Selective blockade of HCN1/HCN2 channels as a potential pharmacological strategy against pain

A prominent role of hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels has been suggested based on their expression and (dys)function in dorsal root ganglion (DRG) neurons, being likely involved in peripheral nociception. Using HCN blockers as antinociceptive drugs is prevented by the widespread distribution of these channels. However, tissue-specific expression of HCN isoforms varies significantly, HCN1 and HCN2 being considered as major players in DRG excitability. We characterized the pharmacological effect of a novel compound, MEL55A, able to block selectively HCN1/HCN2 isoforms, on DRG neuron excitability in-vitro and for its antiallodynic properties in-vivo. HEK293 cells expressing HCN1, HCN2, or HCN4 isoforms were used to verify drug selectivity. The pharmacological profile of MEL55A was tested on mouse DRG neurons by patch-clamp recordings, and in-vivo in oxaliplatin-induced neuropathy by means of thermal hypersensitivity. Results were compared to the non-isoform-selective drug, ivabradine. MEL55A showed a marked preference toward HCN1 and HCN2 isoforms expressed in HEK293, with respect to HCN4. In cultured DRG, MEL55A reduced h amplitude, both in basic conditions and after stimulation by forskolin, and cell excitability, its effect being quantitatively similar to that observed with ivabradine. MEL55A was able to relieve chemotherapy-induced neuropathic pain. In conclusion, selective blockade of HCN1/HCN2 channels, over HCN4 isoform, was able to modulate electrophysiological properties of DRG neurons similarly to that reported for classical Ih blockers, ivabradine, resulting in a pain-relieving activity. The availability of small molecules with selectivity toward HCN channel isoforms involved in nociception might represent a safe and effective strategy against chronic pain

Mathematical modelling of the action potential of human embryonic stem cell derived cardiomyocytes

BACKGROUND: Human embryonic stem cell derived cardiomyocytes (hESC-CMs) hold high potential for basic and applied cardiovascular research. The development of a reliable simulation platform able to mimic the functional properties of hESC-CMs would be of considerable value to perform preliminary test complementing in vitro experimentations. METHODS: We developed the first computational model of hESC-CM action potential by integrating our original electrophysiological recordings of transient-outward, funny, and sodium-calcium exchanger currents and data derived from literature on sodium, calcium and potassium currents in hESC-CMs. RESULTS: The model is able to reproduce basal electrophysiological properties of hESC-CMs at 15 40 days of differentiation (Early stage). Moreover, the model reproduces the modifications occurring through the transition from Early to Late developmental stage (50-110, days of differentiation). After simulated blockade of ionic channels and pumps of the sarcoplasmic reticulum, Ca2+ transient amplitude was decreased by 12% and 33% in Early and Late stage, respectively, suggesting a growing contribution of a functional reticulum during maturation. Finally, as a proof of concept, we tested the effects induced by prototypical channel blockers, namely E4031 and nickel, and their qualitative reproduction by the model. CONCLUSIONS: This study provides a novel modelling tool that may serve useful to investigate physiological properties of hESC-CMs

Molecular and functional evidence of HCN4 and caveolin-3 interaction during cardiomyocyte differentiation from human embryonic stem cells

Maturation of human embryonic stem cell-derived cardiomyocytes (hESC-CM) is accompanied by changes in ion channel expression, with relevant electrophysiological consequences. In rodent CM, the properties of hyperpolarization-activated cyclic nucleotide-gated channel (HCN)4, a major f-channel isoform, depends on the association with caveolin-3 (Cav3). To date, no information exists on changes in Cav3 expression and its associative relationship with HCN4 upon hESC-CM maturation. We hypothesize that Cav3 expression and its compartmentalization with HCN4 channels during hESC-CM maturation accounts for the progression of f-current properties toward adult phenotypes. To address this, hESC were differentiated into spontaneously beating CM and examined at ∼30, ∼60, and ∼110 days of differentiation. Human adult and fetal CM served as references. HCN4 and Cav3 expression and localization were analyzed by real time PCR and immunocyto/histochemistry. F-current was measured in patch-clamped single cells. HCN4 and Cav3 colocalize in adult human atrial and ventricular CM, but not in fetal CM. Proteins and mRNA for Cav3 were not detected in undifferentiated hESC, but expression increased during hESC-CM maturation. At 110 days, HCN4 appeared to be colocalized with Cav3. Voltage-dependent activation of the f-current was significantly more positive in fetal CM and 60-day hESC-CM (midpoint activation, V1/2, ∼ -82 mV) than in 110-day hESC-CM or adult CM (V1/2∼-100 mV). In the latter cells, caveolae disruption reversed voltage dependence toward a more positive or an immature phenotype, with V1/2 at -75 mV, while in fetal CM voltage dependence was not affected. Our data show, for the first time, a developmental change in HCN4-Cav3 association in hESC-CM. Cav3 expression and its association with ionic channels likely represent a crucial step of cardiac maturation