Machanism of methyleugenoc in protecting islet cells from hypoxia/reoxygenation injury / 中华器官移植杂志

ABSTRACT

Objective:To explore the protective effect of methyl eugenol (Me) on islet ischemia/reperfusion (I/R) injury and elucidate its underlying mechanism.Methods:The islets were isolated and purified from 6-8 week male BALB/c mice and divided into four groups of normal control (normal culture without any treatment), hypoxia/reoxygenation (H/R treatment), H/R+ dimethyl sulfoxide (DMSO dosing plus H/R treatment) and H/R+ Me (Me dosing plus H/R). Viability of islet cells in each group was detected by acridine orange (AO)/propidium iodide (PI) double stain.Function of islet cells (insulin secretion) was measured by enzyme-linked immunosorbent assay (ELISA). Murine islet β Min6 cells were selected for detecting the effect of Me on the proliferative activity of normal cultured and H/R treated islet cells under different concentration gradients by CCK8.Then Min6 cells were divided into four groups of normal, H/R, H/R+ DMSO and H/R+ Me.The definition of group was the same as that of primary murine islets.Flow cytometry and Hoechst 33342 nuclear stain were utilized for detecting cell apoptotic rate in each group.The protein expressions of p-JNK, p-p38, JNK, p38, Bcl-2 and Bax were detected by Western blot.And the data were processed by one-way ANOVA or t test.Results:The proportion of dead islet cells in H/R group was (29.47±2.65)% and it was significantly lower than that in normal group (7.63±1.53)%.And the inter-group differences were statistically significant ( P<0.001). The proportion of dead islet cells was (20.63±3.07)% in H/R+ Me group.It was higher than that in H/R group (29.47±2.65)% and in H/R+ DMSO group (30.13±1.50)% and inter-group difference was statistically significant ( P<0.05 & P<0.01). Under the stimulation of high glucose, the insulin secretion level of islet in H/R+ Me group was (1.76+ 0.08) mg/L, which was higher than that in H/R group and H/R+ DMSD group(1.24±0.14)mg/L and(1.27±0.05)mg/L, and the difference was statistically significant[(1.76±0.08) vs. (1.24±0.14) mg/L; (1.76±0.08) vs.(1.27±0.05) mg/L, P<0.01]. There was no significant effect on cell viability after Me dosing within a certain concentration range (0-40 μmol/L). After Me dosing (5 μmol/L), cell viability of H/R-treated Min6 cells was significantly higher than that without Me.And the difference was statistically significant[(1.19±0.03) vs.(1.00±0), P<0.01]. As compared with H/R and H/R+ DMSO groups, overall apoptotic rate declined in H/R+ Me group (Hoechst 33342 stain 14.50%±1.05% vs. 23.30%±1.18%, 14.50%±1.05% vs. 22.77%±1.75%, P<0.001; Flow cytometry 4.36%±0.54% vs. 21.44%±1.02%, 4.36%±0.54% vs. 21.68%±3.06%, P<0.01). The expressions of p-JNK and p-p38 were down-regulated (p-JNK 0.77±0.06 vs. 1.03±0.05, 0.77±0.06 vs.0.93±0.04, P<0.001; p-p38 0.80±0.05 vs. 1.01±0.08; 0.80±0.05 vs. 1.00±0.05, P<0.05) while Bcl-2/Bax ratio rose (1.62±0.13 vs. 0.72±0.10, 1.62±0.13 vs. 0.74±0.13, P<0.01). Conclusions:Me can improve the viability and function of islets and suppress the apoptosis of Min6 cells after H/R.The mechanism is correlated with JNK and p38 MAPK signaling pathways.