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Increasing resistance in antibiotic and chemotherapeutic treatments has been pushing studies of design and evaluation of bioactive peptides. Designing relies on different approaches from minimalist sequences and endogenous peptides modifications to computational libraries. Evaluation relies on microbiological tests. Aiming a deeper understanding, we chose the octapeptide Jelleine-I (JI) for its selective and low toxicity profile, designed small modifications combining the substitutions of Phe by Trp and Lys/His by Arg and tested the antimicrobial and anticancer activity on melanoma cells. Biophysical methods identified environment-dependent modulation of aggregation, but critical aggregation concentrations of JI and analogs in buffer show that peptides start membrane interactions as monomers. The presence of model membranes increases or reduces the partial aggregation of peptides. Compared to JI, analog JIF2WR shows the lowest tendency to aggregation on bacterial model membranes. JI and analogs are lytic to model membranes. Their composition-dependent performance indicates preference for the higher charged anionic bilayers in line with their superior performance toward Staphylococcus aureus and Streptococcus pneumoniae. JIF2WR presented the higher partitioning, higher lytic activity and lower aggregated contents. Despite these increased membranolytic activities, JIF2WR exhibited comparable antimicrobial activity in relation to JI at the expenses of some loss in selectivity. We found that the substitution Phe/Trp (JIF2W) tends to decrease antimicrobial but to increase anticancer activity and aggregation on model membranes and the toxicity toward human cells. However, the concomitant substitution Lys/His by Arg (JIF2WR) modulates some of these tendencies, increasing both the antimicrobial and the anticancer activity while decreasing the aggregation tendency.

Alzheimer's disease (AD) is classically characterized by two major markers: extracellular development of senile plaques and intracellular formation of neurofibrillary tangles. Nonetheless, neuronal glucose hypometabolism and Ca 2+ deregulation have been separately implied in the genesis and progress of the neurodegenerative process. In this sense, the goal of this study was to investigate if modifications in the glucose transport would influence the cellular viability and would be involved with the activity of Ca 2+ removal from the neuron. The total levels of plasma membrane Ca 2+ -ATPase (PMCA) and glucose transporters (GLUT1 and 3), as well as glucose entry and intracellular Ca 2+ dynamics were quantified in neurons maintained at different glucose concentrations or submitted to GLUT3 mRNA interference. The results showed that reduced extracellular glucose impaired neuronal viability from day 8, but didn't change the total protein levels of GLUT1, GLUT3 and PMCA before the onset of the cell death. Conversely, the rate of glucose transport and Ca 2+ concentration was already altered since the 4th day of external glucose reduction. Interestingly, reduction of GLUT3 on plasma membrane led to lower glucose transport and intracellular Ca 2+ accumulation. It was observed that the reduction of glucose transport directed the neuron to decrease the removal and increase of intracellular Ca 2+ at rest. Therefore, we concluded that reduced glucose transport impairs neuronal viability and compromise the activity of Ca 2+ removal from the neuron. Thus, it is expected that changes in glucose transport may lead to a more susceptible condition or trigger a neurodegenerative condition resulting in accumulation of intracellular Ca 2+ ., (Copyright © 2020 IBRO. Published by Elsevier Ltd. All rights reserved.)

Glioblastoma multiforme is the most common and lethal malignant brain tumor. Because of its complexity and heterogeneity, this tumor has become resistant to conventional therapies and the available treatment produces multiple side effects. Here, using multiple experimental approaches, we demonstrate that three mastoparan peptides-Polybia-MP1, Mastoparan X, and HR1-from solitary wasp venom exhibit potent anticancer activity toward human glioblastoma multiforme cells. Importantly, the antiglioblastoma action of mastoparan peptides occurs by membranolytic activity, leading to necrosis. Our data also suggest a direct relation between mastoparan membranolytic potency and the presence of negatively charged phospholipids like phosphatidylserine. Collectively, these data may warrant additional studies for mastoparan peptides as new agents for the treatment of glioblastoma multiforme brain tumor.

Endocannabinoids are amphiphilic molecules that play crucial neurophysiological functions acting as lipid messengers. Antagonists and knockdown of the classical CB1 and CB2 cannabinoid receptors do not completely abolish many endocannabinoid activities, supporting the idea of a mechanism independent of receptors whose mode of action remains unclear. Here we combine gramicidin A (gA) single channel recordings and membrane capacitance measurements to investigate the lipid bilayer-modifying activity of endocannabinoids. Single channel recordings show that the incorporation of endocannabinoids into lipid bilayers reduces the free energy necessary for gramicidin channels to transit from the monomeric to the dimeric conformation. Membrane capacitance demonstrates that the endocannabinoid anandamide has limited effects on the overall structure of the lipid bilayers. Our results associated with the theory of membrane elastic deformation reveal that the action of endocannabinoids on membrane proteins can involve local adjustments of the lipid/protein hydrophobic interface. The current findings shed new light on the receptor-independent mode of action of endocannabinoids on membrane proteins, with important implications towards their neurobiological function., Competing Interests: The authors declare no competing financial interests.

This study shows that MP-1, a peptide from the venom of the Polybia paulista wasp, is more toxic to human leukemic T-lymphocytes than to human primary lymphocytes. By using model membranes and electrophysiology measurements to investigate the molecular mechanisms underlying this selective action, the porelike activity of MP-1 was identified with several bilayer compositions. The highest average conductance was found in bilayers formed by phosphatidylcholine or a mixture of phosphatidylcholine and phosphatidylserine (70:30). The presence of cholesterol or cardiolipin substantially decreases the MP-1 pore activity, suggesting that the membrane fluidity influences the mechanism of selective toxicity. The determination of partition coefficients from the anisotropy of Trp indicated higher coefficients for the anionic bilayers. The partition coefficients were found to be 1 order of magnitude smaller when the bilayers contain cholesterol or a mixture of cholesterol and sphingomyelin. The blue shift fluorescence, anisotropy values, and Stern-Volmer constants are indications of a deeper penetration of MP-1 into anionic bilayers than into zwitterionic bilayers. Our results indicate that MP-1 prefers to target leukemic cell membranes, and its toxicity is probably related to the induction of necrosis and not to DNA fragmentation. This mode of action can be interpreted considering a number of bilayer properties like fluidity, lipid charge, and domain formation. Cholesterol-containing bilayers are less fluid and less charged and have a tendency to form domains. In comparison to healthy cells, leukemic T-lymphocyte membranes are deprived of this lipid, resulting in decreased peptide binding and lower conductance. We showed that the higher content of anionic lipids increases the level of binding of the peptide to bilayers. Additionally, the absence of cholesterol resulted in enhanced pore activity. These findings may drive the selective toxicity of MP-1 to Jurkat cells.