Fibrogenesis and fibrolysis in collagenous colitis. Patterns of procollagen types I and IV, matrix-metalloproteinase-1 and -13, and TIMP-1 gene expression.
(25/1326)
Collagenous colitis is characterized by the deposition of a superficial subepithelial collagenous layer, the pathogenesis of which is unknown. Because the excess matrix deposition is potentially reversible, a labile imbalance between fibrogenesis and fibrolysis may be suspected. Expression of procollagen alpha1(I) and alpha1(IV), matrix-metalloproteinase (MMP)-1 and -13, and tissue inhibitor of metalloproteinase (TIMP)-1 genes was semiquantitated by in situ hybridization on serial biopsies of 12 patients with collagenous colitis and compared to controls. Collagen types I, III, IV, and VI, tenascin, undulin/collagen XIV, and alpha-actin were localized by immunohistology. The superficial collagen layer stained strongly for collagen types I, III, and VI, and particularly for tenascin, but not for undulin. Elevated procollagen alpha1(I), procollagen alpha1(IV), and TIMP-1 transcript levels were found in alpha-actin-positive cells with linear distribution underneath the superficial collagenous layer, whereas MMP-1 RNA expression was variable and restricted to cell clusters. MMP-13 expression was undetectable. The patterns of procollagen alpha1(I)- and alpha1(IV)-specific labeling, combined with an intense tenascin- but absent undulin-specific staining, indicate deposition of an immature interstitial matrix that may be susceptible to degradation. The restricted MMP-1 RNA expression, counteracted by increased TIMP-1 expression, suggests locally impaired fibrolysis as a relevant factor in the pathogenesis of collagenous colitis. (+info)
Differential monocyte chemoattractant protein-1 and chemokine receptor 2 expression by murine lung fibroblasts derived from Th1- and Th2-type pulmonary granuloma models.
(26/1326)
Recent studies suggest that monocyte chemoattractant protein-1 (MCP-1) is involved in fibrosis through the regulation of profibrotic cytokine generation and matrix deposition. Changes in MCP-1, C-C chemokine receptor 2 (CCR2), procollagen I and III, and TGF beta were examined in fibroblasts cultured from normal lung and from nonfibrotic (i.e., Th1-type) and fibrotic (i.e., Th2-type) pulmonary granulomas. Th2-type fibroblasts generated 2-fold more MCP-1 than similar numbers of Th1-type or normal fibroblasts after 24 h in culture. Unlike normal and Th1-type fibroblasts, Th2-type fibroblasts displayed CCR2 mRNA at 24 h after IL-4 treatment. By flow cytometry, CCR2 was present on 40% of untreated Th2-type fibroblasts, whereas CCR2 was present on <20% of normal and Th1-type fibroblasts after similar treatment. IL-4 increased the number of normal fibroblasts with cell-surface CCR2 but IFN-gamma-treatment of normal and Th2-type fibroblasts significantly decreased the numbers of CCR2-positive cells in both populations. Western blot analysis showed that total CCR2 protein expression was markedly increased in untreated Th2-type fibroblasts compared with normal and Th1-type fibroblasts. IL-4 treatment enhanced CCR2 protein in Th1- and Th2-type fibroblasts whereas IFN-gamma treatment augmented CCR2 protein in normal and Th1-type fibroblasts. All three fibroblast populations exhibited MCP-1-dependent TGF-beta synthesis, but only normal and Th2-type fibroblasts showed a MCP-1 requirement for procollagen mRNA expression. Taken together, these findings suggest that lung fibroblasts are altered in their expression of MCP-1, TGF-beta, CCR2, and procollagen following their participation in pulmonary inflammatory processes, and these changes may be important during fibrosis. (+info)
A randomized, double-blind study comparing the effects of beclomethasone and fluticasone on bone density over two years.
(27/1326)
Cross-sectional studies have suggested that asthmatic patients receiving high dose inhaled corticosteroids and intermittent courses of oral corticosteroids have reduced bone mass. This prospective 2-yr study was undertaken to evaluate changes in bone density of patients receiving high doses of inhaled corticosteroids. Patients (n = 33) (males aged 18-50 yrs, females aged 18-40 yrs) on inhaled corticosteroids 1,000-2,000 microg x day(-1), were randomized in a double-blind fashion to either fluticasone propionate (FP) 1,000 microg x day(-1) or beclomethasone dipropionate (BDP) 2,000 microg x day(-1). In parallel, three open control groups of the same age range were studied: asthmatics (n = 8) receiving low dose inhaled corticosteroids (< or =400 microg x day(-1)) (group A); chronic, severe asthmatics (n = 8) receiving oral corticosteroids (> or =10 mg x day(-1) (group B); and healthy untreated volunteers (n = 7) (group C). Bone densitometry scans (quantitative computed tomography (QCT) of spine; dual X-ray absorptiometry of spine, femoral neck, and single photon absorptiometry of forearm) were performed at baseline and after 6, 12 and 24 months of treatment. Biochemical bone marker measurements (serum osteocalcin, bone alkaline phosphatase, pro-collagen type 1 carboxy terminal propeptide, deoxypyridinoline and C-telopeptide of type 1 collagen) were collected every 3 months. Fifteen FP (mean age 36 yrs, six male) and 9 BDP patients (mean age 33 yrs, five male); completed the study. At 0 months, mean bone mineral density (BMD) was lower in patients receiving inhaled corticosteroids (both low dose and high dose) than in normal volunteers. In the FP-treated group, mean vertebral trabecular BMD quantitative computed tomography remained stable with no evidence of decline, whereas there was some decline in the BDP-treated group. The treatment difference between FP and BDP was statistically significant in favour of FP for quantitative computed tomography measurements after 12 months (p = 0.006) and 24 months (p = 0.004). This study suggests that over 24 months, changes in bone density are minimal in patients on high-dose inhaled corticosteroids. (+info)
Hsp47-dependent and -independent intracellular trafficking of type I collagen in corneal endothelial cells.
(28/1326)
PURPOSE: Type I collagen is post-translationally regulated in corneal endothelial cells (CEC): CEC synthesize procollagen I and degrade it intracellularly. We investigated whether there is a Hsp47-independent pathway during intracellular trafficking of procollagen I. METHODS: Specific inhibitors were used to block intracellular transport of procollagen I and Hsp47. Immunocytochemical analysis was performed to determine the intracellular localization of the proteins of interest. RESULTS: When cells were treated with alpha,alpha'-dipyridyl, this specific inhibitor for collagen promoted retention in the endoplasmic reticulum (ER) of some of the underhydroxylated procollagen I, which was colocalized with Hsp47 in CEC. At the same time, another fraction of the alpha,alpha'-dipyridyl-induced underhydroxylated procollagen I was not located in the ER. When CEC were treated with brefeldin A, procollagen I and Hsp47 demonstrated a high degree of colocalization at the ER, whereas the inhibitor had less of an effect on the compartmentalization of procollagen I and prolyl 4-hydroxylase. When CEC were treated with either monensin or bafilomycin A1, procollagen I and Hsp47 were not colocalized: procollagen I was mostly localized at the Golgi area, while Hsp47 predominantly showed ER distribution. When colocalization of procollagen I and prolyl 4-hydroxylase was examined, a major population of procollagen I was not colocalized with prolyl 4-hydroxylase in the ER. CONCLUSIONS: These results indicate that some procollagen I and Hsp47 travel together from the ER to the cis-Golgi compartment and that a major population of procollagen I that may not be properly hydroxylated may be destroyed intracellularly via the Hsp47-independent pathway in CEC. (+info)
Changes in serum levels of type I collagen-related proteins after surgically induced menopause and correlations with bone loss in the lumbar spine.
(29/1326)
The purpose of this prospective study was to characterize the changes in serum levels of two proteins produced during the synthesis and degradation of type I collagen, i.e., the carboxyterminal propeptide of type I procollagen (PICP) and the pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP), respectively, after oophorectomy, and to assess the degree of correlation between changes in the serum values of these proteins and changes in bone mineral density (BMD) of the lumbar spine. Serum levels of PICP, ICTP and bone gla protein (BGP) were determined in 18 women before oophorectomy (baseline) and at 7 days, and 1, 2, 3, 6, 9 and 12 months post-oophorectomy (PO). The BMD of the lumbar spine was measured at baseline, and at 6 months and 12 months PO. ICTP had increased significantly at 7 days PO and peaked between 1 and 3 months PO. PICP and BGP had increased significantly at 2 months PO and remained at high levels thereafter. The percent changes in lumbar BMD from baseline values (% CFB) at 6 months and at 12 months PO were significantly correlated with % CFB in ICTP, but not with % CFB in PICP or BGP. Accordingly, bone resorption is a main determinant of bone mineral loss after oophorectomy and the change in recently-developed bone resorption markers, such as ICTP, is of clinical utility in predicting a degree of subsequent bone loss after surgical menopause. (+info)
Dexamethasone enhances In vitro vascular calcification by promoting osteoblastic differentiation of vascular smooth muscle cells.
(30/1326)
Vascular calcification is often associated with atherosclerotic lesions. Moreover, the process of atherosclerotic calcification has several features similar to the mineralization of skeletal tissue. Therefore, we hypothesized that vascular smooth muscle cells might acquire osteoblastic characteristics during the development of atherosclerotic lesions. In the present study, we investigated the effect of dexamethasone (Dex), which is well known to be a potent stimulator of osteoblastic differentiation in vitro, on vascular calcification by using an in vitro calcification model. We demonstrated that Dex increased bovine vascular smooth muscle cell (BVSMC) calcification in a dose- and time-dependent manner. Dex also enhanced several phenotypic markers of osteoblasts, such as alkaline phosphatase activity, procollagen type I carboxy-terminal peptide production, and cAMP responses to parathyroid hormone in BVSMCs. We also examined the effects of Dex on human osteoblast-like (Saos-2) cells and compared its effects on BVSMCs and Saos-2 cells. The effects of Dex on alkaline phosphatase activity and the cAMP response to parathyroid hormone in BVSMCs were less prominent than those in Saos-2 cells. Interestingly, we detected that Osf2/Cbfa1, a key transcription factor in osteoblastic differentiation, was expressed in both BVSMCs and Saos-2 cells and that Dex increased the gene expression of both transcription factors. These findings suggest that Dex may enhance osteoblastic differentiation of BVSMCs in vitro. (+info)
Proteasomal degradation of unassembled mutant type I collagen pro-alpha1(I) chains.
(31/1326)
We have previously shown that type I procollagen pro-alpha1(I) chains from an osteogenesis imperfecta patient (OI26) with a frameshift mutation resulting in a truncated C-propeptide, have impaired assembly, and are degraded by an endoplasmic reticulum-associated pathway (Lamande, S. R., Chessler, S. D., Golub, S. B., Byers, P. H., Chan, D., Cole, W. G., Sillence, D. O. and Bateman, J. F. (1995) J. Biol. Chem. 270, 8642-8649). To further explore the degradation of procollagen chains with mutant C-propeptides, mouse Mov13 cells, which produce no endogenous pro-alpha1(I), were stably transfected with a pro-alpha1(I) expression construct containing a frameshift mutation that predicts the synthesis of a protein 85 residues longer than normal. Despite high levels of mutant mRNA in transfected Mov13 cells, only minute amounts of mutant pro-alpha1(I) could be detected indicating that the majority of the mutant pro-alpha1(I) chains synthesized are targeted for rapid intracellular degradation. Degradation was not prevented by brefeldin A, monensin, or NH(4)Cl, agents that interfere with intracellular transport or lysosomal function. However, mutant pro-alpha1(I) chains in both transfected Mov13 cells and OI26 cells were protected from proteolysis by specific proteasome inhibitors. Together these data demonstrate for the first time that procollagen chains containing C-propeptide mutations that impair assembly are degraded by the cytoplasmic proteasome complex, and that the previously identified endoplasmic reticulum-associated degradation of mutant pro-alpha1(I) in OI26 is mediated by proteasomes. (+info)
An IL-13 inhibitor blocks the development of hepatic fibrosis during a T-helper type 2-dominated inflammatory response.
(32/1326)
In schistosomiasis, chronic parasite egg-induced granuloma formation can lead to tissue destruction and fibrosis, which causes much of the morbidity and mortality associated with this disease. Here we show the importance of IL-13 in the pathogenesis of schistosomiasis, and demonstrate, perhaps for the first time, the therapeutic efficacy of an IL-13 inhibitor, sIL-13Ralpha2-Fc, in the control of hepatic fibrosis. T-helper type 2 (Th2) cytokines dominate the immune response in mice infected with Schistosoma mansoni, yet the specific contributions of IL-13 and IL-4 to the development of fibrosis were not previously investigated. Our studies demonstrate that both cytokines play redundant roles in granuloma formation, which explains the ability of IL-4-deficient mice to form granulomas around eggs. More importantly, however, these studies demonstrate that IL-13 is the dominant Th2-type cytokine regulating fibrosis. IL-13 stimulated collagen production in fibroblasts, and procollagen I and procollagen III mRNA expression was decreased in sIL-13Ralpha2-Fc-treated mice. Moreover, the reduction in fibrosis observed in IL-4-deficient mice was much less pronounced than that in sIL-13Ralpha2-Fc-treated animals. Fibrosis is a major pathological manifestation of a number of allergic, autoimmune, and infectious diseases. Thus, our findings provide evidence that IL-13 inhibitors may be of general therapeutic benefit in preventing damaging tissue fibrosis resulting from Th2-dominated inflammatory responses. (+info)