From Flexibility to Vulnerability: Targeting P-glycoprotein with Cold Atmospheric Plasma-Derived Reactive Species to Overcome Multidrug Resistance

Multidrug resistance (MDR) remains a major obstacle to the efficacy of chemotherapy in cancer treatment. Experimental evidence highlights the pivotal role of drug efflux transporters, such as P-glycoprotein (Pgp), in this phenomenon. Furthermore, studies underscore the significance of linker region flexibility within Pgp in modulating its function. In this study, we propose a novel non-pharmacological strategy to inhibit Pgp activity by targeting the structural flexibility of its linker region. Using molecular dynamics simulations, we investigated the effects of three reactive species generated by cold atmospheric pressure plasma--hydrogen peroxide (HP), nitric oxide (NO), and molecular oxygen (O2)--on the conformational dynamics of the linker. Comprehensive analyses, including conformational entropy, effective spring constants, polymer-like behavior, and hydrogen bonding networks, revealed that these reactive species substantially restrict the structural flexibility of the linker domain. Among them, HP exhibited the most pronounced stiffening effect, primarily driven by stable electrostatic interactions and the formation of strong hydrogen bonds. This reduction in flexibility is likely to hinder the conformational transitions required for drug efflux, thereby locking Pgp in an inactive or impaired state. Our findings not only provide new insights into the structural dynamics of Pgp in response to cold plasma-derived species, but also open up promising avenues for the development of combinatorial therapeutic strategies aimed at overcoming drug resistance.