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Biomedical subjects

E G Neilson

Publications and source records attributed to E G Neilson.

At least 91 records · Page 5Linked to original sources
PubMed1992

Increases in levels of collagen types I and IV messenger ribonucleic acid in murine kidneys after treatment with ciclosporin.

We investigated changes in the levels of mRNA transcripts encoding types I and IV collagen in the kidney following the administration of ciclosporin (CS) in mice. Daily doses of CS increased the levels of mRNAs encoding collagen types I and IV in whole kidneys harvested 4 weeks after treatment. At this time point, neither a reduction of renal function detected by serum creatinine, nor histologic evidence of interstitial damage were present. Elevated levels of serum creatinine as well as mild interstitial changes did develop, however, 12 weeks after daily treatment with CS. Collagen type I transcripts were almost normal after 12 weeks, whereas levels of type IV mRNA were still elevated. Our findings indicate that increases in transcripts encoding collagens precede a deterioration in renal function and the development of interstitial changes in this murine model of chronic CS nephrotoxicity.

Animals↗
PubMed1992

Tubular antigen-binding proteins repress transcription of type IV collagen in the autoimmune target epithelium of experimental interstitial nephritis.

We have been studying immune interactions with somatic cells using a tubular antigen-binding protein (ThF) secreted by helper T lymphocytes harvested from mice that have an autoimmune form of interstitial nephritis called anti-tubular basement membrane disease. This ThF, although characterized originally because of its ability to induce effector T cells, additionally recognizes the nephritogenic 3M-1 antigen expressed by its target renal tubular epithelium. We believe these proteins, in general, may modulate directly some homeostatic functions in organ-derived cells, and now report that our ThF represses specifically the cellular transcription and secretion of basement membrane type IV collagen in tubular epithelium. These in vitro findings of reduced levels of mRNA encoding type IV collagen correlate well with in situ hybridization studies performed on kidneys expressing early autoimmune lesions, and predict a progressive drop in the expression of type IV collagen in the interstitium. Such a novel and unexpected repression of transcription of type IV collagen might easily impart or facilitate permanent change in the infrastructure of kidney architecture during autoimmune injury and, perhaps, contributes to the process of tubular atrophy attendant to prolonged renal inflammation.

Animals↗
PubMed1992

Angiotensin II stimulates the proliferation and biosynthesis of type I collagen in cultured murine mesangial cells.

A murine mesangial cell line (MMC) was established from the glomeruli of SJL mice to study the influence of angiotensin II (ANG II) on their growth and function in a serum-free culture. Murine mesangial cells exhibit the phenotypic characteristics of mesangial cells, including staining for desmin, vimentin, Thy 1, and types I and IV collagen by immunofluorescence. The addition of daily doses of 10(-6) to 10(-11) mol/l ANG II to MMCs also induced their proliferation in serum-free media. This effect on growth was independent of the presence of insulin in the media, and was receptor mediated, because the specific ANG II-receptor antagonist DuP 753 abolished proliferative growth. Angiotensin II also stimulated mainly the biosynthesis of type I collagen in our MMCs. Transfection of MMCs with chimeric genes containing enhancer/promoter elements for alpha 2(I) and alpha 1(IV) collagens linked to a chloramphenicol acetyltransferase reporter demonstrated that the stimulatory effect of ANG II for type I depends, at least to some extent, on an increase in transcription. These findings indicate collectively that ANG II in serum-free cultures can be a paracrine catalyst for the growth and biosynthesis of type I collagen in mesangial cells.

Angiotensin II↗
PubMed1991

The influence of glucose concentration on angiotensin II-induced hypertrophy of proximal tubular cells in culture.

Incubation of cultured murine proximal tubular cells in serum-free media containing 450 mg/dl of glucose resulted in cellular hypertrophy as defined by an increase in cell size, total protein content, and synthesis after 72 h. 10 nM angiotensin II further increased this hypertrophy, but failed to have any effect on cells grown in 100 mg/dl glucose. This enhancement by angiotensin II was blocked by treatment with 1 microM of the angiotensin-receptor antagonist DuP 753. Although cells incubated in either glucose media exhibited similar high-affinity angiotensin II-receptors, the receptor density was elevated only in cells grown in the presence of high glucose. Stimulation of cells in high glucose for 60 min with 10 nM angiotensin II also reduced significantly intracellular cAMP concentrations. This was not the case for proximal tubular cells cultured in normal glucose. Our results indicate that high glucose and angiotensin II have additive effects on the induction of hypertrophy in renal tubular cells.

Angiotensin II↗
PubMed1991

Molecular characterization of a major nephritogenic domain in the autoantigen of anti-tubular basement membrane disease.

Anti-tubular basement membrane (alpha TBM) disease is a form of primary interstitial nephritis mediated by autoimmune T cells and alpha TBM antibodies. In mice and humans the nephritogenic immune response is directed to a glycoprotein (3M-1) found along the proximal tubule of the kidney. We have isolated cDNAs from an expression library that encodes for the common framework domain of the 3M-1 antigen. This common domain was once related evolutionarily to a family of intermediate filament-associated proteins. Northern hybridization revealed that all isoforms of 3M-1 range between 1700 and 1900 base pairs and in situ hybridization studies indicate that transcripts are found in tubular epithelium. Candidate peptide fragments were deduced and synthesized from the sequence encoding this common framework domain, and one of the peptide residues was able to bind a monoclonal 3M-1-reactive alpha TBM antibody, stimulate the growth of 3M-1-reactive helper T cells, and induce nephritogenic effector T cells capable of producing interstitial nephritis. Our results indicate that a unique, immunodominant region of the 3M-1 antigen is an informative participant in the emergence of autoimmune injury to certain basement membranes.

Amino Acid Sequence↗
PubMed1991

The nephritogenic immune response.

Recent work has improved our understanding of a number of aspects of the nephritogenic immune response. Progress has been made in the understanding of the development of idiotypic networks, and in understanding the structural nature of the targets of self-reactive T cells and the paracrine mediators that are released as part of the local inflammatory response.

Animals↗
PubMed1991

Expression of homeobox genes in a proximal tubular cell line derived from adult mice.

We have been studying the expression of several homeobox genes in cultures of proximal tubular epithelium (MCT cells) harvested from adult mus musculus. Hox genes 2.1, 2.3, and 3.3, in particular, are all expressed at low levels in resting MCT cells. The expression of Hox 2.1 and 3.3 were not influenced by mitogenic (epidermal growth factor: EGF, and platelet-derived growth factor: PDGF) nor by hypertrophogenic cytokines (angiotensin II: Ang II) in serum-free media. Transcripts for Hox 2.3, however, were elevated in MCT cells by Ang II. EGF, and serum treatment, as early as 30 minutes after their addition, whereas no change, or slight reductions were observed with transforming growth factor beta (TGF beta), PDGF, and gamma-interferon (gamma IFN). Hox 2.3 was also super-induced by serum, in the presence of cycloheximide, in cells rested previously in serum-free media, suggesting that new protein synthesis was not required for expressive augmentation. The induction of Hox 2.3, moreover, was not specific for tubular epithelium, since the gene could be activated in tubulointerstitial fibroblasts after treatment with EGF. These experiments collectively represent a first report regarding the characterization of transcripts encoding homeoboxes in adult cells derived from renal tissue. The putative DNA-binding properties of homeobox proteins in general, the prompt and rapid induction of Hox 2.3 by morphogenic cytokines in tubulointerstitial cells, and the observed effect of cycloheximide on this gene, all indicate that Hox 2.3 might have a role in the general activation of mature somatic cells, as an immediate early event. probably in the capacity of a nuclear trans-acting factor.

Animals↗
PubMed1991

Analysis of the cDNA sequence encoding MHC-A beta in tubular epithelium from mouse kidney.

Class II gene products of the major histocompatibility complex (MHC) are not expressed usually in abundance on normal epithelium. The cell surface visibility of such proteins for the immune system is thought to be limited protectively in order to minimize inflammation consequent to the recognition of self-antigens in parenchymal structures by T lymphocytes. In the current experiments we investigated whether the previously recognized sparseness of A beta on the surface of tubular epithelial cells might be accounted for by a protein coding difference deduced from the primary structure of its transcript compared with sequence from lymphoid cells that normally express A beta in generous amounts. We demonstrate, however, using clones obtained from a cDNA library prepared from tubular epithelium harvested from H-2s (A beta/alpha+; E beta/alpha-) mice susceptible to autoimmune interstitial nephritis, that the nucleotide sequence encoding the class II A beta chain in cells from both compartments is essentially identical. Our findings suggest that there is no primary structural aberrancy in the coding region of parenchymal A beta that would contribute to its low expression. The protective tolerance afforded by reduced numbers of class II molecules in normal tissues is, therefore, more likely the result of repressive regulatory processes.

Animals↗
PubMed1991

Molecular mechanisms of tubulointerstitial hypertrophy and hyperplasia.

Adult kidneys, which are principally composed of tubulointerstitium, do not normally regenerate or expand their working pool of functional cells at a very high rate. Loss of kidney tissue, however, can lead to some compensatory renal enlargement. The catalytic forces initiating such exchanges have not been fully articulated by current experimental endeavors. Increasing evidence, nevertheless, does suggest that factors other than simple changes in renal hemodynamics may be involved in this process. Different cellular elements in the tubulointerstitial microenvironment probably modulate changes in tubular enlargement or size through a complex cytokine network. Autocrine and paracrine stimulation of enlargement by different local growth factors also seem to play a pivotal role. After binding to cellular receptors, these factors activate signal transduction pathways resulting in expression of immediate early genes, which by themselves can synchronize the expression of subsequent genes through the medium of transacting factors. The renal enlargement response can also be modified by endocrine hormones that can activate such genes directly and/or stimulate other adjunctive processes, like receptor expression for the regional binding of growth factors. Furthermore, renal enlargement is under negative feedback of inhibitory factors like TGF beta. It is possible, for example, that special genes exist which are only expressed to arrest enlargement. It has been further suggested that activation of the Na+/H+ antiporter is a common denominator in renal enlargement. Recent findings, however, indicate that the activation of this antiporter is not always necessary, and might rather be a parallel event rather than a key phenomena in tubular enlargement. G0/G1 transition of tubular cells seems to involve similar factors in tubular hypertrophy and hyperplasia. The factors which are responsible for the final determination of the enlargement pattern (hypertrophy vs. proliferation) are unknown. The separation between hypertrophy and hyperplasia, although suggested by striking differences in cellular regulation, may be somewhat artificial, since responses leading to tubular enlargement also exist in circumstances where hyperplasia and hypertrophy are combined events. Recently it has been proposed that growth factors stimulate gluconeogenesis in proximal tubular cells producing hyperplasia, whereas factors inhibiting gluconeogenesis might induce hypertrophy. Whether the common pathway message of this intriguing hypothesis is correct still requires further validation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Mechanisms of tubulointerstitial fibrosis.

With regard to tubulointerstitial fibrogenesis we are left with a variety informational gaps regarding nearly all aspects of this clinically important process. Table 2 summarizes a generalized version of fibrogenesis based primarily on investigations in other organs. Extrapolation of data obtained with other fibrogenic systems is useful, but only in so far as it motivates us to adapt and test many of the experimental principles within in the context of the kidney. This begins with a comprehensive examination of the in vivo state, the establishment of adequate animal models, and the dissections of the process in vitro. Key areas for the future are the characterization of the signals involved, the cellular responses to these signals, and the variations in interactions produced by differing inciting fibrogenic conditions.

Extracellular Matrix↗
PubMed1991

Intracellular signaling of transcription and secretion of type IV collagen after angiotensin II-induced cellular hypertrophy in cultured proximal tubular cells.

Physiologic concentrations of angiotensin II (AII) can induce cellular hypertrophy in murine proximal tubular epithelium (MCT cells). This response is characterized by an increase in cell size, new protein synthesis, and by the secretion of new basement membrane type IV collagen in the absence of cellular proliferation. The present study was undertaken to evaluate the second messengers of these AII-induced cellular events with special reference to the increase in type IV collagen secretion. In initial experiments we observed that pretreatment of MCT cells with agents that increase concentrations of intracellular cAMP, like forskolin, dibutyryl cAMP, and isobutyl-methyl-xanthine abolish AII-induced amino acid incorporation, but have no effect on control cells or on their proliferation. In addition, 10(-8) M AII significantly decreased the concentration of intracellular cAMP. Phorbolesters were without significant effect on the hypertrophy or proliferation of AII-stimulated MCT cells or their rested controls. The transfection of MCT cells with reporter genes containing regulatory elements for type IV collagen revealed that the stimulatory effects of AII on collagen type IV depend, at least to some extent, on an increase in gene transcription. Agents increasing intracellular cAMP concentrations inhibited the AII-induced increase in transcription and secretion of collagen type IV, but had no effect on MCT cells grown in media without AII. Our findings provide evidence that AII-induced changes in tubular epithelium leading to the secretion of type IV collagen are mediated by a decrease in intracellular cAMP.

1-Methyl-3-isobutylxanthine↗
PubMed1990

Murine interstitial nephritis. IX. Induction of the nephritogenic effector T cell repertoire with an antigen-specific T cell cytokine.

The experiments presented in this report describe the biochemical and functional characteristics of a soluble Th cell factor (ThF) which can induce a nephritogenic effector T cell repertoire producing autoimmune interstitial nephritis. The ThF is Ag-specific, I-A-restricted, and comprises two chains noncovalently linked as a heterodimer. One chain at approximately 78,000 Mr is related to the TCR/Id and expresses a framework determinant (14-30) common to Ag-binding factors, and the other chain at approximately 82,000 Mr is I-A+. Together these chains can replace their parent cell by providing cognate help to precursor effector T lymphocytes in the presence of accessory cells, tubular Ag, and IL-2.

Animals↗
PubMed1990

Angiotensin II induces cellular hypertrophy in cultured murine proximal tubular cells.

In the present study we demonstrate that a murine proximal tubular cell line (MCT cells), expressing angiotensin II (ANG II) receptors [dissociation constant (Kd) = 0.89 nM; receptor density (R0) = 46,900 receptors/cell] in culture, can be induced to hypertrophy after the daily addition of exogenous ANG II (10(-8) M). This hypertrophic response was characterized by an increase in total cellular protein content, by an enhancement of [3H]leucine incorporation into precipitable proteins, and by an augmentation in cell size by cytofluorography. This ANG II effect producing MCT cell enlargement was demonstrable in the absence of cellular proliferation. Proliferation of MCT cells, however, could be induced by epidermal growth factor (EGF) or platelet-derived growth factor (PDGF), and pretreatment of rested MCT cells with ANG II further enhanced EGF-induced cell division. ANG II-induced hypertrophy in MCT cells was factor specific, in that it could be blocked with saralasin, and not induced by angiotensin I (ANG I). This hypertrophic response was also independent of prostaglandin E2 synthesis but was transducible by pertussis toxin-sensitive G proteins and involved, to some extent, the activation of Na(+)-H+ exchange. ANG II, as well as EGF and/or PDGF, moreover, could induce the cellular oncogenes c-fos, c-myc, c-N-ras, but not c-cis, which suggests that early gene activation is probably not a specific prerequisite for hypertrophy. Our findings demonstrate that ANG II, in culture, can be a single-factor event capable of inducing hypertrophy in proximal tubular cells.

Amiloride↗
PubMed1990

Cyclosporin A stimulates transcription and procollagen secretion in tubulointerstitial fibroblasts and proximal tubular cells.

The brief study described in this report was undertaken to determine whether cyclosporin A had any direct effect on the expression of tubulointerstitial procollagens in cultured renal cells. Our findings indicate that murine tubulointerstitial fibroblasts secreted significantly more procollagen type I after the addition of cyclosporin A, whereas syngeneic proximal tubular cells expressed significantly more types I and IV procollagen after cyclosporin stimulation. These increases in procollagen gene product correlated concordantly with changes in the levels of cytoplasmic mRNA with procollagen-specific cDNA probes. Transfection of these fibroblasts and proximal tubular cells with chimeric gene constructs containing enhancer/promoter elements for alpha2(I) and alpha 1(IV) procollagen linked to a chloramphenicol acetyltransferase reporter gene indicates that the stimulatory effect of cyclosporin on procollagen expression depends, at least to some extent, on an increase in transcriptional activity.

Animals↗
PubMed1989

Protective modulation of class II MHC gene expression in tubular epithelium by target antigen-specific antibodies. Cell-surface directed down-regulation of transcription can influence susceptibility to murine tubulointerstitial nephritis.

We have been studying the factors which permit autoimmune injury to the kidney leading to interstitial nephritis. Nonsusceptible mice develop L3T4+ effector T cells which do not recognize their 3M-1 target Ag, nor produce interstitial lesions in the kidney unless proximal tubular class II MHC Ag expression is increased, for example, by rIFN-gamma. Anti-tubular basement membrane/alpha 3M-1-Ab, normally present in such mice after immunization with 3M-1, produce an opposite result by diminishing class II transcription and expression. This unique antibody-ligand interaction on the surface of proximal tubular epithelium secreting 3M-1 serves as a novel protective regulatory response in interstitial parenchyma. The in vitro studies conveyed in this current report suggest that alpha 3M-1-Ab mediate this protective effect by reducing the transcription of mRNA encoding class II gene products. These findings, within the overall complexity of a nephritogenic immune response, demonstrate the important role certain elements may play in maintaining functional nonsusceptibility to autoimmune injury.

Animals↗