Tuesday, October 16, 2012

Mechanism of Fluoride Toxicity on Biological Systems

N. Agalakova and G. Gusev, Molecular Mechanisms of Cytotoxicity and Apoptosis Induced by Inorganic Fluoride. Russian Academy of Sciences, International Scholarly Research Network, Journal of Cell Biology, Volume 2012, Article ID 403835

http://www.isrn.com/journals/cb/2012/403835/

Summary
While a lot has been written about the potential beneficial effect of low levels of fluoride for dental health, however the adverse effects of fluoride exposure on human health has received very little attention. This is one of the first major reviews of fluoride toxicity published in a peer reviewed scientific journal on cell biology. In this work, scientific experts in molecular biology and biochemical toxicology from the Russian Academy of Sciences have focused attention on the intracellular molecular mechanisms proven to be responsible for cytotoxicity and development of cell death induced by inorganic fluoride as well as the effect of fluoride on critical biological pathways in the body. The authors state that although the toxicity of fluoride is well known, it has been ignored for a long time and highlight that while the WHO recommends an optimal level of fluoride in drinking water, for the preventing of dental caries, when fluoride in drinking water is added to other dietary sources such as toothpaste or rinses, as well as fluoride in other foodstuffs and beverages, the optimal daily uptake for individuals is often exceeded. This results in uncontrolled and unpredictable consumption of fluoride which may often exceed it’s therapeutic value thereby inducing negative health impacts within the population as a whole. The author’s note that during the last decades fluoride was established to be a potent inducer of cell death in many cultured cell types and experimental animal models. Fluoride when ingested into the body alters virtually all known intracellular signalling pathways including G protein- dependent pathways, caspases, and mitochondria- and death receptors-linked mechanisms, as well as triggers a range of metabolic and transcription alterations, including the expression of several apoptosis-related genes, ultimately leading to cell death. Fluoride has been shown to negatively influence many metabolic, structural, and functional cellular functions. The toxic fluoride effects include an induction of inflammatory reactions, cell contractile responses, inhibition of protein synthesis and cell cycle progression, oxidative stress, and DNA damage. Fluoride has been found to alter critical physiological and pathological processes for the body’s defence and repair mechanisms. Fluoride was found to reduce the body’s antioxidative defence mechanism impairing the ability of the body to eliminating free radicals and fight disease. Fluoride effects cellular calcium concentration, interferes with the body’s natural calcium stores and acts to suppress both the Ca2+-pump, or activation of Ca2+ channels in the body as well as interfere with functions of  the brain, heart, kidney,  liver, pineal gland and pancreas. Fluoride interferes with the bodies cellular antioxidant defence systems and stimulates lipid peroxidation (LPO). It is now believed that excessive LPO may be involved in carcinogenesis. Fluoride has also been shown to directly affect Bcl-2 Family Proteins which are critically important for fighting cancer. Fluoride is found to be a known inhibitor of enzymes of glycolytic pathway and the author’s note that while this effect is known for some time it is often underestimated or ignored in the studies of fluoride cytotoxicity and cell death. Fluoride is known to reduce insulin secretion and may contribute to obesity in individuals with diabetics. The authors highlight that knowledge of the intracellular pathways involved in the development of fluoride-induced cell death is still incomplete, noting that this is probably due to complexity and diversity of the molecular events underlying fluoride toxicity and conclude that intensive investigations are required to identify the whole series of events involved in the development of fluoride-induced cytotoxicity and cell death, as well as the mechanisms of their regulation in the human body


Among the scientific findings highlighted by the scientific researchers the following are included:

•    The authors begin by noting that although the toxicity of fluoride is well known, it has been ignored for a long time. It is highlighted that while the WHO recommends an optimal level of fluoride in drinking water, for the preventing of dental caries, when fluoride in drinking water is added to other dietary sources such as toothpaste or rinses, as well as fluoride in other foodstuffs and beverages, the optimal daily uptake for individuals is often exceeded. This the authors point out results in uncontrolled and unpredictable consumption of fluoride which may often exceed it’s therapeutic value thereby inducing negative health impacts within the population.

•    The authors note that there is no convincing evidence on the role of fluoride as essential element for normal human growth and development. In contrast it is highlighted that in recent decades, numerous investigations have established the toxicity of fluoride for cells of different tissues and biological systems.

•    The authors document that the toxicity of fluoride is associated with its high chemical and biological activity. Fluoride freely and rapidly migrates across the biological membranes. After ingestion, fluoride is rapidly and virtually totally absorbed into the blood.

•    The authors find that approximately 50% of the fluoride ingested by our body each day is retained in our bodies (more for certain sensitive subgroups Including babies and diabetics) and distributed between organs and tissues where it accumulates in bones, teeth, pineal glands, and other tissues. The authors observe that the effects of fluoride on cellular metabolism and physiology vary according to cell type, concentration, and time of exposure and that much greater research is required to fully understand the complexity of many of the processes of fluoride toxicity.

•    The report documents that Fluoride has been shown to negatively influence many metabolic, structural, and functional cellular functions. The toxic fluoride effects include an induction of inflammatory reactions, cell contractile responses, inhibition of protein synthesis and cell cycle progression, oxidative stress, and DNA damage. Many of these cellular events ultimately lead to cell death or apoptosis.

•    The report outlines the morphological changes typical for apoptosis include condensation of nuclear chromatin, DNA fragmentation, disintegration of mitochondria, cell shrinkage, membrane blebbing, and formation of apoptotic bodies.

•    The report explains that the molecular mechanisms underlying fluoride-induced apoptosis are different by nature and include the stimulation of G protein-dependent signaling systems, oxidative stress, ATP depletion, activation of the cell surface death receptors, disruption of outer mitochondria membrane, activation of caspases, alterations in the ratio of anti-apoptotic-apoptotic Bcl-2 proteins, upregulation of p53 expression, expression of apoptosis-related genes, endoplasmic reticulum stress and disturbances in protein synthesis.

•    The report identifies that Fluoride exposure increases protein kinase C (PKC) activity which induces cell death.

•    The report documents in detail how Fluoride interferes with Gprotein signalling resulting in inhibition of enzymes and interference with many metabolic reactions in the cells. It is noted that Gproteins are one of the most important classes of proteins in living organisms  which are  involved in transmitting chemical signals. For all essential purposes G proteins are essentially both the gatekeepers and molecular messengers of the cell, transmitting signals from inside to outside. They mediate virtually every important physiological process, from immune system function to taste and smell to the fight-or-flight response in humans. Naturally occurring small molecules which bind to G proteins include adrenaline, prostaglandins, dopamine, somatostatin and adenosine. It is documented that in the pulmonary artery activation of G proteins can initiate a series of events leading to increases in phosphoinositide hydrolysis which plays an important role in regulating cell function resulting in Ca2+ mobilization from intracellular stores. The researchers highlight that scientific evidence found Fluoride to interfere with the body’s natural calcium stores and acted to suppress both the Ca2+-pump, or activation of Ca2+ channels. Increase in Ca2+ concentration might play a key role in the mechanism of  contraction of aortic rings as well as renal injury and necrosis of renal tubules in fluorosis. Further recent scientific research has documented that fluoride calcium interactions may contribute to calcification of human arteries that will increase the risk of coronary disease and stroke.

•    The authors presented evidence  to show how  fluoride effects cellular calcium concentration causes low sperm hyperactivation.

•    In addition the report identifies how Fluoride was found in pancreatic cells to actively interfere with genisteinsensitive tyrosine kinases which is essential for protein, DNA synthesis.

•    The report documents that fluoride inhibited insulin receptors by direct binding to the receptors, as well as fluoride-induced cytotoxicity and cell death.

•    Fluoride was also found to inhibit Mitogen-activated protein kinases (MAPKs). MAPKs are involved in directing cellular responses to a diverse array of stimuli, such as mitogens, osmotic stress, heat shock and proinflammatory cytokines. They regulate proliferation, gene expression, differentiation, mitosis, cell survival, and apoptosis characterised by biochemical events which lead to disintegration of cells and cell death. Importantly the researchers found an increased level of dead cells in the brain of fluoride intoxicated animals.

•    Fluoride was shown to be potent nonspecific inhibitor of protein phosphatases (PPs) activities which affect protein stability, and regulate enzyme activity. Fluoride was found to cause an imbalance in the ionic gradients across the plasma membrane and disturbances in membrane potential while exerting diverse and complicated effects on K+ and Na+ transport across the membrane, loss of cellular K+ and suppression of the erythrocyte membrane critical for antibodies and immunity to disease.

•    Fluoride was found to cause chronic or acute reactive oxygen species (ROS) overproduction, exceeding the capacity of cellular antioxidant defence systems, cause oxidative damage to macromolecules such as DNA and proteins, peroxidation of membrane phospholipids, and mitochondrial depolarization, thus initiating cell disintegration and cell death as well as organ lesions.

•    The authors highlight the general acceptance that Fluoride causes oxidative stress, a recognized mode of fluoride action and toxicity. The author’s further note that this was particularly pronounced in some cell types such as by Fluoride-induced cell death of hair follicles.

•    The authors acknowledges that another important, although indirect, mechanism of fluoride-induced cytotoxicity demonstrated in the cells of many tissues is lipid peroxidation (LPO). Oxidative stress was also shown to be linked to significant changes to lipid peroxidation. A growing body of evidence has shown that excessive LPO may be involved in carcinogenesis.  It was documented that Fluoride exposure in pregnant animals and their offspring during first month of life leads to kidney tissue changes and LPO in the first and second generation of animals. I t was also acknowledged that a direct link between fluoride-induced cell destruction and cell death and elevated LPO was scientifically demonstrated in the different mammals in animal studies.

•    The report highlights how Fluoride may influence superoxide anion  radicals (•O2−) as well as hydrogen peroxide, peroxynitrite, and hydroxyl radicals, all critical physiological and pathological processes for the body’s defence and repair mechanisms.

•    The report addresses how Fluoride was found to enhance Reactive Oxidative Stress (ROS) particularly in the blood, liver, kidneys, and brain of animals consuming fluoride in drinking water. 

•    It was noted that significant morphological abnormalities and apoptosis (cell death) were also observed in the sperm cells of animals exposed to high fluoride doses.

•    Animal studies found reduced fertility of males sub chronically exposed to fluoride.

•    Importantly Fluoride was found to reduce the body’s antioxidative defence mechanism of the body to fight disease. Alongside with aforementioned oxidative stress-related events, fluoride is proven to alter the activity of many antioxidant enzymes such as SOD, GSH-Px, and CAT, playing an important role in the antioxidative cell defence and eliminating free radicals.

•    Equally important a decrease in the activity of free radical scavenging enzymes, SOD, CAT, GST, and GSH-Px, was found in the blood of people exposed to fluoride along with a reduction in antioxidant enzymes in liver, kidney and brain.

•    Other Biochemical Changes induced by fluoride cytotoxicity are elevated Nitric Oxide (NO) generation in blood serum and in the liver of fluoride intoxicated animals. NO is an important signalling molecule and is critical for cellular health.

•    Other cellular compounds notedto be affected by fluoride are transaminases (AST and ALT), creatine kinase (CK), total lipids (TLs), cholesterol, triglycerides (TGs), and low-density lipoproteincholesterol (LDL-c) and high-density lipoprotein-cholesterol (HDL-c); all of which are critical for breaking down amino acids and converting energy storage molecules in the liver. It is als now documented that elevated transaminases are associated with liver damage.

•    The red blood cells of animals exposed to fluoride in drinking water exhibited significant inhibition of the parameters related to heme synthesis pathway like δ-aminolevulinic acid dehydratase and δ-aminolevulinic acid synthetase, accompanied by the depletion of whole brain biogenic amine levels.   Hemoproteins have critically biological functions including the transportation of diatomic gases, chemical catalysis, diatomic gas detection, and electron transfer ATP Depletion. ATP depletion and decreased ATP synthesis are frequently associated with both hypoxic and chemical (toxic) injury. Depletion of ATP to <5% to 10% of normal levels has widespread effects on many critical cellular systems in particular cellular energy metabolism. In humans exposed to fluoride decreases between 70-90% in ATP content have been documented as well as a direct link between F-induced inhibition of glycolysis and apoptosis. Fluoride is a well known inhibitor of enzymes of glycolytic pathway and while this effect is known for some time it is often underestimated or ignored in the studies of fluoride cytotoxicity and cell death. The authors note that since energy supply is a limiting factor in a variety of biochemical processes, ATP depletion can arrest many crucial cellular functions like transmembrane ion transport and protein phosphorylation, disturb membrane potential, and membrane-cytoskeleton interactions, what may finally lead to cell death ATP depletion leads to inhibition of NA+-K+ pump, GSH synthesis and GSH/GSSG membrane transport, thus ATP depletion might be the primary process in the chain of events impairing GSH replenishment and antioxidant defence.

•    Fluoride exposure has been shown to result in DNA fragmentation and DNA damage as well trigger the mitochondria-dependent cell death due to reduction of the enzymatic antioxidant.

•    Fluoride has been shown to directly effect Bcl-2 Family Proteins critically important for fighting cancer. BCL-2 was the first anti-death gene discovered, a milestone with far reaching implications for tumour biology and oncology.

•    Fluoride exposure has been found to alter the levels of p53 protein accompanied by a fall in cell survival rate. p53 plays a major role to the regulation of normal metabolic homeostasis, senescence, fertility, differentiation, and regulation of stem cells and is a tumour suppressor protein that responds to extrinsic and intrinsic stress stimuli, including DNA damage, oncogene activation, and hypoxia. It acts to control the mitochondria redox balance and integrity, and contribute to the regulation of oxidative phosphorylation, glycolysis, nucleotide biosynthesis, fatty acid oxidation, and antioxidant response.

•    Fluoride has been found to alter several cell types, both normal and pathological. Research has demonstrated that human exposure to fluoride in drinking water has been found to alter human genes related to the regulation of the cell cycle and apoptosis as well as inflammation in blood cells. The authors note that similar gene alteration was found in animal studies examining the impact of fluoride on sperm cells where it was demonstrated to affect approximately 100 genes involved in the signal transduction, amino acid phosphorylation, oxidative stress, cell cycle, electron transfer, glycolysis, chemotaxis, spermatogenesis, and apoptosis. Furthermore analysis of the kidney, liver, and cardiac muscle samples of fish exposed to fluoride  similarly found significant alteration of proteins critical for cellular toxicity, nuclear signalling, chromosome segregation  and DNA repair leading to chromosome instability and cell death.

•    Animal studies examining the neurotoxicity of fluoride on the hippocampal neurons in the brain reported that fluoride exposure in addition to DNA damage and cell-cycle regulation, suppressed the expression of neural cell adhesion molecules necessary for the maintenance of cognitive functions of the brain such as learning and memory, while enhancing the gene expression factors which can both promote cell death in response to oxidative stress, thus contributing to neurological dysfunctions.

•    The authors note that there is clear evidence to demonstrate that fluoride is able to induce endoplasmic reticulum (ER) stress which activates the self-protecting mechanisms termed unfolded protein response (UPR) resulting in altering protein essential for healthy DNA function and repair.

•    Accumulating evidence suggests that endoplasmic reticulum (ER) stress plays a role in the pathogenesis of diabetes, contributing to pancreatic β-cell loss and insulin resistance. It was further noted that ER stress may also link obesity and insulin resistance in type 2 diabetes.

•    The authors note that Fluoride induced ER stress was also found in pancreas cells leading to another type of cell death called autophagy.

11 comments:

  1. About this Journal
    ISRN Cell Biology is a peer-reviewed, open access journal that publishes original research articles as well as review articles in all areas of cell biology. ISRN Cell Biology is part of the ISRN series of peer-reviewed, open access journals that are designed to provide a fast peer review process for all submitted manuscripts. Every ISRN journal is collaboratively run by a relatively large, international Editorial Board of experts in the subject area of the journal that work as academics in some of the most prestigious Universities in the World.

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  2. At your instigation I read this report. Heavy going!!!!

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  3. You should be ashamed of yourself, scaremongering and misrepresented the facts.
    http://www.quackwatch.org/03HealthPromotion/fluoride.html

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    1. If you have something contradictory to say about this report, why are you afraid to identify yourself?

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  4. Dear anonymous, when you quote a website to support your position that in the very first sentence cannot even correctly classify what fluoride is you should be very concerned. Fluoride is not a mineral, Fluorine (F), a member of the halogen family, is the most electronegative and reactive of all the elements of Periodic table. Elemental fluorine does not exist in nature but forms inorganic and organic compounds called fluorides. Fluoride is more toxic than lead and like lead in minute doses, accumulates in and can be damaging to brain/mind development of children, producing abnormal behavior in animals and reducing IQ in humans, especially in conjunction with deficiencies of key nutrients such as calcium, iodine and vitamins. It can also contribute to many disease processes. Because it is almost as toxic as arsenic, fluoride's ability to play havoc in the human body should surprise no one. What we have in water fluoridation are fluorosilicates which are synthesized compounds for which no toxicological tests have ever been undertaken to demonstrate they are safe for human consumption, what we also have is a disease burden in ireland that is growing almost exponentially. The HSE and department of Health and a lot more besides should be ashamed of themselves, in fact the people in position of influence who dictate that local authorities must under law put untested chemicals into public water supplies should be in jail. Please inform yourself of the true facts.

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  5. There is a greater power in Unity... would it not be time to Unite with the other groups in Ireland who are fighting against Fluoridation. I have been informing people, person-to-person for the last 12 years or so. Individuals and small groupings do have an impact but it is not enough to really change things in the immediate future.. This is not to lessen anyone's efforts, but surely the sum will be greater than the parts when we share common purpose and move together... Thus far, when we are scattered around in various groups it's like having Jigs and Reels here and there... whereas if we Unite all the Anti-Fluoride movements we will really rattle the boards with a 'Riverdance', and that will get the whole country's attention......;-)

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  6. Btw, Anonymous (Quackwatch fan) it might be enlightening to do a search on Stephen Barrett... who is the head honcho (in fact, he's a genuine Quack himself) on Quackwatch...;-) He is NOT an MD and has shown himself to be a nutter on more than one occasion.. here's one link with some of his exploits, for your entertainment... http://www.quackpotwatch.org/quackpots/quackpots/barrett.htm

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  7. Great stuff! There's actually tonnes of research demonstrating the hazards of flouride on the human body, but to find it you need to look into cell biology and physiology. It's scary how blind people can be..

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