Genotoxic effects of 1-nitropyrene in macrophages are mediated through a p53-dependent pathway involving cytochrome c release, caspase activation, and PARP-1 cleavage

Genotoxic stress from environmental pollutants plays a critical role in cytotoxicity. The most abundant nitro-polycyclic aromatic hydrocarbon in environmental pollutants, 1-nitropyrene (1-NP), is generated during fossil fuel, diesel, and biomass combustion under sunlight. Macrophages, the key regulators of the innate immune system, provide the first line of defense against pathogens. The toxic effects of 1-NP on macrophages remain unclear. Through a lactate dehydrogenase assay, we measured the cytotoxicity induced by 1-NP. Our results revealed that 1-NP induced genotoxicity also named DNA damage, including micronucleus formation and DNA strand breaks, in a concentration-dependent manner. Furthermore, 1-NP induced p53 phosphorylation and nuclear accumulation; mitochondrial cytochrome c release; caspase-3 and -9 activation and cleavage; and poly (ADP-ribose) polymerase-1 (PARP-1) cleavage in a concentration-dependent manner. Pretreatment with the PARP inhibitor, 3-aminobenzamide, significantly reduced cytotoxicity, genotoxicity, and PARP-1 cleavage induced by 1-NP. Pretreatment with the caspase-3 inhibitor, z-DEVD-fmk, significantly reduced cytotoxicity, genotoxicity, PARP-1 cleavage, and caspase 3 activation induced by 1-NP. Pretreatment with the p53 inhibitor, pifithrin-α, significantly reduced cytotoxicity, genotoxicity, PARP-1 cleavage, caspase 3 activation, and p53 phosphorylation induced by 1-NP. We propose that cytotoxicity and genotoxicity induced by 1-NP by PARP-1 cleavage via caspase-3 and -9 activation through cytochrome c release from mitochondria and its upstream p53-dependent pathway in macrophages.

Inotodiol inhibits cells migration and invasion and induces apoptosis via p53-dependent pathway in HeLa cells

BACKGROUND

Inonotus obliquus, namely as Chaga mushroom, is a medicinal and edible fungus, which is widely used in food and medical fields. Inotodiol, a natural lanostane-type triterpenoid with remarkable pharmacological activities, was isolated from Inonotus obliquus, which its potential anti-tumor molecular mechanism was elaborated poorly.

PURPOSE

The aim of the present study was to investigate the effect of Inotodiol on HeLa cell migration, invasion and apoptosis through p53-dependent pathway.

STUDY DESIGN AND METHODS

The potential mechanisms of Inotodiol on HeLa cell anti-metastatic and pro-apoptosis via wound healing assay, trans-well invasion assay, flow cytometry, caspase-3 activity assay and western blot analysis were studied, as well as the involvement of p53 signaling pathway in anti-metastatic and pro-apoptosis of Inotodiol. Besides, the function of tumor suppressor p53 was further verified by small interfering RNA.

RESULTS

Firstly, the cell viability assay showed that low-concentration of Inotodiol had no cytotoxicity to HeLa cells and whereas the concentration above 25 μM significantly inhibited HeLa cell growth and even induced apoptosis. This result was further demonstrated by cell proliferation and morphology assay. Secondly, in vitro wound healing and trans-well invasion assays reported that low-concentration treatment of Inotodiol significantly inhibited cells migration and invasion in a dose-dependent manner, the western blot analysis of matrix mettalloprotinase-2 (MMP2) and matrix mettalloprotinase-9 (MMP9) levels were also decreased. Moreover, Inotodiol notably induced tumor cell apoptosis by Annexin-V-FITC apoptosis assay, which is associated with activation pro-apoptotic proteins of PARP, cleaved caspase-3 and Bax expression, inhibition anti-apoptotic protein Bcl-2 expression. Finally, the anti-tumor activity of Inotodiol was attenuated by silencing p53 tumor suppressor, the result revealed that pre-treatment with p53-specific small interfering RNA (si-p53) markedly inhibited Intodiol-indeuced HeLa cell apoptosis and decreased the caspase-3 activity. What is more, the inhibitory effect of Inotodiol on tumor migration and invasion was blocked under p53 knockdown.

CONCLUSION

To sum up, the present study indicated that Inotodiol possessed the potential to prevent malignant tumor migration and invasion, and it might be a natural active compound candidate for clinical treatment of human cervical cancer.

Long-term exposure to low level of fluoride induces apoptosis via p53 pathway in lymphocytes of aluminum smelter workers

Long-term occupational exposure to low level of fluoride can induce oxidative stress and apoptosis in many cells, including lymphocyte. However, the underlying mechanism remains unclear. Hence, this study was designed to explore the potential oxidative stress and apoptosis of long-term occupational exposure to low level of fluoride in aluminum smelter workers. A total of 120 aluminum smelter workers were recruited in control, low-, middle-, and high-fluoride exposure groups with 30 workers for each group. The peripheral blood samples were collected, centrifuged, and isolated to obtain serum and lymphocyte suspensions. The air and serum fluoride concentrations were detected by fluoride ion-selective electrode method. The lymphocytic apoptosis rate, DNA damage, oxidative stress, and mRNA levels of p53, Bcl-2, and Bax were assessed by Annexin V/PI staining, comet assay, attenuated total reflectance Fourier transform infrared spectroscopy and real-time polymerase chain reaction, respectively. Results showed that the air and serum fluoride concentrations of fluoride-exposed groups were higher than those of the control group (p < 0.05). Fluoride exposure might induce apoptosis, DNA damage and oxidative stress in a dose-dependent manner in lymphocytes (p < 0.05). The expression levels of p53 and Bax were increased with fluoride exposure in lymphocytes (p < 0.05), whereas the Bcl-2 expression was decreased but not significantly. Taken together, these observations indicate that long-term occupational exposure to low level of fluoride may lead to oxidative stress and induce apoptosis through the p53-dependent pathway in peripheral blood lymphocytes of aluminum smelter workers. Serum fluoride level may be the potential biomarker of fluoride exposure.