Angiotensin II (AngII) has pleiotropic effects, the most well known of which is the generation of reactive oxygen species (ROS) and chemokines in inflammatory lesions. Monocyte chemoattractant protein-1 (MCP-1) is considered a major chemokine in the pathogenesis of kidney diseases. We examined signaling pathways of AngII-induced MCP-1 expression and the role of ROS in the murine proximal tubular cells (mProx) using various inhibitors. Furthermore, we compared the signaling pathways between mProx and mesangial cells (MC). AngII-induced MCP-1 protein expression in mProx at 6 h was largely blocked by ROS (N-acetylcysteine; 82 +/- 14%), Ras (N-acetyl-S-trans,trans-farnesyl-L-cysteine; 82 +/- 13%), and nuclear factor-kappaB (NF-kappaB) (parthenolide; 89 +/- 7.9%) inhibitors. Both AT1 receptor (AT1R) (Olmesartan; 41 +/- 12%) and the AT2R (PD123319; 24 +/- 11%) antagonists partially blocked the MCP-1 expression. Furthermore, mitogen-activated protein kinase (MAPK) pathways were also implicated in this protein expression, but it is less dependent on ROS/Ras pathways. In MC, protein kinase (calphostin C; 84 +/- 2.8%) and NF-kappaB (89 +/- 1.4%) inhibitors attenuated acute AngII-induced MCP-1 expression stronger than ROS/Ras inhibitors (1.0 +/- 0.9/29 +/- 9.5%). MAPK pathways, especially p38 MAPK, were involved in MC more than in mProx. AT1R (69 +/- 8.6%) and AT2R (57 +/- 21%) antagonists also were blocked. We suggested that, although NF-kappaB activation has a critical role, signaling pathways are different between mProx and MC. ROS-mediated signaling in mProx may have more contribution to AngII-induced inflammatory responses than to those in MC.

Proteinuria is a key factor in the progression of tubulointerstitial injury. Recently, tubular ischemia as a result of loss of peritubular capillaries has been identified as another major contributor to disease progression, but the relative contribution of these insults on tubulointerstitial damage is unknown. Anti-glomerular basement membrane glomerulonephritis was induced in wild-type (WT) and Fc receptor knockout (FcRKO) mice, which have been shown to be relatively protected against glomerular endothelial injury. Despite comparable degrees of proteinuria, WT mice developed significantly worse renal function than FcRKO mice, along with higher expression of both type I collagen and kidney injury molecule-1 (a sensitive marker of acute tubular injury) by real-time PCR and immunohistochemistry. In addition, compared with FcRKO mice, WT mice exhibited a greater decrease in peritubular red blood cell velocity by intravital videomicroscopy and a marked increase of tissue hypoxia. In vitro, kidney injury molecule-1 expression increased in cultured mouse proximal tubular epithelial cells in response to cellular stresses, including hypoxia, starvation, and exposure to excessive protein; therefore, it is suggested that hypoxic insults more strongly influence tubulointerstitial damage than proteinuria alone in models of subacute renal disease.

Background: Some reports have discussed the synergic effects of angiotensin II receptor blockers and calcium channel blockers on vascular injury or microalbuminuria. The present study examined the effects of combination treatment with olmesartan and azelnidipine on polycystic kidney disease in a mouse model (DBA/2-FG pcy mouse) and its mechanisms. Methods: The mice were divided into the following groups: combination treatment (n = 21), olmesartan treatment alone (n = 23), azelnidipine treatment alone (n = 29) or untreated (n = 26). Mean blood pressure and kidney weight were measured at 4 and 8 weeks after the treatment. Renal expression of angiotensin II, gp91, nitrotyrosine and endothelial NO synthase (eNOS) were examined by immunostaining. In addition, extracellular signal-regulated kinase activation was evaluated by Western blotting. Results: Olmesartan decreased the numbers of angiotensin II and gp91-positive cells, mainly macrophages, and cyst size at 4 weeks. However, only combination treatment suppressed cell infiltration, extracellular signal-regulated kinase activation and interstitial fibrosis with a significant change in the kidney weight/body weight ratio. The azelnidipine and combination treatment increased the numbers of interstitial eNOS-positive cells. Conclusion: The combination treatment protects against cyst enlargement in polycystic kidney disease by suppressing interstitial inflammation, fibrosis and oxidative stress by upregulating eNOS expression during disease course.

Immunoglobulin A nephropathy (IgAN) is characterized by mesangial cell proliferation and mesangial expansion with mesangial depositions of IgA. We have found that electron-dense deposits (EDD) are often observed in areas other than paramesangial areas in glomeruli. To compare electron microscopic findings with light microscopic findings and clinical data, we examined the biopsies from 178 patients with IgAN. Patients were divided into two groups: group A had only paramesangial deposits and group B had deposits not only in paramesangial areas but also in other areas. All patients examined in this study had EDD in glomerular paramesangial areas. Thirty-six patients were included in group B. Cellular crescent formation in glomeruli and urinary protein in group B were significantly higher than those in group A (P < 0.01). Serum albumin and estimated glomerular filtration rate (eGFR) in group B were significantly lower than those in group A (P < 0.05). Group B showed a significant positive correlation with histological severity, which is defined in the Japanese Clinical Guidelines on IgAN. In patients with broad distribution of EDD, urinary protein was significantly increased (P < 0.05). Detailed observation of EDD distribution has an impact on evaluation of the disease activity of IgAN.

Abstract-Inappropriate activation of the intrarenal renin-angiotensin system induces generation of reactive oxygen species and tubulointerstitial inflammation, which contribute to salt-sensitive hypertension (SSHT). Liver-type fatty acid-binding protein is expressed in proximal tubules in humans, but not in rodents, and may play an endogenous antioxidative role. The objective of the present study was to examine the antioxidative effect of liver-type fatty acid-binding protein on post-angiotensin II SSHT model in transgenic mice with selective overexpression of human liver-type fatty acid-binding protein in the proximal tubules. The transgenic mice showed marked protection against angiotensin II-induced SSHT.Overexpression of tubular liver-type fatty acid-binding protein prevented intrarenal T-cell infiltration and also reduced reactive oxygen species generation, intrarenal renin-angiotensin system activation, and monocyte chemotactic protein-1 expression. We also performed an in vitro study using the murine proximal tubular cell lines with or without recombinant liver-type fatty acid-binding protein and murine proximal tubular cell lines transfected with human liver-type fatty acid-binding protein, and found that gene transfection of liver-type fatty acid-binding protein and, in part, recombinant liver-type fatty acid-binding protein administration had significantly attenuated angiotensin II-induced reactive oxygen species generation and the expression of angiotensinogen and monocyte chemotactic protein-1 in murine proximal tubular cell lines. These findings indicated that liver-type fatty acid-binding protein in the proximal tubules may protect against angiotensin II-induced SSHT by attenuating activation of the intrarenal renin-angiotensin system and reducing oxidative stress and tubulointerstitial inflammation. Present data suggest that liver-type fatty acid-binding protein in the proximal tubules may be a novel therapeutic target for SSHT. 14 The expression of renal hL-FABP is upregulated in the pathological conditions in these mice, with tubulointerstitial inflammation and fibrosis being markedly attenuated compared with wild-type (WT) mice.12,14 However, the pathophysiological significance of tubular hL-FABP in local RAS activation and subsequent SSHT remains to be determined. The present study analyzed AngII-induced SSHT in hL-FABPTg mice and investigated the underlying mechanism in PTCs with or without hL-FABP transfection or treatment of recombinant L-FABP peptides (rhL-FABP). MethodsA detailed description of all methods is presented in the online-only Data Supplement. Results AngII-Induced SSHT Was Prevented in hL-FABPTg MiceAll groups had the same level of systolic blood pressure (SBP; 102-112 mm Hg) at the beginning of the study (Figure 1). AngII infusion in the WT mice induced a progressive increase in SBP (159.1±13.7 and 177.2±10.7 mm Hg at weeks 2 and 4, respectively; P<0.001 versus WT before and AngII hL-FABPTg at week 4; Figure 1). However, AngII infusion in hL-FABPTg mice induced a small incre...