Faculty Bibliography

A 79-year-old woman with pseudophakic bullous keratopathy had microkeratome-assisted posterior keratoplasty for the treatment of clinically significant corneal edema. An island of epithelial ingrowth was noted in the flap-graft interface that was not communicating with the flap periphery. Partial lifting of the anterior corneal flap and removal and irrigation of the epithelial cells were successfully performed. A review of reports of microkeratome-assisted posterior penetrating keratoplasty shows epithelial ingrowth is common after this procedure. The presence of posterior sutures, a central location of the epithelial cells, communication with the periphery, and evidence of stromal melting should prompt immediate surgical intervention.

Fuchs' endothelial dystrophy is a common disease that has been widely studied since its initial report in 1910 by Ernst Fuchs. Although its clinical course and pathologic characteristics are well described, the etiology and inheritance pattern are still ambiguous. Ongoing work is evaluating the role of mitochondrial DNA in the pathogenesis of FED. Significant advances in the surgical treatment of FED, in part utilizing some of the techniques of refractive surgery, are promising thus far. Larger case series are needed to fully assess the safety, efficacy and indications of these techniques. Indeed, the time is right to take "a fresh look at an aging disease" [9].

Dramatic advances in our understanding of the molecular genetic basis of Leber's hereditary optic neuropathy (LHON) have revolutionized our ability to diagnose and prognosticate this disease. Unfortunately no corresponding advances in the treatment of LHON have emerged. Glaucoma is a prevalent form of optic neuropathy that has been studied extensively. Lessons learned from treatment of LHON and glaucoma may have important implications for both diseases. LHON presents formidable challenges to the design and conduct of clinical trials. The acutely symptomatic LHON patient with monocular vision loss provides a unique clinical situation in which to test an agent during a critical therapeutic window. Advances in neuroprotection, apoptosis, and neurodegenerative diseases may provide important clues for potential therapeutic agents for LHON. Antioxidants and agents that interfere with the critical steps of mitochondrial-dependent, oxidative stress-induced apoptosis are candidates for future LHON therapy. A variety of neuroprotective agents, under active investigation in other diseases, may be useful in LHON therapy. Effective pharmacotherapy will complement the current management approach that has changed little in the 130 years since LHON was originally described.

Elevated vascular endothelial growth factor (VEGF) levels are required for ocular and tumor angiogenesis in animal models. Ischemic hypoxia is strongly correlated with increased VEGF expression in these systems and is considered a physiologically relevant stimulus. Because ischemic hypoxia is often followed by reperfusion and reactive oxygen intermediate (ROI) generation, we examined the potential role of ROI in the control of VEGF gene expression. Human retinal pigment epithelial cells exposed to superoxide or hydrogen peroxide rapidly increased VEGF mRNA levels. Superoxide-associated mRNA increases were dose dependent, blocked by antioxidants, and associated with elevated VEGF protein levels in conditioned media. Increases in VEGF mRNA levels were also observed in cultured human melanoma and rat glioblastoma cells with superoxide or hydrogen peroxide. Cycloheximide prevented the ROI-associated increases in VEGF mRNA. Transcriptional inhibition with actinomycin D revealed an inducible increase in VEGF mRNA half-life, but nuclear run-on experiments showed no increase in VEGF transcriptional rate. Reoxygenation of human retinal pigment epithelial cells in vitro and ocular reperfusion in vivo increased retinal VEGF mRNA levels. Antioxidants prevented the reperfusion-associated VEGF mRNA increases in retina. We conclude that ROIs increase VEGF gene expression in vitro and during the reperfusion of ischemic retina in vivo. The ROI-associated increases are mediated largely through increases in VEGF mRNA stability.

These studies were carried out to characterize the activation of rat striatal tyroxine hydroxylase produced by depolarization of the medial forebrain bundle and to evaluate the possible role of cyclic AMP as a mediator of this activation. The enzymatic properties of tyrosine hydroxylase following in vivo depolarization were compared to those produced by treatment of striatal synaptosomes with dibutyryl cyclic AMP (dbcAMP). Similar effects were observed with regard to enzyme distribution, altered sensitivity to dopamine-induced inhibition, and activity as a function of tyrosine concentration. However, differences between the two treatments were also apparent. First, treatment with dbcAMP shifted the pH optimum from 6.2 to 7.0. In contrast, electrical stimulation decreased the rate of decline in activity as the pH was increased above the optimum, but did not shift the pH optimum. Second, plots of tyrosine hydroxylase activity versus cofactor concentration revealed two enzyme forms for both control and electrically stimulated preparations. However, dbcAMP treatment converted the enzyme to a single high affinity form. These results can be explained by one of the following: (1) cyclic AMP is the sole mediator of enzyme activation, but does not produce a maximally activated enzyme following in vivo depolarization, (2) cyclic AMP is only one of several mediators involved or (3) cyclic AMP is not involved in depolarization-induced activation, with activation occurring via the mediation of other intracellular messengers, such as calcium.