Botulinum toxin B-induced mouse model of keratoconjunctivitis sicca.

PURPOSE: To develop a mouse model of human chronic dry eye (keratoconjunctivitis sicca [KCS]). METHODS: Under direct visualization with an operating microscope, CBA/J mice received a transconjunctival injection of saline or 1.25, 5, or 20 milliunits (mU) of botulinum toxin B (BTX-B) into the lacrimal gland. The mice were either left unstressed or were subjected to an air blower for 5 h/d, 5 d/wk in fixed temperature and humidity conditions. Tear production and corneal fluorescein staining were evaluated in all groups before injection and at several time points after. Tear production was measured with phenol red-impregnated cotton threads. Corneal fluorescein staining was photographed under cobalt blue light with a digital camera fitted with a macro lens. RESULTS: BTX-B-injected mice displayed significantly decreased tear production until the 4-week time point. Throughout all time points, the addition of environmental blower stress did not appear to alter tear production significantly. Linear regression models, used to evaluate the effects of various doses of BTX-B on tear production, showed that doses higher than 1.25 mU did not provide significantly different outcomes. After 3 days, saline-injected mice showed no corneal staining, whereas BTX-B-injected mice displayed various amounts of staining. At the early time point (day 3), there did not appear to be an additional effect of the blower on corneal fluorescein staining. However, at 1, 2, and 4 weeks, the blower stress appeared to increase the amount of corneal fluorescein staining at each BTX-B dose, although not significantly. Furthermore, at 8 to 10 weeks, in the BTX B-injected groups, corneas had persistent staining, even though tear production had already returned to normal levels. Histopathologic analyses revealed no inflammatory cell infiltration of the stroma or acini of the lacrimal glands and conjunctivae of both saline-injected and BTX-B-injected animals. CONCLUSIONS: Intralacrimal gland injection of BTX-B resulted in persistent corneal fluorescein staining within 3 days, and a significant decrease in aqueous tear production that persisted for 1 month. Intralacrimal gland injection of BTX-B suppressed lacrimation, thereby establishing a dry eye state. This animal model could be a useful tool for investigating the pathogenesis of the chronic condition KCS in humans.

Characterization of a human rhomboid homolog, p100hRho/RHBDF1, which interacts with TGF-alpha family ligands.

The activity of the TGF-alpha-like ligand Spitz in Drosophila depends on Rhomboid, a seven-transmembrane spanning protein that resides in the Golgi and acts as a serine protease to cleave Spitz, thereby releasing the soluble ligand. Several rhomboids in Drosophila have been implicated in the processing of TGF-alpha-like ligands, and consequent EGF receptor activation. The larger number of TGF-alpha-like ligands in vertebrates raises the possibility that they too might be subject to regulation by rhomboid-like proteins. We present the cDNA cloning and polypeptide sequence of an atypically long human rhomboid, which, based on the absence of critical residues for serine protease activity, is not predicted to act as a serine protease. We examined its tissue distribution, in comparison with TGF-alpha and the TGF-alpha-related protein HB-EGF, and the EGF/TGF-alpha receptor, in mouse embryo. This rhomboid, named p100(hRho) or RHBDF1, is a seven-transmembrane protein with a long N-terminal cytoplasmic extension that comprises half of the polypeptide sequence, and is found in the endoplasmic reticulum and Golgi, but not on the cell surface. It is expressed as two forms with different lengths, forms dimers and interacts with TGF-alpha ligands through a luminal interaction with the EGF core ectodomain. Finally, we evaluated the function of p100(hRho)/RHBDF1 in Drosophila, demonstrating that the short, but not the full-length form has functional activity. The characterization of this protein extends our understanding of the rhomboid family of regulatory proteins.

Bilateral endogenous endophthalmitis in a patient with hemoglobin SC disease.

CASE REPORT: Bilateral endogenous endophthalmitis in the setting of pneumococcal bacteremia was diagnosed in a woman with hemoglobin SC disease who presented with decreased vision, increased redness, burning pain, and photophobia. All gram stains and cultures remained negative, and the exact source of her bacteremia was not clear. Nonetheless, early diagnosis and prompt treatment were vital to avoiding a visually devastating outcome. COMMENTS: Aggressive treatment with intravitreal and systemic antibiotics, with or without pars plana vitrectomy, was successful in restoring final visual acuity.