Exploring Serum Biomarkers for Neuropathic Pain in Rat Models of Chemotherapy-Induced Peripheral Neuropathy: A Comparative Pilot Study with Oxaliplatin, Paclitaxel, Bortezomib, and Vincristine.

Blood biomarkers, including neurofilament light chain (NfL), have garnered attention as potential indicators for chemotherapy-induced peripheral neuropathy (CIPN), a dose-limiting adverse effect of neurotoxic anticancer drugs. However, no blood biomarker has been established for routine application or translational research. This pilot study aimed to evaluate a limited panel of blood biomarkers in rat models of CIPN and their correlations with neuropathic pain. CIPN models were induced through repeated injections of oxaliplatin, paclitaxel, bortezomib, and vincristine. Electronic von Frey testing was used to assess tactile allodynia. Post anticancer injections, serum concentrations of 31 proteins were measured. Allodynia thresholds decreased in anticancer-treated animals compared to controls. No consistent modifications were observed in the biomarkers across CIPN models. The most noteworthy biomarkers with increased concentrations in at least two CIPN models were NfL (paclitaxel, vincristine), MCP-1, and RANTES (oxaliplatin, vincristine). Vincristine-treated animals exhibited strong correlations between LIX, MCP-1, NfL, and VEGF concentrations and tactile allodynia thresholds. No single biomarker can be recommended as a unique indicator of CIPN-related pain. Because of the study limitations (single dose of each anticancer drug, young animals, and single time measurement of biomarkers), further investigations are necessary to define the kinetics, specificities, and sensitivities of MCP-1, RANTES, and NfL.

Beneficial Effects of Linseed Supplementation on Gut Mucosa-Associated Microbiota in a Physically Active Mouse Model of Crohn's Disease.

The Western diet, rich in lipids and in n-6 polyunsaturated fatty acids (PUFAs), favors gut dysbiosis observed in Crohn's disease (CD). The aim of this study was to assess the effects of rebalancing the n-6/n-3 PUFA ratio in CEABAC10 transgenic mice that mimic CD. Mice in individual cages with running wheels were randomized in three diet groups for 12 weeks: high-fat diet (HFD), HFD + linseed oil (HFD-LS-O) and HFD + extruded linseed (HFD-LS-E). Then, they were orally challenged once with the Adherent-Invasive Escherichia coli (AIEC) LF82 pathobiont. After 12 weeks of diet, total energy intake, body composition, and intestinal permeability were not different between groups. After the AIEC-induced intestinal inflammation, fecal lipocalin-2 concentration was lower at day 6 in n-3 PUFAs supplementation groups (HFD-LS-O and HFD-LS-E) compared to HFD. Analysis of the mucosa-associated microbiota showed that the abundance of Prevotella, Paraprevotella, Ruminococcus, and Clostridiales was higher in the HFD-LS-E group. Butyrate levels were higher in the HFD-LS-E group and correlated with the Firmicutes/Proteobacteria ratio. This study demonstrates that extruded linseed supplementation had a beneficial health effect in a physically active mouse model of CD susceptibility. Additional studies are required to better decipher the matrix influence in the linseed supplementation effect.

The TOTUM-63 Supplement and High-Intensity Interval Training Combination Limits Weight Gain, Improves Glycemic Control, and Influences the Composition of Gut Mucosa-Associated Bacteria in Rats on a High Fat Diet.

Obesity and prediabetes are the two strongest risk factors of type 2 diabetes. It has been reported that TOTUM-63, a polyphenol-rich plant extract, has beneficial effects on body weight (BW) and insulin resistance in mice fed a high fat diet (HFD). The study aim was to determine whether high-intensity interval training (HIIT) and/or TOTUM-63 supplementation improved body composition and glycemic control and gut microbiota composition in a Western diet-induced obesity rat model. Wistar rats received a standard diet (CTRL; control; n = 12) or HFD (HFD; n = 48) for 16 weeks. Then, HFD rats were divided in four groups: HFD, HFD + TOTUM-63 (T63), HFD + HIIT (HIIT), and HFD + HIIT +T63 (HIIT + T63). Training was performed 4 days/week for 12 weeks. TOTUM-63 was included in diet composition (2%). The HIIT + T63 combination significantly limited BW gain, without any energy intake modulation, and improved glycemic control. BW variation was correlated with increased α-diversity of the colon mucosa microbiota in the HIIT + T63 group. Moreover, the relative abundance of Anaeroplasma, Christensenellaceae and Oscillospira was higher in the HIIT + T63 group. Altogether, these results suggest that the HIIT and TOTUM-63 combination could be proposed for the management of obesity and prediabetes.

High-Intensity Interval Training and α-Linolenic Acid Supplementation Improve DHA Conversion and Increase the Abundance of Gut Mucosa-Associated Oscillospira Bacteria.

Obesity, a major public health problem, is the consequence of an excess of body fat and biological alterations in the adipose tissue. Our aim was to determine whether high-intensity interval training (HIIT) and/or α-linolenic acid supplementation (to equilibrate the n-6/n-3 polyunsaturated fatty acids (PUFA) ratio) might prevent obesity disorders, particularly by modulating the mucosa-associated microbiota. Wistar rats received a low fat diet (LFD; control) or high fat diet (HFD) for 16 weeks to induce obesity. Then, animals in the HFD group were divided in four groups: HFD (control), HFD + linseed oil (LO), HFD + HIIT, HFD + HIIT + LO. In the HIIT groups, rats ran on a treadmill, 4 days.week-1. Erythrocyte n-3 PUFA content, body composition, inflammation, and intestinal mucosa-associated microbiota composition were assessed after 12 weeks. LO supplementation enhanced α-linolenic acid (ALA) to docosahexaenoic acid (DHA) conversion in erythrocytes, and HIIT potentiated this conversion. Compared with HFD, HIIT limited weight gain, fat mass accumulation, and adipocyte size, whereas LO reduced systemic inflammation. HIIT had the main effect on gut microbiota ß-diversity, but the HIIT + LO association significantly increased Oscillospira relative abundance. In our conditions, HIIT had a major effect on body fat mass, whereas HIIT + LO improved ALA conversion to DHA and increased the abundance of Oscillospira bacteria in the microbiota.

Testosterone-androgen receptor: The steroid link inhibiting TRPM8-mediated cold sensitivity.

Recent studies have revealed gender differences in cold perception, and pointed to a possible direct action of testosterone (TST) on the cold-activated TRPM8 (Transient Receptor Potential Melastatin Member 8) channel. However, the mechanisms by which TST influences TRPM8-mediated sensory functions remain elusive. Here, we show that TST inhibits TRPM8-mediated mild-cold perception through the noncanonical engagement of the Androgen Receptor (AR). Castration of both male rats and mice increases sensitivity to mild cold, and this effect depends on the presence of intact TRPM8 and AR. TST in nanomolar concentrations suppresses whole-cell TRPM8-mediated currents and single-channel activity in native dorsal root ganglion (DRG) neurons and HEK293 cells co-expressing recombinant TRPM8 and AR, but not TRPM8 alone. AR cloned from rat DRGs shows no difference from standard AR. However, biochemical assays and confocal imaging reveal the presence of AR on the cell surface and its interaction with TRPM8 in response to TST, leading to an inhibition of channel activity.

Neuregulin 1 treatment improves glucose tolerance in diabetic db/db mice, but not in healthy mice.

Context: Neuregulin 1 (NRG1) and ErbB receptors are involved in glucose homeostasis. However, the effects of the neuregulin 1-ErbB pathway activation on glucose metabolism in liver are controversial.Objective: Assess NRG1 and ErbB signalling in liver and the effects of 8-week treatment with NRG1 on glucose homeostasis in diabetic db/db mice and in control healthy mice.Results: NRG1 improved glucose, insulin and insulin sensitivity index during OGTT in db/db mice, but not in control mice. Compared with healthy mice, phosphorylation of p38, ErbB-1 and ErbB-3 was increased in diabetic mice, and neuregulin 1 treatment increased phosphorylation of p38 and ErbB-4. Conversely, the AKT/FOXO1 pathway was not affected by the 8-week treatment with NRG1.Conclusion: Diabetic mice showed altered NRG1-ErbB pathway in the liver compared with healthy mice. Moreover, chronic NRG1 treatment increased p38 phosphorylation in liver and improved glucose tolerance in diabetic mice, but not in control mice.

Tissue-Specific Oxidative Stress Modulation by Exercise: A Comparison between MICT and HIIT in an Obese Rat Model.

BACKGROUND AND AIM: Exercise is an effective strategy to reduce obesity-induced oxidative stress. The purpose of this study was to compare the effects of two training modalities (moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT)) on the pro/antioxidant status of different tissues in obese Zucker rats. METHODS: Eight-week-old male Zucker rats (fa/fa, n = 36) were subdivided in three groups: MICT, HIIT, and control (no exercise) groups. Trained animals ran on a treadmill (0° slope), 5 days/week for 10 weeks (MICT: 51 min at 12 m·min-1; HIIT: 6 sets of 3 min at 10 m·min-1 followed by 4 min at 18 m·min-1). Epididymal (visceral) and subcutaneous adipose tissue, gastrocnemius muscle, and plasma samples were collected to measure oxidative stress markers (advanced oxidation protein products (AOPP), oxidized low-density lipoprotein (oxLDL)), antioxidant system markers (ferric-reducing ability of plasma (FRAP), superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPx) activities), and prooxidant enzymes (NADPH oxidase and xanthine oxidase (XO) activities, myeloperoxidase content). RESULTS: Compared with the control, MICT increased GPx and catalase activities and the FRAP level in epididymal adipose tissue. HIIT increased the AOPP level in subcutaneous adipose tissue. In the muscle, HIIT increased both SOD and GPx activities and reduced the AOPP level, whereas MICT increased only SOD activity. Finally, plasma myeloperoxidase content was similarly decreased by both training modalities, whereas oxLDL was reduced only in the MICT group. CONCLUSION: Both HIIT and MICT improved the pro/antioxidant status. However, HIIT was more efficient than MICT in the skeletal muscle, whereas MICT was more efficient in epididymal adipose tissue. This suggests that oxidative stress responses to HIIT and MICT are tissue-specific. This could result in ROS generation via different pathways in these tissues. From a practical point of view, the two training modalities should be combined to obtain a global response in people with obesity.

Neuregulin 1 improves complex 2-mediated mitochondrial respiration in skeletal muscle of healthy and diabetic mice.

It has been reported that neuregulin1 (NRG1) improves glucose tolerance in healthy and diabetic rodents. In vitro studies also suggest that NRG1 regulates myocyte oxidative capacity. To confirm this observation in vivo, we evaluated the effect on mitochondrial function of an 8-week treatment with NRG1 in db/db diabetic mice and C57BL/6JRJ healthy controls. NRG1 treatment improved complex 2-mediated mitochondrial respiration in the gastrocnemius of both control and diabetic mice and increased mitochondrial complex 2 subunit content by 2-fold. This effect was not associated with an increase in mitochondrial biogenesis markers. Enhanced ERBB4 phosphorylation could mediate NRG1 effects on mitochondrial function through signalling pathways, independently of ERK1/2, AKT or AMPK.

Acid-Sensing Ion Channel 1a in the amygdala is involved in pain and anxiety-related behaviours associated with arthritis.

Chronic pain is associated with anxiety and depression episodes. The amygdala plays a key role in the relationship between emotional responses and chronic pain. Here, we investigated the role of Acid-Sensing Ion Channels 1a within the basolateral amygdala (BLA), in pain and associated anxiety in a rat model of monoarthritis (MoAr). Administration within the BLA of PcTx1 or mambalgin-1, two specific inhibitors of ASIC1a-containing channels significantly inhibited pain and anxiety-related behaviours in MoAr rats. The effect of PcTx1 was correlated with a reduction of c-Fos expression in the BLA. We examined the expression profile of ASICs and other genes in the amygdala in MoAr and sham animals, and found no variation of the expression of ASIC1a, which was confirmed at the protein level. However, an increase in the BLA of MoAr rats of both PI3Kinase mRNA and the phosphorylated form of Akt, along with Bdnf mRNA, suggest that the BDNF/PI3-kinase/Akt pathway might regulate ASIC1a in BLA neurons as demonstrated in spinal sensitisation phenomenon. We also observed changes in several kinase mRNAs expression (PICK1, Sgk1) that are potentially involved in ASIC1a regulation. These results show a crucial role of ASIC1a channels in the BLA in pain and anxiety-related behaviours during arthritis.

Neuregulin 1 Improves Glucose Tolerance in db/db Mice.

In vitro experiments using rodent skeletal muscle cells suggest that neuregulin 1 (NRG1) is involved in glucose metabolism regulation, although no study has evaluated the role of NRG1 in systemic glucose homeostasis. The purpose of this study was to investigate the effect of chronic and acute NRG1 treatment on glucose homeostasis in db/db mice. To this aim, glucose tolerance tests were performed in 8-week-old male db/db mice after treatment with NRG1 (50µg.kg-1) or saline 3 times per week for 8 weeks. In other experiments, glucose tolerance and pyruvate tolerance tests were performed in db/db mice 15 minutes after a single NRG1 (50µg.kg-1) or saline injection. Liver, adipose tissue, hypothalamus and skeletal muscle were also collected 30 minutes after acute NRG1 (50µg.kg-1) or saline treatment, and the phosphorylation status of the ERBB receptors, AKT (on Ser473) and FOXO1 (on Ser256) was assessed by western blotting. Chronic treatment (8 weeks) with NRG1 improved glucose tolerance in db/db mice. Acute treatment also lowered glycemia and insulinemia during glucose or pyruvate tolerance tests. NRG1 acute injection induced activation of ERBB3 receptors and phosphorylation of AKT and FOXO1 only in liver. Altogether, this study shows that acute and chronic NRG1 treatments improve glucose tolerance in db/db mice. This effect could be mediated through inhibition of hepatic gluconeogenesis.

99mTc-NTP 15-5 Imaging for Cartilage Involvement in Experimental Rheumatoid Arthritis: Comparison with Routinely Used Molecular Imaging Methods and Sensitivity to Chronic Nonsteroidal Antiinflammatory Drug Treatment.

UNLABELLED: This study determined, using the intraarticular complete Freund adjuvant arthritis mice model, whether the radiotracer (99m)Tc-N-(triethylammonium)-3-propyl-[15]ane-N5 ((99m)Tc-NTP 15-5) targeting proteoglycans has a pathophysiologic validity for in vivo imaging of rheumatoid arthritis (RA) and its response to chronic nonsteroidal antiinflammatory drugs. METHODS: We investigated the time course of cartilage remodeling by (99m)Tc-NTP 15-5 scintigraphy, bone damages by (99m)Tc-hydroxymethylene diphosphonate imaging, inflammation by (18)F-FDG PET, and joint proteoglycan content and pain behavior in animals, without and with meloxicam treatment. Paw circumference, thermal pain behavior, and histology as well as proteoglycan content of the whole joint were determined. RESULTS: (99m)Tc-NTP 15-5 showed specific tracer accumulation within RA joints, with a significant increase in scintigraphic ratio observed in RA versus shams from day 3 to day 28. (18)F-FDG evidenced uptake in RA joints from day 15 to day 29. Animals treated with meloxicam (5 mg/kg) exhibited a dose-dependent decrease in both (99m)Tc-NTP 15-5 and (18)F-FDG uptake ratios versus saline-treated animals. (99m)Tc-hydroxymethylene diphosphonate bone scans were only positive at day 14 in RA versus shams, with a significant effect of meloxicam. An increase in proteoglycans of RA joint and thermal pain behavior were observed and were dose-dependently reduced by meloxicam. CONCLUSION: These experimental results bring data in favor of the (99m)Tc-NTP 15-5 radiotracer for assessing, in vivo, cartilage remodeling in RA that could be used to monitor therapy.

Exercise training and return to a well-balanced diet activate the neuregulin 1/ErbB pathway in skeletal muscle of obese rats.

KEY POINTS: Some studies suggest that neuregulin 1 (NRG1) could be involved in the regulation of skeletal muscle energy metabolism in rodents. Here we assessed whether unbalanced diet is associated with alterations of the NRG1 signalling pathway and whether exercise and diet might restore NRG1 signalling in skeletal muscle of obese rats. We show that diet-induced obesity does not impair NRG1 signalling in rat skeletal muscle. We also report that endurance training and a well-balanced diet activate the NRG1 signalling in skeletal muscle of obese rats, possibly via a new mechanism mediated by the protease ADAM17. These results suggest that some beneficial effects of physical activity and diet in obese rats could be partly explained by stimulation of the NRG1 signalling pathway. ABSTRACT: Some studies suggest that the signalling pathway of neuregulin 1 (NRG1), a protein involved in the regulation of skeletal muscle metabolism, could be altered by nutritional and exercise interventions. We hypothesized that diet-induced obesity could lead to alterations of the NRG1 signalling pathway and that chronic exercise could improve NRG1 signalling in rat skeletal muscle. To test this hypothesis, male Wistar rats received a high fat/high sucrose (HF/HS) diet for 16 weeks. At the end of this period, NRG1 and ErbB expression/activity in skeletal muscle was assessed. The obese rats then continued the HF/HS diet or were switched to a well-balanced diet. Moreover, in both groups, half of the animals also performed low intensity treadmill exercise training. After another 8 weeks, NRG1 and ErbB expression/activity in skeletal muscle were tested again. The 16 week HF/HS diet induced obesity, but did not significantly affect the NRG1/ErbB signalling pathway in rat skeletal muscle. Conversely, after the switch to a well-balanced diet, NRG1 cleavage ratio and ErbB4 amount were increased. Chronic exercise training also promoted NRG1 cleavage, resulting in increased ErbB4 phosphorylation. This result was associated with increased protein expression and phosphorylation ratio of the metalloprotease ADAM17, which is involved in NRG1 shedding. Similarly, in vitro stretch-induced activation of ADAM17 in rat myoblasts induced NRG1 cleavage and ErbB4 activation. These results show that low intensity endurance training and well-balanced diet activate the NRG1-ErbB4 pathway, possibly via the metalloprotease ADAM17, in skeletal muscle of diet-induced obese rats.

Monoarthritis-induced emotional and cognitive impairments in rats are sensitive to low systemic doses or intra-amygdala injections of morphine.

Chronic pain is a multidimensional experience that not only includes changes in nociception but also impairments in emotional and cognitive functions, not often taken into account in preclinical research. The present study investigated emotional and cognitive impairments in an animal model of persistent inflammatory pain as well as the involvement of the basolateral complex (BLC) of the amygdala in these components. Monoarthritis was induced by intra-articular injection of complete Freund׳s adjuvant. Mechanical hypersensitivity, anxiety and depressive-like behaviours as well as cognitive capacities were assessed using several tests, such as von Frey, social interaction, open field, saccharin preference, spatial and social recognition memory tests. The effects of morphine administered systemically or into the BLC of the amygdala were also studied. Monoarthritic rats exhibited mechanical hypersensitivity, anxiety and depressive-like behaviours as well as cognitive impairments. Whereas low systemic doses and intra-BLC infusion of morphine failed to reduce mechanical hypersensitivity, they reversed monoarthritis-induced anxiety-like behaviours and cognitive impairments. Our findings further support a crucial role of amygdala in the effect of morphine on emotional/cognitive components of pain and not on mechanical hypersensitivity. Finally, our study highlights the interest of a multi-behavioural approach in the assessment of pain and the analgesic effect of drugs.

Low doses of dextromethorphan have a beneficial effect in the treatment of neuropathic pain.

N-methyl-D-aspartate receptor (NMDAR) antagonists may be given in persistent neuropathic pain, but adverse events especially with ketamine may limit their clinical use. Less central and cognitive adverse events are described with dextromethorphan and memantine. These molecules have been explored in many preclinical and clinical studies, but data are conflicting as regards neuropathic pain alleviation. Dextromethorphan and memantine have been administered to animals after spinal nerve ligation (SNL) to evaluate their antinociceptive/cognitive effects and associated molecular events, including the phosphorylation of several tyrosine (pTyr(1336), pTyr(1472)) residues in the NR2B NMDAR subunit. Spinal nerve ligation and sham animals received dextromethorphan (10 mg/kg, i.p.), memantine (20 mg/kg, i.p.) or saline (1 mL/kg, i.p.). These drugs were administered once symptoms of allodynia and hyperalgesia had developed. Tests were carried out before and after surgery. Tactile allodynia, mechanical hyperalgesia and spatial memory were, respectively, evaluated by von Frey, Randall & Selitto and Y-maze tests and molecular events by Western blot analysis. Spinal nerve-ligated animals displayed nociception and impaired spatial memory. Dextromethorphan, but not memantine, reversed neuropathic pain (NP) symptoms, restored spatial memory integrity and decreased the expression of pTyr(1336)NR2B. Following postoperative administration of dextromethorphan, this study has demonstrated for the first time a concordance between behaviour, cognitive function and molecular events via pTyr(1336)NR2B for neuropathic pain alleviation. Confirmation of these findings in patients would constitute a major step forward in the treatment of neuropathic pain and in the improvement of cognitive function and quality of life.

Alleviating pain hypersensitivity through activation of type 4 metabotropic glutamate receptor.

Hyperactivity of the glutamatergic system is involved in the development of central sensitization in the pain neuraxis, associated with allodynia and hyperalgesia observed in patients with chronic pain. Herein we study the ability of type 4 metabotropic glutamate receptors (mGlu4) to regulate spinal glutamate signaling and alleviate chronic pain. We show that mGlu4 are located both on unmyelinated C-fibers and spinal neurons terminals in the inner lamina II of the spinal cord where they inhibit glutamatergic transmission through coupling to Cav2.2 channels. Genetic deletion of mGlu4 in mice alters sensitivity to strong noxious mechanical compression and accelerates the onset of the nociceptive behavior in the inflammatory phase of the formalin test. However, responses to punctate mechanical stimulation and nocifensive responses to thermal noxious stimuli are not modified. Accordingly, pharmacological activation of mGlu4 inhibits mechanical hypersensitivity in animal models of inflammatory or neuropathic pain while leaving acute mechanical perception unchanged in naive animals. Together, these results reveal that mGlu4 is a promising new target for the treatment of chronic pain.

Fatty acid amide hydrolase-dependent generation of antinociceptive drug metabolites acting on TRPV1 in the brain.

The discovery that paracetamol is metabolized to the potent TRPV1 activator N-(4-hydroxyphenyl)-5Z,8Z,11Z,14Z-eicosatetraenamide (AM404) and that this metabolite contributes to paracetamol's antinociceptive effect in rodents via activation of TRPV1 in the central nervous system (CNS) has provided a potential strategy for developing novel analgesics. Here we validated this strategy by examining the metabolism and antinociceptive activity of the de-acetylated paracetamol metabolite 4-aminophenol and 4-hydroxy-3-methoxybenzylamine (HMBA), both of which may undergo a fatty acid amide hydrolase (FAAH)-dependent biotransformation to potent TRPV1 activators in the brain. Systemic administration of 4-aminophenol and HMBA led to a dose-dependent formation of AM404 plus N-(4-hydroxyphenyl)-9Z-octadecenamide (HPODA) and arvanil plus olvanil in the mouse brain, respectively. The order of potency of these lipid metabolites as TRPV1 activators was arvanil = olvanil>>AM404> HPODA. Both 4-aminophenol and HMBA displayed antinociceptive activity in various rodent pain tests. The formation of AM404, arvanil and olvanil, but not HPODA, and the antinociceptive effects of 4-aminophenol and HMBA were substantially reduced or disappeared in FAAH null mice. The activity of 4-aminophenol in the mouse formalin, von Frey and tail immersion tests was also lost in TRPV1 null mice. Intracerebroventricular injection of the TRPV1 blocker capsazepine eliminated the antinociceptive effects of 4-aminophenol and HMBA in the mouse formalin test. In the rat, pharmacological inhibition of FAAH, TRPV1, cannabinoid CB1 receptors and spinal 5-HT3 or 5-HT1A receptors, and chemical deletion of bulbospinal serotonergic pathways prevented the antinociceptive action of 4-aminophenol. Thus, the pharmacological profile of 4-aminophenol was identical to that previously reported for paracetamol, supporting our suggestion that this drug metabolite contributes to paracetamol's analgesic activity via activation of bulbospinal pathways. Our findings demonstrate that it is possible to construct novel antinociceptive drugs based on fatty acid conjugation as a metabolic pathway for the generation of TRPV1 modulators in the CNS.

Memantine, a promising drug for the prevention of neuropathic pain in rat.

N-methyl-D-aspartate (NMDA) receptor antagonists are used for post-surgery neuropathic pain but severe side-effects limit their clinical use. Memantine, when given after surgery, shows conflicting results as regard to neuropathic pain alleviation. Here memantine is administered in animals before or after spinal nerve ligation (SNL) in order to evaluate the induced antinociceptive/cognitive effects and associated molecular events, including the phosphorylation of several tyrosine (pTyr(1336), pTyr(1472)) and serine (pSer(1303)) residues in the NR2B subunit of the NMDA receptor. Spinal nerve ligated and sham animals received memantine (20mg/kg/day) or vehicle (1ml/kg/day) by intraperitoneal route. Pre-emptive protocol started 4 days before surgery and continued for 2 days post-surgery. In the post-operative protocol, the 7 day-treatment began on the day of surgery. Tests were done before and after surgery. Tactile allodynia, mechanical hyperalgesia and spatial memory were evaluated by von Frey, Randall & Selitto and Y-maze-tests respectively, and molecular events by western-blot analysis. Spinal nerve ligated animals displayed nociception, impaired memory and increased expression of the 3 phosphorylated residues. Post-operative memantine had no beneficial effect. Pre-emptive memantine prevented the development of post-surgical nociception, impairment of spatial memory and did not increase the expression of pTyr(1472)NR2B at spinal, insular and hippocampal levels. Memantine administered a few days before surgery is a promising strategy to alleviate neuropathic pain development and impairment of cognitive function in animals. The pivotal role of pTyr(1472)NR2B must be studied further, and these findings will now be challenged in patients for the prevention of postsurgical neuropathic pain.

New method to discriminate sedative and analgesic effects of drugs in the automated formalin test in rats.

We developed an automated technique based on the detection of pain-related behaviours (like licking or biting) and small activities (mostly grooming) in the formalin pain test. By comparing automated and manual scoring, we determined that the interphase score was mostly independent of pain-related behaviours and it was used as an index of sedative events. The non-pain-related behaviours, still present during the second phase, were eliminated in order to visualize only pain-related behaviours. This new method, validated using classical analgesic (morphine) and sedative drugs (diazepam) could be used to discriminate sedative from analgesic effects of pharmacological treatments in the formalin test.

Invading basement membrane matrix is sufficient for MDA-MB-231 breast cancer cells to develop a stable in vivo metastatic phenotype.

INTRODUCTION: The poor efficacy of various anti-cancer treatments against metastatic cells has focused attention on the role of tumor microenvironment in cancer progression. To understand the contribution of the extracellular matrix (ECM) environment to this phenomenon, we isolated ECM surrogate invading cell populations from MDA-MB-231 breast cancer cells and studied their genotype and malignant phenotype. METHODS: We isolated invasive subpopulations (INV) from non invasive populations (REF) using a 2D-Matrigel assay, a surrogate of basal membrane passage. INV and REF populations were investigated by microarray assay and for their capacities to adhere, invade and transmigrate in vitro, and to form metastases in nude mice. RESULTS: REF and INV subpopulations were stable in culture and present different transcriptome profiles. INV cells were characterized by reduced expression of cell adhesion and cell-cell junction genes (44% of down regulated genes) and by a gain in expression of anti-apoptotic and pro-angiogenic gene sets. In line with this observation, in vitro INV cells showed reduced adhesion and increased motility through endothelial monolayers and fibronectin. When injected into the circulation, INV cells induced metastases formation, and reduced injected mice survival by up to 80% as compared to REF cells. In nude mice, INV xenografts grew rapidly inducing vessel formation and displaying resistance to apoptosis. CONCLUSION: Our findings reveal that the in vitro ECM microenvironment per se was sufficient to select for tumor cells with a stable metastatic phenotype in vivo characterized by loss of adhesion molecules expression and induction of pro-angiogenic and survival factors.

Spinal cord plasticity and acid-sensing ion channels involvement in a rodent model of irritable bowel syndrome.

Irritable bowel syndrome (IBS) is a common functional gastro-intestinal disorder characterized by intractable chronic abdominal pain. In this study, we examined the possible spinal mechanisms underlying colonic hypersensitivity (CHS) using a non-inflammatory rat model of IBS induced by rectal enemas of butyrate, a short-chain fatty acid. We hypothesized that spinal plasticity could be responsible for CHS and that ASIC channels, which are known to support pain-elicited currents in the spinal cord, could contribute to central sensitization in our model of IBS. First, in order to determine if visceral pain relies on changes in spinal activity, we analyzed Fos expression in the spinal cord of rats treated with butyrate following a challenge with repetitive noxious colorectal distension. We found that Fos immunoreactivity was increased in thoracic T10-11-12, lumbar L1-2-6 and sacral S1 spinal segments. In control rats treated with saline, noxious repetitive colorectal distensions evoked Fos expression only in L1-2-6 and S1 spinal segments. Secondly, intrathecal injection of PcTx1, a specific ASIC1A antagonist, in the lumbar spinal cord completely prevented the development of CHS induced by butyrate. ASIC1 and 2 mRNAs, especially ASIC1A, were upregulated in the lumbar spinal cord. ASIC1A could thus contribute to spinal sensitization in our model of IBS, as it is supported by spinal colocalization of ASIC1A and Fos proteins. The whole data pinpoint a potential critical role of thoracic spinal cord in non-inflammatory pain states such as IBS and suggest that ASIC channels are part of the molecular effectors of central sensitization leading to visceral pain.