Amelioration of hyperalgesia by kinin receptor antagonists or kininogen deficiency in chronic constriction nerve injury in rats

OBJECTIVE

The present study was designed to examine the involvement of bradykinin in thermal and mechanical hyperalgesia induced by chronic constriction nerve injury (CCI) using B1 and B2 receptor antagonists and mutant kininogen-deficient rats.

METHODS

Sprague-Dawley (SD) rats and Brown Norway (B/N-) rats given CCI treatment on day 0, were used as a model of neuropathic pain. Either a kinin B1 antagonist des-Arg9-[Leu8]-bradykinin or the receptor B2 antagonist HOE-140 was constantly infused into the left jugular vein of SD rats on days 15 to 22 after CCI. Vehicle-treated rats and sham-operated rats without nerve injury were also prepared as controls. In all rats, we observed pain behavior, and measured the latency period of paw withdrawal from the thermal stimuli and, with von Frey filaments, the mechanical pain threshold, before surgery and on days 14 and 22 after CCI. B/N-Katholiek rats, which congenitally lack plasma kininogen and release no kinin, were also tested for hyperalgesic parameters. Expression of kinin receptor mRNA in the dorsal root ganglia was detected by RT-PCR.

RESULTS

Most of the rats (88%) showed some pain behavior, which was reduced to 67% by a B1 antagonist and to 57% by a B2 antagonist infused between days 15 to 22. Thermal hyperalgesia was significantly reduced from 7.25 +/- 0.41 sec (mean +/- SEM) to 8.36 +/- 0.41 sec in paw withdrawal latency on day 22 by a B1 antagonist and from 7.24 +/- 0.19 sec to 8.23 +/- 0.21 sec by a B2 antagonist (P < 0.05). Mechanical hyperalgesia was also ameliorated from 0.02 +/- 0.007 g force to 0.16 +/- 0.08 g force in pain threshold by a B1 antagonist and from 0.03 +/- 0.007 g force to 0.10 +/- 0.003 g force on day 22 by a B2 antagonist. Moreover, deficient B/N-Katholiek rats showed a low incidence of thermal and mechanical hyperalgesia on day 14. Expression of both B1 and B2 receptor mRNAs was detected in the lumbar dorsal ganglia ipsilateral to the site of the nerve injury.

CONCLUSION

These data suggests that kinin were at least partly involved in yielding nociceptor hypersensitivity up to day 14 after CCI. Bradykinin and its B1 and B2 receptors were involved in the maintenance of hyperalgesia.

The renal kallikrein-kinin system: its role as a safety valve for excess sodium intake, and its attenuation as a possible etiologic factor in salt-sensitive hypertension

The distal tubules of the kidney express the full set of the components of the kallikrein-kinin system, which works independently from the plasma kallikrein-kinin system. Studies on the role of the renal kallikrein-kinin system, using congenitally kininogen-deficient Brown-Norway Katholiek rats and also bradykinin B2 receptor knockout mice, revealed that this system starts to function and to induce natriuresis and diuresis when sodium accumulates in the body as a result of excess sodium intake or aldosterone release, for example, by angiotensin II. Thus, it can be hypothesized that the system works as a safety valve for sodium accumulation. The large numbers of studies on hypertensive animal models and on essential hypertensive patients, particularly those with salt sensitivity, indicate a tendency toward the reduced excretion of urinary kallikrein, although this reduction is modified by potassium intake and impaired renal function. We hypothesize that the reduced excretion of the renal kallikrein may be attributable to a genetic defect of factor(s) in renal kallikrein secretion process and may cause salt-sensitive hypertension after salt intake.

Host prostaglandin E(2)-EP3 signaling regulates tumor-associated angiogenesis and tumor growth

Nonsteroidal antiinflammatories are known to suppress incidence and progression of malignancies including colorectal cancers. However, the precise mechanism of this action remains unknown. Using prostaglandin (PG) receptor knockout mice, we have evaluated a role of PGs in tumor-associated angiogenesis and tumor growth, and identified PG receptors involved. Sarcoma-180 cells implanted in wild-type (WT) mice formed a tumor with extensive angiogenesis, which was greatly suppressed by specific inhibitors for cyclooxygenase (COX)-2 but not for COX-1. Angiogenesis in sponge implantation model, which can mimic tumor-stromal angiogenesis, was markedly suppressed in mice lacking EP3 (EP3(-/-)) with reduced expression of vascular endothelial growth factor (VEGF) around the sponge implants. Further, implanted tumor growth (sarcoma-180, Lewis lung carcinoma) was markedly suppressed in EP3(-/-), in which tumor-associated angiogenesis was also reduced. Immunohistochemical analysis revealed that major VEGF-expressing cells in the stroma were CD3/Mac-1 double-negative fibroblasts, and that VEGF-expression in the stroma was markedly reduced in EP3(-/-), compared with WT. Application of an EP3 receptor antagonist inhibited tumor growth and angiogenesis in WT, but not in EP3(-/-). These results demonstrate significance of host stromal PGE(2)-EP3 receptor signaling in tumor development and angiogenesis. An EP3 receptor antagonist may be a candidate of chemopreventive agents effective for malignant tumors.

Bradykinin inhibits development of myocardial infarction through B2 receptor signalling by increment of regional blood flow around the ischaemic lesions in rats

1 To identify the roles of endogenous kinins in prevention of myocardial infarction (MI), we performed the permanent ligation of coronary artery in rats. 2 The size of MI 12, 24, and 48 h after coronary ligation in kininogen-deficient Brown Norway Katholiek (BN-Ka) rats was significantly larger (49.7+/-0.2%, 49.6+/-2%, and 51.1+/-1%, respectively) than that of kinin-replete Brown Norway Kitasato (BN-Ki) rats (42+/-2%, 38.5+/-4%, and 41.5+/-1%). 3 Hoe140, a bradykinin (BK) B(2) receptor antagonist injected (1.0 mg kg(-1), i.v.) half an hour before, and every 8 h after, coronary ligation, significantly increased the size of MI in Sprague-Dawley rats. Aprotinin, a kallikrein inhibitor, which was infused intravenously (10,000 Units kg(-1) h(-1)) with an osmotic mini-pump, significantly increased the size of an MI 24 h after ligation. 4 When evaluated using microspheres, the regional myocardial blood flow around the necrotic lesion in BN-Ka rats 6 h after ligation was reduced more than that in BN-Ki rats with MI by 41-46%. The same was true in Hoe140-treated BN-Ki rats. 5 FR190997, a nonpeptide B(2) agonist, which was infused (10 microg kg(-1) h(-1)) into the vena cava of BN-Ka rats for 24 h with an osmotic mini-pump, caused significant reduction in the size of MI (38+/-3%), in comparison with the size in vehicle solution-treated rats (51+/-3%). The size of MI in FR190997-treated BN-Ka rats was the same as in BN-Ki rats. 6 These results suggested that endogenous kinin has the capacity to reduce the size of MI via B(2) receptor signalling because of the increase in regional myocardial blood flow around the ischaemic lesion.

Experimental study on hepatic reinnervation after orthotopic liver transplantation in rats

BACKGROUND/AIMS

The present study examined whether extrinsic hepatic reinnervation occurred after orthotopic liver transplantation (OLT) in rats.

METHODS

Inbred male Lewis rats were the recipients and females the donors. Tissue specimens were obtained postoperatively from the stump of a recipient's hepatoduodenal ligament (A), and the hepatic hilus (B) and peripheral parenchyma (C) of liver allografts, up to 6 months post-operation. Specimens were subjected to immunohistochemical examination using growth-associated protein (GAP)-43 as an axonal marker and transmission electron microscopy (TEM) for observing regenerating axons, as well as the polymerase chain reaction assay to detect the rat sex-determining region Y (SRY) protein gene of the regenerating nerves.

RESULTS

At site A, GAP-43-positive nerve axons were identified from day 1 to 1 month post-OLT and SRY protein genes were expressed at and after 3 days post-OLT. At site B, GAP-43-positive axons were observed between 3 days and 1 month, and SRY protein genes were detected at 1 month post-OLT and thereafter. TEM confirmed the presence of regenerating axons at and after 3 days post-OLT.

CONCLUSIONS

The results demonstrated that regenerating nerve fibers originating from the recipients reinnervated liver allografts. This extrinsic innervation occurred shortly after OLT, and most likely terminated after about 3 months.

Potassium-induced increase in renal kallikrein secretion is attenuated in dissected renal connecting tubules of young spontaneously hypertensive rats

It is suggested that attenuation of the renal kallikrein-kinin system (KKS) involved the development of hypertension in young spontaneously hypertensive rats (SHR). In the present study, a comparison was made between young SHR and Wistar Kyoto rats (WKY) to examine the ability to secrete renal kallikrein from the microdissected connecting tubules (CNT) by potassium or an ATP-sensitive potassium channel blocker, 4-morpholinecarboximidine-N-1-adamantyl-N'-cyclohexylhydrochloride (PNU-37883A), both of which are renal kallikrein secretagogues. Maximum effect of potassium on kallikrein secretion was observed 10 min after placing the tubules at concentration of 20 mM. Kallikrein secretion was also increased concentration-dependently by PNU-37883A (0.1, 1, 10, and 100 microM). In the presence of EDTA, NiCl2, verapamil, xestspongin C (an inositol 1,4,5-trisphosphate (IP3) receptor-selective antagonist), or ruthenium red (a ryanodine-sensitive receptor blocker), potassium-induced increase in renal kallikrein secretion was inhibited. Augmentation of renal kallikrein secretion by potassium or PNU-37883A was diminished in SHR compared to WKY. These results indicate that the ability to secrete renal kallikrein by potassium was attenuated in young SHR compared with WKY. Furthermore, it is suggested that the potassium-induced renal kallikrein secretion requires an extracellular Ca2+ entry through Ca2+ channels including L-type Ca2+ channels and Ca2+ release from intracellular Ca2+ stores through IP3 receptor and ryanodine receptor.

Role of kinin and prostaglandin in cutaneous thermal nociception

Involvements of kinin and prostaglandin and their interaction in noxious thermal stimuli were investigated in noninflamed and inflamed rats. The nociceptive response was evaluated from the escape latency of foot withdrawal to the thermal stimuli with a beam of light. The escape latency in kininogens-deficient Brown Norway (B/N-) Katholiek rats was significantly longer than that in the normal strain, B/N-Kitasato rats. The latency in B/N-Kitasato rat was prolonged by administration of a bradykinin (BK) B2 receptor antagonist, FR173657 (30 mg/kg, p.o.), whereas it was shortened by pretreatment with a kininase II inhibitor, captopril (10 mg/kg, i.p.). Both agents did not affect the latency in B/N-Katholiek rats. In normal Sprague-Dawley (SD) rat, administration of indomethacin did not change the escape latency against the thermal stimuli. In contrast, administration of indomethacin or a relatively cyclooxygenase-1-selective inhibitor, mofezolac (10 mg/kg, p.o.) significantly reduced numbers of writhing reaction in mice induced by acetic acid solution. Injection of lipopolysaccharide (1 mg/kg, i.v.) resulted in shortening escape latency at 8 h after the injection in B/N-Kitasato rats. This hyperalgesia could be reversed by pretreatment of the rats with indomethacin, a cyclooxygenase-2-selective inhibitor JTE-522 (10 mg/kg, p.o.), or FR173657, but not with mofezolac. The hyperalgesia was not seen in B/N-Katholiek rats. These results indicate that kinin has major participation in peripheral skin thermal nociception under noninflamed condition, although cyclooxygenases may have little participation. Prostaglandins produced by cyclooxygenase-2 could coordinate with BK to elicit hyperalgesia during inflammation induced by lipopolysaccharide.

Cyclooxygenase-2 inhibitors attenuate increased blood pressure in renovascular hypertensive models, but not in deoxycorticosterone-salt hypertension

COX-2 is an inducible cyclooxygenase (COX) that has been reported to be expressed in the macula densa and surrounding cortical thick ascending limb in normotensive rats. The present study assessed the contribution of COX-2 in three different rat models of hypertension, each characterized by a different activation of the renal renin-angiotensin system. Mean blood pressure (MBP) in the rat 2 kidney-1 clip (2K1C) model was significantly reduced with a COX-2 selective inhibitor, NS-398 (10 mg/kg, p.o., twice a day) (vehicle-administered rats (n = 8): 154 +/- 6 mmHg; NS-398-administered rats (n = 5): 128 +/- 10 mmHg). By contrast, a COX-1 selective inhibitor, mofezolac, did not lower MBP. Increased plasma renin activity (23 +/- 8 ng/kg/h (n = 6) vs. sham operation, 2.4 +/- 0.9 ng/kg/h (n = 4)) was markedly reduced to 6.8 +/- 2.7 ng/ml/h (n = 5) by NS-398, but not by mofezolac. The development of 1 kidney-1 clip (1K1C) hypertension was also inhibited by NS-398 (vehicle (n = 12): 133 +/- 1 mmHg; NS-398 (n = 7): 122 +/- 3 mmHg) accompanied by a reduction in plasma renin activity (3.0 +/- 0.3 ng/ml/h, n = 4) to 1.0 +/- 0.2 ng/ml/h (n = 5). The COX-2 inhibitor increased urinary excretions in the 1K1C model, but not in the 2K1C model. In a deoxycorticosterone acetate (DOCA)-salt model, plasma renin activity was markedly suppressed to less than 0.3 ng/ml/h. The COX-2 inhibitor caused no significant changes in MBP, plasma renin activity, or urinary excretion, suggesting that COX-2 made a lesser contribution in this model. Increased expression of COX-2 mRNA and protein was observed in the kidneys of 1K1C and 2K1C rats, but not in DOCA-salt rats. These results suggest that COX-2 plays a significant role in the development of 2K1C and 1K1C renovascular hypertension, in addition to making a substantial contribution to the diuretic effect in the 1K1C model.

Significance of vascular endothelial cell growth factor up-regulation mediated via a chymase-angiotensin-dependent pathway during angiogenesis in hamster sponge granulomas

Chymase is a serine protease responsible for local production of angiotensin (Ang) II from its precursor Ang I in several species, including humans, dogs, and hamsters. We have previously reported that chymase facilitates angiogenesis in sponge granulation tissues via local production of Ang II. Herein, we report the significance of vascular endothelial growth factor (VEGF) up-regulation mediated by Ang II during angiogenesis in hamster sponge granulomas. Treatment of granulation tissues with an anti-VEGF neutralizing antibody or antisense oligomers against VEGF mRNA significantly reduced Ang II-induced angiogenesis, supporting a significant role for VEGF during angiogenesis. In cultured fibroblasts prepared from granulation tissues, VEGF mRNA was up-regulated in response to Ang II within 2 h and this enhanced expression was abolished in the presence of an Ang II type 1 receptor-selective antagonist, an inhibitor of nuclear factor-kappaB activation, or an activator protein-1 inhibitor. To study the significance of local production of Ang II by chymase, we examined the effects of chymostatin on in vivo angiogenesis. We found that chymostatin markedly inhibited both up-regulation of VEGF mRNA and angiogenesis in granulation tissues treated by compound 48/80 or basic fibroblast growth factor. Our results suggest that Ang II directly acts on fibroblasts in granulation tissue to up-regulate VEGF mRNA and thereby induce angiogenesis. Furthermore, a chymase-Ang II-VEGF pathway may operate in granulation tissue as the primary mediator of angiogenesis.

Pharmacokinetics and pharmacodynamics of TF-505, a novel nonsteroidal 5alpha-reductase inhibitor, in normal subjects treated with single or multiple doses

AIMS

To assess the tolerability, pharmacokinetics and pharmacodynamics of a novel nonsteroidal and noncompetitive inhibitor of type I and type II 5alpha-reductases, (-)-(S)-4-[1-[4-[1-(4-isobutylphenyl) butoxy]benzoyl]indolizin-3-yl]butyric acid (TF-505), after single and multiple oral doses in healthy volunteers.

METHODS

In the single-dose study, six young adult males in each dose group received 25 mg or 50 mg of TF-505, and six older males (>or= 40 years) in each dose group received 75 mg or 100 mg of TF-505. The subjects were given the drug in ascending dose and in the fasting state. Six subjects also received 50 mg of TF-505 after breakfast in a two-period crossover manner. In the multiple-dose study, six older males in each dose group received 12.5 mg or 25 mg TF-505 after breakfast daily for 7 days. Plasma concentrations of TF-505, dihydrotestosterone (DHT) and testosterone were measured. The pharmacokinetics of TF-505 were analysed by a compartment model with first-order absorption, first-order elimination and a lag time. Pharmacokinetic and pharmacodynamic relationships were evaluated by indirect response modelling with inhibition of input.

RESULTS

Maximum plasma concentration (Cmax) and the area under the concentration-time curve (AUC) increased proportionately after the single dose up to 50 mg and with the multiple doses. Linearity was not detected between 75 and 100 mg of TF-505. Dose dependency was also noted for the effect of TF-505 on DHT concentrations following single doses up to 50 mg and multiple doses. Plasma DHT concentrations decreased maximally to 58.2, 49.5, 54.2 and 49.8% of basal values at 8-12 h after single administration of 25, 50, 75 and 100 mg TF-505, respectively, and to 60.5 and 49.4% at the 7th and 5th dose following multiple doses of 12.5 and 25 mg TF-505, respectively. The predicted effect curves matched the observed data when the indirect response model was applied to the time course of the suppressant effect of TF-505 on plasma DHT concentrations after both the single and multiple studies. Fifty percent inhibitory concentrations (IC50) of 0.82, 1.48, 1.31 and 0.88 micro g ml(-1), zero-order rate constants for the onset of plasma DHT concentration changes (kin) of 17.8, 17.4, 17.0 and 10.7% h(-1) and first-order rate constants for increase in plasma DHT concentrations to basal values (kout) of 0.17, 0.16, 0.17 and 0.10 h(-1) for the single study at doses of 25, 50, 75 and 100 mg, respectively, were attained. In the multiple-dose study, IC50s were 1.74 and 1.49 micro g ml(-1) for the 12.5 and 25 mg doses, respectively. No serious adverse events related to TF-505 were observed.

CONCLUSIONS

TF-505 was well tolerated in healthy male volunteers. Accumulation of TF-505 in plasma was not observed during multiple dosing. The indirect response model described the relationships between pharmacokinetics and pharmacodynamics of TF-505. Such modelling is expected to yield an appropriate dosage regimen in subsequent clinical trials.

Suppression of dextran sulfate sodium-induced colitis in kininogen-deficient rats and non-peptide B2 receptor antagonist-treated rats

Various proinflammatory mediators are believed to be involved in the processes and symptoms of ulcerative colitis (UC). To determine whether endogenous kinin enhances the severity of UC, we induced experimental colitis (EC) in kininogen-deficient mutant rats and tested the effect of a non-peptide B2 receptor antagonist. EC was induced in male kininogen-deficient Brown Norway-Katholiek rats (BN-Ka) and normal Brown Norway-Kitasato rats (BN-Ki) with 5% dextran sulfate sodium (DSS). Sprague-Dawley rats (SD) were also used. Colon length, body weight and hematocrit were determined for 7 days. Effects of FR173657, an orally active B2 antagonist, were tested. The colon length was shortened in BN-Ki with DSS treatment, but not in BN-Ka, and the difference between their lengths was significant. The hematocrit value was also reduced in BN-Ki, and the difference in hematocrit between BN-Ki and BN-Ka was significant. In SD, shortening of the colon and reduction in hematocrit were also observable, and both were blunted by FR173657. The survival rate in SD given DSS for 7 days was 68%, but FR173657 treatment restored it significantly to 100%. These results suggest that the endogenous kinins generated from the kallikrein-kinin system have a significant role in the development of EC.

Neutrophil elastase inhibitor attenuates lipopolysaccharide-induced hepatic microvascular dysfunction in mice

The present study was conducted to elucidate the role of neutrophil elastase in lipopolysaccharide (LPS)-induced hepatic microvascular injury by using in vivo microscopy. The intravenous (i.v.) injection of LPS (0.1 mg/kg) in male C3H/HeN mice caused significant hepatic microcirculatory dysfunction: leukocyte adhesion to the sinusoids as well as to the venule, and reduced sinusoidal perfusion, in comparison with vehicle-treated mice. Concomitantly, the serum alanine aminotransferase (ALT) activity at 4 h after LPS injection was significantly increased. The serum concentrations of tumor necrosis factor (TNFalpha) and interleukin-1beta (IL-1beta) at 1 h and at 4 h after LPS injection, respectively, were significantly elevated. Neutrophil elastase inhibitors, ONO-5046 (30 and 90 mg/kg, i.v., 0 and 2 h after LPS injection) or FK706 (30 and 100 mg/kg, i.v., 0 and 2 h after LPS injection) minimized the LPS-induced hepatic microcirculatory dysfunction in a dose-dependent manner. Treatment with ONO-5046 and FK706 significantly reduced the ALT level as well as the serum concentrations of TNFalpha and IL-1beta. In addition, ONO-5046 and FK706 attenuated both hepatic microcirculatory dysfunction and liver injury mediated by TNFalpha and IL-1beta (10 microg/kg i.v.). Furthermore, both ONO-5046 and FK706 improved human neutrophil elastase (10 microg/kg i.v.)-induced hepatic microcirculatory dysfunction, although neutrophil elastase did not increase the levels of TNFalpha and IL-1beta. These results suggest that neutrophil elastase aggravates the LPS-induced hepatic microvascular dysfunction. Neutrophil elastase inhibitors attenuate hepatic microvascular dysfunction in response to LPS by inhibiting TNFalpha and IL-1beta production. Neutrophil elastase inhibitors also reduce the microvascular dysfunction mediated by TNFalpha and IL-1beta as well as by neutrophil elastase.

Enhanced exudation of fibrinogen into the perivascular space in acute inflammation triggered by neutrophil migration

OBJECTIVE

The present experiments were performed to ascertain whether or not all plasma components are extravasated when vascular permeability is increased.

ANIMALS

Male Sprague-Dawley strain rats (specific pathogen-free) 8 weeks old (for histamine exudation) or 9-10 weeks old (for carrageenin pleurisy) were used.

METHODS

Histamine or A-carrageenin was injected into the rat right pleural cavity to induce rat pleurisy. Protein components in the inflammatory exudate and plasma were separated by high performance liquid chromatography. Coagulation time was assessed, and the fibrinogen levels in the pleural exudate were determined by thrombin time. The fibrinogen levels were also visualized by immunoblot analysis. Tumor necrosis factor-alpha (TNF-alpha, 0.4 microg/rat, intrapleurally), anti-rat CD18 monoclonal antibody (anti-CD18 antibody, 1 mg/kg, i. v.) and granulocyte-colony stimulating factor (G-CSF, 100 microg/kg, s.c. twice daily for 4 days) were used.

RESULTS

In the histamine-induced extravasation, the level of plasma protein components with large molecules over 900 kD in the exudate was 62% of that in the rat's own plasma. The amount of fibrinogen in the pleural exudate was 1/8 of that in the plasma and was faintly detected in immunoblot analysis, but it was clearly detected after the treatment of rats with TNF-alpha. In rat carrageenin pleurisy, fibrinogen was hardly detected in immunoblot analysis in the exudate collected 0.5 h after carrageenin, when neutrophils did not migrate into the exudate. However, it was clearly present after neutrophil migration started 2 h later The increase in the neutrophil counts in the exudate caused by G-CSF enhanced the fibrinogen level in the exudate, whereas intravenous injection of anti-CD18 antibody suppressed the fibrinogen level in immunoblot analysis.

CONCLUSIONS

Venular permeability increase in the rat histamine exudation induced minimal extravasation of plasma proteins with large molecules, such as fibrinogen, while fibrinogen molecule was detected in rat carrageenin-injected pleurisy, when neutrophil diapedesis occurred. Thus, only when neutrophils started to migrate into the perivascular space was fibrinogen clearly detected in the exudate.

Suppressed angiogenesis in kininogen-deficiencies

We investigated whether the kinin-generating system enhanced angiogenesis in chronic and proliferative granuloma and in tumor-surrounding stroma. In rat sponge implants, angiogenesis was gradually developed in normal Brown Norway Kitasato rats (BN-Ki). The development of angiogenesis was significantly suppressed in kininogen-deficient Brown Norway Katholiek rats (BN-Ka). The angiogenesis enhanced by basic fibroblast growth factor was also significantly less marked in BN-Ka than in BN-Ki. Naturally occurring angiogenesis was significantly suppressed by B(1) or B(2) antagonist. mRNA of vascular endothelial growth factor was more highly expressed in the granulation tissues in BN-Ki than in BN-Ka. Daily topical injections of aprotinin, but not of soy bean trypsin inhibitor, suppressed angiogenesis. Daily topical injections of low-molecular weight kininogen enhanced angiogenesis in BN-Ka. Topical injections of serum from BN-Ki, but not from BN-Ka, also facilitated angiogenesis in BN-Ka. FR190997, a nonpeptide mimic of bradykinin, promoted angiogenesis markedly, with concomitant increases in vascular endothelial growth factor mRNA. Angiogenesis in the granulation tissues around the implanted Millipore chambers containing Walker-256 cells was markedly more suppressed in BN-Ka than in BN-Ki. Our results suggest that endogenous kinin generated from the tissue kallikrein-kinin system enhances angiogenesis in chronic and proliferative granuloma and in the stroma surrounding a tumor. Thus, the agents for the kinin-generating system and/or kinin receptor signaling may become useful tools for controlling angiogenesis.

Blockade of angiotensin AT1a receptor signaling reduces tumor growth, angiogenesis, and metastasis

It was reported that angiotensin II stimulates angiogenesis in vivo, and angiotensin-converting enzyme (ACE) inhibitors inhibit angiogenesis. We found that an AT1-receptor (AT1-R) antagonist, TCV-116, inhibited tumor growth, tumor-associated angiogenesis, and metastasis in a murine model. Tumor growth of Sarcoma 180 (S-180) cells and of fibrosarcoma (NFSA) cells was strongly inhibited by administration of TCV-116 in the diet at a dose of approximately 100 mg/kg/day. This reduction was accompanied with a marked reduction in tumor-associated angiogenesis. The same treatment also reduced the lung metastasis of intravenously injected Lewis lung carcinoma cells. These effects of TCV-116 were equivalent to those of the ACE inhibitor, lisinopril. In S-180 and NFSA tumor tissues, ACE and AT1a receptor (AT1a-R) mRNAs were expressed when assessed with RT-PCR. AT1b receptor and AT2 receptor, however, were not detected. Immunoreactive AT1-R was detected mainly on the neovascularized vascular endothelial cells in which expression was reduced by TCV-116 and lisinopril. These results suggested that TCV-116 inhibits the angiogenesis, growth, and metastasis of tumors highly dependent on AT1a-R blockade. Blockade of AT1a-R signaling may therefore become an effective novel strategy for tumor chemoprevention.

Expression of the interleukin-8 receptors CXCR1 and CXCR2 on cord-blood-derived cultured human mast cells

BACKGROUND

An increase in mast cell number at sites of inflamed tissues has been observed. However, the expression of CXC chemokine receptors on human mast cells is poorly understood.

METHODS

Cultured human mast cells were raised from human umbilical cord blood cells in the presence of stem cell factor and interleukin-6 (IL-6). The expression of surface chemokine receptors on the mast cells was analyzed by flow cytometry and that of mRNA was examined by the method of reverse transcriptase-polymerase chain reaction (RT-PCR). As functional assays for the receptors, mast cell migration was examined by a microchemotaxis assay and changes in the cytosolic free intracellular calcium concentrations ([Ca2+]i) was measured using fura-2-loaded mast cells, respectively.

RESULTS

Expression of IL-8 receptors CXCR1 and CXCR2 was demonstrated by flow cytometry and of both mRNA by RT-PCR; however, CC chemokine receptors including CCR3 were not expressed on cord-blood-derived cultured human mast cells. IL-8 and its homologues showed chemotactic activity toward them in a dose-dependent manner, and IL-8 induced a dose-dependent rapid and transient increase in [Ca2+]i in the mast cells.

CONCLUSIONS

Our results suggest the surface expression of functional CXCR1 and CXCR2 on cord-blood-derived cultured human mast cells.

AT(2) receptor-dependent vasodilation is mediated by activation of vascular kinin generation under flow conditions

Physiological roles of angiotensin II type 2 receptor (AT(2)) are not well defined. This study was designed to investigate the mechanisms of AT(2)-dependent vascular relaxation by studying vasodilation in pressurized and perfused rat mesenteric arterial segments. Perfusion of angiotensin II in the presence of AT(1) antagonist elicited vascular relaxation, which was completely dependent on AT(2) receptors on endothelium. FR173657 (>1 microM), a bradykinin (BK) B(2)-specific antagonist, significantly suppressed AT(2)-dependent vasodilation (maximum inhibition: 68.5% at 10 microM). Kininogen-deficient Brown Norway Katholiek rats showed a significant reduction in AT(2)-mediated vasodilatory response compared with normal wild-type Brown Norway rats. Indomethacin (>1 microM), aprotinin (10 microM) and soybean trypsin inhibitor (10 microM) also reduced AT(2)-dependent vasodilation. Our results demonstrated that stimulation of AT(2) receptors caused a significant vasodilation through local production of BK in resistant arteries of rat mesentery in a flow-dependent manner. Such vasodilation counterbalances AT(1)-dependent vasoconstriction to regulate the vascular tone.

Effect of FR167653, a novel inhibitor of tumor necrosis factor-alpha and interleukin-1beta synthesis on lipopolysaccharide-induced hepatic microvascular dysfunction in mice

Tumor necrosis factor-alpha (TNFalpha) and interleukin-1 (IL-1) have been recognized as key proinflammatory mediators in the pathogenesis of lipopolysaccharide (LPS)-induced liver injury. In the present study we examined the effect of FR167653, a novel inhibitor of TNFalpha and IL-1 synthesis, on the hepatic microvascular response to LPS using in vivo microscopy. Significant hepatic microvascular responses comprising leukocyte adhesion to the sinusoidal wall and central venules and reduced sinusoidal perfusion appeared 2 and 4 h after LPS (0.1 mg/kg, i.v.) injection in male C3H/HeN mice (LPS sensitive) when compared with male C3H/HeJ mice (LPS resistant). The serum concentrations of TNFalpha at 1.5 h and IL-1beta at 4 h after injection of LPS, as determined by enzyme-linked immunosorbent assay, were significantly higher in C3H/HeN mice than in C3H/HeJ mice. Administration of murine TNFalpha or IL-1beta (10 microg/kg., i.v., respectively) in both C3H/HeN and C3H/HeJ mice elicited the hepatic microvascular responses that were similar to those produced by LPS injection in C3H/HeN mice. FR167653 (1 and 10 mg/kg, i.v., 0 and 2 h after LPS injection) significantly reduced leukocyte adhesion and restored sinusoidal perfusion in a dose-dependent manner in C3H/HeN mice 4 h after LPS injection. The levels of TNFalpha, IL-1beta, and alanine aminotransferase also were significantly lower in FR167653-treated endotoxemic C3H/HeN mice than those in vehicle-treated endotoxemic animals. The results suggest that the hepatic microvascular response to LPS is partly mediated by TNFalpha and IL-1beta, and that FR167653 prevents LPS-induced hepatic microcirculatory dysfunction by inhibiting the production of TNFalpha and IL-1beta.

Cyclooxygenase-2 and adenylate cyclase/protein kinase A signaling pathway enhances angiogenesis through induction of vascular endothelial growth factor in rat sponge implants

Angiogenesis is reportedly enhanced by prostaglandins (PGs). In the present experiment, we tested whether or not COX-2 and adenylate cyclase/protein kinase A (AC/PKA)-dependent VEGF induction enhanced angiogenesis in this model. Angiogenesis was enhanced by topical injection of human recombinant basic fibroblast growth factor (bFGF). The enhanced angiogenesis by bFGF was inhibited by indomethacin or selective COX-2 inhibitors, NS398, nimesulide, and JTE-522. Topical daily injections of 8-bromo-cAMP enhanced angiogenesis in a dose-dependent manner. Forskolin, an activator of AC, also facilitated angiogenesis in a dose-dependent manner, as did amrinone, an inhibitor of phosphodiesterase. VEGF induction was confirmed by the increased levels in the fluids in the sponge matrix after topical injection of 8-bromo-cAMP. Immunohistochemical investigation further revealed the VEGF-expressed cells in the sponge granulation tissues to be fibroblasts, and the intensity of positive reactions was enhanced by bFGF, 8-bromo-cAMP, forskolin, and amrinone. Angiogenesis was inhibited by indometacin or selective COX-2 inhibitors, NS-398, nimesulide, and JTE-522. In addition, angiogenesis without topical injections of the above compounds was also suppressed by SQ22,536, an inhibitor for AC. or H-89, an inhibitor for PKA, with concomitant reductions in VEGF levels. Daily topical injections of neutralizing antibody or anti-sense oligonucleotide against VEGF significantly suppressed angiogenesis. These results suggested that COX-2 and AC/PKA-dependent induction of VEGF certainly enhanced angiogenesis, and that pharmacological tools for controlling this signaling pathway may be able to facilitate the management of conditions involving angiogenesis.

Roles of bradykinin in vascular permeability and angiogenesis in solid tumor

Bradykinin (BK) is involved in tumor angiogenesis. To elucidate the mechanism underlying BK-induced angiogenesis, we evaluated the roles of BK in tumor-associated vascular permeability and angiogenesis in the different phases of tumor development in mice bearing sarcoma 180 cells. The vascular permeability was significantly enhanced in the early growth phase (which peaked at day 5), and was thereafter markedly reduced. By contrast, tumor angiogenesis increased gradually over a 20-day experimental period. Oral administration of a B2 receptor antagonist, FR173657 (30 mg/kg/day), significantly suppressed the vascular permeability, but a B1 antagonist, desArg10-Hoe140 (1 mg/kg/day) did not. An immunohistochemical study revealed the presence of immunoreactive B2 receptor in the endothelial cells in the early phase, whereas B2 receptors were also observed in the stromal fibroblasts in the late phase. We also found that VEGF was detected exclusively in the stromal fibroblasts only in the late phase. Furthermore, VEGF immunoreactivity was attenuated by the treatment with FR173657. Tumor angiogenesis was significantly reduced by treating the tumor tissues with FR173657 both in the early phase (days 1-6, 30 mg/kg/day, oral administration) and in the late phase (days 7-12, 30 mg/kg/day, oral administration), whereas it was inhibited by neutralization with anti-VEGF antibody (1 microg/site/day, local injection) only in the late phase. These results suggest that BK would promote angiogenesis by increasing vascular permeability in the early phase via B2 receptor in the endothelial cells and by promoting up-regulation of VEGF via B2 receptor in the stromal fibroblasts in the late phase.

Nitric oxide is generated in smooth muscle layer by neurokinin A and counteracts constriction in guinea pig airway

It has been reported that several bronchoconstrictors generate nitric oxide (NO), counteracting bronchoconstriction, and removal of bronchial epithelia reduces NO production. However, it has not been elucidated whether neurokinin A (NKA), a potent bronchoconstrictor liberated from nerve terminals, generates NO. Specific questions in this study were (1) does NKA also generate NO, (2) does NO counteract NKA-induced bronchoconstriction, and (3) does the NO generation require bronchial epithelial cells? In an in vivo study exogenous as well as endogenous (capsaicin-induced) NKA increased airway opening pressure (P(ao)) and the exhaled NO level, and both were inhibited by an antagonist selective for NK(2) receptor (a receptor for NKA), SR48968. The exhaled NO level became negligible with an inhibitor of NO synthase (NOS) type 1-3 (N(G)-nitro-L-arginine methyl ester, L-NAME) with increased P(ao), but not with a NOS type 2 inhibitor. In an in vitro study, NKA increased the nitrite/nitrate level in superfused fluid of tracheal segments. Removing smooth muscle reduced nitrite/nitrate in the fluid to negligible levels, while the level was unchanged with removal of the epithelia. Pretreatment with l-NAME enhanced the tension of epithelia-removed tracheal segments. These findings indicate that (1) NKA generates NO, (2) NO counteracts NKA-induced bronchoconstriction, and (3) NKA activates NOS in the muscle layer, independently of bronchial epithelia.

Blockade of bradykinin B(2) receptor suppresses acute pancreatitis induced by obstruction of the pancreaticobiliary duct in rats

1. The involvement of bradykinin (BK) B(2) receptor in acute pancreatitis induced by pancreaticobiliary duct ligation was investigated in rats. 2. The activities of amylase and lipase in the serum, the water content of the pancreas, and vacuolization of the acinar cells were significantly increased 2 h after obstruction of the duct in Sprague-Dawley rats. 3. Elevated serum amylase activity, increased pancreatic oedema, and damage of the pancreatic tissue were significantly less marked in plasma kininogen-deficient, B/N-Katholiek rats than in the normal strain, B/N-Kitasato rats 2 h after the ligation. 4. Obstruction of the pancreaticobiliary duct augmented the level of (1-5)-BK (Arg(1)-Pro(2)-Pro(3)-Gly(4)-Phe(5)), a stable BK metabolite, in the blood from 73.0+/-21.7 pg ml(-1) at 0 h to 149.8+/-38.0 pg ml(-1) at 2 h after the induction of pancreatitis in SD rats. 5. Administration of a BK B(2) receptor antagonist, FR173657 (100 mg kg(-1), p.o.) or Hoe140 (100 nmol kg(-1), s.c.), reduced the elevation of amylase and lipase activities in the serum and of pancreatic water content in a dose-dependent manner. The effective attenuation of oedema formation and vacuolization by the antagonists was also confirmed light-microscopically. In contrast, treatment with gabexate mesilate or indomethacin did not cause significant suppression of the pancreatitis. 6. These findings suggest a possible involvement of kinin B(2) receptor in the present pancreatitis model. Furthermore, they point to the potential usefulness of the B(2) receptor in clinical acute pancreatitis.

A potential role of bradykinin in angiogenesis and growth of S-180 mouse tumors

Angiogenesis is an important event in tumor growth. We evaluated the contribution of endogenous bradykinin to tumor-associated angiogenesis and tumor growth using pharmacological approaches in mice bearing sarcoma 180 cells. The weight of implanted tumors increased in parallel with increased hemoglobin contents (a parameter to evaluate angiogenesis) over a 20-day experimental period. Daily administration of bradykinin B2-receptor antagonists, Hoe140 (0.1 and 1 mg/kg per day, local injection) or FR173657 (30 mg/kg per day, p.o.), significantly suppressed the increment in angiogenesis and tumor weight, but a B1-receptor antagonist, desArg10-Hoe140 (1 mg/kgperday), did not. Administration of a plasma kallikrein inhibitor, soybean trypsin inhibitor (3 mg/site per day), significantly suppressed angiogenesis and tumor growth. In contrast, bradykinin-degrading enzyme inhibitors, captopril and phosphoramidon (500 microg/site per day), enhanced angiogenesis and increased tumor weight. Our results suggest that bradykinin, produced by plasma kallikrein or plasma kallikrein-like enzymes, promote tumor-associated angiogenesis and tumor growth in vivo.

Effect of neutral endopeptidase inhibitor on bradykinin-induced bronchoconstriction

To evaluate whether neutral endopeptidase (NEP) inhibitors have adverse respiratory effects, the influence of a NEP inhibitor on bradykinin (BK)-induced bronchoconstriction was investigated. In anesthetized and artificially ventilated guinea pigs, changes in airway opening pressure (Pao) were measured as an index of bronchoconstriction. An infusion of phosphoramidon (3 mg kg(-1) h(-1)), a NEP inhibitor, significantly enhanced the bronchoconstriction induced by high-dose BK (30 nmol kg(-1), i.v.). Capsaicin (0.1 mg kg(-1), i.v.) and SR48968 (0.3 mg kg(-1), i.v.), an NK2 receptor antagonist, significantly inhibited the phosphoramidon-induced enhancement of BK-induced bronchoconstriction, although FK888 (3 mg kg(-1), i.v.), an NK1 receptor antagonist, did not. Both neurokinin A (NKA) (0.1-3 nmol kg(-1), i.v.) and substance P (SP) (0.1-3 nmol kg(-1), i.v.) induced dose-dependent bronchoconstriction which was enhanced by phosphoramidon infusion, although these enhancements were more prominent in the NKA series. Phosphoramidon partially inhibited BK degradation in lung homogenate, and both NKA and SP degradation in the lung homogenate were significantly suppressed by phosphoramidon. In bronchoalveolar lavage fluid (BALF), levels of NKA and SP were significantly elevated after a bolus of BK with a phosphoramidon infusion. These results suggest that NEP inhibitors may have adverse respiratory effects resulting from inhibition of the degradation of neurokinins, but mainly of NKA, when a large amount of BK is generated.

Adenylate cyclase/protein kinase A signaling pathway enhances angiogenesis through induction of vascular endothelial growth factor in vivo

We previously reported that endogenous prostaglandins (PGs) may increase cAMP facilitated angiogenesis through the induction of vascular endothelial growth factor (VEGF) in rat sponge implantation models. In the present experiment, we tested whether or not adenylate cyclase / protein kinase A (AC/PKA)-dependent VEGF induction enhanced angiogenesis in this model. Topical daily injections of 8-bromo-cAMP enhanced angiogenesis in a dose-dependent manner. Forskolin, an activator of AC, also facilitated angiogenesis as did amrinone, an inhibitor of phosphodiesterase. VEGF induction was confirmed by the increased levels in the fluids in the sponge matrix after topical injection of 8-bromo-cAMP. Immunohistochemical investigation further revealed the VEGF-expressed cells in the sponge granulation tissues to be fibroblasts, and the intensity of positive reactions was enhanced by 8-bromo-cAMP, forskolin and amrinone. Angiogenesis without topical injections of the above compounds was suppressed by SQ22,536, an inhibitor for AC, or H-89, an inhibitor for PKA, with concomitant reductions in VEGF levels. Daily topical injections of neutralizing antibody or anti-sense oligonucleotide against VEGF significantly suppressed angiogenesis. PGE2-induced angiogenesis was suppressed with SQ22,536 or H-89. These results suggested that AC/PKA-dependent induction of VEGF certainly enhanced angiogenesis and that pharmacological tools for controlling this signaling pathway may be able to facilitate the management of conditions involving angiogenesis.