Meprins, cell-surface and secreted oligomeric metalloendopeptidases of the 'astacin'family, are highly expressed at the brush-border membranes of the kidney proximal tubules. The specific role of meprins during acute kidney injury (AKI) is not fully understood. Our studies identified that meprin A is the major matrix-degrading protease in the rat kidney cortex capable of degrading the extracellular matrix (ECM) proteins including collagen IV, fibronectin, laminin, and nidogen in vitro. Our recently published and preliminary studies demonstrated that meprins are also capable of producing biologically active proinflammatory cytokine interleukin 1-beta from its inactive proform and proteolytically processing chemotactic cytokine MCP-1, suggesting that meprins are also important in inflammation. Leukocytes isolated from the peripheral blood or the kidney tissue were found to express meprin beta. Furthermore, our studies demonstrate that, following ischemia-reperfusion- and cisplatin-induced AKI, meprin A is redistributed toward the basolateral side of the proximal tubule. These studies suggest that altered localization of meprin A in places other than the apical brush-border membranes may be deleterious in vivo in acute tubular injury. Preliminary studies suggest that meprin A shedding may involve a member of the ADAM (a disintegrin and metalloproteinase) family. Using in vivo models of cisplatin- and ischemia- reperfusion-induced AKI, we demonstrated that actinonin, a potent inhibitor of meprin A inhibits meprin A in vivo and ameliorates acute kidney injury and meprin A-deficient mice are resistant to cisplatin nephrotoxicity. Interestingly, we observed that nidogen and meprin-beta fragments, undetectable in the urine of normal mice, increased significantly during cisplatin nephrotoxicity and actinonin markedly prevented urinary excretion of nidogen fragments. Thus, a unique opportunity exists to further explore the role and mechanism of action of meprin A in AKI. We hypothesize that meprin A, with its enormous destructive potential, is detrimental to renal proximal tubules due to altered localization during AKI and that understanding its mechanism of action is important in protecting or reducing AKI. We will test the hypothesis through the following specific aims:
The Specific Aims are: 1. Examine the temporal relationship between meprin A redistribution, renal injury, leukocyte infiltration, and meprin A shedding during AKI using experimental models of IR and cisplatin nephrotoxicity. 2. Identification of meprin A-mediated in vivo degradation products of the ECM components during IR and cisplatin nephrotoxicity. 3. Determine the mechanisms of meprin A-mediated inflammatory effects and functional significance of meprin A during AKI using a meprin inhibitor and meprin A-deficient mice. Understanding the underlying role of meprin A in AKI will provide insights for specific therapeutic interventions to prevent acute kidney injury.

Public Health Relevance

Kidney disease is a frequent and serious disease, which affects 5-7% of all hospitalized patients and 30 % of ICU admissions with a high mortality rate and the expenses related for patients with kidney failure are estimated at $10 billion per year. The risk of mortality is greater than 60% among patients who develop AKI and subsequently require hemodialysis. There has been little improvement in mortality over the last four decades. The mechanisms underlying the causes of kidney injury remain poorly defined. The studies proposed in this application are aimed directly at understanding these mechanisms, which will result in appropriate therapeutic interventions.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK081690-03
Application #
8235921
Study Section
Pathobiology of Kidney Disease Study Section (PBKD)
Program Officer
Kimmel, Paul
Project Start
2010-03-01
Project End
2014-02-28
Budget Start
2012-03-01
Budget End
2013-02-28
Support Year
3
Fiscal Year
2012
Total Cost
$207,068
Indirect Cost
$42,728
Name
University of Arkansas for Medical Sciences
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
122452563
City
Little Rock
State
AR
Country
United States
Zip Code
72205
Herzog, Christian; Haun, Randy S; Ludwig, Andreas et al. (2014) ADAM10 is the major sheddase responsible for the release of membrane-associated meprin A. J Biol Chem 289:13308-22
Kaushal, Varsha; Herzog, Christian; Haun, Randy S et al. (2014) Caspase protocols in mice. Methods Mol Biol 1133:141-54
Kaushal, Gur P; Haun, Randy S; Herzog, Christian et al. (2013) Meprin A metalloproteinase and its role in acute kidney injury. Am J Physiol Renal Physiol 304:F1150-8
Ramani, Vishnu C; Kaushal, Gur P; Haun, Randy S (2011) Proteolytic action of kallikrein-related peptidase 7 produces unique active matrix metalloproteinase-9 lacking the C-terminal hemopexin domains. Biochim Biophys Acta 1813:1525-31