Role of Stress on Driving the Intestinal Paracellular Permeability.

The gut epithelium is a polarized monolayer that exhibits apical and basolateral membrane surfaces. Monolayer cell components are joined side by side via protein complexes known as tight junction proteins (TJPs), expressed at the most apical extreme of the basolateral membrane. The gut epithelium is a physical barrier that determinates intestinal permeability, referred to as the measurement of the transit of molecules from the intestinal lumen to the bloodstream or, conversely, from the blood to the gut lumen. TJPs play a role in the control of intestinal permeability that can be disrupted by stress through signal pathways triggered by the ligation of receptors with stress hormones like glucocorticoids. Preclinical studies conducted under in vitro and/or in vivo conditions have addressed underlying mechanisms that account for the impact of stress on gut permeability. These mechanisms may provide insights for novel therapeutic interventions in diseases in which stress is a risk factor, like irritable bowel syndrome. The focus of this study was to review, in an integrative context, the neuroendocrine effects of stress, with special emphasis on TJPs along with intestinal permeability.

Cholecystokinin Outcome on Markers of Intestinal IgA Antibody Response.

Cholecystokinin 8 (CCK8) is an entero-octapeptide that participates in crosstalk with components of intestinal immunity via the CCK receptor (CCKR), but its role in modulation of the IgA response is not fully known under physiological conditions. Male eight-week-old BALB/c mice each were intraperitoneally injected once during 7 days with CCK8, devazapide (CCKR1 antagonist), L365,260 (CCKR2 antagonist) or vehicle (sham group). In intestinal lavages, total and secretory IgA (SIgA) were determined by ELISA; in lamina propria, IgA+ B lymphocytes and IgA+ plasma cells were analyzed by flow cytometry; mRNA levels of polymeric immunoglobulin receptor (pIgR) in epithelial cells and α chain, interleukins (ILs) in lamina propria cells were assessed by qRTPCR. Regarding the sham conditions, IgA+ plasma-cell percentage and IL-2, IL-5, IL-10 and transforming growth factor-ß (TGF-ß) mRNA levels were either increased by CCK8 or decreased by both CCKR antagonists. For IgA/SIgA responses, IL-4/IL-6 mRNA levels were decreased by all drugs and pIgR mRNA was increased by CCK8 and reduced by L365,260. IgA+ B cell percentage and α chain mRNA levels were elicited by CCK8 and L365,260. Data suggested a presumable differential role of CCK/CCKR on the IgA-response; outcome of L365,260 on the elicitation of IgA+ B cells and α chain mRNA needs further examination.

Intestinal Homeostasis under Stress Siege.

Intestinal homeostasis encompasses a complex and balanced interplay among a wide array of components that collaborate to maintain gut barrier integrity. The appropriate function of the gut barrier requires the mucus layer, a sticky cushion of mucopolysaccharides that overlays the epithelial cell surface. Mucus plays a critical anti-inflammatory role by preventing direct contact between luminal microbiota and the surface of the epithelial cell monolayer. Moreover, mucus is enriched with pivotal effectors of intestinal immunity, such as immunoglobulin A (IgA). A fragile and delicate equilibrium that supports proper barrier function can be disturbed by stress. The impact of stress upon intestinal homeostasis results from neuroendocrine mediators of the brain-gut axis (BGA), which comprises a nervous branch that includes the enteric nervous system (ENS) and the sympathetic and parasympathetic nervous systems, as well as an endocrine branch of the hypothalamic-pituitary-adrenal axis. This review is the first to discuss the experimental animal models that address the impact of stress on components of intestinal homeostasis, with special emphasis on intestinal mucus and IgA. Basic knowledge from animal models provides the foundations of pharmacologic and immunological interventions to control disturbances associated with conditions that are exacerbated by emotional stress, such as irritable bowel syndrome.

Outcome of stress on G protein-coupled receptors and hypoxia inducible factor-1α.

Stress drives neuroendocrine signals with detrimental effects to the intestinal homeostasis. The aim of this study was to evaluate the effect of stress on intestinal hypoxia response elements, including G protein-coupled receptor 41 (GPR41), GPR43, and hypoxia inducible factor (HIF)-1α. Groups of five BALB/c mice were subjected to acute (2 h per day) and chronic (2 h per day for 4 days) stress induced by restraint, and the results were compared to those of an unstressed control group. Whole mucosal samples from the colon were collected to evaluate the expression of GPR41, GPR43 and HIF-1α using Western blot chemiluminescent analysis. Compared to the control group, in the chronic stress group the expression of GPR43 (P = 0.0092) and HIF-1α (P < 0.0001) were significantly lower and the expression of GPR41 was similar (P = 0.9184); acute stress significantly increased HIF-1α expression (P = 0.0030) and increased GPR41 expression (P = 0.0937), without affecting GPR43 (P = 0.9184). These findings offer insights into the modulation of hypoxia response elements under stress conditions and their pharmacological implications for developing drugs that mitigate the effects of stress on intestinal homeostasis.

Lactoferrin as a Component of Pharmaceutical Preparations: An Experimental Focus.

Lactoferrin is an 80 kDa monomeric glycoprotein that exhibits multitask activities. Lactoferrin properties are of interest in the pharmaceutical field for the design of products with therapeutic potential, including nanoparticles and liposomes, among many others. In antimicrobial preparations, lactoferrin has been included either as a main bioactive component or as an enhancer of the activity and potency of first-line antibiotics. In some proposals based on nanoparticles, lactoferrin has been included in delivery systems to transport and protect drugs from enzymatic degradation in the intestine, favoring the bioavailability for the treatment of inflammatory bowel disease and colon cancer. Moreover, nanoparticles loaded with lactoferrin have been formulated as delivery systems to transport drugs for neurodegenerative diseases, which cannot cross the blood-brain barrier to enter the central nervous system. This manuscript is focused on pharmaceutical products either containing lactoferrin as the bioactive component or formulated with lactoferrin as the carrier considering its interaction with receptors expressed in tissues as targets of drugs delivered via parenteral or mucosal administration. We hope that this manuscript provides insights about the therapeutic possibilities of pharmaceutical Lf preparations with a sustainable approach that contributes to decreasing the resistance of antimicrobials and enhancing the bioavailability of first-line drugs for intestinal chronic inflammation and neurodegenerative diseases.

Regionalized analysis of gut barrier components in the small intestine of BALB/c mice following chronic immobilization stress.

BACKGROUND: Microbiota and tight junction proteins (TJPs) are components of the gut barrier, and are considered stress targets that have deleterious effects on intestinal homeostasis. OBJECTIVES: This study aimed to evaluate the effects of chronic immobilization stress on selected small intestine homeostasis parameters. MATERIAL AND METHODS: Female BALB/c mice were divided into a stress group that underwent short-term immobilization for 2 h per day for 4 consecutive days, and a non-stressed control group (n = 6 per group). Proximal and distal small intestine samples were excised to assess colony-forming units per gram (CFU/g) of total bifidobacteria in selective agar plates, luminal albumin was assessed using immune-enzymatic assay, pro-inflammatory cytokines were evaluated using reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and TJPs (pore-forming, claudin (Cld)-2; pore-sealing, Cld-4; ambiguous, Cld-7, -12 and -15) were assessed with RT-qPCR and western blotting. RESULTS: Compared with the control group, the stress group had lower body weight and energy intake. In the distal region, the stressed mice had lower bifidobacteria count and messenger ribonucleic acid (mRNA) expression of Cld-2, Cld-4 and Cld-12, though they had more albumin and higher interleukin (IL)-6 mRNA expression. Within the proximal region, the stressed mice had higher mRNA expression of tumor necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), IL-6, Cld-7, Cld-12, and Cld-15, along with lower levels of IL-10 and Cld-4. However, mRNA and protein expression of TJPs were discordant. CONCLUSIONS: These findings indicate divergent stress-induced outcomes in the small intestine, evidenced by the elicitation of a pro-inflammatory response and decreased anti-inflammatory response in the duodenum, and by increased albumin transudation and decreased bifidobacterial growth in the distal region.

Exercise improves intestinal IgA production by T-dependent cell pathway in adults but not in aged mice.

Introduction: Hypermutated high-affinity immunoglobulin A (IgA), neutralizes toxins and drives the diversification of bacteria communities to maintain intestinal homeostasis although the mechanism underlies the impact of moderate aerobic exercise (MAE) on the IgA-generation via T-dependent (TD) is not fully know. Therefore, the aim of this study was to determine the effect of long-time MAE on the production of IgA through the TD pathway in Peyer´s patches of the small intestine from aged mice. Methods: MAE protocol consisted of twenty 3-month-old (young) BALB/c mice running in an endless band at 0° inclination and a speed of 10 m/h for 5 days a week and resting 2 days on the weekend until reaching 6-month-old (adulthood, n=10) or 24-month-old (aging, n=10). Groups of young, adult, or elderly mice were included as sedentary controls (n=10/per group). At 6 or 24 months old, all were sacrificed, and small intestine samples were dissected to prepare intestinal lavages for IgA quantitation by ELISA and to obtain suspensions from Peyer´s patches (PP) and lamina propria (LP) cells for analysis of T, B, and plasma cell subpopulations by flow cytometry and mRNA analysis expression by RT-qPCR of molecular factors related to differentiation of B cells to IgA+ plasma cells, class switch recombination, and IgA-synthesis. Statistical analysis was computed with two-way ANOVA (factor A=age, factor B=group) and p<0.05 was considered for statistically significant differences. Results: Compared to age-matched sedentary control, in exercised elderly mice, parameters were either increased (IgA concentration, IL-21, IL-10 and RDH mRNA expression), decreased (α-chain mRNA, B cells, mIgA+ B cells, mIgM+ B cells and IL-4 mRNA) or unchanged (PP mIgA+ plasmablasts and LP cyt-IgA+ plasma cells). Regarding the exercised adult mice, they showed an up-modulation of IgA-concentration, mRNA expression IL-21, IL-10, and RDH and cells (PP B and T cells, mIgM+ plasmablasts and LP cyt-IgA+plasma cells). Conclusion: Our findings suggest that MAE restored the IgA production in adult mice via the TD cell pathway but does not in aged mice. Other studies are necessary to know in more detail the impact of long-time MAE on the TD pathway to produce IgA in aging.

Lactoferrin and Its Potential Impact for the Relief of Pain: A Preclinical Approach.

Pain is one of the most disabling symptoms of several clinical conditions. Neurobiologically, it is classified as nociceptive, inflammatory, neuropathic and dysfunctional. Opioids and nonsteroidal anti-inflammatory drugs (NSAIDs) are conventionally prescribed for the treatment of pain. Long-term administration of opioids results in the loss of analgesic efficacy, leading to increased dosage, tolerance, and addiction as the main drawbacks of their use, while the adverse effects of NSAIDs include gastric ulcer formation, intestinal bleeding, acute kidney injury, and hepatotoxicity. Lactoferrin is an iron-binding, anti-inflammatory glycoprotein that displays analgesic activities associated, in part, by interacting with the low-density lipoprotein receptor-related protein (LRP), which may result in the regulation of the DAMP-TRAF6-NFκB, NO-cGMP-ATP K+-sensitive channel and opioid receptor signaling pathways. This review summarizes and discusses for the first time the analgesic effects of lactoferrin and its presumable mechanisms based on pre-clinical trials. Given its anti-nociceptive and anti-inflammatory properties, lactoferrin may be used as an adjunct to enhance the efficacy and to decrease the tolerogenic effects of canonical therapeutic drugs prescribed for pain treatment.

Bovine lactoferrin as a Modulator of Neuroendocrine Components of Stress.

Stress is a condition that maintains the homeostasis of the organism through the activation of different neuroendocrine pathways and secretion of a wide array of chemical mediators, including corticotropin-releasing hormone (CRH), neurotransmitters and glucocorticoids hormones. These molecules fulfill important physiological functions, but under stressful conditions, they can induce or aggravate a pathological state depending on type, severity and duration of stress. For this reason, the search for compounds that modulate the activity of the neuroendocrine pathways is crucial for the control of diseases associated with stressful situations. Bovine lactoferrin (bLf) is an iron-binding multifunctional glycoprotein that exhibits modulatory properties on the neuroendocrine system. Bovine lactoferrin affects the production and secretion of neuroendocrine components of the hypothalamus-pituitary-adrenal (HPA) axis. Neuroendocrine mechanisms of bLf entail either the down- or up-modulation of adrenal corticosteroids via HPA pathway activation, nitric oxide (NO) generation and opioid nervous system pathway activation. This manuscript is focused on reviewing the current contributions of bLf modulatory actions on the response of hormones, neurotransmitters involved in stress and behavior. Sustained use of drugs for stress-associated dysfunctions loses efficacy and requires the dose increase by tolerance and drug dependence. Therefore, bLf may be included as a therapeutic and/or adjunctive agent of drugbased therapies for the treatment of stress-associated emotional-disturbances.