SP600125, an anthrapyrazolone inhibitor of Jun N-terminal kinase

Paeonol attenuates isoflurane anesthesia-induced hippocampal neurotoxicity via modulation of JNK/ERK/P38MAPK pathway and regulates histone acetylation in neonatal rat

Objective: Volatile anesthetic such as isoflurane causes widespread neurodegeneration in the developing animal brains and also induces cognitive impairments. Paeonol is a plant-derived phenolic compound possessing numerous bioactive properties. The study investigates the neuroprotective effects of paeonol against isoflurane-induced neurodegeneration and cognitive disturbances in neonatal rats.Methods: Paeonol (50, 100, and 150 mg/kg body weight/day) was given orally to separate groups of neonatal rats from postnatal day 3 (P3) to P21 and were exposed to isoflurane (0.75%; 6 h) on P7.Results: Neuroapoptosis following isoflurane exposure was remarkably reduced by paeonol. Isoflurane-induced elevated cleaved caspase-3, Bad, and Bax expression, were down-regulated on paeonol administration. Paeonol significantly enhanced expression of antiapoptotic proteins (Bcl-2, Bcl-xL, xIAP, c-IAP-1, c-IAP-2, and survivin) and improved acetylation of HK39 and HK412. The expression of histone deacetylases (HDACs)-HDAC2 and HDAC-3 were down-regulated. Isoflurane-induced activation of JNK/p38MAPK signaling and suppressed ERK signaling and were effectively regulated by paeonol. General behavior and freezing responses of the rats were improved. Results of the Morris Water Maze tests revealed improved learning and memory retention on paeonol treatment.Conclusions: Paeonol effectively inhibited neuroapoptosis and improved isoflurane-induced cognitive dysfunctions via regulating histone acetylation and JNK/ERK1/2/p38MAPK signaling pathways.

Prenylated quinolinecarboxylic acid derivative prevents neuronal cell death through inhibition of MKK4

The development of neuroprotective agents is necessary for the treatment of neurodegenerative diseases. Here, we report PQA-11, a prenylated quinolinecarboxylic acid (PQA) derivative, as a potent neuroprotectant. PQA-11 inhibits glutamate-induced cell death and caspase-3 activation in hippocampal cultures, as well as inhibits N-Methyl-4-phenylpyridinium iodide- and amyloid β_1-42-induced cell death in SH-SY5Y cells. PQA-11 also suppresses mitogen-activated protein kinase kinase 4 (MKK4) and c-jun N-terminal kinase (JNK) signaling activated by these neurotoxins. Quartz crystal microbalance analysis and in vitro kinase assay reveal that PQA-11 interacts with MKK4, and inhibits its sphingosine-induced activation. The administration of PQA-11 by intraperitoneal injection alleviates 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced degeneration of nigrostriatal dopaminergic neurons in mice. These results suggest that PQA-11 is a unique MKK4 inhibitor with potent neuroprotective effects in vitro and in vivo. PQA-11 may be a valuable lead for the development of novel neuroprotectants.

ER stress signaling has an activating transcription factor 6α (ATF6)-dependent "off-switch"

In response to an accumulation of unfolded proteins in the endoplasmic reticulum (ER) lumen, three ER transmembrane signaling proteins, inositol-requiring enzyme 1 (IRE1), PRKR-like ER kinase (PERK), and activating transcription factor 6α (ATF6α), are activated. These proteins initiate a signaling and transcriptional network termed the unfolded protein response (UPR), which re-establishes cellular proteostasis. When this restoration fails, however, cells undergo apoptosis. To investigate cross-talk between these different UPR enzymes, here we developed a high-content live cell screening platform to image fluorescent UPR-reporter cell lines derived from human SH-SY5Y neuroblastoma cells in which different ER stress signaling proteins were silenced through lentivirus-delivered shRNA constructs. We observed that loss of ATF6 expression results in uncontrolled IRE1-reporter activity and increases X box-binding protein 1 (XBP1) splicing. Transient increases in both IRE1 mRNA and IRE1 protein levels were observed in response to ER stress, suggesting that IRE1 up-regulation is a general feature of ER stress signaling and was further increased in cells lacking ATF6 expression. Moreover, overexpression of the transcriptionally active N-terminal domain of ATF6 reversed the increases in IRE1 levels. Furthermore, inhibition of IRE1 kinase activity or of downstream JNK activity prevented an increase in IRE1 levels during ER stress, suggesting that IRE1 transcription is regulated through a positive feed-forward loop. Collectively, our results indicate that from the moment of activation, IRE1 signaling during ER stress has an ATF6-dependent "off-switch."

Mechanical stretch aggravates aortic dissection by regulating MAPK pathway and the expression of MMP-9 and inflammation factors

This study aimed to explore whether mechanical stretch aggravated aortic dissection through regulating MAPK pathway, MMP-9, and inflammation factors. We first established aortic dissection model rats. Mechanical stretch (3 g) was exerted on vascular ring of aortic dissection which was also treated by inhibitors of MAPK pathway (SB203580, SP600125, and U0126). HE and Masson staining showed that aortic dissection severity with 3 g tension was worse than that without tension (0 g); after the treatments of diverse inhibitors, the fracture and breakage of the elastic fibers decreased. The expression of MMP-9, TNF-α, IL-1β) p38/p-p38, JNK1/p-JNK1, and ERK1/2/p-ERK1/2 were determined by immunohistochemical analysis, RT-PCR, and western blot. No matter whether tension was exerted or inhibitors were added, there was no change in the expression of p38, JNK1, and ERK1/2. However, compared to the 0 g group, the expression of MMP-9, TNF-α, IL-1β, p-p38, p-JNK1, and p-ERK1/2 was significantly upregulated in the 3 g group (P < 0.05). In both 0 g and 3 g groups, the expression of MMP-9, TNF-α, IL-1β, p-p38, p-JNK1, and p-ERK1/2 was remarkably downregulated after inhibitors treatment (P < 0.05). In conclusion, mechanical stretch aggravated aortic dissection by regulating the MAPK pathway and the consequent expression of MMP-9 and inflammation factors.

Inflammatory production of reactive oxygen species by Drosophila hemocytes activates cellular immune defenses

The production of reactive oxygen species (ROS) is a prominent response to infection among innate immune cells such as macrophages and neutrophils. To better understand the relationship between antimicrobial and regulatory functions of blood cell ROS, we have characterized the ROS response to infection in Drosophila hemocytes. Using fluorescent probes, we find a biphasic hemocyte ROS response to bacterial infection. In the first hour, virtually all hemocytes generate a transient ROS signal, with nonphagocytic cells including prohemocytes and crystal cells displaying exceptionally strong responses. A distinct, and more delayed ROS response starting at 90 min is primarily within cells that have engulfed bacteria, and is sustained for several hours. The early response has a clear regulatory function, as dampening or intensifying the intracellular ROS level has profound effects on plasmatocyte activation. In addition, ROS are necessary and sufficient to activate JNK signalling in crystal cells, and to promote JNK-dependent crystal cell rupture. These findings indicate that Drosophila will be a promising model in which to dissect the mechanisms of ROS stimulation of immune activation.

Synergetic and Antagonistic Molecular Effects Mediated by the Feedback Loop of p53 and JNK between Saikosaponin D and SP600125 on Lung Cancer A549 Cells

We jointly analyzed the changes in cell cycle arrest and distribution, the accumulation of subphase cells, apoptosis, and proliferation in A549 cells treated with Saikosaponin D (Ssd) and JNK inhibitor SP600125 alone or in combination. Our results indicated that cell cycle arrest at G0/G1, S, and G2/M phases was coupled with the accumulation of subG1, subS, and subG2 cells, corresponding to early apoptosis, DNA endoreplication, and later inhibitory proliferation, respectively. Analyzing the expression of 18 cell cycle regulatory genes and JNK and phosphorylated JNK (pJNK) levels revealed an enhancement in these factors by Ssd. Additional SP600125 weakened or eliminated the Ssd-induced increase of these factors except that p53/p21 and Rassfia levels were further improved. Ingenuity Pathway Analysis (IPA) of the interactions of these factors revealed a negative synergistic effect on apoptosis while a positive synergistic effect on proliferative inhibition of the two drugs: (1) Ssd induced apoptosis via the activation of two axes, TGFα-JNK-p53 and TGFα-Rassfia-Mst1. By eliminating the Ssd-induced increase of JNK/pJNK, additional SP600125 weakened the Ssd-induced apoptotic axis of TGFα-JNK-p53 and simultaneously abolished Ssd-induced apoptosis; (2) Ssd inhibited proliferation by the activation of two axes, TGFβ-p53/p21/p27/p15/p16 and TGFα-Rassfia-cyclin D1. By improving the Ssd-induced increase of p53/p21 and Rassfia, additional SP600125 enhanced the two axes of Ssd-induced inhibitory proliferation. Analyzing JNK/pJNK, p53, phospho-p53, and TNF-α levels revealed an opposite association of JNK/pJNK with p53 while consistent with phospho-p53 and TNF-α, which supported the proposals that JNK/pJNK negatively regulated p53 level, while it mediated p53 phosphorylation to transcriptionally activate TNF-α expression of apoptotic gene and trigger apoptosis. With the multiple roles, JNK/pJNK forms a synergetic and antagonistic feedback loop with phospho-p53/p53. Within the feedback loop, (1) Ssd-induced apoptosis depended on JNK/pJNK activities mediating phospho-p53 that activated TNF-α expression; (2) by weakening the negative regulation of JNK/pJNK in p53, SP600125 enhanced p53 level and the Ssd-induced inhibitory proliferation axes of TGFβ-p53/p21/p27/p15/p16. The results indicated the central coordinating roles of the feedback loop in the synergistic and antagonistic effects of the two drugs in A549 cells and provided a rationale for the combination of Ssd with SP600125 in the treatment of lung cancer.

MAPK/ERK and JNK pathways regulate lipid synthesis and cell growth of Chlamydomonas reinhardtii under osmotic stress, respectively

Microalgae have great potential for the production of biofuels due to the ability of the organism to accumulate large quantities of storage lipids under stress conditions. Mitogen activated protein kinase (MAPK) signaling cascades are widely recognized for their role in stress response signal transduction in eukaryotes. To assess the correlation between MAPK activation and lipid productivity, Chlamydomonas reinhardtii was studied under various concentrations of NaCl. The results demonstrated that C. reinhardtii exhibits elevated levels of extracellular-signal regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) activities after undergoing osmotic stress, as well as an increase in cellular lipid content. To establish a more direct causal link between both kinases and lipid productivity, C. reinhardtii was subjected to biochemically induced regulation of ERK and JNK pathways. Activating the MEK-ERK pathway via C6 ceramide treatment increased ERK activation and lipid production simultaneously, while PD98059 mediated inhibition of the pathway yielded opposite results. Interestingly, suppression of the JNK pathway with SP600125 resulted in a substantial decrease in cell viability under osmotic stress. These results suggest that ERK and JNK MAP kinases have important roles in microalgal lipid accumulation and cell growth under osmotic stress, respectively.

FAF1 mediates necrosis through JNK1-mediated mitochondrial dysfunction leading to retinal degeneration in the ganglion cell layer upon ischemic insult

BACKGROUND

Aberrant cell death induced by ischemic stress is implicated in the pathogenesis of ischemic diseases. Fas-associated factor 1 (FAF1) has been identified as a death-promoting protein. This study demonstrates that FAF1 functions in death signaling triggered by ischemic insult.

METHODS

The expression changes of FAF1 and phophorylated JNK1 were detected by Western blotting. Immunoprecipitation was employed to investigate protein-protein interaction. We determined the cell death using flow cytometry and lactate dehydrogenase release measurement. To validate the death-promoting role of FAF1 in the retina, we generated conditional retinal FAF1 knockout mice. We used hematoxylin and eosin staining to detect retinal cell death in retinal ganglion cell layer.

RESULTS

FAF1 was found to function upstream of c-Jun N-terminal kinase 1 (JNK1), followed by mitochondrial dysregulation and necrotic cell death processes upon ischemic insult. We investigated whether FAF1 is involved in the pathogenesis of ischemic diseases using a retinal ischemia model. Indeed, FAF1 potentiated necrosis through JNK1 activation upon ischemic stress in retinal cells demonstrating retinal ganglion-like character. Conditional FAF1 depletion attenuated JNK1 activation in the retinas of Dkk3-Cre;Faf1flox/flox mice and ameliorated death of retinal cells due to elevated intraocular pressure (IOP).

CONCLUSIONS

Our results show that FAF1 plays a key role in ischemic retinal damage and may be implicated in the pathogenesis of retinal ischemic disease.

Cerium Oxide Nanoparticles Sensitize Pancreatic Cancer to Radiation Therapy through Oxidative Activation of the JNK Apoptotic Pathway

Side effects of radiation therapy (RT) remain the most challenging issue for pancreatic cancer treatment. Cerium oxide nanoparticles (CONPs) are currently being tested in pre-clinical trials as an adjuvant to sensitize pancreatic cancer cells to RT and protect normal tissues from the harmful side effects. CONPs were not able to significantly affect RT-induced DNA damage in cancer cells, thereby ruling out sensitization through increased mitotic catastrophe. However, activation of c-Jun terminal kinase (JNK), a key driver of RT-induced apoptosis, was significantly enhanced by co-treatment with CONPs and RT in pancreatic cancer cells in vitro and human pancreatic tumors in nude mice in vivo compared to CONPs or RT treatment alone. Further, CONP-driven increase in RT-induced JNK activity was associated with a marked increase in Caspase 3/7 activation, indicative of apoptosis. We have previously shown that CONPs increase reactive oxygen species (ROS) production in cancer cells. ROS has been shown to drive the oxidation of thioredoxin 1 (TRX1) which results in the activation of apoptosis signaling kinase 1 (ASK1). The increase in ASK1 activation following the co-treatment with CONPs followed by RT suggests that the increased JNK activation is the result of increased TRX1 oxidation. The ability of CONPs to sensitize pancreatic cancer cells to RT was mitigated when the TRX1 oxidation was prevented by mutagenesis of a cysteine residue or when the JNK activation was blocked by an inhibitor. Taken together, these data demonstrate an important mechanism for CONPs in specifically killing cancer cells and provide novel insights into the utilization of CONPs as a radiosensitizer and therapeutic agent for pancreatic cancer.

Cerium Oxide Nanoparticles Sensitize Pancreatic Cancer to Radiation Therapy through Oxidative Activation of the JNK Apoptotic Pathway

Side effects of radiation therapy (RT) remain the most challenging issue for pancreatic cancer treatment. Cerium oxide nanoparticles (CONPs) are currently being tested in pre-clinical trials as an adjuvant to sensitize pancreatic cancer cells to RT and protect normal tissues from the harmful side effects. CONPs were not able to significantly affect RT-induced DNA damage in cancer cells, thereby ruling out sensitization through increased mitotic catastrophe. However, activation of c-Jun terminal kinase (JNK), a key driver of RT-induced apoptosis, was significantly enhanced by co-treatment with CONPs and RT in pancreatic cancer cells in vitro and human pancreatic tumors in nude mice in vivo compared to CONPs or RT treatment alone. Further, CONP-driven increase in RT-induced JNK activity was associated with a marked increase in Caspase 3/7 activation, indicative of apoptosis. We have previously shown that CONPs increase reactive oxygen species (ROS) production in cancer cells. ROS has been shown to drive the oxidation of thioredoxin 1 (TRX1) which results in the activation of apoptosis signaling kinase 1 (ASK1). The increase in ASK1 activation following the co-treatment with CONPs followed by RT suggests that the increased JNK activation is the result of increased TRX1 oxidation. The ability of CONPs to sensitize pancreatic cancer cells to RT was mitigated when the TRX1 oxidation was prevented by mutagenesis of a cysteine residue or when the JNK activation was blocked by an inhibitor. Taken together, these data demonstrate an important mechanism for CONPs in specifically killing cancer cells and provide novel insights into the utilization of CONPs as a radiosensitizer and therapeutic agent for pancreatic cancer.

JNK1 induces hedgehog signaling from stellate cells to accelerate liver regeneration in mice

BACKGROUND & AIMS

To improve outcomes of two-staged hepatectomies for large/multiple liver tumors, portal vein ligation (PVL) has been combined with parenchymal transection (associating liver partition and portal vein ligation for staged hepatectomy [coined ALPPS]) to greatly accelerate liver regeneration. In a novel ALPPS mouse model, we have reported paracrine Indian hedgehog (IHH) signaling from stellate cells as an early contributor to augmented regeneration. Here, we sought to identify upstream regulators of IHH.

METHODS

ALPPS in mice was compared against PVL and additional control surgeries. Potential IHH regulators were identified through in silico mining of transcriptomic data. c-Jun N-terminal kinase (JNK1 [Mapk8]) activity was reduced through SP600125 to evaluate its effects on IHH signaling. Recombinant IHH was injected after JNK1 diminution to substantiate their relationship during accelerated liver regeneration.

RESULTS

Transcriptomic analysis linked Ihh to Mapk8. JNK1 upregulation after ALPPS was validated and preceded the IHH peak. On immunofluorescence, JNK1 and IHH co-localized in alpha-smooth muscle actin-positive non-parenchymal cells. Inhibition of JNK1 prior to ALPPS surgery reduced liver weight gain to PVL levels and was accompanied by downregulation of hepatocellular proliferation and the IHH-GLI1-CCND1 axis. In JNK1-inhibited mice, recombinant IHH restored ALPPS-like acceleration of regeneration and re-elevated JNK1 activity, suggesting the presence of a positive IHH-JNK1 feedback loop.

CONCLUSIONS

JNK1-mediated induction of IHH paracrine signaling from hepatic stellate cells is essential for accelerated regeneration of parenchymal mass. The JNK1-IHH axis is a mechanism unique to ALPPS surgery and may point to therapeutic alternatives for patients with insufficient regenerative capacity.

LAY SUMMARY

Associating liver partition and portal vein ligation for staged hepatectomy (so called ALPPS), is a new two-staged approach to hepatectomy, which induces an unprecedented acceleration of liver regeneration, enabling treatment of patients with liver tumors that would otherwise be considered unresectable. Herein, we demonstrate that JNK1-IHH signaling from stellate cells is a key mechanism underlying the regenerative acceleration that is induced by ALPPS.

AIF promotes a JNK1-mediated cadherin switch independently of respiratory chain stabilization

Apoptosis-inducing factor (AIF) is a mitochondrial flavoprotein occasionally involved in cell death that primarily regulates mitochondrial energy metabolism under normal cellular conditions. AIF catalyzes the oxidation of NADH in vitro, yet the significance of this redox activity in cells remains unclear. Here, we show that through its enzymatic activity AIF is a critical factor for oxidative stress-induced activation of the mitogen-activated protein kinases JNK1 (c-Jun N-terminal kinase), p38, and ERK (extracellular signal-regulated kinase). AIF-dependent JNK1 signaling culminates in the cadherin switch, and genetic reversal of this switch leads to apoptosis when AIF is suppressed. Notably, this widespread ability of AIF to promote JNK signaling can be uncoupled from its more limited role in respiratory chain stabilization. Thus, AIF is a transmitter of extra-mitochondrial signaling cues with important implications for human development and disease.

A novel MtHSP70-FPR1 fusion protein enhances cytotoxic T lymphocyte responses to cervical cancer cells by activating human monocyte-derived dendritic cells via the p38 MAPK signaling pathway

OBJECTIVE

To evaluate the potential effects of recombinant mycobacterium tuberculosis heat shock protein 70-formyl peptide receptor 1 (MtHSP70-FPR1) fusion protein on human monocyte-derived dendritic cell (moDC) maturation; cytotoxic T lymphocyte (CTL) responses to cervical cancer (CC) cells; and the roles of the p38 MAPK, ERK, and JNK pathways in its transition.

METHODS

Monocytes were positively selected with a MACS column with antiCD14 antibody-conjugated microbeads from umbilical cord blood. MoDCs were stimulated with MtHSP70-FPR1, MtHSP70, a mix of MtHSP70 and FPR1, FPR1, or phosphate buffer solution (PBS) as control. Flow cytometry was used to analyze the surface molecule expression of moDCs and IFN-γ-producing CD8⁺ T cells. T cell proliferation was assessed using [3][H]-thymidine assays. The cytotoxicity of moDC-activated T cells against CC cells was evaluated by MTT assays. Cytokine production was determined by enzyme-linked immunosorbent assay. Western blotting was used to investigate protein expression.

RESULTS

Compared with MtHSP70, MtHSP70 + FPR1, FPR1, or PBS-mediated moDCs, MtHSP70-FPR1-pulsed moDCs expressed higher levels of CD80, CD86, CD83, HLA-DR, and CCR7; secreted more IL-12p70, TNF-ɑ and IL-1β; and elicited stronger CTL priming and proliferation, resulting in an effective, HLA-I-dependent killing effect on CC cells. The p38 MAPK, ERK, and JNK pathways were all activated in MtHSP70-FPR1-mediated moDC maturation, but the p38 MAPK pathway played a vital role.

CONCLUSIONS

The excellent capability of MtHSP70-FPR1 fusion protein to induce phenotypical and functional maturation of moDCs and CC-specific CTL responses partly illustrates the potential clinical benefits of DC-based immunotherapy for CC.

Reversine inhibits Colon Carcinoma Cell Migration by Targeting JNK1

Colorectal cancer is one of the most commonly diagnosed cancers and the third most common cause of cancer-related death. Metastasis is the leading reason for the resultant mortality of these patients. Accordingly, development and characterization of novel anti-cancer drugs limiting colorectal tumor cell dissemination and metastasis are needed. In this study, we found that the small molecule Reversine reduces the migration potential of human colon carcinoma cells in vitro. A coupled kinase assay with bio-informatics approach identified the c-Jun N-terminal kinase (JNK) cascade as the main pathway inhibited by Reversine. Knockdown experiments and pharmacological inhibition identified JNK1 but not JNK2, as a downstream effector target in cancer cell migration. Xenograft experiments confirm the effect of JNK inhibition in the metastatic potential of colon cancer cells. These results highlight the impact of individual JNK isoforms in cancer cell metastasis and propose Reversine as a novel anti-cancer molecule for treatment of colon cancer patients.

Capture of Dense Core Vesicles at Synapses by JNK-Dependent Phosphorylation of Synaptotagmin-4

Delivery of neurotrophins and neuropeptides via long-range trafficking of dense core vesicles (DCVs) from the cell soma to nerve terminals is essential for synapse modulation and circuit function. But the mechanism by which transiting DCVs are captured at specific sites is unknown. Here, we discovered that Synaptotagmin-4 (Syt4) regulates the capture and spatial distribution of DCVs in hippocampal neurons. We found that DCVs are highly mobile and undergo long-range translocation but switch directions only at the distal ends of axons, revealing a circular trafficking pattern. Phosphorylation of serine 135 of Syt4 by JNK steers DCV trafficking by destabilizing Syt4-Kif1A interaction, leading to a transition from microtubule-dependent DCV trafficking to capture at en passant presynaptic boutons by actin. Furthermore, neuronal activity increased DCV capture via JNK-dependent phosphorylation of the S135 site of Syt4. Our data reveal a mechanism that ensures rapid, site-specific delivery of DCVs to synapses.

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Syt4-bearing dense core vesicles in axons traffic continually in a circular pattern

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Phosphorylation of S135 of Syt4 by JNK destabilizes Syt4-Kif1A binding

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Destabilized Syt4-Kif1A binding promotes capture of vesicles at synapses by actin

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Neuronal activity increases vesicle capture via S135-dependent JNK phosphorylation

Model Senescent Microglia Induce Disease Related Changes in α-Synuclein Expression and Activity

Aging is the most prominent risk factor for most neurodegenerative diseases. However, incorporating aging-related changes into models of neurodegeneration rarely occurs. One of the significant changes that occurs in the brain as we age is the shift in phenotype of the resident microglia population to one less able to respond to deleterious changes in the brain. These microglia are termed dystrophic microglia. In order to better model neurodegenerative diseases, we have developed a method to convert microglia into a senescent phenotype in vitro. Mouse microglia grown in high iron concentrations showed many characteristics of dystrophic microglia including, increased iron storage, increased expression of proteins, such as ferritin and the potassium channel, Kv1.3, increased reactive oxygen species production and cytokine release. We have applied this new model to the study of α-synuclein, a protein that is closely associated with a number of neurodegenerative diseases. We have shown that conditioned medium from our model dystrophic microglia increases α-synuclein transcription and expression via tumor necrosis factor alpha (TNFα) and mediated through nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). The conditioned medium also decreases the formation of α-synuclein tetramers, associated ferrireductase activity, and increases aggregates of α-synuclein. The results suggest that we have developed an interesting new model of aged microglia and that factors, including TNFα released from dystrophic microglia could have a significant influence on the pathogenesis of α-synuclein related diseases.

PDE4 inhibitor rolipram inhibits the expression of microsomal prostaglandin E synthase-1 by a mechanism dependent on MAP kinase phosphatase-1

Phosphodiesterase‐4 (PDE4) inhibitors have recently been introduced to the treatment of COPD and psoriatic arthritis. Microsomal prostaglandin E synthase‐1 (mPGES‐1) is an inducible enzyme synthesizing PGE₂, the most abundant prostanoid related to inflammation and inflammatory pain. mPGES‐1 is a potential drug target for novel anti‐inflammatory treatments aiming at an improved safety profile as compared to NSAIDs. Here we investigated the effect of the PDE4 inhibitor rolipram on the expression of mPGES‐1 in macrophages; and a potential mediator role in the process for MAP kinase phosphatase‐1 (MKP‐1) which is an endogenous factor limiting the activity of the proinflammatory MAP kinases p38 and JNK. The expression of mPGES‐1 was decreased, whereas that of MKP‐1 was enhanced by rolipram in wild‐type murine macrophages. Interestingly, rolipram did not reduce mPGES‐1 expression in peritoneal macrophages from MKP‐1‐deficient mice. A reduced phosphorylation of JNK, but not p38 MAP kinase, was specifically associated with the decreased expression of mPGES‐1. Accordingly, mPGES‐1 expression was suppressed by JNK but not p38 inhibitor. These findings underline the significance of the increased MKP‐1 expression and decreased JNK phosphorylation associated with the downregulated expression of mPGES‐1 by PDE4 inhibitors in inflammation.

BCL2 inhibitor ABT-199 and JNK inhibitor SP600125 exhibit synergistic cytotoxicity against imatinib-resistant Ph+ ALL cells

Imatinib (IMT), a specific tyrosine kinase inhibitor (TKI), has drastically changed the treatment strategy for Ph+ ALL (Philadelphia chromosome-positive acute lymphoblastic leukemia). However, TKI resistance remains a serious problem for patient prognosis. Here, a Ph+ ALL cell line NphA2 and the IMT-resistant subline NphA2/STIR were analyzed to identify a potential novel treatment strategy. We also examined other Ph+ ALL cells, MR87 and its IMT-resistant subline, MR87/STIR. IMT induced apoptosis of NphA2 and MR87 but had no effect on resistant sublines. Increased phosphorylated ERK and BCL2, but not BCL-XL, were observed in NphA2/STIR compared with NphA2. NphA2/STIR but not NphA2 was moderately sensitive to U0126, an ERK inhibitor. Interestingly, SP600125, a JNK inhibitor, was potent in cell growth inhibition and apoptosis induction of both parental and IMT-resistant NphA2 and MR87 cells. Moreover, NphA2 and MR87 and their IMT-resistant sublines were sensitive to ABT-199, a specific BCL2 inhibitor. The combination of SP600125 and ABT-199 synergistically suppressed both parental and IMT-resistant cells, including one with T315I mutation, suggesting that Ph+ ALL exhibits high sensitivity to ABT-199 and SP600125 regardless of TKI resistance. This combination might be a possible therapeutic strategy for Ph+ ALL in the future.

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SP600125 JNK inhibitor is cytotoxic against imatinib-resistant Ph+ ALL cells.

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BCl2 inhibitor ABT 199 exhibits cytotoxicity against imatinib-resistant Ph+ ALL.

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SP600125 and ABT199 are synergistic in imatinib-resistant Ph+ ALL with T315I.

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Some leukemia cells are sensitive to MCL1 inhibitor maritoclax but not to ABT-199.

Iron-induced oxidative stress stimulates osteoclast differentiation via NF-κB signaling pathway in mouse model

BACKGROUND

Women transitioned to postmenopausal status experience a corresponding gain in iron stores. Recently clinical researches have observed increased serum ferritin level in postmenopausal women, and ferritin level was negatively correlated with bone mineral density.

PURPOSE

To explore the mechanism of iron-induced osteopenia in mouse model.

METHODS

Briefly, in this study, we established an iron accumulation mouse model with ovariectomy. Primary osteoclasts and osteoblasts were extracted for this research. Biomarkers of bone metabolism and cell signaling pathways were measured.

RESULTS

We found that bone mass changed later than ferritin and decreased gradually following overiectomy. We also observed higher levels of bone resorption and oxidative stress when iron was administered. When stimulated with iron, primary osteoclasts derived from bone marrow-derived macrophages (BMMs) underwent differentiation and numerous reactive oxygen species (ROS) were generated. Further, we found that iron activated the JNK, ERK and NF-κB signaling pathways in vivo. In vitro, we found that only NF-κB signaling was stimulated by iron and that suppression of this pathway blocked osteoclast differentiation. To determine whether these effects were related to ROS, osteoclasts were treated with H₂O₂. We found that ROS stimulated osteoclast activity, and that this effect was reversed upon NF-κB suppression.

CONCLUSIONS

These data suggest that ROS might be a downstream factor of iron and regulated NF-κB signaling in osteoclasts in mouse model.

Sialic acid-binding immunoglobulin-like lectin 8 (Siglec-8) is an activating receptor mediating β2-integrin-dependent function in human eosinophils

BACKGROUND

Siglec-8 is a CD33 subfamily cell-surface receptor selectively expressed on human eosinophils. After cytokine priming, Siglec-8 mAb or glycan ligand binding causes eosinophil apoptosis associated with reactive oxygen species (ROS) production. Most CD33-related Siglecs function as inhibitory receptors, but the ability of Siglec-8 to stimulate eosinophil ROS production and apoptosis suggests that Siglec-8 might instead function as an activating receptor.

OBJECTIVE

We sought to determine the role of IL-5 priming and identify the signaling molecules involved in Siglec-8 function for human eosinophils.

METHODS

We used an mAb and/or a multimeric synthetic sulfated sialoglycan ligand recognizing Siglec-8 in combination with integrin blocking antibodies, pharmacologic inhibitors, phosphoproteomics, and Western blot analysis to define the necessity of various proteins involved in Siglec-8 function for human eosinophils.

RESULTS

Cytokine priming was required to elicit the unanticipated finding that Siglec-8 engagement promotes rapid β2-integrin-dependent eosinophil adhesion. Also novel was the finding that this adhesion was necessary for subsequent ROS production and apoptosis. Siglec-8-mediated ROS was generated through reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation because pretreatment of eosinophils with catalase (an extracellular superoxide scavenger) or NSC 23766 (a Rac GTPase inhibitor) completely inhibited Siglec-8-mediated eosinophil apoptosis. Finally, engagement of Siglec-8 on IL-5-primed eosinophils resulted in increased phosphorylation of Akt, p38, and c-Jun N-terminal kinase 1 that was also β2-integrin dependent; pharmacologic inhibition of these kinases completely prevented Siglec-8-mediated eosinophil apoptosis.

CONCLUSIONS

These data demonstrate that Siglec-8 functions uniquely as an activating receptor on IL-5-primed eosinophils through a novel pathway involving regulation of β2-integrin-dependent adhesion, NADPH oxidase, and a subset of protein kinases.

BAG3 Protein Is Involved in Endothelial Cell Response to Phenethyl Isothiocyanate

Phenethyl isothiocyanate (PEITC), a cruciferous vegetable-derived compound, is a versatile cancer chemopreventive agent that displays the ability to inhibit tumor growth during initiation, promotion, and progression phases in several animal models of carcinogenesis. In this report, we dissect the cellular events induced by noncytotoxic concentrations of PEITC in human umbilical vein endothelial cells (HUVECs). In the early phase, PEITC treatment elicited cells' morphological changes that comprise reduction in cell volume and modification of actin organization concomitantly with a rapid activation of the PI3K/Akt pathway. Downstream to PI3K, PEITC also induces the activity of Rac1 and activation of c-Jun N-terminal kinase (JNK), well-known regulators of actin cytoskeleton dynamics. Interestingly, PEITC modifications of the actin cytoskeleton were abrogated by pretreatment with JNK inhibitor, SP600125. JNK signaling led also to the activation of the c-Jun transcription factor, which is involved in the upregulation of several genes; among them is the BAG3 protein. This protein, a member of the BAG family of heat shock protein (Hsp) 70 cochaperones, is able to sustain survival in different tumor cell lines and neoangiogenesis by directly regulating the endothelial cell cycle. Furthermore, BAG3 is involved in maintaining actin folding. Our findings indicate that BAG3 protein expression is induced in endothelial cells upon exposure to a noncytotoxic concentration of PEITC and its expression is requested for the recovery of normal cell size and morphology after the stressful stimuli. This assigns an additional role for BAG3 protein in the endothelial cells after a stress event.

Functional cooperation between HIF-1α and c-Jun in mediating primary and acquired resistance to gefitinib in NSCLC cells with activating mutation of EGFR

OBJECTIVE

Hypoxia-inducible factor 1 (HIF-1) and activator protein 1 (AP-1) are important transcription factors regulating expression of genes involved in cell survival. HIF-1α and c-Jun are key components of HIF-1 and AP-1, respectively, and are regulated by epidermal growth factor receptor (EGFR)-mediated cell signaling and tumor microenvironmental cues. The roles of HIF-1α and c-Jun in development of resistance to EGFR tyrosine kinase inhibitor (TKI) in non-small cell lung cancer (NSCLC) with activating mutation of EGFR have not been explored. In this study, we investigated the roles of HIF-1α and c-Jun in mediating primary and acquired resistance to gefitinib in NSCLC cells with activating mutation of EGFR.

MATERIALS AND METHODS

Changes in HIF-1α protein and in total and phosphorylated c-Jun levels in relation to changes in total and phosphorylated EGFR levels before and after gefitinib treatment were measured using Western blot analysis in NSCLC cells sensitive or resistant to gefitinib. The impact of overexpression of a constitutively expressed HIF-1α (HIF-1α/ΔODD) or a constitutively active c-Jun upstream regulator (SEK1 S220E/T224D mutant) on cell response to gefitinib was also examined. The effect of pharmacological inhibition of SEK1-JNK-c-Jun pathway on cell response to gefitinib was evaluated.

RESULTS

Downregulation of HIF-1α and total and phosphorylated c-Jun levels correlated with cell inhibitory response to gefitinib better than decrease in phosphorylated EGFR did in NSCLC cells with intrinsic or acquired resistance to gefitinib. Overexpression of HIF-1α/ΔODD or SEK1 S220E/T224D mutant conferred resistance to gefitinib. There exists a positive feed-forward regulation loop between HIF-1 and c-Jun. The JNK inhibitor SP600125 sensitized gefitinib-resistant NSCLC cells to gefitinib.

CONCLUSIONS

HIF-1α and c-Jun functionally cooperate in development of resistance to gefitinib in NSCLC cells. The translational value of inhibiting HIF-1α/c-Jun cooperation in overcoming resistance to EGFR TKI treatment of NSCLC cells with activating mutation of EGFR deserves further investigation.

Activation of Host IRE1α-Dependent Signaling Axis Contributes the Intracellular Parasitism of Brucella melitensis

Brucella spp. are intracellular vacuolar pathogens that causes brucellosis, a worldwide zoonosis of profound importance. We previously demonstrated that the activity of host unfolded protein response (UPR) sensor IRE1α (inositol-requiring enzyme 1) and ER-associated autophagy confer susceptibility to Brucella melitensis and Brucella abortus intracellular replication. However, the mechanism by which host IRE1α regulates the pathogen intracellular lifestyle remains elusive. In this study, by employing a diverse array of molecular approaches, including biochemical analyses, fluorescence microscopy imaging, and infection assays using primary cells derived from Ern1 (encoding IRE1) conditional knockout mice, we address this gap in our understanding by demonstrating that a novel IRE1α to ULK1, an important component for autophagy initiation, signaling axis confers susceptibility to Brucella intracellular parasitism. Importantly, deletion or inactivation of key signaling components along this axis, including IRE1α, BAK/BAX, ASK1, and JNK as well as components of the host autophagy system ULK1, Atg9a, and Beclin 1, resulted in striking disruption of Brucella intracellular trafficking and replication. Host kinases in the IRE1α-ULK1 axis, including IRE1α, ASK1, JNK1, and/or AMPKα as well as ULK1, were also coordinately phosphorylated in an IRE1α-dependent fashion upon the pathogen infection. Taken together, our findings demonstrate that the IRE1α-ULK1 signaling axis is subverted by the bacterium to promote intracellular parasitism, and provide new insight into our understanding of the molecular mechanisms of intracellular lifestyle of Brucella.

Inhibitors of heat shock protein 90 augment endothelin‑1‑induced heat shock protein 27 through the SAPK/JNK signaling pathway in osteoblasts

It has been previously reported that endothelin‑1 (ET‑1) stimulates the induction of heat shock protein (HSP) 27 through the activation of p38 mitogen‑activated protein (MAP) kinase and stress‑activated protein kinase/c‑Jun N‑terminal kinase (SAPK/JNK) in osteoblast‑like MC3T3‑E1 cells. The present study investigated whether HSP90, a high‑molecular‑weight HSP, was implicated in the ET‑1‑stimulated HSP27 induction in MC3T3‑E1 cells. The effects of HSP90 inhibitors on the induction of HSP27 were examined. The HSP90 inhibitors geldanamycin and 17‑demethoxygeldanamycin (17‑DMAG) significantly amplified HSP27 induction stimulated by ET‑1 in a dose‑dependent manner. In addition, onalespib (another HSP90 inhibitor) significantly strengthened the ET‑1‑induced HSP27 protein levels. The ET‑1‑stimulated phosphorylation of p38 MAP kinase was minimally affected by geldanamycin, 17‑DMAG or onalespib. Onalespib and 17‑DMAG significantly enhanced the ET‑1‑induced phosphorylation of SAPK/JNK. In addition, SP600125, a SAPK/JNK inhibitor, notably reduced the amplification by onalespib of ET‑1‑induced HSP27. These results suggest that HSP90 limits ET‑1‑stimulated HSP27 induction at a point upstream of SAPK/JNK in osteoblasts. These results suggest that HSP90 may be a novel clinical target for metabolic bone diseases, including osteoporosis.

Role of c-Jun-N-Terminal Kinase in Pregnane X Receptor-Mediated Induction of Human Cytochrome P4503A4 In Vitro

Cytochrome P450 CYP3A4 is the most abundant drug-metabolizing enzyme and is responsible for the metabolism of ∼50% of clinically available drugs. Induction of CYP3A4 impacts the disposition of its substrates and leads to harmful clinical consequences, such as failure of therapy. To prevent such undesirable consequences, the molecular mechanisms of regulation of CYP3A4 need to be fully understood. CYP3A4 induction is regulated primarily by the xenobiotic nuclear receptor pregnane-X receptor (PXR). After ligand binding, PXR is translocated to the nucleus, where it binds to the CYP3A4 promoter and induces its gene expression. PXR function is modulated by phosphorylation(s) by multiple kinases. In this study, we determined the role of the c-Jun N-terminal kinase (JNK) in PXR-mediated induction of CYP3A4 enzyme in vitro. Human liver carcinoma cells (HepG2) were transfected with CYP3A4 luciferase and PXR plasmids, followed by treatment with JNK inhibitor (SP600125; SP) and PXR activators rifampicin (RIF) or hyperforin. Our results indicate that SP treatment significantly attenuated PXR-mediated induction of CYP3A4 reporter activity, as well as gene expression and enzyme activity. JNK knockdown by siRNA (targeting both JNK 1 and 2) also attenuated CYP3A4 induction by RIF. Interestingly, SP treatment attenuated JNK activation by RIF. Furthermore, treatment with RIF increased PXR nuclear levels and binding to the CYP3A4 promoter; SP attenuated these effects. This study shows that JNK is a novel mechanistic regulator of CYP3A4 induction by PXR.

The feedback loop between miR-21, PDCD4 and AP-1 functions as a driving force for renal fibrogenesis

Renal fibrosis is a final common pathway of chronic kidney disease. Sustained activation of fibroblasts is considered to play a key role in perpetuating renal fibrosis but the driving force in the perpetuation stage is only partially understood. To date, some investigations have specifically identified overexpression of microRNA 21 (miR-21) in the progression of kidney fibrosis. Nevertheless, the precise role of miR-21 in fibroblast activation remains largely unknown. In this study, we found that miR-21 was significantly upregulated in activated fibroblasts and that it maintained itself at constant high levels by employing an auto-regulatory loop between miR-21, PDCD4 and AP-1. Persistently upregulated miR-21 suppressed protein expression of Smad7 and, eventually, enhanced the TGF-β1/Smad pathway to promote fibroblast activation. More importantly, we found miR-21 sequestration with miR-21 antagomir or AP-1 inhibitors attenuated unilateral ureteral obstruction (UUO)-induced renal fibrosis. miR-21-knockout mice also suffered far less interstitial fibrosis in response to kidney injury. Altogether, these data suggest that miR-21 is a main driving force of fibroblast activation and keeps its high expression level by employing a double negative autoregulatory loop. Targeting this aberrantly activated feedback loop may provide new therapeutic strategy in treating fibrotic kidneys.

Small molecules capable of activating DNA methylation-repressed genes targeted by the p38 mitogen-activated protein kinase pathway

Regulation of gene expression by epigenetic modifications such as DNA methylation is crucial for developmental and disease processes, including cell differentiation and cancer development. Genes repressed by DNA methylation can be derepressed by various compounds that target DNA methyltransferases, histone deacetylases, and other regulatory factors. However, some additional, unknown mechanisms that promote DNA methylation-mediated gene silencing may exist. Chemical agents that can counteract the effects of epigenetic repression that is not regulated by DNA methyltransferases or histone deacetylases therefore may be of research interest. Here, we report the results of a high-throughput screen using a 308,251-member chemical library to identify potent small molecules that derepress an EGFP reporter gene silenced by DNA methylation. Seven hit compounds were identified that did not directly target bulk DNA methylation or histone acetylation. Analyzing the effect of these compounds on endogenous gene expression, we discovered that three of these compounds (compounds LX-3, LX-4, and LX-5) selectively activate the p38 mitogen-activated protein kinase (MAPK) pathway and derepress a subset of endogenous genes repressed by DNA methylation. Selective agonists of the p38 pathway have been lacking, and our study now provides critical compounds for studying this pathway and p38 MAPK-targeted genes repressed by DNA methylation.

c-Jun N-terminal kinase and p38 mitogen-activated protein kinase pathways link capacitation with apoptosis and seminal plasma proteins protect sperm by interfering with both routes†

The mitogen-activated protein kinase (MAPK), c-Jun N-terminal kinase (JNK), and p38 MAP kinase (p38) signaling cascades are involved in triggering apoptosis in somatic cells. Given that spermatozoa are able to undergo apoptosis, we tested the hypothesis that these pathways might be functional in ram spermatozoa as two signal transduction mechanisms that contribute to the modulation of capacitation and apoptosis. Indirect immunofluorescence and western blot analysis evidenced the presence of JNK and p38 in ram spermatozoa. To verify the involvement of these enzymes in sperm physiology, we determined the effect of specific inhibitors of JNK or p38 on in vitro capacitation induced with either cAMP-elevating agents or epidermal growth factor (EGF). Both inhibitions reduced the EGF-induced capacitation with a decrease in the chlortetracycline capacitated-sperm pattern, protein tyrosine phosphorylation, phosphatidylserine externalization, caspase-3 and -7 activation, and the proportion of DNA-damaged spermatozoa. No significant changes were found in the high-cAMP capacitated samples. The addition of 3.4 mg/ml seminal plasma proteins (SPPs) to the EGF-containing samples, either alone or together with each inhibitor, resulted in a decreased proportion of capacitated sperm pattern, protein tyrosine phosphorylation, loss of plasma membrane integrity, and apoptotic alterations. Furthermore, SPPs significantly reduced the phosphorylation level of JNK and p38 MAPK (active forms). These findings show a relationship between capacitation and apoptosis, and represent a step forward in the knowledge of the SPP protective mechanism in spermatozoa.

Effects of 12C6+ Heavy Ion Radiation on Dendritic Cells Function

Background

Carbon ion radiotherapy has been shown to be more effective in cancer radiotherapy than photon irradiation. Influence of carbon ion radiation on cancer microenvironment is very important for the outcomes of radiotherapy. Tumor-infiltrating dendritic cells (DCs) play critical roles in cancer antigen processing and antitumor immunity. However, there is scant literature covering the effects of carbon ion radiation on DCs. In this study, we aimed to uncover the impact of carbon ion irradiation on bone marrow derived DCs.

Material/Methods

Bone marrow cells were co-cultured with GM-CSF and IL-4 for seven days, and the population of DCs was confirmed with flow cytometry. We used an Annexin V and PI staining method to detect cell apoptosis. Endocytosis assay of DCs was determined by using a flow cytometry method. DCs migration capacity was tested by a Transwell method. We also used ELISA assay and western blotting assay to examine the cytokines and protein expression, respectively.

Results

Our data showed that carbon ion radiation induced apoptosis in both immature and mature DCs. After irradiation, the endocytosis and migration capacity of DCs was also impaired. Interestingly, carbon irradiation triggered a burst of IFN-γ and IL-12 in LPS or CpG treated DCs, which provide novel insights into the combination of immunotherapy and carbon ion radiotherapy. Finally, we found that carbon ion irradiation induced apoptosis and migration suppression was p38 dependent.

Conclusions

Our present study demonstrated that carbon ion irradiation induced apoptosis in DCs, and impaired DCs function mainly through the p38 signaling pathway. Carbon ion irradiation also triggered anti-tumor cytokines secretion. This work provides novel information of carbon ion radiotherapy in DCs, and also provides new insights on the combination of immune adjuvant and carbon ion radiotherapy.

Identification of the hot spot residues for pyridine derivative inhibitor CCT251455 and ATP substrate binding on monopolar spindle 1 (MPS1) kinase by molecular dynamic simulation

Protein kinase monopolar spindle 1 plays an important role in spindle assembly checkpoint at the onset of mitosis. Over expression of MPS1 correlated with a wide range of human tumors makes it an attractive target for finding an effective and specific inhibitor. In this work, we performed molecular dynamics simulations of protein MPS1 itself as well as protein bound systems with the inhibitor and natural substrate based on crystal structures. The reported orally bioavailable 1 h-pyrrolo [3,2-c] pyridine inhibitors of MPS1 maintained stable binding in the catalytic site, while natural substrate ATP could not stay. Comparative study of stability and flexibility of three systems reveals position shifting of β-sheet region within the catalytic site, which indicates inhibition mechanism was through stabilizing the β-sheet region. Binding free energies calculated with MM-GB/PBSA method shows different binding affinity for inhibitor and ATP. Finally, interactions between protein and inhibitor during molecular dynamic simulations were measured and counted. Residue Gly605 and Leu654 were suggested as important hot spots for stable binding of inhibitor by molecular dynamic simulation. Our results reveal an important position shifting within catalytic site for non-inhibited proteins. Together with hot spots found by molecular dynamic simulation, the results provide important information of inhibition mechanism and will be referenced for designing novel inhibitors.

c-Jun-N-terminal phosphorylation regulates DNMT1 expression and genome wide methylation in gliomas

High-grade gliomas (HGG) are the most common brain tumors, with an average survival time of 14 months. A glioma-CpG island methylator phenotype (G-CIMP), associated with better clinical outcome, has been described in low and high-grade gliomas. Mutation of IDH1 is known to drive the G-CIMP status. In some cases, however, the hypermethylation phenotype is independent of IDH1 mutation, suggesting the involvement of other mechanisms. Here, we demonstrate that DNMT1 expression is higher in low-grade gliomas compared to glioblastomas and correlates with phosphorylated c-Jun. We show that phospho-c-Jun binds to the DNMT1 promoter and causes DNA hypermethylation. Phospho-c-Jun activation by Anisomycin treatment in primary glioblastoma-derived cells attenuates the aggressive features of mesenchymal glioblastomas and leads to promoter methylation and downregulation of key mesenchymal genes (CD44, MMP9 and CHI3L1). Our findings suggest that phospho-c-Jun activates an important regulatory mechanism to control DNMT1 expression and regulate global DNA methylation in Glioblastoma.

Acquired resistance to venetoclax (ABT-199) in t(14;18) positive lymphoma cells

The chromosomal translocation t(14;18) in follicular lymphoma (FL) is a primary oncogenic event resulting in BCL-2 over-expression. This study investigates activity of the BH3 mimetic venetoclax (ABT-199), which targets BCL-2, and mechanisms of acquired resistance in FL.

The sensitivity of FL cells to venetoclax treatment correlated with BCL-2/BIM ratio. Cells with similar expression of anti-apoptotic proteins, but with higher levels of BIM were more sensitive to the treatment. Venetoclax induced dissociation of BCL-2/BIM complex and a decrease in mitochondrial potential. Interestingly the population of cells that survived venetoclax treatment showed increased p-ERK1/2 and p-BIM (S69), as well as a decrease in total BIM levels. Venetoclax resistant cells initially showed elevated levels of p-AKT and p-Foxo1/3a, a dissociation of BIM/BCL-2/BECLIN1 complex, and a decrease in SQSTM1/p62 level (indicating increased autophagy) together with a slight decline in BIM expression. After stable resistant cell lines were established, a significant reduction of BCL-2 levels and almost total absence of BIM was observed.

The acquisition of these resistance phenotypes could be prevented via selective ERK/AKT inhibition or anti-CD20 antibody treatment, thus highlighting possible combination therapies for FL patients.

Cholesterol Depletion by TASIN-1 Induces Apoptotic Cell Death through the ER Stress/ROS/JNK Signaling in Colon Cancer Cells

Truncated APC selective inhibitor-1 (TASIN-1) is a recently identified small molecule that selectively kills colorectal cancer cells that express truncated adenomatous polyposis coli (APC) by reducing cellular cholesterol levels. However, the downstream mechanism responsible for its cytotoxicity is not well understood. In this study, we show that TASIN-1 leads to apoptotic cell death via inducing ER stress-dependent JNK activation in human truncated APC colon cancer cells, accompanied by production of reactive oxygen species (ROS). In addition, TASIN-1 inhibits AKT activity through a cholesterol-dependent manner. Human colon tumor xenografts in immunodeficient mice also show the same TASIN-1 induced molecular mechanisms of tumor cell death as observed in vitro Taken together, cholesterol depletion by TASIN-1 treatment induces apoptotic cell death through activating ER stress/ROS/JNK axis and inhibiting AKT pro-survival signaling in colon cancer cells with truncated APC both in vitro and in vivoMol Cancer Ther; 17(5); 943-51. ©2018 AACR.

Inhibiting autophagy overcomes docetaxel resistance in castration-resistant prostate cancer cells

Background

This study investigates the docetaxel-resistant mechanism and explores the effect of tea polyphenols (TP) on autophagy and its related mechanism in human castration-resistant prostate cancer (CRPC) cell lines PC3 and DU145.

Methods

Immunofluorescence assay and annexin V-FITC/PI double staining flow cytometry were used to analyze the apoptosis and autophagy of PC3 and DU145 cells. The expression of autophagy-related proteins was detected by western bolt.

Results

Docetaxel could induce autophagy and apoptosis, together with the expression increase in p-JNK, p-Bcl-2 and Beclin1. The level of autophagy was remarkably decreased, but apoptosis was increased after combining with TP. In addition, the expression of p-mTOR was increased after combining with TP.

Conclusion

Docetaxel induces protective autophagy in CRPC cells by JNK pathway activation and then Bcl-2 phosphorylation and Beclin1 dissociation. TP activates mTOR pathway, which ultimately inhibits docetaxel-induced autophagy and improves therapeutic efficacy of docetaxel in CRPC cells.

Inhibition of the JNK/MAPK signaling pathway by myogenesis-associated miRNAs is required for skeletal muscle development

Skeletal muscle differentiation is controlled by multiple cell signaling pathways, however, the JNK/MAPK signaling pathway dominating this process has not been fully elucidated. Here, we report that the JNK/MAPK pathway was significantly downregulated in the late stages of myogenesis, and in contrast to P38/MAPK pathway, it negatively regulated skeletal muscle differentiation. Based on the PAR-CLIP-seq analysis, we identified six elevated miRNAs (miR-1a-3p, miR-133a-3p, miR-133b-3p, miR-206-3p, miR-128-3p, miR-351-5p), namely myogenesis-associated miRNAs (mamiRs), negatively controlled the JNK/MAPK pathway by repressing multiple factors for the phosphorylation of the JNK/MAPK pathway, including MEKK1, MEKK2, MKK7, and c-Jun but not JNK protein itself, and as a result, expression of transcriptional factor MyoD and mamiRs were further promoted. Our study revealed a novel double-negative feedback regulatory pattern of cell-specific miRNAs by targeting phosphorylation kinase signaling cascade responsible for skeletal muscle development.

TNFSF15 suppresses VEGF production in endothelial cells by stimulating miR-29b expression via activation of JNK-GATA3 signals

Vascular endothelial cell growth factor (VEGF) plays a pivotal role in promoting neovascularization. VEGF gene expression in vascular endothelial cells in normal tissues is maintained at low levels but becomes highly up-regulated in a variety of disease settings including cancers. Tumor necrosis factor superfamily 15 (TNFSF15; VEGI; TL1A) is an anti-angiogenic cytokine prominently produced by endothelial cells in a normal vasculature. We report here that VEGF production in mouse endothelial cell line bEnd.3 can be inhibited by TNFSF15 via microRNA-29b (miR-29b) that targets the 3'-UTR of VEGF transcript. Blocking TNFSF15 activity by using either siRNA against the TNFSF15 receptor known as death domain-containing receptor-3 (DR3; TNFRSF25), or a neutralizing antibody 4-3H against TNFSF15, led to inhibition of miR-29b expression and reinvigoration of VEGF production. In addition, we found that TNFSF15 activated the JNK signaling pathway as well as the transcription factor GATA3, resulting in enhanced miR-29b production. Treatment of the cells either with SP600125, an inhibitor of JNK, or with JNK siRNA, led to eradication of TNFSF15-induced GATA3 expression. Moreover, GATA3 siRNA suppressed TNFSF15-induced miR-29b expression. These findings suggest that VEGF gene expression can be suppressed by TNFSF15-stimulated activation of the JNK-GATA3 signaling pathway which gives rise to up-regulation of miR-29b.

Kinase inhibitors as potential agents in the treatment of multiple myeloma

Recent years have witnessed a dramatic increase in the number of therapeutic options available for the treatment of multiple myeloma (MM) - from immunomodulating agents to proteasome inhibitors to histone deacetylase (HDAC) inhibitors and, most recently, monoclonal antibodies. Used in conjunction with autologous hematopoietic stem cell transplantation, these modalities have nearly doubled the disease's five-year survival rate over the last three decades to about 50%. In spite of these advances, MM still is considered incurable as resistance and relapse are common. While small molecule protein kinase inhibitors have made inroads in the therapy of a number of cancers, to date their application to MM has been less than successful. Focusing on MM, this review examines the roles played by a number of kinases in driving the malignant state and the rationale for target development in the design of a number of kinase inhibitors that have demonstrated anti-myeloma activity in both in vitro and in vivo xenograph models, as well as those that have entered clinical trials. Among the targets and their inhibitors examined are receptor and non-receptor tyrosine kinases, cell cycle control kinases, the PI3K/AKT/mTOR pathway kinases, protein kinase C, mitogen-activated protein kinase, glycogen synthase kinase, casein kinase, integrin-linked kinase, sphingosine kinase, and kinases involved in the unfolded protein response.

Usage of Mitogen-Activated Protein Kinase Small Molecule Inhibitors: More Than Just Inhibition!

We have identified a phenomenon occurring in the usage of proposed “specific” Mitogen-activated protein kinase (MAPK) inhibitors. We found that especially inhibitors of p38 potentiate the activation of other MAPKs in various cell types. This finding will have tremendous impact on the interpretation of all former studies using MAPK inhibitors.

miR-223/Hsp70/JNK/JUN/miR-223 feedback loop modulates the chemoresistance of osteosarcoma to cisplatin

Osteosarcoma (OS) is a primary bone malignancy with a five-year survival rate of 60%; the chemoresistance of OS still remains a huge challenge. Heat shock protein 70 (Hsp70), a member of HSP family, is overexpressed in OS cell lines and involved in the resistance of OS cell lines. In addition, miRNAs have been involved in the carcinogenesis and chemoresistance of OS; of them, miR-223 has been reported to be underexpressed and serve as a tumor suppressor in OS through targeting Hsp90B1, also a member of HSP family. Herein, online tools predicted that Hsp70 might be a direct target of miR-223. In the present study, miR-223 expression was down-regulated in OS tissues and cell lines; miR-223 overexpression enhanced the cellular effects of cisplatin (CDDP) on OS cell lines. Through binding to the HSPA1A 3'UTR, miR-223 could regulate Hsp70 protein levels and downstream JNK/JUN signaling pathway, thus modulating OS cell apoptosis through Hsp70 under CDDP stress. Finally, JUN, a downstream transcription factor of JNK signaling, could bind to the promoter region of miR-223 to promote its transcription. In summary, miR-223, Hsp70 and downstream JNK/JUN formed a feedback loop to modulate the chemoresistance of OS to CDDP.

LanCL1 protects prostate cancer cells from oxidative stress via suppression of JNK pathway

Prostate cancer (PCa) is the most commonly diagnosed malignancy in male. Numerous studies have focused on the molecular mechanisms of carcinogenesis and progression, aiming at developing new therapeutic strategies. Here we describe Lanthionine synthase C-like protein 1 (LanCL1), a member of the LanCL family, is a potential prostate cancer susceptibility gene. LanCL1 promotes prostate cancer cell proliferation and helps protect cells from damage caused by oxidative stress. Suppression of LanCL1 by siRNA results in increased cancer cell apoptosis. Clinical data also indicate that LanCL1 upregulation in human prostate cancers correlates with tumor progression. Finally, we demonstrate that LanCL1 plays such important role through inhibiting JNK pathway. Altogether, our results suggest that LanCL1 protects cells from oxidative stress, and promotes cell proliferation. LanCL1 reduces cell death via suppression of JNK signaling pathway.

Stimulation of JNK Phosphorylation by the PTTH in Prothoracic Glands of the Silkworm, Bombyx mori

In this study, phosphorylation of c-Jun N-terminal kinase (JNK) by the prothoracicotropic hormone (PTTH) was investigated in prothoracic glands (PGs) of the silkworm, Bombyx mori. Results showed that JNK phosphorylation was stimulated by the PTTH in time- and dose-dependent manners. In vitro activation of JNK phosphorylation in PGs by the PTTH was also confirmed in an in vivo experiment, in which a PTTH injection greatly increased JNK phosphorylation in PGs of day-6 last instar larvae. JNK phosphorylation caused by PTTH stimulation was greatly inhibited by U73122, a potent and specific inhibitor of phospholipase C (PLC) and an increase in JNK phosphorylation was also detected when PGs were treated with agents (either A23187 or thapsigargin) that directly elevated the intracellular Ca²⁺ concentration, thereby indicating involvement of PLC and Ca²⁺. Pretreatment with an inhibitor (U0126) of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase (MEK) and an inhibitor (LY294002) of phosphoinositide 3-kinase (PI3K) failed to significantly inhibit PTTH-stimulated JNK phosphorylation, indicating that ERK and PI3K were not related to JNK. We further investigated the effect of modulation of the redox state on JNK phosphorylation. In the presence of either an antioxidant (N-acetylcysteine, NAC) or diphenylene iodonium (DPI), PTTH-stimulated JNK phosphorylation was blocked. The JNK kinase inhibitor, SP600125, markedly inhibited PTTH-stimulated JNK phosphorylation and ecdysteroid synthesis. The kinase assay of JNK in PGs confirmed its stimulation by PTTH and inhibition by SP600125. Moreover, PTTH treatment did not affect JNK or Jun mRNA expressions. Based on these findings, we concluded that PTTH stimulates JNK phosphorylation in Ca²⁺- and PLC-dependent manners and that the redox-regulated JNK signaling pathway is involved in PTTH-stimulated ecdysteroid synthesis in B. mori PGs.

Protective effects of curcumin against doxorubicin-induced toxicity and resistance: A review

Doxorubicin (DOX)-induced toxicity and resistance are major obstacles in chemotherapeutic approaches. Despite effective in the treatment of numerous malignancies, some clinicians have voiced concern that DOX has the potential to cause debilitating consequences in organ tissues, especially the heart. The mechanisms of toxicity and resistance are respectively related to induction of reactive oxygen species (ROS) and up-regulation of ATP-binding cassette (ABC) transporter. Curcumin (CUR) with several biological and pharmacological properties is expected to restore DOX-mediated impairments to tissues. This review is intended to address the current knowledge on DOX adverse effects and CUR protective actions in the heart, kidneys, liver, brain, and reproductive organs. Coadministration of CUR and DOX is capable of ameliorating DOX toxicity pertained to antioxidant, apoptosis, autophagy, and mitochondrial permeability.

Low-dose cadmium activates the JNK signaling pathway in human renal podocytes

Cadmium (Cd) is an environmental toxin. Our previous study demonstrated that low‑dose Cd damages the integrity of the glomerular filtration barrier (GFB); however, the underlying mechanisms are poorly understood. Podocytes are a major component of the GFB, which regulate the passage of proteins. The present study aimed to investigate the effects of low‑dose Cd on human renal podocytes (HRPs). HRPs were treated with Cd and activation of the c-Jun N-terminal kinase (JNK) pathway was examined by western blot analysis. Proliferation, viability and apoptosis of HRPs were evaluated by MTT assay, trypan blue exclusion assay and flow cytometry, respectively. The properties of HRPs were validated by immunofluorescence staining and Phalloidin‑labeling. The results indicated that 4 µM Cd may activate the JNK pathway, and increase the protein expression levels of c‑Jun and c‑Fos. However, proliferation, viability, apoptosis and alignment of the F‑actin cytoskeleton in HRPs were not significantly affected by Cd treatment, with or without SP600125 pretreatment. In addition, the expression levels of CD2‑associated protein and synaptopodin, which are differentiation markers of HRPs, remained unchanged following Cd treatment. These results indicated that low‑dose Cd activates the JNK pathway but does not significantly affect HRP function.

β1 integrin- and JNK-dependent tumor growth upon hypofractionated radiation

Radiation therapy is an effective cancer treatment modality although tumors invariably become resistant. Using the transgenic adenocarcinoma of mouse prostate (TRAMP) model system, we report that a hypofractionated radiation schedule (10 Gy/day for 5 consecutive days) effectively blocks prostate tumor growth in wild type (β1^wt /TRAMP) mice as well as in mice carrying a conditional ablation of β1 integrins in the prostatic epithelium (β1^pc-/- /TRAMP). Since JNK is known to be suppressed by β1 integrins and mediates radiation-induced apoptosis, we tested the effect of SP600125, an inhibitor of c-Jun amino-terminal kinase (JNK) in the TRAMP model system. Our results show that SP600125 negates the effect of radiation on tumor growth in β1^pc-/- /TRAMP mice and leads to invasive adenocarcinoma. These effects are associated with increased focal adhesion kinase (FAK) expression and phosphorylation in prostate tumors in β1^pc-/- /TRAMP mice. In marked contrast, radiation-induced tumor growth suppression, FAK expression and phosphorylation are not altered by SP600125 treatment of β1^wt /TRAMP mice. Furthermore, we have reported earlier that abrogation of insulin-like growth factor receptor (IGF-IR) in prostate cancer cells enhances the sensitivity to radiation. Here we further explore the β1/IGF-IR crosstalk and report that β1 integrins promote cell proliferation partly by enhancing the expression of IGF-IR. In conclusion, we demonstrate that β1 integrin-mediated inhibition of JNK signaling modulates tumor growth rate upon hypofractionated radiation.

Structural and biological evaluation of halogen derivatives of 1,9-pyrazoloanthrones towards the design of a specific potent inhibitor of c-Jun-N-terminal kinase (JNK)

A specifically designed halogen derivatives of anthrapyrazolone for the selective inhibition of JNKs at lower concentrations with minimal off-target effects on MAPKs.

The stress kinase JNK regulates gap junction Cx43 gene expression and promotes atrial fibrillation in the aged heart

BACKGROUND

The stress kinase c-jun N-terminal kinase (JNK) is critical in the pathogenesis of cardiac diseases associated with an increased incidence of atrial fibrillation (AF), the most common arrhythmia in the elderly. We recently discovered that JNK activation is linked to the loss of gap junction connexin43 (Cx43) and enhanced atrial arrhythmogenicity. However, direct evidence for JNK-mediated impairment of intercellular coupling (cell-cell communication) in the intact aged atrium is lacking, as is evidence for whether and how JNK suppresses Cx43 in the aged human atrium.

METHODS AND RESULTS

JNK activity in human atrial samples is correlated with both reduced Cx43 expression and increasing age. Using a unique technique of optical mapping space constant measurement, we found that impaired intercellular coupling and reduced Cx43 were linked to enhanced activation of JNK in intact aged rabbit atria. These JNK-associated alterations were further confirmed in naturally JNK activated aged mice and in cardiac-specific inducible MKK7D (JNK upstream activator) young mice. Moreover, JNK inhibition, using either JNK specific inhibitors in aged wild-type (WT) mice and JNK activator anisomycin-treated young WT mice or JNK1/2 dominant-negative mice with genetically inhibited cardiac JNK activity, completely eliminated these functional abnormalities. Furthermore, we discovered for the first time that long-term JNK activation downregulates Cx43 expression via c-jun suppressed transcriptional activity of the Cx43 gene promoter.

CONCLUSION

Our results demonstrate that JNK is a critical regulator of Cx43 expression, and that augmented JNK activation in aged atria downregulates Cx43 to impair cell-cell communication and promote the development of AF. JNK inhibition may represent a promising therapeutic approach to prevent or treat AF in the elderly.