Development of a Novel Glutamate Receptor Ligand for PET Scans in Neuropsychiatric Systemic Lupus Erythematosus

Neuropsychiatric lupus is comprised of numerous, complex central and peripheral nervous system symptoms whose pathophysiologic mechanisms remain poorly understood. Cross-reactive anti-dsDNA antibodies have been shown to bind NR2A/NR2B subunits of the N-methyl D-aspartate receptor (NMDAR) on neurons and synergize with glutamate in a concentration dependent manner to either modulate receptor function or cause an excitotoxic, non-inflammatory neuronal death. Mice immunized to express anti-NMDAR Aab demonstrate a causal relationship between anti-NMDAR Aab and persistent behavioral and cognitive neuropathology following compromise to the blood brain barrier (BBB) which is necessary for Aab access to the brain. The investigators' previous cross-sectional FDG-PET studies of resting brain glucose metabolism demonstrate robust hypermetabolism in the hippocampus of SLE subjects that associates independently with serum Anti-NMDAR Aab titer and impaired memory. Moreover, the combination of hippocampus hypermetabolism and elevated serum titers of Anti-NMDAR Aab has a higher predictive value for memory impairment than either variable alone. These significant correlations must be tested in a longitudinal study to evaluate the utility of FDG-PET as a biomarker for Anti-NMDAR Aab-mediated brain damage. The proposed longitudinal studies will inform the investigators about correlates of cognitive and behavioral change over time using FDG-PET imaging (Aim 1). Additionally, the investigators will explore NMDAR biology with a novel PET ligand, \[11C\]-CNS5161, used to localize and quantify NMDAR activation (Aim 2) and explore the role of blood brain barrier (BBB) integrity in cognitive and behavioral impairment (Aim 3).