Protective effects of L-type fatty acid-binding protein (L-FABP) in proximal tubular cells against glomerular injury in anti-GBM antibody-mediated glomerulonephritis

Serum protein signatures using aptamer-based proteomics for minimal change disease and membranous nephropathy

Introduction

Minimal change disease (MCD) and membranous nephropathy (MN) are glomerular diseases (glomerulonephritis [GN]) that present with the nephrotic syndrome. Although circulating PLA2R antibodies have been validated as a biomarker for MN, the diagnosis of MCD and PLA2R-negative MN still relies on the results of kidney biopsy or empirical corticosteroids in children. We aimed to identify serum protein biomarker signatures associated with MCD and MN pathogenesis using aptamer-based proteomics.

Methods

Quantitative SOMAscan proteomics was applied to the serum of adult patients with MCD (n = 15) and MN (n = 37) and healthy controls (n = 20). Associations between the 1305 proteins detected with SOMAscan were assessed using multiple statistical tests, expression pattern analysis, and systems biology analysis.

Results

A total of 208 and 244 proteins were identified that differentiated MCD and MN, respectively, with high statistical significance from the healthy controls (Benjamin-Hochberg [BH] P < 0.0001). There were 157 proteins that discriminated MN from MCD (BH P < 0.05). In MCD, 65 proteins were differentially expressed as compared with MN and healthy controls. When compared with MCD and healthy controls, 44 discriminatory proteins were specifically linked to MN. Systems biology analysis of these signatures identified cell death and inflammation as key pathways differentiating MN from MCD and healthy controls. Dysregulation of fatty acid metabolism pathways was confirmed in both MN and MCD as compared with the healthy subjects.

Conclusion

SOMAscan represents a promising proteomic platform for biomarker development in GN. Validation of a greater number of discovery biomarkers in larger patient cohorts is needed before these data can be translated for clinical care.

Relationship of urinary liver-type fatty acid-binding protein with cardiovascular risk factors in the Japanese population without chronic kidney disease: Sasayama study

BACKGROUND

Urinary liver-type fatty acid-binding protein (L-FABP) is a well-known marker of proximal tubular impairment. We evaluated the relationship between cardiovascular disease (CVD) risk factors and levels of L-FABP in a cross-sectional community-based study. Participants with normoalbuminuria and normal estimated glomerular filtration rate (eGFR), that is, non-chronic kidney disease (non-CKD), were enrolled in this study. To the best of our knowledge, this is the first study to focus on the association between CVD risk factors and a proximal tubular marker in the Japanese general population with normoalbuminuria and normal eGFR.

METHODS

The present study is part of the Sasayama study. The participants included 1000 community residents (447 men and 553 women) aged 40-64 years without a history of CVD or renal dysfunction. Out of these participants 375 men and 477 women, defined as non-CKD, were included for further analysis. In each sex, the highest quintile group was considered to have high-normal L-FABP levels. A multiple logistic regression model was used to evaluate the relationship between risk factors for CVD and high-normal L-FABP levels in the non-CKD participants. We performed a similar analysis using the high-normal urinary albumin to creatinine ratio (UACR) as a dependent variable instead of L-FABP.

RESULTS

Among the non-CKD participants, in the highest quintile group (Q5, top 20%), L-FABP was ≥2.17 μg/gCre in men and ≥ 2.83 μg/gCre in women. In women, the multivariate odds ratio was 3.62 (1.45-9.00) for high-normal L-FABP in the presence of diabetes mellitus (DM) compared with that in the group without DM. However, the relationship between DM and the UACR level was not significant. In men, DM was significantly associated with high-normal UACR. However, the relationship with L-FABP levels was not significant.

CONCLUSIONS

The presence of DM was more strongly related to high-normal L-FABP levels than to high-normal UACR in women even at the stage of normoalbuminuria and normal eGFR. Our results were also consistent with the findings of a previous study where women were more prone to nonalbuminuric renal impairment compared to men, although further studies are required to confirm the results.

The effect of lncRNA-ARAP1-AS2/ARAP1 on high glucose-induced cytoskeleton rearrangement and epithelial-mesenchymal transition in human renal tubular epithelial cells

The epithelial-mesenchymal transition (EMT) plays an important role in diabetic renal fibrosis. The ARAP1 gene is located near risk alleles for Type 2 diabetes, and its function has been linked to cytoskeleton rearrangement, Golgi apparatus remodeling, and endocytic trafficking of membrane receptors. The role of ARAP1 and its antisense RNA, ARAP1-AS2, in the pathogenesis of diabetes is unclear. To clarify the roles of ARAP1 and its antisense RNA in diabetes and related complications, we examined if the expression of these transcripts changed under high glucose (HG) conditions. To do this, we examined transcript levels in HK-2 cells, and explored the roles of ARAP1 and ARAP1-AS2 in the EMT process in HK-2 cells. We found increased expression of ARAP1-AS2 and ARAP1 in HK-2 cells under HG condition, and observed that the overexpression of ARAP1-AS2 significantly increased the EMT process. In addition, HG upregulated Cdc42-GTP levels in HK-2 cells, and increased cytoskeleton rearrangement, cell viability, and migration. After knockdown of ARAP1, the level of Cdc42-GTP was decreased; cytoskeleton reorganization, cell viability, and migration processes were decreased; and EMT and expression of fibrosis marker protein. Overall, our results indicated that ARAP1-AS2/ARAP1 may participate in cytoskeleton rearrangement and EMT processes in HK-2 cells through increased Cdc42-GTP levels.

Regulation of PTEN/AKT/FAK pathways by PPARγ impacts on fibrosis in diabetic nephropathy

Renal tubular epithelial-to-mesenchymal transition (EMT) and tubulointerstitial fibrosis (TIF) are important pathological features of diabetic nephropathy (DN). However, the regulatory mechanism underlying EMT and TIF are still unclear. Previous studies showed that the decrease in the expression of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) was closely related to the aggravation of DN, but no published study showed how PTEN participated in the regulation of EMT and TIF. In this study, the rat proximal tubular epithelial cells (NRK52E) and C57BL mice and human kidney tissues were used as the research objects to investigate the mechanism underlying the regulatory effect of peroxisome proliferator-activated receptors γ (PPARγ) on PTEN and its influence on EMT and TIF, the regulation of PTEN's dual activity of lipid phosphatase/protein phosphatase by the serine threonine protein kinase B(AKT)/focal adhesion kinase (FAK) signaling pathway, and the role of PTEN in EMT and TIF. The results showed that PPARγ regulated the expression of PTEN at a transcriptional level and further regulated EMT and TIF. This dual activity could regulate the phosphorylation level of AKT and FAK and also affect FAK transcription. However, the 129 mutant of PTEN (PTEN-G129E) lost the lipid phosphatase activity, and its protein phosphatase activity was involved only in EMT and renal fibrosis through regulating FAK phosphorylation. This study systematically elucidated the role of PPARγ/PTEN/AKT/FAK signaling pathway in EMT and TIF during the pathogenesis of DN.

Protective potential of Angelica sinensis polysaccharide extract against ethylene glycol-induced calcium oxalate urolithiasis

Purpose: To evaluate a Angelica sinensis polysaccharide aqueous extract as a preventive agent in experimentally induced urolithiasis using in- vitro and vivo models.

Material and methods:Angelica sinensis polysaccharide was investigated in vitro to determine its antilithiatic effects on the formation and morphology of calcium oxalate (CaOx) crystals and was analyzed in vivo to determine its ability to prevent CaOx urolithiasis in rats subjected to ethylene glycol-induced urolithiasis. Potassium citrate administration was used in the positive control group. The urolithiasis-related biochemical parameters were evaluated in the rats urine, serum and kidney homogenates. Kidney sections were subjected to histopathological and immunohistochemical analyses, and urolithiasis-related phospho-c-Jun NH2-terminal protein kinase and kidney injury molecule-1proteins were evaluated by Western blot analyses.

Results:Angelica sinensis polysaccharide exhibited concentration-dependent inhibition of CaOx crystal formation. The in vitro assay revealed significant inhibition of crystal formation (6.99 ± 1.07) in the group treated with 4.0 mg/mL Angelica sinensis polysaccharide extract compared with the control group (58.38 ± 5.63; p < .05). In vivo, after treatment with ethylene glycol for 28 days, urinary oxidative stress, oxalate, creatinine, urea and urolithiasis-related protein were significantly increased (p < .05), except for serum oxidative stress (p > .05). The rats administered the extract of Angelica sinensis polysaccharide showed significantly decreased pathological change and CaOx deposition (p < .05) compared with the urolithiatic rats. Significantly reduced levels of urinary oxidative stress, oxalate, creatinine, urea and urolithiasis-related protein were observed in the Angelica sinensis polysaccharide treatment groups (p < .05) compared with the nephrolithic rats.

Conclusion: The results presented here suggest that Angelica sinensis polysaccharide has the potential to inhibit CaOx crystallization in vitro and may present anti-urolithiatic effects in vivo.

Biomarkers of AKI Progression after Pediatric Cardiac Surgery

Background As children progress to higher stages of AKI, the risk for adverse outcomes dramatically increases. No reliable methods exist to predict AKI progression in hospitalized children. To determine if biomarkers of inflammation and kidney injury can predict AKI progression, we conducted a three-center prospective cohort study of children undergoing cardiopulmonary bypass.Methods On the first day of serum creatinine-defined AKI, we measured urine biomarkers (neutrophil gelatinase-associated lipocalin [NGAL], IL-18, kidney injury molecule 1, liver fatty acid binding protein [L-FABP], albumin, and cystatin C) and plasma biomarkers (IFN, IL-1, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-13, TNF-α, NGAL, and cystatin C). We defined AKI progression as a worsening of AKI stage or persisting stage 3 AKI (≥2 consecutive days).Results In all, 176 of 408 (43%) children developed postoperative AKI. Among the children with AKI, we diagnosed stages 1, 2, and 3 AKI in 145 (82.5%), 25 (14%), and six (3.5%) children, respectively, on the first day of AKI; 28 (7%) children had AKI progression. On the first day of AKI, nine of 17 biomarkers were significantly higher in patients with than without AKI progression. Urine L-FABP (among injury biomarkers) and plasma IL-8 (among inflammatory biomarkers) had the highest discrimination for AKI progression: optimism-corrected area under the curve, 0.70; 95% confidence interval, 0.58 to 0.81 and optimism-corrected area under the curve, 0.80; 95% confidence interval, 0.69 to 0.91, respectively.Conclusions If validated in additional cohorts, plasma IL-8 could be used to improve clinical care and guide enrollment in therapeutic trials of AKI.

CDK5 promotes renal tubulointerstitial fibrosis in diabetic nephropathy via ERK1/2/PPARγ pathway

Cyclin-dependent kinase 5 (CDK5) has been documented in podocyte injuries in diabetic nephropathy (DN), however its role in renal tubular epithelial cells has not been elucidated. We report here that CDK5 is detrimental and promotes tubulointerstitial fibrosis (TIF) via the extracellular signal-regulated kinase 1/2 (ERK1/2)/peroxisome proliferator-activated receptor gamma (PPRAγ) pathway in DN. In high glucose cultured NRK52E cells, blocking CDK5 activity inhibited epithelial-to-mesenchymal transition (EMT) and fibrosis via ERK1/2/PPARγ pathway. In diabetic rats, CDK5 inhibitor roscovitine decreased renal fibrosis and improved renal function as demonstrated by a decrease in levels of blood urine nitrogen (BUN), serum creatinine and β2-microglobulin. Further studies revealed that improved renal fibrosis and function in diabetic rats were associated with inactivation of ERK1/2 and PPARγ signaling pathways. In late staged DN patients, the upregulation of CDK5 and p35 activated phosphorylated ERK1/2 and PPARγ, leading to decreased levels of E-cadherin but increased Vimentin and Collagen IV. Accordingly, renal fibrosis and function were worsened as revealed by decreased estimated glomerular filtration rate (eGFR) and increased serum BUN, creatinine, β2-microglobulin, 24-hour proteinuria and urine albumin to creatinine ratio (UACR). These findings demonstrate a novel mechanism that CDK5 increases tubulointerstitial fibrosis by activating the ERK1/2/PPARγ pathway and EMT in DN. CDK5 might have therapeutic potential in diabetic nephropathy.

Mass spectrometric quantification of urinary human liver fatty acid binding protein in renal transplant recipients

RATIONALE

Urinary liver fatty acid binding protein (L-FABP) has been evaluated as a promising early biomarker of renal ischemia in human kidney transplant patients. The use of L-FABP in clinical practice requires that this biomarker be associated with an analytical method that combines specificity, accuracy and robustness. This study aimed to evaluate an optimized multiple reaction monitoring (MRM) method using ultrafast liquid chromatography coupled with tandem mass spectrometry to measure urinary L-FABP levels in renal transplant recipients.

METHODS

Purified recombinant human L-FABP tryptic standard was analyzed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS/MS) and liquid chromatography (LC)/MS/MS to select for peptides that provided specificity and adequate response in developing an MRM method for urinary L-FABP quantification. Human urine samples collected from kidney transplant recipients were isolated, concentrated, precipitated and trypsin digested before mass spectrometric analysis of L-FABP. L-FABP levels were also measured in urine samples by enzyme immunoassay.

RESULTS

The tryptic peptide ion MH(+) of (50) FTITAGSK(57) (m/z 824) provided an adequate signal and was used for quantification of L-FABP under conditions employed for LC/MS/MS analysis. MALDI-TOF-MS/MS spectra obtained by collision-induced dissociation of the parent MH(+) ion (50) FTITAGSK(57) resulted in a y3 product ion that was used for quantitative analysis by the MRM method. Urinary L-FABP content measured by both ELISA and LC/MS/MS after transplantation was significantly higher compared to before transplantation levels. The Spearman correlation coefficient between the two methods was statistically significant. Intra-day and inter-day coefficients of variation provided good repeatability and reproducibility for validation of LC/MS/MS analysis.

CONCLUSIONS

LC/MS/MS quantification of L-FABP may provide a new reference method to determine changes in this potential biomarker in human kidney transplant patients.

Recent insights into the biological functions of liver fatty acid binding protein 1

Over four decades have passed since liver fatty acid binding protein (FABP)1 was first isolated. There are few protein families for which most of the complete tertiary structures, binding properties, and tissue occurrences are described in such detail and yet new functions are being uncovered for this protein. FABP1 is known to be critical for fatty acid uptake and intracellular transport and also has an important role in regulating lipid metabolism and cellular signaling pathways. FABP1 is an important endogenous cytoprotectant, minimizing hepatocyte oxidative damage and interfering with ischemia-reperfusion and other hepatic injuries. The protein may be targeted for metabolic activation through the cross-talk among many transcriptional factors and their activating ligands. Deficiency or malfunction of FABP1 has been reported in several diseases. FABP1 also influences cell proliferation during liver regeneration and may be considered as a prognostic factor for hepatic surgery. FABP1 binds and modulates the action of many molecules such as fatty acids, heme, and other metalloporphyrins. The ability to bind heme is another cytoprotective property and one that deserves closer investigation. The role of FABP1 in substrate availability and in protection from oxidative stress suggests that FABP1 plays a pivotal role during intracellular bacterial/viral infections by reducing inflammation and the adverse effects of starvation (energy deficiency).

Circulating TNF receptors 1 and 2 are associated with the severity of renal interstitial fibrosis in IgA nephropathy

The current study aimed to examine whether the levels of TNF receptors 1 and 2 (TNFR1 and TNFR2) in serum and urine were associated with other markers of kidney injury and renal histological findings, including TNFR expression, in IgA nephropathy (IgAN). The levels of the parameters of interest were measured by immunoassay in 106 biopsy-proven IgAN patients using samples obtained immediately before renal biopsy and in 34 healthy subjects. Renal histological findings were evaluated using immunohistochemistry. The levels of serum TNFRs were higher in IgAN patients than in healthy subjects. The levels of both TNFRs in serum or urine were strongly correlated with each other (r > 0.9). Serum TNFR levels were positively correlated with the urinary protein to creatinine ratio (UPCR) and four markers of tubular damage of interest (N-acetyl-β-D-glucosaminidase [NAG], β2 microglobulin [β2m], liver-type fatty acid-binding protein [L-FABP], and kidney injury molecule-1 [KIM-1]) and negatively correlated with estimated glomerular filtration rate (eGFR). Patients in the highest tertile of serum TNFR levels showed more severe renal interstitial fibrosis than did those in the lowest or second tertiles. The tubulointerstitial TNFR2-, but not TNFR1-, positive area was significantly correlated with the serum levels of TNFRs and eGFR. Stepwise multiple regression analysis revealed that elevated serum TNFR1 or TNFR2 levels were a significant determinant of renal interstitial fibrosis after adjusting for eGFR, UPCR, and other markers of tubular damage. In conclusion, elevated serum TNFR levels were significantly associated with the severity of renal interstitial fibrosis in IgAN patients. However, the source of TNFRs in serum and urine remains unclear.

L-FABP: A novel biomarker of kidney disease

Human liver-type fatty acid-binding protein (hL-FABP), which is found in both the normal and the diseased human kidney, has been observed to bind free fatty acids. Recently, the predictive and prognostic value of L-FABP in kidney diseases has attracted considerable attention. Numerous studies have demonstrated that L-FABP is a promising biomarker of several kidney diseases, and it has also been shown to attenuate renal injury. We performed a literature review regarding the ability of L-FABP to identify patients at risk of developing kidney diseases, including acute kidney injury (AKI) and chronic kidney disease (CKD) and to protect the kidneys in the course of kidney disease.

Association of L-FABP T94A and MTP I128T polymorphisms with hyperlipidemia in Chinese subjects

The purpose of this study was to evaluate the relation between the L-FABP T94A and MTP I128T polymorphisms and hyperlipidemia in Chinese subjects. We recruited 390 volunteers: 201 hyperlipidemic and 189 healthy volunteers. The L-FABP T94A and MTP I128T polymorphisms were genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Anthropometry, lipid profile, and liver function of the subjects were determined. We observed that male carriers of the L-FABP A94 allele had significantly higher body weight (P = 0.012), higher body mass index (BMI) (P = 0.014), and higher plasma triacylglycerol levels (TAG) (P = 0.033) and lower ratios of high-density lipoprotein cholesterol (HDL-C) to total cholesterol (TC) (P = 0.008) than T94 homozygotes. The MTP T128 allele was associated with significantly lower serum TC (P < 0.001) and low-density lipoprotein cholesterol (LDL-C) (P < 0.001) levels in males. There was a direct correlation between the MTP T128 allele and a decreased risk of hyperlipidemia after adjusting for body mass index (OR = 0.327, 95 % CI: 0.178-0.600, P < 0.001). In conclusion, both the MTP I128T and the L-FABP T94A polymorphisms can affect serum lipid levels in the Chinese population. The MTP T128 allele offers protection against hyperlipidemia in the Chinese population.

Development of contrast-induced acute kidney injury after elective contrast media exposure in patients with type 2 diabetes mellitus: effect of albuminuria

BACKGROUND

The influence of albuminuria and urinary pH on the development of contrast-induced acute kidney disease (CI-AKI) in patients with type 2 diabetes mellitus (T2DM) after elective coronary angiography (CAG) or percutaneous coronary intervention (PCI) is unknown.

METHODS

CI-AKI was defined as an increase in serum creatinine >26.4 µmol/L or ≥50% of baseline value within 48 hours after contrast media exposure. Demographics, traditional risk factors, clinical outcomes and CI-AKI incidence were compared between groups. Univariate analysis and multivariate logistic regression were performed to assess risk factors of CI-AKI.

RESULTS

We observed 597 patients with T2DM after CAG or PCI. Patients were divided into 3 groups based on early morning urinary albumin: negative group (urine dipstick negative, n = 483), trace group (urine dipstick trace, n = 60), and positive group (urine dipstick ≥1+, n = 54). CI-AKI occurred in 33 (5.5%) patients, including 19 (3.9%) in the negativealbuminuria group, 4 (6.7%) in the trace group, and 10 (18.5%) in the positive group (p< 0.001), respectively. After adjusting for potential confounding risk factors, positive albuminuria (OR = 3.8, 95% CI: 1.5 to 9.2, p = 0.004) and urinary pH<6 (OR = 2.4, 95% CI: 1.1 to 5.1, p = 0.020) remained significantly associated with CI-AKI.

CONCLUSION

Preprocedural albuminuria and urinary pH <6 are independent risk factors of CI-AKI in patients with T2DM undergoing elective cardiac catheterization, and may be used to identify patients at high risk of post-procedural CI-AKI.

Low levels of urinary liver-type fatty acid-binding protein may indicate a lack of kidney protection during aortic arch surgery requiring hypothermic circulatory arrest

STUDY OBJECTIVE

To examine the change in liver-type fatty acid-binding protein (L-FABP) levels in patients undergoing aortic arch surgery and the correlation between L-FABP and postoperative acute kidney injury.

DESIGN

Prospective observational study.

SETTING

Operating room of a general hospital.

PATIENTS

36 adult patients.

INTERVENTIONS AND MEASUREMENTS

Urine samples were obtained to measure urinary L-FABP at initiation of cardiopulmonary bypass (CPB) and 5 minutes after termination of hypothermic circulatory arrest.

MAIN RESULTS

22 (61.1%) patients developed acute kidney injury within a 48-hour period. L-FABP increases more than a thousand-fold were found. In patients who subsequently developed acute kidney injury, significant increases in L-FABP were noted from 2.9 (3.6) ng/mg of creatinine before CPB to 62.1 (995.6) ng/mg of creatinine 5 minutes after termination of circulatory arrest. Values in patients who did not develop acute kidney injury increased from 1.1 (5.7) ng/mg before CPB to 1133.0 (6358.8) ng/mg of creatinine showing a significant mean difference (P = 0.011). The area under the L-FABP receiver operating characteristic curve at 5 minutes after termination of circulatory arrest was 0.758. A cutoff value of 75.13 ng/mg of creatinine yielded both good sensitivity (1.000) and specificity (0.546) for detecting non-acute kidney injury. Patients who developed acute kidney injury after aortic arch surgery demonstrated lower levels of urinary L-FABP.

CONCLUSIONS

Low levels of urinary L-FABP may indicate kidney injury and lack of renal protection.

Peroxisome proliferator-activated receptor agonists in a battle against the aging kidney

As aging is a complex phenomenon characterized by intraindividual and interindividual diversities in the maintenance of the homeostatic condition of cells and tissues, changes in renal function are not uniform and depend on associated diseases and environmental factors. Multiple studies have investigated the possible underlying mechanisms of age-related decline in kidney function. Evolutionary, molecular, cellular and systemic theories have been postulated to explain the primary disease independent age-related changes and adaptive responses. As peroxisome proliferator-activated receptors (PPARs) are involved in a broad spectrum of biological processes, PPAR activation might have an effect on the prevention of cell senescence. In this review, we will focus on the experimental and clinical evidence of PPAR agonists in a battle against the aging kidney.

Glutathione S-transferase Mu 2-transduced mesenchymal stem cells ameliorated anti-glomerular basement membrane antibody-induced glomerulonephritis by inhibiting oxidation and inflammation

INTRODUCTION

Oxidative stress is implicated in tissue inflammation, and plays an important role in the pathogenesis of immune-mediated nephritis. Using the anti-glomerular basement membrane antibody-induced glomerulonephritis (anti-GBM-GN) mouse model, we found that increased expression of glutathione S-transferase Mu 2 (GSTM2) was related to reduced renal damage caused by anti-GBM antibodies. Furthermore, mesenchymal stem cell (MSC)-based therapy has shed light on the treatment of immune-mediated kidney diseases. The aim of this study was to investigate if MSCs could be utilized as vehicles to deliver the GSTM2 gene product into the kidney and to evaluate its potential therapeutic effect on anti-GBM-GN.

METHODS

The human GSTM2 gene (hGSTM2) was transduced into mouse bone marrow-derived MSCs via a lentivirus vector to create a stable cell line (hGSTM2-MSC). The cultured hGSTM2-MSCs were treated with 0.5 mM H2O2, and apoptotic cells were measured by terminal dUTP nick-end labeling (TUNEL) assay. The 129/svj mice, which were challenged with anti-GBM antibodies, were injected with 10⁶ hGSTM2-MSCs via the tail vein. Expression of hGSTM2 and inflammatory cytokines in the kidney was assayed by quantitative PCR and western blotting. Renal function of mice was evaluated by monitoring proteinuria and levels of blood urea nitrogen (BUN), and renal pathological changes were analyzed by histochemistry. Immunohistochemical analysis was performed to measure inflammatory cell infiltration and renal cell apoptosis.

RESULTS

MSCs transduced with hGSTM2 exhibited similar growth and differentiation properties to MSCs. hGSTM2-MSCs persistently expressed hGSTM2 and resisted H2O2-induced apoptosis. Upon injection into 129/svj mice, hGSTM2-MSCs migrated to the kidney and expressed hGSTM2. The anti-GBM-GN mice treated with hGSTM2-MSCs exhibited reduced proteinuria and BUN (58% and 59% reduction, respectively) and ameliorated renal pathological damage, compared with control mice. Mice injected with hGSTM2-MSCs showed alleviated renal inflammatory cell infiltration and reduced expression of chemokine (C-C motif) ligand 2 (CCL2), interleukin (IL)-1β and IL-6 (53%, 46% and 52% reduction, respectively), compared with controls. Moreover, hGSTM2-MSCs increased expression of renal superoxide dismutase and catalase, which may associate with detoxifying reactive oxygen species to prevent oxidative renal damage.

CONCLUSIONS

Our data suggest that the enhanced protective effect of GSTM2-transduced MSCs against anti-GBM-GN might be associated with inhibition of oxidative stress-induced renal cell apoptosis and inflammation, through over-expression of hGSTM2 in mouse kidneys.

Amelioration of Angiotensin II–Induced Salt-Sensitive Hypertension by Liver-Type Fatty Acid–Binding Protein in Proximal Tubules

Inappropriate activation of the intrarenal renin–angiotensin system induces generation of reactive oxygen species and tubulointerstitial inflammation, which contribute to salt-sensitive hypertension (SSHT). Liver-type fatty acid–binding protein is expressed in proximal tubules in humans, but not in rodents, and may play an endogenous antioxidative role. The objective of the present study was to examine the antioxidative effect of liver-type fatty acid–binding protein on post–angiotensin II SSHT model in transgenic mice with selective overexpression of human liver-type fatty acid–binding protein in the proximal tubules. The transgenic mice showed marked protection against angiotensin II–induced SSHT. Overexpression of tubular liver-type fatty acid–binding protein prevented intrarenal T-cell infiltration and also reduced reactive oxygen species generation, intrarenal renin–angiotensin system activation, and monocyte chemotactic protein-1 expression. We also performed an in vitro study using the murine proximal tubular cell lines with or without recombinant liver-type fatty acid–binding protein and murine proximal tubular cell lines transfected with human liver-type fatty acid–binding protein, and found that gene transfection of liver-type fatty acid–binding protein and, in part, recombinant liver-type fatty acid–binding protein administration had significantly attenuated angiotensin II–induced reactive oxygen species generation and the expression of angiotensinogen and monocyte chemotactic protein-1 in murine proximal tubular cell lines. These findings indicated that liver-type fatty acid–binding protein in the proximal tubules may protect against angiotensin II–induced SSHT by attenuating activation of the intrarenal renin–angiotensin system and reducing oxidative stress and tubulointerstitial inflammation. Present data suggest that liver-type fatty acid–binding protein in the proximal tubules may be a novel therapeutic target for SSHT.

Review and discussion of tubular biomarkers in the diagnosis and management of diabetic nephropathy

The prevalence of diabetic nephropathy has tremendously increased with the relentless rise in the incidence of diabetes over the last couple decades. Diabetic nephropathy is a leading cause of morbidity and mortality, and it invariably leads to an end-stage renal disease (ESRD). In an effort to delay the onset of ESRD systematic screening and appropriate management are needed to evaluate the progression of renal damage in diabetic nephropathy. The reliability of current tests in predicting the onset, progression and response to various regimens for diabetic nephropathy is still under debate; and it has engendered a search for more sensitive and specific urinary biomarkers, especially those reflective of tubular dysfunctions. It is well-known that there is a good correlation between the degree of damage to the tubulo-interstitial compartment and the deterioration of renal functions. In view of this, the utility of urinary biomarkers, reflective of tubular injury, reported in the literature is discussed in this brief review.

Telmisartan counteracts TGF-β1 induced epithelial-to-mesenchymal transition via PPAR-γ in human proximal tubule epithelial cells

Chronic renal failure (CRF) mainly results from kidney fibrosis. Epithelial-to-mesenchymal transition (EMT) occurs in stressed tubular epithelial cells and contributes to renal fibrosis. Transforming growth factor-β1 (TGF-β1) has been shown to initiate and complete the whole EMT process. Peroxisome proliferators-activated receptor-γ (PPAR-γ) exerts anti-inflammatory, anti-fibrotic and vaculo-protective effects on different renal diseases. Telmisartan is a member of angiotensin II (Ang II) receptor blocker (ARB) family. Recent studies show that Telmisartan has a partial agonistic effect on PPAR-γ. Therefore, we tested the hypothesis that Telmisartan reverses the progression of induced EMT by TGF-β1 in cultured human renal proximal tubular epithelial (HK-2) cells. Cultured HK-2 cells were treated with TGF-β1 (3 ng/ml), a combination of TGF-β1 and Telmisartan (10-200 umol/L) and a combination of TGF-β1, Telmisartan and GW9662, a PPAR-γ antagonist for 48 hours. EMT was determined by quantitative real-time PCR analysis of E-cadherin (E-cad), Connective Tissue Growth Factor (CTGF) and PPAR-γ transcript expression and immunocytochemical analysis of E-cad, α-Smooth Muscle Actin (α-SMA) and PPAR-γ protein expression. TGF-β1 induced phenotypic EMT in cultured HK-2 cell line via significantly reduced E-cad expression and significantly increased CTGF, α-SMA expression in association with the loss of epithelial morphology. Telmisartan reversed all EMT markers in a dose-dependent manner which was inhibited by PPAR antagonist GW9662. In the present study, it was suggested that Telmisartan attenuated TGF-β1 induced EMT by agonistic activation of PPAR-γ.