CD28 signaling in primary CD4(+) T cells: identification of both tyrosine phosphorylation-dependent and phosphorylation-independent pathways.

In addition to TCR signaling, the activation and proliferation of naive T cells require CD28-mediated co-stimulation. Once engaged, CD28 is phosphorylated and can then activate signaling pathways by recruiting molecules to its YMNM motif and two PxxP motifs. In this study, we analyzed the relationship between tyrosine phosphorylation and the co-stimulatory function of CD28 in murine primary CD4(+) T cells. Tyrosine phosphorylation is decreased in CD28 where the N-terminal PxxP motif is mutated (nPA). In cells expressing nPA, activation of Akt and functional co-stimulation were decreased. In contrast, where the C-terminal PxxP motif is mutated, tyrosine phosphorylation and activation of the ERK, Akt and NF-κB were intact, but proliferation and IL-2 production were decreased. Using the Y(189) to F mutant, we also demonstrated that in naive CD4(+) T cells, tyrosine at position 189 in the YMNM motif is critical for both tyrosine phosphorylation and the functional co-stimulatory effects of CD28. This mutation did not affect unfractionated T-cell populations. Overall, our data suggest that CD28 signaling uses tyrosine phosphorylation-dependent and phosphorylation-independent pathways.

Population pharmacokinetics and proton pump inhibitory effects of intravenous lansoprazole in healthy Japanese males.

A total of 56 healthy Japanese males were enrolled in single- or multiple- dose pharmacokinetic trials of intravenous lansoprazole administration. The population pharmacokinetics of the drug was evaluated using nonlinear mixed effects model (NONMEM) software. In addition, the effect of CYP2C19 polymorphism on proton pump inhibition by lansoprazole was investigated using 24-h intragastric pH monitoring in the 32 subjects. Time course of serum lansoprazole concentration following intravenous short infusion was well described by a 2-compartment model. The mean volume of the central and peripheral compartments was 0.110 and 0.201 l/kg, respectively. The mean inter-compartment clearance was estimated to be 0.0882 l/h/kg. The population mean value of systemic clearance in the homoEM (CYP2C19 1/ 1), heteroEM (CYP2C19 1/2 and 1/3), and PM (CYP2C19 2/2, 2/3, and 3/3) groups was 0.179, 0.109, and 0.038 l/h/kg, respectively. The mean intragastric pH following twice-daily doses of 30 mg lansoprazole was approximately 6, 5, and 4 in the PM, heteroEM, and homoEM groups, respectively. These findings indicate that large interindividual variability exists in the pharmacokinetics of intravenously administered lansoprazole, but that twice-daily infusion of a 30 mg dose leads to significant and sustained proton pump inhibition, even in the homoEM group, despite the short elimination half-life of the drug.

Effect of water intake on pharmacokinetics of lansoprazole from fast disintegrating tablet in human subjects.

Lansoprazole fast disintegrating tablet (LFDT) has been developed as a multiple unit formulation to increase the QOL of patients, i.e., easy intake without water. However, there is a possibility that patients intake LFDT in accordance with clarithromycin and amoxicillin with water. To study the effect of water on the absorption of lansoprazole (LPZ), the study was carried out using human volunteers. After selected by phenotype of LPZ metabolism, extensive metabolizers (EMs) of LPZ were used in this study. Twelve healthy male EMs intook LFDT containing 30 mg LPZ with 150 mL of water and without-water, i.e., with saliva, to study the pharmacokinetics of LPZ from the gastrointestinal tract by a cross-over manner with one-week washout period under fasted condition in the morning. The mean AUC(0-24s) were 2004.4+/-973.6 ng.h/mL in without-water experiment and 2018.5+/-1159.6 ng.h/mL in the case of with-water experiment. Mean C(maxs) were 851.9+/-450.8 ng/mL in without-water experiment and 830.8+/-456.8 ng/mL in with-water experiment, respectively. ANOVA was applied to the log-transformed AUC(0-24) and C(max) values. The 90% two sided confidence intervals for log-transformed AUC(0-24) was 0.78-1.22 and that for log-transformed C(max) was 0.67-1.37, respectively. By comparing these pharmacokinetic parameters, we may state that there was no significant difference between the two administration modes.

Evaluation of fast disintegrating lansoprazole tablet in human subjects.

Fast disintegrating lansoprazole tablet (LFDT) has been developed as a multiple unit formulation and evaluated using human subjects as compared to the conventional lansoprazole (LPZ) capsule containing enteric coated granules. Twelve healthy male volunteers, who were confirmed as extensive metabolizers (EMs) based on the plasma levels of LPZ sulphone metabolite, were enrolled into the study and genotype of CYP2C19 was confirmed. They kept 30 mg LFDT in their mouths for 2 min and the saliva was recovered without swallow. Eight subjects did not show LPZ in their serum after intake. Although LPZ was detected in 4 subjects' serum, their concentrations were less than 5 ng/mL. LPZ was thought to be not absorbed from the oral cavity. LFDT was orally administered to 12 healthy male EMs at two doses, 15 mg and 30 mg, and serum LPZ concentrations were measured. The mean C(max) and AUC(0-24) were 474.1+/-254.0 ng/mL and 1105.3+/-1101.4 ng.h/mL (15 mg) and 992.8+/-384.3 ng/mL and 2216.5+/-1270.1 ng.h/mL (30 mg). By comparing to that obtained after oral administration of the same doses of LPZ capsule, serum LPZ concentration vs. time curve was almost the same level, i.e., C(max) and AUC(0-24) did not have significant differences. From these results, LFDT has been shown to be equivalent to LPZ capsule and will show the same acid suppressing effects in the clinical situation.