Neuropeptide Y and its C-terminal fragments acting on Y2 receptor: Raman and SERS spectroscopy studies

Neuropeptide Y Y2 and Y5 receptors as potential targets for neuroprotective and antidepressant therapies: Evidence from preclinical studies

There is currently no effective treatment either for neurological illnesses (ischemia and neurodegenerative diseases) or psychiatric disorders (depression), in which the Glu/GABA balance is disturbed and accompanied by significant excitotoxicity. Therefore, the search for new and effective therapeutic strategies is imperative for these disorders. Studies conducted over the last several years indicate that the neuropeptide Y (NPY)-ergic system may be a potential therapeutic target for neuroprotective or antidepressant compounds. This review focuses on the neuroprotective roles of Y2 and Y5 receptors (YRs) in neurological disorders such as ischemia, Alzheimer's disease, Parkinson's disease, Huntington's disease, and in psychiatric disorders such as depression. It summarizes current knowledge on the possible mechanisms underlying the neuroprotective or antidepressant-like actions of Y2R and Y5R ligands. The review also discusses ligands acting at Y2R and Y5R and their limitations as in vivo pharmacological tools. The results from the preclinical studies discussed here may be useful in developing effective therapeutic strategies to treat neurological diseases on the one hand and psychiatric disorders on the other, and may pave the way for the development of novel Y2R and Y5R ligands as candidate drugs for the treatment of these diseases.

Adsorption of (Phe-h5)/(Phe-d5)-substituted peptides from neurotensin family on the nanostructured surfaces of Ag and Cu: SERS studies

This work describes an application of Raman (RS) and surface-enhanced Raman scattering (SERS) to characterize the selective adsorption of two peptides belonging to the neurotensin family peptides, such as kinetensin (KN) and xenopsin-related peptide 2 (XP-2) that are known to stimulate the growth of human tumors. To perform a reliable analysis of SERS spectra, the L-Phe residue (at position 8 or 1 in the amino acid sequence of these peptides) was replaced with L-Phe-d₅ (five protons of L-phenylalanine ring substituted by deuterium). Native and (Phe-d₅)-isotopically labeled peptides were deposited on electrochemically nanostructured surfaces of Ag (AgORC) and Cu (CuORC) from an aqueous solution (H₂O). To determine the share of amide bonds in the interaction with the metallic substrate, SERS spectra of peptides adsorbed on AgORC from heavy water (D₂O) were measured. Also, to determine the effect of the C-end on the SERS spectrum, measurements were made for the KN analog in which the C-terminal L-leucine was removed ([desLeu⁹]KN). Based on the analyses of the spectral profiles, in the spectral range of 600-1650 cm^-1, specific conclusions have been drawn regarding specific aromatic ring···metal interactions and changes in the interaction during substrate change.

Copper Binding Induces Nitration of NPY under Nitrative Stress: Complicating the Role of NPY in Alzheimer's Disease

Neuropeptide Y (NPY) is a 36 amino acid peptide that regulates a multitude of physiological functions in the central nervous system and has been shown to be involved in Alzheimer's disease (AD). A change in copper homeostasis is a remarkable feature of AD, and the dysregulation may contribute to toxicity in neural cells. Moreover, it has been shown that copper could interact with many neuropeptides and result in catalyzing the production of reactive oxygen species, which may lead to peptide oxidation. Besides, copper could also catalyze protein tyrosine nitration under oxidative stress, and there are two tyrosine residues playing an important role in NPY. Therefore, it is also likely that copper has an action on NPY and potentially influences its functions through tyrosine nitration. In this paper, the studies of the interaction of copper with NPY and the copper-catalyzed NPY nitration were performed. The electrochemical techniques, UV-vis spectroscopy, mass spectrometry, and fluorescence titration, have been applied to show that copper can interact with NPY to form a Cu-NPY complex with a conditional dissociation constant of 0.021 μmol/L, and the binding promotes the generation of •OH. Dot blotting results reveal that NPY can be nitrated upon binding with copper under nitrative stress. Furthermore, liquid chromatography-mass spectrometry (LC-MS) identify that the tyrosine residues in NPY are all nitrated during the nitration process, which will cause the inactivation of NPY shown by our previous study. This study supports the hypothesis that copper has a close correlation with NPY and implicates the peptide in AD. These data may provide a new insight into understanding the pathology and pathogenesis of AD.

In Vitro and In Vivo SERS Biosensing for Disease Diagnosis

For many disease states, positive outcomes are directly linked to early diagnosis, where therapeutic intervention would be most effective. Recently, trends in disease diagnosis have focused on the development of label-free sensing techniques that are sensitive to low analyte concentrations found in the physiological environment. Surface-enhanced Raman spectroscopy (SERS) is a powerful vibrational spectroscopy that allows for label-free, highly sensitive, and selective detection of analytes through the amplification of localized electric fields on the surface of a plasmonic material when excited with monochromatic light. This results in enhancement of the Raman scattering signal, which allows for the detection of low concentration analytes, giving rise to the use of SERS as a diagnostic tool for disease. Here, we present a review of recent developments in the field of in vivo and in vitro SERS biosensing for a range of disease states including neurological disease, diabetes, cardiovascular disease, cancer, and viral disease.

NPY binds with heme to form a NPY–heme complex: enhancing peroxidase activity in free heme and promoting NPY nitration and inactivation

NPY binding with heme enhances the peroxidase activity of free heme, resulting in the important tyrosine nitration, which will attenuate its bioactivity.

Single Cell Peptide Heterogeneity of Rat Islets of Langerhans

Measuring the chemical composition of individual cells in mammalian organs can provide critical insights toward understanding the mechanisms leading to their normal and pathological function. In this work, single cell heterogeneity of islets of Langerhans is characterized with high throughput by microscopy-guided single cell matrix-assisted laser desorption/ionization mass spectrometry. Two levels of chemical heterogeneity were observed from the analysis of more than 3000 individual cells. Within a single islet, cellular heterogeneity was evident from the exclusive expression of the canonical biomarkers glucagon, insulin, pancreatic polypeptide (PP), and somatostatin within α-, β-, γ-, and δ-cells, respectively. We localized the neuropeptide WE-14, a known cell-to-cell signaling molecule, to individual δ-cells. Moreover, several unreported endogenous peptides generated by dibasic site cleavages of PP were detected within individual γ-cells. Of these, PP(27-36) was previously shown to activate the human Y4 receptor, suggesting it has a signaling role in vivo. Heterogeneity in cell composition was also observed between islets as evidenced by a 50-fold larger α-cell population in islets of the dorsal pancreas compared to the ventral-derived pancreatic islets. Finally, PP(27-36) was more abundant in γ-cells from the ventral region of the pancreas, indicating differences in the extent of PP-prohormone processing in the two regions of the pancreas.