Scientific Report 2003-2004 - Cleveland Clinic Lerner Research ...

The Department of ImmunologyHyaluronan and Associated Proteins AreCritical to Leukocyte Adhesion in IBDImmune ResponseScott A. Strong, M.D.THE STRONGLABORATORYRESEARCH ASSOCIATESSudip Bandyopadhyay, Ph.D.Alana Majors, Ph.D.TECHNOLOGISTCarol de la Motte, Ph.D.COLLABORATORSAnthony Calabro, Ph.D. 1Anthony Day, Ph.D. 2Judith Drazba, Ph.D. 3Csaba Fulop, Ph.D. 1Vincent Hascall, Ph.D. 1Thomas Wight, Ph.D. 41Dept. of Biomedical Engineering,CCF2Oxford University, UK3Imaging Core, CCF4Univ. of Washington, SeattleOur laboratory is a link between theClinic’s Department of ColorectalSurgery and the Department of Immunologyin the Lerner Research Institute As aphysician-directed laboratory, we are primarilyconcerned with the cellular events involved ininflammation, particularly those pertinent to thechronic inflammatory processes related toCrohn’s disease and ulcerative colitis, collectivelyknown as inflammatory bowel disease (IBD).The overriding hypothesis of our laboratory isthat the bi-directional interaction betweenmesenchymal cells and leukocytes within themicroenvironment of the colonic mucosa iscrucial to inflammation and disease progression.The origin of IBD is thought to bemultifactorial. Environmental triggers, includingmicrobiological agents, initiate and perpetuate animmune response in the intestine of geneticallysusceptible individuals, which results in the clinicalmanifestations of Crohn’s disease and ulcerativecolitis.Viruses are thought to be involved in thepathogenesis of IBD because of the clinicalassociation of respiratory virus infections withsubsequent IBD exacerbations. We have recentlydescribed a novel in vitro mechanism by whichviruses may affect the interactions betweenmesenchymal cells and leukocytes.Normally, colonic mucosal tissue contains apopulation of leukocytes, including T- and B-lymphocytes, plasma cells, histiocytes and mastcells, which are scattered in a network of collagenfibers and smooth muscle cell bundles. In IBD, themucosal immune cell population increasesdramatically, and the infiltrate is predominantlycomposed of mononuclear leukocytes. Further, ahyperplastic thickening of the juxtaposed muscularismucosae cells also occurs. This suggests thatinteractions between leukocytes and mesenchymalsmooth muscle cells are important in thede la Motte, C.A., Hascall, V.C., Calabro, A., Yen-Lieberman, B., and S.A. Strong(1999) Mononuclear leukocytes preferentially bind via CD44 to hyaluronan on humanintestinal mucosal smooth muscle cells after virus infection or treatment withpoly I:C. J. Biol. Chem. 274:30747-30755.Strong, S.A., and C.A. de la Motte (1999) Hyaluronan and colon smooth musclecells. In: Hascall VC, Yanagishita M, eds. Science of Hyaluronan Today (web sitepublication, accessible at http://www.glycoforum.gr.jp/).Itoh, J., de la Motte, C.A., Strong, S.A., Levine, A.D., and C. Fiocchi (2001) DecreasedBax expression by mucosal T cells favours resistance to apoptosis inCrohn’s disease. Gut 49:35-41.de la Motte, C.A., Hascall, V.C., Drazba, J., and S.A. Strong (2001) Poly I:C inducesmononuclear leukocyte-adhesive hyaluronan structures on colon smoothmuscle cells: IaI and versican facilitate adhesion. In Kennedy, J.F., Phillips, G.O.,and P.A. Williams, eds. Hyaluronan: Proceedings of an international meeting, Sept.2000, North East Wales, Inst. of Higher Educ., UK. Vol. 1. Cambridge: Woodhead,pp. 381-388.development of IBD. We have recently shownthat colonic mesenchymal cells can proliferate inresponse to leukocyte-derived pro-inflammatorycytokines.In one of our model systems, virusinfection or poly I:C (viral mimic) treatment ofcolon mucosal smooth muscle cells (M-SMCs)increases mononuclear leukocyte adhesion via M-SMC-expressed hyaluronan interacting withleukocyte-expressed CD44. This mechanism isvery different from the cytokine (TNF-α)-induced mechanism of leukocyte adhesion, whichinvolves VCAM-1 on the M-SMCs interactingwith its integrin ligand, VLA-4, on the mononuclearleukocytes. Treatment of M-SMCs withpoly I:C upregulates the production of hyaluronanby M-SMCs, and mononuclear leukocyte adhesionto poly I:C-treated M-SMCs dramatically increases(10- to 20-fold in most experiments). Inaddition, we have shown that leukocyte activationis not required for binding to hyaluronan onvirus-induced M-SMCs. In human colon tissuesections, we observe a large increase in thehyaluronan content of inflamed mucosa ascompared to non-inflamed tissue, even whenderived from the same patient, supporting therelevance of our in vitro results to in vivo observations.Experimentally, we have been trying toreconcile the issue of why a common bodysubstance, hyaluronan, should also play a role in aninflammatory process such as leukocyte recruitment.Our data suggest that in addition to chemicalcomposition, the arrangement of hyaluronan on thecell surface is important; virus-induced M-SMCsform hyaluronan cable structures that are responsiblefor binding leukocytes, whereas patchy “coat”structures are not involved. We are currentlyinvestigating several hyaluronan-binding proteins,their role in structure formation, and how they maydirectly or indirectly dictate leukocyte adhesion.In addition to leukocyte accumulation, we areinvestigating another possible outcome of mononuclearleukocyte adhesion to hyaluronan (i.e.,activation). Under certain circumstances, leukocytescan be activated by ligation of CD44 (the majorhyaluronan receptor) and can produce proinflammatoryproducts. We speculate that leukocytebinding via the virus-induced hyaluronan pathwaywill result in chemokine, cytokine and proteaseproduction that will perpetuate the cascade ofchronic inflammation through leukocyte recruitmentand activation, as well as colon tissue remodeling.98