1. A high throughput assay method for combined screening of early injury to fish epithelial cells, comprising the steps of:

obtaining primary fish epithelial cells;

carrying out probe marking and co-incubation on the first generation cell obtained by passage of the primary fish epithelial cell by using a probe combination;

based on a high content screening system, selecting fluorescence channels corresponding to different probes, and quantifying the fluorescence expression quantity of the incubated cells;

construction of target Ca based on standardized Euclidean distance⁺⁺The model for comprehensively judging early damage of the fish epithelial cells by 3 dimensions of ROS and MMP is as follows:

in model, Ca⁺⁺ _{Experiment of}And Ca⁺⁺ _{Blank or negative}、MMP_{Experiment of}And MMP_{Blank or negative}、ROS_{Experiment of}And ROS_{Blank or negative}Respectively representing the average fluorescence expression levels of calcium ions, mitochondrial membrane potential and oxidative stress of corresponding groups; s_Ca++、S_MMPAnd S_ROSRespectively, the standard deviations for calcium ions, mitochondrial membrane potential and oxidative stress.

2. The high throughput assay method for the joint screening of early damage to fish epithelial cells according to claim 1, wherein the reactive oxygen species ROS, Ca, are targeted to reactive calcium ion when the first generation cells grow to reach 80% -90% confluency⁺⁺And a probe combination of mitochondrial membrane potential MMP for synchronous labeling.

3. The high throughput assay method for combined screening of early injury to fish epithelial cells according to claim 2, wherein said probe combination comprises CellROX, Calcium Orange and Mito combination or probe combination with equivalent function.

4. The high throughput assay method for combined screening of early injury to epithelial cells in fish according to claim 3, wherein the optimal concentrations of CellROX, Calcium Orange and Mito working solutions are 5 μ M, 100nM and 100nM, respectively.

5. The high throughput analysis method for jointly screening early damage to fish epithelial cells according to claim 1, wherein said probe labeling further comprises Hoechst, and said Hoechst is used to label cell nuclei to localize cells.

6. The high throughput assay method for combined screening of early injury to fish epithelial cells according to claim 5, wherein the Hoechst working optimum concentration is 1 mg/mL.

7. The high throughput assay method for combined screening of early damage to fish epithelial cells according to claim 1, wherein the incubation conditions are: incubating for 20-40 min at room temperature or 37 ℃ in a dark place.

8. Use of the assay according to any one of claims 1 to 7 for screening and determining the extent of early damage after the study of fish infected with bacteria, viruses and parasites.

9. Use of the assay according to any one of claims 1 to 7 for studying the protective effect of drugs on fish infected with bacteria, viruses and parasites and their mechanisms.

10. Use of the assay according to any one of claims 1 to 7 in screening of candidate drugs and study of drug resistance for prevention and treatment of bacterial, viral and parasitic infections in fish.

Background

In the process of freshwater and seawater culture, various diseases of fishes can be caused by pathogenic microorganisms, parasites or non-parasites and other factors, and the skins of the fishes are an important immune protection barrier and can effectively prevent the infection of pathogenic bacteria, fungi, parasites and unicellular algae. The damage can cause diseases such as hemorrhagic disease, viral hemorrhagic septicemia, epithelial cyst disease, scabies and the like, can seriously cause the death of fish schools, and causes huge loss to fishery economy and sustainable development. Wherein aeromonas hydrophila, pseudomonas fluorescens, vibrio parahaemolyticus, enterococcus faecalis, escherichia coli and the like are common bacterial diseases. It has been reported that aeromonas hydrophila infection causes oxidative stress, increases intracellular Reactive Oxygen Species (ROS) and free radical production, and activates antioxidant defense mechanisms, thereby causing body damage; it also stimulates non-specific immune responses, leading to impaired mitochondrial function, etc., and may induce apoptosis in later stages of infection. In addition, BANERJE et al propose that Aeromonas hydrophila infection mode is that the Aeromonas hydrophila is actively endocytosed by macrophage, bacteria depend on host protein to live, and then the homeostasis of cytosolic calcium is changed, the activation of calpain is started, and caspase-3 mediated macrophage apoptosis is promoted in the later stage. At present, the research on the invasion of aeromonas hydrophila is mainly based on in vitro sensitive cell lines, including using phoxina pholiota muscle cell line (FHM), rainbow trout gonad cell line (RTG-2), grass carp kidney cell line (CIK) and other cell lines, and the research on the use of fish epithelial cells is rare; meanwhile, the traditional in-vitro cytotoxicity evaluation is adopted to represent late-stage toxicity, and the synchronous capture and comprehensive evaluation of various important signals of subcellular injury and early-stage injury are seriously insufficient, so that the explanation of related mechanisms and the like are limited.

Disclosure of Invention

The invention aims to provide a high-throughput analysis method for jointly screening early damage of fish epithelial cells, which solves the problems in the prior art and can realize comprehensive judgment of early damage degree of fish infected with bacteria, viruses and parasites; the auxiliary medicine has the protection effect on fishes infected with bacteria, viruses and parasites and the mechanism research thereof, and provides basis and support for candidate medicine screening, drug resistance research and the like.

In order to achieve the purpose, the invention provides the following scheme:

the invention provides a high-throughput analysis method for combined screening of early injury of fish epithelial cells, which comprises the following steps:

obtaining primary fish epithelial cells;

the primary fish epithelial cells are first-generation cells obtained through passage, and then probe labeling and co-incubation are carried out on the first-generation cells by using a probe combination;

based on a high content screening system, selecting fluorescence channels corresponding to different probes, and quantifying the fluorescence expression quantity of the incubated cells;

constructing a target for Ca based on normalized Euclidean distance⁺⁺The method for comprehensively judging early damage of the fish epithelial cells by 3 dimensions such as ROS and MMP comprises the following models:

in model, Ca⁺⁺ _{Experiment of}And Ca⁺⁺ _{Blank or negative}、MMP_{Experiment of}And MMP_{Blank or negative}、ROS_{Experiment of}And ROS_{Blank or negative}Respectively representing the average fluorescence expression levels of calcium ions, mitochondrial membrane potential and oxidative stress of corresponding groups; s_Ca++、S_MMPAnd S_ROSRespectively, the standard deviations for calcium ions, mitochondrial membrane potential and oxidative stress.

Preferably, the first generation cells are grown and confluent to 80% -90% with Reactive Oxygen Species (ROS), activated calcium ion (Ca)⁺⁺) And a Mitochondrial Membrane Potential (MMP) probe.

Preferably, the probe combination is directed against ROS, Ca respectively⁺⁺And MMPs, preferably CellROX, Calcium Orange and Mito combinations from Thermo Fisher or probes and combinations with equivalent functionality.

Preferably, the optimal concentrations of the CellROX, Calcium Orange and Mito working solutions are 5. mu.M, 100nM and 100nM, respectively.

Preferably, the probe label further comprises Hoechst, and the nucleus is labeled with the Hoechst to localize the cell.

Preferably, the optimal working concentration of Hoechst is 1 mg/mL.

Preferably, the incubation conditions are: incubating for 20-40 min at room temperature or 37 ℃ in a dark place.

The invention also provides application of the analysis method in screening and judging the early damage degree of the fish infected with bacteria, viruses and parasites.

The invention also provides application of the analysis method in researching protection effect and mechanism of the medicine on fish infected with bacteria, viruses and parasites.

The invention also provides application of the analysis method in screening candidate drugs for preventing and treating fish infection bacteria, viruses and parasites and drug resistance research.

The invention discloses the following technical effects:

the invention discloses a High-throughput analysis method for jointly Screening early injury of fish epithelial cells, which is mainly based on a High Content Screening (HCS) system, takes the fish epithelial cells as an in vitro research carrier, develops and is suitable for fish epithelial cell culture, probe synchronous marking and active oxygen (ROS), Mitochondrial Membrane Potential (MMP) and active calcium ion (Ca) evaluation⁺⁺) A complete set of methods for the comprehensive analysis of subcellular signals. The example proves that the method has extremely high flux, can effectively support the screening of the candidate drugs for preventing and treating the fish infectious bacteria, and can assist in judging whether the candidate drugs for compound use have combined effects (synergistic, antagonistic or additive effects) and the like. Therefore, the invention constructs a whole set of comprehensive method capable of realizing the induction of early damage degree after fish is infected with bacteria, viruses and parasitesA determination procedure; provides a method for researching the protective effect and mechanism of the drug on fish infected with bacteria, viruses and parasites, and provides support for candidate drug screening, drug resistance research and the like.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a graph showing the change in fluorescence intensity of High Content Screening (HCS) after neomycin (Neo) + thymol (Thy) treatment of "grass carp epithelial cells + Aeromonas hydrophila";

FIG. 2 shows the MMP, ROS and Ca of grass carp epithelial cells infected with Aeromonas hydrophila with single mode and co-exposure of neomycin (Neo) and thymol (Thy)⁺⁺Relative fluorescence expression levels.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The specification and examples are exemplary only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

Example 1 high throughput assay method for combined screening of early damage to fish epithelial cells

1. Primary fish epithelial cell culture

(1) Preparing a culture solution: adding 100 μ L of 10mM Tris solution with pH 7.6 into the tubule to obtain 0.1mg/mL basic fibroblast growth factor (bFGF) stock solution, adding 25 μ L buffer HEPE into 75 μ L buffer solution for dilution, and filtering with 0.22 μm filter; adding 10mL of fetal bovine serum, 1mL of penicillin-streptomycin solution, 175.3 mu L of 2-ME and the bFGF filtrate into 5mL of DMEM medium;

(2) sampling of fish epithelial tissues: selecting about 500g of healthy fish, fasting for 24h, narcotizing with 2-phenoxyethanol, and sterilizing in 70% ethanol for 1 min; the gills and mid-gut sections (mesentery cut off and intestinal wall cut open in tandem) were removed in a sterile room and placed in PBS containing penicillin and streptomycin. Transferring to intercellular, treating with 0.1% sodium hypochlorite for 3min, washing with sterile distilled water for 4 times, washing with 70% ethanol for 1min, washing with PBS for several times, and cutting into tissue blocks of 1mm × 1 mm;

(3) tissue block culture: adding 0.25% trypsin into the tissue block obtained in the above step, digesting with shaking in water bath at 28 deg.C for 20min, and repeatedly blowing with suction tube until a large amount of cells and cells appear under the light microscopePellet, add DMEM medium to stop digestion. Filtering with 100 mesh sterilized filter screen, centrifuging at 1000r/min for 5min, discarding supernatant, adding culture solution to obtain cell suspension, inoculating into 5mL culture flask, and culturing at 25 deg.C with 5% CO₂After culturing for 90min in the incubator, transferring the culture solution and the nonadherent cells into a new culture bottle for continuous culture;

(4) preparing a rat tail collagen solution: the culture flasks or well plates used for the above culture need to be coated in advance. Specifically, 0.1M acetic acid solution is prepared 12-24 hours in advance, and high-pressure steam sterilization is carried out for standby; 0.1M acetic acid is used as a solvent to prepare a rat tail gum solution (preferably C7661 of sigma), the preparation process is continuously vibrated, and the rat tail gum solution is placed for 3-4 hours for later use. When prepared rat tail collagen is subpackaged, the bottom is firstly added with chloroform with the volume of 1/5 of a subpackaging container to be used as a bottom pad;

(5) coating the pore plate: coating needs to simultaneously satisfy 10-15 mu g/cm²Concentration and concentration of 70-80 mul/cm²The volume level is that different 6-pore plates, 24-pore plates, 96-pore plates or culture bottles need to be selected for proper multiple dilution before coating, and the diluted solution selects 30% alcohol; after coating, the mixture is required to be placed overnight and washed with sterile PBS for three times the next day for later use;

(6) purifying the fish epithelial cells: primary cultured epithelial cells were obtained when the cells were seeded onto the coated plates, and when they covered 80% of the plate bottom surface area (48 h). Filtering the obtained epithelial cells by repeated adherence, counting, and adjusting cell density to 5 × 10⁴The cells are inoculated in a culture bottle, placed in an incubator for culture, and repeated for 2 times when the cells cover 80% of the plate bottom; removing the culture medium, washing with PBS, adding 0.25% trypsin for digestion, and adding DMEM culture medium for termination when 80-90% of cells are retracted under a microscope to obtain purified fish epithelial cells;

(7) subculturing: repeatedly beating and centrifuging the purified cells, improving the domestication and anti-stress capability of the primary epithelial cells, and eliminating the cell population when the cells are naturally purified, namely dominant cells are not dominant; and (3) cleaning the cells for the primary epithelial cells for 2-3 times by using a culture solution, discarding supernatant, resuspending the cells, and replacing the culture solution every other day. When in use, primary cells in the growth log phase of 2-5 generations are preferably selected for experiments;

(8) stably culturing cell strains: obtaining a cell strain with stable culture characteristics from primary culture cells or differentiating into a finite bacterial line, and performing culture, passage and recovery in a conventional mode.

2. Combinatorial probe selection, labeling and loading

(1) Epithelial cell preparation: the first generation of cells grew and converged to about 80%, and the preparation concentration was 10%⁵each/mL cell suspension is fully blown, evenly mixed and inoculated to a black 96-well plate, wherein each well is 150 mu L, namely each well is inoculated with 10 mu L⁴And (4) cells. Placing the cell culture plate in an incubator overnight; sucking out the culture solution in the plate before adding the fluorescent probe mixed solution;

(2) and (3) selecting probe combinations: against Reactive Oxygen Species (ROS), reactive calcium ions (Ca)⁺⁺) And Mitochondrial Membrane Potential (MMP)3 early damage sensitive targets, preferably the probe combinations are CellROX (Ex/Em 504/529nm), Calcium Orange (Ex/Em 549/576nm) and Mito (Ex/Em579/599nm), respectively, and the cell nucleus is marked based on Hoechst (Ex/Em361/486nm) to locate the cell;

(3) probe labeling and co-incubation: the probe dilution solution is PBS; after optimization, the optimal working concentration of Hoechst (Ex/Em361/486nM) is 1mg/ml, and the optimal concentrations of CellROX (Ex/Em 504/529nM), Calcium Orange (Ex/Em 549/576nM) and Mito (Ex/Em579/599nM) working solutions are 5 mu M, 100nM and 100nM respectively; then adding the diluted probes into a DMEM culture medium preheated at 28 ℃ in sequence to prepare a mixture of the fluorescent probes, and taking care of avoiding light in the whole process; adding 150 μ L of the probe-containing mixed material solution into each well, incubating for 30min at room temperature or 37 deg.C in the dark, discarding the staining solution, and washing with PBS buffer solution for 2 times;

(4) fixing the plate: adding 100 μ L of 4% paraformaldehyde into each hole of the plate, fixing for 15min, and sucking out; and then 0.2% Triton X-100PBS is adopted for incubation for 10min, and the solution is sucked out and put on a computer to be tested.

3. High throughput assay

Quantitative determination of fluorescence is carried out by using a high content screening instrument, an excitation light fluorescence channel corresponding to a probe is selected during testing, and the optimal field of view (generally 10 fields of view) in a hole is selected and observed at random by using a 20X objective lens; the specific result expression can select a corresponding visual field with good phenotype under a 40 multiplied objective lens, and the result is qualitative; the fluorescent signals expressed by the different channels representing the different signals in the corresponding 10 fields under the well were quantified at 20 × objective. Results were quantified as the average of the total fluorescence intensity of the corresponding channels in all 10 fields of the triplicate experiments to the fluorescence expression intensity of each cell, and the results were finally characterized as the percentage of experimental values relative to blank values for fluorescence intensity quantification described above.

4. Analysis of results

Construction of Ca based on standardized Euclidean distances⁺⁺And 3 dimensions such as ROS and MMP are used for calculating and analyzing the comprehensive judgment model of the early damage of the fish epithelial cells. The control is a positive group, the protective effect of the medicine application on bacteria (fungi, parasites and the like) + fish epithelial cells is researched, and if the d (x, y) value is larger, the comprehensive protective effect of the comprehensive medicine on cells after the bacteria (fungi, parasites and the like) are infected is stronger; the control is a blank group, and the early injury comprehensive effect of the application of the medicament on the epithelial cells of the fish is researched, and if the d (x, y) value is larger, the toxic effect of the medicament on the cells is stronger. The model is as follows:

in model, Ca⁺⁺ _{Experiment of}And Ca⁺⁺ _{Blank or negative}、MMP_{Experiment of}And MMP_{Blank or negative}、ROS_{Experiment of}And ROS_{Blank or negative}Respectively representing the average fluorescence expression levels of calcium ions, mitochondrial membrane potential and oxidative stress of corresponding groups; s_Ca++、S_MMPAnd S_ROSRespectively, the standard deviations for calcium ions, mitochondrial membrane potential and oxidative stress.

Example 2 high throughput analysis method application case for combined screening of early damage of fish epithelial cells

This example was based primarily on the combination of "neomycin (Neo) + thymol (Thy)" to explore whether this combination could effectively control bacterial proliferation without causing severe damage to fish epithelial cells in the "aeromonas hydrophila + fish epithelial cell" system. The specific operation mode is as follows:

1. preparing an antibacterial drug combination solution: DMEM medium is adopted to dilute the antibacterial drugs to the required concentration, the single concentration of neomycin (Neo) drug is 9.78 mug/mL, the single concentration of thymol (Thy) drug is 204.56 mug/mL, and the mixed concentration of Neo and Thy is mixed by 0.5 times of the respective concentration;

2. preparing aeromonas hydrophila liquid: aeromonas hydrophila during the logarithmic growth phase was adjusted to OD 0.1 (about 10) in LB medium⁷CFU/mL), for use;

3. preparing grass carp epithelial cells: preparing grass carp epithelial cells, and preparing to a concentration of 10% when the growth of the cells is converged to about 80%⁵each/mL cell suspension is fully blown, evenly mixed and inoculated to a black 96-well plate, each hole is 100 mu L, namely, each hole is inoculated with 10 mu L⁴Individual cells and in an incubator overnight;

4. high throughput screening assay: the bacterial suspension prepared above was added to the DMEM medium containing the single or combined drugs at a volume ratio of 1:1000 (i.e. the bacterial suspension: the DMEM medium containing the single or combined drugs at a volume ratio of 1: 1000). Old medium was discarded from 96-well plates and 100. mu.L of DMEM medium described above (bacteria to cells ratio of about 20:1) was added to each well. The control group included uninfected cells, and cells without drug addition but with bacterial infection, and 5 wells were set for each group as a parallel. ROS, Ca⁺⁺And MMP is an early damage index induced by bacterial infection, the late damage end point is apoptosis, but the later damage end point can be measured only when cell membranes are still intact, so that after 3 hours of treatment, a fluorescent probe mixture is replaced, incubation is carried out for 40min at 28 ℃, liquid is discarded, and the cell membranes are washed for 2-3 times by PBS. The above processes are all operated under the condition of keeping out light. Selecting proper fluorescence channel, under 20 × objective, selecting 10 fields per hole, and calculating ROS and Ca⁺⁺And MMP strength, three independent replicates were performed to verify test results. The results are shown in FIGS. 1 and 2.

Based on the model, the corresponding d (x, y) results of single drug Try and Neo and binary combination 'Neo + Try' are calculated to judge the comprehensive risk of early injury degree, and whether the combination effect exists between the single drug combination and the binary drug combination is initially judged and proved.

(1) Compared to the positive control, i.e., in the model "aeromonas hydrophila + grass carp epithelial cells", the d (x, y) for the single and combined drugs was calculated as follows:

the Neo single action mode:

d(x，y)＝2.834

secondly, the Try single action mode:

d(x，y)＝2.719

③ the combined action mode of Neo + Try:

d(x，y)＝2.779

and displaying according to the calculation result: the protective ability of the single and 'Try + Neo' binary drug combination to the epithelial cells infected with the aeromonas hydrophila is sequentially ordered from strong to weak: neo > Try + Neo > Try; ② the combined medicine group 'Try + Neo' presents additive action or weak synergistic (weak antagonistic) effect.

(2) The d (x, y) for both single and combination doses was calculated as follows, compared to the blank control, i.e. in the grass carp epithelial cell model:

the Neo single action mode:

d(x，y)＝1.992

secondly, the Try single action mode:

d(x，y)＝1.333

③ the combined action mode of Neo + Try:

d(x，y)＝3.510

and displaying according to the calculation result: the toxic effect of the single and 'Try + Neo' binary drug combination on the grass carp epithelial cells is sequentially ordered from strong to weak: try + Neo > Try; ② the combined medicine group 'Try + Neo' also shows synergistic or weak synergistic effect.

In view of the above results, the preferred sequence is Neo, Try + Neo and Try, because Neo has moderate toxicity to grass carp epithelial cells, but has the strongest protective effect on infected cells, and the comprehensive weight use strategy is optimal; secondly, a combined drug group Try + Neo, which has a moderate protection effect on the germ cells but has the highest cytotoxicity and may present a synergistic effect; try is a natural active ingredient, and has an insignificant protective effect on infected cells and a minimal toxicity on cells. Further more intensive research can be carried out on Try + Neo and Try to ascertain which of the two is the more preferred alternative. The result is also practiced and proved that the invention has good supporting function for the comprehensive diagnosis of early damage of cells, the screening of medication scheme, the research of relevant mechanism and the like, and has extremely high flux.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.