The Stressed Gut: Region-specific Immune and Neuroplasticity Changes in Response to Chronic Psychosocial Stress.

Background/aims: Chronic psychological stress affects gastrointestinal physiology which may underpin alterations in the immune response and epithelial transport, both functions are partly regulated by enteric nervous system. However, its effects on enteric neuroplasticity are still unclear. This study aims to investigate the effects of chronic unpredictable psychological stress on intestinal motility and prominent markers of enteric function.

Identification of Epigenetic Interactions between MicroRNA-30c-5p and DNA Methyltransferases in Neuropathic Pain.

Neuropathic pain is a prevalent and severe chronic syndrome, often refractory to treatment, whose development and maintenance may involve epigenetic mechanisms. We previously demonstrated a causal relationship between miR-30c-5p upregulation in nociception-related neural structures and neuropathic pain in rats subjected to sciatic nerve injury. Furthermore, a short course of an miR-30c-5p inhibitor administered into the cisterna magna exerts long-lasting antiallodynic effects via a TGF-β1-mediated mechanism.

Estrous cycle and ovariectomy-induced changes in visceral pain are microbiota-dependent.

Visceral hypersensitivity (VH) is a hallmark of many functional gastrointestinal disorders including irritable bowel syndrome and is categorized by a dull, diffuse sensation of abdominal pain. Recently, the gut microbiota has been implicated in VH in male mice, but the effects in females have yet to be explored fully. To this end, we now show that somewhat surprisingly, female germ-free mice have similar visceral pain responses to colorectal distension (CRD) as their conventional controls.

BMP-7 protects male and female rodents against neuropathic pain induced by nerve injury through a mechanism mediated by endogenous opioids.

Neuropathic pain is highly prevalent in pathological conditions such as diabetes, herpes zoster, trauma, etc. The severity and refractoriness to treatments make neuropathic pain a significant health concern. The transforming growth factor (TGF-β) family of cytokines is involved in pain modulation.

MicroRNA-30c-5p modulates neuropathic pain in rodents.

Neuropathic pain is a debilitating chronic syndrome that is often refractory to currently available analgesics. Aberrant expression of several microRNAs (miRNAs) in nociception-related neural structures is associated with neuropathic pain in rodent models. We have exploited the antiallodynic phenotype of mice lacking the bone morphogenetic protein and activin membrane-bound inhibitor (BAMBI), a transforming growth factor-β (TGF-β) pseudoreceptor.

Microbiota regulates visceral pain in the mouse.

The perception of visceral pain is a complex process involving the spinal cord and higher order brain structures. Increasing evidence implicates the gut microbiota as a key regulator of brain and behavior, yet it remains to be determined if gut bacteria play a role in visceral sensitivity. We used germ-free mice (GF) to assess visceral sensitivity, spinal cord gene expression and pain-related brain structures.

Obesity Takes Its Toll on Visceral Pain: High-Fat Diet Induces Toll-Like Receptor 4-Dependent Visceral Hypersensitivity.

Exposure to high-fat diet induces both, peripheral and central alterations in TLR4 expression. Moreover, functional TLR4 is required for the development of high-fat diet-induced obesity. Recently, central alterations in TLR4 expression have been associated with the modulation of visceral pain.

BMP-7 attenuates left ventricular remodelling under pressure overload and facilitates reverse remodelling and functional recovery.

Aims: TGF-β regulates tissue fibrosis: TGF-β promotes fibrosis, whereas bone morphogenetic protein (BMP)-7 is antifibrotic. To demonstrate that (i) left ventricular (LV) remodelling after pressure overload is associated with disequilibrium in the signalling mediated by these cytokines, and (ii) BMP-7 exerts beneficial effects on LV remodelling and reverse remodelling.

Methods And Results: We studied patients with aortic stenosis (AS) and mice subjected to transverse aortic constriction (TAC) and TAC release (de-TAC).

TGF-β and opioid receptor signaling crosstalk results in improvement of endogenous and exogenous opioid analgesia under pathological pain conditions.

Transforming growth factor-β1 (TGF-β1) protects against neuroinflammatory events underlying neuropathic pain. TGF-β signaling enhancement is a phenotypic characteristic of mice lacking the TGF-β pseudoreceptor BAMBI (BMP and activin membrane-bound inhibitor), which leads to an increased synaptic release of opioid peptides and to a naloxone-reversible hypoalgesic/antiallodynic phenotype. Herein, we investigated the following: (1) the effects of BAMBI deficiency on opioid receptor expression, functional efficacy, and analgesic responses to endogenous and exogenous opioids; and (2) the involvement of the opioid system in the antiallodynic effect of TGF-β1.

Toll-like receptor 4 regulates chronic stress-induced visceral pain in mice.

Background: Functional gastrointestinal disorders, which have visceral hypersensitivity as a core symptom, are frequently comorbid with stress-related psychiatric disorders. Increasing evidence points to a key role for toll-like receptor 4 (TLR4) in chronic pain states of somatic origin. However, the central contribution of TLR4 in visceral pain sensation remains elusive.

BAMBI (BMP and activin membrane-bound inhibitor) protects the murine heart from pressure-overload biomechanical stress by restraining TGF-β signaling.

Left ventricular (LV) pressure overload is a major cause of heart failure. Transforming growth factors-β (TGF-βs) promote LV remodeling under biomechanical stress. BAMBI (BMP and activin membrane-bound inhibitor) is a pseudoreceptor that negatively modulates TGF-β signaling.

Rodent models of colorectal distension.

Colorectal distension (CRD) is a widely accepted, reproducible method for assessing visceral sensitivity in both clinical and pre-clinical studies. Distension of the colon mirrors the human scenario of visceral pain with regard to intensity and referral of pain in patients. There are several readouts that can be applied to the CRD protocol depending on the species being evaluated, two of which are described in this unit.

Transforming growth factor-β in normal nociceptive processing and pathological pain models.

The transforming growth factor-β (TGF-β) superfamily is a multifunctional, contextually acting family of cytokines that participate in the regulation of development, disease and tissue repair in the nervous system. The TGF-β family is composed of several members, including TGF-βs, bone morphogenetic proteins (BMPs) and activins. In this review, we discuss recent findings that suggest TGF-β function as important pleiotropic modulators of nociceptive processing both physiologically and under pathological painful conditions.

Chronic psychosocial stress induces visceral hyperalgesia in mice.

Experimental and clinical evidence has shown that chronic stress plays an important role in the onset and/or exacerbation of symptoms of functional gastrointestinal disorders. Here, we aimed to investigate whether exposure to a chronic and temporally unpredictable psychosocial stressor alters visceral and somatic nociception as well as anxiety-related behaviour. In male C57BL/6J mice, chronic stress was induced by repeated exposure to social defeat (SD, 2 h) and overcrowding (OC, 24 h) during 19 consecutive days.

BAMBI (bone morphogenetic protein and activin membrane-bound inhibitor) reveals the involvement of the transforming growth factor-beta family in pain modulation.

Transforming growth factors-beta (TGF-betas) signal through type I and type II serine-threonine kinase receptor complexes. During ligand binding, type II receptors recruit and phosphorylate type I receptors, triggering downstream signaling. BAMBI [bone morphogenetic protein (BMP) and activin membrane-bound inhibitor] is a transmembrane pseudoreceptor structurally similar to type I receptors but lacks the intracellular kinase domain.

Facilitation of avoidance behaviour in mice chronically treated with heroin or methadone.

Although the repercussion of chronic treatment with large amounts of opioids on cognitive performance is a matter of concern, the effects of opioid drugs on passive avoidance learning have been scarcely studied. Here, we analyzed the effects of prolonged administration of heroin and methadone, as well as the impact of suffering repeated episodes of withdrawal on fear-motivated learning using the passive avoidance test. Mice received chronic treatment (39 days) with methadone (10 mg/kg/24 h), associated or not with repeated withdrawal episodes, or with heroin (5 mg/kg/12 h).

Chronic administration of heroin to mice produces up-regulation of brain apoptosis-related proteins and impairs spatial learning and memory.

Several studies open up the possibility that chronic exposure to opioid drugs in the CNS would interfere with learning and memory through a neurotoxic effect related to activation of apoptotic pathways. Here, we have analyzed the effects of prolonged heroin administration on sensorimotor and cognitive performance in mice, as well as the associated changes in brain expression of proteins regulating the extrinsic (FasL and Fas) and the mitochondrial (Bcl-2, Bcl-X(L), Bad and Bax) apoptotic pathways. Our findings indicate that chronic heroin did not interfere with mice performance in a battery of sensorimotor tests.

Chronic methadone treatment and repeated withdrawal impair cognition and increase the expression of apoptosis-related proteins in mouse brain.

Objectives: This study analyzes the effects of prolonged administration of methadone and withdrawal on sensorimotor and cognitive performance in mice and explores the associated changes in brain expression of proteins regulating the extrinsic (FasL, Fas, and caspase-8) and the mitochondrial (Bcl-2, Bcl-x(L), Bad, and Bax) apoptotic pathways.

Results: Our findings indicate that, although acute methadone administration impairs some sensorimotor abilities, tolerance to most of the deleterious effects develops after chronic administration. Cognitive abilities in the Morris water maze were impaired by chronic methadone and, to a greater extent, by exposure to precipitated withdrawal every week in the course of methadone treatment.

Modulation of apoptosis in the mouse brain after morphine treatments and morphine withdrawal.

We have examined the effects of acute or chronic morphine and naltrexone-precipitated withdrawal on mouse brain apoptotic cell death. The associated changes in the expression of apoptosis regulatory proteins were also analyzed. After a single dose of morphine, no apoptotic cells were detected by TUNEL or active caspase-3 immunocytochemistry.