Abstract
BackgroundUltraviolet (UV) radiation from sun, particularly its UVB component (290–320 nm), is considered the major etiological cause of skin cancer that impacts over 2 million lives in the United States alone. Recently, we reported that polydisperse colloidal suspension of silver nanoparticles (AgNPs) protected the human keratinocytes (HaCaT) against UVB-induced damage, thus indicating their potential for prevention of skin carcinogenesis. Here we sought out to investigate if size controlled the chemopreventive efficacy of AgNPs against UVB-induced DNA damage and apoptosis.MethodsPercent cell viability was examined by WST-1 assay after treating the cells with various doses (1–10 μg/mL) of AgNPs of different sizes (10, 20, 40, 60 and 100 nm) for 12 and 24 h. For protection studies, cells were treated with AgNPs of different sizes at a uniform concentration of 1 μg/mL. After 3 h, cells were irradiated with UVB (40 mJ/cm2) and dot-blot analysis was performed to detect cyclobutane pyrimidine dimers (CPDs) as an indication of DNA damage. Apoptosis was analyzed by flow cytometry after staining the cells with 7-Amino-Actinomycin (7-AAD) and PE Annexin V. Immunoblot analysis was accomplished by processing the cells for protein extraction and Western blotting using specific antibodies against various proteins.ResultsThe data show that the pretreatment of HaCaT cells with AgNPs in the size range of 10–40 nm were effective in protecting the skin cells from UVB radiation-induced DNA damage as validated by reduced amounts of CPDs, whereas no protection was observed with AgNPs of larger sizes (60 and 100 nm). Similarly, only smaller size AgNPs (10–40 nm) were effective in protecting the skin cells from UV radiation-induced apoptosis. At the molecular level, UVB –irradiation of HaCaT cells led to marked increase in expression of pro-apoptotic protein (Bax) and decrease in anti-apoptotic proteins (Bcl-2 and Bcl-xL), while it remained largely unaffected in skin cells pretreated with smaller size AgNPs (10–40 nm).ConclusionsAltogether, these findings suggest that size is a critical determinant of the UVB-protective efficacy of AgNPs in human keratinocytes.
Highlights
Ultraviolet (UV) radiation from sun, its Ultraviolet B (UVB) component (290–320 nm), is considered the major etiological cause of skin cancer that impacts over 2 million lives in the United States alone
Silver nanoparticles are largely non-toxic to human keratinocytes (HaCaT) To examine the toxicity of AgNPs, HaCaT cells were treated with AgNPs at various concentrations (1, 2, 5 and 10 μg/ml) for 12 and 24 h and the percent viabilities were measured by WST-1 assay
To determine the effect of size of AgNPs on the protection of HaCaT cells from UVB-induced DNA damage, we examined the formation of cyclobutane pyrimidine dimers (CPDs)
Summary
Ultraviolet (UV) radiation from sun, its UVB component (290–320 nm), is considered the major etiological cause of skin cancer that impacts over 2 million lives in the United States alone. We reported that polydisperse colloidal suspension of silver nanoparticles (AgNPs) protected the human keratinocytes (HaCaT) against UVB-induced damage, indicating their potential for prevention of skin carcinogenesis. The traditional approach to protect against the harmful effects of UV-radiations is to apply sunscreen lotion as a Palanki et al BMC Cancer (2015) 15:636 direct barrier on the skin. Sunscreens are formulated to contain UV filters or reflectors, such as zinc oxide nanoparticles and titanium dioxide nanoparticles [9, 10]. Recent studies have shown that zinc oxide nanoparticles and titanium dioxide nanoparticles can have inflammatory/toxic effects on normal skin cells [11, 12]
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