The Role of Histamine H3 Receptors in ENaC‐dependent Sodium Reabsorption in the Cortical Collecting Ducts
Authors: Domondon Mark , Sultanova Regina , Kurashkina Elizaveta , Polina Iuliia , Ilatovskaya Daria 
Published: June 2021

Histamine is an organic compound that is involved in a variety of physiological functions. It is released as an inflammatory response to foreign pathogens, triggering vasodilation and increased vascular permeability leading to the symptoms seen in an allergic reaction. Histamine receptors, H1R‐H4R, are all G‐protein coupled; histamine receptor 3 (H3R) is predominantly expressed in the central nervous system, but its presence has also been observed in non‐neuronal cells. In the kidney, H3R has been reported to be located in the collecting ducts (CD) cells from rats, as well as tubular epithelial cells (TEC) from humans. Some studies have recorded an upregulation of H3R in the kidneys during diseases such as diabetes, however, its specific role in the renal system is yet unclear. The goal of this study was to test if H3R can affect the activity of Epithelial Na+ Channels (ENaC), and thus sodium reabsorption, in the CDs.In order to test this hypothesis, we implemented transepithelial short‐circuit current measurements (Isc) in mpkCCDc14 cells (immortalized mouse cortical collecting ducts cells), as well as Western blotting and immunohistochemical staining. mpkCCDc14 cells were passaged onto permeable Transwell supports. Using an Epithelial Voltohmeter, closed circuit voltage measurements were performed to measure the ENaC‐dependent sodium reabsorption. The experimental groups were exposed to various concentrations of histamine apically (1μM, 10 μM, 50 μM). Voltage and resistance measurements were taken throughout 8 hours after drug application, and amiloride was added in the end to ensure the current was ENaC‐mediated. Our data showed that histamine alone has no effect on ENaC‐driven current when compared to the control (vehicle). We used vasopressin (AVP) as a known ENaC activator, and when cells were stimulated with AVP only (10 nM, basolaterally), we observed a 57% ± 7% increase in current at a 4 hour time point (the peak of the response, n=36). Cells treated with both histamine and AVP exhibited a dose‐dependent decrease in AVP‐mediated ENaC currents. In presence of 10 nM AVP, and 1 μM, 10 μM and 50 μM of histamine, ENaC‐mediated current was 24%±14%, 26%±8% and 36%±16% lower, respectively, compared to AVP only. Basolateral application of histamine did not attenuate response to AVP. WB revealed a robust expression of H3R expression in the renal cortical tissue of the rats; we further showed H3R expression in both the cortical and medullary regions of the Sprague Dawley rat kidney using IHC staining. Specifically, we demonstrated a high level of H3R in the cortical CDs (pronounced apical membrane staining was observed, as well as faint intracellular distribution), and some expression in the glomeruli.In conclusion, we demonstrated that histamine attenuates the effect that AVP has on ENaC‐mediated current in the cortical CD in a dose‐dependent manner. These novel data will provide insight into the role which H3R plays in the sodium reabsorption in physiology and pathophysiology.Support or Funding InformationSupported by NIH and PKD FoundationThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.