Pioneering advanced security solutions for reinforcement learning-based adaptive key rotation in Zigbee networks.

In the rapidly evolving landscape of Internet of Things (IoT), Zigbee networks have emerged as a critical component for enabling wireless communication in a variety of applications. Despite their widespread adoption, Zigbee networks face significant security challenges, particularly in key management and network resilience against cyber attacks like distributed denial of service (DDoS). Traditional key rotation strategies often fall short in dynamically adapting to the ever-changing network conditions, leading to vulnerabilities in network security and efficiency. To address these challenges, this paper proposes a novel approach by implementing a reinforcement learning (RL) model for adaptive key rotation in Zigbee networks. We developed and tested this model against traditional periodic, anomaly detection-based, heuristic-based, and static key rotation methods in a simulated Zigbee network environment. Our comprehensive evaluation over a 30-day period focused on key performance metrics such as network efficiency, response to DDoS attacks, network resilience under various simulated attacks, latency, and packet loss in fluctuating traffic conditions. The results indicate that the RL model significantly outperforms traditional methods, demonstrating improved network efficiency, higher intrusion detection rates, faster response times, and superior resource management. The study underscores the potential of using artificial intelligence (AI)-driven, adaptive strategies for enhancing network security in IoT environments, paving the way for more robust and intelligent Zigbee network security solutions.

High-Precision and Real-Time Measurement of Water Isotope Ratios Based on a Mid-Infrared Optical Sensor.

A compact spectrometer based on a mid-infrared optical sensor has been developed for high-precision and real-time measurement of water isotope ratios. The instrument uses laser absorption spectroscopy and applies the weighted Kalman filtering method to determine water isotope ratios with high precision and fast time response. The precision of the measurements is 0.41‰ for δ18O and 0.29‰ for δ17O with a 1 s time. This is much faster than the standard running average technique, which takes over 90 s to achieve the same level of precision. The successful development of this compact mid-infrared optical sensor opens up new possibilities for its future applications in atmospheric and breath gas research.

Therapeutic effects of Tanshinone IIA and Tetramethylpyrazine nanoemulsions on cognitive impairment and neuronal damage in Alzheimer's disease rat models.

OBJECTIVES: The aim of this study was to investigate the therapeutic effects and related mechanisms of Tanshinone IIA and Tetramethylpyrazine O/W composite nanoemulsions on Alzheimer's disease (AD) rats. METHODS: The therapeutic effect of TSN/TMP O/W NEs on AD rats was evaluated by behavioral tests, H&E, Nissl, and Immunohistochemistry staining. ELISA and Western blot were used to analyze the mechanism. KEY FINDINGS: The results showed that TSN/TMP O/W NEs could down-regulate the expression of Bax and Caspase-3 proteins, decrease the level of MDA, increase the expression of SOD and GSH-Px, and alleviate cognitive impairment in AD rats. CONCLUSIONS: TSN/TMP O/W NEs can inhibit MAPK/ERK/CREB signaling pathway and effectively alleviate cognitive impairment, oxidative stress injury, and neuronal apoptosis in AD rats.

Screening of Poria cocos polysaccharide with immunomodulatory activity and its activation effects on TLR4/MD2/NF-κB pathway.

PCP-W1, the Poria cocos polysaccharide with the strong immunomodulatory activity, was isolated through column chromatography and screened for in vitro immune activity in RAW 264.7 cells in this study. The structure analysis results revealed that the PCP-W1 were composed of galactose, glucose, fucose and mannose in a molar percentage of 35.87: 28.56: 21.77: 13.64. And it exhibited a random coil and branched conformational features with a molecular weight of 18.38 kDa. The main chain consisted of residues→3)-ß-D-Glcp-(1 â†’ 3,6)-ß-D-Glcp-(1 â†’ 3)-ß-D-Glcp-(1 â†’ 6)-ß-D-Glcp-(1 â†’ 6)-α-D-Galp-(1 â†’ 6)-α-D-Galp-(1 â†’ 2,6)-α-D-Galp-(1→6)-α-D-Galp-(1 â†’ 6)-α-D-Galp-(1 â†’ , while branching occurred at ß-D-Glcp-(1→, α-D-Manp-(1→, and α-L-Fucp-(1 â†’ 3)- α-L-Fucp-(1→. The pharmacodynamic studies demonstrated that PCP-W1 activated the release of NO, IL-6, IL-ß, TNF-α, CD86, and ROS to induce polarization of RAW 264.7 murine macrophages towards M1-type through modulation of the TLR4/MD2/NF-κB pathway. The molecular docking results showed that PCP-W1 could primarily dock onto the hydrophobic binding site of TLR4/MD2 complex via its galactose chain. Furthermore, molecular dynamics simulation displayed stable modeling for TLR4-MD2-PCP-W1 complex. Overall, we screened the most immunoactive components of the polysaccharide, analyzed its structure, demonstrated its impact on TLR4/MD2/NF-kB pathway, and studied the interaction between TLR4/MD2 and the polysaccharide fragments. These results provide further support for the structure-activity relationship study of the immunomodulatory effects of Poria cocos polysaccharide.

Is Aggressive Surgery Always Necessary for Suspected Early-Onset Surgical Site Infection after Lumbar Surgery? A 10-Year Retrospective Analysis.

OBJECTIVE: Surgical site infection (SSI) after spinal surgery is still a persistent worldwide health concern as it is a worrying and devastating complication. The number of samples in previous studies is limited and the role of conservative antibiotic therapy has not been established. This study aims to evaluate the clinical efficacy and feasibility of empirical antibiotic treatment for suspected early-onset deep spinal SSI. METHODS: We conducted a retrospective study to identify all cases with suspected early-onset deep SSI after lumbar instrumented surgery between January 2009 and December 2018. We evaluated the potential risks for antibiotic treatment, examined the antibiotic treatment failure rate, and applied logistic regression analysis to assess the risk factors for empirical antibiotic treatment failure. RESULTS: Over the past 10 years, 45 patients matched the inclusion criteria. The success rate of antibiotic treatment was 62.2% (28/45). Of the 17 patients who failed antibiotic treatment, 16 were cured after a debridement intervention and the remaining one required removal of the internal fixation before recovery. On univariate analysis, risk factors for antibiotic treatment failure included age, increasing or persisting back pain, wound dehiscence, localized swelling, and time to SSI (cut-off: 10 days). Multivariate analysis revealed that infection occurring 10 days after primary surgery and wound dehiscence were independent risk factors for antibiotic treatment failure. CONCLUSION: Appropriate antibiotic treatment is an alternative strategy for suspected early-onset deep SSI after lumbar instrumented surgery. Antibiotic treatment for suspected SSI occurring within 10 days after primary surgery may improve the success rate of antibiotic intervention. Patients with wound dehiscence have a significantly higher likelihood of requiring surgical intervention.

Polarization switching in a mid-infrared Er:YAlO3 laser.

We report on a polarization-resolved study of mid-infrared emission properties of Er3+-doped orthorhombic yttrium aluminum perovskite YAlO3 single crystal. For the 4I11/2 → 4I13/2 Er3+ transition, the stimulated emission cross section is 0.20 × 10-20 cm2 at 2919 nm for light polarization E ‖ c. Pumped by an Yb-fiber laser at 976 nm, the 10 at.% Er:YAlO3 laser delivered 1.36 W at 2919 nm with a slope efficiency of 31.4%, very close to the Stokes limit, a laser threshold as low as 33 mW and a linear polarization. Pump-induced polarization switching between E || b and E || c eigen states was observed and explained by excited-state absorption from the terminal laser level.

In-band pumped Kerr-lens mode-locked Tm,Ho-codoped calcium aluminate laser.

We report on a Kerr-lens mode-locked Tm,Ho-codoped calcium aluminate laser with in-band pumping of the Tm ions by a spatially single-mode 1678 nm Raman fiber laser. The structurally disordered CaGdAlO4 host crystal is also codoped also with the passive Lu ion for additional inhomogeneous line broadening. The Tm,Ho,Lu:CaGdAlO4 laser generates soliton pulses as short as 79 fs at a central wavelength of 2073.6 nm via soft-aperture Kerr-lens mode-locking. The corresponding average output power amounts to 91 mW at a pulse repetition rate of ∼86 MHz. The average output power can be scaled to 842 mW at the expense of slightly longer pulses of 155 fs at 2045.9 nm, which corresponds to a peak power of ∼58 kW. To the best of our knowledge, this represents the first demonstration of an in-band pumped Kerr-lens mode-locked Tm,Ho solid-state laser at ∼2 µm.

Growth, spectroscopy and laser operation of Tm,Ho:GdScO3 perovskite crystal.

We report on the growth, polarized spectroscopy and first laser operation of an orthorhombic (space group Pnma) Tm3+,Ho3+-codoped gadolinium orthoscandate (GdScO3) perovskite-type crystal. A single crystal of 3.76 at.% Tm, 0.35 at.% Ho:GdScO3 was grown by the Czochralski method. Its polarized absorption and fluorescence properties were studied revealing a broadband emission around 2 µm. The parameters of the Tm3+ ↔ Ho3+ energy transfer was quantified, P28 = 1.30 × 10-22 cm3µs-1, and P71 = 0.99 × 10-23 cm3µs-1, and the thermal equilibrium lifetime was measured to be 3.5 ms. The crystal-field splitting of Tm3+ and Ho3+ multiplets in Cs symmetry sites of the perovskite structure was determined by low-temperature spectroscopy and the mechanism of spectral line broadening is discussed. The continuous-wave Tm,Ho:GdScO3 laser generated 1.16 W at ∼2.1 µm with a slope efficiency of 50.5%, a laser threshold of 184 mW, a linear laser polarization (E || c) and a spatially single-mode output. The Tm,Ho:GdScO3 crystal is promising for broadly tunable and femtosecond mode-locked lasers emitting above 2 µm.

Comparative efficacy of sweated and non-sweated Salvia miltiorrhiza Bge. extracts on acute myocardial ischemia via regulating the PPARα/RXRα/NF-κB signaling pathway.

Salvia miltiorrhiza Bge. (S. miltiorrhiza) is a well-known traditional Chinese medicine for the treatment of cardiovascular diseases. The processing of S. miltiorrhiza requires the raw herbs to sweat first and then dry. The aim of this study was to investigate the anti-acute myocardial ischemia (AMI) of S. miltiorrhiza extracts (including tanshinones and phenolic acids) before and after sweating, and to further explore whether the "sweating" primary processing affected the efficacy of S. miltiorrhiza. The AMI animal model was established by subcutaneous injection of isoprenaline hydrochloride (ISO). After treatment, the cardiac function of rats was evaluated by electrocardiogram (ECG), biochemical, and histochemical analysis. Moreover, the regulation of S. miltiorrhiza extracts on the peroxisome proliferator-activated receptor α (PPARα)/retinoid X receptor α (RXRα)/nuclear transcription factor-kappa B (NF-κB) signaling pathway of rats was assessed by the Western blotting. The results showed that sweated and non-sweated S. miltiorrhiza extracts including tanshinones and phenolic acids significantly reduced ST-segment elevation in ECG and the myocardial infarction area in varying degrees. Meanwhile, sweated and non-sweated S. miltiorrhiza reversed the activities of aspartate transaminase (AST), lactic dehydrogenase (LDH), creatine kinase-MB (CK-MB), and superoxide dismutase (SOD), as well as the levels of interleukin-6 (IL-6), interleukin-10 (IL-10), and tumor necrosis factor-α (TNF-α) in AMI rats. Concurrently, the results of Western blotting revealed that S. miltiorrhiza extracts regulated the PPARα/RXRα/NF-κB signaling pathway to exert an anti-inflammatory effect. Most importantly, sweated S. miltiorrhiza tanshinones extracts are more effective than the non-sweated S. miltiorrhiza, and the anti-inflammatory efficacy of tanshinones extract was also better than that of phenolic acid extract. Although phenolic acid extracts before and after sweating were effective in anti-AMI, there was no significant difference between them. In conclusion, both tanshinones and phenolic acids extracts of sweated and non-sweated S. miltiorrhiza promote anti-oxidative stress and anti-inflammatory against AMI via regulating the PPARα/RXRα/NF-κB signaling pathway. Further, the comparations between sweated and non-sweated S. miltiorrhiza extracts indicate that sweated S. miltiorrhiza tanshinones extracts have better therapeutic effects on AMI.

[Chemical constituents and pharmacological effects of Nauclea officinalis and predictive analysis of its quality markers].

Nauclea officinalis is a Chinese medicinal material with a high medicinal value, which contains various chemical constituents such as alkaloids, pentacyclic triterpenoids and their saponins, organic phenolic acids and their glycosides, iridoids, and flavonoids. It has antiviral, antibacterial, antipyretic, analgesic, anti-inflammatory, and immunoregulatory functions. This article systematically reviewed the reported chemical constituents and pharmacological effects of N. officinalis. According to the concept of quality markers, the quality markers of N. officinalis were predicted and analyzed from the aspects of plant kinship, specificity of chemical constituents, traditional drug efficacy, measurability of chemical constituents, plasma components, and different producing areas and harvest times, in order to provide a basis for the quality evaluation of N. officinalis.

Controlled release of vitamin A palmitate from crosslinked cyclodextrin organic framework for dry eye disease therapy.

Controlled release drug delivery systems of eye drops are a promising ophthalmic therapy with advantages of good patient compliance and low irritation. However, the lack of a suitable drug carrier for ophthalmic use limits the development of the aforementioned system. Herein, the crosslinked cyclodextrin organic framework (COF) with a cubic porous structure and a uniform particle size was synthesized and applied to solidify vitamin A palmitate (VAP) by using the solvent-free method. The VAP@COF suspension eye drops were formulated by screening co-solvents, suspending agents, and stabilizing agents to achieve a homogeneous state and improve stability. According to the in vitro release study, the VAP@COF suspension exhibited a controlled release of VAP within 12 h. Both the ex vivo corneal contact angle and in vivo fluorescence tracking indicated that the VAP@COF suspension prolonged the VAP residence time on the ocular surface. This suspension accelerated the recovery of the dry eye disease (DED) model in New Zealand rabbits. Furthermore, the suspension was non-cytotoxic to human corneal epithelial cells and non-irritation to rabbit eyes. In summary, the particulate COF is an eye-acceptable novel carrier that sustains release and prolongs the VAP residence time on the ocular surface for DED treatment.

Enhancing Energy Harvesting Efficiency of Flapping Wings with Leading-Edge Magnus Effect Cylinder.

According to the Magnus principle, a rotating cylinder experiences a lateral force perpendicular to the incoming flow direction. This phenomenon can be harnessed to boost the lift of an airfoil by positioning a rotating cylinder at the leading edge. In this study, we simulate flapping-wing motion using the sliding mesh technique in a heaving coordinate system to investigate the energy harvesting capabilities of Magnus effect flapping wings (MEFWs) featuring a leading-edge rotating cylinder. Through analysis of the flow field vortex structure and pressure distribution, we explore how control parameters such as gap width, rotational speed ratio, and phase difference of the leading-edge rotating cylinder impact the energy harvesting characteristics of the flapping wing. The results demonstrate that MEFWs effectively mitigate the formation of leading-edge vortices during wing motion. Consequently, this enhances both lift generation and energy harvesting capability. MEFWs with smaller gap widths are less prone to induce the detachment of leading-edge vortices during motion, ensuring a higher peak lift force and an increase in the energy harvesting efficiency. Moreover, higher rotational speed ratios and phase differences, synchronized with wing motion, can prevent leading-edge vortex generation during wing motion. All three control parameters contribute to enhancing the energy harvesting capability of MEFWs within a certain range. At the examined Reynolds number, the optimal parameter values are determined to be a∗ = 0.0005, R = 3, and ϕ0 = 0°.

The Identification of RPL4 as a Hub Gene Associated with Goat Litter Size via Weighted Gene Co-Expression Network Analysis.

Reproduction in goats is a highly complex and dynamic process of life regulation, involving coordinated regulation from various aspects such as central nervous system regulation, reproductive system development, oocyte maturation, and fertilized egg development. In recent years, researchers have identified numerous genes associated with goat reproductive performance through high-throughput sequencing, single-cell sequencing, gene knockout, and other techniques. However, there is still an urgent need to explore marker genes related to goat reproductive performance. In this study, a single-cell RNA sequencing dataset of oocytes (GSE136005) was obtained from the Gene Expression Omnibus (GEO) database. Weighted Gene Co-expression Network Analysis (WGCNA) was utilized to identify modules highly correlated with goat litter size. Through gene function enrichment analysis, it was found that genes within the modules were mainly enriched in adhesive junctions, cell cycle, and other signaling pathways. Additionally, the top 30 hub genes with the highest connectivity in WGCNA were identified. Subsequently, using Protein-Protein Interaction (PPI) network analysis, the top 30 genes with the highest connectivity within the modules were identified. The intersection of hub genes, key genes in the PPI network, and differentially expressed genes (DEGs) led to the identification of the RPL4 gene as a key marker gene associated with reproductive capacity in goat oocytes. Overall, our study reveals that the RPL4 gene in oocytes holds promise as a biological marker for assessing goat litter size, deepening our understanding of the regulatory mechanisms underlying goat reproductive performance.

Fruquintinib-induced renal-limited thrombotic microangiopathy: a case report.

BACKGROUND: Fruquintinib is a highly selective inhibitor of vascular endothelial growth factor receptor (VEGFR). Currently, there are no reported cases of fruquintinib causing kidney-restrictive thrombotic microangiopathy (TMA) in the available Chinese and foreign literature. CASE PRESENTATION: In this case report, we presented a 73-year-old patient receiving fruquintinib for metastatic colon cancer, manifesting abundant proteinuria, in which kidney-restrictive TMA was also diagnosed through renal biopsy. As far as we were concerned, this was the frst reported in terms of fruquintinib-induced kidney-restrictive TMA confrmed by renal biopsy. CONCLUSION: This case indicates that fruquintinib may result in kidney-restrictive TMA, which is a rare but life-threatening complication of cancer treatment drug. Therefore, regular monitoring of proteinuria and blood pressure is imperative for all patients undergoing anti-VEGF drug therapy. And renal biopsy should be promptly conducted to facilitate early detection of thrombotic microangiopathy.

An effector SsCVNH promotes the virulence of Sclerotinia sclerotiorum through targeting class III peroxidase AtPRX71.

Many plant pathogens secrete effector proteins into the host plant to suppress host immunity and facilitate pathogen colonization. The necrotrophic pathogen Sclerotinia sclerotiorum causes severe plant diseases and results in enormous economic losses, in which secreted proteins play a crucial role. SsCVNH was previously reported as a secreted protein, and its expression is significantly upregulated at 3 h after inoculation on the host plant. Here, we further demonstrated that deletion of SsCVNH leads to attenuated virulence. Heterologous expression of SsCVNH in Arabidopsis enhanced pathogen infection, inhibited the host PAMP-triggered immunity (PTI) response and increased plant susceptibility to S. sclerotiorum. SsCVNH interacted with class III peroxidase AtPRX71, a positive regulator of innate immunity against plant pathogens. SsCVNH could also interact with other class III peroxidases, thus reducing peroxidase activity and suppressing plant immunity. Our results reveal a new infection strategy employed by S. sclerotiorum in which the fungus suppresses the function of class III peroxidases, the major component of PTI to promote its own infection.

RNA-dependent RNA polymerases regulate ascospore discharge through the exonic-sRNA-mediated RNAi pathway.

Ascospores, forcibly released into the air from perithecia, are the primary inoculum for Fusarium head blight. In Fusarium graminearum, the biological functions of four RNA-dependent RNA polymerases (RdRPs) (Fgrdrp1-4) have been reported, but their regulatory mechanisms are poorly understood and the function of Fgrdrp5 is still unknown. In this study, we found that in addition to Fgrdrp1 and Fgrdrp2, Fgrdrp5 also plays an important role in ascospore discharge, and they all participate in the generation of turgor pressure in a polyol-dependent manner. Moreover, these three genes all affect the maturation of ascospores. Deep sequencing and co-analysis of small RNA and mRNA certified that Fgrdrp1, Fgrdrp2, and Fgrdrp5 partly share their functions in the biogenesis and accumulation of exonic small interference RNA (ex-siRNA), and these three RdRPs negatively regulate the expression levels of ex-siRNA corresponding genes, including certain genes associated with ascospore development or discharge. Furthermore, the differentially expressed genes of deletion mutants, those involved in lipid and sugar metabolism or transport as well as sexual development-related transcription factors, may also contribute to the defects in ascospore maturation or ascospore discharge. In conclusion, our study suggested that the components of the dicer-dependent ex-siRNA-mediated RNA interference pathway include at least Fgrdrp1, Fgrdrp2, and Fgrdrp5. IMPORTANCE: We found that in addition to Fgrdrp1 and Fgrdrp2, Fgrdrp5 also plays important roles in ascospore maturation and ascospore discharge of Fusarium graminearum. These three RNA-dependent RNA polymerases participate in the biogenesis and accumulation of exonic small interference RNA and then regulate ascospore discharge.

Nanostructured lipid carriers loaded with morellic acid for enhanced anticancer efficacy: preparation, characterization, pharmacokinetics and anticancer evaluation.

Morellic acid (MA), a typical compound found in Garcinia plants, is known for its anticancer properties. In present study, we isolated MA from resin of Garcinia hanburyi Hook. f. using preparative chromatography. We have successfully prepared MA-loaded nanostructured lipid carriers (MA-NLCs) and refined the production process via orthogonal testing. Optimization of the preparation process resulted in an average particle size of 165.50±1.70 nm with a PDI of 0.19±0.01. The EE% and DL% of MA-NLCs were 78.17±0.34% and 7.25±0.38%, respectively. The zeta potential of MA-NLCs was -21.85±0.67 mV. Comparatively, MA-NLCs showed a greater area under the curve (AUC) and an extended half-life (t1/2) than free MA. Pharmacokinetics analysis revealed that the AUC0-t increased from 4.91±0.65 µg/mL∙min (free MA) to 18.91±3.40 µg/mL∙min (MA-NLCs) and the t1/2 value for MA-NLCs was 7.93-fold longer than that of free MA. In vitro cytotoxic assessments indicated that MA formulations curtailed the proliferation of cancer cells. In vivo, MA-NLCs significantly inhibited the tumor growth in tumor-bearing mouse model. Molecular mechanism studies revealed that up-regulation of apaf-1 and activation of caspase-3, caspase-9 and GSDME by MA-NLCs may trigger to apoptosis and pyroptosis in cancer cells. Consequently, our findings support the potential of NLCs as an effective MA delivery system for the clinical management of cancer.

What influences the performance of carbon emissions in China?-Research on the inter-provincial carbon emissions' conditional configuration impacts.

The severe global warming issue currently threatens humans' existence and development. Countries and international organizations have effectively implemented policies to reduce carbon emissions and investigate low-carbon growth strategies. Reducing carbon emissions is a hot topic that academics and government policy-making departments are concerned about.Through necessary condition analysis (NCA) and fuzzy set qualitative comparative analysis(fsQCA), this paper investigates local governments' configuration linkage effect and path choice to improve carbon emission performance from six dimensions: energy consumption, industrial structure, technological innovation, government support, economic development, and demographic factors. The research findings include the following: (1) Individual condition does not represent necessary conditions for the government's carbon performance. Among the two sets of second-order equivalence configurations(S and Q) (five high-level carbon performance configurations), those dominated by economic development or low energy consumption can produce high-level carbon performance. Therefore, the six antecedent conditions dimensions work together to explain how the government can create high levels of carbon performance. (2)According to the regional comparison, China's eastern, central, and western regions exhibit similarities and differences in the driving forces behind high carbon emission performance. All three regions can demonstrate carbon emission performance when all the factors are combined. However, when constrained by the conditions of each region's resource endowment, the eastern region emphasizes the advantage of economic and technological innovation, the central region favors government support and demographic factors, and the western region prefers upgrading industrial structure based on a specific level of economic development.

Machine learning and new insights for breast cancer diagnosis.

Breast cancer (BC) is the most prominent form of cancer among females all over the world. The current methods of BC detection include X-ray mammography, ultrasound, computed tomography, magnetic resonance imaging, positron emission tomography and breast thermographic techniques. More recently, machine learning (ML) tools have been increasingly employed in diagnostic medicine for its high efficiency in detection and intervention. The subsequent imaging features and mathematical analyses can then be used to generate ML models, which stratify, differentiate and detect benign and malignant breast lesions. Given its marked advantages, radiomics is a frequently used tool in recent research and clinics. Artificial neural networks and deep learning (DL) are novel forms of ML that evaluate data using computer simulation of the human brain. DL directly processes unstructured information, such as images, sounds and language, and performs precise clinical image stratification, medical record analyses and tumour diagnosis. Herein, this review thoroughly summarizes prior investigations on the application of medical images for the detection and intervention of BC using radiomics, namely DL and ML. The aim was to provide guidance to scientists regarding the use of artificial intelligence and ML in research and the clinic.

Ribosomal S6 kinase 2-forkhead box protein O4 signaling pathway plays an essential role in melanogenesis.

Although previous studies have examined the signaling pathway involved in melanogenesis through which ultraviolet (UV) or α-melanocyte-stimulating hormones (α-MSH) stimuli act as key inducers to produce melanin at the stratum basal layer of the epidermis, the signaling pathway regulating melanogenesis is still controversial. This study reports that α-MSH, not UVA and UVB, acted as a major stimulus of melanogenesis in B16F10 melanoma cells. Signaling pathway analysis using gene knockdown technology and chemical inhibitors, the mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK)/p90 ribosomal S6 kinase 2 (RSK2) played an important role in melanogenesis. Unexpectedly, LY294002, a PI3K inhibitor, increased melanogenesis without UV or α-MSH stimulation, suggesting that the PI3K/AKT signaling pathway may not be a major signaling pathway for melanogenesis. Chemical inhibition of the MEKs/ERKs/RSK2 signaling pathway using U0126 or BI-D1870 suppressed melanogenesis by stimulation of UVA or α-MSH stimulation, or both. In particular, the genetic depletion of RSK2 or constitutive active (CA)-RSK2 overexpression showed that RSK2 plays a key role in melanogenesis. Interestingly, forkhead box protein O4 (FOXO4) was phosphorylated by RSK2, resulting in the increase of FOXO4's transactivation activity. Notably, the FOXO4 mutant harboring serine-to-alanine replacement at the phosphorylation sites totally abrogated the transactivation activity and reduced melanin production, indicating that RSK2-mediated FOXO4 activity plays a key role in melanogenesis. Furthermore, kaempferol, a flavonoid inhibiting the RSK2 activity, suppressed melanogenesis. In addition, FOXO4-wt overexpression showed that FOXO4 enhance melanin synthesis. Overall, the RSK2-FOXO4 signaling pathway plays a key role in modulating melanogenesis.