Glucocorticoid-mediated selective reduction of functioning collagen messenger ribonucleic acid

Severe Hypokalaemia, Hypertension, and Intestinal Perforation in Ectopic Adrenocorticotropic Hormone Syndrome

Ectopic adrenocorticotropic hormone (ACTH) syndrome is a rare cause of the Cushing's syndrome. The occurrence of the ectopic ACTH syndrome presenting with severe hypokalaemia, metabolic alkalosis, and hypertension has been highlighted in case reports. However, presentation with lower gastrointestinal perforation is not known. We report the case of a 70-year-old male patient with severe hypokalaemia, metabolic alkalosis, hypertension, and colonic perforation as manifestations of an ACTH-secreting small cell lung carcinoma. Ectopic ACTH syndrome should be kept in mind as a cause of hypokalaemia, hypertension, and intestinal perforation in patients with lung carcinoma.

Effect of cortisol on the proliferation and protein synthesis of human aortic smooth muscle cells in culture

The synthesis of collagen (measured as the formation of non-dialyzable hydroxyproline) and other proteins, and the activity of lysyl oxidase, the enzyme responsible for the formation of cross-links in elastin and collagen, were measured in cultured human aortic smooth muscle cells in the presence of various cortisol concentrations. In addition, the effect of cortisol on the proliferation of the cells was also studied. At concentrations of 10(-6) M and greater, cortisol retarded cell growth markedly, as judged by decreased incorporation of 3H-thymidine by the cells and decreased DNA content of the cultures. At the same concentrations, cortisol increased the synthesis of collagen and other proteins. The magnitude of the increase was similar for collagen and other proteins. The activity of lysyl oxidase was also increased in the presence of 10(-6) and 10(-5) M cortisol, but to a lesser extent than the synthesis of collagen. Other studies using cultured cells have shown that cortisol decreases the synthesis of hyaluronic acid but not of sulphated glycosaminoglycans by smooth muscle cells and does not injure endothelial cells. Considering these findings in the light of the present results, it is suggested that cortisol induces changes in the metabolism of connective tissue macromolecules of smooth muscle cells that can be regarded as atherogenic. However, some other important biological changes associated with atherogenesis (smooth muscle cell proliferation and endothelial injury) do not occur in vascular cells exposed to cortisol.

How do glucocorticoids compare to oligo decoys as inhibitors of collagen synthesis and potential toxicity of these therapeutics?

This article demonstrates how glucocorticoids decrease collagen synthesis. The parameters used to assess procollagen synthesis in our laboratory will be compared to those used by others. This article will note all the pertinent literature on the molecular mechanisms of this down regulation of procollagen synthesis. For example, what are the effects of glucocorticoids at the levels of transcription and translation of collagen mRNAs? Finally, we will define a molecular mechanism to inhibit Type I collagen synthesis by decreasing the binding of the TGF-beta activator protein complex to the TGF-beta element in the distal promoter of the proalpha1 Type I collagen gene, preventing the 2:1 ratio of alpha1 to alpha2 chains in the processed Type I collagen molecule. We will next ask "How do sense oligo decoys decrease Type I collagen synthesis at the in vivo and at the cell levels?" In primary fibrotic cell culture, the double-stranded phosphorothioate oligodeoxynucleotide decoys were more effective than their sense single-stranded counterparts. The molecular mechanism for the decrease in Type I collagen synthesis is the same as glucocorticoids, that is by decreasing the binding of the TGF-beta activator protein complex to the TGF-beta element in the distal promoter of the proalpha1 Type I collagen gene for the transcription of the proalpha1 mRNAs. The reason for using sense oligo decoys as anti-fibrotic agents as compared to the anti-fibrotic glucocorticoids, is that presently marketed and FDA approved glucocorticoids have many untoward side effects which the sense oligo decoys do not have.

Cutaneous manifestations of endocrine disorders: a guide for dermatologists

Dermatologists may commonly see skin lesions that reflect an underlying endocrine disorder. Identifying the endocrinopathy is very important, so that patients can receive corrective rather than symptomatic treatment. Skin diseases with underlying endocrine pathology include: thyrotoxicosis; hypothyroidism; Cushing syndrome; Addison disease; acromegaly; hyperandrogenism; hypopituitarism; primary hyperparathyroidism; hypoparathyroidism; pseudohypoparathyroidism and manifestations of diabetes mellitus. Thyrotoxicosis may lead to multiple cutaneous manifestations, including hair loss, pretibial myxedema, onycholysis and acropachy. In patients with hypothyroidism, there is hair loss, the skin is cold and pale, with myxedematous changes, mainly in the hands and in the periorbital region. The striking features of Cushing syndrome are centripetal obesity, moon facies, buffalo hump, supraclavicular fat pads, and abdominal striae. In Addison disease, the skin is hyperpigmented, mostly on the face, neck and back of the hands. Virtually all patients with acromegaly have acral and soft tissue overgrowth, with characteristic findings, like macrognathia and enlarged hands and feet. The skin is thickened, and facial features are coarser. Conditions leading to hyperandrogenism in females present as acne, hirsutism and signs of virilization (temporal balding, clitoromegaly).A prominent feature of hypopituitarism is a pallor of the skin with a yellowish tinge. The skin is also thinner, resulting in fine wrinkling around the eyes and mouth, making the patient look older. Primary hyperparathyroidism is rarely associated with pruritus and chronic urticaria. In hypoparathyroidism, the skin is dry, scaly and puffy. Nails become brittle and hair is coarse and sparse. Pseudohypoparathyroidism may have a special somatic phenotype known as Albright osteodystrophy. This consists of short stature, short neck, brachydactyly and subcutaneous calcifications. Some of the cutaneous manifestations of diabetes mellitus include necrobiosis lipoidica diabeticorum, diabetic dermopathy, scleredema adultorum and acanthosis nigricans.

Pharmacotherapy and airway remodelling in asthma?

Over the last few decades attention has largely focused on airway inflammation in asthma, but more recently it has been appreciated that there are important structural airway changes which have been grouped together under the term "airway remodelling". It is only now that questions have been asked about the impact of treatment on these structural changes. This review examines the nature of these structural airway changes, the mechanisms of their generation, their potential consequences, and what is known about the ability of anti-asthma treatments to modulate these changes.

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.

Fibrous invasive (Riedel's) thyroiditis with critical response to steroid treatment

The Riedel's thyroiditis is an uncommon form of chronic thyroiditis characterized by an invasive fibrosclerosis of the gland, often involving the surrounding tissues. Usually, the only possible treatment is the surgical decompression of the tissues. We describe a case of aggressive Riedel's thyroiditis with severe compression and dislocation of trachea and esophagus. The surgical approach was uneffective, while an "ex juvantibus" steroid treatment, resulted in a dramatic regression of fibrosclerosis and a complete clinical remission. This report points out the possible effectiveness of corticosteroids in the treatment of selective disorders involving increased fibrogenesis.

Glucocorticoid-induced down regulation of transforming growth factor-beta 1 in adult rat lung fibroblasts

Transforming growth factor-beta 1 mRNA and transforming growth factor beta activity are decreased with exposure of normal adult rat lung fibroblasts to dexamethasone. Dexamethasone caused a decrease in transforming growth factor-beta 1 mRNA within 2 hours, which was sustained at least over a 24-hour period. The decrease in transforming growth factor-beta 1 mRNA was dose related. Dexamethasone treatment of rat lung fibroblasts also resulted in a decrease of transforming growth factor beta activity as determined by the mink lung cell growth inhibition assay. These data indicate that glucocorticoids may regulate collagen synthesis at least in part through the mediation of transforming growth factor-beta 1 in rat lung fibroblasts.

Induction of unilateral pulmonary fibrosis in the rat by cadmium chloride

Intralobar instillation of cadmium chloride (CdCl2) into the left lungs of rats initiated a sequence of events that culminated in massive unilateral intraluminal fibrosis. Early events (days 1 and 2) after CdCl2 administration included infiltration of the treated lung with polymorphonuclear leukocytes, an increase in the number of alveolar macrophages, activation of the macrophages as assessed by the induction of cathepsin L mRNA, and the induction in liver of mRNA for the acute-phase response protein, alpha 1-acid glycoprotein. By days 5 to 7 in the treated lungs, mRNA for procollagen alpha 1(I) increased 20- to 60-fold, and mRNA for procollagen alpha 1(III) increased 4- to 14-fold. These increases were correlated with the almost complete filling of the alveolar spaces with fibroblasts and collagen. The contralateral lung exhibited no significant change in histology but showed a similar induction of collagen gene expression. These increases were tissue-specific, as the livers of these animals showed no change from the control levels of collagen gene expression. Procollagen messages in the treated and contralateral lungs were equally competent for translation into pro-alpha 1(I) and pro-alpha 2(I) polypeptides. Both the treated and contralateral lungs increased hydroxyproline content about 1.5- to 2-fold over 14 days. The contralateral lung, but not the treated lung, showed a 2-fold increase in lung volume. As a result, the collagen density (mg collagen/ml lung volume) doubled in the treated lung but remained constant in the contralateral lung. These data indicate that CdCl2 caused a rapid induction of pulmonary fibrosis in the treated lungs of rats and stimulated histologically normal growth of the contralateral lung.

Modulation of collagen metabolism by glucocorticoids. Receptor-mediated effects of dexamethasone on collagen biosynthesis in chick embryo fibroblasts and chondrocytes

The steroid modulation of collagen metabolism was studied by injecting chick embryos with dexamethasone in vivo, and collagen synthesis was subsequently assayed by pulse-labeling the tissue with [14C]proline in vitro. The synthesis of [14C]hydroxyproline in tendons and sterna from chick embryos treated with dexamethasone was markedly reduced as compared with untreated controls. The inhibition of [3H]hydroxyproline synthesis was accompanied by a similar reduction in type I and II procollagen mRNA levels, as detected by Northern blot and dot blot hybridizations with chick pro alpha 1(I), pro alpha 2(I) and pro alpha 1(II) sequence specific cDNAs. The reduction in type II procollagen mRNA level was shown to be dose dependent. Control experiments indicated that the post-translational hydroxylation of prolyl residues was only slightly decreased in dexamethasone treated animals, and that the specific activity of the intracellular free proline pool and the intracellular degradation of collagen were unchanged. To address the mechanisms of the inhibition of collagen biosynthesis, specific binding of dexamethasone to glucocorticoid receptors in chick embryo tendon and cartilage cells was studied in a whole cell assay using [3H]dexamethasone as the ligand. Matrix-free tendon and cartilage cells had approximately 19,000 and 15,000 receptor sites per cell, respectively, and the binding affinities (Kd) for dexamethasone in tendon and cartilage cells were 2.9 x 10(-9) and 2.3 x 10(-9) M. Comparable values were obtained using a cytosol binding assay. The nuclear binding of dexamethasone in tendon and cartilage cells were similar. The results suggest that the dexamethasone-induced inhibition of collagen production is primarily due to decreased levels of functional procollagen mRNA, possibly resulting from receptor-mediated inhibition of the gene expression on the transcriptional level.

The histological effects on the guinea pig external ear of several constituents of commonly used aural preparations

Medicament contact dermatitis can be troublesome in external ear disease. In this work the effects on the guinea pig external ear of instillation twice daily for 3 weeks of benzalkonium chloride, Cerumol, gentamicin, the pharmaceutical base for Gentisone HC, hydrocortisone and propylene glycol were studied using light microscopy, thickness measurements of tympanic membrane and meatal epidermis, and the mitotic index of meatal epidermis. Benzalkonium chloride induced severe inflammatory changes and markedly increased the thickness measurements and meatal mitotic index. Cerumol also increased the thickness measurements and the mitotic index; there was additionally low grade chronic inflammation in the dermis. Prophylene glycol increased the mitotic index and thickness measurements though no signs of inflammation were seen. Other compounds did not produce significant changes except that hydrocortisone reduced the mitotic index. Contact dermatitis to benzalkonium chloride may be important in persistent ear disease. Cerumenolytic agents ought not to be used for prolonged periods or as prophylaxis.

The effect of Otosporin and Gentisone HC on the mitotic index and thickness of the tympanic membrane and meatal skin in the guinea pig

Otosporin and Gentisone HC ear drops were inserted twice daily for 3 weeks into the external auditory meatuses of guinea pigs. An intraperitoneal injection of vincristine (1 mg/kg.) was given to each animal three hours before it was killed. Temporal bones and attached external auditory meatuses were dissected, tissues were fixed in 10 per cent buffered formalin, decalcified in EDTA, and embedded in JB4 plastic for sectioning at 4 micron. The proliferative activity in the epidermis of the bony meatus and in the lateral surface of the tympanic membrane was obtained by deriving the mitotic indices. After both types of ear drops there was a statistically significant reduction in mitotic indices, the values being about half the control values. The proliferative activity in the tympanic membrane was too low to permit statistical analysis, but no differences were apparent between the groups. The thicknesses of the epidermis and dermis of the bony canal, and of the tympanic membrane, were measured using a Kontron MOP-AMO3 analyser. Although the dermis was thinner as a result of the administration of ear drops, both the epidermis of the bony meatus and that of the tympanic membrane were thicker, all these changes being statistically significant.

Age differences in the effect of hydrocortisone on the synthesis of insoluble elastin in aortic tissue of growing chicks

Glucocorticoids have been shown by others to increase the synthesis of elastin both in aortic tissue of embryo chicks and in cells derived from fetal ligamentum nuchae. This report describes the effects of hydrocortisone on the production of elastin in aortic tissue of developing chick embryos and chicks. While the effect of hydrocortisone on elastin synthesis is stimulatory in the 14 day chick embryo and the day-old chick, the same dose of this glucocorticoid has no effect on elastin production in the 7 day old chick and significantly inhibits synthesis of elastin in the 14 day old chick. These age-related alterations in elastin production in response to hydrocortisone cannot be attributed to an effect of the steroid on the pool size of the radioactively labelled amino acid used to measure elastin synthesis.

Bleomycin selectively elevates mRNA levels for procollagen and fibronectin following acute lung injury

We employed the technique of dot blot hydridization of radiolabeled cDNA probes to examine the role of specific mRNA content in the control of extracellular matrix turnover in the remodeling rat lung. Following bleomycin instillation, total RNA content gradually doubled during the first 5 days following the initial lung injury, then rose much more rapidly during the ensuing 9 days. Individual mRNAs for procollagens I and III and for fibronectin were selectively enriched 2- to 4-fold above total RNA during the first week after bleomycin instillation. No comparable increases were observed in specific RNAs from liver, indicating that the response observed in the lung was not generalized to other organs. Moreover, the increases in mRNA species for procollagen types I or III in the lung could not be related to the influx of inflammatory cells which migrate into the lungs during acute injury, as cells obtained by alveolar lavage contained no mRNAs for procollagens.

Glucocorticoid modulation of collagenase expression in human skin fibroblast cultures. Evidence for pre-translational inhibition

Glucocorticoids inhibit collagenase accumulation in the medium of human skin explant cultures. To examine the mechanism for this process, skin fibroblasts were placed in serum-free medium containing various steroids. Dexamethasone produced a dose-dependent inhibition of trypsin-activatable collagenase in the culture medium with maximal inhibition of approx. 85% at 10(-6) M. Dexamethasone failed to inhibit collagenase activity directly. The decrease in activity in the medium was paralleled by a decrease in immunoreactive protein, suggesting inhibition of enzyme synthesis. The specificity of the effect was shown in two ways. At 10(-6) M steroid, only dexamethasone and hydrocortisone were inhibitory; estradiol, progesterone and testosterone produced less than 10% inhibition. In biosynthetic studies, exposure to 10(-7) M dexamethasone for 24 h produced approx. 50% inhibition of collagenase synthesis but caused no greater than 10% inhibition of total protein synthesis. The T1/2 for achieving the effect was approx. 16 h after initial exposure to dexamethasone. These kinetics were parallel to the inhibition caused by actinomycin D and cordycepin, two inhibitors of transcription, but were longer than that caused by cycloheximide (T 1/2 less than 3 h). To examine this process, cells were cultured in the presence or absence of 10(-6) M dexamethasone prior to harvesting mRNA for cell-free translation. In each case the inhibition or enzyme activity in the intact cells was paralleled by a reduction in translatable collagenase mRNA from the same cells. At the same time, there was no significant inhibition of total protein translation by the steroid. These data suggest that glucocorticoids regulate collagenase synthesis at a pre-translational level, possibly through inhibition of transcription.

Dexamethasone inhibits alpha-fetoprotein gene transcription in neonatal rat liver and isolated nuclei

The effect of dexamethasone on rat alpha-fetoprotein (AFP) expression has been further examined. Quantitation of serum AFP levels from newborns treated with dexamethasone showed a dose-response relationship between the quantity of dexamethasone administered and the reduction in AFP serum level. RNA blots, utilizing cloned AFP cDNA as probe, showed a marked reduction in AFP mRNA in dexamethasone treated livers. The extent of AFP mRNA depletion was correlated with dexamethasone dosage. The effect of dexamethasone on AFP mRNA concentration was relatively rapid; a substantial reduction occurred 12 hours after a single injection. The effect of dexamethasone appeared to be irreversible as hormone withdrawal did not cause AFP mRNA levels to rise. One putative AFP nuclear RNA precursor was identified which rapidly disappeared following dexamethasone treatment. AFP mRNA synthesis was also diminished in nuclei transcribed in vitro. The direct inhibitory effect of glucocorticoid hormone on AFP gene transcription was demonstrated in a reconstituted cell-free nuclear system.

Modulation of glucocorticoid receptor activity by cyclic nucleotides and its implications on the regulation of human skin fibroblast growth and protein synthesis

The modulation of glucocorticoid receptor activity by cyclic nucleotides was studied in cultured human skin fibroblasts. The receptors appeared to be activated in the presence of dibutyryl-cAMP and inactivated by dibutyryl-cGMP. Significantly, the cGMP content of the fibroblasts increased during cell growth, with a concomitant decrease in the glucocorticoid receptor activity, while when the cells reached early confluency the decrease in cGMP content was accompanied by an increase in cAMP and increased activity of the glucocorticoid receptors. In addition, cortisol induced (2'-5')oligoadenylate synthetase in these cells and raised the cellular (2'-5')oligoadenylate concentrations. This resulted in a decrease in both DNA and protein synthesis activity in the cells, a response which correlated with the (2'-5')oligoadenylate concentration. The combination of cortisol and dibutyryl-cAMP had a synergetic stimulatory effect on the (2'-5')oligoadenylate concentration and a synergetic inhibitory effect on protein synthesis. In conclusion, it is demonstrated here that cyclic nucleotides can modulate glucocorticoid receptor activity in cultured human skin fibroblasts, and thus these compounds may indirectly affect cellular metabolism by regulating the cellular responses to glucocorticoids.

Glucocorticoids stimulate collagen and noncollagen protein synthesis in cultured vascular smooth muscle cells

The effect of glucocorticoids on collagen synthesis was examined in cultured bovine aortic smooth muscle (BASM) cells. BASM cells treated with 0.1 microM dexamethasone during their proliferative phase (11 d) were labeled with [3H]proline for 24 h, and the acid-precipitable material was incubated with bacterial collagenase. Dexamethasone produced an approximate twofold increase in the incorporation of proline into collagenase-digestible protein (CDP) and noncollagen protein (NCP) in the cell layer and medium. The stimulation was present in both primary mass cultures and cloned BASM. An increase in CDP and NCP was detected at 0.1 nM, while maximal stimulation occurred at 0.1 microM. Only cells exposed to dexamethasone during their log phase of growth (1-6 d after plating) showed the increase in CDP and NCP when labeled 11 d after plating. The stimulatory effect was observed in BASM cells treated with the natural bovine glucocorticoid, cortisol, dexamethasone, and testosterone, but was absent in cells treated with aldosterone, corticosterone, cholesterol, 17 beta-estradiol, and progesterone. The increase in CDP and NCP was absent in cells treated with the inactive glucocorticoid, epicortisol, and totally abolished by the antagonist, 17 alpha-hydroxyprogesterone, suggesting that the response was mediated by specific cytoplasmic glucocorticoid receptors. Dexamethasone-treated BASM cells showed a 4.5-fold increase in the specific activity of intracellular proline, which was the result of a twofold increase in the uptake of proline and depletion of the total proline pool. After normalizing for specific activity, dexamethasone produced a 2.4- and 2.8-fold increase in the rate of collagen and NCP synthesis, respectively. Cells treated with dexamethasone secreted 1.7-fold more collagen protein in 24 h compared to control cultures. The BASM cells secreted 70% Type I and 30% Type III collagen into the media as assessed by two-dimensional gel electrophoresis. The ratio of these two types was not altered by dexamethasone. The results of the present study demonstrate that glucocorticoids can act directly on vascular smooth muscle cells to increase the synthesis and secretion of collagen and NCP.

Bullous dermatosis caused by Staphylococcus aureus in locus minoris resistentiae

A case of Staphylococcus aureus--induced bullous dermatosis limited to the sites of glucocorticosteroid-induced striae atrophicae is described. Skin with compromised mechanical integrity may be more susceptible to disruption by invasion of bacteria and/or by their exotoxin. The pathogenesis of striae atrophicae and the mechanism of blister formation by S. aureus are reviewed in an effort to relate these two phenomena.

Cortisol decreases the cellular concentration of translatable procollagen mRNA species in cultured human skin fibroblasts

The effect of cortisol on the cellular concentration of translatable procollagen mRNAs was studied in cultured human skin fibroblasts. Cortisol selectively decreased the amount of procollagen mRNAs, in comparison to the total mRNA activity, when the cells were grown in enriched medium conditions, i.e., with 10% newborn calf serum. The selective decrease was first observed after 6 h exposure to 1 microM cortisol. In depleted medium conditions, i.e., with 2% newborn calf serum, the initial response was a stimulatory one, followed after about 12 h by a decrease in the procollagen mRNA activity. The results suggest that the selective inhibitory effect of cortisol on the cellular concentration of translatable procollagen mRNA species needs an optimal serum concentration. Furthermore, the results give support to the hypothesis that the decrease in the procollagen mRNA concentration after cortisol administration is a secondary response, preceded by the induction of some intracellular regulation system.

A local potent glucocorticosteroid decreases the induction of galactosylhydroxylysyl glucosyltransferase in suction blisters but has no effect on basement membrane structures

The effects of local glucocorticosteroid treatment on collagen biosynthesis and basement membrane components were studied in suction blisters in human abdominal skin. Pretreatment with clobetasol-17-propionate, applied three times a day for 4 days, did not affect the activity of galactosylhydroxylysyl glucosyltransferase (GGT) in fresh blisters but post-blistering treatment for 3 days with the steroid markedly inhibited the increase of this enzyme activity during the initial phases of re-epithelialization. The GGT activity was over 50% lower in steroid-treated blisters compared with control values. Protein concentrations and blister fluid volumes were also significantly decreased in healing 3-day blisters after steroid treatment. These results suggest that local glucocorticosteroid decreases either the synthesis of GGT or its release from the tissue into the blister fluid. The treatment did not affect the blister histology nor the early process of re-epithelialization. Immunohistochemically, type IV and V collagens and laminin of the basement membrane zone were similarly located in blisters of steroid-treated and placebo-treated skin, suggesting that local glucocorticosteroid does not affect the integrity of the basement membrane.

Selective inhibition of collagen biosynthesis in the dental pulps of glucocorticoid-treated rabbits

Prednisolone (2 mg/kg) was injected daily for 14 days. Collagen and protein biosynthesis were measured in isolated molar and incisor pulps by the incorporation of [14C]-proline into protein and collagen in vitro. Collagen solubility, free proline content, prolyl hydroxylase activity, collagenolytic activity and DNA and RNA contents were also assayed. Rabbits injected with saline or starved served as controls. Collagen synthesis was inhibited selectively in both prednisolone and starvation groups. No other aspect of collagen and protein metabolism was affected by either prednisolone treatment or starvation. Thus glucocorticoid administration reduces collagen formation in the pulp, resembling the anti-anabolic effect of starvation. Glucocorticoid treatment at high daily dosages, therefore, may disturb normal development and metabolism of teeth.

Regulation of collagen synthesis

Collagen synthesis is a complex orchestration of intracellular and extracellular events. In addition to synthesis of the polypeptide chains more than a dozen modifications of the molecule occur; most of these are enzymatic and specific for collagen. Regulational control of collagen synthesis promises to be equally complex. Examples are described to 4 specific regulatory influences. Ascorbic acid markedly stimulates collagen synthesis without affecting synthesis of other proteins. This effect appears to be unrelated to its cofactor roles for hydroxylation of lysine and proline. Glucocorticoids at microM concentration specifically inhibit collagen synthesis. Tissues treated with glucocorticoids have diminished levels of mRNA for collagen. During collagen synthesis the aminoterminal propeptide of procollagen is cleaved by a specific protease. This peptide appears to be a feedback inhibitor of collagen synthesis. This effect can be demonstrated in cells and in cell-free synthesizing systems. A membrane receptor system may permit the peptide to be recognized and subsequently act as a translational control mechanism. Viral transformation of fibroblasts results in selectively decreased synthesis of collagen. Levels of cytoplasmic and nuclear mRNA are likewise selectively diminished consistent with transcriptional control.