Antitubercular agents. Part 1: synthesis of phthalimido- and naphthalimido-linked phenazines as new prototype antitubercular agents

The preparation and antitubercular properties of a series of phthalimido- and naphthalimido-linked phenazines are described. Some of these new compounds inhibited the growth of Mycobacterium tuberculosis ATCC 27294, Mycobacterium avium ATCC 49601, Mycobacterium intracellulare ATCC 13950 and some clinical isolates.     

The relA homolog of Mycobacterium smegmatis affects cell appearance, viability, and gene expression

The modification of metabolic pathways to allow for a dormant lifestyle appears to be an important feature for the survival of pathogenic bacteria within their host. One regulatory mechanism for persistent Mycobacterium tuberculosis infections is the stringent response. In this study, we analyze the stringent response of a nonpathogenic, saprophytic mycobacterial species, Mycobacterium smegmatis. The use of M. smegmatis as a tool for studying the mycobacterial stringent response was demonstrated by measuring the expression of two M. tuberculosis genes, hspX and eis, in M. smegmatis in the presence and absence of rel(Msm). The stringent response plays a role in M. smegmatis cellular and colony formation that is suggestive of changes in the bacterial cell wall structure.     

Androgen receptor activation by G(s) signaling in prostate cancer cells

The androgen receptor (AR) is activated in prostate cancer patients undergoing androgen ablative therapy and mediates growth of androgen-insensitive prostate cancer cells, suggesting it is activated by nonandrogenic factors. We demonstrate that activated alpha subunit of heterotrimeric guanine nucleotide-binding G(s) protein activates the AR in prostate cancer cells and also synergizes with low concentration of androgen to more fully activate the AR. The G alpha(s) activates protein kinase A, which is required for the nuclear partition and activation of AR. These data suggest a role for G alpha(s) and PKA in the transactivation of AR in prostate cancer cells under the environment of reduced androgen levels.     

Role of protein phosphatase 2A in mGluR5-regulated MEK/ERK phosphorylation in neurons

The regulation of protein phosphorylation requires coordinated interaction between protein kinases and protein phosphatases (PPs). Recent evidence has shown that the Galphaq-protein-coupled metabotropic glutamate receptor (mGluR) 5 up-regulates phosphorylation of MAPK/ERK1/2. However, signaling mechanisms linking mGluR5 to ERK are poorly understood. In this study, roles of a major serine/threonine PP, PP2A, in this event were evaluated in cultured neurons. We found that the PP1/2A inhibitors okadaic acid and calyculin A mimicked the effect of the mGluR5 agonists (RS)-3,5-dihydroxyphenylglycine and (RS)-2-chloro-5-hydroxyphenylglycine in facilitating phosphorylation of ERK1/2 and its upstream kinase, MEK1/2, in a PP2A-dependent but not PP1-dependent manner. Co-administration of either inhibitor with an mGluR5 agonist produced additive phosphorylation of ERK1/2. Enzymatic assays showed a basal level of phosphatase activity of PP2A under normal conditions, and activation of mGluR5 selectively inhibited PP2A, but not PP1, activity. In addition, a physical association of the cytoplasmic C terminus of mGluR5 with PP2A was observed, and ligand activation of mGluR5 reduced mGluR5-PP2A binding. Additional mechanistic studies revealed that mGluR5 activation increased tyrosine (Tyr307) phosphorylation of PP2A, which was dependent on activation of a p60c-Src family tyrosine kinase, but not the epidermal growth factor receptor tyrosine kinase and resulted in dissociation of PP2A from mGluR5 and reduced PP2A activity. Together, we have identified a novel, mGluR5-triggered signaling mechanism involving use- and Src-dependent inactivation of PP2A, which contributes to mGluR5 activation of MEK1/2 and ERK1/2.     

Distinct roles for IL-4 and IL-10 in regulating T2 immunity during allergic bronchopulmonary mycosis

Pulmonary Cryptococcus neoformans infection of C57BL/6 mice is an established model of an allergic bronchopulmonary mycosis that has also been used to test a number of immunomodulatory agents. Our objective was to determine the role of IL-4 and IL-10 in the development/manifestation of the T2 response to C. neoformans in the lungs and lung-associated lymph nodes. In contrast to wild-type (WT) mice, which develop a chronic infection, pulmonary clearance was significantly greater in IL-4 knockout (KO) and IL-10 KO mice but was not due to an up-regulation of a non-T cell effector mechanism. Pulmonary eosinophilia was absent in both IL-4 KO and IL-10 KO mice compared with WT mice. The production of IL-4, IL-5, and IL-13 by lung leukocytes from IL-4 KO and IL-10 KO mice was lower but IFN-gamma levels remained the same. TNF-alpha and IL-12 production by lung leukocytes was up-regulated in IL-10 KO but not IL-4 KO mice. Overall, IL-4 KO mice did not develop the systemic (lung-associated lymph nodes and serum) or local (lungs) T2 responses characteristic of the allergic bronchopulmonary C. neoformans infection. In contrast, the systemic T2 elements of the response remained unaltered in IL-10 KO mice whereas the T2 response in the lungs failed to develop indicating that the action of IL-10 in T cell regulation was distinct from that of IL-4. Thus, although IL-10 has been reported to down-regulate pulmonary T2 responses to isolated fungal Ags, IL-10 can augment pulmonary T2 responses if they occur in the context of fungal infection.     

MucA-mediated coordination of type III secretion and alginate synthesis in Pseudomonas aeruginosa

The type III secretion system (T3SS) of Pseudomonas aeruginosa is an important virulence factor. The T3SS of P. aeruginosa can be induced by a low calcium signal or upon direct contact with the host cells. The exact pathway of signal sensing and T3SS activation is not clear. By screening a transposon insertion mutant library of the PAK strain, mutation in the mucA gene was found to cause repression of T3SS expression under both type III-inducing and -noninducing conditions. Mutation in the mucA gene is known to cause alginate overproduction, resulting in a mucoid phenotype. Alginate production responds to various environmental stresses and plays a protective role for P. aeruginosa. Comparison of global gene expression of mucA mutant and wild-type PAK under T3SS-inducing conditions confirmed the down regulation of T3SS genes and up regulation of genes involved in alginate biosynthesis. Further analysis indicated that the repression of T3SS in the mucA mutant was AlgU and AlgR dependent, as double mutants mucA/algU and mucA/algR showed normal type III expression. An algR::Gm mutant showed a higher level of type III expression, while overexpression of the algR gene inhibited type III gene expression; thus, it seems that the AlgR-regulated product inhibits the expression of the T3SS genes. It is likely that P. aeruginosa has evolved tight regulatory networks to turn off the energy-expensive T3SS when striving for survival under environmental stresses.     

A QSAR study on some series of anti-hepatitis B virus (HBV) agents

A quantitative structure-activity relationship (QSAR) study has been made on some series of anti-hepatitis B virus (HBV) agents, namely, a series of novel bis(L-amino acid) ester prodrugs of 9-[2--(phosphonomethoxy)ethyl]adenine, a similar series of compounds comprising of 2- amino-6-arylthio-9-[2-(phosphonoethoxy)ethyl] purine bis(2,2,2- trifluoroethyl) esters, and a series of 1-isopropylsulfonyl-2-amine benzimidazoles. In each case significant correlations are found between the anti-HBV potencies and some physicochemical and steric properties of the compounds, indicating that for the first two series the activity is controlled by the hydrophobic and the bulk properties of the molecules and, for the third series, the steric and hydrogen bonding properties of compounds are crucial for their anti-HBV potency.     

Comparative effect of Ocimum sanctum, Commiphora mukul, folic acid and ramipril on lipid peroxidation in experimentally-induced hyperlipidemia

Treatment with C. mukul and O. sanctum, showed a significant decrease in cholesterol and triglyceride levels respectively. O. sanctum also significantly increased serum HDL-cholesterol compared to control. Serum MDA levels were significantly reduced in all the treated groups compared to control suggesting that each of the drugs under study were effective in their free radical scavenging action. Erythrocyte SOD activity was increased in all the treatment groups with C. mukul showing the maximum effect followed by O. sanctum, folic acid and ramipril. The erythrocyte CAT activity was significantly increased in all the drug treated groups with maximum increase seen in O. sanctum and ramipril treated groups, whereas lesser effects were observed with C. mukul and folic acid groups. Thus, the indigenous drugs, C. mukul and O. sanctum had beneficial effect on hypercholesterolemic rabbit model, both in terms of lipid profile as well as antioxidant potential. Ocimum sanctum was found to be the most promising of all the drugs. Moreover, it could be hypothesized that these plant products along with folic acid and ramipril can be explored for synergistic effect for treatment for hypercholesterolemic conditions.     

Galanin regulation of LH release in male rats

The present study examines the role of cerebroventricular administered (IIIrd ventricle) galanin on LHRH and LH release in adult and immature male rats. In both age groups, galanin stimulated LHRH synthesis and release from the hypothalamus, leading to a higher release of pituitary LH which in turn increased plasma LH levels. Galantide, a galanin receptor blocker, on the other hand, drastically reduced hypothalamic LHRH and plasma LH while increasing pituitary LH. In vitro incubation of anterior pituitary cells with galanin followed by LHRH resulted in increased release of pituitary LH but not by galanin alone. Galantide exhibited no such effect either alone or with LHRH. These results indicate that galanin is an important regulator for both hypothalamic LHRH and hypophysial LH and its role is independent of age in the case of male rats.