Opiates and infection

Opioid receptors on bone marrow neutrophils modulate chemotaxis and CD11b/CD18 expression

Opiates impair neutrophil-mediated host defense, but the involvement of kappa-opioid receptors in this action has not been defined. The selective kappa-opioid receptor agonist [trans-(+)3,4-dichloro-N-methyl-N[2-(1-pyrrolidinyl)-cyclohexyl]benzeneacetamide methanesulfonate inhibited macrophage inflammatory protein-2-induced chemotaxis of bone marrow neutrophils from C57BL/6 mice. Its effects were concentration-dependent (pIC(50)=10.40+/-0.61) and inhibited by naloxone (K(e)=0.27 nM). The kappa-opioid receptor agonists bremazocine and ICI-204, 488 also inhibited chemotaxis, as did the respective mu- and delta-opioid receptor agonists [D-Ala(2), N-methyl-Phe(4), Gly(5)-ol]enkephalin and [D-Pen(2,5)]enkephalin albeit with lower potencies. U-50,488H also decreased neutrophil expression of the beta(2) integrin CD11b/CD18 (Mac-1) and adhesion to plastic in a naloxone-reversible manner. The results indicate that kappa-opioid receptors expressed by neutrophils rapidly modulate chemotaxis and adhesion in vitro.

The effects of tramadol and morphine on immune responses and pain after surgery in cancer patients

There has been growing interest in determining the possible immune consequences of opioid administration for the management of postoperative pain. We studied the effects of morphine and tramadol on pain and immune function during the postoperative period in 30 patients undergoing abdominal surgery for uterine carcinoma. Phytohemoagglutinin-induced T lymphocyte proliferation and natural killer cell activity were evaluated immediately before and after surgery, and 2 h after the acute administration of either 10 mg of morphine IM or 100 mg tramadol IM for pain. In all patients, phytohemagglutinin-induced lymphoproliferation was significantly depressed by surgical stress. However, in the morphine-treated group, proliferative values remained lower than basal levels for 2 h after treatment, whereas in tramadol-administered patients proliferative values returned to basal levels. Natural killer cell activity was not significantly affected by surgery nor by morphine administration, whereas tramadol significantly enhanced the activity of natural killer cells. Both drugs produced a comparable reduction in postoperative pain. We conclude that, as previously observed in the experimental animal, tramadol and morphine, when administered in analgesic doses, induce different immune effects.

IMPLICATIONS

Recent studies suggest that opioids can have an adverse impact on the immune system. Because surgical stress also induces immune dysfunction, the search for analgesic drugs devoid of immunosuppressive effects is of import. This study compared the effects on immune responses of morphine and of the atypical opioid analgesic, tramadol, given for postoperative pain to gynecological cancer patients. Tramadol and morphine showed comparable analgesic activity; however, tramadol, in contrast to morphine, induced an improvement of postoperative immunosuppression and, therefore, may be preferred to morphine for the treatment of postoperative pain.

Persistent Borna disease virus infection of neonatal rats causes brain regional changes of mRNAs for cytokines, cytokine receptor components and neuropeptides

Borna disease virus (BDV) replicates in brain cells. The neonatally infected rat with BDV exhibits developmental-neuromorphological abnormalities, neuronal cytolysis, and multiple behavioral and physiological alterations. Here, we report on the levels of interleukin-1beta (IL-1beta), IL-1 receptor antagonist (IL-1Ra), tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-beta1 (TGF-beta1), IL-1 receptor type I (IL-1RI), IL-1 receptor accessory protein (IL-1R AcP) I and II, glycoprotein 130, and various neuropeptide mRNAs in the cerebellum, parieto-frontal cortex, hippocampus and hypothalamus of BDV-infected rats at 7 and 28 days postintracerebral BDV inoculation. The data show that cytokine and neuropeptide mRNA components are abnormal and differentially modulated in brain regions. IL-1beta, TNF-alpha and TGF-beta1 mRNA levels were up-regulated in all brain regions following BDV inoculation. The same cerebellar samples from BDV-infected animals exhibited the highest levels of IL-1beta, IL-1Ra, TNF-alpha, IL-1RI, and IL-1R AcP II mRNA expression. The profiles of IL-1beta, IL-1Ra, TNF-alpha, and TGF-beta1 mRNA induction in the cerebellar samples were highly intercorrelated, indicating an association among cytokine ligand mRNAs. Cytokine mRNA induction was differentially up-regulated among brain regions, except for TGF-beta1. Specificity of transcriptional changes in response to BDV infection is also suggested by the up-regulation of cytokine and neuropeptide Y mRNAs associated with down-regulation of pro-opiomelanocortin, and with no change of IL-1R AcPI, dynorphin and leptin receptor mRNAs in the same brain region samples. Other data also show a differential mRNA component modulation in distinct brain regions obtained from the same rats depending on the stage of BDV infection. The conclusion of these studies is that cytokines may play a role in the neuropathophysiology of neonatally BDV-infected rats.

Morphine reduces mortality in mice following ocular infection with HSV-1

To determine the effect of chronic opioid treatment on mice infected with herpes simplex virus (HSV-1), female ICR mice were administered saline or morphine (25 mg/kg) subcutaneously (s.c.) 3 X /day and infected five days later via corneal scarification and inoculation with 150-210 plaque forming units of HSV-1. Mice deprived of morphine succumbed following infection faster than morphine- or saline-maintained mice, and morphine-maintained mice had a higher cumulative survival than either saline-maintained or morphine-deprived mice. There was no significant difference in cytokine mRNA or protein levels by RT-PCR and ELISA, respectively, in the eyes, trigeminal ganglia, cerebellum, or brain stem, comparing morphine-maintained to saline-treated mice. Similarly, there were no differences in the viral load in the eyes and trigeminal ganglia during the acute infection comparing these two groups assayed three and six days post-infection. While there were no differences in the expression of viral transcripts in the eyes and trigeminal ganglia during the acute infection, HSV-1 infected cell polypeptide 27 expression was reduced in the brain stem of morphine-maintained mice. Collectively, the results suggest that mice maintained on morphine antagonize the spread of HSV-1 in the central nervous system and thus, reduce the incidence of viral-induced encephalitis.