Nitric oxide is involved in ibuprofen preemptive analgesic effect in the plantar incisional model of postsurgical pain in mice

Antinociceptive effect of Nephelium lappaceum L. fruit peel and the participation of nitric oxide, opioid receptors, and ATP-sensitive potassium channels

Introduction: Nephelium lappaceum L. (Sapindaceae) is a plant known as rambutan. It is used for various purposes in traditional medicine. Objective: We aimed to evaluate the antinociceptive effects of the ethanol extract of the fruit peel of N. lappaceum (EENL), the mechanisms involved in these effects, and the acute toxicity in zebrafish. Methods: We performed chromatography coupled to mass spectrometry, acute toxicity assay in zebrafish, and evaluation in mice submitted to models of nociception and locomotor activity. Results: We identified (epi)-catechin, procyanidin B, and ellagic acid and its derivatives in EENL. We did not find any toxicity in zebrafish embryos incubated with EENL. The locomotor activity of mice submitted to oral pretreatment with EENL was not changed, but it reduced the abdominal constrictions induced by acetic acid, the licking/biting time in both the first and second phase of formalin testing and capsaicin testing, and carrageenan-induced paw mechanical allodynia. Oral pretreatment with EENL increased latency time in the hot plate test. This antinociceptive effect was significantly reversed by naloxone, L-arginine, and glibenclamide respectively showing the participation of opioid receptors, nitric oxide, and KATP channels as mediators of EENL-induced antinociception. Conclusion: EENL causes antinociception with the participation of opioid receptors, nitric oxide, and KATP channels, and is not toxic to zebrafish.

Unravelling joint cytotoxicity of ibuprofen and oxytetracycline on Chlamydomonas reinhardtii using a programmed cell death-related biomarkers panel

Pharmaceutical active compounds (PhACs) are emerging contaminants that pose a growing concern due to their ubiquitous presence and harmful impact on aquatic ecosystems. Among PhACs, the anti-inflammatory ibuprofen (IBU) and the antibiotic oxytetracycline (OTC) are two of the most used compounds whose presence has been reported in different aquatic environments worldwide. However, there is still scarce information about the cellular and molecular alterations provoked by IBU and OTC on aquatic photosynthetic microorganisms as microalgae, even more if we refer to their potential combined toxicity. To test the cyto- and genotoxicity provoked by IBU, OTC and their binary combination on Chlamydomonas reinhardtii, a flow cytometric panel was performed after 24 h of single and co-exposure to both contaminants. Assayed parameters were cell vitality, metabolic activity, intracellular ROS levels, and other programmed cell death (PCD)-related biomarkers as cytoplasmic and mitochondrial membrane potentials and caspase-like and endonuclease activities. In addition, a nuclear DNA fragmentation analysis by comet assay was carried out. For most of the parameters analysed (vitality, metabolic activity, cytoplasmic and mitochondrial membrane potentials, and DNA fragmentation) the most severe damages were observed in the cultures exposed to the binary mixture (IBU+OTC), showing a joint cyto- and genotoxicity effect. Both PhACs and their mixture caused a remarkable decrease in cell proliferation and metabolic activity and markedly increased intracellular ROS levels, parallel to a noticeable depolarization of cytoplasmic and mitochondrial membranes. Moreover, a strong increase in both caspase and endonuclease activities as well as a PCD-related loss of nuclear DNA integrity was observed in all treatments. Results analysis showed that the PhACs caused cell death on this non-target organism, involving mitochondrial membrane depolarization, enhanced ROS production and activation of PCD process. Thus, PCD should be an applicable toxicological target for unraveling the harmful effects of co-exposure to PhACs in aquatic organisms as microalgae.

Immunologic aspects of migraine: A review of literature

Migraine headaches are highly prevalent, affecting 15% of the population. However, despite many studies to determine this disease's mechanism and efficient management, its pathophysiology has not been fully elucidated. There are suggested hypotheses about the possible mediating role of mast cells, immunoglobulin E, histamine, and cytokines in this disease. A higher incidence of this disease in allergic and asthma patients, reported by several studies, indicates the possible role of brain mast cells located around the brain vessels in this disease. The mast cells are more specifically within the dura and can affect the trigeminal nerve and cervical or sphenopalatine ganglion, triggering the secretion of substances that cause migraine. Neuropeptides such as calcitonin gene-related peptide (CGRP), neurokinin-A, neurotensin (NT), pituitary adenylate-cyclase-activating peptide (PACAP), and substance P (SP) trigger mast cells, and in response, they secrete pro-inflammatory and vasodilatory molecules such as interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF) as a selective result of corticotropin-releasing hormone (CRH) secretion. This stress hormone contributes to migraine or intensifies it. Blocking these pathways using immunologic agents such as CGRP antibody, anti-CGRP receptor antibody, and interleukin-1 beta (IL-1β)/interleukin 1 receptor type 1 (IL-1R1) axis-related agents may be promising as potential prophylactic migraine treatments. This review is going to summarize the immunological aspects of migraine.

Activation of Peripheral Cannabinoid Receptors Synergizes the Effect of Systemic Ibuprofen in a Pain Model in Rat

Pharmacological synergism is a current strategy for the treatment of pain. However, few studies have been explored to provide evidence of the possible synergism between a non-steroidal anti-inflammatory drug (NSAID) and a cannabinoid agonist, in order to establish which combinations might be effective to manage pain. The aim of this study was to explore the synergism between ibuprofen (IBU) and the synthetic cannabinoid WIN 55,212-2 (WIN) to improve pain relief by analyzing the degree of participation of the CB₁ and CB₂ cannabinoid receptors in the possible antinociceptive synergism using an experimental model of pain in Wistar rats. First, the effective dose thirty (ED₃₀) of IBU (10, 40, 80, and 160 mg/kg, subcutaneous) and WIN (3, 10, and 30 µg/p, intraplantar) were evaluated in the formalin test. Then, the constant ratio method was used to calculate the doses of IBU and WIN to be administered in combination (COMB) to determine the possible synergism using the isobolographic method. The participation of the CB₁ and CB₂ receptors was explored in the presence of the antagonists AM281 and AM630, respectively. The combination of these drugs produced a supra-additive response with an interaction index of 0.13. In addition, AM281 and AM630 antagonists reversed the synergistic effect in 45% and 76%, respectively, suggesting that both cannabinoid receptors are involved in this synergism, with peripheral receptors playing a relevant role. In conclusion, the combination of IBU + WIN synergism is mainly mediated by the participation of the CB₂ receptor, which can be a good option for the better management of pain relief.

Effects of Ibuprofen during Exertional Heat Stroke in Mice

Intestinal injury is one of the most prominent features of organ damage in exertional heat stroke (EHS). However, whether damage to the intestine in this setting is exacerbated by ibuprofen (IBU), the most commonly used nonsteroidal anti-inflammatory drug in exercising populations, is not well understood.

PURPOSE

We hypothesized that IBU would exacerbate intestinal injury, reduce exercise performance, and increase susceptibility to heat stroke.

METHODS

To test this hypothesis, we administered IBU via diet to male and female C57/BL6J mice, over 48 h before EHS. Susceptibility to EHS was determined by assessing exercise response using a forced running wheel, housed inside an environmental chamber at 37.5°C. Core temperature (Tc) was monitored by telemetry. Mice were allocated into four groups: exercise only (EXC); EHS + IBU; EXC + IBU; and EHS only. Exercise performance and Tc profiles were evaluated and stomachs, intestines and plasma were collected at 3 h post-EHS.

RESULTS

The EHS + IBU males ran approximately 87% longer when Tc was above 41°C (P < 0.03) and attained significantly higher peak Tc (P < 0.01) than EHS-only mice. Histological analyses showed decreased villi surface area throughout the small intestine for both sexes in the EXC + IBU group versus EXC only. Interestingly, though EHS in both sexes caused intestinal injury, in neither sex were there any additional effects of IBU.

CONCLUSIONS

Our results suggest that in a preclinical mouse model of EHS, oral IBU at pharmacologically effective doses does not pose additional risks of heat stroke, does not reduce exercise performance, and does not contribute further to intestinal injury, though this could have been masked by significant gut injury induced by EHS alone.

Effect of cinnamon on migraine attacks and inflammatory markers: A randomized double-blind placebo-controlled trial

Migraine is the most common type of primary headaches. Increased levels of interleukin-6 (IL-6), calcitonin-gene-related peptide (CGRP) and nitric oxide (NO) lead to inflammation and neurogenic pain. Cinnamon has anti-inflammatory and neuroprotective properties. Thus, the aim of this study was to assess the effect of cinnamon on migraine attacks and inflammatory status. Fifty patients with migraine were randomized to receive either cinnamon powder (three capsules/day each containing 600 mg of cinnamon) or three placebo capsules/day each containing 100 mg of corn starch (control group) for 2 months. Serum levels of IL-6, CGRP and NO were measured at baseline and at the end of the study. The frequency, severity and duration of pain attacks were also recorded using questionnaire. Serum concentrations of IL-6 and NO were significantly reduced in the cinnamon group compared with the control group (p < .05). However, serum levels of CGRP remained unchanged in both groups. The frequency, severity and duration of migraine attacks were significantly decreased in the cinnamon group compared with the control group. Cinnamon supplementation reduced inflammation as well as frequency, severity and duration of headache in patients with migraine. Cinnamon could be regarded as a safe supplement to relieve pain and other complications of migraine.

Effective management of acute postoperative pain using intravenous emulsions of novel ketorolac prodrugs: in vitro and in vivo evaluations

The aim was to prepare intravenous fat emulsions (IFEs) of ketorolac (KTL) ester prodrugs and to investigate the pharmacokinetics and pharmacodynamics of these formulations. Three prodrugs of KTL (KTL-IS, KTL-AX and KTL-BT) were synthesized as a means to increase the lipid solubility of KTL. All KTL prodrugs with higher Log P values presented increased tendency to partition into a blank IFE using extemporaneous addition method - the encapsulation efficiency of KTL-IS IFE and KTL-BT IFE was more than 97%. The particle sizes and zeta potentials of these two formulations were comparable to that of the blank IFE. PK studies in rabbits showed significant larger AUC0-8h (646.969 ± 154.326 mg/L•h-1 for KTL-IS IFE and 559.426 ± 103.057 mg/L•h-1 for KTL-BT IFE) than that of ketorolac tromethamine (KTL-T) injectable (286.968 ± 63.045 mg/L•h-1) and approximately 2-fold increases in the elimination t1/2 over KTL-T. In a rat postoperative pain model, the paw withdrawal thresholds and the paw withdrawal latency after I.V. KTL prodrug IFEs were significantly higher than that after I.V. KTL-T at 3~4 h. Effective controlling of acute postoperative pain in a longer duration can be achieved by using non-addictive ketorolac derivatives intraveneous emulsions.

Thalidomide protects against acute pentylenetetrazol and pilocarpine-induced seizures in mice

Thalidomide was originally developed to treat primary neurological and psychiatric diseases. There are reports of anticonvulsant effects of thalidomide in rats and antiepileptic effects in patients. Hence, thalidomide (100, 200 and 400 mg/kg) was herein administered to mice to evaluate possible protection against seizures induced by the systemic administration of neurotoxins: 10 mg/kg of 4-aminopyridine (4-AP), 90 mg/kg of pentylenetetrazol (PTZ), or 380 mg/kg of pilocarpine. The effect of an NO and COX inhibitor (7-NI and ibuprofen, respectively) was also examined. The results show that thalidomide (1) induces the typical sedative effects, (2) has no anticonvulsant effect in mice treated with 4-AP, and (3) has anticonvulsant effect (400 mg/kg) in mice treated with PTZ and pilocarpine. It was found that 7-NI has an anticonvulsant effect in the pilocarpine model and that thalidomide's effect is not enhanced by its presence. However, thalidomide (200 mg/kg) plus 7-NI or ibuprofen tend to have a toxic effect in PTZ model. On the other hand, the combination of thalidomide and 7-NI or ibuprofen protects against pilocarpine-induced seizures. In conclusion, thalidomide did not exert an anticonvulsant effect for clonic-tonic type convulsions (4-AP), but it did so for seizures induced by PTZ and pilocarpine (representing absence seizures and status epilepticus, respectively). NO and prostaglandins were involved in the convulsive process elicited by pilocarpine.

The role of satellite glial cells in orofacial pain

Some chronic pain conditions in the orofacial region are common, the mechanisms underlying which are unresolved. Satellite glial cells (SGCs) are the glial cells of the peripheral nervous system. In the sensory ganglia, each neuronal body is surrounded by SGCs forming distinct functional units. The unique structural organization enables SGCs to communicate with each other and with their enwrapped neurons via a variety of ways. There is a growing body of evidence that SGCs can influence the level of neuronal excitability and are involved in the development and/or maintenance of pain. The aim of this review was to summarize the latest advances made about the implication of SGCs in orofacial pain. It may offer new targets for the development of orofacial pain treatment.

Activation of satellite glial cells in trigeminal ganglion following dental injury and inflammation

Satellite glial cells (SGCs), a peripheral neuroglial cell, surround neurons and form a complete envelope around individual sensory neurons in the trigeminal ganglia (TG), which may be involved in modulating neurons in inflammation. The purpose of this study was to determine the effect of dental injury and inflammation on SGCs in the TG. Pulp exposure (PX) was performed on the first maxillary molar of 28 rats. The neurons innervating injured tooth in TG were labeled by the retrograde transport of fluoro-gold (FG). Specimens were collected at 1, 3, 7, 14, 21 and 28 days after PX and stained immunohistochemically for glial fibrillary acid protein (GFAP), a marker of SGCs activation, in the TG. We observed that GFAP-immunoreactivity (IR) SGCs enclosed FG-labeled neurons increased in a time-dependent manner after PX. The neurons surrounded by GFAP-IR SGCs were mainly small and medium in size. The GFAP-IR SGCs encircled neurons increased significantly in the maxillary nerve region of the TG at 7-28 days following PX. The results show that dental injury and inflammation induced SGCs activation in the TG. It indicates that activation of SGCs might be implicated in the peripheral mechanisms of pain following dental injury and inflammation.

α-Spinasterol: a COX inhibitor and a transient receptor potential vanilloid 1 antagonist presents an antinociceptive effect in clinically relevant models of pain in mice

BACKGROUND AND PURPOSE

Postoperative pain is one of the most common manifestations of acute pain and is an important problem faced by patients after surgery. Moreover, neuronal trauma or chemotherapeutic treatment often causes neuropathic pain, which induces disabling and distressing symptoms. At present, treatments of both painful conditions are inadequate. α-Spinasterol, which is well characterized as a transient receptor potential vanilloid 1 antagonist, has anti-inflammatory, antioxidant and antinociceptive effects. Therefore, we investigated its antinociceptive potential on postoperative and neuropathic pain, as well as its effect on COX-1 and COX-2 activities.

EXPERIMENTAL APPROACH

Nociceptive responses in a postoperative pain model (surgical incision-induced) or different neuropathic pain models (trauma or chemotherapy-induced) were investigated in mice.

KEY RESULTS

Oral administration of α-spinasterol reduced postoperative pain, when given as a pre- (0.5 h before incision) or post-treatment (0.5 h after incision), and reduced cell infiltration in the injured tissue. α-Spinasterol also reduced the mechanical allodynia induced by partial sciatic nerve ligation and the mechanical and cold allodynia induced by paclitaxel. Moreover, α-spinasterol inhibited COX-1 and COX-2 enzyme activities without altering the body temperature of animals. Importantly, α-spinasterol did not alter spontaneous or forced locomotor activity. Furthermore, it did not cause gastric damage or liver and kidney changes, nor did it alter cell viability in the cerebral cortex and spinal cord slices of mice.

CONCLUSION AND IMPLICATIONS

α-Spinasterol is an effective and safe COX inhibitor with antinociceptive effects in postoperative and neuropathic pain models. Therefore, it is an interesting prototype for the development of novel analgesic drugs.

Prophylactic L-arginine and ibuprofen delay the development of tactile allodynia and suppress spinal miR-155 in a rat model of diabetic neuropathy

Diabetic neuropathy (DN) is a common complication of diabetes mellitus that is hardly reversible at the late stages. Since treatment of neuropathic pain is predominantly symptomatic, a prophylactic measure would be useful. Both ibuprofen and L-arginine exert antiallodynic effects on chronic constriction injury (CCI)-induced cold allodynia. Furthermore, ibuprofen is effective in CCI-induced mechanical allodynia. The aim of the study was to assess the antiallodynic effect of prophylactic ibuprofen and L-arginine in streptozotocin-induced DN in rats and to further investigate the role of spinal miR-155 and nitric oxide (NO) in this effect. Tactile allodynia was assessed weekly by von Frey filaments. Oral daily administration of ibuprofen, L-arginine and their combination, for 4 weeks starting 1 week after streptozotocin injection (ie, before the development of tactile allodynia), resulted in a significant decrease of tactile allodynia compared with the control diabetic group. This was evident in the fifth week of the experiment. The 3 treatments prevented the decrease in muscle fiber diameter and epidermal thickness, seen in the control diabetic group. Furthermore, ibuprofen, L-arginine and their combination prevented the increase in the spinal NO level and miRNA-155, seen in the control diabetic group. In conclusion, both ibuprofen and L-arginine delayed the development of behavioral and histologic changes of DN, with concomitant suppression of spinal miR-155 and NO level. L-arginine being tolerable may be useful prophylactically in diabetic patients.

Changes in nitric oxide synthase isoforms in the trigeminal ganglion of rat following chronic tooth pulp inflammation

Nitric oxide (NO) possibly plays an important role in the events resulting in hyperalgesia. NO synthase (NOS) is a key enzyme in the production of NO. Changes in NOS expression in primary sensory neurons may be involved in the persistent sensory abnormalities that can be induced by inflammation. To assess the possible roles of NOS in trigeminal sensory system, we studied changes in the expression of NOS isoforms in the trigeminal ganglion (TG) following chronic inflammation after pulp exposure (PX) in rats. The neurons innervating injured tooth in the TG were labeled by fluoro-gold (FG). Immunohistochemical staining was used to reveal the presence of NOS. The results showed that within the FG-labeled population, neuron counts revealed a significant increase in the proportion of NOS neurons following PX, in which the frequency of iNOS and nNOS-positive neurons started to increase at 3 and 7day, respectively, and peaked at 28day. There was no eNOS expression observed in the control group and PX-treated groups. The results demonstrate that PX-induced chronic pulpal inflammation results in significant increase of nNOS and iNOS in the TG. It suggests that nNOS and iNOS could be involved in mediation of peripheral processing of nociceptive information following chronic tooth pulp inflammation.

Equivalent intraperitoneal doses of ibuprofen supplemented in drinking water or in diet: a behavioral and biochemical assay using antinociceptive and thromboxane inhibitory dose-response curves in mice

Background. Ibuprofen is used chronically in different animal models of inflammation by administration in drinking water or in diet due to its short half-life. Though this practice has been used for years, ibuprofen doses were never assayed against parenteral dose–response curves. This study aims at identifying the equivalent intraperitoneal (i.p.) doses of ibuprofen, when it is administered in drinking water or in diet.

Methods. Bioassays were performed using formalin test and incisional pain model for antinociceptive efficacy and serum TXB₂ for eicosanoid inhibitory activity. The dose–response curve of i.p. administered ibuprofen was constructed for each test using 50, 75, 100 and 200 mg/kg body weight (b.w.). The dose–response curves were constructed of phase 2a of the formalin test (the most sensitive phase to COX inhibitory agents), the area under the ‘change in mechanical threshold’-time curve in the incisional pain model and serum TXB₂ levels. The assayed ibuprofen concentrations administered in drinking water were 0.2, 0.35, 0.6 mg/ml and those administered in diet were 82, 263, 375 mg/kg diet.

Results. The 3 concentrations applied in drinking water lay between 73.6 and 85.5 mg/kg b.w., i.p., in case of the formalin test; between 58.9 and 77.8 mg/kg b.w., i.p., in case of the incisional pain model; and between 71.8 and 125.8 mg/kg b.w., i.p., in case of serum TXB₂ levels. The 3 concentrations administered in diet lay between 67.6 and 83.8 mg/kg b.w., i.p., in case of the formalin test; between 52.7 and 68.6 mg/kg b.w., i.p., in case of the incisional pain model; and between 63.6 and 92.5 mg/kg b.w., i.p., in case of serum TXB₂ levels.

Discussion. The increment in pharmacological effects of different doses of continuously administered ibuprofen in drinking water or diet do not parallel those of i.p. administered ibuprofen. It is therefore difficult to assume the equivalent parenteral daily doses based on mathematical calculations.