Three-dimensional structure of recombinant human osteogenic protein 1: structural paradigm for the transforming growth factor beta superfamily.

We report the three-dimensional structure of osteogenic protein 1 (OP-1, also known as bone morphogenetic protein 7) to 2.8-A resolution. OP-1 is a member of the transforming growth factor beta (TGF-beta) superfamily of proteins and is able to induce new bone formation in vivo. Members of this superfamily share sequence similarity in their C-terminal regions and are implicated in embryonic development and adult tissue repair. Our crystal structure makes possible the structural comparison between two members of the TGF-beta superfamily. We find that although there is limited sequence identity between OP-1 and TGF-beta 2, they share a common polypeptide fold. These results establish a basis for proposing the OP-1/TGF-beta 2 fold as the primary structural motif for the TGF-beta superfamily as a whole. Detailed comparison of the OP-1 and TGF-beta 2 structures has revealed striking differences that provide insights into how these growth factors interact with their receptors.

Interleukin 1 beta suppresses transforming growth factor-induced inorganic pyrophosphate (PPi) production and expression of the PPi-generating enzyme PC-1 in human chondrocytes.

Articular cartilage chondrocytes have the unique ability to elaborate large amounts of extracellular pyrophosphate (PPi), and transforming growth factor beta (TGF beta) appears singular among cartilage regulatory factors in stimulating PPi production. TGF beta caused a time and dose-dependent increase in intracellular and extracellular PPi in human articular chondrocyte cultures. TGF beta and interleukin 1 beta (IL-1 beta) antagonistically regulate certain chondrocyte functions. IL-1 beta profoundly inhibited basal and TGF beta-induced PPi elaboration. To address mechanisms involved with the regulation of PPi synthesis by IL-1 beta and TGF beta, we analyzed the activity of the PPi-generating enzyme NTP pyrophosphohydrolase (NTPPPH) and the PPi-hydrolyzing enzyme alkaline phosphatase. Human chondrocyte NTPPPH activity was largely attributable to plasma cell membrane glycoprotein 1, PC-1. Furthermore, TGF beta induced comparable increases in the activity of extracellular PPi, intracellular PPi, and cellular NTPPPH and in the levels of PC-1 protein and mRNA in chondrocytes as well as a decrease in alkaline phosphatase. All of these TGF beta-induced responses were completely blocked by IL-1 beta. Thus, IL-1 beta may be an important regulator of mineralization in chondrocytes by inhibiting TGF beta-induced PPi production and PC-1 expression.

Induction of Heme Oxygenase-1 Can Halt and Even Reverse Renal Tubule-Interstitial Fibrosis

Background: The tubule-interstitial fibrosis is the hallmark of progressive renal disease and is strongly associated with inflammation of this compartment. Heme-oxygenase-1 (HO-1) is a cytoprotective molecule that has been shown to be beneficial in various models of renal injury. However, the role of HO-1 in reversing an established renal scar has not yet been addressed. Aim: We explored the ability of HO-1 to halt and reverse the establishment of fibrosis in an experimental model of chronic renal disease. Methods: Sprague-Dawley male rats were subjected to unilateral ureteral obstruction (UUO) and divided into two groups: non-treated and Hemin-treated. To study the prevention of fibrosis, animals were pre-treated with Hemin at days -2 and -1 prior to UUO. To investigate whether HO-1 could reverse established fibrosis, Hemin therapy was given at days 6 and 7 post-surgery. After 7 and/or 14 days, animals were sacrificed and blood, urine and kidney tissue samples were collected for analyses. Renal function was determined by assessing the serum creatinine, inulin clearance, proteinuria/creatininuria ratio and extent of albuminuria. Arterial blood pressure was measured and fibrosis was quantified by Picrosirius staining. Gene and protein expression of pro-inflammatory and pro-fibrotic molecules, as well as HO-1 were performed. Results: Pre-treatment with Hemin upregulated HO-1 expression and significantly reduced proteinuria, albuminuria, inflammation and pro-fibrotic protein and gene expressions in animals subjected to UUO. Interestingly, the delayed treatment with Hemin was also able to reduce renal dysfunction and to decrease the expression of pro-inflammatory molecules, all in association with significantly reduced levels of fibrosis-related molecules and collagen deposition. Finally, TGF-beta protein production was significantly lower in Hemin-treated animals. Conclusion: Treatment with Hemin was able both to prevent the progression of fibrosis and to reverse an established renal scar. Modulation of inflammation appears to be the major mechanism behind HO-1 cytoprotection.

Solution structure of amyloid beta-peptide(1-40) in a water-micelle environment. Is the membrane-spanning domain where we think it is?

The three-dimensional solution structure of the 40 residue amyloid beta-peptide, A beta(1-40), has been determined using NMR spectroscopy at pH 5.1, in aqueous sodium dodecyl sulfate (SDS) micelles, In this environment, which simulates to some extent a water-membrane medium, the peptide is unstructured between residues 1 and 14 which are mainly polar and likely solvated by water. However, the rest of the protein adopts an alpha-helical conformation between residues 15 and 36 with a kink or hinge at 25-27. This largely hydrophobic region is likely solvated by SDS. Based on the derived structures, evidence is provided in support of a possible new location for the transmembrane domain of A beta within the amyloid precursor protein (APP). Studies between pH 4.2 and 7.9 reveal a pH-dependent helix-coil conformational switch. At the lower pH values, where the carboxylate residues are protonated, the helix is uncharged, intact, and lipid-soluble. As the pH increases above 6.0, part of the helical region (15-24) becomes less structured, particularly near residues E22 and D23 where deprotonation appears to facilitate unwinding of the helix. This pH-dependent unfolding to a random coil conformation precedes any tendency of this peptide to aggregate to a beta-sheet as the pH increases. The structural biology described herein for A beta(1-40) suggests that (i) the C-terminal two-thirds of the peptide is an alpha-helix in membrane-like environments, (ii) deprotonation of two acidic amino acids in the helix promotes a helix-coil conformational transition that precedes aggregation, (iii) a mobile hinge exists in the helical region of A beta(1-40) and this may be relevant to its membrane-inserting properties and conformational rearrangements, and (iv) the location of the transmembrane domain of amyloid precursor proteins may be different from that accepted in the Literature. These results may provide new insight to the structural properties of amyloid beta-peptides of relevance to Alzheimer's disease.

Solution structure of methionine-oxidized amyloid beta-peptide (1-40). Does oxidation affect conformational switching?

The solution structure of A beta(1-40)Met(O), the methionine-oxidized form of amyloid beta-peptide A beta(1-40), has been investigated by CD and NMR spectroscopy. Oxidation of Met35 may have implications in the aetiology of Alzheimer's disease. Circular dichroism experiments showed that whereas A beta(1-40) and A beta(1-40)Met(O) both adopt essentially random coil structures in water (pH 4) at micromolar concentrations, the former aggregates within several days while the latter is stable for at least 7 days under these conditions. This remarkable difference led us to determine the solution structure of A beta(1-40)Met(O) using H-1 NMR spectroscopy. In a water-SDS micelle medium needed to solubilize both peptides at the millimolar concentrations required to measure NMR spectra, chemical shift and NOE data for A beta(1-40)Met(O) strongly suggest the presence of a helical region between residues 16 and 24. This is supported by slow H-D exchange of amide protons in this region and by structure calculations using simulated annealing with the program XPLOR. The remainder of the structure is relatively disordered. Our previously reported NMR data for A beta(1-40) in the same solvent shows that helices are present over residues 15-24 (helix 1) and 28-36 (helix 2), Oxidation of Met35 thus causes a local and selective disruption of helix 2. In addition to this helix-coil rearrangement in aqueous micelles, the CD data show that oxidation inhibits a coil-to-beta-sheet transition in water. These significant structural rearrangements in the C-terminal region of A beta may be important clues to the chemistry and biology of A beta(1-40) and A beta(1-42).

Inhibition of COX 1 and 2 prior to Renal Ischemia/Reperfusion Injury Decreases the Development of Fibrosis

Ischemia and reperfusion injury (IRI) contributes to the development of chronic interstitial fibrosis/tubular atrophy in renal allograft patients, Cyclooxygenase (COX) 1 and 2 actively participate in acute ischemic injury by activating endothelial cells and inducing oxidative stress. Furthermore, blockade of COX I and 2 has been associated with organ improvement after ischemic damage. The aim of this study was to evaluate the role of COX I and 2 in the development of fibrosis by performing a COX I and 2 blockade immediately before IRI We subjected C57BI/6 male mice to 60 min of unilateral renal pedicle occlusion, Prior to surgery mice were either treated with indomethacin (IMT) at days -1 and 0 or were untreated. Blood and kidney samples were collected 6 wks after IRI. Kidney samples were analyzed by real-time reverse transcription-poly me rase chain reaction for expression of transforming growth factor beta (TGF-beta), monocyte chemoattractant protein 1 (MCP-1), osteopontin (OPN), tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-1 beta, IL-10, heme oxygenose 1 (HO-1), vimentin, connective-tissue growth factor (CTGF), collagen 1, and bone morphogenic protein 7 (BMP-7), To assess tissue fibrosis we performed morphometric analyses and Sirius red staining. We also performed immunohistochemical analysis of anti-actin smooth muscle, Renal function did not significantly differ between groups. Animals pretreated with IMT showed significantly less interstitial fibrosis than nontreated animals. Gene transcript analyses showed decreased expression of TGF-beta, MCP-1,TNF-alpha, IL-1-beta, vimentin, collagen 1, CTGF and IL-10 mRNA (all P < 0.05), Moreover, HO-I mRNA was increased in animals pretreated with IMT (P < 0.05) Conversely, IMT treatment decreased osteopontin expression and enhanced BMP-7 expression, although these levels did rot reach statistical significance when compared with control expression levels, I he blockade of COX 1 and 2 resulted in less tissue fibrosis, which was associated with a decrease in proinflammatory cytokines and enhancement of the protective cellular response.

Enhanced programmed death 1 (PD-1) and PD-1 ligand (PD-L1) expression in patients with actinic cheilitis and oral squamous cell carcinoma

PD-1 and PD-L1 can be involved in tumor escape, and little is known about the role of these molecules in oral tumors or pre-malignant lesions. In the present study, we investigated the expression of PD-1 and PD-L1 in the blood and lesion samples of patients with actinic cheilitis (AC) and oral squamous cell carcinoma (OSCC). Our results showed that lymphocytes from peripheral blood and tissue samples exhibited high expression of PD-1 in both groups analyzed. Patients with AC presented higher percentage as well as the absolute numbers of CD4(+)PD-1(+) and CD8(+)PD-1(+) lymphocytes in peripheral blood mononuclear cells (PBMC) than healthy individuals, while patients with OSCC presented an increased frequency of CD8(+)PD1(+) in PBMC when compared with controls. On the other hand, increased frequency of CD4(+) and CD8(+) T cells expressing PD-1(+) accumulate in samples from OSCC, and the expression of PD-L1 was intense in OSCC and moderate in AC lesion sites. Lower levels of IFN-gamma and higher levels of TGF-beta were detected in OSCC samples. Our data demonstrate that PD-1 and PD-L1 molecules are present in blood and samples of AC and OSCC patients. Further studies are required to understand the significance of PD-1 and PD-L1 in oral tumors microenvironment.

Dorsal and ventral medullary catecholamine cell groups contribute differentially to systemic interleukin-1 beta-induced hypothalamic pituitary adrenal axis responses

Medial parvocellular paraventricular corticotropin-releasing hormone (mPVN CRH) cells are critical in generating hypothalamic-pituitary-adrenal (HPA) axis responses to systemic interleukin-1 beta (IL-1 beta). However, although it is understood that catecholamine inputs are important in initiating mPVN CRH cell responses to IL-1 beta, the contributions of distinct brainstem catecholamine cell groups are not known. We examined the role of nucleus tractus solitarius (NTS) and ventrolateral medulla (VLM) catecholamine cells in the activation of mPVN CRH, hypothalamic oxytocin (OT) and central amygdala cells in response to IL-1 beta (1 mug/kg, i.a.). Immunolabelling for the expression of c-fos was used as a marker of neuronal activation in combination with appropriate cytoplasmic phenotypic markers. First we confirmed that PVN 6-hydroxydopamine lesions, which selectively depleted catecholaminergic terminals, significantly reduced IL-1 beta -induced mPVN CRH cell activation. The contribution of VLM (A1/C1 cells) versus NTS (A2 cells) catecholamine cells to mPVN CRH cell responses was then examined by placing ibotenic acid lesions in either the VLM or NTS. The precise positioning of these lesions was guided by prior retrograde tracing studies in which we mapped the location of IL-1 beta -activated VLM and NTS cells that project to the mPVN. Both VLM and NTS lesions reduced the mPVN CRH and OT cell responses to IL-1 beta. Unlike VLM lesions, NTS lesions also suppressed the recruitment of central amygdala neurons. These studies provide novel evidence that both the NTS and VLM catecholamine cells have important, but differential, contributions to the generation of IL-1 beta -induced HPA axis responses. Copyright (C) 2001 S. Karger AG, Basel.

FXYD7 is a brain-specific regulator of Na,K-ATPase alpha 1-beta isozymes.

Recently, corticosteroid hormone-induced factor (CHIF) and the gamma-subunit, two members of the FXYD family of small proteins, have been identified as regulators of renal Na,K-ATPase. In this study, we have investigated the tissue distribution and the structural and functional properties of FXYD7, another family member which has not yet been characterized. Expressed exclusively in the brain, FXYD7 is a type I membrane protein bearing N-terminal, post-translationally added modifications on threonine residues, most probably O-glycosylations that are important for protein stabilization. Expressed in Xenopus oocytes, FXYD7 can interact with Na,K-ATPase alpha 1-beta 1, alpha 2-beta 1 and alpha 3-beta 1 but not with alpha-beta 2 isozymes, whereas, in brain, it is only associated with alpha 1-beta isozymes. FXYD7 decreases the apparent K(+) affinity of alpha 1-beta 1 and alpha 2-beta 1, but not of alpha 3-beta1 isozymes. These data suggest that FXYD7 is a novel, tissue- and isoform-specific Na,K-ATPase regulator which could play an important role in neuronal excitability.

Elevated levels of MIC-1/GDF15 in the cerebrospinal fluid of patients are associated with glioblastoma and worse outcome.

For patients with brain tumors identification of diagnostic and prognostic markers in easy accessible biological material, such as plasma or cerebrospinal fluid (CSF), would greatly facilitate patient management. MIC-1/GDF15 (growth differentiation factor 15) is a secreted protein of the TGF-beta superfamily and emerged as a candidate marker exhibiting increasing mRNA expression during malignant progression of glioma. Determination of MIC-1/GDF15 protein levels by ELISA in the CSF of a cohort of 94 patients with intracranial tumors including gliomas, meningioma and metastasis revealed significantly increased concentrations in glioblastoma patients (median, 229 pg/ml) when compared with control cohort of patients treated for non-neoplastic diseases (median below limit of detection of 156 pg/ml, p < 0.0001, Mann-Whitney test). However, plasma MIC-1/GDF15 levels were not elevated in the matching plasma samples from these patients. Most interestingly, patients with glioblastoma and increased CSF MIC-1/GDF15 had a shorter survival (p = 0.007, log-rank test). In conclusion, MIC-1/GDF15 protein measured in the CSF may have diagnostic and prognostic value in patients with intracranial tumors.

Antagonistic regulation of a proline-rich transcription factor by transforming growth factor beta and tumor necrosis factor alpha.

Transforming growth factor beta (TGF-beta) and tumor necrosis factor alpha (TNF-alpha) often exhibit antagonistic actions on the regulation of various activities such as immune responses, cell growth, and gene expression. However, the molecular mechanisms involved in the mutually opposing effects of TGF-beta and TNF-alpha are unknown. Here, we report that binding sites for the transcription factor CTF/NF-I mediate antagonistic TGF-beta and TNF-alpha transcriptional regulation in NIH3T3 fibroblasts. TGF-beta induces the proline-rich transactivation domain of specific CTF/NF-I family members, such as CTF-1, whereas TNF-alpha represses both the uninduced as well as the TGF-beta-induced CTF-1 transcriptional activity. CTF-1 is thus the first transcription factor reported to be repressed by TNF-alpha. The previously identified TGF-beta-responsive domain in the proline-rich transcriptional activation sequence of CTF-1 mediates both transcriptional induction and repression by the two growth factors. Analysis of potential signal transduction intermediates does not support a role for known mediators of TNF-alpha action, such as arachidonic acid, in CTF-1 regulation. However, overexpression of oncogenic forms of the small GTPase Ras or of the Raf-1 kinase represses CTF-1 transcriptional activity, as does TNF-alpha. Furthermore, TNF-alpha is unable to repress CTF-1 activity in NIH3T3 cells overexpressing ras or raf, suggesting that TNF-alpha regulates CTF-1 by a Ras-Raf kinase-dependent pathway. Mutagenesis studies demonstrated that the CTF-1 TGF-beta-responsive domain is not the primary target of regulatory phosphorylations. Interestingly, however, the domain mediating TGF-beta and TNF-alpha antagonistic regulation overlapped precisely the previously identified histone H3 interaction domain of CTF-1. These results identify CTF-1 as a molecular target of mutually antagonistic TGF-beta and TNF-alpha regulation, and they further suggest a molecular mechanism for the opposing effects of these growth factors on gene expression.

Gene transfer of a soluble IL-1 type 2 receptor-Ig fusion protein improves cardiac allograft survival in rats.

OBJECTIVE: Interleukin-1 (IL-1) mediates ischemia-reperfusion injury and graft inflammation after heart transplantation. IL-1 affects target cells through two distinct types of transmembrane receptors, type-1 receptor (IL-1R1), which transduces the signal, and the non-signaling type-2 receptor (IL-1R2), which acts as a ligand sink that subtracts IL-1beta from IL-1R1. We analyzed the efficacy of adenovirus (Ad)-mediated gene transfer of a soluble IL-1R2-Ig fusion protein in delaying cardiac allograft rejection and the mechanisms underlying the protective effect. METHODS: IL-1 inhibition by IL-1R2-Ig was tested using an in vitro functional assay whereby endothelial cells preincubated with AdIL-1R2-Ig or control virus were stimulated with recombinant IL-1beta or tumor necrosis factor-alpha (TNF-alpha), and urokinase-type plasminogen activator (u-PA) induction was measured by zymography. AdIL-1R2-Ig was delivered to F344 rat donor hearts ex vivo, which were placed in the abdominal position in LEW hosts. Intragraft inflammatory cell infiltrates and proinflammatory cytokine expression were analyzed by immunohistochemistry and real-time reverse transcriptase-polymerase chain reaction (RT-PCR), respectively. RESULTS: IL-1R2-Ig specifically inhibited IL-1beta-induced u-PA responses in vitro. IL-1R2-Ig gene transfer reduced intragraft monocytes/macrophages and CD4(+) cell infiltrates (p<0.05), TNF-alpha and transforming growth factor-beta (TGF-beta) expression (p<0.05), and prolonged graft survival (15.6+/-5.7 vs 10.3+/-2.5 days with control vector and 10.1+/-2.1 days with buffer alone; p<0.01). AdIL-1R2-Ig combined with a subtherapeutic regimen of cyclosporin A (CsA) was superior to CsA alone (19.4+/-3.0 vs 15.9+/-1.8 days; p<0.05). CONCLUSIONS: Soluble IL-1 type-2 receptor gene transfer attenuates cardiac allograft rejection in a rat model. IL-1 inhibition may be useful as an adjuvant therapy in heart transplantation.

The role of fibroblast growth factor (FGF) and type beta transforming growth factot beta (TGF beta1, beta2 and beta3) during rat craniofacial development

Growth factors seem to be part of a complex cellular signalling language, in which individual growth factors are the equivalents of the letters that compose words. According to this analogy, informational content lies, not in an individual growth factor, but in the entire set of growth factors and others signals to which a cell is exposed. The ways in which growth factors exert their combinatorial effects are becoming clearer as the molecular mechanisms of growth factors actions are being investigated. A number of related extracellular signalling molecules that play widespread roles in regulating development in both invertebrates and vertebrates constitute the Fibroblast Growth Factor (FGF) and type beta Transforming Growth Factor ((TGF beta). The latest research literature about the role and fate of these Growth factors and their influence in the craniofacial bone growth ad development is reviewed

The role of fibroblast growth factor (FGF) and type beta transforming growth factot beta (TGF beta1, beta2 and beta3) during rat craniofacial development

Growth factors seem to be part of a complex cellular signalling language, in which individual growth factors are the equivalents of the letters that compose words. According to this analogy, informational content lies, not in an individual growth factor, but in the entire set of growth factors and others signals to which a cell is exposed. The ways in which growth factors exert their combinatorial effects are becoming clearer as the molecular mechanisms of growth factors actions are being investigated. A number of related extracellular signalling molecules that play widespread roles in regulating development in both invertebrates and vertebrates constitute the Fibroblast Growth Factor (FGF) and type beta Transforming Growth Factor ((TGF beta). The latest research literature about the role and fate of these Growth factors and their influence in the craniofacial bone growth ad development is reviewed

Diabetes mellitus affects the biomechanical function of the callus and the expression of TGF-beta1 and BMP2 in an early stage of fracture healing

Transforming growth factor beta 1 (TGF-β1) and bone morphogenetic protein-2 (BMP-2) are important regulators of bone repair and regeneration. In this study, we examined whether TGF-β1 and BMP-2 expressions were delayed during bone healing in type 1 diabetes mellitus. Tibial fractures were created in 95 diabetic and 95 control adult male Wistar rats of 10 weeks of age. At 1, 2, 3, 4, and 5 weeks after fracture induction, five rats were sacrificed from each group. The expressions of TGF-β1 and BMP2 in the fractured tibias were measured by immunohistochemistry and quantitative reverse-transcription polymerase chain reaction, weekly for the first 5 weeks post-fracture. Mechanical parameters (bending rigidity, torsional rigidity, destruction torque) of the healing bones were also assessed at 3, 4, and 5 weeks post-fracture, after the rats were sacrificed. The bending rigidity, torsional rigidity and destruction torque of the two groups increased continuously during the healing process. The diabetes group had lower mean values for bending rigidity, torsional rigidity and destruction torque compared with the control group (P<0.05). TGF-β1 and BMP-2 expression were significantly lower (P<0.05) in the control group than in the diabetes group at postoperative weeks 1, 2, and 3. Peak levels of TGF-β1 and BMP-2 expression were delayed by 1 week in the diabetes group compared with the control group. Our results demonstrate that there was a delayed recovery in the biomechanical function of the fractured bones in diabetic rats. This delay may be associated with a delayed expression of the growth factors TGF-β1 and BMP-2.