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Vincristine (VCR) treatment is often associated to painful neuropathy. Its development is independent from antitumoral mechanism and involves neuroinflammation. We investigated the role of the chemokine prokineticin (PK)2 in a mouse model of VCR induced neuropathy using a PK-receptors (PK-R) antagonist to counteract its development. We also evaluated emotional like deficits in VCR mice. VCR (0,1 mg/kg) was i.p. injected in C57BL/6J male mice once a day for 14 consecutive days. Pain, anxiety and depressive like behaviors were assessed in animals. PK2, PK-Rs, cytokines, neuroinflammatory markers (CD68, CD11b, GFAP, TLR4) and ATF3 were evaluated in DRG, spinal cord, prefrontal cortex and hippocampus. The PK-Rs antagonist PC1, was s.c. injected (150 μg/kg) twice a day from day 7 (hypersensitivity state) until day 14. Its effect on pain and neuroinflammation was evaluated. VCR mice developed neuropathic pain but not mood alterations. After 7 days of VCR treatment we observed a neuroinflammatory condition in DRG with high levels of PK-Rs, TLR4, CD68, ATF3 and IL-1β without relevant alterations in spinal cord. At day 14, an upregulation of PK system and a marked neuroinflammation was evident also in spinal cord. Moreover, at the same time, we observed initial alterations in supraspinal brain areas. PC1 treatment significantly counteracted neuropathic pain and blunted neuroinflammation.

The discovery of opioid receptors expression on immune cells has originated a large research activity on the possible modulation by opioid drugs of immune system responses. In the present chapter we describe an easy methodology useful to obtain information about the potential immunomodulatory activity of opioid drugs. An in vivo treatment schedule is used, and macrophages are studied for their ability to release different cytokines.

The hypothesis that pain can predispose to frailty development has been recently investigated in several clinical studies suggesting that frailty and pain may share some mechanisms. Both pain and frailty represent important clinical and social problems and both lack a successful treatment. This circumstance is mainly due to the absence of in-depth knowledge of their pathological mechanisms. Evidence of shared pathways between frailty and pain are preliminary. Indeed, many clinical studies are observational and the impact of pain treatment, and relative pain-relief, on frailty onset and progression has never been investigated. Furthermore, preclinical research on this topic has yet to be performed. Specific researches on the pain-frailty relation are needed. In this narrative review, we will attempt to point out the most relevant findings present in both clinical and preclinical literature on the topic, with particular attention to genetics, epigenetics and inflammation, in order to underline the existing gaps and the potential future interventional strategies. The use of pain and frailty animal models discussed in this review might contribute to research in this area.

Prokineticins (PK) 1 and 2 belong to a new family of chemokines capable to interact with two different G coupled receptors: Prokineticin receptor (PKR)1 and 2. Both prokineticins and their receptors are widely distributed in different tissues and regulate several biological functions. In particular, a role of the PK system in inflammation and nociception has been established. PKRs are expressed in regions of the nervous system associated with pain and in primary sensitive neurons they colocalize with transient potential receptor vanilloid-TRPV1 providing an anatomical interaction in nociceptor sensitization. Moreover, PKs are strongly upregulated in immune and glial cells and sustain a proinflammatory loop in inflamed tissues. Recent evidences indicate that the block of the PK system represents a promising strategy to contrast inflammation and pain.

BACKGROUND Opioid drugs affect immunity, but not all opioid drugs share the same immunomodulatory properties. Tapentadol is an analgesic drug with a dual synergistic mechanism of action: µ-opioid receptor agonism and noradrenaline reuptake inhibition. Weaker µ-opioid receptor agonism combined with noradrenaline reuptake inhibition results in potent analgesia with reduced opioid side effects. We evaluated the impact of tapentadol on splenic cytokine in normal and in hyperalgesia/allodynia mice, comparing it with morphine and reboxetine, a noradrenaline reuptake inhibitor. METHODS Tapentadol, reboxetine, and morphine were injected subcutaneously into naive and mice that underwent sciatic nerve chronic constriction injury, and their effect on splenic cytokines (interferon-γ [IFN-γ], interleukin [IL]-2, IL-10, and IL-4) was measured by enzyme-linked immunosorbent assay after acute or chronic treatment. Nociceptive thresholds, thermal hyperalgesia, and allodynia also were assessed. Data were analyzed with 2-way analysis of variance (behavior) or 1-way analysis of variance (cytokines) followed by Bonferroni post hoc test. RESULTS Primary outcomes of our study were the effects of drugs on splenic cytokines. Our data indicate that acute tapentadol did not modify cytokine production in comparison with animals that received saline, whereas morphine suppressed all the cytokines: saline versus morphine 10 mg/kg (mean difference [MD], 95% confidence interval [CI]: IFN-γ = 12,400 [7760, 17,040], P < .001; IL-2 = 216.2 [47.69, 384.7], P < .01; IL-10 = 868 [523.7, 1212], P < .001; and IL-4 = 17.26 [10.32, 24.20], P < .001). A significant difference also was present between morphine and tapentadol (morphine 10 mg/kg versus tapentadol 20 mg/kg: MD [95% CI]: IFN-γ = -11,600 [-16,240, -6960], P < .001; IL-2 = -334.2 [-502.7, -165.7], P < .001; IL-10 = -959 [-1303, -614.7], P < .001; IL-4 = -18.66 [-25.60, -11.72], P < .001). When chronically injected for 7 days, tapentadol and reboxetine did not significantly affect cytokines when compared with saline-treated animals. The immunoprofile of tapentadol was different from that of morphine also in mice that were in a condition of neuropathic pain. All cytokines appeared significantly decreased in mice that received a chronic constriction injury in comparison with sham animals but, after 7 days of treatment, with a similar antihyperalgesic profile, IL-10 and IL-4 were significantly increased in tapentadol and reboxetine animals in comparison with morphine mice (morphine versus tapentadol: MD [95% CI], IL-10 = -926.4 [-1664, -188.5], P < .01; IL-4 = -8.15 [-12.46, -3.84], P < .001). CONCLUSIONS Acute and chronic tapentadol seem to be protective of splenic cytokines in contrast with morphine, which exerts a generalized suppression on all cytokines.

Background Neuropathy is a dose-limiting side effect of many chemotherapeutics, including bortezomib. The mechanisms underlying this condition are not fully elucidated even if a contribution of neuroinflammation was suggested. Here, we investigated the role of a chemokine family, the prokineticins (PKs), in the development of bortezomib-induced peripheral neuropathy (BIPN), and we used a PK receptor antagonist to counteract the development and progression of the pathology. Methods Neuropathy was induced in male C57BL/6J mice by using a protocol capable to induce a detectable neuropathic phenotype limiting systemic side effects. The presence of allodynia (both mechanical and thermal) and thermal hyperalgesia was monitored over time. Mice were sacrificed at two different time points: 14 and 28 days after the first bortezomib (BTZ) injection. At these times, PK system activation (PK2 and PK-Rs), macrophage and glial activation markers, and cytokine production were evaluated in the main station involved in pain transmission (sciatic nerve, DRG, and spinal cord), and the effect of a PK receptors antagonist (PC1) on the same behavioral and biochemical parameters was assessed. Structural damage of DRG during BTZ treatment and an eventual protective effect of PC1 were also evaluated. Results BTZ induces in mice a dose-related allodynia and hyperalgesia and a progressive structural damage to the DRG. We observed a precocious increase of macrophage activation markers and unbalance of pro- and anti-inflammatory cytokines in sciatic nerve and DRG together with an upregulation of GFAP in the spinal cord. At higher BTZ cumulative dose PK2 and PK receptors are upregulated in the PNS and in the spinal cord. The therapeutic treatment with the PK-R antagonist PC1 counteracts the development of allodynia and hyperalgesia, ameliorates the structural damage in the PNS, decreases the levels of activated macrophage markers, and prevents full neuroimmune activation in the spinal cord. Conclusions PK system may be a strategical pharmacological target to counteract BTZ-induced peripheral neuropathy. Blocking PK2 activity reduces progressive BTZ toxicity in the DRG, reducing neuroinflammation and structural damage to DRG, and it may prevent spinal cord sensitization.

Giada Amodeo,1 Dario Bugada,2–4 Silvia Franchi,1 Giorgia Moschetti,1 Stefania Grimaldi,5 Alberto Panerai,1 Massimo Allegri,2 Paola Sacerdote1 1Department of Pharmacological and Biomolecular Sciences, University of Milano, Milano, Italy; 2Study In Multidisciplinary Pain Research Group, 3Department of Anesthesia and ICU, ASST Papa Giovanni XXIII, Bergamo, Italy; 4Department of Anesthesia and ICU, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy; 5Department of Anesthesia, IRCCS Humanitas Research Center, Rozzano, Italy Introduction: Impaired immune function during the perioperative period may be associated with worse short- and long-term outcomes. Morphine is considered a major contributor to immune modulation. Patients and methods: We performed a pilot study to investigate postoperative immune function by analyzing peripheral blood mononuclear cells’ functionality and cytokine production in 16 patients undergoing major abdominal surgery. All patients were treated with intravenous (i.v.) patient-controlled analgesia with morphine and continuous wound infusion with ropivacaine+methylprednisolone for 24hours. After 24hours, patients were randomized into two groups, one continuing intrawound infusion and the other receiving only i.v. analgesia. We evaluated lymphoproliferation and cytokine production by peripheral blood mononuclear cells at the end of surgery and at 24 and 48hours postoperatively. Results: A significant reduction in TNF-α, IL-2, IFN-γ and lymphoproliferation was observed immediately after surgery, indicating impaired cell-mediated immunity. TNF-α and IFN-γ remained suppressed up to 48hours after surgery, while a trend to normalization was observed for IL-2 and lymphoproliferation, irrespective of the treatment group. A significant inverse correlation was present between age and morphine and between age and lymphoproliferation. No negative correlation was present between morphine and cytokine production. We did not find any differences within the two groups between 24 and 48hours in terms of morphine consumption and immune responses. Conclusion: A relevant depression of cell-mediated immunity is associated with major surgery and persists despite optimal analgesia. Even though morphine may participate in immunosuppression, we did not retrieve any dose-related effect. Keywords: opioids, postoperative pain, cytokines, immunomodulation, lymphoproliferation, surgery&nbsp

Several reasons recently lead to a dramatic increase in the use of opiate analgesics all over the world. Italy has always been a Country where opiates were prescribed less than in other Countries, even those incorrectly called “under-developed Countries”. The reason has to be searched in cultural, regulatory (detention, transport) factors, as well in the caution of practitioners for the side effects of opiates or the fear of inducing addiction. Recently rules have become easier also in Italy and here, aswell as abroad, mainly in the United States, the use of opiates has been rapidly increasing. However, the enthusiasm was followed by several serious doubts that are prompting a reversal of this trend. At present, the suggestion is to use opiates, but to pay a lot of attention to when use them and in which patients. Moreover, this “social” caution, was matched by the observation of a number of problems before unknown that make the use of opiates more difficult than it was previously thought.

Cephalic pain and psychiatric disease physiopathology is one of the most elusive issues in medical research, and the cause might be common. Going through the possible reasons of the failure in understanding the physiopathology of these diseases might be helpful to project new studies that might overcome the difficulties encountered and thus open a window on cephalic pain and psychiatric disease. New approaches to psychiatric disease might be applied to cephalic pain.

Painful neuropathy is one of the complications of diabetes mellitus that adversely affects patients’quality of life. Pharmacological treatments are not fully satisfactory, and novel approaches needed. In a preclinical mouse model of diabetes the effect of both human mesenchymal stromal cells from adipose tissue (hASC) and their conditioned medium (hASC-CM) was evaluated. Diabetes was induced by streptozotocin. After neuropathic hypersensitivity was established, mice were intravenously injected with either 1 × 106 hASC or with CM derived from 2 × 106 hASC. Both hASC and CM (secretome) reversed mechanical, thermal allodynia and thermal hyperalgesia, with a rapid and long lasting effect, maintained up to 12 weeks after treatments. In nerves, dorsal root ganglia and spinal cord of neuropathic mice we determined high IL-1β, IL-6 and TNF-α and low IL-10 levels. Both treatments restored a correct pro/antinflammatory cytokine balance and prevented skin innervation loss. In spleens of streptozotocin-mice, both hASC and hASC-CM re-established Th1/Th2 balance that was shifted to Th1 during diabetes. Blood glucose levels were unaffected although diabetic animals regained weight, and kidney morphology was recovered by treatments. Our data show that hASC and hASC-CM treatments may be promising approaches for diabetic neuropathic pain, and suggest that cell effect is likely mediated by their secretome.

Marijuana abuse is prominent among adolescents. Although Δ9-THC, one of its main components, has been demonstrated to modulate immunity in adults, little is known about its impact during adolescence on the immune system and the long-lasting effects in adulthood. We demonstrate that 10 days of Δ9-THC treatment induced a similar alteration of macrophage and splenocyte cytokines in adolescent and adult mice. Immediately at the end of chronic Δ9-THC, a decrease of proinflammatory cytokines IL- 1β and TNF-α and an increase of anti-inflammatory cytokine IL-10 production by macrophages were present as protein and mRNA in adolescent and adult mice. In splenocytes, Δ9-THC modulated Th1/Th2 cytokines skewing toward Th2: IFN-γ was reduced, and IL-4 and IL-10 increased. These effects were lost in adult animals, 47 days after the last administration. In contrast, in adult animals treated as adolescents, a perturbation of immune responses, although in an opposite direction, was present. In adults treated as adolescents, a proinflammatory macrophage phenotype was observed (IL-1β and TNF-α were elevated; IL-10 decreased), and the production of Th cytokines was blunted. IgM titers were also reduced. Corticosterone concentrations indicate a long-lasting dysregulation of HPA in adolescent mice. We measured blood concentrations of Δ9-THC and its metabolites, showing that Δ9-THC plasma levels in our mice are in the order of those achieved in human heavy smokers. Our data demonstrate that Δ9-THC in adolescent mice triggers immune dysfunctions that last long after the end of abuse, switching the murine immune system to proinflammatory status in adulthood.

This review provides an overview of the immunological effects of commonly used analgesic opioid drugs, focusing mainly on two aspects: the mechanisms involved and the potential clinical relevance. The immunomodulatory effects of morphine have been characterized in animal and human studies. Morphine decreases the effectiveness of both natural and acquired immunity, interfering with intracellular pathways involved in immune regulation, both directly and indirectly via the activation of central receptors. The mechanisms and the targets at the basis of opioid-induced immunomodulation have started to be elucidated, demonstrating an interaction between opioid receptors and several molecules involved in the complex and well orchestrated immune response, such as transcription factors and receptors of both myeloid and lymphoid cells. Due to their widespread and expanding use, the immunological effects of opioid are receiving considerable attention because of concerns that opioid-induced changes in the immune system may affect the outcome of surgery or of variety of disease processes, including bacterial and viral infections and cancer. It is also emerging that not all opioids induce the same immunosuppressive effects and evaluating each opioid profile is important for appropriate analgesic selection. The impact of the opioid-mediated immune effects could be particularly dangerous in selective vulnerable populations, such as the elderly or immunocompromised patients. Indeed, it is evident that the possibility of reaching adequate and equivalent pain control by choosing either immunosuppressive drugs or drugs without an effect on immune responses may be an important consideration in opioid therapy.

Pain has been considered as part of a defensive strategy whose specific role is to signal an immediate active danger to the organism. This definition fits well for acute pain. It does not work well, however, for chronic pain that is maintained even in absence of an ongoing, active threat. Currently, acute and chronic pain are considered to be separate conditions. What follows is a review of the different theories about pain and its history. Different hypotheses regarding pain mechanisms are illustrated. New data emerging from scientific research on chronic pain (migraine in particular) involving innovative imaging techniques are reported and discussed.

A nonphysiological repair of the lesioned nerve leading to the formation of neurinomas, altered nerve conduction, and spontaneous firing is considered the main cause of the events underlying neuropathic pain. It was investigated whether neural stem cell (NSCs) administration could lead to a physiological nerve repair, thus to a reduction of neuropathic pain symptoms such as hyperalgesia and allodynia in a well-established model of this pain (sciatic nerve chronic constriction injury [CCI]). Moreover, since we and others showed that the peripheral nerve lesion starts a cascade of neuroinflammation-related events that may maintain and worsen the original lesion, the effect of NSCs on sciatic nerve pro- and antiinflammatory cytokines in CCI mice was investigated. NSCs injected intravenously, when the pathology was already established, induced a significant reduction in allodynia and hyperalgesia already 3 days after administration, demonstrating a therapeutic effect that lasted for at least 28 days. Responses changed with the number of administered NSCs, and the effect on hyperalgesia could be boosted by a new NSC administration. Treatment significantly decreased proinflammatory, activated antiinflammatory cytokines in the sciatic nerve, and reduced spinal cord Fos expression in laminae I-VI. Moreover, in NSC-treated animals, a reparative process and an improvement of nerve morphology is present at a later time. Since NSC effect on pain symptoms preceded nerve repair and was maintained after cells had disappeared from the lesion site, we suggest that regenerative, behavioral, and immune NSC effects are largely due to microenvironmental changes they might induce at the lesion site. © 2011 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Opioids have been shown to affect both innate and adaptive immunity. We previously showed that morphine affects the macrophage production of pro-inflammatory cytokines after LPS in a NFkB dependent manner. Toll like receptors (TLRs) play a crucial role in the signaling pathways which lead to NFkB activation. TLR4 is considered the Lipopolysaccaride (LPS) receptor. The data here presented show that, in murine macrophages, morphine impacts on the immune function acting on the early step of pathogen recognition. Morphine, when added to RAW 264.7 cells and when injected into mice (s.c. 20 mg/kg) is in fact able to decrease TLR4 both at mRNA and protein level in RAW cells and peritoneal macrophages. In the same cells, the mu opioid receptor (MOR) antagonist Naltrexone increases TLR4 levels, thus suggesting a role of the endogenous opioid system in TLR4 regulation. The effect of the two drugs is moreover lost in case of co-administration. Experiments with MOR KO mice and with DAMGO (MOR specific agonist) confirm that the effect of morphine on TLR4 mRNA in peritoneal macrophages is due to the MOR activation. Moreover the effect on TLR4 is blocked by PTX thus indicating the involvement of a G i protein after MOR binding. This work unveils a clear link between MOR activation and TLR4, suggesting a new possible mechanism at the basis of the peripheral immunosuppressive effect of opioids.

Treatment of diabetes complications remains a substantial challenge. The aim of this study was to explore the ability of the soy isoflavone genistein in attenuating the signs that follow diabetes onset: nociceptive hypersensitivity, oxidative and inflammatory state, nerve growth factor (NGF) decrease and vascular dysfunctions. Genistein (3 and 6 mg/kg) was administered to C57BL/6J streptozotocin diabetic mice from the 2nd till the 5th week after disease induction. The hind paw withdrawal threshold to mechanical stimulation (tactile allodynia) was evaluated by a von Frey filament. The oxidative stress was assessed measuring: reactive oxygen species by fluorimetric analysis, both the lipoperoxide content, as malondialdehyde, the antioxidant enzymatic activities spectrophotometrically and the glutathione content spectrofluorimetrically. Proinflammatory cytokines and NGF were measured in the sciatic nerve by enzyme-linked immunosorbent assay. Aortic inducible (iNOS) and endothelial nitric oxide synthase (eNOS) protein content was measured by western immunoblotting. Genistein relieved diabetic peripheral painful neuropathy, reverted the proinflammatory cytokine and reactive oxygen species overproduction, and restored the NGF content in diabetic sciatic nerve. Furthermore it restored the GSH content and the GSH and GSSG ratio, improved the antioxidant enzymes activities, decreased reactive oxygen species and lipoperoxide level in the brain and liver. Finally it restored the iNOS and eNOS content and the superoxide dismutase activity in thoracic aorta. Hyperglycaemia and weight decrease were not affected. Genistein is able to reverse a diabetes established condition of allodynia, oxidative stress and inflammation, ameliorates NGF content and the vascular dysfunction, thus suggesting its possible therapeutic use for diabetes complications.

Antidepressant drugs are increasingly used in the management of chronic pain. They are mainly prescribed for cancer-related pain and central pain, e.g. phantom or stump pain, post-herpetic neuropathy. However, no controlled clinical trials have validated their in either pathology. Thus, physicians still do not know whether antidepressants are really effective and which might be best. It is still debated whether the effect of antidepressants in the management of chronic pain is limited to the amelioration of frequently concomitant depression or extends to pain itself. To verify both the analgesic effect of tricyclic antidepressants, and the possible relationship between their antidepressant effect and the relief of central pain, we carried out a randomized, within-patient (cross-over) placebo-controlled study in patients suffering from central pain. The results clearly indicate the better analgesic effect of tricyclic antidepressants over placebo (p less than 0.0001). Within the antidepressants tested, chlorimipramine, a blocker of serotonin reuptake, is significantly more effective (p less than 0.0001) than notriptyline, a blocker of noradrenaline reuptake. Finally, the antinociceptive effect is independent of the effects of the two drugs on the symptoms of depression.

There is great interest in soy isoflavones as alternatives to endogenous estrogens not only in hormonal pathologies, but also in inflammatory, neurodegenerative diseases, and pain. We investigated the effect of the isoflavone genistein on neuropathic pain. Genistein binds estrogen receptors (ER) with higher affinity for the ERbeta particularly expressed in neuronal and immune cells. Neuropathy was induced in mice by means of chronic sciatic nerve constriction, and the subcutaneous administration of genistein from the third day after the lesion reversed pain hypersensitivity in a time- and dose-dependent manner. This effect may have been due to the activation of classical nuclear receptor and/or anti-oxidant, anti-inflammatory, and immunomodulating properties of genistein. The fact that a specific ERbeta antagonist prevented both its anti-allodynic and anti-hyperalgesic action, whereas a specific ERalpha antagonist was ineffective and a non-selective ER antagonist only reversed the anti-allodynic effect, suggests the involvement of ERbeta. Antioxidant effects are also involved as the anti-nociceptive dose reversed the increase in reactive oxygen species and malondialdehyde in injured paw tissues, and increased the activity of anti-oxidant enzymes. The phytoestrogen had immunomodulatory and anti-inflammatory activities as it reduced peripheral and central nuclear factor-kappaB, nitric oxide system and pro-inflammatory cytokine over-activation. Taken together, our results suggest that genistein could ameliorate painful neuropathy by multiple mechanisms.

Opiate addiction influences many physiological functions including immune responses. The objective of this study was to investigate the immune system function in heroin addicted patients submitted to methadone or buprenorphine maintenance treatment compared to untreated heroin addicts and healthy controls. Four groups were studied: group A included nine heroin addicted subjects, who were still injecting heroin; groups B and C were composed of 12 patients previously addicted to heroin, being treated with methadone (mean dosage 58+/-12.7 mg/day) or buprenorphine (mean dose 9.3+/-2.3mg/day) since at least 6 months; group D was composed of 15 sex and age matched healthy controls. Lymphoproliferation and peripheral mononuclear cell cultures production of the Th1 cytokines IL-2 and IFN-gamma, the Th2 cytokine IL-4, and of the pro-inflammatory cytokine TNF-alpha were evaluated in all the patients and controls. PHA-lymphoproliferation was lower in untreated heroin addicts than in controls, while it was normal in methadone and buprenorphine treated patients. An altered Th1/Th2 balance, characterized by reduced IL-4, IFN-gamma and TNF-alpha but normal IL-2 levels, was present in untreated heroin addicted subjects, while the Th1/Th2 balance was well conserved in the methadone and buprenorphine groups. These findings suggest that the immune system abnormalities in heroin addicted patients can be restored to almost normal values by controlled treatment with methadone and buprenorphine.

The proinflammatory cytokine tumor necrosis factor-alpha (TNF) is an important mediator in neuropathic pain. We investigated the temporal pattern of TNF mRNA expression in the sciatic nerve, in dorsal root ganglia (DRG) and spinal cord in the mouse chronic constriction injury model of neuropathy with quantitative real-time polymerase chain reaction. Neuropathic pain-like behaviour was monitored by evaluating thermal hyperalgesia and mechanical allodynia. Pain-related behaviour and TNF expression were evaluated 6 h, 1, 3, 7 and 14 days after injury. Naive animals and sham-operated mice were used as controls. We found an early upregulation of sciatic nerve TNF mRNA levels in chronic constriction injury (CCI) and sham-operated animals 6 h after surgery: 1 day later TNF overexpression was present in CCI mice only and disappeared 3 days after injury. The mRNA cytokine levels were elevated in DRG 1 and 3 days after surgery in CCI animals only, while the cytokine was not modulated in the spinal cord. A significant hyperalgesia was present in CCI and sham-operated mice at 6 h and 1 day, while at later time point only CCI mice presented lower thresholds. Mechanical allodynia was already present only in CCI animals 6 h from surgery and remained constant up to the 14 th day. The results indicate that a transient early TNF upregulation takes place in peripheral nervous system after CCI that can activate a cascade of proinflammatory/pronociceptive mediators.

Opioid peptides affect different immune functions. We present evidence that these effects could be mediated by the modulation of Th1/Th2 cytokine production. The acute and chronic treatment with the opioid receptor antagonist naloxone decreased the production of IL-4 by splenocytes of C57BL/6 and Balb/cJ mice, that present a Th1/Th2 dominance, respectively, immunized with the protein antigen KLH. In contrast, IL-2 and IFN-gamma levels were increased after naloxone treatment. These results indicate that naloxone increases Th1 and decreases Th2 cytokine production. Moreover in C57BL/6 mice, naloxone treatment was able to accelerate skin-graft rejection, a Th1-mediated phenomenon, by increasing Th1 cytokine production. The effect of naloxone could be ascribed to the removal of the regulatory effects exerted by endogenous opioid peptides, which could activate Th2 and suppress Th1 cytokines.

The chicken and the egg problem is how, in Italian or in English, some time ago one would have referred to a question as the one to be approached here: "Is migraine a disorder of the central nervous system?" or of the peripheral nervous system? Till some time ago, even an honest basic scientist or clinician could almost equally sustain one or the other origin and find data that substantiate her/his opinion. Nowadays, however, our improved knowledge is pushing in the direction of the central nervous system, although many mechanisms remain unclear. The confusion originates from the important role played by multiple and important bidirectional interactions between the peripheral and the central nervous systems, i.e., the trigeminovascular system and the cerebral cortex. The problems are: Who starts first? Who is not working properly? It appears now that the answer to the question has to be probably searched in the delicate balance present in the central nervous system between excitatory and inhibitory circuits, their adaptation to chronic stimuli and, within these circuits, the balance of neurotransmitters, neuromodulators, transporters and ion channels that keeps them well functioning.

Both the analgesic drugs tramadol and paracetamol are widely used for the symptomatic therapy of osteoarthritis (OA). The aim of this double-blind, randomised study in patients with knee OA was to compare their effects on synovial fluid concentrations of interleukin (IL)-6 and substance P (SP). Moreover, we evaluated plasma and synovial fluid concentrations of tramadol and its active metabolite (O-desmethyl-tramadol, M1) after oral treatment with this drug. Twenty patients were enrolled. A group of 10 patients received tramadol (50 mg three times a day), and another group of 10 patients were treated with paracetamol (500 mg three times a day) for 7 days. Both drugs significantly reduced the intensity of joint pain. The synovial fluid concentrations of SP were significantly reduced only by the treatment with tramadol. In this group of patients, IL-6 synovial fluid concentrations were slightly, but not significantly, decreased. Paracetamol did not significantly change the synovial fluid concentrations of SP and IL-6. After oral administration, a considerable amount of tramadol was measurable in synovial fluid. Both in plasma and synovial fluid the concentrations of M1 were markedly lower than those of tramadol, with a T/M1 ratio of 14.7+/-4.6 and 9.3+/-3.9, respectively. These data demonstrate that the activity of tramadol may involve the modulation of inflammatory mediators. Moreover, they indicate that after oral treatment with tramadol, both the parent drug and its active metabolite can penetrate into synovial fluid.

The effect of chronic stress on immune functions is strongly biased by individual factors. Mice were subjected to a new model of chronic psychosocial stress in which four different subcategories of stressed animals may be identified: Resident Dominants (RD), Resident Subordinates (RS), Intruder Dominants (InD), and Intruder Subordinates (InS). After 7 days of stress, mice were immunized with keyhole limpet hemocyanine (KLH). Their immune functions were investigated 14 days later with stress continuing trough. Importantly, RS mice, which are mice losing territory ownership, were the more affected, having lower IgG, proliferation, and IL-2. RD and InD showed lower IgG while InS showed no immune alteration. In conclusion, loss of resources could be a key factor in determining individual vulnerability to stressful events.

Social isolation and lack of social support have deleterious effects on health, thus being regarded as one of the most relevant causes of diseases in human and other mammalian species. However, only few are the studies aimed at evaluating the psychoneuroimmunological functions of individually housed subjects. The present study was designed to understand how the behavior and the physiology of male house mice might be affected by individual housing. We first analyzed whether individual housing of different duration (1-42 days) would result in immuno-endocrine dysfunction (experiment 1). Then we investigated whether housing conditions would affect the reaction to an acute mild psychological stress (experiments 2 and 3). There were three main findings: first, individually housing mice for increasing time periods did not induce any major immuno-endocrine effects compared to a stable sibling group housing. Therefore, prolonged isolation does not seem to dramatically impair mice immuno-endocrine functions. Second, when exposed to a mild acute stress, i.e. forced exposure to a novel environment, isolated mice showed higher basal corticosterone and lower type 1 (IL-2) and type 2 (IL-4) cytokines as well as splenocytes proliferation compared to group housed male mice. Finally, when faced with a free choice between a novel environment and their home cage, individually housed mice showed reduced neophobic responses resulting in increased exploration of the novel environment, thus suggesting a low anxiety profile. Altogether, our findings suggest that individual housing in itself does not change immunocompetence and corticosterone level, but does affect reactivity to a stressor. In fact, individually housed mice showed high behavioral arousal, as well as altered immuno-endocrine parameters, when challenged with mild psychological novelty-stress.

The association between pain and stress is an old one, but still it is not really clear who comes first. Pain induces stress, and stress induces pain. Pain is part of our homeostatic system and in this way is an emotion, i.e., it tells us that something is out-of-order (control), and emotion drives our behavior and one behavior is stress response. Stress comes from ourselves: the imagination we have or would like to have of us, from the image others give of us, from the goals we assume it is necessary to reach for our well-being or the goals others want us to fulfill. Stress comes from our social condition and the condition we would like, stress comes from dangerous situations we cannot control. Headache easily fits in the picture.

Surgery stress has been shown to be associated in rat with decreased natural killer (NK) cell activity and enhancement of tumor metastasis. We have previously shown that the analgesic drug tramadol stimulates NK activity both in the rodent and in the human. In the present study, we analyze, in the rat, tramadol ability to prevent the effect of experimental surgery on NK activity and on the enhancement of metastatic diffusion to the lung of the NK sensitive tumor model MADB106. The administration of tramadol (20 and 40 mg/kg) before and after laparatomy significantly blocked the enhancement of lung metastasis induced by surgery. In contrast, the administration of 10 mg/kg of morphine was not able to modify this enhancement. The modulation of NK activity seemed to play a central role in the effect of tramadol on MADB106 cells. In fact, both doses of tramadol were able to prevent surgery-induced NK activity suppression, while the drug significantly increased NK activity in normal non-operated animals. Morphine, that in normal rats significantly decreased NK cytotoxicity, did not prevent surgery-induced immunosuppression. The good analgesic efficacy of tramadol combined with its intrinsic immunostimulatory properties suggests that this analgesic drug can be particularly indicated in the control of peri-operative pain in cancer patients.

Non-steroidal anti-inflammatory drugs (NSAIDs) are frequently used as analgesics. Although the results of clinical studies indicate considerable disparity in the analgesic efficacy of NSAIDs, the pre-clinical models generally used for the study of nociception do not allow a clear distinction to be made between the analgesic properties of agents belonging to this family. As clinical pain is characterized by hyperalgesia, we evaluated the effects of NSAIDs with similar chemical structures but different selectivities for cyclo-oxygenase (COX)-1 and COX-2 in a new behavioural model of central hyperalgesia in rats. We assessed the effects of lornoxicam, piroxicam, and meloxicam on the reduction of hindpaw nociceptive thresholds to thermal stimulation produced by a 10% formaldehyde (formalin) injection into rat tail. Each drug was administered intraperitoneally (i.p.) at its ED(50)for the anti-inflammatory effect (namely the inhibition of carrageenan-induced hindpaw oedema). At this dose (1.3 mg kg(-1), 1.0 mg kg(-1), and 5.8 mg kg(-1), respectively), lornoxicam, piroxicam, and meloxicam produced the same anti-inflammatory effect, did not modify thermal nociceptive thresholds, and significantly reduced the hyperalgesia. However, only lornoxicam was fully effective for prevention of hyperalgesia. Our results indicate a dissociation between the anti-inflammatory and the anti-hyperalgesic activity of NSAIDs, where the latter seems to be more evident after the block of both COX-1 and COX-2. Finally, they suggest that our experimental model of thermal hindpaw hyperalgesia can be effectively utilized to assess the ability of different drugs to reduce central sensitization, and thus hyperalgesia.

Cannabis use is frequent among adolescents. Its main component, delta-9-tetrahydrocannabinol (THC), affects the immune system. We recently demonstrated that chronic exposure of adolescent mice to THC suppressed immunity immediately after treatment but that after a washout period THC induced a long-lasting opposite modulation towards a proinflammatory and T-helper-1 phenotype in adulthood. The main objective of this study was to investigate whether the same effect was also present in brain regions such as the hypothalamus and hippocampus. Thirty-three-day-old adolescent and 80-day-old adult male mice were used. Acute THC administration induced a similar reduction of macrophage proinflammatory cytokines and an IL-10 increase in adult and adolescent mice. THC did not affect brain cytokines in adult mice, but a proinflammatory cytokine decrease was evident in the adolescent brain. A similar effect was present in the hypothalamus and hippocampus after 10 days’ THC administration. In contrast, when brain cytokines were measured 47 days after the final THC administration, we observed an inverted effect in adult mice treated as adolescents, i.e., IL-1β and TNF-α increased and IL-10 decreased, indicating a shift toward neuroinflammation. These data suggest that THC exposure in adolescence has long-lasting effects on brain cytokines that parallel those present in the periphery. This modulation may affect vulnerability to immune and behavioural diseases in adulthood.

Our aim was to assess the influence of maternal diet rich in monounsaturated fatty acids on oxidative and molecular parameters in brains of mouse pups as well as their body weight during their lifetime. Female rats received a diet containing 20% of olive oil-enriched diet (OOED) and a standard diet control diet (CD) in different periods: pregnancy, lactation and after weaning until pups' adulthood. On the last prenatal day (Group 1), embryos from OOED group showed smaller body weight, brain weight and lower levels of sulphydryl groups glutathione reduced (GSH) in the brain. On postnatal delay-21 (PND21) (Group 2), pups from OOED group showed higher body weight and brain weight, reduced brain weight/body weight ratio and lower brain lipid peroxidation (LP). On PND70 (Group 3), pups from OOED group showed lower brain LP and higher levels of GSH in prefrontal cortex and lower brain levels of reactive species in the hippocampus. Interestingly, the group of animals whose diet was modified from OOED to CD on PND21 showed greater weight gain compared to the group that remained in the same original diet (OOED) until adulthood. Furthermore, OOED consumption during pregnancy and lactation significantly increased BDNF only, as well as its main transcripts exon IV and VI mRNA levels in the prefrontal cortex. In addition, OOED significantly up-regulated FGF-2 mRNA levels in the prefrontal cortex. These findings open a pioneering line of investigation about dietary adjunctive therapeutic strategies and the potential of healthy dietary habits to prevent neonatal conditions and their influence on adulthood.

The immune system is a complex and finely orchestrated system, and many soluble molecules and receptors contribute to its regulation.Recent studies have suggested that many of the modulatory effects induced by morphine on innate immunity, and in particular the effects on macrophage activation and function, can be due to the modulation of an important macrophage surface receptor, the toll-like receptor (TLR), that is primarily involved in early regulatory steps. In this chapter we describe a RT-real-time PCR method for assessing TLR expression in macrophage after in vivo morphine treatment.

Marijuana abuse is prominent among adolescents. Although Δ(9)-THC, one of its main components, has been demonstrated to modulate immunity in adults, little is known about its impact during adolescence on the immune system and the long-lasting effects in adulthood. We demonstrate that 10 days of Δ(9)-THC treatment induced a similar alteration of macrophage and splenocyte cytokines in adolescent and adult mice. Immediately at the end of chronic Δ(9)-THC, a decrease of proinflammatory cytokines IL- 1β and TNF-α and an increase of anti-inflammatory cytokine IL-10 production by macrophages were present as protein and mRNA in adolescent and adult mice. In splenocytes, Δ(9)-THC modulated Th1/Th2 cytokines skewing toward Th2: IFN-γ was reduced, and IL-4 and IL-10 increased. These effects were lost in adult animals, 47 days after the last administration. In contrast, in adult animals treated as adolescents, a perturbation of immune responses, although in an opposite direction, was present. In adults treated as adolescents, a proinflammatory macrophage phenotype was observed (IL-1β and TNF-α were elevated; IL-10 decreased), and the production of Th cytokines was blunted. IgM titers were also reduced. Corticosterone concentrations indicate a long-lasting dysregulation of HPA in adolescent mice. We measured blood concentrations of Δ(9)-THC and its metabolites, showing that Δ(9)-THC plasma levels in our mice are in the order of those achieved in human heavy smokers. Our data demonstrate that Δ(9)-THC in adolescent mice triggers immune dysfunctions that last long after the end of abuse, switching the murine immune system to proinflammatory status in adulthood.

Neuropathic pain (NP) is a highly invalidating disease resulting as consequence of a lesion or disease affecting the somatosensory system. All the pharmacological treatments today in use give a long lasting pain relief only in a limited percentage of patients before pain reappears making NP an incurable disease. New approaches are therefore needed and research is testing stem cell usage. Several papers have been written on experimental neuropathic pain treatment using stem cells of different origin and species to treat experimental NP. The original idea was based on the capacity of stem cell to offer a totipotent cellular source for replacing injured neural cells and for delivering trophic factors to lesion site; soon the researchers agreed that the capacity of stem cells to contrast NP was not dependent upon their regenerative effect but was mostly linked to a bidirectional interaction between the stem cell and damaged microenvironment resident cells. In this paper we review the preclinical studies produced in the last years assessing the effects induced by several stem cells in different models of neuropathic pain. The overall positive results obtained on pain remission by using stem cells that are safe, of easy isolation, and which may allow an autologous transplant in patients may be encouraging for moving from bench to bedside, although there are several issues that still need to be solved.

The effects of modulation of apoptosis in experimental allergic encephalomyelitis (EAE) in Lewis rats have been investigated using a peptide of the Fas-Ligand protein (FasL-p). The peptide was administered both subcutaneously and intra-cerebro-ventricularly (i.c.v.) after EAE induction. Rats treated subcutaneously with FasL-p showed a worse clinical score as compared to saline treated animals, while i.c.v. treatment with FasL-p did not modify significantly the severity of EAE. Apoptotic lymphomonocytes (identified by TUNEL) infiltrating the brain and the spinal cord were decreased in rats treated i.c.v. with FasL-p. The data suggest that the Fas/Fas-ligand pathway may be modulated by treatments with peptides of Fas-Ligand and that it may be at work within the central nervous system in EAE.

Aims/hypothesis. To test the effects of multifunctional protein 14 (MFP14), which shares structural homology with heat shock proteins (HSPs), on the development of Type I (insulin-dependent) diabetes mellitus in NOD mice. Methods. MFP14 was given to euglycaemic female NOD mice from either the 4th to the 25th or from the 12th until the 35th week, or commencing one day before islet transplantation and until the reappearance of hyperglycaemia. Pancreata from NOD mice treated with multifunctional protein 14 for 14 consecutive weeks until 18 weeks of age were examined histologically for insulitis. Anti-CD3 and/or lipopolysaccharide (LPS)-induced blood levels of interferon (IFN)-γ, interleukin (IL)-4, IL-10, IL-12 and tumour necrosis factor (TNF)-α were measured by ELISA in 10 week-old female NOD mice treated for 6 consecutive weeks with either MFP14 or PBS. Unless otherwise stated, multifunctional protein 14 was administered daily 5 times a week at a dose of 25 μg. Control mice received PBS or, in selected experiments, heat-inactivated MFP14. Results. MFP 14 treated mice had a significantly lower incidence of spontaneous diabetes compared to control mice. The MFP14 was equally effective both upon early and late prophylaxis and the protection persisted until week 50 in mice treated from weeks 4 to 25. Insulitis was significantly reduced by the MFP14. The MFP14 also delayed recurrence of hyperglycaemia in syngeneic islet-transplanted NOD mice. Although MFP14 reduced anti-CD3 and/or LPS-induced blood levels of IFN-γ, TNF-α and IL-12 it increased IL-4 and IL-10. Conclusion/interpretation. The MFP14 could be a possible candidate for the prevention or early treatment of human Type I (insulin-dependent) diabetes mellitus. [Diabetologia (2001) 44: 839–847]

Opioid peptides affect different immune functions. We present evidence that these effects could be mediated by the modulation of TH1/TH2 cytokine production. BALB/cJ mice were immunized with 50 or 100 μg of the protein antigen keyhole-limpet hemocyanin (KLH), and treated acutely or chronically with the opioid antagonist naloxone. One and 2 weeks after immunization, the production of cytokines by splenocytes was evaluated by in vitro restimulation with KLH. The acute and chronic treatment with the opioid receptor antagonist naloxone decreased the production of interleukin (IL)–4 by splenocytes of BALB/cJ mice. In contrast, IL-2 and interferon-γ levels increased after naloxone treatment. Finally, the opioid antagonist diminished the serum immunoglobulin G anti–KLH antibody titers. These results suggest that naloxone increases TH1 and decreases TH2 cytokine production. The effect of naloxone could be ascribed to the removal of the regulatory effects exerted by endogenous opioid peptides, which could therefore activate TH2 and suppress TH1 cytokines.

Complex interactions between the neuroendocrine and the immune systems are present in autoimmune diseases. The central opioid peptide beta-endorphin (BE) has been shown to modulate peripheral immune responses in normal animals. In the present study we analyze the hypothalamic concentrations of this peptide in two models of spontaneous autoimmune disease, the MRL [corrected] lpr/lpr mouse, that develops a lupus-like autoimmune disease, and the obese strain (OS) chickens afflicted with spontaneous autoimmune thyroiditis. In both instances, hypothalamic concentrations of BE are significantly lower than normal controls. In MRL [corrected] lpr/lpr mice, BE is already lower at 1 month of age, when no clinical sign of the disease is yet present. Similarly, low levels of BE are observed in OS chickens before the onset of thyroiditis, i.e., already at the embryonic stage. Moreover, a further decrease of BE is observed in OS chickens in correspondence with the first signs of thyroid mononuclear infiltration. Considering the immunosuppressive effects exerted by central BE, these results are suggestive of the fact that in autoimmune disease prone animals the low hypothalamic concentrations may be one of several factors predisposing for the development of autoimmune disease.

We assessed the clinical and biological effects of high-dose, long-term Naltrexone (NTX) treatment in 11 children (3-11 years), who had been diagnosed as autistic. The drug was given following an open design, for 12 weeks. Beta-Endorphin (beta-END) was assayed in peripheral blood mononuclear cells after 1 and 3 months of treatment, and 6 months after the completion of the course. Baseline beta-END levels were higher than in healthy age-matched controls. In seven patients treatment reduced beta-END, whose levels rose in four children. Autistic symptoms were considerably attenuated in all cases, with functional improvements involving several areas. There was a close correlation between the reduction in beta-END levels and the decrease of social withdrawal, and an evident--though weak--correlation between increases in beta-END and decreases in stereotypy and abnormal speech. Both effects persisted after treatment stopped.

UK-114 is a 14-kDa ubiquitous protein recently sequenced by several groups throughout the world. Its activity ranges from being a tumor antigen, a protein synthesis inhibitor or a specific mu-calpain activator. UK-114 shows structural homologies also with proteins of the MHC-1 binding proteins, and heat shock proteins (HSPs). We investigated the possible effects of UK-114 on T helper cells cytokine profile and the development and progression of experimental autoimmune diseases. Homogeneous recombinant UK-114 was used in all experiments. Treatment of Balb/c male mice for two weeks resulted in the increase of IL-4, and the decrease of TNF-alpha, IFN-gamma, and IL-2 release from stimulated splenocytes, suggesting that UK-114 modulates the Th1/Th2 cytokine profile toward Th2. Similar to that observed with HSP60/65, a single pretreatment of Lewis rats with UK-114 significantly blunted the development of adjuvant-induced arthritis, whereas chronic treatment of 4-week-old female NOD mice dose dependently inhibited the development of diabetes.

We examined the ability of the analgesic drug tramadol to affect the development of inflammation in rats. The acute administration of tramadol significantly reduced the edema and the hyperalgesia induced by yeast injection in the paw. Moreover, in the subcutaneous carrageenin-induced inflammation, tramadol reduced the amount of the exudate, as well as the prostaglandin (PG)E2-like bio- and immuno-activity in the exudate; on the contrary, leukotriene (LT)B4 concentrations in the exudate were not changed. However, tramadol did not affect the ability of macrophages to migrate towards the chemotactic peptide N-formyl-L-methionil-L-leucyl-L-phenylalanine (FMLP). Our results suggest that tramadol is able to inhibit the development of different types of inflammation in the rat without affecting immune mechanisms, and contribute to explain the efficacy of this drug in the treatment of inflammatory pain.

CNS correlates of acute prolonged pain, and the effects of partial blockade of the central beta-endorphin system, were investigated by the quantitative 2-deoxyglucose technique in unanaesthetized, freely moving rats. Experiments were performed during the second, tonic phase of the behavioural response to a prolonged chemical noxious stimulus (s.c. injection of dilute formalin into a forepaw), or after minor tissue injury (s.c. saline injection). During formalin-induced pain, local glucose utilization rates in the CNS were bilaterally increased in the grey matter of the cervical spinal cord, in spinal white matter tracts and in several supraspinal structures, including portions of the medullary reticular formation, locus coeruleus, lateral parabrachial region, anterior pretectal nucleus, the medial, lateral and posterior thalamic regions, basal ganglia, and the parietal, cingulate, frontal, insular and orbital cortical areas. Pretreatment with anti-beta-endorphin antibodies, injected i.c.v., led to increased metabolism in the tegmental nuclei, locus coeruleus, hypothalamic and thalamic structures, putamen, nucleus accumbens, diagonal band nuclei and dentate gyrus, and in portions of the parietal, cingulate, insular, frontal and orbital cortex. In formalin-injected rats, pretreated with anti-beta-endorphin, behavioural changes indicative of hyperalgesia (increased licking response) were found, which were paralleled by a significant enhancement of functional activity in the anterior pretectal nucleus and in thalamo-cortical systems. A positive correlation was found between the duration of the licking response and metabolic activity of several forebrain regions. These results provide a map of the CNS pattern of metabolic activity during tonic somatic pain, and demonstrate a modulatory role for beta-endorphin in central networks that process somatosensory inputs.

Peripheral benzodiazepine receptors (PBR) modulate chemotaxis and cytokine production of monocytes and lymphocytes. Since PBR are decreased in animal models of stress and in patients with anxiety disorders, in the present study we analyze the ability of monocytes obtained from patients suffering from generalized anxiety to migrate towards chemoattracting benzodiazepines. In these patients, the benzodiazepine-induced chemotaxis is completely abolished, while the response to the control chemoattractant formyl-leu-met-phe is still maintained. The chemotaxis responses are not restored after pharmacological treatment of the pathology. The decreased chemotactic response could be linked to a decreased number of PBR receptors present on monocytes of generalized anxiety disorder patients.

SUMMARYChronic Fatigue Syndrome [CFS] has uncertain etiology, and diagnosis overlaps with depression. Since most studies suggest an activation of immune responses in CFS, and the opioid peptide β-en-dorphin [BE] content in peripheral blood mononuclear cells BE was shown to be decreased when the immune system is activated, and increased when it is depressed, it seemed worthwhile to investigate whether BE concentrations in peripheral blood mononuclear cells differed in CFS and depressed patients. β-Endorphin concentrations were measured by radioimmunoassay in peripheral blood mononuclear cells obtained from 24 CFS and six depressed patients, and 16 controls. The data obtained indicate that BE concentrations are decreased in CFS patients when compared with depressed patients and controls. In conclusion, peripheral blood mononuclear cells BE concentrations could be an useful instrument in the differential diagnosis between CFS and depression.

Interleukin-6 (IL-6) is a cytokine released by activated immune cells which has been shown to affect brain function. In this experiment aggressive and affiliative behaviour exhibited during agonistic encounters by transgenic male mice either not expressing (IL-6 -/-) or overexpressing (NSE-hIL-6) IL-6 in the central nervous system was investigated. All subjects were isolated for 24 days before the aggressive encounter and were 52 days old at the time of testing. Subjects were placed for 5 consecutive days in a neutral cage for 15 min with an opponent of the Balb/c strain that had been previously isolated for the same amount of time. The first and the last test sessions were videotaped to evaluate the first approach and the establishment of the social role, respectively. A number of behavioural categories were later scored. When compared with wild-type controls, IL-6 -/- mice showed a higher degree of aggressive behaviour as indicated by a higher frequency of Offensive Upright Posture, an effect more pronounced on the fifth encounter. On the contrary, NSE-hIL-6 subjects showed a tendency to be more involved in affiliative-type social interactions, displaying a higher frequency and duration of behaviours such as Anogenital, Nose or Body Sniff. IL-6 -/- mice showed a clear tendency to exhibit less affiliative interactions compared with their controls while dopamine levels were found to be modified in a number of brain regions in these mice. Overall, these data suggest that IL-6 affects both aggressive and affiliative-type interactions, although the behaviour of the NSE-hIL-6 subjects was less affected than that of the IL-6 -/- group. The effects of the genetic background of the animal in screening the outcome of gene manipulations on behaviour are also discussed.

It has recently become accepted that several cytokines may affect peripheral and central nervous system functions. Consistently with these findings, accumulating evidence points toward an important role for interleukin-1 in the modulation of nociceptive information. Here we review the observations collected after the administration of this cytokine by intracerebroventricular, intrathecal or peripheral route in rats. Taken together, these data suggest that IL-1 can differently affect pain responsivity depending on the dose and the site of action, and clearly demonstrate that this immune factor is deeply involved in the modulation of neuronal functions. J. Neurosci. Res. 53:645–650, 1998. © 1998 Wiley-Liss, Inc.

SUMMARY The continuous infusion of the opioid peptide β-endorphin prolongs skin allograft survival in mice, while the opiate receptor antagonist naloxone, administered together with the opioid at the time of transplantation, abolishes the effect of the opioid. Consistently, naloxone, when given alone at the time of transplantation, but not later, accelerates graft rejection and increases splenocyte IL-2 and interferon-gamma (IFN-γ) production. Splenocyte β-endorphin concentrations are lower in transplanted animals. The effects of exogenous β-endorphin and naloxone suggest that the endogenous opioid peptide β-endorphin exerts a tonic inhibitory effect over early events of T cell-mediated immune responses in vivo. The effects of β-endorphin and naloxone are consistent with the previously shown role of the opioid system in the modulation of the Th1/Th2 cytokine pattern.

To better determine the role of interleukin-6 in the mechanisms that regulate stress-induced immunosuppression, we used in this study an interleukin-6-deficient mice model recently generated by gene targeting. We report here that, in basal conditions, mutant mice are characterized by altered immune functions. Natural killer activity and interleukin-2 production are lower in splenocytes of interleukin-6 deficient mice compared to those of controls, whereas Concanavalin A-induced splenocyte proliferation is comparable with that observed in wild-type mice. Moreover, splenocyte concentrations of the immunosuppressive opioid peptide beta-endorphin are higher in interleukin-6 deficient mice while serum corticosterone concentrations are unchanged. After exposure to 16 h of restraint stress, a significant suppression of the immune parameters is exhibited and a significant increase of splenocyte beta-endorphin concentrations are present in knock-out and normal animals. Finally, corticosterone is normally induced in stressed interleukin-6-deficient mice, thus demonstrating that interleukin-6 is not crucial for the activation of the hypothalamic-pituitary-adrenal axis. In conclusion, our results indicate that interleukin-6 is not a key factor in the immunosuppression observed after restraint stress.

A new simple behavioral method was used for the evaluation of the anti-hyperalgesic properties of tramadol in the rat. At the lowest dose (1.25 mg/kg i.p.), tramadol did not modify thermal nociceptive thresholds, but it was able to prevent and block thermal hindpaw hyperalgesia induced by the tail injection of formalin. Our results provide evidence that tramadol blocks hyperalgesic behaviors without altering nociception, suggesting that this analgesic drug might represent a valid agent against central sensitization.