Barbara Manfredi

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.

Antinociceptive and immunosuppressive effects of opiate drugs: a structure-related activity study.

Although it is well known that morphine induces significant immunosuppression, the potential immunosuppressive activity of morphine derived drugs commonly used in the treatment of pain (codeine, hydromorphone, oxycodone) has never been evaluated. We evaluated in the mouse the effect of the natural opiates (morphine and codeine) and synthetic derivatives (hydromorphone, oxycodone, nalorphine, naloxone and naltrexone) on antinociceptive thresholds and immune parameters (splenocyte proliferation, Natural Killer (NK) cell activity and interleukin‐2 (IL‐2) production). Morphine displayed a potent immunosuppressive effect that was not dose‐related to the antinociceptive effect, codeine possessed a weak antinociceptive effect and limited immunosuppressive activity; nalorphine, a μ‐antagonist and κ‐agonist, exerted a potent immunosuppressive effect, but had very weak antinociceptive activity. The pure κ‐antagonist nor‐BNI antagonized the antinociceptive, but not the immunosuppresive effect of nalorphine. Hydromorphone and oxycodone, potent antinociceptive drugs, were devoid of immunosuppressive effects. The pure antagonists naloxone and naltrexone potentiated immune responses. Our data indicate that the C6 carbonyl substitution, together with the presence of a C7‐8 single bond potentiates the antinociceptive effect, but abolishes immunosuppression (hydromorphone and oxycodone). The single substitution of an allyl on the piperidinic ring resulted in a molecule that antagonized the antinociceptive effect but maintained the immunosuppressive effect. Molecules that carry modifications of C6, the C7‐8 bond and C14, together with an allyl or caboxymethyl group on the piperidinic ring antagonized both the antinociceptive and the immunosuppressive effect of opiates and were themselves immunostimulants.

The hydrogen sulphide-releasing derivative of diclofenac protects against ischaemia–reperfusion injury in the isolated rabbit heart

Hydrogen sulphide (H2S) is an endogenous gaseous mediator active in the multilevel regulation of pathophysiological functions in mammalian cardiovascular tissues.

Evidence for an opioid inhibitory effect on T cell proliferation

The proliferative response of human or rat T lymphocytes to phytohemagglutinin (PHA) or concanavalin A (ConA) was measured after acute (30 min) or chronic (8 days) treatment with the opiate receptor antagonists naloxone or naltrexone. Both in the rat and in the human, proliferation was significantly enhanced by acute treatment with the opiate receptor antagonists. In contrast, after chronic treatment proliferation always decreased. The sudden removal of an opioid inhibitory tone might be the basis for the increased proliferative responses observed after acute treatment. The decrease after chronic treatment could be ascribed to the amplification of the inhibitory effect of endogenous opioids due to the up-regulation of opiate receptors that follows chronic antagonist administration. Receptor binding studies of beta-endorphin receptors on splenocytes of chronically naloxone treated rats confirmed this hypothesis: a higher number of beta-endorphin receptors were expressed on splenocytes of naloxone-treated rats compared to controls (Bmax = 9.8 x 10(-12) vs. 1.16 x 10(-12), respectively).

Effects of tramadol on immune responses and nociceptive thresholds in mice

Abstract Tramadol is a centrally acting analgesic drug with a dual mechanism of action: binding to &mgr;‐opioid receptors and potentiation of the monoaminergic systems. In this study, we evaluated the effects of the acute and chronic administration of tramadol on nociceptive thresholds (by the hot‐plate test) and on immune responses (by measuring Concanavalin A‐induced splenocyte proliferation, IL‐2 production and natural killer activity) in the mouse. After acute subcutaneous administration, tramadol induced antinociception starting from a dose of 20 mg/kg, whereas it significantly enhanced natural killer activity and IL‐2 production at doses as low as 1 mg/kg and splenocyte proliferation starting from a dose of 10 mg/kg. After the chronic administration, the antinociceptive effect of the drug was still present, whereas the immune modifications disappeared. Thus, the pharmacological profile of tramadol is totally different from that of other drugs which bind &mgr;‐opioid receptors. Our results suggest that tramadol could be a good choice for the treatment of pain in patients where immunosuppression may be particularly contraindicated.

The β-endorphin inhibition of mitogen-induced splenocytes proliferation is mediated by central and peripheral paracrine/autocrine effects of the opioid

In this study we show that the opioid peptide beta-endorphin exerts a tonic inhibitory effect on the proliferative response of splenocytes to the polyclonal mitogen phytohemoagglutinin throughout two separate sites of action: one central and one peripheral. The intracerebroventricular administration of beta-endorphin, in fact, induces a significant inhibition of splenocyte proliferation. In contrast, both the intracerebroventricular and the peripheral administration of anti-beta-endorphin gamma globulins induce a significant increase in proliferation. Moreover, an increase of splenocyte proliferation was observed also after the intravenous administration of gamma globulins and intraperitoneal naloxone, and this effect was still present in hypophysectomized rats. The data reported suggest that beta-endorphin exerts a tonic inhibitory effect on proliferation, acting centrally, and peripherally throughout a paracrine/autocrine mechanism. FACS experiments show that the effect observed is not the consequence of an alteration of lymphocyte trafficking induced by the opioid.

Sildenafil reduces L-NAME-induced severe hypertension and worsening of myocardial ischaemia-reperfusion damage in the rat.

Phosphodiesterase‐5 inhibitors are beneficial in pulmonary hypertension and congestive heart failure, the two conditions associated with coronary heart disease and ischaemia. We investigated whether sildenafil counteracts the cardiovascular alterations induced by N ω‐nitro‐L‐arginine methyl ester (L‐NAME) in the rat.

Enalapril and quinapril improve endothelial vasodilator function and aortic eNOS gene expression in l-NAME-treated rats

Endothelial dysfunction ensuing inhibition of nitric oxide synthase (NOS) was investigated in male Sprague-Dawley rats given N(omega)-nitro-L-arginine methyl ester (L-NAME) in drinking water for 8 weeks. Age-matched rats served as controls. L-NAME-treated rats, as compared to control animals, showed: (1) a clear-cut increase in systolic blood pressure; (2) a consistent decrease of endothelial-cell NOS (eNOS) gene expression in aortic tissue; (3) a reduction of the relaxant activity of acetylcholine (ACh, from 10(-10) to 10(-4) M) on norepinephrine-precontracted aortic rings (reduction by 52+/-5%); (4) a marked decrease (-50%) of the basal release of 6-keto-prostaglandin F(1 alpha) (6-keto-PGF(1 alpha)) from aortic rings. In L-NAME-treated rats, administration in the last 2 weeks of either the angiotensin-converting enzyme inhibitor enalapril (1 mg/kg/day) or the cognate drug quinapril (1 mg/kg/day) decreased systolic blood pressure levels, completely restored eNOS mRNA levels in aortic tissue, and allowed a consistent recovery of both the relaxant activity of ACh and the generation of 6-keto-PGF(1 alpha). No difference was present in the ability of the two angiotensin-converting enzyme inhibitors to reverse NAME-induced endothelial dysfunction. These findings indicate that L-NAME-induced hypertension in the rat relies on the marked impairment of the endothelial vasodilator function, with an ensuing contribution by a decreased production of prostacyclin by the endothelial cells. Angiotensin-converting enzyme inhibition by enalapril or quinapril was equally effective in improving endothelial vasodilator function, prostacyclin endothelial production and restoring aortic eNOS mRNA.

Psychoimmunoendocrine Investigation in Anorexia nervosa

Immunological and neuroendocrine parameters were examined in 11 women with anorexia nervosa, 6 restricted and 5 bulimic-anorectics, 17-43 years old with 2-15 years duration of the disease, and in 11 age- and sex-matched psychophysically healthy controls. The T lymphocyte proliferative response to phytohemagglutinin (PHA), plasma adrenocorticotropic hormone (ACTH), cortisol and beta-endorphin (beta-EP) levels was examined in basal conditions and after corticotropin-releasing hormone (CRH) stimulation. Cortisol inhibition by dexamethasone (DST), and basal growth hormone (GH) and prolactin (PRL) levels were also examined. The immune study did not reveal significant differences between patients and controls. ACTH and cortisol basal levels were significantly higher in anorectics, while beta-EP, GH and PRL concentrations did not differ in the two groups. ACTH, beta-EP and cortisol responses to CRH were blunted in anorectics and the DST impaired in 55% of the patients. No correlations were observed between neuroendocrine impairments and the T lymphocyte response to PHA, or between the immunological neuroendocrine parameters and the body mass index of either patients or controls.

Activity of a new hydrogen sulfide-releasing aspirin (ACS14) on pathological cardiovascular alterations induced by glutathione depletion in rats.

We investigated the effects of the hydrogen sulfide (H₂S)-releasing derivatives of aspirin (ACS14) and salicylic acid (ACS21) in a rat model of metabolic syndrome induced by glutathione (GSH) depletion, causing hypertension and other pathological cardiovascular alterations. GSH depletion was induced in normal rats by the GSH-synthase inhibitor buthionine sulfoximine (BSO, 30 mmol/L day for seven days in the drinking water). Systolic blood pressure and heart rate were measured daily by the tail-cuff method, and plasma thromboxane B₂, 6-keto-prostaglandin F(2α), 8-isoprostane, GSH, insulin and glucose were determined at the end of the seven-day BSO schedule. In addition, ischemia/reperfusion-induced myocardial dysfunction and endothelial dysfunction were assayed on isolated heart and aortic rings, respectively. Unlike aspirin and salicylic acid, ACS14 and ACS21 reduced BSO-induced hypertension, also lowering plasma levels of thromboxane B₂, 8-isoprostane and insulin, while GSH remained in the control range. Neither ACS14 nor ACS21 caused gastric lesions. Both restored the endothelial dysfunction observed in aortic rings from BSO-treated rats, and in ischemia/reperfusion experiments they lowered left ventricular end-diastolic pressure, consequently improving the developed pressure and the maximum rise and fall of left ventricular pressure. Together with this improvement of heart mechanics there were reductions in the activity of creatine kinase and lactate dehydrogenase in the cardiac perfusate. This implies that H₂S released by both ACS14 and ACS21 was involved in protecting the heart from ischemia/reperfusion, and significantly limited vascular endothelial dysfunction in aortic tissue and the related hypertension.