Inhibition of low-density lipoprotein uptake by Helicobacter pylori virulence factor CagA.

Helicobacter pylori (H. pylori) infection mainly causes gastroduodenal diseases, including chronic gastritis, peptic ulcer disease and gastric cancer. In recent years, several studies have demonstrated that infection with H. pylori, especially strains harboring the virulence factor CagA (cytotoxin-associated gene A), contribute to the development of non-gastric systemic diseases, including hypercholesterolemia and atherosclerotic cardiovascular diseases. However, mechanisms underlying this association has not been defined. In this study, we carried out a large-scale genetic screen using Drosophila and identified a novel CagA target low-density lipoprotein receptor (LDLR), which aids in the clearance of circulating LDL. We showed that CagA physically interacted with LDLR via its carboxy-terminal region and inhibited LDLR-mediated LDL uptake into cells. Since deficiency of LDLR-mediated LDL uptake has been known to increase plasma LDL and accelerate atherosclerosis, our findings may provide a novel mechanism for the association between infection with CagA-positive H. pylori and hypercholesterolemia leading to atherosclerotic cardiovascular diseases.

Chronic hypoxia-induced slug promotes invasive behavior of prostate cancer cells by activating expression of ephrin-B1.

Advanced solid tumors are exposed to hypoxic conditions over longer periods of time as they grow. Tumor hypoxia is a major factor that induces malignant progression, but most previous studies on tumor hypoxia were performed under short-term hypoxia for up to 72 hours and few studies have focused on tumor response to chronic hypoxic conditions. Here we show a molecular mechanism by which chronic hypoxia promotes invasive behavior in prostate cancer cells. We found that an epithelial-mesenchymal transition (EMT)-driving transcription factor, slug, is specifically upregulated under chronic hypoxia and promotes tumor cell migration and invasion. Unexpectedly, processes associated with EMT, such as loss of E-cadherin, are not observed under chronic hypoxia. Instead, expression of ephrin-B1, a ligand of Eph-related receptor tyrosine kinases, is markedly induced by slug through E-box motifs and promotes cell migration and invasion. Furthermore, slug and ephrin-B1 are highly coexpressed in chronic hypoxic cells of human prostate adenocarcinoma tissues after androgen deprivation, which is known to cause tumor hypoxia. Taken together, these results indicate that chronic hypoxia-induced slug promotes invasive behavior of prostate cancer cells by activating the expression of ephrin-B1. In addition, ephrin-B1 may be a novel therapeutic target in combination with androgen deprivation therapy for aggressive prostate cancer.

Topographic study on nerve-associated lymphatic vessels in the murine craniofacial region by immunohistochemistry and electron microscopy.

The distribution and fine structure of lymphatic vessels associated with nerves was studied by immunohistochemistry in the murine craniofacial region. The tissue sections and blocks were immunostained for LYVE-1, protein gene product 9.5, CD34 and aquaporin-1 to demonstrate the lymphatic vessels, nerves, blood vessels and water channel protein, respectively. Transmission electron microscopic examination was also performed to investigate the relationship between the lymphatics and nerves. In the nasal area, the lymphatics were found in dura mater on the cribriform plate and beneath the nasal mucosa, this supposedly supplying the cerebrospinal fluid drainage route along the olfactory nerves. The proximal portions of the cranial nerves were equipped with the lymphatics in the epineurium. In the distal portions of the nerves, the lymphatics were distributed in close proximity of the perineural sheath, and thus might contribute to maintenance of microenvironment suitable for the nerves by an absorptive activity of the lymphatic endothelial cells. The present findings suggest that the lymphatic system associated with the cranial nerves provides the pathway for transport of cerebrospinal fluid, tissue fluid, and free cells involved in immune response and tumor metastasis in the craniofacial region.

Reconstruction of central lacteals in the murine jejunum following ischemia-reperfusion injury.

The intestinal mucosa is vulnerable to an ischemia-reperfusion (I/R) attendant on some bowel diseases and surgery; thus, the restoration of the mucosal integrity is critical to achieving functional recovery of the intestine injured by I/R. In this histochemical study, we investigated the alteration of the central lacteals--which are essential for the transport of fat, tissue fluid, and immune cells in the intestinal mucosa--in the murine jejunum after I/R. The intestine inflicted with I/R demonstrated mucosal injury involving the inflammatory response, with interstitial edema, disruption of the villous tissue, and subsequent tissue regeneration of the villi. The regenerative villous tissue revealed lymphatic regrowth showing proliferative activity from the residual mucosal lymphatics behind the regenerated blood vasculature. During the regenerative phase, the blood vascular pericytes expressed an intense immunoreaction for VEGF-A, an inducer for monocyte/macrophage recruitment as well as angiogenesis. Also, the F4/80-immunopositive macrophages significantly increased in number in the regenerating villous stroma. Furthermore, the macrophages recruited around the regrowing lacteals expressed the immunoreactivity for VEGF-C, which is a highly specific lymphangiogenic factor. The present study is first to delineate alterations in the central lacteals in the small intestine following I/R, thereby suggesting that the recruitment of the macrophages induced by upregulation of VEGF-A in the pericytes of regenerative blood vessels might promote reconstruction of the central lacteals through their release of VEGF-C.

Scanning electron microscopic observation of immunohistochemically specified stromal cells following the NaOH maceration method.

The present study introduces a method combining immunohistochemistry and a chemical digestion technique applied to scanning electron microscopy (SEM) observation of chemically characterized stromal cells in the myenteric layer of the monkey small intestine. The whole-mount preparation containing the myenteric layer was treated immunohistochemically using small colloidal gold and silver enhancements for detecting a certain type of stromal cell, followed by an alkali maceration method to remove extracellular matrices covering the immunohistochemically stained cells. This method permitted direct SEM observation of the stained stromal cells. Secondary and backscatter electron images clearly visualized the ultrastructure of the immunohistochemically-stained cells and the spatial distribution of the reaction products, respectively. It is suggested that the present method is useful for demonstrating the three-dimensional organization of the chemically specified stromal cells.