Active Flavonoids From Lagotis brachystachya Attenuate Monosodium Urate-Induced Gouty Arthritis via Inhibiting TLR4/MyD88/NF-κB Pathway and NLRP3 Expression.

Xiang Ouyang,Ji-Xiao Zhu,Li-Tao Yi,Min-Xia Guo,Na-Zhi Li,Man-Man Zhang,Jie Cheng

doi:10.3389/fphar.2021.760331

Abstract

Lagotis brachystachya Maxim is a characteristic herb commonly used in Tibetan medicine. Tibetan medicine records it as an important medicine for the clinical treatment of “Yellow Water Disease,” the symptoms of which are similar to that of arthritis. Our previous study showed that the flavonoid fraction extracted from L. brachystachya could attenuate hyperuricemia. However, the effects of the active flavonoids on gouty arthritis remain elusive, and the underlying mechanism is not understood. In the present study, the effects of the active flavonoids were evaluated in rats or Raw264.7 cells with gouty arthritis induced by monosodium urate (MSU) crystal, followed by the detection of TLR4, MyD88, pNF-κB, and NLR family pyrin domain-containing 3 (NLRP3) expression. The swelling of the ankle joint induced by MSU crystal began to be relieved 6 h post the administration with the active flavonoids. In addition, the active flavonoids not only alleviated MSU crystal-induced inflammation in synovial tissues by histopathological examination but also reduced tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β) levels in the joint tissue fluid of MSU crystal-induced rats. Furthermore, Western blot analysis indicated that the active flavonoids reduced the production of these cytokines by inhibiting the TLR4/MyD88/NF-κB pathway and decreasing NLRP3 expression in synovial tissues of rats. More importantly, the inhibition of TLR4/MyD88/NF-κB pathway and NLRP3 expression was also confirmed in MSU-induced Raw264.7 cells. In conclusion, these results indicated that the active flavonoids from L. brachystachya could effectively attenuate gouty arthritis induced by MSU crystal through the TLR4/MyD88/NF-κB pathway and NLRP3 expression in vivo and in vitro, suggesting several potential candidates for the treatment of gouty arthritis.

Highlights

Gouty arthritis is characterized by the deposition of urate in the joint capsule, bursa, cartilage, bone, and other tissues, accompanied by inflammation (Ragab et al, 2017)
The results showed that luteolin, luteoloside, and apigenin could enter into the inhibitory pockets of TLR4 and NLR family pyrin domain-containing 3 (NLRP3), indicating the potential roles in the inhibition of inflammation
Compared with the model group, colchicine and active flavonoids can significantly reduce the swelling of the ankle joint from 6–48 h post monosodium urate (MSU) crystal injection

Summary

Introduction

Gouty arthritis is characterized by the deposition of urate in the joint capsule, bursa, cartilage, bone, and other tissues, accompanied by inflammation (Ragab et al, 2017). A recent study indicated that luteolin-attenuated MSU crystal inducedgouty arthritis via inhibiting the TLR/MyD88/NF-κB pathway (Shen et al, 2020). Several previous studies have shown that luteolin (Dong et al, 2021; Lee et al, 2021), luteoloside (Fan et al, 2014; Wang, Z. et al, 2021), and apigenin (Zhang et al, 2014; Zhao et al, 2019) could inhibit TLR4 signaling and NLRP3 expression. The results showed that luteolin, luteoloside, and apigenin could enter into the inhibitory pockets of TLR4 and NLRP3, indicating the potential roles in the inhibition of inflammation. These observations above provided a speculation that these three flavonoids might alleviate gouty arthritis via the TLR4/MyD88/NF-κB pathway and NLRP3 expression. The effects and underlying mechanism of the three active flavonoids (luteolin, luteoloside, and apigenin) were investigated in vivo and in vitro

Methods

Results

Conclusion