New therapeutic agents for hypertension

The lord of the ring: mandatory role of the kidney in drug therapy of hypertension

Strong evidence supports the idea that total peripheral resistance (TPR) is increased in all forms of human and experimental hypertension. Although the etiological participation of TPR in the origin and long-term maintenance of hypertension has been extensively debated, it now seems clear that the renal, nonadaptive, infinite gain-working, pressure-sensitive natriuresis and diuresis is the main mechanism of blood pressure control in the long term. The tissue, cellular, biochemical, and genetic sensors and executors of this process have not been fully identified yet, but the role of the renal medulla has gained growing attention as the physiopathological scenario in which the key regulatory elements reside. Specifically, the functionality of the renomedullary vasculature seems to be highly responsible for blood pressure control. The vasculature of the renal medulla becomes a new and more specific target for the therapeutic intervention of hypertension. Recent data on the effect of baroreceptor-controlled renal sympathetic activity on the long-term regulation of blood pressure are integrated. The renomedullary effects of the main antihypertensive drugs are discussed, and new perspectives for the therapeutic intervention of hypertension are outlined. Comparison of the genetic program of the renal medulla before and after the development of hypertension in spontaneously hypertensive and experimentally induced animal models might provide a mechanism for identifying the key genes that become activated or suppressed in the development of high blood pressure. These genes, their encoded proteins, or other elements related to their signalling and genetic pathways might serve as new and more specific targets for the pharmacological treatment of abnormally elevated blood pressure. Besides, proteins specifically located to the luminal side of the renomedullary vascular endothelium may serve as potential targets for site-directed drug and gene therapy.

Receptors in cardiovascular disease: review and introduction

Despite recent encouraging declines, cardiovascular disease (CVD) is still responsible for about 50% of premature death in the Western industrialized countries, greater than cancer, AIDS and accidents, combined. Different aspects of the disease have been considered and the main currently available and possible future drugs whose effect is based on interaction with a receptor have been reviewed. Catecholamines receptors ligands, mainly beta-blockers, and the new angiotensin II antagonists represent the most important classes among the established therapies. Investigational approaches such as the oral glycoprotein GPIIb/IIIa antagonists and endothelin, adenosine and neuropeptide Y receptors ligands are discussed. Receptorology represents just a part of the therapeutical approach to CVD, where other classes of drugs with enzyme or ionic channel based mechanisms are largely used and innovative therapies based on the most advanced research techniques could early become reality.

New drugs for the treatment of hypertension

Despite the many outstanding favorable results achieved in the treatment of hypertension, several unmet goals of antihypertensive therapy remain, such as better blood pressure control, greater protection against the organ damage associated with hypertension, better tolerability, and ultimately a more effective prevention of cardiovascular disease. These unmet goals are the reasons why new antihypertensive drugs are synthesized and tested in the clinical practice. This paper briefly mentions the goals of new antihypertensive agents and examines the main pharmacological and clinical features of new classes of antihypertensive drugs, such as angiotensin II receptor blockers, central agents, vasopeptidase inhibitors, and endothelin antagonists. The results of experimental and clinical studies with these new drugs are reviewed, emphasizing some advantages and potential disadvantages of these drugs compared with traditional antihypertensive drugs.

'Seeing through a glass darkly': casting light on imidazoline 'I' sites

Although imidazoline sites have been the subject of research for several years, there is still controversy about their structure, diversity and physiology. The I1 site is thought to exist principally as a binding site and is widely purported to play a role in controlling systemic blood pressure, although this is still unclear. The majority of I2 sites are widely accepted as being allosteric sites on monoamine oxidase; however, even with selective ligands, their exact function remains to be determined. A putative I3 site modulates insulin secretion and could represent the first functional site to be pharmacologically defined with selective agonists and antagonists. The structure and relevance of the proposed endogenous ligand 'clonidine-displacing substance' remains elusive. A potential candidate for this substance is agmatine; however, although it is capable of displacing bound clonidine from imidazoline sites, it lacks the functionality ascribed to the clonidine-displacing substance. In this review, Richard M. Eglen and colleagues assess our knowledge of imidazoline sites in the light of recent data.