Dehydroepiandrosterone sulfate improves visceral sensation and gut barrier in a rat model of irritable bowel syndrome

Progress in research of low-grade inflammation in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common intestinal disease with a prevalence of 10%-15%. However, its pathophysiology is still not completely clear, and it has long been considered as a functional disease. In recent years, it has been found that low-grade inflammation plays a pathogenic role in IBS. Studies have confirmed that there is persistent mucosal inflammation at the microscopic and molecular levels. This review discusses the evidence, role, and clinical relevance of mucosal inflammation in IBS. In addition to mucosal inflammation, neuroinflammation may lead to changes in neuroendocrine pathways and glucocorticoid receptor genes through the "gut-brain" axis, and thus cause IBS through proinflammatory phenotype and hypothalamic pituitary adrenal axis and 5-hydroxytryptamine dysfunction. The observation that IBS patients can benefit from anti-inflammatory therapy also confirms that IBS is associated with inflammation.

Beyond depression and anxiety; a systematic review about the role of corticotropin-releasing hormone antagonists in diseases of the pelvic and abdominal organs

Evidence for beneficial effects of corticotropin releasing hormone (CRH) antagonists in abdominal and pelvic organs is emerging in preclinical studies. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement a compilation of preclinical studies using CRH receptor antagonists as a treatment for abdominal and pelvic disease was carried out. The Animal Research: Reporting of In Vivo Experiments (ARRIVE) essential 10 guidelines were used to determine quality of the included studies. A total of 40 studies from the last 15 years studying irritable bowel syndrome, inflammatory bowel disease, endometriosis, enteritis, stress impact on gastrointestinal processes and exogenous CRH administration effects were included. Blockage of the CRH receptor 1 was mainly associated with beneficial effects while that of CRH receptor 2 worsened studied effects. However, time of administration, route of administration and the animal model used, all had an impact on the beneficial outcomes. Frequency of drugs administered indicated that astressin-2B, astressin and antalarmin were among the most utilized antagonists. Of concern, studies included were predominantly carried out in male models only, representing a gender discrepancy in preclinical studies compared to the clinical scenario. The ARRIVE score average was 13 with ~60% of the studies failing to randomize or blind the experimental units. Despite the failure to date of the CRH antagonists in moving across the clinical trials pipeline, there is evidence for their beneficial effects beyond mood disorders. Future pre-clinical studies should be tailored towards effectively predicting the clinical scenario, including reduction of bias and randomization.

Pathophysiological Commonality Between Irritable Bowel Syndrome and Metabolic Syndrome: Role of Corticotropin-releasing Factor-Toll-like Receptor 4-Proinflammatory Cytokine Signaling

Irritable bowel syndrome (IBS) displays chronic abdominal pain with altered defecation. Most of the patients develop visceral hypersensitivity possibly resulting from impaired gut barrier and altered gut microbiota. We previously demonstrated that colonic hyperpermeability with visceral hypersensitivity in animal IBS models, which is mediated via corticotropin-releasing factor (CRF)-Toll-like receptor 4 (TLR4)-proinflammatory cytokine signaling. CRF impairs gut barrier via TLR4. Leaky gut induces bacterial translocation resulting in dysbiosis, and increases lipopolysaccharide (LPS). Activation of TLR4 by LPS increases the production of proinflammatory cytokines, which activate visceral sensory neurons to induce visceral hypersensitivity. LPS also activates CRF receptors to further increase gut permeability. Metabolic syndrome (MS) is a cluster of cardiovascular risk factors, including insulin resistance, obesity, dyslipidemia, and hypertension, and recently several researchers suggest the possibility that impaired gut barrier and dysbiosis with low-grade systemic inflammation are involved in MS. Moreover, TLR4-proinflammatory cytokine contributes to the development of insulin resistance and obesity. Thus, the existence of pathophysiological commonality between IBS and MS is expected. This review discusses the potential mechanisms of IBS and MS with reference to gut barrier and microbiota, and explores the possibility of existence of pathophysiological link between these diseases with a focus on CRF, TLR4, and proinflammatory cytokine signaling. We also review epidemiological data supporting this possibility, and discuss the potential of therapeutic application of the drugs used for MS to IBS treatment. This notion may pave the way for exploring novel therapeutic approaches for these disorders.

Gut feelings: the microbiota-gut-brain axis on steroids

The intricate connection between central and enteric nervous systems is well established with emerging evidence linking gut microbiota function as a significant new contributor to gut-brain axis signaling. Several microbial signals contribute to altered gut-brain communications, with steroids representing an important biological class that impacts central and enteric nervous system function. Neuroactive steroids contribute pathologically to neurological disorders, including dementia and depression, by modulating the activity of neuroreceptors. However, limited information is available on the influence of neuroactive steroids on the enteric nervous system and gastrointestinal function. In this review, we outline how steroids can modulate enteric nervous system function by focusing on their influence on different receptors that are present in the intestine in health and disease. We also highlight the potential role of the gut microbiota in modulating neuroactive steroid signaling along the gut-brain axis.

Centrally administered butyrate improves gut barrier function, visceral sensation and septic lethality in rats

Short chain fatty acids readily crosses the gut-blood and blood-brain barrier and acts centrally to influence neuronal signaling. We hypothesized that butyrate, a short-chain fatty acid produced by bacterial fermentation, in the central nervous system may play a role in the regulation of intestinal functions. Colonic permeability and visceral sensation was evaluated in rats. Septic lethality was evaluated in a sepsis model induced by subcutaneous administration of both lipopolysaccharide and colchicine. Intracisternal butyrate dose-dependently improved colonic hyperpermeability and visceral nociception. In contrast, subcutaneous injection of butyrate failed to change it. Intracisternal orexin 1 receptor antagonist or surgical vagotomy blocked the central butyrate-induced improvement of colonic hyperpermeability. The improvement of intestinal hyperpermeability by central butyrate or intracisternal orexin-A was blocked by cannabinoid 1 or 2 receptor antagonist. Intracisternal butyrate significantly improved survival period in septic rats. These results suggest that butyrate acts in the central nervous system to improve gut permeability and visceral nociception through cannabinoid signaling. Endogenous orexin in the brain may mediate the reduction of intestinal hyperpermeability by central butyrate through the vagus nerve. We would suggest that improvement of leaky gut by central butyrate may induce visceral antinociception and protection from septic lethality.

Phlorizin attenuates visceral hypersensitivity and colonic hyperpermeability in a rat model of irritable bowel syndrome

Visceral hypersensitivity and impaired gut barrier are crucial contributors to the pathophysiology of irritable bowel syndrome (IBS), and those are mediated via corticotropin-releasing factor (CRF)-Toll like receptor 4-pro-inflammatory cytokine signaling. Phlorizin is an inhibitor of sodium-linked glucose transporters (SGLTs), and known to have anti-cytokine properties. Thus, we hypothesized that phlorizin may improve these gastrointestinal changes in IBS, and tested this hypothesis in rat IBS models, i.e., lipopolysaccharide (LPS) or CRF-induced visceral hypersensitivity and colonic hyperpermeability. The visceral pain threshold in response to colonic balloon distention was estimated by abdominal muscle contractions by electromyogram, and colonic permeability was measured by quantifying the absorbed Evans blue in colonic tissue. Subcutaneous (s.c.) injection of phlorizin inhibited visceral hypersensitivity and colonic hyperpermeability induced by LPS in a dose-dependent manner. Phlorizin also blocked CRF-induced these gastrointestinal changes. Phlorizin is known to inhibit both SGLT1 and SGLT2, but intragastric administration of phlorizin may only inhibit SGLT1 because gut mainly expresses SGLT1. We found that intragastric phlorizin did not display any effects, but ipragliflozin, an orally active and selective SGLT2 inhibitor improved the gastrointestinal changes in the LPS model. Compound C, an adenosine monophosphate-activated protein kinase (AMPK) inhibitor, N^G-nitro-L-arginine methyl ester, a nitric oxide (NO) synthesis inhibitor and naloxone, an opioid receptor antagonist reversed the effects of phlorizin. In conclusions, phlorizin improved visceral hypersensitivity and colonic hyperpermeability in IBS models. These effects may result from inhibition of SGLT2, and were mediated via AMPK, NO and opioid pathways. Phlorizin may be effective for the treatment of IBS.

Blood Dehydroepiandrosterone and Dehydroepiandrosterone Sulfate as Pathophysiological Correlates of Chronic Pain: Analyses Using a National Sample of Midlife Adults in the United States

OBJECTIVE

Identifying biomarkers is a priority in translational chronic pain research. Dehydroepiandrosterone (DHEA) and its sulfated form, DHEA-S, are adrenocortical steroids in the blood with neuroprotective properties that also produce sex hormones. They may capture key sex-specific neuroendocrine mechanisms of chronic pain.

DESIGN

Cross-sectional study.

METHODS

Using data from 1,216 community-dwelling adults aged 34-84 from the Midlife in the United States (MIDUS) cohort, we examined blood DHEA and DHEA-S levels in association with chronic pain in men and women, adjusting for demographics, chronic diseases, medications including opioids, and psychosocial factors. If an association was found, we further explored dose-response relationships by the number of pain locations and the degree of pain interference.

RESULTS

In women, chronic pain was associated with 0.072 lower (95% confidence interval [CI], -0.127 to -0.017) log10 DHEA-S µg/dL, with pain in one to two locations associated with 0.068 lower (95% CI, -0.131 to -0.006) and in three or more locations 0.071 lower (95% CI, -0.148 to 0.007) log10 DHEA-S (P for trend = 0.074). Furthermore for women, low-interference pain was associated with 0.062 lower (95% CI, -0.125 to -0.000), whereas high-interference pain was associated with 0.138 lower (95% CI, -0.233 to -0.043) log10 DHEA-S (P for trend = 0.004). Chronic pain was not associated with DHEA or DHEA-S levels in men or DHEA levels in women.

CONCLUSIONS

Chronic pain and its functional interference correspond to lower blood DHEA-S levels in women.

Imipramine improves visceral sensation and gut barrier in rat models of irritable bowel syndrome

An impaired gut barrier, possibly leading to visceral hypersensitivity has been recently recognized to be one of the pivotal pathophysiology of irritable bowel syndrome (IBS). We previously showed that lipopolysaccharide (LPS), corticotropin-releasing factor (CRF), and repeated water avoidance stress (WAS) induce visceral hypersensitivity and colonic hyperpermeability via pro-inflammatory cytokine signaling (rat IBS models). Although the precise mechanisms of action are unclear, imipramine, a tricyclic antidepressant, improves IBS symptoms, and also has anticytokine properties. In this study, we hypothesized that imipramine improves the gut barrier to ameliorate IBS symptoms. To test this hypothesis, we determined its effects on visceral hypersensitivity and colonic hyperpermeability in rat IBS models. The visceral pain threshold in response to colonic balloon distention was electrophysiologically estimated by abdominal muscle contractions, and colonic permeability was measured by quantifying the absorbed Evans blue in colonic tissue in vivo. Subcutaneous imipramine injection (7, 20, 50 mg/kg) dose-dependently inhibited LPS-induced (1 mg/kg, subcutaneously) visceral hypersensitivity and colonic hyperpermeability. Imipramine also blocked these gastrointestinal (GI) changes induced by CRF (50 μg/kg, intraperitoneally) or repeated WAS (1 h daily for 3 days). Yohimbine (an α₂-adrenoceptors antagonist), sulpiride (a dopamine D₂ receptor antagonist), and naloxone hydrochloride (an opioid receptor antagonist) reversed these effects of imipramine in the LPS model. Therefore, imipramine may block GI changes in IBS via α₂-adrenoceptors, dopamine D₂, and opioid signaling. The improvement in the gut barrier resulting in inhibition of visceral pain is considered a valid mechanism of imipramine to ameliorate IBS symptoms.

Characterizing metabolites and potential metabolic pathways changes to understanding the mechanism of medicinal plant Phellodendri Amurensis cortex against doxorubicin-induced nephritis rats using UPLC-Q/TOF-MS metabolomics

Phellodendri Amurensis cortex (PAC), a famous traditional Chinese herb with good anti-inflammatory efficacy, is used to treat various liver and kidney sickness in clinical practice. However, the potential mechanisms protecting against nephritis of PAC have not been comprehensively elucidated. The aim of this research was to explore the mechanism of PAC against doxorubicin- induced nephritis in rats by characterizing metabolites and potential metabolic pathways changes. The rat models of nephritis were established using 6.5 mg/kg doxorubicin injection from caudal vein for five weeks. The rats in the treatment group were respectively received PAC extract at the dose of 216, 432, and 864 mg/kg once a day during the experiment. Then, urine metabolomics strategy based on ultra-performance liquid chromatography-quadrupole time of flight-tandem mass spectrometry (UPLC-Q/TOF-MS) has been employed to discover the possible significant metabolites and metabolic pathway of nephritis rats. At the end of the experiment, serum, urine and kidney tissue were collected for biochemical and pathological examination. The results showed that PAC treatment notably decreased urinary protein, serum Cr content and renal tissue lesions, and increased serum TP and ALB content. A total of potential twenty- eight metabolites such as 5'-methylthioadenosine, cGMP, dehydroepiandrosterone sulfate, salbuta, 2-phenylaminoadenosine contributing to nephritis rat model were selected and identified in the urine samples. Compared with the model group, the high-dose PAC group can recall 18 metabolites level, the medium-dose group can recall 13 metabolites level, and the low-dose PAC group can recall 8 metabolites level, which were involved in nine primary metabolic pathways such as steroid hormone biosynthesis, alanine,aspartate and glutamate metabolism, cysteine and methionine metabolism as well as glyoxylate and dicarboxylate metabolism. The protein expressions of key enzymes involving methylthioadenosine phosphorylase (Mtap), cytidine deaminase (Cda), thymidine kinase (Tk), argininosuccinate synthase (Ass) in metabolic pathways were further verified by Western blot. The results showed that Phellodendron chinense up-regulated the protein expressions of Cda and Tk and down-regulated the protein expressions of Mtap and Ass. In conclusion, PAC possesses renoprotective effect against doxorubicin-induced nephritis, which may be mediated via regulating differential metabolites, reducing oxidative stress response, improving renal function, enhancing the ability of the immune system, regulating the role of key enzymes.

Losartan improves visceral sensation and gut barrier in a rat model of irritable bowel syndrome

BACKGROUND

Lipopolysaccharide (LPS) or repeated water avoidance stress (WAS) induces visceral allodynia and colonic hyperpermeability via corticotropin-releasing factor (CRF) and proinflammatory cytokines, which is considered to be a rat irritable bowel syndrome (IBS) model. As losartan is known to inhibit proinflammatory cytokine release, we hypothesized that it improves these visceral changes.

METHODS

The threshold of visceromotor response (VMR), that is, abdominal muscle contractions induced by colonic balloon distention was electrophysiologically measured in rats. Colonic permeability was determined in vivo by quantifying the absorbed Evans blue in colonic tissue for 15 minutes spectrophotometrically.

KEY RESULTS

Lipopolysaccharide (1 mg kg^-1 ) subcutaneously (s.c.) reduced the threshold of VMR and increased colonic permeability. Losartan (5-25 mg kg^-1  s.c.) for 3 days inhibited these changes in a dose-dependent manner. Moreover, repeated WAS (1 hour daily for 3 days) or intraperitoneal injection of CRF (50 µg kg^-1 ) induced the similar visceral changes as LPS, which were also eliminated by losartan. These effects by losartan in LPS model were reversed by GW9662 (a peroxisome proliferator-activated receptor-γ [PPAR-γ] antagonist), N^G -nitro-L-arginine methyl ester (a nitric oxide [NO] synthesis inhibitor), or naloxone (an opioid receptor antagonist). Moreover, it also inhibited by sulpiride (a dopamine D₂ receptor antagonist) or domperidone (a peripheral dopamine D₂ antagonist).

CONCLUSION & INFERENCES

Losartan prevented visceral allodynia and colonic hyperpermeability in rat IBS models. These actions may be PPAR-γ-dependent and also mediated by the NO, opioid, and dopamine D₂ pathways. Losartan may be useful for IBS treatment.

Spexin as an anxiety regulator in mouse hippocampus: Mechanisms for transcriptional regulation of spexin gene expression by corticotropin releasing factor

Spexin (SPX) acts as a neuropeptide with pleiotropic functions that can participate in anxiety regulation. Corticotropin releasing factor (CRF) is widely expressed in brain tissues and associated with depression and anxiety and addiction. With the anxious mice under chronic unpredictable stress, we found SPX mRNA expression level in the hippocampus of the brain was significantly reduced, while local CRF mRNA expression level was increased. Furthermore, CRF injection in the hippocampus could also decrease SPX mRNA expression levels in hippocampus and other brain tissues, including pituitary and hypothalamus. With the primary mouse hippocampal cell model, CRF treatment could decrease SPX mRNA expression at hippocampal cell level and this inhibitory effect was mediated only by corticotropin releasing factor receptor 2 (CRFR2) but not corticotropin releasing factor receptor 1 (CRFR1). In HEK293 cells with CRFR2 over-expression, CRF could also inhibit SPX promoter activity coupling with AC/cAMP/PKA and MEK_1/2/Erk_1/2 cascades. In addition, Epac was also involved with the CRF-repressed SPX promoter activity and cross-talked with MEK_1/2/Erk_1/2 pathway. CRF could inhibit SPX gene expression in mouse hippocampus via transcriptional activation at the promoter level with coupling of AC/cAMP and MEK_1/2/Erk_1/2 signaling, which will be relevant to the anxiety response mediated by SPX in central nervous system.

Butyrate inhibits visceral allodynia and colonic hyperpermeability in rat models of irritable bowel syndrome

Lipopolysaccharide (LPS) or repeated water avoidance stress (WAS) induces visceral allodynia and gut hyperpermeability via corticotropin-releasing factor (CRF) and proinflammatory cytokines, which is a rat irritable bowel syndrome (IBS) model. As butyrate is known to suppress the release of proinflammatory cytokine, we hypothesized that butyrate alleviates these colonic changes in IBS models. The visceral pain was assessed by electrophysiologically measuring the threshold of abdominal muscle contractions in response to colonic distention. Colonic permeability was determined by measuring the absorbance of Evans blue in colonic tissue. Colonic instillation of sodium butyrate (SB; 0.37-2.9 mg/kg) for 3 days inhibited LPS (1 mg/kg)-induced visceral allodynia and colonic hyperpermeability dose-dependently. Additionally, the visceral changes induced by repeated WAS (1 h for 3 days) or CRF (50 µg/kg) were also blocked by SB. These effects of SB in the LPS model were eliminated by compound C, an AMPK inhibitor, or GW9662, a PPAR-γ antagonist, N^G-nitro-L-arginine methyl ester, a NO synthesis inhibitor, naloxone or sulpiride. SB attenuated visceral allodynia and colonic hyperpermeability in animal IBS models. These actions may be AMPK and PPAR-γ dependent and also mediated by the NO, opioid and central dopamine D₂ pathways. Butyrate may be effective for the treatment of IBS.