Impact of diabetes mellitus simulations on bone cell behavior through in vitro models.

Diabetes mellitus (DM) is related to impaired bone healing and an increased risk of bone fractures. While it is recognized that osteogenic differentiation and the function of osteoblasts are suppressed in DM, the influence of DM on osteoclasts is still unclear. Hyperglycemia and inflammatory environment are the hallmark of DM that causes dysregulation of various pro-inflammatory cytokines and alternated gene expression in periodontal ligament cells, osteoblasts, osteocytes, osteoclasts, and osteoclast precursors. A methodological review on conceptual and practical implications of in vitro study models is used for DM simulation on bone cells. Several major databases were screened to find literature related to the study objective. Published literature within last 20 years that used in vitro DM-simulated models to study how DM affects the cellular behavior of bone cells were selected for this review. Studies utilizing high glucose and serum acquired from diabetic animals are the mainly used methods to simulate the diabetic condition. The combination with various simulating factors such as lipopolysaccharide (LPS), hydrogen peroxide (H2O2), and advanced glycation end products (AGEs) have been reported in diabetic situations in vitro, as well. Through screening procedure, it was evident DM-simulated conditions exerted negative impact on bone-related cells. However, inconsistent results were found among different reported studies, which could be due to variation in culture conditions, concentrations of the stimulating factors and cell lineage, etc. This manuscript has concisely reviewed currently existing DM-simulated in vitro models and provides valuable insights of detailed components in simulating DM conditions in vitro. Studies using DM-simulated microenvironment revealed that in vitro simulation negatively impacted periodontal ligament cells, osteoblasts, osteocytes, osteoclasts, and osteoclast precursors. Contrarily, studies also indicated beneficial influence on bone-related cells when such conditions are reversed.

Matrigel Scaffolding Enhances BMP9-induced Bone Formation in Dental Follicle Stem/Precursor Cells.

Bone tissue engineering requires a combination of cells, efficient biochemical and physicochemical factors, and biocompatible scaffolds. In this study, we evaluated the potential use of injectable Matrigel as a scaffold for the delivery of rat dental follicle stem/precursor cells (rDFSCs) transduced by bone morphogenetic protein (BMP) 9 to enhance osteogenic differentiation in vitro and promote ectopic bone formation in vivo. Recombinant adenovirus was used to overexpress BMP9 in rDFSCs. Alkaline phosphatase activity was measured using a histochemical staining assay and a chemiluminescence assay kit. Quantitative real-time polymerase chain reaction was used to determine mRNA expression levels of bone-related genes including distal-less homeobox 5 (DLX5), osteopontin (OPN), osterix (Osx), and runt-related transcription factor 2 (Runx2). Matrix mineralization was examined by Alizarin Red S staining. rDFSCs proliferation was analyzed using the Cell Counting Kit-8 assay. Subcutaneous implantation of rDFSCs-containing Matrigel scaffolds was used, and micro-computed tomography analysis, histological evaluation, and trichrome staining of implants extracted at 6 weeks were performed. We found that BMP9 enhanced alkaline phosphatase activity and mineralization in rDFSCs. The expression of bone-related genes (DLX5, OPN, Osx, and Runx2) was also increased as a result of BMP9 stimulation. Micro-computed tomography analysis and histological evaluation revealed that the bone masses retrieved from BMP9-overexpressing rDFSCs were significantly more pronounced in those with than in those without Matrigel. Our results suggest that BMP9 effectively promote osteogenic differentiation of rDFSCs, and Matrigel facilitate BMP9-induced osteogenesis of rDFSCs in vivo.

Cyclic mechanical stretch enhances BMP9-induced osteogenic differentiation of mesenchymal stem cells.

PURPOSE: The purpose of this study was to investigate whether mechanical stretch can enhance the bone morphogenetic protein 9 (BMP9)-induced osteogenic differentiation in MSCs. METHODS: Recombinant adenoviruses were used to overexpress the BMP9 in C3H10T1/2 MSCs. Cells were seeded onto six-well BioFlex collagen I-coated plates and subjected to cyclic mechanical stretch [6% elongation at 60 cycles/minute (1 Hz)] in a Flexercell FX-4000 strain unit for up to 12 hours. Immunostaining and confocal microscope were used to detect cytoskeleton organization. Cell cycle progression was checked by flow cytometry. Alkaline phosphatase activity was measured with a Chemiluminescence Assay Kit and was quantified with a histochemical staining assay. Matrix mineralization was examined by Alizarin Red S Staining. RESULTS: Mechanical stretch induces cytoskeleton reorganization and inhibits cell proliferation by preventing cells entry into S phase of the cell cycle. Although mechanical stretch alone does not induce the osteogenic differentiation of C3H10T1/2 MSCs, co-stimulation with mechanical stretch and BMP9 enhances alkaline phosphatase activity. The expression of key lineage-specific regulators (e.g., osteocalcin (OCN), SRY-related HMG-box 9, and runt-related transcription factor 2) is also increased after the co-stimulation, compared to the mechanical stretch stimulation along. Furthermore, mechanical stretch augments the BMP9-mediated bone matrix mineralization of C3H10T1/2 MSCs. CONCLUSIONS: Our results suggest that mechanical stretch enhances BMP9-induced osteoblastic lineage specification in C3H10T1/2 MSCs.

A New Second Messenger: Bacterial c-di-AMP.

Nucleotide-based second messengers transduce signals originating from both outside and inside the cell to adaptive responses accordingly. c-di-AMP is a newly established second messenger employed by many organisms. We summarize recent advances in bacterial c-di-AMP-mediated signaling, especially the interaction between c-di-AMP signaling and the host.

PTP1B promotes aggressiveness of breast cancer cells by regulating PTEN but not EMT.

Metastasis is a complicated, multistep process and remains the major cause of cancer-related mortality. Exploring the molecular mechanisms underlying tumor metastasis is crucial for development of new strategies for cancer prevention and treatment. In this study, we found that protein tyrosine phosphatase 1B (PTP1B) promoted breast cancer metastasis by regulating phosphatase and tensin homolog (PTEN) but not epithelial-mesenchymal transition (EMT). By detecting PTP1B expression of the specimens from 128 breast cancer cases, we found that the level of PTP1B was higher in breast cancer tissues than the corresponding adjacent normal tissues. Notably, PTP1B was positively associated with lymph node metastasis (LNM) and estrogen receptor (ER) status. In vitro, disturbing PTP1B expression obviously attenuated cell migration and invasion. On the contrary, PTP1B overexpression significantly increased migration and invasion of breast cancer cells. Mechanistically, PTP1B knockdown upregulated PTEN, accompanied with an abatement of AKT phosphorylation and the expression of matrix metalloproteinase 2 (MMP2) and MMP7. Conversely, forced expression of PTP1B reduced PTEN and increased AKT phosphorylation as well as the expression of MMP2 and MMP7. Notably, neither EMT nor stemness of breast cancer cells was regulated by PTP1B. We also found that PTP1B acted as an independent prognostic factor and predicted poor prognosis in ER-positive breast cancer patients. Taken together, our findings provide advantageous evidence for the development of PTP1B as a potential therapeutic target for breast cancer, especially for ER-positive breast cancer patients.

Involvement of Holliday junction resolvase in fluoroquinolone-mediated killing of Mycobacterium smegmatis.

The absence of the Holliday-junction Ruv resolvase of Mycobacterium smegmatis increased the bacteriostatic and bactericidal activities of the fluoroquinolone moxifloxacin, an important antituberculosis agent. The treatment of ruvAB-deficient cells with thiourea and 2,2'-bipyridyl lowered moxifloxacin lethality to wild-type levels, indicating that the absence of ruvAB stimulates a lethal pathway involving reactive oxygen species. A hexapeptide that traps the Holliday junction substrate of RuvAB potentiated moxifloxacin-mediated lethality, supporting the development of small-molecule enhancers for moxifloxacin activity against mycobacteria.

Characterization of a novel mutation in the overlap of tlyA and ppnK involved in capreomycin resistance in Mycobacterium.

Capreomycin (CAP) is an important second-line drug for multidrug-resistant tuberculosis. To further define the drug resistance mechanism of CAP, a Mycobacterium smegmatis transposon mutant library was constructed using Tn5 transposon for screening isolates with enhanced CAP resistance. A mutant (named C4) with fourfold increased CAP resistance was isolated and characterized. Tn5 was found to be inserted into MSMEG_0841, an annotated pseudogene. However, knockout demonstrated that MSMEG_0841 was not responsible for CAP resistance. We further sequenced the whole genome of C4 and found an A to G substitution in the overlap region between tlyA and ppnK, which leads a stop codon mutation in upstream tlyA and a T2A mutation in downstream ppnK. Mutation in the overlap might confer the dysfuction of both genes. tlyA is a known gene involved in CAP action. Overexpression of ppnK in both Escherichia coli and M. smegmatis confer subtle susceptible to CAP. Taken together, our study found that a novel mutation involved in CAP resistance.

Molecular insights into the proteomic composition of porcine treated dentin matrix.

Background: Human-treated dentin matrix (hTDM) has recently been studied as a natural extracellular matrix-based biomaterial for dentin pulp regeneration. However, porcine-treated dentin matrix (pTDM) is a potential alternative scaffold due to limited availability. However, there is a dearth of information regarding the protein composition and underlying molecular mechanisms of pTDM.Methods: hTDM and pTDM were fabricated using human and porcine teeth, respectively, and their morphological characteristics were examined using scanning electron microscopy. Stem cells derived from human exfoliated deciduous teeth (SHEDs) were isolated and characterized using flow cytometry and multilineage differentiation assays. SHEDs were cultured in three-dimensional environments with hTDM, pTDM, or biphasic hydroxyapatite/tricalcium phosphate. The expression of odontogenesis markers in SHEDs were assessed using real-time polymerase chain reaction and immunochemical staining. Subsequently, SHEDs/TDM and SHEDs/HA/TCP complexes were transplanted subcutaneously into nude mice. The protein composition of pTDM was analyzed using proteomics and compared to previously published data on hTDM.Results: pTDM and hTDM elicited comparable upregulation of odontogenesis-related genes and proteins in SHEDs. Furthermore, both demonstrated the capacity to stimulate root-related tissue regeneration in vivo. Proteomic analysis revealed the presence of 278 protein groups in pTDM, with collagens being the most abundant. Additionally, pTDM and hTDM shared 58 identical proteins, which may contribute to their similar abilities to induce odontogenesis. Conclusions: Both hTDM and pTDM exhibit comparable capabilities in inducing odontogenesis, potentially owing to their distinctive bioactive molecular networks.

Beclin-1/LC3-II dependent macroautophagy was uninfluenced in ischemia-challenged vascular endothelial cells.

Autophagy has been extensively studied and occurs in many biological settings. However, a question remains as to whether ischemia enhances Beclin-1/LC3-II-dependent macroautophagy in vascular endothelial cells, as has been previously thought. Furthermore, the effect of the level of autophagy on cell or skin flap survival still requires elucidation. We created a lethal ischemia model in human umbilical vascular endothelial cells (HUVECs), performed quantitative proteomics and bioinformatics analyses, and verified the autophagic status and effect both in vitro and in vivo. The significantly upregulated proteins encoded by autophagy-related genes (ATGs) included ATG2A, ATG3, ATG4B, ATG5, ATG7, ATG9A, ATG12, ATG16, and ATG101. The significantly enhanced lysosomal proteins were cathepsin B, cathepsin D, lysosome-associated membrane protein 1 (LAMP1), and LAMP2. However, the differentially expressed proteins excluded Beclin-1, microtubule-associated protein light chain 3 (LC3)-I, and LC3-II. Western blot analyses verified that the protein expression levels of Beclin-1, LC3-I, and LC3-II were neither upregulated nor downregulated in ischemia-challenged HUVECs. The autophagic status was not enhanced by rapamycin in ischemic HUVECs but appeared to be inhibited by chloroquine. Our in vivo study on rats showed that a downregulation in autophagic status jeopardized skin flap survival. In conclusion, Ischemia neither enhanced nor inhibited Beclin-1/LC3-II-dependent canonical macroautophagy both in vitro and in vivo, in contradiction to previous studies. An appropriate autophagic homeostasis can minimize cell or skin flap damage.

[Corrigendum] Low­intensity pulsed ultrasound promotes periodontal ligament stem cell migration through TWIST1­mediated SDF­1 expression.

Subsequently to the publication of the above paper, an interested reader drew to the authors' attention that the 'Control' and 'AMD3100' panels in Fig. 3B on p. 326 appeared to show strikingly similar data, such that they may have been derived from the same original source; likewise, the 'Control' and 'Scramble' data panels in the 'Untreated' row of data panels in Fig. 5B on p. 327 also appeared to share some of the same data. The authors have re­examined their data, and realized that a pair of the data panels included in these figures were inadvertently selected incorrectly. The corrected versions of Figs. 3 and 5, containing the correct data for the 'Control' panel in Fig. 3B and the 'Control' panel for the 'Untreated' experiments in Fig. 5B, are shown on the next page. These errors did not affect the major conclusions reported in the paper. All the authors have agreed to this Corrigendum, and thank the Editor of International Journal of Molecular Medicine for allowing them the opportunity to publish this. The authors regret these errors went unnoticed during the compilation of the figures in question, and apologize to the readership for any confusion that this may have caused. [the original article was published in International Journal of Molecular Medicine 42: 322­330, 2018; DOI: 10.3892/ijmm.2018.3592].

Different grinding speeds affect induced regeneration capacity of human treated dentin matrix.

Human-treated dentin matrix (hTDM) is a biomaterial scaffold, which can induce implant cells to differentiate into odontoblasts and then form neo-dentin. However, hTDM with long storage or prepared by high-speed handpiece would not to form neo-dentin. In this research, we developed two fresh hTDM with different grinding speeds, which were low-speed hTDM (LTDM) with maximum speed of 500 rpm and high-speed hTDM (HTDM) with a speed of 3,80,000 rpm. Here, we aim to understand whether there were induced regeneration capacity differences between LTDM and HTDM. Scanning electron microscope showed that DFCs grew well on both materials, but the morphology of DFCs and the extracellular matrix was different. Especially, the secreted extracellular matrixes on the inner surface of LTDM were regular morphology and ordered arrangement around the dentin tubules. The transcription-quantitative polymerase chain reaction (qRT-PCR), western blot and immunofluorescence assay showed that the dentin markers DSPP and DMP-1 were about 2× greater in DFCs induced by LTDM than by HTDM, and osteogenic marker BSP was about 2× greater in DFCs induced by HTDM than by LTDM. Histological examinations of the harvested grafts observed the formation of neo-tissue were different, and there were neo-dentin formed on the inner surface of LTDM and neo-cementum formed on the outer surface of HTDM. In summary, it found that the induction abilities of LTDM and HTDM are different, and the dentin matrix is directional. This study lays a necessary foundation for searching the key factors of dentin regeneration in future.

Development of Lipo-γ-AA Peptides as Potent Antifungal Agents.

The emergence of drug-resistant fungal pathogens poses great threats to an increasing number of vulnerable populations worldwide, and the need for novel antifungal agents is imperative. In this work, a series of lipo-γ-AA peptides were synthesized and evaluated for their biological activities. One lead, MW5, exhibited potent and broad-spectrum antifungal activity. In addition, MW5 potently boosted the efficacy of fluconazole against clinical azole-resistant Candida isolates. Mechanistic investigation showed that the lead compound disrupted the cell membrane, significantly boosted the production of reactive oxygen species, and undermined the function of the efflux pump, thus resensitizing drug-resistant Candida albicans to fluconazole. Notably, coadministration of MW5 and fluconazole exhibited potent in vivo antifungal activity in a murine model of mucocutaneous candidiasis. Our results demonstrated that lipo-γ-AA peptides have great promise for use alone or in combination to combat drug-resistant Candida infections.

A Highly Sensitive and Specific Detection Method for Mycobacterium tuberculosis Fluoroquinolone Resistance Mutations Utilizing the CRISPR-Cas13a System.

Objectives: CRISPR-Cas13a system-based nucleic acid detection methods are reported to have rapid and sensitive DNA detection. However, the screening strategy for crRNAs that enables CRISPR-Cas13a single-base resolution DNA detection of human pathogens remains unclear. Methods: A combined rational design and target mutation-anchoring CRISPR RNA (crRNA) screening strategy was proposed. Results: A set of crRNAs was found to enable the CRISPR-Cas13 system to dramatically distinguish fluroquinolone resistance mutations in clinically isolated Mycobacterium tuberculosis strains from the highly homologous wild type, with a signal ratio ranging from 8.29 to 38.22 in different mutation sites. For the evaluation of clinical performance using genomic DNA from clinically isolated M. tuberculosis, the specificity and sensitivity were 100 and 91.4%, respectively, compared with culture-based phenotypic assays. Conclusion: These results demonstrated that the CRISPR-Cas13a system has potential for use in single nucleotide polymorphism (SNP) detection after tuning crRNAs. We believe this crRNA screening strategy will be used extensively for early drug resistance monitoring and guidance for clinical treatment.

Comparison of the biomechanical differences in the occlusal movement of wild-type and BMP9 knockout mice with apical periodontitis.

Apical periodontitis is a common clinical disease caused by bacteria; bacterial metabolites can cause an imbalance in bone homeostasis, bone mass reduction, and tooth loss. Bone resorption in apical periodontitis causes a concentration of stress in the tooth and periodontal tissues during occlusion, which aggravates the disease. Emerging evidence indicates that bone morphogenetic protein 9 (BMP9), also known as growth differentiation factor 2(Gdf2), may play an important role in tooth and dentoalveolar development. Herein, we investigated the role of BMP9 in the development of apical periodontitis and its effects on the biomechanics of dentoalveolar bone. Apical periodontitis models were established in five BMP9 knockout (KO) mice and five C57BL/6 WT (wild-type) mice. At baseline and 14, 28, and 42 days after modeling, in vivo micro-computed tomography analysis and three-dimensional (3D) reconstruction were performed to evaluate the apical lesion in each mouse, and confirm that the animal models were successfully established. Finite element analysis (FEA) was performed to study the stress and strain at the alveolar fossa of each mouse under the same vertical and lateral stress. FEA revealed that the stress and strain at the alveolar fossa of each mouse gradually concentrated on the tooth cervix. The stress and strain at the tooth cervix gradually increased with time but were decreased at day 42. Under the same lingual loading, the maximum differences of the stress and strain at the tooth root in KO mice were greater than those in WT mice. Thus, these findings demonstrate that BMP9 could affect the biomechanical response of the alveolar fossa at the tooth root in mice with apical periodontitis. Moreover, the effects of BMP9 on the biomechanical response of the alveolar bone may be site-dependent. Overall, this work contributes to an improved understanding of the pathogenesis of apical periodontitis and may inform the development of new treatment strategies for apical periodontitis.

Progress on the biomarkers for tuberculosis diagnosis.

Tuberculosis (TB) remains a major threat to global health. Biomarkers derived from pathogen-host interaction can facilitate the monitoring of active TB. The recent progress regarding such biomarkers is summarized, including those can be used from serum, sputum, urine, or breath monitoring. A wide range of potential biomarkers such as protein antigens, cell-free nucleic acids, and lipoarabinomannose were compiled. The possible use of biomarkers for infection identification and monitoring drug efficacy are also presented.

Polyphosphate deficiency affects the sliding motility and biofilm formation of Mycobacterium smegmatis.

Inorganic polyphosphate (polyP) is a ubiquitous linear polymer of hundreds of orthophosphate (Pi) residues linked by ATP-like, high-energy, phosphoanhydride bonds. The gene Rv1026 in Mycobacterium tuberculosis encodes a putative exopolyphosphatase which progressively hydrolyzes the terminal residues of polyP to liberate Pi. Rv1026 was cloned into the expressive plasmid pMV261. The resulting plasmid pRv1026 and the plasmid pMV261 were transformed into M. smegmatis strain mc(2)155 by electroporation. The recombinant M. smegmatis (pRv1026) showed relatively decreased polyP concentration and a phenotype different from the M. smegmatis (pMV261) in sliding motility and biofilm formation. The surfactant Tween 80 can enhance this effect on the sliding motility and biofilm formation of M. smegmatis. There are four different peaks between the gas chromatography of cellular wall fatty acid of the M. smegmatis (pRv1026) and the M. smegmatis (pMV261). These results indicate that polyP deficiency can affect the fatty acid composition of cellular wall and these alteration of cell wall might elucidate the reductive ability of strains to slide and form biofilm. This investigation provides novel recognition about the role of Rv1026, which provides novel clues for further study on the physiological role of Rv1026 in M. tuberculosis.

Ischemia-Challenged human umbilical vascular endothelial cells: Proteomics data.

[Human umbilical vascular endothelial cells (HUVECs) underwent ischemia, ischemia/reperfusion and normal control (sham) treatment and marked as group I, IR and NC, respectively, were detected by quantitative proteomics and bioinformatics analyses. Proteins in Beclin-1/LC3-II-dependent canonical macroautophagy pathway were verified in details. The significantly upregulated proteins encoded by autophagy-related genes (ATGs) included ATG2A, ATG3, ATG4B, ATG5, ATG7, ATG9A, ATG12, ATG16 and ATG101. The significantly enhanced lysosomal proteins comprised Cathepsin B, Cathepsin D, lysosome-associated membrane protein 1 (LAMP1) and LAMP2. However, the differentially expressed proteins excluded Beclin-1, microtubule-associated protein light chain 3 (LC3)-I and LC3-II. Western blot analyses verified that the protein expressions of Beclin-1, LC3-I and LC3-II were neither upregulated nor downregulated in ischemia-challenged HUVECs.].

Agarose-based spheroid culture enhanced stemness and promoted odontogenic differentiation potential of human dental follicle cells in vitro.

Human dental follicle cells (HDFCs) are an ideal cell source of stem cells for dental tissue repair and regeneration and they have great potential for regenerative medicine applications. However, the conventional monolayer culture usually reduces cell proliferation and differentiation potential due to the continuous passage during in vitro expansion. In this study, primary HDFC spheroids were generated on 1% agarose, and the HDFCs spontaneously formed cell spheroids in the agarose-coated dishes. Compared with monolayer culture, the spheroid-derived HDFCs exhibited increased proliferative ability for later passage HDFCs as analysed by Cell Counting Kit-8 (CCK-8). The transcription-quantitative polymerase chain reaction (qRT-PCR), western blot and immunofluorescence assay showed that the expression of stemness marker genes Sox2, Oct4 and Nanog was increased significantly in the HDFC spheroids. Furthermore, we found that the odontogenic differentiation capability of HDFCs was significantly improved by spheroid culture in the agarose-coated dishes. On the other hand, the osteogenic differentiation capability was weakened compared with monolayer culture. Our results suggest that spheroid formation of HDFCs in agarose-coated dishes partially restores the proliferative ability of HDFCs at later passages, enhances their stemness and improves odontogenic differentiation capability in vitro. Therefore, spheroid formation of HDFCs has great therapeutic potential for stem cell clinical therapy.

An iRGD-conjugated prodrug micelle with blood-brain-barrier penetrability for anti-glioma therapy.

Various obstacles impede the chemotherapy efficiency of glioma in clinic, such as blood brain barrier (BBB) and blood brain tumor barrier (BBTB). Ligand-mediated polymeric micelles have shown great potential for improving the efficiency of glioma treatment. Herein, we developed a disulfide bond-conjugated prodrug polymer consisted of camptothecin (CPT) and polyethylene glycol (PEG) with further modification of iRGD peptide. The polymer of CPT-S-S-PEG-COOH could self-assemble into nanosized polymeric micelles with diameter around 100 nm, and loaded with photosensitizer IR780 for combination therapy. The micelles displayed good stability with controlled drug release under physiological environment. Importantly, the iRGD modified polymeric micelles demonstrated favorable ability to cross the BBB and target glioma cells via αv ß integrin and neuropilin-1-mediated ligand transportation in vitro and in vivo. The whole synthesis process is simple and the drug loading content of CPT in the CPT-S-S-PEG-iRGD@IR780 micelles was higher than 10%. Moreover, CPT-S-S-PEG-iRGD@IR780 micelles combined chemotherapy with photodynamic therapy (PDT) displayed more excellent tumor-killing capability than the other groups. Thus, both in vitro and in vivo studies suggested that the targeting prodrug system could not only effectively cross various barriers to reach at glioma site, but also significantly enhance the antitumor effect with laser irradiation. Our findings consequently suggested that CPT-S-S-PEG-iRGD@IR780 micelles with laser irradiation are a promising drug delivery system for glioma therapy.

L-lysine potentiates aminoglycosides against Acinetobacter baumannii via regulation of proton motive force and antibiotics uptake.

Acinetobacter baumannii, a Gram-negative opportunistic pathogen, is a leading cause of hospital- and community-acquired infections. Acinetobacter baumannii can rapidly acquire diverse resistance mechanisms and undergo genetic modifications that confer resistance and persistence to all currently used clinical antibiotics. In this study, we found exogenous L-lysine sensitizes Acinetobacter baumannii, other Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae) and a Gram-positive bacterium (Mycobacterium smegmatis) to aminoglycosides. Importantly, the combination of L-lysine with aminoglycosides killed clinically isolated multidrug-resistant Acinetobacter baumannii and persister cells. The exogenous L-lysine can increase proton motive force via transmembrane chemical gradient, resulting in aminoglycoside acumination that further accounts for reactive oxygen species production. The combination of L-lysine and antibiotics highlights a promising strategy against bacterial infection.