Inhibition of α-melanocyte-stimulating hormone-induced melanogenesis and molecular mechanisms by polyphenol-enriched fraction of Tagetes erecta L. flower

BACKGROUND

The pursuit for safe and efficacious skin-whitening agents has prompted a dedicated exploration of plant-derived compounds. Notably, Tagetes erecta L. flowers have been used as a medicinal extract and possessed in vitro mushroom tyrosinase activity. However, whether polyphenol-enriched fraction extracted from T. erecta L. flowers (TE) regulates melanogenesis within cellular and animal models has not yet been investigated.

PURPOSE

This study aimed to investigate the effect of TE as a prospective inhibitor of melanogenesis.

METHODS

Through advanced UPLC-QTof/MS analysis, the components of TE were analyzed. Anti-melanogenic effects of TE were evaluated in α-melanocyte-stimulating hormone (α-MSH)-stimulated B16F10 melanoma cells by measuring cell viability assay, extracellular and intracellular melanin biosynthesis, cyclic adenosine monophosphate (cAMP) production, and melanogenesis-related gene and protein expression. Zebrafish larvae were employed for in vivo studies, assessing both heart rate and melanogenesis. Furthermore, molecular docking analyses were employed to predict the interaction between TE components and the melanocortin 1 receptor (MC1R). Direct binding activity of TE components to MC1R was compared with [Nle4, d-Phe7]-MSH (NDP-MSH).

RESULTS

TE was found to contain significant phenolic compounds such as patulitrin, quercetagetin, kaempferol, patuletin, and isorhamnetin. This study revealed that TE effectively inhibits melanin biosynthesis in both in vitro and in vivo models. This inhibition was attributed to interference of TE with the cAMP-cAMP response element-binding protein (CREB)-microphthalmia-associated transcription factor (MITF)-tyrosinase pathway, which plays a pivotal role in regulating melanogenesis. Importantly, TE exhibited the remarkable ability to curtail α-MSH-induced melanogenesis in zebrafish larvae without impacting heart rates. Molecular docking analyses predicted that the components of TE possibly interact with the melanocortin 1 receptor, suggesting their role as potential inhibitors of melanin biosynthesis. However, through the direct binding activity compared with NDP-MSH, any TE components did not directly bind to MC1R, suggesting that TE inhibits α-MSH-induced melanogenesis by inhibiting the cAMP-mediated intracellular signaling pathway. The assessment of anti-melanogenic activity, conducted both in vitro and in vivo, revealed that patulitrin and patuletin exhibited significant inhibitory effects on melanin formation, highlighting their potency as major contributors.

DISCUSSION

This investigation demonstrated the considerable potential of TE as a natural remedy endowed with remarkable anti-melanogenic properties. The demonstrated capacity of TE to attenuate melanin production by modulating the cAMP-CREB-MITF-tyrosinase pathway underscores its central role in management of disorders associated with excessive pigmentation. Importantly, the implications of these findings extend to the cosmetics industry, where TE emerges as a prospective and valuable ingredient for the formulation of skin-whitening products. The elucidated interactions between TE components and MC1R not only provide insight into a potential mechanism of action but also elevate the significance of this study. In summary, this study not only contributes to our comprehension of pigmentation-related conditions but also firmly establishes TE as a secure and natural strategy for the regulation of melanin production. The innovative aspects of TE propel it into the forefront of potential interventions, marking a noteworthy advancement in the pursuit of effective and safe solutions for pigmentation disorders.

Derrone Targeting the TGF Type 1 Receptor Kinase Improves Bleomycin-Mediated Pulmonary Fibrosis through Inhibition of Smad Signaling Pathway

Transforming growth factor-β (TGF-β) has a strong impact on the pathogenesis of pulmonary fibrosis. Therefore, in this study, we investigated whether derrone promotes anti-fibrotic effects on TGF-β1-stimulated MRC-5 lung fibroblast cells and bleomycin-induced lung fibrosis. Long-term treatment with high concentrations of derrone increased the cytotoxicity of MRC-5 cells; however, substantial cell death was not observed at low concentrations of derrone (below 0.05 μg/mL) during a three-day treatment. In addition, derrone significantly decreased the expressions of TGF-β1, fibronectin, elastin, and collagen1α1, and these decreases were accompanied by downregulation of α-SMA expression in TGF-β1-stimulated MRC-5 cells. Severe fibrotic histopathological changes in infiltration, alveolar congestion, and alveolar wall thickness were observed in bleomycin-treated mice; however, derrone supplementation significantly reduced these histological deformations. In addition, intratracheal administration of bleomycin resulted in lung collagen accumulation and high expression of α-SMA and fibrotic genes-including TGF-β1, fibronectin, elastin, and collagen1α1-in the lungs. However, fibrotic severity in intranasal derrone-administrated mice was significantly less than that of bleomycin-administered mice. Molecular docking predicted that derrone potently fits into the ATP-binding pocket of the TGF-β receptor type 1 kinase domain with stronger binding scores than ATP. Additionally, derrone inhibited TGF-β1-induced phosphorylation and nuclear translocations of Smad2/3. Overall, derrone significantly attenuated TGF-β1-stimulated lung inflammation in vitro and bleomycin-induced lung fibrosis in a murine model, indicating that derrone may be a promising candidate for preventing pulmonary fibrosis.

Pinostrobin Suppresses the α-Melanocyte-Stimulating Hormone-Induced Melanogenic Signaling Pathway

Pinostrobin is a dietary flavonoid found in several plants that possesses pharmacological properties, such as anti-cancer, anti-virus, antioxidant, anti-ulcer, and anti-aromatase effects. However, it is unclear if pinostrobin exerts anti-melanogenic properties and, if so, what the underlying molecular mechanisms comprise. Therefore, we, in this study, investigated whether pinostrobin inhibits melanin biosynthesis in vitro and in vivo, as well as the potential associated mechanism. Pinostrobin reduced mushroom tyrosinase activity in vitro in a concentration-dependent manner, with an IC₅₀ of 700 μM. Molecular docking simulations further revealed that pinostrobin forms a hydrogen bond, as well as other non-covalent interactions, between the C-type lectin-like fold and polyphenol oxidase chain, rather than the previously known copper-containing catalytic center. Additionally, pinostrobin significantly decreased α-melanocyte-stimulating hormone (α-MSH)-induced extracellular and intracellular melanin production, as well as tyrosinase activity, in B16F10 melanoma cells. More specifically, pinostrobin inhibited the α-MSH-induced melanin biosynthesis signaling pathway by suppressing the cAMP-CREB-MITF axis. In fact, pinostrobin also attenuated pigmentation in α-MSH-stimulated zebrafish larvae without causing cardiotoxicity. The findings suggest that pinostrobin effectively inhibits melanogenesis in vitro and in vivo via regulation of the cAMP-CREB-MITF axis.