Receptor-mediated transport of LIF across blood-spinal cord barrier is upregulated after spinal cord injury.
Leukemia inhibitory factor (LIF) crosses the normal blood-brain and blood-spinal cord barrier (BBB) by a saturable transport system [Pan, W., Kastin, A.J., Brennan, J.M., 2000. Saturable entry of leukemia inhibitory factor from blood to the central nervous system. J. Neuroimmunol. 106, 172-180]. Since LIF is a cytokine beneficial to spinal cord regeneration, understanding the regulation of its transport across the injured BBB may help in the design of strategies for the treatment of spinal cord injury (SCI). In this study, we initially showed that transport of LIF is mediated by its specific receptor LIFRalpha (gp190), using both adult mice and monolayers of mouse brain microvessel endothelial cells. Permeation of radioactively labeled LIF was inhibited not only by excess unlabeled LIF, but also by a blocking antibody to the extracellular domain of gp190 LIFRalpha receptor. This showed that the saturable transport of LIF across the BBB involves LIFRalpha. We then tested the hypothesis that this transport system can be upregulated after SCI. SCI was generated by an established compression method at the upper lumbar level. Transport was studied 1 week after SCI, a time of tissue repair following ischemia and inflammation. Spinal cord uptake of 99mTc-albumin 10 min after intravenous injection was used as an indicator of paracellular permeability of the BBB, its small but significant increase at the injury site indicating the level of persistent BBB disruption. The uptake of 125I-LIF by the injured lumbar spinal cord was significantly greater than that in the uninjured controls as well as that of 99mTc-albumin. Both excess unlabeled LIF and the blocking antibody against LIFRalpha significantly suppressed the increased entry of 125I-LIF without affecting that of 99mTc-albumin. Thus, the increased blood-to-spinal cord permeation of LIF was not solely explained by barrier disruption but involved LIFRalpha. This enhanced transport correlated with increased expression of LIFRalpha shown by immunofluorescent staining and Western blot. Therefore, LIFR at the BBB provides an important target for therapeutic intervention.
Pennington Biomedical Research Center, Baton Rouge, Louisiana 70808, USA. weihong.pan@pbrc.edu
Weihong
W
Pan
Courtney
C
Cain
Yongmei
Y
Yu
Abba J
AJ
Kastin
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001812:Blood-Brain Barrier / Q000503:physiopathology*; D015153:Blotting, Western / Q000379:methods; D002199:Capillary Permeability / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005455:Fluorescent Antibody Technique / Q000379:methods; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism* / Q000493:pharmacokinetics; D007456:Iodine Isotopes / Q000493:pharmacokinetics; D053605:Leukemia Inhibitory Factor; D053680:Leukemia Inhibitory Factor Receptor alpha Subunit; D008297:Male; D051379:Mice; D021381:Protein Transport / Q000502:physiology; D018121:Receptors, Cytokine / Q000276:immunology / Q000502:physiology*; D053606:Receptors, OSM-LIF; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D013997:Time Factors
D000906:Antibodies; D015850:Interleukin-6; D007456:Iodine Isotopes; C507837:LIF protein, human; C507840:LIFR protein, human; D053605:Leukemia Inhibitory Factor; D053680:Leukemia Inhibitory Factor Receptor alpha Subunit; C507838:Lif protein, mouse; C507841:Lifr protein, mouse; D018121:Receptors, Cytokine; D053606:Receptors, OSM-LIF