Arteannuin-B and (3-Chlorophenyl)-2-Spiroisoxazoline Derivative Exhibit Anti-Inflammatory Effects in LPS-Activated RAW 264.7 Macrophages and BALB/c Mice-Induced Proinflammatory Responses via Downregulation of NF-κB/P38 MAPK Signaling

Arteannuin B, a sesquiterpene lactone from Artemisia annua, attenuates inflammatory response by inhibiting the ubiquitin-conjugating enzyme UBE2D3-mediated NF-κB activation

BACKGROUND

Anomalous activation of NF-κB signaling is associated with many inflammatory disorders, such as ulcerative colitis (UC) and acute lung injury (ALI). NF-κB activation requires the ubiquitination of receptor-interacting protein 1 (RIP1) and NF-κB essential modulator (NEMO). Therefore, inhibition of ubiquitation of RIP1 and NEMO may serve as a potential approach for inhibiting NF-κB activation and alleviating inflammatory disorders.

PURPOSE

Here, we identified arteannuin B (ATB), a sesquiterpene lactone found in the traditional Chinese medicine Artemisia annua that is used to treat malaria and inflammatory diseases, as a potent anti-inflammatory compound, and then characterized the putative mechanisms of its anti-inflammatory action.

METHODS

Detections of inflammatory mediators and cytokines in LPS- or TNF-α-stimulated murine macrophages using RT-qPCR, ELISA, and western blotting, respectively. Western blotting, CETSA, DARTS, MST, gene knockdown, LC-MS/MS, and molecular docking were used to determine the potential target and molecular mechanism of ATB. The pharmacological effects of ATB were further evaluated in DSS-induced colitis and LPS-induced ALI in vivo.

RESULTS

ATB effectively diminished the generation of NO and PGE2 by down-regulating iNOS and COX2 expression, and decreased the mRNA expression and release of IL-1β, IL-6, and TNF-α in LPS-exposed RAW264.7 macrophages. The anti-inflammatory effect of ATB was further demonstrated in LPS-treated BMDMs and TNF-α-activated RAW264.7 cells. We further found that ATB obviously inhibited NF-κB activation induced by LPS or TNF-α in vitro. Moreover, compared with ATB, dihydroarteannuin B (DATB) which lost the unsaturated double bond, completely failed to repress LPS-induced NO release and NF-κB activation in vitro. Furthermore, UBE2D3, a ubiquitin-conjugating enzyme, was identified as the functional target of ATB, but not DATB. UBE2D3 knockdown significantly abolished ATB-mediated inhibition on LPS-induced NO production. Mechanistically, ATB could covalently bind to the catalytic cysteine 85 of UBE2D3, thereby inhibiting the function of UBE2D3 and preventing ubiquitination of RIP1 and NEMO. In vivo, ATB treatment exhibited robust protective effects against DSS-induced UC and LPS-induced ALI.

CONCLUSION

Our findings first demonstrated that ATB exerted anti-inflammatory functions by repression of NF-κB pathway via covalently binding to UBE2D3, and raised the possibility that ATB could be effective in the treatment of inflammatory diseases and other diseases associated with abnormal NF-κB activation.

In vitro and in vivo anti-eczema effect of Artemisia annua aqueous extract and its component profiling

ETHNOPHARMACOLOGICAL RELEVANCE

Artemisia annua L. belongs to the Asteraceae family and has a long history of clinical application in China. It has been widely used for centuries to treat fever, malaria, jaundice and some skin diseases (such as scabies and sores). Modern pharmacological studies have shown that it has anti-inflammatory, immunomodulatory, antimalarial and antibacterial effects.

AIM OF STUDY

This study aimed to investigate the anti-eczema effect of A. annua aqueous extract (AAE), profile its potential bioactive components and try to explore its possible underlying mechanisms.

MATERIALS AND METHODS

The MTT assay was employed to assess the cytotoxicity of AAE. The anti-eczema effect of AAE was evaluated using both an in vitro 3D epidermal inflammation model and an in vivo guinea pig itching model. The bioactive components of AAE were characterized by ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry coupled with the UNIFI platform.

RESULTS

In this study, we found that AAE is safe for primary human skin keratinocytes at concentrations ranging from 31.3 μg/mL to 250 μg/mL. Further investigations indicate that AAE can increase the itching threshold, inhibit the expression of the inflammatory cytokine TSLP, and promote the expression of FLG mRNA. Additionally, the utilization of UPLC-QTOF/MS and UNIFI platform enabled us to identify 61 potential bioactive components of AAE, with sesquiterpenes and phenolic acids being the most abundant components.

CONCLUSIONS

In this study, the anti-inflammatory and anti-itch effects of the A. annua extract were revealed, along with sesquiterpenes and phenolic acids were identified as potential bioactive components according to literature. The AAE extract holds potential for utilization in the treatment of eczema.