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Differential behavioral response to thermal stimuli following unilateral or bilateral temporomandibular joint inflammation
Abstracts
E14 Inflammation (260) Treatment with DNA ‘‘decoy’’ that targets COX-2 gene promoter improves mechanical and thermal allodynia after spinal cord injury in rats C Hulsebosch, G Xu, K Johnson, G Unabia, O Nesic-Taylor, and R Perez-Polo; University of Texas Medical Branch at Galveston, Galveston, TX Spinal cord injury (SCI) results in a number of deficits and triggers primary and secondary injury signaling cascades characterized by an early and prolonged inflammatory response. Early after SCI, IL-1B increases, an inflammatory agent, that triggers increased activation of the transcription factor Nuclear FactorkB (NF-kB). NF-kB mediates secondary injuries via regulation of synthesis of proteins that are detrimental to the recovery process and can maintain inflammation in the injured spinal cord. There are different NF-kB subunits and subunit-specific inhibition can be accomplished with synthetic double stranded ‘‘decoy’’ deoxyoligonucleotides containing selective NF-kB protein dimer binding consensus sequences. In this project, DNA ’’decoys’’ target the COX-2 gene promoter NF-kB binding site, attenuate the SCI-induced increases in the levels of COX-2 and iNOS protein levels and significantly decrease cell death and increases in inflammatory signaling. Spinal cord contusion injury and outcomes were measured as described in Experimental Design below. The results demonstrate a significant improvement in locomotor scores, mechanical allodynia (for both cutaneous and pressure), thermal hyperalgesia and improved clinical measures (weight and bladder) in the group treated with COX-2 decoys compared to the vehicle group. Decoy treatment also resulted in significant reductions in COX-2 and iNOS expression following SCI and neuronal rescue. These experiments demonstrate the efficacy of novel interventions in the inflammatory cascade triggered by SCI as a strategy for treatment of SCI-induced physiological functional impairments. The approach is innovative in that it assesses the use of a new technology (DNA promoter decoys) to selectively block injury response mechanisms that can result in neuropathy. Supported by Mission Connect/ TIRR Foundation, The M.D. Anderson Foundation, The Liddell and The Dunn Foundations and NS11255.
The Journal of Pain
P41
(262) Differential behavioral response to thermal stimuli following unilateral or bilateral temporomandibular joint inflammation P Durham, F Garrrett, J Hawkins, and J Hayden; Missouri State University, Springfield, MO Temporomandibular joint disorders (TMD) refer to a cluster of disorders in the masticatory system, including the temporomandibular joint (TMJ) and surrounding tissues, that is estimated to affect nearly 10 million adults. The TMJ is the only bilateral hinge joint in the body, and consequently injury to one side can result in pathology in both joints. However, most TMD research focuses primarily on unilateral joint injury. The goal of our study was to determine behavioral responses to thermal stimuli in both unilateral and bilateral models of TMD. Complete Freund’s adjuvant (CFA) was injected either unilaterally or bilaterally in the TMJ capsule to induce joint inflammation and pain. Thermal behavioral responses were determined using the Hargreaves apparatus and a novel holding device that facilitates reliable testing in the facial region. Animals were acclimated to the device for 3 consecutive days prior to experimental testing. Following basal readings, animals were either injected unilaterally or bilaterally with CFA, or left alone to serve as na€ıve controls. Measurements were recorded 1, 2, 7, and 14 days post CFA injection and the average withdrawal latencies (seconds) for each time point was compared to the initial baseline readings. Interestingly, the unilateral and bilateral CFA injected animals exhibited opposite behavioral responses to thermal stimuli. The unilateral injected animals displayed a decrease in withdrawal latency in the first week post injections. In contrast, animals injected bilaterally showed an increase in response time to thermal stimuli. Both groups returned to basal thermal threshold levels two weeks following CFA injection. There were no changes in withdrawal latency in the control group throughout the two week testing period. Data from our study provide evidence that while unilateral TMJ inflammation causes a prolonged hyperalgesic response to thermal stimuli, bilateral inflammation elicits an anti-nociceptive response. Supported by NIH grant DE017805.
E15 Joint and Muscle Pain (261) A possible role for ASIC3 in peripheral fatigue-enhanced muscle pain
(263) Development and validation of a preclinical model of statin-induced myalgia
N Gregory, K Sluka, and L Frey Law; University of Iowa, Iowa City, IA
R Radhakrishnan, A Light, and R Hughen; University of Southern Nevada, South Jordan, UT
Whole body exercise in mice enhances the nociceptive response to low-doses of muscle insult, either repeated injection of pH 5.0 saline or 0.03% carrageenan. Similarly, peripheral electrical stimulation of the gastrocnemius produces isolated muscle fatigue, which also enhances pain behaviors in response to two pH 5 saline injections, but not to two pH 7.2 saline injections. However, no significant tissue damage or inflammation results from the electrically-stimulated fatigue or two-acid injection models, suggesting these mechanisms do not underlie the enhanced pain response. Repeated muscle contractions produce a myriad of pain-related metabolites, including protons and lactate. ASIC3 is a peripherally-expressed nonselective cation channel that detects proton concentration and is potentiated by lactate. Therefore we tested the hypothesis that ASIC3 contributes to the fatigue-enhanced pain behaviors after two acidic saline injections. Male and female wild type and ASIC3 knockout mice were given pH 5 saline injections on days 1 and 5. Immediately before the second injection, the mice underwent 6 minutes of fatiguing electrical stimulation. One day later, the animals were assessed for primary muscle hyperalgesia by application of force-sensitive tweezers and secondary cutaneous hyperalgesia by repeated applications of calibrated von Frey filaments. Preliminary data suggest ASIC3 may contribute to the enhanced pain response to fatigue in the setting of low dose muscle insult.
Muscle pain (myalgia) is one of the most frequent side effects observed in patients undergoing statin therapy, and is one of the major reasons for non-compliance among these patients. Due to the absence of a suitable pre-clinical model, no studies have hitherto investigated the neurobiological mechanism of muscle pain generation due to statins. In the current study we are planning to develop an animal model of statin-induced muscle pain. Male Sprague-Dawley rats will be used in the study. Baseline threshold to mechanical squeezing will be measured using a modified Randall-Selitto apparatus in both gastrocnemius muscles in 30 SD rats before starting the drug treatment. Since the degree of lipophilicity of statins has been implicated in the level of statin-induced myopathy, two statin drugs with different relative lipophilicites will be used in this study. Simvastatin (relatively lipophilic, 100 mg/kg), pravastatin (relatively hydrophilic; 100 mg/kg) or vehicle will be administered orally in 3 separate groups (n=10 each) of rats once daily for a period of 1 month. After 1 month of treatment, the mechanical thresholds in both gastrocnemius muscles and endurance on treadmill will be measured in all groups. It is expected that rats treated with statins will show a reduction in mechanical threshold (mechanical hyperalgesia) to squeezing compared to controls, which will be indicative of myalgia. If myalgia is observed in these animals as expected, morphine (3 mg/kg., i.p.) will be used to validate the model. This model, if works as expected, will serve as a preclinical tool to explore the pain generation mechanisms in statin-induced myalgia. This model might also help to identify existing analgesic drugs or to discover newer drugs to relieve statin-induced myalgia and thereby improve compliance in patients on chronic statin therapy.
E14 Inflammation (260) Treatment with DNA ‘‘decoy’’ that targets COX-2 gene promoter improves mechanical and thermal allodynia after spinal cord injury in rats C Hulsebosch, G Xu, K Johnson, G Unabia, O Nesic-Taylor, and R Perez-Polo; University of Texas Medical Branch at Galveston, Galveston, TX Spinal cord injury (SCI) results in a number of deficits and triggers primary and secondary injury signaling cascades characterized by an early and prolonged inflammatory response. Early after SCI, IL-1B increases, an inflammatory agent, that triggers increased activation of the transcription factor Nuclear FactorkB (NF-kB). NF-kB mediates secondary injuries via regulation of synthesis of proteins that are detrimental to the recovery process and can maintain inflammation in the injured spinal cord. There are different NF-kB subunits and subunit-specific inhibition can be accomplished with synthetic double stranded ‘‘decoy’’ deoxyoligonucleotides containing selective NF-kB protein dimer binding consensus sequences. In this project, DNA ’’decoys’’ target the COX-2 gene promoter NF-kB binding site, attenuate the SCI-induced increases in the levels of COX-2 and iNOS protein levels and significantly decrease cell death and increases in inflammatory signaling. Spinal cord contusion injury and outcomes were measured as described in Experimental Design below. The results demonstrate a significant improvement in locomotor scores, mechanical allodynia (for both cutaneous and pressure), thermal hyperalgesia and improved clinical measures (weight and bladder) in the group treated with COX-2 decoys compared to the vehicle group. Decoy treatment also resulted in significant reductions in COX-2 and iNOS expression following SCI and neuronal rescue. These experiments demonstrate the efficacy of novel interventions in the inflammatory cascade triggered by SCI as a strategy for treatment of SCI-induced physiological functional impairments. The approach is innovative in that it assesses the use of a new technology (DNA promoter decoys) to selectively block injury response mechanisms that can result in neuropathy. Supported by Mission Connect/ TIRR Foundation, The M.D. Anderson Foundation, The Liddell and The Dunn Foundations and NS11255.
The Journal of Pain
P41
(262) Differential behavioral response to thermal stimuli following unilateral or bilateral temporomandibular joint inflammation P Durham, F Garrrett, J Hawkins, and J Hayden; Missouri State University, Springfield, MO Temporomandibular joint disorders (TMD) refer to a cluster of disorders in the masticatory system, including the temporomandibular joint (TMJ) and surrounding tissues, that is estimated to affect nearly 10 million adults. The TMJ is the only bilateral hinge joint in the body, and consequently injury to one side can result in pathology in both joints. However, most TMD research focuses primarily on unilateral joint injury. The goal of our study was to determine behavioral responses to thermal stimuli in both unilateral and bilateral models of TMD. Complete Freund’s adjuvant (CFA) was injected either unilaterally or bilaterally in the TMJ capsule to induce joint inflammation and pain. Thermal behavioral responses were determined using the Hargreaves apparatus and a novel holding device that facilitates reliable testing in the facial region. Animals were acclimated to the device for 3 consecutive days prior to experimental testing. Following basal readings, animals were either injected unilaterally or bilaterally with CFA, or left alone to serve as na€ıve controls. Measurements were recorded 1, 2, 7, and 14 days post CFA injection and the average withdrawal latencies (seconds) for each time point was compared to the initial baseline readings. Interestingly, the unilateral and bilateral CFA injected animals exhibited opposite behavioral responses to thermal stimuli. The unilateral injected animals displayed a decrease in withdrawal latency in the first week post injections. In contrast, animals injected bilaterally showed an increase in response time to thermal stimuli. Both groups returned to basal thermal threshold levels two weeks following CFA injection. There were no changes in withdrawal latency in the control group throughout the two week testing period. Data from our study provide evidence that while unilateral TMJ inflammation causes a prolonged hyperalgesic response to thermal stimuli, bilateral inflammation elicits an anti-nociceptive response. Supported by NIH grant DE017805.
E15 Joint and Muscle Pain (261) A possible role for ASIC3 in peripheral fatigue-enhanced muscle pain
(263) Development and validation of a preclinical model of statin-induced myalgia
N Gregory, K Sluka, and L Frey Law; University of Iowa, Iowa City, IA
R Radhakrishnan, A Light, and R Hughen; University of Southern Nevada, South Jordan, UT
Whole body exercise in mice enhances the nociceptive response to low-doses of muscle insult, either repeated injection of pH 5.0 saline or 0.03% carrageenan. Similarly, peripheral electrical stimulation of the gastrocnemius produces isolated muscle fatigue, which also enhances pain behaviors in response to two pH 5 saline injections, but not to two pH 7.2 saline injections. However, no significant tissue damage or inflammation results from the electrically-stimulated fatigue or two-acid injection models, suggesting these mechanisms do not underlie the enhanced pain response. Repeated muscle contractions produce a myriad of pain-related metabolites, including protons and lactate. ASIC3 is a peripherally-expressed nonselective cation channel that detects proton concentration and is potentiated by lactate. Therefore we tested the hypothesis that ASIC3 contributes to the fatigue-enhanced pain behaviors after two acidic saline injections. Male and female wild type and ASIC3 knockout mice were given pH 5 saline injections on days 1 and 5. Immediately before the second injection, the mice underwent 6 minutes of fatiguing electrical stimulation. One day later, the animals were assessed for primary muscle hyperalgesia by application of force-sensitive tweezers and secondary cutaneous hyperalgesia by repeated applications of calibrated von Frey filaments. Preliminary data suggest ASIC3 may contribute to the enhanced pain response to fatigue in the setting of low dose muscle insult.
Muscle pain (myalgia) is one of the most frequent side effects observed in patients undergoing statin therapy, and is one of the major reasons for non-compliance among these patients. Due to the absence of a suitable pre-clinical model, no studies have hitherto investigated the neurobiological mechanism of muscle pain generation due to statins. In the current study we are planning to develop an animal model of statin-induced muscle pain. Male Sprague-Dawley rats will be used in the study. Baseline threshold to mechanical squeezing will be measured using a modified Randall-Selitto apparatus in both gastrocnemius muscles in 30 SD rats before starting the drug treatment. Since the degree of lipophilicity of statins has been implicated in the level of statin-induced myopathy, two statin drugs with different relative lipophilicites will be used in this study. Simvastatin (relatively lipophilic, 100 mg/kg), pravastatin (relatively hydrophilic; 100 mg/kg) or vehicle will be administered orally in 3 separate groups (n=10 each) of rats once daily for a period of 1 month. After 1 month of treatment, the mechanical thresholds in both gastrocnemius muscles and endurance on treadmill will be measured in all groups. It is expected that rats treated with statins will show a reduction in mechanical threshold (mechanical hyperalgesia) to squeezing compared to controls, which will be indicative of myalgia. If myalgia is observed in these animals as expected, morphine (3 mg/kg., i.p.) will be used to validate the model. This model, if works as expected, will serve as a preclinical tool to explore the pain generation mechanisms in statin-induced myalgia. This model might also help to identify existing analgesic drugs or to discover newer drugs to relieve statin-induced myalgia and thereby improve compliance in patients on chronic statin therapy.