Abstract
HL-60 human promyelocytic leukocytes express G protein-coupled P2U-purinergic nucleotide receptors (P2UR or P2Y2R) that activate inositol phospholipid hydrolysis and Ca2+ mobilization in response to ATP or UTP. We examined the expression of functional P2UR and P2UR mRNA levels during in vitro differentiation of HL-60 cells by dibutyryl-cAMP (Bt2cAMP), which induces a granulocyte/neutrophil phenotype, or by phorbol-12-myristate-13-acetate (PMA), which induces a monocyte/macrophage phenotype. Both P2UR function and P2UR mRNA levels were only modestly attenuated during granulocytic differentiation by Bt2cAMP. In contrast, P2UR function, as assayed by either Ca2+ mobilization or inositol trisphosphate generation, was greatly reduced in PMA-differentiated cells. This inhibition of P2UR function was strongly correlated with PMA-induced decreases in P2UR mRNA levels, as assayed by Northern blot analysis or reverse transcription-polymerase chain reaction-based quantification. Although PMA induced an early, transient up-regulation of P2UR mRNA, this was rapidly followed by a sustained decrease in P2UR mRNA to a level 5–10-fold lower than that in undifferentiated HL-60 cells. The half-life of the P2UR transcript in HL-60 cells was ∼60 min, and this was not affected by acute exposure (≤4 hr) to Bt2cAMP or PMA. PMA down-regulated P2UR mRNA in THP-1 monocytes and HL-60 granulocytes but not in A431 human epithelial cells or human keratinocytes. P2UR mRNA was also down-regulated in THP-1 monocytes differentiated into inflammatory macrophages by γ-interferon and endotoxin. These data indicate that myeloid leukocytes possess tissue-specific mechanisms for the rapid modulation of P2UR expression and function during differentiation and inflammatory activation.
Footnotes
- Received May 29, 1996.
- Accepted September 27, 1996.
-
Send reprint requests to: George R. Dubyak, Ph.D., Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-4970. E-mail: gxd3{at}po.cwru.edu
-
This work was supported by National Institutes of Health Grant GM36387 (G.P.D.). K.A.M. was supported by National Institutes of Health Training Grant HL07678.
- The American Society for Pharmacology and Experimental Therapeutics
MolPharm articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|