tetracycline and Retinal-Degeneration

The proinflammatory cytokine, interleukin (IL)-1beta, is known to induce vascular dysfunction and cell death. We investigated the role of IL-1beta and caspase-1 (the enzyme that produces it) in diabetes-induced degeneration of retinal capillaries. Caspase-1 activity is increased in retinas of diabetic and galactosemic mice and diabetic patients. First, we investigated the effect of agents known to inhibit caspase-1 (minocycline and tetracycline) on IL-1beta production and retinal capillary degeneration in diabetic and galactose-fed mice. Second, we examined the effect of genetic deletion of the IL-1beta receptor on diabetes-induced caspase activities and retinal capillary degeneration. Diabetic and galactose-fed mice were injected intraperitoneally with minocycline or tetracycline (5 mg/kg). At 2 months of diabetes, minocycline inhibited hyperglycemia-induced caspase-1 activity and IL-1beta production in the retina. Long-term administration of minocycline prevented retinal capillary degeneration in diabetic (6 months) and galactose-fed (13 months) mice. Tetracycline inhibited hyperglycemia-induced caspase-1 activity in vitro but not in vivo. Mice deficient in the IL-1beta receptor were protected from diabetes-induced caspase activation and retinal pathology at 7 months of diabetes. These results indicate that the caspase-1/IL-1beta signaling pathway plays an important role in diabetes-induced retinal pathology, and its inhibition might represent a new strategy to inhibit capillary degeneration in diabetic retinopathy.

Topics: Animals; Capillaries; Caspase 1; Caspase 3; Caspase Inhibitors; Diabetes Mellitus, Experimental; Diabetic Retinopathy; Galactose; Galactosemias; Glucose; Interleukin-1beta; Male; Mice; Mice, Inbred C57BL; Minocycline; Models, Animal; Retinal Degeneration; Retinal Vessels; Signal Transduction; Tetracycline

Viral delivery of neurotrophins or other therapeutic genes is an attractive option for treating retinal degeneration. Regulated expression of these genes in the retina is needed to aid in dose delivery and to promote safety. To evaluate whether tetracycline (tet)-inducible transgenes encapsidated in recombinant adeno-associated viruses (rAAV) can provide controlled gene expression in vitro and in the rat retina, two viruses were constructed: a silencer/activator vector and an inducible doxycycline (dox)-responsive GFP vector. Combinations of these two viruses were subretinally injected into wild-type rats and dox was orally administered through the drinking water. Retinal GFP expression was monitored in vivo with a noninvasive fluorescence imaging method. Eyes were also examined by histology, Western analysis, and electroretinography. Subretinal injection of rAAV efficiently delivers inducible genes to both photoreceptors and retinal pigment epithelial cells. GFP expression was initially observed 1 week postinduction, and GFP protein was undetectable after removal of dox. In uninduced animals, GFP expression was negligible. The dox dosage was varied in vivo and showed a correlation to the level of GFP expression. Thus, transduction of retinal cells with tet-inducible vectors allows for tight regulation of gene expression.

Topics: Animals; Blotting, Western; Cell Line; Cloning, Molecular; Dependovirus; Dose-Response Relationship, Drug; Electroretinography; Gene Expression Regulation; Gene Transfer Techniques; Genes, Reporter; Genetic Vectors; Green Fluorescent Proteins; Humans; Luminescent Proteins; Models, Genetic; Rats; Retina; Retinal Degeneration; Tetracycline; Time Factors; Transduction, Genetic