Naturally occurring polyamines are ubiquitously distributed and play important roles in cell development, amino acid and protein synthesis, oxidative DNA damage, proliferation, and cellular ...differentiation. Macrophages are essential in the innate immune response, and contribute to tissue remodeling. Naïve macrophages have two major potential fates: polarization to (1) the classical pro-inflammatory M1 defense response to bacterial pathogens and tumor cells, and (2) the alternatively activated M2 response, induced in the presence of parasites and wounding, and also implicated in the development of tumor-associated macrophages. ODC, the rate-limiting enzyme in polyamine synthesis, leads to an increase in putrescine levels, which impairs M1 gene transcription. Additionally, spermidine and spermine can regulate translation of pro-inflammatory mediators in activated macrophages. In this review, we focus on polyamines in macrophage activation patterns in the context of gastrointestinal inflammation and carcinogenesis. We seek to clarify mechanisms of innate immune regulation by polyamine metabolism and potential novel therapeutic targets.
Countries endemic for parasitic infestations have a lower incidence of Crohn’s disease (CD) than nonendemic countries, and there have been anecdotal reports of the beneficial effects of helminths in ...CD patients. Tuft cells in the small intestine sense and direct the immune response against eukaryotic parasites. We investigated the activities of tuft cells in patients with CD and mouse models of intestinal inflammation.
We used microscopy to quantify tuft cells in intestinal specimens from patients with ileal CD (n = 19), healthy individuals (n = 14), and TNFΔARE/+ mice, which develop Crohn’s-like ileitis. We performed single-cell RNA sequencing, mass spectrometry, and microbiome profiling of intestinal tissues from wild-type and Atoh1-knockout mice, which have expansion of tuft cells, to study interactions between microbes and tuft cell populations. We assessed microbe dependence of tuft cell populations using microbiome depletion, organoids, and microbe transplant experiments. We used multiplex imaging and cytokine assays to assess alterations in inflammatory response following expansion of tuft cells with succinate administration in TNFΔARE/+ and anti-CD3E CD mouse models.
Inflamed ileal tissues from patients and mice had reduced numbers of tuft cells, compared with healthy individuals or wild-type mice. Expansion of tuft cells was associated with increased expression of genes that regulate the tricarboxylic acid cycle, which resulted from microbe production of the metabolite succinate. Experiments in which we manipulated the intestinal microbiota of mice revealed the existence of an ATOH1-independent population of tuft cells that was sensitive to metabolites produced by microbes. Administration of succinate to mice expanded tuft cells and reduced intestinal inflammation in TNFΔARE/+ mice and anti-CD3E-treated mice, increased GATA3+ cells and type 2 cytokines (IL22, IL25, IL13), and decreased RORGT+ cells and type 17 cytokines (IL23) in a tuft cell-dependent manner.
We found that tuft cell expansion reduced chronic intestinal inflammation in mice. Strategies to expand tuft cells might be developed for treatment of CD.
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Highlights • Arginine as an energy source in the host and pathogen. • Arginine-dependent NO production. • Modulation of arginine metabolism — strategy for immune evasion by pathogens. • Bioengineered ...arginine tagged particles — next generation antimicrobial therapy.
Hepatic TLR4 signaling in obese NAFLD Sharifnia, Torfay; Antoun, Joseph; Verriere, Thomas G C ...
American journal of physiology. Gastrointestinal and liver physiology/American journal of physiology: Gastrointestinal and liver physiology,
08/2015, Letnik:
309, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Nonalcoholic fatty liver disease occurs frequently in the setting of metabolic syndrome, but the factors leading to nonalcoholic steatohepatitis (NASH) are not fully understood. This study ...investigated Toll-like receptor 4 (TLR4) signaling in human liver with the goal of delineating whether activation of this pathway segregates those with nonalcoholic fatty liver from those with NASH. Experiments were performed using liver biopsy tissue obtained from class III obese subjects undergoing bariatric surgery, and extended to an immortalized human hepatocyte HepaRG cell line and primary human hepatocytes. The bacterial endotoxin lipopolysaccharide (LPS) and total free fatty acid levels were significantly increased in plasma of NASH patients. TLR4 mRNA levels were significantly increased in subjects with NASH compared with NAFL as was interferon regulatory factor (IRF) 3 in the myeloid differentiation factor 88-independent signaling pathway. In HepaRG cells, nuclear factor-κB (NF-κB) nuclear translocation and functional activity increased following treatment with the fatty acid, palmitate, and following exposure to LPS compared with hepatocytes stimulated with a lipogenic treatment that induced de novo lipogenesis. Palmitate and LPS induction of NF-κB activity was partially attenuated by chemical- or small-interfering RNA-mediated inhibition of TLR4. Expression of TLR4 and its downstream mediators was upregulated with palmitate and LPS. Similar results were observed using primary human hepatocytes from a lean donor. Interestingly, NF-κB activity assays showed obese donor hepatocytes were resistant to chemical TLR4 inhibition. In conclusion, TLR4 expression is upregulated in a large cohort of NASH patients, compared with those with NAFL, and this occurs within the setting of increased LPS and fatty acids.
Macrophage activation is a critical step in host responses during bacterial infections. Ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine metabolism, has been well studied in ...epithelial cells and is known to have essential roles in many different cellular functions. However, its role in regulating macrophage function during bacterial infections is not well characterized. We demonstrate that macrophage-derived ODC is a critical regulator of M1 macrophage activation during both Helicobacter pylori and Citrobacter rodentium infection. Myeloid-specific Odc deletion significantly increased gastric and colonic inflammation, respectively, and enhanced M1 activation. Add-back of putrescine, the product of ODC, reversed the increased macrophage activation, indicating that ODC and putrescine are regulators of macrophage function. Odc-deficient macrophages had increased histone 3, lysine 4 (H3K4) monomethylation, and H3K9 acetylation, accompanied by decreased H3K9 di/trimethylation both in vivo and ex vivo in primary macrophages. These alterations in chromatin structure directly resulted in up-regulated gene transcription, especially M1 gene expression. Thus, ODC in macrophages tempers antimicrobial, M1 macrophage responses during bacterial infections through histone modifications and altered euchromatin formation, leading to the persistence and pathogenesis of these organisms.
Helicobacter pylori is a Gram-negative bacterium that specifically colonizes the gastric ecological niche. During the infectious process, which results in diseases ranging from chronic gastritis to ...gastric cancer, the host response is characterized by the activation of the innate immunity of gastric epithelial cells and macrophages. These cells thus produce effector molecules such as reactive oxygen species (ROS) to counteract the infection. The generation of ROS in response to H. pylori involves two canonical pathways: 1) the NADPH-dependent reduction of molecular oxygen to generate O2•−, which can dismute to generate ROS; and 2) the back-conversion of the polyamine spermine into spermidine through the enzyme spermine oxidase, leading to H2O2 production. Although these products have the potential to affect the survival of bacteria, H. pylori has acquired numerous strategies to counteract their deleterious effects. Nonetheless, ROS-mediated oxidative DNA damage and mutations may participate in the adaptation of H. pylori to its ecological niche. Lastly, ROS have been shown to play a major role in the development of the inflammation and carcinogenesis. It is the purpose of this review to summarize the literature about the production of ROS during H. pylori infection and their role in this infectious gastric disease.
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•ROS are locally produced in the gastric mucosa during H. pylori infection.•Spermine oxidase and NADPH oxidases are the main sources of ROS in the stomach.•H. pylori has multiple strategies to resist oxidative damage.•ROS-induced mutagenic changes in H. pylori leads to genetic variation and adaptation.•Oxidative stress contributes to H. pylori-induced inflammation and carcinogenesis.
To evaluate the long-term effect of cumulative time exposed to
infection on the progression of gastric lesions.
795 adults with precancerous gastric lesions were randomised to receive anti-
treatment ...at baseline. Gastric biopsies were obtained at baseline and at 3, 6, 12 and 16 years. A total of 456 individuals attended the 16-year visit. Cumulative time of
exposure was calculated as the number of years infected during follow-up. Multivariable logistic regression models were used to estimate the risk of progression to a more advanced diagnosis (versus no change/regression) as well as gastric cancer risk by intestinal metaplasia (IM) subtype. For a more detailed analysis of progression, we also used a histopathology score assessing both severity and extension of the gastric lesions (range 1-6). The score difference between baseline and 16 years was modelled by generalised linear models.
Individuals who were continuously infected with
for 16 years had a higher probability of progression to a more advanced diagnosis than those who cleared the infection and remained negative after baseline (p=0.001). Incomplete-type IM was associated with higher risk of progression to cancer than complete-type (OR, 11.3; 95% CI 1.4 to 91.4). The average histopathology score increased by 0.20 units/year (95% CI 0.12 to 0.28) among individuals continuously infected with
. The effect of cumulative time of infection on progression in the histopathology score was significantly higher for individuals with atrophy (without IM) than for individuals with IM (p<0.001).
Long-term exposure to
infection was associated with progression of precancerous lesions. Individuals infected with
with these lesions may benefit from eradication, particularly those with atrophic gastritis without IM. Incomplete-type IM may be a useful marker for the identification of individuals at higher risk for cancer.
Advancements in our understanding of polyamine molecular and cellular functions have led to increased interest in targeting polyamine metabolism for anticancer therapeutic benefits. The polyamines ...putrescine, spermidine, and spermine are polycationic alkylamines commonly found in all living cells and are essential for cellular growth and survival. This review summarizes the existing research on polyamine metabolism and function, specifically the role of polyamines in gastric immune cell and epithelial cell function. Polyamines have been implicated in a multitude of cancers, but in this review, we focus on the role of polyamine dysregulation in the context of Helicobacter pylori-induced gastritis and subsequent progression to gastric cancer. Due to the emerging implication of polyamines in cancer development, there is an increasing number of promising clinical trials using agents to target the polyamine metabolic pathway for potential chemoprevention and anticancer therapy.
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