Biomedical subjects

M J Czaja

Publications and source records attributed to M J Czaja.

6 recordsLinked to original sources

PubMed1992

Ito cell expression of a nuclear retinoic acid receptor.

Although it has been suggested that retinoids regulate Ito cell proliferation and collagen synthesis, little is known about the ability of Ito cells to respond to retinoids in vivo. Because retinoids may mediate their molecular effects through nuclear receptors, Ito cells were examined for the presence of one of these receptors, nuclear retinoic acid receptor-beta. The modulation of nuclear retinoic acid receptor-beta expression was also studied during cell culture and hepatic fibrogenesis. Northern hybridization analysis revealed that Ito cells freshly isolated from normal rat liver contained nuclear retinoic acid receptor-beta messenger RNA at levels significantly higher than those found in other hepatic cell types. Ito cells also contained messenger RNA for two other nuclear retinoic acid receptors, nuclear retinoic acid receptor-alpha and nuclear retinoic acid receptor-gamma. Using an antibody to human nuclear retinoic acid receptor-beta, the nuclear presence of this receptor was demonstrated in normal Ito cells. In contrast, Ito cells cultured for at least 7 days had no detectable messenger RNA or nuclear staining for nuclear retinoic acid receptor-beta despite a 20 +/- 5-fold increase in the messenger RNA level of another retinoid binding protein, cellular retinol binding protein. Analysis of Ito cells isolated from rats with carbon tetrachloride-induced hepatic fibrosis revealed an 81% +/- 3% decrease in nuclear retinoic acid receptor-beta messenger RNA levels in these cells when compared with normal Ito cells. No difference in the messenger RNA levels of cellular retinol binding protein was found in Ito cells isolated from either normal or fibrotic liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

The effects of hepatic fibrosis on Ito cell gene expression.

While Ito cells appear to be a major source of increased matrix synthesis during hepatic fibrogenesis, the cellular changes that occur in these cells during liver fibrosis have not been well delineated. In this study we examined Ito cell gene expression in isolated cells from normal rats, and rats with carbon tetrachloride-induced fibrosis, in order to better define the changes occurring in these cells during this pathologic process. Specifically, we addressed three questions: (1) which matrix genes are over expressed in Ito cells in fibrotic liver; (2) do these cells increase their expression of the fibrogenic cytokine transforming growth factor-beta 1 (TGF-beta 1); and (3) do Ito cells change their phenotype during hepatic fibrogenesis as reflected by alterations in the expression of their intermediate filament genes? Northern hybridization analysis revealed that Ito cells isolated from fibrotic livers had significant increases in mRNA levels of types I, III and IV procollagen compared to normal cells, while no increases were found in hepatocytes, and Kupffer/endothelial cells had only an increase in type I procollagen mRNA. Analysis of other matrix proteins which increase during hepatic fibrogenesis revealed elevations in laminin B and fibronectin mRNA levels only in Ito cells. Increased Ito cell matrix gene expression was also associated with a 4-fold increase in TGF-beta 1 levels in these cells. No increase in TGF-beta 1 mRNA was found in hepatocytes, and less than a 2-fold increase was found in Kupffer/endothelial cells isolated from fibrotic livers.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Amplification of the metallothionein-1 and metallothionein-2 genes in copper-resistant hepatoma cells.

The molecular basis for increased metallothionein concentrations in copper-resistant hepatoma cells was examined. The copper-resistant cell line HAC600, which is maintained in 600 microns copper, had increased steady-state mRNA levels for both the metallothionein-1 (MT-1) and the metallothionein-2 (MT-2) genes. Levels of mRNA were increased 11-fold for MT-1 and 15-fold for MT-2, with no significant change in alpha-tubulin mRNA content. HAC600NM cells, which are copper-resistant cells kept in a normal copper concentration for over 1 year, also had eight- and tenfold increases in MT-1 and MT-2 mRNA levels. Nuclear run-on assays showed that MT-1 and MT-2 gene transcription was increased nine- and eightfold in HAC600 cells and seven- and tenfold in HAC600NM cells, respectively. Southern blot analysis showed amplification of both metallothionein genes in HAC600 and HAC600NM cells. Thus the molecular basis of increased metallothionein in these hepatoma cells involved a stable gene amplification of both MT genes. The greater increase in metallothionein mRNA levels in HAC600 cells relative to the changes in transcription suggests that posttranscriptional mechanisms of gene regulation may also be acting in these cells.

Animals↗

PubMed1990

Ito-cell gene expression and collagen regulation.

Ito cells are perisinusoidal cells thought to be a major source of collagen in normal and fibrotic livers. These cells appear to have features similar to several cell types but when cultured assume a fibroblast-like morphology. In this study we evaluated the phenotype of both freshly isolated and cultured Ito cells by examining their gene expression. To better define the modulators of Ito-cell collagen synthesis, we also examined the effect of transforming growth factor-beta 1, tumor necrosis factor-alpha and dexamethasone on collagen synthesis by these cells. Northern hybridization analysis revealed that cultured Ito cells expressed different types of procollagen mRNAs than did freshly isolated cells. Cultured cells contained large amounts of type I procollagen mRNA and lesser amounts of types III and IV, whereas freshly isolated cells contained more type IV procollagen mRNA than types I and III. Treatment of cultured cells with either transforming growth factor-beta 1 or tumor necrosis factor-alpha resulted in a greater than three-fold increase in total collagen content, and the effects of these cytokines on Ito-cell collagen synthesis involved different levels of gene regulation. Transforming growth factor-beta 1-treated cells had an approximately threefold increase in their type I procollagen mRNA levels, whereas no increase in this mRNA level was found in tumor necrosis factor-alpha-treated cells. Transforming growth factor-beta 1 treatment induced a twofold increase in transforming growth factor-beta 1 mRNA content in cultured cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed1990

Albumin and collagen gene regulation in alcohol- and virus-induced human liver disease.

Common features of chronic alcoholic liver disease are progressive hypoalbuminemia and a spectrum of liver fibrosis. The molecular mechanisms that account for these effects are still the subject of controversy. Therefore, in the present study we evaluated albumin and collagen gene expression in livers of alcohol abusers and patients with virus-induced liver disease. Albumin and pro alpha 1(I) collagen messenger RNA levels were determined in 30 patients who underwent diagnostic liver biopsy. Of 14 alcoholics, 7 had alcoholic hepatitis alone and the other 7 had cirrhosis plus alcoholic hepatitis. Of 16 nonalcoholic patients with chronic viral infection, 6 had chronic active hepatitis and 10 had cirrhosis plus chronic active hepatitis. Total RNA was extracted from a portion of each biopsy specimen, hybridized with a human albumin or collagen complementary DNA clone, and compared with 2 normal surgical specimens, which served as controls. The Northern hybridization studies showed that (a) despite the presence of inflammation and fibrosis, the albumin messenger RNA levels of alcoholics were similar to those of the controls; (b) these alcoholics had significantly higher levels of albumin messenger RNA than did patients with similar histological levels of disease due to viral infection; and (c) all the categories of patients had markedly increased procollagen messenger RNA levels compared with controls. Given these results it is tempting to speculate that alcohol may actually increase albumin messenger RNA content in humans as it does in animals. Furthermore, the increased procollagen messenger RNA levels in fibrotic livers suggest that an increase in collagen syntheses may be a significant factor in the pathogenesis of hepatic fibrosis.

Adult↗

PubMed1977

Multispecific lymphoid cell surface receptors.

When mice are sequentially immunized with two antigens to give an oligoclonal "double-binding" antibody response, there is a concomitant increase of "double-binding" cell surface receptors on their splenic lymphocytes. Competition studies suggest that the capacity to bind the two ligands, bovine pancreatic ribonuclease (EC 3.1.4.22) and a 2,4-dinitrophenyl (DNP) derivative, is a function of the same molecules. In ribo-nuclease-primed mice, an early response to bovine gamma globulin containing an average of 60 Dnp groups per molecule is the appearance of an increasing number of cells bearing surface receptors binding both ribonuclease and Dnp. Later, these double-binding cells are diluted by cells that bind Dnp, but not ribonuclease. The analogous phenomenon is observed when the two antigens are used in reverse order. While other reports suggest that there may be several different receptors in relatively undifferentiated cells from unimmunized mice, it seems likely that cells committed to antibody production carry a predominant multispecific cell surface immunoglobulin receptor.

Animals↗