Salidroside protects against foam cell formation and apoptosis, possibly via the MAPK and AKT signaling pathways

Figures

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  Fig. 1. Salidroside prevents ox-LDL-induced decrease in the viability of THP1 cells. a THP1 cells were exposed to salidroside at different concentrations (0.1, 1, 10, 25, 50 μM) for 24 h, and cell viability was measured using the CCK8 assay; (b) THP1 cells were exposed to ox-LDL at different concentrations (10, 50, 100, 150, 200 μg/mL) for 24 h, and cell viability was measured using the CCK8 assay; (c) THP1 cells were incubated with salidroside (0.1, 1, 10, 25, 50 μM) for 5 h, followed by treatment with 150 μg/mL ox-LDL for another 24 h. Data are expressed as mean ± standard deviation (SD). # p < 0.05 indicates significant difference from the control group. * p < 0.01 indicates significant difference from the control group

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  Fig. 2. Foam cell formation after 24 h of salidroside pre-treatment. (a) and (b) Oil red staining areas were showed no differences between salidroside-tearted cell groups. However, ox-LDL significantly increased foam cell formation at 10 and 100 μg/mL; (c) THP1 cells were incubated with salidroside (0.1, 1, 10 μM) followed by treatment with 150 μg/mL ox-LDL; (d) Quantitative analysis of foam cell formation. Data are expressed as mean ± standard deviation (SD). Red: Oil red O-positive cells; Scale bars indicate 500 μm; # p < 0.05 indicates significant difference from the control group. * p < 0.01 indicates significant difference from the control group

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  Fig. 3. Salidroside pretreatment affects ABCA1 and LOX1 levels in ox-LDL–induced THP1 cells. (a) Protein expression of ABCA1 in salidroside-treated THP1 cells was analysed by western blotting. β-Actin was used as the control; (b) Quantification of ABCA1 protein expression in salidroside-treated THP1 cells; (c) Protein expression of ABCA1 in ox-LDL-treated THP1 cells was analysed by western blotting. β-Actin was used as the control; (d) Quantification of ABCA1 protein expression in ox-LDL–stimulated THP1 cells; (e) Salidroside treatment significantly decreased LOX1 expression in a dose-dependent manner; (f) Quantification of LOX1 protein expression in salidroside–incubated THP1 cells; (g) Ox-LDL incubation significantly increased LOX1 expression in a dose-dependent manner; (h) Quantification of LOX1 protein expression in the ox-LDL–stimulated THP1 cells; (i) to (k) ABCA1 protein expressions were restored and LOX1 protein expressions were reduced with salidroside treatment in a dose-dependent manner. Data are presented as mean ± standard deviation (SD). # p < 0.05 indicates significant difference from the control group. * p < 0.01 indicates significant difference from the control group

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  Fig. 4. Effect of salidroside pre-treatment on Nrf2/HO1 pathway. (a) to (d) Protein expressions of Nrf2 and HO1 in THP-1 cells treated with salidroside were analyzed by western blotting. β-Actin was used as the control; (e–h) Protein expressions of Nrf2 and HO1 in THP-1 cells analyzed by western blotting. β-Actin was used as the control; (i–k) Nrf2 and treated with ox-LDL were HO1 levels were increased with salidroside treatment in a dose-dependent manner. Data are presented as mean ± standard deviation (SD). # p < 0.05 indicates significant difference from the control group. * p < 0.01 indicates significant difference from the control group

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  Fig. 5. Effect of salidroside on redox parameters after ox-LDL stimulation. (a) and (c) The levels of SOD and GSH were significantly lower in the cells incubated with ox-LDL than in salidroside-treated cells; (b) The levels of MDA were significantly higher in THP1 cells incubated with ox-LDL compared with cells treated with salidroside. # p < 0.05 indicates significant difference between two groups. * p < 0.01 indicates significant difference between two groups

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  Fig. 6. Effect of salidroside pretreatment on ox-LDL–induced THP1 cell apoptosis. (a) THP1 cell apoptosis was determined by flow cytometry. The X and Y axes represent Annexin V and PI fluorescence, respectively; (b) The mean percentage of apoptotic THP1 cells measured by flow cytometry. THP1 cells were treated with or without salidroside for 5 h, followed by treatment with ox-LDL (150 μg/mL) for another 24 h. Data are expressed as mean ± standard deviation (SD). # p < 0.05 indicates significant difference from the control group

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  Fig. 7. Salidroside regulates MAPK and Akt phosphorylation in THP1 cells. a Western blot analysis of p-JNK, total JNK, p-ERK, total ERK, p-p 38, and total p38 levels. β-Actin was used as the control; (b–d) Quantification of p-JNK, total JNK, p-ERK, total ERK, total p38, and p-p38 expression; (e) Western blot analysis of p-Akt and total Akt levels; (f) Quantification of p-Akt, and total Akt expression. Data are presented as mean ± standard deviation (SD). # p < 0.05 indicates significant difference from the control group. * p < 0.01 indicates significant difference from the control group