ABSTRACT: Aquaporins (AQPs) are molecular water channels that play important physiological roles in fluid transporting organs. The expression and function of AQPs in the immune system are largely unknown. CD11(aâ€•d)/CD18 integrins are adhesion molecules expressed on leukocytes, which play a critical role in leukocyte adhesion, migration and host defense. In the present study, we suggest that the expression of aquaporin water channels on spleen CD positive cells, and the content of CD positive splenocytes in aquaporin may regulate the migration of blood cells. Recent studies and their analysis suggested remarkably decreased monocyte/macrophage subpopulation and significantly decreased granulocyte subpopulation. This is the first hypothetical report suggesting an important role of AQP in the trafficking of hemapoietic cells.&nbsp;Key words: Aquaporin, Spleen, Lymphocytes, CD147, ErythrocytesDepartment of Pharmacology, Christian Medical College, Vellore 632002, Tamilnadu, India&nbsp;Please Cite This Article As:Manoj G Tyagi and Premkumar Thangavelu. 2010. A Possible Role of Aquaporin Water Channels in Blood Cell Migration in Spleen; Interaction with Cluster of Differentiation Molecules. J. Exp. Sci. 1(4):41-42. &nbsp

Thangavelu, Manoj G Tyagi* and Premkumar

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   Journal of Experimental Sciences Vol. 1, Issue 4, Pages 41-42 [2010] www.jexpsciences.com * Corresponding Author, Email: tyagi237@indiatimes.com; Tel: 0416-228-4237                                                                                             JES                                                                                                                                                                                                   ISSN: 2218-1768                Regular Article A Possible Role of Aquaporin Water Channels in Blood Cell Migration in Spleen; Interaction with Cluster of Differentiation Molecules    Manoj G Tyagi* and Premkumar Thangavelu  Department of Pharmacology, Christian Medical College, Vellore 632002, Tamilnadu, India ABSTRACT: Aquaporins (AQPs) are molecular water channels that play important physiological roles in fluid transporting organs. The expression and function of AQPs in the immune system are largely unknown. CD11(a―d)/CD18 integrins are adhesion molecules expressed on leukocytes, which play a critical role in leukocyte adhesion, migration and host defense. In the present study, we suggest that the expression of aquaporin water channels on spleen CD positive cells, and the content of CD positive splenocytes in aquaporin may regulate the migration of blood cells. Recent studies and their analysis suggested remarkably decreased monocyte/macrophage subpopulation and significantly decreased granulocyte subpopulation. This is the first hypothetical report suggesting an important role of AQP in the trafficking of hemapoietic cells.  Key words: Aquaporin, Spleen, Lymphocytes, CD147, Erythrocytes The compartments of human spleen are ill defined and the location of T-cell regions with respect to the so-called “central arterioles” is especially controversial. The splenic red pulp cords are formed by fibroblasts and reticular fibers (1,2). They represent the open part of the splenic circulation that receives blood from terminal arterioles and lacks endothelia. The closed part of the splenic circulation consists of the rest of the vascular tree including the splenic red pulp sinuses. Despite this classification, the sinuses have an unusual discontinuous endothelium and basement membrane, which permit erythrocytes to enter from the open circulation of the surrounding cords. Recent results show, that the border between the splenic white and red pulp is more sophisticated in humans than in rats or mice (3,4). They provoke the interpretation that the region where red and white blood cells enter the spleen is species-specific. Recirculating mouse and rat lymphocytes are imagined to enter the white pulp by adherence to the endothelium of the marginal sinus and by migration across the marginal zone (MZ). Thus, they have to cross the wall of a vessel belonging to the closed splenic circulation.  We speculate that in humans the entry of white blood cells into the splenic white and red pulp is different in that it occurs primarily via the open splenic circulation in the perifollicular zone (5). Thus, the white cells need not cross an endothelium, because terminal vessels directly open into this site. Vascular structures similar to the rodent marginal sinus do definitively not exist in humans. We can, however, not exclude that the few capillaries in the perifollicular zone that express CD31 and/or CD34 serve the exit of white blood cells. These vessels are, however, only sparsely distributed. in autopsy specimens. The fact that blood cells are contained in an open part of the splenic circulation in the perifollicular zone is not only demonstrated by the distribution pattern of CD31, CD34, and CD141, but is supported by additional evidence coming from adhesion molecules involved in lymphocyte recirculation.  The spleen is equipped with a unique type of microcirculation permitting lymphocytes to exit from blood under conditions of low shear stress and in absence of high endothelial venules. In addition to erythrocytes, granulocytes, and monocytes, in some specimens with full blown germinal centers large numbers of CD-20 and CD-79 positive B lymphocytes, which are negative or weakly positive for IgD extend from the MZ into the perifollicular zone. On the other hand CD147 has been described as a potential adhesion molecule, which binds to endothelial cells and fibroblasts. For instance, CD147, like CD47, may be part of the recognition of erythrocytes as self, and that blockade of this molecule may prevent erythrocytes from escaping the splenic reticuloendothelial system. Aquaporin water channel CHIP28 is expressed on the erythrocytes and may contribute to distinct physiological functions in the presence of CD147. Alternatively, it is possible that ligation of CD147 alters erythrocyte deformability, leading to their mechanical trapping in the spleen. Taken together, these data strongly suggested that blockade of CD147 on erythrocytes was directly responsible for their trapping in the spleen (6).  Aquaporin water channels are expressed in the spleen but their precise function is not known (7,8). It is quite possible that aquaporin water channels may be requlating the trafficking of blood cells across spleen and in and out of spleen. A role of cluster of differentiation cells is speculated in this entire physiological process. A further possibility is that ligation of CD147 may alter erythrocyte adhesion through an intracellular signaling mechanism. This speculation is based on some recent studies although comprehensive studies need to be conducted (9). The identification of the ligand(s) for CD147 and the cell type expressing it should help elucidate mechanisms involved in CD147-mediated erythrocyte trafficking. The adhesion molecule 4β1-integrin (VLA-4) has been previously shown to play a major role in the trafficking of hematopoietic precursors and their homing to the spleen and liver (10). However, other explanations cannot be ruled out. There may, in fact, be conditions in which the perifollicular zone harbors major numbers of B lymphocytes making a distinction between outer MZ and perifollicular zone rather difficult. These findings clearly suggest that the interpretations by Hsu and colleagues in that we definitively show the human MZ as a B lymphocyte region with a variable content of CD4-positive T lymphocytes. Apart from these two studies, the majority of other immunohistological reports on the human splenic white pulp correspond to our results. With exception of the study by van Krieken and te Velde, the existence of the perifollicular zone went, however, undetected in all these investigations (11). This is also true for other studies, who investigated the distribution of macrophages and dendritic cells in human spleens and described accumulations of monocytes or granulocytes around the follicles. CD147 is a member of the immunoglobulin superfamily and is a highly glycosylated cell surface protein. CD147 is considered an adhesion molecule and has been shown to induce matrix metalloprotease expression by neighboring epithelial cells. It is expressed in various tissues, including brain, leukocytes, endothelial cells, and most tumor cell   lines (12,13). In addition, CD147 is expressed on erythrocyte lineage cells throughout erythroid development, including in mature erythrocytes. Apparently, the interaction of CD147 on erythrocytes and its potential ligand expressed on splenic vasculature is likely to be critical in the recirculation of mature erythrocytes from spleen into the general circulation. We postulate that the role of CD147 in erythrocyte circulation may be in its capacity as an inducer of matrix-degrading metalloproteases, thus actively participating in the exit of circulating erythrocytes from the spleen. Indeed, it was shown that CD147 increases the expression of interstitial collagenase, stromelysin, and gelatinase in stromal fibroblasts (14). However, other explanations cannot be ruled out. For instance, CD147, like CD47, may be part of the recognition of erythrocytes as self, and that blockade of this molecule may prevent erythrocytes from escaping the splenic reticuloendothelial system and possibly aquaporin water channels may contribute in J Exp Sci Vol. 1, Issue 4, Pages 41-42 [2010]   this mechanism. Alternatively, it is possible that ligation of CD147 alters erythrocyte deformability, leading to their mechanical trapping in the spleen. A further possibility is that ligation  of  CD147  may  alter  erythrocyte  adhesion  through  an intracellular  signaling  mechanism. CD147 increases the expression of interstitial collagenase, strome- lysin, and gelatinase in stromal fibroblasts. For e.g Aquaporin-1 (AQP-1), the universal water channel, is responsible for rapid response of cell volume to changes in plasma tonicity. In the membrane of the red cell the concentration of the protein is tightly controlled. It has been shown that AQP-1 is partially lost during in vitro maturation of mouse reticulocytes and that it is associated with exosomes, released throughout this process. AQP-1 in young reticulocytes localizes to the plasma membrane and also in endosomal compartments and exosomes, formed both in vitro and in vivo thus strongly suggesting the role of aquaporins in blood cell cyclization.Recent studies also show that aquaporin water channels are expressed on the CD cells and CD cell population in the spleen is remarkably decreased in aquaporin null mice thus further suggesting their role in immunogenicity and blood cell trafficking (15).  Acknowledgement The authors are grateful to the Indian Council of Medical Research, New Delhi for their financial and moral support.  References 1. B Steininger, P Berth and A Hellinger. The perifollicular and marginal zones of the human splenic white pulp. Am.J.Pathol.159,2,2001 2. B Steiniger, L Ruttinger and P Barth. The three dimensional structure of human splenic white pulp compartments.Jr.Histochem.Cytochem.51(5):655-663,2003 3. Van Ewijk W, Nieuwenhuis P. Compartments, domains and migration pathways of lymphoid cells in the splenic pulp. Experentia, 4: 199-208, 1985 4. Nieuwenhuis P, Ford WL. Comparative migration of B-and T-lymphocytes in the rat spleen and lymph nodes. Cell Immunol.23:254, 1976 5. Brelinska R, Pilgrim C. Macrophages and interdigitating cells: their relationship in migrating lymphocytes in the white pulp of rat spleen. Cell Tissue Res., 233: 671-688, 1983 6. I Coste, J F Gauchat, A Wilson, S Izui, P Jeannin, Y Deineste, H Robson MacDonald, JY Bonnefoy, and T Renno. Unavailability of CD147 leads to selective erythrocyte trapping in the spleen. Blood, 97, 12, 2001 7. M. L. Elkjær, Z. Vajda, L. N. Nejsum, T. -H. Kwon, U. B. Jensen, M. Amiry-Moghaddam, J. Frøkiær, and S. Nielsen. Immunolocalization of AQP9 in Liver, Epididymis, Testis, Spleen, and Brain. Biochemical and Biophysical Research Communications. Volume 276, 3, 1118-1128, 2000 8. K Ishibashi, M Kuwahara, Y Gu, Y Tanaka, F Marumo, Sasaki F. Cloning and functional expression of a new aquaporin (AQP9) abundantly expressed in the peripheral leukocytes permeable to water and urea, but not to glycerol. Biochem.Biophys Res Commun. 244: 268–274, 1998 9. J M Carbrey, L Song, Y Zhou, M Yoshinaga, A Rosek, Y Wang, Y Liu, H L Lujan, S E DiCarlo, S Nielsen, B R Rosen, P Agre, R Mukhopadhyay. Reduced arsenic clearance and increased toxiticy in aquaglyceroporin-9-null mice. PNASc.,15956-15960, 2009 10. Papayannopoulou T, Nakamoto B. Peripheralization of hemopoietic progenitors in primates treated with anti-VLA 4 integrin. Proc Natl Acad Sci U S A.,90:9374-9378, 1993 11. van  Krieken  J.H.J.M. &  J. te  Velde. Immunohistology of the human spleen: an inventory of the localization of lymphocyte subpopulations.Histopathology, Volume 10, Issue 3, pages 285–294, 1986 12. Mutin M, Dignat-George F, Sampol J. Immunologic phenotype of cultured endothelial cells: quantitative analysis of cell surface molecules. Tissue Antigens.50, 449-458, 1997 13. Arroyo AG, Yang JT, Rayburn H, Hynes RO. Alpha 4 integrins regulate the proliferation/differentiation balance of multilineage hematopoietic progenitors in vivo. Immunity.11:555-566, 1999 14. Kataoka H, DeCastro R, Zucker S, Biswas C. Tumor cell-derived collagenase-stimulatory factor increases expression of interstitial collagenase, stromelysin, and 72-kDa gelatinase. Cancer Res.53:3154-3158, 1993 15. Z Na, Q Ying, Z Di, W Wen-juan, L Jia, L Tian Zhou and MA Tong-hui. Remarkably decreased CD11n positive splenocytes in aquaporin 3- null mice. Chem.Res.Chinese Universities, 26(2), 217-220,2010.                                                     Please Cite This Article As: Manoj G Tyagi and Premkumar Thangavelu. 2010. A Possible Role of Aquaporin Water Channels in Blood Cell Migration in Spleen; Interaction with Cluster of Differentiation Molecules. J. Exp. Sci. 1(4):41-42.    

A Possible Role of Aquaporin Water Channels in Blood Cell Migration in Spleen; Interaction with Cluster of Differentiation Molecules

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A Possible Role of Aquaporin Water Channels in Blood Cell Migration in Spleen; Interaction with Cluster of Differentiation Molecules

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