Intramuscular Hemangioma: A Rare Cause of Omalgia.

Intramuscular hemangiomas (IHs) are benign soft-tissue tumors that represent less than 1% of all hemangiomas. This clinical entity is rarely considered as a differential diagnosis in cases of musculoskeletal pain. A healthy 38-year-old woman presented to our office with complaint of left omalgia, with 8 months of evolution, limiting her daily activities. She reported the appearance of tumefaction in the previous 4 months. She was medicated with analgesic and antiinflammatory drugs with no clinical improvement. The objective examination showed limitation of left shoulder abduction (0-90°). The patient underwent a magnetic resonance imaging (MRI), in which a well-circumscribed nodular formation was detected in the deltoid muscle. Then, she underwent a biopsy, which confirmed the diagnosis of hemangioma. The patient was referred for sclerotherapy. Intramuscular hemangiomas are usually observed in young patients. The gold-standard examination for diagnosis is MRI, which often forestalls the need for a biopsy. In many cases, IHs are asymptomatic and tend to involute over time. Despite the low frequency of this clinical entity, it is important to place it as a diagnostic hypothesis in cases of chronic pain of the limbs in young patients with poor therapeutic response to antiinflammatory drugs and analgesia.

Intramuscular Hemangioma: A Rare Cause of Omalgia / Hemangioma intramuscular: Uma causa rara de Omalgia

Abstract Intramuscular hemangiomas (IHs) are benign soft-tissue tumors that represent less than 1% of all hemangiomas. This clinical entity is rarely considered as a differential diagnosis in cases of musculoskeletal pain. A healthy 38-year-old woman presented to our office with complaint of left omalgia, with 8 months of evolution, limiting her daily activities. She reported the appearance of tumefaction in the previous 4 months. She was medicated with analgesic and antiinflammatory drugs with no clinical improvement. The objective examination showed limitation of left shoulder abduction (0-90°). The patient underwent a magnetic resonance imaging (MRI), in which a well-circumscribed nodular formation was detected in the deltoid muscle. Then, she underwent a biopsy, which confirmed the diagnosis of hemangioma. The patient was referred for sclerotherapy. Intramuscular hemangiomas are usually observed in young patients. The gold-standard examination for diagnosis is MRI, which often forestalls the need for a biopsy. In many cases, IHs are asymptomatic and tend to involute over time. Despite the low frequency of this clinical entity, it is important to place it as a diagnostic hypothesis in cases of chronic pain of the limbs in young patients with poor therapeutic response to antiinflammatory drugs and analgesia.

Resumo Os hemangiomas intramusculares (HIs) são tumores benignos de tecidos moles que representam menos de 1% de todos os hemangiomas. Esta entidade clínica raramente é considerada como diagnóstico diferencial nos casos de dor musculoesquelética. Uma paciente do sexo feminino, de 38 anos de idade, saudável, se apresentou ao nosso consultório com queixa de omalgia esquerda, com 8 meses de evolução, que limitava suas atividades diárias. Ela relatou o aparecimento de tumefação 4 meses antes da consulta. A paciente estava medicada com analgésico e antiinflamatório sem melhoria clínica. Ao exame objetivo, ela apresentava limitação da abdução do ombro esquerdo (0-90°). A paciente foi submetida a uma ressonância nuclear magnética (RNM) na qual foi detectada uma formação nodular bem circunscrita no músculo deltoide,. Em seguida, foi realizada uma biópsia que confirmou o diagnóstico de hemangioma. A paciente foi então encaminhada para a realização de escleroterapia. Os HIs normalmente são observados em pacientes jovens. O exame padrão-ouro para o diagnóstico é a RNM, que muitas vezes torna a realização de biópsia desnecessária. Em muitos casos, os HIs são assintomáticos e tendem a involuir com o tempo. Apesar da baixa frequência desta entidade clínica, é importante colocá-la como hipótese de diagnóstico em casos de dor crônica dos membros em pacientes jovens com má resposta terapêutica a antiinflamatórios e analgesia.

Spontaneous reporting of adverse reactions associated with the COVID-19 vaccine in health care professionals: A descriptive observational study conducted in a Portuguese hospital.

Background: The coronavirus disease 2019 (COVID-19) was classified as a pandemic in March 2020 by the World Health Organization. The Pfizer-BioNTech COVID-19 vaccine was the first to be authorized in the European Union, based on data from phase 1, 2, and 3 clinical trials of limited duration. Concerns have been raised regarding the vaccine's safety profile. Some of the adverse drug reactions (ADRs) associated with vaccines may not have been identified during clinical trials. This study aimed to identify ADRs associated with the Pfizer-BioNTech vaccine in health care professionals at a Portuguese tertiary university hospital. Methods: The data used in this analysis consist of ADRs reported through a spontaneous notification system from vaccines administered between December 27, 2020, and January 31, 2021. ADRs were categorized according to the MedDRA terminology. Results: A total of 8,605 Pfizer-BioNTech vaccines were administered to 4568 health care professionals. ADRs were reported among 520 of the vaccines, with an incidence of 13.56% in women and 5.31% in men. The mean age of the population reporting ADRs was 41.52 years, with a standard deviation of 9.83 years. The most frequent ADRs were myalgia (n = 274), headache (n = 199), pyrexia (n = 164), injection site pain (n = 160), fatigue (n = 84), nausea (n = 81), chills (n = 65), lymphadenopathy (n = 64), and arthralgia (n = 53). Hypersensitivity reactions occurred in 15 health care professionals, with no anaphylactic reactions observed. A total of four Important Medical Events were observed, which consisted of two cases of syncope, one case of sudden hearing loss, and one case of transverse myelitis. Conclusion: The vaccine was well-tolerated among the study participants. Reactogenicity was greater after the second dose. The incidence of ADRs was higher in women and individuals aged between 40 to 49 years. Systemic adverse reactions were most frequently reported. Systematic monitoring of ADRs of COVID-19 vaccines in real-life context is essential for a more robust establishment of its safety profile.

The effect of different reconditioning methods on bond strength of rebonded brackets: An in-vitro study.

AIM: To evaluate the effect of three different reconditioning techniques on the shear bond strength (SBS) of rebonded brackets. MATERIALS AND METHODS: Forty-five orthodontic brackets were bonded to human premolar teeth using Transbond™ XT. After debonding, the samples were randomly assigned into equal groups to assess three techniques for the removal of residual adhesive from bracket bases: in Group A, each bracket base was sandblasted with aluminum oxide; in Group B1, each base was cleaned superficially with a greenstone bur; and in Group B2, the bases were thoroughly abraded with a greenstone bur. Subsequently, brackets were rebonded and the SBS and the adhesive remnant index (ARI) were determined. Data were analyzed using one-way analysis of variance (ANOVA), plus Tukey and Kruskal-Wallis post-hoc tests (P ≤ 0.05). RESULTS: The average SBSs were: Group A, 11.75 (±4.83) MPa; Group B1, 8.22 (±4.01) MPa; and Group B2, 7.54 (±2.85) MPa. No statistically significant differences in SBS were found between Groups A and B1(P = 0.051) and Groups B1 and B2(P = 0.885), but there was a significant difference between Groups A and B2(P = 0.016). Regarding ARI scores, there were statistically significant differences between Groups A and B2(P < 0.001) and between B1 and B2(P = 0.014), but not between Groups A and B1(P = 0.068). CONCLUSION: All reconditioning methods were found to have a positive effect, but the sandblasting technique performed best. Brackets reconditioned by sandblasting and superficial grinding mainly showed mixed-type failure, while in samples thoroughly reconditioned by greenstone bur, bonding failure occurred predominantly at the adhesive/bracket interface.

SonoTweezer: An Acoustically Powered End-Effector for Underwater Micromanipulation.

Recent advances in contactless micromanipulation strategies have revolutionized prospects of robotic manipulators as next-generation tools for minimally invasive surgeries. In particular, acoustically powered phased arrays offer dexterous means of manipulation both in air and water. Inspired by these phased arrays, we present SonoTweezer: a compact, low-power, and lightweight array of immersible ultrasonic transducers capable of trapping and manipulation of sub-mm sized agents underwater. Based on a parametric investigation with numerical pressure field simulations, we design and create a six-transducer configuration, which is small compared to other reported multi-transducer arrays (16-256 elements). Despite the small size of array, SonoTweezer can reach pressure magnitudes of 300 kPa at a low supply voltage of 25 V to the transducers, which is in the same order of absolute pressure as multi-transducer arrays. Subsequently, we exploit the compactness of our array as an end-effector tool for a robotic manipulator to demonstrate long-range actuation of sub-millimeter agents over a hundred times the agent's body length. Furthermore, a phase-modulation over its individual transducers allows our array to locally maneuver its target agents at sub-mm steps. The ability to manipulate agents underwater makes SonoTweezer suitable for clinical applications considering water's similarity to biological media, e.g., vitreous humor and blood plasma. Finally, we show trapping and manipulation of micro-agents under medical ultrasound (US) imaging modality. This application of our actuation strategy combines the usage of US waves for both imaging and micromanipulation.

CeFlowBot: A Biomimetic Flow-Driven Microrobot that Navigates under Magneto-Acoustic Fields.

Aquatic organisms within the Cephalopoda family (e.g., octopuses, squids, cuttlefish) exist that draw the surrounding fluid inside their bodies and expel it in a single jet thrust to swim forward. Like cephalopods, several acoustically powered microsystems share a similar process of fluid expulsion which makes them useful as microfluidic pumps in lab-on-a-chip devices. Herein, an array of acoustically resonant bubbles are employed to mimic this pumping phenomenon inside an untethered microrobot called CeFlowBot. CeFlowBot contains an array of vibrating bubbles that pump fluid through its inner body thereby boosting its propulsion. CeFlowBots are later functionalized with magnetic layers and steered under combined influence of magnetic and acoustic fields. Moreover, acoustic power modulation of CeFlowBots is used to grasp nearby objects and release it in the surrounding workspace. The ability of CeFlowBots to navigate remote environments under magneto-acoustic fields and perform targeted manipulation makes such microrobots useful for clinical applications such as targeted drug delivery. Lastly, an ultrasound imaging system is employed to visualize the motion of CeFlowBots which provides means to deploy such microrobots in hard-to-reach environments inaccessible to optical cameras.

Resilient SARS-CoV-2 diagnostics workflows including viral heat inactivation.

There is a worldwide need for reagents to perform SARS-CoV-2 detection. Some laboratories have implemented kit-free protocols, but many others do not have the capacity to develop these and/or perform manual processing. We provide multiple workflows for SARS-CoV-2 nucleic acid detection in clinical samples by comparing several commercially available RNA extraction methods: QIAamp Viral RNA Mini Kit (QIAgen), RNAdvance Blood/Viral (Beckman) and Mag-Bind Viral DNA/RNA 96 Kit (Omega Bio-tek). We also compared One-step RT-qPCR reagents: TaqMan Fast Virus 1-Step Master Mix (FastVirus, ThermoFisher Scientific), qPCRBIO Probe 1-Step Go Lo-ROX (PCR Biosystems) and Luna® Universal Probe One-Step RT-qPCR Kit (Luna, NEB). We used primer-probes that detect viral N (EUA CDC) and RdRP. RNA extraction methods provided similar results, with Beckman performing better with our primer-probe combinations. Luna proved most sensitive although overall the three reagents did not show significant differences. N detection was more reliable than that of RdRP, particularly in samples with low viral titres. Importantly, we demonstrated that heat treatment of nasopharyngeal swabs at 70°C for 10 or 30 min, or 90°C for 10 or 30 min (both original variant and B 1.1.7) inactivated SARS-CoV-2 employing plaque assays, and had minimal impact on the sensitivity of the qPCR in clinical samples. These findings make SARS-CoV-2 testing portable in settings that do not have CL-3 facilities. In summary, we provide several testing pipelines that can be easily implemented in other laboratories and have made all our protocols and SOPs freely available at https://osf.io/uebvj/.

Resilient SARS-CoV-2 diagnostics workflows including viral heat inactivation.

There is a worldwide need for reagents to perform SARS-CoV-2 detection. Some laboratories have implemented kit-free protocols, but many others do not have the capacity to develop these and/or perform manual processing. We provide multiple workflows for SARS-CoV-2 nucleic acid detection in clinical samples by comparing several commercially available RNA extraction methods: QIAamp Viral RNA Mini Kit (QIAgen), RNAdvance Blood/Viral (Beckman) and Mag-Bind Viral DNA/RNA 96 Kit (Omega Bio-tek). We also compared One-step RT-qPCR reagents: TaqMan Fast Virus 1-Step Master Mix (FastVirus, ThermoFisher Scientific), qPCRBIO Probe 1-Step Go Lo-ROX (PCR Biosystems) and Luna ® Universal Probe One-Step RT-qPCR Kit (Luna, NEB). We used primer-probes that detect viral N (EUA CDC) and RdRP (PHE guidelines). All RNA extraction methods provided similar results. FastVirus and Luna proved most sensitive. N detection was more reliable than that of RdRP, particularly in samples with low viral titres. Importantly, we demonstrate that treatment of nasopharyngeal swabs with 70 degrees for 10 or 30 min, or 90 degrees for 10 or 30 min (both original variant and B 1.1.7) inactivates SARS-CoV-2 employing plaque assays, and that it has minimal impact on the sensitivity of the qPCR in clinical samples. These findings make SARS-CoV-2 testing portable to settings that do not have CL-3 facilities. In summary, we provide several testing pipelines that can be easily implemented in other laboratories and have made all our protocols and SOPs freely available at https://osf.io/uebvj/ .

Occupational leg edema-use of compression stockings.

To analyze the use of compression stockings to avoid the formation of occupational edema of the lower limbs in jobs with prolonged orthostatism. We carried out a review of the articles published in PubMed, from the 1st of January 2008 to 31st of December 2018 using the term "Occupational Leg Swelling". Only articles that met the following criteria were selected: prospective, observational and experimental retrospectives articles written in Portuguese or English. The research resulted in 23 articles. After reading the titles and abstracts and applying the inclusion and exclusion criteria, 5 were selected. Prolonged orthostatism is considered a risk factor for the development of chronic venous disease. The use of compression stockings reduces the occupational edema of the lower limbs. Professionals exposed to prolonged orthostatism during their work activity have a higher risk of developing lower limb edema; Despite few studies demonstrated the effectiveness of wearing compression stockings to prevent occupational edema of the lower limbs, they have showed benefit in reducing edema as well as associated symptoms. The use of compression stockings should therefore be recommended to all professionals at increased risk for occupational edema of the lower limbs.

Estimates of the rate of infection and asymptomatic COVID-19 disease in a population sample from SE England.

BACKGROUND: Understanding of the true asymptomatic rate of infection of SARS-CoV-2 is currently limited, as is understanding of the population-based seroprevalence after the first wave of COVID-19 within the UK. The majority of data thus far come from hospitalised patients, with little focus on general population cases, or their symptoms. METHODS: We undertook enzyme linked immunosorbent assay characterisation of IgM and IgG responses against SARS-CoV-2 spike glycoprotein and nucleocapsid protein of 431 unselected general-population participants of the TwinsUK cohort from South-East England, aged 19-86 (median age 48; 85% female). 382 participants completed prospective logging of 14 COVID-19 related symptoms via the COVID Symptom Study App, allowing consideration of serology alongside individual symptoms, and a predictive algorithm for estimated COVID-19 previously modelled on PCR positive individuals from a dataset of over 2 million. FINDINGS: We demonstrated a seroprevalence of 12% (51 participants of 431). Of 48 seropositive individuals with full symptom data, nine (19%) were fully asymptomatic, and 16 (27%) were asymptomatic for core COVID-19 symptoms: fever, cough or anosmia. Specificity of anosmia for seropositivity was 95%, compared to 88% for fever cough and anosmia combined. 34 individuals in the cohort were predicted to be Covid-19 positive using the App algorithm, and of those, 18 (52%) were seropositive. INTERPRETATION: Seroprevalence amongst adults from London and South-East England was 12%, and 19% of seropositive individuals with prospective symptom logging were fully asymptomatic throughout the study. Anosmia demonstrated the highest symptom specificity for SARS-CoV-2 antibody response. FUNDING: NIHR BRC, CDRF, ZOE global LTD, RST-UKRI/MRC.

Curso y envejecimiento en la esquizofrenia institucionalizada: comparación de perfiles de rendimiento cognitivo / Course and aging in institutionalized schizophrenia: A comparison of cognitive performance profiles

Los deficits neurocognitivos en esquizofrenia han sido muy estudiados, pero no existe consenso sobre su curso ni es abundante su análisis en población envejecida. El objetivo del presente trabajo es comparar perfiles neurocognitivos entre sujetos mayores (grupo A) y menores (grupo B) de 65 años con esquizofrenia y entre sujetos mayores con esquizofrenia y controles sanos de la misma edad (grupo C). Participaron 90 sujetos (44 varones, 46 mujeres) divididos en tres grupos según la edad. Los participantes fueron evaluados con el "Examen cognitivo de Cambridge-revisado" (Cambridge Cognitive Examination-Revised, CAMCOG-R) y los subtests de memoria del "Test Barcelona revisado". Se encuentran peores rendimientos (p< 0,05) en el grupo A frente al B (excepto en subpruebas de memoria) y en el grupo A frente al C, siendo el área del lenguaje en la que se observa mayor tamaño del efecto (x2= 0,481). Se concluye que el proceso de envejecimiento produce déficits cognitivos más acusados en esquizofrenia que en población sana y que en general los déficits de los pacientes con esquizofrenia se intensifican con la edad

Neurocognitive deficits in schizophrenia have been studied extensively, but there is no consensus about their course or their analysis in aging population. The objective of the present study is to compare neurocognitive profiles between people over (group A) and under (group B) 65 years of age with schizophrenia and between aging individuals with schizophrenia and healthy individuals of the same age (group C). 90 people enrolled in the study (44 male, 46 female), divided into 3 age groups. The participants were assessed with the Cambridge Cognitive Examination-Revised (CAMCOG-R) and the Memory Subtests of the Barcelona Test - Revised Edition. Worse scores were found (p< .05) when comparing group A with B (except in memory subtests; no difference) and group A with C, being Language the area where more effect size is observed (x2= 0.481). We conclude that the aging process produces more cognitive deficits in schizophrenia than in healthy population and that, in general, the deficits in patients with schizophrenia intensify with age

Structural requirements of glycosaminoglycans for their interaction with HIV-1 envelope glycoprotein gp120.

Heparan sulfate proteoglycans are known to assist HIV-1 entry into host cells, mediated by the viral envelope glycoprotein gp120. We aimed to determine the general structural features of glycosaminoglycans that enable their binding to gp120, by surface plasmon resonance. Binding was found to be dependent on sequence type, size and sulfation patterns. HIV-1 gp120 prefers heparin and heparan sulfate (with at least 16 monomers in length) over chondroitin and dermatan. Sulfate groups were essential to promote this interaction. These results advance the understanding of the molecular-level requirements for virus attachment and cell entry.

Conjugation of cholesterol to HIV-1 fusion inhibitor C34 increases peptide-membrane interactions potentiating its action.

Recently, the covalent binding of a cholesterol moiety to a classical HIV-1 fusion inhibitor peptide, C34, was shown to potentiate its antiviral activity. Our purpose was to evaluate the interaction of cholesterol-conjugated and native C34 with membrane model systems and human blood cells to understand the effects of this derivatization. Lipid vesicles and monolayers with defined compositions were used as model membranes. C34-cholesterol partitions more to fluid phase membranes that mimic biological membranes. Importantly, there is a preference of the conjugate for liquid ordered membranes, rich in cholesterol and/or sphingomyelin, as observed both from partition and surface pressure studies. In human erythrocytes and peripheral blood mononuclear cells (PBMC), C34-cholesterol significantly decreases the membrane dipole potential. In PBMC, the conjugate was 14- and 115-fold more membranotropic than T-1249 and enfuvirtide, respectively. C34 or cholesterol alone did not show significant membrane activity. The enhanced interaction of C34-cholesterol with biological membranes correlates with its higher antiviral potency. Higher partitions for lipid-raft like compositions direct the drug to the receptor-rich domains where membrane fusion is likely to occur. This intermediary membrane binding step may facilitate the drug delivery to gp41 in its pre-fusion state.

Anionic lipids are required for vesicular stomatitis virus G protein-mediated single particle fusion with supported lipid bilayers.

Viral glycoproteins mediate fusion between viral and cellular membranes upon binding to cognate receptors and/or experiencing low pH. Although activation of viral glycoproteins is thought to be necessary and sufficient for fusion, accumulating evidence suggests that additional cellular factors, including lipids, can modulate the fusion process. Understanding the role of lipids in virus entry via endocytosis is impeded by poor accessibility and the highly diverse nature of endosomes. Here we imaged fusion of single retroviral particles pseudotyped with the vesicular stomatitis virus (VSV) G protein with dextran-supported lipid bilayers. Incorporation of diffusible fluorescent labels into the viral membrane and the viral interior enabled detection of the lipid mixing (hemifusion) and content transfer (full fusion) steps of VSV G-mediated fusion at low pH. Although single virus fusion with supported bilayers made of zwitterionic lipids could not be detected, inclusion of anionic lipids, phosphatidylserine, and bis(monoacylglycero)phosphate (BMP), greatly enhanced the efficiency of hemifusion and permitted full fusion. Importantly, lipid mixing always preceded the opening of a fusion pore, demonstrating that VSV G-mediated fusion proceeds through a long-lived hemifusion intermediate. Kinetic analysis of lipid and content transfer showed that the lags between lipid and content mixing defining the lifetime of a hemifusion intermediate were significantly shorter for BMP-containing compared with PS-containing bilayers. The strong fusion-enhancing effect of BMP, a late endosome-resident lipid, is consistent with the model that VSV initiates fusion in early endosomes but releases its core into the cytosol after reaching late endosomal compartments.

Quantitative imaging of endosome acidification and single retrovirus fusion with distinct pools of early endosomes.

Diverse enveloped viruses enter host cells through endocytosis and fuse with endosomal membranes upon encountering acidic pH. Currently, the pH dynamics in virus-carrying endosomes and the relationship between acidification and viral fusion are poorly characterized. Here, we examined the entry of avian retrovirus that requires two sequential stimuli--binding to a cognate receptor and low pH--to undergo fusion. A genetically encoded sensor incorporated into the viral membrane was used to measure the pH in virus-carrying endosomes. Acid-induced virus fusion was visualized as the release of a fluorescent viral content marker into the cytosol. The pH values in early acidic endosomes transporting the virus ranged from 5.6 to 6.5 but were relatively stable over time for a given vesicle. Analysis of viral motility and luminal pH showed that cells expressing the transmembrane isoform of the receptor (TVA950) preferentially sorted the virus into slowly trafficking, less acidic endosomes. In contrast, viruses internalized by cells expressing the GPI-anchored isoform (TVA800) were uniformly distributed between stationary and mobile compartments. We found that the lag times between acidification and fusion were significantly shorter and fusion pores were larger in dynamic endosomes than in more stationary compartments. Despite the same average pH within mobile compartments of cells expressing alternative receptor isoforms, TVA950 supported faster fusion than TVA800 receptor. Collectively, our results suggest that fusion steps downstream of the low-pH trigger are modulated by properties of intracellular compartments harboring the virus.

The role of blood cell membrane lipids on the mode of action of HIV-1 fusion inhibitor sifuvirtide.

Sifuvirtide is a gp41 based peptide that inhibits HIV-1 fusion with the host cells and is currently under clinical trials. Previous studies showed that sifuvirtide partitions preferably to saturated phosphatidylcholine lipid membranes, instead of fluid-phase lipid vesicles. We extended the study to the interaction of the peptide with circulating blood cells, by using the dipole potential sensitive probe di-8-ANEPPS. Sifuvirtide decreased the dipole potential of erythrocyte and lymphocyte membranes in a concentration dependent manner, demonstrating its interaction. Also, the lipid selectivity of the peptide towards more rigid phosphatidylcholines was confirmed based on the dipole potential variations. Overall, the interaction of the peptide with the cell membranes is a contribution of different lipid preferences that presumably directs the peptide towards raft-like domains where the receptors are located, facilitating the reach of the peptide to its molecular target, the gp41 in its pre-fusion conformation.

Quantitative assessment of peptide-lipid interactions. Ubiquitous fluorescence methodologies.

Peptide-membrane interactions have been gaining increased relevance, mainly in biomedical investigation, as the potential of the natural, nature-based and synthetic peptides as new drugs or drug candidates also expands. These peptides must face the cell membrane when they interfere with or participate in intracellular processes. Additionally, several peptide drugs and drug leads actions occur at the membrane level (e.g., antimicrobial peptides, cell-penetrating peptides and enveloped viruses membrane fusion inhibitors). Here we explore fluorescence spectroscopy methods that can be used to monitor such interactions. Two main approaches are considered, centered either on the peptide or on the membrane. On the first, we consider mainly the methodologies based on the intrinsic fluorescence of the aminoacid residues tryptophan and tyrosine. Regarding membrane-centric approaches, we review methods based on lipophilic probes sensitive to membrane potentials. The use of fluorescence constitutes a simple and sensitive method to measure these events. Unraveling the molecular mechanisms that govern these interactions can unlock the key to understand specific biological processes involving natural peptides or to optimize the action of a peptide drug.

HIV-1 fusion inhibitor peptides enfuvirtide and T-1249 interact with erythrocyte and lymphocyte membranes.

Enfuvirtide and T-1249 are two HIV-1 fusion inhibitor peptides that bind to gp41 and prevent its fusogenic conformation, inhibiting viral entry into host cells. Previous studies established the relative preferences of these peptides for membrane model systems of defined lipid compositions. We aimed to understand the interaction of these peptides with the membranes of erythrocytes and peripheral blood mononuclear cells. The peptide behavior toward cell membranes was followed by di-8-ANEPPS fluorescence, a lipophilic probe sensitive to the changes in membrane dipole potential. We observed a fusion inhibitor concentration-dependent decrease on the membrane dipole potential. Quantitative analysis showed that T-1249 has an approximately eight-fold higher affinity towards cells, when compared with enfuvirtide. We also compared the binding towards di-8-ANEPPS labeled lipid vesicles that model cell membranes and obtained concordant results. We demonstrated the distinct enfuvirtide and T-1249 membranotropism for circulating blood cells, which can be translated to a feasible in vivo scenario. The enhanced interaction of T-1249 with cell membranes correlates with its higher efficacy, as it can increase and accelerate the drug binding to gp41 in its pre-fusion state.

Interaction of peptides with biomembranes assessed by potential-sensitive fluorescent probes.

Peptide-membrane interaction is an important step to be evaluated in a study of the activity and mode of action of several bioactive peptides. A variety of methods are available; however, few of them satisfy the criteria of being sensitive, biocompatible, versatile, easy to perform, and allowing real-time monitoring as the use of potential-sensitive fluorescent probes. Here we review methods for detecting the effects of membrane-active peptides, even those that are not intrinsically fluorescent, on the different types of membrane potentials, with a special emphasis on studies conducted with living cells. FPE is a probe sensitive to surface potential and detects electrostatic interactions at the water-lipid interface. Di-8-ANEPPS is sensitive to dipole potential and detects membrane incorporations. Transmembrane potential changes reveal major membrane destabilizations, such as in pore formation. The combination of the information obtained from the three potential variations can lead to a more elucidative picture of the mechanisms of the interaction of relevant peptides with biomembranes.