Metal Bioaccumulation, Cytogenetic and Clinico-Biochemical Alterations in Rattus norvegicus Exposed In Situ to a Municipal Solid Waste Landfill in Lagos, Nigeria

A comprehensive overview on solid waste leachate effects on terrestrial organisms

Leachate is a highly complex waste with high toxicological potential that poses a significant threat to the terrestrial environment. Determining leachate physicochemical parameters and identifying xenobiotics alone is, however, not enough to determine the real environmental impacts. In this context, the use of terrestrial model organisms has been highlighted as a tool in ecotoxicological leachate assessments and as a guiding principle in risk assessments. In this context, this review aimed to present the most current state of knowledge concerning leachate toxicity and the bioassays employed in this evaluation concerning terrestrial plants and animals. To this end, a literature search on leachate effects on terrestrial organisms was carried out using ten search terms, in 32 different combinations, at the Web of Science and Scopus databases. A total of 74 eligible articles were selected. The retrieved studies analyzed 42 different plant and animal species and employed nine endpoints, namely phytotoxicity, genotoxicity, bioaccumulation, antioxidant system, cytotoxicity, reproduction, physiological changes, behavior and lethality. A frequent association of toxic leachate effects with metals was observed, mainly Pb, Cd, Cr, Mg, Zn and Cr, which can cause antioxidant system alterations and cyto- and genotoxicity. These elements have also been associated to reproductive effects in earthworms and mice. Specifically concerning plants, most of the retrieved studies employed Allium cepa in toxicity assays, reporting phytotoxic effects frequently associated to metals and soil parameter changes. Animal studies, on the other hand, mostly employed mice and evaluated genotoxicity and antioxidant system effects. Even with the description of toxic leachate effects in both plants and animals, a lack of knowledge is still noted concerning reproductive, physiological, cytotoxic, and behavioral effects in terrestrial species. We, thus, suggest that further studies be carried out on other animals, advancing our understanding on potential environmental leachate effects, also allowing for human health risk assessments.

Oxidative stress and toxicity produced by arsenic and chromium in broiler chicks and application of vitamin E and bentonite as ameliorating agents

The present study investigated the adverse effects of arsenic and chromium in broilers and ascertained the role of vitamin E and bentonite in alleviating their harmful effects. For this purpose, we experimented on 180 one-day-old broiler chickens. The feed was administered to broiler chicks of groups 2, 6, 7, 8, and 9 chromium @ (270 mg.kg−1 BW). Groups 3, 6, 7, 8, and 9 were administered arsenic @ (50 mg.kg−1 BW). Groups 4, 7, and 9 received vitamin E (150 mg.kg−1 BW), and groups 5, 8, and 9 received bentonite (5%), respectively. Group 1 was kept in control. All the broiler chicks treated with chromium and arsenic showed a significant (p < 0.05) decline in erythrocytic parameters on experimental days 21 and 42. Total proteins decreased significantly, while ALT, AST, urea, and creatinine increased significantly (p < 0.05). TAC and CAT decreased significantly (p < 0.05), while TOC and MDA concentrations increased significantly (p < 0.05) in chromium and arsenic-treated groups on experimental days 21 and 42. Pearson correlation analysis revealed a strong positive correlation between TAC and CAT (Pearson correlation value = 0.961; p < 0.001), similarly TOC and MDA positive correlation (Pearson correlation value = 0.920; p < 0.001). However, TAC and CAT showed a negative correlation between TOC and MDA. The intensity of gross and microscopic lesions was more in chromium (270 mg.kg−1) and arsenic (50 mg.kg−1) singly or in combination-treated groups. Thus, broiler chicks treated with chromium plus arsenic exhibited higher gross and microscopic lesion intensity than other treated groups. Fatty degeneration, severe cytoplasmic vacuolar degeneration, and expansion of sinusoidal spaces were the main lesions observed in the liver. Kidneys showed renal epithelial cells necrosis, glomerular shrinkage, and severe cytoplasmic vacuolar degeneration. Co-administration of bentonite along with chromium and arsenic resulted in partial amelioration (group 8) compared to groups 7 and 9, administered arsenic + chromium + vitamin E and arsenic + chromium + vitamin E + bentonite, respectively. It was concluded that arsenic and chromium cause damage not only to haemato-biochemical parameters but also lead to oxidation stress in broilers. Vitamin E and bentonite administration can ameliorate toxicity and oxidative stress produced by arsenic and chromium.

Mitochondrial dysfunctions elicited by solid waste leachates provide insights into mechanisms of leachates induced cell death and pathophysiological disorders

Emissions (mainly leachates and landfill gases) from solid waste facilities are laden with mixtures of dangerous xenobiotics implicated with significant increase in various pathophysiological disorders including cancer, and eventual mortality of exposed wildlife and humans. However, the molecular mechanisms of solid waste leachates induce pathophysiological disorders and cell death are still largely unknown. Although, evolving evidence implicated generation of reactive oxygen species and oxidative stress as the possible mechanism. Recent scientific reports are linking reactive oxygen species and mitochondrial dysfunctions as the player mechanism in pathophysiological disorder and apoptosis induced by xenobiotics in solid waste leachates. This systematic review presents an explicit discussion of recent scientific findings on the structural and functional alterations in mitochondria induced by solid waste leachates as the molecular mechanisms plausibly responsible for the pathophysiological disorders, cancer and cell death reported in landfill toxicology and epidemiological studies. This review aims to increase scientific understanding on solid waste leachate induced mitochondria dysfunctions as the key player in molecular mechanisms of solid waste induced toxicity. The findings in this review were mainly from using primary cells, cell lines, Drosophila and fish. Whether the findings will similarly be observed in mammalian test systems in vivo and particularly in exposed humans, remained to be investigated. Improvement in technological advancements, enforcement of legislation and regulations, and creation of sophisticated health surveillance against exposure to solid waste leachates, will expectedly mitigate human exposure to solid waste emissions and contamination of the environment.

Landfill soil leachates from Nigeria and India induced DNA damage and alterations in genes associated with apoptosis in Jurkat cell

Landfill soil leachates, containing myriad of xenobiotics, increase genotoxic and cytotoxic stress-induced cell death. However, the underlying mechanism involved in the elimination of the damaged cells is yet to be fully elucidated. This study investigated the apoptotic processes induced in lymphoma (Jurkat) cells by landfill soil leachates from Olusosun (OSL, Nigeria) and Nagpur (NPL, India). Jurkat was incubated with sub-lethal concentrations of OSL and NPL for 24 h and analyzed for DNA fragmentation and apoptosis using agarose gel electrophoresis and Hoechst 33258-PI staining, respectively. Complementary DNA expression profiling of some pro-apoptotic and anti-apoptotic genes regulating apoptosis was also analyzed using real-time PCR (RT-PCR) method. Agarose gel electrophoresis revealed DNA fragmentations in OSL and NPL-treated cells. Hoecsht-33258 - Propidium Iodide (PI) based apoptotic analysis confirmed apoptotic cell death in exposed Jurkat. RT-PCR analysis revealed different fold changes in the pro- and anti-apoptotic genes in OSL and NPL-treated Jurkat. There was significant increase in fold change of the up-regulated genes; apoptosis inducing factor mitochondrion-associated 2 (AIFM2), Fas-associated death domain (FADD), Caspase-2, Caspase-6, BH3 interacting domain death agonist (BID), tumor suppressor (p53), and BCL2 associated agonist of cell death (BAD) and down-regulation of apoptosis inhibitor 5 (API5). Results suggest that OSL and NPL elicited genotoxic stress-related apoptosis in Jurkat. The dysregulation in the expression of genes involved in apoptotic processes in wildlife and human exposed to landfill emissions may increase aetiology of various pathological diseases including cancer.