Endocannabinoid anandamide mediates hypoxic pulmonary vasoconstriction

Abstract

Endocannabinoids are important regulators of organ homeostasis. Although their role in systemic vasculature has been extensively studied, their impact on pulmonary vessels remains less clear. Herein, we show that the endocannabinoid anandamide (AEA) is a key mediator of hypoxic pulmonary vasoconstriction (HPV) via fatty acid amide hydrolase (FAAH)-dependent metabolites. This is underscored by the prominent vasoconstrictive effect of AEA on pulmonary arteries and strongly reduced HPV in FAAH −/− mice and wild-type mice upon pharmacological treatment with FAAH inhibitor URB597. In addition, mass spectrometry measurements revealed a clear increase of AEA and the FAAH-dependent metabolite arachidonic acid in hypoxic lungs of wild-type mice. We have identified pulmonary vascular smooth muscle cells as the source responsible for hypoxia-induced AEA generation. Moreover, either FAAH −/− mice or wild-type mice treated with FAAH inhibitor URB597 are protected against hypoxia-induced pulmonary hypertension and the concomitant vascular remodeling in the lung. Thus, the AEA/ FAAH pathway is an important mediator of HPV and is involved in the generation of pulmonary hypertension. pulmonary vascular tone | cannabinoid E ndocannabinoids have been shown to induce vasorelaxation in systemic vessels which is primarily mediated by the specific cannabinoid 1 and 2 (CB1/CB2) and also other G protein-coupled receptors (e.g., non-CB1/CB2 receptors) (1, 2). Based on these results, especially CB1 receptors have been proposed as promising therapeutic targets for the treatment of arterial hypertension (2). Endocannabinoids are also known to potentially act via their intracellular enzymatic metabolization by the fatty acid amide hydrolase (FAAH) or monoacylglycerol lipase (MAGL) to (vaso)active intermediates (3, 4), but these pathways are considered less important for the regulation of vascular tone in systemic vessels.Pulmonary arteries are unique because of their prominent vasoconstriction in response to hypoxia. Hypoxic vasoconstriction is responsible for adapting perfusion to ventilation in the lungs and therefore also plays an important role in pathophysiological situations characterized by a high ventilation/perfusion mismatch such as acute lung injury or liver cirrhosis (5, 6). In addition, this mechanism potentially contributes to the onset of pulmonary hypertension in response to hypoxia occurring in high altitude or in various respiratory diseases such as chronic obstructive pulmonary disease or fibrosis (7-9). Pulmonary arterial smooth muscle cells are suggested to play a major role in hypoxic vasoconstriction (10), but the precise mechanisms and the underlying signals are still not well understood. Earlier experimental evidence suggested that the endocannabinoid anandamide (AEA) can either enhance (11) or reduce (12) pulmonary arterial tone, and this prompted us to reexplore the role of endocannabinoids in basic physiological and pathophysiological responses of pulmonary arteries using experimental in vitro, ex vivo, and in viv...

Inhibition of FAAH reduces nitroglycerin-induced migraine-like pain and trigeminal neuronal hyperactivity in mice

“…However, we believe that this is not likely to be the case, because exogenously administered AEA rescued the acute hyperalgesia in same animal model of migraine pain (Greco et al, 2010). Furthermore, at least in pulmonary arteries, FAAH-dependent AEA metabolites produce a vasoconstrictive response (Wenzel et al, 2013), which would counteract the vasodilatory response to NTG. Rather, we feel that the effects are best explained by an increased CB1 tone through elevated AEA levels.…”

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“…An experimental study postulated an antifibrotic role for the CB2 receptor in a model of liver fibrosis [15]. Also, the endocannabinoid anandamide has been associated with the regulation of pulmonary vascular resistance [16]. Furthermore, the CB2 receptor acts in cardioprotective manner and influences myocardial remodeling in a murine model of ischemic cardiomyopathy [17].…”