title: Mitogen-activated protein kinase phosphatase-1 (MKP-1) in retinal ischemic preconditioning.
abstract: We previously described the phenomenon of retinal ischemic pre-conditioning (IPC) and we have shown the role of various signaling proteins in the protective pathways, including the mitogen-activated protein kinase p38. In this study we examined the role in IPC of mitogen-activated protein kinase phosphatase-1 (MKP-1), which inactivates p38. Ischemia was produced by elevation of intraocular pressure above systolic arterial blood pressure in adult Wistar rats. Preconditioning was produced by transient retinal ischemia for 5 min, 24 h prior to ischemia. Small interfering RNA (siRNA) to MKP-1 or a control non-silencing siRNA, was injected into the vitreous 6 h prior to IPC. Recovery was assessed by electroretinography (ERG) and histology. The a-and b-waves, and oscillatory potentials (OPs), measured before and 1 week after ischemia, were then normalized relative to pre-ischemic baseline, and corrected for diurnal variation in the normal non-ischemic eye. The P2, or post-photoreceptor component of the ERG (which reflects function of the rod bipolar cells in the inner retina), was derived using the Hood-Birch model. MKP-1 was localized in specific retinal cells using immunohistochemistry; levels of mitogen-activated protein kinases were measured using Western blotting. Injection of siRNA to MKP-1 significantly attenuated the protective effect of IPC as reflected by decreased recovery of the electroretinogram a and b-waves and the P2 after ischemia. The injection of siRNA to MKP-1 reduced the number of cells in the retinal ganglion cell and outer nuclear layers after IPC and ischemia. Blockade of MKP-1 by siRNA also increased the activation of p38 at 24 h following IPC. MKP-1 siRNA did not alter the levels of phosphorylated jun N-terminal kinase (JNK) or extracellular signal-regulated kinase (ERK) after IPC. The results suggest the involvement of dual-specificity phosphatase MKP-1 in IPC and that MKP-1 is involved in IPC by regulating levels of activated MAPK p38.
authors.affiliation: Department of Anesthesia and Critical Care, The University of Chicago, USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Dreixler
authors.forename: Anthony
authors.initials: A
authors.lastname: Bratton
authors.forename: Eugenie
authors.initials: E
authors.lastname: Du
authors.forename: Afzhal R
authors.initials: AR
authors.lastname: Shaikh
authors.forename: Brian
authors.initials: B
authors.lastname: Savoie
authors.forename: Michael
authors.initials: M
authors.lastname: Alexander
authors.forename: Marcus M
authors.initials: MM
authors.lastname: Marcet
authors.forename: Steven
authors.initials: S
authors.lastname: Roth
mesh_terms: D000818:Animals; D015153:Blotting, Western; D018929:Cell Culture Techniques; D054638:Dual Specificity Phosphatase 1 / Q000502:physiology*; D004596:Electroretinography; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D019194:Ischemic Preconditioning; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D010766:Phosphorylation; D034622:RNA Interference; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000201:enzymology / Q000503:physiopathology / Q000517:prevention & control*; D012160:Retina / Q000201:enzymology / Q000503:physiopathology; D051245:Retinal Bipolar Cells / Q000502:physiology; D012164:Retinal Diseases / Q000201:enzymology / Q000503:physiopathology / Q000517:prevention & control*; D012165:Retinal Ganglion Cells / Q000378:metabolism; D012171:Retinal Vessels / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D054638:Dual Specificity Phosphatase 1