Over the last four years, we have demonstrated that hyperhomocysteinemia (hHcys) contributes to the development of glomerular sclerosis associated with hypertension. The molecular mechanisms mediating the pathogenic action of hHcys can be dependent or independent on elevated arterial pressure. It has been shown that NADPH oxidase (NOX) activation independent of elevated arterial pressure initiates the cascade of podocyte injury and consequent glomerular sclerosis during hHcys. Now it is imperative to know how this cascade of glomerular injury is instigated and amplified by activated NOX and redox signaling. The goal of this grant proposal is to test whether the Nlrp3 inflammasome, an intracellular inflammatory machinery is a triggering mechanism for instigation and amplification of the cascade for glomerular injury in hHcys and to determine how NOX activation turns on inflammasomes and how activated inflammasomes work to cause podocyte injury and glomerular sclerosis. We hypothesize that Nlrp3 inflammasomes sense NOX-derived redox signals and thereby turn on the inflammatory response and damage podocytes in glomeruli, ultimately leading to glomerular sclerosis during hHcys. To test this hypothesis, three Specific Aims are proposed.
Specific Aim 1 will determine whether activation of a redox sensor-Nlrp3 inflammasome contributes to podocyte injury and chronic glomerular inflammation and sclerosis in hHcys induced by the folate-free diet in vivo, using Nlrp3-/- mice with or without rescuing Nlrp3 gene and wild type mice with locally silenced Nlrp3 gene.
Specific Aim 2 will address how Nlrp3 inflammasomes are activated in podocytes by increased Hcys levels with a focus on the roles of NOX-mediated redox signaling and corresponding mechanisms mediating its action.
Specific Aim 3 will explore the mechanisms by which activation of Nlrp3 inflammasomes leads to podocyte injury and glomerular dysfunction or sclerosis by studying the actions of inflammasome products such as IL-1b, IL-18 and DAMPs in cultured podocytes and in mice with hHcys induced by the folate-free diet. To our knowledge, these proposed studies represent the first effort in the field to study the role of an intracellular inflammatory machiner, the Nlrp3 inflammasome, as a redox sensor to switch on glomerular inflammation and to directly induce podocyte injury during hHcys.

Public Health Relevance

This project attempts to determine how elevations of plasma homocysteine (Hcys), a toxic amino acid causes hypertension, kidney dysfunction and chronic renal failure with a major focus on Inflammasomes, an active protein complex within cells. When completed, our proposed studies will define a novel triggering mechanism of Hcys-induced kidney injury. Elucidation of this protein complex as an initiating mechanism of kidney injury will help develop new therapeutic strategies for prevention and treatment of high blood pressure or Hcys-induced chronic renal failure.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
2R01DK054927-16
Application #
8575121
Study Section
Special Emphasis Panel (ZRG1-VH-B (90))
Program Officer
Rys-Sikora, Krystyna E
Project Start
1998-06-01
Project End
2018-07-31
Budget Start
2013-08-15
Budget End
2014-07-31
Support Year
16
Fiscal Year
2013
Total Cost
$331,688
Indirect Cost
$114,188
Name
Virginia Commonwealth University
Department
Pharmacology
Type
Schools of Medicine
DUNS #
105300446
City
Richmond
State
VA
Country
United States
Zip Code
23298
Boini, Krishna M; Xia, Min; Koka, Saisudha et al. (2016) Instigation of NLRP3 inflammasome activation and glomerular injury in mice on the high fat diet: role of acid sphingomyelinase gene. Oncotarget 7:19031-44
Li, Guangbi; Xia, Min; Abais, Justine M et al. (2016) Protective Action of Anandamide and Its COX-2 Metabolite against l-Homocysteine-Induced NLRP3 Inflammasome Activation and Injury in Podocytes. J Pharmacol Exp Ther 358:61-70
Xia, Min; Abais, Justine M; Koka, Saisudha et al. (2016) Characterization and Activation of NLRP3 Inflammasomes in the Renal Medulla in Mice. Kidney Blood Press Res 41:208-21
Li, Pin-Lan (2015) Cardiovascular pathobiology of inflammasomes: inflammatory machinery and beyond. Antioxid Redox Signal 22:1079-83
Li, Guangbi; Li, Cai-Xia; Xia, Min et al. (2015) Enhanced epithelial-to-mesenchymal transition associated with lysosome dysfunction in podocytes: role of p62/Sequestosome 1 as a signaling hub. Cell Physiol Biochem 35:1773-86
Abais, Justine M; Xia, Min; Zhang, Yang et al. (2015) Redox regulation of NLRP3 inflammasomes: ROS as trigger or effector? Antioxid Redox Signal 22:1111-29
Hu, Junping; Zhu, Qing; Li, Pin-Lan et al. (2015) Stem cell conditioned culture media attenuated albumin-induced epithelial-mesenchymal transition in renal tubular cells. Cell Physiol Biochem 35:1719-28
Abais, Justine M; Xia, Min; Li, Guangbi et al. (2014) Contribution of endogenously produced reactive oxygen species to the activation of podocyte NLRP3 inflammasomes in hyperhomocysteinemia. Free Radic Biol Med 67:211-20
Wang, Zhengchao; Zhu, Qing; Li, Pin-Lan et al. (2014) Silencing of hypoxia-inducible factor-1α gene attenuates chronic ischemic renal injury in two-kidney, one-clip rats. Am J Physiol Renal Physiol 306:F1236-42
Hu, Junping; Zhu, Qing; Xia, Min et al. (2014) Transplantation of mesenchymal stem cells into the renal medulla attenuated salt-sensitive hypertension in Dahl S rat. J Mol Med (Berl) 92:1139-45

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