Inhibitory effect of the angiotensin converting enzyme inhibitors captopril and enalapril on the conversion of procollagen to collagen.

OBJECTIVE AND DESIGN: Angiotensin converting enzyme inhibitors are reported to inhibit the collagen accumulation involved in left ventricular hypertrophy. We tested the effect of captopril and enalapril on the conversion of procollagen to collagen in short-term tissue cultures in order to study the possible mechanisms by which the antifibrotic effect of this group of inhibitors takes place. METHODS: We employed short-term cartilage and tendon tissue cultures to monitor the conversion of procollagen to collagen. After pulse-labelling with [14C]-proline, the cultures were incubated further with the test compounds in different concentrations for a 180 min chase period. The reaction was stopped and radioactive collagenous peptides were analysed by gel electrophoresis. The amounts of collagenous proalpha and alpha chains were estimated, and the inhibition of procollagen to collagen conversion was calculated relative to 0 min control (100% inhibition) and 180 min control (0% inhibition) samples. RESULTS: Inhibition (50%) was obtained with 7 mmol/l captopril and 22 mmol/l enalapril in the cartilage cultures. Both compounds seemed to inhibit the conversion in clearly lower concentrations in tendon cultures, 4 mmol/l and 7 mmol/l, respectively, were sufficient for 50% inhibition. Angiotensin I, II, saralasin and bradykinin did not have any effect on conversion at 3.5, 9, 2 and 4 mmol/l concentrations, respectively. CONCLUSION: The peptidase inhibitors captopril and enalapril are able to inhibit the conversion of procollagen to collagen, which is a proteolytic process, possibly by inhibiting the specific procollagen proteases. Whether this phenomenon is involved in the antifibrotic property of angiotensin converting enzyme inhibitors warrants further study, as does the question of whether new antifibrotic agents could be developed on this basis.

Carboxyterminal propeptide of type I procollagen in ELF: elevation in asbestosis, but not in pleural plaque disease.

Markers of collagen metabolism may possibly be used in the assessment of pulmonary involvement in asbestosis-related pulmonary diseases. In this study the levels of the carboxyterminal propeptide of type I procollagen (PICP) and the aminoterminal propeptide of type III procollagen (PIIINP) were evaluated in bronchoalveolar lavage fluid (BALF), epithelial lining fluid (ELF) and serum from patients with asbestos related pulmonary and pleural involvement. Forty-two consecutive patients with occupational exposure to asbestos fibres, who underwent bronchoscopy and bronchoalveolar lavage (BAL) at the time of the diagnosis were investigated. Five patients were diagnosed as having asbestosis, while 37 showed no parenchymal involvement. Of the latter group, 25 had pleural plaques, while 12 had no detectable changes in chest radiographs. The patients were followed-up for an average of 7 yrs. The PICP in BALF and ELF was detectable in all patients with asbestosis and in 8/37 subjects without parenchymal involvement. The levels of PICP in BALF and ELF were significantly higher in the asbestosis group compared to the patients without asbestosis (9.8+/-1.8 microg x L(-1) versus 0.6+/-1.3 microg x L(-1), p<0.001 and 488.9+/-208.8 microg x L(-1) versus 22.6+/-50.6 microg x L(-1), p<0.001, respectively). Only 1 patient with asbestosis and 3 patients without parenchymal involvement had detectable levels of PIIINP in BALF. The serum levels of PICP and PIIINP did not differ between the patients with asbestosis and those with exposure to asbestos fibres without asbestosis and were within the normal range. None of the 37 patients exposed to asbestos fibres without parenchymal involvement at the baseline developed asbestosis during the follow-up period of 7 yrs. In conclusion, the data show that the carboxyterminal propeptide of procollagen type I, but not the aminoterminal propeptide of type III procollagen is highly elevated in bronchoalveolar lavage fluid and epithelial lining fluid in patients with asbestosis, but not in those without parenchymal involvement. This suggests that the determination of carboxyterminal propeptide of procollagen type I in bronchoalveolar lavage fluid could be used as a marker of parenchymal involvement in patients exposed to asbestos fibres.

An allele of COL9A2 associated with intervertebral disc disease.

Intervertebral disc disease is one of the most common musculoskeletal disorders. A number of environmental and anthropometric risk factors may contribute to it, and recent reports have suggested the importance of genetic factors as well. The COL9A2 gene, which codes for one of the polypeptide chains of collagen IX that is expressed in the intervertebral disc, was screened for sequence variations in individuals with intervertebral disc disease. The analysis identified a putative disease-causing sequence variation that converted a codon for glutamine to one for tryptophan in six out of the 157 individuals but in none of 174 controls. The tryptophan allele cosegregated with the disease phenotype in the four families studied, giving a lod score (logarithm of odds ratio) for linkage of 4.5, and subsequent linkage disequilibrium analysis conditional on linkage gave an additional lod score of 7.1.

Type III and type I procollagen markers in fibrosing alveolitis.

Deposition of types I and III collagen is a typical feature in the development of pulmonary fibrosis. We assessed the propeptides of these procollagens as prognostic markers in 18 patients with fibrosing alveolitis. We analyzed the amino-terminal propeptide of type III procollagen (PIIINP) and the carboxy-terminal propeptide of type I procollagen (PICP) from samples of bronchoalveolar lavage fluid (BALF) and serum, and also estimated their concentrations in epithelial lining fluid (ELF) by the urea method. The level of PIIINP in serum (p < 0.05), BALF (p < 0.05), and ELF (p < 0.05), and the levels of PICP in BALF (p < 0.001) and ELF (p < 0.001) but not in serum, were significantly increased in the patients with fibrosing alveolitis as compared with 17 controls who had been investigated for minor respiratory symptoms. In the BALF and ELF of patients with fibrosing alveolitis, PICP but not PIIINP had significant negative correlations with the specific diffusion coefficient for carbon monoxide (DLCO/ VA). The amino-terminal propeptide of type III procollagen and the carboxy-terminal propeptide of type I procollagen in BALF correlated significantly with one another. During the follow-up period of 6 yr, seven of the 18 patients with fibrosing alveolitis died of the disease, 3 others died of malignancy, and one patient died from an unknown cause. DLCO (p < 0.05) differed significantly between the surviving patients and those who died of fibrosing alveolitis, and detectable PIIINP in BALF predicted death from fibrosing alveolitis (p = 0.05). In conclusion, these results show that PIIINP in BALF, ELF, and serum, and PICP in BALF and ELF, are increased in patients with fibrosing alveolitis. A high level of PICP in BALF, and especially in ELF, suggests a chronic process and increased synthesis of type I collagen in the lungs, whereas PIIINP in BALF and ELF suggests active disease and a poor prognosis.

Propeptide levels of type III and type I procollagen in the serum and bronchoalveolar lavage fluid of patients with pulmonary sarcoidosis.

No single test is available to reliably assess the activity or prognosis of pulmonary sarcoidosis. In this study, we have evaluated two procollagen markers, aminoterminal propeptide of type III procollagen (PIIINP) and carboxyterminal propeptide of type I procollagen (PICP) in serum and bronchoalveolar lavage fluid (BALF) and compared them to other disease markers of pulmonary sarcoidosis, such as serum level of angiotensin converting enzyme (S-ACE) or serum interleukin-2 receptor (S-IL-2R). Bronchoalveolar lavage was performed in 40 sarcoidosis patients without (stages 0-I) and 20 patients with lung parenchymal involvement (stages II-III), as well as in 17 controls. Serum (S)- and BALF-PIIINP and PICP, S-ACE, S-IL-2R, BALF-albumin, BALF-lymphocytes and mast cells were determined in these patients. BALF-PIIINP was clearly and S-PIIINP slightly elevated in sarcoidosis compared to the controls. Similarly BALF-PICP, but not S-PICP, was significantly higher in sarcoidosis. BALF-PIIINP, but not BALF-PICP correlated with S-ACE and S-IL-2R levels. Patients with lung parenchymal disease had higher S-ACE and BALF-PIIINP, but neither S-IL-2R, S-PIIINP nor S- or BALF-PICP were elevated. S-PIIINP and S-IL-2R but not S-ACE were higher in symptomatic than nonsymptomatic patients. Symptomatic patients with parenchymal disease had elevated BALF-PIIINP whereas in the symptomatic nonparenchymal group S-PIIINP was elevated. In conclusion, this is the first study to evaluate carboxyterminal propeptide of type I procollagen in sarcoidosis and showed elevated levels in bronchoalveolar lavage fluid. In contrast to the levels of bronchoalveolar lavage fluid aminoterminal propeptide of type III procollagen, levels of carboxyterminal propeptide of type I procollagen did not correlate with serum level of angiotensin converting enzyme and serum interleukin-2 receptor levels, suggesting that carboxyterminal propeptide of type I procollagen may be less suitable disease marker in sarcoidosis than aminoterminal propeptide of type III procollagen. However, the role of carboxyterminal propeptide of type I procollagen as an indicator of fibrogenesis must be further studied.

The effect of malotilate on type III and type IV collagen, laminin and fibronectin metabolism in dimethylnitrosamine-induced liver fibrosis in the rat.

BACKGROUND/AIMS: Dimethylnitrosamine-induced liver damage was used as an experimental model to study the effect of malotilate on liver fibrosis. METHODS: Deposition of type III and IV collagens, laminin and fibronectin were studied from liver section by immunohistochemical techniques using specific antibodies. Serum concentrations of aminoterminal propeptide of type III procollagen, and aminoterminal and carboxyterminal domains of type IV collagen were determined by radioimmunoassays from both malotilate-treated and untreated animals with dimethylnitrosamine injury. RESULTS: A significant elevation of all three serum parameters was observed after 3 weeks of hepatic injury in animals without malotilate treatment, and a constant increase was noted in the amounts of hepatic type III and IV collagens, laminin and fibronectin. Malotilate prevented increases in serum markers of type III and IV collagen synthesis as well as accumulation of the collagens, laminin and fibronectin in the liver. CONCLUSIONS: The results suggest that serum marker determinations can be used to monitor changes in type III and IV collagen synthesis in the liver. The data indicate that malotilate has a preventive effect in dimethylnitrosamine-induced experimental hepatic fibrosis.

Biochemical and morphological characterization of carbon tetrachloride-induced lung fibrosis in rats.

The short-term and long-term lung CCl4 injuries in rats were studied by i.p. CCl4 for 2 or 5 weeks, respectively, and the lung injury in the third progression group receiving i.p. CCl4 for 2 weeks followed by 3 weeks without. Acute haemorrhagic interstitial pneumonia resulted from short-term injury; chronic interstitial pneumonia from long term injury, and residua of injury or advanced chronic interstitial pneumonia in the progression group. All groups also exhibited features for diffuse alveolar damage. Connective tissue stains revealed both interstitial and intra-alveolar fibrosis in short-term injury. Hydroxyproline content and the activities of prolyl hydroxylase and galactosylhydroxylysyl glucosultransferase were elevated. This suggests an early onset of pulmonary fibrosis. Immunohistochemistry revealed the interstitial accumulation of BM proteins. In contrast, increased type III pN-collagen could also be found in the intra-alveolar spaces. The degrees of both interstitial and intra-alveolar fibrosis, BM proteins and type III pN-collagen, and also hydroxyproline content were greater in long-term injury, while the progression group showed on average fewer fibrotic changes than did the long-term injury group, but more than the short-term injury pointing to persistence or progression of the changes. Additionally, intra-alveolar crystallized haemoglobin was found following short-term injury. We conclude that CCl4-induced lung injury is an useful experimental model to study pulmonary fibrosis. The mechanism of CCl4 lung injury is not known but free radical-mediated lipid peroxidation is suggested.

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)

Diminished arterial elasticity in diabetes: association with fluorescent advanced glycosylation end products in collagen.

OBJECTIVE: Non-enzymatic glycosylation of proteins occurs in diabetes and advanced glycosylated end products can accumulate in long lived proteins such as vascular collagen and reduce the elasticity of vessel walls. To evaluate the potential association of advanced glycosylated end products in collagen with diminished arterial elasticity in diabetes, 14 diabetic and 14 age and sex matched non-diabetic patients with coronary artery disease were studied. METHODS: Arterial elasticity was assessed in terms of carotid to femoral pulse wave velocity and by measuring the change in ascending aortic diameter induced by pulse pressure. Collagen linked fluorescence, a measure of advanced glycosylated end products, was determined from tissue specimens of the skin, ascending aorta, and right atrial appendage taken during coronary bypass surgery. RESULTS: As a sign of diminished arterial elasticity, carotid to femoral pulse wave velocity was raised (p < 0.01) and change in ascending aortic diameter tended to be diminished (p = 0.09) in the diabetic patients. Collagen linked fluorescence was increased (p < 0.05) in the myocardium of the diabetic group, but the difference in skin and aorta was not significant. Collagen linked fluorescence between the aorta, skin, and myocardium correlated with each other (r = 0.64-0.77). Collagen linked fluorescence in the aorta and myocardium correlated with carotid to femoral pulse wave velocity (r = 0.63 and r = 0.67, respectively) in the diabetic group but not in the control group. CONCLUSIONS: These data suggest that non-enzymatic glycosylation of matrix proteins, and specifically collagen, may modify arterial elasticity in diabetic patients with coronary artery disease.

Two mutations in Marfan syndrome resulting in truncated fibrillin polypeptides.

Biochemical and molecular genetic studies have recently suggested that mutations in the gene coding for fibrillin on chromosome 15 result in Marfan syndrome. To our knowledge, only one mutation in the fibrillin gene has been published. Here we report the results of screening 20 unrelated MFS patients for mutations in fibrillin cDNA by the single-strand conformation polymorphism technique. We found two mutations, both of which appear in the heterozygote form and code for a shortened fibrillin polypeptide. The first mutation is a large in-frame deletion of 366 bases of the fibrillin mRNA, shown to result in a truncated but secreted polypeptide found in the fibroblast culture of the patient. The second mutation is a G-to-A transition resulting in the substitution of a stop codon for a tryptophan codon and thus predicting the premature termination of the polypeptide chain. We screened 60 other, unrelated MFS patients for these mutations as well as for the previously reported mutation (arginine-239 to proline) and found none of the three mutations in any of these patients. These data suggest that most MFS families carry their own distinct mutation.

Increased non-enzymatic glycosylation and reduced solubility of skin collagen in insulin-dependent diabetic patients.

The solubility of skin collagen into acetic acid and by pepsin digestion and the degree of non-enzymatic glycosylation of collagen (ketoamine linkage) in these fractions was determined in skin specimens from 27 insulin-dependent diabetic subjects and from 17 age-matched controls. Glycosylation in acid soluble collagen specimen was significantly increased in the diabetics, 1.9 +/- 1.8 (SD)ng of hexose/micrograms of hydroxyproline in comparison to the controls. 0.9 +/- 0.8 ng of hexose/micrograms of hydroxyproline. No significant difference in this respect was noted in pepsin soluble collagen specimens. The solubility of collagen into acetic acid and by pepsin digestion were significantly reduced in the diabetics. No clear relationships between non-enzymatic glycosylation or collagen solubility and diabetic late complications (nephropathy, retinopathy or limited joint mobility) were noted. We suggest (a) that equilibrium levels of early glycosylation products are different in acid and pepsin soluble collagen specimens. (b) ketoamine linkage glycosylation products by themselves are not directly involved in diabetic late complications and (c) the solubility in acid and digestibility of collagen by pepsin may be an indicator, even though nonspecific, of increased amounts of advanced glycosylation end products.

Malotilate prevents accumulation of type III pN-collagen, type IV collagen, and laminin in carbon tetrachloride-induced pulmonary fibrosis in rats.

Orally administered malotilate was studied as a protective antifibrotic agent with respect to experimentally induced pulmonary fibrosis in rats using immunohistochemical methods. Specific antibodies raised in rabbits against the aminoterminal propeptide of human type III procollagen and against two basement membrane proteins, the 7S domain of human type IV collagen and the P1 fragment of human laminin, were used for the immunohistochemical analysis, and the result was confirmed by morphometry. Intraperitoneally injected carbon tetrachloride significantly increased the volume densities of reticulin fibers, type III pN-collagen, type IV collagen, and laminin, whereas treatment with malotilate completely normalized these. Binding of the antibodies to rat antigens was also demonstrated by immunoelectron microscopy in which the collagen fibers with a typical periodic pattern were labeled positively with rabbit antitype III procollagen, whereas the amorphous basement membrane material reacted positively with rabbit antitype IV collagen and antilaminin, indicating good, specific cross-reactivity between these antibodies and the rat antigens. It is concluded that malotilate prevents the accumulation of type III pN-collagen and two basement membrane proteins, type IV collagen and laminin, in experimental pulmonary fibrosis, and can potentially be developed to provide a useful drug for preventing pulmonary fibrosis in humans.

Predisposition to familial osteoarthrosis linked to type II collagen gene.

The genetic background of two families, in whom a predisposition to primary osteoarthrosis is inherited as a dominant trait, was investigated. Use of restriction fragment length polymorphisms within and around the type II collagen gene on chromosome 12 revealed a linkage between this cartilage-specific gene and primary osteoarthrosis.

Preventive effect of malotilate on dimethylnitrosamine-induced liver fibrosis in the rat.

Dimethylnitrosamine-induced liver damage, which leads to hepatic failure and death of the animal, was prevented by treatment with malotilate. The accumulation of collagen and the morphologic changes caused by dimethylnitrosamine, such as inflammatory cell accumulation and fibrosis, were also prevented by this drug. Malotilate drastically reduced the increases in the amount of type I procollagen alpha 2-chain mRNA and activities of the enzymes prolyl 4-hydroxylase and galactosylhydroxylysyl glucosyltransferase, which are early events in liver fibrosis preceding the deposition of collagen. Even when started 14 days after dimethylnitrosamine induction, malotilate treatment was able to reduce liver damage. We suggest that the effect of malotilate is a result of the inhibition of inflammation.

Morphological, immunohistochemical and ultrastructural changes in dimethylnitrosamine [correction of dimenthylnitrosamine] induced liver injury. Effect of malotilate.

Dimethylnitrosamine (DMN) induced liver injury in rats with cell necrosis, inflammation, hemorrhages, increased collagen type III synthesis and basement membrane component laminin and collagen IV localization in perisinusoidal sites. Malotilate ingestion during DMN treatment abolished inflammation and decreased interstitial collagen deposits and vascularization. It affected clearly less DMN-caused hemorrhage. When malotilate treatment was started subsequently to development of DMN-injury, it also caused decrease in inflammation, though less, as well as in collagen III, BM and fibronectin deposits. We suggest that the mode of the malotilate effect on reducing the DMN-induced fibrosis of the liver is via inhibiting the inflammation, decreased fibronectin deposition possibly also playing a role.

Preventive effect of malotilate on carbon tetrachloride-induced liver damage and collagen accumulation in the rat.

Malotilate is a new drug suggested for use in chronic liver diseases. It is shown here to prevent liver damage caused by CCl4. The concomitant administration of malotilate with CCl4 significantly decreased hydroxyproline accumulation in the liver, liver prolyl 4-hydroxylase and liver and serum galactosylhydroxylysyl glucosyltransferase activities. However, it had no effect on the daily urinary hydroxyproline excretion or the hydroxyproline content of the skin, liver or lungs in normal young growing rats. It also had no specific inhibitory effect on hydroxyproline synthesis or secretion in fibroblast cultures, and did not affect the amount of procollagen-alpha 1(I)-specific mRNAs in these cultures. Thus it seems to have no direct inhibitory effect on collagen metabolism. In addition to inhibition of liver collagen accumulation, malotilate was also able to prevent the development of morphological changes in the liver such as focal necrosis, fatty infiltration and inflammatory changes. It also normalized almost completely the standard liver-function tests. It is possible that malotilate may prevent excessive collagen deposition by inhibiting the inflammation caused by CCl4-induced liver damage.

A light microscopic and biochemical study of carbon tetrachloride-induced pulmonary fibrosis in rats: the preventive effect of malotilate.

Orally administered malotilate was studied as a protective anti-fibrotic agent with respect to experimentally induced pulmonary fibrosis in rats. Intraperitoneally-injected carbon tetrachloride (CCI4) significantly increased the lung weight to body weight ratio, lung total protein and total hydroxyproline content, while the relative protein content of the lungs decreased. CCI4) induction caused diffuse alveolar damage and inflammatory changes mimicking usual interstitial pneumonia with interstitial fibrosis. The morphological findings suggest a primary toxic effect on the lungs. Treatment with malotilate completely normalized the lung weight to body weight ratio, lung total and relative protein content and total hydroxyproline content. Morphologically, malotilate seemed to prevent the exudative inflammatory changes and interstitial fibrosis, but not the primary toxic effect of CCI4 on the capillary endothelium or the alveolar epithelium, the result of which was diffuse alveolar damage. It is concluded that malotilate may be a useful drug for the prevention of pulmonary fibrosis.

Pulmonary emphysema in a nonsmoking patient with Salla disease.

Severe emphysema is reported in a patient with Salla disease, a recessively inherited disorder of sialic acid metabolism that leads to intralysosomal accumulation of free sialic acid in cells of various tissues. The disease is among the rare genetically determined diseases typical of the Finnish population. The patient was 41 yr old at the time of his death. He had been a nonsmoker with no evidence of alpha-1-antitrypsin deficiency. Chest radiographs suggested that severe emphysema had developed during the last 4.5 yr of his life. Emphysema was also documented by postmortem radiography, which showed it to be located mainly in the lower lobes. The uneven distribution of tissue destruction within individual lobules, as shown in histologic sections, indicated a centrilobular type of emphysema, which was probably related to the basic storage disease. Thus, some involvement of storage lysosomes in altering the functioning of pulmonary macrophages is suspected. The serum proteinase inhibitory capacity as well as the alpha-1-antitrypsin phenotypes were normal among 5 brothers and sisters of the patient, 1 of whom was affected by the disease. The exact pathogenetic mechanism(s) for the rapid development of severe emphysema in this rare case of Salla disease remains unclear.

Prevention by zinc of rat lung collagen accumulation in carbon tetrachloride injury.

Orally administered zinc was studied as a protective antifibrotic agent with respect to experimentally caused lung collagen accumulation in rats. Intraperitoneally injected carbon tetrachloride induced a diffuse alveolar damage with interstitial pulmonary fibrosis, and the morphologic findings suggested a primary toxic effect on the lungs. The carbon tetrachloride induction increased significantly the lung to body weight ratio, lung total protein and collagen content, lung total prolyl hydroxylase and galactosylhydroxylysyl glucosyltransferase activities, and daily urinary hydroxyproline excretion. Treatment with 114 mg/L of zinc in the animals' drinking water inhibited the lung prolyl hydroxylase activity and prevented the increases in lung collagen content and urinary hydroxyproline excretion but did not normalize any of the other above parameters. Enhanced lung prolyl hydroxylase activity was noted when a ferrous ion excess was included in the assay in order to reverse the competitive inhibition of the enzyme activity by zinc. It is suggested that zinc has a direct and selective preventive effect on rat lung collagen accumulation by inhibiting procollagen proline hydroxylation.