Published online before print October 15, 2009

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Copyright © 2009 American Society for Investigative Pathology
American Journal of Pathology, doi:10.2353/ajpath.2009.090182

Accepted for publication August 4, 2009.

Article

Double-Stranded DNA Activates Glomerular Endothelial Cells and Enhances Albumin Permeability via a Toll-Like Receptor-Independent Cytosolic DNA Recognition Pathway

Holger Hägele^*, Ramanjaneyulu Allam^*, Rahul D. Pawar^*, Christoph A. Reichel, Fritz Krombach, and Hans-Joachim Anders^*@

From the Department of Nephrology,* Medical Policlinic, University of Munich, Munich, Germany; the Division of Clinical Immunology and Rheumatology, University of Alabama at Birmingham, Birmingham, Alabama; and the Walter Brendel Centre of Experimental Medicine, University of Munich, Munich, Germany

^@ To whom correspondence should be addressed. E-mail: hjanders{at}.med.uni-muenchen.de.

	Abstract

Viral DNA induces potent antiviral immunity by activating dendritic cells; however, the mechanism governing viral DNA-mediated triggering or aggravation of glomerulonephritis is unknown. Glomerular endothelial cells (GEnCs) do not express toll-like receptor (TLR)9, the only DNA-specific TLR. We therefore hypothesized that DNA could activate GEnCs via the recently discovered TLR-independent viral DNA recognition pathway. Indeed, double-stranded non-CpG (B-) DNA activated GEnCs to produce interleukin-6, CCL5/RANTES, CCL2/MCP-1, CXCL10/IP10, interferon (IFN)-, and IFN- when cationic lipids facilitated intracellular DNA uptake. This cytokine production was inhibited by chlorpromazine, suggesting that clathrin-dependent endocytosis is required for B-DNA entry. However, chloroquine and MyD88 inhibition did not affect GEnC activation, suggesting TLR-independent DNA recognition. In addition, IFN- activated cytokine and chemokine mRNA expression, although only CXCL10/IP10 was induced at the protein level, and type I IFN did not activate GEnC in an autocrine-paracrine auto-activation loop. B-DNA complexes induced intercellular adhesion molecule-1 expression at the GEnC surface and increased intercellular adhesion molecule-1-dependent leukocyte adhesion and microvascular extravasation in vivo. Furthermore, B-DNA complexes increased albumin permeability of GEnC monolayers in culture or microvascular dextran leakage in vivo. In addition, B-DNA complexes impaired GEnC proliferation. Thus, complexed B-DNA activates GEnC to produce cytokines, chemokines, and type I IFNs, increases leukocyte adhesion and microvascular permeability, and reduces GEnC proliferation via a MyD88-independent cytosolic DNA recognition pathway. This innate antiviral response program suggests a novel pathomechanism regulating DNA virus-mediated induction or aggravation of glomerulonephritis.