Effects of environmental lead contamination on cattle in a lead/zinc mining area: Changes in cattle immune systems on exposure to lead in vivo and in vitro

Abstract

The Republic of Zambia is rich in mineral resources, such as zinc (Zn) and lead (Pb), and mining is a key industry in Zambia. A previous study of Pb pollution in Kabwe, one of the main mining areas, found that soil was contaminated with high levels of toxic metals over a substantial area. In the present study, the authors focus on toxic metal pollution in cattle, one of the most important domestic animals in Zambia. Blood samples from cattle in Kabwe and a control area (Lusaka) were tested for toxic metal content. They also measured mRNA expression of metal-responsive proteins and cytokines in white blood cells using real-time reverse transcriptase polymerase chain reaction. In the present in vitro study, The authors cultured peripheral blood mononuclear cells (PBMCs) from cattle, exposing them to Pb acetate for 24 h and analyzing mRNA expression of metal-responsive proteins and selected cytokines. Lead concentrations in cattle blood from Kabwe were significantly greater than those from Lusaka, as were the mRNA expressions of metallothionein-2 (MT-2), tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-1β (IL-1β), IL-6, and inducible nitric oxide synthase (iNOS). The present in vitro study demonstrated that Pb exposure led to an increase in the expressions of MT-2, TNF-α, IL-1β, and iNOS, similar to those found in vivo. These results indicate the possibility of immune system modulations in cattle from the Kabwe area.

Lead poisoning in children from townships in the vicinity of a lead–zinc mine in Kabwe, Zambia

“…Despite extensive Pb pollution in Kabwe, comprehensive studies of Pb exposure and poisoning in children in the vicinity of the mine are rare. In animal studies however, high concentrations of Pb were reported in wild rats (Nakayama et al 2011;Nakayama et al 2013) as well as blood and edible organs of cattle (Yabe et al 2011;Ikenaka et al 2012) and chickens (Yabe et al 2013) reared in the vicinity of the mine in Kabwe. Therefore, the objectives of the current study were to investigate BLLs in children under the age of 7 years in townships around the Pb-Zn mine in Kabwe and to identify children with BLLs that require medical intervention.…”

Constitutive Effects of Lead on Aryl Hydrocarbon Receptor Gene Battery and Protection by β‐carotene and Ascorbic Acid in Human HepG2 Cells

“…Pb exists in the environment in a vapor or solid form, and is a ubiquitous, highly toxic, nonessential element. Studies from our laboratory and those of other groups recorded higher levels of Pb than the established maximum permissible limits in different human food items of animal and plant origin, including meat, edible offal, fish, poultry, and crops (Burger and others ; Yabe and others ; Ikenaka and others ; Morshdy and others ). Heavy metals, particularly Pb, are characterized by their persistent occurrence and accumulation (Korashy and El‐Kadi ; ATSDR ).…”

The analysis of blood lead levels changeability over the 5-year observation in workers occupationally exposed to lead

“…Heme biosynthesis does not decrease until the activity of ALAD is inhibited by 80 to 90%, which occurs at a much higher PbB concentration of about 550 µg/L. Consistently, it has been shown that hemoglobin levels do not begin to decrease until PbB levels are 500 µg/L in adults (Ikenaka et al, 2012; Patrick, 2006). In the present study, the mean hemoglobin levels in both examined groups were within the normal ranges and did not differ significantly.…”

“…These results may be caused by lead’s influence on the function of the immune system. It has been shown that lead may cause an imbalance between the Th1 and Th2 type of immunological response and increase levels of the proinflammatory cytokines such as interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α (Ikenaka et al, 2012; Jorissen et al, 2013; Shen et al, 2001). This increase may be due to lead-induced activation of NF-κB, which is one of the principal inducible transcription factors.…”