Inhibition of Janus kinases by tyrosine phosphorylation inhibitor, Tyrphostin AG-490

Genetic Variants Linked to Myocardial Infarction in Individuals with Non-Alcoholic Fatty Liver Disease and Their Potential Interaction with Dietary Patterns

In recent studies, non-alcoholic fatty liver disease (NAFLD) has been associated with a high risk of ischemic heart disease. This study aimed to investigate a genetic variant within a specific gene associated with myocardial infarction (MI) among patients with NAFLD. We included 57,205 participants from a Korean genome and epidemiology study. The baseline population consisted of 45,400 individuals, with 11,805 identified as patients with NAFLD. Genome-wide association studies were conducted for three groups: the entire sample, the healthy population, and patients with NAFLD. We defined the p-value < 1 × 10-5 as the nominal significance and the p-value < 5 × 10-2 as statistically significant for the gene-by-nutrient interaction. Among the significant single-nucleotide polymorphisms (SNPs), the lead SNP of each locus was further analyzed. In this cross-sectional study, a total of 1529 participants (2.8%) had experienced MI. Multivariable logistic regression was performed to evaluate the association of 102 SNPs across nine loci. Nine SNPs (rs11891202, rs2278549, rs13146480, rs17293047, rs184257317, rs183081683, rs1887427, rs146939423, and rs76662689) demonstrated an association with MI in the group with NAFLD Notably, the MI-associated SNP, rs134146480, located within the SORCS2 gene, known for its role in secreting insulin in islet cells, showed the most significant association with MI (p-value = 2.55 × 10-7). Our study identifies candidate genetic polymorphisms associated with NAFLD-related MI. These findings may serve as valuable indicators for estimating MI risk and for conducting future investigations into the underlying mechanisms of NAFLD-related MI.

A CO2-Catalyzed Transamidation Reaction

Transamidation reactions are often mediated by reactive substrates in the presence of overstoichiometric activating reagents and/or transition metal catalysts. Here we report the use of CO₂ as a traceless catalyst: in the presence of catalytic amounts of CO₂, transamidation reactions were accelerated with primary, secondary, and tertiary amide donors. Various amine nucleophiles including amino acid derivatives were tolerated, showcasing the utility of transamidation in peptide modification and polymer degradation (e.g., Nylon-6,6). In particular, N,O-dimethylhydroxyl amides (Weinreb amides) displayed a distinct reactivity in the CO₂-catalyzed transamidation versus a N₂ atmosphere. Comparative Hammett studies and kinetic analysis were conducted to elucidate the catalytic activation mechanism of molecular CO₂, which was supported by DFT calculations. We attributed the positive effect of CO₂ in the transamidation reaction to the stabilization of tetrahedral intermediates by covalent binding to the electrophilic CO₂.

Arbutin Ameliorates Murine Colitis by Inhibiting JAK2 Signaling Pathway

Background and objective: Abnormal activation of Janus kinase 2 (JAK2) promotes the pathogenesis and progress of inflammatory bowel disease (IBD) by stimulating the cytokine traffic. Based on docking studies, arbutin, a natural product extracted from a traditional medicinal plant bearberry, was found to bind to JAK2. The study aimed to investigate the effects and mechanisms of regulating JAK2 by arbutin on colitis in mice.

Methods: A mice colitis model was established to mimic human IBD. The mice freely drank water containing dextran sulfate sodium. Inflammation in epithelial (IEC6) and immune (RAW264.7) cells was analyzed following treatment with lipopolysaccharides (LPS).

Results: Colitis symptoms, including body weight loss, increased disease activity index, and increased colon weight/length ratio, were significantly alleviated by arbutin. Mediators of colonic pro-inflammatory cytokines as well as apoptosis markers in colitis were suppressed by the glycoside. High expression of phosphorylated JAK2 in colitis was significantly reversed by arbutin. The effects of arbutin treatment on colitis were considerably inhibited by the JAK2 inhibitor AG490. LPS-induced inflammatory responses were also suppressed by arbutin, which was notably inhibited by the JAK2 inhibitor AG490.

Conclusion: The findings obtained herein suggest the protective role of arbutin and provide novel insights into alternative colitis treatments, which involve inhibition of the JAK2 signaling pathway.

Piceatannol protects against sepsis-induced myocardial dysfunction via direct inhibition of JAK2

Sepsis-induced myocardial dysfunction (SIMD) represents one of the serious complications secondary to sepsis, which is a leading cause of the high mortality rate among septic cases. Subsequent cardiomyocyte apoptosis, together with the uncontrolled inflammatory response, has been suggested to be closely related to SIMD. Piceatannol (PIC) is verified with potent anti-apoptotic and anti-inflammatory effects, but its function and molecular mechanism in SIMD remain unknown so far. This study aimed to explore the potential role and mechanism of action of PIC in resisting SIMD. The interaction of PIC with JAK2 proteins was evaluated by molecular docking, molecular dynamics (MD) simulation and surface plasmon resonance imaging (SPRi). The cecal ligation and puncture-induced septicemia mice and the LPS-stimulated H9C2 cardiomyocytes were prepared as the models in vivo and in vitro, separately. Molecular docking showed that JAK2-PIC complex had the -8.279 kcal/mol binding energy. MD simulations showed that JAK2-PIC binding was stable. SPRi analysis also showed that PIC has a strong binding affinity to JAK2. PIC treatment significantly ameliorated the cardiac function, attenuated the sepsis-induced myocardial loss, and suppressed the myocardial inflammatory responses both in vivo and in vitro. Further detection revealed that PIC inhibited the activation of the JAK2/STAT3 signaling, which was tightly associated with apoptosis and inflammation. Importantly, pre-incubation with a JAK2 inhibitor (AG490) partially blocked the cardioprotective effects of PIC. Collectively, the findings demonstrated that PIC restored the impaired cardiac function by attenuating the sepsis-induced apoptosis and inflammation via suppressing the JAK2/STAT3 pathway both in septic mice and H9C2 cardiomyocytes.

Role of STAT1 in the resistance of HBV to IFN-α

The objective of the present study was to explore the mechanism of hepatitis B virus (HBV) resistance to interferon (IFN), and the role of signal transducer and activator of transcription 1 (STAT1). HepG2.2.15 cells were stimulated with a long-term (6-24 weeks) low-dose interferon (IFN)α-2b (10-70 IU/ml), so as to construct and screen a HepG2.2.15 cell model resistant to IFNα-2b. The changes of STAT1 and other proteins in the JAK-STAT signaling pathway, before and after drug resistance, were compared. The phosphorylation of STAT1 in HepG2.2.15 cells resistant to IFNα-2b was significantly decreased, and the expression level of 2',5'-oligoadenylate synthetase 1 was downregulated. Decreased phosphorylation of STAT1 in the JAK-STAT signaling pathway a contributor to the development of resistance to IFN-α in HBV.

The JAK2 inhibitor AG490 regulates the Treg/Th17 balance and alleviates DSS-induced intestinal damage in IBD rats

The pathogenesis of inflammatory bowel disease (IBD) remains unclear, and it is currently believed that an imbalance in regulatory T (Treg) cells/T helper 17 cells (Th17 cells) is related to the occurrence and development of IBD. Recently, the JAK2 inhibitor AG490 has been used in animal models such as rheumatoid arthritis and bronchial asthma models and shown to exert immunoregulatory functions that improve disorder in the Treg/Th17 cell balance. This study aimed to evaluate the effect of AG490 on the intestinal inflammatory process in an IBD rat model. A dextran sulfate sodium (DSS)-induced IBD rat model was established, and disease activity index (DAI) scores were calculated. The histopathological damage score was determined by haematoxylin-eosin (H&E) staining. Treg/Th17 cells in the spleen were detected by flow cytometry. The levels of interleukin (IL)-10, IL-6 and IL-17A were detected by enzyme-linked immunosorbent assay (ELISA). AG490 attenuated DSS-induced IBD injury by regulating the Treg/Th17 balance and related cytokine secretion to reduce the DAI and colonic tissue damage. Thus, AG490 may be a new method for effective treatment of IBD.

The influence of central interleukin-6 on behavioral changes associated with acute alcohol intoxication in adult male rats

Recent studies have demonstrated brain cytokine fluctuations associated with acute ethanol intoxication (increased IL-6) and withdrawal (increased IL-1β and TNFα). The purpose of the present studies was to examine the potential functional role of increased central interleukin-6 (IL-6). We utilized two tests of ethanol sensitivity to establish a potential role for IL-6 after high (3.5-4.0 g/kg, intraperitoneally [i.p.]) or moderate (2.0 g/kg, i.p.) doses of ethanol: loss of righting reflex (LORR) and conditioned taste aversion (CTA), respectively. Briefly, guide cannulae were implanted into the third ventricle of adult male Sprague-Dawley rats. In the first experiments, rats were infused with 25, 50, 100, or 200 ng of IL-6; or 0.3, 3.0, or 9.0 μg of the JAK/STAT inhibitor AG490 30 min prior to a high-dose ethanol challenge. Although sleep time was not affected by exogenous IL-6, infusion of AG490 increased latency to lose the righting reflex relative to vehicle-infused rats. Next, we assessed whether IL-6 was sufficient to produce a CTA. Moderately water-deprived rats received intracerebroventricular (i.c.v.) infusions of 25, 50, or 100 ng IL-6 immediately after 60-min access to 5% sucrose solution. Forty-eight hours later, rats were returned to the context and given 60-min access to sucrose solution. IL-6 infusion had no significant effect on sucrose intake when all rats were considered together. However, a median split revealed that low sucrose-consuming rats significantly increased their drinking on test day, an effect that was not seen in rats that received 50 or 100 ng of IL-6. In the last study, AG490 had no effect on ethanol-induced CTA (2 g/kg). Overall, these studies suggest that IL-6 had only a minor influence on ethanol-induced behavioral changes, yet phenotypic differences in sensitivity to IL-6 were apparent. These studies are among the first to examine a potential functional role for IL-6 in ethanol-related behaviors, and may have important implications for understanding the relationship between acute ethanol intoxication and its associated behavioral alterations.

Identification of Chinese Herbal Compounds with Potential as JAK3 Inhibitors

The Janus kinases (JAKs) consist of four similar tyrosine kinases and function as key hubs in the signaling pathways that are implicated in both innate and adaptive immunity. Among the four members, JAK3 is probably the more attractive target for treatment of inflammatory diseases because its inhibition demonstrates the greatest immunosuppression and most profound effect in the treatment of such disorders. Although many JAK3 inhibitors are already available, certain shortcomings have been identified, mostly acquired drug resistance or unwanted side effects. To discover and identify new promising lead candidates, in this study, the structure of JAK3 (3LXK) was obtained from the Protein Data Bank and used for simulation modeling and protein-ligand interaction analysis. The ~36,000 Chinese herbal compounds obtained from TCM Database@Taiwan were virtually screened by AutoDock Vina docking program and filtered with Lipinski's Rules and ADME/T virtual predictions. Because of high occurrence of fake hits during docking, we selected 12 phytochemicals which have demonstrated modulating JAKs expressions among the top 50 chemicals from docking results. To validate whether these compounds are able to directly mediate JAK3 kinase, we have investigated the inhibitory activity using enzymatic activity assays, western blot, and HEK 293 cell STAT5 transactivity assays. The molecular analysis included docking and molecular dynamics (MD) simulations in order to investigate structural conformations and to explore the key amino acids in the interaction between JAK3 kinase and its putative ligands. The results demonstrated that Cryptotanshinone, Icaritin, and Indirubin exhibited substantial inhibitory activity against JAK3 kinase in vitro. The results also provide binding models of the protein-ligand interaction, detailing the interacting amino acid residues at the active ATP-binding domains of JAK3 kinase. In conclusion, our work discovered 3 potential natural inhibitors of JAK3 kinase and could provide new possibilities and stimulate new insights for the treatment of JAK3-targeted diseases.

New insights into the structural dynamics of the kinase JNK3

In this work, we study the dynamics and the energetics of the all-atom structure of a neuronal-specific serine/threonine kinase c-Jun N-terminal kinase 3 (JNK3) in three states: unphosphorylated, phosphorylated, and ATP-bound phosphorylated. A series of 2 µs atomistic simulations followed by a conformational landscape mapping and a principal component analysis supports the mechanistic understanding of the JNK3 inactivation/activation process and also indicates key structural intermediates. Our analysis reveals that the unphosphorylated JNK3 undergoes the ‘open-to-closed’ movement via a two-step mechanism. Furthermore, the phosphorylation and ATP-binding allow the JNK3 kinase to attain a fully active conformation. JNK3 is a widely studied target for small-drugs used to treat a variety of neurological disorders. We believe that the mechanistic understanding of the large-conformational changes upon the activation of JNK3 will aid the development of novel targeted therapeutics.

STAT3/HOTAIR Signaling Axis Regulates HNSCC Growth in an EZH2-dependent Manner

Purpose: PI3K and STAT3 are frequently activated in cancer progression. However, little is known about the underlying mechanisms by which PI3K and STAT3 regulate head and neck squamous cell cancer (HNSCC) growth. The lncRNA HOX transcript antisense RNA (HOTAIR) was found to modulate the progression of HNSCC. In this study, we attempted to establish the correlation of PI3K/STAT3/HOTAIR signaling with the progression of HNSCC and its sensitivity toward platinum-based and targeted anti-EGFR combination therapy.Experimental Design: We first analyzed the STAT3/HOTAIR and PI3K/AKT level in human HNSCC samples. We then activated or suppressed STAT3/HOTAIR and determined the effects on HNSCC cell proliferation in vitro and the growth of UM1 xenograft tumor, an orthotopic model of HNSCC. The sensitivity of HNSCC cells toward cisplatin and cetuximab was determined by in vitro assays.Results: HNSCC samples showed significantly robust expression/activation of STAT3, HOTAIR, PI3K, and AKT, compared with normal squamous epithelium. STAT3 inhibition with WP1066 decreased HOTAIR level and sensitized HNSCC to cisplatin or cetuximab. STAT3 promoted HOTAIR transcription and its interaction with pEZH2-S21, resulting in enhanced growth of HNSCC cells. In addition, overexpression of HOTAIR promoted the growth of UM1 xenograft tumors in vivoConclusions: Our results suggest that STAT3 signaling promotes HNSCC progression via regulating HOTAIR and pEZH2-S21 in HNSCC with PI3K overexpression/activation. These findings provide a rationale to target the STAT3/HOTAIR/pEZH2-S21 regulatory axis for treating patients with HNSCC. Clin Cancer Res; 24(11); 2665-77. ©2018 AACR.

Identification and Analysis of Novel Inhibitors against NS3 Helicase and NS5B RNA-Dependent RNA Polymerase from Hepatitis C Virus 1b (Con1)

Hepatitis C virus (HCV) leads to severe liver diseases, including liver fibrosis, cirrhosis and hepatocellular carcinoma. Non-structural protein 3 helicase (NS3h) and non-structural protein 5B RNA-dependent RNA polymerase (NS5B) are involved in the replication of HCV RNA genome, and have been proved to be excellent targets for discovery of direct-acting antivirals. In this study, two high-throughput screening systems, fluorescence polarization (FP)-based ssDNA binding assay and fluorescence intensity (FI)-based dsRNA formation assay, were constructed to identify candidate NS3h and NS5B inhibitors, respectively. A library of approximately 800 small molecules and crude extracts, derived from marine microorganisms or purchased from the National Compound Resource Center, China, were screened, with three hits selected for further study. Natural compound No.3A5, isolated from marine fungi, inhibited NS3h activity with an IC₅₀ value of 2.8 μM. We further demonstrated that compound No.3A5 inhibited the abilities of NS3h to bind ssDNA in electrophoretic mobility shift assay and to hydrolyze ATP. The NS3h-inhibitory activity of compound No.3A5 was reversible in our dilution assay, which indicated there was no stable NS3h-No.3A5 complex formed. Additionally, compound No.3A5 exhibited no binding selectivity on NS3h or single strand binding protein of Escherichia coli. In NS5B assays, commercial compounds No.39 and No.94 previously reported as kinase inhibitors were found to disrupt dsRNA formation, and their IC₅₀ values were 62.9 and 18.8 μM, respectively. These results highlight how identifying new uses for existing drugs is an effective method for discovering novel HCV inhibitors. To our knowledge, all inhibitors reported in this study were originally discovered with HCV anti-non-structural protein activities in vitro.

Cytokine Signaling in Tumor Progression

Cytokines are molecules that play critical roles in the regulation of a wide range of normal functions leading to cellular proliferation, differentiation and survival, as well as in specialized cellular functions enabling host resistance to pathogens. Cytokines released in response to infection, inflammation or immunity can also inhibit cancer development and progression. The predominant intracellular signaling pathway triggered by cytokines is the JAK-signal transducer and activator of transcription (STAT) pathway. Knockout mice and clinical human studies have provided evidence that JAK-STAT proteins regulate the immune system, and maintain immune tolerance and tumor surveillance. Moreover, aberrant activation of the JAK-STAT pathways plays an undeniable pathogenic role in several types of human cancers. Thus, in combination, these observations indicate that the JAK-STAT proteins are promising targets for cancer therapy in humans. The data supporting this view are reviewed herein.