Kumkum Mishra

Radiation-induced micronucleus formation and DNA damage in human lymphocytes and their prevention by antioxidant thiols.

Thiol family of antioxidants has been considered to be the most effective class of radio protective agents. Present study reports a comparative evaluation of antioxidant thiols, namely N-acetyl cysteine (NAC), glutathione (GSH) and thioproline (TP), on gamma radiation-induced damage to human lymphocytes DNA as assessed by micronucleus (MN) formation and comet assay parameters. Pretreatment of cells with NAC, GSH and TP showed significant protection against DNA damage and MN frequency in irradiated lymphocytes (2-4 Gy). The magnitude of DNA damage protection was found to be concentration dependent (100-300 microM) which followed the order GSH>NAC>TP. Further, antioxidant thiols mediated protection against DNA damage in irradiated lymphocyte showed significant correlation with their ability to decrease intracellular ROS but not to the increase in intracellular GSH. Experiments on the effect of antioxidant thiols on plasmid DNA irradiated under cell free aqueous conditions showed that NAC exerts greater protection than GSH against radiation damage. TP showed similar responses in cellular and plasmid DNA. Greater protection of plasmid DNA by NAC is ascribable to its more potential hydrogen donor ability as revealed by radical chromogen 2,2-diphenyl-1-picrylhydrazyl (DPPH) photometric assay. Thus, present study indicated that radioprotection of lymphocytes DNA by antioxidant thiols are closely correlated to the reduction of cellular oxidative stress, which seems to involve multiple mechanisms.

Selenate mitigates arsenite toxicity in rice (Oryza sativa L.) by reducing arsenic uptake and ameliorates amino acid content and thiol metabolism.

Arsenic (As) is a toxic element with the potential to cause health effects in humans. Besides rice is a source of both amino acids (AAs) and mineral nutrients, it is undesired source of As for billions of people consuming rice as the staple food. Selenium (Se) is an essential metalloid, which can regulate As toxicity by strengthening antioxidant potential. The present study was designed to investigate As(III) stress mitigating effect of Se(VI) in rice. The level of As, thiolic ligands and AAs was analyzed in rice seedlings after exposure to As(III)/Se(VI) alone and As(III)+Se(VI) treatments. Selenate supplementation (As(III) 25μM+Se(VI) 25μM) decreased total As accumulation in both root and shoot (179 & 144%) as compared to As(III) alone treatment. The As(III)+Se(VI) treatment also induced the levels of non-protein thiols (NPTs), glutathione (GSH) and phytochelatins (PCs) as compared to As(III) alone treatment and also modulated the activity of enzymes of thiol metabolism. The content of amino acids (AAs) was significantly altered with Se(VI) supplementation. Importantly, essential amino acids (EAAs) were enhanced in As(III)+Se(VI) treatment as compared to As(III) alone treatment. In contrast, stress related non-essential amino acids (NEAAs) like GABA, Glu, Gly, Pro and Cys showed enhanced levels in As(III) alone treatment. In conclusion, rice supplemented with Se(VI) tolerated As toxicity with reduced As accumulation and increased the nutrition quality by increasing EAAs.

Quantitative Structure – ActivityRelationship (QSAR) of N-Arylsubstituted Hydroxamic Acids as Inhibitors of Human Adenocarinoma Cells A431

Hydroxamic acids the multifunctional molecules with general formula R – C(=O)NROH have interesting medicinal and biological potentiality. The antiproliferative activity of 12 hydroxamic acids has been tested in vitro towards human adenocarcinama cell line by MTT assay. The IC50 values were found to be in the range from 12 to 152.8μM. The most potent product identified is N-p-chlorophenyl-4-nitrobenzohydroxamic acid with IC50 value 12μM. The RP-HPLC experiment of these molecules was performed with 50:50V/V% methanol - water mixture as mobile phase. A QSAR is developed for the human adenocarcinoma cells inhibitory activity of a series of hydroxamic acids (n=1-12) that are structurally related to hydroxyurea. Multivariate analytical tool, projection to latent structures was used to develop a suitably predictive model for the purpose of optimizing and identifying members with more potent inhibitory activity. The crossvalidated Q2cum values for two optimal PLS models of hydroxamic acids are above 0.690 (remarkably higher 0.500), indicating good predictive abilities for log1/IC50 values of HAs. By partial least squares regression, two QSAR models revealed that, besides the essential pharmacophore – NOH.C=O, retention capacity factor, logk, polar surface area, PSA, Dipole moment, Dm, total no. of hydrogen bond donor and acceptor atoms, H, and chlorine atoms attached in upper or/and lower phenyl rings, ICl , are important determinants for the inhibitory potency against A431 cells.

Ellagic acid radiosensitizes tumor cells by evoking apoptotic pathway

Cancer causes millions of deaths each year globally. In most patients, the cause of treatment failure is found associated with the resistance to chemotherapy and radiotherapy. The development of tumor cell resistance evokes multiple intracellular molecular pathways. In addition, the limitation in treatment outcome arises due to unintended cytotoxic effects of the synthetic anticancer drugs to normal cells and tissues. Considerable focus of research is, therefore, devoted to examine plant-based herbal compounds which may prove potential anticancer drug for developing effective cancer therapy. Research results from our laboratory have shown that ellagic acid (EA), a natural flavonoid displays enhanced tumor toxicity in combination with gamma radiation to many types of cancers in vitro as well as in vivo. Studies on the underlying mechanisms of toxicity suggest that EA employs the cellular signaling pathways in producing the observed effects. This paper gives an account of molecular mechanisms of EA-induced apoptosis process in tumor cytotoxicity. It is suggested that EA acts as a novel radiosensitizer for tumors and a radioprotector for normal cells which may offer a novel protocol for cancer treatment.

Thiol antioxidants protect against ionising radiation-induced micronuclei formation in cultured human lymphocytes

The major biological consequences of ionising radiation are generally attributed to the generated free radicals and their reactions with vital cellular components. The level of antioxidants in irradiated cells and animals is generally considered an important determinant of radiobiological damage. The present study aimed to investigate the effect of antioxidants of the thiol family, namely, N-acetyl cysteine (NAC), glutathione (GSH) and thioproline (TP) on the radiation-induced chromosomal damage in human lymphocytes in vitro. The incidence of micronucleus (MN) formation, as measured by the cytochalasin B method, was found to be dependent on low to moderate radiation doses (0-200 cGy). The frequency of MN formation in lymphocytes pretreated with antioxidants was found to decrease with their concentration (100-300 μM). The results show that GSH was a more effective protector than NAC or TP, possibly due to relative radical scavenging efficiency. It was further found that treatment with equimolar concentrations of combined NAC and GSH yielded the most effective reduction in MN frequency compared to other combinations of NAC-TP and GSH-TP. The results suggest that the pretreatment of blood with thiol antioxidants significantly prevented MN formation in the isolated lymphocytes. These results may help in developing protocols for effective protectors against radiation exposure for practical applications.

The involvement of cellular oxidative damage in the apoptotic death induced in γ-irradiated mouse thymocytes

Radiation-induced cellular oxidative damage and the consequent apoptotic death were investigated in mouse thymocytes in the presence or absence of eugenol to understand the mechanism of modification in cellular radiosensitivity. The results showed the radiation-induced generation of intracellular Reactive Oxygen Species (ROS) in γ-irradiated thymocytes, which were detected within a low to moderate dose range of radiation exposure (sub cGy to 2 Gy) using 2′,7′-dichlorodihydrofluorescein diacetate (DCH-FDA) as a fluorescent probe. However, the dose response of the ROS generation was found to be different at low and high doses/rates, which was significantly inhibited when the cells were treated with eugenol. There was a decrease in the mitochondrial membrane potential (ΔΨmt) after the irradiation of cells, which was prevented when cells were pretreated with eugenol. The population of thymocytes with a reduced nuclear diameter was found to progressively increase with the post-irradiation incubation time following exposure to a dose of 5 Gy, which was, however, prevented in the thymocytes that were treated with eugenol. These results followed a pattern that is similar to the annexin-V method that was further verified in control and irradiated samples. We have found a correlation in cellular oxidative stress, a decrease in ΔΨmt and the induction of apoptotic cell death, suggesting the involvement of oxidative damage and alterations in the mitochondria in radiation-induced apoptosis in thymocytes.

Green Synthesis of Nanoparticles: An Emerging Phytotechnology

The metallic particles whose size ranges between 1 and 100 nm in any one of the dimensions are termed as nanoparticles (NPs). Nanoparticles pose a great interest to chemists, physicists, biologists, and engineers for the development of new generation nanodevices, electronics, catalysis, chemistry, energy, and medicine. “Green synthesis” refers to the use of green material (i.e., plants) for the synthesis of any material. Nanoparticles can be synthesized by various ways, viz., laser ablation, gamma irradiation, electron irradiation, chemical reduction, photochemical methods, and microwave processing, which however produce hazardous chemicals as by-product. Green synthesis of NPs is presently becoming popular due to its eco-friendly and cost-effective approach with no use of any toxic chemicals. At the same time, synthesis of NPs through biological methods is not as easy and lots of open challenges are there. Green synthesis of NPs involves the use of water in closed reactors, which is a nontoxic solvent, and applies green techniques like ultrasound and microwave. The reagents used for the synthesis of NPs also include natural compounds such as sugars, vitamins, biodegradable compounds, and microbes. Among these reagents, plant-based materials are the most suitable candidates for large-scale synthesis of NPs. Several plants and their compounds are being used for green synthesis of NPs. This chapter focuses on the range of plants being used for various NP biosynthesis and also gives a view of various applications of NPs in diverse fields.

Ameliorating Effects of Iron and Zinc on Vigna mungo L. Treated with Tannery Effluent

Different dilutions, that is, 25, 50, 75, and 100%, of tannery effluent (TE) were chosen for the present study to assess the phytotoxic effects on Vigna mungo L. For amelioration purposes, different levels and combinations of iron and zinc were supplied to the plants along with 50% TE that is chosen on the basis of prior test under Petri dish culture. Cytotoxic and biochemical analysis and plant tolerance index (PTI) of plant were observed. Mitotic index deceased with increase in effluent concentration whereas abnormality % was increased. The pigments (chlorophyll a, total, and carotenoids) were decreased with increasing treatment levels of TE at both growth stages. However, carotenoid content increased significantly at all dilution levels of TE after first growth stage. Chlorophyll b was increased significantly after 35 days of growth but decreased after 70 days. The protein contents were also significantly decreased with increase in all TE treatments and increased significantly in zinc recovery treatments. Activities of catalase and peroxidase enzymes were significantly affected and increased significantly with effluent treatments. PTI showed an enhanced tolerance capacity of plant with treatment of iron and zinc. A negative correlation was found (r = −0.97) between plant height and different dilutions of effluent whereas it was positively correlated (r = 0.95) with iron and zinc treatments. The study represents the ameliorative effect of iron and zinc for phytotoxic damage in V. mungo caused by tannery effluent.