Sirt3 modulates fatty acid oxidation and attenuates cisplatin-induced AKI in mice.

Fatty acid oxidation (FAO) dysfunction is one of the important mechanisms of renal fibrosis. Sirtuin 3 (Sirt3) has been confirmed to alleviate acute kidney injury (AKI) by improving mitochondrial function and participate in the regulation of FAO in other disease models. However, it is not clear whether Sirt3 is involved in regulating FAO to improve the prognosis of AKI induced by cisplatin. Here, using a murine model of cisplatin-induced AKI, we revealed that there were significantly FAO dysfunction and extensive lipid deposition in the mice with AKI. Metabolomics analysis suggested reprogrammed energy metabolism and decreased ATP production. In addition, fatty acid deposition can increase reactive oxygen species (ROS) production and induce apoptosis. Our data suggested that Sirt3 deletion aggravated FAO dysfunction, resulting in increased apoptosis of kidney tissues and aggravated renal injury. The activation of Sirt3 by honokiol could improve FAO and renal function and reduced fatty acid deposition in wide-type mice, but not Sirt3-defective mice. We concluded that Sirt3 may regulate FAO by deacetylating liver kinase B1 and activating AMP-activated protein kinase. Also, the activation of Sirt3 by honokiol increased ATP production as well as reduced ROS and lipid peroxidation through improving mitochondrial function. Collectively, these results provide new evidence that Sirt3 is protective against AKI. Enhancing Sirt3 to improve FAO may be a potential strategy to prevent kidney injury in the future.

Low serum uric acid levels increase the risk of all-cause death and cardiovascular death in hemodialysis patients.

BACKGROUND: Elevated serum uric acid (SUA) is associated with increased cardiovascular (CV) and all-cause mortality risk in the general population, but the impact of UA on mortality in hemodialysis patients is still controversial. The aim of the study was to explore the relationship between SUA and all-cause mortality and CV mortality in hemodialysis patients. METHODS: This retrospective, observational cohort study included 210 HD patients with a mean age of 56.6 ± 16.6 years. All demographic and laboratory data were recorded at baseline. The Kaplan-Meier method and Cox proportional hazard regression model were used to examine the association between SUA and all-cause mortality and CV mortality in HD patients. RESULTS: With 420 µmol/L (20th percentile) and 644 µmol/L (80th percentile) as the boundary points, the patients were divided into three groups. After a median follow-up of 49.8 months, 68 (32.4%) all-cause deaths and 34 (16.2%) CV deaths were recorded. The Kaplan-Meier method showed that with a decrease in SUA, all-cause mortality (log rank χ2 = 15.61, p = .000), and CV mortality (log rank χ2=14.28, p = .000) increased. Each 100 µmol/L increase in SUA was associated with lower all-cause mortality with an hazard ratio (HR) of 0.792 (0.645-0.972) and lower CV mortality with an HR of 0.683 (0.505-0.924) after adjusting for age, sex, and complications. Compared to the lowest quartile, all-cause mortality [HR 0.351(0.132-0.934), p = .036] and CV mortality [HR 0.112 (0.014-0.925), p = .042] were lower in the highest SUA quartile. CONCLUSION: A lower SUA level in HD patients was associated with a higher risk of all-cause mortality and CV mortality. Moreover, higher SUA concentrations may be cardioprotective in HD patients.

Prevalence, determinants, and clinical significance of masked hypertension and white-coat hypertension in patients with chronic kidney disease.

BACKGROUND: Masked hypertension and white-coat hypertension have been studied among the general population and in hypertensive patients. However, little insight is available on masked and white-coat hypertension among patients with chronic kidney disease (CKD). METHODS: We recruited 1322 CKD patients admitted to our hospital division. Patients were divided into four groups: normotension; white-coat hypertension (WCHT); masked hypertension (MHT); sustained hypertension. Multivariable logistic regression analyses were used to evaluate the correlation between WCHT, MHT and renal/cardiovascular parameters. RESULTS: The prevalence of WCHT and MHT was 10.21% and 16.11%, respectively. Patients with WCHT and MHT had more severe target-organ damage (TOD) than patients with normotension, but had less severe TOD than patients with sustained hypertension. MHT correlated with impaired renal function and left-ventricular hypertrophy, whereas WCHT was associated with abnormal carotid intima media thickness. Age, body mass index, clinic and 24-h systolic blood pressure correlated with MHT, whereas clinic, 24-h diastolic blood pressure and night-time systolic blood pressure was associated with WCHT. CONCLUSIONS: Prevalence of WCHT and MHT was 10.21% and 16.11%, respectively. WCHT and MHT show a close relationship with TOD in CKD patients.

Serum immunoglobulin A/C3 ratio predicts progression of immunoglobulin A nephropathy.

AIM: The serum immunoglobulin A (IgA)/C3 ratio has been shown to be a good predictor of histological lesions and prognosis for patients with IgA nephropathy (IgAN) in Japanese. But its validity in the Chinese population is unclear. We sought to explore the long-term outcomes of IgAN, its clinical and histopathological predictors in Chinese patients. In particular, the role of serum IgA/C3 ratio in the course of IgAN was addressed. METHODS: A total of 217 biopsy-diagnosed IgAN patients were recruited into this prospective cohort with a mean follow-up of 36 months (25-75th percentile, 27-48). Sociodemographics, serum IgA/C3 level, other clinical examinations and Lee's histological grade were measured. The patients with a decline of estimated glomerular filtration rate (eGFR) > 50% or developing end-stage renal disease (ESRD) were defined as progression. RESULTS: A total of 21 patients was found to progress (9.7%). In multivariate analysis, renal end point of IgAN was significantly predicted by proteinuria ≥1 g/day (relative risk (RR) = 2.65, 95% confidence interval (CI) 1.01-7.68), hypertension (RR = 3.15, 95% CI 1.07-9.29), higher Lee's histological grade (RR = 4.67, 95% CI 1.43-15.25) and serum IgA/C3 ratio ≥ 3.32 (RR = 4.31, 95% CI 1.33-13.96). CONCLUSION: A proportion of patients with IgAN developed end stage renal disease in a Chinese group. In addition to some traditional risk factors, we also confirmed that IgA/C3 ratio is a useful predictor of poor outcomes of IgAN in Chinese patients.

The ambulatory arterial stiffness index and target-organ damage in Chinese patients with chronic kidney disease.

BACKGROUND: The ambulatory arterial stiffness index (AASI) can be used to predict cardiovascular morbidity and mortality in hypertensive patients. However, data on AASI in Chinese patients with chronic kidney disease (CKD) is not available. METHODS: This cross-sectional study enrolled 583 CKD patients. Univariate and multivariate analyses were used to evaluate the relationship between AASI and renal function and parameters of cardiovascular injury. RESULTS: Patients with a higher AASI had a higher systolic blood pressure, a lower estimated glomerular filtration rate (eGFR), a higher serum cystatin C, a higher left ventricular mass index (LVMI) and carotid intima-media thickness (cIMT). Univariate analyses showed that AASI was positively correlated with serum cystatin C (r=0.296, P < 0.001), serum creatinine (r=0.182, P < 0.001), and LVMI (r = 0.205, P < 0.001) and negatively correlated with the eGFR (r = -0.200, P < 0.001). Multivariate analyses revealed that serum cystatin C, eGFR, serum creatinine and LVMI were independently correlated with AASI. CONCLUSIONS: These data suggest that AASI was closely correlated with renal function and parameters of cardiovascular injury in Chinese CKD patients. Good quality, long-term, large longitudinal trials to validate the role of AASI in clinical practice for Chinese CKD patients.

Alteration of N6-Methyladenosine RNA Profiles in Cisplatin-Induced Acute Kidney Injury in Mice.

Aim: To identify the alterations of N6-methyladenosine (m6A) RNA profiles in cisplatin-induced acute kidney injury (Cis-AKI) in mice. Materials and Methods: The total level of m6A and the expression of methyltransferases and demethylases in the kidneys were measured. The profiles of methylated RNAs were determined by the microarray method. Bioinformatics analysis was performed to predict the functions. Results: Global m6A levels were increased after cisplatin treatment, accompanied by the alterations of Mettl3, Mettl14, Wtap, Fto, and Alkbh5. A total of 618 mRNAs and 98 lncRNAs were significantly differentially methylated in response to cisplatin treatment. Bioinformatics analysis indicated that the methylated mRNAs predominantly acted on the metabolic process. Conclusion: M6A epitranscriptome might be significantly altered in Cis-AKI, which is potentially implicated in the development of nephrotoxicity.

A retrospective cohort study on the pathology and outcomes of type 2 diabetic patients with renal involvement.

OBJECTIVE: To investigate the association of clinical and histological characteristics and the development of ESRD in T2DM patients with renal involvement. METHODS: We conducted a retrospective analysis of clinical and pathologic data from T2DM patients who underwent renal biopsy (n = 120). RESULTS: The mean age, duration of diabetes, and eGFR were 50.9 ± 11.2 years, 92.8 ± 41.3 months, 55.1 ± 42.3 mL/min/1.73 m2, respectively. Among these patients, 57 (47.5%) were diagnosed with diabetic nephropathy (DN), and 63 (52.5%) with non-diabetic renal disease (NDRD). The most common subtype of NDRD is membranous nephropathy. Compared with the NDRD group, the DN group had a longer duration of diabetes, worse renal function, and a higher proportion of diabetic retinopathy. Kaplan-Meier analysis showed that the 5-year renal survival rate of the DN group was only 41%, whereas that of the NDRD group was 84%. ESRD was defined as eGFR below 15 mL/min/1.73 m2. After multivariate adjustment, the risk of ESRD in DN patients was 3.81 times higher than that in NDRD patients. According to Glomerular Class, the 5-year renal survival rate of type IIA, IIB, III, and IV in the DN group was 88, 56, 28, and 15%, respectively. Kaplan-Meier analysis showed that there was a significant difference in renal survival among different glomerular classes or different interstitial fibrosis and tubular atrophy (IFTA) scores. But Cox proportional hazards analysis indicated that only IFTA score (HR 2.75, 95% CI 1.37-5.51, P = 0.001), but not the glomerular class (HR 1.21, 95% CI 0.73-2.00, P = 0.465), could predict renal outcome when adjusting for multivariate. CONCLUSION: The prognosis of DN patients is significantly worse than that of NDRD patients. Compared with glomerular lesions, tubulointerstitial lesions were associated with higher risk for renal death in DN patients.

The influence of cardiac valvular calcification on all-cause and cardiovascular mortality in maintenance hemodialysis patients.

OBJECTIVE: To investigate the effect of cardiac valve calcification (CVC) on all-cause and cardiovascular mortality in maintenance hemodialysis (MHD) patients. METHODS: A retrospective cohort study was conducted in 183 long-term hemodialysis patients with complete follow-up data from January 1, 2012, to December 30, 2015. The baseline data between CVC and non-CVC groups were compared. Kaplan-Meier method was used to analyze all-cause and cardiovascular mortality. The effect of CVC on prognosis was analyzed using the Cox proportional hazard regression model and subgroup analysis. RESULTS: Among 183 patients under hemodialysis, 104 (56.8%) were males, with an average age of 56.1 ± 17.0 years and 68 (37.2%) were complicated with valvular calcification. The median follow-up period was 30.8 months. All-cause and cardiovascular mortality were 50% vs. 14.8% and 25% vs. 7.0% in the CVC and non-CVC groups, respectively (P < 0.05). Kaplan-Meier indicated that differences in all-cause and cardiovascular mortality were statistically significant between the two groups (P < 0.001). Cox regression analysis showed that CVC significantly increased all-cause (hazards ratio [HR] 2.161 [1.083-4.315]) and cardiovascular mortality (3.435 [1.222-9.651]) after adjusting for multiple factors. Meanwhile, CVC also increases the incidence of new-onset cardiovascular events. Subgroup analysis revealed that all-cause and cardiovascular mortality were significantly higher in patients with aortic valve calcification (AVC) than in patients with mitral valve calcification (MVC). Multivariate calibration showed that AVC increased the risk of cardiovascular death (HR 5.486 [1.802-16.702]) (P < 0.05), whereas MVC did not. By further comparing the echocardiographic data of the two groups, the incidence of LVH and pulmonary hypertension in the AVC group was significantly higher than that in the MVC group. CONCLUSION: Valve calcification increases the risk of all-cause and cardiovascular mortality in MHD patients, also new-onset cardiovascular events, and aortic valve calcification contributes more to the risk of cardiovascular mortality.

Serum IgA1 from patients with IgA nephropathy up-regulates integrin-linked kinase synthesis and inhibits adhesive capacity in podocytes through indirect pathways.

PURPOSE: To investigate the influence of IgA1 isolated from IgA nephropathy (IgAN) patients on integrin-linked kinase (ILK) synthesis and adhesive capacity of podocytes through indirect pathways. METHODS: IgA1 was isolated from healthy control or IgAN patients' sera using jacalin affinity chromatography and S-200 chromatography. Podocytes were treated with medium from mesangial cells incubated with aggregated IgA1 (aIgA1, 100 microg/ml), in the presence or absence of valsartan (10(-5)M) or neutralizing antibodies of tumor necrosis factor-alpha (TNF-alpha, 50 ng/ml). Adhesive capacity of podocytes was assessed by cell counting manually and hexosaminidase assay. Real-time PCR and western blotting were used to detect the expression of ILK. RESULTS: Medium from mesangial cells incubated with aIgA1 from IgAN patients reduced podocyte adhesion to collagen compared with medium from mesangial cells incubated with control medium(RPMI-1640 with 0.5% FBS) (35.0+/-4.8% vs. 60.0+/-2.0%; P < 0.05). While medium from mesangial cells incubated with aIgA1 from IgAN patients upregulated ILK expression in podocytes at mRNA and protein levels compared with medium from mesangial cells without aIgA1 incubated (1.6-fold and 1.38-fold higher than control, respectively, P < 0.05). Defects in podocyte adhesion and up-regulation of ILK synthesis induced by medium from mesangial cells incubated with aIgA1 from IgAN patients can be partially reversed by the pre-treatment for 1 hour with valsartan(P < 0.05), while pre-treatment with neutralizing antibodies of TNF-alpha produced no protective effect on podocytes (P > 0.05). CONCLUSION: Serum IgA1 from IgAN patients may inhibit adhesive capacity and up-regulate ILK synthesis in podocytes through indirect pathways.

Circular RNA expression profiles in cisplatin-induced acute kidney injury in mice.

Aim: This study was carried out to identify the expression profile and role of circRNAs in cisplatin-induced acute kidney injury (AKI). Materials & methods: In this study, an AKI model was established in cisplatin-treated mice, and the expression of circRNAs was profiled by next-generation sequencing. The differential expression levels of selected circRNAs were determined by quantitative real-time polymerase chain reaction. Bioinformatics analysis was conducted to predict the functions. Results: In total, 368 circRNAs were detected to be differentially expressed in response to cisplatin treatment. Bioinformatics analysis indicated that the parental genes of the differentially expressed circRNAs were predominantly implicated in the cell and cell part, cellular process and cancer pathways. Conclusion: CircRNAs might be differentially expressed in AKI, which are potentially involved in pathophysiology of cisplatin-induced nephrotoxicity.

High prevalence of isolated nocturnal hypertension in Chinese patients with chronic kidney disease.

BACKGROUND: Isolated nocturnal hypertension (INH) has been studied among the general population and hypertensive patients. However, little insight is available on the prevalence of INH and its role in target-organ damage among patients with chronic kidney disease (CKD). METHODS AND RESULTS: We recruited 1282 CKD patients admitted to our hospital division. Patients were divided into 4 groups: INH; isolated daytime hypertension; day-night sustained; and ambulatory normotension. Multiple linear regression analyses were used to evaluate the correlation between INH and renal/cardiovascular parameters. A total of 262 (20.44%) CKD patients had isolated nocturnal hypertension and 651 (50.78%) had day-night sustained hypertension, whereas only 350 (27.30%) patients showed normotension and 19 (1.48%) had isolated daytime hypertension. Multivariate logistic regression analysis showed that INH was associated mainly with age, estimated glomerular filtration rate, clinic diastolic blood pressure, and that INH was determined only by age, estimated glomerular filtration rate, and clinic diastolic blood pressure. The prevalence of impaired renal function, left ventricular hypertrophy, and carotid intima-media thickness in patients with INH were higher than in normotensive patients (P<0.05), whereas impaired renal function and left ventricular hypertrophy in these patients were lower than patients in the day-night sustained hypertension group (P<0.05). INH was correlated with estimated glomerular filtration rate, left ventricular mass index, and carotid intima-media thickness according to multiple linear regression analyses. CONCLUSIONS: The prevalence of INH in CKD patients was high, and INH was correlated with target-organ damage in CKD patients.

Nocturnal Hypertension Correlates Better With Target Organ Damage in Patients With Chronic Kidney Disease than a Nondipping Pattern.

Both nocturnal hypertension and nondipping pattern are associated with target organ damages (TODs); however, no data exist with respect to Chinese patients with chronic kidney disease (CKD). The authors recruited 1322 patients with CKD admitted to our hospital division and referred with data in this cross-sectional study. Patients with nocturnal systolic hypertension had a lower estimated glomerular filtration rate (eGFR) and higher left ventricular mass index (LVMI) and carotid intima-media thickness (cIMT) compared with patients with normal nocturnal systolic blood pressure (SPB; all, P<.001), while patients in the dipper and nondipper groups had similar levels of eGFR, LVMI, and cIMT when the patients had a similar nocturnal SBP. Factorial-designed analysis of variance indicated that the main effect of nocturnal SBP was significant for all TOD differences (all, P<.001), but no significance existed with respect to the main effect of the dipper pattern and an interaction between the two factors (all, P>.05). Nocturnal systolic hypertension, rather than nondipping pattern, was an independent risk factor for TOD in CKD patients. Nocturnal hypertension, rather than a nondipping pattern, was better associated with TOD in CKD patients.

Disparate assessment of clinic blood pressure and ambulatory blood pressure in differently aged patients with chronic kidney disease.

BACKGROUND: Ambulatory blood pressure monitoring (ABPM) is recommended to assess hypertensive status in patients with chronic kidney disease (CKD). However, the difference in blood pressure (BP) based on clinic and ambulatory monitoring in CKD patients of different ages is not known. METHODS: We recruited 1116 CKD patients admitted to our hospital division and referred with data in this cross-sectional study. Patients were divided into three groups: young, middle age and old. Inter-method agreement between clinic BP and ABPM in different age groups was assessed using the Kappa (κ) coefficient. Linear and logistic regression analyses were used to evaluate renal and cardiovascular parameters. RESULTS: κ coefficient for inter-method agreement between clinic BP and ABP in patients from young, middle-age and old groups was 0.472 (p<0.001), 0.335 (p<0.001) and 0.102 (p=0.086), respectively. Age was the main factor determining the difference in clinic BP and ABP by multiple linear regression analyses. Prevalence of masked hypertension in older patients was higher than that in young and middle-age patients (p<0.001), and age was associated with the onset of masked hypertension. Age and ABP were independently correlated with estimated glomerular filtration rate (eGFR) and left ventricular mass index (LVMI), whereas age and clinic BP were associated with carotid intima media thickness (cIMT) by linear and logistic regression analyses. CONCLUSIONS: We have provided evidence of disparate assessment of the diagnosis and correlation with TOD from clinic BP and ABP in untreated, different-aged, CKD patients. Good-quality, long-term, large longitudinal trials are needed to validate the role of ABPM for Chinese CKD patients.

High glucose induces activation of the local renin­angiotensin system in glomerular endothelial cells.

Activation of the intrarenal renin­angiotensin system (RAS), which has been identified in podocytes and mesangial cells, is a novel mechanism in the progression of diabetic kidney disease (DKD). The present study aimed to identify the local RAS in glomerular endothelial cells (GEnCs). Rat GEnCs were stimulated by culture medium containing 30 mmol/l glucose for 12, 24, 48 and 72 h. Angiotensin II (Ang II) concentrations in cell lysates and culture media were examined by ELISA and mRNA levels of angiotensinogen and renin in cell lysates were analyzed by quantitative polymerase chain reaction. Ang II type 1 receptor (AT1R), Ang II type 2 receptor (AT2R), renin and angiotensinogen levels in cell lysates were determined by western blot analysis. Localization of intracellular AT1R, AT2R, angiotensinogen and renin was identified by confocal immunofluorescence microscopy. Consequently, high glucose (HG) increased intracellular and extracellular Ang II levels. Captopril and chymostatin (inhibitor of chymase, an enzyme that converts Ang I to Ang II) were able to antagonize HG­induced Ang II generation. Moreover, HG increased angiotensinogen production in GEnCs and reduced renin mRNA expression without altering renin protein production. However, HG decreased AT1R levels and resulted in AT2R shifting from the nuclear to perinuclear region in GEnCs. In conclusion, HG activated the intracellular RAS in rat GEnCs and the underlying mechanism may involve angiotensin­converting enzyme (ACE) and non­ACE pathways. The effects of HG on GEnCs may also involve the substrate and receptors of Ang II.

Effect of valsartan with bedtime dosing on chronic kidney disease patients with nondipping blood pressure pattern.

Nondipping blood pressure (BP) pattern is a potential independent risk factor for chronic kidney disease (CKD). Bedtime administration of valsartan is considered to normalize circadian rhythm and protect the kidneys and heart in CKD patients. However, more clinical trials are needed to confirm this benefit. Sixty patients with nondipping BP pattern and thirty patients with dipping BP pattern were enrolled in this study, and the patients with nondipping BP pattern were randomly divided into two groups and treated with bedtime or awakening doses of valsartan (80-320 mg). Nondipping BP patients treated with bedtime doses of valsartan showed a greater reduction in 24-hour proteinuria and bedtime proteinuria, a greater delayed decline in estimated glomerular filtration rate, and more protection against myocardial hypertrophy (P<.05) compared with patients with the nondipping BP pattern treated with the awakening dose (P<.05). This was similar to patients with dipping BP. No severe clinical complications were recorded in these patients. Valsartan with bedtime dosing in CKD patients with the nondipping BP pattern have better renal and cardiovascular protection. Antihypertensive "chronotherapy" may be useful in clinical practice for CKD patients.

Variability of glomerular filtration rate estimation equations in elderly Chinese patients with chronic kidney disease.

BACKGROUND: Chronic kidney disease (CKD) is recognized worldwide as a public health problem, and its prevalence increases as the population ages. However, the applicability of formulas for estimating the glomerular filtration rate (GFR) based on serum creatinine (SC) levels in elderly Chinese patients with CKD is limited. MATERIALS AND METHODS: Based on values obtained with the technetium-99m diethylenetriaminepentaacetic acid ((99m)Tc-DTPA) renal dynamic imaging method, 319 elderly Chinese patients with CKD were enrolled in this study. Serum creatinine was determined by the enzymatic method. The GFR was estimated using the Cockroft-Gault (CG) equation, the Modification of Diet in Renal Disease (MDRD) equations, the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation, the Jelliffe-1973 equation, and the Hull equation. RESULTS: The median of difference ranged from -0.3-4.3 mL/min/1.73 m(2). The interquartile range (IQR) of differences ranged from 13.9-17.6 mL/min/1.73 m(2). Accuracy with a deviation less than 15% ranged from 27.6%-32.9%. Accuracy with a deviation less than 30% ranged from 53.6%-57.7%. Accuracy with a deviation less than 50% ranged from 74.9%-81.5%. None of the equations had accuracy up to the 70% level with a deviation less than 30% from the standard glomerular filtration rate (sGFR). Bland-Altman analysis demonstrated that the mean difference ranged from -3.0-2.4 mL/min/1.73 m(2). However, the agreement limits of all the equations, except the CG equation, exceeded the prior acceptable tolerances defined as 60 mL/min/1.73 m(2). When the overall performance and accuracy were compared in different stages of CKD, GFR estimated using the CG equation showed promising results. CONCLUSIONS: Our study indicated that none of these equations were suitable for estimating GFR in the elderly Chinese population investigated. At present, based on overall performance, as well as performance in different CKD stages, the CG equation may be the most accurate for estimating GFR in elderly Chinese patients with CKD.

How increased VEGF induces glomerular hyperpermeability: a potential signaling pathway of Rac1 activation.

Despite growing evidence for a pathogenic role of vascular endothelial growth factor (VEGF) in microvascular complications of diabetes, the underlying mechanism responsible for its detrimental effect remains unknown. In the current study, we hypothesized that some of the detrimental effects of VEGF on microvascular endothelial cells in the diabetic milieu stem from its aberrant signaling, which leads to perturbed tight junction assembly and increased endothelial permeability. Using an integrated in vitro approach, we investigated whether the effect of VEGF on endothelial cell permeability involves Rac1 GTPase activation and tight junction disassembly. Rac1 activity was detected by Western blotting in cell membrane protein as well as pull-down assay. The permeability of glomerular endothelial cells monolayer was detected as transendothelial electronic resistance. Then tyrosine phosphorylated occludin protein was detected by Western blotting after immunoprecipitation. N17Rac1 cells are obtained by transfection of glomerular endothelial cells with a dominant negative mutant of Rac1. The data obtained in this study indicate that activation of Rac1 GTPase contributes to VEGF-induced endothelial cell hyperpermeability. We also observed that Rac1 activation leads to increased endothelial permeability through tyrosine phosphorylation of occludin. Indeed, N17Rac1 cells dramatically attenuated the effect of VEGF on phospho-occludin and endothelial cell permeability. These results, when taken together, provide a framework for understanding the role of VEGF-induced Rac1/phospho-occludin pathway in the integrity of endothelial barrier function in the glomerulus.