Abnormal immune function in malignant hypertension

Angiotensin receptor autoantibodies as exposures that modify disease progression: Cross sectional, longitudinal and in vitro studies of prostate cancer

Circulating angiotensin type I receptor (AT1R) agonistic autoantibodies (AT1RaAbs) that bind and chronically activate the receptor have been associated with a number of diseases suggesting that while the autoantibodies are not necessarily causative they may promote disease progression. The prostate has a local renin angiotensin system. The current study examines associations between AT1RaAbs and prostate cancer (PCA), disease-free survival (DFS), overall survival (OS) and AT1RaAb effects on PCA cell phenotype. In a cross-sectional set of serum obtained from 151 men diagnosed with PCA, nonmalignant prostate disease or no disease, higher serum AT1RaAb levels were associated with PCA and non-organ confined PCA. The odds ratio for PCA was 6.3 (95% confidence interval 2.2 to 18) for a positive 1:1600 titer and 18 (95% confidence interval 6.9 to 45) at AT1RaAb levels > 1.04 μg/ml, (p < 0.0001). In a longitudinal set of pre-diagnosis samples from 109 men, DFS hazard ratios of 2.2 (95% confidence interval 1.4 to 3.5) and 1.6 (95% confidence interval 1.0 to 2.5) for most proximal to diagnosis and most distal to diagnosis samples, respectively, were found for high versus low AT1RaAb groups. Hazard ratios for OS in most proximal and distal samples were 2.4 (95% confidence interval 1.6 to 3.6) and 1.8 (95% confidence interval 1.1 to 2.8), respectively. Accelerated failure modeling of survival indicated that a 1 μg/ml increase in AT1RaAb levels was associated with a reduction of DFS and OS by 20% at the most proximal time point and by 15% at the most distal time points. Adjusting for age, did not affect the association with DFS in proximal samples but changed distal time point DFS and OS to a 10% decrease for every 1 μg/ml increase in AT1RaAb. Additional adjustments for body mass index, systolic blood pressure and prostate-specific antigen did not appreciably alter these associations. AT1RaAb treatment of PC3, DU145, and LNCaP cells significantly increased the maximal growth rate approximately 2-fold and invasiveness approximately 3-fold. Conclusions: These observations provide evidence supporting AT1RaAbs as exposures that may modify prostate cancer progression and indicate they may be predictive markers for risk stratification.

Moringa oleifera-rich diet and T cell calcium signaling in spontaneously hypertensive rats

Moringa oleifera is a plant whose fruits, roots and leaves have been advocated for traditional medicinal uses. The physicochemical analysis shows that Moringa oleifera contains more dietary polyunsaturated fatty acids (PUFA) than saturated fatty acids (SFA). The consumption of an experimental diet enriched with Moringa oleifera extracts lowered blood pressure in spontaneously hypertensive rats (SHR), but not in normotensive Wistar-Kyoto (WKY) rats as compared to rats fed an unsupplemented control diet. Anti-CD3-stimulated T cell proliferation was diminished in both strains of rats fed the Moringa oleifera. The experimental diet lowered secretion of interleukin-2 in SHR, but not in WKY rats compared with rats fed the control diet. Studies of platelets from patients with primary hypertension and from SHR support the notion that the concentration of intracellular free calcium [Ca(2+)](i) is modified in both clinical and experimental hypertension. We observed that the basal, [Ca(2+)](i) was lower in T cells of SHR than in those of WKY rats fed the control diet. Feeding the diet with Moringa oleifera extracts to WKY rats did not alter basal [Ca(2+)](i) in T cells but increased basal [Ca(2+)](i) in SHR. Our study clearly demonstrated that Moringa oleifera exerts antihypertensive effects by inhibiting the secretion of IL-2 and modulates T cell calcium signaling in hypertensive rats.

Effect of prazosin on diabetic nephropathy patients with positive α1-adrenergic receptor autoantibodies and refractory hypertension

To investigate the effect of prazosin on patients with diabetic nephropathy (DN), α1-adrenergic receptor (α1-R) autoantibodies and refractory hypertension, a total of 126 patients with DN and hypertension were recruited. The patients were divided into a refractory hypertension group, (n=76) and a non-refractory hypertension group (n=50). The epitope of the second extracellular loop of the α1-R (192–218) was synthesized and an enzyme-linked immunosorbent assay (ELISA) was performed to detect serum autoantibodies. In the group with DN-associated refractory hypertension, the positive rate of autoantibodies against the α1-R was 80.3% (n=61). The 61 patients who were positive for α1-R autoantibodies were randomly divided into a treatment group (n=31) and a control group (n=30). The patients were given drugs at the same dosage and administration, with the exception of prazosin, which was provided only to the patients in the treatment group [1 mg, three times a day (tid)] for a duration of six weeks. Subsequently, prazosin was added (1 mg, tid) to the therapeutic schedule of the patients in the control group and the α1-R autoantibody-negative group for another six weeks. The analysis was carried out on an intention-to-treat basis. The prazosin treatment resulted in significant improvements in hypertension in the treatment group (P<0.05), while there was no marked improvement in the control group. The total effective rate of hypertension improvement was 90.3% in the treatment group, which was higher compared with that of the control group (33.3%). In conclusion, α1-R autoantibodies may play an important role in the pathogenesis of DN with refractory hypertension. Prazosin was demonstrated to be effective and safe in the treatment of DN with refractory hypertension.

Changes in cardiac structure and function in rats immunized by angiotensin type 1 receptor peptides

Angiotensin II (Ang II) is known to induce cardiomyocyte hypertrophy by activating the Ang II type 1 (AT1) receptor. Some studies have demonstrated that the autoantibodies against angiotensin AT1 receptor (AT1-AAs) cause functional effects, which is similar to those observed for the natural agonist Ang II. In this study, we investigated the effects of AT1-AAs on cardiomyocytes' structure and function. Male Wistar rats were immunized with synthetic peptides corresponding to the second extracellular loop of AT1 receptor and Freund's adjuvant. The titers of AT1-AAs in rat serum were detected by enzyme-linked immunosorbent assay every week. Hemodynamic analysis and heart weight (HW) indices were measured on the 4th and 8th months after initial immunization, respectively. Cultured neonatal rat cardiomyocytes were used to observe the hypertrophic effects of AT1-AAs. Results showed that systolic blood pressure and heart rate were significantly increased, the titers of AT1-AAs were also increased after 4 weeks of initial immunization. Compared with control group, the HW/body weight (BW) and left ventricular weight/BW of immunized rats were increased significantly and cardiac function was enhanced compensatively. The cultured neonatal rat cardiomyocytes respond to AT1-AAs stimulation with increased (3)H-leucine incorporation and cell surface area in a dose-dependent manner. These results suggest that the AT1-AAs have an agonist effect similar to Ang II in hypertrophy of cardiomyocytes in vivo and in vitro. AT1-AAs are involved in the pathogenesis of cardiovascular diseases and hypertension.

Correlation between HLA-DRB1, HLA-DQB1 polymorphism and autoantibodies against angiotensin AT(1) receptors in Chinese patients with essential hypertension

BACKGROUND

The autoantibodies (AAs) against angiotensin AT(1) receptors (AT(1) -AAs) have been discovered in patients with preeclampsia, malignant hypertension, and essential hypertension (EH); however, the mechanism of AA production remains to be investigated.

HYPOTHESIS

Polymorphisms of HLA-DRB1 or HLA-DQB1 are related to production of AAs in autoimmune diseases. We hypothesis that the polymorphisms of the HLA molecules are also associated with production of AT(1) -AAs in patients with EH.

METHODS

We enrolled 394 patients with EH and 224 normotensive subjects in this study. Autoantibodies in sera of donors were detected by enzyme-linked immunosorbent assay. The subjects' clinical data were collected, including gender, age, body mass index, blood pressure, smoking status, and diabetes. The patients and the normotensive subjects were classified respectively into AA-positive and AA-negative groups. Typing of DNA for HLA-DRB1 and HLA-DQB1 alleles was done by polymerase chain reaction amplification with sequence-specific primers.

RESULTS

Thirteen HLA-DRB1 and 7 HLA-DQB1 alleles were found in this population. The frequencies of AT(1) -AAs were related to blood pressure level. The frequency of AT(1) -AAs in the EH group was higher than that in the normotensive group (P = 0.0001). The levels of AAs in different groups of EH show a significant difference (P = 0.027). In addition, HLA-DRB1(*) 04 and HLA-DRB1(*) 14 (odds ratio [OR]: 3.06, 95% confidence interval [CI]: 1.56-5.97, P = 0.001; and OR: 2.53, 95% CI: 1.080-5.91, P = 0.033, respectively) were related to AT(1) -AA production in normotensive subjects after adjusting for covariants. The HLA-DRB1(*) 04 allele might be related to AT(1) -AA production in hypertensive subjects, and the P value was of baseline statistical significance after adjusting for blood pressure and other covariants (OR: 1.63, 95% CI: 0.95-2.78, P = 0.070).

CONCLUSIONS

These results suggest a difference in the immunogenetic background between the positive and negative AAs with hypertension or normotension. The HLA-DRB1(*) 04 allele increases the risk for AT(1) -AA production.

Dietary (n-3) polyunsaturated fatty acids exert antihypertensive effects by modulating calcium signaling in T cells of rats

After 10 wk of feeding an experimental diet enriched with (n-3) polyunsaturated fatty acids (PUFA), i.e., eicosapentaenoic acid [EPA, 20:5(n-3)] and [DHA, 22:6(n-3)] (EPAX), blood pressure in spontaneously hypertensive rats (SHR), but not in normotensive Wistar-Kyoto (WKY) rats was reduced relative to rats fed an unsupplemented control diet. Concanavalin A-stimulated T-cell proliferation was diminished in both strains of rats fed the PUFA/EPAX diet. The experimental diet lowered secretion of interleukin-2 in SHR, but not in WKY rats compared with rats fed the control diet. To determine whether there was a defect in calcium homeostasis in T cells during hypertension, we employed the following agents: caffeine, which recruits calcium from the cytosolic Ca(2+)-induced Ca(2+)-release pool; ionomycin, which at low concentrations opens calcium channels; and thapsigargin (TG), which mobilizes [Ca(2+)]i from the endoplasmic reticulum (ER) pool. Caffeine-induced increases in [Ca(2+)]i were not modified by the PUFA/EPAX diet. The ionomycin-induced increases in [Ca(2+)]i in T cells from SHR were greater than in those from WKY rats; consumption of the PUFA/EPAX diet did not modify Ca(2+) influx in cells of either strain. The TG-induced increases in [Ca(2+)]i in T cells from SHR were greater than those in cells from WKY rats. Interestingly, consumption of the experimental diet reduced TG-evoked increases in [Ca(2+)]i in T cells from SHR and increased those in T cells from WKY rats, indicating that the PUFA/EPAX diet could reverse the calcium mobilization from the ER pool in T cells. These results suggest that (n-3) PUFA exert antihypertensive effects and modulate T-cell calcium signaling during hypertension in rats.

Spontaneously hypertensive rat: cholera toxin converts suppression to immunity through a Th2 cell-IL-4 pathway

The spontaneously hypertensive rat (SHR) exhibits a number of T cell dysfunctions that develop concurrently with elevated blood pressure. Studies have shown a mitogen-induced lymphocyte suppression mediated in part by the production of interferon-gamma (IFN-gamma), which stimulated NO production by macrophages. To assess whether this immune suppression is reversible, SHR were immunized with diphtheria toxoid (DT) with or without cholera toxin (CT) as adjuvant. SHR immunized with DT only displayed weak serum immunoglobulin G (IgG) anti-DT titers, tenfold less than similarly treated normotensive Wistar-Kyoto rats (WKYR). SHR CD4+ T cells failed to proliferate upon in vitro stimulation with DT. In contrast, SHR coimmunized with DT and CT showed serum IgG antibody titers similar to WKYR and Brown Norway rats. Coimmunization with CT rescued SHR CD4+ T cells from suppression and supported DT- or B subunit of CT-specific proliferative responses, and these cells produced more interleukin-4 (IL-4) than IFN-gamma, and anti-IFN-gamma antibody treatment enhanced IL-4 production. Exogenous IL-4 increased the proliferation of antigen-specific CD4+ T cells, whereas IFN-gamma was inhibitory. This study shows that the adjuvant CT induces T helper 2-type responses, reversing the T cell dysfunction in the SHR.

Hypertensive arteriolar necrosis revisited

Arteriolar necrosis is the histopathological hallmark of malignant hypertension. In the period from 1940 to 1980, intensive studies of the pathogenesis of hypertensive fibrinoid necrosis were carried out. From studies of mesenteric vessels in animals with experimental hypertension it was discovered that arteriolar necrosis is preceded by an abnormal vascular reaction pattern consisting of alternating constriction and localized dilatations. The development of the abnormal reaction pattern is followed by endothelial hyperpermeability resulting in transsudation of plasma and macromolecules into the wall of the arteriole. The hyperpermeability, and, in turn, arteriolar necrosis, is exclusively found in the dilated segments of the vessel. The abnormal vascular reaction pattern can be induced experimentally by various techniques such as infusion of angiotensin II or stimulation of perivascular nerves, and it can be demonstrated in all target organs. Since 1980 a remarkable falling-off in the research on the pathogenesis of hypertensive arteriolar necrosis has been noted. Recent studies in this area utilizing current knowledge and major advances in microvascular research methods are very few in number. As of today, the chain of pathogenetic processes leading eventually to the all-important lesion of arteriolar fibrinoid necrosis remains poorly understood.

Elevated interleukin-1 beta in the circulation of patients with essential hypertension before any drug therapy: a pilot study

Immune system disturbances have been implicated in the pathogenesis of essential hypertension. The aim of this study was to determine the levels of the interleukin-1 beta and soluble interleukin-2 receptors in serum samples from 114 hypertensive patients before any drug therapy because there are no well-established data regarding these immunologic mediators in essential hypertension. We found increased levels of interleukin-1 beta in 59.6% of patients, while soluble interleukin-2 receptors were not detected. The interleukin-1 beta levels were significantly higher in patients than in healthy controls (P = 0.0001). We conclude that patients with essential hypertension have high levels of interleukin-1 beta but not indicators of cellular immune activation in their sera. Further studies are in progress in order to confirm, explain and assess the clinical utility of the above findings.

Abnormal immune system and hypertension: where are we?

In reviewing the available evidence, the involvement of an immunological mechanism behind hypertension has been proposed. However, whether altered immunological function is a primary factor in the pathogenesis of hypertension or secondary to tissue damage of vascular beds induced by hypertension is still poorly defined. A major difficulty has been the relative paucity of information about the nature of specific immune targets which initiate and perpetuate abnormal immune responses in hypertension. This article will discuss the status of understanding of the involvement of immunological factors in both clinical and experimental hypertension.

Hypertension is not related to suppressed lymphocyte proliferation but to elevated NO synthesis in vascular smooth muscle cells of borderline hypertensive rat

Hypertensive individuals often exhibit immune abnormalities. We have previously reported that spontaneously hypertensive rats (SHR) had a severely depressed lymphocyte proliferation response caused by excessive nitric oxide (NO) from macrophages and vascular smooth muscle cells (VSMC). However, the development of hypertension was not correlated with the lymphocyte depression and elevated NO synthesis in macrophages. In this study, we investigated the effect of hypertension on lymphocytes and the NO synthesis system in borderline hypertensive rats (BHR). BHR became significantly hypertensive after receiving a high sodium diet. The proliferation response of lymphocytes in hypertensive BHR was similar to that of normotensive BHR fed a normal diet or of Wistar Kyoto rats (WKY). NO production in macrophages of hypertensive BHR was not different from that of normotensive BHR or WKY. However, NO production in VSMC was significantly elevated in hypertensive BHR. A positive correlation between blood pressure and VSMC NO production exists in hypertensive BHR. These results suggested that high blood pressure neither affected the lymphocyte function nor influenced the activation of NO synthesis in macrophages. Hypertension, however, may influence the activation of VSMC NO synthesis. In conclusion, hypertension is not causally associated with immune dysfunction as seen in SHR but is related to enhanced NO synthesis in VSMC.