Mitogen-activated Protein Kinase Phosphatase-1 Expression Research Articles

MKP1 may be involved in the occurrence of depression by regulating hippocampal autophagy in rats

BackgroundMitogen-activated protein kinase (MAPK) phosphatase-1 (MKP1) is upregulated in the hippocampus of patients with depression, while pharmacological inhibition of hippocampal MKP1 can mitigate depression-like behaviors in rodents. In addition, MAPK signaling regulates autophagy, and antidepressants were recently shown to target autophagic signaling pathways. We speculated that MKP1 contributes to depression by enhancing hippocampal autophagy through dephosphorylation of the MAPK isoform ERK1/2. MethodsWe established a rat depression model by exposure to chronic unpredictable mild stress (CUMS), and then examined depression-like behaviors in the sucrose preference test (SPT) and forced swimming test (FST) as well as expression changes in hippocampal MKP1, ERK1/2, phosphorylated ERK1/2, and autophagy-related proteins LC3II by Western blotting and immunostaining. These same measurements were repeated in rats exposed to CUMS following hippocampal infusion of a MKP1-targeted shRNA. Finally, the effects of MKP1 expression level on autophagy we examined in rat GMI-R1 microglia. ResultsCUMS-exposed rats demonstrated anhedonia in the SPT and helplessness in the FST, two core depression-like behaviors. Expression levels of MKP1 and LC3II were upregulated in the hippocampus of CUMS rats, suggesting enhanced autophagy, while pERK/ERK was downregulated. Knockdown of hippocampal MKP1 mitigated depression-like behaviors, downregulated hippocampal LC3II expression, and upregulated hippocampal pERK/ERK. Similarly, MKP1 knockdown in GMI-R1 cells upregulated pERK/ERK and reduced the number of LC3II autophagosomes, while MKP1 overexpression had the opposite effects. ConclusionEnhanced hippocampal autophagy via MKP1-mediated ERK dephosphorylation may contribute to the development of depression.

MiR-429-3p mediates memory decline by targeting MKP-1 to reduce surface GluA1-containing AMPA receptors in a mouse model of Alzheimer's disease

Alzheimer's disease (AD) is a leading cause of dementia in the elderly. Mitogen-activated protein kinase phosphatase 1 (MKP-1) plays a neuroprotective role in AD. However, the molecular mechanisms underlying the effects of MKP-1 on AD have not been extensively studied. MicroRNAs (miRNAs) regulate gene expression at the post-transcriptional level, thereby repressing mRNA translation. Here, we reported that the microRNA-429-3p (miR-429-3p) was significantly increased in the brain of APP23/PS45 AD model mice and N2AAPP AD model cells. We further found that miR-429-3p could downregulate MKP-1 expression by directly binding to its 3′-untranslated region (3′ UTR). Inhibition of miR-429-3p by its antagomir (A-miR-429) restored the expression of MKP-1 to a control level and consequently reduced the amyloidogenic processing of APP and Aβ accumulation. More importantly, intranasal administration of A-miR-429 successfully ameliorated the deficits of hippocampal CA1 long-term potentiation and spatial learning and memory in AD model mice by suppressing extracellular signal-regulated kinase (ERK1/2)-mediated GluA1 hyperphosphorylation at Ser831 site, thereby increasing the surface expression of GluA1-containing α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs). Together, these results demonstrate that inhibiting miR-429-3p to upregulate MKP-1 effectively improves cognitive and synaptic functions in AD model mice, suggesting that miR-429/MKP-1 pathway may be a novel therapeutic target for AD treatment.

MKP1 promotes nonalcoholic steatohepatitis by suppressing AMPK activity through LKB1 nuclear retention

Nonalcoholic steatohepatitis (NASH) is triggered by hepatocyte death through activation of caspase 6, as a result of decreased adenosine monophosphate (AMP)-activated protein kinase-alpha (AMPKα) activity. Increased hepatocellular death promotes inflammation which drives hepatic fibrosis. We show that the nuclear-localized mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP1) is upregulated in NASH patients and in NASH diet fed male mice. The focus of this work is to investigate whether and how MKP1 is involved in the development of NASH. Under NASH conditions increased oxidative stress, induces MKP1 expression leading to nuclear p38 MAPK dephosphorylation and decreases liver kinase B1 (LKB1) phosphorylation at a site required to promote LKB1 nuclear exit. Hepatic deletion of MKP1 in NASH diet fed male mice releases nuclear LKB1 into the cytoplasm to activate AMPKα and prevents hepatocellular death, inflammation and NASH. Hence, nuclear-localized MKP1-p38 MAPK-LKB1 signaling is required to suppress AMPKα which triggers hepatocyte death and the development of NASH.

Cod (Gadus) skin collagen peptide powder reduces inflammation, restores mucosal barrier function, and inhibits fibrosis in dextran sodium sulfate-induced colitis in mice

Ethnopharmacological relevanceUlcerative colitis (UC) is a chronic inflammatory bowel disease of unknown etiology. Cod (Gadus), a kind of herb from the Chinese herb. Traditionally, it has used to treat trauma, reduce swelling and relieve pain in order to exert its anti-inflammatory activity. Recent reports based on its hydrolyzed or enzymatic extracts have shown its anti-inflammatory, mucosal barrier protecting properties. However, its mechanism of improvement in ulcerative colitis is not clear. Aim of the studyThis study aimed to explore the preventive and protective effect of cod skin collagen peptide powder (CP) on mice with UC and to explore the underlying mechanism. Materials and methodsMice with dextran sodium sulfate (DSS)-induced UC were treated with CP by gavage, and the anti-inflammatory effects of CP were assessed using general physical, pro-inflammatory cytokine, histopathological, immunohistochemical, macrophage flow cytometry, and inflammatory signaling pathway assays. ResultsCP ameliorates inflammation by upregulating mitogen-activated protein kinase phosphatase-1 (MKP-1) and thereby decreasing the phosphorylation levels of P38 and JNK. It also polarizes macrophages in the colon towards the M2 phenotype, which helps to reduce tissue damage and promotes colon repair. At the same time, CP also inhibits the development of fibrosis, one of the complications of UC, by upregulating ZO-1, Occludin, and downregulating α-SMA, Vimentin, Snail, and Slug. ConclusionIn this study, we found CP reduced inflammation in mice with UC by inducing MKP-1 expression, which caused dephosphorylation of mitogen-activated protein kinase (MAPK). CP also restored mucosal barrier function and inhibited the development of fibrosis complicating UC in these mice. Taken together, these results suggested that CP improved the pathological manifestations of UC in mice, suggesting that it can play a biological role as a nutritional supplement for preventing and treating UC.

The Homeostatic Protein Fam3D Orchestrates Colon Mucosal Protection Against Infection, Inflammation, and Carcinogenesis

Fam3D (FAM3D in human) is a homeostatic protein expressed mainly in gastrointestinal tract that plays an essential role in promoting colon mucosal development and homeostasis. However, the mechanistic basis for the action of Fam3D, particularly its relationship to colon mucosal development and microbiome balance, is less clear. In this study, Fam3D expression was increased in colon epithelial cells of germ-free (GF) <i>Fam3D^+/+</i> mice following <i>E. coli</i> infection and GF <i>Fam3D^-/-</i> mice were more susceptible to <i>E. coli</i> colonization in the colon. In chemically induced colitis and colon cancer, GF <i>Fam3D^-/-</i> mice showed more severe inflammatory responses, colon mucosal damage, and tumorigenesis. Unlike SPF mice, GF <i>Fam3D^-/-</i> mice exhibited decreased production of the gut barrier protein Muc2. Mechanism study revealed that in colon epithelial cells, LPS upregulated Fam3D expression through TLR4, while Fam3D promoted Muc2 production through Fpr1 and Fpr2. In addition, Fam3D also upregulated the expression of MAP kinase phosphatase 1 (MKP-1) which is crucial for restraining inflammatory responses. Fam3D deficiency reduced MKP-1 expression, thereby increasing IL-1β and TNF-α production in colon mucosa of GF mice. Thus, Fam3D is critical in colon homeostasis and constitutes a therapeutic target for inflammatory colon diseases.

Dexamethasone Attenuates the Expression of MMP-13 in Chondrocytes through MKP-1.

Mitogen-activated protein kinase phosphatase-1 (MKP-1) is upregulated in inflammation and reduces the activity of proinflammatory mitogen-activated protein kinases (MAP kinases) by dephosphorylation. MAP kinases are intracellular signaling pathways that mediate the cellular effects of proinflammatory cytokines. In the present study, we investigated the effects of the glucocorticoid dexamethasone on the expression of catabolic enzymes in chondrocytes and tested the hypothesis that these effects are mediated through MKP-1. Dexamethasone was found to significantly attenuate the expression of matrix metalloproteinase (MMP)-13 in human OA chondrocytes as well as in chondrocytes from MKP-1 WT mice, but not in chondrocytes from MKP-1 KO mice. Dexamethasone also increased the expression of MKP-1 in murine and human OA chondrocytes. Furthermore, p38 MAP kinase inhibitors significantly attenuated MMP-13 expression in human OA chondrocytes, while JNK MAP kinase inhibitors had no effect. The results indicate that the effect of dexamethasone on MMP-13 expression in chondrocytes was mediated by an MKP-1 and p38 MAP kinase-dependent manner. These findings, together with previous results, support the concept of MKP-1 as a protective factor in articular chondrocytes in inflammatory conditions and as a potential drug target to treat OA.

Dexmedetomidine alleviates oxygen and glucose deprivation-induced apoptosis in mesenchymal stem cell via downregulation of MKP-1

Bone marrow mesenchymal stem cell (MSC)-based therapy is a novel candidate for heart repair. But ischemia-reperfusion injury leads to low viability of MSC. Dexmedetomidine (Dex) has been found to protect neurons against ischemia-reperfusion injury. It remains unknown if Dex could increase the viability of MSCs under ischemia. The present study is to observe the potential protective effect of Dex on MSCs under ischemia and its underlying mechanisms. Specific mRNAs related to myocardial ischemia in the GEO database were selected from the mRNA profiles assessed in a previous study using microarray. The most dysregulated mRNAs of the specific ones from the above study were subject to bioinformatics analysis at our laboratory. These dysregulated mRNAs possibly regulated apoptosis of cardiomyocytes and were validated in vitro for their protective effect on MSCs under ischemia. MSCs were pre-treated with Dex at 10 μM concentration for 24 h under oxygen-glucose deprivation (OGD). Flow cytometry and TUNEL assay were carried out to detect apoptosis in Dex-pretreated MSCs under OGD. The relative expressions of mitogen-activated protein kinase phosphatase 1 (MKP-1) and related genes were detected by quantitative polymerase chain reaction and western blotting. Microarray data analysis revealed that Dex regulates MAPK phosphatase activity. Dex significantly reduced in vitro apoptosis of MSCs under OGD, which suppressed the synthesis level of Beclin1 and light chain 3 proteins. Dex down-regulated MKP-1 expression and attenuated an OGD-induced change in the mitogen activated protein kinase 3 (MAPK3) signaling pathway. Dex increases the viability of MSC and improves its tolerance to OGD in association with the MKP-1 signaling pathway, thus suggesting the potential of Dex as a novel strategy for promoting MSCs efficacy under ischemia.

LncRNA Riken Attenuated Sevoflurane-Induced Neuroinflammation by Regulating the MicroRNA-101a/MKP-1/JNK Pathway.

The induction of anesthesia in children makes its safety one of the most important global health problems. Neuroinflammation contributes to anesthesia-induced neurotoxicity in young individuals. However, the mechanisms underlying anesthesia-induced neurotoxicity have not been established. In this study, the level of interleukin (IL)-6 in the hippocampus of mice and N2A cells treated with sevoflurane was increased, and long noncoding RNA (LncRNA) Riken was sufficient to decrease sevoflurane-induced neurotoxicity, and the level of inflammatory cytokine IL-6. The RNA pull-down assay verified that miR-101a was bound to lncRNA Riken in N2A cells. In addition, miR-101a blocked the protective effect of lncRNA Riken on anesthesia-induced neuroinflammation. These data suggest that lncRNA Riken attenuated anesthesia-induced neuroinflammation by interacting with microRNA-101a. Finally, we also demonstrated that MAPK phosphatase 1 (MKP-1) was a downstream target of miR-101a, and lncRNA Riken can regulate the expression of MKP-1; the JNK signal transduction pathway has been implicated in sevoflurane-induced IL-6 secretion. Our findings demonstrated that lncRNA Riken alleviated the sevoflurane-induced neurotoxic effects, and the lncRNA Riken/miR-101a/MKP-1/JNK axis plays an important role in the cognitive disorder.

Fasting-Induced Upregulation of MKP-1 Modulates the Hepatic Response to Feeding.

The liver plays a key role in whole-body, glucose and lipid homeostasis. Nutritional signals in response to fasting and refeeding regulate hepatic lipid synthesis. It is established that activation of mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP-1) in response to overnutrition regulates MAPK-dependent pathways that control lipid metabolism in the liver. However, the regulatory mechanisms and the impact of the actions of MKP-1 in hepatic response to fasting remains unclear. We investigated the effect of fasting on the expression of MKP-1 and the impact on hepatic response to feeding. In this study, we demonstrate that fasting stress induced upregulation of hepatic MKP-1 protein levels with a corresponding downregulation of p38 MAPK and JNK phosphorylation in mouse livers. We found that MKP-1-deficient livers are resistant to fasting-induced hepatic steatosis. Hepatic MKP-1 deficiency impaired fasting-induced changes in the levels of key transcription factors involved in the regulation of fatty acid and cholesterol metabolism including Srebf2 and Srebf1c. Mechanistically, MKP-1 negatively regulates Srebf2 expression by attenuating p38 MAPK pathway, suggesting its contribution to the metabolic effects of MKP-1 deficiency in the fasting liver. These findings support the hypothesis that upregulation of MKP-1 is a physiological relevant response and might be beneficial in hepatic lipid utilization during fasting in the liver. Collectively, these data unravel some of the complexity and tissue specific interaction of MKP-1 action in response to changes in nutritional cues, including fasting and excess nutrients

Circular RNA 0006349 Augments Glycolysis and Malignance of Non-small Cell Lung Cancer Cells Through the microRNA-98/MKP1 Axis.

Background: The involvement of dysregulated circular RNAs (circRNAs) in human diseases has been increasingly recognized. In this study, we focused on the function of a newly screened circRNA, circ_0006349, in the progression of non-small-cell lung cancer (NSCLC) and the molecules of action.Methods: The NSCLC circRNA dataset GSE101684, microRNA (miRNA) dataset GSE29250, and mRNA dataset GSE51852 obtained from the GEO database were used to identify the differentially expressed genes in NSCLC samples. Tumor and normal tissues were collected from 59 patients with NSCLC. The expression of circ_0006349, miR-98, and MAP kinase phosphatase 1 (MKP1) in collected tissue samples and in acquired cells was determined. The binding relationships between miR-98 and circ_0006349/MKP1 were predicted and validated. Altered expression of circ_0006349, miR-98, and MKP1 was introduced in NSCLC cells to examine their roles in cell growth, apoptosis, and glycolysis.Results: Circ_0006349 and MKP1 were upregulated, and miR-98 was poorly expressed in the collected tumor tissues and the acquired NSCLC cell lines. Circ_0006349 was identified as a sponge for miR-98 to elevate MKP1 expression. Silencing of circ_0006349 suppressed proliferation and increased apoptosis of Calu-3 and H1299 cells, and it reduced glycolysis, glucose uptake, and the production of lactate in cells. Upon circ_0006349 knockdown, further downregulation of miR-98 or upregulation of MKP1 restored the malignant behaviors of cells.Conclusion: This research demonstrated that circ_0006349 derepressed MKP1 expression by absorbing miR-98, which augmented the proliferation and glycolysis of NSCLC cells and promoted cancer development.

Astragaloside Attenuates Atherosclerosis Coupled Inflammation Through miR-101/Mitogen-Activated Protein Kinase Phosphatase-1 (MKP-1)/p38 Signaling in Mice

This study aimed at elucidating the effect of astragaloside on atherosclerosis coupled inflammation and potential mechanism in mice. C57BL/6J mice were maintained in high-fat diet (HFD) for 12 weeks to induce atherosclerosis, with or without treatment with astragaloside (50 mg/kg). In turn, serum biochemical parameters in mice were also evaluated. Multiple tissue stain assay, including HE, were employed to assess the pathological alterations in arteries, and blood inflammation mediators were examined using ELISA. Expressions of microRNA101 (miR-101), p-p38 and mitogen-activated protein kinase phosphatase-1 (MKP-1) in the arteries were evaluated by qPCR and Western blot. Finally, AML-193 cells were transfected by miR-101 mimics and inhibitors. Expression of miR-101, MKP-1 and downstream inflammation cytokines were then analyzed. High-fat diet (HFD) mice with astragaloside treatment exhibited reduced atherosclerotic plaques size evaluated by oil red o, improved hepatocyte steatosis, and increased collagen fibers in atherosclerotic plaques for more stable plaque. Further, astragaloside treatment suppressed miR-101 transcription and enhanced MKP-1 expression, thus restraining the secretion of inflammation factors in vitro. Moreover, the inhibited impact of astragaloside in inflammatory factors production was ineffective in the presence of miR-101 mimics in AML-193 cells stimulated by LPS. Astragaloside exerted an anti-inflammatory role through miR-101/MKP-1/p38 signaling, for reducing atherosclerotic plaques and alleviate inflammation damage in mice and AML-193 cell.

MAP kinase phosphatase MKP-1 regulates p-ERK1/2 signaling pathway with fluoride treatment

Dental fluorosis is characterized by hypomineralization of tooth enamel caused by ingestion of excessive fluoride during enamel formation. Excess fluoride could have effects on the ERK signaling, which is essential for the ameloblasts differentiation and tooth development. MAP kinase phosphatase-1 (MKP-1) plays a critical role in regulating ERK related kinases. However, the role of MKP-1 in ameloblast and the mechanisms of MKP-1/ERK signaling in the pathogenesis of dental fluorosis are incompletely understood. Here, we adopted an in vitro fluorosis cell model using murine ameloblasts-like LS8 cells by employing sodium fluoride (NaF) as inducer. Using this system, we demonstrated that fluoride exposure led to an inhibition of p-MEK and p-ERK1/2 with a subsequent increase in MKP-1 expression in a dose-dependent manner. We further identified, under high dose fluoride, MKP-1 acted as a negative regulator of the fluoride-induced p-ERK1/2 signaling, leading to downregulation of CREB, c-myc, and Elk-1. Our results identify a novel MKP-1/ERK signaling mechanism that regulates dental fluorosis and provide a framework for studying the molecular mechanisms of intervention and fluorosis remodeling under normal and pathological conditions. MKP-1 inhibitors may prove to be a benefit therapeutic strategy for dental fluorosis treatment.

MKP-1 overexpression is associated with chemoresistance in bladder cancer via the MAPK pathway.

Mitogen activated protein kinase phosphatase-1 (MKP-1) has been revealed to be overexpressed in bladder cancer, particularly in non-muscle invasive bladder cancer. MKP-1 may also be associated with chemotherapy resistance. However, the underlying mechanism is yet to be elucidated. The current study investigated the expression of MKP-1 by performing immunohistochemistry in surgically resected specimens obtained from primary and recurrent patients with bladder cancer. The results revealed that MKP-1 expression increased in recurrent patients. Additionally, a 3D model of the human bladder cancer cell line, RT112, was established to determine the role of MKP-1 in drug resistance. The results demonstrated that MKP-1 overexpression protected bladder cancer cells against cell death. Contrarily, MKP-1 knockdown was revealed to sensitize cells to death. In addition, the application of MAPK inhibitors effectively increased RT112 cell sensitivity to pirarubicin. In conclusion, the results of the current study indicated that MKP-1 treatment resulted in bladder cancer cell chemoresistance via JNK, ERK and p38 pathways. MKP-1 may also serve as a potential therapeutic target for chemoresistance in patients with bladder cancer.

SUN-248 Estradiol Changes Angiotensin II-Induced ERK1/2 Phosphorylation by Different Pathways in the Hypothalamus and Lamina Terminalis

Female gonadal hormones, especially 17β-estradiol (E2), are known to mediate hydromineral homeostasis and blood pressure mainly by attenuating renin-angiotensin system (RAS) actions. The RAS plays an essential role in the maintenance of hydromineral and cardiovascular homeostasis via angiotensin II (ANGII), a key component of the RAS. However, the cellular mechanisms of the interaction between E2 and ANGII and its physiological role are not fully elucidated. Recently, our group showed that ERK1/2 is involved in sodium intake and vasopressin release induced by ANGII in female rats. In addition, E2 decreases ERK1/2 phosphorylation induced by ANGII in the hypothalamus and in structures of the lamina terminalis (LT). Thus, the goal of the present study was evaluated some mechanisms that could be involved in ERK1/2 dephosphorylation induced by E2 in response to ANGII, such as MAPK phosphatase 1 (MKP-1) and GRK5. For this, Wistar female rats (~250g) were submitted to ovariectomy and on the following day they were treated with estradiol cypionate (10µg/rat, sc) or vehicle (corn oil, 0.1mL/rat, sc) for eight days. On the eighth day, the rats received an intracerebroventricular (icv, lateral ventricle) injection of angiotensin II (25ng/2μL/rat) or vehicle (0.9% saline, 2μL/rat). After five min of ANGII injection the animals were decapitated for brain collection for MKP-1 and GRK5 expression analysis by western blot. Data were analyzed using ANOVA two or three-way, followed by Newman-Keuls post-test and the level of significance was set at 5%. It was observed that E2 increased MKP-1 expression only in hypothalamus (F1,18=24.3, p<0.001) in ovariectomized rats, independent of ANGII stimulus. Because the inhibitory effect of E2 on vasopressin release induced by ANGII was reversed by PKC inhibition, it was analyzed the role of PKC on MKP-1 expression and it was observed that PKC inhibition (Chelerythrine, 100µM/2µL/rat) reversed the positive effect of E2 on MKP-1 expression (F1,30=4.7, p<0.05) in the hypothalamus. In addition, E2 decreased GRK5 expression only in the LT (F1,21=12.7, p<0.01) in response to ANGII. Taken together, these results suggest that E2 requires PKC/MKP-1 pathway to decrease ERK1/2 phosphorylation in the hypothalamus and consequent vasopressin release induced by ANGII. While in the LT, the inhibitory effect of E2 involves decreasing GRK5 expression compromising ERK1/2 phosphorylation and sodium intake induced by ANGII. A significant contribution of this work is the identification of some steps of ANGII signaling modulated by E2, which can explain, at least in part, its regulation on the central ANGII effects.

SIRT2 is involved in cisplatin-induced acute kidney injury through regulation of mitogen-activated protein kinase phosphatase-1.

Activation of mitogen-activated protein kinase phosphatase-1 (MKP-1), a dual-specificity protein phosphatase, regulates mitogen-activated protein kinase signaling. C-Jun N-terminal kinase (JNK) and p38 are activated in cisplatin-induced renal injury. However, the change of MKP-1 expression in cisplatin-induced renal injury and the regulatory effect of sirtuin 2 (SIRT2), a nicotinamide adenine dinucleotide-dependent deacetylase, on MKP-1 remains unknown. To address these issues, we used constitutional Sirt2 knockout (KO) mice, transgenic (TG) mice with increased expression of SIRT2 specifically in proximal tubular epithelial cellsand wild-type (WT) mice. Cisplatin nephrotoxicity was induced by intraperitoneal injection of cisplatin. MKP-1 expression in the kidney was decreased after cisplatin treatment. Cisplatin-induced downregulation of MKP-1 was reversed in Sirt2 KO mice kidney and further decreased in Sirt2 TG mice kidney. We observed similar phenomenon with SIRT2-knockdown or SIRT2-overexpressed tubular epithelial cells. Phosphorylation of p38 and JNK, a downstream signal pathway of MKP-1, increased in WT mice kidney following treatment with cisplatin. A decrease in SIRT2 suppressed cisplatin-induced phosphorylation of p38 and JNK in kidney and tubular epithelial cells. Overexpression of SIRT2 further increased phosphorylation of p38 and JNK in kidney and tubular epithelial cells. Acetylation of MKP-1 was significantly increased in SIRT2-knockdown cells and decreased in SIRT2-overexpressed cells after cisplatin stimulation. Sirt2 KO mice and Sirt2 TG mice showed amelioration and aggravation of renal injury, apoptosis, necroptosis and inflammation induced by cisplatin. Our data show that SIRT2 is associated with cisplatin-induced renal injury through regulation of MKP-1 expression.

Therapeutic Effects of Total Saponins From Dioscorea nipponica Makino on Gouty Arthritis Based on the MAPK-PPARγ Signaling Pathway: An In Vitro Study

Gouty arthritis (GA) is an inflammatory disease caused by the deposition of monosodium urate in the synovial membrane and cartilage due to a high concentration of uric acid in the blood. Dioscorea nipponica Makino is widely used in the clinic to treat GA. Total saponins are its main components and showed an anti-inflammatory effect on GA in a previous study. The mitogen-activated protein kinase (MAPK)-peroxisome proliferator-activated receptor γ (PPARγ) signaling pathway plays a key role during the onset of GA; however, little is known about its potential mechanism. Based on in vitro experiments, this study aims to determine the mechanism of total saponins from Dioscorea nipponica Makino (TDN) in treating GA by regulating the MAPK-PPARγ signaling pathway. Fibroblast-like synoviocytes were divided into 3 groups: the model group, which was given 10 µg/L IL-1β to induce proliferation; TDN group (10 µg/L IL-1β + 100 µg/L TDN); and indomethacin group (10 µg/L IL-1β + 100 µg/L indomethacin). Seventy-two hours after treatment, the real-time PCR method was used to detect the mRNA expression levels of extracellular signal regulated kinase 1/2 (ERK1/2), p-38, c-Jun N-terminal kinase (JNK), IKKα, c-Jun, MAPK phosphatase (MKP), vascular cell adhesion molecule 1 (VCAM1), intercellular adhesion molecule 1 (ICAM1), C-X-C motif chemokine ligand 1 (CXCL1), PPARγ, and Adipor2. The Western blot method was used to detect the protein expression of ERK1/2, p-ERK1/2, p-38, p-P38, JNK, p-JNK, IKKα, p-IKKα, c-Jun, p-c-Jun, MKP, p-MKP, VCAM1, ICAM1, CXCL1, PPARγ, and Adipor2. Compared with the model group, the TDN group displayed significantly increased mRNA expression of c-Jun, MKP, CXCL1, PPARγ, and Adipor2 and significantly decreased mRNA expression of ICAM1. Compared with the model group, the TDN group exhibited significantly increased protein expression of MKP and significantly decreased protein expression of p-ERK1/2, p-38, p-JNK, p-IKKα, p-c-Jun, VCAM1, ICAM1, and PPARγ. Our results indicated that TDN could treat GA by influencing the MAPK-PPARγ signaling pathway.

Protective effect of mitogen-activated protein kinase phosphatase 1 on tumor necrosis factor-α-mediated myocardial injury

Objective To investigate the effect of mitogen-activated protein kinase phosphatase 1 (MKP1) on tumor necrosis factor-α (TNF-α)-induced myocardial injury. Methods Wild type (WT) and MKP1 transgene (MKP1) mice were randomly divided into 2 groups separately: WT group, WT+ TNF-α group and MKP1 group, MKP1+ TNF-α group. Mice in the WT+ TNF-α group and the MKP1+ TNF-α group were intraperitoneally injected with TNF-α at a dose of 6 mg/kg. Mice in the WT group and the MKP1 group were intraperitoneally injected with an equal amount of physiological saline. The MKP1 expression, myocardial injury marker level, myocardial mitochondrial division-associated protein 1 (Drp1), antioxidant and respiratory complex expression and mitochondrial apoptosis were measured, and t-test was used to analyze differences between groups. Results As compared with WT+ TNF-α group, MKP1+ TNF-α group showed down-regulation of Drp1 and Mff expression (Drp1: 1.80±0.20 vs. 1.00±0.30, t=-10.134, P<0.05; Mff: 2.80±0.20 vs. 1.10±0.30, t=-8.313, P<0.05), increased expression of glutathione (GSH), superoxide dismutase (SOD) and glutathione peroxidase (GPX) [GSH: (29±2) vs. (49±3) nmol/mg, t=12.127, P<0.05; SOD: (2.2±0.1) vs. (8.1±0.2) U/mg, t=10.301, P<0.05; GPX: (50±4) vs. (172±6) U/mg, t=11.136, P<0.05], increased expression of mitochondrial respiratory recombination Ⅲ and Ⅱ (complex Ⅲ: 1.00±0.20 vs. 2.20±0.12, t=10.715, P<0.05; complex Ⅱ: 1.10±0.09 vs. 1.90±0.08, t=8.312, P<0.05), down-regulation of Caspase-9 and bax expression (Caspase-9: 2.20±0.11 vs. 1.15±0.09, t=-5.210, P<0.05; bax: 2.30±0.12 vs. 1.42±0.09, t=-6.006, P<0.05). Conclusion The mechanism of TNF-α-induced myocardial injury involves excessive division of mitochondria, mitochondrial redox balance, destruction of energy metabolism and mitochondrial apoptosis. MKP1 overexpression can significantly inhibit the development of these adverse reactions, protect mitochondrial function and inhibit myocardial damage. Key words: Mitogen-activated protein kinase phosphatase 1; Tumor necrosis factor-α; Myocardial injury

Interplay of MKP-1 and Nrf2 drives tumor growth and drug resistance in non-small cell lung cancer.

Alterations in KEAP1/ NF-E2 p45-related factor 2 (NFE2L2/Nrf2) signaling pathway have been reported in 23% lung adenocarcinoma patients, suggesting that deregulation of the pathway is a major cancer driver. Here we report that mitogen-activated protein (MAP) kinase phosphatase 1 (MKP-1) drives tumor growth and drug resistance by up regulating transcription factor Nrf2. In non-small cell lung cancer (NSCLC) cells and xenografts, MKP-1 knockdown triggered the down-regulation of the metabolic enzymes and cytoprotective proteins, which are the target genes of Nrf2. Consequently, the cell growth was markedly inhibited with decrease of tumor metabolisms and GSH contents. Moreover, MKP-1 silencing sensitized NSCLC cells to cisplatin treatment. Mechanistically, MKP-1 inhibited the ubiquitylation of Nrf2 via a direct interaction with the transcription factor. Nrf2 was hence stabilized and its transcriptional program was activated. Notably, Nrf2 elevated MKP-1 expression at transcriptional level. In human lung adenoma tumor samples, high levels of expression of MKP-1, Nrf2, and its target gene heme oxygenase 1 were closely correlated. Thus, MKP-1 and Nrf2 form a forward feedback loop in lung cancer cells, which stabilizing and activating Nrf2 to promote anabolic metabolism and GSH biosynthesis. This study uncovers a novel role of MKP-1 in the malignant evolution of cancers.

MKP-1 reduces A\u03b2 generation and alleviates cognitive impairments in Alzheimer\u2019s disease models

Mitogen-activated protein kinase (MAPK) phosphatase 1 (MKP-1) is an essential negative regulator of MAPKs by dephosphorylating MAPKs at both tyrosine and threonine residues. Dysregulation of the MAPK signaling pathway has been associated with Alzheimer’s disease (AD). However, the role of MKP-1 in AD pathogenesis remains elusive. Here, we report that MKP-1 levels were decreased in the brain tissues of patients with AD and an AD mouse model. The reduction in MKP-1 gene expression appeared to be a result of transcriptional inhibition via transcription factor specificity protein 1 (Sp1) cis-acting binding elements in the MKP-1 gene promoter. Amyloid-β (Aβ)-induced Sp1 activation decreased MKP-1 expression. However, upregulation of MKP-1 inhibited the expression of both Aβ precursor protein (APP) and β-site APP-cleaving enzyme 1 by inactivating the extracellular signal-regulated kinase 1/2 (ERK)/MAPK signaling pathway. Furthermore, upregulation of MKP-1 reduced Aβ production and plaque formation and improved hippocampal long-term potentiation (LTP) and cognitive deficits in APP/PS1 transgenic mice. Our results demonstrate that MKP-1 impairment facilitates the pathogenesis of AD, whereas upregulation of MKP-1 plays a neuroprotective role to reduce Alzheimer-related phenotypes. Thus, this study suggests that MKP-1 is a novel molecule for AD treatment.

Inhibition of PTP1B Promotes M2 Polarization via MicroRNA-26a/MKP1 Signaling Pathway in Murine Macrophages

Sepsis is a life-threatening condition that often occurs in the intensive care unit. The excessive activation of the host's immune system at early stages contributes to multiple organ damage. Mitogen-activated protein kinase phosphatase-1 (MKP1) exerts an important effect on the inflammatory process. In our recent bioinformatic analysis, we confirmed that the inhibition of protein tyrosine phosphatase-1B (PTP1B) significantly promoted the expression of MKP1 in murine macrophages. However, the underlying mechanism and its effect on macrophage polarization remain unclear. In this study, we show that the suppression of PTP1B induced upregulation of MKP1 in M1 macrophages. A RayBiotech mouse inflammation antibody assay further revealed that MKP1-knockdown promoted pro-inflammatory cytokine (IL-1β, IL12p70, IL-17, IL-21, IL-23, and TNF-α) secretion but suppressed anti-proinflammatory cytokine (IL-10) production in M2 macrophages. Phospho-proteomics analysis further identified ERK1/2 and p38 as downstream molecules of MKP1. Moreover, we found that the inhibition of PTP1B lowered the expression of miR-26a, showing a negative correlation with MKP1 protein expression. Thus, we concluded that the inhibition of PTP1B contributes to M2 macrophage polarization via reducing mir-26a and afterwards enhancing MKP1 expression in murine macrophages.