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Effect of prostaglandin E2 on ATP-induced Ca2+ responses in human THP-1 monocytic cells

Introduction

To clarify the relation between ATP and prostaglandin E2 (PGE2) in the immunologic system, we investigated the acute and chronic effects of PGE2 on activation of purinergic signaling in monocytes by measuring the ATP-induced elevation of intracellular Ca2+([Ca]i) in fura-2-loaded THP-1 monocytes.

Method

THP-1 monocytes were grown for about 2 days. To examine the chronic effects, PGE2 and dibutyryl cAMP (dbcAMP) were added and incubated for another day. The cell suspensions were washed, loaded with fura-2-AM, and transferred into a quartz cuvette and placed in the thermostat-regulated sample chamber of a dual excitation beam spectrophotometer. To examine the acute effects, ATP was added immediately after PGE2 and dbcAMP into the cuvette. In the chronic experiment, ATP alone was added into the cuvette. Fura-2 fluorescence emission was measured at 510 nm. The [Ca]i was calculated from the ratio of the fluorescence at the two excitation wavelengths.

Results

ATP induced a transient increase in [Ca]i followed by a sustained elevation of [Ca]i. Acutely, PGE2 inhibited both the transient and sustained ATP-induced elevations of [Ca]i. However, this acute inhibitory effect diminished gradually with time and chronic PGE2 accelerated the transient and sustained ATP-induced [Ca]i elevations for 24 hours. Both the acute and chronic effects of PGE2 were mimicked by dbcAMP. In Ca2+-free solution, ATP did not induce the sustained elevation of [Ca]i in control cells or cells pretreated for 24 hours with dbcAMP. This indicates that the ATP-induced sustained elevation of [Ca]i was due to Ca2+ entry. In addition, receptor-operated Ca2+ channel blockers inhibited the sustained ATP-induced elevation of [Ca]i in control cells and cells pretreated with for 24 hours dbcAMP.

Conclusion

Acute PGE2 inhibited the ATP-induced activation of monocytes. On the other hand, chronic PGE2 accelerated monocyte activation by upregulation of receptor-operated Ca2+ channels ROCs). If this mechanism exhibits a physiological role, ROC inhibitors should be developed as new anti-inflammatory agents.

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Goto, M., Murakawa, M., Kimura, J. et al. Effect of prostaglandin E2 on ATP-induced Ca2+ responses in human THP-1 monocytic cells. Crit Care 11, P4 (2007). https://doi.org/10.1186/cc5164

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Keywords

  • PGE2
  • Chronic Effect
  • dbcAMP
  • Dibutyryl
  • Excitation Beam