This grant examines the role of the complement system in the development of ischemic acute renal failure. Our published work demonstrates that complement activation contributes to renal injury after ischemia/reperfusion (I/R), and that activation occurs primarily through the alternative pathway. The alternative pathway has emerged, in recent years, as a critical mediator of injury in a number of different diseases. This system is effective at rapidly eliminating invasive pathogens, but insufficient control of the activating enzymes permits inflammatory injury of host cells. The primary hypothesis of this grant is that hypoxia alters the surface expression of complement inhibitory proteins by proximal tubular epithelial cells. This changes the cells from a complement inhibitory to a complement activating phenotype. Once activated, the alternative pathway triggers generation of pro-inflammatory signals, including C3a, C5a, macrophage inflammatory protein-2 (MIP-2) and keratinocyte derived chemokine (KC). To test this hypothesis we will use in vivo and in vitro models to determine whether the loss of surface inhibition is sufficient to cause spontaneous alternative pathway activation, and the mechanisms by which this surface inhibition is lost after I/R (SA1). Factor H is a potent alternative pathway inhibitor that circulates in high concentrations but fails to prevent alternative pathway mediated injury in certain diseases. We will also examine whether a novel complement inhibitor that targets factor H to the site of complement activation prevents pathological complement activation after renal I/R, and the factors that modulate protection of this surface by endogenous factor H (SA2). Finally, we will examine the mechanisms by which alternative pathway activation in the tubulointerstitium triggers a widespread inflammatory response (SA3). Ischemic acute renal failure is one of the most common causes of acute renal failure, and is associated with a mortality rate of greater than 50% in the intensive care unit setting. A number of complement inhibitors have become available, including a specific inhibitor of the alternative pathway that has been developed by our laboratory and a targeted inhibitor of the alternative pathway that was developed by one of our collaborators. The proposed studies should help delineate the benefits and limitations of complement inhibition as a therapy for ischemic acute renal failure, as well as expand our understanding of complement activation as a mediator of inflammation after renal tubular injury. PROJECT NARRATIVE Ischemic acute renal failure is one of the most common causes of acute renal failure, and is associated with a mortality rate of greater than 50% in the intensive care unit setting. Studies have demonstrated that the complement system is activated within the kidney after ischemia. The proposed experiments examine the complex interactions between the complement system and the kidney. These studies will identify therapies that effectively inhibit the complement system and determine whether these agents will ameliorate ischemic acute renal failure.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Pathobiology of Kidney Disease Study Section (PBKD)
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Kimmel, Paul
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University of Colorado Denver
Internal Medicine/Medicine
Schools of Medicine
United States
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Tong, Hua Hua; Lambert, Garrett; Li, Yong Xing et al. (2014) Deletion of the complement C5a receptor alleviates the severity of acute pneumococcal otitis media following influenza A virus infection in mice. PLoS One 9:e95160
Renner, Brandon; Klawitter, Jelena; Goldberg, Ryan et al. (2013) Cyclosporine induces endothelial cell release of complement-activating microparticles. J Am Soc Nephrol 24:1849-62
Thurman, Joshua M; Kulik, Liudmila; Orth, Heather et al. (2013) Detection of complement activation using monoclonal antibodies against C3d. J Clin Invest 123:2218-30
McCullough, James W; Renner, Brandon; Thurman, Joshua M (2013) The role of the complement system in acute kidney injury. Semin Nephrol 33:543-56
Hu, Xianzhen; Holers, V Michael; Thurman, Joshua M et al. (2013) Therapeutic inhibition of the alternative complement pathway attenuates chronic EAE. Mol Immunol 54:302-8
Strassheim, Derek; Renner, Brandon; Panzer, Sarah et al. (2013) IgM contributes to glomerular injury in FSGS. J Am Soc Nephrol 24:393-406
Thurman, Johua M (2012) Therapeutic regulation of complement in patients with renal disease - where is the promise? Clin Nephrol 77:413-23
Larson, Jennifer D; Thurman, Joshua M; Rubtsov, Anatoly V et al. (2012) Murine gammaherpesvirus 68 infection protects lupus-prone mice from the development of autoimmunity. Proc Natl Acad Sci U S A 109:E1092-100
Sargsyan, Siranush A; Serkova, Natalie J; Renner, Brandon et al. (2012) Detection of glomerular complement C3 fragments by magnetic resonance imaging in murine lupus nephritis. Kidney Int 81:152-9
Takeda, Katsuyuki; Thurman, Joshua M; Tomlinson, Stephen et al. (2012) The critical role of complement alternative pathway regulator factor H in allergen-induced airway hyperresponsiveness and inflammation. J Immunol 188:661-7

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