Empagliflozin Downregulates Renal NHE3 Activity and NaPi‐2 Expression and Reduces Blood Pressure in Hypertensive Rats

Abstract

Sodium-glucose cotransporter 2 (SGLT2) inhibitors, also known as gliflozins, can lower blood pressure (BP) and reduce cardiovascular mortality in hypertensive patients with type 2 diabetes. However, the molecular mechanisms underlying the antihypertensive effects of the SGLT2 inhibitors have not been elucidated. This study tested the hypothesis that empagliflozin, an SGLT2 inhibitor, reduces BP of nondiabetic hypertensive rats and that this effect may be associated with altered expression and/or covalent modification of apical sodium transporters in the renal proximal tubule. To this end, spontaneously hypertensive rats (SHR) and normotensive Wistar rats (12-14 weeks of age) were treated for 2 weeks with empagliflozin 10 mg/kg/day or vehicle (water) orally. BP was measured non-invasively (tail-cuff plethysmography) and invasively (arterial catheterization). Proximal tubule Na+/H+ exchanger isoform 3 (NHE3) activity was assessed by in vivo stationary microperfusion. NHE3 phosphorylated at serine 552 (pNHE3-552), total NHE3 and Na+-dependent phosphate cotransporter type II (NaPi-2) expression in the renal cortex were evaluated by immunoblotting. We found that vehicle-treated SHR exhibited a small increase in BP (9±2 mmHg), whereas empagliflozin reduced BP of hypertensive rats (-10±2 mmHg). No changes in BP were observed in Wistar rats. The in vivo stationary microperfusion analyses showed that empagliflozin inhibited the activity of NHE3 in both hypertensive and normotensive rats. Inhibition of NHE3 activity by empagliflozin was not accompanied by differences in the levels of pNHE3-552 or total NHE3 expression in the renal cortex. On the other hand, NaPi-2 expression was upregulated in the renal cortex of vehicle-treated SHR (226±18 vs. 100±5% in vehicle-treated Wistar rats, p< 0.0001), and treatment with empagliflozin significantly reduced it (163±11 vs. 226±18%, p< 0.01). Renal cortical NaPi-2 abundance was not affected by empagliflozin in normotensive rats. These findings demonstrate empagliflozin lowers blood pressure in nondiabetic hypertensive rats. Moreover, it shows that SGLT2 inhibition may reduce proximal tubule sodium reabsorption via inhibition of NHE3 and downregulation of NaPi-2. Future studies are necessary to evaluate the impact of SGLT2 inhibitors in the distal nephron and its association with the antihypertensive effects of the gliflozins.