No abstract

Preeclampsia (PE) is characterized by new-onset hypertension that usually occurs in the third trimester of pregnancy and is associated with oxidative stress and angiotensin II type 1 receptor agonistic autoantibodies (AT1-AAs). Inhibition of the AT1-AAs in the reduced uterine perfusion pressure (RUPP) rat, a model of PE, attenuates hypertension and many other characteristics of PE. We have previously shown that mitochondrial oxidative stress (mtROS) is a newly described PE characteristic exhibited by the RUPP rat that contributes to hypertension. However, the factors that cause mtROS in PE or RUPP are unknown. Thus, the objective of the current study is to use pharmacologic inhibition of AT1-AAs to examine their role in mtROS in the RUPP rat model of PE. AT1-AA inhibition in RUPP rats was achieved by administration of an epitope-binding peptide (′n7AAc′). Female Sprague-Dawley rats were divided into the following two groups: RUPP and RUPP + AT1-AA inhibition (RUPP + ′n7AAc′). On day 14 of gestation (GD), RUPP surgery was performed; ′n7AAc′ peptide (2 µg/μL) was administered by miniosmotic pumps in a subset of RUPP rats; and on GD19, sera, placentas, and kidneys were collected. mitochondrial respiration and mtROS were measured in isolated mitochondria using the Oxygraph 2K and fluorescent microplate reader, respectively. Placental and renal mitochondrial respiration and mtROS were improved in RUPP + ′n7AAc′ rats compared with RUPP controls. Moreover, endothelial cells (human umbilical vein endothelial cells) treated with RUPP + ′n7AAc′ sera exhibited less mtROS compared with those treated with RUPP sera. Overall, our findings suggest that AT1-AA signaling is one stimulus of mtROS during PE.

BACKGROUND: Preeclampsia is characterized by a new onset of hypertension during pregnancy and is associated with autoantibodies against the angiotensin II type 1 receptor and oxidative stress. There is growing evidence for mitochondrial dysfunction in preeclampsia, however, the culprits for mitochondrial dysfunction are still being defined. We previously demonstrated that angiotensin II type 1 autoantibodies cause renal, placental, and endothelial mitochondrial dysfunction in pregnant rats. However, the role of the angiotensin II type 1 autoantibodies in endothelial mitochondrial function in response to sera from preeclamptics is unknown. Thus, we hypothesized that circulating factors, such as the angiotensin II type 1 autoantibodies, during preeclampsia would negatively impact the vascular endothelial mitochondrial function in human umbilical vein endothelial cells. OBJECTIVE: The objective of the study was to determine a role for circulating angiotensin II type 1 autoantibodies to cause endothelial mitochondrial reactive oxygen species and dysfunction in preeclampsia compared to normal pregnant controls. STUDY DESIGN: Immediately after delivery, sera was collected from preeclamptic patients and normal pregnant controls. The mitochondrial reactive oxygen species were determined from the cells treated overnight with 10% sera from either the control or preeclamptic patients with and without the antiotension II type 1 autoantibodies inhibitor peptide ('n7AAc'). RESULTS: Preeclampsia patients at <34 weeks' gestation exhibited an elevated mean arterial blood pressure. Cells treated with serum from the preeclampsia patients at <34 weeks gestational age showed significantly (P<0.05) greater mitochondrial oxidative stress and reduced respiration than cells treated with the control sera, and these abnormalities were restored with 'n7AAc'. CONCLUSION: This study demonstrates that endothelial mitochondrial dysfunction occurs in response to circulating factors, especially in response to serum from preterm preeclampsia patients, and can be restored by blocking circulating angiotensin II type 1 autoantibodies, thereby indicating a potential new therapeutic target for preeclampsia.

The Reduced Uterine Perfusion Pressure (RUPP) rat model and normal pregnant (NP) rat recipients of RUPP CD4+T cells recapitulate many characteristics of preeclampsia (PE) such as hypertension and oxidative stress. We have shown an important hypertensive role for NK cells to cause mitochondrial (mt) dysfunction in RUPP rats, however the role for RUPP CD4+ T cells to stimulate NK cells is unknown. Therefore, we hypothesize that RUPP induced CD4+ T cells activate NK cells to cause mt dysfunction/ROS as mechanisms of hypertension during pregnancy. We tested our hypothesis by adoptive transfer of RUPP CD4+T cells into NP rats or by inhibiting the activation of RUPP CD4+T cells with Orencia (Abatacept) and examining hypertension, NK cells and mt function. RUPP was performed on gestation day 14, splenic CD4+ T cells were isolated on GD19 and injected into NP rats on gestation day (GD) 13. In a separate groups of rats; Orencia was infused and the RUPP procedure performed. MAP and placental and renal mtROS increased in RUPP (n=7, p<0.05) and NP+RUPP CD4+ T cell recipients (n=13, p<0.05) compared to control NP (n=7) and NP+NPCD4+Tcell recipients (n=5), but was reduced with Orencia (n=13, p<0.05). Placental and renal respiration was reduced in RUPP (n=6, p<0.05) and NP+RUPP CD4+ T cells (n=6, state 3-p<0.05) compared to NP (n=5) and NP+NPCD4+Tcell recipients (n=5), but improved with Orencia (n=9, n=8 p<0.05). These data indicate that CD4+ T cells, independent of NK cells, cause mt dysfunction/ROS contributing to hypertension in response to placental ischemia during pregnancy.

Preeclampsia (PE) is characterized by new onset hypertension during pregnancy and is associated with oxidative stress, placental ischemia, and autoantibodies to the angiotensin II type I receptor (AT1-AA). Mitochondrial (mt) dysfunction in PE and various sources of oxidative stress, such as monocytes, neutrophils, and CD4 + T cells, have been identified as important players in the pathophysiology of PE. We have established the significance of AT1-AA, TNF-α, and CD4 + T cells in causing mitochondrial (mt) dysfunction in renal and placental tissues in pregnant rats. Although the role of mt dysfunction from freshly isolated intact placental mitochondria has been compared in human PE and normally pregnant (NP) controls, variations among preterm PE or term PE have not been compared and mechanisms contributing to mt ROS during PE are unclear. Therefore, we hypothesized PE placentas would exhibit impaired placental mt function, which would be worse in preterm PE patients than in those of later gestational ages. Immediately after delivery, PE and NP patient’s placentas were collected, mt were isolated and mt respiration and ROS were measured. PE patients at either < or >34 weeks gestational age (GA) exhibited elevated blood pressure and decreased placental mt respiration rates (state 3 and maximal). Patients delivering at >34 weeks exhibited decreased Complex IV activity and expression. Placental mtROS was significantly reduced in both PE groups, compared to NP placental mitochondria. Collectively, the study demonstrates that PE mt dysfunction occurs in the placenta, with mtROS being lower than that seen in NP controls. These data indicate why antioxidants, as a potential target or new therapeutic agent, may not be ideal in treating the oxidative stress associated with PE.