Biology subjects

Mani, K.

Publications and source records attributed to Mani, K..

7 recordsLinked to original sources

bioRxiv2026

A splenic reservoir of pro-angiogenic neutrophils supports blood flow recovery after peripheral tissue ischemia

Background: Neutrophils accumulate at sites of ischemic injury, where a distinct subset characterized by CD49d+CXCR4hiVEGFR1hi expression promotes angiogenesis and contributes to blood flow recovery. This study investigated the function, origin, and recruitment mechanisms of these pro-angiogenic neutrophils (PANs) in a murine model of hindlimb ischemia and explored whether a corresponding population responds to acute ischemia in humans. Methods: Using spectral flow cytometry and immunohistochemistry, PANs and classical neutrophils were characterized in ischemic gastrocnemius muscle following hindlimb ischemia in mice. Blood flow recovery was assessed by laser speckle flowmetry. To determine the origin and mobilization mechanisms of PANs, splenectomy, chemical sympathectomy with 6-hydroxydopamine (6-OHDA), and surgical splenic denervation were performed. Translational studies examined blood samples collected during elective abdominal aortic aneurysm repair to assess PAN mobilization following acute lower limb ischemia induced by aortic cross-clamping. Results: PANs rapidly accumulated in ischemic muscle through a CD49d-dependent mechanism, and blockade of CD49d impaired blood flow recovery. During homeostasis, PANs were maintained within a splenic reservoir and were rapidly released into circulation following ischemia. Splenectomy and disruption of splenic sympathetic signaling significantly reduced PAN recruitment to ischemic tissue and impaired functional recovery. Mobilization was driven by ischemia-induced sympathetic activation, which decreased CXCL12 levels in the splenic red pulp, disrupting CXCR4-mediated PAN retention. In humans, a phenotypically similar PAN population was identified in peripheral blood, which increased rapidly following lower limb ischemia during aortic cross-clamping. The speed of this response is consistent with release from an extramedullary reservoir, although its anatomical source remains unknown. Conclusion: These findings identify the spleen as a reservoir of pro-angiogenic neutrophils in mice and reveal a neuroimmune mechanism regulating their mobilization and recruitment after ischemic injury. The rapid appearance of PAN in human circulation after acute ischemia suggests that comparable extramedullary neutrophil reservoirs may also exist in humans.

immunology↗

bioRxiv2026

Impaired proteostasis is an early feature of the diabetic heart in humans and mice

Diabetes and obesity increase cardiac lipid levels leading to cardiomyopathy and heart failure. We hypothesized that intermittent fasting would reduce cardiac lipid levels. Surprisingly, intermittent fasting increased myocardial triglyceride content, but rescued mortality and attenuated cardiomyopathy in mice overexpressing cardiomyocyte acyl-CoA synthetase 1 (MHC-ACSL1). Lipid overload caused cardiomyocyte accumulation of polyubiquitinated protein aggregates containing desmin, a scaffolding intermediate filament protein, which intermittent fasting prevented. Furthermore, intermittent fasting reversed elevated myocardial C16:0 ceramide content, and knockdown of ceramide synthase CerS5 and CerS6 reduced palmitate-induced protein aggregation, highlighting a role for C16:0 ceramides in this pathology. Conversely, impairing aggrephagy with cardiomyocyte-specific p62 ablation induced heart failure in mice fed a high-fat diet, with paradoxically reduced cardiac lipid content. Crucially, non-failing diabetic human hearts also exhibited protein aggregate pathology. Taken together, these results demonstrate that impaired proteostasis characterizes cardiomyopathy from cardiac lipid overload and identify a promising new therapeutic target for this condition.

molecular biology↗

bioRxiv2024

Mitophagy Facilitates Cytosolic Proteostasis to Preserve Cardiac Function

BackgroundProtein quality control (PQC) is critical for maintaining sarcomere structure and function in cardiac myocytes, and mutations in PQC pathway proteins, such as CRYAB (arginine to glycine at position 120, R120G) and BAG3 (proline to lysine at position 209, P209L) induce protein aggregate pathology with cardiomyopathy in humans. Novel observations in yeast and mammalian cells demonstrate mitochondrial uptake of cytosolic protein aggregates. We hypothesized that mitochondrial uptake of cytosolic protein aggregates and their removal by mitophagy, a lysosomal degradative pathway essential for myocardial homeostasis, facilitates cytosolic protein quality control in cardiac myocytes. MethodsMice with inducible cardiac myocyte specific ablation of TRAF2 (TRAF2icKO), which impairs mitophagy, were assessed for protein aggregates with biochemical fractionation and super-resolution imaging in comparison to floxed controls. Induced pluripotent stem cell (iPSC)-derived cardiac myocytes with R120G knock-in to the CRYAB locus were assessed for localization of the CRYAB protein. Transgenic mice expressing R120G CRYAB protein (R120G-TG) were subjected to both TRAF2 gain-of-function (with AAV9-cardiac Troponin T promoter-driven TRAF2 transduction) and TRAF2 loss-of-function (with tamoxifen-inducible ablation of one Traf2 allele) in cardiac myocytes to determine the effect of mitophagy modulation on cardiac structure, function, and protein aggregate pathology. ResultsCardiomyocyte-specific ablation of TRAF2 results accumulation of mitochondrial and cytosolic protein aggregates and DESMIN mis-localization to protein aggregates. Isolated mitochondria take up cardiomyopathy-associated aggregate-prone cytosolic chaperone proteins, namely arginine to glycine (R120G) CRYAB mutant and proline to lysine (P209L) BAG3 mutant. R120G-CRYAB mutant protein increasingly localizes to mitochondria in human and mouse cardiomyocytes. R120G-TG mice demonstrate upregulation of TRAF2 in the mitochondrial fraction with increased mitophagy as compared with wild type. Adult-onset inducible haplo-insufficiency of TRAF2 resulted in accelerated mortality, impaired left ventricular systolic function and increased protein aggregates in R120G-TG mice as compared with controls. Conversely, AAV9-mediated TRAF2 transduction in R120G-TG mice reduced mortality and attenuated left ventricular systolic dysfunction, with reduced protein aggregates and restoration of normal localization of DESMIN, a cytosolic scaffolding protein chaperoned by CRYAB, as compared with control AAV9-GFP group. ConclusionsTRAF2-mediated mitophagy in cardiac myocytes facilitates removal of cytosolic protein aggregates and can be stimulated to ameliorate proteotoxic cardiomyopathy.

cell biology↗

bioRxiv2024

Phosphorylation of CRYAB Induces a Condensatopathy to Worsen Post-Myocardial Infarction Left Ventricular Remodeling.

Protein aggregates are emerging therapeutic targets in rare monogenic causes of cardiomyopathy and amyloid heart disease, but their role in more prevalent heart failure syndromes remains mechanistically unexamined. We observed mis-localization of desmin and sarcomeric proteins to aggregates in human myocardium with ischemic cardiomyopathy and in mouse hearts with post-myocardial infarction ventricular remodeling, mimicking findings of autosomal-dominant cardiomyopathy induced by R120G mutation in the cognate chaperone protein, CRYAB. In both syndromes, we demonstrate increased partitioning of CRYAB phosphorylated on serine-59 to NP40-insoluble aggregate-rich biochemical fraction. While CRYAB undergoes phase separation to form condensates, the phospho-mimetic mutation of serine-59 to aspartate (S59D) in CRYAB mimics R120G-CRYAB mutants with reduced condensate fluidity, formation of protein aggregates and increased cell death. Conversely, changing serine to alanine (phosphorylation-deficient mutation) at position 59 (S59A) restored condensate fluidity, and reduced both R120G-CRYAB aggregates and cell death. In mice, S59D CRYAB knock-in was sufficient to induce desmin mis-localization and myocardial protein aggregates, while S59A CRYAB knock-in rescued left ventricular systolic dysfunction post-myocardial infarction and preserved desmin localization with reduced myocardial protein aggregates. 25-Hydroxycholesterol attenuated CRYAB serine-59 phosphorylation and rescued post-myocardial infarction adverse remodeling. Thus, targeting CRYAB phosphorylation-induced condensatopathy is an attractive strategy to counter ischemic cardiomyopathy.

cell biology↗

bioRxiv2023

Glycoprotein VI is Critical for the Detection and Progression of Abdominal Aortic Aneurysms

A common feature in patients with abdominal aortic aneurysms (AAA) is the formation of a nonocclusive intraluminal thrombus (ILT) in regions of aortic dilation. Platelets are known to maintain hemostasis and propagate thrombosis through several redundant activation mechanisms, yet the role of platelet activation in the pathogenesis of AAA associated ILT is still poorly understood. Thus, we sought to investigate how platelet activation impacts the pathogenesis of AAA. Using RNA-sequencing, we identify that the platelet-associated transcripts are significantly enriched in the ILT compared to the adjacent aneurysm wall and healthy control aortas. We found that the platelet specific receptor glycoprotein VI (GPVI) is among the top enriched genes in AAA ILT and is increased on the platelet surface of AAA patients. Examination of a specific indicator of platelet activity, soluble GPVI (sGPVI), in two independent AAA patient cohorts is highly predictive of a AAA diagnosis and associates more strongly with aneurysm growth rate when compared to D-dimer in humans. Finally, intervention with the anti-GPVI antibody (J) in mice with established aneurysms blunted the progression of AAA in two independent mouse models. In conclusion, we show that levels of sGPVI in humans can predict a diagnosis of AAA and AAA growth rate, which may be critical in the identification of high-risk patients. We also identify GPVI as a novel platelet-specific AAA therapeutic target, with minimal risk of adverse bleeding complications, where none currently exist. KEY POINTSO_LISoluble glycoprotein VI, which is a platelet-derived blood biomarker, predicts a diagnosis of AAA, with high sensitivity and specificity in distinguishing patients with fast from slow-growing AAA. C_LIO_LIBlockade of glycoprotein VI in mice with established aneurysms reduces AAA progression and mortality, indicating therapeutic potential. C_LI

pathology↗

bioRxiv2022

Identification of chemo-sensory genes from antennae of female banana pseudostem weevil, Odoiporous longicollis by transcriptomics approach

In the present study, the female O. longicollis antennal transcriptome was constructed by Illumina Hiseq 2500 sequencing, with the aim of discovering olfaction-related genes. Totally 12, 411 unigenes were identified from the transcriptome assembly and the putative genes functions were annotated using gene ontology tools. We identified 46 putative chemosensory unigenes likely essential for insect olfaction including 19 odorant binding proteins, 3 Niemann-Pick type C (NPC) protein, 6 odorant receptors, 15 ionotropic receptors, and 3 sensory neuron membrane proteins. The key function of these chemosensory genes in the antennae are discussed. Phylogenetic analysis of NPC revealed that the identified proteins had a close relationship with Coleopterans than other insects. This is the first ever report on identification of olfactory genes from O. longicollis which may provide new leads for control of this major pest.

molecular biology↗

bioRxiv2021

TRAF2, an innate immune sensor, reciprocally regulates mitophagy and inflammation to maintain cardiac myocyte homeostasis.

Mitochondrial damage triggers cell death signaling with catastrophic consequences in long-lived and irreplaceable cells, such as cardiac myocytes. Sensing of leaked mitochondrial DNA upon mitochondrial damage is also a potent trigger of inflammation. Whether the innate immune response pathways monitor mitochondrial damage in mitochondria-rich cardiac myocytes to prevent inflammation and cell death, remains unknown. TRAF2, an adaptor protein downstream of innate immune receptors, localizes to the mitochondria in the unstressed heart, with increased mitochondrial targeting in cardiomyopathic human hearts and after cardiac ischemia-reperfusion injury in mice. Inducible cardiomyocyte-specific deletion of TRAF2 in young adult mice impairs mitophagy with rapid decline in mitochondrial quality, upregulates TLR9 expression in cardiac myocytes, and results in inflammation and cell death manifesting as a fulminant cardiomyopathy. Preventing TLR9-mediated mitochondrial DNA sensing and resultant inflammation provides a short-term reprieve from cardiomyopathy, but persistence of damaged mitochondria results in long-term recrudescence. Restoration of wild-type TRAF2, but not the E3 ubiquitin ligase deficient mutant, improves mitochondrial quality and rescues cardiomyopathy to restore homeostasis. Thus, the innate immune response acts via TRAF2 as the first line of defense against mitochondrial damage by orchestrating homeostatic mitophagy to dampen myocardial inflammation and prevent cell death.

cell biology↗