Chronic kidney disease promotes chronic inflammation in visceral white adipose tissue.

White adipose tissue plays an important role in the development of metabolic disturbance, which is a common feature in patients with chronic kidney disease (CKD). The effect of CKD on white adipose tissue remains poorly appreciated. Here, we evaluated the inflammatory potential of visceral white adipose tissue in a rat model of CKD. The results showed that production of proinflammatory cytokines and infiltration of macrophage in the tissue were increased significantly in CKD rats compared with sham rats. Moreover, the primary adipocytes and stromal vascular fraction under the condition of CKD could trigger the inflammatory response in each other. Free fatty acid induced robust inflammatory response in ex vivo peritoneal-derived macrophages from CKD rats, which was associated with reduced activity of silent information regulator T1 (SIRT1). Improvement of SIRT1 activity by an activator could alleviate free fatty acid-induced inflammatory response in the macrophages and inflammation in the white adipose tissue. Moreover, oxidative stress occurred in the tissue and linked with the reduced activity of SIRT1 in macrophages and enhanced release of free fatty acid in the tissue. We thus identified CKD as a risk factor for chronic inflammation in white adipose tissue. These observations might open up new therapeutic strategies for metabolic disturbance in CKD via the modulation of adipose tissue-related pathways.

Advanced oxidation protein products activate intrarenal renin-angiotensin system via a CD36-mediated, redox-dependent pathway.

AIMS: Activation of intrarenal renin-angiotensin system (RAS) has a detrimental effect on the progression of chronic kidney diseases (CKDs), although the regulation of intrarenal RAS remains unclear. The aim of the present study was to evaluate the role of advanced oxidation protein products (AOPPs) in intrarenal RAS activation. RESULTS: AOPPs upregulated the expression of almost all components of RAS and increased activity of angiotensin-converting enzyme in cultured proximal tubular epithelial cells. The triggering effect of AOPP-albumin was 100-times stronger than that of unmodified albumin. The effect of AOPP-albumin was mainly mediated by a CD36-dependent, redox-sensitive signaling involving activation of protein kinase Cα, NADPH oxidase, and nuclear factor-κB/activation protein-1. Chronic AOPP-albumin loading in unilateral nephrectomy rats resulted in deposition of AOPPs in renal tubular cells accompanied with local RAS activation and functional perturbations such as increase in urinary albumin excretion. Accumulation of AOPPs was also detected in human renal tubular cells and correlated with expression of angiotensin II in renal biopsies from 19 patients with IgA nephropathy. INNOVATION AND CONCLUSION: This study demonstrated for the first time that AOPPs modified albumin functions as a strong trigger of intrarenal RAS via a CD36-mediated, redox-dependent pathway. Given the fact that accumulation of AOPPs is prevalent in diabetes and CKD, targeting AOPPs could be a strategy for the therapeutic intervention of CKD. Antioxid. Redox Signal. 18, 19-35.

Changes in pathological pattern and treatment regimens based on repeat renal biopsy in lupus nephritis.

BACKGROUND: Relapses occur frequently in patients with lupus nephritis. Renal biopsy is the gold standard for assessing renal activity and hence guiding the treatment. Whether repeat renal biopsy is helpful during flares of lupus nephritis remains inconclusive. In the present study, we retrospectively reviewed the patients with lupus nephritis who had more than one renal biopsy with the hope to find the clinical value of repeat biopsy. METHODS: Patients who had a diagnosis of lupus nephritis and two or more renal biopsies were selected from the database of the patient pathology registration at this renal division. Renal biopsy was evaluated according to the International Society of Nephrology/Renal Pathology Society (ISN/RPS) classification of lupus nephritis. The pathological patterns and treatment regimens were analyzed after a repeat biopsy. RESULTS: We identified 44 systemic lupus erythematosus patients with serial renal biopsies. In total, there were 94 renal biopsies. Overall, the pathological transition occurred in 64% instances according to the ISN/RPS class. When the transition was analyzed according to proliferative, membranous or mix lesions, it showed different profile: 35% in patients with proliferative lesion, 23.5% patients with mix lesions, 100% in patients with pure membranous lesion. The pathological transition could not be predicted by any clinical characteristics. After the repeat renal biopsy, 34% of patients had a change in their treatment regimens. CONCLUSIONS: The pathological conversion was very prevalent in patients with lupus nephritis. However, the transitions became less prevalent when they were analyzed according to pure membranous, proliferative, and mix lesion. Repeat biopsy might be helpful to avoid unnecessary increased immunosuppression therapy.

[Comparison of different methods for PAS staining of renal biopsy tissue sections].

OBJECTIVE: To compare the performance of a modified PAS staining, traditional PAS staining, Lyon's PAS staining, and Tsunahico Watanabe staining for staining sections of renal biopsy tissue. METHODS: The sections of the renal biopsy tissue were stained with the 4 methods and their staining performance was compared. RESULTS: The modified PAS staining method produced a better contrast and a higher resolution and showed a greater stability after repeated use than the other 3 methods for staining the renal tissue sections (P<0.05). CONCLUSION: The modified PAS staining method shows a better applicability than the other 3 PAS methods for staining sections of renal biopsy tissue.

[Effect of the ethanol extract of Picrorhiza scrophulariiflora on the progression of chronic kidney disease in a rat remnant kidney model].

OBJECTIVE: To investigate the effect of the ethanol extract of Picrorhiza scrophulariiflora (EPS) on renal function and tissue damage in a rat remnant kidney model. METHODS: Rat models of chronic kidney disease induced by 5/6 nephrectomy (5/6 Nx) were randomly assigned into two groups for treatment with a gavage of either EPS or vehicle for 9 weeks. The rats in the control group received only sham operation. RESULTS: Compared with vehicle-treated 5/6 Nx rats, the EPS-treated rats displayed significantly decreased urinary excretion of malondialdehyde, serum levels of AGEs and AOPPs, and increased serum SeGSHPx activities. These changes were associated with attenuated urinary protein excretion, glomerular sclerosis and interstitial fibrosis. CONCLUSION: EPS can obviously improve the renal functions and renal pathologies in rats with chronic kidney disease probably by inhibiting the oxidative stress.

Picrorhiza scrophulariiflora improves accelerated atherosclerosis through inhibition of redox-sensitive inflammation.

BACKGROUND: Accumulation of advanced glycation end products (AGEs) or advanced oxidation protein products (AOPPs) has been identified as a risk factor for accelerated atherosclerosis seen in diabetes and chronic kidney disease. However, little is known about the intervention for atherogenesis associated with these oxidized proteins. The rhizome of Picrorhiza scrophulariiflora (PS) has long been used to treat inflammatory diseases as a traditional medication. The study was performed to test the hypothesis that ethanol extraction of PS (EPS) may improve AGEs- or AOPPs-induced accelerated atherosclerosis in vivo. METHODS AND RESULTS: Hypercholesterolemic or normal rabbits were randomly assigned to 8 groups treated with intravenous injection of AGEs- or AOPPs-modified rabbit serum albumin (AGEs-RSA or AOPPs-RSA), unmodified RSA or vehicle in the presence or absence of EPS (10 mg/kg/2 days) gavage for 10 weeks. Compared with hypercholesterolemic rabbits without EPS treatment, EPS administration significantly decreased the aortic plaque volume and oxidized low density lipoprotein (Ox-LDL) deposition in hypercholesterolemic animals. This was accompanied by significant histological improvement including decrease of intimal and smooth muscle cell proliferation and macrophage influx in affected areas. EPS administration almost completely abolished the accelerated atherosclerosis induced by chronic treatment of AGEs- or AOPPs-RSA in both hypercholesterolemic and normal rabbits. EPS administration significantly restored the AGEs- or AOPPs-induced redox imbalance and inflammation, evidenced by decrease of plasma Ox-LDL, thiobarbituric acid reactive substances and TNF-alpha, and increase of glutathione peroxidase activity. CONCLUSION: These data suggested that EPS may improve atherosclerosis, particularly that induced by AGEs or AOPPs, through inhibition of redox-sensitive inflammation.

Advanced oxidation protein products promote inflammation in diabetic kidney through activation of renal nicotinamide adenine dinucleotide phosphate oxidase.

The involvement of inflammatory processes has been recognized in development and/or progression of diabetic nephropathy. However, the mechanisms involved in the pathogenesis of renal inflammation have not been completely understood. In this study, we tested the hypothesis that accumulation of advanced oxidation protein products (AOPPs), which occurs in diabetes, may promote inflammatory responses in diabetic kidney. Streptozotocin-induced diabetic rats were randomized to iv injection of vehicle, native rat serum albumin (RSA), and AOPPs-modified RSA (AOPPs-RSA) in the presence or absence of oral administration of apocynin. A control group was followed concurrently. Compared with RSA- or vehicle-treated diabetic rats, AOPPs-RSA-treated animals displayed significant increase in renal macrophage infiltration and overexpression of monocyte chemoattractant protein-1 and TGF-beta1. This was associated with deteriorated structural and functional abnormalities of diabetic kidney, such as glomerular hypertrophy, fibronectin accumulation, and albuminuria. AOPP challenge significantly increased nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent superoxide generation in renal homogenates and up-regulated membrane expression of renal NADPH oxidase subunits p47(phox) and gp91(phox). All these AOPPs-induced perturbations in diabetic kidney could be prevented by the NADPH oxidase inhibitor apocynin. These data suggest that chronic accumulation of AOPPs may promote renal inflammation in diabetes probably through activation of renal NADPH oxidase.

Advanced oxidation protein products accelerate renal fibrosis in a remnant kidney model.

Accumulation of plasma advanced oxidation protein products (AOPP) has been found in patients with chronic kidney disease. However, the biologic consequences of AOPP consumption on progression of renal disease still are unclear. For testing of the hypothesis that AOPP accelerate progression of chronic kidney disease, Sprague-Dawley rats were subjected to five-sixths nephrectomy (5/6 Nx) or to sham operation. Rats in each group were randomly assigned in three subgroups (n = 30 in each group) and treated with repeated intravenous injections of AOPP-modified rat serum albumin (RSA), unmodified RSA, or vehicle for indicated period. Compared with RSA- or vehicle-treated 5/6 Nx rats, AOPP RSA-treated 5/6 Nx rats displayed greater proteinuria, higher serum creatinine, and lower creatinine clearance. AOPP challenge resulted in more renal hypertrophy, higher macrophage influx, and greater renal fibrosis in the remnant kidney. Chronic administration of AOPP in sham-operated rats increased urinary protein excretion and renal macrophage infiltration, but histologic renal fibrosis was not observed during the study period. AOPP treatment enhanced AOPP level in renal tissue. This was associated with marked increase of thiobarbituric acid reactive substances, decrease of glutathione peroxidase activity, and upregulated expression of monocyte chemoattractant protein-1 and TGF-beta1 in renal cortex. These data indicate that AOPP might be a new and potentially important mediator of renal fibrosis in the remnant kidney. Chronic accumulation of AOPP promotes renal fibrosis probably via a redox-sensitive inflammatory pathway.

Advanced oxidation protein products accelerate atherosclerosis through promoting oxidative stress and inflammation.

OBJECTIVE: Increased level of plasma advanced oxidation protein products (AOPPs) has been found in patients with uremia and nonuremic subjects with coronary artery disease. This study was conducted to test the hypothesis that AOPPs play a causal role in atherosclerosis. METHODS AND RESULTS: Hypercholesterolemic (0.5% wt/wt diet) or normal rabbits received either repeated intravenous injections of AOPPs modified rabbit serum albumin (AOPPs-RSA) or unmodified RSA for 8 weeks. Compared with RSA- or vehicle-treated hypercholesterolemic rabbits, AOPPs-RSA-treated animals displayed increased atherosclerotic plaque area oxidized low-density lipoprotein (oxLDL) deposition, macrophage infiltration, and smooth muscle cell proliferation. Aortic sections from AOPPs-RSA-treated normal rabbits showed significant focal intima proliferation and mild Oil-Red-O staining lipid deposition in the affected areas, a phenomenon not observed in the RSA- or vehicle-treated controls. Plasma AOPPs levels in AOPPs-treated groups significantly increased in both hypercholesterolemic and normal rabbits compared with their relevant controls. Close correlations were found between plasma levels of AOPPs and the parameters of oxidative stress, eg, oxLDL and thiobarbituric acid reactive substances levels, or glutathione peroxidase activity. A highly significant correlation was also observed between plasma AOPPs and tumor necrosis factor (TNF)-alpha levels. CONCLUSIONS: This study provides in vivo evidence for a causal relationship between chronic AOPPs accumulation and atherosclerosis.

[Advanced glycation end products accelerate atherosclerosis via enhancement of oxidative stress].

OBJECTIVE: To investigate the effect of advanced glycation end products (AGE) on atheromatous plaque formation and its possible mechanisms. METHODS: Fifty rabbits were randomly divided into five groups of 10 rabbits: group A, fed with hypercholesterolemic diet and injected intravenously with AGE modified rabbit serum albumin (AGE-RSA); group B, fed with hypercholesterolemic diet and injected with unmodified RSA; group C, fed with hypercholesterolemic diet; group D, fed with normal diet alone: and group E, fed with normal diet and injected with AGE-RSA. Ten weeks after the rabbits were killed. Their aortas were taken out and stained with Sudan red IV. The extent of atheromatous plaques in the aortas en face was evaluated by computer-assisted morphometry and by histologic examination. Photoshop system was used to measure the percentage of atheromatous plaques in the area of tunica intima. The depositions of AGE, malondialdehyde modified low-density lipoprotein (MDA-LDL), oxidized low-density lipoprotein (ox-LDL) and expression of receptor of AGE (RAGE) in aortic tissue were detected by using immunohistological staining. The circulating AGE, blood lipids, serum selenium glutathione peroxydase (SeGSHPx) activity, malonyldialdehyde (MDA), and oxidized LDL (ox-LDL) were detected before the experiment and after the rabbits were killed. RESULTS: (1) The relative plaque area was significantly increased in group A (50% +/- 8%) compared with in group B (21% +/- 7%) and group C (29% +/- 6%). No plaque could be found in animals fed with normal diet (group D) even in those receiving repeated injections of AGE-RSA (group E). Depositions of ox-LDL, MDA-LDL and AGE in atherosclerotic lesions increased and RAGE expression were upregulated in the rabbits fed with hypercholesterolemic diet and injected with AGE-RSA (group A) compared with the other four groups. (2) All hypercholesterolemic rabbits showed comparable serum levels of triglyceride and cholesterol. However, the serum levels of AGE, ox-LDL and MDA were significantly higher and the serum level of SeGSHPx was relatively lower in group A compared with those in the other four groups. (3) The serum level of AGE was directly correlated with the serum ox-LDL (r = 0.459, P < 0.01) or serum MDA concentration (r = 0.423, P < 0.05), and inversely correlated with the serum level of SeGSHPx (r = - 0.448, P < 0.01). A close correlation was found between the serum level of AGE and endothelium RAGE expression (r = 0.384, P < 0.05) and deposition area of AGE (r = 0.468, P < 0.05) in aorta. CONCLUSION: AGE accelerates the atheromatous plaque formation through induction of oxidative stress and upregulation of RAGE.

[Proteins modified with glycation or oxidation products accelerate atherosclerosis in experimental hypercholesterolemic rabbits].

OBJECTIVE: To investigate whether advanced glycation end products (AGE) or advanced oxidative protein products (AOPP) contributes to atherogenesis in experimental hypercholesterolemic rabbits. METHODS: Hypercholesterolemic (0.5% wt/wt diet) rabbits received repeated intravenous injections of either AGE modified rabbit serum albumin (AGE-RSA) or AOPP modified RSA (AOPP-RSA) for 10 weeks. Three control groups were set as follows: a group fed with high cholesterol diet alone, a group fed with high cholesterol diet and injected with normal RSA, and a group fed with normal diet. The animals were sacrificed and aortas were dissected and stained with Sudan red IV. Atheromatous plaques in the aortas en face were evaluated by computer-assisted morphometry and by histologic examination. Hematological parameters (triglyceride, cholesterol, AGE and AOPP) were also tested. RESULTS: (1) The relative plaque area in rabbits receiving repeated injections of AGE or AOPP was 50.1%+/-7.4% and 62.4%+/-8.8% respectively, both were significantly larger than either that of hypercholesterolemic rabbits (29.8%+/-6.3%, P<0.05) or that of hypercholesterolemic rabbits injected with unmodified RSA (20.9%+/-6.4%, P<0.05). In aortic arch, thoracic aorta and abdominal aorta, atherosclerotic lesions in AGE group and AOPP group were more severe than in any of the control groups. (2)The average thickness of the plaques on thoracic aortas in AGE group [(138.1+/-13.0) microm] and in AOPP group [(147.7+/-13.1) microm ] were significantly thicker than either of that in the group treated with hypercholesterolemic diet alone [(85.7+/-15.0) microm] or that in the group treated with non modified RSA [(95.5+/-15.7) microm]. (3) Glyceride and cholesterol levels in all animals on hypercholesterolemic diet were similar. AGE and AOPP serum levels in groups injected with AGE or AOPP were significantly higher than that in any of the control groups. AGE serum concentrations were positively correlated with the atheromatous plaque area(r=0.408, P=0.005), so were the AOPP serum concentrations (r=0.595, P=0.000). CONCLUSION: AGE or AOPP modified proteins accelerate the formation of atherosclerosis and may contribute to the accelerated atherosclerosis in end stage renal diseases.