Erectile Dysfunction and Altered Contribution of KCa1.1 and KCa2.3 Channels in the Penile Tissue of Type-2 Diabetic db/db Mice

Abstract

Background 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. Aim We hypothesized that in type-2 diabetic mice, the function of KCa2.3 and KCa1.1 channels is impaired in erectile tissue. Methods Erectile function was measured, and corpus cavernosum strips were mounted for functional studies and processed for qPCR and immunoblotting. Outcomes Effects of type 2 diabetes on erectile function, expression and function of calcium-activated potassium channels. Results 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. Clinical Translation 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. Conclusion 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.

A novel reuptake inhibitor, IP2015, induces erection by increasing central dopamine and peripheral nitric oxide release

“…To further investigate the effects of IP2015 in a simple model of erectile dysfunction, before dissecting its underlying pharmacology in vivo, we assessed its effects in db/db mice, a model of Type 2 diabetes. The db/db mice have decreased erectile function compared with normal C57BL/6 mice and heterozygous db/+ control mice (Comerma‐Steffensen et al, 2022). Infusion of IP2015 (1 mg·kg −1 ) in diabetic db/db mice significantly increased the frequency, duration and magnitude of erectile responses (Figure 2h–j).…”

“…Erectile dysfunction occurs in 46% of men with Type 2 diabetes (Gratzke et al, 2010). Type 2 diabetic db/db mice have the most severe erectile dysfunction compared with heterozygous control and normal C57BL/6 mice (Comerma‐Steffensen et al, 2022). Our findings that IP2015 could induce erectile responses reflected by increases in intracavernosal pressure and duration in diabetic mice suggest that IP2015 may improve erectile function in diabetic patients.…”

“…The surgery was non‐recovery with a duration of approximately 3 h, and the anaesthetized animals were killed by cutting the carotid artery at the end of the experiment. Surgical technique and placement of systemic and corporeal pressure monitoring catheters for in vivo erectile physiology studies were performed as previously described for rats and mice (Comerma‐Steffensen et al, 2022; Kun et al, 2009). Briefly, rats were anaesthetized with buffered pentobarbital sodium (Sygehus Apoteket, Aarhus, Denmark; 50 mg·kg −1 ) given intraperitoneally.…”

A review of experimental techniques for erectile function researches and development of medical technology using animal erectile dysfunction models in sexual and reproductive medicine

“…41 Due to abnormalities in leptin, the hormone that causes a feeling of fullness, Zucker Fatty rats, Otsuka Long-Evans Tokushima Fatty (OLETF) rats, db/db mice, and nonobese type 2 diabetes model Gotoh-Kakizaki (GK) rats were used in sexual function studies. [42][43][44][45] It has been reported that these animals are affected by ED.…”

“…Additionally, animal models of type 2 diabetes have been created by rearing animals on a diet containing high amounts of carbohydrates and lipids 41 . Due to abnormalities in leptin, the hormone that causes a feeling of fullness, Zucker Fatty rats, Otsuka Long‐Evans Tokushima Fatty (OLETF) rats, db/db mice, and nonobese type 2 diabetes model Gotoh‐Kakizaki (GK) rats were used in sexual function studies 42–45 . It has been reported that these animals are affected by ED.…”