Transient Receptor Potential Vanilloid 4 Activation-Induced Increase in Glycine-Activated Current in Mouse Hippocampal Pyramidal Neurons

Abstract

Background/Aims: Glycine plays an important role in regulating hippocampal inhibitory/ excitatory neurotransmission through activating glycine receptors (GlyRs) and acting as a co-agonist of N-methyl-d-aspartate-type glutamate receptors. Activation of transient receptor potential vanilloid 4 (TRPV4) is reported to inhibit hippocampal A-type γ-aminobutyric acid receptor, a ligand-gated chloride ion channel. GlyRs are also ligand-gated chloride ion channels and this paper aimed to explore whether activation of TRPV4 could modulate GlyRs. Methods: Whole-cell patch clamp recording was employed to record glycine-activated current (I_Gly) and Western blot was conducted to assess GlyRs subunits protein expression. Results: Application of TRPV4 agonist (GSK1016790A or 5,6-EET) increased I_Gly in mouse hippocampal CA1 pyramidal neurons. This action was blocked by specific antagonists of TRPV4 (RN-1734 or HC-067047) and GlyR (strychnine), indicating that activation of TRPV4 increases strychnine-sensitive GlyR function in mouse hippocampal pyramidal neurons. GSK1016790A-induced increase in I_Gly was significantly attenuated by protein kinase C (PKC) (BIM II or D-sphingosine) or calcium/calmodulin-dependent protein kinase II (CaMKII) (KN-62 or KN-93) antagonists but was unaffected by protein kinase A or protein tyrosine kinase antagonists. Finally, hippocampal protein levels of GlyR α1 α2, α3 and β subunits were not changed by treatment with GSK1016790A for 30 min or 1 h, but GlyR α2, α3 and β subunits protein levels increased in mice that were intracerebroventricularly (icv.) injected with GSK1016790A for 5 d. Conclusion: Activation of TRPV4 increases GlyR function and expression, and PKC and CaMKII signaling pathways are involved in TRPV4 activation-induced increase in I_Gly. This study indicates that GlyRs may be effective targets for TRPV4-induced modulation of hippocampal inhibitory neurotransmission.

Effect of transient receptor potential vanilloid 4 activation on the delayed rectifier potassium current in the hippocampal pyramidal neurons and Kv subunit expression in the hippocampi of mice

“…The inhibition of I K is unlikely due to the decrease in the expression of these three Kv subunits. Previous studies showed that when TRPV4 is chronically or persistently activated, the expression of ion channels and receptors may change [24]. In this study, the hippocampal expression levels of Kv1.2 and Kv2.1 decreased markedly when the mice were injected with GSK1016790A for 3 days (Fig.…”

“…The protein levels of Kv subunits in vehicle-treated PISE mice and HC-067047-treated PISE mice were normalized to those in vehicle-treated control mice. The concentrations of these drugs were chosen according to previous reports [8,9,24].…”

“…Activation of TRPV4 induces inward current, and in the hippocampus, TRPV4 has been proven to participate in modulating resting membrane potential and neuronal excitability [7]. Besides the inward current mediated by TRPV4 per se, activation of TRPV4 may affect the balance of neurotransmitter system function by modulating glutamate receptor, γ-aminobutyric acid receptor, and glycine receptor functions [8,9,24]. In the trigeminal ganglion neurons, activation of TRPV4 by hypotonic stimuli modulated I A and I K differently [13].…”

“…In osteocytes, CaMKII was activated by TRPV4-mediated Ca 2+ in ux [35]. CaMKII has been proven to participate in TRPV4-induced modulation of N-methyl-D-aspartate glutamate receptor and glycine receptor in the hippocampal neurons as well as voltage-gated sodium current in the ventricular myocytes [9,24,36]. It has been reported that the application of KN-93 inhibited a wide range of Kv channels in HEK 293 cells and that this effect was independent of CaMKII [37].…”

Transient receptor potential vanilloid 4 activation inhibits the delayed rectifier potassium channels in hippocampal pyramidal neurons: An implication in pathological changes following pilocarpine‐induced status epilepticus

“…For patch clamp recording, GSK1016790A, 5,6‐EET, HC‐067047, RN1734, 8‐bromoadenosine 3′,5′‐cyclic monophosphate sodium salt (8‐Br‐cAMP), phorbol 12‐myristate 13‐acetate (PMA), and bisindolylmaleimide II (BIM II) were extracellularly applied, and N‐[2‐(p‐Bromocinnamylamino)ethyl]‐5‐isoquinolinesulfonamide dihydrochloride (H‐89), PKI, D‐Sphingosine, and KN62 were added to the pipette solution. The concentrations of these drugs were chosen according to previous reports (Hong et al, 2016; Li, Qu, et al, 2013; Qi et al., 2018).…”