Analysis of the effects of cyclooxygenase (COX)-1 and COX-2 in spinal nociceptive transmission using indomethacin, a non-selective COX inhibitor, and NS-398, a COX-2 selective inhibitor

COX2 expression plays a role in spinal cord injury-induced neuropathic pain

BACKGROUND CONTEXT

Elucidating the mechanism of neuropathic pain (NeP) is crucial as it can result in motor dysfunction and negatively impact quality of life in patients with spinal cord injury (SCI). Although it has been reported that cyclooxygenase 2 (COX2) is involved in NeP in rat models of peripheral nerve injury and that COX2 inhibitors can alleviate NeP, these mechanisms after SCI have not been fully investigated.

PURPOSE

The purpose is to investigate whether the thoracic SCI affects the expression of mRNAs for COX1 and COX2 in the lumbar spinal cord, and the effect of COX2 inhibitor on its behavior.

STUDY DESIGN

Male Sprague-Dawley (SD) rats underwent thoracic (T10) spinal cord contusion injury using an Infinite Horizon (IH) impactor device. SCI rats received COX2 inhibitors (50 μg/day) on days 5 and 6 after SCI.

METHODS

Male SD rats underwent T10 laminectomy under mixed anesthesia, and IH impactors were applied to the same site to create a rat SCI model. Rats that underwent only laminectomy were designated as sham. Lumbar spinal cord at the L4-5 level was harvested at 3, 5, 7, 14, and 28 days after SCI, and COX2 and COX1 were quantified by reverse-transcription PCR (RT-PCR). COX2 expression, expression site, and expression time were determined by immunohistochemistry (IHC) and in situ hybridization histochemistry (ISHH) at the same time points. The expression site and time of COX2 expression were also examined at the same time point by ISHH. On 5th and 6th day after SCI, saline and COX2 inhibitor (50 μg/day) were administered into the subarachnoid space as a single dose, and the two groups were compared in terms of mechanical withdrawal latency using the dynamic plantar esthesiometer, which is an automated von Frey-type system.

RESULTS

COX2 was significantly increased at 5 and 7 days after SCI, but no significant difference in COX1 was observed after SCI by RT-PCR. ISHH targeting COX2 showed clear expression of COX2 in spinal cord vascular endothelial cells at 5 and 7 days after SCI. COX2 expression was almost abolished at day 14 and 28. Behavioral experiments showed that pain was significantly improved from day 2 after COX2 inhibitor administration compared to the saline group, with improvement up to day 14 after SCI, but no significant difference was observed after day 21.

CONCLUSIONS

The present findings suggest that thoracic SCI increased COX2 in vascular endothelial cells in the lumbar spinal cord and that the administration of COX2 inhibitor significantly alleviated mechanical hypersensitivity of the hind-paw following the thoracic SCI. Therefore, endothelial cell derived COX2 in the lumbar spinal cord may be involved in the induction of neuropathic pain in the SCI model rats.

CLINICAL SIGNIFICANCE

The findings in the present study regarding the induction of endothelial COX2 and the effect of its inhibitor on the mechanical hypersensitivity suggest that endothelial cell-derived COX2 is one of the focuses for the treatment for neuropathic pain in the acute phase of SCI.

Transcriptome analysis of hepatopancreas from different living states oriental river prawn (Macrobrachium nipponense) in response to hypoxia

As an important economical freshwater prawn, Macrobrachium nipponense has difficulty with adapting to hypoxia. In this study, comparative transcriptome analysis was used for the first time to explore the differences between different living states of Macrobrachium nipponense under hypoxia. A total of 94.22 Gb clean reads were obtained and assembled into 54,688 unigenes. A total of 224, 266, and 750 differently expressed genes were found in the comparison of the control and death groups, the control and moribund groups, and the control and survived groups, respectively. Three signal pathways closely related to hypoxia were found by enriching of the signal pathways in three comparison groups. In addition, much attention was focused on the differential genes in these pathways. Oxidative stress related genes, such as 70 kDa heat shock protein, phosphoenolpyruvate carboxykinase and cyclooxygenase were differentially expressed in different comparisons. After comparing with previous studies, cyclooxygenase was found to be an important hypoxia-related gene that is fully involved in the hypoxic response. Interestingly, two new genes with no Nr annotation were found in this manuscript. This manuscript will enrich our understanding of oxidative stress response to hypoxia and provide a theoretical basis for the subsequent solution of apoptosis caused by hypoxia.

Indomethacin Disrupts the Formation of β-Amyloid Plaques via an α2-Macroglobulin-Activating lrp1-Dependent Mechanism

Epidemiological studies have implied that the nonsteroidal anti-inflammatory drug (NSAID) indomethacin slows the development and progression of Alzheimer’s disease (AD). However, the underlying mechanisms are notably understudied. Using a chimeric mouse/human amyloid precursor protein (Mo/HuAPP695swe) and a mutant human presenilin 1 (PS1-dE9) (APP/PS1) expressing transgenic (Tg) mice and neuroblastoma (N) 2a cells as in vivo and in vitro models, we revealed the mechanisms of indomethacin in ameliorating the cognitive decline of AD. By screening AD-associated genes, we observed that a marked increase in the expression of α₂-macroglobulin (A2M) was markedly induced after treatment with indomethacin. Mechanistically, upregulation of A2M was caused by the inhibition of cyclooxygenase-2 (COX-2) and lipocalin-type prostaglandin D synthase (L-PGDS), which are responsible for the synthesis of prostaglandin (PG)H₂ and PGD₂, respectively. The reduction in PGD₂ levels induced by indomethacin alleviated the suppression of A2M expression through a PGD₂ receptor 2 (CRTH2)-dependent mechanism. Highly activated A2M not only disrupted the production and aggregation of β-amyloid protein (Aβ) but also induced Aβ efflux from the brain. More interestingly, indomethacin decreased the degradation of the A2M receptor, low-density lipoprotein receptor-related protein 1 (LRP1), which facilitated the brain efflux of Aβ. Through the aforementioned mechanisms, indomethacin ameliorated cognitive decline in APP/PS1 Tg mice by decreasing Aβ production and clearing Aβ from the brains of AD mice.

Research on Nonsteroidal Anti-inflammatory Drugs in Malaysia: A Bibliometric Analysis

Background:

Nonsteroidal anti-inflammatory drugs (NSAIDs) are the most common analgesics used for pain relief. Adverse effects of NSAIDs range from gastrointestinal tract disturbances to increased risk of bleeding, renal injury, and myocardial infarction. In Malaysia, the research productivity of NSAIDs is not well explored.

Objective:

This study examined research productivity of NSAIDs in Malaysia.

Materials and Methods:

This bibliometric study included all published research articles on NSAIDs from 1979 to 2018, which were conducted in Malaysia. The search databases such as Google Scholar, PubMed, ScienceDirect, and Scopus were used. Search terms included NSAIDs and specific drug names such as ibuprofen, celecoxib, and naproxen. Growth of publication, authorship pattern, citation analysis, journal index, type of studies, and geographical distribution of institutions publishing articles on NSAIDs were measured.

Results:

Overall, 111 articles were retrieved from 1979 to 2018. The annual productivity of articles throughout the study fluctuated in which the highest productivity was in 2018, 12.61% (n = 14). Majority of articles were multiple authored, 99.10% (n = 109), and University of Science Malaysia (USM) produced the highest number of articles (30 articles). Most of the articles were International Scientific Indexing-indexed, 52.25% (n = 58), and the main issue studied in most of the articles was the drug formulation of NSAIDs.

Conclusion:

The growth of NSAID research in Malaysia was slow, and the majority of research involved laboratory studies. Clinical studies evaluating the clinical outcomes of NSAIDs in patients, particularly using large healthcare databases are still lacking.

Indomethacin decreases insulin secretion by reducing KCa3.1 as a biomarker of pancreatic tumor and causes apoptotic cell death

Insulinomas originate from pancreatic β cells and it is the most widely known tumor. Indomethacin is a nonsteroidal anti-inflammatory drug, which is used for blocking the production of some natural substances that cause inflammation and decrease pain. In this study, I aimed to investigate the effects of indomethacin on rat insulinoma INS-1 cells. The relationship between cell death and insulin metabolism was determined with the administration of indomethacin. The cell viability by WST-1; the apoptosis and necrosis levels by ELISA kits; malondialdehyde levels by spectrophotometer; and beclin, intracellular insulin, insulin secretion, KCa3.1, insulin receptor (IR), glucose transporter type 2 (GLUT2), activating transcription factor 2 (ATF2), Elk1, c-Jun, Akt and phosphorylated ATF2, Elk1, c-Jun, Akt, intracellular betacellulin and betacellulin secretion levels by Western blot analysis investigated. The Ins1, Ins2, IR, GLUT2, ATF2, Elk1, c-Jun, Akt, and Betacellulin gene expression levels were determined by the real-time quantitative reverse transcription-polymerase chain reaction method. Apoptotic cell death was observed with the administration of indomethacin. The insulin secretion and Ins1, Ins2 gene expression levels decreased. The insulin receptor and GLUT2 levels increased, while KCa3.1 (KCNN4) levels decreased with the administration of indomethacin to insulinoma INS-1 cells. A decrease was observed in the total c-Jun, phosphorylated ATF2, Elk1, c-Jun, and Akt levels. Betacellulin secretion levels increased. In insulinoma INS-1 cells, apoptotic cell death occurred in the following manner: (i) indomethacin might decrease insulin secretion by reducing KCa3.1, (ii) might inactivate the JNK/ERK pathway with the inactivity of transcription factors.

Cytokine and inflammatory mediator effects on TRPV4 function in choroid plexus epithelial cells

The choroid plexus (CP), composed of capillaries surrounded by a barrier epithelium, is the main producer of cerebrospinal fluid (CSF). The CP epithelium regulates the transport of ions and water between the blood and the ventricles, contributing to CSF production and composition. Several studies suggest a connection between the cation channel transient receptor potential vanilloid-4 (TRPV4) and transepithelial ion movement. TRPV4 is a nonselective, calcium-permeable cation channel present in CP epithelia reported to be activated by cytokines and inflammatory mediators. Utilizing the PCP-R (porcine choroid plexus-Riems) cell line, we investigated the effects of various cytokines and inflammatory mediators on TRPV4-mediated activity. Select proinflammatory cytokines (TNF-α, IL-1β, TGF-β1) had inhibitory effects on TRPV4-stimulated transepithelial ion flux and permeability changes, whereas anti-inflammatory cytokines (IL-10, IL-4, and IL-6) had none. Quantitative mRNA analysis showed that these cytokines had no effect on TRPV4 transcription levels. Inhibition of the transcription factor NF-κB, involved in the production and regulation of several inflammatory cytokines, inhibited TRPV4-mediated activity, suggesting a link between TRPV4 and cytokine production. Contrary to published studies, the proinflammatory mediator arachidonic acid (AA) had inhibitory rather than stimulatory effects on TRPV4-mediated responses. However, inhibition of AA metabolism also caused inhibitory effects on TRPV4, suggesting a complex interaction of AA and its metabolites in the regulation of TRPV4 activity. Together these data imply that TRPV4 activity is involved in the inflammatory response; it is negatively affected by proinflammatory mediators. Furthermore, arachidonic acid metabolites, but not arachidonic acid itself, are positive regulators of TRPV4.

Preemptive Analgesic and Antioxidative Effect of Curcumin for Experimental Migraine

OBJECTIVE

Our study aimed to investigate the analgesic and antioxidative stress effects of Curcumin (CC) in experimental migraine induced by Nitroglycerin (NTG) on rats, compared with Indomethacin (ID) and Propranolol (PP) treatments.

MATERIAL AND METHODS

Five groups of 10 rats treated i.p. were investigated: control group (healthy rats) injected with saline solution (0.9%), NTG-control group injected with NTG (1 mg/100 gbw, bw = body weight), and three groups with pretreatment applied 30 min previous to the formalin test (NTG + CC group: Curcumin (10 mg/100 gbw), NTG + PP group: Propranolol (100 μg/100 gbw), and NTG + ID group: Indomethacin (0.5 mg/100 gbw)). Formalin test was performed and number of flinches and shakes were counted. Several oxidative stress parameters were also assessed.

RESULTS

The smallest values of malondialdehyde (MDA), nitric oxide (NOx), and total oxidative status (TOS) were observed on NTG + CC with significant differences as compared with the control group (p < 0.0001). The group pretreated with Curcumin proved significantly smaller number of flinches and shakes compared with both NTG + PP and NTG + ID.

CONCLUSION

Our study demonstrates a superior activity of Curcumin not only versus control, but also versus Propranolol and Indomethacin.

Microglial TNFα Induces COX2 and PGI2 Synthase Expression in Spinal Endothelial Cells during Neuropathic Pain

Prostaglandins (PGs) are typical lipid mediators that play a role in homeostasis and disease. They are synthesized from arachidonic acid by cyclooxygenase 1 (COX1) and COX2. Although COX2 has been reported to be upregulated in the spinal cord after nerve injury, its expression and functional roles in neuropathic pain remain unclear. In this study, we investigated the expression of Cox2, PGI2 synthase (Pgis), and prostaglandin I2 receptor (IP receptor) mRNA in the rat spinal cord after spared nerve injury (SNI). Levels of Cox2 and Pgis mRNA increased in endothelial cells from 24 to 48 h after nerve injury. IP receptor mRNA was constitutively expressed in dorsal horn neurons. A COX2 inhibitor and IP receptor antagonists attenuated pain behavior in the early phase of neuropathic pain. Furthermore, we examined the relationship between COX2 and tumor necrosis factor-α (TNFα) in the spinal cord of a rat SNI model. Levels of TNFα mRNA transiently increased in the spinal microglia 24 h after SNI. The TNF receptors Tnfr1 and Tnfr2 mRNA were colocalized with COX2. Intrathecal injection of TNFα induced Cox2 and Pgis mRNA expression in endothelial cells. These results revealed that microglia-derived TNFα induced COX2 and PGIS expression in spinal endothelial cells and that endothelial PGI2 played a critical role in neuropathic pain via neuronal IP receptor. These findings further suggest that the glia–endothelial cell interaction of the neurovascular unit via transient TNFα is involved in the generation of neuropathic pain.

Evaluation of the anti-inflammatory action of curcumin analog (DM1): Effect on iNOS and COX-2 gene expression and autophagy pathways

This work describes the anti-inflammatory effect of the curcumin-analog compound, sodium 4-[5-(4-hydroxy-3-methoxyphenyl)-3-oxo-penta-1,4-dienyl]-2-methoxy-phenolate (DM1), and shows that DM1 modulates iNOS and COX-2 gene expression in cultured RAW 264.7 cells and induces autophagy on human melanoma cell line A375.

Carnosol protects against spinal cord injury through Nrf-2 upregulation

BACKGROUND

Carnosol is an ortho-diphenolic diterpene with excellent antioxidant potential. The present study was designed to identify the protective role of carnosol against spinal cord injury (SCI)-induced oxidative stress and inflammation in Wistar rats.

METHODS

In the present study, oxidative stress status was determined through estimating total antioxidant capacity, total oxidant status, lipid peroxide content, protein carbonyl and sulfhydryl levels, reactive oxygen species (ROS), antioxidant status (superoxide-dismutase, catalase, glutathione, glutathione peroxidase, glutathione-S-transferase). Inflammatory effects were determined by analyzing the expression of NF-κB and COX-2 through Western blot analysis. Further, carnosol-mediated redox homeostasis was analyzed by determining p-AKT and Nrf-2 levels.

RESULTS

SCI resulted in a significant increase in oxidative stress status through increased ROS generation, total oxidant levels, lipid peroxide content, protein carbonyl and sulfhydryl levels. The antioxidant status in SCI rats was significantly reduced, indicating imbalance in redox status. In addition, the expression of NF-κB and COX-2 was significantly upregulated, while p-AKT and Nrf-2 levels were downregulated in SCI rats. However, treatment with carnosol showed a significant enhancement in the antioxidant status with concomitant decline in oxidative stress parameters. Further, carnosol treatment regulated the key proteins in inflammation and redox status through significant downregulation of NF-κB and COX-2 levels and upregulation of p-AKT and Nrf-2 expression.

CONCLUSION

Thus, the present study shows for the first time on the protective role of carnosol against SCI-induced oxidative stress and inflammation through modulating NF-κB, COX-2 and Nrf-2 levels in Wistar rats.

Enhancement of the physical stability of amorphous indomethacin by mixing it with octaacetylmaltose. inter and intra molecular studies

PURPOSE

To demonstrate a very effective and easy way of stabilization of amorphous indomethacin (IMC) by preparing binary mixtures with octaacetylmaltose (acMAL). In order to understand the origin of increased stability of amorphous system inter- and intramolecular interactions between IMC and acMAL were studied.

METHODS

The amorphous IMC, acMAL and binary mixtures (IMC-acMAL) with different weight ratios were analyzed by using Dielectric Spectroscopy (DS), Differential Scanning Calorimetry (DSC), Raman Spectroscopy, X-ray Diffraction (XRD), Infrared Spectroscopy (FTIR) and Quantitative Structure-Activity Relationship (QSAR).

RESULTS

Our studies have revealed that indomethacin mixed with acetylated saccharide forms homogeneous mixture. Interestingly, even a small amount of modified maltose prevents from recrystallization of amorphous indomethacin. FTIR measurements and QSAR calculations have shown that octaacetylmaltose significantly affects the concentration of indomethacin dimers. Moreover, with increasing the amount of acMAL in the amorphous solid dispersion molecular interactions between matrix and API become more dominant than IMC-IMC ones. Structural investigations with the use of X-ray diffraction technique have demonstrated that binary mixture of indomethacin with acMAL does not recrystallize upon storage at room temperature for more than 1.5 year. Finally, it was shown that acMAL can be used to improve solubility of IMC.

CONCLUSIONS

Acetylated derivative of maltose might be very effective agent to improve physical stability of amorphous indomethacin as well as to enhance its solubility. Intermolecular interactions between modified carbohydrate and IMC are likely to be responsible for increased stability effect in the glassy state.

Cellular, molecular, and epigenetic mechanisms in non-associative conditioning: implications for pain and memory

Sensitization is a form of non-associative conditioning in which amplification of behavioral responses can occur following presentation of an aversive or noxious stimulus. Understanding the cellular and molecular underpinnings of sensitization has been an overarching theme spanning the field of learning and memory as well as that of pain research. In this review we examine how sensitization, both in the context of learning as well as pain processing, shares evolutionarily conserved behavioral, cellular/synaptic, and epigenetic mechanisms across phyla. First, we characterize the behavioral phenomenon of sensitization both in invertebrates and vertebrates. Particular emphasis is placed on long-term sensitization (LTS) of withdrawal reflexes in Aplysia following aversive stimulation or injury, although additional invertebrate models are also covered. In the context of vertebrates, sensitization of mammalian hyperarousal in a model of post-traumatic stress disorder (PTSD), as well as mammalian models of inflammatory and neuropathic pain is characterized. Second, we investigate the cellular and synaptic mechanisms underlying these behaviors. We focus our discussion on serotonin-mediated long-term facilitation (LTF) and axotomy-mediated long-term hyperexcitability (LTH) in reduced Aplysia systems, as well as mammalian spinal plasticity mechanisms of central sensitization. Third, we explore recent evidence implicating epigenetic mechanisms in learning- and pain-related sensitization. This review illustrates the fundamental and functional overlay of the learning and memory field with the pain field which argues for homologous persistent plasticity mechanisms in response to sensitizing stimuli or injury across phyla.

Preventive effects of curcumin against drug- and starvation-induced gastric erosions in rats

The present study was designed to investigate the gastroprotective, analgesic, and antipyretic effects of curcumin (Cur), the major constituent of turmeric. Acetylsalicylic acid (ASA) was used in this study as a standard drug for comparison. The analgesic activity was measured using the Hot-Plate Test. The antipyretic and antiulcer effects were assessed using yeast-induced pyrexia and gastric ulceration, respectively. Curcumin (100 mg/kg) injected intra-peritoneally 1 hr prior to the Hot-Plate Test showed significant analgesic activity expressed by both parameters: an increase in latency time and a reduction in paw licking as compared to the controls. In the animal model of pyrexia, curcumin (100 mg/kg injected intra-peritoneally) exhibited a significant reduction in the rectal temperature after 1 hr, 2 hrs, 4 hrs, and 5 hrs of treatment, indicating the antipyretic effect of curcumin. Rats with orally administered curcumin (200 mg/kg) did not show any lesions on the inner lining of the stomach after a 16 hr fast, indicating the gastroprotective effects of curcumin as compared to saline- and acetylsalicylic acid-administered rats. The significantly low ulcer index in curcumin-treated rats following starvation highlights the gastroprotective characteristics of curcumin.

Co-induction of cyclooxygenase-2 [correction of cyclooxyenase-2] and early growth response gene (Egr-1) in spinal cord in a clinical model of persistent inflammation and hyperalgesia

BACKGROUND

This study characterised the effects of persistent peripheral inflammation of the foot on pain and spinal cord expression of cyclooxygenase-1 and -2 (COX-1 and COX-2) and early growth response gene 1 (Egr-1), known markers of neuronal plasticity, in a clinical model of naturally-occurring inflammatory disease and hyperalgesia in sheep ('footrot'), before and after routine treatment (parenteral treatment with antibiotics and antiseptic footbathing). The temporal pattern of expression of COX-1, COX-2 and Egr-1 mRNA and protein were analysed using real-time PCR and Western blotting.

RESULTS

Animals affected with persistent peripheral inflammation displayed significant hyperalgesia and lameness (a proxy indicator of spontaneous pain) restricted to the inflamed limb. Hyperalgesia and lameness were significantly attenuated 1 day after treatment, and resolved further by day 7 and day 3, respectively. COX-2 but not COX-1, protein expression was up-regulated in spinal cord from lame animals on day 0, before treatment. Following treatment and attenuation of pain behaviours, levels of COX-2 returned to control levels. Significant induction of Egr-1 mRNA and protein were observed in spinal cord from lame animals. Three days after treatment, levels of Egr-1 mRNA returned to control levels, however, Egr-1 protein remained elevated.

CONCLUSION

Elevated levels of spinal COX-2 and Egr-1 protein correlate with the presence of pain and hyperalgesia, and may underlie persistent pain, although a direct causal link has still to be established. Understanding the temporal pattern of expression of key mediators in clinical pain states may lead to better strategies to manage pain.

Estradiol-induced antinociceptive responses on formalin-induced nociception are independent of COX and HPA activation

Estrogen modulates pain perception but how it does so is not fully understood. The aim of this study was to determine if estradiol reduces nociceptive responses in part via hypothalamic-pituitary-adrenal (HPA) axis regulation of cyclooxygenase (COX)-1/COX-2 activity. The first study examined the effects of estradiol (20%) or vehicle with concurrent injection nonsteroidal antiinflammatory drugs (NSAIDs) on formalin-induced nociceptive responding (flinching) in ovariectomized (OVX) rats. The drugs were ibuprofen (COX-1 and COX-2 inhibitor), SC560 (COX-1 inhibitor), or NS398 (COX-2 inhibitor). In a second study, estradiol's effects on formalin-induced nociception were tested in adrenalectomized (ADX), OVX, and ADX+OVX rats. Serum levels of prostaglandins (PG) PGE(2) and corticosterone were measured. Estradiol significantly decreased nociceptive responses in OVX rats with effects during both the first and the second phase of the formalin test. The nonsteroidal antiinflammatory drugs (NSAIDs) did not alter nociception at the doses used here. Adrenalectomy neither altered flinching responses in female rats nor reversed estradiol-induced antinociceptive responses. Estradiol alone had no effect on corticosterone (CORT) or prostaglandin levels after the formalin test, dissociating the effects of estradiol on behavior and these serum markers. Ibuprofen and NS398 significantly reduced PGE2 levels. CORT was not decreased by OVX surgery or by estradiol below that of ADX. Only IBU significantly increased corticosterone levels. Taken together, our results suggest that estradiol-induced antinociception in female rats is independent of COX activity and HPA axis activation.

Luminal endothelial lectins with affinity for N-acetylglucosamine determine flow-induced cardiac and vascular paracrine-dependent responses

Coronary blood flow applied to the endothelial lumen modulates parenchymal functions via paracrine effectors, but the mechanism of flow sensation is unknown. We and others have demonstrated that coronary endothelial luminal membrane (CELM) oligosaccharides and lectins are involved in flow detection, and we proposed that cardiac effects of coronary flow result from a reversible flow-modulated lectin-oligosaccharide interaction. Recently, glycosylated and amiloride-sensitive Na+/Ca++ channels (ENaCs) have been proposed to be involved in the flow-induced endothelial responses. Because N-acetylglucosamine (GlcNac) is one of the main components of glycocalyx oligosaccharides (i.e., hyaluronan [−4GlcUA β1–3GlcNAc β1−]n), the aim of this article is to isolate and define CELM GlcNac-binding lectins and determine their role in cardiac and vascular flow-induced effects. For this purpose, we synthesized a 460-kDa GlcNac polymer (GlcNac-Pol) with high affinity toward GlcNac-recognizing lectins. In the heart, intracoronary administration of GlcNac-Pol upon binding to CELM diminishes the flow-dependent positive inotropic and dromotropic effects. Furthermore, GlcNac-Pol was used as an affinity probe to isolate CELM GlcNac-Pol-recognizing lectins and at least 35 individual lectinic peptides were identified, one of them the β-ENaC channel. Some of these lectins could participate in flow sensing and in GlcNac-Pol-induced effects. We also adopted a flow-responsive and well-accepted model of endothelial-parenchymal paracrine interaction: isolated blood vessels perfused at controlled flow rates. We established that flow-induced vasodilatation (FIV) is blocked by endothelial luminal membrane (ELM) bound GlcNac-Pol, nitro-l-arginine methyl ester and indomethacin, amiloride, and hyaluronidase. The effect of hyaluronidase was reversed by infusion of soluble hyaluronan. These results indicate that GlcNac-Pol inhibits FIV by competing and displacing intrinsic hyaluronan bound to a lectinic structure such as the amiloride-sensitive ENaC. Nitric oxide and prostaglandins are the putative paracrine mediators of FIV.

Eicosanoids in inflammation and cancer: the role of COX-2

Eicosanoids, a family of oxygenated metabolites of eicosapolyenoic fatty acids, such as arachidonic acid, formed via the lipoxygenase, cyclooxygenase (COX) and epoxygenase pathways, play an important role in the regulation of various pathophysiological processes, including inflammation and cancer. COX-2, the inducible isoform of COX, has emerged as the key enzyme regulating inflammation, and promises to play a considerable role in cancer. Although NSAIDs have been in use for centuries, the COX-2 selective inhibitors - coxibs - have emerged as potent anti-inflammatory drugs with fewer gastric side effects. As COX-2 plays a major role in neoplastic transformation and cancer growth, by downregulating apoptosis and promoting angiogenesis, invasion and metastasis, coxibs have a potential role in the prevention and treatment of cancer. Recent studies indicate their possible application in overcoming drug resistance by downregulating the expression of MDR-1. However, the cardiac side effects of some of the coxibs have limited their application in treating various inflammatory disorders and warrant the development of COX-2 inhibitors without side effects. This review will focus on the role of COX-2 in inflammation and cancer, with an emphasis on novel approaches to the development of COX-2 inhibitors without side effects.

Brain cyclooxygenase-2 mediates interleukin-1-induced cellular activation in preoptic and arcuate hypothalamus, but not sickness symptoms

Interleukin-1beta acts on the CNS to induce fever, neuroendocrine activation, and behavioral changes, but cannot passively cross the blood-brain barrier. According to a widely accepted hypothesis interleukin-1beta induces the synthesis of cyclooxygenase-2 at the blood-brain interface, which produces prostaglandins that diffuse into brain parenchyma to activate neurons. We studied the role of brain cyclooxygenase-2 in interleukin-1beta-induced fever, neuroendocrine and behavioral responses and cellular activation by intracerebroventricular infusion of the cyclooxygenase-2 inhibitor NS-398. Central cyclooxygenase-2 inhibition attenuated extracellular signal-regulated kinase-1/2 phosphorylation and c-Fos induction in the median preoptic area and arcuate hypothalamus, but not in other hypothalamic or brainstem structures, after intraperitoneal interleukin-1beta administration. However, the same treatment did not affect interleukin-1beta-induced fever, rises in corticosterone or anorexia. These findings moderate the prevailing view and indicate that brain cyclooxygenase-2-dependent prostaglandin production is important to activation of the median preoptic and arcuate hypothalamus, but not necessarily involved in fever, rises in plasma corticosterone and anorexia after peripheral interleukin-1beta administration.

Antinociceptive and toxicological effects of Dioclea grandiflora seed pod in mice

The acute treatment of mice with an ethanolic extract from the seed pod of Dioclea grandiflora (EDgP) at doses of 75, 150 and 300 mg/kg by intraperitoneal administration produced a significant antinociceptive effect as displayed by the acetic acid-induced writhing test and the formalin test. The antinociception was observed through the first (neurogenic pain) and second (inflammatory pain) phases in the formalin test. The hot plate test did not show an increase in the antinociceptive latency whereas the motor performance was affected by the administration at 300 mg/kg at the beginning (30 minutes) of the observation period but not at later periods (60 and 120 minutes). These results suggest that EDgP has a central antinociceptive action and a possible anti-inflammatory activity in mice.

A new chloroquinolinyl chalcone derivative as inhibitor of inflammatory and immune response in mice and rats

The synthetic chalcone derivative 1-(2,4-dichlorophenyl)-3-(3-(6,7-dimethoxy-2-chloroquinolinyl))-2-propen-1-one (CIDQ) was evaluated for its anti-inflammatory, analgesic and immunomodulatory efficacy in-vitro and in-vivo. CIDQ concentration-dependently inhibited the production of nitric oxide (NO) (IC50 4.3 μM) and prostaglandin E2 (PGE2) (IC50 1.8 μM) in RAW 264.7 macrophages stimulated with lipopolysaccharide. Human mononuclear cell proliferation was significantly inhibited by 10 μM CIDQ. Oral administration of CIDQ (10–30 mg kg−1) in the 24-h zymosan-stimulated mouse air-pouch model produced a dose-dependent reduction of cell migration as well as NO and PGE2 levels in exudates. CIDQ (20 mg kg−1, p.o.) inhibited ear swelling and leucocyte infiltration in the delayed-type hypersensitivity response to 2,4-dinitrofluorobenzene in mice. In the rat adjuvant-arthritis model, this compound reduced joint inflammation as well as PGE2 and cytokine levels. In addition, CIDQ displayed analgesic effects in the phenylbenzoquinone-induced abdominal constriction model in mice and in the late phase of the nociceptive response to formalin. Our findings indicated the potential interest of CIDQ in the modulation of some immune and inflammatory conditions.

Spinal antinociceptive effects of cyclooxygenase inhibition during inflammation: Involvement of prostaglandins and endocannabinoids

Both cyclooxygenase-1 and -2 are expressed in the spinal cord, and the spinal COX product prostaglandin E(2) (PGE(2)) contributes to the generation of central sensitization upon peripheral inflammation. Vice versa spinal COX inhibition is considered an important mechanism of antihyperalgesic pain treatment. Recently, however, COX-2 was shown to be also involved in the metabolism of endocannabinoids. Because endocannabinoids can have analgesic actions it is conceivable that inhibition of spinal COX produces analgesia not only by inhibition of PG synthesis but also by inhibition of endocannabinoid breakdown. In the present study, we recorded from spinal cord neurons with input from the inflamed knee joint and we measured the spinal release of PGE(2) and the endocannabinoid 2-arachidonoyl glycerol (2-AG) in vivo, using the same stimulation procedures. COX inhibitors were applied spinally. Selective COX-1, selective COX-2 and non-selective COX inhibitors attenuated the generation of spinal hyperexcitability when applied before and during development of inflammation but, when inflammation and spinal hyperexcitability were established, only selective COX-2 inhibitors reversed spinal hyperexcitability. During established inflammation all COX inhibitors reduced release of spinal PGE(2) almost equally but only the COX-2 inhibitor prevented breakdown of 2-AG. The reversal of spinal hyperexcitability by COX-2 inhibitors was prevented or partially reversed by AM-251, an antagonist at the cannabinoid-1 receptor. We conclude that inhibition of spinal COX-2 not only reduces PG production but also endocannabinoid breakdown and provide evidence that reversal of inflammation-evoked spinal hyperexcitability by COX-2 inhibitors is more related to endocannabinoidergic mechanisms than to inhibition of spinal PG synthesis.

Synthesis and pharmacological evaluation of N-phenyl-acetamide sulfonamides designed as novel non-hepatotoxic analgesic candidates

In this paper we report the design, synthesis and pharmacological evaluation of a series of N-phenyl-acetamide sulfonamide derivatives (5a-g), planned by structural modification on the prototype paracetamol (1). In this series (5a-g), compound LASSBio-1300 (5e; ID(50)=5.81 micromol/kg) stands out as a new non-hepatotoxic analgesic drug candidate. The increase of area, volume and electrostatic potential of paracetamol's analogues seems to be beneficial to the analgesic activity. Unlike paracetamol (1) and the other analogues (5a, 5d-g), compounds 5b and 5c presented an important anti-hypernociceptive activity associated to inflammatory pain.

The effects of intrathecal cyclooxygenase-1, cyclooxygenase-2, or nonselective inhibitors on pain behavior and spinal Fos-like immunoreactivity

BACKGROUND

Prostaglandins are synthesized by cyclooxygenase (COX) and are thought to play an important role in nociceptive transmission in the spinal cord. Fos expression is an indicator of spinal neuron activation. We examined the role of intrathecal selective and nonspecific COX inhibitors on spinal C-Fos expression.

METHODS

To evaluate the relative contribution of COX-1 and COX-2 in nociceptive transmission in the spinal cord, we assessed the effects of the selective COX-1 inhibitor SC 560, the selective COX-2 inhibitor celecoxib, and the nonselective COX inhibitor ketorolac on formalin-evoked behavior and spinal c-Fos-like immunoreactivity (FLI). Rats received each of the drugs (30, 60, or 90 microg) intrathecally before the subcutaneous administration of formalin (5%, 50 microL) to the plantar surface of a hindpaw. The control group received vehicle intrathecally before the administration of formalin.

RESULTS

Phase 1 flinching behavior decreased in rats given celecoxib or ketorolac 90 mug. Phase 2 flinching behavior decreased in rats given all doses of ketorolac or celecoxib 90 microg (P < 0.05). The FLI was significantly reduced in rats given celecoxib or ketorolac 90 microg for laminae I-II (P < 0.05). By contrast, for laminae V-VI, only the ketorolac 60 or 90 microg treatment group demonstrated a larger decrease in FLI (P < 0.05). The FLI expression in laminae V-VI had a significant correlation with phase 2 flinching behavior (P < 0.05).

CONCLUSIONS

A dual inhibitor of COX-1 and COX-2 suppressed both responses of formalin-evoked behaviors and FLI expression of whole laminae in the lumbar spinal cord. FLI expression of laminae I-II alone may not be a good indicator of the ability to produce anti-hypersensitivity; however, the FLI of laminae V-VI correlates with phase 2 responses.

Additive interaction of intraperitoneal dexmedetomidine and topical nimesulide, celecoxib, and DFU for antinociception

Nimesulide, celecoxib, and DFU (5, 5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulphonyl)phenyl-2(5H)-furanone) are nonsteroidal anti-inflammatory drugs (NSAIDs) with selective cyclo-oxygenase (COX)-2 blocking properties and have potent analgesic and anti-inflammatory activities in oral and parenteral administrations. Dexmedetomidine, a highly selective alpha(2)-adrenoceptor agonist, is an extremely potent antinociceptive agent. The present study was conducted to evaluate the antinociception induced by nimesulide, celecoxib, and DFU when topically applied on the tail in the absence or presence of intraperitoneal dexmedetomidine. Antinociception was measured in the radiant tail-flick test after immersion of the tail of rat into a solution of dimethyl sulfoxide (DMSO) containing nimesulide, celecoxib, or DFU. Antinociceptive effect of all drugs peaked at 60 min and decreased gradually to baseline levels at 240 min. Nimesulide had a potency lower than those of celecoxib, and DFU. The antinociceptive effect of dexmedetomidine was blocked by systemic pretreatment of selective alpha(2)-adrenoceptor antagonist, atipamezole. This suggests that antinociceptive effects of dexmedetomidine involve alpha(2)-adrenoceptors. Combination of topical COX-2 inhibitors with intraperitoneal dexmedetomidine yielded additive analgesic effect. These results demonstrate an additive interaction between topical COX-2 inhibitors with intraperitoneal dexmedetomidine. These observations are significant for physicians to combine selective COX-2 inhibitors and dexmedetomidine in the management of pain.

A nonopioid analgesic acts upon the PAG-RVM axis to reverse inflammatory hyperalgesia

Metamizol (dipyrone) and other nonsteroidal anti-inflammatory drugs (NSAIDs) induce antinociception by acting upon peripheral tissues and upon central nervous system structures, notably the periaqueductal grey matter (PAG) and the spinal cord. Inflammation-induced hyperalgesia is prevented by spinal application of NSAIDs before the inflammation, but once central sensitization is established the spinal effect of NSAIDs is uncertain. The present study examines whether the action upon the PAG contributes to the attenuation of inflammation-induced spinal hyperalgesia by NSAIDs. In deeply anaesthetized rats, responses of spinal multireceptive neurons to mechanical stimulation of the ipsilateral paw and leg were recorded. An inflammation in the paw was induced with carrageenan. Fifty minutes later, neuronal responses to innocuous and noxious stimulation had, respectively, increased to 206 and 304% for paw, and 160 and 190% for leg. When metamizol (150 microg in 0.5 microL) was microinjected into PAG before the inflammation, neuronal hyperexcitability was delayed for approximately 60 min and was much reduced by 215 min. More interestingly, microinjection of metamizol into PAG when hyperexcitability was fully developed depressed neuronal responses down to baseline for approximately 1 h. The effect of PAG metamizol was reversed by microinjection of a GABA(A) agonist into the rostral ventromedial medulla (RVM), which indicates that RVM relays the metamizol effect from PAG onto the spinal cord. These results suggest that, upon clinical administration of NSAIDs, a joint action upon PAG and spinal cord contributes to preventing the development of hyperalgesia but it is mainly the action upon PAG which contributes to reducing fully established hyperalgesia.

Inflammation and Spinal Cord Injury: Infiltrating Leukocytes as Determinants of Injury and Repair Processes

The immune response that accompanies spinal cord injury contributes to both injury and reparative processes. It is this duality that is the focus of this review. Here we consider the complex cellular and molecular immune responses that lead to the infiltration of leukocytes and glial activation, promote oxidative stress and tissue damage, influence wound healing, and subsequently modulate locomotor recovery. Immunomodulatory strategies to improve outcomes are gaining momentum as ongoing research carefully dissects those pathways, which likely mediate cell injury from those, which favor recovery processes. Current therapeutic strategies address divergent approaches including early immunoblockade and vaccination with immune cells to prevent early tissue damage and support a wound-healing environment that favors plasticity. Despite these advances, there remain basic questions regarding how inflammatory cells interact in the injured spinal cord. Such questions likely arise as a result of our limited understanding of immune cell/neural interactions in a dynamic environment that culminates in progressive cell injury, demyelination, and regenerative failure.

Peripheral formalin injection induces long-lasting increases in cyclooxygenase 1 expression by microglia in the spinal cord

Activated glia are a source of substances known to enhance pain, including centrally synthesized prostaglandins. We have previously shown that microglia are activated in the spinal cord following peripheral formalin injection. In the present study, we investigated cyclooxygenase (COX-1 and COX-2) expression in the spinal cord using immunohistochemistry and Western blots in the formalin pain model, to further understand how spinal glia modulate pain processing. We show that both COX-1 and COX-2 are constitutively expressed in the spinal cord. Hind paw formalin injection increased COX-1 expression, beginning at 1 day after injection and lasting at least 2 weeks, the duration of experiments. The COX-2 expression changed considerably less, with a significant increase of COX-2 protein level only observed at 2 h after injection. Double labeling studies showed that COX-1 was expressed in microglia and COX-2 was expressed in neurons. These data indicate that both COX-1 and COX-2 are increased in the spinal cord following formalin injection, but the time course and cellular sources are different, suggesting that both COX-1 (longer time points) and COX-2 (very short time points) may be involved in spinal modulation in the formalin pain model. Our study also suggests that spinal microglial activation may play a role in long-term hyperalgesia through the increased expression of COX-1.

PERSPECTIVE

This article reports that COX-1 expression by microglia is increased in the spinal cord after peripheral formalin injection into the rat hind paw. This result could potentially help clinicians understand how COX-1 may be involved in pain processing and the role microglial activation plays in pain mechanisms.

Different Patterns of Spinal Cyclooxygenase-1 and Cyclooxygenase-2 mRNA Expression in Inflammatory and Postoperative Pain

Levels of cyclooxygenase-2 (COX-2) mRNA, but not those of COX-1, were reported to be raised significantly after peripheral inflammation in the rat spinal cord. The aim of the present study was to ascertain whether this pattern of COX-2 and COX-1 expression applies also to other pain conditions induced by surgical procedure. Experiments were performed on two types of pain models. In a model of postoperative pain, 1 cm longitudinal incision was made through skin, fascia and muscle of the plantar aspect of the right hind paw in anaesthetized rats. In the second model, peripheral inflammation was induced by unilateral, intraplantar injection of carrageenan in the right hind paw. Carrageenan injection or skin incision produced marked and significant reduction of paw withdrawal latencies to noxious radiant heat stimuli after 2 and 6 hr. Under the acute inflammation 2 and 6 hr after carrageenan injection levels of COX-2 mRNA were markedly raised (7.8 and 15.5 times; P<0.001, respectively) while spinal levels of COX-1 mRNA were not significantly altered (n.s.). In contrast, spinal levels of COX-2 mRNA were raised less markedly in a model of postoperative pain (4.9 times at 2 hr; P<0.001 and 2.9 times (n.s.) at 6 hr after surgery) whilst levels of COX-1 mRNA in the lumbar spine were increased significantly (2.3 times; P<0.001) 6 hr after surgery. The present findings indicate that expression of COX-2 mRNA in the spine is less dominant in postoperative pain than in inflammatory pain and that spinal COX-1 mRNA is upregulated in postoperative pain.

Effect of cyclooxygenase inhibitors on the micturition reflex in rats: correlation with inhibition of cyclooxygenase isozymes

OBJECTIVE

To investigate the role of cyclooxygenase (COX) isozymes (COX-1 and -2) in the regulation of bladder volume capacity (BVC) in several rat urodynamic models, using a selection of nonsteroidal anti-inflammatory drugs (NSAIDs), some selective for COX-2, correlating the potency of the tested compounds in the urodynamic models and their in vitro potency as inhibitors of COX isozymes, to verify the relative importance of the different isozymes.

MATERIALS AND METHODS

The effects of an i.v. administration of several nonselective and selective COX-2 inhibitors (indomethacin, meloxicam, naproxen, aspirin, paracetamol, flurbiprofen, nimesulide, NS-398, celecoxib, rofecoxib and L 745337) on bladder filling and voiding were evaluated in conscious and anaesthetized rats by cystometry. The cystometry was done in conscious rats 1 day after catheter implantation, by filling the bladder with dilute acetic acid (0.2%) or saline, and again with saline 5 days after catheterization. Effects on isovolumic bladder contractions in anaesthetized rats were also evaluated.

RESULTS

All the NSAIDs tested dose-dependently increased BVC; their potency at increasing BVC during infusion of the bladder with acetic acid was similar to that evaluated with saline on cystometry 1 day after catheterization. When a nonselective (naproxen) and a selective (nimesulide) COX-2 inhibitor were tested in rats with bladders infused with saline 5 days after catheterization, their effects on BVC were significantly lower than those evaluated at 1 day. All tested compounds dose-dependently inhibited isovolumic bladder contractions in anaesthetized rats. There was a good correlation between the potency in inhibiting the isovolumic bladder contractions in anaesthetized rats and in increasing BVC during cystometry in conscious rats with the bladder infused with acetic acid. The potency of the compounds in the cystometry model with bladders infused with acetic and in the isovolumic bladder voiding contractions correlated well with COX-2 inhibition, but not COX-1.

CONCLUSIONS

Both nonselective and COX-2 selective inhibitors are more active in inhibiting the micturition reflex in rats with bladder overactivity caused by bladder irritation than in normal rats. The potency of the anti-inflammatory compounds in inhibiting bladder overactivity induced by chemical or surgical irritation, and their activity in a cystometrographic model practically independent of bladder irritation (isovolumic bladder contractions in anaesthetized rats), was related to the potency as inhibitors of COX-2 isozyme. This suggests that the involvement of prostaglandins in the micturition reflex in rats is mainly mediated by this isozyme.

The involvement of a cyclooxygenase 1 gene-derived protein in the antinociceptive action of paracetamol in mice

Paracetamol is a widely used analgesic and antipyretic with weak anti-inflammatory properties. Experimental evidence suggests that inhibition of prostaglandin biosynthesis contributes to its pharmacological actions. Three cyclooxygenase (COX) isoenzymes are involved in prostaglandin biosynthesis, COX-1, COX-2 and a recently discovered splice-variant of COX-1, COX-3. Our aim was to identify the relative roles for these enzymes in the antinociceptive action of paracetamol in mice. We compared the antinociceptive action of paracetamol with the non-selective non-steroid anti-inflammatory drug, diclofenac and studied paracetamol antinociception in COX-1 and COX-2 knockout mice. Paracetamol (100-400 mg/kg) inhibited both acetic acid- and iloprost-induced writhing responses. In contrast, diclofenac (10-100 mg/kg) inhibited only acetic acid-induced writhing. Only diclofenac reduced peripheral prostaglandin biosynthesis whereas both drugs reduced central prostaglandin production. Prostaglandin E(2) (PGE(2)) concentrations were reduced in different brain regions by administration of paracetamol. COX-1, COX-2 and COX-3 enzyme proteins were expressed in the same brain regions. The effects of paracetamol on writhing responses and on brain PGE(2) levels were reduced in COX-1, but not COX-2, knockout mice. The selective COX-3 inhibitors, aminopyrine and antipyrine also reduced writhing responses and brain PGE(2) biosynthesis. These results suggest that the antinociceptive action of paracetamol may be mediated by inhibition of COX-3.

Ionizing radiation induces astrocyte gliosis through microglia activation

The aim of this study was to investigate the role of microglia in radiation-induced astrocyte gliosis. We found that a single dose of 15 Gy radiation to a whole rat brain increased immunostaining of glial fibrillary acidic protein in astrocytes 6 h later, and even more so 24 h later, indicating the initiation of gliosis. While irradiation of cultured rat astrocytes had little effect, irradiation of microglia-astrocyte mixed-cultures displayed altered astrocyte phenotype into more processed, which is another characteristic of gliosis. Experiments using microglia-conditioned media indicated this astrocyte change was due to factors released from irradiated microglia. Irradiation of cultured mouse microglial cells induced a dose-dependent increase in mRNA levels for cyclooxygenase-2 (COX-2), interleukin (IL)-1beta, IL-6, IL-18, tumor necrosis factor-alpha and interferon-gamma-inducible protein-10, which are usually associated with microglia activation. Consistent with these findings, irradiation of microglia activated NF-kappaB, a transcription factor that regulates microglial activation. Addition of prostaglandin E2 (PGE2: a metabolic product of the COX-2 enzyme) to primary cultured rat astrocytes resulted in phenotypic changes similar to those observed in mixed-culture experiments. Therefore, it appears that PGE(2) released from irradiated microglia is a key mediator of irradiation-induced gliosis or astrocyte phenotype change. These data suggest that radiation-induced microglial activation and resultant production of PGE2 seems to be associated with an underlying cause of inflammatory complications associated with radiation therapy for malignant gliomas.

Prostaglandins, glutamate and nitric oxide synthase mediate nitroglycerin-induced hyperalgesia in the formalin test

Increasing evidence supports a possible role for nitric oxide (NO) in the transmission of pain signals and in the development of central mechanisms of hyperalgesia. Previously, we have shown that nitroglycerin, an NO donor, is able to induce a long-lasting hyperalgesic state in rats. Nitroglycerin-induced hyperalgesia can be detected as an increase in the nociceptive behavior evoked by the formalin test. In the present study we investigated the possible mediators in the nitroglycerin-induced hyperalgesic state. Male Sprague-Dawley rats were injected with nitroglycerin and pretreated with indomethacin, 5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclo-hepten-5,10-imine hydrogen maleate (MK-801) or N(omega)-nitro-L-arginine methyl ester (L-NAME). The results obtained showed that inhibition of prostaglandins or NO synthesis prevents nitroglycerin-induced hyperalgesia in Phase II of the formalin test. A similar inhibitory effect was also observed following pretreatment with the glutamate antagonist MK801. The present findings point to the role of prostaglandins, NO synthesis and glutamate activity in the induction of nitroglycerin-induced hyperalgesia.

Peripheral inflammation modifies the effect of intrathecal IL-1β on spinal PGE2 production mainly through cyclooxygenase-2 activity. A spinal microdialysis study in freely moving rats

Acute inflammation induces upregulation of IL-1beta both at the site of the peripheral inflammation and in the cerebrospinal fluid (CSF). The central increase of IL-1beta mainly contributes to the development of hypersensitivity. However, the spinal mechanisms for the effects of IL-1beta in nociceptive transmission are incompletely understood. It is also unknown whether previous sensitization changes IL-1beta activity. We therefore investigated the dose-effect relationship of intrathecal (i.t.) IL-1beta on spinal PGE(2) production in the absence and presence of peripheral formalin inflammation with spinal microdialysis in freely moving rats. The possible involvement of cyclooxygenase (COX) isoforms in the IL-1beta-mediated spinal PGE(2) production on the background of peripheral formalin inflammation was further evaluated with the selective COX-1 and COX-2 inhibitors. We found that the i.t. administration of IL-1beta, with doses of 1, 2, 8, or 16 ng, increased PGE(2) levels in CSF in a dose-related fashion. This IL-1beta-evoked PGE(2) release occurred within 30min after IL-1beta administration, peaked at 30-60 min interval, and returned gradually to the baseline level within 4h. Peripheral formalin inflammation in the paw induced a more prolonged effect of spinal IL-1beta with larger PGE(2) releases in the CSF compared with the non-inflammatory state, suggesting that peripheral inflammation enhances central sensitization. The COX-2 inhibitor SC58236 (15 mg/kg) reduced the IL-1beta-mediated PGE(2) increase in CSF by 86% while the COX-1 inhibitor SC58560 (15 mg/kg) had less effect (28%). Our study suggests that mainly the COX-2 enzyme mediates the IL-1beta-induced increase in spinal PGE(2) in the presence of peripheral formalin inflammation.

Analgesic effects of intrathecally administered celecoxib, a cyclooxygenase-2 inhibitor, in the tail flick test and the formalin test in rats

BACKGROUND

The analgesic effects of celecoxib, a cyclooxygenase-2 (COX-2) inhibitor, on formalin-induced pain are still controversial. The purpose of this study was to examine the analgesic effects of intrathecally administered celecoxib on inflammatory induced pain, thermal-induced pain and hemodynamics.

METHODS

Male Sprague-Dawley rats with lumbar intrathecal catheters were tested via their tail withdrawal response to thermal stimulation (tail flick test) and via their paw flinching and shaking response to subcutaneous formalin injection into the hind paw (formalin test) after intrathecal administration of celecoxib. The blood pressure, pulse rate and behavioral side-effects were also examined.

RESULTS

Even the maximum available dose of celecoxib (200 microg/20 microl) had little effect in the tail flick test. In the formalin test, celecoxib induced a dose-dependent decrease in the flinch response in both phases 1 and 2. The 50% effective doses were 0.025 microg (95% confidence interval, 0.007-0.082 microg) in phase 1, 0.026 microg (0.010-0.045 microg) in phase 2a and 0.001 microg (0.00009-0.010 microg) in phase 2b. With the doses used in this study, the blood pressure and pulse rate did not change and no motor disturbance or behavioral side-effects were observed.

CONCLUSION

Intrathecal administration of celecoxib decreased inflammatory acute and facilitated pain without any hemodynamic or behavioral side-effects, but had no effect on acute thermal pain.

Antinociceptive effect of the aqueous extract obtained from roots of Physalis angulata L. on mice

In this study, we attempted to identify the possible antinociceptive action of aqueous extract (AE) obtained from roots of Physalis angulata, known in Brazil as "Camapu", used to treat various pain-related physiological conditions. The AE of Physalis angulata (10-30 mg/kg) given by i.p. or p.o. route, 0.5 and 1h prior, produced significant inhibition of abdominal constrictions caused by acetic acid, with ID(50) values of 18.5 (17.4-19.8) and 21.5 (18.9-24.4)mg/kg and inhibitions of 83+/-8 and 66+/-5%, respectively. The AE (10-60 mg/kg, i.p.) also caused significant inhibition of the late-phase of formalin-induced pain, with an ID(50) value of 20.8 (18.4-23.4)mg/kg and inhibition of 100%. Treatment of mice with AE (60 mg/kg, i.p.) or with morphine (10mg/kg, i.p.) produced a significant increase of the reaction time in the hot-plate test. These results demonstrate, for the first time, that the AE of Physalis angulata produce marked antinociception against the acetic acid-induced visceral pain and inflammatory pain responses induced by formalin in mice. The mechanism by which the AE produces antinociception still remains unclear. However, pharmacological and chemical studies are continuing in order to characterize the mechanism(s) responsible for the antinociceptive action and also to identify the active principles present in Physalis angulata. Moreover, the antinociceptive action demonstrated in the present study supports, at least partly, the ethnomedical uses of this plant.

The Effects of Epidural Deracoxib on the Ground Reaction Forces in an Acute Stifle Synovitis Model

OBJECTIVE

To evaluate the efficacy of epidurally administered deracoxib to mediate the signs of a sodium urate crystal-induced stifle synovitis in dogs, and to compare the efficacy of epidural versus subcutaneously administered deracoxib.

STUDY DESIGN

Experimental, randomized, blinded, placebo-controlled modified cross-over design.

ANIMALS

Random source, adult, mixed breed dogs (n = 24; 14 males, 10 females).

METHODS

Sodium urate crystals were used to create a stifle synovitis model to evaluate the efficacy of deracoxib. Dogs were divided into 4 groups: 3 mg/kg epidural deracoxib, 1.5 mg/kg epidural deracoxib, 3 mg/kg subcutaneous deracoxib, and a placebo (vehicle for deracoxib). Force plate and subjective evaluations were made at time 0, 2, 4, 8, 12, and 24 hours post-treatment. Repeated measures ANOVA with Bonferroni-corrected post hoc comparisons was used to determine significant treatment effects.

RESULTS

Peak vertical force (PVF) and vertical impulse (VI) were both significantly higher in deracoxib treated dogs compared with placebo. For 3 mg/kg epidural and subcutaneous deracoxib, PVF and VI were significantly greater than for 1.5 mg/kg epidural deracoxib. Overall pain score for all deracoxib-treated dogs was significantly lower than for placebo dogs.

CONCLUSIONS

Epidural administration of deracoxib is effective at providing analgesia in an acute joint pain model; however, it does not appear to be more effective than systemic administration.

CLINICAL RELEVANCE

Injectable deracoxib is effective in providing analgesia in acute inflammatory conditions of synovial joints.

Analgesic effects of nonsteroidal antiinflammatory drugs, acetaminophen, and morphine in a mouse model of bone cancer pain

PURPOSE

Bone metastasis is one of the major causes of cancer-related pain, and not all bone cancer pain can be effectively treated. Recently, a mouse model of bone cancer pain was introduced. To test the analgesic effects of nonsteroidal antiinflammatory drugs on bone cancer pain, the authors examined the effects of oral administration of a cyclooxygenase-1 (COX-1) selective inhibitor (SC560), a COX-2 selective inhibitor (celecoxib), and a nonselective COX inhibitor (indomethacin) on bone cancer pain and compared these effects to the effect of orally administered acetaminophen and morphine.

METHODS

An animal model of bone cancer pain was induced by injecting osteolytic murine sarcoma cells in the mouse femur. Drugs were administered orally 2 weeks after tumor-cell implantation, and the level of bone cancer pain was assessed 30, 60, 90, 120, and 180 min after drug administration.

RESULTS

Oral administration of acetaminophen, indomethacin, and morphine, but not of SC560 or celecoxib, produced an analgesic effect on bone cancer pain. Co-administration of a subanalgesic does of morphine with acetaminophen enhanced the analgesic effect of acetaminophen.

CONCLUSION

These data suggest that bone cancer pain is effectively treated by oral administration of indomethacin, acetaminophen, and morphine and that the co-administration of acetaminophen and an opioid provides a beneficial effect when treating of bone cancer pain.

Systemic and Intrathecal Effects of a Novel Series of Phospholipase A2 Inhibitors on Hyperalgesia and Spinal Prostaglandin E2 Release

Phospholipase A(2) (PLA(2)) forms are expressed in spinal cord, and inhibiting spinal PLA(2) induces a potent antihyperalgesia. Here, we examined the antihyperalgesic effects after systemic and i.t. delivery of four compounds constructed with a common motif consisting of a 2-oxoamide with a hydrocarbon tail and a four-carbon tether. These molecules were characterized for their ability to block group IVA calcium-dependent PLA(2) (cPLA(2)) and group VIA calcium-independent PLA(2) (iPLA(2)) in inhibition assays using human recombinant enzyme. The rank ordering of potency in blocking group IVA cPLA(2) was AX048 (ethyl 4-[(2-oxohexadecanoyl)amino]butanoate), AX006 (4-[(2-oxohexadecanoyl)amino]butanoic acid), and AX057 (tert-butyl 4-[(2-oxohexadecanoyl)amino]butanoate) > AX010 (methyl 4-[(2-oxohexadecanoyl)amino]butanoate) and for inhibiting group VIA iPLA(2) was AX048, AX057 > AX006, and AX010. No agent altered recombinant cyclooxygenase activity. In vivo, i.t. (30 mug) and systemic (0.2-3 mg/kg i.p.) AX048 blocked carrageenan hyperalgesia and after systemic delivery in a model of spinally mediated hyperalgesia induced by i.t. substance P (SP). The other agents were without activity. In rats prepared with lumbar i.t. loop dialysis catheters, SP evoked spinal prostaglandin E(2) (PGE(2)) release. AX048 alone inhibited PGE(2) release. Intrathecal SR141617, a cannabinoid CB1 inhibitor at doses that blocked the effects of i.t. anandamide had no effect upon i.t. AX048. These results suggest that AX048 is the first systemically bioavailable compound with a significant affinity for group IVA cPLA(2), which produces a potent antihyperalgesia. The other agents, although demonstrating enzymatic activity in cell-free assays, appear unable to gain access to the intracellular PLA(2) toward which their action is targeted.

Modulation of prostaglandin biosynthesis by nitric oxide and nitric oxide donors

The biosynthesis and release of nitric oxide (NO) and prostaglandins (PGs) share a number of similarities. Two major forms of nitric-oxide synthase (NOS) and cyclooxygenase (COX) enzymes have been identified to date. Under normal circumstances, the constitutive isoforms of these enzymes (constitutive NOS and COX-1) are found in virtually all organs. Their presence accounts for the regulation of several important physiological effects (e.g. antiplatelet activity, vasodilation, and cytoprotection). On the other hand, in inflammatory setting, the inducible isoforms of these enzymes (inducible NOS and COX-2) are detected in a variety of cells, resulting in the production of large amounts of proinflammatory and cytotoxic NO and PGs. The release of NO and PGs by the inducible isoforms of NOS and COX has been associated with the pathological roles of these mediators in disease states as evidenced by the use of selective inhibitors. An important link between the NOS and COX pathways was made in 1993 by Salvemini and coworkers when they demonstrated that the enhanced release of PGs, which follows inflammatory mechanisms, was nearly entirely driven by NO. Such studies raised the possibility that COX enzymes represent important endogenous "receptor" targets for modulating the multifaceted roles of NO. Since then, numerous papers have been published extending the observation across various cellular systems and animal models of disease. Furthermore, other studies have highlighted the importance of such interaction in physiology as well as in the mechanism of action of drugs such as organic nitrates. More importantly, mechanistic studies of how NO switches on/off the PG/COX pathway have been undertaken and additional pathways through which NO modulates prostaglandin production unraveled. On the other hand, NO donors conjugated with COX inhibitors have recently found new interest in the understanding of NO/COX reciprocal interaction and potential clinical use. The purpose of this article is to cover the advances which have occurred over the years, and in particular, to summarize experimental data that outline how the discovery that NO modulates prostaglandin production has impacted and extended our understanding of these two systems in physiopathological events.

Molecular targets in spinal cord injury

The spinal cord can be compared to a highway connecting the brain with the different body levels lying underneath, with the axons being the ultimate carriers of the electrical impulse. After spinal cord injury (SCI), many cells are lost because of the injury. To reconstitute function, damaged axons from surviving neurons have to grow through the lesion site to their initial targets. However, the territory they have to traverse has changed: the highway is full of inhibitory signals (myelin and scar components); the pavement itself has become bumpy (demyelination); and specialized cells are recruited to clear the way (inflammatory cells). Thus, actual strategies to treat spinal injuries aim at providing a permissive environment for regenerating axons and boosting the endogenous potential of axons to regenerate while limiting progression of secondary damage. Here we review some of the strategies currently under consideration to treat spinal injuries.

COX-dependent mechanisms involved in the antinociceptive action of NSAIDs at central and peripheral sites

Despite the diverse chemical structure of aspirin-like drugs, the antinociceptive effect of NSAIDs is mainly due to their common property of inhibiting cyclooxygenases involved in the formation of prostaglandins. Prostaglandins are potent hyperalgesic mediators which modulate multiple sites along the nociceptive pathway and enhance both transduction (peripheral sensitizing effect) and transmission (central sensitizing effect) of nociceptive information. Inhibition of the formation of prostaglandins at peripheral and central sites by NSAIDs thus leads to the normalisation of the increased pain threshold associated with inflammation. The contribution of peripheral and central mechanisms to the overall antinociceptive action of NSAIDs depends on several factors including the location of the targets of drug action, the site of drug delivery and the uptake and distribution to the site of action. The present work reviews the data on the regulation and location of cyclooxygenases at central and peripheral sites of the nociceptive pathway and focuses on the role of COX in the generation and maintenance of pain hypersensitivity. Experimental and clinical evidences are used to evaluate the significance of the peripheral and central antihyperalgesic effects of NSAIDs.