Influx transporters and drug targeting: Application of peptide and cation transporters

Understanding the Transepithelial Transport and Transbilayer Diffusion of the Antihypertensive Peptide Asn-Cys-Trp: Insights from Caco-2 Cell Monolayers and the DPPC Model Membrane

Understanding the transport mechanism of the peptide Asn-Cys-Trp (NCW) is crucial to improving its intestinal absorption and bioavailability. This study investigated the absorption of NCW through Caco-2 cell monolayers and its interaction with the DPPC bilayers. Results revealed that after a 3 h incubation, the Papp (AP-BL) and Papp (BL-AP) values of NCW at a concentration of 5 mmol/L were (22.24 ± 4.52) × 10-7 and (6.63 ± 2.31) × 10-7 cm/s, respectively, with the transport rates of 1.59 ± 0.32 and 0.62 ± 0.20%, indicating its moderate absorption. NCW was found to be transported via PepT1 and paracellular transport pathways, as evidenced by the significant impact of Gly-Pro and cytochalasin D on the Papp values. Moreover, NCW upregulated ZO-1 mRNA expression. Further investigation of the ZO-1-mediated interaction between NCW and tight junction proteins will contribute to a better understanding of the paracellular transport mechanism of NCW. The interaction between NCW and the DPPC bilayers was predominantly driven by entropy. NCW permeated the bilayers through electrostatic, hydrogen bonding, and hydrophobic interactions, resulting in increased fluidity, flexibility, and disorder as well as phase transition and phase separation of the bilayers.

Ergothioneine, recent developments

There has been a recent surge of interest in the unique low molecular weight dietary thiol/thione, ergothioneine. This compound can accumulate at high levels in the body from diet and may play important physiological roles in human health and development, and possibly in prevention and treatment of disease. Blood levels of ergothioneine decline with age and onset of various diseases. Here we highlight recent advances in our knowledge of ergothioneine.

Organic Cation Transporter (OCT/OCTN) Expression at Brain Barrier Sites: Focus on CNS Drug Delivery

Therapeutic delivery to the central nervous system (CNS) continues to be a considerable challenge in the pharmacological treatment and management of neurological disorders. This is primarily due to the physiological and biochemical characteristics of brain barrier sites (i.e., blood-brain barrier (BBB), blood-cerebrospinal fluid barrier (BCSFB)). Drug uptake into brain tissue is highly restricted by expression of tight junction protein complexes and adherens junctions between brain microvascular endothelial cells and choroid plexus epithelial cells. Additionally, efflux transport proteins expressed at the plasma membrane of these same endothelial and epithelial cells act to limit CNS concentrations of centrally acting drugs. In contrast, facilitated diffusion via transporter proteins allows for substrate-specific flux of molecules across the plasma membrane, directing drug uptake into the CNS. Organic Cation Transporters (OCTs) and Novel Organic Cation Transporters (OCTNs) are two subfamilies of the solute carrier 22 (SLC22) family of proteins that have significant potential to mediate delivery of positively charged, zwitterionic, and uncharged therapeutics. While expression of these transporters has been well characterized in peripheral tissues, the functional expression of OCT and OCTN transporters at CNS barrier sites and their role in delivery of therapeutic drugs to molecular targets in the brain require more detailed analysis. In this chapter, we will review current knowledge on localization, function, and regulation of OCT and OCTN isoforms at the BBB and BCSFB with a particular emphasis on how these transporters can be utilized for CNS delivery of therapeutic agents.