Hypervitaminosis D: an underestimated complication of supplementation

Toxicological studies propose that exposure to carbon black nanoparticles induces organ injuries and inflammatory responses. Besides, current understanding of the molecular mechanisms implies that carbon black nanoparticles (CBNP) exposure induces the production of reactive oxygen species (ROS) causing inflammation, mitochondrial dysfunction or disturbance in calcium homeostasis. However, the precise mechanisms whereby CBNP exert these effects in the lung are still not fully understood. To gain insight into the possible mechanism of CBNP exerted toxicity, human alveolar epithelial cells (A549) were exposed to different concentrations of CBNP and for different timepoints. The reaction of the cells was monitored by the systematic use of cell-based measurements of calcium and ROS, in the presence and absence of calcium (Ca2+) pump inhibitors/chelators and antioxidants. Followed by an in-depth PCR analysis of 84 oxidative stress-related genes. The measurements revealed, as compared to the control, that exposure to CBNP nanoparticles leads to the generation of high ROS levels, as well as a disturbance in calcium homeostasis, which remained primarily unchanged even after 24 h of exposure. Nevertheless, in presence of antioxidants N-acetylcysteine (NAC) and Trolox, ROS formation was considerably reduced without affecting the intracellular calcium concentration. On the other hand, Ca2+ pump inhibitors/chelators, BAPTA (1,2-bis(o-amino phenoxy)ethane-N, N, N′, N′-tetraacetic acid) and verapamil not only decreased the Ca2+ overload, but also further decreased the ROS formation, indicating its role in CBNP-induced oxidative stress. Further, a PCR array analysis of A549 cells in presence and absence of the calmodulin (CaM) antagonist W7, indicated toward nine altered oxidative stress-related genes which further confirmed our cytotoxicity results. Obtained data suggested that CBNP exposure elevates calcium ion concentration, which further contributes to oxidative stress, via the calcium-binding protein CaM. Its inhibition with W7 leads to downregulation in gene expression of nine oxidative stress-related genes, which otherwise, as compared to control, show increased gene expression. The results of the study thus confirm that exposure of lung epithelial cells to CBNP leads to oxidative stress; however, the oxidative stress itself is a result of a disturbance in both calcium and ROS homeostasis, and should be considered while searching for a new strategy for prevention of CBNP-induced lung toxicity.

Primary hyperparathyroidism (PHPT) and associated morbidity are comprehensively assessed in elderly females; however, less is known of the disease in younger women. Our objectives were to estimate the prevalence of mild disturbances in calcium homeostasis, which could be analogous with early PHPT, in a premenopausal population, and determine the potential presence of associated morbidity. Initial results from this longitudinal study are from 2002-2004. We conducted a population-based screening of serum (s)-calcium in conjunction with routine mammography. Participants included premenopausal women, 40-50 yr of age (n = 1900). Cases fulfilling previously evaluated biochemical criteria for PHPT (n=214) were matched to controls (n = 214). All participants underwent investigation, including screening of parameters of calcium homeostasis, dual x-ray absorptiometry, and body mass index assessment, and filled out extensive health and quality of life (SF-36) questionnaires. Participants were divided into four groups depending on the relation between s-calcium/intact PTH. Statistical comparisons between cases and controls as well as among the four groups were performed to evaluate morbidity. The prevalence of assumed mild PHPT, i.e. inappropriate intact PTH value in relation to total s-calcium, was estimated to be 5.1% (n = 96). Women with mild disturbances in calcium homeostasis had statistically significant lower bone mineral density in the proximal femur and femoral neck, higher body mass index, and lower scores for vitality and general health in the analysis of SF-36. Mild disturbances in calcium homeostasis in premenopausal women were more prevalent than previously thought and were associated with obesity, lower bone mineral density, and decreased quality of life.

Role of calcium in neuronal cell injury: which subcellular compartment is involved?

The relative contribution of oxygen free radicals, disturbances in calcium homeostasis and Na+/H+ exchange in the development of injury in the ischemic/reperfused heart was investigated. The study was designed to assess whether these factors initiate independent mechanisms of injury or, alternatively, they share a common mechanism of toxicity. Isolated working rat hearts were subjected to different periods (30-55 min) of global ischemia and then were reperfused for 30 min. We compared the effects of oxygen radical scavengers (10 mM dimethylthiourea, DMTU and 0.6 mM desferrioxamine), inhibitors of Na+/H+ exchange (0.15 mM amiloride and 15 microM dimethylamiloride, DMA) and of 0.1 microM diltiazem, which was used to limit calcium overload, given alone or in combination, on the rate of myocardial injury development (recovery of hemodynamic function, LDH release, incidence of severe arrhythmias and structural integrity of cardiomyocytes were estimated at reperfusion following different periods of ischemia). All interventions studied, when given alone, provided nearly equivalent cardioprotection. DMTU or desferrioxamine when applied in combination with diltiazem provided additive cardioprotection, relatively limited, however, as compared to the remarkable cardioprotection achieved by DMTU or desferrioxamine in combination with amiloride. All mechanisms studied may contribute in an equal manner to the rate of injury development in the ischemic/reperfused heart. The oxygen free radicals-induced myocardial injury may be partially attributed to some disturbance in intracellular calcium homeostasis, possibly calcium overload, whereas the damaging effect of the Na+/H+ exchange activated upon reperfusion is probably largely related to some other mechanism.

Channelopathy of the Pancreas Causes Chronic Pancreatitis

Calcium and cancer

Kidney disease is a serious health problem that burdens our healthcare system. It is crucial to find the accurate pathogenesis of various types of kidney disease to provide guidance for precise therapies for patients suffering from these diseases. However, the exact molecular mechanisms underlying these diseases have not been fully understood. Disturbance of calcium homeostasis in renal cells plays a fundamental role in the development of various types of kidney disease, such as primary glomerular disease, diabetic nephropathy, acute kidney injury and polycystic kidney disease, through promoting cell proliferation, stimulating extracellular matrix accumulation, aggravating podocyte injury, disrupting cellular energetics as well as dysregulating cell survival and death dynamics. As a result, preventing the disturbance of calcium homeostasis in specific renal cells (such as tubular cells, podocytes and mesangial cells) is becoming one of the most promising therapeutic strategies in the treatment of kidney disease. The endoplasmic reticulum and mitochondria are two vital organelles in this process. Calcium ions cycle between the endoplasmic reticulum and mitochondria at the conjugation of these two organelles known as the mitochondria-associated endoplasmic reticulum membrane, maintaining calcium homeostasis. The pharmacologic modulation of cellular calcium homeostasis can be viewed as a novel therapeutic method for renal diseases. Here, we will introduce calcium homeostasis under physiological conditions and the disturbance of calcium homeostasis in kidney diseases. We will focus on the calcium homeostasis regulation in renal cells (including tubular cells, podocytes and mesangial cells), especially in the mitochondria- associated endoplasmic reticulum membranes of these renal cells.

A disturbance of calcium homeostasis is believed to play an important role in the neurodegeneration of the brains of Alzheimer disease (AD) patients, but the molecular pathways by which it contributes to the disease are not well understood. Here we studied the activation of two major Ca(2+)-regulated brain proteins, calpain and calcineurin, in AD brain. We found that calpain I is activated, which in turn cleaves and activates calcineurin in AD brain. Mass spectrometric analysis indicated that the cleavage of calcineurin by calpain I is at lysine 501, a position C-terminal to the autoinhibitory domain, which produces a 57-kDa truncated form. The 57-kDa calcineurin maintains its Ca(2+)/calmodulin dependence of the phosphatase activity, but the phosphatase activity is remarkably activated upon truncation. The cleavage and activation of calcineurin correlate to the number of neurofibrillary tangles in human brains. These findings suggest that the overactivation of calpain I and calcineurin may mediate the role of calcium homeostatic disturbance in the neurodegeneration of AD.

VITAMIN D INSUFFICIENCY IN FOUR MAJOR HOSPITALS OF PUNJAB

Over-activation of calpain, a ubiquitous calcium-sensitive protease, has been linked to a variety of degenerative conditions in the brain and several other tissues. Dozens of substrates for calpain have been identified and several of these have been used to measure activation of the protease in the context of experimentally induced and naturally occurring pathologies. Calpain-mediated cleavage of the cytoskeletal protein spectrin, in particular, results in a set of large breakdown products (BDPs) that are unique in that they are unusually stable. Over the last 15 years, measurements of BDPs in experimental models of stroke-type excitotoxicity, hypoxia/ischemia, vasospasm, epilepsy, toxin exposure, brain injury, kidney malfunction, and genetic defects, have established that calpain activation is an early and causal event in the degeneration that ensues from acute, definable insults. The BDPs also have been found to increase with normal ageing and in patients with Alzheimer's disease, and the calpain activity may be involved in related apoptotic processes in conjunction with the caspase family of proteases. Thus, it has become increasingly clear that regardless of the mode of disturbance in calcium homeostasis or the cell type involved, calpain is critical to the development of pathology and therefore a distinct and powerful therapeutic target. The recent development of antibodies that recognize the site at which spectrin is cleaved has greatly facilitated the temporal and spatial resolution of calpain activation in situ. Accordingly, sensitive spectrin breakdown assays now are utilized to identify potential toxic side-effects of compounds and to develop calpain inhibitors for a wide range of indications including stroke, cerebral vasospasm, and kidney failure.

Disturbances of calcium homeostasis might be involved in the pathogenesis of the metabolic derangements associated with uraemia. Indices of glucose and lipoprotein metabolism as well as blood pressure were measured in nine patients with chronic renal failure who were on regular hemodialysis. Seven of them thereafter received alphacal-cidol (a synthetic analogue to active vitamin D) intravenously for three months. Prior to therapy the patients had, compared with age and sex matched controls, impaired glucose tolerance, hyperlipoproteinemia and raised blood pressure. Treatment with alphacalcidol reduced elevated serum levels of parathyroid hormone (PTH). Concomitantly there was a reduction of fasting blood glucose and HbA1C (glycosylated hemoglobin) concentrations and an improvement of the glucose tolerance, whereas insulin concentrations were unaffected. There was a reduction of whole serum triglycerides and an increase of HDL cholesterol. A significant decrease was also observed for systolic blood pressure. This pilot study suggests that treatment with active vitamin D, probably through its effects on calcium metabolism, is beneficial with regard to the metabolic disturbances in uraemia.

The calcium hypothesis of brain aging and neurodegenerative disorders: Significance in diabetic neuropathy

Disturbances of calcium homeostasis within the endoplasmic reticulum may contribute to the development of ischemic-cell damage

Associate Professor of Anesthesiology, Joint Appointment in Medicine (Cardiology) and Health Policy and Man-agement, Johns Hopkins University School of Medicine, Baltimore, Maryland. lfleishe@jhmi.eduFOR much of the latter half of the 20th century, there has been a great deal of interest in establishing and using indices to assess perioperative risk. One of the first and best-known attempts was Dr. Dripps’1use of the American Society of Anesthesiologists (ASA) Physical Status Classification of surgical mortality. Beginning in 1977, with the development of the Cardiac Risk Index by Dr. Goldman et al. , there have been a plethora of such indices related to cardiovascular disease in individuals undergoing noncardiac surgery. 2–4Subsequently, the development and use of risk indices has taken on increasing importance in the arena of cardiac surgery. 5–7These newer indices usually take the form of complex logistic regression analysis of factors predicting outcome, and subsequent assignment of weights to these factors. In this issue of the Journal, Dupuis et al. 8have attempted to simplify the approach to risk of cardiac surgical procedures in a manner similar to the original ASA Physical Status Classification. They developed an index that uses a simple continuous categorization with five classes plus an emergency status. The Cardiac Anesthesia Risk Evaluation (CARE) index showed similar or superior predictive characteristics than the more complex indices. Although investigators continue to develop and refine these indices, do the indices continue to provide value to the clinicians who use them and to the patients for whom they were developed?The underlying assumption in the development of a risk index is that specific factors (disease history, physical findings, laboratory data, nature of surgery) are unmodifiable with respect to their influence on outcome, i.e. , the perioperative period is essentially a “black box.” If a specific factor is left untreated, it could lead to major morbidity. For example, the type and urgency of the planned surgical procedure cannot be changed. However, some factors can be modified once they are identified. For example, a shorter time interval between a planned surgical procedure and previous myocardial infarction was considered one of the most important factors with respect to perioperative cardiac morbidity. 9Although the evidence is not as well-established, it is now clear that the absolute risk related to a specific time interval less than 6 months between the infarct and noncardiac surgery can be modified by medical therapy and coronary interventions and more appropriately approximates the residual ischemic potential after the initial period of myocardial healing and remodeling. 10Therefore, current indices would not include a myocardial infarction within 6 months, but may include active coronary artery disease as shown by the factors included in the Modified Cardiac Risk Index recently published by Lee et al. 4Therefore, one of the core indications from a scientific perspective for the development of a risk index is the identification of risk factors that should be targeted for intervention. If the interventions are successful, the risk factor decreases in importance; however, ignoring the factor may lead to its becoming an important cause of mortality.In developing a risk index, it is important to benchmark it against other known means of assessing risks. It is important to determine if the index predicts morbidity, mortality, or both. Dupuis et al. 8appropriately determined the predictive value of the CARE index against both fatal and nonfatal endpoints. Secondly, it is important to determine if it provides additional or similar information to other known indices. Similar to the ASA Physical Status Classification, the CARE index is simple and incorporates a subjective component of medical comorbidity. Although the subjective nature of the ASA classification can be promulgated as a weakness, its success suggests that anesthesiologists tend to be good at assessing risk and that objective factors alone cannot account for all of the known variation in risk. 11In the case of the current study, it was also important to benchmark the scale against previously developed indices that were computationally much more complex. The authors used the appropriate techniques of assessing sensitivity and specificity on receiver-operating characteristic curves and comparing areas under the curve. Therefore, the value of the current index is its computational ease of use without loss of information compared with established methodologies.The real question is, “What is the additive value of a risk index above simple clinical judgment for both the clinician and the patient?” This leads to the question of exactly how risk indices are used in clinical practice. As previously described, the identification of important risk factors, via an index or simple research protocol, is critical in defining targets for intervention. One of the best examples of this approach has been the Framingham health study, in which hypertension and other public health hazards, on which the public health sector and pharmaceutical industry have focused a great deal of attention, have been identified clearly. 12A second use of a risk index is for comparison between groups. It is now extremely common to risk-adjust outcomes when comparing two different locations or provider characteristics of care. This is seen most commonly in the area of cardiac surgery, a focus of the risk index in the current issue of the Journal. Report cards of mortality and morbidity rates surrounding cardiac surgery by surgeon and hospital have been published by New York State and Pennsylvania and are available on the Internet. 13–16Before public dissemination of mortality rates for individual hospitals and providers, it is critical to risk-adjust outcomes to provide meaningful comparisons to determine appropriateness of care. These report cards frequently incorporate a risk adjustment scheme because much of the outcome differences may be accounted for by differences in patient characteristics. For the case of risk adjustment, a more sophisticated analysis may have greater value than simplistic approaches. Additionally, most risk adjustment models are implemented using claims data (discharge summaries) and International Classification of Disease (ICD-9CM) codes. Therefore, the factors that go into any model must be translated easily into these discharge codes.The final question remains, “Do clinicians really use risk indices for patient management or education?” Internists and cardiologists may use these indicies to determine if a patient’s risk is above some threshold for action. For example, patients with with a Cardiac Risk Index of III may be sent for preoperative testing. Despite the appropriateness of a such an approach, the American Heart Association–American College of Cardiology Guidelines for Perioperative Cardiovascular Evaluation for Noncardiac Surgery does not advocate the use of a risk index, but rather the presence of specific clinical factors in determining the need for testing. 10Because perioperative morbidity and mortality rates are frequently institution specific, the use of established indices to determine thresholds for action is becoming less common. 17When clinicians understand the elements of perioperative risks, they frequently will not use a specific index. In particular, anesthesiologists are extremely good at predicting risks using the simple ASA classification. A recent study showed similar predictive characteristics using the ASA Physical Status Classification and objective risk indices predicting mortality after noncardiac surgery, 11suggesting that a subjective score can do as well as an objective one. Therefore, institutional data and subjective assessment of the anesthesiologist are important in defining a specific numeric risk, which is required rarely by patients, as shown by the low public perception of surgical report cards. 16So where does this leave us in the year 2001? Clearly, anesthesiologists are good at using subjective scores to assess risk, and the currently proposed CARE index fits into this category and may be used in a manner similar to the ASA Physical Status Classification. Physicians from other specialties may continue to use this and other risk indices as means of determining baseline rates of complications in their decision if there is a threshold for action. Importantly, the ability to calculate a simple number (e.g., risk category) may detract from the dissemination of important clinical information because the risk category does not provide the anesthesiologist with the information he or she needs to modify care. Therefore, I believe that risk indices are most useful as a means of risk-stratifying outcomes and comparing populations and as a resource tool to identify areas that warrant targeted interventions but have minimal impact on perioperative care or patient education.

4-PBA rescues hyperoxaluria induced nephrolithiasis by modulating urinary glycoproteins: Cross talk between endoplasmic reticulum, calcium homeostasis and mitochondria