Modulation of Mouse Corpus Cavernosum Smooth Muscle Contractility by EPAC-1 and Kv7 Channels

Thornbury, KD (2026) Modulation of Mouse Corpus Cavernosum Smooth Muscle Contractility by EPAC-1 and Kv7 Channels. Doctoral thesis, Dundalk Institute of Technology.

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Abstract

Penile erection is achieved through relaxation, via cyclic nucleotide signalling, of the corpus cavernosum smooth muscle (CCSM). Erectile dysfunction (ED) is commonly treated using phosphodiesterase-5 inhibitors (PDE5Is), such as Viagra™; however, many men are resistant to PDE5Is, underscoring the need for alternative targets. The exchange protein directly activated by cAMP (EPAC), previously unreported in mouse CCSM, is implicated in smooth muscle relaxation. Additionally, voltage-dependent K+ (Kv) channels, particularly the Kv7 family, may influence CCSM cell membrane potential and contractility. This study investigates the roles of EPAC and Kv7 channels in modulating mouse CCSM contractility. Isometric tension recordings were conducted on mouse CCSM crura, and Ca2+ imaging was performed on enzymatically-dispersed single cells loaded with Fluo-4-AM. EPAC-1 was identified as the predominant isoform, and its activation by 8-pCPT-2'-O-Me-cAMP (007-AM) markedly suppressed Ca2+ oscillations induced by 10μM phenylephrine (PE). In contrast, protein kinase A (PKA) activation had no effect but abolished oscillations induced by lower PE concentrations. Co-activation of EPAC and PKA attenuated contractile responses. Nifedipine (L-type Ca2+ channel blocker), retigabine (Kv7.2-5 activator), and Ani-9 (ANO1 blocker) abolished phasic PE-induced contractions, while tonic contractions were inhibited by blocking inositol 1,4,5-trisphosphate receptors (IP3Rs) with 2-aminoethoxydiphenyl borate or STIM/Orai channels with GSK-7975A. Kcnq5 emerged as the main Kv7 isoform. Retigabine and nifedipine suppressed spontaneous contractions and contractions and Ca2+ oscillations induced by low-concentration PE, whereas Kv7 inhibition with XE-991 enhanced these. Yet, Ca2+ oscillations induced by high-concentration PE persisted in the presence of nifedipine or retigabine. Whole-cell patch-clamp recordings in HEK- 293 cells, expressing Kv7.5 and α1A-adrenoceptors, revealed that PE inhibited Kv7.5 currents, and this effect was prevented by phentolamine in the bath or by PIP2 in the pipette. Our findings identify EPAC-1 and Kv7.5 as key modulators of CCSM contractility in mice, underscoring their potential as therapeutic targets in PDE5I-resistant ED.

Item Type:	Thesis (Doctoral)
Subjects:	Science > Biology
Research Centres:	UNSPECIFIED
Depositing User:	Keith Thornbury
Date Deposited:	11 Aug 2026 08:27
Last Modified:	11 Aug 2026 08:27
URI:	https://eprints.dkit.ie/id/eprint/1055

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