Elevated expression of TREK-TRAAK K2P channels in the retina of adult rd1 mice

AIM: To examine the expression of Twik-related K+ channel 1 (TREK-1), Twik-related K+ channel 2 (TREK-2), and Twik-related arachidonic acid-stimulated K+ channel (TRAAK) in the retina of adult rd1 mice and to detect the protective roles of TREK-TRAAK two-pore-domain K+ (K-2P) channels against retinal degeneration. METHODS: Twenty-eight-day-old C57BL/6J mice and 28-day-old rd1 mice were used in this study. Retinal protein, retinal RNA, and embedded eyeballs were prepared from these two groups of mice. Real-time quantitative polymerase chain reaction and Western blot analyses were used to assess the gene transcription and protein levels, respectively. Retinal structures were observed using hematoxylin and eosin (H&E) staining. Immunohistochemistry was utilized to observe the retinal localization of TREK-TRAAK channels. Current changes in retinal ganglion cells (RGCs) after activation of TREK-TRAAK channels were examined using a patch-clamp technique. RESULTS: Compared with C57BL/6J mice, rd1 mice exhibited significantly higher retinal mRNA and protein expression levels of TREK-1, TREK-2, and TRAAK channels. In both groups, immunohistochemistry showed expression of TREK-TRAAK channels in retinal layers. After addition of the TREK-TRAAK channel agonist arachidonic acid (AA), whole-cell voltage step evoked currents were significantly higher in RGCs from rd1 mice than in RGCs from control C57BL/6J mice, suggesting that TREK-TRAAK channels were opened in RGCs from rd1 mice. CONCLUSION: TREK-TRAAK K2P channels' expression is increased in adult rd1 mice. AA induced the opening of TREK-TRAAK K2P channels in adult rd1 mice and may thus counterbalance depolarization of RGCs and protect the retina from excitotoxicity. TREK-TRAAK channels may play a protective role against retinal degeneration.