Heme deficiency selectively interrupts assembly of mitochondrial complex IV in human fibroblasts: revelance to aging

Risk of cancer in patients with iron deficiency anemia: a nationwide population-based study

Objective

This study evaluated the risk of cancer among patients with iron deficiency anemia (IDA) by using a nationwide population-based data set.

Method

Patients newly diagnosed with IDA and without antecedent cancer between 2000 and 2010 were recruited from the Taiwan National Health Insurance Research Database. The standardized incidence ratios (SIRs) of cancer types among patients with IDA were calculated.

Results

Patients with IDA exhibited an increased overall cancer risk (SIR: 2.15). Subgroup analysis showed that patients of both sexes and in all age groups had an increased SIR. After we excluded patients diagnosed with cancer within the first and first 5 years of IDA diagnosis, the SIRs remained significantly elevated at 1.43 and 1.30, respectively. In addition, the risks of pancreatic (SIR: 2.31), kidney (SIR: 2.23), liver (SIR: 1.94), and bladder cancers (SIR: 1.74) remained significantly increased after exclusion of patients diagnosed with cancer within 5 years after IDA diagnosis.

Conclusion

The overall cancer risk was significantly elevated among patients with IDA. After we excluded patients diagnosed with IDA and cancer within 1 and 5 years, the SIRs remained significantly elevated compared with those of the general population. The increased risk of cancer was not confined to gastrointestinal cancer when the SIRs of pancreatic, kidney, liver, and bladder cancers significantly increased after exclusion of patients diagnosed with IDA and cancer within the first 5 years. This finding may be caused by immune activities altered by IDA. Further study is necessary to determine the association between IDA and cancer risk.

Heme biosynthesis modulation via δ-aminolevulinic acid administration attenuates chronic hypoxia-induced pulmonary hypertension

This study examines how heme biosynthesis modulation with δ-aminolevulinic acid (ALA) potentially functions to prevent 21-day hypoxia (10% oxygen)-induced pulmonary hypertension in mice and the effects of 24-h organoid culture with bovine pulmonary arteries (BPA) with the hypoxia and pulmonary hypertension mediator endothelin-1 (ET-1), with a focus on changes in superoxide and regulation of micro-RNA 204 (miR204) expression by src kinase phosphorylation of signal transducer and activator of transcription-3 (STAT3). The treatment of mice with ALA attenuated pulmonary hypertension (assessed through echo Doppler flow of the pulmonary valve, and direct measurements of right ventricular systolic pressure and right ventricular hypertrophy), increases in pulmonary arterial superoxide (detected by lucigenin), and decreases in lung miR204 and mitochondrial superoxide dismutase (SOD2) expression. ALA treatment of BPA attenuated ET-1-induced increases in mitochondrial superoxide (detected by MitoSox), STAT3 phosphorylation, and decreases in miR204 and SOD2 expression. Because ALA increases BPA protoporphyrin IX (a stimulator of guanylate cyclase) and cGMP-mediated protein kinase G (PKG) activity, the effects of the PKG activator 8-bromo-cGMP were examined and found to also attenuate the ET-1-induced increase in superoxide. ET-1 increased superoxide production and the detection of protoporphyrin IX fluorescence, suggesting oxidant conditions might impair heme biosynthesis by ferrochelatase. However, chronic hypoxia actually increased ferrochelatase activity in mouse pulmonary arteries. Thus, a reversal of factors increasing mitochondrial superoxide and oxidant effects that potentially influence remodeling signaling related to miR204 expression and perhaps iron availability needed for the biosynthesis of heme by the ferrochelatase reaction could be factors in the beneficial actions of ALA in pulmonary hypertension.

RNA-mediated pathogenic mechanisms in polyglutamine diseases and amyotrophic lateral sclerosis

Gene transcription produces a wide variety of ribonucleic acid (RNA) species in eukaryotes. Individual types of RNA, such as messenger, structural and regulatory RNA, are known to play distinct roles in the cell. Recently, researchers have identified a large number of RNA-mediated toxicity pathways that play significant pathogenic roles in numerous human disorders. In this article, we describe various common RNA toxicity pathways, namely epigenetic gene silencing, nucleolar stress, nucleocytoplasmic transport, bi-directional gene transcription, repeat-associated non-ATG translation, RNA foci formation and cellular protein sequestration. We emphasize RNA toxicity mechanisms that involve nucleotide repeat expansion, such as those related to polyglutamine (polyQ) disorders and frontotemporal lobar degeneration-amyotrophic lateral sclerosis.

New insights into Alzheimer's disease amyloid inhibition: nanosized metallo-supramolecular complexes suppress aβ-induced biosynthesis of heme and iron uptake in PC12 cells

Nanosized metallo-supramolecular compounds, [Ni2 L3 ](4+) and [Fe2 L3 ](4+) , can not only strongly inhibit Aβ aggregation but also reduce the peroxidase activity of Aβ-heme. Further studies demonstrate that through blocking the heme-binding site, these two compounds can suppress Aβ-induced biosynthesis of heme and iron uptake in PC12 cells. This work provides new insights into molecular mechanisms of Aβ inhibitors on Aβ-mediated neurotoxicity.

A new perspective on the importance of glycine conjugation in the metabolism of aromatic acids

A number of endogenous and xenobiotic organic acids are conjugated to glycine, in animals ranging from mosquitoes to humans. Glycine conjugation has generally been assumed to be a detoxification mechanism, increasing the water solubility of organic acids in order to facilitate urinary excretion. However, the recently proposed glycine deportation hypothesis states that the role of the amino acid conjugations, including glycine conjugation, is to regulate systemic levels of amino acids that are also utilized as neurotransmitters in the central nervous systems of animals. This hypothesis is based on the observation that, compared to glucuronidation, glycine conjugation does not significantly increase the water solubility of aromatic acids. In this review it will be argued that the major role of glycine conjugation is to dispose of the end products of phenylpropionate metabolism. Furthermore, glucuronidation, which occurs in the endoplasmic reticulum, would not be ideal for the detoxification of free benzoate, which has been shown to accumulate in the mitochondrial matrix. Glycine conjugation, however, prevents accumulation of benzoic acid in the mitochondrial matrix by forming hippurate, a less lipophilic conjugate that can be more readily transported out of the mitochondria. Finally, it will be explained that the glycine conjugation of benzoate, a commonly used preservative, exacerbates the dietary deficiency of glycine in humans. Because the resulting shortage of glycine can negatively influence brain neurochemistry and the synthesis of collagen, nucleic acids, porphyrins, and other important metabolites, the risks of using benzoate as a preservative should not be underestimated.

5-aminolevulinic acid, a precursor of heme, reduces both fasting and postprandial glucose levels in mildly hyperglycemic subjects

OBJECTIVE

The aim of this study was to evaluate the combined effects of 5-aminolevulinic acid phosphate (ALA-P) and iron on the glycemic index in mildly hyperglycemic adults.

METHODS

This double-blind, randomized placebo-controlled trial comprised 212 subjects (ages 35-70 y, fasting plasma glucose 105-125 mg/dL or hemoglobin (Hb)A1c 6.1%-7.1%). These participants were randomly assigned to four groups receiving either one of three doses of ALA-P and iron as sodium ferrous citrate (5 mg and 0.6 mg, 5 mg and 1.8 mg, or 15 mg and 1.8 mg, respectively) or a placebo, administered orally once a day over a 12-wk period.

RESULTS

Fifteen mg ALA-P plus 1.8 mg iron decreased the fasting plasma glucose level (2.32 mg/dL, 95% confidence interval [CI], 0.24-4.42, P = 0.029), serum glycoalbumin (0.22%, 95% CI, 0.02-0.42; P = 0.031), and 2h-oral glucose tolerance test levels (14.2 mg/dL, 95% CI, 1.8-26.6; P = 0.025) more than the placebo. However, the levels of HbA1c, fasting insulin, serum 1,5-anhydro-d-glucitol, and Homeostasis Model of Assessment-Insulin Resistance showed no appreciable changes. The participant numbers with impaired glucose tolerance and impaired fasting glucose decreased in the highest dosage group of ALA-P plus iron compared with the placebo group.

CONCLUSION

An oral intake of ALA would be a novel approach to prevent type 2 diabetes mellitus.

The complex interplay of iron metabolism, reactive oxygen species, and reactive nitrogen species: insights into the potential of various iron therapies to induce oxidative and nitrosative stress

Production of minute concentrations of superoxide (O2(*-)) and nitrogen monoxide (nitric oxide, NO*) plays important roles in several aspects of cellular signaling and metabolic regulation. However, in an inflammatory environment, the concentrations of these radicals can drastically increase and the antioxidant defenses may become overwhelmed. Thus, biological damage may occur owing to redox imbalance-a condition called oxidative and/or nitrosative stress. A complex interplay exists between iron metabolism, O2(*-), hydrogen peroxide (H2O2), and NO*. Iron is involved in both the formation and the scavenging of these species. Iron deficiency (anemia) (ID(A)) is associated with oxidative stress, but its role in the induction of nitrosative stress is largely unclear. Moreover, oral as well as intravenous (iv) iron preparations used for the treatment of ID(A) may also induce oxidative and/or nitrosative stress. Oral administration of ferrous salts may lead to high transferrin saturation levels and, thus, formation of non-transferrin-bound iron, a potentially toxic form of iron with a propensity to induce oxidative stress. One of the factors that determine the likelihood of oxidative and nitrosative stress induced upon administration of an iv iron complex is the amount of labile (or weakly-bound) iron present in the complex. Stable dextran-based iron complexes used for iv therapy, although they contain only negligible amounts of labile iron, can induce oxidative and/or nitrosative stress through so far unknown mechanisms. In this review, after summarizing the main features of iron metabolism and its complex interplay with O2(*-), H2O2, NO*, and other more reactive compounds derived from these species, the potential of various iron therapies to induce oxidative and nitrosative stress is discussed and possible underlying mechanisms are proposed. Understanding the mechanisms, by which various iron formulations may induce oxidative and nitrosative stress, will help us develop better tolerated and more efficient therapies for various dysfunctions of iron metabolism.

Reducing mitochondrial decay with mitochondrial nutrients to delay and treat cognitive dysfunction, Alzheimer's disease, and Parkinson's disease

Mitochondrial decay due to oxidative damage is a contributor to brain aging and age-related neurodegenerative diseases, such as Alzheimer's disease (AD) and Parkinson's disease (PD). One type of mitochondrial decay is oxidative modification of key mitochondrial enzymes. Enzyme dysfunction, that is due to poor binding of substrates and coenzymes may be ameliorated by supplementing adequate levels of substrates or coenzyme precursors. Such supplementation with mitochondrial nutrients (mt-nutrients) may be useful to prevent or delay mitochondrial decay, thus prevent or treat AD and PD. In the present review, we survey the literature to identify mt-nutrients that can (1) protect mitochondrial enzymes and/or stimulate enzyme activity by elevating levels of substrates and cofactors; (2) induce phase-2 enzymes to enhance antioxidant defenses; (3) scavenge free radicals and prevent oxidant production in mitochondria, and (4) repair mitochondrial membrane. Then, we discuss the relationships among mt-nutrient deficiency, mitochondrial decay, and cognitive dysfunction, and summarize available evidence suggesting an effect of mt-nutrient supplementation on AD and PD. It appears that greater effects might be obtained by longer-term administration of combinations of mt-nutrients. Thus, optimal doses of combinations of mt-nutrients to delay and repair mitochondrial decay could be a strategy for preventing and treating cognitive dysfunction, including AD and PD.

Transition between acute and chronic hepatotoxicity in mice is associated with impaired energy metabolism and induction of mitochondrial heme oxygenase-1

The formation of protein inclusions is frequently associated with chronic metabolic diseases. In mice, short-term intoxication with 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) leads to hepatocellular damage indicated by elevated serum liver enzyme activities, whereas only minor morphological changes are observed. Conversely, chronic administration of DDC for several weeks results in severe morphological damage, characterized by hepatocellular ballooning, disruption of the intermediate filament cytoskeleton, and formation of Mallory-Denk bodies consisting predominantly of misfolded keratins, Sqstm1/p62, and heat shock proteins. To evaluate the mechanistic underpinnings for this dichotomy we dissected the time-course of DDC intoxication for up to 10 weeks. We determined body weight change, serum liver enzyme activities, morphologic alterations, induction of antioxidant response (heme oxygenase-1, HO-1), oxidative damage and ATP content in livers as well as respiration, oxidative damage and the presence and activity of HO-1 in endoplasmic reticulum and mitochondria (mtHO-1). Elevated serum liver enzyme activity and oxidative liver damage were already present at early intoxication stages without further subsequent increase. After 2 weeks of intoxication, mice had transiently lost 9% of their body weight, liver ATP-content was reduced to 58% of controls, succinate-driven respiration was uncoupled from ATP-production and antioxidant response was associated with the appearance of catalytically active mtHO-1. Oxidative damage was associated with both acute and chronic DDC toxicity whereas the onset of chronic intoxication was specifically associated with mitochondrial dysfunction which was maximal after 2 weeks of intoxication. At this transition stage, adaptive responses involving mtHO-1 were induced, indirectly leading to improved respiration and preventing further drop of ATP levels. Our observations clearly demonstrate principally different mechanisms for acute and chronic toxic damage.

The negative impact of α-ketoglutarate dehydrogenase complex deficiency on matrix substrate-level phosphorylation

A decline in α-ketoglutarate dehydrogenase complex (KGDHC) activity has been associated with neurodegeneration. Provision of succinyl-CoA by KGDHC is essential for generation of matrix ATP (or GTP) by substrate-level phosphorylation catalyzed by succinyl-CoA ligase. Here, we demonstrate ATP consumption in respiration-impaired isolated and in situ neuronal somal mitochondria from transgenic mice with a deficiency of either dihydrolipoyl succinyltransferase (DLST) or dihydrolipoyl dehydrogenase (DLD) that exhibit a 20-48% decrease in KGDHC activity. Import of ATP into the mitochondrial matrix of transgenic mice was attributed to a shift in the reversal potential of the adenine nucleotide translocase toward more negative values due to diminished matrix substrate-level phosphorylation, which causes the translocase to reverse prematurely. Immunoreactivity of all three subunits of succinyl-CoA ligase and maximal enzymatic activity were unaffected in transgenic mice as compared to wild-type littermates. Therefore, decreased matrix substrate-level phosphorylation was due to diminished provision of succinyl-CoA. These results were corroborated further by the finding that mitochondria from wild-type mice respiring on substrates supporting substrate-level phosphorylation exhibited ~30% higher ADP-ATP exchange rates compared to those obtained from DLST(+/-) or DLD(+/-) littermates. We propose that KGDHC-associated pathologies are a consequence of the inability of respiration-impaired mitochondria to rely on "in-house" mitochondrial ATP reserves.

Interaction of NO with Cu and heme-bound Aβ peptides associated with Alzheimer's disease

Reduced Cu and heme has been invoked to be involved in Alzheimer's disease (AD). Recently the Aβ peptides have been demonstrated to bind heme and Cu simultaneously, and this complex produces significantly more toxic partially reduced oxygen species (PROS) than the Cu or heme-bound Aβ peptides. Here a combination of absorption, EPR, and resonance Raman spectroscopy along with kinetic assays are used to investigate the interaction of nitric oxide (NO) with the physiologically relevant form of Cu and heme-bound Aβ peptides, since a down-regulation of nitric oxide synthase activity is observed in patients suffering from AD. The data indicate that NO oxidizes the Cu(I) sites, making them less toxic toward PROS generation and releases heme from the Aβ peptides ameliorating the effects of heme binding to Aβ peptides associated with AD. This process involves a tyrosine-mediated electron transfer between the Cu and heme sites. These results provide a mechanistic pathway for the possible protective role of NO in AD.

Iron and genome stability: an update

Iron is an essential micronutrient which is required in a relatively narrow range for maintaining metabolic homeostasis and genome stability. Iron participates in oxygen transport and mitochondrial respiration as well as in antioxidant and nucleic acid metabolism. Iron deficiency impairs these biological pathways, leading to oxidative stress and possibly carcinogenesis. Iron overload has been linked to genome instability as well as to cancer risk increase, as seen in hereditary hemochromatosis. Iron is an extremely reactive transition metal that can interact with hydrogen peroxide to generate hydroxyl radicals that form the 8-hydroxy-guanine adduct, cause point mutations as well as DNA single and double strand breaks. Iron overload also induces DNA hypermethylation and can reduce telomere length. The current Recommended Dietary Allowances (RDA) for iron, according with Institute of Medicine Dietary Reference Intake (DRI), is based in the concept of preventing anemia, and ranges from 7mg/day to 18mg/day depending on life stage and gender. Pregnant women need 27mg/day. The maximum safety level for iron intake, the Upper Level (UL), is 40-45mg/day, based on the prevention of gastrointestinal distress associated to high iron intakes. Preliminary evidence indicates that 20mg/day iron, an intake slightly higher than the RDA, may reduce the risk of gastrointestinal cancer in the elderly as well as increasing genome stability in lymphocytes of children and adolescents. Current dietary recommendations do not consider the concept of genome stability which is of concern because damage to the genome has been linked to the origin and progression of many diseases and is the most fundamental pathology. Given the importance of iron for homeostasis and its potential influence over genome stability and cancer it is recommended to conduct further studies that conclusively define these relationships.

Impaired iron status in aging research

Aging is associated with disturbances in iron metabolism and storage. During the last decade, remarkable progress has been made toward understanding their cellular and molecular mechanisms in aging and age-associated diseases using both cultured cells and animal models. The field has moved beyond descriptive studies to potential intervention studies focusing on iron chelation and removal. However, some findings remain controversial and inconsistent. This review summarizes important features of iron dyshomeostasis in aging research with a particular emphasis on current knowledge of the mechanisms underlying age-associated disorders in rodent models.

The effect of 5-aminolevulinic acid on cytochrome c oxidase activity in mouse liver

Background

5-Aminolevulinic acid (ALA) is a precursor of heme that is fundamentally important in aerobic energy metabolism. Among the enzymes involved in aerobic energy metabolism, cytochrome c oxidase (COX) is crucial. In this study, the effect of ALA on cytochrome c oxidase activity was measured.

Findings

c57BL/6N species of mice were administered ALA orally for 15 weeks. After ALA administration, mice were sacrificed and livers were obtained. COX activity in mitochondria from ALA-administered mouse livers was 1.5-fold higher than that in mitochondria from PBS-administered mouse livers (P < 0.05). Furthermore, ATP levels in ALA-administered mouse livers were much higher than those in PBS-administered mouse livers. These data suggest that oral administration of ALA promotes aerobic energy metabolism, especially COX activity.

Conclusions

This is the first report of a drug that functions in aerobic energy metabolism directly. Since COX activity is decreased in various diseases and aging, the pharmacological effects of ALA will be expanding.

Acquisition of temozolomide chemoresistance in gliomas leads to remodeling of mitochondrial electron transport chain

Temozolomide (TMZ) is an oral alkylating agent used for the treatment of high-grade gliomas. Acquired chemoresistance is a severe limitation to this therapy with more than 90% of recurrent gliomas showing no response to a second cycle of chemotherapy. Efforts to better understand the underlying mechanisms of acquired chemoresistance to TMZ and potential strategies to overcome chemoresistance are, therefore, critically needed. TMZ methylates nuclear DNA and induces cell death; however, the impact on mitochondria DNA (mtDNA) and mitochondrial bioenergetics is not known. Herein, we tested the hypothesis that TMZ-mediated alterations in mtDNA and respiratory function contribute to TMZ-dependent acquired chemoresistance. Using an in vitro model of TMZ-mediated acquired chemoresistance, we report 1) a decrease in mtDNA copy number and the presence of large heteroplasmic mtDNA deletions in TMZ-resistant glioma cells, 2) remodeling of the entire electron transport chain with significant decreases of complexes I and V and increases of complexes II/III and IV, and 3) pharmacologic and genetic manipulation of cytochrome c oxidase, which restores sensitivity to TMZ-dependent apoptosis in resistant glioma cells. Importantly, human primary and recurrent pairs of glioblastoma multiforme (GBM) biopsies as well as primary and TMZ-resistant GBM xenograft lines exhibit similar remodeling of the ETC. Overall these results suggest that TMZ-dependent acquired chemoresistance may be due to a mitochondrial adaptive response to TMZ genotoxic stress with a major contribution from cytochrome c oxidase. Thus, abrogation of this adaptive response may reverse chemoresistance and restore sensitivity to TMZ, providing a strategy for improved therapeutic outcomes in GBM patients.

Prevention of mutation, cancer, and other age-associated diseases by optimizing micronutrient intake

I review three of our research efforts which suggest that optimizing micronutrient intake will in turn optimize metabolism, resulting in decreased DNA damage and less cancer as well as other degenerative diseases of aging. (1) Research on delay of the mitochondrial decay of aging, including release of mutagenic oxidants, by supplementing rats with lipoic acid and acetyl carnitine. (2) The triage theory, which posits that modest micronutrient deficiencies (common in much of the population) accelerate molecular aging, including DNA damage, mitochondrial decay, and supportive evidence for the theory, including an in-depth analysis of vitamin K that suggests the importance of achieving optimal micronutrient intake for longevity. (3) The finding that decreased enzyme binding constants (increased Km) for coenzymes (or substrates) can result from protein deformation and loss of function due to an age-related decline in membrane fluidity, or to polymorphisms or mutation. The loss of enzyme function can be compensated by a high dietary intake of any of the B vitamins, which increases the level of the vitamin-derived coenzyme. This dietary remediation illustrates the importance of understanding the effects of age and polymorphisms on optimal micronutrient requirements. Optimizing micronutrient intake could have a major effect on the prevention of cancer and other degenerative diseases of aging.

The Fowler syndrome-associated protein FLVCR2 is an importer of heme

Mutations in FLVCR2, a cell surface protein related by homology and membrane topology to the heme exporter/retroviral receptor FLVCR1, have recently been associated with Fowler syndrome, a vascular disorder of the brain. We previously identified FLVCR2 to function as a receptor for FY981 feline leukemia virus (FeLV). However, the cellular function of FLVCR2 remains unresolved. Here, we report the cellular function of FLVCR2 as an importer of heme, based on the following observations. First, FLVCR2 binds to hemin-conjugated agarose, and binding is competed by free hemin. Second, mammalian cells and Xenopus laevis oocytes expressing FLVCR2 display enhanced heme uptake. Third, heme import is reduced after the expression of FLVCR2-specific small interfering RNA (siRNA) or after the binding of the FY981 FeLV envelope protein to the FLVCR2 receptor. Finally, cells overexpressing FLVCR2 are more sensitive to heme toxicity, a finding most likely attributable to enhanced heme uptake. Tissue expression analysis indicates that FLVCR2 is expressed in a broad range of human tissues, including liver, placenta, brain, and kidney. The identification of a cellular function for FLVCR2 will have important implications in elucidating the pathogenic mechanisms of Fowler syndrome and of phenotypically associated disorders.

ABCG2 reduces ROS-mediated toxicity and inflammation: a potential role in Alzheimer's disease

Alzheimer's disease is characterized by accumulation and deposition of Aβ peptides in the brain. Aβ deposition generates reactive-oxygen species (ROS), which are involved in Alzheimer's inflammatory and neurodegenerative pathology. We have previously observed that, in Alzheimer's disease brain, ABCG2 is up-regulated and AP-1 is activated, but NF-κB is not activated. In the present study, we examine the roles and mechanism of ABCG2 on ROS generation, inflammatory gene expression and signaling, heme homeostasis and Aβ production in cell models and on inflammatory signaling and Aβ deposition in Abcg2-knockout and wild-type mice. Our results show that ABCG2 plays a protective role against oxidative stress by decreasing ROS generation, enhancing antioxidant capacity, regulating heme level, and inhibiting inflammatory response in cell models. ABCG2 inhibits NF-κB activation but has less effect on AP-1 activation induced by ROS. This results in inhibition of interleukin-8 and growth-related oncogene (GRO) expression induced by ROS via NF-κB pathway. Abcg2 deficiency increased Aβ deposition and NF-κB activation in the brains of Abcg2-knockout mice compared with controls. These findings suggest that ABCG2 may relieve oxidative stress and inflammatory response via inhibiting NF-κB signaling pathway in cell models and brain tissues and thus may play a potential protective role in Alzheimer's neuroinflammatory response.

Heme deficiency in Alzheimer's disease: a possible connection to porphyria

Mechanisms that cause Alzheimer's disease (AD), an invariably fatal neurodegenerative disease, are unknown. Important recent data indicate that neuronal heme deficiency may contribute to AD pathogenesis. If true, factors that contribute to the intracellular heme deficiency could potentially alter the course of AD. The porphyrias are metabolic disorders characterized by enzyme deficiencies in the heme biosynthetic pathway. We hypothesize that AD may differ significantly in individuals possessing the genetic trait for an acute hepatic porphyria. We elaborate on this hypothesis and briefly review the characteristics of the acute hepatic porphyrias that may be relevant to AD. We note the proximity of genes encoding enzymes of the heme biosynthesis pathway to genetic loci linked to sporadic, late-onset AD. In addition, we suggest that identification of individuals carrying the genetic trait for acute porphyria may provide a unique resource for investigating AD pathogenesis and inform treatment and management decisions.

Responses of the European flounder Platichthys flesus to the chemical stress in estuaries: load of contaminants, gene expression, cellular impact and growth rate

European flounder responses to the chemical stress were assessed by a comparative approach on four estuaries displaying contrasted patterns of contamination. The contamination typology of the estuaries was investigated by individual measurements of contaminants in fish. Molecular and physiological responses were studied by gene expression, genotoxicity, neurotoxicity and growth rate. Fishes in contaminated estuaries were characterized by high levels of bioaccumulated contaminants, slow energetic metabolism and reduced growth rate, in contrast to the fish responses in the reference site. A seasonal effect was highlighted for contaminated flounder populations, with high PCB levels, high genotoxicity and elevated detoxification rate in summer compared with winter.

The emerging role of iron dyshomeostasis in the mitochondrial decay of aging

Recent studies show that cellular and mitochondrial iron increases with age. Iron overload, especially in mitochondria, increases the availability of redox-active iron, which may be a causal factor in the extensive age-related biomolecular oxidative damage observed in aged organisms. Such damage is thought to play a major role in the pathogenesis of iron overload diseases and age-related pathologies. Indeed, recent findings of the beneficial effects of iron manipulation in life extension in Caenorhabditis elegans, Drosophila and transgenic mice have sparked a renewed interest in the potential role of iron in longevity. A substantial research effort now focuses on developing and testing safe pharmacologic interventions to combat iron dyshomeostasis in aging, acute injuries and in iron overload disorders.

Optimal micronutrients delay mitochondrial decay and age-associated diseases

Three of our research efforts are reviewed, which suggest that optimizing metabolism will delay aging and the diseases of aging in humans. (1) Research on delay of the mitochondrial decay of aging by supplementing rats with lipoic acid and acetyl carnitine. (2) The triage theory, which posits that modest micronutrient deficiencies (common in much of the population) accelerate molecular aging, including mitochondrial decay, and supportive evidence, including an analysis in depth of vitamin K, that suggests the importance of achieving optimal micronutrient intake for longevity. (3) The finding that decreased enzyme binding constants (increased Km) for coenzymes (or substrates) can result from protein deformation and loss of function due to loss of membrane fluidity with age, or to polymorphisms or mutation. The loss of enzyme function can be ameliorated by high doses of a B vitamin, which raises coenzyme levels, and indicates the importance of understanding the effects of age, or polymorphisms, on micronutrient requirements.

Effects of extensively oxidized low-density lipoprotein on mitochondrial function and reactive oxygen species in porcine aortic endothelial cells

Atherosclerotic cardiovascular disease is the leading cause of mortality in the Western world. Dysfunction of the mitochondrial respiratory chain and overproduction of reactive oxygen species (ROS) are associated with atherosclerosis and cardiovascular disease. Oxidation increases the atherogenecity of LDL. Oxidized LDL may be apoptotic or nonapoptotic for vascular endothelial cells (EC), depending on the intensity of oxidation. A previous study demonstrated that nonapoptotic oxidized LDL increased activity of mitochondrial complex I in human umbilical vein EC. The present study examined the impact of extensively oxidized LDL (eoLDL) on oxygen consumption and the activities of key enzymes in the mitochondrial respiratory chain of cultured porcine aortic EC. Oxygraphy detected that eoLDL significantly reduced oxygen consumption in various mitochondrial complexes. Treatment with eoLDL significantly decreased NADH-ubiquinone dehydrogenase (complex I), succinate cytochrome c reductase (complex II/III), ubiquinone cytochrome c reductase (complex III), and cytochrome c oxidase (complex IV) activities and the NAD+-to-NADH ratio in EC compared with mildly oxidized LDL, LDL, or vehicle. Butylated hydroxytoluene, a potent antioxidant, normalized eoLDL-induced reductions in complex I and III enzyme activity in EC. Mitochondria-associated intracellular ROS and release of ROS from EC were significantly increased after eoLDL treatment. These findings suggest that eoLDL impairs enzyme activity in mitochondrial respiratory chain complexes and increases ROS generation from mitochondria of arterial EC. Collectively, these effects could contribute to vascular injury and atherogenesis under conditions of hypercholesterolemia and oxidative stress.

A possible link between iron deficiency and gastrointestinal carcinogenesis

There is definitive evidence that iron overload induces oxidative stress and DNA damage, which can enhance carcinogenic risk. However, other evidence suggests that iron deficiency and anemia also increase oxidative stress and DNA damage, which might increase carcinogenesis risk, especially in the gastrointestinal (GI) tract. The aim of this review is to provide essential background information for the accurate interpretation of future research on iron deficiency and increased GI cancer risk. Based on clinical, epidemiological, and experimental evidence, we discuss how iron deficiency might contribute to increased cancer risk through the impairment of several iron-dependent metabolic functions that are related to genome protection and maintenance (e.g., immune responses against cancer-initiated cells, metabolism of toxic compounds, and redox regulation of DNA biosynthesis and repair). Some epidemiological studies have indicated increased risk of GI tumors among individuals with low iron intake or low somatic iron stores, and in vivo data from rodent cancer models indicates the early progression of GI tumors during iron deficiency. Given the preliminary but consistent evidence relating iron deficiency to cancer risk and the fact that iron deficiency affects about one third of the world's population, further studies are needed to define the extent to which iron deficiency might increase GI cancer risk.

Cause and consequence: mitochondrial dysfunction initiates and propagates neuronal dysfunction, neuronal death and behavioral abnormalities in age-associated neurodegenerative diseases

Age-related neurodegenerative diseases are associated with mild impairment of oxidative metabolism and accumulation of abnormal proteins. Within the cell, the mitochondria appears to be a dominant site for initiation and propagation of disease processes. Shifts in metabolism in response to mild metabolic perturbations may decrease the threshold for irreversible injury in response to ordinarily sublethal metabolic insults. Mild impairment of metabolism accrue from and lead to increased reactive oxygen species (ROS). Increased ROS change cell signaling via post-transcriptional and transcriptional changes. The cause and consequences of mild impairment of mitochondrial metabolism is one focus of this review. Many experiments in tissues from humans support the notion that oxidative modification of the alpha-ketoglutarate dehydrogenase complex (KGDHC) compromises neuronal energy metabolism and enhances ROS production in Alzheimer's Disease (AD). These data suggest that cognitive decline in AD derives from the selective tricarboxylic acid (TCA) cycle abnormalities. By contrast in Huntington's Disease (HD), a movement disorder with cognitive features distinct form AD, complex II+III abnormalities may dominate. These distinct mitochondrial abnormalities culminate in oxidative stress, energy dysfunction, and aberrant homeostasis of cytosolic calcium. Cytosolic calcium, elevations even only transiently, leads to hyperactivity of a number of enzymes. One calcium-activated enzyme with demonstrated pathophysiological import in HD and AD is transglutaminase (TGase). TGase is a crosslinking enzymes that can modulate transcription, inactivate metabolic enzymes, and cause aggregation of critical proteins. Recent data indicate that TGase can silence expression of genes involved in compensating for metabolic stress. Altogether, our results suggest that increasing KGDHC via inhibition of TGase or via a host of other strategies to be described would be effective therapeutic approaches in age-associated neurodegenerative diseases.

Cell survival under stress is enhanced by a mitochondrial ATP-binding cassette transporter that regulates hemoproteins

The ATP-binding cassette (ABC) transporter ABCB6 localizes to the mitochondria, where it imports porphyrins and up-regulates de novo porphyrin synthesis. If ABCB6 also increases the intracellular heme concentration, it may broadly affect the regulation and physiology of cellular hemoproteins. We tested whether the ability of ABCB6 to accelerate de novo porphyrin biosynthesis alters mitochondrial and extramitochondrial heme levels. ABCB6 overexpression increased the quantity of cytosolic heme but did not affect mitochondrial heme levels. We then tested whether the increased extramitochondrial heme would increase the concentration and/or activity of cellular hemoproteins (hemoglobin, catalase, and cytochrome c oxidase). ABCB6 overexpression increased the activity and quantity of hemoproteins found in several subcellular compartments, and reduction of ABCB6 function (by small interfering RNA or knockout) reversed these findings. In complementary studies, suppression of ABCB6 expression sensitized cells to stress induced by peroxide and cyanide, whereas overexpression of ABCB6 protected against both stressors. Our findings show that the ability of ABCB6 to increase cytosolic heme levels produces phenotypic changes in hemoproteins that protect cells from certain stresses. Collectively, these findings have implications for the health and survival of both normal and abnormal cells, which rely on heme for multiple cellular processes.

Human and rodent amyloid-beta peptides differentially bind heme: relevance to the human susceptibility to Alzheimer's disease

Amyloid-beta (Abeta) peptides are implicated in the neurodegeneration of Alzheimer's disease (AD). We previously investigated the mechanism of neurotoxicity of Abeta and found that human Abeta (huAbeta) binds and depletes heme, forming an Abeta-heme complex with peroxidase activity. Rodent Abeta (roAbeta) is identical to huAbeta, except for three amino acids within the proposed heme-binding motif (Site-H). We studied and compared heme-binding between roAbeta and huAbeta. Unlike roAbeta, huAbeta binds heme tightly (K(d)=140+/-60 nM) and forms a peroxidase. The plot of bound (huAbeta-heme) vs. unbound heme fits best to a two site binding hyperbola, suggesting huAbeta possesses two heme-binding sites. Consistently, a second high affinity heme-binding site was identified in the lipophilic region (site-L) of huAbeta (K(d)=210+/-80 nM). The plot of (roAbeta-heme) vs. unbound heme, on the other hand, was different as it fits best to a sigmoidal binding curve, indicating different binding and lower affinity of roAbeta for heme (K(d)=1 microM). The effect of heme-binding to site-H on heme-binding to site-L in roAbeta and huAbeta is discussed. While both roAbeta and huAbeta form aggregates equally, rodents lack AD-like neuropathology. High huAbeta/heme ratio increases the peroxidase activity. These findings suggest that depletion of regulatory heme and formation of Abeta-heme peroxidase contribute to huAbeta's neurotoxicity in the early stages of AD. Phylogenic variations in the amino acid sequence of Abeta explain tight heme-binding to huAbeta and likely contribute to the increased human susceptibility to AD.

Inhibition of heme synthesis alters Amyloid Precursor Protein processing

Decay of mitochondria, energy failure and increased oxidative stress are features commonly detected in brains from Alzheimer's disease (AD) patients. Recent findings indicate that neuronal heme deficiency may contribute to the appearance of those cytopathologies and potentially alter the course of AD. We repressed heme synthesis in cells by inhibiting ferrochelatase enzyme with small interfering RNA and N-methylprotoporphyrin IX. The treatments induced a severe perturbation of mitochondria and energy production, with decrease of the subunit II of Cytochrome c Oxidase, alteration of the membrane potential and a 50% reduction of intracellular ATP. The state and processing of the Amyloid Precursor Protein (APP) was also affected, with the appearance of APP aggregates and a significant decrease (30-40%) of sAPPalpha secretion, associated with perturbation of ADAM10 and TACE, enzymes involved in the alpha-secretase cleavage. The production of sAPPbeta was increased, without augment of Amyloid beta generation. Our findings strengthen the hypothesis that a reduced availability of heme may play a role in AD pathogenesis.

Medication-induced mitochondrial damage and disease

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.

Dynamin-like protein 1 reduction underlies mitochondrial morphology and distribution abnormalities in fibroblasts from sporadic Alzheimer's disease patients

Mitochondrial function relies heavily on its morphology and distribution, alterations of which have been increasingly implicated in neurodegenerative diseases, such as Alzheimer's disease (AD). In this study, we found abnormal mitochondrial distribution characterized by elongated mitochondria that accumulated in perinuclear areas in 19.3% of sporadic AD (sAD) fibroblasts, which was in marked contrast to their normally even cytoplasmic distribution in the majority of human fibroblasts from normal subjects (>95%). Interestingly, levels of dynamin-like protein 1 (DLP1), a regulator of mitochondrial fission and distribution, were decreased significantly in sAD fibroblasts. To explore the potential role of DLP1 in mediating mitochondrial abnormalities in sAD fibroblasts, both the overexpression of a dominant negative DLP1 mutant and the reduced expression of DLP1 by miR RNAi in human fibroblasts from normal subjects significantly increased mitochondrial abnormalities. Moreover, overexpression of wild-type DLP1 in sAD fibroblasts rescued these mitochondrial abnormalities. Based on these data, we conclude that DLP1 reduction causes mitochondrial abnormalities in sAD fibroblasts. We further demonstrate that elevated oxidative stress and increased amyloid beta production are likely the potential pathogenic factors that cause DLP1 reduction and abnormal mitochondrial distribution in AD cells.

Amino acids and mitochondrial biogenesis

Mitochondria are sources of energy production through their role in producing adenosine triphosphate for cell metabolism. Defective mitochondrial biogenesis and function play relevant roles in the pathophysiology of relevant diseases, including obesity, diabetes mellitus, myopathies, and neurodegenerative diseases. Their function is the product of synthesis of macromolecules within the mitochondria and import of proteins and lipids synthesized outside the organelles. Both are required for mitochondrial proliferation and may also facilitate the growth of preexisting mitochondria. Recent evidence indicates that these events are regulated in a complex way by several agonists and environmental conditions, through activation of specific signaling pathways and transcription factors. Nitric oxide (NO) appears to be a novel modulator of mitochondrial biogenesis. High levels of NO acutely inhibit cell respiration by binding to cytochrome c oxidase. Conversely, chronic, low-grade increases of NO stimulate mitochondrial biogenesis in diverse cell types. Here, we suggest that some types of nutrients, including specific mixtures of amino acids, may improve mitochondrial biogenesis and energy production in energy-defective conditions by increasing endothelial NO synthase expression.

Mechanisms of mitochondrial dysfunction and energy deficiency in Alzheimer's disease

Several studies have demonstrated aberrations in the Electron Transport Complexes (ETC) and Krebs (TCA) cycle in Alzheimer's disease (AD) brain. Optimal activity of these key metabolic pathways depends on several redox active centers and metabolites including heme, coenzyme Q, iron-sulfur, vitamins, minerals, and micronutrients. Disturbed heme metabolism leads to increased aberrations in the ETC (loss of complex IV), dimerization of APP, free radical production, markers of oxidative damage, and ultimately cell death all of which represent key cytopathologies in AD. The mechanism of mitochondrial dysfunction in AD is controversial. The observations that Abeta is found both in the cells and in the mitochondria and that Abeta binds with heme may provide clues to this mechanism. Mitochondrial Abeta may interfere with key metabolites or metabolic pathways in a manner that overwhelms the mitochondrial mechanisms of repair. Identifying the molecular mechanism for how Abeta interferes with mitochondria and that explains the established key cytopathologies in AD may also suggest molecular targets for therapeutic interventions. Below we review recent studies describing the possible role of Abeta in altered energy production through heme metabolism. We further discuss how protecting mitochondria could confer resistance to oxidative and environmental insults. Therapies targeted at protecting mitochondria may improve the clinical outcome of AD patients.

Copper supplementation increases yeast life span under conditions requiring respiratory metabolism

To further exploit yeast as a model for cellular aging we have modified the replicative life span assay to force respiration, by replacing glucose with the non-fermentable carbon source glycerol. The growth rates of several different strains varied greatly, with doubling times ranging from 2.7 to 7 h. Life spans of all strains were lower on media containing glycerol than on media containing glucose. However, supplementation of glycerol-containing media with copper resulted in increases in life span of between 17 and 72%; life spans equivalent to or beyond those obtained on glucose media. Addition of copper to glucose medium had no effect on life span. Microarray analysis showed that genes responsible for high affinity import of copper display reduced expression upon addition of copper, while most genes showed no change in expression. No differences in growth rate, oxygen uptake, or the levels of subunit II of the copper-containing cytochrome c oxidase were found between cultures of yeast grown with or without copper supplementation. Copper supplementation greatly extended the life span of sod1 and sod2 strains, suggesting that addition of copper may reduce the generation of superoxide. Forcing yeast to respire places an emphasis on mitochondrial function and may aid in the identification of factors involved in aging in other respiratory-dependent organisms.

Mitochondrial dysfunction and molecular pathways of disease

Since the first mitochondrial dysfunction was described in the 1960s, the medicine has advanced in its understanding the role mitochondria play in health, disease, and aging. 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, have underlying pathophysiological mechanisms in common, namely reactive oxygen species (ROS) production, the accumulation of mitochondrial DNA (mtDNA) damage, resulting in mitochondrial dysfunction. Antioxidant therapies hold promise for improving mitochondrial performance. Physicians seeking systematic treatments for their patients might consider testing urinary organic acids to determine how best to treat them. If in the next 50 years advances in mitochondrial treatments match the immense increase in knowledge about mitochondrial function that has occurred in the last 50 years, mitochondrial diseases and dysfunction will largely be a medical triumph.