The TNF-α antagonist etanercept reverses age-related decreases in colonic SERT expression and faecal output in mice

Amperometry approach curve profiling to understand the regulatory mechanisms governing the concentration of intestinal extracellular serotonin

Enterochromaffin (EC) cells located within the intestinal mucosal epithelium release serotonin (5-HT) to regulate motility tones, barrier function and the immune system. Electroanalytical methodologies have been able to monitor steady state basal extracellular 5-HT levels but are unable to provide insight into how these levels are influenced by key regulatory processes such as release and uptake. We established a new measurement approach, amperometry approach curve profiling, which monitors the extracellular 5-HT level at different electrode-tissue (E-T) distances. Analysis of the current profile can provide information on contributions of regulatory components on the observed extracellular 5-HT level. Measurements were conducted from ex vivo murine ileum and colon using a boron-doped diamond (BDD) microelectrode. Amperometry approach curve profiling coupled with classical pharmacology demonstrated that extracellular 5-HT levels were significantly lower in the colon when compared to the ileum. This difference was due to a greater degree of activity of the 5-HT transporter (SERT) and a reduced amount of 5-HT released from colonic EC cells. The presence of an inhibitory 5-HT4 autoreceptor was observed in the colon, where a 40% increase in extracellular 5-HT was the half maximal inhibitory concentration for activation of the autoreceptor. This novel electroanalytical approach allows estimates of release and re-uptake and their contribution to 5-HT extracellular concentration from intestinal tissue be obtained from a single series of measurements.

Nonlinear DNA methylation trajectories in aging male mice

Although DNA methylation data yields highly accurate age predictors, little is known about the dynamics of this quintessential epigenomic biomarker during lifespan. To narrow the gap, we investigate the methylation trajectories of male mouse colon at five different time points of aging. Our study indicates the existence of sudden hypermethylation events at specific stages of life. Precisely, we identify two epigenomic switches during early-to-midlife (3-9 months) and mid-to-late-life (15-24 months) transitions, separating the rodents' life into three stages. These nonlinear methylation dynamics predominantly affect genes associated with the nervous system and enrich in bivalently marked chromatin regions. Based on groups of nonlinearly modified loci, we construct a clock-like classifier STageR (STage of aging estimatoR) that accurately predicts murine epigenetic stage. We demonstrate the universality of our clock in an independent mouse cohort and with publicly available datasets.

Bifidobacterium animalis sup F1-7 Acts as an Effective Activator to Regulate Immune Response Via Casepase-3 and Bak of FAS/CD95 Pathway

Intestinal microecology was closely related to immune regulation, but the related mechanism was still unclear. This study aimed to reveal how microorganisms improved immune response via casepase-3 and Bak of FAS/CD95 pathway. Bifidobacterium animalis F1-7 inhibited the melanoma B16-F10 cells in vitro effectively; had a potent anticancer effect of lung cancer mice; effectively improved the spleen immune index and CD3+ (75.8%) and CD8+ (19.8%) expression level; strengthened the phagocytosis of macrophages; inhibited the overexpression of inflammatory factors IL-6 (319.10 ± 2.46 pg/mL), IL-8 (383.05 ± 9.87 pg/mL), and TNF-α (2003.40 ± 11.42 pg/mL); and promoted the expression of anti-inflammatory factor IL-10 (406.00 ± 3.59 pg/mL). This process was achieved by promoting caspase-8/3 and BH3-interacting domain death agonist (Bid), Bak genes, and protein expression. This study confirmed the B. animalis F1-7 could act as an effective activator to regulate immune response by promoting the expression of caspase-8/3, Bid and Bak genes, and proteins and by activating the FAS/CD95 pathway. Our study provided a data support for the application of potentially beneficial microorganisms of B. animalis F1-7 as an effective activator to improve immunity.

Research progress in the treatment of slow transit constipation by traditional Chinese medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Slow transit constipation (STC) is a common gastrointestinal disorder seriously impacting patients' quality of life. At present, although conventional chemical drugs effectively control STC symptoms in the short term, the long-term effects are poor, and the side effects are significant. In this regard, traditional Chinese medicine (TCM) offers an opportunity for STC treatment. Many pharmacological and clinical studies have confirmed this efficacy of TCM with multiple targets and mechanisms.

AIM OF THE STUDY

This review attempted to summarize the characteristics of TCM (compound prescriptions, single Chinese herbs, and active ingredients) for STC treatment and discussed their efficacy based on analyzing the pathogenesis of STC.

MATERIALS AND METHODS

The information was acquired from different databases, including PubMed, Web of Science, China National Knowledge Infrastructure, and Wanfang databases. We then focused on the recent research progress in STC treatment by TCM. Finally, the future challenges and trends are proposed.

RESULTS

TCM has good clinical efficacy in the treatment of STC with multi-mechanisms. Based on the theory of syndrome differentiation, five kinds of dialectical treatment for STC by compound TCM prescriptions were introduced, namely: Nourishing Yin and moistening the intestines; Promoting blood circulation and removing blood stasis; Warming Yang and benefiting Qi; Soothing the liver and regulating Qi; and Benefiting Qi and strengthening the spleen. In addition, six single Chinese herbs and eight active ingredients also show good efficacy in STC treatment.

CONCLUSIONS

TCM, especially compound prescriptions, has bright prospects in treating STC attributed to its various holistic effects.

Intestinal Region-Specific and Layer-Dependent Induction of TNFα in Rats with Streptozotocin-Induced Diabetes and after Insulin Replacement

Tumour necrosis factor alpha (TNFα) is essential in neuroinflammatory modulation. Therefore, the goal of this study is to reveal the effects of chronic hyperglycaemia and insulin treatment on TNFα expression in different gut segments and intestinal wall layers. TNFα expression was mapped by fluorescent immunohistochemistry and quantitative immunogold electron microscopy in myenteric ganglia of duodenum, ileum and colon. Tissue TNFα levels were measured by enzyme-linked immunosorbent assays in muscle/myenteric plexus-containing (MUSCLE-MP) and mucosa/submucosa/submucous plexus-containing (MUC-SUBMUC-SP) homogenates. Increasing density of TNFα-labelling gold particles is observed in myenteric ganglia from proximal to distal segments and TNFα tissue levels are much more elevated in MUSCLE-MP homogenates than in MUC-SUBMUC-SP samples in healthy controls. In the diabetics, the number of TNFα gold labels is significantly increased in the duodenum, decreased in the colon and remained unchanged in the ileal ganglia, while insulin does not prevent these diabetes-related TNFα changes. TNFα tissue concentration is also increased in MUSCLE-MP homogenates of diabetic duodenum, while decreased in MUC-SUBMUC-SP samples of diabetic ileum and colon. These findings support that type 1 diabetes has region-specific and intestinal layer-dependent effects on TNFα expression, contributing to the regional damage of myenteric neurons and their intestinal milieu.

Mechanisms underlying the promotion of 5-hydroxytryptamine secretion in enterochromaffin cells of constipation mice by Bifidobacterium and Lactobacillus

BACKGROUND

5-Hydroxytryptamine (5-HT) could play a role in alleviating symptoms in constipation. However, the mechanism underlying the role of intestinal flora in the promotion of 5-HT secretion by enterochromaffin cells (ECs) and regulation of the gastrointestinal endocrine system remains unclear.

METHODS

A constipation mouse model was constructed, and the 5-HT, chromogranin A (CGA), substance P (SP), motilin (MTL), dopamine, and noradrenaline expression levels were measured using enzyme-linked immunosorbent assay(Elisa) and immunofluorescence, and key proteins, such as the transient receptor potential (TRP) ion channels/tryptophan hydroxylase (TPH) and olfactory receptor (OR), were determined using western blot. Flow cytometry and in vivo imaging were used to observe microbial colonization in the intestinal tracts of mice.

KEY RESULTS

Bifidobacterium animalis F1-7 (F1-7), Lactobacillus paraccasei F34-3 (F34-3), and Lactobacillus plantarum FWDG (FWDG) promoted 5-HT secretion. F1-7 and F34-3 induced CGA expression, increased catecholamine secretion, and activated the CGA/α2A adrenoreceptor (ADRα2A) cascade signal in ECs. FWDG increased noradrenaline levels and activated the ADRα2A signal in ECs. SP content increased in F1-7 and F34-3, and MTL expression increased in FWDG via the above signal. F1-7 and F34-3 downregulated TRPV4 and upregulated TPH, whereas FWDG upregulated OR2A4 for promoting 5-HT secretion by ECs. Finally, we observed that F1-7, F34-3, and FWDG were well colonized in the large intestine.

CONCLUSIONS AND INFERENCES

F1-7, F34-3, and FWDG promoted 5-HT secretion in ECs of constipation mice by activating the CGA/ADRα2A cascade signal and regulating the TRP/TPH-OR pathways.

Bifidobacterium animalis F1-7 in combination with konjac glucomannan improves constipation in mice via humoral transport

Probiotics and natural products can promote humoral transport and effectively relieve intestinal motility. This study investigated the effects of probiotics in combination with konjac glucomannan (KGM) and an aqueous extract of Prunus persica on constipation. The growth promotion effect of these natural products on probiotics was investigated using co-culture in vitro. The combined effect of probiotics and natural products on constipation was observed in mice. The tryptophan, tryptamine and short-chain fatty acid levels were determined using enzyme-linked immunosorbent assay, reverse-phase high-performance liquid chromatography, and gas chromatography. The key genes and proteins involved in humoral transport were identified using real-time polymerase chain reaction, western blotting and fluorescence immunoassay. KGM promoted the growth of Bifidobacterium animalis F1-7 in vitro, and a mixture of KGM and B. animalis F1-7 effectively promoted defaecation in mice, increased the faecal water content, shortened the defaecation time and improved the gastrointestinal transit rate. In mice, the KGM + F1-7 mixture reduced the tryptophan level and increased the levels of tryptamine, acetic acid, propionic acid, butyric acid and valeric acid. In addition, the KGM + F1-7 mixture effectively increased the mRNA level of 5-HT₄-G-protein-coupled receptors (5-HT₄GPCR)/mucins-2 (MUC-2) and reduced the level of aquaporins (AQP₃); furthermore, it upregulated the protein level of 5-HT₄GPCR/MUC-2 and downregulated the protein level of AQP₃. These findings indicated that the KGM + F1-7 mixture effectively improved intestinal motility and alleviated constipation through humoral transport-related pathways.

Effects of age and social isolation on murine hippocampal biochemistry and behavior

Social isolation (SI) is a major health risk in older people leading to cognitive decline. This study examined how SI and age influence performance in the novel object recognition (NOR) and elevated plus maze (EPM) tasks in C57BL/6 mice aged 3 or 24 months. Mice were group-housed (groups of 2-3) or isolated for 2 weeks prior to experimentation. Following NOR and EPM testing hippocampal norepinephrine (NE), 5, hydroxytryptamine (5-HT), 5, hydroxyindole acetic acid (5-HIAA), corticosterone (CORT) and interleukin-6 (IL-6) were determined and serum collected for basal CORT analysis. A separate set of mice were exposed to the forced swim test (FST), sacrificed immediately and serum CORT determined. SI impaired performance in the NOR and the FST, reduced hippocampal 5-HT, increased hippocampal IL-6 and increased serum CORT post-FST in young mice. Aged mice either failed to respond significantly to SI (NOR, FST, hippocampal 5-HT, serum CORT post FST) or SI had synergistic effects with age (hippocampal NE, 5-HIAA:5-HT). In conclusion, the lack of response to SI in the aged mice may affect health by preventing them adapting to new stressors, while the synergistic effects of SI with age would increase allostatic load and enhance the deleterious effects of the ageing process.

Developmental and age-dependent plasticity of GABAA receptors in the mouse colon: Implications in colonic motility and inflammation

Lifelong functional plasticity of the gastrointestinal (GI) tract is essential for health, yet the underlying molecular mechanisms are poorly understood. The enteric nervous system (ENS) regulates all aspects of the gut function, via a range of neurotransmitter pathways, one of which is the GABA-GABA_A receptor (GABA_AR) system. We have previously shown that GABA_A receptor subunits are differentially expressed within the ENS and are involved in regulating various GI functions. We have also shown that these receptors are involved in mediating stress-induced colonic inflammation. However, the expression and function of intestinal GABA_ARs, at different ages, is largely unexplored and was the focus of this study. Here we show that the impact of GABA_AR activation on colonic contractility changes from early postnatal period through to late adulthood, in an age-dependant manner. We also show that the highest levels of expression for all GABA_AR subunits is evident at postnatal day (P) 10 apart from the α3 subunit which increased with age. This increase in the α3 subunit expression in late adulthood (18 months old) is accompanied by an increase in the expression of inflammatory markers within the mouse colon. Finally, we demonstrate that the deletion of the α3 subunit prevents the increase in the expression of colonic inflammatory markers associated with healthy ageing. Collectively, the data provide the first demonstration of the molecular and functional plasticity of the GI GABA_AR system over the course of a lifetime, and its possible role in mediating the age-induced colonic inflammation associated with healthy ageing.

Changes in murine anorectum signaling across the life course

BACKGROUND

Increasing age is associated with an increase in the incidence of chronic constipation and fecal impaction. The contribution of the natural aging process to these conditions is not fully understood. This study examined the effects of increasing age on the function of the murine anorectum.

METHODS

The effects of increasing age on cholinergic, nitrergic, and purinergic signaling pathways in the murine anorectum were examined using classical organ bath assays to examine tissue function and electrochemical sensing to determine age-related changes in nitric oxide and acetylcholine release.

KEY RESULTS

Nitrergic relaxation increased between 3 and 6 months, peaked at 12 months and declined in the 18 and 24 months groups. These changes were in part explained by an age-related decrease in nitric oxide (NO) release. Cholinergic signaling was maintained with age by an increase in acetylcholine (ACh) release and a compensatory decrease in cholinesterase activity. Age-related changes in purinergic relaxation were qualitatively similar to nitrergic relaxation although the relaxations were much smaller. Increasing age did not alter the response of the anorectum smooth muscle to exogenously applied ACh, ATP, sodium nitroprusside or KCl. Similarly, there was no change in basal tension developed by the anorectum.

CONCLUSIONS AND INFERENCES

The decrease in nitrergic signaling with increasing age may contribute to the age-related fecal impaction and constipation previously described in this model by partially obstructing defecation.

Interstitial cell network volume is reduced in the terminal bowel of ageing mice

Ageing is associated with impaired neuromuscular function of the terminal gastrointestinal (GI) tract, which can result in chronic constipation, faecal impaction and incontinence. Interstitial cells of cajal (ICC) play an important role in regulation of intestinal smooth muscle contraction. However, changes in ICC volume with age in the terminal GI tract (the anal canal including the anal sphincter region and rectum) have not been studied. Here, the distribution, morphology and network volume of ICC in the terminal GI tract of 3‐ to 4‐month‐old and 26‐ to 28‐month‐old C57BL/6 mice were investigated. ICC were identified by immunofluorescence labelling of wholemount preparations with an antibody against c‐Kit. ICC network volume was measured by software‐based 3D volume rendering of confocal Z stacks. A significant reduction in ICC network volume per unit volume of muscle was measured in aged animals. No age‐associated change in ICC morphology was detected. The thickness of the circular muscle layer of the anal sphincter region and rectum increased with age, while that in the distal colon decreased. These results suggest that ageing is associated with a reduction in the network volume of ICC in the terminal GI tract, which may influence the normal function of these regions.

Factors related to acupuncture response in patients with chronic severe functional constipation: Secondary analysis of a randomized controlled trial

Background

Acupuncture has been demonstrated to be effective and safe for chronic severe functional constipation (CSFC). However, which patients with CSFC will have a better response to acupuncture remains unclear.

Objective

To explore factors related to acupuncture response in patients with CSFC.

Methods

We performed a secondary analysis of a previous multicenter randomized controlled trial consisting of a 2-week run-in period, 8-week treatment, and 12-week follow-up without treatment in which patients with CSFC were randomly allocated to an electroacupuncture group or a sham electroacupuncture group. Responders were defined as participants with an increase of at least one complete spontaneous bowel movement (CSBM) in week 20 compared with the baseline period. The CSBM responder rate in both groups was described, and the baseline characteristics of participants potentially related to acupuncture response were mainly analyzed using logistic regression analysis with bootstrapping techniques.

Results

A total of 1021 participants were analyzed in this study, of whom 516 (50.5%) were classified as responders. The CSBM responder rate in week 20 was significantly greater in the electroacupuncture group than in the sham electroacupuncture group (62.9% vs. 37.9%, respectively; P<0.001). Both age and comorbidity were negatively associated with clinical response: with every one-year increase in age, the likelihood of clinical response was reduced by 1.2% (OR 0.988, 95%CI 0.980 to 0.996; P = 0.005), and patients with comorbidities were approximately 42% less likely to respond to treatment (OR 0.581, 95%CI 0.248 to 0.914; P = 0.001).

Conclusion

CSFC patients with increasing age and comorbidity may be less likely to respond to acupuncture. These findings contribute to guiding clinical practice in terms of pretreatment patient selection. Further research is needed to confirm the association.

Dysbiosis contributes to chronic constipation development via regulation of serotonin transporter in the intestine

Chronic constipation is a prevalent functional gastrointestinal disorder accompanied with intestinal dysbiosis. However, causal relationship between dysbiosis and constipation remains poorly understood. Serotonin transporter (SERT) is a transmembrane transport protein which re-uptakes excessive 5-hydroxytryptamine (5-HT) from effective location to terminate its physiological effects and involves in regulating gastrointestinal motility. In this study, fecal microbiota from patients with constipation and healthy controls were transplanted into the antibiotic depletion mice model. The mice which received fecal microbiota from patients with constipation presented a reducing in intestinal peristalsis and abnormal defecation parameters including the frequency of pellet expulsion, fecal weight and fecal water content. After fecal microbiota transplantation, the SERT expression in the colonic tissue was significantly upregulated, and the content of 5-HT was decreased which negatively correlated with the gastrointestinal transit time. Moverover, fecal microbiota from the mice which received fecal microbiota from patients with constipation also upregulated SERT in Caco-2 cells. Besides, this process accompanied with the decreased abundance of Clostridium, Lactobacillus, Desulfovibrio, and Methylobacterium and an increased tend of Bacteroides and Akkermansia, which also involved in the impairment of intestinal barrier after FMT. Taken together, intestinal dysbiosis may upregulate the SERT expression and contribute to the development of chronic constipation.