Glutathione in its reduced form (GSH) is an antioxidant and also is involved in pheomelanin formation. Thus, it has been long believed that GSH has a skin whitening effect. However, its actual or direct effect is unproven. We evaluated the anti-melanogenic effects of GSH and its derivatives in vitro. We examined change of melanogenesis and its related proteins by GSH itself and its derivatives, including GSH monoethyl ester (GSH-MEE), GSH diethyl ester (GSH-DEE) and GSH monoisopropyl ester (GSH-MIPE) in Melan-A cells, Mel-Ab cells, and B16F10 cells. GSH and GSH-MEE did not display cytotoxic activity, but GSH-MIPE and GSH-DEE did. Intriguingly, GSH itself had no inhibitory effect on melanin production or intracellular tyrosinase activity. Rather, it was GSH-MEE and GSH-MIPE that profoundly reduced the amount of melanin and intracellular tyrosinase activity. Thus, GSH-MEE was selected as a suitable candidate skin-whitening agent and it did not alter melanogenesis-associated proteins such as microphthalmia-associated transcription factor (MITF), tyrosinase, tyrosinase-related protein (TRP)-1, and TRP-2, but it did increase the amount of suggested pheomelanin and suggested pheomelanin/eumelanin ratio. GSH-MEE was effective for anti-melanogenesis, whereas GSH itself was not. GSH-MEE could be developed as a safe and efficient agent for the treatment of hyperpigmentation skin disorders.

Son E, et al. Korean J Physiol Pharmacol. 2020 Mar;24(2):173-183. https://doi.org/10.4196/kjpp.2020.24.2.173

Epidermal keratinocytes are considered as the most important neighboring cells that modify melanogenesis. Our previous study used microarray to show that guanine deaminase (GDA) gene expression is highly increased in melasma lesions. Hence, we investigated the role of GDA in skin pigmentation. We examined GDA expression in post-inflammatory hyperpigmentation (PIH) lesions, diagnosed as Riehl’s melanosis. We further investigated the possible role of keratinocyte-derived GDA in melanogenesis by quantitative PCR, immunofluorescence staining, small interfering RNA-based GDA knockdown, and adenovirus-mediated GDA overexpression. We found higher GDA positivity in the hyperpigmentary lesional epidermis than in the perilesional epidermis. Both UVB irradiation and stem cell factor (SCF) plus endothelin-1 (ET-1) were used, which are well-known melanogenic stimuli upregulating GDA expression in both keratinocyte culture alone and keratinocyte and melanocyte coculture. GDA knockdown downregulated melanin content, while GDA overexpression promoted melanogenesis in the coculture. When melanocytes were treated with UVB-exposed keratinocyte-conditioned media, the melanin content was increased. Also, GDA knockdown lowered SCF and ET-1 expression levels in keratinocytes. GDA in epidermal keratinocytes may promote melanogenesis by upregulating SCF and ET-1, suggesting its role in skin hyperpigmentary disorders.

Background: Cell lines are often used to assess the resistance of anticancer drugs when in vivo analysis is not possible. However, the process for establishing anti-cancer drug resistance in cell cultures in vitro and the subsequent method of then evaluating resistance are not clearly established. Traditionally, the IC₅₀ is the most commonly used indicator of resistance evaluation but it cannot represent the effectiveness of anti-cancer drugs in a clinical setting and lacks reliability because it is heavily affected by the cell doubling time. Hence, new indicators that can evaluate anti-cancer drug resistance are needed. Methods: A novel resistance evaluation methodology was validated in this present study by establishing sunitinib resistance in renal cell carcinoma cells and assessing the cross-resistance of five different anti-cancer drugs. Results: It was confirmed in this present study that the IC₅₀ does not reflect the cell proliferation rates in a way that represents anti-cancer drug resistance. An alternative indicator that can also be clinically meaningful when using in vitro cell line systems is GI₁₀₀. Additionally, the GR₁₀₀ allows different cell populations to be calibrated on the same basis when multiple experimental results are compared. Conclusion: Since the GR₁₀₀ has properties that indicate the efficiency of anti-cancer drugs, both the efficacy and GR₁₀₀ of a particular anti-cancer drug can be used to effectively assess the resistance.

Heart ischemia/reperfusion (I/R) injury is related to iron content. However, the occurrence and mechanism of changes in labile iron pool (LIP) during I/R is debatable. Moreover, the identity of the iron form dominant in LIP during I/R is unclear. Herein, we measured changes of LIP during simulated ischemia (SI) and reperfusion (SR), in which ischemia was simulated in vitro with lactic acidosis and hypoxia. Total LIP did not change in lactic acidosis, whereas LIP, especially Fe³⁺, increased in hypoxia. Under SI, accompanied by hypoxia with acidosis, both Fe²⁺ and Fe³⁺ were significantly increased. Increased total LIP was maintained at 1 h post-SR. However, the Fe²⁺ and Fe³⁺ portion was changed. The increased Fe²⁺ was decreased, and conversely the Fe³⁺ was increased. BODIPY oxidized signal increased and through the time-course these changes correlated with blebbing of cell membrane and SR-induced LDH release. These data suggested lipid peroxidation occurred via Fenton’s reaction. The experiments using bafilomycin A1 and zinc protoporphyrin suggested no role of ferritinophagy or heme oxidation in the increase of LIP during SI. The extracellular source, transferrin assessed using serum transferrin bound iron (TBI) saturation showed that the depletion of TBI reduced SR-induced cell damages and additive saturation of TBI accelerated SR-induced lipid peroxidation. Furthermore, Apo-Tf dramatically blocked the increase of LIP and SR-induced damages. In conclusion, Tf-mediated iron induces the increase of LIP during SI, and it causes Fenton reaction-mediated lipid peroxidation during the early phase of SR.