Development of ACE2 autoantibodies after SARS-CoV-2 infection

Background

Activation of the immune system is implicated in the Post-Acute Sequelae after SARS-CoV-2 infection (PASC) but the mechanisms remain unknown. Angiotensin-converting enzyme 2 (ACE2) cleaves angiotensin II (Ang II) resulting in decreased activation of the AT1 receptor and decreased immune system activation. We hypothesized that autoantibodies against ACE2 may develop after SARS-CoV-2 infection, as anti-idiotypic antibodies to anti-spike protein antibodies.

Methods and findings

We tested plasma or serum for ACE2 antibodies in 67 patients with known SARS-CoV-2 infection and 13 with no history of infection. None of the 13 patients without history of SARS-CoV-2 infection and 1 of the 20 outpatients that had a positive PCR test for SARS-CoV-2 had levels of ACE2 antibodies above the cutoff threshold. In contrast, 26/32 (81%) in the convalescent group and 14/15 (93%) of patients acutely hospitalized had detectable ACE2 antibodies. Plasma from patients with antibodies against ACE2 had less soluble ACE2 activity in plasma but similar amounts of ACE2 protein compared to patients without ACE2 antibodies. We measured the capacity of the samples to inhibit ACE2 enzyme activity. Addition of plasma from patients with ACE2 antibodies led to decreased activity of an exogenous preparation of ACE2 compared to patients that did not have antibodies.

Conclusions

Many patients with a history of SARS-CoV-2 infection have antibodies specific for ACE2. Patients with ACE2 antibodies have lower activity of soluble ACE2 in plasma. Plasma from these patients also inhibits exogenous ACE2 activity. These findings are consistent with the hypothesis that ACE2 antibodies develop after SARS-CoV-2 infection and decrease ACE2 activity. This could lead to an increase in the abundance of Ang II, which causes a proinflammatory state that triggers symptoms of PASC.

Renin-angiotensin system and inflammation update

The most classical view of the renin-angiotensin system (RAS) emphasizes its role as an endocrine regulator of sodium balance and blood pressure. However, it has long become clear that the RAS has pleiotropic actions that contribute to organ damage, including modulation of inflammation. Angiotensin II (Ang II) activates angiotensin type 1 receptors (AT1R) to promote an inflammatory response and organ damage. This represents the pathophysiological basis for the successful use of RAS blockers to prevent and treat kidney and heart disease. However, other RAS components could have a built-in capacity to brake proinflammatory responses. Angiotensin type 2 receptor (AT2R) activation can oppose AT1R actions, such as vasodilatation, but its involvement in modulation of inflammation has not been conclusively proven. Angiotensin-converting enzyme 2 (ACE2) can process Ang II to generate angiotensin-(1-7) (Ang-(1-7)), that activates the Mas receptor to exert predominantly anti-inflammatory responses depending on the context. We now review recent advances in the understanding of the interaction of the RAS with inflammation. Specific topics in which novel information became available recently include intracellular angiotensin receptors; AT1R posttranslational modifications by tissue transglutaminase (TG2) and anti-AT1R autoimmunity; RAS modulation of lymphoid vessels and T lymphocyte responses, especially of Th17 and Treg responses; interactions with toll-like receptors (TLRs), programmed necrosis, and regulation of epigenetic modulators (e.g. microRNAs and bromodomain and extraterminal domain (BET) proteins). We additionally discuss an often overlooked effect of the RAS on inflammation which is the downregulation of anti-inflammatory factors such as klotho, peroxisome proliferator-activated receptor γ co-activator 1α (PGC-1α), transient receptor potential ankyrin 1 (TRPA1), SNF-related serine/threonine-protein kinase (SNRK), serine/threonine-protein phosphatase 6 catalytic subunit (Ppp6C) and n-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP). Both transcription factors, such as nuclear factor κB (NF-κB), and epigenetic regulators, such as miRNAs are involved in downmodulation of anti-inflammatory responses. A detailed analysis of pathways and targets for downmodulation of anti-inflammatory responses constitutes a novel frontier in RAS research.

A novel angiotensin II peptide vaccine without an adjuvant in mice

OBJECTIVES

We recently developed a novel peptide, AJP001, that possesses both a mouse T-cell epitope and adjuvant action. Direct conjugation to the antigen is useful for peptide vaccines without the addition of adjuvants. In this study, the efficacy of an angiotensin (Ang) II and AJP001-conjugated peptide vaccine (AJ-Ang II) was evaluated in mice.

METHODS

The anti-Ang II antibody titer was measured in Balb/C mice following three injections of AJ-Ang II at 2-week intervals. SBP was measured during vaccination of Balb/C mice treated with Ang II infusion (1 μg/kg per min).

RESULTS

AJ-Ang II treatment resulted in an increase in the anti-Ang II antibody titer in a dose-dependent manner without the addition of adjuvants. In the analysis of the humoral immune response, AJ-Ang II mainly elicited IgG1 antibodies and IL-4 and IL-10 production, as measured by an enzyme-linked immune absorbent spot assay, which suggests the induction of a Th2 response. Importantly, cotreatment with purified antibodies attenuated Ang II-induced extracellular signal-regulated kinase phosphorylation and nuclear factor (NF)-κB activation in cultured vascular smooth muscle cells. The SBP in immunized mice was significantly lower than that in nonimmunized mice (135.9 ± 8.5 vs. 154.9 ± 16.8 mmHg, P = 0.02). Furthermore, Ang II-induced perivascular fibrosis in the heart was significantly attenuated in immunized mice, which also exhibited decreased mRNA expression of collagen I/III and transforming growth factor-β.

CONCLUSION

AJ-Ang II may be a simple and useful therapeutic peptide vaccine without the addition of any adjuvants.

Redox regulation of cardiovascular inflammation - Immunomodulatory function of mitochondrial and Nox-derived reactive oxygen and nitrogen species

Oxidative stress is a major hallmark of cardiovascular diseases although a causal link was so far not proven by large clinical trials. However, there is a close association between oxidative stress and inflammation and increasing evidence for a causal role of (low-grade) inflammation for the onset and progression of cardiovascular diseases, which may serve as the missing link between oxidative stress and cardiovascular morbidity and mortality. With the present review we would like to highlight the multiple redox regulated pathways in inflammation, discuss the sources of reactive oxygen and nitrogen species that are of interest for these processes and finally discuss the importance of angiotensin II (AT-II) as a trigger of cardiovascular inflammation and the initiation and progression of cardiovascular diseases.

The interplay between Angiotensin II, TLR4 and hypertension

Hypertension is a multifactorial disease. Although a number of different underlying mechanisms have been learned from the various experimental models of the disease, hypertension still poses challenges for treatment. Angiotensin II plays an unquestionable role in blood pressure regulation acting through central and peripheral mechanisms. During hypertension, dysregulation of the Renin-Angiotensin System is associated with increased expression of pro-inflammatory cytokines and reactive oxygen species causing kidney damage, endothelial dysfunction, and increase in sympathetic activity, among other damages, eventually leading to decline in organ function. Recent studies have shown that these effects involve both the innate and the adaptive immune response. The contribution of adaptive immune responses involving different lymphocyte populations in various models of hypertension has been extensively studied. However, the involvement of the innate immunity mediating inflammation in hypertension is still not well understood. The innate and adaptive immune systems intimately interact with one another and are essential to an effectively functioning of the immune response; hence, the importance of a better understanding of the underlying mechanisms mediating innate immune system during hypertension. In this review, we aim to discuss mechanisms linking Angiotensin II and the innate immune system, in the pathogenesis of hypertension. The newest research investigating Angiotensin II triggering toll like receptor 4 activation in the kidney, vasculature and central nervous system contributing to hypertension will be discussed. Understanding the role of the innate immune system in the development of hypertension may bring to light new insights necessary to improve hypertension management.

Macrophages come to mind as keys to cognitive decline

Cognitive impairment, an underappreciated consequence of hypertension, is linked to cerebral arteriolar disease through poorly defined mechanisms. A study by Faraco et al. in this issue of the JCI points to perturbations of neurovascular unit coupling caused by perivascular macrophages (PVMs) as a cause of hypertension-related cognitive impairment. Angiotensin II (Ang II) was shown to activate PVMs, causing them to produce superoxide and thereby alter the proper functioning of the adjacent arterioles. Faraco and colleagues also show that disruption of the blood-brain barrier occurs in hypertension, allowing circulating Ang II to access PVMs. This study provides important new insight into the role of inflammatory cells in the genesis of vascular dementia.

Functional Local Renin-Angiotensin System in Human and Rat Periodontal Tissue

The initiation or progression of periodontitis might involve a local renin-angiotensin system (RAS) in periodontal tissue. The aim of this study was to further characterize the local RAS in human and rat periodontal tissues between healthy and periodontally-affected tissue. Components of the RAS were investigated using in vitro, ex vivo and in vivo experiments involving both human and Wistar rat periodontium. Although not upregulated when challenged with P. gingivalis-lipopolysaccharide, human gingival and periodontal ligament fibroblasts expressed RAS components. Likewise, healthy and inflamed human gingiva expressed RAS components, some of which were shown to be functional, yet no differences in expression were found between healthy and diseased gingiva. However, in inflamed tissue the immunoreactivity was greater for the AT₁R compared to AT₂R in fibroblasts. When compared to healthy tissue, ACE activity was increased in human gingiva from volunteers with gingivitis. Human-gingiva homogenates generated Ang II, Ang 1-9 and Ang 1-7 when incubated with precursors. In gingiva homogenates, Ang II formation from Ang I was nearly abolished only when captopril and chymostatin were combined. Ang 1-7 formation was significantly greater when human gingiva homogenates were incubated with chymostatin alone compared to incubation without any inhibitor, only captopril, or captopril and chymostatin. In rat gingiva, RAS components were also found; their expression was not different between healthy and experimentally induced periodontitis (EP) groups. However, renin inhibition (aliskiren) and an AT₁R antagonist (losartan) significantly blocked EP-alveolar-bone loss in rats. Collectively, these data are consistent with the hypothesis that a local RAS system is not only present but is also functional in both human and rat periodontal tissue. Furthermore, blocking AT₁R and renin can significantly prevent periodontal bone loss induced by EP in rats.

Regulation of Giα protein expression by vasoactive peptides in hypertension: molecular mechanisms

Guanine nucleotide regulatory proteins (G proteins) play a key role in the regulation of various signal transduction systems, including adenylyl cyclase/cAMP and phospholipase C (PLC)/phosphatidyl inositol (PI) turnover, which are implicated in the modulation of a variety of physiological functions, such as platelet functions, including platelet aggregation, secretion, and clot formation and cardiovascular functions, including arterial tone and reactivity. Several abnormalities in adenylyl cyclase activity, cAMP levels and G proteins have been shown to be responsible for the altered cardiac performance and vascular functions observed in cardiovascular disease states. The enhanced or unaltered levels of inhibitory G proteins (Giα) and mRNA have been reported in different models of hypertension, whereas Gsα levels are shown to be unaltered. The enhanced levels of Giα proteins precede the development of blood pressure and suggest that overexpression of Gi proteins may be one of the contributing factors for the pathogenesis of hypertension. The levels of vasoactive peptides including ET-1 and Ang II and growth factors are augmented in hypertension and contribute to the enhanced expression of Giα proteins in hypertension. In addition, oxidative stress due to enhanced levels of Ang II and ET-1 is enhanced in hypertension and may also be responsible for the enhanced expression of Giα proteins observed in hypertension. Furthermore, Ang II- and ET-1-induced transactivation of growth factor receptor through the activation of MAP kinase signaling is also shown to contribute to the augmented levels of Giα in hypertension. Thus, it appears that the enhanced levels of vasoactive peptides by increasing oxidative stress and transactivation growth factor receptors enhance MAP kinase activity that contribute to the enhanced expression of Giα proteins responsible for the pathogenesis of hypertension. In this review, we describe the role of vasoactive peptides and the signaling mechanisms responsible for the enhanced expression of Giα proteins in hypertension.

Inflammatory monocytes determine endothelial nitric-oxide synthase uncoupling and nitro-oxidative stress induced by angiotensin II

Endothelial nitric-oxide synthase (eNOS) uncoupling and increased inducible NOS (iNOS) activity amplify vascular oxidative stress. The role of inflammatory myelomonocytic cells as mediators of these processes and their impact on tetrahydrobiopterin availability and function have not yet been defined. Angiotensin II (ATII, 1 mg/kg/day for 7 days) increased Ly6C(high) and CD11b(+)/iNOS(high) leukocytes and up-regulated levels of eNOS glutathionylation in aortas of C57BL/6 mice. Vascular iNOS-dependent NO formation was increased, whereas eNOS-dependent NO formation was decreased in aortas of ATII-infused mice as assessed by electron paramagnetic resonance (EPR) spectroscopy. Diphtheria toxin-mediated ablation of lysozyme M-positive (LysM(+)) monocytes in ATII-infused LysM(iDTR) transgenic mice prevented eNOS glutathionylation and eNOS-derived N(ω)-nitro-L-arginine methyl ester-sensitive superoxide formation in the endothelial layer. ATII increased vascular guanosine triphosphate cyclohydrolase I expression and biopterin synthesis in parallel, which was reduced in monocyte-depleted LysM(iDTR) mice. Vascular tetrahydrobiopterin was increased by ATII infusion but was even higher in monocyte-depleted ATII-infused mice, which was paralleled by a strong up-regulation of dihydrofolate reductase expression. EPR spectroscopy revealed that both vascular iNOS- and eNOS-dependent NO formation were normalized in ATII-infused mice following monocyte depletion. Additionally, deletion as well as pharmacologic inhibition of iNOS prevented ATII-induced endothelial dysfunction. In summary, ATII induces an inflammatory cell-dependent increase of iNOS, guanosine triphosphate cyclohydrolase I, tetrahydrobiopterin, NO formation, and nitro-oxidative stress as well as eNOS uncoupling in the vessel wall, which can be prevented by ablation of LysM(+) monocytes.

Visfatin as a novel mediator released by inflamed human endothelial cells

Background

Visfatin is a multifaceted adipokine whose circulating levels are enhanced in different metabolic diseases. Extracellular visfatin can exert various deleterious effects on vascular cells, including inflammation and proliferation. Limited evidence exists, however, on the capacity of human vascular cells to synthesize and release visfatin by themselves, under basal or pro-inflammatory conditions.

Methods and Results

Intracellular visfatin was detected by Western blot in non-stimulated human umbilical vein endothelial cells (HUVEC). However, exposing HUVEC for 18 h to a series of pro-inflammatory stimulus, such as interleukin (IL)-1β (1 to 10 ng/mL), tumor necrosis factor-α (1 to 10 ng/mL) or angiotensin II (10 pmol/L to 1 μmol/L) markedly enhanced intracellular visfatin content. Using IL-1β (10 ng/mL; 18 h), it was determined that the increase in intracellular visfatin, which was paralleled by enhanced visfatin mRNA levels, relied on a signalling mechanism involving both nuclear factor-κB and poly (ADP ribose) polymerase-1 activation. Moreover, IL-1β modified the sub-cellular localization of visfatin; while in non-stimulated HUVEC immunoreactive visfatin predominantly showed an intra-nuclear granular pattern, in IL-1β-inflamed cells an extra-nuclear filamentous staining, co-localising with F-actin fibers and suggesting a secretory pattern, was mainly found. Indeed, IL-1β promoted visfatin secretion, as determined by both ELISA and immunocytochemistry.

Conclusions

Human endothelial cells synthesize and release visfatin, particularly in response to inflammation. We suggest that the inflamed endothelium can be a source of visfatin, which arises as a local inflammatory mediator and a potential therapeutic target to interfere with vascular inflammation.

Angiotensin II is a new component involved in splenic T lymphocyte responses during Plasmodium berghei ANKA infection

The contribution of T cells in severe malaria pathogenesis has been described. Here, we provide evidence for the potential role of angiotensin II (Ang II) in modulating splenic T cell responses in a rodent model of cerebral malaria. T cell activation induced by infection, determined by 3 to 4-fold enhancement in CD69 expression, was reduced to control levels when mice were treated with 20 mg/kg losartan (IC₅₀ = 0.966 mg/kg/d), an AT₁ receptor antagonist, or captopril (IC₅₀ = 1.940 mg/kg/d), an inhibitor of angiotensin-converting enzyme (ACE). Moreover, the production of interferon-γ and interleukin-17 by CD4+ T cells diminished 67% and 70%, respectively, by both treatments. Losartan reduced perforin expression in CD8+ T cells by 33% while captopril completely blocked it. The upregulation in chemokine receptor expression (CCR2 and CCR5) observed during infection was abolished and CD11a expression was partially reduced when mice were treated with drugs. T cells activated by Plasmodium berghei ANKA antigens showed 6-fold enhance in AT₁ levels in comparison with naive cells. The upregulation of AT₁ expression was reduced by losartan (80%) but not by captopril. Our results suggest that the AT₁/Ang II axis has a role in the establishment of an efficient T cell response in the spleen and therefore could participate in a misbalanced parasite-induced T cell immune response during P. berghei ANKA infection.

[Effects of sapindus saponins on inflammatory response mediated by Ang II/p38MAPK pathway and cardiac hypertrophy in spontaneously hypertensive rats]

OBJECTIVE

To investigate the effects of sapindus saponins on myocardial inflammation mediated by Ang II/ p38MAPK signal pathway and cardiac hypertrophy in spontaneously hypertensive rats. And also to explore the correlation of cardiac hypertrophy and inflammation.

METHOD

Thirty-two 16-week-old spontaneously hypertensive rats (SHR) were randomly divided into four groups, one with placebo as model group, one with captopril tablets (27 mg x kg(-1)) as positive control, one with low-dose sapindus saponins (27 mg x kg(-1)), one with high-dose (108 mg x kg(-1)). And another eight healthy Wistar-Kyoto strain (WKY) rats were used as the normal group. The animals were treated for eight weeks, and the indicators detected were as follows: (1) left ventricular mass index (LVMI); (2) the content of Ang II and hs-CRP in plasma were determined by ELISA; (3) the protein expression of AT1R and VEGF were determined by immunohistochemical method; (4) the protein expression of p-p38MAPK in myocardial cells was determined by Western blot.

RESULT

Sapindus saponins reduced LVMI, and blocked the expression level of Ang II, AT1R, p-p38MAPK, VEGF and hs-CRP in myocardial tissue. Vs the SHR model group, there were significant differences (P < 0.05 or P < 0.01).

CONCLUSION

Our findings suggested that sapindus saponins could inhibited cardiac hypertrophy, the possible mechanisms may be related to the inhibition on inflammatory response mediated by Ang II/p38MAPK pathway.

Animal models of pre-eclampsia

The cardinal features of human pre-eclampsia, hypertension and proteinuria, are mimicked in animal models. Increasingly, the accuracy of inducing 'pure' systemic endothelial dysfunction is regarded as critical in differentiating mechanisms of pre-eclampsia from other conditions which induce hypertension (e.g. glomerulonephritis, renal denervation or manipulation of the renin-angiotensin system). A recent study in baboons has identified the timing of induction of maternal endothelial damage after acute uteroplacental ischaemia (UPI). The endothelial changes in the glomerulus are indicative of a direct endothelial toxin and mimic the lesions seen in human pre-eclampsia; the extent of hypertension and proteinuria are also similar. This animal model identifies systemic and placental sFLT-1 (soluble fms-like tyrosine kinase-1) as a potential mediator of endothelial damage. This research involving primates with haemomonochorial placentas makes translation of these results to humans very compelling for understanding the mechanisms of human disease. Similar endothelial dysfunction has been identified in baboons treated with anti-inflammatory inhibitors. Similar studies in rodents have identified a relationship between angiotensin II agonistic antibodies, UPI/reduced uteroplacental perfusion pressure, angiogenic markers, and cytokines. We can now identify vasoconstrictive mediators of the hypertensive and endothelial response such as endothelin 1, the renin-angiotensin system, or other hormones such as oestrogens in primate models.

CYT-006-AngQb, a vaccine against angiotensin II for the potential treatment of hypertension

CYT-006-AngQb, under development by Cytos Biotechnology AG, is a vaccine in which a peptide derived from the angiotensin II molecule is conjugated to the surface of the highly repetitive structure of virus-like particles. CYT-006-AngQb was designed to treat hypertension with the benefit of relatively long-lasting effects that do not require daily dosing. In spontaneously hypertensive rat models, CYT-006-AngQb induced strong angiotensin-II-specific antibodies and reduced systolic blood pressure. In a phase I clinical trial, single doses of CYT-006-AngQb were well tolerated in healthy males. In a phase II trial, multiple doses of CYT-006-AngQb administered to patients with mild-to-moderate hypertension reduced blood pressure; the average half-life was longer than all currently available oral hypertension medications. There were no significant side effects except for local skin reactions at the injection site. Given the novel mechanism of CYT-006-AngQb, and the potential to complement other hypertension treatments, success in ongoing phase II trials in patients with hypertension would potentially make this therapy a valuable addition to the therapeutic armamentarium for hypertension.

Effect of immunisation against angiotensin II with CYT006-AngQb on ambulatory blood pressure: a double-blind, randomised, placebo-controlled phase IIa study

BACKGROUND

Hypertension can be controlled adequately with existing drugs such as angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers. Nevertheless, treatment success is often restricted by patients not adhering to treatment. Immunisation against angiotensin II could solve this problem. We investigated the safety and efficacy of CYT006-AngQb-a vaccine based on a virus-like particle-that targets angiotensin II to reduce ambulatory blood pressure.

METHODS

In this multicentre, double-blind, randomised, placebo-controlled phase IIa trial, 72 patients with mild-to-moderate hypertension were randomly assigned with a computer-generated randomisation list to receive subcutaneous injections of either 100 mug CYT006-AngQb (n=24), 300 mug CYT006-AngQb (24), or placebo (24), at weeks 0, 4, and 12. 24-h ambulatory blood pressure was measured before treatment and at week 14. The primary outcomes were safety and tolerability. Analyses were done by intention to treat. This study is registered with ClinicalTrials.gov, number NCT00500786.

FINDINGS

Two patients in the 100 mug group, three in the 300 mug group, and none in the placebo group discontinued study treatment. All patients were included in safety analyses; efficacy analyses did not include the five dropouts, for whom no data were available at week 14. Five serious adverse events were reported (two in the 100 mug group, two in the 300 mug group, and one in the placebo group); none were deemed to be treatment related. Most side-effects were mild, transient reactions at the injection site. Mild, transient influenza-like symptoms were seen in three patients in the 100 mug group, seven in the 300 mug group, and none in the placebo group. In the 300 mug group, there was a reduction from baseline in mean ambulatory daytime blood pressure at week 14 by -9.0/-4.0 mm Hg compared with placebo (p=0.015 for systolic and 0.064 for diastolic). The 300 mug dose reduced the early morning blood-pressure surge compared with placebo (change at 0800 h -25/-13 mm Hg; p<0.0001 for systolic, p=0.0035 for diastolic).

INTERPRETATION

Immunisation with CYT006-AngQb was associated with no serious adverse events; most observed adverse events were consistent with local or systemic responses similar to those seen with other vaccines. The 300 mug dose reduced blood pressure in patients with mild-to-moderate hypertension during the daytime, especially in the early morning.

FUNDING

Cytos Biotechnology AG.

[Therapeutic novelties in the management of arterial hypertension]

Arterial hypertension is one of the major risk factors for the development of cardiovascular diseases such as heart failure, ischemic heart disease, chronic kidney disease and cerebrovascular events. Adequate blood pressure control is vital for the management of patients with vascular disease. New therapeutic alternatives are appearing on the horizon to improve the degree of blood pressure control in these patients, such as direct renin inhibitors, beta-blockers with additional properties, carotid receptor- stimulating devices and vaccination against arterial hypertension. Direct renin inhibitors are a new family of antihypertensive drugs that have so far shown a good antihypertensive effect and an additive effect on reduction of proteinuria in patients with diabetic nephropathy. Recent meta-analyses suggest that betablockers used as first-line treatment for uncomplicated arterial hypertension could have a less beneficial effect on the development of cardiovascular disease than other antihypertensive drugs. However, the emergence of new subtypes of beta-blockers with other hemodynamic and metabolic properties could change this conception. Carotid receptor-stimulating devices and vaccination against arterial hypertension, although not totally new therapies, are being revitalized, with preliminary results that suggest that they could be used for the treatment of arterial hypertension in patients with a specific profile. Although scientifically stimulating, the long-term beneficial effects of these new therapeutic alternatives on target-organ protection still need to be confirmed.

Angiotensin II-induced C-reactive protein generation: Inflammatory role of vascular smooth muscle cells in atherosclerosis

BACKGROUND

As the major target of Angiotensin II (Ang II) in the vessel wall, vascular smooth muscle cells (VSMCs) are a tentative source to produce C-reactive protein (CRP). However, it is largely unknown if Ang II is capable of inducing CRP production in VSMCs.

METHODS AND RESULTS

Ang II induced a concentration-dependent release of CRP in cultured rat VSMCs as measured by sandwich ELISA. Real-time PCR revealed that Ang II significantly upregulated CRP mRNA level in vitro. Ang II-induced CRP generation in aortic VSMCs was also investigated using double-labeled fluorescent immunohistochemistry and in situ hybridization in subchronic Ang II administration in rats. Losartan but not PD123319 markedly blocked the Ang II-induced CRP production in cultured VSMCs, suggesting that such effect was mediated via Ang II type 1 receptor. Further, Western blotting analysis showed that mitogen-activated protein kinase (MAPK) activation was obligatory in Ang II-induced CRP production, since specific MAPK inhibitor PD098059 almost abolished the action.

CONCLUSIONS

We identified that Ang II is capable of inducing CRP generation in VSMCs, in which Ang II type 1 receptor followed by MAPK signal pathway is involved. It strengthened the role of Ang II-induced CRP production by VSMCs in the inflammatory process in atherosclerosis.

The regulation of the inflammatory response through nuclear factor-kappab pathway by angiotensin IV extends the role of the renin angiotensin system in cardiovascular diseases

The renin angiotensin system (RAS) participates in the pathogenesis of cardiovascular diseases. Although angiotensin II has been considered the effector peptide of RAS, accumulating evidence shows that other RAS peptides also posses important functions, some of them involved in cardiovascular pathology. Many studies support the importance of N-terminal angiotensin degradation product, angiotensin IV (AngIV), in the fields of cognition, renal metabolism, and pathophysiologic conditions. The novel data discussed here show that AngIV could contribute to cardiovascular damage. Angiotensin IV can be generated by degradation of angiotensin II, by aminopeptidase (AP) N, or by other proteases, which could be activated during tissue damage, suggesting that elevated AngIV levels can be found in pathologic conditions. Angiotensin IV binds to a specific receptor, AT(4), which has recently been identified as an insulin-regulated AP. In vascular cells, correspondence between AT(4) binding sites and insulin-regulated AP has been described. Angiotensin IV regulates cell growth in cardiac fibroblasts, endothelial cells, and vascular smooth muscle cells (VSMCs). In VSMC, AngIV, through AT(4), independently of AT(1) and AT(2) receptors, activates the nuclear factor-kappaB pathway and up-regulates several nuclear factor-kappaB-related genes, including the monocyte chemokine monocyte chemoattractant protein-1, the adhesion molecule intercellular adhesion molecule-1, and the cytokines interleukin 6 and tumor necrosis factor alpha. These data indicate that AngIV could be involved in the vascular inflammatory response. Thus, in endothelial cells and VSMC, AngIV up-regulates plasminogen activator inhibitor-1 expression and could participate in thrombus formation. These results reveal novel concepts of RAS in the cardiovascular system, suggesting that AngIV could play an active role in vascular diseases.

A vaccine for hypertension based on virus-like particles: preclinical efficacy and phase I safety and immunogenicity

BACKGROUND

Despite the availability of efficacious drugs, the success of treating hypertension is limited by patients' inconsistent drug intake. Immunization against angiotensin II may offer a valuable alternative to conventional drugs for the treatment of hypertension, because vaccines induce relatively long-lasting effects and do not require daily dosing. Here we describe the preclinical development and the phase I clinical trial testing of a virus-like particle (VLP)-based antihypertensive vaccine.

METHODS AND RESULTS

An angiotensin II-derived peptide was conjugated to the VLP Qbeta (AngQb). AngQb was highly immunogenic in mice and rats. To test for efficacy, spontaneously hypertensive rats (SHR) were immunized with 400 microg AngQb or VLP alone. Group mean systolic blood pressure (SBP) was reduced by up to 21 mmHg (159 +/- 2 versus 180 +/- 5 mmHg, P < 0.001), and total angiotensin II levels (antibody-bound and free) were increased ninefold (85 +/- 20 versus 9 +/- 1 pmol/l, P = 0.002) compared with VLP controls. SHR treated with the angiotensin-converting enzyme (ACE) inhibitor ramipril (1 mg/kg per day by mouth) reached an SBP of 155 +/- 2 mmHg. Twelve healthy volunteers of a placebo-controlled randomized phase I trial were injected once with 100 microg AngQb. Angiotensin II-specific antibodies were raised in all subjects (100% responder rate) and AngQb was well tolerated.

CONCLUSIONS

AngQb reduces blood pressure in SHR to levels obtained with an ACE inhibitor, and is immunogenic and well tolerated in humans. Therefore, vaccination against angiotensin II has the potential to become a useful antihypertensive treatment providing long-lasting effects and improving patient compliance.

The Lipopolysaccharide-Induced Up-Regulation of Bradykinin B2-Receptor in the Mouse Heart Is Mediated by Tumor Necrosis Factor-.ALPHA. and Angiotensin II

Our present study aimed to characterize the effects of lipopolysaccharide (LPS) on the expression of the bradykinin B2-receptor in the mouse heart, which may have a role in cardiac depression during sepsis. We found that LPS induced the up-regulation of B2-receptor mRNA in the heart in vivo and in cultured cardiac myocytes in vitro. Like LPS, tumor necrosis factor-alpha (TNF-alpha) but not interleukin (IL)-1-beta, IL-6 or endothelin-1 stimulated B2-receptor expression in cultured myocytes. The effect of LPS on the expression of B2-receptor mRNA was also mimicked in cardiac myocytes by Ang II via Ang II type 1 (AT1-) receptor. Losartan, an AT1-receptor antagonist, inhibited about 50% of the LPS-induced up-regulation of B2-receptor mRNA in the heart in vivo and in cultured cardiac myocytes in vitro. Furthermore, the up-regulation of B2-receptor mRNA by either LPS or Ang II in cultured myocytes was abolished by anti-TNF-alpha antibody. These results suggest that the up-regulation of cardiac B2-receptor expression by LPS is mediated through TNF-alpha, which is produced in the myocardium by two different mechanisms in an AT1-receptor-dependent and independent manners, implying the role of the cardiac kallikrein-kinin system in the development of cardiac dysfunction during sepsis.

Postnatal Development of the Secretory Activity of the Goat Subcommissural Organ. A Reissner's Fibre and Angiotensin II Immunohistochemical Study

Subcommissural organ (SCO) secretory activity of the goat (variations of Capra hircus, that live in arid conditions) was examined during the postnatal development, using specific antibodies against the Reissner's fibre (AFRU) and angiotensin II (AAGII). The SCO was strongly stained with the anti-glycoproteins that form the Reissner's fibre and lightly marked with the anti-angiotensin II. The AFRU-immunoreactivity (ir) was found in the ependymal and hypendymal cells and in the ventricular and peripheral secretory routes of the goat SCO. The amount AFRU increases at 6 months and decreases at adult age. In contrast, the anti-angiotensin II-ir was mainly found in the adult age, not being practically observed at one postnatal month. The AAGII-ir was mainly found in ependymal cells in which AFRU-ir was downregulated. In addition, we detected the presence of double immunostained for AFRU and AAGII in ependymocytes of the pre-commissural and subcommissural parts. In conclusion the present results may suggest a functional interrelation between AAGII and the secretory activity of the SCO of this kind of goat.

Integrated protein microchip assay with dual fluorescent- and MALDI read-out

A pore chip protein array (PCPA) concept based on a dual readout configuration, fluorescence imaging, and MALDI-TOF MS has been developed. Highly packed, (>4000 spots/cm2), antibody arrays were dispensed on the porous chip by using a piezo-electric microdispenser. Sandwich assay was made after blocking by addition of a secondary antibody either IgG-FITC-labeled or anti-Ang II. The antigen in the first system was a large protein (IgG), and in the other system, a FITC marked peptide Angiotensin II (Ang II) was used. Ang II antibodies showed specificity for Ang II, while the Ang I antibodies showed binding properties for Ang I, II, and Renin. Fluorescence and MALDI TOF MS read-out was made for IgG and Ang II. A major advantage of the dual read-out PCPA approach is that both affinity binding and mass identity are derived. Detection limits for Ang II on the chip is as low as 500 zmol (Ang II).

The intrarenal renin-angiotensin system in autosomal dominant polycystic kidney disease

Hypertension is a common complication of autosomal dominant polycystic kidney disease (ADPKD), often present before the onset of renal failure. A role for the renin-angiotensin system (RAS) has been proposed, but studies of systemic RAS have failed to show a correlation between plasma renin activity and blood pressure in ADPKD. Ectopic renin expression by cyst epithelium was first reported in 1992 (Torres VE, Donovan KA, Sicli G, Holley KE, Thibodeau ST, Carretero OA, Inagami T, McAteer JA, and Johnson CM. Kidney Int 42: 364-373, 1992). It is not known, however, whether other RAS components are also expressed by cysts in ADPKD. We show that, in addition to renin, angiotensinogen (AGT) is produced by some cysts and dilated tubules. Angiotensin-converting enzyme, ANG II type 1 receptor, and ANG II peptide are also present within cysts and in many tubules; and some cyst fluids contain high ANG II concentrations. Additionally, cyst-derived cells in culture continue to express the components of the RAS at both the protein and mRNA levels. We further show that renin is expressed primarily in cysts of distal tubule origin and in cyst-derived cells with distal tubule characteristics, whereas AGT is expressed primarily in cysts of proximal tubule origin and in cyst-derived cells with proximal tubule characteristics. Renin production by cyst-derived cells appears to be regulated by extracellular Na+ concentration. Based on these observations, we propose a model of an autocrine/paracrine RAS in polycystic kidney disease, whereby overactivity of the intrarenal system results in sustained increases in intratubular ANG II concentrations.

Enhanced renal immunocytochemical expression of ANG-(1-7) and ACE2 during pregnancy

Previously we demonstrated that kidney concentration and urinary excretion of angiotensin-(1-7) are increased during normal pregnancy in rats. Since this finding may reflect local kidney production of angiotensin-(1-7), we determined the immunocytochemical distribution of angiotensin-(1-7) and its newly described processing enzyme, ACE2, in kidneys of virgin and 19-day-pregnant Sprague-Dawley rats. Sprague-Dawley rats were killed at the 19th day of pregnancy, and tissues were prepared for immunocytochemical by using a polyclonal antibody to angiotensin- (1-7) or a monoclonal antibody to ACE2. Angiotensin-(1-7) immunostaining was predominantly localized to the renal tubules traversing both the inner cortex and outer medulla. ACE2 immunostaining was localized throughout the cortex and outer medulla and was visualized in the renal tubules of both virgin and pregnant rats. The quantification of angiotensin-(1-7) and ACE2 immunocytochemical staining showed that in pregnant animals, the intensity of the staining increased by 56% and 117%, respectively (P<0.05). This first demonstration of the immunocytochemical distribution of angiotensin-(1-7) and ACE2 in kidneys of pregnant rats shows that pregnancy increases angiotensin-(1-7) immunocytochemical expression in association with increased ACE2 intensity of staining. The findings suggest that ACE2 may contribute to the local production and overexpression of angiotensin-(1-7) in the kidney during pregnancy.

[Change of natural antibody levels in patients with cardiovascular diseases by the use of anti-atherogenic diets with processed soy product foods]

It was investigated the influence of a diet supplemented with soy oil and soy protein on dynamic of clinic manifestation and immune status patients with IND and HBP. The results of investigations indicated that a (?).

On the molecular basis of the recognition of angiotensin II (AII). NMR structure of AII in solution compared with the X-ray structure of AII bound to the mAb Fab131

The high-resolution 3D structure of the octapeptide hormone angiotensin II (AII) in aqueous solution has been obtained by simulated annealing calculations, using high-resolution NMR-derived restraints. After final refinement in explicit water, a family of 13 structures was obtained with a backbone RMSD of 0.73 +/- 0.23 A. AII adopts a fairly compact folded structure, with its C-terminus and N-terminus approaching to within approximately 7.2 A of each other. The side chains of Arg2, Tyr4, Ile5 and His6 are oriented on one side of a plane defined by the peptide backbone, and the Val3 and Pro7 are pointing in opposite directions. The stabilization of the folded conformation can be explained by the stacking of the Val3 side chain with the Pro7 ring and by a hydrophobic cluster formed by the Tyr4, Ile5 and His6 side chains. Comparison between the NMR-derived structure of AII in aqueous solution and the refined crystal structure of the complex of AII with a high-affinity mAb (Fab131) [Garcia, K.C., Ronco, P.M., Verroust, P.J., Brunger, A.T., Amzel, L.M. (1992) Science257, 502-507] provides important quantitative information on two common structural features: (a) a U-shaped structure of the Tyr4-Ile5-His6-Pro7 sequence, which is the most immunogenic epitope of the peptide, with the Asp1 side chain oriented towards the interior of the turn approaching the C-terminus; (b) an Asx-turn-like motif with the side chain aspartate carboxyl group hydrogen-bonded to the main chain NH group of Arg2. It can be concluded that small rearrangements of the epitope 4-7 in the solution structure of AII are required by a mean value of 0.76 +/- 0.03 A for structure alignment and approximately 1.27 +/- 0.02 A for sequence alignment with the X-ray structure of AII bound to the mAb Fab131. These data are interpreted in terms of a biological "nucleus" conformation of the hormone in solution, which requires a limited number of structural rearrangements for receptor-antigen recognition and binding.

Hypotensive activity of ultralow doses of antibodies to factors involved in the regulation of vascular tone

Hypotensive activity of ultralow doses of antibodies to some endogenous substances involved in the regulation of vascular tone was studied on NISAG rats with hereditary stress-induced arterial hypertension. It was found that antibodies to angiotensin II and its receptor in ultralow doses markedly reduced systolic blood pressure, which was reproducible after repeated treatment. The course of peroral treatment with antibodies to endothelin and endothelial NO synthase in ultralow doses did not decrease systolic blood pressure.

Hypotensive effect of potentiated antibodies to angiotensin II and AT1 receptors

Hypotensive activity of ultralow doses of antibodies to angiotensin II and its receptors was studied on adult NISAG rats with hereditary stress-induced arterial hypertension. Antibodies to C-terminal fragment of angiotensin II receptors produced the most pronounced hypotensive effect, which was reproducible after repeated administration. These antibodies decreased systolic blood pressure by 16.40 +/- 0.62 mm Hg. The most rapid hypotensive effect was produced by affinity purified antibodies to angiotensin II: 2 h after administration of these antibodies systolic blood pressure decreased by 12.80 +/- 5.49 mm Hg. Our results indicate that combination treatment with ultralow doses of antibodies to angiotensin II and its receptors hold much promise for the use in clinical practice.

[Diagnostic implications of detecting antibodies to angiotensin-converting enzyme and its substrates]

The results of the analysis of diagnostic significance of examination of natural antibodies (Nab) to agiotensin-converting enzyme (ACE) and its substrates in the serum of hypertensive patients indicate that concentration of Nab to ACE differ from this mean concentration in donors. An elevated level of Nab to ACE may be considered as a compensatory reaction to increased content of the enzyme in vascular endothelium and blood flow. The same patients were examined for antibodies to peptide angiotensin II (AT-II). Enzyme immunoassay has shown that a significantly elevated level of antibodies to AT-II was only in 5 examinees. The same patients had also high Nab to ACE. The study of a group of ischemic heart disease patients with adverse effects attributed to bronchial affection treated with enalapril and diroton (ACE inhibitors) demonstrates that deterioration of cough and external respiration function is not related to exacerbation of existing chronic pulmonary inflammation. None of the patients had elevated body temperature or inflammatory changes in the blood, other signs of inflammation. Enzyme immunoassay also proved that the initial level of Nab equaled mean value for donors or was insignificantly lower. Blood serum patients with side effects contained a significantly (p < 0.02) elevated quantities of Nab to bradikinin vs initial values. Thus, the proposed method of solid phase enzyme immunoassay quantifies Nab to ACE and its substrates in the patients.

Angiotensin receptors contribute to blood pressure homeostasis in salt-depleted SHR

This study evaluated the contribution of angiotensin peptides acting at various receptor subtypes to the arterial pressure and heart rate of adult 9-wk-old male conscious salt-depleted spontaneously hypertensive rats (SHR). Plasma ANG II and ANG I in salt-depleted SHR were elevated sevenfold compared with peptide levels measured in sodium-replete SHR, whereas plasma ANG-(1-7) was twofold greater in salt-depleted SHR compared with salt-replete SHR. Losartan (32.5 micromol/kg), PD-123319 (0.12 micromol. kg(-1). min(-1)), [d-Ala(7)]ANG-(1-7) (10 and 100 pmol/min), and a polyclonal ANG II antibody (0.08 mg/min) were infused intravenously alone or in combination. Combined blockade of AT(2) and AT((1-7)) receptors significantly increased the blood pressure of losartan-treated SHR (+15 +/- 1 mmHg; P < 0.01); this change did not differ from the blood pressure elevation produced by the sole blockade of AT((1-7)) receptors (15 +/- 4 mmHg). On the other hand, sole blockade of AT(2) receptors in losartan-treated SHR increased mean arterial pressure by 8 +/- 1 mmHg (P < 0.05 vs. 5% dextrose in water as vehicle), and this increase was less than the pressor response produced by blockade of AT((1-7)) receptors alone or combined blockade of AT((1-7)) and AT(2) receptors. The ANG II antibody increased blood pressure to the greatest extent in salt-depleted SHR pretreated with only losartan (+11 +/- 2 mmHg) and to the least extent in salt-depleted SHR previously treated with the combination of losartan, PD-123319, and [d-Ala(7)]ANG-(1-7) (+7 +/- 1 mmHg; P < 0.01). Losartan significantly increased heart rate, whereas other combinations of receptor antagonists or the ANG II antibody did not alter heart rate. Our results demonstrate that ANG II and ANG-(1-7) act through non-AT(1) receptors to oppose the vasoconstrictor actions of ANG II in salt-depleted SHR. Combined blockade of AT(2) and AT((1-7)) receptors and ANG II neutralization by the ANG II antibody reversed as much as 67% of the blood pressure-lowering effect of losartan.

Association of angiotensin-converting enzyme with low-density lipoprotein in aortic valvular lesions and in human plasma

BACKGROUND

Recent studies have demonstrated that lesions of aortic sclerosis and stenosis share several similarities with lesions of atherosclerosis. In atherosclerosis, angiotensin-converting enzyme (ACE) is expressed by a subset of macrophages. This study was undertaken to determine whether ACE might be present in aortic sclerosis or stenosis lesions.

METHODS AND RESULTS

Immunohistochemistry was performed on 26 paraffin-embedded human aortic valves. Monospecific antibodies were used to identify ACE, macrophages, angiotensin II type 1 receptor (AT-1 receptor), angiotensin II, and apolipoprotein B. Human low-density lipoprotein (LDL) and high-density lipoprotein (HDL) were isolated from plasma of normal volunteers by sequential density-gradient ultracentrifugation. ACE was not present in normal valves but was present in all valves with aortic sclerosis or stenosis lesions. ACE was detected on a subset of lesion macrophages but was present primarily in an extracellular distribution, where it colocalized with apolipoprotein B. ACE was detected by Western blotting on plasma LDL but not on HDL isolated from normal volunteers. Angiotensin II, the enzymatic product of ACE, was colocalized with ACE in valve lesions. ACE also was colocalized with apolipoprotein B in an adjacent coronary atherosclerotic plaque.

CONCLUSIONS

ACE is present in aortic sclerosis and stenosis lesions, where it may participate in lesion development, as is evidenced by the presence of its enzymatic product, angiotensin II. The observation of an association of ACE with LDL in both lesions and plasma suggests that LDL may deliver ACE to lesions and has implications for the role of ACE-containing LDL in other diseases, such as atherosclerosis.

[Cross-sensitivity between angiotensin-converting enzyme inhibitors and angiotensin II receptor antagonist]

BACKGROUND

Cross-sensitivity between angiotensin-converting enzyme inhibitor-induced angioedema and cough, and angiotensin II receptor antagonist has been reported in the literature. Eczema-like skin reactions have never been documented. We report the first two cases.

CASE REPORTS

Two patients, aged 79 and 88 years, with a history of hypertension, were treated with angiotensin-converting enzyme inhibitors, which had been discontinued because of an eczematiform rash. In spite of substitution with an angiotensin II receptor antagonist, the patients had developed the same eruption. The outcome was favourable after discontinuation of the angiotensin II receptor antagonist. The pharmacologic study suggested the possibility of a cross-sensitivity reaction between these two drugs.

CONCLUSION

We report the first two cases of a cross-sensitivity between angiotensin-converting enzyme inhibitors and angiotensin II receptor antagonist presenting as an eczematiform rash. The exact mechanism is unknown, but clinicians must be aware that angiotensin II receptor antagonist is not a safe alternative in patients who have a history of eczematiform rash secondary to angiotensin-converting enzyme inhibitors, as has been always reported with angioedema.

Angiotensin-induced inflammation and novel approaches to treatment

In a brief period, we have accrued a new view of Ang II. From conventional signaling pathways, our attention was directed toward signal transduction involving specific tyrosine kinases, inducing not only vasocontriction but also proto-oncogene expression, protein synthesis, hypertrophy and growth. More recently, our attention has been directed beyond these effects to inflammatory reactions involving NF-kappa B activation and related gene expression. The mechanisms are not known for certain but probably initially involve the generation of ROS. The subsequent NF-kappa B activation probably involves participation of endothelin signaling and, perhaps, NF-AT3 activation. It is possible that other compounds can also modulate Ang II-induced inflammatory responses.

[Immunoenzyme analysis of natural antibodies to endogenous bioregulators in patients with systemic lupus erythematosus]

Serum levels of autoantibodies to endogenous bioregulators (prostaglandin F2 alpha, angiotensin II, epinephrine, bovine serum albumin, dinitrophenol) were measured in patients with systemic and integumental lupus erythematosus and donors and the diagnostic significance of deviations of these levels from the norm was evaluated. A total of 75 patients with lupus erythematosus aged 19-54 years with disease lasting for 0.5 to 18 months were examined. Significant differences between patients and donors were observed as regards virtually all parameters except IgG to angiotensin II.

[Autoantibodies to vasoactive peptides and angiotensin converting enzyme in patients with systemic diseases of the connective tissue]

AIM

To estimate the level of natural autoantibodies (NAAb) to angiotensin-converting enzyme (ACE) and endogenic mediators affecting vascular tone (bradykinin--BK, angiotensin II--AII, vasopressin--VP) as well as the activity of serum ACE in patients with systemic diseases of the connective tissue.

MATERIAL AND METHODS

Levels of NAAb were measured by enzyme immunoassay in sera from 30 patients with SLE, 19 patients with rheumatoid arthritis (RA) and 36 patients with scleroderma systematica (SS). Serum from donors served control. IgM NAAb to ACE were measured by a new technique. Serum ACE activity was determined by the initial velocity of hydrolysis reaction using spectrofluometry.

RESULTS

IgM NAAb were detected in the sera of both patients and donors. SS patients had the level of NAAb to ACE in diffuse form significantly higher than in limited (p < 0.05). In SLE and SS patients ACE activity was significantly lower (p < 0.05) than in healthy subjects and RA patients. Levels of NAAb to BK was significantly elevated (p < 0.01) in patients with SLE and RA vs donors while to AII in SS patients it was lowered (p < 0.001). Patients with diffuse SS had NAAb to BK higher than patients with SS limited form (p < 0.01). In SLE the lowest levels of NAAb to all the mediators studied were observed in patients with nephritis, for NAAb to VP the differences were significant (p < 0.05). In patients with urinary syndrome concentration of NAAb to BK was significantly higher (p < 0.01), differences between their levels in patients with nephritis and urinary syndrome were also significant (p < 0.05).

CONCLUSION

Further studies are needed for specification of physiological or pathological role of NAAb to endogenic mediators.

[Effects of anti-atherosclerotic low-sodium diet on dynamics of natural antibodies to angiotensin II, bradykinin and vasopressin in blood of patients with hypertension and obesity]

The dynamic of natural antibodies against angiotensin II, bradykinin and vasopressin in blood serum was studied in 75 patients with hypertension and obesity. Universal normalizing effect of the diet consists in decrease of levels of natural antibodies was found.

Location of renin-angiotensin system components in the hypoglossal nucleus of the rat

The renin-angiotensin system (RAS) in the hypoglossal nuclei of the rat was studied by immunohistochemistry. Antibodies to angiotensin AT(1) receptor (AT1), angiotensinogen (ANG), renin (REN), angiotensin converting enzyme (ACE) and angiotensin II (AII) were used. All the components of the RAS with the exception of renin were detected. Light and electron microscopy revealed the following results: ANG was predominantly found in astrocytes, with small amounts in neuronal dendrites; ACE was found in the cytoplasm of neurons, dendrites and astrocyte processes; AT1 was found in the cytoplasm of neurons and dendrites, but not on the membrane; and AII was found mainly in astrocytes with some located in the dendrites and cytoplasm. Right hypoglossal nerve lesion caused an increase in expression of AT1 in neurons as early as 2 days post-lesion. An increase in expression of ANG in astrocytes was also seen, but at a much later time of 3 weeks post-lesion. For AII, staining occurred in both the neurons and astrocytes in the undamaged hypoglossal nucleus. Nerve lesion caused a disappearance of neuronal stains and an increase in astrocyte stains. There were no changes in ACE staining after nerve lesion. We speculate that ANG and AII are made within the astrocytes, whereas ACE could either be uptaken from blood or de novo synthesized. AT1 may potentially be internal soluble receptors. As to the function of AII in the hypoglossal nucleus, the data do not support AII as a neurotransmitter in the hypoglossal nucleus. It may function as a neuromodulator and also be involved in basic cellular activities, e.g. regulation of transcription factors.

Immunocytochemical localization of angiotensin II receptor subtypes and angiotensin II with monoclonal antibodies in the rat adrenal gland

Angiotensin II (Ang II), a major regulator of cardiovascular function and body fluid homeostasis, mediates its biological actions via two subtypes of G protein-coupled receptors, termed AT(1) and AT(2). The primary goal of this study was to raise monoclonal anti-peptide antibodies specific to angiotensin AT(1)- and AT(2)-receptor subtypes and to Ang II itself and using these monoclonal antibodies to determine the intraadrenal localization of AT(1) and AT(2) receptors and Ang II in male adult rats. Immunocytochemistry unambiguously demonstrates a regional colocalization of Ang II and angiotensin II receptors in the adrenal gland. The novel antibodies localized Ang II and the AT(1) receptors to the zona glomerulosa of the cortex and to the medulla whereas AT(2) receptors were limited to the medulla. The specificity of immunostaining was documented by pre-adsorption of the antibody with the immunogenic peptide. Our data underscore that AT(1) appears to mediate most of the physiological actions of Ang II in adrenal. Western blot analysis of rat adrenal protein extracts using AT(1) antibody showed a predominant 73-kDa band and a weaker 97-kDa immunoreactive band corresponding to glycosylated forms of the AT(1) receptor. Immunostaining with anti-AT(2) yielded one major immunoreactive band of 73-kDa size and one additional fainter band of 120 kDa. These antibodies may prove of value in unraveling the subcellular localization and intracellular effector pathways of AT(1) and AT(2).

Interaction of the octapeptide angiotensin II with a high-affinity single-chain Fv and with peptides derived from the antibody paratope

The amino-acid sequence of the very high-affinity anti-angiotensin II monoclonal antibody 4D8 was predicted from the nucleotide sequence of the heavy and light chain variable genes. The single-chain variable fragment (scFv) was constructed and expressed in Escherichia coli as a soluble protein and at the surface of the filamentous M13 phage and was compared with the full-length antibody (Ab). The scFv showed the same specificity profile and affinity constant as the intact antibody (5.0x10(10) and 8.0x10(10) M(-1), respectively, by Scatchard analysis). Several peptides from the set of overlapping dodecapeptides covering the variable domains of 4D8 mAb were found to specifically bind biotinylated angiotensin II: peptides from the L1, L2, L3 and H1 regions had the strongest capacity to bind the antigen.

A new angiotensinergic system in the CNS of the rat

The use of two different polyclonal, affinity-purified, monospecific antibodies to ANG II (called BODE and BODE 1) revealed dissimilar distribution of ANG II immunoreactivity within the rat central nervous system (CNS). The ANG II-like material detected using BODE was concentrated in the neurosecretory hypothalamic nuclei, in the inner layer of the median eminence and in the posterior lobe of the pituitary. In contrast, the BODE 1 antibody did not stain the hypothalamic-neurohypophysial angiotensinergic system, and the staining pattern was much more broadly distributed throughout the CNS. BODE 1 is the first antibody that can be used to verify the locations of endogenous angiotensin and their receptor sites in the CNS. The diverse distribution of the ANG II-like material detected by the two antibodies provides strong evidence for the existence of at least two different angiotensinergic systems in the CNS.

Proinflammatory actions of angiotensins

Many experimental data have suggested that the renin-angiotensin system participates in immune and inflammatory responses. Angiotensin II is involved in several steps of the inflammatory process: mononuclear cells respond to angiotensin II stimulation (cell proliferation and chemotaxis); angiotensin II regulates the recruitment of proinflammatory cells into the site of injury (mediated by the expression of vascular permeability factors, adhesion molecules and chemokines by resident cells); inflammatory cells can produce angiotensin II, and might therefore contribute to the perpetuation of tissue damage. In this review, we summarize the proinflammatory properties of angiotensin II, to demonstrate the novel role of this vasoactive peptide as a true cytokine. We will show the information obtained as a result of the pharmacological blockade of the renin angiotensin system, which has demonstrated that this system is involved in immune and inflammatory diseases. In this aspect, we discuss the molecular mechanism of angiotensin II-induced tissue damage, as well as its contribution to the pathogenesis of several diseases, including atherosclerosis, hypertension and renal damage, showing that angiotensin II plays an active role in the inflammatory response of these diseases.

Chymase-dependent angiotensin II formation in the saphenous vein versus the internal thoracic artery

OBJECTIVES

The great saphenous vein graft is known to be less patent than the internal thoracic artery graft. Recently, we reported that chymase-dependent angiotensin II formation plays an important role in the development of intimal hyperplasia in dog grafted veins. In this study we investigated the levels of angiotensin II-forming enzymes, angiotensin-converting enzyme, and chymase in human saphenous veins and internal thoracic arteries.

METHODS

The saphenous vein and internal thoracic artery specimens were obtained from coronary artery bypass grafts of patients during surgical procedures (saphenous vein, n = 16; internal thoracic artery, n = 16). Activities of angiotensin-converting enzyme and chymase were determined by using the extract from the saphenous vein or internal thoracic artery. Sections of the saphenous vein or internal thoracic artery were stained with van Gieson's elastin stain and were immunostained with anti-human chymase antibody.

RESULTS

The activities of angiotensin-converting enzyme in the saphenous vein and internal thoracic artery were 0.34 +/- 0.12 and 0.32 +/- 0.17 mU/mg protein, respectively, and the difference was not significant. The chymase activity in the saphenous vein was significantly higher than that in the internal thoracic artery (saphenous vein, 10.1 +/- 0.81 mU/mg protein; internal thoracic artery, 6.21 +/- 1.86 mU/mg protein). Chymase-positive cells in the saphenous vein were located in both the media and adventitia, and those in the internal thoracic artery were located only in the adventitia. The number of chymase-positive cells in the saphenous vein was about 2.6 times that in the internal thoracic artery.

CONCLUSION

The chymase activity, but not the angiotensin-converting enzyme activity, was significantly higher in the saphenous vein, suggesting that the high levels of chymase activity may be related to the poorer performance of the saphenous vein for use as a bypass conduit.

Angiotensin, inflammation, hypertension, and cardiovascular disease

We are used to thinking of angiotensin (Ang) II as a regulatory hormone that stimulates constriction of vascular smooth muscle cells, aldosterone release from the adrenal gland, and sodium reabsorption in the renal tubule. We have also become accustomed to understanding that Ang II may be formed and may act locally as a chemokine that induces tyrosine phosphorylation, cell growth, hypertrophy, and differentiation. Viewing Ang II as an inflammatory molecule is stranger still. Nevertheless, recent evidence shows that Ang II is important in stimulating the production of reactive oxygen species and the activation of ancient inflammatory mechanisms. The nuclear factor kappaB (NF-kappaB) is pivotal to these processes. Activation of NF-kappaB stimulates the expression of a gene menagerie that is important to chemoattraction, expression of surface adhesion molecules, coagulation, and inflammation. In addition, Ang II has been shown to regulate cellular immune responses. It stimulates the proliferation of lymphocytes and contributes to their activation via calcineurin-related pathways. Knowledge of these mechanisms may provide additional therapeutic avenues.