Three new compounds from the plant Lippia alva as inhibitors of chemokine receptor 5 (CCR5)

The 70% aqueous methanol extract of the Peruvian plant Lippia alva (Verbenaceae) was found to contain three novel compounds, 1, 2, and 3, which were identified as inhibitors of the chemokine receptor CCR5. The structures of 1-3 were established based on extensive NMR studies. Compounds 1-3 inhibited CCR5 receptor signaling as measured by a calcium mobilization assay with IC(50) values of 5.5, 6.0, and 7.2 microg/mL, respectively.     

Intrinsic contributions of polar amino acid residues toward thermal stability of an ABC-ATPase of mesophilic origin

The nucleotide-binding subunit of phosphate-specific transporter (PstB) from mesophilic bacterium, Mycobacterium tuberculosis, is a unique ATP-binding cassette (ABC) ATPase because of its unusual ability to hydrolyze ATP at high temperature. In an attempt to define the basis of thermostability, we took a theoretical approach and compared amino acid composition of this protein to that of other PstBs from available bacterial genomes. Interestingly, based on the content of polar amino acids, this protein clustered with the thermophiles.     

NF-kappa B hyperactivation has differential effects on the APC function of nonobese diabetic mouse macrophages

Type 1 diabetes is characterized by a chronic inflammatory response resulting in the selective destruction of the insulin-producing beta cells. We have previously demonstrated that dendritic cells (DCs) prepared from nonobese diabetic (NOD) mice, a model for spontaneous type 1 diabetes, exhibit hyperactivation of NF-kappaB resulting in an increased capacity to secrete proinflammatory cytokines and stimulate T cells compared with DCs of nondiabetic strains of mice. In the current study, the activational status of NF-kappaB and its role in regulating the APC function of macrophages (Mphi) prepared from NOD, nonobese resistant (NOR), and BALB/c mice was investigated. Independent of the stimulus, splenic and bone marrow-derived Mphi prepared from NOD mice exhibited increased NF-kappaB activation relative to NOR and BALB/c Mphi. This hyperactivation was detected for different NF-kappaB complexes and correlated with increased IkappaBalpha degradation. Furthermore, increased NF-kappaB activation resulted in an enhanced capacity of NOD vs NOR or BALB/c Mphi to secrete IL-12(p70), TNF-alpha, and IL-1alpha, which was inhibited upon infection with an adenoviral recombinant encoding a modified form of IkappaBalpha. In contrast, elevated NF-kappaB activation had no significant effect on the capacity of NOD Mphi to stimulate CD4(+) or CD8(+) T cells in an Ag-specific manner. These results demonstrate that in addition to NOD DCs, NOD Mphi exhibit hyperactivation of NF-kappaB, which correlates with an increased ability to mediate a proinflammatory response. Furthermore, NF-kappaB influences Mphi APC function by regulating cytokine secretion but not T cell stimulation.     

Selective impairment of protein kinase C isotypes in murine macrophage by Leismania donovani

Leishmania donovani, an obligate intracellular parasite resides and multiplies within macrophage of the reticuloendothelial system. The intracellular signalling mechanism involved in the impaired oxidative response in leishmaniasis has not yet been clearly established. Generation of superoxide anion (O₂ ^–) is supposed to be the first line of host defence during microbial invasion. We found a substantial inhibition of superoxide anion generation in parasitized macrophages, which was just the reverse in case of macrophages challenged with Lipophosphoglycan (LPG) deficient attenuated leishmanial parasite UR-6. The generation of O₂ ^– essentially needs the prior activation of protein kinase C (PKC) mediated phosphorylation events. Our study proposed that phosphorylation of 67, 54, 47 and 36 kDa proteins was attenuated during infection. This was supported by PKC activity study, where Ca-dependent PKC activity was inhibited but, Ca-independent PKC activity was enhanced. This result was further confirmed by using isotype specific pseudosubstrate inhibitors of Ca-dependent PKC and Ca-independent PKC . Application of -pseudosubstrate could not alter the Ca-dependent PKC activity but -pseudosubstrate inhibited the Ca-independent PKC activity in infected macrophages. Our immunoblot analysis with specific antibody against PKC and PKC isotypes showed down regulation of PKC -II expression with concomitant induction of PKC . Such inhibition of Ca-dependent PKC was reversed in macrophages treated with UR-6. Taken together, our observations revealed that infection with L. donovani selectively attenuates both the expression and activity of Ca-dependent PKC .     

Expression of fungal desaturase genes in cultured mammalian cells

Long-chain polyunsaturated fatty acids (LC-PUFA) are important components of cellular structure and function. Most of LC-PUFA are derived from linoleic acid and a-linolenic acid. In plants and fungi, these two acids can be synthesized from oleic acid via the action of two enzymes, 12 and 15-desaturases. Due to lack of these enzymatic activities and the ability to synthesize these two essential fatty acids, animals must obtain them from the diet. In this report, we demonstrated the expression of a fungal 12-desaturase gene in mouse L cells incubated in serum-free medium. The results showed a significant increase in the amount of linoleic acid with a concomitant decrease of oleic acid in cellular lipids. Most of the newly formed linoleic acid was incorporated into cellular phospholipids, particularly phosphatidylcholine. The increase of linoleic acid provided the substrate for the endogenous synthesis of (n-6) LC-PUFA, such as eicosadienoic acid (EDA), dihomo--linoleic acid (DGLA) and arachidonic acid (AA). Prolonged incubation further increased the levels of linoleic acid derived from oleic acid by the action of 12-desaturase, and the levels of 20:2n-6 produced from linoleic acid by the action of the endogenous elongase. However, prolonged incubation suppressed significantly the formation of DGLA and AA. In a separate study, a fungal 6-desaturase gene has also been expressed in the mouse L cells incubated in serum-containing medium. The result shows a significant increase in levels of 20:3n-6 and 20:4n-6. These findings demonstrate that through genetic modification, it is possible to (1) generate cell lines which no longer require dietary 'essential' fatty acids and (2) alter the endogenous fatty acid metabolism to enhance the production of LC-PUFA and their derivatives.     

Production of xylanases by immobilized Aspergillus sp. using lignocellulosic waste

In shake flasks immobilized Aspergillus terreus and Aspergillus niger produced 29IU/ml, 26.7IU/ml xylanases at 10mg/ml, 14mg/ml wheat bran concentration after 48 and 60h of incubation at 37°C respectively. In repeated batch fermentation of immobilized Aspergillus sp. the same biocatalyst could be used for three successive cycles.     

Radiation inactivation of some food-borne pathogens in fish as influenced by fat levels

The influence of low (0·39–1·1%), medium (4·25%) and high (7·1–32·5%) fat levels in fish on radiation inactivation of four food-borne pathogens was investigated. Cells of Listeria monocytogenes 036, Yersinia enterocolitica F5692, Bacillus cereus and Salmonella typhimurium at logarithmic phase were inoculated in 10% fish homogenates and subjected to gamma irradiation at ice temperature (0–1 °C) with doses ranging from 0·05 to 0·8 kGy. The radiation survival curves of L. monocytogenes and B. cereus were characterized by shoulders, while a tailing effect was depicted by cells of Y. enterocolitica and B. cereus . The D₁₀ values in kGy calculated on the exponential part of the curve ranged from 0·2 to 0·3, 0·15 to 0·25, 0·1 to 0·15 and 0·09 to 0·1 for L. monocytogenes 036, B. cereus, Salm. typhimurium and Y. enterocolitica F5692, respectively. This order (D₁₀) of radiation resistance of each organism was not affected by the fat content of the fish. Inoculated pack studies carried out separately with each pathogen in fatty (Indian sardine, 7·1%) and lean (Golden anchovy, 0·39%) fish showed no difference in their survival after exposure to 1 kGy and 3 kGy doses, which corroborated the above observation. The practical significance of these results in the application of the technology is discussed.     

Discovery of novel,orally available benzimidazoles as melanin concentrating hormone receptor 1 (MCHR1) antagonists

Melanin concentrating hormone (MCH) is an important mediator of energy homeostasis and plays role in several disorders such as obesity, stress, depression and anxiety. The synthesis and biological evaluation of novel benzimidazole derivatives as MCHR1 antagonists are described. The in vivo proof of principle for weight loss with a lead compound from this series is exemplified.