Maternal drug use during pregnancy can have detrimental effects on the developing fetus. This may be of particular concern for mothers infected with the human immunodeficiency virus (HIV). HIV-infected mothers often inadvertently pass the virus to their developing offspring, where it has detrimental effects on the central nervous system (CNS) of the developing infant. Children infected with HIV exhibit a variety of cognitive and developmental problems thought to be caused directly or indirectly by HIV infection in the CNS. Drugs of abuse which also have CNS actions are likely to compound the effects of HIV infection. The proposed studies will focus on this issue. We will study the potential for cannabinoids, the active ingredients in the extensively abused drugs marijuana and hashish, to exacerbate the neurodamage produced by HIV infection in the developing CNS. Our studies will address this question at the cellular and molecular levels. The mechanisms responsible for the neuropathology in HIV-infected individual's is still under investigation. However, studies by others have identified two factors that appear to be involved:-(a) a host-derived factor the cytokine interleukin-6 (IL-6), and (b) a viral-derived factor, the HIV-l coat protein gpl20. We will focus on these factors and the potential for cannabinoids to enhance their effects on developing CNS neurons. For the majority of studies we will use an in vitro model system, primary cultures of rodent cerebellar granule neurons, a well characterized developmental model that is relevant to both HIV infection and cannabinoid actions and is well suited to the methodology to be applied. Many important morphological and physiological milestones known to occur during the maturation of these neurons in vivo are expressed in culture and thus are accessible for direct study in vitro. The neurons will be exposed chronically to IL-6 or gp120 alone and in combination via the culture medium to simulate conditions of HIV infection. The effects of acute and chronic cannabinoid exposure on the morphological and physiological development of the granule neurons and on neuronal survival will be assessed with immunohistochemical, electrophysiological and microscopic calcium imaging methods. In addition, studies of cannabinoid effects on brain slices from mouse transgenic models of HIV infection will be pursued, so that neuronal properties more accessible in intact tissue can be examined. Two mouse transgenic models will be studied, one in which IL-6 is overexpressed in the CNS and one in which gp120 is expressed in the CNS (both by expression in genetically manipulated astrocytes). These transgenic models express neuropathology reflective of that observed in the HIV infected CNS and therefore should be useful in vivo models for drug studies. Results from these in vivo studies will provide important information on cannabinoid HIV interactions and their influence on CNS neuronal development and function. Such information is essential for treatment and prevention strategies and for the rational design of therapeutic agents. In addition, our studies will contribute to an understanding of the potential role of endogenous cannabinoids in normal CNS neuronal physiology and development.
