title: Differential dependence of regulatory volume decrease behavior in rabbit corneal epithelial cells on MAPK superfamily activation.
abstract: We characterized the dependence of hypotonicity-induced regulatory volume decrease (RVD) responses on mitogen-activated protein kinase (MAPK) pathway signaling in SV40-immortalized rabbit corneal epithelial cells (RCEC). Following calcein-AM loading, RVD was monitored using a microplate fluorescence reader. Western blot analysis determined MAPK activation. After 30 min, the RVD response restored the relative cell volume to nearly isotonic values, whereas it was inhibited when cells were bathed either in a Cl- -free solution or with the Cl- -channel inhibitors: 5-nitro-2-(3-phenylpropylamino)benzoic acid or niflumic acid. Similar declines occurred with either a high-K+ (20 mM) supplemented solution or the K+ channel inhibitor 4-aminopyridine. Activation of extracellular signal-regulated kinase (ERK), p38, and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) was time and tonicity-dependent. Stimulation of ERK and SAPK/JNK was maximized earlier than that of p38. Activation of ERK and SAPK/JNK was insensitive to Cl- and K+ channel inhibitors, whereas inhibition with either PD98059 or SP600125, respectively, blocked RVD. However, inhibition of p38 with SB203580had no effect on RVD. Suppression of RVD instead blocked p38 activation. Differences in the dependence of RVD activation on Erk1/2 and p38 signaling were validated in dominant negative (d/n)-Erk1 and d/n-p38 cells. Volume-sensitive Cl- and K+ channel activation contributes, in concert, to RVD in RCEC. Therefore, swelling-induced ERK and SAPK/JNK stimulation precedes Cl- and K+ channel activation, whereas p38 activation occurs as a consequence of RVD.
authors.affiliation: Department of Biological Sciences, State College of Optometry, State University of New York, 33 West 42nd Street, New York, NY 10036, USA.
authors.forename: Zan
authors.initials: Z
authors.lastname: Pan
authors.forename: José E
authors.initials: JE
authors.lastname: Capó-Aponte
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang
authors.forename: Zheng
authors.initials: Z
authors.lastname: Wang
authors.forename: Kathryn S
authors.initials: KS
authors.lastname: Pokorny
authors.forename: Peter S
authors.initials: PS
authors.lastname: Reinach
mesh_terms: D000818:Animals; D015153:Blotting, Western / Q000379:methods; D002461:Cell Line, Transformed; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D002713:Chlorine / Q000502:physiology; D004789:Enzyme Activation / Q000502:physiology; D019573:Epithelium, Corneal / Q000166:cytology* / Q000201:enzymology; D005136:Eye Proteins / Q000502:physiology*; D007552:Isotonic Solutions; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D009997:Osmotic Pressure; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology; D011817:Rabbits; D000077331:Ringer's Solution; D015398:Signal Transduction / Q000502:physiology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D005136:Eye Proteins; D007552:Isotonic Solutions; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D002713:Chlorine; D000077331:Ringer's Solution; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4