TPL2 meets p38MAPK: emergence of a novel positive feedback loop in inflammation

Function and Mechanism of Abscisic Acid on Microglia-Induced Neuroinflammation in Parkinson's Disease

Parkinson's disease (PD), as a neurologically implemented disease with complex etiological factors, has a complex and variable pathogenesis. Accompanying further research, neuroinflammation has been found to be one of the possible factors in its pathogenesis. Microglia, as intrinsic immune cells in the brain, play an important role in maintaining microenvironmental homeostasis in the brain. However, over-activation of neurotoxic microglia in PD promotes neuroinflammation, which further increases dopaminergic (DA) neuronal damage and exacerbates the disease process. Therefore, targeting and regulating the functional state of microglia is expected to be a potential avenue for PD treatment. In addition, plant extracts have shown great potential in the treatment of neurodegenerative disorders due to their abundant resources, mild effects, and the presence of multiple active ingredients. However, it is worth noting that some natural products have certain toxic side effects, so it is necessary to pay attention to distinguish medicinal ingredients and usage and dosage when using to avoid aggravating the progression of diseases. In this review, the roles of microglia with different functional states in PD and the related pathways inducing microglia to transform into neuroprotective states are described. At the same time, it is discussed that abscisic acid (ABA) may regulate the polarization of microglia by targeting them, promote their transformation into neuroprotective state, reduce the neuroinflammatory response in PD, and provide a new idea for the treatment of PD and the selection of drugs.

Recent advances in anti-inflammatory active components and action mechanisms of natural medicines

Inflammation is a series of reactions caused by the body's resistance to external biological stimuli. Inflammation affects the occurrence and development of many diseases. Anti-inflammatory drugs have been used widely to treat inflammatory diseases, but long-term use can cause toxic side-effects and affect human functions. As immunomodulators with long-term conditioning effects and no drug residues, natural products are being investigated increasingly for the treatment of inflammatory diseases. In this review, we focus on the inflammatory process and cellular mechanisms in the development of diseases such as inflammatory bowel disease, atherosclerosis, and coronavirus disease-2019. Also, we focus on three signaling pathways (Nuclear factor-kappa B, p38 mitogen-activated protein kinase, Janus kinase/signal transducer and activator of transcription-3) to explain the anti-inflammatory effect of natural products. In addition, we also classified common natural products based on secondary metabolites and explained the association between current bidirectional prediction progress of natural product targets and inflammatory diseases.

Tumor progression locus 2 (TPL2): A Cot-plicated progression from inflammation to chronic liver disease

The cytoplasmic protein tumor progression locus 2 (TPL2), also known as cancer Osaka thyroid (Cot), or MAP3K8, is thought to have a significant role in a variety of cancers and illnesses and it is a key component in the activation pathway for the expression of inflammatory mediators. Despite the tight connection between inflammation and TPL2, its function has not been extensively studied in chronic liver disease (CLD), a major cause of morbidity and mortality worldwide. Here, we analyze more in detail the significance of TPL2 in CLD to shed light on the pathological and molecular transduction pattern of TPL2 during the progression of CLD. This might result in important advancements and enable progress in the diagnosis and treatment of CLD.

Suhuang Antitussive Capsule Ameliorates Corticosteroid Insensitivity in Cough Variant Asthma Guinea Pigs by Inhibiting p38 MAPK Signal Pathway

Methods

The CVA guinea pig model was successfully established by use of ovalbumin (OVA) sensitization and cigarette smoke (CS) exposure. The guinea pigs were divided into 6 groups: a control group, an OVA model group, an OVA + CS model group, a Suhuang treatment group, a BUD treatment group, and a combination (Suhuang and BUD) treatment group. The effects of the treatment were determined by measuring lung function (RI/Cydn) and cough symptoms (coughs number/cough latency) as outcome criteria. The levels of inflammatory cytokines in bronchoalveolar lavage fluid (BALF) were determined by ELISA. Lung tissues were stained by hematoxylin and eosin (H&E). The expressions of GR/total p38 MAPK/p-p38 MAPK were detected by Western blot. The MKP-1 mRNA levels were detected by RT-PCR.

Results

Combination treatment significantly decreased RI/coughs numbers and increased Cydn/cough latency. Significantly, the results indicated that combination treatment decreased injury to pulmonary tissues. Results also revealed that levels of inflammatory cytokines were reduced in all treatment groups but most markedly in the combination treatment group. Moreover, Suhuang treatment significantly ameliorated corticosteroid insensitivity by improving the expression of glucocorticoid receptors (GR). The expressions of total p38 MAPK and p-p38 MAPK in lung tissue were significantly inhibited in the Suhuang and combination treatment groups. The MKP-1 mRNA levels in Suhuang and combination treatment groups were also increased significantly.

Conclusion

Suhuang was effective for reversing corticosteroid insensitivity by regulating the p38 MAPK signal pathway, and combining BUD and Suhuang treatment showed synergistic interactions in CVA guinea pigs. Our findings showed that this combination therapy might be a promising therapeutic agent for CVA and also clarified its underlying mechanism of action, providing a theoretical basis for clinical combination treatment with Suhuang and BUD in CVA patients.

Comparative Transcriptome Analysis of Spleen Reveals Potential Regulation of Genes and Immune Pathways Following Administration of Aeromonas salmonicida subsp. masoucida Vaccine in Atlantic Salmon (Salmo salar)

Aeromonas salmonicida is a global fish pathogen. Aeromonas salmonicida subsp. masoucida (ASM) is classified as atypical A. salmonicida and caused huge losses to salmonid industry in China. Hence, it is of great significance to develop ASM vaccine and explore its protection mechanism in salmonids. In this regard, we conducted RNA-seq analysis with spleen tissue of Atlantic salmon after ASM vaccination to reveal genes, their expression patterns, and pathways involved in immune protections. In our results, a total of 441.63 million clean reads were obtained, and 389.37 million reads were mapped onto the Atlantic salmon reference genome. In addition, 1125, 2126, 1098, 820, and 1351 genes were significantly up-regulated, and 747, 2626, 818, 254, and 908 genes were significantly down-regulated post-ASM vaccination at 12 h, 24 h, 1 month, 2 months, and 3 months, respectively. Subsequent pathway analysis revealed that many differentially expressed genes (DEGs) following ASM vaccination were involved in cytokine-cytokine receptor interaction (TNFRSF11b, IL-17RA, CCR9, and CXCL11), HTLV-I infection (MR1 and HTLV-1), MAPK signaling pathway (MAPK, IL8, and TNF-α-1), PI3K-Akt signaling pathway (PIK3R3, THBS4, and COL2A1), and TNF signaling pathway (PTGS2, TNFRSF21-l, and CXCL10). Finally, the results of qRT-PCR showed a significant correlation with RNA-seq results, suggesting the reliability of RNA-seq for gene expression analysis. This study provided insights into regulation of gene expression and their involved pathways in Atlantic salmon spleen in responses to vaccine, and set the foundation for further study on the vaccine protective mechanism in Atlantic salmon as well as other teleost species.

Foot-and-Mouth Disease Virus Structural Protein VP1 Destroys the Stability of TPL2 Trimer by Degradation TPL2 to Evade Host Antiviral Immunity

Tumor progression locus 2 (TPL2) is a serine/threonine kinase that belongs to the mitogen-activated protein 3 kinase (MAP3K) family, and it plays an important role in pathogen infection. The trimer complex of TPL2, p105, and ABIN2 is essential for maintenance of TPL2 steady-state levels and host cell response to pathogens. Foot-and-mouth disease virus (FMDV) is a positive-strand RNA virus of the family Picornaviridae that encodes proteins capable of antagonizing host immune responses to achieve infection. The VP1 protein of FMDV is a multifunctional protein that can bind host cells and induce an immune response as well as cell apoptosis. However, the role and mechanisms of TPL2 in FMDV infection remain unknown. Here, we determined that FMDV infection could inhibit TPL2, p105, and ABIN2 at the transcription and protein levels, while VP1 could only inhibit TPL2, p105 and ABIN2 at protein level. TPL2 inhibited the replication of FMDV in vivo and in vitro, the 268 to 283 amino-acid region in the TPL2 kinase domain was essential for interaction with VP1. Moreover, VP1 promoted K48-linked polyubiquitination of TPL2 and degraded TPL2 by the proteasome pathway. However, VP1-induced degradation of p105 and ABIN2 was independent of proteasome, autophagy, lysosome, and caspase-dependent pathways. Further studies showed that VP1 destroyed the stability of the TPL2-p105-ABIN2 complex. Taken together, these results revealed that VP1 antagonized TPL2-meditated antivirus activity by degrading TPL2 and destroying its complex. These findings may contribute to understand FMDV-host interactions and improve development of a novel vaccine to prevent FMDV infection.Importance Virus-host interactions are critical for virus infection. This study was the first to demonstrate the antiviral effect of host TPL2 during FMDV replication by increasing production of interferons and antiviral cytokines. Both FMDV and VP1 protein can reduce host TPL2, ABIN2 and p105 to destroy TPL2-p105-ABIN2 trimer complex. VP1 interacted with TPL2 and degrade TPL2 via proteasome pathway to repress TPL2-mediated antivirus activity. This study provided new insights into FMDV immune evasion mechanisms, elucidating new informations regarding FMDV counteraction of host antivirus activity.

Kinase inhibition in autoimmunity and inflammation

Despite recent advances in the treatment of autoimmune and inflammatory diseases, unmet medical needs in some areas still exist. One of the main therapeutic approaches to alleviate dysregulated inflammation has been to target the activity of kinases that regulate production of inflammatory mediators. Small-molecule kinase inhibitors have the potential for broad efficacy, convenience and tissue penetrance, and thus often offer important advantages over biologics. However, designing kinase inhibitors with target selectivity and minimal off-target effects can be challenging. Nevertheless, immense progress has been made in advancing kinase inhibitors with desirable drug-like properties into the clinic, including inhibitors of JAKs, IRAK4, RIPKs, BTK, SYK and TPL2. This Review will address the latest discoveries around kinase inhibitors with an emphasis on clinically validated autoimmunity and inflammatory pathways.

Effect of Acupuncture on the p38 Signaling Pathway in Several Nervous System Diseases: A Systematic Review

Acupuncture is clinically used to treat various diseases and exerts positive local and systemic effects in several nervous system diseases. Advanced molecular and clinical studies have continually attempted to decipher the mechanisms underlying these effects of acupuncture. While a growing understanding of the pathophysiology underlying several nervous system diseases shows it to be related to inflammation and impair cell regeneration after ischemic events, the relationship between the therapeutic mechanism of acupuncture and the p38 MAPK signal pathway has yet to be elucidated. This review discusses the latest advancements in the identification of the effect of acupuncture on the p38 signaling pathway in several nervous system diseases. We electronically searched databases including PubMed, Embase, and the Cochrane Library from their inception to April 2020, using the following keywords alone or in various combinations: "acupuncture", "p38 MAPK pathway", "signaling", "stress response", "inflammation", "immune", "pain", "analgesic", "cerebral ischemic injury", "epilepsy", "Alzheimer's disease", "Parkinson's disease", "dementia", "degenerative", and "homeostasis". Manual acupuncture and electroacupuncture confer positive therapeutic effects by regulating proinflammatory cytokines, ion channels, scaffold proteins, and transcription factors including TRPV1/4, Nav, BDNF, and NADMR1; consequently, p38 regulates various phenomena including cell communication, remodeling, regeneration, and gene expression. In this review article, we found the most common acupoints for the relief of nervous system disorders including GV20, GV14, ST36, ST37, and LI4. Acupuncture exhibits dual regulatory functions of activating or inhibiting different p38 MAPK pathways, contributing to an overall improvement of clinical symptoms and function in several nervous system diseases.

The evolutionarily conserved MAPK/Erk signaling promotes ancestral T-cell immunity in fish via c-Myc-mediated glycolysis

The mitogen-activated protein kinase (MAPK) cascade is an ancient and evolutionarily conserved signaling pathway involved in numerous physiological processes. Despite great advances in understanding MAPK-mediated regulation of adaptive immune responses in mammals, its contribution to T-cell immunity in early vertebrates remains unclear. Herein, we used Nile tilapia (Oreochromis niloticus) to investigate the regulatory roles of MAPK/extracellular signal-regulated kinase (Erk) signaling in ancestral T-cell immunity of jawed fish. We found that Nile tilapia possesses an evolutionarily conserved MAPK/Erk axis that is activated through a classical three-tier kinase cascade, involving sequential phosphorylation of RAF proto-oncogene serine/threonine-protein kinase (Raf), MAPK/Erk kinase 1/2 (Mek1/2), and Erk1/2. In Nile tilapia, MAPK/Erk signaling participates in adaptive immune responses during bacterial infection. Upon T-cell activation, the MAPK/Erk axis is robustly activated, and MAPK/Erk blockade by specific inhibitors severely impairs T-cell activation. Furthermore, signals from MAPK/Erk were indispensable for primordial T cells to proliferate and exert their effector functions. Mechanistically, activation of the MAPK/Erk axis promoted glycolysis via induction of the transcriptional regulator proto-oncogene c-Myc (c-Myc), to ensure the proper activation and proliferation of fish T cells. Our results reveal the regulatory mechanisms of MAPK/Erk signaling in T-cell immunity in fish and highlight a close link between immune signals and metabolic programs. We propose that regulation of T-cell immunity by MAPK/Erk is a basic and sophisticated strategy that evolved before the emergence of the tetrapod lineage. These findings shed light on the evolution of the adaptive immune system.

Low Cellular NAD+ Compromises Lipopolysaccharide-Induced Inflammatory Responses via Inhibiting TLR4 Signal Transduction in Human Monocytes

NAD⁺ is an essential cofactor in reduction-oxidation metabolism with impact on metabolic and inflammatory diseases. However, data elucidating the effects of NAD⁺ on the proinflammatory features of human primary monocytes are scarce. In this study, we explored how NAD⁺ affects TLR4 and NOD-like receptor with a PYD-domain 3 (NLRP3) inflammasome activation, two key innate immune responses. Human primary monocytes were isolated from buffy coats obtained from healthy individuals. Intracellular NAD⁺ was manipulated by nicotinamide riboside and the NAMPT inhibitor FK866. Cells were primed with LPS with or without subsequent NLRP3 activation with ATP or cholesterol crystals to analyze the effects of NAD⁺ levels on TLR4-mediated NF-κB activation and NLRP3 activity, respectively. Cytokine release was quantified, and the downstream signal pathway of TLR4 was investigated with Western blot and proteomic analysis. The impact of sirtuin and PARP inhibition was also explored. Our main findings were: 1) elevated NAD⁺ enhanced IL-1β release in LPS-primed human monocytes exposed to ATP in vitro, 2) both NLRP3-dependent and -independent inflammatory responses in LPS-exposed monocytes were inhibited by NAD⁺ depletion with FK866, 3) the inhibition was not caused by suppression of sirtuins or PARP1, and 4) phosphorylation of several proteins TLR4 signal pathway was inhibited by FK866-mediated NAD⁺ depletion, specifically TAK1, IKKβ, IkBα, MEK 1/2, ERK 1/2, and p38. Hence, we suggest a novel mechanism in which NAD⁺ affects TLR4 signal transduction. Furthermore, our data challenge previous reports of the interaction between NAD⁺ and inflammation and question the use of nicotinamide riboside in the therapy of inflammatory disorders.

Antagonistic Property of G2013 (α-L-Guluronic Acid) on Gene Expression of MyD88, Tollip, and NF-κB in HEK293 TLR2 and HEK293 TLR4

INTRODUCTION

Inhibition of Toll-like receptors (TLRs) signaling plays a crucial role in suppressing the inflammation and available data presenting G2013 as an immunomodulatory agent, therefore, we designed this study to answer whether G2013 can affect the signaling pathway of TLR2 and TLR4.

METHODS

Cytotoxicity study of G2013 was performed by MTT assay. HEK293 TLR2 and HEK293 TLR4 cell lines were cultured and treated with low dose (5µg/ml) and high dose (25µg/ml) of G2013 for 24 hours. Gene expressions of MyD88, Tollip, and NF-κB were defined by quantitative real-time PCR.

RESULTS

The cytotoxicity assay showed that the concentrations lesser than 125μg/ml of G3012 had no apparent cytotoxicity, however, the concentrations of 5µg/ml and 25µg/ml could suppress the mRNA expression of MyD88, Tollip and NF-κB in HEK293 TLR2 and HEK293 TLR4 cell lines.

CONCLUSION

in our study, we verified the linkage between the immunosuppressive property of G2013 and TLR2, TLR4 signaling cascade; but so far, the specific target of G2013 and its molecular mechanism has not been detected yet. We recommend further studies on other Patten Recognition Receptors (PRRs)and other mechanisms of inflammation like oxidative stress to be conducted in the future.

Advancement in TPL2-regulated innate immune response

Tumor progression locus 2 (TPL2) is a serine/threonine kinase that belongs to the MAP3K family. The activated TPL2 regulates the innate immune-relevant signaling pathways, such as ERK, JNK, and NF-κB, and the differentiation of immune cells, for example, CD4+ T and NK cells. Therefore, TPL2 plays a critical role in regulating the innate immune response. The present review summarizes the recent advancements in the TPL2-regulated innate immune response.

Tumor Progression Locus 2 in Hepatocytes Potentiates Both Liver and Systemic Metabolic Disorders in Mice

Tumor progression locus 2 (TPL2), a serine/threonine kinase, has been regarded as a potentially interesting target for the treatment of various diseases with an inflammatory component. However, the function of TPL2 in regulating hepatocyte metabolism and liver inflammation during the progression of nonalcoholic fatty liver disease (NAFLD) is poorly understood. Here, we report that TPL2 protein expression was significantly increased in fatty liver from diverse species, including humans, monkeys, and mice. Further investigations revealed that compared to wild-type (WT) littermates, hepatocyte-specific TPL2 knockout (HKO) mice exhibited improved lipid and glucose imbalance, reserved insulin sensitivity, and alleviated inflammation in response to high-fat diet (HFD) feeding. Overexpression of TPL2 in hepatocytes led to the opposite phenotype. Regarding the mechanism, we found that mitogen-activated protein kinase kinase 7 (MKK7) was the specific substrate of TPL2 for c-Jun N-terminal kinase (JNK) activation. TPL2-MKK7-JNK signaling in hepatocytes represents a promising drugable target for treating NAFLD and associated metabolic disorders. Conclusion: In hepatocytes, TPL2 acts as a key mediator that promotes both liver and systemic metabolic disturbances by specifically increasing MKK7-JNK activation.

p38γ and p38δ: From Spectators to Key Physiological Players

Although the physiological roles of p38γ and p38δ signalling pathways are largely unknown, new genetic and pharmacological tools are providing groundbreaking information on the function of these two stress-activated protein kinases. Recent studies show the importance of p38γ and p38δ in the regulation of processes as diverse as cytokine production, protein synthesis, exocytosis, cell migration, gene expression, and neuron activity, which have an acute impact on the development of pathologies related to inflammation, diabetes, neurodegeneration, and cancer. These recent breakthroughs are resolving some of the questions that have long been asked regarding the function of p38γ and p38δ in biology and pathology.