Ras protein p21 processing enzyme farnesyltransferase in chemical carcinogen—induced murine skin tumors

Farnesylation of ras protein p21 is crucial for the protein's membrane localization, which is essential for its cell-transforming activity, which in turn is thought to be critical for the ultimate induction of cancer. The cytosolic enzyme farnesyltransferase plays a major role in posttranslational modification of p21, but the level of farnesyltransferase activity in mammalian tumors and its relationship to the processing of cytosolic p21 that leads to tumorigenesis are unknown. We report here that farnesyltransferase activity was significantly higher in chemical carcinogen—induced benign skin papillomas in SENCAR mice than in the epidermises of control animals. The enzyme is primarily epidermal in origin, and kinetic studies with cytosol from epidermis and papillomas showed that the reaction was linear with respect to time, substrate concentration, and protein content. Skin papillomas showed significantly elevated levels of both cytosolic and membrane-bound Ha-ras p21, whereas far lesser cytosolic and almost negligible amounts of membrane-bound p21 were present in the epidermis of control mice. There was a positive correlation between increased enzyme activity in papilloma cytosol and the processing of overexpressed cytosolic Ha-ras p21 for its localization to membrane.     

Evaluation of the efficacy of Lawsonia alba in the alleviation of carbon tetrachloride-induced oxidative stress

The hepatoprotective activity of the 50% ethanol extract of the bark of Lawsonia alba syn. L. inermis was investigated against the carbon tetrachloride-induced oxidative stress. Pretreatment of rats with doses of 250 and 500 mg/kg of the plant extract significantly (P < 0.001) lowered serum transaminases (GOT and GPT) and LDH levels, respectively, in a dose dependent manner against the significant (P < 0.001) rise of these damage marker enzymes when challenged with CCl4 (1 ml/kg, orally). Parallel to these changes, the plant extract prevented CCl4-induced oxidative stress by significantly maintaining the levels of reduced glutathione (GSH), its metabolizing enzymes and simultaneously inhibiting the production of free radicals. Pretreatment of rats with the extract also inhibited the peroxidation of microsomal lipids in a dose-dependent manner.     

Inhibitory effect of Emblica officinalis on the in vivo clastogenicity of benzo[a]pyrene and cyclophosphamide in mice

Benzo[a]pyrene (B[a]P) and cyclophosphamide (CP) are potent carcinogens/mutagens. Effect of Emblica officinalis extract administration on the in vivo genotoxicity of B[a]P and CP was studied using bone marrow chromosomal aberration and micronucleus induction tests in mice. Three doses (50, 250 and 500 mg/kg body weight) of the plant extract were administered orally for 7 consecutive days prior to the administration of single dose of mutagens (B[a]P 125 mg/kg oral; CP 40 mg/kg i.p.). It was found that administration of 250 and 500 mg/kg of E. officinalis extract significantly inhibited the genotoxicity of B[a]P as well as CP in both the assay systems. Administration of 50 mg/kg of the plant extract had no inhibitory effect. Vitamin C, a major constituent of E. officinalis when administered at dose level of 9 mg/kg b.w. (the approximate estimated amount present in the highest dose of plant extract, i.e. 500 mg) for 7 days did inhibit chromosomal aberrations and micronuclei induction, but not in a significant manner. Effect of administration of the abovementioned effective doses (250 and 500 mg/kg oral for 7 days) of plant extract and vitamin C (9 mg/kg oral for 7 days) on the hepatic activation and detoxification enzymes was also studied. Significant induction in the levels of glutathione content (GSH) and of antioxidant and detoxification enzymes viz., glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione-S transferase (GST) resulted from plant extract treatment to animals. On the other hand, cytochrome P 450 level was significantly decreased in the plant-extract-treated animals. There was no significant change in cytochrome P 450, GSH contents and activities of enzymes on treatment with vitamin C. The data indicate that the possible mechanism of inhibition by plant extract is mediated by its modulatory effect on hepatic activation and disposition processes.     

Topical tazarotene chemoprevention reduces Basal cell carcinoma number and size in Ptch1+/- mice exposed to ultraviolet or ionizing radiation

Oral retinoids can reduce basal cell carcinoma (BCC) incidence in genetically susceptible patients, and one topical retinoid, tazarotene, has been reported to cure some sporadic BCCs. Therefore, we have tested whether this agent would affect BCCs in Ptch1+/- mice in a controlled chemoprevention trial. We found that topical tazarotene dramatically inhibits the formation of BCCs induced with either UV or ionizing radiation. The ability of tazarotene to inhibit BCC formation in this mouse model provides encouragement for the use of tazarotene in skin cancer chemoprevention trials in humans.     

Inhibition of smoothened signaling prevents ultraviolet B-induced basal cell carcinomas through regulation of Fas expression and apoptosis

Abnormal activation of the hedgehog-signaling pathway is the pivotal abnormality driving the growth of basal cell carcinomas (BCCs), the most common type of human cancer. Antagonists of this pathway such as cyclopamine may therefore be useful for treatment of basal cell carcinomas and other hedgehog-driven tumors. We report here that chronic oral administration of cyclopamine dramatically reduces ( approximately 66%) UVB induced basal cell carcinoma formation in Ptch1(+/-) mice. Fas expression is low in human and murine basal cell carcinomas but is up-regulated in the presence of the smoothened (SMO) antagonist, cyclopamine, both in vitro in the mouse basal cell carcinoma cell line ASZ001 and in vivo after acute treatment of mice with basal cell carcinomas. This parallels an elevated rate of apoptosis. Conversely, expression of activated SMO in C3H10T1/2 cells inhibits Fas expression. Fas/Fas ligand interactions are necessary for cyclopamine-mediated apoptosis in these cells, a process involving caspase-8 activation. Our data provide strong evidence that cyclopamine and perhaps other SMO antagonists are potent in vivo inhibitors of UVB-induced basal cell carcinomas in Ptch1(+/-) mice and likely in humans because the majority of human basal cell carcinomas manifest mutations in PTCH1 and that a major mechanism of their inhibitory effect is through up-regulation of Fas, which augments apoptosis.     

Phosphodiesterase and thymidine phosphorylase-inhibiting salirepin derivatives from Symplocos racemosa

A re-investigation of the chemical constituents of the stem bark of Symplocos racemosa Roxb. led to the isolation of four new glycosides, symplocomoside (1), symponoside (2), symplososide (3) and symploveroside (4). Benzoylsalireposide (5) and salireposide (6) were re-isolated from this plant. The structures of the new compounds were determined by 1D and 2D-homonuclear and heteronuclear NMR spectroscopy, chemical evidence, and by comparison with the published data of the closely related compounds. The glycosides 1-4 displayed in vitro inhibitory activity against phosphodiesterase I with IC50 values of 122 +/- 0.017, 698 +/- 0.06, 722 +/- 0.03, 909 +/- 0.09 microM, respectively. The compounds 1-6 also showed in vitro inhibitory activity against thymidine phosphorylase with IC50 values of 189.96 +/- 1.02, 195.56 +/- 2.36, 207.61 +/- 1.06, 488.89 +/- 4.10, 427.20 +/- 5.36, 354.2 +/- 5.69 microM, respectively while 1 was also found to be a urease inhibitor with an IC50 value of 54.13 +/- 0.71 microM.     

Palm oil alleviates 12-O-tetradecanoyl-phorbol-13-acetate-induced tumor promotion response in murine skin

Palm oil is a rich source of vitamin E, carotenoids, tocotrienols and tocopherols which are natural antioxidants and act as scavengers of oxygen free radicals. 12-O-Tetradecanoyl-phorbol-13-acetate (TPA) is a known oxidant that promotes tumorigenesis in mouse skin through the elaboration of oxidative stress. In this study we therefore assessed the anti-tumor promoting potential of palm oil against TPA-mediated skin tumorigenesis in 7,12-dimethylbenz[a]anthracene-initiated Swiss albino mice. Topical application of palm oil 1 h prior to application of TPA resulted in a significant protection against skin tumor promotion. The animals pre-treated with palm oil showed a decrease in both tumor incidence and tumor yield as compared to the TPA (alone)-treated group. Palm oil application also reduced the development of malignant tumors. Since TPA-induced epidermal ornithine decarboxylase (ODC) activity and [(3)H]thymidine incorporation are conventionally used markers of skin tumor promotion, we also assessed the effect of pre-application of palm oil on these parameters, and it was observed that the application of palm oil prior to the application of TPA alleviated both these TPA-induced markers of tumor promotion. The effect of pre-application of palm oil on TPA-mediated depletion in the non-enzymatic and enzymatic molecules was also assessed and it was observed that palm oil application prior to TPA application resulted in the recovery of TPA-mediated depletion in the levels of these molecules viz. glutathione, glutathione peroxidase, glutathione reductase, glutathione-S-transferase and catalase. Similarly, palm oil also exhibited a protective effect against Fe(2+)-ascorbate-induced lipid peroxidation in the epidermal microsomes. The results of the present study thus suggest that palm oil possesses anti-skin tumor promoting effects, and that the mechanism of such effects may involve the inhibition of tumor promoter-induced epidermal ODC activity, [(3)H]thymidine incorporation and cutaneous oxidative stress.     

Simplified [correction of Simlified] calculation of mean QRS vector (mean electrical axis of heart) of electrocardiogram

In clinical practice assessment of the mean QRS axis (MQRSA) provides information related either with hypertrophy of the ventricles or conduction blocks. The method adopted by clinicians i.e. the inspection of the QRS voltage in six of the limb leads has inherent element of subjectivity of approximately 10degrees. Moreover, in certain condition, when there is ambiguity about differentiation of left axis deviation assessed by inspection method in to either hypertrophy of left ventricles or complete/hemi block of the left bundle branches, accurate measurement of the axis becomes necessary to arrive at the correct diagnosis. Though a formula based on area under R wave and S-wave of the same QRS complex has been derived for accurate measurement of axis, considering its use in the computer software, working with ordinary electrocardiograph the only method for accurate measurement of the QRS axis is plotting method i. e. the net voltages in Lead-I, and III on their respective axes which is not practicable in clinical settings. Although, calculation of MQRSA by area method gives an accurate assessment of MQRSA, some authors prefer measurement of axis by voltage method, as in cases of the right ventricular hypertrophy with a broad S-wave calculation of axis by area method may give erroneous results. Hence, to obtain correct measurement of MQRSA, we have derived a simplified formula based on the net voltage of QRS complexes in Lead-I and Lead-III. The formula derived is as follows, Tan(theta) =(I + 2III) divided by sqrt [3I], where I and III represent net voltage in Lead-I and III, theta = angle subtended with the axis Lead-I. The value of theta can be found by using scientific calculator or the table. In case net voltage of QRS complex in Lead-I being negative, the value of the theta should be subtracted from 180degrees to find the angle of mean QRS vector.