AMELIORATIVE EFFECT OF RESVERATROL ON LEAD-INDUCED ORGAN TOXICITY IN WISTAR RATS

Abstract

Resveratrol is a potent antioxidant found abundantly in grapes and in lesser quantities in peanuts, fruits and other food items. Dozens of reports have shown that resveratrol prevents or slows the progression of a wide variety of illnesses including cancer (colon and melanoma). The aim of this experiment was to investigate the ameliorative effect of resveratrol on lead-induced organ toxicity in wistar rats. The study employed wistar rats (150 – 250 g) which were administered carboxymethylcellulose 10 g/l (control), lead acetate solution (120 mg/kg), lead acetate solution (120 mg/kg) and succimer (10 mg/kg BW); lead acetate solution (120 mg/kg) and resveratrol (200 mg/kg); lead acetate solution (120 mg/kg) and resveratrol (400 mg/kg); and resveratrol alone (400 mg/kg) then administered lead acetate solution (120 mg/kg) daily for 2 weeks and considered as prophylactic group. All treatments were through the oral routes for different days. The acute toxicity of resveratrol was evaluated using the up and down method via oral routes in rats. The animal‟s body weights were recorded on days 1, 7 and 20. Also after animals were euthanized, relative organ weights were evaluated. Blood, plasma and organs samples were evaluated for blood lead levels (BLLs), heamatological analysis, biochemical analysis and histopathology. The LD50 was found to be above 5000 mg/kg. The results showed no significant (p > 0.05) change in body weight (BW) in resveratrol-treated group compared to the positive control group. Resveratrol-pretreated group showed improved BW compared to that of the positive control rats, although the difference was not significant (p > 0.05). There was significant (p < 0.001) decrease in BLLs of resveratrol-treated groups compared to both negative and positive control groups. No significant (p > 0.05) change was recorded for the liver function parameters and electrolytes concentration, when the resveratrol-treated rats were compared to negative and positive control groups. There was significant (p < 0.05) increase in platelet counts in resveratrol-treated group (392.33 ± 31.81) compared to both negative (219.50 ± 30.50) and lead acetate treated group (210.50 ± 24.99). No significant (p > 0.05) change was recorded for the other heamatological parameters, when the resveratrol-treated groups were compared to negative and positive control groups. In the histopathology, the toxic effect of lead recorded in liver, kidney, heart and brain in the positive control group were significant (p < 0.05) when compared to resveratrol-treated groups. The toxic effects caused by lead were reduced to minimal level in resveratrol-treated groups. In conclusion, resveratrol ameliorated the adverse effects induced by lead in male wistar rats. This suggests that resveratrol may contain pharmacological compounds that could be useful in treatment of lead poisoning. CHAPTER ONE

1.0 INTRODUCTION

1.1 Background

Lead is a heavy, low melting, bluish-gray metal that occurs naturally in the Earth’s crust. However, it is rarely found naturally as a metal. It is usually found combined with two or more other elements to form lead compounds. For these reasons, lead has been used by humans for millennia and is widespread today in products as diverse as pipes, storage batteries, pigments and paints, glazes, vinyl products, weights, shot and ammunition, cable covers, and radiation shielding. Tetra-ethyl lead was used extensively from the 1930s to the 1970s as a petrol additive to improve engine performance (Rosner and Markowitz, 1985; Landrigan et al., 2002). Tetra-ethyl lead has been eliminated from the petrol supplies of the majority of countries, but is still used in about nine countries (UNEP, 2008).

Lead poisoning (also known as Plumbism, Colica Pictonum, aturnism, Devon colic, or painter’s colic) is a medical condition in humans and other vertebrates caused by increased levels of the heavy metal lead in the body (Washington, 2011). Lead interferes with a variety of body processes and is toxic to many organs and tissues including the heart, bones, intestines, kidneys, reproductive and nervous systems. It interferes with the development of the nervous system and is therefore particularly toxic to children, causing potentially permanent learning and behaviour disorders. Symptoms include abdominal pain, confusion, headache, anemia, irritability, and in severe cases seizures, coma, and death (Washington, 2011).

Routes of exposure to lead include contaminated air, water, soil, food, and consumer products. Occupational exposure is a common cause of lead poisoning in adults. According to estimates made by the National Institute of Occupational Safety and Health (NIOSH), more than three million workers in the United States are potentially exposed to lead in the workplace (Staudinger and Roth, 1998) . One of the largest threats to children is lead paint that exists in many homes, especially older ones; thus children in older housing with chipping paint or lead dust from moveable window frames with lead paint are at greater risk. Prevention of lead exposure can range from individual efforts (e.g. removing lead-containing items such as piping or blinds from the home) to nationwide policies (e.g. laws that ban lead in products, reduce allowable levels in water or soil, or provide for cleanup and mitigation of contaminated soil, etc.)

Elevated lead in the body can be detected by the presence of changes in blood cells visible with a microscope and dense lines in the bones of children seen on X-ray (Washington, 2011). However, the main tool for diagnosis is measurement of the blood lead level. When blood lead levels are recorded, the results indicate how much lead is circulating within the blood stream, not the amount being stored in the body (Washington, 2011). There are two units for reporting blood lead level, either micrograms per deciliter (µg/dl), or micrograms per 100 grams (µg/100 g) of whole blood, which are numerically equivalent. The US Centers for Disease Control (CDC) has set the standard for elevated blood lead level for adults to be 10 µg/dl of the whole blood. For children however, the number is set much lower at 5 µg/dl of the whole blood down from a previous 10 µg/dl (DCP, 2012). Children are especially prone to the health effects of lead and as a result, blood lead levels must be set lower and closely monitored for contamination (Washington, 2011). The major treatments approaches are the removal of the source of lead and chelation therapy, administration of agents that bind lead so it can be excreted (Washington, 2011).

Humans have been mining and using this heavy metal for thousands of years, poisoning themselves in the process (CDC, 2012). Although lead mining is one of the oldest known occupation and a contributor to environmental hazards, the modern understanding of the small amount of lead necessary to cause harm did not come about until the latter half of the 20th century. No safe threshold for lead exposure has been suggested, that is there is no known amount of lead that is too small to cause body harm.

Resveratrol (3, 5, 4‟-trihydroxystilbene) is a polyphenol that occurs naturally in foods and drinks made from grapes and peanuts, and also in a number of herbal remedies, both alone and as part of plant extracts. Resveratrol attracted little interest until 1992, when it was postulated to explain some of its cardioprotective properties and was thought to account in part for the so-called „French Paradox‟, that is, the finding that the rate of coronary heart disease mortality in France is lower than that observed in other industrialized countries with a similar risk factor profile (Siemann and Creasy, 1992). Since then, reports have shown that resveratrol prevents or slows the progression of a wide variety of illnesses, including cancer, cardiovascular disease (Bradamante et al., 2004) and ischaemic injuries (Sinha et al., 2002).

Resveratrol enhances stress resistance and extends the lifespan of various organisms from yeast to vertebrates (Valenzano et al., 2006); it reduces the incidence of breast cancer (Whitsett and Lamartiniere, 2006; Wesierska-Gadek et al., 2007; Ferry-Dumazet et al., 2002; Joe et al., 2002), cardiovascular diseases (Renaud and de- Lorgeril, 1992; Renaud and Gueguen, 1998), and possesses antioxidant property (Giovannini et al., 2001).

Resveratrol is a potent antioxidant, demonstrated to ameliorate adverse effects of heat stress-induced toxicity (Putics et al., 2008; Das, 2011, Sahin et al., 2012). Information on the ameliorative effect of resveratrol on heavy metals induced organ toxicity is scanty. The present study was undertaken to assess the ameliorative effect of resveratrol on lead induced organ toxicity in rats.

1.2 Statement of Research Problem

Although lead poisoning has been reported for centuries, it is a relatively new phenomenon in Nigeria. The recent unregulated mining activities in Zamfara State which resulted in serious toxicities and medical problems among adults and children alike is a source for concern. These unregulated mining activities are becoming more widespread in Nigeria and if unchecked, the medical and social consequence will be staggering.

Unfortunately, the people involved in this unregulated mining have little/no education and therefore lack the ability to protect themselves from the ensuing toxicities and medical problems. Reports have so far indicated that children are worse affected with little or no medical help coming their way (MSF, 2010; Blacksmith Institute, 2011). As from March – June 2010, 163 death cases of lead poisoning was reported (BBC News, 2010; independent News and Media, 2010) and 355 cases discovered (BBC News, 2010) with 46 % proving fatal (Yahaya and Sahabi, 2010). From May 2009 to May 2010, 25% (118 of 463) of children greater than 5 years of age in the surveyed compounds were reported to have died and 82% (97 of 118) were reported to have had convulsion before death (Lo et al., 2010).

Effects of lead, such as inhibition of aminolevulinic acid dehydratase (ALAD), elevation of aminolevulinic acid (ALA) in urine and increase of free erythrocyte protoporphyrin in blood, have been observed in humans exposed to lead (Moore, 1988).

1.3 Justification

Lead poisoning is increasingly becoming a health problem with catastrophic consequences especially among children, whereas the known remedies are not easily available and affordable. The treatment for lead poisoning involves the use of chelating agents EthyleneDiamineTetraacetic Acid, Dimercaptosuccinic Acid, and Succimer (Graziano et al., 1985; O‟Connor and Rich, 1999) which may not readily be available for such affected rural communities to use.

This therefore necessitates the need for research into possible ethno medicinal forms of treatment that may be easily accessible and affordable. Resveratrol found in grapes, peanut and many other fruits and food items are indigenous and research have shown its therapeutic potentials in curing many medical problems and is reported to have central nervous system, antioxidant, chelating and anti-aging properties (Baur and Sinclair, 2006). These important properties make resveratrol an attractive candidate for investigation with respect to its potential as an antidote/chelating or ameliorative agent in lead poisoning.

1.4 Aim and Objectives of the Study

1.4.1 Aim

The main aim of this study is to evaluate the possible ameliorative effects of resveratrol on lead induced organ toxicity in male wistar rats.

1.4.2 Objectives

The objectives of this study are to:

➢ Assess effects of resveratrol on lead induced toxicities acute and sub-acute in wistar rats.

➢ Determine body and relative organ weight of wistar rats treated with resveratrol in presence of lead.

➢ Determine blood lead levels (BLLs) of wistar rats treated with resveratrol in presence of lead.

➢ Investigate the possible prophylactic effect of resveratrol in preventing lead-induced toxicity in wistar rats.

➢ Evaluate the effect of resveratrol on hematological, biochemical and histo-pathological parameters in lead-induced toxicity in wistar rats.

1.5 Statement of Research Hypothesis

Resveratrol ameliorates the adverse effects of lead induced organ toxicity in wistar rats.