Substance P derivatives as versatile tools for specific delivery of various types of biomolecular cargo

Nanotechnological Advances for Nose to Brain Delivery of Therapeutics to Improve the Parkinson Therapy

Blood-Brain Barrier (BBB) acts as a highly impermeable barrier, presenting an impediment to the crossing of most classical drugs targeted for neurodegenerative diseases including Parkinson's disease (PD). About the nature of drugs and other potential molecules, they impose unavoidable doserestricted limitations eventually leading to the failure of therapy. However, many advancements in formulation technology and modification of delivery approaches have been successful in delivering the drug to the brain in the therapeutic window. The nose to the brain (N2B) drug delivery employing the nanoformulation, is one such emerging delivery approach, overcoming both classical drug formulation and delivery-associated limitations. This latter approach offers increased bioavailability, greater patient acceptance, lesser metabolic degradation of drugs, circumvention of BBB, ample drug loading along with the controlled release of the drugs. In N2B delivery, the intranasal (IN) route carries therapeutics firstly into the nasal cavity followed by the brain through olfactory and trigeminal nerve connections linked with nasal mucosa. The N2B delivery approach is being explored for delivering other biologicals like neuropeptides and mitochondria. Meanwhile, this N2B delivery system is associated with critical challenges consisting of mucociliary clearance, degradation by enzymes, and drug translocations by efflux mechanisms. These challenges finally culminated in the development of suitable surfacemodified nano-carriers and Focused- Ultrasound-Assisted IN as FUS-IN technique which has expanded the horizons of N2B drug delivery. Hence, nanotechnology, in collaboration with advances in the IN route of drug administration, has a diversified approach for treating PD. The present review discusses the physiology and limitation of IN delivery along with current advances in nanocarrier and technical development assisting N2B drug delivery.

Novel NK1R-Targeted 68Ga-/177Lu-Radioconjugates with Potential Application against Glioblastoma Multiforme: Preliminary Exploration of Structure-Activity Relationships

Locoregionally administered, NK1 receptor (NK1R) targeted radionuclide therapy is a promising strategy for the treatment of glioblastoma multiforme. So far, the radiopharmaceuticals used in this approach have been based on the endogenous agonist of NK1R, Substance P or on its close analogues. Herein, we used a well-known, small molecular NK1R antagonist, L732,138, as the basis for the radiopharmaceutical vector. First, 14 analogues of this compound were evaluated to check whether extending the parent structure with linkers of different lengths would not deteriorate the NK1R binding. The tested analogues had affinity similar to or better than the parent compound, and none of the linkers had a negative impact on the binding. Next, five DOTA conjugates were synthesized and used for labelling with ⁶⁸Ga and ¹⁷⁷Lu. The obtained radioconjugates turned out to be fairly lipophilic but showed rather limited stability in human plasma. Evaluation of the receptor affinity of the (radio)conjugates showed that neither the chelator nor the metal negatively impacts the NK1R binding. The ¹⁷⁷Lu-radioconjugates exhibited the binding characteristics towards NK1R similar or better than that of the ¹⁷⁷Lu-labelled derivative of Substance P, which is in current clinical use. The experimental results presented herein, along with their structural rationalization provided by modelling, give insight for the further molecular design of small molecular NK1R-targeting vectors.

Emerging trends of receptor-mediated tumor targeting peptides: A review with perspective from molecular imaging modalities

Natural peptides extracted from natural components such are known to have a relatively short in-vivo half-life and can readily metabolize by endo- and exo-peptidases. Fortunately, synthetic peptides can be easily manipulated to increase in-vivo stability, membrane permeability and target specificity with some well-known natural families. Many natural as well as synthetic peptides target to their endogenous receptors for diagnosis and therapeutic applications. In order to detect these peptides externally, they must be modified with radionuclides compatible with single photon emission computed tomography (SPECT) or positron emission tomography (PET). Although, these techniques mainly rely on physiological changes and have profound diagnostic strength over anatomical modalities such as MRI and CT. However, both SPECT and PET observed to possess lack of anatomical reference frame which is a key weakness of these techniques, and unfortunately, cannot be available freely in most clinical centres especially in under-developing countries. Hence, it is need of the time to design and develop economic, patient friendly and versatile strategies to grapple with existing problems without any hazardous side effects. Optical molecular imaging (OMI) has emerged as a novel technique in field of medical science using fluorescent probes as imaging modality and has ability to couple with organic drugs, small molecules, chemotherapeutics, DNA, RNA, anticancer peptide and protein without adding chelators as necessary for radionuclides. Furthermore, this review focuses on difference in imaging modalities and provides ample knowledge about reliable, economic and patient friendly optical imaging technique rather radionuclide-based imaging techniques.

Improving NK1R-targeted gene delivery of stearyl-antimicrobial peptide CAMEL by conjugating it with substance P

Specificity is a crucial condition that hampers the application of non-viral vectors for cancer gene therapy. In a previous study, we developed an efficient gene vector, stearyl-CAMEL, using N-terminal stearylation of the antimicrobial peptide CAMEL. Substance P (SP), an 11-residue neuropeptide, rapidly enters cells after binding to the neurokinin-1 receptor (NK1R), which is expressed in many cancer cell lines. In this study, the NK1R-targeted gene vector stearyl-CMSP was constructed by conjugating SP to the C-terminus of stearyl-CAMEL. Our results indicated that stearyl-CMSP displayed significant transfection specificity for NK1R-expressing cells compared with that shown by stearyl-CAMEL. Accordingly, the stearyl-CMSP/p53 plasmid complexes had significantly higher antiproliferative activity against HEK293-NK1R cells than they did against HEK293 cells, while the stearyl-CAMEL/p53 plasmid complexes did not show this specificity in antiproliferative activity. Consequently, conjugation of the NK1R-targeted ligand SP is a simple and successful strategy to construct efficient cancer-targeted non-viral gene vectors.

Substance P enhances the local activation of NK1R-expressing c-kit+ cardiac progenitor cells in right atrium of ischemia/reperfusion-injured heart

BACKGROUND

Localization of neurokinin 1 receptor (NK₁R), the endogenous receptor for neuropeptide substance P (SP), has already been described for the right atrium (RA) of the heart. However, the biological role of SP/NK₁R signal pathways in the RA remains unclear. Sprague-Dawley rats were randomly divided into 4 groups (n = 22 each); subjected to sham, ischemia/reperfusion-injury (I/R), I/R with 5 nmole/kg SP injection (SP + I/R), and SP + I/R with 1 mg/kg RP67580 injection (RP, a selective non-peptide tachykinin NK₁R antagonist) (RP/SP + I/R). The left anterior descending coronary artery was occluded for 40 min followed by 1 day reperfusion with SP or SP + RP or without either. After 1 day, both atria and ventricles as well as the heart apexes were collected.

RESULTS

SP promoted the expression of c-Kit, GATA4, Oct4, Nanog, and Sox2 in only the RA of the SP + I/R rats via NK₁R activation. In agreement with these observations, NK₁R-expressing c-Kit⁺ Nkx2.5⁺GATA4⁺ cardiac progenitor cells (CPCs) in the ex vivo RA explant outgrowth assay markedly migrated out from RA^{1 day SP + I/R} approximately 2-fold increase more than RA^{1 day I/R}. Treatment of SP promoted proliferation, migration, cardiosphere formation, and potential to differentiate into cardiomyocytes. Using RP inhibitor, NK₁R antagonist not only inhibited cell proliferation and migration but also reduced the formation of cardiosphere and differentiation of c-Kit⁺ CPCs.

CONCLUSION

SP/NK₁R might play a role as a key mediator involved in the cellular response to c-Kit⁺ CPC expansion in RA of the heart within 24 h after I/R.

Macrocyclic Peptides as Drug Candidates: Recent Progress and Remaining Challenges

Peptides as a therapeutic modality attract much attention due to their synthetic accessibility, high degree of specific binding, and the ability to target protein surfaces traditionally considered "undruggable". Unfortunately, at the same time, other pharmacological properties of a generic peptide, such as metabolic stability and cell permeability, are quite poor, which limits the success of de novo discovered biologically active peptides as drug candidates. Here, we review how macrocyclization as well as the incorporation of nonproteogenic amino acids and various conjugation strategies may be utilized to improve on these characteristics to create better drug candidates. We analyze recent progress and remaining challenges in improving individual pharmacological properties of bioactive peptides, and offer our opinion on interfacing these, often conflicting, considerations, to create balanced drug candidates as a potential way to make further progress in this area.

Design, synthesis and biological studies of a library of NK1-Receptor Ligands Based on a 5-arylthiosubstituted 2-amino-4,6-diaryl-3-cyano-4H-pyran core: Switch from antagonist to agonist effect by chemical modification

A library of 5-arylthiosubstituted 2-amino-4,6-diaryl-3-cyano-4H-pyrans has been synthesized as a new family of non-peptide NK1 receptor ligands by a one-pot cascade process. Their biological effects via interaction with the NK1 receptor were experimentally determined as percentage of inhibition (for antagonists) and percentage of activation (for agonists), compared to the substance P (SP) effect, in IPone assay. A set of these amino compounds was found to inhibit the action of SP, and therefore can be considered as a new family of SP-antagonists. Interestingly, the acylation of the 2-amino position causes a switch from antagonist to agonist activity. The 5-phenylsulfonyl-2-amino derivative 17 showed the highest antagonist activity, while the 5-p-tolylsulfenyl-2-trifluoroacetamide derivative 20R showed the highest agonist effect. As expected, in the case of the 5-sulfinylderivatives, there was an enantiomeric discrimination in favor of one of the two enantiomers, specifically those with (S_S,R_C) configuration. The anticancer activity studies assessed by using human A-549 lung cancer cells and MRC-5 non-malignant lung fibroblasts, revealed a statistically significant selective cytotoxic effect of some of these 2-amino-4H-pyran derivatives toward the lung cancer cells. These studies demonstrated that the newly synthesized 4H-pyran derivatives can be used as a starting point for the synthesis of novel SP-antagonists with higher anticancer activity in the future.

Getting across the cell membrane: an overview for small molecules, peptides, and proteins

The ability to efficiently access cytosolic proteins is desired in both biological research and medicine. However, targeting intracellular proteins is often challenging, because to reach the cytosol, exogenous molecules must first traverse the cell membrane. This review provides a broad overview of how certain molecules are thought to cross this barrier, and what kinds of approaches are being made to enhance the intracellular delivery of those that are impermeable. We first discuss rules that govern the passive permeability of small molecules across the lipid membrane, and mechanisms of membrane transport that have evolved in nature for certain metabolites, peptides, and proteins. Then, we introduce design strategies that have emerged in the development of small molecules and peptides with improved permeability. Finally, intracellular delivery systems that have been engineered for protein payloads are surveyed. Viewpoints from varying disciplines have been brought together to provide a cohesive overview of how the membrane barrier is being overcome.