Peroxisome proliferator-activated receptor ligands affect growth-related gene expression in human leukemic cells

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated nuclear receptors. Three subtypes of PPARs (alpha, beta, and gamma) have been identified in different tissues. PPAR alpha and PPAR gamma ligands inhibit cell proliferation and induce differentiation in several human cell models. We demonstrated that both PPAR alpha (clofibrate and ciprofibrate) and PPAR gamma ligands (troglitazone and 15 deoxy-prostaglandin J2, 15d-PGJ2) inhibited growth, induced the onset of monocytic-like differentiation, and increased the proportion of G0/G1 cells in the HL-60 leukemic cell line. Moreover, 3 days after the treatment with 2.5 microM 15d-PGJ2, an increase in sub-G0/G1 population occurred, compatible with an induction of programmed cell death. To clarify the mechanisms involved in HL-60 growth inhibition due to the effects of PPAR ligands, we investigated their action on the expression of some genes involved in the control of cell proliferation, differentiation, and cell cycle progression such as c-myc, c-myb, and cyclin D1 and D2. Clofibrate (50 microM), ciprofibrate (50 microM), and 15d-PGJ2 (2.5 microM) inhibited c-myb and cyclin D2 expression, whereas they did not affect c-myc and cyclin D1 expression. Only troglitazone (5 microM) decreased c-myc mRNA and protein levels, besides decreasing c-myb and cyclin D2. The down-regulations of c-myb and cyclin D2 expression represent the first evidence of the inhibitory effect exerted by PPAR ligands on these genes. Moreover, the inhibition of c-myc expression by troglitazone may depend on a PPAR-independent mechanism.     

Host-microbe interaction: mechanisms of defensin deficiency in Crohn's disease

Defensins are endogenous antibiotics with microbicidal activity against Gram-negative and -positive bacteria, fungi, enveloped viruses and protozoa. A disturbed antimicrobial defense, as provided by Paneth and other epithelial cell defensins, seems to be a critical factor in the pathogenesis of Crohn's disease, an inflammatory disease of the intestinal tract. Different direct and indirect mechanisms leading to a breakdown of antimicrobial barrier function include direct changes in defensin gene numbers (e.g., copy number polymorphism), genetic mutations in pattern-recognition receptors (e.g., nucleotide-binding oligomerization domain 2) and, as described recently, a differentiation problem of epithelial stem cells mediated by the wingless type (Wnt) pathway. Knowledge regarding the regulation and biology of defensins provides an attractive target to open up new therapeutic avenues.     

Host–microbe interaction: mechanisms of defensin deficiency in Crohn’s disease

Defensins are endogenous antibiotics with microbicidal activity against Gram-negative and -positive bacteria, fungi, enveloped viruses and protozoa. A disturbed antimicrobial defense, as provided by Paneth and other epithelial cell defensins, seems to be a critical factor in the pathogenesis of Crohn’s disease, an inflammatory disease of the intestinal tract. Different direct and indirect mechanisms leading to a breakdown of antimicrobial barrier function include direct changes in defensin gene numbers (e.g., copy number polymorphism), genetic mutations in pattern-recognition receptors (e.g., nucleotide-binding oligomerization domain 2) and, as described recently, a differentiation problem of epithelial stem cells mediated by the wingless type (Wnt) pathway. Knowledge regarding the regulation and biology of defensins provides an attractive target to open up new therapeutic avenues.     

shRNA沉默IRS-1基因对鼠前脂肪细胞分化和PPARγ表达的影响

目的观察胰岛素受体底物-1（IRS-1）基因表达受阻对小鼠3T3-L1前脂肪细胞分化和脂质过氧化物酶体增殖物激活受体γ（PPARγ）表达的影响。方法针对小鼠IRS-1基因开放阅读框上的2个区域合成短发夹核糖核酸[shRNA（M和MH）],以pGenesil-1vector为载体构建带绿色荧光蛋白（GFP）靶标的shRNA质粒。以脂质体LipofectaminTM2000介导转染3T3-L1前脂肪细胞,并设阴性对照（HK）载体转染组。细胞转染后,G418筛选稳定表达的阳性克隆并通过免疫印迹法鉴定。应用0.5mmol/L3-异丁基-1-甲基黄嘌呤（IBMX）、10-6mol/L地塞米松（DEX）和5μg/mL胰岛素（Ins）分别诱导小鼠3T3-L1前脂肪细胞空白对照组、HK载体转染组、M和MH转染组分化,在诱导分化的不同时间点收集细胞。用免疫印迹法检测PPARγ的表达。脂肪细胞内脂滴用油红O染色观察。结果与空白对照组、HK组和转染M组IRS-1shRNA质粒的3T3-L1前脂肪细胞相比,转染MH组IRS-1shRNA质粒的3T3-L1前脂肪细胞IRS-1蛋白表达水平降低70%以上;而MH转染组细胞PPARγ蛋白的表达与前3组3T3-L1前脂肪细胞比较无改变。前3组3T3-L1前脂肪细胞诱导分化为成熟脂肪细胞成功,PPARγ蛋白的表达在脂肪细胞分化成熟过程中逐渐增高。油红O染色显示,随着脂肪细胞的分化成熟,桔红色脂滴逐渐增多;而转染MH组IRS-1shRNA质粒的3T3-L1前脂肪细胞经诱导,油红O染色桔红色脂滴显着减少,直到分化的第8天,才见少许桔红色脂滴,且PPARγ蛋白的表达无变化。结论 IRS-1基因沉默后可抑制3T3-L1前脂肪细胞的分化,并在分化过程中抑制PPARγ的表达,说明IRS-1通过调节PPARγ的表达或与PPARγ共同作用在3T3-L1前脂肪细胞的分化中发挥决定性作用。     

Peroxisome proliferator-activated receptor-gamma agonist rosiglitazone attenuates inflammatory pain through the induction of heme oxygenase-1 in macrophages

Macrophage infiltration to inflammatory sites promotes tissue repair and may be involved in pain hypersensitivity. Peroxisome proliferator-activated receptor (PPAR)γ signaling is known to regulate polarity of macrophages, which are often referred to as proinflammatory (M1) and antiinflammatory (M2) macrophages. We recently showed that the PPARγ agonist rosiglitazone ameliorated the development of postincisional hyperalgesia by increasing the influx of M2 macrophages to inflamed sites. It has been suggested that heme oxygenase (HO)-1, upregulated by PPARγ signaling, promotes differentiation of macrophages to M2 phenotype. In this study, we investigated how rosiglitazone alters pain hypersensitivity by a PPARγHO-1-dependent mechanism during the course of inflammation induced by complete Freund’s adjuvant. Local administration of rosiglitazone alleviated mechanical hyperalgesia, with increased gene induction of HO-1. Phenotype switching of infiltrated macrophages to M2 by rosiglitazone was reversed by an HO-1 inhibitor, tin protoporphyrin, at the inflamed sites. Direct stimulation of peritoneal macrophages with rosiglitazone also increased HO-1 induction in the presence of lipopolysaccharide/interferon-γ. Moreover, rosiglitazone increased gene induction of endogenous opioid proenkephalin, both at inflamed sites and in isolated macrophages. Administration of naloxone blocked the analgesic effects of rosiglitazone. We speculate that rosiglitazone alleviated the development of inflammatory pain, possibly through regulating the M1/M2 balance at the inflamed site by a PPARγ/HO-1-dependent mechanism. PPARγ signaling in macrophages may be a potential therapeutic target for the treatment of acute pain development.     

The enterohepatic nuclear receptors are major regulators of the enterohepatic circulation of bile salts

Recent studies have established that bile salts are signaling molecules, besides their classic function in dietary lipid absorption and cholesterol metabolism. Bile salts signal by activating mitogen-activated protein kinase (MAPK) pathways and nuclear receptors like farnesoid X receptor-alpha (FXRalpha). FXRalpha activation increases the expression of direct FXRalpha target genes involved in bile salt transport and detoxification, and decreases expression of indirect FXRalpha target genes involved in bile salt biosynthesis and uptake. These actions prevent toxic accumulation of bile salts in the enterohepatic organs. A network of interactions with other nuclear receptors and MAPK pathways may protect the liver against pathological elevation of bile salts and cholestasis. Therefore treatment of cholestasis might benefit from the development of FXRalpha agonists.     

The molecular mechanisms by which PPAR gamma/RXR inhibitors improve insulin resistance]

Potent activation of PPAR gamma by thiazolidinediones(TZD) increases TG content of WAT, thereby decreasing TG content of liver/muscle, leading to amelioration of insulin resistance at the expense of obesity. Moderate reduction of PPAR gamma activity by PPAR gamma/RXR inhibitors decreases TG content of WAT/muscle/liver due to increased leptin and increase in fatty-acid combustion and decrease in lipogenesis, thereby ameliorating HF diet-induced obesity and insulin resistance. Moreover, PPAR gamma/RXR inhibitors decrease lipogenesis in WAT, while TZD stimulate adipocyte differentiation and apoptosis, thereby both preventing adipocyte hypertrophy, which is associated with alleviation of insulin resistance presumably due to decreases in FFA, and TNF alpha, and upregulation of adiponectin. We conclude that although by different mechanisms, both PPAR gamma/RXR inhibitors and PPAR gamma agonist improve insulin resistance, which is associated with decreased TG content of muscle/liver and prevention of adipocyte hypertrophy.     

Peripheral mechanisms underlying the essential role of P2X3,2/3 receptors in the development of inflammatory hyperalgesia

Activation of P2X3,2/3 receptors by endogenous ATP contributes to the development of inflammatory hyperalgesia. Given the clinical importance of mechanical hyperalgesia in inflammatory states, we hypothesized that the activation of P2X3,2/3 receptors by endogenous ATP contributes to carrageenan-induced mechanical hyperalgesia and that this contribution is mediated by an indirect and/or a direct sensitization of the primary afferent nociceptors. Co-administration of the selective P2X3,2/3 receptors antagonist A-317491, or the non-selective P2X3 receptor antagonist, TNP-ATP, with carrageenan blocked the mechanical hyperalgesia induced by carrageenan, and significantly reduced the increased concentration of tumor necrosis factor alpha (TNF-α) and chemokine-induced chemoattractant-1 (CINC-1) but not of interleukin-1 beta (IL-1 β) induced by carrageenan. Co-administration of the selective P2X3,2/3 receptors antagonist A-317491 with carrageenan did not affect the neutrophil migration induced by carrageenan. Intrathecal administration of oligonucleotides antisense against P2X3 receptors for seven days significantly reduced the expression of P2X3 receptors in the saphenous nerve and significantly reduced the mechanical hyperalgesia induced by carrageenan. We concluded that the activation of P2X3,2/3 receptors by endogenous ATP is essential to the development of the mechanical hyperalgesia induced by carrageenan. Furthermore, we showed that this essential role of P2X3,2/3 receptors in the development of carrageenan-induced mechanical hyperalgesia is mediated by an indirect sensitization of the primary afferent nociceptors dependent on the previous release of TNF-α and by a direct sensitization of the primary afferent nociceptors.     

PPARγ、PTEN、Akt在胃癌中的表达及其与胃癌生物学行为的关系

目的：检测人胃癌组织中过氧化物酶增殖激活受体γ（PPARγ）、10号染色体缺失张力蛋白同源的磷酸酶基因（PTEN）、丝氨酸/苏氨酸蛋白激酶（Akt）mRNA表达,探讨其与胃癌生物学行为的关系。方法应用逆转录PCR法检测60例人胃癌组织及相应癌旁组织,20名正常胃组织中PPARγ、PTEN、Akt mRNA的表达情况,并分析三者与胃癌分化程度、肿瘤大小、淋巴结转移、远处转移、浸润深度和临床分期及患者性别、年龄之间的关系,同时分析三者的相关性。结果胃癌组织中PPARγ及Akt mRNA表达水平高于癌旁组织及正常胃组织（P＜0.05）,而PTEN mRNA 表达水平明显较癌旁组织及正常胃组织低（P＜0.05）,在癌旁组织与正常胃组织间PPARγ、PTEN、Akt mR-NA的表达水平均无明显差异。胃癌组织中PPARγ、PTEN、Akt mRNA表达量与患者性别、年龄、肿瘤大小及分化程度无关,而与胃癌的 TNM分期、侵犯浆膜、淋巴结转移及远处转移相关（P＜0.05）。PPARγ与PTEN 的表达呈负相关（rs ＝-0.492,P＜0.05）,与 Akt 表达呈正相关（rs ＝0.623,P＜0.05）,PTEN与Akt表达呈负相关（rs ＝-0.565,P＜0.05）。结论 PPARγ、Akt在胃癌中高表达而PTEN呈低表达,三者中存在明显相关,联合检测可作为判断胃癌恶性程度和预后的指标。     

The enterohepatic nuclear receptors are major regulators of the enterohepatic circulation of bile salts

Recent studies have established that bile salts are signaling molecules, besides their classic function in dietary lipid absorption and cholesterol metabolism. Bile salts signal by activating mitogen-activated protein kinase (MAPK) pathways and nuclear receptors like farnesoid X receptor-α (FXRα). FXRα activation increases the expression of direct FXRα target genes involved in bile salt transport and detoxification, and decreases expression of indirect FXRα target genes involved in bile salt biosynthesis and uptake. These actions prevent toxic accumulation of bile salts in the enterohepatic organs. A network of interactions with other nuclear receptors and MAPK pathways may protect the liver against pathological elevation of bile salts and cholestasis. Therefore treatment of cholestasis might benefit from the development of FXRα agonists.     

乳腺癌的钼靶X线分析

目的探讨乳腺癌X线的直接征象和间接征象在乳腺癌诊断中的作用。方法对81例经病理证实的乳腺癌的钼靶X线直接和间接征象进行回顾性分析。结果81例乳腺癌中，凭直接征象或直接征象加间接征象诊断乳腺癌68例，仅凭间接征象诊断乳腺癌13例。结论钼靶X线检查显示乳腺癌的直接和间接征象在乳腺癌诊断中发挥着无可替代的重要作用。     

Chemoprevention of chemically induced skin tumorigenesis by ligand activation of peroxisome proliferator-activated receptor-beta/delta and inhibition of cyclooxygenase 2

Ligand activation of peroxisome proliferator-activated receptor-β/δ (PPARβ/δ) and inhibition of cyclooxygenase-2 (COX2) activity by nonsteroidal anti-inflammatory drugs (NSAID) can both attenuate skin tumorigenesis. The present study examined the hypothesis that combining ligand activation of PPARβ/δ with inhibition of COX2 activity will increase the efficacy of chemoprevention of chemically induced skin tumorigenesis over that observed with either approach alone. To test this hypothesis, wild-type and Pparβ/δ-null mice were initiated with 7,12-dimethylbenz[a]anthracene (DMBA), topically treated with 12-O-tetradecanoylphorbol-13-acetate to promote tumorigenesis, and then immediately treated with topical application of the PPARβ/δ ligand GW0742, dietary administration of the COX2 inhibitor nimesulide, or both GW0742 and nimesulide. Ligand activation of PPARβ/δ with GW0742 caused a PPARβ/δ-dependent delay in the onset of tumor formation. Nimesulide also delayed the onset of tumor formation and caused inhibition of tumor multiplicity (46%) in wild-type mice but not in Pparβ/δ-null mice. Combining ligand activation of PPARβ/δ with dietary nimesulide resulted in a further decrease of tumor multiplicity (58%) in wild-type mice but not in Pparβ/δ-null mice. Biochemical and molecular analysis of skin and tumor samples show that these effects were due to the modulation of terminal differentiation, attenuation of inflammatory signaling, and induction of apoptosis through both PPARβ/δ-dependent and PPARβ/δ-independent mechanisms. Increased levels and activity of PPARβ/δ by nimesulide were also observed. These studies support the hypothesis that combining ligand activation of PPARβ/δ with inhibition of COX2 activity increases the efficacy of preventing chemically induced skin tumorigenesis as compared with either approach alone.     

Roles of PPAR family in bone metabolisms

Bone is a complex tissue which contains osteoclasts, osteoblasts, chondrocytes, adipocytes, hematopoietic cells and immune cells. Since osteoblasts share the same origin with adipocytes in bone marrow cavity, it is assumed that PPAR (peroxisome proliferator-activated receptor) family, which is an important nuclear receptor family for adipocyte differentiation, plays a role in the bone microenvironment. Indeed, recent evidences support the primitive roles of PPAR family in osteoblast differentiation as well as adipocyte differentiation. Furthermore, PPAR family is also implicated in the regulation of differentiation and function of osteoclasts. Here, we summarized the functional roles of PPAR family in bone remodeling and regulation of bone microenvironments. We also discuss the potential mechanisms that regulate expression and function of PPAR family during bone metabolisms.     

Antigen specific receptors on murine B cell lineage. 1. On antibody forming cells in various stages of immune response

In this study it was examined whether or not antigen specific receptors are on direct and indirect plaque-forming cells (PFC). Spleen cells from mice primed both with horse red blood cells (HRBC) and sheep red blood cells (SRBC) were incubated with HRBC to make rosettes and fractionated on Ficoll-Hypaque density gradient. Both direct and indirect HRBC-PFC were depleted from the interface fraction. The depletion was antigen specific and inhibited by the preincubation of spleen cells with antiserum against kappa- or mu-chain for direct PFC and with antiserum against kappa- or gamma 1-chain for indirect PFC. The depletion was not due to the rosette formation mediated by Fc-receptors which might be on antibody forming cells, because PFC were not eliminated by the density gradient sedimentation after incubation of spleen cells with SRBC coated with anti-SRBC IgG antibody in our experimental conditions. Our results show that the antigen specific immunoglobulin receptors are on the cells producing IgG antibody after primary or secondary immunization as well as on the IgM antibody-forming cells even in late stage of immune response.