Extracellular metabolism of 3 `,5 `-cyclic AMP as a source of interstitial adenosine in the rat airways

Author(s)

Pacini, Enio Setsuo Arakaki ^[1] ; Jackson, Edwin Kerry ^[2] ; Godinho, Rosely Oliveira ^[1]

Affiliation

^[1] Univ Fed Sao Paulo EPM Unifesp, Escola Paulista Med, Dept Pharmacol, Div Cellular Pharmacol, Sao Paulo, SP - Brazil

^[2] Univ Pittsburgh, Dept Pharmacol & Chem Biol, Sch Med, Pittsburgh, PA - USA

• Document type: Journal article
• Source: Biochemical Pharmacology; v. 192, OCT 2021.
• Web of Science Citations: 0

Abstract

In the respiratory tract, intracellular 3',5'-cAMP mediates smooth muscle relaxation triggered by the beta(2)-adrenoceptor/Gs protein/adenylyl cyclase axis. More recently, we have shown that beta(2)-adrenoceptor agonists also increase extracellular 3',5'-cAMP levels in isolated rat trachea, which leads to contraction of airway smooth muscle. In many other tissues, extracellular 3',5'-cAMP is metabolized by ectoenzymes to extracellular adenosine, a catabolic pathway that has never been addressed in airways. In order to evaluate the possible extracellular degradation of 3',5'-cAMP into 5'-AMP and adenosine in the airways, isolated rat tracheas were incubated with exogenous 3',5'-cAMP and the amount of 5'-AMP, adenosine and inosine (adenosine metabolite) produced was evaluated using ultraperformance liquid chromatography-tandem mass spectrometry. Incubation of tracheal tissue with 3',5'-cAMP induced a time- and concentration-dependent increase in 5'-AMP, adenosine and inosine in the medium. Importantly, IBMX (non-selective phosphodiesterase (PDE) inhibitor) and DPSPX (selective ectoPDE inhibitor) reduced the extracellular conversion of 3',5'-cAMP to 5'-AMP. In addition, incubation of 3',5'-cAMP in the presence of AMPCP (inhibitor of ecto-5'-nucleotidase) increased extracellular levels of 5'-AMP while drastically reducing extracellular levels of adenosine and inosine. These results indicate that airways express an extracellular enzymatic system (ecto-phosphodiesterase, ecto-5'-nucleotidase and adenosine deaminase) that sequentially converts 3',5'-cAMP into 5'-AMP, adenosine and inosine. The observation that extracellular 3',5'-cAMP is a source of interstitial adenosine supports the idea that the extrusion and extracellular metabolism of 3',5'-cAMP has a role in respiratory physiology and pathophysiology. (AU)

• FAPESP's process: 18/21381-6 - Validation of the "Extracellular cyclic AMP-Adenosine pathway" as a therapeutic target for chronic respiratory diseases.
• Grantee: Rosely Oliveira Godinho
• Support Opportunities: Regular Research Grants