Pathogenesis of cyclosporine-induced hypomagnesemia

Amelioration of Cyclosporine A-Induced Acute Nephrotoxicity by Cordyceps cicadae Mycelia via Mg+2 Reabsorption and the Inhibition of GRP78-IRE1-CHOP Pathway: In Vivo and In Vitro

Fruiting bodies of Cordyceps cicadae (CC) have been reported to have a therapeutic effect in chronic kidney disease. Due to the rare and expensive resources from natural habitats, artificially cultivated mycelia using submerged liquid cultivation of CC (CCM) have been recently developed as an alternative to scarce sources of CC. However, little is known regarding potential protective effects of CCM against cyclosporine A (CsA)-induced acute nephrotoxicity in vivo and in vitro. In this study, male Sprague-Dawley rats were divided into six groups: control, CCM (40 mg and 400 mg/kg, orally), CsA (10 mg/kg, oral gavage), and CsA + CCM (40 mg and 400 mg/kg, orally). At the end of the study on day 8, all rats were sacrificed, and the blood and kidneys retrieved. CsA-induced acute nephrotoxicity was evident by increased levels of blood urea nitrogen (BUN). Levels of the endoplasmic reticulum (ER) resident chaperone glucose regulated protein 78 (GRP 78) were increased significantly in rats with acute nephrotoxicity. BUN and GRP 78 were significantly ameliorated in synchronous oral groups of CCM (40 or 400 mg/kg) plus CsA. Examination of hematoxylin and eosin stained kidney tissues revealed that the combined treatment of CCM slightly improved vacuolization in renal tubules upon CsA-induced damage. CsA-induced down-regulation of protein expression of magnesium ion channel proteins and transient receptor potential melastatin 6 and 7 were abolished by the combined treatment of CCM. CCM has the potential to protect the kidney against CsA-induced nephrotoxicity by reducing magnesium ion wasting, tubular cell damage, and ER stress demonstrated further by human renal proximal tubular epithelial cell line HK-2. Our results contribute to the in-depth understanding of the role of polysaccharides and nucleobases as the main secondary metabolites of CCM in the defense system of renal functions in CsA-induced acute nephrotoxicity.

Longitudinal Study of the Role of Epidermal Growth Factor on the Fractional Excretion of Magnesium in Children: Effect of Calcineurin Inhibitors

BACKGROUND

It was shown in animal models and adults that the epidermal growth factor (EGF) is involved in the pathophysiology of calcineurin inhibitor (CNI) induced renal magnesium loss. In children, however, the exact mechanism remains unclear, which was set as the purpose of the present study.

METHODS

Children with nephrotic syndrome and renal transplant children treated with CNI (n = 50) and non-CNI treated children (n = 46) were included in this study. Urine and serum samples were collected at three time points to determine magnesium, creatinine, and EGF. The magnesium intake was calculated from a food frequency questionnaire.

RESULTS

Serum Mg²⁺ and urinary EGF/creatinine were significantly lower in the CNI treated children, with significantly more CNI-treated children developing hypomagnesaemia. In the latter patients, the fractional excretion of magnesium (FE Mg²⁺) was significantly higher. Urinary EGF, age, renal function, and serum magnesium were independent predictors of the FE Mg²⁺. Only 29% of the children reached the recommended daily intake of magnesium. The magnesium intake did not differ between hypomagnesemic and normomagnesemic patients and was not a predictor of the FE Mg²⁺.

CONCLUSIONS

In CNI-treated children who developed hypomagnesemia, the FE Mg²⁺ was increased. The urinary EGF concentration, age, and renal function are independent predictors of the FE Mg²⁺.

Subclinical magnesium deficiency: a principal driver of cardiovascular disease and a public health crisis

Because serum magnesium does not reflect intracellular magnesium, the latter making up more than 99% of total body magnesium, most cases of magnesium deficiency are undiagnosed. Furthermore, because of chronic diseases, medications, decreases in food crop magnesium contents, and the availability of refined and processed foods, the vast majority of people in modern societies are at risk for magnesium deficiency. Certain individuals will need to supplement with magnesium in order to prevent suboptimal magnesium deficiency, especially if trying to obtain an optimal magnesium status to prevent chronic disease. Subclinical magnesium deficiency increases the risk of numerous types of cardiovascular disease, costs nations around the world an incalculable amount of healthcare costs and suffering, and should be considered a public health crisis. That an easy, cost-effective strategy exists to prevent and treat subclinical magnesium deficiency should provide an urgent call to action.

Immunosuppressants inhibit hormone-stimulated Mg2+ uptake in mouse distal convoluted tubule cells

Immunosuppressants such as cyclosporinA and FK506 (tacrolimus) are widely prescribed to treat numerous disorders and to treat organ transplant recipients. However, cyclosporine A and FK506 are both known to produce hypomagnesaemia. The mechanism of this effect is still unclear. The present study determined the effects of immunosuppressant treatment on the parathyroid hormone (PTH) mediated Mg(2+) uptake and the mitogen-activated protein kinase (MAPK) activation in mouse distal convoluted tubule (MDCT) cells. The intracellular Ca(2+) and Mg(2+) concentrations in a single MDCT cell were measured by using the fluorescentdye Fura-2 AM and Mag-fura-2 AM, respectively. Cyclosporine A and FK506 illicited a transient increase of intracellular Ca(2+) from a basal level of 99 +/- 16 nM to 685 +/- 105 and 608 +/- 96 nM, respectively. In order to determine the Mg(2+) transport, the MDCT cells were Mg(2+)-depleted by culturing them in Mg(2+)-free media for 16 h, and the Mg(2+) uptake was measured by microfluorescence after placing the depleted cells in 1.5mM MgCl(2). The mean rate of Mg(2+) uptake, d([Mg(2+)](i))/dt, was 140 +/- 16 nM/s in the control MDCT cells. PTH increased the Mg(2+) uptake more than 2 times in this cell. Cyclosporine A (10 microM) and FK506 (0.1 microM) did not affect the basal Mg(2+)uptake (140 +/- 16 and 142 +/- 14 nM/s, respectively), but they inhibited the PTH-stimulated Mg(2+) entry, decreasing it from 248+/-12 to 147 +/- 7 and 148 +/- 14 nM/s, respectively. These effects were inhibited by L685818, which is a potent competitive antagonist of FK506. PTH stimulated the extracellular signal-regulated kinase1/2 (ERK1/2) protein synthesis. This PTH-stimulated ERK1/2 activation was inhibited by cyclosporine A and FK506. In the present study, the role of ERK1/2 activation on the PTH-dependent magnesium uptake was examined in MDCT cells, and we showed that immunosuppressants inhibit the hormone-stimulated Mg(2+) uptake into the MDCT cells by inhibiting the MAPK pathway.

Drug-induced hypomagnesaemia : scope and management

Nearly 50 medications have been implicated as inducing hypomagnesaemia, sometimes based on insufficient data regarding clinical significance and frequency of occurrence. In fact, clinical effects attributed to hypomagnaesemia have been reported in only 17 of these drugs. A considerable amount of literature relating to individual drugs has been published, yet a comprehensive overview of this issue is not available and the hypomagnesaemic effect of a drug could be either overemphasised or under-rated. In addition, there are neither guidelines regarding treatment, prevention and monitoring of drug-induced hypomagnesaemia nor agreement as to what serum level of magnesium may actually be defined as 'hypomagnesaemia'. By compiling data from published papers, electronic databases, textbooks and product information leaflets, we attempted to assess the clinical significance of hypomagnesaemia induced by each drug. A practical approach for managing drug-induced hypomagnesaemia, incorporating both published literature and personal experience of the physician, is proposed. When drugs classified as inducing 'significant' hypomagnesaemia (cisplatin, amphotericin B, ciclosporin) are administered, routine magnesium monitoring is warranted, preventive treatment should be considered and treatment of hypomagnesaemia should be initiated with or without overt clinical manifestations. In drugs belonging to the 'potentially significant' category, among which are amikacin, gentamicin, laxatives, pentamidine, tobramycin, tacrolimus and carboplatin, magnesium monitoring is justified when either of the following occurs: clinical manifestations are apparent; persistent hypokalaemia, hypocalcaemia or alkalosis are present; other precipitating factors for hypomagnesaemia coexist; or treatment is with more than one potentially hypomagnesaemic drug. No preventive treatment is required and treatment should be initiated only if hypomagnesaemia is accompanied by symptoms or clinically significant relevant laboratory findings. In those drugs whose hypomagnesaemic effect is labelled as 'questionable', including furosemide and hydrochlorothiazide, routine monitoring and treatment are not required.

Sirolimus does not exhibit nephrotoxicity compared to cyclosporine in renal transplant recipients

Sirolimus and cyclosporine (CsA) prevent acute rejection in man when used as primary therapies in triple drug regimens. Sirolimus does not act via the calcineurin pathway and therefore is not expected to produce the same renal side-effects. This paper presents the pooled 2-year data analysis of renal function parameters from two open-label, randomized, multicenter studies. Patients (18-68 years) receiving a primary renal allograft were randomized to receive concentration-controlled sirolimus (n = 81) or CsA (n = 80), in combination with azathioprine and steroids (n = 83), or mycophenolate mofetil (MMF) and steroids (n = 78). From week 10 through year 2, calculated glomerular filtration rate (GFR) was significantly higher in sirolimus--than in CsA-treated patients (69.3 vs. 56.8 mL/min, at 2 years, p = 0.004). Serum uric acid was significantly higher in the CsA-treated patients and magnesium was significantly lower; these parameters were more likely to be within normal limits in the sirolimus group. Mean serum potassium and phosphorus were lower in sirolimus-treated patients. In conclusion, sirolimus, when administered as primary therapy in combination with azathioprine or MMF, has a favorable safety profile compared to CsA with regards to renal function.

Anaesthesia for patients with a transplanted organ

Increasing numbers of individuals leading normal lives have transplanted organs. They may appear in any hospital for treatment of trauma or general diseases. Common anaesthesia methods can be used for these patients, but safe conduct of anaesthesia requires knowledge of the immunosuppression, risk factors, and altered physiology or drug actions. This article reviews the anaesthesia-related literature on patients with transplanted organs.

Magnesium in disease: a review with special emphasis on the serum ionized magnesium

This review deals with the six main clinical situations related to magnesium or one of its fractions, including ionized magnesium: renal disease, hypertension, pre-eclampsia, diabetes mellitus, cardiac disease, and the administration of therapeutic drugs. Issues addressed are the physiological role of magnesium, eventual changes in its levels, and how these best can be monitored. In renal disease mostly moderate hypermagnesemia is seen; measuring ionized magnesium offers minimal advantage. In hypertension magnesium might be lowered but its measurement does not seem relevant. In the prediction of severe pre-eclampsia, elevated ionized magnesium concentration may play a role, but no unequivocal picture emerges. Low magnesium in blood may be cause for, or consequence of, diabetes mellitus. No special fraction clearly indicates magnesium deficiency leading to insulin resistance. Cardiac diseases are related to diminished magnesium levels. During myocardial infarction, serum magnesium drops. Total magnesium concentration in cardiac cells can be predicted from levels in sublingual or skeletal muscle cells. Most therapeutic drugs (diuretics, chemotherapeutics, immunosuppressive agents, antibiotics) cause hypomagnesemia due to increased urinary loss. It is concluded that most of the clinical situations studied show hypomagnesemia due to renal loss, with exception of renal disease. Keeping in mind that only 1% of the total body magnesium pool is extracellular, no simple measurement of the real intracellular situation has emerged; measuring ionized magnesium in serum has little added value at present.

[Magnesium excretion in urine is not a marker of magnesium deficiency. Reliability of an oral magnesium administration test]

BACKGROUND

Serum magnesium analysis does not reflect body content of magnesium. So substitution is based on empirical maneuvers.

PATIENTS AND METHOD

In a study on 44 patients urinary magnesium excretion was analyzed before and after oral magnesium substitution (40 mval). The provable hypothesis was the estimation that patients in magnesium deficiency under chronical diuretic treatment (n = 11) would have a lower magnesium excretion than patients of the control group (n = 10). Further analysis was done with patients after orthotopic cardiac transplantation (n = 12) and those suffering from coronary heart disease (n = 11).

RESULT

After oral administration of magnesium in all 4 groups there was a rise in blood levels, only significant in the patient group under chronic diuretic treatment. Urinary magnesium excretion, however, showed no significant differences. Patients after cardiac transplantation had the lowest rise in urinary magnesium excretion.

CONCLUSION

There was no clear differentiation by means of this oral magnesium substitution test. Magnesium excretion even after oral substitution is of no value to analyze magnesium deficiency.

Bone metabolism in orthotopic liver transplantation: a prospective study

Bone mineral density (BMD) and mineral metabolism were assessed in 54 patients with end-stage liver disease who were evaluated for orthotopic liver transplantation (OLT) and assessed 3, 6, and 12 months after surgery in 26 patients who underwent OLT. Serum and urinary electrolyte and mineral levels, serum liver function test results, and parathyroid hormone (PTH), osteocalcin (BGP), 25-hydroxyvitamin D, and urinary hydroxyproline levels were assessed. BMD of the lumbar spine was measured at baseline and 3, 6, and 12 months after OLT. At baseline, 40.7% of patients had BMD below the fracture threshold (0.800 g/cm2). Using multiple stepwise regression analysis, we found that BMD was significantly (P < .0001) affected by age, serum creatinine level, and PTH level but not by indices of cholestasis or liver function. In the patients who underwent OLT, a 1.4% reduction (P < .006) was observed in BMD 3 months after OLT. Thereafter, BMD returned to pretransplant values. A significant increase in serum BGP was observed after 6 (P < .02) and 12 (P < . 005) months. PTH levels increased progressively 3 (P < .02), 6 (P < . 001), and 12 (P < .0001) months after OLT. This increase did not seem to be caused by cyclosporine-induced nephropathy. It was concluded that osteopenia is a major complication in hepatic cirrhosis, regardless of its causes. The increase in serum BGP levels 6 and 12 months after OLT indicates metabolic activation of osteoblasts. The increase in PTH levels after OLT warrants further investigation.

Effects of dietary sodium and magnesium on cyclosporin A-induced hypertension and nephrotoxicity in spontaneously hypertensive rats

Arterial hypertension, nephrotoxicity, and magnesium loss are common side effects of the immunosuppressive agent cyclosporin A (CsA). In the present study, the effects of dietary sodium and magnesium on CsA toxicity were examined in spontaneously hypertensive rats. A 6-week treatment with CsA during a moderately low-sodium diet (Na 0.3%, Mg 0.2% of the dry weight of the chow) raised blood pressure only slightly, without evidence of nephrotoxicity. By contrast, CsA during a high-sodium diet (Na 2.6%) produced a pronounced rise in blood pressure as well as marked nephrotoxicity, comprising decreased creatinine clearance, increased levels of serum creatinine and urea, and increased urinary protein excretion. During the high-sodium diet, CsA decreased myocardial and bone magnesium concentration and increased myocardial and renal calcium concentration. Magnesium supplementation (Mg 0.6%) protected against the CsA-induced hypertension and nephrotoxicity during the high-sodium diet. Magnesium supplementation also completely prevented the CsA-induced myocardial magnesium depletion and calcium accumulation in the heart and kidney during the high-sodium diet. Our findings indicate a detrimental interaction between increased sodium intake and CsA treatment and a marked protection by concomitant oral magnesium supplementation.

Comparison of acute rapamycin nephrotoxicity with cyclosporine and FK506

Acute cyclosporine (CsA) nephrotoxicity is characterized by a reduction of glomerular filtration rate (GFR), hypomagnesemia and tubular injury. The mechanisms of CsA's immunosuppressive action and presumably its nephrotoxicity are mediated through inhibition of the renal phosphatase, calcineurin. FK506 (FK), which has a different chemical structure and binding immunophilin, also inhibits calcineurin. We compared the renal effects of these drugs to those of rapamycin (RAPA), which although similar in structure and intracellular binding to FK, does not work by changing calcineurin activity. Rats were given CsA (15 mg/kg/s.c.), FK (6 mg/kg/p.o.), RAPA (3 mg/kg/p.o.) or vehicle (V) for two weeks on a low salt diet. CsA and FK strikingly decreased urinary excretion of nitric oxide, renal blood flow and GFR, whereas RAPA did not. In contrast, all these three drugs caused significant hypomagnesemia associated with inappropriately high fractional excretion of magnesium, suggesting renal magnesium wasting. In addition, with all three drugs there were lesions in the rat kidneys consisting of tubular collapse, vacuolization and nephrocalcinosis. We thus showed that only the calcineurin inhibitors produced glomerular dysfunction in an acute experimental model of nephrotoxicity. The mechanism of hypomagnesemia and tubular injury induced by all three immunosuppressive drugs is unclear but may be independent of calcineurin. The mechanism of renal vasoconstriction on the other hand may be related to inhibition of calcineurin.

Effects of cyclosporine A on the functions of submandibular and parotid glands of rats

1. The present study was designed to investigate the possible effects of long-term (45 days) administration of therapeutic doses of cyclosporine A (25 mg/kg/day), on the functions of submandibular and parotid glands of rats. Pure submandibular and parotid saliva were collected intraorally by microcannulation of the ducts. 2. The weight gains of the treated animals during the study and the weights of the salivary glands at the end of 45 days were reduced significantly as compared with those of controls. 3. Sialochemistry studies revealed a marked decrease in total protein concentration in saliva obtained from submandibular glands (P < 0.05). 4. Determination of electrolyte concentrations in saliva of submandibular gland and serum showed considerable differences between treated and control groups. 5. Significant elevation of amylase activity in serum and parotid saliva was observed in the treated rats in comparison with controls (P < 0.001). 6. Data presented here indicates that long-term administration of therapeutic doses of cyclosporine A causes significant alterations in salivary output and composition.