Biology subjects

Kumar, A.

Publications and source records attributed to Kumar, A..

At least 127 records · Page 7Linked to original sources

bioRxiv2026

High-fat diet rewires gut host-microbiota relationship to derive worse outcomes following Clostridioides difficile infection

AbstractClostridioides difficile is a leading cause of hospital-acquired enteric infections, with outcomes ranging from mild diarrhea to life-threatening pseudomembranous colitis and death. Dietary modulations can influence the course of antibiotic-induced C. difficile infection (CDI), and high-fat diets are associated with increased mortality. Here, we profiled host innate immune cells, cecal microbial composition, and the host transcriptome of normal diet (ND) and high-fat diet (HFD)-fed C57BL/6 male and female mice following experimental CDI during the acute and recovery phases. HFD-fed male mice exhibited delayed disease onset but increased mortality following CDI. During acute infection, HFD-fed males showed increased monocyte infiltration and expansion of CD103CD11b- and CD103-CD11b dendritic cell subsets; transcriptomic modules were enriched for antigen presentation and signatures consistent with T cell activation, coincident with enrichment of Escherichia and Lactococcus. In contrast, during recovery, HFD-fed males and females displayed sustained neutrophil and monocyte infiltration, depletion of eosinophils (prominent in males), tissue-resident Tim4/CD206 macrophage subsets and ILC3s, increased expression of Tlr4 and endothelial activation markers, downregulation of metabolic pathways, and failure to restore cecal microbial diversity. Collectively, these data indicate that high-fat feeding disrupts resolution programs after CDI and promotes progression to severe disease, with the most pronounced susceptibility in males.

microbiology↗

bioRxiv2025

DNA Nanocage-Mediated Aspirin Delivery Mitigates Excitotoxicity and Promotes Neuroprotection in Ischemic Stroke-Induced Zebrafish

Oxidative stress, apoptosis, excitotoxicity, and compromised neuronal function are the hallmarks of ischaemic stroke, a major cause of neurological impairment. Because of their controlled-release properties and biocompatibility, DNA tetrahedron nanostructures (TD) offer a viable platform for targeted drug delivery. In this work, we used a zebrafish larval model of ischaemic stroke to assess the neuroprotective potential of TD-mediated aspirin administration and investigated the TD:Aspirin complexation modes using molecular dynamics (MD) simulations. In addition to morphological abnormalities, elevated reactive oxygen species (ROS), thrombus formation, intracellular calcium accumulation, and dysregulated expression of neuroprotective and apoptotic genes, stroke induction resulted in significant behavioural deficits, including decreased locomotor activity, increased latency, and erratic swimming. Treatment with TD:Aspirin, especially at a 1:100 ratio, markedly improved locomotor behaviour, restored production of BDNF, GDNF, MBP, -tubulin, GRIN2B, SLC8A, NOS1, and caspases, normalised heart rate, lowered ROS generation and apoptosis, and decreased thrombus and calcium deposition. TD:Aspirin showed better efficacy than free Aspirin and TD-only groups, perhaps as a result of improved stability, bioavailability, and sustained release. These results demonstrate the potential of drug delivery via DNA nanocages as a novel therapeutic approach for ischaemic stroke, offering neuroprotection, functional recovery, and neuronal homeostasis restoration. TOC GraphicDNA Nanocage-Mediated Aspirin Delivery Mitigates Excitotoxicity and Promotes Neuroprotection in Ischemic Stroke-Induced Zebrafish O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/696221v1_ufig1.gif" ALT="Figure 1"> View larger version (56K): org.highwire.dtl.DTLVardef@18dd327org.highwire.dtl.DTLVardef@21b8b4org.highwire.dtl.DTLVardef@1e53283org.highwire.dtl.DTLVardef@5771e6_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2025

Identification of Novel Open Reading Frames on the Rabies Virus Antigenome Strand and Assessing Their Expression

Rabies disease can be caused by several lyssaviruses, which are a group of bullet-shaped, enveloped viruses with single-stranded, negative-sense RNA as their genome. Lyssaviruses are known to produce a full complement of genomic RNA (cRNA or antigenome) during their lifecycle. The rabies virus (RABV) is the prototype of the genus and has a genome of 12 kilobases. The RABV genome is known to encode five proteins from the genomic strand. In this study, we examined the coding potential of RABV and identified 17 novel ORFs (nORFs): one on the genomic strand and sixteen on the antigenomic strand. Synteny analysis revealed that several of these nORFs were conserved across the RABV clades. Additionally, five of the nORFs possessed Kozak sequences, and trRosetta predicted well-folded three-dimensional domains in these nORFs. Using LC-MS data of rabies-infected canine brain samples, we identified high-confidence peptides corresponding to the two nORF-coded proteins, nORF9 and nORF12. Furthermore, the structural and sequence similarity analyses indicated that these domains share homology with proteins involved in signalling and transcription.

microbiology↗

bioRxiv2025

Deciphering the functional association of novel variants of BMP7 in isolated congenital heart disease by integrating in vitro and in silico approaches

Bone morphogenetic protein7 (BMP7), an important member of the TGF{beta} superfamily, is known to be vital for embryonic growth and development. To decipher the role of BMP7 in congenital cardiac malformations, genetic screening of 285 CHD cases along with 400 healthy controls individuals was performed by Sanger sequencing method. Five missense variants were identified in 5 unrelated CHD probands with distinct phenotypes. Three novel missense (p.D85V, p.R175W, and p.A283T) variants in the pro-peptide region and two other variants (p.M315I and p.N321S) in the mature domain were documented. In vitro functional analysis revealed WT as well as all five mutant BMP7 proteins localized within ER compartment, which was confirmed by ER-Tracker and SERCA2 staining. Western blot analysis demonstrated enhanced phosphorylation of SMAD1/5 associated with these variants. Furthermore, transactivation assays showed increased activity of BMP-responsive promoters-Id1-luc, Id3-luc, Tlx2-luc, and p(SBE)4-luc with a synergistic effect observed upon AKL2 co-expression. Additionally, overexpression of downstream targets, namely Bmp2, Bmp7, Nkx2.5, Gata4, Irx4, Smad1, Smad4, and Smad5, alongside downregulation of left-right patterning genes (Nodal and Pitx2) and the BMP antagonist Chordin, was observed. Likewise, EdU staining revealed increased cellular proliferation associated with all these variants. Moreover, modeling of secondary and tertiary structures also suggested that these variants might induce conformational changes in BMP7, potentially strengthening its binding affinity with the receptor and thereby amplifying SMAD signaling. Collectively, in vitro and in silico analyses suggest that these BMP7 variants exhibit gain-of-function (GoF) activity, disrupting normal BMP signaling pathways and thereby contributing to the development of CHD.

molecular biology↗

bioRxiv2025

Nucleic acid strand length governs mitochondrial reprogramming and mtROS-associated antiviral responses following TLR3 engagement

Mitochondria are important rheostats that regulate innate sensing processes by producing energy, biosynthetic precursors, and bioactive molecules that affect cellular signaling. When viral nucleic acids engage endosomal and cytosolic pattern recognition receptors (PRR), antiviral immune responses are supported by mitochondrial remodeling but the role of mitochondria in fine tuning ligand-specific responses remains incompletely understood. For example, endosomal TLR3 can detect various lengths of dsRNA (0.4-8 kb) ranging from viral segmented genomes or endogenous nucleic acids have been shown to induce distinct cytokine profiles. However, it is unclear if these differences are associated with differential mitochondrial remodeling. Here, we report that TLR3 engagement with both high (HMW; 1.5-8 kb) or low molecular weight (LMW; 0.2-1 kb) Polyinosinic:polycytidylic acid (Poly(I:C)) is associated with reduced but sustained oxidative phosphorylation (OXPHOS) activity and increased mitochondrial reactive oxygen species (mtROS) production/accumulation to support antiviral responses in bone marrow-derived macrophages (BMDM). They differed in the amount of mtROS production, their spare respiratory capacity (SRC) and their mitochondrial membrane potential (MMP). Interestingly, while uncoupling protein 2 (UCP2) was found required for antiviral cytokine production, it did not contribute to ligand specific responses. Dynamic modulation of complex I of the electron transport chain (ETC), however resulted in the differential accumulation of mtROS (HMW>LMW). Further, selectively targeting the mtROS derived from Complex I leads to augmented type I IFN production. Overall, these findings highlight that targeting specific sources of mtROS without affecting electron flow may be a potential avenue for specific augmentation of antiviral responses during viral infections.

immunology↗

bioRxiv2025

Complete Genome Sequencing and Molecular Characterization of Indigenous Enterovirus A71 Genogroups D and G of India

Enterovirus A71 (EV-A71), a neurotropic member of the Picornaviridae family, comprises seven recognized genogroups (A-G). Despite prior identification of D and G genogroups in India, comprehensive full-genome characterization of these indigenous lineages remains unreported. We performed next-generation sequencing (NGS) and molecular phylogenetic analyses on two Indian isolates: R13223-IND-02 (genogroup D) and V11-2209-01 (genogroup G). Phylogenetic reconstruction revealed robust clustering of these strains within distinct clades, divergent from globally prevalent genogroups B and C, considering bootstrap support [≥]99%. Both D and G genogroups appear geographically restricted to India, while genogroup D persists as an endemic lineage. Comparative genomic analyses demonstrated extensive nucleotide divergence, including numerous non-synonymous substitutions across both structural (VP1-VP4) and non-structural (2A-3D) coding regions. These findings highlight the evolutionary independence and sustained circulation of D and G genogroups in India, suggesting a unique regional evolutionary trajectory. The findings hold significant global relevance, offering valuable insights for molecular surveillance, advancing pathogenesis research, and supporting the development of genogroup-specific vaccine strategies tailored to diverse epidemiological landscapes.

genomics↗

bioRxiv2025

Mosquito Ferritin: A Haem-Binding Iron Store Required for Egg Development and Targetable for Malaria Control

Iron metabolism is essential for both mosquito reproductive fitness and Plasmodium development within the vector, yet this axis remains insufficiently explored as a potential target for malaria control. Ferritin, the major iron-storage protein and a central regulator of iron homeostasis, has not previously been biochemically or functionally characterized in any hematophagous insect. Our computational and phylogenetic analyses reveal that mosquito ferritin represents a unique case, combining conserved iron-binding motifs with distinctive haem-coordinating residues that confer an exceptionally high haem-binding affinity exceeding that of bacterioferritin. In addition, through a screen of multiple iron chelators in Anopheles larvae, we identified potent candidates with potential utility for vector control. Together, these findings establish mosquito ferritin as an evolutionarily distinct and physiologically essential protein, and they highlight iron homeostasis as a promising dual-target axis for next-generation vector control strategies.

biochemistry↗

bioRxiv2025

Proteomic Profiling of Rabid Canine Brain Samples Reveals Dysregulation of Immune Signalling and Neuronal Pathways

Rabies is one of the most feared diseases and has been known to humans for approximately 4,000 years. It is caused by several lyssaviruses and leads to an encephalitis, which is 100% fatal after symptom onset. The most common cause of rabies is the rabies virus (RABV), which leads to around 59,000 human deaths globally every year. The infection leads to drastic changes in host behaviour, but the underlying mechanistic details remain unclear. Although interactions between the viral glycoprotein and host nicotinic acetylcholine receptors have been proposed as drivers of rabies-associated neurological dysfunction, clinical proteomic studies in naturally infected canines have been partially explored. In this study, we conducted a global proteomics analysis of RABV-infected and non-infected canine brain samples in India to unravel the changes in protein expression. Using liquid chromatography combined with mass spectrometry, we identified various host proteins and pathways dysregulated in the infected state. Approximately 700 proteins exhibited differential expression, with around 250 proteins involved in various pathways being significantly upregulated and approximately 500 proteins being significantly downregulated in the infected condition. Network clustering of the dysregulated proteins revealed functional modules, including clathrin-mediated endocytosis, actin cytoskeletal regulation, and the TCA cycle, indicating widespread alterations in cellular trafficking, energy metabolism, and structural integrity. Complementary pathway enrichment through PANTHER identified processes linked to axon guidance, integrin signalling, chemokine and cytokine-mediated inflammation, and cytoskeletal regulation, underscoring the profound impact of rabies virus infection on neuronal connectivity and host immune responses.

microbiology↗

bioRxiv2025

Lipid Droplet Remodeling Safeguards Redox Balance through the DGAT1-PANK2-NRF2 Axis in Mammalian Oocytes and Drives Age-Associated Decline

How lipid droplets (LDs) buffer metabolic stress and redox imbalance in aging oocytes remains poorly understood. Here, we identify de novo LD remodeling as a metabolic capacitor that couples lipid storage to mitochondrial fitness and oxidative resilience in mammalian oocytes. Live imaging revealed pronounced LD dynamics, with LD number peaking at metaphase I and declining by metaphase II, while LD area shifted inversely. Despite stable triacylglyceride and free fatty acid pools, {beta}-oxidation increased sharply, indicating elevated lipid turnover during meiotic progression. Spatial mapping and fatty-acid tracing demonstrated that newly synthesized lipids are actively incorporated into LDs, which arise primarily from the endoplasmic reticulum and engage with lysosomes and mitochondria. Acute inhibition of DGAT1, the rate-limiting enzyme of LD biogenesis, disrupted meiotic maturation and triggered oxidative stress, mitochondrial aggregation, and ultrastructural damage. Proteomic profiling revealed robust PANK2 upregulation and suppression of NRF2-linked antioxidant pathways. Mechanistic analyses showed that {beta}-oxidation blockade, PANK2 inhibition, antioxidant supplementation, or NRF2 activation each partially rescued DGAT1-dependent defects, and genetic validation in NRF2-null oocytes confirmed pathway dependence. Notably, aged oocytes exhibited reduced de novo LD biogenesis and impaired DGAT1-ER organization despite increased LD accumulation, resulting in smaller, metabolically inert droplets and a mismatch between lipid formation and utilization. Inhibiting PANK2 alleviated oxidative stress in aged oocytes, further implicating the DGAT1-PANK2-NRF2 axis in redox control and oocyte quality. Together, these findings establish LD biogenesis as a core metabolic capacitor safeguarding mitochondrial and organelle integrity during meiosis and reveal dysfunction of the DGAT1-PANK2-NRF2 axis as a mechanistic driver of reproductive aging.

cell biology↗

bioRxiv2025

Molecular basis for cellular compartmentalization by an ancient membrane fission mechanism

The emergence of cell compartmentalization depends on membrane fission to create the endomembrane compartments. In eukaryotes, membrane fission is commonly executed by ESCRT-III, a protein complex conserved in all domains of life. However, whether membrane fission was an ancestral ESCRT-III activity predating eukaryogenesis remains unknown. Here we show that ESCRT-IIIA from Asgard Heimdallarchaeota, the closest archaeal relatives of eukaryotes, performs membrane fission through an N-terminal amphipathic helix, which we term Hofund. In eukaryotes, Hofund is fragmented across ESCRT-IIIA paralogs, and disrupting these regions causes severe fission defect in yeast. Remarkably, Heimdallarchaeota Hofund restores fission when fused to defective eukaryotic paralogs. These findings suggest that ESCRT-III-mediated fission arose before eukaryogenesis and later diversified to support the regulatory complexity of eukaryotic compartmentalization.

cell biology↗

bioRxiv2025

Targeting the IRE1α/XBP1 Signaling Axis Suppresses Rhabdomyosarcoma Growth and Promotes Myogenic Differentiation

Rhabdomyosarcoma (RMS) is a pediatric soft-tissue sarcoma arising from mesenchymal progenitors with skeletal muscle features. The unfolded protein response (UPR) maintains proteostasis during endoplasmic reticulum stress, with the IRE1-XBP1 axis representing a key signaling branch. Here, we demonstrate that components of this pathway are significantly upregulated in RMS cell lines and primary tumors. Genetic or pharmacological inhibition of IRE1 or spliced XBP1 (sXBP1) suppresses cell proliferation, promotes terminal myogenic differentiation, and enhances vincristine-induced cytotoxicity in RMS cells. Silencing of sXBP1 further reduces the cancer stem-like cell population and impairs migration and invasion. Mechanistically, IRE1-XBP1 signaling promotes RMS progression through sXBP1-dependent upregulation of BMPR1A and subsequent activation of BMP-SMAD1 signaling. Consistently, inducible knockdown of sXBP1 or pharmacological inhibition of IRE1 endonuclease activity significantly attenuates xenograft RMS growth. Collectively, these findings identify the IRE1-XBP1 axis as a critical regulator of RMS growth, differentiation, and chemoresistance, and support its therapeutic targeting in RMS.

cancer biology↗

bioRxiv2025

Inhibitory Motifs Quench Synchrony Induced by Excitatory Motifs in Biological Neuronal Networks

AO_SCPLOWBSTRACTC_SCPLOWThe connectivity in biological neuronal networks is known to deviate significantly from the random network (Erd[o]s-Renyi) model. Specifically, di-synaptic motifs like reciprocal, convergent, divergent, and chain are found to be either over-represented or under-represented in certain brain regions. Over-representation of such motifs among excitatory neurons is known to induce synchrony. However, cortical activity is typically asynchronous. Thus, it remains unclear how synchrony induced by excitatory motifs may be reduced to physiological levels. To address this question, we systematically vary the prevalence of these four motifs in an Excitatory-Inhibitory (EI) network. We found that over-representation of chain and convergent motifs in the excitatory population led to increased firing rates and greater synchrony. However, this excess synchrony was quenched when we introduced the same type of motifs among inhibitory neurons. Because of the overabundance of motifs, some inhibitory neurons received fewer recurrent inhibitory inputs. Such weakly coupled neurons were primarily driven by uncorrelated external inputs, and therefore, these neurons exerted stronger inhibition on excitatory neurons and reduced both synchrony and firing rates. Thus, we also provide a new mechanism by which synchrony can be controlled in excitatory-inhibitory networks. We predict that the same kind of di-synaptic motifs should be present in both excitatory and inhibitory neurons. Significance StatementComputational models predict that over-representation of di-synaptic motifs among excitatory neurons (as is experimentally observed) should lead to highly synchronous network activity. However, cortical activity is largely asynchronous. To reconcile this mismatch between structural connectivity and network activity we propose a novel mechanism to quench the synchrony. We show that motifs in the inhibitory population can quench the synchrony produced by excitatory motifs. We found that inhibitory neurons that received fewer inhibitory inputs are crucial for quenching the synchrony. Thus, we predict the existence of di-synaptic motifs among inhibitory neurons and argue that modulation of inhibitory neurons with less recurrent connectivity (e.g. SST+ neurons) have a more prominent role in controlling network activity state.

neuroscience↗

bioRxiv2025

Dystonia-associated Torsins sustain CLCC1 function to promote membrane fusion of the nuclear envelope for NPC biogenesis

DYT1 early-onset dystonia is a severe, incurable disorder of the central nervous system caused by mutations in the gene encoding Torsin1A (Tor1A, DYT1). Torsins are ER-resident AAA+-ATPases implicated in lipid metabolism, nuclear pore complex (NPC) biogenesis, and lipoprotein secretion, yet their molecular function that underlies the disease pathology has remained incompletely understood. Here, we have utilized Drosophila melanogaster and human somatic cells as experimental models to shed light on their mode-of-action. Fly germ cells lacking dTorsin are arrested in development and display defects in the final steps of NPC biogenesis due to a failure in fusion of the inner and outer nuclear membranes. Using proximity labelling of Torsin1A in human cells, we identify the conserved membrane protein chloride channel CLIC-like protein 1 (CLCC1) as a novel Torsin binding partner. Absence of human CLCC1 or its Drosophila homolog dClcc1 phenocopied the membrane fusion defects at NPC assembly sites observed upon Torsin deletion. Furthermore, CLCC1 is enriched at arrested fusion sites, suggesting it to be a candidate for the elusive NE membrane fusogen. Importantly, CLCC1/dClcc1 overexpression is sufficient to rescue NPC biogenesis and developmental defects associated with Torsin-loss-of-function. Taken together, our data suggest that Torsin-regulated CLCC1 activity drives membrane fusion during NPC biogenesis and reveal that modulating CLCC1 expression is a promising therapeutic prospect for DYT1 dystonia.

cell biology↗

bioRxiv2025

TAK1 is a key regulator of oncogenic signaling and differentiation blockade in rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is a malignant soft tissue sarcoma with a skeletal muscle phenotype, accounting for approximately 50% of all pediatric soft tissue sarcomas and 8% of all childhood cancers. Although RMS cells express myogenic regulatory factors, they fail to undergo terminal differentiation into mature muscle cells. Transforming growth factor {beta}-activated kinase 1 (TAK1) is a major signaling protein that activates multiple intracellular pathways in response to growth factors, cytokines, and microbial products. Emerging evidence suggests that TAK1 is also an important regulator of self-renewal, proliferation, and differentiation of muscle progenitor cells. However, the role and mechanisms of action of TAK1 in RMS remain completely unknown. In this study, we demonstrate that TAK1 expression and activity are markedly elevated in a panel of RMS cell lines and in patient tumor specimens. Reverse phase protein array (RPPA) analyses revealed that TAK1 regulates the expression and activity of many molecules involved in cell cycle control, cell proliferation, and oncogenic signaling. Genetic knockdown or pharmacological inhibition of TAK1 suppresses RMS cell proliferation, migration, and invasiveness, while also promoting terminal myogenic differentiation. TAK1 inhibits differentiation in RMS, at least in part, through up-regulating YAP1 signaling. Our results also demonstrate that inducible knockdown of TAK1 in human RMS xenografts retards tumor growth and enhances myogenic differentiation in vivo. Collectively, these findings uncover a previously unrecognized role for TAK1 in RMS growth and differentiation, and suggest that TAK1 can be a potential therapeutic target for the treatment of RMS.

cancer biology↗

bioRxiv2025

Transcranial direct current stimulation of the supplementary motor area modulates behavioral and peripheral electrophysiological measures of motor preparation.

Converging evidence has shown that the Supplementary Motor Area (SMA) is involved in the preparation of movements. Such preparatory activity has been traditionally thought to lead to shorter reaction times by allowing the motor network to settle into states favourable to motor execution without directly engaging the peripheral musculature, limiting such preparatory states to central neural processes only. We revisited this question by recording motor unit related activity using high-density surface EMG grid electrodes, from the Anterior Deltoid muscle, a proximal muscle, during a delayed reach task. We observed that anodal stimulation of the supplementary motor area (SMA) enhances motor preparation by shortening reaction times, while simultaneously and preferentially recruiting smaller amplitude motor units. Additionally, we found that the SMA stimulation also produced a subsequent increase in movement velocities due to the increase activation of larger amplitude motor units. Taken together, we suggest that motor preparatory states involve an active interaction between central and peripheral processes with direct descending SMA outputs to the spinal cord providing a link between cortical preparation and muscle readiness, resulting in decreased reaction times. In addition, the increased gain of such central to peripheral interactions also increases the subsequent gain of during the execution phase via modulating larger amplitude motor unit activation, resulting in increased response vigour.

neuroscience↗

bioRxiv2025

Gram-positive bacterial cell wall components inhibit herpes simplex virus infection.

The role of the mucosal microbiome in viral infections remains unclear. Genital herpes, caused by herpes simplex virus 1 and 2 (HSV-1 and HSV-2), is among the most prevalent sexually transmitted infections worldwide. Despite evidence linking vaginal Lactobacillus to protection against sexually transmitted viruses, the specific microbial components and mechanisms that mediate this defense are not well understood. Here, we show that multiple cell wall components from diverse gram-positive bacteria, including lactobacilli, inhibit HSV-1 and HSV-2 infection in cells and in a mouse model of genital herpes infection. Peptidoglycan (PG) and lipoteichoic acid (LTA), both major components of the gram-positive bacterial cell wall, significantly reduced HSV infectivity in vitro and improved survival and disease outcomes in mice. We further showed that Lactobacillus crispatus surface layer proteins SlpA and SlpB bind HSV-1 and inhibit infection. Antiviral effects of cell wall components were dose-dependent, relied on intact PG structure, and, in the case of PG and LTA, were independent of TLR2-mediated host signaling. Collectively, our findings identify a species-independent antiviral function for gram-positive bacterial cell wall components against HSV and suggest that the composition of the mucosal microbiome may play an underappreciated role in suppressing mucosal herpes infection in humans.

microbiology↗

bioRxiv2025

Protocol for the Synthesis of Green Fluorescence Carbon Quantum Dots and Biological Application

Carbon quantum dots (CQDs) are materials that are made up of particles that are only a few n anometers wide. They have no dimensions and can change their fluorescence qualities. They are also verybiocompatible and have a lot of potential to change the chemistry of their surface. Their eco-friendly synthesis from precursors, like citric acid (CA) and ascorbic acid (AA), provides a sustainable approach to highly fluorescent nanomaterials with promising applications in bioimaging, drug delivery, and other biomedical fields. Green-emitting carbon quantum dots (GCQDs) were synthesized via a simple reflux approach using citric acid and ascorbic acid as biomolecular precursors in a solvent solution of ethanol-water (1:2). The obtained GCQDs solution was purified using a dialysis process. Besides this, pH maintenance, lyophilization, and further submission for detailed physicochemical evaluation and characterization are done. The spectroscopic analysis, including UV-visible spectroscopy, fluorescence spectroscopy, and FTIR, confirmed the presence of surface functional groups and strong fluorescence properties and quantum yield calculations of the synthesized GCQDs. Microscopic and structural analyses using XRD, AFM, and TEM revealed the nanoscale, predominantly spherical morphology of the synthesized GCQDs. In addition, in vitro biological evaluations such as MTT assay and cellular uptake analysis were undertaken to evaluate cytocompatibility and intracellular distribution. We study the endocytosis pathway of these GCQDs, with size variations ranging from 3 to 5 nm, in mouse tissue-derived primary cells, tissues, and zebrafish embryos. GCQDs were internalized into mouse kidney and liver primary cells through a clathrin-mediated pathway. The findings confirmed that the produced GCQDs exhibit good water solubility, favorable biocompatibility, and significant potential as candidates for biomedical imaging applications.

bioengineering↗

bioRxiv2025

Acute activation of Gq-signaling in islet macrophages inhibits β-cell insulin secretion through AMPK-sphingolipid axis

Obesity-associated inflammation disrupts pancreatic {beta}-cell function, but the immune-derived signals that directly regulate insulin secretion remain incompletely defined. Here, we identify myeloid Gq signaling as a critical immunometabolic node that links macrophage activation to {beta}-cell dysfunction. For the first time, we employed a chemogenetic approach (DREADDs) to selectively and temporally activate Gq-coupled GPCR signaling in myeloid cells to examine its effect on islet function. Our findings reveal that acute Gq activation in islet-resident macrophages impaired glucose-stimulated insulin secretion, uncovering a previously unrecognized immune-endocrine axis. Conversely, myeloid-specific Gq deletion improves systemic glucose homeostasis, underscoring the physiological relevance of this pathway. Mechanistic analysis revealed that Gq activation in macrophages stimulates AMPK signaling and drives the secretion of sphingolipids. These lipids suppress insulin secretion and introduce a new mechanism for immune-islet communication, extending beyond traditional cytokine-based models. We further identify the lipid-sensing receptor GPR18 as an upstream activator of the Gq-AMPK pathway in macrophages. GPR18 stimulation recapitulated the Gq-dependent sphingolipid secretion and {beta}-cell inhibitory phenotype, which was abolished in myeloid Gq-deficient mice. Collectively, these findings establish a mechanistic framework whereby macrophage Gq signaling integrates lipid sensing and metabolic stress to modulate {beta}-cell function. This work reveals a previously unrecognized macrophage-{beta}-cell communication axis with therapeutic potential for restoring insulin secretion in metabolic diseases such as obesity and type 2 diabetes. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=109 SRC="FIGDIR/small/680858v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@790c4dorg.highwire.dtl.DTLVardef@116cceborg.highwire.dtl.DTLVardef@1e76631org.highwire.dtl.DTLVardef@e65770_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗