Direct evidence for leptin-induced lipid oxidation independent of long-form leptin receptor

Leptin administration has been shown to enhance muscle lipid oxidation in relation to the energy expenditure. Both long-form (Ob-R_L) and short-form leptin receptors (Ob-R_S) are expressed in skeletal muscle, but the role of Ob-R_S is unclear. In the present study, the role of Ob-R_S in leptin-induced lipid oxidation in skeletal muscles was investigated using primary murine myotubes from m/m and db/db mice. Primary myotubes were treated with leptin (0.1, 1, 10, 100 nM) for 24 h. Lipid oxidation was determined by ¹⁴CO₂ production rate from [1-¹⁴C] palmitate. Leptin was found to increase lipid oxidation in a dose- and time-dependent manner in db/db myotubes as well as in m/m myotubes. Leptin significantly increased phosphorylation of JAK2 and STAT3 in both types of myotube. Leptin-induced lipid oxidation was abolished by STAT3 siRNA. To investigate the mechanism underlying leptin-induced lipid oxidation, the effects of pharmacological inhibitors were examined. JAK2 or p38 MAPK inhibitor suppressed leptin-induced lipid oxidation and decreased STAT3 phosphorylation in both types of myotube, respectively. Leptin significantly increased phosphorylation of p38 MAPK, and leptin-induced lipid oxidation was abolished by treatment with p38 MAPK siRNA in both types of myotube. These results suggest that leptin induces lipid oxidation in skeletal muscle through the JAK2/p38 MAPK/STAT3 signaling pathway via not only Ob-R_L but also Ob-R_S.     

信号转导与转录活化蛋白STAT3在肿瘤发生中的作用

STAT3是信号转导与转录活化蛋白（STAT）家族的一个重要成员,也是一个可以被多种调控细胞增殖、分化、发育、存活和炎症的细胞因子、生长因子及肿瘤蛋白所激活的关键信号转导蛋白。在多种肿瘤细胞、细胞性状转化过程和肿瘤形成过程中可以检测到组成性激活的STAT3。我们从STAT3在肿瘤细胞中组成性激活的机制、STAT3作为转录因子对肿瘤细胞调控的机制等方面对STAT3在肿瘤发生中的作用进行简要综述。     

牛膝多糖对哮喘大鼠信号转导子和转录激活子6表达的影响

目的：研究牛膝多糖（ABPS）对支气管哮喘大鼠支气管信号转导子和转录激活子6（STAT6）及其mRNA表达的影响。方法：雄性SD大鼠30只随机分为正常对照组、哮喘组和哮喘＋牛膝多糖组（ABPS组）。留取支气管肺泡灌洗液（BALF）进行细胞总数、嗜酸性粒细胞（E0s）和分类计数;并测定BALF和血清中白细胞介素4（IL-4）浓度;采用免疫组化法和原位杂交法分别检测STAT6蛋白和STAT6 mRNA的表达。结果：①哮喘组BALF中细胞总数、EOS绝对值和EOS占细胞总数的百分比（EOS％）均高于对照组（P〈0．01）,ABPS组上述指标均低于哮喘组（P〈0．01）;②BALF和血清中IL-4浓度哮喘组均高于对照组（均为P〈0.01）,ABPs组均低于哮喘组（均为P〈0．01）;③免疫组化和原位杂交显示,哮喘组支气管STAT6蛋白和STAT6 mRNA表达的平均吸光度（LD）均高于对照组,ABPS组则均低于哮喘组（均为P〈0．01）,其主要表达细胞是上皮细胞。结论：哮喘大鼠支气管STAT6及其mRNA较强表达,上皮细胞是其主要表达细胞;牛膝多糖有抑制哮喘气道EOS性炎症的作用．下调STAT6及其mRNA表达,使IL-4合成减少可能为其重要作用机制。     

维甲酸促进小鼠F9细胞中STAT1的反式激活作用

维甲酸能促进肿瘤细胞的凋亡,诱导体外胚胎干细胞的分化,但作用机制的不明使其应用受到极大限制.因此,更多更全面地了解维甲酸的作用机制具有重要意义.本文构建了信号传导与转录激活因子（STAT1和STAT3）的真核表达载体 ,通过免疫荧光染色、电泳迁移率实验以及双荧光素酶报告基因检测系统证明, 维甲酸诱导可以激活转录因子STAT1促使其进入细胞核,并且增强STAT1蛋白与靶基因启动子的结合能力,从而发挥基因表达调控作用.本文结合后续的STAT1功能分析,试图建立起一种“维甲酸-转录因子-靶基因”的研究模式,有助于维甲酸作用机制的全面、系统的研究.这为临床上使用维甲酸作为抗肿瘤药提供理论基础,同时也为胚胎干细胞多能性调控机制研究提供新思路.     

Sodium salicylate modulates inflammatory responses through AMP‐activated protein kinase activation in LPS‐stimulated THP‐1 cells

Sodium salicylate (NaSal) is a nonsteroidal anti‐inflammatory drug. The putative mechanisms for NaSal's pharmacologic actions include the inhibition of cyclooxygenases, platelet‐derived thromboxane A2, and NF‐κB signaling. Recent studies demonstrated that salicylate could activate AMP‐activated protein kinase (AMPK), an energy sensor that maintains the balance between ATP production and consumption. The anti‐inflammatory action of AMPK has been reported to be mediated by promoting mitochondrial biogenesis and fatty acid oxidation. However, the exact signals responsible for salicylate‐mediated inflammation through AMPK are not well‐understood. In the current study, we examined the potential effects of NaSal on inflammation‐like responses of THP‐1 monocytes to lipopolysaccharide (LPS) challenge. THP‐1 cells were stimulated with or without 10 ug/mL LPS for 24 h in the presence or absence of 5 mM NaSal. Apoptosis was measured by flow cytometry using Annexin V/PI staining and by Western blotting for the Bcl‐2 anti‐apoptotic protein. Cell proliferation was detected by EdU incorporation and by Western blot analysis for proliferating cell nuclear antigen (PCNA). Secretion of pro‐inflammatory cytokines (TNF‐α, IL‐1β, IL‐6) was determined by enzyme‐linked immunosorbent assay (ELISA). We observed that the activation of AMPK by NaSal was accompanied by induction of apoptosis, inhibition of cell proliferation, and increasing secretion of TNF‐α and IL‐1β. These effects were reversed by Compound C, an inhibitor of AMPK. In addition, NaSal/AMPK activation inhibited LPS‐induced STAT3 phosphorylation, which was reversed by Compound C treatment. We conclude that AMPK activation is important for NaSal‐mediated inflammation by inducing apoptosis, reducing cell proliferation, inhibiting STAT3 activity, and producing TNF‐α and IL‐1β.     

Association between genes encoding components of the IL-4/IL-4 receptor pathway and dermatitis in children

Objective

To determine whether IL-4, IL-4Rα and STAT6 polymorphisms are associated with susceptibility to dermatitis in Egyptian children.

Methods

We genotyped three groups of children, consisting of 106 atopic dermatitis (AD) children, 95 non-AD children, and 100 of healthy controls, for IL-4 (− 590 C/T), (− 33 C/T), IL-4Rα (I50V), (Q576R) and STAT6 (2964 G/A), (2892 C/T) gene polymorphisms using PCR-RFLP assay. Total serum IgE and serum IL-4 levels were detected by ELISA.

Results

There was a non-significant association of IL-4 − 590 C/T, − 33 C/T polymorphisms in the children with non-AD or those with AD when compared with the controls. We identified a significant association between IL-4Rα I50V, Q576R polymorphisms and dermatitis susceptibility in AD (p = 0.002, < 0.001 respectively), whereas no such association was observed in non-AD group (p = 0.52, 0.99 respectively). A significant association between STAT6 polymorphisms and both types of dermatitis was found. Patients who were carriers of IL4 − 590C, IL-4Rα I50V G, STAT6 2964 A and STAT6 2892 T had an increased risk of AD [OR and 95% CI: 3.2 (2.5–4.2), p = 0.005]. Furthermore, there was no relation between each polymorphism and serum IL-4 level (p > 0.05 for each) while homozygosity for the risk alleles of IL-4, IL-4Rα and STAT6 SNPs were significantly associated with increased total IgE levels in all subjects.

Conclusion

In Egyptian children, the IL-4Rα and the STAT6 polymorphism may play a role in susceptibility to AD. In addition, gene–gene interaction between the IL-4, the IL-4Rα and the STAT6 significantly increases an individual's susceptibility to AD.     

Altered cAMP-dependent protein kinase subunit immunolabeling in post-mortem brain from patients with bipolar affective disorder

Previous findings of reduced [3H]cAMP binding and increased activities of cAMP-dependent protein kinase (PKA) in discrete post-mortem brain regions from patients with bipolar affective disorder (BD) suggest that PKA, the major downstream target of cAMP, is also affected in this illness. As prolonged elevation of intracellular cAMP levels can modify PKA regulatory (R) and catalytic (C) subunit levels, we sought to determine whether these PKA abnormalities are related to changes in the abundance of PKA subunits in BD brain. Using immunoblotting techniques along with PKA subunit isoform-specific polyclonal antisera, levels of PKA RIalpha, RIbeta, RIIalpha, RIIbeta and Calpha subunits were measured in cytosolic and particulate fractions of temporal, frontal and parietal cortices of post-mortem brain from BD patients and matched, non-neurological, non-psychiatric controls. Immunoreactive levels of cytosolic Calpha in temporal and frontal cortices, as well as that of cytosolic RIIbeta in temporal cortex, were significantly higher in the BD compared with the matched control brains. These changes were independent of age, post-mortem interval or pH and unrelated to ante-mortem lithium treatment or suicide. These findings strengthen further the notion that the cAMP/PKA signaling system is up-regulated in discrete cerebral cortical regions in BD.