Behavioral and Oxidative Stress Changes in Mice Subjected to Combinations of Multiple Stressors Relevant to Irritable Bowel Syndrome

CENTRAL AND PERIPHERAL EFFECT OF MPTP VIA DOSE-DEPENDENT MAGNESIUM MODULATION

Background

Recent studies suggested that MPTP could cause gastrointestinal motility deficits additionally to its nonconclusive and controverted effects on the CNS (behavior and brain oxidative stress) in rats. A possible interaction between MPTP typical impairments and magnesium modulatory potential was previously suggested, as magnesium role was described in neuroprotection, gastrointestinal function, and oxidative stress.

Aim

To investigate the possible modulatory effect of several magnesium intake formulations (via drinking water) in MPTP neurotoxicity and functional gastrointestinal impairment induction.

Materials and Methods

Adult male Wistar rats were subjected to 3-week magnesium intake-controlled diets (magnesium depleted food and magnesium enriched drinking water) previously to acute subcutaneous MPTP treatment (30 mg/ kg body weight). Gastrointestinal motility (one hour stool collection test), and behavioral patterns (Y maze task, elevated plus maze test, open field test, forced swim test) were evaluated. Followingly, brain and bowel samples were collected, and oxidative stress was evaluated (glutathione peroxidase activity, malondial-dehyde concentrations).

Results

MPTP could lead to magnesium intake-dependent constipation-like gastrointestinal motility impairments, anxiety- and depressive-like affective behavior changes, and mild pain tolerance defects. Also, we found similar brain and intestinal patterns in magnesium-dependent oxidative stress.

Conclusion

While the MPTP effects in normal magnesium intake could be regarded as not fully relevant in rat models and limited to the current experimental conditions, the abnormalities observed in the affective behavior, gastrointestinal status, pain tolerance, peripheric and central oxidative status could be indicative of the extent of the systemic effects of MPTP that are not restricted to the CNS level, but also to gastro-intestinal system.

Anxiolytic Effect of Carvedilol in Chronic Unpredictable Stress Model

Anxiety disorders are the most prevalent psychiatric disorders being also a comorbid state of other diseases. We aimed to evaluate the anxiolytic-like effects of carvedilol (CVD), a drug used to treat high blood pressure and heart failure with potent antioxidant effects, in animals exposed to chronic unpredictable stress (CUS). To do this, female Swiss mice were exposed to different stressors for 21 days. Between days 15 and 21, the animals received oral CVD (5 or 10 mg/kg) or the antidepressant desvenlafaxine (DVS 10 mg/kg). On the 22^nd day, behavioral tests were conducted to evaluate locomotor activity (open field) and anxiety-like alterations (elevated plus-maze—EPM and hole board—HB tests). After behavioral determinations, the animals were euthanized, and the adrenal gland, blood and brain areas, prefrontal cortex (PFC), and hippocampus were removed for biochemical analysis. CUS reduced the crossings while increased rearing and grooming, an effect reversed by both doses of CVD and DVS. CUS decreased the number of entries and permanence time in the open arms of the EPM, while all treatments reversed this effect. CUS reduced the number of head dips in the HB, an effect reversed by CVD. The CUS reduced weight gain, while only CVD5 reversed this effect. A reduction in the cortical layer size of the adrenal gland was observed in stressed animals, which CVD reversed. Increased myeloperoxidase activity (MPO) and interferon-γ (IFN-γ), as well as reduction of interleukin-4 (IL-4) induced by CUS, were reversed by CVD. DVS and CVD increased IL-6 in both brain areas. In the hippocampus, DVS caused an increase in IFN-γ. Our data show that CVD presents an anxiolytic effect partially associated with immune-inflammatory mechanism regulation.

ROS-responsive thioketal-linked alginate/chitosan carriers for irritable bowel syndrome with diarrhea therapy

A colon-specific carrier that can protect drugs from the destruction in the gastrointestinal tract is critical for treating irritable bowel syndrome with diarrhea (IBS-D). In this study, chitosan was cross-linked by the thioketal (TK) bond to serve as a ROS-sensitive core of microspheres. Then the chitosan core was coated with an alginate shell. The alginate/chitosan microspheres can protect puerarin against the destruction and elimination in the gastrointestinal tract and release puerarin at the lesion sites in large quantities. The microspheres were characterized using differential scanning calorimetry, Fourier-transform infrared spectroscopy, and scanning electron microscopy. The swelling study showed that microspheres would shrink in an acidic environment. The in vitro release analysis indicated that little puerarin was released at gastric pH but burst release was observed in simulated colonic fluid containing H₂O₂. Fluorescent tracer revealed that the fluorescence of microspheres lasted up to 30 h in the colon, which was beneficial to prolong the action time between puerarin and colon. The in vivo studies indicated that puerarin-loaded microspheres are more effective in the treatment of IBS-D than free puerarin. Altogether, the ROS-responsive alginate/chitosan microspheres may be a promising strategy for IBS-D.

Potential Roles of Enterochromaffin Cells in Early Life Stress-Induced Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders, also known as disorders of the gut–brain interaction; however, the pathophysiology of IBS remains unclear. Early life stress (ELS) is one of the most common risk factors for IBS development. However, the molecular mechanisms by which ELS induces IBS remain unclear. Enterochromaffin cells (ECs), as a prime source of peripheral serotonin (5-HT), play a pivotal role in intestinal motility, secretion, proinflammatory and anti-inflammatory effects, and visceral sensation. ECs can sense various stimuli and microbiota metabolites such as short-chain fatty acids (SCFAs) and secondary bile acids. ECs can sense the luminal environment and transmit signals to the brain via exogenous vagal and spinal nerve afferents. Increasing evidence suggests that an ECs-5-HT signaling imbalance plays a crucial role in the pathogenesis of ELS-induced IBS. A recent study using a maternal separation (MS) animal model mimicking ELS showed that MS induced expansion of intestinal stem cells and their differentiation toward secretory lineages, including ECs, leading to ECs hyperplasia, increased 5-HT production, and visceral hyperalgesia. This suggests that ELS-induced IBS may be associated with increased ECs-5-HT signaling. Furthermore, ECs are closely related to corticotropin-releasing hormone, mast cells, neuron growth factor, bile acids, and SCFAs, all of which contribute to the pathogenesis of IBS. Collectively, ECs may play a role in the pathogenesis of ELS-induced IBS. Therefore, this review summarizes the physiological function of ECs and focuses on their potential role in the pathogenesis of IBS based on clinical and pre-clinical evidence.

Montelukast suppresses the development of irritable bowel syndrome phenotype possibly through modulating NF-κB signaling in an experimental model

Irritable bowel syndrome (IBS) is a functional gut disorder with multi-factorial pathophysiology that causes recurring pain or discomfort in the abdomen, as well as altered bowel habits. Montelukast, a well-known cysteinyl leukotriene receptor 1 (CysLT1R) antagonist, is widely used for the anti-inflammatory management of asthma. The present study aimed to evaluate the effects of pharmacological inhibition of CysLT1R on acetic acid-induced diarrhea-predominant IBS (D-IBS) in rats. Behavioral pain responses to noxious mechanical stimulation were decreased in the montelukast-treated rats as compared to the model animals following colorectal distension (CRD)-induced visceral hypersensitivity. Stool frequency decreased dose-dependently by montelukast in IBS rats exposed to restraint stress. A significantly shorter immobility time was also observed in IBS rats who received montelukast vs IBS group in the forced swimming test (depression-like behavior). Furthermore, there were significant decreases in the NF-κB protein expression, inflammatory cytokine (TNF-α, and IL-1ß) levels, and histopathological inflammatory injuries concomitant with increased anti-inflammatory cytokine, IL-10, in montelukast-treated rats compared with the IBS group. Cysteinyl leukotriene production and CysLT1R mRNA expression showed no remarkable differences among the experimental groups. The present results suggest the possible beneficial effects of montelukast in the management of D-IBS symptoms. The molecular mechanism underlying such effects, at least to some extent, might be through modulating CysLT1R-mediated NF-κB signaling. Yet, more studies are required to demonstrate the clinical potential of this drug for IBS therapy.

Systemic inflammation in the pathogenesis of irritable bowel syndrome associated with obesity

Investigation of the mechanisms promoting the development of irritable bowel syndrome (IBS) in obese patients is one of the most important issues of modern medicine. We examined 97 patients suffering from IBS. The group of comparison included 10 individuals with obesity. The control group included 21 practically healthy individuals. The levels of C-reactive protein (CRP) in the blood serum, tumor necrosis factor-α (TFNα), transforming growth factor-β1 (TGFβ1), interleukin-10 (IL-10), 8-isoprostane (IP), ceruloplasmin (CP) were examined. Endotoxicosis intensity was identified by the content of average molecular peptides in the blood and the Limulus Amebocyte Lysate (LAL) test. In the case of IBS with prevailing diarrhea, especially its comorbid course with obesity, cytokine imbalance was observed, which was manifested by a decreased amount of IL-10 in the blood serum and increased levels of TNFα and TGFβ1. Patients suffering from irritable bowel syndrome with prevailing diarrhea associated with obesity were characterized by high levels of C-reactive protein, fibrinogen and average molecules, increased content of pro-inflammatory cytokines (TFNα and TGFβ1) with a decreased content of IL-10, as well as imbalance of the pro-oxidant and anti-oxidant blood systems (increased content of 8-isoprostane and ceruloplasmin).