Injection Of SB203580 Research Articles

Systemic paracetamol-induced analgesic and antihyperalgesic effects through activation of descending serotonergic pathways involving spinal 5-HT7 receptors

Although some studies have shown the essential role of descending serotonergic pathways and spinal 5-HT1A, 5-HT2A, or 5-HT3 receptors in the antinociceptive effects of paracetamol, other studies have presented conflicting results, and the particular subtype of spinal 5-HT receptors involved in paracetamol-induced analgesia remains to be clarified. Recent studies have demonstrated the importance of spinal 5-HT7 receptors in descending serotonergic pain inhibitory pathways. In this study, we investigated the role of descending serotonergic pathways and spinal 5-HT7 receptors compared with 5-HT3 and 5-HT2A receptors in the antinociceptive and antihyperalgesic effects of paracetamol. Tail-flick, hot plate and plantar incision tests were used to determine nociception in male BALB/c mice. Lesion of serotonergic bulbospinal pathways was performed by intrathecal (i.th.) injection of 5,7-dihydroxytryptamine (5,7-DHT), and spinal 5-HT levels were measured by HPLC. To evaluate the particular subtypes of the spinal 5-HT receptors, the selective 5-HT7, 5-HT3 and 5-HT2A receptor antagonists SB 269970, ondansetron and ketanserin, respectively, were given i.th. after oral administration of paracetamol. Oral paracetamol (200, 400 and 600mg/kg) elicits dose-dependent antinociceptive and antihyperalgesic effects. I.th. pretreatment with 5,7-DHT (50μg) sharply reduced 5-HT levels in the spinal cord. Depletion of spinal 5-HT totally abolished the antinociceptive and antihyperalgesic effects of paracetamol. I.th. injection of SB 2669970 (10μg) blocked the antinociceptive and antihyperalgesic effects of paracetamol, but ondansetron and ketanserin (10μg) did not. Our findings suggest that systemic administration of paracetamol may activate descending serotonergic pathways and spinal 5-HT7 receptors to produce a central antinociceptive and antihyperalgesic effects.

Effects of orexin and glucose microinjected into the hypothalamic paraventricular nucleus on gastric acid secretion in conscious rats

Orexin-A is a novel peptide that appears to play a role in regulation of gastric acid secretion. However, little is known about sites of its action. In addition, evidences suggest that some of orexin-A neurons respond to glucose. In this study, we address the hypothesis which demonstrates that orexin-A and glucose act in the hypothalamic paraventricular nucleus (PVN) to increase gastric acid secretion and juice volume in pyloric-ligated conscious rats. Male Wistar rats were implanted with guide canula directed to the PVN. Orexin-A (3-10 μg), glucose (350-750 ng) SB334867 (6-20 μg) were microinjected. The effect of pretreatment with an orexin-1 receptor antagonist, SB334867, on orexin-A and D-glucose induced acid secretion was assessed. Gastric acid secretion was measured using the pylorus-ligation method, and the amount of gastric acid was determined by titration with 0.01 N NaOH to a pH of 7.0. Intraparaventricular injection of orexin-A or D-glucose stimulated gastric acid secretion in a dose-dependent manner. The PVN injections of orexin-A receptor antagonist, SB334867, were associated with gastric acid secretion decrease and inhibited effects of PVN-injected orexin-A. Orexin-stimulated gastric acid secretion was decreased (~40%) after PVN lesions. Glucose-stimulated gastric acid secretion was also suppressed by intraperitoneal (IP) injection of SB334867. In addition, it was observed that co-injection of orexin-A and glucose at ineffective doses increased gastric secretion significantly. We suggest that orexin-A and glucose effects on the PVN stimulate gastric acid secretion. This stimulatory effect is probably mediated by orexin-1 receptors.

Intraplantar‐injected ceramide in rats induces hyperalgesia through an NF‐κB‐ and p38 kinase‐dependent cyclooxygenase 2/prostaglandin E2pathway

Inflammatory pain represents an important unmet clinical need with important socioeconomic implications. Ceramide, a potent proinflammatory sphingolipid, has been shown to elicit mechanical hyperalgesia, but the mechanisms remain largely unknown. We now demonstrate that, in addition to mechanical hyperalgesia, intraplantar injection of ceramide (10 μg) led to the development of thermal hyperalgesia that was dependent on induction of the inducible cyclooxygenase (COX-2) and subsequent increase of prostaglandin E(2) (PGE(2)). The development of mechanical and thermal hyperalgesia and increased production of PGE(2) was blocked by NS-398 (15-150 ng), a selective COX-2 inhibitor. The importance of the COX-2 to PGE(2) pathway in ceramide signaling was underscored by the findings that intraplantar injection of a monoclonal PGE(2) antibody (4 μg) blocked the development of hyperalgesia. Our results further revealed that COX-2 induction is regulated by NF-κB and p38 kinase activation, since intraplantar injection of SC-514 (0.1-1 μg) or SB 203580 (1-10 μg), well-characterized inhibitors of NF-κB and p38 kinase activation, respectively, blocked COX-2 induction and increased formation of PGE(2) and thermal hyperalgesia in a dose-dependent manner. Moreover, activation of NF-κB was dependent on upstream activation of p38 MAPK, since SB 203580 (10 μg) blocked p65 phosphorylation, whereas p38 kinase phosphorylation was unaffected by NF-κB inhibition by SC-514 (1 μg). Our findings not only provide mechanistic insight into the signaling pathways engaged by ceramide in the development of hyperalgesia, but also provide a potential pharmacological basis for developing inhibitors targeting the ceramide metabolic-to-COX-2 pathway as novel analgesics.

Effects of orexin-A on propofol anesthesia in rats

An active sleep homeostatic process is present during propofol anesthesia. Activation of the orexin system induces wakefulness, and inhibition of the orexin system causes narcolepsy. We hypothesized that orexin would affect propofol anesthesia. The effects of an intracerebroventricular (i.c.v.) injection of orexin-A (OXA) or an orexin-1 (OX-1) receptor antagonist, SB-334867, on the times to the loss and return of the righting reflex induced by propofol were examined in Wistar rats. The effects of propofol or OXA on norepinephrine (NE) and dopamine (DA) release from the prefrontal cortex (PFC) were examined using in vivo microdialysis. An i.c.v. injection of OXA (1nmol) decreased the time to emergence from propofol anesthesia mediated by the OX-1 receptor without changing anesthetic induction (n=8). An i.c.v. injection of SB-334867 (5 and 50nmol) increased the time to emergence from propofol anesthesia without changing anesthetic induction (n=8). Intravenous infusion of propofol decreased NE (48±8%; n=8) and DA (61.2±11%; n=8) release from PFC mediated by the GABA(A) receptor. An i.c.v. injection of OXA reversed the decreases in NE and DA release induced by propofol mediated by the OX-1 receptor (n=8). These results indicate that the orexin system may accelerate the emergence from propofol anesthesia associated with increases in the central noradrenergic and dopaminergic activity.

Influence of intrathecal injection of p38 MAPK inhibitor on BDNF expression in dorsal horn of spinal cord of rats with neuropathic pain

Objective To observe the effect of intrathecal p38 MAPK inhibitor(SB203580) treatment on neuropathic pain and the expression of p38 MAPK and BDNF in dorsal horn of spinal cord in rats with chronic constriction injury(CCI),So as to investigate the possible mechanisms of neuropathic pain.Methods Totally 30 SD rats were evenly randomized into 3 groups(n=10) :sham group receiving intrathecal injection of sodium chloride,control group receiving intrathecal injection of sodium chloride and CCI surgery,and SB203580 group receiving intrathecal injection of SB203580 and CCI surgery.SB203580(0.1 ml/kg) was administered 0.5 h before and 1-14 d after CCI surgery.The mechanical thresholds were tested 24 h before and 4-14 d after CCI surgery.p38 MAPK expression and BDNF release in the dorsal horn were determined using immunohistochemistry method 14 d after CCI surgery.Results The mechanical thresholds in the control and SB203580 groups were significantly lower after CCI surgery compared with that before CCI surgery(P0.05),but there was no significant change in the control group(P0.05).Compared with the sham operation group,the mechanical thresholds were significantly lower in the other two groups after CCI surgery(P0.05).The mechanical threshold of SB203580 group was significantly higher than that of the control group after CCI surgery(P0.05).The p38 MAPK expression and BDNF release were significantly higher in the control and SB203580 groups compared with those in the sham operation group(P0.05),and those in the SB203580 group were significantly lower than those in the control group(P0.05).Conclusion Intrathecal injection of p38 MAPK inhibitor SB203580 can attenuate hyperalgesia in CCI rats through decreasing p38 MAPK expression and BDNF release.

Protective effect ofblocking the signal path of p38 mitogen-activated protein kinase on blood-retinal barrierand retinal ganglion cells in early diabetic rats

：Objective To investigatethe protective effect of blocking the signal path of p38 mitogen-activated protein kinaseon blood-retinal barrier (BRB) and retinal ganglion cells (RGC) in early diabetic rats.Methods A total of 60 Wistar rats were divided into the control and diabetes group, with30 rats in each group. Diabetes was induced in rats in diabetes group by peritonealinjection of streptozotocin (STZ) ; the plasma glucose level of >16.7 mmol/L indicatedthat the diabetes model was set up successfully. The rats in the control group underwentperitoneal injection of equivalent sodium citrate solution. IgG leakage method was used tomeasure the damage of BRB function and vascular leakage. The expression and localizationof caspase-3 and vascular endothelial growth factor (VEGF) in retina of diabetic rats wereexamined by immunohistochemistry analyses. Two weeks after the establishment of thediabtes model, the rats in diabtes group underwent intravitreal injection with SB203580, ap38 inhibitor; six weeks after the injection, the expression of caspase-3 and VEGF wasdetected, and the number of apoptosis RGC was counted via immunofluorescence technique.Results In the contral group, IgG staining located in the blood vessels with littleleakage; while the IgG leakage was much more obvious in the diabetes group eight weeksafter the establishment of the model. Six weeks after intravitreal injection withSB203580, the leakage decreased in diabtes rats. The results of semi-quantitative analysisand fluorescence immunohistochemistry showed that compared with the results in diabetesrats 8 weeks after intravitreal injection (2.9 times much more than that in the controlgroup), the fluorescence expression of VEGF decreased in diabetes rats six weeks afterintravitreal injection (1.8 times much more than that in the control group). The apoptisisRGC number in rats 6 weeks after intravitreal injection of SB203580 was much less thanthat in rats without intravitreal injection (t=5. 731, P<0. 01). Conclusions SB203580can alleviate the disruption of BRB and apoptosis of RGC in early diabetes rats, whichsuggests that p38 MAPK pathways appear to be directly involved in the pathogenesis ofearly diabetic retinopathy. Key words: Diabetic retinopathy/Phisiopathology; P38 mitogen-activated proteinkinases/physiology; Blood-retinal barrier/physiology; Retinal ganglion cells/physiology; Diabetes mellitus, experimental

Effect of the C3a-Receptor Antagonist SB 290157 on Anti-OVA Polyclonal Antibody–Induced Arthritis

It was investigated whether the C3a-receptor antagonist (C3aRA) SB 290157 was involved in the suppression of anti-OVA pAb–induced arthritis because it is well known that anaphylatoxin C3a plays a crucial role in the development of an effective inflammatory response during complement activation. Anti-OVA pAb–induced arthritis was induced in DBA/1J mice by administration of anti-OVA pAb 0.5 h prior to intra-articular (i.a.) injection of OVA (0 h). Two peaks of joint swelling were observed at 0.5 and 3 h. The role of C3aRA in arthritis was investigated by injection of SB 290157 at concentrations of 10 and 30 mg/kg at 0 and 2 h. The antagonist was able to reduce joint swelling only at 3 h, and about 50% inhibition of joint swelling was observed with the concentration of 30 mg/kg. The C3 level was significantly decreased at 3 h compared with naïve mice showing complement consumption. Furthermore, the C3 activation was observed and increased corresponding to the graded concentration of anti-OVA pAb. The results also revealed that the C3aRA was able to reduce the expression of IL-1β in synovial tissue. Taken together, the results suggested that C3aRA may be effective in the inhibition of arthritis.

In vivo evidence that constitutive activity of serotonin2C receptors in the medial prefrontal cortex participates in the control of dopamine release in the rat nucleus accumbens: differential effects of inverse agonist versus antagonist

Control of the mesoaccumbens dopamine (DA) pathway by central serotonin(2C) receptors (5-HT(2C)Rs) involves different 5-HT(2C)R populations located within multiple brain areas. Here, using in vivo microdialysis in halothane-anesthetized rats, we assessed the role of medial prefrontal cortex (mPFC) 5-HT(2C)Rs in the control of basal and activated accumbal DA outflow, to identify the modalities of their recruitment and the role of 5-HT(2C)R constitutive activity. Intra-mPFC injection of the 5-HT(2C)R inverse agonist SB 206553 (0.5 microg/0.2 microL), without effect by itself, decreased accumbal DA outflow induced by morphine (2.5-10 mg/kg, s.c.), haloperidol (0.01 mg/kg, s.c.) or GBR 12909 (2.5 mg/kg, i.p.). Conversely, intra-mPFC injection of the 5-HT(2C)R antagonist SB 242084 (0.5 microg/0.2 microL), without effect by itself, decreased the effect of 10 mg/kg morphine, the only drug enhancing basal 5-HT outflow in the mPFC. The inhibitory effect of SB 206553 on 2.5 mg/kg morphine-stimulated DA outflow was suppressed by the concomitant intra-mPFC injection of SB 242084. Finally, changes of basal DA outflow induced by the 5-HT(2C)R agonist Ro 60-0175 (3 mg/kg, i.p.) or SB 206553 (5 mg/kg, i.p.) were unaffected by intra-mPFC injection of SB 242084. These results, showing that 5-HT(2C)R antagonist and inverse agonist behave differently in vivo, demonstrate that mPFC 5-HT(2C)Rs facilitate activated accumbal DA outflow and that 5-HT(2C)R constitutive activity participates in this interaction.

Involvement of orexin-A on micturition reflex in normal and cyclophosphamide-induced cystitis bladder in rat

The purpose of the present study was to investigate the effect of orexin-A in the spinal cord on bladder function in normal rats and cyclophosphamide (CYP)-induced cystitis rat models. The effects of intrathecal (i.t.) injection of orexin-A (0.01, 0.1 and 1.0 nmol) on bladder function were examined during continuous infusion cystometrogram (CMG) in urethane anesthetized normal and CYP-induced cystitis rats. The effects of i.t. injection of selective orexin-1 receptor (OXR1) antagonist SB334867 (10 nmol) on orexin-A-induced bladder overactivity in normal rats and SB334867 (10 and 30 nmol) on changes in bladder function in normal and CYP-induced cystitis rats were investigated. The effects of intravenous (i.v.) injection of orexin-A (0.3 and 1.0 nmol) on micturition reflex were also investigated in normal rats. I.t. injection of orexin-A (0.1 and 1.0 nmol) significantly decreased the intercontraction intervals (ICI) in normal and CYP-induced cystitis rats. I.t. injection of SB334867 (10 nmol) significantly increased the ICI of orexin-A induced overactive bladder in normal rats and i.t. injection of SB334867 (30 nmol) also increased the ICI in normal rat bladder. However, in CYP-injected cystitis rat models, i.t. injection of SB334867 did not change the bladder function. I.v. injection of orexin-A failed to affect the bladder function in normal rats. Orexin mRNA levels in the lateral hypothalamus were significantly decreased in CYP-induced cystitis rats. These results indicate that orexin-A in the spinal cord activates micturition reflex via OXR1 in normal rats. In addition, OXR1 antagonist did not have any effect on micturition reflex in CYP-induced cystitis rats.

Simple Colloidal Synthesis of Single-Crystal Sb−Se−S Nanotubes with Composition Dependent Band-Gap Energy in the Near-Infrared

We report the first synthesis of high-quality binary and ternary Sb(2)Se(3-x)S(x) nanotubes across the entire compositional range from x = 0 to 3 via a simple, low-cost, colloidal synthetic method of injection of Sb(III)-complex solution into a hot paraffin liquid containing Se, S, or a mixture thereof. In contrast to the classic rolling mechanism, the modular formation of the reported nanotubes follows a four-stage self-seeding process: (i) amorphous nanospheres, (ii) short crystalline nanotubes growing out of relatively large amorphous nanospheres, (iii) long crystalline nanotubes attached to small amorphous nanospheres, and (iv) single-crystal nanotubes. The obtained single-crystal nanotubes have tunable composition, orthorhombic phase, well-defined rectangular cross sections, and growth direction along [001], as revealed by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and selected area electron diffraction studies. UV-vis-NIR absorption spectroscopy reveals that the optical bandgap energy of the Sb(2)Se(3-x)S(x) (0 < or = x < or = 3) nanotubes increases quadratically with the sulfur concentration x with these bandgap energies falling in the range from 1.18 to 1.63 eV at the red edge of the solar spectrum. The present study opens a new avenue to low-cost, large-scale synthesis of high quality semiconductor nanotubes with technological applications in solar energy conversion and also for a wide range of optical nanodevices operating in the near-infrared.

Excitation of cutaneous C nociceptors by intraplantar administration of anandamide

Anandamide has been characterized as both an endocannabinoid and endovanilloid. Consistent with its actions as an endovanilloid, previous studies have demonstrated that anandamide can excite primary sensory neurons in vitro via transient receptor potential vanilloid type one (TRPV1) receptors. In the present study, we sought to determine if anandamide excited cutaneous C nociceptors in vivo and if this excitation correlated with nocifensive behaviors. Using teased-fiber electrophysiological methods in the rat, C nociceptors isolated from the tibial nerve with receptive fields (RFs) on the plantar surface of the hindpaw were studied. Injection of anandamide into the RF dose-dependently excited nociceptors at doses of 10 and 100 μg. The TRPV1 receptor antagonists, capsazepine or SB 366791, were applied to the RF to determine if excitation by anandamide was mediated through TRPV1 receptors. Intraplantar injection of either capsazepine (10 μg) or SB 366791 (3 μg) attenuated the excitation produced by 100 μg anandamide. We also determined whether excitation of C nociceptors by anandamide was associated with nocifensive behaviors. Intraplantar injection of 100 μg anandamide produced nocifensive behaviors that were attenuated by pre-treatment with either capsazepine or SB 366791. Furthermore, we determined if intraplantar injection of anandamide altered withdrawal responses to radiant heat. Neither intraplantar injection of anandamide nor vehicle produced antinociception or hyperalgesia to radiant heat. Our results indicate that anandamide excited cutaneous C nociceptors and produced nocifensive behaviors via activation of TRPV1 receptors.

Contribution of orexin in hypercapnic chemoreflex: evidence from genetic and pharmacological disruption and supplementation studies in mice

We have previously shown that hypercapnic chemoreflex in prepro-orexin knockout mice (ORX-KO) is attenuated during wake but not sleep periods. In that study, however, hypercapnic stimulation had been chronically applied for 6 h because of technical difficulty in changing the composition of the inspired gas mixture without distorting the animal's vigilance states. In the present study we examined possible involvement of orexin in acute respiratory chemoreflex during wake periods. Ventilation was recorded together with electroencephalography and electromyography before and after intracerebroventricular administration of orexin or an orexin receptor antagonist, SB-334867. A hypercapnic (5 or 10% CO(2)) or hypoxic (15 or 10% O(2)) gas mixture was introduced into the recording chamber for 5 min. Respiratory parameters were analyzed only for quiet wakefulness. When mice breathed normal room air, orexin-A and orexin-B but not vehicle or SB-334867 increased minute ventilation in both ORX-KO and wild-type (WT) mice. As expected, hypercapnic chemoreflex in vehicle-treated ORX- KO mice (0.22 +/- 0.03 mlxmin(-1)xg(-1)x% CO(2)(-1)) was significantly blunted compared with that in WT mice (0.51 +/- 0.05 mlxmin(-1)xg(-1)x% CO(2)(-1)). Supplementation of orexin-A or -B (3 nmol) partially restored the hypercapnic chemoreflex in ORX-KO mice (0.28 +/- 0.03 mlxmin(-1).g(-1)x% CO(2)(-1) for orexin-A and 0.32 +/- 0.04 mlxmin(-1)xg(-1)x% CO(2)(-1) for orexin-B). In addition, injection of SB-334867 (30 nmol) in WT mice decreased the hypercapnic chemoreflex (0.39 +/- 0.04 mlxmin(-1)xg(-1)x% CO(2)(-1)). On the other hand, hypoxic chemoreflex in vehicle-treated ORX-KO and SB-334867-treated WT mice was not different from that in corresponding controls. Our findings suggest that orexin plays a crucial role in CO(2) sensitivity at least during wake periods in mice.

Time- and dose-related effects of three 5-HT receptor ligands on the genioglossus activity in anesthetized and conscious rats

Clinical trials in obstructive sleep apnea syndrome patients reported moderate effects of serotoninergic drugs on oropharyngeal apneas, although numerous specific 5-HT ligands highly modulate the genioglossus muscle (GG) activity in experiments performed in anesthetized animals. The purpose of this study was to investigate time- and dose-related effects of central and systemic injections of 8-OHDPAT (5-HT1A agonist), SB224289 (5-HT1B antagonist), and DOI (5-HT2A/2C agonist) on the GG activity in anesthetized and conscious rats. Electromyographic recordings of the GG activity (GGemg) were analyzed after central and systemic injections of each drug in ketamine-xylazine anesthetized rats. Electroencephalograms (EEG), as well as neck and GG muscle activities (Nemg and GGemg), were recorded in 15 additional rats to analyze changes in sleep-wake states before and after systemic injection of the drugs. Central injections of 8-OHDPAT and DOI in anesthetized rats induced clear dose-related increases in phasic and tonic GGemg activities, respectively. The time-responses were inferior to 30 min with 8-OHDPAT and over 50 min with DOI. Moderate increases in phasic GGemg activity were also observed after central, but not peripheral injection of SB and DOI. The total sleep time measured in conscious rats significantly decreased after systemic injections of DOI and 8-OHDPAT, although no change was observed in phasic or tonic GGemg activity. The dose- and time-responses of the DOI in anesthetized rat partly explain the lack of GGemg tonic change in conscious rat. The moderate effect on the GGemg phasic activity of peripheral 5-HT1A ligand injection easily explains the lack of change in conscious rat. The serotonergic modulation of the respiratory component of the GGemg remains complex, but is highly sensitive to 5-HT1A receptors after central injection in rats under anesthesia. Forthcoming therapy in OSAS should be made of mixed profiled neurotransmitters and different routes of administration.

Sciatic Nerve Ligation-Induced Proliferation of Spinal Cord Astrocytes Is Mediated by κ Opioid Activation of p38 Mitogen-Activated Protein Kinase

Partial sciatic nerve ligation (pSNL) markedly increased glial fibrillary acidic protein immunoreactivity (GFAP-IR) 1 week after lesion in the L4-L5 spinal dorsal horn of wild-type, but not in dynorphin knock-out, mice lacking kappa opioid receptors (KOR-/-) or in wild-type mice pretreated with the KOR antagonist nor-binaltorphimine (norBNI). A direct effect of KOR on glial cell proliferation was suggested by the findings that primary cultures of type II GFAP-immunoreactive astrocytes isolated from mouse spinal cord express KOR. Sustained treatment with the kappa agonist U50,488 (trans-3,4-dichloro-N-methyl-N-[2-(1-pyrolytinil)-cyclohexyl]-benzeneacetamide methane sulfonate) significantly increased the proliferation rate of GFAP-immunoreactive astrocytes isolated from wild-type mice, and this effect was blocked by norBNI pretreatment. Proliferation of cultured type II astrocytes may have been stimulated by mitogen-activated protein kinase (MAPK) activation by KOR because (1) U50,488 treatment increased phospho-p38 MAPK-immunoreactivity 247 +/- 44% over untreated cells, (2) the increase in phospho-p38 induced by U50,488 was blocked by norBNI and not evident in KOR-/- cultures, and (3) GFAP-immunoreactive astrocyte proliferation induced by U50,488 was blocked by the p38 MAPK inhibitor SB 203580 [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-1H-imidazole]. Similar mechanisms of astrocyte activation may also be responsible in vivo because intrathecal injection of SB 203580 blocked the increased GFAP-IR in lumbar spinal cord induced by pSNL. Although the relationship between kappa-stimulated astrocyte proliferation and neuropathic pain mechanisms was not directly established in these studies, the results support the hypothesis that KOR activation induces spinal astrocyte proliferation, which may contribute to cellular reorganization after sciatic nerve damage.

P173 THE EFFECTS OF INTRA-ARTICULAR INJECTION OF P38 MAPK INHIBITOR ON MATRIX METALLOPROTEINASE IN CARTILAGE OF EXPERIMENTAL OSTEOARTHRITIS MODEL

Purpose: The primary aim of this study was to investigate, using an experimental rat model of osteoarthritis(OA), the effect of a selective p38 mitogen activated protein kinase inhibitor,SB203580, on the development of structural changes.Additional aims were to assess the effects of the inhibitor on levels of matrixmetalloproteinase 3 (MMP-3) and MMP-13(collagenase 3) in OA cartilage and to explore the relation between the MMP-3,13 expression and the severity of OA. Methods: OA was induced in 40 SD rats by anterior cruciate ligament transection (ACLT).After surgical, rats with OA were randomly divided into A_D groups: Rats of group A received 0.1 ml intra-articular injection of SB203580 at high concentration of 100um/L. Each treatment started immediately after surgery, once a week;those in group B were treated under the same condition using SB203580 with low concentration of 10um/L and those in group C received 0.1ml of intra-articular 0.9% Sodium Chloride injection,animals of group D were not injected as controls after ACLT. The animals were killed 8 weeks after surgery. Macroscopicand histologic studies were performed on the cartilage. The levels of MMP-3,13 in OA cartilage chondrocytes were evaluated by immunohistochemistry and western-blotting. Results: All ACLT knees demonstrated osteoarthritic changes. Cartilage degradation in the control group was significantly more severe than that in the experimental group both on the macroscopic grading scale and on Mankin’s grading scale(P <0.05). Immunohistochemical study showed that in the experimental group MMP-3,13 was predominantly expressed in the superficial and upper intermediate layers of cartilage, and the amount of MMP-3,13 in the experimental group was also lower than that in control group(P <0.05). In western-blotting the amount of MMP3,13 was reduced by the treatment of the inhibitor. The protein levels of MMP-3 and MMP-13 in cartilage of inhibitor injection groups were significantly lower than those of Sodium Chloride group and untreated group. There was no significant difference in MMP-3 and MMP-13 expression between the different concentration inhibitor injection groups. No significant difference in MMP-3 and MMP-13 expression in cartilage was found between Sodium Chloride group and control group. Conclusions: This study demonstrates that, in vivo,SB203580, a selective inhibitor of p38MAPK, can partially decrease the development of some of the structural changes in the early phases of experimental OA and significantly reduces the severity of cartilage degradation. This effect was associated with a reduction in the level of MMP-3,13 in OA cartilage, which probably explains the action of the drug and thus may be a potential drug for the treatment of OA.

Effect of a selective OX 1R antagonist on food intake and body weight in two strains of rats that differ in susceptibility to dietary-induced obesity

An orexin-1 receptor antagonist decreases food intake whereas orexin-A selectively induces hyperphagia to a high-fat diet. In the present study, we evaluated the effect of an orexin antagonist in two strains of rats that differ in their sensitivity to becoming obese while eating a high-fat diet. Male Osborne-Mendel (OM) and S5B/Pl (S5B) rats were treated acutely with an orexin-1 receptor antagonist (SB-334867), after adaptation to either a high-fat (56% fat energy) diet or a low-fat (10% fat energy) diet that were equicaloric for protein (24% energy). Ad libitum fed rats were injected intraperitoneally with SB-334867 at doses of 3, 10 or 30 mg/kg, or vehicle at the beginning of the dark cycle, and food intake and body weight were measured. Hypothalamic prepro-orexin and orexin-1 receptor mRNA expression were analyzed in OM and S5B rats fed at a high-fat or low-fat diet for two weeks. SB-334867 significantly decreased food intake in both strains of rats eating the high-fat diet but only in the OM rats eating the low fat diet. The effect was greatest at 12 and 24 h. Body weight was also reduced in OM rats 1 d after injection of SB-334867 but not in the S5B rats. Prepro-orexin and orexin-1 receptor expression levels did not differ between strains or diets. These experiments demonstrate that an orexin antagonist (SB-334867) reduces food intake and has a greater effect in a rat strain that is susceptible to dietary-induced obesity, than in a resistant strain.