Role of Adipocyte Na/K-ATPase Signaling in the Development and Progression of Uremic Cardiomyopathy By Altering Adipocyte Phenotype - The role of oxidant stress in the pathophysiology of cardiovascular disease has long been a subject of
considerable interest. Although end stage renal disease is relatively uncommon, milder degrees of chronic kidney
disease [CKD] such as CKD 3 are quite common and have been implicated as important determinant in
cardiovascular morbidity and mortality. Oxidant stress plays a key role in the development of renal-failure-
associated cardiomyopathy (also known as uremic cardiomyopathy), both experimentally and clinically.
The “Na/K-ATPase,” a sodium-potassium pump, has been shown by our group to affect cellular signaling
via the “Na/K-ATPase signaling,” which amplifies oxidative stress. We have specifically shown that this pathway
is critical to the pathophysiology of several experimental models of disease including obesity/metabolic syndrome
and experimental uremic cardiomyopathy. We and others have also observed that the adipocyte itself is an
important source of oxidant stress in models with obesity/metabolic syndrome and that mediators directly tied to
the cellular phenotype of these adipocytes play a causal role in the cardiovascular conditions associated with
obesity/metabolic syndrome. This led us to believe that adipocytes could play a central role in uremic
cardiomyopathy. Therefore, we hypothesize that adipocytes create systemic oxidant stress through the Na/K-
ATPase feed-forward oxidant amplification loop in uremic cardiomyopathy and serve as a therapeutic target for
this condition. Our group has developed a cell permeant peptide, NaKtide, from the N domain of the α1 subunit
of the Na/K-ATPase, which inhibits Na/K-ATPase-ROS amplification. Our preliminary results show that the
NaKtide, targeted specifically to adipocyte, attenuates oxidative stress and inflammatory cytokines, in addition
to improving metabolic parameters. Our experimental approach includes studies to determine the role of
adipocyte Na/K-ATPase signaling in the development of experimental uremic cardiomyopathy using a partial
nephrectomy (PNx) mouse model with and without dietary manipulations (Aim 1). We will also target the NaKtide
to the adipocyte using “lentiviral gene transfer” strategy (Aim 1) to determine the role of adipocyte-derived Na/K-
ATPase/Src signaling in the progression of uremic cardiomyopathy. To test the off-target effects of NaKtide, we
will also use lentiviral vectors with tissue specific promoters, including heart and kidney to targeted NaKtide
specially in these tissues. Further, we will target c-Src-shRNA to adipocytes using lentivirus vector, as an
alternate strategy of inhibiting Na/K-ATPase signaling, to demonstrate the role of c-Src as a downstream
mediator of Na/K-ATPase in exacerbating oxidative stress and eventually uremic cardiomyopathy. In Aim 2, we
will employ in vitro protocols for primary adipocytes, isolated from Sham or PNx operated C57BL6 mice and
perform RNASeq analysis to study the adipocyte phenotypic alterations and pathways associated with uremic
cardiomyopathy phenotype. We will also use primary adipocytes isolated from C57BL6 and Na/K-ATPase α1+/-
mice which will be exposed to uremic toxins, subsequently activating Na/K-ATPase signaling, to determine the
activation of specific downstream molecular pathways in vitro that mimic in vivo outcomes. These experiments
will allow us to determine if the Na/K-ATPase signaling and/or adipocytes are potential targets for disease
intervention. These studies if proven may provide a basis for the future studies to ameliorate uremic
cardiomyopathy phenotype.
