Influence of indole acetic acid on antioxidant levels and enzyme activities of glucose metabolism in rat liver

Exploring the biological impact of bacteria-derived indole compounds on human cell health: Cytotoxicity and cell proliferation across six cell lines

Over the past two decades, research has increasingly focused on the interactions between diet, gut microbiota, and host organisms. Recent evidence suggests that tryptophan, an essential amino acid, can be metabolized by gut microbiota into indoles, which have significant biological effects. However, most research is limited to indole and its liver metabolite, indoxyl sulfate. This study examines the cytotoxic effects of five indole derivatives - indole-3-carboxylic acid (I3CA), indole-3-aldehyde (I3A), indole-3-acetic acid (IAA), indole-3-propionic acid (IPA), and 3-methylindole (skatole, 3-MI) - on six human cell lines: adipose-derived mesenchymal stem cells (MSC), hepatocellular carcinoma (HepG2), liver progenitor cells (HepaRG), colorectal carcinoma cells (Caco-2), breast cancer cells (T47D), and lung fibroblast (MRC-5). Results show no sensitivity to indole itself across cell lines. MRC-5 was sensitive to all other compounds (EC50 0.52-49.8 µM). MSCs responded to IPA, I3CA, I3A, and 3-MI (EC50 0.33-1.87 µM), while HepaRG cells were affected by IAA, I3CA, I3A, and 3-MI (EC50 1.98-66.4 µM). T47D cells were sensitive to IPA and IAA, and Caco-2 cells only to IAA (EC50 2.02, 1.68, 0.52 µM, respectively). HepG2 cells showed no change in viability. AhR activation in HepG2-AhR-Lucia cells was triggered by all derivatives, particularly I3A, IPA, and I3CA. Growth experiments revealed I3CA decreased Caco-2 proliferation while increasing T47D proliferation. The findings suggest indole derivatives are generally non-cytotoxic to carcinomas but may adversely affect stem cells, with effects varying across cell lines.

Indole-3-acetic acid and chenodeoxycholic acid attenuate TLR4/NF-κB signaling and endoplasmic reticulum stress in valproic acid-induced neurotoxicity

Valproic acid (VA) is a commonly prescribed medication for epilepsy and other neurological conditions. Although effective, VA use can lead to neurotoxicity, especially with chronic use. This study aimed to investigate the potential neuroprotective properties of indole-3-acetic acid (IAA) and chenodeoxycholic acid (CDCA) in an animal model of VA-induced brain injury. Rats received intraperitoneal injections of VA at a dose of 500 mg/kg/day for 3 weeks. Concurrently, they were orally treated with IAA (40 mg/kg/day) and/or CDCA (90 mg/kg/day). The results showed significantly increased oxidative stress and inflammation markers in the VA-exposed group indicated by the reduced levels of glutathione (GSH, P < 0.0001) and superoxide dismutase (SOD, P < 0.01) and the elevated inflammatory cytokines Interleukin-6 (IL-6, P < 0.0001) and tumor necrosis factor-alpha (TNFα, P < 0.01). VA also induced nuclear factor kappa B (NF-κB, P < 0.01), toll-like receptor 4 (TLR4, P < 0.05), and endoplasmic reticulum (ER) stress markers, as evidenced by increased immunoreactivity of GRP78 (glucose-regulated protein 78, P < 0.0001), transcription factor 6 (ATF-6, P < 0.05) and CHOP (C/EBP homologous protein, P < 0.0001). Treatment with IAA or CDCA attenuated VA-induced neurotoxicity, to a variable extent, by improving oxidative, inflammatory, and ER stress markers. This study demonstrates that IAA and CDCA exert protective effects against VA-induced neurotoxicity by mitigating oxidative stress, inflammation, and ER stress. Further investigations are recommended to validate these findings in other neurotoxicity models.

Relationship Between the Salivary Microbiome and Oral Malodor Metabolites in Older Thai Individuals with Periodontitis and the Cytotoxic Effects of Malodor Compounds on Human Oral Squamous Carcinoma (HSC-4) Cells

Background/Objectives: Halitosis is primarily caused by the activity of oral microorganisms. In this study, we employed metagenomic sequencing and metabolomic approaches to investigate the differences in salivary microbiota and metabolite profiles between individuals with halitosis and periodontitis and healthy controls. Additionally, we expanded the study to examine how oral malodorous compounds interact with human oral squamous carcinoma (HSC-4) cells. Methods: Saliva samples were collected and analyzed using Ultra-High Performance Liquid Chromatography-Mass Spectrometry (UHPLC-MS) to identify metabolites. We then assessed the correlations between the microbiota and metabolites. Furthermore, the impact of oral malodorous substances on HSC-4 cells was investigated by evaluating apoptosis, antioxidant activity, and inflammatory properties. Results: The microbiota and metabolite profiles showed significant differences between the halitosis with periodontitis group and the periodontally healthy group. The halitosis with periodontitis group exhibited significantly higher relative abundances of eight genera: Tannerella, Selenomonas, Bacteroides, Filifactor, Phocaeicola, Fretibacterium, Eubacterium saphenum, and Desulfobulbus. In contrast, the periodontally healthy group showed significantly higher relative abundances of Family XIII UCG-001, Haemophilus, and Streptobacillus. Two metabolites, 2,3-dihydro-1H-indole and 10,11-dihydro-12R-hydroxy-leukotriene E4, were significantly higher in individuals with halitosis and periodontitis. In the treatment of HSC-4 cells with metabolites, dimethyl sulfide (DMS) did not show significant effects while indole appeared to induce cell death in HSC-4 cells by triggering apoptotic pathways. Additionally, both indole and DMS affected the inflammatory and antioxidant properties of HSC-4 cells. Conclusions: This study provides insights into the mechanisms of halitosis by exploring the correlations between microbiota and metabolite profiles. Furthermore, oral metabolites were shown to impact the cellular response of HSC-4 cells.

Gut microbiota-derived tryptophan metabolites regulated by Wuji Wan to attenuate colitis through AhR signaling activation

Disruption of the intestinal mucosal barrier caused by gut dysbiosis and metabolic imbalance is the underlying pathology of inflammatory bowel disease (IBD). Traditional Chinese medicine Wuji Wan (WJW) is commonly used to treat digestive system disorders and showed therapeutic potential for IBD. In this interdisciplinary study, we aim to investigate the pharmacological effects of WJW against experimental colitis by combining functional metabolomics and gut-microbiota sequencing techniques. Treatment with WJW altered the profile of the intestinal microbiota and notably increased the abundance of Lactobacillus, thereby facilitating the conversion of tryptophan into indole-3-acetic acid (IAA) and indoleacrylic acid (IA). These indole derivatives activated the aryl hydrocarbon receptor (AhR) pathway, which reduced colonic inflammation and restored the expression of intestinal barrier proteins. Interestingly, the beneficial effects of WJW on gut barrier function improvement and tryptophan metabolism were disappeared in the absence of gut microbiota. Finally, pre-treatment with the AhR antagonist CH-223191 confirmed the essential role of IAA-mediated AhR activation in the therapeutic effects of WJW. Overall, WJW enhanced intestinal barrier function and reduced colonic inflammation in a murine colitis model by modulating Lactobacillus-IAA-AhR signaling pathway. This study provides novel insights into colitis pathogenesis and presents an effective therapeutic and preventive approach against IBD.

Role of Nrf2/HO-1 and cytoglobin signaling in the protective effect of indole-3-acetic acid and chenodeoxycholic acid against kidney injury induced by valproate

Background

Purpose: Valproate (VPA) is an antiepileptic drug widely used to treat various psychiatric and neurological disorders. Although its use is generally considered safe, chronic administration may lead to kidney injury. The mechanisms underlying VPA kidney toxicity are not entirely explored. This has prompted our investigation into a novel molecular signaling pathway involved in VPA-induced kidney injury and the exploration of strategies to ameliorate this toxicity using indole-3-acetic acid (IAA) and chenodeoxycholic acid (CDCA).

Methods

Rats were divided as follows: group I (control); group II (VPA group), where rats were administered VPA (500 mg/kg, i.p.) daily to induce kidney injury for 3 weeks; and groups III and IV, where rats were orally treated with either IAA (40 mg/kg) or CDCA (90 mg/kg), respectively, 1h post-VPA dose, for 3 weeks. The effects of these compounds on kidney tissues were evaluated with a focus on their antioxidant and anti-inflammatory properties using biochemical, histopathological, and immunohistochemical analyses.

Results

VPA caused a significant reduction in renal glutathione (GSH) and heme oxygenase-1 (HO-1) levels, and superoxide dismutase (SOD) activity, along with a significant elevation in malondialdehyde (MDA) levels. Similarly, tumor necrosis factor-α (TNF-α), interleukin-1beta (IL-1β), and interleukin-6 (IL-6) levels were significantly increased. Immunohistochemical analysis demonstrated a significant decline in the immunoreactivity of nuclear factor erythroid 2-related factor (Nrf2) and cytoglobin antigens in renal cells. However, administration of either IAA or CDCA significantly ameliorated these altered parameters, including Nrf2/HO-1 and cytoglobin levels.

Conclusion

IAA and CDCA alleviated the kidney injury induced by VPA via downregulating the inflammatory response and upregulating the antioxidant capacity in renal tissue.

Indole-3-acetic acid exposure leads to cardiovascular inflammation and fibrosis in chronic kidney disease rat model

Indole-3-acetic acid (IAA), a protein-bound uremic toxin, has been linked to cardiovascular morbidity and mortality in chronic kidney disease (CKD) patients. This study explores the influence of IAA (125 mg/kg) on cardiovascular changes in adenine sulfate-induced CKD rats. HPLC analysis revealed that IAA-exposed CKD rats had lower excretion and increased circulation of IAA compared to both CKD and IAA control groups. Moreover, echocardiography indicated that CKD rats exposed to IAA exhibited heart enlargement, thickening of the myocardium, and cardiac hypertrophy in contrast to CKD or IAA control group. Biochemical analyses supported the finding that IAA-induced CKD rats had elevated serum levels of c-Tn-I, CK-MB, and LDH; there was also evidence of oxidative stress in cardiac tissues, with a significant decrease in SOD and CAT levels, as well as an increase in MDA levels. The gene expression analysis found significant increases in ANP, BNP, β-MHC, TNF-α, IL-1β, and NF-κB levels in IAA-exposed CKD groups in contrast to the CKD or IAA control group. In addition, higher cardiac fibrosis markers, including Col-I and Col-III. The findings of this study indicate that IAA could trigger cardiovascular inflammation and fibrosis in CKD conditions.

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.

Emergence of an Auxin Sensing Domain in Plant-Associated Bacteria

Bacteria have evolved a sophisticated array of signal transduction systems that allow them to adapt their physiology and metabolism to changing environmental conditions. Typically, these systems recognize signals through dedicated ligand binding domains (LBDs) to ultimately trigger a diversity of physiological responses. Nonetheless, an increasing number of reports reveal that signal transduction receptors also bind antagonists to inhibit responses mediated by agonists. The mechanisms by which antagonists block the downstream signaling cascade remain largely unknown. To advance our knowledge in this field, we used the LysR-type transcriptional regulator AdmX as a model. AdmX activates the expression of an antibiotic biosynthetic cluster in the rhizobacterium Serratia plymuthica. AdmX specifically recognizes the auxin phytohormone indole-3-acetic acid (IAA) and its biosynthetic intermediate indole-3-pyruvic acid (IPA) as signals. However, only IAA, but not IPA, was shown to regulate antibiotic production in S. plymuthica. Here, we report the high-resolution structures of the LBD of AdmX in complex with IAA and IPA. We found that IAA and IPA compete for binding to AdmX. Although IAA and IPA binding does not alter the oligomeric state of AdmX, IPA binding causes a higher degree of compactness in the protein structure. Molecular dynamics simulations revealed significant differences in the binding modes of IAA and IPA by AdmX, and the inspection of the three-dimensional structures evidenced differential agonist- and antagonist-mediated structural changes. Key residues for auxin binding were identified and an auxin recognition motif defined. Phylogenetic clustering supports the recent evolutionary emergence of this motif specifically in plant-associated enterobacteria. IMPORTANCE Although antagonists were found to bind different bacterial signal transduction receptors, we are still at the early stages of understanding the molecular details by which these molecules exert their inhibitory effects. Here, we provide insight into the structural changes resulting from the binding of an agonist and an antagonist to a sensor protein. Our data indicate that agonist and antagonist recognition is characterized by small conformational differences in the LBDs that can be efficiently transmitted to the output domain to modulate the final response. LBDs are subject to strong selective pressures and are rapidly evolving domains. An increasing number of reports support the idea that environmental factors drive the evolution of sensor domains. Given the recent evolutionary history of AdmX homologs, as well as their narrow phyletic distribution within plant-associated bacteria, our results are in accordance with a plant-mediated evolutionary process that resulted in the emergence of receptor proteins that specifically sense auxin phytohormones.

Synthesis, Drug-Likeness Evaluation of Some Heterocyclic Moieties Fused Indole Derivatives as Potential Antioxidants

BACKGROUND

Indole and its derivatives have a wide range of pharmacological effects, including analgesic, antimicrobial, antidepressant, anti-diabetic, anti-convulsant, anti-helminthic, and anti-inflammatory properties. They are crucial structural components of many of today's powerful antioxidant medications.

OBJECTIVE

Using the Schotten-Baumann reaction, the indole ring was linked to other key heterocyclic moieties such as morpholine, imidazole, piperidine, and piperazine at the active 3rd position and then tested for antioxidant activity.

METHODS

Synthesis of derivatives was accomplished under appropriate conditions and characterized by IR, NMR (1H and 13C), and mass spectrum. Using the Swiss ADME online application, ADME properties were also determined. The in vitro antioxidant activity was measured using DPPH and Reducing power method.

RESULTS

In the DPPH assay, compounds 5a (IC50=1.01±0.22 μg/mL), 5k (IC50=1.21 ± 0.07 μg/mL), whereas compounds 5a (EC50=23 ± 1.00 μg/mL), 5h (EC50=26±2.42 μg/mL) in the reducing power assay were most potent as compared with standard Ascorbic acid. Compounds 5a, 5h, and 5k demonstrated maximal potency equivalent to standard. Lipinski's rule was followed in ADME outcomes.

CONCLUSION

The synthesis and evaluation of indole derivatives to investigate their antioxidant action has received a lot of attention. These discoveries could lead to more effective antioxidant candidates being designed and developed.

A bacterial chemoreceptor that mediates chemotaxis to two different plant hormones

Indole-3-acetic acid (IAA) is the main naturally occurring auxin and is produced by organisms of all kingdoms of life. In addition to the regulation of plant growth and development, IAA plays an important role in the interaction between plants and growth-promoting and phytopathogenic bacteria by regulating bacterial gene expression and physiology. We show here that an IAA metabolizing plant-associated Pseudomonas putida isolate exhibits chemotaxis to IAA that is independent of auxin metabolism. We found that IAA chemotaxis is based on the activity of the PcpI chemoreceptor and heterologous expression of pcpI conferred IAA taxis to different environmental and human pathogenic isolates of the Pseudomonas genus. Using ligand screening, microcalorimetry and quantitative chemotaxis assays, we found that PcpI failed to bind IAA directly, but recognized and mediated chemoattractions to various aromatic compounds, including the phytohormone salicylic acid. The expression of pcpI and its role in the interactions with plants was also investigated. PcpI extends the range of central signal molecules recognized by chemoreceptors. To our knowledge, this is the first report on a bacterial receptor that responds to two different phytohormones. Our study reinforces the multifunctional role of IAA and salicylic acid as intra- and inter-kingdom signal molecules.

An auxin controls bacterial antibiotics production

The majority of clinically used antibiotics originate from bacteria. As the need for new antibiotics grows, large-scale genome sequencing and mining approaches are being used to identify novel antibiotics. However, this task is hampered by the fact that many antibiotic biosynthetic clusters are not expressed under laboratory conditions. One strategy to overcome this limitation is the identification of signals that activate the expression of silent biosynthetic pathways. Here, we report the use of high-throughput screening to identify signals that control the biosynthesis of the acetyl-CoA carboxylase inhibitor antibiotic andrimid in the broad-range antibiotic-producing rhizobacterium Serratia plymuthica A153. We reveal that the pathway-specific transcriptional activator AdmX recognizes the auxin indole-3-acetic acid (IAA). IAA binding causes conformational changes in AdmX that result in the inhibition of the expression of the andrimid cluster and the suppression of antibiotic production. We also show that IAA synthesis by pathogenic and beneficial plant-associated bacteria inhibits andrimid production in A153. Because IAA is a signalling molecule that is present across all domains of life, this study highlights the importance of intra- and inter-kingdom signalling in the regulation of antibiotic synthesis. Our discovery unravels, for the first time, an IAA-dependent molecular mechanism for the regulation of antibiotic synthesis.

Biochemical and Clinical Impact of Organic Uremic Retention Solutes: A Comprehensive Update

In this narrative review, the biological/biochemical impact (toxicity) of a large array of known individual uremic retention solutes and groups of solutes is summarized. We classified these compounds along their physico-chemical characteristics as small water-soluble compounds or groups, protein bound compounds and middle molecules. All but one solute (glomerulopressin) affected at least one mechanism with the potential to contribute to the uremic syndrome. In general, several mechanisms were influenced for each individual solute or group of solutes, with some impacting up to 7 different biological systems of the 11 considered. The inflammatory, cardio-vascular and fibrogenic systems were those most frequently affected and they are one by one major actors in the high morbidity and mortality of CKD but also the mechanisms that have most frequently been studied. A scoring system was built with the intention to classify the reviewed compounds according to the experimental evidence of their toxicity (number of systems affected) and overall experimental and clinical evidence. Among the highest globally scoring solutes were 3 small water-soluble compounds [asymmetric dimethylarginine (ADMA); trimethylamine-N-oxide (TMAO); uric acid], 6 protein bound compounds or groups of protein bound compounds [advanced glycation end products (AGEs); p-cresyl sulfate; indoxyl sulfate; indole acetic acid; the kynurenines; phenyl acetic acid;] and 3 middle molecules [β₂-microglobulin; ghrelin; parathyroid hormone). In general, more experimental data were provided for the protein bound molecules but for almost half of them clinical evidence was missing in spite of robust experimental data. The picture emanating is one of a complex disorder, where multiple factors contribute to a multisystem complication profile, so that it seems of not much use to pursue a decrease of concentration of a single compound.

Metabolite of tryptophan promoting changes in EEG signal and the oxidative status of the brain

Tryptophan is an essential amino acid precursor of neurotransmitter serotonin and triptamine. During its metabolism, indole-3-acetic acid (IAA) is generated; this substance presents both antioxidant and prooxidant effects in different biological systems in addition to hipoglicemic effects. To date, electroencephalography (EEG) has been used to evaluate the temporal effect of several substances in neurotransmission. The goal of this study was to characterize the effect of IAA in the brain by analysing the EEG signal and evaluate the oxidative status by means of biochemical parameters. The EEG was acquired by using a noninvasive method, and the brain electric signal was analysed by advanced digital signal processing techniques to determinate the energy signal filtered in different band frequencies. Furthermore, the oxidative status of the brain was investigated by measuring the activity of antioxidant enzymes and lipid peroxidation as well as blood glucose rates of the animals treated with different doses of IAA. Our results showed the relationship of IAA administration with changes in EEG signals. The oxidative status of the brain was modified by IAA after 14 days of treatment.

Synthesis, Antioxidant, Antimicrobial, Antimycobacterial, and Cytotoxic Activities of Azetidinone and Thiazolidinone Moieties Linked to Indole Nucleus

2-N-(2-Phenyl-1H-indol-3-yl)imino-4-arylthiazoles (3a–c) were used as key synthons for the preparation of (4-arylthiazol-2-yl)-4-(2-phenyl-1H-indol-3-yl)azetidin-2-ones (4a–c) and 3-(4-arylthiazol-2-yl)-2-(2-phenyl-1H-indol-3-yl)thiazolidin-4-ones (5a–c). These newly synthesized compounds have been characterized with the help of IR,1H NMR,13C NMR, and mass spectral studies. All compounds were screened for their antioxidant, antimicrobial, antimycobacterial, and cytotoxic activities. Some of the compounds displayed excellent activity.

Protective action of indole-3-acetic acid on induced hepatocarcinoma in mice

In this study, we report the protective effects of IAA on diethylnitrosamine (DEN)-induced hepatocarcinogenesis. BALB/c mice received daily IAA at 50 (T(50)), 250 (T(250)), and 500 (T(500)) mg Kg(-1) per body mass by gavage for 15 days. At day 15, animals were administered DEN and sacrificed 4 h later. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were analyzed in sera. In addition, hepatomorphologic alterations, activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR), gene expression of antioxidant enzymes and DNA integrity were evaluated in the liver. IAA administration did not show any alterations in any of the parameters available, except for a reduction of the gene expression for antioxidant enzymes by 55, 56, 27, and 28% for SOD, CAT, GPx, and GR upon T(500), respectively compared with the control. Several hepatic alterations were observed by DEN exposure. Moreover, IAA administration at 3 doses was shown to provide a total prevention of the active reduction of CAT and GR induced by DEN exposure compared with the control. IAA at T(500) was shown to give partial protection (87, 71, 57, and 90% for respectively SOD, CAT, GPx, and GR) on the down-regulation of the enzymes induced by DEN and this auxin showed a partial protection (50%) on DEN-induced DNA fragmentation for both parameters when compared to DEN alone. This work showed IAA hepatocarcinogenesis protection for the first time by means of a DEN-protective effect on CAT and GR activity, and by affecting antioxidant gene expression and DNA fragmentation.