Colloidal Phenol-Amine Coating on Implants for Improved Anti-Inflammation and Osteogenesis

Phenol-amine coatings have attracted significant attention in recent years owing to their adjustable composition and multifaceted biological functionalities. The current preparation of phenol-amine coatings, however, involves a chemical reaction within the solution or interface, resulting in lengthy preparation times and necessitating specific reaction conditions, such as alkaline environments and oxygen presence. The facile, rapid, and eco-friendly preparation of phenol-amine coatings under mild conditions continues to pose a challenge. In this study, we use a macromolecular phenol-amine, Tanfloc, to form a stable colloid under neutral conditions, which was then rapidly adsorbed on the titanium surface by electrostatic action and then spread and fused to form a continuous coating within several minutes. This nonchemical preparation process was rapid, mild, and free of chemical additives. The in vitro and in vivo results showed that the Tanfloc colloid fusion coating inhibited destructive inflammation, promoted osteogenesis, and enhanced osteointegration. These remarkable advantages of the colloidal phenol-amine fusion coating highlight the suitability of its future application in clinical practice.

Host response of Nicotiana benthamiana to the parasitism of five populations of root-lesion nematode, Pratylenchus coffeae, from China

In a recent survey of nematodes associated with tobacco in Shandong, China, the root-lesion nematode Pratylenchus coffeae was identified using a combination of morphology and molecular techniques. This nematode species is a serious parasite that damages a variety of plant species. The model plant benthi, Nicotiana benthamiana, is frequently used to study plant-disease interactions. However, it is not known whether this plant species is a host of P. coffeae. The objectives of this study were to evaluate the parasitism and pathogenicity of five populations of the root-lesion nematode P. coffeae on N. benthamiana.N. benthamiana seedlings with the same growth status were chosen and inoculated with 1,000 nematodes per pot. At 60 days after inoculation, the reproductive factors (Rf = final population densities (Pf)/initial population densities (Pi)) for P. coffeae in the rhizosphere of N. benthamiana were all more than 1, suggesting that N. benthamiana was a good host plant for P. coffeae.Nicotiana. benthamiana infected by P. coffeae showed weak growth, decreased tillering, high root reduction, and noticeable brown spots on the roots. Thus, we determined that the model plant N. benthamiana can be used to study plant-P. coffeae interactions.

[Early efficacy and safety of mini open (air/water medium) endoscopy assisted anterior cervical discectomy and fusion in the treatment of cervical spondylotic myelopathy]

Objective: To investigate the efficacy and safety of mini open (air/water medium) endoscopy assisted anterior cervical discectomy and fusion (MOEA-ACDF) for the treatment of cervical spondylotic myelopathy (CSM). Methods: A follow-up study. The clinical data of 30 patients with CSM treated by MOEA-ACDF from January to December in 2021 in the Henan NO.3 Provincial People's Hospital were retrospectively analyzed. Of the patients, 20 were male and 10 were female, the mean age was (49.8±9.3) years (ranged 28-70 years). The CSM occurred at C3-4 level in 2 cases, at C4-5 level in 3 cases, at C5-6 level in 22 cases and at C6-7 level in 3 cases. Each case was compared at the moment of pre-operation and final follow-up by the Japanese Orthopedic Association (JOA) score, C2-7 Cobb angle, and anterior column height of surgical segment. The postoperative complications were recorded. Prevertebral soft tissue edema and hydrops were assessed. The fusion rate was evaluated. The JOA improvement rate was computed at the final follow-up. Results: All the operations were successfully completed and all the patients received follow-up for (12.7±2.7) months (ranged 9-20 months). The mean operation time was (85.3±11.0) min (ranged 65-110 min). The postoperative drainage volume was (16.7±7.4) ml (ranged 5-35 ml). The JOA score and the C2-7 Cobb angle both improved at the final follow-up when compared with those before the operation (15.3±1.3 vs 12.2±2.3, 15.5°±6.1° vs 12.3°±6.0°, both P<0.001). The anterior column height of surgical segment at the final follow-up was (35.6±2.5) mm, and it was higher than that before the operation [(34.1±2.4) mm](P<0.001). No postoperative complications such as dysphagia, hoarseness, cerebrospinal fluid leakage, nerve injury, hematoma occurred. Postoperative review of cervical MRI revealed 3 cases of prevertebral soft tissue edema and hydrops without obvious symptoms. At the final follow-up, cervical spine X-ray or CT showed that all fusion segments met the criteria for osseous fusion, and the fusion rate was 100%. No complications such as neurological aggravation, internal fixation failure, fusion cage sinking, and adjacent segment degeneration was recorded at the final follow-up. At the final follow-up, the comprehensive efficacy evaluated by JOA improvement rate indicated the excellent and good rate was 90.0%(27/30): 19 cases got an excellent outcome, 8 cases got good and 3 cases got medium outcome. Conclusion: MOEA-ACDF combines the endoscopic system with ACDF technology in the treatment of CSM can achieve satisfactory clinical efficacy with high safety, and effectively restore the cervical intervertebral height and physiological curvature.

[Wine-processed Chuanxiong Rhizoma enhances efficacy of aumolertinib against EGFRmutant non-small cell lung cancer xenografts in nude mouse brain]

OBJECTIVE

To investigate the effect of wine-processed Chuanxiong Rhizoma (WCR) for enhancing the efficacy of aumolertinib against xenografts of epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC) in the brain of nude mice.

METHODS

In a co-culture system of hCMEC/D3 and PC9 NSCLC cells, the effect of aqueous extract of WCR (2 mg/mL) combined with aumolertinib (10 and 20 μmol/L) on apoptosis of PC9 cells was investigated using flow cytometry. The effects of WCR extract (0.5, 1, and 2 mg/mL) on transmembrane transport of 8 μmol/L aumolertinib was examined in ABCB1-MDCK monolayer cells. Western blotting was used to detect the expressions of the tight junction proteins related with blood- brain barrier integrity. A nude mouse model bearing NSCLC xenograft in the brain was established to observe the inhibitory effect of WCR (1 mg/g) combined with aumolertinib (10 mg/kg) on tumor growth.

RESULTS

Compared with aumolertinib (20 μmol/L) alone, WCR extract (2 mg/mL) combined with aumolertinib significantly increased the apoptosis rate of PC9 cells by 21% (P < 0.01). The combined treatment with WCR (0.5, 1, 2 mg/mL) obviously increased apical-basolateral transport of aumolertinib in ABCB1-MDCK monolayer cells (P < 0.05) and significantly lowered the expression levels of zonula occludens-1, claudin-5 and P-glycoprotein (P < 0.05). In the tumor-bearing mice, compared with aumolertinib alone, the combined treatment with WCR and aumolertinib produced stronger inhibitory effect on tumor growth, improved weight loss, and prolonged the survival time of the nude mice (P < 0.05). Pathological examination showed that the combined treatment obviously increased the apoptosis rate of the tumor cells and alleviated neural injuries in the brain. Immunohistochemistry revealed that WCR treatment significantly reduced the expressions of ZO-1 and claudin-5 in the brain of the mice.

CONCLUSION

WCR combined with aumolertinib shows stronger inhibitory effects against tumor xenografts of EGFR-mutant NSCLC possibly due to the effect of WCR in facilitating the transmembrane transport of aumolertinib by downregulating ZO-1, claudin-5 and P-glycoprotein expression.

[Chuanxiong Rhizoma inhibits brain metastasis of lung cancer through multiple active ingredients acting on multiple targets, pathways and biological functions]

OBJECTIVE

To explore the molecular mechanism mediating the inhibitory effect of Chuanxiong Rhizoma against brain metastasis of lung cancer using network pharmacology methods and molecular docking.

METHODS

The chemical components of Chuanxiong Rhizoma and their targets were obtained through the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database. The relevant targets for brain metastasis of lung cancer were screened using the GeneCards database. Clusterpro-filerR package was used to perform GO and KEGG enrichment analysis. Cytoscape and STRING database were used to construct the "active ingredient-target-disease" network and protein-protein interaction (PPI) network of Chuanxiong Rhizoma. The core components of Chuanxiong Rhizoma and their targets in the treatment of lung cancer brain metastasis were screened based on the topological parameters, and the results were verified using molecular docking and in Chuanxiong extract- treated human lung cancer PC9 cells by detecting the core target with Western blotting.

RESULTS

Forty-eight active ingredients of Chuanxiong Rhizoma including (Z)-ligustilide, butylphthalide, oleic acid, and myricetone were screened, which target 49 proteins including INS, BDNF, FOS, VEGFA, PTGS2, ESR1, MAPK14, and PTGS1. These proteins participated in 57 biological functions such as nuclear receptor activity, ligand activation, and transcription factor activity, involving 40 signaling pathways such as prolactin signaling pathway, breast cancer, and etrogen signaling. The results of molecular docking showed that myricetone, butylphthalide, 4-hydroxy-3 butylphthalide, (Z)-ligustilide, and ligustalide-E, among others, had strong affinities to 7 cores targets including BDNF, FOS, PTGS2, and MAPK14. In PC9 cells, treatment with Chuanxiong Rhizoma extract resulted in significant reductions in the phosphorylation levels of PI3K, Akt and VEGF (P < 0.01).

CONCLUSION

Chuanxiong Rhizoma contains multiple active ingredients against brain metastasis lung cancer, and these ingredients act on multiple targets involving multiple signal pathways and biological functions.

E2F1-induced upregulation of lncRNA HCG18 stimulates proliferation and migration in gastric cancer by binding to miR-197-3p

OBJECTIVE

LncRNA HCG18 is considered to be an oncogene in many types of tumors. The aim of this study was to explore the role of lncRNA HCG18 in gastric cancer (GC).

PATIENTS AND METHODS

HCG18 levels in GC tissues were detected. Potential biological influences of HCG18 on GC cell phenotypes were examined by Cell Counting Kit-8 (CCK-8), wound healing and transwell assay. Subsequently, bioinformatics analysis, Chromatin immunoprecipitation (ChIP), Luciferase assay and rescue experiments were conducted to identify the regulatory network of HCG18 in GC.

RESULTS

It was found that HCG18 was upregulated in GC samples, and the knockdown of HCG18 inhibited proliferative and migratory abilities in GC. The transcription factor E2F1 could directly bind to the promoter region of HCG18 and thus activate its transcription. In addition, HCG18 sponged miR-197-3p to stimulate the malignant development of GC.

CONCLUSIONS

HCG18 is upregulated in GC samples by E2F1 induction, which stimulates proliferative and migratory abilities in GC by binding to miR-197-3p.

[Monitoring metrics for short-term exposure to ambient ozone and pulmonary function and airway inflammation in healthy young adults]

OBJECTIVE

To assess the associations of different monitoring metrics for short-term exposure to ambient ozone (O₃) with pulmonary function and airway inflammation in healthy young adults.

METHODS

A total of 97 healthy young college students were recruited and followed in a panel study conducted from December 2017 to June 2018. Each participant underwent 3 follow-up visits, and lung function and fractional exhaled nitric oxide (FeNO) were measured at each visit. Ambient air pollutant concentrations were obtained from the environment monitoring station of Beijing closest to the participant residences, and meteorological data were collected from China Meteorological Data Service Center. Linear mixed-effect models were applied to assess the associations between different monitoring metrics for ambient O₃ short-term exposure with pulmonary function or airway inflammation in the healthy young adults.

RESULTS

During the study period, the P₅₀ (P₂₅, P₇₅) values for ambient O₃ concentration expressed as daily 1-hour maximum (O₃-1 h max), daily maximum 8-hour average (O₃-8 h max) and 24-hour average (O₃-24 h avg) were 102.5 (76.8, 163.0) μg/m³, 91.1 (68.3, 154.3) μg/m³ and 61.6 (36.9, 81.7) μg/m³, respectively. The different monitoring metrics for short-term exposure to ambient O₃ were significantly associated with reduced forced expiratory volume in the first second (FEV₁) and increased FeNO. An interquartile range (IQR) increase in 6-d moving average of O₃-1 h max (IQR=71.5 μg/m³) was associated with a 6.2% (95%CI: －11.8%, －0.5%) decrease in FEV₁ and a 63.3% (95%CI: 13.8%, 134.3%) increase in FeNO. An IQR increase in 7-d moving average of O₃-8 h max (IQR=62.0 μg/m³) was associated with a 6.2% (95%CI: －11.6%, －0.7%) decrease in FEV₁and a 75.5% (95%CI: 19.3%, 158.0%) increase in FeNO. An IQR increase in 5-d moving average of O₃-24 h avg (IQR=32.9 μg/m³) was associated with a 3.7% (95%CI: －7.1%, －0.2%) decrease in FEV₁and a 25.3% (95%CI: 3.6%, 51.6%) increase in FeNO. There was no significant association between the three monitoring metrics for O₃ exposure and peak expiratory flow (PEF).

CONCLUSION

Short-term exposure to ambient O₃ was associated with decreased lung function and increased airway inflammation among the healthy young adults, and daily 1-hour maximum was more sensitively to the respiratory effects of O₃.

AB0588 INFECTION AGGRAVATED DECREASE OF THE LEVEL OF TH17 AND TREG CELLS AND LOW-DOSE IL-2 REBALANCED TH17/TREG IN THE PERIPHERAL BLOOD OF PATIENTS WITH IDIOPATHIC INFLAMMATORY MYOPATHY

Background:

Idiopathic inflammatory myopathies (IIM) are featured by a series of clinical presentation such as proximal muscle weakness, increased serum levels of creatine kinase and other muscle enzymes and involvement of other organs and systems[1, 2], which results in high morbidity and early mortality[3]. We have known the changes of the level of Th17 and Treg cells in IIM in previous studies[4-6]. However, whether infection affects lymphocyte subsets or not and whether the effect of low-dose interleukin-2 (IL-2) can be influenced by the use of immunosuppressants or not are still unclear.

Objectives:

The study aimed to explore the changes of lymphocyte subsets in patients of IIM with or without important organ infection, and the restoration of Th17/Treg after receiving low-dose IL-2.

Methods:

A total of 118 IIM patients were enrolled and classified into infection group and non-infection group based on the important organ infection. Of them, 48 cases were treated with low dose IL-2 (5.0*105IU for 5 days). The absolute number of peripheral total T, B, CD4+T, CD8+T, NK, Th1, Th2, Th17 and Treg cell subsets were analyzed by flow cytometry combined with absolute counting beads. Clinical data, laboratory examinations and the levels of peripheral lymphocyte subsets were analyzed retrospectively.

Results:

In these patients, especially in the infection group, the absolute number of T, CD4+T, CD8+T, NK, Th1, Th2, Th17 and Treg cells were significantly decreased as compared with that in the healthy controls, which were significantly increased by low dose IL-2 (especially Treg cells) treatment. The levels of ESR, LDH and HBDH and the ratio of Th17/Treg were significantly lower than those before IL-2 treatment (Z=-2.237, -2.083, -2.140, -3.663,P=0.025, 0.037, 0.032, 0.000). The 48 cases who received IL-2 treatment were divided into 2 groups according to whether they used immunosuppressants. There was no significant difference in the absolute number of T, B, CD4+T, CD8+T, Th1, Th2, Th17 and Treg cells, the proportion of Th17 and Treg cells and the ratio of Th17/Treg between the 2 groups (P>0.05).

Conclusion:

Global decrease in lymphocyte subsets was found in IIM patients, especially those who had important organ infection. A significant re-balance of Th17/Treg was observed after receiving treatment with low-dose IL-2. Furthermore, the restoration of lymphocyte subsets showed similar degree after treatment with or without immunosuppressants. Low-dose IL-2 may become a potential therapy for IIM patients. The mechanism of lymphocyte decrease in IIM is required further to study.

References:

[1]Clark K E N, Isenberg D A. A review of inflammatory idiopathic myopathy focusing on polymyositis[J]. European Journal of Neurology, 2017.

[2]Tieu J, Lundberg IE, Limaye V. Idiopathic inflammatory myositis. Best Pract Res Clin Rheumatol. 2016. 30(1): 149-68.

[3]Mandel DE, Malemud CJ, Askari AD. Idiopathic Inflammatory Myopathies: A Review of the Classification and Impact of Pathogenesis. Int J Mol Sci. 2017. 18(5).

[4]Zhang SX, Wang J, Sun HH, et al. Circulating regulatory T cells were absolutely decreased in dermatomyositis/polymyositis patients and restored by low-dose IL-2. Ann Rheum Dis. 2019 .

[5]Espinosa-Ortega F, Gómez-Martin D, Santana-De Anda K, Romo-Tena J, Villaseñor-Ovies P, Alcocer-Varela J. Quantitative T cell subsets profile in peripheral blood from patients with idiopathic inflammatory myopathies: tilting the balance towards proinflammatory and pro-apoptotic subsets. Clin Exp Immunol. 2015. 179(3): 520-8.

[6]Feng M, Guo H, Zhang C, et al. Absolute reduction of regulatory T cells and regulatory effect of short-term and low-dose IL-2 in polymyositis or dermatomyositis. Int Immunopharmacol. 2019. 77: 105912.

Acknowledgments:

Thanks for the support of my teachers, classmates and my family.

Disclosure of Interests:

None declared

AB0436 CHANGES OF LYMPHOCYTE SUBSETS AND CLINICAL INDEXES IN PERIPHERAL BLOOD OF PATIENTS WITH ANTI-PHOSPHOLIPID SYNDROME

Background:

Anti-phospholipid Syndrome (APS) is a non-inflammatory autoimmune disease, which can be divided into primary and secondary. Changes in lymphocyte numbers in APS are caused by disruption of the immune balance.

Objectives:

The levels of lymphocyte subsets in peripheral blood of patients with anti-phospholipid syndrome were observed and their clinical indexes were analyzed.

Methods:

53 patients with anti-phospholipid syndrome (APS) were collected as the case group and divided into two groups of A, B according to whether primary and 50 health examiners as the healthy control group. The levels of peripheral lymphocyte subsets and laboratory data [erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), platelets (PLT)]levels in the three groups were analyzed. The measurement data is not subject to normal distribution using the Median-Quartile method for statistical description; multiple sample comparisons using the Kruskal-Wallis H test; p <0.05 as the difference is statistically significant.

Results:

(1) The rates of thrombosis and adverse pregnancy in the two case groups were significantly increased. In the two case groups, the ESR and CRP were higher than those in the healthy control group, and the CRP in group A was higher. (2) Compared with the healthy control group, the levels of CD8+T, CD4+T/CD8+T in case A group were increased,while the levels of total T,CD4+T, CD8+T,CD4+T/CD8+T,Th2 and Treg cells were decreased. However,there was no significant difference in Th17 cells level and Th17/Treg ratio compared with the healthy control group.

Conclusion:

APS patients were more prone to have thrombosis, adverse pregnancy and thrombocytopenia. The changes of lymphocyte subsets were seen in peripheral blood, and the primary and secondary had different directions and different degrees of manifestation.However, whether the secondary factors can aggravate the clinical indicators of APS is still unclear.

References:

[1]Simonin Laurent,Pasquier Elisabeth,Leroyer Christophe et al. Lymphocyte Disturbances in Primary Antiphospholipid Syndrome and Application to Venous Thromboembolism Follow-Up.[J].Clin Rev Allergy Immunol, 2017, 53: 14-27.doi:10.1007/s12016-016-8568-1.

Disclosure of Interests:

None declared

Low Bone Turnover Markers in Young and Middle-Aged Male Patients with Type 2 Diabetes Mellitus

Accumulating evidence has supported an increased risk of osteoporotic fracture in postmenopausal women and elderly men diagnosed with diabetes mellitus. However, it is not uncommon for young and middle-aged male patients diagnosed with type 2 diabetes mellitus (T2DM) to suffer from osteopenia or osteoporosis. Few studies focused on this population group are available. The aim of this study is to evaluate bone metabolic status and investigate the influence of T2DM on bone metabolism in 30-50-year-old men. Anthropometric assessment and blood samples were obtained from 160 patients with T2DM and 69 nondiabetic volunteers. Serum parathyroid hormone (PTH) and bone turnover markers (BTMs), including serum procollagen type I N-terminal peptide (PINP), osteocalcin (OC), and β-cross-linked C-telopeptide of type I collagen (β-CTX), were analysed. No significant differences were observed based on age, body mass index, systolic blood pressure, serum calcium, phosphorus, creatinine, total protein, and albumin levels when comparing T2DM and control groups. Fasting blood glucose, HbA1c, triglyceride (TG), total cholesterol, and low-density lipoprotein cholesterol were significantly increased, while high-density lipoprotein cholesterol was significantly decreased in the T2DM group. Compared with controls, diabetic patients showed lower serum PINP, OC, and PTH levels, whereas serum β-CTX levels were similar between the two groups. Moreover, HbA1c levels were positively correlated with PINP and inversely associated with PTH levels. TG levels were negatively correlated with OC or β-CTX levels. Furthermore, multiple linear regression revealed a positive correlation between HbA1c and PINP levels. These results also revealed a negative association between HbA1c and PTH, and between TG and OC levels, even after adjusting for expected confounder factors. Collectively, these findings indicated that young and middle-aged male patients with T2DM showed a lower turnover state resulting from bone formation inhibition. Glucose and lipid metabolic disorders may affect bone formation through different pathways.

microRNA-935 is reduced in non-small cell lung cancer tissue, is linked to poor outcome, and acts on signal transduction mediator E2F7 and the AKT pathway

BACKGROUND

A potential role for microRNA-935 (miR-935) has been identified in several cancers but not in non-small cell lung cancer (NSCLC). We hypothesised changes in miR-935 in NSCLC, and proposed mechanisms that may further explain its role in carcinogenesis.

METHODS

NSCLC tissue and nearby normal tissue was obtained from 101 patients and was probed by qRT-PCR for miR-935 expression. The role of miR-935 and a potential target (signal transduction factor E2F7) was determined in cell lines by a dual luciferase assay. The function of miR-935 was investigated through metabolic activity (MTT) and transwell migration assays. Western blot and immunocytochemical assays examined protein expression level. Growth of miR-935 transfected or untransfected cells was measured via xenograft tumour formation.

RESULTS

miR-935 was reduced in cancer tissue and was related to lymph node metastases, tumour node metastasis status and poor prognosis (all p < 0.02). In vitro, miR-935 suppressed cell proliferation, migration and invasion in NSCLC cells through targeting E2F7. Furthermore, E2F7 was upregulated in NSCLC tissue associated with poor prognosis (p = 0.0203) of NSCLC patients. miR-935 suppressed the epithelial-mesenchymal transition and AKT pathways in NSCLC and inhibited the tumour growth in vivo.

CONCLUSION

Altered miR-935 in lung cancer biopsy tissue may be a diagnostic tool and could direct treatment. Involvement in carcinogenesis is implied by its suppression of the development of NSCLC via targeting E2F7 and inhibiting AKT pathway.

Liraglutide ameliorates palmitate-induced insulin resistance through inhibiting the IRS-1 serine phosphorylation in mouse skeletal muscle cells

OBJECTIVE

A reduction in insulin-stimulated glucose uptake in skeletal muscles is a characteristic of insulin resistance and type 2 diabetes mellitus (T2DM). The glucagon-like peptide (GLP)-1 agonist liraglutide can reduce blood glucose levels in individuals with T2DM. However, its effect on insulin-induced glucose metabolism in the skeletal muscle of insulin resistance is unknown. We investigated the effects and action mechanisms of liraglutide on insulin resistance (IR) in the skeletal muscle cells treatment with palmitic acid (PA).

METHODS

The cell-surface GLUT4myc levels were determined by an antibody-coupled colorimetric assay. The phosphorylation levels of Akt, PI3K(p85α), AS160, IRS1, IKK, and JNK were determined by western blotting. The quantifications of mRNA levels of TNFα, IL-1β, and IL-6 were determined by real-time PCR. Analysis of variance was used for data analysis.

RESULTS

PA elevated not only phosphorylation of JNK, IRS1 serines, and IKKα/β, but also the expression of IL-6, TNFα and IL-1β in C2C12-GLUT4myc cells. PA can reduce phosphorylation of IRS1 tyrosine. These effects of PA were reversed by liraglutide. In addition, liraglutide can reverse PA-decreased insulin-stimulated cell-surface GLUT4 levels, Akt, PI3K(p85α), and AS160 phosphorylation.

CONCLUSIONS

Liraglutide can enhance insulin-induced GLUT4 translocation by inhibiting IRS1 serine phosphorylation in PA-treated muscle cells.

Oxidation-induced generation of a mild electrophile for proximity-enhanced protein-protein crosslinking

We report a strategy to introduce a reactive electrophile into proteins through the conversion of a chemically inert group into a bioreactive group in response to an inducer molecule. This strategy was demonstrated by oxidation-induced and proximity-enhanced protein-protein crosslinking in the presence of a large excess of free nucleophile.

Fluorogenic protein labeling using a genetically encoded unstrained alkene

A new fluorogenic bioorthogonal reaction between styrene (an unstrained alkene) and a tetrazine was developed.

We developed a new fluorogenic bioorthogonal reaction that is based on the inverse electron-demand Diels–Alder reaction between styrene (an unstrained alkene) and a simple tetrazine. The reaction forms a new fluorophore with no literature precedent. We have identified an aminoacyl-tRNA synthetase/tRNA pair for the efficient and site-specific incorporation of a styrene-containing amino acid into proteins in response to amber nonsense codon. Fluorogenic labeling of purified proteins and intact proteins in live cells were demonstrated. The fluorogenicity of the styrene–tetrazine reaction can be potentially applied to the study of protein folding and function under physiological conditions with low background fluorescence interference.

miR-141 is involved in BRD7-mediated cell proliferation and tumor formation through suppression of the PTEN/AKT pathway in nasopharyngeal carcinoma

Bromodomain containing 7 (BRD7) was identified as a nuclear transcriptional regulatory factor. BRD7 functions as a tumor suppressor in multiple cancers, including nasopharyngeal carcinoma (NPC). In this study, we reported a novel mechanism of BRD7 in NPC progression. We demonstrated that the expression of miR-141 was remarkably increased in NPC tissues and was negatively correlated with the expression of BRD7 and the survival rate of NPC patients. Decreased expression levels of miR-141, including the primary, the precursor and the mature forms of miR-141, were found in BRD7-overexpressing HEK293, 5-8F and HNE1 cells compared the control cells, while there was no obvious effect on the expression levels of the two critical enzymes Drosha and Dicer. BRD7 can negatively regulate the promoter activity of miR-141, while no obvious binding site of BRD7 was found in the potential promoter region of miR-141. Moreover, ectopic expression of miR-141 can significantly promote cell proliferation and inhibit apoptosis in NPC, and rescuing the expression of miR-141 in BRD7-overexpressing NPC cells could partially reverse the tumor suppressive effect of BRD7 on cell proliferation and tumor growth in vitro and in vivo. Furthermore, the activation of the PTEN/AKT pathway mediated by the overexpression of BRD7 could be inhibited by rescuing the expression of miR-141, which accordingly results in the partial restoration of cell proliferation and tumor growth. Our findings demonstrate that the BRD7/miR-141/PTEN/AKT axis has critical roles in the progression of NPC and provide some promising targets for the diagnosis and treatment of NPC.

A photoactivatable Src homology 2 (SH2) domain

A photoactivatable SH2 domain that can be potentially applied as an optogenetic tool to the photocontrol of phosphotyrosine-associated biological processes.

Virtual classroom helps medical education for both Chinese and foreign students

AIMS

The rapid development of computer and internet technology has a strong influence over one's quality of education within different fields of study. To determine the potential benefits of introducing internet into medical school classes, a pilot study was conducted in three different Chinese medical schools.

MATERIALS AND METHODS

Seven hundred and eight medical school undergraduates, 385 dental school students and 366 foreign students were randomly recruited to complete a self-administered questionnaire. The contents included personal information, current usage of computer and internet, and attitudes towards the computerised teaching methods. Two forum groups were created using instant message software and were randomly assigned to two classes, allowing students to freely ask or discuss questions with the help of their teachers in these two virtual classrooms.

RESULTS

All 1539 questionnaires were accepted and analysed. Although there were some differences between Chinese and foreign undergraduates, both group of students were highly proficient in internet usage and navigation. Overwhelmingly, 88.37% of the students owned a computer and frequently logged onto the internet. Most of them believed that the internet is a helpful adjunct to their studies and held positive attitudes towards computerised teaching. Compared to the classes that were not assigned internet forums, the two experimental classes performed significantly better on the examination.

CONCLUSIONS

Our results suggest that computerised teaching methods have significant potential to assist in learning for both Chinese and foreign medical undergraduates.

Reprogramming the fate of human glioma cells to impede brain tumor development

Malignant gliomas, the most common solid tumors in the central nervous system, are essentially incurable due to their rapid growth and very invasive nature. One potential approach to eradicating glioma cells is to force these cells to undergo terminal differentiation and, in the process, to irreversible postmitotic arrest. Here, we show that neurogenin 2 (NGN2, also known as NEUROG2) synergizes with sex-determining region Y-box 11 (SOX11) to very efficiently convert human glioma cells to terminally differentiated neuron-like cells in both cell culture and adult mouse brains. These cells exhibit neuronal morphology, marker expression, and electrophysiological properties. The conversion process is accompanied by cell cycle exit, which dramatically inhibits glioma cell proliferation and tumor development after orthotopic transplantation. Most importantly, intracranial injection of NGN2- and SOX11-expressing virus into the tumor mass also curtails glioma growth and significantly improves survival of tumor-bearing mice. Taken together, this study shows a simple and highly efficient strategy for reprogramming malignant glioma cells into postmitotic cells, which might be a promising therapeutic approach for brain tumors.

Ca²⁺ signals promote GLUT4 exocytosis and reduce its endocytosis in muscle cells

Elevating cytosolic Ca(2+) stimulates glucose uptake in skeletal muscle, but how Ca(2+) affects intracellular traffic of GLUT4 is unknown. In tissue, changes in Ca(2+) leading to contraction preclude analysis of the impact of individual, Ca(2+)-derived signals. In L6 muscle cells stably expressing GLUT4myc, the Ca(2+) ionophore ionomycin raised cytosolic Ca(2+) and caused a gain in cell surface GLUT4myc. Extra- and intracellular Ca(2+) chelators (EGTA, BAPTA-AM) reversed this response. Ionomycin activated calcium calmodulin kinase II (CaMKII), AMPK, and PKCs, but not Akt. Silencing CaMKIIδ or AMPKα1/α2 partly reduced the ionomycin-induced gain in surface GLUT4myc, as did peptidic or small molecule inhibitors of CaMKII (CN21) and AMPK (Compound C). Compared with the conventional isoenzyme PKC inhibitor Gö6976, the conventional plus novel PKC inhibitor Gö6983 lowered the ionomycin-induced gain in cell surface GLUT4myc. Ionomycin stimulated GLUT4myc exocytosis and inhibited its endocytosis in live cells. siRNA-mediated knockdown of CaMKIIδ or AMPKα1/α2 partly reversed ionomycin-induced GLUT4myc exocytosis but did not prevent its reduced endocytosis. Compared with Gö6976, Gö6983 markedly reversed the slowing of GLUT4myc endocytosis triggered by ionomycin. In summary, rapid Ca(2+) influx into muscle cells accelerates GLUT4myc exocytosis while slowing GLUT4myc endocytosis. CaMKIIδ and AMPK stimulate GLUT4myc exocytosis, whereas novel PKCs reduce endocytosis. These results identify how Ca(2+)-activated signals selectively regulate GLUT4 exocytosis and endocytosis in muscle cells.

Fabrication of micro-optical elements on curved substrates by electrostatic induced lithography

This article reports the fabrication and characterization of polymeric micro-optical elements on curved substrates using electrostatic induced lithography.

Unusual localization and translocation of TRPV4 protein in cultured ventricular myocytes of the neonatal rat

TRPV4 protein forms a Ca²⁺-permeable channel that is sensitive to osmotic and mechanical stimuli and responds to warm temperatures, and expresses widely in various kinds of tissues. As for cardiac myocytes, TRPV4 has been detected only at the mRNA level and there were few reports about subcel-lular localization of the protein. The purpose of the present study was to investigate the expression profile of TRPV4 protein in cultured neonatal rat ventricular myocytes. Using Western blots, immunofluorescence, confocal microscopy and immuno-electron microscopy, we have shown that TRPV4 protein was predominantly located in the nucleus of cultured neonatal myocytes. Furthermore, cardiac myocytes responded to hypotonic stimulation by translocating TRPV4 protein out of the nucleus. The significance and mechanism concerning the unusual distribution and translocation of TRPV4 protein in cardiac myocytes remain to be clarified.

TRPC1 expression and distribution in rat hearts

Transient receptor potential canonical (TRPC) proteins have been identified as a family of plasma membrane calcium-permeable channels. TRPC proteins can be activated by various stimuli and act as cellular sensors in mammals. Stretch-activated ion channels (SACs) have been proposed to underlie cardiac mechano-electric feedback (MEF), although the molecular entity of SAC remains unknown. There is evidence suggesting that transient receptor potential canonical 1 (TRPC1) is a stretch-activated ion channel. As a non-selective cation channel, TRPC1 may cause stretch-induced depolarization and arrhythmia and thus may contribute to the MEF of the heart. In this study, we examined the expression patterns of TRPC1 in detail at both the mRNA and protein levels in rat hearts. We isolated total RNA from the left and right atria, and the left and right ventricles, and detected TRPC1 mRNA in these tissues using reverse-transcriptase polymerase chain reaction (RT-PCR). To study the protein localization and targeting, we performed immunohistochemistry and immunofluorescence labeling with the antibody against TRPC1. TRPC1 was detected in the cardiomyocytes of the ventricle and atrium at both the mRNA and protein levels. The cell membrane and T-tubule showed strong fluorescence labeling in the ventricular myocytes. Purkinje cells, the endothelial cells and smooth muscle cells of the coronary arterioles also displayed TRPC1 labeling. No TRPC1 was detected in fibroblasts. In conclusion, TRPC1 is widely expressed in the rat heart, including in working cells, Purkinje cells and vascular cells, suggesting that it plays an important role in the heart. The specific distribution pattern offered a useful insight into its function in adult rat ventricular cells. Further investigations are needed to clarify the role of TRPC1 in regulating cardiac activity, including cardiac MEF.

Prevalence of metabolic syndrome and related metabolic traits in an island population of the Adriatic

BACKGROUND

Metabolic syndrome, a constellation of risk factors associated with cardiovascular disease and Type 2 diabetes, has reached epidemic proportions worldwide. Epidemiological studies in transitional societies will provide insight into the underlying factors that interact in its manifestation.

AIMS

To estimate the prevalence of metabolic syndrome, provide a comparative analysis of two metabolic syndrome definitions and assess clustering and association of metabolic traits and cardiovascular diseases in an Adriatic island population.

SUBJECTS AND METHODS

In a cross-sectional study, data on four anthropometric, blood pressure and 11 biochemical traits were obtained from 1430 adults from the island of Hvar.

RESULTS

Prevalence of metabolic syndrome was 25% and 38.5% based on Adult Treatment Panel III and International Diabetes Federation definitions, respectively. Rates of abdominal obesity, elevated blood glucose and hypertension were high. Among the traits not included in the definitions, levels of LDL, total cholesterol and fibrinogen were markedly elevated. The majority of the phenotypes were significantly associated with the syndrome, the strongest being waist circumference.

CONCLUSION

The Croatian islanders are characterized by a high prevalence of metabolic abnormalities. Central obesity is the strongest contributor of the syndrome. With a high prevalence of dyslipidemia and pro-inflammatory factors, the population is at substantial risk for cardiovascular diseases.

Arterial stiffness and asymptomatic intracranial large arterial stenosis and calcification in hypertensive chinese

BACKGROUND

Intracranial large artery disease (ICLAD), such as stenosis and calcification, is common in Chinese patients with stroke. However, little is known about ICLAD and its association with large arterial stiffness in hypertensive patients.

METHODS

We recruited 270 (mean age 61.0 years, 45.6% male) untreated hypertensive patients without stroke from a community in Shanghai, China. ICLAD was detected by computerized tomographic angiography (CTA). Carotid-femoral pulse wave velocity (cf-PWV), office, and 24-h ambulatory pulse pressure (PP) as well as ambulatory arterial stiffness index (AASI) were determined as the measures of arterial stiffness.

RESULTS

Among all participants, 26 (9.6%) had concurrent intracranial arterial stenosis and calcification, 11 (4.1%) stenosis only, and 71 (26.3%) calcifications only. After adjustment for age, mean arterial pressure, and other covariables, there was significant difference in cf-PWV (13.1 vs. 13.7 vs. 15.0 m/s; P = 0.0015) and 24-h PP (46.7 vs. 48.8 vs. 55.7 mm Hg; P = 0.0007) between patients with normal vessels (n = 162), with stenosis or calcification (n = 82), and with both lesions (n = 26). Multiple ordinal logistic regression analyses showed that both cf-PWV and 24-h PP were independently associated with ICLAD. Odds ratios (95% confidence interval (CI)) of ICLAD after multivariable and mutually adjustment were 1.51 (1.09-2.10) and 1.46 (1.06-2.01) for 1-s.d. increase in cf-PWV and 24-h PP, respectively. No significant association (P ≥ 0.10) with AASI or office PP was observed in multivariable analysis.

CONCLUSION

Increased arterial stiffness was independently associated with ICLAD. cf-PWV and 24-h PP might be useful in identifying those more likely to have ICLAD among hypertensive patients.

Erythromycin inhibited glycinergic inputs to gastric vagal motoneurons in brainstem slices of newborn rats

BACKGROUND

Motilin has been known to stimulate the motility of digestive organs peripherally via activation of motilin receptors located at gastrointestinal (GI) cholinergic nerve endings and/or smooth muscle cells. Recent studies have indicated that motilin may also promote GI motility via actions in the central nervous system; however the sites of action and the mechanisms are not clear yet. The present study aimed to test the hypothesis that motilin receptor agonist erythromycin alters the synaptic inputs of preganglionic gastric vagal motoneurons (GVMs) located in the dorsal motor nucleus of the vagus (DMV).

METHODS

Gastric vagal motoneurons were retrogradely labeled by fluorescent tracer from the stomach wall of newborn rats. Fluorescently labeled GVMs in DMV were recorded using whole-cell patch-clamp in brainstem slices and the effects of motilin receptor agonist erythromycin on the synaptic inputs were examined.

KEY RESULTS

Erythromycin (100 nmol L(-1), 1 μmol L(-1), 10 μmol L(-1)) significantly inhibited the frequency of glycinergic spontaneous inhibitory postsynaptic currents (sIPSCs) of GVMs and significantly inhibited the amplitude at the concentration of 10 μmol L(-1). These responses were prevented by GM-109, a selective motilin receptor antagonist. In the pre-existence of tetradotoxin (TTX, 1 μmol L(-1)), erythromycin (10 μmol L(-1)) caused significant decreases of the glycinergic miniature inhibitory postsynaptic currents (mIPSCs), in both the frequency and the amplitude. However, erythromycin (10 μmol L(-1)) didn't cause significant changes of the GABAergic sIPSCs.

CONCLUSIONS & INFERENCES

Erythromycin selectively inhibits the glycinergic inputs of GVMs.

Preoperative hepatic and regional arterial chemotherapy in the prevention of liver metastasis after colorectal cancer surgery

4090

Background: To investigate whether preoperative hepatic and regional arterial chemotherapy are able to prevent liver metastasis and improve overall survival in patients receiving curative colorectal cancer resection. Methods: Patients with Stage II or Stage III colorectal cancer (CRC) were randomly assigned to receive preoperative hepatic and regional arterial chemotherapy (PHRAC group, n=256) or surgery alone (control group, n=253). The primary endpoint was disease-free survival, whereas the secondary endpoints included liver metastasis-free survival and overall survival. Results: There were no significant differences in overall morbidity between PHRAC and Control groups. During the follow-up period (median, 42 months), the median liver metastasis time for patients with stage III CRC was significantly longer in the PHRAC group (16±3 months v.s. 8±1 months, P=0.01). In stage III patients, there was also significant difference between the two groups with regard to the incidence of liver metastasis (18.9% vs 27.3%, P=0.01), 5-year disease-free survival (70.2% vs 52.0%, P=0.0076), 5-year overall survival (80.3% vs 69.5%, P=0.020) and the median survival time (40.1± 4.6 months vs 36.3 ± 3.2 months, P=0.03). In the PHRAC arm, the risk ratio of recurrence was 0.63 (95% CI, 0.51–0.79, P=0.0001), of death was 0.50(95% CI, 0.32–0.67; P=0.005), and of liver metastasis was 0.70 (95% CI, 0.52–0.86; p=0.01). In contrast, PHRAC seemed to be no benefit for stage II patients. Toxicities, such as hepatic toxicity and leucocyte decreasing, were mild and could be cured with medicine. Conclusions: Preoperative hepatic and regional arterial chemotherapy, in combination with surgical resection, could be able to reduce and delay the occurrence of liver metastasis and therefore improve survival rate in patients with stage III colorectal cancer.

No significant financial relationships to disclose.

Correlation between angiotensinogen gene polymorphisms and essential hypertension in Chinese population

Essential hypertension (EHT) has a genetic basis. Considering the pathological, physiological and biological mechanisms implicated in blood pressure regulation, many candidates have been listed as hypertension genes, of which the angiotensinogen gene (AGT) is weighed as the most promising one.

Five-year survival analysis of liver metastasis of colorectal cancer after hepatic resection

14571

Background: To evaluate the relation between hepatic resecion and survival rate of liver metastasis of colorectal cancer ( LMCC). Methods: Use retrograde case analysis method, 133 cases of LMCC received hepatic resection from 1/1/2000 to 31/12/2005 were included,with attention to the relation between hepatic resection and survival rate. Results: There were 133 cases underwent curative hepatic resection in all 470 LMCC cases, of which 30 cases (30/196,15.3%) in synchronous liver metastasis (SLM) group and 103 cases (103/274,37.6%) in metachronous liver metastasis (MLM) group, P<0.01. Mortality rate related to operation was 3.3%(1/30) in SLM and 1.9%(2/103) in MLM(P<0.05). Until 31/6/2006, all 133 cases were followed-up, 1,3,5 years survival rate and median survival time of SLM (81.0%, 40.3%, 16.5%, 22 months) is similar to that of MLM (88.2%, 49.1%, 31.7%, 25 months, P > 0.05), but the recurrence rate is higher(36.7% vs 20.4%,P=0.03). Compared to 49 cases whose liver metastases focus can be resected but chosen non- operative therapy, 1, 3, 5 years survival rate of 133 resected cases is higher (55.6%, 11.0%, 0 vs 86.2%, 39.2%, 29.4%, P=0.0034). In SLM, 22 cases received I stage resection of the primary colorectal tumor and liver metastasis and 8 cases received liver metastasis resection after the primary surgery (II stage operation). 1, 2, 3 years survival are 90.0% vs 87.5%(P > 0.05),61.4% vs 55.3%(P > 0.05)and 35.4% vs 30.0%(P > 0.05) and the median survival time is 28 months vs 26months(P > 0.05).COX multivariate analysis was used to analyze the prognositic factors. Incision margin =1cm(β=-0.8351,P=0.0363)and reoperation after recurrence(β=- 0.9428,P=0.0411)were protective survival factors, and postoperation recurrence (β=0.6471,P=0.0226) was survival risk factor. Conclusions: Curative hepatic resection is the first choice of liver metastasis of colorectal cancer and can improve survival.

No significant financial relationships to disclose.

Quantifying the contribution of cross-correlation in stimulus feature discrimination in an ensemble of retinal ganglion cells

Based on Poisson variability, the strength of cross-correlation of two spike trains was quantified by a cross-correlation index (CCI). Discriminant analysis with CCI was used to quantify the contribution of cross-correlation in stimulus feature discrimination in an ensemble of retinal ganglion cells. Compared with simulated Poisson cell pair, it was found that cross-correlation carried useful information for stimulus feature discrimination and with the cross-correlation included in the analysis, the color and the intensity discrimination ability of a cell pair increase 4.2% and 2.7%, respectively.

Reduction of insulin-stimulated glucose uptake in L6 myotubes by the protein kinase inhibitor SB203580 is independent of p38MAPK activity

Insulin increases glucose uptake through translocation of the glucose transporter GLUT4 to the plasma membrane. We previously showed that insulin activates p38MAPK, and inhibitors of p38MAPKalpha and p38MAPKbeta (e.g. SB203580) reduce insulin-stimulated glucose uptake without affecting GLUT4 translocation. This observation suggested that insulin may increase GLUT4 activity via p38alpha and/or p38beta. Here we further explore the possible participation of p38MAPK through a combination of molecular strategies. SB203580 reduced insulin stimulation of glucose uptake in L6 myotubes overexpressing an SB203580-resistant p38alpha (drug-resistant p38alpha) but barely affected phosphorylation of the p38 substrate MAPK-activated protein kinase-2. Expression of dominant-negative p38alpha or p38beta reduced p38MAPK phosphorylation by 70% but had no effect on insulin-stimulated glucose uptake. Gene silencing via isoform-specific small interfering RNAs reduced expression of p38alpha or p38beta by 60-70% without diminishing insulin-stimulated glucose uptake. SB203580 reduced photoaffinity labeling of GLUT4 by bio-LC-ATB-BMPA only in the insulin-stimulated state. Unless low levels of p38MAPK suffice to regulate glucose uptake, these results suggest that the inhibition of insulin-stimulated glucose transport by SB203580 is likely not mediated by p38MAPK. Instead, changes experienced by insulin-stimulated GLUT4 make it susceptible to inhibition by SB203580.

Indinavir uncovers different contributions of GLUT4 and GLUT1 towards glucose uptake in muscle and fat cells and tissues

AIMS/HYPOTHESIS

Insulin-dependent glucose influx in skeletal muscle and adipocytes is believed to rely largely on GLUT4, but this has not been confirmed directly. We assessed the relative functional contribution of GLUT4 in experimental models of skeletal muscle and adipocytes using the HIV-1 protease inhibitor indinavir.

METHODS

Indinavir (up to 100 micro mol/l) was added to the glucose transport solution after insulin stimulation of wild-type L6 muscle cells, L6 cells over-expressing either GLUT4myc or GLUT1myc, 3T3-L1 adipocytes, isolated mouse brown or white adipocytes, and isolated mouse muscle preparations.

RESULTS

100 micro mol/l indinavir inhibited 80% of both basal and insulin-stimulated 2-deoxyglucose uptake in L6GLUT4myc myotubes and myoblasts, but only 25% in L6GLUT1myc cells. Cell-surface density of glucose transporters was not affected. In isolated soleus and extensor digitorum longus muscles, primary white and brown adipocytes, insulin-stimulated glucose uptake was inhibited 70 to 80% by indinavir. The effect of indinavir on glucose uptake was variable in 3T3-L1 adipocytes, averaging 45% and 67% inhibition of basal and maximally insulin-stimulated glucose uptake, respectively. In this cell, fractional inhibition of glucose uptake by indinavir correlated positively with the fold-stimulation of glucose uptake by insulin, and was higher with sub-maximal insulin concentrations. The latter finding coincided with an increase only in GLUT4, but not GLUT1, in plasma membrane lawns.

CONCLUSION/INTERPRETATION

Indinavir is a useful tool to assess different functional contributions of GLUT4 to glucose uptake in common models of skeletal muscle and adipocytes.

A scanning electron microscopic study of dentinal erosion by final irrigation with EDTA and NaOCl solutions

AIM

The purpose of this in vitro study was to examine dentinal erosion caused by final irrigation with EDTA and NaOCl.

METHODOLOGY

Twenty-five single-rooted human teeth were instrumented with rotary nickel-titanium Series 29 Profile Instruments. The teeth were divided into five groups and subjected to final irrigation as follows: group A, irrigated with 6% NaOCl (3 mL) for 2 min; group B, 15% EDTA (3 mL) for 1 min; group C, 15% EDTA (3 mL) for 1 min, followed by 6% NaOCl (3 mL) for 2 min; group D, 15% EDTA (3 mL) for 3 min and group E, 15% EDTA (3 mL) for 3 min, followed by 6% NaOCl (3 mL) for 2 min. Photomicrographs of dentinal walls were produced using a scanning electron microscope (3000 x) at 1, 3 and 6 mm from the apex. The amount of debris and dentinal tubule diameter were evaluated, and values were statistically analysed using one-way ANOVA and Fisher's PLSD test.

RESULTS

When the root canal was irrigated with 15% EDTA alone, the dentine had a smooth and plane appearance, and dentinal tubule orifices were regular and separated. When the root canal was irrigated with EDTA followed by NaOCL the dentine was eroded and the dentinal tubule orifices were irregular and rough. Dentinal tubule diameter increased to 3.43 +/- 0.23 microm in group C and to 3.93 +/- 0.44 microm in group E. Significant differences were observed between groups B and C, and between groups D and E (P < 0.05). However, more debris was removed by irrigation with EDTA followed by NaOCl than with EDTA alone (P < 0.05).

CONCLUSIONS

Final irrigation with 6% NaOCl accelerates dentinal erosion following treatment with 15% EDTA.

Differential effects of phosphatidylinositol 3-kinase inhibition on intracellular signals regulating GLUT4 translocation and glucose transport

Phosphatidylinositol (PI) 3-kinase is required for insulin-stimulated translocation of GLUT4 to the surface of muscle and fat cells. Recent evidence suggests that the full stimulation of glucose uptake by insulin also requires activation of GLUT4, possibly via a p38 mitogen-activated protein kinase (p38 MAPK)-dependent pathway. Here we used L6 myotubes expressing Myc-tagged GLUT4 to examine at what level the signals regulating GLUT4 translocation and activation bifurcate. We compared the sensitivity of each process, as well as of signals leading to GLUT4 translocation (Akt and atypical protein kinase C) to PI 3-kinase inhibition. Wortmannin inhibited insulin-stimulated glucose uptake with an IC(50) of 3 nm. In contrast, GLUT4myc appearance at the cell surface was less sensitive to inhibition (IC(50) = 43 nm). This dissociation between insulin-stimulated glucose uptake and GLUT4myc translocation was not observed with LY294002 (IC(50) = 8 and 10 microm, respectively). The sensitivity of insulin-stimulated activation of PKC zeta/lambda, Akt1, Akt2, and Akt3 to wortmannin (IC(50) = 24, 30, 35, and 60 nm, respectively) correlated closely with inhibition of GLUT4 translocation. In contrast, insulin-dependent p38 MAPK phosphorylation was efficiently reduced in cells pretreated with wortmannin, with an IC(50) of 7 nm. Insulin-dependent p38 alpha and p38 beta MAPK activities were also markedly reduced by wortmannin (IC(50) = 6 and 2 nm, respectively). LY294002 or transient expression of a dominant inhibitory PI 3-kinase construct (Delta p85), however, did not affect p38 MAPK phosphorylation. These results uncover a striking correlation between PI 3-kinase, Akt, PKC zeta/lambda, and GLUT4 translocation on one hand and their segregation from glucose uptake and p38 MAPK activation on the other, based on their wortmannin sensitivity. We propose that a distinct, high affinity target of wortmannin, other than PI 3-kinase, may be necessary for activation of p38 MAPK and GLUT4 in response to insulin.

Insulin increases plasma membrane content and reduces phosphorylation of Na(+)-K(+) pump alpha(1)-subunit in HEK-293 cells

Insulin stimulates K(+) uptake and Na(+) efflux via the Na(+)-K(+) pump in kidney, skeletal muscle, and brain. The mechanism of insulin action in these tissues differs, in part, because of differences in the isoform complement of the catalytic alpha-subunit of the Na(+)-K(+) pump. To analyze specifically the effect of insulin on the alpha(1)-isoform of the pump, we have studied human embryonic kidney (HEK)-293 cells stably transfected with the rat Na(+)-K(+) pump alpha(1)-isoform tagged on its first exofacial loop with a hemagglutinin (HA) epitope. The plasma membrane content of alpha(1)-subunits was quantitated by binding a specific HA antibody to intact cells. Insulin rapidly increased the number of alpha(1)-subunits at the cell surface. This gain was sensitive to the phosphatidylinositol (PI) 3-kinase inhibitor wortmannin and to the protein kinase C (PKC) inhibitor bisindolylmaleimide. Furthermore, the insulin-stimulated gain in surface alpha-subunits correlated with an increase in the binding of an antibody that recognizes only the nonphosphorylated form of alpha(1) (at serine-18). These results suggest that insulin regulates the Na(+)-K(+) pump in HEK-293 cells, at least in part, by decreasing serine phosphorylation and increasing plasma membrane content of alpha(1)-subunits via a signaling pathway involving PI 3-kinase and PKC.

GLUT4 translocation precedes the stimulation of glucose uptake by insulin in muscle cells: potential activation of GLUT4 via p38 mitogen-activated protein kinase

We previously reported that SB203580, an inhibitor of p38 mitogen-activated protein kinase (p38 MAPK), attenuates insulin-stimulated glucose uptake without altering GLUT4 translocation. These results suggested that insulin might activate GLUT4 via a p38 MAPK-dependent pathway. Here we explore this hypothesis by temporal and kinetic analyses of the stimulation of GLUT4 translocation, glucose uptake and activation of p38 MAPK isoforms by insulin. In L6 myotubes stably expressing GLUT4 with an exofacial Myc epitope, we found that GLUT4 translocation (t(1/2)=2.5 min) preceded the stimulation of 2-deoxyglucose uptake (t(1/2)=6 min). This segregation of glucose uptake from GLUT4 translocation became more apparent when the two parameters were measured at 22 degrees C. Preincubation with the p38 MAPK inhibitors SB202190 and SB203580 reduced insulin-stimulated transport of either 2-deoxyglucose or 3-O-methylglucose by 40-60%. Pretreatment with SB203580 lowered the apparent transport V(max) of insulin-mediated 2-deoxyglucose and 3-O-methylglucose without any significant change in the apparent K(m) for either hexose. The IC(50) values for the partial inhibition of 2-deoxyglucose uptake by SB202190 and SB203580 were 1 and 2 microM respectively, and correlated with the IC(50) for full inhibition of p38 MAPK by the two inhibitors in myotubes (2 and 1.4 microM, respectively). Insulin caused a dose- (EC(50)=15 nM) and time- (t(1/2)=3 min) dependent increase in p38 MAPK phosphorylation, which peaked at 10 min (2.3+/-0.3-fold). In vitro kinase assay of immunoprecipitates from insulin-stimulated myotubes showed activation of p38 alpha (2.6+/-0.3-fold) and p38 beta (2.3+/-0.2-fold) MAPK. These results suggest that activation of GLUT4 follows GLUT4 translocation and that both mechanisms contribute to the full stimulation of glucose uptake by insulin. Furthermore, activation of GLUT4 may occur via an SB203580-sensitive pathway, possibly involving p38 MAPK.