Dehydroglyasperin D Suppresses Melanin Synthesis through MITF Degradation in Melanocytes.

Licorice (Glycyrrhiza) has been used as preventive and therapeutic material for hyperpigmentation disorders. Previously, we isolated noble compounds including dehydroglyasperin C (DGC), dehydroglyasperin D (DGD) and isoangustone A (IAA) from licorice hexane/ethanol extracts. However, their anti-melanogenic effects and underlying molecular mechanisms are unknown. The present study compared effects of DGC, DGD and IAA on pigmentation in melan-a melanocytes and human epidermal melanocytes (HEMn). DGD exerted the most excellent anti-melanogenic effect, followed by DGC and IAA at non-cytotoxic concentrations. In addition, DGD significantly inhibited tyrosinase activity in vitro cell-free system and cell system. Western blot result showed that DGD decreased expression of microphthalmia-associated transcription factor (MITF), tyrosinase and tyrosinase-related protein-1 (TRP-1) in melan-a cells and HEMn cells. DGD induced phosphorylation of MITF, ERK and Akt signal pathway promoting MITF degradation system. However, DGD did not influence p38 and cAMP-dependent protein kinase (PKA)/CREB signal pathway in melan-a cells. These result indicated that DGD inhibited melanogenesis not only direct regulation of tyrosinase but also modulating intracellular signaling related with MITF level. Collectively, these results suggested a protective role for DGD against melanogenesis.

A novel anti-c-Kit antibody-drug conjugate to treat wild-type and activating-mutant c-Kit-positive tumors.

c-Kit overexpression and activating mutations, which are reported in various cancers, including gastrointestinal stromal tumor (GIST), small-cell lung cancer (SCLC), acute myeloid leukemia, acral melanoma, and systemic mastocytosis (SM), confer resistance to tyrosine kinase inhibitors (TKIs). To overcome TKI resistance, an anti-c-Kit antibody-drug conjugate was developed in this study to treat wild-type and mutant c-Kit-positive cancers. NN2101, a fully human IgG1, was conjugated to DM1, a microtubule inhibitor, through N-succinimidyl-4-(N-maleimidomethyl) cyclohexane-1-carboxylate (SMCC) (to give NN2101-DM1). The antitumor activity of NN2101-DM1 was evaluated in vitro and in vivo using various cancer cell lines. NN2101-DM1 exhibited potent growth-inhibitory activities against c-Kit-positive cancer cell lines. In a mouse xenograft model, NN2101-DM1 exhibited potent growth-inhibitory activities against imatinib-resistant GIST and SM cells. In addition, NN2101-DM1 exhibited a significantly higher anti-cancer effect than carboplatin/etoposide against SCLC cells where c-Kit does not mediate cancer pathogenesis. Furthermore, the combination of NN2101-DM1 with imatinib in imatinib-sensitive GIST cells induced complete remission compared with treatment with NN2101-DM1 or imatinib alone in mouse xenograft models. These results suggest that NN2101-DM1 is a potential therapeutic agent for wild-type and mutant c-Kit-positive cancers.

Sex differences and Tat expression affect dopaminergic receptor expression and response to antioxidant treatment in methamphetamine-sensitized HIV Tat transgenic mice.

Methamphetamine (Meth) abuse is a common HIV comorbidity. Males and females differ in their patterns of Meth use, associated behaviors, and responses, but the underlying mechanisms and impact of HIV infection are unclear. Transgenic mice with inducible HIV-1 Tat protein in the brain (iTat) replicate many neurological aspects of HIV infection in humans. We previously showed that Tat induction enhances the Meth sensitization response associated with perturbation of the dopaminergic system, in male iTat mice. Here, we used the iTat mouse model to investigate sex differences in individual and interactive effects of Tat and Meth challenge on locomotor sensitization, brain expression of dopamine receptors (DRDs) and regulatory adenosine receptors (ADORAs). Because Meth administration increases the production of reactive oxygen species (ROS), we also determined whether the effects of Meth could be rescued by concomitant treatment with the ROS scavenger N-acetyl cysteine (NAC). After Meth sensitization and a 7-day abstinence period, groups of Tat+ and Tat-male and female mice were challenged with Meth in combination with NAC. We confirmed that Tat expression and Meth challenge suppressed DRD mRNA and protein in males and females' brains, and showed that females were particularly susceptible to the effects of Meth on D1-like and D2-like DRD subtypes and ADORAs. The expression of these markers differed strikingly between males and females, and between females in different phases of the estrous cycle, in a Tat -dependent manner. NAC attenuated Meth-induced locomotor sensitization and preserved DRD expression in all groups except for Tat + females. These data identify complex interactions between sex, Meth use, and HIV infection on addiction responses, with potential implications for the treatment of male and female Meth users in the context of HIV, especially those with cognitive disorders.

Development and characterization of a fully human antibody targeting SCF/c-kit signaling.

CD117/c-kit, a tyrosine kinase receptor, plays a critical role in hematopoiesis, pigmentation, and fertility. The overexpression and activation of c-kit are thought to promote tumor growth and have been reported in various cancers, including leukemia, glioblastoma and mastocytosis. To disrupt the SCF/c-kit signaling axis in cancer, we generated a c-kit antagonist human antibody (NN2101) that binds to domain 2/3 of c-kit. This completely blocked the SCF-mediated phosphorylation of c-kit and inhibited TF-1 cell proliferation, erythroleukemia. In addition, the examination of binding affinity using surface plasmon resonance (SPR) assay showed that NN2101 can bind to c-kit of monkeys (KD = 2.92 × 10-10 M), rats (KD = 1.68 × 10-6 M), mice (KD = 11.5 × 10-9 M), and humans (KD = 2.83 × 10-12 M). We showed that NN2101 does not cause antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity. The immunogenicity of NN2101 was similar to that of bevacizumab. Furthermore, the crystal structure of NN2101 Fab was determined and the structure of NN2101 Fab:c-kit complex was modeled. Structural information, as well as mutagenesis results, revealed that NN2101 can bind to the SCF-binding regions of c-kit. Collectively, we generated a c-kit neutralizing human antibody (NN2101) for the treatment of erythroleukemia and characterized its biophysical properties. NN2101 can potentially be used as a therapeutic antibody to treat different cancers.

Ginsenoside F1 attenuates hyperpigmentation in B16F10 melanoma cells by inducing dendrite retraction and activating Rho signalling.

Ginsenoside F1 (GF1) is a metabolite produced by hydrolysis of the ginsenoside Re and Rg1 in Panax ginseng. According to various studies, high amounts of ginseng components are absorbed in the metabolized form, which are key constituents responsible for the biological effects of P. ginseng. Recently, GF1 was reported to have beneficial effects on skin. However, there has not been a sound understanding of its antimelanogenic effect and underlying molecular mechanisms. In this study, GF1 reduced α-melanocyte-stimulating hormone-induced melanin secretion in B16F10 cell culture media by 60%. However, it did not suppress intracellular melanin levels, tyrosinase activity and expression. Immunofluorescence assay showed that GF1 had no effect on melanosome transport, but significantly induced dendrite retraction. Pull-down assay demonstrated that GF1 primarily modulates the Rho family GTPases resulting in dendrite retraction. Collectively, these data suggest that GF1 could act as a potent skin-whitening agent.