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![Representative H&E stained cross-sections from the ileum of young a and old b mice. c Average number of villi per section and villi lenght. d-f Representative H&E stained ileal sections from young d and old e-f mice showing villi degeneration and crypt enlargement. g Crypts depth in old vs. young animals. h Arrowheads point to goblet-like cells containing eosinophilic secretory granules. i-l Electron micrographs of Paneth cell secretory granules from a young i and three old animals j-l. m Average number of Paneth cells per crypt. n Average number of goblet cells per villus. o-q Alcian blue stained ileal sections from a young o and two old p-q animals showing goblet cell hyperplasia and intracellular accumulation of mucin. Histology pictures were taken using a NanoZoomer 2.0 slide scanner (Hamamatsu). Measurements of villi length, villi number and crypt depth were done using NDP.view 2 software (Hamamatsu). Paneth and goblet cell counts were recorded in 40–60 well-preserved villi-crypt axes per animal. r Relative transcript levels for ileal AMPP genes, determined by qPCR using the ddCt method corrected for primer efficiencies according to Pfaffl et al. [22], (n = 16 animals/ group, primer sequences and methods are described in [23]). Statistical differences (Mann–Whitney U test) and are shown by asterisks (*p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001). Scale bars are: (a, b: 500 μm); (d, e, o, p, q: 50 μm); (f, h: 25 μm); (i, j, k, l: 500 nm)](profile/Nathalie-Cote/publication/319354566/figure/fig1/AS:533047172505601@1504099757058/Representative-H-E-stained-cross-sections-from-the-ileum-of-young-a-and-old-b-mice-c.png)
Representative H&E stained cross-sections from the ileum of young a and old b mice. c Average number of villi per section and villi lenght. d-f Representative H&E stained ileal sections from young d and old e-f mice showing villi degeneration and crypt enlargement. g Crypts depth in old vs. young animals. h Arrowheads point to goblet-like cells containing eosinophilic secretory granules. i-l Electron micrographs of Paneth cell secretory granules from a young i and three old animals j-l. m Average number of Paneth cells per crypt. n Average number of goblet cells per villus. o-q Alcian blue stained ileal sections from a young o and two old p-q animals showing goblet cell hyperplasia and intracellular accumulation of mucin. Histology pictures were taken using a NanoZoomer 2.0 slide scanner (Hamamatsu). Measurements of villi length, villi number and crypt depth were done using NDP.view 2 software (Hamamatsu). Paneth and goblet cell counts were recorded in 40–60 well-preserved villi-crypt axes per animal. r Relative transcript levels for ileal AMPP genes, determined by qPCR using the ddCt method corrected for primer efficiencies according to Pfaffl et al. [22], (n = 16 animals/ group, primer sequences and methods are described in [23]). Statistical differences (Mann–Whitney U test) and are shown by asterisks (*p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001). Scale bars are: (a, b: 500 μm); (d, e, o, p, q: 50 μm); (f, h: 25 μm); (i, j, k, l: 500 nm)
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In an effort to understand the mechanisms underlying the high prevalence of gastrointestinal tract disorders in old age, we investigated the expression of intestinal antimicrobial peptides in the terminal small intestine of aged mice. Our results show that old mice have reduced transcript levels of ileal α-defensins and lysozyme, two important type...
Citations
... Although we propose a general framework for considering host-microbiota interactions through diffusible molecules in the mucus, we have a specific biological system in mind, for which some details now follow. Experiments show that the host defense depends on factors secreted by the enterocytes, paneth, and goblet cells [24][25][26][27]. Upon sensing the proximity of bacteria, host intestinal epithelial cells release diffusible antimicrobial peptides (AMP). ...
Complex lifeforms host microbiota, microbes that live synergistically with their host. Accordingly, hosts have mechanisms to defend against and tolerate the microbiota. The intestinal mucus, where these systems collide, plays a pivotal role in managing this relationship, yet lacks an integrative theoretical framework. We propose a minimal model to elucidate dynamics at this interface, focusing on the ileum's mucus defense. The model considers the effect of delay in host antimicrobial peptide secretion and how the host can use two different signals, from the bulk microbiota and from segmented filamentous bacteria (SFB), assuming that the SFB anticipate the bulk microbiota. We propose a theory whereby the host can optimize defense by minimizing antimicrobial peptide production and controlling bacterial exposure. Integrating two recent experiments, we show host dynamics are consistent with sensing both bulk and SFB, supporting our “optimal defense” hypothesis. Therefore, we propose that similar mechanisms could prove advantageous to other species and applicable beyond the ileum's mucus barrier.
... [5,6]). While it has been suggested that the gross architecture of the intestinal epithelium in the small and large intestine is not markedly affected by aging [7,8], studies in rodents and non-human primates suggest that the number of goblet cells increases while expression of α-defensines, lysozyme and F4/80 mRNA expression, as well as NO x levels and protein concentration of tight junction protein decreased with increasing age [9][10][11][12]. These alterations were found to go along with an increase in intestinal permeability [10,13,14] and bacterial endotoxin levels [12,14,15]. ...
... These alterations were found to go along with an increase in intestinal permeability [10,13,14] and bacterial endotoxin levels [12,14,15]. Results of several studies further suggest that these aging-associated alterations are linked to changes of intestinal microbiota in older animals and humans [9,11,12,[16][17][18]. It has been suggested that aging-associated intestinal microbiota dysbiosis and the increase of systemic tumor necrosis factor alpha (TNFα) levels found in old mice may be critical in aging-related intestinal barrier dysfunction [19]. ...
... Interestingly, neither tight junction protein levels nor intestinal permeability were altered in large intestine of animals. Old age has been reported before to be associated with marked changes in diversity and the prevalence of specific bacterial strains in fecal and small intestinal microbiota, as well as elevated levels of bacterial endotoxin in a variety of species [9,12,[14][15][16][17]44]. In baboons, these alterations have been linked to a loss of tight junction proteins in the large intestine [10], while in rodents, being in line with our finding, tight junctions' protein levels were lower in small intestinal tissue [11]. ...
Aging is considered a state of low grade inflammation, occurring in the absence of any overt infection often referred to as `inflammaging´. Maintaining intestinal homeostasis may be a target to extend a healthier status in older adults. Here, we report that even in healthy older men low grade bacterial endotoxemia is prevalent. In addition, employing multiple mouse models, we also show that while intestinal microbiota composition changes significantly during aging, fecal microbiota transplantation to old mice does not protect against aging-associated intestinal barrier dysfunction in small intestine. Rather, intestinal NO homeostasis and arginine metabolism mediated through arginase and NO synthesis is altered in small intestine of aging mice. Treatment with the arginase inhibitor norNOHA prevented aging-associated intestinal barrier dysfunction, low grade endotoxemia and delayed the onset of senescence in peripheral tissue e.g., liver. Intestinal arginine and NO metabolisms could be a target in the prevention of aging-associated intestinal barrier dysfunction and subsequently decline and `inflammaging´.
... One proposed mechanism of this apparent increase of AMP expression in aging populations is partially attributed to a compromised barrier between host and microbe, causing increased inflammation due to increased interactions with microbe-secreted signaling molecules. In support of this, many AMPs become dysregulated in aged mice, and these changes are associated with microbiome changes in the small intestine (Tremblay et al., 2017). In Drosophila, several studies show that aging specifically causes an increase in numerous AMPs (Kounatidis et al., 2017;Badinloo et al., 2018;Hanson and Lemaitre, 2020;Swanson et al., 2020;Wang et al., 2020). ...
Antimicrobial peptides (AMPs) are classically known as important effector molecules in innate immunity across all multicellular organisms. However, emerging evidence begins to suggest multifunctional properties of AMPs beyond their antimicrobial activity, surprisingly including their roles in regulating neuronal function, such as sleep and memory formation. Aging, which is fundamental to neurodegeneration in both physiological and disease conditions, interestingly affects the expression pattern of many AMPs in an infection-independent manner. While it remains unclear whether these are coincidental events, or a mechanistic relationship exists, previous studies have suggested a close link between AMPs and a few key proteins involved in neurodegenerative diseases. This review discusses recent literature and advances in understanding the crosstalk between AMPs and the nervous system at both molecular and functional levels, with the aim to explore how AMPs may relate to neuronal vulnerability in aging.
... In healthy older individuals, the thickness of the gastric and duodenal mucus layer is not altered [71]. In the ileum of old-aged mice, the number of goblet cells per villus displaying larger mucin granules may even be higher [72]. Tremblay et al. report a reduced expression of ileal α-defensins and lysozyme, two antimicrobial peptides produced by Paneth cells [72]. ...
... In the ileum of old-aged mice, the number of goblet cells per villus displaying larger mucin granules may even be higher [72]. Tremblay et al. report a reduced expression of ileal α-defensins and lysozyme, two antimicrobial peptides produced by Paneth cells [72]. In old-aged mice, the thickness of the colonic mucus layer was reported to be reduced when compared to young animals, and this loss in elderly mice could be restored by supplementing Lactobacillus plantarum WCFS1 [73]. ...
... Herein, the excessive formation of reactive oxygen species through both extrinsic and intrinsic measures, including a "Warburg-like reprogramming" [102], seem to be relevant, as shown by results obtained in studies using Drosophila. A changed mucus layer, e.g., changes in the glycosylation pattern of mucins [78], in anti-microbial peptides [72], and in levels of soluble immunoglobulin A [103][104][105], as well as the prevalence of immune cells, e.g., M cells [88] and T cells [106], have also been associated with aging-associated intestinal barrier dysfunction (for an overview, see [78]). Results of in vitro studies in Caco-2 cells suggest that TNFα may alter MLCK protein levels, which are involved in the regulation of tight junction proteins in the small intestinal epithelium [107,108]. ...
The intestinal barrier, composed of the luminal microbiota, the mucus layer, and the physical barrier consisting of epithelial cells and immune cells, the latter residing underneath and within the epithelial cells, plays a special role in health and disease. While there is growing knowledge on the changes to the different layers associated with disease development, the barrier function also plays an important role during aging. Besides changes in the composition and function of cellular junctions, the entire gastrointestinal physiology contributes to essential age-related changes. This is also reflected by substantial differences in the microbial composition throughout the life span. Even though it remains difficult to define physiological age-related changes and to distinguish them from early signs of pathologies, studies in centenarians provide insights into the intestinal barrier features associated with longevity. The knowledge reviewed in this narrative review article might contribute to the definition of strategies to prevent the development of diseases in the elderly. Thus, targeted interventions to improve overall barrier function will be important disease prevention strategies for healthy aging in the future.
... Intestinal secretory cells, particularly Paneth and goblet cells, are responsible for the synthesis and secretion of multiple antimicrobial peptides and proteins as well as mucins that play important roles in maintenance of the intestinal barrier and immunological homeostasis of the gastrointestinal tract. Defects in the differentiation and function of these cells have major detrimental consequences on the integrity and function of the intestinal barrier (Tremblay et al., 2017). The decreases in Muc2 and Lyz1 gene expression levels in the small intestine of senescent SAMP8 mice may be an indicator of a defect in intestinal barrier homeostasis. ...
Impairment of gastrointestinal function and reduction of nutrient absorption associated with aging contribute to increased risk of malnutrition in the elderly population, resulting in physical weakness and vulnerability to disease. The present study was performed to examine the relationships between aging-associated morphological changes of the small intestine and nutrient malabsorption using senescence-accelerated mouse prone 8 (SAMP8) mice. Comparison of the morphology of the small intestine of young (22-week-old) and senescent (43-week-old) SAMP8 mice showed no significant changes in villus length, while the mRNA expression levels of secretory cell marker genes were significantly reduced in senescent mice. In addition, crypts recovered from the small intestine of senescent mice showed a good capacity to form intestinal organoids ex vivo, suggesting that the regenerative capacity of intestinal stem cells (ISCs) was unaffected by accelerated senescence. These results indicated that changes induced by accelerated senescence in the small intestine of SAMP8 mice are different from changes reported previously in normal aging mouse models. Biochemical analyses of serum before and during senescence also indicated that senescent SAMP8 mice are not in a malabsorption state. Furthermore, a diet supplemented with persimmon pectin had a mild effect on the small intestine of senescent SAMP8 mice. Intestinal villus length was slightly increased in the medial part of the small intestine of pectin-fed mice. In contrast, intestinal crypt formation capacity was enhanced by the pectin diet. Organoid culture derived from the small intestine of mice fed pectin exhibited a greater number of lobes per organoid compared with those from mice fed a control diet, and Lyz1 and Olfm4 mRNA levels were significantly increased. In conclusion, accelerated senescence induced exclusive changes in the small intestine, which were not related to nutrient malabsorption. Therefore, the SAMP8 strain may not be a suitable model to evaluate the effects of aging on intestinal homeostasis and nutrient absorption impairment.
... Previous work has indicated that the intestinal capillaries of germ-free mice develop poorly compared to conventional mice, suggesting that the microbiota contributes to the development of intestinal villi [45]. Moreover, the ilea of aged mice were found to exhibit distinct histological features, characterized by a reduction in villus length [46]. We found that the L group mice had longer intestinal villi than those observed in the E group mice ( Figure 2D), indicating that the L group has a higher absorptive capacity and younger histological features than the E group. ...
A close relationship between age and gut microbiota exists in invertebrates and vertebrates, including humans. Long-living people are a model for studying healthy aging; they also have a distinctive microbiota structure. The relationship between the microbiota of long-living people and aging phenotype remains largely unknown. Herein, the feces of long-living people were transplanted into mice, which were then examined for aging-related indices and beneficial bacteria. Mice transplanted with fecal matter from long-living people (L group) had greater α diversity, more probiotic genera (Lactobacillus and Bifidobacterium), and short-chain fatty acid producing genera (Roseburia, Faecalibacterium, Ruminococcus, Coprococcus) than the control group. L group mice also accumulated less lipofuscin and β-galactosidase and had longer intestinal villi. This study indicates the effects that the gut microbiota from long-living people have on healthy aging.
... This suggested that the mechanical protection afforded by the mucus layer, at least in these two locations, is not affected by ageing. In addition, the ileum of aged mice showed a slight increase in the number of goblet cells/villus that displayed larger mucin granules indicative of an increase in mucus abundance (Tremblay et al., 2017). Also, others observed that the overall number of goblet cells in the ileal Peyer's patches (PPs) of ageing mice remained unchanged (Kobayashi et al., 2013). ...
... In mice, it has been observed that the expression of important Paneth cell-derived AMPs, such as α-defenins and lysozyme declined with age; in contrast, other AMPs including regenerating islet-derived protein 3 beta (RegIIIB) and gamma (RegIIIG) as well as β-defensins 1, angiogenin-4 and resistin-like molecule β (RELMβ) were significantly up-regulated in ageing (Tremblay et al., 2017). The exact mechanism underlying the age-related up-regulation of AMPs is not clear. ...
The intestinal epithelial barrier protects the mucosa of the gastrointestinal (GI)-tract and plays a key role in maintaining the host homeostasis. It encompasses several elements that include the intestinal epithelium and biochemical and immunological products, such as the mucus layer, antimicrobial peptides (AMPs) and secretory immunologlobulin A (sIgA). These components are interlinked with the large microbial community inhabiting the gut to form a highly sophisticated biological system that plays an important role on many aspects of human health both locally and systemically. Like any other organ and tissue, the intestinal epithelial barrier is affected by the ageing process. New insights have surfaced showing that critical functions, including intestinal stem cell regeneration and regulation of the intestinal crypt homeostasis, barrier integrity, production of regulatory cytokines, and epithelial innate immunity to pathogenic antigens change across life. Here we review the age-associated changes of the various components of the intestinal epithelial barrier and we highlight the necessity to elucidate further the mechanisms underlying these changes. Expanding our knowledge in this area is a goal of high medical relevance and it will help to define intervention strategies to ameliorate the quality of life of the ever-expanding elderly population.
Chemotherapy remains a major treatment for malignant tumors, yet the application of standard dose intensity chemotherapy is limited due to the side effects of cytotoxic drugs, especially in old populations. The underlying mechanisms of cytotoxicity and strategies to increase the safety and tolerance of chemotherapy remain to be explored. Using 5-fluorouracil (5-FU), a cornerstone chemotherapeutic drug, we demonstrate that the main cause of death in ad libitum (AL) fed mice after 5-FU chemotherapy was infection caused by translocation of intestinal opportunistic pathogens. We show that these opportunistic pathogens greatly increase in the intestine after chemotherapy, which was closely related to loss of intestinal lysozyme. Of note, two weeks of dietary restriction (DR) prior to chemotherapy significantly protected the loss of lysozyme and increased the content of the beneficial Lactobacillus genera, resulting in a substantial inhibition of intestinal opportunistic pathogens and their translocation. The rescue effect of DR could be mimicked by Lysozyme or Lactobacillus gavage. Our study provides the first evidence that DR achieved a comprehensive protection of the intestinal physical, biological and chemical barriers, which significantly improved the overall survival of 5-FU-treated mice. Importantly, the above findings were more prominent in old mice. Furthermore, we show that patients over 65 years old have enriched opportunistic pathogens in their gut microbiota, especially after 5-FU based chemotherapy. Our study reveals important mechanisms for the poor chemotherapy tolerance of the elderly population, which can be significantly improved by short-term DR. This study generates new insights into methods for improving the chemotherapeutic prognosis by increasing the chemotherapy tolerance and safety of patients with malignant tumors.
Cognitive dysfunction is a common symptom experienced by elderly individuals after surgery, resulting in memory problems, difficulties with logical thinking, hallucinations, delusions, and an increased risk of dementia. Despite its prevalence, the underlying cause of postoperative cognitive dysfunction remains unclear. Recent research has uncovered a link between neurodegenerative diseases and the gut microbiota, indicating the need for further investigation into the role of the intestinal flora in postoperative cognitive dysfunction. To address this research gap, we conducted behavioral tests, gene and protein analyses, metagenomics, and non-targeted metabolomics to compare the gut microbiota and metabolomics of mice exposed to anesthesia/surgery that exhibited cognitive impairment with those of age-matched control mice. Our goal was to identify possible correlations between these factors. We found that mice experiencing postoperative cognitive dysfunction had a distinct microbial composition, neuroinflammation, and synaptic damage compared to the control group. Specifically, we observed significant increases in the relative abundances of Bacteroidetes unclassified, Bacteroides acidifaciens, Rikenellaceae bacterium, Muribaculaceae bacterium Isolate-104 HZI, Muribaculaceae bacterium Isolate-110 HZI, and Mucispirillum schaedleri in aged mice exposed to anesthesia and surgery, while the relative abundances of Lachnospiraceae bacterium A2, Lachnospiraceae bacterium A4, Lachnospiraceae bacterium, Blautia, Lachnoclostridium bacterium MD355, Eubacterium rectale, Ruminococcus sp. 1xD21-23, and Butyrivibrio were significantly decreased. Additionally, metabolites, such as thiamine, spermidine, and long-chain unsaturated fatty acids, were down-regulated compared to the control group. These findings suggest that the intestinal metabolic abnormalities observed in elderly mice exposed to anesthesia/surgery may be regulated by the intestinal microbiota, specifically the Lachnospiraceae, Lachnoclostridium, Butyrivibrio, and Eubacterium. Therefore, our study highlights the potential of manipulating the gut microbiota to modulate the host metabolism in order to prevent and manage postoperative cognitive dysfunction.
IMPORTANCE
As the population ages and medical technology advances, anesthesia procedures for elderly patients are becoming more common, leading to an increased prevalence of postoperative cognitive dysfunction. However, the etiology and correlation between the gut microbiota and cognitive dysfunction are poorly understood, and research in this area is limited. In this study, mice with postoperative cognitive dysfunction were found to have reduced levels of fatty acid production and anti-inflammatory flora in the gut, and Bacteroides was associated with increased depression, leading to cognitive dysfunction and depression. Furthermore, more specific microbial species were identified in the disease model, suggesting that modulation of host metabolism through gut microbes may be a potential avenue for preventing postoperative cognitive dysfunction.
