Biology subjects

Murugan, S.

Publications and source records attributed to Murugan, S..

3 recordsLinked to original sources

bioRxiv2025

Proteasomal Dysfunction results in ER stress, Endo MT, oxidative stress, and apoptotic cell death resulting in Fuchs Corneal Endothelial Dystrophy like features in mice

Fuchs Endothelial Corneal Dystrophy (FECD) is the irreversible degeneration of the corneal endothelium. The only treatment is corneal transplantation. To develop therapies for FECD, identifying the cellular causes for the onset and progression of the disease is crucial. While cell culture studies associate elevated oxidative stress, endoplasmic reticulum stress, endothelial-to-mesenchymal transition, and apoptosis with FECD, the causes behind the disease onset remain elusive. Guttae or Descemets membrane deposits are the earliest phenotype associated with FECD and are composed of unfolded proteins. Therefore, we asked if aberrant protein clearance pathways could be responsible for disease pathogenesis. We discovered a dysfunctional ubiquitin-proteasome pathway in a FECD mouse model and end-stage FECD patient samples. Inhibiting the ubiquitin-proteasome pathway in primary corneal endothelial cells resulted in the cellular dysfunctions associated with FECD. Finally, injecting healthy wild-type mice with proteasomal inhibitors resulted in all the major phenotypes associated with FECD, including corneal edema, guttae, and corneal endothelial cell loss. Therefore, this study strongly connects proteasomal dysfunction in FECD onset and progression.

cell biology↗

bioRxiv2024

Released Bacterial ATP Shapes Local and Systemic Inflammation during Abdominal Sepsis

Sepsis causes millions of deaths per year worldwide and is a current global health priority declared by the WHO. Sepsis-related deaths are a result of dysregulated inflammatory immune responses indicating the need to develop strategies to target inflammation. An important mediator of inflammation is extracellular adenosine triphosphate (ATP) that is secreted by inflamed host cells and tissues, and also by bacteria in a strain-specific and growth phase-dependent manner. Here, we investigated the mechanisms by which bacteria release ATP. Using genetic mutant strains of Escherichia coli (E. coli), we demonstrate that ATP release is dependent on ATP synthase within the inner bacterial membrane. In addition, impaired integrity of the outer bacterial membrane and bacterial death notably contribute to ATP release. In a mouse model of abdominal sepsis, local effects of bacterial ATP were analysed using a transformed E. coli bearing an arabinose-inducible periplasmic apyrase hydrolyzing ATP to be released. Abrogating bacterial ATP release shows that bacterial ATP suppresses local immune responses, resulting in reduced neutrophil counts and impaired survival. In addition, bacterial ATP has systemic effects via its transport in outer membrane vesicles (OMV). ATP-loaded OMV are quickly distributed throughout the body and upregulated expression of genes activating degranulation in neutrophils, potentially contributing to the exacerbation of sepsis severity. This study reveals mechanisms of bacterial ATP release and its local and systemic roles in sepsis pathogenesis.

microbiology↗

bioRxiv2023

Characterization of a novel mouse model for Fuchs Endothelial Corneal Dystrophy

PurposeFuchs Endothelial Corneal Dystrophy (FECD) is a progressive blinding disorder prevalent in 4% of Americans over 40. Corneal transplantation is the standard treatment. Animal models with partial FECD features exist, but a model encompassing all the major disease characteristics is desirable to improve the understanding of the pathogenesis and to identify signaling pathways involved in the disease onset and progression. Such an animal model can be helpful to develop intervention strategies. Here, we developed a mouse model that recapitulates all the features of FECD. MethodLoss of function mutations in Slc4a11 and a knock-in mutation in Col8a2 (Q455K) are implicated in FECD. Mice with Slc4a11 and Col8a2 mutations in C57BL/6J background were crossed to generate double mutant mice at F2 generation. At five weeks of age, a subset of the animals were fed tamoxifen-enriched chow or standard chow for two weeks, followed by standard chow. Corneal thickness, endothelial cell density, and guttae were measured at 5 (baseline) and 16 weeks of age. Corneas collected from mice at 16 weeks were stained for tight and adherens junctions, and reactive oxygen species. A lactate assay was performed to evaluate the endothelial pump function. ResultsThe double mutant tamoxifen-fed mice showed increased corneal thickness, decreased endothelial cell density, presence of guttae, and elevated stromal lactate levels. The endothelial cells showed altered morphology with disrupted adherens junctions and elevated ROS. ConclusionOverall, this mouse model recapitulates all the important phenotypic features associated with FECD.

cell biology↗