Novel Dual-Acting Hybrids Targeting Type-2 Cannabinoid Receptors and Cholinesterase Activity Show Neuroprotective Effects In Vitro and Amelioration of Cognitive Impairment In Vivo

Alzheimer's disease (AD) is a neurodegenerative form of dementia characterized by the loss of synapses and a progressive decline in cognitive abilities. Among current treatments for AD, acetylcholinesterase (AChE) inhibitors have efficacy limited to symptom relief, with significant side effects and poor compliance. Pharmacological agents that modulate the activity of type-2 cannabinoid receptors (CB2R) of the endocannabinoid system by activating or blocking them have also been shown to be effective against neuroinflammation. Herein, we describe the design, synthesis, and pharmacological effects in vitro and in vivo of dual-acting compounds that inhibit AChE and butyrylcholinesterase (BChE) and target CB2R. Within the investigated series, compound 4g proved to be the most promising. It achieved IC50 values in the low micromolar to submicromolar range against both human cholinesterase isoforms while antagonizing CB2R with Ki of 31 nM. Interestingly, 4g showed neuroprotective effects on the SH-SY5Y cell line thanks to its ability to prevent oxidative stress-induced cell toxicity and reverse scopolamine-induced amnesia in the Y-maze forced alternation test in vivo.

Helichrysum stoechas (L.) Moench reduces body weight gain and modulates mood disorders via inhibition of silent information regulator 1 (SIRT1) by arzanol

The prevalence of obesity is steadily rising, making safe and more efficient anti-obesity treatments an urgent medical need. Growing evidence correlates obesity and comorbidities, including anxiety and depression, with the development of a low-grade inflammation in peripheral and central tissues. We hypothesized that attenuating neuroinflammation might reduce weight gain and improve mood. We investigated the efficacy of a methanolic extract from Helichrysum stoechas (L.) Moench (HSE), well-known for its anti-inflammatory properties, and its main constituent arzanol (AZL). HPLC-ESI-MS2 and HPLC-UV were used to characterize the extract. HSE effects on mood and feeding behavior was assessed in mice. The mechanism of action of HSE and AZL was investigated in hippocampus samples and SH-SY5Y cells by western blotting and immunofluorescence. Oral administration of HSE for 3 weeks limited weight gain with no significant decrease in food intake. HSE produced an anxiolytic-like and antidepressant-like phenotype comparable to diazepam and amitriptyline, respectively, in the absence of locomotor and cognitive impairments and induced neuroprotective effects in glutamate-exposed SH-SY5Y cells. A dose-dependent reduction of SIRT1 expression was detected in SH-SY5Y cells and in hippocampal samples from HSE-treated mice. The inhibition of the SIRT1-FoxO1 pathway was induced in the hypothalamus. Molecular docking studies proposed a mechanism of SIRT1 inhibition by AZL, confirmed by the evaluation of inhibitory effects on SIRT1 enzymatic activity. HSE limited weight gain and comorbidities through an AZL-mediated SIRT1 inhibition. These activities indicate HSE an innovative therapeutic perspective for obesity and associated mood disorders.

Novel Combination of Choline with Withania somnifera (L.) Dunal, and Bacopa monnieri (L.) Wetts Reduced Oxidative Stress in Microglia Cells, Promoting Neuroprotection

Memory deficit is one of the major negative outcomes of chronic stress. Cholinergic system modulates memory not only through the neuronal cells, but also via interactions with non-neuronal cells, suggesting that microglia can influence synaptic function and plasticity, contributing to cognition and memory function. Withania somnifera (L.) Dunal (WS) and Bacopa monnieri (L.) Wettst (BM), are traditional herbal medicinal products used for the temporary relief of symptoms of stress. The aim of this study was to investigate whether choline (CLN) activity could be enhanced via an association with adaptogens: WS and BM extracts. First, we optimized an in vitro model of corticotropin-releasing hormone (CRH)-induced oxidative stress on microglial BV2 cells. CRH 100 nM reduced BV2 cell viability and induced morphological changes and neurotoxicity after 24 h of microglia stimulation. Moreover, it induced an increase in the production of reactive oxygen species (ROS) and dysregulated antioxidant protein (i.e., SIRT-1 and NRF-2). The association between choline and adaptogens (CBW) 10 μg/mL counteracted the effect of CRH on BV2 cells and reduced the neurotoxicity produced by BV2 CRH-conditioned medium in the SH-SY5Y cell lines. CBW 200 mg/kg produced an ameliorative effect on recognition memory in the novel object recognition test (NORT) test in mice. In conclusion, combining choline with adaptogen plant extracts might represent a promising intervention in chronic stress associated with memory disturbances through the attenuation of microglia-induced oxidative stress.

Chronic alcohol induced mechanical allodynia by promoting neuroinflammation: A mouse model of alcohol-evoked neuropathic pain

BACKGROUND AND PURPOSE

Chronic pain is considered a key factor contributing to alcohol use disorder (AUD). The mechanisms responsible for chronic pain associated with chronic alcohol consumption are unknown. We evaluated the development of chronic pain in a mouse model of alcohol dependence and investigate the role of neuroinflammation.

EXPERIMENTAL APPROACH

The chronic-intermittent ethanol two-bottle choice CIE-2BC paradigm generates three groups: alcohol-dependent with escalating alcohol intake, nondependent (moderate drinking) and alcohol-naïve control male and female mice. We measured mechanical allodynia during withdrawal and after the last voluntary drinking. Immunoblotting was used to evaluate the protein levels of IBA-1, CSFR, IL-6, p38 and ERK2/1 in spinal cord tissue of dependent and non-dependent animals.

KEY RESULTS

We found significant escalation of drinking in the dependent group in male and female compared with the non-dependent group. The dependent group developed mechanical allodynia during 72 h of withdrawal, which was completely reversed after voluntary drinking. We observed an increased pain hypersensitivity compared with the naïve in 50% of non-dependent group. Increased IBA-1 and CSFR expression was observed in spinal cord tissue of both hypersensitivity-abstinence related and neuropathy-alcohol mice, and increased IL-6 expression and ERK1/2 activation in mice with hypersensitivity-related to abstinence, but not in mice with alcohol-evoked neuropathic pain.

CONCLUSIONS AND IMPLICATIONS

The CIE-2BC model induces two distinct pain conditions specific to the type of ethanol exposure: abstinence-related hypersensitivity in dependent mice and alcohol-evoked neuropathic pain in about a half of the non-dependent mice.

Honokiol-Rich Magnolia officinalis Bark Extract Attenuates Trauma-Induced Neuropathic Pain

Neuropathic pain (NP) affects about 8% of the general population. Current analgesic therapies have limited efficacy, making NP one of the most difficult to treat pain conditions. Evidence indicates that excessive oxidative stress can contribute to the onset of chronic NP and several natural antioxidant compounds have shown promising efficacy in NP models. Thus, this study aimed to investigate the pain-relieving activity of honokiol (HNK)-rich standardized extract of Magnolia officinalis Rehder & E. Wilson bark (MOE), well known for its antioxidant and anti-inflammatory properties, in the spared nerve injury (SNI) model. The molecular mechanisms and efficacy toward neuroinflammation were investigated in spinal cord samples from SNI mice and LPS-stimulated BV2 microglia cells. MOE and HNK showed antioxidant activity. MOE (30 mg/kg p.o.) produced an antiallodynic effect in SNI mice in the absence of locomotor impairment, reduced spinal p-p38, p-JNK1, iNOS, p-p65, IL-1ß, and Nrf2 overexpression, increased IL-10 and MBP levels and attenuated the Notch signaling pathway by reducing Jagged1 and NEXT. These effects were prevented by the CB1 antagonist AM251. HNK reduced the proinflammatory response of LPS-stimulated BV2 and reduced Jagged1 overexpression. MOE and HNK, by modulating oxidative and proinflammatory responses, might represent interesting candidates for NP management.

The Selective CB2 Agonist COR167 Reduced Symptoms in a Mice Model of Trauma-Induced Peripheral Neuropathy through HDAC-1 Inhibition

Neuropathic pain is a chronic disabling condition with a 7-10% of prevalence in the general population that is largely undertreated. Available analgesic therapies are poorly effective and are often accompanied by numerous side effects. Growing evidence indicates cannabinoids are a valuable treatment opportunity for neuropathic pain. The endocannabinoid system is an important regulator of pain perception through the CB1 receptors, but CB1 agonists, while largely effective, are not always satisfactory pain-relieving agents in clinics because of their serious adverse effects. Recently, several CB2 agonists have shown analgesic, anti-hyperalgesic, and anti-allodynic activity in the absence of CB1-induced psychostimulant effects, offering promise in neuropathic pain management. The aim of this study was to evaluate the anti-neuropathic activity of a novel selective CB2 agonist, COR167, in a preclinical model of peripheral neuropathy, the spared nerve injury (SNI). Oral COR167, in a dose-dependent manner, attenuated mechanical allodynia and thermal hyperalgesia after acute and repeated administration, showing the absence of tolerance induction. At anti-neuropathic doses, COR167 did not show any alteration in the locomotor behavior. SNI mice showed increased microglial levels of HDAC1 protein in the ipsilateral side of the spinal cord, along with NF-kB activation. COR167 treatment prevented the HDAC1 overexpression and the NF-kB activation and increased the levels of the anti-inflammatory cytokine IL-10 through a CB2-mediated mechanism. Oral administration of COR167 shows promising therapeutic potential in the management of neuropathic pain conditions.

Posttranscriptional Regulation of Gene Expression Participates in the Myelin Restoration in Mouse Models of Multiple Sclerosis: Antisense Modulation of HuR and HuD ELAV RNA Binding Protein

Neuropathic pain is the most difficult-to-treat pain syndrome in multiple sclerosis. Evidence relates neuropathic pain to demyelination, which often originates from unresolved neuroinflammation or altered immune response. Posttranscriptional regulation of gene expression might play a fundamental role in the regulation of these processes. The ELAV RNA-binding proteins HuR and HuD are involved in the promotion of inflammatory phenomena and in neuronal development and maintenance, respectively. Thus, the aim of this study was to investigate the role of HuR and HuD in demyelination-associated neuropathic pain in the mouse experimental autoimmune encephalomyelitis (EAE) model. HuR resulted overexpressed in the spinal cord of MOG_35-55-EAE and PLP_139-151-EAE mice and was detected in CD11b + cells. Conversely, HuD was largely downregulated in the MOG-EAE spinal cord, along with GAP43 and neurofilament H, while in PLP-EAE mice, HuD and neuronal markers remained unaltered. Intranasal antisense oligonucleotide (ASO) delivery to knockdown HuR, increased myelin basic protein expression, and Luxol Fast Blue staining in both EAE models, an indication of increased myelin content. These effects temporally coincided with attenuation of pain hypersensitivity. Anti-HuR ASO increased the expression of HuD in GAP43-expressing cells and promoted a HuD-mediated neuroprotective activity in MOG-EAE mice, while in PLP-EAE mice, HuR silencing dampened pro-inflammatory responses mediated by spinal microglia activation. In conclusion, anti-HuR ASO showed myelin protection at analgesic doses with multitarget mechanisms, and it deserves further consideration as an innovative agent to counteract demyelination in neuropathic pain states.

Cannabidiol-rich non-psychotropic Cannabis sativa L. oils attenuate peripheral neuropathy symptoms by regulation of CB2-mediated microglial neuroinflammation

Neuropathic pain (NP) is a chronic disease that affects the normal quality of life of patients. To date, the therapies available are only symptomatic and they are unable to reduce the progression of the disease. Many studies reported the efficacy of Cannabis sativa L. (C. sativa) on NP, but no Δ9 -tetrahydrocannabinol (Δ9 -THC)-free extracts have been investigated in detail for this activity so far. The principal aim of this work is to investigate the potential pain-relieving effect of innovative cannabidiol-rich non-psychotropic C. sativa oils, with a high content of terpenes (K2), compared to the same extract devoid of terpenes (K1). Oral administration of K2 (25 mg kg-1 ) induced a rapid and long-lasting relief of pain hypersensitivity in a mice model of peripheral neuropathy. In spinal cord samples, K2 reduced mitogen-activated protein kinase (MAPKs) levels and neuroinflammatory factors. These effects were reverted by the administration of a CB2 antagonist (AM630), but not by a CB1 antagonist (AM251). Conversely, K1 showed a lower efficacy in the absence of CB1/CB2-mediated mechanisms. In LPS-stimulated murine microglial cells (BV2), K2 reduced microglia pro-inflammatory phenotype through the downregulation of histone deacetylase 1 (HDAC-1) and nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor (IKBα) and increased interleukin-10 (IL-10) expression, an important antiinflammatory cytokine. In conclusion, these results suggested that K2 oral administration attenuated NP symptoms by reducing spinal neuroinflammation and underline the important role of the synergism between cannabinoids and terpenes.

Zingiber officinale Roscoe Rhizome Extract Exerts Senomorphic and Anti-Inflammatory Activities on Human Endothelial Cells

Aging is related to a low-grade and sterile inflammation called inflammaging, recognized as the main risk factor for age-related disease (ARD) development. Inflammaging is fostered by the repeated activation of immune cells, as well as by the accumulation of senescent cells. Recently, a number of natural compounds have gained attention to be tested as anti-aging therapies, based on their anti-inflammatory activity and/or ability to reduce the pro-inflammatory secretome of senescent cells (senomorphyc activity). Here, we investigated the anti-inflammatory and senomorphic properties of an Asian-native Zingiber officinale Roscoe extract (ZOE), commonly consumed as a food spice and herbal medicine. We employed two models of primary endothelial cells (HUVECs), such as the replicative-senescence and LPS-induced response, to investigate the anti-inflammatory/senomorphic effect of ZOE, and one cellular model of neuroinflammation, i.e., immortalized murine microglial cells (BV2). First, we found that the ZOE treatment induced the inhibition of NF-kB activation in BV2 cells. Among the constituents of ZOE, we showed that the terpenoid-enriched fraction (ZTE) was the component able to counteract the phosphorylation of NF-kB(p65), while 6-gingerol (GIN) and 6-shogaol (SHO) did not produce any significant effect. Further, we observed that the treatment with 10 µg/mL of ZOE exerted anti-inflammatory activity on LPS-stimulated young (y)HUVEC and senomorphyc activity on replicative senescent (s)HUVEC, significantly reducing the expression levels of IL-1β, TNF -α, IL-8, MCP-1, and ICAM-1. Moreover, the ZTE treatment was able to significantly reduce the IL-8 levels secreted in the medium of both LPS-stimulated yHUVEC and sHUVEC. Overall, our data suggest a potential protective role of ZOE on neuroinflammation and endothelial inflammation/activation, thus suggesting its potential relevance in delaying/postponing ARD development and progression, characterized by endothelial dysfunction.

Zingiberene, a non-zinc-binding class I HDAC inhibitor: A novel strategy for the management of neuropathic pain

BACKGROUND

Even though numerous Histone deacetylase inhibitors (HDACi) have been approved for the treatment of different types of cancer, and others are in clinical trials for the treatment of neurodegenerative diseases, the main problem related to the clinical use of available HDACi is their low isoform selectivity which causes undesirable effects and inevitably limits their therapeutic application. Previously, we demonstrated that a standardized Zingiber officinalis Roscoe rhizome extract (ZOE) reduced neuroinflammation through HDAC1 inhibition in a mice model of neuropathy, and this activity was related to terpenes fraction.

HYPOTHESIS/PURPOSE

The aim of this work was to identify the ZOE constituent responsible for the activity on HDAC1 and to study its possible application in trauma-induced neuropathic pain.

METHODS

The ability of ZOE and its terpenes fraction (ZTE) to inhibit HDAC and SIRT isoforms activity and protein expression was assessed in vitro. Then, a structure-based virtual screening approach was applied to predict which constituent could be responsible for the activity. In the next step, the activity of selected compound was tested in an in vitro model of neuroinflammation and in an in vivo model of peripheral neuropathy (SNI).

RESULTS

ZTE resulted to be more potent than ZOE on HDAC1, 2, and 6 isoforms, while ZOE was more active on HDAC8. Zingiberene (ZNG) was found to be the most promising HDAC1 inhibitor, with an IC₅₀ of 2.3 ± 0.1 µM. A non-zinc-binding mechanism of inhibition was proposed based on molecular docking. Moreover, the oral administration of ZNG reduced thermal hyperalgesia and mechanical allodynia in animals with neuropathy after 60 min from administration, and decreased HDAC-1 levels in the spinal cord microglia.

CONCLUSION

We found a new non-zinc-dependent inhibitor of HDAC class I, with a therapeutic application in trauma-related neuropathic pain forms in which microglia-spinal overexpression of HDAC1 occurs. The non-zinc-binding mechanism has the potential to reduce off target effects, leading to a higher selectivity and better safety profile, compared to other HDAC inhibitors.

Investigation on the neuroprotective effect of a cannabidiol-enriched non-psychotropic Cannabis sativa L. extract in an in vitro model of excitotoxicity

The purpose of this study was to evaluate the neuroprotective effect of a cannabidiol-enriched non-psychotropic Cannabis sativa L. extract (CSE) and its main constituents, cannabidiol and β-caryophyllene. An in vitro model of glutamate-induced neuronal excitotoxicity using SH-SY5Y cells was optimized. The impact of CSE on glutamate-impaired cell viability, brain-derived neurotrophic factor release, CB1 protein expression, and ERK levels was evaluated. The involvement of CB1 modulation was verified by the cotreatment with the CB1 antagonist AM4113. CSE was able to significantly protect SH-SY5Y from glutamate-impaired cell viability, and to counteract the changes in brain-derived neurotrophic factor levels, with a mechanism of action involving ERK modulation. Moreover, CSE completely reversed the reduction of CB1 receptor expression induced by glutamate, and the presence of the CB1 antagonist AM4113 reduced CSE effectiveness, suggesting that CBr play a role in the modulation of neuronal excitotoxicity. This work demonstrated the in vitro effectiveness of CSE as a neuroprotective agent, proposing the whole cannabis phytocomplex as a more effective strategy, compared to its main constituents alone, and suggested further investigations by using more complex cell models before moving to in vivo studies.

Dual HDAC/BRD4 Inhibitors Relieves Neuropathic Pain by Attenuating Inflammatory Response in Microglia After Spared Nerve Injury

Despite the effort on developing new treatments, therapy for neuropathic pain is still a clinical challenge and combination therapy regimes of two or more drugs are often needed to improve efficacy. Accumulating evidence shows an altered expression and activity of histone acetylation enzymes in chronic pain conditions and restoration of these aberrant epigenetic modifications promotes pain-relieving activity. Recent studies showed a synergistic activity in neuropathic pain models by combination of histone deacetylases (HDACs) and bromodomain and extra-terminal domain (BET) inhibitors. On these premises, the present study investigated the pharmacological profile of new dual HDAC/BRD4 inhibitors, named SUM52 and SUM35, in the spared nerve injury (SNI) model in mice as innovative strategy to simultaneously inhibit HDACs and BETs. Intranasal administration of SUM52 and SUM35 attenuated thermal and mechanical hypersensitivity in the absence of locomotor side effects. Both dual inhibitors showed a preferential interaction with BRD4-BD2 domain, and SUM52 resulted the most active compound. SUM52 reduced microglia-mediated spinal neuroinflammation in spinal cord sections of SNI mice as showed by reduction of IBA1 immunostaining, inducible nitric oxide synthase (iNOS) expression, p65 nuclear factor-κB (NF-κB) and p38 MAPK over-phosphorylation. A robust decrease of the spinal proinflammatory cytokines content (IL-6, IL-1ß) was also observed after SUM52 treatment. Present results, showing the pain-relieving activity of HDAC/BRD4 dual inhibitors, indicate that the simultaneous modulation of BET and HDAC activity by a single molecule acting as multi-target agent might represent a promise for neuropathic pain relief.

Ylang-ylang (Cananga odorata (Lam.) Hook. f. & Thomson) essential oil reduced neuropathic-pain and associated anxiety symptoms in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Ylang-ylang essential oil (YEO), obtained from the flowers of the tropical tree Cananga odorata (Lam.) Hook. f. & Thomson (family Annonaceae), has been largely used in the traditional medicine with many uses, including anxiety and altered neuronal states. Neuropathic pain is a chronic pain condition with a high incidence of comorbidities, such as anxiety, depression, and other mood disorders, that drastically affect the patient's quality of life. The currently available drugs used for the management of neuropathic pain are inadequate due to poor efficacy and tolerability, highlighting the medicinal need of a better pharmacotherapy. Several clinical studies have reported that massage or inhalation with selected essentials oils reduces symptoms associated to pain and anxiety.

AIM OF THE STUDY

The aim of this study was to investigate the analgesic properties of YEO and its efficacy in reducing neuropathy-associated mood alterations.

MATERIALS AND METHODS

The analgesic properties were tested in the spared nerve injury (SNI) model using male mice. Anxiolytic, antidepressant, and locomotor properties were also evaluated using behavioural tests. Finally, the YEO mechanism of action was investigated in the spinal cord and hippocampus of neuropathic mice.

RESULTS

Oral administration of YEO (30 mg/kg) reduced SNI-induced neuropathic pain and ameliorates pain-related anxiety symptoms that appeared 28 days after surgery. YEO reduced the expression of MAPKs, NOS2, p-p65, markers of neuroinflammation, and promoted normalizing effect on neurotrophin levels (BDNF).

CONCLUSIONS

YEO induced neuropathic pain relief and ameliorated pain-associated anxiety, representing an interesting candidate for the management of neuropathic pain conditions and pain-related comorbidities.

Dual HDAC–BRD4 inhibitors endowed with antitumor and antihyperalgesic activity

Histone deacetylases (HDAC) are enzymes that regulate the concentration of acetylated histones which, in turns, interact with the bromodomain (BRD) of BET (Bromodomain and Extracellular domain) proteins to affect transcriptional activity. Simultaneous blockade of both epigenetic players has shown synergistic effects in a variety of cancer cell lines. In this paper we report the design, synthesis and activity of new dual inhibitors, obtained by adding a methyltriazole moiety to some HDAC inhibitors carrying a benzodiazepine core, which were previously developed by us. An Alphascreen FRET assay showed that the compounds were able to interact with BRD4-1 and BRD4-2 proteins, with some selectivity for the latter, while the HDAC inhibiting properties were measured by means of an immunoprecipitation assay. The antiproliferative activity was tested on C26 adenocarcinoma, SSMC2 melanoma and SHSY5Y neuroblastoma cells. Interestingly, both compounds were endowed with antihyperalgesic activity in the mouse Spared Nerve Injury (SNI) model.

Non-psychotropic Cannabis sativa L. phytocomplex modulates microglial inflammatory response through CB2 receptors-, endocannabinoids-, and NF-κB-mediated signaling

Cannabis sativa L. is increasingly emerging for its protective role in modulating neuroinflammation, a complex process orchestrated among others by microglia, the resident immune cells of the central nervous system. Phytocannabinoids, especially cannabidiol (CBD), terpenes, and other constituents trigger several upstream and downstream microglial intracellular pathways. Here, we investigated the molecular mechanisms of a CBD- and terpenes-enriched C. sativa extract (CSE) in an in vitro model of neuroinflammation. We evaluated the effect of CSE on the inflammatory response induced by exposure to lipopolysaccharide (LPS) in BV-2 microglial cells, compared with CBD and β-caryophyllene (CAR), CB2 receptors (CB2r) inverse and full agonist, respectively. The LPS-induced upregulation of the pro-inflammatory cytokines IL-1β, IL-6, and TNF-α was significantly attenuated by CSE and only partially by CBD, whereas CAR was ineffective. In BV-2 cells, these anti-inflammatory effects exerted by CSE phytocomplex were only partially dependent on CB2r modulation and they were mediated by the regulation of enzymes responsible for the endocannabinoids metabolism, by the inhibition of reactive oxygen species release and the modulation of JNK/p38 cascade with consequent NF-κB p65 nuclear translocation suppression. Our data suggest that C. sativa phytocomplex and its multitarget mechanism could represent a novel therapeutic strategy for neuroinflammatory-related diseases.

Targeting the RNA-Binding Protein HuR as Potential Thera-Peutic Approach for Neurological Disorders: Focus on Amyo-Trophic Lateral Sclerosis (ALS), Spinal Muscle Atrophy (SMA) and Multiple Sclerosis

The importance of precise co- and post-transcriptional processing of RNA in the regulation of gene expression has become increasingly clear. RNA-binding proteins (RBPs) are a class of proteins that bind single- or double-chain RNA, with different affinities and selectivity, thus regulating the various functions of RNA and the fate of the cells themselves. ELAV (embryonic lethal/abnormal visual system)/Hu proteins represent an important family of RBPs and play a key role in the fate of newly transcribed mRNA. ELAV proteins bind AU-rich element (ARE)-containing transcripts, which are usually present on the mRNA of proteins such as cytokines, growth factors, and other proteins involved in neuronal differentiation and maintenance. In this review, we focused on a member of ELAV/Hu proteins, HuR, and its role in the development of neurodegenerative disorders, with a particular focus on demyelinating diseases.

Dual BET/HDAC inhibition to relieve neuropathic pain: Recent advances, perspectives, and future opportunities

Despite the intense research on developing new therapies for neuropathic pain states, available treatments have limited efficacy and unfavorable safety profiles. Epigenetic alterations have a great influence on the development of cancer and neurological diseases, as well as neuropathic pain. Histone acetylation has prevailed as one of the well investigated epigenetic modifications in these diseases. Altered spinal activity of histone deacetylase (HDAC) and Bromo and Extra terminal domain (BET) have been described in neuropathic pain models and restoration of these aberrant epigenetic modifications showed pain-relieving activity. Over the last decades HDACs and BETs have been the focus of drug discovery studies, leading to the development of numerous small-molecule inhibitors. Clinical trials to evaluate their anticancer activity showed good efficacy but raised toxicity concerns that limited translation to the clinic. To maximize activity and minimize toxicity, these compounds can be applied in combination of sub-maximal doses to produce additive or synergistic interactions (combination therapy). Recently, of particular interest, dual BET/HDAC inhibitors (multi-target drugs) have been developed to assure simultaneous modulation of BET and HDAC activity by a single molecule. This review will summarize the most recent advances with these strategies, describing advantages and limitations of single drug treatment vs combination regimens. This review will also provide a focus on dual BET/HDAC drug discovery investigations as future therapeutic opportunity for human therapy of neuropathic pain.

A honokiol-enriched Magnolia officinalis Rehder & E.H. Wilson. bark extract possesses anxiolytic-like activity with neuroprotective effect through the modulation of CB1 receptor

OBJECTIVES

The exposure of neurons to an excessive excitatory stimulation induces the alteration of the normal neuronal function. Mood disorders are among the first signs of alterations in the central nervous system function. Magnolia officinalis bark extract has been extensively used in the traditional medicine systems of several countries, showing several pharmacological activities. Honokiol, the main constituent of M. officinalis, is a GABA modulator and a CB1 agonist, which is deeply investigated for its role in modulating mood disorders.

METHODS

Thus, we evaluated the possible neuroprotective effect of a standardized M. officinalis bark extract (MOE), enriched in honokiol, and its effect on animal mood behavioural tests and in an in vitro model of excitotoxicity.

KEY FINDINGS

MOE showed neuroprotective effect using SH-SY5Y cells, by normalizing brain-derived neurotrophic factor release. Then, we tested the effect of MOE in different behavioural tests evaluating anxiety and depression and we observed a selective anxiolytic-like effect. Finally, we confirmed the involvement of CB1 in the final effect of MOE by the co-administration of the CB1 antagonist, AM251.

CONCLUSION

These results suggest that MOE could be considered an effective and safe anxiolytic candidate with neuroprotective activity.

Combined inhibition of histone deacetylases and BET family proteins as epigenetic therapy for nerve injury-induced neuropathic pain

Current treatments for neuropathic pain have often moderate efficacy and present unwanted effects showing the need to develop effective therapies. Accumulating evidence suggests that histone acetylation plays essential roles in chronic pain and the analgesic activity of histone deacetylases (HDACs) inhibitors is documented. Bromodomain and extra-terminal domain (BET) proteins are epigenetic readers that interact with acetylated lysine residues on histones, but little is known about their implication in neuropathic pain. Thus, the current study was aimed to investigate the effect of the combination of HDAC and BET inhibitors in the spared nerve injury (SNI) model in mice. Intranasal administration of i-BET762 (BET inhibitor) or SAHA (HDAC inhibitor) attenuated thermal and mechanical hypersensitivity and this antiallodynic activity was improved by co-administration of both drugs. Spinal cord sections of SNI mice showed an increased expression of HDAC1 and Brd4 proteins and combination produced a stronger reduction compared to each epigenetic agent alone. SAHA and i-BET762, administered alone or in combination, counteracted the SNI-induced microglia activation by inhibiting the expression of IBA1, CD11b, inducible nitric oxide synthase (iNOS), the activation of nuclear factor-κB (NF-κB) and signal transducer and activator of transcription-1 (STAT1) with comparable efficacy. Conversely, the epigenetic inhibitors showed a modest effect on spinal proinflammatory cytokines content that was significantly potentiated by their combination. Present results indicate a key role of acetylated histones and their recruitment by BET proteins on microglia-mediated spinal neuroinflammation. Targeting neuropathic pain with the combination of HDAC and BET inhibitors may represent a promising new therapeutic option.

Fluorescence Colocalization Analysis of Cellular Distribution of MOR-1

The interaction between neurons and glia is pivotal for the development of chronic opioid tolerance. One of the most important mechanisms of cell-to-cell interaction is the Notch signaling pathway. In this chapter we propose a double-immunofluorescence method to observe and quantify the colocalization of Notch-1 and mu-opioid receptor (MOR-1), using both neuronal and astrocyte markers.

Targeting the RNA-Binding Protein HuR Alleviates Neuroinflammation in Experimental Autoimmune Encephalomyelitis: Potential Therapy for Multiple Sclerosis

Multiple sclerosis (MS) is a chronic autoimmune inflammatory and neurodegenerative disease of the central nervous system characterized by demyelination, axonal loss, and motor dysfunction. Activated microglia are associated with the destruction of myelin in the CNS. Activated microglia produce cytokines and proinflammatory factors, favoring neuroinflammation, myelin damage, and neuronal loss, and it is thought to be involved in the disease pathogenesis. The present study investigated the role of post-transcriptional regulation of gene expression on the neuroinflammation related to experimental autoimmune encephalomyelitis (EAE) in mice, by focusing on HuR, an RNA-binding protein involved in inflammatory and immune phenomena. Spinal cord sections of EAE mice showed an increased HuR immunostaining that was abundantly detected in the cytoplasm of activated microglia, a pattern associated with its increased activity. Intrathecal administration of an anti-HuR antisense oligonucleotide (ASO) decreased the proinflammatory activated microglia, inflammatory infiltrates, and the expression of the proinflammatory cytokines IL-1β, TNF-α, and IL-17, and inhibited the activation of the NF-κB pathway. The beneficial effect of anti-HuR ASO in EAE mice corresponded also to a decreased permeability of the blood-brain barrier. EAE mice showed a reduced spinal CD206 immunostaining that was restored by anti-HuR ASO, indicating that HuR silencing promotes a shift to the anti-inflammatory and regenerative microglia phenotype. Mice that received anti-HuR ASO exhibited improved EAE-related motor dysfunction, pain hypersensitivity, and body weight loss. Targeting HuR might represent an innovative and promising perspective to control neurological disturbances in MS patients.

Attenuation of Anxiety-Like Behavior by Helichrysum stoechas (L.) Moench Methanolic Extract through Up-Regulation of ERK Signaling Pathways in Noradrenergic Neurons

The long-term use of anxiolytic and antidepressant drugs can cause a plethora of side effects and the use of complementary and alternative medicine, which is generally considered safer than conventional medicine, is consistently increasing. Helichrysum stoechas (L.) Moench methanolic extract (HSE) has shown MAO-A inhibitory properties in previous studies. With the aim of obtaining innovative and safer therapies for mood disorders, this study investigated the potential activity of HSE in the management of anxiety- and depression-related symptoms. HSE showed dose-dependent (30-100 mg/kg p.o.) anxiolytic-like activity in the light dark box and marble burying tests, without any antidepressant-like activity, as shown by the results of the tail suspension test. Additionally, HSE did not have any effect on the modulation of pain, which highlights its selectivity in the control of anxiety-related behavior. At active doses, HSE did not produce any sedative effect or result in impaired motor coordination and memory functions. Western blotting experiments showed the ability of HSE to counteract the reduction in the phosphorylation of ERK44/42, to restore brain-derived neurotrophic factor (BDNF) expression and to return cyclic AMP response element binding (CREB) levels to basal levels in noradrenergic hippocampal neurons of mice exposed to an anxiety-related environment, which indicates a protective role against anxiety behavior. These results suggest that oral administration of HSE might represent an interesting opportunity for the management of anxiety disorders.

Zingiber officinale Roscoe rhizome extract alleviates neuropathic pain by inhibiting neuroinflammation in mice

BACKGROUND

Current therapies for neuropathic pain are generally symptomatic and possess several side effects, limiting their prolonged usage.

HYPOTHESIS/PURPOSE

Thus, it is urgent to develop novel and safe candidates for the management of this chronical condition. For this purpose, we investigated the analgesic effect of a standardized extract from Zingiber officinale Roscoe rhizomes (ZOE) obtained by CO2 supercritical extraction, in a mice model of peripheral neuropathy. We also explored the mechanism of action of ZOE and its main constituents using an in vitro model of neuroinflammation.

METHODS

Peripheral mono-neuropathy was induced in mice, by spared nerve injury (SNI). The analgesic effect of ZOE after oral administration was assessed by measuring mechanical and thermal allodynia in SNI mice. The mechanism of action of ZOE and its main constituents were investigated using spinal cords samples and in an in vitro model of neuroinflammation by ELISA, western blotting and immunofluorescence techniques.

RESULTS

Oral administration of ZOE 200 mg kg-1 ameliorated mechanical and thermal allodynia in SNI mice, with a rapid and a long-lasting effect. ZOE did not alter locomotor activity. In BV2 cells and spinal cord samples, ZOE, 6-gingerol and 6-shogaol reduced pERK levels, whereas ZOE and terpene fraction reduced HDAC1 protein levels, inhibited NF-κB signalling activation and decreased IL-1β, TNF-α and IL-6 release. ZOE and each tested constituent had a positive effect on inflammation-impaired SH-SY5Y cell viability.

CONCLUSIONS

The oral administration of ZOE attenuated SNI-induced neuropathic pain symptoms by reducing spinal neuroinflammation, suggesting ZOE as a novel and interesting candidate for the management of neuropathic pain.

Synthesis, biological evaluation and docking studies of a novel class of sulfur-bridged diazabicyclo[3.3.1]nonanes

A small library of 3-thia-7,9-diazabicyclo[3.3.1]nonanes was synthesized and their opioid receptors affinity and selectivity evaluated. Among these novel sulfur-bridged compounds, the (E) 9-[3'-(3-chlorophenyl)-but-2'-en-1'-yl]-7-propionyl-3-thia-7,9-diazabicyclo[3.3.1]nonane 2i emerged as the derivative with the highest μ receptor affinity (K_i = 85 nM) and selectivity (K_i μ/δ = 58.8, K_i μ/κ > 117.6). The antinociceptive activity of 2i was also evaluated in acute thermal pain. Docking studies disclosed the specific pattern of interactions of these derivatives.

Novel Therapeutic Approach for the Management of Mood Disorders: In Vivo and In Vitro Effect of a Combination of L-Theanine, Melissa officinalis L. and Magnolia officinalis Rehder & E.H. Wilson

Mood disorders represent one of the most prevalent and costly psychiatric diseases worldwide. The current therapies are generally characterized by several well-known side effects which limit their prolonged use. The use of herbal medicine for the management of several psychiatric conditions is becoming more established, as it is considered a safer support to conventional pharmacotherapy. The aim of this study was to investigate the possible anxiolytic and antidepressant activity of a fixed combination of L-theanine, Magnolia officinalis, and Melissa officinalis (TMM) in an attempt to evaluate how the multiple modulations of different physiological systems may contribute to reducing mood disorders. TMM showed an anxiolytic-like and antidepressant-like activity in vivo, which was related to a neuroprotective effect in an in vitro model of excitotoxicity. The effect of TMM was not altered by the presence of flumazenil, thus suggesting a non-benzodiazepine-like mechanism of action. On the contrary, a significant reduction in the effect was observed in animals and neuronal cells co-treated with AM251, a cannabinoid receptor type 1 (CB1) antagonist, suggesting that the endocannabinoid system may be involved in the TMM mechanism of action. In conclusion, TMM may represent a useful and safe candidate for the management of mood disorders with an innovative mechanism of action, particularly as an adjuvant to conventional therapies.

Histamine H4 receptor stimulation in the locus coeruleus attenuates neuropathic pain by promoting the coeruleospinal noradrenergic inhibitory pathway

The locus coeruleus (LC) adrenergic nuclei constitute a pain-control inhibitory system nucleus implicated in descending modulation of pain through the action on spinal α₂-adrenoceptors. Histaminergic innervation from the tuberomammillary nucleus of the LC increases firing of noradrenergic neurons and might contribute to pain control. Here we evaluated the contribution of LC histaminergic innervation in descending modulation of neuropathic hypersensitivity, by investigating the role of the histamine H₄ receptor subtype in a mouse model of neuropathic pain. Intra LC administration of the H₄ agonist VUF 8430 attenuated mechanical and thermal allodynia of mice that underwent spared nerve injury (SNI). Similarly, histamine in the LC showed mechanical and thermal anti-hypersensitivity. Pretreatment of LC with JNJ 10191584 (H₄ antagonist) prevented the beneficial effect of VUF 8430 and histamine on nociceptive behaviour. Comparable results were obtained after intrathecal administration of drugs. The intrathecal administration of the α₂-adrenoceptor agonist clonidine ameliorated mechanical and thermal allodynia in SNI mice. The clonidine-induced anti-hypersensitivity effect was prevented by intra LC pretreatment with JNJ 10191584. In addition, clonidine failed to suppress neuropathic pain in H₄ deficient mice. LC H₄ receptors showed a ubiquitous distribution within LC, a neuronal localization and H₄ immunostaining was detected on noradrenergic neurons expressing phosphorylated cAMP response element-binding protein (CREB), a marker of neuronal activation. Under pain pathological conditions H₄ stimulation might promote the activation of the coeruleospinal noradrenergic neurons that exert an inhibitory control over spinal dorsal horn neuronal excitability. Thus, histamine H₄ receptor stimulation may represent a perspective for neuropathic pain management.

Lavender (Lavandula angustifolia Mill.) Essential Oil Alleviates Neuropathic Pain in Mice With Spared Nerve Injury

Low treatment efficacy represents an important unmet need in neuropathic pain patients and there is an urgent need to develop a more effective pharmacotherapy. An increasing number of patients choose complementary medicine to relieve pain. Lavender essential oil (LEO) is approved by the European Medicines Agency as herbal medicine to relieve anxiety and stress. However, the capability of LEO to relieve other nervous system disorders such as neuropathic pain has never been established. Our work aimed to evaluate the antineuropathic properties of lavender on a spared nerve injury (SNI) model of neuropathic pain in mice. An acute oral administration of LEO (100 mg/kg) alleviated SNI-induced mechanical allodynia, evaluated in the von Frey test, with an intensity comparable to the reference drug pregabalin. Investigations into the mechanism of action showed that LEO markedly decreased the phosphorylation of ERK1, ERK2, and JNK1, and decreased the levels of iNOS in the spinal cord; involvement of the endocannabinoid system was also detected using in vitro inhibition of the FAAH and MALG enzymes as well as in vivo experiments with the CB1 antagonist. Conversely, no effect on P38 phosphorylation and NF-kB activation was detected. These antihyperalgesic effects appeared at the same dose able to induce antidepressant-like, anxiolytic-like, and anorexic effects. In addition, gavage with LEO did not significantly alter animals' gross behavior, motor coordination, or locomotor activity, nor impaired memory functions. Oral administration of LEO could represent a therapeutic approach in the management of neuropathic pain states.

The HDAC1/c-JUN complex is essential in the promotion of nerve injury-induced neuropathic pain through JNK signaling

Histone deacetylase inhibitors (HDACIs) interfere with the epigenetic process of histone acetylation and are known to have analgesic properties in models of chronic inflammatory pain. Administration of a selective HDAC1 inhibitor (LG325) in SNI-subjected mice significantly attenuated behavior related to injury-induced pain. Understanding the HDAC1 pathway in epigenetic regulation of pathological pain is of great medical relevance. Spared nerve injury (SNI) mice showed a significant increase in the HDAC1 protein levels within spinal cord in coincidence with the nociceptive phenotype at 1 and 3 weeks after nerve injury. No variation in HDAC3, DNMT3a, AcH3, MBD3 and MeCP2 levels was detected. Increased expression of HDAC1 is accompanied by activation of the JNK-c-Jun signaling pathway. A robust spinal JNK-1 overphosphorylation was observed post nerve-injury along with a selective JNK-dependent increase in p-c-Jun and HDAC1 protein levels. Co-immunoprecipitation experiments showed the presence of a heterodimeric complex between HDAC1 and c-Jun in SNI mice indicating that these transcription factors can act together to regulate transcription through heterodimerization. Stimulation of c-Jun phosphorylation was prevented by the selective HDAC1 inhibitor LG325. We found that HDAC1 was associated with c-Jun in nuclei of spinal dorsal horn astrocytes expressing JNK. On the other hand, the presence of HDAC1 and c-Jun interaction was not detected in control mice. These findings provide new insights into the mechanisms underlying the anti-nociceptive activity of HDAC inhibitors. Taken together, these data support a role for histone deacetylase in the emergence of neuropathic pain.

St. John's Wort Potentiates anti-Nociceptive Effects of Morphine in Mice Models of Neuropathic Pain

Objective

In this study, we compared the efficacy of a combination of PKC-blocker St. John's Wort (SJW) and morphine in mice with painful antiretroviral (2,3-dideoxycitidine [ddC]) and chemotherapic (oxaliplatin) neuropathy.

Methods

Morphine (1 and 5 mg/Kg i.p.), SJW (1 and 5 mg/Kg o.s.), or their combination was administered by systemic injection, and antinociception was determined by using the hot and cold plate tests.

Results

Here we demonstrate the ability of SJW to relieve neuropathic pain in mice neuropathic models and a potentiation of morphine antinociception in thermal pain. The potentiating effect shown by SJW was not secondary to its antinociceptive activity as the increase of the morphine antinociceptive effect was produced at a dose (1mg/kg o.s.) devoid of any capability to modulate the pain threshold in neuropathic pain mice. Further examinations of the SJW main components revealed that hypericin was responsible for the potentiating properties whereas flavonoids were ineffective.

Conclusions

These results show that SJW has notable antinociceptive activity for both neuropathic pain models and could be used in neuropathic pain relief alone or in combination with morphine. These data support the utility of combination SJW/opioid therapy in pain management for antinociceptive efficacy by enhancing opioid analgesia.

Antidepressant-like actions by silencing of neuronal ELAV-like RNA-binding proteins HuB and HuC in a model of depression in male mice

Currently available antidepressant drugs often fail to achieve full remission and patients might evolve to treatment resistance, showing the need to achieve a better therapy of depressive disorders. Increasing evidence supports that post-transcriptional regulation of gene expression is important in neuronal development and survival and a relevant role is played by RNA binding proteins (RBP). To explore new therapeutic strategies, we investigated the role of the neuron-specific ELAV-like RBP (HuB, HuC, HuD) in a mouse model of depression. In this study, a 4-week unpredictable chronic mild stress (UCMS) protocol was applied to mice to induce a depressive-like phenotype. In the last 2 weeks of the UCMS regimen, silencing of HuB, HuC or HuD was performed by using specific antisense oligonucleotides (aODN). Treatment of UCMS-exposed mice with anti-HuB and anti-HuC aODN improved both anhedonia and behavioural despair, used as measures of depressive-like behaviour, without modifying the response of stressed mice to an anxiety-inducing environment. On the contrary, HuD silencing promoted an anxiolytic-like behaviour in UCMS-exposed mice without improving depressive-like behaviours. The antidepressant-like phenotype of anti-HuB and anti-HuC mice was not shown concurrently with the promotion of adult hippocampal neurogenesis in the dentate gyrus, and no increase in the BDNF and CREB content was detected. Conversely, in the CA3 hippocampal region, projection area of newly born neurons, HuB and HuC silencing increased the number of BrdU/NeuN positive cells. These results give the first indication of a role of nELAV in the modulation of emotional states in a mouse model of depression.

Silencing of the RNA-binding protein HuR attenuates hyperalgesia and motor disability in experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system associated with progressive neuronal loss and axonal degeneration. Neuronal lesions and dysfunction lead often to neuropathic pain, the most prevalent and difficult to treat pain syndrome observed in MS patients. Despite its widespread occurrence, the underlying neural mechanisms for MS pain are not fully understood. For a better clarification of the pathophysiology of MS-associated pain, we investigated the role of HuR, an RNA-binding protein that positively regulates the stability of many target mRNAs, including several cytokines. The influence of HuR in the generation of the hypernociceptive response in a mouse model of relapsing-remitting experimental autoimmune encephalomyelitis (RR-EAE), an experimental model of MS, was investigated. HuR silencing, obtained through the repeated intrathecal administration of an antisense oligonucleotide (aODN) anti-HuR, completely attenuated hindpaw mechanical allodynia and thermal hyperalgesia developed by RR-EAE mice. Anti-HuR aODN also reduced severity of motor deficits as reflected by a reduction of clinical EAE score and improvement of rotarod performance. RR-EAE mice showed demyelination in spinal cord sections that was significantly reduced by HuR silencing. Double-staining immunofluorescence studies showed a neuronal localization of HuR within dorsal horn spinal cord, consistent with a neuronal mechanism of action. Our findings suggest the involvement of HuR in the hypernociceptive behaviour of RR-EAE mice providing the first pharmacological assessment of an antiallodynic and antihyperalgesic effect of HuR silencing. These data may provide support for HuR modulation as a therapeutic perspective for the management of MS-related neuropathic pain.

Hypericum perforatum (St John's wort) beyond depression: A therapeutic perspective for pain conditions

ETHNOPHARMACOLOGICAL RELEVANCE

Hypericum perforatum L. (Hypericaceae), popularly called St. John's wort (SJW), has a rich historical background being one of the oldest used and most extensively investigated medicinal herbs. Many bioactivities and applications of SJW are listed in popular and in scientific literature, including antibacterial, antiviral, anti-inflammatory. In the last three decades many studies focused on the antidepressant activity of SJW extracts. However, several studies in recent years also described the antinociceptive and analgesic properties of SJW that validate the traditional uses of the plant in pain conditions.

AIM OF THE REVIEW

This review provides up-to-date information on the traditional uses, pre-clinical and clinical evidence on the pain relieving activity of SJW and its active ingredients, and focuses on the possible exploitation of this plant for the management of pain.

MATERIALS AND METHODS

Historical ethnobotanical publications from 1597 were reviewed for finding local and traditional uses. The relevant data on the preclinical and clinical effects of SJW were searched using various databases such as PubMed, Science Direct, Scopus, and Google Scholar. Plant taxonomy was validated by the database Plantlist.org.

RESULTS

Preclinical animal studies demonstrated the ability of low doses of SJW dry extracts (0.3% hypericins; 3-5% hyperforins) to induce antinociception, to relieve from acute and chronic hyperalgesic states and to augment opioid analgesia. Clinical studies (homeopathic remedies, dry extracts) highlighted dental pain conditions as a promising SJW application. In vivo and in vitro studies showed that the main components responsible for the pain relieving activity are hyperforin and hypericin. SJW analgesia appears at low doses (5-100mg/kg), minimizing the risk of herbal-drug interactions produced by hyperforin, a potent inducer of CYP enzymes.

CONCLUSION

Preclinical studies indicate a potential use of SJW in medical pain management. However, clinical research in this field is still scarce and the few studies available on chronic pain produced negative results. Prospective randomized controlled clinical trials performed at low doses are needed to validate its potential efficacy in humans.

Liposomal Formulation to Increase Stability and Prolong Antineuropathic Activity of Verbascoside

Verbascoside (acteoside) possesses various pharmacological properties for human health, including antioxidant, anti-inflammatory, and antineoplastic properties in addition to numerous wound healing and neuroprotective properties, with an excellent and well-known safety profile. However, its poor chemical stability, due to hydrolysis, limits its use in the clinic. To overcome these limitations, we prepared unilamellar liposomal formulations of verbascoside for parenteral administration.Two formulations were prepared: V-L1 and V-L2, where V-L2 contains phospholipid and cholesterol about 4 times higher than the V-L1 sample, and about 2 times higher than verbascoside. The mean particle size of the liposomes prepared was found to be around 120 nm with a polydispersity index < 0.2. Encapsulation efficacy resulted in 30 %. A total of 82.28 ± 1.79 % of verbascoside was released from the liposomes within 24 hours. Liposomes ameliorate the stability of verbascoside by preventing its hydrolysis.The optimized drug delivery formulation was tested in the paw pressure test in two animal models of neuropathic pain: a peripheral mononeuropathy was produced either by a chronic constriction injury of the sciatic nerve or by an intra-articular injection of sodium monoiodoacetate. The performance of the liposomal formulation was compared with that of the free drug.For evaluating the paw pressure test in chronic constriction injury rats, a liposomal formulation administered i. p. at the dosage of 100 mg/kg showed a longer lasting antihyperalgesic effect in comparison with a 100-mg/kg verbascoside saline solution, as well as in the sodium monoiodoacetate models. The effect appeared 15 min after administration and persisted for up to 60 min.

Histamine H4 receptor agonist-induced relief from painful peripheral neuropathy is mediated by inhibition of spinal neuroinflammation and oxidative stress

BACKGROUND AND PURPOSE

Neuropathic pain is under-treated, with a detrimental effect on quality of life, partly because of low treatment efficacy, but also because pathophysiological mechanisms are not fully elucidated. To clarify the pathobiology of neuropathic pain, we studied the contribution of neuroinflammation and oxidative stress in a model of peripheral neuropathy. We also assessed an innovative treatment for neuropathic pain by investigating the effects of histamine H₄ receptor ligands in this model.

EXPERIMENTAL APPROACH

A peripheral mononeuropathy was induced in mice, by spared nerve injury (SNI). Neuroinflammation and oxidative stress parameters were evaluated by spectrophotometry. The mechanical (von Frey test) and thermal (plantar test) nociceptive thresholds were evaluated.

KEY RESULTS

SNI mice showed increased expression of the pro-inflammatory cytokines IL-1ß and TNF-α, decreased antioxidant enzyme Mn-containing SOD (MnSOD), increased levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG), an indicator of oxidative DNA damage, and of PARP, nuclear enzyme activated upon DNA damage. Intrathecal administration of VUF 8430 (H₄ receptor agonist) reversed the mechanical and thermal allodynia and was associated with decreased expression of IL-1ß, TNF-α, 8-OHdG and PARP and with restoration of MnSOD activity in the spinal cord and sciatic nerve. These effects were prevented by JNJ 10191584 (H₄ receptor antagonist).

CONCLUSION AND IMPLICATIONS

In the SNI mouse model of neuropathic pain, neuronal H₄ receptor stimulation counteracts hyperalgesia and reduces neuroinflammation and oxidative stress in the spinal cord and sciatic nerve. Targeting both oxidative stress and pro-neuroinflammatory pathways through H₄ receptor-mediated mechanisms could have promising therapeutic potential for neuropathic pain management.

Blockade of the spinal BDNF-activated JNK pathway prevents the development of antiretroviral-induced neuropathic pain

Although antiretroviral agents have been used successfully in suppressing viral production, they have also been associated with a number of side effects. The antiretroviral toxic neuropathy induces debilitating and extremely difficult to treat pain syndromes that often lead to discontinuation of antiretroviral therapy. Due to the critical need for the identification of novel therapeutic targets to improve antiretroviral neuropathic pain management, we investigated the role of the JNK signalling pathway in the mechanism of antiretroviral painful neuropathy. Mice were exposed to zalcitabine (2',3'-dideoxycytidine, ddC) and stavudine (2',3'-didehydro-3'-deoxythymidine, d4T) that induced a persistent mechanical allodynia and a transient cold allodynia. Treatment with the JNK blocker SP600125 before antiretroviral administration abolished mechanical hypersensitivity with no effect on thermal response. A robust spinal JNK overphosphorylation was observed on post-injection day 1 and 3, along with a JNK-dependent increase in p-c-Jun and ATF3 protein levels. Co-immunoprecipitation experiments showed the presence of a heterodimeric complex between ATF3 and c-Jun indicating that these transcription factors can act together to regulate transcription through heterodimerization. A rise in BDNF and caspase-3 protein levels was detected on day 1 and BDNF sequestration prevented both caspase-3 and p-JNK increase. These data suggest that BDNF plays a role in the early stages of ddC-induced allodynia by promoting apoptotic events and the activation of a hypernociceptive JNK-mediated pathway. We illustrated the activation of a BDNF-mediated JNK pathway involved in the early events responsible for the promotion of neuropathic pain, leading to a better knowledge of the mechanisms involved in the antiretroviral neuropathy.

SUMMARY

JNK blockade prevents antiretroviral-induced pain hypersensitivity. This may represent a potential prophylactic treatment of neuropathic pain to improve antiretroviral tolerability.

Altered Expression of Cytoskeletal and Axonal Proteins in Oxaliplatin-Induced Neuropathy

BACKGROUND

Oxaliplatin is a platinum compound widely used in the treatment of some solid tumors. Despite its usefulness, oxaliplatin-associated neurotoxicity represents the main dose-limiting factor of this drug. This study examined the structural neuronal effects of oxaliplatin treatment in spinal and supraspinal levels.

METHODS

Protein expression was investigated in the mouse cortex, thalamus, periaqueductal grey (PAG) matter and spinal cord (SC) by Western blotting. Thermal nociception was assessed by the hot plate test.

RESULTS

Results indicate a reduction in the levels of growth associated protein-43 (GAP43) in the cortex and SC areas at the end of thermal hyperalgesic response, while a decrease in neurofilament-H (NfH) phosphorylation was observed in the SC on day 21 when the pain-related manifestation reaches the neurotoxic peak. Counteracting phosphorylated NfH content increases in the SC and cortex regions at day 28 as a result of the beginning of neuro-regeneration process. We also revealed that the levels of HuD, a neuronal-specific RNA-binding protein, decreased, demonstrating the same temporal and regional expression pattern of GAP43. Oxaliplatin chronic treatment induced a region-specific upregulation of γ isoform of protein kinase C (PKC) within thalamus and PAG, and the administration of a PKC inhibitor suggests that PKC activity in these brain regions must be required to maintain the thermal hyperalgesic state.

CONCLUSIONS

These results suggest that changes in the protein levels of the regulatory and structural proteins are due to oxaliplatin-induced neurotoxicity and imply that there is a direct link between structural changes in the central nervous system and chemotherapy-induced neurotoxicity.