Impaired Annulus Fibrosus Development and Vertebral Fusion Cause Severe Scoliosis in Mice with Deficiency of c-Jun NH2-Terminal Kinases 1 and 2.

Mitogen-activated protein kinases, including c-Jun NH2-terminal kinase (JNK), play an important role in the development and function of a large variety of tissues. The skeletal phenotype of JNK1 and JNK2 double-knockout (dKO) mice (JNK1fl/flCol2-Cre/JNK2-/-) and control genotypes were analyzed at different embryonic and postnatal stages. JNK1/2 dKO mice displayed a severe scoliotic phenotype beginning during development that was grossly apparent around weaning age. Alcian blue staining at embryonic day 17.5 showed abnormal fusion of the posterior spinal elements. In adult mice, fusion of vertebral bodies and of spinous and transverse processes was noted by micro-computed tomography, Alcian blue/Alizarin red staining, and histology. The long bones developed normally, and histologic sections of growth plate and articular cartilage revealed no significant abnormalities. Histologic sections of the vertebral column at embryonic days 15.5 and 17.5 revealed an abnormal organization of the annulus fibrosus in the dKOs, with chondrocyte-like cells and fusion of dorsal processes. Spinal sections in 10-week-old dKO mice showed replacement of intervertebral disk structures (annulus fibrosus and nucleus pulposus) by cartilage and bone tissues, with cells staining for markers of hypertrophic chondrocytes, including collagen X and runt-related transcription factor 2. These findings demonstrate a requirement for both JNK1 and JNK2 in the normal development of the axial skeleton. Loss of JNK signaling results in abnormal endochondral bone formation and subsequent severe scoliosis.

JNK2 up-regulates hypoxia-inducible factors and contributes to hypoxia-induced erythropoiesis and pulmonary hypertension.

The hypoxic response is a stress response triggered by low oxygen tension. Hypoxia-inducible factors (HIFs) play a prominent role in the pathobiology of hypoxia-associated conditions, including pulmonary hypertension (PH) and polycythemia. The c-Jun N-terminal protein kinase (JNK), a stress-activated protein kinase that consists of two ubiquitously expressed isoforms, JNK1 and JNK2, and a tissue-specific isoform, JNK3, has been shown to be activated by hypoxia. However, the physiological role of JNK1 and JNK2 in the hypoxic response remains elusive. Here, using genetic knockout cells and/or mice, we show that JNK2, but not JNK1, up-regulates the expression of HIF-1α and HIF-2α and contributes to hypoxia-induced PH and polycythemia. Knockout or silencing of JNK2, but not JNK1, prevented the accumulation of HIF-1α in hypoxia-treated cells. Loss of JNK2 resulted in a decrease in HIF-1α and HIF-2α mRNA levels under resting conditions and in response to hypoxia. Consequently, hypoxia-treated Jnk2-/- mice had reduced erythropoiesis and were less prone to polycythemia because of decreased expression of the HIF target gene erythropoietin (Epo). Jnk2-/- mice were also protected from hypoxia-induced PH, as indicated by lower right ventricular systolic pressure, a process that depends on HIF. Taken together, our results suggest that JNK2 is a positive regulator of HIFs and therefore may contribute to HIF-dependent pathologies.

Cigarette smoke upregulates SPRR3 by favoring c-Jun/Fra1 heterodimerization in human bronchial epithelial cells.

AIM: The airway epithelium of smokers exhibits upregulated SPRR3, an indicator of pathogenic keratinization. The mechanisms underlying this phenomenon require investigation. PATIENTS & METHODS: Human bronchial epithelial (HBE) SPRR3 expression was analyzed by smoking status. Primary HBE cells were exposed to cigarette smoke (CS). SPRR3 expression, SPRR3 promoter activity, AP-1 factor binding and AP-1 factors' effects were analyzed. RESULTS: Current smokers display SPRR3 upregulation relative to never smokers. CS upregulates SPRR3 transcription in an exposure-dependent manner. CS promotes c-Jun and Fra1 binding to the SPRR3-AP-1/TRE site. Wild-type c-Jun and Fra1 upregulate, whereas c-Jun and Fra1, dominant-negative mutants, suppress SPRR3 promoter activity. CONCLUSION: CS induces SPRR3 upregulation in HBE cells by promoting aberrant c-Jun/Fra1 dimerization.

Type 2 Diabetes and Hepatocellular Carcinoma: Risk Factors and Pathogenesis.

PURPOSE OF REVIEW: This review aims to assess the epidemiological evidence for a link between type 2 diabetes and hepatocellular carcinoma and to investigate possible pathophysiological mechanisms. RECENT FINDINGS: The presence of type 2 diabetes significantly increases the risk of developing hepatocellular carcinoma, and treatment with metformin may be associated with a lower risk. Treatment with insulin and sulphonylureas may be associated with increased risk. The pathophysiology underlying development of hepatocellular carcinoma in this context is complex and is likely to involve increased proinflammatory mediators, oxidative stress, JNK-1 activation, increased IGF-1 activity, altered gut microbiota and immunomodulation. Hepatocellular carcinoma incidence is increasing and this is likely to be linked to the increasing incidence of type 2 diabetes, obesity and the metabolic syndrome. These conditions increase the risk of developing hepatocellular carcinoma, and a greater understanding of the underlying pathophysiology may help with the development of novel treatments.

IL-12 and IL-23 Production in Toxoplasma gondii- or LPS-Treated Jurkat T Cells via PI3K and MAPK Signaling Pathways.

IL-12 and IL-23 are closely related in structure, and have been shown to play crucial roles in regulation of immune responses. However, little is known about the regulation of these cytokines in T cells. Here, we investigated the roles of PI3K and MAPK pathways in IL-12 and IL-23 production in human Jurkat T cells in response to Toxoplasma gondii and LPS. IL-12 and IL-23 production was significantly increased in T cells after stimulation with T. gondii or LPS. T. gondii and LPS increased the phosphorylation of AKT, ERK1/2, p38 MAPK, and JNK1/2 in T cells from 10 min post-stimulation, and peaked at 30-60 min. Inhibition of the PI3K pathway reduced IL-12 and IL-23 production in T. gondii-infected cells, but increased in LPS-stimulated cells. IL-12 and IL-23 production was significantly reduced by ERK1/2 and p38 MAPK inhibitors in T. gondii- and LPS-stimulated cells, but not in cells treated with a JNK1/2 inhibitor. Collectively, IL-12 and IL-23 production was positively regulated by PI3K and JNK1/2 in T. gondii-infected Jurkat cells, but negatively regulated in LPS-stimulated cells. And ERK1/2 and p38 MAPK positively regulated IL-12 and IL-23 production in Jurkat T cells. These data indicate that T. gondii and LPS induced IL-12 and IL-23 production in Jurkat T cells through the regulation of the PI3K and MAPK pathways; however, the mechanism underlying the stimulation of IL-12 and IL-23 production by T. gondii in Jurkat T cells is different from that of LPS.

Bone marrow-derived c-jun N-terminal kinase-1 (JNK1) mediates liver regeneration.

Liver regeneration is controlled by a complex network of signaling molecules, and a prominent role for c-jun N-terminal kinase has been suggested during this process. In the present study, we aimed to characterize and define the cell-type-specific contribution of JNK1 activation during liver regeneration. We used hepatocyte-specific JNK1 knockout mice (JNK1(Δhepa)) using the cre/lox-P system. We performed partial hepatectomy (PH) in WT, JNK1(Δhepa) and JNK1(-/-) animals and investigated time-points up to 72 h after PH. Additionally, bone marrow transplantation experiments were conducted in order to identify the contribution of hematopoietic cell-derived JNK1 activation for liver regeneration. Our results show that liver regeneration was significantly impaired in JNK1(-/-) compared to JNK1(Δhepa) and WT animals. These data were evidenced by lower BrdU incorporation and decreased cell cycle markers such as Cyclin A, Cyclin D, E2F1 and PCNA 48 h after PH in JNK1(-/-) compared with JNK1(Δhepa) and WT livers. In JNK1(-/-) mice, our findings were associated with a reduced acute phase response as evidenced by a lower activation of the IL-6/STAT3/SAA-1 cascade. Additionally, CD11b(+)Ly6G(+)-cells were decreased in JNK1(-/-) compared with JNK1(Δhepa) and WT animals after PH. The transplantation of bone marrow-derived JNK1(-/-) into WT recipients caused significant reduction in liver regeneration. Interestingly, the transplantation of JNK1(-/-) into mice lacking JNK1 in hepatocytes only partially delayed liver regeneration. In summary, we provide evidence that (1) JNK1 in hematopoietic cells is crucial for liver regeneration, and (2) a synergistic function between JNK1 in hepatocytes and hematopoietic-derived cells is involved in the hepatic regenerative response.

Stronger learning recruits additional cell-signaling cascades: c-Jun-N-terminal kinase 1 (JNK1) is necessary for expression of stronger contextual fear conditioning.

Increased training often results in stronger memories but the neural changes responsible for these stronger memories are poorly understood. It is proposed here that higher levels of training that result in stronger memories recruit additional cell signaling cascades. This study specifically examined if c-Jun N-terminal kinase 1 (JNK1) is involved in the formation of stronger fear conditioning memories. Wildtype (WT), JNK1 heterozygous (Het), and JNK1 knockout (KO) mice were fear conditioned with 1 trial, 2 trials, or 4 trials. All mice learned both contextual (hippocampus-dependent) and cued (hippocampus-independent) fear conditioning but for contextual fear conditioning only, the JNK1 KO mice did not show higher levels of learning with increased trials. That is, WT mice showed a significant linear increase in contextual fear conditioning as training trials increased from 1 to 2 to 4 trials whereas KO mice showed the same level of contextual fear conditioning as WT mice for 1 trial training but did not have increased levels of contextual fear conditioning with additional trials. These data suggest that JNK1 may not be critical for learning but when higher levels of hippocampus-dependent learning occur, JNK1 signaling is recruited and is necessary for stronger hippocampus-dependent memory formation.

JNK suppresses pulmonary fibroblast elastogenesis during alveolar development.

BACKGROUND: The formation of discrete elastin bands at the tips of secondary alveolar septa is important for normal alveolar development, but the mechanisms regulating the lung elastogenic program are incompletely understood. JNK suppress elastin synthesis in the aorta and is important in a host of developmental processes. We sought to determine whether JNK suppresses pulmonary fibroblast elastogenesis during lung development. METHODS: Alveolar size, elastin content, and mRNA of elastin-associated genes were quantitated in wild type and JNK-deficient mouse lungs, and expression profiles were validated in primary lung fibroblasts. Tropoelastin protein was quantitated by Western blot. Changes in lung JNK activity throughout development were quantitated, and pJNK was localized by confocal imaging and lineage tracing. RESULTS: By morphometry, alveolar diameters were increased by 7% and lung elastin content increased 2-fold in JNK-deficient mouse lungs compared to wild type. By Western blot, tropoelastin protein was increased 5-fold in JNK-deficient lungs. Postnatal day 14 (PND14) lung JNK activity was 11-fold higher and pJNK:JNK ratio 6-fold higher compared to PN 8 week lung. Lung tropoelastin, emilin-1, fibrillin-1, fibulin-5, and lysyl oxidase mRNAs inversely correlated with lung JNK activity during alveolar development. Phosphorylated JNK localized to pulmonary lipofibroblasts. PND14 JNK-deficient mouse lungs contained 7-fold more tropoelastin, 2,000-fold more emilin-1, 800-fold more fibrillin-1, and 60-fold more fibulin-5 than PND14 wild type lungs. Primarily lung fibroblasts from wild type and JNK-deficient mice showed similar differences in elastogenic mRNAs. CONCLUSIONS: JNK suppresses fibroblast elastogenesis during the alveolar stage of lung development.

Reduction of TLR4 mRNA stability and protein expressions through inhibiting cytoplasmic translocation of HuR transcription factor by E2 and/or ERα in LPS-treated H9c2 cardiomyoblast cells.

Our previous results have indicated that Akt mediates 17ß-estradiol (E2) and/or estrogen receptor α (ERα) to inhibit lipopolysaccharide (LPS)-induced JNK activity, tumor necrosis factor α (TNFα) protein expression, and exhibits cardioprotective effects. Toll-like receptor 4 (TLR4) mRNAs often contain AU-rich elements (AREs) in their 3'-untranslated regions (3'UTR) which have a high affinity for RNA-binding proteins. It is not known whether E2 and ERα affect TLR4 mRNA stability and TLR4 protein expression through regulating the RNA-binding proteins, human antigen R (HuR), tristetraprolin (TTP) and AU-binding factor 1 (AUF-1) in myocardial cells. Therefore, we investigated if the LPS in- duces these RNA-binding proteins to regulate TLR4 mRNAs of cardiomyocytes, and whether the E2/ERα reduces the TLR4 mRNA stability induced by LPS through the inhibition of RNA-binding protein expression. Using a doxycycline (Dox)-induced Tet-On ERα H9c2 myocardic cell model, we also aimed to identify whether E2 and/or ERα regulate LPS-induced TLR4 mRNA stability. The results of Western blotting and reverse transcription-PCR assays demonstrated that LPS significantly in- creased the level of cytoplasmic HuR protein and the stability of TLR4 mRNA, and farther induced TLR4 protein expression in H9c2 cells, an effect mediated through the JNK pathway. Interestingly, E2 and/or ERα decreased the cytoplasmic HuR protein level and TLR4 mRNA stability, and farther decreased the level of TLR4 protein induced by LPS in H9c2 cardiomyoblast cells. Therefore, LPS triggered HuR expression which led to enhanced TLR4 mRNA and upregulated TLR4 expression through JNK1/2 in myocardial cells.

Differential roles of JNK, ERK1/2, and p38 mitogen-activated protein kinases on endothelial cell tissue repair functions in response to tumor necrosis factor-α.

Tumor necrosis factor (TNF)-α can alter tissue repair functions in a variety of cells including endothelial cells. However, the mechanism by which TNF-α mediates these functional changes has not fully been studied. We investigated the role of mitogen-activated protein kinases (MAPKs) on mediating the regulatory effect of TNF-α on the tissue repair functions of human pulmonary artery endothelial cells (HPAECs). TNF-α protected HPAECs from undergoing apoptosis induced by serum and growth factor deprivation, augmented collagen gel contraction, and stimulated wound closure. TNF-α activated c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinases 1 and 2 (ERK1/2), and p38. Inhibitors of JNK (SP600125, 5 µM) or ERK1/2 (PD98059, 5 µM) significantly inhibited TNF-α-stimulated cell survival, contraction of collagen gels, and wound closure. In contrast, the p38 inhibitor SB203580 (5 µM) further amplified all of the TNF-α effects on HPAECs. TNF-α specifically activated p38α but not other p38 isoforms and suppression of p38α by an siRNA resulted in further amplification of the TNF-α effect. These results suggest that TNF-α stimulates tissue repair functions of HPAECs, and this may be mediated, at least in part, positively via JNK and ERK1/2, and negatively through p38α. MAPKs may play a role in endothelial cell-mediated tissue repair, especially in an inflammatory milieu where TNF-α is present.

WNT5A/JNK signaling regulates pancreatic cancer cells migration by Phosphorylating Paxillin.

BACKGROUND: Expression of WNT5A associated with aggressive tumor biology and poor clinical outcome of various types of cancer. However its function in the metastasis property of pancreatic cells still needs to be elucidated. METHODS: We detected the expressions of WNT5A, JNK1/p-JNK1 and Paxillin/p-Paxillin in cancer and the para-carcinoma tissues of pancreatic cancer. To understand how WNT5A/JNK signaling affects pancreatic cancer cell migration through the phosphorylation of cellular substrates of Paxillin, In vitro, we knocked down the WNT5A in PANC1, Capan-2 and HT1080 cell lines, and then tested the expression of JNK1. We detected the proteins of phosphorylation of Paxillin after JNK1 was inhibited and then the cells migration assay was evaluated. Moreover, JNK1 functionally phosphorylates serine178 on paxillin in vitro was detected .At last we subsequently observed whether WNT5A/JNK signaling modulates some molecule expressions relevant to focal adhesion (FA) formation and mesenchymal transition (EMT) and cell cycle. RESULTS: WNT5A, p-JNK1 and p-Paxillin were highly expressed in early stage of tumor tissues. In vitro, WNT5A/JNK signaling promotes cell migration in pancreatic cancer by phosphorylating serine178 on Paxillin, an FA adaptor, which means WNT5A may regulate FA's function.WNT5A up-regulates the molecule's expressions relevant to cell adhesion through the phosphorylation of JNK1, including MMP1, MMP2, ICAM and CD44. In addition, WNT5A/JNK signaling promoted the mRNA expressions of vimentin, but decreased in E-Cadherin expression, which suggested its regulatory effects on the EMT processes. WNT5A/JNK signaling didn't modulate cell proliferation. CONCLUSION: WNT5A/JNK signaling initiate cell migration of pancreatic cancer through activation of Paxillin, which suggested WNT5A has the potency of being an effective therapeutic target for the metastasis of pancreatic cancer.

Role of c-Jun N-terminal kinase isoforms in the cellular activity of melanoma cell lines.

BACKGROUND: The c-Jun N-terminal kinase (JNK) is thought to be involved in inflammation, proliferation and apoptosis. AIM: To examine the role of JNK isoforms in metastasis, proliferation, migration and invasion of the malignant melanoma (MM) cell lines SK-MEL-28, SK-MEL-3 and WM164, using a kinase-specific inhibitor or isoform-specific small interfering (si)RNAs. RESULTS: SK-MEL-3, a cell line established from metastatic MM, showed slightly increased phosphorylation of both JNK1 and JNK2, whereas WM164, a cell line derived from primary MM, showed significant phosphorylation of JNK1. A JNK inhibitor, SP600125, inhibited cell proliferation of SK-MEL-3 but not SK-MEL-28 or WM164. Transfection of JNK1-specific siRNA reduced the migratory activity of WM164 cells, while silencing of either JNK1 or JNK2 strongly suppressed the invasive activity of SK-MEL-3. CONCLUSIONS: Our study suggests that JNK isoforms have different roles in MM. Metastasis of MM may be regulated by JNK2, while invasion is regulated by both JNK1 and JNK2. JNK1 and JNK2 respectively mediate cell migration and cell proliferation. Further understanding of the specific roles of JNK isoforms in the pathogenesis of MM may lead to the development of therapies targeting specific isoforms.

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.

Platelet JNK1 is involved in secretion and thrombus formation.

The role of c-Jun NH(2)-terminal kinase 1 (JNK1) in hemostasis and thrombosis remains unclear. We show here, with JNK1-deficient (JNK1(-/-)) mice, that JNK1 plays an important role in platelet biology and thrombus formation. In tail-bleeding assays, JNK1(-/-) mice exhibited longer bleeding times than wild-type mice (396 +/- 39 seconds vs 245 +/- 32 seconds). We also carried out in vitro whole-blood perfusion assays on a collagen matrix under arterial shear conditions. Thrombus formation was significantly reduced for JNK1(-/-) platelets (51%). In an in vivo model of thrombosis induced by photochemical injury to cecum vessels, occlusion times were 4.3 times longer in JNK1(-/-) arterioles than in wild-type arterioles. Moreover, in vitro studies carried out in platelet aggregation conditions demonstrated that, at low doses of agonists, platelet secretion was impaired in JNK1(-/-) platelets, leading to altered integrin alphaIIbbeta3 activation and reduced platelet aggregation, via a mechanism involving protein kinase C. JNK1 thus appears to be essential for platelet secretion in vitro, consistent with its role in thrombus growth in vivo. Finally, we showed that ERK2 and another isoform of JNK affect platelet aggregation through 2 pathways, one dependent and another independent of JNK1.

Role of JNK-1 regulation in the protection of contact-inhibited fibroblasts from oxidative stress.

The molecular signaling events leading to protection from oxidative stress-induced apoptosis upon contact inhibition have not been fully investigated. Previous research has indicated a role for mitogen-activated protein kinases (MAPKs) in the regulation of contact inhibition, and these proteins have also been associated with cell cycle regulation and stress-induced apoptosis. The potential role of the MAPK JNK-1 in the stress-response of actively proliferating and contact-inhibited cells was investigated. Actively proliferating normal fibroblasts (BJ) and fibrosarcoma cells (HT-1080) were stressed with H2O2, and levels of activated JNK-1 and cleaved PARP were ascertained. Similarly, these results were compared with levels of activated JNK-1 and cleaved PARP detected in H2O2-stressed confluent fibrosarcoma or contact-inhibited fibroblast cells. Contact-inhibited fibroblasts were protected from apoptosis in comparison to subconfluent fibroblasts, concurrent with decreased JNK-1 activation. Increased culture density of fibrosarcoma cells was not protective against apoptosis, and these cells did not demonstrate density-dependent alterations in the JNK-1 stress response. This decreased activation of JNK-1 in stressed, contact-inhibited cells did not appear to be dependent upon increased expression of MKP-1; however, over-expression of MKP-1 was sufficient to result in a slight decrease in H2O2-stimulated PARP cleavage. Increasing the antioxidant capacity of fibroblasts through NAC-treatment not only lessened H2O2-stimulated JNK-1 activation, but also did not influence the expression of MKP-1. Taken together, these results suggest that regulation of negative regulation of JNK-1 upon contact inhibition is protective against apoptosis, and that this regulation is independent of MKP-1.

The JNKs differentially regulate RNA polymerase III transcription by coordinately modulating the expression of all TFIIIB subunits.

RNA polymerase (pol) III-dependent transcription is subject to stringent regulation by tumor suppressors and oncogenic proteins and enhanced RNA pol III transcription is essential for cellular transformation and tumorigenesis. Since the c-Jun N-terminal kinases (JNKs) display both oncogenic and tumor suppressor properties, the roles of these proteins in regulating RNA pol III transcription were examined. In both mouse and human cells, loss or reduction in JNK1 expression represses RNA pol III transcription. In contrast, loss or reduction in JNK2 expression induces transcription. The JNKs coordinately regulate expression of all 3 TFIIIB subunits. While JNK1 positively regulates TBP expression, the RNA pol III-specific factors, Brf1 and Bdp1, JNK2 negatively regulates their expression. Brf1 is coregulated with TBP through the JNK target, Elk-1. Reducing Elk-1 expression decreases Brf1 expression. Decreasing JNK1 expression reduces Elk-1 occupancy at the Brf1 promoter, while decreasing JNK2 expression enhances recruitment of Elk-1 to the Brf1 promoter. In contrast, regulation of Bdp1 occurs through JNK-mediated alterations in TBP expression. Altered TBP expression mimics the effect of reduced JNK1 or JNK2 levels on Bdp1 expression. Decreasing JNK1 expression reduces the occupancy of TBP at the Bdp1 promoter, while decreasing JNK2 expression enhances recruitment of TBP to the Bdp1 promoter. Together, these results provide a molecular mechanism for regulating RNA pol III transcription through the coordinate control of TFIIIB subunit expression and elucidate opposing functions for the JNKs in regulating a large class of genes that dictate the biosynthetic capacity of cells.

Hippocampal c-Jun-N-terminal kinases serve as negative regulators of associative learning.

In the adult mouse, signaling through c-Jun N-terminal kinases (JNKs) links exposure to acute stress to various physiological responses. Inflammatory cytokines, brain injury and ischemic insult, or exposure to psychological acute stressors induce activation of hippocampal JNKs. Here we report that exposure to acute stress caused activation of JNKs in the hippocampal CA1 and CA3 subfields, and impaired contextual fear conditioning. Conversely, intrahippocampal injection of JNKs inhibitors sp600125 (30 µm) or D-JNKI1 (8 µm) reduced activity of hippocampal JNKs and rescued stress-induced deficits in contextual fear. In addition, intrahippocampal administration of anisomycin (100 µg/µl), a potent JNKs activator, mimicked memory-impairing effects of stress on contextual fear. This anisomycin-induced amnesia was abolished after cotreatment with JNKs selective inhibitor sp600125 without affecting anisomycin's ability to effectively inhibit protein synthesis as measured by c-Fos immunoreactivity. We also demonstrated milder and transient activation of the JNKs pathway in the CA1 subfield of the hippocampus during contextual fear conditioning and an enhancement of contextual fear after pharmacological inhibition of JNKs under baseline conditions. Finally, using combined biochemical and transgenic approaches with mutant mice lacking different members of the JNK family (Jnk1, Jnk2, and Jnk3), we provided evidence that JNK2 and JNK3 are critically involved in stress-induced deficit of contextual fear, while JNK1 mainly regulates baseline learning in this behavioral task. Together, these results support the possibility that hippocampal JNKs serve as a critical molecular regulator in the formation of contextual fear.

Effect of doublecortin on self-renewal and differentiation in brain tumor stem cells.

Analysis of microarray probe data from glioma patient samples, in conjunction with patient Kaplan-Meier survival plots, indicates that expression of a glioma suppressor gene doublecortin (DCX) favors glioma patient survival. From neurosphere formation in culture, time-lapse microscopic video recording, and tumor xenograft, we show that DCX synthesis significantly reduces self-renewal of brain tumor stem cells (BTSC) in human primary glioma (YU-PG, HF66) cells from surgically removed human glioma specimens and U87 cells in vitro and in vivo. Time-lapse microscopic video recording revealed that double transfection of YU-PG, HF66, and U87 cells with DCX and neurabin II caused incomplete cell cycle with failure of cytokinesis, that is, endomitosis by dividing into three daughter cells from one mother BTSC. Activation of c-jun NH2-terminal kinase 1 (JNK1) after simvastatin (10 nM) treatment of DCX(+) neurabin II(+) BTSC from YU-PG, HF66, and U87 cells induced terminal differentiation into neuron-like cells. dUTP nick end labeling data indicated that JNK1 activation also induced apoptosis only in double transfected BTSC with DCX and neurabin II, but not in single transfected BTSC from YU-PG, HF66, and U87 cells. Western blot analysis showed that procaspase-3 was induced after DCX transfection and activated after simvastatin treatment in YU-PG, HF66, and U87 BTSC. Sequential immunoprecipitation and Western blot data revealed that DCX synthesis blocked protein phosphatase-1 (PP1)/caspase-3 protein-protein interaction and increased PP1-DCX interaction. These data show that DCX synthesis induces apoptosis in BTSC through a novel JNK1/neurabin II/DCX/PP1/caspase-3 pathway.

Distinct roles of stress-activated protein kinases in Fanconi anemia-type C-deficient hematopoiesis.

The underlying molecular mechanisms that promote bone marrow failure in Fanconi anemia are incompletely understood. Evidence suggests that enhanced apoptosis of hematopoietic precursors is a major contributing factor. Previously, enhanced apoptosis of Fanconi anemia type C-deficient (Fancc(-/-)) progenitors was shown to involve aberrant p38 MAPK activation. Given the importance of c-Jun N-terminal kinase (JNK) in the stress response, we tested whether enhanced apoptosis of Fancc(-/-) cells also involved altered JNK activation. In Fancc(-/-) murine embryonic fibroblasts, tumor necrosis factor alpha (TNF-alpha) induced elevated JNK activity. In addition, JNK inhibition protected Fancc(-/-) murine embryonic fibroblasts and c-kit(+) bone marrow cells from TNF-alpha-induced apoptosis. Importantly, hematopoietic progenitor assays demonstrated that JNK inhibition enhanced Fancc(-/-) colony formation in the presence of TNF-alpha. Competitive repopulation assays showed that Fancc(-/-) donor cells cultured with the JNK inhibitor had equivalent levels of donor chimerism compared with Fancc(-/-) donor cells cultured with vehicle control. In contrast, culturing Fancc(-/-) cells with a p38 MAPK inhibitor significantly increased repopulating ability, supporting an integral role of p38 MAPK in maintaining Fancc(-/-) hematopoietic stem cell function. Taken together, these data suggest that p38 MAPK, but not JNK, has a critical role in maintaining the engraftment of Fancc(-/-)-reconstituting cells under conditions of stress.