Anti-nociceptive and anti-inflammatory actions of sulforaphane in chronic constriction injury-induced neuropathic pain mice

Analgesic Effect of Sulforaphane: A New Application for Poloxamer-Hyaluronic Acid Hydrogels

Sulforaphane (SFN) has shown potential as an antioxidant and anti-inflammatory agent. To improve its druggability, we developed new analgesic formulations with sulforaphane-loaded hyaluronic acid (HA)-poloxamer (PL) hydrogel. This study evaluated the pre-clinical safety and effectiveness of these formulations. Effectiveness was tested on Wistar rats divided into groups (n = 15) receiving (IM, 10 mg/kg) SFN formulations or control groups (without SFN). This study used a hind paw incision postoperative pain model to evaluate mechanical hypersensitivity with von Frey filaments. TNF-α, IL-1β, substance P, and CGRP levels verified anti-inflammatory activity in the hind paw tissue. Histopathology of tissues surrounding the injection site was assessed after 2 and 7 days post-treatment. To corroborate drug safety, cell viability of 3T3 and RAW 264.7 cultures was assessed. Additionally, RAW 264.7 cultures primed with carrageenan evaluated nitric oxide (NO) levels. All animals exhibited post-incisional hypersensitivity, and F2 (PL 407/338 (18/2%) + HA 1% + SFN 0.1%) showed a longer analgesic effect (p < 0.05). F2 reduced TNF-α, IL-1β, and CGRP levels (p < 0.05). Histopathological evaluation showed mild to moderate inflammatory reactions after the formulations' injections. F2 produced no significant difference in cell viability (p > 0.05) but reduced NO production (p < 0.05). Thus, our results highlight the biocompatibility and effectiveness of F2.

Anti-Inflammatory Therapeutic Mechanisms of Isothiocyanates: Insights from Sulforaphane

Isothiocyanates (ITCs) belong to a group of natural products that possess a highly reactive electrophilic -N=C=S functional group. They are stored in plants as precursor molecules, glucosinolates, which are processed by the tyrosinase enzyme upon plant tissue damage to release ITCs, along with other products. Isolated from broccoli, sulforaphane is by far the most studied antioxidant ITC, acting primarily through the induction of a transcription factor, the nuclear factor erythroid 2-related factor 2 (Nrf2), which upregulates downstream antioxidant genes/proteins. Paradoxically, sulforaphane, as a pro-oxidant compound, can also increase the levels of reactive oxygen species, a mechanism which is attributed to its anticancer effect. Beyond highlighting the common pro-oxidant and antioxidant effects of sulforaphane, the present paper was designed to assess the diverse anti-inflammatory mechanisms reported to date using a variety of in vitro and in vivo experimental models. Sulforaphane downregulates the expression of pro-inflammatory cytokines, chemokines, adhesion molecules, cycloxyhenase-2, and inducible nitric oxide synthase. The signalling pathways of nuclear factor κB, activator protein 1, sirtuins 1, silent information regulator sirtuin 1 and 3, and microRNAs are among those affected by sulforaphane. These anti-inflammatory actions are sometimes due to direct action via interaction with the sulfhydryl structural moiety of cysteine residues in enzymes/proteins. The following are among the topics discussed in this paper: paradoxical signalling pathways such as the immunosuppressant or immunostimulant mechanisms; crosstalk between the oxidative and inflammatory pathways; and effects dependent on health and disease states.

The Immunomodulatory Effects of Sulforaphane in Exercise-Induced Inflammation and Oxidative Stress: A Prospective Nutraceutical

Sulforaphane (SFN) is a promising molecule for developing phytopharmaceuticals due to its potential antioxidative and anti-inflammatory effects. A plethora of research conducted in vivo and in vitro reported the beneficial effects of SFN intervention and the underlying cellular mechanisms. Since SFN is a newly identified nutraceutical in sports nutrition, only some human studies have been conducted to reflect the effects of SFN intervention in exercise-induced inflammation and oxidative stress. In this review, we briefly discussed the effects of SFN on exercise-induced inflammation and oxidative stress. We discussed human and animal studies that are related to exercise intervention and mentioned the underlying cellular signaling mechanisms. Since SFN could be used as a potential therapeutic agent, we mentioned briefly its synergistic attributes with other potential nutraceuticals that are associated with acute and chronic inflammatory conditions. Given its health-promoting effects, SFN could be a prospective nutraceutical at the forefront of sports nutrition.

Antinociceptive and antiedema effects produced in rats by Brassica oleracea var. italica sprouts involving sulforaphane

Natural products are recognized as potential analgesics since many of them are part of modern medicine to relieve pain without serious adverse effects. The aim of this study was to investigate the antinociceptive and anti-inflammatory activities of an aqueous extract of Brassica oleracea var. italica sprouts (AEBS) and one of its main reported bioactive metabolites sulforaphane (SFN). Antinociceptive activity of the AEBS (30, 100, and 300 mg/kg, i.p. or 1000 and 2000 mg/kg, p.o.) and SFN (0.1 mg/kg, i.p.) was evaluated in the plantar test in rats to reinforce its analgesic-like activity at central level using the reference drug tramadol (TR, 50 mg/kg, i.p.). The anti-inflammatory-like response was determined in the carrageenan-induced oedema at the same dosages for comparison with ketorolac (KET, 20 mg/kg, i.p.) or indomethacin (INDO, 20 mg/kg, p.o.). A histological analysis of the swollen paw was included to complement the anti-inflammatory response. Additionally, acute toxicity observed in clinical analgesics as the most common adverse effects, such as sedation and/or gastric damage, was also explored. As a result, central and peripheral action of the AEBS was confirmed using enteral and parenteral administration, in which significant reduction of the nociceptive and inflammatory responses resembled the effects of TR, KET, or INDO, respectively, involving the presence of SFN. No adverse or toxic effects were observed in the presence of the AEBS or SFN. In conclusion, this study supports that Brassica oleracea var. italica sprouts are a potential source of antinociceptive natural products such as SFN for therapy of pain alone and associated to an inflammation condition.

Advances in Neuropathic Pain Research: Selected Intracellular Factors as Potential Targets for Multidirectional Analgesics

Neuropathic pain is a complex and debilitating condition that affects millions of people worldwide. Unlike acute pain, which is short-term and starts suddenly in response to an injury, neuropathic pain arises from somatosensory nervous system damage or disease, is usually chronic, and makes every day functioning difficult, substantially reducing quality of life. The main reason for the lack of effective pharmacotherapies for neuropathic pain is its diverse etiology and the complex, still poorly understood, pathophysiological mechanism of its progression. Numerous experimental studies, including ours, conducted over the last several decades have shown that the development of neuropathic pain is based on disturbances in cell activity, imbalances in the production of pronociceptive factors, and changes in signaling pathways such as p38MAPK, ERK, JNK, NF-κB, PI3K, and NRF2, which could become important targets for pharmacotherapy in the future. Despite the availability of many different analgesics, relieving neuropathic pain is still extremely difficult and requires a multidirectional, individual approach. We would like to point out that an increasing amount of data indicates that nonselective compounds directed at more than one molecular target exert promising analgesic effects. In our review, we characterize four substances (minocycline, astaxanthin, fisetin, and peimine) with analgesic properties that result from a wide spectrum of actions, including the modulation of MAPKs and other factors. We would like to draw attention to these selected substances since, in preclinical studies, they show suitable analgesic properties in models of neuropathy of various etiologies, and, importantly, some are already used as dietary supplements; for example, astaxanthin and fisetin protect against oxidative stress and have anti-inflammatory properties. It is worth emphasizing that the results of behavioral tests also indicate their usefulness when combined with opioids, the effectiveness of which decreases when neuropathy develops. Moreover, these substances appear to have additional, beneficial properties for the treatment of diseases that frequently co-occur with neuropathic pain. Therefore, these substances provide hope for the development of modern pharmacological tools to not only treat symptoms but also restore the proper functioning of the human body.

Novel Heme Oxygenase-1 Inducers Palliate Inflammatory Pain and Emotional Disorders by Regulating NLRP3 Inflammasome and Activating the Antioxidant Pathway

Chronic pain caused by persistent inflammation is current in multiple diseases and has a strong negative impact on society. It is commonly associated with several mental illnesses, which can exert a negative influence on pain perception, and needs to be eradicated. Nevertheless, actual therapies are not sufficiently safe and effective. Recent reports demonstrate that the induction of heme oxygenase-1 (HO-1) enzyme produces analgesic effects in animals with osteoarthritis pain and reverses the grip strength loss caused by sciatic nerve crush. In this research, we evaluated the potential use of three new HO-1 inducers, 1m, 1a, and 1b, as well as dimethyl fumarate (DMF), for treating persistent inflammatory pain induced by the subplantar injection of complete Freud's adjuvant and the functional deficits and emotional sickness associated. The modulator role of these treatments on the inflammatory and antioxidant pathways were also assessed. Our findings revealed that repeated treatment, for four days, with 1m, 1a, 1b, or DMF inhibited inflammatory pain, reversed grip strength deficits, and reversed the linked anxious- and depressive-like behaviors, with 1m being the most effective. These treatments also suppressed the up-regulation of the inflammasome NLRP3 and activated the expression of the Nrf2 transcription factor and the HO-1 and superoxide dismutase 1 enzymes in the paw and/or amygdala, thus revealing the anti-inflammatory and antioxidant capacity of these compounds during inflammatory pain. Results suggest the use of 1m, 1a, 1b, and DMF, particularly 1m, as promising therapies for inflammatory pain and the accompanying functional disabilities and emotional diseases.

Preconditioning by voluntary wheel running attenuates later neuropathic pain via nuclear factor E2-related factor 2 antioxidant signaling in rats

ABSTRACT

Animal and human studies have shown that exercise prior to nerve injury prevents later chronic pain, but the mechanisms of such preconditioning remain elusive. Given that exercise acutely increases the formation of free radicals, triggering antioxidant compensation, we hypothesized that voluntary running preconditioning would attenuate neuropathic pain by supporting redox homeostasis after sciatic nerve injury in male and female rats. We show that 6 weeks of voluntary wheel running suppresses neuropathic pain development induced by chronic constriction injury across both sexes. This attenuation was associated with reduced nitrotyrosine immunoreactivity-a marker for peroxynitrite-at the sciatic nerve injury site. Our data suggest that prior voluntary wheel running does not reduce the production of peroxynitrite precursors, as expression levels of inducible nitric oxide synthase and NADPH oxidase 2 were unchanged. Instead, voluntary wheel running increased superoxide scavenging by elevating expression of superoxide dismutases 1 and 2. Prevention of neuropathic pain was further associated with the activation of the master transcriptional regulator of the antioxidant response, nuclear factor E2-related factor 2 (Nrf2). Six weeks of prior voluntary wheel running increased Nrf2 nuclear translocation at the sciatic nerve injury site; in contrast, 3 weeks of prior wheel running, which failed to prevent neuropathic pain, had no effect on Nrf2 nuclear translocation. The protective effects of prior voluntary wheel running were mediated by Nrf2, as suppression was abolished across both sexes when Nrf2 activation was blocked during the 6-week running phase. This study provides insight into the mechanisms by which physical activity may prevent neuropathic pain. Preconditioning by voluntary wheel running, terminated prior to nerve injury, suppresses later neuropathic pain in both sexes, and it is modulated through the activation of Nrf2-antioxidant signaling.

Extracellular vesicles derived from microgreens of Raphanus sativus L. var. caudatus Alef contain bioactive macromolecules and inhibit HCT116 cells proliferation

Extracellular vesicles (EVs) are phospholipid bilayer vesicles released from cells, containing natural cargos. Microgreens of Raphanus sativus L. var. caudatus Alef were used in this study as the source of EVs. EVs were isolated by differential centrifugation. The physical properties were determined by dynamic light scattering (DLS) and electron microscopy. The biological and chemical composition were studied by Fourier-transform infrared (FTIR) microspectroscopy and high-performance liquid chromatography analysis, respectively. EVs had a median size of 227.17 and 234.90 ± 23.30 nm determined by electron microscopy and DLS, respectively with a polydispersity index of 0.293 ± 0.019. Electron microscopy indicated the intact morphology and confirmed the size. The FTIR spectra revealed that EVs are composed of proteins as the most abundant macromolecules. Using a curve-fitting analysis, β-pleated sheets were the predominant secondary structure. Notably, the micromolecular biomarkers were not detected. EVs exerted anti-cancer activity on HCT116 colon cancer over Vero normal cells with an IC₅₀ of 448.98 µg/ml and a selectivity index of > 2.23. To conclude, EVs could be successfully prepared with a simple and effective isolation method to contain nano-sized macromolecules possessing anti-cancer activity.

Sulfur compounds: From plants to humans and their role in chronic disease prevention

Sulfur is essential for the health of plants and is an indispensable dietary component for human health and disease prevention. Its incorporation into our food supply is heavily reliant upon the uptake of sulfur into plant tissue and our subsequent intake. Dietary requirements for sulfur are largely calculated based upon requirements for the sulfur-containing amino acids (SAA), cysteine and methionine, to meet the demands for synthesis of proteins, enzymes, co-enzymes, vitamins, and hormones. SAA are found in abundance in animal sources and are relatively low in plants. However, some plants, particularly cruciferous and allium vegetables, produce many protective sulfur-containing secondary metabolites, such as glucosinolates and cysteine sulfoxides. The variety and quantity of these sulfur-containing metabolites are extensive and their effects on human health are wide-reaching. Many benefits appear to be related to sulfur's role in redox biochemistry, protecting against uncontrolled oxidative stress and inflammation; features consistent within cardiometabolic dysfunction and many chronic metabolic diseases of aging. This narrative explores the origins and importance of sulfur, its incorporation into our food supply and dietary sources. It also explores the overarching potential of sulfur for human health, particularly around the amelioration of oxidative stress and chronic inflammation, and subsequent chronic disease prevention.

The Effects of Nuclear Factor Erythroid 2 (NFE2)-Related Factor 2 (Nrf2) Activation in Preclinical Models of Peripheral Neuropathic Pain

Oxidative stress, resulting from an imbalance between the formation of damaging free radicals and availability of protective antioxidants, can contribute to peripheral neuropathic pain conditions. Reactive oxygen and nitrogen species, as well as products of the mitochondrial metabolism such as superoxide anions, hydrogen peroxide, and hydroxyl radicals, are common free radicals. Nuclear factor erythroid 2 (NFE2)-related factor 2 (Nrf2) is a transcription factor encoded by the NFE2L2 gene and is a member of the cap 'n' collar subfamily of basic region leucine zipper transcription factors. Under normal physiological conditions, Nrf2 remains bound to Kelch-like ECH-associated protein 1 in the cytoplasm that ultimately leads to proteasomal degradation. During peripheral neuropathy, Nrf2 can translocate to the nucleus, where it heterodimerizes with muscle aponeurosis fibromatosis proteins and binds to antioxidant response elements (AREs). It is becoming increasingly clear that the Nrf2 interaction with ARE leads to the transcription of several antioxidative enzymes that can ameliorate neuropathy and neuropathic pain in rodent models. Current evidence indicates that the antinociceptive effects of Nrf2 occur via reducing oxidative stress, neuroinflammation, and mitochondrial dysfunction. Here, we will summarize the preclinical evidence supporting the role of Nrf2 signaling pathways and Nrf2 inducers in alleviating peripheral neuropathic pain.

Selected Thiadiazine-Thione Derivatives Attenuate Neuroinflammation in Chronic Constriction Injury Induced Neuropathy

Neuropathic pain refers to a lesion or disease of peripheral and/or central somatosensory neurons and is an important body response to actual or potential nerve damage. We investigated the therapeutic potential of two thiadiazine-thione [TDT] derivatives, 2-(5-propyl-6-thioxo-1, 3, 5-thiadiazinan-3-yl) acetic acid [TDT1] and 2-(5-propyl-2-thioxo-1, 3, 5-thiadiazinan-3-yl) acetic acid [TDT2] against CCI (chronic constriction injury)-induced neuroinflammation and neuropathic pain. Mice were used for assessment of acute toxicity of TDT derivatives and no major toxic/bizarre responses were observed. Anti-inflammatory activity was assessed using the carrageenan test, and both TDT1 and TDT2 significantly reduced carrageenan-induced inflammation. We also used rats for the induction of CCI and performed allodynia and hyperalgesia-related behavioral tests followed by biochemical and morphological analysis using RT-qPCR, immunoblotting, immunohistochemistry and immunofluorescence. Our findings revealed that CCI induced clear-cut allodynia and hyperalgesia which was reversed by TDT1 and TDT2. To determine the function of TDT1 and TDT2 in glia-mediated neuroinflammation, Iba1 mRNA and protein levels were measured in spinal cord tissue sections from various experimental groups. Interestingly, TDT1 and TDT2 substantially reduced the mRNA expression and protein level of Iba1, implying that TDT1 and TDT2 may mitigate CCI-induced astrogliosis. In silico molecular docking studies predicted that both compounds had an effective binding affinity for TNF-α and COX-2. The compounds interactions with the proteins were dominated by both hydrogen bonding and van der Waals interactions. Overall, these results suggest that TDT1 and TDT2 exert their neuroprotective and analgesic potentials by ameliorating CCI-induced allodynia, hyperalgesia, neuroinflammation and neuronal degeneration in a dose-dependent manner.

Sulforaphane alleviates hyperalgesia and enhances analgesic potency of morphine in rats with cancer-induced bone pain

Due to the efficacy and tolerability of the available drugs, the current treatment for cancer-induced bone pain (CIBP) is not considered ideal, and new drugs are required for better treatment results. This study investigated whether intrathecal injection of sulforaphane (SFN) can modulates the noxious behavior associated with CIBP and enhances the analgesic effects of morphine and the possible mechanisms related to these effects were investigated. Walker256 breast cancer cells were injected into the bone marrow cavity of rats to establish the CIBP model. When CIBP rats began to exhibit painful behavior (CIBP 6 days), SFN was injected intrathecally for 7 days. The results showed that SFN alleviated the painful behavioral hypersensitivity caused by cancer, accompanied by nuclear factor, erythroid 2 like 2 (Nrf2), Haem oxygenase 1 (HO-1) activation, nuclear factor kappa B (NF-κB) inhibition and inflammation-related factors (tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-β), interleukin-6 (IL-6), and inducible nitric oxide synthase (iNOS) reduction. In addition, SFN treatment inhibited the proliferation of Walker 256 cells in a dose-dependent manner, promoted mu-opioid receptor (MOR) expression in SH-SY5Y cells and enhanced the antihyperalgesic effects of morphine on CIBP rats by restoring the downregulation of MOR expression in the spinal cord. Interestingly, the antihyperalgesic effects of SFN were partially blocked by opioid receptor antagonists. This study showed that SFN combined with morphine might be a new way to treat CIBP.

An Omega-3-rich Anti-inflammatory Diet Improved Widespread Allodynia and Worsened Metabolic Outcomes in Adult Mice Exposed to Neonatal Maternal Separation

Inflammation plays a key role in the progression and maintenance of chronic pain, which impacts the lives of millions of Americans. Despite growing evidence that chronic pain can be improved by treating underlying inflammation, successful treatments are lacking and pharmaceutical interventions are limited due to drug side effects. Here we are testing whether a 'healthy human' diet (HHD), with or without anti-inflammatory components (HHAID), improves pain-like behaviors in a preclinical model of chronic widespread hypersensitivity induced by neonatal maternal separation (NMS). The HHD and HHAID are isocaloric and macronutrient-matched, have a low glycemic index, and fat content (35 kcal%) that is high in omega-3 fatty acids, while only the HHAID includes a combination of key anti-inflammatory compounds, at clinically relevant doses. Mice on these diets were compared to mice on a control diet with a macronutrient composition commonly used in rodents (20% protein, 70% carbohydrate, 10% fat). Our results demonstrate a benefit of the HHAID on pain-like behaviors in both male and female mice, despite increased caloric intake, adiposity, and weight gain. In female mice, HHAID specifically increased measures of metabolic syndrome and inflammation compared to the HHD and control diet groups. Male mice were susceptible to worsening metabolic measures on both the HHAID and HHD. This work highlights important sexual dimorphic outcomes related to early life stress exposure and dietary interventions, as well as a potential disconnect between improvements in pain-like behaviors and metabolic measures.

The therapeutic potential of Nrf2 inducers in chronic pain: Evidence from preclinical studies

Chronic pain remains an enormous health problem affecting approximatively 30% of the world's population. Opioids as the first line analgesics often leads to undesirable side effects when used long term. Therefore, novel therapeutic targets are urgently needed to the development of more efficacious analgesics. Substantial evidence indicates that excessive reactive oxygen species (ROS) are extremely important to the development of chronic pain. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a master transcription factor regulating endogenous antioxidant defense. Emerging evidence suggests that Nrf2 and its downstream effectors are implicated in chronic inflammatory and neuropathic pain. Notably, controversial results have been reported regarding the expression of Nrf2 and its downstream targets in peripheral and central regions involved in pain transmission. However, our recent studies and results from other laboratories demonstrate that Nrf2 inducers exert potent analgesic effects in various murine models of chronic pain. In this review, we summarized and discussed the preclinical evidence demonstrating the therapeutic potential of Nrf2 inducers in chronic pain. These evidence indicates that Nrf2 activation are beneficial in chronic pain mostly by alleviating ROS-associated pathological processes. Overall, Nrf2-based therapy for chronic pain is an area with great promise, but more research regarding its detailed mechanisms is warranted.

The Neuroimmunology of Chronic Pain: From Rodents to Humans

Chronic pain, encompassing conditions, such as low back pain, arthritis, persistent post-surgical pain, fibromyalgia, and neuropathic pain disorders, is highly prevalent but remains poorly treated. The vast majority of therapeutics are directed solely at neurons, despite the fact that signaling between immune cells, glia, and neurons is now recognized as indispensable for the initiation and maintenance of chronic pain. This review highlights recent advances in understanding fundamental neuroimmune signaling mechanisms and novel therapeutic targets in rodent models of chronic pain. We further discuss new technological developments to study, diagnose, and quantify neuroimmune contributions to chronic pain in patient populations.

The Effect of Rotigotine Extended-Release Microspheres Alone or With Celecoxib on the Inflammatory Pain

Clinical trials of rotigotine extended-release microspheres (RTGT-MS), which provides a sustained release of rotigotine for near 2 weeks in vivo, have been conducted in the treatment of Parkinson’s disease (PD). This study was to investigate the analgesic effect of RTGT-MS, and to know whether RTGT-MS have synergistic interaction with non-steroidal anti-inflammatory drug, celecoxib. The inflammatory pain model of rats was prepared by carrageenan-induced paw edema. The thermal and mechanical stimuli were applied and the hindpaw withdrawal latency (HWL) response was evaluated. Treatment with RTGT-MS increased the HWL in a dose-dependent manner. The ED50 of RTGT-MS was 24.68 ± 1.02 mg/kg. Isobolographic analysis shows that the combination of RTGT-MS and celecoxib resulted in a synergistic antinociceptive effect. Further results demonstrated that antinociceptive effect of RTGT-MS was accompanied with that PKA, cAMP, COX-2, and PGE2 levels were decreased. Chlorpromazine, a dopamine receptor blocker, not only weakened the analgesic effect of RTGT-MS, but also increased the levels of cAMP, PKA, COX-2, and PGE2. These findings provide a rationale for the combination of RTGT-MS and celecoxib in the treatment of PD, which may reduce the dose of celecoxib, thereby lowering the incidence of adverse effects and improving the pain management in PD patients.

The role of carbon monoxide, heme oxygenase 1, and the Nrf2 transcription factor in the modulation of chronic pain and their interactions with opioids and cannabinoids

Chronic pain and its associated comorbidities are difficult to treat, even when the most potent analgesic compounds are used. Thus, research on new strategies to effectively relieve nociceptive and/or emotional disorders accompanying chronic pain is essential. Several studies have demonstrated the anti-inflammatory and antinociceptive effects of different carbon monoxide-releasing molecules (CO-RMs), inducible heme oxygenase 1 (HO-1), and nuclear factor-2 erythroid factor-2 (Nrf2) transcription factor activators in several models of acute and chronic pain caused by inflammation, nerve injury or diabetes. More recently, the antidepressant and/or anxiolytic effects of several Nrf2 transcription factor inducers were demonstrated in a model of chronic neuropathic pain. These effects are mainly produced by inhibition of oxidative stress, inflammation, glial activation, mitogen-activated protein kinases and/or phosphoinositide 3-kinase/phospho-protein kinase B phosphorylation in the peripheral and/or central nervous system. Other studies also demonstrated that the analgesic effects of opioids and cannabinoids are improved when these drugs are coadministered with CO-RMs, HO-1 or Nrf2 activators in different preclinical pain models and that these improvements are generally mediated by upregulation or prevention of the downregulation of µ-opioid receptors, δ-opioid receptors and/or cannabinoid 2 receptors in the setting of chronic pain. We reviewed all these studies as well as studies on the mechanisms of action underlying the effects of CO-RMs, HO-1, and Nrf2 activators in chronic pain. In summary, activation of the Nrf2/HO-1/carbon monoxide signaling pathway alone and/or in combination with the administration of specific analgesics is a valid strategy for the treatment of chronic pain and some associated emotional disorders.

The Integrative Role of Sulforaphane in Preventing Inflammation, Oxidative Stress and Fatigue: A Review of a Potential Protective Phytochemical

Cruciferous vegetables hold a myriad of bioactive molecules that are renowned for possessing unique medicinal benefits. Sulforaphane (SFN) is one of the potential nutraceuticals contained within cruciferous vegetables that is useful for improving health and diseased conditions. The objective of this review is to discuss the mechanistic role for SFN in preventing oxidative stress, fatigue, and inflammation. Direct and indirect research evidence is reported to identify the nontoxic dose of SFN for human trials, and effectiveness of SFN to attenuate inflammation and/or oxidative stress. SFN treatment modulates redox balance via activating redox regulator nuclear factor E2 factor-related factor (Nrf2). SFN may play a crucial role in altering the Keap1/Nrf2/ARE pathway (an intricate response to many stimuli or stress), which induces Nrf2 target gene activation to reduce oxidative stress. In addition, SFN reduces inflammation by suppressing centrally involved inflammatory regulator nuclear factor-kappa B (NF-κB), which in turn downregulates the expression of proinflammatory cytokines and mediators. Exercise may induce a significant range of fatigue, inflammation, oxidative stress, and/or organ damage due to producing excessive reactive oxygen species (ROS) and inflammatory cytokines. SFN may play an effective role in preventing such damage via inducing phase 2 enzymes, activating the Nrf2/ARE signaling pathway or suppressing nuclear translocation of NF-κB. In this review, we summarize the integrative role of SFN in preventing fatigue, inflammation, and oxidative stress, and briefly introduce the history of cruciferous vegetables and the bioavailability and pharmacokinetics of SFN reported in previous research. To date, very limited research has been conducted on SFN’s effectiveness in improving exercise endurance or performance. Therefore, more research needs to be carried out to determine the effectiveness of SFN in the field of exercise and lifestyle factors.

Organosulfur Compounds: A Review of Their Anti-inflammatory Effects in Human Health

Phytonutrients are widely recognized for providing protective human health benefits. Among the phytonutrients, epidemiological and experimental studies show that dietary organosulfur compounds (OSC) play a significant role in preventing various human pathological progressions, including chronic inflammation, by decreasing inflammatory mediators such as nitric oxide (NO), prostaglandin (PG)E₂, interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and IL-17, which are all typical hallmarks of inflammation. Evidence supports OSC in reducing the expression of these markers, thereby attenuating chronic inflammatory processes. Nuclear factor-kappa B (NF-κB) is a key regulating factor during inflammation, and novel evidence shows that OSC downregulates this transcriptional factor, thus contributing to the anti-inflammatory response. In vitro and in vivo studies show that inflammation is mechanistically linked with acute and chronic pathological conditions including cancer, diabetes, obesity, neural dysfunction, etc. Furthermore, a considerable number of experiments have demonstrated that the anti-inflammatory properties of OSC occur in a dose-dependent manner. These experiments also highlight indirect mechanisms as well as potent co-functions for protective roles as antioxidants, and in providing chemoprotection and neuroprotection. In this brief review, we provided an overview of the anti-inflammatory effects of OSC and elucidated probable mechanisms that are associated with inflammation and chronic disorders.

Endogenous opiates and behavior: 2017

This paper is the fortieth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2017 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Organic Isothiocyanates as Hydrogen Sulfide Donors

Significance: Hydrogen sulfide (H₂S), the "new entry" in the series of endogenous gasotransmitters, plays a fundamental role in regulating the biological functions of various organs and systems. Consequently, the lack of adequate levels of H₂S may represent the etiopathogenetic factor of multiple pathological alterations. In these diseases, the use of H₂S donors represents a precious and innovative opportunity. Recent Advances: Natural isothiocyanates (ITCs), sulfur compounds typical of some botanical species, have long been investigated because of their intriguing pharmacological profile. Recently, the ITC moiety has been proposed as a new H₂S-donor chemotype (with a l-cysteine-mediated reaction). Based on this recent discovery, we can clearly observe that almost all the effects of natural ITCs can be explained by the H₂S release. Consistently, the ITC function was also used as an original H₂S-releasing moiety for the design of synthetic H₂S donors and original "pharmacological hybrids." Very recently, the chemical mechanism of H₂S release, resulting from the reaction between l-cysteine and some ITCs, has been elucidated. Critical Issues: Available literature gives convincing demonstration that H₂S is the real player in ITC pharmacology. Further, countless studies have been carried out on natural ITCs, but this versatile moiety has been used only rarely for the design of synthetic H₂S donors with optimal drug-like properties. Future Directions: The development of more ITC-based synthetic H₂S donors with optimal drug-like properties and selectivity toward specific tissues/pathologies seem to represent a stimulating and indispensable prospect of future experimental activities.

Analgesic and Antidepressant Effects of Oltipraz on Neuropathic Pain in Mice by Modulating Microglial Activation

Nerve injury provokes microglial activation, contributing to the sensory and emotional disorders associated with neuropathic pain that do not completely resolve with treatment. In C57BL/6J mice with neuropathic pain induced by chronic constriction of the sciatic nerve (CCI), we evaluated the effects of oltipraz, an antioxidant and anticancer compound, on (1) allodynia and hyperalgesia, (2) microglial activation and pain signaling pathways, (3) oxidative stress, and (4) depressive-like behaviors. Twenty-eight days after surgery, we assessed the effects of oltipraz on the expression of CD11b/c (a microglial marker), phosphoinositide 3-kinase (PI3K)/ phosphorylated protein kinase B (p-Akt), nuclear factor-κB (NF-κB) transcription factor, and mitogen activated protein kinases (MAPK) in the spinal cord, hippocampus, and prefrontal cortex. Our results show that oltipraz alleviates neuropathic pain by inhibiting microglial activation and PI3K/p-Akt, phosphorylated inhibitor of κBα (p-IκBα), and MAPK overexpression, and by normalizing and/or enhancing the expression of antioxidant proteins, nuclear factor erythroid derived-2-related factor 2 (Nrf2), heme oxygenase 1 (HO-1), and NAD(P)H:quinone oxidoreductase-1 (NQO1) in the spinal cord. The inhibition of microglial activation and induction of the Nrf2/HO-1/NQO1 signaling pathway in the hippocampus and/or prefrontal cortex may explain the antidepressant effects of oltipraz during neuropathic pain. These data demonstrate the analgesic and antidepressant effects of oltipraz and reveal its protective and antioxidant properties during chronic pain.

Role of receptor-interacting protein 1/receptor-interacting protein 3 in inflammation and necrosis following chronic constriction injury of the sciatic nerve

Nerve damage often leads to nervous system dysfunction and neuropathic pain. The serine-threonine kinases receptor-interacting protein 1 (RIP1) and 3 (RIP3) are associated with inflammation and cell necrosis. This study aimed to explore the role of RIP1 and RIP3 in sciatic nerve chronic constriction injury (CCI) in mice. On a total of thirty mice, sciatic nerve CCI was performed. The paw withdrawal threshold was measured using Von Frey filaments. The mRNA expression and protein levels of inflammatory factors RIP1 and RIP3 in the dorsal root ganglion (DRG), spinal cord (SC) and hippocampus (HIP) were also determined. We found that paw withdrawal threshold was significantly reduced from the second day after the operation, and the levels of tumour necrosis factor-α and interferon-γ in DRG, SC and HIP were significantly increased on the eighth and 14th days in CCI mice. Furthermore, the downstream signalling molecules of RIP1 and RIP3, GTPase dynamin-related protein-1, NLR family pyrin domain containing-3 (NLRP3) and nuclear factor κB-p65 were upregulated. Increased protein levels of programmed cell death protein 1, which indicate cell death of peripheral and central nervous tissue, were induced by CCI of the sciatic nerve. Overall, this study showed that RIP1 and RIP3 were highly expressed in DRG, SC and HIP of the sciatic nerve in CCI mice and may be involved in chronic neuroinflammation and neuronecrosis.

Treatment With the Delta Opioid Agonist UFP-512 Alleviates Chronic Inflammatory and Neuropathic Pain: Mechanisms Implicated

We investigated whether administration of the δ-opioid receptor (DOR) agonist H-Dmt-Tic-NH-CH(CH2-COOH)-Bid (UFP-512), which also activates nuclear factor erythroid 2-related factor 2 (Nrf2), alleviated chronic inflammatory and/or neuropathic pain and inhibited the depressive-like behaviors associated with persistent neuropathic pain. The possible mechanisms implicated were also assessed. We evaluated the following effects in male C57BL/6J mice with inflammatory pain induced by complete Freund's adjuvant or neuropathic pain caused by the chronic constriction of sciatic nerve: (1) the antinociceptive effects of UFP-512; (2) the effects of UFP-512 on the expression of Nrf2, heme oxygenase 1 (HO-1), NAD(P)H quinone oxidoreductase 1, phosphoinositide 3-kinase (PI3K), protein kinase B (Akt), inducible nitric oxide synthase, DOR, and mitogen-activated protein kinases (MAPK) in the spinal cord of animals with inflammatory or neuropathic pain; (3) the antinociceptive effects of the coadministration of UFP-512 with the Nrf2 activator sulforaphane (SFN); and (4) the antidepressant effects of UFP-512 in animals with depressive-like behaviors associated with neuropathic pain. Our results demonstrated that the intraperitoneal administration of UFP-512 inhibited chronic inflammatory and neuropathic pain and reduced the depressive-like behaviors associated with persistent neuropathic pain. The antiallodynic effects of UFP-512 were significantly augmented when it was coadministered with SFN in both types of chronic pain. The administration of UFP-512 increased/reestablished the spinal cord protein levels of Nrf2 and HO-1 in mice with inflammatory or neuropathic pain. However, while during inflammatory pain UFP-512 inhibited spinal c-Jun N-terminal kinase (JNK) and extracellular signal regulated kinase 1/2 (ERK1/2) phosphorylation induced by peripheral inflammation. This DOR agonist blocked the spinal activated PI3K/Akt signaling pathway under chronic neuropathic pain conditions, but it did not alter the enhanced protein levels of p-JNK or p-ERK1/2 induced by sciatic nerve injury. These results revealed the antinociceptive and antidepressant effects of UFP-512 in animals with chronic pain and the different mechanism of action of this DOR agonist in the presence of inflammatory or neuropathic pain. Our data also suggest the administration of UFP-512 as an alternative for the treatment of chronic pain and the depressive-like behaviors associated with neuropathic pain.

Sorting out the Value of Cruciferous Sprouts as Sources of Bioactive Compounds for Nutrition and Health

Edible sprouts with germinating seeds of a few days of age are naturally rich in nutrients and other bioactive compounds. Among them, the cruciferous (Brassicaceae) sprouts stand out due to their high contents of glucosinolates (GLSs) and phenolic compounds. In order to obtain sprouts enriched in these phytochemicals, elicitation is being increasing used as a sustainable practice. Besides, the evidence regarding the bioavailability and the biological activity of these compounds after their dietary intake has also attracted growing interest in recent years, supporting the intake of the natural food instead of enriched ingredients or extracts. Also, there is a growing interest regarding their uses, consumption, and applications for health and wellbeing, in different industrial sectors. In this context, the present review aims to compile and update the available knowledge on the fundamental aspects of production, enrichment in composition, and the benefits upon consumption of diverse edible cruciferous sprouts, which are sources of phenolic compounds and glucosinolates, as well as the evidence on their biological actions in diverse pathophysiological situations and the molecular pathways involved.

Contribution of Nrf2 Modulation to the Mechanism of Action of Analgesic and Anti-inflammatory Drugs in Pre-clinical and Clinical Stages

Despite the progress that has occurred in recent years in the development of therapies to treat painful and inflammatory diseases, there is still a need for effective and potent analgesics and anti-inflammatory drugs. It has long been known that several types of antioxidants also possess analgesic and anti-inflammatory properties, indicating a strong relationship between inflammation and oxidative stress. Understanding the underlying mechanisms of action of anti-inflammatory and analgesic drugs, as well as essential targets in disease physiopathology, is essential to the development of novel therapeutic strategies. The Nuclear factor-2 erythroid related factor-2 (Nrf2) is a transcription factor that regulates cellular redox status through endogenous antioxidant systems with simultaneous anti-inflammatory activity. This review summarizes the molecular mechanisms and pharmacological actions screened that link analgesic, anti-inflammatory, natural products, and other therapies to Nrf2 as a regulatory system based on emerging evidences from experimental disease models and new clinical trial data.

Sulforaphane Inhibited the Nociceptive Responses, Anxiety- and Depressive-Like Behaviors Associated With Neuropathic Pain and Improved the Anti-allodynic Effects of Morphine in Mice

Chronic neuropathic pain is associated with anxiety- and depressive-like disorders. Its treatment remains a serious clinical problem due to the lack of efficacy of the available therapeutic modalities. We investigated if the activation of the transcription factor Nrf2 could modulate the nociceptive and emotional disorders associated with persistent neuropathic pain and potentiated the analgesic activity of morphine. The possible mechanisms implicated in these effects have been also evaluated. Therefore, in C57BL/6 mice with neuropathic pain induced by the chronic constriction of the sciatic nerve (CCI), we assessed the antinociceptive, anxiolytic, and anti-depressant effects of the repeated intraperitoneal administration of a Nrf2 inducer, sulforaphane (SFN), and the effects of this treatment on the local antinociceptive actions of morphine. The protein levels of Nrf2, heme oxygenase 1 (HO-1), NAD(P)H:quinone oxidoreductase-1 (NQO1), CD11b/c (a microglial activator marker), mitogen-activated protein kinases (MAPK) and μ opioid receptors (MOR) in the spinal cord, prefrontal cortex and hippocampus from mice, at 28 days after CCI, were also evaluated. Our results showed that the repeated administration of SFN besides inhibiting nociceptive responses induced by sciatic nerve injury also diminished the anxiety- and depressive-like behaviors associated with persistent neuropathic pain. Moreover, SFN treatment normalized oxidative stress by inducing Nrf2/HO-1 signaling, reduced microglial activation and JNK, ERK1/2, p-38 phosphorylation induced by sciatic nerve injury in the spinal cord and/or hippocampus and prefrontal cortex. Interestingly, treatment with SFN also potentiated the antiallodynic effects of morphine in sciatic nerve-injured mice by regularizing the down regulation of MOR in the spinal cord and/or hippocampus. This study suggested that treatment with SFN might be an interesting approach for the management of persistent neuropathic pain and comorbidities associated as well as to improve the analgesic actions of morphine.

Topical moringin-cream relieves neuropathic pain by suppression of inflammatory pathway and voltage-gated ion channels in murine model of multiple sclerosis

Background

Neuropathic pain represents the major public health burden with a strong impact on quality life in multiple sclerosis patients. Although some advances have been obtained in the last years, the conventional therapies remain poorly effective. Thus, the discovery of innovative approaches to improve the outcomes for multiple sclerosis patients is a goal of primary importance. With this aim, we investigated the efficacy of the 4-(α−L-rhamnopyranosyloxy)benzyl isothiocyanate (moringin), purified from Moringa oleifera seeds and ready-to-use as topical treatment in experimental autoimmune encephalomyelitis, murine model of multiple sclerosis. Female C57BL/6 mice immunized with myelin oligodendrocyte glycoprotein (MOG_35–55) were topically treated with 2% moringin cream twice daily from the onset of the symptoms until the sacrifice occurred about 21 days after experimental autoimmune encephalomyelitis induction.

Results

Our observations showed the efficacy of 2% moringin cream treatment in reducing clinical and histological disease score, as well as in alleviating neuropathic pain with consequent recovering of the hind limbs and response to mechanical stimuli. In particular, Western blot analysis and immunohistochemical evaluations revealed that 2% moringin cream was able to counteract the inflammatory cascade by reducing the production of pro-inflammatory cytokines (interleukin-17 and interferon-γ) and in parallel by increasing the expression of anti-inflammatory cytokine (interleukin-10). Interestingly, 2% moringin cream treatment was found to modulate the expression of voltage-gated ion channels (results focused on P2X7, Nav 1.7, Nav 1.8 KV4.2, and α2δ-1) as well as metabotropic glutamate receptors (mGluR5 and xCT) involved in neuropathic pain initiation and maintenance.

Conclusions

Finally, our evidences suggest 2% moringin cream as a new pharmacological trend in the management of multiple sclerosis-induced neuropathic pain.

Sulforaphane Modulates Joint Inflammation in a Murine Model of Complete Freund's Adjuvant-Induced Mono-Arthritis

Rheumatoid arthritis (RA) is characterized by inflammation of one or more joints, and affects ~1% of the adult population worldwide. Sulforaphane (SFN) is a natural compound that has been suggested as an antioxidant. Here, SFN’s effects were evaluated in a murine mono-arthritis model. Mono-arthritis was induced in mice by a single intra-articular injection of Complete Freund’s Adjuvant (CFA-10 µg/joint, in 10 µL) into the ipsilateral joint. The contralateral joint received an equal volume of PBS. On the 4th day post-joint inflammation induction, animals received either SFN (10 mg/kg) or vehicle (3% DMSO in saline), intraperitoneally (i.p.), twice a day for 3 days. Joint swelling and secondary mechanical allodynia and hyperalgesia were evaluated over 7 days post-CFA. After this period, animals were culled and their blood and synovial fluid samples were collected for analysis of cell populations, cytokine release and thioredoxin reductase (TrxR) activity. Knee joint samples were also collected for histology. SFN reduced joint swelling and damage whilst increasing the recruitment of Ly6C⁺ and Ly6G⁺ cells to CFA-injected joints. SFN-treated animals presented down-regulation of CD11b and CD62L on synovial fluid Ly6G⁺ cells. Synovial fluid samples obtained from CFA-injected joints and plasma samples of SFN-treated mice presented higher levels of IL-6 and increased activity of TrxR, in comparison with controls. These results indicate that SFN reduces knee joint damage by modulating cell activation/migration to the joints, cytokine production and increasing the activity of TrxR, and therefore, may represent an alternative treatment to joint inflammation.

Role of Transient Receptor Potential Vanilloid 1 in Electroacupuncture Analgesia on Chronic Inflammatory Pain in Mice

Chronic inflammatory pain may result from peripheral tissue injury or inflammation, increasing the release of protons, histamines, adenosine triphosphate, and several proinflammatory cytokines and chemokines. Transient receptor potential vanilloid 1 (TRPV1) is known to be involved in acute to subacute neuropathic and inflammatory pain; however, its exact mechanisms in chronic inflammatory pain are not elucidated. Our results showed that EA significantly reduced chronic mechanical and thermal hyperalgesia in the chronic inflammatory pain model. Chronic mechanical and thermal hyperalgesia were also abolished in TRPV1-/- mice. TRPV1 increased in the dorsal root ganglion (DRG) and spinal cord (SC) at 3 weeks after CFA injection. The expression levels of downstream molecules such as pPKA, pPI3K, and pPKC increased, as did those of pERK, pp38, and pJNK. Transcription factors (pCREB and pNFκB) and nociceptive ion channels (Nav1.7 and Nav1.8) were involved in this process. Inflammatory mediators such as GFAP, S100B, and RAGE were also involved. The expression levels of these molecules were reduced in EA and TRPV1-/- mice but not in the sham EA group. Our data provided evidence to support the clinical use of EA for treating chronic inflammatory pain.

Stable sulforaphane protects against gait anomalies and modifies bone microarchitecture in the spontaneous STR/Ort model of osteoarthritis

Osteoarthritis (OA), affecting joints and bone, causes physical gait disability with huge socio-economic burden; treatment remains palliative. Roles for antioxidants in protecting against such chronic disorders have been examined previously. Sulforaphane is a naturally occurring antioxidant. Herein, we explore whether SFX-01®, a stable synthetic form of sulforaphane, modifies gait, bone architecture and slows/reverses articular cartilage destruction in a spontaneous OA model in STR/Ort mice. Sixteen mice (n=8/group) were orally treated for 3months with either 100mg/kg SFX-01® or vehicle. Gait was recorded, tibiae were microCT scanned and analysed. OA lesion severity was graded histologically. The effect of SFX-01® on bone turnover markers in vivo was complemented by in vitro bone formation and resorption assays. Analysis revealed development of OA-related gait asymmetry in vehicle-treated STR/Ort mice, which did not emerge in SFX-01®-treated mice. We found significant improvements in trabecular and cortical bone. Despite these marked improvements, we found that histologically-graded OA severity in articular cartilage was unmodified in treated mice. These changes are also reflected in anabolic and anti-catabolic actions of SFX-01® treatment as reflected by alteration in serum markers as well as changes in primary osteoblast and osteoclast-like cells in vitro. We report that SFX-01® improves bone microarchitecture in vivo, produces corresponding changes in bone cell behaviour in vitro and leads to greater symmetry in gait, without marked effects on cartilage lesion severity in STR/Ort osteoarthritic mice. Our findings support both osteotrophic roles and novel beneficial gait effects for SFX-01® in this model of spontaneous OA.

Increased seizure susceptibility and other toxicity symptoms following acute sulforaphane treatment in mice

Activation of Nrf2 with sulforaphane has recently gained attention as a new therapeutic approach in the treatment of many diseases, including epilepsy. As a plant-derived compound, sulforaphane is considered to be safe and well-tolerated. It is widely consumed, also by patients suffering from seizure and taking antiepileptic drugs, but no toxicity profile of sulforaphane exists. Since many natural remedies and dietary supplements may increase seizure risk and potentially interact with antiepileptic drugs, the aim of our study was to investigate the acute effects of sulforaphane on seizure thresholds and activity of some first- and second-generation antiepileptic drugs in mice. In addition, some preliminary toxicity profile of sulforaphane in mice after intraperitoneal injection was evaluated. The LD₅₀ value of sulforaphane in mice was estimated at 212.67mg/kg, while the TD₅₀ value - at 191.58mg/kg. In seizure tests, sulforaphane at the highest dose tested (200mg/kg) significantly decreased the thresholds for the onset of the first myoclonic twitch and generalized clonic seizure in the iv PTZ test as well as the threshold for the 6Hz-induced psychomotor seizure. At doses of 10-200mg/kg, sulforaphane did not affect the threshold for the iv PTZ-induced forelimb tonus or the threshold for maximal electroshock-induced hindlimb tonus. Interestingly, sulforaphane (at 100mg/kg) potentiated the anticonvulsant efficacy of carbamazepine in the maximal electroshock seizure test. This interaction could have been pharmacokinetic in nature, as sulforaphane increased concentrations of carbamazepine in both serum and brain tissue. The toxicity study showed that high doses of sulforaphane produced marked sedation (at 150-300mg/kg), hypothermia (at 150-300mg/kg), impairment of motor coordination (at 200-300mg/kg), decrease in skeletal muscle strength (at 250-300mg/kg), and deaths (at 200-300mg/kg). Moreover, blood analysis showed leucopenia in mice injected with sulforaphane at 200mg/kg. In conclusion, since sulforaphane was proconvulsant at a toxic dose, the safety profile and the risk-to-benefit ratio of sulforaphane usage in epileptic patients should be further evaluated.