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In vivo characterization of bone marrow-derived fibroblasts recruited into fibrotic lesions.

Fibroblasts, which are widely distributed and play a key part in tissue fibrosis, are phenotypically and functionally heterogeneous. Recent studies reported that bone marrow can be a source of tissue fibroblast. In the study reported here, we investigated in vivo characterization of bone marrow-derived fibroblasts recruited into various fibrotic lesions. Mice were engrafted with bone marrow isolated from transgenic mice expressing green fluorescent protein (GFP), and fibrotic lesions were induced by cancer implantation (skin), excisional wounding (skin), and bleomycin administration (lung). A small population of GFP+ fibroblast was found even in nonfibrotic skin (8.7% +/- 4.6%) and lung (8.9% +/- 2.5%). The proportion of GFP+ fibroblasts was significantly increased after cancer implantation(59.7% +/- 16.3%) and excisional wounding (32.2% +/- 4.8%), whereas it was not elevated after bleomycin administration (7.1% +/- 2.4%). Almost all GFP+ fibroblasts in fibrotic lesions expressed type I collagen, suggesting that bone marrow-derived fibroblasts would contribute to tissue fibrosis. GFP+ fibroblasts expressed CD45, Thy-1, and alpha-smooth muscle actin at various proportions. Our results suggested that bone marrow-derived fibroblasts expressed several fibroblastic markers in vivo and could be efficiently recruited into fibrotic lesions in response to injurious stimuli; however, the degree of recruitment frequency might depend on the tissue microenvironment.

Animals↗

Corticosteroids, eosinophils and bronchial epithelial cells: new insights into the resolution of inflammation in asthma.

Anti-inflammatory therapy in asthma is reliant on corticosteroids, particularly in their inhaled form. However, steroids are rather non-specific in their actions and they also raise concerns regarding compliance and side-effect Issues. Furthermore, a small proportion of patients with asthma fail to respond to oral glucocorticoids even at high doses. This Article will review the role that steroids and membrane receptor ligation play in the induction of eosinophil apoptosis together with the mechanisms by which corticosteroids enhance the disposal of apoptotic eosinophils by both professional and non-professional phagocytes. Eosinophils are thought to be the major pro-inflammatory effector cell in asthma and their persistence in the airways is probably enhanced by the presence of several asthma-relevant cytokines that prolong eosinophil survival by inhibition of apoptosis (interleukin (IL)-3, IL-5, granulocyte-macrophage colony-stimulating factor, IL-9, IL-13, IL-15). In contrast, a number of signals have been described that accelerate apoptosis in human eosinophils including corticosteroids or ligation of membrane receptors (CD95, CD45, CD69). Thus, the load of lung eosinophils in asthmatic disease is likely to be related to a balance in the tIssue microenvironment between pro- and anti-apoptotic signals. Furthermore, removal of apoptotic eosinophils by phagocytosis by alveolar macrophages or bronchial epithelial cells in a specific receptor-mediated way is as important as the process of apoptosis induction. Corticosteroids enhance the recognition and engulfment of apoptotic eosinophils by macrophages or bronchial epithelial cells. Caspases are key intracellular molecules in the control of apoptosis and defects in caspase-induced apoptosis in eosinophils from steroid-resistant individuals may contribute to the molecular mechanisms underlying glucocorticoid insensitivity in these cells. These findings point the way to new and more targeted anti-inflammatory therapy for asthma and may provide important clues for the development of alternative therapies for glucocorticoid resistance.

Apoptosis↗

Discoidin domain receptor 1 contributes to the survival of lung fibroblast in idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF), characterized by fibroblast proliferation and accumulation of extracellular matrix, including collagen, is a chronic progressive disorder that results in lung remodeling and fibrosis. However, the cellular mechanisms that may make fibroblasts resistant to apoptosis have not been completely elucidated. Discoidin domain receptor 1 (DDR1), a receptor tyrosine kinase whose ligand is collagen, is expressed in vivo and contributes in vitro to leukocyte differentiation and nuclear factor (NF)-kappaB activation, which may play an important role in fibroblast survival. In this study, we examined in vivo and in vitro DDR1 expression and its role in cell survival using fibroblasts obtained from IPF and non-IPF patients. Immunohistochemically, fibroblasts present in fibroblastic foci expressed endogenous DDR1. The DDR1 expression level was significantly higher in fibroblasts from IPF patients, and the predominant isoform was DDR1b. In IPF patients, DDR1 activation in fibroblasts inhibited Fas ligand-induced apoptosis and resulted in NF-kappaB nuclear translocation. Suppression of DDR1 expression in fibroblasts by siRNA abolished these effects, and an NF-kappaB inhibitor abrogated the anti-apoptotic effect of DDR1 activation. We propose that DDR1 contributes to fibroblast survival in the tissue microenvironment of IPF and that DDR1 up-regulation may occur in other fibroproliferative lung diseases as well.

Actins↗

Basement membranes and pulmonary development.

Basement membranes (BM) are specialized extracellular matrices (ECM) which serve as complex interfaces between epithelia, peripheral nerves, or muscle cells and their surrounding tissue microenvironments. Their composition is known to include type IV collagen, laminin, entactin, heparan sulfate proteoglycan (HSPG, perlecan), and chondroitin sulfate proteoglycan (CSPG). By immunohistochemistry, collagen IV, laminin, and entactin are detectable from day 14 of gestation on, and become progressively more prominent with time. Perleaan has not been examined in prentatal lungs, but is widely distributed and abundant in all lung MBs from birth throughout development. CSPG has a somewhat discontinuous and lightly reactive appearance in alveolar BMs at birth but the staining becomes continuous and darker in the adult. This contrasts with glycosaminoglycan, chondroitin sulfate, which is prominently expressed in prenatal and early postnatal stages, but progressively diminishes with advancing development. As an interface between cell populations and surrounding ECMs, BMs act as a physical barrier to some cells and molecules, while serving as attachment points and binding sites for others. Basic fibroblast growth factor is an example of the latter, because it localizes with all BM components by immunostaining throughout development and reflects the multifactorial array of potential effectors in the complex processes of proliferation and differentiation.

Animals↗

Autoreactive T cell hybridoma-derived B cell stimulatory factor(s) governing IgA isotype immunoglobulin production by murine Peyer's patch B cells.

In the present study we investigated whether autoreactive T cells derived from murine Peyer's patches (PP) have the capacity to regulate mucosal B cell differentiation to IgA-producing plasma cells in vitro. We also examined whether B cell development is mediated by lymphokines from immunoregulatory T cells - that is, B cell stimulatory factors (BSF) and cofactors (coBSF) - which include B cell growth factor (BCGF), putative alpha B cell immunoglobulin (Ig) heavy chain switch factor (BSWF alpha), and B cell differentiation factor (BCDF), as well as interleukin-2 (IL-2). To this purpose we developed in vitro a variety of BSF (especially putative BSWF alpha)-producing autoreactive (self-class II molecules responsive) T cell hybridoma cell clones from murine PP, and studied the functional activity of the BSF, especially a putative alpha Ig heavy chain switch (mu----alpha) factors(s). These T hybridome cell lines possessed the surface phenotypes of Thy 1.2, CD4+, CD5+ and CD8- and produced a variety of BSF, including two kinds of BCGF (IL-5, and a BCGF that did not require additional costimulators to induce proliferation of preactivated B cells), putative BSWF alpha/gamma, BCDF, and/or IL-2. The results strongly support the view that the autologous T cell plays an important role not only in B cell proliferation and terminal maturation, but also in alpha heavy chain switching in PP. This T-B cell interation is mediated at least in part through BSF lymphokines elaborated by the autoreactive T cell, probably activated in situ in the lymphoid tissue microenvironment.

Animals↗

The role of cellular and extracellular matrix adhesion proteins in organ transplantation.

The specific adhesion of cells to other cells or to particular tissue microenvironments is a basic function of cell migration and recognition, and underlines many biologic processes including embryogenesis, repair and immunity. Leukocytes express an array of surface receptors broadly known as "accessory adhesion molecules." which mediate most cell-cell interactions, direct lymphocyte traffic between anatomical compartments, and facilitate cellular adhesion to the inflammation or alloantigenic sites (Springer 1990). In addition, adhesion molecules are involved in the process of antigen recognition, and may costimulate cell activation and transformation. These proteins are thought to affect the very early antigen independent events between host leukocytes and vascular endothelium. Because of these activities, the subject of adhesion molecules is gaining interest in the field of organ transplantation, in both conceptualization and development of novel therapeutic strategies (de Sousa et al. 1991, Kupiec-Weglinski et al. 1993a, Heemann et al. 1993).

Animals↗

The effect of interleukin-17 on hematopoietic cells and cytokine release in mouse spleen.

To evaluate whether the response of hematopoietic cells to interleukin-17 (IL-17) depends on the tissue microenvironment in which hematopoiesis occurs, the influence of recombinant mouse IL-17 on spleen hematopoietic cells and cytokine release was assessed in normal mice in vitro and in vivo. In vitro, IL-17 did not significantly affect the growth of granulocyte-macrophage (CFU-GM) and erythroid (BFU-E and CFU-E) derived colonies. A single injection of IL-17 in vivo exhibited stimulatory effects on hematopoietic cells from both granulocytic and erythroid lineages. The increased number of metamyelocytes 48 h after treatment imply to the IL-17-induced stimulation of granulopoiesis. The number of BFU-E was increased at 24 h, while the number of CFU-E increased 6 h and 24 h after treatment. Since the same treatment in the bone marrow decreased the number of CFU-E, it may be concluded that the local microenvironment plays an important role in IL-17-mediated effects on CFU-E. IL-17 increased the release of IL-6 both in vitro and in vivo, but showed tendency to suppress the constitutive secretion of IL-10 by spleen cells. Our results suggest the complexity of target cell response and interplay of secondary induced cytokines by IL-17 in different hematopoietic organs.

Animals↗

Mechanisms of and mitigating strategies for cellular immune responses to CRISPR-associated nucleases in genome editing therapy.

Immunogenicity of CRISPR-associated nucleases (Cas) is a critical barrier to the development of safe and effective genome editing therapies. These proteins inherently pose a risk of immune recognition due to their prokaryotic origins. A multitude of factors, such as the delivery vehicle, the route of administration, components of the therapeutics, tissue microenvironment, and pre-existing immunity, also contribute to the complexity of the host immune response to Cas proteins. As CRISPR-based therapies advance into clinical settings, it is imperative to elucidate and address the immunogenicity of Cas proteins. Here, using Cas9 as an example, we review the current understanding of Cas protein immunogenicity, the challenges it poses for therapeutic application, and strategies to mitigate cellular immune responses to Cas proteins.

AAV↗

Frequent alterations of Smad signaling in human head and neck squamous cell carcinomas: a tissue microarray analysis.

Head and neck squamous cell carcinoma (HNSCC) ranks as the sixth most frequent cancer worldwide. HNSCC cell lines are typically refractory to transforming growth factor-beta (TGF-beta)-mediated cell cycle arrest. A number of these cell lines carry inactivating mutations of the TGF-beta type II (TbetaR-II) receptor, and fail to phosphorylate receptor-associated Smads, Smad2 and Smad3. In addition, we identified several intragenic mutations of the TbetaR-I gene in a small series of metastatic HNSCC specimens, suggesting that disruptions of TGF-beta signaling might contribute to the development and progression of HNSCC. To test this idea, we have now embarked on a larger scale analysis of the patterns of expression and activation of Smads in 170 HNSCC specimens assembled in tissue microarrays. Smad2 protein was expressed by 99% (95% CI: 96-100%) of tumors. The activated form of Smad2, pSmad2, was expressed in 86% (95% CI: 80-91%) of HNSCC, indicating their ability to survive and proliferate in spite of the presence of bioactive TGF-beta within the tissue microenvironment. In the 24 remaining cases (14%; 95% CI: 9-20%), pSmad2 was not detected in the tumor cells, although it was expressed by surrounding stromal cells and capillaries. In addition, 38 tumors (22%; 95% CI: 16-29%) failed to express Smad4 protein. Thus, we found evidence of loss of TGF-beta/Smad signaling in approximately 15-20% of HNSCC specimens, which is consistent with the phenotype of established human SCC lines. Moreover, we found that these Smad signaling defects were associated with a greater tendency for metastatic spread and regional or distant recurrence of HNSCC. These results indicate that inactivation of TGF-beta/Smad signaling occurs frequently in HNSCC and might have an adverse effect on patient outcome.

Blotting, Western↗

Bisphosphonates as cancer drugs.

Bone appears to act like fertilizer for many tumors, including myeloma and metastatic breast cancer. The explanation must lie in interactions between tumor cells and the bone-tissue microenvironment. At this level, too, must lie the explanation of how bisphosphonates address not only cancer osteolysis but also the tumor burden. By inhibiting osteoclasts, the drugs may block a cancer-related vicious cycle.

Antineoplastic Agents↗

Activation of discoidin domain receptor 1 facilitates the maturation of human monocyte-derived dendritic cells through the TNF receptor associated factor 6/TGF-beta-activated protein kinase 1 binding protein 1 beta/p38 alpha mitogen-activated protein kinase signaling cascade.

Maturation of dendritic cells (DCs) is critical for their ability to stimulate resting naive T cells in primary immune responses. Previous studies demonstrated that collagen, such as type I collagen, could facilitate DC maturation; however, the basis of collagen-mediated DC maturation remains unclear. Discoidin domain receptor 1 (DDR1) is a nonintegrin collagen receptor constitutively expressed in a variety of epithelial cells, including tumor cells, and is inducible in leukocytes. In this study, we evaluated the role of DDR1 in DC maturation using human monocyte-derived DCs. Two DDR1 isoforms, DDR1a and DDR1b, were expressed in both immature and mature DCs. Activation of DDR1 on immature DCs resulted in their partial maturation; however, DDR1 activation markedly amplified TNF-alpha- and LPS-induced phenotypic and functional maturation of DCs through activation of p38 mitogen-activated protein kinase (MAPK), suggesting the involvement of DDR1b in this process. Activation of DDR1b on differentiated DDR1b-overexpressing THP-1 cells or DDR1 on mature DCs induced the formation of TNFR associated factor 6 (TRAF6)/TGF-beta-activated kinase 1 binding protein 1beta/p38alpha MAPK complex and p38alpha autophosphorylation. Transfection of differentiated DDR1b-overexpressing THP-1 cells with dominant negative TRAF6 completely abrogated DDR1b-mediated p38 MAPK phosphorylation, indicating a critical role of TRAF6 in DDR1b-mediated p38 MAPK activation. Taken together, our data suggest that DDR1b-collagen interaction augments the maturation of DCs in a tissue microenvironment through a unique TRAF6/TGF-beta-activated kinase 1 binding protein 1beta/p38alpha MAPK signaling cascade and contributes to the development of adaptive immune responses.

Adaptor Proteins, Signal Transducing↗

Activation of discoidin domain receptor 1 on CD14-positive bronchoalveolar lavage fluid cells induces chemokine production in idiopathic pulmonary fibrosis.

Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase activated by collagen. We previously reported the functional expression of DDR1 on human monocyte-derived macrophages in vitro; however, information regarding its role in diseases is limited. Idiopathic pulmonary fibrosis (IPF) is a chronic lung disease, and the lesions contain an abundance of collagen. In this study, we examined DDR1 expression on bronchoalveolar lavage fluid (BALF) cells and investigated its functionality using samples obtained from 28 IPF patients, 13 chronic obstructive pulmonary disease patients, and 14 healthy volunteers. The DDR1 expression level in CD14-positive BALF cells was higher in IPF patients than in chronic obstructive pulmonary disease patients or healthy volunteers. The predominant isoform was DDR1b in the IPF group, while DDR1a was predominant in the other two groups. Using immunohistochemical analysis, we also detected DDR1 expression on infiltrating inflammatory cells in the IPF lesion. In IPF patients, DDR1 activation induced the production of MCP-1, IL-8, MIP-1 alpha, and matrix metalloproteinase-9 (MMP-9) from CD14-positive BALF cells in a p38 MAPK-dependent manner. In contrast, DDR1 activation of CD14-positive BALF cells in the other groups did not induce the production of these chemokines or MMP-9. These chemokines and MMP-9 contribute to the development of IPF and, therefore, we suggest that DDR1 might be associated with the pathogenesis of IPF in the tissue microenvironment.

Adaptor Proteins, Signal Transducing↗

Potentiation of glucocorticoid activity in hypoxia through induction of the glucocorticoid receptor.

Tissue hypoxia is intimately associated with chronic inflammatory disease and may signal to the resolution of inflammatory processes. Glucocorticoid signaling through the glucocorticoid receptor (GR) represents a clinically important endogenous anti-inflammatory pathway. Microarray analysis reveals that the GR is transcriptionally up-regulated by hypoxia in human renal proximal tubular epithelial cells. Hypoxic up-regulation of the GR was confirmed at the level of promoter activity, mRNA, and protein expression. Furthermore, functional potentiation of glucocorticoid activity in hypoxia was observed as an enhancement of dexamethasone-induced glucocorticoid response element promoter activity and enhanced dexamethasone-mediated inhibition of IL-1beta-stimulated IL-8 expression and hypoxia-induced vascular endothelial growth factor expression. Knockdown of enhanced GR gene expression in hypoxia using specific GR small inhibitory RNA (siRNA) resulted in an attenuation of the enhanced glucocorticoid sensitivity. A role for the hypoxia-inducible transcription factor, HIF-1alpha, in the regulation of GR expression and the associated potentiation of glucocorticoid activity in hypoxia was also demonstrated. These results reveal a novel signaling aspect responsible for the incorporation of hypoxic and glucocorticoid stimuli, which we hypothesize to be an important co-operative pathway for the control of gene expression observed in complex tissue microenvironments in inflamed states.

Cell Hypoxia↗

Glucose availability regulates IFN-gamma production and p70S6 kinase activation in CD8+ effector T cells.

Differentiation of CD8+ T cells from the naive to the effector state is accompanied by changes in basal gene expression profiles that parallel the acquisition of effector functions. Among these are metabolism genes, and we now show that 2C TCR transgenic effector CD8+ T cells express higher levels of glycolytic enzymes and display greater glucose uptake, a higher glycolytic rate, and increased lactate production compared with naive cells. To determine whether glucose was required for effector T cell functions, we regulated glucose availability in vitro. Glucose deprivation strongly inhibited IFN-gamma gene expression, whereas IL-2 production was little affected. Inhibition correlated with diminished phosphorylation of p70S6 kinase and eIF4E binding protein 1 and a requirement for de novo protein synthesis, whereas other signaling pathways known to regulate IFN-gamma expression were unaffected. Together, our data reveal that optimal induction of IFN-gamma transcription is a glucose-dependent process, indicate that there are undefined factors that influence IFN-gamma expression, and have implications for regulation of the effector phase of CD8+ T cell responses in tissue microenvironments.

Adaptor Proteins, Signal Transducing↗

Intestinal fibroblast-derived IL-10 increases survival of mucosal T cells by inhibiting growth factor deprivation- and Fas-mediated apoptosis.

Mucosal T cells are essential to immune tolerance in the intestine, an organ constantly exposed to large amounts of dietary and bacterial Ags. We investigated whether local fibroblasts affect mucosal T cell survival, which is critical for maintenance of immune tolerance. Coculture with autologous fibroblasts significantly increased viability of mucosal T cells by inhibiting IL-2 deprivation- and Fas-mediated apoptosis, an effect that was both contact- and secreted product-dependent. Investigation of anti-apoptotic factors in the fibroblast-conditioned medium (FCM) revealed the presence of IL-10 and PGE2, but not IFN-beta, IL-2, or IL-15. Although recombinant IFN-beta, but not PGE2, effectively prevented T cell apoptosis, neutralizing Ab studies showed that only IL-10 blockade significantly increased T cells apoptosis, whereas neutralizing IFN-beta or IFN-alpha failed to inhibit the anti-apoptotic effect of FCM. To confirm that fibroblast-derived IL-10 was responsible for preserving mucosal T cell viability, IL-10 mRNA was demonstrated in fibroblasts by Southern blotting and RT-PCR. When FCM was submitted to HPLC fractionation, only the peak matching rIL-10 contained the anti-apoptotic activity, and this was eliminated by treatment with an IL-10-neutralizing Ab. Finally, when fibroblasts were transiently transfected with IL-10 antisense oligonucleotides, the conditioned medium lost its T cell anti-apoptotic effect, whereas medium from fibroblasts transfected with IFN-beta antisense oligonucleotides displayed the same anti-apoptotic activity of medium from untransfected fibroblasts. These results indicate that local fibroblast-derived IL-10 is critically involved in the survival of mucosal T cells, underscoring the crucial importance of studying organ-specific cells and products to define the mechanisms of immune homeostasis in specialized tissue microenvironments like the intestinal mucosa.

Apoptosis↗

Addressing the role of cell adhesion in tumor cell dormancy.

The dissemination of tumor cells prior to the surgical resection of early stage tumors poses a serious risk to the disease free survival of cancer patients. This risk arises from the latent capacity of these cells to form solid metastatic lesions after a prolonged period of dormancy, exacerbated by the fact that these cells are often refractory to adjuvant chemotherapeutic protocols. Ensuring the long term survival of cancer patients therefore necessitates an understanding of the mechanisms of tumor cell dormancy and the accompanying drug resistance. Experiments designed to compare the biological behavior of metastatic versus nonmetastatic variants of tumor cells provide evidence that there exists a phenomenon of single-cell dormancy which may depend on a reciprocal dialogue between the tumor cell and the tissue microenvironment. Through a combination of 3-dimensional cell culture technique and in vivo models investigators are now beginning to elucidate the molecular mechanisms underlying this phenomenon. Here we review the results of a series of experiments describing the role of cell adhesion events in dictating tumor cell behavior, including the balance between proliferation and dormancy, and the acquisition of drug resistance.

Animals↗

Cytokines (IFNs, TNF-alpha, IL-2 and IL-12) and animal models of cancer.

Cytokines are a complex family of mediators that influence many aspects of tumour cell biology. Whether they are used as a therapy or produced locally during the process of tumorigenesis, they are able to act on tumour cells, on the tumour stroma and on the host itself. Animal models have played key roles in optimizing doses and schedules, and have been useful in determining net effects in the tissue microenvironment. Whilst early studies used xenogeneic and syngeneic systems, more recently gene and protein delivery systems have been used to introduce ectopically expressed high and continuous levels of cytokines. This review will discuss the application of some animal model systems that have been investigated to further understand the role cytokines play in cancer, and will concentrate on those cytokines for which there are the most experimental animal model data.

Animals↗

Differential regulation of allergen-specific antibodies in allergy and specific immunotherapy.

Allergen-specific immunotherapy (SIT) aims to specifically skew an allergic response into a normal immune reaction against an allergen. The response to bee venom (BV) provides an especially suited model to study the immunological mechanisms of SIT in human. The BV-phospholipase A2 (PLA) represents the major antigen/allergen of BV. In SIT of BV allergy both whole BV and T cell epitope peptides of PLA were successfully applied. It appeared that the induction of specific anergy in peripheral T cells and reactivation of the T cells by microenvironmental cytokines represent the basic key steps in the immunological mechanism of SIT. The proliferative and cytokine responses by specific T cells were significantly suppressed simultaneously with an increase in IL-10 after 7 days. The anergic state was fully established after 4 weeks. Neutralization of IL-10 in PBMC by a specific antibody reconstituted the original proliferative and cytokine responses. Intracytoplasmatic cytokine staining revealed that IL-10 was initially produced by activated allergen-specific T cells. IL-10-producing B cells and monocytes were involved at a later stage of SIT and in maintenance of the anergy. The addition of IL-10 to stimulated PBMC or purified B cells inhibited IgE synthesis and enhanced the IgG4 antibody formation. Thus, SIT generates IL-10, which in turn induces specific anergy by autokrine interaction in T cells and counter-regulates IgE and IgG4 production. Particular cytokines from the tissue microenvironment reactivate the T cells to produce distinct Th1 or Th2 cytokine patterns respectively and by this way direct SIT towards successful or unsuccessful treatment. High amounts of allergen administered in SIT preferentially generate Th1 cytokines in T cells and IgG4 antibodies in memory B cells. Further investigations demonstrated that suppression of T cells by IL-10 is an active process, which depends on the expression and participation of CD28.

Allergens↗