3 research outputs found
Liver sinusoidal endothelial cells show reduced scavenger function and downregulation of Fc gamma receptor IIB, yet maintain a preserved fenestration the Glmp gt/gt mouse model of slowly progressing liver fibrosis
Liver sinusoidal endothelial cells (LSECs) are fenestrated endothelial cells with a unique,
high endocytic clearance capacity for blood-borne waste macromolecules and colloids. This
LSEC scavenger function has been insufficiently characterized in liver disease. The
Glmpgt/gt mouse lacks expression of a subunit of the MFSD1/GLMP lysosomal membrane
protein transporter complex, is born normal, but soon develops chronic, mild hepatocyte
injury, leading to slowly progressing periportal liver fibrosis, and splenomegaly. This study
examined how LSEC scavenger function and morphology are affected in the Glmpgt/gt
model. FITC-labelled formaldehyde-treated serum albumin (FITC-FSA), a model ligand for
LSEC scavenger receptors was administered intravenously into Glmpgt/gt mice, aged 4
months (peak of liver inflammation), 9–10 month, and age-matched Glmpwt/wt mice. Organs
were harvested for light and electron microscopy, quantitative image analysis of ligand
uptake, collagen accumulation, LSEC ultrastructure, and endocytosis receptor expression
(also examined by qPCR and western blot). In both age groups, the Glmpgt/gt mice showed
multifocal liver injury and fibrosis. The uptake of FITC-FSA in LSECs was significantly
reduced in Glmpgt/gt compared to wild-type mice. Expression of LSEC receptors stabilin-1
(Stab1), and mannose receptor (Mcr1) was almost similar in liver of Glmpgt/gt mice and agematched controls. At the same time, immunostaining revealed differences in the stabilin-1
expression pattern in sinusoids and accumulation of stabilin-1-positive macrophages in
Glmpgt/gt liver. FcÎłRIIb (Fcgr2b), which mediates LSEC endocytosis of soluble immune
complexes was widely and significantly downregulated in Glmpgt/gt liver. Despite increased collagen in space of Disse, LSECs of Glmpgt/gt mice showed well-preserved fenestrae organized in sieve plates but the frequency of holes >400 nm in diameter was increased, especially in areas with hepatocyte damage. In both genotypes, FITC-FSA also distributed to
endothelial cells of spleen and bone marrow sinusoids, suggesting that these locations may
function as possible compensatory sites of clearance of blood-borne scavenger receptor
ligands in liver fibrosis
Liver sinusoidal cells eliminate blood-borne phage K1F
Phage treatment has regained attention due to an increase in multiresistant
bacteria. For phage therapy to be successful, phages must reach their target bacteria
in sufficiently high numbers. Blood-borne phages are believed to be captured by
macrophages in the liver and spleen. Since liver sinusoids also consist of specialized
scavenger liver sinusoidal endothelial cells (LSECs) and Kupffer cells (KCs), this study
investigated the contribution of both cell types in the elimination of Escherichia coli
phage K1Fg10b::gfp (K1Fgfp) in mice. Circulatory half-life, organ, and hepatocellular
distribution of K1Fgfp were determined following intravenous administration. Internalization of K1Fgfp and effects of phage opsonization on uptake were explored using primary
mouse and human LSEC and KC cultures. When inoculated with 107
virions, >95% of
the total K1Fgfp load was eliminated from the blood within 20 min, and 94% of the total
retrieved K1Fgfp was localized to the liver. Higher doses resulted in slower elimination,
possibly reflecting temporary saturation of liver scavenging capacity. Phage DNA was
detected in both cell types, with a KC:LSEC ratio of 12:1 per population following cell
isolation. Opsonization with plasma proteins increased time-dependent cellular uptake
in both LSECs and KCs in vitro. Internalized phages were rapidly transported along
the endocytic pathway to lysosomal compartments. Reduced viability of intracellular
K1Fgfp corroborated inactivation following endocytosis. This study is the first to identify
phage distribution in the liver at the hepatocellular level, confirming clearance of K1Fgfp
performed mostly by KCs with a significant uptake also in LSECs