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Xiang Chen

Publications and source records attributed to Xiang Chen.

At least 19 recordsLinked to original sources
PubMed2026

Mycobacterium tuberculosis Rv0158 negatively regulates the cGAS-STING pathway mediated type I IFN production and enhances intracellular survival.

BACKGROUND: Type I interferons (IFN) play an important role in the host defense against Mycobacterium tuberculosis (M. tb) infection and disease pathogenesis. Although M. tb has evolved several mechanisms to evade host immune surveillance, the mechanism used to regulate type I IFN expression remains unclear. METHODS: In this study, genome-wide high-throughput loss-of-function screening was performed to screen M. tb determinants that regulate the Type I IFN pathway, and the role for M. tb Rv0158 in inhibiting type I IFN responses was identified in vitro and in vivo. RESULTS: The M. tb coding protein Rv0158 was identified among many transposon (Tn) insertion mutants, which increased the expression of IFN-β and some pro-inflammatory cytokines. The results suggested that Rv0158 is associated with reduced STING protein levels and suppression of cGAS-STING-mediated innate immune responses, suggesting that Rv0158 may indirectly facilitate STING degradation or modulate its stability through host-interacting partners. Rv0158 also down-regulated the transcription of interferon-stimulated genes (ISGs) and increased the bacterial load in mice. CONCLUSION: Overall, our finding identified a new bacterial factor Rv0158, these results reveal an important role for M. tb Rv0158 in inhibiting Type I IFN responses, which improves our understanding of the immune evasion mechanisms of M. tb.

Immune escape↗
PubMed2026

Antibody-drug conjugates against multidrug-resistant cancers: Biomarker-guided patient selection, payload engineering, linker chemistry, and bystander effects.

Antibody-drug conjugates (ADCs) are one of the most significant advancements in modern cancer therapeutics. Combining the target selectivity of monoclonal antibodies with the cytotoxic potential of payloads, ADCs effectively kill cancer cells and offer hope to patients with even refractory cancer types. Beyond simply increasing the number of therapeutic options available for cancer patients, ADCs have become a powerful frontline agent in overcoming multidrug resistance (MDR). As one of the most challenging obstacles to effective cancer care, MDR is mediated by ATP-binding cassette (ABC) transporter-mediated drug efflux, target-based mutations, and dysregulated apoptosis. The clinical success of ADCs specifically engineered to overcome MDR, including in heterogeneous tumors and cancer cells that exhibit bypass signaling, is well established. This is especially evident with trastuzumab deruxtecan (T-DXd) in HER2-low, HER2-positive, and HER2-mutant cancers; sacituzumab govitecan (SG) in TROP2-expressing triple-negative breast cancer (TNBC) and urothelial carcinoma; and enfortumab vedotin in Nectin-4-positive bladder cancer. By overcoming MDR, ADCs have enabled more effective treatment algorithms across multiple malignancies. Most importantly, the clinical application of ADCs has become inextricably linked to cancer genomics. HER2 testing has evolved from a two-tiered system to a continuous spectrum including HER2-ultralow, HER2-low, HER2-positive, and ERBB2-mutant categories. Each of these categories exhibits different eligibility guidelines for ADC patient selection. As cancer cells continue to evolve and develop resistance to even ADCs through mutations and variants, researchers and clinicians have used pharmacogenomics to predict ADC response and resistance. To define the genomic architecture of ADC-resistant tumor subpopulations, single-cell transcriptomic studies and liquid biopsy approaches are being used to enable real-time examination of the tumor genome during ADC therapy, thereby optimizing treatment and circumventing resistance driven by emerging mutations and variants. This review provides a comprehensive analysis of the molecular structure of ADCs, the pharmacological principles underlying their potent cytotoxic activity against MDR cancer cells, the genomic and transcriptomic biomarkers that guide ADC patient selection, and the emerging resistance mechanisms that will shape the next generation of promising ADC development.

Humans↗
PubMed2026

Ligand-Mediated Reprogramming Redirects Liver-Tropic Ionizable Lipid Nanoparticles for Lung-Selective mRNA Delivery.

Systemic delivery of messenger RNA (mRNA) to target tissues and cells using lipid nanoparticles (LNPs) holds transformative potential for gene therapy. However, most clinically validated LNP exhibit strong liver tropism, and redirecting their organ specificity without redesigning entirely new chemistries remains challenging. Here we present a ligand-mediated lipid reprogramming approach that repurposes chemically defined, liver-tropic, ionizable lipids (lipidoids) for mRNA delivery beyond the liver. From a library of 90 degradable lipidoids, we identified 2-t6b as a potent liver-targeting platform. By site-specific displaying of small molecule ligands onto 2-t6b headgroup, we engineered a series of reconfigured lipidoids that achieve lung-specific targeting while retaining the parent delivery scaffold. Ligand7-2-t6b-lipid-functionalized LNP achieved over 200-fold higher mRNA translation in the lungs compared to the parent liver-tropic LNP. Proteomics and molecular docking analysis revealed enhanced binding of the modified lipid to vitronectin, a serum glycoprotein that improves integrin binding and thus promotes cellular uptake and translation efficiency. Ligand-mediated 2-t6b/ligand7 LNPs achieved outperformed efficacy and therapeutic potential in lung-specific genome editing relative to SORT-constructed 2-t6b LNP system. Our modular reprogramming strategy provides a generalizable framework to upgrade existing liver-biased LNPs into lung-selective mRNA carriers, advancing next-generation tissue-specific mRNA therapies for gene editing, protein replacement therapy, and regenerative medicine.

RNA, Messenger↗
PubMed2026

Optimized AAV5-RPGR ORF15 Gene Therapy Rescues Photoreceptor Structure and Function in X-Linked Retinitis Pigmentosa Mouse Model.

PURPOSE: To develop and evaluate an rAAV5-based gene therapy vector expressing an optimized human RPGR ORF15 transgene (rAAV5-RPGR) for the treatment of X-linked retinitis pigmentosa caused by RPGR mutations, addressing the challenges of cloning the unstable wild-type ORF15 sequence. DESIGN: This was a prospective experimental study. SUBJECTS: This was an animal study. METHODS: An optimized RPGR ORF15 sequence was designed to eliminate problematic secondary structures and cryptic splice sites. In vitro expression was validated in HEK 293T and photoreceptor-like 661 W cells. A complete Rpgr knockout mouse model (Rpgr-knockout [KO]) was generated and characterized phenotypically. Therapeutic efficacy was assessed in Rpgr-KO mice via subretinal injection of rAAV5-RPGR at low (1 &#xd7; 10&#x2079; vg/eye), medium (3 &#xd7; 10&#x2079; vg/eye), or high (1 &#xd7; 10&#xb9;&#x2070; vg/eye) doses. Structural and functional outcomes were evaluated at 12- and 14-month postinjection. Short-term safety was assessed in rabbits 1 month after subretinal injection. MAIN OUTCOME MEASURES: Level of RPGR protein expression and Protein isoform profile (elimination of truncated isoforms), Cellular localization of transgene expression and Dose-dependence of expression, outer nuclear layer thickness, and electroretinography parameters. RESULTS: (1) The optimized vector increased RPGR protein expression 3.3-fold in vitro compared to wild-type and eliminated truncated isoforms. (2) Subretinal delivery of rAAV5-RPGR in mice demonstrated dose-dependent transgene expression localized correctly to photoreceptor inner segments. (3) In Rpgr-KO mice, high-dose treatment significantly preserved outer nuclear layer thickness at the injection site (42% greater than controls at 14 months, P < .01) and central retina (P < .05), reduced aberrant rhodopsin mislocalization (P < .01), and partially restored retinal function. ERG showed significantly improved scotopic a-wave (&#x2265;100 vs <90 &#xb5;V in controls at 10 cd&#xb7;s/m&#xb2;) and photopic b-wave amplitudes (49-66 vs 31-46 &#xb5;V at 30 cd&#xb7;s/m&#xb2;) in treated mice. (4) No vector-related toxicity was observed in rabbits. CONCLUSIONS: rAAV5-RPGR mediated efficiently, targeted expression of optimized RPGR-ORF15, significantly preserved photoreceptor structure and function in a severe X-linked retinitis pigmentosa mouse model, and demonstrated a favorable safety profile. This study provides preclinical proof-of-concept for RPGR-targeted gene replacement therapy.

Animals↗
PubMed2026

Comparative evaluation of molecular technologies for the identification of prevalent non-tuberculous mycobacteria in pulmonary infections: a systematic review and meta-analysis.

BACKGROUND: The increasing prevalence of non-tuberculous mycobacteria pulmonary disease (NTM PD) is a burden to public health. Successful management of NTM PD critically depends on accurate species identification and reliable drug susceptibility testing to guide appropriate antibiotic therapy. Emerging molecular technologies offer rapid diagnostic solutions compared to conventional methods, but their performance varies. This study aims to provide a comprehensive evaluation of current molecular techniques for NTM identification and to present a global antibiotic resistance profile. METHODS: A systematic literature search was conducted in PubMed and Web of Science for studies published between 2005 and 2024. Studies applying molecular methods for NTM identification and resistance detection in humans were included. Data on study characteristics, diagnostic methods, sample types, sample sizes, identification sensitivity, and drug susceptibility results were extracted. Meta-analysis was performed using R with the meta4diag package. The quality of included studies was assessed using the QUADAS-2 tool. RESULTS: The analysis included 49 studies on NTM identification and 33 studies on antibiotic resistance. For species identification, all evaluated molecular technologies (MALDI-TOF MS, PCR-based methods, Sequencing, DNA chip, and DNA strip) demonstrated high pooled sensitivities (>0.92). Subgroup analysis revealed that sample type significantly affected performance for MALDI-TOF MS. Preliminary analysis of antibiotic resistance rates revealed varying patterns. For slowly growing mycobacteria, a significantly high Ethambutol resistance rate was observed in M. avium (69.20%). Among rapidly growing mycobacteria, resistance to Imipenem was notable (54.22%), and Clarithromycin resistance varied significantly within the Mycobacterium abscessus complex. CONCLUSION: Emerging molecular technologies have revolutionized the methodology for NTM identification with excellent performance. However, their performance can be influenced by sample type, particularly for MALDI-TOF MS. The alarming and heterogeneous antibiotic resistance patterns also highlight the critical need for rapid and accurate species identification and drug susceptibility testing to inform effective therapeutic strategies. Key messagesMolecular technologies demonstrate high accuracy for NTM identification.Antibiotic resistance is a serious concern with variations among NTM species and subspecies.Rapid and accurate species identification and drug susceptibility testing are crucial for guiding effective clinical management of NTM PD.

Humans↗
PubMed2006

A small interfering CD147-targeting RNA inhibited the proliferation, invasiveness, and metastatic activity of malignant melanoma.

CD147 plays a critical role in the invasive and metastatic activity of malignant melanoma cells by stimulating the surrounding fibroblasts to express matrix metalloproteinases and vascular endothelial growth factor. We developed a system that blocks CD147 in the human malignant melanoma cell line, A375, using RNA interference. By transfecting melanoma cells with the small interfering RNA (siRNA) that targets human CD147, we were able to establish two stable clones in which CD147 expression was significantly down-regulated. This resulted in the decreased proliferation and invasion of A375 cells in vitro. CD147 siRNA also down-regulated the expression of vascular endothelial growth factor in these cells and reduced the migration of vascular endothelial cells. The reduction in the CD147 level suppressed the size of s.c. tumors and the microvessel density in an A375 s.c. nude mouse xenograft model. In addition, the in vivo metastatic potential of A375 cells transfected with CD147 siRNA was suppressed in a nude mouse model of pulmonary metastasis.

Animals↗
PubMed2006

NMR solution structure of BmK-betaIT, an excitatory scorpion beta-toxin without a 'hot spot' at the relevant position.

BmK-betaIT (previously named as Bm32-VI in the literature), an excitatory scorpion beta-toxin, is purified from the venom of the Chinese scorpion Buthus martensii Karsch. It features a primary sequence typical of the excitatory anti-insect toxins: two contiguous Cys residues (Cys37-Cys38) and a shifted location of the fourth disulfide bridges (Cys38-Cys64), and demonstrates bioactivity characteristic of the excitatory beta-toxins. However, it is noteworthy that BmK-betaIT is not conserved with a glutamate residue at the preceding position of the third Cys residue, and is the first example having a non-glutamate residue at the relevant position in the excitatory scorpion beta-toxin subfamily. The 3D structure of BmK-betaIT is determined with 2D NMR spectroscopy and molecular modeling. The solution structure of BmK-betaIT is closely similar to those of BmK IT-AP and Bj-xtrIT, only distinct from the latter by lack of an alpha(0)-helix. The surface functional patch comparison with those of BmK IT-AP and Bj-xtrIT reveals their striking similarity in the spatial arrangement. These results infer that the functional surface of beta-toxins is composed of two binding regions and a functional site. The main binding site is consisted of hydrophobic residues surrounding the alpha(1)-helix and its preceding loop, which is common to all beta-type scorpion toxins affecting Na(+) channels. The second binding site, which determines the specificity of the toxin, locates at the C-terminus for excitatory insect beta-toxin, while rests at the beta-sheet and its linking loop for anti-mammal toxins. The functional site involved in the voltage sensor-trapping model, which characterizes the function of all beta-toxins, is the negatively charged residue Glu15.

Amino Acid Sequence↗
PubMed2006

Quantitative determination of azithromycin in human plasma by liquid chromatography-mass spectrometry and its application in a bioequivalence study.

A sensitive, rapid liquid chromatographic-electrospray ionization mass spectrometric method for determination of azithromycin in human plasma was developed and validated. Azithromycin in plasma (0.2mL) was extracted with methyl tert-butyl ether-hexane (50:50, v/v), organic phase was transferred to another clear 1.5mL Eppendorf tube and evaporated to dryness at 40 degrees C and dissolved in mobile phase, samples were separated using a Thermo Hypersil HyPURITY C18 reversed-phase column (150mmx2.1mm i.d., 5microm), together with a mobile phase containing of 20mM ammonium acetate (pH 5.2)-acetonitrile-methanol (50:40:10, v/v/v) and was isocratically eluted at a flow rate of 0.2mL/min. Azithromycin and its internal standard, clarithromycin, were measured by electrospray ion source in positive selective ion monitoring mode. The method demonstrated that good linearity ranged from 2 to 1000ng/mL with r=0.9977. The limit of quantification for azithromycin in plasma was 2ng/mL with good accuracy and precision. The higher mean extraction recovery, say 81.2% and 75.5% for azithromycin and internal standard (IS), respectively, was obtained in this work. The intra-day and inter-day precision ranged from 4.8% to 8.6% and 6.4% to 10.7% (R.S.D.), respectively. The established method has been successfully applied to bioequivalence study of 2 azithromycin formulations for 24 healthy volunteers.

Administration, Oral↗
PubMed2006

The expression and refolding of isotopically labeled recombinant Matrilysin for NMR studies.

Matrilysin (MMP7) is the smallest member of matrix metalloproteinases (MMPs) family, which are collectively responsible for remodeling of connective tissue. MMP7 plays an essential role in cancer, innate immunity, and in inflammatory disorders, and has been justified as a novel drug target. Here, we report the gene synthesis, overexpression in Escherichia coli, purification and refolding of MMP7. The gene of Matrilysin was synthesized based on PCR method and overexpressed in E. coli in the form of inclusion bodies. The protein was subsequently purified and refolded to yield sufficient quantities for structural and functional studies. The purified protein was characterized by means of MALDI-TOF mass spectroscopy and dynamic light scattering (DLS) analysis. The MS data confirms the correctness of the primary sequence, while DLS experiment proves that the protein exists as a monomeric form. A significantly optimized protocol has been worked out to prepare (15)N and/or (13)C-labeled MMP7 in minimal medium with high yields for NMR studies. Under the various conditions optimized for the purification of MMP7, the yield of the purified protein is estimated to be 18-20 mg from 0.5 L of M9 minimal media. Finally, the (15)N-1H HSQC spectrum of uniformly (15)N-labeled MMP7 sample reveals that the protein is properly folded, and exists in a well-ordered structure.

Carbon Isotopes↗
PubMed2006

Protein kinase-mediated regulation of calcineurin through the phosphorylation of modulatory calcineurin-interacting protein 1.

Calcineurin is a serine/threonine protein phosphatase that plays a critical role in many physiologic processes such as T-cell activation, skeletal myocyte differentiation, and cardiac hypertrophy. We previously showed that active MEKK3 is capable of stimulating calcineurin/nuclear factor of activated T-cells (NFAT) signaling in cardiac myocytes through phosphorylation of modulatory calcineurin-interacting protein 1 (MCIP1). However, the protein kinases that function downstream of MEKK3 to mediate MCIP1 phosphorylation and the mechanism of MCIP1-mediated calcineurin regulation have not been defined. Here, we show that MEK5 and big MAP kinase 1 (BMK1) function downstream of MEKK3 in a signaling cascade that induces calcineurin activity through phosphorylation of MCIP1. Genetic studies showed that BMK1-deficient mouse lung fibroblasts failed to mediate MCIP1 phosphorylation and activate calcineurin/NFAT in response to angiotensin II, a potent NFAT activator. Conversely, restoring BMK1 to the deficient cells restored angiotensin II-mediated calcineurin/NFAT activation. Thus, using BMK1-deficient mouse lung fibroblast cells, we provided the genetic evidence that BMK1 is required for angiotensin II-mediated calcineurin/NFAT activation through MICP1 phosphorylation. Finally, we discovered that phosphorylated MCIP1 dissociates from calcineurin and binds with 14-3-3, thereby relieving its inhibitory effect on calcineurin activity. In summary, our findings reveal a previously unrecognized essential regulatory role of mitogen-activated protein kinase signaling in calcineurin activation through the reversible phosphorylation of a calcineurin-interacting protein, MCIP1.

14-3-3 Proteins↗
PubMed2006

Automated interpretation of subcellular patterns in fluorescence microscope images for location proteomics.

Proteomics, the large scale identification and characterization of many or all proteins expressed in a given cell type, has become a major area of biological research. In addition to information on protein sequence, structure and expression levels, knowledge of a protein's subcellular location is essential to a complete understanding of its functions. Currently, subcellular location patterns are routinely determined by visual inspection of fluorescence microscope images. We review here research aimed at creating systems for automated, systematic determination of location. These employ numerical feature extraction from images, feature reduction to identify the most useful features, and various supervised learning (classification) and unsupervised learning (clustering) methods. These methods have been shown to perform significantly better than human interpretation of the same images. When coupled with technologies for tagging large numbers of proteins and high-throughput microscope systems, the computational methods reviewed here enable the new subfield of location proteomics. This subfield will make critical contributions in two related areas. First, it will provide structured, high-resolution information on location to enable Systems Biology efforts to simulate cell behavior from the gene level on up. Second, it will provide tools for Cytomics projects aimed at characterizing the behaviors of all cell types before, during, and after the onset of various diseases.

Animals↗
PubMed2006

The specific and essential role of MAVS in antiviral innate immune responses.

The mitochondrial antiviral signaling protein (MAVS) mediates the activation of NFkappaB and IRFs and the induction of interferons in response to viral infection. In vitro studies have also suggested that MAVS is required for interferon induction by cytosolic DNA, but the in vivo evidence is lacking. By generating MAVS-deficient mice, here we show that loss of MAVS abolished viral induction of interferons and prevented the activation of NFkappaB and IRF3 in multiple cell types, except plasmacytoid dendritic cells (pDCs). However, MAVS was not required for interferon induction by cytosolic DNA or by Listeria monocytogenes. Mice lacking MAVS were viable and fertile, but they failed to induce interferons in response to poly(I:C) stimulation and were severely compromised in immune defense against viral infection. These results provide the in vivo evidence that the cytosolic viral signaling pathway through MAVS is specifically required for innate immune responses against viral infection.

Adaptor Proteins, Signal Transducing↗
PubMed2006

Automated interpretation of protein subcellular location patterns.

Proteomics is a major current focus of biomedical research, and location proteomics is the important branch of proteomics that systematically studies the subcellular distributions for all proteins expressed in a given cell type. Fluorescence microscopy of labeled proteins is currently the main methodology to obtain location information. Traditionally, microscope images are analyzed by visual inspection, which suffers from inefficiency and inconsistency. Automated and objective interpretation approaches are therefore needed for location proteomics. In this article, we briefly review recent advances in automated imaging interpretation tools, including supervised classification (which assigns location pattern labels to previously unseen images), unsupervised clustering (which groups proteins based on the similarity among their subcellular distributions), and additional statistical tools that can aid cell and molecular biologists who use microscopy in their work.

Automation↗
PubMed2006

Binding interactions of pefloxacin mesylate with bovine lactoferrin and human serum albumin.

The binding of pefloxacin mesylate (PFLX) to bovine lactoferrin (BLf) and human serum albumin (HSA) in dilute aqueous solution was studied using fluorescence spectra and absorbance spectra. The binding constant K and the binding sites n were obtained by fluorescence quenching method. The binding distance r and energy-transfer efficiency E between pefloxacin mesylate and bovine lactoferrin as well as human serum albumin were also obtained according to the mechanism of Förster-type dipole-dipole nonradiative energy-transfer. The effects of pefloxacin mesylate on the conformations of bovine lactoferrin and human serum albumin were also analyzed using synchronous fluorescence spectroscopy.

Animals↗
PubMed2006

Fluorometric study on the interaction between lomefloxacin and bovine lactoferrin.

The binding of lomefloxacin to bovine lactoferrin (BLf) in a dilute aqueous solution was studied using fluorescence spectra. The binding constant (K) and the number of binding sites (n) were obtained by a fluorescence quenching method. The binding distance (r) and energy-transfer efficiency (E) between lomefloxacin and bovine lactoferrin were also obtained according to the mechanism of Foörster-type dipole-dipole nonradiative energy-transfer. The effect of lomefloxacin on the conformation of bovine lactoferrin was also analyzed by synchronous fluorescence spectroscopy. The interaction between lomefloxacin and bovine lactoferrin is strong. Lomefloxacin can affect the conformation of bovine lactoferrin to some degree.

Animals↗
PubMed2006

[Retroperitoneal laparoscopic enucleation of the renal hamartoma].

OBJECTIVE: To investigate the operative technique and the clinical value of retroperitoneal laparoscopic enucleation of the renal hamartoma. METHODS: Twenty-five patients of renal hamartoma received retroperitoneal laparoscopic enucleation. The patients were placed in lateral decubitus position. All laparoscopic surgical procedures were performed retroperitoneally using 3 port-sites. The tumor was exposed and resected along the edge, and the tumor clipped out with a lithotomy forceps. The renal hamartoma was confirmed through a pathological diagnosis during the operation. The resection surface was sutured with fibrin and absorbable hemostatic gauze. RESULTS: The operations were finished successfully in all patients. The diameter of tumors ranged from 1.8 cm x 2.0 cm to 4.5 cm x 4.9 cm. The operative time was 50 - 90 (mean=70) min. The blood loss was 30 - 80 (mean=55) mL. The hospital stay was 7 - 9 (mean=8) days. CONCLUSION: Retroperitoneal laparoscopic enucleation of the renal hamartoma is safe and effective, whose advantages include minimal invasive, less blood loss, short hospital stay, and rapid convalescence.

Adult↗
PubMed2006

Protective effect of resveratrol against oxidative damage of UVA irradiated HaCaT cells.

OBJECTIVE: To observe the photoprotective effect and possible mechanisms of resveratrol for ultraviolet A (UVA) irradiated HaCaT cells. METHODS: HaCaT cells under UVA irradiation with 5J/cm(2) were interfered with 0.01 mmol/L and 0.1 mmol/L resveratrol. The testing objects were divided into a control and a UVA irradiation group, and then we detected the proliferation capacity with methylthiazdyl tetrazolium (MTT) and superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) activity, content of maleic dialdehyde (MDA) with hydroxylamine, colorimetric, thiobarbituric acid (TBA) methods. The ultrastructure was observed under electron microscope. RESULTS: Resveratrol could enhance the proliferation activity, SOD, GSH-Px activity of HaCaT cells under UVA irradiation, decrease the content of MDA in dose-dependent manner (P<0.05). The electron microscope revealed that resveratrol could relieve the injury of HaCaT cells' ultrastructure. CONCLUSION: Resveratrol can relieve the inhibition to HaCaT cell proliferation,injury of their ultrastructure and oxidation by UVA irradiation. The protection is dose-dependent. That resveratrol raises the oxidase activity and clears the oxyradical may account for these results.

Cell Line, Transformed↗