D-cis-Diltiazem Can Produce Oxidative Stress in Healthy Depolarized Rods In Vivo

• Published in: Investigative ophthalmology & visual science 2018-06, Vol.59 (7), p.2999-3010
• Main Authors: Berkowitz, Bruce A, Podolsky, Robert H, Farrell, Benjamin, Lee, Hojun, Trepanier, Christopher, Berri, Ali M, Dernay, Kristin, Graffice, Emma, Shafie-Khorassani, Fatema, Kern, Timothy S, Roberts, Robin
• Format: Article
• Language: English
• Subjects: 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester - pharmacology; Animals; Calcium Channel Agonists - pharmacology; Calcium Channel Blockers - pharmacology; Calcium Channels, L-Type - metabolism; Dark Adaptation - drug effects; Diltiazem - pharmacology; Magnetic Resonance Imaging; Male; Mice; Mice, Inbred C57BL; Oxidative Stress - physiology; Retinal Cell Biology; Retinal Degeneration - physiopathology; Retinal Rod Photoreceptor Cells - drug effects; Retinal Rod Photoreceptor Cells - metabolism; Superoxides - metabolism; Tomography, Optical Coherence
• ISSN: 1552-5783; 0146-0404; 1552-5783
• DOI: 10.1167/iovs.18-23829

New perspectives are needed to understand decades of contradictory reports on the neuroprotective effects of the Cav1.2 L-type calcium channel blocker d-cis-diltiazem in retinitis pigmentosa (RP) models. Here, we address, in vivo, the following two knowledge gaps regarding d-cis-diltiazem's actions in the murine outer retina: (1) do normal mouse rods contain d-cis-diltiazem-insensitive Cav1.2 L-type calcium channels? (2) Can d-cis-diltiazem modify the normal rod redox environment? First, transretinal Cav1.2 L-type calcium channels were noninvasively mapped with manganese-enhanced magnetic resonance imaging (MRI) following agonist Bay K 8644 in C57BL/6 (B6) and in Cav1.2 L-type calcium channel BAY K 8644-insensitive mutant B6 mice. Second, d-cis-diltiazem-treated oxidative stress-vulnerable (B6) or -resistant [129S6 (S6)] mice were examined in vivo (QUEnch-assiSTed [QUEST] MRI) and in whole retina ex vivo (lucigenin). Retinal thickness was measured using MRI. The following results were observed: (1) manganese uptake patterns in BAY K 8644-treated controls and mutant mice identified in vivo Cav1.2 L-type calcium channels in inner and outer retina; and (2) d-cis-diltiazem induced rod oxidative stress in dark-adapted B6 mice but not in light-adapted B6 mice or dark-adapted S6 mice (QUEST MRI). Oxidative stress in vivo was limited to inferior outer retina in dark-adapted B6 mice approximately 1-hour post d-cis-diltiazem. By approximately 4 hours post, only superior outer retina oxidative stress was observed and whole retinal superoxide production was supernormal. All groups had unremarkable retinal thicknesses. D-cis-diltiazem's unexpectedly complex spatiotemporal outer retinal oxidative stress pattern in vivo was dependent on genetic background and rod membrane depolarization, but not apparently dependent on Cav1.2 L-type calcium channels, providing a potential rationale for contradictory results in different RP models.