Corticotropin-releasing factor system in the lateral septum: Implications in the pathophysiology of obesity.

Obesity is a pandemic associated with lifestyles changes. These include excess intake of obesogenic foods and decreased physical activity. Brain areas, like the lateral hypothalamus (LH), ventral tegmental area (VTA), and nucleus accumbens (NAcc) have been linked in both homeostatic and hedonic control of feeding in experimental models of diet-induced obesity. Interestingly, these control systems are regulated by the lateral septum (LS), a relay of γ-aminobutyric (GABA) acid neurons (GABAergic neurons) that inhibit the LH and GABAergic interneurons of the VTA. Furthermore, the LS has a diverse receptor population for neurotransmitters and neuropeptides such as dopamine, glutamate, GABA and corticotropin-releasing factor (CRF), among others. Particularly, CRF a key player in the stress response, has been related to the development of overweight and obesity. Moreover, evidence shows that LS neurons neurophysiologically regulate reward and stress, although there is little evidence of LS taking part in homeostatic and hedonic feeding. In this review, we discuss the evidence that supports the role of LS and CRF on feeding, and how alterations in this system contribute to weight gain obesity.

Early-Life Exposure to Non-Absorbable Broad-Spectrum Antibiotics Affects the Dopamine Mesocorticolimbic Pathway of Adult Rats in a Sex-Dependent Manner.

Gut microbiota with a stable, rich, and diverse composition is associated with adequate postnatal brain development. Colonization of the infant's gut begins at birth when parturition exposes the newborn to a set of maternal bacteria, increasing richness and diversity until one to two first years of age when a microbiota composition is stable until old age. Conversely, alterations in gut microbiota by diet, stress, infection, and antibiotic exposure have been associated with several pathologies, including metabolic and neuropsychiatric diseases such as obesity, anxiety, depression, and drug addiction, among others. However, the consequences of early-life exposure to antibiotics (ELEA) on the dopamine (DA) mesocorticolimbic circuit are poorly studied. In this context, we administered oral non-absorbable broad-spectrum antibiotics to pregnant Sprague-Dawley dams during the perinatal period (from embryonic day 18 until postnatal day 7) and investigated their adult offspring (postnatal day 60) to assess methylphenidate-induced conditioned place preference (CPP) and locomotor activity, DA release, DA and 3,4-dihydroxyphenylacetic acid (DOPAC) content in ventral tegmental area (VTA), and expression of key proteins within the mesocorticolimbic system. Our results show that ELEA affect the rats conduct by increasing drug-seeking behavior and locomotor activity induced by methylphenidate of males and females, respectively, while reducing dopamine striatal release and VTA content of DOPAC in females. In addition, antibiotics increased protein levels of DA type 1 receptor in prefrontal cortex and VTA of female rats, and tyrosine hydroxylase in VTA of adult male and female rats. Altogether, these results suggest that ELEA alters the development of the microbiota-gut-brain axis affecting the reward system and the response to abuse drugs in adulthood.

Gut Susceptibility to Viral Invasion: Contributing Roles of Diet, Microbiota and Enteric Nervous System to Mucosal Barrier Preservation.

The gastrointestinal lumen is a rich source of eukaryotic and prokaryotic viruses which, together with bacteria, fungi and other microorganisms comprise the gut microbiota. Pathogenic viruses inhabiting this niche have the potential to induce local as well as systemic complications; among them, the viral ability to disrupt the mucosal barrier is one mechanism associated with the promotion of diarrhea and tissue invasion. This review gathers recent evidence showing the contributing effects of diet, gut microbiota and the enteric nervous system to either support or impair the mucosal barrier in the context of viral attack.

Sertraline and Citalopram Actions on Gut Barrier Function.

INTRODUCTION: Disruption of intestinal barrier is a key component to various diseases. Whether barrier dysfunction is the cause or effect in these situations is still unknown, although it is believed that translocation of luminal content may initiate gastrointestinal or systemic inflammatory disorders. Since trauma- or infection-driven epithelial permeability depends on Toll-like receptor (TLR) activity, inhibition of TLR signaling has been proposed as a strategy to protect intestinal barrier integrity after infection or other pathological conditions. Recently, selective serotonin recapture inhibitors including sertraline and citalopram were shown to inhibit TLR-3 activity, but the direct effects of these antidepressant drugs on the gut mucosa barrier remain largely unexplored. MATERIALS AND METHODS: To investigate this, two approaches were used: first, ex vivo studies were performed to evaluate sertraline and citalopram-driven changes in permeability in isolated intestinal tissue. Second, both compounds were tested for their preventive effects in a rat model of disrupted gut barrier, induced by a low protein (LP) diet. RESULTS: Only sertraline was able to increase transepithelial electrical resistance in the rat colon both when used in an ex vivo (0.8 µg/mL, 180 min) or in vivo (30 mg/kg p.o., 20 days) fashion. However, citalopram (20 mg/kg p.o., 20 days), but not sertraline, prevented the increase in phospho-IRF3 protein, a marker of TLR-3 activation, in LP-rat ileum. Neither antidepressant affected locomotion, anxiety-like behaviours or stress-induced defecation. CONCLUSION: Our data provides evidence to support the investigation of sertraline as therapeutic strategy to protect intestinal barrier function under life-threatening situations or chronic conditions associated with gut epithelial disruption.

Body dysmorphic disorder in patients with telangiectasias.

BACKGROUND: Chronic venous disease (CVD) patients can present with a spectrum of clinical manifestations ranging from severe ulcerations, thrombosis, and varicose vein hemorrhage to milder ones such as telangiectasias. Some CVD patients have a minimal degree of telangiectasias that are almost invisible to the physician. In spite of successful treatment of these telangiectasias, there are patients that might insist on continuing treatment, focusing excessive attention on what they perceive to be persistent telangiectasias that, in their opinion, must be removed. In these cases, one might be facing a possible body dysmorphic disorder (BDD) diagnosis. METHODS: This is a multicentric study performed in 223 patients with telangiectasias (C1s) seeking treatment; the Body Dysmorphic Disorder Questionnaire (BDDQ) was answered in private by all the patients. Furthermore, each questionnaire was evaluated in accordance with the Diagnostic and Statistical Manual of Mental Disorders (DSM-V) criteria for BDD. RESULTS: From a consecutive sample of 223 patients, 38 patients had criteria for BDD according to the DSM-V; indicating that the prevalence of BDD in patients with telangiectasias is 17%. CONCLUSIONS: Telangiectasias can be a stress trigger that changes the way patients perceive their own appearance. BDD patients tend to focus their attention excessively upon these types of veins and demand unnecessary treatment for minimal telangiectasias in order to diminish their discomfort with their physical appearance. Body dysmorphic disorder occurs in patients with limbs with C1s disease in considerable proportion and, upon evaluation, these patients should be referred to a psychiatrist. The initiation of any treatment for telangiectasias prior to the psychiatric assessment should be avoided.

Do your gut microbes affect your brain dopamine?

Increasing evidence shows changes in gut microbiota composition in association with psychiatric disorders, including anxiety and depression. Moreover, it has been reported that perturbations in gut microbe diversity and richness influence serotonergic, GABAergic, noradrenergic, and dopaminergic neurotransmission. Among these, dopamine is regarded as a main regulator of cognitive functions such as decision making, attention, memory, motivation, and reward. In this work, we will highlight findings that link alterations in intestinal microbiota and dopaminergic neurotransmission, with a particular emphasis on the mesocorticolimbic circuit, which is involved in reward to natural reinforcers, as well as abuse substances. For this, we reviewed evidence from studies carried out on germ-free animals, or in rodents subjected to intestinal dysbiosis using antibiotics, and also through the use of probiotics. All this evidence strongly supports that the microbiota-gut-brain axis is key to the physiopathology of several neuropsychiatric disorders involving those where dopaminergic neurotransmission is compromised. In addition, the gut microbiota appears as a key player when it comes to proposing novel strategies to the treatment of these psychiatric conditions.

Investigating Gut Permeability in Animal Models of Disease.

A growing number of investigations report the association between gut permeability and intestinal or extra-intestinal disorders under the basis that translocation of gut luminal contents could affect tissue function, either directly or indirectly. Still, in many cases it is unknown whether disruption of the gut barrier is a causative agent or a consequence of these conditions. Adequate experimental models are therefore required to further understand the pathophysiology of health disorders associated to gut barrier disruption and to develop and test pharmacological treatments. Here, we review the current animal models that display enhanced intestinal permeability, and discuss (1) their suitability to address mechanistic questions, such as the association between gut barrier alterations and disease and (2) their validity to test potential treatments for pathologies that are characterized by enhanced intestinal permeability.

Anxiogenic effects of a Lactobacillus, inulin and the synbiotic on healthy juvenile rats.

Gut microbiota interventions, including probiotic and prebiotic use can alter behavior in adult animals and healthy volunteers. However, little is known about their effects in younger individuals. To investigate this, male Sprague-Dawley rats (post-natal day 21, PND21) received Lactobacillus casei 54-2-33 (104cfu/ml), inulin as prebiotic (16mg/ml), or both together (synbiotic) via drinking water for 14days. Control rats received water alone. Open field (OF) and elevated plus maze (EPM) behaviors were evaluated at PND34 and 35, respectively. 30min after EPM, brains and trunk blood were collected to evaluate hippocampal 5-HT1A (mRNA and protein) and plasma corticosterone (CORT). Lactobacillus, inulin and synbiotic-treated rats had fewer entries to the OF's center and spent more time in its periphery than controls. Synbiotic-fed rats explored the EPM's open arms longer than probiotic and inulin-fed rats. Synbiotic, but not Lactobacillus nor inulin-fed rats had lower levels of EPM-evoked CORT than controls. Basal CORT levels, evaluated in a naïve cohort, were higher in Lactobacillus- and inulin-fed rats than controls. In naïve synbiotic-fed rats, 5-HT1A mRNA levels were higher in dentate gyrus and cornus ammonis 1 layer (CA1), than in all other naïve groups, while hippocampal 5-HT1A protein levels were lower in bacteria-fed rats than controls. 5-HT1A mRNA changes suggest complex effects of gut microbes on hippocampal gene expression machinery, probably involving endogenous/exogenous bacteria and prebiotics interactions. Importantly, age might also influence their behavioral outcomes. Together, these data suggest that interventions in young rat microbiota evoke early behavioral changes upon stress, apparently in a hypothalamus-pituitary-adrenal axis independent fashion.

Protein Malnutrition During Juvenile Age Increases Ileal and Colonic Permeability in Rats.

Protein malnutrition can lead to morphological and functional changes in jejunum and ileum, affecting permeability to luminal contents. Regarding the large intestine, data are scarce, especially at juvenile age. We investigated whether low-protein (LP) diet could modify ileal and colonic permeability and epithelial morphology in young rats. Isocaloric diets containing 26% (control diet) or 4% protein were given to male rats between postnatal days 40 and 60. LP-diet animals failed to gain weight and displayed decreased plasma zinc levels (a marker of micronutrient deficiency). In addition, transepithelial electrical resistance and occludin expression were reduced in their ileum and colon, indicating increased gut permeability. Macromolecule transit was not modified. Finally, LP diet induced shortening of colonic crypts without affecting muscle thickness. These data show that protein malnutrition increases not only ileum but also colon permeability in juvenile rats. Enhanced exposure to colonic luminal entities may be an additional component in the pathophysiology of protein malnutrition.

What goes around comes around: novel pharmacological targets in the gut-brain axis.

The gut and the brain communicate bidirectionally through anatomic and humoral pathways, establishing what is known as the gut-brain axis. Therefore, interventions affecting one system will impact on the other, giving the opportunity to investigate and develop future therapeutic strategies that target both systems. Alterations in the gut-brain axis may arise as a consequence of changes in microbiota composition (dysbiosis), modifications in intestinal barrier function, impairment of enteric nervous system, unbalanced local immune response and exaggerated responses to stress, to mention a few. In this review we analyze and discuss several novel pharmacological targets within the gut-brain axis, with potential applications to improve intestinal and mental health.

Short-term effects of Poly(I:C) on gut permeability.

The intestinal barrier function depends on an adequate response to pathogens by the epithelium. Toll-like receptor 3 (TLR-3) recognizes double-stranded RNA, a virus-associated molecular pattern. Activation of TLR-3 with Poly(I:C), a synthetic agonist, modulates tissue repair and permeability in other epithelia; however, the effects of local luminal TLR-3 agonists on gut barrier function are unknown. The aim of this investigation was to evaluate short-term effects of Poly(I:C) on rat ileal and colonic permeability ex vivo. We also studied the acute effects of intrarectal administration of Poly(I:C) on colonic barrier function. Ileum tissues displayed decreased transepithelial electrical resistance (TEER) 1h after incubation with 200µg/mL Poly(I:C); however, the mucosa-to-serosa transit of macromolecules (4.4 and 40kDa dextrans - TD4.4 and FD40, respectively) remained unchanged. Conversely, colon tissue preparations stimulated with 200µg/mL Poly(I:C) showed a decreased thinning of the mucosal layer after 2h and a decreased transit of FD40 after 3h, in comparison to controls. There was no change in colonic TEER after 3h of treatment. In addition, colon tissue taken from rats 6h after an intrarectal administration of 100µg Poly(I:C) also showed decreased permeability to FD40 in the everted gut sac assay at 3h post-extraction. Tissue morphology remained unchanged. Our results suggest that an acute exposure to Poly(I:C) reduces colon permeability to macromolecules but increases ileum permeability to electrolytes/small molecules ex vivo. Although the mechanism associated to these effects needs further investigation, to our knowledge this is the first report of a direct effect of a TLR-3 ligand in intestinal barrier function and may be of significance to understand region-specific interactions between gut mucosa and microbiota.

Association of N-cadherin levels and downstream effectors of Rho GTPases with dendritic spine loss induced by chronic stress in rat hippocampal neurons.

Chronic stress promotes cognitive impairment and dendritic spine loss in hippocampal neurons. In this animal model of depression, spine loss probably involves a weakening of the interaction between pre- and postsynaptic cell adhesion molecules, such as N-cadherin, followed by disruption of the cytoskeleton. N-cadherin, in concert with catenin, stabilizes the cytoskeleton through Rho-family GTPases. Via their effector LIM kinase (LIMK), RhoA and ras-related C3 botulinum toxin substrate 1 (RAC) GTPases phosphorylate and inhibit cofilin, an actin-depolymerizing molecule, favoring spine growth. Additionally, RhoA, through Rho kinase (ROCK), inactivates myosin phosphatase through phosphorylation of the myosin-binding subunit (MYPT1), producing actomyosin contraction and probable spine loss. Some micro-RNAs negatively control the translation of specific mRNAs involved in Rho GTPase signaling. For example, miR-138 indirectly activates RhoA, and miR-134 reduces LIMK1 levels, resulting in spine shrinkage; in contrast, miR-132 activates RAC1, promoting spine formation. We evaluated whether N-cadherin/ß-catenin and Rho signaling is sensitive to chronic restraint stress. Stressed rats exhibit anhedonia, impaired associative learning, and immobility in the forced swim test and reduction in N-cadherin levels but not ß-catenin in the hippocampus. We observed a reduction in spine number in the apical dendrites of CA1 pyramidal neurons, with no effect on the levels of miR-132 or miR-134. Although the stress did not modify the RAC-LIMK-cofilin signaling pathway, we observed increased phospho-MYPT1 levels, probably mediated by RhoA-ROCK activation. Furthermore, chronic stress raises the levels of miR-138 in accordance with the observed activation of the RhoA-ROCK pathway. Our findings suggest that a dysregulation of RhoA-ROCK activity by chronic stress could potentially underlie spine loss in hippocampal neurons.

Early-life stress induces persistent alterations in 5-HT1A receptor and serotonin transporter mRNA expression in the adult rat brain.

Early-life experience plays a major role in the stress response throughout life. Neonatal maternal separation (MS) is an animal model of depression with an altered serotonergic response. We hypothesize that this alteration may be caused by differences in 5-HT1A receptor and serotonin transporter (SERT) mRNA expression in brain areas involved in the control of emotions, memory, and fear as well as in regions controlling the central serotonergic tone. To test this, Sprague-Dawley rats were subjected to MS for 3 h daily during postnatal days 2-12. As control, age matched rats were non-separated (NS) from their dams. When animals reached adulthood (11-13 weeks) brain was extracted and mRNA expression of 5-HT1A receptor in amygdala, hippocampus and dorsal raphé nucleus (DRN) and SERT in the DRN was analyzed through in situ hybridisation. Densitometric analysis revealed that MS increased 5-HT1A receptor mRNA expression in the amygdala, and reduced its expression in the DRN, but no changes were observed in the hippocampus in comparison to NS controls. Also, MS reduced SERT mRNA expression in the DRN when compared to NS rats. These results suggest that early-life stress induces persistent changes in 5-HT1A receptor and SERT mRNA expression in key brain regions involved in the development of stress-related psychiatric disorders. The reduction in SERT mRNA indicates an alteration that is in line with clinical findings such as polymorphic variants in individuals with higher risk of depression. These data may help to understand how early-life stress contributes to the development of mood disorders in adulthood.

Communication between gastrointestinal bacteria and the nervous system.

In the past few years, intestinal microbiota has emerged as a novel target for the treatment of gut-brain axis alterations. These include functional gastrointestinal disorders, such as irritable bowel syndrome (IBS), which can be comorbid with stress-related psychiatric conditions. Thus, modulation of the microbiota (e.g. with the use of probiotics) could be proposed as a novel strategy not only for the treatment of IBS but also as an adjuvant for psychiatric treatment of anxiety and depression.

Desipramine prevents stress-induced changes in depressive-like behavior and hippocampal markers of neuroprotection.

Extracellular signal-regulated kinases (ERKs) are widely implicated in multiple physiological processes. Although ERK1/2 has been proposed as a common mediator of antidepressant action in naive rodents, it remains to be determined whether the ERK1/2 pathway plays a role in depressive disorder. Here, we investigated whether chronic restraint stress (14 days) and antidepressant treatment [desipramine (DMI), 10 mg/kg intraperitoneally] induce changes in animal behavior and hippocampal levels of phospho-ERK1/2 and its substrate phospho-cAMP response element-binding protein (CREB). The results indicated that stress-induced depressive-like behaviors were correlated with an increase in P-ERK1/2 and P-CREB in the hippocampus evaluated by immunoblot analysis. As an indication of CREB activity, we evaluated changes in mRNA levels of its target genes. Brain-derived neurotrophic factor (BDNF) mRNA was reduced by stress, an effect prevented by DMI only in the CA3 area of hippocampus. Bcl-2 mRNA was reduced in all hippocampal regions by stress, an effect independent of DMI treatment. However, immunoblot from hippocampal extracts revealed that stress increased BCL-2 levels, an effect prevented by chronic DMI. These results suggest that ERKs and BDNF may be altered in depressive disorder, modifications that are sensitive to DMI action. In contrast, the stress-induced increase in BCL-2 may correspond to a neuroprotective response.

Adrenalectomy promotes a permanent decrease of plasma corticoid levels and a transient increase of apoptosis and the expression of Transforming Growth Factor beta1 (TGF-beta1) in hippocampus: effect of a TGF-beta1 oligo-antisense.

BACKGROUND: Corticosterone reduction produced by adrenalectomy (ADX) induces apoptosis in dentate gyrus (DG) of the hippocampus, an effect related to an increase in the expression of the pro-apoptotic gene bax. However it has been reported that there is also an increase of the anti-apoptotic gene bcl-2, suggesting the promotion of a neuroprotective phenomenon, perhaps related to the expression of transforming growth factor beta1 (TGF-beta1). Thus, we have investigated whether TGF-beta1 levels are induced by ADX, and whether apoptosis is increased by blocking the expression of TGF-beta1 with an antisense oligonucleotide (ASO) administered intracerebrally in corticosterone depleted rats. RESULTS: It was observed an increase of apoptosis in DG, 2 and 5 days after ADX, in agreement with a reduction of corticosterone levels. However, the effect of ADX on the number of apoptotic positive cells in DG was decreased 5 days after the lesion. In CA1-CA3 regions, the effect was only observed 2 days after ADX. TGF-beta1 mRNA levels were increased 2 days after ADX. The sustained intracerebro-ventricular administration of a TGF-beta1 ASO via an osmotic mini pump increased apoptosis levels in CA and DG regions 5 days after ADX as well as sham-operated control animals. No significant effect was observed following a scrambled-oligodeoxynucleotide treatment. CONCLUSION: The changes in both the pattern and the magnitude of apoptotic-cell morphology observed 2 and 5 days after ADX suggest that, as a consequence of the reduction of corticosteroids, some trophic mechanisms restricting cell death to a particular time window are elicited. Sustained intracerebral administration of TGF-beta1 ASO increased the apoptosis promoted by ADX, suggesting that TGF-beta1 plays an anti-apoptotic role in vivo in hippocampus.