N-n-butyl haloperidol iodide inhibits H₂O₂-induced Na⁺/Ca²⁺-exchanger activation via the Na⁺/H⁺ exchanger in rat ventricular myocytes

Abstract

N-n-butyl haloperidol iodide (F₂), a novel compound, has shown palliative effects in myocardial ischemia/reperfusion (I/R) injury. In this study, we investigated the effects of F₂ on the extracellular signal-regulated kinase kinase (MEK)/extracellular signal-regulated kinase (ERK)/Na⁺/H⁺ exchanger (NHE)/Na⁺/Ca²⁺ exchanger (NCX) signal-transduction pathway involved in H₂O₂-induced Ca²⁺ overload, in order to probe the underlying molecular mechanism by which F₂ antagonizes myocardial I/R injury. Acute exposure of rat cardiac myocytes to 100 μM H₂O₂ increased both NHE and NCX activities, as well as levels of phosphorylated MEK and ERK. The H₂O₂-induced increase in NCX current (I_NCX) was nearly completely inhibited by the MEK inhibitor U0126 (1,4-diamino-2,3-dicyano-1,4-bis[o-aminophenylmercapto] butadiene), but only partly by the NHE inhibitor 5-(N,N-dimethyl)-amiloride (DMA), indicating the I_NCX increase was primarily mediated by the MEK/mitogen-activated protein kinase (MAPK) pathway, and partially through activation of NHE. F₂ attenuated the H₂O₂-induced I_NCX increase in a concentration-dependent manner. To determine whether pathway inhibition was H₂O₂-specific, we examined the ability of F₂ to inhibit MEK/ERK activation by epidermal growth factor (EGF), and NHE activation by angiotensin II. F₂ not only inhibited H₂O₂-induced and EGF-induced MEK/ERK activation, but also completely blocked both H₂O₂-induced and angiotensin II-induced increases in NHE activity, suggesting that F₂ directly inhibits MEK/ERK and NHE activation. These results show that F₂ exerts multiple inhibitions on the signal-transduction pathway involved in H₂O₂-induced I_NCX increase, providing an additional mechanism for F₂ alleviating intracellular Ca²⁺ overload to protect against myocardial I/R injury.

Keywords:

• N-n-butyl haloperidol
• hydrogen peroxide
• Na⁺/Ca²⁺ exchanger
• Na⁺/H⁺ exchanger

Acknowledgments

We are grateful for the support from the Center for Neuroscience, Shantou University Medical College for the utilization of the laser confocal microscopy. This work was supported by National Natural Science Foundation of China–Guangdong Joint Funds (U0932005), the National Natural Science Foundation of China (81173048 and 81072633), central government special funds supporting the development of local colleges and universities.

Disclosure

The authors report no conflicts of interest in this work.