Metastatic Melanoma Progression Is Associated with Endothelial Nitric Oxide Synthase Uncoupling Induced by Loss of eNOS:BH4 Stoichiometry.

Melanoma is the most aggressive type of skin cancer due to its high capability of developing metastasis and acquiring chemoresistance. Altered redox homeostasis induced by increased reactive oxygen species is associated with melanomagenesis through modulation of redox signaling pathways. Dysfunctional endothelial nitric oxide synthase (eNOS) produces superoxide anion (O2-•) and contributes to the establishment of a pro-oxidant environment in melanoma. Although decreased tetrahydrobiopterin (BH4) bioavailability is associated with eNOS uncoupling in endothelial and human melanoma cells, in the present work we show that eNOS uncoupling in metastatic melanoma cells expressing the genes from de novo biopterin synthesis pathway Gch1, Pts, and Spr, and high BH4 concentration and BH4:BH2 ratio. Western blot analysis showed increased expression of Nos3, altering the stoichiometry balance between eNOS and BH4, contributing to NOS uncoupling. Both treatment with L-sepiapterin and eNOS downregulation induced increased nitric oxide (NO) and decreased O2• levels, triggering NOS coupling and reducing cell growth and resistance to anoikis and dacarbazine chemotherapy. Moreover, restoration of eNOS activity impaired tumor growth in vivo. Finally, NOS3 expression was found to be increased in human metastatic melanoma samples compared with the primary site. eNOS dysfunction may be an important mechanism supporting metastatic melanoma growth and hence a potential target for therapy.

Da sinalização redox ao estresse oxidativo: Implicações na disfunção endoltelial / Redox signaling to oxidative stress: Implications in endothelial dysfunction

A busca pelo entendimento do papel dos radicais livrese estresse oxidativo no desenvolvimento de doençascardiovasculares vem há mais de 60 anos. Hoje, há umacúmulo de dados que evidenciam a participação de reaçõesoxidativas não somente na fisiopatologia destas doenças,mas também na regulação de vias de sinalização intracelular.Isto se reflete na ineficácia das estratégias de suplementaçãocom antioxidantes na melhora de doenças cardiovasculares.Neste capítulo, discorreremos sobre as características dasprincipais espécies reativas presentes no endotélio, suasfontes biológicas e contribuição tanto na fisiologia quantofisiopatologia do sistema cardiovascular, com ênfase nadisfunção endotelial...

For over 60 years researchers have been trying to understand therole offree radicals and oxidative stress in cardiovasculardiseases.Nowadays there is a considerable data which indicate that reactivespecies are involved in the pathophysiology of cardiovasculardiseases, but also in the regulation of intracellular signalingpathways. This is reflected in the ineffectiveness of the antioxidantsupplementation strategies in ameliorate cardiovasculardisease. This chapter addresses the characteristics of reactivespecies present in the endothelium, their biological sources andcontribution in both the physiology and pathophysiology of thecardiovascular system, with emphasis on endothelial dysfunction...

Protein disulfide isomerase in redox cell signaling and homeostasis.

Thiol proteins may potentially act as redox signaling adaptor proteins, adjusting reactive oxygen species intermediates to specific signals and redox signals to cell homeostasis. In this review, we discuss redox effects of protein disulfide isomerase (PDI), a thioredoxin superfamily oxidoreductase from the endoplasmic reticulum (ER). Abundantly expressed PDI displays ubiquity, interactions with redox and nonredox proteins, versatile effects, and several posttranslational modifications. The PDI family contains >20 members with at least some apparent complementary actions. PDI has oxidoreductase, isomerase, and chaperone effects, the last not directly dependent on its thiols. PDI is a converging hub for pathways of disulfide bond introduction into ER-processed proteins, via hydrogen peroxide-generating mechanisms involving the oxidase Ero1α, as well as hydrogen peroxide-consuming reactions involving peroxiredoxin IV and the novel peroxidases Gpx7/8. PDI is a candidate pathway for coupling ER stress to oxidant generation. Emerging information suggests a convergence between PDI and Nox family NADPH oxidases. PDI silencing prevents Nox responses to angiotensin II and inhibits Akt phosphorylation in vascular cells and parasite phagocytosis in macrophages. PDI overexpression spontaneously enhances Nox activation and expression. In neutrophils, PDI redox-dependently associates with p47phox and supports the respiratory burst. At the cell surface, PDI exerts transnitrosation, thiol reductase, and apparent isomerase activities toward targets including adhesion and matrix proteins and proteases. Such effects mediate redox-dependent adhesion, coagulation/thrombosis, immune functions, and virus internalization. The route of PDI externalization remains elusive. Such multiple redox effects of PDI may contribute to its conspicuous expression and functional role in disease, rendering PDI family members putative redox cell signaling adaptors.

Marcadores bioquímicos de função endotelial e estresse oxidativo / Endothelial function and oxidative stress biomarker

Biomarcadores são essenciais para informação sobre diagnóstico, prognóstico e evolução de doenças e quase uniformemente são desenvolvidos a partir do conhecimento detalhado de mecanismos do processo fisiopatológico, sendo, no caso da aterosclerose ou doenças vasculares, geralmente ligados a função endotelial, inflamação, trombose, e estresse oxidativo. Como características essenciais, um biomarcador de uso clínico deve ser capaz de predizer futuros eventos, proporcionar informação além da disponível a partir de algoritmos como o escore de Framingham sobre risco/prognóstico, e ser medido por ensaios baratos, padronizados, com baixa variabilidade, sem coleta especial de plasma ou de técnicas sofisticadas. Hoje existem inúmeros biomarcadores bem estabelecidos para risco vascular, e alguns novos têm se mostrado promissores e podem trazer importantes informações sobre a fisiopatologia de aterosclerose. Nesse sentido, este capítulo abordará alguns marcadores bioquímicos de função endotelial, bem como alguns biomarcadores estabelecidos e outros emergentes na predição de eventos ateroscleróticos em indivíduos aparentemente saudáveis, que, dessa forma, inclui a discussão de marcadores de inflamação...

Biomarkers are essential to provide information on the diagnosis, prognosis and progression of diseases and are developed based on detailed understanding of pathophysiological process mechanisms, and in the case of atherosclerosis or vascular diseases, are usually related to endothelial function, inflammation, thrombosis, and oxidative stress. A biomarker for clinical use should be capable of predicting future events, providing information on risk/prognosis beyond those available from algorithms such as the Framingham score, and should be measured by low cost, standardized, low variability assays, without special plasma collection or sophisticated techniques. There are many available well-established biomarkers for vascular risk, and some new ones have shown promising results and may provide important information on the pathophysiology of atherosclerosis. Therefore, this chapter will address some biochemical markers of endothelial function as well as some emerging biomarkers to predict atherosclerotic events in apparently healthy subjects, including the discussion of biomarkers of inflammation and oxidative stress. Some definitions on the role of oxidative species in vascular systems are also reviewed and defined, since this is an area of intense scientific work and constant evolution, whose knowledge is required for further discussion and criticism.