Biology subjects

Sharma, N. S.

Publications and source records attributed to Sharma, N. S..

7 recordsLinked to original sources

bioRxiv2024

Leukemia inhibitory factor (LIF) receptor amplifies pathogenic activation of fibroblasts in lung fibrosis

Fibrosis drives end-organ damage in many diseases. However, clinical trials targeting individual upstream activators of fibroblasts, such as TGF{beta}, have largely failed. Here, we target the leukemia inhibitory factor receptor (LIFR) as a "master amplifier" of multiple upstream activators of lung fibroblasts. In idiopathic pulmonary fibrosis (IPF), the most common fibrotic lung disease, we found that lung myofibroblasts had high LIF expression. Further, TGF{beta}1, one of the key drivers of fibrosis, upregulated LIF expression in IPF fibroblasts. In vitro anti-LIFR antibody blocking on human IPF lung fibroblasts reduced induction of profibrotic genes downstream of TGF{beta}1, IL-4 and IL-13. Further, siRNA silencing of LIFR in IPF precision cut lung slices reduced expression of fibrotic proteins. Together, we find that LIFR drives an autocrine positive feedback loop that amplifies and sustains pathogenic activation of IPF fibroblasts downstream of multiple external stimuli, implicating LIFR as a therapeutic target in fibrosis. Significance StatementFibroblasts have a central role in the pathogenesis of fibrotic diseases. However, due to in part to multiple profibrotic stimuli, targeting a single activator of fibroblasts, like TGF{beta}, has not yielded successful clinical treatments. We hypothesized that a more effective therapeutic strategy is identifying a downstream "master amplifier" of a range of upstream profibrotic stimuli. This study identifies the leukemia inhibitory factor receptor (LIFR) on fibrotic lung fibroblasts amplifies multiple profibrotic stimuli, such as IL-13 and TGF{beta}. Blocking LIFR reduced fibrosis in ex vivo lung tissue from patients with idiopathic pulmonary fibrosis (IPF). LIFR, acting as a master amplifier downstream of fibroblast activation, offers an alternative therapeutic strategy for fibrotic diseases.

cell biology↗

bioRxiv2022

Dynamic model of bovine brucellosis to investigate control strategies in endemic settings

Brucellosis imposes substantial impacts on livestock production and public health worldwide. A stochastic, age-structured model incorporating herd demographics was developed describing within- and between-herd transmission of Brucella abortus in dairy cattle herds. The model was fitted to data from a cross-sectional study conducted in Punjab State of India and used to evaluate the effectiveness of control strategies under consideration. Based on model results, stakeholder acceptance and constraints regarding vaccine supply, vaccination of replacement calves in large farms should be prioritised. Test and removal applied at early stages of the control programme where seroprevalence is high would not constitute an effective use of resources. Critically, under current model assumptions, significant numbers of animals removed (culled or not used for breeding) in this strategy would be removed based on false positive results. To achieve sustained reductions in brucellosis, policymakers must commit to maintaining vaccination in the long term, which may eventually reduce frequency of infection in the livestock reservoir to a low enough level for elimination to be a realistic objective. This exercise provided important insights into the control of brucellosis in India, which has the largest cattle population globally, and a general framework for evaluating control strategies in endemic settings.

microbiology↗

bioRxiv2021

Single cell transcriptome mapping identifies a local innate B cell population driving local antibody production and chronic rejection after lung transplantation

Bronchiolitis obliterans syndrome (BOS) due to chronic rejection is the main reason for poor outcomes after lung transplantation (LTx). We and others have recently identified B cells as major contributors to BOS after LTx. The extent of B cell heterogeneity, however, as well as those B cell populations that determine chronic rejection of the lung, remain entirely unclear. Here, we provide a map of cell population heterogeneity and their gene expression patterns during chronic rejection after orthotopic LTx in mice. Out of a total of 14 major comprehensive cell clusters, corresponding to 11 known major cell subpopulations, Mzb1-expressing plasma cells (PCs) were the most prominently increased cell population in lungs with BOS. Scgb1a1-expressing bronchial epithelial cells were depleted, while Cd14-expressing monocytes and Pdgfra-expressing fibroblasts were enriched in BOS grafts. These findings were validated in two different cohorts of human BOS after LTx. MZB1-IgG-double positive PCs infiltrated the airways of patients with BOS, while they were absent from healthy lungs. IgG, but not IgA, IgD, IgE or IgM, were significantly increased in bronchoalveolar lavage from BOS patients, compared with LTx patients who did not develop BOS. Pseudotime and trajectory analysis revealed that a Bhlhe41, Cxcr3, Itgb1-triple positive-B cell subset, also expressing classical markers of the innate-like B-1 B cell population, served as the progenitor pool for Mzb1+ PCs. This progenitor B cell subset accounted for the increase in IgG2c expression and production in BOS lung grafts. Importantly, Aicda-/- mice, which lack all isotypes of Ig (except IgM) were protected from the onset of BOS after LTx. In summary, we provide a detailed atlas of cell population changes of chronic rejection after LTx. We have identified IgG-positive PCs and their progenitors - an innate B cell subpopulation characterized by a specific subset of markers - as the major source of local antibody production and a major contributor to both mouse and human BOS after LTx.

physiology↗

bioRxiv2020

Hypoxia driven oncometabolite L-2HG maintains "stemness"-differentiation balance and facilitates immune suppression in pancreatic cancer

2-hydroxyglutarate (2-HG) has gained considerable importance in glioma and blood cancers that have mutations in the IDH1/2 gene. In the current study we show for the first time that pancreatic tumors produce 2HG in the absence of IDH1/2 mutation. Our study shows that hypoxic pancreatic tumors that have activated lactate dehydrogenase (LDH) activity, produce the L-isoform of 2HG. Metabolic mass spectrometric analysis along with chiral derivatization showed that pancreatic cancer cells as well as stromal cells secrete the L-isomeric form of 2-hydroxyglutarate (L-2HG) when exposed to hypoxic environment. Serum analysis of human pancreatic cancer patients also showed similar accumulation of L-2HG. Our results showed that this abnormally accumulated L-2HG regulates self-renewal by increasing expression of genes associated with stemness (Sox-2, CD133) and by decreasing expression of differentiation genes (Pdx-1, HB9, NKX6.1). Further analysis showed that secreted L-2HG mediates cross talk with immune T-cells and hampers their proliferation and migration thereby suppressing the anti-tumor immunity. In vivo targeting of LDH enzyme with inhibitor (GSK2837808A) showed decrease in L-2HG as well as subsequent tumor regression and sensitization to immune-checkpoint therapy. Present study shows for the first time that hypoxia mediated accumulation of L-2HG drives self-renewal in pancreatic cancer by shifting critical balance of gene expression towards stemness and promotes immune suppression by impairing T cell activation in this disease. Additionally, it indicates that targeting LDH can sensitize pancreatic tumors to anti-PD1 therapy by decreasing L-2HG and reverting their immune evasive function.

cancer biology↗

bioRxiv2020

Stroma secreted IL6 selects for stem-like population and alters pancreatic tumor microenvironment by reprogramming metabolic pathways

Pancreatic adenocarcinoma is a devastating disease with an abysmal survival rate of 9%. A robust fibro-inflammatory and desmoplastic stroma, characteristic of pancreatic cancer, contributes to the challenges in developing viable therapeutic strategies in this disease. Apart from constricting blood vessels and preventing efficient drug delivery to the tumor, the stroma also contributes to aggressive biology of the cancer along with its immune-evasive microenvironment. In this study, we show that in pancreatic tumors, the developing stroma increases tumor initiation frequency in pancreatic cancer cells in vivo by enriching for CD133+ aggressive "stem-like" cells. Additionally, the stromal fibroblasts secrete IL6 as the major cytokine, increases glycolytic flux in the pancreatic tumor cells and increases lactate efflux in the microenvironment via activation of the STAT signaling pathway. We also show that the secreted lactate favors activation of M2 macrophages in the tumor microenvironment, which excludes CD8+ T-cells in the tumor. Our data additionally confirms that treatment of pancreatic tumors with anti-IL6 antibody results in tumor regression as well as decreased CD133+ population within the tumor. Furthermore, inhibiting the lactate efflux in the microenvironment reduces M2 macrophages, and makes pancreatic tumors more responsive to anti-PD1 therapy. This suggests that stromal IL6 driven metabolic reprogramming plays a significant role in the development of an immune evasive microenvironment. In conclusion, our study shows that targeting the metabolic pathways affected by stromal IL6 can make pancreatic tumors amenable to checkpoint inhibitor therapy.

cancer biology↗

bioRxiv2019

Long non-coding RNA GAS5 acts as proliferation brakes in CD133+ cells responsible for tumor recurrence

Presence of quiescent, therapy evasive population often described as cancer stem cells (CSC) or tumor initiating cells (TIC) is often attributed to extreme metastasis and tumor recurrence. This population is typically enriched in a tumor as a result of microenvironment or chemotherapy induced stress. The TIC population adapts to this stress by turning on cell cycle arrest programs that is a \"fail-safe\" mechanism to prevent expansion of malignant cells to prevent further injury. Upon removal of the \"stress\" conditions, these cells restart their cell cycle and regain their proliferative nature thereby resulting in tumor relapse. Growth Arrest Specific 5 (GAS5) is a long-noncoding RNA that plays a vital role in this process. In pancreatic cancer, CD133+ population is a typical representation of the TIC population that is responsible for tumor relapse. In this study, we show for the first time that emergence of CD133+ population coincides with upregulation of GAS5, that reprograms the cell cycle to slow proliferation by inhibiting GR mediated cell cycle control. The CD133+ population further routed metabolites like glucose to shunt pathways like pentose phosphate pathway, that were predominantly biosynthetic in spite of being quiescent in nature but did not use it immediately for nucleic acid synthesis. Upon inhibiting GAS5, these cells were released from their growth arrest and restarted the nucleic acid synthesis and proliferation. Our study thus showed that GAS5 acts as a molecular switch for regulating quiescence and growth arrest in CD133+ population, that is responsible for aggressive biology of pancreatic tumors.

cancer biology↗

bioRxiv2019

Targeting tumor intrinsic metabolic node in pancreatic cancer causes tumor regression, remodels extracellular matrix and sensitizes to anti-PD1 therapy.

Pancreatic ductal adenocarcinoma (PDAC) is considered to be a highly immunosuppressive and heterogenous neoplasm. Despite improved knowledge regarding the genetic background of the tumor and better understanding of the tumor microenvironment, immune checkpoint inhibitor therapy (targeting CTLA-4, PD-1, PD-L1) has not been very successful against PDAC.\n\nThe robust desmoplastic stroma, along with an extensive extracellular matrix (ECM) that is rich in hyaluronan, plays an integral role in this immune evasion. Hexosamine biosynthesis pathway (HBP), a shunt pathway of glycolysis, is a metabolic node in cancer cells that can promote survival pathways on one hand and influence the hyaluronan synthesis in the ECM on the other. The rate-limiting enzyme of the pathway, glutamine-fructose amidotransferase (GFAT1), uses glutamine and fructose 6-phosphate to eventually synthesize UDP-GlcNAc.\n\nIn the current manuscript, we target this glutamine-utilizing enzyme by a small molecule glutamine analog (6-diazo-5-oxo-L-norleucine or DON). Our results show that DON decreases the self-renewal potential and metastatic ability of tumor cell. Further, treatment with DON results in a decrease in hyaluronan and collagen in the tumor microenvironment, leading to an extensive remodeling of the ECM. this in turn, increases CD8+ cytotoxic T-cells infiltration, and makes the tumors tumors more amenable and sensitive to anti-PD1 therapy.

cancer biology↗