BDNF and asthma: For example, BDNF is present in airway smooth muscle cells, and several stimuli can induce its release such as inflammatory cytokines, neurotransmitters, and sex hormones both under physiological and pathological conditions.53-55 The regulated secretion of neurotrophins in these cells is under the control of intracellular Ca2+53,55 and cAMP.56 Moreover, the Val66Met polymorphism in the BDNF gene has been linked to pathological conditions in the airways such as asthma;57,58 whether this polymorphism affects the secretion of BDNF as in neuronal cells needs further investigation.