Antiapoptotic Effect of Tacrolimus on Cytokine-Challenged Human Islets

Abstract

Our goal was to investigate whether previously related antiapoptotic and anti-inflammatory effects of tacrolimus could be useful in protecting human islets cultured in the presence of several proinflammatory mediators. Human islets obtained from cadaveric donors after intraductal infusion with collagenase, mechanical digestion, and continuous Ficoll gradient purification were cultured in RPMI-1640 medium for 24 h. Escherichia coli lipopolysaccharide (10 microg/ml) or interleukin-1 (50 UI/ml) + gamma-IF (1000 UI/ml) and low-dose tacroliumus (5 ng/ml) were added. Homogenized samples (300 IE) from five different donors where assigned to four different experimental groups (control, treatment, cytokines, and cytokines + treatment). To evaluate islet damage and apoptotic response, nucleosome content, Bcl-2 protein levels, caspase-3, -8, and -9 levels, and insulin concentration were measured. Also, TNF-alpha and IL-6 levels where assessed as indicators of the inflammatory response. All proapoptotic markers, TNF-alpha, and IL-6 levels were augmented after both LPS and cytokine stimulation. Tacrolimus reduced significantly all of them and restored baseline values of nucleosome and caspase-9 in both experiments and Bcl-2 and caspase-3 when IL-1 + gamma-IF was added. Twenty-four-hour insulin concentration diminished when LPS or IL-1 + gamma-IF were present. Tacrolimus treatment restored insulin levels in both experiments. These results suggest that in vitro apoptotic events and media insulin concentration decrease after proinflammatory stimulation can be reverted using low-dose tacrolimus.

Effect of Immunosuppressive Agents on Hepatocyte Apoptosis Post-Liver Transplantation

“…Tacrolimus has been shown to promote the generation of reactive oxygen species, mitochondrial dysfunction and apoptosis in Jurkat T-cells[ 8 ]. By contrast, tacrolimus has an anti-apoptotic effect in human islet cells treated with pro-inflammatory cytokines, causing a reduction in TNF-α and down-regulation of caspase-3[ 22 ]. In the current study we found that at therapeutically relevant concentrations, neither cyclosporine nor tacrolimus promoted hepatocyte cell death.…”

Treatment with Tacrolimus and Sirolimus Reveals No Additional Adverse Effects on Human IsletsIn VitroCompared to Each Drug Alone but They Are Reduced by Adding Glucocorticoids

“…Our observation could therefore illustrate a reciprocal inhibition of the two drugs [ 13 ] or that maximum intervention has been reached. Others have shown that sirolimus and tacrolimus have anti-inflammatory properties [ 44 – 47 ]. Compared to our data they use longer exposure time and lower drug dose, which are reasonable explanations for these differences.…”

Targeting Acute Islet Inflammation to Preserve Graft Mass and Long-Term Function

“…Moreover, short-term administration of tacrolimus has been shown to have no effect on islet secretion in healthy human subjects and improves beta cell viability and function when islets are under stress [102,104,105]. Indeed, acute exposure of tacrolimus prevents apoptosis in islets exposed to cytokines in vitro and can restore insulin gene transcription in islets chronically exposed to high glucose within a 48 h window [106,107]. Furthermore, short-term peptide inhibition of the CN downstream target NFAT in islets was shown to prolong graft function in an allogeneic mouse transplant model.…”