Protective effects of Phlomis umbrosa extract on a monosodium iodoacetate-induced osteoarthritis model and prediction of molecular mechanisms using transcriptomics.

BACKGROUND: Phlomis umbrosa Turczaninow root has been traditionally used to treat fractures, rheumatoid arthritis, and arthralgia. However, the effects and mechanisms of P. umbrosa on osteoarthritis (OA) remain poorly understood and a functional genomic approach has not been investigated. AIM: The purpose of this study was to investigate the effects and mechanisms of P. umbrosa extract (PUE) on OA using transcriptomic analysis. METHODS: We performed joint diameter measurements, micro computed tomography, and histopathological analysis of monosodium iodoacetate (MIA)-induced OA rats treated with PUE (200 mg/kg) for 3 weeks. Gene expression profiling in articular cartilage tissue was then performed using RNA sequencing (RNA-seq) followed by signaling pathway analysis of regulatory genes. RESULTS: PUE treatment improved OA based on decreased joint diameter, increased joint morphological parameters, and histopathological features. Many genes involved in multiple signal transduction pathway and collagen activation in OA were differentially regulated by PUE. These included genes related to Wnt/ß-catenin, OA pathway, and sonic hedgehog signaling activity. Furthermore, PUE treatment downregulated cartilage damage factors (MMP-9, MMP-13, ADAMTs4, and ADMATs5) and upregulated chondrogenesis (COL2A1 and SOX-9) by regulating the transcription factors SOX-9, Ctnnb1, and Epas1. CONCLUSION: Based on the results of gene expression profiling, this study highlighted the molecular mechanisms underlying the effects of PUE in MIA-induced OA rats. The findings provide novel insight into the mechanisms by which PUE treatment-induced gene expression changes may influence OA disease progression. Taken together, the results suggest that PUE may be used as a source of therapeutic agents for OA.

In vivo protective effects of upper zone of growth plate and cartilage matrix associated protein against cartilage degeneration in a monosodium iodoacetate induced osteoarthritis model.

Osteoarthritis (OA) is a degenerative disease affecting the majority of over 65 year old people and characterized by cartilage degeneration, subchondral abnormal changes, and inflammation. Despite the enormous socioeconomic burden caused by OA, currently, there is no effective therapy against it. Upper zone of growth plate and cartilage matrix associated protein (UCMA) is a vitamin K dependent protein and has a critical role in pathophysiological conditions associated with bone and cartilage. However, there is no research on the protective role of intra-articular UCMA treatment in OA pathogenesis. Therefore, we aimed to investigate the potential therapeutic role of UCMA in an in vivo model of OA. We report for the first time that intra-articular UCMA injection ameliorated cartilage degeneration in a monosodium iodoacetate induced OA rat model. Furthermore, the OA-induced activation of nuclear factor kappa B and bone morphogenetic protein 2 signals was attenuated by UCMA. Our results indicated that UCMA decreased cartilage oligomeric matrix protein levels but did not affect interleukin 6, total antioxidant status, and total oxidant status levels in the serum. In conclusion, UCMA exhibited a therapeutic potential in the treatment of OA. This protective effect of UCMA is possibly achieved by reducing the aggrecanase activity and the production of inflammatory cytokines.

Effect of Alpinia oxyphylla extract in vitro and in a monosodium iodoacetate-induced osteoarthritis rat model.

BACKGROUND: Osteoarthritis (OA) affects the articular cartilage and subchondral bone of synovial joints and induces proinflammatory and anti-inflammatory pathway dysregulation, leading to pain. This study evaluated the anti-inflammatory and antiosteoarthritis effects of Alpinia oxyphylla extract (AOE) in vitro and in vivo. METHODS: The anti-inflammatory effect of AOE was evaluated in vitro in lipopolysaccharide (LPS)-treated RAW264.7 cells. The antiosteoarthritis effect of AOE was investigated in a monosodium iodoacetate (MIA)-induced rat model of OA. Rats were orally administered AOE (150 mg/kg or 300 mg/kg) or the positive control drug indomethacin (1 mg/kg) 3 days before MIA injection and once daily for 21 days thereafter. RESULTS: AOE significantly decreased the production of nitric oxide (NO, 68.2%), prostaglandin E2 (PGE2, 92.8%), interleukin-1ß (IL-1ß, 77.2%), interleukin-6 (IL-6, 39.9%), and tumor necrosis factor-alpha (TNF-α, 20.7%) and the activation of extracellular signal-regulated kinase (ERK), Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) in LPS-treated RAW264.7 cells at a dose of 100 µg/ml. In addition, AOE attenuated joint pain, suppressed proinflammatory cytokine and mediator production and inhibited cartilage degradation in the MIA-induced rat OA model. CONCLUSION: These results demonstrate that AOE exerts potent anti-inflammatory effects and may be a useful therapeutic candidate against OA.

CBCT analysis of rabbit temporomandibular joints with osteoarthrosis induced by monoiodoacetate and papain / Análisis por TCCB de la articulación temporomandibular de conejos con osteoartrosis inducida por monoiodoacetato y papaina

Osteoarthrosis (OA) is a degenerative disease characterized by loss of joint cartilage, remodelling of the subchondral bone, narrowing of joint spaces and the formation of osteophytes. Animal models are used to study the mechanisms of OA, as well as to test the effects of anti-osteoarthrosis drugs. The objective of the present study was to determine the changes identifiable by imaging techniques occurring in rabbit temporomandibular joints (TMJ) at 15, 25 and 45 days after OA inducement by monoiodoacetate (MIA) and papain. The imaging technology used was cone-beam computerised tomography (CBCT). The model animals were 22 young adult male New Zealand rabbits, divided randomly into three study groups: Four rabbits in the control group, nine in the papain experimental group and nine in the monoiodoacetate (MIA) experimental group. OA was induced by arthrocentesis in the lower compartment of both TMJs. The rabbits were examined by CBCT at 15, 25 and 45 days after the injection of MIA and papain. The mandibular condyles presented loss of their rounded shape, deformation of the condyle or mandibular fossa, cortical irregularity, cortical wear and changes in the dimensions of the condyle. OA induction by MIA and papain generates changes observable by CBCT in the dimensions of the mandibular condyle in rabbits. Both inducers promote signs compatible with OA on the joint surfaces of the TMJ; MIA promotes more expressive changes.

La osteoartrosis (OA) es una enfermedad degenerativa caracterizada por la pérdida de cartílago articular, remodelación ósea subcondral, estrechamiento del espacio articular y formación de osteofitos. El modelo animal es utilizado para estudiar los mecanismos de la OA, así como testar el efecto de drogas anti-osteoartrosis. El objetivo de este estudio fue determinar los cambios imagenológicos, mediante tomografía computarizada cone-beam (TCCB), que se generan en 15, 25 y 45 días, luego de la inducción de OA por medio de Monoiodoacetato (MIA) y Papaína sobre la ATM de conejos. Fueron utilizados 22 conejos machos, adultos jóvenes, de raza New Zealand divididos aleatoriamente en 3 grupos de estudio: 4 conejos para un grupo control, 9 conejos para el grupo experimental con Papaína y 9 conejos para el grupo experimental con monoiodoacetato (MIA). Se realizó la inducción de OA por la técnica de artrocentesis en el compartimiento inferior de ambas ATMs. Se les realizó examen de TCCB en los días 15, 25 y 45 tras la inyección de MIA y de papaina. Los cóndilos mandibulares presentaron pérdida de forma redondeada de cóndilo, deformidad de cóndilo o fosa mandibular, irregularidad de corticales, desgaste de corticales, cambio de dimensiones de cóndilo. La inducción de OA por medio de MIA y papaína genera cambios en la dimensión del cóndilo mandibular de conejos observables a través de TCCB. Además, ambos inductores promueven signos compatibles con OA en las superficies articulares de la ATM, siendo que la MIA promueve cambios más expresivos.

Mori Folium water extract alleviates articular cartilage damages and inflammatory responses in monosodium iodoacetate­induced osteoarthritis rats.

Mori folium, the leaf of Morus alba L. (Moraceae), has been widely used in traditional medicine for the treatment of various diseases. It has been recently reported that Mori folium possesses potential chondroprotective effects in interleukin (IL)­1ß­stimulated human chondrocytes; however, its protective and therapeutic potential against osteoarthritis (OA) in an animal model remains unclear. In this study, as part of an ongoing screening program to evaluate the anti­osteoarthritic potential of Mori folium, the protective effects of a water extract of Mori folium (MF) on cartilage degradation and inflammatory responses in a monosodium iodoacetate (MIA)­induced OA rat model were evaluated. The results demonstrated that administration of MF had a tendency to attenuate the damage to articular cartilage induced by MIA, as determined by knee joint swelling and the histological grade of OA. The elevated levels of matrix metalloproteinases­13 and two bio­markers for the diagnosis and progression of OA, such as the cartilage oligomeric matrix protein and C­telopeptide of type II collagen, were markedly ameliorated by MF administration in MIA­induced OA rats. In addition, MF significantly suppressed the production of pro­inflammatory cytokines, including IL­1ß, IL­6 and tumor necrosis factor­α. MF also effectively inhibited the expression of inducible nitric oxide (NO) synthase and cyclooxygenase­2, thus inhibiting the release of NO and prostaglandin E2. Although further work is required to fully understand the critical role and clinical usefulness, these findings indicate that MF may be a potential therapeutic option for the treatment of OA.

Strenuous running exacerbates knee cartilage erosion induced by low amount of mono-iodoacetate in rats.

BACKGROUND: It is still debated whether strenuous running in the inflammatory phase produces beneficial or harmful effect in rat knees. We examined (1) the dropout rate of rats during a 30-km running protocol, (2) influences of strenuous running and/or low amounts of mono-iodoacetate injection on cartilage, and (3) the effect of strenuous running on synovitis. METHODS: Rats were forced to run 30 km over 6 weeks and the dropout rate was examined. One week after 0.1 mg mono-iodoacetate was injected into the right knee, rats were forced to run either 15 km or not run at all over 3 weeks, after which knee cartilage was evaluated. Synovium at the infrapatellar fat pad was also examined histologically. RESULTS: Even though all 12 rats run up to 15 km, only 6 rats completed 30 km of running. Macroscopically, 0.1 mg mono-iodoacetate induced erosion at the tibial cartilage irrespective of 15 km of running. Histologically, 0.1 mg mono-iodoacetate induced loss of cartilage matrix in the tibial cartilage, and an additional 15 km of strenuous running significantly exacerbated the loss. Synovitis caused by mono-iodoacetate improved after running. CONCLUSIONS: Only 50% of rats completed 30 km of running because of foot problems. Strenuous running further exacerbated tibial cartilage erosion but did not influence synovitis induced by mono-iodoacetate.

Role of the endocannabinoid system in the emotional manifestations of osteoarthritis pain.

In this study, we investigated the role of the endocannabinoid system (ECS) in the emotional and cognitive alterations associated with osteoarthritis pain. The monosodium iodoacetate model was used to evaluate the affective and cognitive manifestations of osteoarthritis pain in type 1 (CB1R) and type 2 (CB2R) cannabinoid receptor knockout and wild-type mice and the ability of CB1R (ACEA) and CB2R (JWH133) selective agonists to improve these manifestations during a 3-week time period. The levels of the endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG) were measured in plasma and brain areas involved in the control of these manifestations. Patients with knee osteoarthritis and healthy controls were recruited to evaluate pain, affective, and cognitive symptoms, as well as plasma endocannabinoid levels and cannabinoid receptor gene expression in peripheral blood lymphocytes. The affective manifestations of osteoarthritis were enhanced in CB1R knockout mice and absent in CB2R knockouts. Interestingly, both ACEA and JWH133 ameliorated the nociceptive and affective alterations, whereas ACEA also improved the associated memory impairment. An increase of 2-AG levels in prefrontal cortex and plasma was observed in this mouse model of osteoarthritis. In agreement, an increase of 2-AG plasmatic levels and an upregulation of CB1R and CB2R gene expression in peripheral blood lymphocytes were observed in patients with osteoarthritis compared with healthy subjects. Changes found in these biomarkers of the ECS correlated with pain, affective, and cognitive symptoms in these patients. The ECS plays a crucial role in osteoarthritis and represents an interesting pharmacological target and biomarker of this disease.

Effect of alcoholic extract of Entada pursaetha DC on monosodium iodoacetate-induced osteoarthritis pain in rats.

BACKGROUND & OBJECTIVES: Osteoarthritis (OA) is a degenerative disease characterized by joint pain and progressive loss of articular cartilage. Entada pursaetha has been traditionally used in the treatment of inflammatory disease, liver ailment, etc. In this study we investigated suppressive effect of ethanolic extract of E. pursaetha (EPE) on monosodium iodoacetate (MIA)-induced osteoarthritis pain and disease progression by histopathological changes in joints in a rat model. METHODS: OA was induced in right knee of rat by intra-articular injection of 3 mg of MIA and characterized by pathological progression of disease and pain of affected joint. Spontaneous movements, mechanical, thermal and cold sensitivity were monitored at days 0 (before drug and MIA injection), 7, 14 and 21 of MIA administration. EPE (30, 100 and 300 mg/kg), vehicle or etoricoxib (10 mg/ kg; reference drug) were administered daily for 21 days by oral route. RESULTS: EPE at various doses significantly reduced mechanical, heat, cold hyperalgesia and increased the horizontal and vertical movements in intra-articular MIA injected rats. EPE prevented the damage to cartilage structure and reduced the cellular abnormalities. Articular cartilage of rats treated with EPE at 300 mg/kg group was almost normal with well-developed smooth surface and chondrocytes were distributed individually or arranged in column. INTERPRETATION & CONCLUSIONS: The present findings showed that the EPE was not only able to mitigate pain and hyperalgesia but also inhibited MIA-induced cartilage degeneration in vivo. EPE may have the potential to become therapeutic modality in the treatment of osteoarthritis. However, further studies need to be done to confirm these findings in other models and clinical trials.

The inhibition of subchondral bone lesions significantly reversed the weight-bearing deficit and the overexpression of CGRP in DRG neurons, GFAP and Iba-1 in the spinal dorsal horn in the monosodium iodoacetate induced model of osteoarthritis pain.

BACKGROUND: Chronic pain is the most prominent and disabling symptom of osteoarthritis (OA). Clinical data suggest that subchondral bone lesions contribute to the occurrence of joint pain. The present study investigated the effect of the inhibition of subchondral bone lesions on joint pain. METHODS: Osteoarthritic pain was induced by an injection of monosodium iodoacetate (MIA) into the rat knee joint. Zoledronic acid (ZOL), a third generation of bisphosphonate, was used to inhibit subchondral bone lesions. Joint histomorphology was evaluated using X-ray micro computed tomography scanning and hematoxylin-eosin staining. The activity of osteoclast in subchondral bone was evaluated using tartrate-resistant acid phosphatase staining. Joint pain was evaluated using weight-bearing asymmetry, the expression of calcitonin gene-related peptide (CGRP) in the dorsal root ganglion (DRG), and spinal glial activation status using glial fibrillary acidic protein (GFAP) and ionized calcium binding adaptor molecule-1 (Iba-1) immunofluorescence. Afferent neurons in the DRGs that innervated the joints were identified using retrograde fluorogold labeling. RESULTS: MIA injections induced significant histomorphological alterations and joint pain. The inhibition of subchondral bone lesions by ZOL significantly reduced the MIA-induced weight-bearing deficit and overexpression of CGRP in DRG neurons, GFAP and Iba-1 in the spinal dorsal horn at 3 and 6 weeks after MIA injection; however, joint swelling and synovial reaction were unaffected. CONCLUSIONS: The inhibition of subchondral bone lesions alleviated joint pain. Subchondral bone lesions should be a key target in the management of osteoarthritic joint pain.

Nordihydroguaiaretic acid attenuates the oxidative stress-induced decrease of CD33 expression in human monocytes.

Nordihydroguaiaretic acid (NDGA) is a natural lignan with recognized antioxidant and beneficial properties that is isolated from Larrea tridentata. In this study, we evaluated the effect of NDGA on the downregulation of oxidant stress-induced CD33 in human monocytes (MNs). Oxidative stress was induced by iodoacetate (IAA) or hydrogen peroxide (H(2)O(2)) and was evaluated using reactive oxygen species (ROS) production, and cell viability. NDGA attenuates toxicity, ROS production and the oxidative stress-induced decrease of CD33 expression secondary to IAA or H(2)O(2) in human MNs. It was also shown that NDGA (20 µ M) attenuates cell death in the THP-1 cell line that is caused by treatment with either IAA or H(2)O(2). These results suggest that NDGA has a protective effect on CD33 expression, which is associated with its antioxidant activity in human MNs.

Monosodium iodoacetate induces apoptosis via the mitochondrial pathway involving ROS production and caspase activation in rat chondrocytes in vitro.

Monosodium iodoacetate (MIA) is an inhibitor of glyceraldehyde-3-phosphate dehydrogenase activity, and causes dose-dependent cartilage degradation resembling the pathological changes of human osteoarthritis (OA). In this study, we assessed the apoptosis induced by MIA and clarified the underlying mechanisms using the primary rat chondrocytes. The apoptosis of primary rat chondrocytes was analyzed by flow cytometry. The levels of mitochondrial membrane potential (ΔΨm) were evaluated using fluorescence spectrophotometer. The production of reactive oxygen species (ROS) was determined by fluorescence spectrophotometer. Apoptosis-related protein cytochrome c and procaspase-3 expressions were examined by Western blotting. We found that MIA treatment induces apoptosis in chondrocytes, as confirmed by increases in the percent of apoptotic cells, up-regulation of cytochrome c and caspase-3 protein levels. Treatment with MIA increases ROS production and decreases the levels of ΔΨm. The antioxidant, N-acetylcysteine (NAC), significantly prevented the production of ROS, the reduction of ΔΨm, the release of cytochrome c and the activation of caspase-3. Further, NAC completely protected the cells from MIA-induced apoptosis. Together these observations suggest that the mechanisms of MIA-induced apoptosis are primarily via ROS production and mitochondria-mediated caspase-3 activation in primary rat chondrocytes.

Progression of cartilage degradation, bone resorption and pain in rat temporomandibular joint osteoarthritis induced by injection of iodoacetate.

BACKGROUND: Osteoarthritis (OA) is an important subtype of temporomandibular disorders. A simple and reproducible animal model that mimics the histopathologic changes, both in the cartilage and subchondral bone, and clinical symptoms of temporomandibular joint osteoarthritis (TMJOA) would help in our understanding of its process and underlying mechanism. OBJECTIVE: To explore whether injection of monosodium iodoacetate (MIA) into the upper compartment of rat TMJ could induce OA-like lesions. METHODS: Female rats were injected with varied doses of MIA into the upper compartment and observed for up to 12 weeks. Histologic, radiographic, behavioral, and molecular changes in the TMJ were evaluated by light and electron microscopy, MicroCT scanning, head withdrawal threshold test, real-time PCR, immunohistochemistry, and TUNEL assay. RESULTS: The intermediate zone of the disc loosened by 1 day post-MIA injection and thinned thereafter. Injection of an MIA dose of 0.5 mg or higher induced typical OA-like lesions in the TMJ within 4 weeks. Condylar destruction presented in a time-dependent manner, including chondrocyte apoptosis in the early stages, subsequent cartilage matrix disorganization and subchondral bone erosion, fibrosis, subchondral bone sclerosis, and osteophyte formation in the late stages. Nociceptive responses increased in the early stages, corresponding to severe synovitis. Furthermore, chondrocyte apoptosis and an imbalance between anabolism and catabolism of cartilage and subchondral bone might account for the condylar destruction. CONCLUSIONS: Multi-level data demonstrated a reliable and convenient rat model of TMJOA could be induced by MIA injection into the upper compartment. The model might facilitate TMJOA related researches.

Characterisation of a peripheral neuropathic component of the rat monoiodoacetate model of osteoarthritis.

Joint degeneration observed in the rat monoiodoacetate (MIA) model of osteoarthritis shares many histological features with the clinical condition. The accompanying pain phenotype has seen the model widely used to investigate the pathophysiology of osteoarthritis pain, and for preclinical screening of analgesic compounds. We have investigated the pathophysiological sequellae of MIA used at low (1 mg) or high (2 mg) dose. Intra-articular 2 mg MIA induced expression of ATF-3, a sensitive marker for peripheral neuron stress/injury, in small and large diameter DRG cell profiles principally at levels L4 and 5 (levels predominated by neurones innervating the hindpaw) rather than L3. At the 7 day timepoint, ATF-3 signal was significantly smaller in 1 mg MIA treated animals than in the 2 mg treated group. 2 mg, but not 1 mg, intra-articular MIA was also associated with a significant reduction in intra-epidermal nerve fibre density in plantar hindpaw skin, and produced spinal cord dorsal and ventral horn microgliosis. The 2 mg treatment evoked mechanical pain-related hypersensitivity of the hindpaw that was significantly greater than the 1 mg treatment. MIA treatment produced weight bearing asymmetry and cold hypersensitivity which was similar at both doses. Additionally, while pregabalin significantly reduced deep dorsal horn evoked neuronal responses in animals treated with 2 mg MIA, this effect was much reduced or absent in the 1 mg or sham treated groups. These data demonstrate that intra-articular 2 mg MIA not only produces joint degeneration, but also evokes significant axonal injury to DRG cells including those innervating targets outside of the knee joint such as hindpaw skin. This significant neuropathic component needs to be taken into account when interpreting studies using this model, particularly at doses greater than 1 mg MIA.

Establishment of a novel objective and quantitative method to assess pain-related behavior in monosodium iodoacetate-induced osteoarthritis in rat knee.

INTRODUCTION: Pain in osteoarthritis (OA) patients can be present at rest but typically worsens with movement of the affected joint. However, useful assessment methods of movement-induced pain in animal models are limited. Here, we describe the reduction of spontaneous activity in a rat model of OA as an objective and quantifiable behavioral pain that can predict the analgesic activity of a variety of agents following single-dose administration. METHODS: OA was induced in male Sprague-Dawley (SD) rats by intra-articular injection of monoiodoacetate (MIA), and the joint degeneration was assessed with histologic and radiographic analyses. Spontaneous activities were measured in nonhabituated rats using standard, photocell-based monitor systems in the dark. To investigate the potential of the OA model to predict analgesic activity, a number of nonsteroidal anti-inflammatory drugs (NSAIDs) and atypical analgesic drugs were used. RESULTS: Biphasic reduction of total distance and number of rears was observed during the course of experiment after administering 1mg and 0.3mg of MIA, respectively. We found that number of rears was the most sensitive to MIA-induce OA and displayed the greatest percentage decrease in activity. Joint degeneration was observed with decreased bone mineral density and loss of articular cartilage 28days post-MIA injection. Appropriate dosage of opioids reversed MIA-induced decrease of number of rears indicating that reduction of this vertical spontaneous activity reflects pain-associated behavior. As high-doses of opioids reduced spontaneous activity, the sedative effect can be distinguished from the analgesic effect. Analgesic treatment indicates the coexistence of an inflammatory pain state (early phase) sensitive to NSAIDs and a non-inflammatory pain state (late phase) resistant to NSAID treatment. DISCUSSION: This study indicates that unlike standard measures of analgesia such as alteration in thermal or mechanical sensitivity, measurement of spontaneous activity is a validated method for measuring the effects of analgesics in rats with OA knee joints. Moreover, the animals require no habituation, and thus behavioral observation subjectivity is eliminated.

Mixture toxicity of S(N)2-reactive soft electrophiles: 2-evaluation of mixtures containing ethyl α-halogenated acetates.

Four ethyl α-halogenated acetates were tested in (1) sham and (2) nonsham combinations and (3) with a nonreactive nonpolar narcotic. Ethyl iodoacetate (EIAC), ethyl bromoacetate (EBAC), ethyl chloroacetate (ECAC), and ethyl fluoroacetate (EFAC), each considered to be an SN2-H-polar soft electrophile, were selected for testing based on their differences in electro(nucleo)philic reactivity and time-dependent toxicity (TDT). Agent reactivity was assessed using the model nucleophile glutathione, with EIAC and EBAC showing rapid reactivity, ECAC being less reactive, and EFAC lacking reactivity at ≤250 mM. The model nonpolar narcotic, 3-methyl-2-butanone (3M2B), was not reactive. Toxicity of the agents alone and in mixture was assessed using the Microtox acute toxicity test at three exposure durations: 15, 30 and 45 min. Two of the agents alone (EIAC and EBAC) had TDT values >100%. In contrast, ECAC (74 to 99%) and EFAC (9 to 12%) had partial TDT, whereas 3M2B completely lacked TDT (<0%). In mixture testing, sham combinations of each agent showed a combined effect consistent with predicted effects for dose-addition at each time point, as judged by EC(50) dose-addition quotient values. Mixture toxicity results for nonsham ethyl acetate combinations were variable, with some mixtures being inconsistent with the predicted effects for dose-addition and/or independence. The ethyl acetate-3M2B combinations were somewhat more toxic than predicted for dose-addition, a finding differing from that observed previously for α-halogenated acetonitriles with 3M2B.

Ongoing pain in the MIA model of osteoarthritis.

Osteoarthritis (OA) is a chronic pain condition characterized by pain during joint use as well as pain at rest (i.e., ongoing pain). Although injection of monosodium iodoacetate (MIA) into the intra-articular space of the rodent knee is a well established model of OA pain that is characterized by changes in weight bearing and hypersensitivity to tactile and thermal stimuli, it is not known if this procedure elicits ongoing pain. Further, the time-course and possible underlying mechanisms of these components of pain remain poorly understood. In these studies, we demonstrated the presence of ongoing pain in addition to changes in weight bearing and evoked hypersensitivity. Twenty-eight days following MIA injection, spinal clonidine blocked changes in weight bearing and thermal hypersensitivity and produced place preference indicating that MIA induces ongoing and evoked pain. These findings demonstrate the presence of ongoing pain in this model that is present at a late-time point after MIA allowing for mechanistic investigation.

Monosodium iodoacetate-induced osteoarthritis produces pain-depressed wheel running in rats: implications for preclinical behavioral assessment of chronic pain.

Pain stimulates some behaviors (e.g., withdrawal responses) and depresses other behaviors (e.g., feeding and locomotion). We are developing methods for testing candidate analgesics using measurements of pain-depressed behaviors. Such assays may model important aspects of clinical pain and complement traditional procedures that measure pain-stimulated behaviors. The present study characterized the effects of a chronic pain manipulation (monosodium iodoacetate (MIA)-induced osteoarthritis) on wheel running in rats. Rats had 24 h voluntary access to running wheels. Duration of running wheel acquisition was manipulated such that rats had either 21 or 7 days of running wheel access prior to MIA administration. Wheel running was monitored for an additional 21 days following MIA administration. MIA produced concentration- and acquisition length-dependent decreases in wheel running. Parallel experiments demonstrated that MIA produced concentration-dependent tactile allodynia and shifts in hind limb weight bearing. MIA was differentially potent across assays with a potency rank: weight-bearing≥von Frey>running wheel. MIA produced greater depression of wheel running in rats with relatively high baseline running rates compared to rats with relatively low baseline running rates. The differential potency of MIA across assays and apparent rate-dependent effects in running wheels may impact our traditional interpretations of preclinical nociceptive and antinociceptive testing.

Oestrogen is important for maintenance of cartilage and subchondral bone in a murine model of knee osteoarthritis.

INTRODUCTION: Oestrogen depletion may influence onset and/or progression of osteoarthritis. We investigated in an ovariectomized mouse model the impact of oestrogen loss and oestrogen supplementation on articular cartilage and subchondral bone in tibia and patella, and assessed bone changes in osteoarthritis development. METHODS: C3H/HeJ mice were divided into four groups: sham-operated, oestrogen depletion by ovariectomy (OVX), OVX with estradiol supplementation (OVX+E) and OVX with bisphosphonate (OVX+BP). Each mouse had one knee injected with low-dose iodoacetate (IA), and the contralateral knee was injected with saline. Cartilage was analysed histologically 12 weeks postsurgery; bone changes were monitored over time using in vivo micro-computed tomography. RESULTS: In tibiae, OVX alone failed to induce cartilage damage, but OVX and IA combination significantly induced cartilage damage. In patellae, OVX alone induced significant cartilage damage, which was enhanced by IA. In both tibiae and patellae, OVX in combination with IA significantly decreased subchondral cortical thickness in an additive manner. OVX+E and OVX+BP inhibited tibial and patellar subchondral cortical thinning, inhibited patellar and tended to diminish tibial cartilage damage. In patellae, IA interacted with BP, leading to increased subchondral cortical and trabecular bone. CONCLUSIONS: This study demonstrates the significance of oestrogen for articular cartilage and subchondral bone and maintenance of healthy joints, supporting an etiological role for altered oestrogen signaling in osteoarthritis either by directly affecting cartilage or increasing susceptibility for an osteoarthritis trigger. The data strongly support the concept of involvement of subchondral bone plate in osteoarthritis.

The effect of nordihydroguaiaretic acid on iodoacetate-induced toxicity in cultured neurons.

Nordihydroguaiaretic acid (NDGA) is present in high concentrations in the desert shrub Creosote bush, Larrea tridentate. This plant has been used in traditional medicine because of its beneficial effects related, at least in part, to its antioxidant properties. Taking into account some evidence about neuroprotective effects elicited by NDGA, we evaluated the effect of this compound on the neurotoxicity induced by iodoacetate (IAA), an inhibitor of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), on cerebellar granule neurons. In addition, as reactive oxygen species play an important role in IAA-induced cytotoxicity, we also studied the enzymatic antioxidant system in IAA-treated cells. We found that IAA caused a dose-dependent decrease in cell viability of cultured neurons with an IC(50) of 18.4 microM and induced increased activity of catalase, glutathione peroxidase, and glutathione-S-transferase. Moreover, NDGA attenuated the toxicity induced by 18.4, 25, and 30 microM of IAA without abolishing the inhibitory effect of IAA on GAPDH activity. Furthermore, NDGA could prevent the inhibitory effect of IAA on aconitase activity, a marker of oxidative stress, suggesting that the protective effect of NDGA on IAA neurotoxicity was associated with the prevention of oxidative stress.

Assessment of movement-evoked pain in osteoarthritis by the knee-bend and CatWalk tests: a clinically relevant study.

UNLABELLED: Although there are several reports on pain behavioral tests in rat models of knee osteoarthritis (OA), most of them focus on the paw. The aim of this study was to investigate pain-related behaviors on the affected knee joint, the primary source of nociception, in animals with mono-iodoacetate-induced OA, using the knee-bend (which provides information on movement pain) and pin-prick tests, and to evaluate nociception elicited by walking using the CatWalk test. The von Frey and Randall-Selitto tests applied to the paw allowed us to compare our study results with previous studies. A further aim was to compare the behavioral nociceptive responses of the most used doses of mono-iodoacetate, 2 and 3 mg. Knee-bend score of OA animals was higher than those of control animals throughout the study (P < .05). At every time point, the ipsilateral hind-paw load of OA rats, as measured by the CatWalk test, was lower than that of control rats (P < .05), and paw withdraw threshold to von Frey filaments was also decreased (P < .01). No changes were observed in pin-prick and Randall-Selitto tests. Results obtained with the 2 doses of mono-iodoacetate were similar. The knee-bend and CatWalk tests are effective for evaluating movement-related nociception, a hallmark of clinical OA, which was present throughout the experimental period. PERSPECTIVE: Behavioral characterization of models of OA pain is important and useful for use in future studies to test pharmacological treatments. Furthermore, it is important to find methods that correlate better with the human symptoms of OA.