Disruption Of Membrane Integrity Research Articles

Study on the Effect of Phillyrin on Streptococcus suis In Vivo and In Vitro

As a zoonotic pathogen, S. suis serotype 2 (SS2) can cause severe diseases in both pigs and humans, and develop resistance to antibiotics. Plant natural compounds are regarded as promising alternatives to conventional antibiotics. Phillyrin is the major bioactive components of Chinese herbal medicine Forsythia suspensa. In this study, we explored the activity and action mechanism of phillyrin against SS2. The results showed that phillyrin could disrupt membrane integrity, destroy intracellular structures, and increase the exosmosis of DNA. Results of PCR revealed that phillyrin affected bacterial-virulence-related genes’ expression levels. Meanwhile, phillyrin significantly decreased the adhesion activity, inhibited lactate dehydrogenase (LDH) secretion, and reduced biofilm formation of SS2 in Newborn pig trachea epithelial (NPTr) cells. Furthermore, phillyrin protected tight junction protein of NPTr cells from SS2. We reported that phillyrin (0.1 mg/kg) treatment after bacterial challenge significantly improved the survival rate, ameliorated pulmonary inflammation, and inhibited the accumulation of multiple cytokines (IL-1, IL-6, IL-8, and TNF-α). Molecular docking showed that phillyrin had a good binding activity with the Ala88 and Asp111 of suilysin (SLY), one of the most important virulence factors of SS2. Collectively, phillyrin possesses antibacterial and anti-inflammatory activities, and is a promising candidate for preventing SS2 infection.

DDDR-28. SPHINGOSINE AND N,N-DIMETHYLSPHINGOSINE MODULATE CHOLESTEROL HOMEOSTASIS IN IDH1MUT GLIOMAS, CAUSING PRO-APOPTOTIC MEMBRANE DEGRADATION

Abstract BACKGROUND Previous work in our team revealed a therapeutic potential for metabolic reprogramming along the sphingolipid pathway within IDH1mut gliomas. The dosing of various IDH1mut glioma subtypes with sphingosine and sphingosine kinase inhibitor (SphKi), N,N-dimethylsphingosine (NDMS) led to the enrichment of pro-apoptotic ceramides and sphingosines while suspending the proliferation of the IDH1mut neurospheres. However, the mechanism of drug action (MOA) was not well understood. We postulated that suppressing the production of S1P production with SphKi treatment combined with the global accumulation of sphingosine and certain ceramides triggers apoptotic membrane stress in highly susceptible IDH1mut gliomas. METHODS We cultured and treated IDH1mut (TS603, BT142 & NCH1681) and IDH1wt (GSC923) glioma cell lines with a combination of NDMS and C17-sphingosine. We used a comprehensive multi-omics approach involving LC-MS lipidomic, RNA sequencing, immunoblotting, flow cytometry, and fluorescent microscopy. RESULTS Following combination treatment, a global increase in sphingosines, ceramides, and their derivatives was accompanied by a decline in cholesterol levels. The transcriptomic expression was elevated for NR1H3, MYLIP, ABCA1, and ABCG1, which regulate the trafficking and biosynthesis of membrane-associated cholesterol. In contrast, total gene expression for catalytic enzymes involved in cholesterol (and isoprenoid) biosynthesis was negatively impacted. In addition, early onset changes included an elevation in the expression of ROCK (a marker for apoptotic membrane blebbing). Moreover, fluorescent microscopy revealed that sphingosine and cholesterol tend to become associated within the cellular membranes. This interaction then saturates the plasma membrane (PM), causing apparent vesiculation, permeation, and disruption of membrane integrity. CONCLUSION The MOA involved concomitant attenuation of cholesterol metabolism and influx in response to membrane saturation with sphingosine-associated cholesterol. As a result, PM stress was incurred, leading to PM disintegration in a blebbing fashion. Our study revealed how reprogramming sphingolipid metabolism increases the susceptibility of IDHmut gliomas to sphingosine-associated cholesterol-induced blebbing and resulting cell death.

Combating Fungal Infections and Resistance with a Dual-Mechanism Luminogen to Disrupt Membrane Integrity and Induce DNA Damage.

Antifungal drug resistance is a critical concern, demanding innovative therapeutic solutions. The dual-targeting mechanism of action (MoA), as an effective strategy to reduce drug resistance, has been validated in the design of antibacterial agents. However, the structural similarities between mammalian and fungal cells complicate the development of such a strategy for antifungal agents as the selectivity can be compromised. Herein, we introduce a dual-targeting strategy addressing fungal infections by selectively introducing DNA binding molecules into fungal nuclei. We incorporate rigid hydrophobic units into a DNA-binding domain to fabricate antifungal luminogens of TPY and TPZ, which exhibit enhanced membrane penetration and DNA-binding capabilities. These compounds exhibit dual-targeting MoA by depolarizing fungal membranes and inducing DNA damage, amplifying their potency against fungal pathogens with undetectable drug resistance. TPY and TPZ demonstrated robust antifungal activity in vitro and exhibited ideal therapeutic efficacy in a murine model of C. albicans-induced vaginitis. This multifaceted approach holds promise for overcoming drug resistance and advancing antifungal therapy.

Restoring Colistin Sensitivity in Multidrug-Resistant Pathogenic E. coli Using Cinacalcet Hydrochloride.

Restoring colistin's efficacy is crucial in addressing the resistance crisis of colistin. This study utilized a high-throughput screening method to identify 43 compounds from 800 FDA-approved drugs that exhibited significant antibacterial effects when combined with colistin. Among these, cinacalcet hydrochloride (CH) was selected for its potential synergistic effect with colistin against multidrug-resistant (MDR) E. coli strains, including mcr-1-positive strains. A series of experiments revealed that the combination of CH and colistin showed strong synergy, especially in mcr-1-positive strains, restoring colistin sensitivity. The combination significantly inhibited bacterial growth and reduced CFU counts more effectively than either drug alone. Additionally, CH and colistin together significantly inhibited biofilm formation and eradicated existing biofilms, as visualized through confocal microscopy. Mechanistic studies showed that the combination increased bacterial membrane permeability and disrupted membrane integrity. The treatment also elevated extracellular ATP release and ROS production, indicating oxidative stress-induced bacterial death. Safety evaluations showed that the combination did not increase toxicity in host cells. Finally, animal models further validated the combination's efficacy. Overall, this study showed that the combination of colistin and CH significantly restored colistin sensitivity in mcr-1-positive E. coli, revealing their synergistic antibacterial mechanism involving membrane damage and oxidative stress, with promising clinical applications.

Antimicrobial activity of novel symmetrical antimicrobial peptides centered on a hydrophilic motif against resistant clinical isolates: in vitro and in vivo analyses.

Increasing antibiotic resistance and the paucity of effective antibiotics necessitate innovative antibacterial agents. Methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen causing bacterial infections with high incidence and mortality rates, showing increasing resistance to clinical drugs. Antimicrobial peptides (AMPs) exhibit significant potential as alternatives to traditional antibiotics. This study designed a novel series of AMPs, characterized by a glycine-serine-glycine-centered symmetrical structure, and our results indicated that AMP W5 exhibited a rapid and effective bactericidal effect against MRSA. AMP W5 also demonstrated excellent biocompatibility and a bactericidal mechanism that disrupted membrane integrity, leading to leakage of cellular contents. The notable reduction in skin bacterial load observed in mouse models reinforced the clinical applicability of AMP W5. This study provides a promising solution for addressing the increasing threat of antibiotic-resistant bacteria and heralds new prospects for clinical applications.

Characterization of a membrane toxin-antitoxin system, tsaAT, from Staphylococcus aureus.

Bacterial toxin-antitoxin (TA) systems consist of a toxin that inhibits essential cellular processes, such as DNA replication, transcription, translation, or ATP synthesis, and an antitoxin neutralizing their cognate toxin. These systems have roles in programmed cell death, defense against phage, and the formation of persister cells. Here, we characterized the previously identified Staphylococcus aureus TA system, tsaAT, which consists of two putative membrane proteins: TsaT and TsaA. Expression of the TsaT toxin caused cell death and disrupted membrane integrity, whereas TsaA did not show any toxicity and neutralized the toxicity of TsaT. Furthermore, subcellular fractionation analysis demonstrated that both TsaA and TsaT localized to the cytoplasmic membrane of S. aureus expressing either or both 3xFLAG-tagged TsaA and 3xFLAG-tagged TsaT. Taken together, these results demonstrate that the TsaAT TA system consists of two membrane proteins, TsaA and TsaT, where TsaT disrupts membrane integrity, ultimately leading to cell death. Although sequence analyses showed that the tsaA and tsaT genes were conserved among Staphylococcus species, amino acid substitutions between TsaT orthologs highlighted the critical role of the 6th residue for its toxicity. Further amino acid substitutions indicated that the glutamic acid residue at position 63 in the TsaA antitoxin and the cluster of five lysine residues in the TsaT toxin are involved in TsaA's neutralization reaction. This study is the first to describe a bacterial TA system wherein both toxin and antitoxin are membrane proteins. These findings contribute to our understanding of S. aureus TA systems and, more generally, give new insight into highly diverse bacterial TA systems.

Unveiling the potential of novel Metschnikowia yeast biosurfactants: triggering oxidative stress for promising antifungal and anticancer activity

BackgroundSophorolipids are glycolipid biosurfactants with potential antibacterial, antifungal, and anticancer applications, rendering them promising for research. Therefore, this study hypothesizes that sophorolipids may have a notable impact on disrupting membrane integrity and triggering the production of reactive oxygen species, ultimately resulting in the eradication of pathogenic microbes.ResultsThe current study resulted in the isolation of two Metschnikowia novel yeast strains. Sophorolipids production from these strains reached maximum yields of 23.24 g/l and 21.75 g/l, respectively, at the bioreactors level. Biosurfactants sophorolipids were characterized using FTIR and LC–MS techniques and found to be a mixture of acidic and lactonic forms with molecular weights of m/z 678 and 700. Our research elucidated sophorolipids’ mechanism in disrupting bacterial and fungal membranes through ROS generation, confirmed by transmission electron microscopy and FACS analysis. The results showed that these compounds disrupted the membrane integrity and induced ROS production, leading to cell death in Klebsiella pneumoniae and Fusarium solani. In addition, the anticancer properties of sophorolipids were investigated on the A549 lung cancer cell line and found that sophorolipid-11D (SL-11D) and sophorolipid-11X (SL-11X) disrupted the actin cytoskeleton, as evidenced by immunofluorescence microscopy. The A549 cells were stained with Acridine orange/Ethidium bromide, which showed that they underwent necrosis. This was confirmed by flow cytometric analysis using Annexin/PI staining. The SL-11D and SL-11X molecules exhibited low levels of haemolytic activity and in-vitro cytotoxicity in HEK293, Caco-2, and L929 cell lines.ConclusionIn this work, novel yeast species CIG-11DT and CIG-11XT, isolated from the bee’s gut, produce significant yields of sophorolipids without needing secondary oil sources, indicating a more economical production method. Our research shows that sophorolipids disrupt bacterial and fungal membranes via ROS production. They suggest they may act as chemo-preventive agents by inducing apoptosis in lung cancer cells, offering the potential for enhancing anticancer therapies.

S100A12 inhibits Streptococcus pneumoniae and aids in wound healing of corneal epithelial cells both in vitro and in vivo

Streptococcus pneumoniae, a leading cause of corneal infections worldwide, are extremely aggressive despite antibiotic sensitivity and exhibit increased resistance towards antibiotics. Antimicrobial peptides are often considered as potent alternatives against antibiotic resistance and here we have investigated the possible roles of S100A12, a host defense peptide, in wound healing and S. pneumoniae infection. S100A12 significantly inhibited growth of S. pneumoniae by disruption of membrane integrity along with increased generation of reactive oxygen species. Additionally, S100A12 accelerated cell migration and wound closure in human corneal epithelial cells and in a murine corneal wound model by activation of EGFR and MAPK signaling pathways.

Ectopic expression of Myomaker and Myomixer in slow muscle cells induces slow muscle fusion and myofiber death

Zebrafish embryos possess two major types of myofibers, the slow and fast fibers, with distinct patterns of cell fusion. The fast muscle cells can fuse, while the slow muscle cells cannot. Here, we show that myomaker is expressed in both slow and fast muscle precursors, whereas myomixer is exclusive to fast muscle cells. The loss of Prdm1a, a regulator of slow muscle differentiation, results in strong myomaker and myomixer expression and slow muscle cell fusion. This abnormal fusion is further confirmed by the direct ectopic expression of myomaker or myomixer in slow muscle cells of transgenic models. Using the transgenic models, we show that the heterologous fusion between slow and fast muscle cells can alter slow muscle cell migration and gene expression. Furthermore, the overexpression of myomaker and myomixer also disrupts membrane integrity, resulting in muscle cell death. Collectively, this study identifies that the fiber-type-specific expression of fusogenic proteins is critical for preventing inappropriate fusion between slow and fast fibers in fish embryos, highlighting the need for precise regulation of fusogenic gene expression to maintain muscle fiber integrity and specificity.

Evaluation of antioxidant prophylactic effects of parsley (Petroselinum crispum) on sepsis following cecal ligation and puncture

Objective: Sepsis causes the release of free oxygen radicals that disrupt membrane integrity, and damage to Mitochondria due to the production of free oxygen radicals and oxidation leads to exacerbation of sepsis, Cecal ligation and puncture (CLP) in rats mimics the characteristics and course of clinical sepsis (Hubbard et al., 2005). Methods: We evaluated the antioxidant effects of Petroselinum crispum (Pc) in a cecal ligation and puncture (CLP)-induced rat sepsis model, in a rat model of sepsis caused by cecal ligation and puncture (CLP). Wistar albino rats were separated into four groups of eight groups: a sham group with incised and sutured abdomens; a Pc extract (PcE) group, which was given 2 g/kg parsley extract for 14 days by gastric gavage; a CLP group, which was subjected to sepsis caused by CLP; and a PcE + CLP group, which was given parsley extract for 14 days. PcE was given for 14 days, after which sepsis was induced via the CLP procedure. The groups were compared in terms of hemogram, biochemical and histological characteristics. Results: The administration of PcE before CLP-induced sepsis increases neutrophil counts, PLTs and TASs, which decrease with sepsis, and decreases biochemical changes (BUN, AST, ALT, LDH, TOS, and OSI), which increase with sepsis, to protect against sepsis. Compared with that in the CLP group, the severity of intestinal infiltration was significantly lower in the PcE + CLP group; however, the degree of epithelial damage in the PcE + CLP group was similar to that in the CLP group. In the PcE + CLP group, the crypt and villus lengths were greater, and the decrease in Paneth cell degranulation intensity was greater than that in the CLP group. Conclusion: Additionally, the morphology of the cells in the PcE + CLP group was similar to that in the sham group. PcE has potential as a prophylactic agent for sepsis.

Marizomib (Salinosporamide A) Promotes Apoptosis in A375 and G361 Melanoma Cancer Cells.

Malignant melanoma-a tumor originating from melanocytes-is characterized by dynamic growth and frequent metastases in the early stage of development. Current therapy methods are still insufficient, and there is a need to search for new ways of treating this malady. The induction of apoptosis-physiological cell death-by proteasome inhibitors is recognized as an effective method of non-invasive elimination of cancer cells. In our research, we wanted to check the potential of marizomib (MZB, salinosporamide A, NPI-0052)-an irreversible proteasome inhibitor derived from the marine actinomycete Salinispora tropica-to induce apoptosis in A375 and G361 malignant melanoma cells. We determined the cytotoxic activity of marizomib by performing an MTT test. Ethidium bromide and acridine orange staining demonstrated the disruption of membrane integrity in the examined cell lines. We confirmed the proapoptotic activity of marizomib by flow cytometry with the use of an FITC-Annexin V assay. A Western blot analysis presented an increase in the expression of proteins related to endoplasmic reticulum (ER) stress as well as markers of the apoptosis. The gathered findings suggest that marizomib induced the ER stress in the examined melanoma cancer cells and directed them towards the apoptosis pathway.

Luteolin exhibits antimicrobial actions against Salmonella Typhimurium and Escherichia coli: Impairment of cell adhesion, membrane integrity, and energy metabolism

There has been an increasing interest in phytochemicals with antimicrobial properties in food safety management. However, the mechanisms of action of phytochemicals remain mostly unknown, preventing their selective applications against biofilms of specific pathogenic bacteria. The objectives of the present study were to understand the antibiofilm and antibacterial properties of luteolin (LUT) and its modes of action against two detrimental foodborne pathogens, Salmonella enterica ser. Typhimurium and enterohemorrhagic Escherichia coli. The focus encompasses biofilm inhibition, interference with cell adhesion, disruption of membrane integrity, and dysfunctions of membrane-linked bacterial electron transport systems and energy metabolism. Our findings evidence that LUT prevents pathogenic biofilm formation on both biotic (eggshell) and abiotic (stainless steel and silicon rubber) surfaces by resisting irreversible cell adhesion and interfering with hydrophobic interactions between bacteria and contact surfaces. Our comprehensive biochemical and visual analyses further reveal that LUT mainly exhibits bactericidal activities by imposing oxidative stress on cells, leading to severe cellular structure damage, inhibition of metabolic and respiratory activities, and dysfunctions of energy metabolism, ultimately resulting in bacterial cell death. This study suggests that LUT has the potential to serve as a solution for developing effective, novel antimicrobials for improving food safety management.

Green algae-produced multimer cathelicidin-RC1 disrupts membrane integrity for inhibiting bacterial growth

Cathelicidin-RC1, extracted from the bullfrog Rana catesbeiana, has been found to effectively combat gram-negative bacteria but has limited inhibitory effects on gram-positive bacteria. Additionally, the specific mechanism of cathelicidin-RC1’s interaction with bacteria remains unclear. In this research, we present the expression analysis of a chimeric peptide composed of three repetitive units of cathelicidin-RC1 (3×cathelicidin-RC1) with a hemagglutinin (HA) and a 6×His tag attached at its C-terminus in Chlamydomonas reinhardtii, leading to the production of a chimeric peptide with a molecular mass of ∼16.2 kDa. The recombinant peptide, 3×cathelicidin-RC1-HA-6×His, demonstrates a wide range of antimicrobial activity, with minimum inhibitory concentration (MIC) values of approximately 20–30 µg/ml and 10–60 µg/ml against gram-positive and negative bacteria, respectively. The minimum bactericidal concentration (MBC) values of 3×cathelicidin-RC1-HA-6×His varies from 1× to 3×MIC. Furthermore, 3×cathelicidin-RC1-HA-6×His demonstrates excellent stability, pH stability, and resistance to digestion by certain proteases. It also exhibits low cytotoxicity and negligible hemolytic activity against rat erythrocytes. Scanning electron microscopy and propidium iodide analysis indicate that 3×cathelicidin-RC1-HA-6×His disrupts bacterial cell membranes, leading to inhibition of bacterial growth. Overall, our findings demonstrate that 3×cathelicidin-RC1-HA-6×His, produced in the heterologous expression host C. reinhardtii, effectively inhibits bacterial growth and holds great promise for potential application.

Does the Electrical Double Layer Contribute to the Mechanism of Action of Antimicrobial Peptides?

AbstractThis concept paper elucidates the possible influence of the electrical double layer (EDL) and the polyelectrolytic nature of bacterial cell walls on the behavior of antimicrobial peptides (AMPs) and lipopeptides. It proposes that the presence of EDL adjacent to lipid membranes may play a crucial role in inducing peptide aggregation and conformational changes, thus affecting their antimicrobial activity. Furthermore, it emphasizes that the negatively charged components in both Gram‐positive and Gram‐negative bacterial cell walls may act as polyelectrolytes, effectively reducing the critical micellization concentration (CMC) of positively charged peptides and lipopeptides. This reduction is expected to facilitate their aggregation, potentially enhancing their accumulation at the bacterial membrane and increasing their effectiveness in disrupting membrane integrity and exerting antimicrobial activity. Therefore, understanding the interplay between EDL effects, polyelectrolytic properties of bacterial cell walls, and the behavior of antimicrobial peptides is essential for elucidating their mechanisms of action and optimizing their therapeutic potential.

PAM-1: an antimicrobial peptide with promise against ceftazidime-avibactam resistant Escherichia coli infection.

Antibiotic misuse and overuse have led to the emergence of carbapenem-resistant bacteria. The global spread of resistance to the novel antibiotic combination ceftazidime-avibactam (CZA) is becoming a severe problem. Antimicrobial peptide PAM-1 offers a novel approach for treating infections caused by antibiotic-resistant bacteria. This study explores its antibacterial and anti-biofilm activities and mechanisms against CZA-resistant Escherichia. Coli (E. coli), evaluating its stability and biosafety as well. The broth microdilution method, growth curve analysis, crystal violet staining, scanning electron microscopy, and propidium iodide staining/N-phenyl-1-naphthylamine uptake experiments were performed to explore the antibacterial action and potential mechanism of PAM-1 against CZA-resistant E. coli. The biosafety in diverse environments of PAM-1 was evaluated by red blood cell hemolysis, and cytotoxicity tests. Its stability was further assessed under different temperatures, serum concentrations, and ionic conditions using the broth microdilution method to determine its minimum inhibitory concentration (MIC). Galleria mellonella infection model and RT-qPCR were used to investigate the in vivo antibacterial and anti-inflammatory effects. In vitro antibacterial experiments demonstrated that the MICs of PAM-1 ranged from 2 to 8 μg/mL, with its effectiveness sustained for a duration of 24 h. PAM-1 exhibited significant antibiofilm activities against CZA-resistant E. coli (p < 0.05). Furthermore, Membrane permeability test revealed that PAM-1 may exert its antibacterial effect by disrupting membrane integrity by forming transmembrane pores (p < 0.05). Red blood cell hemolysis and cytotoxicity tests revealed that PAM-1 exerts no adverse effects at experimental concentrations (p < 0.05). Moreover, stability tests revealed its effectiveness in serum and at room temperature. The Galleria mellonella infection model revealed that PAM-1 can significantly improve the survival rate of Galleria mellonella (>50%)for in vivo treatment. Lastly, RT-qPCR revealed that PAM-1 downregulates the expression of inflammatory cytokines (p < 0.05). Overall, our study findings highlight the potential of PAM-1 as a therapeutic agent for CZA-resistant E. coli infections, offering new avenues for research and alternative antimicrobial therapy strategies.

Microbial- and Plant-Derived Bioactive Peptides and Their Applications against Foodborne Pathogens: Current Status and Future Prospects.

Bioactive peptides (BAPs) obtained from plants and microbes have been thoroughly explored and studied due to their prophylactic properties. The use of BAPs seems to be a promising substitute for several currently available antibiotics because of their antimicrobial properties against foodborne pathogens. BAPs have several other useful properties including antitumor, antihypertensive, antioxidant, antiobesity, and antidiabetic activities. Nowadays, scientists have attempted to recombinantly synthesize bioactive peptides to study their characteristics and potential uses, since BAPs are not found in large quantities in nature. Many pathogenic microorganisms including foodborne pathogens are becoming resistant to various antibiotics. To combat these pathogens, scientists are working to find novel, innovative, and safe antimicrobial agents. Plant- and microbe-based BAPs have demonstrated noteworthy antimicrobial activity against a wide range of pathogenic microorganisms, including foodborne pathogens. BAPs can kill pathogenic microorganisms by disrupting membrane integrity, inhibiting DNA and RNA synthesis, preventing protein synthesis, blocking protein activity, or interacting with certain intracellular targets. In addition, the positive effect of BAP consumption extends to gut microbiota modulation and affects the equilibrium of reactive oxygen species in the gut. This article discusses recombinant BAPs, BAPs generated from plants and microbes, and their antimicrobial applications and modes of action for controlling foodborne pathogens.

The role of ferroptosis as a regulator of oxidative stress in the pathogenesis of ischemic stroke.

Ferroptosis is a unique form of cell death that was first described in 2012 and plays a significant role in various diseases, including neurodegenerative conditions. It depends on a dysregulation of cellular iron metabolism, which increases free, redox-active, iron that can trigger Fenton reactions, generating hydroxyl radicals that damage cells through oxidative stress and lipid peroxidation. Lipid peroxides, resulting mainly from unsaturated fatty acids, damage cells by disrupting membrane integrity and propagating cell death signals. Moreover, lipid peroxide degradation products can further affect cellular components such as DNA, proteins, and amines. In ischemic stroke, where blood flow to the brain is restricted, there is increased iron absorption, oxidative stress, and compromised blood-brain barrier integrity. Imbalances in iron-transport and -storage proteins increase lipid oxidation and contribute to neuronal damage, thus pointing to the possibility of brain cells, especially neurons, dying from ferroptosis. Here, we review the evidence showing a role of ferroptosis in ischemic stroke, both in recent studies directly assessing this type of cell death, as well as in previous studies showing evidence that can now be revisited with our new knowledge on ferroptosis mechanisms. We also review the efforts made to target ferroptosis in ischemic stroke as a possible treatment to mitigate cellular damage and death.

Development of Membrane-Targeting Fluorescent 2-Phenyl-1H-phenanthro[9,10-d]imidazole-Antimicrobial Peptide Mimic Conjugates against Methicillin-Resistant Staphylococcus aureus.

The escalation of multidrug-resistant bacterial infections, especially infections caused by methicillin-resistant Staphylococcus aureus (MRSA), underscores the urgent need for novel antimicrobial drugs. Here, we synthesized a series of amphiphilic 2-phenyl-1H-phenanthro[9,10-d]imidazole-antimicrobial peptide (AMP) mimic conjugates (III1-30). Among them, compound III13 exhibited excellent antibacterial activity against G+ bacteria and clinical MRSA isolates (MIC = 0.5-2 μg/mL), high membrane selectivity, and low toxicity. Additionally, compared with traditional clinical antibiotics, III13 demonstrated rapid bactericidal efficacy and was less susceptible to causing bacterial resistance. Mechanistic studies revealed that III13 targets phosphatidylglycerol (PG) on bacterial membranes to disrupt membrane integrity, leading to an increase in intracellular ROS and leakage of proteins and DNA, ultimately causing bacterial cell death. Furthermore, III13 possessed good fluorescence properties with potential for further dynamic monitoring of the antimicrobial process. Notably, III13 showed better in vivo efficacy against MRSA compared to vancomycin, suggesting its potential as a promising candidate for anti-MRSA medication.

CRISPR antiphage defence mediated by the cyclic nucleotide-binding membrane protein Csx23.

CRISPR-Cas provides adaptive immunity in prokaryotes. Type III CRISPR systems detect invading RNA and activate the catalytic Cas10 subunit, which generates a range of nucleotide second messengers to signal infection. These molecules bind and activate a diverse range of effector proteins that provide immunity by degrading viral components and/or by disturbing key aspects of cellular metabolism to slow down viral replication. Here, we focus on the uncharacterised effector Csx23, which is widespread in Vibrio cholerae. Csx23 provides immunity against plasmids and phage when expressed in Escherichia coli along with its cognate type III CRISPR system. The Csx23 protein localises in the membrane using an N-terminal transmembrane α-helical domain and has a cytoplasmic C-terminal domain that binds cyclic tetra-adenylate (cA4), activating its defence function. Structural studies reveal a tetrameric structure with a novel fold that binds cA4 specifically. Using pulse EPR, we demonstrate that cA4 binding to the cytoplasmic domain of Csx23 results in a major perturbation of the transmembrane domain, consistent with the opening of a pore and/or disruption of membrane integrity. This work reveals a new class of cyclic nucleotide binding protein and provides key mechanistic detail on a membrane-associated CRISPR effector.

Potential effects of nutrition-induced alteration of gut microbiota on inflammatory bowel disease: A review.

Inflammatory bowel disease (IBD), mainly comprising ulcerative colitis and Crohn's disease, is a group of gradually progressive diseases bringing significant mental anguish and imposes serious economic burdens. Interplay of genetic, environmental, and immunological factors have been implicated in its pathogenesis. Nutrients, as crucial environmental determinants, mainly encompassing carbohydrates, fats, proteins, and micronutrients, are closely related to the pathogenesis and development of IBD. Nutrition is essential for maintaining the dynamic balance of intestinal eco-environments to ensure intestinal barrier and immune homeostasis, while this balance can be disrupted easily by maladjusted nutrition. Research has firmly established that nutrition has the potential to shape the composition and function of gut microbiota to affect the disease course. Unhealthy diet and eating disorders lead to gut microbiota dysbiosis and further destroy the function of intestinal barrier such as the disruption of membrane integrity and increased permeability, thereby triggering intestinal inflammation. Notably, appropriate nutritional interventions, such as the Mediterranean diet, can positively modulate intestinal microecology, which may provide a promising strategy for future IBD prevention. In this review, we provide insights into the interplay between nutrition and gut microbiota and its effects on IBD and present some previously overlooked lines of evidence regarding the role of derived metabolites in IBD processes, such as trimethylamine N-oxide and imidazole propionate. Furthermore, we provide some insights into reducing the risk of onset and exacerbation of IBD by modifying nutrition and discuss several outstanding challenges and opportunities for future study.