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

Risk factors for acute kidney injury and kidney relapse in patients with lupus podocytopathy

Background

Patients with lupus podocytopathy show a high incidence of acute kidney injury (AKI) and relapse, but the risk factors and mechanisms were unclear. This study analysed the clinicopathological features and risk factors for AKI and relapse in lupus podocytopathy patients.

Methods

The cohort of lupus podocytopathy was generated by screening the biopsies of patients with lupus nephritis (LN) from 2002 to 2022 and was divided into the mild glomerular lesion (MGL) and focal segmental glomerulosclerosis (FSGS) groups based on glomerular morphological characteristics. The acute (ATI) and chronic (CTI) tubulointerstitial lesions were semi-quantitatively scored. Logistic and Cox regressions were employed to identify the risk factors for AKI and relapse, respectively.

Results

Among 6052 LN cases, 98 (1.6%) were diagnosed as lupus podocytopathy, with 71 in the MGL group and 27 in the FSGS group. All patients presented with nephrotic syndrome and 33 (34.7%) of them had AKI. Seventy-seven (78.6%) patients achieved complete renal response (CRR) within 12 weeks of induction treatment, in which there was no difference in the CRR rate between glucocorticoid monotherapy and combination therapy with glucocorticoids plus immunosuppressants. Compared with the MGL group, patients in the FSGS group had significantly higher incidences of hypertension and haematuria; in addition, they had higher Systemic Lupus Erythematosus Disease Activity Index 2000, ATI and CTI scores but a significantly lower CRR rate. Urinary protein ≥7.0 g/24 h and serum C3 ≤0.750 g/l were independent risk factors for AKI. During a median follow-up of 78 months, 57 cases (60.0%) had relapse and none reached the kidney endpoint. Failure to achieve CRR within 12 weeks, maintenance with glucocorticoid monotherapy and AKI at onset were independent risk factors for kidney relapse.

Conclusions

In this study, histological subtypes of lupus podocytopathy were found to be associated with clinical features and treatment response. In addition, several risk factors associated with AKI occurrence and kidney relapse were identified.

Advances in understanding and treating diabetic kidney disease: focus on tubulointerstitial inflammation mechanisms

Diabetic kidney disease (DKD) is a serious complication of diabetes that can lead to end-stage kidney disease. Despite its significant impact, most research has concentrated on the glomerulus, with little attention paid to the tubulointerstitial region, which accounts for the majority of the kidney volume. DKD's tubulointerstitial lesions are characterized by inflammation, fibrosis, and loss of kidney function, and recent studies indicate that these lesions may occur earlier than glomerular lesions. Evidence has shown that inflammatory mechanisms in the tubulointerstitium play a critical role in the development and progression of these lesions. Apart from the renin-angiotensin-aldosterone blockade, Sodium-Glucose Linked Transporter-2(SGLT-2) inhibitors and new types of mineralocorticoid receptor antagonists have emerged as effective ways to treat DKD. Moreover, researchers have proposed potential targeted therapies, such as inhibiting pro-inflammatory cytokines and modulating T cells and macrophages, among others. These therapies have demonstrated promising results in preclinical studies and clinical trials, suggesting their potential to treat DKD-induced tubulointerstitial lesions effectively. Understanding the immune-inflammatory mechanisms underlying DKD-induced tubulointerstitial lesions and developing targeted therapies could significantly improve the treatment and management of DKD. This review summarizes the latest advances in this field, highlighting the importance of focusing on tubulointerstitial inflammation mechanisms to improve DKD outcomes.

Long Term High Protein Diet Feeding Alters the Microbiome and Increases Intestinal Permeability, Systemic Inflammation and Kidney Injury in Mice

SCOPE

This study evaluates the effects of a chronic high protein diet (HPD) on kidney injury, intestinal permeability and gut microbiota perturbations in a mouse model.

METHOD AND RESULTS

Mice are fed a diet containing either 20% or 52% energy from protein for 24 weeks; protein displaced an equivalent amount of wheat starch. The HPD does not alter glycemic control or body weight. The HPD induces kidney injury as evidenced by increase in albuminuria, urinary kidney injury molecule-1, blood urea nitrogen, urinary isoprostanes and renal cortical NF-κB p65 gene expression. HPD decreases intestinal occludin gene expression, increases plasma endotoxin and plasma monocyte chemoattractant protein-1, indicating intestinal leakiness and systemic inflammation. Cecal microbial analysis reveals that HPD feeding does not alter alpha diversity; however, it does alter beta diversity, indicating an altered microbial community structure with HPD feeding. Predicted metagenome pathway analysis demonstrates a reduction in branched-chain amino acid synthesis and an increase of the urea cycle with consumption of a HPD.

CONCLUSION

These results demonstrate that long term HPD consumption in mice causes albuminuria, systemic inflammation, increase in gastrointestinal permeability and is associated with gut microbiome remodeling with an increase in the urea cycle pathway, which may contribute to renal injury.

Rab27a dependent exosome releasing participated in albumin handling as a coordinated approach to lysosome in kidney disease

Exosomes are increasingly recognized as vehicles of intercellular communication. However, the role of exosome in maintaining cellular homeostasis under stress conditions remained unclear. Here we show that Rab27a expression was upregulated exclusively in tubular epithelial cells (TECs) during proteinuria nephropathy established by adriamycin (ADR) injection and 5/6 nephrectomy as well as in chronic kidney disease patients, leading to the increased secretion of exosomes carrying albumin. The active exosome production promoted tubule injury and inflammation in neighboring and the producing cells. Interferon regulatory factor 1 (IRF-1) was found as the transcription factor contributed to the upregulation of Rab27a. Albumin could be detected in exosome fraction and co-localized with exosome marker CD63 indicating the secretion of albumin into extracellular space by exosomes. Interestingly, inhibition of exosome release accelerated albumin degradation which reversed tubule injury with albumin overload, while lysosome suppression augmented exosome secretion and tubule inflammation. Our findings revealed that IRF-1/Rab27a mediated exosome secretion constituted a coordinated approach to lysosome degradation for albumin handling, which lead to the augment of albumin toxicity as a maladaptive response to maintain cell homeostasis. The findings may suggest a novel therapeutic strategy for proteinuric kidney disease by targeting exosome secretion.

Mesenchymal stem/stromal cells stably transduced with an inhibitor of CC chemokine ligand 2 ameliorate bronchopulmonary dysplasia and pulmonary hypertension

Perinatal bronchopulmonary dysplasia (BPD) is defined as lung injury in preterm infants caused by various factors, resulting in serious respiratory dysfunction and high mortality. The administration of mesenchymal stem/stromal cells (MSCs) to treat/prevent BPD has proven to have certain therapeutic effects. However, MSCs can only weakly regulate macrophage function, which is strongly involved in the development of BPD. 7ND-MSCs are MSCs transfected with 7ND, a truncated version of CC chemokine ligand 2 (CCL2) that promotes macrophage activation, using a lentiviral vector. In the present study, we show in a BPD rat model that 7ND-MSC administration, but not MSCs alone, ameliorated the impaired alveolarization evaluated by volume density and surface area in the lung tissue, as well as pulmonary artery remodeling and pulmonary hypertension induced by BPD. In addition, 7ND-MSCs, but not MSCs alone, reduced M1 macrophages and the messenger RNA expressions of interleukin-6 and CCL2 in the lung tissue. Thus, the present study showed the treatment effect of 7ND-MSCs in a BPD rat model, which was more effective than that of MSCs alone.

Lithium ameliorates tubule-interstitial injury through activation of the mTORC2/protein kinase B pathway

Tubule-interstitial injury (TII) is a critical step in the progression of renal disease. It has been proposed that changes in proximal tubule (PT) albumin endocytosis plays an important role in the development of TII. Some reports have shown protective effects of lithium on kidney injury animal models that was correlated to proteinuria. We tested the hypothesis that lithium treatment ameliorates the development of TII due to changes in albumin endocytosis. Two experimental models were used: (1) TII induced by albumin overload in an animal model; (2) LLC-PK1 cells, a PT cell line. Lithium treatment ameliorates TII induced by albumin overload measured by (1) proteinuria; (2) collagen deposition; (3) area of tubule-interstitial space, and (4) macrophage infiltration. Lithium treatment increased mTORC2 activity leading to the phosphorylation of protein kinase B (PKB) at Ser473 and its activation. This mechanism enhanced albumin endocytosis in PT cells, which decreased the proteinuria observed in TII induced by albumin overload. This effect did not involve changes in the expression of megalin, a PT albumin receptor. In addition, activation of this pathway decreased apoptosis in LLC-PK1 cells, a PT cell line, induced by higher albumin concentration, similar to that found in pathophysiologic conditions. Our results indicate that the protective role of lithium treatment on TII induced by albumin overload involves an increase in PT albumin endocytosis due to activation of the mTORC2/PKB pathway. These results open new possibilities in understanding the effects of lithium on the progression of renal disease.

New Understanding on the Role of Proteinuria in Progression of Chronic Kidney Disease

Proteinuria is identified as an important marker and risk factor of progression in chronic kidney disease. However, the precise mechanism of action in the progress of chronic kidney disease is still unclear. Mesangial toxicity from specific filtered compounds such as albumin-bound fatty acids and transferrin/iron, tubular overload and hyperplasia, and induction of proinflammatory molecules such as MCP-1 and inflammatory cytokines are some of the proposed mechanisms. Reversing intraglomerular hypertension with protein restriction or antihypertensive therapy may be beneficial both by diminishing hemodynamic injury to the glomeruli and by reducing protein filtration. Therefore, understanding proteinuria and its role in renal tubular interstitial inflammation and fibrosis is of great significance for the study of renal protective therapy, such as antiproteinuric treatments, and delaying the progression of chronic renal disease.

Elevated urinary monocyte chemoattractant protein-1 levels in children with Henoch-Schonlein purpura nephritis

BACKGROUND

Chemokine monocyte chemoattractant protein-1 (MCP-1) has been proved as a potential urinary biomarker in nephropathies. The aim of this study was to investigate the urinary monocyte chemoattractant protein-1 (MCP-1) levels and clinical significance in Henoch-Schonlein purpura (HSP) children with and without nephritis and determine the association of MCP-1 with proteinuria.

METHODS

A total of 261 HSP children-with or without nephritis-and 84 healthy control children were enrolled in this study. Of these, 126 HSP nephritis (HSPN) children were subdivided into three groups according to total urine protein in 24 h (TUP): Group A, mild proteinuria group with TUP <25 mg/kg; Group B, moderate proteinuria group with TUP ≥25 mg/kg and <50 mg/kg; Group C, severe proteinuria group with TUP ≥50 mg/kg. Urinary MCP-1 levels were determined by ELISA. Levels of serum creatinine (Cr), blood urea nitrogen (BUN), urinary α₁-micro globulin (α₁-MG), micro-albumin (mAlb), immunoglobulin G (IgG), transferrin (TRF) and TUP were performed to determine their associations with MCP-1.

RESULTS

Urinary MCP-1 was significantly higher in HSPN group in comparison with HSP group and controls (P < 0.05), but no significant difference was found between the HSP group and the healthy group (P > 0.05). The levels of urinary MCP-1 increased in parallel to the enhancement of total urine protein in 24 h in HSPN patients. There were statistically significant differences among these three groups of HSPN children (p < 0.05). Urinary MCP-1 correlated positively with urinary α₁-MG, mAlb, IgG, TRF and TUP in HSPN, whereas no correlation was observed with serum Cr and BUN.

CONCLUSIONS

MCP-1 was elevated in children with HSPN and correlated with proteinuria. Urinary MCP-1 could be used as a suitable, non-invasive biomarker to provide valuable information not only for the diagnosis of HSPN, but also for evaluation of severity of renal damage.

Markers of early progressive renal decline in type 2 diabetes suggest different implications for etiological studies and prognostic tests development

To identify determinants of early progressive renal decline in type 2 diabetes a range of markers was studied in 1032 patients enrolled into the 2nd Joslin Kidney Study. eGFR slopes estimated from serial measurements of serum creatinine during 5-12 years of follow-up were used to define early renal decline. At enrollment, all patients had normal eGFR, 58% had normoalbuminuria and 42% had albuminuria. Early renal decline developed in 6% and in 18% patients, respectively. As determinants, we examined baseline values of clinical characteristics, circulating markers: TNFR1, KIM-1, and FGF23, and urinary markers: albumin, KIM-1, NGAL, MCP-1, EGF (all normalized to urinary creatinine) and the ratio of EGF to MCP-1. In univariate analysis, all plasma and urinary markers were significantly associated with risk of early renal decline. When analyzed together, systolic blood pressure, TNFR1, KIM-1, the albumin to creatinine ratio, and the EGF/MCP-1 ratio remained significant with the latter having the strongest effect. Integration of these markers into a multi-marker prognostic test resulted in a significant improvement of discriminatory performance of risk prediction of early renal decline, compared with the albumin to creatinine ratio and systolic blood pressure alone. However, the positive predictive value was only 50% in albuminuric patients. Thus, markers in plasma and urine indicate that the early progressive renal decline in Type 2 diabetes has multiple determinants with strong evidence for involvement of tubular damage. However, new, more informative markers are needed to develop a better prognostic test for such decline that can be used in a clinical setting.

The Sirt1 activator, SRT1720, attenuates renal fibrosis by inhibiting CTGF and oxidative stress

The transforming growth factor-β1 (TGF-β1)/connective tissue growth factor (CTGF) pathway plays an important role in the pathogenesis and progression of chronic kidney disease. Oxidative stress is also involved in TGF-β1 signalling. Sirtuin 1 (Sirt1) exerts a number of pleiotropic effects, protecting against renal disease, including inhibiting fibrosis and oxidative metabolism. In this study, we investigated the role of the Sirt1 activator, SRT1720, in unilateral ureteral obstruction (UUO)-induced tubulointerstitial fibrosis and aimed to determine whether this role depends on the inhibition of oxidative stress and the TGF-β1/CTGF pathway. Renal fibrosis was induced by UUO in CD1 mice. SRT1720 (100 mg/kg) was administered by intraperitoneal injection for 3 days prior to UUO and this was continued for 7 days following UUO. Histological changes were examined by Masson's trichrome staining. The expression of fibrosis-related factors was evaluated by immunohistochemistry, western blot analysis and RT-qPCR. Apoptosis was also examined. We also examined the superoxide dismutase (SOD), malondialdehyde (MDA), glutathione peroxidase (GPx) and reduced glutathione (GSH) levels. UUO induced renal fibrosis and apoptosis and decreased Sirt1 expression. The administration of SRT1720 increased the Sirt1 levels and partially attenuated UUO-induced renal fibrosis and apoptosis. Furthermore, SRT1720 attenuated the levels of oxidative stress (it decreased the MDA levels, and increased the SOD, GPx and GSH levels), which suggests that it protected the cells against ROS-induced damage. Moreover, SRT1720 effectively inhibited the levels of TGF-β1/CTGF induced by UUO. On the whole, these findings indicate that the Sirt1 activator, SRT1720, exerts protective effects against UUO-induced tubulointerstitial fibrosis. The mechanisms of action of SRT1720 may include, at least in part, the suppression of renal oxidative stress and the TGF-β1/CTGF signalling pathway. The Sirt1 activator may therefore be prove to be a potent therapeutic agent for the treatment of fibrotic kidney disease.

Measures of Urinary Protein and Albumin in the Prediction of Progression of IgA Nephropathy

BACKGROUND AND OBJECTIVES

Proteinuria is an independent predictor for IgA nephropathy (IgAN) progression. Urine albumin-to-creatinine ratio (ACR), protein-to-creatinine ratio, and 24-hour urine protein excretion (UPE) are widely used for proteinuria evaluation in clinical practice. Here, we evaluated the association of these measurements with clinical and histologic findings of IgAN and explored which was the best predictor of IgAN prognosis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients with IgAN were followed up for ≥12 months, were diagnosed between 2003 and 2012, and had urine samples available (438 patients). Spot urine ACR, protein-to-creatinine ratio, and 24-hour UPE at the time of renal biopsy were measured on a Hitachi Automatic Biochemical Analyzer 7180 (Hitachi, Yokohama, Japan).

RESULTS

In our patients, ACR, protein-to-creatinine ratio, and 24-hour UPE were highly correlated (correlation coefficients: 0.71-0.87). They showed good relationships with acknowledged markers reflecting IgAN severity, including eGFR, hypertension, and the biopsy parameter (Oxford severity of tubular atrophy/interstitial fibrosis parameter). However, only ACR presented with positive association with the Oxford segmental glomerulosclerosis/adhesion parameter and extracapillary proliferation lesions. The follow-up time was 37.0 (22.0-58.0) months, with the last follow-up on April 18, 2014. In total, 124 patients reached the composite end point (30% eGFR decline, ESRD, or death). In univariate survival analysis, ACR consistently had better performance than protein-to-creatinine ratio and 24-hour UPE as represented by higher area under the curve using time-dependent survival analysis. When adjusted for well known risk factors for IgAN progression, ACR was most significantly associated with the composite end point (hazard ratio, 1.56 per 1-SD change of standard normalized square root-transformed ACR; 95% confidence interval, 1.29 to 1.89; P<0.001). Compared with protein-to-creatinine ratio and 24-hour UPE, addition of ACR to traditional risk factors resulted in more improvement in the predictive ability of IgAN progression (c statistic: ACR=0.70; protein-to-creatinine ratio =0.68; 24-hour UPE =0.69; Akaike information criterion: ACR=1217.85; protein-to-creatinine ratio =1229.28; 24-hour UPE =1234.96; P<0.001).

CONCLUSIONS

In IgAN, ACR, protein-to-creatinine ratio, and 24-hour UPE had comparable association with severe clinical and histologic findings. Compared with protein-to-creatinine ratio and 24-hour UPE, ACR showed slightly better performance in predicting IgAN progression.

Stop chronic kidney disease progression: Time is approaching

Progression of chronic kidney disease (CKD) is inevitable. However, the last decade has witnessed tremendous achievements in this field. Today we are optimistic; the dream of withholding this progression is about to be realistic. The recent discoveries in the field of CKD management involved most of the individual diseases leading the patients to end-stage renal disease. Most of these advances involved patients suffering diabetic kidney disease, chronic glomerulonephritis, polycystic kidney disease, renal amyloidosis and chronic tubulointerstitial disease. The chronic systemic inflammatory status and increased oxidative stress were also investigated. This inflammatory status influences the anti-senescence Klotho gene expression. The role of Klotho in CKD progression together with its therapeutic value are explored. The role of gut as a major source of inflammation, the pathogenesis of intestinal mucosal barrier damage, the role of intestinal alkaline phosphatase and the dietary and therapeutic implications add a novel therapeutic tool to delay CKD progression.

Therapeutic Potential of Stem Cells from Human Exfoliated Deciduous Teeth in Models of Acute Kidney Injury

Background

Acute kidney injury (AKI) is a critical condition associated with high mortality. However, the available treatments for AKI are limited. Stem cells from human exfoliated deciduous teeth (SHED) have recently gained attention as a novel source of stem cells. The purpose of this study was to clarify whether SHED have a therapeutic effect on AKI induced by ischemia-reperfusion injury.

Methods

The left renal artery and vein of the mice were clamped for 20 min to induce ischemia. SHED, bone marrow derived mesenchymal stem cells (BMMSC) or phosphate-buffered saline (control) were administered into the subrenal capsule. To confirm the potency of SHED in vitro, H₂O₂ stimulation assays and scratch assays were performed.

Results

The serum creatinine and blood urea nitrogen levels of the SHED group were significantly lower than those of the control group, while BMMSC showed no therapeutic effect. Infiltration of macrophages and neutrophils in the kidney was significantly attenuated in mice treated with SHED. Cytokine levels (MIP-2, IL-1β, and MCP-1) in mice kidneys were significantly reduced in the SHED group. In in vitro experiments, SHED significantly decreased MCP-1 secretion in tubular epithelial cells (TEC) stimulated with H₂O₂. In addition, SHED promoted wound healing in the scratch assays, which was blunted by anti-HGF antibodies.

Discussion

SHED attenuated the levels of inflammatory cytokines and improved kidney function in AKI induced by IRI. SHED secreted factors reduced MCP-1 and increased HGF expression, which promoted wound healing. These results suggest that SHED might provide a novel stem cell resource, which can be applied for the treatment of ischemic kidney injury.

The Pathogenesis and Therapeutic Implications of Tubulointerstitial Inflammation in Human Lupus Nephritis

Nephritis is a common complication of systemic lupus erythematosus for which current therapies often prove inadequate. Current lupus nephritis classification systems emphasize glomerular acuity and scarring. However, tubulointerstitial inflammation (TII) and scarring are much better predictors of progression to renal failure. It now is becoming clear that the immunologic features, and probable underlying mechanisms, are very different in lupus glomerulonephritis and TII at the time of biopsy. Although glomerulonephritis is a manifestation of systemic autoimmunity, TII is associated with local in situ adaptive immune cell networks predicted to amplify local inflammation and tissue damage. In addition, poorly defined networks of innate immune cells and effectors likely contribute to the severity of local inflammation. Defining these in situ immune mechanisms should lead to a better understanding of prognostically meaningful lupus nephritis subsets and show novel therapeutic opportunities.

CTGF siRNA ameliorates tubular cell apoptosis and tubulointerstitial fibrosis in obstructed mouse kidneys in a Sirt1-independent manner

Transforming growth factor-β1 (TGF-β1) plays an important role in the pathogenesis and progression of chronic kidney disease. Connective tissue growth factor (CTGF) is a critical fibrogenic mediator of TGF-β1. Mammalian sirtuin 1 (Sirt1) is reported to attenuate renal fibrosis by inhibiting the TGF-β1 pathway. This study was designed to detect whether the delivery of CTGF siRNA in vivo directly ameliorates renal fibrosis. Furthermore, the relationship with Sirt1 underlying the protective effect of CTGF siRNA on interstitial fibrosis and apoptosis was explored. Here, we report that the expressions of CTGF and TGF-β1 were increased while Sirt1 expression and activity were both dramatically decreased in mouse kidneys with unilateral ureteral obstruction. Recombinant human TGF-β1 treatment in HK-2 cells increased CTGF levels and remarkably decreased Sirt1 levels and was accompanied by apoptosis and release of fibrosis-related factors. Recombinant human CTGF stimulation also directly induced apoptosis and fibrosis. The CTGF siRNA plasmid ameliorated tubular cell apoptosis and tubulointerstitial fibrosis, but did not affect Sirt1 expression and activity both in vivo and in vitro. Furthermore, overexpression of Sirt1 abolished TGF-β1-induced cell apoptosis and fibrosis, while Sirt1 overexpression suppressed CTGF expression via stimulation by TGF-β1. This study provides evidence that treatment strategies involving the delivery of siRNA targeting potentially therapeutic transgenes may be efficacious. Our results suggest that the decrease in Sirt1 is associated with the upregulated expression of CTGF in renal fibrosis, and may aid in the design of new therapies for the prevention of renal fibrosis.

Crosstalk between the unfolded protein response and NF-κB-mediated inflammation in the progression of chronic kidney disease

The chronic inflammatory response is emerging as an important therapeutic target in progressive chronic kidney disease. A key transcription factor in the induction of chronic inflammation is NF-κB. Recent studies have demonstrated that sustained activation of the unfolded protein response (UPR) can initiate this NF-κB signaling phenomenon and thereby induce chronic kidney disease progression. A key factor influencing chronic kidney disease progression is proteinuria and this condition has now been demonstrated to induce sustained UPR activation. This review details the crosstalk between the UPR and NF-κB pathways as pertinent to chronic kidney disease. We present potential tools to study this phenomenon as well as potential therapeutics that are emerging to regulate the UPR. These therapeutics may prevent inflammation specifically induced in the kidney due to proteinuria-induced sustained UPR activation.

Fn14 in podocytes and proteinuric kidney disease

Non-proliferative proteinuric diseases are the most common primary glomerular disorders causing end-stage renal disease. These disorders may associate low level glomerular inflammation and podocyte expression of inflammatory mediators. However, the factors regulating podocyte expression of inflammatory mediators in vivo in non-immune disorders are poorly understood. We have now explored the regulation and role of TWEAK receptor Fn14 in mediating glomerular inflammation in cultured podocytes and in experimental and human non-immune proteinuria. Transcriptomics disclosed Fn14 and MCP-1 mRNA upregulation in glomeruli from patients with focal segmental glomerulosclerosis, as well as a correlation between the expression of both transcripts. Increased glomerular Fn14 and MCP-1 mRNA was confirmed in a second focal segmental glomerulosclerosis cohort and was also observed in membranous nephropathy. In human non-proliferative proteinuric kidney diseases podocytes displayed Fn14 and MCP-1 expression and NFκB activation. Podocyte Fn14 was increased in murine protein overload-induced proteinuria. In Fn14 knock-out mice with protein overload-induced proteinuria, glomerular and periglomerular macrophage infiltrates were reduced, as were MCP-1 mRNA and podocyte MCP-1 staining and podocyte numbers preserved as compared to wild-type counterparts. Adenovirus-mediated overexpression of TWEAK increased periglomerular macrophage infiltration in mice without prior kidney injury. In cultured podocytes inflammatory cytokines increased Fn14 mRNA and protein levels. TWEAK activated NFκB and increased MCP-1 mRNA and protein, an effect prevented by the NFκB inhibitor parthenolide. In conclusion, Fn14 activation results in NFκB-mediated pro-inflammatory effects on podocytes that may be relevant for the pathogenesis of non-proliferative proteinuric kidney disease of non-immune origin.

Immune and inflammatory role in renal disease

Chronic and acute renal diseases, irrespective of the initiating cause, have inflammation and immune system activation as a common underlying mechanism. The purpose of this review is to provide a broad overview of immune cells and inflammatory proteins that contribute to the pathogenesis of renal disease, and to discuss some of the physiological changes that occur in the kidney as a result of immune system activation. An overview of common forms of acute and chronic renal disease is provided, followed by a discussion of common therapies that have anti-inflammatory or immunosuppressive effects in the treatment of renal disease.

Inhibition of calcium(2+)/calmodulin-dependent protein kinase type IV ameliorates experimental nephrotic syndrome

OBJECTIVE

Evidence has demonstrated that Ca(2+)/calmodulin-dependent protein kinase type IV (CaMKIV) contributes to altered cytokine production by promoting the production of inflammatory cytokines. This study aimed to explore the protective role and underlying mechanisms of CaMKIV inhibition in experimental nephrotic syndrome.

METHODS

BALB/c mice received single intravenous injections of adriamycin (10 mg/kg) then were sacrificed at two, four and six weeks. In the second study, treatment with KN-93, a CaMKIV inhibitor, or vehicle administered via intraperitoneal injection was started five days after adriamycin injection. Functional and pathologic parameters, the presence of inflammatory infiltration and the expressions of pro-inflammatory cytokines were assessed.

RESULTS

The CaMKIV protein expression levels were upregulated in the mice with adriamycin nephropathy, which was significantly inhibited by KN-93 (p<0.01). As compared with the vehicle-treated controls, KN-93 treatment resulted in marked suppression of proteinuria and serum creatinine at week 6 (p<0.01), but not at two weeks after induction of the disease. KN-93 inhibited glomerulosclerosis and the development of tubulointerstitial lesions. The renal alpha-smooth muscle actin (α-SMA) expression was also significantly suppressed by KN-93 treatment at week 6 (p<0.01). Moreover, KN-93 inhibited the renal monocyte chemoattractant protein-1 (MCP-1) expression, paralleled by a reduction in the interstitial infiltration of macrophages and T-cells (p<0.01).

CONCLUSION

Our findings suggest that activation of CaMKIV signaling is involved in the progression of glomerular diseases with a proteinuric state. Our data therefore justify the development of small molecule CaMKIV inhibitors for the treatment of clinical nephrotic syndrome.

Targeting chemokines in proteinuria-induced renal disease

INTRODUCTION

Proteinuria is a common finding in glomerular diseases that contributes to the progression of chronic kidney injury. Tubular cells reabsorb the excess of albumin and other plasma proteins from the tubular lumen, triggering several pathophysiologic responses, such as overexpression of fibrogenic mediators and inflammatory chemokines. Chemokines are implicated both in the recruitment of inflammatory infiltrate and in a number of physiological and pathological processes related to protein overload.

AREAS COVERED

In recent years, the specific chemokines and their receptors and the intracellular signaling pathways involved in proteinuria-induced renal damage have been identified. This review provides an overview of the role of chemokines and their receptors in proteinuria-related renal disease and summarizes novel therapeutic approaches to restrain the progression of renal damage.

EXPERT OPINION

Inhibition of chemokine-induced biological activities is a promising therapeutic strategy in proteinuric disorders. Neutralizing antibodies and small organic molecules targeting chemokines and chemokine receptors have been proven to prevent inflammation and renal damage in experimental models of protein overload. Some of these compounds are currently being tested in human clinical trials.

Molecular targets for treatment of kidney fibrosis

Renal fibrosis is the culmination of processes driven by signaling pathways involving transforming growth factor-β family of cytokines, connective-tissue growth factor, nuclear factor κB, Wnt/β-catenin, Notch, and other growth factors. Many studies in experimental animal models have directly targeted these pathways and demonstrated efficacy in mitigating renal fibrosis. However, only a small fraction of these approaches have been attempted in human and even fewer have been successfully translated to clinical use for patient with kidney diseases. Drugs with proven efficacy for treatment of kidney diseases and tissue fibrosis exert some of their effects by interfering with components of these pathways. This review considers key molecular mediators of renal fibrosis and their potential as targets for treatment of renal fibrosis.

Low serum cultured adipose tissue-derived stromal cells ameliorate acute kidney injury in rats

Current studies suggest that mesenchymal stromal cells (MSCs) improve acute kidney injury (AKI) via paracrine/endocrine effects. We established human adipose tissue-derived stromal cells (hASCs) cultured in low (2%) serum (hLASCs), which have great potential of tissue regeneration. The present study was performed to investigate the therapeutic effects of hLASCs on AKI and to clarify the mechanisms involved. In low serum, hASCs proliferated well, while human bone marrow-derived stromal cells (hBMSCs) did not. hLASCs secreted higher levels of hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF) than did hASCs cultured in high (20%) serum (hHASCs) or hBMSCs cultured in high serum (hHBMSCs). AKI was induced in nude rats by folic acid, and hLASCs, hHASCs or control medium were administered into the renal subcapsules. hLASCs significantly attenuated acute renal damage, while hHASCs showed far less effect. Furthermore, interstitial fibrosis observed on day 14 was less pronounced in the hLASCs group. Cell tracking experiment showed no evidence of transdifferentiation. Intravenous injection of hLASCs or hHBMSCs or subcapsular injection of hHBMSCs did not ameliorate AKI. Concerning the mechanisms, our in vivo experiments showed that HGF knockdown by siRNA impaired the ability of hLASCs to protect the kidney from acute injury whereas VEGF knockdown did not. In conclusion, hLASCs, but not hHASCs or hHBMSCs, ameliorated AKI via paracrine effects, and HGF is one of the key mediators.

Autologous cell therapy for cisplatin-induced acute kidney injury by using non-expanded adipose tissue-derived cells

BACKGROUND AIMS

Recent studies have demonstrated that cultured mesenchymal stromal cells derived from adipose tissue are useful for regenerative cell therapy. The stromal vascular fraction (SVF) can be obtained readily without culturing and may be clinically applicable. We investigated the therapeutic effects of SVF and used it in the treatment of acute kidney injury (AKI).

METHODS

Liposuction aspirates were obtained from healthy donors who had provided written informed consent. We harvested the SVF and determined the growth factor secretion and anti-apoptotic ability with conditioned medium. To investigate the effect of SVF on AKI, cisplatin was injected into rats and SVF was administrated into the subcupsula of the kidney.

RESULTS

Both human and rat SVF cells secreted vascular endothelial growth factor-A (VEGF) and hepatocyte growth factor (HGF). Human SVF-conditioned media had an anti-apoptotic effect, which was inhibited by anti-HGF antibody (Ab) but not by anti-VEGF Ab. In vivo, SVF significantly ameliorated renal function, attenuated tubular damage and increased the cortical blood flow speed. In the SVF-treated group, VEGF levels in the cortex and HGF levels in both the cortex and medulla, especially tubules in the medulla, were significantly higher. Immunostaining revealed that SVF cells expressing VEGF and HGF and remained in the subcapsule on day 14.

CONCLUSIONS

The present study demonstrates that a subcapsular injection of non-expanded SVF cells ameliorates rat AKI, and that the mechanism probably involves secretion of renoprotective molecules. Administration of human SVF may be clinically applicable and useful as a novel autologous cell therapy against kidney diseases.

Tubulointerstitial injury and the progression of chronic kidney disease

In chronic kidney disease (CKD), once injury from any number of disease processes reaches a threshold, there follows an apparently irreversible course toward decline in kidney function. The tubulointerstitium may play a key role in this common progression pathway. Direct injury, high metabolic demands, or stimuli from various other forms of renal dysfunction activate tubular cells. These, in turn, interact with interstitial tissue elements and inflammatory cells, causing further pathologic changes in the renal parenchyma. The tissue response to these changes thus generates a feed-forward loop of kidney injury and progressive loss of function. This article reviews the mechanisms of this negative cycle mediating CKD.

Suramin alleviates glomerular injury and inflammation in the remnant kidney

BACKGROUND

Recently, we demonstrated that suramin, a compound that inhibits the interaction of multiple cytokines/growth factors with their receptors, inhibits activation and proliferation of renal interstitial fibroblasts, and attenuates the development of renal interstitial fibrosis in the murine model of unilateral ureteral obstruction (UUO). However, it remains unclear whether suramin can alleviate glomerular and vascular lesions, which are not typical pathological changes in the UUO model. So we tested the efficacy of suramin in the remnant kidney after 5/6 nephrectomy, a model characterized by the slow development of glomerulosclerosis, vascular sclerosis, tubulointerstitial fibrosis and renal inflammation, mimicking human disease.

METHODS/FINDINGS

5/6 of normal renal mass was surgically ablated in male rats. On the second week after surgery, rats were randomly divided into suramin treatment and non-treatment groups. Suramin was given at 10 mg/kg once per week for two weeks. In the remnant kidney of mice receiving suramin, glomerulosclerosis and vascular sclerosis as well as inflammation were ameliorated. Suramin also attenuated tubular expression of two chemokines, monocyte chemoattractant protein-1 and regulated upon expression normal T cell expressed and secreted (RANTES). After renal mass ablation, several intracellular molecules associated with renal fibrosis, including NF-kappaB p65, Smad-3, signal transducer and activator of transcription-3 and extracellular regulated kinase 1/2, are phosphorylated; suramin treatment inhibited their phosphorylation. Futhermore, suramin abolished renal ablation-induced phosphorylation of epidermal growth factor receptor and platelet derived growth factor receptor, two receptors that mediate renal fibrosis.

CONCLUSIONS AND SIGNIFICANCE

These findings suggest that suramin attenuates glomerular and vascular injury and reduces inflammatory responses by suppression of multiple growth factor receptor-mediated profibrotic signaling pathways. Therefore, suramin may be a useful drug in preventing the fibrosis and sclerosis that characterizes progression of chronic kidney disease.

Surfactant protein D inhibits lipopolysaccharide-induced monocyte chemoattractant protein-1 expression in human renal tubular epithelial cells: implication for tubulointerstitial fibrosis

Surfactant protein D (SP-D), a member of the C-type lectin (collectin) protein family, plays a critical role in innate host defence against various microbial pathogens and in the modulation of inflammatory responses in the lung. However, little is known about its expression and biological function in the kidney. In this work, we studied SP-D expression in human kidney and cultured human renal proximal tubular epithelial cells (HK-2), and examined the effect of SP-D on proinflammatory cytokine production after lipopolysaccharide (LPS) stimulus. We observed the expression of both SP-D mRNA and protein in human kidney and in-vitro HK-2 cells by immunohistochemistry, Western blot analysis, reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR. To explore the potential role of SP-D in the pathogenesis of tubulointerstitial fibrosis in kidney infection, we examined the production of monocyte chemoattractant protein-1 (MCP-1) in HK-2 cells after LPS treatment. Results showed that the level of MCP-1 in the conditioned medium increased significantly when HK-2 cells were cultured with LPS (>0·1 µg/ml) for 8 h. Of interest, LPS treatment inhibited SP-D expression in HK-2 cells. Furthermore, over-expression of SP-D reduced significantly the LPS-induced expression of MCP-1 in transfected cells. These findings suggest that SP-D in the kidney functions as an anti-inflammatory factor in renal tubular epithelial cells and may modulate tubulointerstitial fibrosis in kidney.

Anticubilin antisense RNA ameliorates adriamycin-induced tubulointerstitial injury in experimental rats

This study was designed to determine the effects of in vivo anticubilin antisense RNA on the uptake of albumin in tubules and on the tubulointerstitial injury in adriamycin-induced proteinuric rats. Adriamycin-treated rats were subjected to intrarenal delivery of adenoviral vectors encoding empty plasmid, cubilin sense RNA expression vector pAd-CUB or anticubilin antisense RNA expression vector pAd-ACUB on day 3. On days 14 and 28, half of the rats in each group were randomly selected to be killed, and blood samples, kidney tissues and 24-hour urine were collected. The diseased rats treated with pAdEasy-ACUB showed a 60% decrease in serum creatinine and glomerular filtration rate. Interestingly, the anticubilin antisense treatment led to a marked increase in albuminuria. Antisense treatment attenuated the histologic changes on both day 14 and day 28. The antisense treatment induced more than 60% recovery of adriamycin-induced injury, accompanied with 85% knockdown in the expression of cubilin protein and markedly decreased albumin deposition. Adriamycin induced an increase in the expression of monocyte chemoattractant protein-1, transforming growth factor-β and regulated on activation in normal T-cell expressed and secreted and the number of infiltrating cells, which was reversed by the antisense treatment. Anticubilin antisense RNA delivered by an adenoviral vector ameliorates albuminuria-induced glomerulosclerosis and tubulointerstitial damage in adriamycin nephrotic rats, indicating that cubilin could be a potential therapeutic target in proteinuric nephropathy.

A truncated analogue of CCL2 mediates anti-fibrotic effects on murine fibroblasts independently of CCR2

The truncated [1+9-76] CCL2 analogue, also known as 7ND, has been described in numerous reports as an anti-inflammatory and anti-fibrotic agent in a wide spectrum of animal models, e.g. models of cardiovascular disease, graft versus host disease and bleomycin-induced pulmonary fibrosis. 7ND has been reported to function as a competitive inhibitor of CCL2 signaling via CCR2 in human in vitro systems. In contrast, the mechanistic basis of 7ND action in animal models has not been previously reported. Here we have studied how 7ND interacts with CCL2 and CCR2 of murine origin. Surprisingly, 7ND was shown to be a weak inhibitor of murine CCL2/CCR2 signaling and displaced murine CCL2 (JE) from the receptor with a K(i)>1 μM. Using surface plasmon resonance, we found that 7ND binds murine CCL2 with a K(d) of 670 nM, which may indicate that 7ND inhibits murine CCL2/CCR2 signaling by a dominant negative mechanism rather than by competitive binding to the CCR2 receptor. In addition we observed that sub-nanomolar levels of 7ND mediate anti-fibrotic effects in CCR2 negative fibroblasts cultured from fibrotic lung of bleomycin-induced mice. Basal levels of extracellular matrix proteins were reduced (collagen type 1 and fibronectin) as well as expression levels of α-smooth muscle actin and CCL2. Our conclusion from these data is that the previously reported effects of 7ND in murine disease models most probably are mediated via mechanisms independent of CCR2.

Osteopontin deficiency protects against aldosterone-induced inflammation, oxidative stress, and interstitial fibrosis in the kidney

Osteopontin (OPN) has been implicated in the pathology of several renal conditions. Recently, we demonstrated in vitro that aldosterone has important roles in collagen synthesis by inducing OPN (Irita J, Okura T, Kurata M, Miyoshi K, Fukuoka T, Higaki J. Hypertension 51: 507–513, 2008). The aim of the present study was to clarify the roles of OPN in aldosterone-mediated renal fibrosis by infusing aldosterone into either wild-type (WT) or OPN knockout mice (OPN−/−). We used uninephrectomized mice treated with aldosterone and high salt to exacerbate renal fibrosis. After 4 wk of treatment with aldosterone, we showed similar increases in systolic blood pressure in both strains of mice. Urine albumin excretion was greater in aldosterone-infused WT mice than in aldosterone-infused OPN−/− mice. Immunohistochemical analysis showed high levels of OPN expression in aldosterone-infused WT mice. Interstitial fibrosis and inflammatory infiltrations were increased in aldosterone-infused WT mice compared with either vehicle-infused WT or aldosterone-infused OPN−/− mice. These changes were ameliorated markedly by eplerenone treatment in aldosterone-infused WT mice. Aldosterone-infused WT mice also had increased expression of NADPH oxidase subunits compared with aldosterone-infused OPN−/− mice. We observed a marked increase in oxidative stress markers in aldosterone-infused WT mice compared with aldosterone-infused OPN−/− mice. These results indicate that OPN is a promoter of aldosterone-induced inflammation, oxidative stress, and interstitial fibrosis in the kidney and suggest that inhibition of OPN may be a potential therapeutic target for prevention of renal injury.

GW501516, a PPARδ agonist, ameliorates tubulointerstitial inflammation in proteinuric kidney disease via inhibition of TAK1-NFκB pathway in mice

Peroxisome proliferator-activated receptors (PPARs) are a nuclear receptor family of ligand-inducible transcription factors, which have three different isoforms: PPARα, δ and γ. It has been demonstrated that PPARα and γ agonists have renoprotective effects in proteinuric kidney diseases; however, the role of PPARδ agonists in kidney diseases remains unclear. Thus, we examined the renoprotective effect of GW501516, a PPARδ agonist, in a protein-overload mouse nephropathy model and identified its molecular mechanism. Mice fed with a control diet or GW501516-containing diet were intraperitoneally injected with free fatty acid (FFA)-bound albumin or PBS(−). In the control group, protein overload caused tubular damages, macrophage infiltration and increased mRNA expression of MCP-1 and TNFα. These effects were prevented by GW501516 treatment. In proteinuric kidney diseases, excess exposure of proximal tubular cells to albumin, FFA bound to albumin or cytokines such as TNFα is detrimental. In vitro studies using cultured proximal tubular cells showed that GW501516 attenuated both TNFα- and FFA (palmitate)-induced, but not albumin-induced, MCP-1 expression via direct inhibition of the TGF-β activated kinase 1 (TAK1)-NFκB pathway, a common downstream signaling pathway to TNFα receptor and toll-like receptor-4. In conclusion, we demonstrate that GW501516 has an anti-inflammatory effect in renal tubular cells and may serve as a therapeutic candidate to attenuate tubulointerstitial lesions in proteinuric kidney diseases.

Bench-to-bedside review: Ventilation-induced renal injury through systemic mediator release--just theory or a causal relationship?

We review the current literature on the molecular mechanisms involved in the pathogenesis of acute kidney injury induced by plasma mediators released by mechanical ventilation. A comprehensive literature search in the PubMed database was performed and articles were identified that showed increased plasma levels of mediators where the increase was solely attributable to mechanical ventilation. A subsequent search revealed articles delineating the potential effects of each mediator on the kidney or kidney cells. Limited research has focused specifically on the relationship between mechanical ventilation and acute kidney injury. Only a limited number of plasma mediators has been implicated in mechanical ventilation-associated acute kidney injury. The number of mediators released during mechanical ventilation is far greater and includes pro- and anti-inflammatory mediators, but also mediators involved in coagulation, fibrinolysis, cell adhesion, apoptosis and cell growth. The potential effects of these mediators is pleiotropic and include effects on inflammation, cell recruitment, adhesion and infiltration, apoptosis and necrosis, vasoactivity, cell proliferation, coagulation and fibrinolysis, transporter regulation, lipid metabolism and cell signaling. Most research has focused on inflammatory and chemotactic mediators. There is a great disparity of knowledge of potential effects on the kidney between different mediators. From a theoretical point of view, the systemic release of several mediators induced by mechanical ventilation may play an important role in the pathophysiology of acute kidney injury. However, evidence supporting a causal relationship is lacking for the studied mediators.

Mesenchymal stem cells stably transduced with a dominant-negative inhibitor of CCL2 greatly attenuate bleomycin-induced lung damage

Acute respiratory distress syndrome (ARDS) is a crippling disease with no effective therapy characterized by progressive dyspnea. Mesenchymal stem cells (MSCs) have emerged as a new therapeutic modality for ARDS because MSCs can attenuate inflammation and repair the damaged tissue by differentiating into several cell types. Macrophages participate in the development of ARDS; however, MSCs only weakly modulate macrophage function. The chemokine CCL2 is a potent inducer of macrophage recruitment and activation, and its expression is elevated in patients with ARDS. We established MSCs that are stably transduced by a lentiviral vector expressing 7ND, a dominant-negative inhibitor of CCL2, to enhance the therapeutic function of MSCs. 7ND-MSCs retained the innate properties of MSCs and produced a large amount of 7ND. Many 7ND-MSCs were detected in bleomycin-treated lungs (immunostaining 24 hours after injection), suggesting that MSCs could work as a drug delivery tool. Mice treated with 7ND-MSCs showed significantly milder weight loss, lung injury, collagen content, accumulation of inflammatory cells and inflammatory mediators that were induced by bleomycin, and subsequent survival benefit. No evidence of 7ND-MSC-induced toxicity was observed during or after treatment. Thus, inhibiting the effects of macrophages may greatly enhance the ability of MSCs to effect lung repair in ARDS.

Role of endogenous hydrogen sulfide on renal damage induced by adriamycin injection

A single injection of adriamycin (ADR) induces marked and persistent proteinuria in rats that progress to glomerular and tubulointerstitial lesions. It has been shown that ADR-induced nephrotoxicity is mediated, at least in part, by oxidative stress that lead to inflammation. Endogenous hydrogen sulfide (H₂S) is synthesized from L-cysteine and is an important signaling molecule in inflammation. This study evaluates the effect of DL-propargylglycine (PAG), an inhibitor of endogenous H₂S formation, on the evolution of renal damage induced by ADR. The rats were injected i.p. with 0.15 M NaCl or PAG (50 mg/kg) 2 h after ADR injection (3.5 mg/kg). Control rats were injected with 0.15 M NaCl or PAG only. Twenty hours urine samples were collected for albuminuria and creatinine measurements on days 1 and 14 after saline or ADR injections and on days 2 and 15 blood samples were collected to measure plasma creatinine, then the rats were killed. The kidneys were removed for H₂S formation evaluation, renal lipid peroxidation and glutathione levels, and histological and immunohistochemical analysis. On day 2 after ADR injection the rats presented increase in oxidative stress associated with neutrophils and macrophages influx in renal tissue. On day 15 the rats also presented increased desmin expression at glomerular edge and vimentin in cortical tubulointerstitium, as well as albuminuria. All these alterations were reduced by PAG injection. The protective effect of PAG on ADR nephrotoxicity was associated to decreased H₂S formation and to restriction of oxidative stress and inflammation in the renal cortex.

A diet with 35% of energy from protein leads to kidney damage in female Sprague-Dawley rats

High-protein (HP) diets for weight loss remain popular despite questions surrounding overall safety. In a recent study using the pig model, we showed that long-term intakes from whole proteins at 35 % energy (en %) cause moderate renal histological damage. To examine whether this observation may be species specific or more generalisable, the effect of this diet in rats was examined. Using plant and animal whole proteins, 70-d-old female Sprague-Dawley rats were randomised to either a normal-protein (NP; 15 en %) or a HP (35 en %) diet for 4, 8, 12 and 17 months. Renal function was assessed by creatinine clearance and urinary protein levels, and pathology was assessed by examination of glomerular hypertrophy, glomerulosclerosis and tubulointerstitial fibrosis. Rats consuming the HP diet had 17 % higher kidney weights (P < 0·0001), three times higher proteinuria (P < 0·0001) and 27 % higher creatinine clearance (P = 0·0012) compared with those consuming the NP diet. Consistent with this, HP-fed rats had larger glomeruli (P < 0·0001) and more glomerulosclerosis (P = 0·0003) compared with NP-fed rats. The HP diet also resulted in altered levels of free monocyte chemoattractant protein-1 (P < 0·0001). The histological changes are consistent with those observed in the pig model. In contrast to the pig model, the elevated proteinuria and creatinine clearance observed in the rat model are also usually observed with HP consumption in human subjects. These results indicate that the rat is a useful model for HP effects on the kidney and, along with previous results using the pig model, suggest that long-term intake of high levels of protein may be detrimental to renal health.

A glimpse of various pathogenetic mechanisms of diabetic nephropathy

Diabetic nephropathy is a well-known complication of diabetes and is a leading cause of chronic renal failure in the Western world. It is characterized by the accumulation of extracellular matrix in the glomerular and tubulointerstitial compartments and by the thickening and hyalinization of intrarenal vasculature. The various cellular events and signaling pathways activated during diabetic nephropathy may be similar in different cell types. Such cellular events include excessive channeling of glucose intermediaries into various metabolic pathways with generation of advanced glycation products, activation of protein kinase C, increased expression of transforming growth factor β and GTP-binding proteins, and generation of reactive oxygen species. In addition to these metabolic and biochemical derangements, changes in the intraglomerular hemodynamics, modulated in part by local activation of the renin-angiotensin system, compound the hyperglycemia-induced injury. Events involving various intersecting pathways occur in most cell types of the kidney.

Chemokines in renal injury

The main function of chemokines is to guide inflammatory cells in their migration to sites of inflammation. During the last 2 decades, an expanding number of chemokines and their receptors have driven broad inquiry into how inflammatory cells are recruited in a variety of diseases. Although this review focuses on chemokines and their receptors in renal injury, proinflammatory IL-17, TGFβ, and TWEAK signaling pathways also play a critical role in their expression. Recent studies in transgenic mice as well as blockade of chemokine signaling by neutralizing ligands or receptor antagonists now allow direct interrogation of chemokine action. The emerging role of regulatory T cells and Th17 cells during renal injury also forges tight relationships between chemokines and T cell infiltration in the development of kidney disease. As chemokine receptor blockade inches toward clinical use, the field remains an attractive area with potential for unexpected opportunity in the future.

Mechanistic connection between inflammation and fibrosis

Fibrosis of the kidney is caused by the prolonged injury and deregulation of normal wound healing and repair processes, and by an excess deposition of extracellular matrices. Despite intensive research, our current understanding of the precise mechanism of fibrosis is limited. There is a connection between fibrotic events involving inflammatory and non-inflammatory glomerulonephritis, inflammatory cell infiltration, and podocyte loss. The current review will discuss the inflammatory response after renal injury that leads to fibrosis in relation to non-inflammatory mechanisms.

Targeting the recruitment of monocytes and macrophages in renal disease

Macrophages convert proinflammatory or anti-inflammatory signals of tissue microenvironments into response mechanisms. These response mechanisms largely derive from evolutionary conserved defense programs of innate host defense, wound healing, and tissue homeostasis. Hence, in many settings these programs lead to renal inflammation and tissue remodeling (ie, glomerulonephritis and sclerosis or interstitial nephritis and fibrosis). There is abundant experimental evidence that blocking macrophage recruitment or macrophage activation can ameliorate renal inflammation and fibrosis. In this review we discuss experimental tools to target renal macrophage recruitment by using antagonists against selectins, chemokines, integrins, or other important cytokines that mediate renal injury via macrophage recruitment, some of these already having been used in clinical trials.

Mechanisms of tubulointerstitial fibrosis

The pathologic paradigm for renal progression is advancing tubulointerstitial fibrosis. Whereas mechanisms underlying fibrogenesis have grown in scope and understanding in recent decades, effective human treatment to directly halt or even reverse fibrosis remains elusive. Here, we examine key features mediating the molecular and cellular basis of tubulointerstitial fibrosis and highlight new insights that may lead to novel therapies. How to prevent chronic kidney disease from progressing to renal failure awaits even deeper biochemical understanding.

The chemokine monocyte chemoattractant protein-1 contributes to renal dysfunction in swine renovascular hypertension

Renal artery stenosis (RAS) causes renovascular hypertension and renal damage, which may result from tissue inflammation. We have previously shown that the kidney in RAS exhibits increased expression of monocyte chemoattractant protein (MCP)-1, but its contribution to renal injury remained unknown. This study tested the hypothesis that MCP-1 contributes to renal injury and dysfunction in the stenotic kidney.

METHODS

Kidney hemodynamics, function, and endothelial function were quantified in pigs after 10 weeks of experimental RAS (n = 7), RAS supplemented with the MCP-1 inhibitor bindarit (RAS + bindarit, 50 mg/kg/day orally, n = 6), and normal controls (n = 8). Renal inflammation was assessed by the immunoreactivity of MCP-1, its receptor chemotactic cytokine receptor 2, and NFkappaB, and oxidative stress by nicotinamide adenine dinucleotide phosphate-oxidase expression and in-situ superoxide production. Renal microvascular density was evaluated by micro-CT and fibrosis by trichrome staining, collagen-I immunostaining, and hydroxyproline content.

RESULTS

After 10 weeks of RAS, blood pressure was similarly elevated in RAS and RAS + bindarit. Compared with normal controls, stenotic RAS kidneys had decreased renal blood flow (5.4 +/- 1.6 vs. 11.4 +/- 1.0 ml/min/kg, P < 0.05) and glomerular filtration rate and impaired endothelial function, which were significantly improved in bindarit-treated RAS pigs (to 8.4 +/- 0.8 ml/min/kg, P < 0.05 vs. RAS). Furthermore, bindarit markedly decreased tubulointerstitial (but not vascular) oxidative stress, inflammation, and fibrosis, and slightly increased renal microvascular density. The impaired renovascular endothelial function, increased oxidative-stress, and fibrosis in the contralateral kidney were also improved by bindarit.

CONCLUSION

MCP-1 contributes to functional and structural impairment in the kidney in RAS, mainly in the tubulointerstitial compartment. Its inhibition confers renoprotective effects by blunting renal inflammation and thereby preserving the kidney in chronic RAS.

Tissue-type plasminogen activator deficiency attenuates peritoneal fibrosis in mice

Peritoneal fibrosis (PF) is an important complication of peritoneal dialysis therapy. The present study was performed to examine the mechanisms of PF in view of the plasminogen activator (PA)/plasmin/matrix metalloproteinase (MMP) cascade. PF was induced in tissue-type PA (tPA) deficient mice and wild-type mice by intraperitoneal injection of chlorhexidine gluconate. Mice were killed on day 21, and tissue samples were taken. Histopathological studies were performed. Plasmin activity, gelatinases activity, and the levels of tPA, transforming growth factor-β1 (TGF-β1), and MMP-2 mRNA were determined. Protein levels of MMP-3, tissue inhibitor of metalloproteinases (TIMP)-1, -2, and -3, phospho-Smad3, membrane-type 1 (MT1)-MMP, and MT3-MMP were also studied. On day 21, tPA +/+ mice showed severe PF, whereas tPA −/− mice showed milder change. Submesothelial basement membranes were dissolved in tPA +/+ mice while they were relatively preserved in tPA −/− mice. The levels of macrophage infiltration, staining for α-smooth muscle actin (α-SMA) and collagen type III, and vascular density were all significantly lower in tPA −/− mice than in tPA +/+ mice. The levels of plasmin activity, pro- and active MMP-2, mRNA expression of tPA and TGF-β1, and phospho-Smad3 protein were also lower in tPA −/− mice. No difference was observed between the two groups concerning the protein levels of MMP-3, TIMP-1, TIMP-2, TIMP-3, MT1-MMP, or MT3-MMP. These results indicate that the presence of tPA enhances inflammation, angiogenesis, and fibrogenesis in the peritoneum of the PF model mice. Activation of the PA/plasmin/MMP cascade may play a pivotal role in the pathogenesis of PF.

Novel culture system of mesenchymal stromal cells from human subcutaneous adipose tissue

Accumulating evidence suggests that the delivery of human adipose tissue-derived stromal cells (hASCs) has great potential as regenerative therapy. This was performed to develop a method for expanding hASCs by reducing the amount of serum required. We demonstrate that hASCs were able to expand efficiently in media containing 2% serum and fibroblast growth factor-2. These cells, or low serum cultured hASCs (hLASCs), expressed cell surface markers similar to those on bone marrow-derived mesenchymal stem cells, and could be differentiated into cells of mesenchymal lineage. Of interest, hLASCs secreted higher levels of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) than hASCs cultured in 20% serum (hHASCs). Moreover, hLASC-conditioned media significantly increased endothelial cell (EC) proliferation and decreased EC apoptosis compared to that obtained from hHASCs or control media only. Antibodies against VEGF and HGF virtually negated these effects. When hASCs were administered into the ischemic hindlimbs of nude rats, hLASCs improved blood flow, increased capillary density, and raised the levels of VEGF and HGF in the muscles as compared with hHASCs. In conclusion, we demonstrate a novel low serum culture system for hASCs, which may have great potential in regenerative cell therapy for damaged organs in the clinical setting.

Ccl2/Mcp-1 blockade reduces glomerular and interstitial macrophages but does not ameliorate renal pathology in collagen4A3-deficient mice with autosomal recessive Alport nephropathy

Lack of the alpha3 or alpha4 chain of type IV collagen (COL4) causes autosomal recessive Alport nephropathy in humans and mice that is characterized by progressive glomerulosclerosis and tubulointerstitial disease. Renal pathology is associated with chemokine-mediated macrophage infiltrates but their contribution to the progression of Alport nephropathy is unclear. We found Ccl2 to be expressed in increasing amounts during the progression of nephropathy in Col4a3-deficient mice; hence, we blocked Ccl2 with anti-Ccl2 Spiegelmers, biostable L-enantiomeric RNA aptamers suitable for in vivo applications. Ccl2 blockade reduced the recruitment of ex vivo-labelled macrophages into kidneys of Col4a3-deficient mice. We therefore hypothesized that a prolonged course of Ccl2 blockade would reduce renal macrophage counts and prevent renal pathology in Col4a3-deficient mice. Groups of Col4a3-deficient mice received subcutaneous injections of either an anti-mCcl2 Spiegelmer or non-functional control Spiegelmer on alternate days, starting from day 21 or 42 of age. Glomerular and interstitial macrophage counts were found to be reduced with Ccl2 blockade by 50% and 30%, respectively. However, this was not associated with an improvement of glomerular pathology, interstitial pathology, or of overall survival of Col4a3-deficient mice. We conclude that Ccl2 mediates the recruitment of glomerular and interstitial macrophages but this mechanism does not contribute to the progression of Alport nephropathy in Col4a3-deficient mice.

Fasudil, a Rho-kinase inhibitor, reverses L-NAME exacerbated severe nephrosclerosis in spontaneously hypertensive rats

BACKGROUND

In this study, we tested the hypothesis that long-term Rho-kinase inhibition would reverse nitro-L-arginine methyl ester-exacerbated nephrosclerosis in spontaneously hypertensive rats and attempted to elucidate the mechanism involved.

METHODS

Five groups (each n = 8) were studied: untreated spontaneously hypertensive rats; nitro-L-arginine methyl ester (50 mg/l in drinking water, for 3 weeks)-treated spontaneously hypertensive rats; nitro-L-arginine methyl ester with fasudil (10 mg/kg/day)-treated spontaneously hypertensive rats; nitro-L-arginine methyl ester for 3 weeks followed by fasudil for 3 weeks-treated spontaneously hypertensive rats (same doses), and nitro-L-arginine methyl ester for 3 weeks followed by untreated for 3 weeks. We examined renal function, blood pressure, histological features, oxidative stress markers, and mRNA expression in the renal cortex.

RESULTS

Nitro-L-arginine methyl ester-treated spontaneously hypertensive rats had higher blood pressure, proteinuria, and serum creatinine and lower creatinine clearance, urinary NO3/NO2 ratio, and urinary cGMP excretion compared with control spontaneously hypertensive rats (all Ps < 0.05). Nitro-L-arginine methyl ester-treated spontaneously hypertensive rats also had increased free radical metabolites and abnormal morphological findings with increased nicotinamide adenine dinucleotide phosphate oxidase activity, phosphorylation of myosin phosphatase targeting subunit-1, and mRNA expression of RhoA, RhoB, RhoC, collagen I and III, transforming growth factor-beta, nicotinamide adenine dinucleotide phosphate subunit, endothelial nitric oxide synthase, plasminogen activator inhibitor, and intercellular adhesion molecule-1 in the renal cortex compared with control spontaneously hypertensive rats. Long-term co-treatment with fasudil slightly improved these indices, but most of them were not statistically significant. Late fasudil treatment significantly improved kidney function, morphological changes, and alterations of mRNA expression in the renal cortex, although late untreated controls did not show any improvement.

CONCLUSION

These results suggest that Rho-kinase inhibition partly reverses hypertensive glomerulosclerosis. The renoprotective effect of the Rho-kinase inhibitor may have multiple mechanisms including inhibition of extracellular matrix production, oxidative stress, adhesion molecule production, and antifibrinolysis.

MCP-1/CCR2 system is involved in high glucose-induced fibronectin and type IV collagen expression in cultured mesangial cells

Monocyte chemoattractant protein-1 (MCP-1) is a potent chemokine that plays an important role in the recruitment of macrophages. Although previous studies have demonstrated the importance of MCP-1 in the pathogenesis of diabetic nephropathy (DN) in terms of inflammation, the role of MCP-1 and its receptor (C-C chemokine receptor 2; CCR2) in extracellular matrix (ECM) accumulation under diabetic conditions has been largely unexplored. This study was undertaken to investigate the functional role of the MCP-1/CCR2 system in high glucose-induced ECM (fibronectin and type IV collagen) protein expression in cultured mesangial cells (MCs). Mouse MCs were exposed to medium containing 5.6 mM glucose (NG), NG+24.4 mM mannitol (NG+M), or 30 mM glucose (HG) with or without mutant MCP-1 (mMCP-1), CCR2 small interfering (si)RNA, or CCR2 inhibitor (RS102895). To examine the relationship between MCP-1 and transforming growth factor (TGF)-β1, MCs were also treated with TGF-β1 (2 ng/ml) with or without mMCP-1 or CCR2 siRNA. Transient transfection was performed with Lipofectamine 2000 for 24 h. Cell viability was determined by an MTT assay, mouse and human MCP-1 and TGF-β1 levels by ELISA, and CCR2 and ECM protein expression by Western blotting. Transfections of mMCP-1 and CCR2 siRNA increased human MCP-1 levels and inhibited CCR2 expression, respectively. HG-induced ECM protein expression and TGF-β1 levels were significantly attenuated by mMCP-1, CCR2 siRNA, and RS102895 ( P < 0.05). MCP-1 directly increased ECM protein expression, and this increase was inhibited by an anti-TGF-β1 antibody. In addition, TGF-β1-induced ECM protein expression was significantly abrogated by the inhibition of the MCP-1/CCR2 system ( P < 0.05). These results suggest that an interaction between the MCP-1/CCR2 system and TGF-β1 may contribute to ECM accumulation in DN.

The role of capillary density, macrophage infiltration and interstitial scarring in the pathogenesis of human chronic kidney disease

To assess the relationship between interstitial capillary density and interstitial macrophages we prospectively measured these factors in situ in 110 patients with chronic kidney disease. Macrophage numbers and urinary MCP-1/CCL2 levels significantly correlated inversely with capillary density which itself significantly correlated inversely with chronic damage and predicted disease progression. In 54 patients with less than 20% chronic damage, there was a significant correlation between the urinary albumin to creatinine ratio and MCP-1/CCL2, and MCP-1/CCL2 and macrophages but not between MCP-1/CCL2 and capillary density. Conversely, in 56 patients with over 20% chronic damage there was no correlation between MCP-1/CCL2 and macrophages but there were significant inverse correlations between capillary density and both macrophages and chronic damage. The expression of VEGF mRNA significantly correlated with macrophage infiltration, capillary density and chronic scarring. In an ischemic-hypertensive subgroup there was upregulation of the hypoxia marker carbonic anhydrase IX and with over 20% chronic damage an increased macrophage to CCR2 ratio. Our study shows that proteinuria and MCP-1/CCL2 are important for macrophage recruitment in early disease. As renal scarring evolves, alternative pathways relating to progressive tissue ischemia secondary to obliteration of the interstitial capillary bed predominate.

Lymphocytes are dispensable for glomerulonephritis but required for renal interstitial fibrosis in matrix defect-induced Alport renal disease

One current theory for the emergence of glomerular nephritis implicates Th1-type cellular responses associated with delayed-type hypersensitivity, involving T cells and macrophages. Using a mouse model for progressive glomerulonephritis, we investigate the role of B and T cells in the pathogenesis of glomerular inflammation. Deletion of alpha3 chain of type IV collagen in mice (alpha3(IV) collagen null mice) results in GBM defects, glomerulonephritis and tubulointerstitial inflammation, fibrosis and significant immune infiltration including activated B- and T-lymphocytes. To evaluate the contribution of lymphocytes to the pathogenesis of glomerulonephritis and renal fibrosis, we generated mice that are deficient in both the alpha3(IV) collagen and Rag-1 (alpha3/Rag-1 DKO). Lymphocyte deficiency significantly reduces fibrosis in the renal interstitium, but ultrastructural GBM defects persist. Interestingly, glomerulonephritis in the double null mice persists at a similar level with comparable proteinuria. Here we demonstrate that despite the presence of B-cell and T-cells in the inflamed glomeruli, their deletion does not impede the emergence of glomerulonephritis but has a negative impact on the progression of renal interstitial fibrosis.