Background & Aims-Hepatocyte transplantation-induced liver inflammation impairs cell engraftment. We defined whether proinflammatory cytokines and chemokines played roles in regulation of hepatocyte engraftment in the liver.

To understand the mechanism of kinesin movement we have investigated the relative configuration of the two kinesin motor domains during ATP hydrolysis using fluorescence polarization microscopy of ensemble and single molecules. We found that: (i) in nucleotide states that induce strong microtubule binding, both motor domains are bound to the microtubule with similar orientations; (ii) this orientation is maintained during processive motion in the presence of ATP; (iii) the neck-linker region of the motor domain has distinct configurations for each nucleotide condition tested. Our results fit well with a hand-over-hand type movement mechanism and suggest how the ATPase cycle in the two motor domains is coordinated. We propose that the motor neck-linker domain configuration controls ADP release.

Background & Aims Hepatic inflammation occurs immediately after cells are transplanted to the liver, but the mechanisms that underlie this process are not fully defined. We examined cyclooxygenase pathways that mediate hepatic inflammation through synthesis of prostaglandins (PG), prostacyclins, thromboxanes and other prostanoids following transplantation of hepatocytes. Methods We transplanted F344 rat hepatocytes into syngeneic dipeptidyl peptidase IV-deficient F344 rats. Changes in cyclooxygenase pathways were analyzed and specific pathways were blocked pharmacologically; the effects on cell engraftment and native liver cells were determined. Results Transplantation of hepatocytes induced hepatic expression of prostaglandin-endoperoxide synthases 1 and 2, which catalyze production of prostaglandin H2, as well as the downstream factor thromboxane synthase, which produces thromboxane A2 (a regulator of vascular and platelet responses in inflammation). Transplanted hepatocytes were in proximity with liver cells that express prostaglandin-endoperoxide synthases. The number of engrafted hepatocytes increased in rats given naproxen or celecoxib before transplantation, but not in rats given furegrelate (an inhibitor of thromboxane synthase) or clopodigrel (an anti-platelet drug). Naproxen and celecoxib did not prevent hepatic ischemia or activation of neutrophils, Kupffer cells or inflammatory cytokines, but they did induce hepatic stellate cells to express cytoprotective genes, vascular endothelial growth factor and hepatocyte growth factor, and matrix-type metalloproteinases and tissue inhibitor of metalloproteinase-1, which regulate hepatic remodeling. Conclusions Activation of cyclooxygenase pathways interferes with engraftment of transplanted hepatocytes in the liver. Pharmacological blockade of prostaglandin-endoperoxide synthases stimulated hepatic stellate cells and improved cell engraftment.