Acetyl L‐carnitine targets adenosine triphosphate synthase in protecting zebrafish embryos from toxicities induced by verapamil and ketamine: An in vivo assessment

Abstract

Verapamil is a Ca2+ channel blocker and is highly prescribed as an anti-anginal, antiarrhythmic and antihypertensive drug. Ketamine, an antagonist of the Ca2+-permeable N-methyl-D-aspartate-type glutamate receptors, is a pediatric anesthetic. Previously we have shown that acetyl L-carnitine (ALCAR) reverses ketamine-induced attenuation of heart rate and neurotoxicity in zebrafish embryos. Here, we used 48 h post-fertilization zebrafish embryos that were exposed to relevant drugs for 2 or 4 h. Heart beat and overall development were monitored in vivo. In 48 h post-fertilization embryos, 2 mM ketamine reduced heart rate in a 2 or 4 h exposure and 0.5 mM ALCAR neutralized this effect. ALCAR could reverse ketamine’s effect, possibly through a compensatory mechanism involving extracellular Ca2+ entry through L-type Ca2+ channels that ALCAR is known to activate. Hence, we used verapamil to block the L-type Ca2+ channels. Verapamil was more potent in attenuating heart rate and inducing morphological defects in the embryos compared to ketamine at specific times of exposure. ALCAR reversed cardiotoxicity and developmental toxicity in the embryos exposed to verapamil or verapamil plus ketamine, even in the presence of 3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester, an inhibitor of intracellular Ca2+ release suggesting that ALCAR acts via effectors downstream of Ca2+. In fact, ALCAR’s protective effect was blunted by oligomycin A, an inhibitor of adenosine triphosphate synthase that acts downstream of Ca2+ during adenosine triphosphate generation. We have identified, for the first time, using in vivo studies, a downstream effector of ALCAR that is critical in abrogating ketamine- and verapamil-induced developmental toxicities. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Mechanistic studies on ketamine-induced mitochondrial toxicity in zebrafish embryos

“…6). In our previous studies (Guo et al, 2017; Kanungo et al, 2012), we reported that ALCAR ameliorated ketamine-induced adverse effects on heart rate. The current results show in the ketamine-treated embryos, an expanded (sac-like), membranous auricle with no looping of the heart (Fig.…”

“…Ketamine-induced cardiac dysfunction has been reported in human fetus (Saarenmaa et al, 2001), infant non-human primates (Hotchkiss et al, 2007), Xenopus (Guo et al, 2016) and zebrafish (Guo et al, 2017; Kanungo et al, 2012; Robinson et al, 2017). Ketamine can affect the right ventricular function and pulmonary artery pressure since it increases pulmonary vascular resistance (Craven, 2007).…”

“…Data from the current study suggest that ketamine-induced reduction in ATP levels resulted from decreased mitochondrial membrane potential and potentially compromised ATP synthase function. In our previous study, we have shown that ALCAR’s beneficial effects to ameliorate ketamine toxicity in the zebrafish involved functional ATP synthase (Guo et al, 2017). Besides having a major role in ATP production, the mitochondrial ATP synthase also reverses ATP hydrolysis activity and thus helps maintain the mitochondrial membrane potential (Appleby et al, 1999).…”

“…We have previously shown in zebrafish embryos that consistent with its effects on the nervous system and heart function in mammals (Hotchkiss et al, 2007; Irifune et al, 1997; Irifune et al, 1991; Kim et al, 2006; Zausig et al, 2009), ketamine adversely affects the motor neurons (Kanungo et al, 2013), serotonergic and dopamine systems (Robinson et al, 2016; Robinson et al, 2015) as well as heart rate (Kanungo et al, 2012). Additionally, we have shown that ALCAR prevents ketamine’s adverse effects on the heart rate (Guo et al, 2017; Kanungo et al, 2012; Robinson et al, 2016; Robinson et al, 2015). Our studies also suggested that ALCAR could function through modulating ATP synthase (Guo et al, 2017).…”

“…Additionally, we have shown that ALCAR prevents ketamine’s adverse effects on the heart rate (Guo et al, 2017; Kanungo et al, 2012; Robinson et al, 2016; Robinson et al, 2015). Our studies also suggested that ALCAR could function through modulating ATP synthase (Guo et al, 2017). …”