Intestinal and cardiac inflammatory response shows enhanced endotoxin receptor (CD14) expression in magnesium deficiency

Magnesium and the Brain: A Focus on Neuroinflammation and Neurodegeneration

Magnesium (Mg) is involved in the regulation of metabolism and in the maintenance of the homeostasis of all the tissues, including the brain, where it harmonizes nerve signal transmission and preserves the integrity of the blood-brain barrier. Mg deficiency contributes to systemic low-grade inflammation, the common denominator of most diseases. In particular, neuroinflammation is the hallmark of neurodegenerative disorders. Starting from a rapid overview on the role of magnesium in the brain, this narrative review provides evidences linking the derangement of magnesium balance with multiple sclerosis, Alzheimer's, and Parkinson's diseases.

Experimental Hypomagnesemia Induces Neurogenic Inflammation and Cardiac Dysfunction

Hypomagnesemia occurs clinically as a result of restricted dietary intake, Mg-wasting drug therapies, chronic disease status and may be a risk factor in patients with cardiovascular disorders. Dietary restriction of magnesium (Mg deficiency) in animal models produced a pro-inflammatory/pro-oxidant condition, involving hematopoietic, neuronal, cardiovascular, renal and other systems. In Mg-deficient rodents, early elevations in circulating levels of the neuropeptide, substance P (SP) may trigger subsequent deleterious inflammatory/oxidative/nitrosative stress events. Evidence also suggests that activity of neutral endopeptidase (NEP, neprilysin), the major SP-degrading enzyme, may be impaired during later stages of Mg deficiency, and this may sustain the neurogenic inflammatory response. In this article, experimental findings using substance P receptor blockade, NEP inhibition, and N-methyl-D-aspartate (NMDA) receptor blockade demonstrated the connection between hypomagnesemia, neurogenic inflammation, oxidative stress and enhanced cardiac dysfunction. Proof of concept concerning neurogenic inflammation is provided using an isolated perfused rat heart model exposed to acute reductions in perfusate magnesium concentrations.

Bacterial Endotoxins and Their Role in Periparturient Diseases of Dairy Cows: Mucosal Vaccine Perspectives

During the periparturient period there is a significant increase in the incidence of multiple metabolic and infectious diseases in dairy cows. Dairy cows are fed high-grain diets immediately after calving to support production of large amounts of milk. Mounting evidence indicates these types of diets are associated with the release of high amounts of endotoxins in the rumen fluid. If infected, the udder and uterus additionally become important sources of endotoxins during the postpartum period. There is increasing evidence that endotoxins translocate from rumen, uterus, or udder into the systemic circulation and trigger chronic low-grade inflammatory conditions associated with multiple diseases including fatty liver, mastitis, retained placenta, metritis, laminitis, displaced abomasum, milk fever, and downer cow syndrome. Interestingly, endotoxin-related diseases are triggered by a bacterial component and not by a specific bacterium. This makes prevention of these type of diseases different from classical infectious diseases. Prevention of translocation of endotoxins into the host systemic circulation needs to take priority and this could be achieved with a new approach: mucosal vaccination. In this review article, we discuss all the aforementioned issues in detail and also report some of our trials with regards to mucosal vaccination of periparturient dairy cows.

Magnesium sulfate inhibits binding of lipopolysaccharide to THP-1 cells by reducing expression of cluster of differentiation 14

We investigated effects of magnesium sulfate (MgSO₄) on modulating lipopolysaccharide (LPS)-macrophage binding and cluster of differentiation 14 (CD14) expression. Flow cytometry data revealed that the mean levels of LPS-macrophage binding and membrane-bound CD14 expression (mCD14) in differentiated THP-1 cells (a human monocytic cell line) treated with LPS plus MgSO₄ (the LPS + M group) decreased by 28.2% and 25.3% compared with those THP-1 cells treated with LPS only (the LPS group) (P < 0.001 and P = 0.037), indicating that MgSO₄ significantly inhibits LPS-macrophage binding and mCD14 expression. Notably, these effects of MgSO₄ were counteracted by L-type calcium channel activation. Moreover, the mean level of soluble CD14 (sCD14; proteolytic cleavage product of CD14) in the LPS + M group was 25.6% higher than in the LPS group (P < 0.001), indicating that MgSO₄ significantly enhances CD14 proteolytic cleavage. Of note, serine protease inhibition mitigated effects of MgSO₄ on both decreasing mCD14 and increasing sCD14. In conclusion, MgSO₄ inhibits LPS-macrophage binding through reducing CD14 expression. The mechanisms may involve antagonizing L-type calcium channels and activating serine proteases.

Effect of magnesium sulfate and thyroxine on inflammatory markers in a rat model of hypothyroidism

Inflammation is a major risk factor for cardiovascular complications. Magnesium sulfate (MgSO4) has anti-inflammatory actions. Therefore we investigated the effects of levothyroxine and MgSO4 on inflammatory markers as C-reactive protein (CRP), interleukin-6, tumor necrosis factor-α (TNF-α), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) in hypothyroid rats. Sixty male rats were divided into 6 groups; normal, normal + MgSO4, hypothyroidism, hypothyroidism + levothyroxine, hypothyroidism + MgSO4, and hypothyroidism + levothyroxine + MgSO4. Thyroxine, triiodothyronine, and thyroid-stimulating hormone (TSH), CRP, interleukin-6, TNF-α, ICAM-1, and VCAM-1 were measured in all rats. Hypothyroidism significantly increased TSH, CRP, interleukin-6, TNF-α, ICAM-1, and VCAM-1 and decreased triiodothronine and thyroxine. Treatment of hypothyroid rats with levothyroxine or MgSO4 significantly decreased CRP, interleukin-6, TNF-α, ICAM-1, and VCAM-1. Combined therapy of hypothyroid rats with levothyroxine and MgSO4 significantly decreased CRP, interleukin-6, TNF-α, ICAM-1, and VCAM-1 compared with hypothyroid rats either untreated or treated with levothyroxine or MgSO4. This study demonstrates that hypothyroid rats have chronic low grade inflammation, which may account for increased risk of cardiovascular diseases. Combined levothyroxine and MgSO4 is better than levothyroxine or MgSO4 alone in alleviating the chronic low grade inflammatory status and therefore reducing the risk of cardiovascular diseases in hypothyroid animals.

Magnesium protects against cisplatin-induced acute kidney injury by regulating platinum accumulation

Despite its success as a potent antineoplastic agent, ∼25% of patients receiving cisplatin experience acute kidney injury (AKI) and must discontinue therapy. Impaired magnesium homeostasis has been linked to cisplatin-mediated AKI, and because magnesium deficiency is widespread, we examined the effect of magnesium deficiency and replacement on cisplatin-induced AKI in physiologically relevant older female mice. Magnesium deficiency significantly increased cisplatin-associated weight loss and markers of renal damage (plasma blood urea nitrogen and creatinine), histological changes, inflammation, and renal cell apoptosis and modulated signaling pathways (e.g., ERK1/2, p53, and STAT3). Conversely, these damaging effects were reversed by magnesium. Magnesium deficiency alone significantly induced basal and cisplatin-mediated oxidative stress, whereas magnesium replacement attenuated these effects. Similar results were observed using cisplatin-treated LLC-PK1 renal epithelial cells exposed to various magnesium concentrations. Magnesium deficiency significantly amplified renal platinum accumulation, whereas magnesium replacement blocked the augmented platinum accumulation after magnesium deficiency. Increased renal platinum accumulation during magnesium deficiency was accompanied by reduced renal efflux transporter expression, which was reversed by magnesium replacement. These findings demonstrate the role of magnesium in regulating cisplatin-induced AKI by enhancing oxidative stress and thus promoting cisplatin-mediated damage. Additional in vitro experiments using ovarian, breast, and lung cancer cell lines showed that magnesium supplementation did not compromise cisplatin's chemotherapeutic efficacy. Finally, because no consistently successful therapy to prevent or treat cisplatin-mediated AKI is available for humans, these results support developing more conservative magnesium replacement guidelines for reducing cisplatin-induced AKI in cancer patients at risk for magnesium deficiency.

Hypomagnesemia and inflammation: clinical and basic aspects

In recent years, increasing awareness of hypomagnesemia has resulted in clinical trials that associate this mineral deficiency with diabetes, metabolic syndrome, and drug therapies for cancer and cardiovascular diseases. However, diagnostic testing for tissue deficiency of magnesium still presents a challenge. Investigations of animal and cellular responses to magnesium deficiency have found evidence of complex proinflammatory pathways that may lead to greater understanding of mediators of the pathobiology in neuronal, cardiovascular, intestinal, renal, and hematological tissues. The roles of free radicals, cytokines, neuropeptides, endotoxin, endogenous antioxidants, and vascular permeability, and interventions to limit the inflammatory response associated with these parameters, are outlined in basic studies of magnesium deficiency. It is hoped that this limited review of inflammation associated with some diseases complicated by magnesium deficiency will prompt greater awareness by clinicians and other health providers and in turn increase efforts to prevent and treat this disorder.

The role of magnesium deficiency in cardiovascular and intestinal inflammation

Hypomagnesemia continues to cause difficult clinical problems, such as significant cardiac arrhythmias where intravenous magnesium therapy can be lifesaving. Nutritional deficiency of magnesium may present with some subtle symptoms such as leg cramps and occasional palpitation. We have investigated dietary-induced magnesium deficiency in rodent models to assess the pathobiology associated with prolonged hypomagnesemia. We found that neuronal sources of the neuropeptide, substance P (SP), contributed to very early prooxidant/proinflammatory changes during Mg deficiency. This neurogenic inflammation is systemic in nature, affecting blood cells, cardiovascular, intestinal, and other tissues, leading to impaired cardiac contractility similar to that seen in patients with heart failure. We have used drugs that block the release of SP from neurons and SP-receptor blockers to prevent some of these pathobiological changes; whereas, blocking SP catabolism enhances inflammation. Our findings emphasize the essential role of this cation in preventing cardiomyopathic changes and intestinal inflammation in a well-studied animal model, and also implicate the need for more appreciation of the potential clinical relevance of optimal magnesium nutrition and therapy.

Changes in intestinal bifidobacteria levels are associated with the inflammatory response in magnesium-deficient mice

Magnesium (Mg) deficiency is a common nutritional disorder that is linked to an inflammatory state characterized by increased plasma acute phase protein and proinflammatory cytokine concentrations. Recent studies have shown that changes in the composition of gut microbiota composition participate in systemic inflammation. In this study, therefore, we assessed the potential role of gut microbiota in intestinal and systemic inflammation associated with Mg deficiency in mice. For this purpose, mice were fed a control or Mg-deficient diet (500 mg vs. 70 mg Mg/kg) for 4 or 21 d. Compared with the mice fed the control diet, mice fed the Mg-deficient diet for 4 d had a lower gut bifidobacteria content (-1.5 log), a 36-50% lower mRNA content of factors controlling gut barrier function in the ileum (zonula occludens-1, occludin, proglucagon), and a higher mRNA content (by approximately 2-fold) in the liver and/or intestine of tumor necrosis factor-alpha, interleukin-6, CCAAT/enhancer binding protein homologous protein, and activating transcription factor 4, reflecting inflammatory and cellular stress. In contrast, mice fed the Mg-deficient diet for 21 d had a higher cecal bifidobacteria content compared with the control group, a phenomenon accompanied by restoration of the intestinal barrier and the absence of inflammation. In conclusion, we show that Mg deficiency, independently of any other changes in nutrient intake, modulates the concentration of bifidobacteria in the gut, a phenomenon that may time-dependently affect inflammation and metabolic disorders in mice.

AZT-induced oxidative cardiovascular toxicity: attenuation by Mg-supplementation

Cardiovascular effects of chronic AZT treatment on SD male rats (185 g) fed either a normal Mg diet (0.1% MgO) or a high Mg diet (0.6% MgO) were examined. AZT treatment (1 mg/ml drinking water) for 3 weeks led to a 5.5-fold (0.88 +/- 0.11 nmol/min/10(6) cells, P < 0.05) elevation in neutrophil basal activity of O2(-) production versus controls (0.16 +/- 0.03 nmol/min, assayed ex vivo as SOD-inhibitable cytochrome c reduction). Concomitantly, plasma 8-isoprostane and PGE(2) levels rose 2.1-fold and 3-fold (both P < 0.05), respectively, compared to control; however, RBC GSH decreased 28% (P < 0.02) with GSSG content increased 3-fold, indicative of systemic oxidative stress. High Mg diet substantially attenuated the AZT-induced neutrophil activation by 70% (0.26 +/- 0.05 nmol/min, P < 0.05); reduced plasma 8-isoprostane and PGE(2) to levels comparable to normal; and RBC GSH was restored back to 92% of control. AZT alone caused moderate, but significant vascular inflammatory lesions in the heart (assessed by H&E staining). Immunohistochemical staining revealed significantly higher (about 4-fold) infiltration of CD11b positive cells (WBC surface marker) in the atria and ventricles of AZT-treated rats. However, these inflammatory pathological markers were minimal in samples of rats treated with AZT plus high Mg diet. Moreover, AZT alone significantly (P < 0.02) decreased rat weight gain by 21% at 3 weeks; Mg-supplementation completely prevented (P < 0.05) the weight gain loss due to AZT intake. It is concluded that high dietary Mg may provide beneficial effects against AZT toxicity due to its systemic antioxidative/anti-inflammatory properties.

Macro- and micronutrient dyshomeostasis in the adverse structural remodelling of myocardium

Hypertension and heart failure are worldwide health problems of ever-increasing proportions. A failure of the heart, during either systolic and/or diastolic phases of the cardiac cycle, has its origins rooted in an adverse structural, biochemical, and molecular remodelling of myocardium that involves its cellular constituents, extracellular matrix, and intramural coronary vasculature. Herein we focus on the pathogenic role of a dyshomeostasis of several macro- (i.e. Ca(2+) and Mg(2+)) and micronutrients (i.e. Zn(2+), Se(2+), and vitamin D) in contributing to adverse remodelling of the myocardium and its failure as a pulsatile muscular pump. An improved understanding of how these macro- and micronutrients account for the causes and consequences of adverse myocardial remodelling carries with it the potential of identifying new biomarkers predictive of risk, onset and progression, and response to intervention(s), which could be monitored non-invasively and serially over time. Moreover, such incremental knowledge will serve as the underpinning to the development of novel strategies aimed at preventing and/or regressing the ongoing adverse remodelling of myocardium. The time is at hand to recognize the importance of macro- and micronutrient dyshomeostasis in the evaluation and management of hypertension and heart failure.

The nerve-heart connection in the pro-oxidant response to Mg-deficiency

Magnesium is a micronutrient essential for the normal functioning of the cardiovascular system, and Mg deficiency (MgD) is frequently associated in the clinical setting with chronic pathologies such as CHF, diabetes, hypertension, and other pathologies. Animal models of MgD have demonstrated a systemic pro-inflammatory/pro-oxidant state, involving multiple tissues/organs including neuronal, hematopoietic, cardiovascular, and gastrointestinal systems; during later stages of MgD, a cardiomyopathy develops which may result from a cascade of inflammatory events. In rodent models of dietary MgD, a significant rise in circulating levels of proinflammatory neuropeptides such as substance P (SP) and calcitonin gene-related peptide among others, was observed within days (1-7) of initiating the Mg-restricted diet, and implicated a neurogenic trigger for the subsequent inflammatory events; this early "neurogenic inflammation" phase may be mediated in part, by the Mg-gated N: -methyl-D-aspartate (NMDA) receptor/channel complex. Deregulation of the NMDA receptor may trigger the abrupt release of neuronal SP from the sensory-motor C-fibers to promote the subsequent pro-inflammatory changes: elevations in circulating inflammatory cells, inflammatory cytokines, histamine, and PGE(2) levels, as well as formation of nitric oxide, reactive oxygen species, lipid peroxidation products, and depletion of key endogenous antioxidants. Concurrent elevations of tissue CD14, a high affinity receptor for lipopolyssacharide, suggest that intestinal permeability may be compromised leading to endotoxemia. If exposure to these early (1-3 weeks MgD) inflammatory/pro-oxidant events becomes prolonged, this might lead to impaired cardiac function, and when co-existing with other pathologies, may enhance the risk of developing chronic heart failure.

Metabolic and immunologic derangements in cardiac cachexia: where to from here?

The onset of cardiac cachexia is characterized by a defined severe weight loss in patients with advanced chronic heart failure and it predicts an increased mortality in these patients. Recent studies with potential therapeutics investigated the effects and efficiency of beta-blockers, ghrelin, or ghrelin-agonists in cachexia. These and other new studies, like the influence of heart transplantation on cardiac cachexia, give prospect into potential therapeutic options in the future. General aim of the treatment strategy is to prevent the onset and retard the progress of cachexia. This could be achieved by modifying the metabolic, neurohormonal and immune system abnormalities, e.g. with beta-blockers and angiotensin-converting enzyme inhibitors. However, these alterations interact in a complex pathophysiological process, which is supposed to end in a vicious circle and thereby the wasting process is further promoted. To interrupt this, an early start of therapy is important to decelerate the development of cardiac cachexia. Many further investigations are needed to find out more about the pathophysiological pathways, to confirm the previous results, and to evaluate new therapeutics.