Dynamic Expression of Hyperpolarization-activated Cyclic Nucleotide-gated Cation Channel 4 Involved in Microwave Induced Pacemaker Cell Injuries

To investigate the mechanisms of microwave induced pacemaker cell injuries, Wistar rats and the primary pacemaker cells of newborn Wistar rats were exposed to microwave at average power density of 50 mW/cm2. Slower spontaneous beating rate, intercellular Ca2＋ aggregation and cell membrane perforation were detected immediately after the exposure. Moreover, hyperpolarizationactivated cyclic nucleotide-gated cation channel 4 （HCN4） was down-regulated immediately after the exposure and up-regulated at 12 h after the exposure. In the sinoatrial node （SAN） of the rats,

Electrophysiology of hyperpolarization-activated cyclic nucleotidegated cation channel 2 and hyperpolarization-activated cyclic nucleotide-gated cation channel 4 expressed in HEK293 cells

The action potential of pacemaker cells in the sino-atrial node forms the automatic rhythm of the heart. The automatic depolarization in phase 4 is me DaSlS of the automaticity in pacemaker cells. Many currents are included in phase 4, such as calcium current, TTX-sensitive sodium current, sustained inward current （Isi）, decay of delayed rectifier potassium current, etc. Funny current （If） has long been recognized as important in this phase and is activated at hyperpolarized potentials during cell diastole and in turn activates other currents to form automatic depolarization.

Hyperpolarization-activated cyclic nucleotide-gated 2 contributes to electroacupuncture analgesia on lumbar disc herniation-induced radicular pain through activation of microglia in spinal dorsal horn

OBJECTIVE:To explore the mechanisms of dorsal root ganglia and spinal microglia cascade cross in electroacupuncture(EA)analgesia in the treatment of lumbar disc herniation.METHODS:A rat model of lumbar disc herniation(LDH)was established,EA was administered at Huantiao(GB30)acupoint 30 min once a day,for 3 d.Before and after modeling,and after EA,mechanical allodynia thresholds were detected.Hyperpolarization-activated cyclic nucleotide-gated 2(HCN2)in dorsal root ganglia was detected by quantitative polymerase chain reaction(qPCR)and Western blot.C-X3-C motif chemokine ligand 1(CX3CL1)and activity of microglia in spinal cord was observed separately via qPCR and immunofluorescence staining.RESULTS:The mechanical allodynia threshold of the right planta of model rats was significantly reduced(P<0.01),EA increased the mechanical pain threshold of rats(P<0.01),and decreased HCN2 mRNA,and protein expression,reduced the expression of CX3CL1 and the activation of microglia.ZD7288(a blocker of HCN channel)reduced the analgesic effect of EA from 1.83±0.84 to 0.74±0.20(P<0.05),and the expression of CX3CL1 in the spinal cord decreased from 0.52±0.11 to 0.15±0.05(P<0.01).CONCLUSION:EA analgesia on the radicular pain of LDH is definite.EA reduced the expression of HCN2 channel in the dorsal root ganglion,thereby decreasing the noxious stimulation entered to microglia in spinal dorsal horn.Our work supports EA is an effective treatment for radicular pain of LDH.

The Role of Cyclic Nucleotide-Gated Ion Channels in Plant Immunity

Since the first plant cyclic nucleotide-gated ion channel （CNGC）, HvCBT1, was identified as a calmodulin bind- ing protein, more than a decade has passed and a substantial amount of work has been done to understand the molecular nature and function of these channel proteins. Based on electrophysiological and heterologous expression analyses, plant CNGCs function as non-selective cation channels and, so far, their biological roles have been reported in defense responses, development, and ion homeostasis. Forward genetic approaches identified four AtCNGCs （AtCNGC2, 4, 11, and 12） to be involved in plant immunity, as null mutants for AtCNGC2, 4, 11, and 12 as well as a gain-of- function mutant for AtCNGC11 and 12 exhibited alterations in defense responses. Since ion flux changes have been reported as one of the early events upon pathogen recognition and also are an essential component for the activation of defense responses, the involvement of CNGCs in these ion flux changes has been suggested. However, the recent detailed characterization of null mutants suggested a more complex involvement of this channel family. In this review, we focus on the discoveries and character- ization of these CNGC mutants and discuss possible roles of CNGCs as components in plant immunity.

ZD 7288,an HCN channel blocker,attenuates chronic visceral pain in irritable bowel syndrome-like rats

AIM: To investigate the effects of ZD 7288, a hyperpolarization-activated cyclic nucleotide-gated (HCN) channel blocker, on rats with chronic visceral pain.

Overexpression of connexin 45 in rat mesenchymal stem cells improves the function as cardiac biological pacemakers

Background Extensive research toward creating a biological pacemaker by enhancement of inward depolarizing current has been performed. However, studies have mainly focused on inducing spontaneous activity and have not adequately addressed ways to improve pacemaker function. In this study we attempted to improve pacemaker function by altering connexin expression in rat mesenchymal stem cells （MSCs） to a phenotype similar to native sinus node pacemaker cells. Methods To generate a biological pacemaker, MSCs were transduced with a cardiac pacemaker gene- hyperpolarization-activated cyclic nucleotide-gated channel 4 （HCN4）, via transfection with a lentiviral vector. Funny current （If） in HCN4~ MSCs was recorded by voltage-clamp. Overexpression of connexin 45 （gene Gja7） in MSCs was achieved by transfection with the plasmid pDsRED2-N1-Gja7-RFP. Double-immunolabelling with anti-connexin 43 and anti-connexin 45 antibodies were used to identify the gap junction channels. The effects of the genetically modified MSCs on cardiomyocyte excitability were determined in MSCs cocultured with neonatal rat ventricular myocytes. Spontaneous action potentials of neonatal rat ventricular myocytes were recorded by current-clamp. Results High level time- and voltage-dependent inward hyperpolarization current that was sensitive to 4 mmol/L Cs＋ was detected in HCN4＋ MSCs, confirming that HCN4 acted as Ir channels in MSCs. Connexin 43 and connexin 45 were simultaneously detected in CX45＋ MSCs. Beating frequency was （82±8） beats per minute （n=-5） in myocytes cocultured with non-transfected control MSCs, versus （129±11） beats per minute （n=-5） in myocytes cocultured with HCN4＋ MSCs. Myocytes cocultured with MSCs cotransfected with HCN4 and connexin 45 had the highest beating frequency at （147±9） beats per minute （n=5）. Conclusion These findings demonstrate that overexpression of connexin 45 and subsequent formation of heteromeric connexin 45/connexin 43 gap junction channels in HCN4 expressing MSCs can improve their function as cardiac biological pacemakers in vitro.