Hydroquinone suppresses IFN-β expression by targeting AKT/IRF3 pathway

TLR4/7-mediated host-defense responses of gingival epithelial cells

Gingival epithelial cells (GECs) are physical and immunological barriers against outward pathogens while coping with a plethora of non-pathogenic commensal bacteria. GECs express several members of Toll-like receptors (TLRs) and control subsequent innate immune responses. TLR4 senses lipopolysaccharide (LPS) while TLR7/8 recognizes single-strand RNA (ssRNA) playing important roles against viral infection. However, their distinct roles in GECs have not been fully demonstrated. Here, we analyzed biological responses of GECs to  LPS and CL075, a TLR7/8 agonist. GE1, a mouse gingival epithelial cell line, constitutively express TLR4 and TLR7, but not TLR8, like primary skin keratinocytes. Stimulation of GE1 cells with CL075 induced cytokine, chemokine, and antimicrobial peptide  expressions, the pattern of which is rather different from that with LPS: higher mRNA levels of interferon (IFN) β, CXCL10, and β-defensin (BD) 14 (mouse homolog of human BD3); lower levels of tumor necrosis factor (TNF), CCL5, CCL11, CCL20, CXCL2, and CX3CL1. As for the intracellular signal transduction of GE1 cells, CL075 rapidly induced significant AKT phosphorylation but failed to activate IKKα/β-NFκB pathway, whereas LPS induced marked IKKα/β-NFκB activation without significant AKT phosphorylation. In contrast, both CL075 and LPS induced rapid IKKα/β-NFκB activation and AKT phosphorylation in a macrophage cell line. Furthermore, specific inhibition of AKT activity abrogated CL075-induced IFNβ, CXCL10, and BD14 mRNA expression in GE1 cells. Thus, TLR4/7 ligands appear to induce rather different host-defense responses of GECs through distinct intracellular signaling mechanisms.

Effect of Shenlingyigan decoction on inflammatory factors related to liver injury regulated by TLR3 signaling pathway

Background

To investigate the therapeutic effect of Shenlingyigan decoction on acute liver injury. Further explored the mechanisms involved in the therapeutic properties of Shenlingyigan decoction by test several key proteins (TLR3, TRIF, TBK1, IRF3, IFNβ, IL-1 and IL-6) within the TLR3 signaling pathway.

Methods

The mouse acute liver injury model group was established by pretreatment with D-GalN and Poly (I:C) induction. The acute liver injury mouse treatment groups were gavage with different doses of Shenlingyigan decoction for 3 days. The therapeutic effects of Shenlingyigan decoction were preliminarily evaluated using organ indices, tissue images, and HE staining. Furthermore, potential associated signaling pathways and target effects were predicted through network pharmacology. Western blot experiments were conducted to examine the expression of relevant proteins (TLR3, TRIF, TBK1, IRF3, IL-1, and IL-6). In addition, immunofluorescence assays were performed to assess the localization of IRF3 and IFNβ expression in the cytoplasm and nucleus. Finally, the effects of Shenlingyigan decoction on the expression of TLR3, TRIF, TBK1 and IRF3 genes were further studied by QT-PCR.

Results

The liver organ index, the tissue photos and HE staining showed that Shenlingyigan decoction could reduce inflammation by decreasing the presence of inflammatory cells and downregulating the expression of IL-1 and IL-6. The result of network pharmacology showed 709 potential drug and disease overlapping targets. Toll-like receptor signaling pathway was related with these targets through KEGG analysis. Besides, TLR3, TBK1, IRF3, IL6, were important targets associated with viral hepatitis. Westernblot and Immunofluorescence analysis showed that Shenlingyigan decoction reduced the expression of TLR3 and TBK1 in mice with liver injury, while increasing the expression of IRF3. Shenlingyigan decoction does not significantly affect the expression of TRIF and IFNβ; however, it enhances the expression of IRF3 in the nucleus, consequently leading to increased expression of IFNβ in the nucleus. The results of QT-PCR showed that Shenlingyigan decoction could down-regulate the expression of TLR3, TRIF and TBK1 genes, and up-regulate the expression of IRF3 gene.

Conclusions

Shenlingyigan decoction participated in immune responses by effecting the expression of TLR3 signaling pathway-related factors to treat the acute liver injury.

The crude extract from the flowers of Trollius chinensis Bunge exerts anti-influenza virus effects through modulation of the TLR3 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

The flowers of Trollius chinensis Bunge (Ranunculaceae) is a traditional Chinese medicine used to treat various inflammatory diseases, including upper respiratory infections, chronic tonsillitis, and pharyngitis. Recently, there has been growing research on the antiviral role of the flowers of T. chinensis Bunge. However, little is known about its anti-influenza virus effects and the underlying mechanisms.

AIM OF THE STUDY

This study aims to evaluate the therapeutic effects of the crude extract from the flowers of T. chinensis Bunge (CEFTC) on mice infected with influenza virus. We further explored its mechanism by detecting the expression of vital proteins (TLR3, TBK1, TAK1, IKKα, IRF3, and IFN-β) related to TLR3 signaling pathway.

MATERIALS AND METHODS

Mice were infected with influenza A virus (H1N1) through the nasal cavity and were intragastrically administered CEFTC at the dose of 0.2 mg/g once daily. The therapeutic effects of CEFTC were evaluated by blood cell count, lung index, spleen index, alveolar lavage fluid testing, and HE staining. Network pharmacology analysis predicted the potential signaling pathway between the flowers of T. chinensis Bunge and pneumonia. The expression of TLR3, TBK1, TAK1, IKKα, IRF3, and IFN-β in lung tissues were examined by Western blot assay. In addition, the immunofluorescence assay was applied to assess the effect of CEFTC on the distribution of IRF3 and IFN-β between nuclei and cytoplasm.

RESULTS

Compared with the infected group, the lung index was markedly reduced, and the pathological damage of the lungs was also attenuated in the CEFTC treatment group. The network pharmacology analysis indicated that the NF-κB pathway was a potential signaling pathway in the flowers of T. chinensis Bunge for the treatment of pneumonia, TLR3, IRF3, and TBK1 were crucial targets associated with pneumonia. Western blot assay demonstrated that in the high-dose virus infected group, CEFTC reduced the expression of TLR3, TAK1, TBK1, and IRF3. Furthermore, CEFTC could increase the nuclear distribution of IRF3 in alveolar epithelial cells after virus infection.

CONCLUSIONS

These results suggested that different doses of influenza virus could cause varying infection symptoms in mice. Moreover, CEFTC could exert anti-influenza virus effects by regulating the expression of TLR3, IRF3, IFN-β, TAK1, and TBK1 in the TLR3 signaling pathway.

The STING-IRF3 pathway is involved in lipotoxic injury of pancreatic β cells in type 2 diabetes

Lipotoxic injury of pancreatic β cells is an important pathological feature in type 2 diabetes mellitus (T2DM). Stimulator of interferon genes (STING) can recognize its own DNA leaked into the cytoplasm from damaged mitochondria or nuclei of the host cell, thus activating its downstream factor interferon regulatory factor 3 (IRF3), causing inflammation and apoptosis. The STING-IRF3 signaling pathway is closely related to glycolipid metabolism, but its relationship with the lipotoxicity of pancreatic β cells has rarely been reported. Here, we investigated the role of the STING-IRF3 signaling pathway in lipotoxicity-induced inflammation, apoptosis, and dysfunction of pancreatic β cells. We examined the activation of STING and IRF3 in islets of db/db mice and identified the role of the STING-IRF3 signaling pathway in palmitic acid (PA)-induced lipotoxic injury of INS-1, a rat insulinoma cell line. STING and phosphorylated IRF3 including downstream interferon-β were upregulated in islets of db/db mice and PA-induced INS-1 cells. Gene silencing of STING or IRF3 ameliorated PA-induced INS-1 cell inflammation and apoptosis, and reversed impaired insulin synthesis. Additionally, PA induced downregulation of the phosphoinositide 3-kinase-AKT signaling pathway, and impaired high glucose-stimulated insulin secretion was reversed after knockdown of STING or IRF3. Our results suggest that activation of the STING-IRF3 pathway triggers inflammation and apoptosis of pancreatic β cells, leading to β-cell damage and dysfunction. Hence, inhibition of this signaling pathway may represent a novel approach for β-cell protection in T2DM.

Hydroquinone inhibits PRV infection in neurons in vitro and in vivo

Pseudorabies virus (PRV) is a prevalent and endemic swine pathogen that causes significant economic losses in the global swine industry. Due to the emergence of PRV mutant strains in recent years, vaccines can't completely prevent and control PRV infection. Therefore, research and development of new vaccines and drugs with inhibitory effects on PRV are of great significance in the prevention and treatment of PR. In this study, we firstly screened a library of 44 FDA-approved drugs and found that hydroquinone (HQ) displayed high anti-PRV activity by inhibiting PRV adsorption onto and internalization into cells. This study revealed that hydroquinone treatment stimulated genes associated with the PI3K-AKT signal pathway. HQ increased AKT mRNA production and activated AKT phosphorylation in N2a cells. This finding suggests that HQ significantly inhibits PRV replication by activating the phosphorylation of AKT. We also conducted in vivo experiments in mice. Hydroquinone significantly reduced the viral loads in mouse tissues and the mortality after PRV infection. The above results indicate that hydroquinone significantly inhibits the replication of PRV mutant strain ZJ01 in ICR mice and has an inhibitory effect on PRV. This study will contribute to the development of a novel prophylactic and therapeutic strategy against PRV infection.

Regulation of 8-Hydroxydaidzein in IRF3-Mediated Gene Expression in LPS-Stimulated Murine Macrophages

Cytokines and chemokines are transcriptionally regulated by inflammatory transcription factors such as nuclear factor-κB (NF-κB), activator protein-1 (AP-1), and interferon regulatory factor (IRF)-3. A daidzein derivative compound, 8-hydroxydaidzein (8-HD), isolated from soy products, has recently gained attention due to various pharmacological benefits, including anti-inflammatory activities. However, regulation of the inflammatory signaling mechanism for 8-HD is still poorly understood, particularly with respect to the IRF-3 signaling pathway. In this study, we explored the molecular mechanism of 8-HD in regulating inflammatory processes, with a focus on the IRF-3 signaling pathway using a lipopolysaccharide (LPS) and polyinosinic:polycytidylic acid [Poly (I:C)] stimulated murine macrophage cell line (RAW264.7). The 8-HD downregulated the mRNA expression level of IRF-3-dependent genes by inhibiting phosphorylation of the IRF-3 transcription factor. The inhibitory mechanism of 8-HD in the IRF-3 signaling pathway was shown to inhibit the kinase activity of IKKε to phosphorylate IRF-3. This compound can also interfere with the TRIF-mediated complex formation composed of TRAF3, TANK, and IKKε leading to downregulation of AKT phosphorylation and reduction of IRF-3 activation, resulted in inhibition of IRF-3-dependent expression of genes including IFN-β, C-X-C motif chemokine 10 (CXCL10), and interferon-induced protein with tetratricopeptide repeats 1 (IFIT1). Therefore, these results strongly suggest that 8-HD can act as a promising compound with the regulatory function of IRF-3-mediated inflammatory responses.

Physalactone and 4β-Hydroxywithanolide E Isolated from Physalis peruviana Inhibit LPS-Induced Expression of COX-2 and iNOS Accompanied by Abatement of Akt and STAT1

In previous studies, withanolides isolated from Physalis peruviana were found to exhibit anti-inflammatory potential by suppressing nitrite production induced by lipopolysaccharide (LPS) treatment. Currently, we selected two of the most potent compounds, 4β-hydroxywithanolide E (1) and physalactone (2), to examine the underlying mechanism of action. With LPS-stimulated RAW 264.7 cells in culture, the compounds inhibited the mRNA and protein expression of iNOS and COX-2. To determine which upstream signaling proteins were involved in these effects, phosphorylation levels of three mitogen-activated protein kinases (MAPKs) including ERK1/2, JNK1/2, and p38, were examined, but found unaffected. Similarly, the degradation of IκBα was not attenuated by the compounds. However, phosphorylation of Akt at the Ser-473 residue was inhibited, as was the phosphorylation of STAT1. Interestingly, the compounds also reduced the protein level of total STAT1, possibly by ubiquitin-dependent protein degradation. In sum, these results indicate the potential of 1 and 2 to mediate anti-inflammatory effects through the unexpected mechanism of inhibiting the transcription of iNOS and COX-2 via Akt- and STAT1-related signaling pathways.

Metabolite-Sensing G Protein Coupled Receptor TGR5 Protects Host From Viral Infection Through Amplifying Type I Interferon Responses

The metabolite-sensing G protein–coupled receptors (GPCRs) bind to various metabolites and transmit signals that are important for proper immune and metabolic functions. However, the roles of metabolite-sensing GPCRs in viral infection are not well characterized. Here, we identified metabolite-sensing GPCR TGR5 as an interferon (IFN)-stimulated gene (ISG) which had increased expression following viral infection or IFN-β stimulation in a STAT1-dependent manner. Most importantly, overexpression of TGR5 or treatment with the modified bile acid INT-777 broadly protected host cells from vesicular stomatitis virus (VSV), newcastle disease virus (NDV) and herpes simplex virus type 1 (HSV-1) infection. Furthermore, VSV and HSV-1 replication was increased significantly in Tgr5-deficient macrophages and the VSV distribution in liver, spleen and lungs was increased in Tgr5-deficient mice during VSV infection. Accordingly, Tgr5-deficient mice were much more susceptible to VSV infection than wild-type mice. Mechanistically, TGR5 facilitates type I interferon (IFN-I) production through the AKT/IRF3-signaling pathway, which is crucial in promoting antiviral innate immunity. Taken together, our data reveal a positive feedback loop regulating IRF3 signaling and suggest a potential therapeutic role for metabolite-sensing GPCRs in controlling viral diseases.

Over-expressed miRNA-200b ameliorates ulcerative colitis-related colorectal cancer in mice through orchestrating epithelial-mesenchymal transition and inflammatory responses by channel of AKT2

Our study was to explore the potential role of miRNA-200b in modulating tumorigenesis in the model of ulcerative colitis-related colorectal cancer (UCRCC) and, further, to decipher the underlying mechanisms associated with this effect. In this study, we examined a greater number of polyps or adenomas, a higher grade of epithelial dysplasia accompanied with a decrease in survival ratio in azoxymethane (AOM)/dextran sulfate sodium (DSS) model mice compared to mice treated with over-expressed miRNA-200b. Surprisingly, enforced miRNA-200b expression significantly suppressed AOM/DSS-induced up-regulation of oncologic markers including β-catenin and CD133. Independent of this, treatment with miRNA-200b obviously attenuated inflammatory responses, as indicated by down-regulating tumor necrosis factor-α (TNF-α), transforming growth factor-β (TGF-β) and blockade of AKT2-mediated NF-κB/IL-6/STAT3 signaling pathway. Furthermore, a simultaneous shift in epithelial-mesenchymal transition (EMT) markers such as E-cadherin and N-cadherin were observed to be increased and decreased, respectively. Coupled with the associated influence of over-expressed miRNA-200b were change in colorectal cell morphology shown by Transmission electron microscope (TEM) and a decrease in expression of rho-kinase2 (ROCK2) together with AKT2 phosphorylation (p-AKT2). Moreover, mice which were transfected with negative control of miRNA-200b possessed results that were in line with that obtained from AOM/DSS model mice. Additionally, we demonstrated that the 3'untranslated region (UTR) of AKT2 was a direct target of miRNA-200b through bioinformatics analysis and dual-luciferase assay. Collectively, these findings suggest that miRNA-200b's contribution to tumor-suppressing program was correlated with EMT and inflammatory responses in a AKT2-dependent manner.

Thymoquinone Suppresses IRF-3-Mediated Expression of Type I Interferons via Suppression of TBK1

Interferon regulatory factor (IRF)-3 is known to have a critical role in viral and bacterial innate immune responses by regulating the production of type I interferon (IFN). Thymoquinone (TQ) is a compound derived from black cumin (Nigella sativa L.) and is known to regulate immune responses by affecting transcription factors associated with inflammation, including nuclear factor-κB (NF-κB) and activator protein-1 (AP-1). However, the role of TQ in the IRF-3 signaling pathway has not been elucidated. In this study, we explored the molecular mechanism of TQ-dependent regulation of enzymes in IRF-3 signaling pathways using the lipopolysaccharide (LPS)-stimulated murine macrophage-like RAW264.7 cell line. TQ decreased mRNA expression of the interferon genes IFN-α and IFN-β in these cells. This inhibition was due to its suppression of the transcriptional activation of IRF-3, as shown by inhibition of IRF-3 PRD (III-I) luciferase activity as well as the phosphorylation pattern of IRF-3 in the immunoblotting experiment. Moreover, TQ targeted the autophosphorylation of TANK-binding kinase 1 (TBK1), an upstream key enzyme responsible for IRF-3 activation. Taken together, these findings suggest that TQ can downregulate IRF-3 activation via inhibition of TBK1, which would subsequently decrease the production of type I IFN. TQ also regulated IRF-3, one of the inflammatory transcription factors, providing a novel insight into its anti-inflammatory activities.