Gliotoxin enhances radiotherapy via inhibition of radiation‐induced GADD45a, p38, and NFκB activation

Abstract

The purpose of the study was to elucidate the mechanism underlying the enhancement of radiosensitivity to 60Co gamma-irradiation in human hepatoma cell line HepG2 pretreated with gliotoxin. Enhancement of radiotherapy by gliotoxin was investigated in vitro with human hepatoma HepG2 cell line. Apoptosis related proteins were evaluated by Western blotting. Annexin V/PI and reactive oxygen species (ROS) were quantified by Flow Cytometric (FACS) analysis. Gliotoxin (200 ng/ml) combined with radiation (4 Gy) treated cells induced apoptosis. Cells treated with gliotoxin (200 ng/ml) prior to irradiation at 4 Gy induced the expression of bax and nitric oxide (NO). The gliotoxin-irradiated cells also increased caspase-3 activation and ROS. Gadd45a, p38, and nuclear factor kappa B (NFkappaB) activated in irradiated cells was inhibited by Gliotoxin. Specific inhibitors of p38 kinase, SB203580, significantly inhibited NFkappaB activation and increased the cytotoxicity effect in cells exposed to gliotoxin combined with irradiation. However, SB203580 did not suppress the activation of Gadd45a in irradiated cells. Gliotoxin inhibited anti-apoptotic signal pathway involving the activation of Gadd45a-p38-NFkappaB mediated survival pathway that prevent radiation-induced cell death. Therefore, gliotoxin, blocking inflammation pathway and enhancing irradiation-induced apoptosis, is a promising agent to increase the radiotherapy of tumor cells.

Resolution of renal inflammation: a new role for NF-κB1 (p50) in inflammatory kidney diseases

“…Inhibition of NF-B activation during the initiation phase of glomerular inflammation by pretreatment with gliotoxin was associated with a downregulation of glomerular MCP-1/CCL2 expression and consecutive reduction of glomerular monocyte/macrophage infiltration confirming the study by Lopez-Franco et al (21). However, blockade by gliotoxin is not specific enough to conclusively clarify the role of NF-B, since activation of transcription factors like NFAT, C/EBP and AP1-Jun/Fos pathways, the p38 and STAT pathways, proteasome complexes, and also oxidation radicals are all inhibited by gliotoxin (7,14). Even more importantly, gliotoxin, like other proteasome inhibitors, might not only block activation of the NF-B pathway but also significantly impairs degradation of active proinflammatory p65/p50 heterodimers bound to the DNA (33).…”

Gliotoxin, identified from a screen of fungal metabolites, disrupts 7SK snRNP, releases P-TEFb and reverses HIV-1 latency

“…4a-b). Consistent with the literature (Hur et al, 2008;Orciuolo et al, 2007;Stanzani et al, 2005;Suen et al, 2001;Sutton et al, 1995;Wichmann et al, 2002;Yamada et al, 2000;Zhou et al, 2000), treatment with higher concentrations of GTX at 100 nM and 1 µM caused apoptosis and death of primary CD4+ and CD8+ T cells as well as B cells, NK cells and monocytes 3c and Supplementary Figs. 3b,.…”

Deficiency in crumbs homolog 2 (Crb2) affects gastrulation and results in embryonic lethality in mice

“…Furthermore, EAG‐mediated p38 activation may also contribute to NF‐κB activation. A specific inhibitor of p38 kinase, SB203580, has been demonstrated to suppress NF‐κB activation and increase cytotoxicity in cells exposed to gliotoxin [Hur et al, 2008]. Therefore, suppression of NF‐κB activity may be the reason for the decreased cell viability in co‐administration of EAG and SB203580.…”