Effects of an adenosine kinase inhibitor and an adenosine deaminase inhibitor on accumulation of extracellular adenosine by equine articular chondrocytes

Anthony M. Tesch Departments of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616.

Search for other papers by Anthony M. Tesch in
Current site
Google Scholar
PubMed
Close
 BS
,
Melinda H. MacDonald Departments of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616.

Search for other papers by Melinda H. MacDonald in
Current site
Google Scholar
PubMed
Close
 DVM, PhD
,
Cynthia Kollias-Baker K. L. Maddy Equine Analytical Chemistry Laboratory, School of Veterinary Medicine, University of California, Davis, CA 95616.

Search for other papers by Cynthia Kollias-Baker in
Current site
Google Scholar
PubMed
Close
 DVM, PhD
, and
Hilary P. Benton Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, CA 95616.

Search for other papers by Hilary P. Benton in
Current site
Google Scholar
PubMed
Close
 PhD

Click on author name to view affiliation information

Abstract

Objective—To investigate accumulation of extracellular adenosine (ADO) by equine articular chondrocytes and to compare effects of adenosine kinase inhibition and adenosine deaminase inhibition on the amount of nitric oxide (NO) produced by lipopolysaccharide (LPS)-stimulated chondrocytes.

Sample Population—Articular cartilage from metacarpophalangeal and metatarsophalangeal joints of 14 horses.

Procedure—Chondrocytes were cultured as monolayers, and cells were incubated with LPS, the adenosine kinase inhibitor 5'-iodotubercidin (ITU), or the adenosine deaminase inhibitor erythro-9-(2-hydroxy-3- nonyl)adenine hydrochloride (EHNA). Concentrations of ADO in cell supernatants were measured by use of reverse-phase high-performance liquid chromatography. Effect of inhibition of enzymatic metabolism of ADO on induced NO production was evaluated by exposing cells to a combination of LPS and ITU or LPS and EHNA.

Results—Articular chondrocytes accumulated extracellular ADO when exposed to LPS or ITU. Chondrocytes exposed to ITU accumulated ADO in a time-dependent manner. Unstimulated chondrocytes did not accumulate ADO. Similarly, EHNA alone did not produce detectable ADO concentrations; however, addition of EHNA and ITU resulted in a synergistic effect on accumulation of ADO. Lipopolysaccharideinduced NO production was more effectively suppressed by exposure to ITU than to EHNA

Conclusions and Clinical Relevance—Equine articular chondrocytes release ADO in response to the proinflammatory stimulus of bacterial LPS. Inhibition of the metabolism of ADO increases accumulation of extracellular ADO. Autocrine release of ADO from chondrocytes may play a role in the cellular response to tissue damage in arthritic conditions, and pharmacologic modulation of these pathways in joints of arthritic horses could be a potential method of therapy. (Am J Vet Res 2002;63:1512–1519)

Abstract

Objective—To investigate accumulation of extracellular adenosine (ADO) by equine articular chondrocytes and to compare effects of adenosine kinase inhibition and adenosine deaminase inhibition on the amount of nitric oxide (NO) produced by lipopolysaccharide (LPS)-stimulated chondrocytes.

Sample Population—Articular cartilage from metacarpophalangeal and metatarsophalangeal joints of 14 horses.

Procedure—Chondrocytes were cultured as monolayers, and cells were incubated with LPS, the adenosine kinase inhibitor 5'-iodotubercidin (ITU), or the adenosine deaminase inhibitor erythro-9-(2-hydroxy-3- nonyl)adenine hydrochloride (EHNA). Concentrations of ADO in cell supernatants were measured by use of reverse-phase high-performance liquid chromatography. Effect of inhibition of enzymatic metabolism of ADO on induced NO production was evaluated by exposing cells to a combination of LPS and ITU or LPS and EHNA.

Results—Articular chondrocytes accumulated extracellular ADO when exposed to LPS or ITU. Chondrocytes exposed to ITU accumulated ADO in a time-dependent manner. Unstimulated chondrocytes did not accumulate ADO. Similarly, EHNA alone did not produce detectable ADO concentrations; however, addition of EHNA and ITU resulted in a synergistic effect on accumulation of ADO. Lipopolysaccharideinduced NO production was more effectively suppressed by exposure to ITU than to EHNA

Conclusions and Clinical Relevance—Equine articular chondrocytes release ADO in response to the proinflammatory stimulus of bacterial LPS. Inhibition of the metabolism of ADO increases accumulation of extracellular ADO. Autocrine release of ADO from chondrocytes may play a role in the cellular response to tissue damage in arthritic conditions, and pharmacologic modulation of these pathways in joints of arthritic horses could be a potential method of therapy. (Am J Vet Res 2002;63:1512–1519)

All Time Past Year Past 30 Days
Abstract Views 37 0 0
Full Text Views 1432 1248 46
PDF Downloads 76 50 2
Advertisement