2003 — 2005 |
Srinivas, Sangly P |
R03Activity Code Description: To provide research support specifically limited in time and amount for studies in categorical program areas. Small grants provide flexibility for initiating studies which are generally for preliminary short-term projects and are non-renewable. |
Myocilin-Induced Er Stress in Trabecular Meshwork Cells @ Indiana University Bloomington
DESCRIPTION (provided by applicant): Certain mutations of MYOC, a gene expressed in trabecular meshwork (TM cells), are associated with the juvenile onset of POAG (primary open angle glaucoma). The gene product of MYOC, myocilin, is a secretory protein of unknown function. Targeted null mutations of MYOC show neither an elevated intraocular pressure nor manifest morphological abnormalities in the TM, indicating that the disease-causing mutations of MYOC produce proteins that cause negative effects in TM cells (called gain-of-function toxicity). What is the nature of this toxicity? What is the molecular mechanism underlying the toxicity? In this project, we hypothesize that certain mutations of MYOC result in unfolding of myocilin leading to its retention and aggregation in the endoplasmic reticulum (ER) of the TM cells. Persistent accumulation of secretory or membrane proteins in the ER lumen is known to cause "ER stress." This stress elicits a unique but complex ER-to-nucleus signaling called "Unfolded Protein Response" (UPR) consisting of mechanisms to restore homeostasis in the ER. A deficiency or overshoot in UPR is known to adversely affect some, if not all of the functions of the ER. Therefore we further hypothesize that retention of aberrant myocilin induces UPR which, in turn, leads to Ca 2+ deregulation in TM cells. A number of studies on the pharmacology of TM have clearly demonstrated that elevated intracellular Ca 2+ increases the contractility of the TM cells and decreases the outflow facility across TM. Thus, the specific aims of this project are to characterize UPR and its mechanisms resulting from overexpression/mutations in MYOC, and to determine the adverse effects of myocilin-induced UPR on Ca2+ homeostasis. UPR induced by overexpression of myocilin and mutant forms of MYOC will be examined in primary cultures of bovine TM and HEK-293T cell line, respectively. As a positive control of UPR, we will employ exogenous drugs known to cause protein unfolding in the ER (e.g., tunicamycin). We will characterize UPR in terms of activation of components of UPR signaling pathways and on activation of various ER-specific chaperones. Ca 2+ deregulation will be investigated by examining transcriptional activation of SERCA Ca2+ ATPase and structural components of capacitative calcium influx pathways. Our techniques and protocols include use of quantitative real-time PCR, Northern blotting, Western blotting, confocal microscopy, and coimmuniprecipitation. These studies will lead to the development of an essential knowledge base and influence research in the field of glaucoma pathophysiology, diagnostics, and therapeutics.
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0.958 |
2008 — 2009 |
Srinivas, Sangly P |
R21Activity Code Description: To encourage the development of new research activities in categorical program areas. (Support generally is restricted in level of support and in time.) |
Kinetics of Drug Penetration Across the Cornea At a Microscopic Level @ Indiana University Bloomington
[unreadable] DESCRIPTION (provided by applicant): Kinetics of Drug Penetration across the Cornea at a Microscopic Level Drugs applied topically to the eye access the intraocular tissues predominantly by penetration across the multi-layered cornea, consisting of a stratified epithelial layer, a thick collagenous stroma and a leaky monolayer of endothelium. Previous studies on topical drug kinetics to the eye have focused mainly on compartmental modeling of transport across the cornea. Such models have disregarded the inherent heterogeneity in the cornea, rendering them incapable of making sufficiently accurate predictions. The disregard for the heterogeneity in the cornea stems from the fact that experimental transcorneal concentration profiles of drugs are unavailable and difficult to obtain. Accordingly, only the average values of the drugs in the cornea, which are usually measured, have been employed in the development of pharmacokinetic modeling of topical drugs to the eye. This project will employ a novel custom-built confocal scanning microfluorometer to measure transcorneal profiles of a series of fluorescent compounds employed as drug analogs across rabbit cornea mounted in vitro. The resulting transcorneal concentration profiles will be employed to develop a phenomenologically-based non-compartmental pharmacokinetic model. The resulting model will then be employed to predict pharmacokinetics for topical administration of the fluorescent drug analogs. These predictions will be compared with in vivo data, which will be obtained for the same fluorescent compounds using another custom-built ocular spot-fluorometer. The latter instrument can measure average fluorescence from the cornea and anterior chamber. Overall, the results from this project involving in vivo and in vitro experiments is expected to yield detailed mechanistic understanding of topical drug kinetics and eventually enable rational drug design as well as the development of optimal drug dosage regimen. PUBLIC HEALTH RELEVANCE: More than 90% of the drugs to the eye are administered by topical administration. In this project, we propose to investigate how the topically administered drugs penetrate across the cornea into the eye. We expect to obtain a mechanistic understanding of the penetration, which is needed for rational drug design and optimal design of dosage regimen. [unreadable] [unreadable] [unreadable]
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0.958 |