Renal fibrosis: not just PAI-1 in the sky

Synergic Renoprotective Effects of Combined ASC Therapy with RAAS Blockade in Experimental Advanced CKD

Global prevalence of chronic kidney disease (CKD) has increased considerably in the recent decades. Overactivity of the renin-angiotensin-aldosterone system (RAAS), associated to renal inflammation and fibrosis, contributes to its evolution. The treatments currently employed to control CKD progression are limited and mainly based on the pharmacological inhibition of RAAS, associated with diuretics and immunosuppressive drugs. However, this conservative management promotes only partial deceleration of CKD evolution and does not completely avoid the progression of the disease and the loss of renal function, which motivates the medical and scientific community to investigate new therapeutic approaches to detain renal inflammation/fibrosis and CKD progression. Recent studies have shown the application of mesenchymal stem cells (mSC) to exert beneficial effects on the renal tissue of animals submitted to experimental models of CKD. In this context, the aim of the present study was to evaluate the effects of subcapsular application of adipose tissue-derived mSC (ASC) in rats submitted to the 5/6 renal ablation model, 15 days after the establishment of CKD, when the nephropathy was already severe. We also verify whether ASC associated to Losartan would promote greater renoprotection when compared to the respective monotherapies. Animals were followed until 30 days of CKD, when body weight, systolic blood pressure, biochemical, histological, immunohistochemical, and gene expression analysis were performed. The combination of ASC and Losartan was more effective than Losartan monotherapy in reducing systolic blood pressure and glomerulosclerosis and also promoted the complete normalization of proteinuria and albuminuria, a significant reduction in renal interstitial macrophage infiltration and downregulation of renal IL-6 gene expression. The beneficial effects of ACS are possibly due to the immunomodulatory and anti-inflammatory role of factors secreted by these cells, modulating the local immune response. Although studies are still required, our results demonstrated that a subcapsular inoculation of ASC, associated with the administration of Losartan, exerted additional renoprotective effect in rats submitted to a severe model of established CKD, when compared to Losartan monotherapy, thus suggesting ASC may be a potential adjuvant to RAAS-blockade therapy currently employed in the conservative management of CKD.

Genome-wide association analysis of venous thromboembolism identifies new risk loci and genetic overlap with arterial vascular disease

Venous thromboembolism is a significant cause of mortality1, yet its genetic determinants are incompletely defined. We performed a discovery genome-wide association study in the Million Veteran Program and UK Biobank, with testing of approximately 13 million DNA sequence variants for association with venous thromboembolism (26,066 cases and 624,053 controls) and meta-analyzed both studies, followed by independent replication with up to 17,672 venous thromboembolism cases and 167,295 controls. We identified 22 previously unknown loci, bringing the total number of venous thromboembolism-associated loci to 33, and subsequently fine-mapped these associations. We developed a genome-wide polygenic risk score for venous thromboembolism that identifies 5% of the population at an equivalent incident venous thromboembolism risk to carriers of the established factor V Leiden p.R506Q and prothrombin G20210A mutations. Our data provide mechanistic insights into the genetic epidemiology of venous thromboembolism and suggest a greater overlap among venous and arterial cardiovascular disease than previously thought.

FFNT25 ameliorates unilateral ureteral obstruction-induced renal fibrosis

Renal fibrosis is a common pathological feature of chronic kidney disease (CKD) patients who progress to end-stage renal disease (ESRD). With the increasing incidence of CKD, it is of importance to develop effective therapies that blunt development of renal fibrosis. FFNT25 is a newly developed molecular compound that could be used to prevent fibrosis. In this study, we administered FFNT25 to rats following unilateral ureteral obstruction (UUO) to investigate its anti-fibrosis mechanism. Thirty-two Sprague-Dawley rats were randomly divided into four groups: (1) control (normal rats), (2) sham-operated, (3) UUO-operated + vehicle, and (4) UUO-operated + FFNT25. Two weeks after UUO, the rats were gavaged with either FFNT25 (20.6 mg/kg/day) or vehicle for two weeks. Serum, urine, and kidney samples were collected at the end of the study. FFNT25 reduced levels of renal fibrosis and decreased mRNA and protein levels of extracellular matrix (ECM) markers α-smooth muscle actin (α-SMA) and plasminogen activator inhibitor-1 (PAI-1) following UUO compared to vehicle treatment (n = 8, p<.05). The current results indicate that FFNT25 can affect both the production and degradation of collagen fibers to reduce fibrosis.

C/EBP homologous protein (CHOP) deficiency ameliorates renal fibrosis in unilateral ureteral obstructive kidney disease

Renal tubulointerstitial fibrosis is an important pathogenic feature in chronic kidney disease and end-stage renal disease, regardless of the initiating insults. A recent study has shown that CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) is involved in acute ischemia/reperfusion-related acute kidney injury through oxidative stress induction. However, the influence of CHOP on chronic kidney disease-correlated renal fibrosis remains unclear. Here, we investigated the role of CHOP in unilateral ureteral obstruction (UUO)-induced experimental chronic tubulointerstital fibrosis. The CHOP knockout and wild type mice with or without UUO were used. The results showed that the increased expressions of renal fibrosis markers collagen I, fibronectin, α-smooth muscle actin, and plasminogen activator inhibitor-1 in the kidneys of UUO-treated wild type mice were dramatically attenuated in the kidneys of UUO-treated CHOP knockout mice. CHOP deficiency could also ameliorate lipid peroxidation and endogenous antioxidant enzymes depletion, tubular apoptosis, and inflammatory cells infiltration in the UUO kidneys. These results suggest that CHOP deficiency not only attenuates apoptotic death and oxidative stress in experimental renal fibrosis, but also reduces local inflammation, leading to diminish UUO-induced renal fibrosis. Our findings support that CHOP may be an important signaling molecule in the progression of chronic kidney disease.

Renal damage following Alloxan-induced diabetes is associated with generation of reactive oxygen species, alterations of p53, TGF-β1, and extracellular matrix metalloproteinases in rats

Renal damage is a common problem in diabetes. Alloxan, a potent hyperglycemic and diabetogenic molecule, can induce diabetes through oxidative stress-related mechanisms. Here, we hypothesize that "Alloxan-induced renal damage is associated with alterations of p53, TGF-β1, and extracellular matrix metalloproteinases." To test our hypothesis, we established an animal model (male abino rats) and induced diabetes by intraperitoneal injection of Alloxan monohydrate. Rats with fasting blood glucose level ≥ 200 mg/dL were considered diabetic and were sacrificed after 14, 28, and 42 day intervals. Tissue levels of malondialdehyde and glutathione levels (markers of oxidative stress), and serum MMP-1 were measured. The expression patterns of p53, TGF-β1were evaluated using Western blot and immunohistochemical methods. TIMP-1 expression pattern was determined using RT-PCR and immunohistochemical methods. Alloxan treatment induced histological features of renal damage (inflammation and fibrosis) and was associated with deterioration of the renal functions (elevated blood urea nitrogen and creatinin levels), hyperglycemia, and oxidative stresss (increased malondialdehyde and decreased glutathione levels). There was over-expression of the TGF-β1 protein (profibrogenic protein), p53 (proapoptotic protein), and alterations of extracellular matrix proteins (low level of serum MMP-1 and over-expression of TIMP-1). Alterations of TGF-β, p53, and extracellular matrix metalloproteinases contribute to the pathogenesis of Alloxan-induced renal damage.

Interactions between HIF-1α and AMPK in the regulation of cellular hypoxia adaptation in chronic kidney disease

Renal hypoxia contributes to chronic kidney disease (CKD) progression, as validated in experimental and human CKD. In the early stages, increased oxygen consumption causes oxygen demand/supply mismatch, leading to hypoxia. Hence, early targeting of the determinants and regulators of oxygen consumption in CKD may alter the disease course before permanent damage ensues. Here, we focus on hypoxia inducible factor-1α (HIF-1α) and AMP-activated protein kinase (AMPK) and on the mechanisms by which they may facilitate cellular hypoxia adaptation. We found that HIF-1α activation in the subtotal nephrectomy (STN) model of CKD limits protein synthesis, inhibits apoptosis, and activates autophagy, presumably for improved cell survival. AMPK activation was diminished in the STN kidney and was remarkably restored by HIF-1α activation, demonstrating a novel role for HIF-1α in the regulation of AMPK activity. We also investigated the independent and combined effects of HIF-1α and AMPK on cell survival and death pathways by utilizing pharmacological and knockdown approaches in cell culture models. We found that the effect of HIF-1α activation on autophagy is independent of AMPK, but on apoptosis it is partially AMPK dependent. The effects of HIF-1α and AMPK activation on inhibiting protein synthesis via the mTOR pathway appear to be additive. These various effects were also observed under hypoxic conditions. In conclusion, HIF-1α and AMPK appear to be linked at a molecular level and may act as components of a concerted cellular response to hypoxic stress in the pathophysiology of CKD.

[The role of inherited thrombophilia and undifferentiated connective tissue dysplasia syndrome in the pathogenesis of female infertility: A clinical and morphological study]

Impaired endometrial receptivity is a major cause of reproductive losses in in vitro fertilization (IVF) cycles given a normal embryo. Its causes may be associated with many diseases, including inherited thrombophilia (IT) and undifferentiated connective tissue dysplasia syndrome (uCTDS). However, endometrial receptivity remains little studied.

OBJECTIVE

to investigate the morphological and immunohistochemical substrates of impaired endometrial receptivity in women with uCTDS, IT, and their concurrence.

SUBJECTS AND METHODS

Antibodies against ER, PgR, LIF, VEGF, and PAI-1 were used to morphologically and immunohistochemically examine pipelle endometrial biopsy specimens taken from 141 women in the implantation window (on days 6-7 after ovulation). In accordance with their clinical diagnoses, the patients were divided into 4 groups: 1) 13 patients with uCTDS; 2) 100 with IT; 3) 19 with uCTDS and IT; 4) 9 healthy surrogate mothers (a control group). In the examined groups, a total of 145 (90.1%) out of all the IVF protocols were unsuccessful. In the remaining 16 (9.9%) patients without exception, miscarriage started at less than 10 weeks' gestation.

RESULTS

In the implantation window, the endometrium was immature in 101 (83.1%) women and corresponded to late proliferation or early secretion phases; 102 (84.3%) women were also found to have no mature pinopodes, pointing to the fact that the endometrial receptivity was very low. Immunohistochemical examination revealed the lower expression of the receptivity marker LIF in the endometrial surface epithelium and its higher expression in the stroma in the study groups (p < 0.05 for the uCTDS and uCTDS+IT groups) and the higher expression of PAI-1 and VEGF in the epithelium, stroma, and endothelium in the study groups than in the control group (p < 0.05), suggesting the intensity of neoangiogenetic processes and impaired fibrinolysis in these patients.

CONCLUSION

uCTDS and IT are risk factors of impaired endometrial receptivity in the pathogenesis of infertility. The manifestations of impaired endometrial receptivity in this case are a decrease in mature pinopodes in the surface epithelium; focal stromal sclerosis; and redistribution of the receptivity marker LIF from the surface epithelium to the stroma, which may be used for diagnosis, prediction, and the development of targeted therapy.

Low-molecular-weight heparin modulates vein wall fibrotic response in a plasminogen activator inhibitor 1-dependent manner

BACKGROUND

Treatment with low-molecular-weight heparin (LMWH) favorably alters the vein wall response to deep venous thrombosis (DVT), although the mechanisms remain unclear. Previous studies have suggested that LMWH alters the levels of circulating plasminogen activator inhibitor 1 (PAI-1), a known mediator of fibrosis, and may improve endogenous fibrinolysis. We hypothesized that LMWH favorably alters the vein wall response by binding of PAI-1 and acceleration of fibrinolysis.

METHODS

Wild-type and PAI-1 -/- mice underwent treatment with LMWH after induction of occlusive DVT. Vein wall and plasma were harvested and analyzed by enzyme-linked immunosorbent assay, zymography, real-time polymerase chain reaction, and immunohistochemistry.

RESULTS

Wild-type mice treated with LMWH exhibited diminished vein wall fibrosis (0.6 ± 0.6 vs 1.4 ± 0.2; P < .01; n = 5) and elevation of circulating PAI-1 (1776 ± 342 vs 567 ± 104 ρg/mL; P < .01; n = 5) compared with untreated controls after occlusive DVT. PAI-1-/- mice treated with LMWH were not similarly protected from fibrosis, despite improved thrombus resolution. Treatment with LMWH was associated with decreased intrathrombus interleukin-lβ (68.6 ± 31.0 vs 223.4 ± 28.9 ρg/mg total protein; P < .01; n = 5) but did not alter inflammatory cell recruitment to the vein wall. PAI-1 -/- mice exhibited significantly elevated intrathrombus (257.2 ± 51.5 vs 4.3 ± 3.8 ρg/mg total protein; n = 5) and vein wall interleukin-13 (187.2 ± 57.6 vs 9.9 ± 1.1 ρg/mg total protein; P < .05; n = 5) as well as vein wall F4/80 positively staining monocytes (53 ± 11 vs 16 ± 2 cells/5 high-power fields; P < .05; n = 4).

CONCLUSIONS

LMWH did not accelerate venous thrombosis resolution but did protect against vein wall fibrosis in a PAI-1-dependent manner in an occlusive DVT model. Lack of PAI-1 correlated with accelerated venous thrombosis resolution but no protection from fibrosis. PAI-1 inhibition as a treatment strategy for DVT is likely to accelerate clearance of the thrombus but may come at the expense of increased vein wall fibrosis.

CLINICAL RELEVANCE

The pathophysiologic mechanism of post-thrombotic syndrome is not well understood clinically or experimentally. In this study, we evaluated the effect of the prominent fibrinolytic mechanism, plasminogen activator inhibitor 1 (PAI-1), and low-molecular-weight heparin (LMWH) on vein wall injury after thrombosis. We show here that LMWH is protective from vein wall fibrosis, but this is abrogated in PAI-1-deleted mice. This is also correlated with monocyte vein wall influx. These data support the clinical observation that LMWH may be protective from post-thrombotic vein wall injury in a PAI-1-dependent manner.

Plasminogen activator-1 overexpression decreases experimental postthrombotic vein wall fibrosis by a non-vitronectin-dependent mechanism

BACKGROUND

Factors associated with postthrombotic syndrome are known clinically, but the underlying cellular processes at the vein wall are not well delineated. Prior work suggests that vein wall damage does not correlate with thrombus resolution but rather with plasminogen activator-1 (PAI-1) and matrix metalloproteinase (MMP) activity.

OBJECTIVE

We hypothesized that PAI-1 would confer post venous thrombosis (VT) vein wall protection via a vitronectin (Vn)-dependent mechanism.

METHODS

A stasis model of VT was used with harvest over 2 weeks, in wild-type, Vn(-/-) , and PAI-1-overexpressing mice (PAI-1 Tg).

RESULTS

PAI-1 Tg mice had larger VT at 6 and 14 days, compared to controls, but Vn(-/-) mice had no alteration of VT resolution. Gene deletion of Vn resulted in an increase in, rather than the expected decrease in, circulating PAI-1 activity. While both Vn(-/-) and PAI-1 Tg had attenuated intimal fibrosis, PAI-1 Tg had significantly less vein wall collagen and a compensatory increase in collagen III gene expression. Both Vn(-/-) and PAI-1 Tg vein wall had less monocyte chemotactic factor-1 and fewer macrophages (F4/80), with significantly less MMP-2 activity and decreased TIMP-1 antigen. Ex vivo assessment of transforming growth factor β-mediated fibrotic response showed that PAI-1 Tg vein walls had increased profibrotic gene expression (collagens I and III, MMP-2, and α-smooth muscle actin) compared with controls, opposite of the in vivo response.

CONCLUSIONS

The absence of Vn increases circulating PAI-1, which positively modulates vein wall fibrosis in a dose-dependent manner. Translationally, PAI-1 elevation may decrease vein wall damage after deep vein thrombosis, perhaps by decreasing macrophage-mediated activities.

Expression of macrophage markers in cryoglobulinemic glomerulonephritis - a possible role of CXCL9

PURPOSE

Cryoglobulinemic glomerulonephritis (CGGN) is a type of membranoproliferative glomerulonephritis (MPGN) that develops in patients with systemic cryoglobulinemia. To date the exact pathogenesis of CGGN remains unclear. It has been suggested that macrophages may be significant contributors to the glomerular injury in this disease. In our study we attempt to characterize the macrophages in human CGGN using classical activation and regulatory macrophage markers.

MATERIAL AND METHOD

We searched our database for renal biopsy cases of CGGN. Macrophages were detected using a monoclonal anti-CD68 antibody. Two groups of macrophage markers were used: classical activation markers, including iNOS, CXCL9 and CCL20, and regulatory markers: SPHK1 and LIGHT. The stains were performed using immunohistochemical method.

RESULTS

Five patients with CGGN were identified. Four patients had systemic cryoglobulinemia and two had a serological evidence of hepatitis C virus infection. In all cases the glomeruli contained numerous macrophages. Staining for activatory macrophage markers revealed a strong nuclear staining for CXCL9 in numerous cells, including those corresponding to the macrophage location. Staining for the other activatory markers, as well as staining for regulatory markers, was not significant.

CONCLUSION

In this study of human CGGN we showed a striking expression of cytokine CXCL9, a classical macrophage activation marker, by the macrophages and possibly other cell types within the glomeruli. This observation points to the possible role of classically activated macrophages in the pathogenesis of MPGN. If this observation is confirmed on a larger group of patients, the cytokine CXCL9 could become a potential therapeutic target for human CGGN.

Ginger extract diminishes chronic fructose consumption-induced kidney injury through suppression of renal overexpression of proinflammatory cytokines in rats

BACKGROUND

The metabolic syndrome is associated with an increased risk of development and progression of chronic kidney disease. Renal inflammation is well known to play an important role in the initiation and progression of tubulointerstitial injury of the kidneys. Ginger, one of the most commonly used spices and medicinal plants, has been demonstrated to improve diet-induced metabolic abnormalities. However, the efficacy of ginger on the metabolic syndrome-associated kidney injury remains unknown. This study aimed to investigate the impact of ginger on fructose consumption-induced adverse effects in the kidneys.

METHODS

The fructose control rats were treated with 10% fructose in drinking water over 5 weeks. The fructose consumption in ginger-treated rats was adjusted to match that of fructose control group. The ethanolic extract of ginger was co-administered (once daily by oral gavage). The indexes of lipid and glucose homeostasis were determined enzymatically, by ELISA and/or histologically. Gene expression was analyzed by Real-Time PCR.

RESULTS

In addition to improve hyperinsulinemia and hypertriglyceridemia, supplement with ginger extract (50 mg/kg) attenuated liquid fructose-induced kidney injury as characterized by focal cast formation, slough and dilation of tubular epithelial cells in the cortex of the kidneys in rats. Furthermore, ginger also diminished excessive renal interstitial collagen deposit. By Real-Time PCR, renal gene expression profiles revealed that ginger suppressed fructose-stimulated monocyte chemoattractant protein-1 and its receptor chemokine (C-C motif) receptor-2. In accord, overexpression of two important macrophage accumulation markers CD68 and F4/80 was downregulated. Moreover, overexpressed tumor necrosis factor-alpha, interleukin-6, transforming growth factor-beta1 and plasminogen activator inhibitor (PAI)-1 were downregulated. Ginger treatment also restored the downregulated ratio of urokinase-type plasminogen activator to PAI-1.

CONCLUSIONS

The present results suggest that ginger supplement diminishes fructose-induced kidney injury through suppression of renal overexpression of macrophage-associated proinflammatory cytokines in rats. Our findings provide evidence supporting the protective effect of ginger on the metabolic syndrome-associated kidney injury.

The extracellular matrix in the kidney: a source of novel non-invasive biomarkers of kidney fibrosis?

Interstitial fibrosis is the common endpoint of end-stage chronic kidney disease (CKD) leading to kidney failure. The clinical course of many renal diseases, and thereby of CKD, is highly variable. One of the major challenges in deciding which treatment approach is best suited for a patient but also in the development of new treatments is the lack of markers able to identify and stratify patients with stable versus progressive disease. At the moment renal biopsy is the only means of diagnosing renal interstitial fibrosis. Novel biomarkers should improve diagnosis of a disease, estimate its prognosis and assess the response to treatment, all in a non-invasive manner. Existing markers of CKD do not fully and specifically address these requirements and in particular do not specifically reflect renal fibrosis. The aim of this review is to give an insight of the involvement of the extracellular matrix (ECM) proteins in kidney diseases and as a source of potential novel biomarkers of renal fibrosis. In particular the use of the protein fingerprint technology, that identifies neo-epitopes of ECM proteins generated by proteolytic cleavage by proteases or other post-translational modifications, might identify such novel biomarkers of renal fibrosis.

Triglycerides are independently associated with albuminuria in Taiwanese Type 2 diabetic patients

BACKGROUND

Lipid abnormalities in albuminuria in patients with Type 2 diabetes differ by race.

AIM

To perform a biochemical investigation of association between dyslipidemia and albuminuria in Type 2 diabetes in Taiwan. MATERIALS/ SUBJECTS AND METHODS: We recruited a total of 2349 Chinese patients with Type 2 diabetes from two medical centers in Taiwan over a 1-yr period. Patients were categorized into those with normoalbuminuria, microalbuminuria, and macroalbuminuria defined as albumin-to-creatinine ratio of <30, 30- 299, and ≥300 μg/mg. We then investigated the significance of the clinical and biochemical parameters and risk of albuminuria.

RESULTS

We found significant differences in total cholesterol (TC) between those with normoalbuminuria and micro/ macroalbuminuria, no significant difference in LDL cholesterol (LDL-C) among the 3 subgroups, a significant difference in HDL cholesterol (HDL-C) between those with normoalbuminuria and macroalbuminuria, and significant increases in triglyceride (TG) paralleling increases in albuminuria. TG was found by logistic regression to be significantly associated with micro/macroalbuminuria in our unadjusted model [odds ratio (OR) = 1.859 (1.596~2.165)], and remained significant after adjusting for various confounders [OR = 1.415 (1.123~1.784)]. Increases in albuminuria paralleled quartile increases in serum TG (p<0.001).

CONCLUSIONS

We conclude that TG increases significantly throughout the 3 stages of albuminuria in Taiwanese Type 2 diabetic patients, but TC, HDL-C, and LDL-C do not.

Honokiol ameliorates renal fibrosis by inhibiting extracellular matrix and pro-inflammatory factors in vivo and in vitro

BACKGROUND AND PURPOSE

Renal fibrosis acts as the common pathway leading to the development of end-stage renal disease. The present study investigated, in vivo and in vitro, the anti-fibrotic and anti-inflammatory effects, particularly on the epithelial to mesenchymal transition of renal tubular cells, exerted by honokiol, a phytochemical used in traditional medicine, and mechanisms underlying these effects.

EXPERIMENTAL APPROACH

Anti-fibrotic effects in vivo were assayed in a rat model of renal fibrosis [the unilateral ureteral obstruction (UUO) model]. A rat tubular epithelial cell line (NRK-52E) was stimulated by transforming growth factor-β1 (TGF-β1) and treated with honokiol to explore possible mechanisms of these anti-fibrotic effects. Gene or protein expression was analysed by Northern or Western blotting. Transcriptional regulation was investigated using luciferase activity driven by a connective tissue growth factor (CTGF) promoter.

KEY RESULTS

Honokiol slowed development of renal fibrosis both in vivo and in vitro. Honokiol treatment attenuated tubulointerstitial fibrosis and expression of pro-fibrotic factors in the UUO model. Honokiol also decreased expression of the mRNA for the chemokine CCL2 and for the intracellular adhesion molecule-1, as well as accumulation of type I (α1) collagen and fibronectin in UUO kidneys. Phosphorylation of Smad-2/3 induced by TGF-β1 and CTGF luciferase activity in renal tubular cells were also inhibited by honokiol.

CONCLUSIONS AND IMPLICATIONS

Honokiol suppressed expression of pro-fibrotic and pro-inflammatory factors and of extracellular matrix proteins. Honokiol may become a therapeutic agent to prevent renal fibrosis.

The Ayurvedic Medicine Salacia oblonga Attenuates Diabetic Renal Fibrosis in Rats: Suppression of Angiotensin II/AT1 Signaling

In human diabetic nephropathy, the extent of tubulointerstitial fibrosis is the leading cause of end-stage renal disease; fibrosis is closely correlated with renal dysfunction. Although a wide array of medicinal plants play a role in the prevention and treatment of diabetes, there are few reports of the application of herbal medicines in amelioration of renal fibrosis, or the underlying mechanisms by which such benefits are mediated. The efficacy of the Ayurvedic antidiabetic medicine Salacia oblonga (SO) root on rat renal fibrosis was investigated. An aqueous extract from SO (100 mg/kg, p.o., 6 weeks) diminished renal glomerulosclerosis and interstitial fibrosis in Zucker diabetic fatty (ZDF) rats, as revealed by van Giesen-staining. SO also reduced renal salt-soluble, acid-soluble and salt-insoluble collagen contents. These changes were accompanied by normalization of hypoalbuminemia and BUN. Gene profiling revealed that the increase in transcripts encoding the glomerulosclerotic mediators collagen I, collagen IV, fibronectin, angiotensin II type 1 receptor (AT1), transforming growth factor (TGF)-β1, plasminogen activator inhibitor (PAI)-1 observed in ZDF rat kidney was suppressed by SO. In rat-derived mesangial cells, similar to the effect of the AT1 antagonist telmisartan, SO and its major component mangiferin suppressed the stimulatory effect of angiotensin II on proliferation and increased mRNA expression and/or activities of collagen I, collagen IV, fibronectin, AT1, TGF-β1 and PAI-1. Considered together the present findings demonstrate that SO attenuates diabetic renal fibrosis, at least in part by suppressing anigiotensin II/AT1 signaling. Further, it now emerges that mangiferin is an effective antifibrogenic agent.

Blockade of osteopontin inhibits glomerular fibrosis in a model of anti-glomerular basement membrane glomerulonephritis

BACKGROUND

In our rat model for anti-GBM GN, severe fibrosis follows glomerular inflammation. A potential role of extracellular matrix protein osteopontin (OPN) in glomerular fibrosis was investigated.

METHODS

Neutralizing OPN antiserum or control normal serum was injected into the experimental rats at late inflammatory/early fibrotic stage. Glomerular inflammation and fibrosis were determined.

RESULTS

OPN antiserum treatment had little effect on glomerular inflammation. However, the antiserum treatment resulted in a significant reduction in number of fibrotic glomeruli (50% of the controls). Histology observation showed that fibrotic tissue in glomeruli of the antiserum treated rats was mild and poorly developed. OPN antiserum treatment resulted in downregulated glomerular expression of collagen 1α1; collagen deposition in the antiserum treated rats reduced to <30% of that for normal serum controls.

CONCLUSION

Neutralization of OPN inhibited progression of fibrosis in vivo when given at early fibrotic stage. Thus, OPN may be a therapeutic target for glomerular fibrosis.

Impact of chemokine receptor CX3CR1 in human renal allograft rejection

Chemokine receptors play pivotal roles for leukocyte recruitment in acute and chronic inflammatory processes. This study was performed to analyze the expression, distribution and cellular localization of CX3CR1 in human renal transplant biopsies and to assess its role as potential diagnostic and prognostic marker. CX3CR1 was prospectively analyzed in 174 renal graft biopsies from patients with normal morphology (n=76), antibody-mediated acute rejection (n=6), acute tubulointerstitial rejection (n=27), acute vascular rejection (n=31), and with acute tubulus necrosis (n=34). Double immunofluorescence was additionally performed for CX3CR1 and CD4, CD8, CD20, CD68, and CD209/DC-SIGN. The number of CX3CR1 positive interstitial cells was significantly higher in the biopsies with acute tubulointerstitial and acute vascular rejection as compared to normal renal allograft biopsies. CX3CR1 positive cells were mainly CD68 positive monocytes/macrophages and CD209/DC-SIGN positive dendritic cells. The percentage of the CX3CR1 positive staining area was a predictor for steroid responsiveness and for worse clinical outcome 3 and 12 months after transplantation. CX3CR1 positive macrophages and/or dendritic cells are significantly elevated in acute renal allograft rejection. As CX3CR1 was associated with outcome parameters, it has to be further evaluated as a prognostic marker in human renal transplantation.

Uridine triphosphate (UTP) induces profibrotic responses in cardiac fibroblasts by activation of P2Y2 receptors

Cardiac fibroblasts (CFs) play a key role in response to injury and remodeling of the heart. Nucleotide (P2) receptors regulate the heart but limited information is available regarding such receptors in CFs. We thus sought to determine if extracellular nucleotides regulate fibrotic responses (e.g., proliferation, migration and expression of profibrotic markers) of CFs in primary culture. UTP increased rat CF migration 3-fold (p<0.001), proliferation by 30% (p<0.05) and mRNA expression of profibrotic markers: alpha smooth muscle actin (alpha-SMA), plasminogen activator inhibitor-1 (PAI-1), transforming growth factor beta, soluble ST2, interleukin-6 and monocyte chemoattractant protein-1 (MCP-1) by 3.0-, 15-, 2.0-, 7.6-, 11-, and 6.1-fold, respectively (p<0.05). PAI-1 protein expression induced by UTP was dependent on protein kinase C (PKC) and extracellular signal-regulated kinase (ERK), based on blockade by the PKC inhibitor Ro-31-8220 and the ERK inhibitor U0126, respectively. The rank order for enhanced expression of PAI-1 and alpha-SMA by nucleotides (UTPgammaS>>UDPbetaS>>ATPgammaS), the expression of P2Y2 receptors as the most abundantly expressed P2Y receptor in rat CFs and a blunted response to UTP in P2Y2(-/-) mice all implicate P2Y2 as the predominant P2Y receptor that mediates nucleotide-promoted profibrotic responses. Additional results indicate that P2Y2 receptor-promoted profibrotic responses in CFs are transient, perhaps as a consequence of receptor desensitization. We conclude that P2Y2 receptor activation is profibrotic in CFs; thus inhibition of P2Y2 receptors may provide a novel means to diminish fibrotic remodeling and turnover of extracellular matrix in the heart.

Progression of glomerular and tubular disease in pediatrics

Chronic kidney disease may be stimulated by many different etiologies, but its progression involves a common, yet complex, series of events that lead to the replacement of normal tissue with scar. These events include altered physiology within the kidney leading to abnormal hemodynamics, chronic hypoxia, inflammation, cellular dysfunction, and activation of fibrogenic biochemical pathways. The end result is the replacement of normal structures with extracellular matrix. Treatments presently are focused on delaying or preventing such progression, and are largely nonspecific. In pediatrics, such therapy is complicated further by pathophysiological issues that render children a unique population.

Renal tubulointerstitial expansion is associated with endothelial dysfunction and inflammation in type 1 diabetes

OBJECTIVE

Diabetic nephropathy has been considered to be primarily of glomerular origin, but there is now compelling evidence that disruption of the tubulointerstitial architecture determines the outcome of diabetic nephropathy in interplay with the glomerular damage. We investigated whether reactive oxidative species, pro-inflammatory cytokines and endothelial dysfunction were implicated in the progression of tubulointerstitial damage in young subjects with type 1 diabetes.

MATERIAL AND METHODS

In a prospective study, we investigated 18 young subjects (mean age 21 years) with type 1 diabetes and microalbuminuria. Quantitative morphometry concerning glomerular and tubulointerstitial changes was performed at baseline (i.e. mean duration of diabetes 10 years) and 2.5 and 8 years later. Markers of endothelial activation and inflammation, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, tumour necrosis factor-alpha, interleukin-6, interleukin-8 and highly sensitive C-reactive protein were measured at baseline and after 8 years. Tissue plasminogen activator antigen and plasminogen activator inhibitor (PAI-1 activity) and asymmetric dimethylargine (ADMA) were measured at baseline and after 2.5 years.

RESULTS

PAI-1 activity at baseline was a significant independent variable of the 8-year increment in interstitial volume fraction (Vv(Int/cortex)). ADMA/L-arginine ratio at baseline was associated with the increment in Vv(Int/cortex) during 2.5 years (p<0.01), still significant after adjustment for covariates (p = 0.02). No associations between Vv(Int/cortex) and glomerular parameters, HaemoglobinA1c and urinary albumin excretion were observed.

CONCLUSIONS

Biomarkers involved in interstitial volume expansion seem to be different from those of mesangial expansion in early diabetic nephropathy. PAI-1 activity may have a predictive role in the development of the tubulointerstitial expansion.

A Profibrotic Effect of Plasminogen Activator Inhibitor Type-1 (PAI-1) in the Heart

Increased expression of PAI-1 is profibrotic in several organs. However, its potentially profibrotic effects in the heart subjected to infarction have not been elucidated. Accordingly, we induced coronary occlusion in 10-week-old mice congenic on a C57BL6 background and in mice overexpressing PAI-1 (PTG) in multiple tissues. Compared with C57BL6 control mice without myocardial infarction (MI), PTG mice exhibited consistently elevated PAI-1 in plasma at 16 weeks of age but virtually identical PAI-1 content in left ventricular (LV) myocardium. However, they exhibited a 2-fold increase in LV PAI-1 content 6 weeks after induction of MI (4.21 ± 1.0 ng/ml tissue protein) compared with that in C57BL6 mice (2.04 ± 0.5, P < 0.05). In 16-week-old mice, ultrasonically delineated LV fractional shortening (FS) was comparable in normal PTG and normal C57BL6 controls. However, 6 weeks after MI, PTG ( n = 21) compared with C57BL6 ( n = 14) mice exhibited markedly thinner LV posterior walls in both diastole (C57BL6 0.79 ± 0.05 mm, PTG 0.55 ± 0.06, P < 0.05) and systole (0.97 ± 0.05 mm, 0.75 ± 0.06, P < 0.05); increased end systolic LV dimensions (4.54 ± 0.2 mm, 5.17 ± 0.2, P < 0.05); and significantly depressed FS, more impaired LV segmental function, and greater mitral E wave amplitude. Compared with fibrosis assessed by Masson staining of sections from apex to base in C57BL6 mice (10.85 ± 0.43% LV area), PTG mice exhibited 33% more LV fibrosis after MI ( P < 0.05). Thus, PAI-1 is profibrotic in the heart subjected to infarction. Accordingly, overexpression of PAI-1 is a promising target for attenuation of heart failure after MI that may be exacerbated by fibrosis.

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.

Increased renal collagen cross-linking and lipid accumulation in nephropathy of Zucker diabetic fatty rats

BACKGROUND

Zucker diabetic fatty (ZDF) rat is a genetic model of type 2 diabetes and obesity. The mechanism underlying nephropathy in ZDF rats, however, remains unclear.

METHODS

ZDF rats were compared to age-matched Zucker lean (ZL) rats. Physiological and blood biochemical parameters, renal glomerular cross-sectional area (hematoxylin-eosin staining), fibrosis (van Giesen staining), collagen composition (Sircol Collagen Assay), lipids (enzymatic method) and mRNA expression (RT-PCR) were determined.

RESULTS

ZDF rats showed an increase in renal-insoluble collagen content and the ratio of renal-insoluble to salt-soluble collagen (2- and 1.5-fold of the control animals). There were increases in renal glomerulosclerosis and interstitial fibrosis in ZDF rats (increased to 2-fold) in the glomerular mesangium and tubulointerstitium, and increased glomerular area. Renal triglyceride accumulated to greater than 2-fold of those levels in ZL rats. These changes were accompanied by hypoalbuminemia, and elevated plasma blood urea nitrogen and uric acid levels. Gene profiling showed increased expression of transcripts encoding the glomerulosclerotic mediator collagens I and IV, plasminogen activator inhibitor-1, transforming growth factor-beta1, and angiotensin II type 1 receptor in ZDF rat kidney. Moreover, renal expression of mRNAs encoding sterol regulatory element-binding protein-1, a nuclear transcription factor that activates genes involved in fatty acid synthesis, and acetyl-CoA carboxylase, a key enzyme that mediates fatty acid synthesis, was increased in ZDF rats.

CONCLUSIONS

Our findings suggest that dysregulated gene expression may result in increased renal collagen cross-linking and lipid accumulation, that may be associated with development of nephropathy in the animal model of type 2 diabetes and obesity.

Angiotensinogen, angiotensine converting enzyme and plasminogen activator inhibitor-1 gene polymorphism in chronic allograft dysfunction

Despite dramatic improvements in first-year patient and graft survival rates, chronic allograft dysfunction (CAD) remains the leading cause of late renal allograft loss, while current immunologic strategies have little effect on this condition. The renin-angiotensin system (RAS) plays an important role in progression of chronic renal disease. It was shown that plasminogen activator inhibitor-1 (PAI-1) functions in the RAS. This study investigates the possible links between angiotensinogen (AGT M235T), angiotensin-converting enzyme (ACE) and PAI-1 genotypes with CAD. Assessments of polymorphism were performed in 127 renal allograft recipients (77 with CAD and 50 with normal renal function). Fifty healthy subjects were also considered for comparison. Genotypes were determined using polymerase chain reaction (PCR) sequence-specific primers and PCR followed by restriction fragment length polymorphism analysis. Kidney recipients with CAD had significantly higher frequencies of the TT than the recipients without CAD (P < 0.05). The transplant recipients with CAD also had significantly higher frequencies of the DD genotype than those without CAD (P < 0.05). No significant differences were observed between the allelic and genotypic distributions of PAI-1 polymorphisms. Therefore, determination of AGT M235T and ACE genotypes prior to transplantation may be useful to identify patients who are at risk for chronic renal transplant dysfunction.

Kruppel-like zinc finger protein Glis2 is essential for the maintenance of normal renal functions

To obtain insight into the physiological functions of the Krüppel-like zinc finger protein Gli-similar 2 (Glis2), mice deficient in Glis2 expression were generated. Glis2 mutant (Glis2(mut)) mice exhibit significantly shorter life spans than do littermate wild-type (WT) mice due to the development of progressive chronic kidney disease with features resembling nephronophthisis. Glis2(mut) mice develop severe renal atrophy involving increased cell death and basement membrane thickening in the proximal convoluted tubules. This development is accompanied by infiltration of lymphocytic inflammatory cells and interstitial/glomerular fibrosis. The severity of the fibrosis, inflammatory infiltrates, and glomerular and tubular changes progresses with age. Blood urea nitrogen and creatinine increase, and Glis2(mut) mice develop proteinuria and ultimately die prematurely of renal failure. A comparison of the gene expression profiles of kidneys from 25-day-old/60-day-old WT and Glis2(mut) mice by microarray analysis showed increased expressions of many genes involved in immune responses/inflammation and fibrosis/tissue remodeling in kidneys of Glis2(mut) mice, including several cytokines and adhesion and extracellular matrix proteins. Our data demonstrate that a deficiency in Glis2 expression leads to tubular atrophy and progressive fibrosis, similar to nephronophthisis, that ultimately results in renal failure. Our study indicates that Glis2 plays a critical role in the maintenance of normal kidney architecture and functions.

Akt kinase targets association of CBP with SMAD 3 to regulate TGFbeta-induced expression of plasminogen activator inhibitor-1

Transforming growth factor-beta (TGFbeta) controls expression of plasminogen activator inhibitor type 1 (PAI-1), which regulates degradation of extracellular matrix proteins in fibrotic diseases. The TGFbeta receptor-specific Smad 3 has been implicated in the PAI-1 expression. The mechanism by which non-Smad signaling contributes to this process is not known. We studied the cross-talk between Smad 3 and PI 3 kinase/Akt signaling in TGFbeta-induced PAI-1 expression in renal mesangial cells. Inhibition of PI 3 kinase and Akt kinase blocked TGFbeta- and Smad 3-mediated expression of PAI-1. In contrast, constitutively active PI 3 kinase and Akt kinase increased PAI-1 expression, similar to TGFbeta. Inhibition of PI 3 kinase and Akt kinase had no effect on TGFbeta-induced Smad 3 phosphorylation and its translocation to the nucleus. Notably, inhibition of PI 3 kinase-dependent Akt kinase abrogated TGFbeta-induced PAI-1 transcription, without affecting binding of Smad 3 to the PAI-1 Smad binding DNA element. However, PI 3 kinase inhibition and dominant negative Akt kinase antagonized the association of the transcriptional coactivator CBP with Smad 3 in response to TGFbeta, resulting in inhibition of Smad 3 acetylation. Together our findings identify TGFbeta-induced PI 3 kinase/Akt signaling as a critical regulator of Smad 3-CBP interaction and Smad 3 acetylation, which cause increased PAI-1 expression.

Modulation of glomerulosclerosis

Regardless of the initial injury, the long-term consequence for the patient depends upon the ensuing balance of profibrotic vs reparative modulators activated. The glomerulus has some capacity for repair. Even when sclerosis has developed with accumulation of extracellular matrix, this lesion may be remodeled, with a change in balance between profibrotic and antifibrotic and collagen synthesis vs proteolytic mediators. We will focus here on the interplay between mediators of fibrosis and reparative mechanisms and potential regression of fibrosis. Based on the clinical efficacy of interventions that inhibit angiotensin, we will focus on factors related to the renin-angiotensin system.

Deleterious effects of lack of cardiac PAI-1 after coronary occlusion in mice and their pathophysiologic determinants

We sought to delineate mechanisms through which the lack of plasminogen activator inhibitor (PAI)-1 in the heart affects remodeling of the heart early after myocardial infarction (MI). MI was induced by coronary occlusion in 10-weeks old PAI-1 knockout (KO) and control mice. Three days after MI, systolic and diastolic function was assessed with high-resolution echocardiography, infarct size was determined biochemically and histologically and accumulation of acute inflammatory cells in zones of infarction was characterized by immunocytochemistry. PAI-1 KO mice exhibited markedly thickened diastolic left ventricular anterior walls (1.38 +/- 0.38 mm vs. 0.77 +/- 0.13 SD), more profound depression of global and regional cardiac function (19 vs. 22% fractional shortening), and greater evidence of diastolic dysfunction (average E wave amplitude = 568 vs. 675 mm/s) all of which were significant. Markedly greater extent of infarction was demonstrated biochemically and histologically in knockout mice compared with controls (76 vs. 29% of the left ventricle, P < 0.05) associated with striking hemorrhage and intense inflammation. Fibrosis normalized for infarct size was markedly reduced (0.006 vs. 0.022 microg hydroxyproline/mg dry weight). Thus, lack of PAI-1 in the heart exerted deleterious effects mediated, at least in part by increased inflammation and hemorrhage and attenuating of fibrosis.

Mechanism of inactivation of plasminogen activator inhibitor-1 by a small molecule inhibitor

The inactivation of plasminogen activator inhibitor-1 (PAI-1) by the small molecule PAI-1 inhibitor PAI-039 (tiplaxtinin) has been investigated using enzymatic analysis, direct binding studies, site-directed mutagenesis, and molecular modeling studies. Previously PAI-039 has been shown to exhibit in vivo activity in various animal models, but the mechanism of inhibition is unknown. PAI-039 bound specifically to the active conformation of PAI-1 and exhibited reversible inactivation of PAI-1 in vitro. SDS-PAGE indicated that PAI-039 inactivated PAI-1 predominantly through induction of PAI-1 substrate behavior. Preincubation of PAI-1 with vitronectin, but not bovine serum albumin, blocked PAI-039 activity while analysis of the reciprocal experiment demonstrated that preincubation of PAI-1 with PAI-039 blocked the binding of PAI-1 to vitronectin. Together, these data suggest that the site of interaction of the drug on PAI-1 is inaccessible when PAI-1 is bound to vitronectin and may overlap with the PAI-1 vitronectin binding domain. This was confirmed by site-directed mutagenesis and molecular modeling studies, which suggest that the binding epitope for PAI-039 is localized adjacent to the previously identified interaction site for vitronectin. Thus, these studies provide a detailed characterization of the mechanism of inhibition of PAI-1 by PAI-039 against free, but not vitronectin-bound PAI-1, suggesting for the first time a novel pool of PAI-1 exists that is vulnerable to inhibition by inactivators that bind at the vitronectin binding site.

Antihypertensive therapy induces compartment-specific chemokine expression and a Th1 immune response in the clipped kidney of Goldblatt hypertensive rats

The present study examined the pathogenesis of interstitial inflammation and fibrosis in antihypertensively treated rats with two-kidney, one-clip hypertension. Hypertensive rats were randomized into four groups: no treatment and moderate, intermediate, and intensified lowering of blood pressure with increasing doses of a vasopeptidase inhibitor for 6 wk. The vasopeptidase inhibitor dose dependently lowered blood pressure. The tubulointerstitial damage was accompanied by a diffuse infiltration of mononuclear cells and circumscript mononuclear inflammatory cell cluster formation consisting mainly of T cells and to a lesser degree of macrophages and B cells. Real-time PCR analyses showed a dose-dependent induction of MCP-1 and the Th1-type chemokines IP10 and Mig as well as their receptor CXCR3 and the Th1 cytokine IFN-γ. In situ hybridization and laser microdissection revealed a strong expression of these Th1-associated transcripts in the clusters and, in the case of MCP-1, also diffusely in the interstitium. The inflammation was accompanied by the appearance of myofibroblasts and synthesis of the fibrogenic factor plasminogen activator inhibitor-1 as well as the collagenase matrix metalloproteinase-2, leading to collagen I upregulation and interstitial scarring. No inflammation or fibrosis was found in normotensive rats treated with the vasopeptidase inhibitor. The renal injury in the clipped kidney is accompanied by compartment-specific chemokine expression and cell cluster formation of Th1 specificity associated with upregulation of fibrogenic proteins and matrix metalloproteinases. These findings suggest that the Th1 chemokines IP10 and Mig as well as their receptor CXCR3 are potential targets for therapeutic interventions in ischemic nephropathy.

Increased plasminogen activator inhibitor type-1 (PAI-1) in the heart as a function of age

Heart failure is associated with advanced age and insulin resistance and is thought to be exacerbated by cardiac fibrosis. Plasminogen activator inhibitor type-1 (PAI-1) has been strongly implicated as a determinant of fibrosis in diverse organs and tissues. Its concentration is increased in blood, and its expression is increased in vessel walls in association with insulin resistance. Accordingly, we sought to determine whether expression of PAI-1 in the heart increases as a function of age of 10 week old and 20 week old normal and insulin resistant transgenic mice thereby potentially predisposing to heart failure. Results obtained indicate that PAI-1 content increases significantly in the heart as a function of age by more than 60%. The increases are much greater than those that can be accounted for by the modest, and statistically insignificant increases in the concentrations of PAI-1 in plasma that were observed to occur as a function of age as well. Thus, PAI-1 increases in the heart is a function of age, occurs in insulin resistant and non-insulin resistant mice, and may contribute to fibrosis predisposing to heart failure associated with advanced age, particularly when insulin resistance is present.

Renoprotective effects of fenofibrate in diabetic rats are achieved by suppressing kidney plasminogen activator inhibitor-1

To investigate mechanisms of protective effects of fenofibrate on the diabetic kidney, male Wistar rats were divided into control, untreated diabetes, and fenofibrate-treated (32 mg kg(-1) d(-1), 8 weeks) diabetes groups. Diabetes induced by streptozotocin (25 mg/kg) and a high-fat diet was characterized by the disorders of plasma glucose and lipids. In untreated diabetic rats, there were increases in glomerular volume, matrix content, expressions of laminin and urinary albumin excretion. These nephropathies were associated with the upregulations of plasminogen activator inhibitor 1 (PAI-1) mRNA expression and its protein activity in the renal cortex, and a significant increase in transforming growth factor beta1 (TGF-beta1) expression. Treatment with fenofibrate suppressed the expression of PAI-I mRNA and its protein activity, and inhibited TGF-beta1 overexpression. It also partially reversed metabolic disorders and pathophysiologic changes associated with diabetic nephropathy. Our results indicate that fenofibrate delays the progression of diabetic nephropathy in rats to some extent. These renoprotective effects are likely to be achieved through suppression of PAI-1 and TGF-beta1 in the renal cortex, and consequently less extracellular matrix deposition.

Impaired fibrinolytic activity in type II diabetes: Correlation with urinary albumin excretion and progression of renal disease

Progression of renal disease and cardiovascular complications in type II diabetes mellitus have been shown to correlate with control of blood glucose, lipids, blood pressure, and smoking. These factors, however, do not appear to totally explain these diabetic complications. Renal disease and cardiovascular complications in type II diabetes are associated with vascular abnormalities and fibrosis, both of which may occur with impaired fibrinolysis. A cross-sectional study was therefore performed in 107 type II diabetic patients recruited from the Denver Metropolitan Area to examine the effect of impaired fibrinolysis, as assessed by the ratio of plasminogen activator inhibitor (PAI-1) to tissue-type plasminogen activator (t-PA). With urinary albumin excretion (UAE) as a risk factor for both renal disease progression and cardiovascular complications, the patients were analyzed with respect to UAE less than and greater than 1 gm/day. The age, blood glucose, hemoglobin A1C, duration of diabetes, lipids, body mass index, and smoking were no different between the groups. As expected, the group with greater UAE had worse renal function, the serum creatinine (1.98 +/- 0.24 vs 1.21 +/- 0.05 mg/dl, P < 0.001) and creatinine clearance (55.5 +/- 6.0 vs 76.8 +/- 2.7 ml/min, P < 0.001) were significantly different. The type II diabetic patients with greater UAE exhibited significantly higher PAI-1/t-PA (2.43 +/- 0.26 vs 1.85 +/- 0.07, P < 0.03). The past history of cardiac complications was also higher (87.5 vs 72.3%, P < 0.07) in the diabetic patients with more impaired fibrinolysis and greater UAE. Thus a prospective, randomized clinical trial in type II diabetes with PAI-1 inhibitors is needed.

Correlative insights into the immunoexpression of transforming growth factor β-1 in acutely rejected renal allografts

Recent data suggest that early changes in the process of acute renal transplant rejection (ARTR) occurring during the first 3 months after transplantation include interstitial fibrosis. Transforming growth factor beta (TGF-beta) has been recognized as a key mediator of renal fibrogenesis; therefore, the present study was conducted to ascertain immunoexpression of TGF-beta in ARTR. Another purpose of our study was to determine whether TGF-beta could correlate with the interstitial area and to examine a possible relationship between TGF-beta and interstitial alpha-smooth muscle actin (alpha-SMA), endothelin-1 (ET-1) expression, interstitial T lymphocytes, and monocytes/macrophages. Twenty-four renal allograft biopsy specimens obtained from patients with ARTR were examined using percutaneous renal biopsy. As a control, we used 11 allograft biopsy specimens obtained from patients without any sign of rejection. Staining intensities of TGF-beta-1 in tubuli and of ET-1 in the endothelium of peritubular capillaries, in arterioles, and in the renal tubular epithelial cells were recorded semiquantitatively, whereas interstitial CD3+ cells, CD68+ cells, alpha-SMA expression, and the interstitial area were assessed quantitatively using computer image analysis system. Our study revealed that in the ARTR group, the mean values of the immunoexpression of TGF-beta-1, ET-1, interstitial CD3+ cells, CD68+ cells, alpha-SMA expression, and the interstitial area were significantly increased as compared with controls. In the ARTR group, there were significant positive correlations between immunostaining of TGF-beta-1 and ET-1, immunostaining of TGF-beta-1 and alpha-SMA, as well as immunostaining of TGF-beta-1 and interstitial volume. The correlation between immunostaining of TGF-beta-1 and CD 3+ cells tended to be negative; however, this did not reach statistical significance. We did not find any significant relationship between TGF-beta-1 and interstitial monocytes/macrophages. In controls, all these correlations were not significant. In conclusion, our correlative study suggests a role of TGF-beta-1 in early interstitial fibrotic changes in acutely rejected renal allografts, and we hypothesize that endothelin-1 and myofibroblasts pathways may play an important role in this process.

Plasminogen activator inhibitor-1 modulates adipocyte differentiation

Increased plasminogen activator inhibitor-1 (PAI-1) is linked to obesity and insulin resistance. However, the functional role of PAI-1 in adipocytes is unknown. This study was designed to investigate effects and underlying mechanisms of PAI-1 on glucose uptake in adipocytes and on adipocyte differentiation. Using primary cultured adipocytes from PAI-1(+/+) and PAI-1(-/-) mice, we found that PAI-1 deficiency promoted adipocyte differentiation, enhanced basal and insulin-stimulated glucose uptake, and protected against tumor necrosis factor-alpha-induced adipocyte dedifferentiation and insulin resistance. These beneficial effects were associated with upregulated glucose transporter 4 at basal and insulin-stimulated states and upregulated peroxisome proliferator-activated receptor-gamma (PPARgamma) and adiponectin along with downregulated resistin mRNA in differentiated PAI-1(-/-) vs. PAI-1(+/+) adipocytes. Similarly, inhibition of PAI-1 with a neutralizing anti-PAI-1 antibody in differentiated 3T3-L1 adipocytes further promoted adipocyte differentiation and glucose uptake, which was associated with increased expression of transcription factors PPARgamma, CCAAT enhancer-binding protein-alpha (C/EBPalpha), and the adipocyte-selective fatty acid-binding protein aP2, thus mimicking the phenotype in PAI-1(-/-) primary adipocytes. Conversely, overexpression of PAI-1 by adenovirus-mediated gene transfer in 3T3-L1 adipocytes inhibited differentiation and reduced PPARgamma, C/EBPalpha, and aP2 expression. This was also associated with a decrease in urokinase-type plasminogen activator mRNA expression, decreased plasmin activity, and increased collagen I mRNA expression. Collectively, these results indicate that absence or inhibition of PAI-1 in adipocytes protects against insulin resistance by promoting glucose uptake and adipocyte differentiation via increased PPARgamma expression. We postulate that these PAI-1 effects on adipocytes may, at least in part, be mediated via modulation of plasmin activity and extracellular matrix components.

Progression of chronic kidney disease: can it be prevented or arrested?

Chronic kidney disease constitutes a highly prevalent health problem worldwide. Left untreated, it progresses inexorably to greater levels of severity at variable rates. The morbid impact of chronic kidney disease is heightened by its role as risk factor for cardiovascular disease. In the past two decades, considerable gains have been realized in retarding progression of chronic kidney disease by emphasizing blood pressure control and blockade of the renin-angiotensin system. Notwithstanding, the therapeutic goal of preventing or arresting chronic kidney disease progression remains unfulfilled. Currently attainable rates of decrease in glomerular filtration rate remain at 2 to 8 mL/min/y depending on the underlying disease. It is now believed that to achieve optimal therapeutic targets (proteinuria of <500 mg/day and decrease in glomerular filtration rate of 1 mL/min/y, the average age-related decline) we must introduce novel strategies and a multifaceted approach to treatment that interrupts multiple mechanisms of progression. To this end, and wherever relevant, new approaches to cause-specific treatment must be applied, such as targeted immunosuppression, intensive glycemic control, gene therapy, and enzyme replacement therapy. Furthermore, in all chronic kidney disease, we must interfere more effectively with the multitude of common mechanisms of progression. Established or putative, such approaches include aggressive blood pressure control; advanced renin-angiotensin system blockade; cytokine modulation and antifibrotic therapy; aldosterone blockade; endothelin blockade, nitric oxide modulation and vasopeptidase inhibition; antioxidant therapy; statin therapy; glycosaminoglycan therapy; anemia therapy; dietary restrictions; lifestyle changes; and pharmacogenomic profiling. Such a concerted, multifaceted approach to management might indeed prevent or arrest progression of chronic kidney disease, or even achieve regression of chronic kidney disease.

Synergistic effect of hypoxia and TNF-alpha on production of PAI-1 in human proximal renal tubular cells

BACKGROUND

Chronic hypoxia has been newly proposed as a common mechanism of tubulointerstitial fibrosis in the progression of various chronic inflammatory renal diseases, where plasminogen activator inhibitor-1 (PAI-1) plays an important role in the accumulation of extracellular matrix (ECM) through inhibition of plasmin-dependent ECM degradation. In the present study, we investigated the presence of PAI-1 in renal tubular cells by immunostaining renal biopsy samples. We also closely examined the effects of hypoxia and tumor necrosis factor-alpha (TNF-alpha) on PAI-1 expression in cultured human proximal renal tubular cells (HPTECs).

METHODS

Confluent cells growth-arrested in Dulbecco's modified Eagle's medium (DMEM) for 24 hours were exposed to hypoxia (1% O(2)) and/or TNF-alpha at 10 ng/mL for up to 48 hours. Amounts of PAI-1 protein and mRNA after stimulation were measured by enzyme-linked immunosorbent assay (ELISA) and TaqMan quantitative polymerase chain reaction (PCR) or cDNA array analysis, respectively, and compared to those in cells incubated under control conditions (18% O(2) without TNF-alpha). Hypoxia-inducible factor-1alpha (HIF-1alpha) was demonstrated by immunoblot and immunofluorescence analyses. Human PAI-1 promoter activity was estimated by luciferase reporter gene assay.

RESULTS

In crescentic glomerulonephritis, clusters of proximal tubules were specifically stained for PAI-1. cDNA array analysis identified PAI-1 as a major gene highly induced by hypoxia in HPTECs. Treatment of 24 hours with hypoxia, TNF-alpha, and their combination induced a 2.8-fold, a 1.8-fold, and a 4.6-fold increase in PAI-1 protein secretion, and produced a 3.6-fold, a 3.3-fold, and a 12.1-fold increase at the PAI-1 mRNA level, respectively. Immunoblot analysis and immunocytochemistry revealed that hypoxia-inducible factor-1alpha (HIF-1alpha) was markedly accumulated in the cell lysates and exclusively translocated to nuclei after 16 hours' exposure of HPTECs to hypoxia but not to TNF-alpha. Luciferase reporter gene assay showed that hypoxia, TNF-alpha, and their combination increased PAI-1 transcription activity by 1.8-fold, 1.4-fold, and 2.2-fold, respectively. A dominant-negative form of HIF-1alpha significantly suppressed PAI-1 transcription activity induced by hypoxia. Inhibition of nuclear factor-kappaB (NF-kappaB) caused a moderate decrease in PAI-1 production under hypoxia.

CONCLUSION

Hypoxia induces PAI-1 expression via remarkable nuclear accumulation of HIF-1alpha and partially via NF-kappaB activation in HPTECs. TNF-alpha can synergistically enhance this hypoxia-induced PAI-1 expression.

Chronic allograft nephropathy: expression and localization of PAI-1 and PPAR-gamma

BACKGROUND

Chronic allograft nephropathy (CAN) is a major cause of loss of renal allografts. Mechanisms postulated to be involved include sequelae of rejection, warm ischaemia time, drug toxicity, ongoing hypertension and dyslipidaemia. Plasminogen activator inhibitor-1 (PAI-1) is implicated not only in thrombosis, but also in fibrosis, by inhibiting matrix degradation, and is expressed in renal parenchymal cells as well as in macrophages. Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is a member of the steroid receptor superfamily, and plays a major beneficial role in lipid regulation, insulin sensitivity and macrophage function, factors that may play a role in CAN. We therefore studied the expression of these molecules in CAN.

METHODS

All renal biopsy/nephrectomy files from Vanderbilt and Nashville VAMC from a 6 year period were reviewed to identify all renal transplant biopsies or nephrectomies more than 6 months after transplant with CAN. CAN was defined as fibrosis in the graft, vascular, interstitial or glomerular. All cases were scored for severity of fibrosis in vasculature (0-3 scale), glomeruli (% affected with either segmental and/or global sclerosis) and interstitial fibrosis (% of sample affected). PAI-1 and PPAR-gamma immunostaining was assessed on a 0-3 scale in glomeruli, vessels and tubules.

RESULTS

Eighty-two patients with a total of 106 samples met entry criteria. The population consisted of 59 Caucasians and 23 African-Americans; 49 males, 33 females with average age 37.9+/-1.7 years. Average time after transplant at time of biopsy was 60.5+/-4.9 months (range 7-229). Glomerulosclerosis extent in CAN was on average 26.5+/-2.4% compared with 3.6+/-1.2% in normal control kidneys from native kidney cancer nephrectomies and 0% in transplanted kidney biopsies from patients obtained > or =6 months after transplantation without CAN. Native control kidneys showed mild interstitial fibrosis (8.0+/-1.2%), whereas transplant controls showed very minimal fibrosis (2.0+/-2.0%). Interstitial fibrosis in CAN kidneys was on average 47.9+/-2.4%. Glomerular PAI-1 and PPAR-gamma staining scores were markedly increased in CAN (1.8+/-0.1, 2.3+/-0.1, respectively) compared with normal control kidneys from native kidney cancer nephrectomies (PAI-1 0.2+/-0.2 and PPAR-gamma 0.4+/-0.2, P<0.001) and transplanted kidney biopsies from patients obtained > or =6 months after transplantation without CAN (PAI-1 0 and PPAR-gamma 0, P<0.001). Tubular PAI-1 and PPAR-gamma staining scores were 1.9+/-0.1 and 1.9+/-0.1, respectively, and also increased over both native and transplant kidney controls (0.8+/-0.2 for both categories for PAI-1, 1.2+/-0.2 for both categories for PPAR-gamma, respectively). Vascular sclerosis in CAN was 1.0+/-0.1 with increased PAI-1 and PPAR-gamma scores (1.7+/-0.1, 1.2+/-0.1, respectively) compared with controls. Infiltrating macrophages were increased in CAN, and were positive for both PAI-1 and PPAR-gamma. Biopsies with less sclerosis overall showed a trend for less PAI-1 and PPAR-gamma staining.

CONCLUSION

PAI-1 and PPAR-gamma are both increased in CAN compared with non-scarred native or transplant control kidneys. We speculate that altered matrix metabolism and macrophage function might be involved in the development of CAN.

Treatment of glomerulonephritis: will we ever have options other than steroids and cytotoxics?

Glomerulonephritis refers to a collection of primary renal disorders and those secondary to a systemic disease, all characterized by inflammation within the glomerulus. Given the underlying immunologic nature of these disorders, they are routinely treated with corticosteriods and various cytotoxic agents. Although in many instances such therapies are successful, they are associated with significant morbidity; as such, alternatives are clearly necessary. Our understanding of the pathogenesis of immunologic glomerular diseases has grown remarkably, in large part from the study of rodent disease models. Fundamental to each disorder is the development of an antigen-specific immune response followed by the effector stage of inflammation. To block the immune response, antigen-specific therapy can be used to induce tolerance, such as through the use of double-stranded DNA molecules in lupus nephritis. Since other antigen systems are less well characterized, inducing a more generalized impairment in the immune response by blocking costimulatory molecules CD40-CD154 and CD28-CD80/86 is a growing approach to treat various immunologic disorders and transplantation. To reduce glomerular inflammation, a variety of effector systems have been targeted, including complement, cytokines/chemokines, adhesion molecules, and mediators of cellular proliferation. Of these, antibodies targeting C5 in the complement system, and antibody and receptor antagonists of tumor necrosis factor-alpha (TNF-alpha) have already been used in glomerular disorders with some promise. Less specific blockade of receptor-mediated events stimulated by platelet-derived growth factors and cell cycle proteins may soon be applied to glomerulonephritis. Finally, interruption of fibrosing pathways, which lead to glomerulosclerosis and interstitial fibrosis common to the end-stage of all glomerulonephritis, is the subject of intense effort which may yield effective biologic therapies. In spite of all these advances, we still are dependent on steroids and cytotoxics to treat glomerulonephritis. To get past this, we must devote significant resources to take observations made in basic research laboratories to develop therapeutics and prove their utility in human disease.

Circulating vitamin E, transforming growth factor β1, and the association with renal disease susceptibility in two racial groups with type 2 diabetes

BACKGROUND

End-stage renal disease caused by diabetes disproportionately affects patients of African origin. The biological mechanism(s) for this observation is unclear. Emerging data from cross-sectional studies suggest that increased oxidative stress and the cytokine, transforming growth factor beta(1), are associated with this phenomenon. Therefore, a pathway involving these factors could alter the vulnerability to renal disease and impact adversely on the rate of loss of renal function.

METHODS

We assessed the relationship between renal function, oxidative stress, and transforming growth factor beta(1) in 58 patients with type 2 diabetes of African and Caucasian origin over 174 patient-years of follow-up. Oxidative stress was assessed by measuring plasma lipid hydroperoxide and vitamin E in the postprandial state. Creatinine clearance was calculated from the Cockcroft-Gault equation. Patients received standardized management of hypertension, hyperglycemia, and hypercholesterolemia. Data were adjusted by multiple regression analysis to account for potential confounders.

RESULTS

Lipid hydroperoxide was higher and vitamin E lower, while there was no difference in fasting transforming growth factor beta(1) between the African (N= 22) and Caucasian (N= 36) patients [5.1(1.2) vs. 4.3 (1.8) micromol/L; P= 0.02 and 29.8 (10.8) vs. 41.3(19.7) micromol/L; P= 0.02 and 6.33 (5.5) vs. 6.84 (3.9) ng/mL; P= 0.73], respectively. The mean (95% confidence interval) of the difference in creatinine clearance between the patients of African and Caucasian origin was -12.5 (-23.4 to -1.7) mL/min; P= 0.015 at baseline, the magnitude of which increased to -17.5 (-28.4 to -6.5) mL/min; P= 0.002 after 3 years. The fall in creatinine clearance from baseline among the patients of African origin was greater for lower levels of vitamin E (rho = 0.48; P= 0.03). Final plasma creatinine was significantly higher in the African patients compared with the Caucasian patients [109.0 (25.8) vs. 94.0 (20.0) micromol/L; P= 0.0017]. In regression analysis, vitamin E was a significant and independent predictor of plasma creatinine (t -3.17, P= 0.003).

CONCLUSION

In these patients with type 2 diabetes, vitamin E is a determinant of renal function, and may explain some of the racial differences in renal disease susceptibility that precedes the divergence in incidence of end-stage renal disease.

Plasminogen activator inhibitor type 1: the two faces of the same coin

PURPOSE OF REVIEW

Plasminogen activator inhibitor type 1 is the primary inhibitor of plasminogen activators. It is often bound to vitronectin, an abundant component of extracellular matrix in many tissues. The aim of this review is to discuss the contradictory results reported concerning the impact of plasminogen activator inhibitor type 1 expression in the kidney and in the vessel wall during pathological conditions.

RECENT FINDINGS

First described as a 'bad guy' promoting the persistence of fibrin deposition and the evolution towards organ fibrosis, plasminogen activator inhibitor type 1 was recently reported to serve an unexpected protective role during fibrin-dependent diseases, such as experimental glomerulonephritis, and during aortic atherosclerosis.

SUMMARY

Plasminogen activator inhibitor type 1 is not only an inhibitor of plasmin generation. Recent data suggest that plasminogen activator inhibitor type 1 is required for the regulation of plasminogen activator-dependent, plasmin-independent processes, and that its expression in vivo critically modulates inflammation, potentially by its capacity to occupy vitronectin binding sites.

Effects of losartan on TIMP-1 and PAI-1 expression in rat hepatic fibrosis

AIM: To investigate the effect of losartan on the expression of tissue inhibitor of metalloproteinase-1 (TIMP-1) and plasminogen activator inhibition-1 (PAI-1) in the liver of rat with hepatic fibrosis.

METHODS: Forty-eight SD rats were randomly divided into four groups: normal control group, model group, losartan-prevention group, losartan-treatment group. Except rats in control group, all rats were given subcutaneous injection of carbon tetrachloride. Rats in prevention and treatment (from the 5th wk) groups were also given losartan via gastrogavage. At the end of 12 weeks, rats were sacrificed. HE and VG stains were used to evaluate the degree of fibrosis; Immunohistochemistry was used to detect the expression of TIMP-1 and PAI-1 in the liver tissue, respectively.

RESULTS: Losartan could greatly attenuate the degree of liver fibrosis (P < 0.05) . Intensity score (IS) of TIMP-1 and PAI-1 in prevention (1.6 900±0.4 228, 1.8 900±0.5 127) and treatment (1.9 000±0.5 925, 2.0 540±0.4 251) groups was weaker than that in model group (2.5 111±0.3 919, 2.8 500±0.2 013) (P < 0.05).

CONCLUSION: Losartan can suppress expression of TIMP-1 and PAI-1, which may be related to its anti-hepatic fibrosis activity.