BDNF and Alzheimer disease: Owing to the important contribution of adenosine pathways to blood-brain-barrier permeability (Kim and Bynoe, 2015), physiological plasticity, neurotrophin actions (Rebola et al., 2008; Jerónimo-Santos et al., 2014) or even to the peripheral adaptive immune system lastly recognized as playing an important role in AD (Linden and Cekic, 2012; Antonioli et al., 2013; Laurent et al., 2018), careful investigations on processes underlying beneficial effects and potential side effects are warranted.