Caragana rosea Turcz Methanol Extract Inhibits Lipopolysaccharide-Induced Inflammatory Responses by Suppressing the TLR4/NF-κB/IRF3 Signaling Pathways

Abstract

Caragana rosea Turcz, which belongs to the Leguminosae family, is a small shrub found in Northern and Eastern China that is known to possess anti-inflammatory properties and is used to treat fever, asthma, and cough. However, the underlying molecular mechanisms of its anti-inflammatory effects are unknown. Therefore, we used lipopolysaccharide (LPS) in RAW264.7 macrophages to investigate the molecular mechanisms that underlie the anti-inflammatory activities of a methanol extract of Caragana rosea (Cr-ME). We showed that Cr-ME reduced the production of nitric oxide (NO) and mRNA levels of iNOS, TNF-α, and IL-6 in a concentration-dependent manner. We also found that Cr-ME blocked MyD88- and TBK1-induced NF-κB and IRF3 promoter activity, suggesting that it affects multiple targets. Moreover, Cr-ME reduced the phosphorylation levels of IκBα, IKKα/β and IRF3 in a time-dependent manner and regulated the upstream NF-κB proteins Syk and Src, and the IRF3 protein TBK1. Upon overexpression of Src and TBK1, Cr-ME stimulation attenuated the phosphorylation of the NF-κB subunits p50 and p65 and IRF3 signaling. Together, our results suggest that the anti-inflammatory activity of Cr-ME occurs by inhibiting the NF-κB and IRF3 signaling pathways.

Lipopolysaccharide-Induced Model of Neuroinflammation: Mechanisms of Action, Research Application and Future Directions for Its Use

“…This dual activation pathway mutually complements and intensifies its action, providing potent pro-inflammatory reaction to bacterial infection. The final result of TLR4 activation is a production of cytokines and chemokines, including IL-1β, IL-6, IL-8, TNF-α, PGE 2 , ROS, NO and type I interferons [ 1 ], [ 22 , 41 ].…”

“…As mentioned earlier, an ideal drug for the treatment of neurodegenerative diseases is not available yet, thus big efforts are being made to develop supportive therapy based on natural substances and extracts. Many plants and animal products have been used for a very long time in the traditional folk medicine to alleviate various conditions, and this premise is often an inspiration for a closer study of their mechanism of action and pharmacological properties [ 41 , 109 ]. Frequently, the first step of investigating anti-inflammatory potential of these substances is the test in LPS-challenged cell lines [ 110 ].…”

“…Studies involving animal models of LPS-induced neuroinflammation are utilized to assess in vivo activity of compounds tested for this purpose for the first time. Both of these methods may be also used with the aim of explaining the exact mechanism of action and specific effects of substances with already established neuroprotective activity [ 41 , 111 , 112 ]. The most important factors limiting the therapeutic use of these substances are often their low bioavailability in humans and not sufficient level of BBB crossing.…”

Emodin treatment of papillary thyroid cancer cell lines in vitro inhibits proliferation and enhances apoptosis via downregulation of NF‑κB and its upstream TLR4 signaling

“…Through molecular interaction and phosphorylation, including recruiting IL-1 and binding to TNF receptor-associated factor 6, activating MEK and AKT, inducing depolymerization of inhibitory factors, cellular NF-κB is activated, resulting in phosphorylation of p65 and p50 (1,(33)(34)(35). In the MyD88-independent pathway, TLR4 directly activates IRF3, which is associated with activation of NF-κB downstream (36). p-p65 and p-p50 can be transferred from the cytoplasm to the nucleus and, as transcription regulators, they participate in activation of the NF-κB pathway (34,37).…”