Cannabinoid receptor agonists enhance syncytia formation in MT-2 cells infected with cell free HIV-1MN

Mini-review: The therapeutic role of cannabinoids in neuroHIV

In the era of combined antiretroviral therapy (cART), human immunodeficiency virus type 1 (HIV-1) is considered a chronic disease with an inflammatory component that specifically targets the brain and causes a high prevalence of HIV-1-associated neurocognitive disorders (HAND). The endocannabinoid (eCB) system has attracted interest as a target for treatment of neurodegenerative disorders, due to the potential anti-inflammatory and neuroprotective properties of cannabinoids, including its potential therapeutic use in HIV-1 neuropathogenesis. In this review, we summarize what is currently known about the structural and functional changes of the eCB system under conditions of HAND. This will be followed by summarizing the current clinical and preclinical findings on the effects of cannabis use and cannabinoids in the context of HIV-1 infection, with specifically focusing on viral load, cognition, inflammation, and neuroprotection. Lastly, we present some potential future directions to better understand the involvement of the eCB system and the role that cannabis use and cannabinoids play in neuroHIV.

Cannabinoid exposure during pregnancy and its impact on immune function

Cannabinoids are the most commonly abused illicit drugs worldwide. While cannabis can be beneficial for certain heath conditions, abuse of potent synthetic cannabinoids has been on the rise. Exposure to cannabinoids is also prevalent in women of child-bearing age and pregnant women. These compounds can cross the placental barrier and directly affect the fetus. They mediate their effects primarily through G-protein coupled cannabinoid receptors, CB1 and CB2. In addition to significant neurological effects, cannabinoids can trigger robust immunomodulation by altering cytokine levels, causing apoptosis of lymphoid cells and inducing suppressor cells of the immune system. Profound effects of cannabinoids on the immune system as discussed in this review, suggest that maternal exposure during pregnancy could lead to dysregulation of innate and adaptive immune system of developing fetus and offspring potentially leading to weakening of immune defenses against infections and cancer later in life. Emerging evidence also indicates the underlying role of epigenetic mechanisms causing long-lasting impact following cannabinoid exposure in utero.

Self-reported lifetime marijuana use and interleukin-6 levels in middle-aged African Americans

BACKGROUND

Research examining the relationship between marijuana and cytokine function has been well developed in the biochemical literature. However, scant literature exists regarding this relationship between inflammatory markers and marijuana use in public health or behavioral studies and is virtually nonexistent in non-neurologically compromised African American samples.

METHODS

The current study examined the differences in serum interleukin-6 (IL-6), a proinflammatory cytokine, between non-drug users (n=78), marijuana only users (n=46) and marijuana plus other drugs users (n=45) in a community-based sample of middle aged African Americans. Participants included 169 African American adults (50.30% female), with a mean age of 45.68 years (SD=11.72 years) from the Washington, DC metropolitan area. Serum was drawn upon entry into the study and the participants completed a demographic questionnaire, which included questions regarding drug use history.

RESULTS

After adjusting for demographic and physiological covariates, analysis of covariance revealed a significant difference between the three groups, F(2,158)=3.08, p=0.04). Post hoc analyses revealed lifetime marijuana only users had significantly lower IL-6 levels (M=2.20 pg/mL, SD=1.93) than their lifetime nonuser counterparts (M=3.73 pg/mL, SD=6.28). No other comparisons among the groups were statistically significantly different.

CONCLUSION

The current findings extend previous cellular and biochemical literature, which identifies an inverse association between IL-6 and marijuana use. Examining this relationship in the psychological and behavioral literature could be informative to the development of clinical interventions for inflammatory diseases.

Epigenetics, drugs of abuse, and the retroviral promoter

Drug abuse alone has been shown to cause epigenetic changes in brain tissue that have been shown to play roles in addictive behaviors. In conjunction with HIV-1 infection, it can cause epigenetic changes at the viral promoter that can result in altered gene expression, and exacerbate disease progression overall. This review entails an in-depth look at research conducted on the epigenetic effects of three of the most widely abused drugs (cannabinoids, opioids, and cocaine), with a particular focus on the mechanisms through which these drugs interact with HIV-1 infection at the viral promoter. Here we discuss the impact of this interplay on disease progression from the point of view of the nature of gene regulation at the level of chromatin accessibility, chromatin remodeling, and nucleosome repositioning. Given the importance of chromatin remodeling and DNA methylation in controlling the retroviral promoter, and the high susceptibility of the drug abusing population of individuals to HIV infection, it would be beneficial to understand the way in which the host genome is modified and regulated by drugs of abuse.

Immunomodulatory properties of kappa opioids and synthetic cannabinoids in HIV-1 neuropathogenesis

Anti-retroviral therapy (ART) has had a tremendous impact on the clinical outcomes of HIV-1 infected individuals. While ART has produced many tangible benefits, chronic, long-term consequences of HIV infection have grown in importance. HIV-1-associated neurocognitive disorder (HAND) represents a collection of neurological syndromes that have a wide range of functional cognitive impairments. HAND remains a serious threat to AIDS patients, and there currently remains no specific therapy for the neurological manifestations of HIV-1. Based upon work in other models of neuroinflammation, kappa opioid receptors (KOR) and synthetic cannabinoids have emerged as having neuroprotective properties and the ability to dampen pro-inflammatory responses of glial cells; properties that may have a positive influence in HIV-1 neuropathogenesis. The ability of KOR ligands to inhibit HIV-1 production in human microglial cells and CD4 T lymphocytes, demonstrate neuroprotection, and dampen chemokine production in astrocytes provides encouraging data to suggest that KOR ligands may emerge as potential therapeutic agents in HIV neuropathogenesis. Based upon findings that synthetic cannabinoids inhibit HIV-1 expression in human microglia and suppress production of inflammatory mediators such as nitric oxide (NO) in human astrocytes, as well as a substantial literature demonstrating neuroprotective properties of cannabinoids in other systems, synthetic cannabinoids have also emerged as potential therapeutic agents in HIV neuropathogenesis. This review focuses on these two classes of compounds and describes the immunomodulatory and neuroprotective properties attributed to each in the context of HIV neuropathogenesis.

Cannabinoid neuroimmune modulation of SIV disease

Marijuana is one of the most commonly used and abused drugs. Δ-9-tetrahydrocannabinol (Δ-9-THC), the primary psychoactive component in marijuana, is FDA-approved to ameliorate AIDS-associated wasting. Because cannabinoid receptors are expressed on cells of the immune system, it is possible that chronic Δ-9-THC use may impact HIV disease progression. Until recently, longitudinal, controlled, systems-approach studies on the effects of cannabinoids on disease progression were lacking. Data from our controlled studies in non-human primates show chronic Δ-9-THC administration prior to and during simian immunodeficiency virus (SIV) infection ameliorates disease progression, attenuates viral load and tissue inflammation, significantly reducing morbidity and mortality of SIV-infected macaques. Identification of possible mechanisms responsible for this modulation of disease progression is complicated due to the multiplicity of cannabinoid-mediated effects, tissue-specific responses to the viral infection, multiple cellular mechanisms involved in inflammatory responses, coordinated neuroendocrine and localized responses to infection, and kinetics of viral replication. Emerging results from our studies reveal that the overall mechanisms mediating the protective effects of cannabinoids involve novel epigenomic regulatory mechanisms in need of systematic investigation. Here, we review the evidence supporting an immunomodulatory role for cannabinoids and its impact on disease progression with focus on HIV/SIV infection.

Drugs of abuse and HIV infection/replication: implications for mother-fetus transmission

Human immunodeficiency virus (HIV) infection and progression of acquired immunodeficiency syndrome (AIDS) can be modulated by a number of cofactors, including drugs of abuse. Opioids, cocaine, cannabinoids, methamphetamine (METH), alcohol, and other substances of abuse have been implicated as risk factors for HIV infection, as they all have the potential to compromise host immunity and facilitate viral replication. Although epidemiologic evidence regarding the impact of drugs of abuse on HIV disease progression is mixed, in vitro studies as well as studies using in vivo animal models have indicated that drugs of abuse have the ability to enhance HIV infection/replication. Drugs of abuse may also be a risk factor for perinatal transmission of HIV. Because high levels of viral load in maternal blood are associated with increased risk of HIV vertical transmission, it is likely that drugs of abuse play an important role in promoting mother-fetus transmission. Furthermore, because the neonatal immune system differs qualitatively from the adult system, it is possible that maternal exposure to drugs of abuse would exacerbate neonatal immunity defects, facilitating HIV infection of neonate immune cells and promoting HIV vertical transmission. The availability and use of antiretroviral therapy for women infected with HIV increase, there is an increasing interest in determining the impact of drug abuse on efficacy of AIDS Clinical Trials Group (ACTG)-standardized treatment regimens for woman infected with HIV in the context of HIV vertical transmission.

Cannabinoids and Viral Infections

Exogenous cannabinoids or receptor antagonists may influence many cellular and systemic host responses. The anti-inflammatory activity of cannabinoids may compromise host inflammatory responses to acute viral infections, but may be beneficial in persistent infections. In neurons, where innate antiviral/pro-resolution responses include the activation of NOS-1, inhibition of Ca²⁺ activity by cannabinoids, increased viral replication and disease. This review examines the effect(s) of cannabinoids and their antagonists in viral infections.

Disruption of IFN-gamma- mediated antiviral activity in neurons: the role of cannabinoids

Interferon-gamma (IFN-gamma) has potent antiviral activity in neurons which is affected by the production of nitric oxide (NO). This study examines the interactions between cannabinoid receptor-1 (CB(1)), IFNgamma-induced pathways, and inhibition of vesicular stomatitis virus (VSV) replication in neuronal cells. CB(1) is abundantly expressed in neurons of the CNS and the NB41A3 neuroblastoma cell line. CB(1) activation of NB41A3 cells by the synthetic cannabinoid, WIN55,212-2, is associated with an inhibition of Ca(2+) mobilization, leading to diminished nitric oxide synthase (NOS)-1 activity and the production of NO, in vitro. This ultimately results in antagonism of IFN-gamma-mediated antiviral activity and enhanced viral replication. Therefore, activation of cells expressing CB(1) by endogenous (or exogenous) ligands may contribute to decreased inflammation and to increased viral replication in neurons and disease in the CNS.

Drugs of abuse, immune modulation, and AIDS

Illicit drugs such as amphetamines, cocaine, marijuana, and opiates alter immune function and decrease host resistance to microbes in vitro and in experimental animal models. Effects on the immune system may be mediated indirectly as a result of drug interactions in the central nervous system (CNS) or directly through activation of cognate receptors on various immune cell types. For marijuana and opioids, seven-transmembranal G protein-coupled receptors have been identified in the CNS and in the immune system that may play a functionally relevant role in immune modulation. There is accumulating evidence that sigma(1) receptors play a comparable role in cocaine-mediated alteration of immune responses. A mode by which these exogenously introduced substances affects immunity and host resistance may be by perturbing the balance of Th(1) proinflammatory versus Th(2) anti-inflammatory cytokines and lipid bioeffectors. However, while illicit drugs have been documented to alter immune functions in vitro and in animal models, there is a paucity of controlled longitudinal epidemiological studies that definitively correlate immunosuppressive effects with increased incidence of infections or immune disorders in humans, including infection with the human immunodeficiency virus (HIV) or disease progression to AIDS.

Effects on the immune system

Marijuana and other exogenous cannabinoids alter immune function and decrease host resistance to microbial infections in experimental animal models and in vitro. Two modes of action by which delta9-tetrahydrocannabinol (THC) and other cannabinoids affect immune responses have been proposed. First, cannabinoids may signal through the cannabinoid receptors CB1 and CB2. Second, at sites of direct exposure to high concentrations of cannabinoids, such as the lung, membrane perturbation may be involved. In addition, endogenous cannabinoids or endocannabinoids have been identified and have been proposed as native modulators of immune functions through cannabinoid receptors. Exogenously introduced cannabinoids may disturb this homoeostatic immune balance. A mode by which cannabinoids may affect immune responses and host resistance maybe by perturbing the balance of T helper (Th)1 pro-inflammatory versus Th2 anti-inflammatory cytokines. While marijuana and various cannabinoids have been documented to alter immune functions in vitro and in experimental animals, no controlled longitudinal epidemiological studies have yet definitively correlated immunosuppressive effects with increased incidence of infections or immune disorders in humans. However, cannabinoids by virtue of their immunomodulatory properties have the potential to serve as therapeutic agents for ablation of untoward immune responses.

Modulation of CB1 mRNA upon activation of murine splenocytes

There is significant evidence that cannabinoids have the ability to exert immunomodulatory effects. The identification of cannabinoid receptors in immune tissues has therefore led to questions about whether these immunomodulatory effects occur via these cannabinoid receptors. The cannabinoid receptor 1 (CB 1), although expressed primarily in the brain, is also expressed in lower amounts in peripheral tissues. Of interest to us is the fact that CB1 is expressed in immune tissues such as spleen, albeit at lower levels than the peripheral cannabinoid receptor, CB2. To examine the function of CBI in immune cells, activation experiments were performed using different stimuli e.g., anti-CD3, phorbol 12-myristate 13-acetate (PMA)/Ionomycin (Io), and PMA/Io + IL-2. Whole spleen cells were cultured in the presence of different stimuli for 0, 2, 4, and 24 hours, harvested at each time point, RNA isolated, and RT-PCR performed. FACS analysis was also performed using CD69 (an early activation marker) to determine whether cells were actually being activated. Results from anti-CD3 stimulation indicated a decrease in CB1 mRNA expression following activation. CB1 mRNA expression in murine splenocytes that were stimulated with PMA/Io in the presence or absence of IL-2 was also modulated. Expression of the message was enhanced upon stimulation with PMA/Io and PMA/Io + IL-2, however, stimulation with PMA/Io + IL-2 led to a stronger increase within 2 to 4 hours with CB1 returning to at or below baseline levels by 24 hours. Expression of CD69 was detected in all stimulated samples thereby indicating that the splenocytes were becoming activated. In summary, anti-CD3 stimulation appeared to decrease CB1 mRNA expression while PMA/Io + IL-2 stimulation significantly increased CB1 mRNA expression. These results demonstrate that the expression of CB1 mRNA is modulated upon cellular activation and that this modulation is dependent on the stimulus that is used.

Cannabinoid receptors and the regulation of immune response

Cannabinoid research underwent a tremendous increase during the last 10 years. This progress was made possible by the discovery of cannabinoid receptors and the endogenous ligands for these receptors. Cannabinoid research is developing in two major directions: neurobehavioral properties of cannabinoids and the impact of cannabinoids on the immune system. Recent studies characterized the cannabinoid-induced response as a very complex process because of the involvement of multiple signalling pathways linked to cannabinoid receptors or effects elicited by cannabinoids without receptor participation. The objective of this review is to present this complexity as it applies to immune response. The functional properties of cannabinoid receptors, signalling pathways linked to cannabinoid receptors and the modulation of immune response by cannabinoid receptor ligands are discussed. Special attention is given to 'endocannabinoids' as immunomodulatory molecules.

Anti-CD40, anti-CD3, and IL-2 stimulation induce contrasting changes in CB1 mRNA expression in mouse splenocytes

The expression and function of cannabinoid receptor 1 (CB1) in mouse immune cells is unclear. Here we show that splenic B cells express more CB1 mRNA than T cells. Furthermore, splenocytes stimulated with the T cell mitogens, PMA/Io and anti-CD3, showed a decrease in CB1 message while cultures stimulated with the B cell mitogen, anti-CD40 antibody, showed an increase in message. In addition, co-treatment with mitogens and IL-2 uniformly caused an increase in CB1 mRNA. It is suggested that signaling pathways activated by T cell mitogens lead to decreased CB1 gene activation while pathways activated by B cell mitogens and IL-2 lead to increased CB1.

Opiate effects on in vitro human retroviral infection

The transmission and progression of the human retroviruses HIV-1 and HTLV-1/2 can be most likely influenced by a variety of "lifestyle cofactors" which includes the use of certain injected pharmaceuticals. Some investigations have suggested that HIV-1 infected individuals who are injecting drug users (IDUs) may undergo an accelerated rate of progression to AIDS. It is known that opioid receptors exist on cells pertinent to immune function, and that the activation or inhibition of these receptors may enhance or down-regulate some cell activities. The mechanisms for these effects have not yet been elucidated, nor have the effects of opioids on retroviral infection models been fully determined. While some work has been performed on the effects of opiates on infection by HIV-1 and SIV virtually no work has been done on the potential effects of this class of drugs on HTLV-1 and 2 infection. The potential effects of opiates on these retroviruses are important because of the higher incidence of infection in IDUs. Because IDUs compose one of the emerging high risk populations for infection with HIV-1 and more recently HTLV it is relevant to analyze the direct and indirect effects of opioids on the progression of retroviral infections. Our preliminary results from in vitro syncytia formation studies suggest a modulation by opioid-selective receptor agonists of in vitro infection by both HIV-1 and HTLV-I. These initial results underscore the necessity for further studies to define and elucidate the role of opiate abuse in the infection by human retroviruses as well as the associated pathogenesis.