Hyperpolarization‐activated cation and T‐type calcium ion channel expression in porcine and human renal pacemaker tissues

Abstract

Renal pacemaker activity triggers peristaltic upper urinary tract contractions that propel waste from the kidney to the bladder, a process prone to congenital defects that are the leading cause of pediatric kidney failure. Recently, studies have discovered that hyperpolarization-activated cation (HCN) and T-type calcium (TTC) channel conductances underlie murine renal pacemaker activity, setting the origin and frequency and coordinating upper urinary tract peristalsis. Here, we determined whether this ion channel expression is conserved in the porcine and human urinary tracts, which share a distinct multicalyceal anatomy with multiple pacemaker sites. Double chromagenic immunohistochemistry revealed that HCN isoform 3 is highly expressed at the porcine minor calyces, the renal pacemaker tissues, whereas the kidney and urinary tract smooth muscle lacked this HCN expression. Immunofluorescent staining demonstrated that HCN(+) cells are integrated within the porcine calyx smooth muscle, and that they co-express TTC channel isoform Cav3.2. In humans, the anatomic structure of the minor calyx pacemaker was assayed via hematoxylin and eosin analyses, and enabled the visualization of the calyx smooth muscle surrounding adjacent papillae. Strikingly, immunofluorescence revealed that HCN3(+) /Cav3.2(+) cells are also localized to the human minor calyx smooth muscle. Collectively, these data have elucidated a conserved molecular signature of HCN and TTC channel expression in porcine and human calyx pacemaker tissues. These findings provide evidence for the mechanisms that can drive renal pacemaker activity in the multi-calyceal urinary tract, and potential causes of obstructive uropathies.

Evidence for Effective Inhibitory Actions on Hyperpolarization-Activated Cation Current Caused by Ganoderma Triterpenoids, the Main Active Constitutents of Ganoderma Spores

“…GTs was also previously reported to exert analgesic actions [11,53], which could be possibly associated with its inhibition of I h in different types of sensory neurons. It is also important to note that the I h was expressed either in urinary bladder, ureter and renal pacemaker tissue or in different types of tumor cells (e.g., lung carcinoma cells) [34,54,55,56,57]; at extent GTs-induced block of I h is linked to its antineoplastic actions or impairments in urine excretion remains to be imperatively evaluated.…”

Loss of HCN2 leads to delayed gastrointestinal motility and reduced energy intake in mice

“…Though HCN channels are generally studied in the heart and brain, these channels have been found to be expressed and regulate function in multiple organ systems [ 14 – 16 , 25 – 33 ]. In particular, HCN2 has been reported to have a functional role in many hormone secreting tissues, including the pancreas and pituitary[ 14 , 16 ].…”

Identification and classification of interstitial cells in the mouse renal pelvis

“…Previous studies have suggested that hyperpolarization‐activated cyclic nucleotide‐gated‐3 (HCN3) channels are expressed in the proximal renal pelvis, and these channels are regulators of renal pelvic peristalsis in multi‐ and unicalyceal species (Hurtado et al . 2010, 2014; Hurtado & Smith, 2016). Antagonists of these channels, namely ZD7288 dysregulate pacemaker activity, leading to ineffective proximal‐to‐distal contractions (Lang, 2010; Hurtado et al .…”

“…2014). The cell type that expresses HCN3 in the renal pelvis is controversial (Feeney & Rosenblum, 2014), but a recent anatomical study suggests that ASMCs express HCN3 in multicalyceal species (Hurtado & Smith, 2016). With the same antibody used previously (Hurtado et al .…”