Pinocembrin protects human brain microvascular endothelial cells against fibrillar amyloid-β(1-40) injury by suppressing the MAPK/NF-κB inflammatory pathways

Potential skin anti-aging effects of main phenolic compounds, tremulacin and tremuloidin from Salix chaenomeloides leaves on TNF-α-stimulated human dermal fibroblasts

The genus Salix spp. has long been recognized as a healing herb for its use in treating fever, inflammation, and pain relief, as well as a food source for its nutritional value. In this study, we aimed to explore the potential bioactive natural products in the leaves of Salix chaenomeloides, commonly known as Korean pussy willow, for their protective effects against skin damage, including aging. Utilizing LC/MS-guided chemical analysis of the ethanol extract of S. chaenomeloides leaves, with a focus on major compounds, we successfully isolated two main phenolic compounds, tremulacin (1) and tremuloidin (2). Subsequently, we investigated the protective effects of tremulacin (1) and tremuloidin (2) in TNF-α-stimulated human dermal fibroblasts (HDFs). The results revealed that both tremulacin (1) and tremuloidin (2) inhibited TNF-α-stimulation-induced ROS, suppressed matrix metalloproteinase-1 (MMP-1) expression, and enhanced collagen secretion. This implies that both tremulacin (1) and tremuloidin (2) hold promise as preventive agents against photoaging-induced skin aging. Furthermore, we assessed the activity of mitogen-activated protein kinases (MAPKs), cyclooxygenase-2 (COX-2), and heme oxygenase 1 (HO-1) to elucidate the mechanism of photoaging inhibition by tremuloidin (2), which exhibited superior efficacy. We found that tremuloidin (2) inhibited ERK and p38 phosphorylation and notably suppressed COX-2 expression while significantly upregulating HO-1 expression. These findings suggest potent anti-inflammatory and antioxidant properties of tremuloidin (2), positioning it as a potential candidate for combating photoaging-induced skin aging.

The natural flavonoid pinocembrin shows antithrombotic activity and suppresses septic thrombosis

Sepsis, an extreme host response to systemic infection, remains one of the leading causes of mortality worldwide. Platelets, which are integral to both thrombosis and inflammation, play a crucial role in the pathophysiology of sepsis. Excessive platelet activation and aggregation significantly increase the risk of thrombosis, thereby elevating mortality in septic patients. However, the etiology and treatment of this condition have not been comprehensively studied. This study identifies pinocembrin, a natural flavonoid compound derived from propolis, as a potential therapeutic agent for mitigating platelet activation and treating sepsis. In vivo, pinocembrin effectively inhibited FeCl3-induced carotid arterial occlusive thrombus formation and collagen/epinephrine-induced pulmonary thromboembolism in mouse models. In vitro, pinocembrin treatment suppressed multiple facets of platelet activation, including aggregation, secretion, and αIIbβ3-mediated signaling events. Mechanistically, pinocembrin repressed platelet functions by inhibiting Src/Syk/PLCγ2/MAPK signaling pathway. Using cecal ligation and puncture (CLP) mouse model to simulate human sepsis, pinocembrin reduced inflammatory cytokine release and septic thrombosis, thereby improving the survival rate of septic mice. Lipopolysaccharide (LPS)-induced model further substantiated these results. Overall, the inhibition of platelet activity by pinocembrin demonstrates significant therapeutic potential for managing life-threatening septic thrombosis.

Natural polyphenol: Their pathogenesis-targeting therapeutic potential in Alzheimer's disease

Alzheimer's disease (AD) is a detrimental neurodegenerative disease affecting the elderly. Clinically, it is characterized by progressive memory decline and subsequent loss of broader cognitive functions. Current drugs provide only symptomatic relief but do not have profound disease-modifying effects. There is an unmet need to identify novel pharmacological agents for AD therapy. Neuropathologically, the characteristic hallmarks of the disease are extracellular senile plaques containing amyloid β-peptides and intracellular neurofibrillary tangles containing hyperphosphorylated microtubule-associated protein tau. Simultaneously, oxidative stress, neuroinflammation and mitochondrial dysfunction in specific brain regions are early events during the process of AD pathologic changes and are associated with Aβ/tau toxicity. Here, we first summarized probable pathogenic mechanisms leading to neurodegeneration and hopefully identify pathways that serve as specific targets to improve therapy for AD. We then reviewed the mechanisms that underlie disease-modifying effects of natural polyphenols, with a focus on nuclear factor erythroid 2-related factor 2 activators for AD treatment. Lastly, we discussed challenges in the preclinical to clinical translation of natural polyphenols. In conclusion, there is evidence that natural polyphenols can be therapeutically useful in AD through their multifaceted mechanism of action. However, more clinical studies are needed to confirm these effects.

Effectiveness of Histopathological Changes of Induced Thin Layer Endometrium by Pentoxifylline and Pentoxifylline-Loaded Poly Lactic-co-Glycolic Acid on Female Rats

Pentoxifylline (PTXF) is a vasoactive agent that plays a significant role in the treatment of thin-layer endometrium cases. The PTXF, also identified as oxpentifylline, is a member of xanthine derivatives and a competitive nonselective phosphodiesterase inhibitor leading to the elevation of intracellular cAMP, inhibition of tumor necrosis factor and leukotriene synthesis, activation of protein kinase A, and reduction of inflammation and innate immunity. Moreover, it is used as an agent to relieve muscle pain in people with peripheral artery disease (vascular irregularities). It is also an acceptable choice for the treatment of radiation-induced fibrosis. Therefore, the present study aimed to determine the advantageous impact of PTXF and PTXF-loaded poly lactic-co-glycolic acid (PLGA) on female rats after being exposed to ethanol to create a thin layer of the endometrium. For this purpose, 50 female rats were selected and divided into five groups (G1: negative normal control, G2: positive control, G3: PLGA only, G4: preference PTXF, and G5: PLGA-PTXF groups) for a 20-day treatment period. In this study, the histopathological section revealed a perfect improvement in the tissues of the uterine horn of female rats that induced endometria and were treated with PLGA-PTXF. In this group of rats, clear healing was achieved and there was an increase in the thickness of endometrium and myometrium, compared to the ordinary PTXF-treated group which had the lowest recovery characteristics. However, the positive control group underwent a significant decrease in terms of endometrium and myometrium thickness as well as vascular and glandular density. This study showed that the PTXF-loaded PLGA had the capacity to heal the thin layer of the endometrium by improving the levels of histopathological changes, especially regarding the thickness of the endometrium and myometrium more than the ordinary PTXF.

Phytochemical study and immunomodulatory activity of Fraxinus excelsior L

OBJECTIVES

Fraxinus excelsior L. (FE) is traditionally used to treat inflammatory and pain disorders. This study aimed to identify the constituents of FE leaves and evaluate the effects of its n-hexane (FEH), ethyl acetate (FEE), methanol (FEM) extracts and constituents on the viability of THP-1 cells and their ability to release pro-inflammatory cytokines.

METHODS

THP-1 cell viability was assessed using an MTT assay. The immunomodulatory activity was evaluated by measuring tumour necrosis factor-alpha (TNF-α) and interleukin 12 (IL-12) released by lipopolysaccharide-stimulated THP-1 cells using enzyme-linked immunosorbent assays.

KEY FINDINGS

Triterpenes, tyrosol esters, alkanes, phytyl and steryl esters, pinocembrin and bis(2-ethylhexyl)phthalate were isolated from FE. The tyrosol esters showed no significant effect on THP-1 cell viability. FEH, FEE, FEM, and pinocembrin, ursolic acid, oleanolic acid had IC50 values of 56.9, 39.9, 124.7 µg/ml and 178.6, 61.5 and 199.8 µM, respectively. FE extracts, ursolic acid, oleanolic acid and pinocembrin significantly reduced TNF-α/IL-12 levels. The tyrosol esters did not significantly affect TNF-α/IL-12 production.

CONCLUSIONS

FE was able to reduce pro-inflammatory cytokine production indicating a mechanistic focus in its use for inflammation and pain. Further investigations are warranted to unravel the mode of action of the tested constituents and discover other potentially active compounds in FE extracts.

Current advances on the therapeutic potential of pinocembrin: An updated review

Pinocembrin (5,7-dihydroxyflavone) is a major flavonoid found in many plants, fungi and hive products, mainly honey and propolis. Several in vitro and preclinical studies revealed numerous pharmacological activities of pinocembrin including antioxidant, anti-inflammatory, antimicrobial, neuroprotective, cardioprotective and anticancer activities. Here, we comprehensively review and critically analyze the studies carried out on pinocembrin. We also discuss its potential mechanisms of action, bioavailability, toxicity, and clinical investigations. The wide therapeutic window of pinocembrin makes it a promising drug candidate for many clinical applications. We recommend some future perspectives to improve its pharmacokinetic and pharmacodynamic properties for better delivery that may also lead to new therapeutic advances.

Propolis: Its Role and Efficacy in Human Health and Diseases

With technological advancements in the medicinal and pharmaceutical industries, numerous research studies have focused on the propolis produced by stingless bees (Meliponini tribe) and Apis mellifera honeybees as alternative complementary medicines for the potential treatment of various acute and chronic diseases. Propolis can be found in tropical and subtropical forests throughout the world. The composition of phytochemical constituents in propolis varies depending on the bee species, geographical location, botanical source, and environmental conditions. Typically, propolis contains lipid, beeswax, essential oils, pollen, and organic components. The latter include flavonoids, phenolic compounds, polyphenols, terpenes, terpenoids, coumarins, steroids, amino acids, and aromatic acids. The biologically active constituents of propolis, which include countless organic compounds such as artepillin C, caffeic acid, caffeic acid phenethyl ester, apigenin, chrysin, galangin, kaempferol, luteolin, genistein, naringin, pinocembrin, coumaric acid, and quercetin, have a broad spectrum of biological and therapeutic properties such as antidiabetic, anti-inflammatory, antioxidant, anticancer, rheumatoid arthritis, chronic obstruct pulmonary disorders, cardiovascular diseases, respiratory tract-related diseases, gastrointestinal disorders, as well as neuroprotective, immunomodulatory, and immuno-inflammatory agents. Therefore, this review aims to provide a summary of recent studies on the role of propolis, its constituents, its biologically active compounds, and their efficacy in the medicinal and pharmaceutical treatment of chronic diseases.

Pinocembrin suppresses oxidized low-density lipoprotein-triggered NLRP3 inflammasome/GSDMD-mediated endothelial cell pyroptosis through an Nrf2-dependent signaling pathway

Pinocembrin (Pin) has been confirmed to exert anti-inflammatory and antiatherosclerotic effects. Here we have explored whether and how Pin would protect vascular endothelial cells against pyroptosis elicited by the exposure to oxidized low density lipoprotein (oxLDL). Our results showed that Pin preconditioning dose-dependently suppressed oxLDL-stimulated HUVEC injury and pyroptosis, which were manifested by improved cell viability, lower lactate dehydrogenase (LDH) levels and DNA damage as well as decreased expression of pyroptosis-related markers, such as NOD-like receptor pyrin domain-containing 3 (NLRP3), apoptosis-associated speck-like protein containing a caspase activation and recruitment domain (ASC), pro-Caspase-1, cleaved Caspase-1, N-terminus of Gasdermin D-N (GSDMD-N), pro-interleukins-1β (pro-IL-1β), IL-1β and inflammatory cytokines (IL-18 and IL-1β). All of the effects were similar to those of MCC950 (an NLRP3 inhibitor). As expected, Pin distinctly activated the Nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidative signaling pathway assessed through increased expressions of Nrf2, heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase 1 (NQO1). Furthermore, after transfection with small interfering RNA of Nrf2, the inhibitory effects of Pin on oxLDL-triggered NLRP3 inflammasome/GSDMD-mediated pyroptosis and oxidative stress in HUVECs were weakened. Additionally, Pin up-regulated Nrf2/HO-1 axis and down-regulated NLRP3 inflammasome/GSDMD-mediated pyroptosis signals in Apoe^-/- mice fed with high fat diet. These results contribute to the understanding of the anti-pyroptosis mechanisms of Pin and provide a reference for future research on the anti-atherosclerotic effect of Pin.

Assessment of the CYP1A2 Inhibition-Mediated Drug Interaction Potential for Pinocembrin Using In Silico, In Vitro, and In Vivo Approaches

Pinocembrin, a bioflavonoid, is extensively used in complementary/alternative medicine. It turns out as a promising candidate against neurodegenerative diseases because of its multifaceted pharmacological action toward neuroprotection. However, literature evidence is still lacking for its inhibitory action on CYP1A2, which is responsible for xenobiotic metabolism leading to the generation of toxic metabolites and bioactivation of procarcinogens. In the present study, our aim was to evaluate the CYP1A2 inhibitory potential of pinocembrin via in silico, in vitro, and in vivo investigations. From the results of in vitro studies, pinocembrin is found to be a potent and competitive inhibitor of CYP1A2. In vitro-in vivo extrapolation results indicate the potential of pinocembrin to interact with CYP1A2 substrate drugs clinically. Molecular docking-based in silico studies demonstrate the strong interaction of pinocembrin with human CYP1A2. In in vivo investigations using a rat model, pinocembrin displayed a marked alteration in the plasma exposure of CYP1A2 substrate drugs, namely, caffeine and tacrine. In conclusion, pinocembrin has a potent CYP1A2 inhibitory action to cause drug interactions, and further confirmatory study is warranted at the clinical level.

Flavonoids as potential phytotherapeutics to combat cytokine storm in SARS-CoV-2

Emergence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, COVID-19, has become the global panic since December 2019, which urges the global healthcare professionals to identify novel therapeutics to counteract this pandemic. So far, there is no approved treatment available to control this public health issue; however, a few antiviral agents and repurposed drugs support the patients under medical supervision by compromising their adverse effects, especially in emergency conditions. Only a few vaccines have been approved to date. In this context, several plant natural products-based research studies are evidenced to play a crucial role in immunomodulation that can prevent the chances of infection as well as combat the cytokine release storm (CRS) generated during COVID-19 infection. In this present review, we have focused on flavonoids, especially epicatechin, epigallocatechin gallate, hesperidin, naringenin, quercetin, rutin, luteolin, baicalin, diosmin, ge nistein, biochanin A, and silymarin, which can counteract the virus-mediated elevated levels of inflammatory cytokines leading to multiple organ failure. In addition, a comprehensive discussion on available in silico, in vitro, and in vivo findings with critical analysis has also been evaluated, which might pave the way for further development of phytotherapeutics to identify the potential lead candidatetoward effective and safe management of the SARS-CoV-2 disease.

Propolis: A useful agent on psychiatric and neurological disorders? A focus on CAPE and pinocembrin components

Propolis consists of a honeybee product, with a complex mix of substances that have been widely used in traditional medicine. Among several compounds present in propolis, caffeic acid phenethyl ester (CAPE), and pinocembrin emerge as two principal bioactive compounds, with benefits in a variety of body systems. In addition to its well-explored pharmacological properties, neuropharmacological activities have been poorly discussed. In an unprecedented way, the present review addresses the current finding on the promising therapeutic purposes of propolis, focusing on CAPE and pinocembrin, highlighting its use on neurological disturbance, as cerebral ischemia, neuroinflammation, convulsion, and cognitive impairment, as well as psychiatric disorders, such as anxiety and depression. In addition, we provide a critical analysis, discussion, and systematization of the molecular mechanisms which underlie these central nervous system effects. We hypothesize that the pleiotropic action of CAPE and pinocembrin, per se or associated with other substances present in propolis may result in the therapeutic activities reported. Inhibition of the pro-inflammatory cascade, antioxidant activity, and positive neurotrophic modulatory effects consist of the main molecular targets attributed to CAPE and pinocembrin in health benefits.

Flavonoids Distinctly Stabilize Lymph Endothelial- or Blood Endothelial Disintegration Induced by Colon Cancer Spheroids SW620

The health effects of plant phenolics in vegetables and other food and the increasing evidence of the preventive potential of flavonoids in “Western Diseases” such as cancer, neurodegenerative diseases and others, have gained enormous interest. This prompted us to investigate the effects of 20 different flavonoids of the groups of flavones, flavonols and flavanones in 3D in vitro systems to determine their ability to inhibit the formation of circular chemorepellent induced defects (CCIDs) in monolayers of lymph- or blood-endothelial cells (LECs, BECs; respectively) by 12(S)-HETE, which is secreted by SW620 colon cancer spheroids. Several compounds reduced the spheroid-induced defects of the endothelial barriers. In the SW620/LEC model, apigenin and luteolin were most active and acacetin, nepetin, wogonin, pinocembrin, chrysin and hispidulin showed weak effects. In the SW620/BEC model acacetin, apigenin, luteolin, wogonin, hispidulin and chrysin exhibited weak activity.

Reactive oxygen species mediate TNF-α-induced inflammatory response in bone marrow mesenchymal cells

Objectives

It is generally believed that the inflammatory response in bone marrow mesenchymal stem cells (BMSCs) transplantation leads to poor survival and unsatisfactory effects, and is mainly mediated by cytokines, including interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α). In this study, we explored the mechanisms underlying the TNF-α-induced inflammatory response in BMSCs.

Materials and Methods

We treated BMSCs with TNF-α (1 and 10 ng/ml) for 5 days. The expression levels of key inflammatory mediators were evaluated by Real-time PCR. Intracellular ROS level was measured by using a 2, 7-dichlorofluorescein diacetate (DCF-DA).

Results

We found that TNF-α treatment dramatically increased the expression levels of some key inflammatory mediators, including IL-6, IL-1β, IFN-γ and transforming growth factor β (TGF-β). Moreover, TNF-α induced intracellular oxidative stress by elevating intracellular reactive oxygen species (ROS) level, which is due to the increase of lipid peroxidation, the reduction of antioxidant Glutathione (GSH) levels and the inhibition of many antioxidant enzyme activities in BMSCs. Interestingly, 5 µM curcumin, a ROS scavenger, dramatically lowered the TNF-α-induced inflammatory response in BMSCs. In addition, TNF-α induced the activation of extracellular-signal-regulated kinases 1/2 (ERK1/2), c-Jun N-terminal kinases (JNK), p38 and their down-stream transcription factors nuclear factor kappa B (NF-κB) pathway.

Conclusion

ROS mediated the TNF-α-induced inflammatory response via MAPK and NF-κB pathway, and may provide a novel strategy to prevent the inflammatory-dependent impairments in BMSCs.

Natural Products and Their Bioactive Compounds: Neuroprotective Potentials against Neurodegenerative Diseases

In recent years, natural products, which originate from plants, animals, and fungi, together with their bioactive compounds have been intensively explored and studied for their therapeutic potentials for various diseases such as cardiovascular, diabetes, hypertension, reproductive, cancer, and neurodegenerative diseases. Neurodegenerative diseases, including Alzheimer's disease, Huntington's disease, Parkinson's disease, and amyotrophic lateral sclerosis are characterized by the progressive dysfunction and loss of neuronal structure and function that resulted in the neuronal cell death. Since the multifactorial pathological mechanisms are associated with neurodegeneration, targeting multiple mechanisms of actions and neuroprotection approach, which involves preventing cell death and restoring the function to damaged neurons, could be promising strategies for the prevention and therapeutic of neurodegenerative diseases. Natural products have emerged as potential neuroprotective agents for the treatment of neurodegenerative diseases. This review focused on the therapeutic potential of natural products and their bioactive compounds to exert a neuroprotective effect on the pathologies of neurodegenerative diseases.

The Nrf2/HO-1 Axis as Targets for Flavanones: Neuroprotection by Pinocembrin, Naringenin, and Eriodictyol

Flavanones are a group of flavonoids that derive from their immediate chalcone precursors through the action of chalcone isomerase enzymes. The Aromatic A and B rings, C4-keto group, and the 15-carbon flavonoid skeleton are all evident in flavanones, but a notable absence of C2-C3 double bond and a lack of oxygenation at C-3 position of the C-ring makes them distinctively different from other groups such as flavonols (e.g., quercetin). On the basis of oxygenation level in the B ring, flavanones can vary from each other as exemplified by pinocembrin (no oxygenation), naringenin (4′-hydroxyl), or eriodictyol (3′,4′-dihydroxyl substitution). These groups are generally weaker free radical scavengers as compared to quercetin and derivatives though eriodictyol has a better free radical scavenging profile within the group due to the presence of the catechol functional moiety. In this communication, their antioxidant potential through the induction of antioxidant defenses is scrutinized. These compounds as exemplified by pinocembrin could induce the nuclear factor erythroid 2-related factor 2- (Nrf2-) heme oxygenase-1 (HO-1) axis leading to amelioration of oxidative stress in cellular and animal models. Their neuroprotective effect through such mechanism is discussed.

Evidence on the Health Benefits of Supplemental Propolis

Propolis is a honey-related product with reported health benefits such as improved immunity, lowered blood pressure, treated allergies and skin conditions. A literature review and narrative synthesis were conducted to investigate the evidence on the reported health benefits and future direction of propolis products. Using a predefined search strategy we searched Medline (OvidSP), Embase and Central for quantitative and qualitative studies (1990-2018). Citation, reference, hand searches and expert consultation were also undertaken. Studies of randomised control trials and observational data on humans with health-related outcomes were included. Collected data were entered into NVivo software (Version 12, QRS International) and analysed using a thematic framework and a narrative synthesis of emergent themes. A total of 63 publications were discussed. The majority were cell-based and animal studies, with a few key human trials conducted. There is significant promise for propolis as an effective antioxidant and anti-inflammatory agent with particular promise in cardiometabolic health.

Pinocembrin attenuates autonomic dysfunction and atrial fibrillation susceptibility via inhibition of the NF-κB/TNF-α pathway in a rat model of myocardial infarction

Previous studies indicate that myocardial infarction (MI) may contribute to atrial fibrillation (AF). Emerging evidence has shown that pinocembrin protects myocardial ischemic injury (I/R)-induced cardiac fibrosis and arrhythmias in animals via its anti-inflammatory or antioxidant activities. However, the effects of pinocembrin on MI-induced atrial arrhythmias remain unknown. Thus, this study aimed to investigate the effects of pinocembrin on autonomic dysfunction and AF susceptibility in MI rats and the possible mechanism. In a standard experimental MI model, Sprague-Dawley rats received permanent ligation of the left anterior descending (LAD) coronary artery and were treated with pinocembrin or saline for 6 days. Our results demonstrated that pinocembrin treatment significantly decreased sympathetic activity, augmented parasympathetic activity, improved heart rate variability (HRV), prolonged the atrial effective refractory period (ERP) and action potential duration (APD), shortened activation latency (AL), lowered the indicibility rate of AF, attenuated atrial fibrosis, and decreased concentrations of norepinephrine (NE), tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6 in the serum and the left atrial (LA). Furthermore, pinocembrin treatment significantly increased the expression levels of Cx43 and Cav1.2 and suppressed the phosphorylation of inhibitor-κBα (IκBα) and the activation of nuclear factor-kappa B (NF-κB)subunit p65. In conclusion, the findings indicate that pinocembrin treatment decreases autonomic remodeling, lowers atrial fibrosis, ameliorates atrial electrical remodeling, and suppresses MI-induced inflammatory responses, which suggests a potential novel strategy for atrial arrhythmias.

Propolis Reduces the Expression of Autophagy-Related Proteins in Chondrocytes under Interleukin-1β Stimulus

Background: Osteoarthritis (OA) is a progressive and multifactorial disease that is associated with aging. A number of changes occur in aged cartilage, such as increased oxidative stress, decreased markers of healthy cartilage, and alterations in the autophagy pathway. Propolis extracts contain a mixture of polyphenols and it has been proved that they have high antioxidant capacity and could regulate the autophagic pathway. Our objective was to evaluate the effect of ethanolic extract of propolis (EEP) on chondrocytes that were stimulated with IL-1β. Methods: Rabbit chondrocytes were isolated and stimulated with IL-1β and treated with EEP. We evaluated cell viability, nitric oxide production, healthy cartilage, and OA markers, and the expression of three proteins associated with the autophagy pathway LC3, ATG5, and AKT1. Results: The EEP treatment reduces the expression of LC3, ATG5, and AKT1, reduces the production of nitric oxide, increases the expression of healthy markers, and reduces OA markers. Conclusions: These results suggest that treatment with EEP in chondrocytes that were stimulated with IL-1β has beneficial effects, such as a decrease in the expression of proteins associated with autophagy, MMP13, and production of nitric oxide, and also increased collagen II.

Advances in Biosynthesis, Pharmacology, and Pharmacokinetics of Pinocembrin, a Promising Natural Small-Molecule Drug

Pinocembrin is one of the most abundant flavonoids in propolis, and it may also be widely found in a variety of plants. In addition to natural extraction, pinocembrin can be obtained by biosynthesis. Biosynthesis efficiency can be improved by a metabolic engineering strategy and a two-phase pH fermentation strategy. Pinocembrin poses an interest for its remarkable pharmacological activities, such as neuroprotection, anti-oxidation, and anti-inflammation. Studies have shown that pinocembrin works excellently in treating ischemic stroke. Pinocembrin can reduce nerve damage in the ischemic area and reduce mitochondrial dysfunction and the degree of oxidative stress. Given its significant efficacy in cerebral ischemia, pinocembrin has been approved by China Food and Drug Administration (CFDA) as a new treatment drug for ischemic stroke and is currently in progress in phase II clinical trials. Research has shown that pinocembrin can be absorbed rapidly in the body and easily cross the blood-brain barrier. In addition, the absorption/elimination process of pinocembrin occurs rapidly and shows no serious accumulation in the body. Pinocembrin has also been found to play a role in Parkinson's disease, Alzheimer's disease, and specific solid tumors, but its mechanisms of action require in-depth studies. In this review, we summarized the latest 10 years of studies on the biosynthesis, pharmacological activities, and pharmacokinetics of pinocembrin, focusing on its effects on certain diseases, aiming to explore its targets, explaining possible mechanisms of action, and finding potential therapeutic applications.

Pinocembrin Protects from AGE-Induced Cytotoxicity and Inhibits Non-Enzymatic Glycation in Human Insulin

Advanced glycation end products (AGEs) are the end products of the glycation reaction and have a great importance in clinical science for their association with oxidative stress and inflammation, which play a major role in most chronic diseases, such as cardiovascular disease, neurodegenerative diseases, and diabetes. Their pathogenic effects are generally induced by the interaction between AGEs and the receptor for advanced glycation end product (RAGE) on the cell surface, which triggers reactive oxygen species production, nuclear factor kB (NF-kB) activation, and inflammation. Pinocembrin, the most abundant flavonoid in propolis, has been recently proven to interfere with RAGE activation in Aβ–RAGE-induced toxicity. In the present study, we investigated the ability of pinocembrin to interfere with RAGE signaling pathways activated by AGEs. Interestingly, pinocembrin was able to inhibit oxidative stress and NF-kB activation in cells exposed to AGEs. In addition, it was able to block caspase 3/7 and 9 activation, thus suggesting an active role of this molecule in counteracting AGE–RAGE-induced toxicity mediated by NF-kB signaling pathways. The ability of pinocembrin to affect the glycation reaction has been also tested. Our data suggest that pinocembrin might be a promising molecule in protecting from AGE-mediated pathogenesis.

Pinocembrin protects endothelial cells from oxidized LDL-induced injury

Oxidized low-density lipoprotein (ox-LDL) is a major risk factor for atherosclerosis and often causes injury to vascular endothelial cells. We found that pinocembrin, a natural antioxidant found in honey and certain herbs, protects human aortic endothelial cells (HAECs) from ox-LDL-induced injury. Pinocembrin suppresses the expression of pro-inflammatory vascular adhesion molecules (VCAM-1, ICAM-1 and E-selectin) and cytokines (TNF-α, IL-1β, and IL-8), as well as ROS production induced by ox-LDL. Pinocembrin potently inhibits the attachment of monocytes to HAEC cells. Mechanistically, pinocembrin suppresses activation of the MAPK kinase p38 and NF-κB pathways in the context of ox-LDL. Our data indicate that pinocembrin is a promising versatile natural compound that can protect endothelial cells from injury.

Asiaticoside Attenuates Cell Growth Inhibition and Apoptosis Induced by Aβ1-42 via Inhibiting the TLR4/NF-κB Signaling Pathway in Human Brain Microvascular Endothelial Cells

Alzheimer's disease (AD) is a very common progressive neurodegenerative disorder with the highest incidence in the world. Dysfunction of the blood-brain barrier (BBB) may be responsible for the pathogenesis and pathology of AD for abnormally transporting amyloid-β (Aβ, the main component of the senile plaques) from the sera into the central nervous system. Aβ peptides induce apoptosis in human brain microvascular endothelial cells (hBMECs), the main component of BBB. Apoptosis in neuronal cells plays a critical role in the pathogenesis of AD. Asiaticoside, a natural glycoside extracted from Centella asiatica (L.) Urban, has an anti-apoptotic effect on hBMECs but the molecule mechanism remains unclear. Therefore, we investigate the protective effect of asiaticoside on Aβ_1-42-induced cytotoxicity and apoptosis as well as associated mechanism in hBMECs with commonly used in vitro methods for clinical development of asiaticoside as a novel anti-AD agent. In the present study, we investigated the effects of asiaticoside on cytotoxicity by Cell Counting Kit-8 assay, mitochondrial membrane potential by JC-1 fluorescence analysis, anti-apoptosis by Hoechst 33258 staining and Annexin V-FITC (fluorescein isothiocyanate) and propidium iodide (PI) analyses, the expressions of TNF-α and IL-6 by enzyme-linked immunosorbent assay (ELISA) and TLR4, MyD88, TRAF6, p-NF-κB p65, and total NF-κB p65 by Western blotting, and nuclear translocation of NF-κB p65 by immunofluorescence analysis in hBMECs. The results showed that pretreatment of asiaticoside (25, 50, and 100 μM) for 12 h significantly attenuated cell growth inhibition and apoptosis, and restored declined mitochondrial membrane potential induced by Aβ_1-42 (50 μM) in hBMECs. Asiaticoside also significantly downregulated the elevated expressions of TNF-α, IL-6, TLR4, MyD88, TRAF6, and p-NF-κB p65, as well as inhibited NF-κB p65 translocation from cytoplasm to nucleus induced by Aβ_1-42 in hBMECs in a concentration-dependent manner. The possible underlying molecular mechanism of asiaticoside may be through inhibiting the TLR4/NF-κB signaling pathway. Therefore, asiaticoside may be developed as a novel agent for the prevention and/or treatment of AD clinically.

Pinocembrin attenuates allergic airway inflammation via inhibition of NF-κB pathway in mice

Pinocembrin, one of the primary flavonoids in propolis, possesses many biological activities, including anti-inflammation, anti-oxidation and immunoregulation. This study aimed to evaluate whether pinocembrin could attenuate ovalbumin (OVA)-induced allergic airway inflammation in mice and to explore the possible mechanism. BALB/c mice sensitized and challenged with OVA were administered intraperitoneally with pinocembrin. Airway inflammation and airway hyperresponsiveness were examined. T-helper type (Th) 2 cytokines in bronchoalveolar lavage fluid (BALF) and OVA-specific immunoglobulin E (IgE) in serum were determined. The activation of nuclear factor kappa B (NF-κB) p65 were also measured. Our results showed that pinocembrin resulted in significant inhibition of pathophysiological signs of allergic asthma, including increased pulmonary eosinophilia infiltration, mucus hypersecretion and airway hyperresponsiveness (AHR). Treatment with pinocembrin significantly reduced Th2 cytokines interleukin (IL)-4, IL-5 and IL-13 in BALF, and OVA-specific IgE in serum. Moreover, pinocembrin treatment suppressed phosphorylation of inhibitor-κBα (IκBα) and NF-κB subunit p65 activation in lung tissue of OVA-sensitized mice. These data suggest that pinocembrin may inhibit allergic airway inflammation, and providing potential benefits in the treatment of inflammatory disease.

Effect of Green and Brown Propolis Extracts on the Expression Levels of microRNAs, mRNAs and Proteins, Related to Oxidative Stress and Inflammation

A large body of evidence highlights that propolis exerts many biological functions that can be ascribed to its antioxidant and anti-inflammatory components, including different polyphenol classes. Nevertheless, the molecular mechanisms are yet unknown. The aim of this study is to investigate the mechanisms at the basis of propolis anti-inflammatory and antioxidant activities. The effects of two brown and green propolis extracts-chemically characterized by RP-HPLC-PDA-ESI-MSn-on the expression levels of miRNAs associated with inflammatory responses (miR-19a-3p and miR-203a-3p) and oxidative stress (miR-27a-3p and miR-17-3p), were determined in human keratinocyte HaCat cell lines, treated with non-cytotoxic concentrations. The results showed that brown propolis, whose major polyphenolic components are flavonoids, induced changes in the expression levels of all miRNAs, and was more active than green propolis (whose main polyphenolic components are hydroxycinnamic acid derivatives) which caused changes only in the expression levels of miR-19a-3p and miR-27a-3p. In addition, only brown propolis was able to modify (1) the expression levels of mRNAs, the target of the reported miRNAs, which code for Tumor Necrosis Factor-α (TNF-α), Nuclear Factor, Erythroid 2 Like 2 (NFE2L2) and Glutathione Peroxidase 2 (GPX2), and (2) the protein levels of TNF-α and NFE2L2. In conclusion, brown and green propolis, which showed different metabolite profiles, exert their biological functions through different mechanisms of action.

Pinocembrin, a novel histidine decarboxylase inhibitor with anti-allergic potential in in vitro

Pinocembrin (5, 7- dihydroxy flavanone) is the most abundant chiral flavonoid found in propolis, exhibiting antioxidant, antimicrobial and anti-inflammatory properties. However, the effect of Pinocembrin on allergic response is unexplored. Thus, current study aimed at investigating the effects of Pinocembrin on IgE-mediated allergic response in vitro. A special emphasis was directed toward histidine decarboxylase (HDC) and other pro-allergic and pro-inflammatory mediators. Preliminary studies, using a microbiological model of Klebsiella pneumoniae, provided first evidences that suggest Pinocembrin as a potential thermal stable inhibitor for HDC. Applying docking analysis revealed possible interaction between Pinocembrin and mammalian HDC. In vitro studies validated the predicted interaction and showed that Pinocembrin inhibits HDC activity and histamine in IgE-sensitized RBL-2H3 in response to dinitrophenol (DNP)-bovine serum albumin (BSA) stimulation. In addition, Pinocembrin mitigated the damage in the mitochondrial membrane, formation of cytoplasmic granules and degranulation as indicated by lower β-hexoseaminidase level. Interestingly, it reduced range of pro-inflammatory mediators in the IgE-mediated allergic response including tumor necrosis factor (TNF)-α, interleukin (IL)-6, nitric oxide (NO), inducible NO synthase (iNOS), phosphorylation of inhibitory kappa B (IкB)-α, prostaglandin (PGE)-2 and cyclooxygenase (COX)-2. In conclusion, current study suggests Pinocembrin as a potential HDC inhibitor, and provides the first evidences it is in vitro anti-allergic properties, suggesting Pinocembrin as a new candidate for natural anti-allergic drugs.

Luteolin Inhibits Fibrillary β-Amyloid1-40-Induced Inflammation in a Human Blood-Brain Barrier Model by Suppressing the p38 MAPK-Mediated NF-κB Signaling Pathways

Amyloid-β peptides (Aβ) exist in several forms and are known as key modulators of Alzheimer's disease (AD). Fibrillary Aβ (fAβ) has been found to disrupt the blood-brain barrier (BBB) by triggering and promoting inflammation. In this study, luteolin, a naturally occurring flavonoid that has shown beneficial properties in the central nervous system, was evaluated as a potential agent to preserve barrier function and inhibit inflammatory responses at the BBB that was injured by fAβ_1-40. We established an in vitro BBB model by co-culturing human brain microvascular endothelial cells (hBMECs) and human astrocytes (hAs) under fAβ_1-40-damaged conditions and investigated the effect of luteolin by analyzing cellular toxicity, barrier function, cytokine production and inflammation-related intracellular signaling pathways. Our results demonstrated that, in cells injured by fAβ_1-40, luteolin increased cell viability of hBMECs and hAs. The cytoprotection of the co-culture against the damage induced by fAβ_1-40 was also increased at both the apical and basolateral sides. Luteolin protected the barrier function by preserving transendothelial electrical resistance and relieving aggravated permeability in the human BBB model after being exposed to fAβ_1-40. Moreover, in both the apical and basolateral sides of the co-culture, luteolin reduced fAβ_1-40-induced inflammatory mediator and cytokine production, including cyclooxygenase-2 (COX-2), tumor necrosis factor α (TNF-α), interleukin 1 β (IL-1β), interleukin 6 (IL-6), and interleukin 8 (IL-8), however it did not show sufficient effects on scavenging intracellular reactive oxygen species (ROS) in hBMECs and hAs. The mechanism of BBB protection against fAβ_1-40-induced injury may be related to the regulation of inflammatory signal transduction, which involves inhibition of p38 mitogen-activated protein kinase (MAPK) activation, downregulation of phosphorylated inhibitory κB kinase (phosphor-IKK) levels, relief of inhibitory κB α (IκBα) degradation, blockage of nuclear factor κB (NF-κB) p65 nuclear translocation, and reduction of the release of inflammatory cytokines. Moreover, the employment of p38 MAPK and NF-κB inhibitors reversed luteolin-mediated barrier function and cytokine release. Taken together, luteolin may serve as a potential therapeutic agent for BBB protection by inhibiting inflammation following fAβ_1-40-induced injury.

Pinocembrin Attenuates Mitochondrial Dysfunction in Human Neuroblastoma SH-SY5Y Cells Exposed to Methylglyoxal: Role for the Erk1/2-Nrf2 Signaling Pathway

Pinocembrin (PB; 5,7-dihydroxyflavanone) is found in propolis and exhibits antioxidant activity in several experimental models. The antioxidant capacity of PB is associated with the activation of the nuclear factor erythroid 2-related factor 2/antioxidant response element (Nrf2/ARE) signaling pathway. The Nrf2/ARE axis mediates the expression of antioxidant and detoxifying enzymes, such as glutathione peroxidase (GPx), glutathione reductase (GR), heme oxygenase-1 (HO-1), and the catalytic (GCLC) and regulatory (GCLM) subunits of the rate-limiting enzyme in the synthesis of glutathione (GSH), γ-glutamate-cysteine ligase (γ-GCL). Nonetheless, it is not clear how PB exerts mitochondrial protection in mammalian cells. Human neuroblastoma SH-SY5Y cells were pretreated (4 h) with PB (0-25 µM) and then exposed to methylglyoxal (MG; 500 µM) for further 24 h. Mitochondria were isolated by differential centrifugation. PB (25 µM) provided mitochondrial protection (decreased lipid peroxidation, protein carbonylation, and protein nitration in mitochondrial membranes; decreased mitochondrial free radical production; enhanced the content of GSH in mitochondria; rescued mitochondrial membrane potential-MMP) and blocked MG-triggered cell death by a mechanism dependent on the activation of the extracellular-related kinase (Erk1/2) and consequent upregulation of Nrf2. PB increased the levels of GPx, GR, HO-1, and mitochondrial GSH. The PB-induced effects were suppressed by silencing of Nrf2 with siRNA. Therefore, PB activated the Erk1/2-Nrf2 signaling pathway resulting in mitochondrial protection in SH-SY5Y cells exposed to MG. Our work shows that PB is a strong candidate to figure among mitochondria-focusing agents with pharmacological potential.

Chemical composition and disruption of quorum sensing signaling in geographically diverse United States propolis

Propolis or bee glue has been used for centuries for various purposes and is especially important in human health due to many of its biological and pharmacological properties. In this work we showed quorum sensing inhibitory (QSI) activity of ten geographically distinct propolis samples from the United States using the acyl-homoserine lactone- (AHL-) dependent Chromobacterium violaceum strain CV026. Based on GC-MS chemical profiling the propolis samples can be classified into several groups that are as follows: (1) rich in cinnamic acid derivatives, (2) rich in flavonoids, and (3) rich in triterpenes. An in-depth analysis of the propolis from North Carolina led to the isolation and identification of a triterpenic acid that was recently isolated from Hondurian propolis (Central America) and ethyl ether of p-coumaric alcohol not previously identified in bee propolis. QSI activity was also observed in the second group US propolis samples which contained the flavonoid pinocembrin in addition to other flavonoid compounds. The discovery of compounds that are involved in QSI activity has the potential to facilitate studies that may lead to the development of antivirulence therapies that can be complementary and/or alternative treatments against antibiotic resistant bacterial pathogens and/or emerging pathogens that have yet to be identified.

Quercetin protects human brain microvascular endothelial cells from fibrillar β-amyloid1-40-induced toxicity

Amyloid beta-peptides (Aβ) are known to undergo active transport across the blood-brain barrier, and cerebral amyloid angiopathy has been shown to be a prominent feature in the majority of Alzheimer׳s disease. Quercetin is a natural flavonoid molecule and has been demonstrated to have potent neuroprotective effects, but its protective effect on endothelial cells under Aβ-damaged condition is unclear. In the present study, the protective effects of quercetin on brain microvascular endothelial cells injured by fibrillar Aβ_1–40 (fAβ_1–40) were observed. The results show that fAβ_1–40-induced cytotoxicity in human brain microvascular endothelial cells (hBMECs) can be relieved by quercetin treatment. Quercetin increases cell viability, reduces the release of lactate dehydrogenase, and relieves nuclear condensation. Quercetin also alleviates intracellular reactive oxygen species generation and increases superoxide dismutase activity. Moreover, it strengthens the barrier integrity through the preservation of the transendothelial electrical resistance value, the relief of aggravated permeability, and the increase of characteristic enzyme levels after being exposed to fAβ_1–40. In conclusion, quercetin protects hBMECs from fAβ_1–40-induced toxicity.