The Pivotal Role of Aryl Hydrocarbon Receptor-Regulated Tight Junction Proteins and Innate Immunity on the Synergistic Effects of Postbiotic Butyrate and Active Vitamin D3 to Defense against Microbial Invasion in Salmonella Colitis

Therapeutic Potential of Nutritional Aryl Hydrocarbon Receptor Ligands in Gut-Related Inflammation and Diseases

A solid scientific foundation is required to build the concept of personalized nutrition developed to promote health and a vision of disease prevention. Growing evidence indicates that nutrition can modulate the immune system through metabolites, which are either generated via microbiota metabolism or host digestion. The aryl hydrocarbon receptor (AhR) plays a crucial role in regulating immune responses, particularly in the gut, and has emerged as a key modulator of gut-mediated inflammation and related diseases. AhR is a ligand-activated transcription factor that responds to environmental, dietary, and microbial-derived signals, influencing immune balance and maintaining intestinal homeostasis. Nutritional AhR ligands play a significant role in modulating intestinal immunity and the function of mucosal immune cells, thereby exerting clinical effects on colitis and innate immunity. Additionally, they have the capacity to orchestrate autophagy, phagocytic cell function, and intestinal epithelial tight junctions. Therapeutic strategies aimed at enhancing AhR activity, restoring gut integrity, and optimizing immune responses hold promise as avenues for future research and potential treatments for critically ill patients.

The role of kynurenines in migraine-related neuroimmune pathways

Migraine, a primary headache disorder whose mechanism remains incompletely understood, appears to involve the activation of the trigeminovascular system (TS) during attacks. Research suggests that inflammatory processes mediated by the immune system may play a role in migraine pathophysiology. Neuroinflammation is often associated with migraine attacks, with cytokines serving as crucial mediators in the process. Elevated levels of pro-inflammatory cytokines, such as interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α), have been observed in the blood and cerebrospinal fluid of individuals experiencing migraine attacks. These cytokines have the capacity to sensitize pain pathways in the brain, thereby increasing sensitivity to pain stimuli. This phenomenon, known as central sensitization, is believed to contribute to the intensity and persistence of migraine pain. Kynurenines, endogenous mediators of glutamatergic mechanisms, can significantly influence the pathophysiology of primary headache disorders. The kynurenine system is collectively known as the kynurenine pathway (KP), which can act on multiple receptors, such as glutamate receptors, aryl hydrocarbon receptors (AhRs), G protein-coupled receptors 35 (GPR35), and α-7 nicotinic acetylcholine (α7 nACh) receptors. These receptors are also found on various cells of the immune system, so the role of the KP in the pathomechanism of primary headaches may also be mediated through them. In this review, our goal is to show a possible link between the receptors of the KP and immune system in the context of inflammation and migraine. Migraine research in recent years has focused on neuropeptides, such as calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating polypeptide (PACAP) as potential pathogenic factors and possible therapeutic approaches. These peptides share many similarities in their characteristics and roles. For instance, they exhibit potent vasodilation, occur in both the peripheral and central nervous systems, and play a role in transmitting nociception and neurogenic inflammation. The investigation of potential connections between the aforementioned neuropeptides and the kynurenine pathway could play a significant role in uncovering the pathomechanism of migraine and identifying new drug candidates.

Unveiling the Novel Benefits of Co-Administering Butyrate and Active Vitamin D3 in Mice Subjected to Chemotherapy-Induced Gut-Derived Pseudomonas aeruginosa Sepsis

Cancer patients face increased susceptibility to invasive infections, primarily due to ulcerative lesions on mucosal surfaces and immune suppression resulting from chemotherapy. Pseudomonas aeruginosa (P. aeruginosa) bacteremia is notorious for its rapid progression into fatal sepsis, posing a significant threat to cancer patients, particularly those experiencing chemotherapy-induced neutropenia. This bacterial infection contributes significantly to morbidity and mortality rates among such individuals. Our latest report showed the mutually beneficial effects of postbiotic butyrate on 1,25-dihydroxyvitamin D3 (1,25D3)-controlled innate immunity during Salmonella colitis. Hence, we investigated the impact of butyrate and 1,25D3 on chemotherapy-induced gut-derived P. aeruginosa sepsis in mice. The chemotherapy-induced gut-derived P. aeruginosa sepsis model was established through oral administration of 1 × 107 CFU of the P. aeruginosa wild-type strain PAO1 in C57BL/6 mice undergoing chemotherapy. Throughout the infection process, mice were orally administered butyrate and/or 1,25D3. Our observations revealed that the combined action of butyrate and 1,25D3 led to a reduction in the severity of colitis and the invasion of P. aeruginosa into the liver and spleen of the mice. This reduction was attributed to an enhancement in the expression of defensive cytokines and antimicrobial peptides within the cecum, coupled with decreased levels of zonulin and claudin-2 proteins in the mucosal lining. These effects were notably more pronounced when compared to treatments administered individually. This study unveils a promising alternative therapy that involves combining postbiotics and 1,25D3 for treating chemotherapy-induced gut-derived P. aeruginosa sepsis.

Role of aryl hydrocarbon receptors in infection and inflammation

The aryl hydrocarbon receptor (AhR) is a transcription factor that is activated by various ligands, including pollutants, microorganisms, and metabolic substances. It is expressed extensively in pulmonary and intestinal epithelial cells, where it contributes to barrier defense. The expression of AhR is pivotal in regulating the inflammatory response to microorganisms. However, dysregulated AhR expression can result in endocrine disorders, leading to immunotoxicity and potentially promoting the development of carcinoma. This review focuses on the crucial role of the AhR in facilitating and limiting the proliferation of pathogens, specifically in relation to the host cell type and the species of etiological agents involved in microbial pathogen infections. The activation of AhR is enhanced through the IDO1-AhR-IDO1 positive feedback loop, which is manipulated by viruses. AhR primarily promotes the infection of SARS-CoV-2 by inducing the expression of angiotensin-converting enzyme 2 (ACE2) and the secretion of pro-inflammatory cytokines. AhR also plays a significant role in regulating various types of T-cells, including CD4+ T cells and CD8+ T cells, in the context of pulmonary infections. The AhR pathway plays a crucial role in regulating immune responses within the respiratory and intestinal barriers when they are invaded by viruses, bacteria, parasites, and fungi. Additionally, we propose that targeting the agonist and antagonist of AhR signaling pathways could serve as a promising therapeutic approach for combating pathogen infections, especially in light of the growing prevalence of drug resistance to multiple antibiotics.

Dietary factors and their influence on immunotherapy strategies in oncology: a comprehensive review

Immunotherapy is emerging as a promising avenue in oncology, gaining increasing importance and offering substantial advantages when compared to chemotherapy or radiotherapy. However, in the context of immunotherapy, there is the potential for the immune system to either support or hinder the administered treatment. This review encompasses recent and pivotal studies that assess the influence of dietary elements, including vitamins, fatty acids, nutrients, small dietary molecules, dietary patterns, and caloric restriction, on the ability to modulate immune responses. Furthermore, the article underscores how these dietary factors have the potential to modify and enhance the effectiveness of anticancer immunotherapy. It emphasizes the necessity for additional research to comprehend the underlying mechanisms for optimizing the efficacy of anticancer therapy and defining dietary strategies that may reduce cancer-related morbidity and mortality. Persistent investigation in this field holds significant promise for improving cancer treatment outcomes and maximizing the benefits of immunotherapy.

The Hazards of Probiotics on Gut-Derived Pseudomonas aeruginosa Sepsis in Mice Undergoing Chemotherapy

Pseudomonas aeruginosa (P. aeruginosa) is a leading cause of nosocomial infections associated with a high mortality rate and represents a serious threat to human health and the increasing frequency of antimicrobial resistance. Cancer patients are more vulnerable to invasive infection due to ulcerative lesions in mucosal surfaces and immune suppression secondary to chemotherapy. In our in vitro study, we observed that probiotics have the potential to yield beneficial effects on intestinal epithelial cells infected with P. aeruginosa. Additionally, probiotics were found to confer advantageous effects on the innate immunity of mice suffering from Salmonella-induced colitis. As a result, we sought to investigate the impact of probiotics on gut-derived P. aeruginosa sepsis induced by chemotherapy. Following chemotherapy, gut-derived P. aeruginosa sepsis was induced in female C57BL/6 mice aged 6-8 weeks, which were raised under specific-pathogen-free (SPF) conditions in an animal center. Prior to the induction of the sepsis model, the mice were administered 1 × 108 colony-forming units (CFU) of the probiotics, namely Lactobacillus rhamnosus GG (LGG) and Bifidobacterium longum (BL) via oral gavage. We observed that LGG or BL amplified the inflammatory mRNA expression in mice undergoing chemotherapy and suffering from gut-derived P. aeruginosa sepsis. This led to a heightened severity of colitis, as indicated by histological examination. Meanwhile, there was a notable decrease in the expression of antimicrobial peptide mRNA along with reduced levels of zonulin and claudin-2 protein staining within mucosal tissue. These alterations facilitated the translocation of bacteria to the liver, spleen, and bloodstream. To our astonishment, the introduction of probiotics exacerbated gut-derived P. aeruginosa sepsis in mice undergoing chemotherapy. Conclusively, we must be prudent when using probiotics in mice receiving chemotherapy complicated with gut-derived P. aeruginosa sepsis.

Bacillus subtilis KC1 prevents Mycoplasma gallisepticum-induced lung injury by enhancing intestinal Bifidobacterium animalis and regulating indole metabolism in chickens

It has been reported that dietary administration of Bacillus subtilis KC1 is effective in alleviating lung injury induced by Mycoplasma gallisepticum (MG) infection in chickens. However, the underlying molecular mechanism of B. subtilis KC1 against MG infection is still unclear. The purpose of this study was to determine whether B. subtilis KC1 could alleviate MG infection-induced lung injury in chickens by regulating their gut microbiota. The results of this study indicate that B. subtilis KC1 supplementation has the potential to alleviate MG infection-induced lung injury as reflected by reduced MG colonization, reduced pathologic changes, and decreased production of pro-inflammatory cytokines. In addition, B. subtilis KC1 supplementation was partially effective in alleviating the gut microbiota disorder caused by MG infection. Importantly, B. subtilis KC1 enriched the beneficial Bifidobacterium animalis in gut and thus reversed indole metabolic dysfunction caused by MG infection. B. subtilis KC1 supplementation increased levels of indole, which enhanced aryl hydrocarbon receptor activation, improving barrier function and alleviating lung inflammation caused by MG. Overall, this study indicates that B. subtilis KC1 has a "gut-lung axis" mechanism that can reduce the severity of MG infection by enriching intestinal B. animalis and regulating indole metabolism.

The Tryptophan and Kynurenine Pathway Involved in the Development of Immune-Related Diseases

The tryptophan and kynurenine pathway is well-known to play an important role in nervous, endocrine, and immune systems, as well as in the development of inflammatory diseases. It has been documented that some kynurenine metabolites are considered to have anti-oxidative, anti-inflammatory, and/or neuroprotective properties. Importantly, many of these kynurenine metabolites may possess immune-regulatory properties that could alleviate the inflammation response. The abnormal activation of the tryptophan and kynurenine pathway might be involved in the pathophysiological process of various immune-related diseases, such as inflammatory bowel disease, cardiovascular disease, osteoporosis, and/or polycystic ovary syndrome. Interestingly, kynurenine metabolites may be involved in the brain memory system and/or intricate immunity via the modulation of glial function. In the further deliberation of this concept with engram, the roles of gut microbiota could lead to the development of remarkable treatments for the prevention of and/or the therapeutics for various intractable immune-related diseases.