This blog is a way of sharing the information and resources that have helped me to recover my son Roo from an Autism Spectrum Disorder. What I have learned is to view our symptoms as the results of underlying biological cause, which can be identified and healed. I say "our symptoms" because I also have a neuro-immune disorder called Myalgic Encephalomyelitis.

And, of course, I am not a doctor (although I have been known to impersonate one while doing imaginative play with my son)- this is just our story and information that has been helpful or interesting to us. I hope it is helpful and interesting to you!


Sunday, December 6, 2015

Mitochondrial Damage from Toxins

Many of the things that are toxic to our bodies are toxic at least in part because of the damage they do to our mitochondria.  Mitochondria are thought to be descended from free living bacteria that formed a symbiotic relationship with eukaryotic cells early on in evolution, and research is now suggesting that they are susceptible to some of the same toxins that bacteria are sensitive to.  Mitochondria are so important to the health and function of our cells that when they are damaged it can result in a very broad spectrum of diseases and dysfunction.  For people whose mitochondria are already injured it is important to limit exposure to additional toxicity.  There are many things that can be toxic to mitochondria, including medication, alcohol, and many metals.

DRUGS:

Drug Toxicity and Mitochondria
(This is a podcast from the advocacy group MitoAction with Dr. James Dykens, who is Director of Investigative Cellular Toxicity at Pfizer Drug Safety Research and Development and author of the 2008 book "Drug Induced Mitochondrial Dysfunction".)
You can read a summary of this information here.

(a webcast with Dr Bruce H. Cohen, who leads the Akron Children’s Hospital Pediatric Neurology Division and specializes in metabolic and mitochondrial diseases)

"Since the first mitochondrial dysfunction was described in the 1960s, the medicine has advanced in its understanding the role mitochondria play in health and disease. Damage to mitochondria is now understood to play a role in the pathogenesis of a wide range of seemingly unrelated disorders such as schizophrenia, bipolar disease, dementia, Alzheimer's disease, epilepsy, migraine headaches, strokes, neuropathic pain, Parkinson's disease, ataxia, transient ischemic attack, cardiomyopathy, coronary artery disease, chronic fatigue syndrome, fibromyalgia, retinitis pigmentosa, diabetes, hepatitis C, and primary biliary cirrhosis. Medications have now emerged as a major cause of mitochondrial damage, which may explain many adverse effects. All classes of psychotropic drugs have been documented to damage mitochondria, as have stain medications, analgesics such as acetaminophen, and many others. While targeted nutrient therapies using antioxidants or their precursors (e. g., N-acetylcysteine) hold promise for improving mitochondrial function, there are large gaps in our knowledge. The most rational approach is to understand the mechanisms underlying mitochondrial damage for specific medications and attempt to counteract their deleterious effects with nutritional therapies. This article reviews our basic understanding of how mitochondria function and how medications damage mitochondria to create their occasionally fatal adverse effects."

(slide show by James A. Dykens Pfizer Drug Safety Research & Development, Sandwich, England)


The following is an excerpt from a brochure for test kits to measure mitochondrial toxicity during drug trials:
"There is an increasing emphasis on reducing attrition through the preclinical and clinical phases of drug development in order to minimize the number of drugs withdrawn from the market, or having their use curtailed by warnings due to adverse effects. This is often because the adverse effect is subtle and does not necessarily lead to histopathology. Among the drugs that have been withdrawn in recent years, several have since been shown to cause serious impairment to mitochondrial function, including cerivastatin (Baycol), troglitazone (Rezulin), nefazodone (Serzone) and tolcapone (Tasmar) [1]. Not surprisingly, there is now much more focus on identifying mitochondrial toxicity early in the development process. Early indicators of mitochondrial toxicity from one or more of these effects are:

• Altered intracellular ATP levels

• Increased intracellular reactive oxygen species (ROS)

• Reduced mtDNA-encoded protein expression

• Increased extracellular acidification

• Altered oxygen consumption

• Reduced membrane potential"

 Drugs in General:
Drug-induced liver injury through mitochondrial dysfunction: mechanisms and detection during preclinical safety studies.
Fundam Clin Pharmacol. 2008 Aug;22(4):335-53
"Mitochondrial dysfunction is a major mechanism whereby drugs can induce liver injury and other serious side effects such as lactic acidosis and rhabdomyolysis in some patients. By severely altering mitochondrial function in the liver, drugs can induce microvesicular steatosis, a potentially severe lesion that can be associated with profound hypoglycaemia and encephalopathy. They can also trigger hepatic necrosis and/or apoptosis, causing cytolytic hepatitis, which can evolve into liver failure. Milder mitochondrial dysfunction, sometimes combined with an inhibition of triglyceride egress from the liver, can induce macrovacuolar steatosis, a benign lesion in the short term. However, in the long term this lesion can evolve in some individuals towards steatohepatitis, which itself can progress to extensive fibrosis and cirrhosis. As liver injury caused by mitochondrial dysfunction can induce the premature end of clinical trials, or drug withdrawal after marketing, it should be detected during the preclinical safety studies.

 Drug-associated mitochondrial toxicity and its detection.
Curr Med Chem. 2005;12(16):1829-39.
"Mitochondrial dysfunction is a fundamental mechanism in the pathogenesis of several significant toxicities in mammals, especially those associated with the liver, skeletal and cardiac muscle, and the central nervous system. These changes can also occur as part of the natural aging process and have been linked to cellular mechanisms in several human disease states including Parkinson's and Alzheimer's, as well as ischemic perfusion injury and the effects of hyperglycemia in diabetes mellitus. Our knowledge of the effects of xenobiotics on mitochondrial function has expanded to the point that chemical structure and properties can guide the pharmaceutical scientist in anticipating mitochondrial toxicity."
"Mitochondrial function is important in the context of muscle survival, hence, the requirement to identify novel mitochondrial targets and develop new therapies to counteract chemical-induced degeneration of mitochondrial function and muscle performance."

 Differentiating Mitochondrial Toxicity from Other Types of Mechanistic Toxicity
"There are several mechanisms by which mitochondria can be adversely affected by chemical compounds. Mitochondrial DNA (mtDNA) replication can be disrupted, as with the case of drugs like AZT that inhibit reverse transcriptase of retroviruses. Some compounds can directly inhibit the electron transport chain or uncouple ATP synthesis from electron transport. Other compounds can inhibit the Krebs cycle, affect mitochondrial membrane permeability or inhibit mitochondrial transporters.

In spite of the critical roles that mitochondria play in all cells and the many ways they can be adversely affected by chemical compounds, mitochondrial toxicity is difficult to identify. Many of the cell lines used in high-throughput drug discovery screens are highly proliferative, immortalized cell lines that, in the presence of glucose, use glycolysis for energy production, despite abundant oxygen and functional mitochondria, a phenomenon known as the Crabtree effect . As a result these cells tend to be resistant to compounds that disrupt mitochondrial oxidative respiration . In addition, almost all cells can tolerate diminished mitochondrial membrane potential as long as minimal capacity is maintained; however, when that minimal capacity is lost, cells die rapidly via apoptosis or necrosis, and mitochondrial toxicity is not often identified as the underlying cause of cell death . Often with mitochondrial toxicity there is a lack of correlation between drug dose and toxicity, and toxicity can be missed in clinical trials because it is often highly dependent on individual genetics and organ history ."

Specific Drugs:
"The aim of the study is to examine the oxidative stress in patients on fluoroquinolones (ciprofloxacin, levofloxacin, gatifloxacin) therapy for complicated urinary tract infections and to correlate with plasma concentrations at different time intervals. Superoxide dismutase (SOD), glutathione, plasma antioxidant status and lipid peroxides were evaluated in 52 patients on different dosage regimens up to 5 days... There was a considerable increase in lipid peroxide levels indicating an enormous oxidative stress. Caution to be taken for patients especially on Ciprofloxacin and Levofloxacin therapy. These studies necessarily warranty the use of exogenous antioxidants as adjuvant in combination with fluoroquinolones, and their benefits should be carefully examined in a controlled clinical setup."
Apoptosis. 2012 May;17(5):516-27
"Vaccines can have adverse side-effects, and these are predominantly associated with the inclusion of chemical additives such as aluminum hydroxide adjuvant. The objective of this study was to establish an in vitro model system amenable to mechanistic investigations of cytotoxicity induced by hepatitis B vaccine, and to investigate the mechanisms of vaccine-induced cell death. The mouse liver hepatoma cell line Hepa1-6 was treated with two doses of adjuvanted (aluminium hydroxide) hepatitis B vaccine... Hepatitis B vaccine exposure increased cell apoptosis as detected by flow cytometry and TUNEL assay. Vaccine exposure was accompanied by significant increases in the levels of activated caspase 3, a key effector caspase in the apoptosis cascade. We conclude that exposure of Hepa1-6 cells to a low dose of adjuvanted hepatitis B vaccine leads to loss of mitochondrial integrity, apoptosis induction, and cell death, apoptosis effect was observed also in C2C12 mouse myoblast cell line after treated with low dose of vaccine (0.3, 0.1, 0.05 μg/ml). In addition In vivo apoptotic effect of hepatitis B vaccine was observed in mouse liver."

Inhibition by aluminum hydroxide of the voltage-dependent closure of the mitochondrial channel, VDAC
Biochim Biophys Acta. 1989 Apr 25;991(1):68-78.
"Micromolar quantities of aluminum have been found (Dill et al. (1987) J. Membrane Biol. 99, 187-196) to reduce the voltage dependence of the mitochondrial outer membrane channel, VDAC, from Neurospora crassa. In the present study, various metallic and organic ions were tested for possible aluminum-like effect, and only the trivalent metals exhibited a similar ability to reduce the channels voltage dependence... While providing new insight into the nature of VDAC's sensor, these results also indicate that aluminum-cell interaction may result from the presence of AI(OH)3 in solution in addition to the widely accepted AI3+-mediated interactions. While the [AI3+] is vanishingly low at neutral pH, the trihydroxide is the major form and should be considered as an important candidate for aluminum-induced cellular effects."
Neurotoxicology. 2014 Mar;41:154-66
"Though it remains unclear whether oxidative stress is a major cause or merely a consequence of cellular dysfunction associated with neurodegenerative diseases, an accumulating body of evidence implicates that impaired mitochondrial energy production and increased mitochondrial oxidative damage is associated with the pathogenesis of neurodegenerative disorders. Being involved in the production of reactive oxygen species, aluminium may impair mitochondrial bioenergetics and may lead to the generation of oxidative stress. In this review, we have discussed the oxidative stress and mitochondrial dysfunctions occurring in Al neurotoxicity."

"Disruption of metal ion homeostasis may lead to oxidative stress, a state where increased formation of reactive oxygen species (ROS) overwhelms body antioxidant protection and subsequently induces DNA damage, lipid peroxidation, protein modification and other effects, all symptomatic for numerous diseases, involving cancer, cardiovascular disease, diabetes, atherosclerosis, neurological disorders (Alzheimer's disease, Parkinson's disease), chronic inflammation and others."

"Metal-induced toxicity and carcinogenicity, with an emphasis on the generation and role of reactive oxygen and nitrogen species, is reviewed. Metal-mediated formation of free radicals causes various modifications to DNA bases, enhanced lipid peroxidation, and altered calcium and sulfhydryl homeostasis. Lipid peroxides, formed by the attack of radicals on polyunsaturated fatty acid residues of phospholipids, can further react with redox metals finally producing mutagenic and carcinogenic malondialdehyde, 4-hydroxynonenal and other exocyclic DNA adducts (etheno and/or propano adducts)."

"The past decade has seen an intense focus on mechanisms of apoptosis. Many important observations on the various signaling pathways mediating apoptotic cell death have been made and our understanding of the importance of apoptosis in both normal growth and development and pathophysiology has greatly increased. In addition, mechanisms of metal-induced toxicity continue to be of interest given the ubiquitous nature of these contaminants. The purpose of this review is to summarize our current understanding of the apoptotic pathways that are initiated by metals, mainly established (arsenic, cadmium, chromium, nickel, beryllium) and possible (lead, antimony, cobalt) human carcinogens. Increased understanding of metal-induced apoptosis is critical to illuminate mechanisms of metal-induced carcinogenesis, as well as the potential of metal species (arsenic) as chemotherapeutic agents."

 Role of metals in neuronal apoptosis: challenges associated with neurodegeneration.
"Apoptosis is a tightly controlled process in which cell death is executed through activation of specific signalling pathways. Within cells, there are positive and negative regulatory pathways of apoptosis, hence it is targeted as 'Double-edged sword', the balance between these pathways dictates the cell fate. The past decade has seen intense focus on the mechanisms of apoptosis. Many important observations on the various signalling pathways mediating apoptotic cell death have been made and our understanding of the importance of apoptosis in both normal growth and development and patho-physiology has greatly increased. In addition, mechanisms of metal-induced toxicity continue to be of interest given the ubiquitous nature of these contaminants. The purpose of this review is to summarize our current understanding of the apoptotic pathways that are initiated by metals in Alzheimer's disease. Increased understanding of metal-induced (direct) and metal-amyloid-beta (indirect) linked neuronal cell death through the formation of reactive oxygen species (ROS) is critical to illuminate mechanisms of metal-induced cell death, as well as the potential role of metal speciation in neurodegeneration."

OTHER TOXINS:

Mitochondria as a Target of Environmental Toxicants
Toxicol. Sci. (2013) First published online: April 29, 2013
"Enormous strides have recently been made in our understanding of the biology and pathobiology of mitochondria. Many diseases have been identified as caused by mitochondrial dysfunction, and many pharmaceuticals have been identified as previously unrecognized mitochondrial toxicants. A much smaller but growing literature indicates that mitochondria are also targeted by environmental pollutants. We briefly review the importance of mitochondrial function and maintenance for health based on the genetics of mitochondrial diseases and the toxicities resulting from pharmaceutical exposure. We then discuss how the principles of mitochondrial vulnerability illustrated by those fields might apply to environmental contaminants, with particular attention to factors that may modulate vulnerability including genetic differences, epigenetic interactions, tissue characteristics, and developmental stage. Finally, we review the literature related to environmental mitochondrial toxicants, with a particular focus on those toxicants that target mitochondrial DNA. We conclude that the fields of environmental toxicology and environmental health should focus more strongly on mitochondria."

Large amounts of mitochondrial toxic agents cross placenta barrier
Science Daily February 20, 2015
"Ten years' worth of scientific studies on mitochondrial toxicity in pregnant women has been reviewed, including exposure to toxic agents such as viruses, certain drugs, pesticides, alcohol and tobacco. These all cause mitochondrial diseases about which very little is known, and which are transmitted from the mother to the fetus."

Acute ethanol administration oxidatively damages and depletes mitochondrial DNA in mouse liver, brain, heart, and skeletal muscles: protective effects of antioxidants.
"Ethanol metabolism causes oxidative stress and lipid peroxidation not only in liver but also in extra-hepatic tissues. We studied the effects of an acute intragastric ethanol administration (5 g/kg) on brain, heart, skeletal muscle, and liver mtDNA in mice. Ethanol administration caused mtDNA depletion and replacement of its supercoiled form by linearized forms in all tissues examined. Maximal mtDNA depletion was about similar (ca. 50%) in all organs studied. It occurred 2 h after ethanol administration in heart, skeletal muscle, and liver but after 10 h in brain. This mtDNA depletion was followed by increased mtDNA synthesis. A secondary, transient increase in mtDNA levels occurred 24 h after ethanol administration in all organs. In hepatic or extra-hepatic tissues, mtDNA degradation and depletion were prevented by 4-methylpyrazole, an inhibitor of ethanol metabolism, and attenuated by vitamin E, melatonin, or coenzyme Q, three antioxidants. In conclusion, our study shows for the first time that ethanol metabolism also causes oxidative degradation of the mitochondrial genome in brain, heart, and skeletal muscles. These effects could contribute to the development of (cardio)myopathy and brain injury in some alcoholic patients. Antioxidants prevent these effects in mice and could be useful in persevering drinkers."

 Viruses as Modulators of Mitochondrial Functions
Advances in Virology Volume 2013 (2013), Article ID 738794, 17 pages
"Mitochondria are multifunctional organelles with diverse roles including energy production and distribution, apoptosis, eliciting host immune response, and causing diseases and aging. Mitochondria-mediated immune responses might be an evolutionary adaptation by which mitochondria might have prevented the entry of invading microorganisms thus establishing them as an integral part of the cell. This makes them a target for all the invading pathogens including viruses. Viruses either induce or inhibit various mitochondrial processes in a highly specific manner so that they can replicate and produce progeny. Some viruses encode the Bcl2 homologues to counter the proapoptotic functions of the cellular and mitochondrial proteins. Others modulate the permeability transition pore and either prevent or induce the release of the apoptotic proteins from the mitochondria. Viruses like Herpes simplex virus 1 deplete the host mitochondrial DNA and some, like human immunodeficiency virus, hijack the host mitochondrial proteins to function fully inside the host cell. All these processes involve the participation of cellular proteins, mitochondrial proteins, and virus specific proteins. This review will summarize the strategies employed by viruses to utilize cellular mitochondria for successful multiplication and production of progeny virus."





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