Protective effects of RGD peptides on islet viability and function / 中华内分泌外科杂志

ABSTRACT

Objective To investigate the effect of argenin-glycin-aspartic acid (RGD) peptides on islet viability and function. Methods Rats were randomly divided into 2 groups 1640 group and RGD group. Ficoll was used to purify islet in a discontinuous-density-gradient way. Islet concentration is 27% ,25% ,23% ,20.5% and 11% respectively. Acridine orange/ethidium bromide(AO/EB) fluorescent staining method was adopted to observe the effect of RGD peptides on islet viability. Radioimmunoassay was adopted to detect insulin level and measure insulin secretion index (SI). Caspase-9 cells and phospho-Akt 473-positive cells were determined by flow cytometry to investigate the influence of RGD peptides on caspase-9 activity and Akt. Results 600-700 IEQ islet was extracted from each rat by Ficoll purification through modified gradient centrifugation. AO/EB stain showed islet survival rate was more than 95% immediately after separation. Islets cultured in the medium of RPMI-1640 showed SI of 1.64 ±0.28 after 1 week, while islets cultured in the medium of RPMI-1640 containing RGD peptides showed SI of 2.28 ± 0.16 (P ＜ 0.05 ). Flow cytometry showed the level of activated caspase-9 was ( 22.66 ± 3.56 ) % if islet was cultured in RPMI-1640 alone for 1 week while the level was( 10.54 ± 1.96) % if islet was cultured in RPMI-1640 containing RGD peptides. There was statistical difference ( P ＜ 0. 05 ). The effect of RGD on Akt phosphorylation was also detected. Akt phosphorylation proportion was (31.47 ±4.08)% 1 week after cultured in RPMI-1640 while the value was(61. 054 ±6.03)% if cultured in RPMI-1640 containing RGD peptides. The difference had statistical significance (P ＜ 0. 05). Conclusion RGD peptides could inhibit apoptosis through the phosphorylation of Akt/PKB.