Antihypertensive treatment: should it be titrated to blood pressure reduction or to target organ damage regression?

Angiopoietin-1 gene therapy attenuates hypertension and target organ damage in nitric oxide synthase inhibited spontaneously hypertensive rats

Background and Objectives

In our previous study, we found that the gene transfer of a potent derivative of cartilage oligomeric matrix protein Angiopoietin-1 (COMP-Ang-1) substantially prevented hypertension, microvascular rarefaction, and target organ damage in spontaneously hypertensive rats (SHRs). The purpose of the present study was to examine the role of nitric oxide (NO) in the therapeutic effects observed after COMP-Ang-1 gene transfer.

Materials and Methods

To exclude the NO-mediated effects in COMP-Ang-1 gene therapy, the SHRs were treated with an NO synthase (NOS) inhibitor, N^w-nitro-L-arginine methyl ester (L-NAME) before the electrophoretic gene transfer.

Results

The pretreatment with L-NAME induced a severe and sustained increase in systolic blood pressure (BP) in a LacZ plasmid transferred control SHR. However, the electrophoretic transfer of a COMP-Ang-1 plasmid instead of LacZ plasmid in L-NAME-pretreated SHRs substantially blocked the development of hypertension without any significant difference in comparison with L-NAME-untreated COMP-Ang-1 plasmid transferred groups. In addition, the COMP-Ang-1 plasmid transfer substantially attenuated microvascular rarefaction and arteriole remodeling in the heart and kidney, which might account for the mild histological alterations observed in the COMP-Ang-1 plasmid transferred group, in contrast to the severe fibrosis and necrosis seen in the LacZ plasmid controls.

Conclusion

These therapeutic outcomes of COMP-Ang-1 gene transfer even in NOS inhibited SHRs suggested that the antihypertensive effect of COMP-Ang-1 was not merely secondary to NO-mediated vasorelaxation, but it may be associated with its ability to protect the vascular endothelium probably via an NO-independent mechanism which serves to attenuate microvascular rarefaction and target organ damage, and also to prevent hypertension by reducing peripheral vascular resistance.

Cardiovascular effects of arginase inhibition in spontaneously hypertensive rats with fully developed hypertension

AIMS

Growing evidence suggests that arginase misregulation plays a key role in the pathophysiology of essential hypertension. In the present study, we investigated the potential cardiovascular therapeutic effects of a long-term treatment with an arginase inhibitor in adult spontaneously hypertensive rats (SHR) with fully developed hypertension.

METHODS AND RESULTS

Treatment of 25-week-old SHR with the arginase inhibitor N(omega)-hydroxy-nor-L-arginine (nor-NOHA, 40 mg/day for 10 weeks) sustainably reduced systolic blood pressure (-30 mmHg, P < 0.05). The antihypertensive effect of nor-NOHA was associated with changes on mesenteric artery reactivity including the restoration of angiotensin-II-induced contraction and acetylcholine-induced vasodilation to the values of normotensive Wistar Kyoto rats. Both nitric oxide synthase and cyclooxygenase-dependent mechanisms account for the improvement of endothelial function afforded by the arginase inhibitor, which in addition blunted hypertension-induced endothelial arginase I overexpression in mesenteric arteries. Nor-NOHA also prevented the remodelling of aorta as measured by collagen content and media/lumen ratio, and improved the compliance of carotid artery in SHR. Cardiac fibrosis assessed by collagen content of left heart ventricle was reduced by nor-NOHA, with no significant effect on cardiac hypertrophy.

CONCLUSION

Our results report that a long-term treatment with an arginase inhibitor reduced blood pressure, improved vascular function, and reduced cardiac fibrosis in SHR with fully developed hypertension. These data suggest that arginase represents a promising novel target for pharmacological intervention in essential hypertension.

Signal transduction of the (pro)renin receptor as a novel therapeutic target for preventing end-organ damage

The (pro)renin receptor ((P)RR) not only represents a novel component of the renin-angiotensin system but is also a promising novel drug target because of its crucial involvement in the pathogenesis of renal and cardiac end-organ damage. This review discusses the signal transduction of the (P)RR with its adapter protein promyelocytic zinc-finger protein, the impact of this receptor, especially on cardiovascular disease, and its putative interaction with renin inhibitors such as aliskiren. Furthermore, the increasing complexity regarding the cellular function of the (P)RR is addressed, which arises by the intimate link with proton pumps and the phosphatase PRL-1, as well as by the presence of different subcellular localizations and of a soluble isoform of the (P)RR. Finally, the rationale and strategy for the development of small-molecule antagonists of the (P)RR, called renin/prorenin receptor blockers, are presented.

Angiopoietin-1 prevents hypertension and target organ damage through its interaction with endothelial Tie2 receptor

Aims

The endothelium has emerged recently as a therapeutic target in the treatment of hypertension because endothelial dysfunction and subsequent vascular rarefaction cause target organ damage and further elevate blood pressure (BP). It led us to hypothesize that one of the endothelial survival factors, a potent derivative of angiopoietin-1 (cartilage oligomeric matrix protein, COMP-Ang-1), could be a novel class of antihypertensive agents that maintain endothelial integrity and function, thereby preventing the development of hypertension and target organ damage.

Methods and results

To study the role of COMP-Ang-1 in preventing hypertension and target organ damage, a COMP-Ang-1 plasmid was electroporated into adductor muscles of 6 weeks old, pre-hypertensive, spontaneously hypertensive rats (SHRs), and the secretion of its expressed protein into the bloodstream was confirmed by western blotting. In comparison with sham and reporter gene transfer, COMP-Ang-1 gene transfer significantly prevented increases in systolic BP and reduced microvascular rarefaction and tissue damage in the heart and kidney. However, overexpression of soluble Tie2 receptor completely abolished these beneficial effects of COMP-Ang-1 gene transfer on SHRs, indicating that expressed COMP-Ang-1 protein has antihypertensive effects in SHRs by binding Tie2 receptors on the vascular endothelium. In particular, COMP-Ang-1 gene-transferred SHRs had significantly higher plasma levels of nitrite than other controls, which was found to be due to that expressed COMP-Ang-1 protein promoted nitrite synthesis by activating endothelial nitric oxide synthase, one of the Tie2 downstream-signalling molecules.

Conclusion

The present study suggests a new potential of endothelial survival factor, COMP-Ang-1, as an antihypertensive agent that effectively reduces the hypertension-associated cardiovascular and renal damage, as well as prevents the further elevation of BP.

O. Blood pressure and cardiorenal responses to antihypertensive therapy in obese women

OBJECTIVE: Blood pressure(BP) and target organ responses to antihypertensive drugs are not well established in hypertensive obese patients. This study is aimed at evaluating the effects of obesity and adiposity distribution patterns on these responses. METHODS: 49 hypertensive obese women were designated to different groups according to waist to hip ratio measurements - 37 with troncular and 12 with peripheral obesity. Patients were treated for 24-weeks on a stepwise regimen with cilazapril alone or a cilazapril/hydrochlorothiazide/amlodipine combination therapy to achieve a BP lower than 140/90mmHg. Ambulatory blood pressure monitoring (ABPM), echocardiography, and albuminuria were assessed before and after the intervention. RESULTS: After 24 weeks, weight loss was less than 2% in both groups. ABPM targets were achieved in 81.5% of patients upon a combination of 2(26.5%) or 3(55.1%) drugs. Similar reductions in daytime-SBP/DBP: -22.5/-14.1(troncular obesity) / -23.6/-14.9mmHg (peripheral obesity) were obtained. Decrease in nocturnal-SBP was greater in troncular obesity patients. Upon BP control, microalbuminuria was markedly decreased, while only slight decrease in left ventricular mass was observed for both groups. CONCLUSIONS: In the absence of weight loss, most patients required combined antihypertensive therapy to control their BP, regardless of their body fat distribution pattern. Optimal target BP and normal albuminuria were achieved in the group as a whole and in both obese patient groups, while benefits to cardiac structure were of a smaller magnitude.

Small artery structure is an independent predictor of cardiovascular events in essential hypertension

OBJECTIVE

Structural abnormality of resistance arteries is a characteristic pathophysiological phenomenon in essential hypertension and can be assessed in vitro as an increase in the media: lumen ratio (M: L) of isolated small arteries. We have investigated whether M: L is a risk predictor in uncomplicated essential hypertensive patients. Recently, high M: L was demonstrated as a prognostic marker in patients at high cardiovascular risk, including normotensive type 2 diabetic patients. Since diabetes is associated with pressure-independent changes in M: L, the relevance of this finding to essential hypertension has been uncertain.

METHODS

We conducted a follow-up survey of 159 essential hypertensive patients, who had previously been submitted to a M: L evaluation while participating in a clinical trial. They composed a homogeneous moderate-risk group, with no concomitant diseases, and represented 1661 years of follow-up.

RESULTS

Thirty patients suffered a documented predefined cardiovascular event during follow-up. Increased relative risk (RR) was associated with M: L >or= 0.083 (mean level of the hypertensive cohort), RR = 2.34 [95% confidence interval (CI) 1.11-4.95], and with M: L >or= 0.098 (mean level of a normotensive control group + 2SD), RR = 2.49 (95% CI 1.21-5.11). Both results remained significant (RR = 2.19, 95% CI 1.04-4.64, and RR = 2.20, 95% CI 1.06-4.56, respectively) when adjusted for Heart Score level (10-year mortality risk-estimate, integrating age, gender, systolic blood pressure, cholesterol and smoking).

CONCLUSION

Abnormal resistance artery structure independently predicts cardiovascular events in essential hypertensive patients at moderate risk.