Evidence for the involvement of descending pain-inhibitory mechanisms in the attenuation of cancer pain by carvacrol aided through a docking study

Antihyperalgesic effect of γ-terpinene complexed in β-cyclodextrin on neuropathic pain model induced by tumor cells

Neuropathic pain is a high-intensity pain that can be caused by compression, transection, injury, nerve infiltration and drug treatment of cancer. Furthermore, drug therapy has low clinical efficacy, many adverse effects and remission of painful symptoms. In this way, natural products derived from plants constitute a promising therapeutic alternative. Therefore, the aim of this study was to evaluate the antihyperalgesic effect of γ-terpinene (γ-TPN) e γ-terpinene in β-cyclodextrin inclusion complexes (TPN/CD) on neuropathic pain induced by tumor cells. Complexation extended the effect time for another 5 h and daily treatment for six days with γ-TPN (50 mg/kg, p.o.) and γ-TPN/β-CD (50 mg/kg, p.o.) significantly reduced (p < 0.001) the mechanical hyperalgesia induced by the administration of 2x106 sarcoma cells 180 in the around the sciatic nerve. In addition, the Grip and Rota-rod techniques demonstrated that there was no interference on the muscle strength and motor coordination of the animals, suggesting that the compound under study does not have central nervous system depressant effects at the doses used. Molecular docking studies demonstrate favorable binding energies between γ-TPN and β-CD, and alpha-2 adrenergic, glutamatergic, opioid and cholinergic receptors. Thus, this study demonstrates the potential of terpinene complexation in controlling neuropathic pain induced by tumor cells.

Promising Effects of Casearins in Tumor-Bearing Mice and Antinociceptive Action against Oncologic Pain: Molecular Docking and In Vivo Findings

Safer analgesic drugs remain a hard challenge because of cardiovascular and/or gastrointestinal toxicity, mainly. So, this study evaluated in vivo the antiproliferative actions of a fraction with casearins (FC) from Casearia sylvestris leaves against human colorectal carcinomas and antihyperalgesic effects on inflammatory- or opiate-based pain relief and oncologic pain in Sarcoma 180 (S180)-bearing mice. Moreover, docking investigations evaluated the binding among Casearin X and NMDA(N-methyl-D-aspartate)-type glutamate receptors. HCT-116 colorectal carcinoma-xenografted mice were treated with FC for 15 days. Antinociceptive assays included chemically induced algesia and investigated mechanisms by pharmacological blockade. Intraplantar region S180-bearing animals received a single dose of FC and were examined for mechanical allodynia and behavior alterations. AutoDock Vina determined molecular interactions among Cas X and NMDA receptor subunits. FC reduced tumor growth at i.p. (5 and 10 mg/kg) and oral (25 mg/kg/day) doses (31.12-39.27%). FC reduced abdominal pain, as confirmed by formalin and glutamate protocols, whose antinociception activity was blocked by naloxone and L-NAME (neurogenic phase) and naloxone, atropine, and flumazenil (inflammatory phase). Meanwhile, glibenclamide potentiated the FC analgesic effects. FC increased the paw withdrawal threshold without producing changes in exploratory parameters or motor coordination. Cas X generated a more stable complex with active sites of the NMDA receptor GluN2B subunits. FC is a promising antitumor agent against colorectal carcinomas, has peripheral analgesic effects by desensitizing secondary afferent neurons, and inhibits glutamate release from presynaptic neurons and/or their action on cognate receptors. These findings emphasize the use of clerodane diterpenes against cancer-related pain conditions.

Metabolomic modelling and neuroprotective effects of carvacrol against acrylamide toxicity in rat's brain and sciatic nerve

The study aimed to investigate the harmful effects of acrylamide (AA), which forms in carbohydrate-rich foods at temperatures above 120°C, on the central and peripheral nervous systems and to evaluate the potential neuroprotective effects of carvacrol (CRV). Male Wistar Albino rats were subjected to AA (40 mg/kg/bw/day) and CRV (50 mg/kg/bw/day) for 15 days. Following the last administration, evaluations revealed disrupted gait, heightened thermal sensitivity and altered paw withdrawal thresholds in AA-exposed rats. Notably, AA reduced glutathione (GSH) and raised malondialdehyde (MDA) levels in both brain and sciatic nerve tissues. AA raised nuclear factor erythroid 2-related factor 2 (Nrf2), caspase 3 and nuclear factor κB (NF-κB) gene expressions while decreasing NR4A2. CRV co-administration mitigated gait abnormalities, elevated GSH levels and lowered MDA levels in both tissues. CRV also modulated gene expression, reducing Nrf2 and NF-κB while increasing NR4A2. Histopathological signs of AA-induced neurodegeneration and elevated glial fibrillary acidic protein levels observed in brain and sciatic nerve tissues were rectified with simultaneous administration of CRV, thereby demonstrating neuroprotective efficacy in both regions. This study is pioneering in demonstrating CRV's neuroprotective potential against AA-induced neurotoxicity in both central and peripheral nervous systems, effectively addressing limitations in the literature. In conclusion, the study revealed AA-induced neurodegeneration in the brain and sciatic nerve, with CRV significantly mitigating this neurotoxicity. This novel research underscores CRV's promise as a neuroprotective agent against AA-induced adverse effects in both the central and peripheral nervous systems.

Antinociceptive Effect of a p-Cymene/β-Cyclodextrin Inclusion Complex in a Murine Cancer Pain Model: Characterization Aided through a Docking Study

Pain is one of the most prevalent and difficult to manage symptoms in cancer patients, and conventional drugs present a range of adverse reactions. The development of β-cyclodextrins (β-CD) complexes has been used to avoid physicochemical and pharmacological limitations due to the lipophilicity of compounds such as p-Cymene (PC), a monoterpene with antinociceptive effects. Our aim was to obtain, characterize, and measure the effect of the complex of p-cymene and β-cyclodextrin (PC/β-CD) in a cancer pain model. Initially, molecular docking was performed to predict the viability of complex formation. Afterward, PC/β-CD was obtained by slurry complexation, characterized by HPLC and NMR. Finally, PC/β-CD was tested in a Sarcoma 180 (S180)-induced pain model. Molecular docking indicated that the occurrence of interaction between PC and β-CD is favorable. PC/β-CD showed complexation efficiency of 82.61%, and NMR demonstrated PC complexation in the β-CD cavity. In the S180 cancer pain model, PC/β-CD significantly reduced the mechanical hyperalgesia, spontaneous nociception, and nociception induced by non-noxious palpation at the doses tested (p < 0.05) when compared to vehicle differently from free PC (p > 0.05). Therefore, the complexation of PC in β-CD was shown to improve the pharmacological effect of the drug as well as reducing the required dose.

Quality-by-Design-Assisted Optimization of Carvacrol Oil-Loaded Niosomal Gel for Anti-Inflammatory Efficacy by Topical Route

Niosomes are multilamellar vesicles that effectively transfer active ingredients into the skin's layers. To improve the active substance's penetration across the skin, these carriers are frequently utilized as topical drug delivery systems. Essential oils (EOs) have garnered significant interest in the field of research and development owing to their various pharmacological activities, cost-effectiveness, and simple manufacturing techniques. However, these ingredients undergo degradation and oxidation over time, leading to a loss of functionality. Niosome formulations have been developed to deal with these challenges. The main goal of this work was to create a niosomal gel of carvacrol oil (CVC) to improve its penetration into the skin for anti-inflammatory actions and stability. By changing the ratio of drug, cholesterol and surfactant, various formulations of CVC niosomes were formulated using Box Behnken Design (BBD). A thin-film hydration technique using a rotary evaporator was employed for the development of niosomes. Following optimization, the CVC-loaded niosomes had shown: 180.23 nm, 0.265, -31.70 mV, and 90.61% of vesicle size, PDI, zeta potential, and EE%. An in vitro study on drug release discovered the rates of drug release for CVC-Ns and CVC suspension, which were found to be 70.24 ± 1.21 and 32.87 ± 1.03, respectively. The release of CVC from niosomes best fit the Higuchi model, and the Korsmeyer-Peppas model suggests that the release of the drug followed the non-Fickian diffusion. In a dermatokinetic investigation, niosome gel significantly increased CVC transport in the skin layers when compared to CVC-conventional formulation gel (CVC-CFG). Confocal laser scanning microscopy (CLSM) of rat skin exposed to the rhodamine B-loaded niosome formulation showed a deeper penetration of 25.0 µm compared to the hydroalcoholic rhodamine B solution (5.0 µm). Additionally, the CVC-N gel antioxidant activity was higher than that of free CVC. The formulation coded F4 was selected as the optimized formulation and then gelled with carbopol to improve its topical application. Niosomal gel underwent tests for pH determination, spreadability, texture analysis, and CLSM. Our findings imply that the niosomal gel formulations could represent a potential strategy for the topical delivery of CVC in the treatment of inflammatory disease.

Therapeutic application of carvacrol: A comprehensive review

Carvacrol is a major natural constituent and is significantly present as an essential oil in aromatic plants and is well known for its numerous biological activities. Therapeutic properties of carvacrol have been demonstrated as anti-oxidant, anticancer, diabetes prevention, cardioprotective, anti-obesity, hepatoprotective and reproductive role, antiaging, antimicrobial, and immunomodulatory properties. The carvacrol biosynthesis has been mediated through mevalonate pathway. Carvacrol has the anticancer ability against malignant cells via decreasing the expressions of matrix metalloprotease 2 and 9, inducing apoptosis, enhancing the expression of pro-apoptotic proteins, disrupting mitochondrial membrane, suppressing extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase signal transduction, and also decreasing the phosphoinositide 3-kinase/protein kinase B. It also decreased the concentrations of alanine aminotransferase, alkaline phosphatase and aspartate aminotransferase, and gamma-glutamyl transpeptidase as well as also restored liver function, insulin level, and plasma glucose level. Carvacrol also has been found to exert antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa, Coagulase-negative staphylococcus, Salmonella spp., Enterococcus sp. Shigella, and Escherichia coli. The current review article summarizes the health-promoting perspectives of carvacrol through various pathways.

γ-Terpinene complexed with β-cyclodextrin attenuates spinal neuroactivity in animals with cancer pain by Ca2+ channel block

OBJECTIVES

Considering that γ-terpinene (γ-TPN) is a monoterpene found in Cannabis oil, with high lipophilicity and limited pharmacokinetics, our objective was to evaluate whether its complexation in β-cyclodextrin (γ-TPN/β-CD) could improve its physicochemical properties and action on cancer pain, as well as verify the mechanisms of action involved.

METHODS

The γ-TPN/β-CD was prepared and submitted to physicochemical characterization. Animals with sarcoma 180 were treated (vehicle, γ-TPN 50 mg/kg, γ-TPN/β-CD 5 mg/kg or morphine) and assessed for hyperalgesia, TNF-α and IL-1β levels, iNOS and c-Fos activity. The effects of γ-TPN on calcium channels were studied by patch-clamp and molecular docking.

RESULTS

β-CD improved the physicochemical properties and prolonged the anti-hyperalgesic effect of γ-TPN. This compound also reduced the levels of IL-1β, TNF-α and iNOS in the tumour, and c-Fos protein in the spinal cord. In addition, it reduced Ca2+ current, presenting favourable chemical interactions with different voltage-dependent calcium channels.

CONCLUSION

These results indicate that the complexation of γ-TPN into β-CD increases its stability and time effect, reducing spinal neuroactivity and inflammation by blocking calcium channels.

α-Phellandrene exhibits antinociceptive and tumor-reducing effects in a mouse model of oncologic pain

Medical reports indicate a prevalence of pain in 50% of patients with cancer. In this context, this article investigated the antinociceptive activity of α-PHE using in vivo Sarcoma-180-induced hypernociception in mice to detail its mechanism(s) of antinociception under different conditions of treatment and tumor progression. Firsty, in vitro cytotoxic action was assessed using melanoma B-16/F-10 and S-180 murine cells and colorimetric MTT assays. For in vivo studies, acute treatment with α-PHE (6.25, 12.5, 25 and 50 mg/kg orally by gavage) was performed on the 1st day after S-180 inoculation. Subacute treatments were performed for 8 days starting on the next day (early protocol) or on day 8 after S-180 inoculation (late protocol). For all procedures, mechanical nociceptive evaluations were carried out by von Frey's technique in the subaxillary region peritumoral tissue (direct nociception) and in right legs of S-180-bearing mice (indirect nociception). α-PHE showed in vitro cytotoxic action on B-16/F-10 and S-180 (CI₅₀ values of 436.0 and 217.9 μg/mL), inhibition of in vivo tumor growth (ranging from 47.3 to 82.7%) and decreased direct (peritumoral tissue in subaxillary region) and indirect (right leg) mechanical nociception in Sarcoma 180-bearing mice with early and advanced tumors under acute or subacute conditions of treatment especially at doses of 25 and 50 mg/kg. It improved serum levels of GSH as well as diminished systemic lipid peroxidation, blood cytokines (interleukin-1β, -4, -6, and tumor necrosis factor-α). Such outcomes highlight α-PHE as a promising lead compound that combines antinociceptive and antineoplasic properties. Its structural simplicity make it a cost-effective alternative, justifying further mechanistic investigations and the development of pharmaceutical formulations. Moreover, the protocols developed and standardized here make it possible to use Sarcoma-180 hypernociception model to evaluate the capacity of new antinociceptive molecules under conditions of cancer-related allodynia.

Monoterpenes as a perspective for the treatment of seizures: A Systematic Review

BACKGROUND

Epilepsy affects more than 65 million people worldwide. Treatment for epileptic seizures is ineffective and has many adverse effects. For this reason, the search for new therapeutic options capable of filling these limitations is necessary.

HYPOTHESIS/PURPOSE

In this sense, natural products, such as monoterpenes, have been indicated as a new option to control neurological disorders such as epilepsy.

STUDY DESIGN

Therefore, the objective of this study was to review the monoterpenes that have anticonvulsive activity in animal models.

METHODS

The searches were performed in the PubMed, Web of Science and Scopus databases in September, 2020 and compiled studies using monoterpenes as an alternative to seizure. Two independent reviewers performed the study selection, data extraction and methodological quality assessment using the Syrcle tool.

RESULTS

51 articles that described the anticonvulsant activity of 35 monoterpenes were selected with action on the main pharmacological target, including GABAA receptors, glutamate, calcium channels, sodium and potassium. In addition, these compounds are capable of reducing neuronal inflammation and oxidative stress caused by seizure.

CONCLUSION

These compounds stand out as a promising alternative for acting through different pharmacological mechanisms, which may not only reduce seizure, but also promote neuroprotective effect by reducing toxicity in brain regions. However, further studies are needed to determine the mechanism of action and safety assessment of these compounds.

Antinociceptive activity of Schinus terebinthifolia leaf lectin (SteLL) in sarcoma 180-bearing mice

ETHNOPHARMACOLOGY RELEVANCE

Schinus terebinthifolia Raddi leaves have been used in folk medicine due to several properties, including antitumor and analgesic effects. The variable efficacy and adverse effects of analgesic drugs have motivated the search for novel antinociceptive agents. It has been reported that the S. terebinthifolia leaf lectin (SteLL) has antitumor activity against sarcoma 180 in mice.

AIM OF THE STUDY

This work aimed to evaluate whether SteLL would reduce cancer pain using an orthotopic tumor model.

MATERIALS AND METHODS

A sarcoma 180 cell suspension was inoculated into the right hind paws of mice, and the treatments (150 mM NaCl, negative control; 10 mg/kg morphine, positive control; or SteLL at 1 and 2 mg/kg) were administered intraperitoneally 24 h after cell inoculation up to 14 days. Spontaneous nociception, mechanical hyperalgesia, and hot-plate tests were performed. Further, the volume and weight of the tumor-bearing paws were measured.

RESULTS

SteLL (2 mg/kg) improved limb use during ambulation. The lectin (1 and 2 mg/kg) also inhibited mechanical hyperalgesia and increased the latency time during the hot-plate test. Naloxone was found to reverse this effect, indicating the involvement of opioid receptors. The tumor-bearing paws of mice treated with SteLL exhibited lower volume and weight.

CONCLUSION

SteLL reduced hyperalgesia due to sarcoma 180 in the paws of mice, and this effect can be related to its antitumor action.

Hepatoprotective Activity of Leptadenia hastata (Asclepiadaceae) on Acetaminophen-Induced Toxicity in Mice: In Vivo Study and Characterization of Bioactive Compounds through Molecular Docking Approaches

MATERIALS AND METHODS

Various aqueous extracts were prepared from this plant and preadministered per os to albino mice 3 h before APAP administration, once daily for one week. Animals from the normal group were given only distilled water while those from negative control received only APAP 250 mg/kg. After treatment, mice were sacrificed, the liver was collected for histopathology analysis, and different biochemical markers (alanine aminotransferase (ALT), superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), malondialdehyde (MDA), and tumor necrosis factor-alpha (TNFα)) were measured. The content of the active extract was analyzed by HPLC/UV. Molecular docking was conducted using iGEMDOCK software, and the drug-likeness and pharmacokinetic profiles were evaluated using Swiss ADME.

RESULTS

APAP administration significantly increased (p < 0.001) ALT in liver homogenates when compared to normal controls whereas the stem decoction at 250 mg/kg significantly (p < 0.001) reduced this activity to a normal value comparable to silymarin 50 mg/kg which is better than leaf and root extracts. Moreover, the stem decoction also significantly reduced the MDA levels (p < 0.05) and increased those of GSH, SOD, and CAT (p < 0.001) at doses of 250 and 500 mg/kg compared to the negative control. A significant (p < 0.001) decrease of TNFα levels and leukocyte infiltration was observed following treatment with this extract. The HPLC/UV analysis of the decoction revealed the presence of dihydroxycoumarin, quinine, and scopoletin with the following retention times: 2.6, 5.1, and 7.01 min, respectively. In silico studies showed that quinine and dihydroxycoumarin had great potentials to be orally administered drugs and possessed strong binding affinities with TNFα, TNF receptor, cyclooxygenase-2, iNOS, cytochrome P450 2E1, and GSH reductase.

CONCLUSION

Based on these results, L. hastata could be considered a source of promising hepatoprotective compounds with antioxidant and anti-inflammatory properties.

Natural products for orofacial nociception in pre-clinical studies: A systematic review

OBJECTIVE

The aim of this systematic review was to summarize the use of natural products (NP) in the treatment of orofacial nociception in animal models.

METHODS

Pre-clinical studies that have evaluated the efficacy of NPs in experimental orofacial nociception were sought in the Medline, Web of Science, Scopus, Embase, SciELO, LILACS and Scholar databases in January 2020, covering the period since the inception of each one. Two reviewers independently selected the studies, extracted the data and evaluated the risk of bias of the included studies.

RESULTS

We included 41 records in qualitative synthesis. Fifty different NPs were investigated. All studies presented positive results for at least one orofacial nociception test. Regarding the risk of bias, most studies presented poor experimental design, mainly lack of randomization and blinding. The main class of isolated compounds tested was terpenes, of which monoterpenes were investigated in the majority of the studies.

CONCLUSION

These results indicate that NPs are effective in treating experimental orofacial nociception and highlight some of these NPs, mainly terpenes, suggesting their potential for translational research.

p-Cymene attenuates cancer pain via inhibitory pathways and modulation of calcium currents

BACKGROUND

Oncological pain is one of the most prevalent and difficult-to-treat symptoms in patients with cancer. p-Cymene (PC) is a monoterpene found in more than 100 different plant species, endowed with various pharmacological properties-particularly antinociceptive.

HYPOTHESIS/PURPOSE

PC has antinociceptive effect in a model of oncologic pain due to the activation of the descending inhibitory pathway of pain.

STUDY DESIGN

A pre-clinical, longitudinal, blind and randomized study.

METHODS

Male Swiss mice were induced with S180 cells in the right hind paw, then treated daily with PC (12.5, 25 and 50 mg/kg, s.c.) and screened for mechanical hyperalgesia, spontaneous nociception, nociception induced by non-noxious palpation, tumor growth, changes in the neuromuscular function and existence of bone degradation in the tumor area. The effect of PC on Ca²⁺ currents (electrophysiological records), histological and neurochemical changes (immunofluorescence for Fos) were also evaluated.

RESULTS

PC reduced (p < 0.05) the mechanical hyperalgesia, the spontaneous (p < 0.001) and non-noxious palpation (p < 0.001) nociceptions, not changing the tumor development, neuromuscular function or histopathological aspects of the paw affected. PC reduced Fos expression in the spinal cord (p < 0.001) and increased this expression in the PAG (p < 0.05) and in the NRM (p < 0.01). PC decreased the density of calcium channel currents (p < 0.05).

CONCLUSION

These results suggest the antinociceptive effect of PC on oncologic pain, probably acting in both ascending and descending pain pathways, and modulating the calcium channel currents in order to exert its effects.

Natural products as a perspective for cancer pain management: A systematic review

BACKGROUND

Cancer is the leading cause of death in the world and one of the main symptoms affecting these individuals is chronic pain, which must be evaluated and treated in its various components. Several drugs are currently used, but beyond the high cost, they have harmful side effects to patients or are transitorily effective. Ergo, there is a need to look for new options for cancer pain relief. Natural products (NPs) present themselves as strong candidates for the development of new drugs for the treatment of chronic pain, such as cancer pain.

PURPOSE

This systematic review aimed to summarize current knowledge about the analgesic profile of NPs in cancer pain.

METHODS

The search included PubMed, Scopus and Web of Science (from inception to June 2018) sought to summarize the articles studying new proposals with NPs for the management of oncological pain. Two independent reviewers extracted data on study characteristics, methods and outcomes.

RESULTS

After an extensive survey, 21 articles were selected, which described the analgesic potential of 15 natural compounds to relieve cancer pain. After analyzing the data, it can be suggested that these NPs, which have targets in central and peripheral mechanisms, are interesting candidates for the treatment of cancer pain for addressing different pharmacological mechanisms (even innovative), but ensuring the safety of these compounds is still a challenge. Likewise, the cannabinoids compounds leave the front as the most promising compounds for direct applicability due to the clinical studies that have already been developed and the background already established about these effects on chronic pain.

CONCLUSION

Regarding these findings, it can be concluded that the variability of possible biological sites of action is strategic for new perspectives in the development of therapeutic proposals different from those available in the current market.

The inclusion complex of carvacrol and β-cyclodextrin reduces acute skeletal muscle inflammation and nociception in rats

BACKGROUND

Skeletal muscle inflammation is strongly associated with pain and may impair regeneration and functional recovery after injury. Since anti-inflammatory and antinociceptive effects have been described for the inclusion complex of carvacrol and β-cyclodextrin (βCD-carvacrol), this study investigated the effects of βCD-carvacrol in a model of acute skeletal muscle inflammation.

METHODS

Muscle injury was induced in male Wistar rats by injection of 3% carrageenan in the gastrocnemius muscle. Rats were orally pretreated with saline (vehicle) or βCD-carvacrol (20, 40, 80 and 180 mg/kg) one hour before administration of carrageenan.

RESULTS

The injection of carrageenan in the gastrocnemius muscle increased tissue myeloperoxidase (MPO) activity (p < 0.001), edema (p < 0.001) and the levels of tumoral necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, macrophage inflammatory protein (MIP-2), but not IL-10 levels. Also, it increased mechanical hyperalgesia and decreased the grip force of animals. Pretreatment with βCD-carvacrol (80 or 160 mg/kg) significantly decreased muscle MPO activity and edema 24 h after injury in comparison to vehicle-pretreated group. Animals pretreated with βCD-carvacrol (160 mg/kg) presented significantly lower levels of IL-1β, IL-6 and MIP-2 and higher levels of IL-10 six hours after induction and lower levels of TNF-α and MIP-2 after 24 h when compared to the vehicle group. Pretreatment with βCD-carvacrol also reduced mechanical hyperalgesia and limited the decrease of grip force (80 or 160 mg/kg; p < 0.001) 6 and 24 h after injury.

CONCLUSION

These results show that βCD-carvacrol reduces inflammation and nociception in a model of acute injury to skeletal muscles.

α-Terpineol reduces cancer pain via modulation of oxidative stress and inhibition of iNOS

α-Terpineol (TP) is present in a wide range of essential oils of the genus Eucalyptus, with recognized potential for a range of biological effects, such as analgesic. Hence, our study aimed to investigate the effect of TP on cancer pain induced by sarcoma 180 in Swiss mice. Our results showed that TP reduced significantly mechanical hyperalgesia and spontaneous and palpation-induced nociception, improved paw use without reducing tumor growth and grip strength. Importantly, no evident biochemical and hematological toxicity was oberved. Furthermore, TP increased the tissue antioxidant capacity due to ferric-reducing antioxidant power (FRAP) and glutathione (GSH). TP also reduced inducible nitric oxide synthase (iNOS) immunocontent in the tumors. Molecular docking estimated that TP binds within the same range of iNOS regions (other iNOS inhibitors), such as N-Nitroarginine methyl ester (L-NAME). These data provide strong evidence that TP may be an interesting candidate for the development of new safe analgesic drugs that are effective for cancer pain control.

Recent development in antihyperalgesic effect of phytochemicals: anti-inflammatory and neuro-modulatory actions

INTRODUCTION

Pain is an unpleasant sensation triggered by noxious stimulation. It is one of the most prevalent conditions, limiting productivity and diminishing quality of life. Non steroidal anti inflammatory drugs (NSAIDs) are widely used as pain relievers in present day practice as pain is mostly initiated due to inflammation. However, due to potentially serious side effects, long term use of these antihyperalgesic drugs raises concern. Therefore there is a demand to search novel medicines with least side effects. Herbal products have been used for centuries to reduce pain and inflammation, and phytochemicals are known to cause fewer side effects. However, identification of active phytochemicals of herbal medicines and clear understanding of the molecular mechanism of their action is needed for clinical acceptance.

MATERIALS AND METHODS

In this review, we have briefly discussed the cellular and molecular changes during hyperalgesia via inflammatory mediators and neuro-modulatory action involved therein. The review includes 54 recently reported phytochemicals with antihyperalgesic action, as per the literature available with PubMed, Google Scholar and Scopus.

CONCLUSION

Compounds of high interest as potential antihyperalgesic agents are: curcumin, resveratrol, capsaicin, quercetin, eugenol, naringenin and epigallocatechin gallate (EGCG). Current knowledge about molecular targets of pain and their regulation by these phytochemicals is elaborated and the scope of further research is discussed.

Carvacrol and human health: A comprehensive review

Carvacrol (CV) is a phenolic monoterpenoid found in essential oils of oregano (Origanum vulgare), thyme (Thymus vulgaris), pepperwort (Lepidium flavum), wild bergamot (Citrus aurantium bergamia), and other plants. Carvacrol possesses a wide range of bioactivities putatively useful for clinical applications such antimicrobial, antioxidant, and anticancer activities. Carvacrol antimicrobial activity is higher than that of other volatile compounds present in essential oils due to the presence of the free hydroxyl group, hydrophobicity, and the phenol moiety. The present review illustrates the state-of-the-art studies on the antimicrobial, antioxidant, and anticancer properties of CV. It is particularly effective against food-borne pathogens, including Escherichia coli, Salmonella, and Bacillus cereus. Carvacrol has high antioxidant activity and has been successfully used, mainly associated with thymol, as dietary phytoadditive to improve animal antioxidant status. The anticancer properties of CV have been reported in preclinical models of breast, liver, and lung carcinomas, acting on proapoptotic processes. Besides the interesting properties of CV and the toxicological profile becoming definite, to date, human trials on CV are still lacking, and this largely impedes any conclusions of clinical relevance.

Protective effect of carvacrol on acetic acid-induced colitis

The pharmacological therapy for inflammatory bowel diseases continues to be problematic, and requires new alternative options. In this study, we tested the hypothesis that carvacrol (CAR), a phenolic monoterpene with anti-inflammatory and antioxidant activities, can treat experimental colitis in mice. C57BL/6 mice (n=8/group) were subjected to intrarectal administration of acetic acid (5%) to induce colitis. Mice were pretreated with CAR (25, 50 or 100mg/kg, p.o.) every 12h for three days prior to the induction. Abdominal hyperalgesia, macroscopic and microscopic colon damage, myeloperoxidase (MPO) activity, tumor necrosis factor (TNF)-α and interleukin (IL)-1β levels, oxidative stress markers, and antioxidant enzyme activities were evaluated. Pretreatment with all doses of CAR significantly decreased abdominal hyperalgesia and colon MPO activity and TNF-α and IL-1β levels. A reduction in macroscopic and microscopic damage (p<0.05) was observed at doses of 50 and 100mg/kg CAR. Pretreatment with CAR significantly reduced lipid peroxidation (for all doses) and increased sulfhydryl groups (at 100mg/kg). This effect was accompanied by a significant increase in catalase, superoxide dismutase, and glutathione peroxidase activities. These findings indicate that CAR protected mice from acetic acid-induced colitis by reducing inflammatory, nociceptive, and oxidative damages.

Fos Protein as a Marker of Neuronal Activity: a Useful Tool in the Study of the Mechanism of Action of Natural Products with Analgesic Activity

Pain treatment is still ineffective in many conditions and remains one of the greatest challenges of modern medicine. Historically, due to the incredible variety of pharmacologically promising natural products (NPs) and the chemical complexity of their compounds, scientists have explored their use as a source of treatment for diseases or symptomatology. Fos protein and its precursor, the gene c-Fos, have been the subject of study in relation to the pathophysiology of pain as a possible tool to aid in its understanding. More recently, it has become a useful tool in the study of NPs with analgesic profile. Thus, this systematic review aimed to investigate the analgesic effect of NPs and derivatives through changes in Fos protein or c-Fos expression in nervous system central. The search terms "analgesics," "Fos," and "drug effects" were used in the databases PubMed, MEDLINE, Scopus, and Embase. Forty-six articles were identified. Twenty-five articles investigated Fos expression in the spinal cord, 1 in dorsal root ganglion, 11 in brain areas, and 9 investigated the association between the spinal cord and brain areas. Although Fos protein expression has been used as a tool in the studies of the mechanism of action of pain in relation to NPs with analgesic activity, the associations between brain areas and the spinal cord-and the possible pathways involved-have not yet been fully elucidated and deserve further study.

D-limonene exhibits superior antihyperalgesic effects in a β-cyclodextrin-complexed form in chronic musculoskeletal pain reducing Fos protein expression on spinal cord in mice

Chronic musculoskeletal pain is one of the main symptoms found in Fibromyalgia with unclear etiology and limited pharmacological treatment. The aim of this study was to complex LIM in β-cyclodextrin (LIM-βCD) and then evaluate its antihyperalgesic effect in an animal model of chronic musculoskeletal pain. Differential scanning calorimetry and scanning electron microscopy was used for the characterization of the inclusion complex. Male Swiss mice were used for experimental procedures where mechanical hyperalgesia, thermal hyperalgesia, muscular strength, Fos immunofluorescence was studied after induction of hyperalgesia. Mechanism of action was also investigated through tail flick test and capsaicin-induced nociception. Endothermic events and morphological changes showed that the slurry complex method was the best method for the complexation. After induction of hyperalgesia, the oral administration of LIM-βCD (50mg/kg) significantly increased the paw withdrawal threshold compared to uncomplexed limonene. Fos immunofluorescence showed that both compounds significantly decreased the number of Fos-positive cells in the dorsal horn. In nociceptive tests, FLU was able to reverse the antinociceptive effect of LIM-βCD. After intraplantar administration of capsaicin, LIM was able to significantly decrease time to lick. LIM-βCD has antihyperalgesic action superior to its uncomplexed form, with possible action in the dorsal horn of the spinal cord. These results suggest the possible applicability of LIM, uncomplexed or complexed with βCD, in conditions such as FM and neuropathic pain, for which there are currently only limited pharmacological options.

Antinociceptive Activity of Borreria verticillata: In vivo and In silico Studies

Borreria verticillata (L.) G. Mey. known vassourinha has antibacterial, antimalarial, hepatoprotective, antioxidative, analgesic, and anti-inflammatory, however, its antinociceptive action requires further studies. Aim of the study evaluated the antinociceptive activity of B. verticillata hydroalcoholic extract (EHBv) and ethyl acetate fraction (FAc) by in vivo and in silico studies. In vivo assessment included the paw edema test, writhing test, formalin test and tail flick test. Wistar rats and Swiss mice were divided into 6 groups and given the following treatments oral: 0.9% NaCl control group (CTRL), 10 mg/kg memantine (MEM), 10 mg/kg indomethacin (INDO), 500 mg/kg EHBv (EHBv 500), 25 mg/kg FAc (FAc 25) and 50 mg/kg FAc (FAc 50). EHBv, FAc 25 and 50 treatments exhibited anti-edematous and peripheral antinociceptive effects. For in silico assessment, compounds identified in FAc were subjected to molecular docking with COX-2, GluN1a and GluN2B. Ursolic acid (UA) was the compound with best affinity parameters (binding energy and inhibition constant) for COX-2, GluN1a, GluN2B, and was selected for further analysis with molecular dynamics (MD) simulations. In MD simulations, UA exhibited highly frequent interactions with residues Arg120 and Glu524 in the COX-2 active site and NMDA, whereby it might prevent COX-2 and NMDA receptor activation. Treatment with UA 10 mg/Kg showed peripheral and central antinociceptive effect. The antinociceptive effect of B. verticillata might be predominantly attributed to peripheral actions, including the participation of anti-inflammatory components. Ursolic acid is the main active component and seems to be a promising source of COX-2 inhibitors and NMDA receptor antagonists.

Evidence for the involvement of TNF-α and IL-1β in the antinociceptive and anti-inflammatory activity of Stachys lavandulifolia Vahl. (Lamiaceae) essential oil and (-)-α-bisabolol, its main compound, in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Stachys lavandulifolia Vahl (Lamiaceae) is a medicinal plant widely used in Turkey and Iranian folk medicine due to its analgesic and anti-inflammatory properties, but little is known about its essential oil.

AIM OF THIS STUDY

We studied the antinociceptive and anti-inflammatory effects of S. lavandulifolia essential oil (EOSl) and (-)-α-bisabolol (BIS), its main compound, in algogen-induced orofacial nociceptive behavior in mice, and assessed the possible involvement of pro-inflammatory cytokines in these profiles.

MATERIALS AND METHODS

The GC-FID and GC-MS analysis of EOSl demonstrated the presence of (-)-α-bisabolol (56.4%), bicyclogermacrene (5.3%), δ-cadinene (4.2%) and spathulenol (2.9%) as the main compounds. Male Swiss mice were pretreated with EOSl (25 or 50mg/kg, p.o.), BIS (25 or 50mg/kg, p.o.), morphine (3mg/kg, i.p.) or vehicle (saline 0.9% with two drops of tween 80, 0.2%), before formalin- (20μl, 2%), capsaicin- (20μl, 2.5µg) or glutamate- (20μl, 25Mm) injection into the right upper lip (perinasal area) in mice. The anti-inflammatory profile of EOSl or BIS (50mg/kg) was assessed by the inflammatory response induced by carrageenan (2% in 0.2mL) in mice (pleurisy model).

RESULTS

Our results showed that p.o. treatment with EOSl and BIS displayed significant inhibitory (p<0.05 or p<0.01 or p<0.001) effects in different orofacial pain tests on mice, but BIS proved to be more effective, significantly reducing nociceptive behavior in all tests including both phases of the formalin test. The analgesic effect is not related to any abnormality since EOSl- or BIS-treated mice exhibited no performance alteration in grip strength. Moreover, EOS1 and BIS exhibited a significant anti-inflammatory effect (p<0.001) in the pleurisy model of inflammation, which seems to be related to a significant reduction (p<0.05) of the pro-inflammatory cytokine TNF-α in BIS treatment, and of the pro-inflammatory cytokine IL-1β (p<0.01) in EOS1 treatment.

CONCLUSION

Our results corroborate the use of S. lavandulifolia in traditional medicine as an analgesic and anti-inflammatory, which seems to be related to (-)-α-Bisabolol, the main compound of EOSl.

Carvacrol suppresses proliferation and invasion in human oral squamous cell carcinoma

Carvacrol, a component of thyme oil, as a novel antitumor agent, has been implicated in several types of cancer cells. However, the mechanisms underlying the effect of carvacrol in human oral squamous cell carcinoma (OSCC) remain unclear. Here, we report that carvacrol significantly inhibits tumor cell proliferation, metastasis and invasion, and induces apoptosis in OSCC. Our results demonstrated that the molecular mechanisms of the effect of carvacrol in Tca-8113 induces G1/S cell cycle arrest through downregulation of CDK regulator CCND1 and CDK4, and upregulation of CDK inhibitor P21. Further analysis demonstrated that carvacrol also inhibited Tca-8113 cells’ clone formation in clonogenic cell survival assay. Student’s t-test (two-tailed) was used to compare differences between groups, and the significance level was P<0.01. Then, treatment of Tca-8113 cells with carvacrol resulted in downregulation of Bcl-2, Cox2, and upregulation of Bax. Carvacrol significantly inhibited the migration and invasion of human OSCC cells by blocking the phosphorylation of FAK and MMP-9 and MMP-2, transcription factor ZEB1, and β-catenin proteins’ expression. Taken together, these results provide novel insights into the mechanism of carvacrol and suggest potential therapeutic strategies for human OSCC.

Natural terpenoids as a promising source for modulation of GABAergic system and treatment of neurological diseases

γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter reducing neural excitability in the mammalian central nervous system (CNS) with three subclasses of receptors. Several conventional drugs and compounds modulate the GABAergic system, demonstrating different pharmacological effects. In this review, interactions of natural terpenoids with the GABAergic system are highlighted with relation to disorders like anxiety, insomnia, convulsion, pain, and cognitive deficits. Terpenoids with various structures affect the function of the GABAergic system via dissimilar mechanisms. Most of the discussed compounds interact with GABA receptors, but especially with the GABAA subtype. This may be due to the fact that researchers tend to assess the interaction of compounds using GABAA receptors. However, bilobalide, a sesquiterpene, showed anticonvulsant properties through the activation of glutamic acid decarboxylase (GAD) enzyme, which is a key enzyme in biosynthesis of GABA. Therefore, further studies evaluating and comparing terpenoids of different classes and their interaction with the GABA system, along with their pharmacokinetic properties, could be worthwhile in future studies.