DOI
https://doi.org/10.25772/WCYW-1724
Author ORCID Identifier
https://orcid.org/0000-0002-0275-635X
Defense Date
2023
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Pharmacology & Toxicology
First Advisor
Ningjun Li
Second Advisor
Aron Lichtman
Third Advisor
Huiping Zhou
Fourth Advisor
Joseph Ritter
Fifth Advisor
Todd Gehr
Abstract
Although cannabinoid receptors (CB) are recognized as targets for renal fibrosis, the role of endogenous cannabinoid anandamide (AEA) and its primary hydrolytic enzyme, fatty acid amide hydrolase (FAAH), in renal fibrogenesis remains unclear. The present study used a mouse model of post-ischemia-reperfusion (PIR) renal injury to test the hypothesis that FAAH participates in renal fibrogenesis. Our results demonstrated that kidneys with PIR injury showed upregulated expression of FAAH in renal proximal tubules, accompanied by decreased AEA levels in the kidneys. Faah knockout mice showed a recovery of the reduced AEA levels and amelioration of PIR injury-triggered increases in blood urea nitrogen, plasma creatinine as well as renal profibrogenic markers and injuries. Correspondingly, a selective FAAH inhibitor, PF-04457845, inhibited the transforming growth factor-beta 1 (TGF-β1)-induced profibrogenic markers in both a human proximal tubular cell line (HK-2 cells) and primary cultured tubular cells from mice. Knockdown of FAAH by siRNA in HK-2 cells had similar effects to those observed with the use of PF-04457845. Studies on tubular cells isolated from Faah-/- mice further validated the protective effects of FAAH inhibition against TGF-β1-induced tubule damage. The CB1 or CB2 receptor antagonist and the exogenous FAAH metabolite – arachidonic acid failed to reverse the protective effects of FAAH inactivation in HK-2 cells. However, a substrate-selective inhibitor of the AEA-cyclooxygenase-2 (COX-2) pathway significantly suppressed the anti-profibrogenic actions of FAAH inhibition. Further, the AEA-COX-2 metabolites, prostamide E2 and prostamide F2a exerted anti-profibrogenic effects in HK-2 cells. We also found that gene silencing of NF-κB/p65 by siRNA inhibited TGF-β1-induced protein expression of FAAH in HK-2 cells, suggesting that TGF-β1-induced activation of NF-κB could be the upstream signaling pathway that increases FAAH activation and expression in PIR injury or TGF-β1-induced FAAH activation. Overall, the results suggest that FAAH activation and the consequent reduction of AEA contribute to renal fibrogenesis and that FAAH inhibition with recovered AEA levels protects against TGF-β1-induced fibrogenesis in renal cells via the AEA-COX-2 pathway independent of CB receptors.
Rights
© Chaoling (Linda) Chen
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
5-6-2023