Chemopreventive potential of piperine in 7,12-dimethylbenz[a]anthracene-induced skin carcinogenesis in Swiss albino mice

The chemopreventive potential of orally administered piperine was studied in Swiss albino mice against 7,12-dimethylbenz[a]anthracene (DMBA)-induced skin carcinogenesis. The mechanistic pathway for the chemopreventive potential of piperine was evaluated by analysing the status of phase I and phase II detoxification agents, lipid peroxidation by-products and antioxidants during DMBA-induced skin carcinogenesis. Skin squamous cell carcinoma was induced in the shaved back of mice, by painting with DMBA (25μg in 0.1ml acetone/mouse) two times weekly for 8 weeks. We observed severe hyperplasia, dysplasia, and well-differentiated squamous cell carcinoma in the 8th, 10th and 15th week of experimental period respectively in mice treated with DMBA alone. Marked alterations in the status of phase I and phase II detoxification agents, lipid peroxidation by-products and antioxidants were observed in tumor bearing mice. Oral administration of piperine (50mgkg(-1) body weight) by gastric gavage significantly prevented the formation of skin tumors during DMBA-induced mouse skin carcinogenesis. Also, piperine administration brought back the status of phase I and phase II detoxification agents, lipid peroxidation by-products and antioxidants to near normal range in DMBA treated mice. The present study thus demonstrates that piperine has significant suppressing effect on cell proliferation during DMBA-induced mouse skin carcinogenesis. The chemopreventive potential of piperine is probably due to its modulating effect on the status of lipid peroxidation, antioxidants and detoxification agents during DMBA-induced skin carcinogenesis.     

Circadian time-dependent chemopreventive potential of withaferin-A in 7,12-dimethyl-benz[a]anthracene-induced oral carcinogenesis

Circadian time-dependent treatment with chemotherapeutic drugs (chronotherapy) optimizes the therapeutic index by maximizing treatment efficacy and minimizing toxicity. The circadian time-dependent chemopreventive and anti-lipid peroxidative efficacy of withaferin-A in 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch carcinogenesis was investigated in the present study. We induced oral squamous cell carcinoma in the buccal pouches of golden Syrian hamsters during the day (4:00, 8:00, 12:00,16:00, 20:00 and 24:00) by application of DMBA three times per week for 14 weeks. The circadian time-dependent tumor incidence, volume and burden were observed in hamsters treated with either DMBA alone or DMBA + withaferin-A. The circadian pattern of lipid peroxidation by-products, as measured by the formation of thiobarbituric acid reactive substances (TBARS) and enzymatic antioxidants [superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx)], was also analyzed in the buccal mucosa of DMBA-treated hamsters. We found the highest incidence of tumor formation at 24.00 h in hamsters treated with DMBA alone as compared to other experimental groups. Circadian dysregulation of lipid peroxidation and antioxidant status was observed in DMBA-treated animals as compared to control animals. Oral (po) administration of withaferin-A (20 mg/kg) completely prevented the formation of tumors between 8.00 h and 12.00 h and synchronized the status of lipid peroxidation and antioxidants in the buccal mucosa of hamsters treated with DMBA alone. Also, oral administration of withaferin-A to DMBA-treated animals significantly reduced the formation of tumors and synchronized the status of lipid peroxidation and antioxidants in the rest of the time intervals. Our study thus suggests that withaferin-A has significant chemopreventive and anti-lipid peroxidative potential in DMBA-induced oral carcinogenesis, probably by interfering with DMBA-induced abnormal cell proliferation in the buccal mucosa.     

Protective effect of Gymnema montanum against renal damage in experimental diabetic rats

Gymnema montanum Hook (Asclepiadaceae), is an endemic plant species of India, traditionally used for diabetes and its management. In this experiment, the ethanol extract of G. montanum (GLEt) at a dose of 200 mg/kg body weight was tested to evaluate its effect on renal damage in alloxan-induced diabetic rats and the efficacy was compared with standard hypoglycemic drug, glibenclamide (600 μg/kg body weight). The GLEt and glibenclamide were administered orally for 3 weeks and the effects on glucose, insulin, renal markers including urea, creatinine and uric acid, lipid peroxidation markers including thiobarbituric reactive substances (TBARS) and hydroperoxides and antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) activities in kidney were studied. In addition, the urinary protein profile was studied using SDS–PAGE. The results indicated that the GLEt significantly normalized the elevated blood glucose, renal markers and lipid peroxidation markers and increased antioxidant levels in diabetic kidney. The diabetic rats excreted large amount of proteins than untreated rats which was normalized during the treatment with GLEt. In conclusion, the GLEt was found to be more effective in reducing oxidative stress, thus confirming the ethnopharmacological use of G. montanum in protecting diabetes and its complications.     

N,N'-Alkane-diyl-bis-3-picoliniums as nicotinic receptor antagonists: inhibition of nicotine-evoked dopamine release and hyperactivity

The current study evaluated a new series of N,N'-alkane-diyl-bis-3-picolinium (bAPi) analogs with C6-C12 methylene linkers as nicotinic acetylcholine receptor (nAChR) antagonists, for nicotine-evoked [3H]dopamine (DA) overflow, for blood-brain barrier choline transporter affinity, and for attenuation of discriminative stimulus and locomotor stimulant effects of nicotine. bAPi analogs exhibited little affinity for alpha4beta2* (* indicates putative nAChR subtype assignment) and alpha7* high-affinity ligand binding sites and exhibited no inhibition of DA transporter function. With the exception of C6, all analogs inhibited nicotine-evoked [3H]DA overflow (IC50 = 2 nM-6 microM; Imax = 54-64%), with N,N'-dodecane-1,12-diyl-bis-3-picolinium dibromide (bPiDDB; C12) being most potent. bPiDDB did not inhibit electrically evoked [3H]DA overflow, suggesting specific nAChR inhibitory effects and a lack of toxicity to DA neurons. Schild analysis suggested that bPiDDB interacts in an orthosteric manner at nAChRs mediating nicotine-evoked [3H]DA overflow. To determine whether bPiDDB interacts with alpha-conotoxin MII-sensitive alpha6beta2-containing nAChRs, slices were exposed concomitantly to maximally effective concentrations of bPiDDB (10 nM) and alpha-conotoxin MII (1 nM). Inhibition of nicotine-evoked [3H]DA overflow was not different with the combination compared with either antagonist alone, suggesting that bPiDDB interacts with alpha6beta2-containing nAChRs. C7, C8, C10, and C12 analogs exhibited high affinity for the blood-brain barrier choline transporter in vivo, suggesting brain bioavailability. Although none of the analogs altered the discriminative stimulus effect of nicotine, C8, C9, C10, and C12 analogs decreased nicotine-induced hyperactivity in nicotine-sensitized rats, without reducing spontaneous activity. Further development of nAChR antagonists that inhibit nicotine-evoked DA release and penetrate brain to antagonize DA-mediated locomotor stimulant effects of nicotine as novel treatments for nicotine addiction is warranted.     

Platelet-derived growth factor receptor beta-mediated phosphorylation of MUC1 enhances invasiveness in pancreatic adenocarcinoma cells

MUC1 is a heterodimeric transmembrane glycoprotein that is overexpressed and aberrantly glycosylated in ductal adenocarcinomas. Differential phosphorylation of the MUC1 cytoplasmic tail (MUC1CT) has been associated with signaling events that influence the proliferation and metastasis of cancer cells. We identified a novel tyrosine phosphorylation site (HGRYVPP) in the MUC1CT by mass spectrometric analysis of MUC1 from human pancreatic adenocarcinoma cell lines. Analyses in vitro and in vivo showed that platelet-derived growth factor receptor beta (PDGFRbeta) catalyzed phosphorylation of this site and of tyrosine in the RDTYHPM site. Stimulation of S2-013.MUC1F cells with PDGF-BB increased nuclear colocalization of MUC1CT and beta-catenin. PDGF-BB stimulation had no significant effect on cell proliferation rate; however, it enhanced invasion in vitro through Matrigel and in vivo tumor growth and metastases. Invasive properties of the cells were significantly altered on expression of phosphorylation-abrogating or phosphorylation-mimicking mutations at these sites. We propose that interactions of MUC1 and PDGFRbeta induce signal transduction events that influence the metastatic properties of pancreatic adenocarcinoma.