Abstract

Disturbances in mitochondrial biogenesis and bioenergetics, combined with neuroinflammation, play cardinal roles in the cognitive impairment during aging that is further exacerbated by transient cerebral ischemia. Both near-infrared (NIR) photobiomodulation (PBM) and Coenzyme Q10 (CoQ10) administration are known to stimulate mitochondrial electron transport that potentially may reverse the effects of cerebral ischemia in aged animals. We tested the hypothesis that the effects of PBM and CoQ10, separately or in combination, improve cognition in a mouse model of transient cerebral ischemia superimposed on a model of aging. We modeled aging by 6-week administration of D-galactose (500 mg/kg subcutaneous) to mice. We subsequently induced transient cerebral ischemia by bilateral occlusion of the common carotid artery (BCCAO). We treated the mice with PBM (810 nm transcranial laser) or CoQ10 (500 mg/kg by gavage), or both, for 2 weeks after surgery. We assessed cognitive function by the Barnes and Lashley III mazes and the What-Where-Which (WWWhich) task. PBM or CoQ10, and both, improved spatial and episodic memory in the mice. Separately and together, the treatments lowered reactive oxygen species and raised ATP and general mitochondrial activity as well as biomarkers of mitochondrial biogenesis, including SIRT1, PGC-1α, NRF1, and TFAM. Neuroinflammatory responsiveness declined, as indicated by decreased iNOS, TNF-α, and IL-1β levels with the PBM and CoQ10 treatments. Collectively, the findings of this preclinical study imply that the procognitive effects of NIR PBM and CoQ10 treatments, separately or in combination, are beneficial in a model of transient global brain ischemia superimposed on a model of aging in mice.

Highlights

  • Aging is a multifactorial process characterized by progressive decline of physiological functions and potential development of a wide array of diseases (López-Otín et al, 2013)

  • We designed the experiments to answer two main questions: Did the cerebral ischemia further exacerbate the effects of artificial aging, and did one or more of three hypothetically beneficial interventions reverse the effects of the aging exacerbated by ischemia? The design of the interventions yielded the assessments below, as applied to each group of mice

  • The one-way ANOVA followed by Tukey test showed that artificially aged (AA) mice delayed the finding of the escape box on the 2nd (p < 0.05), 3rd (p < 0.01), and 4th (p < 0.05) day

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Summary

Introduction

Aging is a multifactorial process characterized by progressive decline of physiological functions and potential development of a wide array of diseases (López-Otín et al, 2013). We modeled natural aging by chronic administration of D-galactose to rodents. D-galactose is a reducing hexose sugar that enters the brain and reacts with many cellular components at high concentration, producing oxidative damage to lipids and DNA (Ho et al, 2003; Sadigh-Eteghad et al, 2017). The chronic D-galactose treatment induces changes that resemble natural aging and mimics several characteristics of brain aging (Wei et al, 2005; Sadigh-Eteghad et al, 2017). The administration to rodents has been shown to cause neurocognitive impairments, including memory deficits, increased inflammatory responses and mitochondrial dysfunction (Shan et al, 2009; SadighEteghad et al, 2017; Salehpour et al, 2017)

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