Gut bacterial quorum sensing molecules and their association with inflammatory bowel disease: Advances and future perspectives.

Inflammatory Bowel Disease (IBD) is an enduring inflammatory disease of the gastrointestinal tract (GIT). The complexity of IBD, its profound impact on patient's quality of life, and its burden on healthcare systems necessitate continuing studies to elucidate its etiology, refine care strategies, improve treatment outcomes, and identify potential targets for novel therapeutic interventions. The discovery of a connection between IBD and gut bacterial quorum sensing (QS) molecules has opened exciting opportunities for research into IBD pathophysiology. QS molecules are small chemical messengers synthesized and released by bacteria based on population density. These chemicals are sensed not only by the microbial species but also by host cells and are essential in gut homeostasis. QS molecules are now known to interact with inflammatory pathways, therefore rendering them potential therapeutic targets for IBD management. Given these intriguing developments, the most recent research findings in this area are herein reviewed. First, the global burden of IBD and the disruptions of the gut microbiota and intestinal barrier associated with the disease are assessed. Next, the general QS mechanism and signaling molecules in the gut are discussed. Then, the roles of QS molecules and their connection with IBD are elucidated. Lastly, the review proposes potential QS-based therapeutic targets for IBD, offering insights into the future research trajectory in this field.

Smartphone digital image colorimetry for quantification of serum proteins.

Colorimetric determination of proteins in serum is proposed based on the biuret method and replacing ultraviolet-visible spectrometric (UV-Vis) detection with a simple and affordable smartphone digital image colorimetric (SDIC) method. Optimum SDIC conditions were found as a detection wavelength of 555 nm, a region of interest of 1600 px2, and 9.0 cm between the detection camera and sample solution. Under the optimum conditions, the coefficient of determination was 0.9982 within a linear dynamic range of 0.022 to 0.35 g dL-1. The precision of the method based on the percent relative standard deviation was below 5%. The limit of detection and limit of quantitation were found to be 0.007 and 0.022 g dL-1 respectively, which were sufficient for the quantification of the total protein, albumin, and globulin in serum. The method was validated with an independent experiment using a UV-Vis method and both methods showed good statistical agreement, indicating the accuracy of the proposed SDIC method.

Conversations in the Gut: The Role of Quorum Sensing in Normobiosis.

An imbalance in gut microbiota, termed dysbiosis, has been shown to affect host health. Several factors, including dietary changes, have been reported to cause dysbiosis with its associated pathologies that include inflammatory bowel disease, cancer, obesity, depression, and autism. We recently demonstrated the inhibitory effects of artificial sweeteners on bacterial quorum sensing (QS) and proposed that QS inhibition may be one mechanism behind such dysbiosis. QS is a complex network of cell-cell communication that is mediated by small diffusible molecules known as autoinducers (AIs). Using AIs, bacteria interact with one another and coordinate their gene expression based on their population density for the benefit of the whole community or one group over another. Bacteria that cannot synthesize their own AIs secretly "listen" to the signals produced by other bacteria, a phenomenon known as "eavesdropping". AIs impact gut microbiota equilibrium by mediating intra- and interspecies interactions as well as interkingdom communication. In this review, we discuss the role of QS in normobiosis (the normal balance of bacteria in the gut) and how interference in QS causes gut microbial imbalance. First, we present a review of QS discovery and then highlight the various QS signaling molecules used by bacteria in the gut. We also explore strategies that promote gut bacterial activity via QS activation and provide prospects for the future.

Anti-Virulence Activity of 3,3'-Diindolylmethane (DIM): A Bioactive Cruciferous Phytochemical with Accelerated Wound Healing Benefits.

Antimicrobial resistance is among the top global health problems with antibacterial resistance currently representing the major threat both in terms of occurrence and complexity. One reason current treatments of bacterial diseases are ineffective is the occurrence of protective and resistant biofilm structures. Phytochemicals are currently being reviewed for newer anti-virulence agents. In the present study, we aimed to investigate the anti-virulence activity of 3,3'-diindolylmethane (DIM), a bioactive cruciferous phytochemical. Using a series of in vitro assays on major Gram-negative pathogens, including transcriptomic analysis, and in vivo porcine wound studies as well as in silico experiments, we show that DIM has anti-biofilm activity. Following DIM treatment, our findings show that biofilm formation of two of the most prioritized bacterial pathogens Acinetobacter baumannii and Pseudomonas aeruginosa was inhibited respectively by 65% and 70%. Combining the antibiotic tobramycin with DIM enabled a high inhibition (94%) of P. aeruginosa biofilm. A DIM-based formulation, evaluated for its wound-healing efficacy on P. aeruginosa-infected wounds, showed a reduction in its bacterial bioburden, and wound size. RNA-seq was used to evaluate the molecular mechanism underlying the bacterial response to DIM. The gene expression profile encompassed shifts in virulence and biofilm-associated genes. A network regulation analysis showed the downregulation of 14 virulence-associated super-regulators. Quantitative real-time PCR verified and supported the transcriptomic results. Molecular docking and interaction profiling indicate that DIM can be accommodated in the autoinducer- or DNA-binding pockets of the virulence regulators making multiple non-covalent interactions with the key residues that are involved in ligand binding. DIM treatment prevented biofilm formation and destroyed existing biofilm without affecting microbial death rates. This study provides evidence for bacterial virulence attenuation by DIM.

Inhibitory Effects of Artificial Sweeteners on Bacterial Quorum Sensing.

Despite having been tagged as safe and beneficial, recent evidence remains inconclusive regarding the status of artificial sweeteners and their putative effects on gut microbiota. Gut microorganisms are essential for the normal metabolic functions of their host. These microorganisms communicate within their community and regulate group behaviors via a molecular system termed quorum sensing (QS). In the present study, we aimed to study the effects of artificial sweeteners on this bacterial communication system. Using biosensor assays, biophysical protein characterization methods, microscale thermophoresis, swarming motility assays, growth assays, as well as molecular docking, we show that aspartame, sucralose, and saccharin have significant inhibitory actions on the Gram-negative bacteria N-acyl homoserine lactone-based (AHL) communication system. Our studies indicate that these three artificial sweeteners are not bactericidal. Protein-ligand docking and interaction profiling, using LasR as a representative participating receptor for AHL, suggest that the artificial sweeteners bind to the ligand-binding pocket of the protein, possibly interfering with the proper housing of the native ligand and thus impeding protein folding. Our findings suggest that these artificial sweeteners may affect the balance of the gut microbial community via QS-inhibition. We, therefore, infer an effect of these artificial sweeteners on numerous molecular events that are at the core of intestinal microbial function, and by extension on the host metabolism.

Assessing the Molecular Targets and Mode of Action of Furanone C-30 on Pseudomonas aeruginosa Quorum Sensing.

Quorum sensing (QS), a sophisticated system of bacterial communication that depends on population density, is employed by many pathogenic bacteria to regulate virulence. In view of the current reality of antibiotic resistance, it is expected that interfering with QS can address bacterial pathogenicity without stimulating the incidence of resistance. Thus, harnessing QS inhibitors has been considered a promising approach to overriding bacterial infections and combating antibiotic resistance that has become a major threat to public healthcare around the globe. Pseudomonas aeruginosa is one of the most frequent multidrug-resistant bacteria that utilize QS to control virulence. Many natural compounds, including furanones, have demonstrated strong inhibitory effects on several pathogens via blocking or attenuating QS. While the natural furanones show no activity against P. aeruginosa, furanone C-30, a brominated derivative of natural furanone compounds, has been reported to be a potent inhibitor of the QS system of the notorious opportunistic pathogen. In the present study, we assess the molecular targets and mode of action of furanone C-30 on P. aeruginosa QS system. Our results suggest that furanone C-30 binds to LasR at the ligand-binding site but fails to establish interactions with the residues crucial for the protein's productive conformational changes and folding, thus rendering the protein dysfunctional. We also show that furanone C-30 inhibits RhlR, independent of LasR, suggesting a complex mechanism for the agent beyond what is known to date.

Anti-Quorum Sensing Activity of Stevia Extract, Stevioside, Rebaudioside A and Their Aglycon Steviol.

Governments are creating regulations for consumers to reduce their sugar intake, prompting companies to increase the ratio of artificial sweeteners in their products. However, there is evidence of some deleterious effects ascribed to the aforementioned synthetic agents and therefore consumers and food manufacturers have turned their attention to natural dietary sweeteners, such as stevia, to meet their sweetening needs. Stevia is generally considered safe; however, emerging scientific evidence has implicated the agent in gut microbial imbalance. In general, regulation of microbial behavior is known to depend highly on signaling molecules via quorum sensing (QS) pathways. This is also true for the gut microbial community. We, therefore, evaluated the possible role of these stevia-based natural sweeteners on this bacterial communication pathway. The use of a commercial stevia herbal supplement resulted in an inhibitory effect on bacterial communication, with no observable bactericidal effect. Purified stevia extracts, including stevioside, rebaudioside A (Reb A), and steviol revealed a molecular interaction, and possible interruption of Gram-negative bacterial communication, via either the LasR or RhlR receptor. Our in-silico analyses suggest a competitive-type inhibitory role for steviol, while Reb A and stevioside are likely to inhibit LasR-mediated QS in a non-competitive manner. These results suggest the need for further safety studies on the agents.

Assessment of the inhibitory activity of the pyrethroid pesticide deltamethrin against human placental glutathione transferase P1-1: A combined kinetic and docking study.

Deltamethrin (DEL), which is a synthetic pyrethroid insecticide, has been used successfully all over the world to treat mosquito nets for the control of malaria. Glutathione S-transferases (GSTs; EC 2.5.1.18) catalyze the conjugation of reduced glutathione (GSH) to a variety of xenobiotics and are normally recognized as detoxification enzymes. Here, we used a colorimetric assay based on the human placental GSTP1-1 (hpGSTP1-1)-catalyzed reaction between GSH and the model substrate 1-chloro-2,4-dinitrobenzene (CDNB) as well as molecular docking to investigate the mechanistic and structural aspects of hpGSTP1-1 inhibition by DEL. We show that DEL is a potent, noncompetitive inhibitor of hpGSTP1-1 with an IC50 value of 6.1 µM and Ki values of 5.61 ±â€¯0.32 µM and 7.96 ±â€¯0.97 µM at fixed [CDNB]-varied [GSH] and fixed [GSH]-varied [CDNB], respectively. DEL appears to be accommodated well in an eccentric cavity located at the interface of the hpGSTP1-1 homodimer, presumably causing conformational changes to the enzyme's substrate-binding sites such that the enzyme is no longer able to transform GSH and CDNB effectively. Correspondingly, considerable maternal exposure to and subsequent accumulation of DEL may interfere with the proper development of the vulnerable fetus, possibly increasing the risk of developing congenital defects.