The application of molecular genetics to the study of familial arterial hypertension

Metabolites and Hypertension: Insights into Hypertension as a Metabolic Disorder: 2019 Harriet Dustan Award

For over 100 years, essential hypertension has been researched from different perspectives ranging from genetics, physiology, and immunology to more recent ones encompassing microbiology (microbiota) as a previously underappreciated field of study contributing to the cause of hypertension. Each field of study in isolation has uniquely contributed to a variety of underlying mechanisms of blood pressure regulation. Even so, clinical management of essential hypertension has remained somewhat static. We, therefore, asked if there are any converging lines of evidence from these individual fields that could be amenable for a better clinical prognosis. Accordingly, here we present converging evidence which support the view that metabolic dysfunction underlies essential hypertension.

Renal angiotensin-converting enzyme and blood pressure control

PURPOSE OF REVIEW

This review presents novel findings regarding the renal angiotensin-converting enzyme (ACE) and its role in blood pressure (BP) control.

RECENT FINDINGS

The textbook flow diagram of the renin-angiotensin system (RAS) shows the pulmonary endothelium as the main source of the ACE that converts angiotensin I to angiotensin II. However, ACE is made in large quantities by the kidneys, which raises the important question of what precisely is the function of renal ACE? Recent studies in gene-targeted mice indicates that renal ACE plays a dominant role in regulating the response of the kidney to experimental hypertension. In particular, renal ACE and locally generated angiotensin II affect the activity of several key sodium transporters and the induction of sodium and water retention resulting in the elevation of BP.

SUMMARY

New experimental data link the renal ACE/angiotensin II pathway and the local regulation of sodium transport as key elements in the development of hypertension.

Synthesis and biological evaluation of new fluorine substituted derivatives as angiotensin II receptor antagonists with anti-hypertension and anti-tumor effects

The synthesis and pharmaceutical activity of new potent non-tetrazole angiotensin II (Ang II) receptor antagonists were described. These compounds were fluorine substituted derivatives of Losartan, Valsartan and Irbesartan with carboxylic acid group as replacements to the known potent tetrazole moiety at the 2'-biphenyl position. Their activities were evaluated by Ang II receptor binding assay as well as by in vivo assay. All of the synthesized compounds showed nanomolar affinity for the AT(1) receptor subtype. The vivo biological evaluation showed that compounds 1a, 2 and 4 produced a dose-dependent antihypertensive effect both in spontaneously hypertensive rats (SHR) and renal hypertensive rats (RHR). Compound 4 especially showed an efficient and long-lasting effect in reducing blood pressure which can last more than 24 h at dose of 10 mg/kg in SHR, which was much better than control Losartan and Valsartan. Compound 4 can also inhibit the prostate cancer in vitro and in vivo. So compound 4 was selected for in-depth investigation as potent, novel and long-lasting non-tetrazole anti-hypertension and anti-tumor drug candidate.

Molecular basis of human hypertension: role of angiotensinogen

Essential hypertension is a common human disease believed to result from the interplay of multiple genetic and environmental determinants. In genetic studies of two large panels of hypertensive sibships from widely separated geographical areas, we obtained evidence of genetic linkage between the angiotensinogen gene (AGT) and hypertension, demonstrated association of AGT molecular variants with the disease, and found significant differences in plasma concentrations of angiotensinogen among hypertensive subjects with different AGT genotypes. The corroboration and replication afforded by these results support the interpretation that molecular variants of AGT constitute inherited predispositions to essential hypertension in humans.

Aldosterone regulation of gene transcription leading to control of ion transport

Aldosterone, like other steroid hormones, initiates its effects by binding to intracellular receptors; these receptors are then able to control the transcription of several genes. The products of these genes eventually modulate the activity of ionic transport systems located in the apical and the basolateral membrane of specialized epithelial cells, thereby modulating the excretion of Na+ and K+ ions. Considerable progress has been made recently in understanding these mechanisms and the structure of the proteins involved in these processes. A novel principle has been discovered to explain the selective effect of aldosterone on its target epithelia. These tissues exclude competing glucocorticoid hormones by the activity of the 11 beta-hydroxysteroid dehydrogenase to allow aldosterone, an enzyme-resistant steroid, to bind to its receptors. Aldosterone induces numerous changes in the activity of membrane ion transport systems and enzymes and cell morphology. Although the enhancement of Na,K-ATPase synthesis and the increase of the number of active Na+ channels in the apical membrane appear as both direct and primary effects, the mechanisms of the other effects remain to be determined. The knowledge of the primary structure of several elements of the aldosterone response system (e.g., mineralocorticoid receptor and Na,K-ATPase) allows us to understand abnormal regulation of Na+ balance at the molecular level and, potentially, to identify genetic alterations responsible for these defects.

Molecular genetics of hypertension

During the last decades the evidence that a genetic component contributes to the development of primary hypertension has been accumulating. The identification of the genes involved in blood pressure regulation, however, is only starting to emerge. The recent advances in recombinant DNA technology provide new molecular genetic strategies in cardiovascular research. In this review we will discuss the testing of candidate genes in vivo by transgenic techniques. Furthermore, we will describe the possibilities to identify the genes implicated in primary hypertension by genetic linkage analysis using polymorphic DNA markers.