| Intestinal radiation injury most often develops following abdominal or pelvic radiation therapy provided as part of the treatment for cancer or pretreatment in hematopoietic stem cells transplantation.This type of injury not only affects quality of life but can also be life threatening in some cases,like those in which patients receive high doses of acute radiation or an accumulated dosage of radiation.Although radiation can cause a variety of gastrointestinal(GI)injury,because the tissue of the small intestine is enriched with highly proliferating cells that are typically more radiosensitive,the doses required to cause small intestinal injury are very close to therapeutic doses.Additional factors involving the nature of radiation therapy increase the risk of injury to the small bowel,such as its mobility and the difficulty in defining the treated area.Patients suffering from radiation-induced small bowel disease usually present with colicky abdominal pain,bloating,loss of appetite,nausea,diarrhea,and fecal urgency during or shortly after a course of radiotherapy.Ionizing radiation induces biological effects via a series of molecular events,set off by reactive oxygen species(ROS).These free radicals,·OH,HO2-,eaq,O2·-,and H3O+,can cause oxidative damage to biological molecules,including DNA,and membranes,resulting in the dysfunction/malfunctioning of biological processes and sometimes even cell death.An increased rate of cell death results in villous denudation,the breakdown of the mucosal barrier,and mucosal inflammation.When the mucosal barrier becomes disrupted,bacterial products and other activating agents gain access to the tissues and stimulate a variety of immune cells to produce cytokines and inflammatory mediators.More seriously,translocation of bacteria may result in fatal problems such as cytokine-mediated systemic inflammatory response syndrome(SIRS),multiple organ failure(MOF)and eventually death.Synthetic radioprotectors like sulfhydryl-containing free-radical-scavenging compounds were discovered in the beginning of the nuclear era,yet due to various reasons,an ideal radioprotector remains elusive.In the last two decades,some natural plant-derived compounds have been demonstrated to possess properties that provide promising radiation countermeasures based on their proven therapeutic potential and the combination of efficacy and low toxicity,with minimum or no side effects.Ginger,one of the useful drugs in traditional Chinese medicine,has been shown to be effective in the prevention of radiotherapy-induced nausea and vomiting.Ginger and its constituents at doses up to 2.0 g daily have demonstrated very low levels of toxicity and high levels of tolerability in both animals and humans.Shogaols are the constituent ginger biophenolics and possess both anti-inflammatory and antioxidant effects.Recently,6-shogaol,a pungent constituent of ginger,has been shown to possess a gastro-protective effect against HCl/ethanol-induced gastric lesions.Therefore,it is worth investigating whether or not 6-shogaol may be a candidate protector against radiation-induced intestinal injury.In this study,we observed that 6-shogaol pretreatment reduced intestinal bacterial/endotoxin translocation in lethally irradiated mice and improved their survival.Particularly,mice that were pretreated with 6-shogaol had a significant mitigation of intestinal fistula and impaired mucosal integrity after exposure to radiation.Moreover,6-shogaol pretreatment inhibited the release of IR-induced inflammatory cytokines and alleviated apoptosis in duodenal tissues.Therefore,6-shogaol,through its aforementioned pharmacological actions,may exert a beneficial effect in protecting the intestinal mucosa from the damage induced by irradiation.This potential protective role could be attributed,in part,to the combined antioxidant effects of its individual components and their anti-inflammatory properties,thus alleviating radiation toxicity to the gastrointestinal tract.Our findings further suggest that it may prove to be therapeutically useful in patients undergoing radiotherapy by obviating the treatment-limiting intestinal side effects.According to recent data from population-based cancer statistics,lung cancer is one of the most serious public problems because it is the leading cause of cancer-related deaths worldwide,with more than one million mortalities each year.These statistics are especially true in China,where lung cancer has been the most common diagnosed cancer,as well as the leading cause of cancer-related deaths.With locally improved advances,NSCLC can be treated with conventional cancer therapies,including ionizing radiation and traditional anti-proliferative chemotherapy.However,recurrence rates remain high at 30-50%,while overall 5-year survival rates remain low at approximately 7-20%.These high mortality rates are attributed to residual lung cancer cells,referred to as cancer stem cells(CSCs),which possess similar properties as stem cells.For example,these cells can exist in quiescent stages,have the ability to self-renew,and are typically resistant to chemotherapeutics and radiotherapy,thus resulting in treatment failure.Natural products constitute a relatively neoteric strategy with strong attraction due to its potential for fewer side effects.Since the 1970s,drug discovery strategy has been based on screening a large quantity of candidates from natural and synthetic compounds,resulting in the modern and rational drug design in discovery process.In this study,we focus on the natural compound,Garcinol,which is isolated from native Guttiferae plants growing in India and South-East Asia.Numerous scientific studies on garcinol have demonstrated that this compound possesses a broad anticancer activity in addition to anti-inflammatory,antioxidant,and antibacterial activity.For instance,garcinol has been shown to sensitize human head and neck carcinoma cells to cisplatin treatment12 and human pancreatic adenocarcinoma cells to gemcitabine treatment.Thus,garcinol could act as a promising compound for targeting cancer stem cell-like cells.Interestingly,when we scanned a panel of NSCLC cell lines(A549,H460,H1299,H1650,H358 and HCC827)to investigate the cytotoxic effect of garcinol,A549 cells were observed to be the most sensitive to garcinol treatment.It has been shown that Aldehyde dehydrogenase ALDH1A1 is preferentially expressed in A549 cells and plays a critical role in maintaining the stemness of A549 cells.ALDH1A1 is one of the stem cell-like markers of NSCLC cell lines.We developed an in vitro screen using RT-PCR to analyze the expression levels of classic stem cell markers in lung cancer.The results showed that garcinol treatment resulted in the downregulation of ALDH1A1 expression.ALDH1A1 promoter contains a CCAAT box at position-75 to-71 upstream of the transcription start site.Accordingly,it is known that CCAAT enhancer binding proteins ?(C/EBP?)are critical forALDH1A1 mRNA expression.We carried out ChIP studies of the ALDH1A1 promoter.Quantitative PCR analysis of ChIP with anti-C/EBP? antibodies from A549 cells revealed an effective occupancy of the C/EBP?-binding site in untreated control cells.Garcinol treatment was found to sharply reduce the occupancy of the C/EBP? binding site by C/EBP?.In addition,the observed increased DDIT3 levels were found to match the decreased levels of ALDH1A1 in garcinol treated cells.Analysis of anti-C/EBP? precipitates showed that garcinol treatment resulted in increased binding of DDIT3 to C/EBP?,which strictly correlated with the observed decreased amount of C/EBP? bound to the ALDH1A promoter and,ultimately,with the reduced levels of ALDH1A3 mRNA.To verify whether the inhibition of ALDH1A1 expression and the resulting anti-tumor potential of garcinol treatment could be translated to an in vivo model.The difference in tumor size was most likely due to a reduction in the proliferation of tumor cells in the garcinol group,as we observed decreased expression of the nuclear antigen Ki-67 by immunohistochemical analysis.We further investigated the effect of garcinol treatment on ALDH1A1 and DDIT3 levels in tumor tissue and found that ALDH1A1 expression levels were downregulated,while DDIT3 expression levels were substantially increased in the garcinol treatment group compared to the control group.These in vivo results are consistent with our in vitro observations described above.Overall,the current results demonstrate that garcinol may represent a potential phytochemical drug for use against NSCLC tumors harboring the ALDH1A1 gene.Further preclinical and clinical experiments are needed to further pursue this avenue. |
PDF Full Text Request