Figures
Abstract
Background
Opioid use is associated with increased incidence of infectious diseases. Although experimental studies have shown that opioids affect various functions of immune cells, only limited data are available from human studies. Drug use is an important risk factor for HIV transmission; however no data are available whether heroin and/or methadone modulate immune response. Therefore, we examined the effect of heroin and methadone use among HIV-infected individuals on the production of cytokines after ex vivo stimulation with various pathogens.
Methods
Treatment naïve HIV-infected individuals from Indonesia were recruited. Several cohorts of individuals were recruited: 1) using heroin 2) receiving methadone opioid substitution 3) using heroin over 1 year ago and 4) controls (never used opioids). Whole blood was stimulated with Mycobacterium tuberculosis, Candida albicans and LPS for 24 to 48 hours. Cytokine production (IL-1 β, IL-6, IL-10, IFN-α, IFN-γ and TNF-α) was determined using multiplex beads assay.
Results
Among 82 individuals, the cytokine levels in unstimulated samples did not differ between groups. Overall, heroin users had significantly lower cytokine response after exposure to LPS (p<0.05). After stimulation with either M. tuberculosis or C. albicans the cytokine production of all groups were comparable.
Citation: Meijerink H, Indrati A, Utami F, Soedarmo S, Alisjahbana B, Netea MG, et al. (2015) Heroin Use Is Associated with Suppressed Pro-Inflammatory Cytokine Response after LPS Exposure in HIV-Infected Individuals. PLoS ONE 10(4): e0122822. https://doi.org/10.1371/journal.pone.0122822
Academic Editor: Wenzhe Ho, Temple University School of Medicine, UNITED STATES
Received: August 25, 2014; Accepted: February 21, 2015; Published: April 1, 2015
Copyright: © 2015 Meijerink et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Data Availability: All relevant data are within the paper.
Funding: Hinta Meijerink has a fellowship from Radboud University Medical Centre Nijmegen; Rudi Wisaksana has a fellowship from the Radboud University; Reinout van Crevel has a VIDI grant from the Netherlands Foundation of Scientific Research (NWO); Bachti Alisjahbana has a post-doc fellowship from the Royal Dutch Academy of Arts and Sciences (KNAW). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Introduction
Opioid use is associated with increased incidence of infectious diseases. Variables, such as sharing needles, nutrition status and homelessness, can influence the frequency of infections, but studies also suggest that immune modulating effects of opioids are a major factor in the increased susceptibility to various infectious agents [1–8]. More specifically, opioids have shown to modulate several aspects of the immune system.
In both human and animal studies, opioid use has been associated with increased susceptibility to microbial infections, including bacterial infections such as staphylococci, streptococci and more specifically Escherichia coli, Salmonella typhimurium and Mycobacterium tuberculosis, the fungi Candida albicans, the parasite Toxoplasma gondii, and viruses such as the herpes virus and Friend leukemia virus [7]. In addition, there is a high risk of blood-born infectious diseases when unsterile needles are used to inject drugs, such as endocarditis, cellulitis, sepsis, hepatitis C and human immunodeficiency virus (HIV) [6]. Injecting drug use (IDU) is responsible for HIV infections in 10% of all cases worldwide, and 30% of cases outside Africa [1]. IDU is not only a risk factor for HIV transmission, but it may also change the natural course of HIV infection, for instance because of co-infections, nutritional deficiencies and/or the immune modulating properties of opioids.
Experimental studies have shown that binding of opioids to the opioid μ-receptors of immune cells affects the function of these cells in various ways. In vitro and animal experiments have shown that opioids modulate phagocytosis, chemotaxis, cytokine response and activity of immune cells; which could have detrimental results for the cellular immunity [6,7]. On the other hand, other studies suggest that the effects of opioids on the immune system are not necessarily deleterious; cells exposed to endogenous opioids in vitro increased natural killer cell activity [9].
The regulation of immune and inflammatory responses is dependent on the functions of cytokines, which is especially important in individuals with an already compromised immune function, such as HIV-infected individuals. The effects of opioids on cytokine production have been investigated in both in vitro and animal experiments [10–19], but only little information is available on in vivo exposure in humans. In addition, the data from previous studies have shown contradicting results. For example the production of IFN-γ can be enhanced [10] or suppressed [11] by various opioids in in vitro studies, whereas in animal experiments the IFN-γ production is often diminished after exposure to opioids [17,18]. The production TNF-α is mostly suppressed by opioids [13,15,16], but some studies show no effect [14] or even an increase in TNF-α [12]. Opioids reduce the IL-8 production [13,19], whereas IL-1β production is often enhanced [12,19]. The differences in results might be explained by experimental set-up, type of cells or animals used, and type of opioid.
Most studies use morphine to test the effects of opioids on immune system. Only limited data are available from human studies; in most of these studies opioids are used for pain relief, either post-surgery or during cancer treatment [20–24]. The main findings of these studies were that morphine suppressed natural killer cell activity, reduced mitogen responses and decreased lymphoproliferation. One study examined the effects of morphine in healthy volunteers [25]: continuous exposure to morphine over a period of 36 hours resulted in suppression of natural killer cell cytotoxicity as well as IFN-γ stimulated and antibody-dependent cytotoxity. All these study suggests that morphine administration can cause measurable suppression of the immune system.
Heroin and methadone are however more commonly associated with HIV infection. As the different opioids are known to have different affinity for the opioid receptors [26–28], one may hypothesize that they exert different immune modulating effects. Only two human studies examined the immunological effects of heroin or methadone. One study compared the effects of methadone and buprenorphine (as opioid substitution) in drug users and found no difference, but cytokine levels were significantly depressed compared to controls [29]. Azarang et al compared the ex vivo cytokine production after stimulation of whole blood between heroin users and healthy controls and found that heroin addicts produce less IFN-γ and more interleukin (IL)10 after stimulation with lipopolysaccharides (LPS) [30]. Even though drug use is not uncommon among HIV-infected individuals, no data are available regarding the effects of heroin or methadone on the immune response in HIV. In the present study, we examined therefore the effect of heroin and methadone use among HIV-infected individuals on the production of cytokines after ex vivo stimulation with various pathogens relevant in the HIV patients.
Methods
Study setting and population
For this study, we included HIV-infected adults (>16 years) from several settings in West-Java, Indonesia; an HIV clinic, a methadone clinic and the community. The collaboration with the clinics and the community was part of a five-year programme (2006–2011) called ‘IMPACT’, aimed to improve prevention, control and treatment of HIV among injecting drug users in West-Java, Indonesia [31]. In these clinics, people with and without a history of IDU, who are at risk for HIV infection or who present with signs and symptoms suggesting HIV/AIDS are counselled and tested for HIV. All testing is voluntary and informed consent is obtained from all study participants. HIV-infected patients are characterised and followed prospectively in a cohort study. To contact individuals in the community we collaborated closely with Rumah Cemara; a local NGO focussing on increasing the quality of life for people with HIV/AIDS and people who use drugs. All subjects selected for this study were antiretroviral treatment naïve HIV-infected and had no signs of active infections, such as acute hepatitis, active tuberculosis or oral thrush. Participants were not tested for (chronic) hepatitis C infection or latent tuberculosis. Individuals had to fit the inclusion criteria of one of the four groups: 1) Active drug users: used heroin in the last 30 days; 2) Methadone clients: received methadone maintenance treatment (MMT) in the last 30 days; 3) Former users: used heroin or methadone over one year ago; 4) Controls: never used heroin or methadone. All participants were informed on the study and signed an informed consent. Data on demographic factors, history of drug use, co-morbidity, self-reported tuberculosis treatment and history of ART were collected through interview with standardized questionnaires. In addition, blood was collected for various purposes, including CD4 cell count, general haematology, flow cytometry and cell stimulation assays. At the time of this study, antiretroviral therapy (ART) was indicated in Indonesia for patients presenting with WHO clinical stage IV or a CD4 count less than 200 cells/μl in accordance with WHO guidelines from 2006. Since 2004, ART can be accessed free of charge in Indonesia.
Ethics Statement
After being informed about the study, all participants provided written consent to participate in this study. No children or minors were included in this study. This study was approved by the Health Research Ethics Committee at the Faculty of Medicine of Padjadjaran University/Dr. Hasan Sadikin General Hospital in Bandung, Indonesia (record number: 190/ UN6.C2.1.2/ KEPK/ PN/ 2011).
Stimulation assay
Cytokine production was examined after whole blood stimulation with various pathogens, namely killed Candida albicans and Mycobacterium tuberculosis as infection with these are often associated with HIV and LPS isolated from Escherichia coli as a TLR4 agonist. Briefly, venous blood was drawn into 5-mL endotoxin-free lithium-heparin tubes (Vacutainer, BD Biosciences) and samples were processed within 4 hours. Blood was diluted 1:5 with culture medium only (RPMI Dutch modified) or in combination with either conidia of heath killed C.albicans (106 cells/ml), M. tuberculosis (10 μg/ml), LPS isolated from E. coli (10 ng/ml). After 24 or 48 hour incubation, blood cultures were centrifuged at 1700rpm for 10 min and supernatants were stored at −20°C until assayed. During this period opioid levels were not measured, nor was the opioid level maintained during incubation. The expression of cytokines IL-1 β, IL-6, IL-10, IFN-α, IFN-γ and TNF-α were measured using a multiplex beads assay (Merck Millipore, Billerica, MA, USA) according to the manufacturer's instructions. The detection limit for the cytokine production was 32pg/μl for IL-1β and IL-6 and 3.2pg/μ for and IL-10, IFN-α, IFN-γ and TNF-α. Based on previous testing we measured the production of IL-1β and IL-6 in 24 hours samples and IL-10, IFN-α, IFN-γ and TNF-α in 48 hour samples.
Statistical analyses
Subjects with CD4 cell counts below 100cells/μl were excluded from statistical analyses. All cytokine levels after stimulation were corrected for the amount of CD4 cells and the unstimulated levels. The production of cytokines was compared between groups using Kruskul-Wallis and Mann Whitney analyses. Results were found statistically significant at a level of 0.05, resulting in a p-value of 0.016 after Bonferroni adjustment for multiple tests. All statistical analysis was performed using the Statistical Product and Services Solutions package (SPSS) version 18.0 and GraphPad Prism version 5.0.
Results
We included a total of 82 ART-naïve HIV-infected individuals with CD4 cell counts above 100cells/μl (Table 1). Overall, controls were slightly younger than the drug user groups (Table 1), but the groups did not differ in CD4 cell counts (p = 0.13, Table 1).
Whole blood from these individuals was stimulated with various pathogens, namely C.albicans, M.tuberculosis and LPS isolated from Escherichia coli. The cytokine production of unstimulated samples was low and did not differ between groups; the median cytokine level was 32pg/μl for IL-1β (p = 0.466), 32.6pg/μl for IL-6 (p = 0.845), 6.7pg/μl for IFN-α (0.947), 4.0pg/μl for IFN-γ (0.431), 3.2pg/μl IL-10 (0.625) and 11.9 pg/μl for TNF-α (p = 0.382).
The results from the stimulated samples showed that generally the cytokine production was significantly lower in heroin users (Fig 1) after exposure to LPS. Interesting the same was not observed after stimulation with C. albicans (Fig 2) and M. tuberculosis (Fig 3). Analysing the effect LPS exposure, significant less IL-1β, IL-6, TNF-α and IFN-γ production was found in heroin users (Fig 1). The production of these cytokines in MMT and previous users was comparable to the controls (Fig 1). No differences were found in the production of IL-10 after exposure to LPS. Stimulation with C. albicans from both heroin users and previous users seemed to produce less IL-1β and IL-6 than from controls; however these differences were not significant (Fig 2). Also the production of the other cytokines was comparable between all groups after exposure to C. albicans. Compared to controls, the IL-6 production after stimulation with M. tuberculosis was lower in heroin users (not significant p = 0.73) and previous users (p = 0.012) (Fig 3). Also the production of IL-1β and TNF-α seems to have the same trend, but the differences were not statistically significant. Overall, not clear differences were found after stimulation with M. tuberculosis (Fig 3). The production of IFN-α was low in all stimulated samples and therefore these data are not shown.
The level of cytokines was corrected for baseline level and number of CD4 cells (and given in pictogram per 105 cells). *Statistically significant difference (p< 0.016 after Bonferroni adjustment for multiple tests). MMT: methadone maintenance treatment; ART: antiretroviral therapy.
The level of cytokines was corrected for baseline level and number of CD4 cells (and given in pictogram per 105 cells). *Statistically significant difference (p< 0.016 after Bonferroni adjustment for multiple tests). MMT: methadone maintenance treatment; ART: antiretroviral therapy.
The level of cytokines was corrected for baseline level and number of CD4 cells (and given in pictogram per 105 cells). *Statistically significant difference (p< 0.016 after Bonferroni adjustment for multiple tests). MMT: methadone maintenance treatment; ART: antiretroviral therapy.
Discussion
In this study we show that the cytokine production is significantly down-regulated in HIV-infected heroin users compared to HIV-infected individuals who do not use opioids. Interesting, the altered cytokine production was only observed when cells were exposed to LPS but not to M. tuberculosis or C. albicans.
We found that LPS-induced cytokines were affected by heroin use, whereas C. albicans and M. tuberculosis-induced cytokines were not. One could argue that the receptors and pathways involved in candida (C-type lectin receptors) and tuberculosis (TLR 2 and NOD2) are less affected by opioids. However, previous studies have also found associations between opioids and these receptors [32–34]. In addition, the cytokine levels after stimulation with M. tuberculosis were relatively high and therefore might mask a difference between groups due to a ceiling effect. In the present study we only found effects of LPS, which is a specific agonist for TLR4; therefore our results suggest that opioids may affect mainly the TLR4-dependent cytokine production. A binding site for opioids on the TLR4 protein complex has indeed been demonstrated [35]. Studies have furthermore shown that both opioid agonists and antagonists alter the expression of TLR4 [36,37] or affect LPS signalling via the TLR4 signalling pathway [38], which strengthen the data of our study. The latter study showed that morphine alone only weakly increased TLR4 activation, but it significant inhibited TLR4 signalling after LPS stimulation. Interesting naltrexone (a μ-opioid antagonist) also significantly inhibited LPS-induced TLR4 activation [38]. Apart from its effect on monocyte/ macrophages, animal studies also indicate that morphine influences the production of TNF-α in mast cells in a TLR4-dependent manner [39]. Interestingly, the interaction between opioids and TLR4 may also work in the opposite direction, as activation of TLR4 can increase the production of endogenous opioids, such as β-endorphin [40]. Furthermore, some studies find that stimulation of TLR4 affects the opioid-induced responses, such as incubated cue-induced heroin-seeking and morphine tolerance [41,42], whereas others find no clear link [43]. Our study is in line with these studies, showing decreased signalling of TLR4 after LPS stimulation in individuals exposed to opioids. Even though we did not stimulate with the whole pathogen of E.coli we believe our results are still relevant to exposure to E.coli, as the TLR4 pathway is one of the most important pathways for this pathogen.
In addition to the mechanisms described above, bacterial translocation in opioid users might also contribute to our findings, as animal studies have shown that morphine increases bacterial translocation [44–46]. Opioid induced intestinal permeability may result in more exposure to microorganism and endotoxins; continuous exposure could result in the well-known process of endotoxin tolerance [47], which may explain our findings of reduced ex vivo production of pro-inflammatory cytokines after LPS exposure in heroin users. While endotoxin tolerance has been thought of as a protective mechanism against septic shock and ischaemia, its incidence is associated with high risks of secondary infections [48]. Various molecular mechanisms have been described that underlie the development of endotoxin tolerance, including defects in the TLR4 signalling pathway, activation of SOCS molecules, stimulation of anti-inflammatory cytokines such as IL-10, or epigenetic regulation [47–49]. In addition to opioids, HIV infection may increase gut permeability and exposure to endotoxins [50,51]. Our data show that response to LPS is diminished which could therefore be due to translocation of bacteria, especially since all study subjects were HIV positive.
In addition, the opioid-induced immunomodulation may be affected by other factors such as chronic hepatitis C infection. In this study we excluded individuals with signs of acute hepatitis but we did not test for (chronic) hepatitis C infection. Hepatitis C is highly prevalent among injecting drug users and we have previous shown that up to 90% of HIV-infected injecting drug users in Indonesia are seropositive for hepatitis C [52]. Previous studies have shown worse clinical outcomes among HIV-infected individuals with hepatitis C antibodies [53–58]. However, the relation between hepatitis C infection and HIV progression prior to ART remains unclear [53–56,59]; the effects of hepatitis C seems to be more pronounced among patients receiving ART [59,60]. A recent study examined the relation between hepatitis C and circulating cytokine levels [50]. Overall, cytokine levels were significantly higher in individuals co-infected with HIV and hepatitis C, while no data were presented about opioid use [50]. Since hepatitis C is strongly correlated with injecting drug use, it is therefore difficult to distinguish between the effects of opioids and hepatitis C.
Only one other study analysed the influence of heroin or morphine use on the cytokine response [30], showing that HIV-negative heroin users produce less IFN-γ and more IL-10 after stimulation with LPS. Interesting, this difference was larger for heroin users compared to morphine. In line with these results, we also found a decrease of IFN-γ after LPS stimulation; however we did not find an increase of IL-10. We found a lot of variance in the production of IL-10, which might have led to not finding a statistically significant difference. Furthermore, we also found a significant difference between heroin and methadone users. We have previous found similar results on the expression of HIV co-receptors [61]. Clinical and illicit opioids, such as morphine, methadone and heroin, exert their effects primarily through the μ-opioid receptor, but all with different affinity and some also bind to other opioid receptors [26–28,62]. In addition, multiple isotypes of the μ-opioid receptor exists, with differences in ligand binding affinity, rates of internalization and resensitisation. This may explain the differences that are observed when heroin, morphine or methadone are used.
Opioid-induced immunosuppression has shown to be mediated either directly via immune cells or via the central nervous system. In this study we focussed on the peripheral aspects of opioid-induced immunomodulation by using ex vivo stimulation of whole blood. However, the immune effects of opioids in vivo may also be affected by the central nervous system, as previously found in animal experiments [63,64]. The effects of opioids are especially important among HIV-infected individuals, as chronic opioid use has been shown to modulate HIV progression and facilitate HIV associated neurocognitive dysfunctions [52,65]. Among other aspects, opioids may modulate epigenetic and transcriptional regulation of the μ-opioids receptor; this may in turn alter the overall physiological effect of opioids which could be important in HIV disease progression [65].
In our study we determined drug use based on interviews and did not perform toxicological tests, which could perhaps result in a bias. However, we worked closely together with employees of a local NGO, who have been in close contact with our subjects for years. In addition, drug test will only show recent use of opioids (up to four days) and therefore might not be reliable in identifying active users that did not use in the previous couple of days. In addition, we do not have HIV viral loads of our study population, which might also affect the production of cytokines. However, we have previously shown that the viral load among people with and without a history of injecting drug use did not differ [52]. Another factor that may influence the cytokine production is HIV subtype, on which we have information in this population. In addition, drug users might have had a different immune status at inclusion. However, in unstimulated samples the cytokine levels were low in all groups. This indicates an inactive immune status of cells in all groups, and can therefore not explain the differences we show.
In conclusion, this is the first study to examine the immonumodulating effects of heroin and methadone in HIV-infected individuals. We show that heroin use decreases the cytokine response to LPS, but not to M. tuberculosis and C. albicans. Especially in HIV-infected individuals these immunomodulating effects of opioids may have deteriorating effects and increase the risk of secondary infections.
Acknowledgments
We would like to thank Dr. Bayu Wahyudi, Director of Hasan Sadikin General Hospital, and Prof. Tri Hanggono Achmad, Dean of the Medical Faculty, Universitas Padjadjaran for encouraging and accommodating research at their institutions. Everyone working at the HIV and methadone clinic is thanked for providing HIV care and collecting the data used for this study. In particular we would like to thank Yusandi Sastra Atmaja, Nuni Haeruni, Dwi Febni Ratnaningsih and Diah Wulandari for their support during patient inclusion and Sabine Tacke for her help in the laboratory. Great appreciation to all Rumah Cemara staff, especially Dehan Mulyana and Hendra Ferdian for helping us with this project, but also for showing us the work they do and all the care they provide. Also we would like to thank Arif Rusman for taking us to all over Bandung to include subjects.
Author Contributions
Conceived and designed the experiments: RvC AvdV RW MN HM. Performed the experiments: HM AI FU SS BA RW. Analyzed the data: HM AI RW AvdV. Contributed reagents/materials/analysis tools: AvdV MN RvC BA RW. Wrote the paper: HM AI AvdV MN RvC.
References
- 1. Finley MJ, Happel CM, Kaminsky DE, Rogers TJ Opioid and nociceptin receptors regulate cytokine and cytokine receptor expression. Cell Immunol 2008; 252: 146–154. pmid:18279847
- 2. Kapadia F, Vlahov D, Donahoe RM, Friedland G The role of substance abuse in HIV disease progression: reconciling differences from laboratory and epidemiologic investigations. Clin Infect Dis 2005; 41: 1027–1034. pmid:16142670
- 3. Wang J, Barke RA, Ma J, Charboneau R, Roy S Opiate abuse, innate immunity, and bacterial infectious diseases. Arch Immunol Ther Exp 2008; 56: 299–309. pmid:18836861
- 4. Donahoe RM, Vlahov D Opiates as potential cofactors in progression of HIV-1 infections to AIDS. J Neuroimmunol 1998; 83: 77–87. pmid:9610676
- 5. Steele AD, Henderson EE, Rogers TJ Mu-opioid modulation of HIV-1 coreceptor expression and HIV-1 replication. Virology 2003; 309: 99–107. pmid:12726730
- 6. Friedman H, Pross S, Klein TW Addictive drugs and their relationship with infectious diseases. FEMS Immunol Med Microbiol 2006; 47: 330–342. pmid:16872369
- 7. Roy S, Ninkovic J, Banerjee S, Charboneau RG, Das S, Dutta R, et al. Opioid drug abuse and modulation of immune function: consequences in the susceptibility to opportunistic infections. J Neuroimmune Pharmacol 2011; 6: 442–465. pmid:21789507
- 8. Nath A, Hauser KF, Wojna V, Booze RM, Maragos W, Prendergast M, et al. Molecular basis for interactions of HIV and drugs of abuse. J Acquir Immune Defic Syndr 2002; 31 Suppl 2: S62–69. pmid:12394784
- 9. Mathews PM, Froelich CJ, Sibbitt WL Jr., Bankhurst AD Enhancement of natural cytotoxicity by beta-endorphin. J Immunol 1983; 130: 1658–1662. pmid:6300232
- 10. Mandler RN, Biddison WE, Mandler R, Serrate SA beta-Endorphin augments the cytolytic activity and interferon production of natural killer cells. J Immunol 1986; 136: 934–939. pmid:2934481
- 11. Peterson PK, Sharp B, Gekker G, Brummitt C, Keane WF Opioid-mediated suppression of interferon-gamma production by cultured peripheral blood mononuclear cells. J Clin Invest 1987; 80: 824–831. pmid:3040807
- 12. Andjelkov N, Elvenes J, Martin J, Johansen O Opiate regulation of IL-1beta and TNF-alpha in cultured human articular chondrocytes. Biochem Biophys Res Commun 2005; 333: 1295–1299. pmid:15979578
- 13. Bastami S, Norling C, Trinks C, Holmlund B, Walz TM, Ahlner J, et al. Inhibitory effect of opiates on LPS mediated release of TNF and IL-8. Acta Oncol 2013; 52: 1022–1033. pmid:23145506
- 14. Bhargava HN, Thomas PT, Thorat S, House RV Effects of morphine tolerance and abstinence on cellular immune function. Brain Res 1994; 642: 1–10. pmid:8032870
- 15. Bonnet MP, Beloeil H, Benhamou D, Mazoit JX, Asehnoune K The mu opioid receptor mediates morphine-induced tumor necrosis factor and interleukin-6 inhibition in toll-like receptor 2-stimulated monocytes. Anesth Analg 2008; 106: 1142–1149, table of contents. pmid:18349186
- 16. Chao CC, Molitor TW, Close K, Hu S, Peterson PK Morphine inhibits the release of tumor necrosis factor in human peripheral blood mononuclear cell cultures. Int J Immunopharmacol 1993; 15: 447–453. pmid:8389331
- 17. Lorenzo P, Portoles A Jr., Beneit JV, Ronda E, Portoles A Physical dependence to morphine diminishes the interferon response in mice. Immunopharmacology 1987; 14: 93–99. pmid:2448267
- 18. Lysle DT, Coussons ME, Watts VJ, Bennett EH, Dykstra LA Morphine-induced alterations of immune status: dose dependency, compartment specificity and antagonism by naltrexone. J Pharmacol Exp Ther 1993; 265: 1071–1078. pmid:7685383
- 19. Gein SV, Gorshkova KG, Tendryakova SP Regulation of interleukin-1beta and interleukin-8 production by agonists of mu and delta opiate receptors in vitro. Neurosci Behav Physiol 2009; 39: 591–595. pmid:19513849
- 20. Yokota T, Uehara K, Nomoto Y Addition of noradrenaline to intrathecal morphine augments the postoperative suppression of natural killer cell activity. J Anesth 2004; 18: 190–195. pmid:15290418
- 21. Beilin B, Shavit Y, Trabekin E, Mordashev B, Mayburd E, Zeidel A, et al. The effects of postoperative pain management on immune response to surgery. Anesth Analg 2003; 97: 822–827. pmid:12933409
- 22. Sacerdote P, Bianchi M, Gaspani L, Manfredi B, Maucione A, Terno G, et al. The effects of tramadol and morphine on immune responses and pain after surgery in cancer patients. Anesth Analg 2000; 90: 1411–1414. pmid:10825330
- 23. Wang ZY, Wang CQ, Yang JJ, Sun J, Huang YH, Tang QF, et al. Which has the least immunity depression during postoperative analgesia—morphine, tramadol, or tramadol with lornoxicam? Clin Chim Acta 2006; 369: 40–45. pmid:16487501
- 24. Hashiguchi S, Morisaki H, Kotake Y, Takeda J Effects of morphine and its metabolites on immune function in advanced cancer patients. J Clin Anesth 2005; 17: 575–580. pmid:16427525
- 25. Yeager MP, Colacchio TA, Yu CT, Hildebrandt L, Howell AL, Weiss J, et al. Morphine inhibits spontaneous and cytokine-enhanced natural killer cell cytotoxicity in volunteers. Anesthesiology 1995; 83: 500–508. pmid:7661350
- 26. Carmody JJ Opiate receptors: an introduction. Anaesth Intensive Care 1987; 15: 27–37. pmid:3032015
- 27. Fowler CJ, Fraser GL Mu-, delta-, kappa-opioid receptors and their subtypes. A critical review with emphasis on radioligand binding experiments. Neurochem Int 1994; 24: 401–426. pmid:7647696
- 28. Drake CT, Chavkin C, Milner TA Opioid systems in the dentate gyrus. Prog Brain Res 2007; 163: 245–263. pmid:17765723
- 29. Neri S, Bruno CM, Pulvirenti D, Malaguarnera M, Italiano C, Mauceri B, et al. Randomized clinical trial to compare the effects of methadone and buprenorphine on the immune system in drug abusers. Psychopharmacology (Berl) 2005; 179: 700–704. pmid:15806416
- 30. Azarang A, Mahmoodi M, Rajabalian S, Shekari MA, Nosratabadi J, Rezaei N T-helper 1 and 2 serum cytokine assay in chronic opioid addicts. Eur Cytokine Netw 2007; 18: 210–214. pmid:17993452
- 31. Wisaksana R, Indrati AK, Fibriani A, Rogayah E, Sudjana P, Djajakusumah TS, et al. Response to first-line antiretroviral treatment among human immunodeficiency virus-infected patients with and without a history of injecting drug use in Indonesia. Addiction 2010; 105: 1055–1061. pmid:20331555
- 32. Zhang Y, Li H, Li Y, Sun X, Zhu M, Hanley G, et al. Essential role of toll-like receptor 2 in morphine-induced microglia activation in mice. Neurosci Lett 2011; 489: 43–47. pmid:21130144
- 33. Dutta R, Krishnan A, Meng J, Das S, Ma J, Banerjee S, et al. Morphine modulation of toll-like receptors in microglial cells potentiates neuropathogenesis in a HIV-1 model of coinfection with pneumococcal pneumoniae. J Neurosci 2012; 32: 9917–9930. pmid:22815507
- 34. Wang J, Ma J, Charboneau R, Barke R, Roy S Morphine inhibits murine dendritic cell IL-23 production by modulating Toll-like receptor 2 and Nod2 signaling. J Biol Chem 2011; 286: 10225–10232. pmid:21245149
- 35. Wang X, Loram LC, Ramos K, de Jesus AJ, Thomas J, Cheng K, et al. Morphine activates neuroinflammation in a manner parallel to endotoxin. Proc Natl Acad Sci U S A 2012; 109: 6325–6330. pmid:22474354
- 36. Schwarz JM, Bilbo SD Adolescent morphine exposure affects long-term microglial function and later-life relapse liability in a model of addiction. J Neurosci 2013; 33: 961–971. pmid:23325235
- 37. Franchi S, Moretti S, Castelli M, Lattuada D, Scavullo C, Panerai AE, et al. Mu opioid receptor activation modulates Toll like receptor 4 in murine macrophages. Brain Behav Immun 2012; 26: 480–488. pmid:22240038
- 38. Stevens CW, Aravind S, Das S, Davis RL Pharmacological characterization of LPS and opioid interactions at the toll-like receptor 4. Br J Pharmacol 2013; 168: 1421–1429. pmid:23083095
- 39. Madera-Salcedo IK, Cruz SL, Gonzalez-Espinosa C Morphine prevents lipopolysaccharide-induced TNF secretion in mast cells blocking IkappaB kinase activation and SNAP-23 phosphorylation: correlation with the formation of a beta-arrestin/TRAF6 complex. J Immunol 2013; 191: 3400–3409. pmid:23960234
- 40. Sauer RS, Hackel D, Morschel L, Sahlbach H, Wang Y, Mousa SA, et al. Toll like receptor (TLR)-4 as a regulator of peripheral endogenous opioid-mediated analgesia in inflammation. Mol Pain 2014; 10: 10. pmid:24499354
- 41. Eidson LN, Murphy AZ Blockade of Toll-like receptor 4 attenuates morphine tolerance and facilitates the pain relieving properties of morphine. J Neurosci 2013; 33: 15952–15963. pmid:24089500
- 42. Theberge FR, Li X, Kambhampati S, Pickens CL, St Laurent R, Bossert JM, et al. Effect of chronic delivery of the Toll-like receptor 4 antagonist (+)-naltrexone on incubation of heroin craving. Biol Psychiatry 2013; 73: 729–737. pmid:23384483
- 43. Mattioli TA, Leduc-Pessah H, Skelhorne-Gross G, Nicol CJ, Milne B, Trang T, et al. Toll-like receptor 4 mutant and null mice retain morphine-induced tolerance, hyperalgesia, and physical dependence. PLoS One 2014; 9: e97361. pmid:24824631
- 44. Kueppers PM, Miller TA, Chen CY, Smith GS, Rodriguez LF, Moody FG Effect of total parenteral nutrition plus morphine on bacterial translocation in rats. Ann Surg 1993; 217: 286–292. pmid:8452407
- 45. Meng J, Yu H, Ma J, Wang J, Banerjee S, Charboneau R, et al. Morphine induces bacterial translocation in mice by compromising intestinal barrier function in a TLR-dependent manner. PLoS One 2013; 8: e54040. pmid:23349783
- 46. Nieuwenhuijs VB, Verheem A, van Duijvenbode-Beumer H, Visser MR, Verhoef J, Gooszen HG, et al. The role of interdigestive small bowel motility in the regulation of gut microflora, bacterial overgrowth, and bacterial translocation in rats. Ann Surg 1998; 228: 188–193. pmid:9712563
- 47. Biswas SK, Lopez-Collazo E Endotoxin tolerance: new mechanisms, molecules and clinical significance. Trends Immunol 2009; 30: 475–487. pmid:19781994
- 48. Bohannon JK, Hernandez A, Enkhbaatar P, Adams WL, Sherwood ER The immunobiology of toll-like receptor 4 agonists: from endotoxin tolerance to immunoadjuvants. Shock 2013; 40: 451–462. pmid:23989337
- 49. Foster SL, Hargreaves DC, Medzhitov R Gene-specific control of inflammation by TLR-induced chromatin modifications. Nature 2007; 447: 972–978. pmid:17538624
- 50.
Fernandez-Botran R, Joshi-Barve S, Ghare S, Barve S, Young M, Plankey M, et al. Systemic Cytokine and Interferon Responsiveness Patterns in HIV and HCV Mono and Co-Infections. J Interferon Cytokine Res 2014.
- 51. Pedersen KK, Pedersen M, Troseid M, Gaardbo JC, Lund TT, Thomsen C, et al. Microbial translocation in HIV infection is associated with dyslipidemia, insulin resistance, and risk of myocardial infarction. J Acquir Immune Defic Syndr 2013; 64: 425–433. pmid:23797689
- 52. Meijerink H, Wisaksana R, Iskandar S, den Heijer M, van der Ven AJ, Alisjahbana B, et al. Injecting drug use is associated with a more rapid CD4 cell decline among treatment naive HIV-positive patients in Indonesia. J Int AIDS Soc 2014; 17: 18844. pmid:24388495
- 53. Piroth L, Duong M, Quantin C, Abrahamowicz M, Michardiere R, Aho LS, et al. Does hepatitis C virus co-infection accelerate clinical and immunological evolution of HIV-infected patients? AIDS 1998; 12: 381–388. pmid:9520167
- 54. Piroth L, Grappin M, Cuzin L, Mouton Y, Bouchard O, Raffi F, et al. Hepatitis C virus co-infection is a negative prognostic factor for clinical evolution in human immunodeficiency virus-positive patients. J Viral Hepat 2000; 7: 302–308. pmid:10886541
- 55. Carlos Martin J, Castilla J, Lopez M, Arranz R, Gonzalez-Lahoz J, Soriano V Impact of chronic hepatitis C on HIV-1 disease progression. HIV Clin Trials 2004; 5: 125–131. pmid:15248136
- 56. Stebbing J, Waters L, Mandalia S, Bower M, Nelson M, Gazzard B Hepatitis C virus infection in HIV type 1-infected individuals does not accelerate a decrease in the CD4+ cell count but does increase the likelihood of AIDS-defining events. Clin Infect Dis 2005; 41: 906–911. pmid:16107994
- 57. Greub G, Genton B, Safary A, Thoelen S, Frei PC Comparison of the reactogenicity and immunogenicity of a two injection combined high-dose hepatitis A and hepatitis B vaccine to those of Twinrix. Vaccine 2000; 19: 1113–1117. pmid:11137246
- 58. De Luca A, Bugarini R, Lepri AC, Puoti M, Girardi E, Antinori A, et al. Coinfection with hepatitis viruses and outcome of initial antiretroviral regimens in previously naive HIV-infected subjects. Arch Intern Med 2002; 162: 2125–2132. pmid:12374521
- 59. Potter M, Odueyungbo A, Yang H, Saeed S, Klein MB, Canadian Co-infection Cohort Study I Impact of hepatitis C viral replication on CD4+ T-lymphocyte progression in HIV-HCV coinfection before and after antiretroviral therapy. AIDS 2010; 24: 1857–1865. pmid:20479633
- 60. Chen TY, Ding EL, Seage Iii GR, Kim AY Meta-analysis: increased mortality associated with hepatitis C in HIV-infected persons is unrelated to HIV disease progression. Clin Infect Dis 2009; 49: 1605–1615. pmid:19842982
- 61.
Meijerink H, Indrati A, Soedarmo S, Utami F, de Jong CA, Alisjahbana B, et al. Heroin use in Indonesia is associated with higher expression of CCR5 on CD4+ cells and lower ex-vivo production of CCR5 ligands. AIDS 2014.
- 62. Smith AP, Lee NM Opioid receptor interactions: local and nonlocal, symmetric and asymmetric, physical and functional. Life Sci 2003; 73: 1873–1893. pmid:12899914
- 63. Coussons ME, Dykstra LA, Lysle DT Pavlovian conditioning of morphine-induced alterations of immune status. J Neuroimmunol 1992; 39: 219–230. pmid:1644897
- 64. Zijlstra F, Veltman DJ, Booij J, van den Brink W, Franken IH Neurobiological substrates of cue-elicited craving and anhedonia in recently abstinent opioid-dependent males. Drug Alcohol Depend 2009; 99: 183–192. pmid:18823721
- 65. Regan PM, Dave RS, Datta PK, Khalili K Epigenetics of micro-opioid receptors: intersection with HIV-1 infection of the central nervous system. J Cell Physiol 2012; 227: 2832–2841. pmid:22034138