H2S inhibits angiotensin II-induced atrial Kv1.5 upregulation by attenuating Nox4-mediated ROS generation during atrial fibrillation

Abstract

Our previous study demonstrated that angiotensin II (Ang II) upregulates the expression of Kv1.5, a promising target for atrial fibrillation (AF) therapy, by activating ROS-dependent P-Smad2/3 and P-ERK 1/2. A recent study showed that hydrogen sulfide (H₂S) may modulate the effects of angiotensin II (Ang II) by inhibiting the NADPH oxidase 4 (Nox4)-ROS signaling in the heart. The present study aimed to determine whether H₂S is involved in the regulation of atrial Kv1.5 via ROS-related mechanisms in AF. Cultured neonatal rat atrial myocytes and a beagle model of AF were used for this study. In the neonatal rat atrial myocytes, quantitative PCR and enzyme immunoassays revealed that the mRNA expression levels of angiotensinogen, angiotensin-converting enzyme, and Ang II type I receptor (AT₁R) and the Ang II supernatant concentration were significantly increased by hydrogen peroxide (H₂O₂) incubation, and these H₂O₂-induced alterations were reversed by diphenyleneiodonium, apocynin and H₂S supplementation. Flow cytometry and Western blotting revealed that blockade of H₂S biosynthesis using dl-propargylglycine increased ROS production and the expression of Ang II and Kv1.5. Sodium hydrosulfide (an exogenous H₂S donor) and Nox4 siRNA inhibited Ang II-induced ROS production and Ang II-induced expression of Kv1.5, P-Smad2/3, P-ERK 1/2. Sodium hydrosulfide suppressed the Ang II-induced upregulation of Nox4. In our beagle AF model, 24 h of rapid atrial pacing (RAP) increased the atrial Ang II concentration, ROS production and the protein expression of Nox4, Kv1.5, P-Smad2/3 and P-ERK 1/2. These RAP-induced changes were inhibited by H₂S supplementation and losartan (an AT₁R blocker) pretreatment. In conclusion, our study indicates that H₂S downregulates Ang II-induced atrial Kv1.5 expression by attenuating Nox4-related ROS-triggered P-Smad2/3 and P-ERK 1/2 activation during AF. H₂S supplementation would be beneficial for AF treatment via the suppression of atrial Kv1.5 expression.

Keywords: Angiotensin II; Atrial fibrillation; Hydrogen sulfide; Kv1.5; Reactive oxygen species.