Adenosine receptor expression in Escherichia coli-infected and cytokine-stimulated human urinary tract epithelial cells.
OBJECTIVE
To assess the expression and regulation of adenosine receptors in unstimulated, uropathogenic Escherichia coli (UPEC)-infected and cytokine-stimulated human urinary tract epithelial cells, and to examine the regulation of interleukin (IL)-6 secretion in response to A(2A) receptor activation.


METHODS
Human urinary tract epithelial cells (A498, T24 and RT4) were grown in cell culture and stimulated with a mixture of pro-inflammatory cytokines (CM) or UPEC. The expression of adenosine receptors was evaluated using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR), Western blot analysis and immunocytochemistry. IL-6 secretion was measured with an enzyme-linked immunosorbent assay.


RESULTS
RT-PCR analysis showed the presence of transcripts for the A(1), A(2A) and A(2B) receptor subtypes but not for the A(3) receptor in A498 kidney epithelial cells. The expression of A(2A) receptor mRNA increased in A498 epithelial cells exposed to CM and UPEC, while A(1) and A(2B) receptor transcripts decreased or remained unchanged. Up-regulation of A(2A) receptors was confirmed at the protein level using Western blot analysis and immunocytochemistry. There was also an increase in A(2A) receptor mRNA in human bladder epithelial cells (T24 and RT4) and in mouse bladder uroepithelium in response to cytokines and UPEC. IL-6 secretion in UPEC-infected A498 cells was decreased by 38% when exposed to the A(2A) receptor agonist CGS 21680.


CONCLUSIONS
Our data showed a subtype-selective plasticity among adenosine receptors in urinary tract epithelial cells in response to UPEC-infection and cytokines. There was a consistent up-regulation of A(2A) receptors in kidney and bladder epithelial cells. Functionally, A(2A) receptor activation reduced UPEC-induced IL-6 secretion. These findings suggest that adenosine might be a previously unrecognized regulator of the mucosal response in urinary tract infection.
Säve
Susanne
S
School of Pure and Applied Natural Sciences, University of Kalmar, Kalmar.
Mjösberg
Jenny
J
Poljakovic
Mirjana
M
Mohlin
Camilla
C
Persson
Katarina
K
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D004847:Epithelial Cells / Q000378:metabolism / Q000382:microbiology; D004927:Escherichia coli Infections / Q000378:metabolism*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D015850:Interleukin-6 / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D043683:Receptors, Adenosine A2 / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation; D014552:Urinary Tract Infections / Q000378:metabolism*; D056689:Uropathogenic Escherichia coli
D015850:Interleukin-6; D043683:Receptors, Adenosine A2