The primary structure of p38 gamma: a new member of p38 group of MAP kinases

Knocking out p38α+p38β+p38γ is required to abort the myogenic program in C2C12 myoblasts and to impose uncontrolled proliferation

The p38 MAPKs' family includes four isoforms, of which only p38α has been considered essential for numerous important processes including mice embryogenesis. It is also considered essential for myoblast to myotube differentiation, as exposure of myoblasts to p38α/β inhibitors or to siRNA that targets p38α suppresses the process. The functions of p38β and p38γ in myoblast differentiation are not clear. We knocked out p38α in C2C12 myoblasts, assuming that the resulting C2p38α-/- cells would not differentiate. They did, however, form mature fibers. We found elevated levels and activation of the p38 activator MKK6 in the C2p38α-/- cells, leading to activation of p38β and p38γ, which are not active in differentiating parental C2C12 cells. Thus, p38α is an inhibitor of p38β+p38γ, which perhaps replace it in promoting differentiation. To test this notion, we generated C2p38α/γ-/- and C2p38α/β-/- cells and found that in both clones, the myogenic program was induced. C2p38β/γ-/- cells also formed myotubes. These observations could be interpreted in two ways: either each p38 isoform can promote, by itself, the myogenic program, or p38 activity is not required at all for the process. Generating C2p38α/β/γ-/- cells in which the myogenic program was shut-off altogether, showed that p38 activity is critical for differentiation. Notably, C2p38α/β/γ-/- cells proliferate uncontrollably and give rise to foci, reminiscence of oncogenically transformed cells. In summary, our study shows that a crosstalk between p38 isoforms functions in C2C12 cells as a safeguard mechanism that ensures resilience of the p38 activity in promoting the myogenic program and enforcing cell cycle arrest.

Asynchronous Pattern of MAPKs' Activity during Aging of Different Tissues and of Distinct Types of Skeletal Muscle

The MAPK p38α was proposed to be a prominent promoter of skeletal muscle aging. The skeletal muscle tissue is composed of various muscle types, and it is not known if p38α is associated with aging in all of them. It is also not known if p38α is associated with aging of other tissues. JNK and ERK were also proposed to be associated with aging of several tissues. Nevertheless, the pattern of p38α, JNK, and ERK activity during aging was not documented. Here, we documented the levels of phosphorylated/active p38α, Erk1/2, and JNKs in several organs as well as the soleus, tibialis anterior, quadriceps, gastrocnemius, and EDL muscles of 1-, 3-, 6-, 13-, 18-, and 24-month-old mice. We report that in most tissues and skeletal muscles, the MAPKs' activity does not change in the course of aging. In most tissues and muscles, p38α is in fact active at younger ages. The quadriceps and the lungs are exceptions, where p38α is significantly active only in mice 13 months old or older. Curiously, levels of active JNK and ERKs are also elevated in aged lungs and quadriceps. RNA-seq analysis of the quadriceps during aging revealed downregulation of proteins related to the extra-cellular matrix (ECM) and ERK signaling. A panel of mRNAs encoding cell cycle inhibitors and senescence-associated proteins, considered to be aging markers, was not found to be elevated. It seems that the pattern of MAPKs' activation in aging, as well as expression of known 'aging' components, are tissue- and muscle type-specific, supporting a notion that the process of aging is tissue- and even cell-specific.

c-Jun N-terminal Kinase (JNK), p38, and Caspases: Promising Therapeutic Targets for the Regulation of Apoptosis in Cancer Cells by Phytochemicals

Abstract:

Carcinogenesis is a process in which uncontrolled cell proliferation forms preneoplastic nodules which precede the appearance of cancer. In normal cells, growth and proliferation are regulated by certain growth and hormonal stimulation, while mutational alterations in these signals render the cells independent and resistant to these signals. In cancer, the critical homeostatic balance between cell growth and apoptosis is lost and the cells continue to survive beyond their normal life span. The activation of c-Jun N-terminal kinase (JNK), p38 and caspases are involved in potential proapoptotic signaling pathways. JNK, p38 MAPK pathway and caspases play a crucial role in the control of apoptosis in response to stress. The most recent and up-to-date literature was evaluated in this study, which describes the role of JNK, p38 MAPK pathway and caspases as therapeutic target in cancer. Chemotherapy uses drugs that are cytotoxic to highly proliferating tumor cells but also kills the non-tumor rapidly proliferating cells in the hair, skin and gastrointestinal tract epithelium, thereby accounting the side effects of these types of treatments. Recently, chemopreventive modalities derived from phytoconstituents present in plants provide a broad-spectrum strategy to overcome the incidence of cancer. Non-toxic, safe and affordable bioavailabilities of chemopreventive agents provide credence support in the field of cancer research compared to conventional therapies that cause serious consequences. Chemoprevention envisages the basic mechanisms like modulating the activity of xenobiotic-metabolizing enzymes, induction of apoptosis, immune system activation, suppressing angiogenesis and the formation of metastasis, antioxidant and anti-inflammatory properties. The present review highlighted the role of phytoconstituents derived from food, vegetables and medicinal plants in the induction of apoptosis in cancer cells, which in turn is mediated by the activation of JNK, p38 MAPK pathways, and caspases.

P38α contributes to TNF-α-induced IL-8 production in human gingival cells

Tumor necrosis factor-alpha (TNF-α) is a major inflammatory cytokine that induces interleukin (IL)-8 production. Although some studies have reported the involvement of the p38 MAPK signaling pathway in TNF-α-induced IL-8 production, its specific regulatory mechanisms in gingival epithelial cells (GECs) are still poorly understood. In the present study, Ca9-22 cells were used as representative GECs to investigate the effect of p38 signaling on TNF-α-induced IL-8 production. We found that TNF-α enhanced IL-8 production in Ca9-22 cells by activating the p38 signaling pathway, and one of its isoforms, p38α, played a key role. P38α deletion markedly inhibited TNF-α-induced IL-8 expression in Ca9-22 cells, while p38α gene rescue could reverse this effect. Further studies revealed that TNF-α-induced IL-8 production was markedly reduced when the threonine 180 and tyrosine 182 p38α phosphorylation sites were targeted for mutagenesis to alanine and phenylalanine, respectively, suggesting their critical role in the process. In conclusion, p38α plays an important role in TNF-α-induced IL-8 production, providing a potential therapeutic target to prevent and treat periodontal disease.

Isoform-specific optical activation of kinase function reveals p38-ERK signaling crosstalk

Evolution has diversified the mammalian proteome by the generation of protein isoforms that originate from identical genes, e.g., through alternative gene splicing or post-translational modifications, or very similar genes found in gene families. Protein isoforms can have either overlapping or unique functions and traditional chemical, biochemical, and genetic techniques are often limited in their ability to differentiate between isoforms due to their high similarity. This is particularly true in the context of highly dynamic cell signaling cascades, which often require acute spatiotemporal perturbation to assess mechanistic details. To that end, we describe a method for the selective perturbation of the individual protein isoforms of the mitogen-activated protein kinase (MAPK) p38. The genetic installation of a photocaging group at a conserved active site lysine enables the precise light-controlled initiation of kinase signaling, followed by investigation of downstream events. Through optical control, we have identified a novel point of crosstalk between two major signaling cascades: the p38/MAPK pathway and the extracellular signal-regulated kinase (ERK)/MAPK pathway. Specifically, using the photoactivated p38 isoforms, we have found the p38γ and p38δ variants to be positive regulators of the ERK signaling cascade, while confirming the p38α and p38β variants as negative regulators.

3-deazaadenosine: A promising novel p38γ antagonist with potential as a breast cancer therapeutic agent

Human p38γ protein kinase, or MAPK12, is a crucial signaling protein that is important in channelizing membrane signals to the nucleus in the MAPK cascade pathway, associated with breast and colorectal cancer, besides other forms of malignancies and atherosclerotic lesions too. P38γ has a significant contribution to the progression of breast carcinoma due to its multifaceted functions. Targeting p38γ for defining potent antagonists against p38γ can turn out to be an attractive and novel means of breast cancer therapeutics. Novel and potent lead molecules were designed utilizing computational drug design methodologies. Using high-throughput virtual screening, 1909 geometrically similar analogs of known inhibitors were generated, primarily using BIRB796, SB202190, ANP, CHEBI: 620708, and CHEBI: 524699. Chemical correctness was ensured using LigPrep for the standalone library, and Prep Wizard for p38γ using Maestro v.11.5. Using the Glide v5.5 flexible docking procedure on a standalone library of p38γ binding sites, we defined 18 potential leads and assessed their ADMET properties. Lead "1", among the proposed four p38γ antagonists with high-scoring and favorable interactions, was considered for 100 ns molecular dynamics simulations. Among the four proposed leads, Lead '1' displayed consistent and stable bonding interactions with p38γ throughout the 100 ns molecular dynamics (MD) simulations. Additionally, it formed water bridges, contributing to its strong association with the protein. Notably, Lead '1' (3-deazaadenosine) exhibited favorable root-mean-square deviation (RMSD) and root-mean-square fluctuation (RMSF) within the acceptable range of pharmacological properties. Thus, 3-deazaadenosine and its mimetic might be promising new directions for developing a novel class of antagonists for breast cancer treatment.

p38γ MAPK Inflammatory and Metabolic Signaling in Physiology and Disease

p38γ MAPK (also called ERK6 or SAPK3) is a family member of stress-activated MAPKs and has common and specific roles as compared to other p38 proteins in signal transduction. Recent studies showed that, in addition to inflammation, p38γ metabolic signaling is involved in physiological exercise and in pathogenesis of cancer, diabetes, and Alzheimer's disease, indicating its potential as a therapeutic target. p38γphosphorylates at least 19 substrates through which p38γ activity is further modified to regulate life-important cellular processes such as proliferation, differentiation, cell death, and transformation, thereby impacting biological outcomes of p38γ-driven pathogenesis. P38γ signaling is characterized by its unique reciprocal regulation with its specific phosphatase PTPH1 and by its direct binding to promoter DNAs, leading to transcriptional activation of targets including cancer-like stem cell drivers. This paper will review recent findings about p38γ inflammation and metabolic signaling in physiology and diseases. Moreover, we will discuss the progress in the development of p38γ-specific pharmacological inhibitors for therapeutic intervention in disease prevention and treatment by targeting the p38γ signaling network.

Synthesis and Preclinical Positron Emission Tomography Imaging of the p38 MAPK Inhibitor [11C]Talmapimod: Effects of Drug Efflux and Sex Differences

Stress-activated kinases are targets of interest in neurodegenerative disease due to their involvement in inflammatory signaling and synaptic dysfunction. The p38α kinase has shown clinical and preclinical promise as a druggable target in several neurodegenerative conditions. We report the radiosynthesis and evaluation of the first positron emission tomography (PET) radiotracer for imaging MAPK p38α/β through radiolabeling of the inhibitor talmapimod (SCIO-469) with carbon-11. [¹¹C]Talmapimod was reliably synthesized by carbon-11 methylation with non-decay corrected radiochemical yields of 3.1 ± 0.7%, molar activities of 38.9 ± 13 GBq/μmol, and >95% radiochemical purity (n = 20). Preclinical PET imaging in rodents revealed a low baseline brain uptake and retention with standardized uptake values (SUV) of ∼0.2 over 90 min; however, pretreatment with the P-glycoprotein (P-gp) drug efflux transporter inhibitor elacridar enabled [¹¹C]talmapimod to pass the blood-brain barrier (>1.0 SUV) with distinct sex differences in washout kinetics. Blocking studies with a structurally dissimilar p38α/β inhibitor, neflamapimod (VX-745), and displacement imaging studies with talmapimod were attempted in elacridar-pretreated rodents, but neither compound displaced radiotracer uptake in the brain of either sex. Ex vivo radiometabolite analysis revealed substantial differences in the composition of radioactive species present in blood plasma but not in brain homogenates at 40 min post radiotracer injection. Digital autoradiography in fresh-frozen rodent brain tissue confirmed that the radiotracer signal was largely non-displaceable in vitro, where self-blocking and blocking with neflamapimod marginally decreased the total signal by 12.9 ± 8.8% and 2.66 ± 2.1% in C57bl/6 healthy controls and 29.3 ± 2.7% and 26.7 ± 12% in Tg2576 rodent brains, respectively. An MDCK-MDR1 assay suggests that talmapimod is likely to suffer from drug efflux in humans as well as rodents. Future efforts should focus on radiolabeling p38 inhibitors from other structural classes to avoid P-gp efflux and non-displaceable binding.

A novel methuosis inducer DZ-514 possesses antitumor activity via activation of ROS-MKK4-p38 axis in triple negative breast cancer

Triple-negative breast cancer (TNBC) is one of the most malignant tumors with poor prognosis. Methuosis is a new type of nonapoptotic cell death characterized by the accumulation of cytoplasmic vacuoles. In this study, we synthesized and screened a series of N-phenyl-4-pyrimidinediamine derivatives in TNBC cells, finding that DZ-514 was the best compound with high toxicity independent of the inhibition of BCL6. DZ-514 decreased cell viability, inhibited cell cycle progression, and induced caspase-independent cell death in TNBC cells. Interestingly, DZ-514 induced cytoplasm vacuolation, which could be blocked by Baf A1, the V-ATPase inhibitor. Furthermore, we found that DZ-514-induced vacuoles were derived from macropinosomes rather than autophagosomes. Most importantly, methuosis induced by DZ-514 was partially mediated by activating the ROS-MKK4-p38 axis. Finally, we demonstrated that DZ-514 significantly inhibited tumor growth in an HCC1806 xenograft mouse model. These findings revealed that the novel methuosis inducer DZ-514 could be developed for TNBC treatment.

Research progress of p38 as a new therapeutic target against morphine tolerance and the current status of therapy of morphine tolerance

With the development of the medical industry, new painkillers continue to appear in people's field of vision, but so far no painkiller can replace morphine. While morphine has a strong analgesic effect, it is also easy to produce pain sensitivity and tolerance. Due to the great inter-individual differences in patient responses, there are few clear instructions on how to optimise morphine administration regimens, which complicates clinicians' treatment strategies and limits the effectiveness of morphine in long-term pain therapy. P38MAPK is a key member of the MAPK family. Across recent years, it has been discovered that p38MAPK rises dramatically in a wide range of morphine tolerance animal models. Morphine tolerance can be reduced or reversed by inhibiting p38MAPK. However, the role and specific mechanism of p38MAPK are not clear. In this review, we synthesise the relevant findings, highlight the function and potential mechanism of p38MAPK in morphine tolerance, as well as the present status and efficacy of morphine tolerance therapy, and underline the future promise of p38MAPK targeted morphine tolerance treatment.

A patent review of MAPK inhibitors (2018 - present)

INTRODUCTION

The mitogen-activated protein kinase (MAPK) family consist of p38 MAP kinases, c-Jun N-terminal kinases (JNKs) and extracellular signal-regulated kinases (ERKs). They are involved in a multitude of diseases, including inflammatory, autoimmune, neurodegenerative, and metabolic diseases as well as cancer. In recent years, further developments in the field of MAPK-inhibitors have been reported, including an isoform or downstream target selective inhibition of MAPKs as well as target protein degradation approaches.

AREAS COVERED

This review summarizes newly patented MAPK-inhibitors that were claimed between 2018 and early 2023. Presented are the patents as well as their corresponding publications, the storyline of development, and clinical trials involving these compounds. This article elaborates a total of 27 patents, which were identified using established search engines.

EXPERT OPINION

Although industrial research on MAPK-inhibitors has been ongoing for more than 20 years, novel clinical trials of MAPK-inhibitors as potential drug candidates are still being conducted in the period under review. Recently reported inhibitors show an excellent selectivity profile and are even achieving selectivity between closely related isoforms. This progression offers the possibility to eliminate unwanted side effects and may finally lead to the approval of the first MAPK-inhibitor.

Plin5, a New Target in Diabetic Cardiomyopathy

Abnormal lipid accumulation is commonly observed in diabetic cardiomyopathy (DC), which can create a lipotoxic microenvironment and damage cardiomyocytes. Lipid toxicity is an important pathogenic factor due to abnormal lipid accumulation in DC. As a lipid droplet (LD) decomposition barrier, Plin5 can protect LDs from lipase decomposition and regulate lipid metabolism, which is involved in the occurrence and development of cardiovascular diseases. In recent years, studies have shown that Plin5 expression is involved in the pathogenesis of DC lipid toxicity, such as oxidative stress, mitochondrial dysfunction, endoplasmic reticulum (ER) stress, and insulin resistance (IR) and has become a key target of DC research. Therefore, understanding the relationship between Plin5 and DC progression as well as the mechanism of this process is crucial for developing new therapeutic approaches and exploring new therapeutic targets. This review is aimed at exploring the latest findings and roles of Plin5 in lipid metabolism and DC-related pathogenesis, to explore possible clinical intervention approaches.

Mitogen-activated protein kinase-activated protein kinase-2 (MK2) and its role in cell survival, inflammatory signaling, and migration in promoting cancer

Cancer and the immune system share an intimate relationship. Chronic inflammation increases the risk of cancer occurrence and can also drive inflammatory mediators into the tumor microenvironment enhancing tumor growth and survival. The p38 MAPK pathway is activated both acutely and chronically by stress, inflammatory chemokines, chronic inflammatory conditions, and cancer. These properties have led to extensive efforts to find effective drugs targeting p38, which have been unsuccessful. The immediate downstream serine/threonine kinase and substrate of p38 MAPK, mitogen-activated-protein-kinase-activated-protein-kinase-2 (MK2) protects cells against stressors by regulating the DNA damage response, transcription, protein and messenger RNA stability, and motility. The phosphorylation of downstream substrates by MK2 increases inflammatory cytokine production, drives an immune response, and contributes to wound healing. By binding directly to p38 MAPK, MK2 is responsible for the export of p38 MAPK from the nucleus which gives MK2 properties that make it unique among the large number of p38 MAPK substrates. Many of the substrates of both p38 MAPK and MK2 are separated between the cytosol and nucleus and interfering with MK2 and altering this intracellular translocation has implications for the actions of both p38 MAPK and MK2. The inhibition of MK2 has shown promise in combination with both chemotherapy and radiotherapy as a method for controlling cancer growth and metastasis in a variety of cancers. Whereas the current data are encouraging the field requires the development of selective and well tolerated drugs to target MK2 and a better understanding of its effects for effective clinical use.

Atypical p38 Signaling, Activation, and Implications for Disease

The mitogen-activated protein kinase (MAPK) p38 is an essential family of kinases, regulating responses to environmental stress and inflammation. There is an ever-increasing plethora of physiological and pathophysiological conditions attributed to p38 activity, ranging from cell division and embryonic development to the control of a multitude of diseases including retinal, cardiovascular, and neurodegenerative diseases, diabetes, and cancer. Despite the decades of intense investigation, a viable therapeutic approach to disrupt p38 signaling remains elusive. A growing body of evidence supports the pathological significance of an understudied atypical p38 signaling pathway. Atypical p38 signaling is driven by a direct interaction between the adaptor protein TAB1 and p38α, driving p38 autophosphorylation independent from the classical MKK3 and MKK6 pathways. Unlike the classical MKK3/6 signaling pathway, atypical signaling is selective for just p38α, and at present has only been characterized during pathophysiological stimulation. Recent studies have linked atypical signaling to dermal and vascular inflammation, myocardial ischemia, cancer metastasis, diabetes, complications during pregnancy, and bacterial and viral infections. Additional studies are required to fully understand how, when, where, and why atypical p38 signaling is induced. Furthermore, the development of selective TAB1-p38 inhibitors represents an exciting new opportunity to selectively inhibit pathological p38 signaling in a wide array of diseases.

p38 MAPK Pathway in the Heart: New Insights in Health and Disease

The p38 mitogen-activated kinase (MAPK) family controls cell adaptation to stress stimuli. p38 function has been studied in depth in relation to cardiac development and function. The first isoform demonstrated to play an important role in cardiac development was p38α; however, all p38 family members are now known to collaborate in different aspects of cardiomyocyte differentiation and growth. p38 family members have been proposed to have protective and deleterious actions in the stressed myocardium, with the outcome of their action in part dependent on the model system under study and the identity of the activated p38 family member. Most studies to date have been performed with inhibitors that are not isoform-specific, and, consequently, knowledge remains very limited about how the different p38s control cardiac physiology and respond to cardiac stress. In this review, we summarize the current understanding of the role of the p38 pathway in cardiac physiology and discuss recent advances in the field.

Unpuzzling COVID-19: tissue-related signaling pathways associated with SARS-CoV-2 infection and transmission

The highly infective coronavirus disease 19 (COVID-19) is caused by a novel strain of coronaviruses - the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) - discovered in December 2019 in the city of Wuhan (Hubei Province, China). Remarkably, COVID-19 has rapidly spread across all continents and turned into a public health emergency, which was ultimately declared as a pandemic by the World Health Organization (WHO) in early 2020. SARS-CoV-2 presents similar aspects to other members of the coronavirus family, mainly regarding its genome, protein structure and intracellular mechanisms, that may translate into mild (or even asymptomatic) to severe infectious conditions. Although the mechanistic features underlying the COVID-19 progression have not been fully clarified, current evidence have suggested that SARS-CoV-2 may primarily behave as other β-coronavirus members. To better understand the development and transmission of COVID-19, unveiling the signaling pathways that may be impacted by SARS-CoV-2 infection, at the molecular and cellular levels, is of crucial importance. In this review, we present the main aspects related to the origin, classification, etiology and clinical impact of SARS-CoV-2. Specifically, here we describe the potential mechanisms of cellular interaction and signaling pathways, elicited by functional receptors, in major targeted tissues/organs from the respiratory, gastrointestinal (GI), cardiovascular, renal, and nervous systems. Furthermore, the potential involvement of these signaling pathways in evoking the onset and progression of COVID-19 symptoms in these organ systems are presently discussed. A brief description of future perspectives related to potential COVID-19 treatments is also highlighted.

p38γ MAPK Is Essential for Aerobic Glycolysis and Pancreatic Tumorigenesis

KRAS is mutated in most pancreatic ductal adenocarcinomas (PDAC) and yet remains undruggable. Here, we report that p38γ MAPK, which promotes PDAC tumorigenesis by linking KRAS signaling and aerobic glycolysis (also called the Warburg effect), is a novel therapeutic target. p38γ interacted with a glycolytic activator PFKFB3 that was dependent on mutated KRAS. KRAS transformation and overexpression of p38γ increased expression of PFKFB3 and glucose transporter GLUT2, conversely, silencing mutant KRAS, and p38γ decreased PFKFB3 and GLUT2 expression. p38γ phosphorylated PFKFB3 at S467, stabilized PFKFB3, and promoted their interaction with GLUT2. Pancreatic knockout of p38γ decreased p-PFKFB3/PFKFB3/GLUT2 protein levels, reduced aerobic glycolysis, and inhibited PDAC tumorigenesis in KPC mice. PFKFB3 and GLUT2 depended on p38γ to stimulate glycolysis and PDAC growth and p38γ required PFKFB3/S467 to promote these activities. A p38γ inhibitor cooperated with a PFKFB3 inhibitor to blunt aerobic glycolysis and PDAC growth, which was dependent on p38γ. Moreover, overexpression of p38γ, p-PFKFB3, PFKFB3, and GLUT2 in PDAC predicted poor clinical prognosis. These results indicate that p38γ links KRAS oncogene signaling and aerobic glycolysis to promote pancreatic tumorigenesis through PFKFB3 and GLUT2, and that p38γ and PFKFB3 may be targeted for therapeutic intervention in PDAC. SIGNIFICANCE: These findings show that p38γ links KRAS oncogene signaling and the Warburg effect through PFKBF3 and Glut2 to promote pancreatic tumorigenesis, which can be disrupted via inhibition of p38γ and PFKFB3.

An overview of mammalian p38 mitogen-activated protein kinases, central regulators of cell stress and receptor signaling

The p38 family is a highly evolutionarily conserved group of mitogen-activated protein kinases (MAPKs) that is involved in and helps co-ordinate cellular responses to nearly all stressful stimuli. This review provides a succinct summary of multiple aspects of the biology, role, and substrates of the mammalian family of p38 kinases. Since p38 activity is implicated in inflammatory and other diseases, we also discuss the clinical implications and pharmaceutical approaches to inhibit p38.

Multi-Kinase Inhibitor with Anti-p38γ Activity in Cutaneous T-Cell Lymphoma

Current cutaneous T-cell lymphoma (CTCL) therapies are marked by an abbreviated response, subsequent drug resistance, and poor prognosis for patients with advanced disease. An understanding of molecular regulators involved in CTCL is needed to develop effective targeted therapies. One candidate regulator is p38γ, a mitogen-activated protein kinase crucial for malignant T-cell activity and growth. p38γ gene expression is selectively increased in CTCL patient samples and cell lines but not in healthy T cells. In addition, gene silencing of p38γ reduced CTCL cell viability, showing a key role in CTCL pathogenesis. Screening p38γ inhibitors is critical for understanding the mechanism of CTCL tumorigenesis and developing therapeutic applications. We prioritized a potent p38γ inhibitor (F7, also known as PIK75) through a high-throughput kinase inhibitor screen. At nanomolar concentrations, PIK75, a multiple kinase inhibitor, selectively killed CD4⁺ malignant CTCL cells but spared healthy CD4⁺ cells; induced significant reduction of tumor size in mouse xenografts; and effectively inhibited p38γ enzymatic activity and phosphorylation of its substrate, DLGH1, in CTCL cells and mouse xenografts. Here, we report that PIK75 has a potential clinical application to serve as a scaffold molecule for the development of a more selective p38γ inhibitor.

Targeting an oncogenic kinase/phosphatase signaling network for cancer therapy

Protein kinases and phosphatases signal by phosphorylation and dephosphorylation to precisely control the activities of their individual and common substrates for a coordinated cellular outcome. In many situations, a kinase/phosphatase complex signals dynamically in time and space through their reciprocal regulations and their cooperative actions on a substrate. This complex may be essential for malignant transformation and progression and can therefore be considered as a target for therapeutic intervention. p38γ is a unique MAPK family member that contains a PDZ motif at its C-terminus and interacts with a PDZ domain-containing protein tyrosine phosphatase PTPH1. This PDZ-coupled binding is required for both PTPH1 dephosphorylation and inactivation of p38γ and for p38γ phosphorylation and activation of PTPH1. Moreover, the p38γ/PTPH1 complex can further regulate their substrates phosphorylation and dephosphorylation, which impacts Ras transformation, malignant growth and progression, and therapeutic response. This review will use the p38γ/PTPH1 signaling network as an example to discuss the potential of targeting the kinase/phosphatase signaling complex for development of novel targeted cancer therapy.

Autoantibody Signaling in Pemphigus Vulgaris: Development of an Integrated Model

Pemphigus vulgaris (PV) is an autoimmune skin blistering disease effecting both cutaneous and mucosal epithelia. Blister formation in PV is known to result from the binding of autoantibodies (autoAbs) to keratinocyte antigens. The primary antigenic targets of pathogenic autoAbs are known to be desmoglein 3, and to a lesser extent, desmoglein 1, cadherin family proteins that partially comprise the desmosome, a protein structure responsible for maintaining cell adhesion, although additional autoAbs, whose role in blister formation is still unclear, are also known to be present in PV patients. Nevertheless, there remain large gaps in knowledge concerning the precise mechanisms through which autoAb binding induces blister formation. Consequently, the primary therapeutic interventions for PV focus on systemic immunosuppression, whose side effects represent a significant health risk to patients. In an effort to identify novel, disease-specific therapeutic targets, a multitude of studies attempting to elucidate the pathogenic mechanisms downstream of autoAb binding, have led to significant advancements in the understanding of autoAb-mediated blister formation. Despite this enhanced characterization of disease processes, a satisfactory explanation of autoAb-induced acantholysis still does not exist. Here, we carefully review the literature investigating the pathogenic disease mechanisms in PV and, taking into account the full scope of results from these studies, provide a novel, comprehensive theory of blister formation in PV.

Stress-Activated Protein Kinases in Spinal Cord Injury: Focus on Roles of p38

Spinal cord injury (SCI) consists of three phases-acute, secondary, and chronic damages-and limiting the development of secondary damage possibly improves functional recovery after SCI. A major component of the secondary phase of SCI is regarded as inflammation-triggered events: induction of cytokines, edema, microglial activation, apoptosis of cells including oligodendrocytes and neurons, demyelination, formation of the astrocytic scar, and so on. Two major stress-activated protein kinases (SAPKs)-c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38 MAPK)-are activated in various types of cells in response to cellular stresses such as apoptotic stimuli and inflammatory waves. In animal models of SCI, inhibition of either JNK or p38 has been shown to promote neuroprotection-associated functional recovery. Here, we provide an overview on the roles of SAPKs in SCI and, in particular, the pathological role of p38 will be discussed as a promising target for therapeutic intervention in SCI.

Kinase Signaling in Apoptosis Induced by Saturated Fatty Acids in Pancreatic β-Cells

Pancreatic β-cell failure and death is considered to be one of the main factors responsible for type 2 diabetes. It is caused by, in addition to hyperglycemia, chronic exposure to increased concentrations of fatty acids, mainly saturated fatty acids. Molecular mechanisms of apoptosis induction by saturated fatty acids in β-cells are not completely clear. It has been proposed that kinase signaling could be involved, particularly, c-Jun N-terminal kinase (JNK), protein kinase C (PKC), p38 mitogen-activated protein kinase (p38 MAPK), extracellular signal-regulated kinase (ERK), and Akt kinases and their pathways. In this review, we discuss these kinases and their signaling pathways with respect to their possible role in apoptosis induction by saturated fatty acids in pancreatic β-cells.

How do kinases contribute to tonicity-dependent regulation of the transcription factor NFAT5?

NFAT5 plays a critical role in maintaining the renal functions. Its dis-regulation in the kidney leads to or is associated with certain renal diseases or disorders, most notably the urinary concentration defect. Hypertonicity, which the kidney medulla is normally exposed to, activates NFAT5 through phosphorylation of a signaling molecule or NFAT5 itself. Hypotonicity inhibits NFAT5 through a similar mechanism. More than a dozen of protein and lipid kinases have been identified to contribute to tonicity-dependent regulation of NFAT5. Hypertonicity activates NFAT5 by increasing its nuclear localization and transactivating activity in the early phase and protein abundance in the late phase. The known mechanism for inhibition of NFAT5 by hypotonicity is a decrease of nuclear NFAT5. The present article reviews the effect of each kinase on NFAT5 nuclear localization, transactivation and protein abundance, and the relationship among these kinases, if known. Cyclosporine A and tacrolimus suppress immune reactions by inhibiting the phosphatase calcineurin-dependent activation of NFAT1. It is hoped that this review would stimulate the interest to seek explanations from the NFAT5 regulatory pathways for certain clinical presentations and to explore novel therapeutic approaches based on the pathways. On the basic science front, this review raises two interesting questions. The first one is how these kinases can specifically signal to NFAT5 in the context of hypertonicity or hypotonicity, because they also regulate other cellular activities and even opposite activities in some cases. The second one is why these many kinases, some of which might have redundant functions, are needed to regulate NFAT5 activity. This review reiterates the concept of signaling through cooperation. Cells need these kinases working in a coordinated way to provide the signaling specificity that is lacking in the individual one. Redundancy in regulation of NFAT5 is a critical strategy for cells to maintain robustness against hypertonic or hypotonic stress.

Gene structure, molecular characterization and transcriptional expression of two p38 isoforms (MAPK11 and MAPK14) from rock bream (Oplegnathus fasciatus)

The p38 kinases are one of the four subgroups of mitogen-activated protein kinase (MAPK) superfamily which are involved in the innate immunity. The p38 subfamily that includes four members namely p38α (MAPK14), p38β (MAPK11), p38γ (MAPK12) and p38δ (MAPK13), regulates the activation of several transcription factors. In this study, a p38β (OfMAPK11) homolog and a p38α (OfMAPK14) homolog of Oplegnathus fasciatus were identified at genomic level. Results clearly showed that both MAPK11 and MAPK14 are well-conserved at both genomic structural- and amino acid (aa)-levels. Genomic sequences of OfMAPK11 (∼ 15.6 kb) and OfMAPK14 (∼ 13.4 kb) had 12 exons. A comparison of exon-intron structural arrangement of these genes from different vertebrate lineages indicated that all the exon lengths are highly conserved, except their terminal exons. Full-length cDNAs of OfMAPK11 (3957 bp) and OfMAPK14 (2504 bp) encoded corresponding proteins of 361 aa and 360 aa, respectively. Both OfMAPK proteins harbored a Ser/Thr protein kinases catalytic domain (S_TKc domain) which includes an activation loop with a dual phosphorylation site (TGY motif) and several specific-binding sites for ATP and substrates. Molecular modeling of the activation loop and substrate binding sites of rock bream MAPKs revealed the conservation of crucial residues and their orientation in 3D space. Transcripts of OfMAPKs were ubiquitously detected in eleven tissues examined, however at different levels. The modulation of OfMAPKs' transcription upon pathogen-associated molecular patterns (PAMPs: flagellin, lipopolysaccharide and poly I:C) and pathogens (Edwardsiella tarda, Streptococcus iniae and rock bream iridovirus) was investigated. Among the seven examined tissues, the flagellin-challenge upregulated the mRNA level of both OfMAPKs in the head kidney. Meanwhile, modulation of OfMAPK mRNA expression in the liver upon other immune-challenges varied in a time-dependent manner. Collectively, these results suggest that OfMAPKs are true members of p38 subfamily, which might be induced by different immune stimuli.

p38γ MAPK Is a Therapeutic Target for Triple-Negative Breast Cancer by Stimulation of Cancer Stem-Like Cell Expansion

Triple-negative breast cancer (TNBC) is highly progressive and lacks established therapeutic targets. p38γ mitogen-activated protein kinase (MAPK) (gene name: MAPK12) is overexpressed in TNBC but how overexpressed p38γ contributes to TNBC remains unknown. Here, we show that p38γ activation promotes TNBC development and progression by stimulating cancer stem-like cell (CSC) expansion and may serve as a novel therapeutic target. p38γ silencing in TNBC cells reduces mammosphere formation and decreases expression levels of CSC drivers including Nanog, Oct3/4, and Sox2. Moreover, p38γ MAPK-forced expression alone is sufficient to stimulate CSC expansion and to induce epithelial cell transformation in vitro and in vivo. Furthermore, p38γ depends on its activity to stimulate CSC expansion and breast cancer progression, indicating a therapeutic opportunity by application of its pharmacological inhibitor. Indeed, the non-toxic p38γ specific pharmacological inhibitor pirfenidone selectively inhibits TNBC growth in vitro and/or in vivo and significantly decreases the CSC population. Mechanistically, p38γ stimulates Nanog transcription through c-Jun/AP-1 via a multi-protein complex formation. These results together demonstrate that p38γ can drive TNBC development and progression and may be a novel therapeutic target for TNBC by stimulating CSC expansion. Inhibiting p38γ activity with pirfenidone may be a novel strategy for the treatment of TNBC.

Identification of a ternary protein-complex as a therapeutic target for K-Ras-dependent colon cancer

A cancer phenotype is driven by several proteins and targeting a cluster of functionally interdependent molecules should be more effective for therapeutic intervention. This is specifically important for Ras-dependent cancer, as mutated (MT) Ras is non-druggable and targeting its interaction with effectors may be essential for therapeutic intervention. Here, we report that a protein-complex activated by the Ras effector p38γ MAPK is a novel therapeutic target for K-Ras-dependent colon cancer. Unbiased proteomic screening and immune-precipitation analyses identified p38γ interaction with heat shock protein 90 (Hsp90) and K-Ras in K-Ras MT, but not wild-type (WT), colon cancer cells, indicating a role of this complex in Ras-dependent growth. Further experiments showed that this complex requires p38γ and Hsp90 activity to maintain MT, but not WT, K-Ras protein expression. Additional studies demonstrated that this complex is activated by p38γ-induced Hsp90 phosphorylation at S595, which is important for MT K-Ras stability and for K-Ras dependent growth. Of most important, pharmacologically inhibition of Hsp90 or p38γ activity disrupts the complex, decreases K-Ras expression, and selectively inhibits the growth of K-Ras MT colon cancer in vitro and in vivo. These results demonstrated that the p38γ-activated ternary complex is a novel therapeutic target for K-Ras-dependent colon cancer.

p38 MAP Kinase Inhibition Reduces Propionibacterium acnes-Induced Inflammation in Vitro

Introduction

Propionibacterium acnes, a ubiquitous skin bacterium, stimulates keratinocytes to produce a number of proinflammatory cytokines and may contribute to inflammatory acne. The aim of the study was to investigate whether P. acnes-induced proinflammatory cytokine release is mediated by P. acnes-induced activation of p38 mitogen-activated protein kinase (p38 MAPK or p38) in human keratinocytes.

Methods

Immunohistochemistry was used to evaluate p38 phosphorylation in human skin samples with or without acne. Primary human keratinocytes and epidermal skin equivalents were exposed to viable P. acnes. Phosphorylation of MAPKs without or with p38 inhibitors was examined by Western blot and cytokine secretion was detected by Enzyme-Linked Immunosorbent Assay (ELISA).

Results

Increased levels of phospho-p38 were observed in human acne lesions, predominantly in follicular and perifollicular keratinocytes. Exposure of cultured human keratinocytes to viable P. acnes resulted in phosphorylation of multiple members of the MAPK family, including rapid and transient activation of p38 and extracellular signal-related kinase (ERK1/2) and relatively slow but sustained activation of c-Jun N-terminal kinases (JNK1/2). Viable P. acnes induced the secretion of interleukin-1α (IL-1α), tumor necrosis factor-α (TNF-α), and IL-8 from human keratinocytes. The phosphorylation of p38 (phospho-p38) and the secretion of cytokines induced by P. acnes in cultured keratinocytes were inhibited by SB203580, a p38α/β inhibitor. Furthermore, SCIO-469, a selective inhibitor of p38α, showed similar effects in cultured keratinocytes. Topical treatment of SCIO-469 inhibited the P. acnes-induced phospho-p38 and cytokine secretion in human epidermal equivalents.

Conclusion

The data demonstrate that P. acnes induces p38-dependent inflammatory responses in keratinocytes, and suggest that p38 may play an important role in the pathogenesis of inflammatory acne.

Funding

Johnson & Johnson.

Electronic supplementary material

The online version of this article (doi:10.1007/s13555-015-0072-7) contains supplementary material, which is available to authorized users.

MAP kinase p38α regulates type III interferon (IFN-λ1) gene expression in human monocyte-derived dendritic cells in response to RNA stimulation

Recognition of viral nucleic acids leads to type I and type III IFN gene expression and activation of host antiviral responses. At present, type III IFN genes are the least well-characterized IFN types. Here, we demonstrate that the p38 MAPK signaling pathway is involved in regulating IFN-λ1 gene expression in response to various types of RNA molecules in human moDCs. Inhibition of p38 MAPK strongly reduced IFN gene expression, and overexpression of p38α MAPK enhanced IFN-λ1 gene expression in RNA-stimulated moDCs. The regulation of IFN gene expression by p38 MAPK signaling was independent of protein synthesis and thus, a direct result of RNA stimulation. Moreover, the RIG-I/MDA5-MAVS-IRF3 pathway was required for p38α MAPK to up-regulate IFN-λ1 promoter activation, whereas the MyD88-IRF7 pathway was not needed, and the regulation was not involved directly in IRF7-dependent IFN-α1 gene expression. The stimulatory effect of p38α MAPK on IFN-λ1 mRNA expression in human moDCs did not take place directly via the activating TBK1/IKKε complex, but rather, it occurred through some other parallel pathways. Furthermore, mutations in ISRE and NF-κB binding sites in the promoter region of the IFN-λ1 gene led to a significant reduction in p38α MAPK-mediated IFN responses after RNA stimulation. Altogether, our data suggest that the p38α MAPK pathway is linked with RLR signaling pathways and regulates the expression of early IFN genes after RNA stimulation cooperatively with IRF3 and NF-κB to induce antiviral responses further.

p38δ MAPK: Emerging Roles of a Neglected Isoform

p38δ mitogen activated protein kinase (MAPK) is a unique stress responsive protein kinase. While the p38 MAPK family as a whole has been implicated in a wide variety of biological processes, a specific role for p38δ MAPK in cellular signalling and its contribution to both physiological and pathological conditions are presently lacking. Recent emerging evidence, however, provides some insights into specific p38δ MAPK signalling. Importantly, these studies have helped to highlight functional similarities as well as differences between p38δ MAPK and the other members of the p38 MAPK family of kinases. In this review we discuss the current understanding of the molecular mechanisms underlying p38δ MAPK activity. We outline a role for p38δ MAPK in important cellular processes such as differentiation and apoptosis as well as pathological conditions such as neurodegenerative disorders, diabetes, and inflammatory disease. Interestingly, disparate roles for p38δ MAPK in tumour development have also recently been reported. Thus, we consider evidence which characterises p38δ MAPK as both a tumour promoter and a tumour suppressor. In summary, while our knowledge of p38δ MAPK has progressed somewhat since its identification in 1997, our understanding of this particular isoform in many cellular processes still strikingly lags behind that of its counterparts.

Identification of p38β as a therapeutic target for the treatment of Sézary syndrome

Cutaneous T-Cell Lymphomas (CTCL) represent a group of hematopoietic malignancies that home to the skin and have no known molecular basis for disease pathogenesis. Sézary syndrome (SS) is the leukemic variant of CTCL. Currently, CTCL is incurable, highlighting the need for new therapeutic modalities. We have previously observed that combined smallmolecule inhibition of protein kinase C (PKC) β and glycogen synthase kinase 3 (GSK3) causes synergistic apoptosis in CTCL cell lines and patient cells. Through microarray analysis of a SS cell line, we surveyed global gene expression following combined PKCβ-GSK3 treatment to elucidate therapeutic targets responsible for cell death. Clinically relevant targets were defined as genes differentially expressed in SS patients that were modulated by combination-drug treatment of SS cells. Gene set enrichment analysis uncovered candidate genes enriched for an immune cell signature, specifically the T-cell receptor and MAPK signaling pathways. Further analysis identified p38 as a potential therapeutic target that is over-expressed in SS patients and decreased by synergistic-inhibitor treatment. This target was verified through small-molecule inhibition of p38 leading to cell death in both SS cell lines and patient cells. These data establish p38 as a SS biomarker and potential therapeutic target for the treatment of CTCL.

p38α mitogen-activated kinase mediates cardiomyocyte apoptosis induced by palmitate

RATIONALE

The mechanisms underlying lipotoxic/diabetic cardiomyopathy remain poorly understood. Saturated fatty acid (SFA) levels, elevated in obesity and type 2 diabetes, induce apoptosis in many cell types including cardiomyocytes. Signaling pathways, including the p38α mitogen-activated kinase (MAPK)-dependent pathway, have been implicated in apoptosis due to a diverse range of insults.

OBJECTIVE

We tested the hypothesis that SFA-induced cardiomyocyte apoptosis is dependent on p38α activation.

METHODS AND RESULTS

Human adult ventricular cardiomyocytes (AC16 cells) were exposed to high physiological levels of palmitate (PA), a SFA. The apoptotic response was measured using annexin-V by flow cytometry, and the p38α-dependent pathway was evaluated using a p38 inhibitor PD169316, and by p38α small interfering RNA (siRNA) knockdown. PA exposure for 16 h dose-dependently increased apoptosis in AC16 cardiomyocytes (control: 2.6±0.6%, 150 μM PA: 3.5±0.9%, 300 μM PA: 11.5±1.6%, n=4, p<0.01). PA did not change total p38α protein levels, but increased p38α phosphorylation dose-dependently (n=5, p<0.01). PD169316 tended to reduce PA-induced apoptosis (n=4, p=0.05). Specific p38α siRNA markedly reduced the expression of p38α but not p38β (n=3, p<0.0001), and dose-dependently attenuated PA-induced apoptosis (control siRNA: 7.7±1.0%, 300 μM PA: 34.4±5.0%, 300 μM PA+30 pmol siRNA: 23.7±4.4%, 300 μM PA+60 pmol siRNA: 19.7±2.6%, 300 μM PA+120 pmol siRNA: 17.3±2.8%, n=4, p<0.0001).

CONCLUSIONS

These results demonstrate that PA induces p38α activation, and reducing p38α expression attenuates PA-induced cardiomyocyte apoptosis. Our results support a potential mechanism by which high plasma SFA levels through p38α activation may lead to the development of lipotoxic/diabetic cardiomyopathy.

Functional roles of p38 mitogen-activated protein kinase in macrophage-mediated inflammatory responses

Inflammation is a natural host defensive process that is largely regulated by macrophages during the innate immune response. Mitogen-activated protein kinases (MAPKs) are proline-directed serine and threonine protein kinases that regulate many physiological and pathophysiological cell responses. p38 MAPKs are key MAPKs involved in the production of inflammatory mediators, including tumor necrosis factor-α (TNF-α) and cyclooxygenase-2 (COX-2). p38 MAPK signaling plays an essential role in regulating cellular processes, especially inflammation. In this paper, we summarize the characteristics of p38 signaling in macrophage-mediated inflammation. In addition, we discuss the potential of using inhibitors targeting p38 expression in macrophages to treat inflammatory diseases.

p38 mitogen-activated protein kinase and mitogen-activated protein kinase-activated protein kinase 2 (MK2) signaling in atrophic and hypertrophic denervated mouse skeletal muscle

Background

p38 mitogen-activated protein kinase has been implicated in both skeletal muscle atrophy and hypertrophy. T317 phosphorylation of the p38 substrate mitogen-activated protein kinase-activated protein kinase 2 (MK2) correlates with muscle weight in atrophic and hypertrophic denervated muscle and may influence the nuclear and cytoplasmic distribution of p38 and/or MK2. The present study investigates expression and phosphorylation of p38, MK2 and related proteins in cytosolic and nuclear fractions from atrophic and hypertrophic 6-days denervated skeletal muscles compared to innervated controls.

Methods

Expression and phosphorylation of p38, MK2, Hsp25 (heat shock protein25_rodent/27_human, Hsp25/27) and Hsp70 protein expression were studied semi-quantitatively using Western blots with separated nuclear and cytosolic fractions from innervated and denervated hypertrophic hemidiaphragm and atrophic anterior tibial muscles. Unfractionated innervated and denervated atrophic pooled gastrocnemius and soleus muscles were also studied.

Results

No support was obtained for a differential nuclear/cytosolic localization of p38 or MK2 in denervated hypertrophic and atrophic muscle. The differential effect of denervation on T317 phosphorylation of MK2 in denervated hypertrophic and atrophic muscle was not reflected in p38 phosphorylation nor in the phosphorylation of the MK2 substrate Hsp25. Hsp25 phosphorylation increased 3-30-fold in all denervated muscles studied. The expression of Hsp70 increased 3-5-fold only in denervated hypertrophic muscles.

Conclusions

The study confirms a differential response of MK2 T317 phosphorylation in denervated hypertrophic and atrophic muscles and suggests that Hsp70 may be important for this. Increased Hsp25 phosphorylation in all denervated muscles studied indicates a role for factors other than MK2 in the regulation of this phosphorylation.

Mitochondrial p38β and manganese superoxide dismutase interaction mediated by estrogen in cardiomyocytes

Aims

While etiology behind the observed acceleration of ischemic heart disease in postmenopausal women is poorly understood, collective scientific data suggest cardioprotective effects of the endogenous female sex hormone, estrogen. We have previously shown that 17β-estradiol (E2) protects cardiomyocytes exposed to hypoxia-reoxygenation (H/R) by inhibiting p38α - p53 signaling in apoptosis and activating pro-survival p38β mitogen activated protein kinase (p38β MAPK), leading to suppression of reactive oxygen species (ROS) post H/R. However, little is known about the mechanism behind the antioxidant actions of E2-dependent p38β. The aim of this study is to determine whether the cytoprotection by estrogen involves regulation of manganese superoxide dismutase (MnSOD), a major mitochondrial ROS scavenging enzyme, via cardiac p38β.

Methods and Results

We identified mitochondrial p38β by immunocytochemistry and by immunoblotting in mitochondria isolated from neonatal cardiomyocytes of Sprague-Dawley rats. E2 facilitated the mitochondrial localization of the active form of the kinase, phosphorylated p38β (p-p38β). E2 also reduced the H/R-induced mitochondrial membrane potential decline, augmented the MnSOD activity and suppressed anion superoxide generation, while the dismutase protein expression remained unaltered. Co-immunoprecipitation studies showed physical association between MnSOD and p38β. p38β phosphorylated MnSOD in an E2-dependent manner in in-vitro kinase assays.

Conclusion

This work demonstrates for the first time a mitochondrial pool of active p38β and E2-mediated phosphorylation of MnSOD by the kinase. The results shed light on the mechanism behind the cytoprotective actions of E2 in cardiomyocytes under oxidative stress.

Induction of p38δ expression plays an essential role in oncogenic ras-induced senescence

Oncogene-induced senescence is a stable proliferative arrest that serves as a tumor-suppressing defense mechanism. p38 mitogen-activated protein kinase (MAPK) has been implicated in oncogene-induced senescence and tumor suppression. However, the specific role of each of the four p38 isoforms in oncogene-induced senescence is not fully understood. Here, we demonstrate that p38δ mediates oncogene-induced senescence through a p53- and p16(INK4A)-independent mechanism. Instead, evidence suggests a link between p38δ and the DNA damage pathways. Moreover, we have discovered a novel mechanism that enhances the expression of p38δ during senescence. In this mechanism, oncogenic ras induces the Raf-1-MEK-extracellular signal-regulated kinase (ERK) pathway, which, in turn, activates the AP-1 and Ets transcription factors that are bound to the p38δ promoter, leading to increased transcription of p38δ. These findings indicate that induction of the prosenescent function of p38δ by oncogenic ras is achieved through 2 mechanisms, transcriptional activation by the Raf-1-MEK-ERK-AP-1/Ets pathway, which increases the cellular concentration of the p38δ protein, and posttranslational modification by MKK3/6, which stimulates the enzymatic activity of p38δ. In addition, these studies identify the AP-1 and Ets transcription factors as novel signaling components in the senescence-inducing pathway.

Vasoactive effects of Aβin isolated human cerebrovessels and in a transgenic mouse model of Alzheimer's disease: Role of inflammation

A beta peptides are the major protein constituents of Alzheimer's disease (AD) senile plaques and also form some deposits in the cerebrovasculature leading to cerebral amyloid angiopathy and hemorrhagic stroke. Functional vascular abnormalities are one of the earlier clinical manifestations in both sporadic and familial forms of AD. Most of the cardiovascular risk factors (for instance, diabetes, hypertension, high cholesterol levels, atherosclerosis and smoking) constitute risk factors for AD as well, suggesting that functional vascular abnormalities may contribute to AD pathology. We studied the effect of A beta on endothelin-1 induced vasoconstriction in isolated human cerebral arteries collected following rapid autopsies. We report that freshly solubilized A beta enhances endothelin-1 induced vasoconstriction in isolated human middle cerebral and basilar arteries. The vasoactive effect of A beta in these large human cerebral arteries is inhibited by NS-398, a selective cyclooxygenase-2 inhibitor and by SB202190, a specific p38 Mitogen Activated Protein Kinase inhibitor suggesting the involvement of a pro-inflammatory pathway. Using a scanner laser Doppler imager, we observed that cerebral blood flow is decreased in the double transgenic APPsw Alzheimer mouse (PS1/APPsw) compared to PS1 littermates and can be improved by chronic treatment with either NS-398 or SB202190. Altogether, our data suggest a link between inflammation and the compromised cerebral hemodynamics in AD.

Molecular modeling of p38α mitogen-activated protein kinase inhibitors through 3D-QSAR and molecular dynamics simulations

The p38 mitogen-activated protein kinase (MAPK) signaling pathway plays an essential role in inflammation and other physiological processes. Because specific inhibitors of p38α and p38β MAPK block the production of the major inflammatory cytokines and other proteins, p38α and p38β MAPK represent promising targets for the treatment of inflammation. In this work, a series of p38α inhibitors based on the structural scaffold of 4-benzoyl-5-aminopyrazole were analyzed using a combination of molecular modeling techniques. We generated three-dimensional quantitative structure-activity relationship (3D-QSAR) models for both comparative molecular field analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA) to highlight the structural requirements for p38 MAPK inhibition. Furthermore, we employed molecular dynamics (MD) simulations and the MM/GBSA method to compare the binding modes and binding free energies of a potent and selective compound interacting with p38α, p38β, p38γ, and p38δ MAPK in detail. Contour maps generated via 3D-QSAR analysis identified several key interactions that were also indicated through MD simulations. The binding free energies calculated via the MM/GBSA method were strongly correlated with experimentally observed biological activities and explained the selective inhibition of p38α and p38β, but not p38γ and p38δ detected here. On the basis of the obtained results, we provide insights regarding the development of novel potent p38α MAPK inhibitors.

Mechanism(s) Involved in Carbon Monoxide-releasing Molecule-2-mediated Cardioprotection During Ischaemia-reperfusion Injury in Isolated Rat Heart

The purpose of the present study was to determine the mechanism(s) involved in carbon monoxide-releasing molecule-2, carbon monoxide-releasing molecule-2-induced cardioprotection. We used the transition metal carbonyl compound carbon monoxide-releasing molecule-2 that can act as carbon monoxide donor in cardiac ischaemia-reperfusion injury model using isolated rat heart preparation. Langendorff's perfused rat hearts when treated with carbon monoxide-releasing molecule-2 (50 μM) for 10 min before global ischaemia exhibited significant reduction in postischaemic levels of myocardial injury markers, creatine kinase and lactate dehydrogenase in coronary effluent. Similarly, pretreatment with carbon monoxide-releasing molecule-2 showed significantly improved postischaemic recovery of heart rate, coronary flow rate, cardiodynamic parameters and reduced infarct size as compared to vehicle control hearts. Perfusion with p38 mitogen-activated protein kinase inhibitor, SB203580, a specific inhibitor of α and β isoform, before and concomitantly with carbon monoxide-releasing molecule-2 treatment abolished carbon monoxide-releasing molecule-2-induced cardioprotection. However, p38 mitogen-activated protein kinase alpha inhibitor, SCIO-469, was unable to inhibit the cardioprotective effect of carbon monoxide-releasing molecule-2. Furthermore, protective effect of carbon monoxide-releasing molecule-2 was significantly inhibited by the protein kinase C inhibitor, chelerythrine, when added before and concomitantly with carbon monoxide-releasing molecule-2. It was also observed that, perfusion with phosphatidylinositol 3-kinase inhibitor, wortmannin, before and concomitantly with carbon monoxide-releasing molecule-2 was not able to inhibit carbon monoxide-releasing molecule-2-induced cardioprotection. Interestingly, we observed that wortmannin perfusion before ischaemia and continued till reperfusion significantly inhibited carbon monoxide-releasing molecule-2-mediated cardioprotection. Our findings suggest that the carbon monoxide-releasing molecule-2 treatment may activate the p38 mitogen-activated protein kinase β and protein kinase C pathways before ischaemia and phosphatidylinositol 3-kinase pathway during reperfusion which may be responsible for the carbon monoxide-releasing molecule-2-mediated cardioprotective effect.

The mitogen-activated protein kinase p38α regulates tubular damage in murine anti-glomerular basement membrane nephritis

p38 mitogen-activated protein kinase (MAPK) is thought to play a central role in acute and chronic inflammatory responses. Whether p38MAPK plays a pathogenic role in crescentic GN (GN) and which of its four isoforms is preferentially involved in kidney inflammation is not definitely known. We thus examined expression and activation of p38MAPK isoforms during anti-glomerular basement membrane (GBM) nephritis. Therefore, p38α conditional knockout mice (MxCre-p38α^Δ/Δ) were used to examine the role of p38α in anti-GBM induced nephritis. Both wild type and MxCre-p38α^Δ/Δ mice developed acute renal failure over time. Histological examinations revealed a reduced monocyte influx and less tubular damage in MxCre-p38α^Δ/Δ mice, whereas glomerular crescent formation and renal fibrosis was similar. Likewise, the levels of pro- and anti-inflammatory cytokines such as TNF, IL-1 and IL-10 were similar, but IL-8 was even up-regulated in MxCre-p38α^Δ/Δ mice. In contrast, we could detect strong down-regulation of chemotactic cytokines such as CCL-2, -5 and -7, in the kidneys of MxCre-p38α^Δ/Δ mice. In conclusion, p38α is the primary p38MAPK isoform expressed in anti-GBM nephritis and selectively affects inflammatory cell influx and tubular damage. Full protection from nephritis is however not achieved as renal failure and structural damage still occurs.

Modulation of Neuronal Survival Factor MEF2 by Kinases in Parkinson's Disease

Parkinson’s disease (PD) is the second most common neurodegenerative disorder due to selective death of neurons in the substantia nigra pars compacta. The cause of cell death remains largely unknown. Myocyte enhancer factor 2 (MEF2) is a group of transcriptional factors required to regulate neuronal development, synaptic plasticity, as well as survival. Recent studies show that MEF2 functions are regulated in multiple subcellular organelles and suggest that dysregulation of MEF2 plays essential roles in the pathogenesis of PD. Many kinases associated with transcription, translation, protein misfolding, autophagy, and cellular energy homeostasis are involved in the neurodegenerative process. Following the first demonstration that mitogen-activated protein kinase p38 (p38 MAPK) directly phosphorylates and activates MEF2 to promote neuronal survival, several other kinase regulators of MEF2s have been identified. These include protein kinase A and extracellular signal regulated kinase 5 as positive MEF2 regulators, and cyclin-dependent kinase 5 (Cdk5) and glycogen synthase kinase 3β as negative regulators in response to diverse toxic signals relevant to PD. It is clear that MEF2 has emerged as a key point where survival and death signals converge to exert their regulatory effects, and dysregulation of MEF2 function in multiple subcellular organelles may underlie PD pathogenesis. Moreover, several other kinases such as leucine-rich repeat kinase 2 and PTEN-induced putative kinase 1 (PINK1) are of particular interest due to their potential interaction with MEF2.

Mechanism for p38α-mediated experimental autoimmune encephalomyelitis

One of the mitogen-activated protein kinases, p38, has been found to play a crucial role in various inflammatory responses. In this study, we analyzed the roles of p38α in multiple sclerosis, using an animal model, experimental autoimmune encephalomyelitis (EAE). p38α(+/-) mice (p38α(-/-) showed embryonic lethality) showed less severe neurological signs than WT mice. Adoptive transfer of lymph node cells (LNC) from sensitized WT mice with MOG(35-55) to naive WT-induced EAE was much more severe compared with the case using LNC from sensitized p38α(+/-) mice. Comprehensive analysis of cytokines from MOG(35-55)-challenged LNC by Western blot array revealed that production of IL-17 was significantly reduced by a single copy disruption of the p38α gene or a p38 inhibitor. Likewise, by a luciferase reporter assay, an electrophoresis mobility shift assay, and characterization of the relationship between p38 activity and IL-17 mRNA expression, we confirmed that p38 positively regulates transcription of the Il17 gene. Furthermore, oral administration of a highly specific p38α inhibitor (UR-5269) to WT mice at the onset of EAE markedly suppressed the progression of EAE compared with a vehicle group. These results suggest that p38α participates in the pathogenesis of EAE through IL-17 induction.

p38γ mitogen-activated protein kinase (MAPK) confers breast cancer hormone sensitivity by switching estrogen receptor (ER) signaling from classical to nonclassical pathway via stimulating ER phosphorylation and c-Jun transcription

Estrogen receptor (ER) α promotes breast cancer growth by regulating gene expression through classical estrogen response element (ERE) binding and nonclassical (interaction with c-Jun at AP-1 sites) pathways. ER is the target for anti-estrogens such as tamoxifen (TAM). However, the potential for classical versus nonclassical ER signaling to influence hormone sensitivity is not known. Moreover, anti-estrogens frequently activate several signaling cascades besides the target ER, and the implications of these "off-target" signaling events have not been explored. Here, we report that p38γ MAPK is selectively activated by treatment with TAM. This results in both phosphorylation of ER at Ser-118 and stimulation of c-Jun transcription, thus switching ER signaling from the classical to the nonclassical pathway leading to increased hormone sensitivity. Unexpectedly, phosphorylation at Ser-118 is required for ER to bind both p38γ and c-Jun, thereby promoting ER relocation from ERE to AP-1 promoter sites. Thus, ER/Ser-118 phosphorylation serves as a central mechanism by which p38γ regulates signaling transduction of ER with its inhibitor TAM.