Solution structure of a novel T‐cell adhesion inhibitor derived from the fragment of ICAM‐1 receptor: Cyclo(1,8)‐Cys‐Pro‐Arg‐Gly‐Gly‐Ser‐Val‐Cys

This study is aimed at elucidating the structure of a novel T‐cell adhesion inhibitor, cyclo(1,8)‐CPRGGSVC using one‐ and two‐dimensional (2D) ¹H NMR and molecular dynamics (MD) simulation. The peptide is derived from the sequence of its parent peptide cIBR (cyclo(1,12)‐PenPRGGSVLVTGC), which is a fragment of intercellular adhesion molecule‐1 (ICAM‐1). Our previous results show that the cyclo(1,8)‐CPRGGSVC peptide binds to the LFA‐1 I‐domain and inhibits heterotypic T‐cell adhesion, presumably by blocking the LFA‐1/ICAM‐1 interactions. The structure of the peptide was determined using NMR and MD simulation in aqueous solution. Our results indicate that the peptide adopts type‐I β‐turn conformation at the Pro2‐Arg3‐Gly4‐Gly5 (PRGG) sequence. The β‐turn structure at the PRGG motif is well conserved in cIBR peptide and ICAM‐1 receptor, which suggests the importance of the PRGG motif for the biological activity of cyclo(1,8)‐CPRGGSVC peptide. Meanwhile, the Gly5‐Ser6‐Val7‐Cys8‐Cys1 (GSVCC) sequence forms a “turn‐like” random coil structure that does not belong to any structured motif. Therefore, cyclo(1,8)‐CPRGGSVC peptide has only one structured region at the PRGG sequence, which may play an important role in the binding of the peptide to the LFA‐1 I‐domain. The conserved β‐turn conformation of the PRGG motif in ICAM‐1, cIBR, and cyclo(1,8)‐CPRGGSVC peptides can potentially be used to design peptidomimetics. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 633–641, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

TGF‐β1 sustains germ cell cyst reservoir via restraining follicle formation in the chicken

The transforming growth factor β (TGF‐β) superfamily members are important molecules that regulate many ovarian functions under normal physiological and pathological conditions. TGF‐β1 and its receptors are highly expressed in the ovarian cells of many species. However, the effect of TGF‐β1 on the capacity of the avian germ cell reservoir remains unknown. In this study, 5‐day‐old chicks were injected with TGF‐β1 (2.5, 12.5, and 62.5 μg/kg body weight) for 3 days to assess the effect of TGF‐β1 on early follicle development. Morphological analysis showed that treatment with TGF‐β1 (12.5 μg/kg) increased the number of germ cell cysts and reduced the number of primordial and growing follicles. The diameter and area of oocytes and follicles were decreased after TGF‐β1 treatment. Immunohistochemical staining of the proliferating cell nuclear antigen revealed that the ratios of the positive somatic and granulosa cells were decreased by 16.2% and 2.48%, respectively. Furthermore, more apoptotic cells were observed in the TGF‐β1 group than those of the control by terminal deoxynucleotidyl transferase dUTP nick end labeling assay. In addition, we cultured the 5d chicken ovaries for 3 days in vitro and found that treatment with TGF‐β1 (10 ng/mL) manifested similar results as the in vivo experiment. However, the negative effect of TGF‐β1 on early ovary development was rescued by treatment with a TGF‐βR1 inhibitor SD208, resulting in increased expression of steroidogenic enzymes and cell cycle‐regulating proteins. In conclusion, TGF‐β1 could maintain the germ cell reservoir by restraining follicle activation involving reduced cell proliferation and steroidogenic enzymes gene expression at the early stage of ovarian development.     

Novel mechanism of cardiac protection by valsartan: synergetic roles of TGF‐β1 and HIF‐1α in Ang II‐mediated fibrosis after myocardial infarction

Transforming growth factor (TGF)‐β1 is a known factor in angiotensin II (Ang II)‐mediated cardiac fibrosis after myocardial infarction (MI). Hypoxia inducible factor‐1 (Hif‐1α) was recently demonstrated to involve in the tissue fibrosis and influenced by Ang II. However, whether Hif‐1α contributed to the Ang II‐mediated cardiac fibrosis after MI, and whether interaction or synergetic roles between Hif‐1α and TGF‐β pathways existed in the process was unclear. In vitro, cardiac cells were incubated under hypoxia or Ang II to mimic ischaemia. In vivo, valsartan was intravenously injected into Sprague–Dawley rats with MI daily for 1 week; saline and hydralazine (another anti‐hypertensive agent like valsartan) was used as control. The fibrosis‐related proteins were detected by Western blotting. Cardiac structure and function were assessed with multimodality methods. We demonstrated in vitro that hypoxia would induce the up‐regulation of Ang II, TGF‐β/Smad and Hif‐1α, which further induced collagen accumulation. By blocking with valsartan, a blocker of Ang II type I (AT1) receptor, we confirmed that the up‐regulation of TGF‐β/Smad and Hif‐1α was through the Ang II‐mediated pathway. By administering TGF‐β or dimethyloxalylglycine, we determined that both TGF‐β/Smad and Hif‐1α contributed to Ang II‐mediated collagen accumulation and a synergetic effect between them was observed. Consistent with in vitro results, valsartan significantly attenuated the expression of TGF‐β/Smad, Hif‐1α and fibrosis‐related protein in rats after MI. Heart function, infarcted size, wall thickness as well as myocardial vascularization of ischaemic hearts were also significantly improved by valsartan compared with saline and hydralazine. Our study may provide novel insights into the mechanisms of Ang II‐induced cardiac fibrosis as well as into the cardiac protection of valsartan.     

Inhibition of bleomycin‐induced pulmonary fibrosis by bone marrow‐derived mesenchymal stem cells might be mediated by decreasing MMP9, TIMP‐1, INF‐γ and TGF‐β

The study was aimed to investigate the mechanism and administration timing of bone marrow‐derived mesenchymal stem cells (BMSCs) in bleomycin (BLM)‐induced pulmonary fibrosis mice. Thirty‐six mice were divided into six groups: control group (saline), model group (intratracheal administration of BLM), day 1, day 3 and day 6 BMSCs treatment groups and hormone group (hydrocortisone after BLM treatment). BMSCs treatment groups received BMSCs at day 1, 3 or 6 following BLM treatment, respectively. Haematoxylin and eosin and Masson staining were conducted to measure lung injury and fibrosis, respectively. Matrix metalloproteinase (MMP9), tissue inhibitor of metalloproteinase‐1 (TIMP‐1), γ‐interferon (INF‐γ) and transforming growth factor β1 (TGF‐β) were detected in both lung tissue and serum. Histologically, the model group had pronounced lung injury, increased inflammatory cells and collagenous fibres and up‐regulated MMP9, TIMP‐1, INF‐γ and TGF‐β compared with control group. The histological appearance of lung inflammation and fibrosis and elevation of these parameters were inhibited in BMSCs treatment groups, among which, day 3 and day 6 treatment groups had less inflammatory cells and collagenous fibres than day 1 treatment group. BMSCs might suppress lung fibrosis and inflammation through down‐regulating MMP9, TIMP‐1, INF‐γ and TGF‐β. Delayed BMSCs treatment might exhibit a better therapeutic effect. Copyright © 2015 John Wiley & Sons, Ltd. Highlights are as follows:

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miR‐21 promotes cardiac fibroblast‐to‐myofibroblast transformation and myocardial fibrosis by targeting Jagged1

Myocardial fibrosis after myocardial infarction (MI) is a leading cause of heart diseases. MI activates cardiac fibroblasts (CFs) and promotes CF to myofibroblast transformation (CMT). This study aimed to investigate the role of miR‐21 in the regulation of CMT and myocardial fibrosis. Primary rat CFs were isolated from young SD rats and treated with TGF‐β1, miR‐21 sponge or Jagged1 siRNA. Cell proliferation, invasion and adhesion were detected. MI model was established in male SD rats using LAD ligation method and infected with recombinant adenovirus. The heart function and morphology was evaluated by ultrasonic and histological analysis. We found that TGF‐β1 induced the up‐regulation of miR‐21 and down‐regulation of Jagged1 in rat CFs. Luciferase assay showed that miR‐21 targeted 3′‐UTR of Jagged1 in rat CFs. miR‐21 sponge inhibited the transformation of rat CFs into myofibroblasts, and abolished the inhibition of Jagged1 mRNA and protein expression by TGF‐β1. Furthermore, these effects of miR‐21 sponge on rat CFS were reversed by siRNA mediated knockdown of Jagged1. In vivo, heart dysfunction and myocardial fibrosis in MI model rats were partly improved by miR‐21 sponge but were aggravated by Jagged1 knockdown. Taken together, these results suggest that miR‐21 promotes cardiac fibroblast‐to‐myofibroblast transformation and myocardial fibrosis by targeting Jagged1. miR‐21 and Jagged1 are potential therapeutic targets for myocardial fibrosis.     

Conditional TGF‐β1 treatment increases stem cell‐like cell population in myoblasts

The limitation in successfully acquiring large populations of stem cell has impeded their application. A new method based on the dedifferentiation of adult somatic cells to generate induced multipotent stem cells would allow us to obtain a large amount of autologous stem cells for regenerative medicine. The current work was proposed to induce a sub‐population of cells with characteristics of muscle stem cells from myoblasts through conditional treatment of transforming growth factor (TGF)‐β₁. Our results show that a lower concentration of TGF‐β₁ is able to promote C2C12 myoblasts to express stem cell markers as well as to repress myogenic proteins, which involves a mechanism of dedifferentiation. Moreover, TGF‐β₁ treatment promoted the proliferation‐arrested C2C12 myoblasts to re‐enter the S‐phase. We also investigated the multi‐differentiation potentials of the dedifferentiated cells. TGF‐β₁ pre‐treated C2C12 myoblasts were implanted into mice to repair dystrophic skeletal muscle or injured bone. In addition to the C2C12 myoblasts, similar effects of TGF‐β₁ were also observed in the primary myoblasts of mice. Our results suggest that TGF‐β₁ is effective as a molecular trigger for the dedifferentiation of skeletal muscle myoblasts and could be used to generate a large pool of progenitor cells that collectively behave as multipotent stem cell‐like cells for regenerative medicine applications.     

Periostin down‐regulation attenuates the pro‐fibrogenic response of hepatic stellate cells induced by TGF‐β1

Liver fibrosis is characterized by an exacerbated accumulation of deposition of the extracellular matrix (ECM), and the activation of hepatic stellate cells (HSC) plays a pivotal role in the development of liver fibrosis. Periostin has been shown to regulate cell adhesion, proliferation, migration and apoptosis; however, the involvement of periostin and its role in transforming growth factor (TGF)‐β1‐induced HSC activation remains unclear. We used RT‐PCR and Western blot to evaluate the expression level of periostin in hepatic fibrosis tissues and HSCs, respectively. Cell proliferation was determined using the Cell Proliferation ELISA BrdU kit, cell cycle was analysed by flow cytometry. The expression of α‐smooth muscle actin (α‐SMA), collagen I, TGF‐β1, p‐Smad2 and p‐Smad3 were determined by western blot. Our study found that periostin was up‐regulated in liver fibrotic tissues and activated HSCs. In addition, siRNA‐periostin suppressed TGF‐β1‐induced HSC proliferation. The HSC transfected with siRNA‐periostin significantly inhibited TGF‐β1‐induced expression levels of α‐SMA and collagen I. Furthermore, TGF‐β1 stimulated the expression of periostin, and siRNA‐periostin attenuated TGF‐β1‐induced Smad2/3 activation in HSCs. These results suggest that periostin may function as a novel regulator to modulate HSC activation, potentially by promoting the TGF‐β1/Smad signalling pathway, and propose a strategy to target periostin for the treatment of liver fibrosis.