Department of Biomedicine, Aarhus University, Aarhus, Denmark.
Department of Biomedical Sciences/Animal Physiology, Veterinary Faculty, Central University of Venezuela, Maracay, Aragua, Venezuela.
J Sex Med. 2022 May 1;19(5):697-710. doi: 10.1016/j.jsxm.2022.02.021.
Activation of endothelial small conductance calcium-activated K+ channels (KCa2.3) and intermediate conductance calcium-activated K+ channels (KCa3.1) leads to vascular relaxation. We found endothelial KCa2.3 down-regulation in the corpus cavernosum diminishes erectile function.
We hypothesized that in type-2 diabetic mice, the function of KCa2.3 and KCa1.1 channels is impaired in erectile tissue.
Erectile function was measured, and corpus cavernosum strips were mounted for functional studies and processed for qPCR and immunoblotting.
Effects of type 2 diabetes on erectile function, expression and function of calcium-activated potassium channels.
In anesthetized diabetic db/db mice, erectile function was markedly decreased compared to non-diabetic heterozygous db/+ mice, and the impairment was even more pronounced compared to normal C57BL/6 mice. qPCR revealed KCa2.3 and KCa1.1α channel expressions were upregulated in corpus cavernosum from db/db mice. Immunoblotting showed down-regulation of KCa2.3 channels in the corpus cavernosum from db/db mice. Acetylcholine relaxations were impaired while relaxations induced by the nitric oxide, donor SNP were unaltered in corpus cavernosum from db/db compared to C57BL/6 and db/+ mice. Apamin, a blocker of KCa2 channels, inhibited acetylcholine relaxation in corpus cavernosum from all experimental groups. In the presence of apamin, acetylcholine relaxation was markedly decreased in corpus cavernosum from db/db vs C57BL/6 and db/+ mice. An opener of KCa2 and KCa3.1 channels, NS309, potentiated acetylcholine relaxations in corpus cavernosum from db/+ and db/db mice. Iberiotoxin, a blocker of KCa1.1 channels, inhibited acetylcholine relaxation in corpus cavernosum from db/+ mice, while there was no effect in tissue from db/db mice.
Erectile function in diabetic db/db mice was severely affected compared to heterozygous and control mice, findings suggesting the non-diabetic db/+ and diabetic db/db mice for translational purpose can be used for drug testing on, respectively, moderate and severe erectile dysfunction. The altered expressions and impaired acetylcholine relaxation in the presence of apamin compared to C57BL/6 mice may suggest decreased KCa1.1 channel function may underpin impaired endothelium-dependent relaxation and erectile dysfunction in diabetic db/db mice.
STRENGTHS & LIMITATIONS: The present study provides a mouse model for type 2 diabetes to test moderate and severe erectile dysfunction drugs. Decreased KCa1.1 channel function contributes to erectile dysfunction, and it is a limitation that it is not supported by electrophysiological measurements.
Our results suggest that the contribution of iberiotoxin-sensitive KCa1.1 channels to relaxation is reduced in the corpus cavernosum, while apamin-sensitive KCa2.3 channels appear upregulated. The impaired KCa1.1 channel function may contribute to the impaired erectile function in diabetic db/db mice.
内皮细胞小电导钙激活钾通道（KCa2.3）和中电导钙激活钾通道（KCa3.1）的激活导致血管松弛。我们发现，海绵体组织中内皮细胞 KCa2.3 的下调会降低勃起功能。
我们假设在 2 型糖尿病小鼠中，KCa2.3 和 KCa1.1 通道的功能在勃起组织中受损。
测量勃起功能，并对海绵体组织进行功能研究，进行 qPCR 和免疫印迹。
在麻醉的糖尿病 db/db 小鼠中，与非糖尿病杂合子 db/+ 小鼠相比，勃起功能明显下降，与正常 C57BL/6 小鼠相比，这种损伤更为明显。qPCR 显示 db/db 小鼠海绵体中 KCa2.3 和 KCa1.1α 通道的表达上调。免疫印迹显示 db/db 小鼠海绵体中 KCa2.3 通道下调。与 C57BL/6 和 db/+ 小鼠相比，乙酰胆碱松弛受损，而由一氧化氮供体 SNP 诱导的松弛不受影响。Apamin，一种 KCa2 通道阻断剂，抑制所有实验组海绵体的乙酰胆碱松弛。在存在 Apamin 的情况下，db/db 小鼠的海绵体乙酰胆碱松弛明显减少。KCa2 和 KCa3.1 通道的 opener NS309 增强了 db/+ 和 db/db 小鼠海绵体的乙酰胆碱松弛。Iberiotoxin，一种 KCa1.1 通道阻断剂，抑制 db/+ 小鼠海绵体的乙酰胆碱松弛，而 db/db 小鼠的组织无影响。
与杂合子和对照组相比，糖尿病 db/db 小鼠的勃起功能受到严重影响，这表明非糖尿病 db/+ 和糖尿病 db/db 小鼠可分别用于中度和重度勃起功能障碍药物的转化研究。与 C57BL/6 小鼠相比，存在 Apamin 时的改变表达和乙酰胆碱松弛受损可能表明 KCa1.1 通道功能的降低可能是糖尿病 db/db 小鼠内皮依赖性松弛和勃起功能障碍的基础。
本研究提供了 2 型糖尿病的小鼠模型，用于测试中度和重度勃起功能障碍药物。减少的 KCa1.1 通道功能有助于勃起功能障碍，这是一个限制，它没有得到电生理测量的支持。
我们的结果表明，在海绵体中，Iberiotoxin 敏感的 KCa1.1 通道对松弛的贡献减少，而 Apamin 敏感的 KCa2.3 通道似乎上调。受损的 KCa1.1 通道功能可能导致糖尿病 db/db 小鼠勃起功能障碍。
