The cannabinoid CB₂ receptor agonist AM1241 enhances neurogenesis in GFAP/Gp120 transgenic mice displaying deficits in neurogenesis.

BACKGROUND AND
PURPOSE: HIV-1 glycoprotein Gp120 induces apoptosis in rodent and human neurons in vitro and in vivo. HIV-1/Gp120 is involved in the pathogenesis of HIV-associated dementia (HAD) and inhibits proliferation of adult neural progenitor cells (NPCs) in glial fibrillary acidic protein (GFAP)/Gp120 transgenic (Tg) mice. As cannabinoids exert neuroprotective effects in several model systems, we examined the protective effects of the CB₂ receptor agonist AM1241 on Gp120-mediated insults on neurogenesis. EXPERIMENTAL APPROACH: We assessed the effects of AM1241 on survival and apoptosis in cultures of human and murine NPCs with immunohistochemical and TUNEL techniques. Neurogenesis in the hippocampus of GFAP/Gp120 transgenic mice in vivo was also assessed by immunohistochemistry. KEY
RESULTS: AM1241 inhibited in vitro Gp120-mediated neurotoxicity and apoptosis of primary human and murine NPCs and increased their survival. AM1241 also promoted differentiation of NPCs to neuronal cells. While GFAP/Gp120 Tg mice exhibited impaired neurogenesis, as indicated by reduction in BrdU⁺ cells and doublecortin⁺ (DCX⁺) cells, and a decrease in cells with proliferating cell nuclear antigen (PCNA), administration of AM1241 to GFAP/Gp120 Tg mice resulted in enhanced in vivo neurogenesis in the hippocampus as indicated by increase in neuroblasts, neuronal cells, BrdU⁺ cells and PCNA⁺ cells. Astrogliosis and gliogenesis were decreased in GFAP/Gp120 Tg mice treated with AM1241, compared with those treated with vehicle. CONCLUSIONS AND IMPLICATIONS: The CB₂ receptor agonist rescued impaired neurogenesis caused by HIV-1/Gp120 insult. Thus, CB₂ receptor agonists may act as neuroprotective agents, restoring impaired neurogenesis in patients with HAD.