Photobiomodulation therapy alleviates repeated closed head injury‐induced anxiety‐like behaviors

Repeated closed head injury (rCHI) is one of the most common brain injuries. Although extensive studies have focused on how to treat rCHI‐induced brain injury and reduce the possibility of developing memory deficits, the prevention of rCHI‐induced anxiety has received little research attention. The current study was designed to assess the effects of photobiomodulation (PBM) therapy in preventing anxiety following rCHI. The rCHI disease model was constructed by administering three repeated closed‐head injuries within an interval 5 days. 2‐min daily PBM therapy using an 808 nm continuous wave laser at 350 mW/cm2 on the scalp was implemented for 20 days. We found that PBM significantly ameliorated rCHII‐induced anxiety‐like behaviors, neuronal apoptosis, neuronal injury, promotes astrocyte/microglial polarization to anti‐inflammatory phenotype, preserves mitochondrial fusion‐related protein MFN2, attenuates the elevated mitochondrial fission‐related protein DRP1, and mitigates neuronal senescence. We concluded that PBM therapy possesses great potential in preventing anxiety following rCHI. PBM therapy promotes glial cell polarization toward the neuroprotective A2/M2 phenotype, preserves mitochondrial dynamics, alleviates secondary injury and neuronal senescence, and produces anxiolytic effects.