Cold Stress Induces Apoptosis in Silver Pomfret via DUSP-JNK Pathway

We cultured silver pomfret for 20 days, decreasing water temperature from 18 to 8 ℃, and sampled muscle every 5 days. Muscle fiber degeneration and apoptosis began to increase at 13 ℃ detected by HE and TUNEL staining. Further analysis of transcriptome revealed that several apoptosis-related pathways were highly enriched by differentially expressed genes (DEGs). We analyzed 10 DEGs from these pathways by RT-qPCR during the temperature-decreasing process. JNK1, PIDD, CytC, Casp 3, and GADD45 were up-regulated after 15 and 20 days, while DUSP3, JNK2, and PARP genes were down-regulated after 15 and 20 days. DUSP5 was up-regulated from 10 to 20 days, and C-JUN was up-regulated after 20 days. We analyzed apoptosis in PaM cells under different temperatures (26 ℃, 23 ℃, 20 ℃, 17 ℃, and 14 ℃). The cell viability significantly declined from 14 to 20 ℃; the TUNEL and IHC results showed that the apoptosis signal increased with the temperature dropping, especially in 17 ℃ and 14 ℃; DUSP5, JNK1, CytC, C-JUN, Casp 3, and GADD45 were up-regulated at 17 ℃ and 14 ℃, and PIDD was up-regulated at 20 ℃, 17 ℃, and 14 ℃. DUSP3 was up-regulated at 20 ℃ but down-regulated at 17 ℃ and 14 ℃, and PARP was down-regulated at 17 ℃ and 14 ℃. JNK2 was up-regulated at 20 ℃ but down-regulated at 17 ℃ and 14 ℃. Our results suggest that DUSP could help inhibit apoptosis in the initial stage of cold stress, but low temperature could down-regulate it and up-regulate JNK-C-JUN, inducing apoptosis in a later stage. These data provide a basis for the study of the response mechanism of fish to cold.

MAPK9 is Correlated with a Poor Prognosis and Tumor Progression in Glioma

BACKGROUND

Glioma has a high incidence in young and middle-aged adults and a poor prognosis. Because of late diagnosis and uncontrollable recurrence of the primary tumor after failure of existing treatments, glioma patients tend to have a poor prognosis. Recent advances in research have revealed that gliomas exhibit unique genetic features. Mitogen-activated protein kinase 9 (MAPK9) is significantly upregulated in mesenchymal glioma spheres and may be a new target for glioma diagnosis. This study aimed to investigate the potential diagnostic significance and predictive value of MAPK9 in glioma.

METHODS

Paraffin-embedded tumor tissues and paracancerous tissues were collected from 150 glioma patients seen at the General Hospital of Northern Theater Command. Immunohistochemistry and western blot assays were used to detect the expression levels of MAPK9. Prognosis and survival analyses were performed using SPSS 26 software for univariate/multivariate analysis and log-rank analysis. Cellular models were used to assess the effect of MAPK9 overexpression and knockdown in vitro.

RESULTS

MAPK9 expression was higher in glioma tissues than in paraneoplastic tissues. Prognostic and survival analyses revealed that the MAPK9 expression level is an independent prognostic factor in glioma patients. In addition, overexpression of MAPK9 significantly promoted the proliferation and migration of primary glioma cells, possibly via the Wnt/β-catenin-regulated EMT pathway.

CONCLUSIONS

MAPK9 is an independent prognostic factor in glioma and is involved in tumor progression.

c-Jun N-terminal kinase (JNK) signaling contributes to cystic burden in polycystic kidney disease

Polycystic kidney disease is an inherited degenerative disease in which the uriniferous tubules are replaced by expanding fluid-filled cysts that ultimately destroy organ function. Autosomal dominant polycystic kidney disease (ADPKD) is the most common form, afflicting approximately 1 in 1,000 people. It primarily is caused by mutations in the transmembrane proteins polycystin-1 (Pkd1) and polycystin-2 (Pkd2). The most proximal effects of Pkd mutations leading to cyst formation are not known, but pro-proliferative signaling must be involved for the tubule epithelial cells to increase in number over time. The c-Jun N-terminal kinase (JNK) pathway promotes proliferation and is activated in acute and chronic kidney diseases. Using a mouse model of cystic kidney disease caused by Pkd2 loss, we observe JNK activation in cystic kidneys and observe increased nuclear phospho c-Jun in cystic epithelium. Genetic removal of Jnk1 and Jnk2 suppresses the nuclear accumulation of phospho c-Jun, reduces proliferation and reduces the severity of cystic disease. While Jnk1 and Jnk2 are thought to have largely overlapping functions, we find that Jnk1 loss is nearly as effective as the double loss of Jnk1 and Jnk2. Jnk pathway inhibitors are in development for neurodegeneration, cancer, and fibrotic diseases. Our work suggests that the JNK pathway should be explored as a therapeutic target for ADPKD.

Autosomal dominant polycystic kidney disease is a leading cause of end stage renal disease requiring dialysis or kidney transplant. During disease development, the cells lining the kidney tubules proliferate. This proliferation transforms normally small diameter tubules into fluid-filled cysts that enlarge with time, eventually destroying all kidney function. Despite decades of research, polycystic kidney disease remains incurable. Furthermore, the precise signaling events involved in cyst initiation and growth remain unclear. The c-Jun N-terminal kinase (JNK), is a major pathway regulating cellular proliferation and differentiation but its importance to polycystic kidney disease was not known. We show that JNK activity is elevated in cystic kidneys and that reducing JNK activity decreases cyst growth pointing to JNK inhibition as a therapeutic strategy for treating polycystic kidney disease.

Phosphorylation and Stabilization of PIN1 by JNK Promote Intrahepatic Cholangiocarcinoma Growth

BACKGROUND AND AIMS

Intrahepatic cholangiocarcinoma (ICC) is a highly aggressive type of liver cancer in urgent need of treatment options. Aberrant activation of the c-Jun N-terminal kinase (JNK) pathway is a key feature in ICC and an attractive candidate target for its treatment. However, the mechanisms by which constitutive JNK activation promotes ICC growth, and therefore the key downstream effectors of this pathway, remain unknown for their applicability as therapeutic targets. Our aim was to obtain a better mechanistic understanding of the role of JNK signaling in ICC that could open up therapeutic opportunities.

APPROACH AND RESULTS

Using loss-of-function and gain-of-function studies in vitro and in vivo, we show that activation of the JNK pathway promotes ICC cell proliferation by affecting the protein stability of peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (PIN1), a key driver of tumorigenesis. PIN1 is highly expressed in ICC primary tumors, and its expression positively correlates with active JNK. Mechanistically, the JNK kinases directly bind to and phosphorylate PIN1 at Ser115, and this phosphorylation prevents PIN1 mono-ubiquitination at Lys117 and its proteasomal degradation. Moreover, pharmacological inhibition of PIN1 through all-trans retinoic acid, a Food and Drug Administration-approved drug, impairs the growth of both cultured and xenografted ICC cells.

CONCLUSIONS

Our findings implicate the JNK-PIN1 regulatory axis as a functionally important determinant for ICC growth, and provide a rationale for therapeutic targeting of JNK activation through PIN1 inhibition.

Placental Insulin/IGF-1 Signaling, PGC-1α, and Inflammatory Pathways Are Associated With Metabolic Outcomes at 4-6 Years of Age: The ECHO Healthy Start Cohort

An adverse intrauterine environment is associated with the future risk of obesity and type 2 diabetes. Changes in placental function may underpin the intrauterine origins of adult disease, but longitudinal studies linking placental function with childhood outcomes are rare. Here, we determined the abundance and phosphorylation of protein intermediates involved in insulin signaling, inflammation, cortisol metabolism, protein glycosylation, and mitochondrial biogenesis in placental villus samples from healthy mothers from the Healthy Start cohort. Using MANOVA, we tested the association between placental proteins and offspring adiposity (fat mass percentage) at birth (n = 109) and infancy (4-6 months, n = 104), and adiposity, skinfold thickness, triglycerides, and insulin in children (4-6 years, n = 66). Placental IGF-1 receptor protein was positively associated with serum triglycerides in children. GSK3β phosphorylation at serine 9, a readout of insulin and growth factor signaling, and the ratio of phosphorylated to total JNK2 were both positively associated with midthigh skinfold thickness in children. Moreover, peroxisome proliferator-activated receptor γ coactivator (PGC)-1α abundance was positively associated with insulin in children. In conclusion, placental insulin/IGF-1 signaling, PGC-1α, and inflammation pathways were positively associated with metabolic outcomes in 4- to 6-year-old children, identifying a novel link between placental function and long-term metabolic outcomes.

Causal roles of stress kinase JNK2 in DNA methylation and binge alcohol withdrawal-evoked behavioral deficits

Excessive binge alcohol intake is a common drinking pattern in humans, especially during holidays. Cessation of the binge drinking often leads to aberrant withdrawal behaviors, as well as serious heart rhythm abnormalities (clinically diagnosed as Holiday Heart Syndrome (HHS)). In our HHS mouse model with well-characterized binge alcohol withdrawal (BAW)-induced heart phenotypes, BAW leads to anxiety-like behaviors and cognitive impairment. We have previously reported that stress-activated c-Jun NH(2)-terminal kinase (JNK) plays a causal role in BAW-induced heart phenotypes. In the HHS brain, we found that activation of JNK2 (but not JNK1 and JNK3) in the prefrontal cortex (PFC), but not hippocampus and amygdala, led to anxiety-like behaviors and impaired cognition. DNA methylation mediated by a crucial DNA methylation enzyme, DNA methyltransferase1 (DNMT1), is known to be critical in alcohol-associated behavioral deficits. In HHS mice, JNK2 in the PFC (but not hippocampus and amygdala) causally enhanced total genomic DNA methylation via increased DNMT1 expression, which was regulated by enhanced binding of JNK downstream transcriptional factor c-JUN to the DNMT1 promoter. JNK2-specific inhibition either by an inhibitor JNK2I or JNK2 knockout completely offset c-JUN-regulated DNMT1 upregulation and restored the level of DNA methylation in HHS PFC to the baseline levels seen in sham controls. Strikingly, either JNK2-specific inhibition or genetic JNK2 depletion or DNMT1 inhibition (by an inhibitor 5-Azacytidine) completely abolished BAW-evoked behavioral deficits. In conclusion, our studies revealed a novel mechanism by which JNK2 drives BAW-evoked behavioral deficits through a DNMT1-regulated DNA hypermethylation. JNK2 could be a novel therapeutic target for alcohol withdrawal treatment and/or prevention.

Both JNK1 and JNK2 Are Indispensable for Sensitized Extracellular Matrix Mineralization in IKKβ-Deficient Osteoblasts

Extracellular matrix mineralization is critical for osteogenesis, and its dysregulation could result in osteoporosis and vascular calcification. IKK/NF-κB activation inhibits differentiation of osteoblasts, and reduces extracellular matrix mineralization, however the underlying mechanisms are poorly understood. In this study, we used CRISPR/Cas9 system to permanently inactivate IKKβ in preosteoblast cells and confirmed that such cells displayed dramatic increase in extracellular matrix mineralization associated with JNK phosphorylation. Such observation was also found in our study using IKKβ-deficient primary murine osteoblasts. Interestingly, we found that in Ikbkb^-/-Mapk8^-/- or Ikbkb^-/-Mapk9^-/- double knockout cells, the enhanced mineralization caused by IKKβ deficiency was completely abolished, and deletion of either Mapk8 or Mapk9 was sufficient to dampen c-Jun phosphorylation. In further experiments, we discovered that absence of JNK1 or JNK2 on IKKβ-deficient background resulted in highly conserved transcriptomic alteration in response to osteogenic induction. Therefore, identification of the indispensable roles of JNK1 and JNK2 in activating c-Jun and promoting osteoblast differentiation on IKKβ-deficient background provided novel insights into restoring homeostasis in extracellular matrix mineralization.

CLEFMA Activates the Extrinsic and Intrinsic Apoptotic Processes through JNK1/2 and p38 Pathways in Human Osteosarcoma Cells

Due to the poor prognosis of metastatic osteosarcoma, chemotherapy is usually employed in the adjuvant situation to improve the prognosis and the chances of long-term survival. 4-[3,5-Bis(2-chlorobenzylidene)-4-oxo-piperidine-1-yl]-4-oxo-2-butenoic acid (CLEFMA) is a synthetic analog of curcumin and possesses anti-inflammatory and anticancer properties. To further obtain information regarding the apoptotic pathway induced by CLEFMA in osteosarcoma cells, microculture tetrazolium assay, annexin V-FITC/PI apoptosis staining assay, human apoptosis array, and Western blotting were employed. CLEFMA dose-dependently decreased the cell viabilities of human osteosarcoma U2OS and HOS cells and significantly induced apoptosis in human osteosarcoma cells. In addition to the effector caspase 3, CLEFMA significantly activated both extrinsic caspase 8 and intrinsic caspase 9 initiators. Moreover, CLEFMA increased the phosphorylation of extracellular signal-regulated protein kinases (ERK)1/2, c-Jun N-terminal kinases (JNK)1/2 and p38. Using inhibitors of JNK (JNK-in-8) and p38 (SB203580), CLEFMA’s increases of cleaved caspases 3, 8, and 9 could be expectedly suppressed, but they could not be affected by co-treatment with the ERK inhibitor (U0126). Conclusively, CLEFMA activates both extrinsic and intrinsic apoptotic pathways in human osteosarcoma cells through JNK and p38 signaling. These findings contribute to a better understanding of the mechanisms responsible for CLEFMA’s apoptotic effects on human osteosarcoma cells.

CaMPK9 increases the stability of CaWRKY40 transcription factor which triggers defense response in chickpea upon Fusarium oxysporum f. sp. ciceri Race1 infection

Physical interaction and phosphorylation by CaMPK9 protects the degradation of CaWRKY40 that induces resistance response in chickpea to Fusarium wilt disease by modulating the transcription of defense responsive genes. WRKY transcription factors (TFs) are the global regulators of plant defense signaling that modulate immune responses in host plants by regulating transcription of downstream target genes upon challenged by pathogens. However, very little is known about immune responsive role of Cicer arietinum L. (Ca) WRKY TFs particularly. Using two contrasting chickpea genotypes with respect to resistance against Fusarium oxysporum f. sp. ciceri Race1 (Foc1), we demonstrate transcript accumulation of different CaWRKYs under multiple stresses and establish that CaWRKY40 triggers defense. CaWRKY40 overexpressing chickpea mounts resistance to Foc1 by positively modulating the defense related gene expression. EMSA, ChIP assay and real-time PCR analyses suggest CaWRKY40 binds at the promoters and positively regulates transcription of CaDefensin and CaWRKY33. Further studies revealed that mitogen Activated Protein Kinase9 (CaMPK9) phosphorylates CaWRKY40 by directly interacting with its two canonical serine residues. Interestingly, CaMPK9 is unable to interact with CaWRKY40 when the relevant two serine residues were replaced by alanine. Overexpression of serine mutated WRKY40 isoform in chickpea fails to provide resistance against Foc1. Mutated WRKY40^{Ser.224/225 to AA} overexpressing chickpea resumes its ability to confer resistance against Foc1 after application of 26S proteasomal inhibitor MG132, suggests that phosphorylation is essential to protect CaWRKY40 from proteasomal degradation. CaMPK9 silencing also led to susceptibility in chickpea to Foc1. Altogether, our results elucidate positive regulatory roles of CaMPK9 and CaWRKY40 in modulating defense response in chickpea upon Foc1 infection.

Protective role of c-Jun N-terminal kinase-2 (JNK2) in ibuprofen-induced acute liver injury

Ibuprofen is a worldwide used non-steroidal anti-inflammatory drug which may cause acute liver injury (ALI) requiring liver transplantation. We aimed to unveil the molecular pathways involved in triggering ibuprofen-induced ALI, which, at present, remain elusive. First, we investigated activation of essential pathways in human liver sections of ibuprofen-induced ALI. Next, we assessed the cytotoxicity of ibuprofen in vitro and developed a novel murine model of ibuprofen intoxication. To assess the role of JNK, we used animals carrying constitutive deletion of c-Jun N-terminal kinase 1 (Jnk1^-/- ) or Jnk2 (Jnk2^-/- ) expression and included investigations using animals with hepatocyte-specific Jnk deletion either genetically (Jnk1^Δhepa ) or by siRNA (siJnk2^Δhepa ). We found in human and murine samples of ibuprofen-induced acute liver failure that JNK phosphorylation was increased in the cytoplasm of hepatocytes and other non-liver parenchymal cells (non-LPCs) compared with healthy tissue. In mice, ibuprofen intoxication resulted in a significantly stronger degree of liver injury compared with vehicle-treated controls as evidenced by serum transaminases, and hepatic histopathology. Next, we investigated molecular pathways. PKCα, AKT, JNK and RIPK1 were significantly increased 8 h after ibuprofen intoxication. Constitutive Jnk1^-/- and Jnk2^-/- deficient mice exhibited increased liver dysfunction compared to wild-type (WT) animals. Furthermore, siJnk2^Δhepa animals showed a dramatic increase in biochemical markers of liver function, which correlated with significantly higher serum liver enzymes and worsened liver histology, and MAPK activation compared to Jnk1^Δhepa or WT animals. In our study, cytoplasmic JNK activation in hepatocytes and other non-LPCs is a hallmark of human and murine ibuprofen-induced ALI. Functional in vivo analysis demonstrated a protective role of hepatocyte-specific Jnk2 during ibuprofen ALI. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

JNK2 silencing and caspase-9 activation by hyperosmotic polymer inhibits tumor progression

c-Jun N-terminal kinase 2 (JNK2) is primarily responsible for the oncogenic transformation of the transcription factor c-Jun. Expression of the proto-oncogene c-Jun progresses the cell cycle from G1 to S phase, but when its expression becomes awry it leads to uncontrolled proliferation and angiogenesis. Delivering a JNK2 siRNA (siJNK2) in tumor tissue was anticipated to reverse the condition with subsequent onset of apoptosis which predominantly requires an efficient delivering system capable of penetrating through the compact tumor mass. In the present study, it was demonstrated that polymannitol-based vector (PMGT) with inherent hyperosmotic properties was able to penetrate through and deliver the siJNK2 in the subcutaneous tumor of xenograft mice. Hyperosmotic activity of polymannitol was shown to account for the enhanced therapeutic delivery both in vitro and in vivo because of the induction of cyclooxygenase-2 (COX-2) which stimulates caveolin-1 for caveolae-mediated endocytosis of the polyplexes. Further suppression of JNK2 and hence c-Jun expression led to the activation of caspase-9 to induce apoptosis and inhibition of tumor growth in xenograft mice model. The study exemplifies PMGT as an efficient vector for delivering therapeutic molecules in compact tumor tissue and suppression of JNK2 introduces a strategy to inhibit tumor progression.

JNK1 as a signaling node in VDR-BRAF induction of cell death in AML

Numerous clinical studies of vitamin D, its derivatives or analogs, have failed to clearly demonstrate sustained benefits when used for the treatment of human malignant diseases. However, given the strong preclinical evidence of anti-neoplastic activity and the epidemiological associations suggesting that vitamin D compounds may have a place in cancer therapy, attempts are continuing to devise new approaches to their therapeutic use. This laboratory has developed a strategy to enhance the effectiveness of the currently standard therapy of Acute Myeloid Leukemia (AML) by the immediate addition of the vitamin D2 analog Doxercalciferol combined with the plant polyphenol-derived Carnosic acid to AML cells previously treated with Cytarabine (AraC). Enhancement of AML cell death was noted to be dependent on VDR and BRAF kinase. Here we document that the stress-related kinase JNK is an important additional component of cell death enhancement in this protocol. Either the Knock-down or the inhibition of JNK activity reduced the enhancement of AraC-induced cell death, and we show that JNK signaling to the apoptosis regulator BIM and Caspase executioners of cell death are downstream of VDR and BRAF. A clear understanding of the molecular basis for the increased efficacy of AraC in the therapy of AML is expected to bring this regimen to a clinical trial.

Deletion of JNK2 prevents vitamin-D-deficiency-induced hypertension and atherosclerosis in mice

The c-Jun N-terminal kinase 2 (JNK2) signaling pathway contributes to inflammation and plays a key role in the development of obesity-induced insulin resistance and cardiovascular disease. Macrophages are key cells implicated in these metabolic abnormalities. Active vitamin D downregulates macrophage JNK activation, suppressing oxidized LDL cholesterol uptake and foam cell formation and promoting an anti-inflammatory phenotype. To determine whether deletion of JNK2 prevents high blood pressure and atherosclerosis known to be induced by vitamin D deficiency in mice, we generated mice with knockout of JNK2 in a background susceptible to diet-induced atherosclerosis (LDLR^-/-). JNK2^-/- LDLR^-/- and LDLR^-/- control mice were fed vitamin D-deficient chow for 8 weeks followed by vitamin D-deficient high fat diet (HFD) for 10 weeks and assessed before and after HFD. There was no difference in fasting glucose, cholesterol, triglycerides, or free fatty acid levels. However, JNK2^-/- mice, despite vitamin D-deficient diet, had 20-30mmHg lower systolic (SBP) and diastolic (DBP) blood pressure before HFD compared to control mice fed vitamin D-deficient diets, with persistent SBP differences after HFD. Moreover, deletion of JNK2 reduced HFD-induced atherosclerosis by 30% in the proximal aorta when compared to control mice fed vitamin D-deficient diets. We have previously shown that peritoneal macrophages obtained from LDLR^-/- mice fed vitamin D-deficient HFD diets have higher foam cell formation compared to those from mice on vitamin D-sufficient HFD. The increased total cellular cholesterol and modified cholesterol uptake in macrophages from mice on vitamin D-deficient HFD were blunted by deletion of JNK2. These data suggest that JNK2 signaling activation is necessary for the atherosclerosis and hypertension induced by vitamin D deficiency.

ROS-JNK1/2-dependent activation of autophagy is required for the induction of anti-inflammatory effect of dihydroartemisinin in liver fibrosis

Accumulating evidence identifies autophagy as an inflammation-related defensive mechanism against diseases including liver fibrosis. Therefore, autophagy may represent a new pharmacologic target for drug development to treat liver fibrosis. In this study, we sought to investigate the effect of dihydroartemisinin (DHA) on autophagy, and to further examine the molecular mechanisms of DHA-induced anti-inflammatory effects. We found that DHA appeared to play an essential role in controlling excessive inflammation. DHA suppressed inflammation in rat liver fibrosis model and inhibited the expression of proinflammatory cytokines in activated hepatic stellate cells (HSCs). Interestingly, DHA increased the autophagosome generation and autophagic flux in activated HSCs, which is underlying mechanism for the anti-inflammatory activity of DHA. Autophagy depletion impaired the induction of anti-inflammatory effect of DHA, while autophagy induction showed a synergistic effect with DHA. Importantly, our study also identified a crucial role for reactive oxygen species (ROS) in the facilitation of DHA-induced autophagy. Antioxidants, such as glutathione and N-acetyl cysteine, significantly abrogated ROS production, and in turn, prevented DHA-induced autophagosome generation and autophagic flux. Besides, we found that c-Jun N-terminal kinase1/2 (JNK1/2) was a downstream signaling molecule of ROS that mediated the induction of autophagy by DHA. Down-regulation of JNK1/2 activity, using selective JNK1/2 inhibitor (SP600125) or siJNK1/2, led to an inhibition of DHA-induced autophagy. Overall, these results provide novel implications to reveal the molecular mechanism of DHA-induced anti-inflammatory effects, by which points to the possibility of using DHA based proautophagic drugs for the treatment of inflammatory diseases.

Molecular clone and characterization of c-Jun N-terminal kinases 2 from orange-spotted grouper, Epinephelus coioides

c-Jun N-terminal kinase 2 (JNK2) is a multifunctional mitogen-activated protein kinases involving in cell differentiation and proliferation, apoptosis, immune response and inflammatory conditions. In this study, we reported a new JNK2 (Ec-JNK2) derived from orange-spotted grouper, Epinephelus coioides. The full-length cDNA of Ec-JNK2 was 1920 bp in size, containing a 174 bp 5'-untranslated region (UTR), 483 bp 3'-UTR, and a 1263 bp open reading frame (ORF), which encoded a putative protein of 420 amino acids. The deduced protein sequence of Ec-JNK2 contained a conserved Thr-Pro-Tyr (TPY) motif in the domain of serine/threonine protein kinase (S-TKc). Ec-JNK2 has been found to involve in the immune response to pathogen challenges in vivo, and the infection of Singapore grouper iridovirus (SGIV) in vitro. Immunofluorescence staining showed that Ec-JNK2 was localized in the cytoplasm of grouper spleen (GS) cells, and moved to the nucleus after infecting with SGIV. Ec-JNK2 distributed in all immune-related tissues examined. After challenging with lipopolysaccharide (LPS), SGIV and polyriboinosinic polyribocytidylic acid (poly I:C), the mRNA expression of Ec-JNK2 was significantly (P < 0.01) up-regulated in juvenile orange-spotted grouper. Over-expressing Ec-JNK2 in fathead minnow (FHM) cells increased the SGIV infection and replication, while over-expressing the dominant-negative Ec-JNK2Δ181-183 mutant decreased it. These results indicated that Ec-JNK2 could be an important molecule in the successful infection and evasion of SGIV.

JNK1 Deficient Insulin-Producing Cells Are Protected against Interleukin-1β-Induced Apoptosis Associated with Abrogated Myc Expression

The relative contributions of the JNK subtypes in inflammatory β-cell failure and apoptosis are unclear. The JNK protein family consists of JNK1, JNK2, and JNK3 subtypes, encompassing many different isoforms. INS-1 cells express JNK1α1, JNK1α2, JNK1β1, JNK1β2, JNK2α1, JNK2α2, JNK3α1, and JNK3α2 mRNA isoform transcripts translating into 46 and 54 kDa isoform JNK proteins. Utilizing Lentiviral mediated expression of shRNAs against JNK1, JNK2, or JNK3 in insulin-producing INS-1 cells, we investigated the role of individual JNK subtypes in IL-1β-induced β-cell apoptosis. JNK1 knockdown prevented IL-1β-induced INS-1 cell apoptosis associated with decreased 46 kDa isoform JNK protein phosphorylation and attenuated Myc expression. Transient knockdown of Myc also prevented IL-1β-induced apoptosis as well as caspase 3 cleavage. JNK2 shRNA potentiated IL-1β-induced apoptosis and caspase 3 cleavage, whereas JNK3 shRNA did not affect IL-1β-induced β-cell death compared to nonsense shRNA expressing INS-1 cells. In conclusion, JNK1 mediates INS-1 cell death associated with increased Myc expression. These findings underline the importance of differentiated targeting of JNK subtypes in the development of inflammatory β-cell failure and destruction.

Autophosphorylation Properties of Inactive and Active JNK2

The c-Jun N-terminal kinases (JNKs) are ubiquitous proteins that phosphorylate their substrates, such as transcription factors, in response to physical stress, cytokines or UV radiation. This leads to changes in gene expression, ensuing either cell cycle progression or apoptosis. Active phospho JNK1 is the main in vivo kinase component of the JNK cascade, whereas JNK2 is presumed not to participate as a kinase during JNK signalling. However, there is evidence that JNK isoforms interact functionally in vivo. Also, a recent chemical genetics investigation has confirmed that JNK transient activation leads to cellular proliferation, whereas a sustained one is pro-apoptotic. Here we investigate the phosphorylation pattern of JNK2, with protein biochemistry tools and tandem mass spectrometry. We choose to focus on JNK2 because of its reported constitutive activity in glioma cells. Our results indicate that purified JNK2 from transfected nonstressed 293T cells is a mixture of the mono-sites pThr183 and pTyr185 of its activation loop and of pThr386 along its unique C-terminal region. Upon UV stimulation, its phosphorylation stoichiometry is upregulated on the activation loop, generating a mixture of mono-pTyr185 and the expected dual-pThr183/pTyr185 species, with the pThr386 specie present but unaltered respect to the basal conditions.

Stathmin mediates hepatocyte resistance to death from oxidative stress by down regulating JNK

Stathmin 1 performs a critical function in cell proliferation by regulating microtubule polymerization. This proliferative function is thought to explain the frequent overexpression of stathmin in human cancer and its correlation with a bad prognosis. Whether stathmin also functions in cell death pathways is unclear. Stathmin regulates microtubules in part by binding free tubulin, a process inhibited by stathmin phosphorylation from kinases including c-Jun N-terminal kinase (JNK). The involvement of JNK activation both in stathmin phosphorylation, and in hepatocellular resistance to oxidative stress, led to an examination of the role of stathmin/JNK crosstalk in oxidant-induced hepatocyte death. Oxidative stress from menadione-generated superoxide induced JNK-dependent stathmin phosphorylation at Ser-16, Ser-25 and Ser-38 in hepatocytes. A stathmin knockdown sensitized hepatocytes to both apoptotic and necrotic cell death from menadione without altering levels of oxidant generation. The absence of stathmin during oxidative stress led to JNK overactivation that was the mechanism of cell death as a concomitant knockdown of JNK1 or JNK2 blocked death. Hepatocyte death from JNK overactivation was mediated by the effects of JNK on mitochondria. Mitochondrial outer membrane permeabilization occurred in stathmin knockdown cells at low concentrations of menadione that triggered apoptosis, whereas mitochondrial β-oxidation and ATP homeostasis were compromised at higher, necrotic menadione concentrations. Stathmin therefore mediates hepatocyte resistance to death from oxidative stress by down regulating JNK and maintaining mitochondrial integrity. These findings demonstrate a new mechanism by which stathmin promotes cell survival and potentially tumor growth.

miR200c attenuates P-gp-mediated MDR and metastasis by targeting JNK2/c-Jun signaling pathway in colorectal cancer

MicroRNA-200c (miR200c) recently emerged as an important regulator of tumorigenicity and cancer metastasis; however, its role in regulating multidrug resistance (MDR) remains unknown. In the current study, we found that the expression levels of miR200c in recurrent and metastatic colorectal cancers were significantly lower, whereas the JNK2 expression was higher compared with primary tumors. We showed that in MDR colorectal cancer cells, miR200c targeted the 3' untranslated region of the JNK2 gene. Overexpression of miR200c attenuated the levels of p-JNK, p-c-Jun, P-gp, and MMP-2/-9, the downstream factors of the JNK signaling pathway, resulting in increased sensitivity to chemotherapeutic drugs, which was accompanied by heightened apoptosis and decreased cell invasion and migration. Moreover, in an orthotopic MDR colorectal cancer mouse model, we demonstrated that overexpression of miR200c effectively inhibited the tumor growth and metastasis. At last, in the tumor samples from patients with locally advanced colorectal cancer with routine postsurgical chemotherapy, we observed an inverse correlation between the levels of mRNA expression of miR200c and JNK2, ABCB1, and MMP-9, thus predicting patient therapeutic outcomes. In summary, we found that miR200c negatively regulated the expression of JNK2 gene and increased the sensitivity of MDR colorectal cancer cells to chemotherapeutic drugs, via inhibiting the JNK2/p-JNK/p-c-Jun/ABCB1 signaling. Restoration of miR200c expression in MDR colorectal cancer may serve as a promising therapeutic approach in MDR-induced metastasis.

The structural pathway of interleukin 1 (IL-1) initiated signaling reveals mechanisms of oncogenic mutations and SNPs in inflammation and cancer

Interleukin-1 (IL-1) is a large cytokine family closely related to innate immunity and inflammation. IL-1 proteins are key players in signaling pathways such as apoptosis, TLR, MAPK, NLR and NF-κB. The IL-1 pathway is also associated with cancer, and chronic inflammation increases the risk of tumor development via oncogenic mutations. Here we illustrate that the structures of interfaces between proteins in this pathway bearing the mutations may reveal how. Proteins are frequently regulated via their interactions, which can turn them ON or OFF. We show that oncogenic mutations are significantly at or adjoining interface regions, and can abolish (or enhance) the protein-protein interaction, making the protein constitutively active (or inactive, if it is a repressor). We combine known structures of protein-protein complexes and those that we have predicted for the IL-1 pathway, and integrate them with literature information. In the reconstructed pathway there are 104 interactions between proteins whose three dimensional structures are experimentally identified; only 15 have experimentally-determined structures of the interacting complexes. By predicting the protein-protein complexes throughout the pathway via the PRISM algorithm, the structural coverage increases from 15% to 71%. In silico mutagenesis and comparison of the predicted binding energies reveal the mechanisms of how oncogenic and single nucleotide polymorphism (SNP) mutations can abrogate the interactions or increase the binding affinity of the mutant to the native partner. Computational mapping of mutations on the interface of the predicted complexes may constitute a powerful strategy to explain the mechanisms of activation/inhibition. It can also help explain how an oncogenic mutation or SNP works.

Structural pathways are important because they provide insight into signaling mechanisms; help understand the mechanism of disease-related mutations; and help in drug discovery. While extremely useful, common pathway diagrams lacking structural data are unable to provide mechanistic insight to explain oncogenic mutations or SNPs. Here we focus on the construction of the IL-1 structural pathway and map oncogenic mutations and SNPs to complexes in this pathway. Our results indicate that computational modeling of protein-protein interactions on a large scale can provide accurate, structural atom-level detail of signaling pathways in the human cell and help delineate the mechanism through which a mutation leads to disease. We show that the mutations either thwart the interactions, activating the proteins even in their absence or stabilize them, leading to the same uncontrolled outcome. Computational mapping of mutations on the interface of the predicted complexes may constitute an effective strategy to explain the mechanisms of mutations- constitutive activation or deactivation.

Inhibition of apolipoprotein A-I expression by TNF-alpha in HepG2 cells: requirement for c-jun

Tumor necrosis factor alpha (TNF α) signals in part through the mitogen activated protein (MAP) kinase c-jun-N-terminal kinase (JNK). Activation of JNK has been shown to promote insulin resistance and dyslipidemia, including reductions in plasma high-density lipoprotein (HDL) and apolipoprotein A-I (apo A-I). To examine how TNF α-mediated JNK activation inhibits hepatic apo A-I production, the effects of c-jun activation on apo A-I gene expression were examined in HepG2 cells. Apo A-I gene expression and promoter activity were measured by Northern and Western blotting and transient transfection. Transient transfection and siRNA were used to specifically over-express or knockout c-jun, c-jun-N-terminal kinase-1 and -2 (JNK1 and JNK2, respectively) and mitogen-activated protein kinase-4 (MKK4). TNF α-treatment of HepG2 cells induced rapid phosphorylation of c-jun on serine 63. In cells treated with phorbol-12-myristate-13-acetate (PMA), apo A-I gene promoter activity was inhibited and apo A-I mRNA content and apo A-I protein secretion decreased. Likewise, over-expression of JNK1 and JNK2 inhibited apo A-I promoter activity. Over-expression of constitutively active MKK4, an upstream protein kinase that directly activates JNK, also inhibited apo A-I promoter activity, while over-expression of a dominant-negative MKK4 de-repressed apo A-I promoter activity in TNF α-treated cells. Inhibition of c-jun synthesis using siRNA but not a control siRNA prevented TNF α-mediated inhibition of apo A-I. These results suggest that the MKK4/JNK/c-jun signaling pathway mediates TNF α-dependent inhibition of apo A-I synthesis.

JNK1 protects against glucolipotoxicity-mediated beta-cell apoptosis

Pancreatic β-cell dysfunction is central to type 2 diabetes pathogenesis. Prolonged elevated levels of circulating free-fatty acids and hyperglycemia, also termed glucolipotoxicity, mediate β-cell dysfunction and apoptosis associated with increased c-Jun N-terminal Kinase (JNK) activity. Endoplasmic reticulum (ER) and oxidative stress are elicited by palmitate and high glucose concentrations further potentiating JNK activity. Our aim was to determine the role of the JNK subtypes JNK1, JNK2 and JNK3 in palmitate and high glucose-induced β-cell apoptosis. We established insulin-producing INS1 cell lines stably expressing JNK subtype specific shRNAs to understand the differential roles of the individual JNK isoforms. JNK activity was increased after 3 h of palmitate and high glucose exposure associated with increased expression of ER and mitochondrial stress markers. JNK1 shRNA expressing INS1 cells showed increased apoptosis and cleaved caspase 9 and 3 compared to non-sense shRNA expressing control INS1 cells when exposed to palmitate and high glucose associated with increased CHOP expression, ROS formation and Puma mRNA expression. JNK2 shRNA expressing INS1 cells did not affect palmitate and high glucose induced apoptosis or ER stress markers, but increased Puma mRNA expression compared to non-sense shRNA expressing INS1 cells. Finally, JNK3 shRNA expressing INS1 cells did not induce apoptosis compared to non-sense shRNA expressing INS1 cells when exposed to palmitate and high glucose but showed increased caspase 9 and 3 cleavage associated with increased DP5 and Puma mRNA expression. These data suggest that JNK1 protects against palmitate and high glucose-induced β-cell apoptosis associated with reduced ER and mitochondrial stress.

TNFα signals via p66(Shc) to induce E-Selectin, promote leukocyte transmigration and enhance permeability in human endothelial cells

Endothelial cells participate in inflammatory events leading to atherogenesis by regulating endothelial cell permeability via the expression of VE-Cadherin and β-catenin and leukocyte recruitment via the expression of E-Selectins and other adhesion molecules. The protein p66^Shc acts as a sensor/inducer of oxidative stress and may promote vascular dysfunction. The objective of this study was to investigate the role of p66^Shc in tumor necrosis factor TNFα-induced E-Selectin expression and function in human umbilical vein endothelial cells (HUVEC). Exposure of HUVEC to 50 ng/ml TNFα resulted in increased leukocyte transmigration through the endothelial monolayer and E-Selectin expression, in association with augmented phosphorylation of both p66^Shc on Ser³⁶ and the stress kinase c-Jun NH₂-terminal protein kinase (JNK)-1/2, and higher intracellular reactive oxygen species (ROS) levels. Overexpression of p66^Shc in HUVEC resulted in enhanced p66^Shc phosphorylation on Ser³⁶, increased ROS and E-Selectin levels, and amplified endothelial cell permeability and leukocyte transmigration through the HUVEC monolayer. Conversely, overexpression of a phosphorylation-defective p66^Shc protein, in which Ser³⁶ was replaced by Ala, did not augment ROS and E-Selectin levels, nor modify cell permeability or leukocyte transmigration beyond those found in wild-type cells. Moreover, siRNA-mediated silencing of p66^Shc resulted in marked reduction of E-Selectin expression and leukocyte transmigration. In conclusion, p66^Shc acts as a novel intermediate in the TNFα pathway mediating endothelial dysfunction, and its action requires JNK-dependent phosphorylation of p66^Shc on Ser³⁶.

NFκB as a potent regulator of inflammation in human adipose tissue, influenced by depot, adiposity, T2DM status, and TNFα

OBJECTIVE

Central obesity and sub-clinical inflammation increase metabolic risk, this study examined the intracellular inflammatory pathways in adipose tissue (AT) that contribute to this risk.

DESIGN AND METHODS

This study therefore addressed the influence of NFκB and JNK activation in human abdominal subcutaneous (AbdSc) and omental (Om) AT, the effect of adiposity, T2DM status and the role of TNFα in vitro, using molecular biology techniques.

RESULTS

Our data showed NFκB activity is increased in Om AT versus AbdSc AT (P<0.01), which was reversed with respect to depot specific activation of JNK (P<0.01). However, T2DM status appeared to preferentially activate NFκB (P<0.001) over JNK. Furthermore, in vitro studies showed recombinant human (rh) TNFα treated AbdSc adipocytes increased NFκB activity over time (2-48 h, P<0.05) whilst JNK activity reduced (2 h, 4 h, P<0.05); inhibitor studies supported a preferential role for NFκB as a modulator of TNFα secretion.

CONCLUSIONS

These studies suggest distinct changes in NFκB and JNK activation, dependent upon AT depot, adiposity and T2DM status, with in vitro use of rh TNFα leading to activation of NFκB. Consequently NFκB appears to play a central role in inflammatory mediated metabolic disease over JNK, highlighting NFκB as a potential key target for therapeutic intervention.

Hispolon induces apoptosis through JNK1/2-mediated activation of a caspase-8, -9, and -3-dependent pathway in acute myeloid leukemia (AML) cells and inhibits AML xenograft tumor growth in vivo

Hispolon is an active phenolic compound of Phellinus igniarius, a mushroom that was recently shown to have antioxidant and anticancer activities in various solid tumors. Here, the molecular mechanisms by which hispolon exerts anticancer effects in acute myeloid leukemia (AML) cells was investigated. The results showed that hispolon suppressed cell proliferation in the various AML cell lines. Furthermore, hispolon effectively induced apoptosis of HL-60 AML cells through caspases-8, -9, and -3 activations and PARP cleavage. Moreover, treatment of HL-60 cells with hispolon induced sustained activation of JNK1/2, and inhibition of JNK by JNK1/2 inhibitor or JNK1/2-specific siRNA significantly abolished the hispolon-induced activation of the caspase-8/-9/-3. In vivo, hispolon significantly reduced tumor growth in mice with HL-60 tumor xenografts. In hispolon-treated tumors, activation of caspase-3 and a decrease in Ki67-positive cells were observed. Our results indicated that hispolon may have the potential to serve as a therapeutic tool to treat AML.

TRPV1 potentiates TGFβ-induction of corneal myofibroblast development through an oxidative stress-mediated p38-SMAD2 signaling loop

Injuring mouse corneas with alkali causes myofibroblast expression leading to tissue opacification. However, in transient receptor potential vanilloid 1 channel (TRPV1-/-) knockout mice healing results in transparency restoration. Since TGFβ is the primary inducer of the myofibroblast phenotype, we examined the mechanism by which TRPV1 affects TGFβ-induced myofibroblast development. Experiments were performed in pig corneas and human corneal fibroblasts (HCFs). Immunohistochemical staining of α-smooth muscle actin (α-SMA) stress fibers was used to visualize myofibroblasts. Protein and phosphoprotein were determined by Western blotting. siRNA transfection silenced TRPV1 gene expression. Flow cytometry with a reactive oxygen species (ROS) reporting dye analyzed intracellular ROS. [Ca2+]I was measured by loading HCF with fura2. In organ cultured corneas, the TRPV1 antagonist capsazepine drastically reduced by 75% wound-induced myofibroblast development. In HCF cell culture, TGF-β1 elicited rapid increases in Ca2+ influx, phosphorylation of SMAD2 and MAPKs (ERK1/2, JNK1/2 and p38), ROS generation and, after 72 hrs myofibroblast development. SMAD2 and p38 activation continued for more than 16 h, whereas p-ERK1/2 and p-JNK1/2 waned within 90 min. The long-lived SMAD2 activation was dependent on activated p38 and vice versa, and it was essential to generate a > 13-fold increase in α-SMA protein and a fully developed myofibroblast phenotype. These later changes were markedly reduced by inhibition of TRPV1 or reduction of the ROS generation rate. Taken together our results indicate that in corneal derived fibroblasts, TGFβ- induced myofibroblast development is highly dependent on a positive feedback loop where p-SMAD2-induced ROS activates TRPV1, TRPV1 causes activation of p38, the latter in turn further enhances the activation of SMAD2 to establish a recurrent loop that greatly extends the residency of the activated state of SMAD2 that drives myofibroblast development.

Melatonin inhibits visfatin-induced inducible nitric oxide synthase expression and nitric oxide production in macrophages

Aberrant expression of inducible nitric oxide synthase (iNOS) in macrophages, which has been reported to be suppressed by melatonin, has an important contribution in the development of pathological inflammation. Visfatin, an adipokine, regulates the expression of various inflammatory factors, leading to inflammation; however, the influence of visfatin on iNOS-driven processes in macrophages is unclear. Here, we report the assessment of the role of visfatin in the regulation of iNOS gene expression in macrophages. Our data show that the levels of iNOS protein in peritoneal macrophages as well as nitric oxide (NO) in blood plasma were significantly lower after lipopolysaccharide treatment in visfatin(+/-) mice than those in the WT mice. In addition, visfatin increases iNOS mRNA and protein levels in RAW 264.7 cells, along with increasing production of NO. The enhancement of iNOS expression was prevented by treating the cells with inhibitors of the Janus kinase 2/signal transducers and activators of transcription 3 (JAK2/STAT3), nuclear factor (NF)-κB, extracellular signal-regulated kinase 1/2, and c-Jun N-terminal kinase pathways. Our results also show that visfatin-induced iNOS expression and NO production were significantly inhibited by melatonin, an effect that was closely associated with a reduction in phosphorylated JAK2/STAT3 levels and with the inhibition of p65 translocation into nucleus. In conclusion, our data show, for the first time, that melatonin suppresses visfatin-induced iNOS upregulation in macrophages by inhibiting the STAT3 and NF-κB pathways. Moreover, our data suggest that melatonin could be therapeutically useful for attenuating the development of visfatin-iNOS axis-associated diseases.

TNF-α induces cytosolic phospholipase A2 expression in human lung epithelial cells via JNK1/2- and p38 MAPK-dependent AP-1 activation

Background

Cytosolic phospholipase A₂ (cPLA₂) plays a pivotal role in mediating agonist-induced arachidonic acid (AA) release for prostaglandin (PG) synthesis during inflammation triggered by tumor necrosis factor-α (TNF-α). However, the mechanisms underlying TNF-α-induced cPLA₂ expression in human lung epithelial cells (HPAEpiCs) were not completely understood.

Principal Findings

We demonstrated that TNF-α induced cPLA₂ mRNA and protein expression, promoter activity, and PGE₂ secretion in HPAEpiCs. These responses induced by TNF-α were inhibited by pretreatment with the inhibitor of MEK1/2 (PD98059), p38 MAPK (SB202190), JNK1/2 (SP600125), or AP-1 (Tanshinone IIA) and transfection with siRNA of TNFR1, p42, p38, JNK2, c-Jun, c-Fos, or ATF2. We showed that TNF-α markedly stimulated p42/p44 MAPK, p38 MAPK, and JNK1/2 phosphorylation which were attenuated by their respective inhibitors. In addition, TNF-α also stimulated c-Jun and ATF2 phosphorylation which were inhibited by pretreatment with SP600125 and SB202190, respectively, but not PD98059. Furthermore, TNF-α-induced cPLA₂ promoter activity was abrogated by transfection with the point-mutated AP-1 cPLA₂ construct. Finally, we showed that TNF-α time-dependently induced p300/c-Fos/c-Jun/ATF2 complex formation in HPAEpiCs. On the other hand, TNF-α induced in vivo binding of c-Jun, c-Fos, ATF2, and p300 to the cPLA₂ promoter in these cells. In an in vivo study, we found that TNF-α induced leukocyte count in BAL fluid of mice and cPLA₂ mRNA levels in lung tissues via MAPKs and AP-1.

Significance

Taken together, these results demonstrated that TNF-α-induced cPLA₂ expression was mediated through p38 MAPK- and JNK1/2-dependent p300/c-Fos/c-Jun/ATF2 complex formation in HPAEpiCs.

Poly(ADP-ribose) polymerase family member 14 (PARP14) is a novel effector of the JNK2-dependent pro-survival signal in multiple myeloma

Regulation of cell survival is a key part of the pathogenesis of multiple myeloma (MM). Jun N-terminal kinase (JNK) signaling has been implicated in MM pathogenesis, but its function is unclear. To elucidate the role of JNK in MM, we evaluated the specific functions of the two major JNK proteins, JNK1 and JNK2. We show here that JNK2 is constitutively activated in a panel of MM cell lines and primary tumors. Using loss-of-function studies, we demonstrate that JNK2 is required for the survival of myeloma cells and constitutively suppresses JNK1-mediated apoptosis by affecting expression of poly(ADP-ribose) polymerase (PARP)14, a key regulator of B-cell survival. Strikingly, we found that PARP14 is highly expressed in myeloma plasma cells and associated with disease progression and poor survival. Overexpression of PARP14 completely rescued myeloma cells from apoptosis induced by JNK2 knockdown, indicating that PARP14 is critically involved in JNK2-dependent survival. Mechanistically, PARP14 was found to promote the survival of myeloma cells by binding and inhibiting JNK1. Moreover, inhibition of PARP14 enhances the sensitization of MM cells to anti-myeloma agents. Our findings reveal a novel regulatory pathway in myeloma cells through which JNK2 signals cell survival via PARP14, and identify PARP14 as a potential therapeutic target in myeloma.

Oppositional regulation of Noxa by JNK1 and JNK2 during apoptosis induced by proteasomal inhibitors

Proteasome inhibitors (PIs) potently induce apoptosis in a variety of tumor cells, but the underlying mechanisms are not fully elucidated. Comparing PI-induced apoptosis susceptibilities of various mouse embryonic fibroblast (MEF) lines differing in their c-jun N-terminal kinase (JNK) 1 and 2 status, we show that several hallmarks of apoptosis were most rapidly detectable in JNK2-/- cells, whereas they appeared only delayed and severely reduced in their intensities in cells expressing JNK2. Consistent with our finding that PI-induced apoptosis requires de novo protein synthesis, the proteasomal inhibitor MG-132 induced expression of the BH3-only protein Noxa at the transcriptional level in a JNK1-dependent, but JNK2-opposing manner. As the knockdown of Noxa blocked only the rapid PI-induced apoptosis of JNK2-/- cells, but not the delayed death occurring in JNK1-/- and JNK1+/+ cells, our data uncover a novel PI-induced apoptosis pathway that is regulated by the JNK1/2-dependent expression of Noxa. Furthermore, several transcription factors known to modulate Noxa expression including ATF3, ATF4, c-Jun, c-Myc, HIF1α, and p53 were found upregulated following MG-132 exposure. From those, only knockdown of c-Myc rescued JNK2-/- cells from PI-induced apoptosis, however, without affecting expression of Noxa. Together, our data not only show that a rapid execution of PI-induced apoptosis requires JNK1 for upregulation of Noxa via an as yet unknown transcription factor, but also that JNK2 controls this event in an oppositional manner.

c-Jun NH2-terminal kinase 1/2 and endoplasmic reticulum stress as interdependent and reciprocal causation in diabetic embryopathy

Embryos exposed to high glucose exhibit aberrant maturational and cytoarchitectural cellular changes, implicating cellular organelle stress in diabetic embryopathy. c-Jun-N-terminal kinase 1/2 (JNK1/2) activation is a causal event in maternal diabetes-induced neural tube defects (NTD). However, the relationship between JNK1/2 activation and endoplasmic reticulum (ER) stress in diabetic embryopathy has never been explored. We found that maternal diabetes significantly increased ER stress markers and induced swollen/enlarged ER lumens in embryonic neuroepithelial cells during neurulation. Deletion of either jnk1 or jnk2 gene diminished hyperglycemia-increased ER stress markers and ER chaperone gene expression. In embryos cultured under high-glucose conditions (20 mmol/L), the use of 4-phenylbutyric acid (4-PBA), an ER chemical chaperone, diminished ER stress markers and abolished the activation of JNK1/2 and its downstream transcription factors, caspase 3 and caspase 8, and Sox1 neural progenitor apoptosis. Consequently, both 1 and 2 mmol/L 4-PBA significantly ameliorated high glucose-induced NTD. We conclude that hyperglycemia induces ER stress, which is responsible for the proapoptotic JNK1/2 pathway activation, apoptosis, and NTD induction. Suppressing JNK1/2 activation by either jnk1 or jnk2 gene deletion prevents ER stress. Thus, our study reveals a reciprocal causation of ER stress and JNK1/2 in mediating the teratogenicity of maternal diabetes.

Insulin-like growth factor 1 receptor (IGF1R) expression and survival in operable squamous-cell laryngeal cancer

INTRODUCTION

Prognosis of patients with operable laryngeal cancer is highly variable and therefore potent prognostic biomarkers are warranted. The insulin-like growth factor receptor (IGFR) signaling pathway plays a critical role in laryngeal carcinogenesis and progression.

PATIENTS AND METHODS

We identified all patients with localized TNM stage I-III laryngeal cancer managed with potentially curative surgery between 1985 and 2008. Immunohistochemical (IHC) expression of IGF1R-alpha, IGF1R-beta and IGF2R was evaluated using the immunoreactive score (IRS) and mRNA levels of important effectors of the IGFR pathway were assessed, including IGF1R, IGF-binding protein 3 (IGFBP3), suppressor of cytokine signaling 2 (SOCS2) and members of the MAP-kinase (MAP2K1, MAPK9) and phosphatidyl-inositol-3 kinase (PIK3CA, PIK3R1) families. Cox-regression models were applied to assess the predictive value of biomarkers on disease-free survival (DFS) and overall survival (OS).

RESULTS

Among 289 eligible patients, 95.2% were current or ex smokers, 75.4% were alcohol abusers, 15.6% had node-positive disease and 32.2% had received post-operative irradiation. After a median follow-up of 74.5 months, median DFS was 94.5 months and median OS was 106.3 months. Using the median IRS as the pre-defined cut-off, patients whose tumors had increased IGF1R-alpha cytoplasm or membrane expression experienced marginally shorter DFS and significantly shorter OS compared to those whose tumors had low IGF1R-alpha expression (91.1 vs 106.2 months, p = 0.0538 and 100.3 vs 118.6 months, p = 0.0157, respectively). Increased mRNA levels of MAPK9 were associated with prolonged DFS (p = 0.0655) and OS (p = 0.0344). In multivariate analysis, IGF1R-alpha overexpression was associated with a 46.6% increase in the probability for relapse (p = 0.0374). Independent predictors for poor OS included node-positive disease (HR = 2.569, p<0.0001), subglottic/transglottic localization (HR = 1.756, p = 0.0438) and IGF1R-alpha protein overexpression (HR = 1.475, p = 0.0504).

CONCLUSION

IGF1R-alpha protein overexpression may serve as an independent predictor of relapse and survival in operable laryngeal cancer. Prospective evaluation of the IGF1R-alpha prognostic utility is warranted.

The requirement of c-Jun N-terminal kinase 2 in regulation of hypoxia-inducing factor-1α mRNA stability

The mRNA of hif-1α is considered as being constitutively and ubiquitously expressed, regardless of the level of oxygen tension. However many recent reports have showed that hif-1α mRNA could be regulated by natural antisense transcripts, potential microRNAs, and low O(2). In this study, it was found that a deficiency of JNK2 expression reduced HIF-1α protein induction in response to nickel treatment resulting from the impaired expression of hif-1α mRNA. Both the promoter luciferase assay and mRNA degradation assay clearly showed that depletion of JNK2 affected stability of hif-1α mRNA, rather than regulated its transcription. In addition, nucleolin, a classic histone chaperone, was demonstrated to physically bind to hif-1α mRNA and maintain its stability. Further investigation indicated that JNK2 regulated nucleolin expression and might in turn stabilize hif-1α mRNA. Collectively, we provided one more piece of evidence for the oncogenic role of JNK2 and nucleolin in regulating the cancer microenvironments by controlling HIF-1α expression.

Mitochondrial HSP70 cognate-mediated differential expression of JNK1/2 in the pollution stressed grey mullets, Mugil cephalus

Cells have evolved different networks of cellular stress responses to adapt during environmental changes and survive combating wide variety of stress. Mitochondrial heat shock protein 70 (mtHSP70) are essential for maintaining cellular homeostasis. c-Jun-N terminal kinase (JNK), a subfamily of MAPK, plays a key role in the transmission of extracellular signal for survival and death. In the present investigation, the differential expression of phosphorylated JNK1/2 with corresponding increases in heat shock transcription factor-1 (HSF-1) under high levels of B-cell lymphoma 2 (Bcl-2), HSP70 transcripts (twofold) and mtHSP70 has been correlated with fish survival in polluted Ennore estuary. This study suggests that in Ennore sample, the amplification in HSP70 transcripts along with corresponding mtHSP70 overexpression might be due to activation of JNK1/2 and HSF-1. This would influence the expression of Bcl-2 protein involved in mitochondrial survival under pollution-stressed condition.

The miR-17 family links p63 protein to MAPK signaling to promote the onset of human keratinocyte differentiation

The p63 protein plays a key role in regulating human keratinocyte proliferation and differentiation. Although some p63-regulating microRNAs (miRNAs) have been identified in the control of epidermal homeostasis, little is known about miRNAs acting downstream of p63. In this paper, we characterized multiple p63-regulated miRNAs (miR-17, miR-20b, miR-30a, miR-106a, miR-143 and miR-455-3p) and elucidated their roles in the onset of keratinocyte differentiation. We identified RB, p21 and multiple MAPKs as targets of these p63-controlled miRNAs. Upon inhibition of most of these miRNAs, we observed defects in commitment to differentiation that could be reversed by siRNA-mediated silencing of their targets. Furthermore, knockdown of MAPK8 and MAPK9 efficiently restored expression of the early differentiation markers keratin 1 and keratin 10 in p63-silenced primary human keratinocytes. These results highlight new mechanistic roles of multiple miRNAs, particularly the miR-17 family (miR-17, miR-20b and miR-106a), as regulatory intermediates for coordinating p63 with MAPK signaling in the commitment of human mature keratinocytes to early differentiation.

Increased JNK1 signaling pathway is responsible for ABCG2-mediated multidrug resistance in human colon cancer

Multidrug resistance remains a major obstacle to effective chemotherapy of colon cancer. ABCG2, as a half-transporter of the G subfamily of ATP-binding cassette transporter genes (ABC transporters), is known to play a crucial role in multidrug resistance. However, the molecular mechanism of controlling ABCG2 expression in drug resistance of colon cancer is unclear and scarcely reported. In the present study, we systematically investigate the potential role of the c-Jun NH2-terminal kinase (JNK) signal pathway in ABCG2-induced multidrug resistance in colon cancer. In the hydroxycamptothecin (HCPT) resistant cell line SW1116/HCPT from human colon cancer cell line SW1116, ABCG2 is the major factor for multidrug resistance, other than well-studied ABCB1 or ABCC1. Our findings indicate that blocking the JNK pathway by pathway inhibitor SP600125 reduces the expression level and transport function of ABCG2 in drug-resistant cells SW116/HCPT. Notably, the experiments of small interfering RNA directed against JNK1 and JNK2 show that only silence of JNK1 gene has the equal effect as SP600125 on dephosphorylation of transcription factor c-Jun and the expression of ABCG2 protein, while the corresponding phenomena were not observed after silence of JNK2 gene. Meanwhile, SP600125 induces the apoptosis of SW116/HCPT cells by promoting the cleavage of PARP and suppressing the anti-apoptotic protein survivin and bcl-2, and increases the sensitivity of SW1116/HCPT to HCPT. Taken together, our work demonstrated that JNK1/c-jun signaling pathway was involved in ABCG2-mediated multidrug resistance in colon cancer cells. Definitely, inhibition of the JNK1/c-jun pathway is useful for reversing ABCG2-mediated drug resistance in HCPT-resistant colon cancer cells.

Phospho-Bcl-x(L)(Ser62) plays a key role at DNA damage-induced G(2) checkpoint

Accumulating evidence suggests that Bcl-xL, an anti-apoptotic member of the Bcl-2 family, also functions in cell cycle progression and cell cycle checkpoints. Analysis of a series of phosphorylation site mutants reveals that cells expressing Bcl-xL(Ser62Ala) mutant are less stable at the G 2 checkpoint and enter mitosis more rapidly than cells expressing wild-type Bcl-xL or Bcl-xL phosphorylation site mutants, including Thr41Ala, Ser43Ala, Thr47Ala, Ser56Ala and Thr115Ala. Analysis of the dynamic phosphorylation and location of phospho-Bcl-xL(Ser62) in unperturbed, synchronized cells and during DNA damage-induced G 2 arrest discloses that a pool of phospho-Bcl-xL(Ser62) accumulates into nucleolar structures in etoposide-exposed cells during G 2 arrest. In a series of in vitro kinase assays, pharmacological inhibitors and specific siRNAs experiments, we found that Polo kinase 1 and MAPK9/JNK2 are major protein kinases involved in Bcl-xL(Ser62) phosphorylation and accumulation into nucleolar structures during the G 2 checkpoint. In nucleoli, phospho-Bcl-xL(Ser62) binds to and co-localizes with Cdk1(cdc2), the key cyclin-dependent kinase required for entry into mitosis. These data indicate that during G 2 checkpoint, phospho-Bcl-xL(Ser62) stabilizes G 2 arrest by timely trapping of Cdk1(cdc2) in nucleolar structures to slow mitotic entry. It also highlights that DNA damage affects the dynamic composition of the nucleolus, which now emerges as a piece of the DNA damage response.

JNK3 maintains expression of the insulin receptor substrate 2 (IRS2) in insulin-secreting cells: functional consequences for insulin signaling

We have recently shown that silencing of the brain/islet specific c-Jun N-terminal Kinase3 (JNK3) isoform enhances both basal and cytokine-induced beta-cell apoptosis, whereas silencing of JNK1 or JNK2 has opposite effects. While it is known that JNK1 or JNK2 may promote apoptosis by inhibiting the activity of the pro-survival Akt pathway, the effect of JNK3 on Akt has not been documented. This study aims to determine the involvement of individual JNKs and specifically JNK3 in the regulation of the Akt signaling pathway in insulin-secreting cells. JNK3 silencing strongly decreases Insulin Receptor Substrate 2 (IRS2) protein expression, and blocks Akt2 but not Akt1 activation by insulin, while the silencing of JNK1 or JNK2 activates both Akt1 and Akt2. Concomitantly, the silencing of JNK1 or JNK2, but not of JNK3, potently phosphorylates the glycogen synthase kinase3 (GSK3β). JNK3 silencing also decreases the activity of the transcription factor Forkhead BoxO3A (FoxO3A) that is known to control IRS2 expression, in addition to increasing c-Jun levels that are known to inhibit insulin gene expression. In conclusion, we propose that JNK1/2 on one hand and JNK3 on the other hand, have opposite effects on insulin-signaling in insulin-secreting cells; JNK3 protects beta-cells from apoptosis and dysfunction mainly through maintenance of a normal IRS2 to Akt2 signaling pathway. It seems that JNK3 mediates its effects mainly at the transcriptional level, while JNK1 or JNK2 appear to mediate their pro-apoptotic effect in the cytoplasm.

Neuronal c-Jun is required for successful axonal regeneration, but the effects of phosphorylation of its N-terminus are moderate

Although neural c-Jun is essential for successful peripheral nerve regeneration, the cellular basis of this effect and the impact of c-Jun activation are incompletely understood. In the current study, we explored the effects of neuron-selective c-Jun deletion, substitution of serine 63 and 73 phosphoacceptor sites with non-phosphorylatable alanine, and deletion of Jun N-terminal kinases 1, 2 and 3 in mouse facial nerve regeneration. Removal of the floxed c-jun gene in facial motoneurons using cre recombinase under control of a neuron-specific synapsin promoter (junΔS) abolished basal and injury-induced neuronal c-Jun immunoreactivity, as well as most of the molecular responses following facial axotomy. Absence of neuronal Jun reduced the speed of axonal regeneration following crush, and prevented most cut axons from reconnecting to their target, significantly reducing functional recovery. Despite blocking cell death, this was associated with a large number of shrunken neurons. Finally, junΔS mutants also had diminished astrocyte and microglial activation and T-cell influx, suggesting that these non-neuronal responses depend on the release of Jun-dependent signals from neighboring injured motoneurons. The effects of substituting serine 63 and 73 phosphoacceptor sites (junAA), or of global deletion of individual kinases responsible for N-terminal c-Jun phosphorylation were mild. junAA mutants showed decrease in neuronal cell size, a moderate reduction in post-axotomy CD44 levels and slightly increased astrogliosis. Deletion of Jun N-terminal kinase (JNK)1 or JNK3 showed delayed functional recovery; deletion of JNK3 also interfered with T-cell influx, and reduced CD44 levels. Deletion of JNK2 had no effect. Thus, neuronal c-Jun is needed in regeneration, but JNK phosphorylation of the N-terminus mostly appears to not be required for its function.

Induction of apoptosis coupled to endoplasmic reticulum stress in human prostate cancer cells by n-butylidenephthalide

BACKGROUND

N-butylidenephthalide (BP) exhibits antitumor effect in a variety of cancer cell lines. The objective of this study was to obtain additional insights into the mechanisms involved in BP induced cell death in human prostate cancer cells.

METHODS/PRINCIPAL FINDINGS

Two human prostate cancer cell lines, PC-3 and LNCaP, were treated with BP, and subsequently evaluated for their viability and cell cycle profiles. BP caused cell cycle arrest and cell death in both cell lines. The G0/G1 phase arrest was correlated with increase levels of CDK inhibitors (p16, p21 and p27) and decrease of the checkpoint proteins. To determine the mechanisms of BP-induced growth arrest and cell death in prostate cancer cell lines, we performed a microarray study to identify alterations in gene expression induced by BP in the LNCaP cells. Several BP-induced genes, including the GADD153/CHOP, an endoplasmic reticulum stress (ER stress)-regulated gene, were identified. BP-induced ER stress was evidenced by increased expression of the downstream molecules GRP78/BiP, IRE1-α and GADD153/CHOP in both cell lines. Blockage of IRE1-α or GADD153/CHOP expression by siRNA significantly reduced BP-induced cell death in LNCaP cells. Furthermore, blockage of JNK1/2 signaling by JNK siRNA resulted in decreased expression of IRE1-α and GADD153/CHOP genes, implicating that BP-induced ER stress may be elicited via JNK1/2 signaling in prostate cancer cells. BP also suppressed LNCaP xenograft tumor growth in NOD-SCID mice. It caused 68% reduction in tumor volume after 18 days of treatment.

CONCLUSIONS

Our results suggest that BP can cause G0/G1 phase arrest in prostate cancer cells and its cytotoxicity is mediated by ER stress induction. Thus, BP may serve as an anticancer agent by inducing ER stress in prostate cancer.

Hepatotoxicity mediated by pyrazole (cytochrome P450 2E1) plus tumor necrosis factor alpha treatment occurs in c-Jun N-terminal kinase 2-/- but not in c-Jun N-terminal kinase 1-/- mice

Cytochrome P450 2E1 (CYP2E1) induction and tumor necrosis factor alpha (TNF-α) production are key risk factors in alcoholic liver injury. Increased oxidative stress from CYP2E1 induction by pyrazole in vivo sensitizes the liver to TNF-α-induced hepatotoxicity by a mechanism involving the activation of c-jun N-terminal kinase (JNK) and mitochondrial damage. The aim of this study was to evaluate whether JNK1 or JNK2 plays a role in this potentiated hepatotoxicity. Wild-type (WT), jnk1(-/-) , and jnk2(-/-) mice were used to identify changes of hepatotoxicity, damage to mitochondria, and production of oxidative stress after pyrazole plus TNF-α treatment. Increased serum alanine aminotransferase, inflammatory infiltration, and central necrosis were observed in the jnk2(-/-) and WT mice treated with pyrazole plus TNF-α, but not in the jnk1(-/-) mice. Pyrazole elevated the activity and protein level of CYP2E1 in all mice. There was a significant increase of malondialdehyde, 4-hydroxynonenal adducts, 3-nitrotyrosine, and inducible nitric oxide synthase in the jnk2(-/-) and WT mice, compared to the jnk1(-/-) mice, upon pyrazole plus TNF-α treatment, or compared to mice treated with either pyrazole alone or TNF-α alone. The antioxidants, catalase, phospholipid hydroperoxide glutathione peroxidase, thioredoxin, and glutathione were lowered, and cytochrome c was released from the mitochondria in the jnk2(-/-) and WT mice. Mitochondrial production of superoxide was increased in the jnk2(-/-) and WT mice, compared to the jnk1(-/-) mice, upon pyrazole plus TNF-α treatment. Electron microscopy showed altered mitochondrial structure in the jnk2(-/-) and WT mice, but not the jnk1(-/-) mice.

CONCLUSIONS

JNK1 plays a role in the hepatotoxicity, mitochondrial dysfunction, and oxidative stress mediated by pyrazole plus TNF-α treatment. These findings raise the question as to the potential mechanisms of JNK1 activation related to alcoholic liver injury.

JNK2 participates in spindle assembly during mouse oocyte meiotic maturation

It is well known that c-Jun N-terminal kinase (JNK) plays pivotal roles in various mitotic events, but its function in mammalian oocyte meiosis remains unknown. In this study, we found that no specific JNK2 signal was detected in germinal vesicle stage. JNK2 was associated with the spindles especially the spindle poles and cytoplasmic microtubule organizing centers at prometaphase I, metaphase I, and metaphase II stages. JNK2 became diffusely distributed and associated with the midbody at telophase I stage. Injection of myc-tagged JNK2α1 mRNA into oocytes also revealed its localization on spindle poles. The association of JNK2 with spindle poles was further confirmed by colocalization with the centrosomal proteins, γ-tubulin and Plk1. Nocodazole treatment showed that JNK2 may interact with Plk1 to regulate the spindle assembly. Then we investigated the possible function of JNK2 by JNK2 antibody microinjection and JNK specific inhibitor SP600125 treatment. These two manipulations caused abnormal spindle formation and decreased the rate of first polar body (PB1) extrusion. In addition, inhibition of JNK2 resulted in impaired localization of Plk1. Taken together, our results suggest that JNK2 plays an important role in spindle assembly and PB1 extrusion during mouse oocyte meiotic maturation.

Redundant roles for cJun-N-terminal kinase 1 and 2 in interleukin-1beta-mediated reduction and modification of murine hepatic nuclear retinoid X receptor alpha

BACKGROUND/AIMS

Retinoid X receptor alpha (RXRalpha), the heterodimeric partner for multiple nuclear receptors (NRs), was shown to be an essential target for inflammation-induced cJun-N-terminal kinase (JNK) signaling in vitro. This study aimed to explore the role of hepatic JNK signaling and its effects on nuclear RXRalpha levels downstream of interleukin-1beta (IL-1beta) in vivo.

METHODS

Effects of IL-1beta on hepatic NR-dependent gene expression, nuclear RXRalpha levels, and roles for individual JNK isoforms were studied in wild-type, Jnk1(-/-), and Jnk2(-/-) mice and in primary hepatocytes of each genotype.

RESULTS

IL-1beta administration showed a time-dependent reduction in expression of the hepatic NR-dependent genes Ntcp, Cyp7a1, Cyp8b1, Abcg5, Mrp2, and Mrp3. IL-1beta treatment for 1h activated JNK and resulted in both post-translational modification and reduction of nuclear RXRalpha. In wild-type primary hepatocytes, IL-1beta modified and reduced nuclear RXRalpha levels time dependently, which was prevented by chemical inhibition of JNK as well as by inhibition of proteasomal degradation. Individual absence of either JNK1 or JNK2 did not significantly influence the reduction or modification of hepatic nuclear RXRalpha by IL-1beta both in vivo and in primary hepatocytes.

CONCLUSIONS

Functional redundancy exists for JNK1 and JNK2 in IL-1beta-mediated alterations of hepatic nuclear RXRalpha levels, stressing the importance of this pathway in mediating the hepatic response to inflammation.

GSK3beta is involved in JNK2-mediated beta-catenin inhibition

Background

We have recently reported that mitogen-activated protein kinase (MAPK) JNK1 downregulates β-catenin signaling and plays a critical role in regulating intestinal homeostasis and in suppressing tumor formation. This study was designed to determine whether JNK2, another MAPK, has similar and/or different functions in the regulation of β-catenin signaling.

Methodology and Principal Findings

We used an in vitro system with manipulation of JNK2 and β-catenin expression and found that activated JNK2 increased GSK3β activity and inhibited β-catenin expression and transcriptional activity. However, JNK2-mediated downregulation of β-catenin was blocked by the proteasome inhibitor MG132 and GSK3β inhibitor lithium chloride. Moreover, targeted mutations at GSK3β phosphorylation sites (Ser33 and Ser37) of β-catenin abrogated JNK2-mediated suppression of β-catenin. In vivo studies further revealed that JNK2 deficiency led to upregulation of β-catenin and increase of GSK3-β phosphorylation in JNK2-/- mouse intestinal epithelial cells. Additionally, physical interaction and co-localization among JNK2, β-catenin and GSK3β were observed by immunoprecipitation, mammalian two-hybridization assay and confocal microscopy, respectively.

Conclusion and Significance

In general, our data suggested that JNK2, like JNK1, interacts with and suppresses β-catenin signaling in vitro and in vivo, in which GSK3β plays a key role, although previous studies have shown distinct functions of JNK1 and JNK2. Our study also provides a novel insight into the crosstalk between Wnt/β-catenin and MAPK JNKs signaling.

c-Jun NH2-terminal kinase activity in subcutaneous adipose tissue but not nuclear factor-kappaB activity in peripheral blood mononuclear cells is an independent determinant of insulin resistance in healthy individuals

OBJECTIVE

Chronic low-grade activation of the immune system (CLAIS) predicts type 2 diabetes via a decrease in insulin sensitivity. Our study investigated potential relationships between nuclear factor-kappaB (NF-kappaB) and c-Jun NH(2)-terminal kinase (JNK) pathways-two pathways proposed as the link between CLAIS and insulin resistance.

RESEARCH DESIGN AND METHODS

Adiposity (dual-energy X-ray absorptiometry), waist-to-hip ratio (WHR), and insulin sensitivity (M, hyperinsulinemic-euglycemic clamp) were measured in 22 healthy nondiabetic volunteers (aged 29 +/- 11 years, body fat 28 +/- 11%). NF-kappaB activity (DNA-binding assay) and JNK1/2 activity (phosphorylated JNK) were assessed in biopsies of the vastus lateralis muscle and subcutaneous adipose tissue and in peripheral blood mononuclear cell (PBMC) lysates.

RESULTS

NF-kappaB activities in PBMCs and muscle were positively associated with WHR after adjustment for age, sex, and percent body fat (both P < 0.05). NF-kappaB activity in PBMCs was inversely associated with M after adjustment for age, sex, percent body fat, and WHR (P = 0.02) and explained 16% of the variance of M. There were no significant relationships between NF-kappaB activity and M in muscle or adipose tissue (both NS). Adipose-derived JNK1/2 activity was not associated with obesity (all P> 0.1), although it was inversely related to M (r = -0.54, P < 0.05) and explained 29% of its variance. When both NF-kappaB and JNK1/2 were examined statistically, only JNK1/2 activity in adipose tissue was a significant determinant of insulin resistance (P = 0.02).

CONCLUSIONS

JNK1/2 activity in adipose tissue but not NF-kappaB activity in PBMCs is an independent determinant of insulin resistance in healthy individuals.

Ultrafine particles from diesel engines induce vascular oxidative stress via JNK activation

Exposure to particulate air pollution is linked to increased incidences of cardiovascular diseases. Ambient ultrafine particles (UFP) from diesel vehicle engines have been shown to be proatherogenic in ApoE knockout mice and may constitute a major cardiovascular risk in humans. We posited that circulating nano-sized particles from traffic pollution sources induce vascular oxidative stress via JNK activation in endothelial cells. Diesel UFP were collected from a 1998 Kenworth truck. Intracellular superoxide assay revealed that these UFP dose-dependently induced superoxide (O(2)(-)) production in human aortic endothelial cells (HAEC). Flow cytometry showed that UFP increased MitoSOX red intensity specific for mitochondrial superoxide. Protein carbonyl content was increased by UFP as an indication of vascular oxidative stress. UFP also up-regulated heme oxygenase-1 (HO-1) and tissue factor (TF) mRNA expression, and pretreatment with the antioxidant N-acetylcysteine significantly decreased their expression. Furthermore, UFP transiently activated JNK in HAEC. Treatment with the JNK inhibitor SP600125 and silencing of both JNK1 and JNK2 with siRNA inhibited UFP-stimulated O(2)(-) production and mRNA expression of HO-1 and TF. Our findings suggest that JNK activation plays an important role in UFP-induced oxidative stress and stress response gene expression.

Inhibition of the mitochondrial permeability transition by cyclosporin A prevents pyrazole plus lipopolysaccharide-induced liver injury in mice

Previous results showed that pyrazole potentiates lipopolysaccharide (LPS)-induced liver injury in mice. Mechanisms involved the overexpression of cytochrome P450 2E1 (CYP2E1), oxidative stress, and activation of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). The current study was carried out to test the hypothesis that the mitochondria permeability transition (MPT) plays a role in this pyrazole plus LPS toxicity. Mice were injected intraperitoneally with pyrazole for 2 days, followed by a challenge with LPS with or without treatment with cyclosporin A (CsA), an inhibitor of the MPT. Serum alanine aminotransferase and aspartate aminotransferase were increased by pyrazole plus LPS treatment, and CsA treatment could attenuate these increases. CsA also prevented pyrazole plus LPS-induced hepatocyte necrosis. Formation of 4-hydroxynonenal protein adducts and 3-nitrotyrosine protein adducts in liver tissue was increased by the pyrazole plus LPS treatment, and CsA treatment blunted these increases. Swelling, cytochrome c release from mitochondria to the cytosol, and lipid peroxidation were increased in mitochondria isolated from the pyrazole plus LPS-treated mice, and CsA treatment prevented these changes. CsA did not prevent the increased levels of inducible nitric oxide synthase (iNOS), tumor necrosis factor-alpha (TNF-alpha), pp38 MAPK, and p-JNK2. In conclusion, although CsA does not prevent elevations in upstream mediators of the pyrazole plus LPS toxicity (iNOS, TNF-alpha, CYP2E1, MAPK), it does protect mice from the pyrazole plus LPS-induced liver toxicity by preventing the MPT and release of cytochrome c and decreasing mitochondrial oxidative stress. These results indicate that mitochondria are the critical targets of pyrazole plus LPS in mediating liver injury.

c-Jun N-terminal kinase 1 is deleterious to the function and survival of murine pancreatic islets

AIMS/HYPOTHESIS

Inhibition of c-jun N-terminal kinase (JNK) favours pancreatic islet function and survival. Since two JNK isoforms are present in the pancreas (JNK1 and JNK2), we addressed their specific roles in experimental islet transplantation.

METHODS

C57BL/6J (wild-type [WT]), Jnk1 (also known as Mapk8)(-/-) and Jnk2 (also known as Mapk9)(-/-) mice were used as donor/recipients in a syngeneic islet transplantation model. Islet cell composition, function, viability, production of cytokines and of vascular endothelial growth factor (VEGF) were also studied in vitro.

RESULTS

Jnk1 ( -/- ) islets secreted more insulin in response to glucose and were more resistant to cytokine-induced cell death compared with WT and Jnk2 (-/-) islets (p < 0.01). Cytokines reduced VEGF production in WT and Jnk2 (-/-) but not Jnk1 ( -/- ) islets; VEGF blockade restored Jnk1 ( -/- ) islet susceptibility to cytokine-induced cell death. Transplantation of Jnk1 ( -/- ) or WT islets into WT recipients made diabetic had similar outcomes. However, Jnk1 ( -/- ) recipients of WT islets had shorter time to diabetes reversal (17 vs 55 days in WT, p = 0.033), while none of the Jnk2 (-/-) recipients had diabetes reversal (0% vs 71% in WT, p = 0.0003). Co-culture of WT islets with macrophages from each strain revealed a discordant cytokine production.

CONCLUSIONS/INTERPRETATION

We have shown a deleterious effect of JNK2 deficiency on islet graft outcome, most likely related to JNK1 activation, suggesting that specific JNK1 blockade may be superior to general JNK inhibition, particularly when administered to transplant recipients.

Silencing Jnk1 and Jnk2 accelerates basal lipolysis and promotes fatty acid re-esterification in mouse adipocytes

AIMS/HYPOTHESIS

Elevated plasma levels of NEFA impair insulin action. Given the positive linear correlation between NEFA released by adipocytes and plasma NEFA levels, identification of mechanisms controlling adipocyte lipolysis and NEFA release could provide a guide to new therapies for insulin resistance and type 2 diabetes.

METHODS

Short hairpin RNA-mediated gene ablation was used to determine the functions of c-Jun N-terminal kinase (JNK)1 and JNK2 in adipocytes.

RESULTS

Combined JNK1/JNK2 deficiency drastically increased basal glycerol release, whereas individual JNK1- or JNK2-deficiency had no effect, indicating that JNK1/JNK2-deficiency enhances basal lipolysis, whereas the alternate subtype compensates for a single JNK subtype deficiency in the regulation of basal lipolysis. The profoundly increased glycerol release associated with JNK1/JNK2-deficiency was not accompanied by a concomitant increase in NEFA release over time. In addition, JNK1-deficiency, but not JNK2-deficiency, drastically decreased NEFA release as compared with that in JNK-intact cells, a result of increased NEFA re-esterification. In microarray, quantitative RT-PCR and western blotting, JNK1-, JNK2- and JNK1/JNK2-deficiencies selectively upregulated many genes involved in NEFA management, without affecting the expression of genes involved in insulin signalling. Assays using reporter genes driven by peroxisome proliferator-activated receptor gamma (PPAR-gamma)-responsive promoters indicate distinct roles for JNK1 and JNK2 in regulating the transcriptional effects of PPAR-gamma.

CONCLUSIONS/INTERPRETATION

While JNK1 and JNK2 have shared roles in the regulation of basal lipolysis, JNK1 has a more profound role in supporting baseline NEFA release. Inhibition of JNK1 activity in adipocytes has potential therapeutic uses for management of elevated circulating NEFA levels at the onset of insulin resistance.