Viral modulation of lipid rafts and their potential as putative antiviral targets

Single-particle adsorption of ultra-small gold nanoparticles at the biomembrane phase boundary

Nanomaterials are revolutionizing biomedical research by enabling the development of novel therapies, with applications ranging from drug delivery and diagnostics to the modulation of specific biological processes. Current research focuses on tasks such as enhancing cellular uptake of materials while preserving their functionality. However, the mechanisms governing interactions between nanomaterials and biological systems-particularly cellular membranes-remain challenging to elucidate due to the complex, dynamic nature of the lipid bilayer environment. This complexity arises from factors such as coexisting lipid domains (conserved regions of lipids) or lipid rafts, as well as cellular behaviors that induce state changes. The heterogeneous membrane landscape may offer unique adsorption properties and other functional effects, making it crucial to understand these interactions for greater biological control in nanotherapeutics. In this work, we systematically expose a phase-separated phospholipid-supported lipid bilayer (SLB)-specifically, a fluid-gel DOPC:DPPC bilayer-to low concentrations of citrate-capped 5 nm gold nanoparticles (AuNPs) to observe the adsorption process of individual AuNPs at the molecular scale. Using atomic force microscopy (AFM), we experimentally detect the adsorption of some AuNPs at the phase boundary. Complementary molecular dynamics (MD) simulations further elucidate the mechanism of single AuNP adsorption at lipid phase boundaries. Our findings indicate that the AuNP preferentially incorporates into the fluid-phase DOPC lipids while maintaining partial association with the gel-phase DPPC lipids due to diffusion effects. During adsorption, the AuNP disrupts lipid organization by increasing lateral lipid mixing across the phase boundary. This disruption to lipid molecular ordering is further evident upon AuNP incorporation into the bilayer. The ability to modulate the spatial organization and structure of lipid molecules has significant implications for therapeutics that leverage lipid diffusion pathways for alternative drug delivery mechanisms or to induce specific lipid behaviors.

Lipid rafts: novel therapeutic targets for metabolic, neurodegenerative, oncological, and cardiovascular diseases

Lipid rafts are specialized microdomains within cellular membranes enriched with cholesterol and sphingolipids that play key roles in cellular organization, signaling, and homeostasis. This review highlights their involvement in protein clustering, energy metabolism, oxidative stress responses, inflammation, autophagy, and apoptosis. These findings clarify their influence on signaling, trafficking, and adhesion while interacting with the extracellular matrix, cytoskeleton, and ion channels, making them pivotal in the progression of various diseases. This review further addresses their contributions to immune responses, including autoimmune diseases, chronic inflammation, and cytokine storms. Additionally, their role as entry points for pathogens has been demonstrated, with raft-associated receptors being exploited by viruses and bacteria to increase infectivity and evade immune defenses. Disruptions in lipid raft dynamics are linked to oxidative stress and cellular signaling defects, which contribute to metabolic, neurodegenerative, and cardiovascular diseases. This review underscores their potential as therapeutic targets, discussing innovations such as engineered lipid raft transplantation. Advances in analytical techniques such as mass spectrometry have expanded our understanding of lipid raft composition and dynamics, opening new directions for research. By consolidating the current insights, we highlight the therapeutic potential of lipid rafts and highlight the need for further exploration of their molecular mechanisms.

N-(3-Oxododecanoyl)-Homoserine Lactone Induces Intestinal Barrier Damage in Piglets via the Lipid Raft-Mediated Apoptosis Pathway

Quorum sensing (QS) is a process by which bacteria sense their population density and regulate behavior accordingly. QS not only regulates bacterial virulence but also directly influences host cells. Previous studies have shown that QS is strongly associated with piglet intestinal health, but the mechanism is not yet clear. For the first time, we have confirmed in a piglet animal model that OdDHL directly damages intestinal cells in weaned piglets, disrupting the intestinal barrier. We also provide a preliminary exploration of the underlying mechanism of these effects. TUNEL assays confirmed that damage to the piglet intestinal barrier coincided temporally and spatially with dysregulated apoptosis. Lipid rafts, key components of the cell membrane, are involved in many biological processes, including the activation of apoptosis-related proteins. Following the disruption of the lipid raft structure in IPEC-J2 cells, the apoptosis rate under OdDHL stimulation decreased by 50%. These data demonstrate that lipid rafts mediate the attachment of OdDHL to porcine intestinal cells; then, OdDHL induces apoptosis in porcine intestinal cells through the mitochondrial and death receptor pathways, thereby compromising the integrity of the porcine intestinal barrier. This study provides foundational insights into the role of QS in piglet intestinal diseases.

Lipid Rafts in Signalling, Diseases, and Infections: What Can Be Learned from Fluorescence Techniques?

Lipid rafts are dynamic microdomains in the membrane, rich in cholesterol and sphingolipids, that are critical for biological processes like cell signalling, membrane trafficking, and protein organization. Their essential role is claimed in both physiological and pathological conditions, including cancer, neurodegenerative diseases, and viral infections, making them a key area of research. Fluorescence-based approaches, including super-resolution fluorescence microscopy techniques, enable precise analysis of the organization, dynamics, and interactions of these microdomains, thanks also to the innovative design of appropriate fluorescent probes. Moreover, these non-invasive approaches allow for the study of live cells, facilitating the collection of quantitative data under physiologically relevant conditions. This review synthesizes the latest insights into the role of lipid rafts in biological and pathological processes and underscores how fluorescence techniques have advanced our understanding of these critical microdomains. The findings emphasize the pivotal role of lipid rafts in health and disease, providing a foundation for future research and potential therapeutic interventions.

The importance of paying attention to the role of lipid-lowering drugs in controlling dengue virus infection

The Flaviviridae family includes the dengue virus (DENV). About half of the world's population is in danger because of the estimated 390 million infections and 96 million symptomatic cases that occur each year. An effective treatment for dengue fever (DF) does not yet exist. Therefore, a better knowledge of how viral proteins and virus-targeted medicines may exert distinct functions depending on the exact cellular region addressed may aid in creating much-needed antiviral medications. Lipids facilitate the coordination of many viral replication phases, from entrance to dissemination. In addition, flaviviruses masterfully plan a significant rearrangement of the host cell's lipid metabolism to foster the growth of new viruses. Recent research has consistently shown the significance of certain lipid classes in flavivirus infections. For instance, in DENV-infected cells, overall cellular cholesterol (CHO) levels are only a little altered, and DENV replication is significantly reduced when CHO metabolism is inhibited. Moreover, statins significantly decrease DENV serotype 2 (DENV-2) titers, indicating that CHO is a prerequisite for the dengue viral cycle. Furthermore, many Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors are now being evaluated in human research. A new pharmacological target for the management of high CHO is PCSK9. Moreover, suppression of PCSK9 has been proposed as a possible defense against DENV. Numerous studies have generally recommended the use of lipid-lowering medications to suppress the DENV. As a result, we have investigated the DENV and popular treatment techniques in this research. We have also examined how lipid metabolism, cellular lipids, and lipid receptors affect DENV replication regulation. Lastly, we have looked at how different lipid-lowering medications affect the DENV. This article also discusses the treatment method's future based on its benefits and drawbacks.

Mycoplasma bovis Invades Non-Phagocytic Cells by Clathrin-Dependent Endocytic Pathways and Escapes from Phagocytic Vesicles

Mycoplasma bovis (M. bovis) is capable of causing pneumonia, arthritis, mastitis, and various other ailments in cattle of all age groups, posing a significant threat to the healthy progression of the worldwide cattle industry. The invasion of non-phagocytic host cells serves as a pivotal mechanism enabling M. bovis to evade the immune system and penetrate mucosal barriers, thereby promoting its spread. To investigate the differences in M. bovis invasion into four types of non-phagocytic cells (Madin-Darby bovine kidney (MDBK) cells, embryonic bovine lung (EBL) cells, bovine embryo tracheal (EBTr) cells and bovine turbinate (BT) cells) and further elucidate its invasion mechanism, this study first optimized the experimental methods for M. bovis invasion into cells. Utilizing laser scanning confocal microscopy, transmission electron microscopy, and high-content live-cell imaging systems, the invasion process of M. bovis into four types of non-phagocytic cells was observed. The invasion rates of three different strains of M. bovis (PG45, 07801, 08M) were quantified through the plate counting method. In order to clarify the specific pathway of M. bovis invasion into cells, chlorpromazine (CPZ), amiloride (AMI), and methyl-β-cyclodextrin (M-β-CD) were used to inhibit CLR-mediated clathrin-dependent endocytosis (CDE) pathway, macropinocytosis, and lipid raft pathway, respectively. Subsequently, the invasion rates of PG45 into these four types of cells were measured. Using siRNA technology, the expression of clathrin (CLR) in EBL cells was knocked down to further verify the role of CLR in the invasion process of M. bovis. The results showed that the optimal conditions for M. bovis to invade non-phagocytic cells were a multiplicity of infection (MOI) of 1000 and an optimal invasion time of 4 h. All three strains of M. bovis have the ability to invade the four types of non-phagocytic cells, yet their invasion abilities vary significantly. Observations from transmission electron microscopy further confirmed that at 120 min post-infection, PG45 had successfully invaded EBL cells and was present within endocytic vesicles. It is noteworthy that almost all PG45 successfully escaped from the endocytic vesicles after 240 min of infection had passed. Through chemical inhibition experiments and CLR protein knockdown experiments, it was found that when the CDE and lipid raft pathways were blocked or CLR protein expression was reduced, the invasion rates of PG45, 07801, and 08M in MDBK, EBL, EBTr, and BT cells were significantly decreased (p < 0.05). The above results indicate that M. bovis can invade all types of non-phagocytic cells through endocytic pathways involving CDE (clathrin-dependent endocytosis) or lipid raft-mediated endocytosis, and possesses the ability to escape from phagosomes.

Increased viperin expression induced by avian infectious bronchitis virus inhibits viral replication by restricting cholesterol synthesis: an in vitro study

With the emergence of new variant strains resulting from high mutation rates and genome recombination, avian infectious bronchitis virus (IBV) has caused significant economic losses to the poultry industry worldwide. Little is known about the underlying mechanisms of IBV-host interactions, particularly how IBV utilizes host metabolic pathways for efficient viral replication and transmission. In the present study, the effects of the cell membrane, viral envelope membrane, and viperin-mediated cholesterol synthesis on IBV replication were explored. Our results revealed significant increase in cholesterol levels and the expression of viperin after IBV infection. Acute cholesterol depletion in the cell membrane and viral envelope membrane by treating cells with methyl-β-cyclodextrin (MβCD) obviously inhibited IBV replication; thereafter, replenishment of the cell membrane with cholesterol successfully restored viral replication, and direct addition of exogenous cholesterol to the cell membrane significantly promoted IBV infection during the early stages of infection. In addition, overexpression of viperin effectively suppressed cholesterol synthesis, as well as IBV replication, whereas knockdown of viperin (gene silencing with siRNA targeting viperin, siViperin) significantly increased IBV replication and cholesterol levels, whereas supplementation with exogenous cholesterol to viperin-transfected cells markedly restored viral replication. In conclusion, the increase in viperin induced by IBV infection plays an important role in IBV replication by affecting cholesterol production, providing a theoretical basis for understanding the pathogenesis of IBV and discovering new potential antiviral targets.

Rationally designed β-cyclodextrin-crosslinked polyacrylamide hydrogels for cell spheroid formation and 3D tumor model construction

In vitro tumor models are essential for understanding tumor behavior and evaluating tumor biological properties. Hydrogels that can mimic the tumor extracellular matrix have become popular for creating 3D in vitro tumor models. However, designing biocompatible hydrogels with appropriate chemical and physical properties for constructing tumor models is still a challenge. In this study, we synthesized a series of β-cyclodextrin (β-CD)-crosslinked polyacrylamide hydrogels with different β-CD densities and mechanical properties and evaluated their potential for use in 3D in vitro tumor model construction, including cell capture and spheroid formation. By utilizing a combination of β-CD-methacrylate (CD-MA) and a small amount of N,N'-methylene bisacrylamide (BIS) as hydrogel crosslinkers and optimizing the CD-MA/BIS ratio, the hydrogels performed excellently for tumor cell 3D culture and spheroid formation. Notably, when we co-cultured L929 fibroblasts with HeLa tumor cells on the hydrogel surface, co-cultured spheroids were formed, showing that the hydrogel can mimic the complexity of the tumor extracellular matrix. This comprehensive investigation of the relationship between hydrogel mechanical properties and biocompatibility provides important insights for hydrogel-based in vitro tumor modeling and advances our understanding of the mechanisms underlying tumor growth and progression.

Parabacteroides distasonis regulates the infectivity and pathogenicity of SVCV at different water temperatures

BACKGROUND

Spring viremia of carp virus (SVCV) infects a wide range of fish species and causes high mortality rates in aquaculture. This viral infection is characterized by seasonal outbreaks that are temperature-dependent. However, the specific mechanism behind temperature-dependent SVCV infectivity and pathogenicity remains unclear. Given the high sensitivity of the composition of intestinal microbiota to temperature changes, it would be interesting to investigate if the intestinal microbiota of fish could play a role in modulating the infectivity of SVCV at different temperatures.

RESULTS

Our study found that significantly higher infectivity and pathogenicity of SVCV infection in zebrafish occurred at relatively lower temperature. Comparative analysis of the intestinal microbiota in zebrafish exposed to high- and low-temperature conditions revealed that temperature influenced the abundance and diversity of the intestinal microbiota in zebrafish. A significantly higher abundance of Parabacteroides distasonis and its metabolite secondary bile acid (deoxycholic acid, DCA) was detected in the intestine of zebrafish exposed to high temperature. Both colonization of Parabacteroides distasonis and feeding of DCA to zebrafish at low temperature significantly reduced the mortality caused by SVCV. An in vitro assay demonstrated that DCA could inhibit the assembly and release of SVCV. Notably, DCA also showed an inhibitory effect on the infectious hematopoietic necrosis virus, another Rhabdoviridae member known to be more infectious at low temperature.

CONCLUSIONS

This study provides evidence that temperature can be an important factor to influence the composition of intestinal microbiota in zebrafish, consequently impacting the infectivity and pathogenicity of SVCV. The findings highlight the enrichment of Parabacteroides distasonis and its derivative, DCA, in the intestines of zebrafish raised at high temperature, and they possess an important role in preventing the infection of SVCV and other Rhabdoviridae members in host fish. Video Abstract.

Mpox (formerly monkeypox): pathogenesis, prevention, and treatment

In 2022, a global outbreak of Mpox (formerly monkeypox) occurred in various countries across Europe and America and rapidly spread to more than 100 countries and regions. The World Health Organization declared the outbreak to be a public health emergency of international concern due to the rapid spread of the Mpox virus. Consequently, nations intensified their efforts to explore treatment strategies aimed at combating the infection and its dissemination. Nevertheless, the available therapeutic options for Mpox virus infection remain limited. So far, only a few numbers of antiviral compounds have been approved by regulatory authorities. Given the high mutability of the Mpox virus, certain mutant strains have shown resistance to existing pharmaceutical interventions. This highlights the urgent need to develop novel antiviral drugs that can combat both drug resistance and the potential threat of bioterrorism. Currently, there is a lack of comprehensive literature on the pathophysiology and treatment of Mpox. To address this issue, we conducted a review covering the physiological and pathological processes of Mpox infection, summarizing the latest progress of anti-Mpox drugs. Our analysis encompasses approved drugs currently employed in clinical settings, as well as newly identified small-molecule compounds and antibody drugs displaying potential antiviral efficacy against Mpox. Furthermore, we have gained valuable insights from the process of Mpox drug development, including strategies for repurposing drugs, the discovery of drug targets driven by artificial intelligence, and preclinical drug development. The purpose of this review is to provide readers with a comprehensive overview of the current knowledge on Mpox.

Alkyl Derivatives of Perylene Photosensitizing Antivirals: Towards Understanding the Influence of Lipophilicity

Amphipathic perylene derivatives are broad-spectrum antivirals against enveloped viruses that act as fusion inhibitors in a light-dependent manner. The compounds target the lipid bilayer of the viral envelope using the lipophilic perylene moiety and photogenerating singlet oxygen, thereby causing damage to unsaturated lipids. Previous studies show that variation of the polar part of the molecule is important for antiviral activity. Here, we report modification of the lipophilic part of the molecule, perylene, by the introduction of 4-, 8-, and 12-carbon alkyls into position 9(10) of the perylene residue. Using Friedel-Crafts acylation and Wolff-Kishner reduction, three 3-acetyl-9(10)-alkylperylenes were synthesized from perylene and used to prepare 9 nucleoside and 12 non-nucleoside amphipathic derivatives. These compounds were characterized as fluorophores and singlet oxygen generators, as well as tested as antivirals against herpes virus-1 (HSV-1) and vesicular stomatitis virus (VSV), both known for causing superficial skin/mucosa lesions and thus serving as suitable candidates for photodynamic therapy. The results suggest that derivatives with a short alkyl chain (butyl) have strong antiviral activity, whereas the introduction of longer alkyl substituents (n = 8 and 12) to the perylenyethynyl scaffold results in a dramatic reduction of antiviral activity. This phenomenon is likely attributable to the increased lipophilicity of the compounds and their ability to form insoluble aggregates. Moreover, molecular dynamic studies revealed that alkylated perylene derivatives are predominately located closer to the middle of the bilayer compared to non-alkylated derivatives. The predicted probability of superficial positioning correlated with antiviral activity, suggesting that singlet oxygen generation is achieved in the subsurface layer of the membrane, where the perylene group is more accessible to dissolved oxygen.

Repurposing Amphotericin B and Its Liposomal Formulation for the Treatment of Human Mpox

Mpox (monkeypox) is a zoonotic viral disease caused by the mpox virus (MPXV). Recently in 2022, a multi-country Mpox outbreak has determined great concern as the disease rapidly spreads. The majority of cases are being noticed in European regions and are unrelated to endemic travel or known contact with infected individuals. In this outbreak, close sexual contact appears to be important for MPXV transmission, and an increasing prevalence in people with multiple sexual partners and in men who have sex with men has been observed. Although Vaccinia virus (VACV)-based vaccines have been shown to induce a cross-reactive and protective immune response against MPXV, limited data support their efficacy against the 2022 Mpox outbreak. Furthermore, there are no specific antiviral drugs for Mpox. Host-cell lipid rafts are small, highly dynamic plasma-membrane microdomains enriched in cholesterol, glycosphingolipids and phospholipids that have emerged as crucial surface-entry platforms for several viruses. We previously demonstrated that the antifungal drug Amphotericin B (AmphB) inhibits fungal, bacterial and viral infection of host cells through its capacity to sequester host-cell cholesterol and disrupt lipid raft architecture. In this context, we discuss the hypothesis that AmphB could inhibit MPXV infection of host cells through disruption of lipid rafts and eventually through redistribution of receptors/co-receptors mediating virus entry, thus representing an alternative or additional therapeutic tool for human Mpox.

LABYRINTHOPEPTIN A2 DISRUPTS RAFT DOMAINS

Labyrinthopeptins constitute a class of ribosomal synthesized peptides belonging to the type III family of lantibiotics. They exist in different variants and display broad antiviral activities as well as show antiallodynic activity. Although their mechanism of action is not understood, it has been described that Labyrinthopeptins interact with membrane phospholipids modulating its biophysical properties and point out to membrane destabilization as its main point of action. We have used all-atom molecular dynamics to study the location of labyrinthopeptin A2 in a complex membrane as well as the existence of specific interactions with membrane lipids. Our results indicate that labyrinthopeptin A2, maintaining its globular structure, tends to be placed at the membrane interface, mainly between the phosphate atoms of the phospholipids and the oxygen atom of cholesterol modulating the biophysical properties of the membrane lipids. Outstandingly, we have found that labyrinthopeptin A2 tends to be preferentially surrounded by sphingomyelin while excluding cholesterol. The bioactive properties of labyrinthopeptin A2 could be attributed to the specific disorganization of raft domains in the membrane and the concomitant disruption of the overall membrane organization. These results support the improvement of Labyrinthopeptins as therapeutic molecules, opening up new opportunities for future medical advances.