Esculetin inhibited fever, pain, and inflammatory responses via binding to HSC70

Viola tianshanica Maxim, a member of the Violaceae plant family, has been traditionally used in Uighur medicine to treat pneumonia, headaches, and other ailments. A preliminary study demonstrated its antipyretic activity; however, the active components responsible for this effect have not yet been elucidated.

In light of the traditional use of Viola tianshanica Maxim as an anti-inflammatory and analgesic agent in Uighur medicine, this study aims to investigate the effects of esculetin, an ethanol-extracted active compound from Viola tianshanica, on inflammation induced by lipopolysaccharide (LPS) and to explore its underlying mechanisms of action. The study seeks to elucidate the molecular pathways through which esculetin exerts its therapeutic effects and to provide scientific evidence supporting its traditional medicinal applications.

The antipyretic effect was evaluated using a yeast-induced hyperthermia model. The antinociceptive effect was assessed using the acetic acid-induced writhing test and the egg white-induced paw edema method. The chemical biology method was used to design and synthesize the alkynyl-esculetin molecular probe, and the potential target protein was identified through network pharmacology analysis, magnetic trapping technology, Western blotting (WB) analysis, cellular thermal shift assay (CETSA), and surface plasmon resonance (SPR).

We observed that esculetin could inhibit fever, pain, and inflammatory responses, suppress LPS-induced cyclooxygenase-2 (COX-2) and prostaglandin E₂ (PGE₂) expression, and reduce the levels of related pro-inflammatory factors, such as interleukin (IL-1β), IL-12, and tumor necrosis factor-alpha. Network pharmacology analysis indicated that the MAPK pathway may play a key role. Meanwhile, gene ontology analysis revealed that heat shock protein binding is involved in this process. Target fishing, CETSA, SPR, and WB assays demonstrated that esculetin targeted heat shock cognate 70 (HSC70) and reduced its protein stability. Additionally, esculetin downregulated the phosphorylation of extracellular signal-regulated kinase, protein kinase B (Akt), p38 mitogen-activated protein kinase (p38/MAPK), and AMP-activated protein kinase (AMPK). Molecular docking indicated that hydrophobic interactions and hydrogen bonding are the primary binding forces. Subsequently, HSC70 knockdown abolished the anti-inflammatory effects of esculetin.

The present study indicates that esculetin exhibited antipyretic, analgesic, and anti-inflammatory effects through binding with HSC70 and downregulated the p38/MAPK pathway. This study provides a new perspective for developing antipyretic, analgesic, and anti-inflammatory drugs.