Acute kidney injury (AKI) is a major determinant of mortality and morbidity in hospitalized patients. Understanding the pathophysiology of AKI is essential for the development of therapy. This application proposes to study the role of Tamm-Horsfall protein (THP) in AKI. This protein is expressed exclusively in the kidney by cells of the thick ascending limbs (TAL) of Henle. In the last few years, we uncovered a key role of THP in mediating a protective tubular cross-talk in AKI. We showed that THP regulates inflammatory signaling and injury to S3 segments, which are neighboring tubules to TAL in the kidney outer medulla. The immediate goal of the current proposal is to study the importance of the interaction of THP with S3 segments in regulating neutrophil infiltration and limiting oxidative stress in AKI. These studies will form the basis to transition into therapeutic applications. Indeed, the PI's long term goal is to understand how the role of THP can be modulated to treat patients who develop AKI. The central hypothesis is that Tamm-Horsfall protein regulates the inflammatory response triggered by ischemic injury in the outer medulla; an effect that requires an interaction of THP with the surrounding tubular elements. This hypothesis has been formulated on the basis of strong preliminary and published data. The following specific aims will be used to investigate this hypothesis.
Aim 1 will investigate the role of THP as a key regulator of neutrophil infiltration in the kidney after AKI.
Aim 2 will study the functional significance of the interaction of THP with neighboring epithelium in kidney injury Aim 2 will investigate therapeutic modulation of THP to inhibit neutrophil influx and promote recovery after AKI This research will involve the use of THP knockout and wild type mice. The animal model used for AKI is renal ischemia-reperfusion injury achieved through renal pedicle clamping. In vitro studies will involve cell lines for proximal tubules. Other techniques used in this work include: Immunofluorescence laser micro-dissection of specific tubular sections, Immunofluoresence confocal and intravital microscopy, flow cytometry, real time- PCR, western blot, various forms of chromatography and mass spectrometry. This research is innovative, because it will uncover novel regulatory functions for THP that may be relevant not only in kidney injury but also in other forms of acute or chronic renal disease. Future strategies that enhance the role of THP in the kidney will be of important therapeutic significance.

Public Health Relevance

Deterioration of kidney function, or acute kidney failure is an important contributing factor to the morbidity and mortality of hospitalized patients. Our proposed research will study the role of a protein, Tamm-Horsfall Protein (THP), that may protect the kidneys in the setting of injury. A better understanding of the role of THP holds promise for future therapeutic stategies that improve outcomes of kidney failure by enhancing the protective role of this protein.

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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Rys-Sikora, Krystyna E
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Indiana University-Purdue University at Indianapolis
Internal Medicine/Medicine
Schools of Medicine
United States
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Micanovic, Radmila; Khan, Shehnaz; Janosevic, Danielle et al. (2018) Tamm-Horsfall Protein Regulates Mononuclear Phagocytes in the Kidney. J Am Soc Nephrol 29:841-856
Ma, Lijie; Liu, Yan; Landry, Nichole K et al. (2017) Point mutation in D8C domain of Tamm-Horsfall protein/uromodulin in transgenic mice causes progressive renal damage and hyperuricemia. PLoS One 12:e0186769