Lentiviral vector-mediated siRNA knockdown of SR-PSOX inhibits foam cell formation in vitro

Aim： To investigate the expression of scavenger receptor that binds phosphatidylserine and oxidized lipoprotein （SR-PSOX）/CXC chemokine ligand 16 （CXCL16） in the human monocyte-derived cell line THP-1, and the effect of lentiviral vectors for the stable delivery of SR-PSOX/CXCL 16 short hairpin RNA on foam cell formation. Methods： A lentiviral expression vector containing enhanced green fluorescence protein （GFP） and SR-PSOX small interfering RNA （siRNA） （Lenti-SR-PSOXsi）, or the control siRNA （Lenti-NC） gene was constructed. A human monocyte-derived cell line THP-1 was transfected with a different multiplicity of infection （MOI） of Lenti-SR-PSOXsi or Lenti-NC, and cultured to obtain stably-transfected THP-1KD and THP-1NC cells. After incubation with oxidatively-modified, low-density lipoprotein （Ox-LDL）, the expression of SR-PSOX/CXCL 16 mRNA was determined by real-time PCR. The expression of the SR-PSOX/CXCL16 protein was detected by flow cytometry analysis. The effect of Lenti-SR-PSOXsi on foam cell formation was assessed by Oil red O-stain analysis. Results： Ox-LDL increased the expres- sion of SR-PSOX/CXCL16 mRNA in a time-and dose-dependent manner in THP-1 cells. Four days after transfection with Lenti-SR-PSOXsi （MOI： 100）, the percentage of GFP expression cells was over 89.3%. The expression of the SR-PSOX/ CXCL 16 mRNA and protein in THP-1KD cells significantly decreased compared with the parent cells, even the THP-1KD cells stimulated with 40 mg/L Ox-LDL. Ox-LDL uptake experiments in THP- 1- and THP- 1KD-derived macrophages indicated that SR-PSOX/CXCL16 deficiency decreased the development of macroph- age-derived foam cell formation. Conclusion： The above data showed that SRPSOX siRNA delivered by using lentiviral vectors in THP- 1 cells was a powerful tool for studying the effect of SR-PSOX, and decreased the expression of the SR- PSOX gene by inhibiting macrophage-derived foam cell formation.