8 research outputs found
Effect of Knockout of <i>Mdr1a</i> and <i>Mdr1b</i> ABCB1 Genes on the Systemic Exposure of a Doxorubicin-Conjugated Block Copolymer in Mice
We
previously elucidated that ATP-binding cassette subfamily B
member 1 (ABCB1) mediates the efflux of doxorubicin-conjugated block
copolymers from HeLa cells. Here, we investigated the role of ABCB1
in the in vivo behavior of a doxorubicin-conjugated polymer in <i>Mdr1<i>a</i>/1b(−/−)</i> mice. The area
under the curve for intravenously administered polymer in <i>Mdr1<i>a</i>/1b(−/−)</i> mice was 2.2-fold
greater than that in wild-type mice. The polymer was mostly distributed
in the liver followed by spleen and less so in the brain, heart, kidney,
and lung. The amount of polymer excreted in the urine was significantly
decreased in <i>Mdr1<i>a</i>/1b(−/−)</i> mice. The amounts of polymers excreted in the feces were similar
in both groups despite the higher systemic exposure in <i>Mdr1<i>a</i>/1b(−/−)</i> mice. Confocal microscopy
images showed polymer localized in CD68<sup>+</sup> macrophages in
the liver. These results show that knockout of ABCB1 prolonged systemic
exposure of the doxorubicin-conjugated polymer in mice. Our results
suggest that ABCB1 mediated the excretion of doxorubicin-conjugated
polymer in urine and feces. Our results provide valuable information
about the behavior of block copolymers in vivo, which is important
for evaluating the pharmacokinetics of active substances conjugated
to block copolymers or the accumulation of block copolymers in vivo
Regulation of macrophage procoagulant responses by the tissue factor cytoplasmic domain in endotoxemia
Tissue factor (TF) is the primary initiator of coagulation, and the TF pathway mediates signaling through protease-activated receptors (PARs). In sepsis, TF is up-regulated as part of the proinflammatory response in lipopolysaccharide (LPS)–stimulated monocytes leading to systemic coagulation activation. Here we demonstrate that TF cytoplasmic domain–deleted (TFΔCT) mice show enhanced and prolonged systemic coagulation activation relative to wild-type upon LPS challenge. However, TFΔCT mice resolve inflammation earlier and are protected from lethality independent of changes in coagulation. Macrophages from LPS-challenged TFΔCT mice or LPS-stimulated, in vitro–differentiated bone marrow–derived macrophages show increased TF mRNA and functional activity relative to wild-type, identifying up-regulation of macrophage TF expression as a possible cause for the increase in coagulation of TFΔCT mice. Increased TF expression of TFΔCT macrophages does not require PAR2 and is specific for toll-like receptor, but not interferon γ receptor, signaling. The presence of the TF cytoplasmic domain suppresses ERK1/2 phosphorylation that is reversed by p38 inhibition leading to enhanced TF expression specifically in wild-type but not TFΔCT mice. The present study demonstrates a new role of the TF cytoplasmic domain in an autoregulatory pathway that controls LPS-induced TF expression in macrophages and procoagulant responses in endotoxemia