N-nitrosamine Mitigation with Nitrite Scavengers in Oral Pharmaceutical Drug Products.

N-nitrosamines are likely human carcinogens. After N-nitrosamine contaminants were detected in pharmaceutical products in 2018, regulatory authorities set a framework for the risk assessment, testing and mitigation of N-nitrosamines in drug products. One strategy to inhibit the formation of N-nitrosamines during the manufacture and storage of drug products involves the incorporation of nitrite scavengers in the formulation. Diverse molecules have been tested in screening studies including the antioxidant vitamins ascorbic acid and α-tocopherol, amino acids, and other antioxidants used in foods or drugs, for inclusion into drug products to mitigate N-nitrosamine formation. This review article outlines key considerations for the inclusion of nitrite scavengers in oral drug product formulations.

Vaccination against influenza with recombinant hemagglutinin expressed by Schizochytrium sp. confers protective immunity.

For the rapid production of influenza vaccine antigens in unlimited quantities, a transition from conventional egg-based production to cell-based and recombinant systems is required. The need for higher-yield, lower-cost, and faster production processes is critical to provide adequate supplies of influenza vaccine to counter global pandemic threats. In this study, recombinant hemagglutinin proteins of influenza virus were expressed in the microalga Schizochytrium sp., an established, fermentable organism grown in large scale for the manufacture of polyunsaturated fatty acids for animal and human health applications. Schizochytrium was capable of exporting the full-length membrane-bound proteins in a secreted form suitable for vaccine formulation. One recombinant hemagglutinin (rHA) protein derived from A/Puerto Rico/8/34 (H1N1) influenza virus was evaluated as a vaccine in a murine challenge model. Protective immunity from lethal challenge with homologous virus was elicited by a single dose of 1.7, 5 or 15 µg rHA with or without adjuvant at survival rates between 80-100%. Full protection (100%) was established at all dose levels with or without adjuvant when mice were given a second vaccination. These data demonstrate the potential of Schizochytrium sp. as a platform for the production of recombinant antigens useful for vaccination against influenza.

The mitochondrial transcription factor A functions in mitochondrial base excision repair.

Mitochondrial transcription factor A (TFAM) is an essential component of mitochondrial nucleoids. TFAM plays an important role in mitochondrial transcription and replication. TFAM has been previously reported to inhibit nucleotide excision repair (NER) in vitro but NER has not yet been detected in mitochondria, whereas base excision repair (BER) has been comprehensively characterized in these organelles. The BER proteins are associated with the inner membrane in mitochondria and thus with the mitochondrial nucleoid, where TFAM is also situated. However, a function for TFAM in BER has not yet been investigated. This study examines the role of TFAM in BER. In vitro studies with purified recombinant TFAM indicate that it preferentially binds to DNA containing 8-oxoguanines, but not to abasic sites, uracils, or a gap in the sequence. TFAM inhibited the in vitro incision activity of 8-oxoguanine DNA glycosylase (OGG1), uracil-DNA glycosylase (UDG), apurinic endonuclease 1 (APE1), and nucleotide incorporation by DNA polymerase γ (pol γ). On the other hand, a DNA binding-defective TFAM mutant, L58A, showed less inhibition of BER in vitro. Characterization of TFAM knockdown (KD) cells revealed that these lysates had higher 8oxoG incision activity without changes in αOGG1 protein levels, TFAM KD cells had mild resistance to menadione and increased damage accumulation in the mtDNA when compared to the control cells. In addition, we found that the tumor suppressor p53, which has been shown to interact with and alter the DNA binding activity of TFAM, alleviates TFAM-induced inhibition of BER proteins. Together, the results suggest that TFAM modulates BER in mitochondria by virtue of its DNA binding activity and protein interactions.

Enhanced catabolism of mitochondrial superoxide/hydrogen peroxide and aging in transgenic Drosophila.

The generation of superoxide anion radicals (O2*-) and hydrogen peroxide (H2O2) during mitochondrial respiration has been widely postulated to be causally linked to the aging process. The hypothesis that a specific enhancement of mitochondrial O2*-/H2O2 catabolism would delay age-associated physiological changes and extend the lifespan was tested by simultaneous overexpression of MnSOD (manganese superoxide dismutase) and catalase, ectopically targeted to the mitochondrial matrix of transgenic Drosophila melanogaster. The increased activities of these antioxidative enzymes resulted in a decrease of mitochondrial H2O2 release and enhancement of free methionine content. The MnSOD/mitochondrial catalase transgenic flies displayed an enhanced resistance to experimental oxidative stress, induced by dietary H2O2 administration or by exposure to 100% ambient oxygen. However, the lifespan of the flies was decreased, by up to 43%, and this effect coincided with (i) an overall decrease in physical fitness, as measured by the speed of walking, and (ii) an age-related decrease in mitochondrial state 3 (ADP-stimulated) respiration. These findings support the notion that mitochondrial O2*-/H2O2 production at physiological levels is essential for normal biological processes leading to the attainment of a normal lifespan.

Free aminothiols, glutathione redox state and protein mixed disulphides in aging Drosophila melanogaster.

The main purpose of the present study was to test the hypothesis that the aging process is associated with a pro-oxidizing shift in the cellular redox state. The amounts of the redox-sensitive free aminothiols (glutathione, cysteine, Cys-Gly and methionine) and protein mixed disulphides were measured at different ages and ambient temperatures in Drosophila melanogaster. GSH/GSSG ratios decreased significantly with increasing age of the flies, due to an increase in GSSG content. Concentrations of Cys-Gly increased and methionine decreased with age. The amounts of protein mixed disulphides, measured as protein-cysteinyl, protein-Cys-Gly and protein-glutathionyl mixed disulphides, increased as a function of age. The pattern of changes in free aminothiol content, glutathione-redox state and protein mixed disulphides varied in proportion to the ambient temperature, which is inversely related to the life expectancy of the flies. Collectively, these results support the idea that the pro-oxidizing shift in the glutathione-redox state, the decrease in methionine content and increase in abundance of protein mixed disulphides are associated with the life expectancy of flies, and are indicative of enhanced oxidative stress during aging.

Ectopic expression of catalase in Drosophila mitochondria increases stress resistance but not longevity.

The goal of this study was to test the hypothesis that the rate of mitochondrial oxidant production governs the aging process of the fruit fly, Drosophila melanogaster. Catalase, an antioxidative enzyme expressed in the cytosol and peroxisomes of Drosophila, was targetted ectopically to the mitochondrial matrix by fusion of a leader peptide derived from ornithine aminotransferase with its N-terminus. The presence of the transgene encoding this fusion protein was associated with moderate (35 +/- 13%) increases in total catalase activity in most lines, and measurable levels of catalase activity in the mitochondria (30-140 U/mg protein). There was no impact on the life span of the flies at 25 degrees C, even in an exceptional line with a 149% increase in total catalase activity, and there was a small decrease in longevity at 29 degrees C. There were no compensatory changes in the rate of metabolism or physical activity, or in the levels of other major antioxidants, suggesting that the aging process was largely unaffected. Resistance to exogenous hydrogen peroxide, paraquat, and cold stress was enhanced, but there was no appreciable effect on resistance to hyperoxia. The results demonstrate the importance of mitochondrial antioxidant levels in the resistance to oxidative stress at the organismal level, and illustrate that different effects on aging and stress resistance may ensue from a single treatment. The main inferences drawn are that: (i) levels of stress resistance may neither be a cause nor a reliable indicator of the rate of aging, and (ii) bolstering antioxidant levels in Drosophila may not delay or slow down the aging process.

Effects of coenzyme Q(10) administration on its tissue concentrations, mitochondrial oxidant generation, and oxidative stress in the rat.

Coenzyme Q (CoQ(10)) is a component of the mitochondrial electron transport chain and also a constituent of various cellular membranes. It acts as an important in vivo antioxidant, but is also a primary source of O(2)(-*)/H(2)O(2) generation in cells. CoQ has been widely advocated to be a beneficial dietary adjuvant. However, it remains controversial whether oral administration of CoQ can significantly enhance its tissue levels and/or can modulate the level of oxidative stress in vivo. The objective of this study was to determine the effect of dietary CoQ supplementation on its content in various tissues and their mitochondria, and the resultant effect on the in vivo level of oxidative stress. Rats were administered CoQ(10) (150 mg/kg/d) in their diets for 4 and 13 weeks; thereafter, the amounts of CoQ(10) and CoQ(9) were determined by HPLC in the plasma, homogenates of the liver, kidney, heart, skeletal muscle, brain, and mitochondria of these tissues. Administration of CoQ(10) increased plasma and mitochondria levels of CoQ(10) as well as its predominant homologue CoQ(9). Generally, the magnitude of the increases was greater after 13 weeks than 4 weeks. The level of antioxidative defense enzymes in liver and skeletal muscle homogenates and the rate of hydrogen peroxide generation in heart, brain, and skeletal muscle mitochondria were not affected by CoQ supplementation. However, a reductive shift in plasma aminothiol status and a decrease in skeletal muscle mitochondrial protein carbonyls were apparent after 13 weeks of supplementation. Thus, CoQ supplementation resulted in an elevation of CoQ homologues in tissues and their mitochondria, a selective decrease in protein oxidative damage, and an increase in antioxidative potential in the rat.

Effects of superoxide dismutase/catalase mimetics on life span and oxidative stress resistance in the housefly, Musca domestica.

The purpose of this study was to determine whether superoxide dismutase/catalase mimetics lengthen the life span of the housefly, Musca domestica, as previously demonstrated for the nematode Caenorhabditis elegans. Various concentrations of Eukarion-8 or Eukarion-134 were administered via the drinking water and the effects on the life span of the flies and amounts of protein carbonyls were determined under normoxic and hyperoxic conditions. These SOD/catalase mimetics neither extended the life span of the flies nor attenuated the protein carbonyl content under normoxic conditions and shortened life span under hyperoxic conditions. Thus, the effect of these SOD/catalase mimetics on the life span of animals seem to be species-specific.