ABSTRACT
Objective: To construct stable cell lines expressing the large conductance Ca2+-activated K+ channel (MaxiK or BK) α-subunit and to explore the mechanism of potassium excretion via BKα channel. Methods:The BKα plasmid with Myc tag was constructed and transfected into HEK293 cell lines by lipofectamine 2000. The positive monoclonal cell lines were screened by G418, and the expression of BKα was detected by Western blotting and the location of BKα by immunofluorescence. The stable cell lines expressing BKα protein was cultured on slides to form a single cell layer, which was perfused with different potassium ion concentrations of 5 mmol/L and 100 mmol/L, and the single channel patch clamp recorded the ion flux of BKα. Wild type and mutants (G77R, G130R, C140R and R297C) of the inwardly rectifying potassium channel (Kir4.1) were transfected into HEK293 cells stably transfected with BKα, and then the membrane protein was extracted. The expression of BKα was detected by Western blotting. Results:Stable cell lines expressing BKα channel were selected from HEK293 cells after transfection and cellular immunofluorescence verified the expression of BKα channel and its expression on the cell membrane. The channel open frequency (Npo) of BKα increased rapidly when perfused with 100 mmol/L potassium. After being transfected with wild type or mutants of Kir4.1, the membrane expression of BKα in the stable cell lines showed significant difference among these groups (P<0.05). Conclusion:The HEK293 cell lines stably expressing BKα have been successfully constructed. BKα channel can be activated by high potassium solutions. The function of the BKα subunit can be related to Kir4.1 channel, which may be attributed to the depolarization of the cells transfected by Kir4.1 mutants.
ABSTRACT
@#Müller cells are the most important glial cells in the vertebrate retina. They extend from the inner limiting membrane to the outer membrane through the entire retina, participate in the blood-retinal barrier, and actively participate in retinal development and promote the maintenance of retinal homeostasis through many intracellular mechanisms. Müller cells play an important role in the development of diabetic retinopathy. The pathophysiological changes in diabetic retinopathy remain to be further studied. This article reviews the pathophysiological changes of Müller cells in diabetic retinopathy and the recent research progress.
ABSTRACT
Objective To evaluate the effect of adenosine receptor antagonist SCH442416 on the expression of Kir2.1,Kir4.1 and TASK-1 in rat Müller cell at an elevated hydrostatic pressure in vitro.Methods Thirty SPF Sprague Dawley rats were purchased from Shanghai Slack Laboratory Animals Ltd.Cultured Müller cells were divided into normal control group (n =6),40 mmHg/24 hours (1 mmHg =0.133 kPa) group (n =6) and adenosine + SCH442416 intervention group (n =6).Müller cells were treated with 40 mmHg pressure for 24 hours in 40 mmHg/24 hours group,and Müller cells were treated with 40 mmHg pressure for 24 hours + 10 μ mol/L adenosine + 100 nmol/L SCH442416 in adenosine + SCH442416 intervention group.The real-time PCR,Western blot,whole-cell patch-clamp recordings and immunohistochemistry were used to detect Kir2.1,Kir4.1 and TASK-1 expression and Müller cells Kir currents.The experimental procedures were in accordance with the National Institutes of Health (NIH) guidelines for the Care and Use of Laboratory,and follow the 3R principle.Results Western blot assay showed that,following 40 mmHg pressure cultured for 24 hours,the expression of Kir4.1 and TASK-1 protein in Müller cell were significantly decreased by 38.6％ and 52.6％ compared with the normal control group,with significant differences between the two groups (both at P =0.000);Kir2.1 protein expression decreased by 14.7％,with insignificant difference between the two groups (P =0.082).Kir4.1 and TASK protein expression in adenosine + SCH442416 intervention group was increased by 60.7％ and 61.4％ compared with the 40 mmHg/24 hours group,with significant differences between the two groups (both at P =0.000);Kir2.1 protein expression in adenosine + SCH442416 intervention group was increased by 8.8％ compared with the 40 mmHg/24 hours group,with insignificant difference between them (P =0.354).Real-time PCR assay showed that,following 40 mmHg pressure cultured for 24 hours,Kir2.1,Kir4.1 and TASK-1 mRNA expression in Müller cells were significantly decreased compared with the normal control group,with significant differences between the two groups (P =0.047,0.001,0.000);Kir4.1 and TASK-1 mRNA expression in Müller cells in the adenosine + SCH442416 intervention group was significantly increased compared with the 40 mmHg/24 hours group,with significant differences between the two groups (P =0.038,0.030);however,there is no significant change in Kir2.1 mRNA expression (P =0.612).Conclusions SCH442416 upregulates the expression of Kir4.1 and TASK-1 mRNA and protein,but weakly affects the expression of Kir2.1.