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Biomedical subjects

L G Fine

Publications and source records attributed to L G Fine.

At least 19 recordsLinked to original sources
PubMed1999

The concept of glomerular self-defense.

The balance between local offense factors and defense machinery determines the fate of tissue injury: progression or resolution. In glomerular research, the most interest has been on the offensive side, for example, the roles of leukocytes, platelets, complement, cytokines, eicosanoids, and oxygen radical intermediates. There has been little focus on the defensive side, which is responsible for the attenuation and resolution of disease. The aim of this review is to address possible mechanisms of local defense that may be exerted during glomerular injury. Cytokine inhibitors, proteinase inhibitors, complement regulatory proteins, anti-inflammatory cytokines, anti-inflammatory eicosanoids, antithrombotic molecules, and extracellular matrix proteins can participate in the extracellular and/or cell surface defense. Heat shock proteins, antioxidants, protein phosphatases, and cyclin kinase inhibitors may contribute to the intracellular defense. This article outlines how the glomerulus, when faced with injurious cells or exposed to pathogenic mediators, defends itself via the intrinsic machinery that is brought into play in resident glomerular cells.

Glomerulonephritis↗
PubMed1999

British contributions to renal physiology: Of dynasties and diuresis.

British contributions to renal physiology trace back to the seminal contribution of William Bowman, who defined the structure of mammalian nephron and its blood supply and pointed out its likely mode of function. A series of contributions followed, which stemmed from a distinguished lineage of physiologists based at University College London and which had, as its high point, the establishment by Ernest H. Starling, in 1899, of a method for measuring oncotic pressure and the subsequent demonstration that glomerular filtration requires a hydrostatic pressure in excess of oncotic pressure in the glomerular capillaries. Arthur Cushny published a monograph on renal function in 1917 which had wide influence. The homeostasis of water and sodium chloride were the subjects of important contributions by Verney and De Wardener, respectively. Little contribution was made by British renal physiologists to the understanding of single nephron function with the emphasis being largely on integrative physiology.

Diuresis↗
PubMed1999

Inference of the existence of high blood pressure as a cause of renal disease in the mid-19th century: observations on vascular structures in the kidney.

Histological examination of the kidney was well under way by the mid-19th century. Pathological changes noted to be present in Bright's disease gave rise to considerable debate in the literature of the time. Toynbee was perhaps the first to note medial hypertrophy and intimal narrowing of blood vessels in the kidney, while Johnson, around the same time, thought that kidney disease was the cause of compressed vessels. Although he later proposed a causal relationship between contraction of vessels and hypertrophy, Johnson never went beyond the insights articulated by Bright himself and failed to make the link between hypertrophy of vessels and persistently raised blood pressure. Traube considered the possibility that cardiac and renal disease could be the consequences of the same unknown disease, but rejected hypertrophy per se as a causal factor. Gull and Sutton disagreed strongly with Johnson and proposed the presence of a general disease which leads to both cardiac hypertrophy and renal disease. But it was Ewald, writing in Germany, who was able to ascribe both cardiac and vascular hypertrophy to increasing tension in the arterial system and he was the first to articulate the effect of hypertension on the kidney.

England↗
PubMed1997

In vivo transfer of engineered macrophages into the glomerulus: endogenous TGF-beta-mediated defense against macrophage-induced glomerular cell activation.

Communication between resident glomerular cells and infiltrating macrophages plays a crucial role in the pathogenesis of glomerular disease. Using matrix metalloproteinase-9 (MMP-9) as an indicator molecule, we examined the interaction between mesangial cells and macrophages. Mesangial cells cocultured with activated macrophages or exposed to macrophage-conditioned media produced abundant MMP-9. We identified the stimulator secreted by macrophages as IL-1 because mesangial cells overexpressing IL-1 receptor antagonist protein showed a blunted expression of MMP-9 in response to the macrophage-conditioned medium. In contrast, culture supernatants of mesangial cells inhibited MMP-9 production by macrophages in a dose-dependent fashion. This inhibitor was identified to be TGF-beta1, since neutralization of TGF-beta1 abrogated the inhibitory effect of the mesangial cell-conditioned medium. To investigate whether activated macrophages induce glomerular MMP-9 expression, and if so, how endogenous TGF-beta1 modulates the induction, stimulated reporter macrophages were transferred into normal rat glomeruli or glomeruli in the regeneration phase of acute anti-Thy-1 glomerulonephritis. In the normal glomeruli, MMP-9 expression was up-regulated in resident cells after the transfer of activated macrophages. This induction was substantially repressed in the regenerating glomeruli that produced active TGF-beta1. These results point to potential mechanisms involved in glomerular control of MMP-9. Based upon the in vitro evidence, TGF-beta1 was identified as an endogenous "defender" that attenuates certain actions of infiltrating macrophages in the glomerulus.

Animals↗
PubMed1997

Genetic manipulation of the kidney.

Successful gene transfer into specific renal structures allows for evaluation of in vivo effects of certain molecules on the structure and function of the kidney. It would also be useful for therapeutic intervention in renal diseases by introducing "beneficial" genes into the affected sites. Towards achieving these goals, several gene transfer approaches have been developed using retrovirus, adenovirus and liposome. By introducing these gene transfer vectors via particular access routes, it is feasible to selectively manipulate the function of certain renal structures. Through the renal circulation, exogenous genes can be targeted to the vasculature and glomerulus, and possibly to the proximal tubules. Using a retrograde approach via the urinary tract, access to the collecting ducts can be gained. Implantation of genetically modified cells under the capsule of the kidney allows for diffusion of transgene products into the interstitium. Transplantation of embryonic metanephric tissues also provides a biological window for genetic manipulation. Furthermore, utilisation of fertilised eggs or embryonic stem cells would enable the creation of "transgenic kidneys" or "gene knockout kidneys". This article summarises the current experience with gene transfer to the kidney and addresses the potential strategies in vivo.

Animals↗
PubMed1997

Hypoxia stimulates proximal tubular cell matrix production via a TGF-beta1-independent mechanism.

Tubulointerstitial fibrosis is characterized by tubular basement membrane thickening and accumulation of interstitial extracellular matrix (ECM). Since chronic low-grade hypoxia has been implicated in the pathogenesis of fibrosis and proximal tubular epithelial cells (PTE) are sensitive to oxygen deprivation, we hypothesized that hypoxia may stimulate ECM accumulation. In human PTE, hypoxia (1% O2, 24 hr) increased total collagen production (15%), decreased MMP-2 activity (55% +/- 13%; control = 100%) and increased tissue inhibitor of metalloproteinase-1 (TIMP-1) protein. Collagen IV mRNA levels decreased while collagen I mRNA increased, suggesting induction of interstitial collagen. Hypoxia-induced changes persisted on re-oxygenation with increased expression of TIMP mRNAs. A potential mediator for these effects is transforming growth factor-beta1 (TGF-beta1), a major pro-fibrogenic factor produced by PTE. Although hypoxia stimulated TGF-beta production (2- to 3-fold), neutralizing anti-TGF-beta1 antibody did not abolish the hypoxia-induced changes in gelatinase activity, TIMP-1, collagen IV or collagen I mRNA expression, implying that TGF-beta1 is not the mediator. Furthermore, exogenous TGF-beta1 (0 to 10 ng/ml) did not mimic hypoxia, as it stimulated MMP-2 activity and increased the expression of collagen IV, collagen I and TIMP-1 mRNA. The data suggest that hypoxia may be an important pro-fibrogenic stimulus independent of TGF-beta1.

Cell Division↗
PubMed1997

Unravelling dropsy: from Marcello Malpighi's discovery of the capillaries (1661) to Stephen Hales' production of oedema in an experimental model (1733).

A modern understanding of oedema formation traditionally begins with Starling's description in 1898 of hydrostatic and oncotic forces acting on the capillary membrane. Clearly, hypotheses of oedema formation predating the knowledge of the existence of capillaries must have been incomplete. Marcello Malpighi first described capillaries in 1661, but although he displayed a good grasp of the principles of the Harveian circulation and believed that oedema fluid (the clinical entity dropsy) was derived from the blood rather than the tissues, we have found no evidence that he realised the central role played by his discovery. However, only 60 years later, Stephen Hales' Haemastaticks reveals the creation of an experimental model for dropsy which led him towards an understanding of oedema formation not far behind Starling.

Anatomy↗
PubMed1996

Transforming growth factor-beta 1 is the predominant paracrine inhibitor of macrophage cytokine synthesis produced by glomerular mesangial cells .

Cross-communication between glomerular cells and infiltrating mononuclear cells plays an important role in the generation of or recovery from glomerular diseases. We found that cultured mesangial cells secrete a factor that inhibits production of proinflammatory cytokines by activated macrophages. Treatment of J774.2 macrophages with conditioned media from rat mesangial cells blunted the transcriptional induction of IL-1 beta, IL-6, and TNF-alpha by LPS. None of the media conditioned by other fibroblastic, epithelial, or endothelial cell lines exhibited the inhibitory effect. Media conditioned by normal rat glomeruli contained a similar inhibitory activity, which was enhanced in an acute model of mesangial proliferative glomerulonephritis. To identify the active component involved, we examined the expression of known macrophage deactivators IL-10, IL-13, and TGF-beta 1 in mesangial cells. Under the basal culture conditions, strong expression of TGF-beta 1 mRNA was observed, whereas expression of neither IL-10 nor IL-13 was detected. Immunoblot analysis and a specific bioassay detected the active form of TGF-beta 1 exclusively in the mesangial cell conditioned media. The inhibitory activity was enhanced by heat treatment, consistent with the known property of TGF-beta. A specific anti-TGF-beta 1 neutralizing Ab abolished the inhibitory effect exerted by the mesangial cell media, and exogenously added TGF-beta1 suppressed macrophage cytokine expression in a dose-dependent manner. These findings demonstrate that mesangial cells and isolated glomeruli secrete a factor which suppresses cytokine expression by activated macrophages, the active entity being identified as TGF-beta 1.

Animals↗
PubMed1996

Mesangial cell-derived transforming growth factor-beta 1 reduces macrophage adhesiveness with consequent deactivation.

Adhesion of macrophages is a crucial event that determines the number and function of macrophages at inflammatory sites. The aim of this study was to elucidate the role of mesangial cells in the regulation of macrophage adhesiveness. J774.2 macrophages were suspended in serial dilutions of mesangial cell conditioned medium (MC medium) and seeded on plastic tissue culture plates. MC medium did not affect the initial adhesion of macrophages but induced subsequent detachment in a concentration-dependent manner. A similar effect was observed when macrophages were plated on plastic coated with laminin, collagen type IV or Matrigel. The reduced adhesiveness was reversible, and cell viability was unaffected by MC medium, indicating that the effect is not due to cytotoxicity. Conditioned media from fibroblastic, epithelial and endothelial cell lines did not induce macrophage detachment. To identify the active component in MC medium, we examined the involvement of transforming growth factor-beta 1 (TGF-beta 1) in the process. Mesangial cells constitutively expressed TGF-beta 1 mRNA, and MC medium contained the active form of TGF-beta 1. Exogenously added TGF-beta 1 induced macrophage detachment in a dose-dependent manner, and an anti-TGF-beta 1 neutralizing antibody partially abolished the activity of MC medium, indicating the involvement of TGF-beta 1 as an active component. Compared to adherent cells, detached macrophages showed reduced mitogenic activity and blunted induction of IL-1 beta and IL-6 in response to lipopolysaccharide. These data demonstrate that TGF-beta 1 is a mesangial cell-derived factor that impairs adhesiveness of macrophages and confers blunted responses to a specific stimulus. These findings suggest one potential mechanism for macrophage clearance from inflamed glomeruli.

Animals↗
PubMed1996

Pexicrine effects of basement membrane components on paracrine signaling by renal tubular cells.

Paracrine interactions between tubular epithelium and interstitial cells have been assumed to be mediated largely by soluble cytokines. While the role of extracellular matrix (ECM) and matrix metalloproteinases (MMPs) in modifying cell function is widely appreciated, the role of the renal tubular basement membrane in modulation of tubulointerstitial function has not been studied. To establish whether those components of the ECM which support tubular epithelial cells also influence cell function (that is, a pexicrine effect), we studied their effects on paracrine signaling between epithelium and fibroblasts. Primary cultures of rat renal proximal tubular epithelial cells (PTE) were cultured on laminin (LN), collagen types-IV and -I (COL-IV, COL-I) and fibronectin (FN). PTE attained confluence more rapidly when grown on LN = COL-IV > COL-I = FN = plastic. On all substrates PTE produced the MMPS, gelatinase-A and -B and collagenase with an apparent increase in gelatinase-A and -B production when cultured on LN. MMPs were found to be secreted both apically and basally with basal secretion predominating, except on LN where secretion was primarily from the apical surface. Cultures of rat renal cortical interstitial fibroblasts were established and characterized. Cortical fibroblasts (CF) were found to secrete gelatinase-A and collagenase. Conditioned medium (CM) from PTE cultured on COL-IV stimulated proliferation of CF but proliferation was unaltered by CM from PTE grown on other substrates. By contrast, co-culture of PTE on LN with CF suppressed collagenase and gelatinase activity in both cell types, indicating a bi-directional, paracrine modulation of MMP production. Thus in the tubulointerstitium, the BM components LN and COL-IV not only fulfill a structural role but act as signaling molecules with differential effects which modify the function of the tubular epithelium and its paracrine interaction with adjacent fibroblasts. The initiation of interstitial fibrosis induced by injury to the tubular basement membrane may reside in the perturbation of this interaction.

Animals↗
PubMed1995

An endothelin-1 mediated autocrine growth loop involved in human renal tubular regeneration.

Renal tubules have the capacity to regenerate following injury. We have investigated the possibility that tubular-derived endothelins, acting as autocrine growth factors, may be involved in this response in human kidney. ET-1 immunoreactivity was demonstrated by immunohistochemical staining in proximal tubules, distal cortical tubules and medullary collecting ducts of human kidney. In cultured human renal proximal tubular cells, RNAase protection assays demonstrated the expression of ET-1 and ET-2 mRNA's, and radioimmunoassay, following separation of conditioned medium by reverse phase HPLC, showed immunoreactive material which co-eluted with ET-1 and ET-2. Competition binding studies revealed the presence of at least two types of endothelin receptor: one with high and one with low affinity for ET-3 relative to ET-1. Analysis of cellular RNA by RT-PCR demonstrated expression of mRNA's for both ETA and ETB receptor subtypes. Combined blockade of ETA and ETB receptors (by PD-145065) but not that of ETA receptors alone (by BQ-123) blocked the mitogenic effect of exogenous or endogenous ET-1 and also profoundly suppressed endogenous ET-1 synthesis. By contrast, incubation with the ETB receptor agonist, BQ-3020, stimulated endogenous ET-1 synthesis. Exposure of the cells to hypoxia (1% O2 for 16 to 24 hr) resulted in specific up-regulation of ET-1 but not ET-2 gene expression. These findings reveal the existence of a hypoxia-inducible, autocrine growth system in human proximal tubular cells, which is mediated by ET-1 through the ETB receptor, and which could function in vivo as an autoregenerative system for restoring tubular integrity after injury. The widespread distribution of ET-1 peptide in different tubular segment suggests that ET-1 mediated tubular regeneration may also occur in other nephron segments.

Binding, Competitive↗
PubMed1995

Transfer of a mutated gene encoding active transforming growth factor-beta 1 suppresses mitogenesis and IL-1 response in the glomerulus.

Using in vivo gene transfer, we examined the anti-inflammatory potential of transforming growth factor-beta 1 (TGF-beta 1) in the renal glomerulus. TGF-beta 1 cDNA, modified to allow for secretion of the active form of TGF-beta 1, was introduced into cultured rat mesangial cells. The responses of the established transfectants were examined in culture. In vitro, the transduced mesangial cells showed a reduced mitogenic response to fetal calf serum and were insensitive to induction of matrix metalloproteinase-9 (MMP-9) by the proinflammatory cytokine IL-1 beta. To examine whether glomeruli which express active TGF-beta 1 in vivo are insensitive to these same stimuli, TGF-beta transfectants were transferred into normal rat glomeruli via renal artery injection. After 24 hours, isolated glomeruli containing transfectants exhibited TGF-beta bioactivity, a reduced mitogenic response, and repressed expression of MMP-9 in response to IL-1 beta. We further examined the responses of these chimeric glomeruli to an in vivo mitogenic stimulus by transferring TGF-beta transfectants into glomeruli of kidneys one day after the induction of anti-Thy-1 nephritis. The mitogenic activity of isolated glomeruli was examined four days after the cell injection. Compared to unmodified or mock cell-containing glomeruli, the in vivo mitogenic activity of glomeruli containing TGF-beta transfectants was significantly repressed. Furthermore, cellular outgrowth from nephritic glomeruli expressing active TGF-beta 1 was also suppressed ex vivo compared to controls. These data indicate that TGF-beta 1 inhibits mitogenesis and IL-1 response of the glomerulus and may, in part, act as a potential early suppressor of glomerular inflammation.

Animals↗
PubMed1995

Roles of hepatocyte growth factor/scatter factor and the met receptor in the early development of the metanephros.

Several lines of evidence suggest that hepatocyte growth factor/scatter factor (HGF/SF), a soluble protein secreted by embryo fibroblasts and several fibroblast lines, may elicit morphogenesis in adjacent epithelial cells. We investigated the role of HGF/SF and its membrane receptor, the product of the c-met protooncogene, in the early development of the metanephric kidney. At the inception of the mouse metanephros at embryonic day 11, HGF/SF was expressed in the mesenchyme, while met was expressed in both the ureteric bud and the mesenchyme, as assessed by reverse transcription PCR, in situ hybridization, and immunohistochemistry. To further investigate the expression of met in renal mesenchyme, we isolated 13 conditionally immortal clonal cell lines from transgenic mice expressing a temperature-sensitive mutant of the SV-40 large T antigen. Five had the HGF/SF+/met+ phenotype and eight had the HGF/SF-/met+ phenotype. None had the HGF/SF+/met- nor the HGF/SF-/met- phenotypes. Thus the renal mesenchyme contains cells that express HGF/SF and met or met alone. When metanephric rudiments were grown in serum-free organ culture, anti-HGF/SF antibodies (a) inhibited the differentiation of metanephric mesenchymal cells into the epithelial precursors of the nephron; (b) increased cell death within the renal mesenchyme; and (c) perturbed branching morphogenesis of the ureteric bud. These data provide the first demonstration for coexpression of the HGF/SF and met genes in mesenchymal cells during embryonic development and also imply an autocrine and/or paracrine role for HGF/SF and met in the survival of the renal mesenchyme and in the mesenchymal-epithelial transition that occurs during nephrogenesis. They also confirm the postulated paracrine role of HGF/SF in the branching of the ureteric bud.

Animals↗