Finally, NF-kappaB and another transcriptional regulator p53 are usually tightly related in their control of cell survival. Opposite to NF-kappaB, p53 mediates cell death signals, usually activated under DNA damage and subsequently involved in cell growth control, DNA damage repair or apoptosis. It was found in this study, DNA damage and cell cycle arrest responses tended to participate with the anti-HSV-1 activity. Although in HEp-2 cells, TCS induced more DNA damage ratio and S and G2/M phase arrest proportion than HSV-1 infected cells, but more p53 was expressed and activated by phosphorylating at Ser 15 by TCS in HSV-1 infected HEp-2 cells than uninfected ones. In the same time the activation of BAX, which promotes the apoptotic function of p53, increased during TCS treatment when infected with HSV-1, the p53 therefore regulates apoptosis in HSV-1 infected cell during TCS treatment. / Firstly, we demonstrated that TCS reduced HSV-1 antigen and DNA content, The IC50 (half maximal inhibitory concentration) of TCS on HSV-1 replication was 2.5 +/- 0.23 mug/ml. The anti-HSV-1 effect of TCS was related to interfering with viral replication during 3 to 15 hours after infection which coincide with early to late viral replication period. TCS had no effect on HSV-1 attachment, penetration or immediate early gene expression. However, the expression of early gene, late gene and virion release were diminished. / Fourthly, the role of the nuclear factor-kappaB (NF-kappaB) in the anti-HSV-1 effect of TCS was explored. NF-kappaB initiates cell survival pathways. It is widely involved in viral infection and replication to make sure virus overcomes the host cells immune response. We found HSV-1 enhanced the activity of NF-kappaB in HEp-2 cells by triggering its translocation from cytoplasm to nuclear. However, during the anti-HSV-1 effect of TCS, TCS suppressed HSV-1-aroused NF-kappaB translocation in HEp-2 cells, the inhibition of NF-kappaB activity in HSV-1-infected cells by TCS treatment tend to abolish the anti-apoptosis effect developed by HSV-1, so that the host cells suffered more extracellular stress and showed more apoptosis ratio than uninfected ones. / Taken together, this study demonstrated TCS interfered with HSV-1 early to late infection period. TCS selectively induced more HSV-1 infected HEp-2 cells to apoptosis than uninfected ones, the selectivity of TCS was due to apoptotic signaling pathway switching from CD95 (Fas/Apo-1)-mediated type I to type II apoptotic pathway. Furthermore, during TCS induced-apoptosis in HSV-1 infected cells, TCS suppressed NF-kappaB activation that triggered by HSV-1 infection. At the meanwhile, p53 participated in the TCS-induced apoptosis regulation in infected cell. / TCS is toxic to cell because its RIP activity, killing of the viral host cells certainly inhibits virus expansion, only when it kills more infected cells, the material could be considered as an anti-viral agent. It was found TCS induced losing of cell viability and enhancing in apoptosis in HEp-2 cells and HSV-1 infected HEp-2 cells. The decrease of cell viability and increase of apoptosis ratio were enhanced when HEp-2 cells were infected with HSV-1 compared with uninfected ones. The 50% of effect concentration (EC50 ) in cytotoxicity and apoptosis were decreased from 24.64 +/- 1.17 mug/ml and 37.57 +/- 1.47 mug/ml in uninfected HEp-2 cells to 3.01 +/- 1.30 mug/ml and 3.89 +/- 1.31 mug/ml in HSV-1 infected HEp-2 cells respectively. / The reason of type I to type II apoptosis pathway transition might due to the activity change of death receptor on HEp-2 cells. The type I apoptotic pathway induced by TCS was related to CD95 (Fas/Apo-1) system activation and signaling pathway. When HEp-2 cells were infected with HSV-1, the CD95 (Fas/Apo-1) was suppressed by HSV-1 infection. As a result, TCS triggered a less CD95 (Fas/Apo-1) dependent type II apoptotic pathway in the infected cells. / Thirdly, TCS activated different apoptotic pathways, namely type I and type II apoptotic pathways, between uninfected and infected cells. The type I apoptotic pathway bypasses the dependence on the mitochondrial but quickly activates a large amount of caspase-8 at the CD95 (Fas/Apo-1) formed death inducing signaling complex (DISC), which amplifies the signal. By contrast, the formation of the DISC in the type II apoptotic pathway is strongly reduced. It depends on loss of the mitochondrial transmembrane potential (DeltaPsi m) and release of cytochrome c and capase-9 activation to mediate apoptosis signal transduction. We found in HSV-1 infected an uninfected HEp-2 cells, TCS induced the loss of DeltaPsim, this DeltaPsim losing was increased when HEp-2 cells were infected with HSV-1. Furthermore, when there were no HSV-1 infection, TCS induced caspase-dependent type I apoptosis pathway that quickly activated large amount of caspase-8 after TCS treatment. However, when infected with HSV-1, this pathway turned into mitochondrial dependent type II pathway involving caspase-9 response, whose apoptosis ratio was diminished by over expressed Bcl-2, which is a hallmark defining type I or type II apoptosis. / Trichosanthin (TCS) is a type I ribosome inactivating protein (RIP), it was found to inhibit human simplex virus type 1 (HSV-I) but the anti-HSV-I mechanism is unclear. HSV-1 is a widely distributed DNA virus, it causes large range of human diseases. During the lytic life cycle of HSV-1, highly regulated cascade of genes are expressed to interfere with host cell metabolism and immune response. In this context the anti-HSV-1 mechanism of TCS in human epithelial carcinoma HEp-2 cells was studied. / He, Dongxu. / Advisers: Wing Ho Yung; Siu Cheung Tam. / Source: Dissertation Abstracts International, Volume: 73-06, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 124-138). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_344979 |
| Date | January 2011 |
| Contributors | He, Dongxu., Chinese University of Hong Kong Graduate School. Division of Physiology. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, theses |
| Format | electronic resource, microform, microfiche, 1 online resource (xiii, 138 leaves : ill. (chiefly col.)) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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