Citronellol reduces orofacial nociceptive behaviour in mice - evidence of involvement of retrosplenial cortex and periaqueductal grey areas

Possible cerebroprotective effect of citronellal: molecular docking, MD simulation and in vivo investigations

This study focused on molecular docking, dynamic simulation, and in vivo approaches to examine the molecular interactions between citronellal (CT) and neurotoxic proteins. In silico studies of CT were performed using proteins involved in the pathophysiology of stroke, such as interleukin-6 (IL-6), interleukin-12 (IL-12), TNF-α, and nitric oxide synthase (NOS), to determine the binding affinity based on their interactions. The docking results of CT revealed that, among the targets, NOS had a better binding energy of -6.4 Kcal/mol. NOS showed good hydrophobic interactions: TYR A, 347; VAL A, 352; PRO A, 350; TYR A, 373 amino acids. Interactions with IL-6, TNF-α, and IL-12 resulted in lower binding affinities of -3.7, -3.9 and -3.1 Kcal/mol. Based on molecular dynamics simulations of 100 ns, the binding affinity of CT (-66.782 ± 7.309 kJ/mol) was well complemented, and NOS stability at the docked site was confirmed. In in vivo studies, cerebral stroke was induced by occlusion of the bilateral common carotid arteries for 30 min and reperfusion for 4 h. CT treatment protected the brain by decreasing cerebral infarction size, increasing GSH(p < 0.001***), decreasing MPO (p < 0.001***), MDA (p < 0.001***), NO production (p < 0.01**), and AChE (p < 0.001***) compared to stroke rats. Histopathological examination revealed that CT treatment reduced the severity of cerebral damage. The investigation concluded that CT strongly binds to NOS, as observed in molecular docking and dynamic simulation studies, which are involved in nitric oxide production, leading to cerebral damage, and CT treatment reduces NO production and oxidative stress parameters, and increases antioxidants via inhibition of NOS function.Communicated by Ramaswamy H. Sarma.

Gaafar AR, Nafidi HA, Bourhia M. Mechanistic Evaluation of Antiarthritic Effects of Citronellol in CFA-Induced Arthritic Rats

Rheumatoid arthritis (RA) is an autoimmune disease characterized by systemic inflammation, joint tissue damage, pain, and synovitis. It leads to deformity of joints, disability, and even premature death. Markers of inflammation are highly expressed in synovium fluid and serum of arthritic patients and play an important role in the pathophysiology of RA. These transcription factors promote the fabrication of type I interferons and inflammatory cytokines. In RA, degradation of synovial cartilage and bone results from stimulation of proinflammatory cytokines. Citronellol (Ct), a monoterpene alcohol, is found in citrus fruits and essential oils of many aromatic plants. It possesses numerous pharmacological properties such as antioxidant activity and potential antinociceptive and anti-inflammatory effects. Keeping in view the significant anti-inflammatory role of Ct, a trial of 28 days was conducted. Ct was administered orally at three different doses (25, 50, and 100) mg/kg in Freund's adjuvant-induced arthritic rats, and the results were compared with piroxicam, chosen as the standard drug. The antiarthritic activity of the compound was evaluated through measurements of arthritic scoring and plethysmometry before and after treatment. The blood biochemical and hematological parameters and histopathological analyses were performed. Additionally, qPCR was conducted to analyze the mRNA expression levels of TNF-α, IL-1β, NF-κB, MMP3, IL-6, and IL-4 in the blood. ELISA was performed to evaluate the levels of PGE2. The results demonstrated that Ct showed significant results at all doses, but the highest dose proved to be most significant in terms of decreasing arthritic scoring and paw edema, indicating the antiarthritic potential of Ct. Furthermore, the compound was found to downregulate all the proinflammatory cytokines (TNF-α, IL-1β, NF-κB, MMP3, and IL-6) and upregulate the anti-inflammatory cytokine (IL-4). The levels of PGE2 were also reduced which further supported the antiarthritic effects of Ct and validated it as a potential antiarthritic candidate.

The Effects of Essential Oils on the Nervous System: A Scoping Review

Essential oils are a mixture of natural aromatic volatile oils extracted from plants. The use of essential oils is ancient, and has prevailed in different cultures around the world, such as those of the Egyptians, Greeks, Persians, and Chinese. Today, essential oils are used in traditional and complimentary medicines, aromatherapy, massage therapies, cosmetics, perfumes and food industries. The screening effect of essential oils has been studied worldwide. They demonstrate a range of biological activities, such as antiparasitic, antifungal, antibacterial, antiviral, antioxidant, anti-inflammatory, anticancer, antiaging, and neuroprotective properties. In this scoping review, we provide a 10-year updated comprehensive assessment of volatile oils and their effects on the nervous system. MEDLINE, Scopus, and Google Scholar were systematically and strategically searched for original studies investigating these effects from 2012 to 2022. Approximately seventy studies were selected as included studies. Among these studies, several outcomes were reported, including antistress, antianxiety, analgesic, cognitive, and autonomic effects. Some essential oils showed developmental benefits, with the potential to induce neurite outgrowth. The neurotransmitter receptor level can also be modified by essential oil application. Physiological and pathophysiological outcome measures were reported. For physiological outcomes, arousal, cognitive performance, circadian eating behavior, emotional modulation, consumer acceptance, preferences, and willingness to buy were investigated. For pathophysiological conditions, pain, depression, anxiety, stress, sleep disorder, mental fatigue, agitated behavior, and quality of life were measured. In conclusion, essential oils showed promising effects on the nervous system, which can be further applied to their use in functional foods, drinks, and alternative therapy.

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.

Increased Accuracy to c-Fos-Positive Neuron Counting

There is not a described method to count the core label of c-Fos-positive neurons, avoiding false-positive and false-negative results. The aim of this manuscript is to provide guidelines for a secure and accurate method to calculate a threshold to select which core of c-Fos-positive neurons marked by immunofluorescence has to be scored. A background percentage was calculated by dividing the intensity value (0 to 255) of the core of c-Fos-positive neurons by its surrounding background from the 8-bit images obtained in a previous study. Using the background percentage from 20% up to 98%, raising 2% once for each score, as threshold to choose which core has to be counted, a script was written for the R program to count the number of the c-Fos-positive neurons and the comparison between control and experimental groups. The differences of the average number of the core counted c-Fos-positive neurons between control and experimental groups, at all thresholds studied, showed a rising value related to an increase of the background percentage threshold as well as a decrease of its p value related to an increase of the threshold of background percentage. For the smallest thresholds (high intensity of label), the differences between groups are suppressed (false negative). However, for the biggest thresholds (nonspecific label), these differences are always the same (false positive). Therefore, to avoid the false-negative and the false-positive values, it was chosen as the threshold of 62% the inflection point of the linear regression, which is equally different from the biggest and smallest values of the differences between groups.

Involvement of nuclear factor κB and descending pain pathways in the anti-hyperalgesic effect of β-citronellol, a food ingredient, complexed in β-cyclodextrin in a model of complex regional pain syndrome - Type 1

Complex regional pain syndrome type 1 (CRPS-1) is a painful syndrome without effective treatment. In order to explore possible new treatments, we used an animal model of CRPS-1 to examine the effects of β-Citronellol (βCT), a monoterpene found in a variety of plants that has been shown to have analgesic effects. We aimed to assess its effects alone, and complexed with β-cyclodextrin (βCD), which has been previously used to enhance the effects of a number of medicines. The βCT-βCD was characterized physiochemically using high performance liquid chromatography (HPLC) and differential scanning calorimetry (DSC) and shown to have 80% efficiency. In the animal model, Swiss mice were treated with βCT, βCT-βCD, vehicle, pregabalin or sham and evaluated for hyperalgesia and motor coordination. Inflammatory mediators were measured by Western blot or ELISA and the descending pain pathway by immunofluorescence. βCT was shown to have an anti-hyperalgesic effect (without affecting motor coordination) that reduced inflammatory mediators and activated the descending pain pathway, and these effects were increased with complexation in βCD. Our results showed βCT-βCD to be a promising treatment for CRPS-1.

Orofacial antinociceptive activity and anchorage molecular mechanism in silico of geraniol

We aimed to evaluate the orofacial antinociceptive effect of geraniol in mice and its molecular anchorage mechanism. Seven mice per group (probabilistic sample) were treated with geraniol (12.5, 25 and 50 mg/kg, i.p.), morphine (6 mg/kg, i.p.) and vehicle (saline + Tween 80 at 0.2%, i.p.) 30 minutes prior to the beginning of the experiment. Injecting glutamate (25 μM), capsaicin (2.5 μg) and formalin (2%) into the right upper lip (perinasal) of the mouse induced nociception. Behavioral analysis of the animals considered the friction time (in seconds) of the mentioned region using hind or front paws by a researcher blinded to the treatment groups. The statistical analysis was performed blindly, considering α = 5%. The results showed that in the glutamate and capsaicin tests, concentrations of 25 mg/kg and 50 mg/kg presented antinociceptive activity (p < 0.005, power> 80%). In the formalin test, geraniol was able to reduce nociception at a concentration of 50 mg/kg (p < 0.005, power> 80%). In the molecular anchorage study, high values of binding between the evaluated substance and receptors of glutamate were observed (metabotropic glutamate receptor, -87.8501 Kcal/mol; N-methyl-D-aspartate, -86.4451 Kcal/mol; α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid, -85.6755 Kcal/mol). Geraniol presented orofacial antinociceptive activity, probably by interacting with glutamate-related receptors.

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.

Ceftriaxone inhibits stress-induced bladder hyperalgesia and alters cerebral micturition and nociceptive circuits in the rat: A multidisciplinary approach to the study of urologic chronic pelvic pain syndrome research network study

AIMS

Emotional stress plays a role in the exacerbation and development of interstitial cystitis/bladder pain syndrome (IC/BPS). Given the significant overlap of brain circuits involved in stress, anxiety, and micturition, and the documented role of glutamate in their regulation, we examined the effects of an increase in glutamate transport on central amplification of stress-induced bladder hyperalgesia, a core feature of IC/BPS.

METHODS

Wistar-Kyoto rats were exposed to water avoidance stress (WAS, 1 hour/day x 10 days) or sham stress, with subgroups receiving daily administration of ceftriaxone (CTX), an activator of glutamate transport. Thereafter, cystometrograms were obtained during bladder infusion with visceromotor responses (VMR) recorded simultaneously. Cerebral blood flow (CBF) mapping was performed by intravenous injection of [¹⁴ C]-iodoantipyrine during passive bladder distension. Regional CBF was quantified in autoradiographs of brain slices and analyzed in three dimensional reconstructed brains with statistical parametric mapping.

RESULTS

WAS elicited visceral hypersensitivity during bladder filling as demonstrated by a decreased pressure threshold and VMR threshold triggering the voiding phase. Brain maps revealed stress effects in regions noted to be responsive to bladder filling. CTX diminished visceral hypersensitivity and attenuated many stress-related cerebral activations within the supraspinal micturition circuit and in overlapping limbic and nociceptive regions, including the posterior midline cortex (posterior cingulate/anterior retrosplenium), somatosensory cortex, and anterior thalamus.

CONCLUSIONS

CTX diminished bladder hyspersensitivity and attenuated regions of the brain that contribute to nociceptive and micturition circuits, show stress effects, and have been reported to demonstrated altered functionality in patients with IC/BPS. Glutamatergic pharmacologic strategies modulating stress-related bladder dysfunction may be a novel approach to the treatment of IC/BPS.

Eplingiella fruticosa (Lamiaceae) essential oil complexed with β-cyclodextrin improves its anti-hyperalgesic effect in a chronic widespread non-inflammatory muscle pain animal model

Eplingiella fruticosa (Lamiaceae), formally known as Hyptis fruticosa, is an important aromatic medicinal herb used in folk medicine in northeastern Brazil. We aimed to evaluate the anti-hyperalgesic effect of essential oil obtained from E. fruticosa (HypEO) complexed with βCD (HypEO-βCD) in a chronic widespread non-inflammatory muscle pain animal model (a mice fibromyalgia-like model, FM). The HypEO was extracted by hydro distillation and its chemical composition was determined by GC-MS/FID. Moreover, Fos protein expression in the spinal cord was assessed by immunofluorescence. (E)-caryophyllene, bicyclogermacrene, 1,8-cineole, α-pinene, β-pinene and 21 other compounds were identified in the HypEO. The treatment with HypEO-βCD produced a longer-lasting anti-hyperalgesic effect compared to HypEO, without alterations in motor coordination or myorelaxant effects. Moreover, HypEO and HypEO-βCD produced a significant anti-hyperalgesic effect over 7 consecutive treatment days. Immunofluorescence assay demonstrated a decrease in Fos protein expression in the spinal cord (p < 0.001). We demonstrated that the anti-hyperalgesic effect produced by HypEO was improved after complexation with β-CD and this seems to be related to the central pain-inhibitory pathway, suggesting the possible use of E. fruticosa for chronic pain management.

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.

Monoterpenes modulating cytokines - A review

Inflammatory response can be driven by cytokine production and is a pivotal target in the management of inflammatory diseases. Monoterpenes have shown that promising profile as agents which reduce the inflammatory process and also modulate the key chemical mediators of inflammation, such as pro and anti-inflammatory cytokines. The main interest focused on monoterpenes were to develop the analgesic and anti-inflammatory drugs. In this review, we summarized current knowledge on monoterpenes that produce anti-inflammatory effects by modulating the release of cytokines, as well as suggesting that which monoterpenoid molecules may be most effective in the treatment of inflammatory disease. Several different inflammatory markers were evaluated as a target of monoterpenes. The proinflammatory and anti-inflammatory cytokines were found TNF-α, IL-1β, IL-2, IL-5, IL-4, IL-6, IL-8, IL-10, IL-12 IL-13, IL-17A, IFNγ, TGF-β1 and IFN-γ. Our review found evidence that NF-κB and MAPK signaling are important pathways for the anti-inflammatory action of monoterpenes. We found 24 monoterpenes that modulate the production of cytokines, which appears to be the major pharmacological mechanism these compounds possess in relation to the attenuation of inflammatory response. Despite the compelling evidence supporting the anti-inflammatory effect of monoterpenes, further studies are necessary to fully explore their potential as anti-inflammatory compounds.

Chronic orofacial pain animal models - progress and challenges

INTRODUCTION

Chronic orofacial pain is one of the most common pain conditions experienced by adults. Animal models are often selected as the most useful scientific methodology to explore the pathophysiology of the disorders that cause this disabling pain to facilitate the development of new treatments. The creation of new models or the improvement of existing ones is essential for finding new ways to approach the complex neurobiology of this type of pain. Areas covered: The authors describe and discuss a variety of animal models used in chronic orofacial pain (COFP). Furthermore, they examine in detail the mechanisms of action involved in orofacial neuropathic pain and orofacial inflammatory pain. Expert opinion: The use of animal models has several advantages in chronic orofacial pain drug discovery. Choosing an animal model that most closely represents the human disease helps to increase the chances of finding effective new therapies and is key to the successful translation of preclinical research to clinical practice. Models using genetically modified animals seem promising but have not yet been fully developed for use in chronic orofacial pain research. Although animal models have provided significant advances in the pharmacological treatment of orofacial pain, several barriers still need to be overcome for better treatment options.

Evidence for the involvement of TNF-α, IL-1β and IL-10 in the antinociceptive and anti-inflammatory effects of indole-3-guanylhydrazone hydrochloride, an aromatic aminoguanidine, in rodents

BACKGROUND

Indole-3-guanylhydrazone hydrochloride (LQM01) is a new derivative of aminoguanidine hydrochloride, an aromatic aminoguanidine.

METHODS

Mice were treated with LQM01 (5, 10, 25 or 50 mg/kg, i.p.), vehicle (0.9% saline i.p.) or a standard drug. The mice were subjected to carrageenan-induced pleurisy, abdominal writhing induced by acetic acid, the formalin test and the hot-plate test. The model of non-inflammatory chronic muscle pain induced by saline acid was also used. Mice from the chronic protocol were assessed for withdrawal threshold, muscle strength and motor coordination. LQM01 or vehicle treated mice were evaluated for Fos protein.

RESULTS

LQM01 inhibits TNF-α and IL-1β production, as well as leukocyte recruitment during inflammation process. The level of IL-10 in LQM01-treated mice increased in pleural fluid. In addition, LQM01 decreased the nociceptive behavior in the acetic acid induced writhing test, the formalin test (both phases) and increased latency time on the hot-plate. LQM01 treatment also decreased mechanical hyperalgesia in mice with chronic muscle pain, with no changes in muscle strength and motor coordination. LQM01 reduced the number of Fos positive cells in the superficial dorsal horn. This compound exhibited antioxidant properties in in vitro assays.

CONCLUSIONS

LQM01 has an outstanding anti-inflammatory and analgesic profile, probably mediated through a reduction in proinflammatory cytokines release, increase in IL-10 production and reduction in neuron activity in the dorsal horn of the spinal cord in mice.

GENERAL SIGNIFICANCE

Beneficial effects of LQM01 suggest that it has some important clinical features and can play a role in the management of 'dysfunctional pain' and inflammatory diseases.

Analgesic-Like Activity of Essential Oil Constituents: An Update

The constituents of essential oils are widely found in foods and aromatic plants giving characteristic odor and flavor. However, pharmacological studies evidence its therapeutic potential for the treatment of several diseases and promising use as compounds with analgesic-like action. Considering that pain affects a significant part of the world population and the need for the development of new analgesics, this review reports on the current studies of essential oils’ chemical constituents with analgesic-like activity, including a description of their mechanisms of action and chemical aspects.

Antinociceptive effect of Aristolochia trilobata stem essential oil and 6-methyl-5-hepten-2yl acetate, its main compound, in rodents

Aristolochia trilobata L. is an aromatic plant, popularly known as "mil-homens", and its essential oil (EO) is generally used to treat colic, diarrhea and dysentery disorders. We evaluated the antinociceptive effect of A. trilobata stem EO and of its major compound, the (R)-(-)-6-methyl-5-hepten-2-yl acetate (sulcatyl acetate: SA), using acetic acid (0.85%)-induced writhing response and formalin-induced (20 μL of 1%) nociceptive behavior in mice. We also evaluated the EO and SA effect on motor coordination, using the rota-rod apparatus. EO (25, 50 and 100 mg/kg) or SA (25 and 50 mg/kg) reduced nociceptive behavior in the writhing test (p<0.001). EO (100 mg/kg) and SA (25 and 50 mg/kg) decreased the nociception on the first phase of the formalin test (p<0.05). On the second phase, EO (25: p<0.01; 50: p<0.05 and 100 mg/kg: p<0.001) and SA (25 and 50 mg/kg; p<0.001) reduced the nociceptive response induced by formalin. EO and SA were not able to cause changes in the motor coordination of animals. Together, our results suggest that EO has an analgesic profile and SA seems to be one of the active compounds in this effect.

Neurotoxicity of fragrance compounds: A review

Fragrance compounds are chemicals belonging to one of several families, which are used frequently and globally in cosmetics, household products, foods and beverages. A complete list of such compounds is rarely found on the ingredients-list of such products, as "fragrance mixtures" are defined as "trade secrets" and thus protected by law. While some information regarding the general toxicity of some of these compounds is available, their neurotoxicity is known to a lesser extent. Here, we discuss the prevalence and neurotoxicity of fragrance compounds belonging to the three most common groups: phthalates, synthetic musks and chemical sensitizers.

Monoterpenes as a renewable source of biologically active compounds

Monoterpenes and their derivatives play an important role in the creation of new biologically active compounds including drugs. The review focuses on the data on various types of biological activity exhibited by monoterpenes and their derivatives, including analgesic, anti-inflammatory, anticonvulsant, antidepressant, anti-Alzheimer, anti-Parkinsonian, antiviral, and antibacterial (anti-tuberculosis) effects. Searching for novel potential drugs among monoterpene derivatives shows great promise for treating various pathologies. Special attention is paid to the effect of absolute configuration of monoterpenes and monoterpenoids on their activity.

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.

Anti-hyperalgesic effect of Lippia grata leaf essential oil complexed with β-cyclodextrin in a chronic musculoskeletal pain animal model: Complemented with a molecular docking and antioxidant screening

BACKGROUND

Due to its unclear pathophysiology, the pharmacological treatment of fibromyalgia is a challenge for researchers. Studies using medicinal plants, such as those from the genus Lippia, complexed with cyclodextrins (CDs) have shown innovative results.

OBJECTIVE

The present research intended to evaluate the effect of an inclusion complex containing β-cyclodextrin (βCD) inclusion complex with Lippia grata (LG) essential oil in a chronic musculoskeletal pain model, its central activity and its possible interaction with neurotransmitters involved in pain.

METHODS

After acid saline-induced chronic muscle pain, male mice were evaluated for primary and secondary hyperalgesia and muscle strength. Moreover, an antagonist assay was performed to assess the possible involvement of the opioidergic, serotonergic and noradrenergic pathways. In addition, Fos protein in the spinal cord was assessed, and a docking study and antioxidant assays were performed.

RESULTS

The treatment with LG-βCD, especially in the dose of 24mg/kg, was able to significantly decrease (p<0.05) the paw withdrawal and muscle threshold. Furthermore, LG-βCD was shown to affect the opioidergic and serotonergic pathways. There were no significant changes in muscle strength. Fos protein immunofluorescence showed a significant decrease in expression in the dorsal horn of the spinal cord. The main compounds of LG showed through the docking study interaction energies with the alpha-adrenergic and μOpioid receptors. In all antioxidant assays, LG exhibited stronger antioxidant activities than LG-βCD.

CONCLUSION

This study suggested that LG-βCD could be considered as a valuable source for designing new drugs in the treatment of chronic pain, especially musculoskeletal pain.

Sesquiterpene lactone! a promising antioxidant, anticancer and moderate antinociceptive agent from Artemisia macrocephala jacquem

Background

Sesquiterpene lactones (STLs) make a diverse and huge group of bio-active constituents that have been isolated from several plant families. However, the greatest numbers are present in Asteraceae family having more than 3000 different reported structures. Recently several researchers have reported that STLs have significant antioxidant and anticancer potentials.

Methods

To investigate the antioxidant, anticancer and antinociceptive potentials of STLs, gravity column chromatography technique was used for isolation from the biologically rich chloroform fraction of Artemisia macrocephala Jacquem. The antioxidant activity of the isolated STLs was determined by DPPH and ABTS free radical scavenging activity, anticancer activity was determined on 3 T3, HeLa and MCF-7 cells by MTT assay while the antinociceptive activity was determined through acetic acid induced writhings, tail immersion method and formalin induced nociception method.

Results

The results showed that the STLs of Artemisia macrocephala possesses promising antioxidant activity and also it decreased the viability of 3 T3, HeLa and MCF-7 cells and mild to moderate antinociceptive activity.

Conclusion

Sesquiterpenes lactones (STLs) are widely present in numerous genera of the family Asteraceae (compositae). They are described as the active constituents used in traditional medicine for the treatment of various diseases. The present study reveals the significant potentials of STL and may be used as an alternative for the management of cancer. Anyhow, the isolated compound is having no prominent antinociceptive potentials.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-016-1517-y) contains supplementary material, which is available to authorized users.

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.

Docking, characterization and investigation of β-cyclodextrin complexed with citronellal, a monoterpene present in the essential oil of Cymbopogon species, as an anti-hyperalgesic agent in chronic muscle pain model

BACKGROUND

Citronellal (CT) is a monoterpene with antinociceptive acute effect. β-Cyclodextrin (βCD) has enhanced the analgesic effect of various substances.

HYPOTHESIS/PURPOSE

To evaluate the effect of CT both complexed in β-cyclodextrin (CT-βCD) and non-complexed, in a chronic muscle pain model (CMP) in mice.

STUDY DESIGN

The complex containing CT in βCD was obtained and characterized in the laboratory. The anti-hyperalgesic effect of CT and CT-βCD was evaluated in a pre-clinical in vivo study in a murine CMP.

METHODS

The complex was characterized through differential scanning calorimetry, derivative thermogravimetry, moisture determination, infrared spectroscopy and scanning electron microscopy. Male Swiss mice were pre-treated with CT (50mg/kg, po), CT-βCD (50mg/kg, po), vehicle (isotonic saline, po) or standard drug (tramadol4 mg/kg, ip). 60 min after the treatment and then each 1h, the mechanic hyperalgesia was evaluated to obtain the time effect. In addition, the muscle strength using grip strength meter and hyperalgesia were also performed daily, for 7 days. We assessed by immunofluorescence for Fos protein on brains and spinal cords of mice. The involvement of the CT with the glutamatergic system was studied with molecular docking.

RESULTS

All characterization methods showed the CT-βCD complexation. CT-induced anti-hyperalgesic effect lasted until 6h (p <0.001) while CT-βCD lasted until 8h (p <0.001vs vehicle and p <0.001vs CT from the 6th h). CT-βCD reduced mechanical hyperalgesia on all days of treatment (p <0.05), without changing muscle strength. Periaqueductal gray (p <0.01) and rostroventromedular area (p <0.05) showed significant increase in the Fos protein expression while in the spinal cord, there was a reduction (p <0.001). CT showed favorable energy binding (-5.6 and -6.1) to GluR2-S1S2J protein based in the docking score function.

CONCLUSION

We can suggest that βCD improved the anti-hyperalgesic effect of CT, and that effect seems to involve the descending pain-inhibitory mechanisms, with a possible interaction of the glutamate receptors, which are considered as promising molecules for the management of chronic pain such as CMP.

Preparation, Characterization, and Pharmacological Activity of Cymbopogon winterianus Jowitt ex Bor (Poaceae) Leaf Essential Oil of β-Cyclodextrin Inclusion Complexes

This study aimed to evaluate the orofacial antinociceptive effect of the Cymbopogon winterianus essential oil (LEO) complexed in β-cyclodextrin (LEO-CD) and to assess the possible involvement of the central nervous system (CNS). The LEO was extracted, chromatographed, and complexed in β-cyclodextrin. The complex was characterized by differential scanning calorimetry (DSC) and thermogravimetry derivative (TG/DTG). Male Swiss mice (2-3 months) were treated with LEO-CD (50-200 mg/kg, p.o.), vehicle (distilled water, p.o.), or standard drug (i.p.) and subjected to the orofacial nociception formalin-, capsaicin-, and glutamate-induced. After the formalin test, the animals were perfused and the brains subjected to immunofluorescence for Fos. The rota-rod test (7 rpm/min) was carried out. Geraniol (37.57%) was the main compound of LEO. DSC and TG/DTG proved the complexation. The orofacial nociceptive behavior was significantly (p < 0.05) reduced. The number of Fos-positive cells was significantly changed in the dorsal raphe nucleus (p < 0.01), locus coeruleus (p < 0.001), trigeminal nucleus (p < 0.05), and trigeminal thalamic tract (p < 0.05). LEO-CD did not cause changes in motor coordination in the rota-rod test. Thus, our results suggested that LEO-CD has an orofacial antinociceptive profile, probably mediated by the activation of the CNS without changing the motor coordination.

Cyclodextrin-complexed Ocimum basilicum leaves essential oil increases Fos protein expression in the central nervous system and produce an antihyperalgesic effect in animal models for fibromyalgia

O. basilicum leaves produce essential oils (LEO) rich in monoterpenes. The short half-life and water insolubility are limitations for LEO medical uses. β-Cyclodextrin (β-CD) has been employed to improve the pharmacological properties of LEO. We assessed the antihyperalgesic profile of LEO, isolated or complexed in β-CD (LEO/β-CD), on an animal model for fibromyalgia. Behavioral tests: mice were treated every day with either LEO/β-CD (25, 50 or 100 mg/kg, p.o.), LEO (25 mg/kg, p.o.), tramadol (TRM 4 mg/kg, i.p.) or vehicle (saline), and 60 min after treatment behavioral parameters were assessed. Therefore, mice were evaluated for mechanical hyperalgesia (von Frey), motor coordination (Rota-rod) and muscle strength (Grip Strength Metter) in a mice fibromyalgia model. After 27 days, we evaluated the central nervous system (CNS) pathways involved in the effect induced by experimental drugs through immunofluorescence protocol to Fos protein. The differential scanning analysis (DSC), thermogravimetry/derivate thermogravimetry (TG/DTG) and infrared absorption spectroscopy (FTIR) curves indicated that the products prepared were able to incorporate the LEO efficiently. Oral treatment with LEO or LEO-βCD, at all doses tested, produced a significant reduction of mechanical hyperalgesia and we were able to significantly increase Fos protein expression. Together, our results provide evidence that LEO, isolated or complexed with β-CD, produces analgesic effects on chronic non-inflammatory pain as fibromyalgia.

Evaluation of the anti-inflammatory and antinociceptive effects of the essential oil from leaves of Xylopia laevigata in experimental models

Xylopia laevigata (Annonaceae) is a medicinal plant used in folk medicine to treat pain and inflammation. Thus, we investigated the possible antioxidant, antinociceptive, and anti-inflammatory effects of X. laevigata leaf essential oil (EOX) in animal models. Our EOX sample showed the presence of γ-muurolene (17.78%), δ-cadinene (12.23%), bicyclogermacrene (7.77%), and α-copaene (7.17%) as main compounds. EOX presented a strong antioxidant potential according to the DPPH, TBARS, and nitrite production tests. Additionally, pretreatment with EOX, in mice, also significantly produced (P < 0.05 or P < 0.001) antinociceptive effect by reduction of nociceptive behavior (in formalin and writhing tests). The EOX showed c-Fos label in the olfactory bulb, piriform cortex, and periaqueductal gray. Acute administration of EOX exhibited a significant (P < 0.01 or P < 0.001) anti-inflammatory profile in the carrageenan-induced peritonitis and by the carrageenan-induced hindpaw edema tests in mice. Our results provide evidence for the use of X. laevigata by traditional medicine practitioners in the management of pain and inflammatory disorders.

Linalool and linalool complexed in β-cyclodextrin produce anti-hyperalgesic activity and increase Fos protein expression in animal model for fibromyalgia

The analgesic activity of (-)-linalool (LIN), a monoterpene present in essential oils of Lamiaceae species, has been previously demonstrated in rodents. However, its possible use in the treatment of fibromyalgia (FM) was never demonstrated. Additionally, as a short half-life is a limitation for the LIN medicinal application, the employment of drug delivery systems has been used to improve pharmaceutical properties of this compound. We investigated the anti-nociceptive effect of LIN, isolated or in β-cyclodextrin complex (LIN-CD), in an animal model of chronic non-inflammatory muscle pain (a FM animal model), as well as its effect on the central nervous system (CNS). Male Swiss mice were subjected to two injections of acidic saline (pH 4; 20 μL/gastrocnemius) and were treated on alternate days, with LIN-CD (25 mg/kg, p.o.), LIN (25 mg/kg, p.o.), tramadol (TRM 4 mg/kg, i.p.), or vehicle (neutral saline). After 60 min, they were screened for mechanical hyperalgesia (von Frey), motor coordination (rotarod), and muscle strength (grip strength meter) for 27 days. The CNS areas involved in the anti-hyperalgesic activity were evaluated by immunofluorescence. LIN or LIN-CD produced a significant reduction (p < 0.001) of mechanical hyperalgesia on chronic non-inflammatory muscle pain model, which remained for 24 h only in LIN-CD, and these compounds significantly (p < 0.05) activated neurons of the locus coeruleus, nucleus raphe magnus, and periaqueductal gray areas. So, our results suggest that LIN-CD improved analgesic profile of LIN, with a probable involvement of descending pain pathways and the anti-nociceptive effect of linalool in an animal model of chronic non-inflammatory muscle pain. So far, only the investigations in animal models of inflammatory pain and supraspinatus were published.

Evidence for the involvement of spinal cord-inhibitory and cytokines-modulatory mechanisms in the anti-hyperalgesic effect of hecogenin acetate, a steroidal sapogenin-acetylated, in mice

Hecogenin is a steroidal sapogenin largely drawn from the plants of the genus Agave, commonly known as ‘sisal’, and is one of the important precursors used by the pharmaceutical industry for the synthesis of steroid hormones. Hecogenin acetate (HA) is a steroidal sapogenin-acetylated that produces antinociceptive activity. Thus, we evaluate the antihyperalgesic profile of HA in mice in inflammatory models, as well as its possible involvement with c-fos expression on spinal cord area and cytokines to produces analgesic profile. Acute pretreatment with HA (5, 10, or 20 mg/kg; i.p.) inhibited the development of mechanical hyperalgesia induced by carrageenan, TNF-α, dopamine and PGE2. Additionally, the immunofluorescence data demonstrated that acute pretreatment with HA, at all doses tested, significantly inhibited Fos-like expression in the spinal cord dorsal horn normally observed after carrageenan-inflammation. Moreover, HA did not affect the motor performance of the mice as tested in the Rota rod test. This antinociceptive profile seems to be related, at least in part, to a reduction of pro-inflammatory cytokines, as IL-1β. The present results suggest that HA attenuates mechanical hyperalgesia by blocking the neural transmission of pain at the spinal cord levels and by cytokines-inhibitory mechanisms.

Antinociceptive activity of Syzygium cumini leaves ethanol extract on orofacial nociception protocols in rodents

CONTEXT

Syzygium cumini (L.) Skeels (Myrtaceae) is a tree with dark purple fruits, popularly known as "jambolão" or "jambolan". In folk medicine, this plant is used for the treatment of diabetes and inflammatory conditions.

OBJECTIVE

We investigated the antinociceptive effect of ethanol extract (EE) from S. cumini leaves on orofacial nociception.

MATERIAL AND METHODS

The antinociceptive effects of the EE obtained from the leaves of S. cumini were evaluated in mice using formalin- and glutamate-induced orofacial nociception.

RESULTS

ESI-MS/MS analyses demonstrated that major constituents in the analyzed samples coincided with the mass of the phenolic acids and flavonoids. In pharmacological approach, pre-treatment with EE (100, 200, or 400 mg/kg, p.o.) significantly reduced (p<0.05 or p<0.01) the percentage of paw licks time during phase 2 (43.2, 47.1, and 57.4%, respectively) of a formalin pain test when compared to control group animals. This effect was prevented by pretreatment with glibenclamide and N(G)-nitro-l-arginine (l-NOARG). The extract, all doses, also caused a marked inhibition (p<0.01 or p<0.001) of glutamate-induced orofacial nociception (38.8, 51.7, and 54.7%) when compared with the control group. No effect was observed with the rota-rod model.

CONCLUSIONS

We can suggest that the antinociceptive effect of the EE is mediated by peripheral mechanisms, possibly involving KATP channels and the nitric oxide pathways. These effects appear to be related to the presence of flavonoids compounds, such as quercetin.

β-cyclodextrin complex containing Lippia grata leaf essential oil reduces orofacial nociception in mice - evidence of possible involvement of descending inhibitory pain modulation pathway

The treatment of orofacial pain remains a major challenge for modern medicine. Thus, we prepared and physicochemically characterized a new β-cyclodextrin complex containing Lippia grata leaf essential oil (β-CD/EO) to investigate their possible antinociceptive activity in animal models of orofacial pain. The results of Differential scanning calorimeter (DSC) and Thermogravimetry/derivative thermogravimetry (TG/DTG) showed that the products prepared by Slurry complexation (SC) method were able to incorporate greater amounts of EO. In the X-ray diffractogram, it was shown that complex between EO and β-CD was formed. Male Swiss mice were pre-treated with β-CD/EO (6, 12 or 24 mg/kg, per os, gavage, p.o.), morphine (5 mg/kg, i.p.) or vehicle (distilled water, p.o.) 1 hr before treatment with formalin (20 μL, 2%), capsaicin (20 μL, 2.5 μg) or glutamate (40 μL, 25 μM) into the right upper lip. Our results demonstrated that p.o. treatment with β-CD/EO was significantly (p < 0.05 or p < 0.001) capable of reducing the nociceptive face-rubbing behaviour in both phases of the formalin test. β-CD/EO-treated mice were also significantly (p < 0.05 or p < 0.001) protected against nociception induced by capsaicin and glutamate. For the action in the central nervous system (CNS), ninety minutes after the treatment, the mice were perfused, the brains collected, crioprotected, cut in a criostate and submitted to an immunofluorescence protocol for Fos protein. The immunofluorescence protocol demonstrated that the β-CD/EO significantly activated (p < 0.05; p < 0.01 or p < 0.001) the motor cortex, the Locus ceruleus, the nucleus raphe magnus and the periaqueductal gray of the CNS. These effects apparently did not alter, in tested doses, the motor coordination of mice in the rota-rod test. Our results proposed that β-CD/EO might present an important draft of drug to the study of new compounds for the treatment of orofacial pain.