Signal-regulated Kinase Mitogen-activated Protein Research Articles

PP2C phosphatase Pic6 suppresses MAPK activation and disease resistance in tomato.

Type 2C protein phosphatases (PP2Cs) are essential for regulating plant immune responses to pathogens. Our study focuses on the tomato PP2C-immunity associated candidate 6 (Pic6), elucidating its role in negatively regulating pattern-triggered immunity (PTI) signaling pathways in tomato. Using reverse transcription quantitative polymerase chain reaction (RT-qPCR), we observed that treatment with microbe-associated molecular patterns (MAMPs)- flg22 and flgII-28-significantly increased Pic6 mRNA levels in wild-type (RG-PtoR) tomato plants. Pic6 features a conserved N-terminal kinase-interacting motif (KIM) and a C-terminal PP2C domain. We produced variants of Pic6 with mutations in these regions, demonstrating their involvements in negatively regulating tomato immunity. Agrobacterium-mediated transient overexpression of Pic6 resulted in enhanced growth of the bacterial pathogen Pseudomonas syringae pv. tomato (Pst) strain DC3000ΔhopQ1-1 compared to a YFP control. Additionally, Pic6 overexpression inhibited mitogen-activated protein kinase (MAPK) activation in response to flg22 and flgII-28 treatments. Importantly, Pic6 exhibited phosphatase activity and interacted with tomato Mkk1/Mkk2 proteins and dephosphorylated them in a KIM-dependent manner. Furthermore, we generated RG-pic6 loss-of-function mutants by CRISPR/Cas9, revealing that the absence of Pic6 heightened MAPK activity and increased resistance to Xanthomonas euvesicatoria strain 85-10 (Xe 85-10) when compared with the wild-type (RG-PtoR) plants. Transcript analyses showed that after flg22/flgII-28 treatment, PTI-reporter genes NAC and osmotin were significantly upregulated in RG-pic6 mutants in comparison to the wild-type (RG-PtoR) plants. Overall, our findings indicate that Pic6 acts as a negative regulator of MAPK signaling and playing a pivotal role in modulating tomato immunity against bacterial pathogens.

EIF4F controls ERK MAPK signaling in melanomas with BRAF and NRAS mutations

The eIF4F translation initiation complex plays a critical role in melanoma resistance to clinical BRAF and MEK inhibitors. In this study, we uncover a function of eIF4F in the negative regulation of the rat sarcoma (RAS)/rapidly accelerated fibrosarcoma (RAF)/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) signaling pathway. We demonstrate that eIF4F is essential for controlling ERK signaling intensity in treatment-naïve melanoma cells harboring BRAF or NRAS mutations. Specifically, the dual-specificity phosphatase DUSP6/MKP3, which acts as a negative feedback regulator of ERK activity, requires continuous production in an eIF4F-dependent manner to limit excessive ERK signaling driven by oncogenic RAF/RAS mutations. Treatment with small-molecule eIF4F inhibitors disrupts the negative feedback control of MAPK signaling, leading to ERK hyperactivation and EGR1 overexpression in melanoma cells in vitro and in vivo. Furthermore, our quantitative analyses reveal a high spare signaling capacity in the ERK pathway, suggesting that eIF4F-dependent feedback keeps the majority of ERK molecules inactive under normal conditions. Overall, our findings highlight the crucial role of eIF4F in regulating ERK signaling flux and suggest that pharmacological eIF4F inhibitors can disrupt the negative feedback control of MAPK activity in melanomas with BRAF and NRAS activating mutations.

Dachaihu Decoction alleviates chronic pancreatitis by regulating MAPK signaling pathway: Insights from network pharmacology and experimental validation

Ethnopharmacological relevanceChronic pancreatitis (CP), a syndrome characterized by inflammatory fibrosis, can impair both the internal and external secretory functions of the pancreas. The global incidence of this disease is gradually increasing. However, the exact pathogenesis remains unclear, resulting in a lack of targeted clinical therapies. According to the principles of traditional Chinese medicine, CP can be attributed to Shaoyang and Yangming syndromes, which manifest as abdominal pain and hypochondriac distension. Dachaihu Decoction (DCHD) is a classic formula from the “Treatise on Febrile and Miscellaneous Disease.” It is frequently prescribed for conditions associated with combined Shaoyang and Yangming syndromes. However, the specific mechanisms by which DCHD prevents and treats CP remain unclear and require further investigation. Aim of the studyUsing a holistic methodology, including network pharmacology, molecular docking, transcriptomic profiling, and animal experimentation, we explored the potential therapeutic mechanisms of DCHD in CP. Materials and methodsIn a mouse model, caerulein was used to induce CP, and DCHD was administered via gastric lavage to assess its therapeutic effect on pancreatic injury caused by caerulein-induced CP. Subsequently, pancreatic tissues were collected for transcriptomic analysis. Screening of DCHD-active ingredient-target pathways for CP treatment was conducted using network pharmacology and further preliminary validation was performed using molecular docking techniques. Additionally, in vivo and in vitro validation was conducted using animal and cells experiments based on the predicted results. ResultsOur findings suggest that DCHD ameliorates pancreatic acinar cell injury, pancreatic inflammation, and fibrosis in mice with CP. Network pharmacology identified 385 potential targets of DCHD associated with CP. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that the therapeutic effect of DCHD on CP may be linked to the mitogen-activated protein kinase (MAPK) signaling pathway. Transcriptomic data supported this finding, as it confirmed that DCHD inhibited the pancreatic MAPK signaling pathway in CP. Molecular docking studies further revealed that the top ten active components of DCHD exhibited strong docking activity with key molecules within the MAPK signaling pathway. Finally, animal experiments confirmed that DCHD effectively reduced the phosphorylation of P38, Jun N-terminal kinase (JNK), and extracellular signal-regulated kinase (ERK) in pancreatic tissues. In addition, the expression of p-P38, p-JNK, and p-ERK was reduced in pancreatic stellate cells and macrophages in the DCHD group. We further treated CP mice, human pancreatic stellate cell line (hPSCs), and macrophage cell line RAW264.7 with the active component baicalin from DCHD, and found that baicalin effectively reduced pancreatic damage in CP. Additionally, the expression of key proteins in the MAPK signaling pathway was significantly decreased in both hPSCs and RAW264.7. ConclusionIn summary, DCHD plays an important role in the treatment of chronic pancreatitis, and it may become a promising drug against the progression of CP. The role of DCHD in alleviating pancreatic inflammatory cell infiltration and fibrosis may be related to the regulation of the MAPK signaling pathway.

Silencing miR-155–5p alleviates hippocampal damage in kainic acid-induced epileptic rats via the Dusp14/MAPK pathway

Epilepsy with recurrent seizures is characterized by neuronal damage and glial proliferation induced by brain inflammation. Recurrent seizures can lead to changes in the microRNA (miRNA) spectrum, significantly influencing the inflammatory response of microglia. MiR-155–5p, as a pro-inflammatory miRNA, is increased in the epileptic brain. However, its specific role in acute seizures remains unknown. The study aimed to develop a new strategy for treating epilepsy by investigating how silencing of miR-155–5p initiated its anticonvulsive mechanism. The level of miR-155–5p was up-regulated in the hippocampus of epileptic immature rats induced by kainic acid (KA). The use of antago-miR-155–5p exerted significant beneficial effects on the seizure scores, brain discharges and cognition in immature rats following KA-induced epilepsy. Antago-miR-155–5p also inhibited neuron damage and microglial activation. Moreover, the silencing of miR-155–5p significantly inhibited the Dual-specificity phosphatase 14 (Dusp14)/ mitogen-activated protein kinase (MAPK) axis in vivo. MiR-155–5p interacted with dusp14 to regulate MAPK signaling way expression, verified by a dual-luciferase reporter assay. The results suggested that the silencing of miR-155–5p might reduce hippocampal damage in epileptic immature rats induced by KA via Dusp14/MAPK signaling way. This implied that miR-155–5p could serve as a therapeutic tool to prevent the development of epilepsy.

Enzyme Is the Name-Adapter Is the Game.

Signaling proteins in eukaryotes usually comprise a catalytic domain coupled to one or several interaction domains, such as SH2 and SH3 domains. An additional class of proteins critically involved in cellular communication are adapter or scaffold proteins, which fulfill their purely non-enzymatic functions by organizing protein-protein interactions. Intriguingly, certain signaling enzymes, e.g., kinases and phosphatases, have been demonstrated to promote particular cellular functions by means of their interaction domains only. In this review, we will refer to such a function as "the adapter function of an enzyme". Though many stories can be told, we will concentrate on several proteins executing critical adapter functions in cells of the immune system, such as Bruton´s tyrosine kinase (BTK), phosphatidylinositol 3-kinase (PI3K), and SH2-containing inositol phosphatase 1 (SHIP1), as well as in cancer cells, such as proteins of the rat sarcoma/extracellular signal-regulated kinase (RAS/ERK) mitogen-activated protein kinase (MAPK) pathway. We will also discuss how these adaptor functions of enzymes determine or even undermine the efficacy of targeted therapy compounds, such as ATP-competitive kinase inhibitors. Thereby, we are highlighting the need to develop pharmacological approaches, such as proteolysis-targeting chimeras (PROTACs), that eliminate the entire protein, and thus both enzymatic and adapter functions of the signaling protein. We also review how genetic knock-out and knock-in approaches can be leveraged to identify adaptor functions of signaling proteins.

MAPK signaling pathway participates in the regulation of intestinal phosphorus and calcium absorption in broiler chickens via 1,25-dihydroxyvitamin D3

Four experiments were performed to investigate the role of the mitogen-activated protein kinase (MAPK) signaling pathway in intestinal absorption of phosphorus (P) and calcium (Ca) in broiler chickens. Experiment 1 assessed how dietary levels of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) influence the gene expression of intestinal P and Ca transporters in broilers. Experiment 2 evaluated the effects of 1,25(OH)2D3 administered via intraperitoneal injection on the extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (p38MAPK) signaling pathways. Experiments 3 and 4 investigated the effect of ERK and p38MAPK inhibitors on the expression of intestinal P and Ca transporters. The findings demonstrated that broilers (1-21 days old) fed a 1,25(OH)2D3-deficient diet (0.625 µg/kg) exhibited reduced body weight, tibia P and Ca levels, and mRNA levels of P transporters (NaPi-IIb, PiT-1, and PiT-2), Ca transporters (NCX1, PMCA1b, and CaBP-D28k), vitamin D receptors (VDR), ERK, and p38MAPK in the duodenum (Experiment 1) (P < 0.05). By comparison, the growth, bone quality, and mRNA levels of genes (except for duodenal NaPi-IIb) in broilers were similar to those in broilers fed the control diet when dietary 1,25(OH)2D3 was adequate (5 µg/kg) (Experiment 1) (P > 0.05). After intraperitoneal injection of 1,25(OH)2D3, the mRNA level of jejunal NaPi-IIb and the protein level of p-p38MAPK/t-p38MAPK in broilers (9-14 days old) decreased (P < 0.05), whereas the mRNA level of CaBP-D28k and the protein level of p-ERK/t-ERK increased (Experiment 2) (P < 0.05). The mRNA and protein expression of jejunal NaPi-IIb and the protein expression of CaBP-D28k in broilers (9-17 days old) treated with the ERK inhibitor PD98059 were greater than those in the control group (Experiment 3) (P < 0.05). Similarly, compared with control broilers, broilers (9-17 days old) treated with the p38MAPK inhibitor SB203580 showed elevated mRNA expression of jejunal NaPi-IIb and CaBP-D28k (Experiment 4) (P < 0.05). These results suggest that adequate supplementation with 1,25(OH)2D3 (5 µg/kg) can restore broiler growth and bone quality by upregulating the transcription of genes involved in intestinal P and Ca absorption. Additionally, the ERK and p38MAPK signaling pathways are implicated in the modulatory effect of 1,25(OH)2D3 on the absorption of P and Ca in broilers.

Therapeutic effect and mechanism of piracetam for the treatment of spinal cord injury in rats through MAPK pathway

To explore mechanism of piracetam for the treatment of spinal cord injury in rats through mitogen-activated protein kinase (MAPK) pathway. Fifty-four healthy 6-week-old SD female rats with body weight of 80 to 100 g were divided into sham operation group, spinal cord injury group and piracetam group by random number table method, with 18 rats in each group. Spinal cord injury model was established in spinal cord injury group and piracetam group using percussion apparatus, while sham operation group did not damage spinal cord. Piracetam group was injected with piracetam injection through tail vein according to 5 ml·kg-1 standard, once a day for 3 days;the other two groups were injected with normal saline at the same dose, the same frequency and the same duration. The rats were sacrificed at 1, 3, and 7 days after surgery, and changes of Basso, Beattie and Bresnahan (BBB) locomotor rating scale was observed and compared. Enzyme-linked immunosorbent assay (ELISA) was used to detect spinal cord inflammatory factors, such as interleukin-6 (IL-6), interleukin-10 (IL-10), interleukin-1β (interleukin-1β), necrosis factor-α (IL-1β) and tumor necrosis factor-α (TNF-α);HE staining was used to observe morphological changes of rats with spinal cord injury, and immunohistochemistry was used to observe expression level of aquaporin 4 (AQP4). The activation of MAPK signaling pathway in spinal cord of rats after spinal cord injury was observed by western blotting (WB). BBB scores of sham operation group on 1, 3 and 7 day were 21 points. In spinal cord injury group, the scores were (1±1), (4±1) and (7±2);piracetam group was (1±1), (5±1), (9±2), respectively;the difference between spinal cord injury group and sham operation group was statistically significant (P<0.05). HE staining showed that no abnormality was found in sham operation group. In spinal cord injury group, bleeding and degeneration of spinal cord tissue appeared at 1 day after operation; flaky necrotic areas were appeared in spinal cord at 3 days after surgery, and spinal cord tissue began to slowly repair at 7 days after surgery. In piracetam group, the bleeding area was less than that of spinal cord injury group at 1 day after surgery;at 3 days after operation, the necrotic area was reduced and the range of nuclear disappearance was reduced; and the spinal cord began to recover slowly at 7 days after surgery. AQP4 staining of spinal cord of rats in sham operation group was weak at 1, 3 and 7 days after modeling, AQP4 staining was deepened and area increased in spinal cord injury group, AQP4 staining of piracetam group was lighter than that of spinal cord injury group, and the positive cells were slightly increased and the staining was slightly darker than that of sham operation group. At 1, 3 and 7 days, the level of IL-6, IL-10, IL-1β and TNF-α in spinal cord injury group were higher than those in sham operation group and piracetam group(P<0.05). Compared with spinal cord injury group, the area of spinal cord bleeding and necrosis were decreased by HE staining in piracetam group, and AQP4 staining was decreased by immunohistochemistry. WB results showed that P-ERK, P-JNK and P-P38 levels in spinal cord injury group at 3 days were higher than those in sham operation group and piracetam group(P<0.05). Piracetam not only showed significant effect in promoting motor function recovery after spinal cord injury, but also showed positive therapeutic potential in reducing lesion area, regulating AQP4 expression to reduce edema, and reducing inflammatory response by regulating MAPK signaling pathway.

PRDX1 exerts a photoprotection effect by inhibiting oxidative stress and regulating MAPK signaling on retinal pigment epithelium

BackgroundThe purpose of this study was to investigate the photoprotection effect of peroxiredoxin 1 (PRDX1) protein in ultraviolet B (UVB) irradiation-induced damage of retinal pigment epithelium (RPE) and its possible molecular mechanism.MethodsARPE-19 cell viability and apoptosis were assessed by MTT assay and flow cytometry, respectively. Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to detect the PRDX1 expression. The corresponding kits were employed to measure the levels or activities of lactate dehydrogenase (LDH), 8-hydroxy-2-deoxyguanosine (8-OHdG), reactive oxygen species (ROS), malondialdehyde (MDA), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD). Western blotting was applied to examine PRDX1 expression and mitogen-activated protein kinase (MAPK) signaling pathway-related proteins.ResultsAfter exposure to 20 mJ/cm2 intensity of UVB irradiation for 24 h, ARPE-19 cells viability was decreased, the leakage degree of LDH and 8-OHdG were increased, and cell apoptosis was elevated. The expression of PRDX1 was significantly down-regulated in UVB-induced ARPE-19 cells. The low expression of PRDX1 was involved in high irradiation intensity. Overexpression of PRDX1 increased cell activity, decreased cell apoptosis, and LDH as well as 8-OHdG leakage in UVB-induced ARPE-19 cells. In addition to alleviating UVB-induced cell damage, PRDX1 overexpression also inhibited UVB-induced oxidative stress (down-regulation of ROS and MDA levels, up-regulation of GSH-Px and SOD activities) and the activation of MAPK signaling pathway in ARPE-19 cells.ConclusionPRDX1 exerts a photoprotection effect on RPE by attenuating UVB-induced cell damage and inhibiting oxidative stress, which can be attributed to the inhibition of MAPK signaling pathway activation.

Morinda Officinalis-derived extracellular vesicle-like particles: Anti-osteoporosis effect by regulating MAPK signaling pathway

BackgroundPostmenopausal osteoporosis (PMOP) is a systemic bone disease characterized by low bone mass and microstructural damage. Morinda Officinalis (MO) contains various components with anti-PMOP activities. Morinda Officinalis-derived extracellular vesicle-like particles (MOEVLPs) are new active components isolated from MO, and no relevant studies have investigated their anti-osteoporosis effect and mechanism. PurposeTo investigate the alleviating effect of MOEVLPs on PMOP and the underlying mechanism. MethodsDifferential centrifugation and ultracentrifugation were used to isolate MOEVLPs from MO. Transmission electron microscopy (TEM), flow nano analyzer, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), agarose gel electrophoresis, and thin-layer chromatography were employed to characterize MOEVLPs. PMOP mouse models were utilized to examine the anti-PMOP effect of MOEVLPs. H&E and immunohistochemical staining were used for drug safety and osteogenic effect assessment. Mouse embryo osteoblast precursor cells (MC3T3-E1) were used in vitro experiments. CCK-8 kit, alizarin red staining, proteomic, bioinformatic analyses, and western blot were used to explore the mechanism of MOEVLPs. ResultsIn this study, MOEVLPs from MO were successfully isolated and characterized. Animal experiments demonstrated that MOEVLPs exhibited specific femur targeting, were non-toxic to the heart, liver, spleen, lung, kidney, and aorta, and possessed anti-PMOP properties. The ability of MOEVLPs to strengthen bone formation was better than that of alendronate. In vitro experiments, results revealed that MOEVLPs did not significantly enhance osteogenic differentiation in MC3T3-E1 cells. Instead, MOEVLPs promoted the proliferation of MC3T3-E1 cells. Proteomic and bioinformatic analyses suggested that the proliferative effect of MOEVLPs was closely associated with the mitogen-activated protein kinase (MAPK) signaling pathway, particularly the altered expression of cAMP response element-binding protein (CREB) and ribosomal S6 kinase 1 (RSK1). Western blot results further confirmed these findings. ConclusionOur studies successfully isolated high-quality MOEVLPs and demonstrated that MOEVLPs can alleviate PMOP by promoting osteoblast proliferation through the MAPK pathway. MOEVLPs have the potential to become a novel and natural anti-PMOP drug.

Methanol extract of Ligusticum chuanxiong Hort. Rhizome ameliorates bilateral common carotid artery stenosis-induced cognitive deficit in mice by altering microglia and astrocyte activation.

In traditional Asian medicine, Ligusticum chuanxiong Hort also known as Conioselinum anthriscoides "Chuanxiong", is mainly used for improving blood circulation or for analgesic and anti-inflammatory purposes, but they also have a long history of use for pain disorders in the head and face, such as headache. Despite the possibility that the plant is effective for diseases such as cerebral infarction and vascular dementia (VaD), the mechanism of action is not well understood. To determine if the dried rhizomes of L. chuanxiong (Chuanxiong Rhizoma, CR) methanol extract (CRex) has activity in a VaD mice model. Through network analysis, we confirm that CR is effective in cerebrovascular diseases. In mice, we induce cognitive impairment, similar to VaD in humans, by chronically reducing the cerebral blood flow by performing bilateral common carotid artery stenosis (BCAS) and administering CRex for 6weeks. We measure behavioral changes due to cognitive function impairment and use immunofluorescence staining to confirm if CRex can inhibit the activation of astrocytes and microglia involved in the inflammatory response in the brain. We quantify proteins involved in the mechanism, such as mitogen-activated protein kinases (MAPK), in the hippocampus and surrounding white matter, and analyze gene expression and protein interaction networks through RNA sequencing to interpret the results of the study. CRex administration rescued cognitive impairment relating to a novel object and inhibited the activation of astrocytes and microglia. Western blotting analysis revealed that CRex regulated the changes in protein expression involved in MAPK signaling such as extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (p38). The administration of CRex suppressed approximately 44% of the pathological changes in gene expression caused by BCAS. CRex extract effectively inhibited cognitive impairment caused by BCAS, and the mechanism through which this occurred is inhibited activation of astrocytes and microglia.

MiR-147b mediated suppression of DUSP8 promotes lung cancer progression

Dual-specificity phosphatase 8 (DUSP8) plays an important role as a selective c-Jun N-terminal kinase (JNK) phosphatase in mitogen-activated protein kinase (MAPK) signaling. In this study, we found that DUSP8 is silenced by miR-147b in patients with lung adenocarcinoma (LUAD), which correlates with poor overall survival. Overexpression of DUSP8 resulted in a tumor-suppressive phenotype in vitro and in vivo experimental models, whereas silencing DUSP8 with a siRNA approach abrogated the tumor-suppressive properties. We found that miR-147b is a posttranscriptional regulator of DUSP8 that is highly expressed in patients with LUAD and is associated with lower survival. NanoString analysis revealed that the MAPK signaling pathway is mainly affected by overexpression of miR-147b, leading to increased proliferation and migration and decreased apoptosis in vitro. Moreover, induction of miR-147b promotes tumor progression in vitro and in vivo experimental models. Knockdown of miR-147b restored DUSP8, decreased tumor progression in vitro, and increased apoptosis via JNK phosphorylation. These results suggest that miR-147b plays a key role in regulating MAPK signaling in LUAD. The link between DUSP8 and miR-147b may provide novel approaches for the treatment of lung cancer.

Systemic Hemodynamics, Cardiac Mechanics, and Signaling Pathways Induced by Extracorporeal Membrane Oxygenation in a Cardiogenic Shock Model.

Peripheral venoarterial extracorporeal membrane oxygenation (VA-ECMO) is increasingly being used in patients suffering from refractory cardiogenic shock (CS). Although considered life-saving, peripheral VA-ECMO may also be responsible for intracardiac hemodynamic changes, including left ventricular overload and dysfunction. Venoarterial extracorporeal membrane oxygenation may also increase myocardial wall stress and stroke work, possibly affecting the cellular cardioprotective and apoptosis signaling pathways, and thus the infarct size. To test this hypothesis, we investigated the effects of increasing the peripheral VA-ECMO blood flow (25-100% of the baseline cardiac output) on systemic and cardiac hemodynamics in a closed-chest CS model. Upon completion of the experiment, the hearts were removed for assessment of infarct size, histology, apoptosis measurements, and phosphorylation statuses of p38 and protein Kinase B (Akt), and extracellular signal-regulated kinase mitogen-activated protein kinases (ERK-MAPK). Peripheral VA-ECMO restored systemic perfusion but induced a significant and blood flow-dependent increase in left ventricular preload and afterload. Venoarterial extracorporeal membrane oxygenation did not affect infarct size but significantly decreased p38-MAPK phosphorylation and cardiac myocyte apoptosis in the border zone.

Streptolysin S induces proinflammatory cytokine expression in calcium ion-influx-dependent manner

Anginosus group streptococci (AGS) are opportunistic pathogens that reside in the human oral cavity. The β-hemolytic strains of Streptococcus anginosus subsp. anginosus (SAA) produce streptolysin S (SLS), a streptococcal peptide hemolysin. In recent clinical scenarios, AGS, including this species, have frequently been isolated from infections and disorders beyond those in the oral cavity. Consequently, investigating this situation will reveal the potential pathogenicity of AGS to ectopic infections in humans. However, the precise mechanism underlying the cellular response induced by secreted SLS and its relevance to the pathogenicity of AGS strains remain largely unknown. This study aims to elucidate the mechanism underlying the host cellular response of the human acute monocytic leukemia cell line THP-1 to secreted SLS. In THP-1 cells incubated with the culture supernatant of β-hemolytic SAA containing SLS as the sole cytotoxic factor, increased Ca2+ influx and elevated expression of proinflammatory cytokines were observed. Significantly reduced expression of SLS-dependent upregulated cytokine genes under Ca2+-chelating conditions suggests that Ca2+ influx triggers SLS-dependent cellular responses. Furthermore, SLS-dependent enhanced expression of IL-8 was also implicated in the activation of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK) signaling pathways. The findings presented in this study are crucial for a comprehensive understanding of the real pathogenicity of SLS-producing β-hemolytic AGS in the latest clinical situations.

Inhibition of Toll-like Receptor 4 (TLR4) Promotes Erythroid and Myeloid Differentiation in Myelodysplastic Syndrome (MDS) and Acute Myeloid Leukemia (AML)

Introduction: The hallmark of Myelodysplastic Syndrome (MDS) is a block in differentiation of hematopoietic precursors resulting in single or multilineage cytopenias. Evaluation of regulatory pathways that are inappropriately overactive and lead to a blockade in erythroid and myeloid differentiation is an important process in determining future therapeutic targets for the treatment of MDS. The Toll-like receptor (TLR) pathways play an important role in the innate immune response and are also highly expressed on hematopoietic stem cells. Aberrant overactivation of these pathways can stimulate inflammation and cytokine production in the marrow microenvironment. Also, while the overactivation of interleukin-1 receptor-associated kinase 4 (IRAK4), tumor necrosis factor receptor associated factor 6 (TRAF6) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathways has been seen in Myelodysplastic Syndrome and Acute Myeloid Leukemia (AML), the upstream signals that drive their activation are not fully identified. Results: We investigated the expression of all TLRs in a large database of MDS CD34+ marrow samples and age-matched controls. Our findings revealed that TLR6 and TLR4 were the most significantly overexpressed receptors in MDS samples (FDR&amp;lt;0.001). Furthermore, we observed that the TLR4 cofactor lymphocyte antigen 96 (LY96), also known as myeloid differentiation factor 2 (MD-2), was also overexpressed in MDS samples when compared to controls. Furthermore, the S100A8 and S100A9 proteins are ligands for TLR4 and were found to be positively associated with severity of anemia in the cohort of MDS samples. These data provided the rationale for determining the functional role of the TLR4 pathway in MDS/AML models. To obtain a potent and specific antibody against TLR4, we inoculated rabbits with recombinant human TLR4 and obtained high affinity antibodies that neutralized TLR4 function at low nano-molar range of doses. The TLR4 polyclonal antibody was able to inhibit lipopolysaccharide (LPS)-induced NF-κb activation in leukemic THP-1 cells. The TLR4 antibody also led to a decrease in proliferative phosphorylated extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinase in leukemic cells. We then treated samples from MDS/AML patients (n=14) with the TLR4 antibody (1 nM dosing) and assessed for erythroid and myeloid growth and differentiation. Fluorescence activated cell sorting (FACS) analysis for erythroid differentiation showed increased expression of either CD71, CD235a or both after treatment with the TLR4 antibody. FACS analysis for myeloid differentiation showed increased expression of either CD11b, CD14 or both after treatment with the TLR4 antibody. This effect was more pronounced in the intermediate/high risk group than in the low-risk group of patients. Conclusion: Inhibition of the TLR4 pathway with a potent TLR4 antibody promotes erythroid and myeloid maturation and relieves the differentiation block on these lineages in MDS patient samples in the in vitro setting. Our preclinical data supports further evaluation of TLR4 inhibition as a therapeutic target in patients with MDS, as anemia and neutropenia are hallmarks of the disease.

Schistosoma mansoni excretory-secretory products induce protein kinase signalling, hyperkinesia, and stem cell proliferation in the opposite sex

Adult male and female schistosomes in copula dwell within human blood vessels and lay eggs that cause the major Neglected Tropical Disease human schistosomiasis. How males and females communicate to each other is poorly understood; however, male-female physical interaction is known to be important. Here, we investigate whether excretory-secretory products (ESPs), released into the external milieu by mature Schistosoma mansoni, might induce responses in the opposite sex. We demonstrate that ESPs adhere to the surface of opposite sex worms inducing the activation of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (p38 MAPK) pathways, particularly in the parasite tegument. Furthermore, we show that mature worms stimulated signalling in juvenile worms. Strikingly, we demonstrate that ESPs from the opposite sex promote stem cell proliferation, in an ERK- and p38 MAPK-dependent manner, in the tegument and within the testes of males, and the ovaries and vitellaria of females. Hyperkinesia also occurs following opposite sex ESP exposure. Our findings support the hypothesis that male and female schistosomes may communicate over distance to modulate key processes underlying worm development and disease progression, opening unique avenues for schistosomiasis control.

Cooperativity and oscillations: Regulatory mechanisms of K-Ras nanoclusters

K-Ras nanoclusters (NCs) concentrate all required molecules belonging to the extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) pathway in a small area where signaling events take place, increasing efficiency and specificity of signaling. Such nanostructures are characterized by controlled sizes and lifetimes distributions, but there is a poor understanding of the mechanisms involved in their dynamics of growth/decay. Here, a minimum computational model is presented to analyze the behavior of K-Ras NCs as cooperative dynamic structures that self-regulate their growth and decay according to their size. Indeed, the proposed model reveals that the growth and the local production of a K-Ras nanocluster depend positively on its actual size, whilst its lifetime is inversely proportional to the root of its size. The cooperative binding between the structural constituents of the NC (K-Ras proteins) induces oscillations in the size distributions of K-Ras NCs allowing them to range within controlled values, regulating the growth/decay dynamics of these NCs. Thereby, the size of a K-Ras NC is proposed as a key factor to regulate cell signaling, opening a range of possibilities to develop strategies for use in chronic diseases and cancer.

SPRY4-dependent ERK negative feedback demarcates functional adult stem cells in the male mouse germline†.

Niche-derived growth factors support self-renewal of mouse spermatogonial stem and progenitor cells through ERK MAPK signaling and other pathways. At the same time, dysregulated growth factor-dependent signaling has been associated with loss of stem cell activity and aberrant differentiation. We hypothesized that growth factor signaling through the ERK MAPK pathway in spermatogonial stem cells is tightly regulated within a narrow range through distinct intracellular negative feedback regulators. Evaluation of candidate extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK)-responsive genes known to dampen downstream signaling revealed robust induction of specific negative feedback regulators, including Spry4, in cultured mouse spermatogonial stem cells in response to glial cell line-derived neurotrophic factor or fibroblast growth factor 2. Undifferentiated spermatogonia in vivo exhibited high levels of Spry4 mRNA. Quantitative single-cell analysis of ERK MAPK signaling in spermatogonial stem cell cultures revealed both dynamic signaling patterns in response to growth factors and disruption of such effects when Spry4 was ablated, due to dysregulation of ERK MAPK downstream of RAS. Whereas negative feedback regulator expression decreased during differentiation, loss of Spry4 shifted cell fate toward early differentiation with concomitant loss of stem cell activity. Finally, a mouse Spry4 reporter line revealed that the adult spermatogonial stem cell population in vivo is demarcated by strong Spry4 promoter activity. Collectively, our data suggest that negative feedback-dependent regulation of ERK MAPK is critical for preservation of spermatogonial stem cell fate within the mammalian testis.

Metformin Promotes Proliferation of Mouse Female Germline Stem Cells by Histone Acetylation Modification of Traf2.

Female germline stem cells (FGSCs) are adult stem cells that can both self-renew and differentiate into mature oocytes. Although small-molecule compounds are capable of regulating the development of FGSCs, the effects and mechanisms of action of metformin, a commonly used drug for diabetes, on FGSCs are largely unknown. Here, we found that metformin promoted the viability and proliferation of FGSCs through H3K27ac modification. To elucidate the mechanism by which metformin promoted FGSCs proliferation, Chromatin Immunoprecipitation Sequencing of histone 3 lysine 27 acetylation (H3K27ac) in FGSCs was performed with or without metformin-treatment. The results indicate that metformin modulates FGSCs via the mitogen-activated protein kinase (MAPK) signaling pathway, and tumor necrosis factor receptor associated factor 2 (Traf2) was identified as an important target gene for H3K27ac modification during FGSCs proliferation. Subsequent experiments showed metformin promoted FGSCs proliferation by H3K27ac modification of Traf2 to regulate MAPK signaling. Our findings deepen understanding of how H3K27ac modifications regulate FGSCs development and provide a theoretical basis for the prevention and treatment of premature ovarian failure, polycystic ovary syndrome, infertility, and related diseases.

TRIM22 promotes the proliferation of glioblastoma cells by activating MAPK signaling and accelerating the degradation of Raf-1

The tripartite motif (TRIM) 22 and mitogen-activated protein kinase (MAPK) signaling pathways play critical roles in the growth of glioblastoma (GBM). However, the molecular mechanism underlying the relationship between TRIM22 and MAPK signaling remains unclear. Here, we found that TRIM22 binds to exon 2 of the sphingosine kinase 2 (SPHK2) gene. An ERK1/2-driven luciferase reporter construct identified TRIM22 as a potential activator of MAPK signaling. Knockout and overexpression of TRIM22 regulate the inhibition and activation of MAPK signaling through the RING-finger domain. TRIM22 binds to Raf-1, a negative regulator of MAPK signaling, and accelerates its degradation by inducing K48-linked ubiquitination, which is related to the CC and SPRY domains of TRIM22 and the C1D domain of Raf-1. In vitro and in vivo, an SPHK2 inhibitor (K145), an ERK1/2 inhibitor (selumetinib), and the nonphosphorylated mutant Raf-1S338A inhibited GBM growth. In addition, deletion of the RING domain and the nuclear localization sequence of TRIM22 significantly inhibited TRIM22-induced proliferation of GBM cells in vivo and in vitro. In conclusion, our study showed that TRIM22 regulates SPHK2 transcription and activates MAPK signaling through posttranslational modification of two critical regulators of MAPK signaling in GBM cells.

Spinal alarmin HMGB1 and the activation of TLR4 lead to chronic stress-induced nociceptive hypersensitivity in rodents

Chronic stress affects millions of people around the world, and it can trigger different behavioral disorders like nociceptive hypersensitivity and anxiety, among others. However, the mechanisms underlaying these chronic stress-induced behavioral disorders have not been yet elucidated. This study was designed to understand the role of high-mobility group box-1 (HMGB1) and toll-like receptor 4 (TLR4) in chronic stress-induced nociceptive hypersensitivity. Chronic restraint stress induced bilateral tactile allodynia, anxiety-like behaviors, phosphorylation of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (p38MAPK) and activation of spinal microglia. Moreover, chronic stress enhanced HMGB1 and TLR4 protein expression at the dorsal root ganglion, but not at the spinal cord. Intrathecal injection of HMGB1 or TLR4 antagonists reduced tactile allodynia and anxiety-like behaviors induced by chronic stress. Additionally, deletion of TLR4 diminished the establishment of chronic stress-induced tactile allodynia in male and female mice. Lastly, the antiallodynic effect of HMGB1 and TLR4 antagonists were similar in stressed male and female rats and mice. Our results suggest that chronic restraint stress induces nociceptive hypersensitivity, anxiety-like behaviors, and up-regulation of spinal HMGB1 and TLR4 expression. Blockade of HMGB1 and TLR4 reverses chronic restraint stress-induced nociceptive hypersensitivity and anxiety-like behaviors and restores altered HMGB1 and TLR4 expression. The antiallodynic effects of HMGB1 and TLR4 blockers in this model are sex independent. TLR4 could be a potential pharmacological target for the treatment of the nociceptive hypersensitivity associated with widespread chronic pain.