Curcumin loading potentiates the chemotherapeutic efficacy of selenium nanoparticles in HCT116 cells and Ehrlich's ascites carcinoma bearing mice

The anticancer properties of selenium (Se) and curcumin nanoparticles in solo formulations as well as in combination with other therapeutic agents have been proved time and again. Exploiting this facet of the two, we clubbed their tumoricidal characteristics and designed curcumin loaded Se nanoparticles (Se-CurNPs) to achieve an enhanced therapeutic effect. We evaluated their therapeutic effects on different cancer cell lines and Ehrlich's ascites carcinoma mouse model. In vitro results showed that Se-CurNPs were most effective on colorectal carcinoma cells (HCT116) compared to the other cancer cell lines used and possessed pleiotropic anticancer effects. The therapeutic effect on HCT116 was primarily attributed to an elevated level of autophagy and apoptosis as evident from significant up-regulation of autophagy associated (LC3B-II) and pro-apoptotic (Bax) proteins, down-regulation of anti-apoptotic (Bcl-2) protein and Cytochrome c (cyt c) release from mitochondria along with reduced NFκB signaling and EMT based machineries marked by downregulation of inflammation (NFκB, phospho-NFκB) and epithelial-mesenchymal transition (CD44, N-cadherin) associated proteins. In vivo studies on Ehrlich's ascites carcinoma (EAC) mice model indicated that Se-CurNPs significantly reduced the tumor load and enhanced the mean survival time (days) of tumor-bearing EAC mice.

Gellan gum-PEI nanocomposites as efficient gene delivery agents

Of the non-viral vectors, a cationic polymer like PEI is an attractive candidate which however, has been negatively impacted due to its marked toxicity. An anionic sugar polymer gelan gum (GG) has been introduced into PEI system to increase transfection efficiency with minimal toxicity. We showed that one of the synthesized (GP1-GP6) GG-PEI nanocomposites (NCs), GP3, exhibited negligible toxicity in in vitro (primary keratinocytes, HEK293, HeLa and HepG2 cells) and in vivo (Drosophila melanogaster) as compared to PEI or lipofectamin. GP3-pDNA complex was found to be transfected efficiently in the above cells as confirmed by FACS analysis (72.0 + 5.5%) while lipofectamine showed only 12.4 + 3.5% efficiency. GP3 mediated GFP specific siRNA delivery resulted in the knockdown of the GFP expression by approximately 77% and JNK (60%). In vivo gene expression studies in mice revealed reporter gene expression in spleen. The study demonstrates that GG blended PEI NCs hold promise for future applications in gene delivery both in vitro and in vivo.

The evolution and distribution of life in the Precambrian eon-global perspective and the Indian record

The discovery of Precambrian microfossils in 1954 opened a new vista of investigations in the field of evolution of life. Although the Precambrian encompasses 87% of the earth's history, the pace of organismal evolution was quite slow. The life forms as categorised today in the three principal domains viz. the Bacteria, the Archaea and the Eucarya evolved during this period. In this paper, we review the advancements made in the Precambrian palaeontology and its contribution in understanding the evolution of life forms on earth. These studies have enriched the data base on the Precambrian life. Most of the direct evidence includes fossil prokaryotes, protists, advanced algal fossils, acritarchs, and the indirect evidence is represented by the stromatolites, trace fossils and geochemical fossils signatures. The Precambrian fossils are preserved in the form of compressions, impressions, and permineralized and biomineralized remains.

Regulation of oxidative stress–mediated apoptosis by diallyl sulfide in DMBA-exposed Swiss mice

Diallyl sulfide, a sulfur-containing volatile compound present in garlic ( Allium sativum), exerts anticarcinogenic activity in various rodent tumor models. In the present study, apoptosis-inhibiting effects of diallyl sulfide against a carcinogenic polycyclic aromatic hydrocarbon, 7,12-dimethyl benz(a)anthracene (DMBA), in Swiss albino mice were observed. The animals were given either 250 μg/mouse or 500 μg/mouse of diallyl sulfide for 1 week after a single intragastric dose of 7,12-dimethyl benz(a)anthracene (50 mg/kg body weight). Results showed that diallyl sulfide supplementation effectively protects against 7,12-dimethyl benz(a)anthracene—induced oxidative stress, characterized by restored antioxidant enzyme levels (up to 64%) and lipid peroxidation (up to 25%). Flow cytometric analysis showed a reduction in apoptotic cell population in hypodiploid region in diallyl sulfide–supplemented animals. Inhibition of apoptosis was preceded by decrease in reactive oxygen species levels and restoration of mitochondrial transmembrane potential followed by decreased DNA fragmentation. In 7,12-dimethyl benz(a)anthracene–exposed animals, downregulation (~30%) of antiapoptotic Bcl-2 and upregulation (~60%) of pro-apoptotic Bax proteins were observed. These alterations were restored significantly by diallyl sulfide supplementation, indicating inhibition of apoptosis. Thus, these results show that diallyl sulfide provides protection against oxidative damage induced by 7,12-dimethyl benz(a)anthracene in mouse liver and may be an effective chemopreventive and therapeutic agent by modulating expression of cell-growth regulatory proteins.

Involvement of nitric oxide in neurodegeneration: a study on the experimental models of Parkinson's disease

The present study was undertaken to explore involvement of nitric oxide (NO) in the experimental models of Parkinson's disease. Neurodegeneration was induced by unilateral injections of 6-hydroxydopamine (6-OHDA) or lipopolysaccharide (LPS) in the right striatum. Lesions were functionally evaluated by amphetamine-induced asymmetrical behaviour and by decrease in the tyrosine hydroxylase (TH) immunostaining. An induction in the expression of iNOS and augmentation in nitrite content was observed in both the models. The extent of increase in iNOS expression was, however, different but the elevation in the nitrite content was comparable in both the models. The increase in iNOS expression inversely correlated with the tyrosine hydroxylase (TH) immunolabeling. Animals pretreated with a NOS inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME), exhibited complete protection against amphetamine induced rotations in both the models. Thus, augmented NO availability subsequent to iNOS induction seems to play an important role in the initial phase of neurodegeneration.

Neuroprotective and neurorescue effect of black tea extract in 6-hydroxydopamine-lesioned rat model of Parkinson's disease

In the present study, an attempt has been made to explore the neuroprotective and neuroreparative (neurorescue) effect of black tea extract (BTE) in 6-hydroxydopamine (6-OHDA)-lesioned rat model of Parkinson's disease (PD). In the neuroprotective (BTE + 6-OHDA) and neurorescue (6-OHDA + BTE) experiments, the rats were given 1.5% BTE orally prior to and after intrastriatal 6-OHDA lesion respectively. A significant recovery in d-amphetamine induced circling behavior (stereotypy), spontaneous locomotor activity, dopamine (DA)-D2 receptor binding, striatal DA and 3-4 dihydroxy phenyl acetic acid (DOPAC) level, nigral glutathione level, lipid peroxidation, striatal superoxide dismutase and catalase activity, antiapoptotic and proapoptotic protein level was evident in BTE + 6-OHDA and 6-OHDA + BTE groups, as compared to lesioned animals. BTE treatment, either before or after 6-OHDA administration protected the dopaminergic neurons, as evident by significantly higher number of surviving tyrosine hydroxylase immunoreactive (TH-ir) neurons, increased TH protein level and TH mRNA expression in substantia nigra. However, the degree of improvement in motor and neurochemical deficits was more prominent in rats receiving BTE before 6-OHDA. Results suggest that BTE exerts both neuroprotective and neurorescue effects against 6-OHDA-induced degeneration of the nigrostriatal dopaminergic system, suggesting that possibly daily intake of BTE may slow down the PD progression as well as delay the onset of neurodegenerative processes in PD.

Co-transplantation of carotid body and ventral mesencephalic cells as an alternative approach towards functional restoration in 6-hydroxydopamine-lesioned rats: implications for Parkinson's disease

Exogenous administration of various neurotrophic factors has been shown to protect neurons in animal model of Parkinson's disease (PD). Several attempts are being made to search a tissue source simultaneously expressing many of these neurotrophic factors. Carotid body (CB) contains oxygen-sensitive glomus cells rich in dopamine (DA) and expresses glial cell line-derived neurotrophic factor, brain-derived neurotrophic factor and neurotrophin-3. We have attempted to study the functional restoration following co-transplantation of CB cells and ventral mesencephalic cells (VMC) in a 6-hydroxydopamine-lesioned rat model of PD. A significant recovery (p < 0.001) in d-amphetamine-induced circling behavior (80%) and spontaneous locomotor activity (85%) was evident in co-transplanted animals at 12 weeks post-transplantation as compared to lesioned animals. Similarly, a significant (p < 0.001) restoration was observed in DA-D(2) receptor binding (77%), striatal DA (87%) and 3,4-dihydroxyphenylacetic acid (DOPAC) (85%) levels and nigral DA (75%) and DOPAC (74%) levels. Functional recovery was accompanied by tyrosine hydroxylase (TH) expression and quantification of TH-positive cells by image analysis revealed a significant restoration in TH-immunoreactive (IR) fiber density in striatum, as well as TH-IR neurons in substantia nigra pars compacta in co-transplanted animals over VMC-transplanted animals. The result suggests that co-transplantation of CB cells along with VMC provides better and long-term functional restoration in the rat model of PD, possibly by supporting the survival of newly grafted cells as well as remaining host DA neurons.

Modulation of altered hepatic foci induction by diallyl sulphide in Wistar rats

Diallyl sulphide (DAS) is a sulphur-containing volatile compound present in garlic (Allium sativum). It has been shown to inhibit a number of chemically induced forms of cancer in experimental animals. The present study demonstrates the inhibitory effect of DAS on the development of diethylnitrosamine (DEN) initiated and 2-acetyl-aminofluorene (2-AAF) promoted preneoplastic altered hepatic foci (AHF) in Wistar rats. AHF were scored and analysed by quantitative stereology using the Image Analysis system from frozen liver sections stained for biological markers, namely glutathione S-transferase, placental form (GST-P), gamma-glutamyl transpeptidase (GGT), adenosine triphosphatase (ATPase), glucose-6-phosphatase (G6 Pase) and alkaline phosphatase (AlkPase). DAS-supplemented rats were found to restore the near-normal levels of enzymes GST-P and GGT when exposed to DEN and 2-AAF. DAS administration following DEN and 2-AAF exposure led to the restoration of enzymic activity of ATPase, G6 Pase and AlkPase, as evident by number and area of the foci. These findings suggest the protective role of DAS in rat hepatocarcinogenesis, by suppressing DEN- and 2-AAF-induced AHF development.

Effect of glial cell line‐derived neurotrophic factor (GDNF) co‐transplantation with fetal ventral mesencephalic cells (VMC) on functional restoration in 6‐hydroxydopamine (6‐OHDA) lesioned rat model of Parkinson's disease: neurobehavioral, neurochemical and immunohistochemical studies

Among trophic factors already known, glial cell line-derived neurotrophic factor (GDNF) and other members of its family have potent and specific action on dopaminergic neurons. In the present investigation an attempt has been made to validate the role of GDNF co-transplantation with fetal ventral mesencephalic cells (VMC) on functional viability and restoration using neurobehavioral, neurochemical and immunohistochemical parameters at 6 weeks post-transplantation in 6-hydroxydopamine (6-OHDA) lesioned rat model of Parkinson's disease (PD). A significant restoration (P<0.01) in D-amphetamine induced rotations, spontaneous and apomorphine induced locomotor activity in rats co-transplanted with VMC and GDNF was observed as compared to VMC alone transplanted rats. Level of dopamine (DA), 3,4-dihydroxy-phenyl acetic acid (DOPAC) and dopamine D2 (DA-D2) receptors in the caudate putamen (CPu) were significantly (P<0.001) restored in co-transplanted group as compared to VMC transplanted or GDNF administered animals. The functional viability of transplanted VMC was confirmed by tyrosine hydroxylase (TH) expression and quantification of TH-positive cells by image analysis revealed a significant restoration in TH-IR fibers density as well as TH-IR neurons counts in co-transplanted animals over VMC transplanted animals. Results suggest that co-transplantation of VMC and GDNF may be a better approach towards functional restoration in 6-OHDA lesioned rat model of Parkinson's disease.

Induced expression of early response genes/oxidative injury in rat pheochromocytoma (PC12) cell line by 6-hydroxydopamine: implication for Parkinson's disease

The expression of early response gene proteins c-Fos, c-Jun, and GAP-43 and their association with 6-hydroxydopamine (6-OHDA)-mediated oxidative injury were investigated using catecholaminergic PC12 cell line. Significant induction in the expression of c-Fos (P < 0.01), c-Jun (P < 0.001) and GAP-43 (P < 0.05) was observed following 2 h exposure to 6-OHDA (10(-6) M), which persisted during 24 h of observation. The exposed cells exhibited an increase in lipid peroxidation (48, 59 and 33%) along with decreased catalase activity (49, 30 and 13%) and glutathione levels (39, 28 and 16%) following 24, 48 and 72 h exposure, respectively. A concentration-dependent functional impairment of mitochondria as studied by 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay and decreased cell survival were also observed following 6-OHDA (10(-4), 10(-5) M) exposure for 24, 48 and 72 h. The results indicate a role of the early response gene in oxidative stress-mediated dopaminergic cell death by 6-OHDA. Similar mechanisms may also be operative in the development of Parkinson's disease, as an increased presence/formation of endogenous 6-OHDA has been reported in Parkinson's patients.

Antimutagenic effect of black tea extract using 'rodent dominant lethal mutation assay'

The antimutagenic effect of black tea extract has been evaluated with the 'Dominant Lethal Assay' in Swiss albino mice using benzo[a]pyrene [BaP] as a mutagen. BaP was given through the intraperitoneal (i.p.) route at a single dose of 100 mg/kg b.w. to male mice once only. The animals were given 1, 2 and 4% aqueous solution of black tea as sole source of drinking solution prior to BaP. The pregnant females were analyzed for living implants, pre- and post-implantation losses. The results revealed that during mating weeks, BaP caused a reduction in implants and an increase in pre- and post-implantation losses. The protective effect of tea solution on BaP-induced mutagenicity was observed. The number of living implants increased and dead implants decreased significantly in the animals kept on 2 and 4% tea solution. The increase in dominant lethal mutation rate by BaP was inhibited by black tea extract. Four percent tea solution alone did not produce dominant lethality, and reveals that it is non-toxic/non-mutagenic to sperm. Hence the study suggests that tea has a protective effect against BaP-induced genetic damage to germ cells in Swiss albino mice.

Histochemical localization of glutathione dependent NBT-reductase in mouse skin

OBJECTIVE

Localization of the glutathione dependent Nitroblue tetrazolium (NBT) reductase in fresh frozen sections of mouse skin and possible dependence of NBT reductase on tissue thiol levels has been investigated.

METHODS

The fresh frozen tissue sections (8 m thickness) were prepared and incubated in medium containing NBT, reduced glutathione (GSH) and phosphate buffer. The staining for GSH was performed with mercury orange.

RESULTS

The activity of the NBT-reductase in mouse skin has been found to be localized in the areas rich in glutathione and actively proliferating area of the skin.

CONCLUSION

The activity of the NBT-reductase seems to be dependent on the glutathione contents.

Tumourigenic studies on deltamethrin in Swiss albino mice

Deltamethrin, an alpha-cyano type II synthetic pyrethroid insecticide is used to control a wide range of insects on a variety of crops. Deltamethrin is reported to cause many adverse effects on non-target species. Deltamethrin is reported to cause DNA damage and micronuclei induction in human lymphocytes. It is highly toxic for other organisms such as aquatic invertebrates, fish and Daphnia. About the tumorigenic risk (both tumour initiating and promoting) associated with deltamethrin exposure, very few reports are available in literature. In the present set of investigations, deltamethrin has been evaluated for its tumorigenic and co-carcinogenic (tumour initiating and tumour promoting) potential following long term dermal exposure in Swiss albino mice. The results revealed that deltamethrin has only tumour initiating potential in both the sexes of Swiss albino mice, initiated with deltamethrin and promoted by standard tumour promoter, 12-O-tetra decanoyl phorbol-13-acetate (TPA). In the single dose initiated mice (deltamethrin 4 mg/kg body weight, once only), 44% males and 43% females developed benign skin tumours. A much higher incidence of tumorigenesis was recorded in multiple dose initiated animals (deltamethrin 4 mg/kg body weight, three times per week for 3 weeks), where 71% male and 75% female mice developed tumours at the site of application of deltamethrin. Deltamethrin exposure failed to show any tumour promoting and complete tumorigenic potential at all the three tested dose levels.

Transplacental carcinogenic potential of the carbamate fungicide mancozeb

We evaluated the effects of mancozeb (Dithane M4-5), a protective carbamate fungicide, on transplacental carcinogenesis in Swiss albino mice. Mancozeb, a polymeric complex of ethylene bis (dithiocarbamate) manganese with zinc salt, is reported to possess carcinogenic and cocarcinogenic activity in various tumor models. In the present study, pregnant Swiss albino mice were administered mancozeb intraperitoneally on the 14th day of gestation. The first filial generation (F1 progeny) was promoted with a well-known tumor promoter 12-o-tetradecanoyl phorbol-13-acetate (TPA). The results revealed a significantly high tumor incidence (72%) in the F1 progeny of the animals initiated with mancozeb or a well known carcinogen 7,12-dimethyl benzanthracene (DMBA) and promoted with TPA in comparison to animals that were either from mothers given only the vehicle (DMSO) and promoted with TPA in F1 progeny or not promoted with TPA in F1 progeny. No significantly higher tumor incidence was observed in any other experimental groups. These results suggest that mancozeb or its metabolites are capable of crossing the placental barrier and can exert DNA damage and tumor initiating consequences in the fetal cells that, after promotion with TPA, get converted into neoplastic cells.

Neurodevelopmental consequences of gestational exposure (GD14-GD20) to low dose deltamethrin in rats

Effect of low level in utero exposure to deltamethrin (DT) (1mg /kg wt.) during gestation day 14-20 was studied on selected neurobehavioral, neurochemical, immunohistochemical parameters in rats at 6 and 12 weeks postnatal period. The significant increase in acetylcholinesterase activity and decrease in (3)H-quinuclidinyl benzilate binding in the hippocampal region of DT exposed animals, suggesting impairment in cholinergic (muscarinic) receptors. A significant decrease in the learning and memory performances was also observed both at 6 and 12 weeks, which is directly correlated with decrease in muscarinic receptor binding. Immunohistochemistry and image analysis of growth associated protein-43, a neuron specific protein present in axonal growth cone and a marker for neuronal differentiation and synaptogenesis, exhibit aberrant increase in its expression in the hippocampus in DT exposed rats at both time periods. The data suggests that low level exposure to DT in utero during brain growth spurt period adversely affects the developing brain and the changes persist even up to 12 weeks postnatal period in rats. Although there is no significant recovery at 12 weeks assessment but still significant impairment persist on biochemical and behavioural parameters.

Effects of black tea extract on transplantable and solid tumors in Swiss albino mice

The chemopreventive effects of green tea and its polyphenols are well documented in the literature. Epidemiological studies have suggested that green tea consumption might be effective in the prevention of certain human cancers. About 80% of the tea is consumed as black tea. Limited studies have been carried out to assess the usefulness of black tea as anti-carcinogen. The present set of investigations were initiated to study the anti-tumorigenic potential of aqueous black tea extract (ATE) in Swiss albino mice in in vivo animal bioassay, using 7, 12 dimethyl-benzanthracene (DMBA) as carcinogen. In the experimental group, 2% ATE was given orally as sole source of drinking water, while the control were allowed to drink normal water, ad lib. The results revealed that drinking of 2% ATE could effectively inhibit the onset of tumorigenesis, cumulative number of tumors and average number of tumors per mouse. In ATE drinking group 44% animals remained tumor free till the termination of experiment, i.e. 26 weeks. In the second set of experiment the preventive efficacy of 2% ATE of different cultivars of black tea, viz orthodox, CTC and dust were tested in Ehrlich Ascites (EA) tumor bearing mice. The preventive effects of ATE were observed in terms of increased life span (ILS). All the cultivars of tea showed more than 25% increase in life span of the animals. Cytotoxic effect of various doses of all three cultivars of black tea was also observed in vitro on EA cells.

Mutagenic evaluation of deltamethrin using rodent dominant lethal assay

The dominant lethal test was used to analyse the mutagenic potential of deltamethrin, a synthetic pyrethroid insecticide, in Swiss albino mice. In the treated series, the animals were exposed orally to three different doses (0.36, 0.72 and 1.08 mg/kg body weight) of deltamethrin dissolved in corn oil. Following the treatment, each male of control, as well as of the treated series, was mated with untreated females, every week for a period of 6 weeks. All mated females were sacrificed on the 13th day of separation and their ovaries and uterus were examined. The results revealed that deltamethrin treatment did not impair the mating capacity and fertility of Swiss albino mice. Mutagenic index, pre- and post-implantation losses were assessed. No significant pre-implantation losses were observed either weekly or averagely. Post-implantation losses were observed at medium and high doses of deltamethrin. A slight increase in dominant lethal mutation rate was observed by increasing doses of deltamethrin in early weeks but decreased in later weeks, so an apparent dose response was not observed.

Evaluation of carcinogenic and co-carcinogenic potential Quinalphos in mouse skin

Quinalphos [O,O-diethyl-O-quinoxalinyl-phosphorothidate] is an organophosphorus pesticide with tremendous utility in mixed pest control due to its insecticidal and acaricidal properties. Apart from its pesticidal property, Quinalphos is known to induce various toxic effects in nontarget species and experimental animals. No studies have been conducted to evaluate the carcinogenic/co-carcinogenic hazards associated with Quinalphos exposure. In the present set of investigations, the tumorigenic potential of Quinalphos has been evaluated following topical exposure in Swiss albino mice. Long-term animal bioassays conducted for the evaluation of complete carcinogenic, tumour-initiating and tumour-promoting potential of Quinalphos revealed that it has only tumour-initiating potential at a dose of 10 mg/kg body weight (b.wt.), in the two-stage mouse skin model of carcinogenesis. Quinalphos exposure failed to produce neoplasia when tested for complete carcinogenic activity at all three tested dose levels or tumour promoting activity.

Inhibition of carcinogen-induced activity of gamma-glutamyl transpeptidase by certain dietary constituents in mouse skin

Cancer chemoprevention, a desirable and important facet of biomedical research, provides a practical approach to identify potentially useful inhibitors of cancer development, and offers an opportunity to study the mechanism of carcinogenesis. During the recent past a number of compounds have been tested for their anticarcinogenic potential specially constituents of human diet. The enzyme gamma-glutamyl transpeptidase (GGT), which catalyses the transfer of glutamyl groups of peptides to other peptides and amino acids, has been proposed as a marker of cell proliferation and neoplasia. It also serves as a tool to evaluate the carcinogenic and cocarcinogenic potential of environmental toxicants. In the present investigations, GGT activity induced by carcinogenic polycyclic aromatic hydrocarbons, viz. 7,12-dimethyl-benz(a)anthracene (DMBA) and benzo(a)pyrene (BaP) was significantly inhibited by diallylsulfide (DAS) and indole-3-carbinol (I3C) in mouse skin. DAS and I3C are constituents of garlic. A significant inhibition in GGT levels was also observed in a strong mitogen (12-o-tetradecanoyl phorbol-13-acetate) induced activity by pretreatment of DAS/I3C in mouse skin. Therefore these dietary constituents seem to be strong modifiers of chemically induced carcinogenesis.

Inhibition of carcinogen induced activity of gamma-glutamyl transpeptidase by certain dietary constituents in mouse skin

Cancer chemoprevention, a desirable and important facet of biomedical research, provides a practical approach to identify potentially useful inhibitors of cancer development, and offers an opportunity to study the mechanism of carcinogenesis. During the recent past a number of compounds have been tested for their anticarcinogenic potential specially constituents of our diet. The enzyme gamma-glutamyl transpeptidase (GGT) which catalyses the transfer of glutamyl groups of peptides to other peptides and amino acid and has been proposed as a marker of cell proliferation and neoplasia. It also serves as a tool to evaluate the carcinogenic and cocarcinogenic potential of environmental toxicants. In the present investigations, GGT activity induced by carcinogenic polycyclic aromatic hydrocarbons, viz. 7,12-dimethylbenz(a)anthracene (DMBA) and benzo(a) pyrene (BaP) was significantly inhibited by diallylsulfide (DAS) and indole-3-carbinol (I3C) in mouse skin. DAS and I3C are constituents of garlic and cruciferous vegetables respectively. A significant inhibition in GGT levels was also observed in a strong mitogen (12-o-tetradecanoyl phorbol-13-acetate) induced activity in mouse skin by pretreatment with DAS/I3C. Therefore these dietary constituents seem to be strong modifiers of chemically induced carcinogenesis.

Antitumour promoting activity of indole-3-carbinol in mouse skin carcinogenesis

There has been growing interest in recent years in the potential of brassica vegetables (cabbage, cauliflower, brussels sprouts, etc.) as vectors for the introduction of anticarcinogenic compounds in the diet. Indole-3-carbinol, a major indole metabolite present in the cruciferous vegetables, has been found to inhibit various rodent tumours when administered prior to or during carcinogen exposure. In this study, the antitumour promoting potential of indole-3-carbinol was studied in a two-stage mouse skin model of carcinogenesis. The animals were initiated with a single subcarcinogenic dose of DMBA. After one week, 250 microg of indole-3-carbinol was applied topically to each animal prior to promotion with 5 microg TPA twice per week. Tumour development was significantly inhibited in indole-3-carbinol-supplemented animals in terms of cumulative numbers of tumours and average tumours per mouse. About 44% of male and 29% of female mice remained tumour-free in this group at the end of the experiment. A significant delay in the tumour induction time was also observed in indole-3-carbinol-supplemented animals. This evidence suggests that indole-3-carbinol, in the manner and dose given, inhibits the development of tumours in the two-stage mouse skin model of carcinogenesis.

Chemopreventive effects of black tea polyphenols in mouse skin model of carcinogenesis

In the present investigations, the antitumorigenic effect of black tea polyphenols (BTP) in two-stage mouse skin model of carcinogenesis was studied. The animals were initiated with a single "subcarcinogenic" topical dose (52 micrograms/200 microliters acetone) of 7, 12-dimethylbenzanthracene (DMBA). To evaluate the anti-tumour initiating activity, BTP was topically applied twice a week for three weeks prior to DMBA application, followed by topical treatment with 12-o-tetradecanoyl phorbol-13-acetate (TPA) (5 micrograms/200 microliters acetone, 2x/wk.) as promoter. For evaluation of antitumor promoting activity, BTP was applied prior to each treatment of TPA. BTP application showed marked inhibitory effect as antitumour initiator as well as antitumour promoter in mouse skin model of two-stage carcinogenesis. Since initiation involves genetic pathway and tumour promotion involves epigenetic pathway, it seems that BTP exerts its antitumorigenic effect by altering both genetic and epigenetic pathways.

Carcinogenicity and co-carcinogenicity studies on propoxur in mouse skin

Propoxur (2-isopropoxyphenyl methylcarbamate) is a widely used broad spectrum carbamate insecticide mainly used to control household pests. Propoxur exposure is reported to inhibit cholinesterase activity in rodents. Apart from other toxic effects, propoxur was found to possess tumorigenic activity in rats after oral administration. Propoxur does not produce tumours in mice or hamsters, or bladder hyperplasia in dogs and monkeys following oral feeding. In this set of investigations the complete carcinogenic, tumour initiating and promoting potential of propoxur was evaluated in male and female Swiss albino mice, since no information was available following dermal exposure of propoxur. The animals were exposed to propoxur through topical painting on the interscapular region at a dose of 100 mg/kg body weight. The results revealed that propoxur has tumour promoting potential on mouse skin following a two-stage initiation-promotion protocol, but it failed to induce the tumour(s) at a significant level, when tested for tumour initiating and complete carcinogenic property.

Antitumour activity of diallyl sulfide on polycyclic aromatic hydrocarbon-induced mouse skin carcinogenesis

Diallyl sulfide (DAS), a major flavour component of garlic, is known to modulate xenobiotic metabolism and possess antitoxic, bactericidal, antineoplastic, hypolipidemic and hypocholesteromic effects. In the present study, the anticarcinogenic activity of DAS on a 7,12-dimethylbenzanthracene (DMBA)- or benzo[a]pyrene (B(a)P)-induced mouse skin model of carcinogenesis was evaluated. DAS was applied topically either 1 h prior to or 1 h after the administration of DMBA or B(a)P. A significant protection from neoplasia was observed in DAS- and DMBA/B(a)P-exposed animals when DAS was applied topically compared to the animals exposed only to DMBA/B(a)P. In the animals where DAS was applied 1 h prior to the application of DMBA, a lower magnitude of neoplasia was recorded in terms of the cumulative number of tumours and average number of tumours per mouse during the entire period of study (28 weeks) compared to the animals exposed to DAS 1 h later, while in B(a)P-exposed animals, the antitumorigenic potential of DAS was more evident in the mice treated with DAS 1 h after the B(a)P exposure compared to the animals treated with DAS 1 h prior to B(a)P. The antitumour activity of DAS was of a much higher magnitude in B(a)P-induced carcinogenesis in comparison to animals exposed to DMBA in terms of tumour incidence, cumulative number of tumours and average number of tumours per mouse. The results suggest that DAS has a protective effect in PAH-induced mouse skin carcinogenesis.

Antitumor activity of diallyl sulfide in two-stage mouse skin model of carcinogenesis

It has been reported that diallyl sulfide (DAS), a sulfur-containing volatile compound in garlic (Allium sativum), exerts anticarcinogenic activity in various rodent tumor models. In the present study, the antitumor property of DAS was tested in Swiss albino mice in the two stage initiation-promotion mouse skin carcinogenesis. Skin cancers were initiated topically with a single subcarcinogenic dose (52 micrograms) of 7, 12-dimethyl benz (a) anthracene (DMBA). Promotion was performed by twice weekly applications of 12-O-tetradecanoyl phorbol-13-acetate (TPA) at a dose of 5 micrograms/animal for 32 weeks. DAS was applied topically (250 micrograms/animal) thrice weekly for 3 weeks for anti-initiating and 1 h prior to each promotion treatment for anti-promoting studies. The results showed that the treatment schedule of DAS can effectively delay the onset of tumorigenesis and reduce the cumulative number of tumors and the average number of tumors per mouse. In groups in which DAS applied prior to initiation or promotion, a significant population of the animals remained tumor-free till the termination of experiment. These findings suggest that DAS can effectively inhibit chemically induced mouse skin carcinogenesis.

Assessment of mutagenic potential of thiram

Thiram is a widely used dithiocarbamate fungicide. In this study, the mutagenicity of thiram was investigated using the micronucleus and dominant lethal tests in Swiss albino mice. A single ip injection of 100 mg thiram/kg body weight, which is the maximum tolerated dose (MTD), significantly induced micronucleus formation in bone marrow cells after 30 and 48 hr of exposure; 50% and 25% of the MTD also induced micronucleus formation after the above time periods. A significant number of dead implants were induced when thiram was given to male mice in the diet at 10% of the oral LD50 during the whole spermatogenesis cycle (8 wk); this post-implantation loss indicates a dominant lethal mutation.

Antitumour activity of protein A in a mouse skin model of two-stage carcinogenesis

Protein A (PA) is an immunostimulating glycoprotein (mol. wt. 43,000 kDa) obtained from Staphylococcus aureus cowan I. The antitumour property of PA is well documented in the literature in various transplantable tumours of rats and mice. In the present set of investigations, the antitumour property of PA was tested in Swiss albino mice in a two-stage initiation-promotion mouse skin carcinogenesis model. The animals were initiated topically with a single subcarcinogenic dose (52 microgram) of 7,12-dimethylbenzanthracene (DMBA). PA was administered intraperitoneally (1 microgram/animal), twice weekly for 2 weeks. Promotion was performed by twice weekly applications of 12-O- tetradecanoyl phorbol-13-acetate (TPA) at a dose of 5 microgram/animal for 32 weeks. The result showed that the treatment schedule can effectively check the onset of tumorigenesis, the cumulative number of tumours and the average number of tumours per mouse. In the PA administered group, 30% of the animals remained tumour free until the termination of the experiments (i.e. 32 weeks of promotion). Thus the present study proves that protein A can effectively inhibit DMBA initiated and TPA promoted mouse skin carcinogenesis.

Carcinogenic and co-carcinogenic studies of thiram on mouse skin

Thiram (tetramethyl thiuram disulfide), a carbamate fungicide, is used in the rubber processing industry as an accelerator and vulcanizing agent. Previous studies evaluated the tumorigenic potential of thiram in rodents, but failed to provide conclusive results. In the present study the tumorigenic potential of thiram was evaluated in Swiss albino mice by a two-stage initiation-promotion protocol and a long-term in vivo bioassay for carcinogenicity. Results revealed that following tumour initiation with thiram and promotion with 12-O-tetradecanoyl phorbol 13-acetate, skin tumours developed, mostly at the site of treatment (dorsal skin) in single and multiple dose-initiated animals. Similarly, papillomatous growths were observed on the dorsal skin of the mice initiated with a single subcarcinogenic dose of dimethylbenzanthracene and promoted with thiram. Thiram failed to provoke tumorigenesis when tested as a complete carcinogen for up to 52 wk and thereafter the study was terminated due to increased mortality. It is concluded that thiram has both tumour initiating and tumour-promoting potential in both sexes of Swiss albino mice following topical exposure at the tested dose level.

Tumour-promoting activity of ninhydrin on mouse skin

Ninhydrin (2,2-dihydroxy-1,3-indanedione; CAS No. 485-47-2) is widely used as a reagent for the detection of free amino and carboxyl groups in proteins and peptides. It is an irritant to mammalian skin. Various toxic effects of ninhydrin have been reported in laboratory animals; however, so far there has been no evaluation of its carcinogenic and co-carcinogenic potential in laboratory animals by long-term in vivo bioassay. Ninhydrin was found to induce the activity of gamma-glutamyl transpeptidase (GGT) in mouse skin but it failed to alter the activity of the enzyme ornithine decarboxylase when compared with animals treated with standard tumour promoter 12-O-tetradecanoyl phorbol-13-acetate (TPA). In the present investigations, the tumour-promoting activity of ninhydrin (including both stage I and stage II of tumour promotion) was tested on Swiss albino mice in a multistage mouse skin model of carcinogenesis. The animals were initiated with a single topical application of 7,12-dimethylbenz-anthracene followed by four topical applications of ninhydrin biweekly as stage I promoter for 2 wk. Stage II promotion was twice weekly through topical application of mezerein. The results revealed that ninhydrin is a strong stage I tumour promoter and its efficacy was comparable with that of TPA at the dose level used in the experiment. However, ninhydrin failed to produce tumours when tested as a stage II or complete tumour promoter on mouse skin.

Carcinogenic and cocarcinogenic studies with carbaryl following topical exposure in mice

Carbaryl (1-naphthyl methyl carbamate: C12H11NO2) CAS Reg. No. 63-25-2) is a widely used broad spectrum carbamate insecticide known to exert various toxic effects on experimental animals. Along with various other toxicological effects carbaryl is reported to increase the incidence of neoplasm in various tissues in rats after oral or intraperitoneal administration. No study has so far been reported in rodents to assess its carcinogenic/cocarcinogenic potential after topical exposure. In this set of investigations, the complete carcinogenic, tumour initiating and tumour promoting property of carbaryl was tested on the skin of female Swiss albino mice. The animals were exposed to carbaryl through topical painting on the interscapular region at a dose of 100 mg/kg body wt. The results revealed that carbaryl has tumour initiating potential, at the test dose, on mouse skin following two stage, initiation-promotion protocol, but, it failed to induce the tumour(s) when tested for complete carcinogenic and tumour promoting properties.

Protection against 7,12-dimethylbenzanthracene-induced tumour initiation by protein A in mouse skin

Protein A is an immunostimulating glycoprotein obtained from Staphylococcus aureus Cowan I. Its antitumour activity is proven in various tumour models. Its ability to provide protection against tumour initiation by the chemical carcinogen 7,12-dimethylbenzanthracene (DMBA) has been investigated in the present study using a mouse skin model of two-stage carcinogenesis. Protein A was administered intraperitoneally (1 microgram/animal 20 g body wt.) twice a week for 2 weeks, prior to initiation by DMBA. The promotion was performed by twice weekly applications of 12-O-tetradecanoyl phorbol-13-acetate (TPA) (3 or 5 micrograms/animal in 100 microliters acetone). Protein A provided significant protection to animals from DMBA-induced tumour initiation as was observed by the decrease in cumulative number of tumours, percent of animals developing tumours, number of tumours per animal and rate of tumour growth. Our data indicate that protein A has anticarcinogenic properties.

Carcinogenic activity of a carbamate fungicide, mancozeb on mouse skin

Mancozeb, a polymeric complex of ethylene bis (dithiocarbamate) manganese with zinc salt is a protective fungicide. In the present study complete carcinogenic activity of mancozeb, has been observed following topical application on dorsal mouse skin. Female Swiss albino mice were exposed to mancozeb at a dose of 100 mg/kg body weight dissolved in 100 microliters dimethyl sulfoxide 3 times per week. Development of tumours was observed after 31 weeks (217 days) of mancozeb application. A high rate of mortality was observed after 54 weeks (378 days) of mancozeb application due to its toxicity and the study was terminated after 60 weeks. On histological examination, these tumours were found mostly to be benign in nature, e.g., squamous cell papillomas and keratoacanthomas.

Tumour initiatory activity of a herbicide diuron on mouse skin

In the present investigation, the tumour initiating activity of a herbicide diuron 3-(3,4 dichlorophenyl)-1,1 dimethyl urea has been observed following multiple topical applications at a dose of 250 mg/kg body weight in a standard two-stage initiation-promotion protocol on mouse skin for carcinogenicity testing. It was found that 9 applications of the herbicide given on the interscapular region in a thrice weekly schedule up to 3 weeks and followed, after 1 week, by the repeated 3 times per week application of a known skin tumour promoter 12-O-tetradecanoyl phorbol 13-acetate (TPA), 5 micrograms dissolved in 100 microliters of acetone in the same initiated area, led to the development of benign skin tumours. However, a single dose of diuron, used for each application as above and followed by repeated TPA applications, with the same dose and painting schedule as in the case of multiple applications, failed to initiate tumour development.

Tumour-promoting ability of mancozeb, a carbamate fungicide, on mouse skin

In this study the tumour-promoting activity of a carbamate fungicide, mancozeb, has been observed following topical application on mouse skin in a two-stage initiation--promotion protocol for carcinogenesis. Female Swiss albino mice were initiated with a single subcarcinogenic dose (52 micrograms) of 7,12-dimethylbenz[a]anthracene painted on the interscapular region. Seven days after initiation the mice underwent topical application of mancozeb (100 mg/kg body wt) three times per week as promoter. Development of tumours was observed after 12 weeks of mancozeb application in 1/14 animals and 100% tumorigenesis was recorded after 17 weeks of mancozeb application. On histological examination, these tumours were found mostly to be benign in nature, e.g. squamous cell papillomas and keratocanthomas.

Evaluation of carcinogenic effect of jute batching oil (JBO-P) fractions following topical application to mouse skin

Jute batching oil (JBO-P), a mineral oil fraction used in the processing of jute fibers, was, as reported in our earlier studies, found to be tumorigenic following repeated topical application to mouse skin. In the present investigation an attempt has been made to identify the carcinogenic constituents of this oil. The JBO was fractionated into (1) PAH free fraction, (2) fraction containing two- and three-ring PAHs and (3) more than three-ring PAH fractions by an enrichment procedure. These three JBO fractions along with unfractionated and reconstituted oil were then subjected to the in vivo assay of complete carcinogenic activity of JBO-P and its fractions following its topical application to mouse skin. The results showed that only unfractionated and reconstituted JBO-P samples per se were able to produce benign skin tumours, while all the other three fractions, i.e. PAH-free fraction, two- and three-ring PAH-containing fraction and more than three-ring PAH-containing fraction failed to produce tumours up to 40 weeks after application. In an extended study, mice belonging to the groups exposed to various fractions of JBO were promoted with 12-O-tetradecanoyl phorbol-13-acetate (TPA), a potent skin tumour promoter, for the two stage initiation-promotion protocol for skin carcinogenesis. After 14 weeks of promotion with TPA, all the surviving animals exposed to the fraction having more than three-ring PAHs developed benign tumours on their backs, while the other two fractions failed to do so.(ABSTRACT TRUNCATED AT 250 WORDS)

Tumour initiating activity of mancozeb--a carbamate fungicide in mouse skin

Mancozeb is a protectant fungicide and is a polymeric complex of ethylene bis(dithiocarbamate)manganese (i.e. Maneb) with zinc salt. In this study, the tumour initiating ability of mancozeb has been observed by a 2-stage initiation-promotion protocol in mouse skin.

Quantification of tumour initiating effect of jute batching oil and its distillates over mouse skin

In order to identify the tumour initiating constituent(s) of a mineral oil, jute batching oil (JBO), used in the processing of jute fibres, it was fractionally distilled in various boiling range fractions. The latter were then subjected to in vivo assessment of their aryl hydrocarbon hydroxylase (AHH) inducing potential in mouse epidermis. Fractions with almost similar AHH inducing potential were regrouped and studied for their tumour initiating potential over mouse skin following two-stage initiation-promotion protocol and using 12-O-tetradecanoyl phorbol-13-acetate (TPA) as tumour promoter. It was noticed that: (1) JBO as initiator, provoked local development of benign skin tumours over mouse back; (2) fractions of JBO boiling below 335 degrees C and above 399 degrees C accounted for most of the tumour initiating potential of the oil; (3) the histological features of the tumours (i.e. benign papillomas and keratoacanthomas) initiated by these fractions were similar to those developed after being initiated with unfractionated or reconstituted JBO; (4) removal of these fractions from JBO may be attempted which could decontaminate the batch oil from most of its tumorigenic components and make it safer for industrial use.