Opioid therapy and immunosuppression: a review

Effects of gabapentin on morphine consumption and pain in severely burned patients

OBJECTIVE

Nociception is the major cause of burn pain and leads to central hyperalgesia. Gabapentin (Gp) is an antihyperalgesic drug that selectively affects central sensitization. We studied the opioid-sparing and analgesic effects of Gp in severely burned patients.

METHODS

Ten patients (mean total burned body surface area (TBSA), 25%), received 2400 mg of oral Gp daily from after burn days 3-24 in addition to standard pain therapy. They were compared to a retrospective matching group. Outcomes were cumulative morphine consumption and mean daily pain scores. Outcomes were recorded during treatment (21 days) and 21 days after treatment.

RESULTS

During treatment and post-treatment phases, patients receiving Gp had cumulative morphine consumption and a mean daily pain score significantly lower than controls.

CONCLUSION

Gp use reduced opioid consumption and lowered pain scores that seemed to extend beyond its pharmacologic action probably result from the ability of Gp to prevent central hyperalgesia induced by burns.

Differential involvement of RelB in morphine-induced modulation of chemotaxis, NO, and cytokine production in murine macrophages and lymphocytes

Acute morphine impairs innate and acquired immunity. The mechanisms involved in immunosuppression have not been well defined yet. The transcription factor NF-kappaB is a central regulator of immunity, and of the NF-kappaB family, RelB is particularly involved in the expression of genes important in immune responses. We investigated the involvement of RelB in morphine-induced immunosuppression in mice deficient for the RelB factor. RelB-/- mice and wild-type (WT) controls were injected s.c. with morphine 20 mg/Kg, and 1 h later, immune parameters were evaluated. Morphine significantly reduced macrophage production of the proinflammatory cytokines IL-1beta, TNF-alpha, and IL-12 in WT animals, and the drug failed to diminish the production of these cytokines in the RelB-/- mice. In contrast, the anti-inflammatory cytokine IL-10 was similarly affected in the two strains. Macrophage NO production was modulated by morphine in WT animals only, and morphine similarly decreased macrophage chemotaxis in the presence or in the absence of RelB. When Th1 and Th2 cytokines were evaluated, we observed a clear morphine-induced reduction of IL-2 and IFN-gamma production by WT splenocytes, whereas no effect of the drug was observed in RelB-/- mice. On the contrary, the production of the Th2 cytokines IL-4 and IL-10 was lessened to the same degree by morphine in WT and RelB-/- mice. In conclusion, our data suggest that RelB is an important target for morphine modulation of proinflammatory and Th1 cytokines. They also indicate that morphine uses multiple intracellular pathways to exert its generalized immunosuppression.

Effects of Ice Massage on Neuropathic Pain in Persons With AIDS

Peripheral neuropathic pain is a unique form of chronic pain that afflicts up to 50% of persons with AIDS. The purpose of this pilot study was to examine the effects of ice massage to reduce neuropathic pain and improve sleep quality and to determine the feasibility of a larger study. A repeated measures design was used. The three treatments consisted of ice massage, dry-towel massage, and presence. Consecutive sampling was used to select 33 persons with AIDS who had neuropathic pain. Although the results of the study were negative, there was a decrease in pain intensity over time with both the ice massage and towel massage, suggesting that the intervention has some clinical benefit.

Immune function, pain, and psychological stress in patients undergoing spinal surgery

STUDY DESIGN

This study was an exploratory repeated measures design comparing patients undergoing two magnitudes of surgery in the lumbar spine: lumbar herniated disc repair and posterior lumbar fusion.

OBJECTIVE

The present study evaluated and compared the effect of perceived pain, perceived stress, anxiety, and mood on natural killer cell activity (NKCA) and IL-6 production among adult patients undergoing lumbar surgery.

SUMMARY OF BACKGROUND DATA

Presurgical stress and anxiety can lead to detrimental patient outcomes after surgery, such as increased infection rates. It has been hypothesized that such outcomes are due to stress-immune alterations, which may be further exacerbated by the extent of surgery. However, psychologic stress, anxiety, and mood have not been previously characterized in patients undergoing spinal surgery.

METHODS

Pain, stress, anxiety, and mood were measured using self-report instruments at T1 (1 week before surgery), T2 (the day of surgery), T3 (the day after surgery), and T4 (6 weeks after surgery). Blood (30 mL) was collected for immune assessments at each time point.

RESULTS

Pain, stress, anxiety, and mood state were elevated at baseline in both surgical groups and were associated with significant reduction in NKCA compared with the nonsurgical control group. A further decrease in NKCA was observed 24 hours after surgery in both surgical groups with a significant rise in stimulated IL-6 production, regardless of the magnitude of surgery. In the recovery period, NKCA increased to or above baseline values, which correlated with decreased levels of reported pain, perceived stress, anxiety, and mood state.

CONCLUSIONS

This study demonstrated that patients undergoing elective spinal surgery are highly stressed and anxious, regardless of the magnitude of surgery and that such psychologic factors may mediate a reduction in NKCA.

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.

Effect of millimeter wave irradiation on tumor metastasis

One of the major side effects of chemotherapy in cancer treatment is that it can enhance tumor metastasis due to suppression of natural killer (NK) cell activity. The present study was undertaken to examine whether millimeter electromagnetic waves (MMWs) irradiation (42.2 GHz) can inhibit tumor metastasis enhanced by cyclophosphamide (CPA), an anticancer drug. MMWs were produced with a Russian-made YAV-1 generator. Peak SAR and incident power density were measured as 730 +/- 100 W/kg and 36.5 +/- 5 mW/cm(2), respectively. Tumor metastasis was evaluated in C57BL/6 mice, an experimental murine model commonly used for metastatic melanoma. The animals were divided into 5 groups, 10 animals per group. The first group was not given any treatment. The second group was irradiated on the nasal area with MMWs for 30 min. The third group served as a sham control for group 2. The fourth group was given CPA (150 mg/kg body weight, ip) before irradiation. The fifth group served as a sham control for group 4. On day 2, all animals were injected, through a tail vein, with B16F10 melanoma cells, a tumor cell line syngeneic to C57BL/6 mice. Tumor colonies in lungs were counted 2 weeks following inoculation. CPA caused a marked enhancement in tumor metastases (fivefold), which was significantly reduced when CPA-treated animals were irradiated with MMWs. Millimeter waves also increased NK cell activity suppressed by CPA, suggesting that a reduction in tumor metastasis by MMWs is mediated through activation of NK cells.

The effect of opioids on the development of postoperative intra-abdominal adhesions

People addicted to opium rarely develop intra-abdominal adhesions after abdominal surgery. We aimed to evaluate the effect of opium or morphine on preventing postoperative adhesions in rats. Sixty-three rats were randomly divided into a control group, opium-addicted group, and morphine-addicted group in a double-blind study. Drug dependency was checked by using naloxone. Animals were then operated on and the cecum was abraded. At reoperation 3 weeks later the magnitude of adhesions was evaluated by a scoring system. There was a significant difference between the control, opium-addicted, and morphine-addicted groups with regard to the length (P < .001), thickness (P < .05), and severity of adhesions (P < .05). Opium or morphine reduces the severity of postoperative adhesions. Elucidation of the opioid receptor(s) involved in this process would enable the use of selective ligands and offer a pharmacologic strategy in preventing adhesion formation.

Opioids and opiates: analgesia with cardiovascular, haemodynamic and immune implications in critical illness

Traumatic injury, surgical interventions and sepsis are amongst some of the clinical conditions that result in marked activation of neuroendocrine and opiate responses aimed at restoring haemodynamic and metabolic homeostasis. The central activation of the neuroendocrine and opiate systems, known collectively as the stress response, is elicited by diverse physical stressor conditions, including ischaemia, glucopenia and inflammation. The role of the hypothalamic-pituitary-adrenal axis and sympathetic nervous system in counterregulation of haemodynamic and metabolic alterations has been studied extensively. However, that of the endogenous opiates/opioid system is still unclear. In addition to activation of the opiate receptor through the endogenous release of opioids, pharmacotherapy with opiate receptor agonists is frequently used for sedation and analgesia of injured, septic and critically ill patients. How this affects the haemodynamic, cardiovascular, metabolic and immune responses is poorly understood. The variety of opiate receptor types, their specificity and ubiquitous location both in the central nervous system and in the periphery adds additional complicating factors to the clear understanding of their contribution to the stress response to the various physical perturbations. This review aims at discussing scientific evidence gathered from preclinical studies on the role of endogenous opioids as well as those administered as pharmacological agents on the host cardiovascular, neuroendocrine, metabolic and immune response mechanisms critical for survival from injury in perspective with clinical observations that provide parallel assessment of relevant outcome measures. When possible, the clinical relevance and corresponding scenarios where this evidence can be integrated into our understanding of the clinical implications of opiate effects will be examined. Overall, the scientific basis to enhance clinical judgment and expectations when using opioid sedation and analgesia in the management of the injured, septic or postsurgical patient will be discussed.

HIV-1 Tat and opiate-induced changes in astrocytes promote chemotaxis of microglia through the expression of MCP-1 and alternative chemokines

Opiates exacerbate human immunodeficiency virus type 1 (HIV-1) Tat(1-72)-induced release of key proinflammatory cytokines by astrocytes, which may accelerate HIV neuropathogenesis in opiate abusers. The release of monocyte chemoattractant protein-1 (MCP-1, also known as CCL2), in particular, is potentiated by opiate-HIV Tat interactions in vitro. Although MCP-1 draws monocytes/macrophages to sites of CNS infection, and activated monocytes/microglia release factors that can damage bystander neurons, the role of MCP-1 in neuro-acquired immunodeficiency syndrome (neuroAIDS) progression in opiate abusers, or nonabusers, is uncertain. Using a chemotaxis assay, N9 microglial cell migration was found to be significantly greater in conditioned medium from mouse striatal astrocytes exposed to morphine and/or Tat(1-72) than in vehicle-, mu-opioid receptor (MOR) antagonist-, or inactive, mutant Tat(delta31-61)-treated controls. Conditioned medium from astrocytes treated with morphine and Tat caused the greatest increase in motility. The response was attenuated using conditioned medium immunoneutralized with MCP-1 antibodies, or medium from MCP-1(-/-) astrocytes. In the presence of morphine (time-release, subcutaneous implant), intrastriatal Tat increased the proportion of neural cells that were astroglia and F4/80+ macrophages at 7 days post-injection. This was not seen after treatment with Tat alone, or with morphine plus inactive Tat(delta31-61) or naltrexone. Glia displayed increased MOR and MCP-1 immunoreactivity after morphine and/or Tat exposure. The findings indicate that MCP-1 underlies most of the response of microglia, suggesting that one way in which opiates exacerbate neuroAIDS is by increasing astroglial-derived proinflammatory chemokines at focal sites of CNS infection and promoting macrophage entry and local microglial activation. Importantly, increased glial expression of MOR can trigger an opiate-driven amplification/positive feedback of MCP-1 production and inflammation.

Human white blood cells synthesize morphine: CYP2D6 modulation

Human plasma contains low, but physiologically significant, concentrations of morphine that can increase following trauma or exercise. We now demonstrate that normal, human white blood cells (WBC), specifically polymorphonuclear cells, contain and have the ability to synthesize morphine. We also show that WBC express CYP2D6, an enzyme capable of synthesizing morphine from tyramine, norlaudanosoline, and codeine. Significantly, we also show that morphine can be synthesized by another pathway via l-3,4-dihydroxyphenylalanine (L-DOPA). Finally, we show that WBC release morphine into their environment. These studies provide evidence that 1) the synthesis of morphine by various animal tissues is more widespread than previously thought and now includes human immune cells. 2) Moreover, another pathway for morphine synthesis exists, via L-DOPA, demonstrating an intersection between dopamine and morphine pathways. 3) WBC can release morphine into the environment to regulate themselves and other cells, suggesting involvement in autocrine signaling since these cells express the mu3 opiate receptor subtype.

The Anti-Inflammatory Effects of Low- and High-Frequency Electroacupuncture Are Mediated by Peripheral Opioids in a Mouse Air Pouch Inflammation Model

BACKGROUND

Although acupuncture has been widely used for complementary therapeutic approaches to treat inflammatory diseases and inflammation-induced pain, the potential anti-inflammatory effects of acupuncture treatment remain controversial in clinical trials, and the underlying mechanisms are still unclear.

OBJECTIVE

The objective was to determine whether electroacupuncture (EA) is able to suppress the peripheral inflammatory response (e.g., zymosan-induced leukocyte migration into air pouch). As part of a mechanistic approach, it was further evaluated whether endogenous opioid systems are involved in the "EA-induced anti-inflammatory effect" (EA-AI).

METHODS

EA (1 or 120 Hz) was performed bilaterally in the Zusanli acupoint (ST36) or in a nonacupoint (gluteal muscle) for 30 min in ICR mice under anesthetic condition. The number of leukocytes that migrated into the air pouch was counted 4 hours after zymosan injection. EA was performed at 0, 0.5, 1, or 2 hours prior to zymosan injection, respectively. To evaluate opioid involvement in EA-AI, intrathecal naloxone (36 microg/mouse) and intraperitoneal naloxone methiodide (30 mg/kg) were administered 10 min before EA stimulation.

RESULTS

Both the 1 and 120 Hz frequencies of EA into Zusanli acupoint at the same time with zymosan injection significantly reduced leukocyte migration into the air pouch as compared with those of control groups (i.e., anesthetic control and needling control into Zusanli acupoint without electrical stimulation). The EA stimulation into nonacupoint did not produce any significant anti-inflammatory effect. EA treatment at 0.5 hours prior to zymosan injection also produced an anti-inflammatory effect but 1 and 2 hours prior to zymosan injection did not elicit any effect. Peripheral opioid blockage significantly reversed EA-AI, whereas spinal opioid blockage did not alter EA-AI.

CONCLUSION

EA can suppress peripheral inflammation through a peripheral opioid mechanism. To achieve the full effectiveness of EA, repeated application is recommended for the treatment of a variety of inflammatory diseases.

Opioids and the immune system

Opioid compounds such as morphine produce powerful analgesia that is effective in treating various types of pain. In addition to their therapeutic efficacy, opioids can produce several well known adverse events, and, as has recently been recognized, can interfere with the immune response. The immunomodulatory activities of morphine have been characterized in animal and human studies. Morphine can decrease the effectiveness of several functions of both natural and adaptive immunity, and significantly reduces cellular immunity. Indeed, in animal studies morphine is consistently associated with increased morbidity and mortality due to infection and worsening of cancer. However, from several animal studies it emerges that not all opioids induce the same immunosuppressive effects, and evaluating each opioid's profile is important for appropriate analgesic selection. Buprenorphine is a potent opioid that is frequently prescribed for chronic pain. Acute intracerebroventricular administration of buprenorphine has been shown in rats not to affect cellular immune responses, while a statistically significant inhibition of the immune response was observed with morphine. In mouse studies, chronic administration of buprenorphine led to immune parameters important for antimicrobial responses or for anti-tumour surveillance (lymphoproliferation, natural killer (NK)-lymphocyte activity, cytokine production, lymphocyte number) being unaffected. In contrast, levels of these immune markers were significantly reduced when the potent micro-agonist fentanyl was administered, but recovered after longer periods as tolerance developed. Because the intrinsic immunosuppressive activity varies between individual opioids, predicting the outcome on immunity can be difficult. To study this, the effects of morphine, fentanyl and buprenorphine on NK-lymphocyte activity depressed by experimental surgery were examined in rats. Treating animals immediately after surgery with equianalgesic doses of morphine and buprenorphine significantly reduced surgery-induced immunosuppression. However, buprenorphine reverted NK-lymphocyte activity to preoperative levels, while in morphine-treated rats NK-lymphocyte activity was ameliorated, although not completely. In contrast, fentanyl did not prevent immunosuppression induced by surgery. Overall, from several animal studies it emerges that buprenorphine has the more favourable profile, being a potent analgesic devoid of intrinsic immunosuppressive activity.

Morphine Induces CD4+ T Cell IL-4 Expression through an Adenylyl Cyclase Mechanism Independent of the Protein Kinase A Pathway

Impaired host defense mechanisms after major operative procedures and trauma are recognized as important factors in the development of infectious complication. Trauma is associated with impaired cellular immunity and CD4+ T cell Th2 differentiation. We have previously implicated morphine treatment as a possible mechanism for Th2 differentiation after injury. In this investigation we first establish that morphine treatment in vivo results in Th2 differentiation and that this effect is mediated through a naltrexone-sensitive opioid receptor. We investigated the intracellular mechanism by which morphine controls CD4+ T cell differentiation and demonstrate that morphine treatment in vitro 1) increases anti CD3/CD28 Ab-induced CD4+ T cell IL-4 protein synthesis, IL-4 mRNA, and GATA-3 mRNA accumulation through a pertussis toxin-sensitive receptor; 2) results in a dose-dependent increase in anti-CD3/CD28 Ab-induced CD4+ T cell cytoplasmic cAMP concentration; and 3) increases the forskolin-stimulated cytoplasmic cAMP level through a pertussis toxin-sensitive receptor. We also demonstrate that chronic morphine treatment increases anti-CD3/CD28 Ab-induced IL-4 promoter activity and IL-4 immunoprotein expression through a p38 MAPK-dependent, but protein kinase A- and Erk1/Erk2-independent, mechanism.

Immunomodulatory effect of morphine: therapeutic implications

The immunosuppressive as well as modulatory effects of morphine have been known in clinical medicine for > 100 years. Recent developments in molecular immunology, including experiments in mu (mu) opioid receptor knockout mice has led to a better understanding of central and peripheral mechanisms involved in this process. Though there is a large volume of literature documenting adverse effects of immunosupression following the use of morphine, several reports confirm its potential usefulness as an immunomodulator. In vitro and in vivo animal experiments have demonstrated wide-spectrum effects of morphine, including anti-inflammatory, antifibrotic, antitumour, cardioprotective and renoprotective. Immunomodulation is an important field in modern medicine with rapid advancement in recent years. Though a final statement regarding the clinical relevance of morphine-induced immunomodulation cannot be made at this juncture, nevertheless, it is worthwhile to review current developments. It may encourage further clinical studies to elucidate the influence of morphine treatment on immune regulation in different specialties of medicine.

The medical complications of heroin use

PURPOSE OF REVIEW

Heroin use is associated with numerous adverse sequelae. As clinical services develop, addiction psychiatrists will increasingly be called upon to help identify and manage the complications of heroin use. This review focuses on recent research into the medical complications of heroin use and looks at strategies to minimize harm associated with this practice.

RECENT FINDINGS

Mortality associated with heroin overdose has increased substantially in many countries. Parenteral use of opioid drugs is a central factor and other risk factors include polydrug use, particularly benzodiazepines and alcohol, mental health issues and environmental factors not conducive to resuscitation. Unravelling the determinants of blood-borne virus transmission continues, the focus shifting from needle sharing to inadvertent sharing of other injecting equipment. Trials addressing the challenges of antiviral therapy in injecting drug users are emerging. A greater understanding of the effects of opioids on immune functioning complements our knowledge of infection in the heroin-using group as well as possibly explaining the reduced response to vaccination in this group.

SUMMARY

Medical complications of heroin affect a number of different organ systems. The role of the addiction specialist is to be aware of these so that early diagnosis and appropriate management is instituted. The latter will generally be done in collaboration with other specialists. The addictions specialist can play a significant role in the development of clinical systems to minimize these complications.