Antioxidants as a Potential Preventive and Therapeutic Strategy for Cadmium

Abstract

Epidemiological studies provide a growing number of evidences that chronic exposure to relatively low levels of cadmium (Cd), nowadays taking place in industrialized countries, may cause health hazard. Thus, growing interest has been focused on effective ways of protection from adverse effects of exposure to this heavy metal. Because numerous effects to Cd's toxic action result from its prooxidative properties, it seems reasonable that special attention should be directed to agents that can prevent or reduce this metal-induced oxidative stress and its consequences in tissues, organs and systems at risk of toxicity, including liver, kidneys, testes, ears, eyes, cardiovascular system and nervous system as well as bone tissue. This review discusses a wide range of natural (plant and animal origin) and synthetic antioxidants together with many plant extracts (e.g. black and green tea, Aronia melanocarpa, Allium sativum, Allium cepa, Ocimum sanctum, Phoenix dactylifera, Physalis peruviana, Zingiber officinale) that have been shown to prevent from Cd toxicity. Moreover, some attention has been focused on the fact that substances not possessing antioxidative potential may also prevent Cd-induced oxidative stress and its consequences. So far, most of the data on the protective effects of the natural and synthetic antioxidants and plant extracts come from studies in animals' models; however, numerous of them seem to be promising preventive/therapeutic strategies for Cd toxicity in humans. Further investigation of prophylactic and therapeutic use of antioxidants in populations exposed to Cd environmentally and occupationally is warranted, given that therapeutically effective chelation therapy for this toxic metal is currently lacking.

The Mechanism of the Osteoprotective Action of a Polyphenol-Rich Aronia melanocarpa Extract during Chronic Exposure to Cadmium is Mediated by the Oxidative Defense System

“…Nowadays, the consumption of aronia berries is widely recommended as one of the most abundant sources of compounds having a beneficial influence on the organism, and the richest source among plant materials of anthocyanins, which are characterized by strong antioxidative properties [13,14,[18][19][20][21]. Data provided by Kowalczyk et al [15] and our recent findings [6,22,23] seem to indicate that the consumption of chokeberries and their products may prevent Cd accumulation in the body and its toxic action. Using a female rat model of low and moderate lifetime human exposure to Cd (1 and 5 mg Cd/kg diets, respectively, for up to 24 months), we have revealed that a polyphenol-rich AME may decrease the gastrointestinal absorption and body burden of this xenobiotic (including its accumulation in the liver, kidneys, and bone tissue) [22], as well as significantly prevent disturbances induced by this heavy metal in the bone turnover, and changes in the bone mineral status [23].…”

“…Zinc not only stimulates osteoblasts proliferation and differentiation, but it also suppresses osteoclasts differentiation by, among others, antagonizing NF-κB activation [27,33,34]. Polyphenols, due to their ability to bind Cd 2+ [4], may decrease the body burden of Cd and thus protect against the effects of its direct and indirect action, resulting in the improvement of the oxidative/antioxidative balance and bone turnover [6,15,22,23]. It is also necessary to take into consideration that the molecular mechanisms of the beneficial impact of polyphenols on bone tissue metabolism might be related to the ability of these compounds to enhance the production of nitric oxide, which is essential for the induction of new bone formation [35], as well as to induce the nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated antioxidant gene expressions and thereby to decrease the oxidative status [7].…”

“…Recently, the possibility of using natural plant ingredients for protection against the dangerous action of xenobiotics to which humans are exposed throughout their lifetime, including Cd, which is one of the most toxic heavy metals, has been of special interest to researchers [1][2][3][4][5][6][7][8][9]. Evidence that even relatively low exposure to Cd contributes to osteoporosis and bone fractures [10][11][12] together with forecasts that the general populationʼs exposure to this element will increase [2] are reasons that growing attention has been focused on searching for an effective means of protection from the unfavorable action of this xenobiotic, including damage to the skeleton.…”

“…Evidence that even relatively low exposure to Cd contributes to osteoporosis and bone fractures [10][11][12] together with forecasts that the general populationʼs exposure to this element will increase [2] are reasons that growing attention has been focused on searching for an effective means of protection from the unfavorable action of this xenobiotic, including damage to the skeleton. It seems that polyphenols, being the most abundant bioactive components in our diet [13,14], are a promising group of compounds playing a role in this protection [3][4][5][6][7][8][9]15]. Owing to the large number of -OH groups, these compounds are capable of chelating metal ions, including Cd 2+ [4,6,14].…”

“…It seems that polyphenols, being the most abundant bioactive components in our diet [13,14], are a promising group of compounds playing a role in this protection [3][4][5][6][7][8][9]15]. Owing to the large number of -OH groups, these compounds are capable of chelating metal ions, including Cd 2+ [4,6,14]. It has been revealed that some food products abundant in polyphenolic compounds, including especially green tea and soybeans, may offer protection against various effects of exposure to Cd; however, the data is very sparse and refers only to chosen compounds [3,[5][6][7][8][9][15][16][17].…”