Neutralization of leukotriene C4 and D4 activity by monoclonal and single-chain antibodies.

BACKGROUND: Cysteinyl leukotrienes (LTs) are key mediators in inflammation. To explore the structure of the antigen-recognition site of a monoclonal antibody against LTC4 (mAbLTC), we previously isolated full-length cDNAs for heavy and light chains of the antibody and prepared a single-chain antibody comprising variable regions of these two chains (scFvLTC). METHODS: We examined whether mAbLTC and scFvLTC neutralized the biological activities of LTC4 and LTD4 by competing their binding to their receptors. RESULTS: mAbLTC and scFvLTC inhibited their binding of LTC4 or LTD4 to CysLT1 receptor (CysLT1R) and CysLT2 receptor (CysLT2R) overexpressed in Chinese hamster ovary cells. The induction by LTD4 of monocyte chemoattractant protein-1 and interleukin-8 mRNAs in human monocytic leukemia THP-1 cells expressing CysLT1R was dose-dependently suppressed not only by mAbLTC but also by scFvLTC. LTC4- and LTD4-induced aggregation of mouse platelets expressing CysLT2R was dose-dependently suppressed by either mAbLTC or scFvLTC. Administration of mAbLTC reduced pulmonary eosinophil infiltration and goblet cell hyperplasia observed in a murine model of asthma. Furthermore, mAbLTC bound to CysLT2R antagonists but not to CysLT1R antagonists. CONCLUSIONS: These results indicate that mAbLTC and scFvLTC neutralize the biological activities of LTs by competing their binding to CysLT1R and CysLT2R. Furthermore, the binding of cysteinyl LT receptor antagonists to mAbLTC suggests the structural resemblance of the LT-recognition site of the antibody to that of these receptors. GENERAL SIGNIFICANCE: mAbLTC can be used in the treatment of inflammatory diseases such as asthma.

Insulin Secretory Defect and Insulin Resistance in Isolated Impaired Fasting Glucose and Isolated Impaired Glucose Tolerance.

OBJECTIVE: To investigate the characteristics of isolated impaired glucose tolerance (IGT) and isolated impaired fasting glucose (IFG), we analyzed the factors responsible for elevation of 2-hour postchallenge plasma glucose (2 h PG) and fasting plasma glucose (FPG) levels. METHODS: We investigated the relationship between 2 h PG and FPG levels who underwent 75 g OGTT in 5620 Japanese subjects at initial examination for medical check-up. We compared clinical characteristics between isolated IGT and isolated IFG and analyzed the relationships of 2 h PG and FPG with clinical characteristics, the indices of insulin secretory capacity, and insulin sensitivity. RESULTS: In a comparison between isolated IGT and isolated IFG, insulinogenic index was lower in isolated IGT than that of isolated IFG (0.43 ± 0.34 versus 0.50 ± 0.47, resp.; p < 0.01). ISI composite was lower in isolated IFG than that of isolated IGT (6.87 ± 3.38 versus 7.98 ± 4.03, resp.; p < 0.0001). In isolated IGT group, insulinogenic index showed a significant correlation with 2 h PG (r = -0.245, p < 0.0001) and had the strongest correlation with 2 h PG (ß = -0.290). In isolated IFG group, ISI composite showed a significant correlation with FPG (r = -0.162, p < 0.0001) and had the strongest correlation with FPG (ß = -0.214). CONCLUSIONS: We have elucidated that decreased early-phase insulin secretion is the most important factor responsible for elevation of 2 h PG levels in isolated IGT subjects, and decreased insulin sensitivity is the most important factor responsible for elevation of FPG levels in isolated IFG subjects.

Relationship and factors responsible for regulating fasting and post-challenge plasma glucose levels in the early stage development of type 2 diabetes mellitus.

AIMS/INTRODUCTION: Elevation of 2-h plasma glucose (2-h PG) levels keeps step with fasting plasma glucose (FPG) levels elevation, but some individuals show dominant elevation of 2-h PG and others FPG. We analyzed dependent and independent relationships between 2-h PG and FPG, and investigated the factors regulating 2-h PG and FPG. MATERIALS AND METHODS: In 1,657 Japanese participants who underwent a 75-g oral glucose tolerance test at the initial examination for a medical check-up, we carried out simple linear regression analysis between 2-h PG and FPG levels on the three patterns of independent variables. We divided the participants into two subgroups: the 2-h PG-side group and the FPG-side from the regression line, and examined the relationships between 2-h PG-FPG and factors responsible for elevation of plasma glucose levels. RESULTS: There was a significant positive correlation between 2-h PG and FPG levels. The regression line of both 2-h PG and FPG as independent variables was in accordance with the regression line of 2-h PG as an independent variable and FPG as a dependent variable. In 2-h PG-side group, age was the independent factor affecting 2-h PG in addition to insulinogenic index and insulin sensitivity index (ISI composite). In the FPG-side group, triglyceride was the independent factor affecting FPG in addition to insulinogenic index and ISI composite. CONCLUSIONS: Two-hour PG was an independent predictor of FPG. In addition to the importance of decreased insulin secretion and insulin sensitivity, age was the strong factor to elevate 2-h PG levels in the 2-h PG-side group and triglyceride was the strong factor to elevate FPG levels in the FPG-side group in the early stage of development of type 2 diabetes.