Pyrrolidine dithiocarbamate augments Hg(2+)-mediated induction of macrophage cell death via oxidative stress-induced apoptosis and necrosis signaling pathways.
Exposure to mercury can lead to several injuries in mammals, including immune system dysfunction, and pyrrolidine dithiocarbamate (PDTC), as a metal chelator and antioxidant, has been indicated to increase the cytotoxic effects of toxic metals. However, the toxicological effects and possible mechanisms of mercury in combination with PDTC are mostly unclear. In this study, we showed that PDTC dramatically increase the cytotoxic effect of HgCl(2) on cultured murine macrophages (RAW 264.7 cells). PDTC augmented HgCl(2)-induced cytotoxic effects by facilitating the entry of mercury into the cells. The Hg(2+)/PDTC complex significantly and rapidly increased the formation of reactive oxygen species (ROS) and decreased intracellular glutathione (GSH) levels in these cells. Flow cytometry analysis showed that the numbers of sub-G1 hypodiploid cells and annexin V-FITC binding cells increased after Hg(2+)/PDTC complex exposure, and several features of mitochondria-dependent apoptosis were also induced, including mitochondrial membrane depolarization, cytosolic cytochrome c release, poly(ADP-ribose) polymerase (PARP) and caspase 3/7 activation, and DNA fragmentation. Moreover, both apoptotic and necrotic cells were detected using acridine orange/ethidium bromide dual staining. Meanwhile, depleted intracellular ATP levels and increased lactate dehydrogenase (LDH) release were observed, suggesting the induction of necrotic cell death processes. These Hg(2+)/PDTC complex-induced cytotoxicity-related signals could be reversed by pretreatment with the antioxidant N-acetylcysteine. In conclusion, these results suggest that Hg(2+)/PDTC complex-induced oxidative stress causes macrophage cell death via both apoptosis and necrosis. These findings imply for the first time that PDTC dramatically increases the uptake and toxicological effects of Hg(2+) instead of detoxification.
School of Chinese Medicine, College of Chinese Medicine, China Medical University, 404 Taichung, Taiwan; Institute of Toxicology, College of Medicine, National Taiwan University, 100 Taipei, Taiwan.
Chun-Fa
CF
Huang
Shing-Hwa
SH
Liu
Shoei-Yn
SY
Lin-Shiau
D000818:Animals; D015415:Biomarkers; D016923:Cell Death / Q000187:drug effects*; D002460:Cell Line; D004347:Drug Interactions; D005786:Gene Expression Regulation / Q000187:drug effects; D008264:Macrophages / Q000187:drug effects*; D008628:Mercury / Q000633:toxicity*; D051379:Mice; D018384:Oxidative Stress / Q000187:drug effects*; D011759:Pyrrolidines / Q000633:toxicity*; D017382:Reactive Oxygen Species; D015398:Signal Transduction / Q000187:drug effects*; D013859:Thiocarbamates / Q000633:toxicity*
D015415:Biomarkers; D011759:Pyrrolidines; D017382:Reactive Oxygen Species; D013859:Thiocarbamates; C020972:pyrrolidine dithiocarbamic acid; D008628:Mercury