Sushobhan Biswas

Naringin ameliorates radiation-induced hepatic damage through modulation of Nrf2 and NF-κB pathways

Understanding the mechanism of ionizing radiation (IR)-induced systemic stress and its modulation by phytocomponents has great significance for the development of novel phyto-radioprotectors. The present study was intended to evaluate the radioprotective effect of naringin (NG), a citrus flavonoid on the modulation of IR-induced activation of the redox-regulated signaling system in murine liver. On the basis of survival analysis, mice were treated with 75 mg kg−1 body weight of NG for three consecutive days before irradiation (6 Gy). Pretreatment with NG significantly prevented the IR-induced generation of intracellular reactive oxygen species (ROS), along with the formation of hepatic thiobarbituric acid reactive substances (TBARS) and cellular nitrite. NG also showed significant reduction in IR-induced nuclear DNA damage through the inhibition of DNA-dependent protein kinase (DNA-PK). Further, the IR-induced cell death was arrested in the presence of NG through the inhibition of p53 mediated stress-activated protein kinase/Jun amino-terminal kinase (SAPK/JNK) pathways and modulation of other molecules of apoptosis pathways. Moreover, NG supported the intracellular defense mechanisms, by maintaining the endogenous antioxidants probably through phosphoinositide 3-kinase/protein kinase-B (PI3K/Akt) guided transcriptional activation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2). In addition, NG inhibited IR-induced inflammation through suppression of NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) followed by the alteration of pro inflammatory factors. Taken together, these results suggested that NG reversed the IR-induced redox-imbalance in murine liver, probably by the inhibition of ROS/p38-MAPK/NF-κB, along with the activation of the PI3K/Akt/Nrf2 pathway and the reduction of apoptosis by interfering with the p53/SAPK/JNK/Bax pathway.

Ferulic acid (FA) abrogates ionizing radiation-induced oxidative damage in murine spleen

Abstract Purpose: The spleen is a crucial organ manifesting immune functions. Thus, radiation-induced oxidative challenge is vulnerable for the spleen. Our major objective was to protect the spleen from radiation-induced anomalous situations and to identify the signaling pathways involved. Materials and methods: Swiss albino mice were treated with ferulic acid (FA) once in a day at a dose of 50 mg/kg body weight for 5 consecutive days before exposing them to single dose of 10 Gy irradiation. The ROS generation and MMP change were determined by flow cytometry. The expression of different signaling proteins was investigated by immunoblotting and immunocytochemistry. Results: FA pretreatment significantly prevented radiation-induced oxidative stress by downregulating TBARS formation and by upregulating SOD and catalase activity. FA scavenged ROS, prevented the alteration of MMP and downregulated the expression of stress marker Cdc42 and apoptotic markers p53, p21, Bax and PTEN. Cell cycle analysis showed DNA damage induced arrest of cells at subG0/G1 phase. Moreover, pretreatment with FA augmented Bcl2 expression and also increased the level of p-PI3K. Conclusion: FA prevented the activation of apoptotic signaling events in the spleen by interfering with the free radical chain reaction and by scavenging superfluous ROS. This is perhaps the first comprehensive study with a mechanistic viewpoint that FA can protect the spleen from ionizing radiation.

Ferulic acid (FA) abrogates γ-radiation induced oxidative stress and DNA damage by up-regulating nuclear translocation of Nrf2 and activation of NHEJ pathway

Abstract The present study was aimed to evaluate the radioprotective effect of ferulic acid (FA), a naturally occurring plant flavonoid in terms of DNA damage and damage related alterations of repair pathways by gamma radiation. FA was administered at a dose of 50 mg/kg body weight for five consecutive days prior to exposing the swiss albino mice to a single dose of 10 Gy gamma radiation. Ionising radiation induces oxidative damage manifested by decreased expression of Cu, Zn-SOD (SOD stands for super oxide dismutase), Mn-SOD and catalase. Gamma radiation promulgated reactive oxygen species (ROS) mediated DNA damage and modified repair pathways. ROS enhanced nuclear translocation of p53, activated ATM (ataxia telangiectasia-mutated protein), increased expression of GADD45a (growth arrest and DNA-damage-inducible protein) gene and inactivated Non homologous end joining (NHEJ) repair pathway. The comet formation in irradiated mice peripheral blood mononuclear cells (PBMC) reiterated the DNA damage in IR exposed groups. FA pretreatment significantly prevented the comet formation and regulated the nuclear translocation of p53, inhibited ATM activation and expression of GADD45a gene. FA promoted the nuclear translocation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and activated NHEJ repair pathway to overcome ROS mediated oxidative stress and DNA damage. Therefore, the current study stated that FA can challenge the oxidative stress by (i) inducing nuclear translocation of Nrf2, (ii) scavenging ROS, and (iii) activating NHEJ DNA repair process.

Smokeless tobacco consumption impedes metabolic, cellular, apoptotic and systemic stress pattern: A study on Government employees in Kolkata, India

Smokeless tobacco (SLT) remains a threat amongst a large population across the globe and particularly in India. The oral use of tobacco has been implicated to cause physiological stress leading to extreme toxicological challenge. The study included 47 SLT-users and 44 non-users providing a spectrum of pathophysiological, clinico-biochemical, antioxidant parameters, cell cycle progression study of PBMC and morphological changes of red blood cells (RBC). The expressions of p53, p21, Bax, Bcl-2, IL-6, TNF- α, Cox-2, iNOS were analyzed from thirteen representative SLT-users and twelve non-users. Difference in CRP, random glucose, serum cholesterol, TG, HLDL-C, LDL-C, VLDL-C, neutrophil count, monocyte count, ESR, SOD (PBMC) and TBARS (RBC membrane) were found to be statistically significant (p < 0.05) between the studied groups. The current study confers crucial insight into SLT mediated effects on systemic toxicity and stress. This has challenged the metabolic condition leading to a rise in the inflammatory status, increased apoptosis and RBC membrane damage. The above findings were substantiated with metabolic, clinical and biochemical parameters. This is possibly the first ever in-depth report and remains an invaluable document on the fatal effects of SLT.

Gossypetin ameliorates ionizing radiation-induced oxidative stress in mice liver--a molecular approach.

Abstract Radioprotective action of gossypetin (GTIN) against gamma (γ)-radiation-induced oxidative stress in liver was explored in the present article. Our main aim was to evaluate the protective efficacy of GTIN against radiation-induced alteration of liver in murine system. To evaluate the effect of GTIN, it was orally administered to mice at a dose of 30 mg/kg body weight for three consecutive days prior to γ-radiation at a dose of 5 Gy. Radioprotective efficacy of GTIN were evaluated at physiological, cellular, and molecular level using biochemical analysis, comet assay, flow cytometry, histopathology, immunofluorescence, and immunoblotting techniques. Ionizing radiation was responsible for augmentation of hepatic oxidative stress in terms of lipid peroxidation and depletion of endogenous antioxidant enzymes. Immunoblotting and immunofluorescence studies showed that irradiation enhanced the nuclear translocation of nuclear factor kappa B (NF-κB) level, which leads to hepatic inflammation. To investigate further, we found that radiation induced the activation of stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK)-mediated apoptotic pathway and deactivation of the NF-E2-related factor 2 (Nrf2)-mediated redox signaling pathway, whereas GTIN pretreatment ameliorated these radiation-mediated effects. This is the novel report where GTIN rationally validated the molecular mechanism in terms of the modulation of cellular signaling system’ instead of ‘ This is the novel report where GTIN is rationally validated in molecular terms to establish it as promising radioprotective agents. This might be fruitful especially for nuclear workers and defense personnel assuming the possibility of radiation exposure.

Radiosensitizing effect of ellagic acid on growth of Hepatocellular carcinoma cells: an in vitro study

Failure of treatment for cancer in clinic by radio/chemotherapy is generally attributed to tumour resistance. Therefore, it is important to develop strategies to increase the cytotoxicity of tumour cells by radiation in combination with unique tumour selective cytotoxic agents. We evaluated the potential of ellagic acid (EA) as an enhancer of oxidative stress in cancer cells. HepG2 cells were treated with EA (10 µM) for 12 h prior to exposure of single 7.5 Gy dose of irradiation. Treatment of HepG2 cells with EA and gamma radiation showed increased reactive oxygen species generation, up regulation of p53 protein expression, decreased survival markers level like p-Akt, p-NF-kB and p-STAT3 which were significantly higher after radiation treatment alone. We also found that combination treatment increased G2/M phase cell population, decreased IL-6, COX–2 and TNF-α expression and caused a loss in mitochondrial membrane potential with decreased level of angiogenesis marker MMP-9. Over expression of Bax and activation of caspase 3 indicated the apoptosis of the cells. The results provided a strong unique strategy to kill cancer cells HepG2, using less radiation dose along with effective pro-oxidant dose of EA.

Herbicide exposure induces apoptosis, inflammation, immune modulation and suppression of cell survival mechanism in murine model

The lymphatic organ, the spleen, is of immense immunological importance as it is the largest blood filter in the mammalian system. The objective of the current study is to explore the detrimental cellular and sub-cellular effects in the spleen, mediated by the widely used herbicide, paraquat (PQ). PQ is an uncoupling agent for the electron transport chain complex in the mitochondria, which promulgates serious alterations in the intracellular oxidative microenvironment. This leads to the activation of a cascade of sub cellular events leading to cell death. Since PQ-induced oxidative damage in the spleen is not well explored, we planned to develop a PQ toxicity model in rodents, addressing its negative effects in the highest molecular terms. The toxicity markers were evaluated in terms of oxidative stress, cellular apoptosis, inflammation and splenomegaly in Swiss albino mice after treatment with PQ. The increase in thiobarbituric acid reactive substances (TBARS), tissue nitrite formation, intracellular reactive oxygen species (iROS) production, depletion of the activities of catalase (CAT), glutathione (GSH), superoxide dismutase (SOD) and the reduction in mitochondrial inner trans membrane potential (MMP) were significant in the PQ treated group compared to the control. A pronounced inhibition of cell proliferative response and increased p53, Bax expression, caspase 3 activities and decreased Bcl-2 were also associated with PQ-induced apoptosis. Moreover, a pro-inflammatory response was apparent in the PQ treated group as indicated by elevated levels of pro-inflammatory markers (TNF-α, IL-6 and COX-2). Thus, this is perhaps the first mechanistic report showing how a herbicide induces the oxidative stress responsible for immunomodulation, apoptosis, as well as splenomegaly in the murine system.

SMOKELESS TOBACCO: ‘BID’ING NEURONAL DEATH

Oleksandr Yagensky, Mahdokht Kohansal Nodehi, Tamara Rabe, Saima Zafar, Inga Zerr, John Jia En Chua, Max Planck Institute for Biophysical Chemistry, G€ottingen, Germany; University Medical Center G€ottingen, G€ottingen, Germany; Reference Center for Neurodegenerative Diseases, Goettingen, Germany; University Medical Center G€ottingen, Goettingen, Germany; Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. Contact e-mail: oleksandr.yagensky@mpibpc.mpg.de

Alteration of murine duodenal morphology and redox signalling events by reactive oxygen species generated after whole body γ-irradiation and its prevention by ferulic acid

Abstract Radiation-induced gastrointestinal syndrome occurs due to the clonogenic loss of crypt cells and villi depopulation, resulting in disruption of the mucosal barrier, bacterial invasion, inflammation, and sepsis. In this study, we investigated the role of ferulic acid (FA) against ionising radiation-induced duodenal injury and subsequent alterations in redox signalling events in wild type male Swiss albino mice. Mice were administered with FA at a dose of 50 mg/kg body weight for 5 consecutive days prior to exposure of 2.5, 5 and 10 Gy doses of γ-radiation. Histopathological and electron microscopic images revealed marked duodenal injuries in a dose-dependent manner. FA prevented radiation induced damage and loss of cryptic stem cells and the shortening of duodenal villus length. FA pretreatment further suppressed NF-κB-dependent activation of inflammatory pathways and augmented Nrf2 nuclear translocation with higher expression of Mn-SOD and heme-oxygenase one (HO1) activity to combat with radiation induced duodenal stress. The colocalisation of NF-κB and Nrf2 transcription factors in the nuclei of the duodenum indicated their interaction in radiation and the FA combination group. Moreover, FA treatment inhibited phosphatidyl serine (PS) externalisation, and loss of mitochondrial membrane potential in duodenal cells. Animals exposed to 10-Gy irradiation exhibited over activation of p53, p21, caspase 3, poly ADP ribose polymerase (PARP) and DNA double-strand break which were ameliorated by FA treatment. Therefore, this article first uncovers the modulatory effect of FA on radiation-induced ROS/NF-κB/Nrf2/p53-caspase 3-PARP axis in the duodenum and establishing biological function of FA in protecting duodenum from radiation damage with a detailed mechanistic approach.