Heterologous Desensitization of Opioid-stimulated Ca2+ Increase by Bradykinin or ATP in NG108-15 Cells

Abstract

Leucine-enkephalin (Leu-EK) dose-dependently elicited an increase in cytosolic Ca2+ concentration ([Ca2+]i) with an EC50 of 1.2 microM via the phosphoinositide cascade in NG108-15 cells. Chronic treatment of cells with [D-Ala2,D-Leu5]enkephalin caused time-dependent homologous desensitization. In the presence of extracellular Ca2+, ATP as well as bradykinin stimulated significantly higher increases in inositol 1,4,5-trisphosphate (IP3) generation than did Leu-EK; however, the magnitude of intracellular Ca2+ pools increased after ATP stimulation, whereas bradykinin depleted intracellular pools. Hence, cells lost their [Ca2+]i response to Leu-EK if bradykinin was first added to induce a [Ca2+]i increase, whereas the response was unchanged if Leu-EK was added after addition of ATP. When Leu-EK was added simultaneously with bradykinin or ATP, an additive response was observed in IP3 generation; however, the rise in [Ca2+]i reached the same level as that induced by bradykinin or ATP alone. In the absence of extracellular Ca2+ in which the replenishment of intracellular pools was not possible, ATP displayed an inhibitory effect similar to that of bradykinin on the Leu-EK-induced [Ca2+]i increase. Prior treatment of cells with Leu-EK slightly heterologously desensitized the action of bradykinin, but had no effect on the ATP response. Our results suggest that a shared intracellular Ca2+ pool is sensitive to the opioid, bradykinin and P2-purinoceptor agonists; however, a defined pool of phosphatidylinositol 4,5-bisphosphate or a specific phospholipase C is responsible for each receptor.

Multiple polyphosphoinositide pathways regulate apoptotic signalling in a dorsal root ganglion derived cell line

“…Chueh et al (1995) proposed that opioids, bradykinin, and ATP all work through either a unique PLC or a unique pool of PtdInsP 2 but we have no evidence to support this. However, we did confirm their observation that exogenous ATP was able to mimic the enhancing effect of opioids on bradykinin action and as reported previously (Goswami et al, 1998), cAMP was able to reverse the chronic effects.…”

“…-Specific opioids such as fentanyl appear to activate phospholipase C acutely by up to 60% in SH-SY5Y human neuroblastoma cells via Ca 2ϩ channel opening (Smart et al, 1995). Further, leu-enkephalin has been shown to elicit a dosedependent increase in InsP 3 and cytosolic Ca 2ϩ in NG108-15 cells (Jin et al, 1992;Chueh et al, 1995), which was 25% of the increase elicited by bradykinin (Francel et al, 1987a, b). However, the actual Ca 2ϩ channels were not characterized, and indirect evidence suggests that they were of the non-neuronal or voltagesensitive L-type.…”

The mRNA Expression of Serotonin 2C Subtype Receptors Uncoupled With Inositol Hydrolysis in NG108-15 Cells

“…5). DICUSSION NG108-15 cells intrinsically express some receptor subtypes that stimulate PI turnover, including receptors of bradykinin B2 (14), histamine H1 (15), purinergic P2 (16), opiate (17), endothelin (18) and angiotensin (19). Since the intracellular signaling systems of PI turnover in NG108-15 are highly developed, the cell is often used to study the cellular physiological functions of inositolphosphate and related systems (20,21), and it is used as a host cell for transfection studies of PI turnover-coupled receptors (22,23).…”

Distinct Effects of Different Calcium-Mobilizing Agents on Cell Death in NG108-15 Neuroblastoma X Glioma Cells

“…TG prevents the uptake of Ca 2ϩ into Ca 2ϩ stores by inhibiting the SERCA and gradually leads to Ca 2ϩ depletion via leak channels. Although BK stimulates Ca 2ϩ release from intracellular Ca 2ϩ stores via the generation of IP 3 , it is possible that intraluminal Ca 2ϩ levels were not depleted because the Ca 2ϩ stores can be refilled by Ca 2ϩ uptake via the SERCA Chueh et al, 1995). Disruption of the mitochondrial membrane potential by the protonophore FCCP not only inhibits Ca 2ϩ accumulation within mitochondria, but also causes the release of trapped Ca 2ϩ from the mitochondria (Huang and Chueh, 1996).…”

“…After TG or FCCP treatment, an increased [Ca 2ϩ ] i was seen because of the discharge of entrapped Ca 2ϩ from respective organelles and Ca 2ϩ content within these two organelles was depleted. Thus, BK, TG, and FCCP all evoked [Ca 2ϩ ] i increase, but the underlying mechanisms are distinct Chueh et al, 1995;Hsu et al, 1995). It is believed that a prolonged [Ca 2ϩ ] i increase promotes cell death.…”