Neuroprotective effects of fatty acid amide hydrolase catabolic enzyme inhibition in a HIV-1 Tat model of neuroAIDS

Abstract

The HIV-1 transactivator of transcription (Tat) is a neurotoxin involved in the pathogenesis of HIV-1 associated neurocognitive disorders (HAND). The neurotoxic effects of Tat are mediated directly via AMPA/NMDA receptor activity and indirectly through neuroinflammatory signaling in glia. Emerging strategies in the development of neuroprotective agents involve the modulation of the endocannabinoid system. A major endocannabinoid, anandamide (N-arachidonoylethanolamine, AEA), is metabolized by fatty acid amide hydrolase (FAAH). Here we demonstrate using a murine prefrontal cortex primary culture model that the inhibition of FAAH, using PF3845, attenuates Tat-mediated increases in intracellular calcium, neuronal death, and dendritic degeneration via cannabinoid receptors (CBR and CBR). Live cell imaging was used to assess Tat-mediated increases in [Ca], which was significantly reduced by PF3845. A time-lapse assay revealed that Tat potentiates cell death while PF3845 blocks this effect. Additionally PF3845 blocked the Tat-mediated increase in activated caspase-3 (apoptotic marker) positive neurons. Dendritic degeneration was characterized by analyzing stained dendritic processes using Imaris and Tat was found to significantly decrease the size of processes while PF3845 inhibited this effect. Incubation with CBR and CBR antagonists (SR141716A and AM630) revealed that PF3845-mediated calcium effects were dependent on CBR, while reduced neuronal death and degeneration was CBR-mediated. PF3845 application led to increased levels of AEA, suggesting the observed effects are likely a result of increased endocannabinoid signaling at CBR/CBR. Our findings suggest that modulation of the endogenous cannabinoid system through inhibition of FAAH may be beneficial in treatment of HAND.

Gene Expression Analysis of Astrocyte and Microglia Endocannabinoid Signaling during Autoimmune Demyelination

“…In this study, the low number of astrocytes and microglial cells purified for analysis precluded us from providing experimental evidence of changes in endocannabinoid contents. In this regard, the development of high-sensitivity liquid chromatography-mass spectrometry techniques allows nowadays the detection of very low amounts of endocannabinoids, but this experimental approach requires a >10 6 cells for accurate and reliable detection of changes in AEA and 2-AG levels [ 55 , 56 , 57 , 58 ]. When evaluating the utility of endocannabinoid measurements as a readout of unbalanced production/metabolism it should also be kept in mind that these alterations may be activity-dependent in vivo and, therefore, not faithfully mirrored upon determination of basal levels in purified cells.…”

A Guide to Targeting the Endocannabinoid System in Drug Design

“…CB1 activation was proved to decrease intracellular Ca levels, thus decreasing neurotoxic glutaminergic activity. CB2 activation was responsible for reduction of neuronal death and degradation [188].…”

Role of epoxy-fatty acids and epoxide hydrolases in the pathology of neuro-inflammation

“…FAAH hydrolyzes, and thus negatively regulates, N-acylethanolamides including the PPAR-α agonists palmitoylethanolamide and oleoylethanolamide and the endocannabinoid arachidonoylethanolamide. Similar to sEH, FAAH is neuroprotective in a number of models of brain injury partially through modulation of the microglia polarization [59,60]. These effects could be attributed primarily to activation of the immunomodulatory cannabinoid receptor 2 (CB 2 R) rather than the CB 1 R. Epoxide metabolites of AEA, called epoxy-fattyethanolamides (EpFEAs), are common metabolites that correspond to both sEH and FAAH signaling that have higher potency on the CB 2 R relative to the CB 1 R [61,62].…”