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Growth factor regulation of intracellular pH homeostasis under hypoxic conditions in isolated equine articular chondrocytes
Author(s) -
Milner Peter I.,
Smith Hannah C.,
Robinson Rebecca,
Wilkins Robert J.,
Gibson John S.
Publication year - 2013
Publication title -
journal of orthopaedic research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1002/jor.22221
Subject(s) - intracellular ph , homeostasis , wortmannin , intracellular , chemistry , reactive oxygen species , hypoxia (environmental) , kinase , blot , phosphorylation , microbiology and biotechnology , medicine , endocrinology , biochemistry , biology , oxygen , protein kinase b , organic chemistry , gene
Hypoxia and acidosis are recognized features of inflammatory arthroses. This study describes the effects of IGF‐1 and TGF‐β 1 on pH regulatory mechanisms in articular cartilage under hypoxic conditions. Acid efflux, reactive oxygen species (ROS), and mitochondrial membrane potential were measured in equine articular chondrocytes isolated in the presence of serum (10% fetal calf serum), IGF‐1 (1, 10, 50, 100 ng/ml) or TGF‐β 1 (0.1, 1, 10 ng/ml) and then exposed to a short‐term (3 h) hypoxic insult (1% O 2 ). Serum and 100 ng/ml IGF‐1 but not TGF‐β 1 attenuated hypoxic regulation of pH homeostasis. IGF‐1 appeared to act through mitochondrial membrane potential stabilization and maintenance of intracellular ROS levels in very low levels of oxygen. Using protein phosphorylation inhibitors PD98059 (25 µM) and wortmannin (200 nM) and Western blotting, ERK1/2 and PI‐3 kinase pathways are important for the effect of IGF‐1 downstream to ROS generation in normoxia but only PI‐3 kinase is implicated in hypoxia. These results show that oxygen and growth factors interact to regulate pH recovery in articular chondrocytes by modulating intracellular oxygen metabolites. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 197–203, 2013