Verapamil induces upregulation of P-glycoprotein expression on human monocyte derived dendritic cells.
Overexpression of P-glycoprotein, a transmembrane drug efflux pump that mediates efflux of chemotherapeutic agents contributes to drug resistance in many leukaemia and other cancerous cells. Non-malignant cells including leukocytes also express P-glycoprotein, but physiologic functions for P-glycoprotein are poorly defined. Recently, P-glycoprotein expression has been described in human mononuclear phagocytes and Langerhans cells. It has been shown to play a role in phagocytic cell transmigration through endothelial-lined vessels in an ablumenal-lumenal direction, a process that mimics their migration into lymphatic vessels. Using the monoclonal antibody 4E3, and the P-glycoprotein antagonist, verapamil, the expression of P-glycoprotein on human monocyte-derived dendritic cells was evaluated. Dendritic cells used in this study were CD1a+, CD11c+, CD14-, CD80+, CD83+, CD86+ and MHC-II(High). The expression of these markers increased significantly as the cells matured. P-glycoprotein expression was upregulated as the dendritic cells matured as well as in the presence of the "inflammatory stress" of the pathogenic bacteria Strept. pyogenes. Addition of verapamil or Strept. pyogenes to the culture medium during the final 24 hours significantly upregulated P-glycoprotein expression. Immortalized cell lines did not upregulate P-glycoprotein in the presence of verapamil. Evaluation of other normal cells showed that P-glycoprotein upregulation in the presence of verapamil was also a characteristic of macrophages. This novel observation of the upregulation of P-glycoprotein in the presence of verapamil appears to be a characteristic of activated myeloid derived antigen presenting cells and suggest that P-glycoprotein is essential for these cells as when it is blocked, they respond by increasing expression of this protein. In summary, this work describes that human dendritic cells generated from plastic-adherent monocytes rapidly upregulate expression of P-glycoprotein as they mature, and in the presence of inflammatory stress and the pharmacological agent verapamil, which blocks P-glycoprotein activity, suggesting that P-glycoprotein may play a role in activation as well as in migration of dendritic cells.
Dermatology Laboratories, Melanoma and Skin Cancer Research Institute, Sydney Cancer Centre, Royal Prince Alfred Hospital at University of Sydney, Sydney, NSW, Australia.
Raj K
RK
Ishri
Scott
S
Menzies
Gary M
GM
Halliday
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D003713:Dendritic Cells / Q000187:drug effects* / Q000378:metabolism / Q000382:microbiology; D019337:Hematologic Neoplasms / Q000378:metabolism; D006801:Humans; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D009000:Monocytes / Q000166:cytology; D020112:Rhodamine 123 / Q000378:metabolism; D013297:Streptococcus pyogenes / Q000472:pathogenicity; D015854:Up-Regulation; D014700:Verapamil / Q000494:pharmacology*
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000911:Antibodies, Monoclonal; D002121:Calcium Channel Blockers; D020112:Rhodamine 123; D014700:Verapamil