The potential of cannabinoids and inhibitors of endocannabinoid degradation in respiratory diseases.

The global incidence of respiratory diseases and complications is increasing. Therefore, new methods of treatment, as well as prevention, need to be investigated. A group of compounds that should be considered for use in respiratory diseases is cannabinoids. There are three groups of cannabinoids - plant-derived phytocannabinoids, synthetic cannabinoids, and endogenous endocannabinoids including the enzymes responsible for their synthesis and degradation. All cannabinoids exert their biological effects through either type 1 cannabinoid receptors (CB1) and/or type 2 cannabinoid receptors (CB2). In numerous studies (in vitro and in vivo), cannabinoids and inhibitors of endocannabinoid degradation have shown beneficial anti-inflammatory, antioxidant, anti-cancer, and anti-fibrotic properties. Although in the respiratory system, most of the studies have focused on the positive properties of cannabinoids and inhibitors of endocannabinoid degradation. There are few research reports discussing the negative impact of these compounds. This review summarizes the properties and mechanisms of action of cannabinoids and inhibitors of endocannabinoid degradation in various models of respiratory diseases. A short description of the effects selected cannabinoids have on the human respiratory system and their possible use in the fight against COVID-19 is also presented. Additionally, a brief summary is provided of cannabinoid receptors properties and their expression in the respiratory system and cells of the immune system.

Opportunities, Challenges and Pitfalls of Using Cannabidiol as an Adjuvant Drug in COVID-19.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection may lead to coronavirus disease 2019 (COVID-19) which, in turn, may be associated with multiple organ dysfunction. In this review, we present advantages and disadvantages of cannabidiol (CBD), a non-intoxicating phytocannabinoid from the cannabis plant, as a potential agent for the treatment of COVID-19. CBD has been shown to downregulate proteins responsible for viral entry and to inhibit SARS-CoV-2 replication. Preclinical studies have demonstrated its effectiveness against diseases of the respiratory system as well as its cardioprotective, nephroprotective, hepatoprotective, neuroprotective and anti-convulsant properties, that is, effects that may be beneficial for COVID-19. Only the latter two properties have been demonstrated in clinical studies, which also revealed anxiolytic and antinociceptive effects of CBD (given alone or together with Δ9-tetrahydrocannabinol), which may be important for an adjuvant treatment to improve the quality of life in patients with COVID-19 and to limit post-traumatic stress symptoms. However, one should be aware of side effects of CBD (which are rarely serious), drug interactions (also extending to drugs acting against COVID-19) and the proper route of its administration (vaping may be dangerous). Clearly, further clinical studies are necessary to prove the suitability of CBD for the treatment of COVID-19.