Potential Mechanisms by which Chronic Benzodiazepine Promotes Motoric Aging in Mice

PURPOSE Benzodiazepines (BZDs) are among the most commonly prescribed medications in elderly to treat hyperexcitatory disorders such as anxiety and insomnia. However, its high or a repeated dose is frequently administered to patients, which often provokes side effects including motoric impairment. Here, we investigated whether chronic BZD (lorazepam) age-dependently deteriorates motoric functions in mice. METHODS To decipher underlying mechanisms, we measured mitochondrial BZD-receptor (mBZD-R) and amyloid-β (Aβ) of which excess amount is associated with mitochondrial deficit and neurodegeneration. We also measured reactive oxygen species (ROS) and cell survival in HT22 cells, the cell line that has been used to determine oxidative mechanisms. Young (3 months old) and old (15 months old) mice received BZD (lorazepam, 1 mg/kg) with or without mBZD-R inhibitor (PK11195) for 4 weeks. Motoric function was tested using Rotarod; a quicker fall from rotating rod indicates a poorer motoric function. Upon humane sacrifice, cerebellum was collected to measure mBZD-R using immunoblot and amyloid-β using sandwich ELISA. Separately, HT22 cells were treated with lorazepam (0-25 µM) for 3 days. The cells were then tested for mitochondrial ROS, whole cell ROS, and cell viability using MitoSox, DCFDA, and Calcein assays, respectively. RESULTS BZD-received old mice showed poorer motoric function, increased mBZD-R, and Aβ accumulation in cerebellum more severely than old control or young-BZD mice. PK11195 injection tended to improve the motoric function of BZD mice. Chronic BZD treatment to HT22 cells showed an increase in mitochondrial ROS in a manner attenuated by PK11195 treatment and accompanied by reduced cell survival. CONCLUSIONS These data suggest that chronic BZD exacerbates the motoric deterioration in aged mice. These data also raise a possibility that a deleterious interaction between mBZD-R and mitochondrial ROS is a part of the underlying mechanistic network responsible for the motoric aging.