Inhibition of T cell cAMP formation by cyclosporin A and FK506

The effect of cyclosporine on the development and expression of cannabinoid tolerance in mice

Cyclosporine, beside its immunosuppressive action, has several effects on different neuronal functions, such as modulation of neurotransmitter release, the inhibition of nitric oxide synthesis and release, the reduction of cAMP production and inhibition of morphine-induced tolerance. In the present study, the effect of cyclosporine on the expression and development of tolerance to WIN 55,212-2, a cannabinoid receptor agonist, was studied. Intra peritoneal (i.p.) injection of WIN 55,212-2 (2-6 mg/kg) induced time-dependent and dose-dependent analgesia and catalepsy in mice. Administration of cyclosporine (20 mg/kg i.p.), 30 min before WIN 55,212-2 (6 mg/kg i.p.), did not change the analgesic and cataleptic effects of WIN 55,212-2. When WIN 55,212-2 (6 mg/kg i.p.) was injected once a day, animals became completely tolerant to the analgesic and cataleptic effects within five and nine days respectively. Cyclosporine (20 mg/kg i.p.) injected once daily, 30 min before WIN 55,212-2, attenuated the development of tolerance to the analgesic and cataleptic effects of WIN 55,212-2 but did not affect the expression of tolerance. Since cyclosporine given chronically by itself did not alter the analgesia and catalepsy induced by acute administration of WIN 55,212-2, our findings suggest cyclosporine may act with some selectivity on the mechanisms involved in development of cannabinoid tolerance.

Regional and endothelial differences in cyclosporine attenuation of adenosine receptor-mediated vasorelaxations

The present study investigated the acute effects of the immunosuppressant drug cyclosporine A on vasorelaxations evoked via activation of adenosine receptors in the phenylephrine-preconstricted rat perfused kidney and isolated aorta. The roles of endothelial relaxing factors in this interaction were also evaluated. The adenosine analogue 5'-N-ethylcarboxamidoadenosine (NECA; kidney, 6 x 10(-9)-1 x 10(-7) mol; aorta, 1 x 10(-9)-1 x 10(-5) M) elicited dose-dependent vasorelaxations. In the perfused kidney, NECA responses were similarly and significantly attenuated by N-nitro-L-arginine methyl ester (L-NAME, nitric oxide synthase inhibitor) or tetraethylammonium (K channel blocker) versus no effect for diclophenac (cyclooxygenase inhibitor). NECA relaxations in the aorta were reduced by the three inhibitors; the reduction in the response evoked by the highest dose of NECA (1 x 10(-5) M) amounted to 37.7 +/- 2.0% (L-NAME), 19.8 +/- 1.7% (tetraethylammonium), and 29.4 +/- 1.1% (diclophenac). A combination of the three inhibitors almost abolished NECA relaxations in the two preparations. Cyclosporine (2 microM) reduced NECA relaxations in the two preparations. In the aorta, cyclosporine attenuation of NECA responses was significantly reduced after exposure to L-NAME or diclophenac but not tetraethyl-ammonium, suggesting selective involvement of nitric oxide and vasodilator prostanoids in the interaction. In contrast, the cyclosporine attenuation of NECA responses in the kidney was reduced by L-NAME or tetraethylammonium. L-arginine, a nitric oxide substrate, partially restored NECA relaxations in cyclosporine-treated preparations. These findings demonstrate that cyclosporine attenuates endothelium-dependent vasorelaxations elicited via activation of adenosine receptors and highlight the interesting possibility that the relative contribution of the endothelial relaxing factors to cyclosporine-NECA interaction is largely region dependent.

Cyclosporine inhibition of vascular endothelial growth factor production in rheumatoid synovial fibroblasts

OBJECTIVE

To determine the antiangiogenic effect of cyclosporin A (CSA) in rheumatoid arthritis (RA).

METHODS

We investigated the effect of CSA on the production of vascular endothelial growth factor (VEGF) by rheumatoid synovial fibroblasts. Fibroblast-like synoviocytes (FLS) were prepared from the synovial tissues of RA patients, and cultured in the presence of CSA. The production of VEGF by FLS was measured in culture supernatants by enzyme-linked immunosorbent assay. The VEGF messenger RNA (mRNA) expression and activator protein 1 (AP-1) binding activity for VEGF transcription were determined by polymerase chain reaction and electrophoretic mobility shift assay, respectively.

RESULTS

CSA dose-dependently inhibited both constitutive and transforming growth factor beta-induced VEGF production at the protein and mRNA levels. The suppressive action of CSA on VEGF synthesis was calcineurin dependent, as evidenced by a comparable inhibition by FK-506. Agonists of cAMP, 3-isobutyl-1-methylxanthine and N-2-O-dibutyryl-cAMP, mimicked the effect of CSA on VEGF production, while a cAMP antagonist, 2',3'-dideoxyadenosine, abrogated the effect of CSA. A gel mobility shift assay showed that the inhibitory effect of CSA was associated with decreased AP-1 binding activity to the VEGF promoter, in a cAMP-dependent manner.

CONCLUSION

CSA may exert an antiangiogenic effect by inhibiting AP-1-mediated VEGF expression in rheumatoid synovial fibroblasts.