Yukio Yuzawa

A Small Interfering RNA Targeting Vascular Endothelial Growth Factor as Cancer Therapeutics

Vascular endothelial growth factor (VEGF) plays a critical role during normal embryonic angiogenesis and also in the pathological angiogenesis that occurs in a number of diseases, including cancer. We developed a novel VEGF blockade system using RNA interference. The small interfering RNA (siRNA) targeting human VEGF almost completely inhibited the secretion of VEGF in a human prostate cancer cell line, PC-3, whereas the control scramble siRNA showed no effects. The VEGF siRNA with atelocollagen dramatically suppressed tumor angiogenesis and tumor growth in a PC-3 s.c. xenograft model. Atelocollagen provided a beneficial delivering means by which stabilization and efficient transfection of the siRNA injected into the tumors were achieved.

Aspects of Immune Dysfunction in End-stage Renal Disease

End-stage renal disease (ESRD) is associated with significantly increased morbidity and mortality resulting from cardiovascular disease (CVD) and infections, accounting for 50% and 20%, respectively, of the total mortality in ESRD patients. It is possible that these two complications are linked to alterations in the immune system in ESRD, as uremia is associated with a state of immune dysfunction characterized by immunodepression that contributes to the high prevalence of infections among these patients, as well as by immunoactivation resulting in inflammation that may contribute to CVD. This review describes disorders of the innate and adaptive immune systems in ESRD, underlining the specific role of ESRD-associated disturbances of Toll-like receptors. Finally, based on the emerging links between the alterations of immune system, CVD, and infections in ESRD patients, it emphasizes the potential role of the immune dysfunction in ESRD as an underlying cause for the high mortality in this patient population and the need for more studies in this area.

Diabetic Endothelial Nitric Oxide Synthase Knockout Mice Develop Advanced Diabetic Nephropathy

The pathogenesis of diabetic nephropathy remains poorly defined, and animal models that represent the human disease have been lacking. It was demonstrated recently that the severe endothelial dysfunction that accompanies a diabetic state may cause an uncoupling of the vascular endothelial growth factor (VEGF)-endothelial nitric oxide (eNO) axis, resulting in increased levels of VEGF and excessive endothelial cell proliferation. It was hypothesized further that VEGF-NO uncoupling could be a major contributory mechanism that leads to diabetic vasculopathy. For testing of this hypothesis, diabetes was induced in eNO synthase knockout mice (eNOS KO) and C57BL6 controls. Diabetic eNOS KO mice developed hypertension, albuminuria, and renal insufficiency with arteriolar hyalinosis, mesangial matrix expansion, mesangiolysis with microaneurysms, and Kimmelstiel-Wilson nodules. Glomerular and peritubular capillaries were increased with endothelial proliferation and VEGF expression. Diabetic eNOS KO mice showed increased mortality at 5 mo. All of the functional and histologic changes were improved with insulin therapy. Inhibition of eNO predisposes mice to classic diabetic nephropathy. The mechanism likely is due to VEGF-NO uncoupling with excessive endothelial cell proliferation coupled with altered autoregulation consequent to the development of preglomerular arteriolar disease. Endothelial dysfunction in human diabetes is common, secondary to effects of glucose, advanced glycation end products, C-reactive protein, uric acid, and oxidants. It was postulated that endothelial dysfunction should predict nephropathy and that correction of the dysfunction may prevent these important complications.

Neointima formation in a restenosis model is suppressed in midkine-deficient mice

Neointima formation is a common feature of atherosclerosis and restenosis after balloon angioplasty. To find a new target to suppress neointima formation, we investigated the possible role of midkine (MK), a heparin-binding growth factor with neurotrophic and chemotactic activities, in neointima formation. MK expression increased during neointima formation caused by intraluminal balloon injury of the rat carotid artery. Neointima formation in a restenosis model was strongly suppressed in MK-deficient mice. Continuous administration of MK protein to MK-deficient mice restored neointima formation. Leukocyte recruitment to the vascular walls after injury was markedly decreased in MK-deficient mice. Soluble MK as well as that bound to the substratum induced migration of macrophages in vitro. These results indicate that MK plays a critical role in neointima formation at least in part owing to its ability to mediate leukocyte recruitment.

Midkine Is Involved in Neutrophil Infiltration into the Tubulointerstitium in Ischemic Renal Injury

Midkine (MK) is a multifunctional heparin-binding protein and promotes migration of neutrophils, macrophages, and neurons. In the normal mouse kidney, MK is expressed in the proximal tubules. After renal ischemic reperfusion injury, its expression in proximal tubules was increased. Immediate increase of MK expression was found when renal proximal tubular epithelial cells in culture were exposed to 5 mM H2O2. Histologically defined tubulointerstitial damage was less severe in MK-deficient (Mdk−/−) than in wild-type (Mdk+/+) mice at 2 and 7 days after ischemic reperfusion injury. Within 2 days after ischemic injury, inflammatory leukocytes, of which neutrophils were the major population, were recruited to the tubulointerstitium. The numbers of infiltrating neutrophils and also macrophages were lower in Mdk−/− than in Mdk+/+ mice. Induction of macrophage inflammatory protein-2 and macrophage chemotactic protein-1, chemokines for neutrophils and macrophages, respectively, were also suppressed in Mdk−/− mice. Furthermore, renal tubular epithelial cells in culture expressed macrophage inflammatory protein-2 in response to exogenous MK administration. These results suggested that MK enhances migration of inflammatory cells upon ischemic injury of the kidney directly and also through induction of chemokines, and contributes to the augmentation of ischemic tissue damage.

Anti-monocyte chemoattractant protein-1 gene therapy attenuates renal injury induced by protein-overload proteinuria.

It has been postulated that protein filtered through glomeruli activates tubular epithelial cells, which secrete vasoactive and inflammatory substances including chemokines, leading to tubulointerstitial renal injury. The present study was designed to investigate the role of monocyte chemoattractant protein-1 (MCP-1) in this process and to evaluate the effectiveness of a kidney-targeted gene transfer technique using hydrodynamic pressure. Naked plasmid encoding 7ND (an MCP-1 antagonist) or a control plasmid was introduced into the left kidney of rats. Three days after gene transfer (day 0), intraperitoneal administration of bovine serum albumin (10 mg/g body wt per day) was started and continued for 14 or 21 d. RT-PCR showed that 7ND mRNA was expressed only in the gene-transfected kidney. Immunostaining showed that 7ND protein was localized in the interstitial cells. Macrophage infiltration was significantly reduced in the left kidney of rats treated with 7ND on days 14 and 21. In the right kidney, such effects were not observed. 7ND also attenuated tubular damage and decreased the number of apoptotic cells. Computer-assisted analysis revealed that the areas positively stained for alpha-smooth muscle actin (alpha SMA), fibronectin-EDA, type I collagen, and collagen fibrils were significantly reduced in the 7ND-treated kidney on day 21. Furthermore, 7ND gene therapy significantly reduced MCP-1 and TGF-beta 1 mRNA expression. These results demonstrate that MCP-1 plays an important role in the development of tubulointerstitial inflammation, tubular damage, and fibrosis induced by proteinuria. The fact that 7ND gene therapy had little effect on the contralateral kidney indicates that 7ND acted locally. This strategy may have a potential usefulness as a gene therapy against tubulointerstitial renal injury.

Effect of lowering uric acid on renal disease in the type 2 diabetic db/db mice

Hyperuricemia has recently been recognized to be a risk factor for nephropathy in the diabetic subject. We tested the hypothesis that lowering uric acid with a xanthine oxidase inhibitor might reduce renal injury in the diabetic mouse. Diabetic (db/db) mice were treated with allopurinol or no treatment for 8 wk. Serum uric acid, renal function, and histology were assessed at death. The direct effect of uric acid in human proximal tubular epithelial cells was also evaluated under normal or high glucose condition. We found that db/db mice developed hyperuricemia, albuminuria, mesangial matrix expansion, and mild tubulointerstitial disease. Allopurinol treatment significantly lowered uric acid levels, reduced albuminuria, and ameliorated tubulointerstitial injury, but it did not prevent mesangial expansion. The mechanism for protection was shown to be due to a reduction in inflammatory cells mediated by a reduction in ICAM-1 expression by tubular epithelial cells. Interestingly, allopurinol did not reduce oxidative stress in the kidney. An inflammatory role of uric acid on tubular cells was also confirmed by our in vitro evidence that uric acid directly induced ICAM-1 expression in the human proximal tubular cell. In conclusion, hyperuricemia has a pathogenic role in the mild tubulointerstitial injury associated with diabetic nephropathy but not glomerular damage in db/db mice. Lowering uric acid may reduce tubulointerstitial injury in diabetes.

Metabolic profiling reveals new serum biomarkers for differentiating diabetic nephropathy

Capillary electrophoresis coupled with time-of-flight mass spectrometry was used to explore new serum biomarkers with high sensitivity and specificity for diabetic nephropathy (DN) diagnosis, through comprehensive analysis of serum metabolites with 78 diabetic patients. Multivariate analyses were used for identification of marker candidates and development of discriminative models. Of the 289 profiled metabolites, orthogonal partial least-squares discriminant analysis identified 19 metabolites that could distinguish between DN with macroalbuminuria and diabetic patients without albuminuria. These identified metabolites included creatinine, aspartic acid, γ-butyrobetaine, citrulline, symmetric dimethylarginine (SDMA), kynurenine, azelaic acid, and galactaric acid. Significant correlations between all these metabolites and urinary albumin-to-creatinine ratios (p < 0.009, Spearman’s rank test) were observed. When five metabolites (including γ-butyrobetaine, SDMA, azelaic acid and two unknowns) were selected from 19 metabolites and applied for multiple logistic regression model, AUC value for diagnosing DN was 0.927 using the whole dataset, and 0.880 in a cross-validation test. In addition, when four known metabolites (aspartic acid, SDMA, azelaic acid and galactaric acid) were applied, the resulting AUC was still high at 0.844 with the whole dataset and 0.792 with cross-validation. Combination of serum metabolomics with multivariate analyses enabled accurate discrimination of DN patients. The results suggest that capillary electrophoresis-mass spectrometry based metabolome analysis could be used for DN diagnosis.

The growth factor midkine regulates the renin-angiotensin system in mice

The renin-angiotensin system plays a pivotal role in regulating blood pressure and is involved in the pathogenesis of kidney disorders and other diseases. Here, we report that the growth factor midkine is what we believe to be a novel regulator of the renin-angiotensin system. The hypertension induced in mice by 5/6 nephrectomy was accompanied by renal damage and elevated plasma angiotensin II levels and was ameliorated by an angiotensin-converting enzyme (ACE) inhibitor and an angiotensin receptor blocker. Notably, ACE activity in the lung, midkine expression in the lung, and midkine levels in the plasma were all increased after 5/6 nephrectomy. Exposure to midkine protein enhanced ACE expression in primary cultured human lung microvascular endothelial cells. Furthermore, hypertension was not induced and renal damage was less severe in midkine-deficient mice. Supplemental administration of midkine protein to midkine-deficient mice restored ACE expression in the lung and hypertension after 5/6 nephrectomy. Oxidative stress might be involved in midkine expression, since expression of NADH/NADPH oxidase-1, -2, and -4 was induced in the lung after 5/6 nephrectomy. Indeed, the antioxidative reagent tempol reduced midkine expression and plasma angiotensin II levels and consequently ameliorated hypertension. These results suggest that midkine regulates the renin-angiotensin system and mediates the kidney-lung interaction after 5/6 nephrectomy.

The E-Selectin Ligand Basigin/CD147 Is Responsible for Neutrophil Recruitment in Renal Ischemia/Reperfusion

E-selectin and its ligands are essential for extravasation of leukocytes in inflammation. Here, we report that basigin (Bsg)/CD147 is a ligand for E-selectin that promotes renal inflammation in ischemia/reperfusion. Compared with wild-type mice, Bsg-deficient (Bsg(-/-)) mice demonstrated striking suppression of neutrophil infiltration in the kidney after renal ischemia/reperfusion. Although E-selectin expression increased similarly between the two genotypes, Bsg(-/-) mice exhibited less renal damage, suggesting that Bsg on neutrophils contribute to renal injury in this model. Neutrophils expressed Bsg with N-linked polylactosamine chains and Bsg(-)(/)(-) neutrophils showed reduced binding to E-selectin. Bsg isolated from HL-60 cells bound to E-selectin, and tunicamycin treatment to abolish N-linked glycans from Bsg abrogated this binding. Furthermore, Bsg(-)(/)(-) neutrophils exhibited reduced E-selectin-dependent adherence to human umbilical vein endothelial cells in vitro. Injection of labeled neutrophils into mice showed that Bsg(-)(/)(-) neutrophils were less readily recruited to the kidney after renal ischemia/reperfusion than Bsg(+/+) neutrophils, regardless of the recipients genotype. Taken together, these results indicate that Bsg is a physiologic ligand for E-selectin that plays a critical role in the renal damage induced by ischemia/reperfusion.