Modulation of the PI3K/Akt Pathway and Bcl-2 Family Proteins Involved in Chicken's Tubular Apoptosis Induced by Nickel Chloride (NiCl₂).

Hongrui Guo,Jing Fang,Bangyuan Wu,Xi Peng,Xun Wang,Jie Deng,Hengmin Cui,Kejie Chen,Junliang Deng,Zhicai Zuo

doi:10.3390/ijms160922989

Abstract

Exposure of people and animals to environments highly polluted with nickel (Ni) can cause pathologic effects. Ni compounds can induce apoptosis, but the mechanism and the pathway of Ni compounds-induced apoptosis are unclear. We evaluated the alterations of apoptosis, mitochondrial membrane potential (MMP), phosphoinositide-3-kinase (PI3K)/serine-threonine kinase (Akt) pathway, and Bcl-2 family proteins induced by nickel chloride (NiCl2) in the kidneys of broiler chickens, using flow cytometry, terminal deoxynucleotidyl transferase 2ʹ-deoxyuridine 5ʹ-triphosphate dUTP nick end-labeling (TUNEL), immunohistochemstry and quantitative real-time polymerase chain reaction (qRT-PCR). We found that dietary NiCl2 in excess of 300 mg/kg resulted in a significant increase in apoptosis, which was associated with decrease in MMP, and increase in apoptosis inducing factor (AIF) and endonuclease G (EndoG) protein and mRNA expression. Concurrently, NiCl2 inhibited the PI3K/Akt pathway, which was characterized by decreasing PI3K, Akt1 and Akt2 mRNA expression levels. NiCl2 also reduced the protein and mRNA expression of anti-apoptotic Bcl-2 and Bcl-xL and increased the protein and mRNA expression of pro-apoptotic Bax and Bak. These results show that NiCl2 causes mitochondrial-mediated apoptosis by disruption of MMP and increased expression of AIF and EndoG mRNA and protein, and that the underlying mechanism of MMP loss involves the Bcl-2 family proteins modulation and PI3K/Akt pathway inhibition.

Highlights

Nickel (Ni) is one of the essential elements found in abundance in the earth’s crust occurring at an average concentration of about 75 μg/g [1]
We investigated whether PI3K/Akt was involved in NiCl2-mediated apoptosis
The results showed that NiCl2 significantly increased the triphosphate dUTP nick end-labeling (TUNEL)-postive cells, which were regarded as the apoptotic cells

Summary

Introduction

Nickel (Ni) is one of the essential elements found in abundance in the earth’s crust occurring at an average concentration of about 75 μg/g [1]. Ni compounds can promote the generation of reactive oxygen species (ROS), interact directly or indirectly with nucleic acids and cause DNA damage [13]. It has been suggested that nickel chloride (NiCl2) can induce DNA damage indirectly through the formation of ROS [14,15,16]. Our previous studies have shown that dietary NiCl2 in excess of 300 mg/kg can cause immunotoxicity, oxidative damage and apoptosis in the kidneys, spleens, small intestines, and cecal tonsils of broiler chickens [18,19,20,21,22,23,24,25,26,27,28]

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