The role of NO-cGMP pathway inhibition in vascular endothelial-dependent smooth muscle relaxation disorder of AT1-AA positive rats: protective effects of adiponectin.

Angiotensin II type 1 receptor autoantibodies (AT1-AA) cause endothelial-dependent smooth muscle relaxation disorder. It is well understood that impairment of the NO-cGMP signaling pathway is one of the mechanisms of endothelial-dependent smooth muscle relaxation disorder. However, it is still unclear whether AT1-AA induces endothelial-dependent smooth muscle relaxation disorder via the impairment of the NO-cGMP signaling pathway. In addition, adiponectin exerts vascular endothelial protection through the NO-cGMP signaling pathway. Therefore, the purpose of this investigation was to assess the mechanism of vascular endothelial-dependent smooth muscle relaxation disorder induced by AT1-AA and the role of adiponectin in attenuating this dysregulation. Serum endothelin-1 (ET-1), adiponectin and AT1-AA were detected by enzyme-linked immunosorbent assay. In preeclamptic patients, there was an increased level of AT1-AA, which was positively correlated with ET-1 and negatively correlated with adiponectin, as elevated levels of ET-1 suggested endothelial injury. AT1-AA-positive animal models were actively immunized with the second extracellular loop of the angiotensin II type 1 receptor (AT1R-ECII) for eight weeks. In thoracic aortas of AT1-AA positive rats, ET-1 was elevated, endothelium-dependent vasodilation was decreased. Paradoxically, as the upstream element of the NO-cGMP signaling pathway, NO production was not decreased but increased, and the ratio of p-VASP/VASP, an established biochemical endpoint of NO-cGMP signaling pathway, was reduced. Moreover, the levels of nitrotyrosine and gp91phox which indicate the presence of peroxynitrite (ONOO-) and superoxide anion (O2·-) were increased. Pretreatment with the ONOO- scavenger FeTMPyP or O2·-scavenger Tempol normalized vasorelaxation. Key enzymes responsible for NO synthesis were also assessed. iNOS protein expression was increased, but p-eNOS(Ser1177)/eNOS was reduced. Preincubation with the iNOS inhibitor 1400 W or eNOS agonist nebivolol restored vasorelaxation. Further experiments showed levels of p-AMPKα (Thr172)/AMPKα, which controls iNOS expression and eNOS activity, to have been reduced. Furthermore, levels of the upstream component of AMPK, adiponectin, was reduced in sera of AT1-AA positive rats and supplementation of adiponectin significantly decreased ET-1 contents, improved endothelial-dependent vasodilation, reduced NO production, elevated p-VASP/VASP, inhibited protein expression of nitrotyrosine and gp91phox, reduced iNOS overexpression, and increased eNOS phosphorylation at Ser1177 in the thoracic aorta of AT1-AA positive rats. These results established that impairment NO-cGMP pathway may aggravate the endothelial-dependent smooth muscle relaxation disorder in AT1-AA positive rats and adiponectin improved endothelial-dependent smooth muscle relaxation disorder by enhancing NO-cGMP pathway. This discovery may shed a novel light on clinical treatment of vascular diseases associated with AT1-AA.

Efficacy of therapeutic plasma exchange on angiotensin II type-1 receptor antibodies on two kidney transplant recipients.

BACKGROUND: Angiotensin II type-1 receptor antibody (AT1RAb) has been reported to cause antibody mediated rejection (AMR) in kidney transplant recipients possibly by contraction of renal arteries. We here report 2 kidney transplant recipients with elevated AT1RAbs and negative HLA donor specific antibodies (DSA) and anti-major histocompatibility complex class I chain-related gene A (MICA) Abs who received therapeutic plasma exchange (TPE) treatment followed by IVIG. CASE 1: Thirty-eight-year-old patient received second kidney transplant for end stage renal disease (ESRD) with chronic rejection. Three years post-transplant, she developed AMR with AT1RAb level >40 U/mL. She received 5 TPE and AT1RAb decreased by 20%, and biopsy showed improvement of AMR. She received another 3 TPE and AT1RAb decreased by 60%. Her creatinine (Cr) was stabilized at around 1.4 mg/dL. CASE 2: Twenty-four-year-old patient received kidney transplant for ESRD with unclear etiology. Two weeks post-transplant, her Cr rose with AT1RAb level at 18 U/mL and biopsy showed possible AMR. She received 6 TPE treatments and AT1RAb decreased by 55% and biopsy showed improvement of AMR. She received weekly TPE for subsequently rising AT1RAb but TPE was discontinued because of unsuccessful decrease of AT1RAb. Her Cr was stabilized at around 1.7 mL/dL. CONCLUSION: We reported 2 patients who received TPE treatments to decrease AT1RAbs. A course of TPE treatment successfully decreased AT1RAb. Histological improvement was observed quickly and Cr was also stabilized following the TPE treatment. Further study is necessary to determine the optimal use of TPE in renal transplant recipients with AT1RAbs.

Evaluation of Antibodies Directed Against Two GPCRs, Anti-AT1R and Anti-ETAR, on Kidney Transplant Outcome.

BACKGROUND: The role of an alloimmune response against non-self-antigens is established in organ transplantation. HLA incompatibilities are mainly responsible for this recognition between donor and recipient, but they may also be involved in the reactivity against other alloantigens expressed on the allograft resulting from an autoimmune response developed against selfantigens. OBJECTIVE: Our study aimed to determine the presence of non-anti-HLA antibodies (anti-AT1R and anti-ETAR) in sera from patients with end-stage renal disease, who underwent kidney transplantation in pre- and post-transplantation samples to study their influence on the development and evolution of acute humoral rejections and DSAs. METHODS: Antibodies (Abs) against two G protein-coupled receptors (GPCRs), angiotensin II type 1 receptor (AT1R) and endothelin-1 type A receptor (ETAR), have been detected in the sera of transplant recipients, who experience allograft dysfunction, patients with coronary heart disease, marginal hypertension and refractory, vascular lesions, myocardial hypertrophy and chronic inflammatory diseases, such as atherosclerosis or sclerosis. RESULTS: Kidney graft recipients were monitored for anti-ETAR, -AT1R, and -HLA Abs in pre-and post-transplant evolution, and anti-AT1R and/or -ETAR Abs were detected in 24% of recipients (22.4% with anti-AT1R Abs and 9.8% with anti-ETAR Abs). Due to acute humoral rejection, Graft loss was detected in 6.4% of patients with anti-GPCRs non-HLA Abs, and 3.2% had DSA anti-HLA Abs. In this research, we have described how the function of the anti-GPCRs autoAbs and how these Abs that activate GPCRs could influence graft outcome. CONCLUSION: In conclusion, there is a high association of non-HLA anti-GPCRs Abs levels with reduced kidney function after transplantation, especially in the presence of DSA anti-HLA Abs. Although more studies are needed, anti-AT1R and anti-ETAR antibodies may be helpful biomarkers that allow the risk of graft loss to be assessed.

ß1-adrenergic and Muscarinic Acetylcholine Type 2 Receptor Antibodies are Increased in Graves' Hyperthyroidism and Decrease During Antithyroid Therapy.

OBJECTIVE: To determine the association between autoantibodies to G-protein-coupled receptors with effect on the cardiovascular system and the cardiac biomarker N-terminal pro-brain natriuretic peptide reflecting heart function in Graves' disease. DESIGN AND METHODS: Sixty premenopausal women with Graves' disease were analyzed for IgG autoantibodies against ß1-adrenergic, muscarinic acetylcholine type 2 and angiotensin II type 1 receptors using enzyme-linked immunosorbent assays based on cell membranes overexpressing receptors in their native conformations. N-terminal pro-brain natriuretic peptide and heart symptoms were analyzed in hyperthyroidism and after 7.5 months of antithyroid treatment. Matched thyroid healthy controls were also assessed. RESULTS: Serum levels of antibodies against the ß1-adrenergic and the muscarinic acetylcholine type 2 receptors were higher in hyperthyroid patients than in controls (median ß1-adrenergic receptor antibodies 1.9 [IQR 1.3-2.7] vs. 1.1 [0.8-1.7] µg/mL, P<0.0001; muscarinic acetylcholine type 2 receptor 20.5 [14.0-38.3] vs. 6.0 [3.2-9.9] U/mL, P<0.0001). These antibodies decreased in euthyroidism (P<0.01), but were still higher than in controls (P<0.01). Angiotensin II type 1 receptor levels did not differ. N-terminal pro-brain natriuretic peptide was higher in hyperthyroidism (240 [134-372] vs. <35 [<35-67] ng/L, P<0.0001), normalized after treatment and did not correlate with autoantibodies. CONCLUSION: Autoantibodies against the ß1-adrenergic and the muscarinic acetylcholine type 2 receptors were increased in Graves' patients, decreased with treatment, but did not correlate with cardiac function. However, an autoimmune effect on the heart cannot be excluded in subpopulations, as the functional properties of the analyzed antibodies remain to be determined.

Pharmacodynamics of kardos administered as monotherapy and in combination with hypothiazide and enalapril in grade I-II arterial hypertension.

Therapy with kardos produced an antiihypertensve effect in patients with grade I-II arterial hypertension. This antiihypertensve effect was considerably potentiated, when kardos was administered in combination with enalapril.

Angiotensin II type-1 receptor antibody (AT1Rab) associated humoral rejection and the effect of peri operative plasma exchange and candesartan.

Angiotensin II type 1 antibodies (AT1Rab) can mediate antibody mediated rejection (AMR). Pre transplant AT1Rab levels, and risk of rejection were assessed in Kidney Transplant Recipients (KTR) transplanted in our centre from 2013 to 2014 (n=145). 14/145 (9.7%) KTR experienced antibody mediated rejection (AMR). The Hazard Ratio for AMR=3.7 [95% CI 2-26] (p=0.009) for KTR with AT1Rab levels >17.5U/ml. 6/11 of KTR with levels >25U/ml experienced AMR. In 2015 (n=80) KTR were transplanted and 6/80 KTR experienced rejection (2 AMR and 4 TCMR with vascular lesions). 7/80 of KTR had AT1Rab 17.5-25U/ml and none experienced rejection and were induced with ATG and candesartan. 7/80 had AT1Rab 25-40U/ml and received pre and post-operative plasma exchange, ATG and candesartan and 1/7 experienced TCMR with a vascular lesion. This perioperative regimen may alter the risk of rejection in patients with high levels of AT1Ab and further studies are needed.