Infrared free electron laser-irradiated polyleucine does not exert aggregates-induced aversive effects on mouse brain

Polyglutamine (polyQ) diseases are devastating neurological disorders that cannot be effectively treated. Repeat-associated non-AUG (RAN) translation has been documented in transcripts in polyQ diseases. RAN products include proteins with polyleucine (polyL) tracts. Similar to polyQ, polyL tends to aggregate, which is toxic to cells and mice. Irradiation with a free electron laser (FEL) tuned at mid-infrared wavelengths can dissociate polyQ aggregates in cultured cells. However, whether FEL dissociates the polyL is unclear. It is also unclear whether brain dysfunction caused by polyL aggregates in mice can be ameliorated by FEL irradiated polyL. Here, we show that FEL at approximately 6 μm can destroy polyL aggregates, as evidenced by scanning electron microscopy, atomic force microscopy, and dot blot analyses. Although polyL aggregates induced low viability and aberrant morphology of cultured astrocytes, FEL irradiated polyL exhibited mild defects. Likewise, the toxicity of polyL-containing microglia in vitro was ameliorated by FEL irradiation. In vivo, mice administered polyL aggregates in the cerebellum induced loss of Purkinje cells, which was ameliorated when FEL irradiated polyL was injected. These results justify the clearing of aggregates by approaches using molecular chaperones, laser irradiation, and ultrasound as a general therapeutic strategy to correct brain dysfunction by the RAN products.