Parathyroid hormone-related protein(1-34) regulates Phex expression in osteoblasts through the protein kinase A pathway

Phex (a phosphate-regulating gene with homologies to endopeptidases on the X chromosome) is expressed predominantly in bone in which it has been implicated in the mineralization process. Multiple factors and hormones, including PTHrP, regulate formation, development, and/or homeostasis of bone. The purpose of the present study was to determine whether PTHrP(1-34) regulates Phex expression and identify the signaling pathway used. Phex mRNA and protein levels were analyzed by RT-PCR and immunoblotting, respectively. In UMR-106 cells, PTHrP(1-34) caused a time- and concentration-dependent decrease in Phex expression. Forskolin, an adenylate cyclase activator, had the same effect. Dibutiryl cAMP also decreased Phex expression, and its effect was blocked by H89, a protein kinase A (PKA) inhibitor. In contrast, 12-O-tetradecanoyl phorbol-13-acetate, a protein kinase C (PKC) activator, increased Phex expression in a time- and dose-dependent manner. This effect was reversed by bisindolylmaleimide Iota, a PKC inhibitor. Bovine PTH(3-34), which activates PKC but not PKA, had no effect. On the contrary, human PTH(1-31), which activates PKA but not PKC, decreased Phex expression. H89 but not bisindolylmaleimide Iota blocked the effect of PTHrP(1-34). PTHrP(1-34) also decreased Phex expression in cultures of fetal rat calvaria cells at d 7 of culture but not at later stages. These data demonstrate that PTHrP(1-34), through PKA, down-regulates Phex expression in osteoblasts.     

1,25-(OH)2D3 down-regulates expression of Phex, a marker of the mature osteoblast

Mutations in the PHEX/Phex gene, which encodes for a protein with homology to neutral endopeptidases, are responsible for human and murine X-linked hypophosphatemia. The present study examined Phex messenger RNA (mRNA) and protein expression in cultured osteoblasts and its regulation by 1,25-(OH)2D3. Phex mRNA levels were quantitated on Northern blots by densitometric analysis relatively to GAPDH mRNA levels. Immunoreactive Phex protein levels were evaluated by immunoprecipitation using a polyclonal rabbit antiserum raised against a mouse Phex carboxy-terminal peptide. Beta-glycerophosphate-induced matrix mineralization in primary osteoblast cultures was associated with significant increases in Phex mRNA and protein. Phex mRNA and protein levels were low or undetectable in proliferating preosteoblastic MC3T3-E1 cells and dramatically increased concomitantly with initiation of matrix mineralization. The pattern of Phex expression, however, was similar in nonmineralizing cultures grown in the absence of beta-glycerophosphate, indicating that the induction of Phex expression in MC3T3-E1 cells was related to cell differentiation rather than matrix mineralization. 1,25-(OH)2D3 inhibited mineral deposition and down-regulated Phex mRNA and protein expression in a time- and dose-dependent manner. These results indicate that Phex is a marker of the fully differentiated osteoblast and that its expression is stimulated during beta-glycerophosphate-induced mineralization in primary osteoblast cultures and down-regulated by 1,25-(OH)2D3, an inhibitor of matrix mineralization. These findings add support for Phex having an important role in bone mineralization.     

Protective effects of dietary curcumin in mouse model of chemically induced colitis are strain dependent

BACKGROUND: Curcumin (diferulolylmethane) has been shown to have a protective role in mouse models of inflammatory bowel diseases (IBD) and to reduce the relapse rate in human ulcerative colitis (UC), thus making it a potentially viable supportive treatment option. Trinitrobenzene sulfonic acid (TNBS) colitis in NKT-deficient SJL/J mice has been described as Th1-mediated inflammation, whereas BALB/c mice are believed to exhibit a mixed Th1/Th2 response. METHODS: We therefore investigated the effect of dietary curcumin in colitis induced in these 2 strains. RESULTS: In the BALB/c mice, curcumin significantly increased survival, prevented weight loss, and normalized disease activity. In the SJL/J mice, curcumin demonstrated no protective effects. Genomewide microarray analysis of colonic gene expression was employed to define the differential effect of curcumin in these 2 strains. This analysis not only confirmed the disparate responses of the 2 strains to curcumin but also indicated different responses to TNBS. Curcumin inhibited proliferation of splenocytes from naive BALB/c mice but not SJL/J mice when nonspecifically stimulated in vitro with concanavalin A (ConA). Proliferation of CD4(+) splenocytes was inhibited in both strains, albeit with about a 2-fold higher IC(50) in SJL/J mice. Secretion of IL-4 and IL-5 by CD4(+) lymphocytes of BALB/c mice but not SJL/J mice was significantly augmented by ConA and reduced to control levels by curcumin. CONCLUSIONS: The efficacy of dietary curcumin in TNBS colitis varies in BALB/c and SJL/J mouse strains. Although the exact mechanism underlying these differences is unclear, the results suggest that the therapeutic value of dietary curcumin may differ depending on the nature of immune dysregulation in IBD.     

Osteomalacia in hyp mice is associated with abnormal phex expression and with altered bone matrix protein expression and deposition

To explore how the loss of Phex function contributes to the pathogenesis of osteomalacia, we examined the abnormalities of mineralization, Phex, and bone matrix protein expression occurring in Hyp mice in vivo and in ex vivo bone marrow cell cultures. The results in vivo show that mineralization was decreased significantly in Hyp mouse bone. Phex protein was identifiable in osteoblasts and osteocytes in wild-type mice, but not in Hyp mice. In Hyp mice, osteocalcin, bone sialoprotein, and vitronectin expression were down-regulated, whereas biglycan and fibrillin-1 expression were up-regulated in osteocytes and bone matrix relative to those in their wild-type counterparts. Parallel studies ex vivo demonstrated that cells derived from 18-day Hyp mouse bone marrow cell cultures had a 3'-Phex deletion, no Phex protein expression, decreased alkaline phosphatase activity, collagen deposition, and calcium accumulation, and reduced osteocalcin, bone sialoprotein, and vitronectin at both the protein and messenger RNA levels. Furthermore conditioned medium from Hyp mouse bone marrow cultures could induce analogous defects in bone marrow cell cultures of wild-type cells. These novel findings indicate that there is an intrinsic osteogenic cell differentiation defect in addition to the known hypomineralization of bone in Hyp mice, which may be inducible by an autocrine/paracrine secreted factor. These results suggest that alterations in the Phex gene may control bone matrix mineralization indirectly by regulating the synthesis and deposition of bone matrix proteins.     

Sex steroid regulation of macrophage migration inhibitory factor in normal and inflamed colon in the female rat

BACKGROUND AND AIMS: Sex steroids influence IBD symptoms. Macrophage migration inhibitory factor (MIF), a target of sex steroids in other inflammatory models, promotes interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha release in colitis. We investigated whether estradiol and progesterone influence MIF, IL-1beta, and TNF-alpha production in experimental colitis. METHODS: Colonic MIF, IL-1beta, and TNF-alpha levels were measured in cyclic and ovariectomized rats, with or without estradiol benzoate (EB) or progesterone (P) replacement. MIF distribution was assessed by immunohistochemistry. Cytokines, myeloperoxidase activity, macroscopic damage, and plasma corticosterone were assessed 24 hours after intrarectal trinitrobenzene sulfonic acid (TNBS), with and without neutralizing anti-MIF antibody. Effects of EB and P on myeloperoxidase activity and MIF concentration were also assessed at 7 days in dextran sulfate sodium-induced colitis. RESULTS: Basal IL-1beta and TNF-alpha contents did not fluctuate during the estrous cycle, while MIF concentrations increased from estrus (estrogen dominance) to metestrus (P dominance; P < .05). EB and P treatment mimicked these effects in ovariectomized rats, and similarly altered MIF immunostaining. Progesterone dominance aggravated TNBS colitis in comparison with estrogen. Progesterone enhanced TNBS-induced MIF (P < .001) and TNF-alpha (P < .01) production, while EB decreased MIF (P < .01) and IL-beta levels (P < .01). Anti-MIF antibody prevented P-mediated up-regulation of TNF-alpha, improved TNBS colitis, and enhanced plasma corticosterone. At 7 days after dextran sulfate sodium, EB decreased myeloperoxidase activity and MIF concentration, while P had no effect. CONCLUSIONS: Estrogen decreases while progesterone increases MIF production in the female rat colon. Changes in basal MIF contents may affect colon susceptibility to inflammation, by modulating TNF-alpha and IL-1beta production during early stages of colitis.     

Curcumin-attenuated trinitrobenzene sulphonic acid induces chronic colitis by inhibiting expression of cyclooxygenase-2

AIM: To explore the possible mechanisms of curcumin in rat colitis induced by tri nitrobenzene suifonic (TNBS) acid. METHODS: Rats with TNBS acid-induced colitis were treated with curcumin (30 mg/kg or 60 mg/kg per day ip). Changes of body weight and histoiogicai scores as well as survival rate were evaluated. Leukocyte infiltration was detected by myeloperoxidase (MPO) activity assay. The expression of cyclooxygenase-2 (COX-2) was detected by RT-PCR and Western blot. Inflammation cytokines were determined by RT-PCR. Local concentration of prostaglandin E2 (PGE2) in colon mucosa was determined by ELISA. RESULTS: Curcumin improved survival rate and histoiogicai image, decreased the macroscopic scores and MPO activity. Also curcumin reduced the expression of COX-2 and inflammation cytokines. In addition, treatment with curcumin increased the PGE2 level. CONCLUSION: Curcumin has therapeutic effects on TNBS acid-induced colitis, the mechanisms seem to be related to COX-2 inhibition and PGE2 improvement.     

姜黄素通过过氧化物酶体增生物激活受体-γ在大鼠实验性结肠炎中发挥抗炎作用

背景：研究显示姜黄素可激活过氧化物酶体增生物激活受体（PPAR）-γ，抑制三硝基苯磺酸（TNBS）诱导的大鼠结肠炎症。目的：以姜黄素和PPAR-γ拮抗剂GW9662单独或联合干预结肠炎模型大鼠，探讨姜黄素在大鼠实验性结肠炎中的抗炎机制。方法：以直肠内注入TNBS／乙醇溶液制备大鼠结肠炎模型。模型大鼠分别腹腔注射二甲基亚砜（DMSO）、姜黄素、GW9662或GW9662＋姜黄素2周，评价各组大鼠的死亡率、结肠损伤评分、血清促炎因子白细胞介素（IL）-2和抗炎因子IL-10水平以及结肠组织PPAR-γ和核因子（NF）-κB的表达。结果：与模型对照组相比，姜黄素能明显降低大鼠死亡率、结肠黏膜大体、组织学损伤评分和血清IL-2水平，升高血清IL-10水平，结肠组织PPAR-γ表达增高，NF-κB表达减低（P〈0．05）；GW9662＋姜黄素组大鼠结肠炎症无明显改善。正常对照组、模型对照组和姜黄素组PPAR-γ与NF-κB的表达均呈负相关（P〈0．01）。结论：姜黄素可通过PPAR-γ途径负性调节NF-κB的表达，在TNBS诱导的大鼠结肠炎中发挥抗炎作用。     

Inhibition of Smad7 with a specific antisense oligonucleotide facilitates TGF-beta1-mediated suppression of colitis

BACKGROUND & AIMS: Defective transforming growth factor (TGF)-beta1 signaling due to high levels of Smad7 is a feature of inflammatory bowel disease (IBD). In this study, we analyzed the effect of reducing Smad7 levels with antisense oligonucleotide on mouse models of colitis. METHODS: Mucosal samples taken from colitic tissue of mice with colitis due to either haptenating reagents (trinitrobenzene sulfonic acid [TNBS] or oxazolone) or to transfer of T cells (SCID transfer colitis) were analyzed for Smad3 and/or Smad7 expression by Western blotting and, in some cases, content of TGF-beta1 by enzyme-linked immunosorbent assay. The effect of oral Smad7 antisense oligonucleotide on mucosal inflammation was assessed. RESULTS: TGF-beta1 levels were increased in the inflamed tissues of mice with colitis induced by either TNBS or oxazolone. Nevertheless, TGF-beta1 did not exert a regulatory effect, probably because TGF-beta1 signaling was blocked, as indicated by the presence of reduced Smad3 phosphorylation and high levels of Smad7. Oral administration of Smad7 antisense oligonucleotide to colitic mice restored TGF-beta1 signaling via Smad3 and ameliorated inflammation in hapten-induced colitis. In addition, Smad7 antisense oligonucleotide had a therapeutic effect on relapsing TNBS-induced colitis but not on cell-transfer colitis. CONCLUSIONS: These data suggest that colitis models associated with high endogenous TGF-beta1 levels and defective TGF-beta1 signaling due to high levels of Smad7 can be ameliorated by down-regulation of Smad7 and by oral administration of Smad7 antisense oligonucleotide. This may represent a new approach to the control of IBD, particularly during active phases when its Smad7 profile resembles that of hapten-induced colitis.     

Suppressor of cytokine signalling 1 in lymphocytes regulates the development of intestinal inflammation in mice

BACKGROUND AND AIMS: Imbalance between pro- and anti-inflammatory cytokines produced by intestinal T cells induces inflammatory bowel diseases (IBD). However, the importance of regulation of cytokine signalling in IBD has not been fully clarified. We have demonstrated that suppressor of cytokine signalling 1 (SOCS1) is expressed in inflamed tissues in an experimental colitis model. In the present study, we investigated the role of SOCS1 in colitis models to clarify the mechanism of IBD development. METHODS: Intestinal T cells in transgenic mice expressing high levels of SOCS1 in lymphocytes (SOCS1Tg mice) were characterised by flow cytometric analysis and cytokine production from intestinal T cells was determined by ELISA. 2,4,6-Trinitrobenzene sulphonic acid (TNBS) induced colitis was induced in SOCS1Tg mice and severity was compared with control littermates by measurement of survival rates. Intracellular signalling was assessed by western blotting analysis. RESULTS: SOCS1Tg mice developed colitis spontaneously with age. Young SOCS1Tg mice less than 15 weeks of age, before the onset of colitis, were susceptible to TNBS induced colitis. Intestinal T cells of SOCS1Tg mice showed increased interferon gamma and tumour necrosis factor alpha production and decreased transforming growth factor beta production. Expression of cytotoxic T lymphocyte associated antigen 4 (CTLA-4), a negative regulator of T cell activation, in SOCS1Tg mice was severely impaired at the protein level although mRNA levels of CTLA-4 in SOCS1Tg mice were comparable with those in control mice. CONCLUSIONS: Our data suggest that SOCS1 plays an important role in the regulation of colitis by controlling intestinal T cell activation mediated through CTLA-4 expression.     

姜黄素对溃疡性结肠炎大鼠的抗炎作用及其对肠黏膜IL-23的影响

目的研究姜黄素对溃疡性结肠炎大鼠肠黏膜IL-23表达的影响,进一步探讨姜黄素对溃疡性结肠炎的抗炎作用机制。方法将80只雄性SD大鼠随机分为正常对照组、模型组、姜黄素组、柳氮磺吡啶(SASP)组,每组均为20只。模型组、姜黄素组、SASP组大鼠分别以100 mg/kg TNBS乙醇溶液灌肠制备大鼠结肠炎模型。正常对照组予相同剂量的0.9%氯化钠溶液灌肠;正常对照组、模型组每日予相同剂量的0.9%氯化钠溶液灌胃;姜黄素组、SASP组自造模第2天起每日分别予100 mg/kg姜黄素溶液及SASP溶液灌胃。造模第8天处死大鼠,采集大鼠结肠标本备检。评价各组大鼠的体质量变化,光镜下观察大鼠肠黏膜组织病理改变并进行病理学评分,评价各组大鼠的疾病活动指数(DAI)、肠黏膜损伤指数(CMDI)及组织学损伤情况(HS);采用RT-PCR方法测定肠黏膜组织IL-23 mRNA水平;Western blot测定肠组织IL-23蛋白表达水平。结果与模型组比较,姜黄素组DAI、CMDI、HS评分及IL-23蛋白、mRNA的表达均有明显降低(P均<0.05),与SASP组比较无统计学差异(P>0.05)。结论姜黄素能显著抑制IL-23的表达,对实验性大鼠结肠炎有明显的抑制作用。     

Establishment of a trinitrobenzene sulfonic acid‐induced rat colitis model

OBJECTIVE : To set up a trinitrobenzene sulfonic acid (TNBS)‐induced colitis model in the rat and to assess its value in research studies of inflammatory bowel disease (IBD). METHODS : A 0.85‐mL enema containing 30 mg TNBS dissolved in 50% ethanol was instilled into the rat colon to induce distal colitis. Control rats were instilled with 50% ethanol or TNBS/saline alone. Macroscopic histological changes of the colon and myeloperoxidase (MPO) activity of the mucosa were evaluated. RESULTS : One week after the TNBS/ethanol enema, hyperemia, edema and ulceration of the colonic mucosa appeared with predominant infiltration of polymorphonuclear leukocytes in the distal colon. Four weeks after TNBS/ethanol enema, ulcers had healed macroscopically and lymphocytes and plasma cells became predominant. The tissue MPO activity increased on the first day after the TNBS/ethanol enema and this increase in MPO activity lasted for 3 weeks, but declined 4 weeks after the TNBS/ethanol enema. In contrast, macroscopic, histological changes and MPO activity returned to normal levels in control rats within the first week. CONCLUSIONS : Trinitrobenzene sulfonic acid/ ethanol‐induced rat distal colitis is an ideal model of IBD and may serve as a tool for the investigation of the pathogenesis of and effects of pharmaceuticals on IBD.     

Expression and significance of nuclear factor κB p65 in colon tissues of rats with TNBS-induced colitis

AIM: To investigate the role of NF-κB in the pathogenesis of TNBS-induced colitis in rats. METHODS: Thirty-two healthy adult Sprague-Dawley (SD) rats were randomly divided into four groups of eight each: normal, NS, model Ⅰ, model Ⅱ groups in our study. Rat colitis model was established through 2-,4-,6-trinitrobenzene sulfonic acid (TNBS) enema. At the end of four weeks, the macroscopical and histological changes of the colon were examined and mucosa myeloperoxidase (MPO)activities assayed. NF-~B p65 expression was determined by Western blot assessment in cytoplasmic and nuclear extracts of colon tissue, and the expressions of TNF-α (and ICAM-1 protein in colon tissue were examined by immunohistochemistry. The relativities between expression of NF-κB p65 and other parameters were analyzed. RESULTS: TNBS enema resulted in pronounced pathological changes of colonic mucosa in model Ⅱ group (macroscopic and histological injury indices 6.25&#177;1.39 and 6.24&#177;1.04, respectively), which were in accordance with the significantly elevated MPO activity (1.69+0.11). And the nuclear level of NF-κB and expression of TNF-α, ICAM-1 in rats of model Ⅱ group were higher than that of normal control(9.7&#177;1.96 vs 1.7&#177;0.15, 84.09&#177;14.52 vs 16.03&#177;6.21,77.69&#177;8.09 vs 13.41&#177;4.91 P&lt;0.01), Linear correlation analysis revealed that there were strong correlations between the nuclear level of NF-κB and the tissue positive expression of TNF-α and ICAM-1, MPO activities, macroscopical and histological indices in TNBS-induced colitis, respectively (r = 0.8235, 0.8780, 0.8572, 0.9152,0.8247; P&lt;0.05). CONCLUSION: NF-κB plays a pivotal role in the pathogenesis of ulcerative colitis, which might account for the up-regulation the expression of TNF-α and ICAM-1.     

Chronic lithium administration ameliorates 2,4,6-trinitrobenzene sulfonic acid-induced colitis in rats; potential role for adenosine triphosphate sensitive potassium channels

Background and Aim: Inflammatory bowel disease (IBD) is a multi‐factorial disease with an unknown etiology characterized by oxidative stress, leukocyte infiltration and a rise in inflammatory cytokines. This study was conducted to investigate lithium in 2,4,6‐trinitrobenzene sulfonic acid (TNBS)‐induced chronic model of experimental IBD, and the contribution of potassium channels as a possible underlying mechanism. Methods: Experimental IBD was induced in rats by a single colonic administration of 10 mg of TNBS. Lithium, Glibenclamide (a potassium channel blocker), Lithium + Glibenclamide, Cromakalim or Lithium + Glibenclamide + Cromakalim were given twice daily for 7 successive days. At the end of the experiment, macroscopic and histopathologic scores, colonic malondialdehyde (MDA), tumor necrosis factor‐α (TNF‐α) level, and myeloperoxidase (MPO) activity as well as plasma lithium level were assessed. Results: Both macroscopic and histological features of colonic injury were markedly ameliorated by lithium. Likewise, the elevated amounts of MPO and MDA were diminished as well as those of TNF‐α (P < 0.05). Glibenclamide reversed the effect of lithium on these markers, Addition of cromakalim abrogated the effects mediated by glibenclamide and markedly decreased MPO activity, MDA level and TNF‐α content (P < 0.0.05). Macroscopic and microscopic scores and biochemical markers were significantly decreased in Cromakalim‐treated animals. No significant difference was observed between TNBS and Glibenclamide groups. Conclusion: Lithium exerts prominent anti‐inflammatory effects on TNBS‐induced colitis in rats. Potassium channels contribute to these beneficial properties.     

No Evidence for an Involvement of the P38 and JNK Mitogen-Activated Protein in Inflammatory Bowel Diseases

Involvement of mitogen-activated protein (MAPK) in inflammatory bowel disease (IBD) remains enigmatic. We sought to evaluate the expression and activity of p38 and JNK MAPK in IBD and 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis; and the effects of a p38 inhibitor, SB203580, in TNBS colitis. P 38 and JNK were quantified in colonic mucosa of 28 IBD patients and 19 controls and in 77 TNBS or control mice treated or not with SB203580. Colitis severity was assessed by survival, macroscopic and microscopic scoring, and molecular markers. Expression and activity of p38 and JNK were similar in IBD patients and controls and not modified by inflammation. In mice, p38 and JNK expression or activity did not increase following the induction of colitis. SB203580 decreased the p38 activity but displayed no clinical nor biological therapeutic effect. In conclusion, these results minimize the role of p38 and JNK in inflammatory colitis and the interest of p38 as a therapeutic target in IBD.