Role of peripheral and central sensitization in the anti-hyperalgesic effect of hecogenin acetate, an acetylated sapogenin, complexed with ß-cyclodextrin: Involvement of NFκB and p38 MAPK pathways.

Neuropathic pain develops due to injury to the somatosensory system, affecting the patient's quality of life. In view of the ineffectiveness of the current pharmacotherapy, substances obtained from natural products (NPs) are a promising alternative. One NP that has been discussed in the literature is hecogenin acetate (HA), a steroidal sapogenin with anti-inflammatory and antinociceptive activity. However, HA has low water solubility, which affects its bioavailability. Thus, the objective of this study was to evaluate the anti-hyperalgesic activity of pure and complexed hecogenin acetate (HA/ßCD) in an animal model of chronic neuropathic and inflammatory pain. The inclusion complex was prepared at a molar ratio of 1:2 (HA:ßCD) by the lyophilization method. For the induction of chronic inflammatory pain, the mice received an intraplantar injection of CFA (complete Freund's adjuvant), and were evaluated for mechanical hyperalgesia and for the levels of myeloperoxidase (MPO) in the skin of the paw after eight days of treatment. HA and HA/ßCD reduced mechanical hyperalgesia in relation to the vehicle group until the fourth and fifth hours, respectively, in the acute evaluation, with a superior effect of the complexed form over the pure form in the second and third hour after treatment (p < 0.001). In the chronic evaluation, HA and HA/ßCD reduced hyperalgesia in relation to the vehicle in the eight days of treatment (p < 0.001). Both pure (p < 0.01) and complexed (p < 0.001) forms reduced myeloperoxidase activity in the skin of the animals' paw. Groups of animals subjected to the same pharmacological protocol were submitted to the partial sciatic nerve ligation (PSNL) model and evaluated for mechanical and thermal hyperalgesia, and cold allodynia. HA and HA/ßCD reduced mechanical hyperalgesia until the fourth and sixth hours, respectively, and both reduced hyperalgesia in relation to the vehicle in the chronic evaluation (p < 0.001). HA and HA/ßCD also reduced thermal hyperalgesia and cold allodynia (p < 0.05 and p < 0.001, respectively). The analysis of the spinal cord of these animals showed a decrease in the levels of the pro-inflammatory cytokines TNF-α, IL-1ß and IL-6 and a reduction in the phosphorylation of NFκB and p38MAPK, as well as a decrease in microglioses compared to the vehicle group. In addition, HA/ßCD reduced the nociception induced by intraplantar injection of agonist TRPA1 (p < 0.01) and TRPM8 (p < 0.05). Treatment for eight days with HA and HA/ßCD showed no signs of gastric or liver damage. HA and HA/ßCD were, therefore, shown to have antinociceptive effects in chronic pain models. Based on our exploration of the mechanisms of the action of HA, these effects are likely to be related to inhibited leukocyte migration, interaction with the TRPA1 and TRPM8 receptors, reduced pro-inflammatory cytokines levels, microglial expression and suppression of NF-κB p65 and p38 MAPK pathway signaling. Therefore, HA/ßCD has great potential for use in the treatment of chronic pain.

Involvement of the PKA pathway and inhibition of voltage gated Ca2+ channels in antihyperalgesic activity of Lippia grata/ß-cyclodextrin.

Neuropathic pain (NP) is a difficult condition to treat because of the modest efficacy of available drugs. New treatments are required. In the study we aimed to investigate the effects of the essential oil from Lippia grata alone or complexed in ß-cyclodextrin (LG or LG-ßCD) on persistent inflammatory and neuropathic pain in a mouse model. We also investigated Ca2+ currents in rat dorsal root ganglion (DRG) neurons. Male Swiss mice were treated with LG or LG/ß-CD (24 mg/kg, i.g.) and their effect was evaluated using an acute inflammatory pleurisy model and nociception triggered by intraplantar injection of an agonist of the TRPs channels. We also tested their effect in chronic pain models: injection of Freund's Complete Adjuvant and partial sciatic nerve ligation (PSNL). In the pleurisy model, LG reduced the number of leukocytes and the levels of TNF-α and IL-1ß. It also inhibited cinnamaldehyde and menthol-induced nociceptive behavior. The pain threshold in mechanical and thermal hyperalgesia was increased and paw edema was decreased in models of inflammatory and neuropathic pain. PSNL increased inflammatory protein contents and LG and LG-ßCD restored the protein contents of TNF-α, NF-κB, and PKA, but not IL-1ß and IL-10. LG inhibited voltage gated Ca2+ channels from DRG neurons. Our results suggested that LG or LG-ßCD produce anti-hyperalgesic effect in chronic pain models through reductions in TNF-α levels and PKA, and inhibited voltage-gated calcium channels and may be innovative therapeutic agents for the management of NP.

Central nervous system and analgesic profiles of Lippia genus

Abstract Many people use medicinal plants to relieve disorders related to the central nervous system, such as depression, epilepsy, anxiety and pain, even though the effectiveness of most of them has not yet been proven through scientific studies. Plants of the Lippia genus, Verbenaceae, are widely used in ethnobotany as a food, for seasoning and in antiseptic remedies. They are also marketed and used for the treatment of different types of pain, including stomach ache, abdominal pain and headache, as well as being used as sedatives, anxiolytics and anticonvulsants. Despite their widespread use, there are no reviews on the central nervous system profile of plants of this genus. Therefore, the databases Medline-PubMed, Embase, Scopus and Web of Science were searched using the terms Lippia and biologic activity. Thirty-five papers were found. Eleven species of Lippia showed central nervous system activity, with leaves and the aerial parts of plants being the most commonly used, especially in aqueous and ethanol extracts or volatile oil. The species are composed mainly of terpenoids and phenylpropanoids, including polyketides, flavonoids and in less quantity some alkaloids. Although several species of Lippia present analgesic activity, most studies have not explored the mechanisms responsible for this effect, however, there is some evidence that volatile oils and constituents of the extracts may be responsible for the relief of some CNS disorders, but the effects on pain modulation seem to be the most exploited so far.

Anti-hyperalgesic effect of Lippia grata leaf essential oil complexed with ß-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 ß-cyclodextrin (ßCD) 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-ßCD, especially in the dose of 24mg/kg, was able to significantly decrease (p<0.05) the paw withdrawal and muscle threshold. Furthermore, LG-ßCD 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-ßCD. CONCLUSION: This study suggested that LG-ßCD could be considered as a valuable source for designing new drugs in the treatment of chronic pain, especially musculoskeletal pain.

Natural products assessed in animal models for orofacial pain – a systematic review

ABSTRACT Orofacial pain is related to tissues of the head, face, neck and all the intraoral structures; it is rather debilitating to the patient and also difficult to treat. There are relatively few studies dedicated to the use of natural products to alleviate orofacial pain in preclinical experiment models (performed in experimental animals which provide support for clinical trials). Main objectives of the present systematic review summarize the studies on natural products assessed in animal models for orofacial pain seeking to give evidence to future development of new pharmaceutical products to manage the orofacial pain. Our review includes a thorough search of literature using the terms of orofacial pain, facial pain, medicinal plants and natural products. This search was performed using to retrieve English language articles in Medline-PubMed, Scopus and Web of Science. A total of eighteen studies were included in our survey for the inclusion criteria. Firstly, this review identified 210 citations from electronic search, after removal of duplicates and screening for relevant titles and abstracts, a total of eighteen articles were selected to the inclusion criteria established. Our findings suggest that natural products can be a promising or a trump tool for the development of new drugs to treat orofacial pain conditions, but the researchers that deal with experimental preclinical trials of new drugs (including natural products or synthetic drugs) for orofacial pain conditions urgently need to show translational evidence (with clinical approach) of these compounds.

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.

A systematic review of the wound-healing effects of monoterpenes and iridoid derivatives.

The search for more effective and lower cost therapeutic approaches for wound healing remains a challenge for modern medicine. In the search for new therapeutic options, plants and their metabolites are a great source of novel biomolecules. Among their constituents, the monoterpenes represent 90% of essential oils, and have a variety of structures with several activities such as antimicrobial, anti-inflammatory, antioxidant and wound healing. Based on that, and also due to the lack of reviews concerning the wound-healing activity of monoterpenes, we performed this systematic review-which provides an overview of their characteristics and mechanisms of action. In this search, the terms "terpenes", "monoterpenes", "wound healing" and "wound closure techniques" were used to retrieve articles published in LILACS, PUBMED and EMBASE until May 2013. Seven papers were found concerning the potential wound healing effect of five compouds (three monoterpenes and two iridoid derivatives) in preclinical studies. Among the products used for wound care, the films were the most studied pharmaceutical form. Monoterpenes are a class of compounds of great diversity of biological activities and therapeutic potential. The data reviewed here suggest that monoterpenes, although poorly studied in this context, are promising compounds for the treatment of chronic wound conditions.

ß-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 ß-cyclodextrin complex containing Lippia grata leaf essential oil (ß-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 ß-CD was formed. Male Swiss mice were pre-treated with ß-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 ß-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. ß-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 ß-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 ß-CD/EO might present an important draft of drug to the study of new compounds for the treatment of orofacial pain.