Mitogen-activated Protein Kinase Activation Research Articles

Abstract 310: Cadherin-dependent modulation of chemosensitivity in oral tumor progression

Abstract The progression of healthy oral epithelia to an oral carcinoma often involves aberrant expression of a group of calcium-dependent transmembrane proteins called cadherins. Histological studies of human tumors have demonstrated increased expression of the epithelial-resident placental (P-cadherin) and ectopic expression of the mesenchymal neuronal (N-cadherin) cadherin in oral dysplasia. We hypothesized that these changes in cadherin expression during early oral tumor development could facilitate increases in survival signaling. We genetically modified dysplastic oral keratinocytes to overexpress P-cadherin or suppress endogenous expression of N-cadherin. P-cadherin overexpression and N-cadherin suppression independently elicited a 3-6-fold decrease in apoptosis levels in response to docetaxel treatment compared to similarly treated controls. We found that in untreated dysplastic cells, P- and N-cadherin expression had positive and negative correlations, respectively, with the activation of the survival-associated enzymes focal adhesion kinase (FAK), mitogen-activated protein kinase (MAPK), and AKT kinase. The total levels of nuclear factor kappa B (NFkb) were positively correlated with P-cadherin overexpression and reciprocally correlated with levels of N-cadherin. In docetaxel-treated dysplastic cells, we observed the reverse effect compared to untreated cells: the increased level of N-cadherin was positively correlated with FAK activity whereas FAK activity was suppressed by P-cadherin. P-cadherin expression in docetaxel-treated cells also increased activation of both MAPK and AKT, whereas alteration of N-cadherin levels had no effect. Because N-cadherin levels are known to increase in late-stage oral tumors, we extended these signaling studies to oral squamous carcinoma cells (OSCCs) expressing low or high levels of N-cadherin. In contrast to its suppression of survival pathways in docetaxel-treated dysplastic cells, in docetaxel-treated OSCCs, N-cadherin expression strongly enhanced phosphorylation of MAPK and AKT, and increased expression of NFkb. N-cadherin overexpression during this treatment also increased expression of the antiapoptotic proteins Mcl-1 and suppressed phosphorylation of the apoptotic regulator signal transducer and activator of transcription 3 (pSTAT3). Increase cadherin expression in all untreated cell lines increased expression of an inducer of epithelial to mesenchymal transition, the transmembrane protein mucin-1 (MUC1). N-cadherin overexpression also increased motility in both cell lines. Taken together, our data demonstrate antiapoptotic signaling directed by increased levels of P-cadherin in oral dysplasia and N-cadherin in OSCC, whereas increased levels of N-cadherin in dysplastic cells directed cellular signaling that were associated with a proapoptotic phenotype. Citation Format: Aaron Mody, Cassandra Decker, Kathryn R. Lawson. Cadherin-dependent modulation of chemosensitivity in oral tumor progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 310.

Abstract 620: Screening of small-molecule MAPK pathway inhibitors on a panel of 130 human cancer cell lines identifies determinants of response in RAS-mutant subgroups

Abstract Oncogenic mutations in members of the RAS family, HRAS, NRAS, and KRAS, are frequently identified in various cancers and often lead to increased signaling of the mitogen-activated protein kinase (MAPK) pathway. KRAS is the most frequently mutated RAS isoform, with a mutation incidence of >10% across all cancers, and up to 70% and 20% in pancreatic and non-small cell lung cancer (NSCLC), respectively. RAS has long been considered to be undruggable, and direct inhibition of RAS with small molecule inhibitors has only recently been achieved, with the approval of the KRAS G12C-mutant selective inhibitors sotorasib and adagrasib for treatment of NSCLC. Indirect targeting of RAS-mutated cancers by inhibitors of downstream components such as MEK and ERK has shown variable responses. Novel insights into MAPK signaling have renewed interest into targeting the MAPK pathway in RAS-mutant cancer, with pan-RAF dimer inhibitors and dual RAF/MEK inhibitors reaching clinical trials. To improve the chances of success, it is important to determine which patient populations are most likely to respond to these inhibitors. To gain more insight into the cellular targeting of MAPK pathway inhibitors, eighteen inhibitors of the MAPK components KRAS, RAF, MEK, and ERK were profiled on a panel of 130 cell lines in cell viability assays (the Oncolines® panel). The cell lines represented a diverse range of tumor tissues and had different genomic backgrounds. Many of the cell lines had mutations in KRAS, NRAS, or BRAF. Drug responses were determined by exposing the cell lines to nine-point duplicate dose ranges of the inhibitors. Using bioinformatics, cell line responses to the inhibitors were related to genomic and transcriptomic features, to identify determinants of drug response in both tissue-agnostic and tissue-specific contexts. The results of our analyses revealed variable responses of KRAS-mutant cell lines to the inhibitors, reflecting clinical responses. Tissue-focused analyses showed that the different responses could be traced back to the different KRAS amino acid substitutions. For instance, in pancreatic cancer cell lines, the KRAS Q61H mutation predicted increased sensitivity to MAPK pathway inhibitors compared to other KRAS amino acid substitutions. Additionally, in tissue groups with a more heterogenous mutation profile, co-mutations explained the decreased effectivity of MAPK pathway inhibitors in KRAS-mutant cell lines, such as PIK3CA mutations in colorectal cancer cell lines. Lastly, a gene expression-based signature of MAPK activity predicted response to MAPK pathway inhibitors, independent of mutation status. Our findings have uncovered determinants of response to MAPK pathway inhibitors in RAS-mutant cell lines. These determinants can serve as markers to select patients who are most likely to benefit from MAPK inhibitors. Citation Format: Jeffrey J. Kooijman, Awan Al Koerdi, Daphne J. Kluitmans, Esmee van den Bossche, Jelle Dylus, Jeroen A. de Roos, Janneke J. Melis, Guido J. Zaman. Screening of small-molecule MAPK pathway inhibitors on a panel of 130 human cancer cell lines identifies determinants of response in RAS-mutant subgroups [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 620.

Histamine H1 Receptor-Mediated JNK Phosphorylation Is Regulated by Gq Protein-Dependent but Arrestin-Independent Pathways.

Arrestins are known to be involved not only in the desensitization and internalization of G protein-coupled receptors but also in the G protein-independent activation of mitogen-activated protein (MAP) kinases, such as extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK), to regulate cell proliferation and inflammation. Our previous study revealed that the histamine H1 receptor-mediated activation of ERK is dually regulated by Gq proteins and arrestins. In this study, we investigated the roles of Gq proteins and arrestins in the H1 receptor-mediated activation of JNK in Chinese hamster ovary (CHO) cells expressing wild-type (WT) human H1 receptors, the Gq protein-biased mutant S487TR, and the arrestin-biased mutant S487A. In these mutants, the Ser487 residue in the C-terminus region of the WT was truncated (S487TR) or mutated to alanine (S487A). Histamine significantly stimulated JNK phosphorylation in CHO cells expressing WT and S487TR but not S487A. Histamine-induced JNK phosphorylation in CHO cells expressing WT and S487TR was suppressed by inhibitors against H1 receptors (ketotifen and diphenhydramine), Gq proteins (YM-254890), and protein kinase C (PKC) (GF109203X) as well as an intracellular Ca2+ chelator (BAPTA-AM) but not by inhibitors against G protein-coupled receptor kinases (GRK2/3) (cmpd101), β-arrestin2 (β-arrestin2 siRNA), and clathrin (hypertonic sucrose). These results suggest that the H1 receptor-mediated phosphorylation of JNK is regulated by Gq-protein/Ca2+/PKC-dependent but GRK/arrestin/clathrin-independent pathways.

Immunosuppressive effects of the mycotoxin patulin in macrophages.

Patulin (PAT) is a fungi-derived secondary metabolite produced by numerous fungal species, especially within Aspergillus, Byssochlamys, and Penicillium genera, amongst which P. expansum is the foremost producer. Similar to other fungi-derived metabolites, PAT has been shown to have diverse biological features. Initially, PAT was used as an effective antimicrobial agent against Gram-negative and Gram-positive bacteria. Then, PAT has been shown to possess immunosuppressive properties encompassing humoral and cellular immune response, immune cell function and activation, phagocytosis, nitric oxide and reactive oxygen species production, cytokine release, and nuclear factor-κB and mitogen-activated protein kinases activation. Macrophages are a heterogeneous population of immune cells widely distributed throughout organs and connective tissue. The chief function of macrophages is to engulf and destroy foreign bodies through phagocytosis; this ability was fundamental to his discovery. However, macrophages play other well-established roles in immunity. Thus, considering the central role of macrophages in the immune response, we review the immunosuppressive effects of PAT in macrophages and provide the possible mechanisms of action.

A pair of soybean malectin-like domain-containing receptor-like kinases jointly regulate pattern-triggered immunity by forming hetero-oligomers

Plant cells perceive pathogen invasion by recognizing microbial patterns using plasma-membrane-localized pattern-recognition receptors (PRRs) to initiate pattern-triggered immunity (PTI), which confers a moderate immunity to most microbes. For instance, the PRR FLS2 (FLAGELLIN SENSING 2) recognizes bacterial flagellin in the presence of the co-receptor BAK1 and activates a series of PTI responses, such as reactive oxygen species (ROS) burst and mitogen-activated protein kinase (MAPK) activation. We previously showed that soybean malectin/malectin-like domain-containing receptor-like kinase (MRLK) protein GmLMM1 negatively regulates PTI by suppressing FLS2-BAK1 interaction. GmLMM1 replicates in tandem with five other GmMRLKs on chromosome 13. Here, we show that GmMRLK32, the closest homolog to GmLMM1 among the tandem genes of GmLMM1, negatively regulates PTI and disease resistance against bacterial and oomycete pathogens. The Gmmrlk32 mutant showed enhanced flg22-induced ROS burst and MAPK activation. We revealed that GmMRLK32 interacts with GmFLS2 and GmBAK1, and suppresses flg22-induced GmFLS2-GmBAK1 dimerization in a manner similar to that of GmLMM1. We further showed that GmMRLK32 specifically interacts with GmLMM1 to regulate PTI. In Nicotiana benthamiana plants, co-expression of GmMRLK32 and GmLMM1 showed a stronger PTI inhibitory effect on PTI activation than expression of GmMRLK32 or GmLMM1 alone. We uncovered a novel mechanism by which GmMRLK32 and GmLMM1 coordinately regulate PTI by forming hetero-oligomer.

MAPK Cascades in Plant Microbiota Structure and Functioning.

Mitogen-activated protein kinase (MAPK) cascades are highly conserved signaling modules that coordinate diverse biological processes such as plant innate immunity and development. Recently, MAPK cascades have emerged as pivotal regulators of the plant holobiont, influencing the assembly of normal plant microbiota, essential for maintaining optimal plant growth and health. In this review, we provide an overview of current knowledge on MAPK cascades, from upstream perception of microbial stimuli to downstream host responses. Synthesizing recent findings, we explore the intricate connections between MAPK signaling and the assembly and functioning of plant microbiota. Additionally, the role of MAPK activation in orchestrating dynamic changes in root exudation to shape microbiota composition is discussed. Finally, our review concludes by emphasizing the necessity for more sophisticated techniques to accurately decipher the role of MAPK signaling in establishing the plant holobiont relationship.

Methyl Jasmonate-induced Increase in Intracellular Magnesium Promotes Apoptosis in Breast Cancer Cells.

Methyl jasmonate (MeJa) is a botanical stress hormone that serves as a defense mechanism to inhibit growth in stressed plants. It is well known that MeJa exhibits an anticancer effect by reducing intracellular ATP, activating reactive oxygen species (ROS) production, and promoting mitogen-activated protein kinase (MAPK) activity. Presently, no report has been published on MeJa-induced changes in intracellular Mg2+ concentration ([Mg2+]i), and TRPM7 as an Mg2+ transporter in cancer cells. Therefore, this study aimed to investigate the Mg2+ homeostatic changes and apoptotic effects following MeJa treatment using the MCF-7 human breast cancer cell line. The MTT assay was used to assess the cell viability and half-inhibitory concentration, microscopic two-photon excitation wavelength spectrophotometry was used to measure the [Mg2+]i, a luminescent assay determined intracellular ATP levels, western blot assay measured TRPM7 levels, antioxidant capacities, endoplasmic reticulum (ER) stress, and MAPK signaling pathways, while the fluorescence assay evaluated ROS concentrations and the cell apoptotic index. This study provides evidence that MeJa has an antiapoptotic effect on MCF-7 cells. The increase in [Mg2+]i led to decreased TRPM7 expression, which is related to elevated ROS production, in addition to elevated ER stress and MAPK signaling pathway activity and decreased ATP content. The increase in [Mg2+]i leads to decreased TRPM7 expression and may be the epicenter of MeJa-induced apoptotic cell death in MCF-7 cells.

HRAS-Mutant Cardiomyocyte Model of Multifocal Atrial Tachycardia.

Germline HRAS gain-of-function pathogenic variants cause Costello syndrome (CS). During early childhood, 50% of patients develop multifocal atrial tachycardia, a treatment-resistant tachyarrhythmia of unknown pathogenesis. This study investigated how overactive HRAS activity triggers arrhythmogenesis in atrial-like cardiomyocytes (ACMs) derived from human-induced pluripotent stem cells bearing CS-associated HRAS variants. HRAS Gly12 mutations were introduced into a human-induced pluripotent stem cells-ACM reporter line. Human-induced pluripotent stem cells were generated from patients with CS exhibiting tachyarrhythmia. Calcium transients and action potentials were assessed in induced pluripotent stem cell-derived ACMs. Automated patch clamping assessed funny currents. HCN inhibitors targeted pacemaker-like activity in mutant ACMs. Transcriptomic data were analyzed via differential gene expression and gene ontology. Immunoblotting evaluated protein expression associated with calcium handling and pacemaker-nodal expression. ACMs harboring HRAS variants displayed higher beating rates compared with healthy controls. The hyperpolarization activated cyclic nucleotide gated potassium channel inhibitor ivabradine and the Nav1.5 blocker flecainide significantly decreased beating rates in mutant ACMs, whereas voltage-gated calcium channel 1.2 blocker verapamil attenuated their irregularity. Electrophysiological assessment revealed an increased number of pacemaker-like cells with elevated funny current densities among mutant ACMs. Mutant ACMs demonstrated elevated gene expression (ie, ISL1, TBX3, TBX18) related to intracellular calcium homeostasis, heart rate, RAS signaling, and induction of pacemaker-nodal-like transcriptional programming. Immunoblotting confirmed increased protein levels for genes of interest and suppressed MAPK (mitogen-activated protein kinase) activity in mutant ACMs. CS-associated gain-of-function HRASG12 mutations in induced pluripotent stem cells-derived ACMs trigger transcriptional changes associated with enhanced automaticity and arrhythmic activity consistent with multifocal atrial tachycardia. This is the first human-induced pluripotent stem cell model establishing the mechanistic basis for multifocal atrial tachycardia in CS.

PKC-independent PI3K signalling diminishes PKC inhibitor sensitivity in uveal melanoma

Protein kinase C (PKC) is activated downstream of gain-of-function GNAQ or GNA11 (GNAQ/GNA11) mutations in over 90% of uveal melanoma (UM). Phase I clinical trials of PKC inhibitors have shown modest response rates with no survival benefit in metastatic UM. Although PKC inhibitors actively suppress mitogen-activated protein kinase (MAPK) signalling in UM, the effect on other UM signalling cascades is not well understood. We examined the transcriptome of UM biopsies collected pre- and post-PKC inhibitor therapy and confirmed that MAPK, but not PI3K/AKT signalling, was inhibited early during treatment with the second-generation PKC inhibitor IDE196. Similarly, in GNAQ/GNA11-mutant UM cell models, PKC inhibitor monotherapy effectively suppressed MAPK activity, but PI3K/AKT signalling remained active, and thus, concurrent inhibition of PKC and PI3K/AKT signalling was required to synergistically induce cell death in a panel of GNAQ/GNA11-mutant UM cell lines. We also show that re-activation of MAPK signalling has a dominant role in regulating PKC inhibitor responses in UM and that PI3K/AKT signalling diminishes UM cell sensitivity to PKC inhibitor monotherapy. Thus, combination therapies targeting PKC and PKC-independent signalling nodes, including PI3K/AKT activity, are required to improve responses in patients with metastatic UM.

HER2 phosphorylation induced by TGF-β promotes mammary morphogenesis and breast cancer progression.

Transforming growth factor β (TGF-β) and HER2 signaling collaborate to promote breast cancer progression. However, their molecular interplay is largely unclear. TGF-β can activate mitogen-activated protein kinase (MAPK) and AKT, but the underlying mechanism is not fully understood. In this study, we report that TGF-β enhances HER2 activation, leading to the activation of MAPK and AKT. This process depends on the TGF-β type I receptor TβRI kinase activity. TβRI phosphorylates HER2 at Ser779, promoting Y1248 phosphorylation and HER2 activation. Mice with HER2 S779A mutation display impaired mammary morphogenesis, reduced ductal elongation, and branching. Furthermore, wild-type HER2, but not S779A mutant, promotes TGF-β-induced epithelial-mesenchymal transition, cell migration, and lung metastasis of breast cells. Increased HER2 S779 phosphorylation is observed in human breast cancers and positively correlated with the activation of HER2, MAPK, and AKT. Our findings demonstrate the crucial role of TGF-β-induced S779 phosphorylation in HER2 activation, mammary gland development, and the pro-oncogenic function of TGF-β in breast cancer progression.

Farrerol Alleviates Cerebral Ischemia-Reperfusion Injury by Promoting Neuronal Survival and Reducing Neuroinflammation.

Ischemia-reperfusion (I/R) injury is a key influencing factor in the outcome of stroke. Inflammatory response, oxidative stress, and neuronal apoptosis are among the main factors that affect the progression of I/R injury. Farrerol (FAR) is a natural compound that can effectively inhibit the inflammatory response and oxidative stress. However, the role of FAR in cerebral I/R injury remains unknown. In this study, we found that FAR reduced brain injury and neuronal viability after cerebral I/R injury. Meanwhile, administration of FAR also reduced the inflammatory response of microglia after brain injury. Mechanistically, FAR treatment directly reduced neuronal death after oxygen glucose deprivation/re-oxygenation (OGD/R) through enhancing cAMP-response element binding protein (CREB) activation to increase the expression of downstream neurotrophic factors and anti-apoptotic genes. Moreover, FAR decreased the activation of nuclear factor kappa-B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways, inhibited microglia activation, and reduced the production of inflammatory cytokines in microglia after OGD/R treatment or LPS stimulation. The compromised inflammatory response by FAR directly promoted the survival of neurons after OGD/R. In conclusion, FAR exerted a protective effect on cerebral I/R injury by directly decreasing neuronal death through upregulating CREB expression and attenuating neuroinflammation. Therefore, FAR could be a potentially effective drug for the treatment of cerebral I/R injury.

Cannabidiol activates MAPK pathway to induce apoptosis, paraptosis, and autophagy in colorectal cancer cells.

Mitogen-activated protein kinase (MAPK) activation by natural compounds is known to be involved in the induction of apoptosis, paraptosis, and autophagy. Cannabidiol (CBD), a bioactive compound found in Cannabis sativa, is endowed with many pharmacological activities. We investigated the cytotoxic effect of CBD in a panel of colorectal cancer (CRC) cells (HT-29, SW480, HCT-116, and HCT-15). CBD induced significant cytotoxicity as evidenced by the results of MTT assay, live-dead assay, and flow cytometric analysis. Since CBD displayed cytotoxicity against CRC cells, we examined the effect of CBD on apoptosis, paraptosis, and autophagy. CBD decreased the expression of antiapoptotic proteins and increased the Annexin-V-positive as well as TUNEL-positive cells suggesting that CBD induces apoptosis. CBD increased the expression of ATF4 (activating transcription factor 4) and CHOP (CCAAT/enhancer-binding protein homologous protein), elevated endoplasmic reticulum stress, and enhanced reactive oxygen species levels indicating that CBD also promotes paraptosis. CBD also induced the expression of Atg7, phospho-Beclin-1, and LC3 suggesting that CBD also accelerates autophagy. Since, the MAPKpathway is a common cascade that is involved in the regulation of apoptosis, paraptosis, and autophagy, we investigated the effect of CBD on the activation of JNK, p38, and ERK pathways. CBD activated all the forms of MAPK proteins and pharmacological inhibition of these proteins reverted the observed effects. Our findings implied that CBD could induce CRC cell death by activating apoptosis, paraptosis, and autophagy through the activation of the MAPK pathway.

Microarray Gene Expression Analysis of Lesional Skin in Canine Pemphigus Foliaceus.

Canine pemphigus foliaceus (PF) is considered the most common autoimmune skin disease in dogs; the mechanism of PF disease development is currently poorly understood. Therefore, this study aimed to characterize the molecular mechanisms and altered biological pathways in the skin lesions of canine PF patients. Using an RNA microarray on formalin-fixed, paraffin-embedded samples, we analyzed the transcriptome of canine PF lesional skin (n = 7) compared to healthy skin (n = 5). Of the 800 genes analyzed, 420 differentially expressed genes (DEGs) (p < 0.05) were found. Of those, 338 genes were significantly upregulated, including pro-inflammatory and Th17-related genes. Cell type profiling found enhancement of several cell types, such as neutrophils, T-cells, and macrophages, in PF skin compared to healthy skin. Enrichment analyses of the upregulated DEGs resulted in 78 statistically significant process networks (FDR < 0.05), including the Janus kinase signal transducer and activator of transcription (JAK-STAT) and mitogen-activated protein kinase (MAPK) signaling. In conclusion, canine PF lesional immune signature resembles previously published changes in human pemphigus skin lesions. Further studies with canine PF lesional skin using next-generation sequencing (e.g., RNA sequencing, spatial transcriptomics, etc.) and the development of canine keratinocyte/skin explant PF models are needed to elucidate the pathogenesis of this debilitating disease.

Identification of myeloid-derived growth factor as a mechanically-induced, growth-promoting angiocrine signal for human hepatocytes

Recently, we have shown that after partial hepatectomy (PHx), an increased hepatic blood flow initiates liver growth in mice by vasodilation and mechanically-triggered release of angiocrine signals. Here, we use mass spectrometry to identify a mechanically-induced angiocrine signal in human hepatic endothelial cells, that is, myeloid-derived growth factor (MYDGF). We show that it induces proliferation and promotes survival of primary human hepatocytes derived from different donors in two-dimensional cell culture, via activation of mitogen-activated protein kinase (MAPK) and signal transducer and activator of transcription 3 (STAT3). MYDGF also enhances proliferation of human hepatocytes in three-dimensional organoids. In vivo, genetic deletion of MYDGF decreases hepatocyte proliferation in the regenerating mouse liver after PHx; conversely, adeno-associated viral delivery of MYDGF increases hepatocyte proliferation and MAPK signaling after PHx. We conclude that MYDGF represents a mechanically-induced angiocrine signal and that it triggers growth of, and provides protection to, primary mouse and human hepatocytes.

Peiminine Exerts Its Anti-Acne Effects by Regulating the NF-κB Pathway.

Peiminine is the main natural alkaloid compound extracted from the Chinese herb Fritillaria. Although peiminine is known for its antioxidant and anti-inflammatory effects in conditions such as mastitis and arthritis, its impact on inflammation induced by Cutibacterisum acnes (C. acnes) has not been explored. The aim of this study was to investigate the effect of peiminine on C. acnes-induced inflammatory responses in the skin and to identify the underlying mechanism involved. We discovered that peiminine inhibits the C. acnes-induced expression of inflammatory mediators such as pro-interleukin-1β (pro-IL-1β), cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in mouse bone marrow-derived macrophages (BMDMs). Peiminine suppressed the activation of nuclear factor-kappa B (NF-κB) without affecting the activation of mitogen-activated protein kinase (MAPK) pathways such as JNK, ERK, and p38 MAPK. In addition, we found that peiminine suppressed inflammatory cytokine expression and ameliorated histological symptoms in C. acnes-induced mouse skin. Our study is the first to provide evidence that peiminine has an inhibitory effect on acne, and it points toward the potential of incorporating peiminine into cosmetic and pharmaceutical formulations for acne treatment.

JNK inhibition enhances cell-cell adhesion impaired by desmoglein3 gene disruption in keratinocytes.

c-Jun NH2-terminal protein kinase (JNK) and p38 are stress-activated mitogen-activated protein kinases (MAPK) that are phosphorylated by various stimuli. It has been reported that the loss of desmoglein (DSG) 3, a desmosomal transmembrane core molecule, in keratinocytes impairs cell-cell adhesion accompanied by p38 MAPK activation. To understand the biological role of DSG3 in desmosomes and its relationship with stress-activated MAPKs, we established DSG3 knockout keratinocytes (KO cells). Wild-type cells showed a linear localization of DSG1 to cell-cell contacts, whereas KO cells showed a remarkable reduction despite the increased protein levels of DSG1. Cell-cell adhesion in KO cells was impaired over time, as demonstrated by dispase-based dissociation assays. The linear localization of DSG1 to cell-cell contacts and the strength of cell-cell adhesion were promoted by the pharmacological inhibition of JNK. Conversely, pharmacological activation of JNK, but not p38 MAPK, in wild-type cells reduced the linear localization of DSG1 in cell-cell contacts. Our data indicate that DSG1 and DSG2 in KO cells cannot compensate for the attenuation of cell-cell adhesion strength caused by DSG3 deficiency and that JNK inhibition restores the strength of cell-cell adhesion by increasing the linear localization of DSG1 in cell-cell contacts in KO cells. Inhibition of JNK signaling may improve cell-cell adhesion in diseases in which DSG3 expression is impaired.

Methanol Extract of Petasites japonicus Promotes Apoptosis via the MAPK and ROS-dependent Signaling Pathways

Background: Petasites japonicus (PJ), also known as Butterbur, has a rich history as a traditional healing remedy across numerous countries. Objectives: This study was designed to evaluate the potential anti-cancer properties of the methanol extract derived from PJ (PJE). Materials and Methods: Cell viability was measured with 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide. Cell cycle analysis, caspase activity assays, western blotting, and reactive oxygen species (ROS) assays were also used to investigate the anticancer effects of PJE on cancer cells. Results: It was shown that PJE inhibited the cell viability of the colon carcinoma cell line Caco-2 (half-maximal inhibitory concentration [IC50]: 268.4 µg/mL), of the hepatocellular carcinoma cell line Hep3B (IC50: 420.2 µg/mL), and of the bladder carcinoma cell line 5637 (IC50: 99.43 µg/mL). Analysis of DNA content indicated an increase in the sub-G1 population of 5637 cells as a result of PJE treatment. Furthermore, PJE caused a reduction in mitochondrial membrane potential and the ratio of Bcl-2 to Bax. Moreover, PJE enhanced the levels of various components involved in the proapoptotic cascade, such as caspase-3, caspase-9, and poly-adenosine diphosphate-ribose polymerase. Moreover, it was observed that PJE modulated mitogen-activated protein kinases (MAPKs) activation and induced an elevation in intracellular production of ROS. Conclusion: These combined results strongly suggest that PJE possesses significant proapoptotic properties as an herbal medicine, acting through ROS-dependent MAPK signaling pathways in bladder cancer cells.

Palmitate induces integrated stress response and lipoapoptosis in trophoblasts

Maternal obesity increases the risk of childhood obesity and programs the offspring to develop metabolic syndrome later in their life. Palmitate is the predominant saturated free fatty acid (FFA) that is transported across the placenta to the fetus. We have recently shown that saturated FFA in the maternal circulation as a result of increased adipose tissue lipolysis in third trimester of pregnancy induces trophoblast lipoapoptosis. Here, we hypothesized that palmitate induces integrated stress response by activating mitogen-activated protein kinases (MAPKs), endoplasmic reticulum (ER) stress and granular stress and lipoapoptosis in trophoblasts. Choriocarcinoma-derived third-trimester placental trophoblast-like cells (JEG-3 and JAR) referred as trophoblasts were exposed to various concentrations of palmitate (PA). Apoptosis was assessed by nuclear morphological changes and caspase 3/7 activity. Immunoblot and immunofluorescence analysis was performed to measure the activation of MAPKs, ER stress and granular stress response pathways. Trophoblasts exposed to pathophysiological concentrations of PA showed a concentration-dependent increase in trophoblast lipoapoptosis. PA induces a caspase-dependent trophoblast lipoapoptosis. Further, PA induces MAPK activation (JNK and ERK) via phosphorylation, and activation of ER stress as evidenced by an increased phosphorylation eIF2α & IRE1α. PA also induces the activation of stress granules formation. Two pro-apoptotic transcriptional mediators of PA-induced trophoblast lipoapoptosis, CHOP and FoxO3 have increased nuclear translocation. Mechanistically, PA-induced JNK is critical for trophoblast lipoapoptosis. However, PA-induced activation of ERK and stress granule formation were shown to be cell survival signals to combat subcellular stress due to PA exposure. In conclusion, PA induces the activation of integrated stress responses, among which small molecule inhibition of JNK demonstrated that activation of JNK is critical for PA-induced trophoblast lipoapoptosis and small molecule activation of stress granule formation significantly prevents PA-induced trophoblast lipoapoptosis.

Anti-Inflammatory Effects of Clematis terniflora Leaf on Lipopolysaccharide-Induced Acute Lung Injury.

For centuries, natural products are regarded as vital medicines for human survival. Clematis terniflora var. mandshurica (Rupr.) Ohwi is an ingredient of the herbal medicine, Wei Ling Xian, which has been used in Chinese medicine to alleviate pain, fever, and inflammation. In particular, C. terniflora leaves have been used to cure various inflammatory diseases, including tonsillitis, cholelithiasis, and conjunctivitis. Based on these properties, this study aimed to scientifically investigate the anti-inflammatory effect of an ethanol extract of leaves of C. terniflora (EELCT) using activated macrophages that play central roles in inflammatory response. In this study, EELCT inhibited the essential inflammatory mediators, such as nitric oxide, cyclooxygenase-2, tumor necrosis factor-α, interleukin- (IL-) 6, IL-1β, and inducible nitric oxide synthase, by suppressing the nuclear factor-κB and mitogen-activated protein kinase activation in macrophages. Acute lung injury (ALI) is a fatal respiratory disease accompanied by serious inflammation. With high mortality rate, the disease has no effective treatments. Therefore, new therapeutic agents must be developed for ALI. We expected that EELCT can be a promising therapeutic agent for ALI by reducing inflammatory responses and evaluated its action in a lipopolysaccharide- (LPS-) induced ALI model. EELCT alleviated histological changes, immune cell infiltration, inflammatory mediator production, and protein-rich pulmonary edema during ALI. Collectively, our results may explain the traditional usage of C. terniflora in inflammatory diseases and suggest the promising potential of EELCT as therapeutic candidate for ALI.

Evodiae Fructus extract suppresses inflammatory response in HaCaT cells and improves house dust mite-induced atopic dermatitis in NC/Nga mice

This study was conducted to assess the effect of Evodiae Fructus 70% ethanol extract (EFE) on the pathology of atopic dermatitis using in vitro and in vivo models. The major compounds in EFE were identified by ultra-performance liquid chromatography with tandem mass spectrometry as rutaecarpine, evodiamine, evodol, dehydroevodiamine, limonin, synephrine, evocarpine, dihydroevocarpine, and hydroxyevodiamine. EFE significantly decreased chemokine levels in tumor necrosis factor-α/interferon-γ-stimulated HaCaT cells. In house dust mite-treated NC/Nga mice, topical application of EFE significantly decreased the dermatitis score, epidermal hyperplasia and thickening, mast cell infiltration, and plasma levels of histamine and corticosterone. Thymic stromal lymphopoietin, CD4+ T cells, interleukin-4, and intercellular adhesion molecule-1 expression in the lesioned skin was reduced in the treated mice. The mechanism of EFE was elucidated using transcriptome analysis, followed by experimental validation using Western blotting in HaCaT cells. EFE down-regulated the activation of Janus kinase (JAK)-signal transducers and activators of transcription (STAT) and mitogen-activated protein kinases (MAPK) signaling pathways in HaCaT cells. EFE improves atopic dermatitis-like symptoms by suppressing inflammatory mediators, cytokines, and chemokines by regulating the JAK-STAT and MAPK signaling pathways, suggesting its use as a potential agent for the treatment of atopic dermatitis.