The ASK1–MAP kinase pathways in immune and stress responses

The Impacts of Animal-Based Diets in Cardiovascular Disease Development: A Cellular and Physiological Overview

Cardiovascular disease (CVD) is the leading cause of death in the United States, and diet plays an instrumental role in CVD development. Plant-based diets have been strongly tied to a reduction in CVD incidence. In contrast, animal food consumption may increase CVD risk. While increased serum low-density lipoprotein (LDL) cholesterol concentrations are an established risk factor which may partially explain the positive association with animal foods and CVD, numerous other biochemical factors are also at play. Thus, the aim of this review is to summarize the major cellular and molecular effects of animal food consumption in relation to CVD development. Animal-food-centered diets may (1) increase cardiovascular toll-like receptor (TLR) signaling, due to increased serum endotoxins and oxidized LDL cholesterol, (2) increase cardiovascular lipotoxicity, (3) increase renin-angiotensin system components and subsequent angiotensin II type-1 receptor (AT1R) signaling and (4) increase serum trimethylamine-N-oxide concentrations. These nutritionally mediated factors independently increase cardiovascular oxidative stress and inflammation and are all independently tied to CVD development. Public policy efforts should continue to advocate for the consumption of a mostly plant-based diet, with the minimization of animal-based foods.

Activation of the CaMKII-Sarm1-ASK1-p38 MAP kinase pathway protects against axon degeneration caused by loss of mitochondria

Mitochondrial defects are tightly linked to axon degeneration, yet the underlying cellular mechanisms remain poorly understood. In Caenorhabditis elegans, PVQ axons that lack mitochondria degenerate spontaneously with age. Using an unbiased genetic screen, we found that cell-specific activation of CaMKII/UNC-43 suppresses axon degeneration due to loss of mitochondria. Unexpectedly, CaMKII/UNC-43 activates the conserved Sarm1/TIR-1-ASK1/NSY-1-p38 MAPK pathway and eventually the transcription factor CEBP-1 to protect against degeneration. In addition, we show that disrupting a trafficking complex composed of calsyntenin/CASY-1, Mint/LIN-10, and kinesin suppresses axon degeneration. Further analysis indicates that disruption of this trafficking complex activates the CaMKII-Sarm1-MAPK pathway through L-type voltage-gated calcium channels. Our findings identify CaMKII as a pivot point between mitochondrial defects and axon degeneration, describe how it is regulated, and uncover a surprising neuroprotective role for the Sarm1-p38 MAPK pathway in this context.

Cadmium induces apoptosis of human granulosa cell line KGN via mitochondrial dysfunction-mediated pathways

Cadmium (Cd) is an important industrial and environmental pollutant, which is closely correlated with female infertility. Although Cd-induced developmental disorders of human ovarian follicles have been widely reported, the underlying mechanisms remain not fully elucidated. In this study, we explored the mechanism underlying Cd-triggered apoptosis in granulosa cells. Following the treatment with various levels of Cd (0, 0.625, 1.25, 2.5 and 5 μM), we found that Cd triggered the death of KGN cells (a human granulosa-like tumor cell line) in a dose- as well as time-dependent manner. The levels of expressions of Bax and Bak were significantly increased, whereas the expression levels of Mcl-1 and Bcl-2 were considerably decreased after being treated with high levels of Cd. We showed that Cd exposure remarkably triggered mitochondrial dysfunction, including increased intracellular ROS and free Ca²⁺ levels, and decreased ATP generation and mitochondrial membrane potential. Furthermore, we found that mitochondrial dysfunction, especially excessive ROS production and intracellular Ca²⁺ overload, serve a vital role in Cd-triggered apoptosis of KGN cells. After using inhibitors to block the corresponding signaling cascades, Cd-mediated apoptosis was markedly repressed by ASK1 and p38 inhibitors in contrast with the control group. This suggests the activation of downstream pathways triggered by mitochondrial dysfunction participates in granulosa cell death and may cause female reproductive toxicity after Cd exposure.

Current Insights of Inhibitors of p38 Mitogen-Activated Protein Kinase in Inflammation

BACKGROUND

The inflammatory process is one of the mechanisms by which our body upholds us from pathogens such as parasites, bacteria, viruses, and other harmful microorganisms. Inflammatory stimuli activate many intracellular signaling pathways such as the nuclear factor-kB (NF-kB) pathway and three mitogen-activated protein kinase (MAPK) pathways, which are mediated through extracellular-signal regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and p38. The p38 has evolved as an enticing target in treating many persistent inflammatory diseases. Hence, designing novel p38 inhibitors targeting MAPK pathways has acquired significance.

OBJECTIVE

Peruse to identify the lead target to discover novel p38MAPK inhibitors with different scaffolds having improved selectivity over the prototype drugs.

METHODS

Structure and the binding sites of p38MAPK were focused. Various scaffolds designed for inhibition and the molecules which have entered the clinical trials are discussed.

RESULTS

This review aspires to present the available information on the structure and the 3D binding sites of p38MAPK, various scaffolds designed for imidazole, urea, benzamide, azoles, quinoxaline, chromone, ketone as a potent p38MAPK inhibitors and their SAR studies and the molecules which have entered the clinical trials.

CONCLUSION

The development of successful selective p38MAPK inhibitors in inflammatory diseases is in progress despite all challenges. It was speculated that p38MAPK also plays an important role in treating diseases such as neuroinflammation, arterial inflammation, vascular inflammation, cancer and so on, which are posing the world with treatment challenges. In this review, clinical trials of drugs are discussed related to inflammatory and its related diseases. Research is in progress to design and develop novel p38MAPK inhibitors with minimal side effects.

Reactions of Malononitrile Dimer with Isothiocyanates

Abstract

The reaction of 2-amino-1,1,3-tricyanopropene (malononitrile dimer) with isothiocyanates leads to 1-substituted 4,6-diamino-2-thioxo-1,2-dihydropyridine-3,5-dicarbonitriles or 4,6-diamino-2-(phenylimino)-2H-thiopyran-3,5-dicarbonitrile, depending on the conditions. Quantum-chemical modeling of the IR spectra and reaction routes for the synthesized compounds was carried out. In silico predictive analysis of potential protein targets, compliance with bioavailability criteria, and ADMET parameters was performed.

DUSP12 acts as a novel endogenous protective signal against hepatic ischemia-reperfusion damage by inhibiting ASK1 pathway

Ischemia–reperfusion injury (IRI) consequent to major liver surgery is a still unmet clinical problem. The activation of endogenous systems of hepatoprotection can prevent the damaging effects of ischemia–reperfusion (IR) as shown by the phenomenon known as ‘ischemic preconditioning’. The identification of endogenous signal mediators of hepatoprotection is of main interest since they could be targeted in future therapeutic interventions. Qiu et al. recently reported in Clin. Sci. (Lond.) (2020) 134(17), 2279–2294, the discovery of a novel protective molecule against hepatic IR damage: dual-specificity phosphatase 12 (DUSP12). IR significantly decreased DUSP12 expression in liver whereas DUSP12 overexpression in hepatocytes protected IRI and DUSP12 deletion in DUSP12 KO mice exacerbated IRI. The protective effects of DUSP12 depended on apoptosis signal-regulating kinase 1 (ASK1) and acted through the inhibition of the ASK1-dependent kinases c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). These results enlighten DUSP12 as a novel intermediate negative regulator of the pro-inflammatory and pro-apoptotic ASK1/JNK-p38 MAPK pathway activated during hepatic IR and identify DUSP12 as potential therapeutic target for IRI.

Bacterial death and TRADD-N domains help define novel apoptosis and immunity mechanisms shared by prokaryotes and metazoans

Several homologous domains are shared by eukaryotic immunity and programmed cell-death systems and poorly understood bacterial proteins. Recent studies show these to be components of a network of highly regulated systems connecting apoptotic processes to counter-invader immunity, in prokaryotes with a multicellular habit. However, the provenance of key adaptor domains, namely those of the Death-like and TRADD-N superfamilies, a quintessential feature of metazoan apoptotic systems, remained murky. Here, we use sensitive sequence analysis and comparative genomics methods to identify unambiguous bacterial homologs of the Death-like and TRADD-N superfamilies. We show the former to have arisen as part of a radiation of effector-associated α-helical adaptor domains that likely mediate homotypic interactions bringing together diverse effector and signaling domains in predicted bacterial apoptosis- and counter-invader systems. Similarly, we show that the TRADD-N domain defines a key, widespread signaling bridge that links effector deployment to invader-sensing in multicellular bacterial and metazoan counter-invader systems. TRADD-N domains are expanded in aggregating marine invertebrates and point to distinctive diversifying immune strategies probably directed both at RNA and retroviruses and cellular pathogens that might infect such communities. These TRADD-N and Death-like domains helped identify several new bacterial and metazoan counter-invader systems featuring underappreciated, common functional principles: the use of intracellular invader-sensing lectin-like (NPCBM and FGS), transcription elongation GreA/B-C, glycosyltransferase-4 family, inactive NTPase (serving as nucleic acid receptors), and invader-sensing GTPase switch domains. Finally, these findings point to the possibility of multicellular bacteria-stem metazoan symbiosis in the emergence of the immune/apoptotic systems of the latter.

Clinical Significance and Systematic Expression Analysis of the Thyroid Receptor Interacting Protein 13 (TRIP13) as Human Gliomas Biomarker

The prognosis of malignant gliomas such as glioblastoma multiforme (GBM) has remained poor due to limited therapeutic strategies. Thus, it is pivotal to determine prognostic factors for gliomas. Thyroid Receptor Interacting Protein 13 (TRIP13) was found to be overexpressed in several solid tumors, but its role and clinical significance in gliomas is still unclear. Here, we conducted a comprehensive expression analysis of TRIP13 to determine the prognostic values. Gene expression profiles of the Cancer Genome Atlas (TCGA), Chinese Glioma Genome Atlas (CGGA) and GSE16011 dataset showed increased TRIP13 expression in advanced stage and worse prognosis in IDH-wild type lower-grade glioma. We performed RT-PCR and Western blot to validate TRIP13 mRNA expression and protein levels in GBM cell lines. TRIP13 co-expressed genes via database screening were regulated by essential cancer-related upstream regulators (such as TP53 and FOXM1). Then, TCGA analysis revealed that more TRIP13 promoter hypomethylation was observed in GBM than in low-grade glioma. We also inferred that the upregulated TRIP13 levels in gliomas could be regulated by dysfunction of miR-29 in gliomas patient cohorts. Moreover, TRIP13-expressing tumors not only had higher aneuploidy but also tended to reduce the ratio of CD8⁺/Treg, which led to a worse survival outcome. Overall, these findings demonstrate that TRIP13 has with multiple functions in gliomas, and they may be crucial for therapeutic potential.

Bisphenol AF induces apoptosis via estrogen receptor beta (ERβ) and ROS-ASK1-JNK MAPK pathway in human granulosa cell line KGN

Bisphenol AF (BPAF) is an emerging environmental pollutant. Although BPAF is widely spread in the environment and human surroundings, its interference with ovarian function has not been fully elucidated. The aim of this study was to identify the mechanism underlying the effect of BPAF on the apoptosis of KGN cells, which maintain the physiological characteristics of ovarian granulosa cells. Our results indicated that BPAF induces KGN cell apoptosis in a concentration- and time-dependent manner. Meanwhile, BPAF exposure significantly promoted the expression of pro-apoptotic proteins, including Bax, Bid and Bak, while the expression of anti-apoptotic proteins, such as Bcl-2, Bcl-xL and Mcl-1, decreased significantly. We further detected a significant increase in intracellular ROS levels in response to high concentrations of BPAF exposure. After blocking the corresponding pathway, it was found that ROS mediates ASK1 and JNK activation. Furthermore, the role of Ca²⁺ overload and estrogen receptor β (ERβ) in BPAF-induced KGN cell apoptosis was also confirmed by using inhibitors. These results suggest that BPAF has potential reproductive toxicity for females, and ROS-ASK1-JNK axis may play a key role in BPAF-induced ovarian dysfunction. In addition, Ca²⁺ overload and ERβ pathway activation may also be an important mechanism of reproductive toxicity of BPAF.

Non-canonical roles of connexins

Gap junctions mediate cellular communication and homeostasis by controlling the intercellular exchange of small and hydrophilic molecules and ions. Gap junction channels are formed by the docking of 2 hemichannels of adjacent cells, which in turn are composed of 6 connexin subunits. Connexin proteins as such can also control the cellular life cycle independent of their channel activities. This has been most demonstrated in the context of cell growth and cell death. Different mechanisms are involved mainly related to direct interaction with cell growth or cell death regulators, but also implying effects on the expression of cell growth and cell death regulators. The present paper focuses on these atypical roles of connexin proteins.

Physiological regulation of reactive oxygen species in organisms based on their physicochemical properties

Oxidative stress is recognized as free radical dyshomeostasis, which has damaging effects on proteins, lipids and DNA. However, during cell differentiation and proliferation and other normal physiological processes, free radicals play a pivotal role in message transmission and are considered important messengers. Organisms maintain free radical homeostasis through a sophisticated regulatory system in which these "2-faced" molecules play appropriate roles under physiological and pathological conditions. Reactive oxygen species (ROS), including a large number of free radicals, act as redox signalling molecules in essential cellular signalling pathways, including cell differentiation and proliferation. However, excessive ROS levels can induce oxidative stress, which is an important risk factor for diabetes, cancer and cardiovascular disease. An overall comprehensive understanding of ROS is beneficial for understanding the pathogenesis of certain diseases and finding new therapeutic treatments. This review primarily focuses on ROS cellular localization, sources, chemistry and molecular targets to determine how to distinguish between the roles of ROS as messengers and in oxidative stress.

NQDI-1 protects against acinar cell necrosis in three experimental mouse models of acute pancreatitis

NQDI-1, an inhibitor of ASK1, has been reported to have protective effects in several experimental human disease models. However, the role of NQDI-1 in acute pancreatitis (AP) has not been reported. In this study, we found that NQDI-1 could attenuate histological damage of pancreatic tissue as well as the levels of serum amylase and lipase in a mouse model of AP induced by caerulein. Moreover, the production of reactive oxygen species (ROS) and the expression of necrosis-related proteins (RIP3 and p-MLKL) were also reduced after NQDI-1 administration. Correspondingly, we elucidated the effect of NQDI-1 in vitro and found that NQDI-1 protected against pancreatic acinar cells necrosis via decreasing the ROS production and RIP3 and p-MLKL expression. In addition, we identified the protective effect of NQDI-1 on AP through two other mouse models induced by l-arginine and pancreatic duct ligation. Taken together, these findings showed that NQDI-1 could reduce the acinar cells necrosis and alleviate the severity of AP, which may afford a new therapeutic target on pancreatic necrosis in AP clinically.

[Functional Analysis of Apoptosis Signal-regulating Kinase Family in a Murine Model of Tumor Metastasis]

Stress-responsive signaling pathways convert cellular stresses into various physiological responses, such as cell proliferation, apoptosis, and inflammation. Signal pathway dysfunction thus induces abnormal cellular behaviors that may lead to tumorigenesis and tumor progression, including metastasis. Tumor metastasis is the spread of tumor cells from primary lesions to other distant tissues/organs. Several types of murine model which mimic the progression of human cancer have been established for preclinical studies to understand the biology of cancer. Mitogen-activated protein kinase (MAPK) cascades are one of the stress-responsive signaling pathways and are intricately involved in both tumor promotion and suppression. Here, we present the diverse roles of apoptosis signal-regulating kinase (ASK) family molecules in tumor formation and progression. ASK family is a member of MAPK kinase kinase (MAP3K) family in the c-Jun N-terminal kinase (JNK) and p38 MAPK pathways and comprises three family members, ASK1, ASK2, and ASK3. Accumulating evidence indicates that ASK1 controls tumorigenesis through the regulation of innate immunity and apoptosis. ASK2 also regulates tumorigenesis via apoptosis. Furthermore, analysis of the experimental lung metastasis model in mice suggests that host ASK1 deficiency attenuates tumor lung metastasis. In this symposium review, we discuss the potential roles of ASK family in the context of tumor metastasis.

Inhibition of apoptosis signal-regulating kinase by paeoniflorin attenuates neuroinflammation and ameliorates neuropathic pain

BACKGROUND

Neuropathic pain is a serious clinical problem that needs to be solved urgently. ASK1 is an upstream protein of p38 and JNK which plays important roles in neuroinflammation during the induction and maintenance of chronic pain. Therefore, inhibition of ASK1 may be a novel therapeutic approach for neuropathic pain. Here, we aim to investigate the effects of paeoniflorin on ASK1 and neuropathic pain.

METHODS

The mechanical and thermal thresholds of rats were measured using the Von Frey test. Cell signaling was assayed using western blotting and immunohistochemistry.

RESULTS

Chronic constrictive injury (CCI) surgery successfully decreased the mechanical and thermal thresholds of rats and decreased the phosphorylation of ASK1 in the rat spinal cord. ASK1 inhibitor NQDI1 attenuated neuropathic pain and decreased the expression of p-p38 and p-JNK. Paeoniflorin mimicked ASK1 inhibitor NQDI1 and inhibited ASK1 phosphorylation. Paeoniflorin decreased the expression of p-p38 and p-JNK, delayed the progress of neuropathic pain, and attenuated neuropathic pain. Paeoniflorin reduced the response of astrocytes and microglia to injury, decreased the expression of IL-1β and TNF-α, and downregulated the expression of CGRP induced by CCI.

CONCLUSIONS

Paeoniflorin is an effective drug for the treatment of neuropathic pain in rats via inhibiting the phosphorylation of ASK1, suggesting it may be effective in patients with neuropathic pain.

CDNF Protein Therapy in Parkinson's Disease

Neurotrophic factors (NTF) are a subgroup of growth factors that promote survival and differentiation of neurons. Due to their neuroprotective and neurorestorative properties, their therapeutic potential has been tested in various neurodegenerative diseases. Bioavailability of NTFs in the target tissue remains a major challenge for NTF-based therapies. Various intracerebral delivery approaches, both protein and gene transfer-based, have been tested with varying outcomes. Three growth factors, glial cell-line derived neurotrophic factor (GDNF), neurturin (NRTN) and platelet-derived growth factor (PDGF-BB) have been tested in clinical trials in Parkinson’s disease (PD) during the past 20 years. A new protein can now be added to this list, as cerebral dopamine neurotrophic factor (CDNF) has recently entered clinical trials. Despite their misleading names, CDNF, together with its closest relative mesencephalic astrocyte-derived neurotrophic factor (MANF), form a novel family of unconventional NTF that are both structurally and mechanistically distinct from other growth factors. CDNF and MANF are localized mainly to the lumen of endoplasmic reticulum (ER) and their primary function appears to be modulation of the unfolded protein response (UPR) pathway. Prolonged ER stress, via the UPR signaling pathways, contributes to the pathogenesis in a number of chronic degenerative diseases, and is an important target for therapeutic modulation. Intraputamenally administered recombinant human CDNF has shown robust neurorestorative effects in a number of small and large animal models of PD, and had a good safety profile in preclinical toxicology studies. Intermittent monthly bilateral intraputamenal infusions of CDNF are currently being tested in a randomized placebo-controlled phase I–II clinical study in moderately advanced PD patients. Here, we review the history of growth factor-based clinical trials in PD, and discuss how CDNF differs from the previously tested growth factors.

Apoptosis signal-regulating kinase 1 activation by Nox1-derived oxidants is required for TNFα receptor endocytosis

Tumor necrosis factor-α (TNFα) is a proinflammatory cytokine that is closely linked to the development of cardiovascular disease. TNFα activates NADPH oxidase 1 (Nox1) and reactive oxygen species (ROS), including superoxide (O₂^·-), production extracellularly is required for subsequent signaling in vascular smooth muscle cells (VSMCs). Apoptosis signal-regulating kinase 1 (ASK1) is a mitogen-activated protein kinase kinase kinase that is activated by oxidation of associated thioredoxin. The role of ASK1 in Nox1-mediated signaling by TNFα is poorly defined. We hypothesized that ASK1 is required for TNFα receptor endocytosis and subsequent inflammatory TNFα signaling. We employed a knockdown strategy to explore the role of ASK1 in TNFα signaling in VSMCs. siRNA targeting ASK1 had no effect on TNFα-induced extracellular O₂^·- production. However, siASK1 inhibited receptor endocytosis as well as phosphorylation of two endocytosis-related proteins, dynamin1 and caveolin1. Intracellular O₂^·- production was subsequently reduced, as were other inflammatory signaling steps including NF-κB activation, IL-6 production, inducible nitric oxide synthase and VCAM expression, and VSMC proliferation. Prolonged exposure to TNFα (24 h) increased tumor necrosis factor receptor (TNFR) subtype 1 and 2 expression, and these effects were also attenuated by siASK1. ASK1 coimmunoprecipitated with both Nox1 and the leucine rich repeat containing 8A anion channel, two essential components of the TNFR1 signaling complex. Activation of ASK1 by autophosphorylation at Thr845 occurs following thioredoxin dissociation, and this requires the presence of Nox1. Thus, Nox1 is part of the multiprotein ASK1 signaling complex. In response to TNFα, ASK1 is activated by Nox1-derived oxidants, and this plays a critical role in translating these ROS into a physiologic response in VSMCs. NEW & NOTEWORTHY Apoptosis signal-regulating kinase 1 (ASK1) drives dynamin1 and caveolin1 phosphorylation and TNFα receptor endocytosis. ASK1 modulates TNFα-induced NF-κB activation, survival, and proliferation. ASK1 and NADPH oxidase 1 (Nox1) physically associate in a multiprotein signaling complex. Nox1 is required for TNFα-induced ASK1 activation.

Dietary phytochemicals with anti-oxidant and pro-oxidant activities: A double-edged sword in relation to adjuvant chemotherapy and radiotherapy?

Many advances have been made in the development and introduction of new anti-cancer drugs to the clinic. However, limited attention has been paid to improving the efficacy of currently available treatments through complementary phytochemical interventions that affect cellular reactive oxygen species (ROS) levels, which are important for the etiology of certain cancers and the effectiveness of radiotherapy and some chemotherapy. In this regard, the maintenance of redox homeostasis may be influenced by the intake of anti-oxidant and pro-oxidant compounds from dietary sources. Interestingly, certain dietary phytochemicals exhibit both anti-oxidant and pro-oxidant activities, depending on their concentration and cellular microenvironment. There is evidence that concurrent administration of some dietary phytochemicals enhances the efficacy of certain cancer treatments by increasing intracellular ROS accumulation. Paradoxically, consumption of the same dietary phytochemicals under conditions that result in the scavenging of ROS might also negatively affect the outcome of ROS-dependent cancer treatments. This review discusses the potential impact of consuming dietary phytochemicals with anti-oxidant and/or pro-oxidant activities on the effectiveness of concurrent chemotherapy and/or radiotherapy in cancer patients.

Apoptosis Signal-regulating Kinase 1 Silencing on Astroglial Inflammasomes in an Experimental Model of Ischemic Stroke

Activation of the inflammasome complex contributes to the inflammatory response and cell death under pathologic conditions. The nucleotide-binding oligomerization domain-like receptor pyrin domain-containing 2 (NLRP2) inflammasome is activated in astrocytes after cerebral ischemia, which can aggravate ischemic damage. Apoptosis signal-regulating kinase 1 (ASK1) is an early activator and immune-regulator after ischemic injury, that can lead to cell death. The objective of the present study was to evaluate the role of ASK1 in controlling NLRP2 inflammasomes in astrocytes after cerebral ischemia. In a mouse model of ischemic stroke, the levels of NLRP2 inflammasome components, and interleukin (IL)-1β and IL-18, were quantified in different brain regions. In addition, an astrocyte cell line was subjected to oxygen-glucose deprivation and reperfusion (OGD/R) injury, and the levels of NLRP2 inflammasome factors, IL-1β and IL-18 were evaluated. Ischemic brain injury activated astrocytes. The levels of NLRP2 inflammasome components, IL-1β and IL-18 productions, and cell death increased in the cortex and striatum after ischemic injury. In cultured astrocytes, NLRP2 inflammasome components, IL-1β and IL-18 levels were upregulated after OGD/R. ASK1 silencing or inhibition efficiently reduced NLRP2 inflammasome components and pro-inflammatory cytokine levels in mice and cultured astrocytes. Our findings identify a key role for ASK1 in regulating astroglial inflammasomes after cerebral ischemia. We suggest ASK1 as one of the main targets for astroglial inflammasomes in ischemic stroke.

Cell Type-Specific Mechanisms in the Pathogenesis of Ischemic Stroke: The Role of Apoptosis Signal-Regulating Kinase 1

Stroke has become a more common disease worldwide. Despite great efforts to develop treatment, little is known about ischemic stroke. Cerebral ischemia activates multiple cascades of cell type-specific pathomechanisms. Ischemic brain injury consists of a complex series of cellular reactions in various cell types within the central nervous system (CNS) including platelets, endothelial cells, astrocytes, neutrophils, microglia/macrophages, and neurons. Diverse cellular changes after ischemic injury are likely to induce cell death and tissue damage in the brain. Since cells in the brain exhibit different functional roles at distinct time points after injury (acute/subacute/chronic phases), it is difficult to pinpoint genuine roles of cell types after brain injury. Many experimental studies have shown the association of apoptosis signal-regulating kinase 1 (ASK1) with cellular pathomechanisms after cerebral ischemia. Blockade of ASK1, by either pharmacological or genetic manipulation, leads to reduced ischemic brain injury and subsequent neuroprotective effects. In this review, we present the cell type-specific pathophysiology of the early phase of ischemic stroke, the role of ASK1 suggested by preclinical studies, and the potential use of ASK suppression, either by pharmacologic or genetic suppression, as a promising therapeutic option for ischemic stroke recovery.

MiR17 improves insulin sensitivity through inhibiting expression of ASK1 and anti-inflammation of macrophages

OBJECTIVES

MicroRNAs (miRNAs) are involved in the pathological progression of various disease including type 2 diabetes (T2D). Chronic inflammation in adipose tissue is a cause of insulin resistance and T2D. MiR-17 palys an anti-inflammatory role in many biological processes. We hypothesized that miR-17 suppressed inflammatory macrophage that is related to insulin resistance in patients with T2D.

METHODS

Macrophage migration and secretion of inflammatory cytokines including TNF-α, IL-6 and IL-1β were detected through transwell migration assay and enzyme-linked immunosorbent assay, respectively. Insulin-stimulated glucose uptake was tested by the radioactivity of tritium-labeled glucose in 3T3-L1 adipocytes. Dual luciferase reporter gene assay was employed to evaluate the interaction between miR-17 and 3'UTR of ASK1.

RESULTS

Our results showed that miR-17 inhibited macrophage infiltration and secretion of TNF-α, IL-6 and IL-1β. Moreover, insulin-stimulated glucose uptake of 3T3-L1 was suppressed by treatment with LPS-induced macrophage conditioned media (CM), whereas the opposite effect was showed after treatment with the CM of macrophages transfected with miR-17. Furthermore, we found that miR-17 directly prevented expression of ASK1 by binding to its 3'UTR.

CONCLUSION

miR-17 improved inflammation-induced insulin resistance by suppressing ASK1 expression in macrophages. These results indicated that miR-17 had an anti-diabetic acitivity by its anti-inflammation effect on macrophage.

Regulation of Microglia and Macrophage Polarization via Apoptosis Signal-Regulating Kinase 1 Silencing after Ischemic/Hypoxic Injury

Inflammation is implicated in ischemic stroke and is involved in abnormal homeostasis. Activation of the immune system leads to breakdown of the blood-brain barrier and, thereby, infiltration of immune cells into the brain. Upon cerebral ischemia, infiltrated macrophages and microglia (resident CNS immune cell) are activated, change their phenotype to M1 or M2 based on the microenvironment, migrate toward damaged tissue, and are involved in repair or damage. Those of M1 phenotype release pro-inflammatory mediators, which are associated with tissue damage, while those of M2 phenotype release anti-inflammatory mediators, which are related to tissue recovery. Moreover, late inflammation continually stimulates immune cell infiltration and leads to brain infarction. Therefore, regulation of M1/M2 phenotypes under persistent inflammatory conditions after cerebral ischemia is important for brain repair. Herein, we focus on apoptosis signal-regulating kinase 1 (ASK1), which is involved in apoptotic cell death, brain infarction, and production of inflammatory mediators after cerebral ischemia. We hypothesized that ASK1 is involved in the polarization of M1/M2 phenotype and the function of microglia and macrophage during the late stage of ischemia/hypoxia. We investigated the effects of ASK1 in mice subjected to middle cerebral artery occlusion and on BV2 microglia and RAW264.7 macrophage cell lines subjected to oxygen-glucose deprivation. Our results showed that ASK1 silencing effectively reduced Iba-1 or CD11b-positive cells in ischemic areas, suppressed pro-inflammatory cytokines, and increased anti-inflammatory mediator levels at 7 days after cerebral ischemia. In cultured microglia and macrophages, ASK1 inhibition, induced by NQDI-1 drug, decreased the expression and release of M1-associated factors and increased those of M2-associated factors after hypoxia/reperfusion (H/R). At the gene level, ASK1 inhibition suppressed M1-associated genes and augmented M2-associated genes. In gap closure assay, ASK1 inhibition reduced the migration rate of microglia and macrophages after H/R. Taken together, our results provide new information that suggests ASK1 controls the polarization of M1/M2 and the function of microglia and macrophage under sustained-inflammatory conditions. Regulation of persistent inflammation via M1/M2 polarization by ASK1 is a novel strategy for repair after ischemic stroke.

MicroRNA-17 Suppresses TNF-α Signaling by Interfering with TRAF2 and cIAP2 Association in Rheumatoid Arthritis Synovial Fibroblasts

TNF-α is a major cytokine implicated in rheumatoid arthritis (RA), and its expression is regulated at the transcriptional and posttranscriptional levels. However, the impact of changes in microRNA expression on posttranslational processes involved in TNF-α signaling networks is not well defined in RA. In this study, we evaluated the effect of miR-17, a member of the miR-17-92 cluster, on the TNF-α signaling pathway in human RA synovial fibroblasts (SFs). We demonstrated that miR-17 expression was significantly low in RA serum, SFs, and synovial tissues, as well as in the serum and joints of adjuvant-induced arthritis rats. RNA-sequencing analysis showed modulation of 664 genes by pre-miR-17 in human RA SFs. Ingenuity pathway analysis of RNA-sequencing data identified the ubiquitin proteasome system in the TNF-α signaling pathway as a primary target of miR-17. Western blot analysis confirmed the reduction in TRAF2, cIAP1, cIAP2, USP2, and PSMD13 expression by miR-17 in TNF-α-stimulated RA SFs. Immunoprecipitation assays showed that miR-17 restoration increased the K48-linked polyubiquitination of TRAF2, cIAP1, and cIAP2 in TNF-α-stimulated RA SFs. Thus, destabilization of TRAF2 by miR-17 reduced the ability of TRAF2 to associate with cIAP2, resulting in the downregulation of TNF-α-induced NF-κBp65, c-Jun, and STAT3 nuclear translocation and the production of IL-6, IL-8, MMP-1, and MMP-13 in human RA SFs. In conclusion, this study provides evidence for the role of miR-17 as a negative regulator of TNF-α signaling by modulating the protein ubiquitin processes in RA SFs.

Syndecan-1 (CD138) Suppresses Apoptosis in Multiple Myeloma by Activating IGF1 Receptor: Prevention by SynstatinIGF1R Inhibits Tumor Growth

Syndecan-1 (Sdc1/CD138) expression is linked to disease severity in multiple myeloma, although the causal basis for this link remains unclear. Here we report that capture of the IGF1 receptor (IGF1R) by Sdc1 suppresses ASK1-dependent apoptosis in multiple myeloma cells. Sdc1 binds two different fractions of IGF1R, one that is constitutively active and a second that is activated by IGF1 ligand. Notably, IGF1R kinase activity in both fractions is blocked by synstatinIGF1R (SSTNIGF1R), a peptide that inhibits IGF1R capture by Sdc1, as well as by a truncated peptide (SSTNIGF1R-T) that appears to be specific for multiple myeloma cells. Mechanistically, we show that ASK1 is bound to active IGF1R and inhibited by Tyr and Ser83/Ser966 phosphorylation. When IGF1R engagement with Sdc1 is blocked by SSTNIGF1R, ASK1 becomes activated, and initiates JNK- and caspase-3-mediated apoptosis. In pharmacologic tests, we find SSTNIGF1R is highly stable in human plasma and displays a half-life of 27 hours in mice, wherein it significantly reduces both the size and neovascularization of CAG myeloma tumor xenografts. Taken together, our results offer a preclinical proof of concept and mechanistic rationale for the exploration of SSTNIGF1R as an experimental therapeutic to dually attack multiple myeloma tumor cell survival and tumor angiogenesis. Cancer Res; 76(17); 4981-93. ©2016 AACR.

Cross-talk between Arg methylation and Ser phosphorylation modulates apoptosis signal-regulating kinase 1 activation in endothelial cells

Protein arginine methyltransferase 5 interacts with and methylates apoptosis signal–regulating kinase 1 at arginine residue 89, thereby negatively regulating its activity by promoting the interaction between ASK1 and Akt and thus phosphorylating ASK1 at serine residue 83.

We describe a novel functional interaction between ASK1 and PRMT5. We show that PRMT5 interacts with and methylates ASK1 at arginine residue 89 and thereby negatively regulates its activity by promoting the interaction between ASK1 and Akt and thus phosphorylating ASK1 at serine residue 83. Furthermore, the association between ASK1 and Akt is enhanced by VEGF stimulation, and PRMT5 is required for this association. Moreover, PRMT5-mediated ASK1 methylation impaired the H₂O₂-induced activity of ASK1, and this inhibitory effect of PRMT5 was abolished by replacement of arginine 89 with Trp or depletion of PRMT5 expression by RNA interference. Together the results demonstrate cross-talk between arginine methylation and serine phosphorylation in ASK1.

Diarachidonoylphosphoethanolamine induces apoptosis of malignant pleural mesothelioma cells through a Trx/ASK1/p38 MAPK pathway

1,2-Diarachidonoyl-sn-glycero-3-phosphoethanolamine (DAPE) induces both necrosis/necroptosis and apoptosis of NCI-H28 malignant pleural mesothelioma (MPM) cells. The present study was conducted to understand the mechanism for DAPE-induced apoptosis of NCI-H28 cells. DAPE induced caspase-independent apoptosis of NCI-H28 malignant pleural mesothelioma (MPM) cells, and the effect of DAPE was prevented by antioxidants or an inhibitor of NADPH oxidase (NOX). DAPE generated reactive oxygen species (ROS) and inhibited activity of thioredoxin (Trx) reductase (TrxR). DAPE decreased an association of apoptosis signal-regulating kinase 1 (ASK1) with thioredoxin (Trx), thereby releasing ASK1. DAPE activated p38 mitogen-activated protein kinase (MAPK), which was inhibited by an antioxidant or knocking-down ASK1. In addition, DAPE-induced NCI-H28 cell death was also prevented by knocking-down ASK1. Taken together, the results of the present study indicate that DAPE stimulates NOX-mediated ROS production and suppresses TrxR activity, resulting in the decrease of reduced Trx and the dissociation of ASK1 from a complex with Trx, allowing sequential activation of ASK1 and p38 MAPK, to induce apoptosis of NCI-H28 MPM cells.

Berberine attenuates CCN2-induced IL-1β expression and prevents cartilage degradation in a rat model of osteoarthritis

Connective tissue growth factor (CTGF; also known as CCN2) is an inflammatory mediator that is abundantly expressed in osteoarthritis (OA). Interleukin-1β (IL-1β) plays a pivotal role in OA pathogenesis. Berberine exhibits an anti-inflammatory effect, but the mechanisms by which it modulates CCN2-induced IL-1β expression in OA synovial fibroblasts (OASFs) remain unknown. We showed that CCN2-induced IL-1β expression is mediated by the activation of αvβ3/αvβ5 integrin-dependent reactive oxygen species (ROS) generation, and subsequent activation of apoptosis signal-regulating kinase 1 (ASK1), p38/JNK, and nuclear factor-κB (NF-κB) signaling pathways. This IL-1β expression in OASFs is attenuated by N-acetylcysteine (NAC), inhibitors of ASK1, p38, or JNK, or treatment with berberine. Furthermore, berberine also reverses cartilage damage in an experimental model of collagenase-induced OA (CIOA). We observed that CCN2 increased IL-1β expression via αvβ3/αvβ5 integrins, ROS, and ASK1, p38/JNK, and NF-κB signaling pathways. Berberine was found to inhibit these signaling components in OASFs in vitro and prevent cartilage degradation in vivo. We suggest a novel therapeutic strategy of using berberine for managing OA.

Apoptosis signal-regulating kinase 1 promotes Ochratoxin A-induced renal cytotoxicity

Oxidative stress and apoptosis are involved in Ochratoxin A (OTA)-induced renal cytotoxicity. Apoptosis signal-regulating kinase 1 (ASK1) is a Mitogen-Activated Protein Kinase Kinase Kinase (MAPKKK, MAP3K) family member that plays an important role in oxidative stress-induced cell apoptosis. In this study, we performed RNA interference of ASK1 in HEK293 cells and employed an iTRAQ-based quantitative proteomics approach to globally investigate the regulatory mechanism of ASK1 in OTA-induced renal cytotoxicity. Our results showed that ASK1 knockdown alleviated OTA-induced ROS generation and Δψm loss and thus desensitized the cells to OTA-induced apoptosis. We identified 33 and 24 differentially expressed proteins upon OTA treatment in scrambled and ASK1 knockdown cells, respectively. Pathway classification and analysis revealed that ASK1 participated in OTA-induced inhibition of mRNA splicing, nucleotide metabolism, the cell cycle, DNA repair, and the activation of lipid metabolism. We concluded that ASK1 plays an essential role in promoting OTA-induced renal cytotoxicity.

Redox systems in Botrytis cinerea: impact on development and virulence

The thioredoxin system is of great importance for maintenance of cellular redox homeostasis. Here, we show that it has a severe influence on virulence of Botrytis cinerea, demonstrating that redox processes are important for host-pathogen interactions in this necrotrophic plant pathogen. The thioredoxin system is composed of two enzymes, the thioredoxin and the thioredoxin reductase. We identified two genes encoding for thioredoxins (bctrx1, bctrx2) and one gene encoding for a thioredoxin reductase (bctrr1) in the genome of B. cinerea. Knockout mutants of bctrx1 and bctrr1 were severely impaired in virulence and more sensitive to oxidative stress. Additionally, Δbctrr1 showed enhanced H2O2 production and retarded growth. To investigate the impact of the second major cellular redox system, glutathione, we generated deletion mutants for two glutathione reductase genes. The effects were only marginal; deletion of bcglr1 resulted in reduced germination and, correspondingly, to retarded infection as well as reduced growth on minimal medium, whereas bcglr2 deletion had no distinctive phenotype. In summary, we showed that the balanced redox status maintained by the thioredoxin system is essential for development and pathogenesis of B. cinerea, whereas the second major cellular redox system, the glutathione system, seems to have only minor impact on these processes.

Requirement of apoptosis-inducing kinase 1 for the induction of bronchial asthma following stimulation with ovalbumin

BACKGROUND

Bronchial asthma is a chronic inflammatory disease of the airway. Apoptosis signal-regulating kinase 1 (ASK1), a member of the mitogen-activated protein kinase kinase kinase family, is activated by environmental stress and plays a crucial role in the induction of apoptosis and inflammation. To examine whether ASK1 is involved in the induction of bronchial asthma, we investigated the role of ASK1 using a genetic approach in the production of cytokines, as well as the development of airway hyperreactivity (AHR) and antibody responses using a murine airway inflammation model.

METHODS

ASK1-deficient (ASK1(-/-)) and control wild-type (WT) mice were immunized with ovalbumin (OVA) without alum intraperitoneally, followed by intranasal administration of OVA. Airway infiltration of inflammatory cells, cytokine production, AHR and antibody production were assayed. The asthmatic phenotype was assessed following intranasal administration of IL-13 or TNF-α.

RESULTS

ASK1(-/-) mice sensitized with OVA displayed an impaired inflammatory cell infiltration into airways and a decreased AHR relative to WT mice. Moreover, the production of OVA-specific IgE antibodies and proasthmatic cytokines (IL-5, IL-13 and TNF-α) was substantially reduced in OVA-stimulated ASK1(-/-) mice. Intranasal administration of IL-13 and OVA enhanced the accumulation of inflammatory cells in OVA-primed ASK1(-/-) mice. The OVA-induced AHR in response to methacholine was enhanced by IL-13 in WT mice but not ASK1(-/-) mice.

CONCLUSIONS

The ASK1 signaling pathway regulates the OVA-induced asthmatic phenotype, specifically AHR sensitivity and cytokine production. Therefore, the ASK1 signaling pathway is a promising target for therapeutic intervention in some asthmatic patients.

Thioredoxin and thioredoxin target proteins: from molecular mechanisms to functional significance

The thioredoxin (Trx) system is one of the central antioxidant systems in mammalian cells, maintaining a reducing environment by catalyzing electron flux from nicotinamide adenine dinucleotide phosphate through Trx reductase to Trx, which reduces its target proteins using highly conserved thiol groups. While the importance of protecting cells from the detrimental effects of reactive oxygen species is clear, decades of research in this field revealed that there is a network of redox-sensitive proteins forming redox-dependent signaling pathways that are crucial for fundamental cellular processes, including metabolism, proliferation, differentiation, migration, and apoptosis. Trx participates in signaling pathways interacting with different proteins to control their dynamic regulation of structure and function. In this review, we focus on Trx target proteins that are involved in redox-dependent signaling pathways. Specifically, Trx-dependent reductive enzymes that participate in classical redox reactions and redox-sensitive signaling molecules are discussed in greater detail. The latter are extensively discussed, as ongoing research unveils more and more details about the complex signaling networks of Trx-sensitive signaling molecules such as apoptosis signal-regulating kinase 1, Trx interacting protein, and phosphatase and tensin homolog, thus highlighting the potential direct and indirect impact of their redox-dependent interaction with Trx. Overall, the findings that are described here illustrate the importance and complexity of Trx-dependent, redox-sensitive signaling in the cell. Our increasing understanding of the components and mechanisms of these signaling pathways could lead to the identification of new potential targets for the treatment of diseases, including cancer and diabetes.

Differential role of hypoxia-inducible factor 1 alpha in toll-like receptor-mediated and allergic inflammatory reactions

Hypoxia-inducible factor 1 (HIF-1) is a transcription complex that plays a pivotal role in cellular adaptation to hypoxic conditions. The role of this factor in inflammatory reactions associated with infections and allergies has recently become evident. In this review we summarize our current knowledge concerning the accumulation and role of HIF-1 in Toll-like receptor-mediated and allergic inflammation. The differential molecular mechanisms used to stabilize this protein in various settings and its ability to support both proinflammatory and angiogenic responses suggest important functional roles in both innate immune responses and allergies. Importantly, the HIF-1 transcription complex is activated in human basophils during IgE-mediated inflammatory responses. It is involved in VEGF expression and subsequent promotion of angiogenesis and in controlling energy metabolism.

Immune and stress response 'cross-talk' in the Drosophila Malpighian tubule

The success of insects is in large part due to their ability to survive environmental stress, including heat, cold, and dehydration. Insects are also exposed to infection, osmotic or oxidative stress, and to xenobiotics or toxins. The molecular mechanisms of stress sensing and response have been widely investigated in mammalian cell lines, and the area of stress research is now so vast to be beyond the scope of a single review article. However, the mechanisms by which stress inputs to the organism are sensed and integrated at the tissue and cellular level are less well understood. Increasingly, common molecular events between immune and other stress responses are observed in vivo; and much of this work stems of efforts in insect molecular science and physiology. We describe here the current knowledge in the area of immune and stress signalling and response at the level of the organism, tissue and cell, focussing on a key epithelial tissue in insects, the Malpighian tubule, and drawing together the known pathways that modulate responses to different stress insults. The tubules are critical for insect survival and are increasingly implicated in responses to multiple and distinct stress inputs. Importantly, as tubule function is central to survival, they are potentially key targets for insect control, which will be facilitated by increased understanding of the complexities of stress signalling in the organism.

Reciprocal inhibition between the transforming growth factor-β-activated kinase 1 (TAK1) and apoptosis signal-regulating kinase 1 (ASK1) mitogen-activated protein kinase kinase kinases and its suppression by TAK1-binding protein 2 (TAB2), an adapter protein for TAK1

Mitogen-activated protein kinase kinase kinases (MAP3Ks) are activated by a wide spectrum of extracellular stimuli and are involved in various cellular events including proinflammatory and oxidative damage response through activations of two specific transcription factors, nuclear factor κB (NF-κB) and activator protein-1 (AP-1). Although members of the MAP3K family have both overlapping and distinct functions, the inter-regulatory mechanism of MAP3Ks remains largely unknown. In this study we demonstrated that transforming growth factor-β-activated kinase 1 (TAK1)-TAK1-binding protein 1 (TAB1) complex negatively regulates ASK1-mediated signaling, and TAB2 reciprocally regulates TAK1-induced NF-κB and apoptosis signal-regulating kinase 1 (ASK1)-mediated AP-1 activations through the TAK1-TAB2 interaction and the interferences of TAK1-ASK1 interaction. TAK1 interacted with the N or C terminus of ASK1 through the C-terminal TAB2 binding domain of TAK1, with resultant inhibition of ASK1-induced AP-1 activation. Interestingly, the interaction between TAK1 and TAB2 significantly attenuated the ASK1-TAK1 interaction through the competitive interaction with ASK1 to TAK1 and resulted in the activations of TAK1-induced activations of NF-κB and AP-1. More interestingly, H(2)O(2)- and TNF-α-induced apoptosis in TAK1-deficient mouse embryo fibroblast cells were dramatically enhanced by overexpression of ASK1, whereas the apoptosis was markedly inhibited by the overexpression of TAK1. Overall, these results demonstrate that TAK1 and its adapter protein, TAB2, reciprocally regulate both TAK1- and ASK1-mediated signaling pathways to direct the activations of NF-κB and AP-1.

Thy28 partially prevents apoptosis induction following engagement of membrane immunoglobulin in WEHI-231 B lymphoma cells

Thy28 protein is conserved among plants, bacteria, and mammalian cells. Nuclear Thy28 protein is substantially expressed in testis, liver, and immune cells such as lymphocytes. Lymphocyte apoptosis plays a crucial role in homeostasis and formation of a diverse lymphocyte repertoire. In this study, we examined whether Thy28 affects induction of apoptosis in WEHI-231 B lymphoma cells following engagement of membrane immunoglobulin (mIg). Once they were established, the Thy28-overexpressing WEHI-231 cells showed similar expression levels of IgM and class I major histocompatibility complex (MHC) molecule compared with controls. The Thy28-overexpressing cells were considerably resistant to loss of mitochondrial membrane potential (ΔΨm), caspase-3 activation, and increase in annexin-positive cells upon mIg engagement. These changes were concomitant with an increase in G1 phase associated with upregulation of p27^Kip1. The anti-IgM-induced sustained activation of c-Jun N-terminal kinase (JNK), which was associated with late-phase hydrogen peroxide (H₂O₂) production, was partially reduced in the Thy28-expressing cells relative to controls. Taken together, the data suggest that in WEHI-231 B lymphoma cells, Thy28 regulates mIg-mediated apoptotic events through the JNK-H₂O₂ activation pathway, concomitant with an accumulation of cells in G1 phase associated with upregulation of p27^Kip1 in WEHI-231 B lymphoma cells.

Endogenous opioid peptides in regulation of innate immunity cell functions

Endogenous opioid peptides comprise a group of bioregulatory factors involved in regulation of functional activity of various physiological systems of an organism. One of most important functions of endogenous opioids is their involvement in the interaction between cells of the nervous and immune systems. Summary data on the effects of opioid peptides on regulation of functions of innate immunity cells are presented.

Apoptosis signal-regulating kinase 1 (Ask1) targeted small interfering RNA on ischemic neuronal cell death

Apoptosis signal-regulating kinase 1 (Ask1) is one of mitogen-activated protein kinase kinase kinase (MAPKKK) for cell differentiation and apoptosis. The aim of the present study is to evaluate whether RNA interference against Ask1 (Ask1-siRNA) down-regulates the expression of Ask1 and prevents apoptotic neuronal cell death after ischemia/reperfusion (I/R) in mice. Mice were subjected to intraluminal suture occlusion of the middle cerebral artery for 1h, followed by reperfusion. The Ask1-siRNA or a control-siRNA was introduced using osmotic pump intracerebroventricularly at 3days before I/R. The expression and mRNA of Ask1 were evaluated by Western blot and RT-PCR after I/R with time. Immunohistochemistry and TUNEL assay were also investigated to evaluate the effect of Ask1 on cerebral infarction by Ask1-siRNA treatment. The expression of Ask1 was increased significantly at 8h after I/R. The level of mRNA and protein of Ask1 down-regulated after treatment of Ask1-siRNA and subsequently cerebral infarction volume was reduced. Our results suggest the increased Ask1 expression induce apoptotic cell death after I/R. And we also demonstrated that Ask1-siRNA attenuates upregulation of Ask1, which was followed by the reduction of infarction in ischemic brain after I/R. Ask1-siRNA could represent a molecular target for prevention of ischemic stroke.

Ras homolog enriched in brain (Rheb) enhances apoptotic signaling

Rheb is a homolog of Ras GTPase that regulates cell growth, proliferation, and regeneration via mammalian target of rapamycin (mTOR). Because of the well established potential of activated Ras to promote survival, we sought to investigate the ability of Rheb signaling to phenocopy Ras. We found that overexpression of lipid-anchored Rheb enhanced the apoptotic effects induced by UV light, TNFα, or tunicamycin in an mTOR complex 1 (mTORC1)-dependent manner. Knocking down endogenous Rheb or applying rapamycin led to partial protection, identifying Rheb as a mediator of cell death. Ras and c-Raf kinase opposed the apoptotic effects induced by UV light or TNFα but did not prevent Rheb-mediated apoptosis. To gain structural insight into the signaling mechanisms, we determined the structure of Rheb-GDP by NMR. The complex adopts the typical canonical fold of RasGTPases and displays the characteristic GDP-dependent picosecond to nanosecond backbone dynamics of the switch I and switch II regions. NMR revealed Ras effector-like binding of activated Rheb to the c-Raf-Ras-binding domain (RBD), but the affinity was 1000-fold lower than the Ras/RBD interaction, suggesting a lack of functional interaction. shRNA-mediated knockdown of apoptosis signal-regulating kinase 1 (ASK-1) strongly reduced UV or TNFα-induced apoptosis and suppressed enhancement by Rheb overexpression. In conclusion, Rheb-mTOR activation not only promotes normal cell growth but also enhances apoptosis in response to diverse toxic stimuli via an ASK-1-mediated mechanism. Pharmacological regulation of the Rheb/mTORC1 pathway using rapamycin should take the presence of cellular stress into consideration, as this may have clinical implications.

Myeloid cell death associated with Toll-like receptor 7/8-mediated inflammatory response. Implication of ASK1, HIF-1 alpha, IL-1 beta and TNF-alpha

Programmed cell death or apoptosis is an important part of the host innate immune defence, especially against ssRNA viruses (influenza virus, HIV-1, ebola virus, hepatitis C virus and many others). Viral ssRNA is recognised by endosomal Toll-like receptors 7 and 8 (TLR7/8) which induce further stages of immune defence against these pathogens. Some of the immune cells die because of inflammatory stress allowing for the selection of those cells which are resistant to stress-induced apoptosis and which are used in further stages of the host immune response. On the other hand, apoptosis could be used as an instrument to suppress the function of activated inflammatory cells. However, the mechanisms underlying death of the inflammatory cells associated with stress induced by ligands of TLR7/8 remain unclear. In this study we have found that programmed death of human myeloid cells from different cell lines associated with ligand-induced TLR7/8-mediated inflammatory stress depends on activation of apoptosis signal-regulating kinase 1 (ASK1). This enzyme is, however, not required for the production of pro-inflammatory cytokines - TNF-α and IL-1β. We have found that released IL-1β and TNF-α are involved in apoptosis of myeloid cells associated with TLR7/8-mediated inflammatory stress. The pro-apoptotic effect of released TNF-α in this case is much lower compared to that of IL-1β.

Evidence for markers of hypoxia and apoptosis in explanted human carotid atherosclerotic plaques

OBJECTIVE

Apoptosis and inflammation are important features of atherosclerotic plaques. We investigated whether a common signal molecule can trigger these two apparently separate pathways. Hypoxia inducible factor (HIF-1α) is known to participate in atherosclerosis and to stimulate apoptosis signal-regulating kinase 1 (ASK-1), one of the mitogen-activated protein kinases, which is activated by various extracellular stimuli and involved in a variety of cellular function.

METHODS

We tested carotid artery specimens from 50 subjects who underwent angioplasty and five age-matched controls for either Western blot or histologic analysis. The hypoxic status was investigated by means of HIF-1α expression in carotid specimens.

RESULTS

HIF-1α was significantly upregulated in carotid specimens with respect to controls (P < .05), ASK-1 was detected in plaques of any composition from lipidic to calcific, and this expression increased with the stage of the plaque and with the expression of inflammatory (p-ERK, RANK-L, OPG) and apoptotic molecules (caspase 9, p-p-38, and p-JNK).

CONCLUSION

Our data suggest that hypoxia is the key regulating factor that triggers inflammation as well as apoptosis in the human atherosclerotic plaque.

Hypoxia-inducible factor 1 as one of the "signaling drivers" of Toll-like receptor-dependent and allergic inflammation

Hypoxia-inducible factor 1 (HIF-1) is a heterodimeric transcription complex which plays a crucial role in cellular adaptation to low oxygen availability. In the last years there has been increasing evidence about the role of this factor in inflammatory/innate immune reactions. It has also been found to contribute to different types of allergic inflammation. In this review the current knowledge about the accumulation and role of HIF-1 in Toll-like receptor-mediated and allergic inflammation is summarized. Differential biochemical mechanisms employed to stabilize the protein in different cases are discussed.

Involvement of hypoxia-inducible factor-1 HiF(1alpha) in IgE-mediated primary human basophil responses

Basophils play a pivotal role in regulating chronic allergic inflammation as well as angiogenesis. Here, we show for the first time that IgE-mediated activation of primary human basophils results in protein accumulation of the alpha-subunit of hypoxia-inducible factor 1alpha (HIF-1alpha), which is differentially regulated compared with signals controlling histamine release. HIF-1 facilitates cellular adaptation to hypoxic conditions such as inflammation and tumour growth by controlling glycolysis, angiogenesis and cell adhesion. ERK and p38 MAPK, but not reactive oxygen species (ROS), ASK1 or PI 3-kinase, were critical for IgE-mediated accumulation of HIF-1alpha, although the latter crucially affected degranulation. Abrogating HIF-1alpha expression in basophils using siRNA demonstrated that this protein is essential for vascular endothelial growth factor (VEGF) mRNA expression and, consequently, release of VEGF protein. In addition, HIF-1alpha protein alters IgE-induced ATP depletion in basophils, thus also supporting the production of the pro-allergic cytokine IL-4.

Reactive oxygen and nitrogen species in normal physiological processes

Abstract Reactive oxygen species (ROS) and reactive nitrogen species have generally been considered as being highly reactive and cytotoxic molecules. Besides their noxious effects, ROS participate in physiological processes in a carefully regulated manner. By way of example, microbicidal ROS are produced in professional phagocytes, ROS function as short-lived messengers having a role in signal transduction and, among other processes, participate in the synthesis of the iodothyronine hormones, reproduction, apoptosis and necrosis. Because of their ability to mediate a crosstalk between key molecules, their role might be dual (at least in some cases). The levels of ROS increase from a certain age, being associated with various diseases typical of senescence. The aim of this review is to summarize the recent findings on the physiological role of ROS. Other issues addressed are an increase in ROS levels during ageing, and the possibility of the physiological nature of this process.

Hyperactivity in novel environment with increased dopamine and impaired novelty preference in apoptosis signal-regulating kinase 1 (ASK1)-deficient mice

Apoptosis signal-regulating kinase 1 (ASK1) is a mitogen-activated protein (MAP) kinase kinase kinase family member, which induces apoptosis in various cells through JNK and p38 MAP kinase cascades. In addition to apoptosis signaling, a number of recent in vitro studies have suggested that ASK1 may play roles in neural function. However, the behavioral significance of ASK1 has remained unclear. Here, we subjected ASK1 (-/-) mice to a battery of behavioral tests and found that they displayed temporary hyperactivity in an open-field test. Activities in the familiar field were normal, indicating that the hyperactivity observed was specific to the novel environment. ASK1 (-/-) mice also exhibited impairment of novelty preference 24h after training and superior performance on the rotarod test. Brain tissue contents of dopamine and 4-dihydroxyphenylacetic acid (DOPAC) were elevated in ASK1 (-/-) mice. Our findings thus demonstrate novel behavioral functions of ASK1, including regulation of locomotor activity, novelty preference, and motor coordination with dopaminergic transmission.

Apoptosis signal-regulating kinase (ASK)-1 mediates apoptosis through activation of JNK1 following engagement of membrane immunoglobulin

Engagement of membrane immunoglobulin (mIg) on WEHI-231 mouse B lymphoma cells results in growth arrest at the G1 phase of the cell cycle, followed by a reduction of mitochondrial membrane potential (DeltaPsim) and apoptosis. WEHI-231 cells resemble immature B cells in terms of the cell surface phenotype and sensitivity to mIg engagement. However, the molecular mechanisms underlying mIg-induced loss of DeltaPsim and apoptosis have not yet been established. In this study, we show that apoptosis signal-regulating kinase 1 (ASK1)-c-Jun N-terminal kinase 1 (JNK1) signaling pathway participates in mIg-induced apoptosis through the generation of reactive oxygen species (ROS). Stimulation of WEHI-231 cells with anti-IgM induces phosphorylation and subsequent activation of ASK1, leading to JNK activation. Anti-IgM stimulation immediately (5 min) induces hydrogen peroxide (H2O2) production with a substantial increase during later time points (36-48 h), accompanied by loss of DeltaPsim and an increase in cells with sub-G1 DNA content. The anti-IgM-induced late-phase H2O2 production, loss of DeltaPsim, and increase in the sub-G1 fraction were all reduced substantially in WEHI-231 cells overexpressing a dominant-negative form of ASK1, compared with control vector alone, but enhanced substantially in cells overexpressing a constitutively active form of ASK1. These mIg-mediated events were also partially abrogated by ROS scavenger N-acetyl-L-cysteine (NAC). Taken together, these results suggest that mIg engagement induces H2O2 production leading to activation of ASK1-JNK1 pathway, creating a feedback amplification loop of ROS-ASK/JNK that leads to loss of DeltaPsim and finally apoptosis.

Apoptosis signal-regulating kinase 1 regulates the expression of caspase-11

Caspase-11 is an inducible caspase involved in the regulation of cell death and inflammation. In the present study, we examined whether apoptosis signal-regulating kinase 1 (Ask1)-mediated signaling pathway is involved in the expression of caspase-11 induced by lipopolysaccharide (LPS). We found that the induction of caspase-11 was suppressed by the inhibitors of NADPH oxidase (Nox) or knockdown of Nox4 that acts downstream of toll-like receptor 4 and generates Ask1-activating reactive oxygen species. Overexpression of dominant negative tumor necrosis factor receptor associate factor 6 also suppressed the induction of caspase-11. Importantly, knockdown or dominant negative form of Ask1 suppressed the induction of caspase-11 following LPS stimulation. Taken together, our results show that Ask1 regulates the expression of caspase-11 following LPS stimulation.

Disulfide-mediated apoptosis of human T-lymphotrophc virus type-I (HTLV-I)-infected cells in patients with HTLV-I-associated myelopathy/ tropical spastic paraparesis

Background

This study was conducted to construct a basis for a therapeutic strategy against human T-lymphotropic virus type-I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) using a compound that contained a disulfide moiety, prosultiamine, which is a homologue of allithiamine originally synthesized by allicin and thiamine-thiol, for the targeting of HTLV-I-infected cells.

Methods

First, we analysed the apoptotic pathway in allicin or prosultiamine treatment against an HTLV-I-infected T-cell line (HCT-1), derived from an HAM/TSP patient, by flow cytometry and western blot. Second, we evaluated the effect of targeting HTLV-I-infected cells in a prosultiamine in vitro treatment and in a clinical trial in HAM/TSP patients by quantitative PCR analysis of HTLV-I proviral load.

Results

Prosultiamine, like allicin, induced caspase-dependent apoptosis against HCT-1 cells. The fact that the loss of mitochondrial membrane potential was recovered in z-VAD-fmk-pretreated HCT-1 cells with prosultiamine treatment suggested that prosultiamine can induce caspase-dependent apoptosis through the mitochondrial pathway. On the basis of data showing that prosultiamine in vitro treatment against peripheral blood CD4+ T-cells of HAM/TSP patients induced a significant decrease of HTLV-I proviral copy numbers by apoptosis of HTLV-I- infected cells, we treated six HAM/ TSP patients with intravenous administration of pro-sultiamine for 14 days. As a result of this treatment, the copy numbers of HTLV-I provirus in peripheral blood decreased to approximately 30–50% of their pretreat-ment levels with some clinical benefits in all patients.

Conclusions

Our results suggest that prosultiamine has the potential to be a new therapeutic tool that targets HTLV-I-infected cells in HAM/TSP.