Protective effects of Y-27632 against cisplatin-induced ototoxicity: A zebrafish model Y-27632 and cisplatin-induced ototoxicity.

Cisplatin is an effective chemotherapy agent against various solid malignancies; however, it is associated with irreversible bilateral sensorineural hearing loss, emphasizing the need for drug development to prevent this complication, with the current options being very limited. Rho-associated coiled-coil-containing protein kinase (ROCK) is a serine-threonine protein kinase involved in various cellular processes, including apoptosis regulation. In this study, we used a transgenic zebrafish model (Brn3C: EGFP) in which hair cells within neuromasts are observed in green under fluorescent microscopy without the need for staining. Zebrafish larvae were exposed to cisplatin alone or in combination with various concentrations of Y-27632, a potent ROCK inhibitor. Hair cell counts, apoptosis assessments using the terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling assay, FM1-43FX labeling assay and behavioral analyses (startle response and rheotaxis) were performed to evaluate the protective effects of Y-27632 against cisplatin-induced ototoxicity. Cisplatin treatment reduced the number of hair cells in neuromasts, induced apoptosis, and impaired zebrafish larval behaviors. Y-27632 demonstrated a dose-dependent protective effect against cisplatin-induced hair cell loss and apoptosis. These findings suggest that Y-27632, as a ROCK inhibitor, mitigates cisplatin-induced hair cell loss and associated ototoxicity in zebrafish.

Interaction Analysis of the Spike Protein of Delta and Omicron Variants of SARS-CoV-2 with hACE2 and Eight Monoclonal Antibodies Using the Fragment Molecular Orbital Method.

In the past 2 years, since the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), multiple SARS-CoV-2 variants have emerged. Whenever a new variant emerges, considerable time is required to analyze the binding affinity of the viral surface proteins to human angiotensin-converting enzyme 2 (hACE2) and monoclonal antibodies. To efficiently predict the binding affinities associated with hACE2 and monoclonal antibodies in a short time, herein, we propose a method applying statistical analysis to simulations performed using molecular and quantum mechanics. This method efficiently predicted the trend of binding affinity for the binding of the spike protein of each variant of SARS-CoV-2 to hACE2 and individually to eight commercial monoclonal antibodies. Additionally, this method accurately predicted interaction energy changes in the crystal structure for 10 of 13 mutated residues in the Omicron variant, showing a significant change in the interaction energy of hACE2. S375F was found to be a mutation that majorly changed the binding affinity of the spike protein to hACE2 and the eight monoclonal antibodies. Our proposed analysis method enables the prediction of the binding affinity of new variants to hACE2 or to monoclonal antibodies in a shorter time compared to that utilized by the experimental method.

Fat Graft with Allograft Adipose Matrix and Magnesium Hydroxide-Incorporated PLGA Microspheres for Effective Soft Tissue Reconstruction.

BACKGROUND: Autologous fat grafting is one of the most common procedures used in plastic surgery to correct soft tissue deficiency or depression deformity. However, its clinical outcomes are often suboptimal, and lack of metabolic and architectural support at recipient sites affect fat survival leading to complications such as cyst formation, calcification. Extracellular matrix-based scaffolds, such as allograft adipose matrix (AAM) and poly(lactic-co-glycolic) acid (PLGA), have shown exceptional clinical promise as regenerative scaffolds. Magnesium hydroxide (MH), an alkaline ceramic, has attracted attention as a potential additive to improve biocompatibility. We attempted to combine fat graft with regenerative scaffolds and analyzed the changes and viability of injected fat graft in relation to the effects of injectable natural, and synthetic (PLGA/MH microsphere) biomaterials. METHODS: In vitro cell cytotoxicity, angiogenesis of the scaffolds, and wound healing were evaluated using human dermal fibroblast cells. Subcutaneous soft-tissue integration of harvested fat tissue was investigated in vivo in nude mouse with random fat transfer protocol Fat integrity and angiogenesis were identified by qRT-PCR and immunohistochemistry. RESULTS: In vitro cell cytotoxicity was not observed both in AAM and PLGA/MH with human dermal fibroblast. PLGA/MH and AAM showed excellent wound healing effect. In vivo, the AAM and PLGA/MH retained volume compared to that in the only fat group. And the PLGA/MH showed the highest angiogenesis and anti-inflammation. CONCLUSION: In this study, a comparison of the volume retention effect and angiogenic ability between autologous fat grafting, injectable natural, and synthetic biomaterials will provide a reasonable basis for fat grafting.

PFN1 Prevents Psoriasis Pathogenesis through IκBζ Regulation.

PFN1 is an actin-binding protein that regulates actin polymerization, cell proliferation, apoptosis, angiogenesis, and carcinogenesis. Its dysregulation has been reported in diverse pathologic diseases; however, the role of PFN1 in psoriasis has not yet been elucidated. In this study, we show that PFN1 expression is increased in both skin and serum of patients with psoriasis. PFN1 was markedly expressed in the epidermis of psoriatic lesions, and its expression positively correlated with psoriasis severity. IL-17A treatment of keratinocytes increased PFN1 expression, whereas TNF-α induced PFN1 expression and secretion. In addition, knockdown of PFN1 with short hairpin RNA resulted in an altered expression of psoriasis-associated inflammatory markers, HBD2, S100A7, S100A9, and Ki-67, and recombinant PFN1 suppressed the IL-17A‒induced inflammatory response in keratinocytes. Interestingly, recombinant PFN1 also suppressed IL-17A‒induced IκBζ, an important player in immune response in psoriasis. Collectively, our results show that PFN1 acts as a negative regulator of psoriatic inflammation through the suppression of IκBζ and that the balanced level of PFN1 is important for IκBζ regulation. Thus, the expression of PFN1 can be used as a biomarker for psoriasis severity, and it can be considered as a possible target for the treatment of psoriasis.

Evaluation of Selective COX-2 Inhibition and In Silico Study of Kuwanon Derivatives Isolated from Morus alba.

Six kuwanon derivatives (A/B/C/E/H/J) extracted from the roots of Morus alba L. were evaluated to determine their cyclooxygenase (COX)-1 and 2 inhibitory effects. Cyclooxygenase (COX) is known as the target enzyme of nonsteroidal anti-inflammatory drugs (NSAIDs), which are the most widely used therapeutic agents for pain and inflammation. Among six kuwanon derivatives, kuwanon A showed selective COX-2 inhibitory activity, almost equivalent to that of celecoxib, a known COX inhibitor. Kuwanon A showed high COX-2 inhibitory activity (IC50 = 14 µM) and a selectivity index (SI) range of >7.1, comparable to celecoxib (SI > 6.3). To understand the mechanisms underlying this effect, we performed docking simulations, fragment molecular orbital (FMO) calculations, and pair interaction energy decomposition analysis (PIEDA) at the quantum-mechanical level. As a result, kuwanon A had the strongest interaction with Arg120 and Tyr355 at the gate of the COX active site (-7.044 kcal/mol) and with Val89 in the membrane-binding domain (-6.599 kcal/mol). In addition, kuwanon A closely bound to Val89, His90, and Ser119, which are residues at the entrance and exit routes of the COX active site (4.329 Å). FMO calculations and PIEDA well supported the COX-2 selective inhibitory action of kuwanon A. It showed that the simulation and modeling results and experimental evidence were consistent.

Comparison of Digital PCR and Quantitative PCR with Various SARS-CoV-2 Primer-Probe Sets.

The World Health Organization (WHO) has declared the coronavirus disease 2019 (COVID-19) as an international health emergency. Current diagnostic tests are based on the reverse transcription-quantitative polymerase chain reaction (RT-qPCR) method, which is the gold standard test that involves the amplification of viral RNA. However, the RT-qPCR assay has limitations in terms of sensitivity and quantification. In this study, we tested both qPCR and droplet digital PCR (ddPCR) to detect low amounts of viral RNA. The cycle threshold (CT) of the viral RNA by RT-PCR significantly varied according to the sequences of the primer and probe sets with in vitro transcript (IVT) RNA or viral RNA as templates, whereas the copy number of the viral RNA by ddPCR was effectively quantified with IVT RNA, cultured viral RNA, and RNA from clinical samples. Furthermore, the clinical samples were assayed via both methods, and the sensitivity of the ddPCR was determined to be equal to or more than that of the RT-qPCR. However, the ddPCR assay is more suitable for determining the copy number of reference materials. These findings suggest that the qPCR assay with the ddPCR defined reference materials could be used as a highly sensitive and compatible diagnostic method for viral RNA detection.

Anti-Inflammatory Activity and ROS Regulation Effect of Sinapaldehyde in LPS-Stimulated RAW 264.7 Macrophages.

We evaluated the anti-inflammatory effects of SNAH in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages by performing nitric oxide (NO) assays, cytokine enzyme-linked immunosorbent assays, Western blotting, and real-time reverse transcription-polymerase chain reaction analysis. SNAH inhibited the production of NO (nitric oxide), reactive oxygen species (ROS), tumor necrosis factor (TNF)-α, and interleukin (IL)-6. Additionally, 100 µM SNAH significantly inhibited total NO and ROS inhibitory activity by 93% (p < 0.001) and 34% (p < 0.05), respectively. Protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) stimulated by LPS were also decreased by SNAH. Moreover, SNAH significantly (p < 0.001) downregulated the TNF-α, IL-6, and iNOS mRNA expression upon LPS stimulation. In addition, 3-100 µM SNAH was not cytotoxic. Docking simulations and enzyme inhibitory assays with COX-2 revealed binding scores of -6.4 kcal/mol (IC50 = 47.8 µM) with SNAH compared to -11.1 kcal/mol (IC50 = 0.45 µM) with celecoxib, a known selective COX-2 inhibitor. Our results demonstrate that SNAH exerts anti-inflammatory effects via suppression of ROS and NO by COX-2 inhibition. Thus, SNAH may be useful as a pharmacological agent for treating inflammation-related diseases.

Rapid Detection of COVID-19 Causative Virus (SARS-CoV-2) in Human Nasopharyngeal Swab Specimens Using Field-Effect Transistor-Based Biosensor.

Coronavirus disease 2019 (COVID-19) is a newly emerging human infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, previously called 2019-nCoV). Based on the rapid increase in the rate of human infection, the World Health Organization (WHO) has classified the COVID-19 outbreak as a pandemic. Because no specific drugs or vaccines for COVID-19 are yet available, early diagnosis and management are crucial for containing the outbreak. Here, we report a field-effect transistor (FET)-based biosensing device for detecting SARS-CoV-2 in clinical samples. The sensor was produced by coating graphene sheets of the FET with a specific antibody against SARS-CoV-2 spike protein. The performance of the sensor was determined using antigen protein, cultured virus, and nasopharyngeal swab specimens from COVID-19 patients. Our FET device could detect the SARS-CoV-2 spike protein at concentrations of 1 fg/mL in phosphate-buffered saline and 100 fg/mL clinical transport medium. In addition, the FET sensor successfully detected SARS-CoV-2 in culture medium (limit of detection [LOD]: 1.6 × 101 pfu/mL) and clinical samples (LOD: 2.42 × 102 copies/mL). Thus, we have successfully fabricated a promising FET biosensor for SARS-CoV-2; our device is a highly sensitive immunological diagnostic method for COVID-19 that requires no sample pretreatment or labeling.

Zika virus infection differentially affects genome-wide transcription in neuronal cells and myeloid dendritic cells.

Zika virus (ZIKV) is an emerging mosquito-borne flavivirus that has attracted global attention and international awareness. ZIKV infection exhibits mild symptoms including fever and pains; however, ZIKV has recently been shown to be related to increased birth defects, including microcephaly, in infants. In addition, ZIKV is related to the onset of neurological disorders, such as a type of paralysis similar to Guillain-Barré syndrome. However, the mechanisms through which ZIKV affect neuronal cells and myeloid dendritic cells and how ZIKV avoids host immunity are unclear. Accordingly, in this study, we analyzed RNA sequencing data from ZIKV-infected neuronal cells and myeloid dendritic cells by comparative network analyses using protein-protein interaction information. Comparative network analysis revealed major genes showing differential changes in the peripheral neurons, neural crest cells, and myeloid dendritic cells after ZIKV infection. The genes were related to DNA repair systems and prolactin signaling as well as the interferon signaling, neuroinflammation, and cell cycle pathways. These pathways were interconnected by the interaction of proteins in the pathway and significantly regulated by ZIKV infection in neuronal cells and myeloid dendritic cells. Our analysis showed that neuronal cell damage occurred through up-regulation of neuroinflammation and down-regulation of the DNA repair system, but not in myeloid dendritic cells. Interestingly, immune escape by ZIKV infection could be caused by downregulation of prolactin signaling including IRS2, PIK3C3, JAK3, STAT3, and IRF1 as well as mitochondria dysfunction and oxidative phosphorylation in myeloid dendritic cells. These findings provide insight into the mechanisms of ZIKV infection in the host and the association of ZIKV with neurological and immunological symptoms, which may facilitate the development of therapeutic agents and vaccines.

Development of Reverse Transcription Loop-Mediated Isothermal Amplification Assays Targeting Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2).

The coronavirus disease 2019 (COVID-19) pandemic now has >2,000,000 confirmed cases worldwide. COVID-19 is currently diagnosed using quantitative RT-PCR methods, but the capacity of quantitative RT-PCR methods is limited by their requirement of high-level facilities and instruments. We developed and evaluated reverse transcription loop-mediated isothermal amplification (RT-LAMP) assays to detect genomic RNA of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative virus of COVID-19. RT-LAMP assays reported in this study can detect as low as 100 copies of SARS-CoV-2 RNA. Cross-reactivity of RT-LAMP assays to other human coronaviruses was not observed. A colorimetric detection method was adapted for this RT-LAMP assay to enable higher throughput.

Colorimetric RT-LAMP Methods to Detect Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2).

Standard diagnostic methods of Coronavirus Disease 2019 (COVID-19) rely on RT-qPCR technique which have limited point-of-care test (POCT) potential due to necessity of dedicated equipment and specialized personnel. LAMP, an isothermal nucleic acid amplification test (NAAT), is a promising technique that may substitute RT-qPCR for POCT of genomic materials. Here, we provide a protocol to perform reverse transcription LAMP targeting SARS-CoV-2. We adopted both real-time fluorescence detection and end-point colorimetric detection approaches. Our protocol would be useful for screening diagnosis of COVID-19 and be a baseline for development of improved POCT NAAT.

The Effect of Hyaluronidase on the Fat Graft.

BACKGROUND: Fat grafting has been widely used for facial rejuvenation and soft tissue reconstruction. However, it is associated with a lower retention rate than expected and complications such as fat necrosis or calcification. Several techniques that may increase the survival rate of fat grafts have been proposed. The techniques that promote the recipient sites vascularity to increase the survival rate of fat grafts include administration of growth factors, platelet- rich plasma, and adipose derived-stem cells or preconditioning of the recipient fat graft site. METHODS: In this study, the authors evaluated the effect of hyaluronidase on autologous fat graft survival by pretreatment with hyaluronidase at the recipient site by using an animal model. In the experimental group, the recipient site of the fat graft was pretreated with hyaluronidase before fat grafting, whereas the control group was pretreated with normal saline. RESULTS: After 8 weeks of fat grafting, the average volume retention was 78.2% in the experimental group and 68.6% in control group. Considerable fibrosis between the fat globules in the control group was confirmed with Masson trichrome staining. CD31 immunofluorescence staining was performed and stained vessels were counted. Counted vessel number was significantly greater in the experimental group than in the control group. CONCLUSIONS: Pretreatment of hyaluronidase on the fat graft recipient site is a good option to enhance the outcome of the fat graft in the clinical setting.

Inhibitory Effect of Sesamolin on Melanogenesis in B16F10 Cells Determined by In Vitro and Molecular Docking Analyses.

BACKGROUND: Melanin protects the skin against the harmful effects of ultraviolet irradiation. However, melanin overproduction can result in several aesthetic problems, including melasma, freckles, age spots and chloasma. Therefore, development of anti-melanogenic agents is important for the prevention of serious hyperpigmentation diseases. Sesamolin is a lignan compound isolated from sesame seeds with several beneficial properties, including potential for melanin inhibition. OBJECTIVE: The aim of this study was to evaluate the anti-melanogenic effect of sesamolin in cell culture in vitro and the underlying mechanism of inhibition using molecular docking simulation. METHODS: Melanogenesis was induced by 3-isobutyl-1-methylxanthine in B16F10 melanoma cells, and the inhibitory effects of sesamolin were evaluated using zymography, a tyrosinase inhibitory activity assay, western blotting, and real-time reverse transcription-polymerase chain reaction analysis. Docking simulations between sesamolin and tyrosinase were performed using Autodock vina. RESULTS: Sesamolin significantly inhibited the expression of melanogenesis-related factors tyrosinase, and tyrosinase-related proteins 1 and 2 at the mRNA and protein levels. Treatment of melanoma cells with 50 µM sesamolin demonstrated the strongest inhibition against intercellular tyrosinase and melanin synthesis without exerting cytotoxic effects. Sesamolin significantly reduced mushroom tyrosinase activity in a dose-dependent manner via a competitive inhibition mechanism. Tyrosinase docking simulations supported that sesamolin (-6.5 kcal/mol) bound to the active site of tyrosinase more strongly than the positive control (arbutin, -5.7 kcal/mol). CONCLUSION: Sesamolin could be developed as a melanogenesis inhibiting agent owing to its dual function in blocking the generation of melanogenesis-related enzymes and inhibiting the enzymatic response of tyrosinase.

Fermented Garlic Extract Increases Oxygen Consumption and UCP-1 mRNA Expression in Human Adipose-Derived Stem Cells.

Fermented garlic, often called black garlic, is a traditional food ingredient used in Asian cuisine and possesses various health benefits including anti-obesity activity. The anti-obesity effects of fermented garlic might, in part, might be mediated through direct actions of its components on adipocytes. To test this hypothesis, we examined whether fermented garlic extract might stimulate the metabolic activity of human adipose-derived stem cells (ADSCs) in culture. Cell viability measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay exhibited a complex doseresponse relationship. The lowest concentration (0.4 mg/ml) reduced cell viability (P<0.05 compared to no extract, Bonferroni's multiple comparison), whereas higher concentrations (0.8 and 1.0 mg/ml) resulted in higher cell viability (P<0.05 as compared to 0.4 mg/ml). However, the extract at concentrations >2 mg/ml markedly decreased cell viability. Higher cell viability observed following treatment with 0.8~1.0 mg/ml might be associated with raised oxygen consumption. Fluorescent dye-based measurement revealed that the garlic extract at 1.0 mg/ml significantly increased oxygen consumption. We also detected a significant increase in mRNA expression levels of uncoupling protein-1 (UCP- 1). These findings suggest that fermented garlic stimulates the basal metabolic activity of human ADSCs.

The Effect of Nefopam Infusion during Laparascopic Cholecystectomy on Postoperative Pain.

Background: While recovery from remifentanil is fast due to its rapid metabolism, it can induce hyperalgesia by activation of N-methyl-D-aspartic acid (NMDA) receptors. Therefore, administration of NMDA receptor antagonists such as ketamine is effective in relieving hyperalgesia caused by remifentanil. A previous study showed that nefopam administration before anesthesia combined with low-dose remifentanil reduced pain and analgesic consumption during the immediate postoperative period. We hypothesized that intraoperative infusion of nefopam during laparoscopic cholecystectomy would be as effective as ketamine in controlling pain during the acute postoperative period after sevoflurane and remifentanil based anesthesia. Methods: Sixty patients scheduled to undergo laparoscopic cholecystectomy were randomly divided into three groups. General anesthesia was maintained with sevoflurane and effect-site target concentration of remifentanil (4 ng/ml) in all patients. An intravenous bolus of nefopam (0.3 mg/kg) was given, followed by continuous infusion (65 µg/kg/h) in Group N (n=20). An intravenous bolus of ketamine (0.3 mg/kg) was administered, followed by continuous infusion (180 µg/kg/h) in Group K (n=20), and Group C received a bolus and subsequent infusion of normal saline equal to the infusion received by Group K (n=20). We compared postoperative Visual Analogue Scale (VAS) scores and analgesic requirements over the first 8 postoperative hours between groups. Results: The pain scores (VAS) and fentanyl requirements for 1 h after surgery were significantly lower in the nefopam and ketamine groups compared with the control group (p<0.05). There were no differences between the nefopam and ketamine groups. The three groups showed no differences in VAS scores and number of analgesic injections from 1 to 8 h after surgery. Conclusion: Intraoperative nefopam infusion during laparoscopic cholecystectomy reduced opioid requirements and pain scores (VAS) during the early postoperative period after remifentanil-based anesthesia.

Soy-Leaf Extract Exerts Atheroprotective Effects via Modulation of Krüppel-Like Factor 2 and Adhesion Molecules.

Soy-leaf extracts exert their cardioprotective effects by inducing endothelium-dependent vasodilation in the arteries, and they favorably modulate the serum lipid profile. In this study, we investigated the atheroprotective effects of an ethanol extract of soy leaf (ESL) in human umbilical vein endothelial cells (HUVECs) and high-cholesterol diet (HCD)-fed low-density lipoprotein receptor deficient (LDLR-/-) mice. ESL induced the expression of Krüppel-like factor 2 (KLF2), an endothelial transcription factor, and endothelial nitric oxide synthase (eNOS), and suppressed the expression of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) through moderate inflammatory signal activation, not only in tumor necrosis factor-α (TNF-α)-stimulated HUVECs but also in 7-ketocholesterol (7-KC)-stimulated HUVECs. ESL supplementation reduced aortic lesion formation in Western diet-fed LDLR-/- mice by 46% (p < 0.01) compared to the HCD group. ESL also markedly decreased the aortic expression levels of VCAM-1, ICAM-1, monocyte chemotactic protein-1 (MCP-1), TNF-α, IL-6, IL-1ß, matrix metallopeptidase 9 (MMP-9), and fractalkine, while the expression of KLF2 was significantly increased. These results suggest that ESL supplementation has potential for preventing HCD-induced atherosclerosis effectively.

Osteoprotective Effects of Polysaccharide-Enriched Hizikia fusiforme Processing Byproduct In Vitro and In Vivo Models.

The traditional manufacturing method used to produce goods from Hizikia fusiforme, utilizes extraction steps with hot water. The byproduct (of hot water extraction) is rich in polysaccharide and is considered a waste. To evaluate the osteogenic effects of the byproduct of H. fusiforme (HFB), osteogenic cells and animal models were used to test it effects on osteogenesis. The HFB-treated mouse myoblast C2C12 cells exhibited significant dose dependently elevated alkaline phosphatase (ALP) activity and slightly increased bone morphogenetic protein-2 (BMP-2). HFB also suppressed the formation of tartrate-resistant acid phosphatase (TRAP) activity and TRAP staining in the bone marrow-derived macrophages (BMM) cells that had been stimulated with the receptor activator of the nuclear factor kB ligand/macrophage colony-stimulating factor kB ligand. In addition, HFB also increased the phosphorylation of extracellular signal-regulated protein kinase (p-ERK) level. Finally, osteogenic effects of HFB were clearly confirmed in the three in vivo models: zebrafish, ovariectomized mice, and mouse calvarial bones. HFB accelerated the rate of skeletal development in zebrafish and prevented much of the mouse femoral bone density loss of ovariectomized mice. Moreover, HFB enhanced woven bone formation over the periosteum of mouse calvarial bones. Our result showed that HFB functions as a bone resorption inhibitor as well as an activator of bone formation in vivo and in osteogenic in vitro cell systems.

Proton pump inhibitors decrease melanogenesis in melanocytes.

Proton pump inhibitors (PPIs) are widely used as inhibitors of gastric juice secretion for treatment of gastroesophageal reflux disease. However, there are no previous studies of the effects on melanogenesis resulting from PPI treatments. Therefore, the aim of the present study was to investigate the effects of PPIs on melanogenesis in melan-a cells derived from immortalized mouse melanocytes. Tyrosinase activity and copper-chelating activity were measured spectrophotometrically. In addition, the melanin content and viability of melan-a cells treated with PPIs were assessed and the mRNA levels of melanogenesis-associated genes were measured by reverse transcription-polymerase chain reaction. Treatment with rabeprazole, but not the other PPIs tested, resulted in strong, dose-dependent inhibition of mushroom tyrosinase (TYR). By contrast, each of the PPIs tested exhibited copper-chelating activity. Treatment of melan-a cells with 100 µM concentrations of the PPIs resulted in significantly reduced melanin synthesis and reduced expression of several melanogenesis-associated genes, including TYR, TYR-related protein-1 (TRP-1) and TRP-2, and microphthalmia-associated transcription factor, but did not result in cytotoxic effects. These results suggest that PPIs inhibit melanin biosynthesis in melan-a cells via the downregulation of melanogenesis-associated genes. Furthermore, the findings indicate that PPIs in general could be utilized as skin-whitening agents and/or as biomaterial for treating hyperpigmentation disorders.