Supplementation with red palm oil increases ß-carotene and vitamin A blood levels in patients with cystic fibrosis.

Patients with cystic fibrosis (CF) show decreased plasma concentrations of antioxidants due to malabsorption of lipid soluble vitamins and consumption by chronic pulmonary inflammation. ß-Carotene is a major source of retinol and therefore is of particular significance in CF. The aim of this study was to investigate the effect of daily intake of red palm oil (RPO) containing high amounts of ß-carotene on the antioxidant levels in CF patients. Sixteen subjects were recruited and instructed to enrich their food with 2 to 3 tablespoons of RPO (~1.5 mg of ß-carotene) daily over 8 weeks. Carotenoids, retinol, and α-tocopherol were measured in plasma at baseline and after intervention. In addition ß-carotene, lycopene, α-tocopherol, and vitamin C were measured in buccal mucosa cells (BMC) to determine the influence of RPO on antioxidant tissue levels. Eleven subjects completed the study properly. Plasma ß-carotene, retinol, and α-carotene of these patients increased, but plasma concentrations of other carotenoids and α-tocopherol as well as concentrations of ß-carotene, lycopene, α-tocopherol, and vitamin C in BMC remained unchanged. Since RPO on a daily basis did not show negative side effects the data suggest that RPO may be used to elevate plasma ß-carotene in CF.

Oxidative stress and antioxidants in carcinogenesis and integrative therapy of cancer.

Oxidative stress is often considered as a causative factor in carcinogenesis. In addition, current knowledge recognizes oxidative stress as a mechanism by which various cancer therapies act against cancer. To ameliorate the side effects of cancer therapy, many of the patients suffering from cancer are subject to adjuvant therapy, which often implies antioxidant supplementation. Yet, the benefits of such adjuvant treatments are still uncertain owing to the lack of appropriate integrative and personalized medical approach. In particular, reactive oxygen species formed during oxidative stress and products of lipid peroxidation are not only cytotoxic, but can modulate signal transduction in cells, which also behave similar to individuals under stress. Accordingly, pro-oxidants and antioxidants might be considered as modifiers of specific cellular redox signaling. Therefore, there is a need to evaluate the potential benefits of antioxidant supplements in healthy persons, and in particular in cancer patients during therapy. Our review will present a summary of the existing knowledge regarding the effects of various antioxidants in cancer therapies, focusing on cellular adaptation to oxidative stress interacting with redox signaling transduction pathways thereby influencing cell growth.

Cytotoxicity of ß-carotene cleavage products and its prevention by antioxidants.

When we investigated the genotoxicity of beta-carotene cleavage products (CPs) in primary rat hepatocytes stimulated to proliferate, we observed dose-dependent increases of chromosomal aberrations, sister chromatid exchanges and micronuclei. In contrast to other genotoxic substances, however, this increased genotoxicity was not accompanied by increased cytotoxicity. As a consequence we observed metaphases showing massive chromosomal damage, indicating inhibition of apoptosis by CPs enabling these cells to proceed in the cell cycle. Since proliferative stimulation by growth factors may support this effect, the in vitro toxicological effects of CPs were studied on proliferatively quiescent primary rat hepatocytes. A significant increase of both apoptosis and necrosis was found. Supplementation with antioxidants did not significantly lower the level of apoptosis, while the level of necrosis was significantly reduced by Trolox and N-acetylcysteine at all concentrations tested as well as ascorbic acid (50 microM) and a combination of Trolox (50 microM) and ascorbic acid (50 microM). These observations indicate that a) the cytotoxic potential in combination with the genotoxic potential of CPs may promote the initiation of cells due to compensatory cell division in exposed tissues and may aggravate inflammatory processes under chronic exposure, and b) the applied antioxidants may protect from cytotoxicity primarily via the detoxification of aldehydic beta-carotene cleavage products.

Beta-carotene degradation products - formation, toxicity and prevention of toxicity.

Carotenoids are widely used as important micronutrients in food. Furthermore, carotenoid supplementation has been used in the treatment of diseases associated with oxidative stress such as various types of cancer, inflammatory diseases or cystic fibrosis. However, in some clinical studies harmful effects have been observed, e.g. a higher incidence of lung cancer in individuals exposed to extraordinary oxidative stress. The causal mechanisms of harmful effects are still unclear. Carotenoid breakdown products (CBPs) including highly reactive aldehydes and epoxides are formed during oxidative attacks in the course of antioxidative action. We investigated the formation of CBPs by stimulated neutrophils (and at further conditions), tested the hypothesis that CBPs may exert mitochondriotoxicity and tried to prevent toxicity in the presence of members of the antioxidative network. Stimulated neutrophils are able to degrade beta-carotene and to generate a number of CBPs. Concerning mitochondriotoxicity, we found that CBPs strongly inhibit state 3 respiration of rat liver mitochondria at concentrations between 0.5 and 20 microM. This was true for retinal, beta-ionone, and for mixtures of cleavage/breakdown products. The inhibition of mitochondrial respiration was accompanied by a reduction in protein sulfhydryl content, decreasing GSH levels and redox state, and elevated accumulation of malondialdehyde. Changes in mitochondrial membrane potential favor functional deterioration in the adenine nucleotide translocator as a sensitive target. The presence of additional antioxidants such as alpha-tocopherol, ascorbic acid, N-acetyl-cysteine or others could mitigate mitochondriotoxicity. The findings reflect a basic mechanism of increasing the risk of cancer induced by carotenoid degradation products.

Beta-carotene breakdown products may impair mitochondrial functions--potential side effects of high-dose beta-carotene supplementation.

Beta-carotene (BC) and other carotenoids are mainly considered as belonging to the group of micronutrients. As they are contained in fruit and vegetables and thus part of human diet, a regular low-dose intake from natural sources is normally assured. In the last decade high-dose supplementation with synthetic carotenoids has been used successfully in the treatment of diseases believed to be associated with oxidative stress. However, in a few clinical studies harmful effects have been observed as well, e.g., a higher incidence of lung cancer after BC was given in high doses to smokers. Our studies aim at shedding light on the causal mechanisms of the known side effects that we have investigated. Possibilities of preventing them are discussed. Obviously, on certain conditions of high-dose carotenoid supplementation, both the antioxidant and prooxidant reactions may arise. Carotenoid breakdown products (CBP) including very reactive aldehydes and epoxides are formed during oxidative attack in the course of antioxidative action. Carotenoid breakdown products inhibit state 3 respiration of isolated rat liver mitochondria at concentrations between 0.5 and 20 microM. In vivo stimulated neutrophils might represent an important source for the generation of CBP, and the lung might be a critical organ in CBP formation. The inhibition of mitochondrial state 3 respiration by CBP is accompanied by a reduced content of protein sulfhydryl groups, decreasing glutathione levels and redox state, and also elevated accumulation of malondialdehyde. Changes in mitochondrial membrane potential favour functional deterioration of the adenine nucleotide translocator (ANT). The findings reflect a basic mechanism of the side effects of BC supplementation in circumstances of severe oxidative stress induced by CBP representing a class of lipid oxidation products. We are striving for safe conditions of carotenoid supplementation in order to protect patients in need of this kind of medical treatment from possible side effects, such as unwanted prooxidative reactions.

Anti-fibrosclerotic effects of shock wave therapy in lipedema and cellulite.

In vivo measurements in 26 female patients with lipedema and cellulite parameters were carried out before and after therapy by means of complex physical decongestive therapy (CPDT) including manual lymph drainage and compression as main components and/or shock wave therapy (SWT). Oxidative stress parameters of blood serum and biomechanic skin properties/smoothening of dermis and hypodermis surface were evaluated. Oxidative stress in lipedema and cellulite was demonstrated by increased serum concentrations of malondialdehyde (MDA) and plasma protein carbonyls compared with healthy control persons. Both MDA and protein carbonyls in blood plasma decreased after serial shock wave application and CPDT. The SWT itself and CPDT itself lead to MDA release from edematous tissue into the plasma. Obviously both therapy types, SWT and CPDT, mitigate oxidative stress in lipedema and cellulite. In parallel SWT improved significantly the biomechanic skin properties leading to smoothening of dermis and hypodermis surface. Significant correlation between MDA depletion of edematous and lipid enriched dermis and improvement of mechanic skin properties was demonstrated. From these findings it is concluded, that a release of lipid peroxidation (LPO) products from edematous dermis is an important sclerosis-preventing effect of SWT and/or CPDT in lipedema and cellulite. Expression of factors stimulating angiogenesis and lymphangiogenesis such as VEGF was not induced by SWT and/or CPDT and, therefore, not involved in beneficial effects by SWT and/or CPDT.

Beta-carotene cleavage products after oxidation mediated by hypochlorous acid--a model for neutrophil-derived degradation.

After beta-carotene failed in certain clinical efficacy trials, there is evidence that the carotenoid might even be harmful, especially to smokers, when given in high dosages. These negative effects might be mediated in part also by carotenoid cleavage products (CPs) having a high reactivity towards biomolecules. The authors postulate that in certain tissues oxidative, nonenzymatic cleavage of carotenoids is carried out primarily by oxidants liberated by polymorphonuclear leukocytes (PML). In this study, we show that beta-carotene is degraded by stimulated PML in vitro. This gives the pathophysiological meaning to our further experiments in which beta-carotene degradation by hypochlorous acid and consecutive CP formation were investigated. While formation of apo-carotenals under these conditions has been studied before, this was not the case for short chain products. Performing gas chromatography mass spectrometry, we were able to identify for the first time 5,6-epoxi-beta-ionone, ionene, beta-cyclocitral, beta-ionone, dihydroactinidiolide, and 4-oxo-beta-ionone as CPs formed after degradation of beta-carotene mediated by hypochlorous acid. Our findings may be of biological relevance because beta-carotene CPs are highly reactive and, therefore, potentially toxic.

Carotenoid cleavage products modify respiratory burst and induce apoptosis of human neutrophils.

Carotenoid supplementation in the treatment of diseases associated with oxidative stress has been recently questioned because of the cell damage and the increased risk of lung cancer in male smokers. Because of the complex role of neutrophils in lung diseases, we investigated whether carotenoid derivatives could affect respiratory burst and apoptosis of human neutrophils purified from peripheral blood. Stimulation of superoxide production was induced by nanomolar and micromolar concentrations of carotenoid cleavage products with aliphatic chains of different length, but not by carotenoids lacking the carbonyl moiety. The stimulatory effect of carotenoid cleavage products was observed in cells activated by phorbol myristate acetate (PMA), while a slight inhibition of superoxide production was noticed with cells activated by the chemotactic tripeptide N-formyl-Met-Leu-Phe (f-MLP). At higher concentrations, carotenoid cleavage products inhibited superoxide production in the presence of both PMA and f-MLP. In the presence of 20 microM carotenoid cleavage products, inhibition of superoxide production was accompanied by DNA fragmentation and increased level of intracellular caspase-3 activity.

Beta-carotene cleavage products induce oxidative stress in vitro by impairing mitochondrial respiration.

Carotenoids are widely used as important micronutrients in food. Furthermore, carotenoid supplementation has been used in the treatment of diseases associated with oxidative stress. However, in some clinical studies harmful effects have been observed, for example, a higher incidence of lung cancer in individuals exposed to extraordinary oxidative stress. The causal mechanisms are still unclear. Carotenoid cleavage products (CCPs), including highly reactive aldehydes and epoxides, are formed during oxidative attacks in the course of antioxidative action. Here, we tested the hypothesis that CCPs may increase oxidative stress by impairing mitochondrial function. We found that CCPs strongly inhibit state 3 respiration of isolated rat liver mitochondria even at concentrations between 0.5 and 20 microM. This was true for retinal, beta-ionone, and mixtures of cleavage products, which were generated in the presence of hypochlorite to mimic their formation in inflammatory regions. The inhibition of mitochondrial respiration was accompanied by a reduction in protein sulfhydryl content, decreasing glutathione levels and redox state, and elevated accumulation of malondialdehyde. Changes in mitochondrial membrane potential favor functional deterioration of the adenine nucleotide translocator. The findings may reflect a basic mechanism of increasing the risk of cancer induced by CCPs.