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The anti‐inflammatory effects of Spirulina platensis extract are mediated, in part, through the induction of an endotoxin tolerance‐like mechanism
Author(s) -
Pham Tho X,
Lee JiYoung
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.916.15
Subject(s) - lipopolysaccharide , tumor necrosis factor alpha , chemokine , cytokine , monocyte , chemistry , splenocyte , stimulation , pharmacology , microbiology and biotechnology , inflammation , immunology , endocrinology , biology , biochemistry , in vitro
Endotoxin tolerance is a phenomenon where exposure of innate immune cells to lipopolysaccharide (LPS) induces a refractory state to subsequent endotoxin exposures, which is characterized by a lack of pro‐inflammatory cytokine and chemokine production. We previously showed that pretreatment of macrophages (MΦ) with Spirulina platensis organic extract (SPE) repressed LPS‐induced inflammatory gene expression and cytokine secretion through the inhibition of nuclear factor κB p65 nuclear translocation. We also demonstrated that splenocytes and resident peritoneal MΦ isolated from C57BL/6J mice fed a high fat/high sucrose (HF/HS) diet containing 0.25% (w/w) SPE for 16 weeks displayed significantly attenuated expression of pro‐inflammatory genes when they were stimulated ex vivo by LPS compared to those from mice on a HF/HS control diet. The objective of this study was to investigate if SPE ameliorates LPS‐induced inflammatory gene expression in MΦ via an endotoxin tolerance‐like mechanism. Compared to naïve MΦ exposed to LPS for the first time, endotoxin tolerant (ET) RAW 264.7 MΦ, bone marrow‐derived MΦ, and THP‐1 MΦ showed significantly less interleukin (IL)‐1β expression after stimulation with 100 ng/mL of LPS, which was also observed with SPE pretreatment. The expression of IL‐6, tumor necrosis factor α, and monocyte chemoattractant protein‐1 was also repressed in ET as well as SPE‐pretreated RAW 264.7 MΦ. Consistent with the repressed expression of pro‐inflammatory genes, the translocation of p65 into the nucleus was markedly reduced in both ET and SPE‐pretreated MΦ upon LPS stimulation. It has been demonstrated that nuclear p50 homodimer and B‐cell lymphoma 3‐encoded protein (BCL3) are increased in monocytes and MΦ with endotoxin tolerance, consequently attenuating p65 transcriptional activity. We found that both SPE‐pretreated and ET RAW 264.7 MΦ had increased nuclear protein levels of p50 and BCL3. Quantification of nuclear p50 and p65 proteins showed that in ET and SPE‐pretreated cells, p50/p65 ratios were increased by more than 3‐fold compared to naïve MΦ when they were stimulated with LPS. In addition, ET MΦ showed significantly increased expression of BCL3, p105, inhibitor of κBα and IL‐ receptor‐associated kinase M, all of which are shown to be increased in endotoxin tolerance. In contrast to the LPS‐induced endotoxin tolerance, SPE significantly increased only BCL3 and p105 expression. At the protein level, endotoxin tolerization increased nuclear p50 proteins, but not BCL3, while SPE increased the nuclear abundance of both. In conclusion, the anti‐inflammatory effect of SPE is at least partly attributable to the induction of an endotoxin tolerance‐like state in macrophages, which shares common characteristics of MΦ endotoxin tolerance, while features distinctive from endotoxin tolerance also exist with SPE treatment. Support or Funding Information USDA AFRI (2014‐01870)