Na⁺/K⁺-ATPase Alpha 2 Isoform Elicits Rac1-Dependent Oxidative Stress and TLR4-Induced Inflammation in the Hypothalamic Paraventricular Nucleus in High Salt-Induced Hypertension

Numerous studies have indicated that a high salt diet inhibits brain Na+/K+-ATPase (NKA) activity, and affects oxidative stress and inflammation in the paraventricular nucleus (PVN). Furthermore, Na+/K+-ATPase alpha 2-isoform (NKA alpha 2) may be a target in the brain, taking part in the development of salt-dependent hypertension. Therefore, we hypothesized that NKA alpha 2 regulates oxidative stress and inflammation in the PVN in the context of salt-induced hypertension. Part I: We assessed NKA subunits (NKA alpha 1, NKA alpha 2, and NKA alpha 3), Na+/K+-ATPase activity, oxidative stress, and inflammation in a high salt group (8% NaCl) and normal salt group (0.3% NaCl). Part II: NKA alpha 2 short hairpin RNA (shRNA) was bilaterally microinjected into the PVN of salt-induced hypertensive rats to knockdown NKA alpha 2, and we explored whether NKA alpha 2 regulates downstream signaling pathways related to protein kinase C gamma (PKC gamma)-dependent oxidative stress and toll-like receptor 4 (TLR4)-induced inflammation in the PVN to promote the development of hypertension. High salt diet increased NKA alpha 1 and NKA alpha 2 protein expression in the PVN but had no effect on NKA alpha 3 compared to the normal salt diet. Na+/K+-ATPase activity and ADP/ATP ratio was lower, but NAD(P)H activity and NF-kappa B activity in the PVN were higher after a high salt diet. Bilateral PVN microinjection of NKA alpha 2 shRNA not only improved Na+/K+-ATPase activity and ADP/ATP ratio but also suppressed PKC gamma-dependent oxidative stress and TLR4-dependent inflammation in the PVN, thus decreasing sympathetic activity in rats with salt-induced hypertension. NKA alpha 2 in the PVN elicits PKC gamma/Rac1/NAD (P)H-dependent oxidative stress and TLR4/MyD88/NF-kappa B-induced inflammation in the PVN, thus increasing MAP and sympathetic activity during the development of salt-induced hypertension.