Herpes stromal keratitis (HSK) is a chronic inflammatory condition that develops in response to a recurrent corneal infection with herpes simplex virus-1 (HSV-1). HSK is the leading cause of infection-induced corneal blindness in the United States. Clinical manifestation of HSK involves the development of opacity and neovascularizationintotheavascularcornea.Newlyformedleakybloodvesselsinthecornealstromaobscure thevisualaxis,traffictheleukocytes(mostlyneutrophils)intotheinflamedcornea,andcausethecornealedema. The current mainstay of HSK treatment requires the long-term use of oral antiviral drugs and the topical application of steroids. The prolonged use of topical steroids causes a predisposition to herpetic reactivation, cataract development, and increased intraocular pressure (IOP), which may cause the development of glaucoma.AbetterunderstandingofcellularandmoleculareventsinvolvedinthepathogenesisofHSKcould provide novel therapeutic targets to reduce the severity of HSK. The focus of this application is to understand themechanismsbywhichInsulin-likegrowthfactorbindingprotein-3(IGFBP-3)regulatesthepathogenesisof HSK.IGFBP-3exertsitseffectthroughinsulin-likegrowthfactor(IGF)-independentand-dependentmechanisms. In an IGF-independent manner, IGFBP-3 is known to induce cellular senescence. The cellular senescence is reportedtoinhibitviralreplication.TheIGF-dependentactivityofIGFBP-3involvessequestrationofIGF-1and IGF-2 molecules and limiting their bioavailability to IGF-1R, and thereby regulates IGF-1R signaling. Our preliminaryresultsshowedanelevatedexpressionofIGFBP-3inHSV-1infectedcorneasofB6mice,whereas a significantly reduced amount of IGFBP-3 protein was detected in the circulation of infected B6 mice when compared to uninfected B6 mice. The infected corneas of IGFBP-3 knockout (IGFBP-3 KO) mice showed an increased viral load. Besides, increased phosphorylation of IGF-1R, the first step in IGF-1R signaling, was determined in leukocytes infiltrating the HSK developing corneas of IGFBP-3 KO than B6 mice. A significant increase in hemangiogenesis and opacity was measured in infected corneas of IGFBP-3 KO than B6 mice. Together, these results led us to hypothesize that IGFBP-3 enhances viral clearance, reduces angiogenesis, and decreases the survival and effector function of myeloid cells in HSK developing corneas. Therefore, enhancingtheIGFBP-3proteinlevelinHSV-1infectedcorneashouldalleviatetheseverityofHSK.
Three aims areproposedtotestourhypothesis.
AimI willtestthehypothesisthathypoxiaenhancesIGFBP-3expression incornealepithelialcells,andanincreasedlevelofIGFBP-3inducessenescenceinepithelialcells,andcellular senescence promotes HSV-1 clearance from the infected cornea.
Aim II will test the hypothesis that IGF-1R signaling in myeloid and vascular endothelial cells control the severity of HSK.
Aim III will test the hypothesis thatincreasingIGFBP-3proteininHSV-1infectedcorneaalleviatestheseverityofHSK.
ThegoalofthisapplicationistodeterminetheunderlyingmechanismsbywhichInsulin-likegrowthfactorbinding protein-3(IGFBP-3)reducesviralload,hemangiogenesis,andthesurvivalandeffectorfunctionofneutrophils inherpesstromalkeratitisdevelopingcorneas.
