Anti-Inflammatory Effect of an Apigenin-Maillard Reaction Product in Macrophages and Macrophage-Endothelial Cocultures

Apigenin accelerates wound healing in diabetic mice by promoting macrophage M2-type polarization via increasing miR-21 expression

The alteration of inflammatory phenotype by macrophage polarization plays an important role in diabetic wound repair. Apigenin has been reported to be anti-inflammatory and promote tissue repair; however, whether it regulates macrophage polarization to participate in diabetic wound repair remains to be investigated. We found that apigenin promoted miR-21 expression in LPS-stimulated RAW264.7 cells, inhibited cellular M1-type factor TNF-α and IL-1β secretion and increased M2-type factor IL-10 and TGF-β secretion, and accelerated macrophage conversion from M1 type to M2 type, whereas this protective effect of apigenin was counteracted by a miR-21 inhibitor. Moreover, we established a macrophage-HUVECs cell in vitro co-culture system and found that apigenin accelerated the migration, proliferation, and VEGF secretion of HUVECs by promoting macrophage miR-21 expression. Further, mechanistic studies revealed that this was mediated by the TLR4/Myd88/NF-κB axis. In in vivo study, diabetic mice had significantly delayed wound healing compared to non-diabetic mice, accelerated wound healing in apigenin-treated diabetic mice, and decreased M1-type macrophages and increased M2-type macrophages in wound tissues.

Scavenging Glyoxal and Methylglyoxal by Synephrine Alone or in Combination with Neohesperidin at High Temperatures

α-Dicarbonyl compounds, such as glyoxal (GO) and methylglyoxal (MGO), are a series of chemical hazards that exist in vivo and in vitro, posing a threat to human health. We aimed to explore the scavenging effects on GO/MGO by synephrine (SYN) alone or in combination with neohesperidin (NEO). First, through LC-MS/MS, we confirmed that both SYN and NEO could effectively remove GO and form GO adducts, while NEO could also clear MGO by forming MGO adducts, and its ability to clear MGO was stronger than that of GO. Second, a synergistic inhibitory effect on GO was found when SYN and NEO were used in combination by using the Chou-Talalay method; on the other hand, SYN could promote NEO to clear more MGO, although SYN could not capture MGO. Third, after synthesizing four GO/MGO-adducts (SYN-GO-1, SYN-GO-3, NEO-GO-7, and NEO-MGO-2) and identifying their structure through NMR, strict correlations between the GO/MGO-adducts and the GO/MGO-clearance rate were found when using SYN and NEO alone or in combination. Furthermore, it was inferred that the synergistic effect between SYN and NEO stems from their mutual promotion in capturing more GO by the quantitative analysis of the adducts in the combined model. Finally, a study was conducted on flowers of Citrus aurantium L. var. amara Engl. (FCAVA, an edible tea) rich in SYN and NEO, which could serve as an effective GO and MGO scavenger in the presence of both GO and MGO. Therefore, our study provided well-defined evidence that SYN and NEO, alone or in combination, could efficiently scavenge GO/MGO at high temperatures, whether in the pure form or located in FCAVA.

Necroptosis in Pneumonia: Therapeutic Strategies and Future Perspectives

Pneumonia remains a major global health challenge, necessitating the development of effective therapeutic approaches. Recently, necroptosis, a regulated form of cell death, has garnered attention in the fields of pharmacology and immunology for its role in the pathogenesis of pneumonia. Characterized by cell death and inflammatory responses, necroptosis is a key mechanism contributing to tissue damage and immune dysregulation in various diseases, including pneumonia. This review comprehensively analyzes the role of necroptosis in pneumonia and explores potential pharmacological interventions targeting this cell death pathway. Moreover, we highlight the intricate interplay between necroptosis and immune responses in pneumonia, revealing a bidirectional relationship between necrotic cell death and inflammatory signaling. Importantly, we assess current therapeutic strategies modulating necroptosis, encompassing synthetic inhibitors, natural products, and other drugs targeting key components of the programmed necrosis pathway. The article also discusses challenges and future directions in targeting programmed necrosis for pneumonia treatment, proposing novel therapeutic strategies that combine antibiotics with necroptosis inhibitors. This review underscores the importance of understanding necroptosis in pneumonia and highlights the potential of pharmacological interventions to mitigate tissue damage and restore immune homeostasis in this devastating respiratory infection.

Does an apple a day keep away diseases? Evidence and mechanism of action

Apples and their products exemplify the recently reemphasized link between dietary fruit intake and the alleviation of human disease. Their consumption does indeed improve human health due to their high phytochemical content. To identify potentially relevant articles from clinical trials, some epidemiological studies and meta-analyses, and in vitro and in vivo studies (cell cultures and animal models), PubMed was searched from January 1, 2012, to May 15, 2022. This review summarized the potential effects of apple and apple products (juices, puree, pomace, dried apples, extracts rich in apple bioactives and single apple bioactives) on health. Apples and apple products have protective effects against cardiovascular diseases, cancer, as well as mild cognitive impairment and promote hair growth, healing of burn wounds, improve the oral environment, prevent niacin-induced skin flushing, promote the relief of UV-induced skin pigmentation, and improve the symptoms of atopic dermatitis as well as cedar hay fever among others. These effects are associated with various mechanisms, such as vascular endothelial protection, blood lipids lowering, anti-inflammatory, antioxidant, antiapoptotic, anti-invasion, and antimetastatic effects. Meanwhile, it has provided an important reference for the application and development of medicine, nutrition, and other fields.

Anti-inflammatory activities of flavonoid derivates

BACKGROUND AND PURPOSE

Flavonoids are a group of phytochemicals found abundantly in various plants. Scientific evidence has revealed that flavonoids display potential biological activities, including their ability to alleviate inflammation. This activity is closely related to their action in blocking the inflammatory cascade and inhibiting the production of pro-inflammatory factors. However, as flavonoids typically have poor bioavailability and pharmacokinetic profile, it is quite challenging to establish these compounds as a drug. Nevertheless, progressive advancements in drug delivery systems, particularly in nanotechnology, have shown promising approaches to overcome such challenges.

REVIEW APPROACH

This narrative review provides an overview of scientific knowledge about the mechanism of action of flavonoids in the mitigation of inflammatory reaction prior to delivering a comprehensive discussion about the opportunity of the nanotechnology-based delivery system in the preparation of the flavonoid-based drug.

KEY RESULTS

Various studies conducted in silico, in vitro, in vivo, and clinical trials have deciphered that the anti-inflammatory activities of flavonoids are closely linked to their ability to modulate various biochemical mediators, enzymes, and signalling pathways involved in the inflammatory processes. This compound could be encapsulated in nanotechnology platforms to increase the solubility, bioavailability, and pharmacological activity of flavonoids as well as reduce the toxic effects of these compounds.

CONCLUSION

In Summary, we conclude that flavonoids and their derivates have given promising results in their development as new anti-inflammatory drug candidates, especially if they formulate in nanoparticles.

Apigenin attenuates atherosclerosis and non-alcoholic fatty liver disease through inhibition of NLRP3 inflammasome in mice

Apigenin (APN), a flavone found in several plant foods with various biological properties such as anti-obesity, anti-inflammation and other abilities, alleviates atherosclerosis and non-alcoholic fatty liver disease (NAFLD) induced by a high fat diet (HFD) in mice. However, the underlying mechanisms have not been fully understood. In this study, we investigated the role of NLRP3 in anti-atherosclerosis and anti-NAFLD effect of APN in mouse models with NLRP3 deficiency. Atherosclerosis and NAFLD models were established by treatment of low density lipoprotein receptor-deficient (Ldlr^-/-) mice and NLRP3^-/- Ldlr^-/- mice with a HFD diet (20% fat and 0.5% cholesterol) with or without APN. En face lipid accumulation analysis, plasma lipid levels, hepatic lipid accumulation and inflammation were analyzed and quantified. For in vitro experiments, HepG2 cells were stimulated by LPS plus oleic acid (OA) in the absence or presence of APN (50 μM). Lipid accumulation and the effect of APN on the NLRP3/NF-κB signaling pathway were investigated. APN administration partly reversed atherosclerosis and hepatic lipid accumulation, and decreased body weight and plasma lipid levels in Ldlr^-/- mice when fed a HFD. Compared with Ldlr^-/- mice, NLRP3^-/- Ldlr^-/- mice showed more severe atherosclerosis and hepatic lipid accumulation. Treating the HepG2 cells with APN reduced lipid accumulation. APN also inhibited activation of the NLRP3/ NF-κB signaling pathway stimulated by OA together with LPS. Our results indicate that APN supplementation prevents atherosclerosis and NAFLD via NLRP3 inhibition in mice, and suggest that APN might be a potential therapeutic agent for the prevention of atherosclerosis and NAFLD.

Spinach (Spinacia oleracea) microgreen prevents the formation of advanced glycation end products in model systems and breads

The formation of advanced glycation end products (AGEs) in daily diets poses a great threat to human health, since AGEs are closely related to some chronic metabolic diseases. In this study, we investigated the antiglycative capabilities of some popular microgreens in chemical model. Our data indicated that baby spinach (Spinacia oleracea) had the highest antiglycative activity during 4-wks incubation, with antioxidation being the main action route. Moreover, a bread model was set up to evaluate its antiglycative potential in real food model. The results showed that the fortification of baby spinach in bread significantly inhibited AGEs formation, with acceptable taste and food quality. Further study revealed that the antiglycative components were mainly distributed in leaves, which were separated via column chromatography and tentatively identified as chlorophyll derivatives. In summary, this study highlighted the antiglycative benefits of baby spinach which can be developed into healthy functional foods.

Flavonoids regulate tumor-associated macrophages - From structure-activity relationship to clinical potential (Review)

In recent years, the strategy for tumor therapy has changed from focusing on the direct killing effect of different types of therapeutic agents on cancer cells to the new mainstream of multi-mode and -pathway combined interventions in the microenvironment of the developing tumor. Flavonoids, with unique tricyclic structures, have diverse and extensive immunomodulatory and anti-cancer activities in the tumor microenvironment (TME). Tumor-associated macrophages (TAMs) are the most abundant immunosuppressive cells in the TME. The regulation of macrophages to fight cancer is a promising immunotherapeutic strategy. This study covers the most comprehensive cognition of flavonoids in regulating TAMs so far. Far more than a simple list of studies, we try to dig out evidence of crosstalk at the molecular level between flavonoids and TAMs from literature, in order to discuss the most relevant chemical structure and its possible relationship with the multimodal pharmacological activity, as well as systematically build a structure-activity relationship between flavonoids and TAMs. Additionally, we point out the advantages of the macro-control of flavonoids in the TME and discuss the potential clinical implications as well as areas for future research of flavonoids in regulating TAMs. These results will provide hopeful directions for the research of antitumor drugs, while providing new ideas for the pharmaceutical industry to develop more effective forms of flavonoids.

6-C-(E-Phenylethenyl)-naringenin, a Styryl Flavonoid, Inhibits Advanced Glycation End Product-Induced Inflammation by Upregulation of Nrf2

Styryl flavonoids can be formed during the thermal processing of meats and flavonoid-enriched foods, showing high potentials in the prevention of different diseases. In this study, the protective effects of several styryl flavonoids against advanced glycation end product (AGE)-induced inflammation were evaluated, with 6-C-(E-phenylethenyl)-naringenin (6-PN) showing the strongest activity among them. The results indicated that 6-PN significantly ameliorated AGE-induced damages in human umbilical vein endothelial cells, including inhibition of pro-inflammatory cytokines and reactive oxygen species (ROS) production through downregulating the protein levels of the receptor for AGEs (RAGE) and NADPH oxidase. Notably, 6-PN possessed a much higher bioavailability than its parental compound, naringenin. Furthermore, 6-PN also promoted the activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway that was suppressed by AGEs, and the anti-inflammatory effects of 6-PN disappeared when the cells were treated with ML385, a Nrf2 inhibitor. Hence, 6-PN might inhibit AGE-induced inflammation by the RAGE/ROS/Nrf2 signaling pathway.

Facilitating Reparative Dentin Formation Using Apigenin Local Delivery in the Exposed Pulp Cavity

Apigenin, a natural product belonging to the flavone class, affects various cell physiologies, such as cell signaling, inflammation, proliferation, migration, and protease production. In this study, apigenin was applied to mouse molar pulp after mechanically pulpal exposure to examine the detailed function of apigenin in regulating pulpal inflammation and tertiary dentin formation. In vitro cell cultivation using human dental pulp stem cells (hDPSCs) and in vivo mice model experiments were employed to examine the effect of apigenin in the pulp and dentin regeneration. In vitro cultivation of hDPSCs with apigenin treatment upregulated bone morphogenetic protein (BMP)- and osteogenesis-related signaling molecules such as BMP2, BMP4, BMP7, bone sialoprotein (BSP), runt-related transcription factor 2 (RUNX2), and osteocalcin (OCN) after 14 days. After apigenin local delivery in the mice pulpal cavity, histology and cellular physiology, such as the modulation of inflammation and differentiation, were examined using histology and immunostainings. Apigenin-treated specimens showed period-altered immunolocalization patterns of tumor necrosis factor (TNF)-α, myeloperoxidase (MPO), NESTIN, and transforming growth factor (TGF)-β1 at 3 and 5 days. Moreover, the apigenin-treated group showed a facilitated dentin-bridge formation with few irregular tubules after 42 days from pulpal cavity preparation. Micro-CT images confirmed obvious dentin-bridge structures in the apigenin-treated specimens compared with the control. Apigenin facilitated the reparative dentin formation through the modulation of inflammation and the activation of signaling regulations. Therefore, apigenin would be a potential therapeutic agent for regenerating dentin in exposed pulp caused by dental caries and traumatic injury.

Anti-inflammatory effects of the immobilization of SEMA4D on titanium surfaces in an endothelial cell/macrophage indirect coculture model

In this study, we established a procedure to prepare a Semaphorin4D (SEMA4D)-immobilized titanium surface and explored its effects on macrophage behaviors in an endothelial cell/macrophage indirect coculture model. The SEMA4D-bovine serum albumin complex was immobilized onto a preprocessed poly L-lysine titanium surface through NaOH hydrothermal treatment and self-assembly technology. All titanium specimens were examined for surface microstructure, surface element composition, and surface wettability by field emission scanning electron microscopy, x-ray photoelectron spectroscopy (XPS), and water contact angle measurement, respectively. Subsequently, we constructed an endothelial cell/macrophage indirect coculture model and evaluated the activation of NF-κB signaling pathway and the expression of proinflammatory cytokines (TNFα, IL-6, and IL-1β) in macrophages. In XPS analysis, the SEMA4D-immobilized titanium surface appeared as a loose porous structure covered with uniform film, which exhibited better hydrophilicity than the control smooth titanium surface. In the indirect coculture model, SEMA4D attenuated the activation of NF-κB signaling pathway of lipopolysaccharide-stimulated THP-1 macrophages, thereby downregulating the expression of proinflammatory cytokines in macrophages. In conclusion, SEMA4D could be immobilized on titanium surfaces through NaOH hydrothermal treatment and self-assembly technology. Meanwhile, SEMA4D immobilization altered the characteristics of the titanium surfaces, which negatively regulated macrophage behaviors in the endothelial cell/macrophage indirect coculture model.

Hepatoprotective Effect of Apigenin Against Liver Injury via the Non-canonical NF-κB Pathway In Vivo and In Vitro

Apigenin, a flavonoid found in many plants, has various biological properties. We aimed to investigate the anti-inflammatory and anti-oxidative activity of apigenin against carbon tetrachloride (CCl₄)-induced acute liver injury in mice and hydrogen peroxide (H₂O₂)-induced oxidative stress in HepG2 cells and possible mechanism. In vivo, apigenin significantly reduced alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity in serum of mice challenged by CCl₄ and markedly alleviated the lipid peroxidation as indicated by the increased level of superoxide dismutase (SOD), reduced glutathione (GSH), glutathione peroxidases (GSH-Px) and catalase (CAT), and the decreased malondialdehyde (MDA) in liver tissue. Apigenin also ameliorated inflammation by downregulating tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and upregulating IL-10. Consistently, the elevated ALT and AST level; the impaired balance between SOD, GSH activity, and excessive ROS; and the increased gene expression of TNF-α and IL-6 resulting from H₂O₂-induced oxidative stress were restored by apigenin. Moreover, the results from Western blot, real-time qPCR, and immunofluorescence assay indicated that apigenin enhanced the activity of TNF receptor-associated factor (TRAF) 2/3 and cellular inhibitor of apoptosis protein (c-IAP) 1, ameliorated NF-κB-inducing kinase (NIK), and mediated the nuclear translocation of NF-κB2, therefore had an inhibitory effect on the non-canonical NF-κB pathway which was activated in both models. siNIK canceled the protective effect of apigenin on H₂O₂-induced HepG2 cells. Altogether, our results demonstrated that apigenin mitigated liver injury by ameliorating inflammation and oxidative stress through suppression of the non-canonical NF-κB pathway, indicating the potential of apigenin for treatment of the liver injury.

Mechanistic studies of inhibition on acrolein by myricetin

Acrolein (ACR) is an unsaturated aldehyde with high activity and toxicity and is produced in vivo and in food. This study investigated the impact of B-ring structure on the trapping of ACR by flavonols and the trapping mechanism and efficacy of ACR by myricetin. Galangin, kaempferol, quercetin, and myricetin, which possess the same A- and C-ring but different numbers of -OH groups on the B-ring, were selected for this study. Our results suggested that increasing the number of -OH groups on the B-ring can enhance the ACR trapping efficacy of flavonol and myrectin was identified as the most active flavonol. The adducts of myricetin with ACR under different ratios and incubation times were analyzed using LC-MS/MS. We also purified and identified the major mono- and di-ACR-myricetin adducts. Furthermore, myricetin could dose-dependently inhibit the formation of ACR in cookies through the formation of mono- and di-ACR adducts.

Dicarbonyl Stress at the Crossroads of Healthy and Unhealthy Aging

Dicarbonyl stress occurs when dicarbonyl metabolites (i.e., methylglyoxal, glyoxal and 3-deoxyglucosone) accumulate as a consequence of their increased production and/or decreased detoxification. This toxic condition has been associated with metabolic and age-related diseases, both of which are characterized by a pro-inflammatory and pro-oxidant state. Methylglyoxal (MGO) is the most reactive dicarbonyl and the one with the highest endogenous flux. It is the precursor of the major quantitative advanced glycated products (AGEs) in physiological systems, arginine-derived hydroimidazolones, which accumulate in aging and dysfunctional tissues. The aging process is characterized by a decline in the functional properties of cells, tissues and whole organs, starting from the perturbation of crucial cellular processes, including mitochondrial function, proteostasis and stress-scavenging systems. Increasing studies are corroborating the causal relationship between MGO-derived AGEs and age-related tissue dysfunction, unveiling a previously underestimated role of dicarbonyl stress in determining healthy or unhealthy aging. This review summarizes the latest evidence supporting a causal role of dicarbonyl stress in age-related diseases, including diabetes mellitus, cardiovascular disease and neurodegeneration.