Methadone vs morphine: comparison of their effect on phagocytic functions

The immunomodulatory effects of opioids and implications for intensive care unit populations

Analgesia within the intensive care unit (ICU) is often achieved via the utilization of opioids in alignment with current guidelines. Recent evidence has not only demonstrated the potential impact of opioids in suppression of immune function, but also the potential harm of immunosuppression of patients within the ICU. Despite the potential immunosuppression seen with opioids in this at-risk population, their use remains frequent. In this review, we highlight the potential immunomodulatory impact of opioids within the critically ill and considerations for their use.

Immunosuppressive aspects of analgesics and sedatives used in mechanically ventilated patients: an underappreciated risk factor for the development of ventilator-associated pneumonia in critically ill patients

OBJECTIVE

To evaluate the evidence describing the immunosuppressive and pharmacokinetic properties of commonly used analgesic and sedation agents in critically ill patients.

DATA SOURCES

MEDLINE (January 1980-September 2013) was searched.

STUDY SELECTION AND DATA EXTRACTION

All in vitro and in vivo studies that evaluated the immune-modulating properties of analgesic and sedation agents commonly used in the critically ill were included. Full-text and abstract-only articles (noted) were included in this review. Inclusion criteria were met by 46 studies and were evaluated.

DATA SYNTHESIS

Analgesic and sedation agents have been shown to be immunosuppressive in a variety of models. In vitro models use a variety of immune cells to demonstrate the immunosuppressive properties of opioids, benzodiazepines, and to a lesser extent, propofol. In each case, animal studies provide more robust data supporting the concept that opioids, benzodiazepines, and propofol exhibit immunosuppressive activities ranging from innate to adaptive immune alterations. Human studies, though more limited, provide further support that these agents inhibit the immune response. In contrast, data have shown that dexmedetomidine may attenuate the immune system. Clinical trial data evaluating the immunosuppressive properties of these agents is limited.

CONCLUSIONS

Analgesic and sedation agents have clearly been shown to alter cellular function and other mediators of the immune system; yet the clinical impact remains to be fully elucidated. The mechanism by which sedation interruption reduces ventilator-associated pneumonia may in fact be a reduction in immunosuppressive effects. Studies linking the immune-modulating effects of analgesic and sedation agents in critically ill patients are needed.

Age-Dependent Neuroimmune Modulation of IGF-1R in the Traumatic Mice

Background

Age-dependent neuroimmune modulation following traumatic stress is accompanied by discordant upregulation of Fyn signaling in the frontal cortex, but the mechanistic details of the potential cellular behavior regarding IGF-1R/Fyn have not been established.

Methods

Trans-synaptic IGF-1R signaling during the traumatic stress was comparably examined in wild type, Fyn (−/−) and MOR (−/−) mice. Techniques included primary neuron culture, in vitro kinase activity, immunoprecipitation, Western Blot, sucrose discontinuous centrifugation. Besides that, [³ H] incorporation was used to assay lymphocyte proliferation and NK cell activity.

Results

We demonstrate robust upregulation of synaptic Fyn activity following traumatic stress, with higher amplitude in 2-month mice than that in 1-year counterpart. We also established that the increased Fyn signaling is accompanied by its molecular connection with IGF-1R within the synaptic zone. Detained analysis using Fyn (−/−) and MOR (−/−) mice reveal that IGF-1R/Fyn signaling is governed to a large extent by mu opioid receptor (MOR), and with age-dependent manner; these signaling cascades played a central role in the modulation of lymphocyte proliferation and NK cell activity.

Conclusions

Our data argued for a pivotal role of synaptic IGF-1R/Fyn signaling controlled by MOR downstream signaling cascades were crucial for the age-dependent neuroimmune modulation following traumatic stress. The result here might present a new quality of synaptic cellular communication governing the stress like events and have significant potential for the development of therapeutic approaches designed to minimize the heightened vulnerability during aging.

Sedation & immunomodulation

As the armamentarium for sedation in the critically ill expands, opportunities will develop to modulate the immune responses of patients by way of the direct immune and neural-immune interactions of the sedatives. Control of autonomic activity through the use of appropriate sedation may be critical in this matter. Likewise analgesic-based sedation, with increased opioid dosage, may not prove beneficial in the setting of infection; whether avoidance of morphine in preference for a fentanyl derivative will help is unclear. However, as the immune effects seem dependent on the m receptor, it is improbable that a significant difference would be uncovered. Similarly, the present evidence suggests benzodiazepines are deleterious in infection; further studies are required urgently to evaluate this evidence. As an alternative to benzodiazepine-based sedation, dexmedetomidine has shown a remarkable 70% mortality benefit in a small secondary analysis of septic patients from the MENDS trial. Further powered clinical studies should now be undertaken to investigate the potential benefit of the α2-adrenoceptor agonist in this setting, with comparisons with propofol.

Opioid drug abuse and modulation of immune function: consequences in the susceptibility to opportunistic infections

Infection rate among intravenous drug users (IDU) is higher than the general public, and is the major cause of morbidity and hospitalization in the IDU population. Epidemiologic studies provide data on increased prevalence of opportunistic bacterial infections such as TB and pneumonia, and viral infections such as HIV-1 and hepatitis in the IDU population. An important component in the intravenous drug abuse population and in patients receiving medically indicated chronic opioid treatment is opioid withdrawal. Data on bacterial virulence in the context of opioid withdrawal suggest that mice undergoing withdrawal had shortened survival and increased bacterial load in response to Salmonella infection. As the body of evidence in support of opioid dependency and its immunosuppressive effects is growing, it is imperative to understand the mechanisms by which opioids exert these effects and identify the populations at risk that would benefit the most from the interventions to counteract opioid immunosuppressive effects. Thus, it is important to refine the existing animal model to closely match human conditions and to cross-validate these findings through carefully controlled human studies. Better understanding of the mechanisms will facilitate the search for new therapeutic modalities to counteract adverse effects including increased infection rates. This review will summarize the effects of morphine on innate and adaptive immunity, identify the role of the mu opioid receptor in these functions and the signal transduction activated in the process. The role of opioid withdrawal in immunosuppression and the clinical relevance of these findings will also be discussed.

Potentiating effect of morphine on oral Salmonella enterica serovar Typhimurium infection is μ-opioid receptor-dependent

Previous studies from our laboratory demonstrated that mice treated with morphine pellets are sensitized to Salmonella enterica, serovar Typhimurium infection. However, the opioid receptor antagonist, naltrexone, only partially blocked the effect of morphine, raising the possibility that the opioid might have some of its effects through a nonopioid receptor. To further clarify whether sensitization to infection is an opioid receptor-dependent phenomenon, μ-opioid receptor knockout (MORKO) mice were used in the present study. Wild-type (WT) and MORKO mice were treated with morphine and their sensitivity to oral Salmonella infection was assessed by mortality, bacterial burdens in gut associated lymphoid tissue and in blood and peritoneal fluid, and by levels of pro-inflammatory cytokines in plasma. MORKO animals treated with morphine were refractory to a sublethal dose of Salmonella, while similar treatment of WT animals resulted in 100% mortality. WT animals treated with morphine had high bacterial loads in all organs tested, while morphine-treated MORKO animals had no culturable Salmonella in any organs. Pro-inflammatory cytokine levels were elevated in morphine-treated WT but not MORKO mice infected with Salmonella. These results provide definitive evidence that the morphine-mediated enhancement of oral Salmonella infection is dependent on the μ-opioid receptor.

Sedation & immunomodulation

The management of critically ill patients necessitates the use of sedatives and analgesics to provide patient comfort and cooperation. These drugs exert profound effects on all organ systems, not only the central nervous system, and this article describes the immunologic effects of the commonly used critical care sedatives: propofol, the benzodiazepines, opioids, and alpha(2)-adrenoceptor agonists. Benzodiazepines, opioids, and possibly even propofol worsen outcome in animal models of infection, whereas preliminary evidence suggests that the alpha(2)-adrenoceptor agonist, dexmedetomidine, may improve outcomes in the setting of infection. Given the burden of sepsis and secondary infections in critical care, choice of sedation may need to be carefully considered to preserve immune responses in critically ill patients.

"I inject less as I have easier access to pipes": injecting, and sharing of crack-smoking materials, decline as safer crack-smoking resources are distributed

Among injection drug users (IDUs) in Ottawa, the capital of Canada, prevalence rates of HIV (20.6 percent) and hepatitis C HCV (75.8 percent) are among the highest in Canada. Recent research evidence suggests the potential for HCV and HIV transmission through the multi-person use of crack-smoking implements. On the basis of this scientific evidence, in April 2005, Ottawa's needle exchange programme (NEP) commenced distributing glass stems, rubber mouthpieces, brass screens, chopsticks, lip balm and chewing gum to reduce the harms associated with smoking crack. This study aims to evaluate the impact of this initiative on a variety of HCV- and HIV-related risk practices. Active, street-recruited IDUs who also smoked crack consented to personal interviews and provided saliva samples for HCV and HIV testing at four time points: 6-months pre-implementation (N=112), 1-month (N=114), 6-months (N=157) and 12-months (N=167) post-implementation. Descriptive and univariate analyses were completed. Following implementation of the initiative, a significant decrease in injecting was observed. Pre-implementation, 96 percent of IDUs reported injecting in the month prior to the interview compared with 84 percent in the 1-month, and 78 percent in the 6- and 12-month post-implementation interviews (p<.01). Conversely, approximately one-quarter of participants at both the 6- and 12-month post-implementation evaluation points reported that they were smoking crack more frequently since the availability of clean equipment--25 and 29 percent, respectively. In addition to a shift to a less harmful method of drug ingestion, HCV- and HIV-related risks associated with this method were reduced. Among crack-smoking IDUs sharing pipes, the proportion sharing "every time" declined from 37 percent in the 6-month pre-implementation stage, to 31 percent in the 1-month, 12 percent in the 6-month and 13 percent in the 12-month post-implementation stages (p<.01). Since distributing safer crack-smoking materials by a NEP contributes to transition to safer methods of drug ingestion and significantly reduces disease-related risk practices, other NEPs should adopt this practice.

Injection drug use and the hepatitis C virus: considerations for a targeted treatment approach--the case study of Canada

Infection with the hepatitis C virus (HCV) is a major public health burden in Canada and globally. The literature shows that injection drug use is currently the primary transmission route for HCV, and that a majority of injection drug users (IDUs) are currently infected with HCV in Canada. This article first reviews the burden of HCV within IDU populations and the transmission risks and the treatment implications specific to IDUs. Traditionally, IDUs have been excluded from HCV treatment unless abstaining from illicit drug use. However, recent research suggests that categorical exclusion is not medically necessary. A series of key questions about the feasibility of offering HCV treatment to IDUs in the specific Canadian context are considered, including concerns related to the motivation of treatment for IDUs, treatment delivery, treatment side effects, HCV reinfection, and the social environment. The article concludes that treatment of HCV-infected illicit drug users is both feasible and may be necessary to reduce transmission and adverse outcomes in this high-risk population.

Withdrawal from morphine in mice suppresses splenic macrophage function, cytokine production, and costimulatory molecules

We have previously shown that abstinence from morphine by either abrupt (AW) or precipitated (PW) withdrawal induces greater than 80% suppression in the capacity to mount an in vitro plaque-forming cell (PFC) response to sheep red blood cells at 24-h post withdrawal. Present studies on the mechanisms of immunosuppression showed that addition of normal unfractionated spleen cells, macrophage-enriched adherent cells, or CD11b(+) purified macrophages, to spleen cells taken from withdrawn mice, restored immune responses. Spleen cells from mice undergoing withdrawal also had decreased splenic mRNA and/or protein levels of IL-1beta, IL-1Ra, TNF-alpha, IL-12, and IFN-gamma. Addition of IL-1beta or IFN-gamma to AW cultures was able to reverse their immunosuppression. These results strongly suggest that morphine withdrawal results in a deficit of macrophage function.

Long-term methadone treatment: effect on CD4+ lymphocyte counts and HIV-1 plasma RNA level in patients with HIV infection

The objective was to examine the effect of methadone on CD4+ lymphocyte counts and viral load and to expect to document the safety of methadone maintenance in patients with human immune deficiency syndrome. This is a retrospective chart analysis comparing the trends in CD4+ count and viral load in two populations of 21 human immunodeficiency virus (HIV) infected patients, one on methadone maintenance and a methadone non-using group. Each methadone user was matched with a control methadone non-user that had a similar CD4+ at the beginning of the study. For the CD4+ count we compared the slope of regression for each couple of patients. In 15 patients we also collected the viral load, which was measured at 4-6 monthly intervals. The mean length of follow-up was 811 days for the methadone group and 797 days in the control group. There was no statistical difference in the treatment received by the two groups of patients during the study. The slope of regression of CD4+ count showed a significantly steeper decline in the methadone-using patients compared with the methadone non-users (r= 0.487; p< 0.05). The evolution of the HIV-1 RNA levels was the same during the follow-up of mean 186 months in a few of the patients in each of the two groups. Long-term methadone use was associated with a significantly faster decrease of CD4+ count in HIV-1 affected patients compared with methadone non-users. HIV-1 RNA data were found in too few patients to enable any conclusions about the development of viral load in the two groups.

Morphine Up-regulates expression of substance P and its receptor in human blood mononuclear phagocytes and lymphocytes

In vitro and in vivo studies have indicated that there is an important relationship between morphine and neuropeptide substance P (SP). We therefore investigated the interaction of morphine and cultured human immune cells on the expression of SP, a neuropeptide which we have recently demonstrated to be produced by human monocytes and lymphocytes. Morphine up-regulated SP production in human mononuclear phagocytes and lymphocytes at both the mRNA and the protein level. In addition, morphine induced SP receptor (NK-1R) expression in human lymphocytes. The specific morphine receptor antagonist (naltrexone) blocked morphine-induced SP expression in human mononuclear phagocytes, supporting the concept of authentic morphine receptor-mediated regulation. Since SP modulates neurogenic inflammation and immunologic events, these data suggest that morphine-induced SP expression in cells of the immune system may be of importance in the pathogenesis of immune-mediated diseases, including neuroimmunologic diseases and AIDS.

Morphine modulates NF kappa B activation in macrophages

Chronic use of morphine affects the immune system and predisposes an individual to opportunistic infections. Macrophages play an important role in conferring a first line of defense against invading pathogens. Understanding the mechanisms by which morphine affects the functioning of macrophages would have significant therapeutic benefit in treatment against infections such as HIV and AIDS related syndromes. Two of the major cytokines secreted by activated macrophages are Interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha). Our studies show that morphine differentially modulates lipopolysaccharide (LPS) induced expression of IL-6 and TNF-alpha. Nanomolar concentrations of morphine synergize with LPS and augment the secretion of both IL-6 and TNF-alpha. However, at micromolar concentrations morphine inhibits LPS induced synthesis of IL-6 and TNF-alpha. Expression of both these cytokine genes is dependent on the activation of a transcription factor, NF kappa B. Interestingly, morphine treatment also modulated the activation of NF kappa B by LPS. Pretreatment with a low dose of morphine (nanomolar) resulted in an increase in NF kappa B activation. In contrast pretreatment with a high dose of morphine (micromolar) led to a significant decrease in NF kappa B activation. Furthermore unlike the augmentation which was naloxone reversible, the inhibition of NF kappa B by morphine was not reversed by naloxone, suggesting the involvement of a nonclassical opioid receptor.

Opioid mediated effects on the immune system: sympathetic nervous system involvement

Opioids have been hypothesized to suppress parameters of immune function by acting within the central nervous system to increase the activity of the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system. Production of catecholamines and adrenocorticoids have been demonstrated to be responsible for many of the observed immunomodulatory effects which occur following opioid administration. In general, the sympathetic nervous system has been shown to play a role in regulating lymphocyte proliferation and natural killer cell activity as well as several other parameters of immune function. Here, we will focus primarily on the role of the sympathetic nervous system in modulating opioid induced immunosuppression. The role of the hypothalamic-pituitary adrenal axis is reviewed elsewhere in this issue.

Opiates and infection

This review on the effects of opiate use on infectious diseases discusses the complete spectrum of infections in the opiate user, including those of the lung, the GI tract, the skin, the skeletal system, and the CNS. There is both increased prevalence and increased severity of bacterial and viral infections in injection drug users with the outcome of increased morbidity and mortality. The experimental administration of opiates has lead to a greater understanding of the effects on susceptibility to and progression of infectious diseases. Animal models of opiate dependence and infection are reviewed with specific attention to cases in which the opiate-mediated effects are harmful and in which cases they are beneficial.

Effect of morphine on Fc-mediated phagocytosis by murine macrophages in vitro

Acute exposure to morphine has been shown to inhibit phagocytosis in murine macrophages, whereas chronic exposure results in apparent desensitization. We now show that morphine may be either inhibitory or stimulatory depending on concentration and exposure time. Furthermore, under some conditions drug withdrawal from putatively desensitized cells will result in inhibition of phagocytosis, suggesting that a state akin to dependence has developed. Desensitization can also develop with intermittent exposures if the opiate-free period between drug exposures is shorter than 4 h. These effects of morphine on macrophages are important in understanding the role of this drug as an immunomodulatory agent.

Inhibition of swine microglial cell phagocytosis of Cryptococcus neoformans by femtomolar concentrations of morphine

Microglia are important immune effector cells within the brain. The phagocytosis of nonopsonized Cryptococcus neoformans by swine microglia was used as an in vitro model for studies on cellular mechanisms of opiate-mediated immunomodulation in the brain. Morphine inhibited potently (IC50 approximately 10(-16) M) the phagocytosis of C. neoformans by primary cultures of neonatal pig microglia. The mu opioid agonist Tyr-D-Ala-Gly-N-Me-Phe-Gly-ol (DAMGO) also suppressed phagocytosis but with a much lower potency than morphine (IC50 approximately 10(-8) M). The inhibitory effects of morphine and DAMGO were blocked by equimolar concentrations of naloxone and by the selective mu opiate receptor antagonist beta-funaltrexamine. Pertussis toxin but not cholera toxin reversed the inhibitory effects of both morphine and DAMGO. Our data suggest that morphine inhibits phagocytosis of C. neoformans by swine microglia via a mechanism involving mu opiate receptors coupled to a pertussis toxin-sensitive Gi/G(o) protein signaling pathway.

Inhibition of primary murine macrophage cytokine production in vitro following treatment with the kappa-opioid agonist U50,488H

Previous work in our laboratory has shown that both mu- and kappa-opioid agonists exhibit immunosuppressive activity for antibody responses in vitro. Our earlier work has suggested that both accessory cells and T cells may be altered following treatment with the kappa-opioid agonist U50,488H. We intend to further determine the identity of the immune cell population(s) which are affected by opioid treatment, and to determine the nature of the opioid receptor type expressed on these cells. In this study, non- elicited peritoneal macrophages were treated simultaneously with the kappa-agonist U50,488H and lipopolysaccharide (LPS), and the levels of the cytokines interleukin (IL)-1, IL-6 and tumor necrosis factor (TNF)-alpha were determined. The results show that U50,488H had a suppressive effect on the production of TNF-alpha and IL-1 at concentrations as low as 1 nM, while IL-6 was suppressed at concentrations as low as 10 nM. Additional experiments utilizing the opiate antagonist naloxone and the kappa-selective antagonist norbinaltorphimine (norBNI) were performed in order to further characterize the opioid receptor involved in the cytokine suppression produced by treatment with U50,488H. Results showed that naloxone was able to partially block U50,488H suppression while norBNI was able to completely reverse the suppression of IL-6 production. These results suggest that macrophage/monocyte function is significantly modulated following activation of the kappa-opioid receptor.

Granulocyte defects and opioid receptors in chronic exposure to heroin or methadone in humans

In order to elucidate better the immunological effect of opioid abuse in the absence of HIV infection as a confounding factor, granulocyte function was investigated in three groups of HIV-negative subjects, including 20 active parenteral heroin abusers (H), 20 long-term methadone-maintained former opiate abusers (M) and 20 healthy controls (C). Chemotaxis to N-formyl methionyl-leucyl-phenylalanine (fMLP), casein and activated plasma were markedly and similarly reduced (approx. 50%) in both H and M groups, as was true for superoxide production after fMLP and PMA stimulation, 47% decrease of C values. Polymorphonuclear (PMN) of H and M subjects also exhibited a very marked and similar reduction in the expression of CD11b/CD18 integrin receptors after fMLP treatment, with values that were less than 10% of those in controls, as observed by flow cytometry. In parallel, PMN of H and M individuals presented an approximately four-fold increase in opioid receptors numbers compared to controls, a significant inverse correlation existing between the increase in opiate receptors and defective chemotaxis. The possible mechanism underlying the observed changes in PMN of H and M individuals is discussed.

Combined effect of fluconazole and thymosin alpha 1 on systemic candidiasis in mice immunosuppressed by morphine treatments

Treatment of systemic infection with Candida albicans with a combination of an antifungal agent (i.e. fluconazole) and a thymus-derived immunostimulant (i.e. thymosin alpha 1 (T alpha 1)) in mice immunosuppressed by morphine treatments was investigated. In normal mice, fluconazole given after infection with 10(6) C. albicans cells was more effective than in mice treated with morphine. Combination treatment with fluconazole and T alpha 1 prolonged survival and reduced the fungal burden in the kidneys of immunosuppressed mice. We also investigated the influence of this combined treatment on killing properties of polymorphonuclear leucocytes (PMN) and natural killer (NK) cell activity, inhibited by morphine administrations. Treatment with T alpha 1 or fluconazole as single agents promoted a recovery of normal NK cell activity and intracellular killing of C. albicans by PMN, while the combination significantly increased both of these responses, probably through the modulation of lymphokine production. Our data suggest that the additive effect of T alpha 1 and fluconazole is due to a direct antifungal action and activation of the immunocompetence.

The effect of methadone on immunological parameters among HIV-positive and HIV-negative drug users

Our objective was to assess the effects of methadone use on immune parameters. A convenience sample of men and women drug injectors who knew their HIV serostatus were enrolled in a longitudinal observational study of HIV illness. During analysis of baseline data, differences were noted in immune parameters among Methadone users. Study participants were recruited in Manhattan, New York, from a methadone maintenance clinic, and infectious disease clinic of an inner city hospital, and a drug-free community center. The participants were 220 men and women, current or former drug injectors, approximately half of them HIV-antibody positive and the rest HIV-antibody negative. Candidates with opportunistic infections and secondary neoplasms were excluded. Methadone users were compared to nonmethadone users for absolute and percentage counts of CD4, CD8, and activated T lymphocytes; CD4/CD8 ratio; an HIV symptom check list; and medical staging. The results discussed in this paper were formulated after data collection was complete. Our data indicate that methadone treatment, while not significantly affecting absolute CD4 lymphocyte count, is associated with a lower CD4 percentage and CD4/CD8 cell ratio, and with a higher CD8 absolute count and percentage. These differences are present regardless of HIV serostatus. Our findings should be interpreted with caution since we did not set out to investigate the effects of methadone on the immune system. Nevertheless, if it is corroborated that methadone has a detrimental effect on the immune system, finding alternatives to methadone-maintenance treatment for drug injectors will be a necessity.

Marijuana usage in relation to harmfulness ratings, perceived likelihood of negative consequences, and defense mechanisms in high school students

This study investigated high school students' marijuana usage patterns in relation to their harmfulness ratings of 15 licit and illicit drugs, perceived negative consequences from using marijuana, and types of defense mechanisms employed. Subjects were classified into one of five pattern-of-use groups based on marijuana usage: principled nonusers, nonusers, light users, moderate users, and heavy users. Principled nonusers (individuals who have never used marijuana and would not do so if it was legalized) rated marijuana, hashish, cocaine, and alcohol as significantly more harmful than heavy users. A cluster analysis of the drugs' harmfulness ratings best fit a three cluster solution and were named medicinal drugs, recreational drugs, and hard drugs. In general, principled nonusers rated negative consequences from using marijuana as significantly more likely to occur than other groups. Principled nonusers and heavy users utilized reversal from the Defense Mechanism Inventory, which includes repression and denial, significantly more than nonusers, indicating some trait common to the two extreme pattern-of-use groups.

Macrophage functions in drugs of abuse-treated mice

The in vivo effect of morphine, methadone and cocaine on murine peritoneal macrophage-mediated cytostasis and macrophage supernatant mediated cytostasis was investigated. In addition, the activity of drugs of abuse was studied on IL-1 alpha and TNF production by activated murine macrophages. A highly depressive effect on macrophage-mediated cytostatic activity and a decrease of IL-1 alpha and TNF levels were found in the supernatants of activated macrophages observed in morphine- and cocaine-treated mice. Conversely, a significant impairment of macrophage functions was not observed in methadone-treated mice. Our results suggest that the inhibition of macrophage defensive functions caused by drugs of abuse may be an important cofactor in the pathogenesis of infectious diseases.

Thymosin alpha one restores murine T-cell-mediated responses inhibited by in vivo cocaine administration

The effects of different in vivo thymosin alpha one (T alpha 1) treatments on T-cell responses inhibited by cocaine abuse were studied. Administration during cocaine treatment promoted a faster recovery of normal natural killer (NK) cell activity after the suspension of abuse. Suspension of cocaine plus repeated T alpha 1 administrations strongly restored NK activity and, interestingly, spleen cells from mice treated with T alpha 1 during and after cocaine administration achieved a very rapid recovery and the greatest stimulation of natural cytotoxicity. This last treatment also restored the cocaine-inhibited specific T-cell response (i.e. allogeneic cytotoxic T-lymphocyte (CTL) generation) and abrogated the cocaine-induced suppression of interferon gamma (IFN-gamma), interleukin 2 (IL-2) and IL-4 production. Finally restoration and induction of thymic cellularity were significant when T alpha 1 was given during and after cocaine administration. The present investigation provides evidence for the first time that thymic hormones could be of potential value in controlling cocaine-induced impairment of T-cell-mediated immunity in the mouse.

Immunological consequences of zidovudine treatment in control and morphine or methadone treated mice

The effects of acute and chronic zidovudine (AZT) administration on immunologic test responses of mice were studied. The effects of AZT administration combined with morphine or methadone treatment, were also studied separately comparing the effects of each drug. We noted that AZT-treatment did not modify the T-lymphocyte subsets (L3T4/LyT2 rate), whereas morphine-treatment and AZT plus morphine treatment decreased the percentage of T helper cells. Acute and chronic AZT-treatment increased Natural Killer cell (NK) activity and also recovered the decreased NK cell activity produced by morphine-treatment. AZT-treatment, morphine-treatment, AZT plus morphine treatment and AZT plus methadone treatment strongly depressed the phagocytic physiological activity of Polymorphonuclear leukocytes (PMNs). Another evidence of immunologic responsiveness against AZT was the reduction of the mitogenic and antigenic response of lymphocytes. These results suggest a negative role of AZT-treatment especially on phagocytic activity and confirms a depressive effect of morphine-treatment on several immune functions studied. Furthermore, there is no indication of additive or synergistic toxic effects of AZT, morphine and methadone on the immune functions above that seen with each of these drugs when tested alone.

Physiological basis for neuroimmunomodulation

A large number of clinical and experimental observations indicate that immune responses may be modulated by the central nervous system (CNS). The immune system (IS) and CNS are known to communicate via the endocrine and the autonomic nervous systems. In this overview, we will focus on the immunomodulating role of neurotransmitters and neuropeptides. Immune cells appear to express membrane antigens similar to those of neural cells. Similarities re-enforce analogies between CNS and IS cells. The concept that the CNS modulates immune functions implies that the immune system feeds back information to the CNS. In fact, interleukins have neuroendocrine functions whether they are produced at the periphery by immune cells or at the CNS level by glial cells. Finally, the possible endocrine functions of lymphocytes are described and it is suggested that a complete regulatory loop between immune and neuro-endocrine systems exists. Studies in neuro-immunomodulation are of great importance from a theoretical point of view, the CNS-IS inter-relationships may not be considered only between the CNS and the periphery but also at the level of the immune micro-environment which may be considered as an immune-neuro-endocrine complex.

Phagocytosis in Tetrahymena thermophila: naloxone-reversible inhibition by opiates

1. Nanomolar concentrations of opiates inhibit phagocytosis in the ciliated protozoan Tetrahymena thermophila. 2. Naloxone and naltrexone counteract the effect of the opiate agonists tested. 3. The dose-response curves are U-shaped, with no detectable effect at low or high concentrations. 4. An increase in extracellular calcium and dopamine counteract the inhibition caused by metenkephalin. 5. The recognition mechanism for opiates in Tetrahymena cannot be classified as belonging to any of the mammalian opiate receptor subtypes and is perhaps a primitive receptor.

Immunomodulation by morphine and marijuana

The immunomodulatory effects of morphine and the active components of marijuana, particularly tetrahydrocannabinol, on various aspects of the host immune parameters include alterations in humoral, cell-mediated and innate immunity. Most studies have shown immunosuppressive effects due to use of these abused substances, although there are reports that they may not produce any deleterious effect and may even enhance some aspects of host immunity. They reduce resistance to cancer growth and microbial pathogens in animals.