Glycyrrhetinic acid blocks SARS-CoV-2 infection by activating the cGAS-STING signalling pathway.

BACKGROUND AND PURPOSE: Traditional Chinese medicine (TCM) played an important role in controlling the COVID-19 pandemic, but the scientific basis and its active ingredients are still weakly studied. This study aims to decipher the underlying anti-SARS-CoV-2 mechanisms of glycyrrhetinic acid (GA). EXPERIMENTAL APPROACH: GA's anti-SARS-CoV-2 effect was verified both in vitro and in vivo. Homogeneous time-resolved fluorescence assays, biolayer interferometry technology, and molecular docking were employed to examine interactions of GA with human stimulator of interferon genes (hSTING). Immunofluorescence staining, western blot, and RT-qPCR were used to investigate nuclear translocation of interferon regulatory factor 3 (IRF3) and levels of STING target genes. Pharmacokinetics of GA was studied in mice. KEY RESULTS: GA could directly bind to Ser162 and Tyr240 residues of hSTING, thus up-regulating downstream targets and activation of the STING signalling pathway. Such activation is crucial for limiting the replication of SARS-CoV-2 Omicron in Calu-3 cells and protecting against lung injury induced by SARS-CoV-2 Omicron infection in K18-ACE2 transgenic mice. Immunofluorescence staining and western blot indicated that GA increased levels of phosphorylated STING, phosphorylated TANK-binding kinase-1, and cyclic GMP-AMP synthase (cGAS). Importantly, GA increased nuclear translocation of IRF3. Pharmacokinetic analysis of GA in mice indicated it can be absorbed into circulation and detected in the lung at a stable level. CONCLUSION AND IMPLICATIONS: Activation of the cGAS-STING pathway through the GA-STING-IRF3 axis is essential for the antiviral activity of GA in mice, providing new insights into the potential translation of GA for treating SARS-CoV-2 in patients.

Peroxide derivatives as SARS-CoV-2 entry inhibitors.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of the ongoing coronavirus disease 2019 (COVID-19) pandemic. Host cell invasion is mediated by the interaction of the viral spike protein (S) with human angiotensin-converting enzyme 2 (ACE2) through the receptor-binding domain (RBD). In this work, bio-layer interferometry (BLI) was used to screen a series of fifty-two peroxides, including aminoperoxides and bridged 1,2,4 - trioxolanes (ozonides), with the aim of identifying small molecules that interfere with the RBD-ACE2 interaction. We found that two compounds, compound 21 and 29, exhibit the activity to inhibit RBD-ACE2. They are further demonstrated to inhibit SARS-CoV-2 cell entry, as shown in pseudovirus assay and experiment with authentic SARS-CoV-2. A comprehensive in silico analysis was carried out to study the physicochemical and pharmacokinetic properties, revealing that both compounds have good physicochemical properties as well as good bioavailability. Our results highlight the potential of small molecules targeting RBD inhibitors as potential therapeutic drugs for COVID-19.

San Wu Huangqin decoction regulates inflammation and immune dysfunction induced by influenza virus by regulating the NF-κB signaling pathway in H1N1-infected mice.

ETHNOPHARMACOLOGICAL RELEVANCE: The San Wu Huangqin Decoction (SWHD), which is made from the dried root of Sophora flavescens Aiton (Kushen in Chinese), the dried root of Scutellaria baicalensis Georgi (Huangqin in Chinese), and the dried root tuber of Rehmannia glutinosa (Gaertn.) DC. (Dihuang in Chinese), is a traditional Chinese formula used to treat prolonged fever and inflammatory diseases in clinics and proven to inhibit influenza virus effectively in our previous study. AIM OF THE STUDY: This work was performed to study the regulation of SWHD on inflammation and immune dysfunction induced by the influenza virus and the underlying mechanism in the treatment of SWHD. METHODS: In this study, the influenza virus A/PR/8/34 (H1N1)-infected mouse model was used to investigate the regulation of SWHD on inflammation and immune dysfunction induced by H1N1. The pathological changes, the capacity of proliferation of T and B lymphocytes, the cytotoxicity of natural killer (NK) cells, and the levels of IL-6, TNF-α, IL-1ß, IL-4, and IFN-γ in the serum, bronchoalveolar lavage fluid (BALF), and lung were analyzed. The effects of type 1 T helper cell (Th1) and type 2 T helper cell (Th2) immune responses were discussed indirectly. In addition, the expression levels of p-p65, p65, IKKα/ß, p-IκBα, and IκBα in relation to the NF-κB pathway were measured using Western blot analysis, or immunohistochemical assay. RESULTS: SWHD decreased the pathological changes in lung tissues, promoted the proliferation of T and B lymphocytes, enhanced NK cell activity, and accelerated the phagocytic function of macrophages in H1N1-infected mice. At the same time, SWHD decreased the levels of IL-6, TNF-α, IL-1ß, IFN-γ, and increased the level of IL-4 in the serum, BALF, and lung of model mice. Moreover, the p-p65, p65, and IκBα protein expression levels were inhibited, whereas the p-IκBα protein expression levels were improved in the lungs of H1N1-infected mice. CONCLUSIONS: SWHD can inhibit the replication of the H1N1 virus and reduced the excessive inflammation and immune dysfunction induced by the H1N1 virus in the body. This work provides rich experimental basis for further anti-inflammation research of SWHD and sets the foundation for the development of a viral inflammation drug of traditional Chinese medicine.