Effects of Citral on Lipopolysaccharide-Induced Inflammation in Human Umbilical Vein Endothelial Cells

A universal plasma metabolites-derived signature predicts cardiovascular disease risk in MAFLD

BACKGROUND

Metabolic associated fatty liver disease (MAFLD) is a novel concept proposed in 2020, which is more practical for identifying patients with fatty liver disease with high risk of disease progression. Fatty liver is a driver for extrahepatic complications, particularly cardiovascular diseases (CVD). Although the risk of CVD in MAFLD could be predicted by carotid ultrasound test, a very early stage prediction method before the formation of pathological damage is still lacking.

METHODS

Stool microbiomes and plasma metabolites were compared across 196 well-characterized participants encompassing normal controls, simple MAFLD patients, MAFLD patients with carotid artery pathological changes, and MAFLD patients with diagnosed coronary artery disease (CAD). 16S rDNA sequencing data and untargeted metabolomic profiles were interrogatively analyzed using differential abundance analysis and random forest (RF) machine learning algorithm to identify discriminatory gut microbiomes and metabolomic.

RESULTS

Characteristic microbial changes in MAFLD patients with CVD risk were represented by the increase of Clostridia and Firmicutes-to-Bacteroidetes ratios. Faecalibacterium was negatively correlated with mean-intima-media thickness (IMT), TC, and TG. Megamonas, Bacteroides, Parabacteroides, and Escherichia were positively correlated with the exacerbation of pathological indexes. MAFLD patients with CVD risk were characterized by the decrease of lithocholic acid taurine conjugate, and the increase of ethylvanillin propylene glycol acetal, both of which had close relationship with Ruminococcus and Gemmiger. Biotin l-sulfoxide had positive correlation with mean-IMT, TG, and weight. The general auxin pesticide beta-naphthoxyacetic acid and the food additive glucosyl steviol were both positively correlated with the increase of mean-IMT. The model combining the metabolite signatures with 9 clinical parameters accurately distinguished MAFLD with CVD risk in the proband and validation cohort. It was found that citral was the most important discriminative metabolite marker, which was validated by both in vitro and in vivo experiments.

CONCLUSIONS

Simple MAFLD patients and MAFLD patients with CVD risk had divergent gut microbes and plasma metabolites. The predictive model based on metabolites and 9 clinical parameters could effectively discriminate MAFLD patients with CVD risk at a very early stage.

Mechanisms and Applications of Citral's Antimicrobial Properties in Food Preservation and Pharmaceuticals Formulations

Citral is a monoterpene constituted by two isomers known as neral and geranial. It is present in different plant sources and recognized as safe (GRAS) by the Food and Drug Administration (FDA). In recent years, investigations have demonstrated that this compound exhibited several biological activities, such as antibacterial, antifungal, antibiofilm, antiparasitic, antiproliferative, anti-inflammatory, and antioxidant properties, by in vitro and in vivo assays. Additionally, when incorporated into different food matrices, citral can reduce the microbial load of pathogenic microorganisms and extend the shelf life. This compound has acceptable drug-likeness properties and does not present any violations of Lipinski's rules, which could be used for drug development. The above shows that citral could be a compound of interest for developing food additives to extend the shelf life of animal and vegetable origin foods and develop pharmaceutical products.

An update on the effects of food-derived active peptides on the intestinal microecology

The intestinal microecology is a research hotspot, and neologisms related to the gut such as gut-brain axis, gut-lung axis, gut-bone axis, gut-skin axis, gut-renal axis, and gut-liver axis have emerged from recent research. Meticulous investigation has discovered that food-derived active peptides (FDAPs) are bioactive substances that optimize the structure of the gut microbiota to improve human health. However, few reviews have summarized and emphasized the nutritional value of FDAPs and their mechanisms of action in regulating the composition of the gut microbiota. We aim to provide an update on the latest research on FDAPs by comparing, summarizing, and discussing the potential food sources of FDAPs, their physiological functions, and regulatory effects on the intestinal microecology. The key findings are that few studies have analyzed the potential mechanisms and molecular pathways through which FDAPs maintain intestinal microecological homeostasis. We found that an imbalance in the ratio of Bacteroidetes and Firmicutes in the gut microbiota and abnormal production of short-chain fatty acids are key to the occurrence and development of various diseases. This review provides theoretical support for future comprehensive research on the digestion, distribution, metabolism, and excretion of FDAPs and the mechanisms underlying the interactions between FDAPs and the intestinal microecology.

Orofacial anti-hypernociceptive effect of citral in acute and persistent inflammatory models in rats

Orofacial pain has significant psychological and physiological effects. Citral (3,7-dimethyl-2,6-octadienal) is the main component of Cymbopogon citratus (DC) Stapf, an herb with analgesic properties. Although citral has been considered a potent analgesic, its putative effects on orofacial pain are still unknown.

OBJECTIVE

The objective of this study is to test the hypothesis that citral modulates orofacial pain using two experimental models: formalin-induced hyperalgesia in the vibrissae area and during persistent temporomandibular hypernociception using Complete Freund's Adjuvant - CFA test.

METHODS

For the formalin test, citral (100 and 300 mg/kg, oral gavage) or its vehicle (Tween 80, 1 %) were given 1 h before the formalin injection subcutaneously (sc) into the vibrissae area. For the CFA model, we analyzed the prophylactic (100 mg/kg of citral by oral gavage, 1 h before CFA injection) and the chronic therapeutic (citral treatment 1-hour post-CFA injection and daily post-CFA injection) effect of citral or its vehicle in animals treated with CFA for 8 days.

RESULTS

Citral caused a decrease in formalin-induced local inflammation and the time spent performing nociceptive behavior in a dose-dependent fashion. Similarly, prophylactic and therapeutic citral treatment decreased the CFA-induced persistent mechanical hypernociception in the temporomandibular area.

CONCLUSION

Our data strengthen the notion that citral plays a powerful antinociceptive role by decreasing orofacial hypernociception in formalin and CFA models.

Citral protects against LPS-induced endometritis by inhibiting ferroptosis through activating Nrf2 signaling pathway

INTRODUCTION

Endometritis is the inflammatory condition of the uterus. Citral, a component of lemongrass oil, is known to exhibit anti-inflammatory activity.

AIM

The effects of citral on LPS-induced endometritis were tested and the mechanisms were investigated.

METHODS

LPS-induced endometritis mice model was established and the effects of citral were detected using this model. Inflammatory cytokines were tested by ELISA. Ferroptosis was assessed by detecting GSH, ATP, MDA, and Fe²⁺ levels. Signaling pathway was tested by western blot analysis.

RESULTS

Citral prevented LPS-induced endometritis through attenuating uterine pathological changes and inflammatory cytokine release. Meanwhile, citral prevents LPS-induced ferroptosis through attenuating MDA and Fe²⁺ levels, as well as increasing ATP and GSH levels. Furthermore, citral up-regulated Nrf2 and HO-1 expression and attenuated NF-κB activation. In addition, in Nrf2 knockdown mice, the inhibitory roles of citral on ferroptosis and endometritis were largely reversed.

CONCLUSION

Taken together, citral inhibited LPS-induced endometritis through preventing ferroptosis, which were regulated by Nrf2 signaling pathway.

Revealing the Protective Effect of Topically Applied Cymbopogon citratus Essential Oil in Human Skin through A Contact Model

Preparations of the Cymbopogon citratus leaves are used in folk medicine for the treatment of inflammatory processes. The present study investigated the proposed anti-inflammatory properties of C. citratus essential oil (EOCC) in human skin in vivo using the methylnicotinate (MN) microinflammation skin model. Skin exposure to MN causes a disturbance that triggers the production of reactive oxygen species and evokes a short duration microinflammatory reaction that might be explored to meet this objective. Fourteen participants of both sexes were selected after providing informed consent. Three areas (3 cm × 3 cm) were drawn on both forearms. One randomly chosen area was treated for 14 days, twice a day, with a polyacrylic acid gel containing 5% EOCC. Remaining areas were used as controls. Results revealed a clear protective effect at the EOCC-treated site. The MN reaction showed significantly lower transepidermal water loss, blood perfusion, erythema, and edema when compared with the other areas. Furthermore, the methodology here proposed is an innovative approach to study the clinical impact of these substances on human skin, contributing to an evidence-based support regarding the interest of using these products in human health.

Natural Monoterpenes as Potential Therapeutic Agents against Atherosclerosis

Traditional herbal medicines based on natural products play a pivotal role in preventing and managing atherosclerotic diseases, which are among the leading causes of death globally. Monoterpenes are a large class of naturally occurring compounds commonly found in many aromatic and medicinal plants. Emerging evidence has shown that monoterpenes have many biological properties, including cardioprotective effects. Remarkably, an increasing number of studies have demonstrated the therapeutic potential of natural monoterpenes to protect against the pathogenesis of atherosclerosis. These findings shed light on developing novel effective antiatherogenic drugs from these compounds. Herein, we provide an overview of natural monoterpenes' effects on atherogenesis and the underlying mechanisms. Monoterpenes have pleiotropic and multitargeted pharmacological properties by interacting with various cell types and intracellular molecular pathways involved in atherogenesis. These properties confer remarkable advantages in managing atherosclerosis, which has been recognized as a multifaceted vascular disease. We also discuss limitations in the potential clinical application of monoterpenes as therapeutic agents against atherosclerosis. We propose perspectives to give new insights into future preclinical research and clinical practice regarding natural monoterpenes.

Exploring the Anti-Hypertensive Potential of Lemongrass—A Comprehensive Review

Simple Summary

Lemongrass is an herb used in folk medicine for the treatment of hypertension, although its pharmacological potential has not yet been thoroughly studied. This paper provides the first comprehensive review on the anti-hypertensive potential of lemongrass, from in vitro to clinical studies. Even though the composition of lemongrass is dependent on its geographical origin, citral constitutes its major compound. Both citral and lemongrass display vasorelaxant activity ex vivo, promoting the secretion of endothelial vasodilators and the blockage of calcium channels in the vascular smooth muscle. Additionally, citral also displays a negative chronotrope effect. In animal models and in human subjects, lemongrass significantly decreases blood pressure, probably due to the combination of the above-mentioned effects together with diuretic activity. Future preclinical studies are necessary to identify other anti-hypertensive compounds/pathways, as well as to better characterize the safety profile of lemongrass.

Abstract

Lemongrass (Cymbopogon citratus (DC) Stapf) is a herb commonly used in folk medicine for many purposes. However, its anti-hypertensive potential has not yet been thoroughly studied. This paper reviews the anti-hypertensive effects of both lemongrass and its main compound citral in in vitro, ex vivo, preclinical and clinical studies. Lemongrass essential oil contains terpenes and their derivatives, whereas extracts contain different classes of polyphenols. Both citral and lemongrass display vasorelaxant activity ex vivo, acting by the promotion of endothelial nitric oxide/prostanoids secretion together with the blockage of calcium channels in the vascular smooth muscle. Citral also displays a negative chronotrope effect, probably due to a centrally mediated enhancement of parasympathetic activity. In both healthy and hypertensive animals, the acute administration of lemongrass results in a decrease in blood pressure, sometimes accompanied by a compensatory increase in heart rate. Similarly, in healthy and hypertensive human subjects, the consumption of lemongrass tea decreases blood pressure. Additionally, a weak/moderate diuretic activity has also been reported in animals and humans, although the mechanisms of action remain elusive. Future preclinical studies are necessary to identify other compounds with anti-hypertensive activity and additional pharmacological pathways. Although well tolerated, the safety profile of lemongrass should be better characterized.

Tamquam alter idem: formal similarities in a subset of reports on anti-inflammatory compounds in the years 2008–2019

A literature search on the in vitro testing of anti-inflammatory compounds of natural origin revealed a considerable number of studies adopting a similar template for data reporting in the years up to 2019. Sixty-five such reports appear to have been published between the years 2008 and 2019. Interestingly, this format template was clearly recognizable by a few hallmarks, such as a precise way of plotting cell viability data, extremely consistent endpoints, and the way these were graphically represented. In some instances the similarities extended to some textual features, such as in the case of figure legends. The similarity was so high that chance can be excluded and these studies can be safely assumed to have intentionally followed a template. By 2020, however, no new reports following this format have been published. Although a consistent and reproducible formatting for data reporting may improve report readability, this phenomenon should also be closely scrutinized to assess the rationale why it occurred, the validity of the endpoints that were chosen and why it was then abandoned. The present report reviewed the mean features of this format, traced its origin and its evolution over time, while discussing the limitations of this model.

Inflammation induced by lipopolysaccharide advanced androgen receptor expression and epithelial-mesenchymal transition progress in prostatitis and prostate cancer

Background

To explore the mechanism of prostatic inflammation on prostate cancer (PCa) by comparing the changes of prostate epithelial cells and PCa cells in an inflammatory environment.

Methods

First, immunohistochemistry (IHC) was used to compare the level of expression of TNF-α, IL-1β, IL-6, and TGF-β between benign prostatic hyperplasia (BPH), prostatitis, and PCa. Then primary prostate epithelial cells were sampled from patients who were suspected of PCa and had histological prostatitis (HP) confirmed by pathological biopsy. Lipopolysaccharide (LPS) or BAY11-7082 were used to investigate the change of androgen receptor (AR) and AR-mediated transcription, epithelial-mesenchymal transition (EMT) in primary prostate epithelial cells, and lymph node carcinoma of the prostate (LNCap) cells.

Results

TNF-α, IL-1β, IL-6, and TGF-β were significantly increased in HP and PCa compared with those in BPH patients. The proliferation of primary prostate epithelial cells and LNCap cells got the inflection point at LPS 10 µg/mL. In an inflammatory environment with 10 µg/mL LPS, both primary prostate epithelial cell and LNCap cell viability increased, and AR, AR-mediated transcription, and EMT processes were significantly increased. Inhibitors of NF-κB with 10 nM BAY11-7082 decreased AR, AR-mediated transcription, and EMT processes.

Conclusions

NF-κB regulates AR expression and EMT in prostatitis and PCa, and NF-κB inhibitors may have potential therapeutic value.

Citral mitigates inflammation of Caco-2 cells induced by Cronobacter sakazakii

The aim of this study was to explore the anti-inflammatory effect and mechanism of citral in Cronobacter sakazakii-stimulated Caco-2 cells. Safe doses of citral were first determined in Caco-2 cells....

Citral alleviates peptidoglycan-induced inflammation and disruption of barrier functions in porcine intestinal epithelial cells

Peptidoglycan (PGN) is a major polymer in bacterial cell walls and may constrain gut functionality and lower intestinal efficiencies in livestock. Citral has been reported to exhibit antibacterial and anti-inflammatory biological activities, improving the gastrointestinal function of swine. However, the protective effect of citral against PGN-elicited cellular responses and possible underlying mechanisms are unknown. In this study, the porcine jejunal epithelial cell line (IPEC-J2) was challenged with PGN from Staphylococcus aureus (S. aureus) or Bacillus subtilis (B. subtilis) to explore PGN-induced inflammatory responses. Our data showed that the inflammatory response stimulated by PGN from harmful bacteria (S. aureus) was more potent than that from commensal bacteria (B. subtilis) in IPEC-J2 cells. Based on the inflammatory model by PGN from S. aureus, it was demonstrated that PGN could significantly induce inflammatory cytokine production and influence nutrient absorption and barrier function in a dose-dependent manner. However, the PGN-mediated immune responses were remarkably suppressed by citral. In addition, citral significantly attenuated the effect of PGN on the intestine nutrient absorption and barrier function. The expression of TLR2 was strongly induced by PGN stimulation, which was suppressed by citral. All data nominated that citral downregulated PGN-induced inflammation via TLR2-mediated activation of the NF-κB signaling pathway in IPEC-J2 cells. Furthermore, the results also indicate that the PGN degradation through the inclusion of enzymes (e.g., muramidase) as well as the inclusion of citral for attenuating inflammation may improve pig gut health and functionality.

Citral modulates human monocyte responses to Staphylococcus aureus infection

Staphylococcus aureus is a Gram-positive bacterium that is considered an important human pathogen. Due to its virulence and ability to acquire mechanisms of resistance to antibiotics, the clinical severity of S. aureus infection is driven by inflammatory responses to the bacteria. Thus, the present study aimed to investigate the modulating role of citral in inflammation caused by S. aureus infection. For this, we used an isolate obtained from a nasal swab sample of a healthy child attending a day-care centre in Vitória da Conquista, Bahia, Brazil. The role of citral in modulating immunological factors against S. aureus infection was evaluated by isolating and cultivating human peripheral blood mononuclear cells. The monocytes were treated with 4%, 2%, and 1% citral before and after inoculation with S. aureus. The cells were analysed by immunophenotyping of monocyte cell surface molecules (CD54, CD282, CD80, HLA-DR, and CD86) and cytokine dosage (IL-1β, IL-6, IL-10, IL-12p70, IL-23, IFN-γ, TGF-β, and TNF-α), and evaluated for the expression of 84 genes related to innate and adaptive immune system responses. GraphPad Prism software and variables with P values < 0.05, were used for statistical analysis. Our data demonstrated citral’s action on the expression of surface markers involved in recognition, presentation, and migration, such as CD14, CD54, and CD80, in global negative regulation of inflammation with inhibitory effects on NF-κB, JNK/p38, and IFN pathways. Consequently, IL-1β, IL-6, IL-12p70, IL-23, IFN-γ, and TNF-α cytokine expression was reduced in groups treated with citral and groups treated with citral at 4%, 2%, and 1% and infected, and levels of anti-inflammatory cytokines such as IL-10 were increased. Furthermore, citral could be used as a supporting anti-inflammatory agent against infections caused by S. aureus. There are no data correlating citral, S. aureus, and the markers analysed here; thus, our study addresses this gap in the literature.

Systematic review of Ethiopian medicinal plants used for their anti-inflammatory and wound healing activities

ETHNOPHARMACOLOGICAL RELEVANCE

Plant materials are used worldwide as complementary and alternative therapeutics for the treatment of various illnesses. In Ethiopia, folk medicines are utilized across a wide range of cultures and settings. Ethiopia has numerous plant species of which around 12% are endemic, making it a rich source of medicinal plants that are potentially important for human wellbeing.

AIM OF THE STUDY

The aim of this study was to assess Ethiopian medicinal plants with anti-inflammatory or wound healing activities, in an attempt to compile the information required for further investigation of their potential role in the management of lymphoedema.

METHODS

A systematic review protocol was developed according to the preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) statement. The protocol for this review was registered on PROSPERO with registration number CRD42019127471. This review considers all controlled in vivo and in vitro anti-inflammatory and wound healing studies evaluating the efficacy and safety of Ethiopian medicinal plants. The search strategy included all articles containing descriptors such as Ethiopia, medicinal plants, herbal products, care, management, lymphoedema, lymphedema, swelling, podoconiosis, elephantiasis, wound, wound healing, inflammation, an anti-inflammatory that were published until June 28, 2019. Outcomes were measured as the percentage of inflammatory and pro-inflammatory cell inhibition, as the percentage of carrageenan-induced oedema (anti-inflammation) inhibition, and the percentage of cell migration and proliferation (wound healing). For quality assessment of individual animal studies, the Risk of Bias tool for animal intervention studies (SYRCLE's RoB tool) criteria were used. For quality assessment of individual in vitro studies, the OECD guidelines and the WHO Good Laboratory Practice (GLP) handbook were used.

RESULTS

A total of 46 articles on anti-inflammatory and 17 articles on wound healing properties were reviewed. For the in vivo studies, Swiss albino mice and Wistar rats were used, and the concentration of plant extracts or fractions administered to the lab animals varied considerably. Acetone extract of Vernonia amygdalina showed the fastest anti-inflammatory activity at lower concentrations in carrageenan-induced paw oedema.

CONCLUSION

Lawsonia inermis, Azadirachta indica, Achyranthes aspera, and Cuminum cyminum are the most studied plant species in terms of anti-inflammatory activity, while Lawsonia inermis and Azadirachta indica are the most studied ones for wound healing. The most common in vivo techniques used for the anti-inflammatory and the wound healing assays were carrageenan-induced paw oedema, and excision and incision wound models, respectively.

Anti-inflammatory and analgesic properties of Moroccan medicinal plants: Phytochemistry, in vitro and in vivo investigations, mechanism insights, clinical evidences and perspectives

Moroccan medicinal plants exhibit several pharmacological properties such as antimicrobial, anticancer, antidiabetic, analgesic, and anti-inflammatory effects, which are related to the presence of numerous bioactive compounds, including phenolic acids, flavonoids, and terpenoids. In the present review, we systematically evaluate previously published reports on the anti-inflammatory and analgesic effects of Moroccan medicinal plants. The in vitro investigations revealed that Moroccan medicinal plants inhibit several enzymes related to inflammatory processes, whereas in vivo studies noted significant anti-inflammatory and analgesic effects as demonstrated using different experimental models. Various bioactive compounds exhibiting in vitro and in vivo anti-inflammatory and analgesic effects, with diverse mechanisms of action, have been identified. Some plants and their bioactive compounds reveal specific secondary metabolites that possess important anti-inflammatory effects in clinical investigations. Our review proposes the potential applications of Moroccan medicinal plants as sources of anti-inflammatory and analgesic agents.

•

Anti-inflammatory and analgesic effects of Moroccan medicinal plants were highlighted.

•

Chemical nature of Moroccan medicinal plants with anti-inflammatory and analgesic effects was reported.

•

Insights into anti-inflammatory mechanisms of bioactive compounds were highlighted.

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Toxicological investigations of Moroccan medicinal plants were reviewed.

Chemical Properties and Therapeutic Potential of Citral, a Monoterpene Isolated from Lemongrass

BACKGROUND

Citral is one of the main components of lemongrass oil present at a concentration of 65-85% approximately and is generally separated by steam refining. It is an important component in the manufacturing of scents, citrus chemicals, cosmetics, food and pharmaceutical products.

OBJECTIVES

This article aims at reviewing the published literature to highlight the metabolism, extraction strategies and therapeutic significance of citral for improving the scope of its application in the food and pharma industry.

DISCUSSIONS

Apart from steam refining, there are other techniques like solvent extraction, supercritical fluid extraction and ultrasonication by which citral can be extracted and the method of extraction defines its quality. It is an unstable molecule and undergoes rapid deterioration on exposure to air. Citral is biosynthesized by the plants through the 5 carbon precursor isopentenyl diphosphate (IPP) units utilizing two diverse biochemical pathways, acetate- mevalonate (acetate- MVA) pathway or 2C-methylerythritol-4-phosphate (MEP). Orally Citral was absolutely digested in the gastrointestinal tract and its metabolism leads to the discharge of metabolites which include a number of acids and a biliary glucuronide. There is no scientific evidence about the long term bioavailability of citral in the body and it has no adverse effect on tissue related to its accumulation and delayed excretion. Citral exhibits various important therapeutic properties like antimicrobial, antioxidant, anticancer, anti-diabetic and anti-inflammatory.

CONCLUSION

Citral is a potent biomolecule with various important biological activities and therapeutic implications. Strategies are required to increase the stability of citral which could increase its applications.

Citral Effects on the Expression Profile of Brain-Derived Neurotrophic Factor and Inflammatory Cytokines in Status Epilepticus-Induced Rats Using the Lithium-Pilocarpine Model

Epilepsy is one of the most common neurological disorders. About one-third of people with epilepsy are refractory to available treatments. Studies suggest that mechanisms linked to the immune response and inflammatory process are related to seizure disorders. Citral is a monoterpene found in the essential oil of several plants, as in Cymbopogon citratus, used to make teas and has been the subject of numerous researches, from which it has been possible to demonstrate antiseizure and anti-inflammatory activities. In this study, the effects of citral on status epilepticus (SE) induced by the lithium-pilocarpine model in rats were investigated. Quantitative reverse transcription PCR (RT-qPCR) evaluated latency for seizure development, neuronal death in the hippocampus, and expression of the brain-derived neurotrophic factor (BDNF), tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), interleukin-1β ( IL-1β) and factor nuclear kappa B (NF-κB) genes. The results revealed that citral was able to increase latency until the first seizure, decrease neuronal death 2 h after SE and inhibit overexpression of proinflammatory genes.

In vitro effects of citral on the human myometrium: Potential adjunct therapy to prevent preterm births

BACKGROUND

Premature infants contribute to infant morbidity and mortality especially in low resource settings. Information on tocolytic and/or anti-inflammatory effects of several plant extracts, such as citral, could help prevent preterm birth cases and reduce the number of preterm infants. The aim of this study was to evaluate the in vitro tocolytic and anti-inflammatory effect of citral on myometrial tissues of the human uterus.

METHODS

Myometrial samples from uteri obtained after hysterectomy were used in functional tests to evaluate the inhibitory effect of citral on PGF-2α induced contractions. The intracellular cyclic adenosine monophosphate (cAMP) levels generated in response to citral in human myometrial homogenates were measured by ELISAs. Forskolin was used as a positive control. The anti-inflammatory effect of citral was determined through the measurement of two pro-inflammatory cytokines, tumor necrosis factor-α (TNFα) and interleukin (IL)-1β, and the anti-inflammatory cytokine IL-10, in human myometrial explants stimulated with lipopolysaccharide (LPS).

RESULTS

Citral was able to induce a significant inhibition of PGF-2α induced contractions at the highest concentration level (p < .05). Citral caused a concentration-dependent increase in myometrial cAMP levels (p < .05) and a concentration-dependent decrease in LPS-induced TNFα and IL-1β production, while IL-10 production increased significantly (p < .05). The anti-inflammatory and tocolytic effects induced by citral could be associated with an increase in cAMP levels in human myometrial samples.

CONCLUSION

These properties place citral as a potentially safe and effective adjuvant agent in preterm birth cases, an obstetric and gynecological problem that requires urgent attention.

Hypothermic Effect of Acute Citral Treatment during LPS-induced Systemic Inflammation in Obese Mice: Reduction of Serum TNF-α and Leptin Levels

Citral is a mixture of monoterpenes present in the essential oil of several plants, such as Cymbopogon citratus and Zingiber officinale, possessing anti-inflammatory, anti-ulcerogenic, and antipyretic actions. We investigated the action of citral on body temperature (Tb) and inflammatory signaling in eutrophic and obese mice during Systemic Inflammation (SI) induced by Lipopolysaccharide (LPS). Thus, we assessed the effect of citral (25, 100, and 300 mg/kg) and ibuprofen in LPS-induced SI in Swiss male mice fed a standard diet (SD) or high-fat diet (HFD) for 12 weeks. Following SI induction, we measured Tb and collected the serum, hypothalamus, and gastric mucosa for biochemical measurements. Acute treatment with citral decreased the Tb of both SD and HFD-fed animals. Citral (300 mg/kg) treatment caused a significantly lower Tb variation in HFD-fed animals than in those fed the SD. Citral reduced peripheral levels of tumor necrosis factor (TNF)-α in SD and HFD mice and decreased serum leptin concentration in HFD mice 90 min after the LPS challenge. Furthermore, citral also reduced interleukin (IL)-6 levels in the hypothalamus of obese mice. In summary, citral effectively reduced Tb during SI by reducing inflammatory mediators with a distinct action profile in HFD mice when compared with SD.

Citral Protects Human Endothelial Cells Against Hydrogen Peroxide-induced Oxidative Stress

OBJECTIVES

Oxidative stress plays a major role in endothelial dysfunction. Citral is a monoterpene aldehyde with antioxidant properties. This study aimed to investigate the effect of citral on human umbilical vein endothelial cells (HUVECs) under hydrogen peroxide (H2O2)-induced oxidative stress.

MATERIALS AND METHODS

The cells were treated with citral (0.625-10 μg/mL) for 24 h before exposure to H2O2 (0.5 mM, 2 h). Cell viability was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. The hydroperoxide concentrations and ferric reducing ability of plasma (FRAP) were measured in intra- and extracellular fluids.

RESULTS

Pretreatment of HUVECs with citral at concentrations of 5 and 10 μg/mL significantly enhanced the cell viability in H2O2-induced cytotoxicity. It reduced intracellular hydroperoxide levels at the concentrations of 5 and 10 μg/mL and extracellular hydroperoxide levels at the concentrations of 2.5-10 μg/mL. Pretreatment with citral significantly increased the FRAP value in intra- and extracellular fluids at the concentration range of 1.25-10 μg/mL.

CONCLUSION

Antioxidant and cytoprotective effects were found for citral against oxidative damage induced by H2O2 in human endothelial cells. However, more studies in this area are needed to assess its clinical value for prevention and treatment of cardiovascular diseases.

Citral Inhibits the Inflammatory Response and Hyperalgesia in Mice: The Role of TLR4, TLR2/Dectin-1, and CB2 Cannabinoid Receptor/ATP-Sensitive K+ Channel Pathways

Citral ((2E)-3,7-dimethylocta-2,6-dienal), a bioactive component of lemongrass, inhibits oxidant activity, nuclear factor kappa B (NF-κB) activation, and cyclooxygenase-2 (COX-2) expression, even as it activates peroxisome proliferator-activated receptor (PPAR)-α and γ. Additionally, citral produces long-lasting inhibition of transient receptor potential (TRP) channels that are found in sensory neurons, such as TRPV1-3 and TRPM8, while it transiently blocks TRPV4 and TRPA1. Here, the effect of citral in experimental models of acute inflammation and hyperalgesia in mice, and the underlying citral mechanisms of action were investigated. ADMET properties and molecular targets were predicted using the online server. The immunomodulatory and antihyperalgesic effects of citral were evaluated, using mechanical and thermal stimuli, at different time-points on carrageenan, lipopolysaccharides (LPS), and zymosan-induced paw edema and hyperalgesia in mice. ADMET analysis ensures that the citral has not violated Lipinski's rule of five, indicating its safety consumption, and molecular target prediction software identified that citral is a potential fatty acid amide hydrolase (FAAH) inhibitor. Oral treatment with citral (50-300 mg/kg) significantly inhibited carrageenan-induced paw edema and thermal allodynia. Furthermore, citral modulated the inflammation induced by LPS and zymosan, toll-like receptor (TLR) 4, and TLR2/dectin-1 ligands, respectively. Moreover, pretreatment with cannabinoid receptor type 2 (CB2R) antagonists and ATP-sensitive K⁺ channel inhibitor, but not with a cannabinoid receptor type 1 (CB1R) antagonist, significantly reversed the anti-inflammatory effect of citral. Intriguingly, citral did not cause any relevant action in the central nervous system, and it was safe when assessed in a 14 day toxicity assay in male mice. Therefore, citral constitutes a promising, innovative, and safe molecule for the management of immunoinflammatory conditions and pain states.

Terpenoids, Cannabimimetic Ligands, beyond the Cannabis Plant

Medicinal use of Cannabis sativa L. has an extensive history and it was essential in the discovery of phytocannabinoids, including the Cannabis major psychoactive compound—Δ9-tetrahydrocannabinol (Δ9-THC)—as well as the G-protein-coupled cannabinoid receptors (CBR), named cannabinoid receptor type-1 (CB1R) and cannabinoid receptor type-2 (CB2R), both part of the now known endocannabinoid system (ECS). Cannabinoids is a vast term that defines several compounds that have been characterized in three categories: (i) endogenous, (ii) synthetic, and (iii) phytocannabinoids, and are able to modulate the CBR and ECS. Particularly, phytocannabinoids are natural terpenoids or phenolic compounds derived from Cannabis sativa. However, these terpenoids and phenolic compounds can also be derived from other plants (non-cannabinoids) and still induce cannabinoid-like properties. Cannabimimetic ligands, beyond the Cannabis plant, can act as CBR agonists or antagonists, or ECS enzyme inhibitors, besides being able of playing a role in immune-mediated inflammatory and infectious diseases, neuroinflammatory, neurological, and neurodegenerative diseases, as well as in cancer, and autoimmunity by itself. In this review, we summarize and critically highlight past, present, and future progress on the understanding of the role of cannabinoid-like molecules, mainly terpenes, as prospective therapeutics for different pathological conditions.

Citral-induced analgesia is associated with increased spinal serotonin, reduced spinal nociceptive signaling, and reduced systemic oxidative stress in arthritis

ETHNOPHARMACOLOGICAL RELEVANCE

Citral (3,7-dimethyl-2,6-octadienal) is the main component of Cymbopogon citratus (DC) Stapf, an herb with analgesic properties. Arthritic pain is the main unpleasant component of rheumatoid arthritis. The pharmacological approaches used to treat arthritic pain are often accompanied by adjuvant drugs or non-pharmacological treatments, showing a constant need in identifying new efficient analgesic drugs.

AIM OF THE STUDY

To test the hypothesis that citral, which is a monoterpenoid compound with therapeutic properties, reduces nociception, spinal pro-nociceptive and pro-inflammatory signaling, and systemic oxidative stress in arthritic rats.

MATERIALS AND METHODS

Complete Freund's adjuvant (CFA) was administrated in the left knee joint of rats. Oral treatment with citral was performed during eight days and mechanical allodynia was monitored during the period of treatment to evaluate the analgesic effect of citral. We assessed the levels of serotonin (5-hydroxytryptamine, 5-HT) in the lumbar dorsal horn of the spinal cord (DHSC) and the profiles of expression of the glycogen synthase kinase-3β (GSK3β), which is a 5-HT-regulated intracellular protein, and of the stress-activated protein kinase (SAPK)/jun N-terminal kinase (JNK) in the DHSC. Plasma levels of superoxide dismutase (SOD) were assessed as an indicator of oxidative stress.

RESULTS

Administration of CFA induced mechanical allodynia associated with reduced spinal GSK3β phosphorylation, increased spinal SAPK/JNK phosphorylation, and increased plasma SOD levels. Oral administration of citral reversed mechanical allodynia, increased endogenous spinal 5-HT levels, reduced spinal SAPK/JNK phosphorylation, and reduced plasma SOD levels.

CONCLUSION

Citral shows anti-nociceptive effects in an animal model of arthritic pain by modulating spinal nociceptive signaling.

Targets and pathways involved in the antitumor activity of citral and its stereo-isomers

This review provides a comprehensive analysis of the anticancer potential of the natural product citral (CIT) found in many plants and essential oils, and extensively used in the food and cosmetic industry. CIT is composed of two stereoisomers, the trans-isomer geranial being a more potent anticancer compound than the cis-isomer neral. CIT inhibits cancer cell proliferation and induces cancer cell apoptosis. Its pluri-factorial mechanism of anticancer activity is essentially based on three pillars: (i) a drug-induced accumulation of reactive oxygen species in cancer cells leading to an oxidative burst and DNA damages, (ii) a colchicine-like inhibition of tubulin polymerization and promotion of microtubule depolymerization, associated with an inhibition of the microtubule affinity-regulating kinase MARK4, and (iii) a potent inhibition of the aldehyde dehydrogenase isoform ALDH1A3 which is associated with cancer stem cell proliferation and chemoresistance. This unique combination of targets and pathways confers a significant anticancer potential. However, the intrinsic potency of CIT is limited, mainly because the drug is not very stable and has a low bioavailability and it does not present a high selectivity for cancer cells versus non-tumor cells. Stable formulations of CIT, using cyclodextrins, biodegradable polymers, or various nano-structured particles have been designed to enhance the bioavailability, to increase the effective doses window and to promote the anticancer activity. The lack of tumor cell selectivity is more problematic and limits the use of the drug in cancer therapy. Nevertheless, CIT offers interesting perspectives to design more potent analogues and drug combinations with a reinforced antitumor potential.

The Ovotransferrin-Derived Peptide IRW Attenuates Lipopolysaccharide-Induced Inflammatory Responses

IRW (Ile-Arg-Trp), a bioactive peptide isolated from egg ovotransferrin, has been shown to exert anti-inflammatory effects. In this study, the effects of IRW on inflammatory cytokines and microbiota were explored in human umbilical vein endothelial cells (HUVECs) and a lipopolysaccharide (LPS)-induced rat model of inflammatory peritonitis. Rats were injected intraperitoneally with LPS to establish peritonitis. HUVECs were exposed to IRW for 12 h before introducing LPS. Notably, IRW exerted beneficial effects against LPS-induced peritonitis, specifically, by reducing the serum levels of tumour necrosis factor (TNF)-α and interleukin (IL)-6 and myeloperoxidase (MPO) activity (P<0.05). A faecal microbiota analysis revealed that IRW significantly increased the Shannon and decreased the Simpson indices (P<0.05). Furthermore, IRW treatment significantly inhibited the LPS-induced enhancement of TNF-α, IL-8, intercellular cell adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) expression in HUVECs (P<0.05). In conclusion, IRW supplementation inhibited the inflammatory mediator synthesis and LPS-induced inflammatory responses and influenced the gut microbiota.

Citral, A Monoterpene Protect Against High Glucose Induced Oxidative Injury in HepG2 Cell In Vitro-An Experimental Study

INTRODUCTION

Diabetes mellitus, a major metabolic disorder associated with hyperglycaemia is one of the leading cause of death in many developed countries. However, use of natural phytochemicals have been proved to have a protective effect against oxidative damage.

AIM

To investigate the effect of citral, a monoterpene on high glucose induced cytotoxicity and oxidative stress in human hepatocellular liver carcinoma (Hep G2) cell line.

MATERIALS AND METHODS

Cells were treated with 50 mM concentration of glucose for 24 hours incubation following citral (30 μM) was added to confluent HepG2 cells. Cell viability, Reactive Oxygen Species (ROS) generation, DNA damage, lipid peroxidation, antioxidants and Mitogen Activated Protein Kinases (MAPKs) signaling were assessed in citral and/or high glucose induced HepG2 cells.

RESULTS

Cells treated with glucose (50 mM), resulted in increased cytotoxicity, ROS generation, DNA damage, lipid peroxidation and depletion of enzymatic and non enzymatic antioxidants. In contrast, treatment with citral (30 μM) significantly decreased cell cytotoxicity, ROS generation, DNA damage, lipid peroxidation and increased antioxidants enzymes in high glucose induced HepG2 cells. In addition, the present study highlighted that high glucose treated cells showed increased expression of Extracellular Signal Regulated Protein Kinase-1 (ERK-1), c-Jun N-terminal Kinase (JNK) and p38 in HepG2 cells. On the other hand treatment with citral significantly suppressed the expression of ERK-1, JNK and p38 in high glucose induced HepG2 cells.

CONCLUSION

Citral protects against high glucose induced oxidative stress through inhibiting ROS activated MAPK signaling pathway in HepG2 cells.

Lemongrass (Cymbopogon flexuosus) essential oil demonstrated anti-inflammatory effect in pre-inflamed human dermal fibroblasts

Lemongrass (Cymbopogon flexuosus) essential oil (LEO), which has citral as its main component, has exhibited anti-inflammatory effect in both animal and human cells. In this study, we evaluated the anti-inflammatory activity of a commercially available LEO in pre-inflamed human dermal fibroblasts. We first studied the impact of LEO on 17 protein biomarkers that are critically associated with inflammation and tissue remodeling. LEO significantly inhibited production of the inflammatory biomarkers vascular cell adhesion molecule 1 (VCAM-1), interferon gamma-induced protein 10 (IP-10), interferon-inducible T-cell alpha chemoattractant (I-TAC), and monokine induced by gamma interferon (MIG); decreased levels of the tissue remodeling biomarkers collagen-I and III, epidermal growth factor receptor (EGFR), and plasminogen activator inhibitor (PAI-1); and inhibited the immunomodulatory biomarker macrophage colony-stimulating factor (M-CSF). Furthermore, we studied the impact of LEO on genome-wide gene expression profiles. LEO significantly modulated global gene expression and robustly impacted signaling pathways, many of which are critical for inflammation and tissue remodeling processes. This study provides the first evidence of the anti-inflammatory activity of LEO in human skin cells and indicates that it is a good therapeutic candidate for treating inflammatory conditions of the skin.

Inhibition of Cronobacter sakazakii Virulence Factors by Citral

Cronobacter sakazakii is a foodborne pathogen associated with fatal forms of necrotizing enterocolitis, meningitis and sepsis in neonates and infants. The aim of this study was to determine whether citral, a major component of lemongrass oil, could suppress putative virulence factors of C. sakazakii that contribute to infection. Sub-inhibitory concentrations of citral significantly decreased motility, quorum sensing, biofilm formation and endotoxin production. Citral substantially reduced the adhesion and invasion of C. sakazakii to Caco-2 cells and decreased bacterial survival and replication within the RAW 264.7 macrophage cells. Citral also repressed the expression of eighteen genes involved in the virulence. These findings suggest that citral has potential to be developed as an alternative or supplemental agent to mitigate the infections caused by C. sakazakii.

Peroxisome proliferator-activated receptor (PPAR) α and δ activators induce ICAM-1 expression in quiescent non stimulated endothelial cells

Background

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that are implicated in the regulation of lipid and glucose homeostasis. PPAR agonists have been shown to control inflammatory processes, in part by inhibiting the expression of distinct proinflammatory genes such as vascular cell adhesion molecule-1 (VCAM-1), IL-8, and intercellular adhesion molecule-1 (ICAM-1). ICAM-1 is an important endothelial membrane receptor that facilitates the transmigration of leukocytes across the endothelium. To date, the influence of PPARα and δ activators on the expression of ICAM-1 in non-induced, quiescent endothelial cells has been unclear. Therefore, we examined the effects of various PPARα and δ agonists on the expression of ICAM-1 in non-stimulated primary human endothelial cells.

Results

We found that PPARα and PPARδ agonists significantly induced ICAM-1 surface, intracellular protein, and mRNA expression in a time and concentration-dependent manner. The PPARδ induced ICAM-1 expression could be paralleled with a significantly increased T-cell adherence to the endothelial cells whereas PPARα failed to do so. Transcriptional activity studies using an ICAM-1 reporter gene constructs revealed that PPARδ, but not PPARα agonists induced gene expression by stimulating ICAM-1 promoter activity via an Sp1 transcription factor binding site and inhibit the binding of the transcription factors Sp1 and Sp3. Furthermore, we performed mRNA stability assays and found that PPARα and PPARδ agonists increased ICAM-1 mRNA stability.

Conclusion

Therefore, our data provide the first evidence that PPARα and PPARδ agonists induce ICAM-1 expression in non-stimulated endothelial cells via transcriptional and posttranscriptional mechanisms.