Interleukin 6‐Mediated Mineralocorticoid Receptor Translocation and Total Sodium Uptake Occurs via JAK2/STAT3

Hypertension is an inflammatory disease that is a leading cause of death and disability worldwide and is characterized by increased sodium (Na+) reabsorption. The beneficial effect of mineralocorticoid receptor (MR) antagonists in reducing blood pressure suggests a role for the MR in hypertension. Interestingly, the classical MR ligand, aldosterone (Aldo) is not always increased during hypertension. Elevated levels of the pro‐inflammatory cytokine, interleukin 6 (IL‐6); however, have been observed in the serum of hypertensive individuals. Cytokines elicit intracellular effects through various signaling mechanisms, including the Janus Kinase (JAK)/Signal Transducer and Activation of Transcription (STAT) pathway. There are multiple isoforms of each of these kinases that have been implicated in other IL‐6‐mediated inflammatory responses in the kidney; however, no empirical studies thus far have investigated how IL‐6 increases Na+ chloride cotransporter (NCC)‐mediated Na+ reabsorption. We hypothesize that the JAK2/STAT3 signaling pathway is involved in MR‐mediated activation of distal Na+ transporters. Using an in vitro model of a late distal convoluted tubule cell line, we have previously we have shown that IL‐6 activates JAK2 and STAT3 kinases using immunofluorescence probing and western blot techniques. We have also previously demonstrated that IL‐6 transactivates the MR and increases its activity via a JAK/STAT3 mechanism in transiently transfected mDCT15 cells using luciferase reporter assay studies. To visualize the effect of IL‐6‐mediated JAK2/STAT3 induction of MR nuclear translocation, we transfected mDCT15 cells with eGFP‐tagged MR constructs. Cells were incubated and treated with either: vehicle, IL‐6 [100ng/mL], IL‐6 + NSC33994 (JAK2 inhibitor, [10μM]), or IL‐6 + NSC74859 (STAT3 inhibitor, [50μM]) for 30 min. Images were collected using confocal microscopy. To demonstrate the role of IL‐6‐stimulated JAK2/STAT3 signaling on total Na + reabsorption, we performed Na + uptake studies using CoroNa Green (fluorescent Na + indicator, 6μM, 30 min). mDCT15 cells were treated with: vehicle, IL‐6 (100ng/mL), IL‐6 receptor subunit gp130 inhibitor (SC144, 2 μM), JAK2 inhibitor (NSC33994, 10 μM), STAT3 inhibitor (NSC, 50μM) or an MR antagonist (spironolactone, 10 nM). In the presence of both JAK2 and STAT3 inhibitors, IL‐6 MR translocation was reduced (JAK2) or completely inhibited (STAT3). When IL‐6 receptor, STAT3, and MR activity was inhibited, we observed reduced Na+ uptake levels. This suggests that IL‐6 activation of the MR increases distal Na+ uptake via an IL‐6 induced JAK/STAT3 mechanism. Overall, we are working to identify a novel mechanism of IL‐6 mediated distal Na+ transporter activation via MR induction, in order to demonstrate an alternative mechanism for increased Na+ reabsorption in hypertension when serum aldosterone levels are not increased, but elevated cytokine levels are observed. Together, our data suggests a mechanism for IL‐6‐mediated activation of the MR via a JAK2/STAT3 signaling pathway. Support or Funding Information NIH DK115660, American Society of Nephrology Gottschalk to BMW This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .