Knockout of the c-Jun N-terminal Kinase 2 aggravates the development of mild chronic dextran sulfate sodium colitis independently of expression of intestinal cytokines TNFα, TGFB1, and IL-6

Design, synthesis and biological evaluation of novel O-substituted tryptanthrin oxime derivatives as c-Jun N-terminal kinase inhibitors

The c-Jun N-terminal kinase (JNK) family includes three proteins (JNK1-3) that regulate many physiological processes, including inflammatory responses, morphogenesis, cell proliferation, differentiation, survival, and cell death. Therefore, JNK represents an attractive target for therapeutic intervention. Herein, a panel of novel tryptanthrin oxime analogs were synthesized and evaluated for JNK1-3 binding (K_d) and inhibition of cellular inflammatory responses (IC₅₀). Several compounds exhibited submicromolar JNK binding affinity, with the most potent inhibitor being 6-(acetoxyimino)indolo[2,1-b]quinazolin-12(6H)-one (1j), which demonstrated high JNK1-3 binding affinity (K_d = 340, 490, and 180 nM for JNK1, JNK2, and JNK3, respectively) and inhibited lipopolysaccharide (LPS)-induced nuclear factor-κB/activating protein 1 (NF-κB/AP-1) transcription activity in THP-1Blue cells and interleukin-6 (IL-6) production in MonoMac-6 monocytic cells (IC₅₀ = 0.8 and 1.7 μM, respectively). Compound 1j also inhibited LPS-induced production of several other proinflammatory cytokines, including IL-1α, IL-1β, granulocyte-macrophage colony-stimulating factor (GM-CSF), monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor (TNF) in MonoMac-6 cells. Likewise, 1j inhibited LPS-induced c-Jun phosphorylation in MonoMac-6 cells, directly confirming JNK inhibition. Molecular modeling suggested modes of binding interaction of selected compounds in the JNK3 catalytic site that were in agreement with the experimental JNK3 binding data. Our results demonstrate the potential for developing anti-inflammatory drugs based on these nitrogen-containing heterocyclic systems.

The lipid peroxidation product EKODE exacerbates colonic inflammation and colon tumorigenesis

Oxidative stress is emerging as an important contributor to the pathogenesis of colorectal cancer (CRC), however, the molecular mechanisms by which the disturbed redox balance regulates CRC development remain undefined. Using a liquid chromatography–tandem mass spectrometry-based lipidomics, we found that epoxyketooctadecenoic acid (EKODE), which is a lipid peroxidation product, was among the most dramatically increased lipid molecules in the colon of azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced CRC mice. This is, at least in part, due to increased oxidative stress in colon tumors, as assessed by analyzing gene expression of oxidative markers in AOM/DSS-induced CRC mice and human CRC patients in the Cancer Genome Atlas (TCGA) database. Systemic, short-time treatment with low-dose EKODE increased the severity of DSS-induced colitis, caused intestinal barrier dysfunction and enhanced lipopolysaccharide (LPS)/bacterial translocation, and exacerbates the development of AOM/DSS-induced CRC in mice. Furthermore, treatment with EKODE, at nM doses, induced inflammatory responses via JNK-dependent mechanisms in both colon cancer cells and macrophage cells. Overall, these results demonstrate that the lipid peroxidation product EKODE is an important mediator of colonic inflammation and colon tumorigenesis, providing a novel mechanistic linkage between oxidative stress and CRC development.

Genome-wide association study of an unusual dolphin mortality event reveals candidate genes for susceptibility and resistance to cetacean morbillivirus

Infectious diseases are significant demographic and evolutionary drivers of populations, but studies about the genetic basis of disease resistance and susceptibility are scarce in wildlife populations. Cetacean morbillivirus (CeMV) is a highly contagious disease that is increasing in both geographic distribution and incidence, causing unusual mortality events (UME) and killing tens of thousands of individuals across multiple cetacean species worldwide since the late 1980s. The largest CeMV outbreak in the Southern Hemisphere reported to date occurred in Australia in 2013, where it was a major factor in a UME, killing mainly young Indo-Pacific bottlenose dolphins (Tursiops aduncus). Using cases (nonsurvivors) and controls (putative survivors) from the most affected population, we carried out a genome-wide association study to identify candidate genes for resistance and susceptibility to CeMV. The genomic data set consisted of 278,147,988 sequence reads and 35,493 high-quality SNPs genotyped across 38 individuals. Association analyses found highly significant differences in allele and genotype frequencies among cases and controls at 65 SNPs, and Random Forests conservatively identified eight as candidates. Annotation of these SNPs identified five candidate genes (MAPK8, FBXW11, INADL, ANK3 and ACOX3) with functions associated with stress, pain and immune responses. Our findings provide the first insights into the genetic basis of host defence to this highly contagious disease, enabling the development of an applied evolutionary framework to monitor CeMV resistance across cetacean species. Biomarkers could now be established to assess potential risk factors associated with these genes in other CeMV-affected cetacean populations and species. These results could also possibly aid in the advancement of vaccines against morbilliviruses.

Role of pregnane X-receptor in regulating bacterial translocation in chronic liver diseases

Bacterial translocation (BT) has been impeccably implicated as a driving factor in the pathogenesis of a spectrum of chronic liver diseases (CLD). Scientific evidence accumulated over the last four decades has implied that the disease pathologies in CLD and BT are connected as a loop in the gut-liver axis and exacerbate each other. Pregnane X receptor (PXR) is a ligand-activated transcription factor and nuclear receptor that is expressed ubiquitously along the gut-liver-axis. PXR has been intricately associated with the regulation of various mechanisms attributed in causing BT. The importance of PXR as the mechanistic linker molecule in the gut-liver axis and its role in regulating bacterial interactions with the host in CLD has not been explored. PubMed was used to perform an extensive literature search using the keywords PXR and bacterial translocation, PXR and chronic liver disease including cirrhosis. In an adequate expression state, PXR acts as a sensor for bile acid dysregulation and bacterial derived metabolites, and in response shapes the immune profile beneficial to the host. Activation of PXR could be therapeutic in CLD as it counter-regulates endotoxin mediated inflammation and maintains the integrity of intestinal epithelium. This review mainly focuses PXR function and its regulation in BT in the context of chronic liver diseases.

c-Jun N-terminal kinase 2 promotes enterocyte survival and goblet cell differentiation in the inflamed intestine

c-Jun N-terminal kinases (JNKs) contribute to immune signaling but their functional role during intestinal mucosal inflammation has remained ill defined. Using genetic mouse models, we characterized the role of JNK1 and JNK2 during homeostasis and acute colitis. Epithelial apoptosis, regeneration, differentiation, and barrier function were analyzed in intestinal epithelium-specific (ΔIEC) or complete JNK1 and bone marrow chimeric or complete JNK2 deficient mice as well as double-knockout animals (JNK1^ΔIECJNK2^-/-) during homeostasis and acute dextran sulfate sodium (DSS)-induced colitis. Results were confirmed using human HT-29 cells and wild-type or JNK2-deficient mouse intestinal organoid cultures. We show that nonhematopoietic JNK2 but not JNK1 expression confers protection from DSS-induced intestinal inflammation reducing epithelial barrier dysfunction and enterocyte apoptosis. JNK2 additionally enhanced Atonal homolog 1 expression, goblet cell and enteroendocrine cell differentiation, and mucus production under inflammatory conditions. Our results identify a protective role of epithelial JNK2 signaling to maintain mucosal barrier function, epithelial cell integrity, and mucus layer production in the event of inflammatory tissue damage.

Pregnane X Receptor Activation Attenuates Inflammation-Associated Intestinal Epithelial Barrier Dysfunction by Inhibiting Cytokine-Induced Myosin Light-Chain Kinase Expression and c-Jun N-Terminal Kinase 1/2 Activation

The inflammatory bowel diseases (IBDs) are chronic inflammatory disorders with a complex etiology. IBD is thought to arise in genetically susceptible individuals in the context of aberrant interactions with the intestinal microbiota and other environmental risk factors. Recently, the pregnane X receptor (PXR) was identified as a sensor for microbial metabolites, whose activation can regulate the intestinal epithelial barrier. Mutations in NR1I2, the gene that encodes the PXR, have been linked to IBD, and in animal models, PXR deletion leads to barrier dysfunction. In the current study, we sought to assess the mechanism(s) through which the PXR regulates barrier function during inflammation. In Caco-2 intestinal epithelial cell monolayers, tumor necrosis factor-α/interferon-γ exposure disrupted the barrier and triggered zonula occludens-1 relocalization, increased expression of myosin light-chain kinase (MLCK), and activation of c-Jun N-terminal kinase 1/2 (JNK1/2). Activation of the PXR [rifaximin and [[3,5-Bis(1,1-dimethylethyl)-4-hydroxyphenyl]ethenylidene]bis-phosphonic acid tetraethyl ester (SR12813); 10 μM] protected the barrier, an effect that was associated with attenuated MLCK expression and JNK1/2 activation. In vivo, activation of the PXR [pregnenolone 16α-carbonitrile (PCN)] attenuated barrier disruption induced by toll-like receptor 4 activation in wild-type, but not Pxr-/-, mice. Furthermore, PCN treatment protected the barrier in the dextran-sulfate sodium model of experimental colitis, an effect that was associated with reduced expression of mucosal MLCK and phosphorylated JNK1/2. Together, our data suggest that the PXR regulates the intestinal epithelial barrier during inflammation by modulating cytokine-induced MLCK expression and JNK1/2 activation. Thus, targeting the PXR may prove beneficial for the treatment of inflammation-associated barrier disruption in the context of IBD.

Validation study of peripheral blood diagnostic test for acute rejection in kidney transplantation

BACKGROUND

Diagnosing acute rejection (AR) in kidney transplant recipients typically requires an invasive kidney biopsy. A previous study has suggested that expression of five genes in peripheral blood can indicate the presence of AR in American pediatric kidney transplant recipients. This study aims to validate if these five genes are also useful to diagnose AR in Korean adult kidney transplant patients.

METHODS

Blood samples were collected from 143 patients (39 biopsy-proven AR, 84 stable patients, and 20 other graft injuries) at an average of 9 months posttransplantation and performed real-time PCR for five-gene biomarkers (DUSP1, NKTR, MAPK9, PSEN1, and PBEF1).

RESULTS

Patients with acute cellular rejection (ACR) had a significantly decreased level of MAPK9 and a significantly increased level of PSEN1 when compared with controls and also with patients with other graft injury (OGI). In multivariate logistic regression analysis, for discrimination between ACR and OGI, an excellent diagnostic accuracy was observed in the gene sets but five-gene set generated a higher AUC than two-gene set. With clinical variables combined to these gene sets, the diagnostic accuracy increased in both five-gene set and two-gene set.

CONCLUSIONS

These results support the validity of 5 gene-set for the prediction of AR in Asian adult kidney transplant recipients and suggest the promising role of the peripheral blood gene test in the diagnosis of AR in kidney transplantation.

Jnk2 deletion disrupts intestinal mucosal homeostasis and maturation by differentially modulating RNA-binding proteins HuR and CUGBP1

Homeostasis and maturation of the mammalian intestinal epithelium are preserved through strict regulation of cell proliferation, apoptosis, and differentiation, but the exact mechanism underlying this process remains largely unknown. c-Jun NH2-terminal kinase 2 (JNK2) is highly expressed in the intestinal mucosa, and its activation plays an important role in proliferation and also mediates apoptosis in cultured intestinal epithelial cells (IECs). Here, we investigated the in vivo function of JNK2 in the regulation of intestinal epithelial homeostasis and maturation by using a targeted gene deletion approach. Targeted deletion of the jnk2 gene increased cell proliferation within the crypts in the small intestine and disrupted mucosal maturation as indicated by decreases in the height of villi and the villus-to-crypt ratio. JNK2 deletion also decreased susceptibility of the intestinal epithelium to apoptosis. JNK2-deficient intestinal epithelium was associated with an increase in the level of the RNA-binding protein HuR and with a decrease in the abundance of CUG-binding protein 1 (CUGBP1). In studies in vitro, JNK2 silencing protected intestinal epithelial cell-6 (IEC-6) cells against apoptosis and this protection was prevented by inhibiting HuR. Ectopic overexpression of CUGBP1 repressed IEC-6 cell proliferation, whereas CUGBP1 silencing enhanced cell growth. These results indicate that JNK2 is essential for maintenance of normal intestinal epithelial homeostasis and maturation under biological conditions by differentially modulating HuR and CUGBP1.

The impact of JNK inhibitor D-JNKI-1 in a murine model of chronic colitis induced by dextran sulfate sodium

Purpose:

The c-Jun N-terminal kinases (JNK) are involved in the activation of T cells and the synthesis of proinflammatory cytokines. Several studies have established the relevance of the JNK pathway in inflammatory bowel diseases. The present study analyzed the therapeutic effect of D-JNKI-1, a specific JNK-inhibiting peptide, in a low-dose dextran sulfate sodium (DSS) model of chronic colitis.

Methods:

DSS colitis was induced in female C57/BL6 mice by cyclic administration using different concentrations of DSS (1.0% and 1.5%). Mice in the intervention groups received subcutaneous administration of 1 μg/kg D-JNKI-1 on days 2, 12, and 22. They were monitored daily to assess the severity of colitis, body weight, stool consistency, and the occurrence of occult blood or gross rectal bleeding using evaluation of the disease activity index. The animals were sacrificed after 30 days, and the inflamed intestine was histologically evaluated using a crypt damage score. Immunohistochemical quantification of CD4⁺ and CD8⁺ cells was also carried out.

Results:

Administration of 1 μg/kg D-JNKI-1 resulted in a significant decrease in the disease activity index (P = 0.013 for 1.0% DSS; P = 0.007 for 1.5% DSS). As a mild form of colitis was induced, histological examination did not show any distinct damage to the mucosa and crypts. However, expression of CD4⁺ and CD8⁺ cells was reduced in mice treated with D-JNKI-1 (not significant).

Conclusion:

Administration of D-JNKI-1 resulted in a clinical attenuation of chronic DSS colitis, and a therapeutic effect of D-JNKI-1 must therefore be assumed. The decrease in CD4⁺ and CD8⁺ cells may reflect the influence of D-JNKI-1 on T-cell activation, differentiation, and migration.