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

cc5164 CCJ Poster presentation Effect of prostaglandin E2 on ATP-induced Ca2+ responses in human THP-1 monocytic cells Goto M Murakawa M Kimura J Matsuoka I

Fukushima Medical University, Fukusima, Japan

Takasaki University of Health and Welfare, Gunma, Japan

Critical Care 27th International Symposium on Intensive Care and Emergency Medicine Meeting abstracts 27th International Symposium on Intensive Care and Emergency Medicine Brussels, Belgium

27–30 March 2007

http://www.intensive.org 1364-8535 2007 11 Suppl 2 P4 10.1186/cc5164 22 3 2007 2007 BioMed Central Ltd.

Introduction

To clarify the relation between ATP and prostaglandin E₂(PGE₂) in the immunologic system, we investigated the acute and chronic effects of PGE₂on 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, PGE₂and 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 PGE₂and 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]_iwas calculated from the ratio of the fluorescence at the two excitation wavelengths.

Results

ATP induced a transient increase in [Ca]_ifollowed by a sustained elevation of [Ca]_i. Acutely, PGE₂inhibited both the transient and sustained ATP-induced elevations of [Ca]_i. However, this acute inhibitory effect diminished gradually with time and chronic PGE₂accelerated the transient and sustained ATP-induced [Ca]_ielevations for 24 hours. Both the acute and chronic effects of PGE₂were mimicked by dbcAMP. In Ca²⁺-free solution, ATP did not induce the sustained elevation of [Ca]_iin control cells or cells pretreated for 24 hours with dbcAMP. This indicates that the ATP-induced sustained elevation of [Ca]_iwas due to Ca²⁺entry. In addition, receptor-operated Ca²⁺channel blockers inhibited the sustained ATP-induced elevation of [Ca]_iin control cells and cells pretreated with for 24 hours dbcAMP.

Conclusion

Acute PGE₂inhibited the ATP-induced activation of monocytes. On the other hand, chronic PGE₂accelerated 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.