Toxicity assessment of metallic nickel nanoparticles in various biological models: An interplay of reactive oxygen species, oxidative stress, and apoptosis

Nickel nanoparticles (Ni-NPs) are widely used for multiple purposes in industries. Ni-NPs exposure is detrimental to ecosystems owing to widespread use, and so their toxicity is important to consider for real-world applications. This review mainly focuses on the notable pathophysiological activities of Ni-NPs in various research models. Ni-NPs are stated to be more toxic than bulk forms because of their larger surface area to volume ratio and are reported to provoke toxicity through reactive oxygen species generation, which leads to the upregulation of nuclear factor-κB and promotes further signaling cascades. Ni-NPs may contribute to provoking oxidative stress and apoptosis. Hypoxia-inducible factor 1α and mitogen-activated protein kinases pathways are involved in Ni-NPs associated toxicity. Ni-NPs trigger the transcription factors p-p38, p-JNK, p-ERK1/2, interleukin (IL)-3, TNF-α, IL-13, Fas, Cyt c, Bax, Bid protein, caspase-3, caspase-8, and caspase-9. Moreover, Ni-NPs have an occupational vulnerability and were reported to induce lung-related disorders owing to inhalation. Ni-NPs may cause serious effects on reproduction as Ni-NPs induced deleterious effects on reproductive cells (sperm and eggs) in animal models and provoked hormonal alteration. However, recent studies have provided limited knowledge regarding the important checkpoints of signaling pathways and less focused on the toxic limitation of Ni-NPs in humans, which therefore needs to be further investigated.