A prenylated flavonoid, 10-oxomornigrol F, exhibits anti-inflammatory effects by activating the Nrf2/heme oxygenase-1 pathway in macrophage cells

Naturally-derived modulators of the Nrf2 pathway and their roles in the intervention of diseases

Cumulative evidence has verified that persistent oxidative stress is involved in the development of various chronic diseases, including pulmonary, neurodegenerative, kidney, cardiovascular, and liver diseases, as well as cancers. Nuclear factor erythroid 2-related factor 2 (Nrf2) plays a pivotal role in regulating cellular oxidative stress and inflammatory reactions, making it a focal point for disease prevention and treatment strategies. Natural products are essential resources for discovering leading molecules for new drug research and development. In this review, we comprehensively outlined the progression of the knowledge on the Nrf2 pathway, Nrf2 activators in clinical trials, the naturally-derived Nrf2 modulators (particularly from 2014-present), as well as their effects on the pathogenesis of chronic diseases.

Exploring the pathophysiological influence of heme oxygenase-1 on neuroinflammation and depression: A study of phytotherapeutic-based modulation

BACKGROUND

The heme oxygenase (HO) system plays a significant role in neuroprotection and reduction of neuroinflammation and neurodegeneration. The system, via isoforms HO-1 and HO-2, regulates cellular redox balance. HO-1, an antioxidant defense enzyme, is highlighted due to its association with depression, characterized by heightened neuroinflammation and impaired oxidative stress responses.

METHODOLOGY

We observed the pathophysiology of HO-1 and phytochemicals as its modulator. We explored Science Direct, Scopus, and PubMed for a comprehensive literature review. Bibliometric and temporal trend analysis were done using VOSviewer.

RESULTS

Several phytochemicals can potentially alleviate neuroinflammation and oxidative stress-induced depressive symptoms. These effects result from inhibiting the MAPK and NK-κB pathways - both implicated in the overproduction of pro-inflammatory factors - and from the upregulation of HO-1 expression mediated by Nrf2. Bibliometric and temporal trend analysis further validates these associations.

CONCLUSION

In summary, our findings suggest that antidepressant agents can mitigate neuroinflammation and depressive disorder pathogenesis via the upregulation of HO-1 expression. These agents suppress pro-inflammatory mediators and depressive-like symptoms, demonstrating that HO-1 plays a significant role in the neuroinflammatory process and the development of depression.

Phytochemistry and pharmacology of natural prenylated flavonoids

Prenylated flavonoids are a special kind of flavonoid derivative possessing one or more prenyl groups in the parent nucleus of the flavonoid. The presence of the prenyl side chain enriched the structural diversity of flavonoids and increased their bioactivity and bioavailability. Prenylated flavonoids show a wide range of biological activities, such as anti-cancer, anti-inflammatory, neuroprotective, anti-diabetic, anti-obesity, cardioprotective effects, and anti-osteoclastogenic activities. In recent years, many compounds with significant activity have been discovered with the continuous excavation of the medicinal value of prenylated flavonoids, and have attracted the extensive attention of pharmacologists. This review summarizes recent progress on research into natural active prenylated flavonoids to promote new discoveries of their medicinal value.

The preventive effect of Mori Ramulus on oxidative stress-induced cellular damage in skeletal L6 myoblasts through Nrf2-mediated activation of HO-1

The aim of the present study is to investigate the preventive effect of water extract of Mori Ramulus (MRWE) on oxidative stress-mediated cellular damages in rat skeletal L6 myoblasts. Our results demonstrated that MRWE pretreatment markedly improved cell survival and suppressed cell cycle arrest at the G2/M phase and apoptosis in hydrogen peroxide (H2O2)-treated L6 cells. H2O2-triggered DNA damage was also notably reduced by MRWE, which since it was correlated with protection of reactive oxygen species (ROS) production. Additionally, H2O2 stimulated cytosolic release of cytochrome c and up-regulation of Bax/Bcl-2 ratio, whereas MRWE suppressed these changes following by H2O2. Moreover, MRWE inhibited the cleavage of poly(ADP-ribose) polymerase as well as the activity of caspase-3 by H2O2. Furthermore, MRWE enhanced H2O2-mediated expression of nuclear factor erythroid 2-associated factor 2 (Nrf2) and its representative downstream enzyme, heme oxygenase-1 (HO-1). However, the protective effects of MRWE on H2O2-induced ROS production, cell cycle arrest and apoptosis were significantly attenuated by HO-1 inhibitor. In conclusion, our present results suggests that MRWE could protect L6 myoblasts from H2O2-induced cellular injury by inhibiting ROS generation along with Nrf2-mediated activation of HO-1, indicating this finding may expand the scope of application of Mori Ramulus in medicine.

Synthesis, antioxidant, in silico and computational investigation of 2,5-dihydroxyacetophenone derived chloro-substituted hydroxychalcones, hydroxyflavanones and hydroxyflavindogenides

An imbalance between reactive oxygen species (ROS) and their elimination by antioxidants damages the cell and infect whole organism. The biological defence system against oxidative stress injury is Kelch-like ECH associated protein 1 (Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response elements (ARE) pathways. Antioxidants activate the Nrf2-ARE-Keap1 pathway and suppress the oxidative stress. Flavonoids are well known medicinal compounds inheriting antioxidant efficacy and wide spectrum of pharmacological activities. The study is aimed to synthesise, characterize and evaluate pharmacological activities of synthesized chloro-derivatives of flavonoids. Chloro-derivatives of flavonoids were synthesized and characterized by IR, ¹H NMR and ¹³C NMR. Antioxidant potential of each synthesized compound was evaluated and then subjected to molecular docking with Keap1 (PDB ID: 2FLU) for the activation of Nrf2 and computational studies were performed by using DFT approach. Among the synthesized compounds compound 1a exhibited lower IC₅₀ value. While docking and computational studies infer that compound 3c is a good Nrf2 activator and radical scavenger with highest docking score and lower energy gaps and IP values compared to references. Hence, it might be considered for further molecular studies for the treatment of inflammatory diseases through Nrf2-ARE-Keap1 pathway. Communicated by Ramaswamy H. Sarma.HighlightsChloro-substituted hydroxychalcones, hydroxyflavanones and hydroxyflavindogenides were synthesized.Antioxidant potential was accessed, compound 1a exhibited good antioxidant potential.In silico study was performed with Keap1, compound 3c have shown highest docking score with Keap1.DFT approach was used to explore the structure activity relationship.

TNF-α Inhibitors from Natural Compounds: An Overview, CADD Approaches, and their Exploration for Anti-inflammatory Agents

Inflammation is a natural process that occurs in the organism in response to harmful external agents. Despite being considered beneficial, exaggerated cases can cause severe problems for the body. The main inflammatory manifestations are pain, increased temperature, edema, decreased mobility, and quality of life for affected individuals. Diseases such as arthritis, cancer, allergies, infections, arteriosclerosis, neurodegenerative diseases, and metabolic problems are mainly characterized by an exaggerated inflammatory response. Inflammation is related to two categories of substances: pro- and anti-inflammatory mediators. Among the pro-inflammatory mediators is Tumor Necrosis Factor-α (TNF-α). It is associated with immune diseases, cancer, and psychiatric disorders which increase its excretion. Thus, it becomes a target widely used in discovering new antiinflammatory drugs. In this context, secondary metabolites biosynthesized by plants have been used for thousands of years and continue to be one of the primary sources of new drug scaffolds against inflammatory diseases. To decrease costs related to the drug discovery process, Computer-Aided Drug Design (CADD) techniques are broadly explored to increase the chances of success. In this review, the main natural compounds derived from alkaloids, flavonoids, terpene, and polyphenols as promising TNF-α inhibitors will be discussed. Finally, we applied a molecular modeling protocol involving all compounds described here, suggesting that their interactions with Tyr⁵⁹, Tyr¹¹⁹, Tyr¹⁵¹, Leu⁵⁷, and Gly¹²¹ residues are essential for the activity. Such findings can be useful for research groups worldwide to design new anti-inflammatory TNF-α inhibitors.

Exopolysaccharides of Bacillus amyloliquefaciens Amy-1 Mitigate Inflammation by Inhibiting ERK1/2 and NF-κB Pathways and Activating p38/Nrf2 Pathway

Bacillus amyloliquefaciens is a probiotic for animals. Evidence suggests that diets supplemented with B. amyloliquefaciens can reduce inflammation; however, the underlying mechanism is unclear and requires further exploration. The exopolysaccharides of B. amyloliquefaciens amy-1 displayed hypoglycemic activity previously, suggesting that they are bioactive molecules. In addition, they counteracted the effect of lipopolysaccharide (LPS) on inducing cellular insulin resistance in exploratory tests. Therefore, this study aimed to explore the anti-inflammatory effect and molecular mechanisms of the exopolysaccharide preparation of amy-1 (EPS). Consequently, EPS reduced the expression of proinflammatory factors, the phagocytic activity and oxidative stress of LPS-stimulated THP-1 cells. In animal tests, EPS effectively ameliorated ear inflammation of mice. These data suggested that EPS possess anti-inflammatory activity. A mechanism study revealed that EPS inhibited the nuclear factor-κB pathway, activated the mitogen-activated protein kinase (MAPK) p38, and prohibited the extracellular signal-regulated kinase 1/2, but had no effect on the c-Jun-N-terminal kinase 2 (JNK). EPS also activated the anti-oxidative nuclear factor erythroid 2–related factor 2 (Nrf2) pathway. Evidence suggested that p38, but not JNK, was involved in activating the Nrf2 pathway. Together, these mechanisms reduced the severity of inflammation. These findings support the proposal that exopolysaccharides may play important roles in the anti-inflammatory functions of probiotics.

Cytotoxic and Anti-Inflammatory Triterpenoids in the Vines and Leaves of Momordica charantia

The vines and leaves of Momordica charantia L. are used as herbal medicines to treat inflammation-related disorders. However, their safety profile remains uncharacterized, and the constituents in their extracts that exert anti-inflammatory and adverse effects remain unclear. This study isolated the characteristic cucurbitane-type triterpenoid species in the vines and leaves of M. charantia L. and analyzed their cytotoxicity, anti-inflammatory effects, and underlying mechanisms. Four structurally related triterpenoids—momordicines I, II, IV, and (23E) 3β,7β,25-trihydroxycucurbita-5,23-dien-19-al (TCD)—were isolated from the triterpenoid-rich fractions of extracts from the vines and leaves of M. charantia. Momordicine I was cytotoxic on normal cells, momordicine II exerted milder cytotoxicity, and momordicine IV and TCD had no obvious adverse effects on cell growth. TCD had anti-inflammatory activity both in vivo and in vitro. In lipopolysaccharide-stimulated RAW 264.7 cells, TCD inhibited the inhibitor kappa B kinase/nuclear factor-κB pathway and enhanced the expression of nuclear factor erythroid 2-related factor 2, heme oxygenase-1, and glutamate-cysteine ligase modifier subunit through the extracellular signal-regulated kinase1/2 and p38. Thus, the vines and leaves of M. charantia should be used with caution. An extraction protocol that can enrich TCD but remove momordicine I would likely enhance the safety of the extract.

Targeting macrophage polarization by Nrf2 agonists for treating various xenobiotics-induced toxic responses

Macrophages can polarize into different phenotypes in response to different microenvironmental stimuli. Macrophage polarization has been assigned to two extreme states, namely proinflammatory M1 and anti-inflammatory M2. Accumulating evidences have demonstrated that M1 polarized macrophages contribute to various toxicants-induced deleterious effects. Switching macrophages from proinflammatory M1 phenotype toward anti-inflammatory M2 phenotype could be a promising approach for treating various inflammatory diseases. Studies in the past few decades have revealed that nuclear factor erythroid 2-related factor 2 (Nrf2) can modulate the polarization of macrophages. Specifically, activation of Nrf2 could block M1 stimuli-induced production of proinflammatory cytokines and chemokines, and shift the polarization of macrophages toward M2 by cross-talking with nuclear factor kappa-B (NF-κB), mitogen-activated protein kinases (MAPKs), peroxisome proliferator-activated receptor γ (PPARγ), and autophagy. Importantly, a great number of studies have confirmed the beneficial effects of natural and synthesized Nrf2 agonists on various inflammatory diseases; however, most of these compounds are far away from clinical application due to lack of characterization and defects of study designs. Interestingly, some endogenous Nrf2 inducers and compounds with dual activities (such as the Nrf2 inducing and CO releasing effects) exhibit potent anti-inflammatory effects, which points out an important direction for future researches.

Promising Antioxidant Activity of Erythrina Genus: An Alternative Treatment for Inflammatory Pain?

The negative impact that oxidative stress has on health is currently known. The complex mechanism of free radicals initiates a series of chain reactions that contribute to the evolution or development of different degenerative disorders. Likewise, these disorders are usually accompanied by inflammatory processes and, therefore, pain. In this sense, reactive oxygen species (ROS) have been shown to promote the nociceptive process, but effective treatment of pain and inflammation still represents a challenge. Over time, it has been learned that there is no single way to relieve pain, and as long as there are no other alternatives, the trend will continue to apply multidisciplinary management, such as promote the traditional use of the Erythrina genus to manage pain and inflammation. In this sense, the Erythrina genus produces a wide range of secondary metabolites, including flavanones, isoflavones, isoflavones, and pterocarpans; these compounds are characterized by their antioxidant activity. Phenolic compounds have demonstrated their ability to suppress pro-oxidants and inhibit inflammatory signaling pathways such as MAPK, AP1, and NFκB. Although there is preclinical evidence supporting its use, the pharmacological effect mechanisms are not entirely clear. Nowadays, there is a fast advancement in knowledge of the disciplines related to drug discovery, but most of nature's medicinal potential has not yet been harnessed. This review analyzes the decisive role that the Erythrina genus could play in managing inflammatory pain mediated by its compounds and its uses as an antioxidant.

The Anti-Inflammatory Effect of Trichilia martiana C. DC. in the Lipopolysaccharide-Stimulated Inflammatory Response in Macrophages and Airway Epithelial Cells and in LPS-Challenged Mice

A number of species of the genus Trichilia (Meliaceae) exhibit anti-inflammatory effects. However, the effect of Trichilia martiana C. DC. (TM) on lipopolysaccharide (LPS)-induced inflammation has not, to the best of our knowledge, yet been determined. Therefore, in the present study, the antiinflammatory effect of TM on LPS-stimulated RAW264.7 macrophages was evaluated. The ethanol extract of TM (TMEE) significantly inhibited LPS-induced nitric oxide (NO), prostaglandin 2 (PGE₂), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). TMEE also reduced the levels of inflammatory cytokines, including tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β and IL-6. The upregulation of mitogen-activated protein kinases (MAPKs) and NF-κB activation was revealed to be downregulated following TMEE pretreatment. Furthermore, TMEE was indicated to lead to the nucleus translocation of nuclear factor erythroid-derived 2-related factor 2 (Nrf2) and the expression of heme oxygenase-1 (HO-1). In H292 airway epithelial cells, the pretreatment of TMEE significantly downregulated the production of LPS-stimulated IL-1β, and TMEE was indicated to increase the expression of HO-1. In animal models exhibiting LPS-induced acute lung injury (ALI), treatment with TMEE reduced the levels of macrophages influx and TNF-α production in the bronchoalveolar lavage fluid (BALF) of ALI mice. Additionally, TMEE significantly downregulated the activation of ERK, JNK and IκB, and upregulated the expression of HO-1 in the lungs of ALI mice. In conclusion, the results of the current study demonstrated that TMEE could exert a regulatory role in the prevention or treatment of the endotoxin-mediated inflammatory response.

miR‑155 modulates high glucose‑induced cardiac fibrosis via the Nrf2/HO‑1 signaling pathway

Cardiac fibrosis is a major pathological manifestation of diabetic cardiomyopathy, which is a leading cause of mortality in patients with diabetes. MicroRNA (miR)‑155 is upregulated in cardiomyocytes in cardiac fibrosis, and the aim of the present study was to investigate if the inhibition of miR‑155 was able to ameliorate cardiac fibrosis by targeting the nuclear factor erythroid‑2‑related factor 2 (Nrf2)/heme oxygenase‑1 (HO‑1) signaling pathway. H9C2 rat cardiomyocytes were cultured with high glucose (HG; 30 mM) to establish an in vitro cardiac fibrosis model that mimicked diabetic conditions; a miR‑155 inhibitor and a miR‑155 mimic were transfected into H9C2 cells. Following HG treatment, H9C2 cells exhibited increased expression levels of miR‑155 and the fibrosis markers collagen I and α‑smooth muscle actin (α‑SMA). In addition, the expression levels of endonuclear Nrf2 and HO‑1 were decreased, but the expression level of cytoplasmic Nrf2 was increased. Moreover, oxidative stress, mitochondrial damage and cell apoptosis were significantly increased, as indicated by elevated reactive oxygen species, malonaldehyde and monomeric JC‑1 expression levels. In addition, superoxide dismutase expression was attenuated and there was an increased expression level of released cytochrome‑c following HG treatment. Furthermore, it was demonstrated that expression levels of Bcl‑2 and uncleaved Poly (ADP‑ribose) polymerase were downregulated, whereas Bax, cleaved caspase‑3 and caspase‑9 were upregulated after HG treatment. However, the miR‑155 inhibitor significantly restored Nrf2 and HO‑1 expression levels, and reduced oxidative stress levels, the extent of mitochondrial damage and the number of cells undergoing apoptosis. Additionally, the miR‑155 inhibitor significantly reversed the expression levels of collagen I and α‑SMA, thus ameliorating fibrosis. Furthermore, the knockdown of Nrf2 reversed the above effects induced by the miR‑155 inhibitor. In conclusion, the miR‑155 inhibitor may ameliorate diabetic cardiac fibrosis by reducing the accumulation of oxidative stress‑related molecules, and preventing mitochondrial damage and cardiomyocyte apoptosis by enhancing the Nrf2/HO‑1 signaling pathway. This mechanism may facilitate the development of novel targets to prevent cardiac fibrosis in patients with diabetes.

Anti-inflammatory and cytotoxic activities of constituents isolated from the fruits of Ziziphus jujuba var. inermis Rehder

Three new sesquilignans, zijusesquilignans A-C (1-3), together with fifteen known compounds (4-18), were isolated from fruits of Ziziphus jujuba var. inermis Rehder (Rhamnaceae). Their chemical structures were established using spectroscopic analyses including 1D- and 2D-NMR, HR-EIMS, and ECD spectra. These compounds were assessed for their inhibitory effects on nitric oxide (NO) production. Of these compounds, 1-3 and 17 displayed inhibitory effects on NO production, with IC₅₀ values ranging from 18.1 to 66.4 μM. Pretreatment with 1 and 17 significantly suppressed LPS-induced expression of nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein in cells. Moreover, compounds 1-3, 7, 9, and 17 exhibited cytotoxic activities against three human tumor cell lines, with IC₅₀ values ranging from 8.4 to 44.9 μM.

Sophoflavanones A and B, two novel prenylated flavanones from the roots of Sophora flavescens

In our ongoing investigation of the bioactive compounds from the extract of the roots of Sophora flavescens, two novel prenylated flavanones, named sophoflavanones A (1) and B (2), each with an unusual pyran ring were isolated. Their structures, as well as their absolute configurations, were elucidated based on spectroscopic data including a comparison of their experimental and calculated electronic circular dichroism (ECD) spectra. Additionally, compounds 1 and 2 showed moderate antioxidant activities against Fe²⁺/cysteine-induced toxicity at a concentration of 0.1 µM (inhibition values of 71.65% and 72.49%, respectively, using vitamin C as a positive control (87.83%)).