as a result of extensive research , the present inventors revealed that a polypeptide of a thioredoxin family ( trxs ) bonds directly with a macrophage migration inhibitory factor ( mif ) having inflammatory effect , as its new function . based on the study , the inventors conclude that trxs is useful to select the substances affecting the bond between mif and trxs , and the present invention is completed . hereinafter , an embodiment of the screening method according to the present invention will be explained in detail . the screening method of the present invention selects a substance to strengthen a bond between trxs and mif . ( a ) mixing a binding substance such as trxs ( to be described in detail below ) with a test substance ; ( c ) monitoring a bond state between the binding substance mixed with test substance and mif to be compared to a bond state between a sole binding substance ( without being mixed with the test substance ) and mif . as a result of the analysis , if the bond between the binding substance mixed with test substance and mif is stronger than the bond between a sole binding substance ( without being mixed with the test substance ) and mif , the test substance strengthens the bond between the binding substance and mif . the binding substance ( such as trxs ) bonds with mif , and inhibits mif activity as a mif inhibitor . the selected substance which strengthens the bond between the binding substance and mif remarkably exhibits the effect of the binding substance as a mif inhibitor . various peptides , lipids , and sugar chains may be used for the test substance . it was confirmed with the screening method of the present invention that nitrosoglutathione and prostaglandin i2 strengthen the bond between trxs and mif . therefore , the composition comprising at least one selected from nitrosoglutathione or prostaglandin i2 is preferably used to strengthen the bond between trxs and mif . also , prostaglandin j2 ( pgj2 ) family , hyaluronan , s_nitrosylation , glutathionylation , and the like may be used . molecular interaction analysis ( biacore ) utilizing surface plasmon resonance ( spr ) phenomenon may be used for the method in order to confirm the bond state between the binding substance and mif . this anaysis enables to monitor the molecular interaction in real time without any labels . for the molecular interaction analysis , mif is immobilized in a sensor chip as a ligand , and the mixture of the binding substance ( such as trxs ) and the test substance is used as an analyte to analyze the bond state ( interaction ) between the binding substance mixed with the test substance and mif . thus , the analysis result is compared with the bond state between the binding substance without being mixed with the test substance and mif to screen the test substance . the binding substance of the present invention indicates following ( 1 ) to ( 4 ). the following ( 1 ) to ( 4 ) may be used alone or in combination : ( 2 ) a polypeptide having trxs amino acid sequence in which one or more amino acid is deleted , replaced or added , and having the equivalent activity to trxs ; the equivalent activity to the polypeptide belonging to the thioredoxin family ( trxs ) means the activity which enables to bond directly with mif . trxs is polypeptides having oxidoreduction activity of dithiol or disulfide bond , and originally existing in cellular organisms ( see jp2002 - 179588 ). trxs of the present invention includes not only natural polypeptides extracted from animals including human , plants , escherichia coli , yeast , and the like , but also polypeptides extracted from yeast or escherichia coli by gene recombination or polypeptides produced by the chemical synthesis . however , polypeptides originally derived from human , polypeptides produced by gene recombination in escherichia coli or yeast based on the human origin polypeptide , or synthetic peptide having the same or analogous sequence as the human origin polypeptide may be preferably used in view of less effect on the biological body . trxs has an active site including cysteine residues (- cys - x1 - x2 - cys -: x1 and x2 represent any amino acid residue , respectively , and may be same or different ), and it is a molecular group having a similar three - dimensional structure . in addition to the above , trxs of the present invention may include trxs in which partial amino acid is deleted or replaced as well as trxs fused with other amino acid or peptide , as far as keeping oxidoreduction activity of dithiol or disulfide bond . for specific examples of the active site , - cys - gly - pro - cys -, cys - pro - tyr - cys -, - cys - pro - his - cys - and cys - pro - pro - cys - are exampled . among them , - cys - gly - pro - cys - is preferably used because the sequence is well preserved over species , and experimental results of mouse model are reliably applied to human . for trxs , in particular , thioredoxin ( trx ) and glutaredoxin of which active sites are - cys - gly - pro - cys - are used . thioredoxin ( trx ) may be derived from human , escherichia coli , or yeast , and glutaredoxin may be derived from human or escherichia coli . here , human thioredoxin derived from human ( htrx ) is a polypeptide consisting of 105 amino acid shown in the sequence number 1 . the base sequence of htrx is shown in the sequence number 2 . the specific methods for extracting trxs from human cells are shown below . ( a ) a method for extracting trxs from human - derived cell strains ( see jp1 - 85097 ) a modified trx based on the human thioredoxin of the sequence number 1 produced by known genetic engineering procedures may be used , as far as keeping the ability for bonding directly with mif . the modified trx may include trx in which one or more amino acid except at 32 and 35 positions of the sequence number 1 , preferably except at 32 to 35 positions , is replaced , deleted , added or inserted . polypeptide belonging to the above thioredoxin family ( trxs ) may be used in single kind of peptide or more than two kinds of peptides . further , the polypeptide described in ( 1 ) and ( 2 ) in cells may be produced to use the coding genes described in ( 3 ) and ( 4 ). next , mif used in the screening method of the present invention will be explained below . mif exists in various animal species including humans . it is a 12 . 3 - kda protein consisting of 115 amino acid residues shown in the sequence number 3 , and has a redox active domain : cys - x - x - cys - motif ( x may be any amino acid ) in the molecule . therefore , it belongs to the thioredoxin family . mif is expressed in not only lymphocytes but also various organs such as brain and kidney . it is strongly expressed in uriniferous tubular epithelial cells in the kidney , and also expressed in actively proliferating basal membrane cells in skin and cornea . mif - expression cells and tissues may include t cells , monocytes / macrophages , dendritic cells , mesangial cells , uriniferous tubular epithelial cells , corneal epithelial cells , hepatocytes , ova , sertoli cells , keratinocytes , osteoblasts , synovial cells , adipocytes , astrocytes , cancer cells , mucosa and pituitary . the present invention is not to be limited in scope by the followings . the binding substance ( such as trxs ) bonds directly with mif having inflammatory effect so as to reduce mif activity and inhibit the inflammation caused by mif ( and fibrosis caused by the inflammation ). for details , it is considered that the binding substance ( such as trxs ) bonds directly with the redox active domain of mif in order to inhibit the mif activity . the binding substance ( such as trxs ) inhibits the cell internalization ( incorporation ) of mif so as to reduce the inflammation caused by mif ( and fibrosis caused by the inflammation ). the screening method of the present invention allows to select the substance which strengthens the bond between the binding substance ( such as trxs ) and mif . therefore , the screening method of the present invention enables to seek the substance which further strengthens the effect of the binding substance ( such as trxs ) on mif . hereinafter , the present invention will be specifically explained referring to the examples below , but it is not limited to these examples . confirmatory experiment of the bond between trx and mif in cells the bonds between trx and mif in atl2 cells and hl60 cells were confirmed with an immunoprecipitation method ( to be described in detail below ). atl2 cells ; human adult t - cell leukemia cell strain ( see publication jp62 - 19532 , tagaya , y ., y . maeda , a . mitsui , n . kondo , h . matsui , j . hamuro , n . brown , k . arai , t . yokota , h . wakasugi , et al 1989 . embo j . 8 : 75 ) hl60 cells ; human acutepromyelocytic leukemia cell strain ( provided by dr . yodoi junji , institute for virus research in kyoto university ) the cells were cultured with rpmi 1640 ( sigma inc .) medium containing 10 % fcs , 100 u / ml penicillin and 100 μg / ml streptomycin in a 175 cm 2 flask . 1 × 10 7 ˜ 8 / cell of the cells were collected and centrifugated at 1 , 000 rpm and 4 ° c . for 15 minutes . the obtained precipitation was dissolved with lysis buffer and left on the ice for 30 minutes . the solution was centrifugated at 1 , 000 rpm and 4 ° c . for 15 minutes . the obtained supernatant was used for the immunoprecipitation experiment . the concentration of the protein was measured with dc protein assay kit ( bio rad inc .). 20 μl protein g sepharose and 500 μg of the cell solution were added to a microtube , and phosphate buffer was used to adjust the amount to 1 ml . the obtained solution was reacted at 4 ° c . for 3 hours with a small rotary incubator . the cell solution was centrifugated at 15 , 000 rpm and 4 ° c . for 2 minutes . the obtained supernatant was added to a new microtube , and 20 μl protein g sepharose and 4 μg / ml anti mif antibody were also added thereto . for a control , anti rabbit antibody was used instead of the anti mif antibody . the reaction was carried out with a small rotary incubator at 4 ° c . for overnight . the reaction solution was centrifugated at 15 , 000 rpm and 4 ° c . for 2 minutes . the precipitation was washed with washing buffer ( 50 mm tris - hcl ( ph7 . 5 ), 150 mm nacl , 0 . 1 % np40 ). the precipitation added to sds - page sample buffer was provided to 15 % sds page gel . after the cataphoresis , a western blotting was performed ( with the anti trx antibody ) ( adf11 antibody ) to confirm the bond ( fig1 ). fig1 shows that trx bonds directly with mif in both atl2 cells and hl60 cells . the bond between trx and mif outside atl2 cells was confirmed with an immunoprecipitation method . ( see publication jp62 - 19532 , tagaya , y ., y . maeda , a . mitsui , n . kondo , h . matsui , j . hamuro , n . brown , k . arai , t . yokota , h . wakasugi , et al 1989 . embo j . 8 : 75 ) 1 × 10 5 / cell of the atl2 cells were cultured with rpmi 1640 ( sigma inc .) medium containing 100 u / ml penicillin and 100 μg / ml streptomycin in a 175 cm 2 flask for 3 days . then , the medium was collected and centrifugated at 10 , 000 rpm and 4 ° c . for 15 minutes . then , fcs was added to the obtained supernatant to adjust the final concentration to 10 %, and the solution was concentrated with amicon ultra - 4 . the obtained concentrated - solution was used for the immunoprecipitation experiment . 20 μl protein g sepharose and 30 μl of the culture supernatant were added to a microtube , and phosphate buffer was used to adjust the amount to 1 ml . the obtained solution was reacted at 4 ° c . for 3 hours with a small rotary incubator . the cell solution was centrifugated at 15 , 000 rpm and 4 ° c . for 2 minutes . the obtained supernatant was added to a new microtube , and 20 μl protein g sepharose and 4 μg / ml of the anti mif antibody were also added thereto . for a control , anti rabbit antibody was used instead of the anti mif antibody . the reaction was carried out with a small rotary incubator at 4 ° c . for overnight . the reaction solution was centrifugated at 15 , 000 rpm and 4 ° c . for 2 minutes . the precipitation was washed with washing buffer ( 50 mm tris - hcl ( ph7 . 5 ), 150 mm nacl , 0 . 1 % np40 ). the precipitation added to sds - page sample buffer was provided to 15 % sds page gel . after the cataphoresis , a western blotting was performed ( with the anti trx antibody ) ( adf11 antibody ) to confirm the bond ( fig2 ). fig2 shows that trx bonds directly with mif outside atl2 cells . mif is internalized ( incorporated ) into cells by the autocrine or paracrine action to induce the production of inflammatory cytokine tnf - alpha ( α ) or il - 1 . thus , the effects of trx on the cell internalization of mif were examined to clarify the inflammation response control mechanism . recombinant mif ( rmif ); his - tagged recombinant mif was expressed in escherichia coli by using expression vector pqe30 ( qiagen inc . ), and column - purified with magnehis ™ protein purification system ( promega corp .). atl2 cells were cultured with rpmi 1640 medium containing 10 % fcs , 100 u / ml penicillin and 100 μg / ml streptomycin in a 75 cm 2 flask . 1 × 10 6 / cell of atl2 cells were added to a 24 well plate . rtrx having the final concentration of 0 to 250 μg / ml and 25 μg / ml rmif were also added thereto , and cultured under the condition of 0 . 5 % co 2 at 37 ° c . for 24 hours . after cells were collected , the precipitation was mixed with sds - page sample buffer , and then electrophoresed on a 15 % sds - page gel . after the electrocataphoresis , a western blotting was performed to detect mif internalized in the cells with anti his - tagged antibody . the change of the band by the western blotting was analyzed with a densitometer . the result is shown in fig3 . fig3 shows that trx inhibits the internalization of mif into the atl2 cells . this means that trx inhibits the internalization of mif into cells so as to reduce the inflammatory response . trx &# 39 ; s inhibition of mif activity was confirmed by measuring a concentration of inflammatory cytokine tnf - α ( to be described in detail below ). raw 264 . 7 cells ; mouse - derived macrophage cell strains ( provided by dr . ishii yasuyuki , riken , research center for allergy and immunology ) raw 264 . 7 cells were cultured with rpmi 1640 medium containing 10 % fcs , 100 u / ml penicillin and 100 μg / ml streptomycin in a 75 cm 2 flask . raw 264 . 7 cells were added to a 24 well plate ( 1 × 10 6 / cell ). mif having a final concentration of 10 ng / ml and 0 to 500 ng / ml trx were also added thereto , and left under the condition of 5 % co 2 at 37 ° c . for 4 hours . further , 100 ng / ml of lps was added to the plate ( described as lps (+)), and the plate was left under the condition of 5 % co 2 at 37 ° c . for 4 hours . then , the medium was collected . amount of the generated tnf - alpha ( α ) was measured with duo set elisa development system mouse tnf - α kit . the measuring method was based on the protocol attached to the kit . the measurement result is shown in fig4 . fig4 shows that rtrx inhibits the activity of rmif depending on the concentration of rtrx , and inhibits the production of mif - derived tnf - alpha , which is an inflammatory cytokine . from the results shown in the above examples 1 to 3 , it is found that trx bonds directly with mif to inhibit the transfer of mif into cells . the result of the example 4 shows that the polypeptide of the thioredoxin family inhibits the internalization of mif into cells . this results in inhibiting the production of tnf - alpha and the inflammatory response . thus , trx is effective for widely various disorders caused by mif . the bond between trx and mif was confirmed with a molecular interaction analysis ( biacore ) ( hereinafter , referred to as “ molecular interaction analysis ”) utilizing surface plasmon resonance ( spr ) phenomenon . recombinant mif ( rmif ); his - tagged rmif was expressed in escherichia coli by using expression vector pqe30 ( qiagen inc . ), and column - purified with magnehis ™ protein purification system ( promega corp .). recombinant trx ( rtrx ); his - tagged rtrx was expressed in escherichia coli by using expression vector pqe80l ( qiagen inc . ), and column - purified with magnehis ™ protein purification system ( promega corp .). rmif was immobilized in a cm5 sensor chip as a ligand . the ligand was adjusted to include mif less or equal to 200 nm by using running buffer , 10 mm hepes ( ph7 . 4 ), 150 mm nacl , 3 mm edta and 0 . 005 % tween 20 . then , rtrx was used as an analyte to analyze the interaction between rtrx and rmif . the concentration of rtrx was changed to 2 μm , 4 μm , 6 μm , 8 μm , 10 μm and 12 μm for the analysis . fig5 shows the molecular interaction analysis result of example 5 . as shown in fig5 , the surface plasmon resonance phenomenon increases depending on the concentration of rtrx . this shows that the bond between rtrx and rmif is concentration - dependent . also , the experiment with the same method for using a sensor chip nta ( ni - histag ) showed the same result . it was confirmed with a molecular interaction analysis whether the cysteine residues at 32 and 35 positions ( the active site of trx ) affect the bond between trx and mif or not . rdm trx ; ( the rtrx of example 5 in which the cysteine residues at 32 and 35 positions were converted to serine ) rc35s trx ; ( the rtrx of example 5 in which the cysteine residue at 35 position of the rtrx was converted to serine ) rmif was immobilized in a cm5 sensor chip as a ligand , wherein the concentration of rmif was adjusted to less than or equal to 200 nm . then , rwt trx , rdm trx and rc35s trx were used as analytes to analyze the interaction between these rtrx and rmif in both oxidation and reduction states , respectively . in the oxidation state , running buffer , 10 mm hepes ( ph7 . 4 ), 150 mm nacl , 3 mm edta and 0 . 005 % tween 20 were used to adjust the ligand . in the reduction state , 1m dtt was used in addition to the running buffer , 10 mm hepes ( ph7 . 4 ), 150 mm nacl , 3 mm edta and 0 . 005 % tween 20 to adjust the ligand . fig6 shows the result of the molecular interaction analysis of example 6 . tables 1 and 2 show the dissociation constant value ( kd value ) calculated from fig6 . table 1 shows kd values of rtrx and rmif in the oxidation state . table 2 shows kd values of rtrx and rmif in the reduction state . as shown in fig6 and tables 1 and 2 , it was confirmed that all of rwt trx , rdm trx and rc35s trx bonded directly with rmif . in particular , the bond between rmif and rc35s trx was stronger than the bond between rwt trx or rdm trx and mif . it was also confirmed that rwt trx and rdm trx showed almost no changes in the dissociation constant values in both the oxidation state and the reduction state , and rc35s trx showed the strong bond with rmif in the oxidation state . this shows that the trx active site cys - gly - pro - cys ( at 32 to 35 positions ) includes a part with redox dependency and a part without redox dependency . [ screening experiment of a molecular affecting the bond between trx and mif ] for several test substances , it was confirmed with a molecular interaction analysis whether they strengthened the bond between trx and mif or not . rmif was immobilized in a cm5 sensor chip as a ligand . the ligand was adjusted to have the rmif concentration of less or equal to 200 nm by using running buffer , 10 mm hepes ( ph7 . 4 ), 150 mm nacl , 3 mm edta and 0 . 005 % tween 20 . then , n - acetylglucosamine , nitrosoglutathione and prostaglandin i2 were mixed with rtrx , respectively , to form three types of analytes . in each analyte , the concentration of rtrx was 5 μm and the concentration of the test substance was 500 μm . for prostaglandin i2 , the analyte having its concentration of 5 μm was also analyzed . fig7 shows the molecular interaction analysis result by using analytes produced by mixing the three types of test substances with rtrx , respectively . fig7 also shows the molecular interaction analysis result by using only rtrx ( 5 μm ). fig8 shows the molecular interaction analysis result by using n - acetylglucosamine as a test substance . fig8 also shows the molecular interaction analysis results by using only rtrx ( 5 μm ) and only n - acetylglucosamine ( 500 μm ), respectively . fig9 shows the molecular interaction analysis result by using nitrosoglutathione as a test substance . fig9 also shows the molecular interaction analysis results by using only rtrx ( 5 μm ) and only nitrosoglutathione ( 500 μm ), respectively . fig1 shows the molecular interaction analysis result by using prostaglandin i2 as a test substance . fig1 also shows the molecular interaction analysis results by using only rtrx ( 5 μm ) and only prostaglandin i2 ( 500 μm ), respectively . fig1 shows the molecular interaction analysis result by using an analyte mixing rtrx and prostaglandin i2 as a test substance , wherein the concentration of the prostaglandin i2 is 5 μm and 500 μm . as shown in fig7 to 11 , it was confirmed that nitrosoglutathione and prostaglandin i2 were mixed with rtrx , respectively , to remarkably strengthen the bond between rtrx and rmif . this shows that nitrosoglutathione and prostaglandin i2 are the substances which strengthen the bond between trxs and mif . as shown above , the screening method of the present invention allows to screen a substance which strengthens the bond between trxs and mif .
disclosed is a screening method which can select a substance having an influence on the binding between thioredoxin and mif . the screening method is characterized in that a test substance capable of enhancing the binding between a polypeptide belonging to the thioredoxin family and a macrophage migration inhibitory factor is selected through the steps of mixing at least one binding substance selected from the substances to shown below with the test substance , allowing the binding substance to bind to the macrophage migration inhibitory factor , and confirming the binding between the binding substance and the macrophage migration inhibitory factor : a polypeptide belonging to the thioredoxin family ; a protein which comprises an amino acid sequence produced by deleting , substituting or adding one or several amino acid residues in an amino acid sequence for a polypeptide belonging to the thioredoxin family and has the same activity as that of a polypeptide belonging to the thioredoxin family ; a gene encoding the polypeptide ; and a gene encoding the protein .