We analyzed Ca2+-permeating nonselective cation channels (NSCs) mediating thrombin-induced contraction of human umbilical vein endothelial cells (HUVECs). A Ca2+ chelater, BAPTA-AM (10μM), significantly inhibited the thrombin-induced contraction of HUVECs.Thrombin induced inward currents at -60mV in the presence of intracellular MgATP. Removal of extracellular Ca2+ significantly decreased the currents. A selective phospholipase C inhibitor, U73122 (1μM) but not its inactive analogue, U73343 (1μM) almost completely inhibited the currents. Neither a selective inhibitor of Ca2+-ATPase of endoplasmic reticulum, thapsigargin (1μM) nor a diacylglycerol analogue, 1-oleoyl-2-acetyl-glycerol (30μM) activated the currents. However, a selective protein kinase C inhibitor, bisindolylmaleimide I (500nM) significantly inhibited the currents. The thrombin-induced currents were significantly inhibited by SKF96365 (50μM) but not by La3+ (1mM), ruthenium red (10μM) or flufenamic acid (100μM). As assessed with RT-PCR, HUVECs expressed transient receptor potential (TRP) M4,7, TRPV1,2,4, TRPC1,4 and 6 subunits of NSCs. These results indicate that thrombin activates Ca2+-permeating NSCs containing TRPC4 through protein kinase C in HUVECs. Thus, drugs specifically inhibiting TRPC4-containing channels might be effective to control fatal diseases such as sepsis where thrombin mediates the vicious cycle between inflammation and coagulation.
A 48-year-old man was admitted to our hospital after suffering from fever, dyspnea, and disturbance of gait for four days before admission. A chest X-ray taken in the emergency unit showed ground glass-like infiltrates in the left upper lung field and blood examinations demonstrated increases in serum CRP, CPK, and AST and a decrease in sodium. Bacterial pneumonia was diagnosed and the patient was started on intravenous administration of doripenem. On hospital day 2, a second chest X-ray revealed that the infiltration had worsened, causing exacerbation of his hypoxemia. We immediately shifted to a combination therapy of pazufloxacin, minomycin, and erythromycin since the Legionella species was suspected to be infecting bacterium. Legionella antigen present in urinalysis on day 3 confirmed this diagnosis. However, the patient’s respiratory condition had rapidly deteriorated, necessitating the use of a respirator. His condition gradually improved with the intensive treatment and he was discharged on hospital day 23. Prompt diagnosis and treatment is necessary for Legionella pneumonia since this disease is one of the main sources of communityacquired pneumonia causing severe symptoms despite of appropriate treatment. Thus, clinicians should bear Legionella pneumonia in mind when treating cases with suspected pneumonia who show the specific clinical findings of this disease, such as an increase in serum AST and a decrease in sodium.
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