UC Merced

Background

During inflammation, stressed or infected cells can release adenosine triphosphate (ATP) to the extracellular medium, which can be hydrolyzed to adenosine by ectonucleotidases such as ectonucleoside triphosphate diphosphohydrolase 1 (CD39) and 5'-nucleotidase (CD73). The role of CD73 in the modulation of cytokine release by human gingival fibroblasts (HGFs) remains underexplored. Here, we investigated whether CD73-mediated hydrolysis of extracellular ATP (eATP) could affect interleukin (IL)-1β-induced CXCL8 secretion.

Methods

The levels of mRNA expression of adenosine receptors, CD39 and CD73 of periodontitis samples were retrieved from a public database. Moreover, HGF mRNA levels were measured by quantitative reverse transcription-polymerase chain reaction (RT-qPCR) after 3, 6, or 24 hours of IL-1β stimulation. IL-1β-induced CXCL8 protein levels were measured after pretreatment with 100-µM eATP in the presence or absence of CD73 inhibitor. The effect of eATP degradation to adenosine on CXCL8 levels was investigated using agonist and antagonist of adenosine receptors.

Results

Levels of CD39, CD73, and adenosine receptor mRNA were differentially modulated by IL-1β. ATP pretreatment impaired IL-1β-induced CXCL8 secretion and required activation of heme oxygenase-1 (HO-1) and phosphorylated adenosine monophosphate-activated protein kinase (pAMPK). The inhibition of CD73 or the inhibition of adenosine receptors abrogated the ATP effect on CXCL8 secretion.

Conclusions

CD73-generated adenosine dampens IL-1β-induced CXCL8 in HGFs and involves HO-1 and pAMPK signaling. These results imply that CD73 is a negative regulator of the inflammatory microenvironment, suggesting that this ectoenzyme could be involved in the generation of deficient CXCL8 gradient in chronic inflammation.