Faculty Collaboration Database

Parallel regulation of extracellular ATP and inorganic pyrophosphate: roles of growth factors, transduction modulators, and ANK. Connect Tissue Res 2011 Apr;52(2):139-46

Date

07/08/2010

Pubmed ID

20604715

DOI

10.3109/03008207.2010.491928

Scopus ID

2-s2.0-79952310245 (requires institutional sign-in at Scopus site)   61 Citations

Abstract

OBJECTIVE: Extracellular inorganic pyrophosphate (ePPi) is a key regulator of pathologic mineralization in articular cartilage. Articular chondrocytes generate ePPi by the transportation of intracellular PPi (iPPi) through transport mechanisms such as ANK or by the degradation of extracellular adenosine triphosphate (eATP) by ectoenzymes. Although numerous modulators of ePPi have been characterized, little is known about eATP elaboration in cartilage. We sought to determine (1) whether eATP is coordinately regulated with ePPi and (2) whether ANK transports ATP.

METHODS: Primary articular chondrocytes were treated with factors known to modulate ePPi levels including growth factors (TGFβ1 and IGF-1), anion channel inhibitors, and chemicals that alter adenylyl cyclase and protein kinase C activities. Additional chondrocyte monolayers were infected with adenovirus containing functional (Ad-ANK) or mutated (Ad-ANK mutant) ANK sequences. eATP levels were measured with a bioluminescent assay.

RESULTS: TGFβ1 enhanced eATP accumulation by 33%, whereas IGF-1 decreased eATP accumulation by 63% and attenuated TGFβ1-induced eATP release by 72%. Forskolin and probenecid diminished eATP accumulation by 55% and 89%. Phorbol-12-myristate-13-acetate increased eATP by 29%. Transfection of chondrocytes with Ad-ANK caused a 10-fold increase in eATP compared with control values.

CONCLUSION: Modulation of eATP by various factors paralleled their effects on ePPi production, suggesting a shared pathway of ePPi and eATP production and implicating ANK in eATP transport. As eATP directly contributes to pathologic mineralization in articular cartilage, understanding eATP regulation may lead to effective therapies for crystal-associated arthritis.

Author List

Costello JC, Rosenthal AK, Kurup IV, Masuda I, Medhora M, Ryan LM

Authors

Meetha Medhora Professor in the Radiation Oncology department at Medical College of Wisconsin
Ann K. Rosenthal MD Associate Dean, Professor in the Medicine department at Medical College of Wisconsin
Lawrence M. Ryan MD Emeritus Professor in the Medicine department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Adenosine Triphosphate
Adenoviridae
Adenylyl Cyclases
Animals
Calcification, Physiologic
Cartilage, Articular
Chondrocytes
Colforsin
Diphosphates
Extracellular Space
Genetic Vectors
Humans
Hydrolysis
Insulin-Like Growth Factor I
Intercellular Signaling Peptides and Proteins
Membrane Proteins
Phosphate Transport Proteins
Probenecid
Protein Kinase C
Sus scrofa
Transforming Growth Factor beta1