Renal TLR4 mRNA expression correlates with inflammatory marker MCP-1 and profibrotic molecule TGF-ß1 in patients with chronic kidney disease.

BACKGROUND: Toll-like receptor-4 (TLR4) has been implicated in the pathogenesis of different renal diseases in rodent models. However, in human kidney disease, TLR4 expression and regulation is not well understood. We hypothesized that renal TLR4 expression plays a role in chronic kidney disease (CKD) and is associated with proteinuria, kidney function, histological diagnosis, and inflammatory mediators. METHODS: We quantified TLR4 mRNA as well as expression of macrophage chemoattractant protein-1 (MCP-1), transforming growth factor-ß1 (TGF-ß1) and interleukin-6 (IL-6) in human kidney biopsies from 70 patients with CKD. We measured kidney function, urinary MCP-1 protein excretion, and the amount of chronic damage. Macrophage load was quantified by CD68 and vascularization by CD34 immunostaining. RESULTS: TLR4 expression correlated significantly with MCP-1 and TGF-ß1 expression. High TLR4 expression was associated with high IL-6 expression. TLR4 expression was significantly upregulated in patients with severe proteinuria, and in patients with chronic ischemic renal damage and IgA nephropathy, when compared to patients with thin glomerular basement membrane disease. TLR4 expression did not correlate with creatinine clearance, renal outcome, macrophage load or chronic damage. CONCLUSIONS: We show for the first time that renal TLR4 expression was significantly associated with the pro-inflammatory marker MCP-1 and the profibrotic molecule TGF-ß1 in kidney biopsies from patients with CKD, suggesting that increased expression of TLR4 is an important feature of CKD.

CD248+ stromal cells are associated with progressive chronic kidney disease.

Stromal fibroblasts are the primary cells of the kidney that produce fibrotic matrix. CD248 is a stromal marker expressed on fibroblasts and pericytes within the human kidney. Here, we tested whether CD248 expression in the kidney colocalizes with fibrosis and if it is associated with known determinants of chronic kidney disease (CKD). CD248 expression was located and quantified in situ by immunohistochemistry in kidney biopsies from 93 patients with IgA nephropathy and compared with 22 archived biopsies encompassing normal kidney tissue as control. In normal kidney tissue, CD248 was expressed by resident pericytes, stromal fibroblasts, and was upregulated in human CKD. The expression was linked to known determinants of renal progression. This relationship was maintained in a multivariate analysis with CD248 expression linked to renal survival. CD248 was expressed by a population of α-smooth muscle actin (SMA)(+) myofibroblasts and α-SMA(-) stromal cells but not expressed on CD45(+) leukocytes. Thus, CD248 defines a subset of stromal cells, including but not limited to some myofibroblasts, linked to albuminuria and tubulointerstitial damage during tissue remodeling in CKD.

Chemokines in vasculitis.

The systemic vasculitides are a group of diseases where the primary pathological process is inflammatory injury to blood vessel walls. Their clinical manifestations are highly variable and range from organ specific disease to a systemic illness that can lead, if untreated, to multi-organ failure and death. The kidneys are often involved in systemic vasculitis, particularly in small vessel vasculitis, where the glomerular capillary bed is a target for injury. This leads to a vasculitic glomerulonephritis, with focal segmental inflammation and perivascular leukocyte accumulation evolving to extracapillary accumulation of mononuclear cells (including crescents). The kinetics of leukocyte infiltration and involvement in this setting are in part dependent on the combinatorial expression of chemokines and their receptors. We discuss the evidence base for the role of the chemokine network in the renal disease of small vessel vasculitis and extend this to non-renal aspects of small vessel vasculitis other systemic vasculitides.

Identification of the optimal donor quality scoring system and measure of early renal function in kidney transplantation.

BACKGROUND: The early identification of kidney allografts at risk of later dysfunction has implications for clinical practice. Donor quality scoring systems (preoperative) and measures of early allograft function (first week postoperative) have previously shown practical utility. This study aimed to determine the optimal parameter(s) (preoperative and postoperative) with greatest predictive power for the development of subsequent allograft dysfunction. METHODS: Consecutive deceased donor renal transplants (n=217) were studied. In each, the following measures were assessed: Preoperative donor quality scores: expanded criteria donor status; Deceased Donor Score (Nyberg et al., Am J Transplant 2003;3:715); Donor Risk Score (Schold et al., Am J Transplant 2005; 5(4 pt 1): 757); and delayed graft function (DGF) Nomogram (Irish et al., J Am Soc Nephrol 2003; 14: 2967). Postoperative early function measures: dialysis requirement and duration; extended DGF definition (Boom et al., Kidney Int 2000; 58: 859); creatinine at day 5 and day 7; creatinine reduction ratios at day 2 and day 7; and urine output posttransplantation. Primary outcome measures were creatinine at 12 months and the development of chronic kidney disease stage 4T. RESULTS: Of donor scoring systems, Donor Risk Score was best associated with subsequent allograft function. Of early function measures: the extended definition of DGF, creatinine at day 5, and dialysis duration showed greatest predictive power in the patient population overall, those not requiring postoperative dialysis, and those requiring dialysis, respectively. No scores or early function measures were associated with change in creatinine between 6 and 12 months. CONCLUSIONS: This study validates and identifies the optimal early predictive parameter available for kidney transplant recipients, with implications for refining early postoperative management and potential utility in organ allocation policy.

Reduction of the vitamin D hormonal system in kidney disease is associated with increased renal inflammation.

To examine any potential role for 1,25-dihydroxyvitamin D (1,25(OH)2D) in inflammation associated with chronic kidney disease we measured vitamin D metabolites, markers of inflammation and gene expression in 174 patients with a variety of kidney diseases. Urinary MCP-1 protein and renal macrophage infiltration were each significantly but inversely correlated with serum 1,25(OH)2D levels. Logistic regression analysis with urinary MCP-1 as binary outcome showed that a 10-unit increase in serum 1,25(OH)2D or 25OHD resulted in lower renal inflammation. Analysis of 111 renal biopsies found that renal injury was not associated with a compensatory increase in mRNA for the vitamin D-activating enzyme 25-hydroxyvitamin D-1alpha-hydroxylase (CYP27B1), its catabolic counterpart 24-hydroxylase, or the vitamin D receptor. There was, however, a significant association between tissue MCP-1 and CYP27B1. Patients with acute renal inflammation had a significant increase in urinary and tissue MCP-1, macrophage infiltration, and macrophage and renal epithelial CYP27B1 expression but significantly lower levels of serum 1,25(OH)2D in comparison to patients with chronic ischemic disease despite similar levels of renal damage. In vitro, 1,25(OH)2D attenuated TNFalpha-induced MCP-1 expression by human proximal tubule cells. Our study indicates that renal inflammation is associated with decreased serum vitamin D metabolites and involves activation of the paracrine/autocrine vitamin D system.

Increased incidence of infections following the late introduction of mycophenolate mofetil in renal transplant recipients.

BACKGROUND: Late introduction of mycophenolate mofetil (MMF) is used in renal transplant patients to allow calcineurin inhibitor (CNI) withdrawal. This change in treatment may alter the immunosuppressive load predisposing patients to infections. To assess this we have analysed infection rates in 30 consecutive patients with chronic allograft nephropathy commenced on MMF for CNI withdrawal. Methods and results. The study period was from 12 months pre-commencement to 12 months post-commencement. At commencement, patient mean age was 51.2 +/- 12.9 years and mean time post-transplant was 3170 +/- 2130 days. Estimated glomerular filtration rate (eGFR) at the start of the study period and at conversion was 30.7 +/- 12.1 ml/min and 23.1 +/- 9.9 ml/min, respectively. The mean dose of MMF post-conversion was 1575 +/- 428 mg/day. Estimated GFR had stabilized at 12 months post-conversion to 25.3 +/- 12.2 ml/min. There was a significant increase in infections following conversion: pre-conversion, 26.7% (8/30); post-conversion, 66.6% (20/30) (chi(2) = 24.5, P < 0.0005). There was an inverse correlation between eGFR at conversion and infection rates post-conversion (r = -0.379, P = 0.039). There were no hospitalizations for infection pre-conversion and 6 patients (20%) were hospitalized post-conversion, for a total of 285 days (7-107). CONCLUSION: There is significant morbidity associated with an increased incidence of infection after late introduction of MMF at standard doses in renal transplant recipients. This risk may be related to GFR at the time of conversion.

The role of capillary density, macrophage infiltration and interstitial scarring in the pathogenesis of human chronic kidney disease.

To assess the relationship between interstitial capillary density and interstitial macrophages we prospectively measured these factors in situ in 110 patients with chronic kidney disease. Macrophage numbers and urinary MCP-1/CCL2 levels significantly correlated inversely with capillary density which itself significantly correlated inversely with chronic damage and predicted disease progression. In 54 patients with less than 20% chronic damage, there was a significant correlation between the urinary albumin to creatinine ratio and MCP-1/CCL2, and MCP-1/CCL2 and macrophages but not between MCP-1/CCL2 and capillary density. Conversely, in 56 patients with over 20% chronic damage there was no correlation between MCP-1/CCL2 and macrophages but there were significant inverse correlations between capillary density and both macrophages and chronic damage. The expression of VEGF mRNA significantly correlated with macrophage infiltration, capillary density and chronic scarring. In an ischemic-hypertensive subgroup there was upregulation of the hypoxia marker carbonic anhydrase IX and with over 20% chronic damage an increased macrophage to CCR2 ratio. Our study shows that proteinuria and MCP-1/CCL2 are important for macrophage recruitment in early disease. As renal scarring evolves, alternative pathways relating to progressive tissue ischemia secondary to obliteration of the interstitial capillary bed predominate.

Increased expression of mineralocorticoid effector mechanisms in kidney biopsies of patients with heavy proteinuria.

BACKGROUND: Aldosterone has emerged as a deleterious hormone in the heart, with mineralocorticoid receptor (MR) blockade reducing mortality in patients with severe heart failure. There is also experimental evidence that aldosterone contributes to the development of nephrosclerosis and renal fibrosis in rodent models, but little is known of its role in clinical renal disease. METHODS AND RESULTS: We quantified MR, serum- and glucocorticoid-regulated kinase 1 (sgk1), and mRNA expression of inflammatory mediators such as macrophage chemoattractant protein-1 (MCP-1), transforming growth factor-beta1, and interleukin-6 in 95 human kidney biopsies in patients with renal failure and mild to marked proteinuria of diverse etiologic origins. We measured renal function, serum aldosterone, urinary MCP-1 protein excretion, and the amount of chronic renal damage. Macrophage invasion was quantified by CD68 and vascularization by CD34 immunostaining. Serum aldosterone correlated negatively with creatinine clearance (P<0.01) and positively with renal scarring (P<0.05) but did not correlate with MR mRNA expression or proteinuria. Patients with heavy albuminuria (>2 g/24 h; n=15) had the most renal scarring and the lowest endothelial CD34 staining. This group showed a significant 5-fold increase in MR, a 2.5-fold increase in sgk1 expression and a significant increase in inflammatory mediators (7-fold increase in MCP-1, 3-fold increase in transforming growth factor-beta1, and 2-fold increase in interleukin-6 mRNA). Urinary MCP-1 protein excretion and renal macrophage invasion were significantly increased in patients with heavy albuminuria. CONCLUSIONS: These studies support animal data linking aldosterone/MR activation to renal inflammation and proteinuria. Further studies are urgently required to assess the potential beneficial effects of MR antagonism in patients with renal disease.

Macrophages and progressive tubulointerstitial disease.

Macrophages and progressive tubulointerstitial disease. In chronic renal disease, tubulointerstitial inflammation and injury is associated with infiltrating macrophages. As a consequence of primary injury, proteinuria, chronic hypoxia, and glomerular-derived cytokines may all differentially modulate the expression of factors that promote macrophage recruitment. In addition to adhesion molecules and chemokines, products of complement system and renin-angiotensin system activation may direct this process. Once present at interstitial sites, macrophages interact with resident cells and extracellular matrix to generate a proinflammatory microenvironment that amplifies tissues injury and promotes scarring. There is now increasing evidence for the efficacy of interventions directed against factors that recruit, activate, or are produced by macrophages. A detailed understanding of the biology of this area may lead to the further development of therapies that will improve the outcome of renal disease.

Efficacy of the accelerated hepatitis B vaccination schedule used in haemodialysis patients post-exposure to virus: a single-centre experience.

BACKGROUND: The hepatitis B (HB) vaccination regime currently recommended for use in the UK for both preventative and post-exposure purposes is the accelerated regime, although there have been no recent reports of its efficacy. This observational study reports on the response rate achieved and longevity of protection conferred with this regime in a large number of haemodialysis patients following an episode of HB exposure. METHODS: One-hundred and five patients received primary vaccination (vaccine administered at 0, 1 and 2 months). Eighty-six completed the regime, receiving a booster dose at month 12. Measuring antibodies to HB surface antigen (anti-HBS) 6 weeks after receiving the third and fourth doses assessed patients' response. Seventy-seven patients subsequently had anti-HBs measured at month 24. RESULTS: The response rate (anti-HBS >10 mIU/ml) to primary vaccination and the complete regime was 33 and 73%, respectively. Non-European patients responded better to primary vaccination than Europeans (P=0.014). Those receiving steroids responded less well to the complete vaccination regime (P=0.007). Patient's age, sex, renal diagnosis, diabetes mellitus, time on dialysis, dialysis adequacy, erythropoietin dose, hepatitis C or body weight did not affect response rates. By month 24, 24 responders (44%) had lost seroprotection. Antibody levels achieved with vaccination by transient responders was significantly lower than persistent responders. No patients became HB surface antigen positive during the 2-year study. CONCLUSION: Reserving the accelerated vaccination to the post-exposure scenario will expose many more patients to the risk of HB cross-infection than if used prophylactically. Regular monitoring is required if seroprotection is to be maintained.