Essential role of stem cell factor–c‐Kit signalling pathway in bleomycin‐induced pulmonary fibrosis

Stem cell factor ( SCF ) and its receptor c‐Kit have been implicated in tissue remodelling and fibrosis. Alveolar fibroblasts from patients with diffuse interstitial fibrosis secrete more SCF . However, its precise role remains unclear. In this study the potential role of the SCF –c‐Kit axis in pulmonary fibrosis was examined. Fibrosis was induced by intratracheal instillation of bleomycin ( BLM ), which caused increased SCF levels in plasma, bronchoalveolar lavage fluid ( BALF ) and lung tissue, as well as increased expression by lung fibroblasts. These changes were accompanied by increased numbers of bone marrow‐derived c‐Kit + cells in the lung, with corresponding depletion in bone marrow. Both recombinant SCF and lung extracts from BLM ‐treated animals induced bone‐marrow cell migration, which was blocked by c‐Kit inhibitor. The migrated cells promoted myofibroblast differentiation when co‐cultured with fibroblasts, suggesting a paracrine pathogenic role. Interestingly, lung fibroblast cultures contained a subpopulation of cells that expressed functionally active c‐Kit, which were significantly greater and more responsive to SCF induction when isolated from fibrotic lungs, including those from patients with idiopathic pulmonary fibrosis ( IPF ). This c‐Kit + subpopulation was α SMA ‐negative and expressed lower levels of collagen I but significantly higher levels of TGF β than c‐Kit‐negative cells. SCF deficiency achieved by intratracheal treatment with neutralizing anti‐ SCF antibody or by use of Kitl Sl / Kitl Sl ‐d mutant mice in vivo resulted in significant reduction in pulmonary fibrosis. Taken together, the SCF –c‐Kit pathway was activated in BLM ‐injured lung and might play a direct role in pulmonary fibrosis by the recruitment of bone marrow progenitor cells capable of promoting lung myofibroblast differentiation. Copyright © 2013 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98368/1/path4177.pd

Telomerase and Telomere Length in Pulmonary Fibrosis

In addition to its expression in stem cells and many cancers,telomerase activity is transiently induced inmurine bleomycin (BLM)induced pulmonary fibrosis with increased levels of telomerase transcriptase (TERT) expression, which is essential for fibrosis. To extend these observations to human chronic fibrotic lung disease,we investigated the expression of telomerase activity in lung fibroblasts from patients with interstitial lung diseases (ILDs), including idiopathic pulmonaryfibrosis (IPF).The resultsshowedthat telomerase activity was induced in more than 66% of IPF lung fibroblast samples, in comparison with less than 29% from control samples,some of which were obtained from lung cancer resections. Less than 4%of the humanIPF lung fibroblast samples exhibited shortened telomeres,whereas less than 6% of peripheral blood leukocyte samples from patients with IPF or hypersensitivity pneumonitis demonstrated shortened telomeres. Moreover, shortened telomeres in lategeneration telomerase RNA component knockout mice did not exert a significant effect on BLM-induced pulmonary fibrosis. In contrast, TERT knockout mice exhibited deficient fibrosis that was independent of telomere length. Finally, TERT expression was up-regulated by a histone deacetylase inhibitor, while the induction of TERT in lung fibroblastswasassociatedwiththebindingofacetylatedhistoneH3K9to the TERT promoter region. These findings indicate that significant telomerase inductionwas evident in fibroblasts from fibroticmurine lungs and a majority of IPF lung samples, whereas telomere shortening was not a common finding in the human blood and lung fibroblast samples. Notably, the animal studies indicated that the pathogenesis of pulmonary fibrosis was independent of telomere length

Reptiles from southern Benin, West Africa, with the description of a new Hemidactylus (Gekkonidae), and a country-wide checklist

We report on a collection of reptiles made in southern Benin, mostly in the vicinity of Lama Forest, a relict rain forest surrounded by savannah habitats within the the so-called Dahomey gap. 48 species (3 chelonian, 20 saurian and 25 ophidian species were encountered) are listed with the respective voucher material and commented in respect to taxonomic or ecological information. Five lizard species (Agama sylvanus, Hemidactylus ansorgei, H. lamaensis n. sp., Holaspis guentheri, Varanus ornatus) and two snake species (Natriciteres variegata, Amblyodipsas unicolur) are new for the fauna of Benin, the second Hemidactylus species being even new to science. Some other species are reported from Benin for only the second time. This commented list of species collected from southern Benin is followed by a general country-wide checklist, which is based on literature data and also some unpublished records from northern Benin, among them the remarkable rediscovery of Agama gracilimembris, 9 decades after its original description from this country

Dual roles of IL-4 in lung injury and fibrosis.

Increased lung IL-4 expression in pulmonary fibrosis suggests a potential pathogenetic role for this cytokine. To dissect this role, bleomycin-induced pulmonary inflammation and fibrosis were analyzed and compared in wild type (IL-4(+/+)) vs IL-4-deficient (IL-4(-/-)) mice. Lethal pulmonary injury after bleomycin treatment was higher in IL-4(-/-) vs IL-4(+/+) mice. By administration of anti-CD3 Abs, we demonstrated that this early response was linked to the marked T lymphocyte lung infiltration and to the overproduction of the proinflammatory mediators such as TNF-alpha, IFN-gamma, and NO in IL-4(-/-) mice. In contrast to this early anti-inflammatory/immunosuppressive role, during later stages of fibrosis, IL-4 played a profibrotic role since IL-4(-/-) mice developed significantly less pulmonary fibrosis relative to IL-4(+/+) mice. However, IL-4 failed to directly stimulate proliferation, alpha-smooth muscle actin, and type I collagen expression in lung fibroblasts isolated from the wild-type mice. Upon appropriate stimulation with other known fibrogenic cytokines, fibroblasts from IL-4(-/-) mice were relatively deficient in the studied parameters in comparison to fibroblasts isolated from IL-4(+/+) mice. Taken together, these data suggest dual effects of IL-4 in this model of lung fibrosis: 1) limiting early recruitment of T lymphocytes, and 2) stimulation of fibrosis chronically

Eosinophils and T lymphocytes possess distinct roles in bleomycin-induced lung injury and fibrosis

Leukocyte infiltration is characteristic of lung injury and fibrosis, and its role during tissue repair and fibrosis is incompletely understood. We found that overexpression of IL-5 in transgenic mice (IL-5(TG)) or by adenoviral gene transfer increased bleomycin (blm)-induced lung injury, fibrosis, and eosinophilia. Surprisingly, blm-treated IL-5-deficient (IL-5(-/-)) mice also developed pronounced pulmonary fibrosis but characterized by marked T lymphocyte infiltration and absence of eosinophilia. In both murine strains however, induction of lung TGF-beta expression was evident. Purified lung eosinophils from blm-treated IL-5(TG) mice stimulated alpha-smooth muscle actin and collagen expression in mouse lung fibroblasts, without affecting proliferation. Furthermore instillation of purified eosinophils into murine lungs resulted in extension of blm-induced lung fibrosis, thus confirming a role for eosinophils. However, lung T lymphocytes from blm-treated IL-5(-/-) mice were able to stimulate fibroblast proliferation but not a-smooth muscle actin or collagen expression. Blocking T cell influx by anti-CD3 Abs abrogated lung fibrosis, thus also implicating T lymphocytes as a key participant in fibrosis. Pulmonary fibrosis in IL-5(TG) mice was preferentially associated with type 2 cytokines (IL-4 and IL-13), whereas fibrotic lesions in IL-5(-/-) animals were accompanied by proinflammatory cytokine (TNF-alpha, IL-1beta, and IFN-gamma) expression. We suggest that eosinophils and T cells contribute distinctly to the development of blm-induced lung fibrosis potentially via their production of different cytokine components, which ultimately induce TGF-beta expression that is intimately involved with the fibrosis

The in vivo fibrotic role of FIZZ1 in pulmonary fibrosis.

FIZZ (found in inflammatory zone) 1, a member of a cysteine-rich secreted protein family, is highly induced in lung allergic inflammation and bleomycin induced lung fibrosis, and primarily expressed by airway and type II alveolar epithelial cells. This novel mediator is known to stimulate α-smooth muscle actin and collagen expression in lung fibroblasts. The objective of this study was to investigate the in vivo effects of FIZZ1 on the development of lung fibrosis by evaluating bleomycin-induced pulmonary fibrosis in FIZZ1 deficient mice. FIZZ1 knockout mice exhibited no detectable abnormality. When these mice were treated with bleomycin they exhibited significantly impaired pulmonary fibrosis relative to wild type mice, along with impaired proinflammatory cytokine/chemokine expression. Deficient lung fibroblast activation was also noted in the FIZZ1 knockout mice. Moreover, recruitment of bone marrow-derived cells to injured lung was deficient in FIZZ1 knockout mice. Interestingly in vitro FIZZ1 was shown to have chemoattractant activity for bone marrow cells, including bone marrow-derived dendritic cells. Finally, overexpression of FIZZ1 exacerbated fibrosis. These findings suggested that FIZZ1 exhibited profibrogenic properties essential for bleomycin induced pulmonary fibrosis, as reflected by its ability to induce myofibroblast differentiation and recruit bone marrow-derived cells

Telomerase Regulation of Myofibroblast Differentiation

Telomerase activity, which has wide expression in cancerous cells, is induced in lung proliferating fibroblasts. It is preferentially expressed in fibroblasts versus myofibroblasts. It is unknown whether regulation of telomerase expression is related to the process of fibroblast differentiation into myofibroblasts. The objective of this study was to clarify such a potential link between telomerase expression and myofibroblast differentiation. Telomerase inhibitor, 3′-azido-2′,3′-dideoxythymidine, or antisense oligonucleotide to the telomerase RNA component was used to inhibit the induced fibroblast telomerase activity. The results showed that inhibition of induced telomerase increased α-smooth muscle actin expression, an indicator of myofibroblast differentiation. In contrast, induction of telomerase by basic fibroblast growth factor inhibited α-smooth muscle actin expression. These findings suggest that the loss of telomerase activity is closely associated with myofibroblast differentiation and possibly functions as a trigger for myofibroblast differentiation. Conversely, expression of telomerase suppresses myofibroblast differentiation