Involvement of ObRb receptor, nitric oxide, and BKCa channel signaling pathways in leptin-induced relaxation of pregnant mouse uterus.

The purpose of this study was to determine the receptor subtype and the underlying mechanisms involved in the relaxant effect to leptin in mid- and late-pregnant mouse uterus. We determined the relative mRNA expression of receptor subtypes, eNOS, and BKCa channel by quantitative PCR and also the overall receptor expression by immunohistochemistry. Isometric tension studies were conducted to evaluate the effects of leptin and to delineate its mechanisms. A selective siRNA for the ObRb receptor was used to determine the participation of the receptor subtype in biochemical and molecular effects of leptin. The relaxant response to leptin was greater in mid-pregnancy compared to late pregnancy and was mediated by the activation of BKCa channels by eNOS-derived nitric oxide in an ObRb receptor-dependent manner. In comparison to mid-pregnancy, expression of short forms (mainly ObRa receptor) of the receptor was significantly increased in late pregnancy, whereas ObRb receptor expression was similar in both phases. The results of the study suggest that ObRb receptor mediates leptin-induced increase in eNOS expression and NO synthesis. Leptin-induced eNOS expression and activation cause cGMP-independent stimulation of BKCa channels causing uterine relaxation. Increased short forms of the receptors and reduced BKCa channels exert a negative effect on uterine relaxation in late pregnancy. Leptin may have a physiological role in maintaining uterine quiescence in mid-pregnancy and its reduced relaxant response in late gestation may facilitate labor. Further, ObRb receptor agonists may be useful in the management of preterm labor.

Recoding anaerobic regulator fnr of Salmonella Typhimurium attenuates it's pathogenicity.

AIMS: How recoding of fnr, an anaerobic regulatory gene, affects pathogenicity related parameters of Salmonella Typhimurium (STM). METHODS AND RESULTS: The fnr gene was recoded by substituting all of it's codons with synonymous rare codons of STM. Recoding fnr gene severely reduced the ability of the recoded mutant to compete with wild strain under nutrient depletion condition. Mutants were also less motile than the wild strain and their biofilm forming ability was significantly decreased as compared to wild strain. The recoded strain showed significant reduced survival within murine macrophages (RAW264.7) and monocyte derived macrophage of poultry origin. The colonisation ability of recoded mutant in liver and spleen of mice on day 5 of post infection was significantly reduced. The recoded strain exhibited significant reduction in faecal shedding on day 1 and 5 after infection. CONCLUSIONS: Our study showed that recoding the anaerobic regulator fnr of STM significantly compromised its growth, decreased motility, biofilm forming ability and survival within macrophages. Further, the recoded fnr strain showed reduced colonisation ability and faecal shedding in mice. Thus, these findings highlight that recoding the global anaerobic regulator fnr of Salmonella Typhimurium attenuates its pathogenicity.