A novel synthetic Piper amide derivative NED-180 inhibits hyperpigmentation by activating the PI3K and ERK pathways and by regulating Ca2+ influx via TRPM1 channels

Molecular mechanisms underlying Tao-Hong-Si-Wu decoction treating hyperpigmentation based on network pharmacology, Mendelian randomization analysis, and experimental verification

CONTEXT

Hyperpigmentation, a common skin condition marked by excessive melanin production, currently has limited effective treatment options.

OBJECTIVE

This study explores the effects of Tao-Hong-Si-Wu decoction (THSWD) on hyperpigmentation and to elucidate the underlying mechanisms.

MATERIALS AND METHODS

We employed network pharmacology, Mendelian randomization, and molecular docking to identify THSWD's hub targets and mechanisms against hyperpigmentation. The Cell Counting Kit-8 (CCK-8) assay determined suitable THSWD treatment concentrations for PIG1 cells. These cells were exposed to graded concentrations of THSWD-containing serum (2.5%, 5%, 10%, 15%, 20%, 30%, 40%, and 50%) and treated with α-MSH (100 nM) to induce an in vitro hyperpigmentation model. Assessments included melanin content, tyrosinase activity, and Western blotting.

RESULTS

ALB, IL6, and MAPK3 emerged as primary targets, while quercetin, apigenin, and luteolin were the core active ingredients. The CCK-8 assay indicated that concentrations between 2.5% and 20% were suitable for PIG1 cells, with a 50% cytotoxicity concentration (CC50) of 32.14%. THSWD treatment significantly reduced melanin content and tyrosinase activity in α-MSH-induced PIG1 cells, along with downregulating MC1R and MITF expression. THSWD increased ALB and p-MAPK3/MAPK3 levels and decreased IL6 expression in the model cells.

DISCUSSION AND CONCLUSION

THSWD mitigates hyperpigmentation by targeting ALB, IL6, and MAPK3. This study paves the way for clinical applications of THSWD as a novel treatment for hyperpigmentation and offers new targeted therapeutic strategies.

Fermented Aronia melanocarpa Inhibits Melanogenesis through Dual Mechanisms of the PI3K/AKT/GSK-3β and PKA/CREB Pathways

UV light causes excessive oxidative stress and abnormal melanin synthesis, which results in skin hyperpigmentation disorders such as freckles, sunspots, and age spots. Much research has been carried out to discover natural plants for ameliorating these disorders. Aronia melanocarpa contains various polyphenolic compounds with antioxidative activities, but its effects on melanogenesis have not been fully elucidated. In this study, we investigated the inhibitory effect of fermented Aronia melanocarpa (FA) fermented with Monascus purpureus on melanogenesis and its underlying mechanism in the B16F10 melanoma cell line. Our results indicate that FA inhibited tyrosinase activity and melanogenesis in alpha-melanocyte-stimulating hormone (α-MSH)-induced B16F10 cells. FA significantly downregulated the PKA/CREB pathway, resulting in decreased protein levels of tyrosinase, TRP-1, and MITF. FA also inhibited the transcription of MITF by increasing the phosphorylation levels of both GSK3β and AKT. Interestingly, we demonstrated that these results were owing to the significant increase in gallic acid, a phenolic compound of Aronia melanocarpa produced after the fermentation of Monascus purpureus. Taken together, our research suggests that Aronia melanocarpa fermented with Monascus purpureus acts as a melanin inhibitor and can be used as a potential cosmetic or therapeutic for improving hyperpigmentation disorders.

Retinal TRP channels: Cell-type-specific regulators of retinal homeostasis and multimodal integration

Transient receptor potential (TRP) channels are a widely expressed family of 28 evolutionarily conserved cationic ion channels that operate as primary detectors of chemical and physical stimuli and secondary effectors of metabotropic and ionotropic receptors. In vertebrates, the channels are grouped into six related families: TRPC, TRPV, TRPM, TRPA, TRPML, and TRPP. As sensory transducers, TRP channels are ubiquitously expressed across the body and the CNS, mediating critical functions in mechanosensation, nociception, chemosensing, thermosensing, and phototransduction. This article surveys current knowledge about the expression and function of the TRP family in vertebrate retinas, which, while dedicated to transduction and transmission of visual information, are highly susceptible to non-visual stimuli. Every retinal cell expresses multiple TRP subunits, with recent evidence establishing their critical roles in paradigmatic aspects of vertebrate vision that include TRPM1-dependent transduction of ON bipolar signaling, TRPC6/7-mediated ganglion cell phototransduction, TRP/TRPL phototransduction in Drosophila and TRPV4-dependent osmoregulation, mechanotransduction, and regulation of inner and outer blood-retina barriers. TRP channels tune light-dependent and independent functions of retinal circuits by modulating the intracellular concentration of the 2nd messenger calcium, with emerging evidence implicating specific subunits in the pathogenesis of debilitating diseases such as glaucoma, ocular trauma, diabetic retinopathy, and ischemia. Elucidation of TRP channel involvement in retinal biology will yield rewards in terms of fundamental understanding of vertebrate vision and therapeutic targeting to treat diseases caused by channel dysfunction or over-activation.

A Novel Furocoumarin Derivative, 5-((diethylamino)me-13 thyl)-3-phenyl-7H-furo [3,2-g] chromen-7-one Upregulates Melanin Synthesis via the Activation of cAMP/PKA and MAPKs Signal Pathway: In Vitro and In Vivo Study

Psoralen, a major furocoumarin component of the Fructus Psoralen (FP), in combination with ultraviolet radiation, cures abnormal pigmentation disorder. In a previous study, we synthesized a series of linear furocoumarins with different substituents, out of which 5-((diethylamino)methyl)-3-phenyl-7H-furo [3,2-g] chromen-7-one (encoded as 5D3PC) showed better pigmenting effect than others in B16 cells. In this study, we examined the mechanism underlying the melanogenic effect of 5D3PC both in vivo and in vitro. To examine the pigmentation effect, the B16 and human melanocyte cell lines, PIG1 and PIG3V melanocytes were incubated with 5D3PC. In animal experiments, C57BL/6 mice received 5% hydroquinone and were administrated with 5D3PC for 30 days. 5D3PC upregulated the melanin synthesis and tyrosinase in B16 cell, PIG1 and PIG3V. The expression level of tyrosinase (TYR), tyrosinase-related protein-1 (TRP-1) and tyrosinase-related protein-2 (TRP-2), microphthalmia-associated transcription factor (MITF), cyclic adenosine monophosphate (cAMP), phosphorylation of cAMP-responsive element binding protein (p-CREB), phosphorylation of p38 mitogen-activated protein kinase (MAPK), c- phosphorylation of Jun N-terminal kinase (p-JNK) was significantly higher in 5D3PC-treated B16 cells. The oral administration of 5D3PC attenuated the depigmentation of the C57BL/6 vitiligo mice model by increasing the numbers of melanin-containing hair follicles, melanogenic protein, and melanogenesis-relative genes expression in skin tissues.

The Function of Autophagy as a Regulator of Melanin Homeostasis

Melanosomes are melanocyte-specific organelles that protect cells from ultraviolet (UV)-induced deoxyribonucleic acid damage through the production and accumulation of melanin and are transferred from melanocytes to keratinocytes. The relatively well-known process by which melanin is synthesized from melanocytes is known as melanogenesis. The relationship between melanogenesis and autophagy is attracting the attention of researchers because proteins associated with autophagy, such as WD repeat domain phosphoinositide-interacting protein 1, microtubule-associated protein 1 light chain 3, autophagy-related (ATG)7, ATG4, beclin-1, and UV-radiation resistance-associated gene, contribute to the melanogenesis signaling pathway. Additionally, there are reports that some compounds used as whitening cosmetics materials induce skin depigmentation through autophagy. Thus, the possibility that autophagy is involved in the removal of melanin has been suggested. To date, however, there is a lack of data on melanosome autophagy and its underlying mechanism. This review highlights the importance of autophagy in melanin homeostasis by providing an overview of melanogenesis, autophagy, the autophagy machinery involved in melanogenesis, and natural compounds that induce autophagy-mediated depigmentation.

Protective Role of Capsaicin in Neurological Disorders: An Overview

Different pathological conditions that begin with slow and progressive deformations, cause irreversible affliction by producing loss of neurons and synapses. Commonly it is referred to as 'protein misfolding' diseases or proteinopathies and comprises the latest definition of neurological disorders (ND). Protein misfolding dynamics, proteasomal dysfunction, aggregation, defective degradation, oxidative stress, free radical formation, mitochondrial dysfunctions, impaired bioenergetics, DNA damage, neuronal Golgi apparatus fragmentation, axonal transport disruption, Neurotrophins (NTFs) dysfunction, neuroinflammatory or neuroimmune processes, and neurohumoral changes are the several mechanisms that embark the pathogenesis of ND. Capsaicin (8-Methyl-N-vanillyl-6-nonenamide) one of the major phenolic components in chili peppers (Capsicum) distinctively triggers the unmyelinated C-fiber and acts on Transient Receptor Potential Vanilloid-1, which is a Ca²⁺ permeable, non-selective cation channel. Several studies have shown the neuroprotective role of capsaicin against oxidative damage, behavioral impairment, with 6-hydroxydopamine (6-OHDA) induced Parkinson's disease, pentylenetetrazol-induced seizures, global cerebral ischemia, and streptozotocin-induced Alzheimer's disease. Based on these lines of evidence, capsaicin can be considered as a potential constituent to develop suitable neuro-pharmacotherapeutics for the management and treatment of ND. Furthermore, exploring newer horizons and carrying out proper clinical trials would help to bring out the promising effects of capsaicin to be recommended as a neuroprotectant.

Mitigative Effects of PFF-A Isolated from Ecklonia cava on Pigmentation in a Zebrafish Model and Melanogenesis in B16F10 Cells

Melanin synthesis is a defense mechanism that prevents skin damage, but excessive accumulation of melanin occurs in the skin in various reactions such as pigmentation, lentigines, and freckles. Although anti-melanogenic effects have been demonstrated for various naturally occurring marine products that inhibit and control tyrosinase activity, most studies have not been extended to in vivo applications. Phlorofucofuroeckol-A (PFF-A, 12.5-100 µM) isolated from Ecklonia cava has previously been shown to have tyrosinase-mitigative effects in B16F10 cells, but it has not been evaluated in an in vivo model, and its underlying mechanism for anti-melanogenic effects has not been studied. In the present study, we evaluated the safety and efficacy of PFF-A for anti-melanogenic effects in an in vivo model. We selected low doses of PFF-A (1.5-15 nM) and investigated their mitigative effects on pigmentation stimulated by α-MSH in vivo and their related-mechanism in an in vitro model. The findings suggest that low-dose PFF-A derived from E. cava suppresses pigmentation in vivo and melanogenesis in vitro. Therefore, this study presents the possibility that PFF-A could be utilized as a new anti-melanogenic agent in the cosmeceutical industries.

TRPM Channels in Human Diseases

The transient receptor potential melastatin (TRPM) subfamily belongs to the TRP cation channels family. Since the first cloning of TRPM1 in 1989, tremendous progress has been made in identifying novel members of the TRPM subfamily and their functions. The TRPM subfamily is composed of eight members consisting of four six-transmembrane domain subunits, resulting in homomeric or heteromeric channels. From a structural point of view, based on the homology sequence of the coiled-coil in the C-terminus, the eight TRPM members are clustered into four groups: TRPM1/M3, M2/M8, M4/M5 and M6/M7. TRPM subfamily members have been involved in several physiological functions. However, they are also linked to diverse pathophysiological human processes. Alterations in the expression and function of TRPM subfamily ion channels might generate several human diseases including cardiovascular and neurodegenerative alterations, organ dysfunction, cancer and many other channelopathies. These effects position them as remarkable putative targets for novel diagnostic strategies, drug design and therapeutic approaches. Here, we review the current knowledge about the main characteristics of all members of the TRPM family, focusing on their actions in human diseases.

UP256 Inhibits Hyperpigmentation by Tyrosinase Expression/Dendrite Formation via Rho-Dependent Signaling and by Primary Cilium Formation in Melanocytes

Skin hyperpigmentation is generally characterized by increased synthesis and deposition of melanin in the skin. UP256, containing bakuchiol, is a well-known medication for acne vulgaris. Acne sometimes leaves dark spots on the skin, and we hypothesized that UP256 may be effective against hyperpigmentation-associated diseases. UP256 was treated for anti-melanogenesis and melanocyte dendrite formation in cultured normal human epidermal melanocytes as well as in the reconstituted skin and zebrafish models. Western blot analysis and glutathione S-transferase (GST)-pull down assays were used to evaluate the expression and interaction of enzymes related in melanin synthesis and transportation. The cellular tyrosinase activity and melanin content assay revealed that UP256 decreased melanin synthesis by regulating the expression of proteins related on melanogenesis including tyrosinase, TRP-1 and -2, and SOX9. UP256 also decreased dendrite formation in melanocytes via regulating the Rac/Cdc42/α-PAK signaling proteins, without cytotoxic effects. UP256 also inhibited ciliogenesis-dependent melanogenesis in normal human epidermal melanocytes. Furthermore, UP256 suppressed melanin contents in the zebrafish and the 3D human skin tissue model. All things taken together, UP256 inhibits melanin synthesis, dendrite formation, and primary cilium formation leading to the inhibition of melanogenesis.

Natural skin-whitening compounds for the treatment of melanogenesis (Review)

Melanogenesis is the process for the production of melanin, which is the primary cause of human skin pigmentation. Skin-whitening agents are commercially available for those who wish to have a lighter skin complexions. To date, although numerous natural compounds have been proposed to alleviate hyperpigmentation, insufficient attention has been focused on potential natural skin-whitening agents and their mechanism of action from the perspective of compound classification. In the present article, the synthetic process of melanogenesis and associated core signaling pathways are summarized. An overview of the list of natural skin-lightening agents, along with their compound classifications, is also presented, where their efficacy based on their respective mechanisms of action on melanogenesis is discussed.

Synaptotagmin-4 promotes dendrite extension and melanogenesis in alpaca melanocytes by regulating Ca2+ influx via TRPM1 channels

Synaptotagmin-4 (SYT4) is a membrane protein that regulates membrane traffic in neurons in a calcium-dependent or calcium-independent manner. In melanocytes, the intracellular free calcium ion (Ca2+ ) may be important for dendrite growth and melanogenesis. Mammalian melanocytes originating from neural crest cells produce melanins. Therefore, we predicted that SYT4 might play a role in melanogenesis and the dendrite morphology of melanocytes. To investigate whether SYT4 is involved in melanocyte physiology, SYT4 was overexpressed in alpaca melanocytes and B16-F10 cells. The results showed that SYT4 overexpression resulted in a phenotype consistent with melanogenesis and dendrite extension. At the molecular level, SYT4 interacted with extracellular regulated MAP kinase (ERK) to decrease p-ERK activity, which negatively regulated CREB expression. Furthermore, cyclic AMP-responsive element-binding protein (CREB) was upregulated and caused the downregulation of the expression of melanogenic regulatory proteins, including microphthalmia-associated transcription factor (MITF), tyrosinase (TYR), tyrosinase-related protein-1 (TYRP1), dopachrome tautomerase (DCT), and transient receptor potential melastatin 1 (TRPM1). Intracellular free Ca2+ promoted the upregulation of calcium/calmodulin dependent protein kinase IV (CAMK4) expression, which phosphorylated CREB (p-CREB). In turn, p-CREB participated in the transcription of MITF. These results demonstrated that SYT4 promoted melanogenesis through dendrite extension and tyrosinase activity, during which the regulation of Ca2+ influx via the TRPM1 channel was a key factor. SIGNIFICANCE OF THE STUDY: Intracellular Ca2+ is important for the function and survival of melanocytes and melanoma cells. SYT4 stimulated melanogenesis through calcium. These results provide evidence that SYT4 regulates Ca2+ influx through TRPM1 to cause melanogenesis and axonal elongation in alpaca melanocytes and further suggesting that the growth and metastasis of melanoma is controlled by the inhibited expression of SYT4 in melanoma cells.

Annona squamosa L. leaves inhibit alpha-melanocyte-stimulating hormone (α-MSH) stimulated melanogenesis via p38 signaling pathway in B16F10 melanoma cells

BACKGROUND

Annona squamosa L. is a branched shrub, which is believed to be originated from the America and West Indies. Fruits of this plant are commonly known as custard apple, sugar apple, or sweetsops. A number of studies have proven a range of biological activities associated with various parts of A. squamosa.

AIMS

The main aim of the present investigation was to evaluate potential inhibitory effects of A. squamosa leaf extract (ALE) on melanogenesis and its underlying mechanisms in B16F10 murine melanoma cells.

METHODS

Inhibitory effects of A. squamosa leaf extract (ALE) on melanogenesis were primarily assessed by determining melanin contents. Effects of ALE on tyrosinase activity and the expression of proteins associated with melanogenesis were then determined. GC-MS analysis was carried out to identify the phytochemical profile of A. squamosa leaf extract.

RESULTS

Antimelanogenic effects of ALE were found to exert through the inhibition of melanocyte inducing transcription factor (MITF) and activation of p38. GC-MS analysis identified ent-kaur-16-en-19-ol, 18-oxokauran-17-yl acetate, and β-sitosterol as major phytochemicals.

CONCLUSION

To our knowledge, this is the first study on the antimelanogenic effects of A. squamosa leaves, rationalizing the use A. squamosa leaf extract as a natural depigmentation agent for the treatment of skin diseases and the development of cosmetic products with enhanced skin-lightening capabilities.

Structural and molecular modelling studies of antimelanogenic piper-amide TRPM1 antagonists

Piper-amides exhibit diverse biological activities, including antimelanogenic effects. In our previous studies, we identified a potent piper-amide derivative that inhibited melanogenesis via the TRPM1 calcium channel. Despite its potential as a therapeutic target, the three-dimensional structure of TRPM1 is still not available. Thus, structure-guided compound design and the discovery of novel inhibitors of melanogenesis have been limited. In the present study, a series of computational methods, including homology modelling, docking, molecular dynamics simulation and field-based pharmacophore modelling, were integrated to explore the structural features of natural piper-amide-like compounds related to the TRPM1 target. These studies suggested the binding mode and provided a 3D pharmacophore model of the ligands, which can be helpful in understanding the TRPM1-ligand interactions at the molecular level and in designing potent antagonists of TRPM1.

Pyruvic acid/ethyl pyruvate inhibits melanogenesis in B16F10 melanoma cells through PI3K/AKT, GSK3β, and ROS-ERK signaling pathways

Melanin is the main product of human melanocytes and functions to protect skin from ultraviolet (UV) radiation while conferring color to skin and hair. Tyrosinase is the rate-limiting enzyme for melanin synthesis along with tyrosinase-related protein (TRP)-1 and TRP-2. Microphthalmia-associated transcription factor regulates tyrosinase gene expression and is in turn regulated by extracellular signal-regulated kinase (ERK), phosphoinositide 3-kinase (PI3K)/AKT, and glycogen synthase kinase (GSK)3β signaling pathways. Pyruvic acid (PA) is an energy source for ATP synthesis in the tricarboxylic acid cycle that also acts as a reactive oxygen species (ROS) scavenger. As UV irradiation induces melanin synthesis and ROS generation, we speculated that PA or ethyl pyruvate (EP), a stable form of pyruvate, regulates melanogenesis. B16F10 melanoma cells served as a melanin synthesis model. Treatment with PA or EP suppressed melanin synthesis while increasing intracellular ROS levels, which was accompanied by increased ERK phosphorylation in the case of EP treatment. PA and EP induced GSK3β phosphorylation and activated PI3K/AKT signaling, leading to decreased melanin synthesis. These results indicate that PA and EP inhibit melanogenesis via PI3K/AKT and GSK3β signaling and targeting the ERK and GSK3β pathways, respectively. Thus, PA and EP can potentially be used for treatment of hyperpigmentation disorders.

Attenuation of melanogenesis by Nymphaea nouchali (Burm. f) flower extract through the regulation of cAMP/CREB/MAPKs/MITF and proteasomal degradation of tyrosinase

Medicinal plants have been used to treat diseases from time immemorial. We aimed to examine the efficacy of the ethyl acetate fraction of Nymphaea nouchali flower extract (NNFE) against melanogenesis process, and the underlying mechanisms in vitro and in vivo. Paper spray ionisation mass spectroscopy and (+) mode electrospray ionisation revealed the presence of seven flavonoids, two spermidine alkaloids, 3,4,8,9,10-pentahydroxy-dibenzo[b,d]pyran-6-one, and shoyuflavone C in NNFE. NNFE (100 µg/mL) significantly inhibited the monophenolase and diphenolase activities of mushroom tyrosinase at 94.90 ± 0.003% and 93.034 ± 0.003%, respectively. NNFE significantly suppressed cellular tyrosinase activity and melanin synthesis in vitro in melan-a cells and in vivo in HRM2 hairless mice. Furthermore, NNFE inhibited tyrosinase (TYR), tyrosinase-related protein (TYRP)-1, TYRP-2, and microphthalmia-associated transcription factor (MITF) expression, thereby blocking melanin synthesis. In particular, NNFE suppressed cAMP production with subsequent downregulation of CREB phosphorylation. Additionally, it stimulated MAP kinase phosphorylation (p38, JNK, and ERK1/2) and the proteasomal debasement pathway, leading to degradation of tyrosinase and MITF and the suppression of melanin production. Moreover, selective inhibitors of ERK1/2, JNK, and p38 attenuated NNFE inhibitory effects on melanogenesis, and MG-132 (a proteasome inhibitor) prevented the NNFE-induced decline in tyrosinase protein levels. In conclusion, these findings indicate that NNFE is a potential therapy for hyperpigmentation.

Antimelanogenic Effect of an Oroxylum indicum Seed Extract by Suppression of MITF Expression through Activation of MAPK Signaling Protein

In this study, the antimelanogenic effect of an ethyl acetate fraction of Oroxylum indicum Vent. seeds (OISEA) and its underlying mechanisms in melan-a cells were investigated. Antimelanogenesis activity was confirmed by assessing inhibition of tyrosinase activity and melanin content in the cells. Both transcriptional and translational expression of microphthalmia-associated transcription factor (MITF), tyrosinase, and tyrosinase related protein-1 and 2 (TYRP-1 and TYRP-2), were also examined. The results depicted that pretreatment of OISEA significantly inhibits not only tyrosinase activity, but melanin production and intracellular tyrosinase activity. By repressing the expression of tyrosinase, TYRP-1, TYRP-2, and MITF, OISEA interrupted melanin production. Additionally, OISEA interfered with the phosphorylation of p38, extracellular signal-regulated kinase 1/2 (ERK1/2), and c-Jun N-terminal kinase (JNK), with the reversal of OISEA-induced melanogenesis inhibition after treatment with the specific inhibitors SB239063, U0126, and SP600125. Overall, these results suggest that OISEA can stimulate p38, ERK1/2, JNK phosphorylation, and subsequent suppression of melanin, leading to the inhibition of melanogenic enzymes and melanin production, possibly owing to the presence of polyphenolic compounds.

Sageretia thea fruit extracts rich in methyl linoleate and methyl linolenate downregulate melanogenesis via the Akt/GSK3β signaling pathway

BACKGROUND/OBJECTIVES

Sageretia thea is traditionally used as a medicinal herb to treat various diseases, including skin disorders, in China and Korea. This study evaluated the inhibitory effect of Sageretia thea fruit on melanogenesis and its underlying mechanisms in B16F10 mouse melanoma cells. The active chemical compounds in anti-melanogenesis were determined in Sageretia thea.

MATERIALS/METHODS

Solvent fractions from the crude extract were investigated for anti-melanogenic activities. These activities and the mechanism of anti-melanogenesis in B16F10 cells were examined by determining melanin content and tyrosinase activity, and by performing western blotting.

RESULTS

The n-hexane fraction of Sageretia thea fruit (HFSF) exhibited significant anti-melanogenic activity among the various solvent fractions without reducing viability of B16F10 cells. The HFSF suppressed the expression of tyrosinase and tyrosinase-related protein 1 (TRP1). The reduction of microphthalmia-associated transcription factor (MITF) expression by the HFSF was mediated by the Akt/glycogen synthase kinase 3 beta (GSK3β) signaling pathway, which promotes the reduction of β-catenin. Treatment with the GSK3β inhibitor 6-bromoindirubin-3'-oxime (BIO) restored HFSF-induced inhibition of MITF expression. The HFSF bioactive constituents responsible for anti-melanogenic activity were identified by bioassay-guided fractionation and gas chromatography-mass spectrometry analysis as methyl linoleate and methyl linolenate.

CONCLUSIONS

These results indicate that HFSF and its constituents, methyl linoleate and methyl linolenate, could be used as whitening agents in cosmetics and have potential for treating hyperpigmentation disorders in the clinic.

Cold stress-induced brain injury regulates TRPV1 channels and the PI3K/AKT signaling pathway

Transient receptor potential vanilloid 1 (TRPV1) is a nonselective cation channel that interacts with several intracellular proteins in vivo, including calmodulin and Phosphatidylinositol-3-Kinase/Protein Kinase B (PI3K/Akt). TRPV1 activation has been reported to exert neuroprotective effects. The aim of this study was to examine the impact of cold stress on the mouse brain and the underlying mechanisms of TRPV1 involvement. Adult male C57BL/6 mice were subjected to cold stress (4°C for 8h per day for 2weeks). The behavioral deficits of the mice were then measured using the Morris water maze. Expression levels of brain injury-related proteins and mRNA were measured by western blot, immunofluorescence or RT-PCR analysis. The mice displayed behavioral deficits, inflammation and changes in brain injury markers following cold stress. As expected, upregulated TRPV1 expression levels and changes in PI3K/Akt expression were found. The TRPV1 inhibitor reduced the levels of brain injury-related proteins and inflammation. These data suggest that cold stress can induce brain injury, possibly through TRPV1 activation and the PI3K/Akt signaling pathway. Suppression of inflammation by inhibition of TRPV1 and the PI3K/Akt pathway may be helpful to prevent cold stress-induced brain injury.

TRPM channels as potential therapeutic targets against pro-inflammatory diseases

The immune system protects our body against foreign pathogens. However, if it overshoots or turns against itself, pro-inflammatory diseases, such as rheumatoid arthritis, inflammatory bowel disease, or diabetes develop. Ions, the most basic signaling molecules, shape intracellular signaling cascades resulting in immune cell activation and subsequent immune responses. Mutations in ion channels required for calcium signaling result in human immunodeficiencies and highlight those ion channels as valued targets for therapies against pro-inflammatory diseases. Signaling pathways regulated by melastatin-like transient receptor potential (TRPM) cation channels also play crucial roles in calcium signaling and leukocyte physiology, affecting phagocytosis, degranulation, chemokine and cytokine expression, chemotaxis and invasion, as well as lymphocyte development and proliferation. Therefore, this review discusses their regulation, possible interactions and whether they can be exploited as targets for therapeutic approaches to pro-inflammatory diseases.

Capsaicin reduces Alzheimer-associated tau changes in the hippocampus of type 2 diabetes rats

Type 2 diabetes (T2D) is a high-risk factor for Alzheimer’s disease (AD) due to impaired insulin signaling pathway in brain. Capsaicin is a specific transient receptor potential vanilloid 1 (TRPV1) agonist which was proved to ameliorate insulin resistance. In this study, we investigated whether dietary capsaicin could reduce the risk of AD in T2D. T2D rats were fed with capsaicin-containing high fat (HF) diet for 10 consecutive days (T2D+CAP). Pair-fed T2D rats (T2D+PF) fed with the HF-diet of average dose of T2D+CAP group were included to control for the effects of reduced food intake and body weight. Capsaicin-containing standard chow was also introduced to non-diabetic rats (NC+CAP). Blood glucose and insulin were monitored. The phosphorylation level of tau at individual sites, the activities of phosphatidylinositol 3 kinase/protein kinase B (PI3K/AKT) and glycogen synthase kinase-3β (GSK-3β) were analyzed by Western blots. The results revealed that the levels of phosphorylated tau protein at sites Ser199, Ser202 and Ser396 in hippocampus of T2D+CAP group were decreased significantly, but these phospho-sites in T2D+PF group didn’t show such improvements compared with T2D group. There were almost no changes in non-diabetic rats on capsaicin diet (NC+CAP) compared with the non-diabetic rats with normal chow (NC). Increased activity of PI3K/AKT and decreased activity of GSK-3β were detected in hippocampus of T2D+CAP group compared with T2D group, and these changes did not show in T2D+PF group either. These results demonstrated that dietary capsaicin appears to prevent the hyperphosphorylation of AD-associated tau protein by increasing the activity of PI3K/AKT and inhibiting GSK-3β in hippocampus of T2D rats, which supported that dietary capsaicin might have a potential use for the prevention of AD in T2D.

Demethyleugenol β-Glucopyranoside Isolated from Agastache rugosa Decreases Melanin Synthesis via Down-regulation of MITF and SOX9

Agastache rugosa (Fisch. & C. A. Mey.) Kuntze has been well-known for its antioxidative properties. This study investigated the anti-melanogenesis effect of demethyleugenol β-d-glucopyranoside (1) from A. rugosa by studying molecular regulation of melanogenesis in melan-a mouse melanocytes and normal human epidermal melanocytes (NHEMs) and in in vivo models. The SRY (sex-determining region on the Y chromosome)-related high-mobility group (HMG) box 9 (SOX9), one of the critical factors that affect skin pigmentation, is up-regulated. Interestingly, 1 down-regulated the expression of SOX9 and microphthalmia-associated transcription factor (MITF). Reduction of these two transcription factors resulted in a decrease in melanogenic enzymes such as tyrosinase, tyrosinase-related protein 1, and dopachrome tautomerase. As a result, 1 significantly inhibited melanin synthesis in melan-a mouse melanocytes and NHEMs. In addition, the anti-melanogenic effect of 1 was confirmed in zebrafish and reconstructed skin tissue models. In conclusion, 1, as a potent SOX9 regulator, ameliorates skin pigmentation.