The Lack of Relationship between an Endothelin-1 Gene Polymorphism (Ala288Ser) and Incidence of Hypertension: A Retrospective Cohort Study among Japanese Workers

Human lymphatic filariasis: genetic polymorphism of endothelin-1 and tumor necrosis factor receptor II correlates with development of chronic disease

BACKGROUND

Hydrocele and elephantiasis are 2 clinically very diverse and often mutually exclusive chronic manifestations of human bancroftian filariasis. Plasma levels of endothelin-1 (ET-1), a major angiogenic factor, and tumor necrosis factor receptors (TNFRs) that regulate host inflammation have been associated with development of chronic filariasis, although their genetic basis are not known.

METHODS

We studied polymorphisms of ET-1 (Ala288Ser) and TNFR-II (Met196Arg) genes by means of the polymerase chain reaction confronting 2 pairs primers method and restriction fragment length polymorphism, respectively. Plasma ET-1 level was measured by enzyme-linked immunosorbent assay.

RESULTS

Met196Arg genotype frequency of TNFR-II polymorphism was significantly greater in hydrocele patients, compared with elephantiasis patients (OR, 4.34 [95% CI, 2.04-9.20]). Conversely, a significantly high prevalence of the Ala288Ser mutation of ET-1 was observed in elephantiasis patients, compared with hydrocele cases (OR, 2.15 [95% CI, 1.13-4.10]). Decreased plasma ET-1 levels associated significantly with Ala288Ser mutation in the study population. A combined analysis indicated a 23-fold higher risk for developing elephantiasis in individuals with TNFR-II (Met196Met) and ET-1 mutants (Ala288Ser + Ser288Ser).

CONCLUSIONS

ET-1 (Ala288Ser) and TNFR-II (Met196Arg) polymorphisms are associated with development of one or the other form of chronic disease in bancroftian filariasis.

Genetic variation in the endothelin system: do polymorphisms affect the therapeutic strategies?

Endothelin-1 (ET-1) exerts multiple biological effects, including vasoconstriction and the stimulation of cell proliferation in tissues both within and outside of the cardiovascular system. ET-1 is synthesized by ET-converting enzymes (ECE), chymases (CMAs), and non-ECE metalloproteases through a process regulated in an autocrine fashion in vascular and nonvascular cells. ET-1 acts through the activation of G(i)protein-coupled receptors. ET(A) receptors mediate vasoconstriction and cell proliferation, whereas ET(B) receptors are important for aldosterone secretion, endothelial cell (EC) migration, the release of nitric oxide (NO) and prostacyclin, the clearance of ET-1, and the inhibition of ECE-1. ET is activated in scleroderma, hypertension, atherosclerosis, restenosis, heart failure, idiopathic cardiomyopathy, and renal failure. Tissue concentrations more reliably reflect the activation of the ET system because of the predominantly abluminal secretion of the peptide. Experimental studies and clinical trials have demonstrated that ET-1 plays a major role in normal cardiovascular homeostasis and in the functional and structural changes observed in arterial and pulmonary hypertension, glomerulosclerosis, atherosclerosis, and heart failure. Accordingly, ET antagonists are promising new agents in the treatment of cardiovascular diseases. Single nucleotide polymorphisms (SNPs) of the genes of preproET-1, ECE-1, CMA, ET(A) and ET(B) receptors have been identified and can be important for their functional regulation. However, for most of them the association with disease conditions and the evidence for a functional role remain controversial. Thus, even though ET antagonists are being used for the treatment of pulmonary hypertension, there is no convincing evidence for a role of SNPs in affecting the therapeutic strategies.