Radioprotective Activity of Naturally Occurring Organosulfur Compounds

Radioprotective Potential of Nutraceuticals and their Underlying Mechanism of Action

Radiations are an efficient treatment modality in cancer therapy. Besides the treatment effects of radiations, the ionizing radiations interact with biological systems and generate reactive oxygen species that interfere with the normal cellular process. Previous investigations of synthetic radioprotectors have shown less effectiveness, mainly owing to some limiting effects. The nutraceuticals act as efficient radioprotectors to protect the tissues from the deleterious effects of radiation. The main radioprotection mechanism of nutraceuticals is the scavenging of free radicals while other strategies are involved modulation of signaling transduction of pathways like MAPK (JNK, ERK1/2, ERK5, and P38), NF-kB, cytokines, and their protein regulatory genes expression. The current review is focused on the radioprotective effects of nutraceuticals including vitamin E, -C, organosulphur compounds, phenylpropanoids, and polysaccharides. These natural entities protect against radiation-induced DNA damage. The review mainly entails the antioxidant perspective and mechanism of action of their radioprotective activities on a molecular level, DNA repair pathway, anti-inflammation, immunomodulatory effects, the effect on cellular signaling pathways, and regeneration of hematopoietic cells.

Gamma-irradiation-induced testicular oxidative stress and apoptosis: Mitigation by l-carnitine

The current study evaluated the potential ameliorative and protective impacts of l-carnitine (L-CAR) against γ-irradiation (RAD)-induced oxidative stress and apoptosis in mice testes. Male Swiss mice were allocated into four groups (n = 7). Group 1 served as a control that received saline intraperitoneally (IP). Group 2 received L-CAR (10 mg/kg bw/day; IP in saline) for 17 days. Group 3 received saline for 17 days and on day 7 exposed to RAD at a dose of 0.1 Gy per day for consecutive 10 days. Group 4 (L-CAR + RAD), received L-CAR same as in group 2 and on day 7 exposed to RAD for consecutive 10 days. Testicular antioxidants (malondialdehyde, MDA; γ-glutamyl-cysteine synthetase, gGCS; and catalase) were altered by γ-irradiation. Preadministration of L-CAR protected γ-irradiated mice from altered changes induced by γ-irradiation. γ-Irradiation affected the mRNA expression of pro-apoptotic, apoptotic, and anti-apoptotic genes (c-jun, c-fos, Bcl-xl, caspase-3, and BAX). All altered genes were ameliorated by prior l-carnitine administration to γ-irradiated mice. Testicular cells showed deformities and edema with congestion in seminiferous tubules and strong immunoreactivity for caspase-9 and a decrease in immunoreactivity of Bcl-2 in histological and immunohistochemical examination. Prior administration of L-CAR to γ-irradiated mice protected this group from reported changes in caspase-9 and Bcl-2 immunostaining. In conclusion, the current study provides evidence for the protective and ameliorative impacts of L-CAR against γ-irradiation-induced testicular oxidative stress and apoptosis at biochemical, molecular, and cellular levels.

Radiation-Induced Reactions in The Liver - Modulation of Radiation Effects by Lifestyle-Related Factors

Radiation has a wide variety of effects on the liver. Fibrosis is a concern in medical fields as one of the acute effects of high-dose irradiation, such as with cancer radiotherapies. Cancer is also an important concern following exposure to radiation. The liver has an active metabolism and reacts to radiations. In addition, effects are modulated by many environmental factors, such as high-calorie foods or alcohol beverages. Adaptations to other environmental conditions could also influence the effects of radiation. Reactions to radiation may not be optimally regulated under conditions modulated by the environment, possibly leading to dysregulation, disease or cancer. Here, we introduce some reactions to ionizing radiation in the liver, as demonstrated primarily in animal experiments. In addition, modulation of radiation-induced effects in the liver due to factors such as obesity, alcohol drinking, or supplements derived from foods are reviewed. Perspectives on medical applications by modulations of radiation effects are also discussed.

Cardioprotective effect of zingerone against oxidative stress, inflammation, and apoptosis induced by cisplatin or gamma radiation in rats

Despite their clinical benefits in cancer treatment, the deleterious effects on heart following chemo/radiotherapy are of increasing importance. Zingerone, a natural polyphenol, possesses multiple biological activities, such as antioxidant and anti-inflammatory. Thus, the current study was designed to assess the potential cardioprotective effects of zingerone against cisplatin or γ-radiation. Zingerone was given by intragastric intubation (25 mg/kg) daily for three successive weeks prior to the induction of cardiotoxicity using a single dose of cisplatin (20 mg/kg, i.p.) or a whole body γ-irradiation at a single dose of 6 Gy. Zingerone pre-treatment significantly reduced the abnormalities in heart histology and the increase in the cardiotoxicity indices, serum lactate dehydrogenase, and creatine kinase-MB activities, as well as plasma cardiac troponin T and B-natriuretic peptide, induced by cisplatin or γ-radiation. Further, zingerone, except for superoxide dismutase, notably ameliorated the state of oxidative stress as evidenced by a significant decrease in malondialdehyde level accompanied with a significant increase in the reduced glutathione content and catalase activity. Additionally, zingerone mitigated the increase in the inflammatory markers including serum level of tumor necrosis factor-alpha, cardiac myeloperoxidase activity, and cyclooxygenase-2 protein expression. Moreover, zingerone alleviated the elevation of caspase-3 gene expression and the prominent nuclear DNA fragmentation and attenuated the decrease in mitochondrial complexes' activities. This study sheds the light on a probable protective role of zingerone as an antioxidant, anti-inflammatory, and antiapoptotic agent against cisplatin- or γ-radiation-induced cardiotoxicity and holds a potential in regard to therapeutic intervention for chemo/radiotherapy mediated cardiac damage.

Interactions between TGF-β1, canonical WNT/β-catenin pathway and PPAR γ in radiation-induced fibrosis

Radiation therapy induces DNA damage and inflammation leading to fibrosis. Fibrosis can occur 4 to 12 months after radiation therapy. This process worsens with time and years. Radiation-induced fibrosis is characterized by fibroblasts proliferation, myofibroblast differentiation, and synthesis of collagen, proteoglycans and extracellular matrix. Myofibroblasts are non-muscle cells that can contract and relax. Myofibroblasts evolve towards irreversible retraction during fibrosis process. In this review, we discussed the interplays between transforming growth factor-β1 (TGF-β1), canonical WNT/β-catenin pathway and peroxisome proliferator-activated receptor gamma (PPAR γ) in regulating the molecular mechanisms underlying the radiation-induced fibrosis, and the potential role of PPAR γ agonists. Overexpression of TGF-β and canonical WNT/β-catenin pathway stimulate fibroblasts accumulation and myofibroblast differentiation whereas PPAR γ expression decreases due to the opposite interplay of canonical WNT/β-catenin pathway. Both TGF-β1 and canonical WNT/β-catenin pathway stimulate each other through the Smad pathway and non-Smad pathways such as phosphatidylinositol 3-kinase/serine/threonine kinase (PI3K/Akt) signaling. WNT/β-catenin pathway and PPAR γ interact in an opposite manner. PPAR γ agonists decrease β-catenin levels through activation of inhibitors of the WNT pathway such as Smad7, glycogen synthase kinase-3 (GSK-3 β) and dickkopf-related protein 1 (DKK1). PPAR γ agonists also stimulate phosphatase and tensin homolog (PTEN) expression, which decreases both TGF-β1 and PI3K/Akt pathways. PPAR γ agonists by activating Smad7 decrease Smads pathway and then TGF-β signaling leading to decrease radiation-induced fibrosis. TGF-β1 and canonical WNT/β-catenin pathway promote radiation-induced fibrosis whereas PPAR γ agonists can prevent radiation-induced fibrosis.

Diosmin attenuates radiation-induced hepatic fibrosis by boosting PPAR-γ expression and hampering miR-17-5p-activated canonical Wnt-β-catenin signaling

BACKGROUND

Liver fibrosis is one of the major complications from upper right quadrant radiotherapy. MicroRNA-17-5p (miR-17-5p) is hypothesized to act as a regulator of hepatic stellate cell (HSCs) activation by activation of the canonical Wnt-β-catenin pathway. Diosmin (Dios), a citrus bioflavonoid, is known to possess potent antioxidant, anti-inflammatory, and anti-apoptotic properties.

PURPOSE

To explore the molecular mechanisms that underlie radiation-induced liver fibrosis, and to evaluate the possible influence of Dios on the miR-17-5p-Wnt-β-catenin signaling axis during fibrogenesis provoked by irradiation (IRR) in rats. Also, the effect of Dios on hepatic peroxisome proliferator activated receptor-γ (PPAR-γ) expression as a regulator for HSC activation was considered.

METHODS

We administered 100 mg·(kg body mass)^-1·day^-1 (per oral) of Dios were administered to IRR-exposed rats (overall dose of 12 Gy on 6 fractions of 2 Gy each) for 6 successive weeks.

RESULTS

Data analysis revealed that Dios treatment mitigated oxidative stress, enhanced antioxidant defenses, alleviated hepatic inflammatory responses, abrogated pro-fibrogenic cytokines, and stimulated PPAR-γ expression. Dios treatment repressed the miR-17-5p activated Wnt-β-catenin signaling induced by IRR. Moreover, Dios treatment restored the normal hepatic architecture and reversed pathological alterations induced by IRR.

CONCLUSION

We hypothesize that the stimulation of PPAR-γ expression and interference with miR-17-5p activated Wnt-β-catenin signaling mediates the antifibrotic properties of Dios.

Protective effect of Withania somnifera against radiation-induced hepatotoxicity in rats

The aim of this study was to investigate the protective effect of root extract of Withania somnifera (WS) against gamma-irradiation-induced oxidative stress and DNA damage in hepatic tissue after whole body gamma-irradiation. Fourty male albino rats were divided into four groups. In the control group, rats were administered vehicle by tube for 7 consecutive days. The second group were administered WS (100mg/kg, by gavage) for 7 consecutive days. Animals in the third group were administered vehicle by tube for 7 consecutive days, then exposed to single dose gamma-irradiation (6 Gy). The fourth group received WS for 7 consecutive days, one hour later rats were exposed to gamma-irradiation. Irradiation hepatotoxicity was manifested biochemically by an increase in hepatic serum enzymes, significant elevation in levels of malondialdehyde (MDA) and total nitrate/nitrite NO(x), significant increase in heme oxygenase activity (HO-1), as well as a significant decrease in reduced glutathione (GSH) content and the activities of antioxidant enzymes, including superoxide dismutase (SOD) and glutathione peroxidase (GSHPx) in hepatic tissues. Marked DNA damage was observed. WS pretreatment showed significant decrease in serum hepatic enzymes, hepatic NO(x) and MDA levels and DNA damage, significant HO-1 induction and significant increase in SOD, GSHPx activities and GSH content compared to irradiated group. These observations suggest that WS could be developed as a potential preventive drug for ionizing irradiation induced hepatotoxicity disorders via enhancing the antioxidant activity and induction of HO-1.

Protective effect of Biophytum sensitivum (L.) DC on radiation-induced damage in mice

The radioprotective effect of Biophytum sensitivum methanol extract was studied using in vivo mice model . Animals were exposed to whole body gamma irradiation (6 Gy/animal) after treatment with B. sensitivum (50mg/kg b.wt.) followed by estimation of cytosolic enzymes, level of antioxidants, hematological parameters, bone marrow cellular progenitors, serum cytokine levels and spleen hematopoietic colonies. Administration of B. sensitivum could reduce the enhanced level of ALP, GPT and LPO levels in irradiated animals. B. sensitivum could significantly enhance the glutathione (GSH) content in liver and intestinal mucosa of irradiated animals. B. sensitivum treatment could enhance the Total WBC count, cellularity of bone marrow, alpha-esterase positive cells, and relative organ weight of spleen as well as thymus. The number of hematopoietic colonies on the surface of the spleen was found to be enhanced after B. sensitivum treatment. B. sensitivum treatment could also stimulate the production of cytokines such as IL-1beta, IFN-gamma and GM-CSF in animals exposed to whole body gamma irradiation. The present investigation suggests that the protective effect of Biophytum sensitivum on Radiation-Induced hemopoietic damage is mediated through immunomodulation as well as sequential induction of IL-1beta, GM-CSF and IFN-gamma.

Biological properties of garlic and garlic-derived organosulfur compounds

Medicinal properties of garlic (Allium sativum) have been widely known and used since ancient times till the present. Garlic enhances immune functions and has antibacterial, antifungal and antivirus activities. It is known to prevent platelet aggregation, and to have hypotensive and cholesterol- and triglyceride-lowering properties, although the latter features have been questioned. This review is focused on anticancer efficacy of Allium sativum, and attempts to explain the mechanisms of this action. Medicinal properties of garlic rely upon organosulfur compounds mostly derived from alliin. Organosulfur compounds originating from garlic inhibit carcinogen activation, boost phase 2 detoxifying processes, cause cell cycle arrest mostly in G2/M phase, stimulate the mitochondrial apoptotic pathway, increase acetylation of histones. Garlic-derived sulfur compounds influence also gap-junctional intercellular communication and participate in the development of multidrug resistance. This review presents also other little known aspects of molecular action of garlic-derived compounds, like modulation of cellular redox state, involvement in signal transduction and post-translational modification of proteins by sulfane sulfur or by formation of mixed disulfides (S-thiolation reactions).

Diallyl sulfide induces apoptosis in Colo 320 DM human colon cancer cells: involvement of caspase-3, NF-kappaB, and ERK-2

Chemoprevention is regarded as one of the most promising and realistic approaches in the prevention of human cancer. Diallyl sulfide (DAS), an organosulfur component of garlic has been known for its chemopreventive activities against various cancers and also in recent years, numerous investigations have shown that sulfur-containing compounds induce apoptosis in multiple cell lines and experimental animals. Thus the present study was focused to elucidate the anticancerous effect and the mode of action of DAS against Colo 320 DM colon cancer cells. DAS induced apoptosis in Colo 320 DM cells was revealed by flow cytometer analysis and phosphatidyl serine exposure. DAS also promoted cell cycle arrest substantially at G2/M phase in Colo 320 DM cells. The production of reactive oxygen intermediates, which were examined by 2,7-dichlorodihydrofluorescein diacetate (H2DCF-DA), increased with time, after treatment with DAS. The activities of alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) were decreased upon DAS treatment, which shows the antiproliferative and the cytotoxic effects, respectively. The expression of NF-kappaB was upregulated in DAS treated cells, compared to normal cells. Further, DAS promoted the expression of caspase-3 and suppression of Extracellular Regulatory Kinase-2 (ERK-2) activity in Colo 320 DM cells that was determined by Western blot analysis. In conclusion, DAS increased the production of ROS, caused cell cycle arrest, decreased cell proliferation and induced apoptosis in Colo 320 DM cells. Thus, this study put forward DAS as a drug that can possibly be used to treat cancers.

Antiangiogenic activity of Diallyl Sulfide (DAS)

Antiangiogenic activity of Diallyl sulfide (DAS) was studied using in vivo as well as in vitro models. In vivo antiangiogenic activity was studied using B16F-10 melanoma cell induced capillary formation in C57BL/6 mice. DAS significantly inhibited tumour directed capillary formation. Studies of serum cytokine profile of angiogenesis induced animals clearly showed that DAS significantly reduced the production of proinflammatory cytokines such as IL-1beta, IL-6, TNF-alpha and GM-CSF which are known proangiogenic factors. The serum level of VEGF, an important proangiogenic factor, in angiogenesis induced animals was found to be significantly reduced upon treatment with DAS which may be due to its efficacy in the down regulation of VEGF mRNA expression. Administration of DAS significantly enhanced the production of antiangiogenic factors such as IL-2 and TIMP. In vitro studies using rat aortic ring assay showed that administration of DAS at no n-toxic concentrations significantly inhibited microvessel sprouting. Studies using Human umbilical vein endothelial cells (HUVECs) clearly demonstrated that administration of DAS significantly retarded endothelial cell proliferation, migration, invasion and tube formation. These data clearly suggests that antiangiogenic activity of DAS can be related to its negative regulation of proangiogenic factors such as VEGF and proinflammatory cytokines and positive regulation of antiangiogenic factors such as IL-2 and TIMP.