High cholesterol diet exacerbates blood-brain barrier disruption in LDLr–/– mice : impact on cognitive function

Background: Evidence has revealed an association between familial hypercholesterolemia and cognitive impairment. In this regard, a connection between cognitive deficits and hippocampal blood-brain barrier (BBB) breakdown was found in low-density lipoprotein receptor knockout mice (LDLr–/–), a mouse model of familial hypercholesterolemia. Objective: Herein we investigated the impact of a hypercholesterolemic diet on cognition and BBB function in C57BL/6 wild-type and LDLr–/– mice. Methods: Animals were fed with normal or high cholesterol diets for 30 days. Thus, wild-type and LDLr–/– mice were submitted to memory paradigms. Additionally, BBB integrity was evaluated in the mice’s prefrontal cortices and hippocampi. Results: A tenfold elevation in plasma cholesterol levels of LDLr–/– mice was observed after a hypercholesterolemic diet, while in wild-type mice, the hypercholesterolemic diet exposure increased plasma cholesterol levels only moderately and did not induce cognitive impairment. LDLr–/– mice presented memory impairment regardless of the diet. We observed BBB disruption as an increased permeability to sodium fluorescein in the prefrontal cortices and hippocampi and a decrease on hippocampal claudin-5 and occludin mRNA levels in both wild-type and LDLr–/– mice treated with a hypercholesterolemic diet. The LDLr–/– mice fed with a regular diet already presented BBB dysfunction. The BBB-increased leakage in the hippocampi of LDLr–/– mice was related to high microvessel content and intense astrogliosis, which did not occur in the control mice. Conclusion: Therefore, LDLr–/– mice seem to be more susceptible to cognitive impairments and BBB damage induced by exposure to a high cholesterol diet. Finally, BBB disruption appears to be a relevant event in hypercholesterolemia-induced brain alterations

Protonectin peptides target lipids, act at the interface and selectively kill metastatic breast cancer cells while preserving morphological integrity

© 2021 Elsevier Inc. All rights reserved.Despite the need for innovative compounds as antimicrobial and anticancer agents, natural sources of peptides remain underexplored. Protonectin (PTN), a cationic dodecapeptide of pharmacological interest, presents large hydrophobicity that is associated with the tendency to aggregate and supposedly influences bioactivity. A disaggregating role was assigned to PTN' N-terminal fragment (PTN1-6), which enhances the bioactivity of PTN in a 1:1 mixture (PTN/PTN1-6). Spectroscopic techniques and model membranes (phospholipid bilayers and SDS micelles) revealed that environment-dependent aggregation is reduced for PTN/PTN1-6, but cytotoxicity of PTNs on MDA-MB-231 breast cancer showed the same CC50 values around 16 µM and on MCF-10A epithelial breast cells 6 to 5-fold higher values, revealing a selective interaction. Since PTN1-6 lacks activity on breast cells, its presence should differently affect PTN activity, suggesting that aggregation could modulate activity depending on the membrane characteristics. Indeed, increased partitioning and lytic activity of PTN/PTN1-6 were found in model membranes independently of charge density, but affected by the curvature tendency. PTN and PTN/PTN1-6 do not alter morphology and roughness of cancer cells, indicating a superficial interaction with membranes and consistent with results obtained in NMR experiments. Our results indicate that aggregation of PTNs depends on the membrane characteristics and modulates the activity of the peptides.This work was supported by the Fundação de Amparo à Pesquisa do Estado de São Paulo – FAPESP [Funding Projects Nos. 2012/24259-0, 2014/08372-7, 2016/50178-8] and Fundação para a Ciência e a Tecnologia, Portugal – FCT I. P. [Funding PTDC/BBB-BQB/1693/2014]. DSA has a postdoctoral fellowship (FAPESP grant# 2015/25620-7) and also thanks CAPES for former scholarships. DBM and FDO acknowledge, respectively, CAPES scholarships and FCT I.P. fellowship [PD/BD/135046/2017]. The Brazilian BioscienceNational Laboratory (LNBio) is acknowledged for the NMR timemachine [proposal RMN-23300].info:eu-repo/semantics/publishedVersio

Synthesis and characterization of peptide-chitosan conjugates (PepChis) with lipid bilayer affinity and antibacterial activity

© 2019 American Chemical SocietyAntimicrobial peptides appear among innovative biopolymers with potential therapeutic interest. Nevertheless, issues concerning efficiency, production costs, and toxicity persist. Herein, we show that conjugation of peptides with chitosans can represent an alternative in the search for these needs. To increase solubility, deacetylated and degraded chitosans were prepared. Then, they were functionalized via N-succinimidyl-S-acetylthiopropionate or via glutathione (GSH), an endogenous peptide linker. To the best of our knowledge, it is the first time that GSH is used as a thiolating agent for the conjugation of peptides. Next, thiolated chitosans were conjugated through a disulfide bond with designed shortchain peptides, one of them derived from the antimicrobial peptide Jelleine-I. Conjugates and respective reaction intermediates were characterized by absorciometry, attenuated total reflectance−Fourier transform infrared, and 1H NMR. Zeta potential measurements showed the cationic nature of these biomacromolecules and their preferential partitioning to Gram-positive bacterial-like model membranes. In vitro investigation using representative Gram-positive and -negative bacteria (Staphylococcus aureus and Escherichia coli, respectively) showed that the conjugation strategies lead to enhanced activity in relation to the unconjugated peptide and to the unconjugated chitosan. The obtained products showed selectivity toward S. aureus at low cytotoxicity as determined in NIH/3T3 cells. Overall, our study demonstrates that an appropriate choice of antimicrobial peptide and chitosan characteristics leads to increased antimicrobial activity of the conjugated product and represents a strategy to modulate the activity and selectivity of antimicrobials resorting to low-cost chemicals. The present proposal starts from less expensive raw materials (chitosan and short-chain peptide), is based on aqueous solvents, and minimizes the use of reactants with a higher environmental impact. The final biopolymer contains the backbone of chitosan, just 3−6% peptide derived from royal jelly and GSH, all of them considered safe for human use or as a physiological molecule.This work was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo—FAPESP nos. 2012/24259-0, 2012/02065-0, 2014/08372-7, 2015/07548-7, 2016/13368-4, 2016/50178-8, FCT (Fundação para a Ciência e a Tecnologia, Portugal) grant PTDC/QEQ-MED/4412/2014, and European Commission, Marie S. Curie action RISE, H2020-MSCA-RISE-2014, grant 644167. DBM was a recipient of the CAPES scholarships, LMS is a recipient of the CNPq scholarship, and AC and SAD are recipients of scholarships PD/BD/136866/2018 and PD/BD/114425/2016 from FCT, respectively.info:eu-repo/semantics/publishedVersio