Sulfur mustard induces immune sensitization in hairless guinea pigs

Sulfur mustard (SM, bis-(2-chloroethyl) sulfide) is a well known chemical warfare agent that may cause long-term debilitating injury. Because of the ease of production and storage, it has a strong potential for chemical terrorism; however, the mechanism by which SM causes chronic tissue damage is essentially unknown. SM is a potent protein alkylating agent, and we tested the possibility that SM modifies cellular antigens, leading to an immunological response to "altered self" and a potential long-term injury. To that end, in this communication, we show that dermal exposure of euthymic hairless guinea pigs induced infiltration of both CD4(+) and CD8(+) T cells into the SM-exposed skin and strong upregulated expression of proinflammatory cytokines and chemokines (TNF-alpha, IFN-gamma, and IL-8) in distal tissues such as the lung and the lymph nodes. Moreover, we present evidence for the first time that SM induces a specific delayed-type hypersensitivity response that is associated with splenomegaly, lymphadenopathy, and proliferation of cells in these tissues. These results clearly suggest that dermal exposure to SM leads to immune activation, infiltration of T cells into the SM-exposed skin, delayed-type hypersensitivity response, and molecular imprints of inflammation in tissues distal from the site of SM exposure. These immunological responses may contribute to the long-term sequelae of SM toxicity.

ALK-5 mediates endogenous and TGF-beta1-induced expression of connective tissue growth factor in embryonic lung

Transforming growth factor-beta1 (TGF-beta1) has been implicated as a major negative regulator of lung branching morphogenesis. Since connective tissue growth factor (CTGF) is a downstream mediator of TGF-beta1 effects on mesenchymal cells, we hypothesized that TGF-beta1 induces CTGF expression in mouse embryonic lung explants and that CTGF mediates TGF-beta1 inhibition of branching morphogenesis. We show that addition of TGF-beta1 to the serum-free medium of embryonic day (E)12.5 lung explant cultures inhibited branching morphogenesis and induced CTGF mRNA expression in time- and dose-dependent manners. In contrast to basal endogenous CTGF protein, which was exclusively localized in the distal airway epithelium, TGF-beta1-induced CTGF protein was localized in both the epithelium and the mesenchyme. Addition of exogenous CTGF to culture medium directly inhibited branching morphogenesis. To identify the signal transduction pathway through which TGF-beta1 induces CTGF, we used SB431542, a specific inhibitor for TGF-beta type I receptor (TbetaRI)/ALK-5 to block TGF-beta1-induced Smad2/3 phosphorylation. Consequently, SB431542 stimulated normal branching morphogenesis and blocked TGF-beta1 inhibition of branching. Furthermore, SB-431542 blocked both endogenous and TGF-beta1-induced expression of CTGF mRNA and protein. These results demonstrate for the first time that TGF-beta1 induces CTGF expression in mouse embryonic lung explants, that CTGF inhibits branching morphogenesis, and that both endogenous and TGF-beta1-induced CTGF expression are mediated by the TbetaRI/ALK-5-dependent Smad2 signaling pathway.

Coincidence of connective tissue growth factor expression with fibrosis and angiogenesis in postoperative peritoneal adhesion formation

PURPOSE

To investigate the relationship between connective tissue growth factor (CTGF) and fibrosis and angiogenesis in postoperative peritoneal adhesion formation.

METHODS

Adhesions were performed in 35 rats by creation of a peritoneal patch. Animals were sacrificed at 7 different time-points over 3 weeks. Adhesions and uninjured peritoneum from all animals were assessed by Northern blotting for CTGF and collagen-I mRNA and by immunohistochemistry for CTGF localization, degree of fibrosis and angiogenesis.

RESULTS

Persistent adhesions formed in all animals. CTGF and collagen-I mRNA were increased in adhesions compared to uninjured peritoneum (p < 0.05 for both). The temporal expression pattern depicted delayed peak levels of collagen-I mRNA with increasing tendency for both transcripts at the end of the observation period. Fibrosis within adhesions correlated positively with time after surgery (r = 0.85; p < 0.001) and showed typical signs of chronic tissue fibrosis at later time points. Angiogenesis was detected in adhesions but not in uninjured peritoneum (p = 0.001) and coincided with the spatial and temporal expression of CTGF protein in fibroblasts and vascular endothelial cells.

CONCLUSIONS

The co-expression of CTGF with increasing fibrosis and angiogenesis in postoperative peritoneal adhesions suggests a role for CTGF as critical molecule in fibrous adhesive disease and target for future adhesion prevention.

Microarray analysis of in vitro pericyte differentiation reveals an angiogenic program of gene expression

The vasculature consists of endothelial cells (ECs) lined by pericyte/vascular smooth muscle cells (vSMCs). Pericyte/vSMCs provide support to the mature vasculature but are also essential for normal blood vessel development. To determine how pericyte-EC communication influences vascular development, we used the well-established in vitro model of TGFbeta-stimulated differentiation of 10T1/2 cells into pericyte/vSMCs. Microarray analysis was performed to identify genes that were differentially expressed by induced vs. uninduced 10T1/2 cells. We discovered that these cells show an angiogenic program of gene expression, with up-regulation of several genes previously implicated in angiogenesis, including VEGF, IL-6, VEGF-C, HB-EGF, CTGF, tenascin C, integrin alpha5, and Eph receptor A2. Up-regulation of some genes was validated by Western blots and immunocytochemistry. We also examined the functional significance of these gene expression changes. VEGF and IL-6 alone and in combination were important in 10T1/2 cell differentiation. Furthermore, we used a coculture system of 10T1/2 and human umbilical vein ECs (HUVECs), resulting in the formation of cordlike structures by the HUVECs. This cordlike structure formation was disrupted when neutralizing antibodies to VEGF or IL-6 were added to the coculture system. The results of these studies show that factors produced by pericytes may be responsible for recruiting ECs and promoting angiogenesis. Therefore, a further understanding of the genes involved in pericyte differentiation could provide a novel approach for developing anti-angiogenic therapies.

Release of biologically active TGF-beta1 by alveolar epithelial cells results in pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive fatal fibrotic lung disease. Transforming growth factor (TGF)-beta1 is present in a biologically active conformation in the epithelial cells lining lesions with advanced IPF. To determine the role of aberrant expression of biologically active TGF-beta1 by alveolar epithelial cells (AECs), the AECs of explanted normal rat lungs were transfected with the TGF-beta1 gene using the retrovirus pMX-L-s223,225-TGF-beta1. In situ hybridization using a digoxigenin-labeled cDNA of the puromycin resistance gene contained in the pMX demonstrated that pMX-L-s233,225-TGF-beta1 was selectively transfected into AECs of the explants. Conditioned media overlying explants obtained 7 days after being treated with pMX-L-s223,225-TGF-beta1 contained 14.5 +/- 3.15 pg/ml of active TGF-beta1. With the use of Masson's trichrome staining of explant sections obtained 14 days after transfection, there were lesions similar to those in IPF, characterized by type II AEC hyperplasia, interstitial thickening, extensive increase in interstitial and subepithelial collagen, an increase in the number of fibroblasts, and areas resembling fibroblast buds. Collagens I, III, IV, and V and fibronectin were increased in explants treated with pMX-L-s223,225-TGF-beta1. The findings in the current study suggest that IPF may be a disorder of epithelial cells and not inflammatory cells.

GM-CSF increases airway smooth muscle cell connective tissue expression by inducing TGF-beta receptors

Fibrosis around the smooth muscle of asthmatic airway walls leads to irreversible airway obstruction. Bronchial epithelial cells release granulocyte/macrophage colony-stimulating factor (GM-CSF) in asthmatics and are in close proximity to airway smooth muscle cells (ASMC). The findings in this study demonstrate that GM-CSF induces confluent, prolonged, serum-deprived cultures of ASMC to increase expression of collagen I and fibronectin. GM-CSF also induced ASMC to increase the expression of transforming growth factor (TGF)-beta receptors type I, II, and III (TbetaR-I, TbetaR-II, TbetaR-III), but had no detectable effect on the release of TGF-beta1 by the same ASMC. The presence of GM-CSF also induced the association of TGF-beta1 with TbetaR-III, which enhances binding of TGF-beta1 to TbetaR-II. The induction of TbetaRs was parallel to the increased induction of phosphorylated Smad2 (pSmad2) and connective tissue growth factor (CTGF), indicative of TGF-beta-mediated connective tissue synthesis. Dexamethasone decreased GM-CSF-induced TbetaR-I, TbetaR-II, TbetaR-III, pSmad2, CTGF, collagen I, and fibronectin. In conclusion, GM-CSF increases the responsiveness of ASMC to TGF-beta1-mediated connective tissue expression by induction of TbetaRs, which is inhibited by corticosteroids.

Selective stimulation of collagen synthesis in the presence of costimulatory insulin signaling by connective tissue growth factor in scleroderma fibroblasts

OBJECTIVE

To examine the mechanism of collagen induction by connective tissue growth factor (CTGF), a profibrotic cytokine overexpressed in the skin of patients with systemic sclerosis (SSc).

METHODS

Dermal fibroblasts from 7 SSc patients and 7 matched healthy adult donors were stimulated with CTGF in the presence or absence of the culture-medium supplement, insulin-transferrin-selenium (ITS). Expression of collagen protein was analyzed by a (3)H-proline incorporation assay. To identify the signaling pathways mediating CTGF induction of collagen, pharmacologic inhibitors were used, including rottlerin, a protein kinase C delta (PKC delta) inhibitor.

RESULTS

Collagen levels in both SSc and normal fibroblasts were increased after treatment with transforming growth factor beta in serum-free medium, whereas no stimulation was observed following addition of CTGF. In the presence of ITS, CTGF (2.5 ng/ml) potently stimulated collagenous protein levels in SSc cell lines (n = 5); however, CTGF was not stimulatory in the majority of normal fibroblasts (n = 6). ITS alone induced collagen levels in normal fibroblasts to the levels observed in SSc skin fibroblasts, thereby diminishing the hallmark difference in basal collagen levels in these cell types. Insulin was the ITS component responsible for promoting the basal and CTGF stimulation of collagenous proteins. Rottlerin, the PKC delta inhibitor, down-regulated collagen synthesis in normal and SSc fibroblasts cultured in ITS, and inhibited the stimulatory effects of CTGF in cooperation with insulin or of insulin (500 ng/ml) alone.

CONCLUSION

Increased responsiveness of SSc fibroblasts to CTGF-mediated collagen synthesis requires the costimulatory activation of insulin signaling pathways to induce matrix production. Blockade of this effect via rottlerin may suggest that PKC delta is a downstream signaling molecule necessary for CTGF stimulation of collagen synthesis.

Connective tissue growth factor in pterygium: simultaneous presence with vascular endothelial growth factor - possible contributing factor to conjunctival scarring

BACKGROUND

Various growth factors have been detected in pterygium and been associated with its vasculogenesis. The basic pathophysiological mechanisms responsible especially for the fibrotic activity in pterygium are, however, not yet known. Connective tissue growth factor (CTGF) has been shown to be substantially involved in various processes of fibrosis. We report on the presence of CTGF in pterygium and its simultaneous presence with vascular endothelial growth factor (VEGF).

METHODS

Samples of pterygium were collected during surgery with informed consent of the patients. Specific, non-commercial primary antibodies against CTGF were used to detect CTGF using immunohistochemistry. Specificity of antibodies was confirmed with Western-blot analysis. The same specimens were stained with commercial antibodies for VEGF. Additionally RT-PCR analysis was performed from pterygium samples.

RESULTS

CTGF was detected in the epithelium of all samples as well as in some stromal keratocytes. The RT-PCR confirmed the identity of CTGF in these samples. The staining pattern differed slightly from that of VEGF, which was detected in all samples. The control sections were negative.

CONCLUSION

CTGF is present in the epithelium of a majority of pterygia and probably contributes to fibrosis. Simultaneous presence with VEGF suggests growth factor interaction and possible involvement in apoptotic dysregulation.

Detection of connective tissue growth factor (CTGF) in human tear fluid: preliminary results

PURPOSE

Connective tissue growth factor (CTGF) is one of the main regulators of fibrosis. We aimed to evaluate its presence in the human tear fluid of healthy individuals.

METHODS

A total of 70 tear fluid samples were collected from eight volunteers prior to and after stimulation of reflex tears with onion vapour. Specific ELISA analysis was performed with goat IgG against human CTGF.

RESULTS

Connective tissue growth factor was detected in seven samples (10%), with maximum levels of 17 ng/mL in basal tears. Induction of reflex tearing resulted in a fast and significant decrease of CTGF concentrations (r = - 0.95). No CTGF was detected in 90% of the samples.

CONCLUSION

Connective tissue growth factor may occur in tear fluid in healthy human eyes. This indicates a possible role for tear fluid CTGF in ocular surface fibrosis and wound healing.

TGF-beta and CTGF have overlapping and distinct fibrogenic effects on human renal cells

Transforming growth factor-beta (TGF-beta) and connective tissue growth factor (CTGF) are ubiquitously expressed in various forms of tissue fibrosis, including fibrotic diseases of the kidney. To clarify the common and divergent roles of these growth factors in the cells responsible for pathological extracellular matrix (ECM) deposition in renal fibrosis, the effects of TGF-beta and CTGF on ECM expression in primary human mesangial (HMCs) and human proximal tubule epithelial cells (HTECs) were studied. Both TGF-beta and CTGF significantly induced collagen protein expression with similar potency in HMCs. Additionally, alpha(2)(I)-collagen promoter activity and mRNA levels were similarly induced by TGF-beta and CTGF in HMCs. However, only TGF-beta stimulated collagenous protein synthesis in HTECs. HTEC expression of tenascin-C (TN-C) was increased by TGF-beta and CTGF, although TGF-beta was the more potent inducer. Thus both growth factors elicit similar profibrogenic effects on ECM production in HMCs, while promoting divergent effects in HTECs. CTGF induction of TN-C, a marker of epithelial-mesenchymal transdifferentiation (EMT), with no significant induction of collagenous protein synthesis in HTECs, may suggest a more predominant role for CTGF in EMT rather than induction of excessive collagen deposition by HTECs during renal fibrosis.

Detection of connective tissue growth factor in human aqueous humor

PURPOSE

Connective tissue growth factor (CTGF) has been shown to be substantially involved in various processes of fibrosis. We investigated if CTGF is present in aqueous humor (AH).

METHODS

Samples from AH were collected from 10 volunteers during cataract surgery. Specific ELISA analysis was performed with goat IGG against human CTGF.

RESULTS

CTGF was above the detection limit of the assay in 80% of the samples. The concentration of CTGF in the anterior chamber fluid was 1.24 +/- (SD) 0.26 ng/ml.

CONCLUSION

CTGF is present in a majority of AH samples, possibly representing a constant component in this fluid. The origin and physiological importance of CTGF is yet unclear. The involvement of CTGF in processes of intraocular fibrosis and wound healing is possible.

Transforming growth factor-beta-stimulated connective tissue growth factor expression during corneal myofibroblast differentiation

PURPOSE

Transforming growth factor beta1 (TGF-beta) stimulates the differentiation of myofibroblasts as indicated by the nascent expression of alpha-smooth muscle (alpha-SM) actin protein and its organization into stress fibers. Downstream messengers of TGF-beta in the conversion from the fibroblast to the myofibroblast phenotype were investigated. Whether TGF-beta increases the transcription of a second growth factor, connective tissue growth factor 1 (CTGF), which could mediate myofibroblast differentiation, was evaluated. CTGF, a newly identified growth factor, is highly expressed in dermal granulation tissue.

METHODS

In this study, primary cultures of rabbit corneal fibroblasts were exposed to growth factors to investigate CTGF mRNA and protein expression during myofibroblast differentiation. Statistical analysis was used to evaluate the impact of growth factor treatment on myofibroblast differentiation.

RESULTS

. TGF-beta treatment induced both CTGF mRNA and protein in rabbit corneal fibroblasts; in contrast, fibroblast growth factor-2 (FGF) and heparin led to a decrease in CTGF mRNA. Addition of recombinant CTGF to rabbit corneal fibroblast cultures did not significantly increase alpha-SM actin mRNA or protein nor did it appear to affect assembly of alpha-SM actin stress fibers.

CONCLUSIONS

This is the first study to present evidence for the induction of CTGF by TGF-beta treatment of corneal fibroblasts. It is doubtful that CTGF is the TGF-beta mediator of the corneal fibroblast to myofibroblast transition because CTGF does not induce alpha-SM actin in subconfluent fibroblast cultures. CTGF may play a supporting role in myofibroblast differentiation.

Retinal pigment epithelial cells produce PDGF-like proteins and secrete them into their media

Human retinal pigment epithelial cells at confluence were used to condition serum-free Dulbecco's modified Eagle's medium. Conditioned media were exhaustively dialyzed against 0.5 N acetic acid, lyophilized, and subjected to Western blot analysis, using as primary antibody an IgG fraction prepared from goat antiserum directed against human platelet-derived growth factor. Native platelet-derived growth factor was resolved as a band with Mr of 30 kDa under non-reducing conditions, while bands with Mr of 36-38 kDa and 18.5 kDa were resolved from retinal pigment epithelial cell-conditioned media. Acid extracts of retinal pigment epithelial cells also contained bands at 36-38 kDa and media conditioned for 48 hr exhibited much denser bands than media conditioned for 24 hr. No bands were detected when non-immune goat IgG fractions were substituted for primary antibody and when conditioned media were prepared from several human fibroblast lines in the same manner as those prepared from retinal pigment epithelial cells, no detectable bands or only a faint shadow at 36 kDa were seen. Retinal pigment epithelial cell-conditioned media prepared in the presence of [35S]methionine were loaded on an anti-platelet-derived growth factor IgG affinity column, eluted, and subjected to SDS-polyacrylamide gel electrophoresis. Bands with Mr slightly less than 36 kDa and 18 kDa were visualized by autoradiography, demonstrating that the platelet-derived growth factor-like proteins in retinal pigment epithelial cell-conditioned media are newly synthesized. Two fractions eluted from the column also markedly stimulated fibroblast chemotaxis and incorporation of [3H]thymidine, both of which were neutralized by soluble anti-platelet-derived growth factor IgG. These data suggest that retinal pigment epithelial cells in culture produce platelet-derived growth factor-like proteins and secrete them into their media where they are capable of stimulating fibroblast chemotaxis and proliferation.

Type V collagen in human amnion is a 12 nm fibrillar component of the pericellular interstitium

Immunoelectron microscopy was utilized to detect type V collagen in human amnion. Monospecific antibodies to type V collagen were detected with protein A-gold conjugates in tissue sections and epoxy-embedded sections of human amnion. Type V collagen was localized to the immediate vicinity of the basal lamina, but was distinct from laminin and type IV collagen, which localized only to the lamina lucida and lamina densa, respectively, of the basal lamina. At high magnification, 12 nm unbanded fibrils were seen to be labelled by anti-type V collagen antibody; these fibrils extended from the lamina densa of the basal lamina well into the interstitial matrix. In comparison, only the amorphous matrix of the lamina densa showed labelling with anti-type IV collagen antibodies. Anti-laminin antibodies labelled the lamina lucida. Quantitative analysis of grain distribution revealed the laminin labelling to be centered over the distal half of the lamina lucida (mean distance from the cell surface = 70 nm). In contrast, type IV collagen was centered over the lamina densa (mean = 115 nm). Both distributions were essentially Gaussian and distinct from the broad distribution of type V collagen. Type I collagen fibers with characteristic 67 nm periodicity were unlabelled with antibodies to type V collagen, although labelled type V fibrils were frequently enmeshed among the type I fibers. Antibodies to type I collagen labelled these fibers but not the type V fibrils. The results indicate that in human amnion, type V collagen is a 12 nm diameter, unbanded fibril which extends from the lamina densa of the basal lamina into the adjacent interstitial matrix. We hypothesize that type V collagen functions as a network of anchoring fibrils between the cell basal lamina and the extracellular matrix, especially type I collagen fibres. Type V collagen thus appears to be a unique interstitial collagen.

Can collagen metabolism be controlled?

The rate of repair of severely burned tissue may be limited by the availability of both non-damaged connective tissue cells and factors which control their movement and proliferation. Supplementation of wounds with chemotactic and growth factors contained in a matrix support may be useful in accelerating the healing of these wounds. Addition of dermal fibroblasts to this matrix may also be beneficial in preventing the formation of contracted scars. Future studies directed at identifying and isolating these factors and testing their efficiency in in vivo wound systems should prove useful in developing new approaches to severe wound care and for individuals who suffer from poor wound healing such as diabetics or aged people.

Localization of basement membrane components after dermal-epidermal junction separation

Adult human skin was separated at the dermal-epidermal junction (DEJ) by 4 published methods that involved different mechanisms of action: cold 1 M salt (tissue extraction), cold trypsinization (enzymatic), induction of a suction blister (mechanical), and warm phosphate-buffered saline (protease activation). The localization of DEJ macromolecules was studied after each separation method. By all of the methods tested, bullous pemphigoid antigen remained closely associated with the epidermis while laminin, the basement membrane heparan sulfate proteoglycan, and collagen types IV and V remained with the dermal side of the separation. The bullous pemphigoid antigen is, then, the DEJ component most closely associated with the epidermal basal cell. Of the basement membrane components tested, only the basement membrane heparan sulfate proteoglycan was trypsin-sensitive.

Platelet-derived growth factor in chemotactic for fibroblasts

Chemotaxis assays in modified Boyden chambers were used to detect fibroblast chemoattractants in materials released from early-stage inflammatory cells, namely, mast cells, platelets, and neutrophils. Strong attractant activity was found in substances released from platelets. This activity was accounted for mainly by the platelet-derived growth factor (PDGF), which is released from the platelets and which was active as a chemoattractant at 0.5-1.0 mitogenic units/ml. The mitogenic activity of purified PDGF, measured by [3H]thymidine incorporation, occurs at a similar concentration range. By varying the gradient of PDGF, we demonstrated that PDGF stimulates chemotaxis rather than random motility. Preincubation of suspensions of fibroblasts in the presence of PDGF decreased the subsequent migration of cells to a gradient of PDGF as well as to a gradient of fibronectin, which is also in attractant for fibroblasts. The chemotactic response of fibroblasts to PDGF was not inhibited by hydroxyurea or azidocytidine but was inhibited by actinomycin D and cycloheximide, suggesting that synthesis of RNA and proteins but not of DNA is required for the chemotactic response to occur. Fibroblast growth factor, epidermal growth factor, nerve growth factor, and insulin were not chemotactic for human skin fibroblasts, suggesting that the chemoattractant activity of PDGF for fibroblasts is not a general property of growth factors and mitogens. These results suggest that PDGF could have two functions in wound healing: to attract fibroblasts to migrate into the clot and then to induce their proliferation.