Pterygium epithelium abnormal differentiation related to activation of extracellular signal-regulated kinase signaling pathway in vitro

AIMTo investigate whether the abnormal differentiation of the pterygium epithelium is related to the extracellular signal-regulated kinase (ERK) signaling pathway in vitro.METHODSThe expression levels of phosphorylated ERK (P-ERK), keratin family members including K19 and K10 and the ocular master control gene Pax-6 were measured in 16 surgically excised pterygium tissues and 12 eye bank conjunctiva. In colony-forming cell assays, the differences in clone morphology and in K10, K19, P-ERK and Pax-6 expression between the head and body were investigated. When cocultured with the ERK signaling pathway inhibitor PD98059, the changes in clone morphology, colony-forming efficiency, differentiated marker K10, K19 and Pax-6 expression and P-ERK protein expression level were examined by immunoreactivity and Western blot analysis.RESULTSThe expression of K19 and Pax-6 decreased in the pterygium, especially in the head. No staining of K10 was found in the normal conjunctiva epithelium, but it was found to be expressed in the superficial cells in the head of the pterygium. Characteristic upregulation of P-ERK was observed by immunohistochemistry. The clone from the head with more differentiated cells in the center expressed more K10, and the clone from the body expressed more K19. The P-ERK protein level increased in the pterygium epithelium compared with conjunctiva and decreased when cocultured with PD98059. The same medium with the ERK inhibitor PD98059 was more effective in promoting clonal growth than conventional medium with 3T3 murine feeder layers. It was observed that the epithelium clone co-cultured with the inhibitor had decreased K10 expression and increased K19 and Pax-6 expression.CONCLUSIONWe suggest ERK signaling pathway activation might play a role in the pterygium epithelium abnormal differentiation.

Research progress of the role and mechanism of extracellular signal-regulated protein kinase 5(ERK5) pathway in pathological pain

Extracellular signal-regulated protein kinase 5 （ERK5）, also known as big mitogen-activated protein kinase 1 （MAPK1）, is an important member of ERK family, which is a subfamily of the large MAPK family. ERK5 is expressed in many tissues, including the dorsal root ganglion （DRG） neurons and the spinal cord. In this review, we focus on elaborating ERK5-associated pathway in pathological pain, in which the ERK5/CREB （cyclic adenosine monophos- phate （cAMP）-response element-binding protein） pathway plays a crucial role in the transduction of pain signal and contributes to pain hypersensitivity. ERK5 activation in the spinal dorsal horn occurs mainly in microglia. The activation of ERK5 can be mediated by N-methyI-D-aspartate （NMDA） receptors. We also elaborate the relationship between ERK5 activation and nerve growth factor-tyrosine kinase A （NGF-TrkA）, and the connection between ERK5 activation and brain-derived neurotrophic factor （BDNF） in pathological pain in detail.

ERK signaling pathway may induce gemcitabine chemoresistance in pancreatic cancer cell line SW1990 by regulating the expression of mdr-1 and RRM1 gene

Objective： To investigate the relationship between extracellular signal-regulated kinase （ERK） pathway, multidrug resistance gene （mdr-1）, ribonucleotide recluctase M1 （RRM1） gene and their roles in gemcitabine （GEM） chemoresistance in pancreatic cancer cell line SW1990. Methods： The GEM-resistance cell model was constructed by a stepwise method. Immunohistochemistry was used to measure the expression of ERK protein （ERK1/2） in the established cell strains in a semiquantitative way. The mRNA expression of mdr-1 and RRM1 were detected by RT-PCR. MTT assay was performed to determine the IC50 value. Results： The established GEM-resistant cell strains were able to gain stable growth and passage ability in the medium contained different concentration levels of GEM （0, 30, 60, 100, 150 and 200 nmol/L）. The expression of ERK protein, mdr-1 and RRM1 gene were elevated accompanied by the increase of GEM concentration. There was a highly positive correlation between mdr-1, RRM1 expression and GEM-resistanca level （r = 0.960, P = 0.002 and r = 0.966, P = 0.002）. The expression of ERK protein also correlated with the mdr-1 and RRM1 level （r = -0.943, P = 0.005 and r = -0.883, P = 0.02）. At the GEM-resistance level of 200 nmol/L, the grey scale value of ERK1/2 was 164.22 ±13.17, mdr-1/β-actin and RRM1/β-actin were 1.41 ±0.04 and 1.45 ± 0.18, respectively; after treated with ERK pathway inhibitor U0126, these values synchronously decreased to 186.85 ± 13.14, 0.2 3± 0.02 and 0.21 ± 0.03, respectively; inversely, the ERK1/2 grey scale value was 106.55 ± 16.45, mdr-l/β-actin and RRMl/β-actin were 1.50± 0.07 and 1.52 ± 0.12, respectively, which presented a tendency of synchronously increase after treated with ERK pathway activator EGF. The IC50 values in GEM-resistant cells of 0 nmol/L and 200 nmol/L levels were 4.104 and 10.20, respectively. After treated with U0126, these values decreased to 3.26 and 4.50, respectively; while treated with EGF, the IC50 values increased to 8.89 and 17.17, respectively. Conclusion： The ERK pathway may induce the GEM-chemoresistance in pancreatic cell line SW1990 through the participation in the regulation of the mdr-1 and RRM1 gene expression.

Isoleucine, an Essential Amino Acid, Induces the Expression of Human <i>β</i>Defensin 2 through the Activation of the G-Protein Coupled Receptor-ERK Pathway in the Intestinal Epithelia

Anti-microbial peptides are essential for the intestinal innate immunity that protects the intestinal epithelia from attacks by foreign pathogens. Human β-defensin (HBD) is one of the pivotal anti-microbial peptides that are expressed in the colonic epithelia. This study investigated the effect and the signaling mechanism of inducible β-defensin HBD2 by an essential amino acid, isoleucine (Ile) in colonic epithelial cells. Here we examined the expression level of HBD2 on induction of Ile in epithelial cells, and checked this pathway. HBD2 mRNA was induced by co-incubation with IL-1α and Ile in Caco2 cells, but not by Ile alone. An inhibitor of either ERK or Gi, a subunit of G-proteins, reduced the induction of HBD2 mRNA by Ile. The treatment with Ile also increased the intracellular calcium ion concentration, thus suggesting that the GPCR and ERK signaling pathway mediate the effects of Ile. These results indicate that an essential amino acid, Ile, enhances the expression of an inducible β-defensin, namely HBD2, by IL-1α through the activation of GPCRs and ERK signaling pathway. The administration of Ile may therefore represent a possible option to safely treat intestinal inflammation.

Imbalanced expression of mitogen-activated protein kinase phosphatase-1 and phosphorylated extracellular signal-regulated kinases in lung squamous cell carcinoma

Objective： Mitogen-activated protein kinases （MAPKs） are correlated with a more malignant phenotype in many cancers. This study was designed to evaluate the predictive value of the expression of MAPK phosphatase-1 （MKP-1） and phosphorylated extracellular signal-regulated kinase 1/2 （p-ERKl/2）, as the key regulatory mechanism of the MAPKs, in lung squamous cell carcinoma （SCC）. Methods： We assessed the expressions of MKP-1 and p-ERK1/2 in twenty subjects at different differentiation degree of SCC and five normal lungs by immunohistochemistry and real-time reverse transcriptase polymerase chain reaction （RT-PCR） analysis. Results： Immunohistochemistry and real-time RT-PCR assay showed that the expression of MKP-1 was gradually decreased as tissue type went from normal lung tissues to increasingly undifferentiated carcinoma, and it was negatively correlated with tumor differentiation （P〈0.01）. However, the expression of p-ERK1/2 or ERKl/2 was gradually increased as tissue type went from normal lung tissues to increasingly undifferentiated carcinoma, and it was positively correlated with tumor differentiation （P〈0.01）. Conclusions： Our data indicates the relevance of MKP-1 and p-ERK1/2 in SCC as a potential positive and negative prognostic factor. The imbalanced expression of MKP-1 and p-ERKl/2 may play a role in the development of SCC and these two molecules may be new targets for the therapy and prognosis of SCC.

Moxibustion eases chronic inflammatory visceral pain through regulating MEK, ERK and CREB in rats

AIM To investigate the effects of herb-partitioned moxibustion(HPM) on phosphorylation of mitogen-activated extracellular signal-regulated kinase(MEK)1, extracellular signal-regulated kinase(ERK)1/2 and c AMP response element binding protein(CREB) in spinal cord of rats with chronic inflammatory visceral pain(CIVP), and to explore the central mechanism of HPM in treating CIVP.METHODS Male Sprague-Dawley rats were randomized into normal, model, HPM, sham-HPM, MEK-inhibitor and dimethyl sulfoxide(DMSO) groups. The CIVP model was established using an enema mixture of trinitrobenzene sulfonic acid and ethanol. HPM was applied at bilateral Tianshu(ST25) and Qihai(CV6) acupoints in the HPM group, while in the sham-HPM group, moxa cones and herb cakes were only placed on the same points but not ignited. The MEK-inhibitor and DMSO groups received L5-L6 intrathecal injection of U0126 and 30% DMSO, respectively. Abdominal withdrawal reflex(AWR), mechanical withdrawal threshold(MWT) and thermal withdrawal latency(TWL) were applied for the assessment of pain behavior. The colonic tissue was observed under an optical microscope after hematoxylin-eosin staining. Expression of phosphor(p)MEK1, p ERK1/2 and p CREB in rat spinal cord was detected using Western blotting. The levels of MEK, ERK and CREB m RNA in rat spinal cord were detected using real-time polymerase chain reaction. RESULTS Compared with the normal group, the AWR scores were increased significantly(P < 0.01) and the MWT and TWL scores were decreased significantly(P < 0.05) in the model, sham-HPM and DMSO groups. Compared with the model group, the AWR scores were decreased significantly(P < 0.01) and the MWT and TWL scores were increased significantly in the HPM and MEK-inhibitor groups(P < 0.05). Compared with the sham-HPM and DMSO groups, the AWR scores were decreased significantly(P < 0.01) and the MWT and TWL scores were increased significantly(P < 0.05) in the HPM and MEK-inhibitor groups. Compared with the normal group, the expression of p MEK1, p ERK1/2 and p CREB proteins and the levels of MEK, ERK and CREB m RNA in rat spinal cord were increased significantly in the model, sham-HPM and DMSO groups(P < 0.01 or < 0.05). Compared with the model group, the expression of p MEK1, p ERK1/2 and p CREB proteins and the levels of MEK, ERK and CREB m RNA in rat spinal cord were reduced significantly in the HPM and MEK-inhibitor groups(P < 0.01 or < 0.05). Compared with the sham-HPM and DMSO groups, expression of p MEK1, p ERK1/2 and p CREB proteins and the levels of MEK, ERK and CREB m RNA in rat spinal cord were reduced significantly in the HPM and MEK-inhibitor groups(P < 0.01 or < 0.05). CONCLUSION HPM down-regulates protein phosphorylation of MEK1, ERK1/2 and CREB, and m RNA expression of MEK, ERK and CREB, inhibiting activation of the MEK/ERK/CREB signaling pathway in the spinal cord of CIVP rats, which is possibly a critical central mechanism of the analgesic effect of HPM.

Down-regulation of HIV-1 Infection by Inhibition of the MAPK Signaling Pathway

The human immunodeficiency virus type 1 （HIV-1） can interact with and exploit the host cellular machinery to replicate and propagate itself. Numerous studies have shown that the Mitogen-activated protein kinase （MAPK） signal pathway can positively regulate the replication of HIV-1, but exactly how each MAPK pathway affects HIV-1 infection and replication is not understood. In this study, we used the Extracellular signal-regulated kinase （ERK） pathway inhibitor, PD98059, the Jun N-terminal kinase （JNK） pathway inhibitor, SP600125, and the p38 pathway inhibitor, SB203580, to investigate the roles of these pathways in HIV-1 replication. We found that application of PD98059 results in a strong VSV-G pseudotyped HIV-1NL4-3 luciferase reporter virus and HIV-1NL4-3 virus inhibition activity. In addition, SB203580 and SP600125 also elicited marked VSV-G pseudotyped HIV-INL4-3 luciferase reporter virus inhibition activity but no HIV-1NL4-3 virus inhibition activity. We also found that SB203580 and SP600125 can enhance the HIV-1 inhibition activity of PD98059 when cells were treated with all three MAPK pathway inhibitors in combination. Finally, we show that HIV-1 virus inhibition activity of the MAPK pathway inhibitors was the result of the negative regulation of HIV-1 LTR promoter activity.

Bim和细胞外调节蛋白在肝癌多药耐药细胞中的表达

目的检测人肝癌耐药细胞Hep G-2/ADM和亲本细胞Hep G-2中ERK1,ERK2、ERK5和Bim的表达,探讨其对肝癌细胞多药耐药的影响。方法小剂量缓慢诱导法诱导建立人肝癌耐药细胞株Hep G-2/ADM;CCK-8法测定Hep G-2/ADM对多种化疗药物的交叉耐药性;Western-blotting检测MRP-1,P-gp,ERK1,ERK2,ERK5和Bim蛋白水平的表达;荧光定量PCR检测Bim mRNA的表达。结果化疗药物能够体外诱导肿瘤细胞产生耐药性,Hep G-2/ADM对ADM、5-FU和CDDP的耐药指数分别为6.8,4.1和4.5,且高表达MRP-1和P-gp蛋白;与亲本细胞Hep G-2相比,Hep G-2/ADM中ERK1,ERK2和ERK5的表达均升高,ERK1蛋白磷酸化水平无显著变化,ERK2磷酸化水平下降,且p-ERK1/2与ERK1/2的比值下降;Bim的mRNA和蛋白表达均下降。结论细胞外调节蛋白激酶ERKs和Bcl-2家族的促凋亡蛋白Bim的表达与人肝癌多药耐药的发生密切相关。

缓激肽对PDGF诱导的肾小球系膜细胞增殖的影响

[目的]探讨缓激肽(bradykinin,BK)对血小板源生长因子(PDGF)诱导的系膜细胞增殖的影响及与ERK信号途径相关性。[方法]BK预孵系膜细胞,采用PDGF-BB刺激系膜细胞,应用MTT法测细胞增殖,ELISA法测Ⅳ型胶原,应用Western法检测ERK蛋白表达,并应用BK受体特异性阻断剂HOE-140进一步研究BK对ERK通路的作用。[结果](1)BK抑制PDGF所致的系膜细胞增殖,与单用PDGF-BB组比较差异有非常显著性意义(P<0.05)。(2)BK抑制PDGF-BB所致系膜细胞Ⅳ型胶原分泌,与单用PDGF-BB组比较差异有显著性意义(P<0.05)。(3)BK抑制PDGF-BB所致的系膜细胞ERK1/2磷酸化表达,与单用PDGF-BB组比较差异有显著性意义(P<0.01),HOE-140能阻断BK对于PDGF-BB/ERK1/2途径磷酸化的抑制作用。[结论]BK抑制PDGF诱导的系膜细胞增殖及细胞外基质分泌,该作用可能是通过抑制PDGF诱导的ERK1/2途径激活实现。

Endostatin inhibits fibrosis by modulating the PDGFR/ERK signal pathway:an in vitro study

Accumulating evidence indicates that endostatin inhibits fibrosis. However, the mechanism is yet to be clarified. The aim of this study is to evaluate the effect of endostatin on platelet-derived growth factor-BB （PDGF-BB）- or transforming growth factor β1 （TGF-β1）-induced fibrosis in cultured human skin fibroblasts, and to further examine the molecular mechanisms involved. Human dermal flbroblasts were cultured in Dulbecco＇s modified Eagle＇s medium （DMEM） and serum-starved for 48 h before treatment. Cells were grouped as follows： ＂PDGF-BB＂, ＂PDGF-BB＋ endostatin＂, ＂TGF-β1＂, ＂TGF-β1＋endostatin＂, ＂endostatin＂, and ＂blank control＂. The fibroblasts were stimulated with either TGF-β1 or PDGF-BB for 72 h in order to set up the fibrosis model in vitro. The cells were co-cultured with either TGF-β1 or PDGF-BB and endostatin and were used to check the inhibiting effect of endostatin. A blank control group and an endostatin group were used as negative control groups. The biomarkers of fibrosis, including the expression of collagen I, hydrroxyproline, and α-smooth muscle actin （a-SMA）, were evaluated using an enzyme-linked immune- sorbent assay （ELISA） and Western blot. The expression of phosphorylated PDGF receptor β （p-PDGFRβ）, PDGFRβ, phosphorylated extracellular signal-regulated kinase （p-ERK）, and ERK was detected using Western blot and im- munofiuorescent staining was used to explore the mechanisms. Both PDGF-BB and TGF-β1 significantly up-regulated the expression of collagen I, hydroxyproline, and a-SMA. Endostatin significantly attenuated both the PDGF-BB- and TGF-β1-induced over-expression of collagen I, hydroxyproline, and a-SMA. PDGF-BB and TGF-β1 both promoted the expression of PDGFR, ERK, and p-ERK. Endostatin inhibited the expression of PDGFR and p-ERK but did not affect the expression of total ERK. Endostatin inhibited hypertrophic scar by modulating the PDGFRI3/ERK pathway. En- dostatin could be a promising multi-target drug in future fibrosis therapy.

Cyclooxygenase-2 inhibitor inhibits hippocampal synaptic reorganization in pilocarpine-induced status epilepticus rats

Objective： To examine modulations caused by cyclooxygenase-2 （COX-2） inhibitors on altered microenvironments and overbalanced neurotransmitters in pilocarpine-induced epileptic status rats and to investigate possible mechanisms. Methods： Celecoxib （a COX-2 inhibitor） was administered 45 min prior to pilocarpine administration. The effects of COX-2 inhibitors on mlPSCs （miniature GABAergic inhibitory postsynaptic currents） of CA3 pyramidal cells in the hippocampus were recorded. Expressions of COX-2, c-Fos, newly generated neurons, and activated microgliosis were analyzed by immunohistochemistry, and expressions of c^-subunit of y-amino butyric acid （GABAA） receptors and mitogen-activated protein kinase/extracellular signal-regulated protein kinase （MAPK/ERK） activity were detected by Western blotting. Results： Pretreatment with celecoxib showed protection against pilocarpine-induced seizures. Celecoxib prevented microglia activation in the hilus and inhibited the abnormal neurogenesis and astrogliosis in the hippocampus by inhibiting MAPK/ERK activity and c-Fos transcription. Celecoxib also up-regulated the expression of GABAA receptors. NS-398 （N-2-cyclohexyloxy-4-nitrophenyl-methanesulfonamide）, another COX-2 inhibitor, enhanced the frequency and decay time of mIPSCs. Conclusion： The COX-2 inhibitor celecoxib decreased neuronal excitability and prevented epileptogenesis in pilocarpine-induced status epilepticus rats. Celecoxib regulates synaptic reorganization by inhibiting astrogliosis and ectopic neurogenesis by attenuating MAPK/ERK signal activity, mediated by a GABAergic mechanism.

Identification of key genes involved in axon regeneration and Wallerian degeneration by weighted gene co-expression network analysis

Peripheral nerve injury repair requires a certain degree of cooperation between axon regeneration and Wallerian degeneration.Therefore,investigating how axon regeneration and degeneration work together to repair peripheral nerve injury may uncover the molecular mechanisms and signal cascades underlying peripheral nerve repair and provide potential strategies for improving the low axon regeneration capacity of the central nervous system.In this study,we applied weighted gene co-expression network analysis to identify differentially expressed genes in proximal and distal sciatic nerve segments from rats with sciatic nerve injury.We identified 31 and 15 co-expression modules from the proximal and distal sciatic nerve segments,respectively.Functional enrichment analysis revealed that the differentially expressed genes in proximal modules promoted regeneration,while the differentially expressed genes in distal modules promoted neurodegeneration.Next,we constructed hub gene networks for selected modules and identified a key hub gene,Kif22,which was up-regulated in both nerve segments.In vitro experiments confirmed that Kif22 knockdown inhibited proliferation and migration of Schwann cells by modulating the activity of the extracellular signal-regulated kinase signaling pathway.Collectively,our findings provide a comparative framework of gene modules that are co-expressed in injured proximal and distal sciatic nerve segments,and identify Kif22 as a potential therapeutic target for promoting peripheral nerve injury repair via Schwann cell proliferation and migration.All animal experiments were approved by the Institutional Animal Ethics Committee of Nantong University,China(approval No.S20210322-008)on March 22,2021.

Combination of Quercetin, Hirudin and Cinnamaldehyde Promotes Schwann Cell Differentiation and Myelination against High Glucose by Inhibiting ERK Signaling Pathway

Objective:To investigate the therapeutic and synergistic effects of QHC(combination of quercetin(Q),hirudin(H)and cinnamaldehyd(C))on Schwann cell differentiation and myelination against high glucose(HG)induced injury.Methods:Primary-culture Schwann cells exposed to HG(50 mmol/L)for 72 h and Schwann cell–dorsal root ganglion(DRG)neuron cocultures exposed to HG(50 mmol/L)for 7 days were employed as in vitro model of diabetic neuropathy.The cells were randomly divided into 10 groups:control(CON,25 mmol/L glucose),HG(50 mmol/L glucose),HG plus 10μmol/L quercetin(Q),HG plus 0.04 IU/mL hirudin(H),HG plus 100 nmol/L cinnamaldehyd(C),HG plus 10μmol/L quercetin and 0.04 IU/mL hirudin(QH),HG plus 10μmol/L quercetin and 50 nmol/L cinnamaldehyd(QC),HG plus 0.04 IU/mL hirudin and 50 nmol/L cinnamaldehyd(HC),HG plus 10μmol/L quercetin,0.04 IU/mL hirudin and 50 nmol/L cinnamaldehyd(QHC)or 10μmol/L U0126.Cell differentiation was evaluated by periaxin immunofluorescence staining.The protein expression levels of myelin protein zero(P0),myelin basic protein(MBP),myelin-associated glycoprotein(MAG),extracellular signal-regulated kinase(ERK),p-ERK,p-c-Jun,c-Jun,notch intracellular domain(NICD)and the mRNA expression levels of P0,MBP,MAG,Krox-20,Notch1 and Jagged1 were detected by Western blotting and real-time quantitative PCR analysis.The secretion of ciliary neurotrophic factor(CNTF)was determined by enzyme-linked immunosorbent assay(ELISA).The number and length of the myelin segments were evaluated by MBP immunofluorescence staining.The expression and the location of p-ERK in cocultures were detected by MAG and p-ERK immunofluorescence double staining.Results:Co-treatment with Q,C,H and their combination promoted Schwann cell differentiation,increased CNTF secretion,up-regulated the protein and m RNA expressions of myelin,and increased the number and length of the myelin segments(P<0.01 or P<0.05).In particular,the combination therapy of Q,H and C was superior to the respective monotherapy(P<0.01).Combination therapy of QHC exhibited higher inhibitory activities for ERK signaling related molecules than each monomer or the combination of the two monomers(P<0.01).Conclusions:QHC combination yielded synergy in promoting Schwann cell differentiation and myelination and the protective effect may involve in the inhibition of ERK signaling pathway,providing scientific evidence for better understanding of combination of Q,H and C in clinical applications.