Changes in gene expression in rat thymocytes identified by cDNA array support the occurrence of oxidative stress in early magnesium deficiency

Malnutrition and Allergies: Tipping the Immune Balance towards Health

Malnutrition, which includes macro- and micronutrient deficiencies, is common in individuals with allergic dermatitis, food allergies, rhinitis, and asthma. Prolonged deficiencies of proteins, minerals, and vitamins promote Th2 inflammation, setting the stage for allergic sensitization. Consequently, malnutrition, which includes micronutrient deficiencies, fosters the development of allergies, while an adequate supply of micronutrients promotes immune cells with regulatory and tolerogenic phenotypes. As protein and micronutrient deficiencies mimic an infection, the body's innate response limits access to these nutrients by reducing their dietary absorption. This review highlights our current understanding of the physiological functions of allergenic proteins, iron, and vitamin A, particularly regarding their reduced bioavailability under inflamed conditions, necessitating different dietary approaches to improve their absorption. Additionally, the role of most allergens as nutrient binders and their involvement in nutritional immunity will be briefly summarized. Their ability to bind nutrients and their close association with immune cells can trigger exaggerated immune responses and allergies in individuals with deficiencies. However, in nutrient-rich conditions, these allergens can also provide nutrients to immune cells and promote health.

Magnesium and the Hallmarks of Aging

Magnesium is an essential ion in the human body that regulates numerous physiological and pathological processes. Magnesium deficiency is very common in old age. Age-related chronic diseases and the aging process itself are frequently associated with low-grade chronic inflammation, called 'inflammaging'. Because chronic magnesium insufficiency has been linked to excessive generation of inflammatory markers and free radicals, inducing a chronic inflammatory state, we formerly hypothesized that magnesium inadequacy may be considered among the intermediaries helping us explain the link between inflammaging and aging-associated diseases. We show in this review evidence of the relationship of magnesium with all the hallmarks of aging (genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, altered intercellular communication, disabled autophagy, dysbiosis, and chronic inflammation), which may positively affect the human healthspan. It is feasible to hypothesize that maintaining an optimal balance of magnesium during one's life course may turn out to be a safe and economical strategy contributing to the promotion of healthy aging. Future well-designed studies are necessary to further explore this hypothesis.

Prognostic Value of Magnesium in COVID-19: Findings from the COMEPA Study

Magnesium (Mg) plays a key role in infections. However, its role in coronavirus disease 2019 (COVID-19) is still underexplored, particularly in long-term sequelae. The aim of the present study was to examine the prognostic value of serum Mg levels in older people affected by COVID-19. Patients were divided into those with serum Mg levels ≤1.96 vs. >1.96 mg/dL, according to the Youden index. A total of 260 participants (mean age 65 years, 53.8% males) had valid Mg measurements. Serum Mg had a good accuracy in predicting in-hospital mortality (area under the curve = 0.83; 95% CI: 0.74-0.91). Low serum Mg at admission significantly predicted in-hospital death (HR = 1.29; 95% CI: 1.03-2.68) after adjusting for several confounders. A value of Mg ≤ 1.96 mg/dL was associated with a longer mean length of stay compared to those with a serum Mg > 1.96 (15.2 vs. 12.7 days). Low serum Mg was associated with a higher incidence of long COVID symptomatology (OR = 2.14; 95% CI: 1.30-4.31), particularly post-traumatic stress disorder (OR = 2.00; 95% CI: 1.24-16.40). In conclusion, low serum Mg levels were significant predictors of mortality, length of stay, and onset of long COVID symptoms, indicating that measuring serum Mg in COVID-19 may be helpful in the prediction of complications related to the disease.

Could soluble minerals be hazardous to human health? Evidence from fibrous epsomite

From a toxicological point of view, particulates and fibres with high solubility in water and/or in biological environments have not been considered in detail and the knowledge to date in this area is very scarce. In this study, the water-soluble natural epsomite fibres from Perticara Mine (Italy) were investigated using SEM-EDS, XRPD, ICP-AES and alpha spectrometry measurements which were combined and integrated to characterise the fibres' morphology, crystal chemistry and mineralogy. The morphological and morphometric results showed that most of the fibres are of inhalable size (D_ae 5.09 μm) and can be potentially adsorbed from all parts of the respiratory tract. Chemical analysis reveals significant amounts of toxic elements (As, Co, Fe, Mn, Ni, Sr, Ti, Zn) and surprisingly high contents of radioactive isotopes (²¹⁰Po and ²²⁸Th) in epsomite crystals, making the inhalation of these fibres potentially hazardous to human health. Through this study, we want to focus on soluble minerals, such as epsomite, which can be present in both natural and anthropic environments and have never been considered from the point of view of their potential hazard.

Hepatic Response of Magnesium-Restricted Wild Type Mice

Magnesium-deficiency is implicated in many metabolic disorders, e.g., type 2 diabetes and metabolic syndrome, representing risk factors for non-alcoholic fatty liver disease (NAFLD). This study aims to investigate the contribution of magnesium-restriction to the development of NAFLD. Magnesium-deficiency was induced in C57BL/6 mice by feeding a magnesium-deficient-diet. Metabolic markers as well as markers of inflammation and liver function were assessed. Furthermore, liver tissue was examined histopathologically and compared with specimens from high-fat-diet fed and control mice. Finally, the hepatic inflammatory response was quantified by determining hepatic IL-6, TNFα, and MCP-1. Magnesium-restriction resulted in at least a 2-fold significant reduction of serum magnesium levels compared to the high-fat-diet fed and control mice, whereas the hepatic magnesium content was decreased due to high-fat-diet feeding. No changes in metabolic markers in magnesium-restricted mice were observed, while the cholesterol content was elevated in high-fat-diet fed mice. Magnesium-restricted mice additionally featured inflammation and enlarged hepatocytes in liver histology. Furthermore, magnesium-restricted and high-fat-diet fed mice exhibited elevated hepatic TNFα levels compared to control mice. Accordingly, our data suggest that magnesium is involved in hepatic inflammatory processes and hepatocyte enlargement, key histological features of human NAFLD, and may therefore contribute to development and progression of the disease.

Magnesium in Infectious Diseases in Older People

Reduced magnesium (Mg) intake is a frequent cause of deficiency with age together with reduced absorption, renal wasting, and polypharmacotherapy. Chronic Mg deficiency may result in increased oxidative stress and low-grade inflammation, which may be linked to several age-related diseases, including higher predisposition to infectious diseases. Mg might play a role in the immune response being a cofactor for immunoglobulin synthesis and other processes strictly associated with the function of T and B cells. Mg is necessary for the biosynthesis, transport, and activation of vitamin D, another key factor in the pathogenesis of infectious diseases. The regulation of cytosolic free Mg in immune cells involves Mg transport systems, such as the melastatin-like transient receptor potential 7 channel, the solute carrier family, and the magnesium transporter 1 (MAGT1). The functional importance of Mg transport in immunity was unknown until the description of the primary immunodeficiency XMEN (X-linked immunodeficiency with Mg defect, Epstein-Barr virus infection, and neoplasia) due to a genetic deficiency of MAGT1 characterized by chronic Epstein-Barr virus infection. This and other research reporting associations of Mg deficit with viral and bacterial infections indicate a possible role of Mg deficit in the recent coronavirus disease 2019 (COVID-19) and its complications. In this review, we will discuss the importance of Mg for the immune system and for infectious diseases, including the recent pandemic of COVID-19.

A Review of the Action of Magnesium on Several Processes Involved in the Modulation of Hematopoiesis

Magnesium (Mg²⁺) is an essential mineral for the functioning and maintenance of the body. Disturbances in Mg²⁺ intracellular homeostasis result in cell-membrane modification, an increase in oxidative stress, alteration in the proliferation mechanism, differentiation, and apoptosis. Mg²⁺ deficiency often results in inflammation, with activation of inflammatory pathways and increased production of proinflammatory cytokines by immune cells. Immune cells and others that make up the blood system are from hematopoietic tissue in the bone marrow. The hematopoietic tissue is a tissue with high indices of renovation, and Mg²⁺ has a pivotal role in the cell replication process, as well as DNA and RNA synthesis. However, the impact of the intra- and extracellular disturbance of Mg²⁺ homeostasis on the hematopoietic tissue is little explored. This review deals specifically with the physiological requirements of Mg²⁺ on hematopoiesis, showing various studies related to the physiological requirements and the effects of deficiency or excess of this mineral on the hematopoiesis regulation, as well as on the specific process of erythropoiesis, granulopoiesis, lymphopoiesis, and thrombopoiesis. The literature selected includes studies in vitro, in animal models, and in humans, giving details about the impact that alterations of Mg²⁺ homeostasis can have on hematopoietic cells and hematopoietic tissue.

Magnesium improves cisplatin-mediated tumor killing while protecting against cisplatin-induced nephrotoxicity

Approximately 30% of all cancer patients treated with cisplatin, a widely used broad-spectrum chemotherapeutic agent, experience acute kidney injury (AKI). Almost all patients receiving cisplatin have magnesium (Mg) losses, which are proposed to aggravate AKI. Currently, there are no methods to successfully treat or prevent cisplatin-AKI. Whereas Mg supplementation has been shown to reduce AKI in experimental models and several small clinical trials, the effects of Mg status on tumor outcomes in immunocompetent tumor-bearing mice and humans have not been investigated. The purpose of this study was to further examine the effects of Mg deficiency (±Mg supplementation) on cisplatin-mediated AKI and tumor killing in immunocompetent mice bearing CT26 colon tumors. Using a model where cisplatin alone (20 mg/kg cumulative dose) produced minimal kidney injury, Mg deficiency significantly worsened cisplatin-mediated AKI, as determined by biochemical markers (blood urea nitrogen and plasma creatinine) and histological renal changes, as well as markers of renal oxidative stress, inflammation, and apoptosis. By contrast, Mg supplementation blocked cisplatin-induced kidney injury. Using LLC-PK₁ renal epithelial cells, we observed that Mg deficiency or inhibition of Mg uptake significantly enhanced cisplatin-induced cytotoxicity, whereas Mg supplementation protected against cytotoxicity. However, neither Mg deficiency nor inhibition of Mg uptake impaired cisplatin-mediated killing of CT26 tumor cells in vitro. Mg deficiency was associated with significantly larger CT26 tumors in BALB/c mice when compared with normal-fed control mice, and Mg deficiency significantly reduced cisplatin-mediated tumor killing in vivo. Finally, Mg supplementation did not compromise cisplatin's anti-tumor efficacy in vivo.

Effects of magnesium deficiency--more than skin deep

Dead Sea and magnesium salt therapy are two of the oldest forms of treatment for skin disease and several other disorders, supported by a body of largely anecdotal evidence. In this paper we review possible pathways for penetration of magnesium ions through the epidermis to reach the circulation, in turn replenishing cellular magnesium levels. We also discuss mechanisms for intercellular movement of magnesium ions and possible mechanisms for the interaction between magnesium ions and inflammatory mediators. Upon addition of magnesium ions in vitro, the expression of inflammatory mediators such as tumour necrosis factor α (TNFα) and nuclear factor κβ (NFκβ) is down regulated. Dysregulation of these and other inflammatory mediators has been linked to several inflammatory disorders, including asthma, arthritis, atherosclerosis and neuroinflammation.

Association of dietary magnesium intake with radiographic knee osteoarthritis: results from a population-based study

OBJECTIVE

To examine the cross-sectional association between dietary magnesium intake and radiographic knee osteoarthritis (OA) among African American and white men and women.

METHODS

The presence of radiographic knee OA was examined among participants from the Johnston County Osteoarthritis Project and was defined as a Kellgren/Lawrence grade of at least 2 in at least 1 knee. The Block Food Frequency Questionnaire was used to assess magnesium intake. Effect modifiers were explored by testing interactions of magnesium intake and selected factors based on previous studies. The multivariable logistic regression model with standard energy adjustment method was used to estimate the relationship between magnesium intake and radiographic knee OA.

RESULTS

The prevalence of knee OA was 36.27% among the 2,112 participants. The relationship between magnesium intake and radiographic knee OA was found to be modified by race (P for interaction = 0.03). An inverse threshold association was observed among whites. Compared to participants in the lowest quintile, the relative odds of radiographic knee OA were cut by one-half for participants in the second quintile of magnesium intake (odds ratio 0.52, 95% confidence interval 0.34-0.79); further magnesium intake did not provide further benefits (P for trend = 0.51). A statistically significant association was not observed among African Americans.

CONCLUSION

A modest inverse threshold association was found between dietary magnesium intake and knee OA in whites, but not in African Americans. Further studies are needed to confirm these results and to elucidate the possible mechanisms of action for the racial modification.

Update on the assessment of magnesium status

Magnesium (Mg) is the fourth most abundant mineral in the body and the most abundant intracellular divalent cation, with essential roles in many physiological functions. Consequently, the assessment of Mg status is important for the study of diseases associated with chronic deficiency. In spite of intense research activities there is still no simple, rapid, and accurate laboratory test to determine total body Mg status in humans. However, serum Mg < 0.75 mmol/l is a useful measurement for severe deficiency, and for values between 0.75 and 0.85 mmol/l a loading test can identify deficient subjects. The loading test seems to be the gold standard for Mg status, but is unsuitable in patients with disturbed kidney and intestinal functions when administered orally. There is also a need to reach a consensus on a standardized protocol in order to compare results obtained in different clinical units. Other cellular Mg measurements, such as total or ionized Mg, frequently disagree and more research and systematic evaluations are needed. Muscle Mg appears to be a good marker, but biopsies limit its usefulness, as is the case with bone Mg, the most important but heterogeneous Mg compartment. The development of new and non invasive techniques such as nuclear magnetic resonance (NMR) may provide valuable tools for routinely analysing ionized Mg in tissues. With the development of molecular genetics techniques, the recent discovery of Transient Receptor Potential Melastatin channels offers new possibilities for the sensitive and rapid evaluation of Mg status in humans.

Dietary magnesium and DNA repair capacity as risk factors for lung cancer

Magnesium (Mg) is required for maintenance of genomic stability; however, data on the relationship between dietary Mg intake and lung cancer are lacking. In an ongoing lung cancer case-control study, we identified 1139 cases and 1210 matched healthy controls with data on both diet and DNA repair capacity (DRC). Dietary intake was assessed using a modified Block-NCI food frequency questionnaire and DRC was measured using the host-cell reactivation assay to assess repair in lymphocyte cultures. After adjustment for potential confounding factors including DRC, the odds ratios (ORs) and 95% confidence intervals (CIs) for lung cancer with increasing quartiles of dietary Mg intake were 1.0, 0.83 (0.66-1.05), 0.64 (0.50-0.83) and 0.47 (0.36-0.61), respectively, for all subjects (P-trend < 0.0001). Similar results were observed by histology and clinical stage of lung cancer. Low dietary Mg intake was associated with poorer DRC and increased risk of lung cancer. In joint effects analyses, compared with those with high dietary Mg intake and proficient DRC, the OR (95% CI) for lung cancer in the presence of both low dietary Mg and suboptimal DRC was 2.36 (1.83-3.04). Similar results were observed for men and women. The effects were more pronounced among older subjects (>60 years), current or heavier smokers, drinkers, those with a family history of cancer in first-degree relatives, small cell lung cancer and late-stage disease. These intriguing results need to be confirmed in prospective studies.

Cell (patho)physiology of magnesium

There is an unsettled debate about the role of magnesium as a ‘chronic regulator’ of biological functions, as opposed to the well-known role for calcium as an ‘acute regulator’. New and old findings appear to delineate an increasingly complex and important role for magnesium in many cellular functions. This review summarizes the available evidence for a link between the regulation of intracellular magnesium availability and the control of cell growth, energy metabolism and death, both in healthy and diseased conditions. A comprehensive view is precluded by technical difficulties in tracing magnesium within a multicompartment and dynamic environment like the cell; nevertheless, the last few years has witnessed encouraging progress towards a better characterization of magnesium transport and its storage or mobilization inside the cell. The latest findings pave the road towards a new and deeper appreciation of magnesium homoeostasis and its role in the regulation of essential cell functions.

Mg2+ deprivation elicits rapid Ca2+ uptake and activates Ca2+/calcineurin signaling in Saccharomyces cerevisiae

To learn about the cellular processes involved in Mg(2+) homeostasis and the mechanisms allowing cells to cope with low Mg(2+) availability, we performed RNA expression-profiling experiments and followed changes in gene activity upon Mg(2+) depletion on a genome-wide scale. A striking portion of genes up-regulated under Mg(2+) depletion are also induced by high Ca(2+) and/or alkalinization. Among the genes significantly up-regulated by Mg(2+) starvation, Ca(2+) stress, and alkalinization are ENA1 (encoding a P-type ATPase sodium pump) and PHO89 (encoding a sodium/phosphate cotransporter). We show that up-regulation of these genes is dependent on the calcineurin/Crz1p (calcineurin-responsive zinc finger protein) signaling pathway. Similarly to Ca(2+) stress, Mg(2+) starvation induces translocation of the transcription factor Crz1p from the cytoplasm into the nucleus. The up-regulation of ENA1 and PHO89 upon Mg(2+) starvation depends on extracellular Ca(2+). Using fluorescence resonance energy transfer microscopy, we demonstrate that removal of Mg(2+) results in an immediate increase in free cytoplasmic Ca(2+). This effect is dependent on external Ca(2+). The results presented indicate that Mg(2+) depletion in yeast cells leads to enhanced cellular Ca(2+) concentrations, which activate the Crz1p/calcineurin pathway. We provide evidence that calcineurin/Crz1p signaling is crucial for yeast cells to cope with Mg(2+) depletion stress.

TRPM7 and TRPM2-Candidate susceptibility genes for Western Pacific ALS and PD?

Recent findings implicating TRPM7 and TRPM2 in oxidative stress-induced neuronal death thrust these channels into the spotlight as possible therapeutic targets for neurodegenerative diseases. In this review, we describe how the functional properties of TRPM7 and TRPM2 are interconnected with calcium (Ca(2+)) and magnesium (Mg(2+)) homeostasis, oxidative stress, mitochondrial dysfunction, and immune mechanisms, all principal suspects in neurodegeneration. We focus our discussion on Western Pacific Amyotrophic Lateral Sclerosis (ALS) and Parkinsonism Dementia (PD) because extensive studies conducted over the years strongly suggest that these diseases are ideal candidates for a gene-environment model of etiology. The unique mineral environment identified in connection with Western Pacific ALS and PD, low Mg(2+) and Ca(2+), yet high in transition metals, creates a condition that could affect the proper function of these two channels.

Magnesium and neoplasia: From carcinogenesis to tumor growth and progression or treatment

Magnesium is involved in a wide range of biochemical reactions that are crucial to cell proliferation, differentiation, angiogenesis, and apoptosis. Changes in magnesium availability have been shown to influence biological responses of immuno-inflammatory cells. Equally plausible seems to be an involvement of magnesium in the multistep and interconnected processes that lead to tumor formation and development; however, the "how" and "when" of such an involvement remain to be defined. Here, we reviewed in vitro and in vivo data that indicated a role for magnesium in many biological and clinical aspects of cancer (from neoplastic transformation to tumor growth and progression or pharmacologic treatment). In adopting this approach we went through a full circle from molecular aspects to observational or epidemiological studies that could reconcile in a unifying picture the otherwise fragmentary or puzzling data currently available on the role of magnesium in cancer.

Allogeneic activation is attenuated in a model of mouse lung perfused with magnesium-deficient blood

Hypomagnesemia, which is frequently observed in patients treated with calcineurin inhibitors to prevent rejection after allogeneic transplantation, has been associated with a faster rate of decline in allograft function. The effect of hypomagnesemia on lung allograft has not been reported yet. In our model of isolated mouse lung, we have evaluated the early effects of allogeneic lung perfusion with blood from magnesium (Mg)-deficient mice for 3 h on lung activation and remodelling, compared to isogeneic perfusion. Hypomagnesemia (0.21+/-0.07 mmol Mg(2+)/l) was observed in blood from Mg-deficient mice, but no inflammatory pattern. The mRNA level of the intercellular adhesion molecule (ICAM)-1, but neither of the vascular cell adhesion molecule (VCAM)-1, nor of the cytokines tumor necrosis factor (TNF)alpha and interleukin (IL)-2, was enhanced (p<0.05). Although caspase-3 mRNA was transiently enhanced, no apoptotic cells were evidenced in lung tissues even after 3 h. Using cDNA array, we found that the genes encoding RANKL, RANK, TNFR2, NFATX, IL-1R2, IL-6R gp130, SOCS3, PDGFRB, P63, CSF3R, CXCL1, CXCL5, CX3CL1, CSF1, which are involved in inflammation and apoptosis regulation, were markedly up-regulated in allogeneic conditions. Our results support a limited allogeneic activation and an early stage of the inflammatory process in lung, at the time of inflammatory cell recruitment without lung tissue remodelling, as a result of hypomagnesemia. These findings suggest that cyclosporine-related hypomagnesemia, observed in most of the transplanted patients, does not constitute an additional risk for lung allograft outcome.

Ultraviolet influence on catalase activity and mineral content in eyeballs of gibel carp (Carassius auratus gibelio)

UV radiation present in the environment may induce several eye disorders including inflammation and cataract. The aim of this work was to study catalase activity and Mg, Cu, Ca and Zn contents in the eyeballs of gibel carp exposed to ecologically relevant doses of UV radiation (0.09 kJ/m2 for UV-A and 0.98 kJ/m2 for UV-B) simulated in laboratory conditions. Ultraviolet exposure resulted in significant reduction of catalase activity in the eyeballs of tested fish. Reductions in Mg, Cu and Ca contents after UV exposure were also observed. The differences in Mg and Cu levels between control and UV exposed animals were statistically significant, whereas the reduction of Ca level was insignificant. Zinc level in the eyeballs of UV-exposed fish was significantly higher than in non-irradiated specimens. The results suggest that ultraviolet radiation affects prooxidant/antioxidant balance and Mg, Cu, Zn contents in the eyes of fish living in shallow habitats. These may lead to cataract formation.

Magnesium and the inflammatory response: potential physiopathological implications

The purpose of this review is to summarize experimental findings showing that magnesium modulates cellular events involved in inflammation. Experimental magnesium deficiency in the rat induces after a few days a clinical inflammatory syndrome characterized by leukocyte and macrophage activation, release of inflammatory cytokines and acute phase proteins, excessive production of free radicals. Increase in extracellular magnesium concentration, decreases inflammatory response while reduction in the extracellular magnesium results in cell activation. Because magnesium acts as a natural calcium antagonist, the molecular basis for inflammatory response is probably the result of modulation of intracellular calcium concentration. The priming of phagocytic cells, the opening calcium channel and activation of N-methyl-d-aspartate (NMDA) receptors, the activation of nuclear factor-kappa B (NFkappaB) have been considered as potential mechanisms. Moreover, magnesium deficiency induces a systemic stress response by activation of neuro endocrinological pathways. As nervous and immune systems interact bidirectionally, the roles of neuromediators have also been considered. Magnesium deficiency contributes to an exaggerated response to immune stress and oxidative stress is the consequence of the inflammatory response. Inflammation contributes to the pro-atherogenic changes in lipoprotein metabolism, endothelial dysfunction, thrombosis, hypertension and explains the aggravating effect of magnesium deficiency on the development of metabolic syndrome. Further studies are still needed to assess more accurately the role of magnesium in immune response in humans, but these experimental findings in animal models suggest that inflammation is the missing link to explain the role of magnesium in many pathological conditions.

Assessment of adenyl residue reactivity within model nucleic acids by surface enhanced Raman spectroscopy

We rank the reactivity of the adenyl residues (A) of model DNA and RNA molecules with electropositive subnano size [Ag]n+ sites as a function of nucleic acid primary sequences and secondary structures and in the presence of biological amounts of Cl- and Na+ or Mg2+ ions. In these conditions A is markedly more reactive than any other nucleic acid bases. A reactivity is higher in ribo (r) than in deoxyribo (d) species [pA>pdA and (pA)n>>(pdA)n]. Base pairing decreases A reactivity in corresponding duplexes but much less in r than in d. In linear single and paired dCAG or dGAC loci, base stacking inhibits A reactivity even if A is bulged or mispaired (A.A). dA tracts are highly reactive only when dilution prevents self-association and duplex structures. In d hairpins the solvent-exposed A residues are reactive in CAG and GAC triloops and even more in ATC loops. Among the eight rG1N2R3A4 loops, those bearing a single A (A4) are the least reactive. The solvent-exposed A2 is reactive, but synergistic structural transitions make the initially stacked A residues of any rGNAA loop much more reactive. Mg2+ cross-bridging single strands via phosphates may screen A reactivity. In contrast d duplexes cross-bridging enables "A flipping" much more in rA.U pairs than in dA.T. Mg2+ promotes A reactivity in unpaired strands. For hairpins Mg2+ binding stabilizes the stems, but according to A position in the loops, A reactivity may be abolished, reduced, or enhanced. It is emphasized that not only accessibility but also local flexibility, concerted docking, and cation and anion binding control A reactivity.

Transient Receptor Potential Melastatin 7 Ion Channels Regulate Magnesium Homeostasis in Vascular Smooth Muscle Cells

Magnesium modulates vascular smooth muscle cell (VSMC) function. However, molecular mechanisms regulating VSMC Mg 2+ remain unknown. Using biochemical, pharmacological, and genetic tools, the role of transient receptor potential membrane melastatin 7 (TRPM7) cation channel in VSMC Mg 2+ homeostasis was evaluated. Rat, mouse, and human VSMCs were studied. Reverse transcriptase polymerase chain reaction and immunoblotting demonstrated TRPM7 presence in VSMCs (membrane and cytosol). Angiotensin II (Ang II) and aldosterone increased TRPM7 expression. Gene silencing using small interfering RNA (siRNA) against TRPM7, downregulated TRPM7 (mRNA and protein). Basal [Mg 2+ ] i , measured by mag fura-2AM, was reduced in siRNA-transfected cells (0.39±0.01 mmol/L) versus controls (0.54±0.01 mmol/L; P <0.01). Extracellular Mg 2+ dose-dependently increased [Mg 2+ ] i in control cells (E max 0.70±0.02 mmol/L) and nonsilencing siRNA-transfected cells (E max 0.71±0.04 mmol/L), but not in siRNA-transfected cells (E max 0.5±0.01 mmol/L). The functional significance of TRPM7 was evaluated by assessing [Mg 2+ ] i and growth responses to Ang II in TRPM7 knockdown cells. Acute Ang II stimulation decreased [Mg 2+ ] i in control and TRPM7-deficient cells in a Na + -dependent manner. Chronic stimulation increased [Mg 2+ ] i in control, but not in siRNA-transfected VSMCs. Ang II–induced DNA and protein synthesis, measured by 3 [H]-thymidine and 3 [H]-leucine incorporation, respectively, were increased in control and nonsilencing cells, but not in TRPM7 knockdown VSMCs. Our data indicate that VSMCs possess membrane-associated, Ang II–, and aldosterone-regulated TRPM7 channels, which play a role in regulating basal [Mg 2+ ] i , transmembrane Mg 2+ transport and DNA and protein synthesis. These novel findings identify TRPM7 as a functionally important regulator of Mg 2+ homeostasis and growth in VSMCs.

Dietary magnesium depletion does not promote oxidative stress but targets apical cells within the mouse caput epididymidis

It is well documented that a dietary deficiency in magnesium can induce oxidative stress and an inflammatory response in animal models. In our study, we have investigated these responses in the mouse epididymis after mice had been fed a magnesium-deficient diet for a 2-week duration. The extracellular and intracellular concentrations of magnesium where shown to be depleted on this diet. This was followed, however, only in the liver of the Mg-deficient animals, by an increase in both alpha 2-macroglobulin (alpha-2m), an acute phase marker, and interleukin-6 transcripts suggesting that an inflammatory response had been initiated. These changes were correlated with a decrease in circulating neutrophils. To address the question of whether or not peroxidation was induced in mouse epididymis following hypomagnesia, we have monitored the level of endogenous peroxidation, their ability to respond to induced peroxidation as well as the expression and activity of the enzymatic glutathione peroxidase (GPX) antioxidant family. To evaluate if the epididymis had evolved specific protections against peroxidation, other organs such as the liver and the kidney were monitored in parallel. We detected no evidence for increased peroxidation in any of the mouse organs tested. However, GPX activity was found to be significantly lower in the liver and the kidney of Mg-deficient animals while it was unchanged in the epididymides of the same animals during the deficiency. Histological analysis of the epididymis showed no major difference in the overall cytological aspect of the organ. Segment 2 of the caput, however presented a significant increase in the number of apically located cells or blebbing cells. Immunohistochemical analysis proved that these cells were epididymal apical cells and not infiltrated leukocytes. These observations suggested that the mouse caput epididymidis segment 2 specifically responded to Mg deficiency via the apical cells. Finally, a comparative analysis of stress response genes was conducted in control and magnesium-deficient caput epididymidis samples. It brought forward some genes that might be involved in the peculiar response of the caput epithelium following hypomagnesia.

Aldosteronism and peripheral blood mononuclear cell activation: a neuroendocrine-immune interface

Aldosteronism eventuates in a proinflammatory/fibrogenic vascular phenotype of the heart and systemic organs. It remains uncertain whether peripheral blood mononuclear cells (PBMCs) are activated before tissue invasion by monocytes/macrophages and lymphocytes, as is the case for responsible pathogenic mechanisms. Uninephrectomized rats treated for 4 weeks with dietary 1% NaCl and aldosterone (ALDOST, 0.75 microg/h) with or without spironolactone (Spi, 100 mg/kg per daily gavage) were compared with unoperated/untreated and uninephrectomized/salt-treated controls. Before intramural coronary vascular lesions appeared at week 4 of ALDOST, we found (1) a reduction of PBMC cytosolic free [Mg2+]i, together with intracellular Mg2+ and Ca2+ loading, whereas plasma and cardiac tissue Mg2+ were no different from controls; (2) increased H2O2 production by monocytes and lymphocytes together with upregulated PBMC gene expression of oxidative stress-inducible tyrosine phosphatase and Mn2+-superoxide dismutase and the presence of 3-nitrotyrosine in CD4+ and ED-1-positive inflammatory cells that had invaded intramural coronary arteries; (3) B-cell activation, including transcription of immunoglobulins, intracellular adhesion molecule-1, and CC and CXC chemokines and their receptors; (4) expansion of B lymphocyte subset and myosin heavy chain class II-expressing lymphocytes; and (5) autoreactivity with gene expression for antibodies to acetylcholine receptors and a downregulation of RT-6.2, which is in keeping with cell activation and associated with autoimmunity. Spi cotreatment attenuated the rise in intracellular Ca2+, the appearance of oxidative/nitrosative stress in PBMCs and invading inflammatory cells, and alterations in PBMC transcriptome. Thus, aldosteronism is associated with an activation of circulating immune cells induced by iterations in PBMC divalent cations and transduced by oxidative/nitrosative stress. ALDO receptor antagonism modulates this neuroendocrine-immune interface. The full text of this article is available online at http://www.circresaha.org.

Magnesium deficiency induces apoptosis in primary cultures of rat hepatocytes

The effects of extracellular magnesium (Mg) concentration on the rate of apoptosis in rat hepatocytes in primary culture were examined. After overnight attachment, incubations were conducted for up to 72 h in serum-free media containing low (0-0.4 mmol/L), physiological (0.8 mmol/L) or high (2 and 5.6 mmol/L) Mg concentrations. At 72 h, we observed numerous rounded hepatocytes on top of a shrunken cell monolayer at extracellular Mg concentrations < 0.8 mmol/L. These morphological features were associated with Mg-dependent differences in the total protein levels. The various Mg concentrations did not affect DNA synthesis; however, at a concentration < 0.8 mmol/L, the susceptibility of cultured rat hepatocytes to oxidative stress was increased as shown by the reduced glutathione concentration (10.6 +/- 2.8 vs. 37.3 +/- 4.1 nmol/mg protein with 0 and 0.8 mmol/L, respectively; P < 0.05) and increased lipid peroxidation (0.36 +/- 0.03 vs. 0.21 +/- 0.01 nmol malondialdehyde/mg protein with 0 and 0.8 mmol/L, respectively; P < 0.05). Fluorescence microscopy after Hoechst dye staining revealed numerous apoptotic figures in Mg-free monolayers compared with 0.8 and 5.6 mmol/L Mg conditions. These observations were confirmed quantitatively by flow-cytometric analysis after propidium iodide staining. The proportion of subdiploid cells decreased with increasing Mg concentration; for example, it was greater at 72 h in Mg-free cultures (76%) than in cultures containing 0.8 mmol/L or 5.6 mmol/L Mg (28%; P < 0.05). Caspase-3 was highly activated in Mg-free cultures after 48 h of treatment compared with 0.8 and 5.6 mmol/L conditions (P < 0.05). Overall, these results show that extracellular Mg deficiency has a negative effect on the survival of cultured rat hepatocytes by inducing apoptosis; however, supplementation of extracellular Mg did not reduce the spontaneous apoptosis that occurred over time in rat hepatocyte cultures.

Aldosteronism: an immunostimulatory state precedes proinflammatory/fibrogenic cardiac phenotype

Chronic inappropriate (relative to dietary Na+ intake) elevations in circulating aldosterone (ALDO), termed aldosteronism, are associated with remodeling of intramural arteries of the right and left heart. Lesions appear at week 4 of treatment with ALDO and 1% dietary NaCl in uninephrectomized rats (ALDOST) and include invading monocytes, macrophages and lymphocytes with intracellular evidence of oxidative and nitrosative stress, myofibroblasts, and perivascular fibrosis. In this study, we tested the hypothesis that an immunostimulatory state with activated circulating peripheral blood mononuclear cells (PBMCs) precedes this proinflammatory and profibrogenic cardiac phenotype and is initiated by reduction in the cytosolic free Mg2+ concentration ([Mg2+]i). At 1 and 4 wk of ALDOST (preclinical and clinical stages, respectively), we monitored serum Mg2+, PBMC [Mg2+]i and cytosolic free [Ca2+] (via fluorimetry), and expressed genes (via microchip array) as well as markers of oxidative and nitrosative stress in plasma [alpha1-antiproteinase activity (alpha1-AP)] and cardiac tissue (immunohistochemical detection of gp91phox subunit of NADPH oxidase and 3-nitrotyrosine). Age- and gender-matched unoperated and untreated (UO) rats and uninephrectomized salt-treated (UN) rats served as controls. Serum [Mg2+] was unchanged by ALDOST. In contrast with UO and UN, [Mg2+]i and plasma alpha1-AP were each reduced (P < 0.05) at weeks 1 and 4. The decline in PBMC [Mg2+]i was accompanied by Ca2+ loading. Differential (twofold and higher) expression (up- and downregulation) in PBMC transcriptomes was present at week 1 and progressed at week 4. Involved were genes for the alpha1-isoform of Na+-K+-ATPase, the ATP-dependent Ca2+ pump, antioxidant reserves, inducible nitric oxide synthase, and PBMC activation with autoimmune responses. Expression of 3-nitrotyrosine and activation of gp91phox were seen in inflammatory cells that invaded intramural arteries. Thus early in aldosteronism (preclinical stage), an immunostimulatory state featuring activated circulating PBMCs with reduced ionized [Mg2+]i and oxidative and nitrosative stress precedes and may even predispose to coronary vascular lesions that first appear at week 4.

Morphological and immune response alterations in the intestinal mucosa of the mouse after short periods on a low-magnesium diet

The importance of Mg for the immune function is well recognized; however, there is no information available about the effect of Mg intake on the modulation of local immune response in the intestine. Thus, in the present study the hypothesis that short periods of Mg deprivation can affect intestinal mucosa and local immune response was tested. For this purpose, OF1 female mice were fed a semipurified diet (1000 mg Mg/kg diet). For 3 d before immunization and 1 d after, half of the animals were fed a Mg-deficient diet (30 mg Mg/kg diet), three immunizations per os were performed every 3 weeks with Escherichia coli producing the CS31A capsule-like protein (1010 or bacteria per animal). Mice were killed 10 d after the last immunization. The level of specific anti CS31A immunoglobulin (Ig) G and IgA in the serum and secretory IgA in the intestinal secretions and faeces were measured by ELISA. The results indicated that administration of a high dose of immunogen with a low-Mg diet led to lower specific IgA levels in the intestinal mucus and serum. Administration of a low dose of immunogen with a low-Mg diet led to lower IgA and IgG levels in the serum and secretory IgA coproantibodies. To assess alterations of intestinal mucosa caused by a low-Mg diet for a short period, histological and scanning electron microscopy analyses were performed on samples from mice (not submitted to the vaccination protocol) after 3 d on the Mg-deficient diet. These analyses showed several alterations, suggesting perturbations in the growth of the intestinal mucosa. These changes were accompanied by modifications in the expression of several genes involved in cell growth and stress response. From this present work, it may be concluded that short periods of Mg deprivation can affect the intestinal mucosa and local immune response of the intestine.

Nutrigenomics: exploiting systems biology in the nutrition and health arena

Nutritional sciences are discovering the application of the so-called "omics" sciences. Propelled by the recent unravelling of the human genome and the coinciding technological developments, genotyping, transcriptomics, proteomics and metabolomics are now available to nutritional research. In the future we are likely to see new screening tools for the selection of bioactive nutrients, new biomarkers for the in vivo efficacy of nutrients, and better insight into the influence of genetic polymorphisms on nutrient metabolism. However, are these promises just based on biotechnological hype or is a real fundamental change in human nutritional sciences at hand?