Screening of Microbial Extracts for Anticancer Compounds Using Streptomyces Kinase Inhibitor Assay.

Eukaryotic kinases are known to play an important role in signal transduction pathways by phosphorylating their respective substrates. Abnormal phosphorylations by these kinases have resulted in diseases. Hence inhibitors of kinases are of considerable pharmaceutical interest for a wide variety of disease targets, especially cancers. A number of reports have been published which indicate that eukaryotic-like kinases may complement two-component kinase systems in several bacteria. In Streptomyces sp. such kinases have been found to have a role in formation of aerial hyphae, spores, pigmentation & even in antibiotic production in some strains. Eukaryotic kinase inhibitors are seen to inhibit formation of aerial mycelia in Streptomyces without inhibiting vegetative mycelia. This property has been used to design an assay to screen for eukaryotic kinase inhibitors. The assay involves testing of compounds against Streptomyces 85E ATCC 55824 using agar well diffusion method. Inhibitors of kinases give rise to "bald" colonies where aerial mycelia and sporulation inhibition is seen. The assay has been standardized using known eukaryotic protein kinase inhibiting anticancer agents like AG-490, AG-1295, AG-1478, Flavopiridol and Imatinib as positive controls, at a concentration ranging from 10 µg/well to 100 µg/well. Anti-infective compounds which are not reported to inhibit eukaryotic protein kinases were used as negative controls. A number of microbial cultures have been screened for novel eukaryotic protein kinase inhibitors. Further these microbial extracts were tested in various cancer cell lines like Panel, HCT116, Calul, ACHN and H460 at a concentration of 10 µg/mL/ well. The anticancer data was seen correlating well with the Streptomyces kinase assay thus validating the assay.

The long-term regulation of food intake and body weight depends on the availability of thyroid hormones in the brain.

OBJECTIVES: We evaluated the contribution of the thyroid hormones to the long-term maintenance of feeding behavior and body weight, while distinguishing their direct central effects from those resulting from the metabolic rate in the peripheral tissues. METHODS: We assessed the effect of hypothyroidism on the long-term (6 months) regulation of food intake, body weight, and energy expenditure in rats. We then generated the recovery of a euthyroid condition in the brain while maintaining a low T3 availability for the peripheral organs, i.e. a combined condition of central euthyroidism with peripheral hypothyroidism, with the aid of a pharmacological combination. RESULTS: Hypothyroidism caused a decrease in the daily food intake, body weight, and body temperature. The food intake and body temperature stabilized at a lower value, whereas body weight kept decreasing at a constant rate. The administration of exogenous T4 increased food intake and body-weight gain, but had no effect on body temperature. CONCLUSIONS: The thyroid hormones are necessary for the long-term regulation of energy intake, storage, and expenditure by different mechanisms. The feeding behavior seems to be partially dependent on a direct action of the thyroid hormones on the brain and this effect is independent of the energy expenditure in the peripheral organs. The body weight is closely dependent on the thyroid status and its maintenance seems to involve thyroid action on mechanisms other than feeding and metabolic rate.

Enhancing antibiotic activity: a strategy to control Acinetobacter infections.

OBJECTIVES: The emergence of antibiotic resistance has seriously diminished antibiotic efficacy and an increasing number of infections are becoming difficult to treat. One approach to the restoration of antibiotic activity is to administer them in conjunction with non-antibiotic compounds that depress resistance mechanisms. We describe the activity of ellagic and tannic acids as adjuvants that enhance the activity of aminocoumarin antibiotics against multidrug-resistant (MDR) Acinetobacter baumannii. METHODS: Adjuvant activity of plant phenolics was tested using growth inhibition assays in combination with subinhibitory concentrations of novobiocin. The antibacterial susceptibilities of susceptible and MDR A. baumannii to a variety of antibiotics were determined in the absence and presence of ellagic and tannic acids. The effect of the adjuvants on bacterial outer membrane function was examined by using the fluorescence dye 1-N-phenylnaphthylamine (NPN). The efflux pump inhibition was measured by the intracellular accumulation of ethidium bromide (EtBr) and pyronin Y. RESULTS: At 40 microM, ellagic and tannic acids enhanced the activity of novobiocin, coumermycin, chlorobiocin, rifampicin and fusidic acid against A. baumannii. There were no increases in the uptake of NPN or in the accumulation of EtBr after strains were treated with these adjuvants; however, the intracellular accumulation of pyronin Y by the treated cells was significantly increased, suggesting that ellagic and tannic acids act as efflux pump inhibitors. CONCLUSIONS: Susceptibility of MDR A. baumannii to a variety of antibiotics was enhanced in the presence of ellagic and tannic acids. The use of such plant compounds might provide effective treatments for resistant Gram-negative bacterial infections.