Differential neuroprotective and anti-inflammatory effects of dimethyl fumarate, monomethyl fumarate and cannabidiol in neurons and microglia
Dimethyl fumarate (DMF) is an immunomodulatory treatment for multiple sclerosis (MS) that can cross the blood-brain barrier, presenting neuroprotective potential. Its mechanism of action is not fully understood and there is a need to characterize if DMF or its bioactive metabolite monomethyl fumarate (MMF) exert neuroprotective properties. The combination of adjuvant agents such as cannabidiol (CBD) could be relevant to enhance neuroprotection. The aim of this study was to compare the effects of DMF, MMF and CBD on neuroprotective and immunomodulatory pathways in neurons and microglia in vitro. We found that DMF and CBD, but not MMF, activated the Nrf2 antioxidant pathway in neurons. Similarly, only DMF and CBD, but not MMF, prevented the LPS-induced activation of the inflammatory pathway NF-kB in microglia. However, the 3 drugs inhibited the production of nitric oxide in microglia and protected neurons against apoptosis. Transcriptomically, DMF, MMF and CBD exhibited differential effects on these pathways, with DMF achieving the most pronounced changes.  Our results show that DMF and MMF, despite being structurally related, present differences in their mechanisms of action that could be relevant for the achievement of neuroprotection in MS patients and the potential of CBD as an adjuvant therapy in neuroprotection. Overall design: We treated primary hippocampal neurons with DMF, MMF or CBD and their respective vehicles (DMSO for DMF and MMF, EtOH for CBD) for 4 and 24 hours, to compare the transcriptomic changes induced by each drug. We carried out 3 independent experiments