The KCa3.1 Channel Blocker TRAM-34 and Minocycline Prevent Fructose-Induced Hypertension in Rats

Abstract

BACKGROUND: High fructose consumption increases blood pressure through microglia-related neuroinflammation in rats. Since intermediate-conductance calcium-activated potassium channels (KCa3.1) potentiates microglial reactivity, we examined whether the pretreatment with the KCa3.1 channel blocker TRAM-34 or minocycline prevents hypertension development in fructose-fed rats. METHODS: The study involved male Wistar rats that were given either high fructose (10% in drinking water) or tap water for 21 days. Fructose groups also received minocycline or TRAM-34 systemically for 21 days. We measured systolic and diastolic blood pressure (SBP and DBP), heart rate (HR) periodically with tail-cuff; proinflammatory cytokines, and insulin levels in plasma via Enzyme-linked immunosorbent assay (ELISA), and neuroinflammatory markers in the nucleus tractus solitarii (NTS) by qPCR at the end of 21 days. We also examined endothelium-dependent hyperpolarization (EDH)-type vasorelaxations in isolated mesenteric arteries of the rats ex vivo. RESULTS: SBP, DBP, and HR increased in the fructose group. Both minocycline and TRAM-34 significantly prevented these increases. Fructose intake also increased plasma interleukin-6, interleukin-1β, tumor necrosis factor-α, and insulin levels, whereas pretreatment with TRAM-34 prevented these increases as well. Iba-1, but not cluster of differentiation-86 levels were significantly higher in the NTS samples of fructose-fed hypertensive rats which implied microglial proliferation. EDH-type vasorelaxations mediated by endothelial KCa3.1 attenuated in the fructose group; however, TRAM-34 did not cause further deterioration in the relaxations. CONCLUSIONS: TRAM-34 is as effective as minocycline in preventing fructose-induced hypertension without interfering with EDH-type vasodilation. Furthermore, TRAM-34 relieves high fructose-associated systemic inflammation.