A New Class of Molecular Targeted Radioprotectors: GSK-3β Inhibitors

Abstract

Purpose-Development of new treatments is critical to effective protection against radiationinduced injury. Here we investigate the potential of developing small molecule inhibitors of GSK-3β, SB216763 or SB415286, as radioprotective agents to attenuate intestinal injury.Methods and Materials-Survival study was done using C57/BL6 mice to evaluate radioprotective effect of GSK-3β inhibitors. TUNEL assay and immunohistochemical staining for Bax and Bcl-2 were used to assess apoptosis in small intestines of the treated mice. Clonogenic survival study, apoptosis assays (staining with Annexin V or DAPI), and immunoblot analysis of β-catenin, Bcl-2, Bax, and caspase-3 were done using IEC-6 cells.Results-Pretreatment with SB415286 significantly improved survival of mice irradiated with 8 and 12 Gy. Mice pretreated with SB216763 or SB415286 showed significant reduction in TUNELand Bax-positive and an increase in Bcl-2-positive cells in intestinal crypts at 4 and/or 12 h after radiation with 4 and/or 8 Gy compared to radiation alone. Pretreatment of irradiated IEC-6 cells with GSK-3β inhibitors significantly increased clonogenic survival compared to cells treated with radiation alone. This increase was due to the attenuation of radiation-induced apoptosis, as demonstrated by Annexin V and DAPI assays, and immunoblot analysis of Bcl-2, Bax, and caspase-3. Conflict of interest notification: NonePublisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Conclusion-GSK-3β small molecule inhibitors protect mouse intestines from radiation-induced damage in cell culture and in vivo and improve survival of mice. Molecular mechanisms of this protection involve attenuated radiation-induced apoptosis regulated by Bcl-2, Bax and caspase-3. Therefore, GSK-3β inhibitors reduce deleterious consequences of intestinal irradiation and thereby improve quality of life during radiation therapy. NIH Public Access

GSK-3 – at the crossroads of cell death and survival

“…This damage could be prevented in mice with the administration of GSK-3 inhibitors, and rescued hippocampal neurons as well as intestinal crypt cells when the animals were treated with cirradiation (Thotala et al, 2010;Thotala et al, 2008). These data support the role of GSK-3 in the induction of Puma and in apoptosis upon DNA damage in vivo, and might open a therapeutic avenue for protection of healthy tissue from chemotherapy-induced damage, a major side effect during cancer therapy.…”

Glycogen synthase kinase 3β inhibitor (2′Z,3′E)-6-bromo-indirubin-3′-oxime enhances drug resistance to 5-fluorouracil chemotherapy in colon cancer cells

“…Conversely, pharmacological inhibition of GSK-3β led to a decrease in expression of NF-κB target genes Bcl-2 and a subsequent increase in apoptosis in pancreatic cancer, renal cancer and chronic lymphocytic leukemia B cells [14,15,25] . In this study, we found that the level of Bcl-2 protein in SW480 and SW620 cells was down-regulated with increasing doses of BIO, and the change of Bcl-2 protein in colon cancer was different from that in normal intestinal cells [24] , while consistent with the above tumor cells [14,15,25] . E2F-1 is the extremely important transcription factor in Rb/E2F-1 pathway, affecting cell proliferation, apoptosis and cell cycle process.…”

“…GSK-3β might regulate NF-κB-mediated gene transcription [14] . It has been observed in the normal intestinal mucosa radioprotective effect experiment that GSK-3β inhibitors could up-regulate Bcl-2 expression and inhibit apoptosis [24] . Conversely, pharmacological inhibition of GSK-3β led to a decrease in expression of NF-κB target genes Bcl-2 and a subsequent increase in apoptosis in pancreatic cancer, renal cancer and chronic lymphocytic leukemia B cells [14,15,25] .…”

Pharmacological strategies to spare normal tissues from radiation damage: useless or overlooked therapeutics?

“…A case in point is the intestine. By protecting intestinal crypt cells from radiation-induced apoptosis, small GSK-3β inhibitors enhanced survival in mice after IR [36].…”