Biology subjects

Dhar, D.

Publications and source records attributed to Dhar, D..

9 recordsLinked to original sources

bioRxiv2026

Targeting Microbial Bile Salt Hydrolase Reprograms Bile Acid Metabolism and Ameliorates Metabolic Dysfunction-Associated Steatohepatitis in Mice

Microbial bile salt hydrolase (BSH) plays a central role in shaping bile acid composition and gut-liver metabolic signaling, yet its therapeutic potential in metabolic dysfunction-associated steatohepatitis (MASH) remains incompletely defined. Here, we evaluated the efficacy of the non-absorbable BSH inhibitor GR-7 in a diet induced mouse model of steatohepatitis using early and late intervention strategies with different dosing regimens. GR-7 reduced food intake and exerted stage- and dose-dependent therapeutic effects, with early intervention robustly suppressing hepatic fibrosis even at low dose, whereas late-stage administration of high-dose GR-7 markedly reduced hepatic steatosis and inflammation, as evidenced by decreased liver weight, hepatic triglyceride and cholesterol levels, and plasma ALT. Although late intervention did not result in statistically significant histological reversal of fibrosis, a trend toward improvement was observed, together with suppression of fibrogenic gene expression, suggesting that prolonged treatment may further enhance antifibrotic efficacy. Mechanistically, GR-7 effectively inhibited microbial BSH activity in vivo, leading to reduced cecal unconjugated primary and secondary bile acids--including deoxycholic acid and lithocholic acid, which was associated with improved gut barrier integrity and reduced hepatic inflammation. In parallel, BSH inhibition reprogrammed hepatic bile acid metabolism toward activation of the alternative CYP27A1-mediated synthesis pathway, accompanied by reduced food intake, thereby contributing to improved hepatic lipid accumulation. Furthermore, late-stage high-dose treatment selectively remodeled the hepatic immune landscape rather than fully restoring homeostasis, highlighting immune recalibration as a key component of therapeutic response. Together, these findings identify microbial BSH inhibition as a promising microbiome-targeted therapeutic strategy for MASH. HighlightsO_LIThe non-absorbable BSH inhibitor GR-7 improves steatosis, inflammation, and fibrosis in of Western diet-induced steatohepatitis model in mice in a dose-dependent manner. C_LIO_LIGR-7 reduces food intake and body weight gain. C_LIO_LIGR-7 reduces cytotoxic secondary bile acids, including DCA and LCA. C_LIO_LIGR-7 reprograms hepatic bile acid metabolism and immune responses. C_LI

pharmacology and toxicology↗

bioRxiv2026

A Translational Model of MASLD-Associated HFpEF Defines Mitochondrial Dysfunction and Cardiac Plasticity During Disease Progression and Regression

Metabolic dysfunction-associated steatotic liver disease (MASLD) and its progressive form, metabolic dysfunction-associated steatohepatitis (MASH), are strongly linked to cardiac dysfunction, particularly, heart failure with preserved ejection fraction (HFpEF), yet the mechanisms underlying this association remain unclear because robust integrative preclinical models are lacking and the liver and heart are rarely studied as a coordinated system. Here we show that Alms1-/- (Foz/Foz) mice fed a Western diet develop MASH with advanced liver fibrosis accompanied by a HFpEF-like phenotype characterized by left ventricular hypertrophy, impaired cardiomyocyte contractility, reduced {beta}-adrenergic reserve, elevated BNP, and increased mortality despite ejection fraction >50%. Liver fibrosis emerged as a parameter strongly associated with the cardiac dysfunction. Remarkably, dietary reversal improved hepatic architecture, normalized cardiac function, and improved survival, revealing marked plasticity of the liver-heart axis. Analyses of left ventricular (LV) remodeling revealed mitochondrial dysfunction, altered substrate utilization, and extracellular matrix remodeling in the LV, with consistent concordance to human HFpEF transcriptomic signatures. Ultrastructural studies confirmed mitochondrial injury and sarcomeric disorganization, linking metabolic failure to impaired cardiomyocyte performance. Together, these findings identify mitochondrial dysfunction as an important feature of MASLD-associated HFpEF-like cardiac dysfunction and establish the Foz/Foz model as a powerful platform for investigating pathophysiological pathways linking metabolic liver disease to cardiac dysfunction and for testing mechanism-based therapeutic strategies. STRUCTURED ABSTRACTO_ST_ABSBackgroundC_ST_ABSMetabolic dysfunction associated steatotic liver disease (MASLD) and its advanced form, MASH, are closely linked to cardiac dysfunction, particularly heart failure with preserved ejection fraction (HFpEF). However, the mechanisms underlying MASLD-associated HFpEF and its reversibility remain poorly understood, largely due to the lack of robust preclinical models. Here, we established a translational model of MASLD-associated cardiac dysfunction that recapitulates the key features of human HFpEF. We applied functional and transcriptomic analyses of the left ventricle (LV) to define the pathways associated with cardiac dysfunction and its reversibility. MethodsAlms1-/- (Foz/Foz) mice and wild-type littermates were fed normal chow (NC) or Western diet (WD) for up to 36 weeks (wk). Reversibility was modeled by switching WD-fed Foz/Foz mice at 12wk back to NC for 12wk. Cardiac assessment included echocardiography, invasive hemodynamics with dobutamine stimulation, histopathology, electron microscopy and isolated cardiomyocyte contractility. LV transcriptomes were profiled by bulk RNA sequencing and analyzed by differential expression and pathway enrichment. ResultsFoz/Foz mice on WD for 24wk developed metabolic syndrome and MASH with advanced liver fibrosis. Cardiac phenotyping showed LV hypertrophy, impaired cardiomyocyte contractility, reduced {beta}-adrenergic reserve, elevated plasma BNP, and increased mortality while the ejection fraction was preserved (>50%), consistent with HFpEF. The progression of cardiac dysfunction was closely associated with liver fibrosis that developed during MASH. Switching WD-fed Foz/Foz mice at 12wk to normal chow diet reversed hepatic fibrosis, restored LV function, and reduced mortality, demonstrating plasticity of the liver-heart axis. LV transcriptomic analysis revealed that cardiac impairment in these mice was associated with mitochondrial dysfunction, altered substrate utilization, extracellular matrix remodeling, and metabolic stress; pathways that are similarly dysregulated in human HFpEF. Cardiac electron microscopy revealed swollen mitochondria with disrupted cristae, which improved following dietary intervention. ConclusionsMitochondrial dysfunction and fibroinflammatory remodeling are prominent features of MASLD-associated cardiac dysfunction. Reversal of hepatic and cardiac phenotypes with dietary intervention, together with elucidation of underlying pathways, establish the Foz/Foz model as a useful translational platform for studying liver-heart axis in MASLD. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=120 SRC="FIGDIR/small/708088v2_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@60bd2aorg.highwire.dtl.DTLVardef@1234a09org.highwire.dtl.DTLVardef@1d1c5aborg.highwire.dtl.DTLVardef@1086089_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2024

Scrutinized lipid utilization disrupts Amphotericin-B responsiveness in clinical isolates of Leishmania donovani

The management of Leishmania donovani (LD), responsible for fatal visceral leishmaniasis (VL), faces increasing challenges due to rising drug-unresponsiveness, leading to increasing treatment failures. While hypolipidemia characterizes VL, LD, a cholesterol auxotroph, relies on host lipid scavenging for its intracellular survival. The aggressive pathology, in terms of increased organ parasite load, observed in hosts infected with antimony-unresponsive-LD (LD-R) as compared to their sensitive counterparts (LD-S), highlights LD-Rs heightened reliance on host lipids. Here we report that LD-R-infection promotes fluid-phase endocytosis in the host, selectively accumulating neutral lipids while excluding oxidized-LDL. LD-R enhances the fusion of endocytosed LDL-vesicles with its phagolysosomal membrane and inhibits cholesterol mobilization from these vesicles by suppressing NPC-1. This provides LD-R amastigotes with excess lipids, supporting their rapid proliferation and membrane synthesis. This excess LDL-influx leads to an eventual accumulation of neutral lipid droplets around LD-R amastigotes, thereby increasing their unresponsiveness towards Amphotericin-B, a second-line amphiphilic antileishmanial. Notably, VL patients showing relapse with Amphotericin-B treatment exhibited significantly lower serum LDL and cholesterol than cured cases. Treatment with Aspirin, a lipid droplet blocker, reduced lipid droplets around LD-R amastigotes, restoring Amphotericin-B responsiveness.

microbiology↗

bioRxiv2024

Genetic variation in the activity of a TREM2-p53 signaling axis determines oxygen-inducedlung injury

Bronchopulmonary dysplasia (BPD), a chronic lung disease, is the most common major complication of preterm birth. Supplemental oxygen administration, while lifesaving in the neonatal period, remains a key determinant of BPD pathophysiology. Exposure of the immature lung to increased levels of oxygen elicits an inflammatory response resulting in abnormal lung development. However, not every premature infant is equally sensitive to develop BPD. Using genetically diverse mouse strains, we show that the innate immune response activated in the lungs of mice sensitive to hyperoxia that develop BPD-like lung injury differs from mice resilient to disease. Specifically, we identified a selective upregulation of triggering receptor expressed on myeloid cells 2 (TREM2) on lung macrophages and monocytes in the hyperoxia-sensitive C57BL/6J mouse strain. We show that loss of function of TREM2 signaling in myeloid cells resulted in a dramatically improved phenotype after neonatal hyperoxia exposure characterized by a dampened immune response, preserved alveolar structure, and preserved cell proliferative potential supporting normal lung development. At the molecular level, inhibition of TREM2 signaling dampened the magnitude of p53 activation and resulted in cell cycle arrest instead of apoptosis. These findings show that TREM2 is a critical regulator of the pathogenic innate immune response to hyperoxia and highlight its importance as a potential therapeutic target for mitigating injury in the hyperoxia-exposed developing lung.

immunology↗

bioRxiv2024

Estrogen receptor alpha (ERα) driven trans-regulation of mitotic checkpoint complex (MCC) components affects the clinical outcome of breast cancer

Hormone receptors (HR), namely estrogen receptor (ER) and progesterone receptor (PR), are prevalent in most malignant tumors. Although previous literature provided clues for ER in regulating mitosis and ploidy status in breast cancer (BC) cells, reports on the mitotic regulators being the targets of HR are sparse. To delve deeper into ERs impact on mitotic execution, our study focuses on examining its transcriptional activity on the core mitotic checkpoint complex (MCC) components, which are involved in ploidy maintenance. The expression of the core MCC components (Bub3, Mad2, and BubR1) was analyzed by quantitative-PCR and immunohistochemistry in breast tumors and adjacent normal tissues from the cancer genome atlas-breast invasive carcinoma collection (TCGA BRCA) dataset and in a prospective cohort of Eastern Indian breast cancer affected individuals. The preliminary data from these cohorts indicated an influence of ER on the two MCC components, namely Mad2 and BubR1. Subsequently, luciferase reporter assays and chromatin immunoprecipitation were performed which revealed that ER promotes transcriptional activation of MAD2 and BUB1B through direct recruitment on these promoters, showing affects in mitotic outcome. Interestingly, the ectopic introduction of ER, in an HR-ve breast cancer line, MDA-MB-231, significantly reduced the percent aneuploidy. Moreover, we found that overexpression of MAD2 and BUB1B is associated with poorer survival in HR-positive (HR+ve) patients in both cohorts. Our findings provide insights into the specific role of ER-mediated transcriptional regulation of mitosis and ploidy outcome. Targeting the deregulated MCC components thus offers translational potential for the therapeutic management of breast cancer.

cancer biology↗

bioRxiv2023

Sequences at gene segment termini inclusive of untranslated regions and partial open reading frames play a critical role in mammalianorthoreovirus S gene packaging

Mammalian orthoreovirus (MRV) is a prototypic member of the Spinareoviridae family and has ten double-stranded RNA segments. One copy of each segment must be faithfully packaged into the mature virion, and prior literature suggests that nucleotides (nts) at the terminal ends of each gene likely facilitate their packaging. However, little is known about the precise packaging sequences required or how the packaging process is coordinated. Using a novel approach, we have determined that 200 nts at each terminus, inclusive of untranslated regions (UTR) and parts of the open reading frame (ORF), are sufficient for packaging each S gene segment (S1-S4) individually and together into replicating virus. Further, we mapped the minimal sequences required for packaging the S1 gene segment to 25 5' nts and 50 3' nts. The S1 UTRs alone are not sufficient, but are necessary for packaging, as mutations of the 5' or 3' UTRs led to a complete loss of virus recovery. Using a second novel assay, we determined that 50 5'nts and 50 3' nts of S1 are sufficient to package a non-viral gene segment into MRV. The 5' and 3' termini of the S1 gene are predicted to form a panhandle structure and specific mutations within the predicted stem of the panhandle region led to a significant decrease in viral recovery. Additionally, mutation of six nts that are conserved in the three major serotypes of MRV and are predicted to form an unpaired loop in the S1 3'UTR, led to a complete loss of viral recovery. Overall, our data provide strong experimental proof that MRV packaging signals lie at the terminal ends of the S gene segments and offer support that the sequence requirements for efficient packaging of the S1 segment include a predicted panhandle structure and specific sequences within an unpaired loop in the 3' UTR.

microbiology↗

bioRxiv2020

Understanding the adaptive evolution of mitochondrial genomes in intertidal chitons

Mitochondria are the centre of energy metabolism in eukaryotic cells and its genes are thus key to the evolution of molecular mechanisms that metabolize cellular energy. Intertidal zone is one of the most stressful environments with extreme shifts in temperature, salinity, pH and oxygen concentrations. Marine molluscs, particularly chitons belong to the ecologically dominant organisms in this extreme environment, symbolizing an ideal model to understand mitochondrial stress adaptation. Here, we used concatenated mitochondrial genetic components separately from seven chitons of the intertidal zone to reconstruct phylogenetic relationships among these species. We performed selection analyses considering sites and branches of individual protein-coding genes to identify potentially adaptive residues and localize them in the protein structures of mt subunits. Our results exhibited significant amino acid changes in sites under diversifying selection of all the protein-coding genes, indicative of the adaptive evolution of mitochondrial genome in chitons. Furthermore, we obtained sites in the transmembrane helices lining the proton translocation channel as well as in surrounding loop regions, providing implication towards functional modification of the OXPHOS proteins essential for survival in dynamic environment of the intertidal zone.

evolutionary biology↗

bioRxiv2019

Extended insight into the preponderance of LRRs - a docking & simulation study with members of the TLR1 subfamily

The widespread structural motif of Leucine-rich repeats (LRR) constitute the extracellular part of the Toll-like receptor (TLR) family preceded by an intracellular Toll/interleukin-1 receptor (TIR) domain at the C-terminus. The benefit of using LRRs in these pattern recognition receptors (PRR) that are responsible for early detection of pathogens to elicit inflammatory/innate immune response still remains elusive. Phylogenetic analyses (Maximum Likelihood and Bayesian Inference) of nine TLR (TLR 1-9) genes from 36 mammals reconfirmed the existence of two distinct clades, one (TLR1/2/6) for recognizing bacterial cell wall derivatives and another (TLR7/8/9) for various nucleic acids. TLR3, TLR4 and TLR5 showed independent line of evolution. The distinction of the TLR1 subfamily to form heterodimers within its members and the existence of the paralogs TLR1 and TLR6 therein, was appealing enough to carry out further studies with the extracellular recognition domain. Dimerizing and ligand binding residues from the crystal structures of TLR1 and TLR6 were interchanged to generate chimeric proteins. The dimer forming ability of these variants with their common partner, TLR2, were checked before running MD simulations. The chimeras were compared with wild type dimers to find no significant alterations in the overall structure. Finally, interchanged ligands were docked to the variants to ratify reversal of the binding function. Intriguingly, sequence change in substantial numbers, 16 in TLR1 and 18 in TLR6, preserves the native scaffold offered by LRRs. This exercise thus depicts how the LRR motif has been advantageous to be selected as an evolutionarily conserved motif for essential cellular processes.

bioinformatics↗

bioRxiv2018

Insights into the evolution of extracellular leucine rich repeats in metazoans with special reference to Toll-like receptor 4

The importance of the widely spread leucine-rich repeat (LRR) motif has been studied considering TLRs, the LRR-containing protein involved in animal immune response. The protein connects intracellular signalling with a chain of molecular interaction through the presence of LRRs in the ectodomain and TIR in the endodomain. Domain analyses with human TLR1-9 reported ectodomain with tandem repeats, transmembrane domain and TIR domain. The repeat number varied across members of TLRs and remains characteristic to a particular member. Analysis of gene structure revealed absence of codon interruption with TLR3 and TLR4 as exceptions. Extensive study with TLR4 from metazoans confirmed the presence of 23 LRRs in tandem. Distinct clade formation using coding and amino acid sequence of individual repeats illustrated independent evolution. Although ectodomain and endodomain exhibited differential selection pressure, however, within the ectodomain, the individual repeats displayed positive, negative and neutral selection pressure depending on their structural and functional significance.

bioinformatics↗