Brazilian Bioluminescent Beetles: Reflections on Catching Glimpses of Light in the Atlantic Forest and Cerrado

ABSTRACT Bioluminescence - visible and cold light emission by living organisms - is a worldwide phenomenon, reported in terrestrial and marine environments since ancient times. Light emission from microorganisms, fungi, plants and animals may have arisen as an evolutionary response against oxygen toxicity and was appropriated for sexual attraction, predation, aposematism, and camouflage. Light emission results from the oxidation of a substrate, luciferin, by molecular oxygen, catalyzed by a luciferase, producing oxyluciferin in the excited singlet state, which decays to the ground state by fluorescence emission. Brazilian Atlantic forests and Cerrados are rich in luminescent beetles, which produce the same luciferin but slightly mutated luciferases, which result in distinct color emissions from green to red depending on the species. This review focuses on chemical and biological aspects of Brazilian luminescent beetles (Coleoptera) belonging to the Lampyridae (fireflies), Elateridae (click-beetles), and Phengodidae (railroad-worms) families. The ATP-dependent mechanism of bioluminescence, the role of luciferase tuning the color of light emission, the "luminous termite mounds" in Central Brazil, the cooperative roles of luciferase and superoxide dismutase against oxygen toxicity, and the hypothesis on the evolutionary origin of luciferases are highlighted. Finally, we point out analytical uses of beetle bioluminescence for biological, clinical, environmental, and industrial samples.

Antioxidant enzyme activities in the lymphoid organs and macrophages of rats trained to perform moderate exercise

Strenous exercise and high levels of athletic competition may suppress immune function, increasing susceptibility to infections. Infections are often associated with a reduction in athletic performance and can have permanent or lethal consequences. Recent research, however; suggests that regular paraticipation in moderate exercise has an immunoenhancing effect but the mechanism involved remains unknown. This study examined the effect of moderate exercise (70 per cent of maximal oxygen consumption - swimming for 1 hour daily at 32 degrees Celsius with 5 per cent body weight extra load attached to the tail) training on antioxidant enzyme activities and lipid peroxidation in the lymphoid organs (mesenteric lymph nodes, thymus and spleen) and macrophages of rats. This modality of physical effort reduced the content of lipide peroxides in the lymphoid organs. The authors assumed that this effect of exercise training resulted in increased activity of antioxidant enzymes: Glutathione peroxidase in the mesenteric lymph nodes (2.1 fold) and spleen (3-fold), catalase in the spleen (5-fold) and Mn-superoxide dismutase (SOD) in the thymus (28 per cent). The exercise training increased the hydrogen peroxide production and phagocytic capacity in macrophages which was accompanied by a higher Mn-SOD activity. Therefore, a moderate exercise may be the able to improve immune function due to changes in the oxidative metabolism of the lymphoid organs and macrophages.

Singlet molecular oxygen: generation, reactivity, identification and biological effects

Electronically excited singlet molecular oxygen ((1)O2)) is of great importance in chemical and biological systems due to its high reactivity and involvement in physiological and pathological processes. It is a simple and useful reagent in organic synthesis of peroxides, endoperoxides, hydroperoxides, and dioxetanes. In biological systems, (1)O2 has been implicated in: i) Defense mechanisms of living organisms such as phagocytosis; ii) degradative oxidation of endogenous hallucinogens; iii) hormonal activity of prostaglandins; iv) photochemotherapy utilizing the photodynamic action of synthetic dyes; v) photosensitivity to drugs like chlorpromazine and vi) inborn errors of metabolism exemplified by erythropoietic porphyria. The high reactivity of (1)O2 with unsaturated compounds, sulfides and amines arises from its high electrophilicity and relatively long lifetime (2-4 ms in H2O and ~700 ms in CCI4). Thus, biological targets for (1)O2 having the above functional groups include unsaturated fatty acids, proteins, and DNA. Extensively conjugated biomolecules such as carotenoids act as chemical and physical quenchers of (1)O2 and hence provide protective mechanisms against the deleterious effects of this excited state of molecular oxygen. However, due to the difficulties involved in obtaining (1)O2 free from other reactive contaminants, there is a paucity of detailed studies on the mentioned aspects of (1)O2 biochemistry. Chemical and dye-sensitized photophysical methods are available to prepare (1)O2. The aim of this work is to give a general view on (1)O2 with regard to its chemical generation, reactivity with biologically important compounds, detection and its role in biological systems.

Mitochondrial oxidative damage promoted by a synergism betweem Ca2+ and prooxidants: inner membrane permeabilization and mtDNA breakage

Oxidative damage of mitochondria induced by a synergism between Ca2+ and prooxidants is mediated by the attack of mitochondria-generated reactive oxygen species to membrane proteins, lipids and DNA. This results in mitochondrial DNA fragmentation, lipid peroxidation and oxidation of vicinal protein thiols producing high molecular weight membrane protein aggregates. The membrane protein alterations lead to a condition called mitochondrial membrane permeability transition, characterized by formation of nonspecific membrane protein pores sensitive to cyclosporin A, EGTA, dithiothreitol, Mg2+ and ADP. We propose that these alterations are related to the mechanisms by which cells are killed by a series of toxins, xenobiotics or pathological conditions such as prolonged hypoxia or ischemia/reperfusion.

Enolizable carbonyl and imino metabolites may act as endogenous sources of reactive oxygen species

Highly reactive oxyradicals and electronically excited triplet carbonyls can be generated in vitro by iron complexes and heme enzyme-catalyzed aerobic oxidation of synthetic or naturally occurring substances capable of enolization in aqueous medium. Monoenols and enamines, obtained by (alpha-methyne-carbonyl and -imine enolization, undergo dioxygen insertion and ultimately originate triplet species; e.g., isobutanal, 3-methylacetoacetone, Schiff bases. In turn, (alpha-hydroxy- and (alpha-aminocarbonyls (e.g., carbohydrates, 5-aminolevulinic acid) tautomerize to enediols and enolamines and yield oxyradicals, initiated by electron transfer to dioxygen, as polyphenols (e.g., 6-hydroxydopamine) and polyphenolamines do. Free radicals and excited species have been implicated in several normal and pathological processes. We here briefly review our contributions to this research area, emphasizing a possible in vivo prooxidant role for 5-aminolevulinic acid, the heme precursor accumulated in several porphyric disorders (e.g., lead poisoning, acut intermittent porphyria, tyrosinosis).

Superóxido dismutase como antiinflamatório em Endodontia / Superoxide dismutase used as an antiinflammatory in Endodontics

As propriedades antioxidantes e antiinflamatórias da superóxido dismutase bovina, eletroforeticamente pura, têm sido amplamente exploradas na investigaçäo da natureza e terapia de várias patologias de origem genética e adquiridas. Entre elas, incluem-se doenças ligadas à distúrbios na via biossintética do grupo heme (hematopatologias), desordens com manifestaçöes neuropsiquiátricas e doenças degenerativas de juntas. Neste trabalho, säo apresentados uma revisäo sucinta de trabalhos recentes na área de "toxicidade de oxigênio" e resultados preliminares da investigaçäo do uso da superóxido dismutase como antiinflamatório alternativo para corticóides no tratamento de canais radiculares. De vinte e dois casos tratados com esta enzima, cerca de 70 por cento tiveram um pós-operatório bem sucedido e cerca de 25 por cento , avaliados como regulares. Os casos foram acompanhados radiograficamente e através de relato da sintomatologia no pós-operatório pelos pacientes