Abstract: 【Abstract】 Objective To evaluate the effect of curcumin on phagocytic function of macrophages after the stimulation with exosomes from patients with systemic lupus erythematosus （SLE）. Methods From February 2016 to November 2017, 18 patients with active SLE and 18 healthy controls were enrolled from Guangzhou Institute of Dermatology and Sun Yat-sen Memorial Hospital, Sun Yat-sen University, and serum exosomes were extracted from these subjects. The exosomes from the healthy controls （CON-exo） and SLE patients （SLE-exo） as well as different concentrations （1, 5, 20 μmol/L） of curcumin were used alone or in combination to stimulate the acute monocytic leukemia cell line THP-1-derived macrophages. After coincubation of the stimulated macrophages with pHrodo?Red indicator, flow cytometry was performed to determine the average fluorescence intensity, immunofluorescence staining to calculate the proportion of pHrodo?Red-positive macrophages, and then the phagocytic activity of macrophages was assessed. Western blot analysis was conducted to determine the protein expression of CD14 in the stimulated macrophages. Statistical analysis was carried out by Student-t test for comparison between two groups, one-way analysis of variance for comparison among several groups, and least significant difference （LSD）-t test for multiple comparisons. Results Flow cytometry showed that there were significant differences in the relative fluorescence intensity of macrophages among the CON-exo group, CON-exo + 20 μmol/L curcumin group, SLE-exo group and SLE-exo + 20 μmol/L curcumin group （101.3% ± 14.05%, 94.27% ± 14.13%, 41.02% ± 9.54% and 87.33% ± 15.01%, respectively; F = 10.81, P < 0.01）, and immunofluorescence staining revealed that the proportion of pHrodo Red-positive macrophages significantly differed among the above 4 groups （82.16% ± 5.20%, 81.33% ± 4.51%, 54.20% ± 9.31% and 71.23% ± 5.43% respectively; F = 12.42, P < 0.01）. The fluorescence intensity of macrophages and proportion of pHrodo-positive macrophages were both significantly lower in the SLE-exo group than in the CON-exo group （t = 5.26, 5.35 respectively, both P < 0.01） and SLE-exo + 20 μmol/L curcumin group （t = 3.97, 3.26 respectively, both P < 0.05）. Western blot analysis showed that there were significant differences in the protein expression of CD14 among the CON-exo group, SLE-exo group, SLE-exo + 1 μmol/L curcumin group, SLE-exo + 5 μmol/L curcumin group and SLE-exo + 20 μmol/L curcumin group （96.33% ± 13.65%, 30.67% ± 5.86%, 45.24% ± 8.89%, 72.81% ± 6.62% and 90.67% ± 12.66% respectively; F = 24.57, P < 0.01）. The protein expression of CD14 was significantly lower in the SLE-exo group than in the CON-exo group（t = 8.06, P < 0.001）, SLE-exo + 5 μmol/L curcumin group and SLE-exo + 20 μmol/L curcumin group（t = 5.08, 7.38, both P < 0.001）, and the CD14 level showed an increasing trend along with the increase in the concentration of curcumin. Conclusion Exosomes from SLE patients markedly inhibit the phagocytosis of macrophages, while curcumin can reverse this inhibitory effect.

Key words: Lupus erythematosus, systemic, Exosomes, Curcumin, Macrophages, Cytophagocytosis