• The Korean Journal of Physiology and Pharmacology
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• 제21권1호
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• pp.133-140
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• 2017

Conflicting evidence has been obtained regarding whether transient receptor potential cation channels (TRPC) are store-operated channels (SOCs) or receptor-operated channels (ROCs). Moreover, the Ca/Na permeability ratio differs depending on whether the current-voltage (I-V) curve has a doubly rectifying shape or inward rectifying shape. To investigate the calcium permeability of TRPC4 channels, we attached GCaMP6s to TRPC4 and simultaneously measured the current and calcium signals. A TRPC4 specific activator, (-)-englerin A, induced both current and calcium fluorescence with the similar time course. Muscarinic receptor stimulator, carbachol, also induced both current and calcium fluorescence with the similar time course. By forming heteromers with TRPC4, TRPC1 significantly reduced the inward current with outward rectifying I-V curve, which also caused the decrease of calcium fluorescence intensity. These results suggest that GCaMP6s attached to TRPC4 can detect slight calcium changes near TRPC4 channels. Consequently, TRPC4-GCaMP6s can be a useful tool for testing the calcium permeability of TRPC4 channels.

• 한국생물물리학회:학술대회논문집
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• 한국생물물리학회 1997년도 학술발표회
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• pp.16-16
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• 1997

Extracelluar ATP evokes many biological processes, including neuronal excitation and neurotransmitter secretion, through activation of purinergic P2 receptors. Although excitatory and inhibitory receptor-operated channels (ROC) and voltage-dependent calcium channels (VDCC) have been reported to be altered by acute and chronic exposure to ethanol, little is known of the ethanol effects on purinergic receptor-operated channels in neuronal cells.(omitted)

• 한국생물물리학회:학술대회논문집
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• 한국생물물리학회 1999년도 학술발표회 진행표 및 논문초록
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• pp.68-68
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• 1999

Extracellular A TP is known to function as a neurotransmitter and as a modulator in the variety of cell types. In PC12 cells, extracellular A TP elevates [Ca$\^$2＋/]j through receptor-operated Ca$\^$2＋/ channels and through the activation of phospholipase C, thereby facilitating the secretion of neurotransmitters.(omitted)

• BMB Reports
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• 제50권6호
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• pp.323-328
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• 2017

Lysophosphatidylcholine (LPC) is a major phospholipid component of oxidized low-density lipoprotein (ox-LDL) and is implicated in its atherogenic activity. This study investigated the effects of LPC on cell viability, intracellular calcium homeostasis, and the protective mechanisms of chlorogenic acid (CGA) in human umbilical vein endothelial cells (HUVECs). LPC increased intracellular calcium ($[Ca^{2+}]_i$) by releasing $Ca^{2+}$ from intracellular stores and via $Ca^{2+}$ influx through store-operated channels (SOCs). LPC also increased the generation of reactive oxygen species (ROS) and decreased cell viability. The mRNA expression of Transient receptor potential canonical (TRPC) channel 1 was increased significantly by LPC treatment and suppressed by CGA. CGA inhibited LPC-induced $Ca^{2+}$ influx and ROS generation, and restored cell viability. These results suggested that CGA inhibits SOC-mediated $Ca^{2+}$ influx and ROS generation by attenuating TRPC1 expression in LPC-treated HUVECs. Therefore, CGA might protect endothelial cells against LPC injury, thereby inhibiting atherosclerosis.

• Journal of Ginseng Research
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• 제18권2호
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• pp.95-101
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• 1994

Saponin of Panax ginseng (C.A. Meyer) is composed of Protopanaxatriol (PT) and Protopanaxa- diol (PD). We investigated the effects of PT and PD on the contractility and $^{45}Ca$ uptake in the pig coronary artery. Isometric tension in the helical strips and $^{45}Ca$ uptake in the ring strips were measured in the presence or absence of PT and PD. PT and PD did not affect the high K+ (40 mM)-induced contraction but relaxed the ACh-induced contraction in a dose4ependent manner (1~10 mg/dl). The vasorelaxing effect of PT on the ACh-induced contraction was more potent than that of PD. Those relaxations were partially suppressed by the rubbing of endothelium removal. ACh-induced contraction in the $Ca^{2+}$-free Tyrode's solution was suppressed by the pretreatment of PT or PD. Following the depletion of ACh-sensitive intracellular $Ca^{2+}$ pool, ACh-induced contraction was suppressed by the pratreatment of PT or PD. With the pretreatment of PT or PD, $^{45}Ca$ uptake by high K+ (43 mM) was not changed but that by ACh was suppressed in the pig coronary artery. From the above results, we suggested that the vasorelaxing effect of PT and PD of Panax ginseng was due to inhibition of intracellular $Ca^{2+}$ release, inhibition of $Ca^{2+}$ uptake via receptor-operated $Ca^{2+}$ channels and in part a release of vasorelaxing factor from endothelium in pig coronary artery.

• International Journal of Oral Biology
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• 제46권3호
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• pp.134-139
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• 2021

Under physiological conditions, calcium (Ca²⁺) regulates essential functions of polarized secretory cells by the stimulation of specific Ca²⁺ signaling mechanisms, such as increases in intracellular Ca²⁺ concentration ([Ca²⁺]_i) via the store-operated Ca²⁺ entry (SOCE) and the receptor-operated Ca²⁺ entry (ROCE). Homer proteins are scaffold proteins that interact with G protein-coupled receptors, inositol 1,4,5-triphosphate (IP₃) receptors, Orai1-stromal interaction molecule 1, and transient receptor potential canonical (TRPC) channels. However, their role in the Ca²⁺ signaling in exocrine cells remains unknown. In this study, we investigated the role of Homer2 in the Ca²⁺ signaling and regulatory channels to mediate SOCE and ROCE in pancreatic acinar cells. Deletion of Homer2 (Homer2^-/-) markedly increased the expression of TRPC3, TRPC6, and Orai1 in pancreatic acinar cells, whereas these expressions showed no difference in whole brains of wild-type and Homer2^-/- mice. Furthermore, the response of Ca²⁺ entry by carbachol also showed significant changes to the patterns regulated by specific blockers of SOCE and ROCE in pancreatic acinar cells of Homer2^-/- mice. Thus, these results suggest that Homer2 plays a critical role in the regulatory action of the [Ca²⁺]_i via SOCE and ROCE in mouse pancreatic acinar cells.

• The Korean Journal of Physiology and Pharmacology
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• 제18권5호
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• pp.377-381
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• 2014

Propofol is a widely used anesthetic. Many studies have shown that propofol has direct effects on blood vessels, but the precise mechanism is not fully understood. Secondary intrapulmonary artery rings from male rats were prepared and mounted in a Multi Myograph System. The following constrictors were used to induce contractions in isolated artery rings: high $K^+$ solution (60 mmol/L); U46619 solution (100 nmol/L); 5-hydroxytryptamine (5-HT; $3{\mu}mol/L$); or phenylephrine (Phe; $1{\mu}mol/L$). The relaxation effects of propofol were tested on high $K^+$ or U46619 precontracted rings. Propofol also was added to induce relaxation of rings preconstricted by U46619 after pretreatment with the nitric oxide synthase inhibitor $N^G$-nitro-L-arginine methyl ester (L-NAME). The effects of propofol on $Ca^{2+}$ influx via the L-type $Ca^{2+}$ channels were evaluated by examining contraction-dependent responses to $CaCl_2$ in the absence or presence of propofol (10 to $300{\mu}mol/L$). High $K^+$ solution and U46619 induced remarkable contractions of the rings, whereas contractions induced by 5-HT and Phe were weak. Propofol induced dose-dependent relaxation of artery rings precontracted by the high $K^+$ solution. Propofol also induced relaxation of rings precontracted by U46619 in an endothelium-independent way. Propofol at different concentrations significantly inhibited the $Ca^{2+}$-induced contractions of pulmonary rings exposed to high $K^+$-containing and $Ca^{2+}$-free solution in a dose-dependent manner. Propofol relaxed vessels precontracted by the high $K^+$ solution and U46619 in an endothelium-independent way. The mechanism for this effect may involve inhibition of calcium influx through voltage-operated calcium channels (VOCCs) and receptor-operated calcium channels (ROCCs).

• 약학회지
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• 제41권5호
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• pp.666-671
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• 1997

We studied effects of genistein and tyrphostin, inhibitors of tyrosine kinase, on contractions induced by high $K^+$ and norepinephrine in rat aorta. Genistein $(10^{-6}{\sim}10^{-4}M)$ and tyrphostin ($(10^{-5}{\sim}10^{-4}M)$) inhibited high $K^+$ and norepinephrine-induced sustained contractions, respectively in a concentration-dependent manner. High $K^+$ and norepinephrine caused an increase in $^{45}Ca^{2+}$ uptake while $10^{-4}M$ genistein and tyrphostin inhibited the $K^+$ and norepinephrine-increased $^{45}Ca^{2+}$ uptake, respectively. These results show that inhibitor of tyrosine kinase blocks the voltage-and receptor-operated $Ca^{2+}$ channels in rat aorta, respectively.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1996년도 춘계학술대회
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• pp.19-29
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• 1996

The neurological manifestations of AIDS include dementia, encountered even in the absence of opportunistic superinfection or malignancy. The AIDS Dementia Complex appears to be associated with several neuropathological abnormalities, including astrogliosis and neuronal injury or loss. How can HIV-1 result in neuronal damage if neurons themselves are only rarely, if ever, infected by the vitus\ulcorner In vitro experiments from several different laboratiories have lent support to the existence of HIV- and immune-related toxins. In one recently defined pathway to neuronal injury, HIV-infected macrophages/microglia as well as macrophages activated by HIV-1 envelope protein gp120 appear to secrete excitants/neurotoxins. These substances may include arachidonic acid, platelet-activating factor, free radicals (NO - and O$_2$), glutamate, quinolinate, cysteine, cytokines (TNF-${\alpha}$, IL1-B, IL-6), and as yet unidentified factors emanating from stimulated macrophages and possibly reactive astrocytes. A final common pathway for newonal suscepubility appears to be operative, similar to that observed in stroke, trauma, epilepsy, and several neurodegenerative diseases, including Huntington's disease, Parkinson's disease, and amyotrophic lateral sclerosis. This mechanism involves excessive activation of N-methyl-D-aspartate (NMDA) receptor-operated channels, with resultant excessive influx of Ca$\^$2+/ leading to neuronal damage, and thus offers hope for future pharmacological intervention. This chapter reviews two clinically-tolerated NMDA antagonists, memantine and nitroglycerin; (ⅰ) Memantine is an open-channel blocker of the NMDA-associated ion channel and a close congener of the anti-viral and anti-parkinsonian drug amantadine. Memantine blocks the effects of escalating levels of excitotoxins to a greater degree than lower (piysiological) levels of these excitatory amino acids, thus sparing to some extent normal neuronal function. (ⅱ) Niuoglycerin acts at a redox modulatory site of the NMDA receptor/complex to downregulate its activity. The neuroprotective action of nitroglycerin at this site is mediated by n chemical species related to nitric oxide, but in a higher oxidation state, resulting in transfer of an NO group to a critical cysteine on the NMDA receptor. Because of the clinical safety of these drugs, they have the potential for trials in humans. As the structural basis for redox modulation is further elucidated, it may become possible to design even better redox reactive reagents of chinical value. To this end, redox modulatory sites of NMDA receptors have begun to be characterized at a molecular level using site-directed mutagenesis of recombinant subunits (NMDAR1, NMDAR2A-D). Two types of redox modulation can be distinguished. The first type gives rise to a persistent change in the functional activity of the receptor, and we have identified two cysteine residues on the NMDARI subunit (#744 and #798) that are responsible for this action. A second site, presumably also a cysteine(s) because <1 mM N-ethylmaleimide can block its effect in native neurons, underlies the other, more transient redox action. It appears to be at this, as yet unidentified, site on the NMDA receptor that the NO group acts, at least in recombinant receptors.

• The Korean Journal of Physiology and Pharmacology
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• 제28권1호
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• pp.93-103
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• 2024

Satellite glial cells (SGCs), a major type of glial cell in the autonomic ganglia, closely envelop the cell body and even the synaptic regions of a single neuron with a very narrow gap. This structurally unique organization suggests that autonomic neurons and SGCs may communicate reciprocally. Glial Ca²⁺ signaling is critical for controlling neural activity. Here, for the first time we identified the machinery of store-operated Ca²⁺ entry (SOCE) which is critical for cellular Ca²⁺ homeostasis in rat sympathetic ganglia under normal and pathological states. Quantitative realtime PCR and immunostaining analyses showed that Orai1 and stromal interaction molecules 1 (STIM1) proteins are the primary components of SOCE machinery in the sympathetic ganglia. When the internal Ca²⁺ stores were depleted in the absence of extracellular Ca²⁺, the number of plasmalemmal Orai1 puncta was increased in neurons and SGCs, suggesting activation of the Ca²⁺ entry channels. Intracellular Ca²⁺ imaging revealed that SOCE was present in SGCs and neurons; however, the magnitude of SOCE was much larger in the SGCs than in the neurons. The SOCE was significantly suppressed by GSK7975A, a selective Orai1 blocker, and Pyr6, a SOCE blocker. Lipopolysaccharide (LPS) upregulated the glial fibrillary acidic protein and Toll-like receptor 4 in the sympathetic ganglia. Importantly, LPS attenuated SOCE via downregulating Orai1 and STIM1 expression. In conclusion, sympathetic SGCs functionally express the SOCE machinery, which is indispensable for intracellular Ca²⁺ signaling. The SOCE is highly susceptible to inflammation, which may affect sympathetic neuronal activity and thereby autonomic output.