Icariin Ameliorates Efferocytosis Dysfunction of Alveolar Macrophages Stimulated by Cigarette Smoke Extract via PPARγ Signaling Pathway / 中国实验方剂学杂志

ABSTRACT

ObjectiveTo investigate the mechanism of icariin in ameliorating efferocytosis dysfunction and inflammatory response of alveolar macrophages induced by cigarette smoke extract via the peroxisome proliferator-activated receptor gamma （PPARγ） signaling pathway. MethodThe untreated rat alveolar macrophages （NR8383） were taken as the blank group. The NR8383 cells treated with 10% cigarette smoke extract were divided into model， low-， medium-， and high-dose （10， 20， 40 μmol·L-1） icariin， PPARγ inhibitor， and PPARγ inhibitor + low-， medium-， and high-dose icariin groups. Alamar blue colorimetry was employed to examine the proliferation and toxicity of icariin on NR8383 cells. The efferocytosis rate of NR8383 cells was detected by flow cytometry. Enzyme-linked immunosorbent assay was employed to measure the levels of tumor necrosis factor-alpha （TNF-α）， transforming growth factor-β1 （TGF-β1）， and milk fat globule-epidermal growth factor 8 （MFG-E8）. Western blot and Real-time fluorescence quantitative polymerase chain reaction （Real-time PCR） were employed to determine the protein and mRNA levels， respectively， of PPARγ， CD36， and RAS-related C3 botulinum toxin substrate 1 （Rac1）. ResultThe efferocytosis dysfunction model of NR8383 was established with the cigarette smoke extract. Compared with the blank control group， the model group showed decreased efferocytosis rate （P<0.05）， elevated TNF-α level （P<0.05）， lowered TGF-β1 and MFG-E8 levels （P<0.01）， and down-regulated mRNA and protein levels of PPARγ， CD36， and Rac1 （P<0.05， P<0.01）. Compared with the model group， the treatment with icariin increased the efferocytosis rate （P<0.05， P<0.01）， lowered the TNF-α level （P<0.01）， elevated TGF-β1 and MFG-E8 levels （P<0.05）， and up-regulated the protein and mRNA levels of PPARγ， CD36， and Rac1 （P<0.05， P<0.01）. Compared with icariin alone， PPARγ inhibitor + icariin decreased the efferocytosis rate （P<0.05） and down-regulated the protein and mRNA levels of PPARγ （P<0.05， P<0.01）. In addition， PPARγ inhibitor + low-dose icariin down-regulated the protein level of CD36 （P<0.01） and PPARγ inhibitor + low-/medium-dose icariin up-regulated the protein level of Rac1 （P<0.05）. ConclusionIcariin ameliorates the cigarette smoke extract-induced efferocytosis dysfunction of alveolar macrophage by regulating the PPARγ signaling pathway and cytoskeletal structure rearrangement.