The Protective Effect of Indole-3-Acetic Acid (IAA) on H2O2-Damaged Human Dental Pulp Stem Cells Is Mediated by the AKT Pathway and Involves Increased Expression of the Transcription Factor Nuclear Factor-Erythroid 2-Related Factor 2 (Nrf2) and Its Downstream Target Heme Oxygenase 1 (HO-1)

Indole-3-acetic acid attenuates pulmonary fibrosis by modulating lung microbiota, inhibiting fibroblast activation, and alleviating alveolar epithelial cell senescence

AIM

Pulmonary fibrosis (PF) is a relentlessly progressive disorder characterized by high mortality and limited effective therapeutic options. Indole-3-acetic acid (IAA), originally recognized as a plant hormone, is also identified as a tryptophan-derived metabolite catabolized from microbiota in mammals. IAA has exhibited antioxidative, anti-inflammatory, and anti-tumor effects in various disorders, yet its role in PF remains elusive.

MAIN METHODS

Bleomycin (BLM) was employed to induce PF in a mouse model. TGF-β1 was utilized in primary mouse lung fibroblasts (pMLFs) to establish a pro-fibrotic in vitro cellular model, and in A549 cells to create an in vitro cellular senescence model. The therapeutic effects of IAA on PF were evaluated using hematoxylin-eosin staining, immunofluorescence staining, western blotting, SA-β-gal assay, and network pharmacology analysis. Additionally, the effect of IAA on lung microbiota of PF was investigated using 16S rRNA gene sequencing analysis.

KEY FINDINGS

we observed a significant reduction in IAA levels in both PF patients and mouse models. Moreover, we demonstrated the therapeutic potential of IAA in alleviating PF in BLM-induced mouse models, showing a dose-dependent response. Mechanistically, we delineated three perspectives. Firstly, IAA promoted autophagic flux by inhibiting the PI3K/AKT/mTOR pathway, thereby suppressing lung fibroblast differentiation and extracellular matrix (ECM) deposition. Secondly, IAA attenuated alveolar epithelial cell senescence by modulating the PI3K/AKT and HIF-1 pathways. Lastly, IAA displayed the ability to mitigate PF by modulating the structure and composition of lung microbiota.

SIGNIFICANCE

Our study demonstrates that IAA alleviates PF through multiple pathways, highlighting its potential as a therapeutic agent.

Indole-3-Acetic Acid Esterified with Waxy, Normal, and High-Amylose Maize Starches: Comparative Study on Colon-Targeted Delivery and Intestinal Health Impact

Background: Accumulating research suggests that metabolites produced by gut microbiota are essential for maintaining a balanced gut and immune system. Indole-3-acetic acid (IAA), one of tryptophan metabolites from gut microbiota, is critical for gut health through mechanisms such as activating aryl hydrocarbon receptor. Delivery of IAA to colon is beneficial for treatment of gastrointestinal diseases, and one promising strategy is IAA esterified starch, which is digested by gut microbes in colon and releases loaded IAA. Amylose content is a key structural characteristic that controls the physicochemical properties and digestibility of starch.

METHODS

In the current study, IAA was esterified with three typical starches with distinct amylose content to obtain indolyl acetylated waxy maize starch (WMSIAA), indolyl acetylated normal maize starch (NMSIAA), and indolyl acetylated high-amylose maize starch (HAMSIAA). The study comparatively analyzed their respective physicochemical properties, how they behave under in vitro digestion conditions, their ability to deliver IAA directly to the colon, and their effects on the properties of the gut microbiota.

RESULTS

The new characteristic peak of 1H NMR at 10.83 ppm, as well as the new characteristic peak of FTIR spectra at 1729 cm-1, represented the successful esterification of IAA on starch backbone. The following in vitro digestion study further revealed that treatment with indolyl acetylation significantly elevated the resistant starch content in the starch samples. In vivo experimental results demonstrated that WMSIAA exhibited the most significant increase in IAA levels in the stomach, whereas HAMSIAA and NMSIAA demonstrated the most remarkable increases in IAA levels in the small intestine and colon, respectively. The elevated IAA levels in the colon are conducive to promoting the growth of beneficial intestinal bacteria and significantly alleviating DSS-induced colitis.

CONCLUSIONS

This research presents innovative insights and options for the advancement of colon-specific drug delivery systems aimed at preventing and curing gastrointestinal disorders.

Indole-3-Acetic Acid Protects Against Lipopolysaccharide-induced Endothelial Cell Dysfunction and Lung Injury through the Activation of USP40

Lung microvascular endothelial cell (EC) dysfunction is the pathological hallmark of acute respiratory distress syndrome. Heat shock protein 90 (HSP90) is a key regulator in control of endothelial barrier disruption and inflammation. Our recent study has demonstrated that ubiquitin-specific peptidase 40 (USP40) preserves endothelial integrity by targeting HSP90β for its deubiquitination and inactivation. Indole-3-acetic acid (IAA), a plant hormone of the auxin class, can also be catabolized from dietary tryptophan by the intestinal microbiota. Accumulating evidence suggests that IAA reduces oxidative stress and inflammation and promotes intestinal barrier function. However, little is known about the role of IAA in endothelial cells and acute lung injury. In this study, we investigated the role of IAA in lung endothelial cell function in the context of acute lung injury. IAA exhibited EC barrier protection against LPS-induced reduction in transendothelial electrical resistance and inflammatory responses. The underlying mechanism of IAA on EC protective effects was investigated by examining the influence of IAA on degrees of HSP90 ubiquitination and USP40 activity. We identified that IAA, acting as a potential activator of USP40, reduces HSP90 ubiquitination, thereby protecting against LPS-induced inflammation in human lung microvascular endothelial cells as well as alleviating experimental lung injury. Furthermore, the EC protective effects of IAA against LPS-induced EC dysfunction and lung injury were abolished in USP40-deficient human lung microvascular endothelial cell and lungs of USP40 EC-specific knockout (USP40cdh5-ECKO) mice. Taken together, this study reveals that IAA protects against LPS-induced EC dysfunction and lung injury through the activation of USP40.

Gut microbial metabolites in MASLD: Implications of mitochondrial dysfunction in the pathogenesis and treatment

With an increasing prevalence, metabolic dysfunction-associated steatotic liver disease (MASLD) has become a major global health problem. MASLD is well-known as a multifactorial disease. Mitochondrial dysfunction and alterations in the gut bacteria are 2 vital events in MASLD. Recent studies have highlighted the cross-talk between microbiota and mitochondria, and mitochondria are recognized as pivotal targets of the gut microbiota to modulate the host's physiological state. Mitochondrial dysfunction plays a vital role in MASLD and is associated with multiple pathological changes, including hepatocyte steatosis, oxidative stress, inflammation, and fibrosis. Metabolites are crucial mediators of the gut microbiota that influence extraintestinal organs. Additionally, regulation of the composition of gut bacteria may serve as a promising therapeutic strategy for MASLD. This study reviewed the potential roles of several common metabolites in MASLD, emphasizing their impact on mitochondrial function. Finally, we discuss the current treatments for MASLD, including probiotics, prebiotics, antibiotics, and fecal microbiota transplantation. These methods concentrate on restoring the gut microbiota to promote host health.

The implication of LPS/TLR4 and FXR receptors in hepatoprotective efficacy of indole-3-acetic acid and chenodeoxycholic acid

AIM

Valproic acid (VPA) belongs to the first-generation antiepileptic drugs, yet its prolonged use can cause life-threatening liver damage. The importance of our study is to investigate the protective effect of indole-3-acetic acid (IAA), chenodeoxycholic acid (CDCA) and their combination on VPA-induced liver injury focusing on lipopolysaccharides (LPS)/toll-like receptor 4 (TLR4) pathway and farnesoid X receptor (FXR).

METHODS

Thirty rats were randomly assigned into five groups, normal control group, VPA group received 500 mg/kg of VPA intraperitoneally. The remaining groups were orally treated with either 40 mg/kg of IAA, 90 mg/kg of CDCA, or a combination of both, along with VPA. All treatments were administered one hour after the administration of VPA for three weeks.

KEY FINDINGS

VPA group showed significant elevations in the liver weight/body weight ratio, serum aminotransferases, triglyceride, and total cholesterol levels. Hepatic glutathione (GSH) level and superoxide dismutase (SOD) activity were significantly decreased, while malondialdehyde (MDA) level, tumor necrosis factor-α (TNF-α), interleukin-1beta (IL-1β), lipopolysaccharide (LPS) and caspase 3 were significantly increased. Likewise, immunohistochemical analysis revealed that TLR4 expression was elevated, whereas FXR expression was downregulated in hepatocytes. IAA substantially ameliorated all previously altered parameters, whereas CDCA treatment showed a partial improvement compared to IAA. Surprisingly, combination therapy of IAA with CDCA showed an additive effect only in the hepatic expression of TLR4 and FXR proteins.

SIGNIFICANCE

IAA could be a promising protective agent against VPA-induced liver injury.

Can different agents reduce the damage caused by bleaching gel to pulp tissue? A systematic review of basic research

Objectives

This study aimed to investigate the effectiveness of different topical/systemic agents in reducing the damage caused by bleaching gel to pulp tissue or cells.

Materials and Methods

Electronic searches were performed in July 2023. In vivo and in vitro studies evaluating the effects of different topical or systemic agents on pulp inflammation or cytotoxicity after exposure to bleaching agents were included. The risk of bias was assessed.

Results

Out of 1,112 articles, 27 were included. Nine animal studies evaluated remineralizing/anti-inflammatories agents in rat molars subjected to bleaching with 35%-38% hydrogen peroxide (HP). Five of these studies demonstrated a significant reduction in inflammation caused by HP when combined with bioglass or MI Paste Plus (GC America), or following KF-desensitizing or Otosporin treatment (n = 3). However, orally administered drugs did not reduce pulp inflammation (n = 4). Cytotoxicity (n = 17) was primarily assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay on human dental pulp cells and mouse dental papilla Cell-23 cells. Certain substances, including sodium ascorbate, butein, manganese chloride, and peroxidase, were found to reduce cytotoxicity, particularly when applied prior to bleaching. The risk of bias was high in animal studies and low in laboratory studies.

Conclusions

Few in vivo studies have evaluated agents to reduce the damage caused by bleaching gel to pulp tissue. Within the limitations of these studies, it was found that topical agents were effective in reducing pulp inflammation in animals and cytotoxicity. Further analyses with human pulp are required to substantiate these findings.

Trial Registration

PROSPERO Identifier: CRD42022337192.

Profiling Analysis of Tryptophan Metabolites in the Urine of Patients with Parkinson's Disease Using LC-MS/MS

Although Parkinson's disease (PD) is a representative neurodegenerative disorder and shows characteristic motor impediments, the pathophysiological mechanisms and treatment targets for PD have not yet been clearly identified. Since several tryptophan metabolites produced by gut microbiota could pass the blood-brain barrier and, furthermore, might influence the central nervous system, tryptophan metabolites within the indole, kynurenine, and serotonin metabolic pathways might be the most potent targets for PD development. Furthermore, most metabolites are circulated via the blood, play roles in and/or are metabolized via the host organs, and finally are excreted into the urine. Therefore, profiling the overall tryptophan metabolic pathways in urine samples of patients with PD is important to understanding the pathological mechanisms, finding biomarkers, and discovering therapeutic targets for PD. However, the development of profiling analysis based on tryptophan metabolism pathways in human urine samples is still challenging due to the wide physiological ranges, the varied signal response, and the structural diversity of tryptophan metabolites in complicated urine matrices. In this study, an LC-MS/MS method was developed to profile 21 tryptophan metabolites within the indole, kynurenine, and serotonin metabolic pathways in human urine samples using ion-pairing chromatography and multiple reaction monitoring determination. The developed method was successfully applied to urine samples of PD patients (n = 41) and controls (n = 20). Further, we investigated aberrant metabolites to find biomarkers for PD development and therapeutic targets based on the quantitative results. Unfortunately, most tryptophan metabolites in the urine samples did not present significant differences between control and PD patients, except for indole-3-acetic acid. Nonetheless, indole-3-acetic acid was reported for the first time for its aberrant urinary levels in PD patients and tentatively selected as a potential biomarker for PD. This study provides accurate quantitative results for 21 tryptophan metabolites in biological samples and will be helpful in revealing the pathological mechanisms of PD development, discovering biomarkers for PD, and further providing therapeutic targets for various PD symptoms. In the near future, to further investigate the relationship between gut microbial metabolites and PD, we will employ studies on microbial metabolites using plasma and stool samples from control and PD patients.

Determination of tryptophan and its indole metabolites in follicular fluid of women with diminished ovarian reserve

Tryptophan (TRP) and its indole metabolites exhibit numerous biological effects, especially their antioxidant properties. This study used untargeted metabolomics in conjunction with targeted metabolomics to investigate the differential expression of tryptophan and its indole metabolites in follicular fluid (FF) of diminished ovarian reserve (DOR) and normal ovarian reserve (NOR) populations. This study included patients with DOR (n = 50) and females with NOR (n = 35) who received in vitro fertilization and embryo transfer. Untargeted metabolomics suggests that diminished ovarian reserve affects the metabolic profile of FF, TRP and indole metabolites were significantly down-regulated in the DOR group. Targeted metabolomics quantification revealed that the levels of TRP, IPA and IAA in the FF of the DOR group were significantly lower than those of the NOR group (P < 0.01). The concentration of TRP in FF is positively correlated with the available embryo rate in NOR females. These results provide data support to explore the pathogenesis of DOR and to look for new biomarkers and ovarian protectors. Additionally, alterations in TRP and its indole metabolites in FF may indirectly reflect the interaction between intestinal flora and the follicular microenvironment.

Multi-omics analysis reveals changes in tryptophan and cholesterol metabolism before and after sexual maturation in captive macaques

Rhesus macaques (Macaca mulatta, RMs) are widely used in sexual maturation studies due to their high genetic and physiological similarity to humans. However, judging sexual maturity in captive RMs based on blood physiological indicators, female menstruation, and male ejaculation behavior can be inaccurate. Here, we explored changes in RMs before and after sexual maturation based on multi-omics analysis and identified markers for determining sexual maturity. We found that differentially expressed microbiota, metabolites, and genes before and after sexual maturation showed many potential correlations. Specifically, genes involved in spermatogenesis (TSSK2, HSP90AA1, SOX5, SPAG16, and SPATC1) were up-regulated in male macaques, and significant changes in gene (CD36), metabolites (cholesterol, 7-ketolithocholic acid, and 12-ketolithocholic acid), and microbiota (Lactobacillus) related to cholesterol metabolism were also found, suggesting the sexually mature males have stronger sperm fertility and cholesterol metabolism compared to sexually immature males. In female macaques, most differences before and after sexual maturity were related to tryptophan metabolism, including changes in IDO1, IDO2, IFNGR2, IL1Β, IL10, L-tryptophan, kynurenic acid (KA), indole-3-acetic acid (IAA), indoleacetaldehyde, and Bifidobacteria, indicating that sexually mature females exhibit stronger neuromodulation and intestinal immunity than sexually immature females. Cholesterol metabolism-related changes (CD36, 7-ketolithocholic acid, 12-ketolithocholic acid) were also observed in female and male macaques. Exploring differences before and after sexual maturation through multi-omics, we identified potential biomarkers of sexual maturity in RMs, including Lactobacillus (for males) and Bifidobacterium (for females) valuable for RM breeding and sexual maturation research.

Sodium selenite preserves rBM-MSCs' stemness, differentiation potential, and immunophenotype and protects them against oxidative stress via activation of the Nrf2 signaling pathway

BACKGROUND

The physiological level of reactive oxygen species (ROS) is necessary for many cellular functions. However, during the in-vitro manipulations, cells face a high level of ROS, leading to reduced cell quality. Preventing this abnormal ROS level is a challenging task. Hence, here we evaluated the effect of sodium selenite supplementation on the antioxidant potential, stemness capacity, and differentiation of rat-derived Bone Marrow MSCs (rBM-MSCs) and planned to check our hypothesis on the molecular pathways and networks linked to sodium selenite's antioxidant properties.

METHODS

MTT assay was used to assess the rBM-MSCs cells' viability following sodium selenite supplementation (concentrations of: 0.001, 0.01, 0.1, 1, 10 µM). The expression level of OCT-4, NANOG, and SIRT1 was explored using qPCR. The adipocyte differentiation capacity of MSCs was checked after Sodium Selenite treatment. The DCFH-DA assay was used to determine intracellular ROS levels. Sodium selenite-related expression of HIF-1α, GPX, SOD, TrxR, p-AKT, Nrf2, and p38 markers was determined using western blot. Significant findings were investigated by the String tool to picture the probable molecular network.

RESULTS

Media supplemented with 0.1 µM sodium selenite helped to preserve rBM-MSCs multipotency and keep their surface markers presentation; this also reduced the ROS level and improved the rBM-MSCs' antioxidant and stemness capacity. We observed enhanced viability and reduced senescence for rBM-MSCs. Moreover, sodium selenite helped in rBM-MSCs cytoprotection by regulating the expression of HIF-1 of AKT, Nrf2, SOD, GPX, and TrxR markers.

CONCLUSIONS

We showed that sodium selenite could help protect MSCs during in-vitro manipulations, probably via the Nrf2 pathway.

Exopolysaccharide of Enterococcus faecium L15 promotes the osteogenic differentiation of human dental pulp stem cells via p38 MAPK pathway

Background

Bone has important functions in the body. Several researchers have reported that the polysaccharides and lipopolysaccharide derived from microbes can promote osteogenic differentiation of stem cells. Enterococcus faecium, a lactic acid bacterium (LAB), produces several bioactive metabolites and has been widely applied in the food and nutraceutical industries. The exopolysaccharide (EPS) from LAB has also been extensively examined for its postbiotic effects and for its in vivo and in vitro functionalities. However, studies on promoting bone differentiation using polysaccharides from LAB are lacking. Therefore, the purpose of this study was to investigate the effect of E. faecium L15 extract and EPS on osteogenic differentiation of human dental pulp stem cells (hDPSCs) and to identify the underlying mechanisms.

Methods

hDPSCs were obtained from dental pulp tissue, and L15 extract and EPS were isolated from L15. Gene and protein expression of the osteogenic differentiation markers were analyzed with qPCR and western blotting and the possible signaling pathways were also investigated using western blotting. Osteogenic differentiation potential was examined by alkaline phosphatase (ALP) staining and alizarin red s (ARS) staining. In addition, osteogenic differentiation potential of L15 EPS was explored in ex vivo culture of neonate murine calvaria.

Results

The calcium deposition and ALP activity were enhanced by addition of L15 extract or EPS. The expression levels of RUNX2, ALP, and COL1A1 mRNA and the protein expression levels of RUNX2, ALP, and BMP4 were increased in hDPSCs treated with the L15 extract or EPS. The L15 EPS treatment enhanced phosphorylation of the p38 mitogen-activated protein kinase (MAPK). The L15 EPS-induced increases in RUNX2, ALP, and BMP4 expression were suppressed by the p38 MAPK inhibitor SB203580. The promoting effect of L15 EPS on osteogenic differentiation was not only seen in hDPSCs, but also in osteoblast precursors. ALP activity and the expression of RUNX2, ALP, and COL1A1 increased in the L15 EPS-treated osteoblast precursors. In addition, L15 EPS increased bone thickness of neonate murine calvaria in ex vivo culture.

Conclusions

The stimulatory effect of L15 extract and EPS on osteogenic differentiation occurred through the p38 MAPK pathway, and L15 EPS enhanced new bone formation in neonate murine calvaria. These data suggest that L15 EPS has therapeutic potential applicable to bone regeneration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03151-0.

Indole-3-Acetic Acid Alters Intestinal Microbiota and Alleviates Ankylosing Spondylitis in Mice

Ankylosing spondylitis (AS) is a systemic, chronic, and inflammatory autoimmune disease associated with the disorder of intestinal microbiota. Unfortunately, effective therapies for AS are lacking. Recent evidence has indicated that indole-3-acetic acid (IAA), an important microbial tryptophan metabolite, can modulate intestinal homeostasis and suppress inflammatory responses. However, reports have not examined the in vivo protective effects of IAA against AS. In this study, we investigated the protective effects and underlying mechanisms through which IAA acts against AS. We constructed a proteoglycan (PG)-induced AS mouse model and administered IAA (50 mg/kg body weight) by intraperitoneal injection daily for 4 weeks. The effects of IAA on AS mice were evaluated by examining disease severity, intestinal barrier function, aryl hydrocarbon receptor (AhR) pathway, T-helper 17 (Th17)/T regulatory (Treg) balance, and inflammatory cytokine levels. The intestinal microbiota compositions were profiled through whole-genome sequencing. We observed that IAA decreased the incidence and severity of AS in mice, inhibited the production of pro-inflammatory cytokines (tumor necrosis factor α [TNF-α], interleukin [IL]-6, IL-17A, and IL-23), promoted the production of the anti-inflammatory cytokine IL-10, and reduced the ratios of pro-/anti- inflammatory cytokines. IAA ameliorated pathological changes in the ileum and improved intestinal mucosal barrier function. IAA also activated the AhR pathway, upregulated the transcription factor forehead box protein P3 (FoxP3) and increased Treg cells, and downregulated the transcription factors retinoic acid receptor–related orphan receptor gamma t (RORγt) and signal transducer and activator of transcription 3 (STAT3) and decreased Th17 cells. Furthermore, IAA altered the composition of the intestinal microbiota composition by increasing Bacteroides and decreasing Proteobacteria and Firmicutes, in addition to increasing the abundances of Bifidobacterium pseudolongum and Mucispirillum schaedleri. In conclusion, IAA exerted several protective effects against PG-induced AS in mice, which was mediated by the restoration of balance among the intestinal microbial community, activating the AhR pathway, and inhibiting inflammation. IAA might represent a novel therapeutic approach for AS.

Effects of Dietary Indole-3-Acetate Sodium on Laying Performance, Egg Quality, Serum Hormone Levels and Biochemical Parameters of Danzhou Chickens

This study was conducted to investigate the effects of indole-3-acetate sodium (IAA-Na) inclusion in diets on the egg production performance, egg quality, intestinal tissue morphology, serum hormone levels and biochemical parameters of Danzhou chickens to preliminarily explore the efficacy of IAA-Na as a feed additive. A total of 192 Danzhou chickens (50 weeks old) were randomly assigned to 2 groups of 96. The diets for the treatment group consisted of the basal diets, supplemented with IAA-Na (200 mg/kg). The formal feeding trial lasted for four weeks. The results showed that the feed supplemented with IAA-Na not only increased the laying rate (p < 0.05) and egg yolk ratio (0.05 < p < 0.1), but also significantly reduced the feed:egg ratio (p < 0.05). In addition, the dietary supplementation of IAA-Na significantly increased the serum estradiol levels (p < 0.05) and decreased serum alkaline phosphatase activity (p < 0.05). Compared with the control group, the addition of IAA-Na to the diet had no significant effect on the intestinal tissue morphology or serum antioxidant capacity of Danzhou chickens. This study preliminarily provides evidence that dietary IAA-Na can improve laying performance, indicating that IAA-Na is a potentially effective feed additive for laying hens, but further studies are required before arriving at definite conclusions.

From Suppressor T cells to Regulatory T cells: How the Journey That Began with the Discovery of the Toxic Effects of TCDD Led to Better Understanding of the Role of AhR in Immunoregulation

Aryl hydrocarbon receptor (AhR) was identified in the early 1970s as a receptor for the ubiquitous environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin), which is a member of halogenated aromatic hydrocarbons (HAHs). TCDD was found to be highly toxic to the immune system, causing thymic involution and suppression of a variety of T and B cell responses. The fact that environmental chemicals cause immunosuppression led to the emergence of a new field, immunotoxicology. While studies carried out in early 1980s demonstrated that TCDD induces suppressor T cells that attenuate the immune response to antigens, further studies on these cells were abandoned due to a lack of specific markers to identify such cells. Thus, it was not until 2001 when FoxP3 was identified as a master regulator of Regulatory T cells (Tregs) that the effect of AhR activation on immunoregulation was rekindled. The more recent research on AhR has led to the emergence of AhR as not only an environmental sensor but also as a key regulator of immune response, especially the differentiation of Tregs vs. Th17 cells, by a variety of endogenous, microbial, dietary, and environmental ligands. This review not only discusses how the role of AhR emerged from it being an environmental sensor to become a key immunoregulator, but also confers the identification of new AhR ligands, which are providing novel insights into the mechanisms of Treg vs. Th17 differentiation. Lastly, we discuss how AhR ligands can trigger epigenetic pathways, which may provide new opportunities to regulate inflammation and treat autoimmune diseases.

Bacterial Natural Compounds with Anti-Inflammatory and Immunomodulatory Properties (Mini Review)

Inflammation is part of the body's complex biological response to harmful stimuli such as damaged cells, pathogens, or irritants. It is a protective response involving blood cells, immune cells, and molecular mediators. The inflammation not only can eliminate the primary cause of cell injury but also clears out necrotic cells, tissue damaged from the original insults and inflammatory process. Furthermore, it can initiate tissue repair. Pro-inflammatory cytokines are produced predominantly by activated macrophages and are involved in the up-regulation of inflammatory reactions. They are involved in further regulating inflammatory reactions. There is ample evidence that some pro-inflammatory cytokines, such as interleukin 1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α), are involved in the pathological pain process. Some of the natural compounds promote cytokines production and inhibit inflammatory responses. The natural compounds which are produced from microorganisms such as omega-3 fatty acid, cyclic peptide, antimicrobial peptide, oligosaccharides, and polysaccharides can reduce inflammation and could be easily incorporated into the diet without any adverse effects. For example, SCFA (short-chain fatty acids), peptide bacteriocin, and polycyclic peptide bacteriocin (nisin) could be used in the treatment of atherosclerosis, orthopedic postoperative infections, and mycobacterium tuberculosis infection, respectively. Also, fatty acids (saturated and unsaturated fatty acids) can be introduced as anti-inflammatory drugs. This review article summarizes bacterial natural compounds with modulating effects on cytokines that are surveyed which may have potential anti-inflammatory drug-like activity.

Anti-Inflammatory and Anti-Oxidative Activity of Indole-3-Acetic Acid Involves Induction of HO-1 and Neutralization of Free Radicals in RAW264.7 Cells

The cellular and molecular mechanisms by which indole-3-acetic acid (IAA), a tryptophan-derived metabolite from gut microbiota, attenuates inflammation and oxidative stress has not been fully elucidated. The present study was to unearth the protective effect and underlying mechanism of IAA against lipopolysaccharide (LPS)-induced inflammatory response and free radical generation in RAW264.7 macrophages. IAA significantly ameliorated LPS-induced expression of interleukin-1β (IL-1β), interleukin-6 (IL-6), and monocyte chemoattractant protein-1 (MCP-1) as well as generation of reactive oxidative species (ROS) and nitric oxide (NO). LPS-triggered nuclear translocation of nuclear factor kappa B (NF-κB) p65 was mitigated by IAA treatment. Further, an up-regulation of heme oxygenase-1 (HO-1) was observed in IAA-treated cells in dose-dependent manner under both normal and LPS-stimulated condition. Interference of HO-1 activity by tin protoporphyrin IX (SnPP) impeded the alleviative effects of IAA on expression of IL-1β and IL-6 induced by LPS, whereas demonstrated no effect on its suppression of ROS and NO production. This result suggests a HO-1-dependent anti-inflammatory effect of IAA and its direct scavenging action on free radicals. Treatment with CH-223191, a specific antagonist of aryl hydrocarbon receptor (AhR), showed no significant effects on the beneficial role of IAA against inflammation and free radical generation. In summary, our findings indicate that IAA alleviates LPS-elicited inflammatory response and free radical generation in RAW264.7 macrophages by induction of HO-1 and direct neutralization of free radicals, a mechanism independent of AhR.

Indole-3-Acetic Acid Alleviates Nonalcoholic Fatty Liver Disease in Mice via Attenuation of Hepatic Lipogenesis, and Oxidative and Inflammatory Stress

Recent evidences have linked indole-3-acetic acid (IAA), a gut microbiota-derived metabolite from dietary tryptophan, with the resistance to liver diseases. However, data supporting IAA-mediated protection against nonalcoholic fatty liver disease (NAFLD) from an in vivo study is lacking. In this study, we assessed the role of IAA in attenuating high-fat diet (HFD)-induced NAFLD in male C57BL/6 mice. Administration of IAA (50 mg/kg body weight) by intraperitoneal injection was found to alleviate HFD-induced elevation in fasting blood glucose and homeostasis model assessment of insulin resistance (HOMA-IR) index as well as plasma total cholesterol, low-density lipoprotein cholesterol (LDL-C), and glutamic-pyruvic transaminase (GPT) activity. Histological examination further presented the protective effect of IAA on liver damage induced by HFD feeding. HFD-induced an increase in liver total triglycerides and cholesterol, together with the upregulation of genes related to lipogenesis including sterol regulatory element binding-protein 1 (Srebf1), steraroyl coenzyme decarboxylase 1 (Scd1), peroxisome proliferator-activated receptor gamma (PPARγ), acetyl-CoA carboxylase 1 (Acaca), and glycerol-3-phosphate acyltransferase, mitochondrial (Gpam), which were mitigated by IAA treatment. The results of reactive oxygen species (ROS) and malonaldehyde (MDA) level along with superoxide dismutase (SOD) activity and glutathione (GSH) content in liver tissue evidenced the protection of IAA against HFD-induced oxidative stress. Additionally, IAA attenuated the inflammatory response of liver in mice exposed to HFD as shown by the reduction in the F4/80-positive macrophage infiltration and the expression of monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-α (TNF-α). In conclusion, our findings uncover that IAA alleviates HFD-induced hepatotoxicity in mice, which proves to be associated with the amelioration in insulin resistance, lipid metabolism, and oxidative and inflammatory stress.

2,4-D causes oxidative stress induction and apoptosis in human dental pulp stem cells (hDPSCs)

2,4-Dicholorophenoxy acetic acid (2,4-D) is a worldwide used hormone herbicide. Human dental pulp stem cells (hDPSCs) as a potential source of mesenchymal stem cells provide a confident model system for the assessments of chemicals in vitro. The main objective of this study was to examine the biological effects and damages attributed to 2,4-D on hDPSCs. hDPSCs were isolated from third molar pulp tissues and their mesenchymal identity were evaluated. Then, hDPSCs were treated with increasing concentrations of 2,4-D (0.1 μM-10 mM). Cell viability assay and cumulative cell counting were carried out to address 2,4-D effects on biological parameters of hDPSCs. Cell cycle distribution, ROS level and ALP activity were measured before and after treatment. AO/EB staining and caspase 3/7 activity were investigated to detect the possible mechanisms of cell death. Flow-cytometric immunophenotyping and differentiation data confirmed the mesenchymal identity of cultivated hDPSCs. 2,4-D treatment caused a hormetic response in the viability and growth rate of hDPSCs. G0/G1 cell cycle arrest, enhanced ROS level, and reduced ALP activity were detected in hDPSCs treated with EC50 dose of 2,4-D. AO/EB staining showed a higher percentage of alive cells in lower concentrations of the herbicide. The increment in 2,4-D dose and the number of early and late apoptotic cells were increased. DAPI staining and caspase 3/7 assay validated the induction of apoptosis. 2,4-D concentrations up to 100 μM did not affect hDPSCs viability and proliferation. The intense cellular oxidative stress and apoptosis were observed at higher concentration.

Establishing a role for environmental toxicant exposure induced epigenetic remodeling in malignant transformation

Humans are exposed to a wide variety of environmental exposures throughout their lifespan. These include both naturally occurring toxins and chemical toxicants like pesticides, herbicides, and industrial chemicals, many of which have been implicated as possible contributors to human disease susceptibility [1-3]. We, and others, have hypothesized that environmental exposures may cause adaptive epigenetic changes in regenerative cell populations and developing organisms, leading to abnormal gene expression and increased disease susceptibility later in life [3]. Common epigenetic changes include changes in miRNA expression, covalent histone modifications, and methylation of DNA. Importantly, due to their heritable nature, abnormal epigenetic modifications which occur within stem cells may be particularly deleterious. Abnormal epigenetic changes in regenerative cell linages can be passed onto a large population of daughter cells and can persist for long periods of time. It is well established that an accumulation of epigenetic changes can lead to many human diseases including cancer [4-6]. Subsequently, it is imperative that we increase our understanding of how common environmental toxins and toxicants can induce epigenetic changes, particularly in stem cell populations. In this review, we will discuss how common environmental exposures in the United States and around the world may lead to epigenetic changes and discuss potential links to human disease, including cancer.

Save your gut save your age: The role of the microbiome in stem cell ageing

The tremendous importance of microbiota in microbial homoeostasis, alterations in metabolism and both innate and adaptive immune systems has been well established. A growing body of evidence support that dysbiosis or compositional changes in gut microbiota is linked to the ageing of stem cells in terms of dysregulations of metabolism, aberrant activation of the immune system as well as promoting epigenetic instability of stem cell. In this concise review, we elucidate recent emerging topics on microbiotic alterations and underlying mechanisms in stem cell ageing.

The Importance of Yeasts on Fermentation Quality and Human Health-Promoting Compounds

Non-Saccharomyces are important during wine fermentation once they influence wine composition. In the early stages of wine fermentation, and together with indigenous or commercial strains of Saccharomyces cerevisiae, non-Saccharomyces are able to transform grape-must sugars into ethanol, CO2, and other important secondary metabolites. A better understanding of yeast biochemistry will allow the selection of yeast strains that have defined specific influences on fermentation efficiency, wine quality, and the production of human health-promoting compounds. Yeast metabolism produces compounds derived from tryptophan, melatonin, and serotonin, which are found in fermented beverages, such as wine and beer. Melatonin is a neurohormone secreted from the pineal gland and has a wide-ranging regulatory and neuroprotective role, while serotonin, as well as being a precursor of melatonin synthesis, is also a neurotransmitter. This review summarizes the importance of some conventional and nonconventional yeast strains’ alcoholic fermentations, especially in the production of metabolites that promote human health and thus, attract consumers attention towards fermented beverages. A brief reference is also made on fermented beverages containing probiotics, namely kombucha, also known as kombucha tea, and its interesting microorganism’s symbiotic relationships named SCOBY.

Total C-21 steroidal glycosides, isolated from the root tuber of Cynanchum auriculatum Royle ex Wight, attenuate hydrogen peroxide-induced oxidative injury and inflammation in L02 cells

Oxidative stress plays an important role in the pathology of liver disorders. Total C-21 steroidal glycosides (TCSGs), isolated from the root tuber of Cynanchum auriculatum Royle ex Wight, have been reported to exert numerous effects, including liver protective and antioxidant effects. In order to investigate the potential mechanisms underlying the protective effects of TCSGs on liver function, the present study used the human normal liver cell line, L02, to evaluate the effects of TCSGs on hydrogen peroxide (H₂O₂)-induced oxidative injury and inflammatory responses. The L02 cells were pretreated with various concentrations of TCSGs, followed by exposure to 1.5 mM H₂O₂. Cell viability was determined by a 3-(4,5-dimethylthiazol-2-yl)-2,5-di-phenyltetrazolium bromide (MTT) assay. The levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and nitric oxide (NO) were measured using colorimetric assays. The activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and the production of malondialdehyde (MDA) were also determined. Intracellular reactive oxygen species (ROS) levels were detected using a fluorescent probe. H₂O₂-induced oxidative toxicity was attenuated following treatment with TCSGs, as indicated by the increase in cell viability, the decreased levels of ALT, AST, LDH, NO, MDA and ROS, and the increased activities of SOD, CAT and GSH-Px. To further explore the possible mechanisms of action of TCSGs, the nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor-κB (NF)-κB pathways were examined. The results revealed that treatment with TCSGs markedly induced Nrf2 nuclear translocation and upregulated the expression of heme oxygenase-1 (HO-1) in the L02 cells damaged by H₂O₂. In addition, pretreatment with TCSGs inhibited the NF-κB signaling pathway by blocking the degradation of the inhibitor of nuclear factor κBα (IκBα), thereby reducing the expression and nuclear translocation of NF-κB, as well as reducing the expression of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2). On the whole, the findings of this study demonstrate that TCSGs can protect L02 cells against H₂O₂-induced oxidative toxicity and inflammatory injury by increasing the expression of Nrf2 and HO-1, mediated by the NF-κB signaling pathway.