Bacterial translocation is reduced by a specific nutritional combination in mice with chemotherapy-induced neutropenia

Gastrointestinal Microbiota in Gastric Cancer: Potential Mechanisms and Clinical Applications-A Literature Review

Emerging evidence highlights the crucial role of gastrointestinal microbiota in the pathogenesis of gastric cancer. Helicobacter pylori (H. pylori) infection stands out as a primary pathogenic factor. However, interventions such as anti-H. pylori therapy, gastric surgeries, immunotherapy, and chronic inflammation significantly remodel the gastric microbiome, implicating a broader spectrum of microorganisms in cancer development. These microbial populations can modulate gastric carcinogenesis through various mechanisms, including sustained chronic inflammation, bacterial genotoxins, alterations in short-chain fatty acids, elevated gastrointestinal bile acids, impaired mucus barrier function, and increased concentrations of N-nitrosamines and lactic acid. The dynamic changes in gut microbiota also critically influence the outcomes of anti-cancer therapies by modifying drug bioavailability and metabolism, thus affecting therapeutic efficacy and side effect profiles. Additionally, the effectiveness of radiotherapy can be significantly impacted by gut microbiota alterations. Novel therapeutic strategies targeting the microbiome, such as dietary interventions, probiotic and synbiotic supplementation, and fecal microbiota transplantation, are showing promise in cancer treatment. Understanding the intricate relationship between the gut microbiota and gastric cancer is essential for developing new, evidence-based approaches to the prevention and treatment of this malignancy.

Review on the effect of chemotherapy on the intestinal barrier: Epithelial permeability, mucus and bacterial translocation

Chemotherapy kills fast-growing cells including gut stem cells. This affects all components of the physical and functional intestinal barrier, i.e., the mucus layer, epithelium, and immune system. This results in an altered intestinal permeability of toxic compounds (e.g., endotoxins) as well as luminal bacterial translocation into the mucosa and central circulation. However, there is uncertainty regarding the relative contributions of the different barrier components for the development of chemotherapy-induced gut toxicity. This review present an overview of the intestinal mucosal barrier determined with various types of molecular probes and methods, and how they are affected by chemotherapy based on reported rodent and human data. We conclude that there is overwhelming evidence that chemotherapy increases bacterial translocation, and that it affects the mucosal barrier by rendering the mucosa more permeable to large permeability probes. Chemotherapy also seems to impede the intestinal mucus barrier, even though this has been less clearly evaluated from a functional standpoint but certainly plays a role in bacteria translocation. Combined, it is however difficult to outline a clear temporal or succession between the different gastrointestinal events and barrier functions, especially as chemotherapy-induced neutropenia is also involved in intestinal immunological homeostasis and bacterial translocation. A thorough characterization of this would need to include a time dependent development of neutropenia, intestinal permeability, and bacterial translocation, ideally after a range of chemotherapeutics and dosing regimens.

Murine response to the opportunistic bacterium Pseudomonas aeruginosa infection in gut dysbiosis caused by 5-fluorouracil chemotherapy-induced mucositis

AIMS

This manuscript aims to explain the relationship between mucositis caused by 5-FU over gut bacterial species and susceptibility to opportunistic infection caused by P. aeruginosa.

MAIN METHODS

BALB/c mice were intraperitoneally treated with PBS or 5-FU. Bodyweight and faecal consistency were checked daily. Mice faecal DNA was extracted, and bacterial phylogenetic groups were analysed using qPCR or high-throughput sequencing. Immunofluorescence was used to evaluate BMDM activation by mice-treated faecal content. Mice were challenged intratracheally with virulent P. aeruginosa, and the CFU and histology were analysed. Faecal microbiota were transplanted to evaluate the gut microbiota and resistance to pulmonary P. aeruginosa recovery.

KEY FINDINGS

The animals treated with 5-FU presented mucositis with great weight loss, altered faecal consistency, bacterial gut dysbiosis and histological changes in the intestinal mucosa. Mice under 5-FU treatment were more susceptible to lung infection by the bacteria P. aeruginosa and had more extensive tissue damage during their lung infection with greater pro-inflammatory gene expression. It was observed that the mucositis remained in the groups with 5-FU even with the FMT. The results caused by mucositis in animals that received allogeneic FMT were reversed, however, with a decrease in P. aeruginosa susceptibility in animals treated with 5-FU and allogeneic FMT compared to animals treated with 5-FU and autologous FMT.

SIGNIFICANCE

Treatment with 5-FU in a murine model makes it more susceptible to pulmonary infection by the bacterium P. aeruginosa, FMT offers an opportunity to protect against this susceptibility to infection.

Risk Factors for Bacteremia After Endoscopic Procedures in Hospitalized Patients With a Focus on Neutropenia

BACKGROUND

The risk for bacteremia following endoscopic procedures varies among studies. A low neutrophil count is considered as a risk factor.

OBJECTIVE

To assess risk factors for bacteremia following endoscopic procedures, focusing on neutropenia.

METHODS

This was a retrospective analysis of all inpatients undergoing endoscopic procedures between 2005 and 2018 with neutrophil count taken within 72 hours before the procedure in a tertiary center in Israel. The primary outcome was positive blood culture within 48 hours following the procedure of bacteria that was not cultured before. Risk factors for bacteremia were assessed and multivariate logistic regression models were built. In neutropenic patients, comparator groups were used to assess the risk related to the procedure and neutropenia.

RESULTS

Of 13,168 patients included, postprocedural bacteremia was recorded in 103 (0.8%). Neutropenia, low albumin level, male gender, older age, preprocedure fever, and admitting department were associated with increased risk for bacteremia in both univariate and multivariate analyses. A multivariate model including these factors was found to be predictive of bacteremia (area under the curve 0.82; 95% confidence interval, 0.78-0.88). In neutropenic patients, the risk of postendoscopic bacteremia (4.2%) was not significantly different compared with neutropenic patients undergoing bronchoscopy (1.8%, P=0.14) or from the rate of bacteremia-to-neutropenic episodes ("background risk") in neutropenic patients in general (6.3%, P=0.33).

CONCLUSIONS

Postendoscopic bacteremia is a rare event among inpatients. Although neutropenia was found to be a risk factor for bacteremia, it was not higher than the background risk in these patients. Models highly predictive of bacteremia were developed and should be validated.

Stachyose inhibits vancomycin-resistant Enterococcus colonization and affects gut microbiota in mice

Vancomycin-resistant Enterococcus (VRE) caused nosocomial infections are rising globally. Multiple measures have been investigated to address this issue, altering gut microbiota through dietary intervention represents one of such effort. Stachyose can promote probiotic growth, which makes it a good candidate for potentially inhibiting VRE infection. This study aimed to determine whether stachyose inhibits VRE colonization and investigated the involvement of gut microbiota this effect of stachyose. In VRE-infection experiment, 6-week old female C57/6 J mice pre-treated with vancomycin were infected with 2 × 10⁸ CFU VRE via gavage. These mice then received oral administration of stachyose or PBS as control for 7days. Two groups of uninfected mice were also received daily gavage of stachyose or PBS for 7 days to observe the impact of stachyose treatment on normal mice. Fresh fecal and colon samples were collected, then VRE colonization, gut microbiota and gene expression were respectively assessed using cultivation, 16s rRNA sequencing and RNA-sequencing in two parallel experiment, respectively. In VRE-infected mice, stachyose treatment significantly reduced VRE colonization on days 9 and 10 post-infection. Stachyose treatment increased the relative abundance of Porphyromonadaceae, Parabacteroides, and Parabacteroides distasonis compared to the PBS-treated infection mice (P < 0.01). Uninfected mice treated with stachyose showed a significant increase in Lactobacillaceae and Lactobacillus compared to the PBS-treated uninfected mice(P < 0.05). RNA-sequencing results showed that stachyose treatment in VRE-infected mice increased expression of genes involved in TNF and IL-17 signaling pathways. Stachyose treatment also up-regulated Hsd17b14, Cyp3a44, Arg1, and down-regulated Pnliprp2, Ces1c, Pla2g4c genes involving in metabolic pathway in uninfected mice. In conclusion, stachyose supplementation can effectively inhibit VRE colonization and probably altering composition of the microbiome, which can in turn result in changes in expression of genes. Stachyose may also benefit health by increasing the abundance of Lactobacillus and expression of genes involving in metabolic pathway in normal mice.

Conventional myelosuppressive chemotherapy for non-haematological malignancy disrupts the intestinal microbiome

Background

The gut microbiota influences many aspects of host physiology, including immune regulation, and is predictive of outcomes in cancer patients. However, whether conventional myelosuppressive chemotherapy affects the gut microbiota in humans with non-haematological malignancy, independent of antibiotic exposure, is unknown.

Methods

Faecal samples from 19 participants with non-haematological malignancy, who were receiving conventional chemotherapy regimens but not antibiotics, were examined prior to chemotherapy, 7–12 days after chemotherapy, and at the end of the first cycle of treatment. Gut microbiota diversity and composition was determined by 16S rRNA gene amplicon sequencing.

Results

Compared to pre-chemotherapy samples, samples collected 7–12 days following chemotherapy exhibited increased richness (mean 120 observed species ± SD 38 vs 134 ± 40; p = 0.007) and diversity (Shannon diversity: mean 6.4 ± 0.43 vs 6.6 ± 0.41; p = 0.02). Composition was significantly altered, with a significant decrease in the relative abundance of gram-positive bacteria in the phylum Firmicutes (pre-chemotherapy median relative abundance [IQR] 0.78 [0.11] vs 0.75 [0.11]; p = 0.003), and an increase in the relative abundance of gram-negative bacteria (Bacteroidetes: median [IQR] 0.16 [0.13] vs 0.21 [0.13]; p = 0.01 and Proteobacteria: 0.015 [0.018] vs 0.03 [0.03]; p = 0.02). Differences in microbiota characteristics from baseline were no longer significant at the end of the chemotherapy cycle.

Conclusions

Conventional chemotherapy results in significant changes in gut microbiota characteristics during the period of predicted myelosuppression post-chemotherapy. Further study is indicated to link microbiome changes during chemotherapy to clinical outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08296-4.

Nutritional Interventions in Cancer Cachexia: Evidence and Perspectives From Experimental Models

Cancer cachexia is a complex metabolic syndrome characterized by involuntary skeletal muscle loss and is associated with poor clinical outcome, decreased survival and negatively influences cancer therapy. No curative treatments are available for cancer cachexia, but nutritional intervention is recommended as a cornerstone of multimodal therapy. Optimal nutritional care is pivotal in the treatment of cancer cachexia, and the effects of nutrients may extend beyond provision of adequate energy uptake, targeting different mechanisms or metabolic pathways that are affected or deregulated by cachexia. The evidence to support this notion derived from nutritional intervention studies in experimental models of cancer cachexia is systematically discussed in this review. Moreover, experimental variables and readout parameters to determine skeletal muscle wasting and cachexia are methodologically evaluated to allow critical comparison of similar studies. Single- and multinutrient intervention studies including qualitative modulation of dietary protein, dietary fat, and supplementation with specific nutrients, such as carnitine and creatine, were reviewed for their efficacy to counteract muscle mass loss and its underlying mechanisms in experimental cancer cachexia. Numerous studies showed favorable effects on impaired protein turnover and related metabolic abnormalities of nutritional supplementation in parallel with a beneficial impact on cancer-induced muscle wasting. The combination of high quality nutrients in a multitargeted, multinutrient approach appears specifically promising, preferentially as a multimodal intervention, although more studies investigating the optimal quantity and combination of nutrients are needed. During the review process, a wide variation in timing, duration, dosing, and route of supplementation, as well as a wide variation in animal models were observed. Better standardization in dietary design, and the development of experimental models that better recapitulate the etiology of human cachexia, will further facilitate successful translation of experimentally-based multinutrient, multimodal interventions into clinical practice.

Animal models of chemotherapy-induced mucositis: translational relevance and challenges

Chemotherapy for cancer patients induces damaging tissue reactions along the epithelium of the gastrointestinal tract (GIT). This chemotherapy-induced mucositis (CIM) is a serious side effect of cytotoxic drugs, and several animal models of CIM have been developed, mainly in rodents and piglets, to help understand the progression of CIM and how to prevent it. Animal models allow highly controlled experimental conditions, detailed organ (e.g., GIT) insights, standardized, clinically relevant treatment regimens, and discovery of new biomarkers. Still, surprisingly few results from animal models have been translated into clinical CIM management and treatments. The results obtained from specific animal models can be difficult to translate to the diverse range of CIM manifestations in patients, which vary according to the antineoplastic drugs, dose, underlying (cancer) disease, and patient characteristics (e.g., age, genetics, and body constitution). Another factor that hinders the direct use of results from animals is inadequate collaboration between basic science and clinical science in relation to CIM. Here, we briefly describe CIM pathophysiology, particularly the basic knowledge that has been obtained from CIM animal models. These model studies have indicated potential new preventive and ameliorating interventions, including supplementation with natural bioactive diets (e.g., milk fractions, colostrum, and plant extracts), nutrients (e.g., polyunsaturated fatty acids, short-chain fatty acids, and glutamine), and growth factor peptides (e.g., transforming growth factor and glucagon-like peptide-2), as well as manipulations of the gut microbiota (e.g., prebiotics, probiotics, and antibiotics). Rodent CIM models allow well-controlled, in-depth studies of animals with or without tumors while pig models more easily make clinically relevant treatment regimens possible. In synergy, animal models of CIM provide the basic physiological understanding and the new ideas for treatment that are required to make competent decisions in clinical practice.

The role of polymorphonuclear neutrophils during HIV-1 infection

It is well-recognized that human immunodeficiency virus type-1 (HIV-1) mainly targets CD4⁺ T cells and macrophages. Nonetheless, during the past three decades, a huge number of studies have reported that HIV-1 can directly or indirectly target other cellular components of the immune system including CD8⁺ T cells, B cells, dendritic cells, natural killer cells, and polymorphonuclear neutrophils (PMNs), among others. PMNs are the most abundant leukocytes in the human circulation, and are known to play principal roles in the elimination of invading pathogens, regulating different immune responses, healing of injured tissues, and maintaining mucosal homeostasis. Until recently, little was known about the impact of HIV-1 infection on PMNs as well as the impact of PMNs on HIV-1 disease progression. This is because early studies focused on neutropenia and recurrent microbial infections, particularly, during advanced disease. However, recent studies have extended the investigation area to cover new aspects of the interactions between HIV-1 and PMNs. This review aims to summarize these advances and address the impact of HIV-1 infection on PMNs as well as the impact of PMNs on HIV-1 disease progression to better understand the pathophysiology of HIV-1 infection.

Gut microbiota modulation of chemotherapy efficacy and toxicity

Evidence is growing that the gut microbiota modulates the host response to chemotherapeutic drugs, with three main clinical outcomes: facilitation of drug efficacy; abrogation and compromise of anticancer effects; and mediation of toxicity. The implication is that gut microbiota are critical to the development of personalized cancer treatment strategies and, therefore, a greater insight into prokaryotic co-metabolism of chemotherapeutic drugs is now required. This thinking is based on evidence from human, animal and in vitro studies that gut bacteria are intimately linked to the pharmacological effects of chemotherapies (5-fluorouracil, cyclophosphamide, irinotecan, oxaliplatin, gemcitabine, methotrexate) and novel targeted immunotherapies such as anti-PD-L1 and anti-CLTA-4 therapies. The gut microbiota modulate these agents through key mechanisms, structured as the 'TIMER' mechanistic framework: Translocation, Immunomodulation, Metabolism, Enzymatic degradation, and Reduced diversity and ecological variation. The gut microbiota can now, therefore, be targeted to improve efficacy and reduce the toxicity of current chemotherapy agents. In this Review, we outline the implications of pharmacomicrobiomics in cancer therapeutics and define how the microbiota might be modified in clinical practice to improve efficacy and reduce the toxic burden of these compounds.

Bacterial translocation in critical illness

Bacterial translocation involves the passage of intestinal bacteria to extraintestinal sites and has been shown to increase morbidity and mortality in critical illness. This review outlines the pathophysiology of bacterial translocation, host defence mechanisms, and reviews the evidence for the clinical management of critically ill patients in order to minimise the negative outcomes associated with bacterial translocation.

Associations between gastrointestinal toxicity, micro RNA and cytokine production in patients undergoing myeloablative allogeneic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) is a procedure with a high risk of treatment related mortality. The primary aim of the present study was to examine associations between markers of gastrointestinal toxicity, markers of systemic inflammation, and plasma levels of microRNA (miRNA) -155 and -146a during the first month after HSCT. The secondary aim was to characterize the impact of the toxic-inflammatory response on the function of circulating leukocytes during immune recovery. Thirty HSCT patients were included. Gastrointestinal injury was monitored by toxicity scores, lactulose-mannitol test and plasma citrulline, as a measure of the enterocyte population. Nadir of citrulline and maximum of oral toxicity scores, intestinal permeability, CRP and plasma levels of IL-6 and IL-10 was seen at day +7 post-HSCT. miRNA-155 and mi-RNA-146a showed an inverse relation with significantly elevated miRNA-155 and decreased miRNA-146a levels, from day 0 to day +28 compared with pre-conditioning levels. Citrulline levels below the median at day +7 were associated with higher spontaneous production of IL-6 and TNF-α as well as higher in vitro stimulated production of IL-17A at day +21. This study is the first to demonstrate that toxic responses to chemotherapy are accompanied by differential regulation of miRNAs with opposing effects on immune regulation. We find that a proinflammatory miRNA profile is sustained during the first three weeks after the transplantation, indicating that these miRNAs may play a role in the regulation of the inflammatory environment during immune reconstitution after HSCT.

Leaky gut and the liver: A role for bacterial translocation in nonalcoholic steatohepatitis

Gut flora and bacterial translocation (BT) play important roles in the pathogenesis of chronic liver disease, including cirrhosis and its complications. Intestinal bacterial overgrowth and increased bacterial translocation of gut flora from the intestinal lumen predispose patients to bacterial infections, major complications and also play a role in the pathogenesis of chronic liver disorders. Levels of bacterial lipopolysaccharide, a component of gram-negative bacteria, are increased in the portal and/or systemic circulation in several types of chronic liver disease. Impaired gut epithelial integrity due to alterations in tight junction proteins may be the pathological mechanism underlying bacterial translocation. Preclinical and clinical studies over the last decade have suggested a role for BT in the pathogenesis of nonalcoholic steatohepatitis (NASH). Bacterial overgrowth, immune dysfunction, alteration of the luminal factors, and altered intestinal permeability are all involved in the pathogenesis of NASH and its complications. A better understanding of the cell-specific recognition and intracellular signaling events involved in sensing gut-derived microbes will help in the development of means to achieve an optimal balance in the gut-liver axis and ameliorate liver diseases. These may suggest new targets for potential therapeutic interventions for the treatment of NASH. Here, we review some of the mechanisms connecting BT and NASH and potential therapeutic developments.