Abstract
Toll-like receptor (TLRs) are important innate immune receptors, and TLR2 and TLR4 play an important role in intestinal mucosal innate immunity. It has been found that nickel (Ni) can affect the immune system in broilers. The purpose of this study was to analyze changes in TLR2-2 and TLR4 mRNA expression levels in the intestinal mucosal immunity system of broilers induced by dietary nickel chloride (NiCl2) using quantitative real-time polymerase chain reaction (qRT-PCR) assays. Two hundred and forty one-day-old avian broilers were divided into four groups and fed on a corn-soybean basal diet as control diet or the same basal diet supplemented with 300, 600 and 900 mg/kg of NiCl2 for 42 days. Results showed that the TLR2-2 and TLR4 mRNA expression levels in the intestinal mucosa and the cecal tonsil were lower (p < 0.05 or p < 0.01) in the 300, 600 and 900 mg/kg groups than those in the control group. It was concluded that dietary NiCl2 in excess of 300 mg/kg could reduce TLR2-2 and TLR4 mRNA expression levels in the intestinal mucosa and cecal tonsil in broilers, implying that the innate immunity in intestinal mucosal immune system could be impaired by pathways involving injured surface epithelium cells or/and the inhibition of the TLR signal transduction.
Highlights
Nickel (Ni) is used in a wide variety of industrial and consumer applications [1], and it is known to be an essential element for animals [2,3]
It is reported that Ni2+ can directly trigger an innate immune response in resident skin cells that is necessary for mounting an allergic hypersensitivity reaction to Ni2+ [44], and Ni may interact with Toll-Like Receptors (TLRs) signal transduction, a critical pathway involved in the sensing of pathogen-associated molecular patterns and the production of proinflammatory mediators, a process dependent on induction of NF-κB activation
It is reported that TLR2 and TLR4 play important roles in the mucosal epithelial barrier function [52,53]
Summary
Nickel (Ni) is used in a wide variety of industrial and consumer applications [1], and it is known to be an essential element for animals [2,3]. As an important metal pollutant, Ni is of considerable concern because its concentration is rapidly increasing in soils of different parts of the World and it is taken up by plants. Ni or Ni compounds can enter the food chain and cause deleterious effects on animals [4]. Human exposure to Ni metal and/or Ni oxide may occur via the main exposure routes (inhalation, ingestion or dermal contact) at occupational settings. Exposure to Ni metal or Ni- containing alloys can occur via coins [5,6,7]. Ionic Ni (Ni2+) is thought to be the actual carcinogenic species because it can bind to cellular components, including nuclear proteins and DNA [8]
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