In vitro enhanced chemotaxis of CD25+ mononuclear cells in patients with familial IgAN through glomerulotubular interactions

Tubulointerstitial infiltration of immunocompetent cells is often associated with a more rapid progression in IgA nephropathy (IgAN). Using an in vitro Transwell coculture system, we examined the chemotactic response of peripheral blood mononuclear cells to proximal tubular epithelial cells (PTEC) following activation by conditioned medium prepared from mesangial cells cultured with macromolecular IgA1 from 60 patients with multiplex familial IgAN (MpIgAN) and 91 of their asymptomatic relatives; 43 patients with sporadic IgAN (SpIgAN) and 90 of their asymptomatic relatives; and 43 healthy subjects. Compared with SpIgAN patients, PTEC activated by conditioned medium from patients with MpIgAN had elevated gene expression of a spectrum of C-C, C-X-C chemokines and proinflammatory cytokines, with prominent expressions of interleukin-6, interleukin-8, and tumor necrosis factor-α. In response to conditioned medium from patients with familial IgAN, there was a significant increase in chemotaxis of CD45+ cells, CD3+, CD4+, CD8+, CD20+ lymphocytes, and monocytes with CD25 expression. Our findings suggest that compared with SpIgAN patients, macromolecular IgA1 taken from MpIgAN patients is more pathogenic to cultured PTEC through a glomerulotubular interaction. A long-term follow-up is needed to better define the prognostic course for familial IgAN and to clarify the risk of developing IgAN in initially asymptomatic relatives from a multiplex IgAN family.

The acetyl-coenzyme A carboxylase beta (ACACB) gene is associated with nephropathy in Chinese patients with type 2 diabetes

BACKGROUND

A single-nucleotide polymorphism (SNP), rs2268388, in the acetyl-coenzyme A carboxylase beta (ACACB) gene is associated with susceptibility to type 2 diabetic nephropathy (T2DN) in Japanese and European-American populations. Whether this association also exists in Chinese patients is unclear. Attempts at replication in small Singaporean and Korean samples were not significant.

METHODS

Eight ACACB SNPs were genotyped in 595 subjects with type 2 diabetes mellitus born in Hong Kong or southern China, 295 with advanced T2DN and 300 with long-standing diabetes lacking nephropathy. Association analyses were focused primarily on SNP rs2268388 and secondarily on flanking SNPs and haplotypes.

RESULTS

Adjusting for age, gender and diabetes duration, ACACB SNP rs2268388 was significantly associated with advanced T2DN (odds ratio = 2.39; recessive model; P = 0.0129).

CONCLUSION

These results in the Chinese replicate the association between T2DN and rs2268388, as seen in Japanese and European Americans. The ACACB gene and attendant alterations in fatty acid oxidation may play important roles in susceptibility to T2DN. Targeting this pathway may provide novel treatment options for the prevention of diabetic nephropathy.

Inflammation in peritoneal dialysis

During peritoneal dialysis, peritoneal cells are repeatedly exposed to a non-physiological hypertonic environment with high glucose content and low pH. Current sterile dialysis solutions cause inflammation in the submesothelial compact zone that leads to fibrosis, neoangiogenesis, progressive increases in solute transfer and even ultrafiltration failure. The peritoneal dysfunction will further be amplified with the development of an epithelial-to-mesenchymal transition of mesothelial cells and the dissipation of the osmotic driving force through increased area and solute transport that accompanied neoangiogenesis of the submesothelial microvasculature. The alteration in the peritoneal membrane will further be aggravated by peritonitis, advanced glycation end-products and glucose degradation products. Finally, there are emerging new data supporting a pro-inflammatory role of peritoneal adipocytes.

Sleep apnea is a novel risk predictor of cardiovascular morbidity and death in patients receiving peritoneal dialysis

Sleep apnea syndrome is increasingly recognized in peritoneal dialysis patients; however, its prognostic implication in this population is unknown. To study this, we prospectively followed the clinical outcome of 93 peritoneal dialysis patients with baseline polysomnography. Of these, 51 were diagnosed with the syndrome defined by an apnea-hypopnea index (AHI) of at least 15 per hour. During a median follow-up of 41 months, there were 30 deaths, of which 17 were due to cardiovascular causes. Kaplan-Meier analysis for the entire follow-up period indicated that patients with sleep apnea at baseline had significantly higher all-cause and cardiovascular mortality during follow-up than those without. Minimal nocturnal saturation and desaturation indices were predictors of mortality and cardiovascular events at univariate analysis. Multivariable Cox regression analysis identified significant sleep apnea syndrome at baseline as an independent predictor of increased all-cause mortality independent of age, male gender, and diabetic status. Further, an absolute increase in the AHI was associated with an incremental risk of cardiovascular events. Thus, sleep apnea syndrome, detected at the start of peritoneal dialysis, is a novel risk predictor for subsequent mortality and cardiovascular events.

Colonic Diverticulosis as a Risk Factor for Peritonitis in Chinese Peritoneal Dialysis Patients

Objectives

The risk of development of enteric peritonitis in Chinese peritoneal dialysis (PD) patients with colonic diverticulosis is not known. There have been no reports on whether colonic diverticulosis may affect peritonitis outcomes. The objectives of this study were to examine whether colonic diverticulosis is a risk factor for the development of enteric peritonitis and to study its influence on the outcome of enteric peritonitis.

Patients and Methods

All continuous ambulatory PD patients that had barium enema and colonoscopic examinations performed between January 1994 and January 2006 were included. They were divided into 2 groups: patients with diverticulosis and patients without diverticulosis. Their demographic and clinical characteristics, colonic examination findings, and peritonitis data were compared and analyzed.

Results

104 Chinese patients received 110 colonoscopies and 51 barium enema examinations. 25 patients (24.0%) had colonic diverticulosis. Patients with diverticulosis were older (65.4 ± 14.7 vs 58.4 ± 14.0 years, p = 0.033). The most common site of involvement of diverticulosis was the ascending colon (56%). 128 episodes of enteric peritonitis were recorded in 49 patients. Compared with patients without enteric peritonitis, more patients in the enteric peritonitis group had diverticulosis (38.8% vs 10.9%, p = 0.001) and diverticulosis most often involved the ascending colon (20.4% vs 7.3%, p = 0.082). Multivariate logistic regression analysis showed that the presence of diverticulosis (hazard ratio 5.17, 95% confidence interval 1.86 – 14.40; p = 0.002) and diverticulosis involving the ascending colon (hazard ratio 6.89, 95% confidence interval 1.43 – 33.32, p = 0.016) were independent risk factors for the development of enteric peritonitis. Enteric peritonitis in patients with diverticulosis had a higher but nonsignificant treatment failure rate (26.9% vs 18.4%, p = 0.282).

Conclusion

In this selected cohort of PD patients with indications of colonic examinations, diverticulosis, especially involving the ascending colon, may be a risk factor for the development of enteric peritonitis. Colonic diverticulosis does not appear to affect the outcome of enteric peritonitis. Further studies are warranted to determine ways to prevent enteric peritonitis in PD patients with diverticulosis.

Mechanism of chronic aristolochic acid nephropathy: role of Smad3

Aristolochic acid nephropathy (AAN) has become a worldwide disease and is the most severe complication related to the use of traditional Chinese medicine. However, the pathogenic mechanisms of AAN remain unclear and therapies are limited. The present study tested the hypothesis that transforming growth factor (TGF)-beta/Smad3 may be a key pathway leading to chronic AAN. This was examined in vivo in Smad3 wild-type/knockout (WT/KO) mice and in vitro in tubular epithelial cells with knockdown of Smad2 or Smad3. Results revealed that chronic administration of aristolochic acid (AA) resulted in a severe AAN characterized by progressive renal dysfunction and tubulointerstitial fibrosis including epithelial-mesenchymal transition (EMT) in Smad3 WT mice, but not in Smad3 KO mice, suggesting a critical role for Smad3 in the development of AAN. This was further tested in vitro. We found that AA was able to activate Smad signaling to mediate EMT and renal fibrosis via both TGF-beta-dependent and JNK/MAP kinase-dependent mechanisms because blockade of JNK and specific knockdown of Smad3, but not Smad2, were able to attenuate AA-stimulated collagen matrix expression and EMT. In conclusion, TGF-beta/Smad3 may be an essential mediator for chronic AAN. Results from this study indicate that specific blockade of the TGF-beta/Smad3 signaling pathway may have therapeutic potential for chronic AAN.

Renoprotection by rosiglitazone in accelerated type 2 diabetic nephropathy: Role of STAT1 inhibition and nephrin restoration

BACKGROUND

Rosiglitazone (Ros) has been shown to attenuate CXCL8 and ICAM-1 overexpression in renal tubular cells exposed to glycated albumin. The present study explores whether this can be translated into renoprotection in vivo. Uninephrectomized (Unx) type 2 diabetic db/db mice were chosen as a model of accelerated diabetic nephropathy.

METHODS

Uninephrectomy was performed in 10-week-old db/db mice. They were then treated with vehicle, metformin or Ros for 8 weeks.

RESULTS

Unx-db/db mice treated with Ros had lower serum creatinine and albuminuria, less severe glomerulosclerosis, tubulointerstitial injury, fewer infiltrating macrophages, and less proliferating nuclear antigen-positive tubular cells compared with mice treated with metformin that had a similar level of glycemic control and insulin resistance. In addition, Ros but not metformin attenuated renal cortical expression of CCL2, MIP-2, and ICAM-1 and inhibited p-STAT1 signal activation. Ros also increased glomerular nephrin expression.

CONCLUSIONS

Our results delineated the biochemical and histologic characteristics of Unx-db/db mice and demonstrated the in vivo glucose-independent anti-inflammatory mechanisms of Ros in nephropathy of accelerated murine type 2 diabetes.

A Prospective Randomized Study Comparing Tenckhoff Catheters Inserted using the Triple Incision Method with Standard Swan Neck Catheters

Background and Objective

The downward directed exit of the swan neck catheter may decrease the risk of exit-site infection (ESI). The percentage of migrations of the swan neck catheter seems to be less than the conventional Tenckhoff catheter and the swan neck catheter is more expensive and cannot be manipulated by guidewire technique if tip migration occurs. In this study, the conventional Tenckhoff catheter was used. The straight tunnel was converted to an arcuate one using the triple incision method, resulting in a downward directed exit. The arcuate tunnel was created by passing the catheter through an additional incision located between the paramedian incision and the exit site. We compared the infective and mechanical complications of the Tenckhoff catheter with a downward exit, implanted using the triple incision method, with the swan neck catheter.

Patients and Methods

101 new peritoneal dialysis patients were prospectively randomized to receive either the Tenckhoff catheter with a downward exit, implanted using the triple incision method, or the swan neck catheter. Each patient was followed up for 24 months. 50 patients were in the triple incision method group (TIMG) and 51 were in the swan neck catheter group (SNCG).

Results

Over a mean period of 18.9 ± 8.0 months of follow-up, ESI occurred in 35 patients (70%) in TIMG and 37 patients (72.5%) in SNCG ( p = 0.83). The ESI rates were 0.71 and 1.0 episodes/catheter-year in TIMG and SNCG respectively ( p = 0.21). The peritonitis rates were similar in the 2 groups (0.64 episodes/year in TIMG and 0.68 episodes/year in SNCG, p = 0.47). More patients in TIMG had tip migration [15 patients (30%) in TIMG vs 10 patients (19.6%) in SNCG] but the difference was not statistically significant. Repositioning of the catheter by guidewire manipulation was successful in patients in TIMG but not in SNCG. Overall catheter survival at 12 and 24 months was 95% and 83% in TIMG and 93% and 79% in SNCG respectively ( p = 0.72).

Conclusion

By using the conventional Tenckhoff catheter with a downward exit created using the triple incision method, high catheter survival rates with infective and mechanical complication rates similar to those of the swan neck catheter can be achieved. The triple incision method has the additional advantages of lower cost and the catheter can be manipulated by guidewire technique if tip migration occurs.

Long-term study of mycophenolate mofetil treatment in IgA nephropathy

Since the efficacy of mycophenolate mofetil (MMF) to treat immunoglobulin A (IgA) nephropathy is controversial, we extended our original study by following 40 Chinese patients with established IgA nephropathy for 6 years. All patients were maintained on their angiotensin blockade medication and half were randomized to receive MMF for 6 months. After 6 years, 11 patients required dialysis (2 from the MMF and 9 from the control group). Significantly, only 3 treated (as compared to 10 control) patients reached the composite end point of serum creatinine doubling or end-stage renal disease. Linear regression showed the annualized decline in the estimated glomerular filtration rate was significantly less in the MMF-treated group. Urinary protein excretion and the albumin-to-creatinine ratio were lower with MMF treatment during the first 24 months, beyond which there was no difference between groups. Multivariable Cox regression analysis showed that the baseline estimated glomerular filtration rate and proteinuria, and change in the urine albumin-to-creatinine ratio at 1 year to be important predictors of progression to end-stage renal disease. We found that among Chinese patients with IgA nephropathy who had mild histologic lesions and persistent proteinuria despite maximal angiotensin blockade, MMF treatment may result in transient and partial remission of proteinuria in the short-term and renoprotection in the long-term.

Non-viral Smad7 gene delivery and attenuation of postoperative peritoneal adhesion in an experimental model

BACKGROUND

Postoperative intra-abdominal adhesion is associated with high morbidity and mortality. Smad7, a protein that occupies a strategic position in fibrogenesis, inhibits the transforming growth factor (TGF) beta/Smad signalling pathway. In this study the therapeutic potential of exogenous Smad7 in preventing fibrogenesis in postoperative intra-abdominal adhesion was investigated.

METHODS

Intra-abdominal adhesion was induced in a rodent model by peritoneal abrasion. Smad7 was delivered into the peritoneal cavity by a non-viral ultrasound-microbubble-mediated naked gene transfection system. The effect of Smad7 transgene on adhesion formation was studied by measuring changes in TGF-beta, fibrogenic factors, alpha-SMA and Smad2/3 activation in the anterior abdominal wall.

RESULTS

Four weeks after surgical abrasion, all rats developed significant peritoneal adhesion with enhanced TGF-beta expression, increased levels of extracellular matrix components and activated myofibroblasts, accompanied by decreased Smad7 expression and increased Smad2/3 activation. In rats treated with the Smad7 transgene, the incidence and severity of peritoneal adhesion were significantly reduced, with biochemical downregulation of fibrogenic factors and inhibition of Smad2/3 activation. Serial quantitation using magnetic resonance imaging revealed a significant reduction in adhesion areas from day 14 onwards.

CONCLUSION

Ultrasound-microbubble-mediated gene transfection provides timely targeted gene delivery for the treatment of postoperative peritoneal adhesions.

Activation of p53 promotes renal injury in acute aristolochic acid nephropathy

Ingestion of aristolochic acid (AA) can cause AA nephropathy (AAN), in which excessive death of tubular epithelial cells (TECs) characterize the acute phase. AA forms adducts with DNA, which may lead to TEC apoptosis via p53-mediated signaling. We tested this hypothesis both by studying p53-deficient mice and by blocking p53 in TECs with its inhibitor pifithrin-alpha. AA induced acute AAN in wild-type mice, resulting in massive apoptotic and necrotic TEC death and acute renal failure; p53 deficiency or pharmacologic inhibition attenuated this injury. In vitro, AA induced apoptotic and necrotic death of TEC in a time- and dosage-dependent manner, with apoptosis marked by a 10-fold increase in cleaved caspase-3 and terminal deoxynucleotidyl transferase-mediated digoxigenin-deoxyuridine nick-end labeling-positive/Annexin V-positive propidium iodide-negative TECs (all P < 0.001). AA induced dephosphorylation of STAT3 and the subsequent activation of p53 and TEC apoptosis. In contrast, overexpression of STAT3, p53 inhibition, or p53 knockdown with small interfering RNA all attenuated AA-induced TEC apoptosis. Taken together, these results suggest that AA induces TEC death via apoptosis by dephosphorylation of STAT3 and posttranslational activation of p53, supporting the hypothesis that p53 promotes renal injury in acute AAN.

Retroperitoneal leakage as a cause of acute ultrafiltration failure: its associated risk factors in peritoneal dialysis

BACKGROUND

Ultrafiltration failure is an important clinical problem in patients on maintenance peritoneal dialysis (PD) and is associated with high morbidity and mortality. Acute ultrafiltration failure (AUFF) is usually secondary to mechanical problems with the peritoneal catheter or peritoneal leakage. Retroperitoneal leakage (RPL) is an important cause of AUFF and often poses diagnostic difficulty. Herein we analyze the incidence of AUFF secondary to RPL in our centers and study its associated risk factors.

METHODS

After excluding causes due to mechanical problems with the peritoneal catheter, patients complicated by AUFF underwent computerized tomographic peritoneography (CTP) or magnetic resonance imaging of the peritoneal cavity (MRP) to determine any RPL. Other patients on maintenance PD without RPL served as controls for comparison of risk factors. Demographic and peritoneal membrane characteristics, including history of hernia and pleuroperitoneal leakage, were analyzed.

RESULTS

During the 5-year study period, 36 patients in a cohort of 743 patients on maintenance PD developed AUFF. 23 of these 36 patients were found to have RPL, which was confirmed by either CTP (n = 16) or MRP (n = 7). The duration of PD at the time of RPL and the dialysate-to-plasma ratio of creatinine at 4 hours were 49.3 +/- 24.5 (range 0.5 - 87.9) months and 0.70 +/- 0.09 respectively. Incidences of hernia (52.2%) and pleuroperitoneal communication (34.8%) were significantly higher than in PD patients without RPL (13% and 7% respectively, p = 0.001). Logistic regression analysis identified hernia and pleuroperitoneal communication as the risk factors for RPL. The odds ratios for RPL with hernia and pleuroperitoneal communication were 6.62 [95% confidence interval (CI) 2.35 - 18.69, p < 0.001] and 6.23 (95% CI 1.83 - 21.19, p = 0.003) respectively.

CONCLUSION

RPL was not uncommon in patients with AUFF. A high index of suspicion for RPL is needed in the management of patients with history of hernia or pleuroperitoneal communication presenting with AUFF.

Retroperitoneal Leakage as a Cause of Acute Ultrafiltration Failure: Its Associated Risk Factors in Peritoneal Dialysis

Background

Ultrafiltration failure is an important clinical problem in patients on maintenance peritoneal dialysis (PD) and is associated with high morbidity and mortality. Acute ultrafiltration failure (AUFF) is usually secondary to mechanical problems with the peritoneal catheter or peritoneal leakage. Retroperitoneal leakage (RPL) is an important cause of AUFF and often poses diagnostic difficulty. Herein we analyze the incidence of AUFF secondary to RPL in our centers and study its associated risk factors.

Methods

After excluding causes due to mechanical problems with the peritoneal catheter, patients complicated by AUFF underwent computerized tomographic peritoneography (CTP) or magnetic resonance imaging of the peritoneal cavity (MRP) to determine any RPL. Other patients on maintenance PD without RPL served as controls for comparison of risk factors. Demographic and peritoneal membrane characteristics, including history of hernia and pleuroperitoneal leakage, were analyzed.

Results

During the 5-year study period, 36 patients in a cohort of 743 patients on maintenance PD developed AUFF. 23 of these 36 patients were found to have RPL, which was confirmed by either CTP ( n = 16) or MRP ( n = 7). The duration of PD at the time of RPL and the dialysate-to-plasma ratio of creatinine at 4 hours were 49.3 ± 24.5 (range 0.5 – 87.9) months and 0.70 ± 0.09 respectively. Incidences of hernia (52.2%) and pleuroperitoneal communication (34.8%) were significantly higher than in PD patients without RPL (13% and 7% respectively, p = 0.001). Logistic regression analysis identified hernia and pleuroperitoneal communication as the risk factors for RPL. The odds ratios for RPL with hernia and pleuroperitoneal communication were 6.62 [95% confidence interval (CI) 2.35 – 18.69, p < 0.001] and 6.23 (95% CI 1.83 – 21.19, p = 0.003) respectively.

Conclusion

RPL was not uncommon in patients with AUFF. A high index of suspicion for RPL is needed in the management of patients with history of hernia or pleuroperitoneal communication presenting with AUFF.

Sleep disturbances and sleep apnea in patients on chronic peritoneal dialysis

Sleep disturbances in chronic peritoneal dialysis (PD) patients are increasingly widely recognized. These include changes in sleep architecture, sleep apnea syndrome, restless legs syndrome, periodic limb movement disorder and excessive daytime sleepiness. Some of these entities will be addressed in this review. The study tools for detecting sleep-related disorders in PD patients range from self-reported questionnaires (subjective) to standard overnight polysomnographic measurements (objective). Both these tools identify a high prevalence (over 50%) of sleep-related disorders among dialysis patients. Among these, sleep apnea syndrome is one of the most widely reported sleep-related disorders in PD. Sleep apnea in PD may be attributed to chronic fluid overload and uremia, leading to both obstructive and central forms of apneas. The exact underlying pathophysiology, however, is complex and likely involves a combination of multiple factors. There are preliminary data that nocturnal PD may be advantageous over conventional continuous ambulatory peritoneal dialysis in correcting sleep apnea associated with PD. Randomized studies are needed for confirmation.

Protective effect of peroxisome proliferator-activated receptor-gamma agonists on activated renal proximal tubular epithelial cells in IgA nephropathy

BACKGROUND

We have previously demonstrated a glomerulo-tubular 'crosstalk' operating in the pathogenesis of tubulointerstitial injury in IgA nephropathy (IgAN). The present study aims to explore any possible beneficial effect of a peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonist in alleviating the tubulointerstitial inflammation in IgAN.

METHODS

Human proximal tubular epithelial cells (PTEC) were pre-treated with increasing concentration of a PPAR-gamma agonist rosiglitazone or troglitazone (0-5 microM) followed by further incubation with the conditioned medium (IgA-HMC) collected from human mesangial cells (HMC) incubated with polymeric IgA isolated from IgAN patients. Gene expression of interleukin-6 (IL-6) and angiotensin II type 1 receptor (ATR1) was detected by reverse transcription-polymerase chain reaction (RT-PCR); protein expression of IL-6 and ATR1 was determined by ELISA and western blot, respectively. The mitogen-activated protein kinase extracellular signal-related kinase 1/2 (ERK1/2) activation was examined by western blot.

RESULTS

An IgA-HMC conditioned medium prepared from IgAN patients increased gene expression and protein synthesis of IL-6 and ATR1 in PTEC when compared with a conditioned medium prepared from healthy controls. The upregulated gene expression and protein synthesis of IL-6 and ATR1 in PTEC induced by the IgA-HMC conditioned medium were readily attenuated following pre-treatment with a PPAR-gamma agonist, thiazolidinedione (TZD). The ATR1-downregulating effect exerted by the PPAR-gamma agonist occurred through the inhibition of ERK1/2 activation. The PPAR-gamma antagonist, GW9662, significantly attenuated the inhibitory action of rosiglitazone on the increased synthesis of IL-6 and ATR1 protein.

CONCLUSION

Our current findings suggest that the PPAR-gamma agonist attenuates excessive inflammatory response in activated PTEC in IgAN through suppressing ATR1 expression. This ATR1-downregulating effect is likely through the inhibition of ERK1/2 activation and is found to be PPAR-gamma dependent. TZDs may possibly be new therapeutic additives to established treatment regime for renin-angiotensin system (RAS) blockade in IgAN.

Improvement in sleep apnea during nocturnal peritoneal dialysis is associated with reduced airway congestion and better uremic clearance

BACKGROUND AND OBJECTIVES

Among peritoneal dialysis (PD) patients, nocturnal PD (NPD) is known to improve sleep apnea compared with continuous ambulatory peritoneal dialysis (CAPD), but the contributing factors are unclear.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

Thirty-eight incident ESRD patients underwent overnight polysomnography (PSG) during NPD and CAPD. Bioelectrical impedance analysis, magnetic resonance imaging of the upper airway, and urea kinetics (Kt/V) during sleep were measured on both occasions.

RESULTS

The prevalence of severe sleep apnea (apnea-hypopnea index, AHI > or = 15/h) was 21.1% during NPD, and 42.1% during CAPD. Mean AHI increased from 9.6 +/- 2.7/h during NPD to 21.5 +/- 4.2/h during CAPD. Both obstructive and central apnea worsened after conversion to CAPD. NPD achieved greater reductions in total body water, hydration fraction, and net ultrafiltration than CAPD during sleep. Overnight peritoneal Kt/V and creatinine clearance were lower after conversion. Both peritoneal Kt/V and peritoneal creatinine clearance correlated with AHI, as did their changes after conversion. Volumetric magnetic resonance imaging revealed reduced pharyngeal volumes and cross-sectional area, and tongue enlargement after conversion.

CONCLUSIONS

Improvement in sleep apnea during NPD versus CAPD is associated with better fluid and uremic clearance and reduced upper airway congestion during sleep.

Disruption of the Smad7 gene promotes renal fibrosis and inflammation in unilateral ureteral obstruction (UUO) in mice

BACKGROUND

The present study tested the hypothesis that disruption of Smad7 function may accelerate renal fibrosis and inflammation.

METHODS

This was investigated in a unilateral ureteral obstruction (UUO) model induced in wild-type (WT) and Smad7DeltaE1 mice in which functional Smad7 is disrupted by deleting exon I in the Smad7 gene. Renal fibrosis and inflammation after UUO were examined by histology, real-time PCR, western blot analyses and immunohistochemistry.

RESULTS

Seven days after UUO, severe tubulointerstitial fibrosis developed in WT mice as evidenced by a marked increase in alpha-SMA, collagen I and III extracellular matrix. This was associated with a significant upregulation of renal TGF-beta1 and CTGF and activation of Smad2/3. Interestingly, compared to WT UUO mice, Smad7DeltaE1 mice with UUO exhibited a further increase in TGF-beta/Smad2/3-dependent renal fibrosis. Moreover, compared to WT UUO mice, deletion of the Smad7 gene also sustained NF-kappaB activation and thus enhanced further renal inflammation such as macrophage infiltration and upregulation of TNF-alpha, MCP-1, OPN and ICAM-1.

CONCLUSION

Smad7 is a critical negative regulator of TGF-beta/Smad2/3 and NF-kappaB signalling and plays a negative regulating role in both renal fibrosis and inflammation after UUO. Results from this study further support the notion that Smad7 may be a therapeutic agent for kidney diseases.

Regulation of CCN2/CTGF and related cytokines in cultured peritoneal cells under conditions simulating peritoneal dialysis

BACKGROUND

Continuous ambulatory peritoneal dialysis (CAPD) is a major treatment modality for end-stage renal failure. The peritoneal membrane exhibits pathological changes that correlate with the duration of dialysis. These changes are due to the exposure of the peritoneum to non-physiologic peritoneal dialysis solution (PDS) with a high glucose content, and containing potentially toxic substances including glucose degradation products (GDP) and advanced glycation end products (AGE). Connective tissue growth factor (CTGF/CCN2) is one of the determinants of progressive fibrosis and peritoneal membrane dysfunction in CAPD. In this study, we examined the CCN2 expression and its regulation in peritoneal resident cells using a cell culture model.

METHODS

The expression of transforming growth factor-beta (TGF-beta), CCN2 and vascular endothelial growth factor (VEGF) in human peritoneal mesothelial cells (HPMC), human peritoneal fibroblasts (HPF) or endothelial cell line EA.hy926 (EC) cultured with various PDS and their components was examined by quantitative PCR (qPCR). The modulation of CCN2 synthesis under the crosstalk between HPMC and HPF or EC was examined using a conditioned medium transfer system in which HPMC was exposed to conditioned media obtained from HPF or EC incubated with PDS and their components. The differential effects of TGF-beta, CCN2 and VEGF in inducing the expression of transcriptional factors as well as interleukin-6 (IL-6), matrix metallopeptidase 9 (MMP-9) and collagen I were examined by electrophoretic mobility-shift assay (EMSA) and qPCR.

RESULTS

PDS and their components differentially modulated the expression of TGF-beta, CCN2 and VEGF in HPMC, HPF and EC. The expression of CCN2 by HPMC was significantly increased after cultured with a HPF-conditioned medium and an EC-conditioned medium. Neutralizing anti-TGF-beta antibodies reduced but not completely abolished the CCN2 synthesis in HPMC cultured with the HPF- or EC-conditioned medium. CCN2, TGF-beta and VEGF activated distinct transcriptional factors in HPMC, which resulted in divergent biological responses in terms of IL-6, MMP-9 and collagen I mRNA expression.

CONCLUSION

AGE and GDPs in PDS differentially regulate the synthesis of CCN2 by peritoneal resident cells. The CCN2 synthesis by HPMC can be further amplified by TGF-beta released from HPF or EC. The differential activation of different transcriptional factors and diverse response of HPMC towards CCN2, TGF-beta and VEGF suggest that these cytokines/growth factors have an overlapping and distinct role on HPMC.

Podocyte injury induced by mesangial-derived cytokines in IgA nephropathy

BACKGROUND

We have previously documented that human mesangial cell (HMC)-derived tumour necrosis factor-alpha (TNF-alpha) is an important mediator involved in the glomerulo-tubular communication in the development of interstitial damage in IgA nephropathy (IgAN). With the strategic position of podocytes, we further examined the function of podocytes in IgAN.

METHODS

Podocyte markers were examined in renal tissues by immunofluorescence. In vitro experiments were conducted with podocytes cultured with polymeric IgA (pIgA) or conditioned medium prepared from HMC incubated with pIgA (IgA-HMC conditioned medium).

RESULTS

Glomerular immunostaining for nephrin or ezrin was significantly weaker in patients with IgAN. The immunostaining of IgA and nephrin was distinctly separate with no co-localization. In vitro experiments revealed no effect of pIgA on the expression of these podocyte proteins as IgA from IgAN patients did not bind to podocytes. In contrast, IgA conditioned medium prepared from IgAN patients down-regulated the expression of these podocyte proteins as well as other podocyte markers (podocin and synaptopodin) in cultured podocytes. The mRNA expression of nephrin, erzin, podocin but not synaptopodin correlated with the degree of proteinuria and creatinine clearance. The down-regulation was reproducible in podocytes cultured with TNF-alpha or transforming growth factor-beta (TGF-beta) at concentration comparable to that in the IgA-HMC conditioned medium. The expression of these podocyte proteins was restored partially with a neutralizing antibody against TNF-alpha or TGF-beta and fully with combination of both antibodies.

CONCLUSION

Our finding suggests podocyte markers are reduced in IgAN. An in vitro study implicates that humoral factors (predominantly TNF-alpha and TGF-beta) released from mesangial cells are likely to alter the glomerular permeability in the event of proteinuria and tubulointerstitial injury in IgAN.

Procalcitonin Fails to Differentiate Inflammatory Status or Predict Long-Term Outcomes in Peritoneal Dialysis-Associated Peritonitis

Background

Peritonitis is the major complication in patients undergoing maintenance peritoneal dialysis (PD) and is associated with a significant risk of mortality. Previously, we have shown that patients treated for peritonitis and having prolonged elevation of C-reactive protein (CRP) are associated with higher mortality. The underlying cause for the chronic systemic inflammation remains unknown. We studied serum procalcitonin (PCT), which has been reported as an accurate marker for infection and inflammation, with respect to being a diagnostic and prognostic indicator of persistent chronic inflammation after peritonitis in patients with PD-related peritonitis.

Methods

We conducted a prospective study on PD patients that developed PD-related peritonitis. Blood samples obtained at routine check-up before the onset of peritonitis were taken as baseline (D0). When patients developed PD-related peritonitis, serial blood samples were obtained on day 1 (D1), day 7 (D7), and day 42 (D42) for PCT, CRP, and other inflammatory markers. Patients were followed up for at least 2 years, during which outcomes of peritonitis and causes of death were recorded. Serum levels of CRP and PCT at day 42 were analyzed to assess for long-term prognosis.

Results

35 patients [female 42.9%; mean age 63.8 ± 13.1 years; 12 (34.3%) diabetics] were recruited. The onset of peritonitis was 3.61 ± 3.56 years after PD initiation and median residual renal function at that time was 1.06 (range 0 – 6.1) mL/min. Median total white cell counts in PD effluent at days 1, 3, 7, and 42 were 3505/mm3 (range 377 – 20500/mm3), 297 (8 – 5880)/mm3, 34 (0 – 5290)/mm3, and 10 (0 – 115)/mm3, respectively. Twelve (34.3%) and 14 (40%) PD effluents grew gram-positive and gram-negative micro-organisms respectively; others were culture negative. Median PCT was increased significantly at day 1 [2.00 (0.12 – 58.7) ng/mL, p < 0.001], day 7 [0.76 (0.13 – 15.25) ng/mL, p < 0.001], and day 42 [0.30 (0.13 – 0.79) ng/mL, p = 0.005] compared to baseline [0.20 (0.09 – 0.69) ng/mL]. Seven of 35 patients had false-negative results on day 1 (range 0.12 – 0.46) when PCT <0.5 ng/mL was used as the cutoff value for diagnosing peritonitis. For the long-term prognostic outcome, CRP at day 42 was significantly better than PCT in assessing overall prognosis (CRP: AUC 0.712, 95% CI 0.534 – 0.890 vs PCT: AUC 0.652, 95% CI 0.448 – 0.855). In Kaplan–Meier survival analysis, patients with elevated CRP (>3.0 mg/L) were associated with poorer long-term survival ( p = 0.04) but elevated PCT at the 25th, 50th, or 75th percentiles failed to provide prognostic value.

Conclusions

PD patients after peritonitis may be associated with prolonged systemic inflammation. CRP was a better serum marker for monitoring inflammatory status and predicting long-term prognosis in our study. Although serum PCT is elevated in some patients at the time of peritonitis, its value in making a diagnosis and predicting long-term prognosis remains doubtful.