Biology subjects

Shee, S.

Publications and source records attributed to Shee, S..

5 recordsLinked to original sources

bioRxiv2026

BCG vaccination mitigates tau pathology and restores cognitive function in PS19 mice.

Retrospective studies in patients with non-muscle invasive bladder cancer (NMIBC) have reported a significant reduction in Alzheimers disease (AD) incidence (12-78%) among Bacillus Calmette-Guerin (BCG) recipients versus controls. To investigate the underlying mechanisms, we evaluated BCG in the PS19 mouse model of tauopathy. We found that BCG administration reduced hippocampal phospho-tau and microgliosis while preserving neuronal markers. In vivo volumetric T2-MRI demonstrated attenuation of brain atrophy accompanied by increased glutamate-weighted CEST-MRI signals. Functionally, BCG-treated mice showed improved performance in the novel object recognition test (NORT), as well as improved body-weight maintenance and survival. Transcriptomic profiling of the hippocampus revealed near complete normalization of the PS19 disease-associated gene expression signature towards that of healthy controls. Flow cytometric profiling of brain myeloid populations demonstrated a reduction in activated resident microglia, but total microglia cells remain elevated. Moreover, an increase of the co-stimulatory marker CD80 on the recruited peripheral myeloid cells ensues following BCG treatment. Consistent with this shift in myeloid state, primary brain myeloid cells from BCG-treated mice also exhibited enhanced phagocytosis of FITC-labeled tau fibrils and increased lactate production. Together, these findings indicate that BCG induces systemic and CNS myeloid cell reprogramming that limits neuroinflammation, enhances tau clearance, and rescues cognitive and neurodegenerative phenotypes in a tauopathy model. BCG is a safe, readily available therapy that merits consideration as a preventive agent against dementia. One sentence summaryBCG therapy prevents tauopathy in PS19 mouse model.

neuroscience↗

bioRxiv2025

Loss of the PPE71-esxX-esxY-PPE38 locus drives adaptive transcriptional responses and hypervirulence of Mycobacterium tuberculosis Lineage 2

Mycobacterium tuberculosis (M.tb) is remarkable for its immense global disease burden and low mutation rate. Despite strong selective pressure, M.tb shows frequent deletions at the PPE71-38 locus, most notably in hypervirulent L2 Beijing strains. Here, we show that loss of the PPE71- 38 locus causes increased stress response gene expression and increased triglyceride levels. In addition, we demonstrate that re-introduction of PPE71 into the L2 strain HN878 suppresses the baseline elevation of these transcripts, while overexpression of PPE71 increases the localization of PE_PGRS proteins and lipoproteins to the M.tb outer mycomembrane. Mouse infection confirmed the hypervirulence of the PPE71-38 deletion strain and conversely showed that PPE71 overexpression attenuates M.tb. Our results indicate that loss of PPE71-38 is sufficient to drive an adaptive transcriptional response seen in M.tb L2 strains that likely contributes to the hypervirulence of this lineage.

microbiology↗

bioRxiv2025

Elimination of senescent cells with senolytic host-directed therapy reduces tuberculosis progression in mice

By eliciting lung necrosis, which enhances aerosol transmission, Mycobacterium tuberculosis (Mtb) sustains its long-term survival as a human pathogen. In studying the human-like necrotic granuloma lesions characteristic of Mtb-infected B6.Sst1S mice, we found that lung myeloid cells display elevated senescence markers: cell cycle arrest proteins p21 and p16, the DNA damage marker {gamma}H2A.X, senescence-associated {beta}-galactosidase activity, and senescence-associated secretory phenotype (SASP). These markers were also elevated in Mtb-infected aged wild type (WT) mice but not in young WT mice. Global transcriptomics data revealed upregulation of pro-survival (PI3K, MAPK) and anti-apoptotic pathways in Mtb-infected B6.Sst1S macrophages. As senescent cells are terminally growth-arrested yet metabolically active cells that release tissue-damaging, immunosuppressive SASP, we treated Mtb-infected mice with a cocktail of three senolytic drugs (dasatinib, quercetin, and fisetin) designed to kill senescent cells. Senolytic drug treatment prolonged survival and reduced Mtb lung counts in B6.Sst1S and aged WT mice to a greater degree than young WT mice and concomitantly reduced lung senescence markers. These findings indicate that (1) Mtb infection may induce lung myeloid cells to enter a senescent state and that these cells may promote disease progression, and (2) senolytic drugs merit consideration for human clinical trials against tuberculosis (TB). Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=134 SRC="FIGDIR/small/645957v2_ufig1.gif" ALT="Figure 1"> View larger version (65K): org.highwire.dtl.DTLVardef@1ce7eeeorg.highwire.dtl.DTLVardef@1ef55d4org.highwire.dtl.DTLVardef@1ebef03org.highwire.dtl.DTLVardef@98b61f_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIMtb lung infection results in recruitment of both restrictive and permissive myeloid cells to the nascent granuloma. C_LIO_LIMtb infection induces certain permissive myeloid cells to enter a senescent state, characterized by cell cycle arrest and they promote local immunosuppression. C_LIO_LITreatment with a Senolytic drug cocktail, which kills senescent cells, augments host resistance against Mtb proliferation, lethality and immunopathology. C_LI

microbiology↗

bioRxiv2023

Mycobacterium tuberculosis methyltransferase perturbs host epigenetic programming to promote bacterial survival

Mycobacterium tuberculosis (Mtb) has evolved several mechanisms to counter host defense arsenal for its proliferation. We show that Mtb employs multi-pronged approach to modify host epigenetic machinery for its survival upon infection. It secretes methyltransferase (MTase) Rv2067c into macrophages, trimethylating K79 of histone H3 in non-nucleosomal context. Rv2067c downregulates host MTase DOT1L, decreasing its H3K79me3 mark added nucleosomally on pro-inflammatory response genes. Consequent inhibition of caspase8 dependent apoptosis and enhancement of RIPK3 mediated necrosis results in increased pathogenesis. In parallel, Rv2067c enhances the expression of SESTRIN3, NLRC3 and TMTC1 enabling the pathogen to overcome host inflammatory and oxidative response. We provide structural basis for differential methylation of H3 by Rv2067c and DOT1L. The structure of Rv2067c and DOT1L explain how their action on H3K79 is temporally and spatially separated enabling Rv2067c to effectively intercept the host epigenetic circuit and downstream signalling.

microbiology↗

bioRxiv2022

Moxifloxacin-mediated killing of Mycobacterium tuberculosis involves respiratory downshift, reductive stress, and ROS accumulation

Moxifloxacin is central to treatment of multidrug-resistant tuberculosis. Effects of moxifloxacin on Mycobacterium tuberculosis redox state were explored to identify strategies for increasing lethality and reducing the prevalence of extensively resistant tuberculosis. A non-invasive redox biosensor and an ROS-sensitive dye revealed that moxifloxacin induces oxidative stress correlated with M. tuberculosis death. Moxifloxacin lethality was mitigated by supplementing bacterial cultures with an ROS scavenger (thiourea), an iron chelator (bipyridyl), and, after drug removal, an antioxidant enzyme (catalase). Lethality was also reduced by hypoxia and nutrient starvation. Moxifloxacin increased the expression of genes involved in the oxidative stress response, iron-sulfur cluster biogenesis, and DNA repair. Surprisingly, and in contrast with Escherichia coli studies, moxifloxacin decreased expression of genes involved in respiration, suppressed oxygen consumption, increased the NADH/NAD+ ratio, and increased the labile iron pool in M. tuberculosis. Lowering the NADH/NAD+ ratio in M. tuberculosis revealed that NADH-reductive stress facilitates an iron-mediated ROS surge and moxifloxacin lethality. Treatment with N-acetyl cysteine (NAC) accelerated respiration and ROS production, increased moxifloxacin lethality, and lowered the mutant prevention concentration. Moxifloxacin induced redox stress in M. tuberculosis inside macrophages, and co-treatment with NAC potentiated the anti-mycobacterial efficacy of moxifloxacin during nutrient starvation, inside macrophages, and in mice where NAC restricted the emergence of resistance. Thus, oxidative stress, generated in a novel way, contributes to moxifloxacin-mediated killing of M. tuberculosis. The results open a way to make fluoroquinolones more effective anti-tuberculosis agents and provide a mechanistic basis for NAC-mediated enhancement of fluoroquinolone lethality in vitro and in vivo. Author Summary A new paradigm was revealed for stress-mediated bacterial death in which moxifloxacin treatment of M. tuberculosis decreases respiration rate (respiration increases in E. coli). Although moxifloxacin-induced, ROS-mediated bacterial death was observed, it derived from elevated levels of NADH and iron, a phenomenon not seen with antibiotic-treated E. coli. Nevertheless, stimulation of respiration and ROS by N-acetyl cysteine (NAC) enhanced moxifloxacin-mediated killing of M. tuberculosis, thereby reinforcing involvement of ROS in killing. NAC stimulation of moxifloxacin-mediated killing of M. tuberculosis and restriction of the emergence of resistance in a murine model of infection emphasize the importance of lethal action against pathogens. The work, plus published benefits of NAC to TB patients, encourage studies of NAC-based enhancement of fluoroquinolones.

microbiology↗