Bone Cancer Pain Model Research Articles

Animal models of bone cancer pain: Systematic review and meta-analyses

Pain can significantly decrease the quality of life of patients with advanced cancer. Current treatment strategies often provide inadequate analgesia and unacceptable side effects. Animal models of bone cancer pain are used in the development of novel pharmacological approaches. Here we conducted a systematic review and meta-analysis of publications describing in vivo modelling of bone cancer pain in which behavioural, general health, macroscopic, histological, biochemical, or electrophysiological outcomes were reported and compared to appropriate controls. In all, 150 publications met our inclusion criteria, describing 38 different models of bone cancer pain. Reported methodological quality was low; only 31% of publications reported blinded assessment of outcome, and 11% reported random allocation to group. No publication reported a sample size calculation. Studies that reported measures to reduce bias reported smaller differences in behavioural outcomes between tumour-bearing and control animals, and studies that presented a statement regarding a conflict of interest reported larger differences in behavioural outcomes. Larger differences in behavioural outcomes were reported in female animals, when cancer cells were injected into either the tibia or femur, and when MatLyLu prostate or Lewis Lung cancer cells were used. Mechanical-evoked pain behaviours were most commonly reported; however, the largest difference was observed in spontaneous pain behaviours. In the spinal cord astrocyte activation and increased levels of Substance P receptor internalisation, c-Fos, dynorphin, tumor necrosis factor-α and interleukin-1β have been reported in bone cancer pain models, suggesting several potential therapeutic targets. However, the translational impact of animal models on clinical pain research could be enhanced by improving methodological quality.

Antinociceptive effects of the selective CB2 agonist MT178 in inflammatory and chronic rodent pain models

Cannabinoid CB2 receptor activation by selective agonists has been shown to produce analgesic effects in preclinical models of inflammatory, neuropathic, and bone cancer pain. In this study the effect of a novel CB2 agonist (MT178) was evaluated in different animal models of pain. First of all, in vitro competition binding experiments performed on rat, mouse, or human CB receptors revealed a high affinity, selectivity, and potency of MT178. The analgesic properties of the novel CB2 agonist were evaluated in various in vivo experiments, such as writhing and formalin assays, showing a good efficacy comparable with that produced by the nonselective CB agonist WIN 55,212-2. A dose-dependent antiallodynic effect of the novel CB2 compound in the streptozotocin-induced diabetic neuropathy was found. In a bone cancer pain model and in the acid-induced muscle pain model, MT178 was able to significantly reduce mechanical hyperalgesia in a dose-related manner. Notably, MT178 failed to provoke locomotor disturbance and catalepsy, which were observed following the administration of WIN 55,212-2. CB2 receptor mechanism of action was investigated in dorsal root ganglia where MT178 mediated a reduction of [3H]-d-aspartate release. MT178 was also able to inhibit capsaicin-induced substance P release and NF-κB activation. These results demonstrate that systemic administration of MT178 produced a robust analgesia in different pain models via CB2 receptors, providing an interesting approach to analgesic therapy in inflammatory and chronic pain without CB1-mediated central side effects.

A new rat model of bone cancer pain produced by rat breast cancer cells implantation of the shaft of femur at the third trochanter level

Bone cancer pain remains one of the most challenging cancer pains to fully control. In order to clarify bone cancer pain mechanisms and examine treatments, animal models mimicking the human condition are required. In our model of Walker 256 tumor cells implantation of the shaft of femur at the third trochanter level, the anatomical structure is relatively simple and the drilled hole is vertical and in the cortical bone only 1–2 mm in depth without injury of the distal femur. Pain behaviors and tumor growth were observed for 21 days. And neurochemical changes were further investigated in this model. The results showed that cancer-bearing rats demonstrated a decreased limb use score from day 14, an increased spontaneous flinching and guarding times from day 7 and a decreased withdrawal threshold from day 6. The tumor infiltration of bone was monitored by MRI and further verified by histological examination. C-fos and the capsaicin receptor (TRPV1) positive neurons were more expressed in cancer-bearing rats and the substance P expression has no difference, suggesting that neurons were activated in the model. Our animal model demonstrated time-dependent tumor growth and pain behaviors and will be a novel animal model of bone cancer pain in the future.

Suppression of KCNQ/M (Kv7) potassium channels in dorsal root ganglion neurons contributes to the development of bone cancer pain in a rat model

Bone cancer pain has a strong impact on the quality of life of patients, but is difficult to treat. Better understanding of the pathogenic mechanisms underlying bone cancer pain will likely lead to the development of more effective treatments. In the present study, we investigated whether inhibition of KCNQ/M channels contributed to the hyperexcitability of primary sensory neurons and to the pathogenesis of bone cancer pain. By using a rat model of bone cancer pain based on intratibial injection of MRMT-1 tumour cells, we documented a prominent decrease in expression of KCNQ2 and KCNQ3 proteins and a reduction of M-current density in small-sized dorsal root ganglia (DRG) neurons, which were associated with enhanced excitability of these DRG neurons and the hyperalgesic behaviours in bone cancer rats. Coincidently, we found that inhibition of KCNQ/M channels with XE-991 caused a robust increase in the excitability of small-sized DRG neurons and produced an obvious mechanical allodynia in normal rats. On the contrary, activation of the KCNQ/M channels with retigabine not only inhibited the hyperexcitability of these small DRG neurons, but also alleviated mechanical allodynia and thermal hyperalgesia in bone cancer rats, and all of these effects of retigabine could be blocked by KCNQ/M-channel antagonist XE-991. These results suggest that repression of KCNQ/M channels leads to the hyperexcitability of primary sensory neurons, which in turn causes bone cancer pain. Thus, suppression of KCNQ/M channels in primary DRG neurons plays a crucial role in the development of bone cancer pain.

Differential activation of the μ‐opioid receptor by oxycodone and morphine in pain‐related brain regions in a bone cancer pain model

Bone cancer pain is chronic and often difficult to control with opioids. However, recent studies have shown that several opioids have distinct analgesic profiles in chronic pain. To clarify the mechanisms underlying these distinct analgesic profiles, functional changes in the μ-opioid receptor were examined using a mouse femur bone cancer (FBC) model. In the FBC model, the B(max) of [(3) H]-DAMGO binding was reduced by 15-45% in the periaqueductal grey matter (PAG), region ventral to the PAG (vPAG), mediodorsal thalamus (mTH), ventral thalamus and spinal cord. Oxycodone (10(-8) -10(-5) M) and morphine (10(-8) -10(-5) M) activated [(35) S]-GTPγS binding, but the activation was significantly attenuated in the PAG, vPAG, mTH and spinal cord in the FBC model. Interestingly, the attenuation of oxycodone-induced [(35) S]-GTPγS binding was quite limited (9-26%) in comparison with that of morphine (46-65%) in the PAG, vPAG and mTH, but not in the spinal cord. Furthermore, i.c.v. oxycodone at doses of 0.02-1.0 μg per mouse clearly inhibited pain-related behaviours, such as guarding, limb-use abnormalities and allodynia-like behaviour in the FBC model mice, while i.c.v. morphine (0.05-2.0 μg per mouse) had only partial or little analgesic effect on limb-use abnormalities and allodynia-like behaviour. These results show that μ-opioid receptor functions are attenuated in several pain-related regions in bone cancer in an agonist-dependent manner, and suggest that modification of the μ-opioid receptor is responsible for the distinct analgesic effect of oxycodone and morphine.

A micro-imaging study linking bone cancer pain with tumor growth and bone resorption in a rat model

Bone metastases represent a frequent complication of advanced breast cancer. As tumor growth-induced bone remodeling progresses, episodes of severe pain and fractures of weight-bearing limbs increase. All of these skeletal-related events influence the patient's quality of life and survival. In the present study, we sought to determine whether some of these pain-related behaviors could be directly correlated to tumor progression and bone remodeling. For this purpose, we used a rat model of bone cancer pain based on the implantation of mammary carcinoma cells in the medullary cavity of the femur. The bone content and tumor growth were monitored over time by magnetic resonance imaging (MRI) and micro X-ray computed tomography (μCT). The same animals were evaluated for changes in their reflexive withdrawal responses to mechanical stimuli (allodynia) and weight-bearing deficits. As assessed by MRI, we found a negative correlation between tumor volume and allodynia or postural deficits throughout the experiment. Using μCT, we found that the bone volume/total volume (BV/TV) ratios for trabecular and cortical bone correlated with both mechanical hypersensitivity and weight-bearing impairment. However, whereas trabecular BV/TV stabilized between days 7 and 10 post-tumor detection, the cortical bone loss reached its maximum at that time. Our imaging approach also allowed us to consistently detect the tumor before the onset of pain, paving the way for the preemptive identification of at-risk patients. Altogether, these results improve our understanding of the events leading to tumor-induced bone pain and could eventually help in the design of novel strategies for the management of bone diseases.

144. Analgesic Effect of Crotalphine in a New Model of Rat Bone Cancer Pain

144. Analgesic Effect of Crotalphine in a New Model of Rat Bone Cancer Pain

Effect of intrathecal injection of KN93, a CaMKII inhibitor, on the expression of spinal NR2B in a mouse model of bone cancer pain

Af filiated Drum Tower Hospital, Medical School of Nanjing Universit y, Department of Anaesthesiology, Nanjing, China

Chronic administration of the selective P2X3, P2X2/3 receptor antagonist, A-317491, transiently attenuates cancer-induced bone pain in mice

The purinergic P2X3 and P2X2/3 receptors are in the peripheral nervous system almost exclusively confined to afferent sensory neurons, where they are found both at peripheral and central synapses. The P2X3 receptor is implicated in both neuropathic and inflammatory pain. However, the role of the P2X3 receptor in chronic cancer-induced bone pain is less known. Here we investigated the effect of systemic acute and chronic administration of the selective P2X3, P2X2/3 receptor antagonist (5-[[[(3-Phenoxyphenyl)methyl][(1S)-1,2,3,4-tetrahydro-1-naphthalenyl]amino]carbonyl]-1,2,4-benzenetricarboxylic acid sodium salt hydrate) (A-317491) in a murine model of cancer-induced bone pain. Chronic administration of A-317491 (30μmol/kgs.c., b.i.d.) resulted in a transient attenuation of pain related behaviours in the early stage of the bone cancer model, but had no effect in the late and more progressed stage of bone cancer. Also, acute administration of A-317491 (100μmol/kgs.c.) had no effect in the progressed stage of the bone cancer pain model. Thus, systemically administered A-317491 did not demonstrate a robust effect in the present mouse model of cancer-induced bone pain.

Pharmacology of Modality-Specific Transient Receptor Potential Vanilloid-1 Antagonists That Do Not Alter Body Temperature

The transient receptor potential vanilloid-1 (TRPV1) channel is involved in the development and maintenance of pain and participates in the regulation of temperature. The channel is activated by diverse agents, including capsaicin, noxious heat (≥ 43°C), acidic pH (< 6), and endogenous lipids including N-arachidonoyl dopamine (NADA). Antagonists that block all modes of TRPV1 activation elicit hyperthermia. To identify efficacious TRPV1 antagonists that do not affect temperature antagonists representing multiple TRPV1 pharmacophores were evaluated at recombinant rat and human TRPV1 channels with Ca(2+) flux assays, and two classes of antagonists were identified based on their differential ability to inhibit acid activation. Although both classes of antagonists completely blocked capsaicin- and NADA-induced activation of TRPV1, select compounds only partially inhibited activation of the channel by protons. Electrophysiology and calcitonin gene-related peptide release studies confirmed the differential pharmacology of these antagonists at native TRPV1 channels in the rat. Comparison of the in vitro pharmacological properties of these TRPV1 antagonists with their in vivo effects on core body temperature confirms and expands earlier observations that acid-sparing TRPV1 antagonists do not significantly increase core body temperature. Although both classes of compounds elicit equivalent analgesia in a rat model of knee joint pain, the acid-sparing antagonist tested is not effective in a mouse model of bone cancer pain.

Functional up‐regulation of P2X3 receptors in dorsal root ganglion in a rat model of bone cancer pain

Cancer-induced bone pain remains a clinical challenge due to the poor understanding of the mechanisms. Recent study revealed extracellular adenosine triphosphate (ATP) and P2X receptors may be implicated in nociceptive signalling under cancer pain state. Therefore, here we investigated the potential role of P2X(3) receptor in a rat model of bone cancer pain. Walker 256 tumour cells were inoculated into the left tibia of Wistar rats. The model was verified by X-ray imaging, pathology and behaviour examinations. The expression of P2X(3) receptors in dorsal root ganglia (DRG) was examined. Functional significance of altered P2X(3) receptors was investigated by measuring influx upon α,β-meATP stimulation in acutely dissociated DRG neurons. Moreover, A-317491, an antagonist of P2X(3) receptors, was administrated intrathecally or locally to evaluate its analgesia effect in the cancer pain animals. The P2X(3) receptor was up-regulated for about 50% in DRG neurons in rats with bone cancer at both protein and mRNA levels and correlated with the pain behaviour in bone cancer rats. A 51.9% increase of α,β-me ATP (10 μM, for 4 s) evoked transient response currents and a higher percentage of neurons responsive to the application of α,β-me ATP was detected in bone cancer rats. Intrathecal or local injection of A-317491 significantly attenuated pain behaviour induced by bone cancer. These results suggest that the P2X(3) receptor is functionally up-regulated in DRG in cancer rats. P2X(3) receptor is a promising target for therapeutic intervention in cancer patients for pain management.

Activation of spinal TDAG8 and its downstream PKA signaling pathway contribute to bone cancer pain in rats

Bone cancer pain is difficult to treat and has a strong impact on the quality of life of patients. Few therapies have emerged because the molecular mechanisms underlying bone cancer pain are poorly understood. Recently, T-cell death-associated gene 8 (TDAG8) has been shown to participate in complete Freund's adjuvant-induced chronic inflammatory pain. In this study, we aimed to examine whether TDAG8 and its downstream protein kinase A (PKA) pathway are involved in bone cancer pain. A bone cancer pain model was made by inoculation of Walker 256 cells into the intramedullary space of rat tibia. Spinal TDAG8 expression was increased after inoculation with tumor cells. Intrathecal TDAG8 siRNA attenuated bone cancer pain behaviors during the initiation and maintenance phases; there were also concomitant decreases in TDAG8 mRNA and protein levels in spinal cord. Moreover, we found spinal PKA and phosphorylated cAMP response element-binding (pCREB) protein levels were up-regulated in the rat model of bone cancer pain. Knockdown of TDAG8 resulted in reduced bone cancer pain-induced spinal PKA and pCREB protein expression in two procedures. Furthermore, intrathecal H-89 (a PKA inhibitor) significantly attenuated bone cancer pain behaviors in rats. Our results suggest a causal relationship between TDAG8 expression and the initiation and maintenance of bone cancer pain. Activation of spinal TDAG8 contributes to bone cancer pain through the PKA signaling pathway in rats. These findings may lead to novel strategies for the treatment of bone cancer pain.

Intrathecal administration of roscovitine attenuates cancer pain and inhibits the expression of NMDA receptor 2B subunit mRNA

Cancer pain is one of the most severe chronic pains. The mechanisms underlying cancer pain are still unclear. Because of the pain-relieving effects of Cdk5 (Cyclin-dependent kinase 5) antagonist roscovitine in inflammation pain models, we tested whether roscovitine would induce antihyperalgesia in cancer pain. Our previous study showed that the NR2B (N-methyl-d-aspartate receptor 2B) in the spinal cord participates in bone cancer pain in mice. In this study, we used a mouse model of bone cancer pain to investigate whether roscovitine could attenuate bone cancer pain by regulating the expression level of NR2B mRNA in spinal cord. C3H/HeJ mice were inoculated into the intramedullary space of the right femur with Osteosarcoma cells to induce ongoing bone cancer pain behaviors. At day 14 after operation, inoculation of Osteosarcoma cells significantly enhanced mechanical allodynia and thermal hyperalgesia, which was attenuated by intrathecal administration of different doses of roscovitine. Correlated with the pain behaviors changes, RT-PCR experiments in our study revealed that there was a marked increase in the expression of NR2B mRNA in spinal cord after operation, which was attenuated by intrathecal administration of roscovitine. These results suggest that roscovitine may be a useful adjunct therapy for bone cancer pain, and NR2B in spinal cord may participate in this effect.

17β-estradiol modifies TRPV1 mRNA expression in DRG neurons

While it has been demonstrated that women experience greater cancer pain and pain severity than men, the potential role of estrogen in regulating nociception particularly as it relates to tumor pain remains unclear. Current data indicate that estrogens act directly on the nervous system to affect the severity of pain, but the mechanisms underlying this effect are unclear. A major nociceptive mechanism associated with the development of cancer pain is activation of the transient receptor potential vanilloid-1 (TRPV1) channel. TRPV1 is a Ca2+-permeable ionotropic receptor activated by multiple sensory stimuli including heat, acid, and protons. Antagonism of the TRPV1 channel attenuates nociception in a mouse bone cancer pain model. Both estrogen (ER) and TRPV1 receptors are known to be expressed on dorsal root ganglion (DRG) neurons, whose axons transmit pain from the periphery to the spinal cord. This raises the question of whether estrogen can alter TRPV1 receptor expression or function particularly in pain states like cancer pain. The present study was designed to evaluate the effects of estrogen on pain sensitivity and TRPV1 expression in the DRG of male and female C3H mice in a mouse model of bone cancer pain. One goal was to determine whether estrogen modulates nociceptive receptors in the DRG in a manner consistent with its effects on pain sensitivity. This study demonstrated that exposure to 17β-estradiol in gonadectomized males (ORCH+E), but the lack of this same hormone in gonadectomized females (OVX), significantly reduced the mRNA levels of TRPV1 in lumbosacral DRG neurons and this correlated with a reduction in tumor-induced nociception. Our results suggest that modulation of 17β-estradiol causes a down regulation in TRPV1 expression in DRG neurons, which may be associated with a reduction in fibrosarcoma-induced mechanical allodynia in both male female mice.

Formaldehyde up-regulates TRPV1 through MAPK and PI3K signaling pathways in a rat model of bone cancer pain

Our previous study showed that tumor tissue-derived formaldehyde at low concentrations plays an important role in bone cancer pain through activating transient receptor potential vanilloid subfamily member 1 (TRPV1). The present study further explored whether this tumor tissue-derived endogenous formaldehyde regulates TRPV1 expression in a rat model of bone cancer pain, and if so, what the possible signal pathways are during the development of this type of pain. A rat model of bone cancer pain was established by injecting living MRMT-1 tumor cells into the tibia. The formaldehyde levels were determined by high performance liquid chromatography, and the expression of TRPV1 was examined with Western blot and RT-PCR. In primary cultured dorsal root ganglion (DRG) neurons, the expression of TRPV1 was assessed after treatment with 100 µmol/L formaldehyde with or without pre-addition of PD98059 [an inhibitor for extracellular signal-regulated kinase], SB203580 (a p38 inhibitor), SP600125 [an inhibitor for c-Jun N-terminal kinase], BIM [a protein kinase C (PKC) inhibitor] or LY294002 [a phosphatidylinositol 3-kinase (PI3K) inhibitor]. In the rat model of bone cancer pain, formaldehyde concentration increased in blood plasma, bone marrow and the spinal cord. TRPV1 protein expression was also increased in the DRG. In primary cultured DRG neurons, 100 μmol/L formaldehyde significantly increased the TRPV1 expression level. Pre-incubation with PD98059, SB203580, SP600125 or LY294002, but not BIM, inhibited the formaldehyde-induced increase of TRPV1 expression. Formaldehyde at a very low concentration up-regulates TRPV1 expression through mitogen-activated protein kinase and PI3K, but not PKC, signaling pathways. These results further support our previous finding that TRPV1 in peripheral afferents plays a role in bone cancer pain.

Increased expression of tetrodotoxin-resistant sodium channels Nav1.8 and Nav1.9 within dorsal root ganglia in a rat model of bone cancer pain

In attempt to understand the underlying mechanisms of cancer-induced bone pain, we investigated the presence of two tetrodotoxin-resistant sodium channels, Nav1.8 (SNS/PN3) and Nav1.9 (SNS2/NaN), in dorsal root ganglia (DRG) neurons in an animal model of bone cancer pain. Thirty-six female Sprague-Dawley rats were randomized into three groups: Sham operation group (Sham), cancer-bearing animals killed after 7 days (C7) and cancer-bearing animals killed after 14 days group (C14). After establishment of bone cancer pain model, behavioral tests were carried out to determine the paw withdrawal threshold (PWT) of mechanical and thermal hyperalgesia, respectively. Real-time RT-PCR, Western bolt and Immunofluorescence were used to determine the mRNA and protein expression of Nav1.8 and Nav1.9 in ipsilateral lumbar 4-5 DRG. Compared to Sham group, PWT of mechanical and thermal hyperalgesia in C14 group displayed a significant decrease (P<0.01) from post-operation day (POD) 5 and POD7 to the end point of the observation, respectively. Compared to Sham group, the relative mRNA expression of Nav1.8 and Nav1.9 exhibited a significant up-regulation in C14 group (8.9 times and 9 times, respectively, P<0.01) but not C7 group (1.5 times and 2.4 times, respectively). Western blot and Immunofluorescence revealed an apparent increase of Nav1.8 (P<0.05) and Nav1.9 (P<0.05) protein in C14 group compared with Sham group. The up-regulation of mRNA and protein levels of Nav1.8 and Nav1.9 suggested their potential involvement in the development and maintenance of bone cancer pain.

Enhanced Excitability of Small Dorsal Root Ganglion Neurons in Rats with Bone Cancer Pain

BackgroundPrimary and metastatic cancers that affect bone are frequently associated with severe and intractable pain. The mechanisms underlying the development of bone cancer pain are largely unknown. The aim of this study was to determine whether enhanced excitability of primary sensory neurons contributed to peripheral sensitization and tumor-induced hyperalgesia during cancer condition. In this study, using techniques of whole-cell patch-clamp recording associated with immunofluorescent staining, single-cell reverse-transcriptase PCR and behavioral test, we investigated whether the intrinsic membrane properties and the excitability of small-sized dorsal root ganglion (DRG) neurons altered in a rat model of bone cancer pain, and whether suppression of DRG neurons activity inhibited the bone cancer-induced pain.ResultsOur present study showed that implantation of MRMT-1 tumor cells into the tibial canal in rats produced significant mechanical and thermal hyperalgesia in the ipsilateral hind paw. Moreover, implantation of tumor cells provoked spontaneous discharges and tonic excitatory discharges evoked by a depolarizing current pulse in small-sized DRG neurons. In line with these findings, alterations in intrinsic membrane properties that reflect the enhanced neuronal excitability were observed in small DRG neurons in bone cancer rats, of which including: 1) depolarized resting membrane potential (RMP); 2) decreased input resistance (Rin); 3) a marked reduction in current threshold (CT) and voltage threshold (TP) of action potential (AP); 4) a dramatic decrease in amplitude, overshot, and duration of evoked action potentials as well as in amplitude and duration of afterhyperpolarization (AHP); and 5) a significant increase in the firing frequency of evoked action potentials. Here, the decreased AP threshold and increased firing frequency of evoked action potentials implicate the occurrence of hyperexcitability in small-sized DRG neurons in bone cancer rats. In addiotion, immunofluorescent staining and single-cell reverse-transcriptase PCR revealed that in isolated small DRG neurons, most neurons were IB4-positive, or expressed TRPV1 or CGRP, indicating that most recorded small DRG neurons were nociceptive neurons. Finally, using in vivo behavioral test, we found that blockade of DRG neurons activity by TTX inhibited the tumor-evoked mechanical allodynia and thermal hyperalgesia in bone cancer rats, implicating that the enhanced excitability of primary sensory neurons underlied the development of bone cancer pain.ConclusionsOur present results suggest that implantation of tumor cells into the tibial canal in rats induces an enhanced excitability of small-sized DRG neurons that is probably as results of alterations in intrinsic electrogenic properties of these neurons. Therefore, alterations in intrinsic membrane properties associated with the hyperexcitability of primary sensory neurons likely contribute to the peripheral sensitization and tumor-induced hyperalgesia under cancer condition.

Effect of CCL2 neutralizing antibody on pain behaviour and spinal microglia activation in rat bone cancer model

Objective To investigate the role of CCL2 in pain facilitation and spinal mechanisms in the rat model of bone cancer pain.Methods The bone cancer pain model was developed by inoculating.Walker 256 mammary gland carcinoma cells into the rat tibia medullary cavity.SD female rats were divided into 5 groups randomly ( n =8):sham group( group Ⅰ),sham + CCL2 antibody group( group Ⅱ),BCP group( group Ⅲ),BCP +control lgG group ( group Ⅳ),BCP + CCL2 antibody group ( group Ⅴ ).VonFrey threshold was measured one day before operation and 1 st,3 rd,5th,7th,10th,14th,21 st after operation.CCL2 antibody or control lgG was injected intrathecally from 10th to 12th day.The expression of the spinal Iba-1 ( microglial marker) in rat lumbar4-5 was detected by immunohistochemistry assay.Results From the 10th to 21st day after operation,the PMWT of group Ⅲ rats were ( 1.78 ±0.38)g,( 1.70 ±0.17)g,( 1.35 ±0.07 )g;group Ⅳ rats were (2.99 ±0.67)g,(2.52 ±0.75)g,(1.13±0.07)g ; and group Ⅴ rats were (5.88±0.66)g,(7.81 ±0.75)g,(6.19±0.53)g.Compared with group Ⅲ,the PMWT of group Ⅴ was remarkly higher (P＜0.01) ; group Ⅳ had no obvious statistical significance (P＞0.05).At the 14th day after operation,the MOD of group Ⅲ,Ⅳ and Ⅴ rats were (151.3 ±10.8 ),( 149.2 ± 10.6),(74.5 ± 5.0),Compared with group Ⅲ,the MOD of group Ⅴ was significantly increased (P＜0.01 ),group Ⅳ had no obvious statistical significance (P ＞ 0.05 ).Conclusion Intrathecal injection of CCL2 antibody can remarkly attenuate established pain facilitation of tibial bone cancer pain rats,and significantly suppress the expression of Iba-1.It suggests that CCL2 is involved in the bone cancer pain via activation of spinal microglia. Key words: Bone cancer pain; Hyperalgesic; Microglia; CCL2; Spinal mechanism

Effects of intrathecal methotrexate on mechanical allodynia in rats with tibial bone cancer pain

Objective To investigate effects of intrathecal methotrexate on mechanical allodynia in rats with tibial bone cancer pain.Methods Forty-eight female SD rats weighing 150-180 g were randomly divided into 6 groups ( n =8 each):group Ⅰ sham operation + artificial cerebrospinal fluid(SA group),group Ⅱ sham operation + methotrexate 200 μg(SM group),group Ⅲ bone cancer pain + artificial cerebrospinal fluid(CA group),group Ⅳ-Ⅵ bone cancer pain + different doses of methotrexate (CM1-3 groups).The model of tibial bone cancer pain was induced by injecting Walker-256 cell into the tibial marrow cavity.CA and CM1-3 groups were intrathecal injected artificial cerebrospinal fluid,methotrexate 50,100 and 200 μg.SA and SM200 groups were intrathecal injected artificial cerebrospinal fluid and methotrexate 200 μg.The mechanical withdrawl threshold (MWT) was measured at day 1 before Walker-256 injection (baseline),7 day after injection (T0 ) and 2,4,8,24 hour and 1,3,5,7 days after intrathecal injection ( T1-8 ).Results Compered with the baseline,MWT was decrease in CA and CM1-s groups.Competed with To,MWT was decreased at T5-8 in CA group,MWT was increased at T3-5 in CM1 group,at T2-6 in CM2 group and at T2-7 in CM3 groups.MWT was decrease in CA and CM1-3 groups as compered with SA group; MWT was increased at T4-7 in CM1 group and at T3-7 in CM2 and CM3 groups.Conclusion Intrathecal injection of methotrexate can reduce tibial bone cancer pain in rats. Key words: Bone neoplasms; Pain; Methotrexate; Injections,spinal

Antiallodynic effects of propentofylline Elicited by interrupting spinal glial function in a rat model of bone cancer pain

The activation of microglia and astrocytes in the spinal cord is involved in the progress of cancer pain. Propentofylline (PPF), a glial modulating agent, alleviates pain hypersensitivity in neuropathic pain models. The present study investigated the potential roles of PPF in a preclinical rat model of bone caner pain established by inoculating Walker 256 cells into the left tibia. At day 9 postinoculation, single administration of PPF (10 μg/10 μl, i.t.) significantly but transiently suppressed mechanical allodynia induced by bone cancer. Repeated application of PPF (10 μg/10 μl, i.t., once daily from days 9 to 12) persistently relieved mechanical allodynia on the side ipsilateral to surgery. Immunohistochemistry and ELISA showed that microglia and astrocytes in the spinal cord were activated, and the production of glia-derived proinflammatory cytokines interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α) markedly increased at day 12 postinoculation in the cancer group. Intrathecal injection of PPF (10 μg/10 μl) significantly inhibited the activation of spinal glial cells and the expression of proinflammatory cytokines. These results suggest that the glial modulating agent PPF has antiallodynic effects on bone cancer pain and has potential utility for clinical treatment of cancer pain.