In the United States, 31 states, the District of Columbia, Puerto Rico, and Guam have legalized medical marijuana, which is also permitted for recreational use in 9 states, as well as in the District of Columbia. However, marijuana, derived from Cannabis sativa and Cannabis indica, is regulated as a schedule I drug in the United States at the federal level. (Some believe that the federal status may change in the coming year as a result of the Democratic Party’s takeover in the House of Representatives.1)
Cannabis species contain hundreds of various substances, of which the cannabinoids are the most studied. More than 113 biologically active chemical compounds are found within the class of cannabinoids and their derivatives,2 which have been used for centuries in natural medicine.3 The legal status of marijuana has long hampered scientific research of cannabinoids. Nevertheless, the number of studies focusing on the therapeutic potential of these compounds has steadily risen as the legal landscape of marijuana has evolved.
Findings over the last 20 years have shown that cannabinoids present in C. sativa exhibit anti-inflammatory activity and suppress the proliferation of multiple tumorigenic cell lines, some of which are moderated through cannabinoid (CB) receptors.4 In addition to anti-inflammatory properties, .3 Recent research has demonstrated that CB receptors are present in human skin.4
The endocannabinoid system has emerged as an intriguing area of research, as we’ve come to learn about its convoluted role in human anatomy and health. It features a pervasive network of endogenous ligands, enzymes, and receptors, which exogenous substances (including phytocannabinoids and synthetic cannabinoids) can activate.5 Data from recent studies indicate that the endocannabinoid system plays a significant role in cutaneous homeostasis, as it regulates proliferation, differentiation, and inflammatory mediator release.5 Further, psoriasis, atopic dermatitis, pruritus, and wound healing have been identified in recent research as cutaneous concerns in which the use of cannabinoids may be of benefit.6,7 We must also consider reports that cannabinoids can slow human hair growth and that some constituents may spur the synthesis of pro-inflammatory cytokines.8,9This column will briefly address potential confusion over the psychoactive aspects of cannabis, which are related to particular constituents of cannabis and specific CB receptors, and focus on the endocannabinoid system.
Psychoactive or not?
C. sativa confers biological activity through its influence on the G-protein-coupled receptor types CB1 and CB2,10 which pervade human skin epithelium.11 CB1 receptors are found in greatest supply in the central nervous system, especially the basal ganglia, cerebellum, hippocampus, and prefrontal cortex, where their activation yields psychoactivity.2,5,12,13 Stimulation of CB1 receptors in the skin – where they are present in differentiated keratinocytes, hair follicle cells, immune cells, sebaceous glands, and sensory neurons14 – diminishes pain and pruritus, controls keratinocyte differentiation and proliferation, inhibits hair follicle growth, and regulates the release of damage-induced keratins and inflammatory mediators to maintain cutaneous homeostasis.11,14,15
CB2 receptors are expressed in the immune system, particularly monocytes, macrophages, as well as B and T cells, and in peripheral tissues including the spleen, tonsils, thymus gland, bone, and, notably, the skin.2,16 Stimulation of CB2 receptors in the skin – where they are found in keratinocytes, immune cells, sebaceous glands, and sensory neurons – fosters sebum production, regulates pain sensation, hinders keratinocyte differentiation and proliferation, and suppresses cutaneous inflammatory responses.14,15
The best known, or most notorious, component of exogenous cannabinoids is delta9-tetrahydrocannabinol (delta9-THC or simply THC), which is a natural psychoactive constituent in marijuana.3 In fact, of the five primary cannabinoids derived from marijuana, including cannabidiol (CBD), cannabichromene (CBC), cannabigerol (CBG), cannabinol (CBN), and THC, only THC imparts psychoactive effects.17
CBD is thought to exhibit anti-inflammatory and analgesic activities.18 THC has been found to have the capacity to induce cancer cell apoptosis and block angiogenesis,19 and is thought to have immunomodulatory potential, partly acting through the G-protein-coupled CB1 and CB2 receptors but also yielding effects not related to these receptors.20In a 2014 survey of medical cannabis users, a statistically significant preference for C. indica (which contains higher CBD and lower THC levels) was observed for pain management, sedation, and sleep, while C. sativa was associated with euphoria and improving energy.21