Expression of Endoplasmic Reticulum-Mediated Stress Proteins in FK506-Treated T-Lymphocytes

Clinical efficacy of tacrolimus for treating myasthenia gravis and its influence on lymphocyte subsets

BACKGROUND

This study aimed to determine the clinical efficacy and effects of tacrolimus in treating myasthenia gravis (MG).

METHODS

A total of 45 outpatients and inpatients were divided into a tacrolimus group (n=15) and non-tacrolimus group (n=30): those in the former group were treated with 3mg/day of tacrolimus for 24 weeks, while those in the latter (control) group took other immunosuppressants (prednisone, azathioprine combined with prednisone). Each group was evaluated at weeks 4, 8, 12, 16, 20 and 24 by Myasthenia Gravis Foundation of America Quantitative Myasthenia Gravis (MGFA-QMG) Test, activities of daily living (ADL) profiles, and manual muscle (MMT) and fatigue tests. Dynamic changes in CD4⁺CD25^+high cells were tested by flow cytometry. Inflammatory cytokines were also evaluated in the tacrolimus group.

RESULTS

Efficacy index scores decreased significantly compared with baseline at every test week in both groups (P<0.01), although improvements were more evident with than without tacrolimus treatment (F=9.312, P<0.01 vs. F=24.551, P<0.01 and F=10.710, P<0.01). At week 24, peripheral blood CD4⁺CD25^+high T cells with tacrolimus decreased significantly (P<0.01), but increased significantly without tacrolimus (P<0.01). During treatment, CD19⁺BAFF-R B cells in peripheral blood decreased in both groups (P<0.05). Interferon (IFN)-γ concentrations in peripheral blood also diminished significantly with tacrolimus (P<0.01).

CONCLUSION

A relatively low dose of tacrolimus can affect multiple immune-system targets and, thus, can treat MG effectively in terms of both clinical symptoms and immunological responses.

Impaired mitochondrial calcium uptake caused by tacrolimus underlies beta-cell failure

BACKGROUND

One of the most common side effects of the immunosuppressive drug tacrolimus (FK506) is the increased risk of new-onset diabetes mellitus. However, the molecular mechanisms underlying this association have not been fully clarified.

METHODS

We studied the effects of the therapeutic dose of tacrolimus on mitochondrial fitness in beta-cells.

RESULTS

We demonstrate that tacrolimus impairs glucose-stimulated insulin secretion (GSIS) in beta-cells through a previously unidentified mechanism. Indeed, tacrolimus causes a decrease in mitochondrial Ca²⁺ uptake, accompanied by altered mitochondrial respiration and reduced ATP production, eventually leading to impaired GSIS.

CONCLUSION

Our observations individuate a new fundamental mechanism responsible for the augmented incidence of diabetes following tacrolimus treatment. Indeed, this drug alters Ca²⁺ fluxes in mitochondria, thereby compromising metabolism-secretion coupling in beta-cells.