MKP-1 Expression Research Articles

Manuka Essential Oil Triggers Apoptosis and Activation of c-Jun N-Terminal Kinase in Fibroblasts and Fibrosarcoma Cells

Manuka essential oil has long been used in traditional medicine, though the effects of the oil on cancer cells have limited studies. The goal of this project was to treat cancer cell lines with manuka essential oil at different concentrations and to ascertain the effects on the cell proliferation of normal fibroblast (CUA-4) and on fibrosarcoma (HT-1080) cells. Cell lines were grown on 24-well plates, and subconfluent cultures were treated with varying concentrations of manuka oil for 24 h. The effect of the oil on proliferation and viability was measured through direct cell counting using trypan blue dye exclusion and through the use of an MTT assay. As the concentration of oil increased, proliferation of all cell lines tested decreased with increasing dosage, concurrently with a decrease in MTT activity. To determine if the decrease in cell numbers observed from manuka oil treatment is the result of apoptosis, PARP cleavage assays were performed, confirming that the treatment caused apoptosis in both normal fibroblasts and fibrosarcoma cells. The stress-activated MAPK protein, JNK, was activated by manuka essential oil treatment, occurring synergistically with a decrease in MKP-1 expression.

GR/P300 Regulates MKP1 Signaling Pathway and Mediates Depression-like Behavior in Prenatally Stressed Offspring.

Accumulating evidence suggests that prenatal stress (PNS) increases offspring susceptibility to depression, but the underlying mechanisms remain unclear. We constructed a mouse model of prenatal stress by spatially restraining pregnant mice from 09:00-11:00 daily on Days 5-20 of gestation. In this study, western blot analysis, quantitative real-time PCR (qRT‒PCR), immunofluorescence, immunoprecipitation, chromatin immunoprecipitation (ChIP), and mifepristone rescue assays were used to investigate alterations in the GR/P300-MKP1 and downstream ERK/CREB/TRKB pathways in the brains of prenatally stressed offspring to determine the pathogenesis of the reduced neurogenesis and depression-like behaviors in offspring induced by PNS. We found that prenatal stress leads to reduced hippocampal neurogenesis and depression-like behavior in offspring. Prenatal stress causes high levels of glucocorticoids to enter the fetus and activate the hypothalamic‒pituitary‒adrenal (HPA) axis, resulting in decreased hippocampal glucocorticoid receptor (GR) levels in offspring. Furthermore, the nuclear translocation of GR and P300 (an acetylation modifying enzyme) complex in the hippocampus of PNS offspring increased significantly. This GR/P300 complex upregulates MKP1, which is a negative regulator of the ERK/CREB/TRKB signaling pathway associated with depression. Interestingly, treatment with a GR antagonist (mifepristone, RU486) increased hippocampal GR levels and decreased MKP1 expression, thereby ameliorating abnormal neurogenesis and depression-like behavior in PNS offspring. In conclusion, our study suggested that the regulation of the MKP1 signaling pathway by GR/P300 is involved in depression-like behavior in prenatal stress-exposed offspring and provides new insights and ideas for the fetal hypothesis of mental health.

Dexamethasone Suppresses IL-33-exacerbated Malignant Phenotype of U87MG Glioblastoma Cells via NF-κB and MAPK Signaling Pathways.

Interleukin (IL)-33 is highly expressed in glioblastoma (GBM) and promotes tumor progression. Targeting IL-33 may be an effective strategy for the treatment of GBM. Dexamethasone (DEX) is a controversial drug routinely used clinically in GBM therapy. Whether DEX has an effect on IL-33 is unknown. This study aimed to investigate the effect of DEX on IL-33 and the molecular mechanisms involved. U87MG cells were induced by tumor necrosis factor (TNF)-α to express IL-33 and then treated with DEX. The mRNA levels of IL-33, NF-κB p65, ERK1/2, and p38 were determined by real-time quantitative PCR. The expression of IL-33, IkBα (a specific inhibitor of NF-κB) and MKP-1 (a negative regulator of MAPK), as well as the phosphorylation of NF-κB, ERK1/2 and p38 MAPK, were detected by Western blotting. The secretion of IL-33 was measured by ELISA. The proliferation, migration and invasion of U87MG cells were detected by CCK8 and transwell assays, respectively. DEX significantly reduced TNF-α-induced production of IL-33 in U87MG cells, which was dependent on inhibiting the activation of the NF-κB, ERK1/2 and p38 MAPK signaling pathways, and was accompanied by the increased expression of IkBα but not MKP-1. Furthermore, the proliferation, migration and invasion of U87MG cells exacerbated by IL-33 were suppressed by DEX. DEX inhibited the production and tumor-promoting function of IL-33. Whether DEX can benefit GBM patients remains controversial. Our results suggest that GBM patients with high IL-33 expression may benefit from DEX treatment and deserve further investigation.

Hepatocyte-specific mitogen-activated protein kinase phosphatase 1 in sexual dimorphism and susceptibility to alcohol induced liver injury.

It is well established that females are more susceptible to the toxic effects of alcohol, although the exact mechanisms are still poorly understood. Previous studies noted that alcohol reduces the expression of mitogen-activated protein kinase phosphatase 1 (MKP1), a negative regulator of mitogen-activated protein kinases (MAPK) in the liver. However, the role of hepatocyte- specific MKP1 in the pathogenesis of alcohol-associated liver disease (ALD) remains uncharacterized. This study aimed to evaluate the role of hepatocyte-specific MKP1 in the susceptibility and sexual dimorphism in alcohol-induced liver injury. C57Bl/6 mice were used in an intragastric ethanol feeding model of alcohol-associated steatohepatitis (ASH). Hepatocyte-specific Mkp1-/- knockout and (Mkp1+/+ "f/f" male and female mice were subjected to the NIAAA chronic plus binge model. Primary mouse hepatocytes were used for in vitro studies. Liver RNA sequencing was performed on an Illumina NextSeq 500. Liver injury was evaluated by plasma alanine transaminase (ALT), hepatic ER stress and inflammation markers. Statistical analysis was carried out using ANOVA and the unpaired Student's t-test. ASH was associated with the severe injury accompanied by increased endoplasmic reticulum (ER) stress and significant downregulation of Dusp1 mRNA expression. In vitro, ethanol treatment resulted in a time-dependent decrease in Dusp1 mRNA and protein expression in primary hepatocytes in both males and females; however, this effect was significantly more pronounced in hepatocytes from females. In vivo, female mice developed more liver injury in a chronic plus binge model which was accompanied by a significant decrease in liver Dusp1 mRNA expression. In comparison, liver Dusp1 was not changed in male mice, while they developed milder injury to alcohol. Mkp1 deletion in hepatocytes led to increased alcohol induced liver injury, ER stress and inflammation in both sexes. Hepatocyte Mkp1 plays a significant role in alcohol induced liver injury. Alcohol downregulates Mkp1 expression in hepatocytes in a sex dependent manner and could play a role in sexual dimorphism in increased female susceptibility to alcohol.

Weight loss and vitamin D improve hyporesponsiveness to corticosteroids in obese asthma.

Obesity negatively impacts on asthma response to inhaled corticosteroids by unknown mechanisms. Objective: To demonstrate that the poor response to inhaled corticosteroids in obese asthma is associated with an impaired anti-inflammatory activity of corticosteroids and vitamin D deficiency, both improved by weight loss. 23 obese asthmatics (OA) [18 females; median age (interquartile range) 56 (51-59) years], 14 non-obese asthmatics (NOA) [11 females; 53 (43-60) years], 15 obese (O) [13 females; 47 (45-60) years], and 19 healthy controls (HC) [14 females; 43 (34-56) years] were enrolled. 10 OA and 11 O patients were evaluated at baseline (V1) and six months after (V2) bariatric surgery. Corticosteroid response was measured by dexamethasone inhibition of peripheral blood mononuclear cell (PBMC) proliferation. Lung function, serum levels of leptin, adiponectin, and vitamin D were measured at V1 and V2. We found a reduced response to dexamethasone in PBMCs of O and OA patients with respect to NOA and HC subjects, that inversely correlated with the diponectin/leptin ratio and vitamin D levels. Bariatric surgery improved corticosteroid responses in O and OA patients and normalized adiponectin/leptin ratio and vitamin D levels. Exposure of PBMCs to vitamin D potentiated the antiproliferative effects of corticosteroids. Dexamethasone and vitamin D induced similar MKP-1 expression in O and OA patients. We found a reduced response to dexamethasone in PBMCs of O and OA patients with respect to NOA and HC subjects, that inversely correlated with the adiponectin/leptin ratio and vitamin D levels. Bariatric surgery improved corticosteroid responses in O and OA patients and normalized adiponectin/leptin ratio and vitamin D levels. Exposure of PBMCs to vitamin D potentiated the antiproliferative effects of corticosteroids. Dexamethasone and vitamin D induced similar MKP-1 expression in O and OA patients.

MKP-1 regulates the inflammatory activation of microglia against Alzheimer's disease.

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases leading to dementia in elderly people. Microglia-mediated neuroinflammation plays an important role in AD pathogenesis, so modulation of neuroinflammation has emerged as an essential therapeutic method to improve AD. The current study aims to investigate whether MKP-1 can regulate microglia phenotype and inflammatory factor release in AD and explore its possible mechanisms. Amyloid precursor protein/PS1 double transgenic mice and wild-type mice were selected to study the locations of microglia and amyloid-β (Aβ) plaques in different regions of mice brains. Changes in MKP-1 of microglia were detected using AD model mice and AD model cells. Changes in phenotype and the release of inflammatory factors within immortalized BV2 murine microglia were investigated by regulating the expression of MKP-1. The distribution of microglia and Aβ plaques in the AD brain was region-specific. MKP-1 expression was downregulated in AD mice, and in vitro, with increasing Aβ concentrations, MKP-1 expression was reduced. MKP-1 over-expression increased M2 microglia but decreased M1 microglia accompanied by changes in inflammatory factors and inhibition of MKP-1 yielded the opposite result. MKP-1 regulated microglia phenotype and inflammatory factor release in AD through modulation of the p38 signaling pathway.

The reduced SCFA-producing gut microbes are involved in the inflammatory activation in Kawasaki disease.

Kawasaki disease (KD), an acute febrile systemic vasculitis in children, has become the leading cause of acquired heart disease in developed countries. Recently, the altered gut microbiota was found in KD patients during the acute phase. However, little is known about its characteristics and role in the pathogenesis of KD. In our study, an altered gut microbiota composition featured by the reduction in SCFAs-producing bacteria was demonstrated in the KD mouse model. Next, probiotic Clostridium butyricum (C. butyricum) and antibiotic cocktails were respectively employed to modulate gut microbiota. The use of C. butyricum significantly increased the abundance of SCFAs-producing bacteria and attenuated the coronary lesions with reduced inflammatory markers IL-1β and IL-6, but antibiotics depleting gut bacteria oppositely deteriorated the inflammation response. The gut leakage induced by dysbiosis to deteriorate the host's inflammation was confirmed by the decreased intestinal barrier proteins Claudin-1, Jam-1, Occludin, and ZO-1, and increased plasma D-lactate level in KD mice. Mechanistically, SCFAs, the major beneficial metabolites of gut microbes to maintain the intestinal barrier integrity and inhibit inflammation, was also found decreased, especially butyrate, acetate and propionate, in KD mice by gas chromatography-mass spectrometry (GC-MS). Moreover, the reduced expression of SCFAs transporters, monocarboxylate transporter 1 (MCT-1) and sodium-dependent monocarboxylate transporter 1 (SMCT-1), was also shown in KD mice by western blot and RT-qPCR analyses. As expected, the decrease of fecal SCFAs production and barrier dysfunction were improved by oral C. butyricum treatment but was deteriorated by antibiotics. In vitro, butyrate, not acetate or propionate, increased the expression of phosphatase MKP-1 to dephosphorylate activated JNK, ERK1/2 and p38 MAPK against excessive inflammation in RAW264.7 macrophages. It suggests a new insight into probiotics and their metabolites supplements to treat KD.

Eriocitrin attenuates sepsis-induced acute lung injury in mice by regulating MKP1/MAPK pathway mediated-glycolysis.

Metabolic reprogramming has been shown to aggravate sepsis-induced acute lung injury. In particular, enhanced glycolysis is closely associated with inflammation and oxidative stress. Eriocitrin (ERI) is a natural flavonoid found in citrus fruit that exhibits various pharmacological activities, with antioxidant, anti-inflammatory, anti-diabetic, and anti-tumor properties. However, the role of ERI in lung injury is not well understood. We established a septic mouse model of acute lung injury (ALI) using lipopolysaccharide (LPS) for induction. Primary peritoneal macrophages were isolated to verify the relevant molecular mechanism. Tissues were assessed for lung pathology, pro-inflammatory cytokines, markers of oxidative stress, and protein and mRNA expression levels. In vivo experiments showed that ERI effectively alleviated LPS-induced pathological injury, suppress the inflammatory response (TNF-α, IL-1β, IL-6 levels) and decreased oxidative stress (MDA, ROS) in murine lung tissue. In vitro, ERI increased the resistance of LPS-treated cells to excessive inflammation and oxidative stress by inhibiting the enhancement of glycolysis (indicated by expression levels of HIF-1α, HK2, LDHA, PFKFB3, and PKM2). Specifically, the beneficial effects of ERI following LPS-induced lung injury occurred through promoting the expression of MKP1, which mediates the inactivation of the MAPK pathway to inhibit enhanced glycolysis. These results demonstrate that ERI has a protective effect on sepsis-induced ALI by regulating MKP1/MAPK pathway mediated-glycolysis. Hence, ERI is a promising candidate against ALI via inhibiting glycolysis.

Blockade of neutrophil extracellular traps ameliorates toluene diisocyanate-induced steroid-resistant asthma.

Toluene diisocyanate (TDI)-induced asthma is characterized by mixed inflammation dominated by neutrophils, and is refractory to steroid treatment. Neutrophil extracellular traps (NETs) play an important role in severe asthma, but their role in TDI-induced asthma models is unclear. This study focused on the role and mechanism of NETs in steroid-resistant TDI-induced asthma. Induced sputum was collected from 85 asthmatic patients and 25 healthy controls to detect eDNA. A murine TDI-induced asthma model was prepared, and asthmatic mice were given dexamethasone or DNase I. In vitro, the human bronchial epithelial cell line HBE was stimulated with NETs or TDI-human serum albumin (TDI-HSA). Asthma patients had higher sputum eDNA compared to healthy subjects. In asthma patients, eDNA was positively correlated with sputum neutrophils, and negatively correlated with FEV1%predicted. Airway inflammation, airway reactivity, Th2 cytokine levels in lymph supernatant, and levels of NETs were significantly increased in the TDI-induced asthmatic mice. These increases were suppressed by DNase I, but not by dexamethasone. Inhibition of NETs improved interleukin (IL)-8 and MKP1 mRNA expression, and reduced phosphorylation of GR-S226 induced by TDI. Inhibition of NETs improved airway epithelial barrier disruption, as well as p38 and ERK signaling pathways in TDI-induced asthmatic mice. In vitro, NETs promoted the expression of IL-8 mRNA in HBE cells, and reduced the expression of MKP1. IL-8 elevation induced by NETs was suppressed by a p38 inhibitor or ERK inhibitor, but not by dexamethasone. Pretreatment with RAGE inhibitor reduced NETs induced p38/ERK phosphorylation and IL-8 levels in HBE cells. Our data suggest that targeting NETs might effectively improved TDI-induced airway inflammation and airway epithelial barrier function. This may potentially be a treatment for patients with steroid-resistance asthma.

MKP-1 Deficiency Exacerbates Skin Fibrosis in a Mouse Model of Scleroderma

Scleroderma is a chronic fibrotic disease, where proinflammatory and profibrotic events precede collagen accumulation. MKP-1 [mitogen-activated protein kinase (MAPK) phosphatase-1] downregulates inflammatory MAPK pathways suppressing inflammation. MKP-1 also supports Th1 polarization, which could shift Th1/Th2 balance away from profibrotic Th2 profile prevalent in scleroderma. In the present study, we investigated the potential protective role of MKP-1 in scleroderma. We utilized bleomycin-induced dermal fibrosis model as a well-characterized experimental model of scleroderma. Dermal fibrosis and collagen deposition as well as the expression of inflammatory and profibrotic mediators were analyzed in the skin samples. Bleomycin-induced dermal thickness and lipodystrophy were increased in MKP-1-deficient mice. MKP-1 deficiency enhanced collagen accumulation and increased expression of collagens, 1A1 and 3A1, in the dermis. Bleomycin-treated skin from MKP-1-deficient mice also showed enhanced expression of inflammatory and profibrotic factors IL-6, TGF-β1, fibronectin-1 and YKL-40, and chemokines MCP-1, MIP-1α and MIP-2, as compared to wild-type mice. The results show, for the first time, that MKP-1 protects from bleomycin-induced dermal fibrosis, suggesting that MKP-1 favorably modifies inflammation and fibrotic processes that drive the pathogenesis of scleroderma. Compounds enhancing the expression or activity of MKP-1 could thus prevent fibrotic processes in scleroderma and possess potential as a novel immunomodulative drug.

Glutamine ameliorates hyperoxia-induced hippocampal damage by attenuating inflammation and apoptosis via the MKP-1/MAPK signaling pathway in neonatal rats.

Glutamine (Gln) is an immunomodulatory protein that mediates oxidative stress, inflammation, and apoptosis, but has not been reported in the treatment of hyperoxia (Hyp)-induced brain injury. The aim of this study was to determine whether Gln could improve hyp-induced brain injury in neonatal rats to and later learning and memory dysfunction, and to explore its possible mechanisms. We prepared a model of neonatal rat brain injury caused by normobaric hyperoxia while administered with Gln for 7days for evaluation. Learning memory function was assessed with the Morris water maze test. Histological analysis, protein expression analysis, oxidative stress and inflammation level analysis were performed using hippocampal tissue. Gln treatment significantly reduced brain tissue water content, oxidative stress levels, microglia activation and inflammatory factor expression, and attenuated tissue damage and apoptosis in the hippocampal region. Gln ameliorates hyp-induced learning, memory impairment in neonatal rats in water maze test. It also increased MKP-1 protein expression and decreased p-p38, p-ERK and p-JNK. Therefore, it is hypothesized that Gln may exert neuroprotective effects by increasing MKP-1 expression to negatively regulate MAPK signaling, with potential cognitive improvement in hyp-induced brain injury.

Salicylate Sodium Suppresses Monocyte Chemoattractant Protein-1 Production by Directly Inhibiting Phosphodiesterase 3B in TNF-α-Stimulated Adipocytes.

As a worldwide health issue, obesity is associated with the infiltration of monocytes/macrophages into the adipose tissue causing unresolved inflammation. Monocyte chemoattractant protein-1 (MCP-1) exerts a crucial effect on obesity-related monocytes/macrophages infiltration. Clinically, aspirin and salsalate are beneficial for the treatment of metabolic diseases in which adipose tissue inflammation plays an essential role. Herein, we investigated the effect and precise mechanism of their active metabolite salicylate on TNF-α-elevated MCP-1 in adipocytes. The results indicated that salicylate sodium (SAS) could lower the level of MCP-1 in TNF-α-stimulated adipocytes, which resulted from a previously unrecognized target phosphodiesterase (PDE), 3B (PDE3B), rather than its known targets IKKβ and AMPK. The SAS directly bound to the PDE3B to inactivate it, thus elevating the intracellular cAMP level and activating PKA. Subsequently, the expression of MKP-1 was increased, which led to the decrease in p-EKR and p-p38. Both PDE3B silencing and the pharmacological inhibition of cAMP/PKA compromised the suppressive effect of SAS on MCP-1. In addition to PDE3B, the PDE3A and PDE4B activity was also inhibited by SAS. Our findings identify a previously unrecognized pathway through which SAS is capable of attenuating the inflammation of adipocytes.

TOB is an effector of the hippocampus-mediated acute stress response

Stress affects behavior and involves critical dynamic changes at multiple levels ranging from molecular pathways to neural circuits and behavior. Abnormalities at any of these levels lead to decreased stress resilience and pathological behavior. However, temporal modulation of molecular pathways underlying stress response remains poorly understood. Transducer of ErbB2.1, known as TOB, is involved in different physiological functions, including cellular stress and immediate response to stimulation. In this study, we investigated the role of TOB in psychological stress machinery at molecular, neural circuit, and behavioral levels. Interestingly, TOB protein levels increased after mice were exposed to acute stress. At the neural circuit level, functional magnetic resonance imaging (fMRI) suggested that intra-hippocampal and hippocampal-prefrontal connectivity were dysregulated in Tob knockout (Tob-KO) mice. Electrophysiological recordings in hippocampal slices showed increased postsynaptic AMPAR-mediated neurotransmission, accompanied by decreased GABA neurotransmission and subsequently altered Excitatory/Inhibitory balance after Tob deletion. At the behavioral level, Tob-KO mice show abnormal, hippocampus-dependent, contextual fear conditioning and extinction, and depression-like behaviors. On the other hand, increased anxiety observed in Tob-KO mice is hippocampus-independent. At the molecular level, we observed changes in factors involved in stress response like decreased stress-induced LCN2 expression and ERK phosphorylation, as well as increased MKP-1 expression. This study introduces TOB as an important modulator in the hippocampal stress signaling machinery. In summary, we reveal a molecular pathway and neural circuit mechanism by which Tob deletion contributes to expression of pathological stress-related behavior.

The pan-JAK inhibitor LAS194046 reduces neutrophil activation from severe asthma and COPD patients in vitro

Non-T2 severe asthma and chronic obstructive pulmonary disease (COPD) are airway chronic inflammatory disorders with a poor response to corticosteroids. LAS194046, a novel pan-Janus kinase (JAK) inhibitor, shows inhibitory effects on T2 allergic lung inflammation in rats. In this work we analyze the effects of LAS194046, fluticasone propionate and their combination in neutrophils from non-T2 severe asthma and COPD patients in vitro. Neutrophils from 23 healthy subjects, 23 COPD and 21 non-T2 severe asthma patients were incubated with LAS194046 (0.01 nM–1 µM), fluticasone propionate (0.1 nM–1 µM) or their combination and stimulated with lipopolysaccharide (LPS 1 µM). LAS194046 shows similar maximal % inhibition and potency inhibiting IL-8, MMP-9 and superoxide anion release in neutrophils from healthy, COPD and asthma. Fluticasone propionate suppresses mediator release only in neutrophils from healthy patients. The combination of LAS194046 with fluticasone propionate shows synergistic anti-inflammatory and anti-oxidant effects. The mechanisms involved in the synergistic effects of this combination include the increase of MKP1 expression, decrease of PI3Kδ, the induction of glucocorticoid response element and the decrease of ERK1/2, P38 and JAK2/STAT3 phosphorylation compared with monotherapies. In summary, LAS194046 shows anti-inflammatory effects in neutrophils from COPD and severe non-T2 asthma patients and induces synergistic anti-inflammatory effects when combined with fluticasone propionate.

STAMBPL1 promotes breast cancer cell resistance to cisplatin partially by stabilizing MKP-1 expression.

Dual-specificity mitogen-activated protein kinase phosphatase-1 (MKP-1/DUSP1/CL-100) has been documented to promote breast cancer cell survival and chemoresistance. MKP-1 is an unstable protein that is ubiquitinated and degraded via the ubiquitin-proteasome system. However, it is not clear how MKP-1 protein stability is regulated in breast cancer. In this study, we performed a genome-wide siRNA library screen of deubiquitinases (DUBs) and identified STAMBPL1 as an MKP-1 DUB in breast cancer cells. STAMBPL1 interacts with MKP-1 and stabilizes MKP-1 via deubiquitination. Both STAMBPL1 and MKP-1 depletion sensitize breast cancer cells to cisplatin in vitro and in vivo, and ectopic overexpression of MKP-1 partially rescues STAMBPL1 depletion-induced cisplatin sensitivity. Furthermore, STAMBPL1 and MKP-1 depletion increased breast cancer sensitivity to cisplatin by increasing the phosphorylation and activation of c-Jun N-terminal protein kinase (JNK). Collectively, our findings not only identify STAMBPL1 as an MKP-1 DUB but also reveal a critical mechanism that regulates MKP-1 expression in breast cancer. Our findings indicate that the STAMBPL1/MKP-1 axis represents a potential therapeutic target in breast cancer.

Cannabinoid Receptor Type 2 Agonist Reduces Morphine Tolerance via Mitogen Activated Protein Kinase Phosphatase Induction and Mitogen Activated Protein Kinase Dephosphorylation

Morphine is an opioid drug often used in treating moderate to severe pain. However, morphine tolerance in patients limits its used in clinical settings. Our previous study showed that a cannabinoid type 2 (CB2) receptor agonist attenuated morphine tolerance. However, the exact mechanism by which CB2 agonists reduce morphine tolerance remains unclear. In this study, we investigated the effect of mitogen activated protein kinase (MAPK) and mitogen activated protein kinase phosphatases 1 and 3 (MKP-1 and MKP-3) on the regulation of morphine tolerance by CB2 receptor agonist. Chronic morphine treatments for 7 days reduced the protein expression of MKP-1 and MKP-3 in the spinal cord and increased the phosphorylation of p38, ERK1/2 and the level of proinflammatory mediator, such as IL-1β, IL-6 and TNF-α. Coadministration of CB2 receptor agonist AM1241 alleviated the inhibition of MKP-1 and MKP-3 by chronic morphine administration and reduced the expression of phosphorylated MAPK and proinflammatory factors. The effect of the CB2 receptor agonist on morphine-induced downregulation of MKP-1 and MKP-3 was reversed by the MKP-1 and MKP-3 antagonist triptolide. Our findings suggested that CB2 receptor agonist may induce the expression of MKP-1 and MKP-3 to promote MAPK dephosphorylation and reduce the production of downstream cytokine, thereby reducing morphine tolerance. This finding suggested that MKPs may serve as a new target for alleviating morphine tolerance.

Aging-Dependent Downregulation of SUV39H1 Histone Methyltransferase Increases Susceptibility to Stress-Induced Depressive Behavior.

Aging induces cellular and molecular changes including gene expression alteration in the brain, which might be associated with aging-induced decrease in stress coping ability. In the present study, we investigate how aging changes the ability to cope with stress and increases sensitivity to stress. Aged mice show decreased expression of SUV39H1 histone methyltransferase and increased expression of Mkp-1 in the hippocampus. The siRNA-mediated knockdown of SUV39H1 increases Mkp-1 expression and suppresses p-CREB and Bdnf expression in HT22 cells and in the hippocampus of mice. Chromatin immunoprecipitation assays indicate that the levels of SUV39H1 and methylated histone-H3 bound to the promoter of the Mkp-1 in the hippocampus are reduced in aged mice. Aged mice exhibit depression-like behavior following weak stress that does not induce depressive behavior in young mice. Rosmarinic acid, a phenolic compound that increases SUV39H1 expression, reverses stress-induced changes of SUV39H1, Mkp-1, and Bdnf expression in the hippocampus via an overlapping but distinct mechanism from those of fluoxetine and imipramine and produces anti-depressive effects. These results suggest that aging increases susceptibility to stress via downregulation of SUV39H1 and resulting changes in SUV39H1-regulated signaling pathways in the hippocampus.

β-Caryophyllene attenuates lipopolysaccharide-induced acute lung injury via inhibition of the MAPK signalling pathway.

Acute lung injury (ALI) is a pulmonary manifestation of an acute systemic inflammatory response, which is associated with high morbidity and mortality. Accordingly, from the perspective of treating ALI, it is important to identify effective agents and elucidate the underlying modulatory mechanisms. β-Caryophyllene (BCP) is a naturally occurring bicyclic sesquiterpene that has anti-cancer and anti-inflammatory activities. However, the effects of BCP on ALI have yet to be ascertained. ALI was induced intratracheally, injected with 5 mg/kg LPS and treated with BCP. The bone marrow-derived macrophages (BMDMs) were obtained and cultured then challenged with 100 ng/ml LPS for 4 h, with or without BCP pre-treatment for 30 min. BCP significantly ameliorates LPS-induced mouse ALI, which is related to an alleviation of neutrophil infiltration and reduction in cytokine production. In vitro, BCP was found to reduce the expression of interleukin-6, interleukin-1β and tumour necrosis factor-α, and suppresses the MAPK signalling pathway in BMDMs, which is associated with the inhibition of TAK1 phosphorylation and an enhancement of MKP-1 expression. Our data indicate that BCP protects against inflammatory responses and is a potential therapeutic agent for the treatment of LPS-induced acute lung injury.

MKP-1 is required to limit myeloid-cell mediated oral squamous cell carcinoma progression and regional extension

Mitogen-activated protein kinases (MAPKs) require MAPK phosphatases (MKPs) for deactivation of MAPK intracellular signaling. MKP-1 (encoded by Dusp1) is a key negative regulator of MAPKs and prior reports have indicated that MKP-1 regulates oral cancer-associated inflammation and leukocyte infiltration. ObjectiveTo determine the significance of myeloid-based expression of MKP-1 in oral cancer. MethodsThe Cancer Genome Atlas (TCGA) was used to address DUSP1 expression in oral squamous cell carcinoma (OSCC). Syngeneic and carcinogen-induced mouse models using global and myeloid-specific Dusp-1 deficient mice with immunophenotypic, histologic, and transcriptomic analyses and in vitro migration assays. ResultsData from TCGA indicates the DUSP1 expression is inversely related to oral cancer burden and nodal involvement. Using murine models of OSCC, the role of MKP-1 signaling in tumor associated macrophages (TAMs) was assessed. Dusp1-deficient mice had increased tumor burden and TAM infiltrate with increased M2 macrophage polarization. Transcriptomic signatures of TAMs from Dusp1-deficent mice indicated a pro-metastatic phenotype as well as concomitant differences in myeloid-associated genes, cytokine/chemokine signaling, and Notch signaling consistent with tumor progression. In vitro and in vivo assays revealed mouse OSCC cells had a higher migration rate using TAM cell-free supernatant from Dusp1 deficiency mice compared to controls with enhanced regional cervical lymph node metastasis, respectively. To validate TAM studies using implantable mouse models, an OSCC progression model with conditional myeloid-specific Dusp-1 deficient mice demonstrated enhanced OSCC disease progression, characterized by advanced onset, histological stage, and tumor burden. ConclusionMyeloid-based Dusp1-deficiency increases OSCC burden and metastasis through alteration in TAM recruitment, gene profile, and polarity suggesting that MKP-1 could be a viable target to reprogram TAM to limit local/regional OSCC extension.

Knockout of MAPK Phosphatase-1 Exaggerates Type I IFN Response during Systemic Escherichia coli Infection.

We have previously shown that Mkp-1-deficient mice produce elevated TNF-α, IL-6, and IL-10 following systemic Escherichia coli infection, and they exhibited increased mortality, elevated bacterial burden, and profound metabolic alterations. To understand the function of Mkp-1 during bacterial infection, we performed RNA-sequencing analysis to compare the global gene expression between E. coli-infected wild-type and Mkp-1 -/- mice. A large number of IFN-stimulated genes were more robustly expressed in E. coli-infected Mkp-1 -/- mice than in wild-type mice. Multiplex analysis of the serum cytokine levels revealed profound increases in IFN-β, IFN-γ, TNF-α, IL-1α and β, IL-6, IL-10, IL-17A, IL-27, and GMSF levels in E. coli-infected Mkp-1 -/- mice relative to wild-type mice. Administration of a neutralizing Ab against the receptor for type I IFN to Mkp-1 -/- mice prior to E. coli infection augmented mortality and disease severity. Mkp-1 -/- bone marrow-derived macrophages (BMDM) produced higher levels of IFN-β mRNA and protein than did wild-type BMDM upon treatment with LPS, E. coli, polyinosinic:polycytidylic acid, and herring sperm DNA. Augmented IFN-β induction in Mkp-1 -/- BMDM was blocked by a p38 inhibitor but not by an JNK inhibitor. Enhanced Mkp-1 expression abolished IFN-β induction by both LPS and E. coli but had little effect on the IFN-β promoter activity in LPS-stimulated RAW264.7 cells. Mkp-1 deficiency did not have an overt effect on IRF3/7 phosphorylation or IKK activation but modestly enhanced IFN-β mRNA stability in LPS-stimulated BMDM. Our results suggest that Mkp-1 regulates IFN-β production primarily through a p38-mediated mechanism and that IFN-β plays a beneficial role in E. coli-induced sepsis.