Effects of marijuana on macrophage function

Maternal marijuana use, adverse pregnancy outcomes, and neonatal morbidity

BACKGROUND

The Eunice Kennedy Shriver National Institute of Child Health and Human Development Stillbirth Collaborative Research Network previously demonstrated an association between stillbirth and maternal marijuana use as defined by the presence of 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid in the umbilical cord homogenate. However, the relationship between marijuana use and perinatal complications in live births is uncertain.

OBJECTIVE

Our aim was to examine if maternal marijuana use is associated with increased odds of adverse pregnancy outcomes and neonatal morbidity among live-born controls in the Stillbirth Collaborative Research Network cohort.

STUDY DESIGN

We conducted a secondary analysis of singleton, live-born controls in the Stillbirth Collaborative Research Network data set. Marijuana use was measured by self-report and/or the presence of 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid in umbilical cord homogenate. Tobacco use was measured by self-report and/or presence of any cotinine in maternal serum. Adverse pregnancy outcome was a composite of small for gestational age, spontaneous preterm birth resulting from preterm labor with or without intact membranes, and hypertensive disorders of pregnancy. Neonatal morbidity included neonatal intensive care unit admission and composite neonatal morbidity (pulmonary morbidity, necrotizing enterocolitis, seizures, retinopathy of prematurity, infection morbidity, anemia requiring blood transfusion, neonatal surgery, hyperbilirubinemia, neurological morbidity, or death prior to hospital discharge). Effect of maternal marijuana use on the probability of an adverse outcome was estimated using weighted methodology to account for oversampling in the original study. 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid cord homogenate analysis was performed in the subset of women for whom biospecimens were available. Comparisons using logistic modeling, χ², and t tests were weighted to account for oversampling of preterm births and non-Hispanic blacks. Results are reported as weighted percent and unweighted frequencies.

RESULTS

Maternal marijuana use was identified in 2.7% (unweighted frequency 48/1610) of live births. Use was self-reported by 1.6% (34/1610) and detected by 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid in cord homogenate for 1.9% (17/897), n = 3 overlapping. Rate of tobacco use was 12.9% (217/1610), with 10.7% (167/1607) by self-report and 9.5% (141/1313) by serum cotinine. The composite adverse pregnancy outcome was not significantly increased in women with marijuana use compared to nonusers (31.2% vs 21.2%; P = .14). After adjustment for tobacco, clinical, and socioeconomic factors, marijuana use was not associated with the composite adverse pregnancy outcome (adjusted odds ratio, 1.29; 95% confidence interval, 0.56-2.96). Similarly, among women with umbilical cord homogenate and serum cotinine data (n = 765), marijuana use was not associated with adverse pregnancy outcomes (adjusted odds ratio, 1.02; 95% confidence interval, 0.18-5.66). Neonatal intensive care unit admission rates were not statistically different between groups (16.9% users vs 9.5% nonusers, P = .12). Composite neonatal morbidity or death was more frequent among neonates of mothers with marijuana use compared to nonusers (14.1% vs 4.5%; P = .002). In univariate comparisons, the components of the composite outcome that were more frequent in neonates of marijuana users were infection morbidity (9.8% vs 2.4%; P < .001) and neurologic morbidity (1.4% vs 0.3%; P = .002). After adjustment for tobacco, race, and other illicit drug use, marijuana use was still associated with composite neonatal morbidity or death (adjusted odds ratio, 3.11; 95% confidence interval, 1.40-6.91).

CONCLUSION

Maternal marijuana use was not associated with a composite of small for gestational age, spontaneous preterm birth, or hypertensive disorders of pregnancy. However, it was associated with an increased risk of neonatal morbidity.

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.

[The endogenous cannabinoid system. Therapeutic implications for neurologic and psychiatric disorders]

For about 5,000 years, cannabis has been used as a therapeutic agent. There has been growing interest in the medical use of cannabinoids. This is based on the discovery that cannabinoids act with specific receptors (CB1 and CB2). CB1 receptors are located in specific brain areas (e.g. cerebellum, basal ganglia, and hippocampus) and CB2 receptors on cells of the immune system. Endogenous ligands of the cannabinoid receptors were also discovered (e.g. anandamids). Many physiologic processes are modulated by the two subtypes of cannabinoid receptor: motor functions, memory, appetite, and pain. These innovative neurobiologic/pharmacologic findings could possibly lead to the use of synthetic and natural cannabinoids as therapeutic agents in various areas. Until now, cannabinoids were used as antiemetic agents in chemotherapy-induced emesis and in patients with HIV-wasting syndrome. Evidence suggests that cannabinoids may prove useful in some other diseases, e.g. movement disorders such as Gilles de la Tourette's syndrome, multiple sclerosis, and pain. These new findings also explain the acute adverse effects following cannabis use.

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.

Cannabinoid-mediated exacerbation of brain infection by opportunistic amebae

Recent reports indicate a higher frequency of brain infections with opportunistic amebae of the genus Acanthamoeba among immune compromised individuals, including AIDS patients. We have demonstrated, using a murine model of Granulomatous Amebic Encephalitis (GAE), that the major psychoactive and immune suppressive component in marijuana delta-9-tetrahydrocannabinol (THC) exacerbates infection by these amebae. Mice administered THC and infected with Acanthamoeba exhibited dose-related higher mortalities than infected vehicle controls. The greater severity of disease for THC-treated mice was accompanied by decreased accumulation of macrophage-like cells at focal sites of infection in the brain. Furthermore, THC administration resulted in decreased levels of mRNA for the pro-inflammatory cytokines interleukin-1 alpha, interleukin-1 beta, and tumor necrosis factor alpha for neonatal rat microglia co-cultured with Acanthamoeba. These results indicate a potential for marijuana to alter the capacity of brain macrophage-like cells to mount a full complement of immune responsiveness to brain infection by opportunistic amebae.

Drugs and immunity: cannabinoids and their role in decreased resistance to infectious disease

Marijuana, Cannabis sativa, elicits a variety of effects in experimental animals and humans. Delta-9-tetrahydrocannabinol (THC) is the major psychoactive component in marijuana. This substance has been shown, also, to be immunosuppressive and to decrease host resistance to bacterial, protozoan, and viral infections. Macrophages, T lymphocytes, and natural killer cells appear to be major targets of the immunosuppressive effects of THC. Definitive data which directly link marijuana use to increased susceptibility to infection in humans currently is unavailable. However, cumulative reports indicating that THC alters resistance to infection in vitro and in a variety of experimental animals support the hypothesis that a similar effect occurs in humans.

Regulation of immune functions in rat splenocytes after acute and chronic in vivo treatment with CP-55,940, a synthetic cannabinoid compound

Changes in mitogen-induced splenocyte proliferation and NK activity were evaluated after acute (1 h) and chronic (6 d) in vivo treatment of rats with the synthetic cannabinoid compound CP-55,940. At a dose of 0.4 mg/kg i.p. it significantly inhibited the splenocyte proliferative response to PHA and NK activity but half this dose (0.2 mg/kg) had no effect on immune responses. Pretreatment of rats with the cannabinoid receptor CB1 antagonist SR141716A did not antagonize the CP-55,940-induced immunosuppression, excluding the activation of this receptor subtype in the mediation of this effect. When immune function studies were done on rats tolerant to CP-55,940-induced analgesia, full tolerance also developed for the inhibition of splenocyte proliferation and NK activity. The data provided indicate that CB1 cannabinoid receptors are not involved in mediating the acute and chronic effects of cannabinoids on the immune system and suggest a possible implication of CB2 receptor although other modalities of CP-55,940 action can not be ruled out.

Identification of an endogenous 2-monoglyceride, present in canine gut, that binds to cannabinoid receptors

In this study, we report the isolation from canine intestines of 2-arachidonyl glycerol (2-Ara-Gl). Its structure was determined by mass spectrometry and by direct comparison with a synthetic sample. 2-Ara-Gl bound to membranes from cells transiently transfected with expression plasmids carrying DNA of either CB1 or CB2--the two cannabinoid receptors identified thus far--with Ki values of 472 +/- 55 and 1400 +/- 172 nM, respectively. In the presence of forskolin, 2-Ara-Gl inhibited adenylate cyclase in isolated mouse spleen cells, at the potency level of delta 9-tetrahydrocannabinol (delta 9-THC). Upon intravenous administration to mice, 2-Ara-Gl caused the typical tetrad of effects produced by THC: antinociception, immobility, reduction of spontaneous activity, and lowering of the rectal temperature. 2-Ara-Gl also shares the ability of delta 9-THC to inhibit electrically evoked contractions of mouse isolated vasa deferentia; however, it was less potent than delta 9-THC.

Delta-9-tetrahydrocannabinol treatment results in a suppression of interleukin-2-induced cellular activities in human and murine lymphocytes

Delta-9-tetrahydrocannabinol (THC), the major psychoactive component in marijuana, has been shown to suppress a variety of interleukin-2-(IL-2)-dependent cellular functions in both murine and human lymphocytes. These effects were examined in both human peripheral blood lymphocytes (hPBL) and the IL-2-dependent murine cytotoxic T-cell line CTLL-2. Interleukin-2-induced thymidine uptake and uridine uptake were suppressed in a dose related manner when cells were co-incubated for 48 h with 100 U rhIL-2/ml and 1-10 micrograms THC/ml. Interleukin-2-induced protein synthesis was also suppressed in a dose related manner over this THC concentration range, with the hPBL being more susceptible to the suppressive effect of THC than the CTLL-2 cells. Autoradiographic analysis of the synthesized proteins from hPBL cell lysates reveals a generalized suppression of all nascent proteins in THC-treated cultures. Human natural killer cell activity is only affected at the highest concentration tested (10 micrograms THC/ml) while lymphokine-(IL-2)-activated natural killer cell activity is affected throughout the range of 1-10 micrograms THC/ml. Together these results suggest that THC interferes with the IL-2:IL-2 receptor signaling cascade at one or possibly many points causing a decrease in IL-2-induced metabolic activity and cytolytic function.

Suppression by delta-9-tetrahydrocannabinol of lipopolysaccharide-induced and intrinsic tyrosine phosphorylation and protein expression in mouse peritoneal macrophages

Lipopolysaccharide (LPS, 100 ng/mL)-induced tyrosine phosphorylation of four proteins (p41, p42, p77, and p82) in mouse resident peritoneal macrophages was observed using a monoclonal anti-phosphotyrosine antibody PY20 immunoblotting method. Macrophages pretreated for 3 hr with 1 microgram delta-9-tetrahydrocannabinol (THC)/mL had decreased tyrosine phosphorylation of p77 and p82 after incubation with LPS for 30 min. Simultaneous treatment of macrophages with THC (10 micrograms/mL) plus LPS for 30 min had a similar effect on p77 and p82 tyrosine phosphorylation. When the THC pretreatment protocol was combined with the simultaneous treatment protocol, 0.5 and 5 micrograms THC/mL, respectively, completely blocked LPS-induced p77 and p82 tyrosine phosphorylation. However, neither simultaneous treatment with THC nor pre- and simultaneous treatment had any effect on LPS-induced tyrosine phosphorylation of p41 and p42 in macrophages. Pretreatment with 1 microgram THC/mL followed by simultaneous treatment with 10 micrograms THC/mL induced a p43 protein that showed tyrosine phosphorylation in place of p41 and p42. Further analysis of THC effects on macrophages revealed an increase in tyrosine phosphorylation as an immediate early even after THC treatment. Prolonged treatment of macrophages with THC resulted in a broad suppression of tyrosine phosphorylation and some cellular protein expression. Three cellular proteins (p65, p70, and p72) seemed most susceptible to inhibition by THC. The data suggest that suppression of tyrosine phosphorylation by THC in macrophages may be one of the mechanisms associated with inhibition of cell function, including the suppression of tumor necrosis factor-alpha release from macrophages.