Improved metabolic control in patients with non-insulin-dependent diabetes mellitus is associated with a slower accumulation of glycation products in collagen.

Twenty-one patients with non-insulin-dependent diabetes in poor metabolic control were subjected to intensified therapy, in most cases with insulin, to investigate whether it is possible to slow down the accumulation of advanced glycosylation end products of collagen by improving glycaemic control. Fasting and mean daily blood glucose, serum fructosamine and glycohaemoglobin levels, as well as glycation of collagen were measured before and after 1.5 years of intensified therapy. All these parameters except for fructosamine correlated significantly with fasting blood glucose and glycohaemoglobin when measured before the insulin therapy was started, when the patients had had poor but stable metabolic control for a long period of time. After 1.5 years of intensified therapy the level of glycation of collagen did not significantly correlate with the fasting blood glucose or glycohaemoglobin levels, suggesting that the non-enzymatic glycosylation of collagen reflects a longer period of metabolic control of diabetes than the glycohaemoglobin level. Intensified treatment improved previously poor metabolic control in patients with non-insulin-dependent diabetes, and this improvement was reflected in a decrease in fasting and mean daily blood glucose levels, serum fructosamine and glycohaemoglobin concentrations, and in the level of early products of glycation of collagen. The average content of advanced glycosylation end products of collagen, assayed in terms of collagen-linked fluorescence did not decrease. However, they accumulated more slowly in the patient tercile with the greatest decrease in the level of fasting blood glucose than in the tercile with the smallest decrease, and even a decrease in fluorescence was observed in the patients with the greatest improvement in the metabolic control.(ABSTRACT TRUNCATED AT 250 WORDS)

Interstitial collagenase is expressed by keratinocytes that are actively involved in reepithelialization in blistering skin disease.

Migrating keratinocytes actively involved in reepithelialization in dermal wounds acquire a collagenolytic phenotype upon contact with the dermal matrix. To determine whether this phenotype is associated with repair in other forms of wounds, we assessed collagenase expression in 50 specimens representing a variety of blistering skin diseases, including subtypes of epidermolysis bullosa, porphyria cutanea tarda, bullous pemphigoid, pemphigus, transient acantholytic dermatosis, and suction blisters. Distinct from that seen in chronic ulcers or in normal healing by second intention, reepithelialization in these blistering conditions was not necessarily associated with a complete loss of basement membrane, as determined by immunostaining for type IV collagen. Collagenase mRNA was detected in the basal keratinocytes of several specimens of epidermolysis bullosa simplex (six of 10) and of pemphigus (three of seven), as well as in one quarter of transient acantholytic dermatosis samples in the presence of an intact basement membrane. In contrast, three of nine porphyria cutanea tarda, one third of epidermolysis bullosa acquisita, and one of 10 bullous pemphigoid samples had collagenase-positive basal keratinocytes with the basement membrane disrupted. The collagenase-positive lesions generally represented older blisters with evidence of epithelial regeneration. Collagenase was also expressed in suction blisters at 2 and 5 d after induction of the blister, but was shut off when the epidermis had healed. Other metalloproteinases were expressed occasionally, if at all. Our results suggest that keratinocyte migration is associated with collagenase expression and that contact of keratinocytes with the dermal matrix is not necessarily needed for collagenase induction.

Effect of phenytoin and nifedipine on collagen gene expression in human gingival fibroblasts.

Phenytoin (PHT), a widely used anticonvulsant, and nifedipine (NF), an anti-anginal drug, cause clinically similar gingival overgrowths in some patients. The aim of this work was to investigate their effects on collagen and protein synthesis and cellular proliferation in normal human gingival fibroblasts in vitro. Gingival fibroblasts were cultured from biopsies taken from three healthy individuals during operations on maxillary canines and incubated with various concentrations of NF (100 and 200 ng/ml) and PHT (5 and 10 micrograms/ml) for up to 7 days. The results showed that NF and PHT have a specific effect in reducing total protein and collagen synthesis but do not influence cell proliferation in healthy gingival fibroblasts in vitro. In addition the level of mRNA for type I collagen was decreased after incubation of the cells with the drugs for 1 or 2 days. The decrease in the level of type I collagen mRNA seemed to be specific since the level of type IV collagenase mRNA used as a reference RNA did not decrease.

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.

Paraproteinemia in patients with scleredema. Clinical findings and serum effects on skin fibroblasts in vitro.

Four patients with paraproteinemia and scleredema were studied. Histologic features included marked thickening and fibrosis of the dermis and subcutis. Variable amounts of mucin deposits were detected in the interfibrillar spaces. Serum from one patient significantly stimulated collagen production in normal skin fibroblast cultures, whereas serum from another patient stimulated collagen production in autologous cell cultures. Moreover, serum from one patient stimulated the [35S]sulfate incorporation into the fibroblasts. Circulating serum factors, possibly related to the paraprotein, may enhance the synthesis of extracellular macromolecules by dermal fibroblasts in these patients, thus providing a mechanism for dermal fibrosis.

Demonstration of cellular retinoic acid binding protein (CRABP) in chick embryo tendon cells and effects of retinoids on collagen synthesis in tendon and sterna.

The binding of all-trans-retinoic acid (all-trans RA) to specific cytosol proteins and the effects of retinoids on procollagen synthesis were studied in chick-embryo tendon cells. For the receptor assay, tendon cytosols were incubated with [3H]all-trans-RA in the presence or absence of 100-fold excess of nonlabeled all-trans-RA up to 20 hr at +4 degrees and unbound retinoid was removed by charcoal-dextran treatment or by gel filtration chromatography. The results indicated that chick-embryo tendon cells contained cellular retinoic acid binding protein (CRABP). The binding of [3H]all-trans-RA could be displaced by 13-cis-retinoic acid, but not by retinol or etretinate. In contrast no CRABP could be found in cartilage cells isolated from sterna or in whole sterna. The treatment of tendon cytosol with proteases (pronase, trypsin, chymotrypsin) abolished the specific binding of [3H]all-trans-RA. Gel filtration studies on Sephadex G-100 indicated an apparent molecular weight of 14,500-15,000 daltons for the all-trans-retinoic acid binding protein. All-trans-RA markedly decreased procollagen synthesis in isolated chick-embryo tendon cells, the inhibition being concentration dependent; the decrease was about 58% of the control in the presence of 10(-5) M all-trans-RA. Similar decrease was noted with 13-cis-RA and etretinate, while retinol was less effective. In isolated cartilage cells the dose of 10(-5) M of all-trans-retinoic acid decreased drastically total protein and collagen synthesis. The mannosylation of procollagen, the conversion of procollagen to collagen and the size of procollagen chains were not significantly affected. The results of the present study indicate that CRABP is not expressed in sterna of chick-embryos, and in contrast high levels of CRABP could be found in tendons. However, retinoids modulated collagen synthesis in both tissues. Thus it is possible that retinoids can affect the metabolism of different collagen types also in clinical use.

Proteolytic enzymes in blister fluids from patients with dermatitis herpetiformis.

Proteolytic enzymes may be involved in blister formation in dermatitis herpetiformis (DH). We have examined collagenase, gelatinase and elastase-like enzyme activities in fluids collected from spontaneous blisters and from suction blisters raised on developing DH-lesions induced by application of potassium iodide. Control suction blisters were raised on unaffected DH-skin and on healthy volunteers. High enzyme activities were found in spontaneous blisters, and suction blister fluids obtained from developing lesions showed increased levels of gelatinase and elastase-like enzymes. Inhibitor studies revealed that a part of the elastase-like enzyme activity might be derived from inflammatory cells. Gel filtration chromatography disclosed two separate elastase-like enzymes which, as they had high molecular weights, could be either enzyme-inhibitor complexes or aggregates.

Glucocorticoid action on connective tissue: from molecular mechanisms to clinical practice.

Glucocorticosteroids are highly effective in treating various acute and chronic diseases, but their long-term use is often accompanied by side effects, such as osteoporosis of skeleton and bones and atrophy of the skin. Clinically, many of these side effects involve changes in connective tissue. Glucocorticoid effects on connective tissue metabolism are, however, sometimes beneficial for instance, in the treatment of keloids or autoimmune connective tissue diseases. Recent advances in the biochemical technology have provided tools to examine the molecular mechanisms by which glucocorticoids affect connective tissue. These studies have shown distinct alterations in the extracellular matrix as a result of glucocorticoid treatment. This knowledge is useful for the further development of glucocorticosteroids with desirable action spectrum and with minimal side effects.

Demonstration of cellular retinoic acid binding protein in cultured human skin fibroblasts.

Previous studies have indicated that retinoids, such as all-trans-retinoic acid and 13-cis-retinoic acid, can modulate connective tissue metabolism in human skin fibroblast cultures. Such effects could be mediated through binding of these retinoids to specific cellular binding proteins. In the present study we have demonstrated cellular retinoic acid binding protein using both whole cell and cytosol binding assays with [3H]all-trans-retinoic acid or [3H]13-cis-retinoic acid as the ligand. Specific binding of [3H]all-trans-retinoic acid could be demonstrated by both techniques and the binding could be displaced by unlabelled all-trans-retinoic acid and 13-cis-retinoic acid, but not by retinol or RO-10-9359 (etretinate) in a 100-fold excess. Gel filtration chromatography of the cytosol proteins after incubation with [3H]all-trans-retinoic acid demonstrated that the specific binding protein had an apparent molecular weight of approximately 15 000 daltons. Thus, the cellular retinoic acid binding protein demonstrated in human skin fibroblasts may mediate the effects of the retinoids on connective tissue metabolism in these cells.

Modulation of procollagen gene expression by retinoids. Inhibition of collagen production by retinoic acid accompanied by reduced type I procollagen messenger ribonucleic acid levels in human skin fibroblast cultures.

Recent clinical observations have suggested that retinoids, which are in frequent use in dermatology, can affect the connective tissue metabolism in skin and other tissues. In this study, we examined the effects of several retinoids on the metabolism of collagen by human skin fibroblasts in culture. Incubation of cultured fibroblasts with all-trans-retinoic acid or 13-cis-retinoic acid, in 10(-5) M or higher concentrations, markedly reduced the procollagen production, as measured by synthesis of radioactive hydroxyproline. The effect was selective in that little, if any, inhibition was noted in the incorporation of [3H]leucine into the noncollagenous proteins, when the cells were incubated with the retinoids in 10(-5) M concentration. Similar reduction in procollagen production was noted with retinol and retinal, whereas an aromatic analogue of retinoic acid ethyl ester (RO-10-9359) resulted in a slight increase in procollagen production in these cultures. The reduction in procollagen production by all-trans-retinoic acid was accompanied by a similar reduction in pro alpha 2(I) of type I procollagen specific messenger RNA (mRNA), as detected by dot blot and Northern blot hybridizations. Hybridizations with human fibronectin and beta-actin specific DNA probes indicated that the levels of the corresponding mRNAs were not affected by the retinoids, further suggesting selectivity in the inhibition of procollagen gene expression. Further control experiments indicated that all-trans-retinoic acid, under the culture conditions employed, did not affect the posttranslational hydroxylation of prolyl residues, the mannosylation of newly synthesized procollagen, the specific radioactivity of the intracellular prolyltransfer RNA pool, or DNA replication. All-trans-retinoic acid also elicited a reduction in trypsin-activatable collagenase, but not in the activity of prolyl hydroxylase or an elastaselike neutral protease in the fibroblast cultures. Incubation of three fibroblast lines established from human keloids with all-trans-retinoic acid or 13-cis-retinoic acid also resulted in a marked reduction in procollagen production. The results, therefore, suggest that further development of retinoids might provide a novel means of modulating collagen gene expression in patients with various diseases affecting the connective tissues.

Characterization and partial purification of a neutral protease from the serum of a patient with autosomal recessive pulmonary emphysema and cutis laxa.

Serum enzyme activity in 81 patients with various medical and dermatologic problems was determined with succinyl-(L-alanyl)3-p-nitroanilide as substrate. Values exceeding the limit of mean +/- 3 SD in healthy controls were detected in 16 patients. The highest activity, greater than 80 times the mean in the controls, was found in a 20-year-old patient with severe pulmonary emphysema and cutis laxa. The enzyme activity in the patient's serum was enhanced by Ca2+ and was inhibited by metal chelators but not by serine protease inhibitors. The pH optimum of the enzyme was 7.6. The enzyme was partially purified by gel filtration chromatography. Enzyme activity eluted in two major peaks with apparent molecular weights of greater than 10(7) daltons (peak I) and approximately 2.5 X 10(5) daltons (peak II). When compared with the elution patterns in the patient's mother and a healthy control, the elevated enzyme activity in the patient's serum was associated with peak I. The partially purified enzyme in peak I was not complexed with alpha 2-macroglobulin. The peak I enzyme was capable of degrading tropoelastin and a synthetic dinitrophenyl peptide at a glycyl-isoleucyl sequence, but not native or denatured collagen.

Retinoid modulation of connective tissue metabolism in keloid fibroblast cultures.

Recent observations have suggested that retinoids might affect the metabolism of the extracellular matrix of connective tissues. In this study, we examined the effects of tretinoin (all-trans-retinoic acid) and isotretinoin (13-cis-retinoic acid) on the production of procollagen in keloid fibroblast cultures that were characterized by enhanced procollagen synthesis in vitro. The activities of three enzymes relevant to connective tissue metabolism, prolyl hydroxylase, collagenase, and an elastaselike neutral protease were also determined. The results demonstrated that collagen production was markedly reduced in cultures treated with either one of the retinoids. The activity of prolyl hydroxylase, a key enzyme in the intracellular biosynthesis of collagen, was not affected, while the production of collagenase was markedly reduced by the retinoids. In contrast, the activity of an elastaselike neutral protease in the cell culture medium was markedly enhanced by both retinoids. The results, therefore, indicate a differential modulation of connective tissue metabolism by retinoids in keloid cell cultures.

Demonstration of elastin gene expression in human skin fibroblast cultures and reduced tropoelastin production by cells from a patient with atrophoderma.

Atrophoderma is a rare dermal disorder characterized by a patchy distribution of areas apparently devoid of elastic fibers. Skin fibroblast cultures were established from the normal and affected dermis of a patient with this disorder. Human tropoelastin was identified in culture medium by use of electroblotting and anti-elastin antisera. An enzyme-linked immunosorbent assay was used to establish that significantly less elastin accumulated in the media of cultured cells from lesional fibroblasts over a 3-d period. Since elastin biosynthesis in most tissues is under pretranslational control, molecular hybridization to a nick-translated genomic elastin probe was performed; however, elastin messenger RNA levels were equivalent in both cell strains. Both strains produced less elastin than did normal skin fibroblasts. Extracellular proteolysis of elastin was evaluated as a possible mechanism. Elastase activity was increased and porcine tropoelastin was degraded four times faster, on a per-cell basis, in lesional fibroblast cultures than in cells derived from an unaffected site. The two cell strains exhibited no significant differences in collagen production or collagenase activity. These results are the first demonstration of elastin production by cultured human skin fibroblasts, and they suggest that the primary defect in atrophoderma may be a result of enhanced degradation of newly synthesized elastin precursors.

Pharmacological inhibition of excessive collagen deposition in fibrotic diseases.

Excessive accumulation of collagen is a major pathological feature in diseases characterized by tissue fibrosis. Although several therapeutic approaches have been attempted in such patients, currently no treatment modality would specifically reduce collagen deposition in tissues. In this paper we discuss the mode of action of compounds that interfere with collagen production on the posttranslational level. First, structural analogs of proline, cis-4-hydroxy-L-proline and L-azetidine-2-carboxylic acid, which are incorporated into the newly synthesized polypeptides of procollagen during translation, prevent the polypeptides from folding into a stable triple-helical conformation. As a consequence, the nonhelical polypeptides are subject to degradation by proteases, thus leading to reduced deposition of collagen fibers. Second, several naturally occurring amino acids, polyamines, and their structural analogs prevent the removal of the carboxy-terminal extensions during the extracellular conversion of procollagen to collagen. Because the precursor molecules that contain the carboxy-terminal extensions are unable to assemble into functional fibers, collagen deposition is again reduced. Further development of these and related compounds, with appropriate tissue targeting, could potentially provide us with novel means to reduce the excessive deposition of collagen in fibrotic processes.

Anetoderma: biochemical and ultrastructural demonstration of an elastin defect in the skin of three patients.

Three patients with localized cutaneous lesions characteristic of anetoderma were studied. Clinically, the onset of the disease was between the ages of 17 and 25, and numerous flaccid, saclike skin lesions developed over several subsequent years. Histologically, the lesions were characterized by paucity and fragmentation of the elastic fibers. Electron microscopy demonstrated that the elastic fibers, both in papillary and deep reticular dermis in the lesional skin, were fragmented and irregular in appearance. The concentration of elastin, determined by a radioimmunoassay of desmosine, an elastin-specific cross-link compound, was markedly reduced in the lesions, as compared with unaffected skin from the same patients or with normal skin from unrelated control subjects. In contrast, the concentrations of hydroxyproline, an index of collagen, or deoxyribonucleic acid (DNA), a measure of cellularity, were not changed in the lesions. Thus, the results indicate that in the three patients studied, the elastic fibers are defective and reduced in quantity. These observations suggest that the deficiency of elastin in the dermis may lead to development of the cutaneous lesions of anetoderma.

Ultraviolet radiation-induced connective tissue changes in the skin of hairless mice.

Hairless mice (Skh/ hr1 ) were exposed to ultraviolet A (UVA; peak irradiance at 365 nm), or to ultraviolet B (UVB; peak irradiance at 313 nm) radiation. The animals received 12 treatments on alternate days. Connective tissue changes in the skin were monitored by assaying hydroxyproline and desmosine as an indication of collagen and elastin concentrations, respectively. The activities of prolyl hydroxylase and collagen glucosyl-transferase, enzymes participating in the biosynthesis of collagen, were also assayed. The concentration of elastin was significantly increased in mice treated with UVA or UVB. The concentration of collagen was unaffected by the treatments, but the activity of prolyl hydroxylase, reflecting collagen synthetic capacity, was decreased in UVA-treated mice. The collagen glucosyl-transferase activity was unchanged. Irradiation of purified human prolyl hydroxylase with UVA in vitro decreased the enzyme activity at higher doses, but UVB had no effect. The results indicate that definitive changes in the biochemistry of dermal connective tissues can be induced by exposure of mice to UV irradiation.

Demonstration of collagenase and elastase activities in the blister fluids from bullous skin diseases. Comparison between dermatitis herpetiformis and bullous pemphigoid.

We have investigated potential mechanisms for blister formation by assaying proteolytic enzymes in the blister fluids of patients with various bullous diseases. Blister fluids were obtained from patients with dermatitis herpetiformis (DH), bullous pemphigoid (BP), chronic bullous disease of childhood (CBDC), and pemphigus vulgaris (PV). The cells were recovered by centrifugation, and the supernatants as well as the cell pellets were assayed first for collagenase activity using [3H]proline-labeled type I collagen as substrate. Collagenase activity could be detected in most cases with DH, BP, and CBDC, while no activity was found in 2 cases of PV or in 5 control blister fluids obtained from suction blisters induced in healthy control subjects. Elastase activity was assayed in the same blister fluids by using a synthetic substrate succinyl-(L-alanyl)3-paranitroanilide or soluble [14C]valine-labeled tropoelastin. High levels of elastase activity were present in all DH patients, while lower, but clearly detectable, levels were found in BP, CBDC, and PV. The enzyme activity in BP was inhibited by Na2EDTA, but not by phenylmethylsulfonyl fluoride (PMSF), and Ca2+ stimulated the activity, suggesting that the enzyme in BP was a metalloproteinase. In cell-free supernatants of the DH blister fluids, the elastase activity was markedly decreased by PMSF, indicating that most of the enzyme activity was due to a serine protease. The cells recovered from DH blister fluids also contained high levels of elastase activity which could be inhibited by PMSF but not by Na2EDTA. Thus, in DH, the elastase activity is probably derived from polymorphonuclear leukocytes abundantly present in the lesions. The results indicate that active proteases are present in the blister fluids of skin diseases, and they may play a mechanistic role in the blister formation by degrading connective tissue components of the dermis and the dermal-epidermal junction.