Cytochrome P450 Oxidase 2C Inhibition Adds to ω-3 Long-Chain Polyunsaturated Fatty Acids Protection Against Retinal and Choroidal Neovascularization.

OBJECTIVE: Pathological ocular neovascularization is a major cause of blindness. Increased dietary intake of ω-3 long-chain polyunsaturated fatty acids (LCPUFA) reduces retinal neovascularization and choroidal neovascularization (CNV), but ω-3 LCPUFA metabolites of a major metabolizing pathway, cytochrome P450 oxidase (CYP) 2C, promote ocular pathological angiogenesis. We hypothesized that inhibition of CYP2C activity will add to the protective effects of ω-3 LCPUFA on neovascular eye diseases. APPROACH AND RESULTS: The mouse models of oxygen-induced retinopathy and laser-induced CNV were used to investigate pathological angiogenesis in the retina and choroid, respectively. The plasma levels of ω-3 LCPUFA metabolites of CYP2C were determined by mass spectroscopy. Aortic ring and choroidal explant sprouting assays were used to investigate the effects of CYP2C inhibition and ω-3 LCPUFA-derived CYP2C metabolic products on angiogenesis ex vivo. We found that inhibition of CYP2C activity by montelukast added to the protective effects of ω-3 LCPUFA on retinal neovascularization and CNV by 30% and 20%, respectively. In CYP2C8-overexpressing mice fed a ω-3 LCPUFA diet, montelukast suppressed retinal neovascularization and CNV by 36% and 39% and reduced the plasma levels of CYP2C8 products. Soluble epoxide hydrolase inhibition, which blocks breakdown and inactivation of CYP2C ω-3 LCPUFA-derived active metabolites, increased oxygen-induced retinopathy and CNV in vivo. Exposure to selected ω-3 LCPUFA metabolites of CYP2C significantly reversed the suppression of both angiogenesis ex vivo and endothelial cell functions in vitro by the CYP2C inhibitor montelukast. CONCLUSIONS: Inhibition of CYP2C activity adds to the protective effects of ω-3 LCPUFA on pathological retinal neovascularization and CNV.

Optimization of an Image-Guided Laser-Induced Choroidal Neovascularization Model in Mice.

The mouse model of laser-induced choroidal neovascularization (CNV) has been used in studies of the exudative form of age-related macular degeneration using both the conventional slit lamp and a new image-guided laser system. A standardized protocol is needed for consistent results using this model, which has been lacking. We optimized details of laser-induced CNV using the image-guided laser photocoagulation system. Four lesions with similar size were consistently applied per eye at approximately double the disc diameter away from the optic nerve, using different laser power levels, and mice of various ages and genders. After 7 days, the mice were sacrificed and retinal pigment epithelium/choroid/sclera was flat-mounted, stained with Isolectin B4, and imaged. Quantification of the area of the laser-induced lesions was performed using an established and constant threshold. Exclusion criteria are described that were necessary for reliable data analysis of the laser-induced CNV lesions. The CNV lesion area was proportional to the laser power levels. Mice at 12-16 weeks of age developed more severe CNV than those at 6-8 weeks of age, and the gender difference was only significant in mice at 12-16 weeks of age, but not in those at 6-8 weeks of age. Dietary intake of omega-3 long-chain polyunsaturated fatty acid reduced laser-induced CNV in mice. Taken together, laser-induced CNV lesions can be easily and consistently applied using the image-guided laser platform. Mice at 6-8 weeks of age are ideal for the laser-induced CNV model.

Requirement for pectin methyl esterase and preference for fragmented over native pectins for wall-associated kinase-activated, EDS1/PAD4-dependent stress response in Arabidopsis.

The wall-associated kinases (WAKs) have a cytoplasmic protein kinase domain that spans the plasma membrane and binds pectin in the extracellular matrix of plants. WAKs are required for cell expansion during Arabidopsis seedling development but are also an integral part of the response to pathogens and stress that present oligogalacturonides (OGs), which subsequently bind to WAKs and activate a MPK6 (mitogen-activated protein kinase)-dependent pathway. It was unclear how WAKs distinguish native pectin polymers and OGs to activate one or the other of these two pathways. A dominant allele of WAK2 constitutively activates the stress response, and we show here that the effect is dependent upon EDS1 and PAD4, transcriptional activators involved in the pathogen response. Moreover, the WAK2 dominant allele is suppressed by a null allele of a pectin methyl esterase (PME3) whose activity normally leads to cross-linking of pectins in the cell wall. Although OGs activate a transcriptional response in wild type, the response is enhanced in a pme3/pme3 null, consistent with a competition by OG and native polymers for activation of WAKs. This provides a plausible mechanism for WAKs to distinguish an expansion from a stress pathway.