Gen Zheng

Corticosterone Mediates Reciprocal Changes in CB 1 and TRPV1 Receptors in Primary Sensory Neurons in the Chronically Stressed Rat

BACKGROUND & AIMS Chronic stress is associated with visceral hyperalgesia in functional gastrointestinal disorders. We investigated whether corticosterone plays a role in chronic psychological stress-induced visceral hyperalgesia. METHODS Male rats were subjected to 1-hour water avoidance (WA) stress or subcutaneous corticosterone injection daily for 10 consecutive days in the presence or absence of corticoid-receptor antagonist RU-486 and cannabinoid-receptor agonist WIN55,212-2. The visceromotor response to colorectal distension was measured. Receptor protein levels were measured and whole-cell patch-clamp recordings were used to assess transient receptor potential vanilloid type 1 (TRPV1) currents in L6-S2 dorsal root ganglion (DRG) neurons. Mass spectrometry was used to measure endocannabinoid anandamide content. RESULTS Chronic WA stress was associated with visceral hyperalgesia in response to colorectal distension, increased stool output and reciprocal changes in cannabinoid receptor 1 (CB1) (decreased) and TRPV1 (increased) receptor expression and function. Treatment of WA stressed rats with RU-486 prevented these changes. Control rats treated with serial injections of corticosterone in situ showed a significant increase in serum corticosterone associated with visceral hyperalgesia, enhanced anandamide content, increased TRPV1, and decreased CB1 receptor protein levels, which were prevented by co-treatment with RU-486. Exposure of isolated control L6-S2 DRGs in vitro to corticosterone reproduced the changes in CB1 and TRPV1 receptors observed in situ, which was prevented by co-treatment with RU-486 or WIN55,212-2. CONCLUSIONS These results support a novel role for corticosterone to modulate CB1 and TRPV1-receptor pathways in L6-S2 DRGs in the chronic WA stressed rat, which contributes to visceral hyperalgesia observed in this model.

Epigenetic Regulation of Genes That Modulate Chronic Stress-Induced Visceral Pain in the Peripheral Nervous System

BACKGROUND & AIMS Chronic stress alters the hypothalamic-pituitary-adrenal axis, increases gut motility, and increases the perception of visceral pain. We investigated whether epigenetic mechanisms regulate chronic stress-induced visceral pain in the peripheral nervous systems of rats. METHODS Male rats were subjected to 1 hour of water avoidance stress each day, or given daily subcutaneous injections of corticosterone, for 10 consecutive days. L4-L5 and L6-S2 dorsal root ganglia (DRG) were collected and compared between stressed and control rats (placed for 1 hour each day in a tank without water). Levels of cannabinoid receptor 1 (CNR1), DNA (cytosine-5-)-methyltransferase 1 (DNMT1), transient receptor potential vanilloid type 1 (TRPV1), and EP300 were knocked down in DRG neurons in situ with small interfering RNAs. We measured DNA methylation and histone acetylation at genes encoding the glucocorticoid receptor (NR3C1), CNR1, and TRPV1. Visceral pain was measured in response to colorectal distention. RESULTS Chronic stress was associated with increased methylation of the Nr3c1 promoter and reduced expression of this gene in L6-S2, but not L4-L5, DRGs. Stress also was associated with up-regulation in DNMT1-associated methylation of the Cnr1 promoter and down-regulation of glucocorticoid-receptor-mediated expression of CNR1 in L6-S2, but not L4-L5, DRGs. Concurrently, chronic stress increased expression of the histone acetyltransferase EP300 and increased histone acetylation at the Trpv1 promoter and expression of the TRPV1 receptor in L6-S2 DRG neurons. Knockdown of DNMT1 and EP300 in L6-S2 DRG neurons of rats reduced DNA methylation and histone acetylation, respectively, and prevented chronic stress-induced increases in visceral pain. CONCLUSIONS Chronic stress increases DNA methylation and histone acetylation of genes that regulate visceral pain sensation in the peripheral nervous system of rats. Blocking epigenetic regulatory pathways in specific regions of the spinal cord might be developed to treat patients with chronic abdominal pain.

Corticosterone mediates stress-related increased intestinal permeability in a region-specific manner.

Background  Chronic psychological stress (CPS) is associated with increased intestinal epithelial permeability and visceral hyperalgesia. It is unknown whether corticosterone (CORT) plays a role in mediating alterations of epithelial permeability in response to CPS.

Chronic Stress and Peripheral Pain: Evidence for Distinct, Region-specific Changes in Visceral and Somatosensory Pain Regulatory Pathways

Chronic stress alters the hypothalamic-pituitary-adrenal (HPA) axis and enhances visceral and somatosensory pain perception. It is unresolved whether chronic stress has distinct effects on visceral and somatosensory pain regulatory pathways. Previous studies reported that stress-induced visceral hyperalgesia is associated with reciprocal alterations of endovanilloid and endocannabinoid pain pathways in DRG neurons innervating the pelvic viscera. In this study, we compared somatosensory and visceral hyperalgesia with respect to differential responses of peripheral pain regulatory pathways in a rat model of chronic, intermittent stress. We found that chronic stress induced reciprocal changes in the endocannabinoid 2-AG (increased) and endocannabinoid degradation enzymes COX-2 and FAAH (decreased), associated with down-regulation of CB1 and up-regulation of TRPV1 receptors in L6-S2 DRG but not L4-L5 DRG neurons. In contrast, sodium channels Nav1.7 and Nav1.8 were up-regulated in L4-L5 but not L6-S2 DRGs in stressed rats, which was reproduced in control DRGs treated with corticosterone in vitro. The reciprocal changes of CB1, TRPV1 and sodium channels were cell-specific and observed in the sub-population of nociceptive neurons. Behavioral assessment showed that visceral hyperalgesia persisted, whereas somatosensory hyperalgesia and enhanced expression of Nav1.7 and Nav1.8 sodium channels in L4-L5 DRGs normalized 3 days after completion of the stress phase. These data indicate that chronic stress induces visceral and somatosensory hyperalgesia that involves differential changes in endovanilloid and endocannabinoid pathways, and sodium channels in DRGs innervating the pelvic viscera and lower extremities. These results suggest that chronic stress-induced visceral and lower extremity somatosensory hyperalgesia can be treated selectively at different levels of the spinal cord.

Chronic stress and intestinal barrier dysfunction: Glucocorticoid receptor and transcription repressor HES1 regulate tight junction protein Claudin-1 promoter

Chronic stress and elevated glucocorticoid hormone are associated with decreases in the intestinal epithelial tight junction protein claudin-1 (CLDN1). Human/rat CLDN1 promoters contain glucocorticoid response elements (GREs) and adjacent transcription repressor HES1 binding N-boxes. Notch signaling target HES1 expression was high and glucocorticoid receptor (NR3C1) low at the crypt base and the pattern reversed at the crypt apex. Chronic stress reduced overall rat colon HES1 and NR3C1 that was associated with CLDN1 downregulation. Chromatin-immunoprecipitation experiments showed that HES1 and NR3C1 bind to the CLDN1 promoter in rat colon crypts. The binding of NR3C1 but not HES1 to CLDN1 promoter significantly decreased in chronically stressed animals, which was prevented by the NR3C1 antagonist RU486. We employed the 21-day Caco-2/BBe cell model to replicate cell differentiation along the crypt axis. HES1 siRNA treatment early in differentiation increased CLDN1. In contrast, stress levels of cortisol decreased CLDN1 in late differentiation stage but not in the early stage. HES1 was high, whereas NR3C1 and CLDN1 were low in the early stage which reversed in the late stage, e.g. HES1/NR3C1 binding to CLDN1 promoter demonstrates a dynamic and reciprocal pattern. These results suggest that chronic stress impairs colon epithelium homeostasis and barrier function via different mechanisms along the crypt axis.

3D Cell Nuclear Morphology: Microscopy Imaging Dataset and Voxel-Based Morphometry Classification Results

Cell deformation is regulated by complex underlying biological mechanisms associated with spatial and temporal morphological changes in the nucleus that are related to cell differentiation, development, proliferation, and disease. Thus, quantitative analysis of changes in size and shape of nuclear structures in 3D microscopic images is important not only for investigating nuclear organization, but also for detecting and treating pathological conditions such as cancer. While many efforts have been made to develop cell and nuclear shape characteristics in 2D or pseudo-3D, several studies have suggested that 3D morphometric measures provide better results for nuclear shape description and discrimination. A few methods have been proposed to classify cell and nuclear morphological phenotypes in 3D, however, there is a lack of publicly available 3D data for the evaluation and comparison of such algorithms. This limitation becomes of great importance when the ability to evaluate different approaches on benchmark data is needed for better dissemination of the current state of the art methods for bioimage analysis. To address this problem, we present a dataset containing two different cell collections, including original 3D microscopic images of cell nuclei and nucleoli. In addition, we perform a baseline evaluation of a number of popular classification algorithms using 2D and 3D voxel-based morphometric measures. To account for batch effects, while enabling calculations of AUROC and AUPR performance metrics, we propose a specific cross-validation scheme that we compare with commonly used k-fold cross-validation. Original and derived imaging data are made publicly available on the project web-page: http://www.socr.umich.edu/projects/3d-cell-morphometry/data.html.

Hypothesis: Caco-2 cell rotational 3D mechanogenomic turing patterns have clinical implications to colon crypts

Colon crypts are recognized as a mechanical and biochemical Turing patterning model. Colon epithelial Caco‐2 cell monolayer demonstrated 2D Turing patterns via force analysis of apical tight junction live cell imaging which illuminated actomyosin meshwork linking the actomyosin network of individual cells. Actomyosin forces act in a mechanobiological manner that alters cell/nucleus/tissue morphology. We observed the rotational motion of the nucleus in Caco‐2 cells that appears to be driven by actomyosin during the formation of a differentiated confluent epithelium. Single‐ to multi‐cell ring/torus‐shaped genomes were observed prior to complex fractal Turing patterns extending from a rotating torus centre in a spiral pattern consistent with a gene morphogen motif. These features may contribute to the well‐described differentiation from stem cells at the crypt base to the luminal colon epithelium along the crypt axis. This observation may be useful to study the role of mechanogenomic processes and the underlying molecular mechanisms as determinants of cellular and tissue architecture in space and time, which is the focal point of the 4D nucleome initiative. Mathematical and bioengineer modelling of gene circuits and cell shapes may provide a powerful algorithm that will contribute to future precision medicine relevant to a number of common medical disorders.

898 Chronic Stress-Induced Visceral Hyperalgesia: Evidence That the Formation of CB1 and TRPV1 Receptor Complexes Modulates Pain in Dorsal Root Ganglion (DRG) Neurons

Introduction: PGD2 is an important mediator released after mast cell activation. Our previous studies demonstrated PGD2 sensitizes esophageal nodose C-fibers to increase their response to esophageal distension. This study aims to determine the underlying mechanism of the sensitization process. Methods: PGD2 DP1 receptor expressions in nodose neurons were determined by immunofluorescent-staining, Western blot, and RT-PCR. Extracellular single fiber recordings were performed from vagal nodose neurons using ex vivo esophageal-vagal preparations with intact nerve endings in the esophagus. We recorded action potentials evoked by esophageal distensions before and after perfusion of PGD2 with/without pretreatment of DP1 receptor antagonist BWA 868C. Whole-cell patch-clamp recording was performed to investigate the action of PGD2 on isolated nodose neurons. Viscermotor responses (VMR) to esophageal distension were recorded by electromyography from acromiotrapezius muscles in animals receiving PGD2 injection (20 μl, 100 nM) into the wall of the esophagus before and after truncal vagatomy. Results: DP1 receptor expressions were identified in nodose neurons by immunofluorescent-labeling, Western blot, and RT-PCR. 98% of DP1positive neurons were of smalland medium-diameters (φ 0.05, n=4). Whole-cell patch-clamp recording from isolated nodose neurons demonstrated PGD2 (1 μM) depolarized recorded neurons (13±2 mV, n=5) accompanied by an increase in the neuronal input resistance from 360±20 to 420±25 MΩ. IV relationship studies showed current reversed at 105 mV suggesting the effect was mediated by the closure of K+ channel(s). Compared to controls, PGD2 injection into the esophagus significantly enhanced esophageal distension evoked-VMRs at distension pressures 20, 40, 60, and 80 mmHg respectively (p <0.05, n=3). Left truncal vagatomy attenuated PGD2induced enhancements of VMR in response to esophageal distension (p <0.05, n=3) indicating the participation of vagal afferent pathway in this sensitization process. Conclusion: These data demonstrate mast cell mediator PGD2 plays a crucial role in sensitization of esophageal nodose C-fiber neurons to induce esophageal mechanical hypersensitivity. This sensitization effect is mediated via DP1 receptor and involves downstream K+ channel.

Chronic Stress-Induced Visceral Hyperalgesia: Evidence for Epigenetic Regulation of DNA Methyltransferase I (Dnmt1) in Dorsal Root Ganglion (DRG) Neurons Innervating the Colon in the Rat

Introduction: Increasing evidence suggests that chronic stress alters behavior and modifies epigenetic regulation of genes in the central nervous system. DNA methylation, catalyzed by DNA methyltransferases (DNMTs), is an important epigenetic mechanism of transcriptional control of gene expression. We reported previously that chronic psychological stress induced visceral hyperalgesia and differential alterations in the expression of several genes in DRG neurons innervating the colon in the rat. A potential role for epigenetic regulation in peripheral sensory pathways has not been investigated. Objectives: We examined the hypothesis that DNMTs play an important role in the regulation of chronic stress-induced visceral hyperalgesia. Methods: Male rats were exposed to 1-hour water avoidance (WA) stress daily for 10 consecutive days as a chronic stress paradigm. SiRNA for DNMT1 was administrated in situ to L6-S2 DRGs every other day during the stress procedure. The visceromotor response (VMR) to colorectal distension was measured. Retrograde labeling with cholera toxin B (CTB)-FITCwas employed to identify colonDRG neurons. Immunofluorescence andWestern blot analysis were used to assess protein expression. In Vitro studies were performed in isolated control DRGs in the presence or absence of corticosterone (CORT; 10 μM) and RU-486 (corticoid receptor antagonist, 500 nM). Results: WA stress rats demonstrated significant increases in the level of DNMT1 and DNMT3b but not DNMT3a in L6-S2 DRGs compared with the controls. Enzyme activity assessment showed a 42% increase in DNMT1 activity in L6-S2 DRGs in stressed rats. Immunofluorescence studies revealed a significant increase in DNMT1 in small-sized, C-fiber neurons in WA stressed rats (52.3±2.2%) compared with the control (31.7±1.6%). Retrograde labeling demonstrated that 72.0±2.1% of the CTB-FITC labeled colonic DRG neurons were positive for DNMT1 in stressed rats compared to 40.0±6.5% in controls (P<0.05; n=4). The VMR in WA stressed rats was increased 68% and 92% above control responses at pressures of 40 and 60 mm Hg, respectively. Treatment of stressed rats with siRNA for DNMT1 prevented the VMR enhancement and changes in DNMT1 proteins levels in L6-S2 DRGs. In addition, treatment of control L6-S2 DRGs In Vitro with CORT (10 μM) increased DNMT1 expression level that was prevented by RU-486 (500 nM) (P<0.05). Conclusions: These data support the novel and provocative interpretation that: 1. Chronic stress induces epigenetic regulation of genes in primary nociceptive neurons; 2. DNA methyltransferase 1 (DNMT1) plays an important role in modulation of chronic stress-induced visceral hyperalgesia; and 3. DNA methyltransferases represent a potential target for treatment of functional GI disorders associated with visceral hyperalgesia.

Rotational 3D mechanogenomic Turing patterns of human colon Caco-2 cells during differentiation

Recent reports suggest that actomyosin meshwork act in a mechanobiological manner alter cell/nucleus/tissue morphology, including human colon epithelial Caco-2 cancer cells that form polarized 2D epithelium or 3D sphere/tube when placed in different culture conditions. We observed the rotational motion of the nucleus in Caco-2 cells in vitro that appears to be driven by actomyosin network prior to the formation of a differentiated confluent epithelium. Caco-2 cell monolayer preparations demonstrated 2D patterns consistent with Allan Turing’s “gene morphogen” hypothesis based on live cell imaging analysis of apical tight junctions indicating the actomyosin meshwork. Caco-2 cells in 3D culture are frequently used as a model to study 3D epithelial morphogenesis involving symmetric and asymmetric cell divisions. Differentiation of Caco-2 cells in vitro demonstrated similarity to intestinal enterocyte differentiation along the human colon crypt axis. We observed rotational 3D patterns consistent with gene morphogens during Caco-2 cell differentiation. Single- to multi-cell ring/torus-shaped genomes were observed that were similar to complex fractal Turing patterns extending from a rotating torus centre in a spiral pattern consistent with gene morphogen motif. Rotational features of the epithelial cells may contribute to well-described differentiation from stem cells to the luminal colon epithelium along the crypt axis. This dataset may be useful to study the role of mechanobiological processes and the underlying molecular mechanisms as determinants of cellular and tissue architecture in space and time, which is the focal point of the 4D nucleome initiative.