Amelioration of enteric dysbiosis by polyoxotungstates in mice gut
Graphical abstract
Introduction
Alteration in composition and function of the gut microbial communities has been linked with a large number of major chronic diseases, including inflammatory, metabolic, autoimmune, and neurodegenerative diseases [1]. Inflammatory bowel disease (IBD) is one of the most common diseases that causes abdominal pain, cramping, and unexplained weight loss. IBD has substantially increased during the last decades due to genetic, environmental, geographical, and mental factors [2]. Colitis is an IBD that caused inflammation and sores along colon and rectum. Since the symptoms may range from mild to severe, e.g., a possible feature of colitis-associated colorectal cancer, urgent medical attention is recommended. Colitis is characterized by the outgrowth of opportunistic pathogenic bacteria which alter host susceptibility to inflammatory and microbial stimulus. During the period of colitis onset, both dietary and microbial factors influence the composition of the host gut bioactive molecules, which in turn modulates the frequencies and functionalities of immune cells [3].
Common approaches for treating colitis mainly focus on suppressing host immune reactions by supplying immunosuppressive drugs based on small molecules or biologics [4]. The effectiveness of vedolizumab [5], a monoclonal antibody that inhibits the gut-selective α4β7 integrin, was investigated as maintenance therapy in patients with moderately to severely active ulcerative colitis. Maintenance treatment with mirikizumab [6], a monoclonal antibody against the p19 subunit of interleukin 23, was proved effective in inducing a clinical response after 12 weeks. Although numerically higher proportions of patients treated with biologics had clinical responses compared with those given placebo. Nonetheless, these therapies neither restore the damage to the mucus layer of intestinal tract nor address the dysbiosis of the gut microbial communities [7]. Nanotherapeutics on gut homeostasis have resulted in positive outcomes for the treatment of inflammatory disease [8]. To make substantial progress, more efforts are needed to develop nanosystems for targeting inflamed colon and modulating intestinal microbiota while ameliorating inflammatory response against colitis.
Living organisms utilize the features of metal ions to complete a series of life processes that cannot be replaced by other organic substances. Metal oxides, such as tungstates, play an important role in oxygen transport, electron transfer, protein structure and function regulation, ion transport, isomerization, and catalytic degradation of DNA and RNA [[9], [10], [11]]. Normally, tungsten is not the essential chemical element to life forms. While it has been used to build chemical systems to mimic the nitrogenase for dinitrogen activation and reduction [[12], [13], [14]].
Polyoxotungstates (POTs) are a class of engineered sub-nanosized metal oxides that are extensively applied in material [[15], [16]], chemical [[17], [18], [19]], and biological science [[20], [21], [22], [23], [24], [25]]. Especially, the allosteric site that is considered responsible for enzyme inhibition by voluminous and negatively charged POTs, such as heteropolytungstates for two P-type ATPases inhibition [20], acetylcholinesterase inhibition [21], nucleoside triphosphate diphosphohydrolase inhibition [22], and nucleotidase inhibition [23]. Much of the higher valent tungsten is reminiscent of the nonmetals such as they readily undergo polymerization to form anionic POTs similar to the reactions of phosphate [26], which is analogous to the polyoxovanadates [27]. But the difference with phosphorus and polyoxovanadates is, tungsten, analogous to molybdenum, can mediate oxygen atom transfer (OAT) reactions [28] in prokaryotes. Therefore, POT is more likely to interfere with the respiratory chain of prokaryotic cells. For example, because of the high similarity between the chemical properties of Mo and W [[29], [30]], tungsten can abolish periplasmic nitrate-reductase activity in anaerobically grown bacteria Paracoccus pantotrophus and Escherichia coli by replacing molybdenum in the molybdopterin cofactor [[26], [31]].
Many major chronic diseases, such as inflammatory, have been associated with intestinal microbial dysbiosis. To develop an alternative nanosystem for targeting inflamed colon and modulating intestinal microbiota but with negligible influence to the host, here, structurally stable Preyssler-type POT ([NaP5W30O110]14−) [32] was investigated the effect on amelioration of inflammatory response against colitis in dextran sulphate sodium (DSS)-induced colitis mice model. [NaP5W30O110]14− sub-nano clusters were assembled with peptides (peptide-[NaP5W30O110]14− complexes, P5W30 complexes for short) to prevent the gelation of [NaP5W30O110]14− with DSS and enhance their membrane permeability. The symptoms of C57BL/6 J mice with colitis were relieved by measuring the mouse body weight loss and the mRNA levels of proinflammatory markers in the caecum and proximal colon after P5W30 complexes treatment. Endogenous Enterobacteriaceae was analysed to investigate the effect of P5W30 complexes on the restriction of imbalanced expansion of anaerobic Enterobacteriaceae. The putative mechanisms of P5W30 complexes may be attributed to their specific inhibition toward the bacterial nitrate reductase activity, which subsequently alleviates the adverse effects of enteric bacteria dysbiosis.
Section snippets
Materials
Trimethylamine-N-oxide (TMAO), sodium dodecyl sulfate (SDS), Hog mucin, hematoxylin and eosin staining solutions were purchased from Sigma-Aldrich (USA). Luria-Bertani (LB) broth, LB agar, blond agar and MacConkey agar were purchased from Huankai Microbial (Guangdong, China). Euglena gracilis (EG) medium was purchased from Hopebio (Shandong, China). Dextran sodium sulfate was purchased from Yeasen Biotechnology (Shanghai, China). Sodium tungstate, calcium malate, glycerin, K2HPO4, NH4Cl, sodium
Results and discussion
- 1.1.
Characterization and Effect of Polyoxotungstates on decreasing intestinal inflammation.
To investigate the effect of POTs on relieving intestinal inflammation, Preyssler-type [NaP5W30O110]14− clusters were dispersed in water, and the solution was used to treat C57BL/6 J mice with DSS-induced colitis by replacing drinking water. To avoid non-specific assembly with DSS, [NaP5W30O110]14− clusters were allowed to non-covalent interact with peptides for the formation of P5W30 complexes (Fig. 1A)
Conclusions
In conclusion, Preyssler-type POTs were complexed with peptides to exert the positive influence on mouse models of colitis. The P5W30 complex treatment reduced the severity of intestinal inflammation in mice gut by decreasing proinflammatory cytokines, decreased the pathological damage regions by over 50%, and promoted the recovery from body weight loss. Furthermore, the P5W30 complexes caused minimal changes in the microbiota composition under homeostatic conditions and no obvious negative
Declaration of competing interest
There are no conflicts to declare.
Abbreviations
cDNA complementary DNA CFU colony-forming units CXCL1 C-X-C motif chemokine ligand 1 CXCL2 C-X-C motif chemokine ligand 2 DLS dynamic light scattering DSS dextran sulphate sodium EG Euglena gracilis medium Gapdh glyceraldehyde-phosphate dehydrogenase H&E hematoxylin and eosin IBD inflammatory bowel disease IC50 half maximal inhibitory concentration IFN-γ interferon-γ IL-6 interleukine-6 iNOS inducible nitric oxide synthase IR infrared spectra KWW Kohlrausch-Williams-Watts equation LB Luria-Bertani broth LCN2
Graphical abstracts
Tungstate-based complexes treatment reduced the severity of intestinal inflammation in mouse models of colitis by decreasing proinflammatory cytokines, and promoted the recovery from body weight loss, while caused minimal changes in the microbiota composition under homeostatic conditions.
Declaration of Competing Interest
None.
Acknowledgment
This work was financially supported by National Natural Science Foundation of China (22101086, 31801638), the Natural Science Foundation of Guangdong Province (No. 2021A1515010271), and the fund of Key Laboratory of Fermentation Engineering (Ministry of Education) (202105FE09).
Author statement.
Kun Chen: Conceptualization, Methodology, Investigation, Resources, Writing-Original Draft, Visualization, Funding acquisition. Yuan Liu: Validation, Writing-Review & Editing. Mu Li: Validation, Software,
Declaration of interests
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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