Cyclophosphamide-induced HCN1 channel upregulation in interstitial Cajal-like cells leads to bladder hyperactivity in mice

Abstract

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are confirmed to be expressed in bladder interstitial Cajal-like cells (ICC-LCs), but little is known about their possible role in cystitis-associated bladder dysfunction. The present study aimed to determine the functional role of HCN channels in regulating bladder function under inflammatory conditions. Sixty female wild-type C57BL/6J mice and sixty female HCN1-knockout mice were randomly assigned to experimental and control groups, respectively. Cyclophosphamide (CYP)-induced cystitis models were successfully established in these mice. CYP treatment significantly enhanced HCN channel protein expression and Ih density and significantly altered bladder HCN1 channel regulatory proteins. Carbachol (CCH) and forskolin (FSK) exerted significant effects on bladder ICC-LC [Ca2+]i in CYP-treated wild-type (WT) mice, and HCN1 channel ablation significantly decreased the effects of CCH and FSK on bladder ICC-LC [Ca2+]i in both naive and CYP-treated mice. CYP treatment significantly potentiated the spontaneous contractions and CCH (0.001–10 μM)-induced phasic contractions of detrusor strips, and HCN1 channel deletion significantly abated such effects. Finally, we demonstrated that the development of CYP-induced bladder overactivity was reversed in HCN1−/− mice. Taken together, our results suggest that CYP-induced enhancements of HCN1 channel expression and function in bladder ICC-LCs are essential for cystitis-associated bladder hyperactivity development, indicating that the HCN1 channel may be a novel therapeutic target for managing bladder hyperactivity.

Hyperpolarization-Activated Cyclic Nucleotide-Gated Non-selective (HCN) Ion Channels Regulate Human and Murine Urinary Bladder Contractility

“…With respect to the isoform, our data on HCN1 knock-out mice revealed that phasic contractions presented with higher contraction amplitudes compared to wildtype mice, but the increased tonic contraction in the presence of ZD7288 was not altered in HCN1-deficient mice. This supports the view that HCN1 may be a major HCN channel subtype on ICC involved in phasic contraction frequency regulation and is consistent with previous reports that have identified HCN1 on ICC ( He et al, 2012 ; Liu et al, 2017 ).…”

Increased Piezo1 channel activity in interstitial Cajal-like cells induces bladder hyperactivity by functionally interacting with NCX1 in rats with cyclophosphamide-induced cystitis

“…Moreover, it has been shown that Ca 2+ signaling in bladder ICC-LCs is upregulated or downregulated in bladder dysfunction associated with suprasacral or sacral spinal cord injury, respectively 36 . In our previous research, we demonstrated that bladder ICC-LC hyperactivity accounted for bladder hyperactivity in CYP-induced chronic cystitis, which was characterized by excessive Ca 2+ entry into cells upon carbachol application 12 . Furthermore, Ca 2+ overload in cardiomyocytes is closely related to cardiac dysfunction 37 , 38 .…”

“…We performed single-cell RT-PCR to confirm the authenticity of isolated bladder ICC-LCs, according to our previous description 12 . After electrophysiological testing, a single bladder ICC-LC was sucked into the recording pipette by applying negative pressure.…”

“…The data on functional changes in IC/PBS are still limited. Although we have found that bladder ICC-LC hyperactivity induced by alterations in the hyperpolarization-activated cyclic nucleotide 1 (HCN1) channel are involved in cyclophosphamide (CYP)-induced cystitis 12 , investigations attempting to more comprehensively elucidate the mechanisms underlying the functional role of bladder ICC-LCs in cystitis will be beneficial in developing more therapeutic strategies for cystitis-associated bladder dysfunction.…”

HCN as a Mediator of Urinary Homeostasis: Age-Associated Changes in Expression and Function in Adrenergic Detrusor Relaxation

“…Next, while historically regarded as standard HCN blocking agents, CsCl, and ZD-7288 are not highly specific for HCN blockade. In both cases, drug concentrations were chosen based on prior reports using these agents for HCN block in bladder or gut (8,11,(20)(21)(22)(23). Two agents with differing contaminating effects were chosen with the thought that similar responses in our experiments, as we found, would provide reassurance that observed effects were HCN-mediated.…”