P38α-Selective Mitogen-Activated Protein Kinase Inhibitor for Improvement of Cultured Human Islet Recovery

Objectives: We investigated whether the recovery of cultured human islets is improved through the addition of a p38α-selective mitogen-activated protein kinase inhibitor, SD-282, to clinically used serum-free culture medium. Methods: Immediately after isolation, islets were cultured for 24 hours in medium alone (control) or medium containing dimethyl sulfoxide, 0.1 μM SD-282, or 0.3 μM SD-282. Cytokine expression, apoptotic β-cell percentage, and islet function were assessed postculture. Results: Expression of p38 and phosphorylated p38 in islets increased during culture. Interleukin 6 mRNA expression in cultured islets, as well as IL-6, IL-8, and granulocyte-macrophage colony-stimulating factor released into the medium, was significantly reduced by adding SD-282. The apoptotic β-cell percentage was significantly lower in islets cultured with 0.1 μM SD-282, but not 0.3 μM, as compared with the control. Stimulation indices measured in vitro were higher but without significance (P = 0.06); the function of transplanted islets in diabetic NODscid mice was also better in 0.1-μM SD-282 group as compared with control. Conclusions: Better islet function was obtained by adding 0.1 μM SD-282 to the serum-free culture medium. This improvement was associated with suppression of cytokine production and prevention of β-cell apoptosis. However, this beneficial effect was diminished at a higher concentration. Abbreviations: ELISA - enzyme-linked immunosorbent assay, HSP27 - heat shock protein 27, ICAM-1 - intercellular adhesion molecule 1, IL - interleukin, IFN - interferon, JNK - c-Jun NH2-terminal kinase, LSC - laser scanning cytometry, MAPK - mitogen-activated protein kinase, LPS - lipopolysaccharide, MCP-1 - monocyte chemoattractant protein 1, PECAM-1 - platelet/endothelial cell adhesion molecule 1, RT-PCR - real-time reverse transcription polymerase chain reaction, TNF-α - tumor necrosis factor-α, TUNEL - terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling