Diferentes papéis do óxido nítrico com ênfase nas neoplasias

Abstract

RESUMOO Óxido Nítrico (ON) é gerado por uma família de isoenzimas, através da catálise enzimática do aminoácido essencial L-arginina, que resulta na formação de L-citrulina e ON. O ON está envolvido em muitos processos fisiológicos dos mamíferos, que incluem a neurotransmissão, controle da pressão sangüínea, inflamação, reações imunológicas e nos mecanismos de defesa contra microorganisnos e tumores. O descontrole na síntese de ON está implicado na patogênese de doenças cardiovasculares, autoimunidade, rejeição de transplantes, doenças degenerativas, na sépsis, na genotoxicidade e no surgimento de neoplasias. O ON também foi incriminado como agente de iniciação da carcinogênese, que, associado a outros fatores, poderia levar ao descontrole da citoestase e da diferenciação celular. A diversidade de efeitos do ON parece estar relacionada às concentrações de ON gerados, à sensibilidade individual das células e à duração do fenômeno.Palavra-chave: óxido nítrico, câncer. ABSTRACTNitric Oxide (NO) is generated by a family of isoenzymes, through the enzymatic catalisis of the aminoacid L-arginine, which leads to the production of L-citruline and NO. It is involved in many physiologic processes of mammals, including neurotransmition, blood pressure control, inflammation, immune responses and also in the mechanism of defense against invasive organisms and tumors. The uncontrolled syntesis of NO is thought to take part in the pathogenesis of cardiovascular diseases, auto-immunity, graft rejection, degenerative diseases, as well as in sepsis, genotoxicity and also in neoplasia development. The NO is also considered the initial agent of carcinogenesis, which could lead to uncontrolled cytostasis and cellular differentiation when associated to other factors. The diversity of NO effects seems to be related to the concentration that is generated, to the individual sensibility of cells and the duration of this phenomenon.

Helicobacter pylori genotype and polymorphisms in DNA repair enzymes: Where do they correlate in gastric cancer?

“…On the other hand, the persistent inflammatory process due to H. pylori infection generates large amounts of reactive oxygen species (ROS), which can cause high DNA oxidative damage levels 16, 17 and, therefore, requires continuous repair. The base excision repair pathway (BER) is the most important mechanism in the repair of oxidative damage DNA 18, 19.…”

Lichen Metabolites Modulate Hydrogen Peroxide and Nitric Oxide in Mouse Macrophages

“…Key words: Lichens, Hydrogen Peroxide, Nitric Oxide Nitric oxide (NO) is involved in many physiological processes in mammals, including neurotransmission, blood pressure control, infl ammation, immune responses and also in the mechanism of defense against invasive organisms and tumours (Costa et al, 2003). It is identifi ed as the major effector molecule in the destruction of tumour cells by activated macrophages.…”

Immunostimulatory effects of the phenolic compounds from lichens on nitric oxide and hydrogen peroxide production

“…NO has cytotoxic properties and it is produced during host defense against invasive organisms and immunologic reactions. It is also involved in many physiologic processes of mammals, including neurotransmition, blood pressure control and inflammation (Costa et al, 2003;Garcia & Stein, 2006).…”