Involvement of renal tubular Toll-like receptor 9 in the development of tubulointerstitial injury in systemic lupus

Mario Negri Institute for Pharmacological Research, Bergamo, Italy.
Arthritis & Rheumatology (Impact Factor: 7.76). 05/2007; 56(5):1569-78. DOI: 10.1002/art.22524
Source: PubMed


Toll-like receptor 9 (TLR-9), a receptor for CpG DNA, has been implicated in the activation of immune cells in lupus. We undertook this study to determine whether the expression of TLR-9 in resident renal cells in lupus nephritis is related to the development of tubulointerstitial injury.
TLR-9 was analyzed in selectively retrieved renal tissue from (NZB x NZW)F1 mice at different stages of disease by laser capture microdissection combined with real-time quantitative reverse transcriptase-polymerase chain reaction, and in renal biopsy specimens from lupus nephritis patients by immunohistochemistry. We investigated for the molecular component responsible for TLR-9 activation by cultured proximal tubular cells in serum from patients with lupus.
Renal tissue from NZB x NZW mice displayed robust TLR-9 expression localized to proximal tubular cells. TLR-9 levels correlated with proteinuria and tubulointerstitial injury to the extent that a cyclin-dependent kinase inhibitor, while reducing proteinuria and renal structural damage, prevented tubular TLR-9 generation in lupus mice. Consistently, exaggerated TLR-9 staining was found in proximal tubular cells of lupus patients, which correlated with tubulointerstitial damage. DNA-containing immune complexes purified from sera of patients with lupus induced TLR-9 in cultured proximal tubular cells. This was prevented by CCGG-rich short oligonucleotides, specific antagonists of CpG DNA, indicating that the DNA component of immune complexes was required for TLR-9 stimulation.
These findings suggest that tubular TLR-9 activation has a pathogenetic role in tubulointerstitial inflammation and damage in experimental and human lupus nephritis, and they indicate a novel target for future therapies.

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    • "For this analysis, total RNA was isolated from kidney using the Absolutely RNA Miniprep Kit (Agilent Technologies, La Jolla, CA) and cDNA using SS VILO Master Mix (Life Technologies, Carlsbad, CA). PCR was performed using Tlr9–specific primers [19], SYBR Green PCR Master Mix (Life Technologies) and the Applied Biosystems 7500 Real-Time PCR System. "
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    ABSTRACT: We evaluated the ability of a macromolecular prodrug of dexamethasone (P-Dex) to treat lupus nephritis in (NZB × NZW)F1 mice. We also explored the mechanism underlying the anti-inflammatory effects of this prodrug. P-Dex eliminated albuminuria in most (NZB × NZW)F1 mice. Furthermore, P-Dex reduced the incidence of severe nephritis and extended lifespan in these mice. P-Dex treatment also prevented the development of lupus-associated hypertension and vasculitis. Although P-Dex did not reduce serum levels of anti-dsDNA antibodies or glomerular immune complexes, P-Dex reduced macrophage recruitment to the kidney and attenuated tubulointerstitial injury. In contrast to what was observed with free dexamethasone, P-Dex did not induce any deterioration of bone quality. However, P-Dex did lead to reduced peripheral white blood cell counts and adrenal gland atrophy. These results suggest that P-Dex is more effective and less toxic than free dexamethasone for the treatment of lupus nephritis in (NZB × NZW)F1 mice. Furthermore, the data suggest that P-Dex may treat nephritis by attenuating the renal inflammatory response to immune complexes, leading to decreased immune cell infiltration and diminished renal inflammation and injury.
    Full-text · Article · Nov 2013 · PLoS ONE
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    • "TLR-9 activation also regulates the production of anti-dsDNA antibodies in lupus-prone mice [60, 154]. The expression of TLR-9 in resident renal cells is arguable since some researchers have shown TLR-9 to localize solely on infiltrating cells [155], whilst other researchers have observed increased TLR-9 expression in tubular epithelial cells and glomerular cells during active lupus nephritis [156, 157]. Increased tubular expression of TLR-9 correlates with proteinuria and tubulo-interstitial injury in lupus patients, whereas increased glomerular TLR-9 expression is associated with a higher activity index [156, 157]. "
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    ABSTRACT: Systemic lupus erythematosus is characterized by a breakdown of self-tolerance and production of autoantibodies. Kidney involvement (i.e., lupus nephritis) is both common and severe and can result in permanent damage within the glomerular, vascular, and tubulo-interstitial compartments of the kidney, leading to acute or chronic renal failure. Accumulating evidence shows that anti-dsDNA antibodies play a critical role in the pathogenesis of lupus nephritis through their binding to cell surface proteins of resident kidney cells, thereby triggering the downstream activation of signaling pathways and the release of mediators of inflammation and fibrosis. This paper describes the mechanisms through which autoantibodies interact with resident renal cells and how this interaction plays a part in disease pathogenesis that ultimately leads to structural and functional alterations in lupus nephritis.
    Full-text · Article · Jun 2012 · Clinical and Developmental Immunology
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    • "Exposure to high protein concentrations stimulates proximal tubular cells to secrete proinflammatory mediators, including monocyte chemoattractant protein 1 [24], regulation upon activation, normal T-cell expressed and secreted (RANTES) [25], IL-8 [26], complement factor C3 [27], and transforming growth factor beta [28]. During lupus nephritis, proximal tubules have been shown to alter their expression of several molecules involved in inflammatory processes, including intracellular adhesion molecule 1, CD40, and Toll-like receptor 9 [29,30]. "
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    ABSTRACT: Metallothionein (MT) isoforms I + II are polypeptides with potent antioxidative and anti-inflammatory properties. In healthy kidneys, MT-I+II have been described as intracellular proteins of proximal tubular cells. The aim of the present study was to investigate whether the renal MT-I+II expression profile is altered during lupus nephritis. Immunohistochemistry was performed on renal biopsies from 37 patients with lupus nephritis. Four specimens of healthy renal tissue served as controls. Clinicopathological correlation studies and renal survival analyses were performed by means of standard statistical methods. Proximal tubules displaying epithelial cell MT-I+II depletion in combination with luminal MT-I+II expression were observed in 31 out of 37 of the lupus nephritis specimens, but not in any of the control sections (P = 0.006). The tubular MT score, defined as the median number of proximal tubules displaying this MT expression pattern per high-power microscope field (40x magnification), was positively correlated to the creatinine clearance in the lupus nephritis cohort (P = 0.01). Furthermore, a tubular MT score below the median value of the cohort emerged as a significant predictor of a poor renal outcome in renal survival analyses. Thus, patients with a tubular MT score < 1.0 had a 6.2-times higher risk of developing end-stage renal disease than patients with a tubular MT score >or= 1.0 (P = 0.03). Lupus nephritis is associated with significant alterations in renal MT-I+II expression. Our data indicate that important prognostic information can be deduced from the renal MT-I+II expression profile in systemic lupus erythematosus patients with nephritis.
    Full-text · Article · Jul 2008 · Arthritis research & therapy
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