干细胞因子对糖尿病小鼠结肠Cajal间质细胞的干预效应

Insulin regulates the expression of stem cell factor in rat colonic smooth muscle cells

AIM: To investigate the effect of insulin on the expression of stem cell factor (SCF) in rat colonic smooth muscle cells.

METHODS: Rat colonic smooth muscle cells (SMCs) were separated by mechanical and enzymatic methods and identified by immunofluorescence staining of α-actin. Identified colonic SMCs were randomly divided into two groups: cells treated with different concentrations of insulin (0, 2.5, 5, 20, 40, 80 mg/L) and those treated with insulin for different durations (0, 8, 16, 24 h). The expression of SCF was detected by Western blot and RT-PCR. MTT assay was used to measure the proliferation of colonic SMCs.

RESULTS: At a concentration of 5 mg/L, insulin remarkably promoted the proliferation of colonic SMCs (0.052 ± 0.006 vs 0.018 ± 0.006, P < 0.05). Insulin at a concentration of 2.5, 5 or 20 mg/L promoted SCF expression in colonic SMCs (protein: 0.735 ± 0.035, 0.754 ± 0.057, 0.741 ± 0.051 vs 0.658 ± 0.024; mRNA: 0.688 ± 0.077, 0.690 ± 0.080, 0.698 ± 0.074 vs 0.528 ± 0.053; all P < 0.05), but there were no marked differences in the expression levels of SCF protein and mRNA among these three groups of cells. When the dosage of insulin was elevated to 40 mg/L, SCF expression reached its peak (protein: 0.899 ± 0.048 vs 0.658 ± 0.024; mRNA: 0.938 ± 0.117 vs 0.528 ± 0.053; both P < 0.05). The expression of SCF reached the peak at 16 hours after insulin treatment (protein: 0.899 ± 0.011 vs 0.628 ± 0.015; mRNA: 1.038 ± 0.053 vs 0.709 ± 0.042; both P < 0.05).

CONCLUSION: Insulin promotes cell proliferation and up-regulates SCF expression in rat colonic SMCs.

Transfection with siRNA against ERK1/2 inhibits IGF-1-induced stem cell factor expression in colonic smooth muscle cells

AIM: To investigate how insulin-like growth factor-1 (IGF-1) regulates the expression of stem cell factor (SCF) in colonic smooth muscle cells (SMCs).

METHODS: After rat colonic SMCs were treated with different concentrations of IGF-1 (0, 50, 100, 150 μg/L) for different durations (0, 5, 15, 30, 45, 60 min), the levels of phosphorylated ERK1/2 and SCF were determined by RT-PCR and Western blot. Rat colonic SMCs were then transfected with siRNA against ERK1/2 to examine the impact of ERK1/2 down-regulation on IGF-1-induced SCF expression.

RESULTS: After treatment with IGF-1, the level of phosphorylated ERK1/2 in colonic SMCs reached a peak at about 15 min (0.417 ± 0.036 vs 0.101 ± 0.015; P < 0.05). The optimal concentration of IGF-1 to induce the expression of phosphorylated ERK1/2 and SCF was 100 μg/L (0.790 ± 0.051 vs 0.336 ± 0.013; 0.765 ± 0.061 vs 0.289 ± 0.021, both P < 0.05). After treatment with IGF-1, the expression levels of phosphorylated ERK1/2, total ERK1/2, and SCF in colonic SMCs transfected with siRNA against ERK1/2 were lower than those in the control group (0.284 ± 0.021 vs 0.732 ± 0.005; 0.256 ± 0.015 vs 0.712 ± 0.023; 0.219 ± 0.020 vs 0.673 ± 0.013; 0.621 ± 0.027 vs 1.725 ± 0.012; 0.821 ± 0.019 vs 1.751 ± 0.043; 0.275 ± 0.061 vs 0.531 ± 0.047; all P < 0.05).

CONCLUSION: IGF-1 treatment up-regulated the expression of phosphorylated ERK1/2 and SCF in colonic SMCs, while transfection with siRNA against ERK1/2 down-regulated IGF-1-induced expression of phosphorylated ERK1/2 and SCF, suggesting that the ERK/MAPK pathway may be involved in IGF-1-induced expression of phosphorylated ERK1/2 and SCF.

Insulin-like growth factor-1 upregulates the expression of stem cell factor in rat colonic smooth muscle cells

AIM: To investigate the effects of insulin-like growth factor-1 (IGF-1) on the expression of stem cell factor (SCF) in rat colonic smooth muscle cells (SMCs).

METHODS: Rat colonic SMCs were separated, cultured, and identified by immunofluorescence staining of α-actin. Cultured colonic SMCs were divided into IGF-1 treatment group and IGF-1 receptor antibody intervention group. Cells in the IGF-1 treatment group incubated with different concentrations (0, 5, 10, 50, 100 and 150 μg/L) of IGF-1 for different durations (0, 8, 16, 24 and 48 hours), while those in the IGF-1 receptor antibody intervention group were treated with IGF-1 and different concentrations of IGF-1 receptor monoclonal antibody (0, 50, 100 and 150 μg/L). The expression of SCF in colonic SMCs was examined by Western blot and quantitative reverse transcription-polymerase chain reaction.

RESULTS: Although IGF-1 at low concentrations (5 and 10 μg/L) had no significant impact on the expression of SCF mRNA and protein in SMCs (all P > 0.05), IGF-1 at moderate or high concentrations (50, 100 and 150 μg/L) significantly upregulated the expression of SCF mRNA and protein (all P < 0.05). The optimum concentration of IGF-1 to upregulate SCF expression in vitro was 100 μg/L (0.820 ± 0.061 vs 0.167 ± 0.015 and 1.269 ± 0.219 vs 0.560 ± 0.023, respectively; both P < 0.05), and the peak expression of SCF occurred 16 hours after incubation with IGF-1 (0.420 ± 0.034 vs 0.209 ± 0.001 and 1.407 ± 0.133 vs 0.477 ± 0.041, respectively; both P < 0.05). IGF-1 receptor monoclonal antibody could inhibit the expression of SCF in SMCs in a dose-dependent manner (all P < 0.05).

CONCLUSION: IGF-1 can upregulate the expression of SCF in colonic SMCs perhaps in an IGF-1 receptor-dependent manner.