The energy supply of the heart is very high and mainly depends on aerobic metabolism. The high oxygen consumption is further increased by rises in heart rate, contractility and ventricular wall. For this reason, a proper maintenance of the balance between oxygen supply and consumption is extremely important; changes in this balance may result in ischemia (Boyette and Manna, 2023). Sudden myocardial ischemia (I) is usually caused by the acute rupture of an atherosclerotic plaque and the obstruction of a coronary artery leading to an acute coronary syndrome and acute myocardial infarction (AMI) (Basalay et al., 2020). When blood flow and oxygen delivery is limited, anaerobic metabolic processes will be activated finally resulting in damage to the cardiac tissue. Reperfusion (R), which restores the blood supply to the cardiac muscle, halts the progression of myocardial ischemic injury but simultaneously produces sublethal to lethal reperfusion injury in marginally viable myocardium aggravating its damage. In consequence, both events lead to the myocardial ischemia/reperfusion (I/R) injury (Buja, 2023; Wang et al., 2023). Multiple mechanisms are involved in the pathogenesis of the ischemic and reperfusion period including changes in cell metabolism, impairment of mitochondrial function, enhanced inflammatory response, disability of autophagy, platelet-dependent activation of leukocytes, escalating overproduction of reactive oxygen species (ROS) and intracellular calcium overload (Kalogeris et al., 2016; Buja, 2023; Ferdinandy et al., 2023; Liu et al., 2023).

Numerous compounds including cannabinoids have been suggested for protection of the heart against I/R injury. Cannabinoids can be divided into three groups, i.e., (i) phytocannabinoids found in the cannabis plants Cannabis sativa or indica, including psychoactive Δ⁹-tetrahydrocannabinol (∆⁹-THC) and non-psychoactive cannabidiol (CBD), (ii) synthetic cannabinoids, e.g., WIN55212-2 and HU-210 and (iii) endocannabinoids (ECBs), such as anandamide (AEA) and 2-arachidonoylglycerol (2-AG). Removal of the endocannabinoids from the biophase occurs by degradation (e.g., by fatty acid amide hydrolase, FAAH, and monoacylglycerol lipase, MAGL) and cannabinoid reuptake [Figure 1, (Toczek and Malinowska, 2018; Maccarrone et al., 2023),]. Cannabinoids act, although with strongly differing affinity, via the G protein-coupled classical cannabinoid receptors (CBRs) CB₁ and CB₂ (Figure 1), some G protein-coupled orphan receptors (GPRs, e.g., GPR55), transient receptor potential vanilloid 1 (TRPV1) receptors and nuclear peroxisome proliferator-activated receptors (PPARs).

Gene and/or protein expression of CB₁Rs and CB₂Rs has been detected in the left human ventricle, right atrium, coronary artery endothelial and smooth muscle cells and epicardial adipose tissue. Cannabinoid receptors have also been identified in hearts of the guinea pig and in the left ventricle and left atrium of rat and mouse (Rajesh et al., 2010; 2022; Szekeres et al., 2018; Weresa et al., 2022). CB₁Rs are localized on arterial and capillary endothelial cells, whereas CB₂Rs are found on cardiomyocytes and endothelial cells of larger arteries (Lépicier et al., 2007). Moreover, presynaptic CB₁Rs are also present on sympathetic nerve endings innervating human (Molderings et al., 1999) and rat (Ishac et al., 1996) heart. CB₂Rs are also localized in rodent myocardial fibroblasts, B cells, and T cells (Defer et al., 2009; Puhl, 2020). CB₁Rs were also identified in mice cardiac fibroblasts (Valenta et al., 2018) although their function has not been evaluated.

Depending on the type of cannabinoid receptor, its stimulation causes opposite effects (Pacher et al., 2018; Rorabaugh et al., 2023). Thus, CB₁R activation induces a negative inotropic effect (also in humans: Bonz et al., 2003; Sterin-Borda et al., 2005), decreases noradrenaline release from the cardiac sympathetic nerve endings (Ishac et al., 1996; Molderings et al., 1999), leads to vasodilatation of rat coronary artery (e.g., Szekeres et al., 2018), stimulates oxidative stress and cell death in human endothelial cells and cardiomyocytes (Rajesh et al., 2010), increases smooth muscle proliferation and promotes vascular inflammation, atherosclerosis and cardiac injury (Pacher et al., 2018). On the other hand, CB₂R stimulation produces a positive inotropic effect (e.g., Sterin-Borda et al., 2005), decreases the acute inflammatory response and consequent oxidative stress in immune and activated endothelial cells (Rajesh et al., 2022) and reduces cardiac fibrosis by diminishing fibroblast-myoblast transformation and collagen production (Defer et al., 2009).

Proper cannabinoid signalling might play a protective role against cardiac injury caused by an imbalance in oxygen supply and demand. As shown in Figure 1, activation of CB₁Rs leads to deleterious consequences resulting from enhancement in oxidative stress, immune cell migration, inflammation, proliferation and fibrosis. On the other hand, CB₂ receptor activation mainly has a beneficial effect by an influence opposite in direction to that of the CB₁Rs (Pacher et al., 2018; Smoum et al., 2022). However, despite previously observed cardioprotective effects mediated mainly via CB₂ receptor activation [for review, see (Lamontagne et al., 2006; Pacher and Haskó, 2008; Steffens and Pacher, 2012; Maslov et al., 2016; Tang et al., 2021; Rorabaugh et al., 2023; More et al., 2024)] the number of studies reporting cardioprotective effects of cannabinoids in different cardiac disorders seems to decline. The previous studies are not even included in the most recent analysis of multitarget strategies proposed to reduce myocardial I/R injury (Davidson et al., 2019; Heusch, 2023). For better understanding the obstacles for the translation from successful preclinical studies on cardioprotection to clinical practice, the COST ACTION cardioprotection consortium proposed an in vivo set of step-by-step criteria. This approach is termed IMproving Preclinical Assessment of Cardioprotective Therapies (IMPACT) and its aim is to improve the likelihood of translating novel cardioprotective interventions into the clinical setting for patient benefit [(Lecour et al., 2021); for details, see below]. Although the IMPACT criteria primarily consider infarct size in experiments in vivo, we decided to extend our analysis to other effects, such as inflammation or cardiac contractility to assay the possible broad spectrum of cardiac effects of cannabinoids.

The first aim of this review is to summarize the current knowledge about the potential cardioprotective role of the (endo)cannabinoid system under hypoxia, ischemia and reperfusion. Data from humans with coronary heart disease (mainly determinations of endocannabinoid levels) are described first (Table 1), followed by animal studies in which the putative cardioprotective role of cannabinoids in ischemic preconditioning is considered (Table 2). Then, we describe in vivo experiments on animals exposed to temporary (I/R studies) or permanent occlusion (acute myocardial infarction studies) of the left descending artery (LAD) (Tables 3, 4) and in vitro experiments on isolated cardiomyocytes undergoing hypoxia and on isolated hearts subjected to LAD occlusion, low-flow or global no-flow (Table 5). In the second part of the review, we evaluate whether the in vivo models and experimental protocols considered here (Tables 3, 4) fulfil the IMPACT criteria and allow translation of the cardioprotective effects of cannabinoids in I/R injury to clinical settings.

To find the relevant articles dealing with the cardioprotective effects of cannabinoids against ischemia-reperfusion injury, we performed a comprehensive search in the PubMed, Medline and EMBASE databases (closed in February 2024). Because there is a substantial amount of research in the databases that deal with ischemia in the nervous system or perinatal hypoxia-ischemia, we added the word “cardiac” to each search. The following key phrases were used: “cardiac ischemia cannabinoid” (which yielded 205 results), “cardiac hypoxia cannabinoid” (21 results), “cardiac preconditioning cannabinoid” (16 results), “human cardiac ischemia cannabinoid” (130 results) and “myocardial infarction cannabinoid” (180 results). Based on the approved therapeutic uses of cannabidiol, search phrases also included “cannabidiol” coupled to “cardiac ischemia”, “cardiac hypoxia” and “myocardial infarction” (a total of 35 results). Titles, abstracts, and full texts of the identified papers were analyzed, and duplicate articles or those with non-relevant content were excluded; only articles in English were considered. In total, 52 publications were included in this review, which are summarized in Table 1-5. A schematic representation of the typical protocols for ischemia, hypoxia or acute myocardial infarction used in the above studies is given in Figure 2.

The endocannabinoid system is activated during various cardiac disorders in humans (Table 1). Thus, higher endocannabinoid levels (2-AG, AEA or both) were found in patients with coronary artery disease (CAD) and at the ruptured plaque site of the infarct-related coronary artery in patients with AMI (Maeda et al., 2009; Wang et al., 2012) and CAD (Sugamura et al., 2009; Jehle et al., 2019) in comparison to peripheral arteries. Interestingly, the endocannabinoid level was higher in the coronary artery of patients with non-ST-elevation myocardial infarction (NSTEMI) compared to CAD (Jehle et al., 2019) and in the blood of patients with severe chronic heart failure (CHF) in comparison to controls (Weis et al., 2010). Note that, in the latter study, CHF might have been due to ischemia or to other reasons.

As shown in Table 1, there are differences as to which endocannabinoid is enhanced under pathological conditions even within the same disease. Thus, in AMI, the 2-AG level in the infarct-related coronary artery was higher in the paper by Wang et al. (2012) but undetectable in the publication by Maeda et al. (2009). The above discrepancy probably results from methodological differences. For example, Jehle et al. (2019) underlined the influence of the site of blood sampling, i.e., venous (Sugamura et al., 2009) versus arterial (Jehle et al., 2019). Of course, one cannot exclude a higher heterogeneity of the experimental groups in humans than in experimental animals. Importantly, as mentioned above, the endocannabinoid levels (AEA and 2-AG) in infarct-related coronary arteries were higher than those in blood samples drawn from distinct locations.

Additionally, in coronary atherectomy samples, CB₁R mRNA expression was more markedly increased in patients with unstable angina than in those with stable angina (Sugamura et al., 2009). The expression of CB₁Rs and CB₂Rs was also studied in human left ventricular myocardium of patients with chronic heart failure (CHF) and controls (Weis et al., 2010). In healthy myocardium, mRNA transcripts of CB₁Rs and CB₂Rs were expressed similarly whereas in the myocardium of CHF patients a shift of the CB₁/CB₂R ratio towards the expression of CB₂Rs was observed (Table 1).

An abnormal lipid profile belongs to the risk factors important for cardiovascular disease. Targeted lipidomics analysis showed the existence of two subgroups within the ischemic end-stage failing human left ventricle, the first one resembling controls and the second one presenting with an altered lipid profile. Interestingly, only in the second subgroup decreased 2-AG and increased AEA, N-acylethanolamine and free fatty acids levels as well as a robust reduction in cardiac MAGL activity occurred (van Esbroeck et al., 2020).

The question arises, whether activation of the endocannabinoid system in humans is beneficial or has pathological relevance in myocardial infarction. Unfortunately, we are not able to answer this question based on only few publications related to rather small patient groups (Table 1). Data obtained on cardiac experimental models suggest mainly protective effects of endocannabinoids (see below). On the other hand, an increase in endocannabinoid levels in humans (Table 1) was accompanied by enhanced serum levels of reactive oxygen species (ROS) and tumor necrosis factor-α (TNF-α) in infarct-related coronary artery (Wang et al., 2012) or correlated with peak troponin and IL-6 levels (Jehle et al., 2019) but correlations, of course, do not prove a causal relationship.

Almost four decades ago, Murry and colleagues discovered that brief episodes of ischemia followed by short-lasting reperfusion before a sustained period of coronary artery occlusion reduced infarct size in dogs (Murry et al., 1986). This was the beginning of the development of research on “conditioning” phenomena used to reduce infarct size by brief periods of I/R on the heart. Ischemic preconditioning is considered the gold standard of cardioprotection (Basalay et al., 2020). In remote preconditioning, brief episodes of I/R are administered to organs or tissues other than the heart and can be easily applied in a non-invasive way, e.g., using a blood pressure cuff on an arm or a leg (Lang and Kim, 2022; Penna et al., 2022; Comità et al., 2023; Ferdinandy et al., 2023; Zhao et al., 2023). Another way to protect the heart against the consequences of I/R injury is pharmacological conditioning (i.e., volatile anesthetics, opioids or α₂-adrenoceptor agonists), a concept that is based on the administration of specific drugs mimicking the effect of ischemic preconditioning (Roth et al., 2021; Penna et al., 2022; Ferdinandy et al., 2023). Controlled occlusions or pharmacological interventions activate a molecular self-defense program which delays the progression of infarction. The subsequent activation of multiple endogenous cardioprotective mechanisms including adenosine, protein kinase, calcium signalling, nitric oxide release, reduction in ROS but also the involvement of autacoids, hormones, neurotransmitters and cytokines lead to cardioprotection and reduce infarct size (Penna et al., 2022; Heusch, 2023).

The endocannabinoid system is suggested to play a role in preconditioning-induced cardioprotection as well. Importantly, its involvement was confirmed in different models of preconditioning (Table 2): ischemic preconditioning (Bouchard et al., 2003), remote preconditioning (Hajrasouliha et al., 2008), propofol- (Sun et al., 2017), NO- (Wagner et al., 2006), heat stress- (Joyeux et al., 2002) and LPS-induced preconditioning (Lamontagne et al., 2006) that led to the reduction in the infarct size (Lagneux and Lamontagne, 2001; Joyeux et al., 2002; Wagner et al., 2006; Sun et al., 2007; Hajrasouliha et al., 2008). Moreover, they were associated with prevention of ischemia-induced endothelial dysfunction (Bouchard et al., 2003), anti-oxidative (Sun et al., 2017), anti-arrhythmic effects (Hajrasouliha et al., 2008) and an improvement in cardiac contractility (Wagner et al., 2006).

The involvement of ECBs in the above studies was confirmed by three approaches (Table 2). Firstly, propofol- (Sun et al., 2017) and NO-preconditioning (Wagner et al., 2006) enhanced the release of AEA and 2-AG in heart and serum in in vivo studies in mice after LAD occlusion and in isolated neonatal rat ventricle cells exposed to hypoxia (Sun et al., 2017) and of 2-AG in perfused rat heart (Wagner et al., 2006). Secondly, the beneficial effect of propofol was mimicked by the FAAH inhibitor URB597 and the selective endocannabinoid reuptake inhibitor VDM11 (Sun et al., 2017), drugs that increase endocannabinoid levels, and the effect of ischemic preconditioning (Bouchard et al., 2003) was also obtained with 2-AG and palmitoylethanolamide (PEA). Moreover, 2-AG and its metabolically stable derivative noladinether mimicked the cardioprotective effects of NO-induced preconditioning (Wagner et al., 2006). Thirdly, the beneficial effect of preconditioning and ECBs was reversible and blocked mainly by the CB₂R antagonists SR144528 and AM630 (Lagneux and Lamontagne, 2001; Joyeux et al., 2002; Bouchard et al., 2003; Sun et al., 2017). However, a contribution of CB₁Rs is also suggested due to the blockade of beneficial effects by AM251 (Wagner et al., 2006) or rimonabant (Bouchard et al., 2003).

It was not the purpose of this review to analyze the cellular mechanisms of cardioprotective cannabinoids (beyond the level of receptors) and for this reason they are summarized here only briefly. Tables 1-5 show that the potential cellular pathways of cardioprotective cannabinoids have been examined in few studies only.

Several recent reviews have highlighted cardioprotective mechanisms that can regulate mitochondrial function, autophagy processes, modulation of energy metabolism, inflammation and apoptosis, and protect from ischemia-reperfusion injury (Ferdinandy et al., 2023). They include activation of PI3K (phosphoinositide-3-kinase (PI3K) and Akt (protein kinase B) (Deng and Zhou, 2023), ERK1/2 (extracellular signal-regulated kinase) (Kong et al., 2019), Pink1/Parkin (PTEN-induced kinase 1 (PINK1) and the E3 ubiquitin ligase Parkin) (Yu and Miyamoto, 2021), AMPK (AMP-activated protein kinase) (Pakesh et al., 2022), p38 MAPK (p38 mitogen-activated protein kinase) (Ruiz et al., 2018) and TGF-β (transforming growth factor-β1)-dependent activation of Smad-dependent cascades (Humeres et al., 2022).

Regarding the cardioprotective effects of CB₂R stimulation against I/R injury, the possible involvement of the pro-survival PI3K/Akt pathway (Li et al., 2013a; 2013b; Wang et al., 2014), the ERK1 pathway (Montecucco et al., 2009) and induction of autophagy via the Pink1/Parkin pathway (Liu et al., 2021) was shown. Moreover, in mice with deletion of CB₂Rs deterioration of the autophagy process related to inhibition of cardiac protective AMPK signaling was described (Hu et al., 2019). In an in vitro study, the anti-fibrotic and anti-oxidative actions of CB₂R activation leading to the inhibition of the TGF-β1/Smad3 pathway was shown (Li et al., 2016). Blockade of CB₁Rs with AM251 reduced the damage of cardiomyocytes exposed to hypoxia by activation of the AMPK pathway (Hu et al., 2023). With respect to the cannabidiol-dependent cardioprotective actions against I/R injury, the PI3K/Akt and MAPK/ERK pathways were shown as the only cellular mechanisms (Franco-Vadillo et al., 2021). Conversely, the enhancement of cardiac injury during ischemia mediated via activation of GPR55 receptors was dependent on the activation of the ROCK/p38 MAPK (Rho-assisted protein kinase/p38 mitogen-activated protein kinase) pathway (Robertson-Gray et al., 2019). Consequently, further research is necessary to determine the exact cellular signaling pathways by which cannabinoids produce beneficial (or detrimental) effects on the heart.

Little information is so far available with respect to the cellular sources of ECBs during I/R or AMI. Endocannabinoids and enzymes involved in their synthesis were found in rat cardiac tissues, endothelial cells and macrophage-derived cell lines, which means that cardiac function and coronary perfusion might be modulated by endocannabinoids derived not only from cardiac tissues but also from circulating cells like macrophages and platelets (Pacher and Haskó, 2008; Puhl, 2020).

Various drugs or surgical interventions have been shown to reduce infarct size and to improve cardiac function and healing in preclinical studies but despite the optimistic results none of the drugs/interventions could be implemented for preventing myocardial ischemia/reperfusion injury in patients with AMI (Bolli, 2021; Heusch, 2023). Promising cardioprotective effects have also been found in preclinical studies of cannabinoids including mainly CB₂R agonists and the multitarget CBD (for review, see (Lamontagne et al., 2006; Pacher and Haskó, 2008; Steffens and Pacher, 2012; Maslov et al., 2016; Tang et al., 2021) but drugs for the use in humans have so far not been developed. The question arises, why successful preclinical results for the treatment of acute myocardial infarction do not translate well into clinical practice (Heusch, 2023)?

To solve the above problem, the European Union (EU) CARDIOPROTECTION COST ACTION published in 2021 gives step-by-step criteria for Improving Preclinical Assessment of Cardioprotective Therapies (IMPACT) that should be met to improve the likelihood of translating novel cardioprotective interventions into the clinical setting (Lecour et al., 2021). They consist of three steps and their minimum criteria are given here (Figure 3). STEP 1 means that experiments should be validated in one species of small animals (e.g., mouse, rat or rabbit) in a single centre in an acute I/R injury model (minimum of 2 h but preferably 24 h of reperfusion). The end-point of the study should be the measurement of infarct size relative to area at risk and possibly also coronary microvascular obstruction. STEP 2 requires validation in small animal models in the presence of at least one confounder since a variety of factors (age, sex, diabetes, hypertension, dyslipidemia) and co-medications (platelet inhibitors, anesthetics, anti-diabetic drugs, statins and nitrates) might interfere with the end-points of the treatment. STEP 3 includes criteria for validation in large animal models. The importance of experiments on small animals with comorbidities and co-medications as well as on large animals have recently been underlined also by other groups (Lindsey et al., 2021; Penna et al., 2022; Ferdinandy et al., 2023; Wang et al., 2023).

Since IMPACT accepts in vivo preclinical studies only, we have checked the studies regarding cardioprotective effects of CB₂R activation and collected in Table 3. Only nine studies met the criteria of STEP 1 (Di Filippo et al., 2004; Defer et al., 2009; Montecucco et al., 2009; Wang et al., 2012; Li et al., 2013a; 2013b; Duerr et al., 2014; 2015; Liu et al., 2023) The minimum criteria of STEP 2 were partially met by two studies only. Although the latter studies were performed on diabetic and/or fatty rats after I/R (González et al., 2011) or mice after AMI (Pawar et al., 2022) changes in infarct size were not determined. Finally, studies in large animals (STEP 3) are still lacking (Figure 3).

The EU CARDIOPROTECTION COST ACTION also stresses the importance of multitarget therapies as effective tools against myocardial ischemia/reperfusion injury (Davidson et al., 2019) With respect to the multitarget CBD we have found that only four among the seven papers in Table 4 met the minimum criteria of STEP 1 (Durst et al., 2007; Walsh et al., 2010; Feng et al., 2015). Studies on small animals with comorbidities or on large animals (STEP 2 and 3, respectively) have not been performed at all (Figure 3). The article by Garberg et al. (2016) on newborn piglets undergoing global hypoxia and treated with a high dose of CBD could not be considered in our analysis since cardiac ischemia was not quantified directly in that paper.

Apart from CBD and from drugs leading to CB2 receptor activation, only the study by Lim et al. (2009), dedicated to the cardioprotector effects of the CB₁ receptor antagonist rimonabant, meets the criteria of STEP 1 and STEP 2 (Table 4).

Most of the studies in which potential cardioprotective properties of cannabinoids against I/R injury and AMI were examined took place before the IMPACT criteria were established. So, the experiments were conducted under experimental protocols in which reperfusion was not examined or, if so, was not long enough. Furthermore, compounds were administered prior to the onset of ischemia and the area of infarction was not always assessed in relation to the area at risk. Thus, the putative cardioprotective properties of cannabinoids against I/R and AMI should be re-evaluated in experiments on small animals under appropriate conditions and on large animals.

Our literature review reveals that the protocols used to induce ischemia/hypoxia and the compounds under study extremely varied. Furthermore, most experiments were conducted on healthy rodents and cannabinoids were administered once only. Therefore, we were unable to give details to (1) the best timing of (endo)cannabinoid administration, i.e., before, during or after ischemia (from the clinical perspective, the best time for treatment is after ischemia or AMI, but this time of administration had been chosen by few of the studies only); (2) the effect of (endo)cannabinoids in animals with comorbidities and under chronic drug treatment; (3) the detrimental effects of the blockade of endocannabinoid degradation since only few studies of that type had been performed (Schloss et al., 2019; Rajlic et al., 2022). Moreover, the cardioprotective effects of (endo)cannabinoids in the human heart had been examined in few studies only (Table 1). Finally, in the light of the fact that the major heart receptors, the β-ARs, are essential for adjusting the heart to ischemia-reperfusion injury, it is unsatisfactory that the cross-talk between these receptors and the cannabinoid receptors had been examined in one study only (Meeran et al., 2021).

A detailed review of all publications regarding cardiac effects of cannabinoids clearly shows that cannabinoids exert cardioprotective effects in cardiac preconditioning, I/R and AMI. Beneficial cardiac actions result mainly from the activation of CB₂Rs although positive effects of the endocannabinoid AEA, the phytocannabinoid THC and the multitarget CBD were also described. Importantly, endocannabinoid levels were enhanced in acute and chronic cardiac disorders in humans including AMI.

In 2021 the strict step-by-step criteria for Improving Preclinical Assessement of Cardioprotective Therapies (IMPACT) have been established by the EU CARDIOPROTECTION COST ACTION (Lecour et al., 2021). In our evaluation of the papers regarding the cardioprotective effects of cannabinoids in the context of various protocols and models none of the publications so far met all IMPACT criteria. Thus, additional experiments are needed to confirm the cardioprotective activities of cannabinoids on small animals with comorbidities and on large animals. One should also keep in mind that it is necessary that the infarct size be expressed in relation to the area at risk. Additionally, as a result of our review of the literature, we have been able to identify the main directions in which intensive research should be conducted in order to gain a closer understanding of the cardioprotective effects of cannabinoids. Thus, the proper moment of administration of drugs (so far generally administered before ischemia, i.e., before the moment most difficult to predict for the patient) should be identified, since early reperfusion constitutes the critical time to perform life-saving interventions (Gibson, 2001; Heusch, 2020). Moreover, one should consider the use of a new generation of CB₂Rs agonists (characterized, e.g., by a better solubility) that have shown promising results in preclinical studies related to analgesic and anti-inflammatory effects (Bryk and Starowicz, 2021; Whiting et al., 2022). With respect to the putative therapeutic application of FAAH or MAGL inhibitors (Toczek and Malinowska, 2018; Maccarrone et al., 2023) one should be particularly careful because chronic enhancement of the endocannabinoid tone caused detrimental cardiac effects in animal models (Schloss et al., 2019; Rajlic et al., 2022). Importantly, more new data regarding the cardiac endocannabinoid system in humans under pathological conditions are also needed.

Taken together, we believe that it is too early to place great hopes on the future cardioprotective application of cannabinoids (including CB₂R agonists) in myocardial ischemia. Thus, tools and methods used for further studies must be well elaborated in order to meet the current shortcomings in our knowledge regarding the cardioprotective actions of cannabinoids against I/R injury.