Topical Area: Dietary Bioactive Components
Macrophage activation has become implicated in the pathogenesis of obesity and type 2 diabetes that are now recognized as chronic pro-inflammatory diseases.
However, the mechanisms by which macrophages mediated the enhanced inflammation associated with metabolic defects are not completely understood.This study examined whether 1-20 μM asaronic acid (2,4,5-trimethoxybenzoic acid), identified as one of purple perilla constituents, counteracted inflammatory activation of diabetic macrophages with M1 phenotypes through blocking NF-KB pathway/JAK-STAT signaling.
J774A.1 murine macrophages were incubated with 2 μg/ml lipopolysaccharide (LPS) or 33 mM glucose in the absence and presence of 1-20 μΜ asaronic acid, which led to M1 or diabetic inflammatory state at 48h. The M1 macrophage biomarkers were estimated by conducting Western blot analysis, IHC and ELISA with specific antibodies. Asaronic acid at ≤20 μM was nontoxic during 72 h-incubation.
The presence of asaronic acid reduced the LPS-promoted secretion of pro-inflammatory IL-6 and MCP-1. LPS elevated the induction of the M1 markers of toll-like receptor 4, CD36 and CD68 in macrophages. The LPS exposure to macrophages enhanced NF-κB transactivation, STAT1/ STAT3 activation and SOCS3 induction. However, asaronic acid suppressed the aforementioned effects of LPS. On the other hand, high glucose stimulated macrophages to express advanced glycation end products, receptor for AGE , hypoxia inducible factor-1α and VEGF. Furthermore, glucose enhanced the induction of TLR4 and inducible nitric oxide synthase and IL-6 production in macrophages. Asaronic acid encumbered NF-κB transactivation, activation of JAK2, STAT1/STAT3, and SOCS3 induction in glucose- supplemented macrophages.
These results clearly demonstrated for the first time that asaronic acid may limit diabetic inflammatory activation of macrophages toward the M1 phenotype through inhibition of TLR4- and IL-6-mediated NF-κB pathway/JAK-STAT signaling entailing AGE-RAGE interaction.
Funding Sources :
This work (Grants No. C0501612) was supported by project for Cooperative R&D between Industry, Academy, and Research Institute funded Korea Ministry of SMEs and Startups in 20.