Bleomycin treatment of chick fibroblasts causes an increase of polysomal type I procollagen mRNAs. Reversal of the bleomycin effect by dexamethasone

Biochemical pathways leading to collagen deposition in pulmonary fibrosis

Fibrosis in the lung is well described histologically. There is destruction of the normal architecture with the appearance of inflammatory cells and connective tissue components, particularly collagen. Biochemical evidence for an increased deposition of collagen in man has been demonstrated in patients with both acute and chronic forms of pulmonary fibrosis. Studies of collagen metabolism in man are equivocal but there is convincing evidence for an increased synthesis rate in animal models of pulmonary fibrosis. Collagen degradation has been little studied but may be important, given the recent evidence indicating quite rapid turnover of lung collagen and a decreased degradation of collagen in experimental disease. The distribution of collagen types has been studied in man, where there is some evidence for the production of type III collagen in the early active phase of disease with a preponderance of type I collagen in the late stages. The cellular mechanisms leading to these changes are uncertain but the alveolar macrophage may play a central role, since it is capable of releasing factors which expand the fibroblast population as well as attracting new fibroblasts to the site of injury. These pathways are described for what is essentially the normal physiological response of scar formation, which has pathological consequences in the lung, a tissue requiring thin membranes at its epithelial and endothelial surfaces, in order to perform its main function of gas exchange.

Collagen secretion after photodynamic therapy versus scar-inducing anti-cancer modalities: an in vitro study

Photodynamic therapy (PDT) has been associated anecdotally with good quality healing and an absence of scar formation. Our previous studies, examining the levels of the collagen specific molecular chaperone Hsp47, have noted differences in the response after photodynamic therapy and hyperthermia at both the transcriptional and translational levels. In the present study the levels of Hsp47 after exposure to two chemotherapeutic agents (bleomycin and mitomycin). ionising radiation, hyperthermia and haematoporphyrin ester (HpE) mediated PDT were compared in both mouse and human fibroblast cell lines. A rapid assay for soluble collagen has also been used to quantify soluble collagen levels at early time points after treatment. Peak Hsp47 levels were found to correlate well with peak collagen levels. The results show that the levels of collagen measured in vitro are elevated in modalities associated with scarring in vivo but not after HpE-PDT.

Early phase collagen synthesis in lungs of rats exposed to bleomycin

Skin wound healing exhibits type III collagen synthesis occurring transiently as early as 10 h after injury, with subsequent synthesis of type I to form a scar. We hypothesized that similar collagen type switching also occurred in the bleomycin model of lung fibrosis in the rat. We could measure elevated lung collagen synthesis rates as early as 4 days after administration of bleomycin. Collagen type I:III ratios in whole lung remained constant for the first 7 days at the control level of 2:1, then increased to as high as 5:1 at day 21. Procollagen mRNA content, expressed as a ratio of type I:III mRNAs, was consistent with the protein synthesis data and the observed ratio of collagen types being made by the lungs at the various time points evaluated. We conclude that a transient increase in type III relative to type I collagen does not occur in the bleomycin rat lung model. Therefore, the sequence of type-specific collagen expression and deposition in the skin wound healing model is not entirely analogous to this widely used animal model of pulmonary fibrosis.

Lung morphometry and collagen and elastin content: changes during normal development and after prenatal hormone exposure in sheep

This study examined whether the improvement in lung function after prenatal hormone exposure coincided with changes in lung morphometry or in collagen and elastin content. Fetal lambs received a single intramuscular injection of betamethasone (0.5 mg/kg) plus L-thyroxine (T4) (15 micrograms/kg) or vehicle control 48 h before delivery at 121, 128, or 135 d gestational age (d 121, d 128, d 135, term = 150 d). T4 was administered in conjunction with betamethasone in an attempt to enhance the maturational response. The right-upper lobes were instillation fixed at 30 cm H2O by Karnovsky's fixative after a 40-min period of mechanical ventilation. A number of significant changes occurred between d 121 and d 135 in control animals: alveolar airspace volume increased by 270%; despite a 40% reduction in alveolar septal thickness, alveolar septal volume did not change appreciably, suggesting a "redistribution" of septal tissue into the formation of secondary alveolar septa, which doubled in number; and both parenchymal collagen and elastin volume increased significantly, whereas pleural collagen and elastin volume did not change. In contrast to the changes seen in control animals, exposure to betamethasone plus T4 led to alveolar septal thinning at each gestational age without an associated increase in secondary septal number, a 40% decrease in alveolar septal volume, and a proportionate reduction in parenchymal elastin at d 121. Although attenuation of alveolar septa coincides with redistribution of septal tissue into the formation of secondary septa during normal maturation, exposure to betamethasone plus T4 promotes thinning of alveolar septa in the absence of secondary septal formation, which results in a loss of alveolar septal tissue.

Perspective article: transforming growth factor-beta: crossroad of glucocorticoid and bleomycin regulation of collagen synthesis in lung fibroblasts

Fibrosis is a consequence of injury which is characterized by accumulation of excess collagen and other extracellular matrix components, resulting in the destruction of normal tissue architecture and function. Transforming growth factor-beta, a potent wound healing agent, has also been shown to be an agent that can produce fibrosis because it is a potent stimulator of collagen synthesis. Both glucocorticoids and bleomycin have recently been shown to affect collagen synthesis in opposite directions, by utilizing a common pathway of involving transforming growth factor-beta activator protein binding to the transforming growth factor-beta element. This article presents a mechanistic overview of collagen synthesis regulation by glucocorticoids and bleomycin through the transforming growth factor-beta pathway.

Glucocorticoids coordinately regulate type I collagen pro alpha 1 promoter activity through both the glucocorticoid and transforming growth factor beta response elements: a novel mechanism of glucocorticoid regulation of eukaryotic genes

Glucocorticoids have previously have shown to decrease Type I collagen synthesis in vivo and in fibroblast cell culture. Several studies have demonstrated that glucocorticoids decrease Type I procollagen gene expression. These latter studies have included uridine incorporation into pro alpha 1 (I) and pro alpha 2 (I) mRNAs and nuclear run-off experiments. Using the ColCat 3.6 plasmid, which contains part of the 5' flanking region of the pro alpha 1 (I) collagen gene and the reporter gene, chloramphenicol acetyltransferase, the present studies demonstrate by stable transfection of fetal rat skin fibroblasts that dexamethasone down regulates the promoter activity of the pro alpha 1 (I) collagen gene. The glucocorticoid-mediated down-regulation of procollagen gene expression was demonstrated using the ColCat 3.6, 2.4, 1.7, or 0.9 plasmid. In addition, competitive oligonucleotide transfection experiments and site specific mutation of the glucocorticoid response element (GRE) in the whole ColCat 3.6 plasmid did not eliminate the effect. The possibility existed that another cis-element in the 5' flanking region of the pro alpha 1 (I) collagen gene was also required for the collagen glucocorticoid-mediated down-regulation of procollagen gene expression, since TGF-beta has been shown to stimulate in a decrease of transforming growth factor-beta (TGF-beta) secretion into the media. Gel mobility studies demonstrated that glucocorticoid treatment of rat skin fibroblasts decreased glucocorticoid receptor binding to the GRE and TGF-beta activator protein to the TGF-beta element which were brought back to control values by coordinate exogenous TGF-beta treatment. Thus the interaction of these TGF-beta molecules with cellular membrane receptors and subsequent transduction is dramatically decreased resulting in less signals to regulate collagen gene expression. These data indicate that glucocorticoids coordinately regulate procollagen gene expression through both the GRE and TGF-beta elements. Depression of procollagen gene expression by glucocorticoids through the TGF-beta element is mediated by decreased TGF-beta secretion, possibly involving a secondary effect on regulatory protein(s) encoded by noncollagenous protein gene(s). The present studies provide the basis for a novel mechanism of glucocorticoid-mediator regulation of eukaryotic genes containing the TGF-beta element.

Culture of urethral fibroblasts: cell morphology, proliferation and extracellular matrix synthesis

The in vitro morphology and proliferative activity of urethral fibroblasts were characterized from primary isolates of fetal bovine urethral spongiosum. Cells were identified as fibroblastic based on their spindle-shaped morphology and lack of expression of phenotypic markers characteristic of either urethral smooth muscle or epithelial cells. Urethral fibroblasts proliferated at a steady rate and did not exhibit contact-inhibition of growth in a culture medium of Medium 199 supplemented with 10% newborn calf serum. Both immunohistochemistry and metabolic labeling analyses of extracellular matrix synthesis demonstrated the presence of collagen types I and III, and fibronectin. Quantitation of the collagenous components of the cell medium revealed that urethral fibroblasts synthesize 85% type I collagen, 14% type III collagen and < 1% type V collagen. In contrast, the urethral fibroblast cell layer matrix consisted of 98% type I collagen, < 1% type III and < 1% type V collagen.

Alveolar type II cell-fibroblast interactions, synthesis and secretion of surfactant and type I collagen

During alveolar development and alveolar repair close contacts are established between fibroblasts and lung epithelial cells through gaps in the basement membrane. Using co-culture systems we have investigated whether these close contacts influence synthesis and secretion of the principal surfactant apoprotein (SP-A) by cultured rat lung alveolar type II cells and the synthesis and secretion of type I collagen by fibroblasts. The alveolar type II cells remained cuboidal and grew in colonies on fibroblast feeder layers and on Matrigel-coated cell culture inserts but were progressively more flattened on fixed fibroblast monolayers and plastic. Alveolar type II cells cultured on plastic released almost all their SP-A into the medium by 4 days. Alveolar type II cells cultured on viable fibroblasts or Matrigel-coated inserts above fibroblasts accumulated SP-A in the medium at a constant rate for the first 4 days, and probably recycle SP-A by endocytosis. The amount of mRNA for SP-A was very low after 4 days of culture of alveolar type II cells on plastic, Matrigel-coated inserts or fixed fibroblast monolayers: relatively, the amount of mRNA for SP-A was increased 4-fold after culture of alveolar type II cells on viable fibroblasts. Co-culture of alveolar type II cells with confluent human dermal fibroblasts stimulated by 2- to 3-fold the secretion of collagen type I into the culture medium, even after the fibroblasts' growth had been arrested with mitomycin C. Collagen secretion, by fibroblasts, also was stimulated 2-fold by conditioned medium from alveolar type II cells cultured on Matrigel. The amount of mRNA for type I collagen increased only modestly when fibroblasts were cultured in this conditioned medium. This stimulation of type I collagen secretion diminished as the conditioned medium was diluted out, but at high dilutions further stimulation occurred, indicating that a factor that inhibited collagen secretion also was being diluted out. The conditioned medium contained low levels of IGF-1 and the stimulation of type I collagen secretion was abolished when the conditioned medium was pre-incubated with antibodies to insulin-like growth factor 1 (IGF-1). There are important reciprocal interactions between alveolar type II cells and fibroblasts in co-culture. Direct contacts between alveolar type II cells and fibroblasts appear to have a trophic effect on cultured alveolar type II cells, increasing the levels of mRNA for SP-A. Rat lung alveolar type II cells appear to release a factor (possibly IGF-1) that stimulates type I collagen secretion by fibroblasts.

Bladder smooth muscle cells in culture: I. Identification and characterization

This report documents the growth and culture characteristics of human and fetal bovine bladder smooth muscle cells in vitro. Bladder smooth muscle cell strains have been identified by their spindle shaped morphology, noncontact inhibited growth characteristics and the expression of smooth muscle cell specific alpha-actin. Extracellular matrix protein biosynthesis by these cells in vitro has been characterized by metabolic labeling of proteins with [14C] radiolabeled proline and analysis by SDS gel electrophoresis. These studies demonstrate that bladder smooth muscle cells synthesize predominantly types I and III collagen, and fibronectin. In addition type III collagen exists in both a partially processed (pN alpha 1[III]) form and processed form. Complementary immunohistochemical studies show localization of type I, III, and IV collagens, and fibronectin to bladder smooth muscle cell extracellular matrix. We conclude that both fetal bovine and human smooth muscle bladder cells are capable of secreting the classic components of the surrounding connective tissue.

Polyinosinic-polycytidylic acid, an interferon inducer, ameliorates bleomycin-induced lung fibrosis in mice

The inhibitory effect of polyinosinic-polycytidylic acid (Poly IC), an inducer of interferons, on bleomycin-induced lung collagen accumulation was investigated in mice. Poly IC (10 mg/kg, intraperitoneally) or saline was given for 2 days and immediately prior to intratracheal instillation of bleomycin (0.125 units/mouse) or an equivalent volume of saline and thereafter daily for 13 days. Lung hydroxyproline levels in saline-saline (control), Poly IC-saline (Poly IC), bleomycin-saline and bleomycin-Poly IC groups averaged 279, 287, 459, and 358 micrograms/lung, respectively. The bleomycin + Poly IC mice had significantly less lung hydroxyproline than bleomycin mice, but significantly more hydroxyproline than control or Poly IC mice. Similarly, bleomycin + Poly IC mice had significantly less protein in bronchoalveolar lavage fluid (BALF) supernatant than bleomycin mice, but significantly more protein than control or Poly IC mice. Total cell counts for cells recovered from BALF showed significant increases of 174 and 167% in bleomycin and bleomycin + Poly IC as compared to controls, while the Poly IC group showed a significant decrease of 47% which was primarily due to a decrease in alveolar macrophages. The bleomycin group had significantly more neutrophils, monocytes, macrophages, and lymphocytes than control mice, while bleomycin + Poly IC mice lacked the significant increase in lymphocytes. Bleomycin + Poly IC mice had significantly more monocytes than the bleomycin group. All bleomycin-treated mice had lung lesions, but no lesions were observed in control or Poly IC mice. Bleomycin + Poly IC mice had significantly more (58%) lesions than bleomycin. In contrast, the volume of interstitial lesion in bleomycin + Poly IC mice showed significantly less extracellular fibers (decreased by 62%) and no difference in fibroblasts as compared to bleomycin mice. Fibrotic lesions in bleomycin mice were multifocal and varied from large areas of organized connective tissue to thickened septa lined by cuboidal epithelial cells. Interstitial lesions in bleomycin + Poly IC had a significantly greater volume of mononuclear phagocytes and lymphocytes, but less organized connective tissue than the bleomycin group. Poly IC treatment ameliorated bleomycin-induced lung collagen accumulation.

In vitro and in vivo induction of squamous cell carcinoma antigen (SCC) in a uterine cervical cancer cell line (SKG-IIIa) with peplomycin and sodium butyrate

In order to investigate the effect of an antisquamous cell carcinoma drug, peplomycin, the new analogue of bleomycin, on the production of a squamous cell carcinoma-associated tumor marker termed "SCC" (or TA-4), we carried out in vitro and in vivo experiments using the uterine cervical epidermoid cancer cell line SKG-IIIa, together with the investigation of the effect of sodium butyrate which was reported to be one of the representative gene modulators. In vitro production of SCC was biochemically and immunocytochemically confirmed in SKG-IIIa cells. Immunocytochemistry using anti-SCC antibody revealed that the total number of SCC-positive cells increased after the treatment with peplomycin (1.6 fold) or sodium butyrate (1.5 fold). The total amount of SCC in cultured medium, intracellular SCC, and cell debris during 5 days of culturation also increased with peplomycin (1.8 fold) and sodium butyrate (1.4 fold). These data strongly suggest that SCC production of SKG-IIIa cells is stimulated by peplomycin and sodium butyrate in vitro. In vivo experiments were also performed by administering peplomycin to nude rats with heterotransplanted tumors of SKG-IIIa, and transient elevations of serum SCC level (113% to 238% of the initial values) were observed, suggesting that SCC production of cancer cells is also stimulated by peplomycin in vivo.

Bleomycin: a pharmacologic tool in the study of the pathogenesis of interstitial pulmonary fibrosis

Bleomycin is a unique DNA-interactive antitumor agent that has become a popular tool in studies of the pathogenesis of interstitial pulmonary fibrosis. The biochemical and morphological changes seen in the lungs of many species after bleomycin simulate those seen in humans. The availability of these animal models of interstitial pulmonary fibrosis also provides the opportunity to investigate novel pharmacological approaches to preventing this disease.

Elevated pro alpha 2(I) collagen mRNA levels in cultured scleroderma fibroblasts result from an increased transcription rate of the corresponding gene

Fibroblasts cultured from affected and unaffected skin sites of three scleroderma patients were studied for the activation of type I collagen gene expression. Dot blot hybridizations with pro alpha 2(I) collagen specific cDNA probe revealed 2.9-4.8-fold increases in pro alpha 2(I) mRNA levels in the affected fibroblasts over the unaffected control cells. Transcription rate of the pro alpha 2(I) gene in the nuclei isolated from the same cells was 2.0-3.7-fold higher in the scleroderma fibroblasts than in the controls. The results show that scleroderma fibroblasts have undergone activation of collagen gene expression at the transcriptional level, which subsequently results in elevated procollagen mRNA levels, overproduction of collagen, and development of dermal fibrosis.

Bleomycin enhances the tyrosinase activity of human malignant melanoma cells in culture

By application of bleomycin fine pigmentations on basal cell layers will appear in irritated parts of the skin. Therefore we investigated the effect of bleomycin on the tyrosinase activity. Bleomycin was determined to exhibit a strong cytostatic activity on human melanoma cells in culture (ED50 concentration = 0.21 microgram/ml) whereas the viability of the cells was not affected. Incubation of pigmented human melanoma cells in the presence of bleomycin containing culture medium (1-100 ng/ml) at 37 degrees C for different periods of time resulted in a marked increase of tyrosinase activity. The level of enzyme activity reached 140% if the controls were set to 100%. Direct addition of bleomycin to the crude cell extract produced no detectable stimulatory effect. There were no significant stimulation if the cells were grown with bleomycin in serum-free culture medium. The serum content influences the activity of tyrosinase in a marked degree. The serum concentration for half-maximal stimulation of tyrosinase was calculated to be 14.2%. Furthermore the inflammatory mediator histamine was found to stimulate tyrosinase in melanoma cells. There were no additional stimulatory effect if cells were incubated in the presence of both histamine and bleomycin. These results suggest that bleomycin is able to enhance tyrosinase activity in intact cell systems. Further a possible role of serum and/or inflammatory factors in the stimulatory process must be considered.

Effects of intratracheal administration of bleomycin or saline in pair-fed and control-fed hamsters on daily food intake and on plasma levels of glucose, cortisol, and insulin, and lung levels of calmodulin, calcium, and collagen

In the present study, the effects of intratracheal administration of bleomycin have been examined on daily food intake and on plasma levels of glucose, cortisol, and insulin, and on lung levels of calmodulin, calcium, and collagen in hamsters. Since bleomycin treatment caused nutritional deficiency leading to loss of body weight, we have included pair-fed and control-fed as control groups in order to rule out the nutritional deficiency-related effects on these measurements. Bleomycin-treated animals showed a dramatic decrease in daily food intake and body weight as compared to control-fed animals. Bleomycin-treated animals were hyperglycemic when compared to nutritionally comparable pair-fed animals and had plasma glucose levels similar to those of control-fed animals. Plasma cortisol levels in bleomycin-treated and pair-fed animals showed a time-dependent increasing trend, whereas plasma insulin levels in both groups tended to decrease. The lung levels of calmodulin and calcium in bleomycin-treated animals were significantly increased when compared with the pair-fed or control-fed group. Bleomycin-treated animals had significantly higher levels of lung collagen than pair-fed or control-fed at 7 and 13 days after treatment. The lung collagen content in pair-fed animals was significantly less than that of control-fed at 13 days. It was concluded that a disturbance in carbohydrate metabolism and increased lung levels of calmodulin and calcium might be somehow involved in fibroproliferative changes of the lung in bleomycin-treated animals.

Activation of type I collagen genes in cultured scleroderma fibroblasts

Fibroblasts cultured from affected skin areas of five patients with cutaneous scleroderma were found to produce increased amounts of collagen when compared with nonaffected control cells. Total RNA was isolated from the cultures and analyzed for its level of pro alpha 1 (I)collagen mRNA by hybridization of RNA blots with a cloned cDNA probe. The levels of pro alpha 1 (I)collagen mRNAs relative to total RNA were two- to sixfold higher in the samples from affected cells, accounting for the increased synthesis of type I collagen. Cytoplasmic dot hybridizations were performed to measure the cellular content of pro alpha 1 (I)collagen mRNA: up to ninefold increases in the level of this mRNA per cell were found. Upon subculturing, scleroderma fibroblasts were found to reduce gradually the increased synthesis of collagen to the level of nonaffected controls by the tenth passage. The levels of type I collagen mRNAs were also reduced, but more slowly. The results suggest that in scleroderma fibroblasts the genes for type I collagen are activated at procollagen mRNA level or that they are more stable and that the activating factors are lost during prolonged cell culture because cells from affected areas lose their activated state.