Biology subjects

Xiang, B.

Publications and source records attributed to Xiang, B..

10 recordsLinked to original sources

bioRxiv2025

Two Small Proteins Enable N2O Reduction in Acidic Environments

Denitrifying bacteria are major contributors to nitrous oxide (N2O) emissions, which rise with global soil acidification, likely because low pH impairs maturation of the periplasmic enzyme N2O reductase (NosZ) in most bacteria. While some bacteria can reduce N2O under acidic conditions, the underlying mechanism remain unclear. Here, we isolated bacteria from acidic soils and identified strains that efficiently reduce N2O at low pH. They carry two novel proteins, NosP and NosQ, along with NosZ clade I. Functional analyses of deletion mutants demonstrated that NosP and NosQ are essential for the maturation of NosZ at low pH, but are not required at circumneutral pH. Cryo-EM analysis indicates that NosPQ forms a protective complex with NosZ, safeguarding its maturation under acidic conditions. Metagenomic analysis shows that nosPQ genes are widely distributed across diverse bacterial taxa and soil types. Our findings reveal a key molecular adaptation mechanism for N2O reduction in acidic environments and provide valuable insights for developing efficient N2O mitigation strategies.

biochemistry↗

bioRxiv2023

Early life exposure to cigarette smoke is associated with lung function changes and primes gene expression and DNA methylation changes at Cyp1a1 upon exposure later in life

Prenatal and early life exposure to cigarette smoke (CS) have repeatedly been shown to induce stable, long-term changes in DNA methylation (DNAm) in offspring. It has been hypothesized that these changes might be functionally related to the known outcomes of prenatal and early life CS exposure, which include impaired lung development, altered lung function and increased risk of asthma and wheeze. However, to date, few studies have examined DNAm changes induced by prenatal CS in tissues of the lung, and even fewer have attempted to examine the specific influences of prenatal versus early postnatal exposures. Here, we have established a mouse model of CS exposure which isolates the effects of prenatal and early postnatal CS exposures in early life. We have used this model to measure the effects of prenatal and/or postnatal CS exposures on lung function and immune cell infiltration as well as DNAm and expression of Cyp1a1, a candidate gene previously observed to demonstrate DNAm differences upon CS exposure in humans. Our study revealed that exposure to CS prenatally and in the early postnatal period cause long-lasting differences in offspring lung function, gene expression and lung Cyp1a1 DNAm, which wane over time but are reestablished upon re-exposure to CS in adulthood. This study creates a testable mouse model which can be used to investigate the effects of prenatal and early postnatal CS exposures and will contribute to the design of intervention strategies to mediate these detrimental effects.

genetics↗

bioRxiv2022

Differential Impact of Doxorubicin Dose on Cell Death and Autophagy Pathways during Acute Cardiotoxicity.

Doxorubicin (DOX) is an effective anthracycline used in chemotherapeutic regimens for a variety of haematological and solid tumors. However, its utility remains limited by its well-described, but poorly understood cardiotoxicity. Despite numerous studies describing various forms of regulated cell death and their involvement in DOX-mediated cardiotoxicity, the predominate form of cell death remains unclear. Part of this inconsistency lies in a lack of standardization of in vivo and in vitro model design. To this end, the objective of this study was to characterize acute low- and high-dose DOX exposure on cardiac structure and function in C57BL/6N mice, and evaluate regulated cell death pathways and autophagy both in vivo and in cardiomyocyte culture models. Acute low-dose DOX had little impact on cardiac structure or function; however, acute high-dose DOX elicited substantial cardiac necrosis resulting in diminished cardiac mass and volume, with a corresponding reduced cardiac output, and without impacting ejection fraction or fibrosis. Low-dose DOX consistently activated caspase-signaling with evidence of mitochondrial permeability transition. However, acute high-dose DOX had only modest impact on common necrotic signaling pathways, but instead led to an inhibition in autophagic flux. Intriguingly, when autophagy was inhibited in cultured cardiomyoblasts, DOX-induced necrosis was enhanced. Collectively, these observations implicate inhibition of autophagy flux as an important component of the acute necrotic response to DOX, but also suggest that acute high-dose DOX exposure does not recapitulate the disease phenotype observed in human cardiotoxicity.

physiology↗

bioRxiv2021

Identification of SSX2IP/Msd1 as a Wtip-binding partner by targeted proximity biotinylation

Wilms tumor-1-interacting protein (Wtip) is a LIM-domain-containing adaptor that links cell junctions with actomyosin complexes and modulates actomyosin contractility and ciliogenesis in Xenopus embryos. The Wtip C-terminus with three LIM domains binds binds Shroom3 and modulates Shroom3-induced apical constriction in ectoderm cells. We found that the N-terminal domain localizes to the basal bodies in skin multiciliated cells, but its interacting partners remain largely unknown. Using a novel targeted proximity biotinylation approach with anti-GFP antibody attached to the biotin ligase BirA in the presence of GFP-Wtip-N, we identified SSX2IP as the candidate binding protein. SSX2IP, also known as Msd1 or ADIP, is a centriolar satellite protein that functions as a targeting factor for ciliary membrane proteins. Wtip physically associated with SSX2IP and the two proteins formed mixed spherical aggregates in overexpressing cells in a dose-dependent manner, in a process that resembles phase separation. These results suggest that the interaction between SSX2IP and Wtip is relevant to their functions at the centrosome and basal bodies. The described antibody targeting of biotin ligase should be applicable to other GFP-tagged proteins.

biochemistry↗

bioRxiv2021

The Cardiolipin Transacylase Tafazzin Regulates Basal Insulin Secretion and Mitochondrial Function in Pancreatic Islets from Mice

ObjectiveTafazzin (TAZ) is a cardiolipin (CL) biosynthetic enzyme important for maintaining mitochondrial function. TAZ impacts both the species and content of CL in the inner mitochondrial membrane which are essential for normal cellular respiration. In pancreatic {beta}-cells, mitochondrial function is closely associated with insulin secretion. However, the role of TAZ and CL in the secretion of insulin from pancreatic islets remains unknown. MethodsMale 4-month-old doxycycline-inducible TAZ knock-down (TAZ KD) mice and wild-type littermate controls were utilized. Immunohistochemistry was used to assess {beta}-cell morphology in whole pancreas sections, while ex vivo insulin secretion, CL content, RNA-Seq analysis and mitochondrial oxygen consumption were measured from isolated islet preparations. ResultsEx vivo insulin secretion under non-stimulatory low-glucose concentrations was reduced [~]52% from islets isolated from TAZ KD mice. Mitochondrial oxygen consumption under low-glucose conditions was also reduced [~]58% in islets from TAZ KD animals. TAZ-deficiency in pancreatic islets was associated with significant alteration in CL molecular species and reduced oxidized CL content. In addition, RNA-Seq of isolated islets showed that TAZ KD increased expression of extracellular matrix genes which are linked to pancreatic fibrosis, activated stellate cells and impaired {beta}-cell function. ConclusionThese data indicate a novel role for TAZ in regulating normal {beta}-cell function, particularly under low-glucose conditions.

physiology↗

bioRxiv2020

Misoprostol Treatment Prevents Hypoxia-Induced Cardiac Dysfunction, Aberrant Cardiomyocyte Mitochondrial Dynamics and Permeability Transition Through Bnip3 Phosphorylation

Systemic hypoxia is a common element in most perinatal emergencies and is a known driver of Bnip3 expression in the neonatal heart. Bnip3 plays a prominent role in the evolution of necrotic cell death, disrupting ER calcium homeostasis and initiating mitochondrial permeability transition (MPT). Emerging evidence suggests a cardioprotective role for the prostaglandin E1 analogue misoprostol during periods of hypoxia, but the mechanisms for this protection are not completely understood. Using a combination of mouse and cell models, we tested if misoprostol is cardioprotective during neonatal hypoxic injury by altering Bnip3 function. Here we report that hypoxia elicits mitochondrial-fragmentation, MPT, reduced ejection fraction, and evidence of necroinflammation, which were abrogated with misoprostol treatment or Bnip3 knockout. Through molecular studies we show that misoprostol leads to PKA-dependent Bnip3 phosphorylation at threonine-181, and subsequent redistribution of Bnip3 from mitochondrial Opa1 and the ER through an interaction with 14-3-3 proteins. Taken together, our results demonstrate a role for Bnip3 phosphorylation in the regulation of cardiomyocyte contractile/metabolic dysfunction, and necroinflammation. Furthermore, we identify a potential pharmacological mechanism to prevent neonatal hypoxic injury.

cell biology↗

bioRxiv2020

Berberine alleviates adiposity and cardiac dysfunction in offspring exposed to gestational diabetes mellitus

The most robust risk factor for type 2 diabetes in childhood is prior exposure to diabetes during gestation. Currently, there are few evidence-based strategies to attenuate the of risk of metabolic syndrome in offspring exposed to gestational diabetes mellitus (GDM). Berberine (BBR) is an isoquinoline alkaloid extracted from Chinese herbs and exhibits glucose lowering properties. It has been used safely for centuries in humans. Our objective was to determine whether BBR treatment improves health outcomes in the mouse offspring of GDM dams. Dams were fed either a lean low-fat diet (Lean, LF,10% kcal fat) or a GDM-inducing high-fat/high sucrose diet (GDM, HF, 45% kcal fat) prior to breeding and throughout pregnancy. The resulting Lean and GDM-exposed offspring were randomly assigned a LF, HF or HF diet containing BBR (160 mg/kg/d) for 12 weeks. We determined that BBR treatment significantly reduced body weight ([~]20%), % body fat ([~]40%) and gonadal fat pad mass ([~]60%) compared to HF-fed GDM offspring. Furthermore, BBR treatment of HF-fed GDM offspring normalized insulin levels in the plasma and isolated pancreatic islets. Differences in food consumption did not contribute to altered body composition in BBR treated mice, as levels remained similar between experimental groups. Alternatively, BBR-treatment was associated with increased whole-body oxygen consumption (VO2), activity and heat production. Additionally, we determined that HF-fed GDM offspring developed a cardiomyopathy, characterized by increased isovolumetric contraction ([~]150%, IVCT), relaxation time ([~]70%, IVRT), elevated cardiac triglyceride ([~]120%) and reduced mitochondrial function (30%, spare capacity) compared to LF fed Lean controls. BBR treatment normalized heart function, reduced triglyceride levels and maintained mitochondrial function. Our data supports BBR as a potential pharmacotherapeutic approach to improve health outcomes in individuals exposed to GDM. Key Points SummaryO_LIGestational diabetes mellitus is a common metabolic complication of pregnancy which is increasing worldwide due to the prevalence of obesity. C_LIO_LIIt is known that individuals exposed to gestational diabetes have elevated risk of developing metabolic syndrome however there are few evidence-based strategies which provide protection. C_LIO_LIBerberine is a natural compound found in Chinese herbs which has been safely used for centuries to treat type 2 diabetes mellitus. C_LIO_LIWe determined that berberine treatment of offspring exposed to gestational diabetes attenuated weight gain, reduced insulin levels and normalized both heart and pancreatic function. C_LIO_LIOur data supports berberine as a potential pharmacotherapeutic approach to improve health outcomes in individuals exposed to gestational diabetes. C_LI

physiology↗

bioRxiv2020

Calcium ion chelation preserves platelet function during cold storage

ObjectivePlatelet transfusion is a life-saving therapy to prevent or treat bleeding in patients with thrombocytopenia or platelet dysfunction. However, for more than six decades, safe and effective strategies for platelet storage have been an impediment to widespread use of platelet transfusion. Refrigerated platelets are cleared rapidly from circulation, precluding cold storage of platelets for transfusion. Consequently, platelets are stored at room temperature (RT) with an upper limit of 5 days due to risks of bacterial contamination and loss of platelet function. This practice severely limits platelet availability for transfusion. This study is to identify the mechanism of platelet clearance after cold storage and develop a method for platelet cold storage. Approach and ResultsWe found that rapid clearance of cold-stored platelets was largely due to integrin activation and apoptosis. Deficiency of integrin {beta}3 or caspase-3 prolonged cold-stored platelets in circulation. Pre-treatment of platelets with EGTA, a cell impermeable calcium ion chelator, reversely inhibited cold storage-induced platelet activation and consequently prolonged circulation of cold-stored platelets. Moreover, transfusion of EGTA-treated, cold-stored platelets, but not RT-stored platelets, into the mice deficient in glycoprotein Ib significantly shortened tail-bleeding times and diminished blood loss. ConclusionIntegrin activation and apoptosis is the underlying mechanism of rapid clearance of platelets after cold storage. Addition of a cell impermeable calcium ion chelator to platelet products is potentially a simple and effective method to enable cold storage of platelets for transfusion.

cell biology↗

bioRxiv2020

ScRNA-seq discover cell cluster change under OAB: ACE2 expression reveal possible alternation of 2019-nCoV infectious pathway

ObjectivePrevious study indicated that bladder cells which express ACE2 were a potential infection route of 2019-nCov. This study observed some differences of bladder cell cluster and their ACE2 expression between OAB mice and healthy mice, indicating the change of infectious possibility and pathway under overactive bladder (OAB) circumstance. Material and methodPubic dataset acquisition was used to get ACE2 expression in normal human bladder and mice bladder (GSE129845). We built up over OAB model and studied the impact on cell typing and ACE2 expression. By way of using single-cell RNA sequencing (scRNA-seq) technique, bladder cell clustering and ACE2 expression in various cell types were measured respectively. ResultIn pubic database (healthy human and mice bladder), ACE2 expression in humans and mice is concentrated in bladder epithelial cells. The disappearance of umbrella cells, a component of bladder epithelial, was found in our OAB model. In the two mouse bladder samples, ACE2 expression of epithelial cells is 34.1%, also the highest of all cell types. ConclusionThe disappearance of umbrella cell may alternate the infection pathway of 2019-nCov and relate to the onset and progression of OAB.

cell biology↗

bioRxiv2020

A fast genetically encoded fluorescent sensor for faithful in vivo acetylcholine detection in mice, fish, worms and flies

Here we design and optimize a genetically encoded fluorescent indicator, iAChSnFR, for the ubiquitous neurotransmitter acetylcholine, based on a bacterial periplasmic binding protein. iAChSnFR shows large fluorescence changes, rapid rise and decay kinetics, and insensitivity to most cholinergic drugs. iAChSnFR revealed large transients in a variety of slice and in vivo preparations in mouse, fish, fly and worm. iAChSnFR will be useful for the study of acetylcholine in all animals.

neuroscience↗