Synergistic Effects of Heavy Metals and Pesticides in Living Systems

MINI REVIEW published: 11 October 2017 doi: 10.3389/fchem.2017.00070 Synergistic Effects of Heavy Metals and Pesticides in Living Systems Nitika Singh, Vivek Kumar Gupta, Abhishek Kumar and Bechan Sharma* Department of Biochemistry, Faculty of Science, University of Allahabad, Allahabad, India Edited by: Cesare Indiveri, University of Calabria, Italy Reviewed by: Elena A. Ostrakhovitch, Frontiers in Bioscience Research Institute, United States Elia Ranzato, Università degli Studi del Piemonte Orientale “Amedeo Avogadro,” Italy *Correspondence: Bechan Sharma Specialty section: This article was submitted to Cellular Biochemistry, a section of the journal Frontiers in Chemistry Received: 29 April 2017 Accepted: 11 September 2017 Published: 11 October 2017 Citation: Singh N, Gupta VK, Kumar A and Sharma B (2017) Synergistic Effects of Heavy Metals and Pesticides in Living Systems. Front. Chem. 5:70. doi: 10.3389/fchem.2017.00070 Frontiers in Chemistry | www.frontiersin.org 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. Keywords: contamination, risk assessment, combined interaction, synergistic effect, heavy metal, pesticide INTRODUCTION Heavy metals are those inorganic elements which have five times the specific gravity of water (Fergusson, 1990). According to the Agency for Toxic Substances and Disease Registry (2007), arsenic, lead, cadmium (Cd), and mercury have serious health implications among the heavy metals (Csavina et al., 2012; Sharma et al., 2014; Gupta et al., 2015a). Among many heavy metals listed into the d-orbital elements of modern periodic table, arsenic, Cd, mercury, and lead have got prime importance because of their patho-physiological significance as their bioaccumulation in living systems may cause severe damage to the vital organs, namely reproductive systems, nervous system, gastrointestinal tract, and mucous tissues (Sharma et al., 2014; Gupta et al., 2015b). Though the exact mechanism of their pathogenicity is not known but there are reports from various laboratories indicating that the exposure of these heavy metals or their excess accumulation in the body tissues may induce production of free radicals [reactive oxygen species (ROS) and reactive nitrogen species (RNS)] which lead to the production of oxidative stress (OS) (Figure 1; Flora et al., 2008; Sharma et al., 2014; Gupta et al., 2015a; Asmat et al., 2016). Free radicals have been implicated into DNA damage, oxidation of thiol group(s) of proteins, and lipid peroxidation (LPO) (Figure 1; Valko et al., 2005) which is associated with the onset of 1 October 2017 | Volume 5 | Article 70 Singh et al. Heavy Metals and Pesticide Toxicity et al., 2012; Chen et al., 2012). The combination exposure of chlorpyrifos (CPF) and Cd has been reported to decrease the mitochondrial potential and induced reactive oxygen species (Xu et al., 2017b). Some xenobiotics are recalcitrant in nature (Godheja et al., 2016) i.e., they are highly resistant to environmental degradation, such as synthetic organochlorines, natural organic compounds like polyaromatic hydrocarbons. The organochlorines contain carbon, chlorine and hydrogen; the carbon to halide bond being highly resistant to degradation. Therefore, the organochlorines are degraded very slowly and hence remain in the environment or/and inside the organisms after exposure for longer duration (Wandiga, 2001). Carbamates are derived from carbamic acid and used to kill insects/pests (Struger et al., 2016) in a similar fashion as organophosphates. It has been shown that carbofuran is highly neurotoxic and may modulate the functions of acetylcholinesterase (AChE) (Gupta et al., 2016). Organocarbamate pesticides are a class of insecticides which are not broad spectrum in insecticidal function as compared to organophosphates. Most of the carbamates are extremely toxic to hymenoptera (Brunner et al., 2001). It is thirdlargest order of insects which contains over 150,000 species of arthropods. It comprises the sawflies, wasps, bees, and ants hence the precautions must be taken to avoid exposure to these insects. The pesticide (organocarbamate) exposure to the humans may occur through the inhalation of contaminated air, dermal contact to soils, air and water, drinking water and eating contaminated food (Agrawal and Sharma, 2010). Organophosphates are also a group of wide spectrum pesticides which are reported to be highly neurotoxic and causes several diseases to humans (Agrawal and Sharma, 2010; Gupta and Sharma, 2016). The present article illustrates an updated account of the synergistic effects of heavy metals and the pesticides into different organs of the animals and humans. The manuscript provides a synthesis of existing knowledge on the synergistic effect of heavy metals and pesticides in living system. various diseases. The Cd and lead are reported to be neurotoxic by inhibiting acetylcholinesterase (AChE) in blood (Gupta et al., 2015b,c) and brain (Gupta et al., 2015b,c), respectively. All heavy metals are toxic in sufficient quantities (Everson et al., 1988; Zukowska and Biziuk, 2008; Taghipour et al., 2014). Because of their presence in our environment and similarity with biochemical activity of some factors involved in the biochemical pathways, lead, mercury, Cd, and arsenic mimics their functions and are of particular interest. Heavy metals produce toxicity by forming complexes with cellular compounds containing sulfur, oxygen, or nitrogen (Aguilera et al., 2017; Kumar et al., 2017; Trost and Tracy, 2017) on entering into our body through food, drinking water, and air. These complexes inactivate or modulate the critical enzyme systems or/protein structures leading to cellular dysfunction and necrosis (Sharma (...truncated)