Increased expression of transforming growth factor beta isoforms (beta 1, beta 2, beta 3) in bleomycin-induced pulmonary fibrosis

Co-localization of immunoreactive transforming growth factor-beta 1 and decorin in bronchial biopsies from asthmatic and normal subjects

Airway wall remodelling is an established pathological feature of asthma but its causes are not well understood. One cytokine of potential relevance is transforming growth factor-beta1 (TGF-beta 1). The immunolocalization of TGF-beta 1 and of its small binding proteoglycan decorin have been examined in the airways of normal subjects and atopic asthmatics. Bronchial biopsy specimens were obtained by fibreoptic bronchoscopy, processed into glycolmethacrylate resin, and stained immunohistochemically using specific antibodies. Immunoreactive TGF-beta 1 was principally localized extracellularly in association with subepithelial connective tissue. Some staining of bronchial epithelial cells was also evident, but otherwise there was little intracellular staining. The overall pattern of immunohistochemical staining was indistinguishable in biopsy specimens from asthmatic and control subjects. Comparison of adjacent sections demonstrated the co-localization of immunoreactivity for TGF-beta 1 and decorin in the mucosa. It is concluded that immunoreactive TGF-beta 1 in human airways is principally extracellular and that matrix-associated TGF-beta 1 is likely to be bound at least in part to decorin. This interaction may provide a reservoir of TGF-beta 1 that can be released in an active form in response to appropriate stimuli.

Immunohistochemical and gelatin zymography studies for matrix metalloproteinases in bleomycin-induced pulmonary fibrosis

The role of various matrix metalloproteinases (MMP) and tissue inhibitor of metalloproteinases-2 (TIMP-2), and the gelatinolytic activities of MMP involved in the process of bleomycin-induced pulmonary fibrosis in rabbits were investigated. Male Japanese white rabbits were intubated with tracheal tubes under anesthesia, and bleomycin hydrochloride in sterile saline or only sterile saline was administered through the tracheal tubes. The animals were killed 1, 3, 7, 14 and 28 days after the administration of bleomycin (n = 3) or saline (n = 2). Light microscopic immunohistochemistry for MMP-1 (interstitial collagenase), MMP-2 (gelatinase A), MMP-9 (gelatinase B) and TIMP-2 was performed. The gelatinolytic activities of lung tissue homogenates were studied by gelatin zymography. In the early stages, the gelatinolytic activity of MMP-9 was predominant. MMP-9 localized in the infiltrating neutrophils, macrophages, bronchial and bronchiolar epithelial cells. The alveolar epithelial basement membrane was frequently disrupted in the early stages, where MMP-9 possibly contributed to the disruption. In the late stages, the gelatinolytic activities of the latent and active forms of MMP-2 were predominant, and MMP-2 localized in the regenerated alveolar epithelial cells in addition to the bronchial epithelial cells. MMP-2, especially its active form, possibly plays a role in alveolar epithelial cell regeneration. The localization of MMP-1 was similar to that of MMP-9. TIMP-2 localized in the epithelial cells and in some fibroblasts in fibrotic lesions. TIMP-2 possibly plays a role in extracellular matrix deposition in balance with MMP.

Lung smooth muscle differentiation

The vascular and visceral smooth muscle tissues of the lung perform a number of tasks that are critical to pulmonary function. Smooth muscle function often is compromised as a result of lung disease. Though a great deal is known about regulation of smooth muscle cell replication and cell and tissue contractility, much less is understood regarding the phenotype of the contractile protein machinery of lung smooth muscle cells. This review focuses on the expression of cytoskeletal and contractile proteins of lung vascular and airway smooth muscle cells during development, in the adult and during vascular and airway remodeling. Emphasis is placed on the expression of the heavy chain of smooth muscle myosin, as well as the regulation of its gene. Important areas for future research are discussed.

Gene expression of profibrotic mediators in bronchiolitis obliterans syndrome after lung transplantation

Bronchiolitis obliterans syndrome (BOS) develops in one-third of lung transplant recipients. A fibroproliferative process involving mesenchymal cells is observed histopathologically. In order further to evaluate the pathomechanisms of BOS, the gene expression of platelet-derived growth factor (PDGF)-B and transforming growth factor (TGF)-beta 1 in bronchoalveolar lavage (BAL) cells of six lung transplant recipients and appropriate controls was studied. Equal amounts of total RNA were submitted to semiquantitative reverse transcription/polymerase chain reaction (RT-PCR), amplifying actin, PDGF-B and TGF-beta 1 using established protocols and primer sets. The signal/actin ratio was calculated based on laser densitometry measurements. TGF-beta 1 transcripts were detected in all samples, and a slight increase in BOS patients was observed. PDGF-B mRNA was increased in BAL samples from BOS patients compared to unaffected recipients and controls. Plotting the FEV1 in percent of vital capacity and the PDGF expression in BOS patients revealed an increased PDGF signal preceding lung function deterioration. The data were consistent with the hypothesis based mainly on in vitro findings that PDGF and TGF-beta contribute to the development of BOS.

Regulation of transforming growth factor-beta1 mRNA expression by taurine and niacin in the bleomycin hamster model of lung fibrosis

We have reported that taurine (T) and niacin (N) inhibit the expression of procollagen type I and type III genes at the level of gene transcription in the bleomycin (BL) hamster model of lung fibrosis. In the present study, we have investigated the effects of TN in diet on the temporal expression of transforming growth factor-beta1 (TGF-beta1) mRNA and TGF-beta1 protein production in the same model of lung fibrosis to determine whether the decreased transcription of procollagen genes is associated with downregulation of TGF-beta1 mRNA. Our results demonstrate that expression of TGF-beta1 mRNA in lungs is increased in BL-treated hamsters in the BL + control diet (CD) group, compared to saline controls in the saline-instilled (SA) + CD group, by 3.5-, 2.5-, 4-, and 2-fold at 3, 7, 14, and 21 d, respectively, and TN treatment caused significant decreases in TGF-beta1 mRNA expression in BL-treated animals in the BL + TN group from Day 3 through Day 21. In addition, TN treatment also reduced TGF-beta1 protein in bronchoalveolar lavage fluid (BALF) from BL-treated animals in the BL + TN group. These decreases in TGF-beta1 mRNA and TGF-beta1 protein correlated with decreased lung collagen content in hamsters in the BL + TN group as demonstrated in our earlier study. To confirm that the TGF-beta1 activity observed in BALF is reflected at the transcriptional level, total RNA was isolated from lavaged cells. Reverse transcriptase-polymerase chain reaction analysis demonstrated maximal expression of TGF-beta1 mRNA transcripts in BL-treated lavaged cells from animals in the BL + CD group and only low levels were detected in both saline control groups, and in BL + TN-treated lavaged cells. Nuclear runoff analysis indicated that TN-mediated reduction of TGF-beta1 mRNA steady-state levels was a result of decreased gene transcription, suggesting a transcriptional downregulation mechanism. Our results indicate that the combined treatment with TN ameliorates BL-induced lung fibrosis, at least in part, via inhibition of TGF-beta1 mRNA expression.

Induction of tumor necrosis factor-alpha as a cause of bleomycin-related toxicity

BACKGROUND

The application of bleomycin is characterized by acute side effects, such as fever, chills, and sometimes hypotension and tachypnea. Furthermore, bleomycin is known to induce pneumonitis. There are several indications that the induction of cytokines by bleomycin is involved in the development of these side effects.

METHODS

In this study, the authors determined the plasma levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and transforming growth factor-beta (TGF-beta) before and after bleomycin infusion in 14 patients treated for disseminated nonseminomatous germ cell tumor.

RESULTS

Compared with the pretreatment value, TNF-alpha was significantly increased 3, 4.5, and 24 hours after bleomycin infusion. For IL-1beta and TGF-beta, no significant alterations were observed within 24 hours after administration of bleomycin.

CONCLUSIONS

The increase in TNF-alpha after administration of bleomycin suggests a role for this cytokine in the development of the acute side effects and probably also in the occurrence of bleomycin-induced pulmonary toxicity. The involvement of IL-1beta and TGF-beta deserve further study.

Induction of PDGF receptor-alpha in rat myofibroblasts during pulmonary fibrogenesis in vivo

Platelet-derived growth factor (PDGF) is a potent mitogen for mesenchymal cells. Induction of the PDGF receptor-alpha (PDGF-R alpha) in vitro enhances PDGF-induced mitogenesis and chemotaxis. Thus we investigated whether the PDGF-R alpha is induced in vivo during pulmonary fibrogenesis using a vanadium pentoxide (V2O5) model of lung injury. PDGF-R alpha mRNA expression was induced 24 h postinstillation. PDGF-R beta mRNA was constitutively expressed and did not increase. Western blotting showed upregulation of PDGF-R alpha protein by 48 h, and immunohistochemical analysis localized PDGF-R alpha primarily in mesenchymal cells residing within fibrotic lesions. Upregulation of PDGF-R alpha in vivo preceded mesenchymal cell hyperplasia (3-7 days) and collagen deposition by day 15. Supernatants from alveolar macrophages treated with V2O5 in vitro released upregulatory activity for PDGF-R alpha on cultured lung myofibroblasts, and this activity was blocked by the interleukin-1-receptor antagonist. These data suggest that interleukin-1 beta-mediated induction of PDGF-R alpha in vivo is important to lung myofibroblast hyperplasia during fibrogenesis.

Enhanced expression of TGF-betas and their receptors in human acute pancreatitis

OBJECTIVES

To determine which mechanisms are involved in pancreatic remodeling, repair, and fibrosis after acute necrotizing pancreatitis (NP) in humans.

SUMMARY BACKGROUND DATA

Transforming growth factor betas (TGF-betas) are multifunctional polypeptides that have been implicated in the regulation and formation of extracellular matrix and fibrosis. They exert their functions by binding to specific receptors. In this study, we analyze the expression of TGF-beta1, TGF-beta2, and TGF-beta3 and their receptors type I (Tbeta-RI [ALK5]), type II (Tbeta-RII), and type III (Tbeta-RIII) in NP.

PATIENTS

Pancreatic tissue samples were obtained from 6 female and 8 male patients with a median age of 65 years (range, 37 to 77 years) undergoing surgery for NP. The median Ranson score of the patients was 6 (range, 2 to 9). The operation was performed a median 5.5 days (range, 4 to 17 days) after the onset of acute pancreatitis. Pancreatic tissue obtained from 12 previously healthy organ donors (6 male, 6 female; median age of 43 years) served as controls.

METHODS

The expression of TGF-beta1, TGF-beta2, TGF-beta3, Tbeta-RI (ALK5), Tbeta-RII, Tbeta-RIII, and collagen type I mRNA was analyzed by Northern blot analysis. In addition, immunohistochemical analysis using polyclonal antibodies was performed to detect TGF-beta1, TGF-beta2, TGF-beta3, Tbeta-RI (ALK5), and Tbeta-RII.

RESULTS

Northern blot analysis showed an increase in TGF-betas and their receptors in NP tissue samples compared with samples from normal controls. The increase was 3.5-fold for TGF-beta1 (p < 0.05), 2.7-fold for TGF-beta2 (p < 0.05), 3.5-fold for TGF-beta3 (p < 0.05), 10-fold for Tbeta-RI (ALK5) (p < 0.05), 5.7-fold for Tbeta-RII (p < 0.05), and 1.4-fold for Tbeta-RIII (not significant). Collagen type I mRNA was also markedly increased in NP samples and correlated with the level of TGF-betas. Immunohistochemical analysis demonstrated intense TGF-beta1, TGF-beta2, TGF-beta3, Tbeta-RI (ALK5), and Tbeta-RII immunoreactivity in the remaining acinar and ductal cells in most NP samples; in the normal control pancreas, there was weak to moderate immunoreactivity for these factors only in some acinar cells and a few ductal cells.

CONCLUSION

The marked increase in expression of TGF-betas and their signaling receptors Tbeta-RI (ALK5) and Tbeta-RII suggests a role for TGF-betas in the repair process after the onset of NP in humans and raises the possibility that TGF-betas might be involved in tissue remodeling and the fibrotic reaction that occurs in the pancreas after necrosis.

Transforming growth factor beta s and wound healing

The Transforming Growth Factor beta superfamily (TGF beta) is one of the most complex groups of cytokines with widespread effects on many aspects of growth and development. The TGF beta isoforms and other family members, e.g. Activins and BMPs, have diverse effects in similar physiological situations. TGF beta is involved in the wound healing process. The three mammalian isoforms (TGF beta 1, 2 and 3) and recently other family members, e.g. Activin, have been localised in healing wounds. Manipulation of the ratios of TGF beta superfamily members, particularly the ratio of TGF beta 1 relative to TGF beta 3, reduces scarring and fibrosis. Such manipulations include reducing the levels of TGF beta 1/TGF beta 2 using neutralising antibodies or preventing the activation of TGF beta s. In chronic or impaired wounds the exogenous addition of TGF beta superfamily members accelerates aspects of the healing process. This review summarises evidence for the role of TGF beta superfamily members in wound healing and how modulation of TGF beta levels can prevent scarring and fibrosis.

Fibrosis in chronic rejection of human liver allografts: expression patterns of transforming growth factor-TGFbeta1 and TGF-beta3

Activation and transformation of lipocytes (Ito cells, stellate cells) into alpha-actin-positive myofibroblast-like cells is an essential step in the initiation of liver fibrosis. Transforming growth factor-beta (TGF-beta) is considered an important mediator of this process. In order to determine mechanisms of fibrotic deposition in a hepatic transplant setting, we analyzed 10 chronically rejected human liver allografts for the expression of extracellular matrix (ECM) molecules, myofibroblast-like cells (alpha-actin), macrophages, and TGF-beta1 and -beta3. Using single- and double-immunohistochemical staining techniques, all specimens investigated showed increased deposition of the ECM proteins fibronectin, tenascin, undulin, and collagen VI with a characteristic densification especially in pericentral areas. Likewise, strong accumulation of alpha-actin-positive cells and TGF-beta1-expressing macrophages was observed in the same fields, supporting the concept of lipocyte activation/transformation and subsequent ECM production fostered by macrophage-derived TGF-beta1. In contrast, TGF-beta3 was found to be mainly expressed by a markedly increased number of lipocytes. Interestingly, distribution of TGF-beta3 corresponded to that of tenascin, an ECM molecule known to be involved in early matrix organization, suggesting that TGF-beta3 may likewise act mainly in early stages of fibrogenesis. Furthermore, TGF-beta3 restriction to high numbers of a single cell type (i.e., lipocytes) implied a possible role in cell proliferation through autocrine loops. In conclusion, fibrosis in chronic rejection seems to follow similar mechanisms as in non-transplanted livers but additionally suggests differential temporal and functional roles for the TGF-beta isoforms 1 and 3 in the course of a multistep process leading to lipocyte transformation and ECM production.

Induction of interleukin-1 and interleukin-8 mRNAs and proteins by TGF beta 1 in rat lung alveolar epithelial cells

The transforming growth factor-beta (TGF-beta) has been shown to increase in lung injury and in fibrotic states of the lung. In the current study, we sought to investigate whether TGF beta 1 induced the expression of IL-1 alpha and IL-8 in rat alveolar epithelial cells. We evaluated TGF beta 1, IL-1 alpha, and IL-8 expression by immunofluorescence in silica-injured and saline-treated control rat lungs. Antibodies to IL-1 alpha, IL-8, and TGF beta 1 showed intense staining in silica-injured lungs as compared to saline-instilled lungs. Primary isolated type II cells from silica-injured lungs showed increased expression of IL-1 alpha as compared to saline-instilled lungs. To evaluate the effects of TGF beta 1, we treated an immortalized rat type II cell-derived cell line (LM5) with 100 pg/ml of TGF beta 1 in serum-free medium for 0-24 hours and analyzed the expression of IL-1 alpha and IL-8 mRNAs and proteins using semiquantitative RT-PCR, Northern blot analysis, Western blot analysis, and immunohistochemistry. Densitometric analysis of Northern blots showed modest constitutive expression of IL-1 alpha gene in untreated control LM5 cells. TGF beta 1 treatment resulted in an increase in IL-1 alpha mRNA, that reached maximum levels (4-fold) by 2 hours and remained elevated for 4-16 hours, with a subsequent decline by 24 hours. Similarly, Northern blot and RT-PCR analysis demonstrated that TGF beta 1 treatment resulted in maximum induction of IL-8 mRNA (6- 8.5-fold) within 1-4 hours. The levels remained elevated for up to 24 hours afterwards. Western blot analysis results further confirmed the expression of both IL-1 alpha and IL-8 proteins by LM5 cells. TGF beta 1 treatment resulted in increased expression of both IL-1 alpha and IL-8 proteins. Immunofluorescence studies demonstrated increased staining of IL-1 alpha by TGF beta 1 as compared to untreated cells. These results suggest that TGF beta 1 may regulate IL-1 alpha and IL-8 expression in alveolar epithelial cells and contribute to polymorphonuclear leukocyte recruitment and lung injury in clinical states with increased TGF beta 1.

Biochemical analysis of the interaction of fibronectin with IgG and localization of the respective binding sites

Fibronectin (Fn), a mosaic protein composed of multiple copies of three different module types (Fl, F2 and F3), has been found associated with circulating immune complexes (ICs) and immunoglobulin (Ig) aggregates in a variety of IC diseases and myeloproliferative disorders. We have previously shown that a proteolytic fragment of Mr = 25,900 Da, from the NH2-terminal domain of Fn, composed of five type 1 modules (1Fl -5Fl) binds to the major Ig classes under physiologic conditions, suggesting that the presence of Fn in ICs and cryoglobulins results from a physicochemical binding interaction between these two molecules. Using an ELISA, we now show that the interaction between Fn and IgG is: (1) not influenced by any other constituent of plasma; (2) unaffected by temperature; and (3) has an estimated Kd of 3.77 x 10(-9) M. In addition, we have further delineated the respective sites involved in the interaction between Fn and IgG. Recombinant type l module pairs (1Fl.2Fl and 4Fl.5Fl) from the NH2-terminus of Fn, expressed in yeast, were employed in an ELISA and affinity chromatography and compared with the 25.9 kDa (1Fl - 5Fl) fragment and intact Fn for binding to IgG. The 4Fl.5Fl and the 25.9 kDa fragment bound to immobilized IgG and inhibited Fn binding to IgG to nearly the same extent as the intact molecule (IC50: Fn = 6.77 x 1O(-9) M; 25.9 kDa fragment = 5 x 10(-9) M; 4Fl.5Fl = 7.6 x 10(-9) M). Thus, the binding site for IgG on the Fn molecule is localized to and completely conferred by the 4Fl.5Fl module pair (residues 151-244). Similar experiments using papain-generated Fab and Fc fragments of IgG localized the Fn binding site on IgG to the Fe region of the IgG molecule. Fn bound to the Fc fragment with a nearly identical Kd of 3.69 x 10(-9) M, as to intact IgG (3.77 x 10(-9) M). These studies support the hypothesis that the interaction between Fn and Ig may contribute to the pathophysiology of immune complex related disorders.