According to the state of mitochondrial respiration, the respiratory chain generates superoxide anions converted into hydrogen peroxide. Two uncoupling proteins (UCP) able to modulate the coupling between the respiratory chain and ATP synthesis are now identified and could be involved in mitochondrial H2O2 generation. UCP1 is specific to brown adipose tissue (BAT) whereas UCP2 is expressed in numerous tissues, particularly in monocytes/macrophages. Preincubation of BAT mitochondrial fractions with GDP, an inhibitor of UCP1, induced a rise in mitochondrial membrane potential (assessed by rhodamine 123 uptake) and H2O2 production. An uncoupling agent reversed this effect. Liver mitochondria exhibited a similar phenotype. GDP was also able to raise membrane potential and H2O2 production of the mitochondria from nonparenchymal cells expressing UCP2, but was completely ineffective on mitochondria from hepatocytes deprived of UCP2. The GDP effect was also observed with mitochondrial fractions of the spleen or thymus, which highly expressed UCP2. Altogether, these results strongly suggest that UCP2 is sensitive to GDP and that the UCPs, particularly UCP2, are able to modulate H2O2 mitochondrial generation. This supports a role for UCP2 in cellular (patho-) physiological processes involving free radicals generated by mitochondria, such as oxidative damage, inflammation, or apoptosis.

Reactive carbonyl compounds (RCCs) formed during lipid peroxidation and sugar glycoxidation, namely Advanced lipid peroxidation end products (ALEs) and Advanced Glycation end products (AGEs), accumulate with ageing and oxidative stressrelated diseases, such as atherosclerosis, diabetes or neurodegenerative diseases. RCCs induce the 'carbonyl stress' characterized by the formation of adducts and cross-links on proteins, which progressively leads to impaired protein function and damages in all tissues, and pathological consequences including cell dysfunction, inflammatory response and apoptosis. The prevention of carbonyl stress involves the use of free radical scavengers and antioxidants that prevent the generation of lipid peroxidation products, but are inefficient on pre-formed RCCs. Conversely, carbonyl scavengers prevent carbonyl stress by inhibiting the formation of protein cross-links. While a large variety of AGE inhibitors has been developed, only few carbonyl scavengers have been tested on ALE-mediated effects. This review summarizes the signalling properties of ALEs and ALE-precursors, their role in the pathogenesis of oxidative stress-associated diseases, and the different agents efficient in neutralizing ALEs effects in vitro and in vivo. The generation of drugs sharing both antioxidant and carbonyl scavenger properties represents a new therapeutic challenge in the treatment of carbonyl stress-associated diseases.

Atherosclerosis is a multifocal alteration of the vascular wall of medium and large arteries characterized by a local accumulation of cholesterol and non-resolving inflammation. Atherothrombotic complications are the leading cause of disability and mortality in western countries. Neovascularization in atherosclerotic lesions plays a major role in plaque growth and instability. The angiogenic process is mediated by classical angiogenic factors and by additional factors specific to atherosclerotic angiogenesis. In addition to its role in plaque progression, neovascularization may take part in plaque destabilization and thromboembolic events. Anti-angiogenic agents are effective to reduce atherosclerosis progression in various animal models. However, clinical trials with anti-angiogenic drugs, mainly anti-VEGF/VEGFR, used in anti-cancer therapy show cardiovascular adverse effects, and require additional investigations.

alpha-Tocopheryl succinate (alpha-TOS) is a semisynthetic vitamin E analogue with high pro-apoptotic and anti-neoplastic activity [Weber, T et al. (2002) Clin. Cancer Res. 8, 863-869]. Previous studies suggested that it acts through destabilization of subcellular organelles, including mitochondria, but compelling evidence is missing. Cells treated with alpha-TOS showed altered mitochondrial structure, generation of free radicals, activation of the sphingomyelin cycle, relocalization of cytochrome c and Smac/Diablo, and activation of multiple caspases. A pan-caspase inhibitor suppressed caspase-3 and -6 activation and phosphatidyl serine externalization, but not decrease of mitochondrial membrane potential or generation of radicals. For alpha-TOS, but not Fas or TRAIL, apoptosis was suppressed by caspase-9 inhibition, while TRAIL- and Fas-resistant cells overexpressing cFLIP or CrmA were susceptible to alpha-TOS. The central role of mitochondria was confirmed by resistance of mtDNA-deficient cells to alpha-TOS, by regulation of alpha-TOS apoptosis by Bcl-2 family members, and by anti-apoptotic activity of mitochondrially targeted radical scavengers. Co-treatment with alpha-TOS and anti-Fas IgM showed their cooperative effect, probably by signaling via different, convergent pathways. These data provide an insight into the molecular mechanism, by which alpha-TOS kills malignant cells, and advocate its testing as a potential anticancer agent or adjuvant.