Amelioration of enteric dysbiosis by polyoxotungstates in mice gut

Highlights

• Polyoxotungstate (POT)-based complexes ameliorate bacteria dysbiosis in mice.

• POT complexes reduce body weight loss caused by colitis.

• POT complexes indirectly lower the expression of proinflammatory markers.

• Peptides enhance the biological function of POT complexes.

• POT complexes show no detectable

Abstract

Here we show that Preyssler-type polyoxotungstates (Preyssler-type POTs, [NaP₅W₃₀O₁₁₀]⁻¹⁴) complexed with peptides can prevent the dysbiotic expansion of anaerobic bacteria of the Enterobacteriaceae family. In a dextran sulfate sodium (DSS)-induced colitis model, symptom remission of C57BL/6 J mice with colitis is achieved by orally treated with POT complexes. Ten days of daily administration of POT complexes reduces 5% body weight loss and the mRNA levels of proinflammatory markers (77% reduction for Il6, 73% reduction for Tnf, 91% reduction for Cxcl1) in the caecum and proximal colon. Bacterial population analysis reveals that these Enterobacteriaceae population in the caecal content decline by one order of magnitude after administration of POT complexes. POT complexes exert anti-inflammatory effects indirectly on the host immune system by inhibition of malignant expansion of anaerobic Enterobacteriaceae during gut inflammation. Furthermore, POTs show negligible effect on bacterial growth in vitro, healthy mice and their microbiota composition under homeostatic conditions. Rationally designed POT complexes will provide distinctive approach to improve enteric bacteria dysbiosis-associated gut inflammation by balancing bacterial communities.

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.