What is the clinical evidence from this study?

Study design: Other. Population: Cardiac fibrosis. Intervention: Adenosine vs. Absence of adenosine. Primary outcome: [3H]proline and [3H]leucine incorporation.

What question did this study set out to answer?

The central aim is to examine how adenosine affects collagen and protein synthesis in cardiac fibroblasts.

April 1, 1998

Adenosine Inhibits Collagen and Protein Synthesis in Cardiac Fibroblasts

Key Result

Adenosine inhibits fetal calf serum-induced collagen and total protein synthesis in rat cardiac fibroblasts via activation of A2B receptors.

Key Points

The central aim is to examine how adenosine affects collagen and protein synthesis in cardiac fibroblasts.
Cardiac fibroblast monolayers were stimulated with 2.5% fetal calf serum and exposed to various adenosine modulators.
Assessments measured [3H]proline and [3H]leucine incorporation as markers for collagen and protein synthesis.
Effects were analyzed with specific adenosine receptor antagonists to determine receptor involvement.
Adenosine and its analogues inhibited FCS-induced [3H]proline and [3H]leucine incorporation in a concentration-dependent manner.
Inhibition was blocked by A2 antagonists, confirming the role of A2B receptors and excluding A1 as a significant player.
Endogenous adenosine may protect against cardiac fibrosis, though this remains to be conclusively proven.

Structured PICO

Population

In vitro study using rat left ventricular cardiac fibroblasts to evaluate the effects of adenosine on collagen and protein synthesis.

Intervention

Exogenous and endogenous adenosine, 2-chloroadenosine, or modulators of adenosine levels (erythro-9-(2-hydroxy-3-nonyl) adenine, dipyridamole, iodotubericidin)

Comparator

Absence of adenosine or its modulators

Outcome

[3H]proline and [3H]leucine incorporation (markers of collagen and total protein synthesis)surrogate

Adenosine inhibits collagen and total protein synthesis in cardiac fibroblasts via A2B receptors, suggesting a potential protective role against cardiac fibrosis.

Limitations

These studies suggest, but do not prove, that endogenous adenosine may protect against cardiac fibrosis.

Abstract

The objective of this study was to characterize the effects of exogenous and endogenous (cardiac fibroblast-derived) adenosine on 3Hproline and 3Hleucine incorporation, which are reliable markers of collagen and total protein synthesis, respectively, in rat left ventricular cardiac fibroblasts. Growth-arrested confluent cardiac fibroblast monolayers were stimulated with 2.5% fetal calf serum (FCS) in the presence and absence of adenosine, 2-chloroadenosine (stable adenosine analogue), or modulators of adenosine levels including (1) erythro-9-(2-hydroxy-3-nonyl) adenine (adenosine deaminase inhibitor), (2) dipyridamole (adenosine transport blocker), and (3) iodotubericidin (adenosine kinase inhibitor). All agents inhibited in a concentration-dependent fashion FCS-induced 3Hproline and 3Hleucine incorporation. These effects were blocked by KF17837 (selective A2 antagonist) and 1,3-dipropyl-8-(p-sulfophenyl)xanthine (A1/A2 receptor antagonist) but not by 8-cyclopentyl-1,3-dipropylxanthine (selective A1 antagonist), thus excluding the participation of A1 receptors. The lack of effect of CGS21680 (selective A2A agonist) excluded involvement of A2A receptors, thus suggesting a major role for A2B receptors. Comparisons of the inhibitory potencies of N6-cyclopentyladenosine (selective A1 agonist), 5'-N-ethylcarboxamidoadenosine (A1/A2 agonist), and 5'-N-methylcarboxamidoadenosine (A1/A2 agonist) were consistent with that of an A2B receptor subtype mediating the inhibitory effects. We conclude that adenosine inhibits FCS-induced collagen and total protein synthesis in cardiac fibroblasts via activation of A2B receptors. These studies suggest, but do not prove, that endogenous adenosine may protect against cardiac fibrosis.