Inflammatory cytokine gene expression in the urinary sediment of patients with lupus nephritis

Messenger RNA expression of glomerular podocyte markers in the urinary sediment of acquired proteinuric diseases

BACKGROUND

Podocyte slit diaphragm plays an important role in the control of glomerular permeability. We hypothesize that studying the gene expression profile of podocyte in urinary sediment may provide diagnostic and prognostic information on acquired proteinuric diseases.

METHODS

We studied 28 patients who required kidney biopsy for acquired proteinuric diseases (diabetic glomerulosclerosis, 9 cases; IgA nephropathy, 10 cases; minimal change disease, 5 cases; membranous nephropathy, 5 cases). We also studied 10 cases of diabetic microalbuminuria and 9 healthy controls. The mRNA expressions of nephrin (NephRNA), podocin (PodRNA) and synaptopodin (SynRNA) in urinary sediment were measured by real time quantitative PCR. After recruitment, all patients were followed for at least 12 months.

RESULTS

There were significant differences in the NephRNA and PodRNA in the urinary sediment between diagnosis groups (p<0.005). On the other hand, SynRNA was only marginally significant between diagnosis groups (p<0.05). Although statistically significant, the degree of proteinuria had only modest correlations with the urinary expression of nephrin. After a median follow up for 23 months, there was a significant correlation between the rate of decline in renal function and NephRNA (r=0.559, p=0.001) and PodRNA (r=0.530, p=0.002), but not SynRNA (r=0.054, p=NS). The correlation remained statistically significant after multivariate analysis to adjust for the degree of proteinuria and initial renal function.

CONCLUSIONS

Urinary mRNA expression of podocyte markers, such as nephrin and podocin, are significantly different between proteinuric disease categories. Further, NephRNA and PodRNA correlated with the rate of decline in renal function. Our results suggest that urinary podocyte gene expression may be a useful non-invasive tool which provides additional information for the management of proteinuric diseases.

Glomerulonephritis, Th1 and Th2: what's new?

Glomerulonephritis (GN), the major worldwide cause of chronic renal disease and renal failure, shows a wide spectrum of histological patterns, severity of injury and clinical outcomes that may be related to the nature of the nephritogenic immune response. In the majority of cases, there is evidence of a central role for cognate immunity in the initiation of human GN and contributions of both humoral and cellular effector mechanisms have been demonstrated in both humans and in animal models. T helper cell subsets are known to activate different immune effector mechanisms which influence disease outcomes in infectious and autoimmune diseases and evidence is now accumulating that Th1 and Th2 subsets direct diverging effector pathways that lead to different patterns and severity of glomerular injury in GN. Th1-predominant responses appear to be associated strongly with proliferative and crescentic forms of GN that result in severe renal injury, while Th2 responses are associated with membranous patterns of injury. The challenge remains to understand fully the relevance of T helper cell subset responses to the spectrum of human GN and to apply this new knowledge to the development of more potent and selective therapeutic strategies.

Spotlight on the role of hormonal factors in the emergence of autoreactive B-lymphocytes

Pathogenic autoimmunity requires a combination of inherited and acquired factors. In as much as hormones influence the sexual dimorphism of the immune system, it is possible that they can initiate or accelerate an autoimmune process, and contribute to gender-biased autoimmune disorders. Not only natural hormones, but also endocrine disruptors, such as environmental estrogens, may act in conjunction with other factors to override immune tolerance to self-antigens. In lupus, murine and human studies demonstrate that female sex hormones are implicated in disease pathogenesis. In the B cell compartment, both prolactin and estrogen are immunomodulators that affect maturation, selection and antibody secretion. Their impact may be based on their capacity to allow autoreactive B cells to escape the normal mechanisms of tolerance and to accumulate in sufficient numbers to cause clinically apparent disease. Both hormones lead to the survival and activation of autoreactive B cells, but they skew B cell maturation towards different directions, with prolactin inducing T cell-dependent autoreactive follicular B cells and estrogen eliciting T cell-independent autoreactive marginal zone B cells. Differential modulation of the cytokine milieu by hormones may also affect the development and activation of specific mature B cell subsets. This novel insight suggests that targeted manipulation of these pathways may represent a promising avenue in the treatment of lupus and other gender-biased autoimmune diseases.

IL-2-mediated apoptosis of kidney tubular epithelial cells is regulated by the caspase-8 inhibitor c-FLIP

BACKGROUND

Tubular epithelial cells (TECs) are essential in the maintenance of kidney function. Apoptosis of TECs occur during acute and chronic renal allograft rejection as well as other forms of renal injury, including autoimmune nephritis. The regulation of TEC apoptosis by proinflammatory cytokines associated with renal inflammation [e.g., interleukin (IL)-2 and interferon-gamma (IFN-gamma)] has not been extensively investigated.

METHODS

Apoptosis in murine TECs was determined by FACS with annexin-V or ligation-mediated-polymerase chain reaction (LM-PCR) and mRNA levels by reverse transcription (RT)-PCR or Northern blot. Protein expression was observed using Western blot.

RESULTS

IL-2R (CD25) was expressed by murine TECs and up-regulated by IL-2. Both IL-2 and IFN-gamma induced TEC apoptosis and activated caspase-8. Apoptosis with IL-2 was concentration-dependent and blocked by z-IETD-fmk, a specific caspase-8 inhibitor. Apoptosis with IFN-gamma was associated with increased surface expression of Fas, while IL-2 had no effect on Fas. IL-2 did not induce apoptosis in Fas-deficient TECs (M3.1-lpr) suggesting IL-2 regulation of caspase-8 activity requires Fas. Consistent with this, IL-2 but not IFN-gamma was found to decrease mRNA and protein expression of c-FLIP, an endogenous caspase-8 inhibitor in murine TECs. Overexpression of c-FLIP in TECs (CS3.7-FLIP) blocked apoptosis and caspase-8 activation with both IFN-gamma and IL-2. c-FLIP expression was found in kidney cortex, primary and cloned TECs, suggesting c-FLIP is likely a key regulator of caspase-8-mediated apoptosis in vivo.

CONCLUSION

This is the first report of c-FLIP regulation by IL-2 in renal TECs. Augmentation of c-FLIP in TECs may enhance an endogenous mechanism by which TECs normally resist injury to caspase-8-mediated apoptosis and thus may be a useful and novel strategy to prevent tubular injury in transplant rejection and autoimmune nephritis.

Clinical relevance of the expression of P-glycoprotein on peripheral blood lymphocytes to steroid resistance in patients with systemic lupus erythematosus

OBJECTIVE

P-glycoprotein (P-gp) of membrane transporters leads to drug resistance by the exclusion of intracellular drugs, including corticosteroids. Some patients with highly active systemic lupus erythematosus (SLE) show poor response to corticosteroids; however, the mechanisms of steroid resistance remain unclear. The aim of this study was to elucidate the clinical relevance of P-gp expression on lymphocytes to steroid resistance in patients with active SLE.

METHODS

Flow cytometric analyses of the expression of P-gp on peripheral blood lymphocytes from 20 normal volunteers and 80 SLE patients were performed. Steroid-exclusion analysis of peripheral blood mononuclear cells (PBMCs) was conducted by using radioisotope-labeled dexamethasone.

RESULTS

P-gp was expressed at significantly high levels on most of the peripheral blood lymphocytes from SLE patients, whereas normal lymphocytes had only marginal expression. The quantity of P-gp on SLE lymphocytes correlated with the disease activity in each patient, as estimated by the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). Furthermore, in SLE patients whose SLEDAI scores were >12 despite taking >0.5 mg/kg/day of prednisolone, P-gp expression on lymphocytes was markedly increased, and intracellular dexamethasone in their PBMCs was significantly decreased. However, intensive immunosuppressive treatment in these SLE patients resulted in successful control of disease activity, which occurred in parallel with a marked reduction of P-gp on lymphocytes.

CONCLUSION

The overexpression of P-gp on lymphocytes might lead to exclusion of corticosteroids from lymphocytes, resulting in steroid resistance in patients with highly active SLE. Reduction of P-gp expression achieved by intensive immunosuppressive treatment overcame the steroid resistance. We therefore propose that measurement of P-gp expression on lymphocytes is useful in the assessment of steroid resistance and is a good marker for indicating the need for intensive immunosuppressive treatment in patients with highly active SLE.

Nonparathyroid hormone-mediated calcium resorption in a rat model of immune glomerulonephritis

Skeletal demineralization is a frequent accompaniment of chronic renal disease and is likely multifactorial. We studied the role of inflammation in stimulating bone resorption in a rat model of glomerulonephritis (GN). Three-week-old Sprague-Dawley rats received either saline (n = 8) or horse spleen apoferritin and lipopolysaccharide (HSA/LPS, n = 8) by intraperitoneal injection, for 6 weeks; afterward, they were observed for either an additional 3 weeks (9 weeks total; n = 4 from each group) or 14 weeks (20 weeks total; n = 4 from each group). Kidneys were analyzed by histomorphometry, and blood and urine samples were obtained to assess bone resorption. Whole-body and isolated femur Dual-Energy X-ray Absorptiometry (DEXA) scans were performed at the end of each study. HSA/LPS-treated animals developed a proliferative GN by 9 weeks, which is associated with proteinuria but no change in renal function. Between 9 and 20 weeks, there was evidence of an increasing interstitial inflammation (1381 +/- 67 interstitial cells/mm(2) at 9 weeks and 1818 +/- 28 interstitial cells/mm(2) at 20 weeks.) There was also evidence of bone resorbing activity as assessed by experimental/control (E/C) < 1.0 at 9 (E/C plasma = 0.66 +/- 0.05) and 20 (E/C plasma = 0.52 +/- 0.04) weeks. Parathyroid hormone (PTH) levels were normal at all time points, and no differences in bone mineral density were found. This model produces not only an immune glomerular/tubular injury, but also a stimulus for bone resorption that is related to objective measures of inflammation severity. The bone resorption is not caused by renal insufficiency, hyperparathyroidism, or steroid therapy. This model will prove useful in other studies of the role of renal inflammation in skeletal disorders.

Coordinate overexpression of interferon-alpha-induced genes in systemic lupus erythematosus

OBJECTIVE

To study the contribution of interferon-alpha (IFNalpha) and IFNgamma to the IFN gene expression signature that has been observed in microarray screens of peripheral blood mononuclear cells (PBMCs) from patients with systemic lupus erythematosus (SLE).

METHODS

Quantitative real-time polymerase chain reaction analysis of healthy control PBMCs was used to determine the relative induction of a panel of IFN-inducible genes (IFIGs) by IFNalpha and IFNgamma. PBMCs from 77 SLE patients were compared with those from 22 disease controls and 28 healthy donors for expression of IFIGs.

RESULTS

Expression of IFNalpha-inducible genes was significantly higher in SLE PBMCs than in those from disease controls or healthy donors. The level of expression of all IFIGs in PBMCs from SLE patients with IFNalpha pathway activation correlated highly with the inherent responsiveness of those genes to IFNalpha, suggesting coordinate activation of that cytokine pathway. Expression of genes preferentially induced by IFNgamma was not significantly increased in SLE PBMCs compared with control PBMCs. IFNalpha-regulated gene-inducing activity was detected in some SLE plasma samples.

CONCLUSION

The coordinate activation of IFNalpha-induced genes is a characteristic of PBMCs from many SLE patients, supporting the hypothesis that IFNalpha is the predominant stimulus for IFIG expression in lupus.

Urine chemokines as biomarkers of human systemic lupus erythematosus activity

The purpose of this study was to evaluate urine monocyte chemoattractant protein-1 (MCP-1) and IL-8 as biomarkers of SLE flare. Urine was collected every 2 mo from patients who were followed prospectively in the Ohio SLE Study. Renal and nonrenal flares were identified and MCP-1 and IL-8 were measured by specific ELISA in samples that were collected at flare. When available, MCP-1 and IL-8 were also measured in urine samples before and after flare. For comparison, MCP-1 and IL-8 were measured in the urine of healthy individuals and in renal and nonrenal SLE patients with stable disease activity (disease controls). Most patients were receiving maintenance immunosuppressive therapy before flare. At renal flare, mean urine MCP-1 (uMCP-1) was significantly greater than uMCP-1 at nonrenal flare and from healthy volunteers and renal disease controls. The level of uMCP-1 correlated with the increase in proteinuria at flare and was higher in patients with proliferative glomerulonephritis and in patients with impaired renal function. Urine MCP-1 was increased beginning 2 to 4 mo before flare. Patients who responded to therapy showed a slow decline in uMCP-1 over several months, whereas nonresponders had persistently high uMCP-1. In contrast, uIL-8 did not change with disease activity and was not elevated at renal or nonrenal flare compared with disease controls. In conclusion, uMCP-1 but not uIL-8 is a sensitive and specific biomarker of renal SLE flare and its severity, even in patients who receive significant immunosuppressive therapy. Persistently elevated uMCP-1 after treatment may indicate ongoing kidney injury that may adversely affect renal prognosis.

Messenger RNA expression of target genes in the urinary sediment of patients with chronic kidney diseases

BACKGROUND

The degree of renal scarring in kidney biopsy is an important prognostic factor in patients with chronic kidney diseases. We hypothesize that gene expression in the urinary sediment reflects the degree of renal damage.

METHODS

We studied 29 patients with chronic kidney disease who underwent kidney biopsy (12 immunoglobulin-A nephropathy and 17 glomerulosclerosis) and 10 healthy controls. The mRNA expressions of a panel of target genes in urinary sediment were measured by real-time quantitative polymerase chain reaction. The results were compared with the degree of histological damage and renal function decline.

RESULTS

There were significant differences in the urinary expression of transforming growth factor-beta (TGF-beta), monocyte chemotactic protein-1 (MCP-1) and collagen IV between disease groups and controls. Urinary TGF-beta mRNA expression correlated significantly with estimated glomerular filtration rate (r = -0.412, P = 0.029) and the degree of tubulointerstitial scarring (r = 0.418, P = 0.024). Urinary MCP-1 expression correlated with the degree of glomerulosclerosis (r = 0.450, P = 0.014), but not tubulointerstitial scarring. Urinary MCP-1 expression correlated with its corresponding level by enzyme-linked immunosorbent assay (ELISA) (r = 0.650, P<0.001), but TGF-beta expression did not correlate with its ELISA level. Urinary TGF-beta gene expression correlated with its intra-renal expression in glomeruli (r = 0.701, P<0.001) and tubulointerstitium (r = 0.573, P = 0.001) by immunohistochemistry, while urinary MCP-1 gene expression correlated with its staining in glomeruli (r = 0.576, P = 0.001) but not tubulointerstitium. After 12 months, there was a significant inverse correlation between the rate of renal function decline and urinary expression of connective tissue growth factor (r = -0.471, P = 0.010) and collagen I (r = -0.399, P = 0.032), but not TGF-beta or MCP-1.

CONCLUSIONS

Amongst the target genes examined, the mRNA expression of TGF-beta in urinary sediment correlated with renal function, the degree of histological damage and intra-renal level in patients with chronic kidney diseases. Measurement of TGF-beta mRNA expression in urine may be a useful non-invasive tool for assessing the severity of renal damage in patients with chronic kidney diseases.

Expression of chemokine and fibrosing factor messenger RNA in the urinary sediment of patients with lupus nephritis

OBJECTIVE

Lupus nephritis is characterized by intrarenal inflammation. To assess the extent and severity of disease activity and renal involvement, this study examined the expression of transforming growth factor beta (TGFbeta) and monocyte chemoattractant protein 1 (MCP-1) in the urinary sediment of patients with systemic lupus erythematosus (SLE).

METHODS

We studied 106 patients with SLE who were classified according to their disease status as those with active disease, those with disease in remission, and those with nonrenal SLE. Ten healthy subjects were used as controls. Lupus activity was assessed by the SLE Disease Activity Index (SLEDAI). If renal biopsy was performed, the histologic activity index and chronicity index were determined, and a morphometry analysis of renal scarring was performed. The urinary expresssion of TGFbeta and MCP-1 messenger RNA (mRNA) was studied by real-time quantitative polymerase chain reaction, and the corresponding protein concentrations of TGFbeta and MCP-1 in the urine were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Expression of TGFbeta and MCP-1 mRNA in the urinary sediment was significantly elevated in the active disease group (P < 0.001 for both). These expression levels of TGFbeta and MCP-1 mRNA correlated with the SLEDAI score (TGFbeta r = 0.71, P < 0.001; MCP-1 r = 0.72, P < 0.001), and also significantly correlated with the histologic activity index (TGFbeta r = 0.487, P = 0.004; MCP-1 r = 0.357, P = 0.038). The urinary protein concentration of MCP-1, but not of TGFbeta, correlated with the SLEDAI score (r = 0.66, P < 0.001). However, neither the protein concentration of TGFbeta nor that of MCP-1 as measured by ELISA in the urine correlated with the histologic activity index.

CONCLUSION

The measurement of urinary mRNA expression may be a noninvasive method for the assessment of lupus disease activity and the severity of renal involvement in patients with lupus nephritis.

Advances in the clinical laboratory assessment of urinary sediment

Urinalysis has been used extensively in clinical practice to aid in the diagnosis of various renal and urologic diseases. The innovation of urinalysis is marching on right along with the rapid developments in biotechnology and astride from the solo urine cytology to sophisticated studies of individual component in the urinary sediment. In this review article, we focus on the use of flow cytometry and other technical advances in the examination of urinary sediment, the detection of urologic malignancies by the presence of microsatellite alteration in the urinary sediment, as well as the quantification of cytokine messenger RNA (mRNA) expression in urinary sediment by reverse transcription and real-time quantitative polymerase chain reaction (RT-QPCR). Notably, the study of cytokine mRNA expression in urinary sediment by RT-QPCR has recently been reported to provide important diagnostic information in kidney allograft recipients and patients with lupus nephritis. This simple and non-invasive method requires further study to determine its role in risk stratification and monitoring of therapeutic response in patients with other kidney diseases.