TRPA1 channel contributes to myocardial ischemia-reperfusion injury

Cardiolipin in myocardial ischaemia-reperfusion injury: From molecular mechanisms to clinical strategies

Myocardial reperfusion injury occurs when blood flow is restored after ischemia, an essential process to salvage ischemic tissue. However, this phenomenon is intricate, characterized by various harmful effects. Tissue damage in ischemia-reperfusion injury arises from various factors, including the production of reactive oxygen species, the sequestration of proinflammatory immune cells in ischemic tissues, the induction of endoplasmic reticulum stress, and the occurrence of postischemic capillary no-reflow. Secretory phospholipase A2 (sPLA2) plays a crucial role in the eicosanoid pathway by releasing free arachidonic acid from membrane phospholipids' sn-2 position. This liberated arachidonic acid serves as a substrate for various eicosanoid biosynthetic enzymes, including cyclooxygenases, lipoxygenases, and cytochromes P450, ultimately resulting in inflammation and an elevated risk of reperfusion injury. Therefore, the activation of sPLA2 directly correlates with the heightened and accelerated damage observed in myocardial ischemia-reperfusion injury (MIRI). Presently, clinical trials are in progress for medications aimed at sPLA2, presenting promising avenues for intervention. Cardiolipin (CL) plays a crucial role in maintaining mitochondrial function, and its alteration is closely linked to mitochondrial dysfunction observed in MIRI. This paper provides a critical analysis of CL modifications concerning mitochondrial dysfunction in MIRI, along with its associated molecular mechanisms. Additionally, it delves into various pharmacological approaches to prevent or alleviate MIRI, whether by directly targeting mitochondrial CL or through indirect means.

TRPA1 as a promising target in ischemia/reperfusion: A comprehensive review

Ischemic disorders, including myocardial infarction, cerebral ischemia, and peripheral vascular impairment, are the main common reasons for debilitating diseases and death in Western cultures. Ischemia occurs when blood circulation is reduced in tissues. Reperfusion, although commanded to return oxygen to ischemic tissues, generates paradoxical tissue responses. The responses include generating reactive oxygen species (ROS), stimulating inflammatory responses in ischemic organs, endoplasmic reticulum stress, and the expansion of postischemic capillary no-reflow, which intensifies organ damage. Multiple pathologic processes contribute to ischemia/reperfusion; therefore, targeting different pathologic processes may yield an effective therapeutic approach. Transient Receptor Potential A1 (TRPA1) belongs to the TRP family of ion channels, detects a broad range of chemicals, and promotes the transduction of noxious stimuli, e.g., methylglyoxal, ROS, and acrolein effects are attributed to the channel's sensitivity to intracellular calcium elevation or phosphoinositol phosphate modulation. Hypoxia and ischemia are associated with oxidative stress, which activates the TRPA1 channel. This review describes the role of TRPA1 and its related mechanisms that contribute to ischemia/reperfusion. Relevant articles were searched from PubMed, Scopus, Web of Sciences, and Google Scholar electronic databases, up to the end of August 2023. Based on the evidence presented here, TRPA1 may have protective or deteriorative functions during the ischemia/reperfusion process. Its function depends on the activation level, the ischemic region, the extent of lesions, and the duration of ischemia.

Research Progress on TRPA1 in Diseases

For a long time, the physiological activity of TRP ion channels and the response to various stimuli have been the focus of attention, and the physiological functions mediated by ion channels have subtle links with the occurrence of various diseases. Our group has been engaged in the study of ion channels. In recent years, the report rate of TRPA1, the only member of the TRPA subfamily in the newly described TRP channel, has been very high. TRPA1 channels are not only abundantly expressed in peptidergic nociceptors but are also found in many nonneuronal cell types and tissues, and through the regulation of Ca2+ influx, various neuropeptides and signaling pathways are involved in the regulation of nerves, respiration, circulation, and various diseases and inflammation throughout the body. In this review, we mainly summarize the effects of TRPA1 on various systems in the body, which not only allows us to have a more systematic and comprehensive understanding of TRPA1 but also facilitates more in-depth research on it in the future.

The Dysfunction of Ca2+ Channels in Hereditary and Chronic Human Heart Diseases and Experimental Animal Models

Chronic heart diseases, such as coronary heart disease, heart failure, secondary arterial hypertension, and dilated and hypertrophic cardiomyopathies, are widespread and have a fairly high incidence of mortality and disability. Most of these diseases are characterized by cardiac arrhythmias, conduction, and contractility disorders. Additionally, interruption of the electrical activity of the heart, the appearance of extensive ectopic foci, and heart failure are all symptoms of a number of severe hereditary diseases. The molecular mechanisms leading to the development of heart diseases are associated with impaired permeability and excitability of cell membranes and are mainly caused by the dysfunction of cardiac Ca2+ channels. Over the past 50 years, more than 100 varieties of ion channels have been found in the cardiovascular cells. The relationship between the activity of these channels and cardiac pathology, as well as the general cellular biological function, has been intensively studied on several cell types and experimental animal models in vivo and in situ. In this review, I discuss the origin of genetic Ca2+ channelopathies of L- and T-type voltage-gated calcium channels in humans and the role of the non-genetic dysfunctions of Ca2+ channels of various types: L-, R-, and T-type voltage-gated calcium channels, RyR2, including Ca2+ permeable nonselective cation hyperpolarization-activated cyclic nucleotide-gated (HCN), and transient receptor potential (TRP) channels, in the development of cardiac pathology in humans, as well as various aspects of promising experimental studies of the dysfunctions of these channels performed on animal models or in vitro.

Activation of TRPA1 in Bladder Suburothelial Myofibroblasts Counteracts TGF-β1-Induced Fibrotic Changes

The activation of the transient receptor potential ankyrin 1 (TRPA1) channel has anti-fibrotic effects in the lung and intestine. Suburothelial myofibroblasts (subu-MyoFBs), a specialized subset of fibroblasts in the bladder, are known to express TRPA1. However, the role of the TRPA1 in the development of bladder fibrosis remains elusive. In this study, we use the transforming growth factor-β1 (TGF-β1) to induce fibrotic changes in subu-MyoFBs and assess the consequences of TRPA1 activation utilizing RT-qPCR, western blotting, and immunocytochemistry. TGF-β1 stimulation increased α-SMA, collagen type I alpha 1 chain(col1A1), collagen type III (col III), and fibronectin expression, while simultaneously suppressing TRPA1 in cultured human subu-MyoFBs. The activation of TRPA1, with its specific agonist allylisothiocyanate (AITC), inhibited TGF-β1-induced fibrotic changes, and part of these inhibition effects could be reversed by the TRPA1 antagonist, HC030031, or by reducing TRPA1 expression via RNA interference. Furthermore, AITC reduced spinal cord injury-induced fibrotic bladder changes in a rat model. The increased expression of TGF-β1, α-SMA, col1A1 and col III, and fibronectin, and the downregulation of TRPA1, were also detected in the mucosa of fibrotic human bladders. These findings suggest that TRPA1 plays a pivotal role in bladder fibrosis, and the negative cross talk between TRPA1 and TGF-β1 signaling may represent one of the mechanisms underlying fibrotic bladder lesions.

New Drug Targets and Preclinical Modelling Recommendations for Treating Acute Myocardial Infarction

Acute myocardial infarction (AMI) is the leading cause of morbidity and mortality worldwide and the primary underlying risk factor for heart failure. Despite decades of research and clinical trials, there are no drugs currently available to prevent organ damage from acute ischaemic injuries of the heart. In order to address the increasing global burden of heart failure, drug, gene, and cell-based regeneration technologies are advancing into clinical testing. In this review we highlight the burden of disease associated with AMI and the therapeutic landscape based on market analyses. New studies revealing the role of acid-sensitive cardiac ion channels and other proton-gated ion channels in cardiac ischaemia are providing renewed interest in pre- and post-conditioning agents with novel mechanisms of action that may also have implications for gene- and cell-based therapeutics. Furthermore, we present guidelines that couple new cell technologies and data resources with traditional animal modelling pipelines to help de-risk drug candidates aimed at treating AMI. We propose that improved preclinical pipelines and increased investment in drug target identification for AMI is critical to stem the increasing global health burden of heart failure.

TRPA1 as Target in Myocardial Infarction

Transient receptor potential cation channel subfamily A member 1 (TRPA1), an ion channel primarily expressed on sensory neurons, can be activated by substances occurring during myocardial infarction. Aims were to investigate whether activation, inhibition, or absence of TRPA1 affects infarcts and to explore underlying mechanisms. In the context of myocardial infarction, rats received a TRPA1 agonist, an antagonist, or vehicle at different time points, and infarct size was assessed. Wild type and TRPA1 knockout mice were also compared in this regard. In vitro, sensory neurons were co-cultured with cardiomyocytes and subjected to a model of ischemia-reperfusion. Although there was a difference between TRPA1 activation or inhibition in vivo, no experimental group was different to control animals in infarct size, which also applies to animals lacking TRPA1. In vitro, survival probability of cardiomyocytes challenged by ischemia-reperfusion increased from 32.8% in absence to 45.1% in presence of sensory neurons, which depends, at least partly, on TRPA1. This study raises doubts about whether TRPA1 is a promising target to reduce myocardial damage within a 24 h period. The results are incompatible with relevant enlargements of infarcts by TRPA1 activation or inhibition, which argues against adverse effects when TRPA1 is targeted for other indications.

Differential immunostaining patterns of transient receptor potential (TRP) ion channels in the rat nodose ganglion

Vagal afferents regulate numerous physiological functions including arterial blood pressure, heart rate, breathing, and nociception. Cell bodies of vagal afferents reside in the inferior vagal (nodose) ganglia and their stimulation by various means is being considered as a way to regulate cardiorespiratory responses and control pain sensations. Stimulation of the nodose by exposure to infrared light is recently being considered as a precise way to elicit responses. These responses would likely involve the activity of temperature-sensitive membrane-bound channels. While papers have been published to track the expression of these transient receptor potential ion channels (TRPs), further studies are warranted to determine the in situ expression of the endogenous TRP proteins in the nodose ganglia to fully understand their pattern of expression, subcellular locations, and functions in this animal model. TRP ion channels are a superfamily of Na⁺ /Ca²⁺ -channels whose members are temperature- and/or mechano-sensitive and therefore represent a potential set of proteins that will be activated directly or indirectly by infrared light. Here, we report the spatial localization of six TRP channels, TRPV1, TRPV4, TRPM3, TRPM8, TRPA1, and TRPC1, from nodose ganglia taken from juvenile male Sprague-Dawley rats. The channels were detected using immunohistology with fluorescent tags on cryosections and imaged using confocal microscopy. All six TRP channels were detected with different levels of intensity in neuronal cell bodies and some were also detected in axonal fibers and blood vessels. The TRP receptors differed in their prevalence, in their patterns of expression, and in subcellular expression/localization. More specifically, TRPV1, TRPV4, TRPA1, TRPM8, TRPC1, and TRPM3 were found in vagal afferent cell bodies with a wide range of immunostaining intensity from neuron to neuron. Immunostaining for TRPV1, TRPV4, and TRPA1 appeared as fine particles scattered throughout the cytoplasm of the cell body. Intense TRPV1 immunostaining was also evident in a subset of axonal fibers. TRPM8 and TRPC1 were expressed in courser particles suggesting different subcellular compartments than for TRPV1. The localization of TRPM3 differed markedly from the other TRP channels with an immunostaining pattern that was localized to the periphery of a subset of cell bodies, whereas a scattering or no immunostaining was detected within the bulk of the cytoplasm. TRPV4 and TRPC1 were also expressed on the walls of blood vessels. The finding that all six TRP channels (representing four subfamilies) were present in the nodose ganglia provides the basis for studies designed to understand the roles of these channels in sensory transmission within vagal afferent fibers and in the responses elicited by exposure of nodose ganglia to infrared light and other stimuli. Depending on the location and functionality of the TRP channels, they may regulate the flux of Na⁺ /Ca²⁺ -across the membranes of cell bodies and axons of sensory afferents, efferent (motor) fibers coursing through the ganglia, and in vascular smooth muscle.

Reactive Oxygen Species Cause Exercise-Induced Angina in a Myocardial Ischaemia-Reperfusion Injury Model

Percutaneous coronary intervention (PCI) effectively treats obstructive coronary artery syndrome. However, 30–40% patients continue to have angina after a successful PCI, thereby reducing patient satisfaction. The mechanisms underlying persistent angina after revascularisation therapy are still poorly understood; hence, the treatment or guideline for post-PCI angina remains unestablished. Thus, this study aimed to investigate the mechanisms underlying effort angina in animals following myocardial ischaemia-reperfusion (I/R) injury. Phosphorylated extracellular signal-regulated kinase (p-ERK), a marker for painful stimulation-induced neuronal activation, was used for the investigation. After a forced treadmill exercise (FTE), the number of p-ERK-expressing neurons increased in the superficial dorsal horn of the I/R model animals. Moreover, FTE evoked hydrogen peroxide (H₂O₂) production in the I/R-injured heart, inducing angina through TRPA1 activation on cardiac sensory fibres. Notably, the treatment of a TEMPOL, a reactive oxygen species scavenger, or TRPA1^−/− mice successfully alleviated the FTE-induced p-ERK expression in the dorsal horn. The production of H₂O₂, a reactive oxygen species, through physical exercise contributes to angina development following I/R. Hence, our findings may be useful for understanding and treating angina following revascularisation therapy.

Energy-sparing by 2-methyl-2-thiazoline protects heart from ischaemia/reperfusion injury

AIMS

Cardiac ischaemia/reperfusion (I/R) injury remains a critical issue in the therapeutic management of ischaemic heart failure. Although mild hypothermia has a protective effect on cardiac I/R injury, more rapid and safe methods that can obtain similar results to hypothermia therapy are required. 2-Methyl-2-thiazoline (2MT), an innate fear inducer, causes mild hypothermia resulting in resistance to critical hypoxia in cutaneous or cerebral I/R injury. The aim of this study is to demonstrate the protective effect of systemically administered 2MT on cardiac I/R injury and to elucidate the mechanism underlying this effect.

METHODS AND RESULTS

A single subcutaneous injection of 2MT (50 mg/kg) was given prior to reperfusion of the I/R injured 10 week-old male mouse heart and its efficacy was evaluated 24 h after the ligation of the left anterior descending coronary artery. 2MT preserved left ventricular systolic function following I/R injury (ejection fraction, %: control 37.9 ± 6.7, 2MT 54.1 ± 6.4, P < 0.01). 2MT also decreased infarct size (infarct size/ischaemic area at risk, %: control 48.3 ± 12.1, 2MT 25.6 ± 4.2, P < 0.05) and serum cardiac troponin levels (ng/mL: control 8.9 ± 1.1, 2MT 1.9 ± 0.1, P < 0.01) after I/R. Moreover, 2MT reduced the oxidative stress-exposed area within the heart (%: control 25.3 ± 4.7, 2MT 10.8 ± 1.4, P < 0.01). These results were supported by microarray analysis of the mouse hearts. 2MT induced a transient, mild decrease in core body temperature (°C: -2.4 ± 1.4), which gradually recovered over several hours. Metabolome analysis of the mouse hearts suggested that 2MT minimized energy metabolism towards suppressing oxidative stress. Furthermore, 18F-fluorodeoxyglucose-positron emission tomography/computed tomography imaging revealed that 2MT reduced the activity of brown adipose tissue (standardized uptake value: control 24.3 ± 6.4, 2MT 18.4 ± 5.8, P < 0.05). 2MT also inhibited mitochondrial respiration and glycolysis in rat cardiomyoblasts.

CONCLUSIONS

We identified the cardioprotective effect of systemically administered 2MT on cardiac I/R injury by sparing energy metabolism with reversible hypothermia. Our results highlight the potential of drug-induced hypothermia therapy as an adjunct to coronary intervention in severe ischaemic heart disease.

Guidelines for in vivo mouse models of myocardial infarction

Despite significant improvements in reperfusion strategies, acute coronary syndromes all too often culminate in a myocardial infarction (MI). The consequent MI can, in turn, lead to remodeling of the left ventricle (LV), the development of LV dysfunction, and ultimately progression to heart failure (HF). Accordingly, an improved understanding of the underlying mechanisms of MI remodeling and progression to HF is necessary. One common approach to examine MI pathology is with murine models that recapitulate components of the clinical context of acute coronary syndrome and subsequent MI. We evaluated the different approaches used to produce MI in mouse models and identified opportunities to consolidate methods, recognizing that reperfused and nonreperfused MI yield different responses. The overall goal in compiling this consensus statement is to unify best practices regarding mouse MI models to improve interpretation and allow comparative examination across studies and laboratories. These guidelines will help to establish rigor and reproducibility and provide increased potential for clinical translation.

The effects of iloprost and beta3 receptor agonist on TRPA1 and TRPC1 immunreactivity in an experimental lower extremty ischemia-reperfusion injury model

BACKGROUND

In this study, we aimed to investigate the effects of antioxidant iloprost (ILO) and ß3 adrenergic receptor agonist (BRL) on transient receptor potential ankyrin 1 (TRPA1) and transient receptor potential canonical 1 (TRPC1) ion channels on an experimental ischemia and reperfusion injury model in 30 male Wistar albino rats aged 8-10 weeks.

METHODS

Wistar Albino rats aged were divided into 5 equal groups. Group I Sham operation, Group II IR (ischemiareperfusion) procedure, Group III IR + intravenous ILO administration, Group IV IR + intraperitoneal BRL administration, and Group V IR + intravenous ILO + intraperitoneal BRL administration group. Two ng/kg/min ILO intravenous infusion was applied to the ILO group. A single dose of 5 mcg/kg BRL intraperitoneal was applied to BRL group. TOS (total oxidant status), TRPA1, and TRPC1 levels were measured with ELISA (enzyme linked immunosorbent assay) in serum, immunohistochemical staining in musculus quadriceps femoris tissue.

RESULTS

Compared with the sham group, the IR group had a statistically significant increase in serum levels of TOS (p = 0.004), TRPA1 (p = 0.002), and TRPC1 (p = 0.008) along with TRPA1- and TRPC1-immunoreactivity (p = 0.005, each) in the tissue. When compared with the IR group in terms of serum levels of TRPA1 and tissue TRPA1-immunoreactivity, although there was no statistically significant difference in the IR+Ilo (p = 0.257 and p = 0.429, respectively), IR+Brl (p = 0.024 and p = 0.177, respectively), and IR+Ilo+Brl (p = 0.024 and p = 0.329, respectively) groups, serum levels of TOS and TRPC1 along with tissue TRPC1-immunoreactivity were statistically significantly reduced in the IR+Ilo (p = 0.002, p = 0.008, and p = 0.004, respectively), IR+Brl (p = 0.004, p = 0.008, and p = 0.004, respectively), and IR+Ilo+Brl groups (p = 0.002, p = 0.008, and p = 0.004, respectively).

DISCUSSION

In IR group serum TOS, TRPA1 and TRPC1 levels ,and tissue TRPA1 and TRPC1 immunoreactivity were statistically significant increase when compared to the sham group. In IR+ILO, IR+BRL and IR+ILO+BRL groups serum TRPA1 and tissue TRPA1 immunoreactivity did not change when compared to IR group. Serum TOS and TRPC1 levels, tissue TRPC1 immunoreactivty were statistically significant decreased when compared to IR group. More detailed and expanded population studies are needed to discuss our results.

TRP Channels as Sensors of Aldehyde and Oxidative Stress

The transient receptor potential (TRP) cation channel superfamily comprises more than 50 channels that play crucial roles in physiological processes. TRP channels are responsive to several exogenous and endogenous biomolecules, with aldehydes emerging as a TRP channel trigger contributing to a cellular cascade that can lead to disease pathophysiology. The body is not only exposed to exogenous aldehydes via tobacco products or alcoholic beverages, but also to endogenous aldehydes triggered by lipid peroxidation. In response to lipid peroxidation from inflammation or organ injury, polyunsaturated fatty acids undergo lipid peroxidation to aldehydes, such as 4-hydroxynonenal. Reactive aldehydes activate TRP channels via aldehyde-induced protein adducts, leading to the release of pro-inflammatory mediators driving the pathophysiology caused by cellular injury, including inflammatory pain and organ reperfusion injury. Recent studies have outlined how aldehyde dehydrogenase 2 protects against aldehyde toxicity through the clearance of toxic aldehydes, indicating that targeting the endogenous aldehyde metabolism may represent a novel treatment strategy. An addition approach can involve targeting specific TRP channel regions to limit the triggering of a cellular cascade induced by aldehydes. In this review, we provide a comprehensive summary of aldehydes, TRP channels, and their interactions, as well as their role in pathological conditions and the different therapeutical treatment options.

Acrolein but not its metabolite, 3-Hydroxypropylmercapturic acid (3HPMA), activates vascular transient receptor potential Ankyrin-1 (TRPA1): Physiological to toxicological implications

Acrolein, an electrophilic α,β-unsaturated aldehyde, is present in foods and beverages, and is a product of incomplete combustion, and thus, reaches high ppm levels in tobacco smoke and structural fires. Exposure to acrolein is linked with cardiopulmonary toxicity and cardiovascular disease risk. The hypothesis of this study is the direct effects of acrolein in isolated murine blood vessels (aorta and superior mesenteric artery, SMA) are transient receptor potential ankyrin-1 (TRPA1) dependent. Using isometric myography, isolated aorta and SMA were exposed to increasing levels of acrolein. Acrolein inhibited phenylephrine (PE)-induced contractions (approximately 90%) in aorta and SMA of male and female mice in a concentration-dependent (0.01-100 μM) manner. The major metabolite of acrolein, 3-hydroxypropylmercapturic acid (3HPMA), also relaxed PE-precontracted SMA. As the SMA was 20× more sensitive to acrolein than aorta (SMA EC50 0.8 ± 0.2 μM; aorta EC50 > 29.4 ± 4.4 μM), the mechanisms of acrolein-induced relaxation were studied in SMA. The potency of acrolein-induced relaxation was inhibited significantly by: 1) mechanically-impaired endothelium; 2) Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME); 3) guanylyl cyclase (GC) inhibitor (ODQ); and, 4) a TRPA1 antagonist (A967079). TRPA1 positive immunofluorescence was present in the endothelium. Compared with other known TRPA1 agonists, including allyl isothiocyanate (AITC), cinnamaldehyde, crotonaldehyde, and formaldehyde, acrolein stimulated a more potent TRPA1-dependent relaxation. Acrolein, at high concentration [100 μM], induced tension oscillations (spasms) independent of TRPA1 in precontracted SMA but not in aorta. In conclusion, acrolein is vasorelaxant at low levels (physiological) yet vasotoxic at high levels (toxicological).

Proline hydroxylase domain-containing enzymes regulate calcium levels in cardiomyocytes by TRPA1 ion channel

The proline hydroxylase domain-containing enzymes (PHDs) acts as cellular oxygen sensors, inducing a series of responses to hypoxia, especially during the regulation of metabolism and energy homeostasis. The increase of Ca²⁺ in cardiomyocytes, induced by the opening of PHD signaling pathway, is the key initiation signal necessary for the PHD-mediated regulation of the energy metabolism pathway, but the underlying molecular mechanism remains incompletely understood. This study used PHD inhibitors (PHIs) and PHD2-specific RNA interference (PHD2shRNA) to inhibit PHD signals in cardiomyocytes to explore whether transient receptor potential ankyrin 1 (TRPA1) is involved in the regulation of calcium ion influx in the PHD activation pathway associated with to AMP-activated protein kinase (AMPK). The Fluo-3AM probe was used to measure changes in free intracellular calcium ion concentrations, and western blot analysis was used to detect the levels of phosphorylated (P)-AMPK, TRPA1, and P-Ca²⁺/calmodulin-dependent protein kinase Ⅱ (CaMKⅡ) levels. The PHI-mediated inhibition of PHD resulted in an increase in free Ca²⁺ fluorescence in cardiomyocytes, which activated AMPK, TRPA1, and CaMKⅡ. The TRPA1 inhibitor HC030031, the CaMKII inhibitor KN93, and a ryanodine inhibitor (Ryanodine) were all able to inhibit the PHI-induced increase in intracellular Ca²⁺ and AMPK activation. Both PHIs and PHD2shRNA were able to effectively activate CaMKII and TRPA1. However, an inositol 1,4,5-triphosphate receptor (IP3R) inhibitor and the protein kinase A (PKA) inhibitor H89 did not significantly inhibit the PHI-induced increase in intracellular Ca²⁺ and AMPK activation. These results indicated that PHD might activate the CaMKⅡ pathway through the TRPA1 ion channel, inducing the release of calcium from the sarcoplasmic reticulum through ryanodine receptor 2 (RyR2), activating AMPK to initiate the protective effects of hypoxia in cardiomyocytes.

No functional TRPA1 in cardiomyocytes

AIM

There is mounting evidence that TRPA1 has a role in cardiac physiology and pathophysiology. We aim to clarify the site of TRPA1 expression in the heart and in particular whether the channel is expressed in cardiomyocytes.

METHODS

Due to the high calcium conductance of TRPA1, and marginal calcium changes being detectable, microfluorimetry in primary mouse cardiomyocytes, and in the cardiomyocyte cell lines H9c2 and HL-1, was applied. TRPA1 mRNA in mouse and human hearts, primary cardiomyocytes, and the cardiac cell lines were quantified. Dorsal root ganglia served as control for both methods.

RESULTS

In addition to AITC, the more potent and specific TRPA1 agonists JT010 and PF-4840154 failed to elicit a TRPA1-mediated response in native and electrically paced primary cardiomyocytes, and the cardiomyocyte cell lines H9c2 and HL-1. There were only marginal levels of TRPA1 mRNA in cardiomyocytes and cardiac cell lines, also in conditions of cell differentiation or inflammation, which might occur in pathophysiological conditions. Similarly, TRPV1 agonist capsaicin did not activate primary mouse cardiomyocytes, did not alter electrically paced activity in these, and did not activate H9c2 cells or alter spontaneous activity of HL-1 cells. Human pluripotent stem cells differentiated to cardiomyocytes had no relevant TRPA1 mRNA levels. Also in human post-mortem heart samples, TRPA1 mRNA levels were substantially lower compared with the respective dorsal root ganglion.

CONCLUSION

The results do not question a role of TRPA1 in the heart but exclude a direct effect in cardiomyocytes.

Therapeutic Inhibition of Acid Sensing Ion Channel 1a Recovers Heart Function After Ischemia-Reperfusion Injury

Background: Ischemia-reperfusion injury (IRI) is one of the major risk factors implicated in morbidity and mortality associated with cardiovascular disease. During cardiac ischemia, the build-up of acidic metabolites results in decreased intracellular and extracellular pH that can reach as low as 6.0-6.5. The resulting tissue acidosis exacerbates ischemic injury and significantly impacts cardiac function. Methods: We used genetic and pharmacological methods to investigate the role of acid sensing ion channel 1a (ASIC1a) in cardiac IRI at the cellular and whole organ level. Human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) as well as ex vivo and in vivo models of IRI were used to test the efficacy of ASIC1a inhibitors as pre- and post-conditioning therapeutic agents. Results: Analysis of human complex trait genetics indicate that variants in the ASIC1 genetic locus are significantly associated with cardiac and cerebrovascular ischemic injuries. Using hiPSC-CMs in vitro and murine ex vivo heart models, we demonstrate that genetic ablation of ASIC1a improves cardiomyocyte viability after acute IRI. Therapeutic blockade of ASIC1a using specific and potent pharmacological inhibitors recapitulates this cardioprotective effect. We used an in vivo model of myocardial infarction (MI) and two models of ex vivo donor heart procurement and storage as clinical models to show that ASIC1a inhibition improves post-IRI cardiac viability. Use of ASIC1a inhibitors as pre- or post-conditioning agents provided equivalent cardioprotection to benchmark drugs, including the sodium-hydrogen exchange inhibitor zoniporide. At the cellular and whole organ level, we show that acute exposure to ASIC1a inhibitors has no impact on cardiac ion channels regulating baseline electromechanical coupling and physiological performance. Conclusions: Collectively, our data provide compelling evidence for a novel pharmacological strategy involving ASIC1a blockade as a cardioprotective therapy to improve the viability of hearts subjected to IRI.

Acrolein scavenger dimercaprol offers neuroprotection in an animal model of Parkinson's disease: implication of acrolein and TRPA1

BACKGROUND

The mechanisms underlying lesions of dopaminergic (DA) neurons, an essential pathology of Parkinson's disease (PD), are largely unknown, although oxidative stress is recognized as a key factor. We have previously shown that the pro-oxidative aldehyde acrolein is a critical factor in PD pathology, and that acrolein scavenger hydralazine can reduce the elevated acrolein, mitigate DA neuron death, and alleviate motor deficits in a 6-hydroxydopamine (6-OHDA) rat model. As such, we hypothesize that a structurally distinct acrolein scavenger, dimercaprol (DP), can also offer neuroprotection and behavioral benefits.

METHODS

DP was used to lower the elevated levels of acrolein in the basal ganglia of 6-OHDA rats. The acrolein levels and related pathologies were measured by immunohistochemistry. Locomotor and behavioral effects of 6-OHDA injections and DP treatment were examined using the open field test and rotarod test. Pain was assessed using mechanical allodynia, cold hypersensitivity, and plantar tests. Finally, the effects of DP were assessed in vitro on SK-N-SH dopaminergic cells exposed to acrolein.

RESULTS

DP reduced acrolein and reversed the upregulation of pain-sensing transient receptor potential ankyrin 1 (TRPA1) channels in the substantia nigra, striatum, and cortex. DP also mitigated both motor and sensory deficits typical of PD. In addition, DP lowered acrolein and protected DA-like cells in vitro. Acrolein's ability to upregulate TRPA1 was also verified in vitro using cell lines.

CONCLUSIONS

These results further elucidated the acrolein-mediated pathogenesis and reinforced the critical role of acrolein in PD while providing strong arguments for anti-acrolein treatments as a novel and feasible strategy to combat neurodegeneration in PD. Considering the extensive involvement of acrolein in various nervous system illnesses and beyond, anti-acrolein strategies may have wide applications and broad impacts on human health.

Role of TRPA1 in Tissue Damage and Kidney Disease

TRPA1, a nonselective cation channel, is expressed in sensory afferent that innervates peripheral targets. Neuronal TRPA1 can promote tissue repair, remove harmful stimuli and induce protective responses via the release of neuropeptides after the activation of the channel by chemical, exogenous, or endogenous irritants in the injured tissue. However, chronic inflammation after repeated noxious stimuli may result in the development of several diseases. In addition to sensory neurons, TRPA1, activated by inflammatory agents from some non-neuronal cells in the injured area or disease, might promote or protect disease progression. Therefore, TRPA1 works as a molecular sentinel of tissue damage or as an inflammation gatekeeper. Most kidney damage cases are associated with inflammation. In this review, we summarised the role of TRPA1 in neurogenic or non-neurogenic inflammation and in kidney disease, especially the non-neuronal TRPA1. In in vivo animal studies, TRPA1 prevented sepsis-induced or Ang-II-induced and ischemia-reperfusion renal injury by maintaining mitochondrial haemostasis or via the downregulation of macrophage-mediated inflammation, respectively. Renal tubular epithelial TRPA1 acts as an oxidative stress sensor to mediate hypoxia-reoxygenation injury in vitro and ischaemia-reperfusion-induced kidney injury in vivo through MAPKs/NF-kB signalling. Acute kidney injury (AKI) patients with high renal tubular TRPA1 expression had low complete renal function recovery. In renal disease, TPRA1 plays different roles in different cell types accordingly. These findings depict the important role of TRPA1 and warrant further investigation.

Renal Tubular Epithelial TRPA1 Acts as An Oxidative Stress Sensor to Mediate Ischemia-Reperfusion-Induced Kidney Injury through MAPKs/NF-κB Signaling

Oxidative stress and inflammation play important roles in the pathophysiology of acute kidney injury (AKI). Transient receptor potential ankyrin 1 (TRPA1) is a Ca2+-permeable ion channel that is sensitive to reactive oxygen species (ROS). The role of TRPA1 in AKI remains unclear. In this study, we used human and animal studies to assess the role of renal TRPA1 in AKI and to explore the regulatory mechanism of renal TRPA1 in inflammation via in vitro experiments. TRPA1 expression increased in the renal tubular epithelia of patients with AKI. The severity of tubular injury correlated well with tubular TRPA1 or 8-hydroxy-2'-deoxyguanosine expression. In an animal model, renal ischemia-reperfusion injury (IR) increased tubular TRPA1 expression in wild-type (WT) mice. Trpa1^-/- mice displayed less IR-induced tubular injury, oxidative stress, inflammation, and dysfunction in kidneys compared with WT mice. In the in vitro model, TRPA1 expression increased in renal tubular cells under hypoxia-reoxygenation injury (H/R) conditions. We demonstrated that H/R evoked a ROS-dependent TRPA1 activation, which elevated intracellular Ca²⁺ level, increased NADPH oxidase activity, activated MAPK/NF-κB signaling, and increased IL-8. Renal tubular TRPA1 may serve as an oxidative stress sensor and a crucial regulator in the activation of signaling pathways and promote the subsequent transcriptional regulation of IL-8. These actions might be evident in mice with IR or patients with AKI.

Human induced pluripotent stem cell-based platform for modeling cardiac ischemia

Ischemic heart disease is a major cause of death worldwide, and the only available therapy to salvage the tissue is reperfusion, which can initially cause further damage. Many therapeutics that have been promising in animal models have failed in human trials. Thus, functional human based cardiac ischemia models are required. In this study, a human induced pluripotent stem cell derived-cardiomyocyte (hiPSC-CM)-based platform for modeling ischemia-reperfusion was developed utilizing a system enabling precise control over oxygen concentration and real-time monitoring of the oxygen dynamics as well as iPS-CM functionality. In addition, morphology and expression of hypoxia-related genes and proteins were evaluated as hiPSC-CM response to 8 or 24 h hypoxia and 24 h reoxygenation. During hypoxia, initial decrease in hiPSC-CM beating frequency was observed, after which the CMs adapted to the conditions and the beating frequency gradually increased already before reoxygenation. During reoxygenation, the beating frequency typically first surpassed the baseline before settling down to the values close the baseline. Furthermore, slowing on the field potential propagation throughout the hiPSC-CM sheet as well as increase in depolarization time and decrease in overall field potential duration were observed during hypoxia. These changes were reversed during reoxygenation. Disorganization of sarcomere structures was observed after hypoxia and reoxygenation, supported by decrease in the expression of sarcomeric proteins. Furthermore, increase in the expression of gene encoding glucose transporter 1 was observed. These findings indicate, that despite their immature phenotype, hiPSC-CMs can be utilized in modeling ischemia-reperfusion injury.

CGRP derived from cardiac fibroblasts is an endogenous suppressor of cardiac fibrosis

AIMS

Aberrant activation of cardiac fibroblasts leads to cardiac fibrosis, and evolving evidences suggest that endogenous bioactive substances derived from cardiac fibroblasts regulate cardiac fibroblasts activation in an autocrine/paracrine manner. Here we first presented evidence that cardiac fibroblasts can synthesize and secrete calcitonin gene-related peptide (CGRP), therefore, this study aimed to investigate the role of cardiac fibroblasts-derived CGRP in cardiac fibroblasts activation and its regulative mechanism.

METHODS AND RESULTS

The abundantly expression of CGRP in rat, mouse, and human myocardium allowed us to explore the cellular origin of CGRP, and found that the cardiac CGRP was mainly derived from cardiac fibroblasts. Activating TRPA1 with a specific agonist allyl isothiocyanate promoted the synthesis and secretion of CGRP, as well as intracellular Ca2+. These effects were reversed by TRPA1-specific antagonist HC030031 and Ca2+ chelator BAPTA-AM. TGF-β1 was applied to induce the activation of cardiac fibroblasts, and found that TGF-β1 can increase the mRNA expression and secretion levels of CGRP in cardiac fibroblasts. Either CGRP8-37 (CGRP receptor antagonist) or α-CGRP small interfering RNA (siRNA) aggravated TGF-β1-induced proliferation, differentiation, collagen production, and instigated inflammation in cardiac fibroblasts. Moreover, TGF-β1-induced NF-κB activation including IκBα phosphorylation and p65 nuclear translocation were also promoted by CGRP8-37 and α-CGRP siRNA. NF-κB inhibitor pyrrolidinedithiocarbamate ammonium (PDTC) reversed the effects of CGRP8-37 on NF-κB activation. The promotive effects of CGRP8-37 on TGF-β1-induced activation of cardiac fibroblasts were all reversed by PDTC. Monocrotaline (MCT) induces pulmonary arterial hypertension, progressively leading to right ventricular fibrosis. This model of cardiac fibrosis was developed here to test the potentially beneficial effects of TRPA1 activation in vivo. The non-toxic TRPA1 agonist Cinnamaldehyde (CA) inhibited MCT-induced elevation in right ventricle systolic pressure, RV/LV + S, and right ventricular collagen accumulation, as well as down-regulation of CGRP. CA increased the synthesis and secretion of CGRP, and inhibited TGF-β1-induced activation in cardiac fibroblasts.

CONCLUSION

Our data suggested an autocrine role for cardiac fibroblasts-derived CGRP in suppressing activation of cardiac fibroblasts through inhibiting NF-κB activation. Increasing autocrine CGRP by activating TRPA1 can ameliorate cardiac fibrosis. These findings support the notion that CGRP derived from cardiac fibroblasts is an endogenous suppressor of cardiac fibrosis.

Effect of Quercetin-Loaded Mesoporous Silica Nanoparticles on Myocardial Ischemia-Reperfusion Injury in Rats and Its Mechanism

BACKGROUND

Quercetin has potential value in treating cardiovascular diseases, but it is not suitable for clinical application due to its own water solubility. The limitation of quercetin can be distinctly ameliorated by delivering it with nanocarriers.

OBJECTIVE

To determine the effect of quercetin-loaded mesoporous silica nanoparticles (Q-MSNs) on myocardial ischemia-reperfusion injury in rats and its mechanism.

METHODS

Q-MSNs were synthesized, and the morphology of Q-MSNs and MSNs was characterized by transmission electron microscopy and dynamic light scattering technique, respectively. Healthy rats were enrolled and randomly divided into a sham operation control group, an ischemia-reperfusion (IR) group, an IR+Q group, an IR+Q-MSNs group, and an MSNs group (each n = 10). Rats in the sham operation group were not treated with ischemia reperfusion, but given normal perfusion meantime. Rats in the sham operation control group, IR group, and MSNs group were given normal saline for 10 days before ischemia reperfusion, and rats in the IR+Q group and IR+Q-MSNs group were given drugs by gavage for 10 days before ischemia reperfusion. Primary myocardial cells were sampled from SD neonatal rats to construct hypoxia/reoxygenation myocardial cell models. The myocardial cells were assigned to a control group, IR group, quercetin (Q) group, Q-MSNs group, and MSNs group. Except for the control group, all the other groups were treated with hypoxia/reoxygenation. Cells in the Q group were treated with quercetin (10 μM, 20 μM, 40 μM) for 24 h in advance and then treated with measures to cause hypoxia-reoxygenation injury. Cells in the Q-MSNs group were treated with the same concentration of loaded quercetin and the same method used for the Q group. The myocardial apoptosis, myocardial infarction, ventricular remodeling, hemodynamic indexes, physiological and biochemical indexes, and JAK2/STAT3 pathway expression of each group were detected, and the apoptosis, viability, oxidative stress, and JAK2/STAT3 pathway expression of primary myocardial cells in each group were also detected.

RESULTS

Quercetin significantly activated the JAK2/STAT3 pathway in vivo and in vitro, and MSNs intensified the activation. Compared with quercetin, Q-MSNs were more effective in inhibiting cell apoptosis and oxidative stress, reducing myocardial infarction size, improving ventricular remodeling and cardiac function-related biochemical indexes, and promoting the recovery of cardiac blood flow.

CONCLUSION

Q-MSNs can significantly enhance the activation effect of quercetin on JAK2/STAT3 pathway, thus enhancing its protection on the heart of MIRI rats.

Allyl isothiocyanate (AITC) activates nonselective cation currents in human cardiac fibroblasts: possible involvement of TRPA1

The effects of allyl isothiocyanate (AITC), transient receptor potential ankyrin 1 (TRPA1) agonist, on cultured human cardiac fibroblasts were examined by measuring intracellular Ca²⁺ concentration [Ca²⁺]_i and whole-cell voltage clamp techniques. AITC (200 μM) increased Ca²⁺ entry in the presence of [Ca²⁺]_i. Ruthenium red (RR) (30 μM), and La³⁺ (0.5 mM), a general cation channel blocker, inhibited AITC-induced Ca²⁺ entry. Under the patch pipette filled with Cs⁺- and EGTA-solution, AITC induced the current of a reversal potential (Er) of approximately +0 mV. When extracellular Na⁺ ion was changed by NMDG⁺, the inward current activated by AITC was markedly reduced. La³⁺ and RR inhibited the AITC-induced current. The conventional RT-PCR analysis, Western blot, and immunocytochemical studies showed TRPA1 mRNA and protein expression. The present study shows the first evidence for functional Ca²⁺-permeable nonselective cation currents induced by AITC, possibly via TRPA1 in human cardiac fibroblast.

IcyHot analgesic topical cream limits cardiac injury in rodents

Little is known whether topical analgesic creams, whose natural products enter the blood stream after application, affect myocardial infarct size. Here we tested whether topical analgesic creams can trigger remote cardioprotection and the mechanism involved. Male Sprague Dawley rats were used for an in vivo rodent model consisting of 30 minutes left anterior descending coronary artery ischemia and 2 hours of reperfusion followed by infarct size assessment. The topical analgesic IcyHot, applied to the abdomen prior to ischemia, reduced myocardial infarct size versus control (41 ± 3* vs 62 ± 1, n= 6/group, *P < 0.001). In contrast, the topical analgesic creams Preparation H, Aspercreme Heat, or Tiger Balm did not alter infarct size. IcyHot, unlike Preparation H, increased circulating methyl salicylate levels during reperfusion (3.0 ± 0.6 vs 0.4 ± 0.2 mg/dL, n = 6, *P < 0.001, measured at the internal jugular vein). Methyl salicylate (10 μM) applied to isolated adult cardiac myocytes during reoxygenation reduced cell death when compared to vehicle (21% ± 2%* vs 30% ± 2% of trypan blue positive cells, n = 9/group, *P < 0.01). Further, treatment with the TRP ankyrin 1 (TRPA1) inhibitors TCS-5861528 (1 μM) or AP-18 (1 μM) blocked the methyl salicylate-induced protective effect in isolated adult cardiomyocytes. In intact rodents, either of the TRPA1 inhibitors (1 mg/kg, intravenous) given prior to IcyHot topical application blocked IcyHot-induced infarct size reduction. IcyHot also reduced infarct size when applied 24 hours prior to myocardial ischemia or during myocardial ischemia versus control. Together, these findings support IcyHot analgesic cream can trigger remote cardioprotection through releasing methyl salicylate into the bloodstream with cardioprotection occurring by a TRPA1-dependent mechanism.

Interrelation between ROS and Ca2+ in aging and age-related diseases

Calcium (Ca2+) and reactive oxygen species (ROS) are versatile signaling molecules coordinating physiological and pathophysiological processes. While channels and pumps shuttle Ca2+ ions between extracellular space, cytosol and cellular compartments, short-lived and highly reactive ROS are constantly generated by various production sites within the cell. Ca2+ controls membrane potential, modulates mitochondrial adenosine triphosphate (ATP) production and affects proteins like calcineurin (CaN) or calmodulin (CaM), which, in turn, have a wide area of action. Overwhelming Ca2+ levels within mitochondria efficiently induce and trigger cell death. In contrast, ROS comprise a diverse group of relatively unstable molecules with an odd number of electrons that abstract electrons from other molecules to gain stability. Depending on the type and produced amount, ROS act either as signaling molecules by affecting target proteins or as harmful oxidative stressors by damaging cellular components. Due to their wide range of actions, it is little wonder that Ca2+ and ROS signaling pathways overlap and impact one another. Growing evidence suggests a crucial implication of this mutual interplay on the development and enhancement of age-related disorders, including cardiovascular and neurodegenerative diseases as well as cancer.

Transient Receptor Potential Ankyrin Type-1 Channels as a Potential Target for the Treatment of Cardiovascular Diseases

Cardiovascular disease is one of the chronic conditions with the highest mortality rate in the world. Underlying conditions such as hypertension, metabolic disorders, and habits like smoking are contributors to the manifestation of cardiovascular diseases. The treatment of cardiovascular diseases is inseparable from the development of drugs. Consequently, this has led to many researchers to focus on the search for effective drug targets. The transient receptor potential channel Ankyrin 1 (TRPA1) subtype is a non-selective cation channel, which belongs to the transient receptor potential (TRP) ion channel. Previous studies have shown that members of the TRP family contribute significantly to cardiovascular disease. However, many researchers have not explored the role of TRPA1 as a potential target for the treatment of cardiovascular diseases. Furthermore, recent studies revealed that TRPA1 is commonly expressed in the vascular endothelium. The endothelium is linked to the causes of some cardiovascular diseases, such as atherosclerosis, myocardial fibrosis, heart failure, and arrhythmia. The activation of TRPA1 has a positive effect on atherosclerosis, but it has a negative effect on other cardiovascular diseases such as myocardial fibrosis and heart failure. This review introduces the structural and functional characteristics of TRPA1 and its importance on vascular physiology and common cardiovascular diseases. Moreover, this review summarizes some evidence that TRPA1 is correlated to cardiovascular disease risk factors.

Acute and chronic vascular effects of inhaled crotonaldehyde in mice: Role of TRPA1

Although crotonaldehyde (CR) is an abundant α,β-unsaturated aldehyde in mainstream cigarette smoke (MCS), the cardiovascular toxicity of inhaled CR is largely unexplored. Thus, male C57BL/6 J mice were exposed acutely (1 h, 6 h, and 4d) and chronically (12 weeks) to CR (at levels relevant to MCS; 1 and 3 ppm), and cardiovascular and systemic outcomes were measured in vivo and in vitro. Diastolic blood pressure was decreased (hypotension) by both acute and chronic CR exposure. Vascular toxicity of inhaled CR was quantified in isolated aorta in response to agonists of contraction (phenylephrine, PE) and relaxation (acetylcholine, ACh; sodium nitroprusside, SNP). Although no change in contractility was observed, ACh-induced relaxations were augmented after both acute and chronic CR exposures whereas SNP-induced relaxation was enhanced only following 3 ppm CR exposure. Because CR is a known agonist of the transient receptor potential ankyrin 1 (TRPA1) channel, male TRPA1-null mice were exposed to air or CR (4d, 1 ppm) and aortic function assessed in vitro. CR exposure had no effect on TRPA1-null aortic function indicating a role of TRPA1 in CR effects in C57BL/6 J mice. Notably, CR exposure (4d, 1 ppm) had no effect on aortic function in female C57BL/6 J mice. This study shows that CR inhalation exposure induces real-time and persistent vascular changes that promote hypotension-a known risk factor for stroke. Because of continued widespread exposures of humans to combustion-derived CR (environmental and tobacco products), CR may be an important cardiovascular disease risk factor.

Localization of TRPA1 channels and characterization of TRPA1 mediated responses in dural and pial arteries in vivo after intracarotid infusion of Na2S

BACKGROUND

The Transient Receptor Potential Ankyrin 1 (TRPA1) channel might play a role in migraine. However, different mechanisms for this have been suggested. The purpose of our study was to investigate the localization and significance of TRPA1 channels in rat pial and dural arteries.

METHODS

Immunofluorescence microscopy was used to localize TRPA1 channels in dural arteries, pial arteries, dura mater and trigeminal ganglion. The genuine closed cranial window model was used to examine the effect of Na₂S, a donor of the TRPA1 channel opener H₂S, on the diameter of pial and dural arteries. Further, we performed blocking experiments with TRPA1 antagonist HC-030031, calcitonin gene-related peptide (CGRP) receptor antagonist olcegepant and K_Ca3.1 channel blocker TRAM-34.

RESULTS

TRPA1 channels were localized to the endothelium of both dural and pial arteries and in nerve fibers in dura mater. Further, we found TRPA1 expression in the membrane of trigeminal ganglia neuronal cells, some of them also staining for CGRP. Na₂S caused dilation of both dural and pial arteries. In dural arteries, this was inhibited by HC-030031 and olcegepant. In pial arteries, the dilation was inhibited by TRAM-34, suggesting involvement of the K_Ca3.1 channel.

CONCLUSION

Na₂S causes a TRPA1- and CGRP-dependent dilation of dural arteries and a K_Ca3.1 channel-dependent dilation of pial arteries in rats.

Crotonaldehyde-induced vascular relaxation and toxicity: Role of endothelium and transient receptor potential ankyrin-1 (TRPA1)

INTRODUCTION

Crotonaldehyde (CR) is an electrophilic α,β-unsaturated aldehyde present in foods and beverages and is a minor metabolite of 1,3-butadiene. CR is a product of incomplete combustion, and is at high levels in smoke of cigarettes and structural fires. Exposure to CR has been linked to cardiopulmonary toxicity and cardiovascular disease.

OBJECTIVE

The purpose of this study was to examine the direct effects of CR in murine blood vessels (aorta and superior mesenteric artery, SMA) using an in vitro system.

METHODS AND RESULTS

CR induced concentration-dependent (1-300 μM) relaxations (75-80%) in phenylephrine (PE) precontracted aorta and SMA. Because the SMA was 20× more sensitive to CR than aorta (SMA EC50 3.8 ± 0.5 μM; aorta EC50 76.0 ± 2.0 μM), mechanisms of CR relaxation were studied in SMA. The CR-induced relaxation at low concentrations (1-30 μM) was inhibited by: 1) mechanically-impaired endothelium; 2) Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME); 3) guanylyl cyclase (GC) inhibitor (ODQ); 4) transient receptor potential ankyrin-1 (TRPA1) antagonist (A967079); and, 5) by non-vasoactive level of nicotine (1 μM). Similarly, a TRPA1 agonist, allyl isothiocyanate (AITC; mustard oil), stimulated SMA relaxation dependent on TRPA1, endothelium, NO, and GC. Consistent with these mechanisms, TRPA1 was present in the SMA endothelium. CR, at higher concentrations (100-300 μM), induced tension oscillations (spasms) and irreversibly impaired contractility (a vasotoxic effect enhanced by impaired endothelium).

CONCLUSIONS

CR relaxation depends on a functional endothelium and TRPA1, whereas vasotoxicity is enhanced by endothelium dysfunction. Thus, CR is both vasoactive and vasotoxic along a concentration continuum.

Myocardial ischaemia reperfusion injury and cardioprotection in the presence of sensory neuropathy: Therapeutic options

During the last decades, mortality from acute myocardial infarction has been dramatically reduced. However, the incidence of post‐infarction heart failure is still increasing. Cardioprotection by ischaemic conditioning had been discovered more than three decades ago. Its clinical translation, however, is still an unmet need. This is mainly due to the disrupted cardioprotective signalling pathways in the presence of different cardiovascular risk factors, co‐morbidities and the medication being taken. Sensory neuropathy is one of the co‐morbidities that has been shown to interfere with cardioprotection. In the present review, we summarize the diverse aetiology of sensory neuropathies and the mechanisms by which these neuropathies may interfere with ischaemic heart disease and cardioprotective signalling. Finally, we suggest future therapeutic options targeting both ischaemic heart and sensory neuropathy simultaneously.

LINKED ARTICLES

This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.23/issuetoc

Mammalian Transient Receptor Potential TRPA1 Channels: From Structure to Disease

The transient receptor potential ankyrin (TRPA) channels are Ca²⁺-permeable nonselective cation channels remarkably conserved through the animal kingdom. Mammals have only one member, TRPA1, which is widely expressed in sensory neurons and in non-neuronal cells (such as epithelial cells and hair cells). TRPA1 owes its name to the presence of 14 ankyrin repeats located in the NH₂ terminus of the channel, an unusual structural feature that may be relevant to its interactions with intracellular components. TRPA1 is primarily involved in the detection of an extremely wide variety of exogenous stimuli that may produce cellular damage. This includes a plethora of electrophilic compounds that interact with nucleophilic amino acid residues in the channel and many other chemically unrelated compounds whose only common feature seems to be their ability to partition in the plasma membrane. TRPA1 has been reported to be activated by cold, heat, and mechanical stimuli, and its function is modulated by multiple factors, including Ca²⁺, trace metals, pH, and reactive oxygen, nitrogen, and carbonyl species. TRPA1 is involved in acute and chronic pain as well as inflammation, plays key roles in the pathophysiology of nearly all organ systems, and is an attractive target for the treatment of related diseases. Here we review the current knowledge about the mammalian TRPA1 channel, linking its unique structure, widely tuned sensory properties, and complex regulation to its roles in multiple pathophysiological conditions.

The TRPA1 Channel in the Cardiovascular System: Promising Features and Challenges

The transient receptor potential ankyrin 1 (TRPA1) channel is a calcium-permeable nonselective cation channel in the plasma membrane that belongs to the transient receptor potential (TRP) channel superfamily. Recent studies have suggested that the TRPA1 channel plays an essential role in the development and progression of several cardiovascular conditions, such as atherosclerosis, heart failure, myocardial ischemia-reperfusion injury, myocardial fibrosis, arrhythmia, vasodilation, and hypertension. Activation of the TRPA1 channel has a protective effect against the development of atherosclerosis. Furthermore, TRPA1 channel activation elicits peripheral vasodilation and induces a biphasic blood pressure response. However, loss of channel expression or blockade of its activation suppressed heart failure, myocardial ischemia-reperfusion injury, myocardial fibrosis, and arrhythmia. In this paper, we review recent research progress on the TRPA1 channel and discuss its potential role in the cardiovascular system.

Non-Analgesic Symptomatic or Disease-Modifying Potential of TRPA1

TRPA1, a versatile ion channel of the Transient Receptor Potential (TRP) channel family, detects a large variety of chemicals and can contribute to signal processing of other stimuli, e.g., due to its sensitivity to cytosolic calcium elevation or phosphoinositolphosphate modulation. At first, TRPA1 was found on sensory neurons, where it can act as a sensor for potential or actual tissue damage that ultimately may elicit pain or itch as warning symptoms. This review provides an update regarding the analgesic and antipruritic potential of TRPA1 modulation and the respective clinical trials. Furthermore, TRPA1 has been found in an increasing amount of other cell types. Therefore, the main focus of the review is to discuss the non-analgesic and particularly the disease-modifying potential of TRPA1. This includes diseases of the respiratory system, cancer, ischemia, allergy, diabetes, and the gastrointestinal system. The involvement of TRPA1 in the respective pathophysiological cascades is so far mainly based on pre-clinical data.

Comparative effects of parent and heated cinnamaldehyde on the function of human iPSC-derived cardiac myocytes

Many e-cigarette products contain cinnamaldehyde as a primary constituent of cinnamon flavorings. When used as a food additive, cinnamaldehyde is generally regarded as safe for ingestion. However, little is known about the effects of cinnamaldehyde or its degradation products, generated after heating and inhalation, which may lead to elevated circulatory exposure to the heart. Hence, in this study, we tested the in vitro cardiac toxicity of cinnamaldehyde and its thermal degradation products generated by heating at low (200 ± 50 °C) and high temperatures (700 ± 50 °C) on the contractility, rhythmicity and electrical signaling properties of human induced pluripotent stem cell-derived cardiac myocytes (hiPSC-CMs). Cellular impedance measurements on spontaneously beating hiPSC-CMs revealed that cinnamaldehyde significantly alters contraction-dependent signal amplitude, beating rate, and cell morphology. These effects were attenuated after cinnamaldehyde was subjected to heating at low or high temperatures. Current clamp analysis of hiPSC-CM action potentials (APs) showed only modest effects of acute application of 1-100 μM cinnamaldehyde on resting membrane potential, while prolonged (~20 min) application of 100 μM cinnamaldehyde resulted in progressive depolarization and loss of rhythmic AP spiking activity. Collectively, these results suggest that micromolar levels of cinnamaldehyde could alter cardiac excitability, in part by impairing the processes that regulate membrane potential and depolarization. Our results further suggest that heating cinnamaldehyde by itself does not directly lead to the formation of products with greater cardiotoxicity in vitro.