Therapeutic effects of the superoxide dismutase mimetic compound MnIIMe2DO2A on experimental articular pain in rats

Development of Hydrogen Sulfide-Releasing Carbonic Anhydrases IX- and XII-Selective Inhibitors with Enhanced Antihyperalgesic Action in a Rat Model of Arthritis

An effective therapeutic approach based on the anti-inflammatory action of hydrogen sulfide (H₂S) and inhibition of carbonic anhydrases (CAs) IX and XII is proposed here for the management of arthritis. H₂S is a human gasotransmitter that modulates inflammatory response at low concentrations. Inhibition of CAs IX and XII can repristinate normal pH in the acidic inflamed synovial fluid, alleviating arthritis symptoms. We report here the design of H₂S donor—CA inhibitor (CAI) hybrid derivatives. The latter were tested in vitro as inhibitors of human CAs I, II, IV, IX, and XII, showing a markedly increased inhibition potency/isoform selectivity compared to the CAI synthetic precursors. The best compounds demonstrated the ability to consistently release H₂S and produce a potent pain-relieving effect in a rat model of arthritis. Compound 26 completely reverted the pain state 45 min after administration with enhanced antihyperalgesic effect in vivo compared to the single H₂S donor, CAI fragment, or their co-administration.

Anti-Inflammatory Effects Induced by a Polyphenolic Granular Complex from Olive (Olea europaea, Mainly Cultivar coratina): Results from In Vivo and Ex Vivo Studies in a Model of Inflammation and MIA-Induced Osteoarthritis

MOMAST^® GR25 is a polyphenolic granular complex from olive pressing juice with high total content in polyphenols. In this work, we evaluated the possible anti-inflammatory effects of MOMAST^® GR25 in both acute and chronic inflammatory models. MOMAST^® GR25 decreased the levels of prostaglandin (PG) E₂ and 8-iso-PGF_2α in isolated rat colon, liver, and heart specimens stimulated with lipopolysaccharide (LPS). In vivo, compared to controls, rats treated with MOMAST^® GR25 (100 mg/kg to 1 g/kg) showed a significant reduction in both licking/biting time in the formalin test. In a rat model of osteoarthritis by monoiodoacetate (MIA) injection, MOMAST^® GR25 showed pain-relieving properties when acutely administered, reducing mechanical hyperalgesia and spontaneous pain. Moreover, a repeated daily treatment with MOMAST^® GR25 (300 mg/kg) fully counteracted osteoarticular pain without the development of tolerance to the antinociceptive effect. Taken together, our present findings showed that MOMAST^® GR25 could represent a potential strategy for the treatment of inflammation and pain.

Superoxide dismutase as multipotent therapeutic antioxidant enzyme: Role in human diseases

Reactive oxygen species (ROS) is consistently recognized as a threat to living organisms, especially for human beings. For proper working of cellular signaling, functioning, and survival, a strict and balanced level of ROS is necessary. Superoxide dismutase (SOD); a group of metalloenzymes provides an important antioxidant defense mechanism, required to preserve the level of ROS in the body. The enzyme reveals the therapeutic potential against various diseases due to a deficiency in the ROS level. The review illustrates the numerous clinical aspects of SOD in various physiological and pathological conditions such as cancer, diabetes, arthritis, cardiovascular, neurodegenerative diseases, etc., with the mechanism of action. Despite limitations, the SOD enzyme has proved as a powerful tool against diseases, and various forms of conjugates and mimetics have been developed and reported to make it more efficient. Extensive studies need in this direction for use of natural SOD-based therapeutics for the prevention and cure of diseases.

Synthesis and anti-rheumatoid arthritis activities of 3-(4-aminophenyl)-coumarin derivatives

Rheumatoid arthritis is a chronic systemic disease characterised by an unknown aetiology of inflammatory synovitis. A large number of studies have shown that synoviocytes show tumour-like dysplasia in the pathological process of RA, and the changes in the expression of related cytokines are closely related to the pathogenesis of RA. In this thesis, a series of novel 3-(4-aminophenyl) coumarins containing different substituents were synthesised to find new coumarin anti-inflammatory drugs for the treatment of rheumatoid arthritis. The results of preliminary activity screening showed that compound 5e had the strongest inhibitory activity on the proliferation of fibroid synovial cells, and it also had inhibitory effect on RA-related cytokines IL-1, IL-6, and TNF-α. The preliminary mechanism study showed that compound 5e could inhibit the activation of NF-κB and MAPKs signal pathway. The anti-inflammatory activity of compound 5ein vivo was further determined in the rat joint inflammation model.

Intra-Articular Route for the System of Molecules 14G1862 from Centella Asiatica: Pain Relieving and Protective Effects in a Rat Model of Osteoarthritis

Current pharmacological therapies for the management of chronic articular diseases are far from being satisfactory, so new strategies need to be investigated. We tested the intra-articular pain relieving properties of a system of molecules from a characterized Centella asiatica extract (14G1862) in a rat model of osteoarthritis induced by monoiodoacetate (MIA). 14G1862 (0.2–2 mg mL⁻¹) was intra-articularly (i.a.) injected 7 days after MIA, behavioural and histological evaluations were performed 14, 30 and 60 days after treatments. Moreover, the effect of 14G1862 on nitrate production and iNOS expression in RAW 264.7 macrophages stimulated with LPS was assessed. In vitro, 14G1862 treatment attenuated LPS-induced NO production and iNOS expression in a comparable manner to celecoxib. In vivo, 14G1862 significantly reduced mechanical allodynia and hyperalgesia, spontaneous pain and motor alterations starting on day 14 up to day 60. The efficacy was higher or comparable to that evoked by triamcinolone acetonide (100 μg i.a.) used as reference drug. Histological evaluation highlighted the improvement of several morphological parameters in MIA + 14G1862-treated animals with particularly benefic effects on joint space and fibrin deposition. In conclusion, i.a. treatment with Centella asiatica is a candidate to be a novel effective approach for osteoarthritis therapy.

Novel formyl peptide receptor (FPR) agonists with pyridinone and pyrimidindione scaffolds that are potentially useful for the treatment of rheumatoid arthritis

The resolution of inflammation is an active response involving the interaction of pro-resolving mediators with specific receptors, such as N-formyl peptide receptor 2 (FPR2). FPRs represent potentially important therapeutic targets for the treatment of some pathologies, including asthma and rheumatoid arthritis. Previously, we identified selective or mixed FPR agonists with a pyridazin-3(2H)-one scaffold, all containing a 4-bromophenylacetamide fragment at N-2. The most effective compounds in this series were EC3, a potent mixed FPR1/FPR2/FPR3 agonist, and EC10, which had a preference for FPR1. We report here a new series of pyridinone and pyrimidindione derivatives containing the 4-(bromophenyl)acetamide substituent that was essential for activity in the pyridazinone series. All new compounds were evaluated for FPR agonist activity in HL60 cells transfected with FPR1 or FPR2 and in human neutrophils. While most of the pyridinone derivatives had reasonable FPR agonist activity in the submicromolar/micromolar range, the pyrimidindione derivatives were less active. Compound 2a (N-(4-bromophenyl)-2-[3-cyano-5-(3-methoxyphenyl)-6-methyl-2-oxopyridin-1(2H)-yl]acetamide) was the most active pyridinone derivative and had a 10-fold preference for FPR2 (EC₅₀ = 120 nM) versus FPR1 (EC₅₀ = 1.6 μM). To assess their therapeutic activity, compounds 2a, EC3, and EC10 were evaluated in vivo using a rat model of rheumatoid arthritis. All three compounds increased the pain threshold and reduced pain hypersensitivity in the treated rats versus control rats, although 2a and EC10 were much more effective than EC3. Thus, these FPR agonists represent potential leads to develop for the treatment of inflammatory diseases such as rheumatoid arthritis.

Intra-Articular Hyaluronic Acid and Chondroitin Sulfate: Pharmacokinetic Investigation in Osteoarthritic Rat Models

Background

Viscosupplementation of synovial fluid with intra-articular (IA) injections of hyaluronic acid (HA) is widely used for symptomatic treatment of osteoarthritis (OA). Herein we present HCS, a new combination of chemicals, associating HA and chondroitin sulfate (CS), both members of the glycosaminoglycan (GAGs) family, which are major components of the joint. HA provides viscosity to the synovial fluid and CS provides elasticity to the cartilage. Reduced levels of HA and CS are observed in OA joints and are associated with progressive cartilage damage and loss.

Objective

The objective of the study was to evaluate the pharmacokinetic (PK) properties of both HA and CS after IA administration in a validated OA animal model.

Methods

Motion impairment measurements and histological examinations were used to validate the ability of an IA injection of mono-iodoacetate (MIA) in the knee of rats to induce OA symptoms. Then, the PK properties of HA and CS after IA administration were characterized and each active ingredient was independently profiled: HA was labeled with tritium (3H-HA) and CS was labeled with carbon 14. (14C-CS) The final radio-labeled solution reproduced the cold HCS formulation.

Results

Four male Sprague-Dawley rats received a 1 mg MIA injection on day 1, then motor impairment was monitored from day 4 to day 18. Chondrocyte necrosis, loss of GAGs and other cartilage damage were observed. Twelve other rats received a MIA IA injection on day 1 then a radio-labeled HCS IA injection (50 µL) on day 8. Plasma and knee cartilage were collected postadministration and the terminal half-life was similar in both matrices (about 5 days), for both 3H-HA and 14C-CS.

Conclusions

Despite differences in their molecular size, HA and CS showed PK behavior similarly characterized by prolonged residence inside the joint and slow release in plasma, favoring long-term beneficial effects. (Curr Ther Res Clin Exp. 2020; 92:XXX-XXX).

Bioisosteric Development of Multitarget Nonsteroidal Anti-Inflammatory Drug-Carbonic Anhydrases Inhibitor Hybrids for the Management of Rheumatoid Arthritis

Multitarget nonsteroidal anti-inflammatory drug (NSAID)-carbonic anhydrase inhibitor (CAI) agents for the management of rheumatoid arthritis are reported. The evidence of the plasma stability of the amide-linked hybrids previously reported prompted us to investigate their pain-relieving mechanism of action. A bioisosteric amide to ester substitution yielded a series of derivatives showing potent target CAs inhibition and to undergo cleavage in rat or human plasma depending on the NSAID portion. A selection of derivatives were assayed in vitro to indirectly evaluate their effect on COX-1 and COX-2. MD simulations demonstrated that the entire hybrids are also able to efficiently bind the COX active site. In a rat model of RA, the most promising derivative (5c) showed major antihyperalgesic action compared with the equimolar coadministration of the single agents. The gathered data provided new insights on the action mechanism of these multitarget compounds, which induce markedly improved pain relief compared with the parent NSAIDs.

The Pharmacology of Pain Associated With the Monoiodoacetate Model of Osteoarthritis

The high incidence of osteoarthritis (OA) in an increasingly elderly population anticipates a dramatic rise in the number of people suffering from this disease in the near future. Because pain is the main reason patients seek medical help, effective pain management-which is currently lacking-is paramount to improve the quality of life that OA sufferers desperately seek. Good animal models are, in this day and age, fundamental tools for basic research of new therapeutic pathways. Several animal models of OA have been characterized, but none of them reproduces entirely all symptoms of the disease. Choosing between different animal models depends largely on which aspect of OA one aims to study. Here, we review the current understanding of the monoiodoacetate (MIA) model of OA. MIA injection in the knee joint leads to the progressive disruption of cartilage, which, in turn, is associated with the development of pain-like behavior. There are several reasons why the MIA model of OA seems to be the most adequate to study the pharmacological effect of new drugs in pain associated with OA. First, the pathological changes induced by MIA share many common traits with those observed in human OA (Van Der Kraan et al., 1989; Guingamp et al., 1997; Guzman et al., 2003), including loss of cartilage and alterations in the subchondral bone. The model has been extensively utilized in basic research, which means that the time course of pain-related behaviors and histopathological changes, as well as pharmacological profile, namely of commonly used pain-reducing drugs, is now moderately understood. Also, the severity of the progression of pathological changes can be controlled by grading the concentration of MIA administered. Further, in contrast with other OA models, MIA offers a rapid induction of pain-related phenotypes, with the cost-saving consequence in new drug screening. This model, therefore, may be more predictive of clinical efficacy of novel pharmacological tools than other chronic or acute OA models.

Antioxidant-Conjugated 1,2,4-Triazolo[4,3-a]pyrazin-3-one Derivatives: Highly Potent and Selective Human A2A Adenosine Receptor Antagonists Possessing Protective Efficacy in Neuropathic Pain

New 8-amino-6-aryl-1,2,4-triazolo[4,3-a]pyrazin-3-ones were designed to obtain dual antioxidant-human A_2A adenosine receptor (hA_2A AR) antagonists. Two sets of compounds were synthesized, the first featuring phenol rings at the 6-position, the second bearing the lipoyl and 4-hydroxy-3,5-di-tertbut-benzoyl residues appended by different linkers on the 6-phenyl ring. Several new triazolopyrazines (1-21) were potent and selective hA_2A AR antagonists (K_i = 0.17-54.5 nM). Compounds 11, 15, and 21, featuring antioxidant moieties, and compound 12, lacking the antioxidant functionality, reduced oxaliplatin-induced toxicity in microglia cells, the most active being the lipoyl-derivative 15 and the (4-hydroxy-3,5-di-tert-butyl)benzoyl-analogue 21 which were effective in reducing the oxygen free radical level. The lipoyl-derivative 15 was also able to revert oxaliplatin-induced neuropathy in the mouse. In vivo efficacy of 15 makes it a promising neuroprotective agent in oxidative stress-related diseases.

Spirocyclic sulfonamides with carbonic anhydrase inhibitory and anti-neuropathic pain activity

A novel series of 4-oxo-spirochromane bearing primary sulfonamide group were synthetized as Carbonic Anhydrase inhibitors (CAIs) and tested for their management of neuropathic pain. Indeed, CAs have been recently validated as novel therapeutic targets in neuropathic pain. All compounds, here reported, showed strong activity against hCA II and hCA VII with K_I values in the low or sub-nanomolar range. Two compounds (6d and 6l) showed good neuropathic pain attenuating effects and longer duration than drug reference acetazolamide in an animal model of oxaliplatin induced neuropathy.

Synthesis and Evaluation of Carbonic Anhydrase Inhibitors with Carbon Monoxide Releasing Properties for the Management of Rheumatoid Arthritis

Carbon monoxide (CO) is a gas endogenously produced in humans, reported to exhibit anti-inflammatory and cytoprotective effects at low concentration. In this context, CO releasing molecules (CORMs) are attracting enormous interest. Herein, we report a series of small-molecule hybrids consisting of a carbonic anhydrase (CA; EC 4.2.1.1) inhibitor linked to a CORM tail section (CAI-CORMs). All compounds were screened in vitro for their inhibition activity against the human (h) CA I, II, IV, IX, and XII isoforms. On selected CAI-CORM hybrids, the CO releasing properties were evaluated, along with their pain-relieving effect, in a model of rheumatoid arthritis. One CAI-CORM hybrid (5b) induced a higher pain-relieving effect compared to the one exerted by the single administration of CAI (5a) and CORM (15b) fragments, shedding light on the possibility to enhance the pain relief effect of CA inhibitors inserting a CO releasing moiety on the same molecular scaffold.

N-aryl-N'-ureido-O-sulfamates: Potent and selective inhibitors of the human Carbonic Anhydrase VII isoform with neuropathic pain relieving properties

Herein we report for the first time an efficient synthetic procedure for the preparation of N-aryl-N'-ureido-O-sulfamates (AUSs) as a new class of Carbonic Anhydrase Inhibitors (CAIs). The compounds were tested for the inhibition of several human (h) Carbonic Anhydrase (CA; EC 4.2.1.1) isoforms. Interesting inhibition activity and high selectivity against CA VII and XII versus CA I and II, with K_Is in the low nanomolar range, were observed. Molecular modeling studies allowed us to decipher the structural features underpinning the selective inhibitory profile of AUSs towards isoforms CAs VII and XII. A selection of sulfamates showed promising neuropathic pain modulating effects in an in vivo animal model of oxaliplatin induced pain.

Aqueous and methanol extracts of Paullinia pinnata L. (Sapindaceae) improve inflammation, pain and histological features in CFA-induced mono-arthritis: Evidence from in vivo and in vitro studies

ETHNOPHARMACOLOGICAL RELEVANCE

Paullinia pinnata L. (Sapindaceae) is an African woody vine, traditionally used for the treatment of itch and pain-related conditions such as rheumatoid arthritis.

AIM

This work evaluates, in vitro and in vivo, the anti-inflammatory and analgesic effects of aqueous (AEPP) and methanol (MEPP) extracts from Paullinia pinnata leaves.

METHODS

AEPP and MEPP (100, 200 and 300 mg/kg/day) were administered orally in monoarthritic rats induced by a unilateral injection of 50 μl of Complete Freund's Adjuvant (CFA) in the ankle joint. During the 14 days of treatment, pain and inflammation were evaluated alternatively in both ankle and paw of the CFA-injected leg. Malondialdehyde (MDA) and glutathione (GSH) levels were assessed in serum and spinal cord. Histology of soft tissue of the ankle was also analyzed. For in vitro studies, AEPP and MEPP (10, 30 and 100 μg/ml) were evaluated against nitric oxide (NO) production by macrophages that were either non-stimulated or stimulated with LPS, 8-Br-AMPc and the mixture of both substances after 8 h exposure. These extracts were also evaluated on TNF-α and IL-1β production in cells stimulated with LPS for 8 h. Finally, the ability of the extracts to bind to neuroactive receptors was evaluated in vitro using competitive binding assays with >45 molecular targets.

RESULTS

AEPP and MEPP significantly reduced by 20-98% (p < 0.001) the inflammation and pain sensation in both the ankle and paw. AEPP significantly increased glutathione levels (p < 0.05) in serum. Both extracts reduced MDA production in serum and spinal cord (p < 0.001), and significantly improved tissue reorganization in treated arthritic rats. P. pinnata extracts did not affect NO production in non-stimulated macrophages but significantly reduced it by 47-88% in stimulated macrophages. AEPP and MEPP also significantly inhibited TNF-α (35-68%) and IL-1β (31-36%) production in LPS stimulated macrophages. No cytotoxic effect of plant extracts was observed. MEPP showed concentration-dependent affinity for Sigma 2 receptors with an IC₅₀ of 50 μg/ml.

CONCLUSION

These results demonstrate the analgesic and anti-inflammatory effects of P. pinnata extracts on monoarthritis and further support its traditional use for pain and inflammation. These activities are at least partly due to the ability of these extracts to inhibit the production of NO, TNF-α, IL-1β and to likely modulate Sigma 2 receptors.

Benzensulfonamides bearing spyrohydantoin moieties act as potent inhibitors of human carbonic anhydrases II and VII and show neuropathic pain attenuating effects

Carbonic Anhydrases have been recently validated as novel therapeutic targets in neuropathic pain. In this study, we combine the anticonvulsant propriety of spyrohydantoin and the CA inhibitor moiety of benzenesulfonamide to synthesize a novel series of spyrohydantoin bearing sulfonamides with strong activity against hCA II and VII. These isoforms are present in the nervous system and largely expressed both at the central as well as at peripheral level and can be modulated for pain relief. The crystal structures of hCA II in complex with selected compounds 5a-c demonstrate the importance of the tail in the binding modes within the isoform. Finally, in vivo, in an animal model of oxaliplatin induced neuropathy, compounds with organoselenium tails (8b-c) showed potent neuropathic pain attenuating effects. Taken together, these data strongly suggest the translational utility of these inhibitors as novel pain relievers.

A small molecule promotes cartilage extracellular matrix generation and inhibits osteoarthritis development

Degradation of extracellular matrix (ECM) underlies loss of cartilage tissue in osteoarthritis, a common disease for which no effective disease-modifying therapy currently exists. Here we describe BNTA, a small molecule with ECM modulatory properties. BNTA promotes generation of ECM components in cultured chondrocytes isolated from individuals with osteoarthritis. In human osteoarthritic cartilage explants, BNTA treatment stimulates expression of ECM components while suppressing inflammatory mediators. Intra-articular injection of BNTA delays the disease progression in a trauma-induced rat model of osteoarthritis. Furthermore, we identify superoxide dismutase 3 (SOD3) as a mediator of BNTA activity. BNTA induces SOD3 expression and superoxide anion elimination in osteoarthritic chondrocyte culture, and ectopic SOD3 expression recapitulates the effect of BNTA on ECM biosynthesis. These observations identify SOD3 as a relevant drug target, and BNTA as a potential therapeutic agent in osteoarthritis.

Pain Relieving Effect of-NSAIDs-CAIs Hybrid Molecules: Systemic and Intra-Articular Treatments against Rheumatoid Arthritis

To study new target-oriented molecules that are active against rheumatoid arthritis-dependent pain, new dual inhibitors incorporating both a carbonic anhydrase (CA)-binding moiety and a cyclooxygenase inhibitor (NSAID) were tested in a rat model of rheumatoid arthritis induced by CFA intra-articular (i.a.) injection. A comparison between a repeated per os treatment and a single i.a. injection was performed. CFA (50 µL) was injected in the tibiotarsal joint, and the effect of per os repeated treatment (1 mg kg⁻¹) or single i.a injection (1 mg mL⁻¹, 50 µL) with NSAIDs-CAIs hybrid molecules, named 4 and 5, was evaluated. The molecules 4 and 5, which were administered daily for 14 days, significantly prevented CFA-induced hypersensitivity to mechanical noxious (Paw pressure test) and non-noxious stimuli (von Frey test), the postural unbalance related to spontaneous pain (Incapacitance test) and motor alterations (Beam balance test). Moreover, to study a possible localized activity, 4 and 5 were formulated in liposomes (lipo 4 and lipo 5, both 1 mg mL⁻¹) and directly administered by a single i.a. injection seven days after CFA injection. Lipo 5 decreased the mechanical hypersensitivity to noxious and non-noxious stimuli and improved motor coordination. Oral and i.a. treatments did not rescue the joint, as shown by the histological analysis. This new class of potent molecules, which is able to inhibit at the same time CA and cyclooxygenase, shows high activity in a preclinical condition of rheumatoid arthritis, strongly suggesting a novel attractive pharmacodynamic profile.

[Ru(bpy)2(NO)SO3](PF6), a Nitric Oxide Donating Ruthenium Complex, Reduces Gout Arthritis in Mice

Monosodium urate crystals (MSU) deposition induces articular inflammation known as gout. This disease is characterized by intense articular inflammation and pain by mechanisms involving the activation of the transcription factor NFκB and inflammasome resulting in the production of cytokines and oxidative stress. Despite evidence that MSU induces iNOS expression, there is no evidence on the effect of nitric oxide (NO) donors in gout. Thus, the present study evaluated the effect of the ruthenium complex donor of NO {[Ru(bpy)₂(NO)SO₃](PF₆)} (complex I) in gout arthritis. Complex I inhibited in a dose-dependent manner MSU-induced hypersensitivity to mechanical stimulation, edema and leukocyte recruitment. These effects were corroborated by a decrease of histological inflammation score and recruitment of Lysm-eGFP⁺ cells. Mechanistically, complex I inhibited MSU-induced mechanical hypersensitivity and joint edema by triggering the cGMP/PKG/ATP-sensitive K (+) channels signaling pathway. Complex I inhibited MSU-induced oxidative stress and pro-inflammatory cytokine production in the knee joint. These data were supported by the observation that complex I inhibited MSU-induced NFκB activation, and IL-1β expression and production. Complex I also inhibited MSU-induced activation of pro-IL-1β processing. Concluding, the present data, to our knowledge, is the first evidence that a NO donating ruthenium complex inhibits MSU-induced articular inflammation and pain. Further, complex I targets the main physiopathological mechanisms of gout arthritis. Therefore, it is envisaged that complex I and other NO donors have therapeutic potential that deserves further investigation.

Budlein A, a Sesquiterpene Lactone From Viguiera robusta, Alleviates Pain and Inflammation in a Model of Acute Gout Arthritis in Mice

Background: Gout is the most common inflammatory arthritis worldwide. It is a painful inflammatory disease induced by the deposition of monosodium urate (MSU) crystals in the joints and peri-articular tissues. Sesquiterpene lactones (SLs) are secondary metabolite biosynthesized mainly by species from the family Asteraceae. It has been demonstrated that SLs present anti-inflammatory, analgesic, antitumoral, antiparasitic, and antimicrobial activities. In this study, we aimed at evaluating the efficacy of the SL budlein A in a model of acute gout arthritis in mice. Methods: Experiments were conducted in male Swiss or male LysM-eGFP mice. Animals were treated with budlein A (1 or 10 mg/kg) or vehicle 30 min before stimulus with MSU (100 μg/10 μL, intra-articular). Knee joint withdrawal threshold and edema were evaluated using electronic von Frey and caliper, respectively, 1-15 h after MSU injection. Leukocyte recruitment was determined by counting cells (Neubauer chamber), H&E staining, and using LysM-eGFP mice by confocal microscopy. Inflammasome components, Il-1β, and Tnf-α mRNA expression were determined by RT-qPCR. IL-1β and TNF-α production (in vitro) and NF-κB activation (in vitro and in vivo) were evaluated by ELISA. In vitro analysis using LPS-primed bone marrow-derived macrophages (BMDMs) was performed 5 h after stimulation with MSU crystals. For these experiments, BMDMs were either treated or pre-treated with budlein A at concentrations of 1, 3, or 10 μg/mL. Results: We demonstrated that budlein A reduced mechanical hypersensitivity and knee joint edema. Moreover, it reduced neutrophil recruitment, phagocytosis of MSU crystals by neutrophils, and Il-1β and Tnf-α mRNA expression in the knee joint. In vitro, budlein A decreased TNF-α production, which might be related to the inhibition of NF-κB activation. Furthermore, budlein A also reduced the IL-1β maturation, possibly by targeting inflammasome assembly in macrophages. Conclusion: Budlein A reduced pain and inflammation in a model of acute gout arthritis in mice. Therefore, it is likely that molecules with the ability of targeting NF-κB activation and inflammasome assembly, such as budlein A, are interesting approaches to treat gout flares.

The spinal NR2BR/ERK2 pathway as a target for the central sensitization of collagen-induced arthritis pain

Objective

Pain management is a huge challenge in the treatment of rheumatoid arthritis (RA), and central sensitization is reportedly involved in the development of pain. The current study was undertaken to explore the possible role of N-methyl-D-aspartate receptors (NMDARs) in the spinal mechanism of central sensitization in RA using a collagen-induced arthritis (CIA) model.

Methods

Mechanical hypersensitivity was assessed in C57BL/6 mice, before and after the induction of CIA via administration of chick type II collagen. Analgesic drugs, receptor antagonist, and kinase inhibitor were administrated intrathecally in the spinal cord. Protein expression and phosphorylation changes were detected via immunoblotting.

Results

CIA mice developed significant mechanical hypersensitivity, and spinal administration of the NMDAR antagonist D-2-amino-5-phosphonovaleric acid (D-APV) effectively attenuated peripheral pain hypersensitivity. There was specific enhancement of synaptic NR2B-containing NMDAR (NR2BR) expression in the spinal dorsal horns of the mice. Both the increased total protein expression of NR2B subunit and the enhanced total phosphorylation level of NR2B subunit at 1472 tyrosine promoted the synaptic expression of NMDAR in the mice. Intrathecal injection of tramadol suppressed synaptic NMDAR expression mainly by changing the synaptic phosphorylation state of NR2B subunit at Tyr1472. Extracellular signal-regulated protein kinases 2 (ERK2) activity synchronized with the synaptic expression of NR2BR, which was downregulated by the action of tramadol.

Conclusion

Specific enhancement of NR2BR in the spinal dorsal horn may be vital for central sensitization in the CIA model of RA. The NR2BR/ERK2 pathway may be a promising target for pain management in RA patients.

Discovery of Novel Nonsteroidal Anti-Inflammatory Drugs and Carbonic Anhydrase Inhibitors Hybrids (NSAIDs-CAIs) for the Management of Rheumatoid Arthritis

Herein we report the design as well as the synthesis of a new series of dual hybrid compounds consisting of the therapeutically used nonsteroidal-anti-inflammatory drugs (NSAIDs; i.e., indometacin, sulindac, ketoprofen, ibuprofen, diclofenac, ketorolac, etc., cyclooxygenase inhibitors) and the carbonic anhydrase inhibitor (CAIs) fragments of the sulfonamide type. Such compounds are proposed as new tools for the management of ache symptoms associated with rheumatoid arthritis (RA) and related inflammation diseases. The majority of the hybrids reported were effective in inhibiting the ubiquitous human (h) CA I and II as well as the RA overexpressed hCAs IX and XII isoforms, with K_I values comprised of the low-medium nanomolar ranges. The antihyperalgesic activity of selected compounds was assessed by means of the paw-pressure and incapacitance tests using an in vivo RA model, and among them the hybrids 6B and 8B showed potent antinociceptive effects lasting up to 60 min after administration.

Effects of a water extract of Lepidium meyenii root in different models of persistent pain in rats

Lepidium meyenii (Walp.), commonly called maca, is an Andean crop belonging to the Brassicaceae family. Maca hypocotils are habitually consumed as customary food as well as traditional remedies for pathological conditions such as infertility. Moreover, the characterization of maca extracts revealed the presence of compounds that are able to modulate the nervous system. Aimed to evaluate the efficacy of L. meyenii in persistent pain, the present study analyzed the effects of a commercial root extract from maca in different animal models reproducing the most common causes of chronic painful pathologies. A qualitative characterization of this commercial extract by high performance liquid chromatography-mass spectrometry and tandem mass spectrometry analyses allowed us to confirm the presence of some macamides known as bioactive constituents of this root and the absence of the main aromatic glucosinolates. The acute oral administration of maca extract is able to reduce mechanical hypersensitivity and postural unbalance induced by the intra-articular injection of monoiodoacetate and the chronic-constriction injury of the sciatic nerve. Furthermore, L. meyenii extract reverts pain threshold alterations evoked by oxaliplatin and paclitaxel. A good safety profile in mice and rats was shown. In conclusion, the present maca extract could be considered as a therapeutic opportunity to relieve articular and neuropathic pain.

Reactive oxygen species scavengers ameliorate mechanical allodynia in a rat model of cancer-induced bone pain

Cancer-induced bone pain (CIBP) is a frequent complication in patients suffering from bone metastases. Previous studies have demonstrated a pivotal role of reactive oxygen species (ROS) in inflammatory and neuropathic pain, and ROS scavengers exhibited potent antinociceptive effect. However, the role of spinal ROS remains unclear. In this study, we investigated the analgesic effect of two ROS scavengers in a well-established CIBP model. Our results found that intraperitoneal injection of N-tert-Butyl-α-phenylnitrone (PBN, 50 and 100 mg/kg) and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (Tempol, 100 and 200 mg/kg) significantly suppressed the established mechanical allodynia in CIBP rats. Moreover, repeated injection of PBN and Tempol showed cumulative analgesic effect without tolerance. However, early treatment with PBN and Tempol failed to prevent the development of CIBP. Naive rats received repetitive injection of PBN and Tempol showed no significant change regarding the nociceptive responses. Finally, PBN and Tempol treatment notably suppressed the activation of spinal microglia in CIBP rats. In conclusion, ROS scavengers attenuated established CIBP by suppressing the activation of microglia in the spinal cord.

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PBN and Tempol could suppress established mechanical allodynia in CIBP rats.

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Repeated injection of PBN and Tempol showed cumulative analgesic effect.

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PBN and Tempol failed to prevent the development of CIBP.

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PBN and Tempol could suppress the microglia activation in CIBP rats.

Pain relieving and protective effects of Astragalus hydroalcoholic extract in rat arthritis models

OBJECTIVES

The evaluation of the pharmacological profile of the dried 50% hydroalcoholic extract (50%HA) of Astragali radix in two different animal models of articular damage resembling osteoarthritis and rheumatoid arthritis.

METHODS

Sodium monoiodoacetate (MIA) or complete Freund's adjuvant (CFA) was intra-articular injected (day 0) in the rat tibiotarsal joint to induce damages mimicking osteoarthritis or rheumatoid arthritis. Pain measurements (responses to non-noxious and noxious stimuli, spontaneous pain, articular pain) were assessed on days 7 and 14. On day 14, the tibiotarsal joints were explanted in order to measure the diameter and to assess histological evaluations. Furthermore, the plasmatic concentrations of inflammatory and anti-inflammatory cytokines were measured.

KEY FINDINGS

A single administration of 50%HA (300 mg/kg per os) significantly reduced both MIA-induced pain and CFA-induced pain (78% and 96% pain relief, respectively). The repeated administration prevented the development of hypersensitivity on day 14. The haematoxylin/eosin staining revealed that 50% HA attenuated joint alterations in MIA-injected rats, and furthermore, the joint inflammatory infiltrate was reduced in both models (by about 50%). In CFA-treated rats, 50%HA lowered the plasmatic levels of the pro-inflammatory cytokines interleukin-1β and tumour necrosis factor-α as well as the joint diameter.

CONCLUSIONS

The 50% hydroalcoholic extract of Astragali radix is a valuable candidate for the adjuvant treatment of articular diseases.

Photobiomodulation therapy by NIR laser in persistent pain: an analytical study in the rat

Over the past three decades, physicians have used laser sources for the management of different pain conditions obtaining controversial results that call for further investigations. In order to evaluate the pain relieving possibilities of photobiomodulation therapy (PBMT), we tested two near infrared (NIR) laser systems, with different power, against various kinds of persistent hyperalgesia animal models. In rats, articular pain was reproduced by the intra-articular injection of sodium monoiodoacetate (MIA) and complete Freund's adjuvant (CFA), while compressive neuropathy was modelled by the chronic constriction injury of the sciatic nerve (CCI). In MIA and CFA models, (NIR) laser (MLS-Mphi, ASA S.r.l., Vicenza, Italy) application was started 14 days after injury and was performed once a day for a total of 13 applications. In MIA-treated animals, the anti-hyperalgesic effect of laser began 5 min after treatment and vanished after 60 min. The subsequent applications evoked similar effects. In CFA-treated rats, laser efficacy started 5 min after treatment and disappeared after 180 min. In rats that underwent CCI, two treatment protocols with similar fluence but different power output were tested using a new experimental device called Multiwave Locked System laser (MLS-HPP). Treatments began 7 days after injury and were performed during 3 weeks for a total of 10 applications. Both protocols reduced mechanical hyperalgesia and hindlimb weight bearing alterations until 60 min after treatment with a higher efficacy recorded for the animals treated using the higher power output. In conclusion, this study supports laser therapy as a potential treatment for immediate relief of chronic articular or neuropathic pain.

Design and Synthesis of Novel Nonsteroidal Anti-Inflammatory Drugs and Carbonic Anhydrase Inhibitors Hybrids (NSAIDs-CAIs) for the Treatment of Rheumatoid Arthritis

We report the synthesis of a series of hybrid compounds incorporating 6- and 7-substituted coumarins (carbonic anhydrase, CA inhibitors) derivatized with clinically used NSAIDs (indomethacin, sulindac, ketoprofen, ibuprofen, diclofenac, ketorolac, etc., cyclooxygenase inhibitors) as agents for the management of rheumatoid arthritis (RA). Most compounds were effective in inhibiting the RA overexpressed hCA IX and XII, with K_I values in the low nanomolar-subnanomolar ranges. The antihyperalgesic activity of such compounds was assessed by means of the paw-pressure and incapacitance tests using an in vivo RA model. Among all tested compounds, the 7-coumarine hybrid with ibuprofen showed potent and persistent antihyperalgesic effect up to 60 min after administration.

Acute effect of Capparis spinosa root extracts on rat articular pain

ETHNOPHARMACOLOGICAL RELEVANCE

Capparis spinosa L. originates from dry regions of Asia and Mediterranean basin. In traditional medicine of these areas, infusions from caper root are considered to be beneficial for the treatment of rheumatism, gout and against abdominal pains.

AIM OF THE STUDY

To evaluate the pain relieving properties of a Syrian cultivar of Capparis spinosa roots in rat models of osteoarthritis and rheumatoid arthritis.

MATERIALS AND METHODS

Decoction (DEC) and hydroalcoholic extract (EtH₂O) were obtained from powdered roots; the latter was further separated in CH₂Cl₂ and aqueous (H₂O-Res) fractions. The extracts were characterized in terms of spermidine alkaloids by HPLC/DAD/MS and stachydrine by NMR. Different amount of free and glycosilated forms of capparispine and analogues (from 0.5% w/w for DEC up to 7.6% w/w for CH₂Cl₂ fraction) were detected. Rat models of rheumatoid arthritis and osteoarthritis were induced by the intra-articular administration of Complete Freund's Adjuvant (CFA) or monosodium iodoacetate (MIA), respectively.

RESULTS

Fourteenth days after CFA or MIA injection, the different preparations of Capparis spinosa (3, 30, 100 and 300mgkg^-1) were acutely administered p.o.. Powdered roots (300mgkg^-1), DEC (100mgkg^-1), and EtH₂O (300mgkg^-1) significantly reduced hypersensitivity to mechanical noxious stimuli as well as spontaneous pain evaluated as hind limb bearing alterations in both models. The CH₂Cl₂ and the H₂O-Res (30mgkg^-1) were the most potent in reverting pain threshold alterations despite the different content of free alkaloids.

CONCLUSIONS

Capparis spinosa extracts relieved pain related to rheumatoid arthritis and osteoarthritis after single administration. A synergistic effect due to a specific "phytochemical mixture" is suggested.

Effects of the neutrophil elastase inhibitor EL-17 in rat adjuvant-induced arthritis

OBJECTIVES

Neutrophil elastase (NE), a granule-associated enzyme, participates in connective tissue breakdown and promotes cytokine release and specific receptor activation during various inflammatory diseases like RA. NE is increased in the SF and cartilage of RA patients and represents a target for the development of new therapeutic possibilities. The present research aimed to evaluate the preclinical pharmacological profile of the N-benzoylpyrazole derivative EL-17, a potent and selective NE inhibitor, in a rat model of RA.

METHODS

Complete Freund's Adjuvant (CFA) was injected in the tibiotarsal joint and the effect of acute or repeated treatments with EL-17 (1-30 mg/kg by mouth) were evaluated.

RESULTS

On day 14 after CFA injection, a single administration of EL-17 significantly reduced CFA-dependent hypersensitivity to mechanical noxious stimuli and the postural unbalance related to spontaneous pain. To evaluate the preventive efficacy, EL-17 was administered daily starting from the day of CFA treatment. Behavioural measurements performed on days 7 and 14 showed a progressive efficacy of EL-17 against hypersensitivity to mechanical noxious and non-noxious stimuli, as well as a decrease of hind limb weight-bearing alterations. Histological evaluation of the tibiotarsal joint (day 14) demonstrated significant prevention of articular derangement after EL-17 (30 mg/kg) treatment. The protective effects of EL-17 directly correlated with a complete reversion of the plasma NE activity increase induced by CFA.

CONCLUSIONS

The NE inhibitor EL-17 relieved articular pain after acute administration. Furthermore, repeated treatment reduced the development of hypersensitivity and protected joint tissue, revealing a disease-modifying profile.

Effect of the SOD mimetic MnL4 on in vitro and in vivo oxaliplatin toxicity: Possible aid in chemotherapy induced neuropathy

BACKGROUND

One of the most discomfortable dose-limiting adverse reactions of effective drugs for the treatment of solid tumors is a peripheral neuropathy which is the main reason for dose reduction and discontinuation of the therapy. We identified oxidative stress as one target of oxaliplatin toxicity in the search of possible adjuvant therapies to prevent neuropathy and alleviate pain. Therefore, we studied an effective SOD mimetic compound, MnL4, as a possible adjuvant treatment in in vitro cellular cultures and in vivo on a rat model of oxaliplatin-induced neuropathy.

METHODS AND RESULTS

All rat manipulations were carried out according to the European Community guidelines for animal care. We performed experiments on SH-SY5Y, HT-29 and primary cortical rat astrocytes. Incubation with 100 µM oxaliplatin increased superoxide anion production and caspase 3/7 activity in the neuronal cell line SH-SY5Y and cortical astrocytes. MnL4 (10 µM) significantly reduced the increase in superoxide anion in both cell types, but prevented caspase 3/7 activity only in astrocytes. MnL4 reduced lipid peroxidation induced by oxaliplatin and normalized the intracellular calcium signal evoked by ATP and acetylcholine in astrocytes, preincubated with oxaliplatin. MnL4 did not interfere with the concentration- and time-dependent cytotoxic effects of oxaliplatin on the cancer cell lines HT-29 and LoVo. In vivo MnL4 reduced the response at mechanical noxious and mechanical and thermal non-noxious stimuli in oxaliplatin treated animals. Rat rota-rod performances were improved.

CONCLUSION

Since MnL4 exerts its beneficial effects without interfering with the anticancer activity of oxaliplatin, it could be proposed as adjuvant to prevent and reduce oxaliplatin induced neuropathy.

What is the effect of nicotinic acetylcholine receptor stimulation on osteoarthritis in a rodent animal model?

OBJECTIVES

Despite the rising number of patients with osteoarthritis, no sufficient chondroprotective and prophylactic therapy for osteoarthritis has been established yet. The purpose of this study was to verify whether stimulation of the nicotinic acetylcholine receptor via nicotine has a beneficial effect on cartilage degeneration in the development of osteoarthritis and is capable of reducing the expression of proinflammatory cytokines and cartilage degrading enzymes in synovial membranes after osteoarthritis induction.

METHODS

Experimental osteoarthritis was induced in Lewis rats using a standardized osteoarthritis model with monoiodoacetate. A total of 16 Lewis rats were randomized into four groups: control, sham + nicotine application, osteoarthritis, and osteoarthritis + nicotine application. Nicotine (0.625 mg/kg twice daily) was administered intraperitoneally for 42 days. We analyzed histological sections, radiological images and the expression of the proinflammatory cytokines, such as interleukin-1β, tumor necrosis factor-α and interleukin-6, and of matrix metalloproteases 3, 9 and 13 and tissue inhibitors of metalloprotease-1 in synovial membranes via quantitative polymerase chain reaction.

RESULTS

Histological and x-ray examination revealed cartilage degeneration in the osteoarthritis group compared to control or sham + nicotine groups (histological control vs osteoarthritis: p = 0.002 and x-ray control vs osteoarthritis: p = 0.004). Nicotine treatment reduced the cartilage degeneration without significant differences. Osteoarthritis induction led to a higher expression of proinflammatory cytokines and matrix metalloproteases as compared to control groups. This effect was attenuated after nicotine administration. The differences of proinflammatory cytokines and matrix metalloproteases did not reach statistical significance.

CONCLUSION

With the present small-scale study, we could not prove a positive effect of nicotinic acetylcholine receptor stimulation on osteoarthritis due to a conservative statistical analysis and the consecutive lack of significant differences. Nevertheless, we found promising tendencies of relevant parameters that might prompt further experiments designed to evaluate the potency of stimulation of this receptor system as an additional treatment approach for osteoarthritis.

ROS/oxidative stress signaling in osteoarthritis

Osteoarthritis is the most common joint disorder with increasing prevalence due to aging of the population. Its multi-factorial etiology includes oxidative stress and the overproduction of reactive oxygen species, which regulate intracellular signaling processes, chondrocyte senescence and apoptosis, extracellular matrix synthesis and degradation along with synovial inflammation and dysfunction of the subchondral bone. As disease-modifying drugs for osteoarthritis are rare, targeting the complex oxidative stress signaling pathways would offer a valuable perspective for exploration of potential therapeutic strategies in the treatment of this devastating disease.

Widespread pain reliever profile of a flower extract of Tanacetum parthenium

BACKGROUND

Tanacetum parthenium L., commonly called Feverfew, is known for anti-inflammatory and anti-migraine properties.

PURPOSE

Aimed to individuate new therapeutical strategies to control acute and persistent pain induced by different origins we tested two hydroalcoholic extracts obtained from Feverfew flowers and leaves, respectively.

STUDY DESIGN

Extracts were characterized according to the European Pharmacopoeia monograph. Both the extracts were tested after acute per os administration in the dose range 30-1000 mg kg(-1). The anti-nociceptive properties were evaluated by the Writhing test in mice.

RESULTS

The number of abdominal contractions was dose dependently reduced by the flower extract. It reduced mechanical hypersensitivity (Paw pressure test) related to the acute inflammatory phase induced by carrageenan similarly to diclofenac and ibuprofen. In the osteoarthritis model induced by intra articular injection of monoiodoacetate (MIA) the flower extract significantly increased the pain threshold peaking 30 min after treatment. Moreover, it was effective in the chronic constriction injury model of neuropathic pain showing activity similar to the anti-epileptic drug gabapentin. The flower extract activity was confirmed in rat models of chemotherapy-induced neuropathic pain. The mechanical hypersensitivity induced by repeated treatments with the anticancer drug oxaliplatin and with the antiviral dideoxycytidine was significantly reduced after a single injection of Feverfew flower extract. The leaf extract showed lesser efficacy and potency and it was devoid of any effect in carrageenan-, MIA- and chemotherapy-induced pain.

CONCLUSION

The present Feverfew flower extract behaves as a potent pain reliever in acute, inflammatory, articular and neuropathic pain. It appears as a natural strategy potentially suitable for the treatment of different kinds of pain.

Protection of coronary endothelial cells from cigarette smoke-induced oxidative stress by a new Mn(II)-containing polyamine-polycarboxilate scavenger of superoxide anion

Oxidative stress plays a major role in cardiovascular injury and dysfunction induced by cigarette smoke. Smoke-borne pro-oxidants impair endothelial function and predispose to thrombosis, inflammation and atherosclerosis. This in vitro study evaluates whether Mn(II)(4,10-dimethyl-1,4,7,10-tetraazacyclododecane-1,7-diacetate).2H2O (Mn(II)(Me2DO2A)), a polyamine-polycarboxilate, Mn(II)-containing O2(-) scavenger, has a direct protective action on guinea pig coronary endothelial (GPCE) cells exposed to cigarette smoke extracts (CSE). Mn(II)(Me2DO2A) (1-10μmol/l) was added to the culture medium together with CSE and maintained for 4h. In parallel experiments, the inactive congener Zn(II)(Me2DO2A), in which Zn(II) replaced the functional Mn(II) center in the same organic scaffold, was used as negative control. Mn(II)(Me2DO2A), mostly at the higher doses (5 and 10μmol/l), significantly increased GPCE cell viability (trypan blue assay), improved mitochondrial activity (MTT test, mitochondrial membrane potential Δψ), reduced cellular apoptosis (mPTP, caspase-3 activity, TUNEL assay), decreased intracellular ROS levels (H2DCFDA), lipoperoxidation (BODIPY 581/591) and decreased protein nitrosylation. Of note, Zn(II)(Me2DO2A) did not preserve cell viability. These findings suggest that Mn(II)(Me2DO2A) is a promising O2(-) scavenging compound able to protect from cigarette smoke-induced oxidative cell injury. In perspective, should its efficacy be confirmed in future in vivo studies, this molecule might represent a therapeutic or preventive drug to counteract cigarette smoke toxicity.

α7 Nicotinic Receptor Promotes the Neuroprotective Functions of Astrocytes against Oxaliplatin Neurotoxicity

Neuropathies are characterized by a complex response of the central nervous system to injuries. Glial cells are recruited to maintain neuronal homeostasis but dysregulated activation leads to pain signaling amplification and reduces the glial neuroprotective power. Recently, we highlighted the property of α7 nicotinic-acetylcholine-receptor (nAChR) agonists to relieve pain and induce neuroprotection simultaneously with a strong increase in astrocyte density. Aimed to study the role of α7 nAChR in the neuron-glia cross-talk, we treated primary rat neurons and astrocytes with the neurotoxic anticancer drug oxaliplatin evaluating the effect of the α7 nAChR agonist PNU-282987 (PNU). Oxaliplatin (1 μM, 48 h) reduced cell viability and increased caspase-3 activity of neuron monocultures without damaging astrocytes. In cocultures, astrocytes were not able to protect neurons by oxaliplatin even if glial cell metabolism was stimulated (pyruvate increase). On the contrary, the coculture incubation with 10 μM PNU improved neuron viability and inhibited apoptosis. In the absence of astrocytes, the protection disappeared. Furthermore, PNU promoted the release of the anti-inflammatory cytokine TGF-β1 and the expression of the glutamate-detoxifying enzyme glutamine synthetase. The α7 nAChR stimulation protects neurons from oxaliplatin toxicity through an astrocyte-mediated mechanism. α7 nAChR is suggested for recovering the homeostatic role of astrocytes.

Delay of morphine tolerance by palmitoylethanolamide

In spite of the potency and efficacy of morphine, its clinical application for chronic persistent pain is limited by the development of tolerance to the antinociceptive effect. The cellular and molecular mechanisms underlying morphine tolerance are complex and still unclear. Recently, the activation of glial cells and the release of glia-derived proinflammatory mediators have been suggested to play a role in the phenomenon. N-Palmitoylethanolamine (PEA) is an endogenous compound with antinociceptive effects able to reduce the glial activation. On this basis, 30 mg kg⁻¹ PEA was subcutaneously daily administered in morphine treated rats (10 mg kg⁻¹ intraperitoneally, daily). PEA treatment significantly attenuated the development of tolerance doubling the number of days of morphine antinociceptive efficacy in comparison to the vehicle + morphine group. PEA prevented both microglia and astrocyte cell number increase induced by morphine in the dorsal horn; on the contrary, the morphine-dependent increase of spinal TNF-α levels was not modified by PEA. Nevertheless, the immunohistochemical analysis revealed significantly higher TNF-α immunoreactivity in astrocytes of PEA-protected rats suggesting a PEA-mediated decrease of cytokine release from astrocyte. PEA intervenes in the nervous alterations that lead to the lack of morphine antinociceptive effects; a possible application of this endogenous compound in opioid-based therapies is suggested.

Efficacy of drugs with different mechanisms of action in relieving spontaneous pain at rest and during movement in a rat model of osteoarthritis

Patients with osteoarthritis (OA) suffer from joint pain aggravated by movement, which affect their quality of life. In the present study, a weight bearing paradigm for pain at rest and a gait paradigm for pain during movement were tested in rats with unilateral knee arthritis induced by an intra-articular injection of sodium monoiodoacetate (MIA). At week 3 after MIA (1mg/knee) injection, animals developed pain-associated, right-left imbalances of weight distribution (weight bearing) or foot print parameters (gait). Diclofenac, at doses up to 30 mg/kg orally (p.o.), did not have a significant effect on either paradigm. Morphine rectified the weight bearing and gait imbalances at 1 and 3mg/kg subcutaneously, respectively. The weak opioid and serotonin/norepinephrine reuptake inhibitor (SNRI) tramadol also significantly corrected the indices at 10mg/kg (weight bearing) and 100mg/kg p.o. (gait). The SNRI duloxetine at 30 mg/kg p.o. corrected the weight bearing imbalance but not gait imbalance. We assessed the effect of different drugs on pain-induced disturbances in weight distribution and gait in MIA-induced arthritic rats. Analgesic drugs, each with different mechanisms of action, were less effective in rectifying the imbalance in gait than that in weight distribution. The assessment of the effect of analgesics on not only rest pain but pain during movement is valuable for the comprehensive examination of their therapeutic efficacies in OA.

Low dose native type II collagen prevents pain in a rat osteoarthritis model

Background

Osteoarthritis is the most widespread joint-affecting disease. Patients with osteoarthritis experience pain and impaired mobility resulting in marked reduction of quality of life. A progressive cartilage loss is responsible of an evolving disease difficult to treat. The characteristic of chronicity determines the need of new active disease modifying drugs. Aim of the present research is to evaluate the role of low doses of native type II collagen in the rat model of osteoarthritis induced by sodium monoiodoacetate (MIA).

Methods

1, 3 and 10 mg kg^-1 porcine native type II collagen were daily per os administered for 13 days starting from the day of MIA intra-articular injection.

Results

On day 14, collagen-treated rats showed a significant prevention of pain threshold alterations induced by MIA. Evaluation were performed on paws using mechanical noxious (Paw pressure test) or non-noxious (Electronic Von Frey test) stimuli, and a decrease of articular pain was directly measured on the damaged joint (PAM test). The efficacy of collagen in reducing pain was as higher as the dose was lowered. Moreover, a reduced postural unbalance, measured as hind limb weight bearing alterations (Incapacitance test), and a general improvement of motor activity (Animex test) were observed. Finally, the decrease of plasma and urine levels of CTX-II (Cross Linked C-Telopeptide of Type II Collagen), a biomarker of cartilage degradation, suggests a collagen-dependent decrease of structural joint damage.

Conclusions

These results describe the preclinical efficacy of low dosages of native type II collagen as pain reliever by a mechanism that involves a protective effect on cartilage.