Histopathological and biochemical studies on pancreatic fibrosis in WBN/Kob rats

 We investigated the time-course of changes in pancreatic fibrosis accompanied with pancreatitis in WBN/Kob rats. The areas of fibrosis and fatty replacement were analysed morphometrically, and biochemical measurements of pancreatic and plasma prolyl hydroxylase and of pancreatic collagenase were assessed. Male rats showed acute pancreatitis at 2–3 months of age, lesions that later underwent a transition to widespread fibrosis. The fibrosis then decreased, and the fibrotic tissue was replaced with adipose tissue. Morphometrically, the fibrotic area reached its maximal size when the rats were 4 months old, diminishing thereafter. The fibrosis occurred mainly in the intralobular space, and was principally attributable to type-III collagen. Type-I collagen scarcely appeared throughout the experimental period. α-Smooth muscle actin appeared in and around myofibroblasts that developed in an early stage and diminished later in accordance with the progressive manner of fibrosis. The plasma prolyl hydroxylase level was higher in males than in females from 4 through 10 months of age. Pancreatic collagenase activity in the males also increased during the same period. These findings suggest that pancreatic fibrosis in male WBN/Kob rats is affected by the balance between prolyl hydroxylase and collagenase. Received: 1 October 1998 / Accepted: 2 October 1998     

Increases in lung prolyl hydroxylase and superoxide dismutase activities during bleomycin-induced lung fibrosis in hamsters

Intratracheal administration of bleomycin causes pulmonary fibrosis in hamsters. Using this model the activities of lung prolyl hydroxylase and superoxide dismutase and the accumulation of neutral salt soluble and insoluble collagens have been determined. One unit of bleomycin was injected intratracheally to hamsters, whereas control animals received an equivalent volume of sterile saline by the same route. Total lung prolyl hydroxylase activity was significantly elevated at all times following bleomycin treatment. The activity was increased as early as 2 days, peaked to a maximum value of 400% of the control at 14 days, followed by a sharp decline to 235% and 180% of the control activity at 21 and 28 days after bleomycin treatment, respectively. Except for the earliest time (2 days), lung prolyl hydroxylase specific activity was also significantly elevated at all times after bleomycin treatment. A significant increase in both total and specific activities of lung superoxide dismutase was also observed at all times after bleomycin treatment. Total activity peaked to a maximum value of 315% of the control activity at 14 days and the specific activity to a maximum value of 190% of the control at 21 days after bleomycin treatment. Thereafter, both activities declined, but were still significantly elevated over the control at 28 days after the treatment. Lung proline pool size was significantly increased at all times and attained a maximum value of 372% of the control at 14 days after bleomycin treatment. Increases in the lung prolyl hydroxylase and superoxide dismutase activities and in the proline pool size preceded the significant increases in neutral salt soluble and insoluble collagens which occurred at 7 days after bleomycin treatment and continued to be significantly elevated for the remaining period of the study.     

Collagen and non-collagen protein synthesis in the lungs of rats exposed to a trypsin aerosol.

In rat lungs, 24 h after a 10 min inhalation of a nebulized 1% (w/v) trypsin solution, there was a 25% increase in lung weight. The incorporation of 3H-tryptophane and 2,3-[3H]-proline into trichloroacetic acid insoluble material was decreased although there was no alteration in prolyl hydroxylase activity. Although hydroxyproline formation was decreased, this decrease was probably due to the general decrease in protein synthesis. Ninety-six hours after inhalation of the trypsin solution there was an increase in non-collagen protein biosynthesis. Proline incorporation and hydroxyproline formation were both increased more than the tryptophane incorporation increase at this same time point. These increases were accompanied by an increase in prolyl hydroxylase activity. These experiments indicate that major changes in protein biosynthesis occur in lung tissues after inhalation of proteolytic enzymes and demonstrate the temporal biochemical changes which occur in lung injury.     

Effects of granulocyte colony-stimulating factor on the kinetics of inflammatory cells in the peripheral blood and pulmonary lesions during the development of bleomycin-induced lung injury in rats

We evaluated the effects of granulocyte colony-stimulating factor (G-CSF) on the kinetics of inflammatory cells during the development of inflammation in bleomycin (BLM)-induced lung injury. G-CSF (100 microg/kg/day, s.c.) was administered to rats treated with or without BLM (2 mg/200 microl, intratracheally) for up to 14 days (Day 14) immediately after BLM treatment. In the BLM + G-CSF group, the lung injury score increased on Days 1 and 14, and the score of lung fibrosis on Day 14, respectively. Except for neutrophils, there were no effects of G-CSF on the number of inflammatory cells both in the peripheral blood and in the lung in both BLM-treated and -untreated rats at the acute inflammatory phase. In the G-CSF-treated groups, the number of neutrophil counts in the peripheral blood drastically increased on Day 1, temporally decreased on Day 3, and increased again on Days 7 and 14. The number of neutrophils in the lung markedly increased on Day 1 and then remained at a plateau level until Day 14. The neutrophil alkaline phosphatase score in the lung commenced to increase on Day 1, reached the maximal level on Day 7, and then remained at a plateau level until Day 14. Correlations between the numbers of neutrophils in the lung and the peripheral blood or the lung lesion score were only observed on Day 14. These findings suggest that the exacerbating effect of G-CSF on the lung injury coincided with the increase in the number of alkaline phosphatase-positive neutrophils infiltrating in the pulmonary lesion at the acute inflammatory phase and it lasted to the fibrogenic phase. The exacerbating effect of G-CSF on the severe BLM-induced lung injury seems to be related not only to the pulmonary accumulation of activated neutrophils but also to the severity of lung injury caused by the direct effects of BLM.     

Poly(ADP-ribose) synthetase activity during bleomycin-induced lung fibrosis in hamsters

Bleomycin damages cellular DNA and is a potent inducer of pulmonary fibrosis. It has been shown to act through a superoxide-mediated mechanism. We are interested in determining the biochemical mechanisms involved in fibrosis and in this preliminary study we have examined the temporal relationship between early biochemical events associated with DNA damage and fibrosis, in lungs of hamsters after administration of 0.75 unit of bleomycin. The activities of poly(ADP-ribose) synthetase, an enzyme associated with DNA repair, inducible superoxide dismutase (SOD) and prolyl hydroxylase as well as the tissue levels of NAD+ and hydroxyproline in the lung were determined. All three enzyme activities expressed as per milligram DNA or per lung, increased upon bleomycin treatment over the saline-administered controls. Lung poly(ADP-ribose) synthetase activity which is sensitive to DNA breaks, increased first (24% over control in 1 day, P less than 0.0001), attained the maximum value on the 5th day (952% over control, P less than 0.0001), and started to decline thereafter and approached near the control value on 14th day. Bleomycin treatment induced a rapid change in the level of lung NAD+. After 1 day the level of NAD+ was reduced by 42% compared to the control (P less than 0.001), further declined to 65% (P less than 0.001) on the 3rd day, and stayed at that level until the 7th day. On the 14th day, however, the NAD+ level was still lower (29%, P less than 0.05) but approaching the value in the control animals. The activity of prolyl hydroxylase showed significant increase on the 3rd day (50% over control, P less than 0.0001) after bleomycin administration. The enzyme activity continued to increase until the end of the experiment (490% of control, P less than 0.0001, on Day 14). The content of undialyzable hydroxyproline, a marker for collagen, was also increased significantly in the lung tissue on the 3rd day (30% over control, P less than 0.05), continued to increase and reached the highest level on the 14th day (71% over control, P less than 0.001). A significant increase in the activity of SOD (19% over control, P less than 0.001) was seen on the 5th day which continued to increase and attained the highest value on Day 14 (115% over control, P less than 0.0001).(ABSTRACT TRUNCATED AT 400 WORDS)     

Collagen production in fat-storing cells after carbon tetrachloride intoxication in the rat. Immunoelectron microscopic observation of type I, type III collagens, and prolyl hydroxylase

Monospecific antibodies directed against type I, type III collagens, and prolyl hydroxylase were used to clarify the process of liver fibrosis after CCl4 intoxication in rats by the direct immunoperoxidase method. In acute CCl4 intoxication, fat-storing cells (FSCs) were increased in number in the areas of necrosis around the central veins. These FSCs exhibited intense positive stainings for type I, type III collagens, and prolyl hydroxylase in well-developed rough endoplasmic reticula and Golgi apparatus. This was the direct evidence that the collagens formed after CCl4 intoxication are produced by FSCs. In chronic CCl4 intoxication, increased FSCs in and around the fibers also contained strong immunoreactive materials of both collagens and prolyl hydroxylase mainly in the rough endoplasmic reticula. These collagens were also present in the Golgi apparatus and vesicles close to the cytoplasmic membrane, demonstrating the exocytic process of collagen formation of FSCs. In contrast, faint immunoreactions of both collagens were found in the rough endoplasmic reticula and Golgi apparatus of hepatocytes during the process of fibrosis. These findings indicate that FSCs play an important role in fibrogenesis after acute and chronic CCl4 intoxication in the rat.     

Essential role of MMP-12 in Fas-induced lung fibrosis

Acute lung injury (ALI) is characterized by an early inflammatory response followed by a late fibroproliferative phase, and by an increase in the bronchoalveolar lavage fluid (BALF) concentrations of bioactive soluble FasL (sFasL). Activation of Fas (CD95) has been associated with the development of lung fibrosis in mice. The goal of this study was to determine the mechanisms that link Fas activation with the development of fibrosis in the lungs. We treated mice with three daily intratracheal instillations of a Fas-activating monoclonal antibody (Jo2) or a control IgG, and studied the animals at sequential times. Mice treated with Jo2 had increased caspase-3 activation in alveolar wall cells on Days 2, 4, and 7; an inflammatory response peaking on Day 7, and increased total lung collagen on Day 21. Gene expression profiling performed on Days 2, 4, and 7 showed sequential activation of co-regulated profibrotic genes, including marked up-regulation of matrix metalloproteinase 12 (MMP-12). Targeted deletion of MMP-12 protected mice from Fas-induced pulmonary fibrosis, even though the inflammatory responses in the lungs were similar to those of wild-type mice. Compared with wild-type mice, the mmp12(-/-) mice showed decreased expression of the profibrotic genes egr1 and cyr61. We conclude that Fas activation in the lungs induces a complex response that includes apoptosis, inflammation, and eventually fibrosis, and that MMP-12 is essential for the fibrotic phenotype. We speculate that MMP-12 activity is required for activation of the profibrotic genes egr1 and cyr61.     

Report on stage III Pig-a mutation assays using benzo[a]pyrene

Genotoxicity assays were conducted on rats treated with benzo[a]pyrene (BaP) as part of Stage III of a validation study on the Pig-a gene mutation assay. Assays were performed at the U.S. FDA-NCTR and Bayer-Germany. Starting on Day 1, groups of five 6- to 7-week-old male Fischer 344 (F344, used at FDA-NCTR) and Han Wistar rats (Bayer) were given 28 daily doses of 0, 37.5, 75, or 150 mg/kg BaP; blood was sampled on Days -1, 4, 15, 29, and 56. Pig-a mutant frequencies were determined on Days -1, 15, 29, and 56 in total red blood cells (RBCs) and reticulocytes (RETs) as RBC(CD59-) and RET(CD59-) frequencies; percent micronucleated-RETs (%MN-RET) were measured on Days 4 and 29. RBC(CD59-) and RET(CD59-) frequencies increased in a dose- and time-dependent manner, producing significant increases by Day 29 in both rat models. The responses for RETs were stronger than those for RBCs, and the responses in F344 rats were stronger than in Han Wistar rats. BaP also produced significant increases in %MN-RET frequency at Days 4 and 29, with the responses being greater in F344 than Han Wistar rats. The overall findings were consistent with those of the reference laboratory using Han Wistar rats. Finally, mutation assays performed on splenocytes from Day 56 F344 rats indicated that BaP mutant frequencies were three to fivefold higher for the Hprt gene than the Pig-a gene. The results indicate that the Pig-a RET and RBC assays are reproducible, transferable, and show promise for integrating gene mutation into 28-day repeat-dose studies.     

Measurements of enzymes of collagen synthesis in rats with experimental silicosis

The levels of two enzymes of collagen biosynthesis namely lysyl oxidase and prolyl hydroxylase were measured in the lungs of rats 3 and 6 weeks after receiving a single intratracheal instillation of silica or sterile saline. Circulating levels of lysyl oxidase were also estimated. Significant increased lung-enzyme activities were observed in the silica-exposed rats at both time intervals. Plasma levels of lysyl oxidase were also found to be raised in the silica-exposed rats. These changes were not, however, accompanied by profound pathological alterations. These results demonstrate that after exposure to silica histologically detectable fibrosis is preceded by significant changes in the activities of enzymes associated with collagen synthesis.     

Increased serum immunoreactive prolyl hydroxylase in rats with carrageenan-induced granuloma and adjuvant arthritis

The authors developed a competitive enzyme immunoassay for serum immunoreactive prolyl hydroxylase (SIRPH) as a marker of fibrogenesis, and examined the changes in SIRPH concentrations in rats with carrageenan-induced granuloma and adjuvant arthritis. The effects of such anti-inflammatory agents as prednisolone, pranoprofen, indomethacin, and hydrocortisone were also investigated. Prolyl hydroxylase activity in rats with carrageenan-induced granuloma and adjuvant arthritis increased inflammatory granulation tissue, and the concentrations of SIRPH also increased time dependently. The nontreated controls showed a constant low level of SIRPH. After treatment with anti-inflammatory agents or removal of the granuloma, SIRPH levels decreased coincident with the improvement of clinical symptoms. It was assumed that immunoreactive prolyl hydroxylase was released into the blood stream as a result of increased turnover of the enzyme protein owing to fibrotic disorders. SIRPH could be a useful biochemical marker for assessing therapeutic effects through the actual activity of fibrogenesis.     

Measurements of enzymes of collagen synthesis in rats with experimental silicosis.

The levels of two enzymes of collagen biosynthesis namely lysyl oxidase and prolyl hydroxylase were measured in the lungs of rats 3 and 6 weeks after receiving a single intratracheal instillation of silica or sterile saline. Circulating levels of lysyl oxidase were also estimated. Significant increased lung-enzyme activities were observed in the silica-exposed rats at both time intervals. Plasma levels of lysyl oxidase were also found to be raised in the silica-exposed rats. These changes were not, however, accompanied by profound pathological alterations. These results demonstrate that after exposure to silica histologically detectable fibrosis is preceded by significant changes in the activities of enzymes associated with collagen synthesis.     

Increases in renal epsilon-(gamma-glutamyl)-lysine crosslinks result from compartment-specific changes in tissue transglutaminase in early experimental diabetic nephropathy: pathologic implications

Diabetic nephropathy (DN) is characterized by an early, progressive expansion and sclerosis of the glomerular mesangium leading to glomerulosclerosis. This is associated with parallel fibrosis of the renal interstitium. In experimental renal scarring, the protein cross-linking enzyme, tissue transglutaminase (tTg), is up-regulated and externalized causing an increase in its crosslink product, epsilon-(gamma-glutamyl)-lysine, in the extracellular space. This potentially contributes to the extracellular matrix (ECM) accumulation central to tissue fibrosis by increasing deposition and inhibiting breakdown. We investigated if a similar mechanism may contribute to the ECM expansion characteristic of DN using the rat streptozotocin model over 120 days. Whole kidney epsilon-(gamma-glutamyl)-lysine (HPLC analysis) was significantly increased from Day 90 (+337%) and peaked at Day 120 (+650%) (p < 0.05). Immunofluorescence showed this increase to be predominantly extracellular in the peritubular interstitial space, but also in individual glomeruli. Total kidney transglutaminase (Tg) was not elevated. However, using a Tg in situ activity assay, increased Tg was detected in both the extracellular interstitial space and glomeruli by Day 60, with a maximal 53% increase at Day 120 (p < 0.05). Using a specific anti-tTg antibody, immunohistochemistry showed a similar increase in extracellular enzyme in the interstitium and glomeruli. To biochemically characterize glomerular changes, glomeruli were isolated by selective sieving. In line with whole kidney measurement, there was an increase in glomerular epsilon-(gamma-glutamyl) lysine (+361%); however, in the glomeruli this was associated with increases in Tg activity (+228%) and tTg antigen by Western blotting (+215%). Importantly, the ratio of glomerular epsilon-(gamma-glutamyl) lysine to hydroxyproline increased by 2.2-fold. In DN, changes in the kidney result in increased translocation of tTg to the extracellular environment where high Ca(2+) and low GTP levels allow its activation. In the tubulointerstitium this is independent of increased tTg production, but dependent in the glomerulus. This leads to excessive ECM cross-linking, contributing to the renal fibrosis characteristic of progressive DN.     

Prolyl hydroxylase and collagen metabolism after experimental mycardial infarction.

Mature male Sprague-Dawley rats were subjected to an isoproterenol-induced myocardial infarction. Animals were sacrificed on a daily basis in order to assess the temporal changes in prolyl hydroxylase activity and collagen metabolism during the acute stages of myocardial necrosis and repair. Total myocardial hydroxyproline, as an indexof collagen content, increased promptly and markedly, beginning on day 4, and remained elevated thereafter. The incorporation of (14Cl)-proline into definitive hydroxyproline of mature collagen was also increased. The activity of the enzyme prolyl hydroxylase, which regulates the rate of conversion of proline to hydroxyproline in collagen, was elevated by day 2, remained high through day4, and then declined to a relatively constant but still slightly elevated level throughout the period of repair. It is believed that changes in these parameters of collagen metabolism reflect changes in myocardial fibroblastic cell and ground substance pertinent to fundamental aspects of repair of the injuried myocardium.     

Fibrosis markers in heavy alcohol drinkers

Alcoholic intake has increased in society in recent years. gamma-GTP is used as a marker of liver damage by alcohol intake, but there is no reliable marker of pancreatic fibrosis. We used animal experiments and clinical data to identify a new reliable marker of early-stage pancreatic fibrosis. Pancreatic fibrosis is induced by intra-peritoneal injection of diethyldithiocarbamate. Pancreas tissue was extracted and measured. Human pure pancreatic juice was collected by endoscopic procedures. Prolyl hydroxylase in pancreas tissue is increased in the early stage of pancreatic fibrosis. Secretion of matrix metalloproteinase from pancreatic stellate cells is increased by diethyldithiocarbamate stimulation. Pancreatic stellate cells, prolyl hydroxylase and a tissue inhibitor of metalloproteinase in human pure pancreatic juice is increased in heavy alcohol drinkers and normalized in former alcohol drinkers. Active matrix metalloproteinase 2 is detected in pure pancreatic juice of chronic pancreatitis patients. Treatment with oral camostat increases pancreatic secretory trypsin inhibitor in chronic pancreatitis patients. Experimental and clinical data indicated that matrix metalloproteinase 2 and prolyl hydroxylase are candidates as markers of early-stage pancreatic fibrosis. Clinical data showed that tissue inhibitor of metalloproteinase and pancreatic secretory trypsin inhibitor in pure pancreatic juice had potential as markers of early-stage pancreatic fibrosis.     

Increased serum type IV collagen peptide in carbon tetrachloride-treated rats

We developed a competitive enzyme-immunoassay for serum type IV collagen peptide as a marker of fibrogenesis, and examined the relationship between serum type IV collagen peptide and hepatic disorder in CCl4-treated rats. The rats were treated for 8 weeks and signs of liver damage began to appear from about week 2. With the progression of these signs to liver fibrosis, type IV collagen increased in the fibrous septa and especially in the perisinusoidal walls, where the increase was manifested as development of a real basement membrane beneath the sinusoidal endothelial cells. In CCl4-treated rats, serum type IV collagen peptide significantly increased with the progression of liver fibrosis. When CCl4 administration was stopped, the collagen peptide rapidly decreased without any rebound rise. An intimate relationship was found between the production of serum type IV collagen peptide and liver prolyl hydroxylase activity and the amount of collagen deposited in the liver. These results suggest that serum type IV collagen peptide will be a useful biochemical marker for the early detection of fibrogenesis in the liver.     

Contribution of hepatic reticuloendothelial system to glomerular IgA deposition in rat liver injury.

Liver damage was induced in rats by a single dose of dimethylnitrosamine or D-galactosamine. In the dimethylnitrosamine model, marked glomerular IgA deposition occurred between Days 4 and 28, with its peak at Day 14. Serum IgA levels were significantly increased at Days 2 and 4, then gradually decreased, and normalized at Day 14. In the D-galactosamine model, however, no such deposition was observed, though serum IgA levels similarly increased on Days 2 and 4. IgA content in high molecular weight fraction from serum increased at Day 3 in both models. This increment remained at Day 7 only in the dimethylnitrosamine model, in which carbon clearance from the circulation was significantly decreased at Day 3. These data suggest that dysfunction of the hepatic reticuloendothelial system is a factor contributing to glomerular IgA deposition occurring in liver injury.     

IL-12p40(-/-) mice treated with intratracheal bleomycin exhibit decreased pulmonary inflammation and increased fibrosis.

Pulmonary lymphohistiocytic inflammation and fibrosis characterize bleomycin (BLM) lung injury. IL-12, a p70 cytokine produced primarily by macrophages and dendritic cells, promotes T-helper-1-mediated inflammation. IL-12 production by blood monocytes and bronchoalveolar large mononuclear cells (BAMC) was investigated at Days 1-14 following intratracheal administration of BLM. In the lung, BAMC showed a large peak of IL-12 expression at Day 5 that returned rapidly toward baseline. IL-12p40(-/-) mice treated with BLM intratracheally showed less pulmonary mononuclear cell inflammation at Day 7 than wild-type controls, whereas pulmonary fibrosis and hydroxyproline content were increased in IL-12p40(-/-) mice at Day 14. The expression of IP-10, RANTES, and eotaxin were decreased in IL-12p40(-/-) mice and lung IL-6 expression was increased, all compared to controls. We conclude that IL-12 promotes the lymphohistiocytic response to BLM and may inhibit the late development of pulmonary fibrosis.     

Busulfan-induced apoptosis in rat placenta.

In order to investigate the effects of busulfan on the placenta, we examined the sequential histopathological changes in the placenta from rats exposed to busulfan during gestation days (Days) 12-14. Busulfan was intraperitoneally administered at 10 mg/kg on Days 12, 13 and 14, and the placentas were sampled on Day 13.5, 14.5, 15, 16 or 21. Macroscopically, small placenta was seen on Day 21 with scattered white spots and white peripheral rim. Histopathologically, in the treated group, there were increased apoptosis and decreased mitotic activities in the trophoblasts of the labyrinth zone on Days 13.5, 14.5, 15 and 16. In the basal zone, slightly increased apoptosis was seen on Day 13.5 and slightly decreased mitotic activity on Day 14.5. On Day 21, the labyrinth zone in the treated group was reduced in diameter. Degeneration and necrosis of trophoblasts, a diminution in thickness of the trophoblastic septa with a deposition of calcium and an irregular dilation of the maternal blood space were scattered in the labyrinth zone, although there were no conspicuous changes in the basal zone. The anti-proliferative effects of busulfan could have inhibited the development of the labyrinth zone, and led to small placentas. The fetotoxicity and teratogenicity of busulfan might be also responsible for these placental changes.