Anti-inflammatory effects of pigment epithelium-derived factor in diabetic nephropathy

Amelioration of renal alterations in obese type 2 diabetic mice by vasohibin-1, a negative feedback regulator of angiogenesis

The involvement of VEGF-A as well as the therapeutic efficacy of angiogenesis inhibitors in diabetic nephropathy have been reported. We recently reported the therapeutic effects of vasohibin-1 (VASH-1), an endogenous angiogenesis inhibitor, in a type 1 diabetic nephropathy model (Nasu T, Maeshima Y, Kinomura M, Hirokoshi-Kawahara K, Tanabe K, Sugiyama H, Sonoda H, Sato Y, Makino H. Diabetes 58: 2365-2375, 2009). In this study, we investigated the therapeutic efficacy of VASH-1 on renal alterations in obese mice with type 2 diabetes. Diabetic db/db mice received intravenous injections of adenoviral vectors encoding human VASH-1 (AdhVASH-1) and were euthanized 8 wk later. AdhVASH-1 treatment resulted in significant suppression of glomerular hypertrophy, glomerular hyperfiltration, albuminuria, increase in the CD31(+) glomerular endothelial area, F4/80(+) monocyte/macrophage infiltration, the accumulation of type IV collagen, and mesangial matrix. An increase in the renal levels of VEGF-A, VEGFR-2, transforming growth factor (TGF)-β1, and monocyte chemoattractant protein-1 in diabetic animals was significantly suppressed by AdhVASH-1 (immunoblotting). AdhVASH-1 treatment significantly recovered the loss and altered the distribution patterns of nephrin and zonula occludens (ZO)-1 and suppressed the increase in the number of fibroblast-specific protein-1 (FSP-1(+)) and desmin(+) podocytes in diabetic mice. In vitro, recombinant human VASH-1 (rhVASH-1) dose dependently suppressed the upregulation of VEGF induced by high ambient glucose (25 mM) in cultured mouse podocytes. In addition, rhVASH-1 significantly recovered the mRNA levels of nephrin and the protein levels of ZO-1 and P-cadherin and suppressed the increase in protein levels of desmin, FSP-1, Snail, and Slug in podocytes under high-glucose condition. Taken together, these results suggest the potential use of VASH-1 as a novel therapeutic agent in type 2 diabetic nephropathy mediated via antiangiogenic effects and maintenance of podocyte phenotype in association with antiproteinuric effects.

Decreased concentrations of pigment epithelium-derived factor in peritoneal fluid of patients with endometriosis

To determine whether patients with endometriosis have altered levels of pigment epithelium-derived factor (PEDF) in peritoneal fluid, concentrations of PEDF in peritoneal fluid collected from 42 patients with endometriosis and 30 patients without endometriosis were measured with enzyme-linked immunosorbent assay. We detected significantly lower levels of peritoneal fluid PEDF in patients with endometriosis compared with patients without endometriosis, suggesting that peritoneal fluid PEDF plays a role in the pathogenesis of this disorder.

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.

Pigment epithelium-derived factor is an intrinsic antifibrosis factor targeting hepatic stellate cells

The liver is the major site of pigment epithelium-derived factor (PEDF) synthesis. Recent evidence suggests a protective role of PEDF in liver cirrhosis. In the present study, immunohistochemical analyses revealed lower PEDF levels in liver tissues of patients with cirrhosis and in animals with chemically induced liver fibrosis. Delivery of the PEDF gene into liver cells produced local PEDF synthesis and ameliorated liver fibrosis in animals treated with either carbon tetrachloride or thioacetamide. In addition, suppression of peroxisome proliferator-activated receptor gamma expression, as well as nuclear translocation of nuclear factor-kappa B was found in hepatic stellate cells (HSCs) from fibrotic livers, and both changes were reversed by PEDF gene delivery. In culture-activated HSCs, PEDF, through the induction of peroxisome proliferator-activated receptor gamma, reduced the activity of nuclear factor-kappa B and prevented the nuclear localization of JunD. In conclusion, our observations that PEDF levels are reduced during liver cirrhosis and that PEDF gene delivery ameliorates cirrhosis suggest that PEDF is an intrinsic protector against liver cirrhosis. Direct inactivation of HSCs and the induction of apoptosis of activated HSCs may be two of the mechanisms by which PEDF suppresses liver cirrhosis.

Angiogenesis and chronic kidney disease

The number of patients requiring renal replacement therapy due to end-stage renal disease (ESRD) is increasing worldwide. The prevalence of chronic kidney disease (CKD), and the importance of CKD as a risk factor in development of ESRD and in complicating cardiovascular disease (CVD) have been confirmed. In recent years, the involvement of angiogenesis-related factors in the progression of CKD has been studied, and the potential therapeutic effects on CKD of modulating these factors have been identified. Vascular endothelial growth factor (VEGF)-A, a potent pro-angiogenic factor, is involved in the development of the kidney, in maintenance of the glomerular capillary structure and filtration barrier, and in the renal repair process after injury. VEGF-A is also involved in the development of early diabetic nephropathy, demonstrated by the therapeutic effects of anti-VEGF-A antibody. Angiopoietin (Ang)-1 induces the maturation of newly formed blood vessels, and the therapeutic effects of Ang-1 in diabetic nephropathy have been described. In experimental models of diabetic nephropathy, the therapeutic effects of angiogenesis inhibitors, including angiostatin, endostatin and tumstatin peptides, the isocoumarin NM-3, and vasohibin-1, have been reported.

Further analysis of the involvement of angiogenesis-related factors in the development of CKD is required. Determining the disease stage at which therapy is most effective and developing an effective drug delivery system targeting the kidney will be essential for pro-or anti-angiogenic strategies for patients with CKD.

Pigment epithelium-derived factor stimulates tumor macrophage recruitment and is downregulated by the prostate tumor microenvironment

Pigment epithelium-derived factor (PEDF) is a potent inhibitor of angiogenesis but whether it has additional effects on the tumor microenvironment is largely unexplored. We show that overexpression of PEDF in orthotopic MatLyLu rat prostate tumors increased tumor macrophage recruitment. The fraction of macrophages expressing inducible nitric oxide synthase, a marker of cytotoxic M1 macrophages, was increased, suggesting that PEDF could enhance antitumor immunity. In addition, PEDF overexpression reduced vascular growth both in the tumor and in the surrounding normal tissue, slowed tumor growth, and decreased lymph node metastasis. Contrary, extratumoral lymphangiogenesis was increased. PEDF expression is, for reasons unknown, often decreased or lost during prostate tumor progression. When AT-1 rat prostate tumor cells, expressing high levels of PEDF messenger RNA (mRNA) and protein, were injected into the prostate, PEDF is markedly downregulated, suggesting that factors in the microenvironment suppressed its expression. One such factor could be macrophage-derived tumor necrosis factor alpha (TNFalpha). A fraction of the accumulating macrophages expressed TNFalpha, and TNFalpha treatment downregulated the expression of PEDF protein and mRNA in prostate AT-1 tumor cells in vitro and in the rat ventral prostate in vivo. PEDF apparently has multiple effects in prostate tumors: it suppresses angiogenesis and metastasis, but it also causes macrophage accumulation. Accumulating macrophages may inhibit tumor growth, but they may also suppress PEDF and enhance lymph angiogenesis and, in this way, eventually enhance tumor growth.

Pigment epithelium-derived factor induces interleukin-10 expression in human macrophages by induction of PPAR gamma

AIM

In search for the anti-inflammation mechanism of PEDF, we investigate whether pigment epithelium-derived factor (PEDF) induces the gene expression of interleukin (IL)-10 in human macrophages and determine the molecular basis of this induction.

MAIN METHODS

Human macrophages derived from a monocytic cell line, THP-1, and peripheral monocytes were treated with PEDF. IL-10 expression was assessed by quantitative real-time PCR, enzyme-linked immunosorbent assay, semi-quantitative reverse transcriptase (RT)-PCR, and promoter-reporter assay. Activity of extracellular signal-regulated kinase 2 (ERK2) and p38 mitogen-activated protein kinase (MAPK) was assessed by immunoblotting using antibodies targeting phosphorylated kinases forms. Elk-1 and ATF-2 phosphorylation was determined as well. Pharmacological inhibitors were used to examine the involvement of ERK, p38 MAPK, and peroxisome proliferator-activated receptor gamma (PPARgamma) on the IL-10 expression induced by PEDF.

KEY FINDINGS

PEDF increased the levels of IL-10 mRNA and protein in THP-1 cells and human macrophages derived from peripheral monocytes. Blockade of activity of ERK or p38 MAPK attenuated PEDF effects on induction of PPARgamma and IL-10. PEDF increased the transcriptional activity of IL-10 promoter. The effect was synergistically augmented by PPARgamma agonist, but attenuated by inhibitors of PPARgamma, ERK or p38 MAPK. These results showed that PEDF promotes IL-10 expression at transcriptional level, and that this is achieved through the ERK2/p38MAPK-dependent PPARgamma expression.

SIGNIFICANCE

The anti-inflammatory property of PEDF may in part through the induction of IL-10 in macrophages. Our study supports the therapeutic potential of PEDF and PPARgamma agonists in inflammatory diseases.

Attenuation of diabetes-induced renal dysfunction by multiple exposures to low-dose radiation is associated with the suppression of systemic and renal inflammation

Renal protection against diabetes-induced pathogenic injuries by multiple exposures to low-dose radiation (LDR) was investigated to develop a novel approach to the prevention of renal disease for diabetic subjects. C57BL/6J mice were given multiple low-dose streptozotocin (STZ; 6 x 60 [corrected] mg/kg) to produce a type 1 diabetes. Two weeks after diabetes onset, some of diabetic mice and age-matched nondiabetic mice were exposed whole body to 25 mGy X-rays every other day for 2, 4, 8, 12, and 16 wk. Diabetes caused a significant renal dysfunction, shown by time-dependent increase in urinary microalbumin (Malb) and decrease in urinary creatinine (Cre), and pathological changes, shown by significant increases in renal structural changes and PAS-positive staining. However, diabetes-induced renal dysfunction and pathological changes were significantly, albeit partially, attenuated by multiple exposures to LDR. Furthermore, LDR protection against diabetes-induced renal dysfunction and pathological changes was associated with a significant suppression of diabetes-increased systemic and renal inflammation, shown by significant increases in serum and renal TNFalpha, ICAM-1, IL-18, MCP-1, and PAI-1 contents. To further explore the mechanism by which LDR prevents diabetes-induced renal pathological changes, renal oxidative damage was examined by Western blotting and immunohistochemical staining for 3-nitrotyrosine and 4-hydroxynonenal. Significant increase in oxidative damage was observed in diabetic mice, but not diabetic mice, with LDR. Renal fibrosis, examined by Western blotting of connective tissue growth factor and Masson's trichrome staining, was also evident in the kidneys of diabetic mice but not diabetic mice with LDR. These results suggest that multiple exposures to LDR significantly suppress diabetes-induced systemic and renal inflammatory response and renal oxidative damage, resulting in a prevention of the renal dysfunction and fibrosis.

Vasohibin-1, a negative feedback regulator of angiogenesis, ameliorates renal alterations in a mouse model of diabetic nephropathy

OBJECTIVE

The involvement of proangiogenic factors such as vascular endothelial growth factor as well as the therapeutic efficacy of angiogenesis inhibitors in early diabetic nephropathy has been reported. Vasohibin-1 (VASH-1) is a unique endogenous angiogenesis inhibitor that is induced in endothelial cells by proangiogenic factors. We investigated the therapeutic efficacy of VASH-1 in an early diabetic nephropathy model.

RESEARCH DESIGN AND METHODS

Streptozotocin- induced type 1 diabetic mice received intravenous injections of adenoviral vectors encoding VASH-1 (AdhVASH-1) or beta-gal (AdLacZ) every other week and were killed after 28 days.

RESULTS

Treatment with AdhVASH-1 resulted in sustained increase in the protein levels of VASH-1 in the liver and sera, in the absence of any inflammatory alterations. AdhVASH-1 treatment significantly suppressed renal hypertrophy, glomerular hypertrophy, glomerular hyperfiltration, albuminuria, increase of the CD31(+) glomerular endothelial area, F4/80(+) monocyte/macrophage infiltration, the accumulation of type IV collagen, and mesangial matrix compared with AdLacZ-treated diabetic mice. Increase in the renal levels of transforming growth factor-beta1, monocyte chemoattractant protein-1, and receptor for advanced glycation end products in diabetic animals was significantly suppressed by AdhVASH-1 (real-time PCR and immunoblot). VASH-1 significantly suppressed the increase of transforming growth factor-beta, monocyte chemoattractant protein-1, and receptor for advanced glycation end products, induced by high ambient glucose in cultured mouse mesangial cells. Increased phosphorylation of VEGFR2 was suppressed in AdVASH-1-treated diabetic animals and in cultured glomerular endothelial cells. Endogenous mouse VASH-1 was localized to the mesangial and endothelial area in glomeruli of diabetic mice.

CONCLUSIONS

These results suggest the potential therapeutic efficacy of VASH-1 in treating early diabetic nephropathy potentially mediated via glomerular endothelial and mesangial cells.

Lipopolysaccharide directly alters renal tubule transport through distinct TLR4-dependent pathways in basolateral and apical membranes

Bacterial infection of the kidney is associated with renal tubule dysfunction and dysregulation of systemic electrolyte balance. Whether bacterial molecules directly affect renal tubule transport is unknown. We examined the effects of LPS on HCO3(-) absorption in the isolated rat and mouse medullary thick ascending limb (MTAL). LPS decreased HCO3(-) absorption when added to bath or lumen. The MEK/ERK inhibitor U0126 eliminated inhibition by bath LPS but had no effect on inhibition by lumen LPS. Conversely, the mammalian target of rapamycin (mTOR) inhibitor rapamycin eliminated inhibition by lumen LPS but had no effect on inhibition by bath LPS. Inhibiting basolateral Na(+)/H(+) exchange with amiloride eliminated inhibition of HCO3(-) absorption by lumen but not bath LPS. Confocal immunofluorescence showed expression of TLR4 in basolateral and apical membrane domains. Inhibition of HCO3(-) absorption by bath and lumen LPS was eliminated in MTALs from TLR4(-/-) mice. Thus LPS inhibits HCO3(-) absorption through distinct TLR4-dependent pathways in basolateral and apical membranes. These results establish that bacterial molecules can directly impair the transport function of renal tubules, identifying a new mechanism contributing to tubule dysfunction during bacterial infection. The LPS-induced reduction in luminal acidification may contribute to Gram-negative pathogenicity by promoting bacterial adherence and growth and impairing correction of infection-induced systemic acid-base disorders.

Characterization of PEDF: a multi-functional serpin family protein

Pigment epithelium-derived factor (PEDF) is a 50 kDa secreted glycoprotein that belongs to the non-inhibitory serpin family group. PEDF has been described as a natural angiogenesis inhibitor with neurotrophic and immune-modulation properties; it balances angiogenesis in the eye and blocks tumor progression. The mechanisms underlying most of these events are not completely clear; however, it appears that PEDF acts via multiple high affinity ligands and cell receptors. In this review article, we will summarize the current knowledge on the biochemical properties of PEDF and its receptors, the multimodal activities of PEDF and finally address the therapeutic potential of PEDF in treating angiogenesis-, neurodegeneration- and inflammation-related diseases.

Systemic administration of HMG-CoA reductase inhibitor protects the blood-retinal barrier and ameliorates retinal inflammation in type 2 diabetes

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) are frequently used lipid-lowering drugs in type 2 diabetes. Recent emerging evidence suggests that statins protect cardiovascular function via lipid-independent mechanisms. However, the potential role of statins in diabetic retinopathy in type 2 diabetes is largely unclear. In the present study we have investigated the effect of lovastatin on blood-retinal barrier and inflammatory status in the retina of db/db mice and in cultured retinal cells. Male C57BL/KsJ db/db mice were randomly chosen to receive gastric gavage of lovastatin (10mg/kg/day) or vehicle control for 6 weeks. Retinal vascular permeability, the tight junction and inflammation were determined. The results showed that db/db mice at the age of 19 weeks exhibited significantly increased retinal vascular leakage and decreased tight junction protein level in the retina. Moreover, the expression of pro-inflammatory factors, e.g. ICAM-1 and TNF-alpha, was drastically up-regulated in diabetic retina. Lovastatin treatment normalized all of these changes. In cultured bovine retinal capillary endothelial cells (RCECs) and human ARPE-19 cells, lovastatin attenuated the decrease of tight junction protein (occludin) and adherens junction protein (VE-cadherin) expression-induced by TNF-alpha, a major pro-inflammatory cytokine in diabetic retinopathy. Lovastatin also attenuated TNF-alpha expression in RCEC. Towards the mechanism, we showed that lovastatin ameliorated ICAM-1 expression-induced by hypoxia and TNF-alpha in both RCECs and ARPE-19 cells, in part through inhibition of NF-kappaB activation. Taken together, these findings indicate that lovastatin protects blood-retinal barrier in diabetic retinopathy, which is likely via its anti-inflammatory effects.

Intervention with cilostazol attenuates renal inflammation in streptozotocin-induced diabetic rats

AIMS

An inflammatory reaction is commonly found in the pathogenesis of diabetic nephropathy (DN). Cilostazol, a type 3 phosphodiesterase (PDE) inhibitor, has been previously reported to be anti-inflammatory, independent of an anti-platelet property. In the present study, we evaluated the hypothesis that cilostazol has protective effects on diabetic nephropathy by modulating the inflammatory process.

MAIN METHODS

Cilostazol was administered (27 or 9 mg kg(-1)d(-1)) to streptozotocin (STZ)-induced diabetic rats for eight weeks. We studied the kidney expression of vascular cell adhesion molecule (VCAM)-1 and intercellular adhesion molecule (ICAM)-1 by immunofluorescence, western blotting and real-time PCR. The renal monocyte chemoattractant protein (MCP)-1 and vascular endothelial growth factor (VEGF) levels were examined by ELISA. The nuclear factor (NF)-kappaB-DNA binding activity was assessed by electrophoresis mobility shift assay (EMSA).

KEY FINDINGS

Our results showed cilostazol inhibited diabetes-induced hypertrophy of the glomeruli and infiltration of inflammatory cells, as well as the increase in the VCAM-1 and ICAM-1 mRNA and protein expression, and MCP-1 and VEGF contents in the kidneys. Consistent with these findings, cilostazol attenuated the enhanced activation of NF-kappaB in diabetic rats.

SIGNIFICANCE

These results demonstrate that the renoprotective effects of cilostazol may be mediated by its anti-inflammatory actions, including inhibition of NF-kappaB activation and the subsequent decrease in proinflammatory factors, such as VCAM-1, ICAM-1, MCP-1 and VEGF expression in kidneys of diabetic rats.