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Session 15 Oral Abstract Session Neuropathogenesis Session Time: Tuesday, 10 am - 12:30 pm Room 606-609

12:15   70. An in Vitro Model of Antiretroviral Toxic Neuropathy in Dorsal Root Ganglion Sensory Neurons S. Keswani*, C. Hasan, J. McArthur, J. Griffin, and A. Hoke Johns Hopkins Univ. Sch. of Med., Baltimore, MD Background: Nucleoside analogue reverse transcriptase inhibitors (NRTIs) are an essential component of HAART, substantially reducing the morbidity and mortality of HIV infection. However, the use of many of these drugs has been associated with a painful, sensory neuropathy, possibly via neuronal mitochondrial dysfunction, that often necessitates drug discontinuation by the patient. Development of therapeutic drugs for treatment or prevention of this toxic neuropathy is hampered by the fact that there are no good established in vivo or in vitro models of NRTI-induced sensory neuropathy. Methods: Dissociated dorsal root ganglia isolated from rat embryos of 15 days' gestation were plated on a Schwann cell monolayer. Varying concentrations of ddC, ddI, d4T, AZT, or vehicle control were added, and after 4 hours of incubation, the cells were fixed and immunostained with anti-BIII-tubulin antibody, a neuronal marker. Using unbiased stereological methods, neurite-bearing neurons were counted and expressed as a percentage of all BIII-tubulin-positive cells. To study possible NRTI-induced mitochondrial dysfunction, the cells were incubated with 5muM of the above NRTIs or vehicle control for 4 hours, stained with the mitochondrial potentiometric dye JC-1 (Molecular Probes), and imaged with confocal microscopy. Results: There was clear dose-dependent inhibition of neuritic growth by ddC, ddI and d4T. 50% inhibition of neuritic growth was seen at 5muM ddC, 10muM ddI and 20muM d4T. In contrast, AZT did not cause any observable neurotoxicity. Confocal imaging of JC-1-stained neurons revealed mitochondrial membrane potentials of 100%, 30%, 30%, 65%, and 100% in control, ddC, ddI, d4T, and AZT-treated samples, respectively. Conclusions: We have established an in vitro model of NRTI neurotoxicity in primary sensory neurons. This in vitro model correlates well with the clinical profile of NRTIs, in that the potency with which each NRTI inhibits neuritic outgrowth parallels the potency of each drug in causing peripheral neuropathy in HIV positive patients i.e. ddC > ddI >d4T. Furthermore, AZT, which does not cause a peripheral neuropathy in humans, does not cause any neurotoxicity in our model. NRTI neurotoxicity may be mediated by neuronal mitochondrial dysfunction, with effects on mitochondrial membrane potential being observed as early as 4 hours after incubation with NRTI.

©2002 9th Conference on Retroviruses and Opportunistic Infections