The fundamental gap in understanding endogenous neuroprotection evoked by ischemic tolerance impedes identification of therapeutic targets for retinal ischemia, a major cause of visual loss. Involvement of inflamma- tion, glial activation, oxidative stress, and neurodegeneration in chronic retinal ischemic diseases such as di- abetic retinopathy, suggests a primary role for neuroprotection. The long-term goal is to decipher the mechan- isms of endogenous ischemic tolerance, as an innovative modulator of ischemic injury. The overall objective is to understand the activation, control, and downstream mechanisms of two key proteins, Akt and p38, in ischemic tolerance. The central hypothesis is that their activation, individually or together, drives retinal endo- genous tolerance. Underlying the hypothesis is the applicant's results in a rat model wherein p38 evoked, while blocking specific Akt subtypes, attenuated ischemic tolerance. Akt or p38 knockdown inhibited the conceptual- ly-related post-ischemic conditioning (transient ischemia after the damaging ischemia). Rationale for the pro- posal is that, after understanding these signaling mechanisms, the pathways can be precisely tuned, potential- ly translating into effective treatment for the >10 million/year at risk for retinal ischemia. The central hypothesis will be tested in three specific aims: 1) Identify p38 neuroprotective signaling, 2) Identify Akt neuroprotective signaling, 3) Determine mechanisms of delayed post-ischemic conditioning related to p38 and Akt.
In Aim 1, an established RNA interference approach (siRNA) will examine p38's control and downstream mechanisms in ischemic tolerance.
In Aim 2, siRNA will block Akt, and a novel Akt phosphomimetic viral vector whose efficacy is supported by preliminary data, will overexpress Akt subtypes. Measuring substrates of Akt subtypes, and pathway cross-talk will illuminate the mechanisms of neuroprotection.
In Aim 3, using the PI's delayed retinal ischemic post-conditioning model, examination of Akt, p38, and downstream mediators will elucidate the me- chanisms of restoration of post-ischemic neuronal function. Experimental outcomes will be measured in Aims 1-3 by modern, validated molecular and physiological approaches that are well established in the applicant's lab. Innovatively exploiting endogenous neuroprotection by providing ischemic tolerance will yield novel targets to treat ischemic disease by engaging cell survival mechanisms. The proposed research is significant because it is expected to vertically advance and expand understanding of how the retina's endogenous cellular machi- nery can be harnessed to prevent or treat ischemia, while increasing understanding of cell survival signaling in vivo. Ultimately, this knowledge has potential to transform treatment of retinal ischemia by identifying novel, specific molecular interventional targets that will help to decrease the growing problem of visual loss and disa- bility from ischemic disease in the retina.

Public Health Relevance

Retinal ischemia is a common cause of visual impairment and blindness. The proposed research is relevant to public health because identifying the mechanisms of endogenous retinal ischemic tolerance mediated by pro- tein kinase-related signaling is ultimately expected to stimulate development of safe, effective, and innovative treatment or prevention strategies for people at risk for ischemic diseases, as well as enhanced understanding of cellular signaling in vivo. Thus the proposed research is relevant to the part of NIH's mission that pertains to developing fundamental knowledge that will help to reduce the burdens of human disability.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY010343-18
Application #
8404012
Study Section
Biology and Diseases of the Posterior Eye Study Section (BDPE)
Program Officer
Shen, Grace L
Project Start
1994-01-01
Project End
2014-12-31
Budget Start
2013-01-01
Budget End
2013-12-31
Support Year
18
Fiscal Year
2013
Total Cost
$370,500
Indirect Cost
$133,000
Name
University of Chicago
Department
Anesthesiology
Type
Schools of Medicine
DUNS #
005421136
City
Chicago
State
IL
Country
United States
Zip Code
60637
Dreixler, John C; Poston, Jacqueline N; Balyasnikova, Irina et al. (2014) Delayed administration of bone marrow mesenchymal stem cell conditioned medium significantly improves outcome after retinal ischemia in rats. Invest Ophthalmol Vis Sci 55:3785-96
Dreixler, John C; Poston, Jacqueline N; Shaikh, Afzhal R et al. (2011) Delayed post-ischemic conditioning significantly improves the outcome after retinal ischemia. Exp Eye Res 92:521-7
David, Joel; Melamud, Aleksandr; Kesner, Leo et al. (2011) A novel calpain inhibitor for treatment of transient retinal ischemia in the rat. Neuroreport 22:633-6
Dreixler, John C; Bratton, Anthony; Du, Eugenie et al. (2011) Mitogen-activated protein kinase phosphatase-1 (MKP-1) in retinal ischemic preconditioning. Exp Eye Res 93:340-9
Dreixler, John C; Sampat, Ajay; Shaikh, Afzhal R et al. (2011) Protein kinase B (Akt) and mitogen-activated protein kinase p38? in retinal ischemic post-conditioning. J Mol Neurosci 45:309-20
Dreixler, John C; Shaikh, Afzhal R; Alexander, Michael et al. (2010) Post-ischemic conditioning in the rat retina is dependent upon ischemia duration and is not additive with ischemic pre-conditioning. Exp Eye Res 91:844-52
Dreixler, John C; Hemmert, Jonathan W; Shenoy, Shanti K et al. (2009) The role of Akt/protein kinase B subtypes in retinal ischemic preconditioning. Exp Eye Res 88:512-21
Dreixler, John C; Barone, Frank C; Shaikh, Afzhal R et al. (2009) Mitogen-activated protein kinase p38alpha and retinal ischemic preconditioning. Exp Eye Res 89:782-90
Roth, S (2009) Perioperative visual loss: what do we know, what can we do? Br J Anaesth 103 Suppl 1:i31-40
Shen, Yang; Drum, Melinda; Roth, Steven (2009) The prevalence of perioperative visual loss in the United States: a 10-year study from 1996 to 2005 of spinal, orthopedic, cardiac, and general surgery. Anesth Analg 109:1534-45

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