfunction leading to pregnancy-induced hypertension is unresolved. In contrast to previous reports, this study reveals that the presence of classic B2 lymphocytes and peritoneal and circulating B1 lymphocytes is not required for development of hypertension following third trimester placental ischemia in a rat model of pregnancy-induced hypertension.

Effect of nicotine on placental ischemia-induced complement activation and hypertension in the rat.

Preeclampsia is a pregnancy-specific condition manifested by new-onset maternal hypertension with systemic inflammation, including increased innate immune system complement activation. While exact pathophysiology is unknown, evidence suggests that inadequate spiral artery invasion and resulting utero-placental insufficiency is the initiating event. Cigarette smoking during pregnancy decreases the risk of preeclampsia. Nicotine, a major component of cigarettes, stimulates the efferent cholinergic anti-inflammatory pathway through peripherally expressed nicotinic acetylcholine receptors (nAChR) and is known to attenuate ischemia-reperfusion injury in kidney and liver. Prior studies indicated that complement activation was critical for placental ischemia-induced hypertension in a rat model. Thus, it was hypothesized here that nicotine was responsible for the protective effect of cigarette smoking in preeclampsia and would attenuate placental ischemia-induced systemic complement activation and hypertension. The Reduced Utero-placental Perfusion Pressure (RUPP) model in the pregnant rat was employed to induce placental ischemia, resulting in complement activation, fetal resorptions, and hypertension. On gestation day (GD)14, nicotine (1 mg/kg) or saline was administered via subcutaneous injection prior to RUPP surgery and daily through GD18. On GD19, placental ischemia significantly increased mean arterial pressure (MAP) in saline injected animals. However, the placental ischemia-induced increase in blood pressure was not evident in nicotine-treated animals and nicotine treatment significantly increased MAP variability. Circulating C3a was measured as an indicator of complement activation and increased C3a in RUPP compared to Sham persisted with nicotine treatment, as did fetal resorptions. These data suggested to us that nicotine may contribute to the decreased risk of preeclampsia with cigarette smoking, but this protective effect was confounded by additional effects of nicotine on the cardiovascular system.