The human immunodeficiency virus type 1 (HIV-1) glycoprotein gp120 causes neuronal cell death; however, the molecular mechanisms of the neurotoxic effect remain largely unresolved. It has been suggested that gp120 evokes cell death by inducing the release of neurotoxins, including glutamate. The objective of this work was to examine the role of glutamate in gp120-mediated neurotoxicity. We used as an experimental tool cerebellar granule cells prepared from 8-day-old rat cerebella, in which both glutamate and gp120 cause cell death. Cerebellar granule neurons were exposed to gp120 or glutamate alone or in combination with the glutamate receptor antagonist MK801 as well as other antiglutamatergic compounds. Cell viability was measured at various times by using several markers of cell death and apoptosis. MK801, at a concentration that blocked glutamate-induced neuronal cell death, failed to prevent gp120-mediated apoptotic cell death. Moreover, interleukin-10, which has previously been shown to block glutamate toxicity in these neurons, was not neuroprotective against gp120. Because gp120 toxicity is mediated by activation of the chemokine receptor CXCR4, neurons were incubated with the CXCR4 inhibitor AMD3100. This compound prevented gp120- but not glutamate-mediated cell death. These findings suggest that gp120 is toxic to neurons even in the absence of the virus and that the toxic mechanism involves primarily activation of CXCR4 receptor. Therefore, antagonists to the CXCR4 receptor may be more suitable compounds for inhibiting HIV-1 neurotoxicity.
Copyright 2003 Wiley-Liss, Inc.