P-gp In Immune Regulation

Introduction: P-glycoprotein (P-gp), a 170 kd glycoproteinencoded by the multidrug resistant gene ( mdr) mdrl in humans,mdrla and mdrlb in mice, is a member of a highly conserved superfamily of ATP-binding cassette transport proteins. P-gp is expressed in epithelial cells of several organs including brain, liver, intestine, kidney, adrenal gland and testis. It is also expressed in peripheral blood leucocytes of different phenotypes including CD4, CD8, CD19, and natural killer cells. Expression of P-gp is believed to be a protective mechanism against xenobiotics. Evidence is accumulating that mdr has a wider function than just drug efflux. Mdrla gene knockout mice (mdrla^-/-) also have an impairment in the blood-brain barrier and are susceptible to severe, spontaneous, intestinal inflammation even under specific pathogen-free conditions. P-gp over-expressing multidrug-resistant cells exhibit increased resistance to viral infections. This resistance is thought to occur at the point of virus envelope fusion with the plasma membrane. Viruses, including HIV, herpes simplex virus, and certain retroviruses have been known to express reduced infectivity under condition of high P-gp expression. Furthermore P-gp has been suggested to influencemigration of dendritic cells from the periphery to lymph nodes. Most study of P-gp have focused on its efflux function, especially in drug therapy-resistance of tumours, and several inhibitors of P-gp have been developed and are being currently tested in clinical trials. However, the safety of using P-gp inhibitors during chemotherapy of tumour patients has not yet been demonstrated, and requires a further understanding of its physiological functions.Objective: The present study investigates: ? The role P-gp plays in ectromelia virus (EV) infection, a natural mouse pathogens causing mousepox.(2) Whether P-gp plays a role in immune response.Method: ? Mortality of mice infected with EV. Groups (n = 6)of female FVB and mdrla"'" mice were infected with 1 01, 10^, or 10^ pfu EV via the hind footpad. Mice were monitored over a 30 days period for survival. (2) levels of liver enzymes in serum of wt andmdrla"/' mice infected with EV by standard laboratory methods. Histopathological examination of liver and spleen were performed inwt and mdrla"/" mice infected with EV. (3) EV replication in vivo and in vitro were estimated by plaque formation on BSC-1 cell monolayer; ? EV specific antibody and cytokine analysis was performed by Sandwich ELISA. (§) Cytolytic T-cell potential in spleen, kinetics of induction of NK and EV-immune CTL in spleen and lymph node, allogeneic stimulating capacity of splenocytes of wt and mdrla''" mice was assayed using the standard 5*Cr release assay. (6) Phenotype analysis of splenocytes was performed by flow cytometry.Result: ? Mdrla^" mice are definitely more susceptible to EV infection than wt mice(p < 0.05). (D Wt and mdrla"/- mice had similar elevated AST and ALT levels and their histological damage of liver and spleen in two strains mice had not seen significant difference in the 6 days after ectromelia virus infected.? Mdrl a'1'mice had consistently lower virus titers in the examined organs as compared to wt mice. In all cell types and at all times tested, cells from wt mice supported equal or higher viral replication than cellsfrom mdrla'/" mice. ? Lake of P-gp does not alter EV-mediated cytokine release, antibody responses, cytolytic T cell potential, NK and CTL function, and allogeneic stimulating capacity. (5) No difference in the composition of splenic subsets in these two strains was noted including CD4 + , CD8 + , CD19 + , NK1.1+ and CDllc+ cells.Conclusion: P-gp plays an important role in EV infection by as yet undefined mechanisms; P-gp does not play an essential role in currently investigated cellular and humoral immune response.Introduction: The murine multiple drug resistace gene, mdrla, encodes a 170KD transmembrane protein (P-gp) that is expressed in many tissues including intestinal epithelial cells, a subset of lymphoid cells, hematopoietic cells, and cells at the blood-brain barrier. The function of mdrla in each of these different cells types and tissues is unknown. Although it is well known that P-gp can actively pump toxic drugs out of cells, their natural in vivo role is not full understood. Inflammatory bowel disease, including Crohn's disease and ulcerative colitis (UC), is a chronic, relapsing, tissue-destructive disorder. The etiology of these disease remains unknown despite many years of investigation. In the current study we observe that mdrla"''" housed under specific pathogen-free conditions develop spontaneous intestinal inflammation. Iizasa et al found that the expression and function of P-gp are reduced before intense inflammatory symptoms appear in the large intestine of mice with dextran sodium sulfate-induced colitis. Yacyshyn et al found that less P-gp-170 surface expression on UC CD3+ intestinal lymphocytes compared to controls and Crohn's disease. A decrease in P-gpl70 activity was also measured using the Rhl23 functional assay. To examine the role of P-gp in ulcerative colitis we have studied theimmunopathologic alteration of multiple drug resistance gene mdrla knockout mice with colitis.Objective: To observe the role of the P-GP in ulcerative colitis.Methods: The clinical, pathological and imrauno -histochemical characteristics were observed in FVB control mice and mdrla"7" mice with or without inflammation of intestinal tract. The functions of T cell and B cell in those mice were analyzed.Results Approximately 21% of the 124 mdrla"7" mice had symptoms of colitis such as diarrhea and anus abscission in this study; pathologic changes of above mice were similar to the human active ulcerative colitis. CD4+ T cells and B cell infiltrated into the proper lamina was observed by immunohistochemistry staining in mdrla"''" mice with colitis compared with FVB mice. There are massive increases in serum antibody titers of all types in mdrla"''" mice with active colitis, but no difference in serum antibody titers and T cell functions compared with FVB mice and mdrla"7" mice without active colitis.Conclusion: Mdrla knockout mouse could appear colitis and its pathogenesis is independent of T and B cell in the body and may be associative with intestinal epithelial barrier.Introduction: Dendritic cells (DC) represent a heterogenous population of cells specialized in antigen capture, processing, and presentation to T cells. Being the most potent antigen-presenting cells, they play a key role in the initiation of immune response and are considered as promising tools for immunotherapy. Various cellular and molecular factors control their physiological functions. In particular, P-glycoprotein initially characterized as a membrane efflux pump conferring drug resistance to tumoral cells and belonging to the ATP binding cassette transporters superfamily, has been recently shown to be expressed by Langherans cells, a subtype of DC found in skin. For such cells, P-gp has been found to be directly involve in their migration from skin to lymph nodes in vitro. The mechanism by which P-gp facilitates migration remains unknown.Objective: To study the influence for P-glycoprotein (P-gp) during the migration of dendritic cells (DC) from skin to draining lymph nodes in vivo.Methods: Splenic DCs from FVB and mdrla""/" mice were purified using magnetic adsorption cell sorting (MACS) and labelledwith fluorescent cell tracker reagents CFSE, then injected intoFVB/N and mdrla'/" mice via hind footpad. Draining lymph nodes were collected at day 2 post-injection and the number of homing DCs were determined by fluorescence-activated cell sorter.Results: DCs from mdrla" " mice migrating to draining lymph nodes were less than that from wt mice, but no difference with recipients.Conclusion: P-gp (mdrla type) influences the migration of DC.