The goal of this study is to define the effect of delta-9-tetrahydrocannabinol (THC), the major psychoactive and immunosuppressive component in marijuana, on microglia within the brain. Microglia are a resident population of macrophages, which constitute a major element of the immune system of the brain. These cells respond to trauma and infection by migrating to sites of injury, produce proinflammatory cytokines and cytotoxic substances, and phagocytize infectious agents and damaged tissue. Microglia, also, have been implicated in neuropathological processes, such as AIDS dementia and multiple sclerosis as a consequence of chronic activation. We have demonstrated that microglia in vitro express CB1 and CB2 cannabinoid receptors, the latter of which are present at high levels when these cells are in an inflammatory state. These receptors have been shown to play a role in cannabinoid-mediated modulation of immune cell functions at non-neuronal sites and our preliminary data suggest that they play a similar role in microglia. We propose to assess for functional linkages for CB1 and CB2 receptors in cannabinoid-mediated modulation of microglial functions. These studies are highly significant since recognition that specified activities are linked functionally to cannabinoid receptors would provide insight regarding therapeutic regimens for ablating inflammatory processes which contribute to AIDS-associated and other forms of neuropathogenesis. The hypothesis to be tested is that THC and other cannabinoids alter select functional activities of microglia and do so by a cannabinoid receptor-mediated process. In order to test this hypothesis, the following Specific Aims are proposed as guidelines to the research. First, we will define the pattern of cannabinoid receptor expression by microglia in the brain. We have demonstrated that microglia differentially express CB1 and CB2 receptors in vitro in relation to cell activation and will establish whether these events occur in vivo. Organotypic brain slice experiments as well as in vivo infectivity studies will be performed. Cannabinoid receptor expression will be assessed using histological, immunocytochemical, pharmacological, and molecular approaches. Second, we will define the functional relevance of cannabinoid receptors on microglia. We have demonstrated that microglia in vitro, when in """"""""responsive"""""""" and """"""""primed"""""""" inflammatory states, express high levels of the CB2 receptor. We will assess for cannabinoid-mediated effects through this receptor on functions associated with these activation states including chemotaxis, chemokinesis, phagocytosis, and antigen processing. Functional assays will employ paired cannabinoid enantiomers, receptor subtype-specific antagonists, and cannabinoids exhibiting differential ligand binding affinities to establish structure-activity relationships.

Agency
National Institute of Health (NIH)
Institute
National Institute on Drug Abuse (NIDA)
Type
Research Project (R01)
Project #
5R01DA015608-03
Application #
6768734
Study Section
AIDS and Related Research 8 (AARR)
Program Officer
Rapaka, Rao
Project Start
2002-09-30
Project End
2006-06-30
Budget Start
2004-07-01
Budget End
2006-06-30
Support Year
3
Fiscal Year
2004
Total Cost
$295,715
Indirect Cost
Name
Virginia Commonwealth University
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
105300446
City
Richmond
State
VA
Country
United States
Zip Code
23298
Raborn, Erinn S; Marciano-Cabral, Francine; Buckley, Nancy E et al. (2008) The cannabinoid delta-9-tetrahydrocannabinol mediates inhibition of macrophage chemotaxis to RANTES/CCL5: linkage to the CB2 receptor. J Neuroimmune Pharmacol 3:117-29
Rocha-Azevedo, B; Jamerson, M; Cabral, G A et al. (2007) The interaction between the amoeba Balamuthia mandrillaris and extracellular matrix glycoproteins in vitro. Parasitology 134:51-8
Klein, Thomas W; Cabral, Guy A (2006) Cannabinoid-induced immune suppression and modulation of antigen-presenting cells. J Neuroimmune Pharmacol 1:50-64
Cabral, Guy A (2006) Localization of cannabinoid receptors using immunoperoxidase methods. Methods Mol Med 123:41-69
Cabral, Guy A (2006) Drugs of abuse, immune modulation, and AIDS. J Neuroimmune Pharmacol 1:280-95
Cabral, Guy A (2005) Lipids as bioeffectors in the immune system. Life Sci 77:1699-710
Cabral, G A; Marciano-Cabral, F (2005) Cannabinoid receptors in microglia of the central nervous system: immune functional relevance. J Leukoc Biol 78:1192-7
Marciano-Cabral, Francine; Ludwick, Christina; Puffenbarger, Robyn A et al. (2004) Differential stimulation of microglial pro-inflammatory cytokines by Acanthamoeba culbertsoni versus Acanthamoeba castellanii. J Eukaryot Microbiol 51:472-9
Marciano-Cabral, Francine; Han, Kathy; Powell, Eric et al. (2003) Interaction of an Acanthamoeba human isolate harboring bacteria with murine peritoneal macrophages. J Eukaryot Microbiol 50 Suppl:516-9
Olson, John M; Kennedy, Suzanne J; Cabral, Guy A (2003) Expression of the murine CB2 cannabinoid receptor using a recombinant Semliki Forest virus. Biochem Pharmacol 65:1931-42