Toxins

Symptoms of Clostridioides difficile infection (CDI) are primarily caused by two major protein toxins, toxin A (TcdA) and toxin B (TcdB). In addition, approximately 5-30% of C. dif[fi]cile strains produce a third toxin, C. difficile binary toxin (CDT), which is has been associated with enhanced virulence and severe disease. CDT consists of an enzymatic component CDTa, and a binding and translocation component CDTb, which mediates the delivery of CDTa into host cells. CDTb contains two receptor-binding domains, RBD1 and RBD2. Recent structural studies suggest that RBD2 plays a critical role in the formation and stabilization of the di-heptameric CDTb assembly required for efficient intoxication of host cells. In this study, we evaluated the immunogenicity and protective potential of RBD1 and RBD2 using in silico, in vitro and in vivo approaches. Sequence analysis demonstrated that RBD2 is highly conserved among diverse CDT-producing C. difficile ribotypes and toxinotypes. Immunization of mice with RBD2, but not RBD1 conferred effective protection against direct CDT challenge. Moreover, RBD2 immunization protected hamsters against infection with a CDT-only-producing C. difficile strain (DSM 101085; TcdA-TcdB-CDT). Mechanistically, anti-RBD2 serum, but not anti-RBD1 serum, effectively neutralized CDT-mediated cytotoxicity, as demonstrated by inhibition of cell rounding in Vero cells. Collectively, these findings identify RBD2 as a promising vaccine antigen targeting CDT and provide functional evidence supporting its critical role in CDT-mediated host-cell intoxication. Incorporation of RBD2 into multivalent C. difficile vaccines may broaden protection against hypervirulent, CDT-producing strains.

The type VII secretion system (T7SS) is a membrane-embedded protein export pathway found in mycobacteria and Gram-positive bacteria. Recently it was shown that Mycobacterium abscessus uses its ESX-4 variant of the T7SS to secrete a toxin, EatA, which targets arabinogalactan present in the mycobacterial cell envelope. Prior to its export, EatA forms a complex with a pair of small proteins from the WXG100 family, TapA1 and TapA2. Here we investigated a structural model of the EatA N-terminal domain in complex with TapA1 and TapA2 using site-directed mutagenesis and bacterial 2-hybrid assays. Our results are consistent with the three proteins forming a stacked bundle of alpha-helices. Structural modelling also predicted an interaction of the EatA-TapA1-TapA2 complex with EsxT-EsxU, a second pair of WXG100-family proteins that are likely required for the mechanistic operation of ESX-4. Whilst we could demonstrate a potential interaction between TapA2 and EsxT by bacterial 2-hybrid analysis, we were not able to purify a complex of all five proteins.

Ivermectin is an important broad-spectrum anthelmintic used to treat nematode parasites including gastro-intestinal infections of humans and animals. The mode of action for Ivermectin is understood to involve activation of inhibitory glutamate-gated chloride channels (GluCls). Ivermectin has also been reported to inhibit the release of extracellular vesicles (EVs). We found that EVs are released from the whole intestine of the gastro-intestinal parasite, Ascaris suum. Proteomic analysis identified 1,574 proteins within these intestinal EVs, including 96 nematode proteins with putative immune-associated functions based on homology to proteins involved in host immune processes and 130 proteins with predicted digestive functions. Comparative analysis following ivermectin exposure revealed 38 differentially abundant proteins that included the putative immune-related proteins: transthyretin-like proteins, a small heat-shock antigen, a phospholipase A2, and the NF-{kappa}B subunit p105. Thus, ivermectin modulated the potential immune-related cargo of intestinal EVs. The ivermectin inhibition of intestinal EV release was concentration-dependent with an IC50 of 64 nM. We also identified the expression of GluCl subunit receptor genes in the Ascaris intestine. The potent inhibitory effect of ivermectin on the release of these EVs from the nematode intestine and the expression of GluCl channel subunits sheds further light on the site and mechanisms of action of this important anthelmintic.

Background and aims Model systems for bile duct disorders are needed for testing therapeutic interventions. Current models have poor human relevance or limited potential for recreating the complex bile duct microenvironment at scale. We aimed to generate a humanized microphysiological system to model and treat cholangiopathies. Methods An in vitro bile duct was created using 3D printed microfluidic chips containing a collagen-embedded canal seeded with patient-derived primary human cholangiocytes. Barrier permeability and compound transport across the epithelium was measured, and disruption of the barrier was performed with lipopolysaccharide treatment. The duct was challenged with the known hepatotoxicant Chlorpromazine. Biliatresone was used to model biliary-atresia and treated using N-acetyl-L-cysteine. Results Cholangiocytes in the bile duct chip established a tight, polarized epithelial barrier. Verapamil and Linerixibat inhibited transport of rhodamine 123 and cholyl-lys-fluorescein respectively with 66 % (p = 0.0004) and 57 % (p = 0.03) reduction. 10 g/mL lipopolysaccharide led to a loss of epithelial barrier integrity, measured by an increase of over 1000 % in leakage of both 3 kDa (p = 0.0002) and 10 kDa dextran (p = 0.0001) along with upregulation of cytokines. Chlorpromazine displayed dose-dependent toxicity with EC50 values of 84, 140 and 96 M for three patient lines. Biliatresone induced a dose-dependent abnormal phenotype with loss of viability. The induced phenotype could be treated with N-acetyl-L-cysteine, improving viability from 23 % to 59 % (p < 0.0001) with treatment of 2 g/mL Biliatresone. Conclusions Our novel platform allows complex studies of bile duct biology, testing of off-target effects from drugs and treatment of a disease phenotype.

Kinema is a traditional fermented soybean food indigenous to the eastern Himalayan regions of Nepal and India. The fermentation process is primarily mediated by the bacterium Bacillus subtilis, which produces several bioactive compounds and enzymes with potential therapeutic applications. Considering the growing burden of cardiovascular diseases and the need for effective fibrinolytic agents for thrombolytic therapy, this study aimed to extract, partially purify, and evaluate the thrombolytic potential of kinemakinase derived from kinema prepared from white soybeans. Partial purification of the enzyme was achieved using ammonium sulfate precipitation. Thrombolytic activity was assessed in vitro using human blood clots, where three enzyme dilutions demonstrated clot lysis ranging from 66% to 68%, indicating considerable fibrinolytic potential. In silico analyses were also performed to investigate the structural and functional characteristics of the enzyme. The tertiary structure obtained from UniProt was modeled using the Robetta server and refined with GalaxyRefine. Docking with fibrin using ClusPro 2.0 and molecular dynamics simulations using iMODS confirmed favorable interaction and structural stability, while disulfide engineering enhanced protein stability. The findings suggest that kinema-derived kinemakinase may serve as a promising alternative thrombolytic agent, warranting further biochemical characterization and dosage optimization.

Severe dengue can damage the liver through unestablished mechanisms. We investigated the role of myeloperoxidase (MPO), a neutrophil enzyme, in dengue through patients, fatal liver samples, and mouse infection models. Observations from two independent clinical cohorts revealed elevated plasma MPO levels in dengue and, in one cohort, MPO was further linked to liver injury markers during the critical phase of disease, whereas livers from dengue fatal cases revealed MPO build-up in the vicinity of CD177+ activated neutrophils. In mice, dengue led to MPO overexpression, oxidative damage, and broad activation of innate and systemic inflammatory pathways in livers. Blocking MPO activity alleviated these and improved survival in one model and delayed disease progression without preventing death in another. These findings establish MPO as a functional mediator of severe dengue-associated liver injury and inflammation, which warrants further preclinical investigation into its hepatic pathogenic mechanism and its validity as target for therapeutic intervention.

Microcystin-LR (MC-LR), a cyanobacterial toxin produced during harmful algal blooms, is an increasing environmental and public health concern as the frequency and intensity of harmful algal blooms continue to rise globally. While the effects of MC-LR have been extensively studied in young organisms, much less is known about how aging influences susceptibility to cyanotoxin exposure. Here, we used the naturally short-lived turquoise killifish, Nothobranchius furzeri, to investigate transcriptional responses to low-level MC-LR exposure in a senescent vertebrate. Approximately 8-month-old GRZ killifish were exposed to a low dose of 0.5 g/L MC-LR, followed by whole-body RNA sequencing and sex-stratified differential expression analysis. Despite identical experimental conditions and exposure, males and females exhibited strikingly distinct transcriptional responses, with 313 differentially expressed genes (DEGs) in males and 263 in females and only 27 DEGs shared between the sexes. Among the shared responses, pck1, a key regulator of gluconeogenesis, was strongly downregulated in both sexes, accompanied by altered expression of genes associated with mitochondrial function, metabolic regulation, extracellular matrix remodeling, and genome maintenance. Males exhibited prominent remodeling of skeletal muscle and contractile programs, supported by enrichment of sarcomeric, myofilament, and contractile-fiber-associated genes. In contrast, females showed pronounced alterations in reproductive and metabolic programs, including vitellogenin- and zona pellucida-associated transcripts. Cell/tissue associated marker-module analysis further revealed distinct sex-dependent shifts in structural, neural, immune, metabolic, and reproductive transcriptional signatures. Together, these findings demonstrate that MC-LR elicits a broad but strongly sex-dependent transcriptional response in senescent N. furzeri, involving responses in multiple physiological systems. Our study identifies biological sex as an important determinant of cyanotoxin responses in an aging context and establishes naturally aged N. furzeri as a tractable vertebrate model for investigating interactions between environmental exposure and biological aging.

People are widely exposed to the antimicrobial cetylpyridinium chloride (CPC) via consumer products, but CPC is a mitochondrial toxicant with potency comparable to that of canonical mitotoxicants. CPC is largely unregulated despite growing usage, bioavailability, and ability to cross the blood-brain barrier. Previously, we showed, in several cell types at non-cytotoxic and exposure-relevant doses, CPC inhibits ATP and OCR, endpoints of the electron transport chain (ETC). Mitochondrial toxicity is linked to multiple diseases (e.g., diabetes, Parkinsons, myalgic encephalomyelitis), but CPC has not been studied epidemiologically, and little mechanistic information is available. To determine why OCR and ATP are hampered by CPC, we hypothesized that CPC inhibits individual ETC components, cardiolipin, or TCA enzymes. Here, we show that, in primary human skin cells, an immune mast cell model, and isolated mitochondria, CPC apparently inhibits multiple ETC Complexes. Detailed investigation pinpointed the mechanism to the distal end of ETC: Complex III-cytochrome C-Complex IV. Using multiple approaches, we show that CPC does not directly inhibit any of the Complexes (not even Complex I as earlier reported), nor TCA enzymes, nor coenzyme Q. Yet, we found that CPC exhibits mitotoxicity as potent as cyanide. Anionic lipid cardiolipin attracts cytochrome C to the inner mitochondrial membrane so that it may shuttle electrons from Complex III to IV. Despite not altering levels of cardiolipin, CPC hinders cytochrome C by electrostatically interfering with cardiolipin. To aid epidemiology, risk analysis, and predictive toxicology, we have determined the precise biochemical mechanism of action of this ubiquitous compound.

Therapy of ischemic stroke is currently limited to pharmacological and/or mechanical recanalization. There are no neuroprotective therapies approved for use during the rehabilitative phase of ischemic stroke, which is characterized by neurodegenerative changes. Thus, the search for neuroprotective compounds capable of preventing neuronal death caused by pathogenetic cascades triggered during hypoxia is an urgent task. In this study, we demonstrate increased culture viability following pre- and post-incubation with salicyl-carnosine (SC) in a model of oxygen glucose deprivation on a primary culture of rat cortical neurons. Its neuroprotective properties were greater than that of acetylsalicylic acid and carnosine, and it was effective in lower concentrations. In addition, SC protected the culture from NMDA-induced excitotoxicity. We also showed the passage of SC into neurons, and the presence of its direct antioxidant activity in a model of paraquat-induced oxidative stress. The neuroprotective effects of SC are associated with a decrease in the level of pro-apoptotic protein Bak and a decrease in the activation of kinase p38, as well as an increase in the activation of kinase ERK1/2. The acquired data suggests that SC is a promising neuroprotective compound, and warrants further investigation in vivo.

Snake venom metalloproteinases (SVMPs) are major drivers of pathology following viper envenomation and represent important targets for the development of next-generation recombinant antivenoms. PIII SVMPs are among the most potent haemorrhagic toxins and contain disintegrin-like (Dis) and cysteine-rich (C-rich) accessory domains. Despite their biomedical importance, the mechanistic roles of these accessory domains in substrate recognition and catalysis remain poorly understood. We produced recombinant full-length and domain-deletion variants of two functionally distinct PIII SVMPs: the broadly proteolytic, cytotoxic cPIII and the highly specific prothrombin activator Ecarin. Proteins were expressed as latent zymogens in insect cells, auto-activated by Zn2+, and analysed using enzymatic, blood clotting, and cell-based assays. Progressive removal of the C-rich and Dis domains reduced zymogen auto-activation and markedly diminished catalytic activity in both toxins. In cPIII, domain deletion caused a stepwise loss of proteolytic and cytotoxic activity without altering substrate preference. In Ecarin, removal of the accessory domains strongly impaired prothrombin activation, and thus plasma clotting, demonstrating a critical role in substrate recognition. Conversely, deletion of the C-rich domain increased fibrinogenolytic activity, revealing a substrate-dependent gatekeeping function. Deglycosylation showed that N-linked glycans modulate SVMP activity in a construct-dependent manner. Recombinant Ecarin closely recapitulated the biochemical properties of the native venom-derived toxin. Our data support a model in which PIII SVMP accessory domains enhance substrate positioning and catalytic efficiency while selectively restricting access to non-cognate substrates. These findings establish accessory-domain-mediated substrate recognition as a key determinant of SVMP function, informing rational antivenom design.

The Bacillus cereus group comprises bacteria of biotechnological interest, but also raises health concerns. Some bacteria in this group are opportunistic human pathogens, mainly causing foodborne gastrointestinal infections. As of today, the presence, sequence variability, or expression of genes encoding toxins or other virulence factors are insufficient to predict the potential of a given isolate to cause the diarrheal form of the disease. To address this limitation, we developed a sandwich ELISA to quantify the NheA and Sphingomyelinase (SMase) proteins in culture supernatants to test them as markers of pathogenic potential. Application of the assay to a collection of B. cereus group isolates revealed that strains associated with food poisoning outbreaks produce significantly more NheA and SMase than those isolated from the environment or from commercial products. Statistical analyses show that the combined quantification of NheA and SMase provides robust discrimination between pathogenic and non-pathogenic (environmental and commercial) profiles. These results demonstrate that the quantitative assessment of both NheA and SMase production can serve as a reliable biomarker for distinguishing diarrheic food poisoning isolates from harmless strains.

In human dorsal root ganglia (DRG), and trigeminal (TG) neurons, the various voltage-gated sodium channel (Nav) isoforms play critical roles in the firing of action potentials, which drive electrical impulses that encode somatosensations including, itch, and pain. The SCN11A gene encodes the tetrodotoxin (TTX)-resistant voltage-gated sodium channel Nav1.9, characterized by unique gating properties. Unlike other isoforms, the Nav1.9 channel activates and inactivates slowly and has a hyperpolarized voltage-dependence of activation and depolarized voltage-dependence of inactivation. This leads to a large window current that has been suggested to function as a regulator of the resting membrane potential of neurons. Mutations in Nav1.9 channels lead to congenital insensitivity to pain (gain-of-function) or familial episodic pain syndrome (loss-of-function) suggesting the channel is a critical mediator of pain. Despite its relevance in pain pathophysiology, most existing data relies on rodent models or heterologous expression systems, leaving the specific pharmacology and biophysical behavior of these channels in human primary neurons largely unknown. In this study, we pharmacologically isolated and characterized native Nav1.9 channel currents in human DRG and TG neurons to compare their biophysical profiles. Our findings reveal significant kinetic and voltage-dependent differences between the two populations. Specifically, Nav1.9 channels in TG neurons exhibit a right-shifted steady-state inactivation curve, a larger window current, and faster activation kinetics compared to those in DRG neurons. In addition, conditions that simulate inflammatory states in-vivo greatly potentiates the Nav1.9 currents consistent with similar observations in rodent models. By detailing these distinct biophysical properties, this research offers crucial insights into Nav1.9 channel function relevant for drug discovery efforts aimed at developing analgesics for both acute and chronic pain.

BackgroundOutbreaks of fluconazole-resistant Candida parapsilosis have recently emerged worldwide. In Spain, this phenomenon has been reported since 2020, mainly involving isolates from different clones harbouring the Y132F mutation at Erg11. MethodsWe analysed the expansion of fluconazole resistant C. parapsilosis strains within the national antifungal resistance surveillance program. Genetic clustering and relationships were assessed using microsatellite typing and whole genome sequencing. FindingsWe identified the expansion of three distinct clones carrying the Y132F mutation. Additionally, there was an increase in strains harbouring the G458S mutation, most of which belonged to a clonal complex, although other less prevalent clones were also detected. G458S isolates showed higher resistance to azoles than Y132F strains, particularly to voriconazole and isavuconazole. This increased resistance was associated with mutations in the Tac1 transcriptional regulator and duplication of a chromosomal region containing Tac1 and Erg11. One G458S isolate without mutation at Tac1 exhibited lower MIC values. Furthermore, two isolates carried the K143R mutation, and a distinct group of resistant strains without detectable ERG11 mutations was also identified. Resistant cases were detected across 31 hospitals in 12 autonomous regions. InterpretationOur findings indicate a concerning nationwide expansion of antifungal-resistant C. parapsilosis in Spain, involving multiple resistance mechanisms and clonal lineages, with implications for antifungal treatment and infection control strategies.

The DUP240 gene family in Saccharomyces cerevisiae encodes ten proteins containing two transmembrane domains (TMDs). Despite decades of interest driven by their high sequence similarity, little functional information exists regarding whether Dup240 family members share redundant or distinct roles. In this study, we combined computational modelling, subcellular localisation, and functional assays across the family to identify shared and unique features. Computational modelling revealed that Ktd1 possesses a unique structural element adjacent to its TMD region. Out of six successfully localised family members, Ktd1 was the only protein predominantly targeted to the vacuolar membrane and the sole Dup240 required for defence against the K28 killer toxin. Computational predictions further indicated that Ktd1 undergoes extensive post-translational regulation, containing multiple validated phosphorylation sites. Screening potential regulatory kinases and phosphatases identified several enzymes required for K28 defence, which were independently validated using liquid-based toxin sensitivity assays. A multicopy suppressor screen demonstrated that KTD1 overexpression rescued K28 sensitivity across most enzyme mutant backgrounds, confirming Ktd1 acts downstream or in parallel to many factors. However, the phosphatase Sit4 and the kinase Hog1 scored as most likely co-factors in Ktd1 mediated defence. Live-cell fluorescence imaging of these two enzymes revealed no dramatic spatial re-localisation during K28 exposure, suggesting that phospho-dependent regulation of Ktd1-mediated defence may occur through transient signalling events. Together, these findings identify Ktd1 as the central effector of the Dup240 family in toxin defence and provide a mechanistic framework for understanding Dup240 regulation.

Parkinson's disease (PD) is a progressive neurodegenerative condition characterized by the loss of dopaminergic (DA) neurons and alpha-synuclein aggregation, with ferroptosis playing a critical pathological role. This study investigated the neuroprotective potential of Kocuria rhizophila strain CDMP12, a marine bacterium isolated from the Gulf of Mannar, India, using Caenorhabditis elegans models of PD. Dietary supplementation with K. rhizophila (CDMP12) significantly preserved DA neuron structure, rescued neuro-sensory and motor deficits, and attenuated both alpha-synuclein expression in the C. elegans models. Transcriptomic and qRT-PCR analyses revealed that CDMP12 systematically suppressed ferroptosis by significantly downregulating iron and lipid regulatory genes such as smf-3, ftn-1, and acs-4, while upregulating the protective antioxidant gene gpx-1. Furthermore, BODIPY staining demonstrated that CDMP12 treatment markedly reduced lipid peroxidation, lowering the oxidized-to-non-oxidized lipid ratio in PD worms. Collectively, these findings identify K. rhizophila (CDMP12) as a promising marine-derived neuroprotective candidate that mitigates PD-associated pathology, accompanied by reduced alpha-synuclein burden, preservation of DA neuronal function, and attenuation of ferroptosis-associated molecular and lipid peroxidation signatures.

Transient receptor potential vanilloid 4 (TRPV4) is a Ca2+-permeable non-selective cation channel and its activating stimuli include anandamide, bisandrographolide, citric acid, arachidonic acid metabolic products by epoxygenases, hypo-osmotic cell swelling, and warm temperature. TRPV4 is involved in Ca2+-dependent signal transduction in several tissues. Since the activation of TRPV4 facilitates adherens junction formation in the skin epithelium, compounds that activate TRPV4 are expected to maintain or improve the barrier function of epidermal cells. In this study, we found that the extract of Arachis hypogaea (A. hypogaea) activate human TRPV4 (hTRPV4). In the Ca2+-imaging experiment, the application of A. hypogaea extract exhibited an increase in intracellular Ca2+ concentration ([Ca2+]i) in HEK293T cells expressing hTRPV4. The [Ca2+]i increases by application of A. hypogaea extract were not observed in HEK293T cells expressing hTRPV1, mouse TRPV2, hTRPV3, hTRPM8, or hTRPA1. We then examined the physicochemical properties of the components responsible for TRPV4 activation. Ethanol extracts of A. hypogaea caused an increase in [Ca2+]i in hTRPV4-expressing HEK293JN cells, whereas water, chloroform, and hexane extracts showed no activity. Moreover, the application of A. hypogaea extract enhanced transepithelial electrical resistance in the keratinocyte monolayer. These results suggest that A. hypogaea extract may contribute to the maintenance and improvement of the epidermal barrier function.

Endophytic fungi associated with the Himalayan yew (Taxus wallichiana) represent an underexplored source of bioactive secondary metabolites. This study investigated the extracellular metabolites of Annulohypoxylon purpureonitens isolated from Nepalese T. wallichiana using bioactivity screening combined with LCMS/MS-based metabolomics. The fungal extract exhibited broad-spectrum antibacterial activity, showing the strongest inhibition against Staphylococcus aureusand Enterococcus faecalis (MIC = 500 ug/mL). It also displayed notable antioxidant capacity(DPPH, ABTS, TPC &TFC) and cytotoxicity against HeLa and MCF-7 cancer cell lines. Metabolite profiling via GNPS molecular networking, manual MS/MS validation, and MASST reverse metabolomics putatively identified diverse compounds, including hydroquinidine, chlorogenic acid, muramic acid, and cordycepin conjugates widely distributed across public microbial datasets. Overall, A. purpureonitens is a promising source of multifunctional metabolites, laying a foundation for future compound isolation and functional characterization.

Nisin is a promising antimicrobial peptide widely used in food preservation due to its efficacy against Gram-positive spoilage and pathogenic bacteria. Although Nisin is increasingly applied in the food sector, the biopeptide suffers from instability within food matrixes and can rapidly lose its antimicrobial potential following interaction with food biomolecules. Thus, it is necessary to investigate approaches that can be employed to extend the stability and activity of Nisin. Hence, the aim of this study was to develop and characterise a chitosan-alginate polyelectrolyte microencapsulation system capable of enhancing Nisin stability while retaining antimicrobial activity. The microencapsulation of Nisin was achieved by pre-gelation of alginate using calcium chloride and subsequent direct electrostatic interaction between cationic Nisin and chitosan with pre-gelled anionic alginate at pH 5.0. Following microcapsule formation, physicochemical and structural characterisation was performed using Zeta potential determination and measurement of the polydispersity index (PDI) via dynamic light scattering. SEM micrographs were used to confirm morphology, while Fourier-transform infrared (FTIR) spectroscopy and high-performance liquid chromatography (HPLC) were utilised to assess chemical integrity and functional group preservation of encapsulated Nisin. Following this, stable microcapsules with diameters ranging from 150-200 nm and smooth surface morphology were obtained. Microcapsule formation was strongly influenced by formulation parameters, particularly pH, calcium ion concentration, and chitosan content, with deviations from optimal acidic conditions (< pH 5.0) resulting in aggregation, increased polydispersity, and reduced encapsulation efficiency. The microcapsules were monodispersed (PDI {approx} 0.30) and electrostatically stable, exhibiting a Zeta potential of approximately +36 mV. These microcapsules remained stable over a prolonged storage period of 21 days under refrigerated conditions while retaining antimicrobial activity against Bacillus cereus. Encapsulation efficiency reached approximately 65%, confirming effective retention of Nisin within the polymer matrix. Overall, the findings demonstrate that chitosan-alginate ionic gelation is a non-denaturing and effective encapsulation strategy for extending the functional stability of Nisin. These microcapsules show strong potential as natural antimicrobial delivery systems for food and beverage applications, particularly in acidic food matrices, with implications for improved food safety and shelf-life extension.

Gabapentin (GBP) and pregabalin (PGB) are widely used gabapentinoids. Previously, we have demonstrated, for the first time, that GBP and PGB modulate the nociceptive response to noxious heat in C. elegans at an optimal concentration. In the current study, we use C. elegans and paired thermal nociception assays with direct internal drug concentration measurements to characterize the pharmacokinetic (PK)/pharmacodynamic (PD) relationship of both compounds. Neither drug altered baseline mobility or quadrant preference, confirming that behavioral effects reflected genuine antinociceptive action. Both GBP and PGB produced dose- and time-dependent reductions in thermal avoidance, with 500 uM exposures generating a biphasic, V-shaped time course in which suppression of thermal sensitivity deepened before partially reversing. This partial reversal occurred later with PGB than with GBP. Internal concentrations confirmed dose-dependent absorption and retention for both drugs, yet at 500 uM, internal drug levels remained elevated through 360 min even as behavioral avoidance recovered, indicating that the recovery limb reflects active counter-regulation rather than passive clearance, consistent with previously reported transcriptional and proteomic signatures. Exposure-response profiles were notably flat, suggesting a saturable pharmacodynamic ceiling. Molecular modeling revealed conserved electronic pharmacophores supporting shared alpha-2-delta engagement, alongside shape-descriptor differences that may contribute to divergent absorption kinetics. These findings position C. elegans as a valuable model for dissecting gabapentinoid PK/PD relationships. Beyond mechanistic insight, these findings support the continued investigation of C. elegans as a screening platform whose validation could help address the 3R (Replacement, Reduction, Refinement) principles guiding animal research.

Biopreservatives including nisin and its derivatives are becoming more desirable in the food processing industry because of the growing demand for naturally preserved and minimally processed foods free from artificial preservatives. However, ensuring microbiological safety while meeting these consumer preferences remains a major challenge. This has necessitated the continuous investigation of potential new antimicrobial agents produced by naturally occurring microorganisms. Hence, this study explored the synthesis, characterisation, and optimisation of a bacteriocinogenic lactic acid bacterium and its antimicrobial product, possibly novel bacteriocin (Nisin 2A) from Lactococcus lactis isolated from commercial brined cheese. The isolation was achieved by screening for wild-type bacteriocin-producing lactic acid bacteria from dairy products using MRS media. Screening was performed using antagonism assays, yielding five producer organisms. Of these, the isolate whose metabolites exhibited the most potent antimicrobial activity was identified as Lactococcus lactis, which synthesised an active antimicrobial peptide designated as Nisin 2A, with a molecular mass of approximately 3.3 kDa as determined by UHPLC-MS and SDS-PAGE. Production of Nisin 2A was scaled up through fed-batch fermentation of Lactococcus lactis in modified MRS broth following process optimisation using a Plackett-Burman experimental design and purified by ammonium sulphate precipitation and solid-phase extraction (SPE). Furthermore, the antimicrobial potential of the bacteriocin was evaluated by the agar well diffusion assay and quantified using the tube dilution method. The purified peptide demonstrated broad-spectrum antimicrobial activity, particularly against the test Gram-positive bacteria Bacillus cereus and retained its bioactivity across a wide pH range (3-9) and high thermal conditions (up to 100 {degrees}C). Furthermore, it had high sensitivity to proteolytic enzymes (Proteinase K and Trypsin). Notably, the peptide was thermostable and retained up to 90% of its initial activity after thermal treatment and maintained consistent inhibitory performance after extended storage. These findings highlight the potential application of Nisin 2A as a natural biopreservative in food systems.