JP2020115143A - Peroxiredoxin expression enhancer - Google Patents

Abstract

To provide a novel peroxiredoxin expression enhancer.SOLUTION: A peroxiredoxin expression enhancer has extract from plants of Ziziphus, Rhamnaceae, as an active ingredient.SELECTED DRAWING: Figure 1

Description

The present invention relates to a peroxiredoxin expression-enhancing agent.

Peroxiredoxin is known as an enzyme having an antioxidant action that plays an important role in maintaining biological functions because it prevents denaturation and damage of proteins, lipids and nucleic acids by its antioxidant action.
In humans, the existence of six isoforms is known as peroxiredoxin. Among them, peroxiredoxin 1-3 is present in the epidermis, peroxiredoxin 1-2 is expressed more as it is closer to the granule layer, and peroxiredoxin 3 is often expressed in the basal layer.

Further, peroxiredoxin is known to suppress the active oxygen generated by UV, and UVA is known to increase the expression of peroxiredoxin 1, and UVB is known to increase the expression of peroxiredoxin 2.
Further, it has been suggested that increased expression of peroxiredoxin is involved in extension of lifespan, and in particular, decreased expression of peroxiredoxin 6 is involved in increased incidence of skin cancer. (See, for example, Non-Patent Document 1).

Dried fruits of jujuba (Ziziphus jujuba), which is a plant belonging to the genus Date (Ziziphus) of the family Rhamnaceae, or dried relatives thereof, are also known as turmeric and are used as a herbal medicine. In recent years, the extract has been blended in a skin external preparation as having a predetermined function.
For example, Patent Document 1 describes a melanin-containing keratinocyte mitogen containing an extract of jujube fruits and the like, and a pigmentation inhibitor containing the same. In addition, Patent Document 2 describes that a skin cosmetic containing an extract of Triticum aurium has an antiaging effect and a beautiful skin effect.

JP, 2014-19683, A JP, 2009-40694, A

Biomolecules 2015,5,545-589

Increasing the expression of peroxiredoxin in cells has attracted attention not only in the field of beauty, but also in the field of prevention and treatment of diseases.
Therefore, an object of the present invention is to provide a novel peroxiredoxin expression enhancer.

Another object of the present invention is to provide a screening method for a peroxiredoxin expression enhancer.

Since it is known that sebum and especially free fatty acids increase in summer, the present inventors have found that oleic acid, a kind of free fatty acids, affects the expression of peroxiredoxin in the epidermis. I examined.
As a result, the presence of oleic acid increases the expression of GM-CSF (Granulocyte Macrophage colony-stimulating Factor) in epidermal cells, and the presence of GM-CSF causes peroxiredoxin in epidermal cells. Was found to decrease.
And, it was found that the jujuba extract of jujuba has an action of increasing the expression of peroxiredoxin, and in particular, has an action of increasing the expression of peroxiredoxin in the presence of oleic acid which is a free fatty acid. It was
The present inventor has completed the present invention based on the above findings.

The present invention which solves the above-mentioned problems is a peroxiredoxin expression-enhancing agent which comprises an extract of a plant belonging to the genus Ziziphus of the family Rhamnaceae as an active ingredient.

The peroxiredoxin expression-enhancing agent of the present invention is preferably for use in reducing the expression of peroxiredoxin in epidermal cells due to an increase in free fatty acids in the skin.

Examples of the free fatty acid include oleic acid which is a main component of free fatty acid in the skin.

In a preferred form of the invention, the plant is jujuba (Ziziphus jujuba).

The preferred form of the peroxiredoxin expression-enhancing agent of the present invention is an external preparation or an oral preparation.

A preferred form of the peroxiredoxin expression-enhancing agent of the present invention further comprises a melanin production inhibitor. The melanin production inhibitor is preferably a compound selected from tranexamic acid and its derivatives.
This makes it possible to obtain an excellent effect of increasing the expression of peroxiredoxin.

The present invention also provides a screening method characterized by screening an active ingredient of a peroxiredoxin expression-enhancing agent using the expression level of peroxiredoxin in the presence of free fatty acid as an index.

The peroxiredoxin expression-enhancing agent of the present invention is excellent in the action of increasing the expression of peroxiredoxin in epidermal cells, which decreases in the presence of free fatty acids.
The peroxiredoxin expression-enhancing agent of the present invention prevents, ameliorates the deterioration of skin function, and the conditions and diseases caused by the deterioration of skin function during the season (spring to summer) when free fatty acids mainly consisting of oleic acid increase in the skin. Excellent therapeutic effect.

It is a figure which shows the change of the expression level of peroxiredoxin in a human keratinocyte by addition of a jujube extract (Pleurotus cornucopia extract). It is a figure (photograph) which shows the change of the expression level of GM-CSF in human keratinocytes by the addition of oleic acid. The circular image corresponds to the nucleus of the cell, and the dot-shaped relatively white portion around the cell corresponds to GM-CSF. It is a figure which shows the change of the expression level of peroxiredoxin in human keratinocytes by addition of GM-CSF. It is a figure which shows the change of the expression level of peroxiredoxin in human keratinocytes by the addition of oleic acid, and the change of the expression level of peroxiredoxin in human keratinocytes by the addition of jujube extract (Taiso extract) in the presence of oleic acid. .. FIG. 6 is a graph showing changes in the expression level of peroxiredoxin in human keratinocytes due to the addition of tripalmitin. It is a figure which shows the change of the expression level of peroxiredoxin in human keratinocytes by the addition of the mixture of jujube extract (Tamisu extract) and tranexamic acid.

The peroxiredoxin expression-enhancing agent of the present invention contains, as an active ingredient, an extract of a plant belonging to the genus Ziziphus of the family Rhamnaceae.

As the plant, jujuba (Ziziphus jujuba) can be preferably used. The part of jujube used preferably contains at least one of fruits, pericarps, ears, seeds, and seed coats, and particularly preferably fruits. A polar solvent such as water or alcohol can be preferably used as the extraction solvent. For example, the extract is preferably obtained by drying and refining the fruit, if necessary, and then extracting with a solvent selected from hot water, ethanol, hydrous ethanol, butylene glycol, and hydrous butylene glycol. For example, an aqueous solution containing 10 to 90% by mass, preferably 30 to 60% by mass of ethanol or 1,3-butylene glycol may be mentioned. Dried jujube or dried fruits of plants related to jujube are also called thixium. As an extract of Taisou, it is possible to use, for example, a turmeric extract manufactured by Ichimaru Falcos.

The peroxiredoxin expression-enhancing agent of the present invention contains the above-mentioned extract as an active ingredient.
The peroxiredoxin expression-enhancing agent of the present invention is preferably in the form of an external preparation or an oral preparation. Examples of the external preparation include cosmetics, quasi-drugs, skin external medicines and the like. Moreover, those dosage forms are not particularly limited. Among them, the form of a cosmetic that can be continuously used is preferable because of the relationship with the use of increasing the expression of peroxiredoxin, and among them, the forms such as lotion, beauty essence, emulsion, cream, gel, and sun care products are preferable. ..
Further, as the oral preparation, a supplement having a dosage form such as a tablet, a granule, a drink, or a food or drink is preferable.

The content of the extract, which is the active ingredient in the peroxiredoxin expression-enhancing agent, is preferably 0.0001 to 10% by mass, and more preferably 0.001 to 5% by mass in the case of an external preparation, based on the dry mass. It is% by mass. Further, in the case of an oral preparation, it is preferably 0.01 to 80% by mass, more preferably 0.1 to 50% by mass, based on the dry mass.

It is known that peroxiredoxin plays an important role in cell repair because its antioxidant activity is known and it prevents denaturation and damage of proteins, lipids and nucleic acids. Further, peroxiredoxin is known to be involved in cell proliferation and apoptosis, and it has been suggested that peroxiredoxin is involved in the pathogenesis of liver cancer, skin cancer, diabetes, Alzheimer's disease, Parkinson's disease and the like.

Therefore, the peroxiredoxin expression-enhancing agent of the present invention can be used as an antioxidant. Further, the peroxiredoxin expression enhancer of the present invention, cell activation, anti-aging, dermatitis, skin symptoms or diseases such as pigmentation, cancer such as liver cancer and skin cancer, diabetes, Alzheimer's disease, Parkinson's disease, arteriosclerosis. It can be used as an agent for the prevention, improvement or treatment of
In addition, the peroxiredoxin expression-enhancing agent of the present invention is particularly useful for preventing and improving the deterioration of the skin condition caused by active oxygen. Such deterioration of the skin condition includes such phenomena as pigmentation, fine irregularities on the skin, conspicuous pores, texture, wrinkles, sagging, spots, dullness, and dryness.

As shown in Examples described later, the peroxiredoxin expression-enhancing agent of the present invention is excellent in the effect of increasing peroxiredoxin expression in epidermal cells in the presence of oleic acid. Therefore, the peroxiredoxin expression-enhancing agent of the present invention is preferably used for reducing the expression of peroxiredoxin in epidermal cells due to an increase in free fatty acid mainly composed of oleic acid in the skin.

That is, the peroxiredoxin expression-enhancing agent of the present invention is useful for improving a skin condition in which free fatty acids mainly containing oleic acid are increased. It is known that the increase of free fatty acid mainly composed of oleic acid is observed in the season from spring to summer (J. Soc. Cosmet. Chem. Jpn. 34 (4) 365-373 (2000)). Therefore, it is effective that the peroxiredoxin expression-enhancing agent of the present invention is in the form of a skin external preparation or cosmetic used from spring to summer.

From this point of view, the peroxiredoxin expression-enhancing agent of the present invention is also preferably in the form of an external preparation for skin such as sunscreen cosmetics combined with an ultraviolet protective agent. By having such a form, it suppresses melanin production by ultraviolet rays by the effect of an ultraviolet protective agent, and suppresses skin symptoms such as pigmentation due to an increase in free fatty acids which is a factor different from ultraviolet rays. It is possible to improve comprehensively against the deterioration of the skin condition which is likely to occur during the spring-summer season.

As the above-mentioned ultraviolet protective agent, para-aminobenzoic acid type ultraviolet absorber, anthranilic acid type ultraviolet absorber, salicylic acid type ultraviolet absorber, cinnamic acid type ultraviolet absorber, benzophenone type ultraviolet absorber, sugar type ultraviolet absorber, 2- Examples thereof include ultraviolet absorbers such as (2′-hydroxy-5′-t-octylphenyl)benzotriazole and 4-methoxy-4′-t-butyldibenzoylmethane.

From the above viewpoint, the peroxiredoxin expression-enhancing agent of the present invention is also preferably in the form of a skin external preparation such as a whitening cosmetic in combination with a melanin production inhibitor. By having such a form, it is possible to suppress melanin production by ultraviolet rays, and suppress skin symptoms such as pigmentation due to an increase in free fatty acids which is a factor different from ultraviolet rays, and the spring to summer It is possible to comprehensively improve the deterioration of the skin condition that tends to occur during the season.
Furthermore, as shown in Examples described later, it was confirmed that the combination of the extract as the active ingredient and the melanin production inhibitor enhances the peroxiredoxin expression effect of the extract as the active ingredient. Therefore, by combining these, the excellent effect of the peroxiredoxin expression enhancer can be obtained.

Examples of the melanin production inhibitor include tranexamic acid, alkylamides of tranexamic acid, esters, tranexamic acid derivatives such as multimers, alkylresorcinols such as 4-butylresorcinol, arbutin, ascorbic acid, glucoside ascorbic acid and 3-O-. Preferable examples include ascorbic acid derivatives such as ethyl ascorbic acid, and particularly preferable examples include tranexamic acid and tranexamic acid derivatives. Moreover, these may form the salt.

When the melanin production inhibitor is contained in combination, the content mass thereof is 0.0001 to 5 times, preferably 0.001 to 2 times, more preferably 0.01 to 1 times the active ingredient (dry mass). It may be doubled.

Further, the content of the melanin production inhibitor is preferably 0.01 to 30% by mass, more preferably 0.1 to 10% by mass in the case of the external preparation. In the case of an oral preparation, it is usually 0.01 to 80% by mass, preferably 0.1 to 50% by mass, more preferably 1 to 30% by mass.

The peroxyredoxin expression-enhancing agent of the present invention preferably has a free fatty acid content of 5% by mass or less, preferably 1% by mass or less, and particularly preferably does not contain it.

The peroxiredoxin expression-enhancing agent of the present invention can contain, in addition to the active ingredient, optional ingredients usually used in cosmetics within a range not impairing the effects of the invention. Such optional components include polyethylene glycol, glycerin, 1,3-butylene glycol, erythritol, sorbitol, xylitol, maltitol, propylene glycol, dipropylene glycol, diglycerin, isoprene glycol, 1,2-pentanediol, 2,4. -Hexylene glycol, 1,2-hexanediol, 1,2-octanediol, and other polyols, fatty acid soaps (sodium laurate, sodium palmitate, etc.), potassium lauryl sulfate, anionic surfactants such as alkylsulfate triethanolamine ether Agents, cationic surfactants such as stearyltrimethylammonium chloride, benzalkonium chloride, and laurylamine oxide, imidazoline-based amphoteric surfactants (2-cocoyl-2-imidazolinium hydroxide-1-carboxyethyloxy disodium Salts, etc.), betaine-based surfactants (alkylbetaines, amidobetaines, sulfobetaines, etc.), amphoteric surfactants such as acylmethyltaurine, sorbitan fatty acid esters (sorbitan monostearate, sorbitan sesquioleate, etc.), glycerin Fatty acids (glycerin monostearate, etc.), propylene glycol fatty acid esters (propylene glycol monostearate, etc.), hydrogenated castor oil derivatives, glycerin alkyl ethers, POE sorbitan fatty acid esters (POE sorbitan monooleate, polystearate monostearate) Ethylene sorbitan, etc.), POE sorbit fatty acid esters (POE-sorbit monolaurate, etc.), POE glycerin fatty acid esters (POE-glycerin monoisostearate, etc.), POE fatty acid esters (polyethylene glycol monooleate, POE distearate, etc.) , POE alkyl ethers (POE2-octyldodecyl ether, etc.), POE alkyl phenyl ethers (POE nonyl phenyl ether, etc.), Pluronic types, POE/POP alkyl ethers (POE, POP2-decyl tetradecyl ether, etc.), TE Tronics, POE castor oil, hydrogenated castor oil derivatives (POE castor oil, POE hydrogenated castor oil, etc.), sucrose fatty acid esters, nonionic surfactants such as alkyl glucosides, sodium pyrrolidone carboxylic acid, lactic acid, sodium lactate, etc. Moisturizing ingredients, surface-treated, mica, talc, kaolin, synthetic mica, charcoal Powders of calcium oxide, magnesium carbonate, silicic acid anhydride (silica), aluminum oxide, barium sulfate, etc., which may be surface-treated, inorganic oxides of cobalt oxide, ultramarine blue, navy blue, zinc oxide, surface-treated May be, composite pigments such as iron oxide titanium dioxide sintered body, may be surface-treated, titanium mica, fish phosphorus foil, pearl agents such as bismuth oxychloride, may be laked Red No. 202 , Red 228, Red 226, Yellow 4, Blue 404, Yellow 5, Red 505, Red 230, Red 223, Orange 201, Red 213, Yellow 204, Yellow 203, Blue No. 1, green No. 201, purple No. 201, red No. 204, etc., organic powders such as polyethylene powder, polymethylmethacrylate, nylon powder, organopolysiloxane elastomer, etc., lower alcohols such as ethanol, isopropanol, etc. , Vitamin A or its derivative, vitamin B ₆ hydrochloride, vitamin B ₆ tripalmitate, vitamin B ₆ dioctanoate, vitamin B ₂ or its derivative, vitamin B ₁₂ , vitamin B ₁₅ or its derivative, etc., α- Vitamin Es such as tocopherol, β-tocopherol, γ-tocopherol and vitamin E acetate, vitamins D, vitamin H, pantothenic acid, pantethine, pyrroloquinoline quinone and the like can be mentioned.

The screening method of the present invention is characterized by screening the active ingredient of a peroxiredoxin expression-enhancing agent using the expression level of peroxiredoxin in the presence of free fatty acid as an index.

As shown in Examples described later, it was found that the expression of peroxiredoxin was reduced in the presence of free fatty acids such as oleic acid. On the other hand, as described above, it is known that free fatty acids such as oleic acid in the skin increase from spring to summer. From these findings, if it is possible to screen a component that increases the expression of peroxiredoxin in the presence of free fatty acids, from the viewpoint of conventional UV protection, suppression of melanin production, etc. against improvement of skin condition in spring to summer. It is possible to screen for useful components in view of the increased expression of antioxidant enzymes in biological skin, which is different from the above.

The screening method of the present invention comprises adding a free fatty acid such as oleic acid and a test substance to a culture system of epidermal cells, and measuring the expression level of peroxiredoxin. The expression level of peroxiredoxin can be measured by a conventional method such as immunoassay or qRT-PCR.

Further, by carrying out the screening method in the presence of free fatty acid such as oleic acid, it becomes possible to screen for a component that increases the expression of peroxiredoxin in the presence of free fatty acid.

<Test Example 1> Jujube extract addition test This test was carried out for the purpose of measuring the change in the expression level of peroxiredoxin due to the jujube extract addition.
In the present test, as a jujube extract, tanso extract manufactured by Ichimaru Falcos was used (the same applies to the following test examples). Further, as a comparative example, rose hip extract manufactured by Maruzen was used.

Newborn keratinocytes (Kurashiki Spinning Co., Ltd.) were seeded at 5.0×10 ⁴ cells/well and cultured for 24 hours. Subsequently, 1% by mass of each of the turmeric extract and the rose hip extract was added, and the mixture was cultured for 24 hours. After the culture was completed, the cells were collected and the expression level of peroxiredoxin mRNA was measured by qRT-PCR. In addition, as a control, the one cultured in the same manner with the addition of only the solvent was used.

The results are shown in Figure 1.
As shown in FIG. 1, the expression level of peroxiredoxin was increased when control extract was added to the control, whereas the expression level of peroxiredoxin was not increased when rose hip extract was added. It was confirmed that it could not be seen.
From this, it was revealed that the jujube extract has an action of increasing the expression of peroxiredoxin. In addition, it was revealed that rosehip extract, which is known to have an antioxidant effect, has no effect of increasing the expression of peroxiredoxin.

<Test Example 2> Jujube Extract Addition Test in the Presence of Free Fatty Acid This test was conducted for the purpose of measuring GM-CSF expression, peroxiredoxin expression, and action of jujube extract against the expression of free fatty acid.

(1) Expression of GM-CSF by addition of oleic acid This test was conducted for the purpose of measuring the change in the expression level of GM-CSF by addition of free fatty acid. In this test, oleic acid (manufactured by Wako Pure Chemical Industries, Ltd.), which is one of the major free fatty acids in sebum, was used as the free fatty acid.

Newborn keratinocytes (Kurashiki Spinning Co., Ltd.) were seeded at 7.0×10 ⁴ cells/well and cultured for 24 hours. Subsequently, 5 μM of oleic acid was added and the cells were cultured for 24 hours. After completion of the culture, the cells were fixed with 4% paraformaldehyde, immunostained with an anti-GM-CSF antibody (manufactured by Abcam Co.), and observed under a microscope. In addition, as a control, the same culture was used without adding oleic acid.

The results are shown in Figure 2.
As shown in FIG. 2, in the sample to which oleic acid was added, an increase in the expression level of GM-CSF in the cells was observed as compared with the control in which this was not added (an increase in red fluorescence around the nucleus was detected). ..
From this, it was shown that the presence of free fatty acids such as oleic acid increased the expression of GM-CSF.

(2) Expression of peroxiredoxin by addition of GM-CSF This test was conducted for the purpose of measuring the effect of GM-CSF on the expression of peroxiredoxin.
Newborn keratinocytes (Kurashiki Spinning Co., Ltd.) were seeded at 5.0×10 ⁴ cells/well and cultured for 24 hours. Subsequently, GM-CSF was added at 50 ng/mL and cultured for 24 hours. After the culture was completed, the cells were collected and the expression level of peroxiredoxin mRNA was measured by qRT-PCR. In addition, as a control, the one cultured in the same manner with the addition of only the solvent was used.

Results are shown in FIG.
As shown in FIG. 3, in the sample to which GM-CSF was added, a decrease in the expression level of peroxiredoxin in cells was observed as compared to the control in which it was not added.
From this, it was shown that the presence of GM-CSF decreased the expression of peroxiredoxin.

Considering the results of (1) and (2), it can be seen that the addition of oleic acid increases the expression level of GM-CSF in the cells and thus the expression level of peroxiredoxin in the cells.

(3) Jujube extract addition test The purpose of this test is to measure the change in the expression level of peroxiredoxin due to the addition of free fatty acid, which is a constituent of sebum, and the change in the expression amount of peroxiredoxin due to the addition of jujube extract. I went there.
In this test, oleic acid, which is one of the major free fatty acids in sebum, was used.

Newborn keratinocytes (Kurashiki Spinning Co., Ltd.) were seeded at 5.0×10 ⁴ cells/well and cultured for 24 hours. Subsequently, 5 μM of oleic acid or 5 μM of oleic acid and 1% by mass of turmeric extract were added, and the mixture was cultured for 24 hours. After the culture was completed, the cells were collected and the expression level of peroxiredoxin mRNA was measured by qRT-PCR. In addition, as a control, the one cultured in the same manner with the addition of only the solvent was used.

The results are shown in Fig. 4.
As shown in FIG. 4, it was confirmed that the expression level of peroxiredoxin was decreased by adding oleic acid. In addition, it was confirmed that the addition of oleic acid and turmeric extract increased the expression level of peroxiredoxin to the same level as the control in the system to which oleic acid was added.
From this, it was revealed that the jujube extract has an action of increasing the expression of peroxiredoxin. In particular, jujube extract was found to have an action of increasing the expression of peroxiredoxin in the presence of free fatty acids such as oleic acid.

(4) Triglyceride addition test This test confirmed the change in the expression level of peroxiredoxin due to the addition of triglyceride, which is a constituent of sebum, and the decrease in the expression level of peroxiredoxin is unique to the presence of free fatty acids. It was done for the purpose of confirming that there is.
In this test, tripalmitin was used as triglyceride.

Newborn keratinocytes (Kurashiki Spinning Co., Ltd.) were seeded at 5.0×10 ⁴ cells/well and cultured for 24 hours. Subsequently, tripalmitin (10 μM) was added, and the mixture was cultured for 24 hours. After the culture was completed, the cells were collected and the expression level of peroxiredoxin mRNA was measured by qRT-PCR. In addition, as a control, the one cultured in the same manner with the addition of only the solvent was used.

Results are shown in FIG.
As shown in FIG. 5, in the sample to which tripalmitin was added, a decrease in the expression level of peroxiredoxin in cells was not observed as compared with the control in which it was not added.

From the results of (3) and (4), it was shown that the decrease in the expression of peroxiredoxin specifically occurs due to the presence of free fatty acid, which is one of the sebum components.

<Test Example 3> Jujube extract-melanin production inhibitor mixture addition test This test was carried out for the purpose of measuring the change in the expression level of peroxiredoxin due to the addition of the mixture of jujube extract and melanin production inhibitor.
Tranexamic acid was used as a melanin production inhibitor.

Newborn keratinocytes (Kurashiki Spinning Co., Ltd.) were seeded at 5.0×10 ⁴ cells/well and cultured for 24 hours. Subsequently, 1% by mass of tanix extract, a mixture of 1% by mass of tanix extract and 400 μg/mL of tranexamic acid, and 400 μg/mL of tranexamic acid were added, and the mixture was cultured for 24 hours. After the culture was completed, the cells were collected and the expression level of peroxiredoxin mRNA was measured by qRT-PCR. In addition, as a control, the one cultured in the same manner with the addition of only the solvent was used.

The results are shown in Fig. 6.
As shown in FIG. 6, it was confirmed that the expression level of peroxiredoxin was significantly increased in the case of adding the mixture of the turmeric extract and tranexamic acid, as compared with the case of adding tranexamic acid alone. On the other hand, it was confirmed that when tranexamic acid was added alone, no increase in the expression level of peroxiredoxin was observed.
From this, it was revealed that the action of increasing the expression of peroxiredoxin in the jujuba extract was enhanced by combining jujuba extract and tranexamic acid.

<Example 1> Cosmetic A lotion, which is a cosmetic of the present invention, was prepared according to the formulation shown in Table 1 below.

<Example 2> Cosmetics A lotion, which is a cosmetic of the present invention, was prepared according to the formulation shown in Table 2 below.

<Example 3> Food The food of the present invention was prepared according to the formulation shown in Table 3 below. That is, the prescription ingredients were tumbled phase granulated with 10 parts by weight of water (“New Malmerizer” manufactured by Fuji Paudal Co., Ltd.) and tableted to obtain 1 g of tablet-shaped food.

The present invention can be applied to cosmetics, supplements and foods and drinks.

Claims (3)

A screening method comprising screening an active ingredient of a peroxiredoxin expression-enhancing agent using the expression level of peroxiredoxin in the presence of free fatty acid as an index. The screening method according to claim 1, wherein the expression level of the peroxiredoxin is measured by adding a free fatty acid and a test substance to a culture system of epidermal cells. The screening method according to claim 1 or 2, wherein the free fatty acid is oleic acid.