Pantothenate is required in Neurospora crassa for assembly of subunit peptides of cytochrome c oxidase and ATPase/ATP synthase

Neuroprotective Effects of Dexpanthenol on Rabbit Spinal Cord Ischemia/Reperfusion Injury Model

OBJECTIVE

Dexpanthenol (DXP) reportedly protects tissues against oxidative damage in various inflammation models. This study aimed to evaluate its effects on oxidative stress, inflammation, apoptosis, and neurological recovery in an experimental rabbit spinal cord ischemia/reperfusion injury (SCIRI) model.

METHODS

Rabbits were randomized into 5 groups of 8 animals each: group 1 (control), group 2 (ischemia), group 3 (vehicle), group 4 (methylprednisolone, 30 mg/kg), and group 5 (DXP, 500 mg/kg). The control group underwent laparotomy only, whereas other groups were subjected to spinal cord ischemia by aortic occlusion (just caudal to the 2 renal arteries) for 20 min. After 24 h, a modified Tarlov scale was employed to record neurological examination results. Malondialdehyde and caspase-3 levels and catalase and myeloperoxidase activities were analyzed in tissue and serum samples. Xanthine oxidase activity was measured in the serum. Histopathological and ultrastructural evaluations were also performed in the spinal cord.

RESULTS

After SCIRI, serum and tissue malondialdehyde and caspase-3 levels and myeloperoxidase and serum xanthine oxidase activities were increased (P < 0.05-0.001). However, serum and tissue catalase activity decreased significantly (P < 0.001). DXP treatment was associated with lower malondialdehyde and caspase-3 levels and reduced myeloperoxidase and xanthine oxidase activities but increased catalase activity (P < 0.05-0.001). Furthermore, DXP was associated with better histopathological, ultrastructural, and neurological outcome scores.

CONCLUSIONS

This study was the first to evaluate antioxidant, anti-inflammatory, antiapoptotic, and neuroprotective effects of DXP on SCIRI. Further experimental and clinical investigations are warranted to confirm that DXP can be administered to treat SCIRI.

Mitochondrial Complex I Is a Global Regulator of Secondary Metabolism, Virulence and Azole Sensitivity in Fungi

Recent estimates of the global burden of fungal disease suggest that that their incidence has been drastically underestimated and that mortality may rival that of malaria or tuberculosis. Azoles are the principal class of antifungal drug and the only available oral treatment for fungal disease. Recent occurrence and increase in azole resistance is a major concern worldwide. Known azole resistance mechanisms include over—expression of efflux pumps and mutation of the gene encoding the target protein cyp51a, however, for one of the most important fungal pathogens of humans, Aspergillus fumigatus, much of the observed azole resistance does not appear to involve such mechanisms. Here we present evidence that azole resistance in A. fumigatus can arise through mutation of components of mitochondrial complex I. Gene deletions of the 29.9KD subunit of this complex are azole resistant, less virulent and exhibit dysregulation of secondary metabolite gene clusters in a manner analogous to deletion mutants of the secondary metabolism regulator, LaeA. Additionally we observe that a mutation leading to an E180D amino acid change in the 29.9 KD subunit is strongly associated with clinical azole resistant A. fumigatus isolates. Evidence presented in this paper suggests that complex I may play a role in the hypoxic response and that one possible mechanism for cell death during azole treatment is a dysfunctional hypoxic response that may be restored by dysregulation of complex I. Both deletion of the 29.9 KD subunit of complex I and azole treatment alone profoundly change expression of gene clusters involved in secondary metabolism and immunotoxin production raising potential concerns about long term azole therapy.

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.

Low micronutrient intake may accelerate the degenerative diseases of aging through allocation of scarce micronutrients by triage

Inadequate dietary intakes of vitamins and minerals are widespread, most likely due to excessive consumption of energy-rich, micronutrient-poor, refined food. Inadequate intakes may result in chronic metabolic disruption, including mitochondrial decay. Deficiencies in many micronutrients cause DNA damage, such as chromosome breaks, in cultured human cells or in vivo. Some of these deficiencies also cause mitochondrial decay with oxidant leakage and cellular aging and are associated with late onset diseases such as cancer. I propose DNA damage and late onset disease are consequences of a triage allocation response to micronutrient scarcity. Episodic shortages of micronutrients were common during evolution. Natural selection favors short-term survival at the expense of long-term health. I hypothesize that short-term survival was achieved by allocating scarce micronutrients by triage, in part through an adjustment of the binding affinity of proteins for required micronutrients. If this hypothesis is correct, micronutrient deficiencies that trigger the triage response would accelerate cancer, aging, and neural decay but would leave critical metabolic functions, such as ATP production, intact. Evidence that micronutrient malnutrition increases late onset diseases, such as cancer, is discussed. A multivitamin-mineral supplement is one low-cost way to ensure intake of the Recommended Dietary Allowance of micronutrients throughout life.

Mitochondrial function and toxicity: role of the B vitamin family on mitochondrial energy metabolism

The B vitamins are water-soluble vitamins required as coenzymes for enzymes essential for cell function. This review focuses on their essential role in maintaining mitochondrial function and on how mitochondria are compromised by a deficiency of any B vitamin. Thiamin (B1) is essential for the oxidative decarboxylation of the multienzyme branched-chain ketoacid dehydrogenase complexes of the citric acid cycle. Riboflavin (B2) is required for the flavoenzymes of the respiratory chain, while NADH is synthesized from niacin (B3) and is required to supply protons for oxidative phosphorylation. Pantothenic acid (B5) is required for coenzyme A formation and is also essential for alpha-ketoglutarate and pyruvate dehydrogenase complexes as well as fatty acid oxidation. Biotin (B7) is the coenzyme of decarboxylases required for gluconeogenesis and fatty acid oxidation. Pyridoxal (B6), folate and cobalamin (B12) properties are reviewed elsewhere in this issue. The experimental animal and clinical evidence that vitamin B therapy alleviates B deficiency symptoms and prevents mitochondrial toxicity is also reviewed. The effectiveness of B vitamins as antioxidants preventing oxidative stress toxicity is also reviewed.

Mineral and vitamin deficiencies can accelerate the mitochondrial decay of aging

Mitochondrial oxidative decay, which is a major contributor to aging, is accelerated by many common micronutrient deficiencies. One major mechanism is inhibition of the pathway of heme biosynthesis in mitochondria, which causes a deficit of heme-a. Heme-a, only found in Complex IV, is selectively diminished, resulting in oxidant leakage and accelerated mitochondrial decay, which leads to DNA damage, neural decay, and aging. We emphasize those deficiencies, which appear to cause damage through this mechanism, particularly minerals such as iron (25% of menstruating women ingest <50% of the RDA) or zinc (10% of the population ingest <50% of the RDA). Several vitamin deficiencies, such as biotin or pantothenic acid, also increase mitochondrial oxidants through this mechanism. Additionally, other minerals such as magnesium and manganese that play a role in mitochondrial metabolism, but do not affect heme directly, are discussed. An optimum intake of micronutrients could tune up metabolism and give a marked increase in health, particularly for the poor, elderly, and obese, at little cost.

Delaying the mitochondrial decay of aging

Mitochondrial dysfunction may be a principal underlying event in aging, including the degenerative diseases of aging such as brain degeneration. Mitochondria provide energy for basic metabolic processes, and their decay with age impairs cellular metabolism and leads to cellular decline. Progress over the last decade in delaying the mitochondrial decay of aging is reviewed.

Executive Summary: Conference on Dietary Supplement Use in the Elderly - Proceedings of the Conference Held January 14-15, 2003, Natcher Auditorium, National Institutes of Health, Bethesda, MD

Several issues prompted the need for this conference. Among these were the reported high prevalence (> 50%) of use of supplements among individuals over 50 years of age, inadequate scientific evidence supporting the safety and benefits of use among these individuals, and a report issued by the General Accounting Office (GAO) in 2001. This GAO report entitled "Health Products for Seniors: 'Anti-Aging' Products Pose Potential for Physical and Economic Harm," arose from concerns among legislators that seniors were spending money from their limited incomes on products that were not only ineffective but also potentially harmful. The conference was organized around three sessions to address the issues highlighted above, which were usage of dietary supplements among the elderly, age-related changes and issues that affect the use of supplements, and the evidence base supporting the use of supplements in disease prevention and health maintenance. Each session was followed by a panel discussion. This Executive Summary is organized around the three major discussion topics. The summary does not explicitly follow the order of the conference presentations; rather it is intended to capture and examine the current research gaps in knowledge and identify future research opportunities. These research opportunities, as expressed by the conference speakers, panelists, and attendees are summarized at the end of this paper under five thematic areas: usage behaviors, methodology, pre-clinical studies and clinical studies, informational databases, and education and dissemination.

A role for supplements in optimizing health: the metabolic tune-up

An optimum intake of micronutrients and metabolites, which varies with age and genetic constitution, would tune up metabolism and give a marked increase in health, particularly for the poor, young, obese, and elderly, at little cost. (1) DNA damage. Deficiency of vitamins B-12, folic acid, B-6, C or E, or iron or zinc appears to mimic radiation in damaging DNA by causing single- and double-strand breaks, oxidative lesions or both. Half of the population may be deficient in at least one of these micronutrients. (2) The Km concept. Approximately 50 different human genetic diseases that are due to a poorer binding affinity (Km) of the mutant enzyme for its coenzyme can be remedied by feeding high-dose B vitamins, which raise levels of the corresponding coenzyme. Many polymorphisms also result in a lowered affinity of enzyme for coenzyme. (3) Mitochondrial oxidative decay. This decay, which is a major contributor to aging, can be ameliorated by feeding old rats the normal mitochondrial metabolites acetyl carnitine and lipoic acid at high levels. Many common micronutrient deficiencies, such as iron or biotin, cause mitochondrial decay with oxidant leakage leading to accelerated aging and neural decay.

NADH dehydrogenase in Neurospora crassa contains myristic acid covalently linked to the ND5 subunit peptide

The mitochondrial, proton-pumping NADH:ubiquinone oxidoreductase consists of at least 35 subunits whose synthesis is divided between the cytosol and mitochondria; this complex I catalyzes the first steps of mitochondrial electron transfer and proton translocation. Radiolabel from [(3)H]myristic acid was incorporated by Neurospora crassa into the mitochondrial-encoded, approximately 70 kDa ND5 subunit of NADH dehydrogenase, as shown by immunoprecipitation. This myristate apparently was linked to the peptide through an amide linkage at an invariant lysine residue (Lys546), based upon analyses of proteolysis products. The myristoylated lysine residue occurs in the predicted transmembrane helix 17 (residues 539-563) of ND5. A consensus amino acid sequence around this conserved residue exists in homologous subunits of NADH dehydrogenase. Cytochrome c oxidase subunit 1, in all prokaryotes and eukaryotes, contains this same consensus sequence surrounding the lysine which is myristoylated in N. crassa.

Cytochrome c oxidase in Neurospora crassa contains myristic acid covalently linked to subunit 1

Radiolabel from [3H]myristic acid was incorporated by Neurospora crassa into the core catalytic subunit 1 of cytochrome c oxidase (EC 1.9.3.1), as indicated by immunoprecipitation. This modification of the subunit, which was specific for myristic acid, represents an uncommon type of myristoylation through an amide linkage at an internal lysine, rather than an N-terminal glycine. The [3H]myristate, which was chemically recovered from the radiolabeled subunit peptide, modified an invariant Lys-324, based upon analyses of proteolysis products. This myristoylated lysine is found within one of the predicted transmembrane helices of subunit 1 and could contribute to the environment of the active site of the enzyme. The myristate was identified by mass spectrometry as a component of mature subunit 1 of a catalytically active, purified enzyme. To our knowledge, fatty acylation of a mitochondrially synthesized inner-membrane protein has not been reported previously.

Presence of an acyl carrier protein in NADH:ubiquinone oxidoreductase from bovine heart mitochondria

The amino-acid sequence of a subunit of NADH:ubiquinone oxidoreductase from bovine heart mitochondria has been determined and is closely related to those of acyl carrier proteins that are involved in fatty acid biosynthesis in Escherichia coli and plants. Evidence for the presence of covalently attached pantetheine-4'-phosphate in the bovine protein has been obtained by determination of the molecular mass of the isolated subunit by electrospray mass spectrometry, before and after incubation of the protein at alkaline pH under reducing conditions. This decreased the molecular mass from 10,751.6 to 10,449.4, a difference of 302.2 mass units; the value calculated from the protein sequence with one covalently attached pantetheine-4'-phosphate is 10,449.8. The acyl group which is removed by alkaline reduction, appears to be attached via a thioester linkage. By analogy with the bacterial protein it is likely that the attachment site of the pantetheine-4-phosphate is serine-44, which is found in a highly conserved region of the sequence. At present the function of the acyl carrier protein in mitochondrial complex I is not understood.

Pantothenic acid in health and disease

In summary, the vitamin pantothenic acid is an integral part of the acylation carriers, CoA and acyl carrier protein (ACP). The vitamin is readily available from diverse dietary sources, a fact which is underscored by the difficulty encountered in attempting to induce pantothenate deficiency. Although pantothenic acid deficiency has not been linked with any particular disease, deficiency of the vitamin results in generalized malaise clinically. In view of the fact that pantothenate is required for the synthesis of CoA, it is surprising that tissue CoA levels are not altered in pantothenate deficiency. This suggests that the cell is equipped to conserve its pantothenate content, possibly by a recycling mechanism for utilizing pantothenate obtained from degradation of pantothenate-containing molecules. Although the steps involved in the conversion of pantothenate to CoA have been characterized, much remains to be done to understand the regulation of CoA synthesis. In particular, in view of what is known about the in vitro regulation of pantothenate kinase, it is surprising that the enzyme is active in vivo, since factors that are known to inhibit the enzyme are present in excess of the concentrations known to inhibit the enzyme. Thus, other physiological regulatory factors (which are largely unknown) must counteract the effects of these inhibitors, since the pantothenate-to-CoA conversion is operative in vivo. Another step in the biosynthetic pathway that may be rate limiting is the conversion of 4'-phosphopantetheine (4'-PP) to dephospho-CoA, a step catalyzed by 4'-phosphopantetheine adenylyl-transferase. In mammalian systems, this step may occur in the mitochondria or in the cytosol. The teleological significance of these two pathways remains to be established, particularly since mitochondria are capable of transporting CoA from the cytosol. Altered homeostasis of CoA has been observed in diverse disease states including starvation, diabetes, alcoholism, Reye syndrome (RS), medium-chain acyl CoA dehydrogenase deficiency, vitamin B12 deficiency, and certain tumors. Hormones, such as glucocorticoids, insulin, and glucagon, as well as drugs, such as clofibrate, also affect tissue CoA levels. It is not known whether the abnormal metabolism observed in these conditions is the result of altered CoA metabolism or whether CoA levels change in response to hormonal or nonhormonal perturbations brought about in these conditions. In other words, a cause-effect relation remains to be elucidated. It is also not known whether the altered CoA metabolism (be it cause or result of abnormal metabolism) can be implicated in the manifestations of a disease. Besides CoA, pantothenic acid is also an integral part of the ACP molecule.(ABSTRACT TRUNCATED AT 400 WORDS)

Neurospora mitochondria contain an acyl-carrier protein

Mitochondria of Neurospora crassa were found to contain a protein which was labelled with [14C]pantothenic acid and which carried an acyl group. This protein, when purified 6000-fold, closely resembled the bacterial and chloroplast acyl-carrier protein(s) [ACP(s)] in its physical and chemical properties. The predominant acyl group esterified to the purified protein was 3-hydroxytetradecanoate, as determined by gas chromatographic mass spectrometry. The amino acid sequence of the tryptic peptide carrying the 4'-phosphophantetheine moiety showed a high degree of sequence similarity to the analogous bacterial and chloroplast ACP peptide sequences. The possible functions of this ACP in lipid metabolism are discussed in view of the fact that Neurospora has a separate cytoplasmic enzyme complex which carries out the de novo biosynthesis of fatty acids.