Vascular endothelial growth factor (VEGF) is an important regulator of vasculogenesis and vascular permeability. Hepatic sinusoidal endothelial cells (SECs) possess sieve-like pores that form an anastomosing labyrinth structure by the deeply invaginated plasma membrane. Caveolin is the principal structural protein in caveolae. In this study, we examined the role of VEGF on the fenestration and permeability of SECs and the relation with caveolin-1. SECs isolated from rat livers by collagenase infusion method were cultured for 24 h with (10 or 100 ng/ml) or without VEGF. The cells were then examined by transmission and scanning electron microscopy (EM). The expression of caveolin was investigated by confocal immunofluorescence, immunogold EM, and Western blot. Endocytosis and intracellular traffic was studied using horseradish peroxidase (HRP) reaction as a marker of fluid phase transport in SECs. Both transmission and scanning EM showed an increased number of sinusoidal endothelial fenestrae (SEF) in SECs cultured with VEGF. By confocal immunofluorescence, SECs cultured with VEGF displayed prominent caveolin-l-positive aggregates in the cytoplasm, especially surrounding the nucleus region. Immunogold EM depicted increased caveolin-1 reactivity on vesicles and vacuoles of VEGF-treated SECs compared with VEGF-nontreated cells. However, there was no change in the level of caveolin-1 protein expression on Western blot. After HRP injection, an increase of electron-dense tracer filled the SEF in cells treated with VEGF. Our results suggested that VEGF induced fenestration in SECs, accompanied by an increased number of caveolae-like vesicles. Increased caveolin-1 might be associated with vesicle formation but not with fenestration. Increased fenestration may augment hepatic sinusoidal permeability and transendothelial transport.

Caveolin, the principal structural protein in caveolae, is involved in signal transduction. The aim of the present study was to clarify the distribution and ultrastructural localization of caveolin-1 in hepatic sinusoidal endothelial cells (SECs) and hepatic stellate cell (HSCs) by confocal microscopy and the electron immunogold method. Liver tissue sections were prepared from male Wistar rats. SECs and HSCs were isolated from rat livers by collagenase infusion. For immunohistochemistry, liver sections were reacted with anticaveolin-1 antibody. The localization and distribution of caveolin-1 were identified by confocal immunofluorescence. The ultrastructural localization of caveolin-1 on SECs and HSCs was identified by electron microscopy using the immunogold method. Immunohistochemical studies using liver tissues localized caveolin-1 in sinusoidal lining cells, bile canaliculi, portal vein, and hepatic artery. By confocal microscopy, caveolin-1 was mainly demonstrated at the Golgi complex in SECs and HSCs. Under an electron microscope, immunogold particles indicating the presence of caveolin-1 were demonstrated on the plasma membrane of sinusoidal endothelial fenestrae (SEF) and vesicles in SECs. Under an electron microscope, immunogold particles indicating the presence of caveolin-1 were demonstrated on the plasma membrane of caveolae and vesicles in HSCs. We concluded that caveolin-1 is localized from SEFs to the Golgi complex in SECs and from caveolae to the Golgi complex in HSCs.

Grey mould (Botrytis cinerea) is a very successful necrotroph, causing serious losses in more than 200 crop hosts. This study investigated the antifungal effect of 405-nm light on this pathogen. Our results suggest that the excitation of endogenous porphyrins and subsequent accumulation of singlet oxygen contribute to the 405-nm light-mediated photoinactivation of grey mould. The development of symptoms in detached tomato leaves inoculated with B. cinerea spores was significantly inhibited by irradiation with 405-nm light, indicating that this wavelength of light has a potential use in controlling plant diseases caused by B. cinerea.

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Enhanced expression of APJ on HSCs in cirrhosis indicates markedly increased vascular remodeling.

The presence of actin-like microfilaments in the vicinity of sinusoidal endothelial fenestrae (SEF) indicates that the cytoskeleton of sinusoidal endothelial cells (SEC) plays an important role in the modulation of SEF. Rho has emerged as an important regulator of the actin cytoskeleton, and consequently cell morphology. The present study aimed to examine how a Rho stimulator; lysophosphatidic acid (LPA), and a Rho inhibitor; bacterial toxin C3 transferase (C3-transferase), affect the morphology of SEF. Monolayers of SEC culture were established by infusing a rat liver with collagenase for 30 min and then culturing in RMPI medium for 24 h. The cells were separated into three groups; control, LPA-treated (15 lM), and C3-transferase-treated (15 lg/ml) groups. SEF morphology was observed by scanning electron microscopy. Formation of F-actin stress fibers was observed by confocal microscopy. Rho A and phosphorylated myosin light-chain kinase were analyzed by Western blotting. Active Rho was measured by Ren's modification. Treatment of SECs with LPA contracted the SEF, concomitant with increases in F-actin stress fiber and actin microfilament, and high expression of phosphorylated myosin light-chain kinase. Following treatment with C3-transferase, SEF dilated and fused, concomitant with a loss of F-actin and microfilament, and low expression of phosphorylated myosin light chain. Rho A expression does not change by both treatments. In conclusion, these results indicate that Rho modulates fenestral changes in SEC via regulation of the actin cytoskeleton.

No abstract

Enhanced caveolin-1 expression may be associated with a significant reduction in NO catalytic activity in cirrhosis.