Ammonium Glycyrrhizinate Prevents Apoptosis and Mitochondrial Dysfunction Induced by High Glucose in SH-SY5Y Cell Line and Counteracts Neuropathic Pain in Streptozotocin-Induced Diabetic Mice.

Glycyrrhiza glabra, commonly known as liquorice, contains several bioactive compounds such as flavonoids, sterols, triterpene, and saponins; among which, glycyrrhizic acid, an oleanane-type saponin, is the most abundant component in liquorice root. Diabetic peripheral neuropathy is one of the major complications of diabetes mellitus, leading to painful condition as neuropathic pain. The pathogenetic mechanism of diabetic peripheral neuropathy is very complex, and its understanding could lead to a more suitable therapeutic strategy. In this work, we analyzed the effects of ammonium glycyrrhizinate, a derivate salt of glycyrrhizic acid, on an in vitro system, neuroblastoma cells line SH-SY5Y, and we observed that ammonium glycyrrhizinate was able to prevent cytotoxic effect and mitochondrial fragmentation after high-glucose administration. In an in vivo experiment, we found that a short-repeated treatment with ammonium glycyrrhizinate was able to attenuate neuropathic hyperalgesia in streptozotocin-induced diabetic mice. In conclusion, our results showed that ammonium glycyrrhizinate could ameliorate diabetic peripheral neuropathy, counteracting both in vitro and in vivo effects induced by high glucose, and might represent a complementary medicine for the clinical management of diabetic peripheral neuropathy.

New insights on the arylpiperazinylalkyl pyridazinone ET1 as potent antinociceptive and anti-inflammatory agent.

Pyridazine derivatives, such as arylpiperazinylalkyl pyridazinones, display antinociceptive effects to thermal and chemical stimuli. Here, we extended our previous knowledge on the pharmacological profile of 4-amino-6-methyl-2-(3-(4-(4-methylcyclohexa-1,3-dien-1-yl)piperazin-1-yl)propyl)-5-vinylpyridazin-3(2H)-one, here referred as ET1, paving the way for the comprehension of its complete mechanism of action. To this aim, we have evaluated the mouse behavioural responses in several animal models of pain, the effect of ET1 in the murine model of zymosan-induced paw oedema and air-pouch, assessing the cytokines and the cellular phenotype and finally, an in vitro radioligand binding study was performed on a panel of 30 different receptors. In the formalin test, ET1 reduced both neurogenic and inflammatory phase of nociception induced by the aldehyde. Similarly, ET1 strongly reduced paw licking response in the capsaicin test, the abdominal stretching in the writhing test and the carrageenan-induced thermal hyperalgesia. ET1 also evoked a long-lasting reduction of thermal hyperalgesia. Furthermore, ET1 produced a long-lasting anti-inflammatory effect in the zymosan-induced mouse paw oedema and air-pouch through the selective inhibition of inflammatory monocytes recruitment and the modulation of IL-1ß, IL-6, TNF-α and MCP-1. Binding experiments confirmed an inhibitory effect on adrenergic α1A, α1B and α2A receptors subtypes and, for the first time, a moderate affinity was observed for the following receptors: histamine H1, imidazoline I2, sigma non-opioid intracellular receptor 1 and σ2. These results prompt ET1 as a potent analgesic and anti-inflammatory agent, and support the possibility that it may be suitable for clinical applications in a wide-range of inflammatory-based diseases.

On resin click-chemistry-mediated synthesis of novel enkephalin analogues with potent anti-nociceptive activity.

Here, we report the chemical synthesis of two DPDPE analogues 7a (NOVA1) and 7b (NOVA2). This entailed the solid-phase synthesis of two enkephalin precursor chains followed by a CuI-catalyzed azide-alkyne cycloaddition, with the aim of improving in vivo analgesic efficacy versus DPDPE. NOVA2 showed good affinity and selectivity for the µ-opioid receptor (KI of 59.2 nM, EC50 of 12.9 nM, EMax of 87.3%), and long lasting anti-nociceptive effects in mice when compared to DPDPE.

Long-Lasting, Antinociceptive Effects of pH-Sensitive Niosomes Loaded with Ibuprofen in Acute and Chronic Models of Pain.

Ibuprofen is one of the non-steroidal anti-inflammatory drugs (NSAIDs) widely used to treat pain conditions. NSAIDs encounter several obstacles to passing across biological membranes. To overcome these constraints, we decided to study the effects of a new pH-sensitive formulation of niosomes containing Polysorbate 20 derivatized by Glycine and loaded with ibuprofen (NioIbu) in several animal models of pain in mice. We performed two tests commonly used to study acute antinociceptive activity, namely the writhing test and the capsaicin test. Our results demonstrated that NioIbu, administered 2 h before testing, reduced nociception, whereas the free form of ibuprofen was ineffective. In a model of inflammatory pain, hyperalgesia induced by zymosan, NioIbu induced a long-lasting reduction in hyperalgesia in treated mice. In a model of neuropathic pain induced by sciatic nerve chronic constriction, NioIbu reduced both neuropathy-induced allodynia and hyperalgesia. The results obtained in our experiments suggest that pH-sensitive niosomes containing Polysorbate 20 derivatized by Glycine is an effective model for NSAIDs delivery, providing durable antinociceptive effects and reducing the incidence of side effects.

Nociceptin /Orphanin FQ Peptide (NOP) Receptor Modulators: An Update in Structure-Activity Relationships.

Nociceptin /Orphanin FQ Peptide" receptor (NOPr) is a G-protein-coupled receptor with the nociceptin/orphanin FQ peptide (N/OFQ) as endogenous agonist. It is expressed in the nervous system as well as in some non-neural tissues. Its activation has pronociceptive effect at the supraspinal level, whereas at the spinal level it produces nociceptive effects at low doses and antinociceptive effects at higher doses. NOPr is also involved in mood and blood pressure regulation, immunoregulation, airway constriction, feeding, urination, bowel motility, learning and memory. Selective NOPr agonists have been tested clinically as anxiolytics and antitussives, and the antagonists as analgesics, antidepressants and in the treatment of alcohol addiction. Two NOPr radioligands have also been tested in humans as neuroimaging agents. Furthermore, the partial agonist peptide SER100 and N/OFQ have been used in clinical trials, respectively for congestive heart failure and overactive bladder. The evidence of interactions between NOP and µ-opioid receptor (MOPr) receptors has been exploited in the use of mixed NOPr/MOPr modulators as analgesics and in the treatment of drug addiction. These drugs are devoid of typical opioid liabilities. In this review, we outline the latest advances in the structure-activity relationships (SAR) of NOPr agonists and antagonists, with emphasis on affinity, activity, selectivity and pharmacokinetic features.

Cyclic Biphalin Analogues Incorporating a Xylene Bridge: Synthesis, Characterization, and Biological Profile.

In this work we enhanced the ring lipophilicity of biphalin introducing a xylene moiety, thus obtaining three cyclic regioisomers. Novel compounds have similar in vitro activity as the parent compound, but one of these (6a) shows a remarkable increase of in vivo antinociceptive effect. Nociception tests have disclosed its significant high potency and the more prolonged effect in eliciting analgesia, higher than that of biphalin and of the disulfide-bridge-containing analogue (7).

"Curcumin-loaded Poly (d, l-lactide-co-glycolide) nanovesicles induce antinociceptive effects and reduce pronociceptive cytokine and BDNF release in spinal cord after acute administration in mice".

Given the poor bioavailability of curcumin, its antinociceptive effects are produced after chronic intravenous administration of high doses, while poly (d,l-lactide-co-glycolide)-loaded vesicles (PLGA) can improve drug delivery. This paper investigates the antinociceptive effects of curcumin-loaded PLGA nanovesicles (PLGA-CUR) administered via intravenous (i.v.) or intrathecal (i.t.) routes at low and high doses. The following models of pain were used: formalin test, zymosan-induced hyperalgesia and sciatic nerve ligation inducing neuropathic allodynia and hyperalgesia. PLGA-CUR administered intravenously was able to reduce the response to nociceptive stimuli in the formalin test and hyperalgesia induced by zymosan. Curcumin, instead, was inactive. Low-dose i.t. administration of PLGA-CUR significantly reduced allodynia produced by sciatic nerve ligation, whereas low doses of curcumin did not change the response to nociceptive stimuli. Long-lasting antinociceptive effects were observed when high doses of PLGA-CUR were administered intrathecally. At high doses, i.t. administration of curcumin only exerted rapid and transient antinociceptive effects. Measurement of cytokine and BDNF in the spinal cord of neuropathic mice demonstrate that the antinociceptive effects of PLGA-CUR depend on the reduction in cytokine release and BDNF in the spinal cord. The results demonstrate the effectiveness of PLGA-CUR and suggest that PLGA-CUR nanoformulation might be a new potential drug in the treatment of pain.

Gender differences in pain and its relief.

There is much evidence to suggest that gender is an important factor in the modulation of pain. Literature data strongly suggest that men and women differ in their responses to pain: they are more variable in women than men, with increased pain sensitivity and many more painful diseases commonly reported among women. Gender differences in pharmacological therapy and non-pharmacological pain interventions have also been reported, but these effects appear to depend on the treatment type and characteristics. It is becoming very evident that gender differences in pain and its relief arise from an interaction of genetic, anatomical, physiological, neuronal, hormonal, psychological and social factors which modulate pain differently in the sexes. Experimental data indicate that both a different modulation of the endogenous opioid system and sex hormones are factors influencing pain sensitivity in males and females. This brief review will examine the literature on sex differences in experimental and clinical pain, focusing on several biological mechanisms implicated in the observed gender-related differences.

Evaluation of the analgesic effect of 4-anilidopiperidine scaffold containing ureas and carbamates.

Fentanyl is a powerful opiate analgesic typically used for the treatment of severe and chronic pain, but its prescription is strongly limited by the well-documented side-effects. Different approaches have been applied to develop strong analgesic drugs with reduced pharmacologic side-effects. One of the most promising is the design of multitarget drugs. In this paper we report the synthesis, characterization and biological evaluation of twelve new 4-anilidopiperidine (fentanyl analogues). In vivo hot-Plate test, shows a moderate antinociceptive activity for compounds OMDM585 and OMDM586, despite the weak binding affinity on both µ and δ-opioid receptors. A strong inverse agonist activity in the GTP-binding assay was revealed suggesting the involvement of alternative systems in the brain. Fatty acid amide hydrolase inhibition was evaluated, together with binding assays of cannabinoid receptors. We can conclude that compounds OMDM585 and 586 are capable to elicit antinociception due to their multitarget activity on different systems involved in pain modulation.

Exosomal clusterin, identified in the pericardial fluid, improves myocardial performance following MI through epicardial activation, enhanced arteriogenesis and reduced apoptosis.

BACKGROUND: We recently demonstrated that epicardial progenitor cells participate in the regenerative response to myocardial infarction (MI) and factors released in the pericardial fluid (PF) may play a key role in this process. Exosomes are secreted nanovesicles of endocytic origin, identified in most body fluids, which may contain molecules able to modulate a variety of cell functions. Here, we investigated whether exosomes are present in the PF and their potential role in cardiac repair. METHODS AND RESULTS: Early gene expression studies in 3day-infarcted mouse hearts showed that PF induces epithelial-to-mesenchymal transition (EMT) in epicardial cells. Exosomes were identified in PFs from non-infarcted patients (PFC) and patients with acute MI (PFMI). A shotgun proteomics analysis identified clusterin in exosomes isolated from PFMI but not from PFC. Notably, clusterin has a protective effect on cardiomyocytes after acute MI in vivo and is an important mediator of TGFß-induced. Clusterin addition to the pericardial sac determined an increase in epicardial cells expressing the EMT marker α-SMA and, interestingly, an increase in the number of epicardial cells ckit(+)/α-SMA(+), 7days following MI. Importantly, clusterin treatment enhanced arteriolar length density and lowered apoptotic rates in the peri-infarct area. Hemodynamic studies demonstrated an improvement in cardiac function in clusterin-treated compared to untreated infarcted hearts. CONCLUSIONS: Exosomes are present and detectable in the PFs. Clusterin was identified in PFMI-exosomes and might account for an improvement in myocardial performance following MI through a framework including EMT-mediated epicardial activation, arteriogenesis and reduced cardiomyocyte apoptosis.