Recovery of hepatocytes from attack by the pore former amphotericin B.
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ABSTRACT:
SUBMITTER: Binet A
PROVIDER: S-EPMC1149317 | biostudies-other | 1988 Jul
REPOSITORIES: biostudies-other
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Project description:BackgroundAcute kidney injury (AKI) is a common complication of treatment with liposomal amphotericin B (LAmB). The trajectory of renal recovery after LAmB-associated AKI has not been well described, nor has effect of LAmB dose on recovery of renal function been explored.ObjectiveCharacterize the pattern of renal recovery after incident AKI during LAmB and determine potential influencing factors.MethodsThis retrospective cohort study analyzed patients who developed a ?50% increase in serum creatinine while on LAmB. Patients were followed up until complete renal recovery or death or for 30 days, whichever occurred first. The primary outcome was complete renal recovery, defined as serum creatinine convalescence to within 10% of the patient's pretreatment baseline. Multivariable modeling was used to identify independent predictors of renal recovery.ResultsNinety-eight patients experienced nephrotoxicity during LAmB, 94% of which received doses <7 mg/kg/day. Fifty-one patients at least partially recovered renal function and, of these, 32 exhibited complete recovery after a mean 9.8 ± 7.8 days. No statistical relationship was found between LAmB dose at the time of AKI or cumulative exposure to LAmB and the likelihood of renal recovery. Concomitant nephrotoxins, age, and pretreatment renal function did not modify this effect in multivariable analysis.Conclusion and relevanceOur data suggests that LAmB dose did not impact the likelihood of renal recovery. Additional investigation is needed to confirm these findings when aggressive dosing strategies are employe. Additional research is also warranted to further characterize the course of recovery after LAmB-associated nephrotoxicity and comprehensive spectrum of renal outcomes.
| S-EPMC6369474 | biostudies-literature
Project description:A series of amides of the antifungal antibiotic amphotericin B (AmB) and its conjugates with benzoxaboroles was tested to determine whether they form pores in lipid bilayers and to compare their channel characteristics. The tested derivatives produced pores of larger amplitude and shorter lifetime than those of the parent antibiotic. The pore conductance was related to changes in the partial charge of the hydrogens of the hydroxyl groups in the lactone ring that determined the anion coordination in the channel. Neutralization of one of the polar group charges in the AmB head during chemical modification produced a pronounced effect by diminishing the dwell time of the polyene channel compared to modification of both groups. In this study, compounds that had a modification of one carboxyl or amino group were less effective in initializing phase separation in POPC-membranes compared to derivatives that had modifications of both polar groups as well as the parent antibiotic. The effects were attributed to the restriction of the aggregation process by electrical repulsion between charged derivatives in contrast to neutral compounds. The significant correlation between the ability of derivatives to increase the permeability of model membranes-causing the appearance of single channels in lipid bilayers or inducing calcein leakage from unilamellar vesicles-and the minimal inhibitory concentration indicated that the antifungal effect of the conjugates was due to pore formation in the membranes of target cells.
| S-EPMC5706719 | biostudies-literature
Project description:Pore formation by membrane-active peptides, naturally encountered in innate immunity and infection, could have important medical and technological applications. Recently, the well-studied lytic peptide melittin has formed the basis for the development of combinatorial libraries from which potent pore-forming peptides have been derived, optimized to work under different conditions. We investigate three such peptides, macrolittin70, which is most active at neutral pH; pHD15, which is active only at low pH; and MelP5_Δ6, which was rationally designed to be active at low pH but formed only small pores. There are three, six, and six acidic residues in macrolittin70, pHD15, and MelP5_Δ6, respectively. We perform multi-microsecond simulations in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) of hexamers of these peptides starting from transmembrane orientations at neutral pH (all residues at standard protonation), low pH (acidic residues and His protonated), and highly acidic environments in which C-termini are also protonated. Previous simulations of the parent peptides melittin and MelP5 in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) are repeated in POPC. We find that the most potent pore-forming peptides exhibit strong interpeptide interactions, including salt bridges, H-bonds, and polar interactions. Protonation of the C-terminus promotes helicity and pore size. The proximity of the peptides allows fewer lipid headgroups to line the pores than in previous simulations, making the pores intermediate between barrel stave and toroidal. Based on these structures and geometrical arguments, we attempt to rationalize the factors that under different conditions can increase or decrease pore stability and propose mutations that could be tested experimentally.
| S-EPMC7175419 | biostudies-literature
Project description:The membrane attack complex (MAC) is a hetero-oligomeric protein assembly that kills pathogens by perforating their cell envelopes. The MAC is formed by sequential assembly of soluble complement proteins C5b, C6, C7, C8 and C9, but little is known about the rate-limiting steps in this process. Here, we use rapid atomic force microscopy (AFM) imaging to show that MAC proteins oligomerize within the membrane, unlike structurally homologous bacterial pore-forming toxins. C5b-7 interacts with the lipid bilayer prior to recruiting C8. We discover that incorporation of the first C9 is the kinetic bottleneck of MAC formation, after which rapid C9 oligomerization completes the pore. This defines the kinetic basis for MAC assembly and provides insight into how human cells are protected from bystander damage by the cell surface receptor CD59, which is offered a maximum temporal window to halt the assembly at the point of C9 insertion.
| S-EPMC6502846 | biostudies-literature
Project description:Human body-surface epithelia coexist in close association with complex bacterial communities and are protected by a variety of antibacterial proteins. C-type lectins of the RegIII family are bactericidal proteins that limit direct contact between bacteria and the intestinal epithelium and thus promote tolerance to the intestinal microbiota. RegIII lectins recognize their bacterial targets by binding peptidoglycan carbohydrate, but the mechanism by which they kill bacteria is unknown. Here we elucidate the mechanistic basis for RegIII bactericidal activity. We show that human RegIIIα (also known as HIP/PAP) binds membrane phospholipids and kills bacteria by forming a hexameric membrane-permeabilizing oligomeric pore. We derive a three-dimensional model of the RegIIIα pore by docking the RegIIIα crystal structure into a cryo-electron microscopic map of the pore complex, and show that the model accords with experimentally determined properties of the pore. Lipopolysaccharide inhibits RegIIIα pore-forming activity, explaining why RegIIIα is bactericidal for Gram-positive but not Gram-negative bacteria. Our findings identify C-type lectins as mediators of membrane attack in the mucosal immune system, and provide detailed insight into an antibacterial mechanism that promotes mutualism with the resident microbiota.
| S-EPMC4160023 | biostudies-literature
Project description:Pore-forming toxins (PFTs) are a class of proteins implicated in a wide range of virulent bacterial infections and diseases. These toxins bind to target membranes and subsequently oligomerize to form functional pores that eventually lead to cell lysis. While the protein undergoes large conformational changes on the bilayer, the connection between intermediate oligomeric states and lipid reorganization during pore formation is largely unexplored. Cholesterol-dependent cytolysins (CDCs) are a subclass of PFTs widely implicated in food poisoning and other related infections. Using a prototypical CDC, listeriolysin O (LLO), we provide a microscopic connection between pore formation, lipid dynamics, and leakage kinetics by using a combination of Förster resonance energy transfer (FRET) and fluorescence correlation spectroscopy (FCS) measurements on single giant unilamellar vesicles (GUVs). Upon exposure to LLO, two distinct populations of GUVs with widely different leakage kinetics emerge. We attribute these differences to the existence of oligomeric intermediates, sampling various membrane-bound conformational states of the protein, and their intimate coupling to lipid rearrangement and dynamics. Molecular dynamics simulations capture the influence of various membrane-bound conformational states on the lipid and cholesterol dynamics, providing molecular interpretations to the FRET and FCS experiments. Our study establishes a microscopic connection between membrane binding and conformational changes and their influence on lipid reorganization during PFT-mediated cell lysis. Additionally, our study provides insights into membrane-mediated protein interactions widely implicated in cell signaling, fusion, folding, and other biomolecular processes.
| S-EPMC6600976 | biostudies-literature
Project description:Pediatric MS patients suffer from severe first and second relapse but better recovery explained by difference in age-restricted transcriptional profiles associated with antigen-presentation and B-cell activation Herein, we compared the blood mononuclear cell transcriptome of pediatric and adult MS patients with recovery (PDMS-rec, ADMS-rec) and without recovery (PDMS-norec, ADMS-norec) 6 months after relapse. Healthy pediatric and adult subjects (PDC, ADC) were used as controls.
2021-01-27 | GSE146383 | GEO
Project description:UV-induced DNA damage causes repression of RNA synthesis. Following the removal of DNA lesions, transcription recovery operates through a process that is not understood yet. Here we show that knocking-out of the histone methyltransferase DOT1L in mouse embryonic fibroblasts (MEF(DOT1L)) leads to a UV hypersensitivity coupled to a deficient recovery of transcription initiation after UV irradiation. However, DOT1L is not implicated in the removal of the UV-induced DNA damage by the nucleotide excision repair pathway. Using FRAP and ChIP experiments we established that DOT1L promotes the formation of the pre-initiation complex on the promoters of UV-repressed genes and the appearance of transcriptionally active chromatin marks. Treatment with Trichostatin A, relaxing chromatin, recovers both transcription initiation and UV-survival. Our data suggest that DOT1L secures an open chromatin structure in order to reactivate RNA Pol II transcription initiation after a genotoxic attack.
| S-EPMC3701700 | biostudies-literature
Project description:It is well known that hepatitis B virus infections can be transient or chronic, but the basis for this dichotomy is not known. To gain insight into the mechanism responsible for the clearance of hepadnavirus infections, we have performed a molecular and histologic analysis of liver tissues obtained from transiently infected woodchucks during the critical phase of the recovery period. We found as expected that clearance from transient infections occurred subsequent to the appearance of CD4(+) and CD8(+) T cells and the production of interferon gamma and tumor necrosis factor alpha in the infected liver. These events were accompanied by a significant increase in apoptosis and regeneration of hepatocytes. Surprisingly, however, accumulation of virus-free hepatocytes was delayed for several weeks following this initial influx of lymphocytes. In addition, we observed that chronically infected animals can exhibit levels of T-cell accumulation, cytokine expression, and apoptosis that are comparable with those observed during the initial phase of transient infections. Our results are most consistent with a model for recovery predicting replacement of infected hepatocytes with regenerated cells, which by unknown mechanisms remain protected from reinfection in animals that can be cured.
| S-EPMC111485 | biostudies-literature
Project description:Background and purposeJuxtacortical spots are detected frequently on fluid-attenuated inversion recovery (FLAIR) images, but have not been extensively researched in patients with transient ischemic attack (TIA). We hypothesized that juxtacortical spots on FLAIR images are partly associated with right-to-left shunt (RLS) in TIA without clear etiology. The possibility of an association between the presence of RLS and juxtacortical spots on FLAIR images in patients with TIA without clear etiology was investigated, and the imaging findings of patients with and without RLS were compared.MethodsThis was a retrospective study of TIA patients who visited our tertiary stroke center consecutively within 72 hours of TIA onset. Cryptogenic TIA was defined as no clear etiology despite a routine diagnostic workup. The presence of RLS was examined by transcranial Doppler with an agitated saline test or transesophageal echocardiography. Juxtacortical spots were defined as small and round hyperintensities in the juxtacortex on FLAIR images, excluding white-matter hyperintensities.ResultsOf the 132 patients with cryptogenic TIA examined for this study, 70 (53.0%) had RLS. Juxtacortical spots on FLAIR images were detected more frequently in patients with RLS than in those without. The independent factors for the presence of juxtacortical spots were RLS [odds ratio (OR)=3.802, 95% confidence interval (95% CI)=1.74-8.2; p=0.001] and age (OR=1.058, 95% CI=1.01-1.10; p=0.004) by multivariate analysis. The number of juxtacortical spots was significantly higher among patients with a moderate-to-large RLS than in those with a small or no RLS.ConclusionsThe findings of the present study demonstrate a significant association between the presence of RLS and the occurrence of juxtacortical spots on FLAIR images in patients with cryptogenic TIA.
| S-EPMC3633187 | biostudies-literature