Treatment with a Ca(2+) channel blocker, barnidipine, reduces platelet-derived growth factor B-chain mRNA in glomeruli of spontaneously hypertensive rats

Characterization of calmodulin binding to the orphan nuclear receptor Errgamma

The estrogen receptor-related receptor gamma (ERRgamma/ ERR3/NR3B3), a member of the nuclear receptor superfamily, activates transcription in the absence of ligands. In order to identify ligand-independent mechanisms of activation, we tested whether calmodulin (CaM), a key regulator of numerous cellular processes and a predominant intracellular receptor for Ca2+-signals, interacts with ERRgamma. In vitro pull-down experiments with calmodulin-Sepharose demonstrated a Ca2+-dependent interaction with cellularly expressed ERRgamma. As shown by truncation analysis, the CaM binding site is highly unusual in that it is composed of two discontinuous elements. Moreover, by surface plasmon resonance (SPR) biosensor technology, we detected a direct interaction of immobilized bacterially expressed ERR-gamma fusion protein with Ca2+-calmodulin. This is best described by a model which assumes a conformational change of the initially formed complex to a more stable form. Whereas in vitro DNA binding was calmodulin-independent, transient transfection analysis revealed a Ca2+-influx-dependent ERRgamma-mediated transcriptional activation of a luciferase reporter gene. Thus, we propose that CaM acts as a mediator in the Ca2+-dependent modulation of ERRgamma.

Barnidipine

Bamidipine is an antihypertensive drug belonging to the dihydropyridine (DHP) group of calcium antagonists. It is available in a modified-release formulation which has a gradual onset of action and is effective in a single daily oral dose of 10 to 20 mg. Bamidipine has selective action against cardiovascular calcium antagonist receptors and its antihypertensive action is related to the reduction of peripheral vascular resistance secondary to its vasodilatory action. The clinical antihypertensive efficacy of barnidipine is similar to that of other DHP calcium antagonists such as nitrendipine and amlodipine, and antihypertensives belonging to other drug classes such as atenolol and enalapril. Barnidipine has been found to be as efficacious and well tolerated as hydrochlorothiazide in the management of hypertension in elderly patients. Barnidipine is generally well tolerated. As with other DHP calcium antagonists, vasodilator adverse events such as headache, flushing and peripheral oedema account for most of the adverse events reported with its use and are usually transient. Oedema is less frequent than with amlodipine and nitrendipine. Its use is not associated with reflex tachycardia.

Are calcium antagonists effective in preventing complications of hypertension and progression of renal disease?

Long-acting calcium antagonists have been shown to be safe and effective in lowering blood pressure, both as first-line agents and in combination with other classes of antihypertensive drug. They have also been shown to reduce the incidence of cerebrovascular and cardiovascular events in elderly patients with predominantly systolic hypertension. It is clear that reduced morbidity and mortality in hypertension is related to the degree to which blood pressure is reduced, regardless of the therapy used. This is the single most important conclusion of all recent trials, especially in the sub-group of hypertensive patients with diabetes. The World Health Organization-International Society of Hypertension guidelines acknowledge this and do not make specific recommendations as to initial therapy in the absence of other medical factors. However the use of thiazide diuretics and beta-blockers has strong support from large placebo-controlled trials in patients with mild-moderate essential hypertension. The British Hypertension Society and JNC VI guidelines restrict their recommendations for the use of calcium antagonists to isolated systolic hypertension and angina, or when other agents have failed, are contraindicated or are not tolerated. However, their efficacy in lowering blood pressure, their tolerability and potentially beneficial secondary effect on proteinuria, especially in combination with an angiotensin-converting enzyme inhibitor, still make them attractive antihypertensive agents. The results of further long-term outcome trials that make direct comparisons between calcium antagonists and other classes of antihypertensive drug are still awaited. Unlike angiotensin-converting enzyme inhibitors, the antiproteinuric effect of calcium antagonists, even that of the non-dihydropyridine type, seems to depend on an adequate and stable reduction in blood pressure.