Reduced cyclosporin accumulation in multidrug-resistant cells

Area of Science:

• Pharmacology
• Cell Biology
• Biochemistry

Background:

• Multidrug resistance (MDR) is a significant challenge in medicine, often mediated by efflux pumps like P-glycoprotein.
• Cyclosporine, an immunosuppressant, exhibits toxicity, particularly in the kidneys, a site of high P-glycoprotein expression.

Purpose of the Study:

• To investigate the role of P-glycoprotein in cellular cyclosporine accumulation.
• To determine if verapamil can overcome P-glycoprotein-mediated reduction of cyclosporine uptake.
• To explore the impact of P-glycoprotein on cyclosporine accumulation in renal cells.

Main Methods:

• Comparison of cyclosporine accumulation in drug-sensitive (AuxB1 CHO) and multidrug-resistant (CHRC5 CHO) cell lines with varying P-glycoprotein expression.
• Assessment of verapamil's effect on cyclosporine accumulation in resistant cells and renal cell lines (rat mesangial and LLCPK1).
• Evaluation of cyclosporine's effect on vinblastine accumulation in resistant and sensitive cell lines.

Main Results:

• Cyclosporine accumulation was reduced by over 50% in P-glycoprotein-overexpressing resistant cells compared to sensitive cells.
• Verapamil treatment restored cyclosporine accumulation in resistant cells.
• Cyclosporine concentration influenced its own accumulation, suggesting self-regulation via P-glycoprotein interaction.
• Cyclosporine also reversed P-glycoprotein-mediated differences in vinblastine accumulation.
• Verapamil increased cyclosporine accumulation by approximately 70% in renal cell lines.

Conclusions:

• Cellular cyclosporine accumulation is significantly regulated by its interaction with P-glycoprotein.
• Verapamil can overcome P-glycoprotein-mediated efflux of cyclosporine.
• These findings have implications for understanding cyclosporine pharmacokinetics and toxicity, especially in renal tissues.