Ferran Jardi

Plasticity of dorsal root ganglion neurons in a rat model of post-infectious gut dysfunction: potential implication of nerve growth factor

Abstract Objective. Intestinal infections are suggested as a risk factor for the development of irritable bowel syndrome (IBS)-like visceral hypersensitivity. The mechanisms implicated might involve long-term changes in visceral afferents, with implication of nerve growth factor (NGF). We explored plastic changes in dorsal root ganglia (DRGs) receiving innervation from the gut and the potential implication of NGF in a rat model of IBS-like post-infectious gut dysfunction. Materials and methods. Rats were infected with Trichinella spiralis larvae. Thirty days post-infection, inflammatory markers, including interleukins (ILs) and mucosal mast cell infiltration (rat mast cell protease II [RMCPII]), and NGF and TrkA expression was determined in the jejunum and colon (RT-qPCR). In the same animals, morphometry (neuronal body size) and NGF content (immunofluorescence) were assessed in thoracolumbar DRG neurons. Results. In infected animals, a low-grade inflammatory-like response, characterized by up-regulated levels of RMCPII and IL-6, was observed in the jejunum and colon. TrkA expression was increased in the jejunum, whereas the colon showed a slight reduction. NGF levels remained unaltered regardless the gut region. Overall, the mean cross-sectional area of DRG neurons was increased in T. spiralis-infected animals, with a reduction in both TrkA and NGF staining. Conclusions. Results suggest that during T. spiralis infection in rats, there is a remodeling of sensory afferents that might imply a NGF-mediated mechanism. Plastic changes in sensory afferents might mediate the long-lasting functional alterations that characterize this model of IBS. Similar mechanisms might be operating in patients with post-infectious-IBS.

NGF is involved in oral ovalbumin‐induced altered colonic contractility in rats: evidence from the blockade of TrkA receptors with K252a

Background  Nerve growth factor (NGF)‐mucosal mast cell (MMC) interaction has been implicated in the remodeling of enteric circuitries and associated functional changes. We investigated the involvement of NGF and its receptor TrkA in the altered colonic contractile activity observed in the model of oral ovalbumin (OVA)‐induced MMC hyperactivity in rats. We also studied the role of colonic MMCs as a source of NGF.

Persistent alterations in colonic afferent innervation in a rat model of postinfectious gut dysfunction: Role for changes in peripheral neurotrophic factors

Visceral hypersensitivity in the inflamed gut is related partly to the effects of peripheral neurotrophic factors (NTFs) on local afferent neurons. However, alterations in sensory afferents of distant areas remain unexplored. Using the Trichinella spiralis infection model, which causes a jejunitis, we investigated the remodeling of colonic afferents and the potential role of NTFs.

Lipopolysaccharides Facilitate Colonic Motor Alterations Associated to the Sensitization to a Luminal Antigen in Rats

Background/Aims Enteric dysbiosis is a risk factor for dietary proteins-associated intestinal alterations, contributing to the development of food allergies and the symptomatology of functional gastrointestinal disorders, mainly irritable bowel syndrome (IBS). We explored if a dysbiotic-like state, simulated by intraperitoneal administration of bacterial lipopolysaccharides (LPS), facilitates the sensitization to a luminal antigen, ovalbumin (OVA), in rats. Methods Rats were exposed to oral OVA for 1 week, alone or with LPS. Thereafter, colonic histology, goblet cell density, mucosal eosinophils and mucosal mast cell (MMC) and connective tissue mast cell (CTMC) were evaluated. Colonic expression (real-time quantitative polymerase chain reaction) of interleukins, IFN-α1 and integrins was assessed to determine local immune responses. Luminal and wall adhered microbiota were characterized by fluorescence in situ hybridization. Colonic contractility (in vitro) served to assess functional changes associated to OVA and/or LPS. Results Neither OVA nor LPS, alone or combined, lead to structural alterations, except for a reduced goblet cell density in OVA-LPS-treated rats. MMC density was unaffected, while CTMC counts increased within the submucosa of OVA-LPS-treated animals. Marginal immune activation (IFN-α1 up-regulation) was observed in OVA-LPS-treated rats. LPS induced a dysbiotic-like state characterized by decreased luminal bacterial counts, with a specific loss of clostridia. LPS facilitated Clostridium spp. wall adherence, an effect prevented by OVA. Colonic contractility was altered in OVA-LPS-treated animals, showing increased basal activity and enhanced motor responses to OVA. Conclusions Changes in gut microbiota and/or direct effects of LPS might enhance/facilitate local neuroimmune responses to food antigens leading to motor alterations similar to those observed in IBS.

Mo2036 Remodeling of Colonic Sensory Afferents in a Rat Model of Post-Infectious Gut Dysfunction: Implication of Neurotrophic Factors

Background: Inflammation-induced visceral hypersensitivity is associated, at least partially, to peripheral sensitization of sensory afferents by locally released neurotrophic factors. Aims: Here, we explore the potential role of neurotrophic factors in long-term changes in visceral afferents innervating non-primary areas of inflammation (colon) in a rat model of Trichinella spiralis (TS)-induced gut dysfunction. Methods: Inflammatory-like changes, mucosal mast cells (MMCs) dynamics, and expression of nerve growth factor (NGF) and glial cell linederived neurotrophic factors (GDNF, artemin and neurturin) were determined in the colon of control and TS-infected rats, up to day 30 post-infection (PI). Markers of sensory afferents (high affinity nerve growth factor receptor, TrkA; GDNF family receptor alpha 3, GFRα3; calcitonin gene-related peptide, CGRP; and transient receptor potential vanilloid channel1, TRPV1) were assessed in thoracolumbar (T12-L2, TL) and lumbosacral (L6-S2, LS) DRGs. Functionality of colonic afferents at 14 and 30 days PI was determined by assessing changes in TRPV1 levels in TL and LS DRGs following intracolonic capsaicin. Results: TS infection induced a primary jejunitis with concomitant inflammatory-like changes in the colon: an increase in histological scores, IL-13 up-regulation and MMC infiltration (Table 1). Inflammation was partly resolved at day 30 PI, except for a persistent MMC infiltrate (Table 1). Colonic expression of neurotrophic factors showed a transient reduction by day 14 PI (25%50%), with the exception of artemin that showed a biphasic response with an up-regulation (by 30%; P<0.05) at day 30 PI (Table 2). Overall, TS infection did not affect DRG expression of none of the genes assessed, except for a transient down-regulation of TPRV1 in TL DRGs at day 14 PI. Afferent stimulation with intracolonic capsaicin induced a down-regulation of TRPV1 expression in TL and LS DRGs, an effect significantly enhanced in LS DRGs of TSinfected rats, at either 14 or 30 days PI (Table 2). Intracolonic capsaicin also up-regulated peripheral artemin in non-infected rats, an effect absent in TS-infected animals at day 30 PI (Table 2). Capsaicin-induced changes in colonic expression of artemin correlated negatively with the down-regulation of TRPV1 in LS DRGs. Conclusions: During intestinal inflammation, changes in expression of neurotrophic factors and remodeling of visceral afferents are observed outside the primary region affected by the inflammatory insult. These observations suggest that extended remodelation of sensory afferents, probably related to local changes in neurotropins, might occur during inflammatory conditions of the gut. Similar mechanisms might be operating in states of widespread alterations of visceral sensitivity. Table 1 Colonic inflammation-related changes during T. spiralis infection

Bacterial Lipopolysaccharides Interact With Oral Ovalbumin to Induce Food-Antigen-Related IBS-Like Alterations of Colonic Motility in Rats

G A A b st ra ct s showed a 2-fold (p<0.05) increase in Brain-derived neurotrophic factor (BDNF) mRNA and a 50% decrease in the mRNA of Kv1.1 channels, compared with controls. BDNF protein was increased 50% (p<0.05) in the thoracic spinal cord. Intrathecal administration of Kv1.1 siRNA in naive rats significantly increased sensitivity to gastric distention, suggesting that the suppression of Kv1.1 contributes to GHS. Intrathecal treatment with a BDNF antagonist, trkB-Fc, significantly reduced gastric hypersensitivity in FD rats. Nerve growth factor (NGF) protein expression was 75% (p<0.05) greater in fundic muscularis externa of FD rats. Systemic treatment with an NGF antibody significantly attenuated gastric hypersensitivity. The plasma concentration of norepinephrine was significantly greater in FD rats, compared with control rats. Treatment of fundic muscularis externa In Vitro with norepinephrine produced a 50% (p<0.05) increase in NGF expression. Sodium butyrate, a histone deacetylase inhibitor, treatment in sensitized FD rats significantly reduced both gastric hypersensitivity and NGF expression in the fundus. Conclusions: Neonatal inflammatory insult induces persistent gastric hypersensitivity in adulthood. A persistent increase in plasma norepinephrine mediates GHS by elevating NGF in muscularis externa, which suppresses Kv1.1 channels in DRGs and enhances BDNF in DRGs and thoracic spinal cord. The normalization of gastric hypersensitivity by sodium butyrate suggests epigenetic dysregulation of genes.