The role of T cell stimulated agonistic autoantibodies to the angiotensin II type I receptor (AT1-AA) in mediating multiorgan dysfunction in IL-17 induced hypertension during pregnancy

PROBLEM

Preeclampsia (PE), new-onset hypertension during pregnancy accompanied by organ dysfunction, is associated with chronic inflammation including elevated IL-17, CD4+ T cells, B cells and natural killer (NK) cells. IL-17 can serve as a signal for either the adaptive or innate immune activation. We have previously shown that IL-17 contributes to increased blood pressure in association with elevated TH17 cells, NK cells and B cells secreting angiotensin II type 1 receptor agonistic autoantibodies (AT1-AA) during pregnancy. Moreover, we have shown an important role for CD4+T cells and AT1-AA in multiorgan dysfunction as measured by mitochondrial oxidative stress (mt ROS). However, we do not know the role of adaptive immune cells such as T cells or B cells secreting AT1-AA in mediating the PE phenotype in response to elevated IL-17.

METHOD OF STUDY

In order to answer this question, we infused IL-17 (150 pg/day i.p.) into either Sprague Dawley (SD) or athymic nude rats via mini-osmotic pump from gestational day (GD) 14-19 of pregnancy. On GD 19, blood pressure was determined and NK cells, mtROS and respiration and AT1-AA production from B cells were measured.

RESULTS

Infusion of IL-17 increased blood pressure in the presence or absence of T cells. Mean arterial pressure (MAP) increased with IL-17 from 98 ± 2 mm Hg (n = 12) to 114 ± 2 (n = 12) in SD rats and from 99 ± 4 mm Hg (n = 7) versus 115 ± 2 mm Hg (n = 7) in athymic nude rats. Similar trends were seen in NK cells and placental mt ROS. Knowing that IL-17 stimulates AT1-AA in SD pregnant rats, we included a group of SD and athymic nude pregnant rats infused with IL-17 and the AT1-AA inhibitor peptide ('n7AAc'). The inhibitor attenuated blood pressure (104.9 ± 3.2, p = .0001) and normalized NK cells and mt function in SD pregnant rats. Importantly, the AT1-AA was not produced in pregnant nude IL-17 treated rats, nor did 'n7AAc' effect MAP, in nude athymic rats.

CONCLUSION

These findings suggest two conclusions; one is that IL-17 causes hypertension and multiorgan dysfunction in the absence of T cells and AT1-AA, possibly through its activation of innate cells and secondly, in the presence of T cells, blockade of the AT1-AA attenuates the effect of IL-17. This study indicates the critical effects of elevated IL-17 during pregnancy and suggest treatment modalities to consider for PE women.

The role of immune cells and mediators in preeclampsia

Preeclampsia is a hypertensive disorder of major concern in pregnancy than can lead to intrauterine growth restriction, placental abruption and stillbirth. The pathophysiology of preeclampsia is multifactorial, including not only kidney dysfunction but also endothelial dysfunction, as the maternal endothelium becomes exposed to placental factors that are released into the circulation and increase systemic levels of vasoconstrictors, oxidative stress, anti-angiogenic factors and inflammatory mediators. Importantly, inflammation can lead to insufficient placental perfusion and low birthweight in offspring. Various innate and adaptive immune cells and mediators have been implicated in the development of preeclampsia, in which oxidative stress is associated with activation of the maternal inflammatory response. Immune cells such as regulatory T cells, macrophages, natural killer cells, and neutrophils are known to have major causative roles in the pathology of preeclampsia, but the contributions of additional immune cells such as B cells, inflammatory cytokines and anti-angiotensin II type 1 receptor autoantibodies are also now recognized. Immunological interventions, therefore, have therapeutic potential in this disease. Here, we provide an overview of the immune responses that are involved in the pathogenesis of preeclampsia, including the role of innate and adaptive immune cells and mediators.

CD4+ T cells cause renal and placental mitochondrial oxidative stress as mechanisms of hypertension in response to placental ischemia

The reduced uterine perfusion pressure (RUPP) rat model and normal pregnant (NP) rat recipients of RUPP CD4+ T cells recapitulate many characteristics of preeclampsia such as hypertension and oxidative stress. We have shown an important hypertensive role for natural killer (NK) cells to cause mitochondrial dysfunction in RUPP rats; however, the role for RUPP CD4+ T cells to stimulate NK cells is unknown. Therefore, we hypothesized that RUPP-induced CD4+ T cells activate NK cells to cause mitochondrial dysfunction/reactive oxygen species (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 mitochondrial function. RUPP was performed on gestation day (GD) 14, and splenic CD4+ T cells were isolated on GD 19 and injected into NP rats on GD 13. In a separate group of rats, Orencia was infused and the RUPP procedure was performed. Mean arterial pressure and placental and renal mitochondrial ROS increased in RUPP (n = 7, P < 0.05) and NP + RUPP CD4+ T-cell recipients (n = 13, P < 0.05) compared with control NP (n = 7) and NP + NP CD4+ T-cell 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-cell recipients (n = 6, state 3 P < 0.05) compared with NP (n = 5) and NP + NP CD4+ T-cell 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 mitochondrial dysfunction/ROS contributing to hypertension in response to placental ischemia during pregnancy.

Abstract P269: Circulating Factors in Response to Placental Ischemia Cause Vascular Endothelial Mitochondrial Oxidative Stress

Introduction: Preeclampsia (PE) is associated with placental ischemia, new onset hypertension, oxidative stress and endothelial dysfunction. Factors linking placental ischemia with endothelial dysfunction and hypertension are not completely understood. Mitochondrial (mt) dysfunction (dys) is a major source of reactive oxygen species (ROS) and we have shown that placental ischemia causes oxidative stress in RUPP rats. We hypothesize that circulating factors in RUPP rats cause vascular endothelial mt dys and mt ROS as a contributor to endothelial dysfunction and hypertension during pregnancy.

Methods: Female Sprague Dawley rats were dived into two groups; normal pregnant (NP) and RUPP rats. On gestational day (GD) 14, RUPP surgery was performed, GD18 carotid catheters were inserted, and GD19 conscious blood pressure (MAP) was measured. GD 19 placentas were collected and mitochondria were isolated for respiration and ROS measurements. Mt ROS was measured spectrophotometrically in HUVECs incubated with 10% serum from NP or RUPP rats using MitoSox Red.

Results: MAP was elevated in RUPP (n=9) compared to NP rats (n=9) (122±2 vs. 104±2 mmHg, p<0.05). State 3 (313±16 vs 423±15 pmol/sec/mg, p<0.05) and maximal (244±13 vs 300±11 pmol/sec/mg, p<0.05) respiration rates were significantly reduced in placental mitochondria from RUPP (n=7) vs NP (n=8) rats. RUPP placental mitochondria show 35-fold increase in ROS production compared NP mitochondria (p<0.05). HUVECs incubated with RUPP (n=7) serum showed significantly increased ROS vs NP (n=7) serum (9±3 vs 3±1, % gated, p=0.05).

Conclusion: Reduced placental mitochondrial respiration and increased mt ROS support the hypothesis that mt dys and mt ROS occurs in response to placental ischemia. Importantly, increased ROS from endothelial cells in response to RUPP serum indicate the importance of circulating factors to cause vascular mt dyst and mt ROS.

IL-10 supplementation increases Tregs and decreases hypertension in the RUPP rat model of preeclampsia

OBJECTIVE

The reduced uterine perfusion pressure (RUPP) rat model of preeclampsia was used to determine the effects of added interleukin-10 (IL-10) on Tregs and hypertension in response to placental ischemia and how the decrease in these anti-inflammatory factors mediates the pathophysiology of preeclampsia.

METHODS

IL-10 (2.5 ng/kg/d) was infused via osmotic mini-pump implanted intraperitoneally on day 14 of gestation and, at the same time, the RUPP procedure was performed.

RESULTS

IL-10 reduced mean arterial pressure (p < 0.001), decreased CD4(+) T cells (p = 0.044), while increasing Tregs (p = 0.043) which led to lower IL-6 and TNF-α (p = 0.008 and p = 0.003), reduced AT1-AA production (p < 0.001), and decreased oxidative stress (p = 0.029) in RUPP rats.

CONCLUSION

These data indicate that IL-10 supplementation increases Tregs and helps to balance the altered immune system seen during preeclampsia.

Hypertension, inflammation and T lymphocytes are increased in a rat model of HELLP syndrome

OBJECTIVE

An animal model of hemolysis, elevated liver enzymes, low platelet count (HELLP) was used to determine if T lymphocytes accompany hypertension and increased inflammatory cytokines.

METHODS

sFlt-1 (4.7 µg/kg/day) and sEndoglin (7 µg/kg/day) were infused into normal pregnant rats (HELLP rats) for 8 days.

RESULTS

HELLP was associated with increased mean arterial pressure (p = 0.0001), hemolysis (p = 0.044), elevated liver enzymes (p = 0.027), and reduced platelets (p = 0.035). HELLP rats had increased plasma levels of TNFα (p = 0.039), IL-6 (p = 0.038) and IL-17 (p = 0.04). CD4(+) and CD8(+) T lymphocytes were increased.

CONCLUSION

These data support the hypothesis that T cells are associated with hypertension and inflammation.

Vitamin D Supplementation Suppresses Hypoxia-Stimulated Placental Cytokine Secretion, Hypertension and CD4+ T Cell Stimulation in Response to Placental Ischemia

OBJECTIVE

To investigate a role of Vitamin D in the pathogenesis of preeclampsia (PE), and to discern any potential benefits of Vitamin D supplementation on hypertension in the RUPP rat model of PE.

STUDY DESIGN

Blood and placentas from normal pregnancies (NP) and PE were collected following elective cesarean delivery without evidence of infection. Circulating Vitamin D was extracted by HPLC and measured via mass spectrometry. Media for placenta explants was supplemented with Vitamin D and exposed to hypoxic (1% O2) or normoxic (6% O2) conditions for 24 hours. ELISAs were performed on media and normalized to total protein to determine cytokine secretion. RUPP rats were supplemented with vitamin D by oral gavage, and blood pressure (MAP) and pup weights were measured in NP and RUPP rats with or without Vitamin D supplementation. Flow cytometry was used to evaluate CD4⁺ Tcells in control RUPP rats and RUPP rats treated with Vitamin D.

RESULTS

Inflammatory cytokine secretion was higher (p<0.05) while the anti-inflammatory cytokine, IL-10, was significantly lower in the media of PE placentas compared to NP (p=0.005). Vitamin D supplementation decreased hypoxia stimulated pro-inflammatory cytokine secretion (p=0.003) in the media of PE placentas. Vitamin D decreased MAP and circulating CD4⁺ T cells in the RUPP rat model of PE (p<0.05).

CONCLUSION

Vitamin D supplementation may be useful in the treatment or prevention of hypertensive disorders in pregnancy.

Abstract 542: Progesterone Supplementation Attenuates Hypertension And AT1-AA in Response Tt Elevated IL-6 During Pregnancy

Preeclampsia is a multi-system disorder defined as new-onset hypertension with proteinuria developing after 20 weeks gestation. Preeclampsia remains a significant contributor to maternal morbidity and mortality, with great impact in perinatal morbidity. Research efforts throughout the world have focused on alternative therapies for the treatment of preeclampsia to the mainstay treatment of delivery of the fetus and placenta. 17-alpha-hydroxyprogesterone caproate (17-OHP) is a synthetic metabolite of progesterone used effectively for the prevention of recurrent preterm birth in singleton pregnancies. Previously we identified potential role for 17-OHP as an anti-inflammatory that suppressed inflammatory cytokines, hypertension and endothelin-1 in response to placental ischemia in the RUPP rat model of preeclampsia. In the current study we examined a role 17-OHP to blunt the pathophysiological effects to elevated IL-6 during pregnancy. IL-6 induced hypertension during pregnancy occurs with increased renin activity, autoantibodies to the angiotensin II type I receptor (AT1-AA) and reduced kidney function. This experiment was performed in the following groups of normal pregnant rats: NP (n=5); NP+17-OHP (n=6); NP+IL-6 (n=10); NP+IL-6+17-OHP (n=10). To test our hypothesis IL-6 (5ng/day) was infused via miniosmotic pump into normal pregnant rats beginning on day 14 of gestation and 17-OHP (3.32mg/kg) was diluted in normal saline and injected on day 18. Blood pressure (MAP) determination and serum collection was performed on day 19 of gestation. MAP in NP was 100+3mmHg which increased with IL-6 to 112+4mmHg, p <0.05. Pregnant rats given 17-OHP alone had a MAP of 99+3mmHg and MAP only increased to 103+2mmHg in IL-6+17-OHP. AT1-AA was 1.2+0.5 bpm in NP rats and increased to 17+9 bpm with IL-6 infusion. Administration of 17-OHP significantly blunted AT1-AA to 4+0.8bpm in NP+IL-6+17-OHP. Importantly, this study illustrates that 17-OHP attenuates hypertension and AT1-AA in response to elevated IL-6 during pregnancy and could lend hope to a new potential therapeutic for preeclampsia.

Elucidating immune mechanisms causing hypertension during pregnancy

Preeclampsia is associated with hypertension and increased infant and maternal morbidity and mortality. The underlying cause of preeclampsia is largely unknown, but it is clear that an immunological component plays a key pathophysiological role. This review will highlight immunological key players in the pathology of preeclampsia and discuss their role in the pathophysiology observed in the reduced placental perfusion (RUPP) rat model of preeclampsia.

Responses to dural puncture during institution of combined spinal-epidural analgesia: a comparison of 27 gauge pencil-point and 27 gauge cutting-edge needles

Pencil-point spinal needles are popular for combined spinal-epidural analgesia because they cause less dural puncture headache than cutting-edge spinal needles. However many parturients move, grimace, vocalise or experience paraesthesia or dysaesthesia during dural puncture when performing 'needle through needle' combined spinal-epidural analgesia. We compared dural puncture responses induced by pencil-point and cutting-edge needles (both 27 gauge). With institutional approval, 115 parturients presenting for elective caesarean section or labour analgesia were audited. After lignocaine infiltration, a Tuohy-type needle was inserted to loss of resistance to saline at a mid-lumbar interspace, and either a 27 gauge cutting-edge or 27 gauge pencil-point needle was inserted 'needle through needle' through the dura. During dural penetration, the occurrence of patient movement, grimacing or vocalisation was noted by a blinded observer, as was the patient's response to the question "Did you feel that?" asked by the anaesthetist. The audit comprised two similar groups of patients (caesarean section, n=30; labour analgesia, n=85). In both groups, grimacing and movement during thecal penetration occurred more frequently with pencil-point needles (P < 0.05 and P < 0.025, respectively). Pooled data analysis revealed that pencil-point and cutting-edge needles induced grimacing and movement in 17 (22%) and 2 (5%), spontaneous vocalisation in 4 (5%) and 1 (3%) and was perceived by 13 (17%) and 3 (8%) parturients (P < 0.025, P=NS, P=NS), respectively. Overall, 34 and 6 objective and subjective patient responses (P < 0.005) occurred when inserting these needles, respectively. Dural puncture by a 27 gauge pencil-point needle inserted 'needle through needle' when instituting combined spinal-epidural analgesia induces more iatrogenic responses than a 27 gauge cutting-edge needle.