Reviving resilience: MEcPP-mediated ASK1-IMPα-9-TRP2 stress-responsive module.

Chloroplasts are not only critical photosynthesis sites in plants, but they also participate in plastidial retrograde signaling in response to developmental and environmental signals. MEcPP (2-C-Methyl-D-erythritol-2,4-cyclopyrophosphate) is an intermediary in the methylerythritol phosphate (MEP) pathway in chloroplasts. It is a critical precursor for the synthesis of isoprenoids and terpenoid derivatives, which play crucial roles in plant growth and development, photosynthesis, reproduction, and defense against environmental constraints. Accumulation of MEcPP under stressful conditions triggers the expression of IMPα-9 and TPR2, contributing to the activation of abiotic stress-responsive genes. In this correspondence, we discuss plastidial retrograde signaling in support of a recently published paper in Molecular Plant (Zeng et al. 2024). We hope that it can shed more insight on the retrograde signaling cascade.

Apoptosis signal-regulating kinase 1 promotes inflammation in senescence and aging.

Cellular senescence is a stress-induced, permanent cell cycle arrest involved in tumor suppression and aging. Senescent cells secrete bioactive molecules such as pro-inflammatory cytokines and chemokines. This senescence-associated secretory phenotype (SASP) has been implicated in immune-mediated elimination of senescent cells and age-associated chronic inflammation. However, the mechanisms regulating the SASP are incompletely understood. Here, we show that the stress-responsive kinase apoptosis signal-regulating kinase 1 (ASK1) promotes inflammation in senescence and aging. ASK1 is activated during senescence and increases the expression of pro-inflammatory cytokines and chemokines by activating p38, a kinase critical for the SASP. ASK1-deficient mice show impaired elimination of oncogene-induced senescent cells and an increased rate of tumorigenesis. Furthermore, ASK1 deficiency prevents age-associated p38 activation and inflammation and attenuates glomerulosclerosis. Our results suggest that ASK1 is a driver of the SASP and age-associated chronic inflammation and represents a potential therapeutic target for age-related diseases.

Abrogating PDK4 activates autophagy-dependent ferroptosis in breast cancer via ASK1/JNK pathway.

BACKGROUND: Targeting ferroptosis mediated by autophagy presents a novel therapeutic approach to breast cancer, a mortal neoplasm on the global scale. Pyruvate dehydrogenase kinase isozyme 4 (PDK4) has been denoted as a determinant of breast cancer metabolism. The target of this study was to untangle the functional mechanism of PDK4 in ferroptosis dependent on autophagy in breast cancer. METHODS: RT-qPCR and western blotting examined PDK4 mRNA and protein levels in breast cancer cells. Immunofluorescence staining appraised light chain 3 (LC3) expression. Fe (2 +) assay estimated total iron level. Relevant assay kits and C11-BODIPY (591/581) staining evaluated lipid peroxidation level. DCFH-DA staining assayed intracellular reactive oxygen species (ROS) content. Western blotting analyzed the protein levels of autophagy, ferroptosis and apoptosis-signal-regulating kinase 1 (ASK1)/c-Jun N-terminal kinase (JNK) pathway-associated proteins. RESULTS: PDK4 was highly expressed in breast cancer cells. Knockdown of PDK4 induced the autophagy of breast cancer cells and 3-methyladenine (3-MA), an autophagy inhibitor, countervailed the promoting role of PDK4 interference in ferroptosis in breast cancer cells. Furthermore, PDK4 knockdown activated ASK1/JNK pathway and ASK1 inhibitor (GS-4997) partially abrogated the impacts of PDK4 absence on the autophagy and ferroptosis in breast cancer cells. CONCLUSION: To sum up, deficiency of PDK4 activated ASK1/JNK pathway to stimulate autophagy-dependent ferroptosis in breast cancer.

Lycopene Alleviates Endoplasmic Reticulum Stress in Steatohepatitis through Inhibition of the ASK1-JNK Signaling Pathway.

Lycopene has been proven to alleviate nonalcoholic steatohepatitis (NASH), but the precise mechanisms are inadequately elucidated. In this study, we found a previously unknown regulatory effect of lycopene on the apoptosis signal-regulating kinase 1 (ASK1) signaling pathway in both in vivo and in vitro models. Lycopene supplementation (3 and 6 mg/kg/day) exhibited a significant reduction in lipid accumulation, inflammation, and fibrosis of the liver in mice fed with a high-fat/high-cholesterol diet or a methionine-choline-deficient diet. RNA sequencing uncovered that the mitogen-activated protein kinases signaling pathway, which is closely associated with inflammation and endoplasmic reticulum (ER) stress, was significantly downregulated by lycopene. Furthermore, we found lycopene ameliorated ER swelling and decreased the expression levels of ER stress markers (i.e., immunoglobulin heavy chain binding protein, C/EBP homologous protein, and X-box binding protein 1s). Especially, the inositol-requiring enzyme 1α involved in the ASK1 phosphorylation was inhibited by lycopene, resulting in the decline of the subsequent c-Jun N-terminal kinase (JNK) signaling cascade. ASK1 inhibitor DQOP-1 eliminated the lycopene-induced inhibition of the ASK1-JNK pathway in oleic acid and palmitic acid-induced HepG2 cells. Molecular docking further indicated hydrophobic interactions between lycopene and ASK1. Collectively, our research indicates that lycopene can alleviate ER stress and attenuate inflammation cascades and lipid accumulation by inhibiting the ASK1-JNK pathway.

Co-targeting ASK1 and THRß synergistically improves steatohepatitis and fibrosis in a MASH animal model.

PURPOSE: Metabolic dysfunction-associated steatohepatitis (MASH) is a liver disease that has gained widespread attention globally. Unfortunately, there is no approved treatment for this condition yet. However, recent research has identified Apoptosis signal-regulating kinase 1 (ASK1) and thyroid hormone receptor-ß (THR-ß) as potential targets for treating MASH. Although the individual effects of these two targets have been studied, their combinatory effect has not been well defined. Therefore, further research is needed to investigate the potential benefits of targeting both ASK1 and THR-ß for treating MASH. METHODS: We established a MASH model using the HFHFrC diet (high fat, high fructose, and cholesterol) and carbon tetrachloride (CCL4). Forty mice were evenly assigned to four groups: vehicle, GS4997 (an ASK1 inhibitor), MGL3196 (a THRß agonist), GS4997+ MGL3196 combination (combo). The drugs were administered for 8 weeks, after which the mice were sacrificed for serum biochemical tests, liver TG and TC evaluation, liver histopathological study, and gene expression validation. RESULTS: GS4997 and MGL3196, when used in combination, have been shown to have synergistic effects on various parameters. Firstly, they synergistically reduced body weight and liver body weight ratio. Secondly, this combination also synergistically lowered AST and TC. Thirdly, synergistic effects were also observed in liver TG and TC reduction. Fourthly, we further confirmed that GS4997 mildly improved liver inflammation, ballooning, and fibrosis, but exhibited incredible histopathological efficacy when combined with MGL3196. Finally, this combinatory effect can be interpreted by synergistically regulating lipid-related genes such as Dio1, Ctp1-α, and Cat, inflammation-related genes such as Il-6, Il-8, and Mcp-1, and fibrosis-related genes such as Tgf-ß, Col1α1, and Col6α3. CONCLUSION: GS4997 and MGL3196, when used in combination, have been shown to have a comprehensive effect on MASH by synergistically regulating lipid, inflammation, and fibrosis-related gene expression through co-targeting ASK1 and THRß.

Follicle stimulating hormone controls granulosa cell glutamine synthesis to regulate ovulation.

Polycystic ovary syndrome (PCOS) is the leading cause of anovulatory infertility. Inadequate understanding of the ovulation drivers hinders PCOS intervention. Herein, we report that follicle stimulating hormone (FSH) controls follicular fluid (FF) glutamine levels to determine ovulation. Murine ovulation starts from FF-exposing granulosa cell (GC) apoptosis. FF glutamine, which decreases in pre-ovulation porcine FF, elevates in PCOS patients FF. High-glutamine chow to elevate FF glutamine inhibits mouse GC apoptosis and induces hormonal, metabolic, and morphologic PCOS traits. Mechanistically, follicle-development-driving FSH promotes GC glutamine synthesis to elevate FF glutamine, which maintain follicle wall integrity by inhibiting GC apoptosis through inactivating ASK1-JNK apoptotic pathway. FSH and glutamine inhibit the rapture of cultured murine follicles. Glutamine removal or ASK1-JNK pathway activation with metformin or AT-101 reversed PCOS traits in PCOS models that are induced with either glutamine or EsR1-KO. These suggest that glutamine, FSH, and ASK1-JNK pathway are targetable to alleviate PCOS.

Participation of ASK-1 in the cardiomyocyte-protective role of mechanical ventilation in a rat model of myocardial infarction.

Non-invasive positive-pressure ventilation (NIPPV) has been demonstrated to exhibit a cardioprotective function in a rat model of myocardial infarction (MI). However, the mechanism underlying NIPPV-mediated MI progression requires further investigation. We aimed to investigate the effectiveness and corresponding mechanism of NIPPV in an acute MI-induced heart failure (HF) rat model. Thirty each of healthy wild type (WT) and apoptosis signal-regulating kinase 1 (ASK-1)-deficient rats were enrolled in this study. MI models were established via anterior descending branch ligation of the left coronary artery. The corresponding data indicated that NIPPV treatment reduced the heart infarct area, myocardial fibrosis degree, and cardiac function loss in MI rats, and ameliorated apoptosis and reactive oxygen species (ROS) levels in the heart tissue. Furthermore, the expression level of ASK-1 level, a key modulator of the ROS-induced extrinsic apoptosis pathway, was upregulated in the heart tissues of MI rats, but decreased after NIPPV treatment. Meanwhile, the downstream cleavage of caspase-3, caspase-9, and PARP, alongside p38 phosphorylation and FasL expression, exhibited a similar trend to that of ASK-1 expression. The involvement of ASK-1 in NIPPV-treated MI in ASK-1-deficient rats was examined. Although MI modeling indicated that cardiac function loss was alleviated in ASK-1-deficient rats, NIPPV treatment did not confer any clear efficiency in cardiac improvement in ASK-1-knockdown rats with MI modeling. Nonetheless, NIPPV inhibited ROS-induced extrinsic apoptosis in the heart tissues of rats with MI by regulating ASK-1 expression, and subsequently ameliorated cardiac function loss and MI-dependent pathogenic changes in the heart tissue.

LncRNA MEG3 regulates ASK1/JNK axis-mediated apoptosis and autophagy via sponging miR-23a in granulosa cells of yak tertiary follicles.

Apoptosis and autophagy in granulosa cells (GCs) are highly related to follicular development and atresia. It has also been reported that they are related to LncRNA MEG3, miR-23a and apoptosis signal-regulating kinase 1 (ASK-1). However, their relationship to follicular development and the extent to which follicle stimulating hormone (FSH) or luteinizing hormone (LH) can regulate this process remain unknown. Here, we found that ASK1 and JNK were expressed in the GCs of gonadotropin-dependent follicles, and those levels were significantly higher (p < 0.05) in yak Tertiary follicles compared to that of Secondary follicles and Graafian follicles. Then, the effect of LncRNA MEG3 / miR-23a on apoptosis and autophagy via ASK1/JNK (c-Jun N-terminal kinase) in yak GCs was studied. Overexpressing LncRNA MEG3 reduced miR-23a levels and p-967 protein expression, but enhanced ASK1 and JNK mRNA levels as well as t-ASK1, p-845, t-JNK, and p-JNK proteins levels. And Up-regulation of LncRNA MEG3 promoted apoptosis while attenuating autophagy. The targeting relationship between miR-23a and the binding sites of LncRNA MEG3 and ASK1 was also confirmed with the dual luciferase reporter assay. And, the relationship between LncRNA MEG3 and miR-23a was observed as a negative feedback regulation, and changes in LncRNA MEG3 and miR-23a levels can alter the expression of ASK1/JNK axis in yaks GCs. In addition, FSH (10 µg/mL) or LH (100 µg/mL) ability to reverse the effects of LncRNA MEG3 on miR-23a levels and ASK1/JNK axis-mediated apoptosis and autophagy was verified in yak GCs. This is significantly beneficial for decreasing abnormal follicular atresia for yaks tertiary follicles.

Thioredoxin 1 overexpression attenuated diabetes-induced endoplasmic reticulum stress in Müller cells via apoptosis signal-regulating kinase 1.

As one of the common and serious chronic complications of diabetes mellitus (DM), the related mechanism of diabetic retinopathy (DR) has not been fully understood. Müller cell reactive gliosis is one of the early pathophysiological features of DR. Therefore, exploring the manner to reduce diabetes-induced Müller cell damage is essential to delay DR. Thioredoxin 1 (Trx1), one of the ubiquitous redox enzymes, plays a vital role in redox homeostasis via protein-protein interactions, including apoptosis signal-regulating kinase 1 (ASK1). Previous studies have shown that upregulation of Trx by some drugs can attenuate endoplasmic reticulum stress (ERS) in DR, but the related mechanism was unclear. In this study, we used DM mouse and high glucose (HG)-cultured human Müller cells as models to clarify the effect of Trx1 on ERS and the underlying mechanism. The data showed that the diabetes-induced Müller cell damage was increased significantly. Moreover, the expression of ERS and reactive gliosis was also upregulated in diabetes in vivo and in vitro. However, it was reversed after Trx1 overexpression. Besides, ERS-related protein expression, reactive gliosis, and apoptosis were decreased after transfection with ASK1 small-interfering RNA in stable Trx1 overexpression Müller cells after HG treatment. Taken together, Trx1 could protect Müller cells from diabetes-induced damage, and the underlying mechanism was related to inhibited ERS via ASK1.

IFT20 Confers Paclitaxel Resistance by Triggering ß-arrestin-1 to Modulate ASK1 Signaling in Breast Cancer.

ABSTRACT: System paclitaxel-based chemotherapy is the first-line treatment regimen of defense against breast cancer, but inherent or acquired chemotherapy resistance remains a major obstacle in breast cancer therapy. Elucidating the molecular mechanism of chemoresistance is essential to improve the outcome of patients with breast cancer. Here, we demonstrate that intraflagellar transport 20 (IFT20) is positively associated with shorter relapse-free survival in patients with system paclitaxel-based chemotherapy. High-expressed IFT20 in breast cancer cells increases resistance to cell death upon paclitaxel treatment; in contrast, IFT20 knockdown enhances apoptosis in breast cancer cells in response to paclitaxel. Mechanistically, IFT20 triggers ß-arrestin-1 to bind with apoptosis signal-regulating kinase 1 (ASK1) and promotes the ubiquitination of ASK1 degradation, leading to attenuating ASK1 signaling and its downstream JNK cascades, which helps cells to escape from cell death during paclitaxel treatment. Our results reveal that IFT20 drives paclitaxel resistance through modulating ASK1 signaling and identifies IFT20 as a potential molecular biomarker for predicting the response to paclitaxel therapeutic in breast cancer. IMPLICATIONS: IFT20 drives paclitaxel resistance through modulating ASK1 signaling and IFT20 may act as a potential molecular biomarker for predicting the response to paclitaxel therapeutic in breast cancer.

ASK1-ER stress pathway-mediated fibrotic-EV release contributes to the interaction of alveolar epithelial cells and lung fibroblasts to promote mechanical ventilation-induced pulmonary fibrosis.

Recent clinical research has revealed that mechanical ventilation (MV) can initiate pulmonary fibrosis and induce mechanical ventilation-induced pulmonary fibrosis (MVPF). However, the underlying mechanism remains largely uncharacterized. Based on a mouse model of MVPF and an alveolar epithelial cell cyclic strain model, the present study explores the possible mechanism of MVPF. Single-cell RNA-sequencing and EV RNA-sequencing analysis revealed that MV promoted apoptosis signal-regulating kinase 1 (ASK1)-mediated endoplasmic reticulum (ER) stress pathway activation and extracellular vesicle (EV) release from alveolar epithelial cells. Furthermore, the ASK1-ER stress pathway was shown to mediate mechanical stretch (MS)- or MV-induced EV release and lung fibroblast activation in vivo and in vitro. These processes were suppressed by ER stress inhibitors or by silencing ASK1 with ASK1- short hairpin RNA (shRNA). In addition, MVPF was suppressed by inhibiting ASK1 and ER stress in vivo. Therefore, the present study demonstrates that ASK1-ER stress pathway-mediated fibrotic-EV release from alveolar epithelial cells contributes to fibroblast activation and the initiation of pulmonary fibrosis during MV. The inhibited release of EVs targeting the ASK1-ER stress pathway might be a promising treatment strategy for MVPF.

The role and regulation of apoptosis signal-regulated kinase 1 in liver disease.

ASK1, also known as MAP3K5, plays a vital role in the MAPK pathway. The MAPK pathway has a variety of biological functions and plays an important role in regulating cell proliferation, differentiation, and apoptosis. Studies have shown that ASK1 is involved in apoptosis, inflammation, oxidative stress, and other processes and plays an essential role in various liver diseases. Therefore, ASK1 can be a therapeutic target for treating liver disease. Here, we initially summarized the effect of ASK1 on liver disease and described the differential regulation of ASK1, including phosphorylation, ubiquitination and methylation, by which the effects of ASK1 on some liver diseases can be inhibited. Although much has been discovered about the phosphorylation of ASK1, the effects of other post-transcriptional modifications on the activity of ASK1 require further exploration. We hope that by summarizing the existing regulatory mechanism we can shed new light on the research and provide new ideas for finding ASK1-targeting drugs.

The mechanism underlying the TC-G 1008 rescue of reactive oxygen species (ROS)-induced osteoblast apoptosis by the upregulation of peroxiredoxin 1.

Osteoporosis is a common bone disease in the elderly with high morbidity and mortality. Previous studies have shown ROS-revulsive osteoblast apoptosis to be involved in the pathogenesis of osteoporosis. At present, a research hotspot exists on the topic of the ROS-targeted clinical treatment of osteoporosis. TC-G 1008, a potent and selective GPR39 agonist, exerts a conspicuous influence on a myriad of cellular processes, ranging from cellular redox status, to gene expression, to cell apoptosis. However, the underlying mechanism by which TC-G 1008 regulates osteoblast function under oxidative stress has not yet been elucidated. The purpose of this study was to investigate the effect and underlying mechanism of TC-G 1008 in the rescue of ROS-induced apoptosis by upregulating peroxiredoxin (Prx1). In this study, experimental results demonstrated that TC-G 1008 could activate GPR39, which then accelerated ROS obliteration and apoptosis inhibition in osteoblasts via Prx1 upregulation through the nuclear factor (erythroid-derived 2)-related factor 2 (Nrf2). Interestingly, being regarded as an 'information' molecule rather than an anti-oxidase molecule, Prx1 was shown to restrict the dissociation of the apoptosis signal-regulating kinase 1 (ASK1)/thioredoxin (Trx) under oxidative stress, which signified the activation of the ASK1 pathway, thereby resulting in the suppression of apoptosis. In summary, this study explores the double mechanism of TC-G 1008 in osteoblast apoptosis amelioration under oxidative stress through (i) ROS elimination and (ii) ASK1/Trx signal suppression, both of which contribute to increased Prx1 expression, and the results suggest that TC-G 1008 has great potential in the clinical treatment of osteoporosis.

Catalytic activity in vitro of the human protein kinase ASK1 mutants: Experimental and molecular simulation study.

Kinases have become an important class of targets for drug discovery since the milestone approval of imatinib in 2001. Although a great success has been achieved for targeting kinases with over 70 inhibitors approved by the FDA, it is inevitable that drug resistance would emerge during treatment. Thus, assessment of the kinase mutations is an essential issue for the development of the next generation inhibitors. Apoptosis signal-regulating kinase 1 (ASK1) is a crucial regulator of classical mitogen-activated protein kinase cascade that is being explored under several clinical trials as a promising target. Herein, we investigate the catalytic activity in vitro of ASK1 by constructing two mutants: M754T and H729L, from gatekeeper and αC-helix, respectively. Compared to wild type, the mutation of M754T and H729L results in a roughly 3-fold and 2-fold decrease in binding affinity experimentally. In addition, their binding modes with substrate are theoretically predicted and compared by molecular dynamics. Trajectory analyses of simulations indicate that the decrease of binding affinity should be attributed to the loss of H-bond interaction with gatekeeper methionine. Unexpectedly, the conformation of αC-helix in H729L mutant did not alter significantly during the simulations, although the putatively important H-bond with H729 is lost. These simulations showed the regulatory role of H729 in αC-helix is maintained by leucine residue through the interaction with non-polar residues around H729 site.

Phosphoproteomics identifies pathways underlying the role of receptor-interaction protein kinase 3 in alcohol-associated liver disease and uncovers apoptosis signal-regulating kinase 1 as a target.

Receptor-interaction protein kinase 3 (RIP3), a critical determinant of the necroptotic pathway of programmed cell death, contributes to injury in murine models of alcohol-associated liver disease (ALD); however, the underlying mechanisms are unknown. We investigated the effect of chronic ethanol feeding on the hepatic phosphoproteome in C57BL/6 and RIP3-deficient (Rip3-/- ) mice, focusing on death receptor (DR) signaling pathways. C57BL/6 and Rip3-/- mice were fed an ethanol-containing liquid diet or pair-fed control diet. A label-free mass spectrometry-based approach identified differentially phosphorylated proteins that were mapped to pathways affected by ethanol and Rip3 genotype. Identified targets were validated in both the murine model of ALD and in liver tissue from patients with alcohol-associated hepatitis (AH) and healthy controls. Chronic ethanol dysregulated hepatic tumor necrosis factor-induced DR signaling pathways. Of particular importance, chronic ethanol feeding to C57BL/6 mice decreased the phosphorylation of apoptosis signal-regulating kinase 1 (ASK1) at serine (S)1036/S1040 (S1029/S1033 human), sites linked with the inhibition of ASK1 death-promoting activity. This decrease in phosphorylation of inhibitory sites was muted in Rip3-/- mice. Decreased phosphorylation at S1033 was also lower in liver of patients with severe AH compared to healthy controls, and phosphorylation at the ASK1 activation site (threonine [Thr]-838) was increased in patients with AH. The net impact of these changes in phosphorylation of ASK1 was associated with increased phosphorylation of p38, a downstream target of ASK1, in patients with AH and C57BL/6 but not Rip3-/- mice. Similarly, chronic ethanol feeding affected the c-Jun N-terminal kinase pathway in C57BL/6 but not Rip3-/- mice. Taken together, our data indicate that changes in inhibitory phosphorylation of ASK1 are an important target in ALD and suggest the involvement of noncanonical functions of Rip3 in ALD.

ASK1 signaling regulates phase-specific glial interactions during neuroinflammation.

Neuroinflammation is well known to be associated with neurodegenerative diseases. Apoptosis signal-regulating kinase 1 (ASK1) is a mitogen-activated protein kinase kinase kinase that has been implicated in neuroinflammation, but its precise cellular and molecular mechanisms remain unknown. In this study, we generated conditional knockout (CKO) mice that lack ASK1 in T cells, dendritic cells, microglia/macrophages, microglia, or astrocytes, to assess the roles of ASK1 during experimental autoimmune encephalomyelitis (EAE). We found that neuroinflammation was reduced in both the early and later stages of EAE in microglia/macrophage-specific ASK1 knockout mice, whereas only the later-stage neuroinflammation was ameliorated in astrocyte-specific ASK1 knockout mice. ASK1 deficiency in T cells and dendritic cells had no significant effects on EAE severity. Further, we found that ASK1 in microglia/macrophages induces a proinflammatory environment, which subsequently activates astrocytes to exacerbate neuroinflammation. Microglia-specific ASK1 deletion was achieved using a CX3CR1CreER system, and we found that ASK1 signaling in microglia played a major role in generating and maintaining disease. Activated astrocytes produce key inflammatory mediators, including CCL2, that further activated and recruited microglia/macrophages, in an astrocytic ASK1-dependent manner. Astrocyte-specific analysis revealed CCL2 expression was higher in the later stage compared with the early stage, suggesting a greater proinflammatory role of astrocytes in the later stage. Our findings demonstrate cell-type-specific roles of ASK1 and suggest phase-specific ASK1-dependent glial cell interactions in EAE pathophysiology. We propose glial ASK1 as a promising therapeutic target for reducing neuroinflammation.

Clinical investigation of lipopolysaccharide in the persistence of metabolic syndrome (MS) through the activation of GRP78-IRE1α-ASK1 signaling pathway.

OBJECTIVE: Endoplasmic reticulum stress (ERS) might play a pivotal role in the persistence of metabolic syndrome (MS). Lipopolysaccharide (LPS) derived from various gram-negative bacteria could result in the ERS. Therefore, we aimed to investigate the association between LPS and ERS in MS. METHOD: We enrolled 86 patients with MS and 42 healthy people aged 35-65 years. Body weight, waist circumference, blood pressure were measured. LPS, LBP and inflammation factors, fasting plasma glucose (FPG), insulin, total cholesterol (TC), triglyceride, high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), free fatty acid (FFA) were analyzed in blood plasma of patient's cohort. Body mass index (BMI) and HOMA-IR were calculated. The mRNA and protein expression of ERS GRP78, IRE1α, ASK1 and IKKß, JNK1 were measured in blood plasma of patient's cohort by RT-PCR and Elisa. MS was defined by the updated National Cholesterol Education Program Adult Treatment Panel III criterion for Asian Americans. RESULTS: BMI, waist circumference, blood pressure, FPG, insulin, HOMA-IR, TC, triglyceride, HDL-C, LDL-C, FFA and LPS, LBP, TNF-α, CRP, IL-1, IL-6, MCP-1 were significantly higher in patients with MS than healthy people (P < 0.001). The correlation analysis suggested that LPS were associated with TNF-α, IL-1, IL-6, MCP-1, LBP, FFA, HOMA-IR potently (P < 0.05). The marker gene and protein expressions of ERS (GRP78, IRE1α, ASK1, IKKß and JNK) were significantly overexpressed in patients with MS and were positive correlation with LPS (P < 0.05). CONCLUSION: LPS may play an important role in mediating chronic low-grade inflammation by activating the ERS GRP78-IRE1α-ASK1 signaling pathway, contributing to the persistence of MS.

DUSP9 alleviates hepatic ischemia/reperfusion injury by restraining both mitogen-activated protein kinase and IKK in an apoptosis signal-regulating kinase 1-dependent manner.

Hepatic ischemia/reperfusion (I/R) injury occurs frequently in various liver operations and diseases, but its effective treatment remains inadequate because the key switch that leads to hepatic explosive inflammation has not been well disclosed. Dual specificity phosphatase 9 (DUSP9) is widely involved in the innate immune response of solid organs and is sometimes regulated by ubiquitin. In the present study, we find that DUSP9 is reduced in mouse hepatic I/R injury. DUSP9 enrichment attenuates hepatic inflammation both in vivo and in vitro as revealed by western blot analysis and qRT-PCR. In contrast, DUSP9 depletion leads to more severe I/R injury. Mechanistically, DUSP9 inhibits the phosphorylation of apoptosis signal-regulating kinase 1 (ASK1) by directly binding to ASK1, thereby decreasing tumor necrosis factor receptor-associated factor 6 (TRAF6), K63 ubiquitin and the phosphorylation of p38/JNK1 instead of ERK1. The present study documents a novel role of DUSP9 in hepatic I/R injury and implies the potential of targeting the DUSP9/ASK1 axis towards mitogen-activated protein kinase and TRAF6/inhibitor of κB kinase pathways.

Structural Insights Support Targeting ASK1 Kinase for Therapeutic Interventions.

Apoptosis signal-regulating kinase (ASK) 1, a member of the mitogen-activated protein kinase kinase kinase (MAP3K) family, modulates diverse responses to oxidative and endoplasmic reticulum (ER) stress and calcium influx. As a crucial cellular stress sensor, ASK1 activates c-Jun N-terminal kinases (JNKs) and p38 MAPKs. Their excessive and sustained activation leads to cell death, inflammation and fibrosis in various tissues and is implicated in the development of many neurological disorders, such as Alzheimer's, Parkinson's and Huntington disease and amyotrophic lateral sclerosis, in addition to cardiovascular diseases, diabetes and cancer. However, currently available inhibitors of JNK and p38 kinases either lack efficacy or have undesirable side effects. Therefore, targeted inhibition of their upstream activator, ASK1, stands out as a promising therapeutic strategy for treating such severe pathological conditions. This review summarizes recent structural findings on ASK1 regulation and its role in various diseases, highlighting prospects for ASK1 inhibition in the treatment of these pathologies.