Determination of Major Endogenous FAHFAs in Healthy Human Circulation: The Correlations with Several Circulating Cardiovascular-Related Biomarkers and Anti-Inflammatory Effects on RAW 264.7 Cells.

Fatty acid esters of hydroxy fatty acids (FAHFAs) are newly discovered long-chain fatty acids. However, the major endogenous FAHFAs in healthy human circulation, their correlation with cardiovascular (CV) biomarkers, and their anti-inflammatory effects have not been investigated and remain unclear. In the present study, a total of 57 healthy subjects were recruited. Liquid chromatography-mass spectrometry (LC-MS) was developed for the simultaneous determination of seven FAHFAs, four long-chain fatty acids, and four non-traditional circulating CV-related biomarkers. We found two major types of FAHFAs in healthy human circulation, palmitoleic acid ester of 9-hydroxystearic acid (9-POHSA), and oleic acid ester of 9-hydroxystearic acid (9-OAHSA). Both 9-POHSA and 9-OAHSA had a strong positive correlation with each other and were negatively correlated with fasting blood glucose, S-adenosyl-l-homocysteine (SAH), and trimethylamine N-oxide (TMAO), but not with l-homocysteine. 9-POHSA was also positively correlated with l-carnitine. Moreover, we confirmed that both 9-POHSA and 9-OAHSA exhibited an anti-inflammatory effect by suppressing LPS stimulated cytokines, including IL-1ß and IL-6 in RAW 264.7 cells. In addition, palmitoleic acid also had a positive correlation with 9-POHSA and 9-OAHSA. As far as we know, this is the first report showing the major endogenous FAHFAs in healthy subjects and their CV protection potential which might be correlated with SAH and TMAO reduction, l-Carnitine elevation, and their anti-inflammatory effects.

Eating right for a healthier heart: Food choice contributes to cardiometabolic benefits and reduction of carotid intima-media thickness.

OBJECTIVES: Diets may alter an individual's metabolism and inflammation, collectively leading to the modulation of cardiovascular health and disease process. The aim of this study was to investigate the effects of diets and diet-associated metabolites on metabolic profiles, inflammatory status, and severity of atherosclerosis. METHODS: A cross-sectional study was conducted with 81 healthy adults in Taiwan. A food frequency questionnaire was obtained for evaluating dietary intake. Carotid intima-media thickness (CIMT), a relevant marker of subclinical atherosclerosis, was measured by ultrasound. RESULTS: Consumption of instant noodles and sugary beverages was associated with worse metabolic profiles. In contrast, the intake of fresh fruit and green vegetables was correlated with better metabolic parameters. Sugary beverages were dose-dependently correlated with higher expressions of toll-like receptor (TLR)2 and TLR4 on monocytes, whereas fresh fruit intake was associated with lower TLRs. Furthermore, consumption of green vegetables, brown rice, and >2000 mL/d of water was inversely correlated with CIMT. The diet-associated metabolites including trimethylamine N-oxide and S-adenosyl-l-homocysteine, were positively associated with CIMT, whereas l-lysine and l-carnitine were associated with decreased CIMT. Interestingly, intake of strict vegetarian foods resulted in lower serum total cholesterol levels without a detectable effect on inflammatory status or CIMT. CONCLUSIONS: Independent of the pattern of strict vegetarian foods, individuals who consumed more vegetables, fresh fruit, and water showed better cardiovascular health as evidenced by their metabolic and inflammatory status and CIMT results.

Admission policies and methods at crossroads: a review of medical school admission policies and methods in seven Asian countries.

Selecting the right applicants is an important part of medical student admission. While one universally accepted selection criterion is academic capacity, there are other criteria such as communication skills and local criteria (e.g., socio-cultural values) that are no less important. This article reviews the policies and methods of selection to medical schools in seven countries with varying socio-economic conditions and healthcare systems. Senior academics involved in medical education in Indonesia, Japan, Malaysia, the Philippines, Singapore, Sri Lanka, and Taiwan completed a pre-agreed pro-forma per each country to describe the country's admission policies and methods. The details were then compared and contrasted. This review identifies tension between many of the policies and methods used in medical school admissions, such as between the need to assess non-cognitive abilities and widen access, and between the need for more medical professionals and the requirement to set high entry standards. Finding the right balance requires careful consideration of all variables, including the country's human resource needs; socio-economic status; graduates' expected competencies; and the school's vision, mission, and availability of resources.

A comparison of L-carnitine and several cardiovascular-related biomarkers between healthy vegetarians and omnivores.

OBJECTIVE: A plant-based diet has been associated with a reduced risk of cardiovascular (CV) diseases. This study aimed to determine the levels and correlations of CV-related biomarkers and the beneficial role of dietary habits. METHODS: A total of 63 healthy vegetarians (n = 32) and omnivores (n = 31) were recruited. The baseline characteristics were recorded and measured (including lipid profiles, blood glucose, etc.). Liquid chromatography-mass spectrometry method was developed for the simultaneous determination of seven circulating CV-related biomarkers. RESULTS: L-carnitine (L-Car), L-methionine, and ascorbic acid (AA) were significantly higher in vegetarians than in omnivores. In the vegetarians, L-Car had a negative correlation with triacylglycerols (P = 0.042) and blood glucose (P = 0.048) and a positive correlation with high-density lipoprotein cholesterol (P = 0.049). L-Car was also positively correlated with L-lysine (P = 0.009), L-methionine (P = 0.006), and AA (P = 0.035). The vegetarians' AA also had a negative correlation with L-homocysteine (P = 0.028). In the omnivores, L-Car was negatively correlated with total cholesterol (P = 0.008), low-density lipoprotein cholesterol (P = 0.004), and high-density lipoprotein cholesterol (P = 0.038). Omnivores' body mass index was positively correlated with L-homocysteine (P = 0.033), and age was positively correlated with trimethylamine N-oxide (P < 0.001) and blood glucose (P = 0.007), but not in vegetarians. CONCLUSIONS: Our results suggest that vegetarians have an elevated level of L-Car, which might be associated with endogenous biosynthesis and diet composition. Circulating L-Car might play an important role in CV protection, especially in vegetarians.

Glycolic acid attenuates UVB-induced aquaporin-3, matrix metalloproteinase-9 expression, and collagen degradation in keratinocytes and mouse skin.

Ultraviolet-B exposure causes an inflammatory response, photoaged skin, and degradation of extracellular matrix proteins including collagen and elastin. The regulation of these genes was suggested as an important mechanism to attenuate skin aging. Glycolic acid (GA) is commonly present in fruits and recently used to treat dermatological diseases. We reported that GA slows down cell inflammation and aging caused by UVB. Little is known about GA retarding the skin premature senescence or how to impede these events. To investigate the potential of GA to regulate the expression of MMPs and collagen, GA was topically applied onto human keratinocytes and the C57BL/6J mice dorsal skin. In the present study, we demonstrated that GA reduced UVB-induced type-I procollagen expression and secretory collagen levels. GA reverted and dose-dependently increased the level of aquaporin-3 (AQP3), the expression of which was down-regulated by UVB. The UV-induced MMP-9 level and activity were reduced by GA pre-treatment. Concomitantly, GA reverted mitogen-activated protein kinase (MMP-9) activation and inhibited the extracellular signal-regulated kinase activation (p38, pERK) triggered by UVB. The animal model also presented that GA attenuated the wrinkles caused by UVB on the mouse dorsal skin. Finally, GA triggers the transient receptor potential vanilloid-1 (TRPV-1) channel to initiate the anti-photoaging mechanism in keratinocytes. These findings clearly indicated that the mechanisms of GA promote skin protection against UVB-induced photoaging and wrinkle formation. GA might be an important reagent and more widely used to prevent UVB-induced skin aging.

Dual Effects of Alpha-Hydroxy Acids on the Skin.

AHAs are organic acids with one hydroxyl group attached to the alpha position of the acid. AHAs including glycolic acid, lactic acid, malic acid, tartaric acid, and citric acid are often used extensively in cosmetic formulations. AHAs have been used as superficial peeling agents as well as to ameliorate the appearance of keratoses and acne in dermatology. However, caution should be exercised in relation to certain adverse reactions among patients using products with AHAs, including swelling, burning, and pruritus. Whether AHAs enhance or decrease photo damage of the skin remains unclear, compelling us to ask the question, is AHA a friend or a foe of the skin? The aim of this manuscript is to review the various biological effects and mechanisms of AHAs on human keratinocytes and in an animal model. We conclude that whether AHA is a friend or foe of human skin depends on its concentration. These mechanisms of AHAs are currently well understood, aiding the development of novel approaches for the prevention of UV-induced skin damage.

Purification of Single Photons from Room-Temperature Quantum Dots.

Single photon emitters are indispensable to photonic quantum technologies. Here, we demonstrate waveform-controlled high-purity single photons from room-temperature colloidal quantum dots. The purity of the single photons does not vary with the excitation power, thereby allowing the generation rate to be increased without compromising the single-photon quality.

Topical application of glycolic acid suppresses the UVB induced IL-6, IL-8, MCP-1 and COX-2 inflammation by modulating NF-κB signaling pathway in keratinocytes and mice skin.

BACKGROUND: Glycolic acid (GA), commonly present in fruits, has been used to treat dermatological diseases. Extensive exposure to solar ultraviolet B (UVB) irradiation plays a crucial role in the induction of skin inflammation. The development of photo prevention from natural materials represents an effective strategy for skin keratinocytes. OBJECTIVE: The aim of this study was to investigate the molecular mechanisms underlying the glycolic acid (GA)-induced reduction of UVB-mediated inflammatory responses. METHODS: We determined the effects of different concentrations of GA on the inflammatory response of human keratinocytes HaCaT cells and C57BL/6J mice dorsal skin. After GA was topically applied, HaCaT and mice skin were exposed to UVB irradiation. RESULTS: GA reduced the production of UVB-induced nuclear factor kappa B (NF-κB)-dependent inflammatory mediators [interleukin (IL)-1ß, IL-6, IL-8, cyclooxygenase (COX)-2, tumor necrosis factor-α, and monocyte chemoattractant protein (MCP-1)] at both mRNA and protein levels. GA inhibited the UVB-induced promoter activity of NF-κB in HaCaT cells. GA attenuated the elevation of senescence associated with ß-galactosidase activity but did not affect the wound migration ability. The topical application of GA inhibited the genes expression of IL-1ß, IL-6, IL-8, COX-2, and MCP-1 in UVB-exposed mouse skin. The mice to UVB irradiation after GA was topically applied for 9 consecutive days and reported that 1-1.5% of GA exerted anti-inflammatory effects on mouse skin. CONCLUSION: We clarified the molecular mechanism of GA protection against UVB-induced inflammation by modulating NF-κB signaling pathways and determined the optimal concentration of GA in mice skin exposed to UVB irradiation.

Deep Dermatophytosis Caused by Zoophilic Strain of Trichophyton interdigitale with Successful Treatment of Itraconazole.

We report a 66-year-old female patient with deep dermatophytosis caused by zoophilic strain of Trichophyton interdigitale, a rare granulomatous presentation of Trichophyton species infection in patients with underlying systemic diseases, and she was successfully cured by itraconazole. Since the identification of Trichophyton mentagrophytes complex had been misused for years, a brief discussion of molecular diagnosis and taxonomy of T. mentagrophytes complex is given. The pathogenesis and comparison with cases reported in the literature are also discussed.

Hair growth effect of traditional Chinese medicine BeauTop on androgenetic alopecia patients: A randomized double-blind placebo-controlled clinical trial.

The aim of the present study was to evaluate the treatment effects of BeauTop in alopecia by observing its effectiveness in improving androgenetic alopecia. Hair growth was observed using a dermatoscope and clinical photos, and was scored by three dermatologists. Dermatologists evaluated and selected suitable participants for this study using the Norwood scale or Ludwig scale. A total of 40 participants with androgenetic alopecia were recruited in this study, and 32 participants completed the 6-month trial. The results revealed that in the BeauTop treatment group, 9/17 participants (52.9%) showed increased hair growth. Changes in hair growth were as follows: No change, 47.1% patients; minimally improved, 5.9% patients; moderately improved, 29.4% patients; and significantly improved, 17.6% patients. In the placebo group, 2/15 participants (13%) showed increased hair growth. A Chi-square test was performed and attained a value of 0.01

Photoprotective Potential of Glycolic Acid by Reducing NLRC4 and AIM2 Inflammasome Complex Proteins in UVB Radiation-Induced Normal Human Epidermal Keratinocytes and Mice.

Exposure to UVB radiation induces inflammation and free radical-mediated oxidative stress through reactive oxygen species (ROS) that play a crucial role in the induction of skin cancer. Glycolic acid (GA) is frequently used in cosmetics and dermatology. The aim of the study was to analyze the photoprotective mechanisms through which GA retards UVB-induced ROS accumulation and inflammation in normal human epidermal keratinocytes (NHEKs) and mice skin, respectively. NHEK cell line and C57BL/6J mice were treated with GA (0.1 or 5 mM) for 24 h followed by UVB irradiation. ROS accumulation, DNA damage, and expression of inflammasome complexes (NLRP3, NLRC4, ASC, and AIM2) were measured in vitro. Epidermal thickness and inflammasome complex proteins were analyzed in vivo. GA significantly prevented UVB-induced loss of skin cell viability, ROS formation, and DNA damage (single and double strands DNA break). GA suppressed the mRNA expression levels of NLRC4 and AIM2 among the inflammasome complexes. GA also blocked interleukin (IL)-1ß by reducing the activity of caspase-1 in the NHEKs. Treatment with GA (2%) inhibited UVB-induced inflammation marker NLRC4 protein levels in mouse dorsal skin. The photoprotective activity of GA was ascribed to the inhibition of ROS formation and DNA damage, as well as a reduction in the activities of inflammasome complexes and IL-1ß. We propose that GA has anti-inflammatory and photoprotective effects against UVB irradiation. GA is potentially beneficial to the protection of human skin from UV damage.

Glycolic Acid Silences Inflammasome Complex Genes, NLRC4 and ASC, by Inducing DNA Methylation in HaCaT Cells.

AHAs (α-hydroxy acids), including glycolic acid (GA), have been widely used in cosmetic products and superficial chemical peels. Inflammasome complex has been shown to play critical roles in inflammatory pathways in human keratinocytes. However, the anti-inflammatory mechanism of GA is still unknown. The aim of this study is to investigate the relationship between the expression of the inflammasome complex and epigenetic modification to elucidate the molecular mechanism of the anti-inflammatory effect of GA in HaCaT cells. We evaluated NLRP3, NLRC4, AIM2, and ASC inflammasome complex gene expression on real-time polymerase chain reaction (PCR). Methylation changes were detected in these genes following treatment with DNA methyltransferase (DNMT) inhibitor 5-aza-2'-deoxycytidine (5-Aza) with or without the addition of GA using methylation-specific PCR (MSP). GA inhibited the expressions of these inflammasome complex genes, and the decreases in the expressions of mRNA were reversed by 5-Aza treatment. Methylation was detected in NLRC4 and ASC on MSP, but not in NLRP3 or AIM2. GA decreased NLRC4 and ASC gene expression by increasing not only DNA methyltransferase 3B (DNMT-3B) protein level, but also total DNMT activity. Furthermore, silencing of DNMT-3B (shDNMT-3B) increased the expressions of NLRC4 and ASC. Our data demonstrated that GA treatment induces hypermethylation of promoters of NLRC4 and ASC genes, which may subsequently lead to the hindering of the assembly of the inflammasome complex in HaCaT cells. These results highlight the anti-inflammatory potential of GA-containing cosmetic agents in human skin cells and demonstrate for the first time the role of aberrant hypermethylation in this process.

Nanodiamonds protect skin from ultraviolet B-induced damage in mice.

BACKGROUND: Solar ultraviolet (UV) radiation causes various deleterious effects, and UV blockage is recommended for avoiding sunburn. Nanosized titanium dioxide and zinc oxide offer effective protection and enhance cosmetic appearance but entail health concerns regarding their photocatalytic activity, which generates reactive oxygen species. These concerns are absent in nanodiamonds (NDs). Among the UV wavelengths in sunlight, UVB irradiation primarily threatens human health. RESULTS: The efficacy and safety of NDs in UVB protection were evaluated using cell cultures and mouse models. We determined that 2 mg/cm(2) of NDs efficiently reduced over 95% of UVB radiation. Direct UVB exposure caused cell death of cultured keratinocyte, fibroblasts and skin damage in mice. By contrast, ND-shielding significantly protected the aforementioned pathogenic alterations in both cell cultures and mouse models. CONCLUSIONS: NDs are feasible and safe materials for preventing UVB-induced skin damage.

Triggering apoptotic death of human epidermal keratinocytes by malic Acid: involvement of endoplasmic reticulum stress- and mitochondria-dependent signaling pathways.

Malic acid (MA) has been commonly used in cosmetic products, but the safety reports in skin are sparse. To investigate the biological effects of MA in human skin keratinocytes, we investigated the potential cytotoxicity and apoptotic effects of MA in human keratinocyte cell lines (HaCaT). The data showed that MA induced apoptosis based on the observations of DAPI staining, DNA fragmentation, and sub-G1 phase in HaCaT cells and normal human epidermal keratinocytes (NHEKs). Flow cytometric assays also showed that MA increased the production of mitochondrial superoxide (mito-SOX) but decreased the mitochondrial membrane potential. Analysis of bioenergetics function with the XF 24 analyzer Seahorse extracellular flux analyzer demonstrated that oxygen consumption rate (OCR) was significantly decreased whereas extracellular acidification rate (ECAR) was increased in MA-treated keratinocytes. The occurrence of apoptosis was proved by the increased expressions of FasL, Fas, Bax, Bid, caspases-3, -8, -9, cytochrome c, and the declined expressions of Bcl-2, PARP. MA also induced endoplasmic reticulum stress associated protein expression such as GRP78, GADD153, and ATF6α. We demonstrated that MA had anti-proliferative effect in HaCaT cell through the inhibition of cell cycle progression at G0/G1, and the induction of programmed cell death through endoplasmic reticulum stress- and mitochondria-dependent pathways.

Herpes zoster-associated severity and duration of pain, health-related quality of life, and healthcare utilization in Taiwan: a prospective observational study.

BACKGROUND: To assess the severity and duration of herpes zoster (HZ)-associated pain (ZAP) and its impact on quality of life (QoL) and healthcare utilization (HCRU) from a patient perspective in routine care in Taiwan. METHODS: A prospective, observational, single-cohort study was conducted in five centers across Taiwan. Patients were recruited at different time points during their HZ episode and were followed for ≤180 days. ZAP was assessed with the Initial Zoster Impact Questionnaire and the Zoster Brief Pain Inventory, QoL with the EQ-5D, and HCRU with a simple questionnaire. RESULTS: A total of 150 patients were included with a mean age of 64.9 years and mean time since rash onset of 18.8 days. Prodromal pain was experienced by 64.7% of patients, of whom 91.8% reported moderate-to-severe pain. At enrollment, 98.0% of patients experienced ZAP. Mean ± SD worst pain score decreased from 5.95 ± 3.09 at enrollment to 2.65 ± 2.98 at 30 days and 0.28 ± 0.83 at 180 days. Postherpetic neuralgia was observed in 20.7% of patients. Mean ± SD EQ-5D score significantly decreased (P < 0.001) from 0.91 ± 0.16 before rash onset to 0.67 ± 0.18 after rash onset, showing significant QoL deterioration up to 60 days. The impact of HZ on QoL and pain severity was similar across age groups. Significant HCRU was observed including visits to the doctor (83.3% of patients), specialist (30.7%), emergency department (24.7%), physiotherapist (23.3%), and hospitalizations (20.7%). CONCLUSION: Severe morbidity and significant HCRU are associated with HZ in Taiwan, supporting the need for early intervention and preventive strategies to reduce the HZ-associated burden of illness.

Cantharidin induces G2/M phase arrest by inhibition of Cdc25c and Cyclin A and triggers apoptosis through reactive oxygen species and the mitochondria­dependent pathways of A375.S2 human melanoma cells.

Cantharidin (CTD), a component of natural mylabris (Mylabris phalerata Pallas) was reported to have high cytotoxicity in many human cancer cell lines. However, it was not reported to affect human melanoma A375.S2 cells. In the present study, we found that CTD induced cell morphological changes and decreased the percentage of viable cells and induced G2/M phase arrest and induction of apoptosis in A375.S2 cells. Results also showed that CTD induced the generation of reactive oxygen species (ROS) and Ca2+ and decreased mitochondria membrane potential and lead to the release of cytochrome c, AIF and Endo G. Further investigation revealed that CTD induced A375.S2 cells with an increase of caspase activation and caspase-dependent apoptotic proteins to trigger correlated pathway mechanisms according to western blotting results. Western blotting was used for examining the changes of G2/M phase arrest and apoptosis-associated protein expression and confocal laser microscopy was used to examine the translocation apoptosis-associated protein. Results showed that CTD increased the protein expression of caspase-3, -8 and -9, cytochrome c, Bax, Bid, Endo G and AIF but inhibited the levels of Bcl-2 and Bcl-x. CTD induced ER stress-associated protein expression such as GRP78, IRE1ß, ATF6α and caspase-12. Based on those observations, we suggest that CTD may have potential as a novel anti-cancer agent for the treatment of skin cancer.

Atopic diseases and systemic lupus erythematosus: an epidemiological study of the risks and correlations.

Both atopic diseases and systemic lupus erythematosus (SLE) are immune disorders that may lead to physical complications or multi-system comorbidities. This population-based case-control study was designed to evaluate the risk of SLE associated with atopic diseases. Using a national insurance claims dataset in Taiwan, we identified 1673 patients newly diagnosed with SLE and 6692 randomly selected controls frequency matched for gender, age and index date. The odds ratios (OR) for SLE were calculated for associations with allergic rhinitis, allergic conjunctivitis, atopic dermatitis and asthma. The SLE patients were predominantly female (82.5%) with a mean age of 40.1 (SD = 18.2). The patients with SLE had a higher rate of atopic dermatitis (6.81% vs. 3.06%), and asthma (10.6% vs. 7.64%) was approximately 2 times more common in the patients with lupus than in those without. The patients with atopic disease (atopic dermatitis, allergic rhinitis, allergic conjunctivitis and asthma) were at a significant risk for SLE. The overall risk for SLE increased as the number of atopic diseases increased from 1.46 to 2.29, compared with-individuals without the diseases (p < 0.0001). In conclusion, this population-based case-control study demonstrates a significant relationship between atopic diseases and the risk of SLE, especially for females. Atopic dermatitis plays a stronger role than other types of atopic disease in association with SLE.

Perceptions on gender awareness and considerations in career choices of medical students in a medical school in Taiwan.

The trend of medical career choice in the younger generation has resulted in deficiency of manpower in the four major disciplines of internal medicine, surgery, obstetrics/gynecology, and pediatrics, which will threaten people's health care in Taiwan. However, perceptions of gender awareness and factors affecting the career choices of medical students have not been investigated systemically in Taiwan. To explore the perceptions on gender awareness and considerations in career choices, we recruited 280 1(st)- and 7(th)-year male and female medical students at a Medical University for the study. A modified Nijmegen questionnaire using a 5-point Likert scale containing medical curricula (18 items), gender awareness (13 items), and career inclination (9 items) was adopted as the investigation tool in our study. The response rate was 75% (224/280). With regard to gender, the 1(st)-year male students had greater confidence in being a physician than the female students (p < 0.05), and female students subjectively suggested an advantage to communicate with patients or colleagues (p < 0.05). Faculty attitude in treating students differently by gender was more prominent in the 7(th)-year than in the 1(st)-year students (p < 0.001), and they felt male preceptors typically were more enthusiastic to teach and to rank higher grades to female than to male students; however, this was not observed among female preceptors. Both male and female students showed a low level of agreement that clinical skills and performance of a physician were significantly different by gender and "female physicians are more empathetic and provide more communications than male physicians". Factors influencing career choices of medical students, including "personal interests/talents" and "academic achievement of the specialty," were not significantly different by gender. Factors included "training and learning environments of the specialty", "risk of lawsuit", and "economic incentive" were more appreciated by the senior than the junior students (p < 0.05). Effect of "family" or "spouse" did not differ significantly regardless of gender or seniority. The 7(th)-year students had experiences in clinical medicine and had different considerations in career choice in comparison to the 1(st)-year students, and gender played a role in senior students. In addition, the senior rather than the junior students regarded "training and learning environments", "risk of lawsuit", and "economic incentive" as more important factors affecting the career choices, and male students paid more attention to these issues. Other factors such as fixed hours of duty with no emergency, easier lifestyle, and more time to take care his/her families were also important factors affecting career choice in medical students regardless of their gender; however, the junior students disclosed lower concern on the issues. In addition, four major misperceptions of gender and health issues were prevalent in the 7(th)-year students; therefore, we recognized the importance of integrating gender issues into medical curriculum to diminish gender misunderstanding and prejudice, and to provide gender-specific health care is mandatory in Taiwan.

Citric acid induces cell-cycle arrest and apoptosis of human immortalized keratinocyte cell line (HaCaT) via caspase- and mitochondrial-dependent signaling pathways.

Citric acid is an alpha-hydroxyacid (AHA) widely used in cosmetic dermatology and skincare products. However, there is concern regarding its safety for the skin. In this study, we investigated the cytotoxic effects of citric acid on the human keratinocyte cell line HaCaT. HaCaT cells were treated with citric acid at 2.5-12.5 mM for different time periods. Cell-cycle arrest and apoptosis were investigated by 4,6-diamidino-2-phenylindole dihydrochloride (DAPI) staining, flow cytometry, western blot and confocal microscopy. Citric acid not only inhibited proliferation of HaCaT cells in a dose-dependent manner, but also induced apoptosis and cell cycle-arrest at the G2/M phase (before 24 h) and S phase (after 24 h). Citric acid increased the level of Bcl-2-associated X protein (BAX) and reduced the levels of B-cell lymphoma-2 (BCL-2), B-cell lymphoma-extra large (BCL-XL) and activated caspase-9 and caspase-3, which subsequently induced apoptosis via caspase-dependent and caspase-independent pathways. Citric acid also activated death receptors and increased the levels of caspase-8, activated BH3 interacting-domain death agonist (BID) protein, Apoptosis-inducing factor (AIF), and Endonuclease G (EndoG). Therefore, citric acid induces apoptosis through the mitochondrial pathway in the human keratinocyte cell line HaCaT. The study results suggest that citric acid is cytotoxic to HaCaT cells via induction of apoptosis and cell-cycle arrest in vitro.