Murine models of human neuropathic pain

AbstractNeuropathic pain refers to pain that originates from pathology of the nervous system. Diabetes, infection (herpes zoster), nerve compression, nerve trauma, and autoimmune diseases are examples of diseases that may cause neuropathic pain. Unfortunately no satisfactory treatment is yet available for this type of pain. This consideration has led to an explosion of interest for the underlying mechanisms, accompanied by a growing number of animal models. In recent years, most of the neuropathic pain models initially developed in the rat have been translated to mice in order to exploit the resource represented by genetically modified mice. Obviously the most useful animal models of pain would be ones in which the etiology of the pain would be endogenous and not induced by the experimenters: together with the classic models based on peripheral nerve ligation, in the last years other techniques are being developed that mimic more closely clinical pain syndromes, often by attempting to induce the disease associated to neuropathic pain. Although several variables must be taken into account when using animal models for mimicking clinical neuropathic pain, the huge number of models that are now reproducible and well characterized should help to reach important goals in the comprehension of mechanisms and to discover novel therapeutic target for this disease

Peripheral Mechanisms of Dental Pain: The Role of Substance P

Current evidence supports the central role of neuropeptides in the molecular mechanisms underlying dental pain. In particular, substance P, a neuropeptide produced in neuron cell bodies localised in dorsal root and trigeminal ganglia, contributes to the transmission and maintenance of noxious stimuli and inflammatory processes. The major role of substance P in the onset of dental pain and inflammation is increasingly being recognised. Well-grounded experimental and clinical observations have documented an increase in substance P concentration in patients affected by caries, pulpitis, or granulomas and in those undergoing standard orthodontic or orthodontic/dental care procedures. This paper focuses on the role of substance P in the induction and maintenance of inflammation and dental pain, in order to define future lines of research for the evaluation of therapeutic strategies aimed at modulating the complex effects of this mediator in oral tissues

Nimesulide in painful OA of the knee

Summary Objective:  This study was designed to investigate the analgesic effects of nimesulide and celecoxib in patients with knee osteoarthritis (OA). In patients with joint effusion, the effects of these non-steroidal anti-inflammatory drugs (NSAIDs) on synovial fluid concentrations of substance P (SP), interleukin (IL)-6 and IL-8 also were evaluated. Methods:  Patients were randomly assigned either nimesulide (100 mg twice a day) or celecoxib (200 mg once a day) for 2 weeks. The intensity of joint pain was assessed with a 100-mm visual analogue scale (VAS). Furthermore, patients completed questions about analgesic efficacy and overall tolerability of the treatments on a five-point categorial scale. Synovial fluid samples were drawn at baseline, 30 min after the first drug intake (day 1), and 30 min after the last drug intake (day 14). Results:  We enrolled 44 patients, 20 of whom had a joint effusion. In this group, the effects of nimesulide were more marked than for celecoxib, with evidence of a faster onset of the analgesic action. Both after a single or repeated administration, nimesulide significantly reduced the synovial fluid concentrations of SP and IL-6. Celecoxib, on the other hand, did not change the concentrations of SP and significantly reduced the levels of IL-6 only on day 14. None of the drugs affected IL-8. Both drugs were generally well tolerated. Conclusions:  These results provide evidence that nimesulide is an effective agent for the symptomatic treatment of OA. The effect on inflammatory pain mediators is consistent with the fast analgesic action of this NSAID

Effects of NSAIDs on the Release of Calcitonin Gene-Related Peptide and Prostaglandin E2 from Rat Trigeminal Ganglia

Nonsteroidal anti-inflammatory drugs (NSAIDs) are frequently used to treat migraine, but the mechanisms of their effects in this pathology are not fully elucidated. The trigeminal ganglia and calcitonin gene-related peptide (CGRP) have been implicated in the pathophysiology of migraine. The release of CGRP and prostaglandin E 2 (PGE 2 ) from freshly isolated rat trigeminal ganglia was evaluated after oral administration of nimesulide, etoricoxib, and ketoprofen, NSAIDs with different pharmacological features. Thirty minutes after oral administration, nimesulide, 10 mg/Kg, decreased the GCRP release induced by an inflammatory soup, while the other NSAIDs were ineffective at this point in time. Two hours after oral nimesulide (5 and 10 mg/Kg) and ketoprofen (10 mg/Kg), but not of etoricoxib, a significant decrease in the CGRP release was observed. All drugs reduced PGE 2 , although with some differences in timing and doses, and the action on CGRP does not seem to be related to PGE 2 inhibition. The reduction of CGRP release from rat trigeminal ganglia after nimesulide and ketoprofen may help to explain the mechanism of action of NSAIDs in migraine. Since at 30 minutes only nimesulide was effective in reducing CGRP release, these results suggest that this NSAID may exert a particularly rapid effect in patients with migraine

Antagonism of the prokineticin system prevents and reverses allodynia and inflammation in a mouse model of diabetes

Neuropathic pain is a severe diabetes complication and its treatment is not satisfactory. It is associated with neuroinflammation-related events that participate in pain generation and chronicization. Prokineticins are a new family of chemokines that has emerged as critical players in immune system, inflammation and pain. We investigated the role of prokineticins and their receptors as modulators of neuropathic pain and inflammatory responses in experimental diabetes. In streptozotocin-induced-diabetes in mice, the time course expression of prokineticin and its receptors was evaluated in spinal cord and sciatic nerves, and correlated with mechanical allodynia. Spinal cord and sciatic nerve pro- and anti-inflammatory cytokines were measured as protein and mRNA, and spinal cord GluR subunits expression studied. The effect of preventive and therapeutic treatment with the prokineticin receptor antagonist PC1 on behavioural and biochemical parameters was evaluated. Peripheral immune activation was assessed measuring macrophage and T-helper cytokine production. An up-regulation of the Prokineticin system was present in spinal cord and nerves of diabetic mice, and correlated with allodynia. Therapeutic PC1 reversed allodynia while preventive treatment blocked its development. PC1 normalized prokineticin levels and prevented the up-regulation of GluN2B subunits in the spinal cord. The antagonist restored the pro-/anti-inflammatory cytokine balance altered in spinal cord and nerves and also reduced peripheral immune system activation in diabetic mice, decreasing macrophage proinflammatory cytokines and the T-helper 1 phenotype. The prokineticin system contributes to altered sensitivity in diabetic neuropathy and its inhibition blocked both allodynia and inflammatory events underlying disease

Nimesulide inhibits protein kinase C epsilon and substance P in sensory neurons – comparison with paracetamol

In this paper we describe new actions of nimesulide and paracetamol in cultured peripheral neurons isolated from rat dorsal root ganglia (DRG). Both drugs were able to decrease in a dose-dependent fashion the number of cultured DRG neurons showing translocation of protein kinase C epsilon (PKCɛ) caused by exposure to 1 μM bradykinin or 100 nM thrombin. In addition, the level of substance P (SP) released by DRG neurons and the level of preprotachykinin mRNA expression were measured in basal conditions and after 70 minutes or 36 hours of stimulation with nerve growth factor (NGF) or with an inflammatory soup containing bradykinin, thrombin, endothelin-1, and KCl. Nimesulide (10 μM) significantly decreased the mRNA levels of the SP precursor preprotachykinin in basal and in stimulated conditions, and decreased the amount of SP released in the medium during stimulation of neurons with NGF or with the inflammatory soup. The effects of paracetamol (10 μM) on such response was lower. Nimesulide completely inhibited the release of prostaglandin E2 (PGE2) from DRG neurons, either basal or induced by NGF and by inflammatory soup, while paracetamol decreased PGE2 release only partially. Our data demonstrate, for the first time, a direct effect of two drugs largely used as analgesics on DRG neurons. The present results suggest that PKCɛ might be a target for the effect of nimesulide and paracetamol, while inhibition of SP synthesis and release is clearly more relevant for nimesulide than for paracetamol mechanism of action

Prokineticin System Is a Pharmacological Target to Counteract Pain and Its Comorbid Mood Alterations in an Osteoarthritis Murine Model

Osteoarthritis (OA) is the most prevalent joint disease associated with chronic pain. OA pain is often accompanied by mood disorders. We addressed the role of the Prokineticin (PK) system in pain and mood alterations in a mice OA model induced with monosodium iodoacetate (MIA). The effect of a PK antagonist (PC1) was compared to that of diclofenac. C57BL/6J male mice injected with MIA in the knee joint were characterized by allodynia, motor deficits, and fatigue. Twenty-eight days after MIA, in the knee joint, we measured high mRNA of PK2 and its receptor PKR1, pro-inflammatory cytokines, and MMP13. At the same time, in the sciatic nerve and spinal cord, we found increased levels of PK2, PKR1, IL-1β, and IL-6. These changes were in the presence of high GFAP and CD11b mRNA in the sciatic nerve and GFAP in the spinal cord. OA mice were also characterized by anxiety, depression, and neuroinflammation in the prefrontal cortex and hippocampus. In both stations, we found increased pro-inflammatory cytokines. In addition, PK upregulation and reactive astrogliosis in the hippocampus and microglia reactivity in the prefrontal cortex were detected. PC1 reduced joint inflammation and neuroinflammation in PNS and CNS and counteracted OA pain and emotional disturbances

The prokineticin receptor agonist Bv8 decreases IL-10 and IL-4 production in mice splenocytes by activating prokineticin receptor-1

<p>Abstract</p> <p>Background</p> <p>Bv8, prokineticin-1, or endocrine gland-vascular endothelial growth factor, and prokineticin-2 are recently isolated peptide agonists of two G protein-coupled receptors, prokineticin receptor-1 (PROKR 1) and PROKR 2, and have been described as affecting a number of myeloid cell functions. We evaluated the impact of Bv8 on lymphoid cells by investigating its ability to modulate T cell cytokine balance in mouse.</p> <p>Results</p> <p>The production of T-helper1 cytokines (IL-2, IFN-γ and IL-1β), the T-helper 2 cytokine IL-4, and the anti-inflammatory cytokine IL-10 by mouse splenocytes was evaluated after polyclonal stimulation or immunisation with the keyhole limpet hemocyanin protein antigen by measuring cytokine levels. When added <it>in vitro </it>to Con-A-stimulated splenocytes, Bv8 significantly increased IL-1β and decreased IL-4 and IL-10; IL-2 and IFN-γ were not affected. Similar results were obtained when Bv8 was administered <it>in vivo</it>. In KLH-immunised mice, splenocytes restimulated <it>in vitro </it>with KLH and Bv8 produced significantly smaller amounts of IL-4 and IL-10. KLH-induced IL-10 and IL-4 production was also significantly blunted in animals administered Bv8 <it>in vivo </it>at the time of KLH immunisation or two weeks later. The Bv8-induced effects were lost in mice lacking the PROKR 1 gene, thus indicating that PROKR 1 is the receptor involved in the modulation of cytokines.</p> <p>Conclusion</p> <p>These findings indicate that Bv8/prokineticin-1 is a novel modulator of lymphoid functions, and may be a suitable target for new immunopharmacological strategies.</p