Adapalene, an RAR agonist, exerts anti-inflammatory effects by regulating macrophage polarization through...

Area of Science:

• Immunology
• Molecular Biology
• Pharmacology

Background:

• Nuclear receptors, like retinoic acid receptors (RARs), regulate gene expression.
• The role of RARs in macrophage inflammatory responses is not fully understood.
• Adapalene is a selective agonist for RARβ and RARγ.

Purpose of the Study:

• To investigate the anti-inflammatory effects of adapalene in macrophages.
• To elucidate the mechanisms underlying adapalene's anti-inflammatory actions.
• To evaluate adapalene's efficacy in vivo models of inflammation and obesity.

Main Methods:

• RAW264.7 macrophage cell line treated with lipopolysaccharide (LPS) and adapalene.
• RARβ knockdown using small interfering RNA (siRNA) and inhibition with LE135.
• Analysis of MAPK, PI3K/Akt, NF-κB, and STAT3 signaling pathways.
• In vivo studies using C57BL/6J mice and high-fat diet (HFD)-induced obese mice.

Main Results:

• Adapalene inhibited LPS-induced inflammation in a dose-dependent manner.
• Anti-inflammatory effects were dependent on RARβ activation.
• Adapalene suppressed MAPK and PI3K/Akt pathways, inhibiting NF-κB nuclear translocation.
• Adapalene promoted M2 macrophage polarization and increased STAT3 phosphorylation.
• In vivo, adapalene protected against LPS-induced inflammation, liver damage, and mortality.
• Adapalene ameliorated liver inflammation in obese mice.

Conclusions:

• Adapalene exhibits significant anti-inflammatory properties in macrophages via RARβ activation.
• Adapalene modulates key inflammatory signaling pathways.
• Adapalene demonstrates therapeutic potential for inflammatory and metabolic diseases.