Chronic treatment with FK506 increases p70 S6 kinase activity associated with reduced nitric oxide synthase activity in rabbit hearts

Blood concentration of tacrolimus and age predict tacrolimus-induced left ventricular dysfunction after bone marrow transplantation in adults

PURPOSE

Tacrolimus (TAC) is used for the prophylaxis and treatment of acute graft-versus-host disease after bone marrow transplantation (BMT). However, few have reported on TAC-induced left ventricular hypertrophy. This study aimed to assess the relationship between blood concentration of TAC and development of TAC-induced left ventricular (TI-LV) dysfunction in adult BMT patients with hematologic malignant diseases, and to evaluate whether TAC concentration can predict TI-LV dysfunction occurrence in these patients.

METHODS

We enrolled 16 consecutive patients (mean age 44.6 ± 13.0 years) who received TAC after BMT. Echocardiography was performed before and after BMT, and blood concentrations of TAC were evaluated in terms of AUC₁₅ (area sum of TAC > 15 ng/ml during follow-up). We assessed the relationship between AUC₁₅ and development of TI-LV dysfunction after TAC.

RESULTS

During the follow-up period (mean duration 47.6 ± 13.7 days), interventricular septum thickness (IVST, P = 0.001) and posterior wall thickness (PWT, P < 0.001) increased, and E' decreased (P = 0.006). AUC₁₅ was associated with post-IVST (R = 0.627, P = 0.009), post-PWT (R = 0.669, P = 0.005), and post-E' (R = - 0.767, P = 0.001). In multivariate analysis, AUC₁₅ and age independently predicted the increase in IVST and PWT and decrease in E' after BMT. The combination of AUC₁₅ and older age predicted post-PWT with a sensitivity of 77.8% and specificity of 71.4%.

CONCLUSION

TAC concentrations should be maintained at < 15 ng/ml and age should be considered in patients undergoing BMT to avoid TI-LV dysfunction.

Co-administration of tacrolimus suppresses pharmacokinetic modulation of multiple subcutaneously administered human interferon-alpha in Beagle dogs

Specific antibody production is an important issue in crossover pharmacokinetic (PK) studies of protein-based formulations. We recently reported that intravenous co-administration of tacrolimus with multiple human interferon-alpha (h-IFN) administrations successfully suppressed the production of anti-h-IFN antibodies in rats. Since crossover PK studies are preferentially carried out using larger animals such as dogs or monkeys that are capable of accepting the same dosage formulations as those for clinical use, we extended our study of co-administration of tacrolimus with multiple h-IFN administrations to beagle dogs in the present study. Beagle dogs were subcutaneously administered 0.5 million IU/kg of h-IFN once a week for 4 weeks. In some experiments, tacrolimus at 0.01 or 0.1 mg/kg was intravenously co-administered at the same time as the h-IFN administration. Co-administration of the lower dose of tacrolimus (0.01 mg/kg) failed to suppress the anti-h-IFN IgG responses, while co-administration of the higher dose (0.1 mg/kg) successfully suppressed these responses. Moreover, co-administration of tacrolimus had little effect on the serum creatinine concentrations, suggesting that multiple administrations of tacrolimus at the concentrations examined did not cause severe renal disorders. Taken together, the present data confirm that co-administration of tacrolimus is a promising way to assess crossover PK studies of human or humanized proteinic formulations in beagle dogs.

Calcineurin is required for translational control of protein synthesis in rat pancreatic acini

CCK increases the rate of net protein synthesis in rat pancreatic acini by activating initiation and elongation factors required for translation. The immunosuppressant FK506 inhibits the Ca2+-calmodulin-dependent phosphatase calcineurin in pancreatic acinar cells and blocks pancreatic growth induced by chronic CCK treatment. To test a requirement for calcineurin in the activation of the translational machinery stimulated by CCK, we evaluated the effects of FK506 on protein synthesis and on regulatory initiation and elongation factors in rat pancreatic acini in vitro. CCK acutely increased protein synthesis in acini from normal rats with a maximum increase at 100 pM CCK to 170 ± 11% of control. The immunosuppressant FK506 dose-dependently inhibited CCK-stimulated protein synthesis over the same concentration range that blocked calcineurin activity, as assessed by dephosphorylation of the calcineurin substrate calcium-regulated heat-stable protein of 24 kDa. Another immunosuppressant, cyclosporin A, inhibited protein synthesis, but its effects appeared more complex. FK506 also inhibited protein synthesis stimulated by bombesin and carbachol. FK506 did not significantly affect the activity of the initiation factor-2B, or the phosphorylation of the initiation factor-2α, ribosomal protein protein S6, or the mRNA cap binding protein eukaryotic initiation factor (eIF) 4E. Instead, blockade of calcineurin with FK506 reduced the phosphorylation of the eIF4E binding protein, reduced the formation of the eIF4F complex, and increased the phosphorylation of eukaryotic elongation factor 2. From these results, we conclude that calcineurin activity is required for protein synthesis, and this action may be related to an effect on the formation of the mRNA cap binding complex and the elongation processes.