Acid stress increases gene expression of proinflammatory cytokines in Madin-Darby canine kidney cells.
Metabolic acidosis is thought to exacerbate chronic kidney disease in part by stimulating the release of potentially injurious substances. To define the genes whose expression is affected by exposure to an acidic milieus, we examined the effect of exposure of MDCK cells to pH 7.4 and pH 7.0 for 24 h on gene expression using a canine derived microarray. Exposure to this pH stress for 24 h led to increased expression of 278 genes (2.2% of the transcriptome) by at least 2-fold and 60 of these (21%) were upregulated by >3-fold. On the other hand, 186 genes (1.5% of the transcriptome) were downregulated by at least 2-fold and 16 of these (9%) were downregulated by 3-fold or more. Ten percent of the genes upregulated by at least threefold encode proinflammatory cytokine proteins, including colony stimulating factor 2, chemokine ligand 7, chemokine ligand 20, chemokine ligand 8, and interleukin-1α. Two others encode metallopeptidases. The most highly upregulated gene encodes a protein, lubricin, shown to be important in preventing cartilage damage and in tissue injury or repair. Upregulation of four genes was confirmed by quantitative PCR. Housekeeping genes were not increased. To examine the effect of decreasing medium pH, we measured intracellular pH (pH(i)) using 2,7-bis (2-carboxyethyl)5-carboxyfluorescein. With extracellular pH (pH(o)) of 7.0, pH(i) fell and remained depressed. These findings suggest that a pH stress alone can increase renal expression of proinflammatory and other genes that contribute to renal injury.
Medical Services, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA 90073, USA.
Suraja
S
Raj
David R
DR
Scott
Thomas
T
Nguyen
George
G
Sachs
Jeffrey A
JA
Kraut
D000138:Acidosis / Q000503:physiopathology*; D000818:Animals; D016207:Cytokines / Q000096:biosynthesis*; D004285:Dogs; D015536:Down-Regulation; D005452:Fluoresceins; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000378:metabolism*; D061985:Madin Darby Canine Kidney Cells; D008840:Microfilament Proteins / Q000096:biosynthesis; D009219:Myosin-Light-Chain Kinase / Q000096:biosynthesis; D040081:Protein Array Analysis; D051742:Transcription Factor CHOP / Q000096:biosynthesis; D059467:Transcriptome / Q000187:drug effects; D015854:Up-Regulation
D016207:Cytokines; D005452:Fluoresceins; D008840:Microfilament Proteins; D051742:Transcription Factor CHOP; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein; D009219:Myosin-Light-Chain Kinase