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Biomedical subjects

W A Border

Publications and source records attributed to W A Border.

At least 19 recordsLinked to original sources
PubMed2006

Noninhibitory PAI-1 enhances plasmin-mediated matrix degradation both in vitro and in experimental nephritis.

Plasminogen activator inhibitor-type 1 (PAI-1) is thought to be profibrotic by inhibiting plasmin generation, thereby decreasing turnover of pathological extracellular matrix (ECM). A mutant, noninhibitory PAI-1 (PAI-1R) was recently shown by us to increase glomerular plasmin generation and reduce disease in anti-thy-1 nephritis. Here, in vitro and in vivo studies were performed to determine whether enhanced plasmin-dependent ECM degradation underlies the therapeutic effect of PAI-1R. 3H-labeled ECM was produced by rat mesangial cells (MCs). The effect of wild-type PAI-1 (wt-PAI-1) and PAI-1R on ECM degradation by newly plated MCs was measured by the release of 3H into medium. In vivo, anti-thy-1 nephritis was assessed in normal, untreated diseased and PAI-1R treated rats with or without the plasmin/plasminogen inhibitor, tranexamic acid (TA). wt-PAI-1 totally inhibited plasmin generation and reduced ECM degradation by 76% when exogenous plasminogen was added. Although PAI-1R alone had no effect, PAI-1R in the presence of wt-PAI-1 reversed the wt-PAI-1 inhibition of ECM degradation in a time- and dose-dependent manner (P<0.001). Plasmin activity and zymography were consistent with ECM degradation. Plasmin inhibitors: alpha2-antiplasmin, aprotinin, and TA completely blocked PAI-1R's ability to normalize ECM degradation (P<0.001). Consistent with the in vitro results, TA reversed PAI-1R-induced reductions in glomerular fibrin and ECM accumulation. Other measures of disease severity were either unaltered or partially reversed. PAI-1R reduces pathological ECM accumulation, in large part through effectively competing with native PAI-1 thereby restoring plasmin generation and increasing plasmin-dependent degradation of matrix components.

Animals↗
PubMed2006

Perspectives on blockade of TGFbeta overexpression.

Many approaches to blocking profibrotic TGFbeta overexpression are under way. Therapeutic targeting of TGFbeta-Smad signaling holds promise for slowing or halting progressive renal disease. In this issue, Fukasawa et al., using the unilateral ureteral obstruction model, provide a new target for therapeutic intervention by identifying loss of the Smad corepressors Ski and SnoN as a mechanism that amplifies the profibrotic actions of TGFbeta.

Animals↗
PubMed2001

t-PA promotes glomerular plasmin generation and matrix degradation in experimental glomerulonephritis.

BACKGROUND: In addition to its well-known role in degrading fibrin, recent evidence suggests that plasmin degrades matrix proteins and activates prometalloproteinases. Plasmin is generated from plasminogen by tissue plasminogen activator (t-PA). We hypothesized that t-PA treatment increases plasmin generation in nephritic glomeruli and degrades pathological matrix leading to a therapeutic reduction in matrix accumulation. METHODS: Anti-Thy-1 nephritis was induced by injection of OX-7 antibody. Rats were given twice daily intravenous injections of saline (disease control group) or human recombinant t-PA (rt-PA; 1 mg/kg body weight) on days 3 through 5. Proteinuria, glomerular matrix protein staining, and glomerular mRNA levels for transforming growth factor-beta 1 (TGF-beta 1), fibronectin, and plasminogen activator inhibitor type 1 (PAI-1) were evaluated at day 6. Localization of rt-PA, plasmin generation by glomeruli in vitro, and glomerular production and content of active TGF-beta1 were also investigated. RESULTS: Compared with disease control animals, proteinuria and staining score for periodic acid-Schiff (2.75 +/- 0.17 vs. 1.41 +/- 0.09), fibronectin-EDA+ (19 +/- 2 vs. 14 +/- 1), laminin (35 +/- 2 vs. 25 +/- 2), type I collagen (33 +/- 1 vs. 21 +/- 3), and type IV collagen (27 +/- 2 vs. 23 +/- 1) were significantly reduced in treated rats (P < 0.01). Glomerular TGF-beta 1, fibronectin, and PAI-1 mRNA levels were unchanged. rt-PA colocalized with fibrin along glomerular capillary walls and in the mesangium. Nephritic glomeruli in vitro had decreased plasmin activity, which was elevated by an in vivo presacrifice injection of rt-PA. Glomerular production and content of active TGF-beta 1 were unchanged by the rt-PA injection. CONCLUSIONS: : These results show that injected rt-PA binds to fibrin in nephritic glomeruli, thus increasing plasmin generation and promoting pathological matrix degradation without activating latent TGF-beta. Agents that increase plasmin generation, such as t-PA, may have potential as antifibrotic therapies.

Animals↗
PubMed2001

Maximizing hemodynamic-independent effects of angiotensin II antagonists in fibrotic diseases.

Better understanding of the hemodynamic-independent actions of the renin-angiotensin system (RAS) may lead to improved therapies for heart, kidney, and liver fibrosis. The conventional view of the RAS is that its role is solely hemodynamic. Pharmacologic blockade of the RAS is beneficial in treating hypertension, as well as primary renal and cardiac diseases. Recent findings from clinical trials and several laboratories that used different experimental approaches have revealed a whole new dimension to the RAS that is beyond the realm of hemodynamics. The RAS is best viewed as part of a system of interconnected molecules biologically designed to be activated after tissue injury to promote tissue repair and, when in excess, tissue fibrosis. This new understanding of the RAS has important clinical implications. It predicts and explains why blockade of the RAS with angiotensin-converting enzyme inhibitors (ACEI), the newer receptor antagonists, or both together, will significantly slow the progression of fibrotic disease. However, it further suggests that higher doses and/or a combination of angiotensin II blockade with another agent or agents might truly halt progressive fibrosis.

Angiotensin II↗
PubMed2000

Tandem antifibrotic actions of L-arginine supplementation and low protein diet during the repair phase of experimental glomerulonephritis.

BACKGROUND: Based upon the central role transforming growth factor-beta (TGF-beta) overexpression appears to play in renal fibrotic diseases, we have recently advocated reduction of TGF-beta as a therapeutic target. As part of efforts to determine the strength of this approach, we have undertaken studies to quantitate the effects of currently used and promising therapies in terms of their potential to reduce markers of disease in anti-thymocyte-serum (ATS)-glomerulonephritis in the rat. Here we assess the therapeutic effect of L-arginine supplementation, which has been shown to reduce fibrosis in a number of hypertensive models, given alone or in combination with low protein diet and started 24 hours after disease induction. METHODS: Glomerulonephritis was induced by intravenous injection of OX-7 monoclonal antibody into 200 g Sprague-Dawley rats. Twenty-four hours later animals were placed in groups that were either untreated, treated with 1% L-arginine in drinking water or 6% protein diets or both. On the fifth day of disease 24-hour urine specimens were collected and systemic blood pressure was measured. On the sixth day rats were anesthetized. Kidneys were perfused, tissue was taken for PAS staining and glomeruli were isolated. Aliquots of glomeruli were used for RNA preparation and for culture to determine 72-hour production of TGF-beta, fibronectin and plasminogen activator-type 1 (PAI-1), which were assayed by ELISA on culture supernatants. Measures of nitrate and nitrite (NOx) production included plasma NOx, urinary NOx and glomerular production of NOx in culture. RESULTS: All disease measures except proteinuria and including matrix accumulation, TGF-beta, fibronectin and PAI-1 production and mRNA expression for TGF-beta, fibronectin and PAI-1 were significantly and similarly reduced by about 50% in groups treated with L-arginine or with low protein diet. Proteinuria was reduced in low protein treated but not in L-arginine supplemented rats. Neither systemic blood pressure nor measures of NO synthesis showed differences between groups that could be attributed to L-arginine supplementation. In contrast, disease-related increases in glomerular production of NOx were markedly reduced by low protein. Combined therapy resulted in small, but statistically significant decreases in most measures of disease. CONCLUSIONS: L-arginine supplementation reduces fibrotic disease in ATS-induced glomerulonephritis if started after disease induction. The absence of evidence for increased NO production related to L-arginine supplementation suggests that L-arginine is acting here through different pathways from those demonstrated in hypertensive models of disease. The data support the ideas that TGF-beta reduction is a valid therapeutic target and that quantitation of TGF-beta reduction is a useful approach for comparing antifibrotic drug candidates.

Animals↗
PubMed2000

Angiotensin II blockade and low-protein diet produce additive therapeutic effects in experimental glomerulonephritis.

BACKGROUND: Transforming growth factor-beta (TGF-beta) overexpression plays a key role in the accumulation of extracellular matrix in acute and chronic renal diseases. Recent studies have suggested that the degree of reduction in pathological TGF-beta overexpression can be used as a therapeutic index to evaluate the antifibrotic potential of pharmacological angiotensin II (Ang II) blockade in renal disease. Using this target, we found that treatment with the angiotensin I-converting enzyme inhibitor enalapril or the Ang II type 1 receptor antagonist losartan reduced TGF-beta overexpression more effectively at doses clearly higher than those required to control blood pressure. However, both forms of Ang II blockade were only partially effective in normalizing TGF-beta expression. This study investigated whether a greater antifibrotic, TGF-beta-reducing benefit can be achieved when Ang II blockade is combined with dietary protein restriction. METHODS: Mesangioproliferative glomerulonephritis was induced in male Sprague-Dawley rats on a normal-protein diet. Treatment with a low-protein diet and/or maximally effective doses of enalapril or losartan was started one day after disease induction. On the fifth day, 24-hour urine protein excretion was measured. On the sixth day, cortical kidney tissue was taken for periodic acid-Schiff staining. Isolated glomeruli were used for mRNA extraction or were placed in culture for determination of production of TGF-beta1, the matrix protein fibronectin, and the protease inhibitor plasmin activator inhibitor type 1 (PAI-1) by enzyme-linked immunosorbent assay. RESULTS: Compared with untreated nephritic animals on a normal-protein diet, a single treatment with enalapril, losartan, or low-protein diet significantly reduced glomerular TGF-beta production, albeit to a similar degree of approximately 45%. A moderate, but significant further reduction in pathological TGF-beta expression of a total of 65% for enalapril and 60% for losartan was achieved when these drugs were combined with low-protein feeding. This reduction in TGF-beta overexpression paralleled decreased proteinuria, glomerular matrix accumulation, and overproduction of fibronectin and PAI-1. CONCLUSIONS: Ang II blockade and low-protein diet have additive effects on disease reduction, suggesting that disease progression in humans with chronic renal failure may be slowed more effectively when Ang II blockade and low-protein diet are combined. Since maximal pharmacological Ang II inhibition was used, it is likely that dietary protein restriction further reduces pathological TGF-beta overexpression by mechanisms different from those of enalapril or losartan.

Angiotensin II↗
PubMed1999

Gene therapy by transforming growth factor-beta receptor-IgG Fc chimera suppressed extracellular matrix accumulation in experimental glomerulonephritis.

BACKGROUND: The evidence that transforming growth factor-beta (TGF-beta) is a key mediator in the pathogenesis of fibrotic diseases is now supported by several lines of investigation. This evidence provides a certain base for targeting TGF-beta as an antifibrotic agent. METHODS: We generated a chimeric cDNA, termed TGF beta RII/Fc, encoding an extracellular domain of the TGF-beta type II receptor fused to the IgG-Fc domain, and tested whether TGF beta RII/Fc could be a novel strategy for treating glomerular diseases. RESULTS: In cultured BNul-7 cells, recombinant TGF beta RII/Fc reversed the antiproliferative response induced by TGF-beta 1. In addition, TGF beta RII/Fc diminished the TGF-beta 1-induced production of EIIIA-positive fibronectin in cultured normal rat kidney cells. We then introduced the chimeric cDNA into the muscle of the nephritic rats by the hemagglutinating virus of Japan liposome-mediated gene transfer method in order to block the TGF-beta activity in nephritic glomeruli through systemic delivery of chimeric molecules. Treatment with TGF beta RII/Fc gene transfection could suppress the glomerular TGF-beta mRNA in nephritic rats with a comparable effect in the reduction of extracellular matrix accumulation. CONCLUSION: TGF beta RII/Fc successfully inhibited the action of TGF-beta in vitro and in vivo, and gene therapy by chimeric TGF beta RII/Fc might be feasible for the therapy of glomerulosclerosis.

Animals↗
PubMed1999

Increased levels of transforming growth factor-beta in HIV-associated nephropathy.

BACKGROUND: Human immunodeficiency virus-associated nephropathy (HIVAN) is a renal disease of unknown pathogenesis. Recent evidence suggests that the fibrogenic cytokine transforming growth factor-beta (TGF-beta) might be involved. We hypothesized that overproduction of TGF-beta in the kidney might be involved in the pathogenesis of HIVAN. METHODS: The mRNA and protein expression of TGF-beta isoforms, TGF-beta 1, TGF-beta 2, and TGF beta 3, deposition of matrix proteins induced by TGF-beta, and levels of HIV Tat protein were studied in HIVAN. Controls included normal and diseased kidneys from HIV-positive and -negative patients. The ability of Tat to induce production of TGF-beta and matrix proteins was also studied in human mesangial cells. RESULTS: Normal kidneys, thin basement membrane nephropathy, and minimal change disease were negative for the three TGF-beta isoforms and Tat. In HIVAN, levels of TGF-beta isoforms and Tat were significantly increased, along with the expression of TGF-beta mRNA and deposition of matrix proteins stimulated by TGF-beta. Increased levels of TGF-beta isoforms, but not Tat, were also found in other glomerular diseases characterized by matrix accumulation. HIV infection, in the absence of HIVAN, was not associated with an increase in TGF-beta or Tat expression. Tat stimulated the expression and production of TGF-beta 1 and matrix proteins by human mesangial cells. CONCLUSIONS: Our findings suggest that overproduction of TGF-beta is involved in the pathogenesis of HIVAN.

AIDS-Associated Nephropathy↗
PubMed1999

L-Arginine supplementation increases mesangial cell injury and subsequent tissue fibrosis in experimental glomerulonephritis.

BACKGROUND: Mesangial cell lysis in the antithymocyte serum (ATS)-induced model of glomerulonephritis is dependent on the generation of cytotoxic nitric oxide (NO) through transient induction of NO synthase (iNOS). We hypothesized that increased availability of L-arginine (L-Arg) during mesangial cell lysis might provide iNOS with increased substrate leading to increased lysis, and that this increased lysis would be reflected in more severe fibrotic disease at day 6. METHODS: To ensure whole body equilibration with high L-Arg at the time of injury, rats were pretreated with 1% L-Arg in drinking water for one week prior to the administration of ATS. Animals were sacrificed six hours after ATS injection when previous experiments had indicated iNOS induction had occurred and at six days. At six hours, plasma was obtained for L-Arg levels and nitrite/nitrate (NOx) content. Renal tissues were taken for histological evaluation of glomerular cell counts, macrophage infiltration (ED-1), and iNOS expression. Glomeruli were isolated for detection of iNOS mRNA and placed in culture to study the dependence of NO production on L-Arg concentration. In rats sacrificed at six days, L-Arg supplementation was stopped 16 hours after ATS injection. Fibrotic disease was evaluated by urinary protein excretion, histological assessment of glomerular cell number, matrix accumulation, and production of transforming growth factor-beta1 and matrix components fibronectin and plasminogen activator inhibitor type-1 (PAI-1) by isolated glomeruli in culture. RESULTS: At six hours, the glomerular cell number was significantly reduced by ATS injection (P < 0.01) and further significantly (P < 0. 05) reduced by L-Arg feeding [normal control (NC) = 64.2 +/- 1, ATS = 53.4 +/- 0.7, ATS + L-Arg = 50.8 +/- 0.7]. Disease increased macrophage infiltration and iNOS protein and iNOS mRNA levels markedly (P < 0.01), whereas L-Arg feeding did not further increase these variables. Plasma L-Arg levels (nmol/ml) were reduced by disease (NC = 121 +/- 9, ATS = 84 +/- 13, P < 0.01) and elevated by L-Arg feeding (ATS + L-Arg = 166 +/- 12, P < 0.01). Plasma NOx was significantly increased by ATS and further increased by ATS + L-Arg (P < 0.05). Production of NOx by cultured glomeruli showed striking L-Arg concentration dependence in six hours but not in normal glomeruli. In the group sacrificed at day 6, day 2 proteinuria was higher in the ATS + L-Arg group compared with the ATS alone group (P < 0.05). Measures of fibrotic disease at day 6 all showed large increases over control with ATS alone (P < 0.01), and further small, but significant increases when L-Arg was combined with ATS (P < 0.05). CONCLUSIONS: The results indicate that if given during disease induction, L-Arg supplementation can enhance iNOS-dependent tissue injury by providing increased substrate. Although the increase in injury with L-Arg supplementation was small, it led to increased fibrosis at day 6. These data predict that in diseases with repeated iNOS-dependent tissue injury, L-Arg supplementation may produce cumulative increases in tissue fibrosis.

Animals↗
PubMed1999

From rats to man: a perspective on dietary L-arginine supplementation in human renal disease.

Experimental studies have shown both therapeutic and detrimental consequences of modifying dietary L-arginine intake in renal diseases which likely reflect the complexity of L-arginine metabolism. L-Arginine intake is semi-essential and provides substrate for a number of L-arginine metabolites involved in renal pathology. Dietary L-arginine restriction has been identified as a key mediator of the beneficial effects of low protein diets on human renal fibrosis. Supplementing dietary L-arginine in renal diseases with increased iNOS expression appears to be detrimental and thus, may be harmful in immune-mediated human kidney disorders. Increasing L-arginine intake is beneficial in experimental models of hypertensive renal disease. Based upon available data, we believe additional questions must be answered experimentally, not only to prevent an adverse outcome in humans, but to enhance our chances of human trials which will result in substantially better amelioration of disease than currently available.

Animals↗
PubMed1998

Targeting TGF-beta overexpression in renal disease: maximizing the antifibrotic action of angiotensin II blockade.

BACKGROUND: Overproduction of transforming growth factor-beta (TGF-beta) is a key mediator of extracellular matrix accumulation in fibrotic diseases. We hypothesized that the degree of reduction of pathological TGF-beta expression can be used as a novel index of the antifibrotic potential of angiotensin II (Ang II) blockade in renal disease. METHODS: One day after induction of Thy 1.1 glomerulonephritis, rats were treated with increasing doses of the Ang I converting enzyme (ACE) inhibitor enalapril and/or the Ang II receptor blocker losartan in the drinking water. Six days after disease induction the therapeutic effect on glomerular TGF-beta overexpression was evaluated. RESULTS: Both enalapril and losartan reduced TGF-beta overproduction in a dose-dependent manner, showing a moderate reduction at doses known to control blood pressure in renal forms of hypertension. A maximal reduction in TGF-beta expression of approximately 45% was seen for both drugs starting at 100 mg/liter enalapril and 500 mg/liter losartan, with no further reduction at doses of enalapril up to 1000 mg/liter or losartan up to 2500 mg/liter. Co-treatment with both drugs was not superior to single therapy. Consistent with our hypothesis that reduction in TGF-beta expression is a valid target, other disease measures, including glomerular matrix accumulation, glomerular production and mRNA expression of the matrix protein fibronectin and the protease inhibitor plasminogen-activator-inhibitor type 1 (PAI-1) closely followed TGF-beta expression. CONCLUSIONS: The data suggest that these therapies act through very similar pathways and that, in order to more effectively treat renal fibrosis, these drugs must be combined with other drugs that act by different mechanisms.

Angiotensin II↗
PubMed1998

Interactions of transforming growth factor-beta and angiotensin II in renal fibrosis.

Overproduction of transforming growth factor-beta clearly underlies tissue fibrosis in numerous experimental and human diseases. Transforming growth factor-beta's powerful fibrogenic action results from simultaneous stimulation of matrix protein synthesis, inhibition of matrix degradation, and enhanced integrin expression that facilitates matrix assembly. In animals, overexpression of transforming growth factor-beta by intravenous injection, transient gene transfer, or transgene insertion has shown that the kidney is highly susceptible to rapid fibrosis. The same seems true in human disease, where excessive transforming growth factor-beta has been demonstrated in glomerulonephritis, diabetic nephropathy, and hypertensive glomerular injury. A possible explanation for the kidney's particular susceptibility to fibrosis may be the recent discovery of biologically complex interactions between the renin-angiotensin system and transforming growth factor-beta. Alterations in glomerular hemodynamics can activate both the renin-angiotensin system and transforming growth factor-beta. Components of the renin-angiotensin system act to further stimulate production of transforming growth factor-beta and plasminogen activator inhibitor leading to rapid matrix accumulation. In volume depletion, transforming growth factor-beta is released from juxtaglomerular cells and may act synergistically with angiotensin II to accentuate vasoconstriction and acute renal failure. Interaction of the renin-angiotensin system and transforming growth factor-beta has important clinical implications. The protective effect of inhibition of the renin-angiotensin system in experimental and human kidney diseases correlates closely with the suppression of transforming growth factor-beta production. This suggests that transforming growth factor-beta, in addition to blood pressure, should be a therapeutic target. Higher doses or different combinations of drugs that block the renin-angiotensin system or entirely new drug strategies may be needed to achieve a greater antifibrotic effect.

Angiotensin II↗
PubMed1997

Dual effects of angiotensin II on the plasminogen/plasmin system in rat mesangial cells.

Previous studies indicate that angiotensin II (Ang II) stimulates extracellular matrix synthesis through induction of transforming growth factor-beta (TGF-beta) expression. Here we investigate Ang II effects on the plasmin protease system. Plasmin both degrades extracellular matrix itself and activates metalloproteinases which then degrade collagens. Plasmin production is determined by the balance between plasminogen activators (PA) and their inhibitors (PAI-1,2). The data presented here indicate that Ang II treatment of mesangial cells in culture markedly increases PAI-1 gene transcription and PAI-1 mRNA levels but does not change the half life of PAI-1 mRNA. Increased PAI-1 protein was detected 24 hours after Ang II stimulation with a concomitant decrease of PA activity. To determine whether these effects were mediated by TGF-beta, cells were coincubated with Ang II and neutralizing antibody to TGF-beta. Induction of PAI-1 at four hours was not altered but the prolonged effect of Ang II on PAI-1 protein synthesis was markedly diminished. Thus, Ang II acts both through rapid, direct transcriptional up-regulation of the PAI-1 gene and through induction of TGF-beta, providing sustained changes in the PAI-1/PA system, which would favor extracellular matrix accumulation by inhibiting turnover. These data provide further evidence that Ang II can act as a potent fibrogenic molecule independent of its effects on blood pressure.

Angiotensin II↗