Aberrant gut microbiota and fecal metabolites in patients with coal-burning endemic fluorosis in Guizhou, China

PKC-θ is an important driver of fluoride-induced immune imbalance of regulatory T cells/effector T cells

Fluoride is unnecessary in the human body. Long-term fluoride exposure may lead to immune system abnormalities. However, the mechanism remains unclear. This study aim to explore the mechanism of fluoride interference in the immune system and also identify the key indicators of fluoride-induced immune damage. Questionnaires were used to collect basic information. Multiple linear analyses and other statistical methods were used in order to process the data. Flow cytometry was used to detect relevant immunomarkers and analyze immune damage. Simultaneously, Wistar rats and cell models exposed to fluoride were established to detect the effects of fluoride on immune homeostasis. The results showed that sex, residence time, smoking, and Corona Virus Disease 2019 (COVID-19) infection may indirectly influence fluoride-induced immune damage. In residents of fluoride-exposed areas, there was a significant decrease in CD3+ T lymphocytes and CD4+ and CD8+ cells and a downward trend in the CD4+/CD8+ cell ratio. CD4+CD8+/CD4+, regulatory T cells (Tregs), and Tregs/effector T cells (Teffs) ratios showed opposite changes. Fluoride inhibits T cell activation by inhibiting the expression and phosphorylation of Protein Kinase C-θ (PKC-θ), hinders the internalization of T cell receptors, and affects NF-kB and c-Jun protein expression, leading to homeostatic Treg/Teff imbalance in vivo and in vitro experiments. This study represents the first evidence suggesting that PKC-θ may be the key to immune imbalance in the body under fluoride exposure. It is possible that Tregs/Teffs cell ratio provide a reference point for the diagnosis and treatment of fluoride-induced immune damage.

Progress in research on the role of fluoride in immune damage

Excessive fluoride intake from residential environments may affect multiple tissues and organs; however, the specific pathogenic mechanisms are unclear. Researchers have recently focused on the damaging effects of fluoride on the immune system. Damage to immune function seriously affects the quality of life of fluoride-exposed populations and increases the incidence of infections and malignant tumors. Probing the mechanism of damage to immune function caused by fluoride helps identify effective drugs and methods to prevent and treat fluorosis and improve people's living standards in fluorosis-affected areas. Here, the recent literature on the effects of fluoride on the immune system is reviewed, and research on fluoride damage to the immune system is summarized in terms of three perspectives: immune organs, immune cells, and immune-active substances. We reviewed that excessive fluoride can damage immune organs, lead to immune cells dysfunction and interfere with the expression of immune-active substances. This review aimed to provide a potential direction for future fluorosis research from the perspective of fluoride-induced immune function impairment. In order to seek the key regulatory indicators of fluoride on immune homeostasis in the future.

Gut microbiota-derived 5-hydroxyindoleacetic acid from pumpkin polysaccharides supplementation alleviates colitis via MAPKs-PPARγ/NF-κB inhibition

Polysaccharides from Pumpkin (Cucurbita moschata Duchesne) (PPs) have many pharmacological activities, including anti-oxidant, immune, and intestinal microbiota regulation. These activities have provided some reminders of its potential therapeutic effect on ulcerative colitis (UC), but this has not yet been confirmed. This study preliminarily confirmed its significant anti-UC activity superior to Salicylazosulfapyridine. The average molecular weight of PPs was 3.10 × 105 Da, and PPs mainly comprised Mannose, Rhamnose, Galacturonic acid, Galactosamine, Glucose, and Xylose with molar ratios of 1.58:3.51:34.54:1.00:3.25:3.02. PPs (50, 100 mg/kg) could significantly resist dextran sodium sulfate induced UC on C57BL/6 mice by improving gut microbiota dysbiosis, such as the changes of relative abundance of Bacteroides, Culturomica, Mucispirillum, Escherichia-Shigella, Alistipes and Helicobacter. PPs also reverse the abnormal inflammatory reaction, including abnormal level changes of TNF-α, IFN-γ, IL-1β, IL-4, IL-6, IL-10, and IL-18. Metabolomic profiling showed that PPs supplementation resulted in the participation of PPAR and MAPK pathways, as well as the increase of 5-hydroxyindole acetic acid (5-HIAA) level. 5-HIAA also exhibited individual and synergistic anti-UC activities in vivo. Furthermore, combination of PPs and 5-HIAA could also elevate the levels of PPARγ in nuclear and inhibit MAPK/NF-ĸB pathway in the colon. This study revealed that PPs and endogenous metabolite 5-HIAA might be developed to treat UC.

Genomic and metabonomic methods reveal the probiotic functions of swine-derived Ligilactobacillus salivarius

BACKGROUND

As substitutes for antibiotics, probiotic bacteria protect against digestive infections caused by pathogenic bacteria. Ligilactobacillus salivarius is a species of native lactobacillus found in both humans and animals. Herein, a swine-derived Ligilactobacillus salivarius was isolated and shown to colonize the ileal mucous membrane, thereby promoting nutritional digestion, absorption, and immunity. To evaluate its probiotic role, the entire genome was sequenced, the genetic information was annotated, and the metabolic information was analyzed.

RESULTS

The phylogenetic relationship indicated that the bacteria was closer to L. salivarius MT573555.1 and MT585431.1. Functional genes included transporters, membrane proteins, enzymes, heavy metal resistance proteins, and putative proteins; metabolism-related genes were the most abundant. The six types of metabolic pathways secreted by L. salivarius were mainly composed of secretory transmembrane proteins and peptides. The secretory proteins of L. salivarius were digestive enzymes, functional proteins that regulate apoptosis, antibodies, and hormones. Non-targeted metabolomic analysis of L. salivarius metabolites suggested that ceramide, pyrrolidone- 5- carboxylic acid, N2-acetyl-L-ornithine, 2-ethyl-2-hydroxybutyric acid, N-lactoyl-phenylalanine, and 12 others were involved in antioxidation, repair of the cellular membrane, anticonvulsant, hypnosis, and appetite inhibition. Metabolites of clavaminic acid, antibiotic X14889C, and five other types of bacteriocins were identified, namely phenyllactic acid, janthitrem G, 13-demethyl tacrolimus, medinoside E, and tertonasin. The adherence and antioxidation of L. salivarius were also predicted. No virulence genes were found.

CONCLUSION

The main probiotic properties of L. salivarius were identified using genomic, metabonomic, and biochemical assays, which are beneficial for porcine feeding. Our results provided deeper insights into the probiotic effects of L. salivarius.