Effects of diabetes and hypertension on macrophage infiltration and matrix expansion in the rat kidney

Mechanisms of podocyte injury and implications for diabetic nephropathy

Albuminuria is the hallmark of both primary and secondary proteinuric glomerulopathies, including focal segmental glomerulosclerosis (FSGS), obesity-related nephropathy, and diabetic nephropathy (DN). Moreover, albuminuria is an important feature of all chronic kidney diseases (CKDs). Podocytes play a key role in maintaining the permselectivity of the glomerular filtration barrier (GFB) and injury of the podocyte, leading to foot process (FP) effacement and podocyte loss, the unifying underlying mechanism of proteinuric glomerulopathies. The metabolic insult of hyperglycemia is of paramount importance in the pathogenesis of DN, while insults leading to podocyte damage are poorly defined in other proteinuric glomerulopathies. However, shared mechanisms of podocyte damage have been identified. Herein, we will review the role of haemodynamic and oxidative stress, inflammation, lipotoxicity, endocannabinoid (EC) hypertone, and both mitochondrial and autophagic dysfunction in the pathogenesis of the podocyte damage, focussing particularly on their role in the pathogenesis of DN. Gaining a better insight into the mechanisms of podocyte injury may provide novel targets for treatment. Moreover, novel strategies for boosting podocyte repair may open the way to podocyte regenerative medicine.

Twist1 in podocytes ameliorates podocyte injury and proteinuria by limiting CCL2-dependent macrophage infiltration

The transcription factor Twist1 regulates several processes that could impact kidney disease progression, including epithelial cell differentiation and inflammatory cytokine induction. Podocytes are specialized epithelia that exhibit features of immune cells and could therefore mediate unique effects of Twist1 on glomerular disease. To study Twist1 functions in podocytes during proteinuric kidney disease, we employed a conditional mutant mouse in which Twist1 was selectively ablated in podocytes (Twist1-PKO). Deletion of Twist1 in podocytes augmented proteinuria, podocyte injury, and foot process effacement in glomerular injury models. Twist1 in podocytes constrained renal accumulation of monocytes/macrophages and glomerular expression of CCL2 and the macrophage cytokine TNF-α after injury. Deletion of TNF-α selectively from podocytes had no impact on the progression of proteinuric nephropathy. By contrast, the inhibition of CCL2 abrogated the exaggeration in proteinuria and podocyte injury accruing from podocyte Twist1 deletion. Collectively, Twist1 in podocytes mitigated urine albumin excretion and podocyte injury in proteinuric kidney diseases by limiting CCL2 induction that drove monocyte/macrophage infiltration into injured glomeruli. Myeloid cells, rather than podocytes, further promoted podocyte injury and glomerular disease by secreting TNF-α. These data highlight the capacity of Twist1 in the podocyte to mitigate glomerular injury by curtailing the local myeloid immune response.

Renal expression of cytokines and chemokines in diabetic nephropathy

BACKGROUND

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease worldwide. Inflammatory mediators have been implicated in the pathogenesis of DN, thus considered an inflammatory disease. However, further studies are required to assess the renal damage caused by the action of these molecules. Therefore, the objective of this study was to analyze the expression of cytokines and chemokines in renal biopsies from patients with DN and to correlate it with interstitial inflammation and decreased renal function.

METHODS

Forty-four native renal biopsies from patients with DN and 23 control cases were selected. In situ expression of eotaxin, MIP-1α (macrophage inflammatory protein-1α), IL-8 (interleukin-8), IL-4, IL-10, TNF-α (tumor necrosis factor-α), TNFR1 (tumor necrosis factor receptor-1), IL-1β, and IL-6 were evaluated by immunohistochemistry.

RESULTS

The DN group showed a significant increase in IL-6 (p < 0.0001), IL-1β (p < 0.0001), IL-4 (p < 0.0001) and eotaxin (p = 0.0012) expression, and a decrease in TNFR1 (p = 0.0107) and IL-8 (p = 0.0262) expression compared to the control group. However, there were no significant differences in IL-10 (p = 0.4951), TNF-α (p = 0.7534), and MIP-1α (p = 0.3816) expression among groups. Regarding interstitial inflammation, there was a significant increase in IL-6 in scores 0 and 1 compared to score 2 (p = 0.0035), in IL-10 in score 2 compared to score 0 (p = 0.0479), and in eotaxin in score 2 compared to scores 0 and 1 (p < 0.0001), whereas IL-8 (p = 0.0513) and MIP-1α (p = 0.1801) showed no significant differences. There was a tendency for negative correlation between eotaxin and estimated glomerular filtration rate (eGFR) (p = 0.0566).

CONCLUSIONS

Our results indicated an increased in situ production of cytokines and chemokines in DN, including IL-6, IL-1β, IL-4, and eotaxin. It was observed that, possibly, eotaxin may have an important role in the progression of interstitial inflammation in DN and in eGFR decrease of these patients.

Uremic Serum Induces Inflammation in Cultured Human Endothelial Cells and Triggers Vascular Repair Mechanisms

Inflammation and cardiovascular disease (CVD) are common in end-stage renal disease (ESRD) patients whose vascular endothelium is in direct contact with the uremic toxins found in the blood. These toxins are believed to affect vascular injury and repair process, which is impaired in ESRD patients. The exact mechanisms behind these interactions are not clear. So, we wanted to investigate what happens at the molecular level of endothelial cells when exposed to uremic serum from ESRD patients with diabetes and/or hypertension and its effect on the expression of molecules associated with vascular injury and repair. Cultured human endothelial cells (ECV304) were incubated in the presence of normal or uremic sera from ESRD patients with diabetes and/or hypertension. The expressions of monocyte chemoattractant protein 1 (MCP-1), vascular endothelial growth factor (VEGF), and stromal cell-derived factor 1 (SDF-1) were investigated in endothelial cells (ECV304) by real-time PCR and ELISA. The expression of MCP-1, VEGF, and SDF-1 was elevated in endothelial cells upon exposure to uremic sera from ESRD patients with diabetes and/or hypertension when compared with cells treated with healthy serum. MCP-1 expression in endothelial cells treated with uremic serum from ESRD patients with hypertension only was significantly increased compared with its expression in other cohorts. Exposure of endothelial cells to uremic serum causes endothelial injury and inflammation characterized by an increase in MCP-1 expression. This injury activates the initiation of vascular repair process in these cells by increasing the expression of VEGF and SDF-1. These molecules can be important biomarkers of chronic kidney disease-associated CVD.

Association between dyslipidemia and CCL2 in patients undergoing hemodialysis

INTRODUCTION

Hemodialysis (HD) is associated with high risk for cardiovascular diseases including acute myocardial infarction, stroke and congestive heart failure. C-C Motif Chemokine Ligand 2 (CCL2), also known monocyte chemotactic protein-1 (MCP-1) can be produced by a variety of cells, reaching increased levels in dyslipidemic chronic kidney disease (CKD) patients undergoing HD treatment. The main of this study was to evaluate the association between of CCL2 plasma levels and dyslipidemia in CKD patients undergoing HD.

METHODS

A cross-sectional study enrolled 160 Brazilian HD patients. CCL2 plasma levels were measured by capture ELISA. The association between CCL2 levels and dyslipidemia was investigated using linear regression, adjusted for classic and non-classical CVD risk factors.

RESULTS

A significant association was observed between CCL2 levels and dyslipidemia (P = 0.029), even after adjustment for possible confounding variables, such as age, gender, body mass index, diabetes mellitus, HD time, urea pre-hemodialysis and interdialytic weight gain (P = 0.045).

CONCLUSION

Our findings show that CCL2 levels are associated with dyslipidemia, which suggests a role of this cytokine in the pathogenesis of cardiovascular disease in HD patients. A better understanding of this pathogenesis could contribute to the discovery of new therapeutic targets that would reduce cardiovascular complications in these patients.

Tetracycline impregnation affects degradation of porcine collagen matrix in healthy and diabetic rats

OBJECTIVES

The present study evaluated the degradation of collagen matrix (CM) immersed in tetracycline (TTC) or phosphate-buffered saline (PBS) in diabetic and normoglycemic rats.

MATERIALS AND METHODS

Diabetes was induced in 15 rats by systemic streptozotocin (STZ) (experimental); 15 healthy rats served as controls. One day before implantation 60 CM disks, 5 mm in diameter, were labeled with biotin: 30 were immersed in tetracycline (TTC) and 30 in PBS. One disk of each type was implanted subdermally in each rat. Animals were euthanized after 3 weeks, and tissue specimens containing the disks were prepared for histologic analysis. Horseradish peroxidase (HRP)-conjugated streptavidin was used to detect the remaining biotinylated collagen. Residual collagen area within the CM disks was analyzed and compared to baseline.

RESULTS

Diabetes significantly increased the CM degradation. Immersion of the CM disks in a 50-mg/mL TTC solution before implantation decreased its degradation both in diabetic and normoglycemic rats.

CONCLUSIONS

Diabetes significantly increases collagen matrix degradation; immersion of collagen matrix in TTC before implantation decreases its degradation in both diabetic and normoglycemic conditions.

CLINICAL RELEVANCE

Immersion of medical collagen devices in TTC may be an effective means to decrease their resorption rate and increase their effectiveness, especially in situations with increased degradation such as diabetes.

Renal protection by low dose irbesartan in diabetic nephropathy is paralleled by a reduction of inflammation, not of endoplasmic reticulum stress

Diabetes can disrupt endoplasmic reticulum (ER) homeostasis which leads to ER stress. ER stress-induced renal apoptosis seems to be involved in the development of diabetic nephropathy. The present study was designed to investigate the contribution of reduced ER stress to the beneficial effects of an angiotensin receptor blocker. Insulin-dependent diabetes mellitus was induced by streptozotocin injections to hypertensive mRen2-transgenic rats. After 2weeks animals were treated with 0.7mg/kg/day irbesartan. Blood glucose, blood pressure and protein excretion were assessed. Expression of ER stress markers was measured by real-time PCR. Immunohistochemistry was performed to detect markers of ER stress, renal damage and infiltrating cells. Glomerulosclerosis and apoptosis were evaluated. Diabetic mRen2-transgenic rats developed renal injury with proteinuria, tubulointerstitial cell proliferation as well as glomerulosclerosis and podocyte injury. Moreover, an increase in inflammation, podocyte ER stress and apoptosis was detected. Irbesartan somewhat lowered blood pressure and reduced proteinuria, tubulointerstitial cell proliferation and glomerulosclerosis. Podocyte damage was ameliorated but markers of ER stress (calnexin, grp78) and apoptosis were not reduced by irbesartan. On the other hand, inflammatory cell infiltration in the tubulointerstitium and the glomerulus was significantly attenuated. We conclude that irbesartan reduced renal damage even in a very low dose. The beneficial effects of low dose irbesartan were paralleled by a reduction of blood pressure and inflammation but not by a reduction of ER stress and apoptosis. Thus, sustained endoplasmic reticulum stress in the kidney does not necessarily lead to increased inflammation and tubulointerstitial or glomerular injury.

Inhibition of collagen I accumulation reduces glomerulosclerosis by a Hic-5-dependent mechanism in experimental diabetic nephropathy

Glomerulosclerosis of any cause is characterized by loss of functional glomerular cells and deposition of excessive amounts of interstitial collagens including collagen I. We have previously reported that mesangial cell attachment to collagen I leads to upregulation of Hic-5 in vitro, which mediates mesangial cell apoptosis. Furthermore, glomerular Hic-5 expression was increased during the progression of experimental glomerulosclerosis. We hypothesized that reducing collagen I accumulation in glomerulosclerosis would in turn lower Hic-5 expression, reducing mesangial cell apoptosis, and thus maintaining glomerular integrity. We examined archive renal tissue from rats undergoing experimental diabetic glomerulosclerosis, treated with the transglutaminase-2 inhibitor NTU281. Untreated animals exhibited increased glomerular collagen I accumulation, associated with increased glomerular Hic-5 expression, apoptosis, and mesangial myofibroblast transdifferentiation characterized by α-smooth muscle actin (α-SMA) expression. NTU281 treatment reduced glomerular collagen I accumulation, Hic-5 and α-SMA expression, and apoptosis. Proteinurea and serum creatinine levels were significantly reduced in animals with reduced Hic-5 expression. In vitro studies of Hic-5 knockdown or overexpression show that mesangial cell apoptosis and expression of both α-SMA and collagen I are Hic-5 dependent. Together, these data suggest that there exists, in vitro and in vivo, a positive feedback loop whereby increased levels of collagen I lead to increased mesangial Hic-5 expression favoring not only increased apoptosis, but also mesangial myofibroblast transdifferentiation and increased collagen I expression. Prevention of collagen I accumulation interrupts this Hic-5-dependent positive feedback loop, preserving glomerular architecture, cellular phenotype, and function.

Podocyte as a potential target of inflammation: role of pioglitazone hydrochloride in patients with type 2 diabetes

OBJECTIVE

To observe the effects of pioglitazone hydrochloride on urinary sediment podocalyxin and monocyte chemoattractant protein-1 (MCP-1) excretion in patients with type 2 diabetes and to explore its possible renoprotective mechanisms.

METHODS

Ninety-eight patients with uncontrolled type 2 diabetes, who were previously prescribed metformin, acarbose, or both, were randomly assigned to a DP group (add-on pioglitazone; n = 49) or a DS group (add-on sulfonylurea; n = 49).

RESULTS

After 12 weeks of treatment, both add-on pioglitazone therapy (the DP group) and add-on sulfonylurea therapy (the DS group) demonstrated a similar improvement in fasting blood glucose and hemoglobin A1c, but systolic and diastolic blood pressure declined significantly in only the DP group. Moreover, the DP group showed significantly better efficacy in reducing urinary MCP-1 excretion in comparison with the DS group. Furthermore, both urinary albumin and urinary sediment podocalyxin excretion decreased significantly in the DP group but not in the DS group. The urinary sediment podocalyxin to creatinine ratio had a positive correlation with urinary albumin to creatinine ratio (r = 0.624; P<.01) and urinary MCP-1 to creatinine ratio (r = 0.346; P<.01).

CONCLUSION

Pioglitazone treatment revealed a podocyte-protective capacity in patients with type 2 diabetes, and the underlying mechanisms may be partly attributed to its effective suppression of excessive local renal inflammation.

Increased inflammatory biomarkers in hypertensive type 2 diabetic patients: improvement after angiotensin II type 1 receptor blockade

Diabetes and hypertension increasingly are recognized as pro-inflammatory conditions. We tested the hypothesis that in patients with hypertension and type 2 diabetes, blood pressure (BP) reduction with an angiotensin receptor blocker (ARB), valsartan, or with a beta blocker, atenolol, is associated with a decreased inflammatory response. Normotensive subjects and hypertensive patients with type 2 diabetes (40 to 70 years of age) participated in the study. Patients (n = 28) were randomized to double-blind treatment for 1 year with valsartan (80-160 mg) or atenolol (50-100 mg) daily, added to previous therapy. Age-matched controls (n = 12) were also studied. Serum levels of cytokines (IL-6, IL-18), chemokines (MCP-1), and adhesion molecules (sICAM, sE-selectin) were measured by enzyme-linked immunosorbent assay (ELISA) as indices of systemic and vascular inflammation, before and 1 year after treatment. BP was similarly reduced by valsartan and atenolol. Glycemic control and lipid profiles were comparable in the two groups and did not change significantly with antihypertensive therapy. Serum levels of all inflammatory markers were increased in patients before treatment (by two- to four-fold vs. controls, P < .05). IL-6, IL-18, sICAM, and MCP-1 levels were reduced by valsartan (three-fold, P < .05). Only IL-18 was reduced by atenolol compared with pretreatment levels (P < .05). These data indicate that proinflammatory mediators are significantly increased in hypertensive type 2 diabetic patients and that despite similar BP lowering by valsartan and atenolol and similar glucose levels in both treated groups, global inflammatory status was improved only in the valsartan group. Our findings suggest that antihypertensive treatment, particularly with an ARB, ameliorates inflammatory processes in diabetic hypertensive patients. Such effects, which are independent of BP and glycemic control, may contribute to cardiovascular protection.

Opposing effects of diabetes and tetracycline on the degradation of collagen membranes in rats

BACKGROUND

Increased collagenolytic activity, characteristic of uncontrolled diabetes, may compromise collagen membrane (CM) survival. Tetracycline (TCN) possesses anticollagenolytic properties and delays CM degradation in healthy animals. This study evaluates the degradation of TCN--immersed and -non-immersed CMs in rats with diabetes compared to those with normoglycemia.

METHODS

Diabetes was induced in 15 12-week-old male Wistar rats by injection of 65 mg/kg streptozotocin. The control group consisted of 15 rats with normoglycemia. Sixty bilayered CM disks were labeled before implantation with aminohexanoyl-biotin-N-hydroxy-succinimide ester, of which 30 were immersed in 50 mg/mL TCN solution (experimental) or phosphate-buffered saline (PBS) (control). In each animal, two disks (control and experimental) were implanted in two midsagittal calvarial defects in the parietal bone. Similar non-implanted disks served as baseline. After 3 weeks, animals were euthanized, and the calvaria and overlying soft tissues were processed for demineralized histologic analysis. Horseradish peroxidase-conjugated streptavidin was used to detect the biotinylated collagen. The area of residual collagen within the membrane disks was measured and analyzed with a digital image analysis system. Several slides from each specimen were also stained with hematoxylin and eosin. Statistical analysis consisted of paired and unpaired t tests.

RESULTS

The amount of residual collagen in PBS-immersed disks was lower in rats with diabetes compared to rats with normoglycemia (69% of baseline versus 93%, respectively, P <0.001). TCN immersion increased the amount of residual collagen contents in both diabetic (83% of baseline) and healthy (97.5% of baseline) animals (P <0.0001).

CONCLUSION

Diabetes increases CM degradation, whereas immersion in 50 mg/mL TCN solution before implantation presents an opposite effect.

Hypertensive nephropathy in children - do we diagnose early enough?

BACKGROUND/AIMS

The aim was to evaluate the level of neutrophil gelatinase-associated lipocalin (NGAL), interleukin 18 (IL-18) and retinol binding protein (RBP) in children with primary hypertension and no features of hypertensive nephropathy.

METHODS

The study group consisted of 19 children (15 males) aged 14.8 ± 2.18 years with primary hypertension. Estimated glomerular filtration rate (eGFR) and albumin/creatinine ratio (ACR) were within the normal range. Mean blood pressure (BP) was 141/79 mmHg (mean systolic BP percentile was 98, mean diastolic BP percentile was 80). Ambulatory BP measurement (ABPM), blood and urine biochemical measurements and features of end organ damage were assessed. The control group consisted of 20 healthy children.

RESULTS

Hypertensive children showed significantly increased serum and urine NGAL concentration vs controls. Urine RBP was significantly higher in the study group vs controls. A positive correlation was found between urine NGAL and the index of mean systolic BP measured in ABPM, between urine IL-18 and the index of office diastolic BP, between serum NGAL and ACR, and between urine NGAL concentration and serum HDL.

CONCLUSION

In children with primary hypertension, increased serum and urine NGAL may reflect kidney injury earlier than typical markers of hypertensive nephropathy.

Protective effect of TRPV1 against renal fibrosis via inhibition of TGF-β/Smad signaling in DOCA-salt hypertension

To investigate the effects of the transient receptor potential vanilloid type 1 (TRPV1) channel on renal extracellular matrix (ECM) protein expression including collagen deposition and the transforming growth factor β (TGF-β)/Smad signaling pathway during salt-dependent hypertension, wild-type (WT) and TRPV1-null (TRPV1⁻/⁻) mutant mice were uninephrectomized and given deoxycorticosterone acetate (DOCA)-salt for 4 wks. TRPV1 gene ablation exaggerated DOCA-salt-induced impairment of renal function as evidenced by increased albumin excretion (μg/24 h) compared with WT mice (83.7 ± 7.1 versus 28.3 ± 4.8, P < 0.05), but had no apparent effect on mean arterial pressure (mmHg) as determined by radiotelemetry (141 ± 4 versus 138 ± 3, P > 0.05). Morphological analysis showed that DOCA-salt-induced glomerulosclerosis, tubular injury and macrophage infiltration (cells/mm²) were increased in TRPV1⁻/⁻ compared with WT mice (0.74 ± 0.08 versus 0.34 ± 0.04; 3.14 ± 0.26 versus 2.00 ± 0.31; 68 ± 5 versus 40 ± 4, P < 0.05). Immunostaining studies showed that DOCA-salt treatment decreased nephrin but increased collagen type I and IV as well as phosphorylated Smad2/3 staining in kidneys of TRPV1⁻/⁻ compared with WT mice. Hydroxyproline assay and Western blot showed that DOCA-salt treatment increased collagen content (μg/mg dry tissue) and fibronectin protein expression (%β-actin arbitrary units) in the kidney of TRPV1⁻/⁻ compared with WT mice (26.7 ± 2.7 versus 17.4 ± 1.8; 0.93 ± 0.07 versus 0.65 ± 0.08, P < 0.05). Acceleration of renal ECM protein deposition in DOCA-salt-treated TRPV1⁻/⁻ mice was accompanied by increased TGF-β1, as well as phosphorylation of Smad2/3 protein expression (%β-actin arbitrary units) compared with DOCA-salt-treated WT mice (0.61 ± 0.07 versus 0.32 ± 0.05; 0.57 ± 0.07 versus 0.25 ± 0.05; 0.71 ± 0.08 versus 0.40 ± 0.06, P < 0.05). These results show that exaggerated renal functional and structural injuries are accompanied by increased production of ECM protein and activation of the TGF-β/Smad2/3 signaling pathway. These data suggest that activation of TRPV1 attenuates the progression of renal fibrosis possibly via suppression of the TGF-β and its downstream regulatory signaling pathway.

Novel C-C chemokine receptor 2 antagonists in metabolic disease: a review of recent developments

INTRODUCTION

C-C chemokine ligand 2 (CCL2), also known as monocyte chemoattractant protein-1, and its receptor, C-C chemokine receptor 2 (CCR2), play important roles in various inflammatory diseases. Recently, it has been reported that the CCL2/CCR2 pathway also has an important role in the pathogenesis of metabolic syndrome through its association with obesity and related systemic complications.

AREAS COVERED

This review focuses on the roles of CCR2 in the pathogenesis of adipose tissue inflammation and other organ damage associated with metabolic syndrome, which is still a matter of debate in many studies. It also covers the use of novel CCR2 antagonists as therapies in such conditions.

EXPERT OPINION

There is abundant experimental evidence that the CCL2/CCR2 pathway may be involved in chronic low-grade inflammation of adipose tissue in obesity and related metabolic diseases. Although animal models of diabetes and obesity, as well as human trials, have produced controversial results, there is continued interest in the roles of CCR2 inhibition in metabolic disease. Further identification of the mechanisms for recruitment and activation of phagocytes and determination of the roles of other chemokines are needed. Future study of these fundamental questions will provide a clearer understanding of adipose tissue biology and potential therapeutic targets for treatment of obesity-related metabolic disease, including diabetic nephropathy.

High-dose enalapril treatment reverses myocardial fibrosis in experimental uremic cardiomyopathy

AIMS

Patients with renal failure develop cardiovascular alterations which contribute to the higher rate of cardiac death. Blockade of the renin angiotensin system ameliorates the development of such changes. It is unclear, however, to what extent ACE-inhibitors can also reverse existing cardiovascular alterations. Therefore, we investigated the effect of high dose enalapril treatment on these alterations.

METHODS

Male Sprague Dawley rats underwent subtotal nephrectomy (SNX, n = 34) or sham operation (sham, n = 39). Eight weeks after surgery, rats were sacrificed or allocated to treatment with either high-dose enalapril, combination of furosemide/dihydralazine or solvent for 4 weeks. Heart and aorta were evaluated using morphometry, stereological techniques and TaqMan PCR.

RESULTS

After 8 and 12 weeks systolic blood pressure, albumin excretion, and left ventricular weight were significantly higher in untreated SNX compared to sham. Twelve weeks after SNX a significantly higher volume density of cardiac interstitial tissue (2.57±0.43% in SNX vs 1.50±0.43% in sham, p<0.05) and a significantly lower capillary length density (4532±355 mm/mm(3) in SNX vs 5023±624 mm/mm(3) in sham, p<0.05) were found. Treatment of SNX with enalapril from week 8-12 significantly improved myocardial fibrosis (1.63±0.25%, p<0.05), but not capillary reduction (3908±486 mm/mm(3)) or increased intercapillary distance. In contrast, alternative antihypertensive treatment showed no such effect. Significantly increased media thickness together with decreased vascular smooth muscles cell number and a disarray of elastic fibres were found in the aorta of SNX animals compared to sham. Both antihypertensive treatments failed to cause complete regression of these alterations.

CONCLUSIONS

The study indicates that high dose ACE-I treatment causes partial, but not complete, reversal of cardiovascular changes in SNX.

Rosuvastatin prevents proteinuria and renal inflammation in nitric oxide-deficient rats

OBJECTIVE

The aim of the present study was to assess the effects of rosuvastatin on renal injury and inflammation in a model of nitric oxide deficiency.

METHODS

Male Wistar rats were randomly divided into four groups (n = 10/group) and treated for 28 days with saline (CTRL); 30 mg/kg/day L-NAME (L-name); L-NAME and 20 mg/kg/day rosuvastatin (L-name+ROS-20); or L-NAME and 2 mg/kg/day rosuvastatin (L-name+ROS-2). Systolic blood pressure was measured by plethysmography in the central artery of the tail. The serum total cholesterol, triglycerides, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, creatinine, nitric oxide, interleukin-6, and tumor necrosis factor alpha levels were analyzed. Urine samples were taken to measure the albumin: urinary creatinine ratio. Kidneys were sectioned and stained with hematoxylin/eosin and Masson's trichrome. Immunohistochemical analysis of the renal tissue was performed to detect macrophage infiltration of the glomeruli.

RESULTS

The systolic blood pressure was elevated in the L-name but not the L-name+rosuvastatin-20 and L-name+rosuvastatin-2 groups. The L-name group had a significantly reduced nitric oxide level and an increased interleukin-6 and tumor necrosis factor alpha level, albumin: urinary creatinine ratio and number of macrophages in the renal glomeruli. Rosuvastatin increased the nitric oxide level in the L-name+rosuvastatin-2 group and reduced the interleukin-6 and tumor necrosis factor alpha levels, glomerular macrophage number and albumin:urinary creatinine ratio in the L-name+rosuvastatin-20 and L-name+rosuvastatin-2 groups.

CONCLUSION

Rosuvastatin treatment reduced glomerular damage due to improvement in the inflammatory pattern independent of the systolic blood pressure and serum lipid level. These effects may lead to improvements in the treatment of kidney disease.

Octylguanidine ameliorates the damaging effect of mercury on renal functions

Mercurials are known to induce morphological and functional modifications in kidney. The protective effect of octylguanidine on the injury induced by Hg(2+) on renal functions was studied. Octylguanidine administered at a dose of 10 mg/kg body weight prevented the damage induced by Hg(2+) administration at a dose of 3 mg/kg body weight. The findings indicate that octylguanidine spared mitochondria from Hg(2+)-poisoning by preserving their ability to retain matrix content, such as accumulated Ca(2+) and pyridine nucleotides. The hydrophobic amine also protected mitochondria from the Hg(2+)-induced loss of the transmembrane potential, and from the oxidative injury of mitochondrial DNA. In addition, octylguanidine maintained renal functions, such as normal values of creatinine clearance and blood urea nitrogen (BUN), and serum creatinine after Hg(2+) administration. It is proposed that octylguanidine protects kidney by inhibiting Hg(2+) uptake to kidney tissue, and in consequence its binding to mitochondrial membrane through a screening phenomenon, in addition to its known action as inhibitor of permeability transition.

MCP-1: chemoattractant with a role beyond immunity: a review

BACKGROUND

Monocyte Chemoattractant Protein (MCP)-1, a potent monocyte attractant, is a member of the CC chemokine subfamily. MCP-1 exerts its effects through binding to G-protein-coupled receptors on the surface of leukocytes targeted for activation and migration. Role of MCP-1 and its receptor CCR2 in monocyte recruitment during infection or under other inflammatory conditions is well known.

METHOD

A comprehensive literature search was conducted from the websites of the National Library of Medicine (http://www.ncbl.nlm.nih.gov) and Pubmed Central, the US National Library of Medicine's digital archive of life sciences literature (http://www.pubmedcentral.nih.gov/). The data was assessed from books and journals that published relevant articles in this field.

RESULT

Recent and ongoing research indicates the role of MCP-1 in various allergic conditions, immunodeficiency diseases, bone remodelling, and permeability of blood - brain barrier, atherosclerosis, nephropathies and tumors.

CONCLUSION

MCP-1 plays an important role in pathogenesis of various disease states and hence MCP-1 inhibition may have beneficial effects in such conditions.

Effect of Nippostrongylus brasiliensis L3 ES on inflammatory mediator gene transcription in lipopolysaccharide lung inflammation

The anti-inflammatory properties of parasitic helminths have been largely linked to their excretory-secretory (ES) products. Some studies have noted a lack of TNF-alpha production and limited recruitment of neutrophils into the lungs after Nippostrongylus brasiliensis infection. We previously reported that instillation of ES from L3 larvae of N. brasiliensis to the lungs could inhibit the recruitment of neutrophils on a background of LPS-induced inflammation. A similar reduction in neutrophil recruitment was observed in this study. This reduction was associated with the significant inhibition in gene transcription of the adhesion molecule, ICAM-1, and the chemokine, MIP-2 in bronchoalveolar lavage (BAL) cells. The LPS-stimulated gene transcription of the pro-inflammatory cytokines TNF-alpha and IL-1beta was also significantly reduced by L3 ES. Inducible nitric oxide synthase (iNOS) is normally elevated in classically activated macrophages, however, in this case gene transcription of iNOS was inhibited by L3 ES and may suggest a phenotype change to anti-inflammatory. The general inhibition of pro-inflammatory mediators observed in this study suggests that infective stage L3 larvae excrete and/or secrete inhibitory products capable of modifying the normally potent LPS inflammatory response.

Renoprotection by statins is linked to a decrease in renal oxidative stress, TGF-beta, and fibronectin with concomitant increase in nitric oxide bioavailability

Clinical and experimental studies have provided evidence suggesting that statins exert renoprotective effects. To investigate the mechanisms by which statins may exert renoprotection, we utilized the hypertensive Dahl salt-sensitive (DS) rat model, which manifests cardiovascular and renal injury linked to increased angiotensin II-dependent activation of NADPH oxidase and decreased nitric oxide (NO) bioavailability. DS rats given high salt diet (4% NaCl) for 10 wk exhibited hypertension [systolic blood pressure (SBP) 200 +/- 8 vs. 150 +/- 2 mmHg in normal salt diet (0.5% NaCl), P < 0.05], glomerulosclerosis, and proteinuria (158%). This was associated with increased renal oxidative stress demonstrated by urinary 8-F(2alpha)-isoprostane excretion and NADPH oxidase activity, increased protein expression of transforming growth factor (TGF)-beta (63%) and fibronectin (181%), increased mRNA expression of the proinflammatory molecules monocyte chemoattractant protein-1 (MCP-1) and lectin-like oxidized LDL receptor-1 (LOX-1), as well as downregulation of endothelial NO synthase (eNOS) activity (-44%) and protein expression. Return to normal salt had no effect on SBP or any of the measured parameters. Atorvastatin (30 mg.kg(-1).day(-1)) significantly attenuated proteinuria and glomerulosclerosis and normalized renal oxidative stress, TGF-beta1, fibronectin, MCP-1 and LOX-1 expression, and eNOS activity and expression. Atorvastatin-treated rats showed a modest reduction in SBP that remained in the hypertensive range (174 +/- 8 mmHg). Atorvastatin combined with removal of high salt normalized SBP and proteinuria. These findings suggest that statins mitigate hypertensive renal injury by restoring the balance among NO, TGF-beta1, and oxidative stress and explain the added renoprotective effects observed in clinical studies using statins in addition to inhibitors of the renin-angiotensin system.

Can rodent models of diabetic kidney disease clarify the significance of early hyperfiltration?: recognizing clinical and experimental uncertainties

In the past, hyperfiltration and increased glomerular capillary pressure have been identified as important determinants of the development of DN (diabetic nephropathy). Recently, some basic research and clinical reviews on DN have omitted identifying hyperfiltration as an important risk factor. At the same time, different rodent models of DN have been described without and with documented hyperfiltration. In the present review, the importance of hyperfiltration is reassessed, reviewing key clinical and research studies, including the first single nephron studies in a mouse model of DN. From clinical studies of Type 1 and Type 2 diabetes mellitus, it is clear that many patients do not have early hyperfiltration and, even when present, its contribution to subsequent DN remains uncertain. Key mechanisms underlying hyperfiltration in rodent models are reviewed. Findings on intrarenal NO metabolism and the control of single-nephron GFR (glomerular filtration rate) in rodent models of DN are also presented. Characterization of valid experimental models of DN should include a careful delineation of the absence or presence of early hyperfiltration, with special efforts made to establish the specific role hyperfiltration may play in the emergence of DN.

The monocyte chemoattractant protein-1/cognate CC chemokine receptor 2 system affects cell motility in cultured human podocytes

In crescentic glomerulonephritis (GN), monocyte chemoattractant protein-1 (MCP-1) is overexpressed within the glomeruli, and MCP-1 blockade has renoprotective effects. Adult podocytes are in a quiescent state, but acquisition of a migratory/proliferative phenotype has been described in crescentic GN and implicated in crescent formation. The cognate CC chemokine receptor 2 (CCR2), the MCP-1 receptor, is expressed by other cell types besides monocytes and has been implicated in both cell proliferation and migration. We investigated whether MCP-1 binding to CCR2 can induce a migratory/proliferative response in cultured podocytes. MCP-1 binding to CCR2 enhanced podocyte chemotaxis/haptotaxis in a concentration-dependent manner and had a modest effect on cell proliferation. Closure of a wounded podocyte monolayer was delayed by CCR2 blockade, and CCR2 was overexpressed at the wound edge, suggesting a role for CCR2 in driving podocyte migration. Immunohistochemical analysis of kidney biopsies from patients with crescentic GN demonstrated CCR2 expression in both podocytes and cellular crescents, confirming the clinical relevance of our in vitro findings. In conclusion, the MCP-1/CCR2 system is functionally active in podocytes and may be implicated in the migratory events triggered by podocyte injury in crescentic GN and other glomerular diseases.

Renal injury in streptozotocin-diabetic Ren2-transgenic rats is mainly dependent on hypertension, not on diabetes

Induction of streptozotocin (STZ) diabetes in hypertensive rats transgenic for the mouse ren-2 gene (TGR) has been described as a model of progressive diabetic nephropathy. We investigated the long-term course of STZ diabetes in TGR and appropriate Sprague-Dawley control rats (SD) and tested the role of angiotensin-dependent hypertension by treating rats with the angiotensin II type 1 receptor blocker losartan (1 mg·kg−1·day−1) via osmotic minipumps. Five weeks after STZ injection, diabetes developed in TGR and SD. Urinary albumin excretion was increased by diabetes and, to a much higher degree, by hypertension. The effects of hypertension and diabetes were not additive, and only the effects of hypertension were ameliorated by losartan. A similar pattern was observed for cell proliferation and macrophage infiltration in the kidney. In contrast, the effects of hypertension and diabetes on glomerular collagen IV accumulation were additive 5 wk after STZ injection. In a long-term study for 20 wk after STZ, survival was better in STZ-treated TGR than in normoglycemic TGR, whereas all SD survived. Impaired creatinine clearance and increased macrophage infiltration as well as glomerular and interstitial matrix deposition were prominent in TGR compared with SD, regardless of the presence or absence of diabetes. In conclusion, STZ diabetes in TGR may be useful to study glomerular and interstitial matrix deposition early in the course of diabetes. However, the long-term course of this animal model resembles severe hypertensive nephrosclerosis, rather than progressive diabetic nephropathy.

Beneficial effects of docosahexaenoic acid on active avoidance performance in 1K-1C hypertensive rats

The present study evaluated the role of chronic docosahexaenoic acid (DHA) supplementation on active avoidance learning task performance in experimental hypertension. Male Wistar rats were randomly divided into five experimental groups as follows: control, sham, DHA treated, 1K-1C hypertensive, and 1K-1C hypertensive+DHA treated. Hypertension was induced in 1K-1C rats via placing a silver clip (0.20-mm ID) around the left renal artery following a right uninephrectomy. DHA (36 mg/kg/day) was given to the treatment groups for 60 days by gastric gavage. Arterial blood pressure was measured by using the tail-cuff method. Active avoidance responses were determined by an automated shuttle-box. In brain (cerebrum) and hippocampus tissues, thiobarbituric acid reactive substances (TBARS) and nitrite levels were measured by fluorometric methods. DHA supplementation decreased blood pressure in hypertensive rats. Data from active avoidance training indicated that performance of active avoidance learning tasks were significantly impaired in 1K-1C hypertensive rats, but was completely restored by DHA supplementation. Increased cerebrum TBARS levels in 1K-1C rats were abolished by DHA administration. Cerebrum nitrite levels were lower in the DHA, 1K-1C and 1K-1C+DHA treated groups compared to controls. Hippocampus nitrite levels were lower in DHA treated and 1K-1C hypertensive rats compared to controls and higher in 1K-1C+DHA treated rats compared to the 1K-1C group. Our data indicates that DHA supplementation improves the performance of active avoidance learning tasks which is impaired in experimental hypertension. These affirmative changes might be due to a DHA-induced decrease in lipid peroxidation which may in turn limit the consumption of nitric oxide (NO) which promotes active avoidance learning.

Hypertension induces oxidative stress but not macrophage infiltration in the kidney in the early stage of experimental diabetes mellitus

BACKGROUND

The combination of diabetes and hypertension increases the incidence and severity of kidney disease in an additive manner. Inflammatory and oxidative stress mechanisms contribute to renal damage in both diabetes and hypertension. Therefore, we investigated whether renal macrophage infiltration and oxidative stress events are additive from the beginning in diabetic animals with coexisting hypertension.

METHODS

Diabetes was induced in spontaneously hypertensive rats (SHRs) and their genetically normotensive control Wistar Kyoto (WKY) rats by streptozotocin injection at 12 weeks of age for 10 days, and the effects of hyperglycemia on renal macrophage infiltration and oxidative stress were evaluated.

RESULTS

Blood pressure was higher in SHR than in WKY groups. Markers of oxidative stress-induced DNA and protein modification, 8-hydroxy- 2'-deoxyguanosine (8-OHdG) and nitrotyrosine, respectively, and the antioxidant glutathione levels were found to be similar in WKY-control and WKY-diabetic groups. However, 8-OHdG was significantly elevated (p = 0.014), the nitrotyrosine level tended to be elevated (p = 0.068) and the glutathione level was significantly reduced (p = 0.034) in the SHR-diabetic group compared to the SHR-control group. On the other hand, glomerular and tubulointerstitial macrophage infiltration was significantly higher in both WKY-diabetic and SHR-diabetic groups than the respective control groups.

CONCLUSIONS

A short duration of diabetes mellitus induces renal oxidative stress in the presence of hypertension; however, renal macrophage infiltration becomes evident in early diabetes regardless of the presence or absence of hypertension. We conclude that the combination of diabetes and hypertension adversely affects oxidative stress in the kidney, but the combination has no additive effect on renal macrophage infiltration, at least in early diabetes.

Renal and vascular hypertension-induced inflammation: role of angiotensin II

PURPOSE OF REVIEW

We will focus on the recent findings concerning the inflammatory response in vascular and renal tissues caused by hypertension.

RECENT FINDINGS

Angiotensin II is one of the main factors involved in hypertension-induced tissue damage. This peptide regulates the inflammatory process. Angiotensin II activates circulating cells, and participates in their adhesion to the activated endothelium and subsequent transmigration through the synthesis of adhesion molecules, chemokines and cytokines. Among the intracellular signals involved in angiotensin II-induced inflammation, the production of reactive oxygen species and the activation of nuclear factor-kappaB are the best known.

SUMMARY

The pharmacological blockade of angiotensin II actions, by angiotensin-converting enzyme inhibitors or angiotensin receptor antagonists, results in beneficial organ protective effects, in addition to the effects of these agents on blood pressure control, that can be explained by the blockade of the angiotensin II-induced pro-inflammatory response. These data provide a rationale for the use of blockers of the renin-angiotensin system to prevent vascular and renal inflammation in patients with hypertension.

Angiotensin II compartmentalization within the kidney: effects of salt diet and blood pressure alterations

PURPOSE OF REVIEW

All components of the renin-angiotensin-aldosterone system are present within the kidney. Renin, renin receptor, angiotensinogen and angiotensin AT1 and AT2 receptor and aldosterone synthase messenger RNA and protein are present in close proximity to the renal vasculature and tubules. The interaction between the different components of the renin-angiotensin-aldosterone system determines the level of activity of this system and in turn may influence the regulation of blood pressure and renal sodium handling.

RECENT FINDINGS

Angiotensin through the stimulation of its subtype AT2 receptor regulates sodium excretion, renin synthesis and secretion. Aldosterone synthase mRNA and protein are expressed in glomeruli, renal vasculature and tubules, and are regulated by angiotensin AT1 receptor, diabetes and salt. Although aldosterone is known to influence renal tubular channels with the subsequent enhancement of sodium reabsorption, it is not clear if the renally produced aldosterone also influences renal sodium handling or blood pressure regulation. In addition, angiotensin II influences kidney function and structure through the stimulation of renal inflammation. New data suggest that the renal AT1 receptor plays an important role in the determination of blood pressure levels, and this effect is unique and non-redundant in the actions of extrarenal AT1 receptors.

SUMMARY

The finding of new functions and components of the renin-angiotensin-aldosterone system clearly adds new knowledge to our understanding of how angiotensin II influences the kidney and blood pressure.