Cyclosporin A inhibits angiotensin II-induced c-Jun NH(2)-terminal kinase activation but not protein synthesis in vascular smooth muscle cells

Calcineurin inhibitors cyclosporin A and tacrolimus protect against podocyte injury induced by puromycin aminonucleoside in rodent models

Podocyte injury and the appearance of proteinuria are features of minimal-change disease (MCD). Cyclosporin A (CsA) and tacrolimus (FK506) has been reported to reduce proteinuria in patients with nephrotic syndrome, but mechanisms remain unknown. We, therefore, investigated the protective mechanisms of CsA and FK506 on proteinuria in a rat model of MCD induced by puromycin aminonucleoside (PAN) and in vitro cultured mouse podocytes. Our results showed that CsA and FK506 treatment decreased proteinuria via a mechanism associated to a reduction in the foot-process fusion and desmin, and a recovery of synaptopodin and podocin. In PAN-treated mouse podocytes, pre-incubation with CsA and FK506 restored the distribution of the actin cytoskeleton, increased the expression of synaptopodin and podocin, improved podocyte viability, and reduced the migrating activities of podocytes. Treatment with CsA and FK506 also inhibited PAN-induced podocytes apoptosis, which was associated with the induction of Bcl-xL and inhibition of Bax, cleaved caspase 3, and cleaved PARP expression. Further studies revealed that CsA and FK506 inhibited PAN-induced p38 and JNK signaling, thereby protecting podocytes from PAN-induced injury. In conclusion, CsA and FK506 inhibit proteinuria by protecting against PAN-induced podocyte injury, which may be associated with inhibition of the MAPK signaling pathway.

Calcineurin-dependent and calcineurin-independent signal transduction pathways activated as part of pancreatic growth

OBJECTIVE

We have recently reported that pancreatic growth driven by cholecystokinin released endogenously by feeding the synthetic trypsin inhibitor camostat requires the Ca-activated phosphatase calcineurin. In the present study, we evaluated a number of signal transduction pathways for their activation as part of the growth response and whether their activation was dependent on calcineurin.

METHODS

Male ICR mice were fed with either chow or chow plus 1 mg/g of camostat. FK506 was administered at 3 mg/kg. After various times from 12 hours to 10 days, pancreatic samples were prepared and assayed for activity of various signal transduction pathway components.

RESULTS

Camostat feeding increased the activation of extracellular signal-regulated kinases, c-Jun NH2-terminal kinases, and phosphorylation of the translation factor eukaryotic initiation factor 4E and activated the mammalian target of rapamycin pathway that leads to phosphorylation of the ribosomal protein S6 and of the eukaryotic initiation factor 4E binding protein but with different time courses. Treatment of mice with the calcineurin inhibitor FK506 totally blocked c-Jun NH2-terminal kinase activation, partially blocked the mammalian target of rapamycin pathway, and had no effect on extracellular signal-regulated kinase activation or the phosphorylation of eukaryotic initiation factor 4E.

CONCLUSIONS

The pancreatic growth response is accompanied by activation of a number of signaling pathways regulating transcription and translation, some of which are dependent on and some independent of calcineurin.

Cyclosporin a affects signaling events differentially in human gingival fibroblasts

Gingival overgrowth is a common side-effect of the administration of cyclosporin A (CSA), phenytoin, and calcium blockers. To identify the signaling mechanisms possibly involved in the overgrowth, we examined how CSA affects the activities of MAP kinases and transcription factors in human gingival fibroblasts (HGF). The HGF were treated with CSA and TNF-alpha or PDGF. DNA-binding activity of NFAT, NFkappaB, and AP-1 transcription factors was determined by gel shift assay, and JNK, p38, and ERK1 and ERK2 activation was assessed by Western blot analysis of immunoprecipitates. The CSA inhibited NFAT, NFkappaB, and p38 and JNK activities; however, ERK1 and ERK2 were not affected significantly. AP-1 activity increased approximately 4.5-fold. Our results indicate that CSA affects signaling molecules in HGF differently from other cell types, and that a CSA-induced increase in AP-1 activity may affect the expression of fibrogenic molecules in gingiva and promote gingival overgrowth.

Conversion From Cyclosporine Microemulsion to Tacrolimus-Based Immunoprophylaxis Improves Cholesterol Profile in Heart Transplant Recipients With Treated but Persistent Dyslipidemia: The Canadian Multicentre Randomized Trial of Tacrolimus vs Cyclosporine Microemulsion

BACKGROUND

Tacrolimus improves lipid profile in renal and liver transplant recipients. The impact of conversion from cyclosporine microemulsion (Neoral) to tacrolimus (Prograf) in a large randomized study of stable heart transplant recipients with treated but persistent mild dyslipidemia is reported.

METHODS

One hundred twenty-nine long-term (>or=12 months) cyclosporine microemulsion-treated heart transplant recipients with low-density lipoprotein cholesterol >2.5 mmol/liter and/or a total cholesterol/high-density lipoprotein cholesterol ratio >4 were recruited for the study. Complete lipid profile was assessed before (baseline) and after 6 months of treatment with either cyclosporine microemulsion maintenance (n=64) or tacrolimus conversion (n=65).

RESULTS

At 6 months, tacrolimus-converted patients exhibited a greater decrease in total cholesterol (from 5.51 +/- 0.16 to 4.88 +/- 1.22 mmol/liter [tacrolimus], vs 5.61 +/- 1.36 to 5.38 +/- 0.87 mmol/liter [cyclosporine]; p = 0.0078). This decrease in cholesterol was caused largely by a decrease in low-density lipoprotein cholesterol (-0.41 +/- 0.54 [tacrolimus] vs -0.13 +/- 0.55 [cyclosporine]; p=0.0018). There were no changes in high-density lipoprotein cholesterol and triglyceride levels, but apolipoprotein B therapy was reduced in tacrolimus-converted vs cyclosporine-maintained patients (p=0.0003). By 6 months, 23.7% of tacrolimus- vs 6.7% of cyclosporine-treated patients met the target lipid levels for high-risk patients (p=0.0094). Conversion from cyclosporine to tacrolimus resulted in decreases in blood urea nitrogen, creatinine, and uric acid without any changes in glucose, HbA(1C), and insulin levels.

CONCLUSIONS

Conversion from cyclosporine microemulsion- to tacrolimus-based immunoprophylaxis resulted in decreased cholesterol, apolipoprotein B, urea, creatinine, and uric acid without any clinically evident perturbation of glucose metabolism in stable heart transplant recipients with treated but persistent mild dyslipidemia.

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.

Gβγ signaling and Ca2+ mobilization co-operate synergistically in a Sos and Rac-dependent manner in the activation of JNK by Gq-coupled receptors

The mechanism by which G(q)-coupled receptors stimulate the c-Jun N-terminal kinase (JNK) activity has not been fully delineated. Here, we showed that stimulation of endogenous G(q)-coupled receptors in human hepatocarcinoma HepG2 cells resulted in an Src family kinase- and Ca(2+)-dependent JNK activation. Cos-7 cells transfected with HA-tagged JNK and various G(q)-coupled receptors also exhibited similar characteristics and provided further evidence for the involvement of Gbetagamma, an upstream intermediate for Src family kinases. The Ca(2+) and Gbetagamma signals operate in a high degree of independence. Transient expression of Gbetagamma subunits and elevation of cytoplasmic Ca(2+) level by thapsigargin activated JNK in a synergistic fashion. JNK activities triggered by G(q)-coupled receptors, Gbetagamma and thapsigargin were all suppressed by dominant negative (DN) mutants of Son of sevenless (Sos) and Rac. We propose that the co-operative effect between Gbetagamma-mediated signaling and the increased intracellular Ca(2+) level represents a robust mechanism for the stimulation of JNK by G(q)-coupled receptors.