An NF-κB pathway-mediated positive feedback loop amplifies Ras activity to pathological levels in mice.

Genetic mutations that give rise to active mutant forms of Ras are oncogenic and found in several types of tumor. However, such mutations are not clear biomarkers for disease, since they are frequently detected in healthy individuals. Instead, it has become clear that elevated levels of Ras activity are critical for Ras-induced tumorigenesis. However, the mechanisms underlying the production of pathological levels of Ras activity are unclear. Here, we show that in the presence of oncogenic Ras, inflammatory stimuli initiate a positive feedback loop involving NF-κB that further amplifies Ras activity to pathological levels. Stimulation of Ras signaling by typical inflammatory stimuli was transient and had no long-term sequelae in wild-type mice. In contrast, these stimuli generated prolonged Ras signaling and led to chronic inflammation and precancerous pancreatic lesions (PanINs) in mice expressing physiological levels of oncogenic K-Ras. These effects of inflammatory stimuli were disrupted by deletion of inhibitor of NF-κB kinase 2 (IKK2) or inhibition of Cox-2. Likewise, expression of active IKK2 or Cox-2 or treatment with LPS generated chronic inflammation and PanINs only in mice expressing oncogenic K-Ras. The data support the hypothesis that in the presence of oncogenic Ras, inflammatory stimuli trigger an NF-κB-mediated positive feedback mechanism involving Cox-2 that amplifies Ras activity to pathological levels. Because a large proportion of the adult human population possesses Ras mutations in tissues including colon, pancreas, and lung, disruption of this positive feedback loop may be an important strategy for cancer prevention.

Characteristics of gabexate mesilate-induced cell injury in porcine aorta endothelial cells.

Gabexate mesilate (GM), a serine protease inhibitor, often causes severe vascular injury, when injected in high concentration. In the present study, we investigated the mechanisms for the cytotoxicity of GM on porcine aorta endothelial cells (PAECs). GM (0.5 - 5.0 mM) decreased cell viability in a dose-dependent manner and caused cell injury, whilst nafamostat mesilate (NM), another serine protease inhibitor, or mesilate itself had no effect on cell viability. zVAD-fmk, a pancaspase inhibitor, or zDEVD-fmk, a caspase-3 inhibitor, did not affect the GM (1.5 mM)-induced decrease of cell viability. Apoptotic cells or DNA fragmentation were also not observed after GM treatment. Moreover, Ca(2+) chelators, a nitric oxide (NO) synthase inhibitor, antioxidants, and radical scavengers had no effect on the GM-induced cell injury. On the other hand, cellular ATP content was decreased in the GM (2.0 mM)-treated cells. Surprisingly, GM (2.0 mM) immediately increased cellular uptake of propidium iodine. These findings suggest that GM induces necrotic cell death via injury of the cell membrane.

Morphological relationship between intercalated duct and pancreatic islet in streptozotocin and/or camostat mesilate administrations in the chicken.

Present electron microscopical and immunocytochemistrical studies elucidated some morphological relationship between intercalated duct (ICD) and pancreatic islet cells in the chicken in streptozotocin (STZ) and/or camostat mesilate (CM) administrations. Twenty-one chickens were set into four experimental groups: (1) control group, (2) STZ administration group, (3) CM administration group, and (4) STZ + CM administration group. Cytoplasms of ICD cells stained more strongly with eosin in STZ administration group than other groups, and electron-dense materials and intercalated processes between ICD and islet cells were also increasing in time dependence in STZ administration. Number of pancreatic islet in STZ + CM co-administration was about 3.1 times larger than other groups. Many small sized cells were detected at surrounding area of ICD and they incorporated 5-bromo-2'-deoxyuridine better than other experimental groups. Present morphological data suggested that ICD cells might support some tolerances of pancreatic endocrine cells against toxic substances and also involve in regeneration of new pancreatic islet cells in STZ + CM co-administration.