Inhibition of UV-C light-induced apoptosis in liver cells by 2,3,7,8-tetrachlorodibenzo-p-dioxin
MetadataShow full item record
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a highly toxic pollutant ubiquitously present in the environment. Most of the toxic effects of TCDD are believed to be mediated by high-affinity binding to the aryl hydrocarbon receptor (AhR) and subsequent effects on gene transcription. TCDD causes cancer in multiple tissues in different animal species and is classified as a class 1 human carcinogen. In initiation-promotion studies TCDD was shown to be a potent liver tumor promotor. Among other theories it has been hypothesized that TCDD acts as a tumor promotor by preventing initiated cells from undergoing apoptosis. We examined the effects of TCDD on ultraviolet C (UV-C) light-induced apoptosis in primary rat hepatocytes and Huh-7 human hepatoma cells. TCDD inhibits UV-C light-induced apoptosis in both cell types. This effect is seen with chromatin condensation and fragmentation and appears to be mediated by the AhR in rat hepatocytes. Apoptosis induced by UV-C light in these cells is caspase-dependent and is accompanied by alterations in apoptosis-related gene expression such as up-regulation of proapoptotic bcl-2 family genes like bak and bax, and a marked down regulation of the expression of the antiapoptotic bcl-2. TCDD treatment of irradiated hepatocytes induces the expression of some apoptosis-related genes (birc3, dad1, pycard, tnf). Upstream apoptotic events, namely caspase activation and caspase substrate cleavage are not inhibited by TCDD treatment. We hypothesize that TCDD inhibits late-stage apoptotic events that lead to internucleosomal DNA fragmentation, maintaining chromosomal integrity probably in order to sustain metabolic capacity and hepatic elimination of substrates despite of an initiation of apoptosis. © The Author 2009. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved.
Showing items related by title, author, creator and subject.
Tomek, M.; Akiyama, T.; Dass, Crispin (2012)Objectives: Bcl-2 is a protein that inhibits apoptosis, leading to cell survival. The Bcl-2 family has six different anti-apoptotic proteins, three pro-apoptotic proteins that are similar in structure, and other integrating ...
γ-Tocotrienol is a novel inhibitor of constitutive and inducible STAT3 signalling pathway in human hepatocellular carcinoma: Potential role as an antiproliferative, pro-apoptotic and chemosensitizing agentRajendran, P.; Li, F.; Manu, K.; Shanmugam, M.; Loo, S.; Kumar, Alan Prem; Sethi, G. (2011)BACKGROUND AND PURPOSE Activation of signal transducer and activator of transcription 3 (STAT3) play a critical role in the survival, proliferation, angiogenesis and chemoresistance of tumour cells. Thus, agents that ...
Celastrol suppresses growth and induces apoptosis of human hepatocellular carcinoma through the modulation of STAT3/JAK2 signaling cascade In Vitro and In VivoRajendran, P.; Li, F.; Shanmugam, M.; Kannaiyan, R.; Goh, J.; Wong, K.; Wang, W.; Khin, E.; Tergaonkar, V.; Kumar, Alan Prem; Luk, J.; Sethi, G. (2012)Cumulative evidences(s) have established that the constitutive activation of STAT3 plays a pivotal role in the proliferation, survival, metastasis, and angiogenesis and thus can contribute directly to the pathogenesis of ...