Akio Nakatsuka

Unproductive cleavage and the inactivation of protease‐activated receptor‐1 by trypsin in vascular endothelial cells

Using fura‐2 fluorometry of [Ca2+]i in response to thrombin, trypsin and protease‐activated receptor activating peptides (PAR‐APs), we determined whether trypsin cleaves protease‐activated receptor 1 (PAR1) and activates it in the endothelial cells of the porcine aortic valves and human umbilical vein. Once stimulated with thrombin, the subsequent application of trypsin induced a [Ca2+]i elevation similar to that obtained without the preceding stimulation with thrombin in the valvular endothelial cells. However, the preceding stimulation with trypsin abolished the subsequent response to thrombin, but not to bradykinin or substance P. The response to PAR1‐AP (SFLLRNP) was significantly (P<0.05) reduced by the preceding stimulation with thrombin and PAR1‐AP in the valvular endothelial cells, while, importantly, it remained unaffected by the preceding stimulation with either trypsin or PAR2‐AP (SLIGRL). The response to PAR2‐AP was reduced by the preceding stimulation with trypsin and PAP2‐AP. PAR1‐AP attenuated the subsequent responses not only to thrombin and PAR1‐AP but also to trypsin and PAR2‐AP, while PAR2‐AP specifically attenuated the subsequent responses to trypsin and PAR2‐AP. In human umbilical vein endothelial cells, a higher affinity PAR1‐AP (haPAR1‐AP) (Ala‐pF‐Arg‐Cha‐HArg‐Tyr‐NH2) specifically attenuated the responses to thrombin but not trypsin. On the other hand, the response to haPAR1‐AP was significantly (P<0.05) attenuated by the preceding stimulation with thrombin but not trypsin. In conclusion, trypsin cleaved PAR1 but did not activate it in the endothelial cells. Moreover, the trypsin‐cleaved PAR1 was no longer responsive to thrombin.

“Mass-forming” pancreatitis masquerades as pancreatic carcinoma

SummaryConclusionWhen a patient with a hypervascular pancreatic mass has a history of alcoholism and pancreatitis, and normal serum levels of CA 19-9, mass-forming pancreatitis should be kept in mind as a differential diagnosis of pancreatic carcinoma.BackgroundChronic and/or acute pancreatitis sometimes produces a pancreatic mass; and differentiation from pancreatic carcinoma is of clinical importance.MethodsA total of 13 Japanese patients with mass-forming pancreatitis were retrospectively reviewed in order to clarify clinical features which can differentiate between mass-forming pancreatitis and pancreatic carcinoma.ResultsSix of the 13 paitents had a history of chronic pancreatitis or acute pancreatitis from 8 mo to 11 yr previously. Eleven patients were alcoholic. Serum carcinoembryonic antigen and carbohydrate antigen 19-9 levels were within normal limit in 9 of 12 patients examined and in all 12 patients ecamined, respectively. The pancreatic mass was located in the head of the pancreas in 9 patients, in the body in 1 and in the tail in 3. The mean greatest diameter of the mass was 2.8 cm. Six of the 13 pancreatic masses were hypoechoic by ultrasonography. Ten of the 13 pancreatic masses were of low-density by computed tomography. Two of the five masses examined were hypervascular at arterial and/or venous phase by angiography. Significant factors differentiating from pancreatic carcinoma were age, alcoholism, history of pancreatitis, serum levels of CA 19-9 and hypervascularity. Follow-up ultrasonography and/or computed tomography showed diminution of the mass in 1 to 2 mo in four patients, together with decrease of serum carcinoembryonic antigen and/or carbohydrate antigen 19-9 levels in two of the four patients.

Hepatocyte growth factor and invasion-stimulatory activity are induced in pleural fluid by surgery in lung cancer patients

Hepatocyte growth factor (HGF) is a stromal cell-derived cytokine that can stimulate matrix invasion by carcinoma cells. We analysed the concentrations of HGF and invasion-stimulatory activity in pleural fluid after lung surgery. The concentration of HGF in pleural fluids was measured by enzyme-linked immunosorbent assay in seven patients who underwent pulmonary resection for primary or metastatic lung cancer. The effect of the pleural fluid on cancer cell invasion across reconstituted basement membrane (Matrigel) was assessed with a Boyden chamber assay using a lung adenocarcinoma cell line, A549. HGF levels in the pleural fluid after lung surgery ranged from 6.0 to 23.0 ng ml–1 (average: 10.2 ± 4.3 ng ml–1). The matrix invasion of lung carcinoma cells in the presence of the pleural fluid was significantly higher than that in the presence of culture medium alone or sera from normal subjects (P < 0.01). The invasion-stimulatory activity of the pleural fluid was strongly inhibited by HGF-neutralizing antibody. Positive correlation was found between the HGF level and invasion-stimulatory activity in the pleural fluids and normal sera (P = 0.0073). This is the first report demonstrating that the lung surgery induces a considerable amount of HGF, which is closely correlated with the invasion-stimulatory activity of the pleural fluid.