Abstract
BackgroundCarcinogenicity of nickel compounds has been well documented. However, the carcinogenic effect of metallic nickel is still unclear. The present study investigates metallic nickel nano- and fine particle-induced apoptosis and the signal pathways involved in this process in JB6 cells. The data obtained from this study will be of benefit for elucidating the pathological and carcinogenic potential of metallic nickel particles.ResultsUsing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, we found that metallic nickel nanoparticles exhibited higher cytotoxicity than fine particles. Both metallic nickel nano- and fine particles induced JB6 cell apoptosis. Metallic nickel nanoparticles produced higher apoptotic induction than fine particles. Western-blot analysis showed an activation of proapoptotic factors including Fas (CD95), Fas-associated protein with death domain (FADD), caspase-8, death receptor 3 (DR3) and BID in apoptotic cells induced by metallic nickel particles. Immunoprecipitation (IP) western blot analysis demonstrated the formation of the Fas-related death-inducing signaling complex (DISC) in the apoptotic process. Furthermore, lamin A and beta-actin were cleaved. Moreover, we found that apoptosis-inducing factor (AIF) was up-regulated and released from mitochondria to cytoplasm. Interestingly, although an up-regulation of cytochrome c was detected in the mitochondria of metallic nickel particle-treated cells, no cytochrome c release from mitochondria to cytoplasm was found. In addition, activation of antiapoptotic factors including phospho-Akt (protein kinase B) and Bcl-2 was detected. Further studies demonstrated that metallic nickel particles caused no significant changes in the mitochondrial membrane permeability after 24 h treatment.ConclusionIn this study, metallic nickel nanoparticles caused higher cytotoxicity and apoptotic induction than fine particles in JB6 cells. Apoptotic cell death induced by metallic nickel particles in JB6 cells is through a caspase-8/AIF mediated cytochrome c-independent pathway. Lamin A and beta-actin are involved in the process of apoptosis. Activation of Akt and Bcl-2 may play an important role in preventing cytochrome c release from mitochondria to the cytoplasm and may also be important in the carcinogenicity of metallic nickel particles. In addition, the results may be useful as an important reference when comparing the toxicities of different nickel compounds.
Highlights
Carcinogenicity of nickel compounds has been well documented
scanning electron microscopy (SEM) images of the metallic nickel particles Metallic nickel nano- or fine particles were prepared by sonification
The results showed that both metallic nickel nano- and fine particles could induce JB6 cell apoptosis demonstrated by the positive staining of YP at an early exposure time (24 h) in a dose range of 0.1–20 μg/cm2 (Figure 3A)
Summary
Carcinogenicity of nickel compounds has been well documented. the carcinogenic effect of metallic nickel is still unclear. The data obtained from this study will be of benefit for elucidating the pathological and carcinogenic potential of metallic nickel particles. Carcinogenicity of nickel compounds has been well documented [2,3,4]. The carcinogenic effect of metallic nickel is still unclear [5]. The International Agency for Research on Cancer (IARC), classified all nickel compounds as human carcinogens in 1990 [7]. Evidences from studies in experimental animals suggest that metallic nickel is reasonably anticipated to be a human carcinogen [5]
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