Mercury toxicity in pregnant and lactating rats: zinc and N-acetylcysteine as alternative of prevention

Proximal tubular transport of Metallothionein-Mercury complexes and protection against nephrotoxicity

Mercury (Hg) is an important environmental toxicant to which humans are exposed on a regular basis. Mercuric ions within biological systems do not exist as free ions. Rather, they are bound to free sulfhydryl groups (thiols) on biological molecules. Metallothionein (MT) is a cysteine-rich, metal-binding protein that has been shown to bind to heavy metals and reduce their toxic effects in target cells and organs. Little is known about the effect of MT on the handing and disposition of Hg. Therefore, the current study was designed to test the hypothesis that overexpression of MT alters the corporal disposition of Hg and reduces its nephrotoxicity. Furthermore, the current study examined the transport of Hg-MT complexes in isolated proximal tubules. Rats were treated with saline or Zn followed by injection with a non-nephrotoxic (0.5 µmol kg-1), moderately nephrotoxic (1.5 µmol kg-1), or significantly nephrotoxic (2.25 µmol kg-1) dose of HgCl2 (containing radioactive Hg). Pretreatment with Zn increased mRNA expression of MT and enhanced accumulation of Hg in the renal cortex of male and female rats. In addition, injection with Zn also protected animals from Hg-induced nephrotoxicity. Studies using isolated proximal tubules from rabbit kidney demonstrated that Hg-MT is taken up rapidly at the apical and basolateral membranes. The current findings suggest that at least part of this uptake occurs through an endocytic process. This study is the first to examine the uptake of Hg-MT complexes in isolated proximal tubules. Overall, the findings of this study suggest that supplementation with Zn may be a viable strategy for reducing the risk of Hg intoxication in at-risk populations.

Mutagenic, Carcinogenic, and Teratogenic Effect of Heavy Metals

Heavy metal (HM)-induced toxicity and its associated complications have become a major issue in the medical world. HMs are not biodegradable, enter into the food chain, and gets accumulated in the living systems. Increased concentrations and accumulation of HMs can cause severely damaging effects and severe complications in living organisms and can even lead to the death of the organism. In Ayurvedic medicine, ingredients of natural origin, including whole plants or certain portions of the plant, animal sources, and minerals, are used for therapeutic purposes as medicine, both alone and in combination. HM such as cadmium, copper, zinc, lead, chromium, nickel, and arsenic cause hazardous effects on animals, human health, and the environment. This review focuses on mutagenic, carcinogenic, and teratogenic effects of HM , mechanism, organ toxicity, available remedies in the market, and their side effects. Also, emphasis is given to alternative systems of medicine to treat HM toxicity.

Occupational and environmental mercury exposure and human reproductive health - a review

Mercury is a toxic heavy metal. Humans are exposed to mercury through several sources including environmental, occupational, contaminated food and water and from mercury-containing dental amalgam. Mercury exposure is known to harm the nervous system profoundly, and have a negative impact on digestive and immune systems, and other organs. To review and discuss the effect of mercury exposure through environmental or occupational routes on human reproduction, pregnancy, and its outcome. Published information about the potential toxic effects of mercury on human reproduction were collected and summarized. Literature was identified by systematic search using relevant keywords. Literature review revealed a number of negative impacts of mercury on human reproduction. These included effects on semen quality, including reduced sperm count, motility, and changes in morphology that may reduce fertility potential. There may also be an effect in changing reproductive hormone levels. Mercury exposure might also affect pregnancy but the data concerning mercury effects on female reproduction are limited except for some data about mercury exposure and poor pregnancy outcomes. Available data indicate that mercury exposure may have a toxicity effect on reproductive potential, especially in males. Prenatal mercury exposure may affect pregnancy or its outcome and this appears to be dependent upon dose, duration, and timing of exposure. Nutritional status of exposed individual might also influence the impact of mercury.

Toxic metals that interact with thiol groups and alteration in insect behavior

Toxic metals, such as mercury (Hg), lead (Pb), cadmium (Cd), and copper (Cu), are widespread in the biosphere, and human activities have contributed to their continuous release into the ecosystems. Metal-induced toxicity has been extensively studied in mammals; however, the effects of these metals on insects' behavior have been explored to far lesser degree. As the main mechanism of toxicity, the cationic metals, explored in this review, have high affinity for thiol-containing molecules, disrupting the function of several proteins and low-molecular-weight thiol-containing molecules. Existing literature has corroborated that Hg, Pb, Cd, and Cu can disrupt locomotor and mating behaviors, but their effects on insects' memory and learning have yet to be fully characterized. Though field studies on metal-induced toxicity in insects are limited, results from Drosophila melanogaster as an experimental model suggest that insects living in contaminated environments can have behavioral foraging and reproductive deficits, which may cause population decline. In this review, we address the interaction between metals and endogenous thiol groups, with emphasis on alterations in insect behavior.

Ethanol leaf extract of Psychotria microphylla rich in quercetin restores heavy metal induced redox imbalance in rats

Psychotria microphylla is a plant found in Africa and many parts of the world where the leaves are locally used in folk medicine for the treatment of toxicity related liver diseases. We investigated the antioxidant potentials of ethanol leaf extract of Psychotria microphylla (ELE-PM) in restoring hepatic redox dysregulations in rats exposed to heavy metals. HPLC was used in quantifying the bioactive compounds in ELE-PM. DPPH (1,1-diphenyl-2 picrylhydrazyl), FRAP (Ferric reducing antioxidant power) and NO (Nitric Oxide) assays were used for in vitro studies. The in vivo studies involved 30 rats randomly divided into 5 groups (n = 6). Group 1 received normal saline (2 mg/kg), group 2, 3, 4 and 5 received a combined solution of Pb(NO3)2 (11.25 mg/kg) and HgCl2 (0.4 mg/kg) respectively. After 7 days of heavy metal exposure, groups 3, 4 and 5 received a daily bolus administration of 200, 400 and 600 mg/kg body weight of EE-PM respectively through oral intubation for 28 days. HPLC quantification revealed a high amount of quercetin (27.43 ± 0.04 mg/100g), lower amounts of gallic acid (7.60 ± 0.06 mg/100g) and rutin (0.38 ± 0.009 mg/100g). Additionally, ELE-PM demonstrated strong inhibitory potentials against free radical scavenging activity generated in vitro. More interestingly, administration of ELE-PM significantly ameliorated hepatic redox dysregulations elicited by the exposure of the rats to heavy metals in a dose dependent pattern. ELE-PM is highly rich in flavonoid compound quercetin and perhaps this may be responsible for the strong antioxidant potentials exhibited in this investigation.