Sarcoendoplasmic Reticulum Ca²⁺ ATPase. A Critical Target in Chlorine Inhalation–Induced Cardiotoxicity

Abstract

Autopsy specimens from human victims or experimental animals that die due to acute chlorine gas exposure present features of cardiovascular pathology. We demonstrate acute chlorine inhalation-induced reduction in heart rate and oxygen saturation in rats. Chlorine inhalation elevated chlorine reactants, such as chlorotyrosine and chloramine, in blood plasma. Using heart tissue and primary cardiomyocytes, we demonstrated that acute highconcentration chlorine exposure in vivo (500 ppm for 30 min) caused decreased total ATP content and loss of sarcoendoplasmic reticulum calcium ATPase (SERCA) activity. Loss of SERCA activity was attributed to chlorination of tyrosine residues and oxidation of an important cysteine residue, cysteine-674, in SERCA, as demonstrated by immunoblots and mass spectrometry. Using cardiomyocytes, we found that chlorine-induced cell death and damage to SERCA could be decreased by thiocyanate, an important biological antioxidant, and by genetic SERCA2 overexpression. We also investigated a U.S. Food and Drug Administration-approved drug, ranolazine, used in treatment of cardiac diseases, and previously shown to stabilize SERCA in animal models of ischemia-reperfusion. Pretreatment with ranolazine or istaroxime, another SERCA activator, prevented chlorine-induced cardiomyocyte death. Further investigation of responsible mechanisms showed that ranolazine-and istaroximetreated cells preserved mitochondrial membrane potential and ATP after chlorine exposure. Thus, these studies demonstrate a novel critical target for chlorine in the heart and identify potentially useful therapies to mitigate toxicity of acute chlorine exposure. Clinical RelevanceThis study defines impact of inhalation of a toxic gas, chlorine, on a critical cardiac calcium pump, sarcoendoplasmic reticulum Ca 21 ATPase (SERCA). It also demonstrates that therapeutic strategies that protect or modify SERCA function could be useful approaches for emergent resuscitation of severe chlorine inhalation victims.Chlorine is a commonly used chemical in industry and society. Acute chlorine inhalation toxicity can occur due to accidents at swimming pools and/or involving water purification systems, after transportation accidents, upon industrial exposure, with misuse of domestic cleaners, during military operations, and, more recently, through chemical terrorism. In the

Phosgene- and chlorine-induced acute lung injury in rats: Comparison of cardiopulmonary function and biomarkers in exhaled breath

“…An involvement of different types of nociceptive reflexes leading to bradycardia and dysregulated hemodynamics was postulated elsewhere . Interestingly, somewhat similar reduction in heart rate were demonstrated after acute chlorine inhalation exposure of rats at 500 ppm for 30 min) which was associated with decreased total ATP content and loss of sarcoendoplasmic reticulum calcium ATPase, SERCA, activity (Ahmad et al, 2014). It is beyond the scope of this paper to reiterate the wealth of information available on mechanistic research of phosgene (Diller, 1985a,b,b;Duniho et al, 2002;IPCS, 1998;Liu et al, 2013;Luo et al, 2013;Pauluhn et al, 2007).…”

Hyaluronan mediates airway hyperresponsiveness in oxidative lung injury

“…HOCl has been shown to fracture H-HA in vitro (26), and HOCl generated by the action of activated neutrophils may contribute to the formation of L-HA in vivo. In addition, other reactive intermediates, such as chlorinated fatty acids (56) and chloramines (1,68) known to be generated in the bronchoalveolar lavage and plasma of Cl 2 -exposed rodents, may contribute to L-HA formation. Our data show clearly that exposure of H-HA to Cl 2 gas fragments HA, leading to the formation of L-HA.…”

Formation of chlorinated lipids post-chlorine gas exposure

“…We also appreciate that there are a myriad of other Cl 2 -dependent products that are likely formed after Cl 2 gas exposure that could be used as biomarkers. While some, such as chloramines, may mediate Cl 2 gas toxicity (18,43), their relatively short lifetimes in vivo preclude them as useful biomarkers. to the periphery to elicit extrapulmonary effects characterized by eNOS inhibition, which leads to the hypothesis that plasma Cl-lipids formed after Cl 2 gas exposure may mediate extrapulmonary toxicities to the vasculature and heart (13,15,16).…”