Effects of a Novel Selective Agonist for Prostaglandin Receptor Subtype EP4on Hyperalgesia and Inflammation in Monoarthritic Model

2002 ◽  
Vol 97 (1) ◽  
pp. 170-176 ◽  
Author(s):  
Keiichi Omote ◽  
Tomoyuki Kawamata ◽  
Yoshito Nakayama ◽  
Hiroki Yamamoto ◽  
Mikito Kawamata ◽  
...  

Background Cytokines have crucial role in the development and maintenance of inflammation and pain in arthritis. Activation of prostaglandin receptor subtype EP(4) suppresses cytokine production in immune cells. The purpose of this study was to evaluate whether a novel EP(4) agonist would be able to suppress thermal and mechanical hyperalgesia and paw swelling in acute and chronic phases in rat monoarthritic model. Methods Monoarthritis was induced by an injection of complete Freund's adjuvant (CFA) intracapsularly into the tibiotarsal joint of the rats. Withdrawal latencies to thermal stimulation on the hind paw, withdrawal thresholds to mechanical stimulation, paw volume, and ankle diameter were measured 24 h and 4 weeks after the CFA injection. A novel selective EP(4) receptor agonist, ONO-AE1-329 (10, 25, or 50 microg) or saline was administered intracapsularly into the joint. Results Withdrawal latencies and withdrawal thresholds were significantly (P < 0.05) shortened and decreased, respectively, on the arthritic side but not on the contralateral side 24 h and 4 weeks after the CFA injection. In addition, significant (P < 0.05) increases in paw volume and ankle diameter on the arthritic side were observed. Intracapsularly administered ONO-AE1-329 showed significant (P < 0.05) inhibition of thermal and mechanical hyperalgesia and significant (P < 0.05) decrease in paw volume and ankle diameter in a dose-dependent manner at 24 h and 4 weeks after CFA. Conclusion Intracapsular administration of EP(4) receptor agonist effectively inhibited mechanical and thermal hyperalgesia and inflammatory reactions in acute and chronic monoarthritis. An EP(4) agonist would be a potential strategy for inflammatory pain in arthritis.

1996 ◽  
Vol 270 (3) ◽  
pp. H857-H868 ◽  
Author(s):  
R. M. Touyz ◽  
J. Fareh ◽  
G. Thibault ◽  
B. Tolloczko ◽  
R. Lariviere ◽  
...  

Vasoactive peptides may exert inotropic and chronotropic effects in cardiac muscle by modulating intracellular calcium. This study assesses effects of angiotensin II (ANG II) and endothelin-1 (ET-1) on intracellular free calcium concentration ([Ca2+]i) in cultured cardiomyocytes from neonatal and adult rats. [Ca2+]i was measured microphotometrically and by digital imaging using fura 2 methodology. Receptor subtypes through which these agonists induce responses were determined pharmacologically and by radioligand binding studies. ANG II and ET-1 increased neonatal atrial and ventricular cell [Ca2+]i transients in a dose-dependent manner. ANG II (10(-11) to 10(-7) M) failed to elicit [Ca2+]i responses in adult cardiomyocytes, whereas ET-1 increased [Ca2+]i in a dose-dependent manner. The ETA receptor antagonist BQ-123 significantly reduced (P 7< 0.05) ET-1 induced responses, and the ETB receptor agonist IRL-1620 (10(-7) to 10(-5) M) significantly increased (P < 0.05) [Ca2+]i in neonatal and adult cardiomyocytes. ET-1 binding studies demonstrated 85% displacement by BQ-123 and approximately 15% by the ETB receptor agonist sarafotoxin S6c, suggesting a predominance of ETA receptors. Competition binding studies for ANG II failed to demonstrate significant binding on adult ventricular myocytes, indicating the absence or presence of very few ANG II receptors. These data demonstrate that ANG II and ET-1 have stimulatory [Ca2+]i effects on neonatal cardiomyocytes, whereas in adult cardiomyocytes, ANG II-induced effects are insignificant, and only ET-1-induced responses, which are mediated predominantly via ETA receptors, are preserved. Cardiomyocyte responses to vasoactive peptides may thus vary with cardiac development.


2007 ◽  
Vol 292 (3) ◽  
pp. G746-G752 ◽  
Author(s):  
Zhuan Liao ◽  
Zhao-Shen Li ◽  
Yan Lu ◽  
Wei-Zhong Wang

Previous studies have suggested that somatostatin inhibits pancreatic secretion at a central vagal site, and the dorsal vagal complex (DVC) is involved in central feedback inhibition of the exocrine pancreas. The aim of this study was to investigate the effect of exogenous somatostatin in the DVC on pancreatic secretion and the somatostatin receptor subtype(s) responsible for the effect. The effects of somatostatin microinjected into the DVC on pancreatic secretion stimulated by cholecystokinin octapeptide (CCK-8) or 2-deoxy-d-glucose (2-DG) were examined in anesthetized rats. To investigate the somatostatin inhibitory action site, a somatostatin receptor antagonist [SRA; cyclo(7-aminoheptanoyl-Phe-d-Trp-Lys-Thr)] was microinjected into the DVC before intravenous infusion of somatostatin and CCK-8/2-DG. The effects of injection of a somatostatin receptor-2 agonist (seglitide) and combined injection of somatostatin and a somatostatin receptor-2 antagonist (CYN 154806) in the DVC on the pancreatic secretion were also investigated. Somatostatin injected into the DVC significantly inhibited pancreatic secretion evoked by CCK-8 or 2-DG in a dose-dependent manner. SRA injected into the DVC completely reversed the inhibitory effect of intravenous administration of somatostatin. Seglitide injected into the DVC also inhibited CCK-8/2-DG-induced pancreatic protein secretion. However, combined injection of somatostatin and CYN 154806 did not affect the CCK-8/2-DG-induced pancreatic secretion. Somatostatin in the DVC inhibits pancreatic secretion via somatostatin receptor-2, and the DVC is the action site of somatostatin for its inhibitory effect.


2005 ◽  
Vol 18 (3) ◽  
pp. 403-415 ◽  
Author(s):  
L. Ottonello ◽  
M. Bertolotto ◽  
F. Montecucco ◽  
P. Dapino ◽  
F. Dallegri

Monocytes and macrophages play a key role in the initiation and persistence of inflammatory reactions. The possibility to interfere with the survival of these cells, once recruited and activated at sites of inflammation, is an attractive therapeutic option. Although resting monocytes are susceptible to pharmacologically induced apoptosis, no data are available about the possibility to modulate the survival of activated monocytes. The present work was planned to investigate if dexamethasone is able to promote apoptosis of human monocytes activated by immune complexes. When monocytes were cultured with immune complexes, a dose-dependent inhibition of apoptosis was observed. Dexamethasone stimulated apoptosis of resting and activated monocytes in a dose-dependent manner. Both the immune complex inhibitory activity and dexamethasone stimulatory properties depend on NF-kB/XIAP and Ras/MEK/ERK/CD95 pathways. In fact, the exposure of monocytes to immune complexes increased NF-kB activation and XIAP expression, which in turn were inhibited by dexamethasone. On the other hand, immune complex-stimulated monocytes displayed a reduced expression of CD95, which is prevented by dexamethasone, as well as by MEK inhibitor U0126. Furthermore, anti-CD95 ZB4 mAb prevented dexamethasone-induced apoptosis in immune complex-stimulated monocytes. Similarly, ZB4 inhibited dexamethasone-mediated augmentation of caspase 3 activity. The present findings suggest that Fc triggering by insoluble immune complexes result in the activation of two intracellular pathways crucial for the survival of monocytes: 1. Ras/MEK/ERK pathway responsible for the down-regulation of CD95 expression; 2. NF-kB pathway governing the expression of XIAP. Both the pathways are susceptible to inhibition by monocyte treatment with pharmacologic concentrations of dexamethasone.


2004 ◽  
Vol 32 (3) ◽  
pp. 869-877 ◽  
Author(s):  
MR Nicol ◽  
VJ Cobb ◽  
BC Williams ◽  
SD Morley ◽  
SW Walker ◽  
...  

Vasoactive intestinal peptide (VIP) shows a wide tissue distribution and exerts numerous physiological actions. VIP was shown in a dose-dependent manner to increase cortisol secretion in the NCI-H295R human adrenocortical carcinoma (H295) cell line (threshold dose 3.3x10(-10) M, maximal dose 10(-7) M), coupled with a parallel increase in cAMP accumulation. Receptor-specific agonists were employed to determine which of the two known VIP receptor subtypes was involved in cortisol secretion. Treatment with the VPAC1 receptor agonist, [K(15), R(16), L(27)]VIP(1-7)/GRF(8-27), produced a dose-dependent increase in H295 cell cortisol secretion (threshold dose 10(-11) M, maximal dose 10(-7) M) similar to that seen with VIP. Meanwhile, the high-affinity VPAC2 receptor agonist, RO-25-1553, failed to stimulate significantly cortisol or cAMP production from H295 cells. Inhibition of VIP-mediated H295 cell cortisol secretion by PG97-269, a competitive VPAC1-specific antagonist, produced parallel shifts of the dose-response curve and a Schild regression slope of 0.99, indicating competitive inhibition at a single receptor subtype. VIP is known also to interact with the PAC1 receptor, albeit with lower affinity (EC(50) of approximately 200 nM) than the homologous ligand, PACAP (EC(50) of approximately 0.5 nM). PACAP stimulated cortisol secretion from H295 cells (EC(50) of 0.3 nM), suggesting the presence of functional PAC1 receptors. However, stimulation of cortisol secretion by nanomolar concentrations of VIP (EC(50) of 5 nM), coupled with real-time PCR estimation that VPAC1 receptor transcripts appear 1000-fold more abundant than PAC1 transcripts in H295 cells, makes it unlikely that VIP signals via PAC1 receptors. Together, these data suggest that VIP directly stimulates cortisol secretion from H295 cells via activation of the VPAC1 receptor subtype.


1997 ◽  
Vol 273 (5) ◽  
pp. G1036-G1043 ◽  
Author(s):  
Hong-Gang Wang ◽  
Toshishige Shibamoto ◽  
Takashige Miyahara

We determined the constrictive effects of endothelin (ET)-1 on the hepatic vascular resistance distribution and the receptor subtype responsible for the effect in isolated rabbit livers perfused via the portal vein with 5% albumin-Krebs solution. The sinusoidal pressure was estimated using the double vascular occlusion pressure. The basal portal venous resistance comprised 59% of the total portal-hepatic venous resistance. In response to a bolus injection of ET-1 (0.05–5 μg), which led to a final concentration of 0.1–10 nM in the recirculating perfusate, the portal venous resistance increased in a dose-dependent manner, whereas the hepatic venous resistance did not change significantly at any concentration. This hepatic vasoconstriction was associated with liver weight loss. The selective portal venous constriction induced by ET-1 was confirmed in livers perfused retrogradely from the hepatic vein to the portal vein. The ET-1-induced hepatic vasoconstriction was significantly attenuated by the selective ETA receptor antagonist BQ-123 (1 μM). The ETB receptor antagonist BQ-788 (1 μM) also attenuated the constriction at ET-1 concentrations less than 10 nM. The combination of BQ-123 and BQ-788 tended to inhibit the hepatic vasoconstriction more effectively than BQ-123 alone. These results suggest that ET-1 selectively constricts the portal vein via both ETA and ETB receptors, with predominance of ETA receptor in isolated albumin-Krebs-perfused rabbit livers.


2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
K. Tominaga ◽  
T. Kido ◽  
M. Ochi ◽  
C. Sadakane ◽  
A. Mase ◽  
...  

The traditional Japanese medicine rikkunshito ameliorates the nitric oxide-associated delay in gastric emptying. Whether rikkunshito affects gastric motility associated with 5-hydroxytryptamine (serotonin: 5-HT) receptors or dopamine receptors is unknown. We examined the effects of rikkunshito on the delay in gastric emptying induced by 5-HT or dopamine using the phenol red method in male Wistar rats. 5-HT (0.01–1.0 mg kg−1, i.p.) dose dependently delayed gastric emptying, similar to the effect of the 5-HT3receptor agonist 1-(3-chlorophenyl) biguanide (0.01–1.0 mg kg−1, i.p.). Dopamine also dose dependently delayed gastric emptying. The 5-HT3receptor antagonist ondansetron (0.04–4.0 mg kg−1) and rikkunshito (125–500 mg kg−1) significantly suppressed the delay in gastric emptying caused by 5-HT or 1-(3-chlorophenyl) biguanide. Hesperidin (the most active ingredient in rikkunshito) suppressed the 5-HT-induced delayed gastric emptying in a dose-dependent manner, the maximum effect of which was similar to that of ondansetron (0.4 mg kg−1). The improvement obtained by rikkunshito or ondansetron in delaying gastric emptying was completely blocked by pretreatment with atropine. Rikkunshito appears to improve delay in gastric emptying via the antagonistic action of the 5-HT3receptor pathway.


2021 ◽  
Vol 22 (12) ◽  
pp. 6380
Author(s):  
João de Sousa Valente ◽  
Khadija M Alawi ◽  
Sabah Bharde ◽  
Ali A. Zarban ◽  
Xenia Kodji ◽  
...  

Recently, we found that the deletion of TRPC5 leads to increased inflammation and pain-related behaviour in two animal models of arthritis. (-)-Englerin A (EA), an extract from the East African plant Phyllanthus engleri has been identified as a TRPC4/5 agonist. Here, we studied whether or not EA has any anti-inflammatory and analgesic properties via TRPC4/5 in the carrageenan model of inflammation. We found that EA treatment in CD1 mice inhibited thermal hyperalgesia and mechanical allodynia in a dose-dependent manner. Furthermore, EA significantly reduced the volume of carrageenan-induced paw oedema and the mass of the treated paws. Additionally, in dorsal root ganglion (DRG) neurons cultured from WT 129S1/SvIm mice, EA induced a dose-dependent cobalt uptake that was surprisingly preserved in cultured DRG neurons from 129S1/SvIm TRPC5 KO mice. Likewise, EA-induced anti-inflammatory and analgesic effects were preserved in the carrageenan model in animals lacking TRPC5 expression or in mice treated with TRPC4/5 antagonist ML204.This study demonstrates that while EA activates a sub-population of DRG neurons, it induces a novel TRPC4/5-independent analgesic and anti-inflammatory effect in vivo. Future studies are needed to elucidate the molecular and cellular mechanisms underlying EA’s anti-inflammatory and analgesic effects.


2011 ◽  
Vol 301 (6) ◽  
pp. H2271-H2278 ◽  
Author(s):  
Ryan Boyd ◽  
Matthew T. Rätsep ◽  
Li Li Ding ◽  
Hui Di Wang

The adventitia has been recognized to play important roles in vascular oxidative stress, remodeling, and contraction. We recently demonstrated that adventitial fibroblasts are able to express endothelin (ET)-1 in response to ANG II. However, it is unclear whether ET-1 receptors are expressed in the adventitia. We therefore investigated the expression and roles of both ETA and ETB receptors in collagen synthesis and ET-1 clearance in adventitial fibroblasts. Adventitial fibroblasts were isolated and cultured from the mouse thoracic aorta by the explant method. Cultured cells were treated with ANG II (100 nmol/l) or ET-1 (10 pM) in the presence or absence of the ANG II type 1 receptor antagonist losartan (100 μM), the ET-1 receptor antagonists BQ-123 (ETA receptor, 1 μM) and BQ-788 (ETB receptor, 1 μM), and the ETB receptor agonist sarafotoxin 6C (100 nM). ET-1 peptide levels were determined by ELISA, whereas ETA, ETB, and collagen levels were determined by Western blot analysis. ANG II increased ET-1 peptide levels in a time-dependent manner. ANG II increased ETA and ETB receptor protein levels as well as collagen in a similar fashion. ANG II-induced collagen was reduced while in the presence of BQ-123, suggesting a role for the ETA receptor in the regulation of the extracellular matrix. ANG II treatment in the presence of BQ-788 significantly increased ET-1 peptide levels. Conversely, the ETB receptor agonist sarafotoxin 6C significantly decreased ET-1 peptide levels. These data implicate a role for the ETB receptor in the clearance of the ET-1 peptide. In conclusion, both ETA and ETB receptors are expressed in adventitial fibroblasts, which paves the ground for the biological significance of adventitial ET-1. The ETA receptor subtype mediates collagen I expression, whereas the ETB receptor subtype may play a protective role through increasing the clearance of the ET-1 peptide.


1992 ◽  
Vol 8 (6) ◽  
pp. 567-573 ◽  
Author(s):  
Renata Siliprandi ◽  
Roberto Canella ◽  
Giorgio Carmignoto ◽  
Nicola Schiavo ◽  
Anna Zanellato ◽  
...  

AbstractThe present study provides evidence that the adult mammalian retina is highly sensitive to the excitotoxic action of NMDA. In particular, we have investigated the effects of a single intravitreal injection of different doses of N-methyl-D-aspartate (NMDA) (2–200 nmoles) on the adult rat retina. Morphological evaluation of transverse sections of retinae demonstrated a dose-dependent loss of cells in the ganglion cell layer (GCL) and a reduction in the thickness of the inner plexiform layer. No obvious alterations were noted in the more distal retinal layers. Quantitative analyses of Nissl-stained whole-mounted retinae revealed that administration of 20 nmoles of NMDA resulted in a 70% loss of cells with a soma diameter greater than 8 μm (presumed retinal ganglion cells); a 20% loss of cells with a soma diameter smaller than 8 μm (presumed displaced amacrine cells) was also observed. In addition, NMDA produced a dose-dependent decrease of retinal choline acetyltransferase (ChAT) activity, suggesting that NMDA affects cholinergic amacrine cells as well. MK-801, a non-competitive NMDA antagonist, completely prevented the NMDA-induced loss of cells in the GCL and blocked, in a dose-dependent manner, the NMDA-induced decrease of ChAT activity. The excitotoxic action of NMDA observed in these experiments is thus likely mediated through the NMDA receptor subtype. This ”in vivo” model may be utilized to identify potential drugs that antagonize or limit the deleterious effects consequent to NMDA receptor overstimulation in the central nervous system.


2000 ◽  
Vol 93 (2) ◽  
pp. 520-528 ◽  
Author(s):  
Tomoyuki Kawamata ◽  
Keiichi Omote ◽  
Hajime Sonoda ◽  
Mikito Kawamata ◽  
Akiyoshi Namiki

Background The studies on the mechanisms of ketamine antinociception have led to conflicting results. In this study, the authors investigated the contribution of supraspinal monoaminergic descending inhibitory system to ketamine analgesia for acute nociception and inflammation-induced hyperalgesia. Methods Male Sprague-Dawley rats were used. The paw withdrawal latencies to radiant heat stimuli were measured to assess the thermal nociceptive threshold. The analgesic effects of intrathecal or intraperitoneal ketamine were examined in the rats that received unilateral intraplantar carrageenan and in those that were untreated. In addition, it was examined whether pretreatment with intrathecal yohimbine or methysergide inhibited the analgesic effects of ketamine. Using an intrathecal microdialysis method, noradrenaline and 5-hydroxytryptamine concentrations in lumbar cerebrospinal fluid were measured after intraperitoneal ketamine in both saline- and carrageenan-treated rats. Results In the untreated rats, intraperitoneal but not intrathecal ketamine produced antinociceptive effects in a dose-dependent manner. Pretreatment with intrathecal yohimbine or methysergide inhibited these antinociceptive effects. Intraplantar carrageenan significantly reduced paw withdrawal latencies on the injected paw but not on the contralateral paw. Both intraperitoneal and intrathecal ketamine reversed the shortened paw withdrawal latencies on the injected side in a dose-dependent manner without any effects on the contralateral side. Neither yohimbine nor methysergide inhibited these antihyperalgesic effects. In analyses of monoamines, the magnitude of increase in monoamines after intraperitoneal ketamine was significantly smaller in the carrageenan-treated rats than in the saline-treated rats. Conclusion These results demonstrated that ketamine produced antinociceptive effects through an activation of the monoaminergic descending inhibitory system, whereas, in a unilateral peripheral inflammation-induced hyperalgesic state, the monoaminergic system did not contribute to the antihyperalgesic effects of ketamine. The mechanisms of the antinociceptive and antihyperalgesic properties of ketamine are different.


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