Peter J. Gaskill, Ph.D. - US grants

[unreadable] DESCRIPTION (provided by applicant): The goal of this proposal is to increase the understanding of the mechanisms contributing the exacerbation of neurological complications in Human Immunodeficiency Virus (HIV) infected drug abusers. The use of dopaminergic drugs, such as cocaine and methamphetamine, increases both the incidence and severity of HIV-induced neurological disease in HIV infected individuals. These drugs act by increasing extracellular dopamine levels in the central nervous system (CMS). Studies show that increased extracellular dopamine exacerbates HIV induced CMS pathology, but the mechanisms that mediate this effect are not fully characterized. Macrophages, the major target for HIV in the CMS, also play a central role in the neuropathology of HIV infection. The preliminary data in this proposal show that dopamine treatment increases HIV replication in macrophages, and demonstrate the presence of dopamine receptors on the surface of the eels. These data indicate that dopamine may play a direct role in the development of HIV induced CMS pathology through dopamine mediated modulation of HIV infection of macropahges. To determine the mechanism mediating this effect, studies in this proposal will fully characterize the pharmacology and kinetics of dopamine-mediated increase in HIV replication in macrophages. HIV infection in the presence of dopamine receptor agonists and antagonists will determine which dopamine receptors mediate the increase in HIV replication in macrophages. To examine the mechanism mediating this effect, studies will examine crosstalk between the active dopamine receptors and the HIV receptor CD4, and coreceptors CXCR4 and CCR5 as well as dopamine-induced alterations in the viral entry, integration, and budding processes. Experiments will also use protein kinase inhibitors during HIV infection to examine the signaling pathways involved in dopamine enhanced HIV replication. Defining the mechanisms by which dopamine increases HIV replication in macrophages will contribute to the understanding and treatment of the heightened incidence and severity of neurological disease among HIV infected drug users. [unreadable] [unreadable] PUBLIC HEALTH RELEVANCE: HIV infection can result in a variety of neurological complications that are exacerbated by drugs of abuse. Defining the mechanisms by which drug abuse increases the incidence and severity of HIV induced neurological complications will increase the understanding of HIV infection in the brain and help to develop intervention strategies to limit the devastating consequences of neurologic impairment in HIV infected drug users. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): In regions of the world such as Eastern Europe and South-East Asia, the HIV pandemic is being driven by the spread of HIV within drug-abusing populations. As HIV infected individuals live longer with the success of CART, neurological complications are emerging as a significant health issue, particularly among HIV-infected drug abusers. HIV infected individuals who abuse methamphetamine and cocaine show a significant increase in the incidence and severity of neuropathology and in the development of HIV-associated neurological disorders (HAND). The mechanism(s) leading to the acceleration HAND remain unclear;however, both cocaine and methamphetamine act by increasing in extracellular levels of the neurotransmitter dopamine (DA) within the central nervous system (CNS). Our findings demonstrate that dopamine increases HIV replication in primary human macrophages, which are the primary target for HIV infection in the CNS. Our research showed that this increase in macrophage HIV replication is due, at least in part, to the infection of greater numbers of macrophages through the activation of a D2-like dopamine receptor. Additionally, studies in simian immunodeficiency virus infected rhesus macaques showed that increased extracellular dopamine enhances intracerebral HIV replication and exacerbates central nervous system pathology. Together, these studies indicate that the effects of dopamine on HIV infection of macrophages could be a common mechanism by which drug abuse exacerbates the development of HAND. Macrophages are the primary targets and sources of HIV in the CNS, as well as a major immune responder and a major source of cytokines and chemokines. Cytokines and chemokines increase neuroinflammation and mediate the recruitment of uninfected macrophages to sites of inflammation, enabling the virus to spread to uninfected macrophage populations. Our data show that dopamine not only increases HIV replication in macrophages, but it activates dopamine receptor mediated signaling, modulates activation of chemotatic proteins and alters cytokine production. These data suggest that drug-induced increases in dopamine would not only increase the extent of HIV infection in the CNS, but could also enhance the spread of HIV to uninfected macrophages and alter the macrophage response to infection. To characterize the mechanism(s) by which dopamine increases HIV infection in macrophages and alters macrophage immune function, we will define dopamine mediated changes in the HIV replication cycle in macrophages, examine alterations in macrophage chemotaxis and production of inflammatory cytokines/chemokines, and characterize the DR signaling pathways in macrophages mediating these functions. We hypothesize that dopamine increases HIV infection in macrophages and alters macrophage functions through activation of dopamine receptors and transporter, contributing to the exacerbated the development of HAND in HIV infected drug abusers. PUBLIC HEALTH RELEVANCE: As HIV infected individuals live longer, neurological complications are emerging as a significant health issue, especially among HIV-infected drug abusers. Drug abuse increases the incidence and severity of HIV associated neurological disease, but the mechanism(s) by which this occurs are unclear. We demonstrated that dopamine, a neurotransmitter common to the actions of all drugs of abuse, increases HIV replication in macrophages, the major target cell for HIV in the brain. We propose to define the mechanism by which dopamine increases HIV replication and to characterize dopamine mediated changes in macrophage function.

? DESCRIPTION (provided by applicant): Approximately 35 million people are infected with HIV worldwide. HIV enters the central nervous system (CNS) soon after initial infection, infecting primarily macrophages. Infected cells produce new virus and act as viral reservoirs within the CNS, enabling HIV to escape the effects of combinatorial anti-retroviral therapy (cART). Infected macrophages also release neurotoxic factors that contribute to the development of neuroinflammation and HIV-associated neurocognitive disorders (HAND). HIV+ drug abusers are especially vulnerable to the accelerated development of HIV-associated neuropathogenesis, and more than 10% of HIV+ individuals around the world abuse drugs. The mechanisms by which illicit drugs contribute to HIV-associated CNS damage are unclear, but all addictive substances increase extracellular dopamine in the CNS. We showed dopamine increases HIV replication in human macrophages by increasing the entry of the virus into these cells. The dopamine concentration that increases HIV entry is present in the CNS as a result of most types of drug abuse, indicating that CNS macrophages in HIV infected drug abusers are exposed to elevated dopamine. Thus, drug abuse could increase HIV entry into macrophages as soon as the virus enters the brain, rapidly expanding the size of the CNS reservoir and accelerating the development of HAND. The CNS is seeded before the initiation of cART, and even during cART low-level viral replication can persist in the CNS. Additionally, HIV+ drug abusers have poor adherence to cART and drug use during a break from therapy could significantly enhance the impact of the viral rebound. Thus, understanding the impact of dopamine on HIV infection of macrophages is essential to treatment of HIV+ drug abusers, even in the era of cART. This proposal will address this issue using both in vitro systems and a primate model of acute CNS infection in the presence of elevated dopamine. Our in vitro studies will precisely characterize the mechanism(s) by which dopamine increases HIV entry, suggesting new targets to be exploited as the basis for novel entry inhibitors or therapeutic strategies. The primate model will demonstrate the impact of dopamine in acute CNS infection in vivo, and provide a scaffold in which to examine the use of dopamine receptor antagonists with pre-exposure prophylaxis (PrEP) regimens, or as adjuvant therapy to be administered with cART in HIV+ drug abusers or others using therapeutics which affect the dopaminergic system. This system will also characterize the impact of dopamine on CNS infection and the neuroimmune response, providing contraindication data for clinicians using dopaminergic drugs in HIV+ individuals.

DAT18-01. Abuse of stimulants, such as cocaine and methamphetamine, results in a variety of serious health conditions, and drug abusers have poorer health outcomes than non-drug using, demographically similar populations. In the central nervous system, the use of stimulants induces neuroinflammation through a greater release of inflammatory factors and recruitment of additional leukocytes. This predisposes drug abusers to a higher incidence of neuropsychiatric, cerebrovascular and motor disorders, and can also exacerbate the neuropathogenic impact of infection with HIV, HCV and a number of bacterial pathogens. The precise pathways by which stimulants mediate these effects are not clear, but many of these effects could be induced by drug-associated activation of specific inflammatory triggers such as NF- kB. However, direct links between stimulants and these neuroinflammatory mechanisms have not been described. The premise of this proposal is that dopamine acts as a common mechanism by which stimulants activate myeloid cell NF-kB and thereby initiate or exacerbate neuroinflammation. Use of all stimulants acutely increases CNS dopamine levels, exposing cells in dopamine-rich brain regions to aberrantly high dopamine concentrations. Among these cell populations are myeloid cells, such as perivascular macrophages and microglia, which are the primary immune cells in the CNS. Our published research shows that acute exposure to elevated dopamine increases myeloid production of inflammatory cytokines, such as IL-1b, IL-6, CXCL8 and CXCL10. Our preliminary data suggest that dopamine acts by activating the NF- kB pathway and priming the NLRP3 inflammasome, a complex that regulates the release of IL-1b, a master regulator of inflammation. The specific pathways mediating this effect are not clear, and therefore these studies will generate detailed information about specific dopamine receptors, gene and protein targets mediating dopamine activation of NF-kB and NLRP3 in human macrophages. Determining the specific signaling mechanisms and genes involved in dopamine induced increases in NF-kB activity will indicate pathways that could be targeted to ameliorate the neuroinflammatory effects of stimulant use, significantly improving the long-term health outcomes of stimulant users. The data developed in this proposal will serve as a basis for future projects examining the modulation of the myeloid dopaminergic system as a therapeutic strategy for limiting the increased incidence of neurologic disease and inflammation associated with drug abuse. These projects will examine both novel effectors and the repurposing of existing dopaminergic therapeutics to ameliorate inflammation in the stimulant abusing population.