N-Nicotinoyl dopamine, a novel niacinamide derivative, retains high antioxidant activity and inhibits skin pigmentation

Therapeutic Potential of Dopamine and Related Drugs as Anti-Inflammatories and Antioxidants in Neuronal and Non-Neuronal Pathologies

Dopamine (DA), its derivatives, and dopaminergic drugs are compounds widely used in the management of diseases related to the nervous system. However, DA receptors have been identified in nonneuronal tissues, which has been related to their therapeutic potential in pathologies such as sepsis or septic shock, blood pressure, renal failure, diabetes, and obesity, among others. In addition, DA and dopaminergic drugs have shown anti-inflammatory and antioxidant properties in different kinds of cells.

AIM

To compile the mechanism of action of DA and the main dopaminergic drugs and show the findings that support the therapeutic potential of these molecules for the treatment of neurological and non-neurological diseases considering their antioxidant and anti-inflammatory actions.

METHOD

We performed a review article. An exhaustive search for information was carried out in specialized databases such as PubMed, PubChem, ProQuest, EBSCO, Scopus, Science Direct, Web of Science, Bookshelf, DrugBank, Livertox, and Clinical Trials.

RESULTS

We showed that DA and dopaminergic drugs have emerged for the management of neuronal and nonneuronal diseases with important therapeutic potential as anti-inflammatories and antioxidants.

CONCLUSIONS

DA and DA derivatives can be an attractive treatment strategy and a promising approach to slowing the progression of disorders through repositioning.

Simon S. Asoprisnil, a Selective Progesterone Receptor Modulator (SPRM), Inhibits Melanosome Export in B16F10 Cells and HEMn-DP Melanocytes

Previous studies have reported that estrogen hormone promotes melanogenesis while progesterone inhibits it. A selective estrogen receptor modulator (SERM), tamoxifen, has been shown to promote melanogenesis; however, to date, there have been no reports on the effects of a selective progesterone receptor modulator (SPRM) on melanogenesis. In the present study, we hypothesized that asoprisnil (AP), a SPRM, inhibits melanogenesis. AP was tested for cytotoxicity to B16F10 mouse melanoma cells for screening the nontoxic concentrations using MTS cytotoxicity assay. Extracellular and intracellular melanin levels were estimated at nontoxic concentrations of AP. To evaluate the direct effect of AP on tyrosinase enzyme, tyrosinase activity and copper chelating activities were measured. Next, the effects of AP on melanogenesis were tested in normal human melanocytes, neonatal, darkly pigmented (HEMn-DP). Our results demonstrate that AP was nontoxic at a concentration range of 10-50 μM in B16F10 cells; AP at 50 μM significantly suppressed extracellular melanin levels comparable to kojic acid at 500 μM, with no significant effect on intracellular melanin levels. The mechanism of melanogenesis inhibition was studied to assess if AP downregulated tyrosinase activity in cell lysates or in a cell-free system. However, AP was found to increase intracellular tyrosinase activity without any effect on tyrosinase enzyme activity or copper chelating activity in a cell-free system, indicating that AP inhibits melanogenesis by mechanisms other than direct effects on tyrosinase enzyme activity. The capacity of AP to inhibit melanosome export was further validated in HEMn-DP cells; AP significantly suppressed dendricity at concentrations of 20 and 30 μM in the absence of effects on melanin synthesis or intracellular tyrosinase activity. In addition, AP was nontoxic to human keratinocytes (HaCaT) at these concentrations, validating its safety for topical use. Taken together, our preliminary results demonstrate that AP might be repurposed as a candidate therapeutic for treatment of hyperpigmentation disorders via a unique mechanism, which encompasses a selective inhibition of melanosome export.

A Novel Peptide, Nicotinyl⁻Isoleucine⁻Valine⁻Histidine (NA⁻IVH), Promotes Antioxidant Gene Expression and Wound Healing in HaCaT Cells

Nicotinamide (NA), a water-soluble vitamin B₃, has been shown to exert cellular-protective effects against reactive oxygen species (ROS). In order to improve the cellular-protective effects of NA, we synthesized a novel compound, nicotinyl–isoleucine–valine–histidine (NA–IVH), by combining NA with jellyfish peptides’ IVH. In the present study, we examined the cellular-protective effects of the novel synthetic nicotinyl-peptide, NA–IVH. We found that NA–IVH enhances the radical scavenging activity with a robust increase of the nuclear factor (erythroid-derived 2)-like factor (Nrf2) expression in human HaCaT keratinocytes. In addition, NA–IVH protected the cells from hydrogen peroxide (H₂O₂)-induced cell death. Interestingly, NA–IVH exhibited an improved wound-healing effect in a high glucose condition, possibly through the regulation of reactive oxygen species (ROS). Collectively, our results imply that a novel nicotinyl-peptide, NA–IVH, has a wound-healing effect in a hyperglycemic condition, possibly by modulating excessive ROS.

Downregulation of melanogenesis: drug discovery and therapeutic options

Melanin, primarily responsible in humans for hair, eye and skin pigmentation, is produced by melanocytes through a process called melanogenesis. However, the abnormal accumulation of melanin causes dermatological problems such as café-au-lait macules ephelides (freckles), solar lentigo (age spots) and melasma, as well as cancer and vitiligo. Hence the regulation of melanogenesis is very important for treating hyperpigmentary disorders. Numerous antimelanogenic agents that target tyrosinase activity and/or stability, melanosome maturation, transfer and trafficking, or melanogenesis-related signaling pathways have been developed. This article reviews recent advances in research and development of human tyrosinase and melanogenesis-related signaling pathway inhibitors. Attempts have been made to provide a complete description of the mechanism of action of inhibitors on various melanogenesis signaling pathways.

N-Nicotinoyl dopamine inhibits skin pigmentation by suppressing of melanosome transfer

We investigated the inhibitory effects of a niacinamide derivative, N-Nicotinoyl dopamine (NND) on melanogenesis. NND inhibits melanosome transfer in a normal human melanocyte-keratinocyte co-culture system and through phagocytic ability without affecting viability of cells while it did not show inhibitory effects of tyrosinase and melanin synthesis in B16F10 mouse melanoma cells. In addition, safety of NND was verified through performing neural stem cell morphology assay. Our findings indicate that NND may potentially be used for cosmetic industry for improvement of skin whitening and therapies related with several skin disorders, and the effect of NND may be acquired via reduction of melanosome transfer.

N-Nicotinoyl tyramine, a novel niacinamide derivative, inhibits melanogenesis by suppressing MITF gene expression

We synthesized and investigated the inhibitory effects of a novel niacinamide derivative, N-nicotinoyltyramine (NNT) on melanogenesis. NNT inhibited melanin production in B16F10 murine melanoma cells stimulated with α-melanocyte stimulating hormone (α-MSH), in human melanocyte and in three-dimensional cultured human skin model. NNT did not affect the catalytic activity of tyrosinase, but acted as an inhibitor of microphthalmia-associated transcription factor (MITF) and tyrosinase expressions in B16F10 cells. These findings suggest that the hypopigmentary effect of NNT results from the down-regulation of MITF and subsequently of tyrosinase, although NNT did not directly inhibit tyrosinase activity. In addition, safety of NNT was verified through performing neural stem cell morphology assay and Human repeated insult patch test as whitening agent. Our findings indicate that NNT may be a potential and non-skin irritant whitening agent for use in cosmetics and in the medical treatment of pigmentary disorders.

Topical treatment of hyperpigmentation disorders

Hyperpigmentation has traditionally been a relatively difficult condition to treat, especially in darker racial ethnic groups. Multiple topical agents available act upon different steps of the pigmentation pathway. We review these topical agents, their mechanisms of action, and their effectiveness as monotherapy and in combination with other compounds. Ultimately, combination therapy is the most efficacious when considering overall depigmentation as well as treatment time required to achieve clinical improvement.

Dioxinodehydroeckol inhibits melanin synthesis through PI3K/Akt signalling pathway in α-melanocyte-stimulating hormone-treated B16F10 cells

Antimelanogenic activity has previously been reported in ethyl acetate fraction of Ecklonia stolonifera. In this study, using the isolated dioxinodehydroeckol from the fraction, we sought to investigate an antimelanogenic signalling pathway in α-melanocyte-stimulating hormone (α-MSH)-stimulated B16F10 melanoma cells. Treatment with dioxinodehydroeckol inhibited the cellular melanin contents and expression of melanogenesis-related proteins, including microphthalmia-associated transcription factor (MITF), tyrosinase and tyrosinase-related proteins TRP-1 and TRP-2. Moreover, dioxinodehydroeckol stimulated phosphorylation of Akt in a dose-dependent manner without affecting phosphorylation of ERK. These data suggest that dioxinodehydroeckol reduces melanin synthesis through the MITF regulation dependent upon PI3K/Akt signalling pathway.

Nicotinamide, NAD(P)(H), and Methyl-Group Homeostasis Evolved and Became a Determinant of Ageing Diseases: Hypotheses and Lessons from Pellagra

Compartmentalized redox faults are common to ageing diseases. Dietary constituents are catabolized to NAD(H) donating electrons producing proton-based bioenergy in coevolved, cross-species and cross-organ networks. Nicotinamide and NAD deficiency from poor diet or high expenditure causes pellagra, an ageing and dementing disorder with lost robustness to infection and stress. Nicotinamide and stress induce Nicotinamide-N-methyltransferase (NNMT) improving choline retention but consume methyl groups. High NNMT activity is linked to Parkinson's, cancers, and diseases of affluence. Optimising nicotinamide and choline/methyl group availability is important for brain development and increased during our evolution raising metabolic and methylome ceilings through dietary/metabolic symbiotic means but strict energy constraints remain and life-history tradeoffs are the rule. An optimal energy, NAD and methyl group supply, avoiding hypo and hyper-vitaminoses nicotinamide and choline, is important to healthy ageing and avoids utilising double-edged symbionts or uncontrolled autophagy or reversions to fermentation reactions in inflammatory and cancerous tissue that all redistribute NAD(P)(H), but incur high allostatic costs.