CN116217674B

CN116217674B - Antibacterial/anti-inflammatory polypeptide and application thereof

Info

Publication number: CN116217674B
Application number: CN202310070122.7A
Authority: CN
Inventors: 李义龙; 杨悌平; 王登; 刘惠清; 王新波; 宫焕章; 李向群
Original assignee: Hunan Jiudian Pharmaceutical Co Ltd
Current assignee: Hunan Jiudian Pharmaceutical Co Ltd
Priority date: 2023-02-07
Filing date: 2023-02-07
Publication date: 2024-08-02
Anticipated expiration: 2043-02-07
Also published as: CN116217674A; CN118834275A

Abstract

The invention belongs to the technical field of biomedical polypeptides, and in particular relates to an antibacterial/anti-inflammatory polypeptide and application thereof in preparing a medicament for preventing, treating or relieving antibacterial and/or anti-inflammatory related diseases. The polypeptide has short amino acid sequence, simple structure, convenient synthesis and high antibacterial/anti-inflammatory activity, can be used for preventing and treating diseases caused by microbial infection, and has good effect on healing skin wounds.

Description

Antibacterial/anti-inflammatory polypeptide and application thereof

Technical Field

The invention belongs to the technical field of biological medicines, and particularly relates to an antibacterial/anti-inflammatory polypeptide and application thereof in preparing a medicament for preventing, treating or relieving antibacterial and anti-inflammatory related diseases.

Background

Skin wounds are generally indicated to be direct injuries due to external forces or injuries caused by soft tissue infection, and can cause local inflammatory reactions, and cause local reddening and swelling or pain and suppuration. After a common skin injury, traditional inflammatory conditions (red, swollen, hot) are caused by intravascular fluid and blood leakage and local lymphatic drainage obstruction. Due to the damage of the cells, some vasoactive substances, such as histamine, serotonin and catecholamines, are released, causing a short vasoconstriction and then vasodilation, allowing fluid and cells to enter the site of the extravascular damage. In clinic, the existing treatment means mainly comprise antibiotics, which become the most extensive drugs for skin injury, however, with the application of antibiotics in a large amount, bacterial drug resistance becomes a main problem of the treatment means, and bacterial infection causes self inflammatory reaction of human body, and also delays skin healing and causes the existence of wound scars. Skin injuries such as scalds, burns and ulcers which are common in daily life are mainly antibacterial and are not properly treated, so that clinical demands which are not satisfied exist.

Therefore, the novel antibacterial/anti-inflammatory drugs become hot points for research and development in the fields of domestic and foreign human medicine, nutrition, food science, immunology and the like, and the development of biological antibacterial peptides is expected to solve the problem of bacterial drug resistance, and meanwhile, the antibacterial peptides with the anti-inflammatory effect can effectively meet the clinical requirements in the field of skin wounds, so that the antibacterial peptides have wide development and application prospects.

The human Thrombin C-terminal derived sequence TCP (Thrombin-derived C-TERMINALPEPTIDES) is firstly formed by selectively hydrolyzing a blood coagulation factor into Thrombin-derived C-terminal peptide with the size of about 2kDa, has the length of 25 amino acids, contains two action targets, can be combined with a hydrophobic bag on a human leukocyte surface differentiation antigen CD14 besides the action of LPS on the surface of bacteria, plays an anti-endotoxin function in human body in vitro and in vivo, and prevents the problems of shock caused by sepsis and the like. The prior researches show that the TCP-25 can effectively inhibit staphylococcus aureus, gram negative pseudomonas aeruginosa and subcutaneous infection pseudomonas in vitro, reduce the response of macrophages to serum Lipase (LPS) in vivo, and has a certain therapeutic potential in promoting wound healing and reducing scar hyperplasia. Therefore, the TCP-25 has a double-target action mechanism, belongs to antibacterial and anti-inflammatory simultaneous performance, and has advantages in specificity, clinical curative effect and toxic and side effects. Based on the characteristics of a dual action mechanism, high broad-spectrum bacteriostasis, low toxicity and the like of TCP-25, the invention provides an antibacterial/anti-inflammatory polypeptide, and is expected to develop a wound healing medicament with prospect.

Disclosure of Invention

The following is merely illustrative of some aspects of the invention and is not limited in this regard. These aspects and others are described more fully below. All references in this specification are hereby incorporated by reference in their entirety. When the disclosure of the present specification is different from that of the cited document, the disclosure of the present specification controls.

The invention aims to provide a novel polypeptide with antibacterial and/or anti-inflammatory effects, aiming at the problems of clinical requirements which are not met in skin wound treatment. In a first aspect, the invention provides a polypeptide or a pharmaceutically acceptable salt thereof, which is characterized by comprising an amino acid sequence shown in the following formula (I):

G-X¹-X²-G-X³-Y-X⁴-H-X⁵-X⁶-X⁷-L-X⁸-K-W-X⁹-X¹⁰-K-X¹¹-X¹²-X¹³-X¹⁴-X¹⁵-X¹⁶-X¹⁷

(I)

Wherein:

x ¹-X¹⁷ are each independently selected from any amino acid and at least one of X ¹-X¹⁷ is alanine A or a derivative thereof, including d-alanine dA or 2-methylalanine.

In some embodiments, the X ¹ and X ⁸ are each independently selected from K, dK, A, dA, K or a derivative of a.

In some embodiments, the X ² is selected from Y, dY, A, dA, Y or a derivative of a.

In some embodiments, the X ³、X⁶ and X ¹⁵ are each independently selected from F, dF, A, dA, F or a derivative of a.

In some embodiments, the X ⁴ is selected from T, dT, A, dA, T or a derivative of a.

In some embodiments, the X ⁵ and X ¹¹ are each independently selected from V, dV, A, dA, V or a derivative of a.

In some embodiments, the X ⁷ is selected from R, dR, A, dA, R or a derivative of a.

In some embodiments, the X ⁹ and X ¹² are each independently selected from I, dI, A, dA, T or a derivative of a.

In some embodiments, the X ¹⁰ and X ¹⁴ are each independently selected from Q, dQ, A, dA, Q or a derivative of a.

In some embodiments, the X ¹³ is selected from D, dD, A, dA, D or a derivative of a.

In some embodiments, the X ¹⁶ is selected from G, dG, A, dA, G or a derivative of a.

In some embodiments, the X ¹⁷ is selected from E, dE, A, dA, E or a derivative of a.

In one aspect, the invention provides a polypeptide or a pharmaceutically acceptable salt thereof, comprising an amino acid sequence of formula (I):

(I)

Wherein:

at least one of X ¹-X¹⁷ is alanine A or a derivative thereof, including alanine dA or 2-methylalanine;

X ¹ and X ⁸ are each independently selected from K, dK, A, dA, K or a derivatives of a;

x ² is selected from Y, dY, A, dA, Y or a derivative of a;

X ³、X⁶ and X ¹⁵ are each independently selected from F, dF, A, dA, F or a derivatives of a;

x ⁴ is selected from T, dT, A, dA, T or a derivative of a;

X ⁵ and X ¹¹ are each independently selected from V, dV, A, dA, V or a derivatives of a;

X ⁷ is selected from R, dR, A, dA, R or a derivative of a;

X ⁹ and X ¹² are each independently selected from I, dI, A, dA, T or a derivatives of a;

X ¹⁰ and X ¹⁴ are each independently selected from Q, dQ, A, dA, Q or a derivatives of a;

x ¹⁶ is selected from G, dG, A, dA, G or a derivative of a;

x ¹⁷ is selected from E, dE, A, dA, E or a derivative of A.

In another aspect, the invention provides a polypeptide or a pharmaceutically acceptable salt thereof, which has an amino acid sequence of one of Seq ID No.1 to Seq ID No. 17.

In one aspect, the invention relates to a pharmaceutical composition comprising a polypeptide according to any one of the invention. In some embodiments, the pharmaceutical compositions of the present invention further comprise at least one of a pharmaceutically acceptable carrier, excipient, diluent, adjuvant, and vehicle.

In another aspect, the invention relates to the use of said polypeptide or pharmaceutical composition for the manufacture of a medicament for preventing, treating or alleviating a disease, wherein said medicament is for preventing, treating or alleviating a bacterial infection and/or inflammatory infection disease.

In some embodiments, the bacterial infection and/or inflammatory infectious disease includes, but is not limited to, skin infection, skin wound infection, burn infection, scald infection, pneumonia, tuberculosis, diabetic foot, tonsillitis, bacillary dysentery, meningitis, scarlet fever, sphagitis, bronchitis, gastritis, appendicitis, glomerulonephritis, endocarditis, pericarditis, cystitis, pelvic inflammatory disease, cervicitis.

The beneficial effects of the invention are as follows: the polypeptide has remarkable antibacterial/anti-inflammatory effects, high affinity with a target point, low MIC value of the minimum inhibitory concentration and larger diameter of an inhibition zone; the cyclic structure of the polypeptides of the invention is beneficial to improving the stability of the polypeptides and does not produce significant cytotoxicity to mammalian cells.

Drawings

Fig. 1: mass spectrum of compound 4

Fig. 2: high Performance Liquid Chromatography (HPLC) of compound 4

Detailed Description

The meaning of the term "peptide" or "polypeptide" is well known to those skilled in the art. Typically, a peptide or polypeptide is one in which two or more amino acids are linked by an amide bond, which is formed by the amino group of one amino acid and the carboxyl group of an adjacent amino acid. The polypeptides described herein may comprise naturally occurring amino acids or non-naturally occurring amino acids. May be modified to include at least two amino acids such as analogs, derivatives, functional mimics, pseudopeptides, and the like. Unless a specific modification is indicated at the N-or C-terminus, a polypeptide comprising a specific amino acid sequence includes unmodified and modified amino and/or carboxy termini, as is well known to those skilled in the art. A polypeptide of a particular amino acid sequence may include modified amino acids and/or additional amino acids unless the N-and/or C-terminus comprises a modification that prevents further addition of an amino acid. Such modifications include, for example, acetylation of the N-terminus and/or amidation of the C-terminus.

The polypeptides of the invention may be modified by engineering to form polypeptide derivatives. Various adaptations and modifications of polypeptides may be made as is well known to those skilled in the art. Typical engineering modifications include, but are not limited to, N-terminal acetylation, C-terminal amidation, d-amino acid substitutions, unnatural amino acid substitutions, fatty acid modifications, or combinations of the foregoing. The present invention includes any modification of the polypeptides that are well known. For example, a polypeptide derivative may include chemical modifications to the polypeptide such as alkylation, acylation, carbamylation, iodination, or any other modification that produces a polypeptide derivative. The engineered modification of the polypeptide may comprise an engineered amino acid, e.g., hydroxyproline or carboxyglutamic acid, and may include amino acids linked by non-peptide bonds.

Other modifications to the polypeptides of the invention may be made by substitution of natural amino acids in the polypeptide with unnatural amino acids, including, but not limited to, 2-amino fatty acid (Aad), 3-amino fatty acid (β Aad), β -alanine, β -amino propionic acid (βAla), 2-amino butyric acid (Abu), 4-amino butyric acid, piperidine carboxylic acid (4 Abu), 6-amino caproic acid (Acp), 2-amino heptanoic acid (Ahe), 2-amino isobutyric acid (Aib), 3-amino isobutyric acid (βAib), 2-amino pimelic acid (Apm), 2, 4-diaminobutyric acid (Dbu), desmin (Des), 2' -diaminopimelic acid (Dpm), 2, 3-diaminopropionic acid (Dpr), N-ethyl glycine (EtGly), N-ethyl asparagine (EtAsn), hydroxylysine (Hyl), isohydroxylysine (aHyl), 3-hydroxyproline (3 Hyp), 4-hydroxyproline (4 Hyp), isodesmin (Ide), isodesmethylglycine (Mevalin) (N-valine) (N-methyl-6, N-valine (Mevalin) (N-methyl-N-valine) (N-methyl-N-valine) (N-6), all modified alpha-amino acids may be substituted by the corresponding beta-, gamma-or omega-amino carboxylic acids.

The term "amino acid" refers to a molecule containing both amino and carboxyl groups. Suitable amino acids include, but are not limited to, the D-and L-isomers of naturally occurring amino acids, as well as non-naturally occurring amino acids prepared by organic synthesis or other metabolic pathways. As used herein, the term amino acid includes, but is not limited to, alpha-amino acids, natural amino acids, unnatural amino acids, and amino acid analogs.

The term "naturally occurring amino acid" refers to any of the 20L-amino acids commonly found in peptides synthesized in nature, namely the L-isomers of alanine (Ala or A), arginine (Arg or R), asparagine (Asn or N), aspartic acid (Asp or D), cysteine (Cys or C), glutamic acid (Glu or E), glutamine (Glu or Q), glycine (Gly or G), histidine (His or H), isoleucine (Ile or I), leucine (Leu or L), lysine (Lys or K), methionine (Met or M), phenylalanine (Phe or F), proline (Pro or P), serine (Ser or S), threonine (Thr or T), tryptophan (Trp or W), tyrosine (Tyr or Y) and valine (Val or V).

A "conservative amino acid substitution" is an amino acid substitution in which an amino acid residue is replaced with an amino acid residue having a similar side chain. Families of amino acid residues with similar side chains have been defined in the art. These families include amino acids with basic side chains (e.g., K, R, H), acidic side chains (e.g., D, E), uncharged polar side chains (e.g., G, N, Q, S, T, Y, C), nonpolar side chains (e.g., A, V, L, I, P, F, M, W), beta-branched side chains (e.g., T, V, I), and aromatic side chains (e.g., Y, F, W, H). Thus, for example, it is predicted that a non-essential amino acid residue in a polypeptide is preferably substituted with another amino acid residue from the same side chain family. Other examples of acceptable substitutions are those based on isostatically considerations (e.g., norleucine for methionine) or other properties (e.g., 2-thienyl alanine for phenylalanine).

The polypeptides of the invention may be prepared using methods well known to those skilled in the art, including well known methods of chemical synthesis. Thus, when the polypeptide or derivative thereof comprises one or more non-standard amino acids, it is highly likely to be prepared by chemical synthesis. In addition to the use of chemical synthesis methods to prepare polypeptides or derivatives thereof, can also be prepared by expression of the encoding nucleic acids. This is particularly true for the preparation of polypeptides containing only natural amino acids or derivatives thereof, in which case well-known methods of preparation of nucleic acid-encoding polypeptide sequences can be used (see Sambrook etal.,Molecula r Cloning:ALa bora tory Manua l,Third Ed.,Cold Spring Ha rbor Laboratory,NewYork(2001);Ausubel et al.,Current Protocols in Molecular Biology,John Wiley and Sons,Baltimore,MD(1999)). the polypeptide can be expressed in an organism and purified by well-known purification techniques.

The term "alkylene" refers to a divalent alkyl group (i.e., -R-).

The term "alkenyl" refers to a straight or branched hydrocarbon chain having one or more carbon-carbon double bonds. The alkenyl moiety contains the indicated number of carbon atoms. For example, C2-C10 means that the group contains 2 to 10 (inclusive) carbon atoms.

The term "alkynyl" refers to a straight or branched hydrocarbon chain having one or more carbon-carbon triple bonds.

Regarding sequence identity. Sequence identity is calculated by sequence alignment according to methods known in the art. To determine the percent identity of two amino acid sequences, the sequences were aligned for optimal comparison. For example, gaps can be introduced in the sequence of the first amino acid sequence for optimal alignment with the second amino acid sequence. The amino acid residues at the corresponding amino acid positions are then compared. When a position in the first sequence is occupied by the same amino acid residue as the corresponding position in the second sequence, the molecules are identical at that position. The percent identity between two sequences is a function of the number of identical positions shared by the sequences. Thus% identity = number of identical positions/total number of overlapping positions multiplied by 100.

In this comparison, the sequences may be the same length or may be different lengths. The optimal sequence alignment for determining the comparison window can be carried out by local homology algorithms of Smith and Waterman (J.Theor. Biol., 1981), by homology alignment algorithms of Needleman and Wunsch (J.mol. Biol, 1972), by methods of Pearson and Lipman, searching for similarity (Proc. Natl. Acad. Sci. U.S.A., 1988), by computerized implementation of these algorithms (GAP, BESTFIT, FASTA and TFASTA, genetic Computer Group,575,Science Drive,Madison,Wisconsin in Wisconsin genetics software package 7.0) or, for example, using publicly available computer software such as BLAST. When such software is used, default parameters, such as gap penalties or extension penalties, are preferably used. The best alignment resulting from the various methods was selected (i.e., yielding the highest percent identity across the comparison window).

In particular embodiments, the amino acid sequence of the staple peptide has at least 90%, 93% or 95% sequence identity to SEQ ID NO. 1, and amino acid residues 1-24 of the amino acid sequence are identical to amino acid residues 1-24 of SEQ ID NO. 1.

The term "pharmaceutical composition" relates to a pharmaceutical composition comprising a therapeutically effective amount of a polypeptide of the invention and a pharmaceutically acceptable carrier or excipient. As used herein, "pharmaceutically acceptable carrier" or "pharmaceutically acceptable excipient" includes any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and physiologically compatible analogs. Examples of pharmaceutically acceptable carriers or excipients include one or more of the following: water, brine, phosphate buffered saline, dextrose, glycerol, ethanol and the like, and combinations thereof. In any case, it is preferred that it includes an isotonic agent, for example, a sugar, a polyalcohol such as mannitol, sorbitol, or sodium chloride in the composition. Pharmaceutically acceptable substances, such as wetting amounts or trace amounts of auxiliary substances, such as wetting or emulsifying agents, preservatives or buffers which enhance the shelf life and effectiveness of the antibody or antibody portion, may also be included. Optionally, a disintegrant, such as cross-linked polyvinylpyrrolidone, agar, alginic acid or a salt thereof, such as sodium alginate, may be included. In addition to excipients, the pharmaceutical composition may include one or more of the following: carrier proteins such as serum albumin, buffers, binders, sweeteners and other flavoring agents; colorants and polyethylene glycols.

Compositions may be in a wide variety of forms, for example, liquid, semi-solid, and solid dosage forms, such as liquid solutions (e.g., injectable and infusible solutions), dispersions or suspensions, tablets, pills, powders, liposomes, and suppositories. The preferred form will depend on the intended route of administration and the therapeutic application. In one embodiment, the composition is in the form of an injectable or infusible liquid, for example, similar to those used for passive immunization of humans with antibodies. In one embodiment, the mode of administration is parenteral (e.g., intravenous, subcutaneous, intraperitoneal, intramuscular), in one embodiment, the polypeptide is administered by intravenous injection or infusion. In another embodiment, the polypeptide is administered by intramuscular or subcutaneous injection.

Other routes of administration suitable for the pharmaceutical composition include, but are not limited to, rectal, transdermal, vaginal, transmucosal or enteral administration.

The "pharmaceutically acceptable salts", i.e., pharmaceutically acceptable salts, of the present invention can be synthesized from the polypeptide, basic or acidic moiety using conventional chemical methods. In general, such salts can be prepared by reacting the free acid form of these polypeptides with a stoichiometric amount of a suitable base (e.g., na, ca, mg or K hydroxide, carbonate, bicarbonate, etc.), or by reacting the free base form of these polypeptides with a stoichiometric amount of a suitable acid. Such reactions are generally carried out in water or an organic solvent or a mixture of both. Generally, it is desirable to use a non-aqueous medium such as diethyl ether, ethyl acetate, ethanol, isopropanol or acetonitrile where appropriate. In, for example, "Remington's Pharmaceutical Sciences", 20 th edition, mack Publishing Company, easton, pa., (1985); and "manual of pharmaceutically acceptable salts: a list of other suitable salts can be found in the nature, selection and application (Handbook of Pharmaceutical Salts：Properties,Selection,and Use)",Stahl and Wermuth(Wiley-VCH,Weinheim,Germany,2002).

Pharmaceutically acceptable salts may be pharmaceutically acceptable acid addition salts which may be formed by the reaction of a polypeptide of the invention with inorganic and/or organic acids, for example, salts with inorganic acids such as hydrochloric, hydrobromic, nitric, phosphoric or sulfuric acids and the like; salts with organic acids such as acetic acid, trifluoroacetic acid, propionic acid, malonic acid, oxalic acid, maleic acid, fumaric acid, malic acid, citric acid, gluconic acid, mandelic acid, tartaric acid, stearic acid, succinic acid, sulfosalicylic acid, lactic acid, benzoic acid, benzenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, toluenesulfonic acid, naphthalenedisulfonic acid, and the like.

The pharmaceutically acceptable salt may be a pharmaceutically acceptable base addition salt, which may be formed by the action of a polypeptide of the invention with an inorganic base and/or an organic base. Inorganic bases from which salts may be derived include, for example, ammonium salts and metals of groups I to XII of the periodic Table. In certain embodiments, the salt is derived from sodium, potassium, ammonium, calcium, magnesium, iron, silver, zinc, and copper; particularly suitable salts include ammonium, potassium, sodium, calcium and magnesium salts. Organic bases from which salts may be derived include primary, secondary and tertiary amines, substituted amines including naturally occurring substituted amines, cyclic amines, basic ion exchange resins, and the like. Some organic amines include, for example, isopropylamine, benzathine (benzathine), choline salts (cholinate), diethanolamine, diethylamine, lysine, meglumine (meglumine), piperazine and tromethamine.

In addition, the polypeptides disclosed herein, including their salts, may also exist in the form of their hydrates or in the form of solvents (e.g., ethanol, DMSO, etc.) containing them, and may be used for crystallization. The disclosed compounds may form solvates inherently or by design with pharmaceutically acceptable solvents (including water); thus, the compounds of the present invention include solvated and unsolvated forms.

Examples

EXAMPLE 1 preparation of Compound 4

The polypeptide compound and the derivative thereof provided by the disclosure adopt a solid phase synthesis method to synthesize a linear precursor thereof, and the target crude peptide is obtained after cutting. The synthetic vector was Fmoc-Glu (OtBu) -WANG RESIN resin. In the synthesis process, fmoc-Glu (OtBu) -WANG RESIN resin is fully swelled in N, N-Dimethylformamide (DMF), then the solid phase carrier and the activated amino acid derivative are repeatedly condensed, washed, deprotected Fmoc, washed and subjected to the next round of amino acid condensation to reach the length of the polypeptide chain to be synthesized, and finally trifluoroacetic acid is used for preparing the polypeptide chain: water: triisopropylsilane: and (2) reacting the mixed solution of the phenylsulfide (90:2.5:2.5:5:5, v: v: v) with resin to crack the polypeptide from the solid phase carrier, and settling the polypeptide by frozen methyl tertiary butyl ether to obtain a crude product of the target polypeptide. Purifying and separating the crude polypeptide in acetonitrile/water system of 0.1% trifluoroacetic acid by C-18 reversed phase preparative chromatographic column to obtain pure product of polypeptide and its derivative.

Experimental reagent

Step 1: linear precursor peptide chain synthesis

The linear precursor peptide chain of Compound 4G-K-Y-G-F-Y-A-H-V-F-R-L-K-K-W-I-Q-K-V-I-D-Q-F-G-E

320Mg (0.1 mmol) of Fmoc-Glu (OtBu) -WANG RESIN resin was fully swollen in DMF for 1h. The following linear precursor sequences were then synthesized in the order from the second G at the carboxy terminus to the amino terminus. Each coupling cycle proceeds as follows:

Fmoc-deprotection was performed twice for 8min each with 20% piperidine/DMF (20% v/v,10 mL).

DMF washing resin 6-8 times until neutral pH.

0.5Mmol Fmoc-AA,0.5mmol 6-chlorobenzotriazol-1, 3-tetramethyluronium Hexafluorophosphate (HCTU) and 1mmol 4-methylmorpholine (NMM) were dissolved in DMF and the resin was added and reacted for 1h at room temperature.

The resin was washed 4-6 times with DMF before the next amino acid coupling.

The linear polypeptide was synthesized and the resin was washed 5 times with DMF and 5 times with DCM. The resin was dried in vacuo.

Step 2: linear precursor peptide chain cleavage

Freshly prepared cut cocktail (10 mL) trifluoroacetic acid: water: triisopropylsilane: benzenothioether (90:2.5:2.5:5:, v: v: v) was added to the resin obtained in step 1, and the reaction was carried out at room temperature with shaking for 2 hours. After the reaction was completed, the reaction solution was filtered, and the resin was washed with trifluoroacetic acid, combined with the reaction solution, and precipitated with 4-fold volume of cold MTBE to obtain a crude product. The crude product was washed 3 times with MTBE and placed in vacuum for drying.

Step 3: purification preparation of polypeptides

And (3) dissolving the crude polypeptide obtained in the step (2) by using a 20% acetonitrile aqueous solution, filtering by using a 0.45 mu m membrane, and separating by using a reversed-phase high performance liquid chromatography system, wherein the buffer solution is A (0.1% trifluoroacetic acid, aqueous solution) and B (0.1% trifluoroacetic acid, acetonitrile). Wherein the chromatographic column is BR C-18 (Siro) reversed phase chromatographic column, the detection wavelength of the chromatograph in the purification process is set to 230nm, the flow rate is 15mL/min, and the gradient is 15-35% acetonitrile in 40min. And collecting the relevant fractions of the product, combining the fractions with the purity of more than 95% after HPLC identification, and freeze-drying to obtain the polypeptide pure product.

Step 4: detection and characterization method

And (3) determining the purity and the molecular weight of the compound of the polypeptide pure product in the step (3) through the combination of analytical high performance liquid chromatography and liquid chromatography/mass spectrometry.

Biological evaluation

Example 2 molecular minimum inhibitory concentration MIC functional test

The antibacterial activity of the compounds is determined by measuring the minimum inhibitory concentration MIC (Minimal inhibitory concentrations) of the molecules against E.coli ATCC 25922, staphylococcus aureus ATCC 29213 and Pseudomonas aeruginosa ATCC 27853.

The bacteria for testing the minimum inhibitory concentration are frozen in a low-temperature refrigerator at the temperature of-80 ℃ and recovered 2 days in advance when in use. Scraping a little frozen liquid bacteria by a sterile inoculating loop, streaking and inoculating on a TSA solid culture medium plate, and placing the plate into a common incubator to be cultured for about 20 hours at 35+/-2 ℃. 5-10 colonies of similar morphology were picked from the above dishes with a sterile inoculating loop and streaked again onto the corresponding solid medium plates. Then placing the mixture into a common incubator to culture for 20 hours at 35+/-2 ℃. From the solid culture dish, 5-10 bacterial single colonies were picked and resuspended in 500. Mu.l of sterile physiological saline (0.9% NaCl) and the OD 600 was adjusted to 0.15 with a spectrophotometer. Bacteria were diluted 300-fold to an inoculation concentration of-2 x 10 ⁵ CFU/ml using 1.02x camdb (containing 0.02% bsa) equilibrated to room temperature.

The candidate polypeptide was dissolved in DMSO to 3.2mg/ml stock, and twice gradient diluted with DMSO sequentially, 11 dilutions. Transfer 2. Mu.l of the polypeptide compound to the corresponding wells of the assay plate and add more than 98. Mu.l of the prepared bacterial inoculum to the assay plate. The highest detected concentration of the compound was 256. Mu.g/ml. The test plate is put into a centrifugal machine at 800rpm for 30 seconds, is vibrated for 1 minute at 400rpm on a plate vibrator, is evenly mixed, and is put into a common incubator for 20 hours at 35+/-2 ℃. The test plate was placed on a plate reader, and the reflector was adjusted to observe and record bacterial growth in each well. At the same time, each test plate was photographed with QCount system and the OD600 value of the bacteria in each well was read with SpectraMaxplus 384. The test results are shown in table 1 below:

Table 1: minimum inhibitory concentration MIC (Minimal inhibitory concentrations) of compound

As can be seen from the data in Table 1, the compound provided by the invention has better antibacterial effect on escherichia coli ATCC 25922 and staphylococcus aureus ATCC 29213, and the minimum antibacterial concentration MIC (Minimal inhibitory concentrations) on escherichia coli ATCC 25922 and staphylococcus aureus ATCC 29213 is between 4 and 128 mug/mL.

Example 3 Radial diffusion detection (Radial DiffusionAssay, RDA) functional test

The invention evaluates the antimicrobial activity of different polypeptides by measuring the diameter of the resulting inhibition zone of the molecule against E.coli ATCC 25922, staphylococcus aureus ATCC 29213 and Pseudomonas aeruginosa ATCC 27853.

The bacteria are frozen in a low-temperature refrigerator at the temperature of minus 80 ℃ and recovered 2 days in advance when in use. A small amount of frozen bacteria was scraped using a sterile inoculating loop and streaked onto TSA solid medium plates and incubated in an incubator at 35.+ -. 2 ℃ for about 20 hours. Several bacterial single colonies were individually picked from solid dishes and resuspended in 1mL of TSB and OD600 was adjusted to 1.0 using a spectrophotometer. The resuspended bacteria were re-inoculated into 10mL TSB at a ratio of 1:100 and cultured to mid-log phase at 37℃at 200 rpm. After centrifugation of the culture at 4000rpm for 10min, the supernatant was discarded and the pellet was resuspended in an equal volume of 10mM Tris buffer (pH=7.4). The OD600 was adjusted to-0.15 using a spectrophotometer. The compound to be tested is diluted to 0.8mg/mL and then is respectively used for detecting pseudomonas aeruginosa, escherichia coli and staphylococcus aureus. A bottom agar with a TSB concentration of 0.03% (W/V), a low electroosmotic agarose concentration of 1% (W/V) and a Tween-20 concentration of 0.02% (V/V) was prepared, and after autoclaving, the agar was cooled to 42-46 ℃. Bacteria with OD600 of 0.15 were added to the bottom agar in a ratio of 1:300, mixed well, poured into a petri dish and coagulated at room temperature. Using a gel punch, 9 wells of 4mm diameter were punched into the petri dish, 6. Mu.L of the test compound (0.8 mg/mL) was added to the wells as shown in FIG. 1, and incubated at 37℃for 3 hours to allow the sample to spread well into the underlying agar. Preparing top agar with TSB concentration of 6% (W/V) and low electroosmosis agarose concentration of 1% (W/V), autoclaving, cooling to 42-46 deg.C, adding 15mL of top agar into the culture dish, solidifying, and culturing at 37deg.C for about 20 hr. Wherein the agar containing Pseudomonas aeruginosa was poured onto a 15cm dish to allow the bottom agar containing bacteria to contact air, thereby allowing the bacteria to grow sufficiently. The inoculated bacteria liquid was diluted from 10 ^-1 to 10 ^-3 in sequence with liquid medium. Mu.l of the bacterial dilutions described above were spread evenly on TSA plates. After the medium was absorbed by TSA for 10 minutes, the plates were reversed and incubated in an incubator at 35.+ -. 2 ℃ for 20 hours. Each petri dish was photographed using QCount system, and the diameter of each zone of inhibition was measured and recorded. The results are shown in Table 2.

Table 2: antibacterial Activity of the Compounds- -Radial diffusion assay (Radial DiffusionAssay, RDA)

As can be seen from the data in Table 2, the compounds provided by the invention have better antibacterial effects on escherichia coli ATCC 25922, staphylococcus aureus ATCC 29213 and pseudomonas aeruginosa ATCC 27853, and the diameters of antibacterial rings on escherichia coli ATCC 25922, staphylococcus aureus ATCC 29213 and pseudomonas aeruginosa ATCC 27853 are between 5.5 and 9 mm.

Example 4 inhibition of LPS-activated TLR4 cell fluorescein reporter gene expression by polypeptide (IC 50)

The experimental cells are HEK293/TLR4/NF-kB-Luc cells (Cat: CBP 74128) produced by Nanjing department Bai biotechnology Co., ltd, and are recovered and cultured according to the cell culture requirement. The detection kit adopts One-Step Luciferase ASSAY SYSTEM (Bioscience Cat: 60690), and the reagent is prepared and used according to the instruction.

HEK293/TLR4/NF-kB-Luc cells were grown in culture (MEM, 10%FBS,1%Non-ESSENTIAL AMINO ACIDS (NEAA), 1mM Napyruvate,100 μg/ml Hygromycin B,1% Puromycin). The cell growth density reaches 80-90% of that of the culture flask, the cells are firstly rinsed by DPBS, and then digested by 0.25% pancreatin (containing 0.5mM EDTA); collecting cell suspension into a centrifuge tube, centrifuging at 1000rpm for 3min, and removing the supernatant culture medium; cells were resuspended by adding 6-8ml fresh growth medium according to 1: 3-1: the specific strain of 8 was passaged and cultured in a 5% CO ₂ incubator at 37 ℃. Liquid exchange or passaging is performed every 2-3 days after passaging.

HEK293/TLR4/NF-kB-Luc cells were passaged to the required cell numbers, and after cell digestion and resuspension, the cell suspensions were plated into 384-well white-bottomed cell culture plates at 6000 cells/well, 25. Mu.l/well, and incubated at 37℃for 4d with 5% CO ₂ for sample detection.

Determination of LPS use concentration:

Lipopolysaccharide (LPS) was dissolved at 5mg/ml in sterile water, LPS was diluted at 1X Loadingbuffer to 60 μg/ml (6X), and 3-fold gradient dilutions were sequentially performed at 1X Loading buffer for a total of 12 concentrations. Transferring 5 μl of diluted LPS solution to a 384-well white transparent cell culture plate incubated for 4d, incubating at 37 ℃ for 6h, diluting the solution A and the solution B with the Luciferase ASSAY SYSTEM reagent according to the volume ratio of 100:1 for 1h, adding 30 μl/well Luciferase ASSAY SYSTEM reagent to the cell plate, and shaking at 350rpm for 15min at room temperature and in the dark. The chemiluminescent activity was detected using an enzyme-labeled instrument Cytation, the EC80 range of LPS was 0.06-0.1 μg/ml, and the EC80 concentration was selected for the experiment.

Inhibition of LPS by polypeptide to activate TLR4 cell luciferase reporter gene:

The polypeptide was dissolved in sterile water at 500. Mu.M, diluted with 1X Loadingbuffer to a concentration of 120. Mu.M (12X), and sequentially subjected to 3-fold gradient dilution with 1X Loading buffer for a total of 7 concentrations. LPS was diluted to 1.2 μg/ml (12X) with 1X Loadingbuffer.

Taking 25 μl of polypeptide (12×) with different concentrations after gradient dilution, and mixing with 25 μl of LPS (12×) in equal volume; mu.l of polypeptide and LPS premix was added to the 384 well white background cell plates incubated for 4d and incubated for 6h at 37 ℃. The Luciferase ASSAY SYSTEM reagent was mixed with the solution A and the solution B at a volume ratio of 100:1 at 1 hour in advance, 30. Mu.l/well of the Luciferase ASSAY SYSTEM reagent was added to the above-mentioned cell plate, and the mixture was subjected to shaking at 350rpm for 15 minutes at room temperature in the dark, and the chemiluminescent activity was detected by using an enzyme-labeled instrument Cytation. The specific values are shown in Table 3 (wherein the IC50 value of TCP-25 is 6.81.+ -. 1.4. Mu.m).

Table 3: inhibition of LPS-activated TLR4 cell fluorescein reporter gene expression (IC 50) by the compound

As can be seen from Table 3, the compounds of the present invention have remarkable anti-inflammatory effects compared with the positive group (TCP-25), the IC50 value is remarkably lower than that of the positive control group, and the activity multiple is 1.18-1.74 times higher than that of the positive control group.

While the preferred embodiments of the present application have been described in detail, the present application is not limited to the embodiments described above, and various equivalent modifications and substitutions can be made by those skilled in the art without departing from the spirit of the present application, and these equivalent modifications and substitutions are intended to be included in the scope of the present application as defined in the appended claims.

Claims

1. A polypeptide, characterized in that the amino acid sequence of the polypeptide is Seq ID No. 1.

2. A pharmaceutical composition comprising the polypeptide of claim 1.

3. The pharmaceutical composition of claim 2, further comprising a pharmaceutically acceptable carrier.

4. Use of the polypeptide of claim 1 or the pharmaceutical composition of claim 2 or 3 in the manufacture of a medicament for the prevention or treatment of infectious diseases of a bacterium selected from at least one of escherichia coli, staphylococcus aureus or pseudomonas aeruginosa.

5. The use according to claim 4, wherein the bacterium is selected from at least one of escherichia coli ATCC 25922, staphylococcus aureus ATCC 29213 and pseudomonas aeruginosa ATCC 27853.