Novel strategies for the treatment of inflammatory hyperalgesia

Chemical characterization and pharmacological assessment of polysaccharide free, standardized cashew gum extract (Anacardium occidentale L.)

ETHNOPHARMACOLOGICAL RELEVANCE

The cashew gum (Anacardium occidentale L.) is used in traditional Brazilian medicine in the treatment of inflammatory conditions, asthma, diabetes, and gastrointestinal disturbances.

AIM OF THE STUDY

In the present study, we aimed at forming a chemical characterization and investigation of the antinociceptive and anti-inflammatory activities of the aqueous extract of cashew gum without the presence of polysaccharides in its composition (CGE).

MATERIALS AND METHODS

The CGE was obtained after the precipitation and removal of polysaccharides through the use of acetone. After, the acetone was removed by rotaevaporation, and the concentrated extract was lyophilized. The chemical characterization of CGE was performed by liquid chromatography mass spectrometry (LC-MS) and tandem mass spectrometry (MS/MS) analyses. Mice were used for the evaluation of the antinociceptive and anti-inflammatory activities. CGE was analyzed via the Irwin test, acetic acid-induced writhing test, formalin-induced pain test, and carrageenan-induced paw edema test. The motor activity or probable sedation was verified through the chimney, open-field, and sodium pentobarbital-induced sleep tests. We investigated if the analgesic and anti-inflammatory effects of CGE depend of reduction in PGE₂ levels, were performed the carrageenan or PGE₂-induced hyperalgesia tests.

RESULTS

The chemical characterization of CGE showed the presence of anacardic acids as the predominant phytoconstituents. The treatment with CGE (75, 150, and 300mg/kg, p.o.) inhibited the number of writhing in a dose-dependent manner. With an intermediate dose, CGE did not cause motor impairment with the chimney test or alterations in either the open-field or sodium pentobarbital-induced sleep. In the formalin-induced pain test, CGE (150mg/kg, p.o.) produced an antinociceptive effect only in the first phase of the test, suggesting anti-inflammatory activity. With the same dosage, CGE also reduced the carrageenan-induced paw edema at all hours of the test, confirming its anti-inflammatory effect. Furthermore, CGE (150mg/kg, p.o.) presented an antihyperalgic effect at all hours of the carrageenan-induced hyperalgesia test. However, this dose of CGE was not able to reduce the hyperalgesia induced by PGE₂, suggesting that the anti-inflammatory effect of this extract depends on the reduction in the PGE₂ levels.

CONCLUSION

The anacardic acids are the predominant phytoconstituents identified in the CGE. The action mechanisms of CGE suggest the reduction in the PGE₂ levels. These findings support the use of cashew gum in popular medicine and demonstrate that part of its antinociceptive and anti-inflammatory effects should also be attributed to the presence of anacardic acids in its composition, independent of the presence of polysaccharides.

Buddleja thyrsoides Lam. crude extract presents antinociceptive effect on an arthritic pain model in mice

Arthritis is a chronic inflammatory disease which reduces the life quality of affected individuals. Therapeutic tools used for treating inflammatory pain are associated with several undesirable effects. Buddleja thyrsoides Lam., known as ‘Barbasco’ or ‘Cambara’, is mostly used in several disorders and possesses antirheumatic, anti-inflammatory, and analgesic properties. Here, we investigated the antinociceptive and anti-inflammatory effects of the B. thyrsoides crude extract applied orally and topically in acute pain models and an arthritic pain model induced by complete Freund's adjuvant (CFA) paw injection in male mice (25–30 g). The high-performance liquid chromatography (HPLC) of the B. thyrsoides extract crude revealed the presence of the lupeol, stigmasterol, and β-sitosterol. The stability study of the B. thyrsoides gel did not show relevant changes at low temperatures. The oral treatment with the B. thrysoides extract prevented the capsaicin-induced spontaneous nociception and the acetic acid-induced abdominal writhing, but did not alter the thermal threshold in the tail immersion test. The B. thyrsoides antinociceptive effect was not reversed by naloxone in the capsaicin test. The B. thyrsoides oral or topical treatment reversed the CFA-induced mechanical allodynia and thermal hyperalgesia with maximum inhibition (Imax) of 69 ± 6 and 68 ± 5% as well as 78 ± 15 and 87 ± 12%, respectively. Moreover, the topical but not oral treatment inhibited the CFA-induced cell infiltration, but did not reduce the paw edema significantly. The oral treatment with B. thyrsoides did not cause adverse effects. These findings suggest that the oral or topical treatment with B. thyrsoides presents antinociceptive actions in an arthritic pain model without causing adverse effects.

Molecular Docking Studies of Phytocompounds from the Phyllanthus Species as Potential Chronic Pain Modulators

The study of inflammatory pain has been one of the most rapidly advancing and expanding areas of pain research in recent years. Studies from our lab have demonstrated the chronic pain-modulating potential of the Phyllanthus species and their probable interaction with various inflammatory mediators involving enzymes like COX-2 and PGE synthase, cytokines like TNF-alpha and IL-1 beta, and with the NMDA receptor. Inflammatory mediators which play a crucial role in chronic inflammatory hyperalgesia and its subsequent modulation were selected for their interactions with 86 structurally diverse phytoconstituents identified from the Phyllanthus species.

The docking analysis of the target proteins with the phytochemical ligands was performed using VLifeMDS software. The docking scores and analysis of the interactions of the phytocompounds with target proteins suggest that important molecules like lupeol, phyllanthin, hypopyllanthin, corilagin, epicatechin, and most of the other compounds have the ability to bind to multiple targets involved in inflammatory hyperalgesia.

Our study strongly suggests that the findings of the present study could be exploited in the future for designing ligands in order to obtain novel molecules for the treatment and management of chronic pain.

Simultaneous tissue profiling of eicosanoid and endocannabinoid lipid families in a rat model of osteoarthritis

We describe a novel LC method for the simultaneous and quantitative profiling of 43 oxylipins including eicosanoids, endocannabinoids, and structurally related bioactive lipids with modified acyl groups. The LC-MS/MS method uses switching at a defined time between negative and positive electrospray ionization modes to achieve optimal detection sensitivity for all the lipids. The validated method is linear over a range of 0.01–5 nmol/g (0.1–50 nmol/g for 2-arachidonoyl glycerol) with intra- and interday precision and accuracy between 1.38 and 26.76% and 85.22 and 114.3%, respectively. The method successfully quantified bioactive lipids in different tissue types in the rat, including spinal cord, dorsal root ganglia (DRGs), knee joint, brain, and plasma. Distinct regional differences in the pattern of lipid measured between tissue types were observed using principle component analysis. The method was applied to analyze tissue samples from an established preclinical rat model of osteoarthritis (OA) pain and showed that levels of 12-hydroxyeicosatetraenoic acid were significantly increased in the OA rat knee joint compared with controls, and that 15-hydroxyeicosatetraenoic acid was significantly increased in the DRGs in the model of OA compared with controls. The developed LC-MS/MS method has the potential to provide detailed pathway profiling in tissues and biofluids where the disruption of bioactive oxylipins may be involved in disease states.

Kinin-mediated inflammation in neurodegenerative disorders

The mediatory role of kinins in both acute and chronic inflammation within nervous tissues has been widely described. Bradykinin, the major representative of these bioactive peptides, is one of a few mediators of inflammation that directly stimulates afferent nerves due to the broad expression of specific kinin receptors in cell types in these tissues. Moreover, kinins may be delivered to a site of injury not only after their production at the endothelium surface but also following their local production through the enzymatic degradation of kininogens at the surface of nerve cells. A strong correlation between inflammatory processes and neurodegeneration has been established. The activation of nerve cells, particularly microglia, in response to injury, trauma or infection initiates a number of reactions in the neuronal neighborhood that can lead to cell death after the prolonged action of inflammatory substances. In recent years, there has been a growing interest in the effects of kinins on neuronal destruction. In these studies, the overexpression of proteins involved in kinin generation or of kinin receptors has been observed in several neurologic disorders including neurodegenerative diseases such Alzheimer's disease and multiple sclerosis as well as disorders associated with a deficiency in cell communication such as epilepsy. This review is focused on recent findings that provide reliable evidence of the mediatory role of kinins in the inflammatory responses associated with different neurological disorders. A deeper understanding of the role of kinins in neurodegenerative diseases is likely to promote the future development of new therapeutic strategies for the control of these disorders. An example of this could be the prospective use of kinin receptor antagonists.

Pharmacotherapy of low back pain: targeting nociceptive and neuropathic pain components

AIM

To review pharmacological management of chronic low back pain (LBP), with respect to management of nociceptive and neuropathic components.

METHODS

Studies were identified by a PubMed search of English-language papers from the last 10  years, with additional hand searches of relevant reviews.

DISCUSSION

Paracetamol, non-steroidal anti-inflammatory drugs and cyclo-oxygenase-2 inhibitors target the nociceptive component of chronic LBP, and do not affect neuropathic pain mechanisms. Antidepressants target the neuropathic component of chronic LBP; however, conflicting efficacy results have been reported. Opioids target both nociceptive and to a lesser extent neuropathic pain. They are effective in chronic LBP, but many patients require higher doses or combination treatment. The long-term efficacy of opioids in chronic LBP has been questioned because of the absence of high-quality data and concerns regarding tolerability and dependence. The topical preparation lidocaine 5% plaster, indicated in post-herpetic neuralgia, is effective in localized neuropathic pain in patients with chronic LBP. Pregabalin is ineffective as monotherapy for chronic LBP but is effective when combined with celecoxib or opioids. Muscle relaxant monotherapy is ineffective in chronic LBP. Combination therapy is often necessary in patients with chronic LBP, in order to manage both nociceptive and neuropathic pain components.

CONCLUSION

Chronic LBP often comprises both nociceptive and neuropathic components, therefore a multimodal and individualized treatment approach is necessary. Combining drugs with different mechanisms of action (e.g. an agent with µ-receptor activity plus an agent of a different class) represents a rational approach to management of chronic LBP with both nociceptive and neuropathic components.