Abstract
Alternatively activated macrophages have been reported to be helpful to alleviate systematic lupus erythematosus (SLE), and azithromycin could serve as an immunomodulator by promoting alternatively activated macrophage phenotype. However, the effect of azithromycin in SLE and the involved mechanism remain undetermined. The aim of this study is to characterize azithromycin and the underlying mechanism contributing to SLE therapy. First, we compared monocytes from SLE patients and matched healthy donors, and found monocytes from SLE patients exhibited more CD14+CD86+ cells, impaired phagocytic activity, and elevated interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α (the classical activated phenotype), which could be blocked by azithromycin. On the contrary, there were fewer CD14+CD163+ cells in SLE patients, accompanied by decreased arginase (Arg)-1 and found in inflammatory zone (Fizz)-1 (the alternatively activated phenotype). And IL-10, the crucial immune regulatory factor secreted by alternatively activated monocytes/macrophages, also showed a decreased trend in SLE patients. In addition, all these markers were up-regulated after azithromycin treatment. Next, we used activated lymphocyte-derived-DNA to imitate SLE macrophages in vitro to investigate the possible mechanism involved. Azithromycin showed the same effect in imitated SLE macrophages, with distinct Akt phosphorylation at 30 min and 12 h. After inhibiting Akt phosphorylation by LY294002, the down-regulation of CD80, IL-1β, IL-6, and TNF-α caused by azithromycin raised again, meanwhile, the up-regulation of CD206, Arg-1, Fizz-1, and IL-10 due to azithromycin was abolished. Additionally, insulin-like growth factor 1 (IGF-1), the specific agonist of Akt, played a similar role to azithromycin in imitated SLE macrophages. Taken together, our data indicated a novel role of azithromycin in alleviating SLE by promoting alternatively activated macrophage phenotype, and the PI3K/Akt signaling pathway was involved. Our findings provide a rationale for further investigation of novel therapeutic strategy for SLE patients.
Highlights
Systematic lupus erythematosus (SLE) is a multisystem autoimmune disorder which typically affects women of childbearing age
To further examine the function of monocytes, we detected levels of Arg-1, Fizz-1, and IL-10 exhibited a lower trend in SLE patients (N = 6). *p < 0.05, **p < 0.01 the mRNA levels of IL-1β, IL-6, tumor necrosis factor (TNF)-α, Arg-1, Fizz-1, and IL-10
According to the above process, we suggest the macrophage dysfunction might be the initiator of the onset of SLE
Summary
Systematic lupus erythematosus (SLE) is a multisystem autoimmune disorder which typically affects women of childbearing age. The pathogenesis of SLE is not Macrophages, the innate immune cells, are known for the powerful phagocytosis and high plasticity. The typical M1 and M2 induced by traditional stimuli (LPS/IFN-γ, IL-4/IL-10/IL-13) are extremes of a spectrum in a galaxy of phenotypic and functional states[9]. The traditional stimuli, and the local environmental factors could shape macrophage properties ranging from M1 to M29–11. Compared with the lupus-resistant mice, MRL-Faslpr mice fail to shift the macrophage phenotype from the “destroy” (M1) to the “heal” (M2), the persistent inflammatory infiltration triggers lupus nephritis[15]. The SLE patients who received mesenchymal stem cell transplantation show M2 polarity recovery and increased phagocytosis, accompanied with remission[17,18]. All suggest a potential target for SLE treatment by M2 modulation
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