Inhibition of Vascular Adhesion Protein 1 Protects Dopamine Neurons From the Effects of Acute Inflammation and Restores Habit Learning in the Striatum

Abstract

\n BackgroundChanges in dopaminergic neural function can be induced by an acute inflammatory state that, by altering the integrity of the neurovasculature, induces neuronal stress, cell death and causes functional deficits. Effectively blocking these effects of inflammation could, therefore, reduce both neuronal and functional decline. To test this hypothesis, we inhibited vascular adhesion protein 1 (VAP-1), a membrane bound protein expressed on endothelial cell surface, that mediates leukocyte extravasation and induces oxidative stress. MethodWe induced dopaminergic neuronal loss by infusing lipopolysaccharide (LPS) directly into the substantia nigra (SN) in rats and administered the VAP-1 inhibitor, PXS-4681A, daily. ResultsLPS resulted in an acute inflammatory response, the loss of dopaminergic neurons in the SN, reduced dopaminergic projection to SN target regions, particularly the dorsolateral striatum (DLS), and a deficit in habit learning, a key function of the DLS. In an attempt to protect SN neurons from this inflammatory response we found that VAP-1 inhibition not only reduced neutrophil infiltration in the SN and striatum but also reduced the associated microglia and astrocyte response in the striatum. We found VAP-1 inhibition protected dopaminergic neurons in the SN, their projections to the striatum and promoted the functional recovery of habit learning. Thus, we reversed the loss of habitual actions, a function usually dependent on dopamine release in DLS and sensitive to striatal dysfunction. ConclusionsWe establish, therefore, that VAP-1 inhibition has an anti-inflammatory profile that may have beneficial in the treatment of dopaminergic dysfunction caused by an acute inflammatory state in the brain.