Contribution of Zinc-Dependent Delayed Calcium Influx via TRPC5 in Oxidative Neuronal Death and its Prevention by Novel TRPC Antagonist

Sang Eun Park,Insuk So,Bumwoo Park,Hye Min Lim,Chansik Hong,Jung Jin Hwang,Antonio Riccio,Jae-Young Koh,In-Jeoung Baek,Dong Eun Kim,Dong-Jun Bae,Mi-Ha Park,Sang-Yeob Kim,Ji Hoon Song,Tae-Youn Kim,Bo-Ra Seo,Joo-Yong Lee,Woo Hyun Shim,Jee-Won Sul

doi:10.1007/s12035-018-1258-7

Abstract

Oxidative stress is a key mediator of neuronal death in acute brain injuries, such as epilepsy, trauma, and stroke. Although it is accompanied by diverse cellular changes, increases in levels of intracellular zinc ion (Zn2+) and calcium ion (Ca2+) may play a critical causative role in oxidative neuronal death. However, the mechanistic link between Zn2+ and Ca2+ dyshomeostasis in neurons during oxidative stress is not well-understood. Here, we show that the exposure of cortical neurons to H2O2 led to a zinc-triggered calcium influx, which resulted in neuronal death. The cyclin-dependent kinase inhibitor, NU6027, inhibited H2O2-induced Ca2+ increases and subsequent cell death in cortical neurons, without affecting the early increase in Zn2+. Therefore, we attempted to identify the zinc-regulated Ca2+ pathway that was inhibited by NU6027. The expression profile in cortical neurons identified transient receptor potential cation channel 5 (TRPC5) as a candidate that is known to involve in the generation of epileptiform burst firing and epileptic neuronal death (Phelan KD et al. 2012a; Phelan KD et al. 2013b). NU6027 inhibited basal and zinc-augmented TRPC5 currents in TRPC5-overexpressing HEK293 cells. Consistently, cortical neurons from TRPC5 knockout mice were highly resistant to H2O2-induced death. Moreover, NU6027 is neuroprotective in kainate-treated epileptic rats. Our results demonstrate that TRPC5 is a novel therapeutic target against oxidative neuronal injury in prolonged seizures and that NU6027 is a potent inhibitor of TRPC5.

Highlights

Reactive oxygen species (ROS) play important pathological roles in numerous neurological disorders, such as seizure, ischemic stroke, and brain and spinal cord trauma [1,2,3]
While searching for neuroprotective drugs effective against oxidative stress-induced cell death, we found that the Cyclin-Dependent Kinase (CDK) inhibitor NU6027 (Fig. 1a) markedly reduced H2O2-induced release of Lactate dehydrogenase (LDH), a quantitative biochemical marker for neuronal death, in primary mixed cortical cultures containing
The main findings of this study are that neuronal death induced by oxidative stress, such as H2O2, is mediated by early transient increases in Zn2+ and delayed prolonged increases in Ca2+ and that these events are mechanistically linked

Summary

Introduction

Reactive oxygen species (ROS) play important pathological roles in numerous neurological disorders, such as seizure, ischemic stroke, and brain and spinal cord trauma [1,2,3]. The overactivation of glutamate receptors induces increases in [Ca2+]i during neuronal death, TRP channels may mediate oxidative stressinduced increases in [Ca2+]i in case of brain injuries [6]. TRP channels are further grouped into seven subfamilies: TRPC, TRPM, TRPV, TRPA, TRPP, TRPML, and TRPN. These TRP channels have been implicated in many physiological events, including development and neuroplasticity [8]. TRP channels play important roles in neuronal death, such as capsaicintriggered TRPV1 activation in mesencephalic dopaminergic neuronal death [9], amyloid β- and H2O2-induced TRPM2 activation in striatal cell death [10], and ROS-mediated TRPM7 activation in ischemic neuronal injury [11]. The role of TRPCs in neuronal death has not drawn much attention

Methods

Results

Conclusion