The role of the cylooxygenase pathway in nociception and pain

GC-MS analysis, molecular docking, and pharmacokinetic studies of Multidentia crassa extracts' compounds for analgesic and anti-inflammatory activities in dentistry

Plant extracts have been useful for oral health or dentistry. However, only a few evidence-based justifications exist. This study evaluated Multidentia crassa (Hiern) Bridson & Verdc, one of the oral health-used plants in Malawi. Gas chromatography-mass spectrometry (GC-MS) and Fourier transform infrared (FT-IR) identified the extracts' compounds. The pharmacokinetics of the identified compounds were studied using pkCSM and SwissADME, and molecular docking studies were used to identify potential drug candidates for oral health by predicting the binding affinity of the compounds to cyclooxygenases, interleukin-1 beta receptors, odontoblast cold sensor proteins, and purinergic receptor P2X3. FT-IR analysis showed characteristic peaks of phenols, carboxylic acids, alkenes, alkyl halides, amines, esters, ethers, aromatics, and lipids. GC-MS results showed the presence of 58 bioactive phytocompounds, some of which have various pharmacological activities relevant to oral health. Molecular docking further validated stigmastan-3,5-diene's potency for analgesic and anti-inflammatory purposes. Based on a literature review, this is the first report on the bioactive compounds of M. crassa extracts showing analgesic and anti-inflammatory effects. This study's results can lead to new herbal and conventional medicines. Therefore, we recommend in vivo and in vitro studies to elucidate the pharmacological effects of the plant extracts.

Mechanically Derived Tissue Stromal Vascular Fraction Acts Anti-inflammatory on TNF Alpha-Stimulated Chondrocytes In Vitro

Enzymatically isolated stromal vascular fraction (SVF) has already shown to be effective as a treatment for osteoarthritis (OA). Yet, the use of enzymes for clinical purpose is highly regulated in many countries. Mechanical preparation of SVF results in a tissue-like SVF (tSVF) containing intact cell−cell connections including extracellular matrix (ECM) and is therefore less regulated. The purpose of this study was to investigate the immunomodulatory and pro-regenerative effect of tSVF on TNFα-stimulated chondrocytes in vitro. tSVF was mechanically derived using the Fractionation of Adipose Tissue (FAT) procedure. Characterization of tSVF was performed, e.g., cellular composition based on CD marker expression, colony forming unit and differentiation capacity after enzymatic dissociation (from heron referred to as tSVF-derived cells). Different co-cultures of tSVF-derived cells and TNFα-stimulated chondrocytes were analysed based on the production of sulphated glycosaminoglycans and the anti-inflammatory response of chondrocytes. Characterization of tSVF-derived cells mainly contained ASCs, endothelial cells, leukocytes and supra-adventitial cells. tSVF-derived cells were able to form colonies and differentiate into multiple cell lineages. Co-cultures with chondrocytes resulted in a shift of the ratio between tSVF cells: chondrocytes, in favor of chondrocytes alone (p < 0.05), and IL-1β and COX2 gene expression was upregulated in TNFα-treated chondrocytes. After treatment with (a conditioned medium of) tSVF-derived cells, IL-1β and COX2 gene expression was significantly reduced (p < 0.01). These results suggest mechanically derived tSVF stimulates chondrocyte proliferation while preserving the function of chondrocytes. Moreover, tSVF suppresses TNFα-stimulated chondrocyte inflammation in vitro. This pro-regenerative and anti-inflammatory effect shows the potential of tSVF as a treatment for osteoarthritis.

Repurposing of digoxin in pain and inflammation: An evidence-based study

In recent years, the drug repositioning strategy has gained considerable attention in the drug discovery process that involves establishing new therapeutic uses of already known drugs. In line with this, we have identified digoxin a cardiac glycoside, as a potent inhibitor of soluble epoxide hydrolase (sEH) enzyme employing in silico high throughput screening protocols and further confirmed using in vitro cell-free sEH inhibitory assay and in vivo preclinical studies in rodents for its repurposing in hyperalgesia, inflammation, and related disorders. Oral administration of digoxin at dose 0.2 mg/kg significantly reduced (p < .0001) the allodynia in mice induced by using hot plate (3.6 ± 1.9) and tail-flick test (7.58 ± 0.9). In addition, digoxin at a dose of 0.2 mg/kg showed marked reduction (94%, p < .0001) in acetic acid-induced abdominal contraction in rats. Further, digoxin also demonstrated antipyretic activity (37.04 ± 0.2, p < .0001) and showed notable reduction (0.60 ± 0.06) in carrageenan-induced paw edema in rats. Also, the histopathological evaluation revealed that digoxin treatment attenuated the edema, neutrophil infiltration, and alveolar septal thickening in lung tissue. These findings are novel and highlight the newer insights towards repurposing digoxin as a new lead in the treatment of hyperalgesia, inflammation, and related disorders.

Neuropharmacological basis for multimodal analgesia in chronic pain

Managing chronic pain remains a major unmet clinical challenge. Patients can be treated with a range of interventions, but pharmacotherapy is the most common. These include opioids, antidepressants, calcium channel modulators, sodium channel blockers, and nonsteroidal anti-inflammatory drugs. Many of these drugs target a particular mechanism; however, chronic pain in many diseases is multifactorial and induces plasticity throughout the sensory neuroaxis. Furthermore, comorbidities such as depression, anxiety, and sleep disturbances worsen quality of life. Given the complexity of mechanisms and symptoms in patients, it is unsurprising that many fail to achieve adequate pain relief from a single agent. The efforts to develop novel drug classes with better efficacy have not always proved successful; a multimodal or combination approach to analgesia is an important strategy in pain control. Many patients frequently take more than one medication, but high-quality evidence to support various combinations is often sparse. Ideally, combining drugs would produce synergistic action to maximize analgesia and reduce side effects, although sub-additive and additive analgesia is still advantageous if additive side-effects can be avoided. In this review, we discuss pain mechanisms, drug actions, and the rationale for mechanism-led treatment selection.Abbreviations: COX - cyclooxygenase, CGRP - calcitonin gene-related peptide, CPM - conditioned pain modulation, NGF - nerve growth factor, NNT - number needed to treat, NMDA - N-methyl-d-aspartate, NSAID - nonsteroidal anti-inflammatory drugs, TCA - tricyclic antidepressant, SNRI - serotonin-noradrenaline reuptake inhibitor, QST - quantitative sensory testing.

Antinociceptive and Anti-Inflammatory Effects of Recombinant Crotamine in Mouse Models of Pain

Crotamine, a toxin found in the venom of the South American rattlesnake Crotalus durissus terrificus, has been reported to have antinociceptive effects. We purified recombinant crotamine expressed in Escherichia coli and investigated its antinociceptive and anti-inflammatory effects using the hot-plate test, acetic-acid-induced writhing method, and formalin test in mice. Recombinant crotamine was administered intraperitoneally (0.04–1.2 mg kg⁻¹) or intraplantarly (0.9–7.5 μg 10 μL⁻¹) before the tests. The paw volume was measured with a plethysmometer. To evaluate the antagonistic and anti-inflammatory effects of naloxone, subcutaneous naloxone (4 mg kg⁻¹) or intraplantar naloxone (5 μg 10 μL⁻¹) was administered before recombinant crotamine. For tumor necrosis factor (TNF)-α assays, blood was drawn 3 h after formalin injection and measured using enzyme-linked immunosorbent assay. Intraperitoneal and intraplantar recombinant crotamine had antinociceptive and anti-inflammatory effects, neither of which were affected by pre-treatment with naloxone. The mean serum TNF-α levels were significantly lower in the intraperitoneal recombinant crotamine (0.4 and 1.2 mg kg⁻¹) or intraplantar (2.5 and 7.5 μg 10 μL⁻¹) recombinant crotamine groups than in the saline group and were not affected by naloxone pre-treatment. In conclusion, recombinant crotamine possesses significant antinociceptive and anti-inflammatory effects that do not appear to be related to the opioid receptor. The antinociceptive and anti-inflammatory effects of intraperitoneal or intraplantar recombinant crotamine are related to TNF-α.

Quantification of computational fluid dynamics simulation assists the evaluation of protection by Gypenosides in a zebrafish pain model

In recent years, due to its rapid reproduction rate and the similarity of its genetic structure to that of human, the zebrafish has been widely used as a pain model to study chemical influences on behavior. Swimming behaviors are mediated by motoneurons in the spinal cord that drive muscle contractions, therefore a knowledge of internal muscle mechanics can assist the understanding of the effects of drugs on swimming activity. To demonstrate that the technique used in our study can supplement biological observations by quantifying the contribution of muscle effects to altered swimming behaviours, we have evaluated the pain/damage caused by 0.1% acetic acid to the muscle of 5 dpf zebrafish larvae and the effect of protection from this pain/damage with the saponin Gypenosides (GYP) extracted from Gynostemma pentaphyllum. We have quantified the parameters related to muscle such as muscle power and the resultant hydrodynamic force, proving that GYP could alleviate the detrimental effect of acetic acid on zebrafish larvae, in the form of alleviation from swimming debility, and that the muscle status could be quantified to represent the degree of muscle damage due to the acetic acid and the recovery due to GYP. We have also linked the behavioral changes to alteration of antioxidant and inflammation gene expression. The above results provide novel insights into the reasons for pain-related behavioral changes in fish larvae, especially from an internal muscle perspective, and have quantified these changes to help understand the protection of swimming behaviors and internal muscle by GYP from acetic acid-induced damage.

Melatonin antagonizes lipopolysaccharide-induced pulpal fibroblast responses

Background

Pulpal inflammation is known to be mediated by multiple signaling pathways. However, whether melatonin plays regulatory roles in pulpal inflammation remains unclear. This study aimed at elucidating an in situ expression of melatonin and its receptors in human pulpal tissues, and the contribution of melatonin on the antagonism of lipopolysaccharide (LPS)-infected pulpal fibroblasts.

Methods

Melatonin expression in pulpal tissues harvested from healthy teeth was investigated by immunohistochemical staining. Its receptors, melatonin receptor 1 (MT1) and melatonin receptor 2 (MT2), were also immunostained in pulpal tissues isolated from healthy teeth and inflamed teeth diagnosed with irreversible pulpitis. Morphometric analysis was subsequently performed. After LPS infection of cultured pulpal fibroblasts, cyclo-oxygenase (COX) and interleukin-1 β (IL-1 β) transcripts were examined by using reverse transcription-polymerase chain reaction (RT-PCR). Analysis of mRNA expression was performed to investigate an antagonism of LPS stimulation by melatonin via COX and IL-1 β induction. Mann-Whitney U test and One-way ANOVA were used for statistical analysis to determine a significance level.

Results

Melatonin was expressed in healthy pulpal tissue within the odontoblastic zone, cell-rich zone, and in the pulpal connective tissue. Furthermore, in health, strong MT1 and MT2 expression was distributed similarly in all 3 pulpal zones. In contrast, during disease, expression of MT2 was reduced in inflamed pulpal tissues (P-value< 0.001), but not MT1 (P-value = 0.559). Co-culturing of melatonin with LPS resulted in the reduction of COX-2 and IL-1 β expression in primary pulpal fibroblasts, indicating that melatonin may play an antagonistic role to LPS infection in pulpal fibroblasts.

Conclusions

Human dental pulp abundantly expressed melatonin and its receptors MT1 and MT2 in the odontoblastic layers and pulpal connective tissue layers. Melatonin exerted antagonistic activity against LPS-mediated COX-2 and IL-1 β induction in pulpal fibroblasts, suggesting its therapeutic potential for pulpal inflammation and a possible role of pulpal melatonin in an immunomodulation via functional melatonin receptors expressed in dental pulp.

Quantification of the influence of drugs on zebrafish larvae swimming kinematics and energetics

The use of zebrafish larvae has aroused wide interest in the medical field for its potential role in the development of new therapies. The larvae grow extremely quickly and the embryos are nearly transparent which allows easy examination of its internal structures using fluorescent imaging techniques. Medical treatment of zebrafish larvae can directly influence its swimming behaviours. These behaviour changes are related to functional changes of central nervous system and transformations of the zebrafish body such as muscle mechanical power and force variation, which cannot be measured directly by pure experiment observation. To quantify the influence of drugs on zebrafish larvae swimming behaviours and energetics, we have developed a novel methodology to exploit intravital changes based on observed zebrafish locomotion. Specifically, by using an in-house MATLAB code to process the recorded live zebrafish swimming video, the kinematic locomotion equation of a 3D zebrafish larvae was obtained, and a customised Computational Fluid Dynamics tool was used to solve the fluid flow around the fish model which was geometrically the same as experimentally tested zebrafish. The developed methodology was firstly verified against experiment, and further applied to quantify the fish internal body force, torque and power consumption associated with a group of normal zebrafish larvae vs. those immersed in acetic acid and two neuroactive drugs. As indicated by our results, zebrafish larvae immersed in 0.01% acetic acid display approximately 30% higher hydrodynamic power and 10% higher cost of transport than control group. In addition, 500 μM diphenylhydantoin significantly decreases the locomotion activity for approximately 50% lower hydrodynamic power, whereas 100 mg/L yohimbine has not caused any significant influences on 5 dpf zebrafish larvae locomotion. The approach has potential to evaluate the influence of drugs on the aquatic animal’s behaviour changes and thus support the development of new analgesic and neuroactive drugs.

Releasing Behavior of Lipopolysaccharide from Gelatin Modulates Inflammation, Cellular Senescence, and Bone Formation in Critical-Sized Bone Defects in Rat Calvaria

Lipopolysaccharide (LPS) is a well-known strong inducer of inflammation. However, there is little information regarding how LPS-release behavior affects cellular senescence at the affected area. In this paper, we demonstrate that a vacuum-heating technique (dehydrothermal treatment) can be utilized to prepare an LPS sustained-release gelatin sponge (LS-G). LPS sustained release from gelatin leads to the long-term existence of senescent cells in critical-sized bone defects in rat calvaria. Three types of gelatin sponges were prepared in this study: a medical-grade gelatin sponge with extremely low LPS levels (MG), LS-G, and a LPS rapid-release gelatin sponge (LR-G). Histological (H-E) and immunohistochemical (COX-2, p16, and p21) staining were utilized to evaluate inflammatory reactions and cellular senescence one to three weeks after surgery. Soft X-ray imaging was utilized to estimate new bone formation in the defects. The LR-G led to stronger swelling and COX-2 expression in defects compared to the MG and LS-G at 1 week. Despite a small inflammatory reaction, LS-G implantation led to the long-term existence of senescent cells and hampered bone formation compared to the MG and LR-G. These results suggest that vacuum heating is a viable technique for preparing different types of materials for releasing bacterial components, which is helpful for developing disease models for elucidating cellular senescence and bone regeneration.

Pain Management in Abdominal Wall Reconstruction

Background:

In abdominal wall reconstruction, adequate pain control and minimization of narcotic consumption are essential to improving patient outcomes and satisfaction. Previous studies have examined the role of individual strategies, such as neuraxial analgesia and multimodal analgesia. However, there has not been a study that examined all potential determinants of postoperative narcotic requirements, including intraoperative strategies.

Methods:

Consecutive patients who underwent abdominal wall reconstruction were reviewed. Preoperative factors (chronic preoperative narcotic usage, indication for abdominal wall reconstruction, administration of neuraxial analgesia), intraoperative factors (intraoperative narcotics administered, method of mesh fixation), and postoperative factors (multimodal analgesia, complications) were collected. The main outcomes were daily amount of opioids used and length of hospital stay.

Results:

Ninety-three patients were included in the study. Patients who had an epidural required lower doses of opioids postoperatively, while those on chronic preoperative opioids, those whose mesh was fixated using transfascial sutures, and those who received large doses of opioids intraoperatively required higher doses of postoperative opioids. Hospital length of stay was longer in patients who received transfascially sutured mesh and those on chronic opioids preoperatively.

Conclusions:

This study provides potential strategies to improve pain control and minimize narcotic consumption postoperatively in patients undergoing abdominal wall reconstruction. Intraoperative administration of opioids should be minimized to avoid the development of tolerance. Epidural analgesia reduces postoperative narcotic requirement and may be especially beneficial in patients at highest risk for postoperative pain, including those on chronic opioids, and those in whom transfascial sutures are used for mesh fixation.

Copy number variation in ALOX5 and PTGER1 is associated with NSAIDs-induced urticaria and/or angioedema

OBJECTIVE

Cross-intolerance to NSAIDs is a class of drug hypersensitivity reaction, of which NSAIDs-induced urticaria and/or angioedema (NIUA) are the most frequent clinical entities. They are considered to involve dysregulation of the arachidonic acid pathway; however, this mechanism has not been confirmed for NIUA. In this work, we assessed copy number variations (CNVs) in eight of the main genes involved in the arachidonic acid pathway and their possible genetic association with NIUA.

MATERIALS AND METHODS

CNVs in ALOX5, LTC4S, PTGS1, PTGS2, PTGER1, PTGER2, PTGER3, and PTGER4 were analyzed using TaqMan copy number assays. Genotyping was carried out by real-time quantitative PCR. Individual genotypes were assigned using the CopyCaller Software. Statistical analysis was carried out using GraphPad prism 5, PLINK, EPIDAT, and R version 3.1.2.

RESULTS AND CONCLUSION

A total of 151 cases and 139 controls were analyzed during the discovery phase and 148 cases and 140 controls were used for replication. CNVs in open reading frames were found for ALOX5, PTGER1, PTGER3, and PTGER4. Statistically significant differences in the CNV frequency between NIUA and controls were found for ALOX5 (Pc=0.017) and PTGER1 (Pc=1.22E-04). This study represents the first analysis showing an association between CNVs in exonic regions of ALOX5 and PTGER1 and NIUA. This suggests a role of CNVs in this pathology that should be explored further.

Self-assembling ultrashort NSAID-peptide nanosponges: multifunctional antimicrobial and anti-inflammatory materials

This paper outlines the design, synthesis and characterisation of innovative NSAID-peptide gelators which demonstrate antimicrobial and anti-inflammatory properties and have potential use as multifunctional materials for biomedical applications.

Modeling nociception in zebrafish: a way forward for unbiased analgesic discovery

Acute and chronic pain conditions are often debilitating, inflicting severe physiological, emotional and economic costs and affect a large percentage of the global population. However, the development of therapeutic analgesic agents based primarily on targeted drug development has been largely ineffective. An alternative approach to analgesic development would be to develop low cost, high throughput, untargeted animal based behavioral screens that model complex nociceptive behaviors in which to screen for analgesic compounds. Here we describe the development of a behavioral based assay in zebrafish larvae that is effective in identifying small molecule compounds with analgesic properties. In a place aversion assay, which likely utilizes supraspinal neuronal circuitry, individually arrayed zebrafish larvae show temperature-dependent aversion to increasing and decreasing temperatures deviating from rearing temperature. Modeling thermal hyperalgesia, the addition of the noxious inflammatory compound and TRPA1 agonist allyl isothiocyanate sensitized heat aversion and reversed cool aversion leading larvae to avoid rearing temperature in favor of otherwise acutely aversive cooler temperatures. We show that small molecules with known analgesic properties are able to inhibit acute and/or sensitized temperature aversion.

Synergistic antinociceptive effect and gastric safety of the combination of docosahexaenoic acid and indomethacin in rats

The use of analgesics is limited by the presence of significant adverse side effects. Thus, combinations of non-steroidal anti-inflammatory drugs (NSAIDs) with other antinociceptive agents are frequently used to decrease these adverse reactions. The aims of this work were to evaluate the antinociceptive interaction of the systemic administration of the combination of DHA and indomethacin through an isobolographic analysis of the theoretical and experimental antinociceptive effect and to demonstrate the gastric safety of the mixture compared with indomethacin alone. Female Wistar rats were orally administered indomethacin (1-10 mg/kg), DHA (100-300 mg/kg), or the DHA-indomethacin mixture at a fixed-ratio combination (1:1, 1:3, 3:1), and the antinociceptive effects of these treatments were evaluated through the formalin (1%) test. An isobolographic analysis was performed to characterize the antinociceptive interaction between DHA and indomethacin. The degree of gastric injury in all of the rats was determined 1 h after the formalin test. The theoretical ED₃₀ values (Zadd) for the 1:1, 1:3, and 3:1 combinations were 73.48 ± 8.96, 37.75 ± 4.50, and 109.2 ± 13.43 mg/kg, p.o., respectively, and the experimental ED30 values (Zexp) were 43.63 ± 5.18, 13.13 ± 1.61, and 54.20 ± 6.53, respectively. The isobolographic analysis showed that the three fixed-ratio combinations studied exhibited a synergistic interaction. Furthermore, the gastric damage induced by indomethacin was abolished when this drug was combined with DHA. These data suggest that the systemic administration of the DHA-indomethacin combination induces a synergistic and gastric safety effect.

p300 exerts an epigenetic role in chronic neuropathic pain through its acetyltransferase activity in rats following chronic constriction injury (CCI)

BACKGROUND

Neuropathic pain is detrimental to human health; however, its pathogenesis still remains largely unknown. Overexpression of pain-associated genes and increased nociceptive somato-sensitivity are well observed in neuropathic pain. The importance of epigenetic mechanisms in regulating the expression of pro- or anti-nociceptive genes has been revealed by studies recently, and we hypothesize that the transcriptional coactivator and the histone acetyltransferase E1A binding protein p300 (p300), as a part of the epigenetic mechanisms of gene regulation, may be involved in the pathogenesis of neuropathic pain induced by chronic constriction injury (CCI). To test this hypothesis, two different approaches were used in this study: (I) down-regulating p300 with specific small hairpin RNA (shRNA) and (II) chemical inhibition of p300 acetyltransferase activity by a small molecule inhibitor, C646.

RESULTS

Using the CCI rat model, we found that the p300 expression was increased in the lumbar spinal cord on day 14 after CCI. The treatment with intrathecal p300 shRNA reversed CCI-induced mechanical allodynia and thermal hyperalgesia, and suppressed the expression of cyclooxygenase-2 (COX-2), a neuropathic pain-associated factor. Furthermore, C646, an inhibitor of p300 acetyltransferase, also attenuated mechanical allodynia and thermal hyperalgesia, accompanied by a suppressed COX-2 expression, in the spinal cord.

CONCLUSIONS

The results suggest that, through its acetyltransferase activity in the spinal cord after CCI, p300 epigenetically plays an important role in neuropathic pain. Inhibiting p300, using interfering RNA or C646, may be a promising approach to the development of new neuropathic pain therapies.

CASE plots for the chemotype-based activity and selectivity analysis: a CASE study of cyclooxygenase inhibitors

Structure-activity characterization of molecular databases plays a central role in drug discovery. However, the characterization of large databases containing structurally diverse molecules with several end-points represents a major challenge. For this purpose, the use of chemoinformatic methods plays an important role to elucidate structure-activity relationships. Herein, a general methodology, namely Chemotype Activity and Selectivity Enrichment plots, is presented. Chemotype Activity and Selectivity Enrichment plots provide graphical information concerning the activity and selectivity patterns of particular chemotypes contained in structurally diverse databases. As a case study, we analyzed a set of 658 compounds screened against cyclooxygenase-1 and cyclooxygenase-2. Chemotype Activity and Selectivity Enrichment plots analysis highlighted chemotypes enriched with active and selective molecules against cyclooxygenase-2; all this in a simple 2D graphical representation. Additionally, the most active and selective chemotypes detected in Chemotype Activity and Selectivity Enrichment plots were analyzed separately using the previously reported dual activity-difference maps. These findings indicate that Chemotype Activity and Selectivity Enrichment plots and dual activity-difference maps are complementary chemoinformatic tools to explore the structure-activity relationships of structurally diverse databases screened against two biological end-points.

Mitragynine inhibits the COX-2 mRNA expression and prostaglandin E₂ production induced by lipopolysaccharide in RAW264.7 macrophage cells

ETHNOPHARMACOLOGICAL RELEVANCE

[corrected] Mitragyna speciosa Korth (Rubiaceae) is one of the medicinal plants used traditionally to treat various types of diseases especially in Thailand and Malaysia. Its anti-inflammatory and analgesic properties in its crude form are well documented. In this study, the cellular mechanism involved in the anti-inflammatory effects of mitragynine, the major bioactive constituent, was investigated.

MATERIALS AND METHODS

The effects of mitragynine on the mRNA and protein expression of COX-1 and COX-2 and the production of prostaglandin E(2) (PGE(2)) were investigated in LPS-treated RAW264.7 macrophage cells. Quantitative RT-PCR was used to assess the mRNA expression of COX-1 and COX-2. Protein expression of COX-1 and COX-2 were assessed using Western blot analysis and the level of PGE(2) production was quantified using Parameter™ PGE(2) Assay (R&D Systems).

RESULTS

Mitragynine produced a significant inhibition on the mRNA expression of COX-2 induced by LPS, in a dose dependent manner and this was followed by the reduction of PGE(2) production. On the other hand, the effects of mitragynine on COX-1 mRNA expression were found to be insignificant as compared to the control cells. However, the effect of mitragynine on COX-1 protein expression is dependent on concentration, with higher concentration of mitragynine producing a further reduction of COX-1 expression in LPS-treated cells.

CONCLUSIONS

These findings suggest that mitragynine suppressed PGE(2) production by inhibiting COX-2 expression in LPS-stimulated RAW264.7 macrophage cells. Mitragynine may be useful for the treatment of inflammatory conditions.

Epoxygenated fatty acids and soluble epoxide hydrolase inhibition: novel mediators of pain reduction

The soluble epoxide hydrolase (sEH) enzyme was discovered while investigating the metabolism of xenobiotic compounds in the Casida laboratory. However, an endogenous role of sEH is to regulate the levels of a group of potent bioactive lipids, epoxygenated fatty acids (EFAs), that have pleiotropic biological activities. The EFAs, in particular the arachidonic acid derived epoxy eicosatrienoic acids (EETs), are established autocrine and paracrine messengers. The most recently discovered outcome of inhibition of sEH and increased EFAs is their effects on the sensory system and in particular their ability to reduce pain. The inhibitors of sEH block both inflammatory and neuropathic pain. Elevation of EFAs, in both the central and peripheral nervous systems, blocks pain. Several laboratories have now published a number of potential mechanisms of action for the pain-reducing effects of EFAs. This paper provides a brief history of the discovery of the sEH enzyme and argues that inhibitors of sEH through several independent mechanisms display pain-reducing effects.

Knockdown of L calcium channel subtypes: differential effects in neuropathic pain

The maintenance of chronic pain states requires the regulation of gene expression, which relies on an influx of calcium. Calcium influx through neuronal L-type voltage-gated calcium channels (LTCs) plays a pivotal role in excitation-transcription coupling, but the involvement of LTCs in chronic pain remains unclear. We used a peptide nucleic acid (transportan 10-PNA conjugates)-based antisense strategy to investigate the role of the LTC subtypes Ca(V)1.2 and Ca(V)1.3 in long-term pain sensitization in a rat model of neuropathy (spinal nerve ligation). Our results demonstrate that specific knockdown of Ca(V)1.2 in the spinal dorsal horn reversed the neuropathy-associated mechanical hypersensitivity and the hyperexcitability and increased responsiveness of dorsal horn neurons. Intrathecal application of anti-Ca(V)1.2 siRNAs confirmed the preceding results. We also demonstrated an upregulation of Ca(V)1.2 mRNA and protein in neuropathic animals concomitant to specific Ca(V)1.2-dependent phosphorylation of the cAMP response element (CRE)-binding protein (CREB) transcription factor. Moreover, spinal nerve ligation animals showed enhanced transcription of the CREB/CRE-dependent gene COX-2 (cyclooxygenase 2), which also depends strictly on Ca(V)1.2 activation. We propose that L-type calcium channels in the spinal dorsal horn play an important role in pain processing, and that the maintenance of chronic neuropathic pain depends specifically on channels comprising Ca(V)1.2.

The role of translational regulation in ultraviolet C light-induced cyclooxygenase-2 expression

AIMS

The role of ultraviolet C light (UVC)-induced phosphorylation of the eukaryotic initiation factor 2 (eIF2) in the regulation of cyclooxygenase-2 (COX-2) expression at both transcriptional and translational levels is investigated.

MAIN METHODS

Western analysis was used to determine COX expressions. Immunoprecipitation after [(35)S]-Met/Cys metabolic labeling was used to determine the rate for COX-2 synthesis and turnover. Quantitative real-time PCR was used to determine COX-2 mRNA levels. Ingenuity Pathways Analysis 6 was used for mapping COX-2 activation network.

KEY FINDINGS

UVC induces COX-2 expression in wild-type mouse embryo fibroblasts (MEF(S/S)) and that the inducibility is reduced in MEF(A/A) cells in which the phosphorylation site, Ser-51 in the eIF2alpha, is replaced with a nonphosphorylatable Ala (S51A). UVC-induced transcription of COX-2 is delayed in MEF(A/A) cells, which correlates with NF-kappaB activation as previously reported (Wu, S, Tan, M, Hu, Y, Wang, JL, Scheuner, D, Kaufman, RJ, Ultraviolet light activates NFkappaB through translational inhibition of IkappaBalpha synthesis. The Journal of Biological Chemistry, 279, 34898-34902, 2004). The translational efficiency of COX-2 is higher in MEF(A/A) cells than in MEF(S/S) cells at 4 h, but not at 24 h post-UVC. The translation efficiency is correlated to the ratio of activated COX-2 binding protein HuR/TIAR. In addition, the newly synthesized COX-2 protein is more stable in MEF(A/A) cells than in MEF(S/S) cells. The results demonstrated a complex and dynamic regulation of COX-2 expression.

SIGNIFICANCE

UVC induces a prolonged expression of COX-2. While transcriptional regulation of COX-2 expression is intensively studied, the role of translational regulation of COX-2 synthesis upon UVC-irradiation is not yet clear. This study elucidated a novel eIF2alpha phosphorylation-centered network for the regulation of COX-2 expression after UVC-irradiation.

Mechanisms of pain in nonmalignant disease

PURPOSE OF REVIEW

To review key mechanisms underlying the transmission of nociceptive information from the periphery to the central nervous system implicated in different acute pain states.

RECENT FINDINGS

Advances in molecular and transgenic approaches have helped to identify novel therapeutic targets for the treatment of pain from tissue and nerve damage such as acid-sensing ion channels, transient receptor potential and NaV channels. The subsequent development of selective pharmacological ligands has also strengthened the role of other receptors such as hyperpolarization-activated cyclic nucleotide-gated channels and the further development of subunit specific antagonists, such as those available for NR2B, will further advance our understanding of the mechanisms involved in nociceptive transmission.

SUMMARY

Inflammatory and neuropathic pain differ considerably in their peripheral mechanisms but certain central spinal and brain mechanisms are common to both. The mechanisms of pain are not fully established but are thought to be underpinned by changes in the expression of receptors (nociceptive plasticity), central spinal hyperexcitability (central sensitization) and alterations in descending control from the midbrain. This review considers these mechanisms and highlights recent advances in the understanding of pain perception.

Gene expression profile of dorsal root ganglion in a lumbar radiculopathy model

STUDY DESIGN

DNA array analysis of dorsal root ganglion (DRG) using a rat model with nerve root constriction.

OBJECTIVE

To determine the molecular changes in the DRG adjacent to the injured nerve root in a lumbar radiculopathy model.

SUMMARY OF BACKGROUND DATA

DNA array analysis in lumbar radiculopathy model has so far focused on the spinal dorsal horn. The molecular changes in the DRG adjacent to the injured nerve root in lumbar radiculopathy remain to be determined.

METHODS

Bilateral L5 DRGs were removed from 12 Sprague-Dawley rats on days 2, 7, 14, and 21 after nerve root ligation and on day 7 from 3 rats with sham operation. The aRNAs from the DRGs with nerve root ligation were labeled with Cy5 dye and those from the opposite side DRG (control) were labeled with Cy3 dye, and then hybridized to a 7793-spot Panorama Micro Array. It was considered to be significantly upregulated, when an average expression ratio of Cy5 to Cy3 was 2 or more. Genes upregulated were classified into early phase group (upregulated on day 2), midphase group (upregulated on days 7 and 14), and continuous group (upregulated from day 2 to 21). Seventeen genes were subjected to validation analysis with real-time quantitative PCR.

RESULTS

There were 16 upregulated genes in the early phase group, 56 genes in the midphase group, and 17 genes in the continuous group. Functional categorization revealed dominantly upregulated gene categories in each group; transcription/translation in the early phase group, enzyme/metabolism in the midphase group, and structure in the continuous group. Validation analysis of 17 genes demonstrated mean relative expression of 2.0 or more in all but 1 gene in the DRGs with nerve root ligation and none of them in the DRGs with sham operation.

CONCLUSION

The genes identified in this study, especially those involved in pain signaling and inflammation, serve as potential targets for molecular-based therapy for lumbar radiculopathy.

Age-related difference in nociceptive behavior between SAMP6 and SAMR1 strains

Senescence accelerated prone mouse 6 (SAMP6) mice have been known to be a model for accelerated aging. Compared with the normal control senescence accelerated resistant mouse 1 (SAMR1) mice, although the SAMP6 mice have normal bone mass at 4 months, they exhibit a significantly lower bone mass at 8 months. It was recently reported that SAMP6 has memory deficit at 4 months of age, indicating that the change of nervous function might be already detected at 4 months of age. To assess whether SAMP6 mice exhibit an age-related abnormality of nociceptive transmission, we examined a battery of tests using the von Frey test for mechanically induced response, the hot plate test for thermally induced response, and the formalin paw test for chemically induced response. SAMP6 and SAMR1 showed similar response patterns in the von Frey test and the hot plate test. In the formalin paw test, 1-month-old SAMP6 and SAMR1 had similar responses, while 4-month-old SAMP6 exhibited attenuated phase 2 response, but normal phase 1 response. These findings indicate that onset of age-related phenotypes in SAMP6 differs in different tissues. SAMP6 could be useful to delineate the involvement of age-related nociceptive mechanisms.

Enhanced bladder capacity and reduced prostaglandin E2-mediated bladder hyperactivity in EP3 receptor knockout mice

Nonsteroidal anti-inflammatory cyclooxygenase inhibitors that function to reduce prostaglandin E2 (PGE2) production have been widely reported as effective agents in models of urinary bladder overactivity. We therefore investigated a potential role for the PGE2 receptor, EP3, in urinary bladder function by performing conscious, freely moving cystometry on EP3 receptor knockout (KO) mice. EP3 KO mice demonstrated an enhanced bladder capacity compared with wild-type (WT) mice ( approximately 185% of WT) under control conditions, based on larger voided and infused bladder volumes. Infusion of the EP3 receptor agonist GR63799X into the bladder of WT mice reduced the bladder capacity. This was ineffective in EP3 KO mice that demonstrated a time-dependent increase in bladder capacity with GR63799X, an effect similar to that observed with vehicle in both genotypes. In addition, infusion of PGE2 into WT mice induced bladder overactivity, an effect that was significantly blunted in the EP3 KO mice. The data reported here provide the first evidence supporting a functional role for EP3 receptors in normal urinary bladder function and implicate EP3 as a contributor to bladder overactivity during pathological conditions of enhanced PGE2 production, as reported previously in overactive bladder patients.

Prospective, Double-Blinded, Randomized, Placebo-Controlled Comparison of Local Anesthetic and Nonsteroidal Anti-Inflammatory Drugs for Postoperative Pain Management after Laparoscopic Surgery

Compared with the open approach, laparoscopy has been shown to significantly reduce postoperative pain. Improving postoperative analgesia in laparoscopic surgery is an area of continued interest. The goal of this study was to compare the efficacy of local anesthetic infiltration with or without preoperative nonsteroidal anti-inflammatory drugs. Patients undergoing elective laparoscopic cholecystectomy were enrolled in an Institutional Review Board-approved, prospective, double-blinded, randomized, placebo-controlled comparison study. Patients were randomized into four groups: Group I, preoperative oral administration of a placebo medication and prein cision local infiltration of 40 mL of 0.5 per cent bupivicaine at trocar sites; Group II, preoperative oral administration of 50 mg of rofecoxib; Group III, preoperative oral administration of 50 mg of rofecoxib and preincision local infiltration of 40 mL of 0.5 per cent bupivicaine into skin, muscle, and peritoneum; and Group IV, preoperative oral administration of a placebo medication. Postoperative pain scores were assessed at 4 hours, 8 hours, 12 hours, and 24 hours using a visual analog scale. Postoperative analgesic use, complications, and length of stay were recorded. Statistical significance was defined as P < 0.05. Fifty-five patients (46 women and 9 men) were enrolled in this study and underwent a standardized, elective, laparoscopic cholecystectomy for mild, symptomatic cholelithiasis (96.4%) and gallbladder polyps (3.6%). No patient had pain immediately before surgery. Postoperative analgesic requests, visual analog scale results, incidence of postoperative vomiting at 4 hours, 8 hours, 12 hours, and 24 hours, in addition to length of stay, were not statistically different between the four groups. No complications occurred. The use of preoperative rofecoxib, 0.5 per cent bupivicaine infiltration, or both for postoperative analgesia did not decrease postoperative pain or decrease length of stay after laparoscopic cholecystectomy compared with placebo. Preoperative administration of an oral anti-inflammatory pain medication, infiltration of a local anesthetic, or both had no greater effect than placebo in controlling discomfort after a laparoscopic cholecystectomy. The challenge of preempting postoperative pain continues and will require further investigation.