Ka-Bik Lai

Endotoxemia is related to systemic inflammation and atherosclerosis in peritoneal dialysis patients.

BACKGROUND AND OBJECTIVES Systemic inflammatory state is a hallmark of peritoneal dialysis (PD) patients, but its etiology remains obscure. Because circulating microbial products are an important cause of systemic immune activation in other conditions such as HIV infection, it was hypothesized that endotoxemia is a cause of systemic inflammatory state and atherosclerosis in PD patients. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Plasma lipopolysaccharide (LPS) levels in 30 consecutive new PD patients were measured. The result was compared with serum C-reactive protein (CRP) level, peritoneal transport status, history of pre-existing cardiovascular diseases, and carotid intima media thickness (IMT) by Doppler ultrasound. RESULTS Among the 30 PD patients, there were 17 men. The average age was 53.7 +/- 15.1 yr. The average endotoxin concentration of PD patients was 0.44 +/- 0.18 EU/ml, which was significantly higher than that of patients with chronic kidney disease secondary to Ig-A nephropathy (IgAN) (0.035 +/- 0.009 EU/ml, P < 0.0001) and the controls (0.013 +/- 0.007 EU/ml, P < 0.0001). In PD patients, plasma LPS concentration had a significant correlation with serum CRP (r = 0.415, P = 0.025) and serum albumin level (r = -0.394, P = 0.034). In contrast, plasma LPS level did not correlate with Charlsons Comorbidity Index, peritoneal transport characteristics, or nutritional indices. Patients with pre-existing cardiovascular disease (CVD) had higher plasma LPS level than those without CVD (0.53 +/- 0.19 versus 0.36 +/- 0.16 EU/ml, P = 0.016). Plasma LPS level correlated with carotid IMT (r = 0.438, P = 0.016). CONCLUSIONS It was found that endotoxemia was probably common in PD patients, and the degree of circulating endotoxemia might be related to the severity of systemic inflammation and features of atherosclerosis. This result suggests that endotoxemia may have a contributory role to the systemic inflammatory state and accelerated atherosclerosis in PD patients.

The gene expression of type 17 T-helper cell-related cytokines in the urinary sediment of patients with systemic lupus erythematosus

OBJECTIVE We studied the role of type 17 Th cells (TH17) in the pathogenesis of SLE. METHODS We quantified the mRNA expression of IL-17, -23, -27 and retinoic-acid-related orphan receptor (ROR)-gamma, the regulator for the development and function of TH17, in the urinary sediment of 23 subjects with active lupus nephritis, 25 subjects with a history of lupus nephritis in remission, 30 SLE patients with no history of renal involvement and 8 healthy subjects. RESULTS All three groups of lupus patients had a higher urinary expression of TH17-related cytokines than the controls. However, urinary expression of IL-17 and -27 was found to be inversely correlated with the SLEDAI score (r = -0.252 and -0.258, respectively; P < 0.05 for both). For patients with active lupus nephritis, the histological activity index of kidney biopsy was also found to be inversely correlated with the urinary expression of ROR-gamma (r = -0.447; P = 0.032), IL-17 (r = -0.454; P = 0.029) and IL-23 (r = -0.455; P = 0.029). Urinary expression of IL-17, -23, -27 and ROR was also found to be inversely correlated with the urinary expression of IFN-gamma and T-bet, the key transcription factor of type 1 Th cells. After 6 months of treatment, urinary IL-27 expression rose significantly in patients with complete response (from 2.07 +/- 1.62 to 3.70 +/- 1.69; P = 0.028) but remained unchanged in those with partial or no response (from 2.60 +/- 1.87 to 2.52 +/- 1.94; P = 0.9). CONCLUSIONS The urinary expression of TH17-related genes is increased in SLE patients. The degree of up-regulation, however, is inversely related to systemic and renal lupus activity, as well as urinary expression of TH1-related genes. Urinary expression of TH17-related genes increased again after successful immunosuppressive treatment of active disease. Our findings suggest a regulatory role of TH17-related cytokines in pathogenesis of lupus nephritis.

Intrarenal cytokine gene expression in lupus nephritis

Background: Lupus nephritis is characterised by intrarenal inflammation and lymphocyte activation. Aim: To examine the profile of cytokine gene expression in glomerulus and tubulointerstitium in patients with lupus nephritis. Methods: 36 consecutive patients with systemic lupus erythematosus having active renal disease were recruited, and they were required to undergo kidney biopsy. Glomerular and tubulointestitial cytokine expression of interleukin (IL)2, 4, 10, 12, 18, interferon γ (IFN)γ, T-bet (the Th1 transcription factor), GATA-3 (the Th2 transcription factor), transforming growth factorβ and monocyte chemoattractant protein (MCP)1 were studied by laser microdissection of the renal biopsy specimen, followed by real-time quantitative PCR. Results: There were 13 patients with World Health Organization class III nephritis, 14 patients with class IV nephritis and 9 patients with class V nephritis. There was a significant correlation between serum C3, C4 and anti-double strand DNA antibody level with glomerular expression of T-bet, IFNγ and IL2. There was a significant correlation between histological activity index and glomerular expression of IL12, IL18, IL10 and MCP1. In addition, the degree of glomerular leucocyte infiltration significantly correlated with glomerular expression of IFNγ, IL10, IL12 and IL18. By contrast, histological chronicity index correlated with the tubulointerstitial expression of IL2, MCP1 and GATA-3. Conclusions: Intraglomerular expression of certain target genes correlate with the severity of systemic as well as histological activity, whereas the tubulointerstitial expression of other target genes correlate with the degree of chronic kidney scarring. This result may shed light on the immunopathogenesis of lupus nephritis.

Podocyte loss in human hypertensive nephrosclerosis.

BACKGROUND Podocyte injury probably plays important roles in the pathogenesis of hypertensive nephropathy, but human data are limited. We studied glomerular podocyte count and intrarenal expression of podocyte-associated molecules in patients with hypertensive nephrosclerosis. METHODS We studied 41 consecutive patients with biopsy-proven hypertensive nephropathy, 10 cadaveric kidney donors, and 9 healthy subjects. Intrarenal and urinary mRNA expression of podocyte-associated molecules was quantified and podocyte number was determined by stereological method. RESULTS Intrarenal mRNA expression levels of nephrin, podocin, and synaptopodin were lower, and urinary mRNA expression levels were higher in patients with hypertensive nephropathy than controls. Glomerular podocyte number was significantly lower in patients with hypertensive nephrosclerosis than kidney donors (545 +/- 237 vs. 773 +/- 296 per glomeruli, P < 0.02). Podocyte density and intrarenal gene expression of podocyte-associated molecules significantly correlated with estimated glomerular filtration rate (GFR) and inversely correlated with blood pressure and the degree of renal fibrosis. Intrarenal gene expression of nephrin significantly correlated with change in renal function decline. CONCLUSION This study demonstrates a decrease in podocyte number and intrarenal gene expression of podocyte-associated molecules in patients with hypertensive nephrosclerosis. We observed correlations between glomerular podocyte density and intrarenal expression of podocyte-associated molecules with renal function and the degree of renal fibrosis, suggesting podocyte loss may play an important role in the pathogenesis of hypertensive nephrosclerosis.

Messenger RNA Expression of Podocyte-Associated Molecules in the Urinary Sediment of Patients with Diabetic Nephropathy

Background: Podocyte loss plays an important role in the pathogenesis of diabetic nephropathy. We hypothesize that messenger RNA expression of podocyte-associated molecules in urinary sediment may provide important clinical information in patients with diabetic nephropathy. Method: We studied 21 patients with biopsy-proven diabetic nephropathy and 9 healthy controls. The mRNA expression of nephrin, podocin, synaptopodin, Wilms’ tumor-1 (WT-1) and α-actinin-4 in urinary sediment were measured by real-time quantitative polymerase chain reaction. The degree of histological damage was quantified by morphometric analysis. Patients were then followed for an average of 25.63 ± 10.76 months. The rate of glomerular filtration rate (GFR) decline was calculated by the least-square regression. Results: There were significant differences in nephrin, podocin, synaptopodin, α-actinin-4 (p < 0.01 for all comparisons) and WT-1 (p = 0.028) expression between patients and normal controls. Urinary nephrin expression was significantly correlated with proteinuria (r = 0.502, p = 0.020); urinary synaptopodin was significantly correlated with proteinuria (r = 0.585, p = 0.005), serum creatinine (r = 0.516, p = 0.017) and estimated GFR (r = –0.560, p = 0.008), and urinary WT-1 expression was significantly correlated with the degree of tubulointerstitial fibrosis (r = 0.558, p = 0.009). There was no significant correlation between GFR decline and urinary expression of target genes. Conclusion: Urinary mRNA expressions of nephrin, podocin, synaptopodin, WT-1 and α-actinin-4 are higher in patients with diabetic nephropathy than in normal controls. Urinary nephrin and synaptopodin expressions are correlated with baseline clinical parameters such as proteinuria or renal function, while WT-1 expression is related to the degree of histological damage. Our results suggest that urinary mRNA expression of podocyte-associated molecules may be used for risk stratification of diabetic nephropathy.

Urinary Expression of Kidney Injury Markers in Renal Transplant Recipients

BACKGROUND AND OBJECTIVES The outcome of renal transplantation after an episode of acute rejection is difficult to predict, even with an allograft biopsy. We examined whether urinary expression of specific biomarker mRNA could be used as a noninvasive prognostic marker in kidney transplant recipients. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS We studied 63 kidney transplant recipients who require graft biopsy because of progressive worsening of kidney function. The mRNA of neutrophil gelatinase-associated lipocalin, kidney injury molecule-1 (KIM-1), IL-18, surfactant protein-C, and S100 calcium-binding proteins A8 and A9 in urinary sediment were quantified. RESULTS Urinary expressions of neutrophil gelatinase-associated lipocalin, KIM-1, and IL-18, but not other target genes, were significantly different between histologic groups (P < 0.0001 for all). After followed for an average of 39.7 ± 21.1 months, the rate of renal function decline significantly correlated with urinary KIM-1 expression (r = -0.434, P = 0.0004) but not other target genes. At 48 months, the graft survival rate for the high and low KIM-1 groups were 46.2 and 78.6%, respectively. After adjusting for confounding variables, each log of higher urinary KIM-1 expression conferred an ~2.9-fold higher risk of developing graft failure (95% confidence interval, 1.3- to 6.2-fold; P = 0.006). The result remained similar when only patients with no acute cellular rejection were analyzed. CONCLUSIONS In kidney allograft recipients, urinary KIM-1 expression provides prognostic information in relation to the rate of renal function decline, irrespective of the kidney pathology.

Urinary messenger RNA expression of podocyte-associated molecules in patients with diabetic nephropathy treated by angiotensin-converting enzyme inhibitor and angiotensin receptor blocker.

BACKGROUND Podocyte injury and its subsequent loss in urine play an important role in the pathogenesis of diabetic nephropathy; blockade of the renin-angiotensin system may ameliorate the damage. METHODS In a non-randomized setting, we studied 71 patients with diabetic nephropathy on a stable dose of angiotensin-converting enzyme inhibitor (ACEI). In 37 patients, angiotensin receptor blocker (ARB) was added (the combination group); ACEI alone was continued in the other 34 (the control group). The mRNA expressions of nephrin, podocin, and synaptopodin in urinary sediment were measured at 0 and 12 weeks. RESULTS Baseline glomerular filtration rate (GFR) correlated with the urinary expression of nephrin (r=0.320, P=0.007), podocin (r=0.336, P=0.004), and synaptopodin (r=0.350, P=0.003). After adjusting for the baseline expression, the combination group had a significantly lower urinary synaptopodin expression (7.49 (95% confidence interval CI, 0.62-115.29) vs 14.83 (95% CI, 1.03-241.43), P=0.026) than the control group after 12 weeks of treatment. The percentage change in urinary podocin expression over 12 weeks of treatment had a modest correlation with the rate of GFR decline in 1 year (r=-0.243, P=0.041). CONCLUSION In patients with diabetic nephropathy, urinary mRNA expression of podocyte markers correlated with baseline renal function. Urinary expression of synaptopodin was lower after 12 weeks of ACEI and ARB combination therapy. Our result suggests that serial measurement of urinary podocyte markers may have a value for the monitoring of therapeutic response.

Differential effects of transforming growth factor-beta on the synthesis of connective tissue growth factor and vascular endothelial growth factor by peritoneal mesothelial cell.

Background: Previous studies found that transforming growth factor-β (TGF-β) plays a conflicting role in peritoneal fibrosis. We hypothesise that TGF-β acts on peritoneal mesothelial cells (PMC) via VEGF and CTGF as downstream mediators. Methods: The effect of TGF-β in primary culture of rat PMC was studied. VEGF and CTGF mRNA expression was examined by real time quantitative polymerase chain reaction (RT-QPCR), and VEGF antigen level in cell supernatant by ELISA. Results: Incubation of rat PMC with TGF-β resulted in a time- (3–72 h) and concentration- (0–50 pg/ml) dependent increase in VEGF mRNA expression, and VEGF protein level in the cell supernatant. When stimulated with TGF-β 100 pg/ml, there was a 20-fold up-regulation of VEGF mRNA expression (p < 0.001). The CTGF mRNA expression and protein level of PMC was slightly increased at low concentration of TGF-β (50 pg/ml) but decreased at a higher concentration (100 pg/ml or above). The effect of TGF-β on PMC CTGF, but not VEGF, gene expression was inhibited by Smad decoy oligodeoxynucleotide. The effect of TGF-β on PMC VEGF gene expression and protein synthesis was inhibited by PD98059 (a specific MAP kinase inhibitor) and chelerythrine (a specific protein kinase C inhibitor), but not cholera toxin (activator of cyclic AMP) or herbimycin A (inhibitor of protein tyrosine kinase). The up-regulation of CTGF mRNA expression was inhibited by PD98059, but not chelerythrine, cholera toxin or herbimycin A. Furthermore, CTGF gene expression in TGF-β-stimulated PMC was inhibited by co-administration of recombinant VEGF. Conclusions: Our data demonstrate that TGF-β induces PMC production of VEGF and CTGF via different signalling pathways. At high concentration of TGF-β, VEGF production predominates and CTGF production was inhibited. Since CTGF and VEGF have different biologic effects, our results may explain the complex activity of TGF-β in peritoneal physiology.

Discrepancy between Intrarenal Messenger RNA and Protein Expression of ACE and ACE2 in Human Diabetic Nephropathy

Background: The intrarenal angiotensin-converting enzyme (ACE) and type 2 ACE (ACE2) play important roles in the pathogenesis of diabetic nephropathy, but human data are limited. We studied glomerular and tubulointerstitial mRNA and the protein expression of ACE and ACE2 in patients with diabetic nephropathy. Methods: We studied renal biopsy specimens of 22 patients with diabetic nephropathy and 11 transplant donors as normal controls. Intrarenal mRNA expression of ACE and ACE2 was measured by laser microdissection and real-time quantitative polymerase chain reaction; expression at the protein level was determined by immunostaining. Results: Glomerular and tubulointerstitial mRNA expression levels of ACE and ACE2 were significantly higher in patients with diabetic nephropathy than in normal controls (p < 0.001 for all comparisons). Glomerular ACE and ACE2 protein levels of patients with diabetic nephropathy were significantly higher than those of kidney donors (4.90 ± 2.55% vs. 2.64 ± 0.98%, p = 0.022, and 7.40 ± 3.36% vs. 4.37 ± 2.36%, p = 0.017, respectively). The tubulointerstitial ACE at the protein level, however, was similar between diabetic patients and controls (8.76 ± 4.18% vs. 10.44 ± 6.61%, p = 0.453), and the tubulointerstitial ACE2 at the protein level was significantly lower in diabetic nephropathy (16.48 ± 7.68% vs. 23.23 ± 7.65%, p = 0.025). Conclusion: The mRNA expression of ACE and ACE2 increased in both the glomerular and tubulointerstitial area of diabetic nephropathy. However, the tubulointerstitial ACE expression at the protein level remained unchanged, while that of ACE2 actually decreased. Our results suggest a posttranscriptional modulation of tubulointerstitial ACE and ACE2 expression. Experimental data of intrarenal mRNA expression of ACE and ACE2 should be interpreted with caution.

Increased release of von Willebrand factor antigen from endothelial cells by anti-DNA autoantibodies.

OBJECTIVE--To determine whether antibodies to double stranded DNA (anti-dsDNA) have a pathogenic role in systemic lupus erythematosus (SLE). METHODS--IgG was purified from 17 patients with SLE (median anti-dsDNA titre 1212 IU/ml) and nine healthy controls (median titre 40 IU/ml). Anti-dsDNA depleted polyclonal IgG (median anti-dsDNA titre 17 IU/ml) was also prepared from sera of the 17 patients by affinity chromatography on a DNA cellulose column. Binding to antiendothelial cell antibodies (AECA) and expression of von Willebrand factor (VWF) antigen by cultured human umbilical vein endothelial cells (HUVECs) were studied by flow cytometry. RESULTS--The percentage of HUVECs binding to AECA or expressing VWF was greater for cells incubated with IgG from patients with SLE than for cells incubated with control IgG, though values did not reach statistical significance; nevertheless, HUVECs incubated with IgG from patients expressed a greater mean fluorescence intensity with AECA (p = 0.0001) and greater VWF expression (p = 0.019). Both the fluorescence intensity and percentage of HUVECs binding to AECA or expressing VWF were significantly greater in HUVEC incubated with IgG containing anti-dsDNA than in those incubated with anti-dsDNA depleted IgG. The concentration of VWF in the supernatant was significantly increased in HUVECs incubated with IgG containing anti-dsDNA compared with control IgG or anti-dsDNA depleted IgG. Pretreatment of HUVECs with native DNA before incubation with IgG from lupus patients did not increase binding to AECA, or expression or release of VWF. CONCLUSIONS--Our study provides in vitro evidence that antibodies to DNA have a pathogenic role in the induction of inflammatory injury of the vascular endothelium in SLE.