Hepatic collagen proline hydroxylase activity in alcoholic liver disease

Enzymes of Fibrosis in Chronic Liver Disease

Introduction: Liver fibrosis has been extensively studied at the cellular and molecular level, but very few data exist on the final enzymatic stages of collagen synthesis (prolyl hydroxylase, PH) and degradation (matrix metalloproteinases, MMPs), particularly in primary biliary cholangitis (PBC). Aim: We studied enzyme activities in liver tissue from patients with chronic liver diseases and compared them to normal livers. Patients: Eighteen patients with PBC of early and late stages (Ludwig’s classification) and seven on treatment with ursodeoxycholate (UDCA) were studied and compared to 34 patients with alcoholic liver disease (ALD), 25 patients with chronic viral liver disease and five normal biopsies. Sera were available from a total of 140 patients. Methods: The tritiated water released from the tritiated proline was measured in PH assessment. 14C intact and heat-denatured collagen substrates were used to measure collagenase and gelatinases, respectively. 3H Elastin was the substrate for elastase. In serum, ELISAs were used for MMP-1, TIMP-1, and TIMP-2 measurements while MMP-2 and MMP-9 were estimated by zymography. Results: PH was significantly increased in early and late PBC. Collagenase was reduced only in the late stages (p < 0.01), where the ratio PH/collagenase was increased. UDCA treatment restored values to almost normal. Gelatinases were reduced in late stages (p < 0.05). In contrast to PBC and ALD fibrosis, collagen synthesis is not increased in viral fibrosis. The balance shifted towards collagen deposition due to reduced degradation. Interestingly, gelatinolytic activity is not impaired in ALD. Elastase was similar to controls in all diseases studied. TIMP-1 was reduced in early PBC and viral and alcoholic hepatitis and cirrhosis (p < 0.001). Conclusions: (1) There is evidence that collagen synthesis increases in the early stages of PBC, but the collagenolytic mechanism may compensate for the increased synthesis. (2) In viral disease, fibrosis may be due to decreased degradation rather than increased synthesis. (3) The final biochemical stages of liver fibrosis may be quantitatively different according to underlying etiology.

Short-Term Inhalation of Ultrafine Zinc Particles Could Alleviate Cardiac Dysfunctions in Rats of Myocardial Infarction

It is not clear for inhalation of ultrafine metal particles in air pollution to impair human health. In the study, we aimed to investigate whether short-term (4 weeks) inhalation of ultrafine zinc particles could deteriorate the cardiac and hemodynamic functions in rats of myocardial infarction (MI). MI was induced in Wistar rats through coronary artery ligation surgery and given an inhalation of ultrafine zinc particles for 4 weeks (post-MI 4 weeks, 4 days per week, and 4 h per day). Cardiac strain and strain rate were quantified by the speckle tracking echocardiography. The pressure and flow wave were recorded in the carotid artery and analyzed by using the Womersley model. Myocardial infarction resulted in the LV wall thinning, LV cavity dilation, remarkable decrease of ejection fraction, dp/dt Max, −dp/dt Min, myocardial strain and strain rates, and increased LV end-diastolic pressure, as well as impaired hemodynamic environment. The short-term inhalation of ultrafine zinc particles significantly alleviated cardiac and hemodynamic dysfunctions, which could protect from the MI-induced myocardial and hemodynamic impairments albeit it is unknown for the long-term inhalation.

Alcohol-induced myocardial fibrosis in metallothionein-null mice: prevention by zinc supplementation

Alcohol-induced cardiomyopathy including fibrosis has been recognized clinically for a long time, but its pathogenesis is incompletely understood. Studies using experimental animals have not fully duplicated the pathological changes in humans, and animal models of alcoholic cardiac fibrosis are not available. In the present study, we have developed a mouse model in which cardiac hypertrophy and fibrosis were produced in metallothionein-knockout (MT-KO) mice fed an alcohol-containing liquid diet for 2 months. The same alcohol feeding did not produce cardiac fibrosis in the wild-type (WT) control mice, although there was no difference in the alcohol-induced heart hypertrophy between the WT controls and the MT-KO mice. Zinc supplementation prevented cardiac fibrosis but did not affect heart hypertrophy in the alcohol-fed MT-KO mice, suggesting a specific link between zinc homeostasis and cardiac fibrosis. Serum creatine phosphokinase activity was significantly higher in the alcohol-administered MT-KO mice than in the WT mice, and zinc supplementation decreased serum creatine phosphokinase activities and eliminated the difference between the groups. Thus, disturbance in zinc homeostasis due to the lack of MT associates with alcohol-induced cardiac fibrosis and more severe cardiac injury, making the MT-KO mouse model of alcohol-induced cardiac fibrosis a useful tool to investigate specific factors involved in the alcoholic cardiomyopathy.

Serum markers for hepatic fibrosis in alcoholic liver disease: which is the best marker, type III procollagen, type IV collagen, laminin, tissue inhibitor of metalloproteinase, or prolyl hydroxylase?

Although various serum markers for the evaluation of hepatic fibrosis have been introduced, it remains unclear which is the best marker to evaluate the hepatic fibrosis observed in alcoholic liver disease (ALD). In this study, we measured serum concentrations of the immunoreactive beta-subunit of prolyl hydroxylase, procollagen type III peptide, the 7S domain (7S-IV) and triple-helix domain (TH-IV) of type IV collagen, laminin, and tissue inhibitor of metalloproteinase (TIMP) in patients with and without ALD (non-ALD), and controls to evaluate the best serum marker reflecting the characteristic histologic features of ALD. After Azan-Mallory and silver-impregnated reticulin staining, histologic specimens were examined; and the degree of hepatic fibrosis was classified as mild, moderate, or severe. Although serum concentrations of all markers, except for TIMP, in patients with each type and stage of liver disease were higher than cut-off values and these concentrations increases with the progression of liver disease, statistical analyses indicate that serum TH-IV concentration is the best marker to distinguish ALD from non-ALD. A good correlation was also found between the hepatic type IV collagen content and serum TH-IV, but not serum 7S-IV concentration. Moreover, after abstinence from alcohol, serum concentrations of TH-IV decreased more quickly than other serum markers. These results clearly suggest that, compared with other markers, serum concentration of TH-IV may more strongly reflect the histologic features of ALD. However, other serum markers, except for TIMP, may be useful in evaluating the degree of hepatic fibrosis.

Hepatic collagen synthesis in patients with alcoholic and nonalcoholic liver disease

To examine the synthesis of hepatic collagen in patients with alcoholic and nonalcoholic liver disease, liver biopsy specimens were incubated in vitro with 14C-proline, and the radioactivity of the newly synthesized protein-bound 14C-hydroxyproline was measured. Mean hepatic collagen synthesis was 0.82 +/- 0.19 pmole of 14C-hydroxyproline/g liver/2 h in control subjects without histological liver fibrosis. Hepatic collagen synthesis was increased in patients with alcoholic and nonalcoholic liver diseases, especially in those with alcoholic fibrosis, alcoholic cirrhosis and chronic active hepatitis. The raised collagen synthesis in alcoholic liver disease rapidly decreased after withdrawal of alcohol. When alcoholic liver disease were compared with nonalcoholic liver disease, there was no significant difference in hepatic collagen synthesis.

Biochemical markers of hepatic fibrosis

Most liver diseases lead to a pathobiochemical reaction termed liver fibrosis. This is a dynamic process implying different rates of progression or regression. Thus, histological examination of a liver biopsy is essential for a diagnosis but biochemical tests are necessary for assessing the activity of the process and monitoring its evolution. We review the most important constituents of liver connective tissue and the biochemical tests developed for evaluating liver fibrosis. The aminopeptide of type III procollagen is the most widely used parameter: two different radioimmunoassays have been developed with different affinities for the two circulating forms of the molecule. The determination of serum P3P reveals an elevation of blood levels both in acute and chronic liver diseases. In the first, serum P3P is an index of hepatic necrosis and inflammation which correlates with other biochemical parameters. In the second it is an index of active fibrogenesis. Moreover, in primary biliary cirrhosis this parameter is an independent prognostic variable and an important predictor of survival. Other immunoassays exist for different collagen cleavage products, but their clinical value is not established. Laminin and fibronectin are the principal structural glycoproteins in liver. Fibronectin determination does not seem to be of clinical value in liver disease. In contrast, serum laminin correlates with the severity of portal venous pressure in advanced liver disease. Its concentration parallels the severity of varices and may indicate the risk of bleeding. Hyaluronate is a high molecular weight polysaccharide, raised serum concentrations reflect both its increased synthesis by activated fibroblasts and its impaired catabolism by the liver. Thus, it may be useful for evaluating and monitoring the progression of chronic liver disease. The measurement of the activity of prolyl 4-hydroxylase as well as that of lysine oxidase and other enzymes has been proposed, but their clinical value is not sufficiently demonstrated. A panel of tests (e.g., laminin, hyaluronate and the aminopeptide of type III procollagen) seems to be recommended for a biochemical assessment of liver fibrosis in clinical practice.

Changes in serum and hepatic levels of immunoreactive prolyl hydroxylase in two models of hepatic fibrosis in rats

Changes in serum and hepatic levels of immunoreactive prolyl hydroxylase (IRPH) as well as cellular localization of the enzyme were studied in 2 models of hepatic fibrosis, which was induced in male rats either by subcutaneous administration of CCl4 (Group A) or by intraperitoneal injection of porcine serum (Group B). Hepatic fibrosis appeared at the 8th week in Group A and at the 12th week in Group B, and liver cirrhosis developed at the 16th week in both models. Although tissue contents of hydroxyproline (HP) and IRPH increased in both models, only HP levels correlated with the degree of fibrosis. Serum IRPH levels and serum asparate aminotransferase (AST) activities increased, showing a significant positive correlation, in group A, whereas both remained in a control range in Group B. Moreover, in another model which received a single intraperitoneal injection of CCl4, serum IRPH showed a marked increase and then a rapid decrease in parallel with the change in serum AST. Immunohistochemical analysis also showed a difference between the two fibrosis models: in group A, IRPH was positive mainly in parenchymal cells in the peripheral zone of the pseudolobulus, while in group B the staining was diffuse. These results indicate that the elevation of serum IRPH is, at least in part, due to the parenchymal cell damage, and that IRPH levels should be carefully evaluated when being used as a parameter to estimate the activity of fibrogenesis in the liver.

Prevalence and prediction of osteopenia in chronic liver disease

To obtain information on the prevalence and clinical and laboratory correlates of osteopenia in patients with chronic liver disease, we measured bone densities and 30 selected laboratory variables in 133 subjects (70 men, 63 women) with liver disease. Thirty-two had alcoholic liver disease, 18 had primary biliary cirrhosis, 16 had primary sclerosing cholangitis, 48 had other forms of cirrhosis (cryptogenic, posthepatic) and 19 had chronic hepatitis or fibrosis without cirrhosis. Bone densities of the lumbar spine and three sites of the proximal femur (neck, Ward's triangle, greater trochanter) were estimated by dual-photon absorptiometry. Bone densities at all sites were significantly correlated to one another (r = 0.4 to 0.9; 95% confidence intervals = 0.24-0.54 to 0.81-0.90; p less than 0.0001 for all). Compared with an age- and gender-matched reference group, patients with liver disease had highly significant decreases in bone densities (greater than 2 standard deviations below control values; p less than 0.0008 at all sites). Decreases were particularly marked (24% to 42%) at Ward's triangle, the site of the femoral neck particularly prone to fracture. The prevalence of decreased bone densities ranged from 10% to 56%, depending on the site studied and the nature of the liver disease. Among 30 laboratory variables studied, there were significant (p less than 0.05) correlations with bone densities at more than one site for urinary creatinine (r = 0.21, 0.25), urinary calcium (r = -0.18, -0.23), serum total alkaline phosphatase (r = -0.18, -0.27) and the liver-1 isozyme of serum alkaline phosphatase (r = -0.19, -0.26).(ABSTRACT TRUNCATED AT 250 WORDS)

Synthesis of lysyl oxidase in experimental hepatic fibrosis

The synthesis of lysyl oxidase, which initiates the cross-linking of collagen and elastin, was investigated in carbon tetrachloride (CCl4) induced fibrotic liver of rat. Lysyl oxidase activity of the fibrotic liver was 4 times greater than that of normal liver. mRNAs from the livers of normal and CCl4-treated rats were prepared for in vitro protein synthesis and the products were analyzed by immunoprecipitation with a monoclonal antibody against lysyl oxidase. The mRNAs from the fibrotic liver gave more than 3 times higher level of messenger copies for lysyl oxidase than did mRNAs from normal liver. The molecular weight of the nascent lysyl oxidase was 48,000.

Evaluation of fibrosis in the disse space in noncirrhotic alcoholic liver disease

In 40 alcoholic noncirrhotic patients, we performed a liver biopsy and determined the wedged hepatic vein pressure, the free hepatic vein pressure, and the intrahepatic vein pressure. In 27 of them, the serum concentration of the N-terminal peptide of type III procollagen (PIIIP) and of the laminin P1 fragment was measured. All the liver biopsies were studied by light and transmission electronic microscopy. A score of collagenization of the Disse space (six classes) was performed using transmission electronic microscopy. 37 of the 40 patients had pathological collagenization of the Disse space which was correlated with intrahepatic pressure (p less than 0.01). The lamin P1 blood level in patients (1.38 +/- 0.51 U/ml) was increased, compared to the values of our controls (0.99 +/- 0.10 U/ml, p less than 0.01) and was correlated with the wedge hepatic vein pressure (p less than 0.01). The PIIIP blood level was not significantly increased except when Mallory bodies were found in hepatocytes (p less than 0.05). The laminin P1 blood level seemed to be a good biological marker for detection of liver fibrosis in long-term alcoholic intake.

Serum lysyl oxidase activity in patients with various liver diseases

Serum lysyl oxidase activity was examined in patients with various liver diseases. The activity of the enzyme was detected mainly in the serum fraction of the supernatant 80% saturated with (NH4)2SO4, and its molecular weight was estimated to be about 30,000 by Sephadex G-150 column filtration. Mean serum lysyl oxidase activity in 18 healthy controls was 129 +/- 50 (+/- SEM) cpm/ml and was significantly increased in patients with acute hepatitis, chronic active hepatitis, alcoholic liver disease and primary biliary cirrhosis, but not in those with chronic inactive hepatitis or liver cirrhosis. Serum lysyl oxidase activity was not correlated with the histological grade of hepatic fibrosis, but appeared to reflect active hepatic fibrogenesis in patients with liver diseases.

Measurement of connective tissue parameters in serum for diagnosis and follow-up of liver fibrosis

Hepatic fibrogenesis, i.e. activated synthesis and excessive intercellular deposition of connective tissue molecules (collagens, adhesive glycoproteins, proteoglycans) occurs in chronic alcoholic and viral liver injury and, less frequently, in some other conditions. The process may be monitored biochemically by the radioimmunoassay of some connective tissue molecules or their fragments and by the measurement of the activity of certain enzymes in serum. Currently, the radioimmunoassay of the aminoterminal propeptide of type III procollagen in serum reflects best the activity of liver fibrogenesis. The serum level of laminin, a high molecular weight basement membrane glycoprotein, was found to be correlated with an elevated portal venous pressure.

Serum procollagen type III peptide as a marker of hepatic fibrogenesis in alcoholic hepatitis

To evaluate if serum procollagen type III peptide levels reflect the extent of liver fibrosis and hepatic collagen synthesis, we have studied 19 patients with histologically proven alcoholic hepatitis and 9 chronic alcoholics with normal liver histology or minimal steatosis. Serum procollagen peptide type III was measured at the time of liver biopsy, and determination of hepatic prolyl-hydroxylase activity, as an index of collagen synthesis, was performed in all liver samples. Hepatic prolyl-hydroxylase activity and serum procollagen peptide levels were significantly higher in patients with alcoholic hepatitis (959 +/- 115 cpm/mg and 33.2 +/- 5.3 ng/ml, respectively) than in alcoholics from the control group (537 +/- 62 cpm/mg and 10.9 +/- 1.5 ng/ml, respectively) (p less than 0.05 and p less than 0.01, respectively). All patients with alcoholic hepatitis had fibrosis (10 mild and 9 severe). Prolyl-hydroxylase activity and procollagen peptide levels were significantly higher in alcoholic hepatitis patients with severe fibrosis than in those with mild fibrosis (1208 +/- 154 cpm/mg vs. 734 +/- 138 cpm/mg, p less than 0.05 and 49.1 +/- 8.8 ng/ml vs. 20.4 +/- 2.6 ng/ml, p less than 0.01). Furthermore, a close correlation was found between the hepatic prolyl-hydroxylase activity and the serum level of procollagen peptide (r = 0.76, p less than 0.001). We conclude that the serum procollagen peptide level is a good marker of hepatic fibrogenesis in alcoholic hepatitis; thus, its serial measurement could be useful in identifying patients in progress to cirrhosis and in assessing the therapeutic efficiency of antifibrogenic drugs.

Diagnostic value of serum procollagen peptide measurements in alcoholic liver disease

Procollagen type I carboxyterminal and type III aminoterminal peptide concentrations were measured in sera of 60 patients with alcoholic and 14 with nonalcoholic liver disease to study whether these assays are useful as clinical tests to differentiate various stages of alcoholic liver injury. Both propeptides were markedly elevated in alcoholic hepatitis and cirrhosis: procollagen type III peptide in 90% and type I peptide in 60-80% of these patients. Moderately increased values were found less frequently in patients with fatty liver. These tests did not differentiate patients with simple fatty liver from those with fatty liver and early fibrosis. There was a significant difference in serum procollagen type III peptide between fatty liver and both alcoholic hepatitis and cirrhosis (p less than 0.001), and in type I peptide between fatty liver and alcoholic hepatitis (p less than 0.005). Although serum peptide values correlated with the degree of liver fibrosis, appreciable overlap of values was found between the various groups. The peptide concentrations also seemed to be related to the degree of hepatic inflammation, and the highest values were observed in a subgroup of patients with alcoholic hepatitis in whom numerous Mallory bodies were found. The data suggest that in alcoholic liver diseases, serum collagen propeptide determination may be useful in diagnosing severe alcoholic hepatitis.

Hepatic peptidyl prolyl hydroxylase activity and liver fibrosis--a prospective study of 94 infants and children with hepatobiliary disorders

To assess whether hepatic peptidyl prolyl hydroxylase (PPH) activity could serve as a practical quantitative indicator of hepatic fibrosis or aid in the categorization, diagnosis or prognosis of hepatobiliary disorders in infancy and childhood, the activity of this enzyme has been determined prospectively by a tritium release method in 97 biopsies from 94 infants and children with the following conditions: acute hepatitis of infancy, 10 patients; extrahepatic biliary atresia, 13; previous hepatitis of infancy, 8; alpha-1-antitrypsin deficiency, 6; chronic active hepatitis, 17; chronic persistent hepatitis, 5; glycogen storage disease, 5; and 25 patients with a miscellanea of other liver disorders. PPH activity was considered in relation to diagnosis, biochemical and histological abnormality and subsequent prognosis over a 4-year period. Five liver biopsies which showed no histological abnormality were considered as "controls" having PPH values of 0.72 +/- 0.47 (mean +/- S.D.). PPH activity was significantly elevated in acute hepatitis of infancy, 9 of the 10 infants having PPH greater than 1.66 units (i.e., mean +/- 2 S.D. of the "control" value). Nine infants (70%) with extrahepatic biliary atresia also had PPH activity above this value, as did two with alpha-1-antitrypsin deficiency and 12 patients all in different diagnostic categories. PPH activity did not correlate with hepatic fibrosis as indicated by hepatic hydroxyproline concentration or by histological assessment, or with biochemical tests of liver function within any diagnostic group or in the series as a whole. PPH activity was similar in biopsies with and without histological features of cirrhosis.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of fat-storing cells in Disse space fibrogenesis in alcoholic liver disease

Liver biopsy samples from 40 chronic alcoholic patients, including 9 with minimal changes of the liver, 6 with mild hepatic fibrosis, 14 with moderate fibrosis, and 11 with severe fibrosis (cirrhosis) were studied by electron microscopy to assess fibrogenesis in the Disse space and the role of fat-storing cells in this process. In the Disse space of normal liver, collagen fibers are few, and while lipid droplets containing fat-storing cells exist, their rough endoplasmic reticulum (RER) is inconspicuous. In the course of progressive hepatic fibrosis, collagen in the Disse space increased. This was significantly associated with gradual development of RER in fat-storing cells, confirmed by morphometric analysis. It is likely, therefore, that the development of RER in the fat-storing cells is a morphological correlative of their activated fibrogenesis and transformation into fibroblasts. To further clarify this, the rate of collagen synthesis was measured by the method of in vitro incorporation of [3H]proline into collagen in 17 liver biopsy samples from alcoholic patients and compared with the degree of morphological changes of RER in fat-storing cells. In liver samples with well-developed RER in fat-storing cells, a significantly higher rate of collagen synthesis was observed. These results suggest that in alcoholic liver injury, fat-storing cells may play an important role in Disse space fibrogenesis.

Hepatic collagenolytic cathepsin in patients with chronic liver disease

Human hepatic collagenolytic cathepsin consisted of a major component having a molecular weight of 25 000 and a minor one of 35 000; the former is indistinguishable for cathepsin B in its enzymatic properties. Hepatic collagenolytic cathepsin increased in chronic active liver disease in proportion to hepatic hydroxyproline content. The ratio of collagenolytic cathepsin to hepatic hydroxyproline content remained within the normal range in chronic hepatitis, but decreased significantly in cirrhosis. These results suggest that collagenolytic cathepsin participates, at least partly, in the progress of hepatic fibrosis.

Radioimmunoassay for type III procollagen peptide and its application to human liver disease

A sensitive and specific radioimmunoassay was developed for the precursor-specific peptide segment located at the amino end of bovine type III procollagen. Human material showed high cross-reactivity in this assay. Two forms of human procollagen peptides were detected in body fluids. The larger peptide (45K) was found in serum and ascites, and resembled the whole precursor-specific segment which is presumably released from human type III procollagen by a single enzymatic cleavage. The smaller peptide (10K) was found mainly in urine indicating that further degradation of circulating procollagen peptides is required prior to their passage through the kidney. Compared to peptide concentrations in normal human serum two to twenty-fold increases were observed in all patients with alcoholic liver disease, in fifteen of seventeen patients with acute hepatitis, and in ten of fourteen patients with chronic active hepatitis. Much higher levels were detected in ascites fluid. Patients with rheumatoid arthritis and other diseases showed far smaller elevations of the serum peptide. In alcoholic liver disease peptide levels correlated well with inflammation and necrosis observed in liver biopsies, but not with other laboratory parameters.

Hepatic prolyl hydroxylase and collagen synthesis in patients with alcoholic liver disease

Hepatic prolyl hydroxylase activity and collagen synthesis were measured in patients with alcoholic liver disease to determine the feasibility of using the enzyme prolyl hydroxylase as a marker of hepatic fibrogenesis. Alcoholic patients with liver histopathology consistent with normal, steatosis, alcoholic hepatitis, early cirrhosis, or advanced cirrhosis were analysed for liver prolyl hydroxylase activity and in vitro collagen synthesis. Prolyl hydroxylase activity and the rate of in vitro collagen synthesis were correlated when these parameters were measured in samples of the same liver biopsy. Mean prolyl hydroxylase activity was significantly raised in all groups of alcoholic patients with alcoholic liver disease, except those with steatosis, when compared with alcoholic patients with normal morphology. Alcoholic patients with early cirrhosis had enzyme activity (mean +/- SE: 1.367 +/-0.162 mU/mg protein) significantly raised over all other groups. Mean enzyme activity was less raised (0.985 +/- 0.097 mU/mg protein) in patients with advanced cirrhosis. The percentage of collagen synthesis in patients with early or advanced cirrhosis was also raised compared with alcoholic patients with normal morphology. Prolyl hydroxylase activity and the rate of collagen synthesis are significantly correlated (r=0.62). These findings suggest that hepatic prolyl hydroxylase activity is a useful indicator of hepatic fibrogenesis and its measurement on available liver biopsy tissue should be a potent diagnostic tool reflecting active fibrogenesis and predicting progression of alcoholic liverdisease.

Studies of nucleic acid and collagen synthesis: current status in assessing liver repair

Much progress has been made in delineating biochemical, physiologic and morpholigic events in liver regeneration and collagen synthesis. Pharmacologic agents have been purported to be helpful in facilitating repair and preventing fibrosis. Objective indices are now available to monitor their effectiveness in man.