Changes in autacoid and neuropeptide contents of lung cells in asbestos-induced pulmonary fibrosis

Vasoactive intestinal peptide attenuates bleomycin-induced murine pulmonary fibrosis by inhibiting epithelial-mesenchymal transition: Restoring autophagy in alveolar epithelial cells

Vasoactive intestinal peptide (VIP) is an intrapulmonary neuropeptide with multi-function, including anti-fibrosis. However, the exact role of VIP in pulmonary fibrosis has not been documented. Here, we investigated the protective effect of VIP against pulmonary fibrosis in a murine model induced by bleomycin (BLM). We found that the overexpression of VIP mediated by the adenoviral vector significantly attenuated the lung tissue destruction, reduced the deposition of the extracellular matrix, and inhibited the expression of alpha-smooth muscle actin (α-SMA) in the lungs of mice received BLM. Mechanismly, we found that VIP significantly suppressed the transforming growth factor-beta 1 (TGF-β1)-induced epithelial-mesenchymal transition (EMT) and inhibited the matrix-producing ability of alveolar epithelial cells in vitro. Furthermore, we found that TGF-β1 depressed the autophagy and an autophagy inductor partly reversed the TGF-β1-induced EMT in alveolar epithelial cells. The impaired autophagy was also observed in the lungs of BLM-treated mice, which was restored by VIP treatment. And VIP treatment enhanced autophagy in TGF-β1-stimulated alveolar epithelial cells, contributing to its anti-EMT effect. In summary, our data, for the first time, show that VIP attenuates BLM-induced pulmonary fibrosis in mice with anti-EMT effect through restoring autophagy in alveolar epithelial cells. This study provides a possibility that inhaled long-acting VIP may be an anti-fibrotic drug in the treatment of pulmonary fibrosis.

Strain-specific steroidal control of pituitary function

We have previously shown that 7B2 null mice on the 129/SvEvTac (129) genetic background die at 5 weeks of age with hypercorticosteronemia due to a Cushing's-like disease unless they are rescued by adrenalectomy; however, 7B2 nulls on the C57BL/6NTac (B6) background remain healthy, with normal steroid levels. Since background exerts such a profound influence on the phenotype of this mutation, we have evaluated whether these two different mouse strains respond differently to high circulating steroids by chronically treating wild-type 129 and B6 mice with the synthetic steroid dexamethasone (Dex). Dex treatment decreased the dopamine content of the neurointermediate lobes (NIL) of 129 mice, leading to NIL enlargement and increased total D(2)R mRNA in the 129, but not the B6, NIL. Despite the decrease in this inhibitory transmitter, Dex-treated 129 mice exhibited reduced circulating alpha-melanocyte-stimulating hormone (alpha-MSH) along with reduced POMC-derived peptides compared with controls, possibly due to reduced POMC content in the NIL. In contrast, Dex-treated B6 mice showed lowered cellular ACTH, unchanged alpha-MSH and beta-endorphin, and increased circulating alpha-MSH, most likely due to increased cleavage of NIL ACTH by increased PC2. Dex-treated 129 mice exhibited hyperinsulinemia and lowered blood glucose, whereas Dex-treated B6 mice showed slightly increased glucose levels despite their considerably increased insulin levels. Taken together, our results suggest that the endocrinological response of 129 mice to chronic Dex treatment is very different from that of B6 mice. These strain-dependent differences in steroid sensitivity must be taken into account when comparing different lines of transgenic or knockout mice.

Transcriptional regulation of plasminogen activator inhibitor-1 by transforming growth factor-β, activin A and microphthalmia-associated transcription factor

Plasminogen activator inhibitor-1 (PAI-1) is a key molecule that regulates turnover of the extracellular matrix. In the present study, we characterized PAI-1 gene expression in mast cells and melanocytes. In bone marrow-derived cultured mast cells, up-regulation of the PAI-1 gene was observed upon treatment with TGF-beta1, and was regulated at the transcriptional level. Microphthalmia-associated transcription factor (MITF), a member of the basic helix-loop-helix leucine zipper family of tissue-specific transcription factors predominantly expressed in mast cells, melanocytes and osteoclasts, also stimulated PAI-1 gene transcription, and TGF-beta1 did not increase PAI-1 mRNA levels in mast cells from mi/mi mice expressing dominant-negative MITF. MITF isoforms regulated TGF-beta1-induced transcription of PAI-1 differently; MITF-E-mediated transcription was further increased by TGF-beta1, whereas transcriptional activation by TGF-beta1 was blocked by MITF-M or MITF-mc expression. In contrast, activin A, another member of the TGF-beta family, enhanced transcription induced by MITF-M, as well as by MITF-E, although MITF-mc blocked activin A-induced transcription of PAI-1. Different regulation of PAI-1 gene expression upon TGF-beta1 and activin A treatment was also detected in B16 melanocytes; TGF-beta1 transiently increased the PAI-1 mRNA level, whereas activin A had prolonged effects on up-regulation of PAI-1. Our results on the control of PAI-1 gene expression by MITF isoforms, TGF-beta1 and activin A suggest that discrete regulation of the plasminogen activator system occurs in a cell type-specific manner.

Amphiregulin expression in human mast cells and its effect on the primary human lung fibroblasts

BACKGROUND

Amphiregulin is a member of the epidermal growth factor family and has been shown to stimulate the proliferation of human keratinocytes in an autocrine manner.

OBJECTIVE

The aim of the present study was to examine the expression change of growth factors, especially amphiregulin, in human mast cells induced by IgE cross-linking.

METHODS

Microarray analysis and RT-PCR were used to analyze the gene expression profile of human cord blood-derived mast cells (CBMCs) stimulated with IgE cross-linking. Protein secretion in the supernatants of CBMCs was measured by means of ELISA. Double-immunofluorescence staining was used to analyze the expression in the lung mast cells.

RESULTS

Of the 64 different growth factor genes analyzed, 5 were found to be substantially upregulated. Among them, amphiregulin mRNA was induced by 44-fold in CBMCs on activation through IgE cross-linking. Secretion of amphiregulin protein was evident in CBMCs 8 hours after stimulation. Amphiregulin was also expressed in human lung mast cells from patients with asthma, as demonstrated by means of double-immunofluorescence staining. Amphiregulin promoted the proliferation of the primary human lung fibroblasts, and amphiregulin-treated primary human lung fibroblasts showed a marked increase in the expression of c-fos , a proto-oncogene that facilitates or is required for the proliferation of a wide variety of cells.

CONCLUSION

Human CBMCs secreted amphiregulin on IgE cross-linking, and the amphiregulin induced proliferation of primary human lung fibroblasts. These data suggest that local release of amphiregulin by human mast cells could play an important role in lung fibrosis by promoting the proliferation of primary human lung fibroblasts.

Influence of IgE-mediated activation of cultured human mast cells on proliferation and type I collagen production by human dermal fibroblasts

BACKGROUND

Mast cells have been suggested to be involved in fibrotic conditions, but it still remains unknown whether IgE-mediated activation of human mast cells promotes fibrogenesis by human fibroblasts.

OBJECTIVE

The purpose of this study was to determine whether IgE-mediated activation of cultured human mast cells can promote fibrogenesis by cultured human dermal fibroblasts.

METHODS

Mast cells derived from human umbilical cord blood cells were incubated with IgE and then activated by anti-IgE, and histamine release was measured. IgE-sensitized mast cells were cocultured with fibroblasts from normal dermis and activated with anti-IgE to induce histamine release, after which proliferation and type I collagen synthesis by the fibroblasts were determined.

RESULTS

Coculture of subconfluent human dermal fibroblasts with IgE-sensitized mast cells did not affect fibroblast proliferation. However, fibroblast proliferation was increased by activated mast cells, and a significant increase was observed in the presence of 10(5) or 3 x 10(5) mast cells/mL. The promotion of fibroblast proliferation by mast cells (3 x 10(5)/mL) was partly inhibited by ketotifen at a concentration that significantly reduced histamine release from mast cells. On the other hand, IgE-mediated activation of mast cells did not increase type I collagen production by confluent human dermal fibroblasts.

CONCLUSION

IgE-mediated activation of cultured human mast cells could increase the proliferation of human dermal fibroblasts, but did not promote type I collagen production by the fibroblasts under the conditions tested.

Production of fibrogenic cytokines by cord blood-derived cultured human mast cells

BACKGROUND

Mast cells are a potential source of cytokines, but their contribution to nonallergic inflammatory conditions, such as fibrosis, remains unclear.

OBJECTIVE

We investigated whether cord blood-derived cultured human mast cells could produce fibrogenic cytokines by IgE-mediated activation.

METHODS

Mast cells were obtained from human cord blood mononuclear cells by culture with stem cell factor and IL-6. The mast cells were incubated with human myeloma IgE and were activated with anti-IgE. The expression of messenger RNA for fibrogenic cytokines was examined by the reverse-transcription polymerase chain reaction, and cytokine protein was assayed by enzyme-linked immunosorbent assay, or bioassay.

RESULTS

Cultured human mast cells constitutively expressed mRNA for transforming growth factor-beta(1), and its expression was not increased by anti-IgE stimulation. The cells released this factor into the culture medium spontaneously, which showed bioactivity after heat treatment. The mast cells also expressed mRNA for platelet-derived growth factor A, which was enhanced with a peak at 3 hours by stimulation with anti-IgE. Conditioned medium from nonactivated mast cells did not contain basic fibroblast growth factor, but this cytokine was released into the medium in a time-dependent manner after stimulation with anti-IgE.

CONCLUSION

Human mast cells activated by IgE-mediated stimulation show production of fibrogenic cytokines that varies depending on the cytokine, which suggests possible involvement of mast cell cytokines in the development of fibrosis.

Cord blood-derived human cultured mast cells produce transforming growth factor beta1

BACKGROUND

Mast cells frequently accumulate at the site of fibrosis and their contribution has been suspected in the pathogenesis of fibrotic conditions. However, it still remains unknown whether human mast cells synthesize transforming growth factor beta1 (TGF-beta1).

OBJECTIVE

We have investigated whether cord blood-derived human cultured mast cells express messenger RNA (mRNA) for TGF-beta and produce bioactive TGF-beta1.

METHODS

Mast cells were obtained by culturing mononuclear cells from cord blood in the presence of stem cell factor and interleukin-6. Expression of mRNA for TGF-beta1 was examined by the method of reverse transcriptase-polymerase chain reaction (RT-PCR). Immunocytochemical staining for TGF-beta and growth-inhibitory assay using Mv1Lu cells were also performed.

RESULTS

The cultured human mast cells constitutively expressed mRNA for TGF-beta1. With calcium ionophore A23187, the intensity of the PCR-amplified band for TGF-beta1 was not increased. Immunocytochemical staining showed that the cultured mast cells were positive for both latency-associated peptide and activated forms of TGF-beta. Bioassay with Mv1Lu cells and R 4-2 mutant cells showed that mast-cell conditioned medium had a bioactivity of TGF-beta1.

CONCLUSION

Cord blood-derived human cultured mast cells constitutively express mRNA for TGF-beta1 and produce functional TGF-beta1. Because TGF-beta1 has been shown to be highly fibrogenic, these results may highlight a novel role for human mast cells in tissue fibrosis.

Mast cell tryptase stimulates both human dermal fibroblast proliferation and type I collagen production

BACKGROUND

Mast cell tryptase has been shown to be mitogenic for fibroblasts, however, it still remains unknown whether mast cell tryptase stimulates collagen production by human derrmal fibroblasts.

OBJECTIVE

We have investigated the effect of mast cell tryptase on type I collagen production by human dermal fibroblasts as well as the proliferation of the fibroblasts.

METHODS

Tryptase isolated from human lung tissue was added to the culture of fibroblasts from normal dermis, and the fibroblast proliferation and the activity of type I collagen synthesis in the supernatants were assayed, respectively.

RESULTS

Fibroblast proliferation was increased with tryptase in a concentration-dependent manner, and a significant increase was observed in the presence of tryptase at concentrations from 0.01 to 10 microg/mL. The increase of fibroblast proliferation with 3 microg/mL tryptase was significantly reduced by 15 microg/mL antitryptase IgG antibody, which was demonstrated to inhibit fibrinogenolysis of tryptase. On the other hand, the production of type I collagen by the fibroblasts was significantly increased with tryptase at a concentration of 10 microg/mL. The collagen production in the presence of 10 microg/mL tryptase was significantly inhibited by 50 microg/mL antitryptase IgG antibody.

CONCLUSION

Tryptase increases not only the proliferation of human dermal fibroblasts but also type I collagen production.

Alveolar macrophage inhibition of lung-associated NK activity: involvement of prostaglandins and transforming growth factor-beta 1

Natural killer (NK) activity plays an important role in host defense. It is likely that this defensive role is shaped by compartmental and local environmental factors. The present study investigated the regulatory effects of alveolar macrophages (AM) on lung-associated NK activity. AM and lung lymphocytes (LL) were permitted to interact in a two-chamber system which prohibited cell contact but supported diffusion of soluble factors. AM were found to inhibit NK activity from LL in a time-dependent and reversible manner. The inhibitory event was shown to be mediated by soluble factors acting upon a post-binding event(s) in the lytic pathway of LL. AM inhibition was sensitive to indomethacin treatment (10(-5) M), which caused a decrease in prostaglandin E2 (PGE2) concentrations. Quantitation of PGE2 levels and treatment of LL with exogenous PGE2 indicated that the inhibitory effect could not be exclusively due to PGE2. It was subsequently found that exogenous transforming growth factor-beta 1 (TGF-beta 1) also inhibited LL NK activity and that treatment of inhibitory AM supernatant with a neutralizing antibody to TGF-beta 1 adsorbs up to 55% of its inhibitory activity. Moreover, the amount of TGF-beta 1 found in AM-LL co-culture media (25 pg/mL) correlated well with the level of NK inhibition observed. By contrast, platelet-derived growth factor and nitric oxide did not play a significant role in mediating AM suppression. Taken together, the data suggest that AM inhibit lung NK activity by interfering with post-binding lytic event(s) through the production of PGE2 and TGF-beta 1.

Bombesin-like peptides in alveolar macrophage: increased release in pulmonary inflammation and fibrosis

Rat bronchoalveolar cells (99% alveolar macrophages (AM] were obtained by bronchoalveolar lavage and examined for their content of bombesin-like immunoreactivity (BLI) by radioimmunoassay (RIA), immunocytochemistry and high performance liquid chromatography (HPLC) analysis. Rat AM contained and released in their culture media significant levels of BLI, the major molecular form corresponding to gastrin-releasing peptide (GRP). Release of BLI by AM was not affected by in vitro activation of AM with lipopolysaccharide and muramyl dipeptide, but was enhanced following in vivo treatment with inflammatory agents. AM from animals with inflammation and fibrosis released higher levels of BLI than controls at 3 and 6 weeks after treatment. These changes were correlated with a significant increase in the proportion of low density mature AM as determined by Percoll density gradient fractionation. Together, our data indicate that increased release of BLI by AM may be related to AM maturation and support a role for bombesin-like peptides as modulator(s) of inflammatory reactions.

Effects of biological response modifiers on lung natural killer activity

Natural killer (NK) activity plays an important role in host defense against tumors, especially once augmented by immunomodulators. It is likely that the modulation of NK cells is a reflection of the environment in which they reside. The current study was undertaken to characterize the response profile of lung interstitial lymphocyte natural killer (LLNK) activity to various biological response modifiers (BRM) in vitro after short term incubation (18h). The presented data show that treatment of lung lymphocytes with human recombinant interleukin 2 (rIL-2), purified rat interferon alpha/beta (IFN-alpha/beta), or murine recombinant tumor necrosis factor alpha (rTNF-alpha) resulted in a dose-dependent increase in LLNK activity. The maximum stimulation was similar for rIL-2 and IFN-alpha/beta, although a much higher concentration of IFN-alpha/beta was required to reach this level of stimulation. The maximum response to rTNF-alpha treatment was about half that seen with rIL-2 or IFN-alpha/beta and it, too, required a high concentration. By contrast, rat recombinant interferon gamma (rIFN-gamma) or murine recombinant interleukin 1 (rIL-1) failed to alter LLNK activity significantly when used alone. Furthermore, doses of IFN-alpha/beta and rTNF-alpha that had little enhancing effect were able to synergize with a suboptimal dose of rIL-2, whereas rIL-1 and rIFN-gamma failed to do so. These data demonstrate the response of lung NK activity to BRM treatment, which is important for the responsible and effective use of BRM. However the spectrum of lung NK cell response to BRM is smaller than that previously reported for NK cells from other anatomic compartments.

Modulation of lung-associated natural killer activity by resident and activated alveolar macrophages

Alveolar macrophages (AM) freshly obtained by bronchoalveolar lavage suppressed significantly, in a dose-dependent fashion, lung interstitial lymphocytes cytotoxicity against the NK-sensitive target cells, YAC-1. Kinetic experiments revealed that AM-mediated suppression of NK activity was seen following short-term incubation of AM with lymphocytes (4 h) and was unchanged after a 24 h co-culture period. Freshly obtained lung lymphocytes and lymphocytes incubated for 24 h were similarly inhibited by AM. In addition, incubation of AM for 24 h did not abrogate their suppressive effect on lung NK activity. Interestingly, AM-conditioned media, also caused a significant inhibition of lung NK activity. Furthermore, in vitro activation of AM with lipopolysaccharide (LPS, 5 micrograms/ml) and muramyl dipeptide (MDP, 20 micrograms/ml) significantly enhanced the inhibitory effect of AM on lung NK activity. Similarly, in vivo activation of AM locally by intratracheal instillation of attapulgite, an inflammatory agent, resulted in greater AM-mediated down regulation. Taken together, these data indicate that lung NK activity is modulated by locally derived factors and suggest that pharmacologic manipulation of AM may play a determining role in the activation of lung NK activity by biological response modifiers (BRM).