1. INTRODUCTION
Cannabis is the most widely used illicit substance worldwide, and both the use and misuse of this substance is increasing in many countries. In Europe, the lifetime prevalence of cannabis use is about five times higher than that of other illicit substances. Many concerns have been raised regarding the adverse effects of cannabis use during adolescence, with suggestions that it may lead to the development of substance use disorders or mental disorders, such as psychosis, depression, bipolar disorder or anxiety (Campeny et al., 2020). However, there is data arguing that cannabis is a safe and natural alternative for the treatment of a variety of medical and mental health conditions (Maccarrone et al., 2017). Thus, one of the outstanding challenges is to define the neuropathological mechanisms specifically altered by cannabis that may trigger psychiatric conditions in vulnerable populations. Unfortunately, despite the enormous amount of information coming from animal models, genetic and human neuroimaging data (Szutorisz and Hurd, 2016; Bloomfield et al., 2019), there is still an important lack of information from human neuronal tissue and live cells that addresses the effects of cannabis in the nervous system.
In adulthood, the differentiation of precursor cells into neurons continues in several brain structures and in some peripheral tissue, such as the olfactory neuroepithelium (ON). In the ON, olfactory sensory neurons are continually regenerated throughout life from stem or progenitor cells by neurogenesis, these populations located at the apical and basal membranes (Leung et al., 2007). Thus, the ON contains multipotent cells that can proliferate in vitro and that can differentiate into multiple cell types, including neurons and glia (Matigian et al., 2010). As they can be easily collected through nasal brushing, several studies have demonstrated the utility of the ON as a surrogate tissue to investigate disease related events that affect neurons in the brain. For example, cells isolated from the ON have been used to study the molecular profiles associated with such disease states, showing alterations in cell signalling pathways involved in cell proliferation, neurogenesis and cell adhesion in schizophrenia (Feron et al., 1999; McCurdy et al., 2006). In bipolar disorder, the cell death of ON cells is enhanced, and these cells display alterations of the cytoskeleton and in cell migration (McCurdy et al., 2006; Solis-Chagoyan et al., 2013; Munoz-Estrada et al., 2015). In the field of cannabis, we previously showed that ON cells obtained from cannabis users exhibit changes in the cannabinoid CB1 receptor, and in serotonin 2A receptor heteromer expression and function, both of which were associated with cognitive performance (Galindo et al., 2018). Furthermore, the macromolecular profile of ON cells is also altered in cannabis users, these cells displaying a modified lipid composition, as well as an increase in DNA and histone methylation (Saladrigas-Manjon et al., 2020).
We now explore the effect of prolonged cannabis use on protein expression in ON cells in the belief that this may provide novel insights into the cellular processes that are deregulated by cannabis consumption, events that may be related with neuropsychiatric disorders. We examined alterations in relevant cellular processes, and adopted a label-free proteomic approach to identify potential changes in functional pathways in ON cells as result of prolonged cannabis consumption.
2. MATERIALS AND METHODS