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+(K2P) 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 patchclamp 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.
AIM: To investigate the expression of TWIK-related arachidonic acid-stimulated K+ channel(TRAAK) in retinal degeneration mice(rd1) and further evaluate how TRAAK affect photoreceptor cell apoptosis.METHODS: The rd1 mice were distributed into blank(no treatment), control(1.4% DMSO, intraperitoneal injection) and riluzole groups(4 mg/kg·d, intraperitoneal injection) from postnatal 7 d to 10, 14 and 18 d;C57 group(no treatment), as age-matched wild-type control. The thickness of the outer nuclear layer(ONL) of retina was detected by paraffin section hematoxylin and eosin staining. The expression of TRAAK and the apoptosis of the ONL cells were detected by immunostaining, Western blotting, and real-time polymerase chain reaction. RESULTS: The channel agonist riluzole activated TRAAK and delayed the apoptosis of photoreceptor cells in ONL layer of rd1 mice. Both at mRNA and protein levels, after riluzole treatment, TRAAK expression was significantly upregulated, when compared with the control and blank group. Then we detected a series of apoptosis related mRNA and protein. The anti-apoptotic factor Bcl-2 downregulated and the pro-apoptotic factors Bax and cleaved-caspase-3 upregulated significantly. CONCLUSION: Riluzole elevates the expression of TRAAK and inhibits the development of apoptosis. Activation of TRAAK may have some potential effects to put off photoreceptor apoptosis.
Lei WangKang-Pei ShiHan LiHao HuangWen-Bin WuChu-Sheng CaiXiao-Tong ZhangXiao-Bo Zhu
