Caffeic acid N-[3,5-bis(trifluoromethyl)phenyl] amide as a non-steroidal inhibitor for steroid 5α-reductase type 1 using a human keratinocyte cell-based assay and molecular dynamics.

Caffeic acid derivatives containing amide moieties similar to those of finasteride and dutasteride were synthesized. An in vitro inhibitory activity evaluation of caffeic acid (1) and its amide derivatives (2 - 4) against the steroid 5α-reductase type 1 (SRD5A1) produced by human keratinocyte cells coupled with the non-radioactive high-performance thin-layer chromatography detection revealed that caffeic acid N-[3,5-bis(trifluoromethyl)phenyl] amide (4) was a promising non-steroidal suppressor, with a half-maximal inhibitory concentration (IC50) of 1.44 ± 0.13 µM and relatively low cytotoxicity with an IC50 of 29.99 ± 8.69 µM. The regulatory role of compound 4 against SRD5A1 involved both suppression of SRD5A1 expression and mixed mode SRD5A1 inhibition. The Ki value of compound 4 was 2.382 µM based on the whole-cell kinetic studies under specific conditions. Molecular docking and molecular dynamics simulations with AlphaFold generated the human SRD5A1 structure and confirmed the stability of compound 4 at the SRD5A1 catalytic site with greater interactions, including hydrogen bonding of the key M119 amino-acid residue than those of finasteride and dutasteride. Thus, compound 4 shows the potential for further development as an SRD5A1 suppressor for androgenic alopecia treatment.

Recycled Sericin Hydrolysates Modified by Alcalase® Suppress Melanogenesis in Human Melanin-Producing Cells via Modulating MITF.

Because available depigmenting agents exhibit short efficacy and serious side effects, sericin, a waste protein from the silk industry, was hydrolyzed using Alcalase® to evaluate its anti-melanogenic activity in human melanin-producing cells. Sericin hydrolysates consisted of sericin-related peptides in differing amounts and smaller sizes compared with unhydrolyzed sericin, as respectively demonstrated by peptidomic and SDS-PAGE analysis. The lower half-maximum inhibitory concentration (9.05 ± 0.66 mg/mL) compared with unhydrolyzed sericin indicated a potent effect of sericin hydrolysates on the diminution of melanin content in human melanoma MNT1 cells. Not only inhibiting enzymatic activity but also a downregulated expression level of tyrosinase was evident in MNT1 cells incubated with 20 mg/mL sericin hydrolysates. Quantitative RT-PCR revealed the decreased mRNA level of microphthalmia-associated transcription factor (MITF), a tyrosinase transcription factor, which correlated with the reduction of pCREB/CREB, an upstream cascade, as assessed by Western blot analysis in MNT1 cells cultured with 20 mg/mL sericin hydrolysates for 12 h. Interestingly, treatment with sericin hydrolysates for 6-24 h also upregulated pERK, a molecule that triggers MITF degradation, in human melanin-producing cells. These results warrant the recycling of wastewater from the silk industry for further development as a safe and effective treatment of hyperpigmentation disorders.

Cajanin Suppresses Melanin Synthesis through Modulating MITF in Human Melanin-Producing Cells.

Despite its classification as a non-life-threatening disease, increased skin pigmentation adversely affects quality of life and leads to loss of self-confidence. Until now, there are no recommended remedies with high efficacy and human safety for hyperpigmentation. This study aimed to investigate anti-melanogenic activity and underlying mechanism of cajanin, an isoflavonoid extracted from Dalbergia parviflora Roxb. (Leguminosae) in human melanin-producing cells. Culture with 50 µM cajanin for 48-72 h significantly suppressed proliferation in human melanoma MNT1 cells assessed via MTT viability assay. Interestingly, cajanin also efficiently diminished melanin content in MNT1 cells with the half maximum inhibitory concentration (IC50) at 77.47 ± 9.28 µM. Instead of direct inactivating enzymatic function of human tyrosinase, down-regulated mRNA and protein expression levels of MITF and downstream melanogenic enzymes, including tyrosinase, TRP-1 and Dct (TRP-2) were observed in MNT1 cells treated with 50 µM cajanin for 24-72 h. Correspondingly, treatment with cajanin modulated the signaling pathway of CREB and ERK which both regulate MITF expression level. Targeted suppression on MITF-related proteins in human melanin-producing cells strengthens the potential development of cajanin as an effective treatment for human hyperpigmented disorders.

Flavonoids increase melanin production and reduce proliferation, migration and invasion of melanoma cells by blocking endolysosomal/melanosomal TPC2.

Two-pore channel 2 (TPC2) resides in endolysosomal membranes but also in lysosome-related organelles such as the melanin producing melanosomes. Gain-of-function polymorphisms in hTPC2 are associated with decreased melanin production and blond hair color. Vice versa genetic ablation of TPC2 increases melanin production. We show here an inverse correlation between melanin production and melanoma proliferation, migration, and invasion due to the dual activity of TPC2 in endolysosomes and melanosomes. Our results are supported by both genetic ablation and pharmacological inhibition of TPC2. Mechanistically, our data show that loss/block of TPC2 results in reduced protein levels of MITF, a major regulator of melanoma progression, but an increased activity of the melanin-generating enzyme tyrosinase. TPC2 inhibition thus provides a twofold benefit in melanoma prevention and treatment by increasing, through interference with tyrosinase activity, the synthesis of UV blocking melanin in melanosomes and by decreasing MITF-driven melanoma progression by increased GSK3ß-mediated MITF degradation.

Synthesis, Biological Evaluation and Molecular Docking of Avicequinone C Analogues as Potential Steroid 5α-Reductase Inhibitors.

Avicequinone C (5a), a furanonaphthoquinone isolated from the Thai mangrove Avicennia marina has been shown previously to have interesting steroid 5α-reductase type 1 inhibitory activity. In this study, a series of avicequinone C analogues containing furanonaphthoquinone with different degrees of saturation and substituents at the furan ring were synthesized. The resulting synthetic avicequinone C and analogues (5a-f) along with some related compounds including 2,5-dihydroxy-1,4-benzoquinone (6) and natural naphthoquinones such as lawsone (7a) and lapachol (7b) were evaluated for their in vitro cell viability and steroid 5α-reductase type 1 inhibitory activities using the cultured cell line of human keratinocytes (HaCaT). This cell-based bioassay was performed based on a direct detection of the enzymatic product dihydrotestosterone (2) by using a non-radioactive high performance thin layer chromatography (HPTLC) method. Among the furanonaphthoquinones in this series, 5e having a propionic substituent at furan ring possessed approximately 22-fold more potent than the original isolated compound 5a. However, the compounds without furan motif such as 6, 7a and b could not inhibit the activity of steroid 5α-reductase. Molecular docking results of the in silico three-dimensional steroid 5α-reductase type 1-reduced nicotinamide adenine dinucleotide phosphate (NADPH) binary complex was performed via AutoDock Vina and it illustrated that the furanonaphthoquinone moiety and the substituent at furan ring might play a key role as pharmacophores for the steroid 5α-reductase inhibitory activity.