Olive secoiridoid oleuropein and its semisynthetic acetyl-derivatives reduce LPS-induced inflammatory response in murine peritoneal macrophages via JAK-STAT and MAPKs signaling pathways

Anti-inflammatory activities of Levilactobacillus brevis KU15147 in RAW 264.7 cells stimulated with lipopolysaccharide on attenuating NF-κB, AP-1, and MAPK signaling pathways

Probiotics confer many beneficial effects on several illnesses, ranging from microbial diarrhea to inflammatory diseases. This study was conducted on whether Levilactobacillus brevis KU15147 obtained from kimchi has anti-inflammatory effects in RAW 264.7 cells stimulated with lipopolysaccharide (LPS) and antioxidant potential. L. brevis KU15147 reduced nitric oxide and prostaglandin E2 levels with decreasing the activation of inducible nitric oxide synthase and cyclooxygenase-2 without cell cytotoxicity. In addition, L. brevis KU15147 attenuated proinflammatory cytokine production including tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 in RAW 264.7 cells stimulated with LPS. Additionally, L. brevis KU15147 reduced the activity of nuclear factor-κB, activator protein-1, and mitogen-activated protein kinase signaling pathways. Furthermore, L. brevis KU15147 downregulated the production of reactive oxygen species. Therefore, L. brevis KU15147 was concluded that had an inhibition effect on LPS-induced inflammatory responses and can be used in functional foods to suppress inflammatory diseases.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01318-w.

Oleuropein reduces LPS-induced inflammation via stimulating M2 macrophage polarization

Oleuropein (OLEU) is the most prevalent phenolic component in olive varieties, and it has been considered for its powerful antioxidant properties in therapeutic applications. OLEU has anti-inflammatory properties and performs this property by suppressing inflammatory cells' function and reducing oxidative stress caused by various factors. This study investigated the ability of OLEU to polarize LPS-stimulated murine macrophage (MQ) cell RAW 264.7 into M1/M2 macrophages. As a first step, the cytotoxicity effects of OLEU were evaluated on LPS-stimulated RAW 264.7 cells using the thiazolyl blue (MTT) colorimetric test. Then, cytokines production, gene expression (Real-Time PCR), and functions (Nitrite oxide assay and phagocytosis assay) of OLEU-treated LPS-stimulated RAW 264.7 cells were evaluated. Our findings demonstrated that OLEU could reduce nitrite oxide (NO) production in LPS-stimulated RAW 264.7 cells by downregulating the inducible nitric oxide synthase gene expression. Furthermore, OLEU therapy decreases the expression of M1-associated pro-inflammatory cytokines production (IL-12, IFN-γ, and TNF-α) and genes expression (iNOS, TNF-α) while increasing the M2-associated anti-inflammatory gene expression and cytokines production (IL-10, and TGF-β). Based on the result, OLEU may be considered a potential therapeutic approach for inflammatory diseases due to its possible effects on oxidative stress-related factors, cytokine expression and production, and phagocytosis.

Aucubin Exerts Neuroprotection against Forebrain Ischemia and Reperfusion Injury in Gerbils through Antioxidative and Neurotrophic Effects

Aucubin is an iridoid glycoside that displays various pharmacological actions including antioxidant activity. However, there are few reports available on the neuroprotective effects of aucubin against ischemic brain injury. Thus, the aim of this study was to investigate whether aucubin protected against damage to hippocampal function induced by forebrain ischemia-reperfusion injury (fIRI) in gerbils, and to examine whether aucubin produced neuroprotection in the hippocampus against fIRI and to explore its mechanisms by histopathology, immunohistochemistry, and Western analysis. Gerbils were given intraperitoneal injections of aucubin at doses of 1, 5, and 10 mg/kg, respectively, once a day for seven days before fIRI. As assessed by the passive avoidance test, short-term memory function following fIRI significantly declined, whereas the decline in short-term memory function due to fIRI was ameliorated by pretreatment with 10 mg/kg, but not 1 or 5 mg/kg, of aucubin. Most of the pyramidal cells (principal cells) of the hippocampus died in the Cornu Ammonis 1 (CA1) area four days after fIRI. Treatment with 10 mg/kg, but not 1 or 5 mg/kg, of aucubin protected the pyramidal cells from IRI. The treatment with 10 mg/kg of aucubin significantly reduced IRI-induced superoxide anion production, oxidative DNA damage, and lipid peroxidation in the CA1 pyramidal cells. In addition, the aucubin treatment significantly increased the expressions of superoxide dismutases (SOD1 and SOD2) in the pyramidal cells before and after fIRI. Furthermore, the aucubin treatment significantly enhanced the protein expression levels of neurotrophic factors, such as brain-derived neurotrophic factor and insulin-like growth factor-I, in the hippocampal CA1 area before and after IRI. Collectively, in this experiment, pretreatment with aucubin protected CA1 pyramidal cells from forebrain IRI by attenuating oxidative stress and increasing neurotrophic factors. Thus, pretreatment with aucubin can be a promising candidate for preventing brain IRI.

Effects of Oleacein, a New Epinutraceutical Bioproduct from Extra Virgin Olive Oil, in LPS-Activated Murine Immune Cells

The present study was designed to evaluate the immunomodulatory effects of the secoiridoid from extra virgin olive oil, oleacein (OLA), deepening into the possible signaling pathways involved in LPS-activated murine peritoneal macrophages. Moreover, we have explored OLA-induced epigenetic changes in histone markers and related cytokine production in murine LPS-stimulated murine splenocytes. Murine cells were treated with OLA in the presence or absence of LPS (5 μg/mL) for 18 or 24 h. OLA modulated the oxidative stress and the inflammatory response produced by LPS stimulation in murine peritoneal macrophages, by the inhibition of pro-inflammatory cytokines (TNF-α, IL-6, IL-1β, IFN-γ, IL-17 and IL-18) and ROS production and the expression of pro-inflammatory enzymes such as iNOS, COX-2 and m-PGES1. These protective effects could be due to the activation of the Nrf-2/HO-1 axis and the inhibition of JAK/STAT, ERK and P38 MAPKs and inflammasome canonical and non-canonical signaling pathways. Moreover, OLA modulated epigenetic modifications throughout histone methylation deacetylation (H3K18ac) and (H3K9me3 and H3K27me) in LPS-activated spleen cells. In conclusion, our data present OLA as an interesting anti-inflammatory and antioxidant natural compound that is able to regulate histone epigenetic markers. Nevertheless, additional in vivo studies are required to further investigate the beneficial effects of this EVOO secoiridoid, which might be a promising epinutraceutical bioproduct for the management of immune-related inflammatory diseases.

Ligstroside aglycon, an extra virgin olive oil secoiridoid, prevents inflammation by regulation of MAPKs, JAK/STAT, NF-κB, Nrf2/HO-1, and NLRP3 inflammasome signaling pathways in LPS-stimulated murine peritoneal macrophages

Ligstroside aglycon (LA) is one of the main polyphenols in extra virgin olive oil (EVOO); nevertheless, it is scarcely investigated. The aim of this study was to evaluate the immunomodulatory and anti-inflammatory effects of LA on lipopolysaccharide (LPS)-stimulated murine peritoneal macrophages, as well as the potential signaling pathways involved. Isolated macrophages were treated with LA (50, 25, and 12.5 μM) in the presence or absence of LPS (5 μg ml^-1) for 18 h. Cell viability was determined using the sulforhodamine B (SRB) assay. Nitric oxide (NO) and pro-inflammatory cytokine production was analyzed by the Griess method and enzyme-linked immunosorbent assay (ELISA), respectively. Protein expression of pro-inflammatory markers and signaling pathways were evaluated by western blot analysis. LA showed significant antioxidant and anti-inflammatory effects through decreasing oxidative stress markers such as NO production, inducible nitric oxide synthase (iNOS) and NADPH oxidase-1 (NOX-1) protein expression. Besides, LA was able to reduce pro-inflammatory cytokine levels and modulate cyclo-oxygenase-2 (COX-2), and microsomal prostaglandin E synthase-1 (mPGEs-1) protein overexpression. The mechanisms underlying these protective effects could be related via activation of nuclear factor (erythroid-derived 2)-like (Nrf2)/heme oxygenase 1 (HO-1) and inhibition of nuclear factor kappa-B (NF-κB), mitogen-activated protein kinases (MAPKs), and Janus kinase/signal transducer and activation of transcription (JAK2/STAT3) signaling pathways. In addition, LA inhibited non-canonical and canonical activation of a nucleotide-binding (NOD)-like receptor (NLRP3) inflammasome. We conclude that LA showed significant antioxidant and anti-inflammatory activities in LPS-stimulated murine peritoneal macrophages. However, further in vivo studies are warranted to further investigate the bioactivity of this interesting compound that might be a promising natural agent for the treatment of immune-inflammatory diseases.

A Comprehensive Review on the Anti-Cancer Effects of Oleuropein

In Mediterranean cuisine and culture, olive oil and olive fruits play a significant role. Many people believe that those who consume olive oil and its fruit live longer and have a decreased risk of illness. Olive leaves were used to treat a range of diseases in ancient times, including malaria fever and lower earaches. Although it was not understood at the time what key components were responsible for these effects because they had not yet been discovered, Oleuropein is now recognized as one of the primary elements in immature olive fruits and leaves. Later research was carried out to determine the effects of this molecule, and it was determined that it functions as an antioxidant. Oleuropein consumption has aided in cancer treatment over the years, and this was assumed to be owing to its antioxidant properties. Oleuropein’s effects on cancer, however, go beyond that; it is now known that Oleuropein functions as both an anti-proliferative and an apoptotic promoter in many cancer cells. The kinetics and dosages of Oleuropein and the mechanisms behind its involvement and effects in cancer are explored in this review. Finally, the effects of Oleuropein in combination with anticancer medicines are investigated.

Olive Leaves (Olea europaea L) Extract Loaded Lipid Nanoparticles: Optimization of Processing Parameters by Box-Behnken Statistical Design, in-vitro Characterization, and Evaluation of Anti-oxidant and Anti-microbial Activity

The present study was aimed to prepare and evaluated solid lipid nanoparticles (SLNs) of olive leaves extract powder (OLP) which contained many anti-oxidant and antimicrobial agents like oleuropein, a natural polyphenol. The major issue concern OLP was the instability due to environmental conditions and hence compromised bioactivity. To overcome this problem, SLNs were designed by hot homogenous followed by sonication technique to protect the drug and improve its antioxidant and antimicrobial activity. Lipids like compritol 888ATO and surfactant like tween 80 were used for the development and stabilization of SLNS and optimization was done by Box-Behnken statistical design (3x3). The optimized batch (F9) showed particle size, entrapment efficiency, PDI, and zeta potential 277.46 nm, 80.48%, 0.275, and －23.18 mV respectively. Optimized formulation (F9) exhibited a sustained release pattern up to 24 h with first-order release kinetic (R² = 0.9984) and the mechanism of drug release was found to be Fickian diffusion type (n = 0.441). Upon the stability study, it could be found that SLNs formulation was stable. Anti-oxidation and anti-microbial studies were conducted on optimized formulation and findings suggested that SLNs showed an improved radical scavenging activity and anti-microbial activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria. Finally, it was concluded that developed SLNs were able to protect and suitable for the delivery of OLP.

Dietary oleuropein and its acyl derivative ameliorate inflammatory response in peritoneal macrophages from pristane-induced SLE mice via canonical and noncanonical NLRP3 inflammasomes pathway

Systemic lupus erythematosus (SLE) is a multifactorial autoimmune disease without an effective and safe treatment. Besides, macrophages are the major components of the innate immune system and play a critical role in the inflammation process in SLE. Secoiridoids from olive tree are phenolic compounds which have shown important pharmacological effects. Particularly, oleuropein (OL) has shown antioxidant, anti-inflammatory and immunomodulatory properties suggesting a potential application in a large number of inflammatory and reactive oxygen species (ROS)-mediated diseases. In addition, different studies have shown the importance of acyl derivatives of natural phenols due to their better hydrophilic/lipophilic balance.

The effect of dietary phytochemicals on nuclear factor erythroid 2-related factor 2 (Nrf2) activation: a systematic review of human intervention trials

We conducted a systematic review of human trials examining the effects of dietary phytochemicals on Nrf2 activation. In accordance with the PRISMA guidelines, Medline, Embase and CAB abstracts were searched for articles from inception until March 2020. Studies in adult humans that measured Nrf2 activation (gene or protein expression changes) following ingestion of a phytochemical, either alone or in combination were included. The study was pre-registered on the Prospero database (Registration Number: CRD42020176121). Twenty-nine full-texts were retrieved and reviewed for analysis; of these, eighteen were included in the systematic review. Most of the included participants were healthy, obese or type 2 diabetics. Study quality was assessed using the Cochrane Collaboration Risk of Bias Assessment tool. Twelve different compounds were examined in the included studies: curcumin, resveratrol and sulforaphane were the most common (n = 3 each). Approximately half of the studies reported increases in Nrf2 activation (n = 10); however, many were of poor quality and had an unclear or high risk of bias. There is currently limited evidence that phytochemicals activate Nrf2 in humans. Well controlled human intervention trials are needed to corroborate the findings from in vitro and animal studies.

A New Peracetylated Oleuropein Derivative Ameliorates Joint Inflammation and Destruction in a Murine Collagen-Induced Arthritis Model via Activation of the Nrf-2/Ho-1 Antioxidant Pathway and Suppression of MAPKs and NF-κB Activation

Oleuropein (OL), an olive tree secoiridoid and its peracetylated derivate (Per-OL) have exhibited several beneficial effects on LPS-stimulated macrophages and murine experimental systemic lupus erythematosus (SLE). This study was designed to evaluate dietary Per-OL in comparison with OL supplementation effects on collagen-induced arthritis (CIA) murine model. Three-weeks-old DBA-1/J male mice were fed from weaning with a standard commercial diet or experimental enriched-diets in 0.05 % (w/w) OL, 0.05% and 0.025% Per-OL. After six weeks of pre-treatment, arthritis was induced by bovine collagen type II by tail base injection (day 0) and on day 21, mice received a booster injection. Mice were sacrificed 42 days after the first immunization. Both Per-OL and OL diets significantly prevented histological damage and arthritic score development, although no statistically significant differences were observed between both compounds. Also, serum collagen oligomeric matrix protein (COMP), metalloprotease (MMP)-3 and pro-inflammatory cytokines levels were ameliorated in paws from secoiridoids fed animals. Mitogen-activated protein kinases (MAPK)s and nuclear transcription factor-kappa-B (NF-κB) activations were drastically down-regulated whereas nuclear factor E2-related factor 2 (Nrf2) and heme-oxygenase-1 (HO-1) protein expressions were up-regulated in those mice fed with OL and Per-OL diets. We conclude that both Per-OL and its parent compound, OL, supplements might provide a basis for developing a new dietary strategy for the prevention of rheumatoid arthritis.

Monoterpenes as a perspective for the treatment of seizures: A Systematic Review

BACKGROUND

Epilepsy affects more than 65 million people worldwide. Treatment for epileptic seizures is ineffective and has many adverse effects. For this reason, the search for new therapeutic options capable of filling these limitations is necessary.

HYPOTHESIS/PURPOSE

In this sense, natural products, such as monoterpenes, have been indicated as a new option to control neurological disorders such as epilepsy.

STUDY DESIGN

Therefore, the objective of this study was to review the monoterpenes that have anticonvulsive activity in animal models.

METHODS

The searches were performed in the PubMed, Web of Science and Scopus databases in September, 2020 and compiled studies using monoterpenes as an alternative to seizure. Two independent reviewers performed the study selection, data extraction and methodological quality assessment using the Syrcle tool.

RESULTS

51 articles that described the anticonvulsant activity of 35 monoterpenes were selected with action on the main pharmacological target, including GABAA receptors, glutamate, calcium channels, sodium and potassium. In addition, these compounds are capable of reducing neuronal inflammation and oxidative stress caused by seizure.

CONCLUSION

These compounds stand out as a promising alternative for acting through different pharmacological mechanisms, which may not only reduce seizure, but also promote neuroprotective effect by reducing toxicity in brain regions. However, further studies are needed to determine the mechanism of action and safety assessment of these compounds.

Counteracting role of nuclear factor erythroid 2-related factor 2 pathway in Alzheimer's disease

A salient pathological features in Alzheimer's disease includes redox impairment and neuroinflammation. Nuclear factor erythroid 2-related factor 2 (Nrf2) and Nuclear factor kappa B (NF-ҡB) are the two key transcription factors that regulate cellular responses to redox impairment and neuroinflammation respectively. An effective way to confer neuroprotection in central nervous system (CNS) is the activation of a transcription factor i.e Nuclear factor erythroid 2-related factor 2 (Nrf2). An enhancer element known as Antioxidant Response Element (ARE) mediates the expression of phase II detoxification enzymes. Nrf2 is a nuclear transcription factor that binds to ARE thereby transcribing expression of several antioxidant genes. Kelch ECH associating protein-1 (Keap1), a culin 3-based E3 ligase, polyubiquitinates Nrf2 and targets it for its degradation. Disruption in the interaction between Keap1/Nrf2 can increase the brain's endogenous antioxidant capacity and thereby responsible for cell defence against oxidative stress and neuroinflammation in Alzheimer's disease (AD). The current review discusses about Keap1-Nrf2-ARE structure and function with special emphasis on the various pathways involved in positive and negative modulation of Nrf2, namely Phosphoinositide 3- kinase (PI3K), Glycogen synthase kinase-3β (GSK-3β), Nuclear factor kappa-b (NF-ҡb), Janus kinase/signal transducer and activator of transcription (JAK-STAT),Tumour Necrosis Factor- α (TNF-α), p38Mitogen-activated protein kinases (p38MAPK), Cyclic AMP response element binding protein (CREB) and intrinsic & extrinsic apoptotic pathway. Furthermore, this review highlights the miscellaneous Nrf2 activators as promising therapeutic agents for slowingdown the progression of AD.

Oral delivery of oleuropein-loaded lipid nanocarriers alleviates inflammation and oxidative stress in acute colitis

Inflammation and oxidative stress pathways have emerged as novel targets in the management of inflammatory bowel diseases (IBD). Targeting the drug to the inflamed colon remains a challenge. Nanostructured lipid carriers (NLCs) have been reported to accumulate in inflamed colonic mucosa. The antioxidant/antiinflamatory polyphenol oleuropein (OLE) was loaded in NLCs (NLC-OLE). NLC-OLE showed to be more effective in decreasing the TNF-α secretion and intracellular reactive oxygen species (ROS) by activated macrophages (J774) compared to the conventional form of OLE. OLE efficacy was preserved within NLC-OLE ameliorating inflammation in a murine model of acute colitis: reduced levels of TNF-α and IL-6, decreased neutrophil infiltration and improved histopathology of the colon were reported. In addition, NLC-OLE enhanced the ROS scavenging activity of OLE in the colon after oral administration. These data suggest that the proposed NLC-OLE could be a promising drug delivery system for OLE in IBD treatment.

Osteoarthritis treatment with a novel nutraceutical acetylated ligstroside aglycone, a chemically modified extra-virgin olive oil polyphenol

Recent studies have shown that dietary patterns confer protection from certain chronic diseases related to oxidative stress, the immune system and chronic low-grade inflammatory diseases. The aim of this study was to evaluate the anti-inflammatory potential and the capacity to attenuate cartilage degradation using extra-virgin olive oil–derived polyphenols for the treatment of osteoarthritis. Results show that both nutraceuticals ligstroside aglycone and acetylated ligstroside aglycone showed an anti-inflammatory profile. Acetylated ligstroside aglycone significantly reduced the expression of pro-inflammatory genes including NOS2 and MMP13 at both RNA and protein levels; decreased nitric oxide release; and, importantly, reduced proteoglycan loss in human osteoarthritis cartilage explants. Our study demonstrated that a new synthetic acetylated ligstroside aglycone derivative offers enhanced anti-inflammatory profile than the natural nutraceutical compound in osteoarthritis. These results substantiate the role of nutraceuticals in osteoarthritis with implications for therapeutic intervention and our understanding of osteoarthritis pathophysiology.

Encapsulation of Oleuropein in Nanostructured Lipid Carriers: Biocompatibility and Antioxidant Efficacy in Lung Epithelial Cells

Oxidative damage has been linked to a number of diseases. Oleuropein (OLE), a natural occurring polyphenol from olive leaves (Olea europaea L.), is known to be a potent antioxidant compound with inherent instability and compromised bioavailability. Therefore, in this work, nanostructured lipid carriers (NLCs) were proposed for OLE encapsulation to protect and improve its antioxidant efficacy. The lipid matrix, composed of olive oil and Precirol, was optimized prior to OLE encapsulation. The characterization of the optimized oleuropein-loaded NLCs (NLC-OLE) showed a mean size of 150 nm, a zeta potential of −21 mV, an encapsulation efficiency of 99.12%, sustained release profile, and improved radical scavenging activity. The cellular in vitro assays demonstrated the biocompatibility of the NLCs, which were found to improve and maintain OLE antioxidant efficacy in the A549 and CuFi-1 lung epithelial cell lines, respectively. Overall, these findings suggest a promising potential of NLC-OLE to further design a pulmonary formulation for OLE delivery in lung epithelia.

Potential Protective Role Exerted by Secoiridoids from Olea europaea L. in Cancer, Cardiovascular, Neurodegenerative, Aging-Related, and Immunoinflammatory Diseases

Iridoids, which have beneficial health properties, include a wide group of cyclopentane [c] pyran monoterpenoids present in plants and insects. The cleavage of the cyclopentane ring leads to secoiridoids. Mainly, secoiridoids have shown a variety of pharmacological effects including anti-diabetic, antioxidant, anti-inflammatory, immunosuppressive, neuroprotective, anti-cancer, and anti-obesity, which increase the interest of studying these types of bioactive compounds in depth. Secoiridoids are thoroughly distributed in several families of plants such as Oleaceae, Valerianaceae, Gentianaceae and Pedialaceae, among others. Specifically, Olea europaea L. (Oleaceae) is rich in oleuropein (OL), dimethyl-OL, and ligstroside secoiridoids, and their hydrolysis derivatives are mostly OL-aglycone, oleocanthal (OLE), oleacein (OLA), elenolate, oleoside-11-methyl ester, elenoic acid, hydroxytyrosol (HTy), and tyrosol (Ty). These compounds have proved their efficacy in the management of diabetes, cardiovascular and neurodegenerative disorders, cancer, and viral and microbial infections. Particularly, the antioxidant, anti-inflammatory, and immunomodulatory properties of secoiridoids from the olive tree (Olea europaea L. (Oleaceae)) have been suggested as a potential application in a large number of inflammatory and reactive oxygen species (ROS)-mediated diseases. Thus, the purpose of this review is to summarize recent advances in the protective role of secoiridoids derived from the olive tree (preclinical studies and clinical trials) in diseases with an important pathogenic contribution of oxidative and peroxidative stress and damage, focusing on their plausible mechanisms of the action involved.

Oleuropein and its peracetylated derivative negatively regulate osteoclastogenesis by controlling the expression of genes involved in osteoclast differentiation and function

OL and Per-OL impair transcriptional gene circuits able to support osteoclastogenesis from human blood monocytes.