ACTIVE PEPTIDE FOR INHIBITING AMPA RECEPTOR AND PREPARATION METHOD AND USE THEREOF
20180094028 ยท 2018-04-05
Inventors
- Muyi Cai (Beijing, CN)
- Huaiyu Gu (Beijing, CN)
- Jun Lu (Beijing, CN)
- Xingchang Pan (Beijing, CN)
- Yong Ma (Beijing, CN)
- Liang Chen (Beijing, CN)
Cpc classification
C07K1/34
CHEMISTRY; METALLURGY
C07K1/36
CHEMISTRY; METALLURGY
C12P21/06
CHEMISTRY; METALLURGY
International classification
Abstract
Provided is an active peptide for inhibiting an AMPA receptor and a preparation method and use thereof. The method for preparing the active peptide comprises the following steps: 1) soaking a salmon skin and crushing, adding water and beating, and then adjusting pH to 6.5-7.5; 2) subjecting to a first enzymolysis using a neutral protease; 3) subjecting to a second enzymolysis using papain enzyme and then inactivating enzyme; and 4) centrifuging the enzymatic hydrolysate, and then subjecting the centrifuged supernatant to membrane filtration, concentration and decoloration, to prepare the active peptide. The active peptide contains a tetrapeptide with an amino-acid sequence of Glu-Gly-Ala-Arg. The tetrapeptide has good solubility, can selectively inhibit neuronal synaptic transmission caused by an AMPA receptor, and has a significant antiepileptic effect.
Claims
1. A method for preparing an active peptide, comprising the following steps: 1) soaking a salmon skin and crushing, adding water and beating, and then adjusting pH to 6.5-7.5, to obtain a slurry; 2) subjecting the slurry to a first enzymolysis by using a neutral protease, to obtain a first enzymatic hydrolysate; 3) subjecting the first enzymatic hydrolysate to a second enzymolysis by using papain enzyme and then inactivating enzyme, to botain a second enzymatic hydrolysate; and 4) centrifuging the second enzymatic hydrolysate, and then subjecting the centrifuged supernatant to membrane filtration, concentration and decoloration, to prepare the active peptide; wherin the active peptide contains a tetrapeptide with an amino-acid sequence of Glu-Gly-Ala-Arg.
2. The method according to claim 1, wherein an alkaline solution with a mass content of 0.1-0.5% is used to soak the salmon skin, a mass/volume ratio of the salmon skin to the alkaline solution is controlled to 1:(2-4), and soaking time is 5-20 h.
3. The method according to claim 1, wherein the amount of the neutral protease is 50-500 U/g, and the amount of the papain is 100-1000 U/g, and an amount ratio of the neutral protease to the papain is 1:(1-3).
4. The method according to claim 1, wherein a temperature of the first enzymolysis is controlled to 30-60 C., time of the first enzymolysis is 4-6 h, and a temperature of the second enzymolysis is controlled to 30-60 C., and time of the second enzymolysis is 1-3 h.
5. The method according to claim 3, wherein a temperature of the first enzymolysis is controlled to 30-60 C., time of the first enzymolysis is 4-6 h, and a temperature of the second enzymolysis is controlled to 30-60 C., and time of the second enzymolysis is 1-3 h.
6. The method according to claim 1, wherein the membrane filtration is proceeded with a ceramic membrane with a pore diameter of 50-1000 nm.
7. The method according to claim 1, further comprising: separating and purifying the active peptide by using a reversed phase high performance liquid chromatography, to obtain the tetrapeptide with an amino acid sequence of Glu-Gly-Ala-Arg.
8. An active peptide prepared according to the method of claim 1.
9. A tetrapeptide for inhibiting an AMPA receptor, wherein the tetrapeptide has an amino acid sequence of Glu-Gly-Ala-Arg.
10. Use of the active peptide of claim 8 in preparation of an antiepileptic food or drug.
11. Use of the tetrapeptide for inhibiting an AMPA receptor of claim 9 in preparation of an antiepileptic food or drug.
12. A method for treating epilepsy, comprising administrating to an epileptic patient a drug containing a therapeutically effective amount of a tetrapeptide with an amino acid sequence of Glu-Gly-Ala-Arg.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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DETAILED DESCRIPTION
[0034] To make objects, technical solutions and advantages of the present application more clear, technical solutions in examples of the present application will be clearly and completely described with reference to drawings and the examples of the present application. Obviously, the examples described are part of examples of the present application, rather than all examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative work belong to the protection scope of the present application.
[0035] Raw materials used in each example of the present application and sources thereof are as follows: Neutral protease: from Novozymes biotechnology Co., Ltd; [0036] TTX, PTX, CNQX, APV, NMDA, and AMPA: from TOCRIS Bioscience; [0037] Papain, PTZ: From Sigma Aldrich; and [0038] Synthetic EGAR: from Shanghai Qiang Yao Co., Ltd.
EXAMPLE 1
Preparation of an Active Peptide
[0039] 1. Preparation of the Active Peptide
[0040] 5 kg of salmon skin is settled to a volume of 15 L by NaOH solution with a mass content of 0.2%, soaked for 12 h at normal temperature, and drained. The salmon skin is crushed, and beaten with deionized water that is 5 times salmon skin weight, and after pH is adjusted to 7.0, a slurry is obtained.
[0041] Neutral protease is added to the above slurry in an amount of 0.1% (i.e. 400 U/g salmon skin), and is subjected to enzymolysis for 5 hours at 50 C. Then papain is added to enzymatic hydrolysate in an amount of 0.2% (i.e. 400 U/g salmon skin), and the enzymolysis is continuously proceeded for 2 h at 60 C. After completion of the enzymolysis, enzyme inactivation is proceeded for 10 minutes at 100 C.
[0042] The enzymatic hydrolysate is centrifuged after the enzyme inactivation, and the centrifuged supernatant is subjected to membrane filtration by using a ceramic membrane (from Xiamen Starmen) with a pore diameter of 200 nm, clear liquid obtained after membrane filtration is concentrated to a concentration of 30 Baume by using R-151 concentrator (from BUCHI, Switzerland), then an activated carbon is added to the concentrated solution in an amount of 20%, to decolorize at 55 C. for 1 hour. After filtering to remove the activated carbon, the clear liquid is spray-dried, to obtain 620 g of active peptide.
[0043] 2. Structural Identification of the Active Peptide
[0044] The active peptide prepared as above is diluted to a concentration of 2 mg/mL with deionized water, a gradient elution is performed using RP-HPLC (XBridge BEH130, 4.6*250 nm, Waters company, US). Elution conditions are as follows: [0045] Mobile phase A: V(water):V(trifluoroacetic acid)=100:0.1; [0046] Mobile phase B: V(acetonitrile):V(water):V(trifluoroacetic acid)=80:20:0.1; [0047] Detection wavelength: UV220 nm; [0048] Flow velocity: 0.6 mL/min; [0049] Column temperature: 32 C.; [0050] Injection volume: 50 L; [0051] Gradient program: 0-10 min, mobile phase B: 0%-5%; 10-20 min, mobile phase B: 5%-5%; 20-35 min, mobile phase B: 5%-9%; 35-45 min, mobile phase B: 9%-13%;
[0052] 45-60 min, mobile phase B: 13%-13%; 60-70 min, mobile phase B: 13%-70%; and 70-90 min, mobile phase B:70%-70%.
[0053] As shown in
TABLE-US-00001 TABLE 1 Polypeptide sequence in each component Component No. Polypeptide sequence 1 WYN, NTTM, NGGGGS, PALH 2 AGGP, QK, MADT, NK, NPR 3 TQ, RGF, NAGK, SR, QGAK 4 YSAP, DAGK, GR, SSP, KR, AK, GGH, DSGDG 5 AGPS, GAAGR, AP, VDGK, RER 6 PQ, GPR, GPQG, TGVE, ARGGK, EGAR 7 VR, LN, VTGK, GHAGE, VGGK, GHGR 8 SPGAG, FTE, AGGPLG, TGGPK, GAGGMT 9 AAGPGL, VEKEKH, TGPK, LQ 10 SGGE, NVG, GPAG, PNH, PH 11 VL, LIE, TPT
EXAMPLE 2
Molecular Dynamic Simulation Test
[0054] AMBER11 simulation suite is used for molecular dynamic simulation and data analysis. Full atom point charge force field (AMBER FF03) shows a good balance between the results of -helix and -sheet and is used to describe a peptide. Aqueous solvent is expressly represented by TIP3P model. Parameters generated by EGAR are as follows: after geometry optimization, electrostatic potential of EGAR is obtained at HF/6-31G**level. Part of charges is derived from use of a restricted electrostatic potential (RESP) method to match gas phase electrostatic potential, and other mechanical parameters of EGAR molecule are taken from AMBER GAFF parameter set. The missing interaction parameters in the ligand are generated using antechamber tools in AMBER. The system is firstly minimized using steepest descent algorithm in 2000 steps, and then is subjected to MD simulation of 5 nanoseconds by using NPT entirety. Pressure is coupled to 1 bar with 1.0 ps anisotropic connection time, and the temperature during simulation is maintained at 300K with 0.1 PS coupling time. Long-range electrostatic is calculated with the particle mesh Ewald Method (PEM). SHAKE is used to limit a hydrogen atom-connecting bond, so that time step is 2.0 fs in simulation. Two fixed points, 0.8 nanometers and 1.2 nanometers, are used to evaluate non-bonded interaction respectively. Then, binding energy at 300K is estimated by using MM-GBSA. CPU of 192 AMD Opteron (tm) processor (2.0 GHz) is used for the above calculation.
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[0056] The above results show: EGAR can stably bind to an AMPA receptor.
EXAMPLE 3
Animal Experiment
[0057] This animal experiment protocol is approved by the animal care and use committee of Zhongshan University, and meets the experimental animal usage criteria of national health mechanism.
[0058] 1. Reagents, Animals and Materials
[0059] ACSF: containing 124 mM sodium chloride, 2.5 mM potassium chloride, 2 mM calcium chloride, 2 mM magnesium chloride, 1.25 mM sodium dihydrogen phosphate, 26 mM sodium bicarbonate and 10 mM glucose; and saturated to pH 7.2-7.4 with 95% O.sub.2/5% CO.sub.2.
[0060] C57BL/6 mice: 2-3 weeks old, 15-20 grams, each captive in a cage at 20-22 C., free access to food and water, and kept in an environment of 12 hour light/dark cycle.
[0061] EGAR solution: a synthetic EGAR freeze-dried powder is dissolved in 115 L of distilled water to be used as a stock solution, and during experiment the stock solution is diluted with the above AXSF to EGAR solutions with final concentrations of 100 M, 50 M, 20 M, and 1 M respectively for use.
[0062] Internal liquid: containing 140 mM potassium gluconate, 5 mM sodium chloride, 1 mM calcium chloride, 2 mM MgATP, 10 mM EGTA and 10 mM HEPES, pH 7.2-7.4, being subject to aseptic filtration before recording.
[0063] External liquid: containing 140 mM sodium chloride, 5 mM potassium chloride, 1.5 mM calcium chloride, 1 mM magnesium chloride, 10 mM HEPES and 10 mM glucose, pH 7.2-7.4; being subject to aseptic filtration before recording.
[0064] 2. Preparation of Brain Tissue
[0065] Hippocampus is taken from a C57BL/6 mouse to do whole-cell recording. The mouse is deep narcotized with 20% urethane before being decollated, then its brain is rapidly removed and immersed in ice-cold ACSF, then the brain is trimmed, and fixed onto a vibration slicer (Leica VT1000A, Germany) to be cut into coronal slices of 350 microns. The slices are incubated with ACSF for at least 1 hour at room temperature before recording.
[0066] 3. Electrophysiological Experiment
[0067] The slices of the hippocampus are transferred to an underwater recording room (Warner instrument). In the recording room, the slices are continuously perfused with ACSF at a speed of 3ml/min, and whole-cell records of neurons of CA1 region of the hippocampus are performed by those experimenters who are not distinguished between a control group and a treated group. The neurons are identified through morphological recognition using an infrared ray differential interference phase-contrast microscope (BX51W, Olympus, Japan). A borosilicate microtube of 1.5 mm (external diameter)0.86 mm (internal diameter) is drawn via a flame Brown electrode drawing instrument (P-97, Sutter instrument) using a 4 stage drawing scheme, to form a recording electrode with a resistance between 6-9 megohms. The recording electrode for recording is filled with above-mentioned internal liquid, and a whole-cell recording is proceeded by using above-mentioned external liquid.
[0068] Bipolar polytetrafluoroethylene insulated iridium is used to perform a voltage-clamp recording of excitatory postsynaptic currents (EPSCs), and platinum microelectrode (AM system) is induced at a frequency of 0.0167 Hz. Records are taken by a Multiclamp 700B amplifier, filtered at 10 kHz, sampled at 200 microseconds, and recorded to a personal computer by using pClamp10.2 software, and then analyzed by using Axon Digidata 1440A and pClamp10.2 (Molecular Devices).
[0069] Experiments mentioned below are carried out respectively, and the results are represented by an average valueS.E.M. In addition to data analysis of cumulative probability by the means of K-S test, statistical analyses of biological data are all performed by using T-test. All the statistical analyses are done by using SPSS 13.0 software.
[0070] (1) EPSCs of slices treated by EGAR are recorded, while EPSCs of slices without EGAR treatment is as contrast, and 10 M of PTX is added into the external liquid to separate mEPSCs out.
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[0072] The above results show: in isolated hippocampal slices experiment, a certain concentration of EGAR can inhibit excitatory postsynaptic current (EPSC) and micro excitatory postsynaptic current (mEPSC).
[0073] (2) after blocking components of NMDA receptor-mediated EPSCs by adding 50 M of D-APV to ACSF and blocking AMPAR-mediated EPSCs by adding 10 M of CNQX to ACSF, remaining EPSCs of both them are also recorded. 10 M of PTX is added in external liquid to isolate mEPSCs. After 10 M of CNQX and 20 M of EGAR and also 50 M of D-APV(an antagonist of NMDA receptor) and 20 M of EGAR are added to ACSF, mEPSCs are also recorded. By adding 10 M of CNQX or 50 M of D-APV to ACSF, NMDAR-mediated or AMPAR-mediated mEPSCs are isolated.
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[0075] The above results show: EGAR can selectively inhibit AMPAR-mediated excitatory postsynaptic current (EPSC).
[0076] (3) With regard to a NMDAR-mediated current record, 100 M of NMDA is added into the above-mentioned external liquid; and with regard to an AMPAR-mediated current record, 20 M of AMPA is added into above-mentioned external liquid.
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[0078] The above results show: EGAR can selectively inhibit AMPA-mediated micro excitatory postsynaptic current (mEPSC).
[0079] (4) With regard to records of currents induced by NMDA, 100 M of NMDA is added into above-mentioned external liquid; with regard to records of currents induced by AMPA, 20 M of AMPA is added into above-mentioned external liquid.
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[0081] The above results show: EGAR can selectively inhibit a current induced by AMPA.
[0082] (5) In an experiment of nominal zero magnesium, magnesium ions are replaced by sodium ions with the same osmotic concentration.
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[0084] The above results show: EGAR can inhibit epilepsy-like discharge of a hippocampal neuron inducted by a low magnesium external liquid.
[0085] (6) Effect of EGAR on electrophysiological properties of a neuron, and the results are shown in Table 2.
TABLE-US-00002 TABLE 2 Effect of EGAR on electrophysiological properties of a neuron 20 uM of EGAR Control group treated group Resting potential, mV 68.57 2.16 65.57 1.23 Input resistance, M 163.71 7.29 164.57 9.96 Membrane capacitance, pF 20.64 0.79 19.07 0.67 Amplitude, mV 89.43 0.2 87.61 1.18 Action potential half width, ms 0.95 0.01 0.99 0.01 Frequency, Hz 14.11 3.84 13.53 2.42 Threshold potential, mV 46.26 0.5 45.61 0.2
[0086] The results of table 2 show: EGAR has no significant effect on electrophysiological parameters of a CA1 neuron.
[0087] 4. Model of PTZ-Induced Epilepsy Seizure
[0088] In order to determine anticonvulsive effect of EGAR, the degree of epilepsy after EGAR treatment is evaluated for the model of PTZ-induced epilepsy seizure. EGAR is injected into animals earlier 30 minutes than PTZ. The animals are randomly divided into 4 groups, and each group has 10 animals. 4 groups are given EGAR at 0, 1, 10 and 100 mg/kg respectively. All animals are intraperitoneally injected with PTZ at a dose of 55 mg/kg, and this dose can produce clonic seizures in all control animals.
[0089] Behaviors of mice are observed for 30 minutes immediately after PTZ injection. Two well-trained observers who do not know previous results analyze the behaviors of mice. Mice are placed in a transparent plastic cage, and are observed for 30 minutes. The cage is thoroughly cleaned by using wet/dry cloth and any olfactory clue is removed with 70% ethanol. Animals that show rampage and forelimb clonus or more serious behavior (rampage, clonus and fall down) are considered to be epilepsy in mouse brain edge. Epilepsy seizure is scored according to the following criteria: 0, no response; 1, immobile; 2, taste movement and grasping; 3, tremor; 4, head shaking; 5, rampage and forelimb clonus; 6, rampage, clonus and fall down; 7, death.
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[0091] The above results show: in a behavioral experiment, EGAR can mitigate tic symptom of PTZ-inducted mouse epilepsy and extend the preclinical period of epilepsy seizure.
[0092] Finally it should be noted that: the above examples are merely illustrative of technical solutions of the present application, rather than to be limiting thereof; although the present application is described in detail with reference to foregoing examples, those skilled in the art shall understand: the technical solution described in foregoing examples can also be modified, or equivalently replaced with respect to part or all technical features therein; however, these modifications or replacements will not make essence of corresponding technical solutions depart from scope of the technical solutions of the examples of the present application.