Plasma Proteins Associated with Chronic Histopathologic Lesions on Kidney Biopsy

Key Points

Proteomic profiling identified 35 blood proteins associated with chronic histopathologic lesions in the kidney. Testican-2 was expressed in the glomerulus, released by the kidney into circulation, and inversely associated with glomerulosclerosis severity. NELL1 was expressed in tubular epithelial cells, released by the kidney into circulation, and inversely associated with interstitial fibrosis and tubular atrophy severity.

Background

The severity of chronic histopathologic lesions on kidney biopsy is independently associated with higher risk of progressive CKD. Because kidney biopsies are invasive, identification of blood markers that report on underlying kidney histopathology has the potential to enhance CKD care.

Methods

We examined the association between 6592 plasma protein levels measured by aptamers and the severity of interstitial fibrosis and tubular atrophy (IFTA), glomerulosclerosis, arteriolar sclerosis, and arterial sclerosis among 434 participants of the Boston Kidney Biopsy Cohort. For proteins significantly associated with at least one histologic lesion, we assessed renal arteriovenous protein gradients among 21 individuals who had undergone invasive catheterization and assessed the expression of the cognate gene among 47 individuals with single-cell RNA sequencing data in the Kidney Precision Medicine Project.

Results

In models adjusted for eGFR, proteinuria, and demographic factors, we identified 35 proteins associated with one or more chronic histologic lesions, including 20 specific for IFTA, eight specific for glomerulosclerosis, and one specific for arteriolar sclerosis. In general, higher levels of these proteins were associated with more severe histologic score and lower eGFR. Exceptions included testican-2 and NELL1, which were associated with less glomerulosclerosis and IFTA, respectively, and higher eGFR; notably, both of these proteins demonstrated significantly higher levels from artery to renal vein, demonstrating net kidney release. In the Kidney Precision Medicine Project, 13 of the 35 protein hits had cognate gene expression enriched in one or more cell types in the kidney, including podocyte expression of select glomerulosclerosis markers (including testican-2) and tubular expression of several IFTA markers (including NELL1).

Conclusions

Proteomic analysis identified circulating proteins associated with chronic histopathologic lesions, some of which had concordant site-specific expression within the kidney.

Modeling Doxorubicin-Induced Cardiomyopathy With Fibrotic Myocardial Damage in Wistar Rats

Background

Cardiovascular complications, arising after anthracycline chemotherapy, cause a significant deterioration in the life quality and expectancy of those patients who were previously successfully treated for malignant neoplasms. A number of clinical studies have demonstrated that patients with cardiotoxicity manifested during anthracyclines therapy also have extensive fibrotic changes in the cardiac muscle in the long term. Given the lack of an unambiguous understanding of the mechanisms of fibrotic changes formation under doxorubicin treatment in the myocardium, there is the obvious necessity to create a relevant experimental model of chronic doxorubicin-induced cardiomyopathy with fibrotic myocardial lesions and delayed development of diastolic dysfunction.

Methods

The study was divided into two stages: first stage (creation of acute doxorubicin cardiomyopathy) - 35 male Wistar rats; second stage (creation of chronic doxorubicin cardiomyopathy) - 40 male Wistar rats. The animals were split into eight groups (two control ones and six experimental ones), which determined the doxorubicin dose (first stage: 25, 20.4, 15 mg/kg; second stage: 5, 10, 15 mg/kg, intraperitoneally) and the frequency of injection. Echocardiographic, hematological, histological, and molecular methods were used to confirm the successful modeling of acute and chronic doxorubicin-induced cardiomyopathy with fibrotic lesions.

Results

A model of administration six times every other day with a cumulative dose of doxorubicin 20 mg/kg is suitable for evaluation of acute cardiotoxicity. The 15 mg/kg doxorubicin dose is highly cardiotoxic; what's more, it correlates with progressive deterioration of the clinical condition of the animals after 2 months. The optimal cumulative dose of doxorubicin leads to clinical manifestations confirmed by echocardiographic, histological, molecular changes associated with the development of chronic doxorubicin-induced cardiomyopathy with fibrotic lesions of the left ventricular of the cardiac muscle and ensure long-term survival of animals is 10 mg/kg doxorubicin. A dose of 5 mg/kg of the doxorubicin does not ensure the development of fibrous changes formation.

Conclusion

We assume that cumulative dose of 10 mg/kg with a frequency of administration of six times in 2 days can be used to study the mechanisms of anthracycline cardiomyopathy development.

Pigment epithelium-derived factor inhibits advanced glycation end product-induced proliferation, VEGF and MMP-9 expression in breast cancer cells via interaction with laminin receptor

Pigment epithelium-derived factor (PEDF) is one of the adipocytokines with multifaceted functions, which may serve a role in the development of various types of cardiometabolic disorders. Advanced glycation end products (AGEs) have been shown to contribute to numerous aging-associated disorders, such as cancer. However, it remains unclear whether and how PEDF exerts antitumor effects in AGE-exposed human breast cancer MCF-7 cells, and therefore this was explored in the present study. NADPH oxidase activity was measured with luciferase assay, while gene and protein expression levels were evaluated with quantitative PCR and western blot analysis, respectively. AGEs significantly increased NADPH oxidase-driven superoxide generation, cytochrome b-245 β chain (gp91phox) and receptor for AGE (RAGE) mRNA expression, proliferation, mRNA and protein expression levels of vascular endothelial growth factor (VEGF), and matrix metalloproteinase (MMP)-9 mRNA expression in MCF-7 cells, all of which were dose-dependently inhibited by PEDF. Neutralizing antibody against laminin receptor (LR-Ab) significantly blocked these beneficial effects of PEDF in AGE-exposed MCF-7 cells. Furthermore, as in AGE-treated cells, PEDF dose-dependently inhibited the NADPH oxidase-driven superoxide generation, gp91phox, RAGE and MMP-9 mRNA expression, proliferation, mRNA and protein expression levels of VEGF in non-treated control MCF-7 cells, and these effects were also reversed by LR-Ab. LR levels were not affected by the treatment with AGEs, PEDF or LR-Ab. The present study suggested that PEDF may exert antitumor effects in AGE-exposed breast cancer cells by suppressing NADPH oxidase-induced ROS generation and VEGF and MMP-9 expression via interaction with LR. Since PEDF expression is decreased in breast cancer tissues, pharmacological upregulation or restoration of PEDF may inhibit the growth and metastasis of breast cancer.

Targeting angiogenesis and lymphangiogenesis in kidney disease

The kidney is permeated by a highly complex vascular system with glomerular and peritubular capillary networks that are essential for maintaining the normal functions of glomerular and tubular epithelial cells. The integrity of the renal vascular network depends on a balance of proangiogenic and antiangiogenic factors, and disruption of this balance has been identified in various kidney diseases. Decreased levels of the predominant proangiogenic factor, vascular endothelial growth factor A (VEGFA), can result in glomerular microangiopathy and contribute to the onset of preeclampsia, whereas upregulation of VEGFA has roles in diabetic kidney disease (DKD) and polycystic kidney disease (PKD). Other factors that regulate angiogenesis, such as angiopoietin 1 and vasohibin 1, have been shown to be protective in animal models of DKD and renal fibrosis. The renal lymphatic system is important for fluid homeostasis in the kidney, as well as the transport of immune cells and antigens. Experimental studies suggest that the lymphangiogenic factor VEGFC might have protective effects in PKD, DKD and renal fibrosis. Understanding the physiological and pathological roles of factors that regulate angiogenesis and lymphangiogenesis in the kidney has led to the development of novel therapeutic strategies for kidney diseases.

Therapeutic Potential of Pigment Epithelium-derived Factor in Cancer

Pigment epithelium-derived factor (PEDF) is one of the serine protease inhibitors with multifunctional properties, which is produced by various types of organs and tissues. There is an accumulating body of evidence that PEDF plays an important role in the maintenance of tissue homeostasis. Indeed, PEDF not only works as an endogenous inhibitor of angiogenesis, but also suppresses oxidative stress, inflammatory and thrombotic reactions in cell culture systems, animal models, and humans. Furthermore, we, along with others, have found that PEDF inhibits proliferation of, and induces apoptotic cell death in, numerous kinds of tumors. In addition, circulating as well as tumor expression levels of PEDF have been inversely associated with tumor growth and metastasis. These observations suggest that supplementation of PEDF proteins and/or enhancement of endogenous PEDF expression could be a novel therapeutic strategy for the treatment of cancer. Therefore, in this paper, we review the effects of PEDF on diverse types of cancer, and discuss its therapeutic perspectives.

Serum pigment epithelium-derived factor: Relationships with cardiovascular events, renal dysfunction, and mortality in the Veterans Affairs Diabetes Trial (VADT) cohort

BACKGROUND

To determine if serum pigment epithelium-derived factor (PEDF) levels predict cardiovascular events, renal dysfunction and mortality in the Veterans Affairs Diabetes Study (VADT).

METHODS

PEDF was evaluated in relation to subsequent cardiovascular outcomes, mortality, and renal dysfunction (defined as urinary albumin creatinine ratio (ACR) ≥300 mg/g), or chronic kidney disease (CKD) stages 3 (eGFR<60 ml/min) or 4 (eGFR<60 and <30 ml/min respectively). PEDF was measured by ELISA on sera from 881 participants collected a median (range) of 1.7 (0-5.0) years post-baseline, and later, from 832 participants 4.0 (1.5-6.9) years post-baseline.

RESULTS

In 743 participants, PEDF was measured at both time-points. PEDF increased over time from (mean ± SD) 10.5 ± 4.03 to 11.0 ± 4.86 ng/ml (paired t-test p = 0.0092). Lower eGFR (p < 0.01), higher serum creatinine (p < 0.01) and urinary ACR (p < 0.01) were associated with increasing PEDF. Multivariate event time models included either one or two follow-up windows (i.e., between first and second PEDF measures; and, when available, from second PEDF measure until study-end). PEDF tertiles were not associated with cardiovascular events, but were significantly associated with all-cause mortality [HR = 2.00 (1.03, 3.89) comparing first to third tertile] in models adjusted for age, minority status, VADT treatment arm and prior cardiovascular event status. Higher PEDF levels also associated with development of kidney dysfunction with adjusted HRs (95% CI comparing third to first PEDF tertiles: 2.74 (1.71, 4.39) for stage 3 CKD; and 3.84 (95% CI: 1.17, 12.5) for stage 4 CKD.

CONCLUSIONS

Over 2-years, higher serum PEDF levels predicted advanced nephropathy in patients with type 2 diabetes.

p53 mediates PEDF‑induced autophagy in human umbilical vein endothelial cells through sestrin2 signaling

Autophagy is a conserved catabolic process by which cytoplasmic components are delivered into lysosomes for degradation. Pigment epithelium‑derived factor (PEDF) has been reported to be associated with autophagy and can induce p53 expression; however, the mechanism relating PEDF with autophagy in endothelial cells remains poorly understood. The present study aimed to investigate the association between the PEDF‑p53‑sestrin pathway and autophagy in human umbilical vein endothelial cells (HUVECs). PEDF‑induced autophagy was examined by fluorescence microscopy and western blot analysis. p53 small interfering (si)RNA and sestrin2 siRNA were constructed and transfected into HUVECs prior to PEDF treatment. The protein expression levels of microtubule‑associated protein light chain 3 (LC3) I, LC3 II and p62 were evaluated by western blot analysis, and the mRNA expression levels of p53 and sestrin2 were determined using reverse transcription‑quantitative polymerase chain reaction analysis. The regulation of mechanistic target of rapamycin (mTOR) was reflected by p70S6 kinase (p70S6K) and eukaryotic translation initiation factor 4E‑binding protein 1 (4E‑BP1) protein expression levels, as determined by western blot analysis. PEDF could induce HUVEC autophagy by sequentially inducing p53 and sestrin2 expression, as observed by fluorescence microscopy and western blot analysis. Conversely, the induction of sestrin2 by PEDF was eliminated by p53 siRNA. In addition, p53 siRNA and sestrin2 siRNA could attenuate PEDF‑induced HUVEC autophagy. Inhibition of mTOR may be the mechanism responsible for PEDF‑induced autophagy; as p70S6K and 4E‑BP1 phosphorylation levels were significantly upregulated in p53 siRNA‑treated and sestrin2 siRNA‑treated groups. The findings of the present study indicated that PEDF may trigger autophagy in HUVECs by inducing p53 and sestrin2 expression, and inhibiting mTOR expression; these findings may contribute to the improved understanding of diseases, including cancer and atherosclerosis.

Mesenchymal stem cells attenuate adriamycin-induced nephropathy by diminishing oxidative stress and inflammation via downregulation of the NF-kB

AIM

This study aimed to evaluate the molecular mechanism mitigating progress of chronic nephropathy by mesenchymal stem cells (MSCs).

METHODS

Rats were divided into normal control (Normal), adriamycin (ADR)+vehicle (CON), and ADR+MSC (MSC) groups. Nephropathy was induced by ADR (4 mg/kg) and MSCs (2 × 10⁶ ) were injected. Rats were euthanized 1 or 6 weeks after ADR injection. NF-kB, MAPKs, inflammation, oxidative stress, profibrotic molecules, and nephrin expression were evaluated. Electron and light microscopy were used for structural analysis. MSCs were co-cultured with renal tubular epithelial cells or splenocytes to evaluate relation with oxidative stress and inflammatory molecules RESULTS: Adriamycin treatment upregulated inflammation, oxidative stress, and profibrotic molecules; this was mitigated by MSCs. Glomerulosclerosis and interstitial fibrosis were observed in ADR-treated groups, and were more prominent in the CON group than in the MSC group. Fusion of foot processes and loss of slit diaphragms were also more prominent in the CON group than in the MSC group. In vitro, MSCs reduced oxidative stress related molecules, inflammatory cytokines, and NF-kB transcription. MSC- or ADR-induced regulation of NF-kB transcriptional activity was confirmed by a luciferase reporter assay.

CONCLUSIONS

Mesenchymal stem cells attenuate ADR-induced nephropathy by diminishing oxidative stress and inflammation via downregulation of NF-kB.

Renoprotective Effects of a Highly Selective A3 Adenosine Receptor Antagonist in a Mouse Model of Adriamycin-induced Nephropathy

The concentration of adenosine in the normal kidney increases markedly during renal hypoxia, ischemia, and inflammation. A recent study reported that an A3 adenosine receptor (A3AR) antagonist attenuated the progression of renal fibrosis. The adriamycin (ADX)-induced nephropathy model induces podocyte injury, which results in severe proteinuria and progressive glomerulosclerosis. In this study, we investigated the preventive effect of a highly selective A3AR antagonist (LJ1888) in ADX-induced nephropathy. Three groups of six-week-old Balb/c mice were treated with ADX (11 mg/kg) for four weeks and LJ1888 (10 mg/kg) for two weeks as following: 1) control; 2) ADX; and 3) ADX + LJ1888. ADX treatment decreased body weight without a change in water and food intake, but this was ameliorated by LJ1888 treatment. Interestingly, LJ1888 lowered plasma creatinine level, proteinuria, and albuminuria, which had increased during ADX treatment. Furthermore, LJ1888 inhibited urinary nephrin excretion as a podocyte injury marker, and urine 8-isoprostane and kidney lipid peroxide concentration, which are markers of oxidative stress, increased after injection of ADX. ADX also induced the activation of proinflammatory and profibrotic molecules such as TGF-β1, MCP-1, PAI-1, type IV collagen, NF-κB, NOX4, TLR4, TNFα, IL-1β, and IFN-γ, but they were remarkably suppressed after LJ1888 treatment. In conclusion, our results suggest that LJ1888 has a renoprotective effect in ADX-induced nephropathy, which might be associated with podocyte injury through oxidative stress. Therefore, LJ1888, a selective A3AR antagonist, could be considered as a potential therapeutic agent in renal glomerular diseases which include podocyte injury and proteinuria.

Pigment epithelium-derived factor inhibits caveolin-induced interleukin-8 gene expression and proliferation of human prostate cancer cells

Caveolin-1 (Cav), a primary protein component of caveolae, is overexpressed in prostate cancer, thereby promoting growth and metastasis of this tumor. By contrast, pigment epithelium-derived factor (PEDF) has been shown to inhibit tumor growth and metastasis, including that of prostate cancer, via its anti-angiogenic and anti-inflammatory effects. Although it was recently demonstrated that PEDF binds to Cav and blocks its pro-inflammatory actions in endothelial cells, it remains unclear whether PEDF also inhibits the tumor-promoting effects of Cav in cultured prostate cancer cells. The present study examined the effects of PEDF on cell growth, in addition to the gene expression of interleukin-8 (IL-8), which is involved in prostate cancer progression, in the PC-3 human prostate cancer cell line. Exogenous Cav led to a dose-dependent upregulation of the mRNA expression of IL-8 in PC-3 cells, which was blocked by treatment with 1 or 10 nM PEDF, or following the overexpression of small interfering RNAs directed against Cav. Cav (10 nM) increased DNA synthesis in PC-3 cells, which was again suppressed by the administration of 10 nM PEDF. The results of the present study indicated that PEDF may inhibit Cav-induced increases in IL-8 gene expression and proliferation of PC-3 cells. Therefore, the suppressive effects of PEDF in prostate cancer may, in part, be ascribed to its inhibitory actions on Cav.

Oxidative/Nitrative Stress and Inflammation Drive Progression of Doxorubicin-Induced Renal Fibrosis in Rats as Revealed by Comparing a Normal and a Fibrosis-Resistant Rat Strain

Chronic renal fibrosis is the final common pathway of end stage renal disease caused by glomerular or tubular pathologies. Genetic background has a strong influence on the progression of chronic renal fibrosis. We recently found that Rowett black hooded rats were resistant to renal fibrosis. We aimed to investigate the role of sustained inflammation and oxidative/nitrative stress in renal fibrosis progression using this new model. Our previous data suggested the involvement of podocytes, thus we investigated renal fibrosis initiated by doxorubicin-induced (5 mg/kg) podocyte damage. Doxorubicin induced progressive glomerular sclerosis followed by increasing proteinuria and reduced bodyweight gain in fibrosis-sensitive, Charles Dawley rats during an 8-week long observation period. In comparison, the fibrosis-resistant, Rowett black hooded rats had longer survival, milder proteinuria and reduced tubular damage as assessed by neutrophil gelatinase-associated lipocalin (NGAL) excretion, reduced loss of the slit diaphragm protein, nephrin, less glomerulosclerosis, tubulointerstitial fibrosis and matrix deposition assessed by periodic acid–Schiff, Picro-Sirius-red staining and fibronectin immunostaining. Less fibrosis was associated with reduced profibrotic transforming growth factor-beta, (TGF-β1) connective tissue growth factor (CTGF), and collagen type I alpha 1 (COL-1a1) mRNA levels. Milder inflammation demonstrated by histology was confirmed by less monocyte chemotactic protein 1 (MCP-1) mRNA. As a consequence of less inflammation, less oxidative and nitrative stress was obvious by less neutrophil cytosolic factor 1 (p47^phox) and NADPH oxidase-2 (p91^phox) mRNA. Reduced oxidative enzyme expression was accompanied by less lipid peroxidation as demonstrated by 4-hydroxynonenal (HNE) and less protein nitrosylation demonstrated by nitrotyrosine (NT) immunohistochemistry and quantified by Western blot. Our results demonstrate that mediators of fibrosis, inflammation and oxidative/nitrative stress were suppressed in doxorubicin nephropathy in fibrosis-resistant Rowett black hooded rats underlying the importance of these pathomechanisms in the progression of renal fibrosis initiated by glomerular podocyte damage.

Kidney pericytes: roles in regeneration and fibrosis

Renal pericytes have been neglected for many years, but recently they have become an intensively studied cell population in renal biology and pathophysiology. Pericytes are stromal cells that support vasculature, and a subset of pericytes are mesenchymal stem cells. In kidney, pericytes have been reported to play critical roles in angiogenesis, regulation of renal medullary and cortical blood flow, and serve as progenitors of interstitial myofibroblasts in renal fibrogenesis. They interact with endothelial cells through distinct signaling pathways and their activation and detachment from capillaries after acute or chronic kidney injury may be critical for driving chronic kidney disease progression. By contrast, during kidney homeostasis it is likely that pericytes serve as a local stem cell population that replenishes differentiated interstitial and vascular cells lost during aging. This review describes both the regenerative properties of pericytes as well as involvement in pathophysiologic conditions such as fibrogenesis.

Translational profiles of medullary myofibroblasts during kidney fibrosis

Myofibroblasts secrete matrix during chronic injury, and their ablation ameliorates fibrosis. Development of new biomarkers and therapies for CKD will be aided by a detailed analysis of myofibroblast gene expression during the early stages of fibrosis. However, dissociating myofibroblasts from fibrotic kidney is challenging. We therefore adapted translational ribosome affinity purification (TRAP) to isolate and profile mRNA from myofibroblasts and their precursors during kidney fibrosis. We generated and characterized a transgenic mouse expressing an enhanced green fluorescent protein (eGFP)-tagged L10a ribosomal subunit protein under control of the collagen1α1 promoter. We developed a one-step procedure for isolation of polysomal RNA from collagen1α1-eGFPL10a mice subject to unilateral ureteral obstruction and analyzed and validated the resulting transcriptional profiles. Pathway analysis revealed strong gene signatures for cell proliferation, migration, and shape change. Numerous novel genes and candidate biomarkers were upregulated during fibrosis, specifically in myofibroblasts, and we validated these results by quantitative PCR, in situ, and Western blot analysis. This study provides a comprehensive analysis of early myofibroblast gene expression during kidney fibrosis and introduces a new technique for cell-specific polysomal mRNA isolation in kidney injury models that is suited for RNA-sequencing technologies.

Comparison of trichostatin A and valproic acid treatment regimens in a mouse model of kidney fibrosis

Histone deacetylase (HDAC) inhibitors are promising new compounds for the therapy of fibrotic diseases. In this study we compared the effect of two HDAC inhibitors, trichostatin A and valproic acid, in an experimental model of kidney fibrosis. In mice, doxorubicin (adriamycin) can cause nephropathy characterized by chronic proteinuria, glomerular damage and interstitial inflammation and fibrosis, as seen in human focal segmental glomerulosclerosis. Two treatment regimens were applied, treatment was either started prior to the doxorubicin insult or delayed until a significant degree of proteinuria and fibrosis was present. Pre-treatment of trichostatin A significantly hampered glomerulosclerosis and tubulointerstitial fibrosis, as did the pre-treatment with valproic acid. In contrast, the development of proteinuria was only completely inhibited in the pre-treated valproic acid group, and not in the pre-treated trichostatin A animals. In the postponed treatment with valproic acid, a complete resolution of established doxorubicin-induced proteinuria was achieved within three days, whereas trichostatin A could not correct proteinuria in such a treatment regimen. However, both postponed regimens have comparable efficacy in maintaining the kidney fibrosis to the level reached at the start of the treatments. Moreover, not only the process of fibrosis, but also renal inflammation was attenuated by both HDAC inhibitors. Our data confirm a role for HDACs in renal fibrogenesis and point towards a therapeutic potential for HDAC inhibitors. The effect on renal disease progression and manifestation can however be different for individual HDAC inhibitors.

Glucagon-like peptide-1 receptor agonist inhibits asymmetric dimethylarginine generation in the kidney of streptozotocin-induced diabetic rats by blocking advanced glycation end product-induced protein arginine methyltranferase-1 expression

Advanced glycation end products (AGEs) and their receptor (RAGE) play a role in diabetic nephropathy. Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, contributes to diabetic nephropathy. We have found that glucagon-like peptide-1 (GLP-1) inhibits the AGE-induced inflammatory reactions in endothelial cells. However, effects of GLP-1 on the AGE-RAGE-ADMA axis are unknown. This study examined the effects of GLP-1 on reactive oxygen species (ROS) generation, gene expression of protein arginine methyltransfetase-1 (PRMT-1), an enzyme that mainly generates ADMA, and ADMA levels in human proximal tubular cells. Streptozotocin-induced diabetic rats received continuous i.p. infusion of 0.3 μg of vehicle or 1.5 μg of the GLP-1 analog exendin-4 per kilogram of body weight for 2 weeks. We further investigated whether and how exendin-4 treatment reduced ADMA levels and renal damage in streptozotocin-induced diabetic rats. GLP-1 inhibited the AGE-induced RAGE and PRMT-1 gene expression, ROS, and ADMA generation in tubular cells, which were blocked by small-interfering RNAs raised against GLP-1 receptor. Exendin-4 treatment decreased gene expression of Rage, Prmt-1, Icam-1, and Mcp-1 and ADMA level; reduced urinary excretions of 8-hydroxy-2'-deoxyguanosine and albumin; and improved histopathologic changes of the kidney in diabetic rats. Our present study suggests that GLP-1 receptor agonist may inhibit the AGE-RAGE-mediated ADMA generation by suppressing PRMT-1 expression via inhibition of ROS generation, thereby protecting against the development and progression of diabetic nephropathy.

Adenoviral E4 gene stimulates secretion of pigmental epithelium derived factor (PEDF) that maintains long-term survival of human glomerulus-derived endothelial cells

Renal glomerular endothelial cells are specialized cells with an important role in physiological filtration and glomerular disease. However, maintenance of human primary endothelial cells requires stimulation with serum and growth factors that often results in modification of the cells properties. Previously, expression of early adenovirus region E4 was shown to help maintaining long-term survival of human endothelial cells in serum free media without addition of growth factors. In the current study, we showed that media conditioned with human epithelial cells stably transfected with Ad E4 region also supported survival of human glomerulus-derived endothelial cells in serum-free media. Mass-spectrometry analysis of the conditioned media identified pigmental epithelium derived factor (PEDF) as a major component of the conditioned media. PEDF expression in 293-E4 cells was validated by RT-PCR, Western blot and ELISA analysis. PEDF expression was detected in mouse glomeruli. Supplementation with recombinant PEDF supported survival of primary endothelial cells and the cells transformed with SV40 large T antigen in serum-free media, and extended the life-span of both cell cultures. PEDF did not inhibit FGF-2 stimulated growth and tubulogenesis of endothelial cells. Thus we demonstrated that adenoviral E4 region stimulated expression and secretion of PEDF by human renal epithelial cells that acted as a survival factor for glomerulus-derived endothelial cells.

Proteinuria elevates asymmetric dimethylarginine levels via protein arginine methyltransferase-1 overexpression in a rat model of nephrotic syndrome

AIMS

Proteinuria is an independent risk factor for cardiovascular disease (CVD) in patients with chronic kidney disease (CKD). Asymmetric dimethylarginine (ADMA) is a mediator of endothelial dysfunction and is associated with proteinuria in CKD patients. Thus, ADMA can partially account for the increased risk of CVD in CKD patients presenting proteinuria. However, a causal relationship between proteinuria and ADMA remains to be demonstrated.

MAIN METHODS

We first investigated whether and how proteinuria might increase ADMA levels in adriamycin (ADR)-treated rats. Next, we examined the effects of human serum albumin (HSA) on ADMA production by human renal proximal tubular epithelial cells (RPTECs) cultured in vitro.

KEY FINDINGS

Proteinuria was associated with ADMA levels in ADR treated rats. Although ADR treatment did not affect the expression levels of the dimethylarginine dimethylaminohydrolase (DDAH)-1 or -2 enzymes that degrade ADMA, it significantly increased the expression levels of protein arginine methyltransferase-1 (PRMT-1) that facilitates the production of ADMA. HSA increased the generation of reactive oxygen species in RPTECs, which was blocked by the anti-oxidant N-acetylcysteine (NAC) or an inhibitor of NADPH oxidase. Furthermore, HSA increased ADMA generation by RPTECs in a dose- and time-dependent manner and induced gene expression of PRMT-1 but not DDAHs, which were also suppressed by NAC.

SIGNIFICANCE

Our data suggest that proteinuria might enhance ADMA generation in tubular cells, at least in part via the overexpression of PRMT-1 triggered by oxidative stress. Our findings thereby propose a mechanistic link between proteinuria and ADMA levels in CKD patients.

Podocyte injury and overexpression of vascular endothelial growth factor and transforming growth factor-beta 1 in adriamycin-induced nephropathy in rats

The aim of this study is to investigate the expression of nephrin, vascular endothelial growth factor (VEGF), transforming growth factor-beta 1 (TGF-β1), and podocyte number in adriamycin (ADR)-induced nephropathy. A total of 60 male Sprague-Dawley rats were randomly divided into the control group and the ADR nephropathy group. The nephropathy was induced by tail-vein injection of ADR (4 mg/kg) twice at a 14-day interval. The expression levels of nephrin, VEGF, and TGF-β1 in glomeruli were assessed by immunohistochemistry and western blotting. The podocyte number was also evaluated after anti-Wilms' tumor-1 (WT1) immunohistochemical staining. In addition, the urinary protein content, biochemical parameters in serum samples and glomerular sclerosis index (SI) were compared between groups. In the ADR nephropathy group, the expression levels of nephrin was significantly decreased with the fusion of podocyte foot processes at 6 weeks after the first ADR injection, which was associated with a marked proteinuria. A decrease in podocyte number and an increase in SI with the overexpression of both VEGF and TGF-β1 were also observed in the glomeruli at 10 weeks after the first ADR injection. This was associated with focal segmental glomerulosclerosis (FSGS). The study data suggest that podocyte injury and decreased nephrin, as well as increased VEGF and TGF-β1, may contribute to the development of proteinuria and FSGS in ADR-induced nephropathy in rats.

Anticubilin antisense RNA ameliorates adriamycin-induced tubulointerstitial injury in experimental rats

This study was designed to determine the effects of in vivo anticubilin antisense RNA on the uptake of albumin in tubules and on the tubulointerstitial injury in adriamycin-induced proteinuric rats. Adriamycin-treated rats were subjected to intrarenal delivery of adenoviral vectors encoding empty plasmid, cubilin sense RNA expression vector pAd-CUB or anticubilin antisense RNA expression vector pAd-ACUB on day 3. On days 14 and 28, half of the rats in each group were randomly selected to be killed, and blood samples, kidney tissues and 24-hour urine were collected. The diseased rats treated with pAdEasy-ACUB showed a 60% decrease in serum creatinine and glomerular filtration rate. Interestingly, the anticubilin antisense treatment led to a marked increase in albuminuria. Antisense treatment attenuated the histologic changes on both day 14 and day 28. The antisense treatment induced more than 60% recovery of adriamycin-induced injury, accompanied with 85% knockdown in the expression of cubilin protein and markedly decreased albumin deposition. Adriamycin induced an increase in the expression of monocyte chemoattractant protein-1, transforming growth factor-β and regulated on activation in normal T-cell expressed and secreted and the number of infiltrating cells, which was reversed by the antisense treatment. Anticubilin antisense RNA delivered by an adenoviral vector ameliorates albuminuria-induced glomerulosclerosis and tubulointerstitial damage in adriamycin nephrotic rats, indicating that cubilin could be a potential therapeutic target in proteinuric nephropathy.

Administration of pigment epithelium-derived factor inhibits left ventricular remodeling and improves cardiac function in rats with acute myocardial infarction

Oxidative stress and inflammation are involved in cardiac remodeling after acute myocardial infarction (AMI). We have found that pigment epithelium-derived factor (PEDF) inhibits vascular inflammation through its anti-oxidative properties. However, effects of PEDF on cardiac remodeling after AMI remain unknown. We investigated whether PEDF could inhibit left ventricular remodeling and improve cardiac function in rats with AMI. AMI was induced in 8-week-old Sprague-Dawley rats by ligation of the left ascending coronary artery. Rats were treated intravenously with vehicle or 10 μg PEDF/100 g b.wt. every day for up to 2 weeks after AMI. Each rat was followed until 16 weeks of age. PEDF levels in infarcted areas and serum were significantly decreased at 1 week after AMI and remained low during the observational periods. PEDF administration inhibited apoptotic cell death and oxidative stress generation around the infarcted areas at 2 and 8 weeks after AMI. Further, PEDF injection suppressed cardiac fibrosis by reducing transforming growth factor-β and type III collagen expression, improved left ventricular ejection fraction, ameliorated diastolic dysfunction, and inhibited the increase in left ventricular mass index at 8 weeks after AMI. The present study demonstrated that PEDF could inhibit tissue remodeling and improve cardiac function in AMI rats. Substitution of PEDF may be a novel therapeutic strategy for cardiac remodeling after AMI.

Renal tubular angiogenic dysregulation in anti-Thy1.1 glomerulonephritis

Peritubular vascular changes and hypoxia after glomerular injury may explain subsequent tubulointerstitial injury and fibrosis. Several studies suggested that the expected tubulointerstitial angiogenic response is actively suppressed in this setting. The mechanism of this aberrant response has not been clearly identified. We used a common model of glomerular injury in rats to assess vascular changes and to identify potential factors associated with this aberrant response. Anti-Thy1.1 antibody administration (1 or 4 weekly doses) led to a dose-dependent renal damage characterized by elevated urea and tubulointerstitial fibrosis as assessed by Picro-Sirius Red staining. We quantified peritubular capillaries using CD31 and CD34 immunohistochemistry and showed that tubular angiogenic dysregulation was associated with peritubular capillary rarefaction. Using laser capture microdissection, we demonstrated an early induction of fibrogenic and angiogenic factors in the glomeruli and a subsequent dysregulated angiogenic response in the tubulointerstitial compartment. Proximal tubules of anti-Thy1.1-treated animals had increased pigment epithelial-derived factor (PEDF) expression by immunohistochemistry. Protein taken by laser capture microdissection also showed that PEDF was upregulated. Temporally associated with PEDF expression was a transient downregulation of tubular hypoxia-inducible factor (HIF)1α. In a human proximal tubular cell culture, we show that PEDF downregulates HIF1α protein and gene expression in cells exposed to 1% oxygen. In anti-Thy1.1 glomerulonephritis, there is aberrent tubular angiogenesis associated with glomerular injury and tubulointersititial fibrosis. We showed that PEDF may be involved by downregulating HIF1α. Further work is needed to elucidate the mechanism of PEDF upregulation and action in the tubules.

The applied biochemistry of PEDF and implications for tissue homeostasis

Pigment epithelium-derived factor (PEDF) is an endogenously produced glycoprotein with a spectrum of biological roles across diverse pathologies. Recent research has focused on the biochemical properties of PEDF and its associated receptors. This review discusses the recent developments in PEDF biochemistry and how this new knowledge will help progress our understanding of PEDF as a molecular mediator for anti-angiogenesis and -tumorigenesis. Additionally, pathophysiological roles for PEDF in healing and tissue homeostasis are being revealed and our enhanced understanding of the interactions between PEDF and its receptors may yet prove useful in propelling PEDF towards clinical application.

Protective role of pigment epithelium-derived factor (PEDF) in early phase of experimental diabetic retinopathy

BACKGROUND

Pigment epithelium-derived factor (PEDF) is the most potent inhibitor of angiogenesis in the mammalian eye, thus suggesting that PEDF may protect against proliferative diabetic retinopathy. However, a role for PEDF in early diabetic retinopathy remains to be elucidated. We investigated here whether and how PEDF could prevent the development of diabetic retinopathy.

METHODS

Streptozotocin-induced diabetic rats were treated with or without intravenous injection of PEDF for 4 weeks. Early neuronal derangements were evaluated by electroretinogram (ERG) and immunofluorescent staining of glial fibrillary acidic protein (GFAP). Expression of PEDF and 8-hydroxydeoxyguanosine (8-OHdG), a marker of oxidative stress, was localized by immunofluorescence. Vascular endothelial growth factor (VEGF) and p22phox expression were evaluated with western blots. Breakdown of blood retinal barrier (BRB) was quantified with fluorescein isothiocynate (FITC)-conjugated dextran. NADPH oxidase activity was measured with lucigenin luminescence.

RESULTS

Retinal PEDF levels were reduced, and amplitudes of a- and b-wave in the ERG were decreased in diabetic rats, which were in parallel with GFAP overexpression in the Müller cells. Further, retinal 8-OHdG, p22phox and VEGF levels and NADPH oxidase activity were increased, and BRB was broken in diabetic rats. Administration of PEDF ameliorated all of the characteristic changes in early diabetic retinopathy.

CONCLUSIONS

Results suggest that PEDF could prevent neuronal derangements and vascular hyperpermeability in early diabetic retinopathy via inhibition of NADPH oxidase-driven oxidative stress generation. Substitution of PEDF may offer a promising strategy for halting the development of diabetic retinopathy.