There is a widespread repeated exposure of the population to the pesticides and heavy metals of occupational and environmental origin. Such population is forced to undergo continuous stress imposed by combined exposure of the heavy metals and different classes of the pesticides used in agricultural as well as health practices. The existing reports from several workers have indicated that heavy metals and pesticides in combination may lead more severe impact on the human health when compared to their individual effects. Such a combination of pesticides and heavy metals may also change or influence the detection of exposure. Several studies in past have shown the synergistic toxic effects of heavy metals and pesticides. Such evaluations have revealed the synergistic interactions of various heavy metals and pesticides in animals as well as humans. The aim of the present article is to provide a synthesis of existing knowledge on the synergistic effects of heavy metal and pesticides in living systems. The information included in this article may be useful for different environment protection agencies and policy makers to consider the combined effects of heavy metals and pesticides on humans while designing strategies toward environmental protection and safety regulations about human health.

Exposure to mixture of pesticides in agricultural practices pose a serious threat to the nontarget animals. In present work, we have evaluated the synergistic effect of cartap and malathion on rat liver followed by impact of Aloe vera leaves aqueous extract, which is not known. The animals in eight groups were used; each containing six rats: Group 1 acted as a control, Group 2—control with A. vera leaves aqueous extract, Group 3—with cartap, Group 4—with malathion, Group 5—with mixture of cartap and malathion, Group 6—cartap with the pretreatment of A. vera leaf extract, Group 7—malathion with the pretreatment of A. vera leaf extract, Group 8—mixture of cartap and malathion with the pretreatment of A. vera leaf extract . The animals treated for 15 days were killed after 24hr of last treatment. The biochemical studies in the rat liver demonstrated significant perturbations in the levels of nonenzymatic (glutathione and malondialdehyde) and enzymatic (superoxide dismutase, catalase, and glutathione‐ S‐transferase) antioxidative indices. The histopathological examination of liver revealed serious congestion in central vein and the disorganization of hepatic cords due to pesticide treatment. The administration of A. vera leaves aqueous extract was able to markedly protect rat liver from the pesticides‐induced toxicity. The data indicated that pesticides were able to significantly induce oxidative stress which was substantially reduced by the application of plant extract .

The effects of lead exposure on mammals are reported to be devastating. Lead is present in all the abiotic environmental components such as brass, dust, plumbing fixtures, soil, water, and lead mixed imported products. Its continuous use for several industrial and domestic purposes has caused a rise in its levels, thereby posing serious threats to human health. The mechanisms involved in lead-induced toxicity primarily include free-radical-mediated generation of oxidative stress which directly imbalances the prooxidants and the antioxidants in body. The toxicity of lead involves damage primarily to major biomolecules (lipid, protein, and nucleic acids) and liver (hepatotoxicity), nervous system (neurotoxicity), kidney (nephrotoxicity) and DNA (genotoxicity), present in animals and humans. The activation of c-Jun NH2-terminal kinase, phosphoinositide 3-kinase, or Akt and p38 mitogen activated protein kinase signaling pathways are important for lead cytotoxicity. Lead increased apoptosis through signaling cascade and associated factors and significantly impairs cell differentiation and maturation. In addition, lead has great impact on metabolic pathways such as heme synthesis, thereby leading to the onset of anemia in lead exposed people. This review encompasses an updated account of varied aspects of lead-induced oxidative stress and the biomolecular consequences such as perturbations in physiological processes, apoptosis, carcinogenesis, hormonal imbalance, loss of vision, and reduced fertility and their possible remediation through synthetic (chelators) and natural compounds (plant-based principles). This paper is primarily concerned with the biomedical implications of lead-induced generation of free radical and the toxicity management in the mammalian system.

Almost all the environmental components including both the abiotic and biotic factors have been consistently threatened by excessive contamination of heavy metals continuously released from various sources. Different heavy metals have been reported to generate adverse effects in many ways. Heavy metals induced neurotoxicity and impairment in signalling cascade leading to cell death (apoptosis) has been indicated by several workers. On one hand, these metals are required by the cellular systems to regulate various biological functions of normal cells, while on the other their biomagnification in the cellular systems produces adverse effects. The mechanism by which the heavy metals induce neurotoxicity follows free radicals production pathway(s) specially the generation of reactive oxygen species and reactive nitrogen species. These free radicals produced in excess have been shown to create an imbalance between the oxidative and antioxidative systems leading to emergence of oxidative stress, which may cause necrosis, DNA damage, and many neurodegenerative disorders. This mini review summarizes the current knowledge available on the protective role of varied natural products isolated from different herbs/plants in imparting protection against heavy metals (cadmium, lead, arsenic, and mercury) mediated neurotoxicity.

The indiscriminate use of carbofuran to improve crop productivity causes adverse effects in nontargets including mammalian systems. The objective of this study was to evaluate carbofuran induced oxidative stress in rat brain stem and its attenuation by curcumin, a herbal product. Out of 6 groups of rats, 2 groups received two different doses of carbofuran, that is, 15 and 30% of LD50, respectively, for 30 days. Out of these, 2 groups receiving same doses of carbofuran were pretreated with curcumin (100 mg/kg body weight). The levels of antioxidants, TBARS, GSH, SOD, catalase, and GST were determined in rat brain stem. The 2 remaining groups served as placebo and curcumin treated, respectively. The data suggested that carbofuran at different doses caused significant alterations in the levels of TBARS and GSH in dose dependent manner. The TBARS and GSH contents were elevated. The activities of SOD, catalase, and GST were significantly inhibited at both doses of carbofuran. The ratio of P/A was also found to be sharply increased. The pretreatment of curcumin exhibited significant protection from carbofuran induced toxicity. The results suggested that carbofuran at sublethal doses was able to induce oxidative stress in rat brain which could be attenuated by curcumin.

Graphical abstract

Lead induced neurotoxicity in the people engaged in different occupations has received wide attention but very little studies have been carried out to monitor occupational neurotoxicity directly due to lead exposure using biochemical methods. In the present paper an endeavour has been made in order to assess the lead mediated neurotoxicity by in vitro assay of the activity of acetylcholinesterase (AChE) from human erythrocytes in presence of different concentrations of lead. The results suggested that the activity of this enzyme was localized in membrane bound fraction and it was found to be highly stable up to 30 days when stored at −20°C in phosphate buffer (50 mM, pH 7.4) containing 0.2% Triton X-100. The erythrocyte's AChE exhibited K m for acetylcholinesterase to be 0.1 mM. Lead caused sharp inhibition of the enzyme and its IC50 value was computed to be 1.34 mM. The inhibition of the enzyme by lead was found to be of uncompetitive type (K i value, 3.6 mM) which negatively influenced both the V max and the enzyme-substrate binding affinity. Taken together, these results indicate that AChE from human erythrocytes could be exploited as a surrogate biomarker of lead induced neurotoxicity particularly in the people occupationally exposed to lead.

Aloe vera has been the most useful medicinal herb in the world since ancient times due to its vast biological effects. The presence of high content of bioactive compounds make Aloe vera a promising complementary and alternative agent in disease prevention. The effectiveness of A. vera-based medicines against pesticide toxicity has never been evaluated. It was therefore envisaged to develop an A. vera-based strategy to protect the non-target animals from adverse effects of the pesticides. This article illustrates the ameliorating effect of aqueous extract (AE) of A. vera leaves against the cartap and malathion toxicity. To evaluate the protective impact of A. vera against cartap (Ctp), malathion (Mtn) and a mixture of both pesticides, the animals were divided in eight groups, each containing six rats: Group 1- C (control), Group 2- AE + C, Group 3- Ctp, Group 4- Mtn, Group 5- Ctp + Mtn, Group 6- AE + Ctp, Group 7- AE + Mtn, Group 8- AE + Ctp + Mtn. Wistar rats exposed to Ctp, Mtn and Ctp + Mtn, displayed significant change in body weight. It was observed that the WBC level increased significantly in Mtn and Ctp + Mtn challenged groups. The contents of TNF-α and IL-6 in serum increased expressively in the Ctp, Mtn and Ctp + Mtn challenged groups. Rats treated with Ctp, Mtn and Ctp + Mtn displayed significant alterations in the levels of antioxidative indices (MDA, GSH, GST, GPx, SOD and CAT). Significant alterations were recorded in the activities of AST, ALT, ACP and ALP in Ctp, Mtn and Ctp + Mtn challenged groups. The histopathological results of liver supported the biochemical data. The pre-treatment of rats with the aqueous extract of A. vera leaves significantly protected them from the toxicity of pesticides. These results suggested that A. vera extract may be used as a promising natural agent for the management of pesticide induced toxicity.