The emerging harm of antioxidants in carcinogenesis

Sulforaphane: Its "Coming of Age" as a Clinically Relevant Nutraceutical in the Prevention and Treatment of Chronic Disease

A growing awareness of the mechanisms by which phytochemicals can influence upstream endogenous cellular defence processes has led to intensified research into their potential relevance in the prevention and treatment of disease. Pharmaceutical medicine has historically looked to plants as sources of the starting materials for drug development; however, the focus of nutraceutical medicine is to retain the plant bioactive in as close to its native state as possible. As a consequence, the potency of a nutraceutical concentrate or an extract may be lower than required for significant gene expression. The molecular structure of bioactive phytochemicals to a large extent determines the molecule's bioavailability. Polyphenols are abundant in dietary phytochemicals, and extensive in vitro research has established many of the signalling mechanisms involved in favourably modulating human biochemical pathways. Such pathways are associated with core processes such as redox modulation and immune modulation for infection control and for downregulating the synthesis of inflammatory cytokines. Although the relationship between oxidative stress and chronic disease continues to be affirmed, direct-acting antioxidants such as vitamins A, C, and E, beta-carotene, and others have not yielded the expected preventive or therapeutic responses, even though several large meta-analyses have sought to evaluate the potential benefit of such supplements. Because polyphenols exhibit poor bioavailability, few of their impressive in vitro findings have been replicated in vivo. SFN, an aliphatic isothiocyanate, emerges as a phytochemical with comparatively high bioavailability. A number of clinical trials have demonstrated its ability to produce favourable outcomes in conditions for which there are few satisfactory pharmaceutical solutions, foreshadowing the potential for SFN as a clinically relevant nutraceutical. Although myrosinase-inert broccoli sprout extracts are widely available, there now exist myrosinase-active broccoli sprout supplements that yield sufficient SFN to match the doses used in clinical trials.

Polyphenol-associated oxidative stress and inflammation in a model of LPS-induced inflammation in glial cells: do we know enough for responsible compounding?

Cyanidin and chlorogenic acid are polyphenols from plant origin that are present in many common fruits, particularly in berries. To corroborate the protective or detrimental effects of both compounds from a neuro-inflammatory perspective, in vitro experiments were carried out in human astrocytes (U-373). Astrocytes were pre-treated with a range of concentrations of either cyanidin, chlorogenic acid or a combined treatment for a period of 30 min, before exposure to Escherichia coli lipopolysaccharide (LPS) challenge for 23.5 h, after which cytotoxicity (propidium iodide exclusion assay), cytoprotective effects (XTT assay) and effects on functional capacity (secretion of pro-inflammatory cytokines IL-6 and MCP-1) were evaluated. No treatment resulted in cytotoxicity, but high dose (20 µg/mL) LPS significantly reduced mitochondrial reductive capacity (p < 0.001). This effect was prevented in a dose-dependent manner by both cyanidin and chlorogenic acid, as well as by the combination treatment. However, in the absence of LPS, IL-6 secretion was significantly increased in response to 2 µM of either cyanidin or chlorogenic acid (both p < 0.0001), as well as the combination treatment (p < 0.01). MCP-1 secretion followed a similar trend, but did not reach statistical significance. Although we acknowledge the requirement for in vivo investigations to validate our interpretations, current data highlight the potential risk for antioxidant toxicity that is linked to high dose supplementation with single compound antioxidants. Research focused at elucidating synergistic effects between different antioxidants is required to minimise risk of adverse effects.

Plant-Based Nutraceutical Increases Plasma Catalase Activity in Healthy Participants: A Small Double-Blind, Randomized, Placebo-Controlled, Proof of Concept Trial

Oxidative stress resulting from dietary, lifestyle and environmental factors is strongly associated with tissue damage and aging. It occurs when there is either an overproduction of reactive oxygen species (i.e., oxidants) or decreased bioavailability of antioxidants that can scavenge them. The objective of this 12-week double-blind placebo-controlled study was to assess the efficacy of a nutraceutical at augmenting antioxidant status. Healthy adults (25-45 y) were randomized to either a treatment group (Product B, n = 23) or a placebo group (control, n = 20). No significant effect of Product B was observed for anthropometric variables or markers of glucose and lipid regulation. Biomarkers of oxidative stress were likewise not altered following the 12-week intervention. Plasma catalase concentrations were significantly elevated following 12 weeks of Product B as compared to the control group (+6.1 vs. -10.3 nmol/min/mL, p = 0.038), whereas other measures of antioxidant capacity were not significantly different between the groups. Product B effectively augmented concentrations of the anti-aging antioxidant catalase in healthy adults.

Sulforaphane and Other Nutrigenomic Nrf2 Activators: Can the Clinician's Expectation Be Matched by the Reality?

The recognition that food-derived nonnutrient molecules can modulate gene expression to influence intracellular molecular mechanisms has seen the emergence of the fields of nutrigenomics and nutrigenetics. The aim of this review is to describe the properties of nutrigenomic activators of transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2), comparing the potential for sulforaphane and other phytochemicals to demonstrate clinical efficacy as complementary medicines. Broccoli-derived sulforaphane emerges as a phytochemical with this capability, with oral doses capable of favourably modifying genes associated with chemoprevention. Compared with widely used phytochemical-based supplements like curcumin, silymarin, and resveratrol, sulforaphane more potently activates Nrf2 to induce the expression of a battery of cytoprotective genes. By virtue of its lipophilic nature and low molecular weight, sulforaphane displays significantly higher bioavailability than the polyphenol-based dietary supplements that also activate Nrf2. Nrf2 activation induces cytoprotective genes such as those playing key roles in cellular defense mechanisms including redox status and detoxification. Both its high bioavailability and significant Nrf2 inducer capacity contribute to the therapeutic potential of sulforaphane-yielding supplements.

Cisplatin hepatotoxicity mediated by mitochondrial stress

CONTEXT

Chemotherapy has long been the keystone of cancer regimen, and comprehensive research has been done on the development of more potent and less toxic anti-cancer agents. Cisplatin (CP) is a potent and extensively used chemotherapeutic agent. There is paucity of literature involving role of mitochondria in mediating CP-induced hepatic toxicity, and its underlying mechanism remains unclear. Oxidative stress is a well-established biomarker of the mitochondrial toxicity.

OBJECTIVE

This study evaluates the dose-dependent effects of CP-induced mitotoxicity under in vitro conditions, using mitochondria from rat liver.

MATERIALS AND METHODS

The aim of our study was to determine the effect of CP with different concentrations in isolated liver mitochondria as an in vitro model.

RESULTS

CP exposure showed significantly compromised level of non enzymatic and enzymatic antioxidants with higher extent of lipid and protein oxidation. CP also caused significant alterations in the activity of respiratory chain enzymes (complex I-III and V) in liver mitochondria.

DISCUSSION AND CONCLUSION

It is suggested that mitochondria can be employed as a model for future investigations of anticancer drug-induced hepatotoxicity under in vitro conditions. Studies with selected pharmaceuticals and nutraceuticals might certainly play a definite role in deciphering cellular and molecular mechanisms of CP-induced hepatotoxicity and its amelioration.

Sulforaphane: translational research from laboratory bench to clinic

Cruciferous vegetables are widely acknowledged to provide chemopreventive benefits in humans, but they are not generally consumed at levels that effect significant change in biomarkers of health. Because consumers have embraced the notion that dietary supplements may prevent disease, this review considers whether an appropriately validated sulforaphane-yielding broccoli sprout supplement may deliver clinical benefit. The crucifer-derived bioactive phytochemical sulforaphane is a significant inducer of nuclear factor erythroid 2-related factor 2 (Nrf2), the transcription factor that activates the cell's endogenous defenses via a battery of cytoprotective genes. For a broccoli sprout supplement to demonstrate bioactivity in vivo, it must retain both the sulforaphane-yielding precursor compound, glucoraphanin, and the activity of glucoraphanin's intrinsic myrosinase enzyme. Many broccoli sprout supplements are myrosinase inactive, but current labeling does not reflect this. For the benefit of clinicians and consumers, this review summarizes the findings of in vitro studies and clinical trials, interpreting them in the context of clinical relevance. Standardization of sulforaphane nomenclature and assay protocols will be necessary to remove inconsistency and ambiguity in the labeling of currently available broccoli sprout products.

Antioxidants may not always be beneficial to health

Some results from cohort investigations indicate that supplemental antioxidants cannot decrease the risks for some diseases and even can play an inverse role because the antioxidant may not be involved in metabolism or may be a pro-oxidant in vivo. Therefore, further studies are required to identify conditions of an antioxidant converting into a pro-oxidant and the pathway of an antioxidant being a metabolic component. Additionally, long-term investigations on large-scale cohorts are required in order to clarify which disease is suitable for antioxidant therapy and how antioxidant intake can really maintain health.

Defective antioxidant systems in cervical cancer

Cervical cancer remains a great problem for woman health, as it is the second deadly cancer of females worldwide. The infection of human papilloma virus (HPV) is the major risk factor for this cancer, although several other factors are also associated. Oxidative stress or antioxidant deficiency has been frequently identified to be associated with cervical cancer. Defects in the antioxidant enzyme systems are reported to play important role behind this antioxidant deficiency, which is responsible for the production of reactive oxygen species and ultimately, DNA damage in cervical cells. In response, cells become more vulnerable to HPV infection for cervical cancer development. Recently, antioxidant therapies or dietary supplementation of antioxidants have gained considerable interests in the cervical cancer treatment. In this study, we have reviewed the association of defective antioxidant systems and cervical cancer development. The recent advances in both of the basic and clinical research focusing on possible antioxidant therapy have also been discussed.