Aberrant activation of atypical protein kinase C in carbon tetrachloride-induced oxidative stress provokes a disturbance of cell polarity and sealing of bile canalicular lumen.

Polarized hepatocytes contain tight junctions (TJs), which are among the most important junctions for sealing the bile canalicular lumen from the sinusoidal space. Alterations in TJs are implicated in chronic cholestatic liver diseases, such as primary biliary cirrhosis and primary sclerosing cholangitis, which have lipid peroxidation marker elevations or antioxidant vitamin decreases. However, the effect of oxidative stress on hepatocyte polarity or liver morphology is unknown. We found that carbon tetrachloride (CCl4)-induced oxidative stress resulted in disassembly of TJs. Ultrastructural analysis revealed disruption in TJs, Golgi morphology, and expansion of the bile canalicular lumen size in CCl4-treated hepatocytes. The Par complex [Par-3-atypical protein kinase C (aPKC) and Par-6 ternary complex] regulates TJs and lumen formation, and the Par-3-aPKC complex formation was inhibited by CCl4 treatment. Moreover, the antioxidant compound vitamin E prohibited a CCl4-induced disturbance in TJs and Par-3-aPKC complex formation. aPKC phosphorylates Par-3 and down-regulates its own affinity with Par-3. Importantly, aPKC kinase activity and Par-3 phosphorylation were significantly increased in CCl4-treated rat livers. These results indicate that the Par-3-aPKC complex plays a crucial role in the maintenance of hepatocyte polarity and sealing of the bile canalicular lumen. Our findings suggest that bile canalicular lumen expansion might explain the presence of cholestasis in patients with primary biliary cirrhosis and primary sclerosing cholangitis.

Carbon tetrachloride-induced hepatic injury through formation of oxidized diacylglycerol and activation of the PKC/NF-κB pathway.

Protein kinase C (PKC) participates in signal transduction, and its overactivation is involved in various types of cell injury. PKC depends on diacylglycerol (DAG) for its activation in vivo We have previously reported that DAG peroxides (DAG-O(O)H) activate PKC in vitro more strongly than unoxidized DAG, suggesting that DAG-O(O)H, if generated in vivo under oxidative stress, would act as an aberrant signal transducer. The present study examined whether DAG-O(O)H are formed in carbon tetrachloride (CCl(4))-induced acute rat liver injury in association with activation of the PKC/nuclear factor (NF)-κB pathway. A single subcutaneous injection of CCl(4) resulted in a marked increase in hepatic DAG-O(O)H content. At the molecular level, immunohistochemistry and subcellular fractionation combined with immunoblotting localized PKCα, ßI, ßII and δ isoforms to cell membranes, while immunoblotting showed phosphorylation of the p65 subunit of NF-κB, and immunoprecipitation using isoform-specific anti-PKC antibodies revealed specific association of PKCα and p65. In addition, expression of tumor necrosis factor α (TNFα) and neutrophil invasion increased in the CCl(4)-treated rats. Furthermore, we demonstrated that Vitamin E, one of the most important natural antioxidants that suppresses peroxidation of membrane lipids, significantly inhibited the CCl(4)-induced increase in hepatic DAG-O(O)H content and TNFα expression as well as phosphorylation of PKCα and p65. These data demonstrate for the first time that DAG-O(O)H are generated in the process of CCl(4)-induced liver injury, resulting in activation of the PKC/NF-κB pathway and TNFα-mediated aggravation of liver injury.

Reduced Expression of Hugl 1 Contributes to the Progression of Lung Squamous Cell Carcinoma.

Cell polarity and cell-cell adhesion play a critical role in the regulation of normal tissue architecture and function. Disruption of cell adhesion and cell polarity is often associated with neoplastic tumors. Loss of apical-basal polarity in epithelial cells is one of the hallmarks of aggressive and invasive cancers. Several polarity proteins including atypical protein kinase C (aPKC), Par 6, Par 3, and Lethal giant larvae (Lgl, the human homologues of which are called Hugl 1 and Hugl 2) are localized at the leading edge of migrating cells, and play critical roles during directional migration. Herein, we investigated the expression of aPKC, Par 6, Par 3, Hugl 1, and Hugl 2 in lung squamous cell carcinoma (SqCC). An inverse correlation was observed between the expression of Hugl 1 and lung SqCC progression. Results of immunohistochemistry and real-time RT-PCR analyses showed that reduced expression of Hugl 1 predicts poor survival in lung SqCC patients. The expression of Hugl 1 was inversely correlated with both overall survival rate and tumor stage. On the other hand, no associations were observed between the expressions of Hugl 2, Par 6, and Par 3 and lung SqCC progression. These findings indicate that the reduced expression of Hugl 1 could be considered as a poor prognostic factor in human lung cancers.

Notch signaling may be involved in the abnormal differentiation of epidermal keratinocytes in psoriasis.

Localization of each keratin isoform differs among epidermal layers. Proliferating basal cells synthesize keratin 14 (K14) and suprabasal cells express keratin 10 (K10) in normal skin. Notch signaling is essential for keratinocyte differentiation. Notch1 is expressed in all epidermal layers, Notch2 in the basal cell layer and Notch3 in basal cell and spinous cell layers in normal epidermis. It has been poorly elucidated how localization and expression levels of Notch molecules are related to epidermal molecular markers K10 and K14 in psoriatic skin with abnormal differentiation of epidermal tissue. This study aimed to investigate the relationship between abnormal differentiation of epidermal cells in psoriatic skin and expression of Notch molecules. We investigated keratins (K14 and K10) and Notches (1, 2, 3 and 4) using immunohistochemistry in psoriatic skin (n=30) and normal skin (n=10). In normal skin, K14 and K10 were discretely observed in the basal cell layer and suprabasal layer, respectively. In psoriatic skin, K14 was expressed in the pan epidermal layer while it and K10 were co-expressed in some middle suprabasal layer cells. Notch1, 2, 3, and 4 localized in all epidermal layers in normal skin. In psoriatic skin, Notch1, 2, and 4 mainly localized in suprabasilar layers and Notch3 is lacalized in pan epidermal, suprabasilar, and basilar layers. Protein and mRNA of Notch1, 2, and 3 isoforms decreased in psoriatic epidermis compared with normal epidermis. These data suggest that decrements in these Notch molecules might cause aberrant expression of K10 and K14 leading to anomalous differentiation of the epidermis in psoriatic lesions.

Localization of aPKC lambda/iota and its interacting protein, Lgl2, is significantly associated with lung adenocarcinoma progression.

Atypical protein kinase C lambda/iota (aPKC λ/ι) is expressed in several human cancers; however, the correlation between aPKC λ/ι localization and cancer progression in human lung adenocarcinoma (LAC) remains to be clarified. We found that patients with a high level of aPKC λ/ι expression in LAC had significantly shorter overall survival than those with a low level of aPKC λ/ι expression. In addition, localization of aPKC λ/ι in the apical membrane or at the cell-cell contact was associated with both lymphatic invasion and metastasis. The intercellular adhesion molecule, E-cadherin, was decreased in LACs with highly expressed aPKC λ/ι at the invasion site of tumor cells. This result suggested that the expression levels of aPKC λ/ι and E-cadherin reflect the progression of LAC. On double-immunohistochemical analysis, aPKC λ/ι and Lgl2, a protein that interacts with aPKC λ/ι, were co-localized within LACs. Furthermore, we found that Lgl2 bound the aPKC λ/ι-Par6 complex in tumor tissue by immune-cosedimentation analysis. Apical membrane localization of Lgl2 was correlated with lymphatic invasion and lymph node metastasis. These results thus indicate that aPKC λ/ι expression is altered upon the progression of LAC. This is also the first evidence to show aPKC λ/ι overexpression in LAC and demonstrates that aPKC λ/ι localization at the apical membrane or cell-cell contact is associated with lymphatic invasion and metastasis of the tumor.

A case of pancreatic solid-pseudopapillary neoplasm with marked ossification.

A cystic lesion of the pancreas was detected in a 25-year-old asymptomatic woman during a company medical checkup. Abdominal computed tomography (CT) revealed an ossified lesion in the pancreatic body, and the patient was referred to us for further management. Abdominal ultrasound and endoscopic ultrasound showed a hypoechoic mass with a large ossific focus, measuring 25 mm in the pancreatic body. CT and magnetic resonance imaging (MRI) showed a nonenhancing tumor lesion with a large calcific focus, measuring 20 mm in the pancreatic body. Endoscopic retrograde pancreatography revealed mild stenosis of the main pancreatic duct near the ossific focus in the pancreatic body. From the above, a pancreatic solid-pseudopapillary neoplasm (SPN) was suspected, and resection of the pancreatic body was performed. Intraoperatively, a whitish tumor measuring about 20 mm was recognized. Histopathologically, moderately large-sized tumor cells containing eosinophilic cytoplasm were arranged in a pseudopapillary formation, and infiltrated the surrounding normal tissue with ossification. Immunostaining was positive for α1-antitrypsin, not inconsistent with the diagnosis of SPN. We report this case of pancreatic SPN with ossification and a review of the literature.