BACKGROUND: Over-expression of the membrane glycoprotein called P-glycoprotein has been widely observed in a variety of both normal and neoplastic cells. P-glycoprotein is a pump molecule that transports hydrophobic drugs (including steroids) and toxins outside the cells, thus inhibiting their therapeutic or toxic effects. The gene encoding P-glycoprotein is named multidrug resistance-1 (MDR-1). OBJECTIVE: To evaluate the functional activity of P-glycoprotein in lymphocytes and monocytes from patients with systemic lupus erythematosus. METHODS: 30 systemic lupus erythematosus patients and 20 healthy controls were studied. Peripheral blood mononuclear cells isolated by gradient centrifugation were incubated in the presence of daunorubicin (a fluorescent drug extruded by P-glycoprotein) at 37 degrees C or 4 degrees C for 30 min. P-glycoprotein activity was then analyzed using flow cytometry. Results were expressed as the percentage of lymphocytes or monocytes with high P-glycoprotein activity (i.e., low fluorescence). RESULTS: Mean fluorescence values for lymphocytes and monocytes were comparable between patients and healthy controls. However, because our method allowed to measure P-glycoprotein function at the single-cell level, we were able to show that the mean percentage of lymphocytes with high P-glycoprotein activity was increased in the patients (11.51% +/- 14.3%) as compared to the healthy controls (0.71% +/- 0.57%) (P < 0.05). Moreover, P-glycoprotein activity was lower in the patients in clinical remission than in those with active disease. CONCLUSIONS: Our results suggest that P-glycoprotein function might affect glucocorticoid requirements in systemic lupus erythematosus.
BACKGROUND: Over-expression of the membrane glycoprotein called P-glycoprotein has been widely observed in a variety of both normal and neoplastic cells. P-glycoprotein is a pump molecule that transports hydrophobic drugs (including steroids) and toxins outside the cells, thus inhibiting their therapeutic or toxic effects. The gene encoding P-glycoprotein is named multidrug resistance-1 (MDR-1). OBJECTIVE: To evaluate the functional activity of P-glycoprotein in lymphocytes and monocytes from patients with systemic lupus erythematosus. METHODS: 30 systemic lupus erythematosuspatients and 20 healthy controls were studied. Peripheral blood mononuclear cells isolated by gradient centrifugation were incubated in the presence of daunorubicin (a fluorescent drug extruded by P-glycoprotein) at 37 degrees C or 4 degrees C for 30 min. P-glycoprotein activity was then analyzed using flow cytometry. Results were expressed as the percentage of lymphocytes or monocytes with high P-glycoprotein activity (i.e., low fluorescence). RESULTS: Mean fluorescence values for lymphocytes and monocytes were comparable between patients and healthy controls. However, because our method allowed to measure P-glycoprotein function at the single-cell level, we were able to show that the mean percentage of lymphocytes with high P-glycoprotein activity was increased in the patients (11.51% +/- 14.3%) as compared to the healthy controls (0.71% +/- 0.57%) (P < 0.05). Moreover, P-glycoprotein activity was lower in the patients in clinical remission than in those with active disease. CONCLUSIONS: Our results suggest that P-glycoprotein function might affect glucocorticoid requirements in systemic lupus erythematosus.
Authors: Andrea Picchianti-Diamanti; Maria Manuela Rosado; Marco Scarsella; Bruno Laganà; Raffaele D'Amelio Journal: Int J Mol Sci Date: 2014-03-20 Impact factor: 5.923