Low-level lighy therapy (LLLT) using red or near-infrared light is generally used clinically for patients suffering from various diseases. LLLT is known to stimulate, treat, regenerate and protect the dying tissue that has been damaged or degenerated. Photomodulation using low-level light emitting diode (LED) therapy has been widely used to treat neuropsychiatric disorders. However, the effect of photomodulation using LED on the status epilepticus has been unknown. Status epilepticus is the serious neurological diseases caused by the abnormal electrical activity, leading to severe and widespread cell damage in the brain. Pharmacological models include kainic acid and pilocarpine that induced synapse loss and subsequent neuronal death in cultured rat hippocampal neurons. In this study, we investigated the effect of LLLT at 660 nm on status epilepticus-induced synapse loss of cultured rat hippocampal neurons. The optimum energy irradiation in cell viability experiments using PC12 cells was estimated to be 30 Joules. Synaptic activity of neurons was measured by quantifying green fluorescence intensity expressing postsynaptic density 95 (PSD95), which is widely used as a marker of excitatory postsynaptic sites. As a result, LLLT at 660 nm showed synapto-protective effect on both kainic acid and pilocarpine-induced synapse loss. Furthermore, LLLT prevented neuronal death caused by kainic acid or pilocarpine. These studies indicate that LLLT has synapto-protective effects at early phase of status epilepticus via distinct mechanism. These results suggest that photomodulation using LLLT at 660 nm can be useful for preventing neurodegenerative diseases, especially status epilepticus.
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