Abnormal platelet Ca2+ handling accompanied by increased cytosolic free Mg2+ in essential hypertension

The Role of Magnesium in the Development of Cardiovascular Diseases and the Possibility of their Prevention and Correction with Magnesium Preparations (Part 1)

The article is devoted to the influence of magnesium on the homeostasis of the body and, in particular, on the cardiovascular system. It describes the importance of the presence and effects of magnesium on various key processes and functions occurring in the body. The reasons for the lack of magnesium and ways to replenish it both in the natural way (eating, certain foods) and magnesium preparations are considered. The article provides examples of large randomized studies that prove the importance of the influence of normal magnesium levels on human health in general and on the state of the cardiovascular system. These studies show how magnesium deficiency increases the risk of cardiovascular diseases and how it can be reduced. It is also shown which trace elements and vitamins are closely related to magnesium metabolism, and how they (in particular, potassium and vitamin B6) improve and facilitate the normalization of magnesium levels. It is noted how comorbidity decreases with the normalization of magnesium level – the higher the magnesium level in the blood plasma (closer to the upper limit and more), the less comorbidity and longer life expectancy. Magnesium is an absolutely essential ion and a good medicine. Magnesium deficiency and hypomagnesemia are quite common, difficult to diagnose (due to underestimation and rare level control) and accompany many diseases of the cardiovascular system and beyond. The widespread use of organic magnesium salts would improve the situation as a whole, due to their universal multiple effect on many processes in the body. This is an integral part of therapeutic and preventive measures in patients with already existing diseases and in people who do not have diseases, but who are at risk due to existing hypomagnesemia.

Magnesium in disease

Although the following text will focus on magnesium in disease, its role in healthy subjects during physical exercise when used as a supplement to enhance performance is also noteworthy. Low serum magnesium levels are associated with metabolic syndrome, Type 2 diabetes mellitus (T2DM) and hypertension; consequently, some individuals benefit from magnesium supplementation: increasing magnesium consumption appears to prevent high blood pressure, and higher serum magnesium levels are associated with a lower risk of developing a metabolic syndrome. There are, however, conflicting study results regarding magnesium administration with myocardial infarction with and without reperfusion therapy. There was a long controversy as to whether or not magnesium should be given as a first-line medication. As the most recent trials have not shown any difference in outcome, intravenous magnesium cannot be recommended in patients with myocardial infarction today. However, magnesium has its indication in patients with torsade de pointes and has been given successfully to patients with digoxin-induced arrhythmia or life-threatening ventricular arrhythmias. Magnesium sulphate as an intravenous infusion also has an important established therapeutic role in pregnant women with pre-eclampsia as it decreases the risk of eclamptic seizures by half compared with placebo.

[Magnesium deficiency in cardiology]

The paper considers the consequences and causes of magnesium deficiency in patients with cardiovascular diseases. The features of magnesium metabolism in atherosclerosis, hypertension, and heart failure are described. Prospects of magnesium therapy in cardiology practice are discussed.

Transient receptor potential melastatin 6 and 7 channels, magnesium transport, and vascular biology: implications in hypertension

Magnesium, an essential intracellular cation, is critically involved in many biochemical reactions involved in the regulation of vascular tone and integrity. Decreased magnesium concentration has been implicated in altered vascular reactivity, endothelial dysfunction, vascular inflammation, and structural remodeling, processes important in vascular changes and target organ damage associated with hypertension. Until recently, very little was known about mechanisms regulating cellular magnesium homeostasis, and processes controlling transmembrane magnesium transport had been demonstrated only at the functional level. Two cation channels of the transient receptor potential melastatin (TRPM) cation channel family have now been identified as magnesium transporters, TRPM6 and TRPM7. These unique proteins, termed chanzymes because they possess a channel and a kinase domain, are differentially expressed, with TRPM6 being found primarily in epithelial cells and TRPM7 occurring ubiquitously. Vascular TRPM7 is modulated by vasoactive agents, pressure, stretch, and osmotic changes and may be a novel mechanotransducer. In addition to its magnesium transporter function, TRPM7 has been implicated as a signaling kinase involved in vascular smooth muscle cell growth, apoptosis, adhesion, contraction, cytoskeletal organization, and migration, important processes involved in vascular remodeling associated with hypertension and other vascular diseases. Emerging evidence suggests that vascular TRPM7 function may be altered in hypertension. This review discusses the importance of magnesium in vascular biology and implications in hypertension and highlights the transport systems, particularly TRPM6 and TRPM7, which may play a role in the control of vascular magnesium homeostasis. Since the recent identification and characterization of Mg2+-selective transporters, there has been enormous interest in the field. However, there is still a paucity of information, and much research is needed to clarify the exact mechanisms of magnesium regulation in the cardiovascular system and the implications of aberrant transmembrane magnesium transport in the pathogenesis of hypertension and other vascular diseases.

Altered calcium signaling in platelets from nitric oxide-deficient hypertensive rats

Background

In the present study we have analyzed the mechanisms of calcium entry and mobilization in platelets obtained from rats chronically treated with the nitric oxide synthesis inhibitor, N-nitro L-arginine methyl ester [L-NAME, 40 mg/kg/day, 5 days). The platelets were obtained the day of the experiment, washed and loaded with fura-2. The intracellular calcium levels were determined in suspension of cells by means of fluorescence spectroscopy.

Results

Basal calcium levels were always elevated in the platelets of the L-NAME-treated rats, both in the presence and in the absence of extracellular calcium. The administration of thrombin in the absence and in the presence of extracellular calcium induced important elevations in calcium levels that were always of greater magnitude in the platelets of the L-NAME-treated rats than in those of the controls. The addition of calcium to thapsigargin-treated platelets produced a massive elevation in calcium levels in both groups that was significantly greater in the platelets obtained from the hypertensive rats than in those of the controls.

Conclusions

It is concluded that the arterial hypertension induced by the reduction of nitric oxide alters the regulation of platelet calcium levels so that elevated baseline levels and calcium entry and mobilization are enhanced. This could be the result of direct or indirect effects of the lack of nitric oxide synthesis in platelets or in other tissues.