Free energy profiles of temozolomide crossing brain plasma membranes

Abstract

Temozolomide is an efficient small-molecule drug mostly employed for the treatment of glioblastoma, a tumor attacking both the spinal cord and the brain. Understanding the interactions of temozolomide with different lipids at the brain cell membrane can help elucidate how temozolomide permeates through cell membranes and its membrane-crossing ability. In the present work, we have constructed a simplified brain plasma membrane model to explore temozolomides microscopic structure and dynamics by means of all-atom microsecond scale molecular dynamics simulations. The preferential location of temozolomide is at the solvent-aqueous fluid surrounding the brain membrane, but it can access the interface with the membrane regularly, eventually binding to lipids of the choline and cerebroside classes. The free energy barriers of temozolomide related to brain-like plasma membrane crossing were investigated by adaptive biasing force methods, revealing values ranging from 18.5 to 66.5 kcal/mol at temperatures of 323 K and 310 K, respectively. Our results suggest that temozolomide cannot cross the membrane by pure diffusion at the normal human body temperature but that rising the temperature significantly increases the probability of barrier crossing. This fact is mainly due to the crucial role played by cholesterol and lipids of the cerebroside class. The findings reported in this work can be used to optimize the molecular design of temozolomide and to develop new analogs with better pharmacokinetic properties. Author summaryGlioblastoma is a devastating tumor affecting the brain and spinal cord, which has in the FDA-approved drug temozolomide its main clinical treatment. The present study explores how temozolomide interacts with several lipids in brain-like cell membranes. Our findings show that at normal body temperature temozolomide cannot cross the membrane by pure diffusion, but that higher temperatures significantly enhance its ability to cross the membrane by reducing the free energy barriers. Temozolomide interacts differently with several lipids and sterols depending on the temperature, which affects its permeability. This implies that temozolomide will cross the outer layer of the brain membrane only with the help of driving agents, such as intermembrane proteins. Our research suggests that temozolomide may be more effective at higher temperatures and cancer patients with fever might need a lower dose. Importantly, cholesterol plays a key role in blocking temozolomide from crossing brain-like membranes, so reducing dietary intake of cholesterol and cerebroside lipids could help modify brain cell membranes, making it easier for temozolomide to target cancer cells effectively and potentially reducing side effects.