The present work characterizes the effects of synthetic E-cadherin peptide (HAV) on blood–brain barrier (BBB) integrity using various techniques including magnetic resonance imaging (MRI) and near-infrared fluorescent imaging (NIRF). The permeability of small molecular weight permeability marker gadolinium diethylenetriaminepentaacetate (Gd-DTPA) contrast agent, the large molecular weight permeability marker, IRDye 800CW PEG, and the P-glycoprotein (P-gp) efflux transporter contrast agent, rhodamine 800 (R800), were examined in the presence and absence of HAV peptide. The results consistently demonstrated that systemic iv administration of HAV peptide resulted in a reversible disruption of BBB integrity and enhanced the accumulation of all the dyes examined. The magnitude of increase ranged from 2-fold to 5-fold depending on the size and the properties of the permeability markers. The time frame for BBB disruption with HAV peptide was rapid, occurring within 3–6 min following injection of the peptide. Furthermore, modulation of BBB permeability was reversible with the barrier integrity being restored within 60 min of the injection. The increased BBB permeability observed following HAV peptide administration was not attributable to changes in cerebral blood flow. These studies support the potential use of cadherin peptides to rapidly and reversibly modulate BBB permeability of a variety of therapeutic agents.

One of the major hurdles in developing therapeutic agents is the difficulty in delivering drugs through the intestinal mucosa and blood-brain barriers (BBB). The goal here is to describe the general structures of the biological barriers and the strategies to enhance drug delivery across these barriers. Prodrug methods used to improve drug penetration via the transcellular pathway have been successfully developed, and some prodrugs have been used to treat patients. The use of transporters to improve absorption of some drugs (e.g., antiviral agents) has also been successful in treating patients. Other methods, including (a) blocking the efflux pumps to improve transcellular delivery and (b) modulation of cell-cell adhesion in the intercellular junctions to improve paracellular delivery across biological barriers are still in the investigational stage.

It is challenging to deliver molecules to the brain for diagnosis and treatment of brain diseases. This is primarily due to the presence of the blood-brain barrier (BBB), which restricts the entry of many molecules into the brain. In this study, cyclic ADT peptides (ADTC1, ADTC5, and ADTC6) have been shown to modify the BBB to enhance the delivery of marker molecules (e.g., 14C-mannitol, Gd-DTPA) to the brain via the paracellular pathways of the BBB. The hypothesis is that these peptides modulate cadherin interactions in the adherens junctions of the vascular endothelial cells forming the BBB to increase paracellular drug permeation. In vitro studies indicated that ADTC5 had the best profile to inhibit adherens junction resealing in MDCK cell monolayers in a concentration-dependent manner (IC50 = 0.3 mM) with a maximal response at 0.4 mM. Under the current experimental conditions, ADTC5 improved the delivery of 14C-mannitol to the brain about twofold compared to the negative control in the in situ rat brain perfusion model. Furthermore, ADTC5 peptide increased in vivo delivery of Gd-DTPA to the brain of Balb/c mice when administered intravenously (i.v.). In conclusion, ADTC5 has the potential to improve delivery of diagnostic and therapeutic agents to the brain.

The objective was to optimize and evaluate the in vivo activities of our novel bifunctional peptide inhibitor (BPI), which alters immune response in autoimmune diseases by modulating the immunological synapse formation. Previously, we have designed PLP-BPI and GAD-BPI by conjugating myelin proteolipid protein (PLP) 139-151 and glutamic acid decarboxylase (GAD) [208][209][210][211][212][213][214][215][216][217] , respectively, with CD11a 237-246 via a spacer peptide. PLP-BPI and GAD-BPI suppressed the disease progression in experimental autoimmune encephalomyelitis (EAE) and in type-1 diabetes, respectively. In this study, various PLP-BPI derivatives were synthesized and evaluated in the EAE model. Intravenous injections of PLP-BPI derivatives prevented the disease progression more efficiently than did unmodified PLP-BPI. Production of interleukin-17, a potent pro-inflammatory cytokine found commonly among MS patients, was significantly low in Ac-PLP-BPI-NH 2 -2-treated mice. Treatment given after the disease onset could dramatically ameliorate the disease. BPI induced anaphylactic responses at a lower incidence than PLP 139-151 . In conclusion, PLP-BPI derivatives can effectively suppress the disease severity and morbidity of EAE by postonset therapeutic treatment as well as prophylactic use.

E-cadherin-mediated cell-cell interactions in the zonula adherens play an important role in the formation of the intercellular tight junctions found in the blood-brain barrier. However, it is also responsible for the low permeation of drugs into the brain. In this study, HAV6 peptide derived from the EC1 domain of E-cadherin was found to enhance the permeation of 14 C-mannitol and [ 3 H(G)]-daunomycin through the blood brain barrier of the in situ rat brain perfusion model. In addition, HAV6 peptide and verapamil have a synergistic effect in enhancing the BBB permeation of daunomycin. A new intercellular-junction resealing assay was also developed using Caco-2 monolayers to evaluate new peptides (BLG2, BLG3, and BLG4) derived from the bulge regions of the EC2, EC3, and EC4 domains of E-cadherin. BLG2 and BLG4 peptides but not BLG3 peptides were found to be effective in blocking the resealing of the intercellular junctions. The positive control peptides (ADT10, ADT6, and HAV10) block the resealing of the intercellular junctions in a concentration-dependent manner. All these findings suggest that E-cadherin-derived peptides can block E-cadherin-mediated cell-cell interactions. These findings demonstrate that cadherin peptides may offer a useful targeted permeation enhancement of therapeutic agents such as anticancer drugs into the brain. KeywordsE-cadherin; cell-cell adhesion; HAV peptides; ADT peptides; intercellular junctions; adherens junction; Caco-2 cell monolayers Many drug molecules have difficulty in crossing the intestinal mucosa and the blood-brain barrier (BBB).1 , 2 For proteins and peptides, their size and hydrophilicity prevent them from crossing these biological barriers. They cannot penetrate the paracellular pathway due to the presence of intercellular tight junctions.3 Intercellular tight junctions are circumferential zipper-like seals between adjacent endothelial cells of the BBB. The tight junctions have multiple functions, including maintaining cell polarity to prevent the mixing of membrane proteins between the apical and basolateral membranes4 and functioning as a gate to control the paracellular passage of ions and solutes.5 The adheren junctions consist of major transmembrane proteins called classical cadherins (i.e., E-cadherin), which generate intercellular contacts through trans-pairing between cadherins on opposing cells.6 , 7 The * To whom correspondence should be addressed Dr. Teruna J. Siahaan, Department of Pharmaceutical Chemistry, The University of Kansas, 2095 Constant Ave., Lawrence, KS 66047, Phone: 785-864-7327, Fax: 785-864-5736, siahaan@ku.edu. NIH Public Access Author ManuscriptMol Pharm. Author manuscript; available in PMC 2012 February 7. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript tight junctions of BBB begin to restrict the diffusion of molecules with molecular weight higher than 180 Da and there is a relationship between molecular size and brain absorption.5 Although small hydrophobic anticancer agents can readily partition i...