The renin-angiotensin-aldosterone system and fibrinolysis in progressive renal disease

Molecular Mechanisms and Therapeutic Targets for Diabetic Kidney Disease

Diabetic kidney disease has a high global disease burden and substantially increases risk of kidney failure and cardiovascular events. Despite treatment, there is substantial residual risk of disease progression with existing therapies. Therefore, there is an urgent need to better understand the molecular mechanisms driving diabetic kidney disease to help identify new therapies that slow progression and reduce associated risks. Diabetic kidney disease is initiated by diabetes-related disturbances in glucose metabolism, which then trigger other metabolic, hemodynamic, inflammatory, and fibrotic processes that contribute to disease progression. This review summarizes existing evidence on the molecular drivers of diabetic kidney disease onset and progression, focusing on inflammatory and fibrotic mediators-factors that are largely unaddressed as primary treatment targets and for which there is increasing evidence supporting key roles in the pathophysiology of diabetic kidney disease. Results from recent clinical trials highlight promising new drug therapies, as well as a role for dietary strategies, in treating diabetic kidney disease.

Loss of heparin-binding protein prevents necrotizing glomerulonephritis: first clues hint at plasminogen activator inhibitor-1

The orchestration of acute inflammatory kidney injury is subject to widespread influences and involves cytokines as well as chemokines released by resident as well as infiltrating cells. Although intense research efforts have been made in the field, it still unravels yet novel key molecules involved in the pathogenesis of this kidney disease. A heparin-binding growth factor denoted midkine is expressed by various cell types following stress of tissue damage. Specific functions relate to orchestration of reparative and inflammatory processes by promoting migration of leucocytes and release of chemokines with ensuing angiogenesis. Midkine appears as a double-edged sword with beneficial or harmful effects in injured tissues. Here, we discuss a recent publication that provides evidence for the beneficial role of midkine in progressive glomerulonephritis, most likely due to blockade of plasminogen activator inhibitor-1 release.

Epithelial-mesenchymal crosstalk alteration in kidney fibrosis

The incidence of chronic kidney diseases (CKD) is constantly rising, reaching epidemic proportions in the western world and leading to an enormous threat, even to modern health-care systems, in industrialized countries. Therapies of CKD have greatly improved following the introduction of drugs targeting the renin-angiotensin system (RAAS) but even this refined pharmacological approach has failed to stop progression to end-stage renal disease (ESRD) in many individuals. In vitro historical data and recent new findings have suggested that progression of renal fibrosis might occur as a result of an altered tubulo-interstitial microenvironment and, more specifically, as a result of an altered epithelial-mesenchymal crosstalk. Here we the review biological findings that support the hypothesis of an altered cellular crosstalk in an injured local tubulo-interstitial microenvironment leading to renal disease progression. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

2010 Young Investigator Award winner: Therapeutic aprotinin stimulates osteoblast proliferation but inhibits differentiation and bone matrix mineralization

STUDY DESIGN

Analysis of the effect of antifibrinolytics on in vitro bone formation.

OBJECTIVE

As the direct effect of antifibrinolytics on bone formation is unknown, we examined whether antifibrinolytics routinely used in spine surgery, namely, aprotinin and aminocaproic acid, affect osteoblast function in vitro.

SUMMARY OF BACKGROUND DATA

Antifibrinolytics are used in spine surgery to prevent intraoperative blood loss and decrease the need for transfusion. They are either delivered systemically or included as a component of most tissue sealants. Although the role of the fibrinolytic system in wound healing is well established, reports of indirect effects on normal bone biology are emerging. This suggests that the pharmacological targeting of this system may also influence skeletal mass and integrity.

METHODS

Osteoblast progenitor cells were cultured with therapeutic doses of aprotinin and aminocaproic acid. The effect of the antifibrinolytics on osteoblast development was determined by measuring cellular viability and proliferation, quantification of matrix mineralization, and genetic analysis of osteoblast differentiation markers. Protease inhibition profiles of the antifibrinolytics were determined by amidolytic chromogenic assays.

RESULTS

Therapeutic concentrations of aprotinin dose-dependently inhibited plasmin's proteolytic activity, stimulated osteoblast proliferation, and inhibited osteoblast differentiation and matrix mineralization. Aprotinin inhibition of osteoblast differentiation and matrix mineralization could be recovered by removing aprotinin from culture or stimulating cells with bone morphogenetic protein-2 or plasmin. Conversely, aminocaproic acid inhibited plasmin's proteolytic activity significantly less than aprotinin and had no effect on osteoblast proliferation, differentiation, or matrix mineralization in its therapeutic range.

CONCLUSION

These findings demonstrate that the antifibrinolytics have drastically different effects on osteoblasts due in part to different efficacies of protease inhibition. Further, this work suggests that the fibrinolytic proteases and their inhibitors have great potential to regulate bone by affecting the processes that control osteoblast growth and differentiation.

PAI-1 and kidney fibrosis

Substantial evidence demonstrates a link of increased plasminogen activator inhibitor-1 (PAI-1) and glomerulosclerosis and kidney fibrosis, providing a novel therapeutic option for prevention and treatment of chronic kidney diseases. Several mechanisms contributing to increased PAI-1 will be addressed, including classic key profibrotic factors such as the renin-angiotensin-system (RAS) and transforming growth factor-beta (TGF-b???and novel molecules identified by proteomic analysis, such as thymosin- b4. The fibrotic sequelae caused by increased PAI-1 in kidney depend not only on its classic inhibition of tissue-type and urokinase-type plasminogen activators (tPA and uPA), but also its influence on cell migration.

Effect of renin-angiotensin-aldosterone system triple blockade on non-diabetic renal disease: addition of an aldosterone blocker, spironolactone, to combination treatment with an angiotensin-converting enzyme inhibitor and angiotensin II receptor blocker

Although dual blockade of the renin-angiotensin-aldosterone system (RAAS) with the combination of an angiotensin-converting enzyme inhibitor (ACE-I) and angiotensin II receptor blocker (ARB) is generally well-established as a treatment for nephropathy, this treatment is not fully effective in some patients. Based on the recent evidence implicating aldosterone in renal disease progression, this study was conducted to examine the efficacy of blockade with three different mechanisms by adding an aldosterone blocker in patients who do not respond adequately to the dual blockade. A 1-year randomized, open-label, multicenter, prospective controlled study was conducted, in which 32 non-diabetic nephropathy patients with proteinuria exceeding 0.5 g/day were enrolled after more than 12 weeks of ACE-I (5 mg enalapril) and ARB (50 mg losartan) combination treatment. These patients were allocated into two groups of 16 patients each: a triple blockade group in which 25 mg of spironolactone daily was added to the ACE-I and ARB combination treatment, and a control group in which 1 mg of trichlormethiazide or 20 mg of furosemide was added to the combination treatment instead of spironolactone depending upon the creatinine level. After 1 year of treatment, the urinary protein level decreased by 58% (p<0.05) with the triple blockade but was unchanged in the controls. Furthermore, urinary type IV collagen level decreased by 40% (p<0.05) with the triple blockade but was unchanged in the controls. The decreases in urinary protein and urinary type IV collagen were not accompanied by a decrease in blood pressure. Mean serum creatinine, potassium and blood pressure did not change significantly by either treatment. In conclusion, triple blockade of the RAAS was effective for the treatment of proteinuria in patients with non-diabetic nephropathy whose increased urinary protein had not responded sufficiently to a dual blockade.

Emerging drugs for complications of end-stage liver disease

BACKGROUND

The prevalence of end-stage liver disease is rising rapidly and constitutes a major healthcare burden currently. Many cases are diagnosed at a later stage when liver transplantation is the only effective treatment option. There is thus an urgent need for novel treatments to reverse the earlier stages of cirrhosis as well as to treat the many associated life-threatening complications.

OBJECTIVES

To review the current drugs available for treating the complications of advanced liver disease. To address novel treatment strategies that are in development, with particular reference to the rapidly developing area of antifibrotic therapy. To assess how the obstacles that have so far impeded the development of effective new drugs for end-stage liver disease may be overcome in the future.

METHODS

The literature was reviewed to define current therapies and therapies in clinical trials. We used the current models of the molecular basis of liver fibrogenesis to determine potential new therapeutic targets for antifibrotic therapy.

CONCLUSIONS

Insights into the pathogenesis of liver injury and fibrosis have opened up new avenues for therapy and there are now candidates and targets with real potential for the development of a new generation of antifibrotic therapies.

SGK1-dependent upregulation of connective tissue growth factor by angiotensin II

Angiotensin II has previously been shown to trigger fibrosis, an effect involving connective tissue growth factor (CTGF). The signaling pathways linking angiotensin II to CTGF formation are, however, incompletely understood. A gene highly expressed in fibrosing tissue is the serum- and glucocorticoid-inducible kinase SGK1. The present study explored whether SGK1 is transcriptionally regulated by angiotensin II and participates in the angiotensin II-dependent regulation of CTGF expression. To this end, experiments have been performed in human kidney fibroblasts and mouse lung fibroblasts from gene-targeted mice lacking SGK1 (sgk1-/-) and their wild-type littermates (sgk1+/+). In human renal fibroblasts, SGK1 and CTGF protein expression were enhanced by angiotensin II (10 nM) within 4 h. In sgk1+/+ mouse fibroblasts, SGK1 transcript levels were significantly increased after 4 h of angiotensin II treatment. Angiotensin II stimulated both transcript and protein abundance of CTGF in fibroblasts from sgk1+/+ mice, effects significantly blunted in fibroblasts of sgk1-/- mice. In conclusion, angiotensin II stimulates the expression of SGK1, which is in turn required for the stimulating effect of angiotensin II on the expression of CTGF. Thus, SGK1 presumably contributes to the profibrotic effect of angiotensin II.

Effects of pioglitazone and candesartan on renal fibrosis and the intrarenal plasmin cascade in spontaneously hypercholesterolemic rats

The profibrotic effect of plasminogen activator inhibitor-1 (PAI-1) in renal fibrosis is widely recognized, but its mechanism remains controversial especially in chronic progressive kidney disease. In the present study, pioglitazone (Pio) and candesartan (CD), which are reported to inhibit PAI-1, were administered to spontaneously hypercholesterolemic (SHC) rats, a model of chronic progressive kidney disease. Therapeutic effects and effects on the intrarenal plasmin cascade were examined. Eight-wk-old SHC rats were used as controls. Oral administration of vehicle alone, Pio, or CD was performed starting at 8 wk of age and was continued for 24 wk. The degree of renal fibrosis was evaluated by sirius red staining of kidney sections and by total collagen assay of renal homogenates. The renal PAI-1 protein level was assessed by Western blotting, and plasmin activity was analyzed by chromogenic assay and casein gel zymography. Urinary protein and blood urea nitrogen were significantly increased in the vehicle-treated group, but the increase was attenuated in the Pio- and CD-treated groups. This correlated well with the degree of fibrosis as assessed by sirius red staining and total collagen assay. The PAI-1 protein level was also increased significantly in the vehicle-treated group, and the increase was attenuated in the Pio- and CD-treated groups. Despite the presumed plasmin-inhibitory function of PAI-1, plasmin activity changed in parallel with PAI-1. These results suggest that Pio and CD inhibit PAI-1 and exert renoprotective effects against chronic progressive renal disease, but its action is independent of the regulatory function on plasmin activity.

Immunopathogenesis of hepatitis C virus infection and hepatic fibrosis: New insights into antifibrotic therapy in chronic hepatitis C

Fibrosis and cirrhosis represent the consequences of a sustained wound-healing response to chronic liver injury of any cause. Chronic hepatitis C virus (HCV) has emerged as a leading cause of cirrhosis in the USA and throughout the world. HCV may induce fibrogenesis directly by hepatic stellate cell activation or indirectly by promoting oxidative stress and apoptosis of infected cells. The ultimate result of chronic HCV injury is the accumulation of extracellular matrix with high density type I collagen within the subendothelial space of Disse, culminating in cirrhosis with hepatocellular dysfunction. The treatment of hepatitis C with the combination of pegylated interferon and ribavirin is still both problematic and costly, has suboptimal efficacy, serious side effects and a high level of intolerance, and is contraindicated in many patients. Hence, new approaches have assumed greater importance, for which there is an urgent need. The sustained progress in understanding the pathophysiology of hepatic fibrosis in the past two decades has increased the possibility of developing drugs specifically targeting the fibrogenic process. Future efforts should identify genetic markers associated with fibrosis risk in order to tailor the treatment of HCV infection based on genetically regulated pathways of injury and/or fibrosis. Such advances will expand the arsenal to overcome liver fibrosis, particularly in patients with hepatic diseases who have limited treatment options, such as those patients with chronic hepatitis C who have a high risk of fibrosis progression and recurrent HCV disease after liver transplantation.

Aldosterone blockade: an emerging strategy for abrogating progressive renal disease

In recent years, there has been a striking paradigm shift with respect to our understanding of the widespread effects of aldosterone. Whereas the role of angiotensin II in mediating progressive renal disease and heart failure has been documented extensively, more recent evidence has implicated aldosterone as an important pathogenetic factor in addition to angiotensin II in the development of these diseases. The focus of this review is aldosterone and progressive renal dysfunction. The extensive preclinical and clinical evidence supporting the efficacy of aldosterone blockade in abrogating proteinuria is summarized. The frequency and clinical importance of aldosterone "escape" is reviewed. Therapeutic considerations to reduce the incidence of hyperkalemia with aldosterone blockade are discussed. The studies reviewed have several important clinical implications for considering new treatment algorithms for patients with incipient nephropathy. Because full doses of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers attenuate but do not abrogate progression of renal dysfunction, add-on aldosterone blockade therapy may constitute a rational therapeutic strategy for retarding progression of renal disease.

Therapeutic targets in the treatment of allograft fibrosis

The dramatic improvements in short-term graft survival and acute rejection rates could only have been dreamed of 20 years ago. Late graft loss following kidney transplantation is now the critical issue of this decade. Frequently, graft loss is associated with the development of tubular atrophy and interstitial fibrosis within the kidney (i.e. chronic allograft nephropathy; CAN). Major treatment strategies in this disorder are non-specific and the focus of intervention has been on limiting injurious events. Following graft injury is a fibrogenesis phase featuring both proliferative and infiltrative responses mediated by chemokines, cytokines and growth factors. In particular, TGFbeta has been strongly implicated in the pathogenesis of chronic injury and epithelial-mesenchymal transformation (EMT) may be part of this process. The cascade of events results in matrix accumulation, due to either increased production and/or reduced degradation of matrix. Recent investigations into the pathogenesis of tissue fibrosis have suggested a number of new strategies to ameliorate matrix synthesis. While the majority of therapies have focused on TGFbeta, this may not be an ideal maneuver in transplant settings and alternative targets identified in other fibrotic diseases will be discussed. Attacking graft fibrosis should be a new focus in organ transplantation.

Interleukin-1β enhances the angiotensin-induced expression of plasminogen activator inhibitor-1 through angiotensin receptor upregulation in human astrocytes

Plasminogen activator inhibitor-1 (PAI-1) regulates not only fibrinolysis but extracellular matrix remodeling, and angiotensin II is known to play an important role in controlling the expression of PAI-1 in astrocytes. We have studied the effect of interleukin-1beta (IL-1beta), one of major cytokines also active in the nervous system, on the angiotensin II-induced expression of PAI-1 in human astrocytes. Cultures of normal human astrocytes were stimulated with IL-1beta and angiotensin II, and the expression of mRNAs for angiotensin II type 1 receptor (AT1) and PAI-1 was analyzed by reverse transcription-polymerase chain reaction (RT-PCR) or real-time quantitative PCR. PAI-1 protein in astrocyte-conditioned medium was measured by enzyme-linked immunosorbent assay (ELISA). IL-1beta enhanced the expression of AT1 in astrocytes in time- and concentration-dependent manners. After 24-h stimulation, 10 ng/ml IL-1beta and 10 nM angiotensin II increased the levels of PAI-1 protein in astrocyte-conditioned medium by 1.9-fold and 1.8-fold of the basal value, respectively. There was no synergistic effect when the cells were stimulated simultaneously with IL-1beta and angiotensin II. When the cells were stimulated, with angiotensin II, 16 h after the stimulation with IL-1beta, the production of PAI-1 was enhanced by 1.4-fold as compared to the cells stimulated only with IL-1beta. CV-11794, an AT1 antagonist, inhibited the enhanced PAI-1 production in response to angiotensin II. We conclude that IL-1beta increases angiotensin II-induced PAI-1 secretion by astrocytes through the induction of AT1, and the enhanced secretion of PAI-1 may modulate functions of plasminogen activators in the nervous system.

Antifibrotic agents for liver disease

Complications from chronic hepatitis C (HCV) and recurrent HCV post-transplant are responsible for significant morbidity and mortality in the United States and Europe. Current antiviral therapies are at best, effective in up to 50% of patients in the pre-transplant setting, and in the post-transplant setting are associated with more limited efficacy and increased toxicity. With this reduced efficacy of antiviral strategies in the post-transplant setting, new approaches are urgently needed. Substantial progress has been made in understanding the pathogenesis of hepatic fibrosis over the last 20 years, which has yielded potential new therapeutic targets. The prospect of antifibrotic therapies is nearing reality in order to reduce progression to cirrhosis, thereby reducing morbidity, mortality and the need for re-transplantation. Current and evolving approaches primarily target the activated hepatic stellate cells, which are the main source of extracellular matrix, along with related fibrogenic cell types. Key issues yet to be clarified include the optimal duration of antifibrotic therapies, endpoints of clinical trials, indications in clinical practice and whether combination therapies might yield synergistic activity.

Systemic infusion of angiotensin II exacerbates liver fibrosis in bile duct-ligated rats

Recent evidence indicates that the renin-angiotensin system (RAS) plays a major role in liver fibrosis. Here, we investigate whether the circulatory RAS, which is frequently activated in patients with chronic liver disease, contributes to fibrosis progression. To test this hypothesis, we increased circulatory angiotensin II (Ang II) levels in rats undergoing biliary fibrosis. Saline or Ang II (25 ng/kg/h) were infused into bile duct-ligated rats for 2 weeks through a subcutaneous pump. Ang II infusion increased serum levels of Ang II and augmented bile duct ligation-induced liver injury, as assessed by elevated liver serum enzymes. Moreover, it increased the hepatic concentration of inflammatory proteins (tumor necrosis factor alpha and interleukin 1beta) and the infiltration of CD43-positive inflammatory cells. Ang II infusion also favored the development of vascular thrombosis and increased the procoagulant activity of tissue factor in the liver. Livers from bile duct-ligated rats infused with Ang II showed increased transforming growth factor beta1 content, collagen deposition, accumulation of smooth muscle alpha-actin-positive cells, and lipid peroxidation products. Moreover, Ang II infusion stimulated phosphorylation of c-Jun and p42/44 mitogen-activated protein kinase and increased proliferation of bile duct cells. In cultured rat hepatic stellate cells (HSCs), Ang II (10(-8) mol/L) increased intracellular calcium and stimulated reactive oxygen species formation, cellular proliferation and secretion of proinflammatory cytokines. Moreover, Ang II stimulated the procoagulant activity of HSCs, a newly described biological function for these cells. In conclusion, increased systemic Ang II augments hepatic fibrosis and promotes inflammation, oxidative stress, and thrombogenic events.

Inhibition of Plasminogen Activator Inhibitor-1 by Angiotensin II Receptor Blockers on Cyclosporine-Treated Renal Allograft Recipients

INTRODUCTION

We previously showed that proteinuria from a renal graft was significantly decreased by administration of losartan potassium, an angiotensin II receptor blockers (ARB). To further evaluate the mechanism, we performed another clinical study focusing on the change in plasma plasminogen activator inhibitor-1 (PAI-1) levels among cyclosporine (CyA)-treated renal allograft recipients.

METHODS

Among 12 hypertensive CyA-treated kidney transplant patients, four received 25 to 50 mg/day of losartan; four, 4 to 8 mg/day of candesartan cilexetil; and another four, 20 to 40 mg/day of nifedipine. Four CyA-treated kidney-transplanted patients without hypertension were selected as a control group. Informed consent was obtained from all participants. PAI-1 and serum creatinine (S-Cr) levels were monitored every 3 months for 1 year.

RESULTS

Considering the pretreatment of PAI-1 as 100%, the mean percent of PAI-1 at 1 year after the onset of study for losartan, candesartan, nifedipine, and control groups were 78.6 +/- 6.7%, 81.4 +/- 8.0%, 96.7 +/- 7.6%, and 110.4 +/- 9.2%, respectively. The ARB groups demonstrated significant differences from the control group (P < .01), while the nifedipine group did not. S-Cr levels among ARB-administered groups were increased slightly but temporarily. As for S-Cr levels, no significant differences were seen among the four groups.

CONCLUSIONS

Control of hypertension itself is important for all renal graft recipients; however, PAI-1 reduction by ARBs was thought to be a key for renal preservation. We expect that ARBs will contribute to prolonged renal allograft survival.

Regression of glomerulosclerosis with high-dose angiotensin inhibition is linked to decreased plasminogen activator inhibitor-1

The potential and possible mechanisms for regression of existing glomerulosclerosis by angiotensin II type 1 receptor antagonist (AT1RA) and/or angiotensin I converting enzyme inhibitor (ACEI) were investigated. Adult male Sprague Dawley rats underwent 5/6 nephrectomy (Nx). Glomerulosclerosis was assessed by renal biopsy 8 wk later, and rats were divided into groups with equal biopsy sclerosis and treated for the next 4 wk until they were killed at 12 wk as follows: Control with no further treatment (CONT), high-dose AT1RA, high-dose ACEI, and varying AT1RA+ACEI combinations. Hypertension and proteinuria induced by 5/6 Nx were significantly decreased by all treatments, except high-dose ACEI, which showed persistent proteinuria. High-dose AT1RA and ACEI markedly decreased progression of sclerosis, with -2.3% average decrease in sclerosis from biopsy to autopsy in AT1RA versus 194% increase in CONT (P < 0.0001). Glomerulosclerosis regressed, with less severe lesions at the time when the rats were killed than at biopsy in 62% of AT1RA-treated and 57% of ACEI-treated rats. In contrast, only 17 to 33% of rats in combination groups had regression. Alternatively, these data might be viewed as reflecting halting of progression, as some groups had higher BP and proteinuria. However, this potential confounding effect does not negate the effects to achieve regression of sclerosis in these rats. Regression was not explained by changes in mRNA of TGF-beta1 and matrix metalloproteinase-2 and -9 but was linked to decreased tissue inhibitor of metalloproteinase-1 and plasminogen activator inhibitor-1. It is concluded that angiotensin inhibition mediates regression in part by effects on matrix modulation.

Smad6s regulates plasminogen activator inhibitor-1 through a protein kinase C-beta-dependent up-regulation of transforming growth factor-beta

Plasminogen activator inhibitor-1 (PAI-1) is a serpin class protease inhibitor that plays a central role in the regulation of vascular function and tissue remodeling by modulating thrombosis, inflammation, and the extracellular matrix. A central mediator controlling PAI-1 is transforming growth factor-beta (TGF-beta), which induces its expression and promotes fibrosis. We have found that a unique member of the Smad family of signal transduction molecules, Smad6s, modulates the expression of PAI-1. Overexpression of Smad6s in endothelial cells increases promoter activity and PAI-1 secretion, and an antisense to Smad6s suppresses the induction of PAI-1 by TGF-beta. The effect of Smad6s on the PAI-1 promoter appeared to be the result of increase binding of the forkhead winged helix factor FoxD1 to a TGF-beta-responsive element. Furthermore, the effect of Smad6s on PAI-1 up-regulation and on FoxD1 binding was found to result from up-regulation of TGF-beta and could be inhibited by the blocking TGF-beta signaling with Smad7. The ability of Smad6s to regulate the TGF-beta promoter and subsequent PAI-1 induction was suppressed by a selective protein kinase C-beta (PKC-beta) inhibitor. Consistent with the in vitro data, we found that increased Smad6s in diseased vessels correlated with increased TGF-beta and PAI-1 levels. Overall, our results demonstrate that the level of Smad6s can alter the level of TGF-beta and the subsequent induction of PAI-1 via a FoxD1 transcription site. Furthermore, our data suggest that this process, which is up-regulated in diseased vessels, can be modulated by the inhibition of PKC-beta.

Contribution of Angiotensin II to Alcohol-Induced Pancreatic Fibrosis in Rats

The mechanisms by which alcohol causes pancreatic fibrosis remain unknown. Recent studies have demonstrated that angiotensin II contributes to the development of fibrosis in liver, kidney, and heart injury. Here, the effects of angiotensin-converting enzyme inhibitor (captopril) and angiotensin II receptor antagonist (losartan) on alcohol-induced pancreatic fibrosis were examined in an intragastric ethanol-feeding model. Male rats were fed a high-fat liquid diet with either ethanol (16-20 g/kg/day) or isocaloric maltose-dextrin (control) for 4 weeks. Subgroups daily received captopril (60 mg/kg/day), losartan (3 mg/kg/day), or no additional agent included in liquid diets. Mean urine alcohol concentrations in all groups fed ethanol were more than 270 mg/dl and not significantly different. Dietary alcohol caused diffuse gland atrophy and interlobular and intralobular fibrosis with mild structural distortion in the pancreas, an effect that was blunted by captopril or losartan treatment. Alcohol also increased the number of alpha-smooth muscle actin-positive cells and transforming growth factor-beta mRNA expression in the pancreas. These increases were blunted significantly by captopril or losartan treatment. These data suggest that angiotensin II contributes to the development of chronic alcohol-induced pancreatic fibrosis through its stimulation of transforming growth factor-beta expression.

The pathogenesis of fibrosis and renal disease in scleroderma: Recent insights from glomerulosclerosis

Acute and chronic renal diseases remain common complications of systemic sclerosis. Although treatment for acute scleroderma renal crisis may arrest the rapid progression of renal disease, many patients develop persistent renal dysfunction. Based on recent insights gained from progressive renal diseases of diverse etiologies, novel approaches to understanding the pathobiology of scleroderma renal disease may be applicable. Key factors involved in progression of renal disease include accumulation of extracellular matrix in the glomerular and tubulointerstitial compartments, epithelial to mesenchymal transformation, and vascular changes. The relevant factors mediating these events include the renin-angiotensin system, the profibrotic growth factors, transforming growth factor-beta and connective tissue growth factor, and reactive oxygen species. Much of the molecular details of the role of these factors have been revealed and promise to alter the practice of therapy of progressive renal disease.

Increased expression of plasminogen activator inhibitor-1 in cardiomyocytes contributes to cardiac fibrosis after myocardial infarction

Plasminogen activator inhibitor-1 (PAI-1) plays a critical role in tissue fibrosis by inactivating matrix metalloproteinases, which might effect on the progression of left ventricular dysfunction. However, little has been known about the expression of PAI-1 during cardiac remodeling. We used a mouse model of myocardial infarction (MI) by coronary ligation, in which the progression of left ventricular remodeling was confirmed by echocardiography. Histological examination showed that interstitial and perivascular fibrosis progressed in the post-MI (PMI) heart at 4 weeks after the procedure. We observed the dramatic induction of cardiac PAI-1 mRNA and PAI-1 antigen in plasma in the PMI mice, as compared with the sham-operated (sham) mice. In situ hybridization analysis demonstrated that strong signals for PAI-1 mRNA were localized to cardiomyocytes in the border of infarct area and around fibrous lesions, and to perivascular mononuclear cells, which seemed to be mast cells, only in hearts of the PMI mice. Importantly, less development of cardiac fibrosis after MI was observed in mice deficient in PAI-1 as compared to wild-type mice. The mRNA expression of cytokines, transforming growth factor-beta, and tumor necrosis factor-alpha, was also increased in hearts of the PMI mice, but not in the sham mice. These observations suggest that cardiomyocytes and mast cells contribute to the increased PAI-1 expression, resulting in the development of interstitial and perivascular fibrosis in the PMI heart, and that the regional induction of cytokines may be involved in this process.

Model of robust induction of glomerulosclerosis in mice: importance of genetic background

BACKGROUND

Increasing evidence suggests that genetic background plays an important role in the development of progressive glomerulosclerosis. The remnant kidney model (RKM) of progressive renal disease has been used extensively in rats. However, C57BL/6 mice are resistant to glomerulosclerosis with RKM induced by either pole amputation or renal artery ligation. A pole resection protocol, applied in 129/Sv mice, induced only mild glomerulosclerosis. We present here a highly reproducible, modified RKM approach to successfully establish a glomerulosclerosis model in mice.

METHODS

Male C57BL/6 (N = 17), 129/Sv (N = 20) and Swiss-Webster (N = 3) mice underwent RKM as follows: the lower branch of the left renal artery was ligated to produce about one third infarct; the upper pole of the left kidney (about one third kidney size) was removed by cautery and the right kidney was nephrectomized to induce a total 5/6 nephrectomy (Nx). In some C57BL/6 mice, 7/8 nephrectomy was induced by removing additional renal mass from the upper pole of the left kidney by cautery. Systolic blood pressure (BP) was measured in conscious mice using a tail-cuff blood pressure monitor and animals were sacrificed at 9, 12, 18, and 24 weeks after nephrectomy. Kidneys were harvested for morphologic analysis.

RESULTS

BP in C57BL/6 mice increased slightly after 5/6 nephrectomy over time without significant difference compared to baseline blood pressure except at 8 weeks (blood pressure at week 0, 98 +/- 1 mm Hg; week 4, 105 +/- 2 mm Hg; week 8, 113 +/- 4 mm Hg; and week 12, 110 +/- 3 mm Hg). Blood presssure remained normal in C57BL/6 mice at 18 weeks after 7/8 nephrectomy (103 +/- 2 mm Hg). Blood pressure in 129/Sv mice increased significantly after 5/6 nephrectomy from 4 to 12 weeks (week 0, 112 +/- 3 mm Hg; week 4, 161 +/- 9 mm Hg; week 8, 166 +/- 5 mm Hg; and week 12, 176 +/- 5 mm Hg; P < 0.01 weeks 4, 8, and 12 vs. week 0 blood pressure). Urine protein excretion in C57BL/6 mice increased only at 4 weeks after 5/6 nephrectomy, and was back to normal at 8 and 12 weeks (week 0, 13.2 +/- 1.4 mg/24 hours; week 4, 20.5 +/- 1.8 mg/24 hours; week 8, 18.8 +/- 1.6 mg/24 hours; and week 12, 17.2 +/- 1.2 mg/24 hours, P < 0.05 week 4 vs. week 0). 129/Sv mice developed significant proteinuria 12 weeks after 5/6 nephrectomy compared to their baseline and to levels achieved in C57BL/6 mice (week 0, 17.2 +/- 1 mg/24 hours; week 4, 14.9 +/- 1.8 mg/24 hours; week 8, 23.8 +/- 6.7 mg/24 hours; and week 12, 36.3 +/- 6.6 mg/24 hours, P < 0.01 week 12 vs. week 0; P < 0.01 129/Sv vs. C57BL/6 at week 12). Mortality varied in response to nephrectomy injury in the different strains. Ten percent of C57BL/6 and 43% of 129/Sv died within 12 weeks after 5/6 nephrectomy. Although 50% of C57BL/6 mice died by 12 weeks after 7/8 nephrectomy, there was only mild glomerulosclerosis (<5%) in C57BL/6 mice even at 24 weeks after 5/6 nephrectomy or 18 weeks after 7/8 nephrectomy. In contrast, glomerulosclerosis was marked in both 129/Sv mice and Swiss-Webster mice as early as 9 weeks after 5/6 nephrectomy: 42% of glomeruli showed sclerosis in 129/Sv mice [average sclerosis index (SI), 0 to 4+ scale, 1.08] vs. 24% in Swiss-Webster mice (average SI, 0.57). Tubulointerstitial fibrosis developed in parallel with glomerulosclerosis in both 129/Sv and Swiss-Webster mice.

CONCLUSION

We conclude that genetic background is one of the important factors determining the susceptibility to the development of glomerulosclerosis in mice. We speculate that the superior effects of renal artery ligation plus cautery to produce glomerulosclerosis may result from higher blood pressure responses due to local ischemia activating the renin-angiotensin system.