Reactive Oxygen Species Modulation of Na/K-ATPase Regulates Fibrosis and Renal Proximal Tubular Sodium Handling (original) (raw)
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Na/K-ATPase Signaling and Salt Sensitivity: The Role of Oxidative Stress
Antioxidants, 2017
Other than genetic regulation of salt sensitivity of blood pressure, many factors have been shown to regulate renal sodium handling which contributes to long-term blood pressure regulation and have been extensively reviewed. Here we present our progress on the Na/K-ATPase signaling mediated sodium reabsorption in renal proximal tubules, from cardiotonic steroids-mediated to reactive oxygen species (ROS)-mediated Na/K-ATPase signaling that contributes to experimental salt sensitivity.
Journal of Biological Chemistry, 2011
We have observed that, in renal proximal tubular cells, cardiotonic steroids such as ouabain in vitro signal through Na/K-ATPase, which results in inhibition of transepithelial 22 Na ؉ transport by redistributing Na/K-ATPase and NHE3. In the present study, we investigate the role of Na/K-ATPase signaling in renal sodium excretion and blood pressure regulation in vivo. In Sprague-Dawley rats, high salt diet activated c-Src and induced redistribution of Na/K-ATPase and NHE3 in renal proximal tubules. In Dahl salt sensitive (S) and resistant (R) rats given high dietary salt, we found different effects on blood pressure but, more interestingly, different effects on renal salt handling. These differences could be explained by different signaling through the proximal tubular Na/K-ATPase. Specifically, in Dahl R rats, high salt diet significantly stimulated phosphorylation of c-Src and ERK1/2, reduced Na/K-ATPase activity and NHE3 activity, and caused redistribution of Na/K-ATPase and NHE3. In contrast, these adaptations were either much less effective or not seen in the Dahl S rats. We also studied the primary culture of renal proximal tubule isolated from Dahl S and R rats fed a low salt diet. In this system, ouabain induced Na/K-ATPase/c-Src signaling and redistribution of Na/K-ATPase and NHE3 in the Dahl R rats, but not in the Dahl S rats. Our data suggested that impairment of Na/K-ATPase signaling and consequent regulation of Na/K-ATPase and NHE3 in renal proximal tubule may contribute to salt-induced hypertension in the Dahl S rat. . 2 The abbreviations used are: BP, blood pressure; CTS, cardiotonic steroids; EE, early endosome; ERK1/2, extracellular signal-regulated kinases 1 and 2; MBG, marinobufagenin; NHE3, sodium/hydrogen exchanger isoform 3; RPT, renal proximal tubule; HS, high salt diet; LS, low salt diet.
The Na/K-ATPase Signaling Regulates Natriuresis in Renal Proximal Tubule
Innovative Bioanalysis [Working Title]
For decades, the Na/K-ATPase has been proposed and recognized as one of the targets for the regulation of renal salt handling. While direct inhibition of the Na/K-ATPase ion transport activity and sodium reabsorption was the focus, the underlying mechanism is not well understood since decreases in basolateral Na/K-ATPase activity alone do not appear sufficient to decrease net sodium reabsorption across the renal tubular epithelium. The newly appreciated signaling function of Na/K-ATPase, which can be regulated by Na/K-ATPase ligands (cardiotonic steroids (CTS)) and reactive oxygen species (ROS), has been widely confirmed and provides a mechanistic framework for natriuresis regulation in renal proximal tubule (RPT). The focus of this review aims to understand, in renal proximal tubule, how the activation of Na/K-ATPase signaling function, either by CTS or ROS, stimulates a coordinated reduction of cell surface Na/K-ATPase and sodium/hydrogen exchanger isoform 3 (NHE3) that leads to ultimately decreases in net transcellular sodium transport/reabsorption.
Journal of Biological Chemistry, 2013
Background: Na/K-ATPase signaling regulates sodium reabsorption in renal proximal tubules. Results: Carbonylation modification of the Na/K-ATPase ␣1 subunit regulates Na/K-ATPase signaling and subsequent transepithelial sodium transport. Conclusion: ROS is involved in the Na/K-ATPase signaling transduction in a feed-forward mechanism. Significance: ROS regulates Na/K-ATPase signaling and sodium transport in LLC-PK1 cells. Cardiotonic steroids (such as ouabain) signaling through Na/K-ATPase regulate sodium reabsorption in the renal proximal tubule. We report here that reactive oxygen species are required to initiate ouabain-stimulated Na/K-ATPase⅐c-Src signaling. Pretreatment with the antioxidant N-acetyl-L-cysteine prevented ouabain-stimulated Na/K-ATPase⅐c-Src signaling, protein carbonylation, redistribution of Na/K-ATPase and sodium/proton exchanger isoform 3, and inhibition of active transepithelial 22 Na ؉ transport. Disruption of the Na/K-ATPase⅐c-Src signaling complex attenuated ouabain-stimulated protein carbonylation. Ouabain-stimulated protein carbonylation is reversed after removal of ouabain, and this reversibility is largely independent of de novo protein synthesis and degradation by either the lysosome or the proteasome pathways. Furthermore, ouabain stimulated direct carbonylation of two amino acid residues in the actuator domain of the Na/K-ATPase ␣1 subunit. Taken together, the data indicate that carbonylation modification of the Na/K-ATPase ␣1 subunit is involved in a feed-forward mechanism of regulation of ouabain-mediated renal proximal tubule Na/K-ATPase signal transduction and subsequent sodium transport. The Na/K-ATPase ␣1 subunit directly interacts with c-Src kinase via two pairs of domain interactions to form a functional receptor complex (1, 2), i.e. the Na/K-ATPase⅐c-Src signaling complex. The Na/K-ATPase ␣1 subunit provides the ligandbinding site, and the associated c-Src functions as the kinase moiety, amplifying and converting the binding signal to the stimulation of multiple protein kinase cascades, including c-Src and PI3K. In addition, ROS 2 generation is an integrated component of Na/K-ATPase signaling. Ouabain stimulates a Rasdependent ROS generation via Na/K-ATPase signaling (3, 4), and increases in ROS induced by glucose oxidase (GO) stimulate Na/K-ATPase endocytosis (5). Increases in oxidative stress inhibit Na/K-ATPase activity and promote its susceptibility to degradation (6, 7). Furthermore, oxidative modifications, such as glutathionylation of cysteine residue(s) of the Na/K-ATPase 1 subunit (8) and ␣ subunit (9), inhibit Na/K-ATPase activity, by either stabilizing the enzyme in an E2-prone conformation or by blocking the ATP-binding site. Recently, we reported that CTS, signaling through the Na/ K-ATPase, inhibits renal proximal tubule (RPT)-mediated sodium reabsorption and thus increases sodium excretion to counterbalance sodium retention and the related blood pressure increase (10-16). Impairment of the RPT Na/K-ATPase⅐c-Src signaling contributes to experimental Dahl salt-sensitive hypertension (16). However, there is no difference in the Na/K-ATPase ␣1 subunit gene (Atp1a1) coding (17), ouabain sensitivity (18), and expression (16) between the Dahl salt-resistant and salt-sensitive rats (Jr strains). Moreover, acute salt loading causes higher plasma CTS levels in the salt-sensitive rat when compared with the salt-resistant rat (19). These observations indicate the presence of other regulatory factor(s) that regulate Na/K-ATPase signaling. We report here that protein carbonylation of the Na/K-ATPase ␣1 subunit actuator (A) domain is involved in RPT Na/K-ATPase signal transduction in a feed-forward mechanism. EXPERIMENTAL PROCEDURES Chemicals and Antibodies-All chemicals, except as mentioned otherwise, were obtained from Sigma. Proteasome
Journal of the American Heart Association, 2016
We have demonstrated that cardiotonic steroids, such as ouabain, signaling through the Na/K-ATPase, regulate sodium reabsorption in the renal proximal tubule. By direct carbonylation modification of the Pro222 residue in the actuator (A) domain of pig Na/K-ATPase α1 subunit, reactive oxygen species are required for ouabain-stimulated Na/K-ATPase/c-Src signaling and subsequent regulation of active transepithelial (22)Na(+) transport. In the present study we sought to determine the functional role of Pro222 carbonylation in Na/K-ATPase signaling and sodium handling. Stable pig α1 knockdown LLC-PK1-originated PY-17 cells were rescued by expressing wild-type rat α1 and rat α1 with a single mutation of Pro224 (corresponding to pig Pro222) to Ala. This mutation does not affect ouabain-induced inhibition of Na/K-ATPase activity, but abolishes the effects of ouabain on Na/K-ATPase/c-Src signaling, protein carbonylation, Na/K-ATPase endocytosis, and active transepithelial (22)Na(+) transport...
International journal of molecular sciences, 2018
In 1972 Neal Bricker presented the "trade-off" hypothesis in which he detailed the role of physiological adaptation processes in mediating some of the pathophysiology associated with declines in renal function. In the late 1990's Xie and Askari published seminal studies indicating that the Na⁺/K⁺-ATPase (NKA) was not only an ion pump, but also a signal transducer that interacts with several signaling partners. Since this discovery, numerous studies from multiple laboratories have shown that the NKA is a central player in mediating some of these long-term "trade-offs" of the physiological adaptation processes which Bricker originally proposed in the 1970's. In fact, NKA ligands such as cardiotonic steroids (CTS), have been shown to signal through NKA, and consequently been implicated in mediating both adaptive and maladaptive responses to volume overload such as fibrosis and oxidative stress. In this review we will emphasize the role the NKA plays in this ...
Frontiers in physiology, 2016
Na/K-ATPase signaling has been implicated in different physiological and pathophysiological conditions. Accumulating evidence indicates that oxidative stress not only regulates the Na/K-ATPase enzymatic activity, but also regulates its signaling and other functions. While cardiotonic steroids (CTS)-induced increase in reactive oxygen species (ROS) generation is an intermediate step in CTS-mediated Na/K-ATPase signaling, increase in ROS alone also stimulates Na/K-ATPase signaling. Based on literature and our observations, we hypothesize that ROS have biphasic effects on Na/K-ATPase signaling, transcellular sodium transport, and urinary sodium excretion. Oxidative modulation, in particular site specific carbonylation of the Na/K-ATPase α1 subunit, is a critical step in proximal tubular Na/K-ATPase signaling and decreased transcellular sodium transport leading to increases in urinary sodium excretion. However, once this system is overstimulated, the signaling, and associated changes in...
The regulation of proximal tubular salt transport in hypertension: an update
Current Opinion in Nephrology and Hypertension, 2009
Purpose of review-Renal proximal tubular sodium reabsorption is regulated by sodium transporters, including the sodium glucose transporter, sodium amino acid transporter, sodium hydrogen exchanger isoform 3 and sodium phosphate cotransporter type 2 located at the luminal/ apical membrane, and sodium bicarbonate cotransporter and Na + /K + ATPase located at the basolateral membrane. This review summarizes recent studies on sodium transporters that play a major role in the increase in blood pressure in essential/polygenic hypertension. Recent findings-Sodium transporters and Na + /K + ATPase are segregated in membrane lipid and nonlipid raft microdomains that regulate their activities and trafficking via cytoskeletal proteins. The increase in renal proximal tubule ion transport in polygenic hypertension is primarily due to increased activity of NHE3 and Cl/HCO 3 exchanger at the luminal/apical membrane and a primary or secondary increase in Na + /K + ATPase activity.