Exosomes-Mediated Signaling Pathway: A New Direction for Treatment of Organ Ischemia-Reperfusion Injury.

Ischemia reperfusion (I/R) is a common pathological process which occurs mostly in organs like the heart, brain, kidney, and lung. The injury caused by I/R gradually becomes one of the main causes of fatal diseases, which is an urgent clinical problem to be solved. Although great progress has been made in therapeutic methods, including surgical, drug, gene therapy, and transplant therapy for I/R injury, the development of effective methods to cure the injury remains a worldwide challenge. In recent years, exosomes have attracted much attention for their important roles in immune response, antigen presentation, cell migration, cell differentiation, and tumor invasion. Meanwhile, exosomes have been shown to have great potential in the treatment of I/R injury in organs. The study of the exosome-mediated signaling pathway can not only help to reveal the mechanism behind exosomes promoting reperfusion injury recovery, but also provide a theoretical basis for the clinical application of exosomes. Here, we review the research progress in utilizing various exosomes from different cell types to promote the healing of I/R injury, focusing on the classical signaling pathways such as PI3K/Akt, NF-κB, Nrf2, PTEN, Wnt, MAPK, toll-like receptor, and AMPK. The results suggest that exosomes regulate these signaling pathways to reduce oxidative stress, regulate immune responses, decrease the expression of inflammatory cytokines, and promote tissue repair, making exosomes a competitive emerging vector for treating I/R damage in organs.

AKAP1 in Renal Patients with AHF to Reduce Ferroptosis of Cardiomyocyte.

BACKGROUND: This study mainly investigated the mechanism and effects of AKAP1 in renal patients with acute heart failure (AHF). METHODS: Patients with renal patients with AHF and normal volunteers were collected. The left anterior descending arteries (LAD) of mice were ligated to induce myocardial infarction. RESULTS: AKAP1 messenger RNA (mRNA) expression was found to be down-regulated in renal patients with AHF. The serum levels of AKAP1 mRNA expression were negatively correlated with collagen I/III in patients. AKAP1 mRNA and protein expression in the heart tissue of mice with AHF were also found to be down-regulated in a time-dependent manner. Short hairpin (Sh)-AKAP1 promotes AHF in a mouse model. AKAP1 up-regulation reduces reactive oxygen species (ROS)-induced oxidative stress in an In Vitro model. AKAP1 up-regulation also reduces ROS-induced lipid peroxidation ferroptosis in an In Vitro model. AKAP1 induces NDUFS1 expression to increase GPX4 activity levels. AKAP1 protein interlinked with the NDUFS1 protein. Up-regulation of the AKAP1 gene reduced NDUFS1 ubiquitination, while down-regulation of the AKAP1 gene increased NDUFS1 ubiquitination in a model. In vivo imaging showed that the sh-AKAP1 virus reduced NDUFS1 expression in the heart of a mouse model. CONCLUSIONS: AKAP1 reduced ROS-induced lipid peroxidation ferroptosis through the inhibition of ubiquitination of NDUFS by mitochondrial damage in model of renal patients with AHF, suggest a novel target for AHF treatment.

Recent Advances in Biodegradable and Biocompatible Synthetic Polymers Used in Skin Wound Healing.

The treatment of skin wounds caused by trauma and pathophysiological disorders has been a growing healthcare challenge, posing a great economic burden worldwide. The use of appropriate wound dressings can help to facilitate the repair and healing rate of defective skin. Natural polymer biomaterials such as collagen and hyaluronic acid with excellent biocompatibility have been shown to promote wound healing and the restoration of skin. However, the low mechanical properties and fast degradation rate have limited their applications. Skin wound dressings based on biodegradable and biocompatible synthetic polymers can not only overcome the shortcomings of natural polymer biomaterials but also possess favorable properties for applications in the treatment of skin wounds. Herein, we listed several biodegradable and biocompatible synthetic polymers used as wound dressing materials, such as PVA, PCL, PLA, PLGA, PU, and PEO/PEG, focusing on their composition, fabrication techniques, and functions promoting wound healing. Additionally, the future development prospects of synthetic biodegradable polymer-based wound dressings are put forward. Our review aims to provide new insights for the further development of wound dressings using synthetic biodegradable polymers.

Fabrication of Fibrin/Polyvinyl Alcohol Scaffolds for Skin Tissue Engineering via Emulsion Templating.

In the search for a novel and scalable skin scaffold for wound healing and tissue regeneration, we fabricated a class of fibrin/polyvinyl alcohol (PVA) scaffolds using an emulsion templating method. The fibrin/PVA scaffolds were formed by enzymatic coagulation of fibrinogen with thrombin in the presence of PVA as a bulking agent and an emulsion phase as the porogen, with glutaraldehyde as the cross-linking agent. After freeze drying, the scaffolds were characterized and evaluated for biocompatibility and efficacy of dermal reconstruction. SEM analysis showed that the formed scaffolds had interconnected porous structures (average pore size e was around 330 µm) and preserved the nano-scale fibrous architecture of the fibrin. Mechanical testing showed that the scaffolds' ultimate tensile strength was around 0.12 MPa with an elongation of around 50%. The proteolytic degradation of scaffolds could be controlled over a wide range by varying the type or degree of cross-linking and by fibrin/PVA composition. Assessment of cytocompatibility by human mesenchymal stem cell (MSC) proliferation assays shows that MSC can attach, penetrate, and proliferate into the fibrin/PVA scaffolds with an elongated and stretched morphology. The efficacy of scaffolds for tissue reconstruction was evaluated in a murine full-thickness skin excision defect model. The scaffolds were integrated and resorbed without inflammatory infiltration and, compared to control wounds, promoted deeper neodermal formation, greater collagen fiber deposition, facilitated angiogenesis, and significantly accelerated wound healing and epithelial closure. The experimental data showed that the fabricated fibrin/PVA scaffolds are promising for skin repair and skin tissue engineering.

GelNB molecular coating as a biophysical barrier to isolate intestinal irritating metabolites and regulate intestinal microbial homeostasis in the treatment of inflammatory bowel disease.

Inflammatory bowel disease (IBD) is a chronic, immune-mediated inflammatory disease characterized by the destruction of the structure and function of the intestinal epithelial barrier. Due to the poor remission effect and severe adverse events associated with current clinical medications, IBD remains an incurable disease. Here, we demonstrated a novel treatment strategy with high safety and effective inflammation remission via tissue-adhesive molecular coating. The molecular coating is composed of o-nitrobenzaldehyde (NB)-modified Gelatin (GelNB), which can strongly bond with -NH2 on the intestinal surface of tissue to form a thin biophysical barrier. We found that this molecular coating was able to stay on the surface of the intestine for long periods of time, effectively protecting the damaged intestinal epithelium from irritations of external intestinal metabolites and harmful flora. In addition, our results showed that this coating not only provided a beneficial environment for cell migration and proliferation to promote intestinal repair and regeneration, but also achieved a better outcome of IBD by reducing intestinal inflammation. Moreover, the in vivo experiments showed that the GelNB was better than the classic clinical medication-mesalazine. Therefore, our molecular coating showed potential as a promising strategy for the prevention and treatment of IBD.

Breaking the Iron Homeostasis: A "Trojan Horse" Self-Assembled Nanodrug Sensitizes Homologous Recombination Proficient Ovarian Cancer Cells to PARP Inhibition.

Poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitors are used in ovarian cancer treatment and have greatly improved the survival rates for homologous recombination repair (HRR)-deficient patients. However, their therapeutic efficacy is limited in HRR-proficient ovarian cancer. Thus, sensitizing HRR-proficient ovarian cancer cells to PARP inhibitors is important in clinical practice. Here, a nanodrug, olaparib-Ga, was designed using self-assembly of the PARP inhibitor olaparib into bovine serum albumin through gallic acid gallium(III) coordination via a convenient and green synthetic method. Compared with olaparib, olaparib-Ga featured an ultrasmall size of 7 nm and led to increased suppression of cell viability, induction of DNA damage, and enhanced cell apoptosis in the SKOV3 and OVCAR3 HRR-proficient ovarian cancer cells in vitro. Further experiments indicated that the olaparib-Ga nanodrug could suppress RRM2 expression, activate the Fe2+/ROS/MAPK pathway and HMOX1 signaling, inhibit the PI3K/AKT signaling pathway, and enhance the expression of cleaved-caspase 3 and BAX protein. This, in turn, led to increased cell apoptosis in HRR-proficient ovarian cancer cells. Moreover, olaparib-Ga effectively restrained SKOV3 and OVCAR3 tumor growth and exhibited negligible toxicity in vivo. In conclusion, we propose that olaparib-Ga can act as a promising nanodrug for the treatment of HRR-proficient ovarian cancer.

Single-Cell RNA Sequencing Reveals the Tissue Architecture in Human High-Grade Serous Ovarian Cancer.

PURPOSE: The heterogeneity of high-grade serous ovarian cancer (HGSOC) is not well studied, which severely hinders clinical treatment of HGSOC. Thus, it is necessary to characterize the heterogeneity of HGSOC within its tumor microenvironment (TME). EXPERIMENTAL DESIGN: The tumors of 7 treatment-naïve patients with HGSOC at early or late stages and five age-matched nonmalignant ovarian samples were analyzed by deep single-cell RNA sequencing (scRNA-seq). RESULTS: A total of 59,324 single cells obtained from HGSOC and nonmalignant ovarian tissues were sequenced by scRNA-seq. Among those cells, tumor cells were characterized by a set of epithelial-to-mesenchymal transition (EMT)-associated gene signatures, in which a combination of NOTCH1, SNAI2, TGFBR1, and WNT11 was further selected as a genetic panel to predict the poor outcomes of patients with HGSOC. Matrix cancer-associated fibroblasts (mCAF) expressing α-SMA, vimentin, COL3A, COL10A, and MMP11 were the dominant CAFs in HGSOC tumors and could induce EMT properties of ovarian cancer cells in the coculture system. Specific immune cell subsets such as C7-APOBEC3A M1 macrophages, CD8+ TRM, and TEX cells were preferentially enriched in early-stage tumors. In addition, an immune coinhibitory receptor TIGIT was highly expressed on CD8+ TEX cells and TIGIT blockade could significantly reduce ovarian cancer tumor growth in mouse models. CONCLUSIONS: Our transcriptomic results analyzed by scRNA-seq delineate an ecosystemic landscape of HGSOC at early or late stages with a focus on its heterogeneity with TME. The major applications of our findings are a four-EMT gene model for prediction of HGSOC patient outcomes, mCAFs' capability of enhancing ovarian cancer cell invasion and potential therapeutic value of anti-TIGIT treatment.

Global characterization of extrachromosomal circular DNAs in advanced high grade serous ovarian cancer.

High grade serous ovarian cancer (HGSOC) is the most aggressive subtype of ovarian cancer and HGSOC patients often appear with metastasis, leading to the poor prognosis. Up to date, the extrachromosomal circular DNAs (eccDNAs) have been shown to be involved in cancer genome remodeling but the roles of eccDNAs in metastatic HGSOC are still not clear. Here we explored eccDNA profiles in HGSOC by Circle-Sequencing analysis using four pairs of primary and metastatic tissues of HGSOC patients. Within the differentially expressed eccDNAs screened out by our analysis, eight candidates were validated by outward PCR and qRT-PCR analysis. Among them, DNMT1circle10302690-10302961 was further confirmed by FISH assay and BaseScope assay, as the most significantly down-regulated eccDNA in metastatic tumors of HGSOC. Lower expression of DNMT1circle10302690-10302961 in both primary and metastatic tumors was associated with worse prognosis of HGSOC. Taken together, our finding firstly demonstrated the eccDNAs landscape of primary and metastatic tissues of HGSOC. The eccDNA DNMT1circle10302690-10302961 can be considered as a potential biomarker or a therapeutically clinical target of HGSOC metastasis and prognosis.

The label-free separation and culture of tumor cells in a microfluidic biochip.

Circulating tumor cells (CTCs) from liquid biopsy have shown a strong correlation to the clinical outcome of cancer patients. The enumeration and cytological analysis of CTCs have attracted increasing efforts for cancer disease management amid immunotherapy and personalized medicine. However, both enumeration and cytological analysis are challenging due to the rarity of CTCs and the lack of integrated solutions for the minimal risk of cell loss in the course of CTC procurement. We report a simple microfluidic chip permitting a one-stop solution for streamlining the on-chip cell separation, capture, immunofluorescence assay and/or in situ culture of isolated cells devoid of risky manual steps. Our results showed effective trapping of single cells, doublets and cell lumps isolated from blood in the same device. On-chip immunostaining revealed normal cell morphology and the characterization of cell expansion uncovered an altered cell growth curve with a reduced lag phase as compared to the conventional culture despite closely matching cell growth rates. The cells were viable and functional for as long as 11 days inside our chip and cell migration was also readily observed, with lumps showing greater aggressiveness than single cells. With these results, we expect promising applications of our one-stop solution for liquid biopsy via CTCs.

Cyclin-dependent kinase 9 promotes cervical cancer development via AKT2/p53 pathway.

Aberrant activation of cyclin-dependent kinase 9 (CDK9) is widespread in human cancers. However, the underlying mechanisms of CDK9 activation and the therapeutic potential of CDK9 inhibition in cervical cancer remain largely unknown. Here, we report that CDK9 is gradually upregulated during cervical lesion progression and regulated by HPV16 E6. CDK9 levels are highly correlated with FIGO stage, pathological grade, deep-stromal invasion, tumor size, and lymph nodes metastasis. Knockdown of CDK9 by specific siRNA inhibits cervical cancer cell proliferation in vitro, as well as tumorigenesis in vivo. CDK9 inhibition causes a significant decreased AKT2 and increased p53 protein expression revealing novel CDK9-regulatory mechanisms. Overexpression of AKT2 rescued the suppressive effects caused by CDK9 knockdown, suggesting that AKT2 induction is essential for CDK9-induced transformation. Moreover, CDK9 expression was positively correlated with AKT2 and negatively correlated with p53 in cervical cancer tissues with HPV16 infection. Our findings demonstrate for the first time that CDK9 acts as a proto-oncogene in cervical cancer, modulating cell proliferation and apoptosis through AKT2/p53 pathway. Therefore, our data provide novel mechanistic insights into the role of CDK9 in cervical cancer development. © 2018 IUBMB Life, 71(3):347-356, 2019.

miR-424 targets AKT3 and PSAT1 and has a tumor-suppressive role in human colorectal cancer.

BACKGROUND: Recent advances in cancer biology have uncovered critical roles for microRNAs in regulating tumor responses. This study is to elucidate the role of miR-424 in colorectal cancer development. MATERIALS AND METHODS: miR-424 expression was analyzed by qRT-PCR. The role of miR-424 was studied in cell lines and animal models. The downstream targets of miR-424 were determined by microarray analysis. RESULTS: We found that miR-424 expression was downregulated in human colorectal cancer cell lines and patient biopsies. We demonstrated that miR-424 functioned as a tumor suppressor by suppressing colorectal cancer growth in vitro and in vivo and enhancing apoptosis. Using microarray screening, we subsequently presented evidence that miR-424 directly targeted the 3' untranslated regions of the AKT serine/threonine kinase 3 (AKT3) and phosphoserine aminotransferase 1 (PSAT1) mRNAs via luciferase assay. Furthermore, AKT3 or PSAT1 silencing partially recapitulated the effects of miR-424. CONCLUSION: This newly identified miR-424/AKT3-SAT1 axis may represent a novel therapeutic strategy for future treatment of colorectal cancer.

Isolation of cells from whole blood using shear-induced diffusion.

Extraction of cells of interest directly from whole blood is in high demand, yet extraordinary challenging due to the complex hemodynamics and hemorheology of the sample. Herein, we describe a new microfluidic platform that exploits the intrinsic complex properties of blood for continuous size-selective focusing and separation of cells directly from unprocessed whole blood. The novel system only requires routinely accessible saline solution to form a sandwiched fluid configuration and to initiate a strong effect of shear-induced diffusion of cells, which is coupled with fluid inertia for effective separation. Separations of beads and cells from whole blood have been successfully demonstrated with high efficiency (89.8%) at throughput of 6.75 mL/hr (106-107 cells/s) of whole blood. Rapid isolation of circulating tumor cells (CTCs) from peripheral blood sample of hepatocarcinoma patients is also shown as a proof of principle.

A flexible cell concentrator using inertial focusing.

Cell concentration adjustment is intensively implemented routinely both in research and clinical laboratories. Centrifuge is the most prevalent technique for tuning biosample concentration. But it suffers from a number of drawbacks, such as requirement of experienced operator, high cost, low resolution, variable reproducibility and induced damage to sample. Herein we report on a cost-efficient alternative using inertial microfluidics. While the majority of existing literatures concentrate on inertial focusing itself, we identify the substantial role of the outlet system played in the device performance that has long been underestimated. The resistances of the outlets virtually involve in defining the cutoff size of a given inertial filtration channel. Following the comprehensive exploration of the influence of outlet system, we designed an inertial device with selectable outlets. Using both commercial microparticles and cultured Hep G2 cells, we have successfully demonstrated the automated concentration modification and observed several key advantages of our device as compared with conventional centrifuge, such as significantly reduced cell loss (only 4.2% vs. ~40% of centrifuge), better preservation of cell viability and less processing time as well as the increased reproducibility due to absence of manual operation. Furthermore, our device shows high effectiveness for concentrated sample (e.g., 1.8 × 106 cells/ml) as well. We envision its promising applications in the circumstance where repetitive sample preparation is intensely employed.

A transcriptomic landscape of human papillomavirus 16 E6-regulated gene expression and splicing events.

The oncoprotein E6 of high-risk human papillomavirus (HPV) is responsible for the initiation and progression of cervical cancer. In the present study, we performed RNA-sequencing analysis in HPV16 E6-expressing 293T cells and identified 56 differentially expressed genes (DEGs) and a number of cellular pathways significantly affected. We confirmed nine of these DEGs in both cell models and clinical tissue samples. Furthermore, we performed de novo transcriptome assembly of 1128 novel human transcripts and identified 22 that are differentially expressed in the presence of HPV16 E6. In addition, our analysis revealed distinct alternative splicing events in response to HPV16 E6 expression. Overall, the present study provides a comprehensive portrait of transcriptional and splicing signatures, as well as previously unknown genes differentially expressed in response to HPV16 E6, which prompts the need for a complete annotation of the HPV16 E6-regulated transcriptome.

miR-2861 acts as a tumor suppressor via targeting EGFR/AKT2/CCND1 pathway in cervical cancer induced by human papillomavirus virus 16 E6.

Persistent infection with oncogenic human papillomavirus viruses (HPVs) is a casual factor for cervical cancer and its precursors, and the abnormal constitutive expression of viral oncoprotein E6 is a key event during the malignant transformation. Here, we performed miRNA microarray to identify changes of miRNAs following ectopic HPV16 E6 overexpression in HEK293T cells and found miR-2861 was greatly decreased in both HEK293T and HaCaT cells expressing HPV16 E6 compared to vector control. Further, we demonstrated a biological link among HPV16 E6, miR-2861, EGFR, AKT2, and CCND1 in cervical cancer cells. We showed that miR-2861 was downregulated in cervical cancer tissues and negatively correlated with advanced tumor stage and lymph node metastasis. Overexpression of miR-2861 suppressed cervical cancer cell proliferation and invasion and enhanced apoptosis. Subsequent investigation revealed that EGFR, AKT2, and CCND1 were all the direct targets of miR-2861. Importantly, silencing EGFR, AKT2, and/or CCND1 recapitulated the cellular effects seen upon miR-2861 overexpression. Restoration of EGFR, AKT2, and/or CCND1 counteracted the effects of miR-2861 expression. Thus, we identified a new pathway employing miR-2861, EGFR, AKT2, and CCND1 that may mediate HPV16 E6 induced initiation and progression of cervical cancer.

CUL2 overexpression driven by CUL2/E2F1/miR-424 regulatory loop promotes HPV16 E7 induced cervical carcinogenesis.

It has been shown that HPV16 E7, but not other genotypes, can bind to scaffold protein CUL2 during inducing cervical carcinogenesis, but the expression level, associated regulating mechanism, and potential carcinogenicity of CUL2 itself is still unknown as yet. Here, we demonstrated that CUL2 was specifically overexpressed in HPV16 positive cervical cancer cells and tissues, and CUL2 expression was significantly increased along with the cervical lesion progression and positively correlated with HPV16 E7. CUL2 knockdown slowed the growth of xenograft tumors in mouse models. Importantly, CUL2 specifically bound to HPV16 E7, but not HPV18 E7. Moreover, CUL2 acted as a direct target of miR-424, and reversely suppressed miR-424; E2F transcription factor 1 (E2F1) suppressed miR-424 expression; CUL2 bound to E2F1 and promoted E2F1 expression. Our results indicate the existence of a regulatory loop among CUL2, E2F1, and miR-424 in HPV16 positive cervical cancer cells. Our results suggest that E7 recruited CUL2, driven by CUL2/E2F1/miR-424 regulatory loop, is overexpressed and accelerates HPV16-induced cervical carcinogenesis. Our findings may serve as one of the explanations for a clinical phenomenon that HPV16 possesses the strongest cervical carcinogenicity among high-risk HPV genotypes.

Cyclin b1 suppresses colorectal cancer invasion and metastasis by regulating e-cadherin.

Cyclin B1, a mitotic cyclin, has been implicated in malignances. However, its contribution to colorectal cancer invasion and metastasis are still not well understood. Here, we demonstrated that the invasion and metastasis of colorectal cancer is regulated by Cyclin B1. Overexpression of Cyclin B1 was observed in colorectal cancer tissues, but this elevated expression was negatively associated with lymph node metastasis, distant metastasis stage, and TNM stage. The Kaplan-Meier survival analysis proved that low Cyclin B1 expression was associated with poor overall survival of patients with colorectal cancer. Inhibition of Cyclin B1 in colorectal cancer cells enhanced the cell migration and invasion of three different colorectal cancer cell lines. In studying the possible mechanism by which Cyclin B1 suppresses colorectal cancer invasion and metastasis, we observed that suppression of Cyclin B1 decreased the expression of E-cadherin protein level. Our findings suggest that Cyclin B1 could suppress the invasion and metastasis of colorectal cancer cells through regulating E-cadherin expression, which enables the development of potential intervention strategies for colorectal cancer.

Study on the mechanism of the interaction between acteoside and pepsin using spectroscopic techniques.

The interaction of acteoside with pepsin has been investigated using fluorescence spectra, UV/vis absorption spectra, three-dimensional (3D) fluorescence spectra and synchronous fluorescence spectra, along with a molecular docking method. The fluorescence experiments indicate that acteoside can quench the intrinsic fluorescence of pepsin through combined quenching at a low concentration of acteoside, and static quenching at high concentrations. Thermodynamic analysis suggests that hydrogen bonds and van der Waal's forces are the main forces between pepsin and acteoside. According to the theory of Förster's non-radiation energy transfer, the binding distance between pepsin and acteoside was calculated to be 2.018 nm, which implies that energy transfer occurs between acteoside and pepsin. In addition, experimental results from UV/vis absorption spectra, 3D fluorescence spectra and synchronous fluorescence spectra imply that pepsin undergoes a conformation change when it interacts with acteoside.

Chk1-induced CCNB1 overexpression promotes cell proliferation and tumor growth in human colorectal cancer.

The high morbidity and mortality of colorectal cancer pose a significant public health problem worldwide. Here we assessed the pro-cancer efficacy and mechanism of action of CCNB1 in different colorectal cancer cells. We provided evidence that CCNB1 mRNA and protein level were upregulated in a subset of human colorectal tumors, and positively correlated with Chk1 expression. Repression of Chk1 caused a significant decrease in cell proliferation and CCNB1 protein expression in colorectal cancer cells. Furthermore, downregulation of CCNB1 impaired colorectal cancer proliferation in vitro and tumor growth in vivo. Specifically, suppression of CCNB1 caused a strong G 2/M phase arrest in both HCT116 and SW480 cells, interfering with the expression of cdc25c and CDK1. Additionally, CCNB1 inhibition induced apoptotic death in certain colorectal cancer cells. Together, these results suggest that CCNB1 is activated by Chk1, exerts its oncogenic role in colorectal cancer cells, and may play a key role in the development of a novel therapeutic approach against colorectal cancer.

[Molecular mechanisms of quinolone resistance in Aeromonas hydrophilia].

OBJECT: To study the resistance mechanisms to quinolones in Aeromonas hydrohila isolated from aquatic animals. METHODS: The drug-resistant spectrum of 23 strains was determined. Quinolone-resistance determining regions of gyrA and parC genes in both screened and in-vitro induction drug-resistant strains were analyzed. Then the detection of quinolone drugs relative efflux pump genes qepA, oqxA and mdfA was performed. The qnrA, qnrB, qnrC, qnrD and qnrS genes were also analyzed at the same time. RESULTS: All organisms were resistant to more than 5 drugs; 39.1% (9/23) of the isolates were quinolone resistant, of which 55.6% (5/9) were enrofloxacin resistant. All the enrofloxacin-resistant isolates harbored qnrS gene, but none of the enrofloxacin-resistant strains harbored qnrA, qnrB, qnrC , qnrD genes and the efflux pump genes of qepA, oqxA and mdfA. AH19 possessed the gyrA and parC genes double mutation, plasmid-mediated quinolone resistance gene qnrS and efflux pump, 3 drug resistance mechanisms simultaneously, while the two drug-resistant mechanisms of AH4, AH7 and AH20 were gyrA and parC genes double mutation and qnrS gene. GyrA gene mutation and qnrS gene occurred in AH6. Compared to the strain ATCC7966, the in-vitro induction drug-resistant strain ATCC7966-QR had both the gyrA and parC genes mutation. CONCLUSION: The mechanisms of resistance to quinolones in the A. hydrophila isolates of this study mainly depended on the existence of plasmid-mediated gene qnrS and the variation of the target site of quinolone drugs, whereas, the drug resistance mechanism relying on the efflux pump system only existed in individual strains.