Kazuhisa Kamata

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 B1 or B2 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.

Endogenous prostaglandin I2 regulates the neural emergency system through release of calcitonin gene related peptide.

Background: We previously reported that endogenous prostaglandin I2, generated by a mild irritant, sensitised calcitonin gene related peptide (CGRP) containing sensory nerves and facilitated the release of CGRP and gastric mucosal protection against ethanol. Administration of capsaicin also inhibited ethanol induced gastric mucosal injury through immediate release of CGRP from primary sensory neurones, which is termed the neural emergency system. In the present study, we tested whether endogenous prostaglandin I2 also modulates the cytoprotective action of capsaicin using prostaglandin I receptor knockout mice (IP−/−). Methods: The stomachs of IP−/− or their wild-type counterparts (IP+/+), anaesthetised with urethane (1.225 g/kg), were doubly cannulated from the oesophageal and duodenal sides, and the gastric mucosa was perfused (1 ml/min) with physiological saline. Perfusate was changed to 50% ethanol alone, or 50% ethanol containing capsaicin (16∼1600 μM). The injured area was estimated at the end of each perfusion experiment. In some animals, CGRP-(8–37), a CGRP antagonist (0.3 mg/kg), or indomethacin (1 mg/kg) was intravenously injected before perfusion of 50% ethanol containing capsaicin. Results: Capsaicin inhibited the injured area in a dose dependent manner. Fifty per cent ethanol containing capsaicin (480 μM) immediately increased intragastric levels of CGRP although 50% ethanol alone did not. The protective action of capsaicin (480 μM) against ethanol was completely abolished by intravenous injection of CGRP-(8–37). Indomethacin also inhibited the protective action of capsaicin, and this was accompanied by reduced levels of intragastric CGRP. Intragastric levels of prostaglandin E2 were not increased by capsaicin treatment but those of 6-keto-prostaglandin F1α, a metabolite of prostaglandin I2, were markedly increased. No protective action of capsaicin was observed in IP−/− which lacked the ability to increase intragastric CGRP levels in response to ethanol containing capsaicin. The CGRP content of the stomach from untreated IP−/− did not differ from those in IP+/+. Capsaicin (160 μM) together with intragastric perfusion of beraprost sodium (PGI2 analogue, 2.5 μg/ml) showed enhanced protection against ethanol induced injury. This enhanced protection was completely blocked by intravenous injection of CGRP-(8–37). Conclusions: The present results suggest that endogenous prostaglandin I2 enhances the protective action of the capsaicin mediated neural emergency system against ethanol induced gastric mucosal injury through enhancement of CGRP release.

Calcitonin gene‐related peptide released by capsaicin suppresses myoelectrical activity of gastric smooth muscle

Background:  It is widely accepted that the inhibition of gastric motor activity as well as the maintenance of gastric mucosal blood flow and mucous secretion are important for the homeostasis of the gastric mucosa. The present study was performed to ascertain whether or not capsaicin, which can protect the stomach from noxious stimuli, affects gastric motor activity.

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.

Prevention of Ethanol-induced Gastric Mucosal Microcirculatory Disturbances by Mild Irritant Through the Actions of Calcitonin Gene-Related Peptide and Prostaglandin I2 in Rats

Disturbances in the gastric mucosal microcirculation are thought to be an important cause of injury, and observation of the microcirculation is therefore important for revealing the pathophysiology of that injury. In the present study, we investigated the mechanism of adaptive cytoprotection of 1 M NaCl against ethanol [1] by observing the microcirculation in the basal part of the gastric mucosa of rats using intravital microscopy [2–4] to clarify the mediators involved in the maintenance of the integrity of the mucosal blood flow.