An intestinal paracellular pathway biased toward positively-charged macromolecules

Area of Science:

• Pharmacology and Drug Delivery
• Gastrointestinal Physiology
• Molecular Biology

Background:

• Developing oral peptide therapeutics is hindered by the lack of effective intestinal absorption mechanisms.
• Existing methods struggle to safely and consistently enhance macromolecular uptake across the intestinal epithelium.
• Previous research identified a peptide, PIP 640, that activates an endogenous mechanism to control intestinal permeability.

Purpose of the Study:

• To investigate the specific mechanisms by which PIP 640 alters intestinal epithelial permeability.
• To determine the impact of PIP 640 on tight junction proteins and macromolecule transport.
• To assess the potential of PIP 640 for enhancing the oral delivery of therapeutic peptides.

Main Methods:

• Utilized Caco-2 cell monolayers to study apical-to-basolateral (AB) transport of dextran molecules.
• Analyzed changes in tight junction (TJ) protein expression and cellular distribution, including claudin-2.
• Compared PIP 640 effects with those of pro-inflammatory cytokines (TNF-α and IFN-γ) and conducted in vivo studies in rats.

Main Results:

• PIP 640 enhanced the transport of 4-kDa dextran but not 10-kDa dextran across Caco-2 monolayers.
• Observed increased claudin-2 expression and a shift in its distribution from the nucleus to the cell membrane.
• PIP 640-induced permeability changes favored positively-charged macromolecules and were distinct from cytokine effects.

Conclusions:

• PIP 640 activates a claudin-2 dependent pathway to transiently increase paracellular permeability.
• This mechanism enhances the transport of small therapeutic peptides, particularly cationic ones, in vitro and in vivo.
• PIP 640 presents a promising strategy for developing oral formulations of peptide-based drugs.