Interactions between astrocytes and neurons in the brainstem involved in restraint water immersion stress-induced gastric mucosal damage. Neuroreport. 2016;27:151-159. [PMID: 26720891 DOI: 10.1097/wnr.0000000000000515]

Protective effect of alpha-ketoglutarate against water-immersion restraint stress-induced gastric mucosal damage in mice

Gastric lesions have several aetiologies, among which stress is the most prominent. Therefore, identification of new therapies to prevent stress is of considerable importance. Alpha-ketoglutarate (α-kg) several beneficial effects and has shown promise in combating oxidative stress, inflammation, and premature aging. Thus, this study aimed to evaluate the protective effect of α-kg in a gastric damage model by water-immersion restraint stress (WIRS). Pretreatment with α-kg decreased stress-related histopathological scores of tissue oedema, cell loss, and inflammatory infiltration. The α-kg restored the percentage of type III collagen fibres. Mucin levels were preserved as well as the structure and area of the myenteric plexus ganglia were preserved after pretreatment with α-kg. Myeloperoxidase (MPO) levels and the expression of pro-inflammatory cytokines (TNF-α and IL-1β) were also reduced following α-kg pretreatment. Decreased levels of glutathione (GSH) in the stress group were restored by α-kg. The omeprazole group was used as standard drug e also demonstrated improve on some parameters after the exposition to WIRS as inflammatory indexes, GSH and mucin. Through this, was possible to observe that α-kg can protect the gastric mucosa exposed to WIRS, preserve tissue architecture, reduce direct damage to the mucosa and inflammatory factors, stimulate the production of type III collagen and mucin, preserve the myenteric plexus ganglia, and maintain antioxidant potential. Due to, we indicate that α-kg has protective activity of the gastric mucosa, demonstrating its ability to prevent damage associated with gastric lesions caused by stress.

Dexmedetomidine improves the acute stress reactivity of male rat through interventions of serum- and glucocorticoid-inducible kinase 1 and nNOS in the bed nucleus of the stria terminalis

Moderate acute stress responses are beneficial for adaptation and maintenance of homeostasis. Exposure of male rat to stress induces effects in the bed nucleus of the stria terminalis (BNST), for it can be activated by the same stimuli that induce activation of the hypothalamic-pituitary-adrenal axis. However, the underlying mechanism of the BNST on male stress reactivity remains unclear. In this study, we explored whether systematic administration of dexmedetomidine (DEXM) altered the acute stress reactivity through its effect on the BNST. Male Sprague-Dawley rats in the stress (STRE) group, DEXM group, and the DEXM + GSK-650394 (GSK, an antagonist of serum- and glucocorticoid-inducible kinase 1 (SGK1)) group, except those in the vehicle (VEH) group, underwent 1-h restraint plus water-immersion (RPWI) exposure. All the rats proceeded the open field test (OFT) 24 h before RPWI and 1 h after RPWI. After the second OFT, the rats received VEH, DEXM (75 μg/kg i.p.), or were pretreated with GSK (2 μM i.p.) 0.5 h ahead of DEXM respectively. The third OFT was conducted 6 h after drug administration and then the rats were sacrificed. The rats that experienced RPWI showed dramatically elevated serum corticosterone (CORT), multiplied neuronal nitric oxide synthase (nNOS) and SGK1 in the BNST, and terrible OFT behavior. We discovered when the nNOS and SGK1 were decreased in the rat BNST through DEXM treatment, the serum CORT was reduced and the OFT manifestation was ameliorated, whereas these were restrained by GSK application. Our results reveal that modest interventions to SGK1 and nNOS in the BNST improve the male rat reactivity to acute stress, and DEXM was one modulator of these effects.

Neurons and Astrocytes in Ventrolateral Periaqueductal Gray Contribute to Restraint Water Immersion Stress-Induced Gastric Mucosal Damage via the ERK1/2 Signaling Pathway

BACKGROUND

The restraint water immersion stress (RWIS) model includes both psychological and physical stimulation, which may lead to gastrointestinal disorders and cause gastric mucosal damage. The ventrolateral periaqueductal gray (VLPAG) contributes to gastrointestinal function, but whether it is involved in RWIS-induced gastric mucosal damage has not yet been reported.

METHODS

The expression of glial fibrillary acidic protein, neuronal c-Fos, and phosphorylated extracellular signal regulated kinase 1/2 in the VLPAG after RWIS was assessed using western blotting and immunocytochemical staining methods. Lateral ventricle injection of astrocytic toxin L-a-aminoadipate and treatment with extracellular signal-regulated kinase (ERK)1/2 signaling pathway inhibitor PD98059 were further used to study protein expression and distribution in the VLPAG after RWIS.

RESULTS

The expression of c-Fos, glial fibrillary acidic protein, and phosphorylated extracellular signal regulated kinase 1/2 in the VLPAG significantly increased following RWIS and peaked at 1 hour after RWIS. Lateral ventricle injection of the astrocytic toxin L-a-aminoadipate significantly alleviated gastric mucosal injury and decreased the activation of neurons and astrocytes. Treatment with the ERK1/2 signaling pathway inhibitor PD98059 obviously suppressed gastric mucosal damage as well as the RWIS-induced activation of neurons and astrocytes in the VLPAG.

CONCLUSIONS

These results suggested that activation of VLPAG neurons and astrocytes induced by RWIS through the ERK1/2 signaling pathway may play a critical role in RWIS-induced gastric mucosa damage.

Nervous mechanisms of restraint water-immersion stress-induced gastric mucosal lesion

Stress-induced gastric mucosal lesion (SGML) is one of the most common visceral complications after trauma. Exploring the nervous mechanisms of SGML has become a research hotspot. Restraint water-immersion stress (RWIS) can induce GML and has been widely used to elucidate the nervous mechanisms of SGML. It is believed that RWIS-induced GML is mainly caused by the enhanced activity of vagal parasympathetic nerves. Many central nuclei, such as the dorsal motor nucleus of the vagus, nucleus of the solitary tract, supraoptic nucleus and paraventricular nucleus of the hypothalamus, mediodorsal nucleus of the thalamus, central nucleus of the amygdala and medial prefrontal cortex, are involved in the formation of SGML in varying degrees. Neurotransmitters/neuromodulators, such as nitric oxide, hydrogen sulfide, vasoactive intestinal peptide, calcitonin gene-related peptide, substance P, enkephalin, 5-hydroxytryptamine, acetylcholine, catecholamine, glutamate, γ-aminobutyric acid, oxytocin and arginine vasopressin, can participate in the regulation of stress. However, inconsistent and even contradictory results have been obtained regarding the actual roles of each nucleus in the nervous mechanism of RWIS-induced GML, such as the involvement of different nuclei with the time of RWIS, the different levels of involvement of the sub-regions of the same nucleus, and the diverse signalling molecules, remain to be further elucidated.

Medial prefrontal cortex exacerbates gastric dysfunction of rats upon restraint water‑immersion stress

Restraint water-immersion stress (RWIS) can induce a gastric mucosal lesions within a few hours. The medial prefrontal cortex (mPFC) is involved in the RWIS process. The present study investigated the modulatory effects and molecular mechanisms of the mPFC on gastric function under an RWIS state. Male Wistar rats were divided into four groups; namely, the control, RWIS 4 h (RWIS for 4 h only), sham-operated and bilateral-lesioned (bilateral-lesioned mPFC) groups. The gastric erosion index (EI) and gastric motility (GM) were determined, and the proteomic profiles of the mPFC were assessed by isobaric tags for relative and absolute quantitation (iTRAQ) coupled with two-dimensional liquid chromatography and tandem mass spectrometry. Additionally, iTRAQ results were verified by western blot analysis. Compared with the RWIS 4 h group and the sham-control group, the bilateral-lesioned group exhibited a significantly lower EI (P<0.01). In the bilateral-lesioned group, RWIS led to a significant decrease in EI and GM. When comparing the control and RWIS 4 h groups, 129 dysregulated proteins were identified, of which 88 were upregulated and 41 were downregulated. Gene Ontology functional analysis demonstrated that 29 dysregulated proteins, including postsynaptic density protein 95, were directly associated with axon morphology, axon growth and synaptic plasticity. Ingenuity pathway analysis revealed that the dysregulated proteins were mainly involved in neurological disease signaling pathways, including the NF-κB and ERK signaling pathways. These data indicated that the presence of the mPFC exacerbates gastric mucosal injury in awake rats during RWIS. Although the quantitative proteomic analysis elucidated the nervous system molecular targets associated with the production of gastric mucosal lesions, such as the role of PSD95. The underlying molecular mechanisms of synaptic plasticity need to be further elucidated.

Proteomics of the mediodorsal thalamic nucleus of rats with stress-induced gastric ulcer

BACKGROUND

Stress-induced gastric ulcer (SGU) is one of the most common visceral complications after trauma. Restraint water-immersion stress (RWIS) can cause serious gastrointestinal dysfunction and has been widely used to study the pathogenesis of SGU to identify medications that can cure the disease. The mediodorsal thalamic nucleus (MD) is the centre integrating visceral and physical activity and contributes to SGU induced by RWIS. Hence, the role of the MD during RWIS needs to be studied.

AIM

To screen for differentially expressed proteins in the MD of the RWIS rats to further elucidate molecular mechanisms of SGU.

METHODS

Male Wistar rats were selected randomly and divided into two groups, namely, a control group and an RWIS group. Gastric mucosal lesions of the sacrificed rats were measured using the erosion index and the proteomic profiles of the MD were generated through isobaric tags for relative and absolute quantitation (iTRAQ) coupled with two-dimensional liquid chromatography and tandem mass spectrometry. Additionally, iTRAQ results were verified by Western blot analysis.

RESULTS

A total of 2853 proteins were identified, and these included 65 dysregulated (31 upregulated and 34 downregulated) proteins (fold change ratio ≥ 1.2). Gene Ontology (GO) analysis showed that most of the upregulated proteins are primarily related to cell division, whereas most of the downregulated proteins are related to neuron morphogenesis and neurotransmitter regulation. Ingenuity Pathway Analysis revealed that the dysregulated proteins are mainly involved in the neurological disease signalling pathways. Furthermore, our results indicated that glycogen synthase kinase-3 beta might be related to the central mechanism through which RWIS gives rise to SGU.

CONCLUSION

Quantitative proteomic analysis elucidated the molecular targets associated with the production of SGU and provides insights into the role of the MD. The underlying molecular mechanisms need to be further dissected.

Altered Neuronal Activity in the Central Nucleus of the Amygdala Induced by Restraint Water-Immersion Stress in Rats

Restraint water-immersion stress (RWIS), a compound stress model, has been widely used to induce acute gastric ulceration in rats. A wealth of evidence suggests that the central nucleus of the amygdala (CEA) is a focal region for mediating the biological response to stress. Different stressors induce distinct alterations of neuronal activity in the CEA; however, few studies have reported the characteristics of CEA neuronal activity induced by RWIS. Therefore, we explored this issue using immunohistochemistry and in vivo extracellular single-unit recording. Our results showed that RWIS and restraint stress (RS) differentially changed the c-Fos expression and firing properties of neurons in the medial CEA. In addition, RWIS, but not RS, induced the activation of corticotropin-releasing hormone neurons in the CEA. These findings suggested that specific neuronal activation in the CEA is involved in the formation of RWIS-induced gastric ulcers. This study also provides a possible theoretical explanation for the different gastric dysfunctions induced by different stressors.

Astrocytes and neurons in locus coeruleus mediate restraint water immersion stress-induced gastric mucosal damage through the ERK1/2 signaling pathway

Restraint water-immersion stress (RWIS) is considered to be a compound stress model that includes psychological and physical stimulation and may cause gastric mucosal damage. Studies have shown that locus coeruleus (LC) is involved in the gastrointestinal function, but whether it is involved in RWIS-induced gastric mucosal damage has not yet been reported. Here, we investigated the expression of glial fibrillary acidic protein (GFAP), c-Fos, and phosphorylation extracellular signal regulated kinase 1/2 (p-ERK1/2) in the LC after RWIS using immunocytochemical staining and western blotting in order to explore whether the ERK1/2 signaling pathway interacts with the neuron-astrocyte network in the LC during RWIS and whether it is involved in causing RWIS-induced gastric mucosal damage. Expression of c-Fos, GFAP, and p-ERK1/2 increased significantly following RWIS and peaked at 3 h after RWIS. After intracerebroventricular injection of c-Fos antisense oligodeoxynucleotides (ASO) and astrocytic toxin L-a-aminoadipate (L-AA), the gastric mucosal damage and the activation of neurons and astrocytes in the LC significantly decreased. Intracerebroventricular injection of ERK1/2 signaling pathway inhibitor PD98059 suppressed gastric mucosal damage as well as the RWIS-induced activation of neurons and astrocytes in the LC. Activation of LC neurons and astrocytes induced by RWIS through the ERK1/2 signaling pathway may play a critical role in RWIS-induced gastric mucosa damage.

Hypothalamic Astrocytes Respond to Gastric Mucosal Damage Induced by Restraint Water-Immersion Stress in Rat

Restraint water-immersion stress (RWIS), a compound stress model, includes both psychological and physical stimulation. Studies have shown that neurons in the hypothalamus are involved in RWIS, but the role of astrocytes and the interactions between astrocytes and neurons in RWIS are not clear. Here, we tested our hypothesis that hypothalamus astrocytes are involved in RWIS and interact with neurons to regulate gastric mucosal damage induced by RWIS. The expression of Glial fibrillary acidic protein (GFAP) and c-Fos in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) significantly increased following the RWIS. GFAP and c-Fos expression are similar in the temporal pattern, peaked at 1 h after the RWIS, then reduced gradually, and reached a maximal level again at 5 h which show “double-peak” characteristics. Intracerebroventricular administration of astroglial toxin L-a-aminoadipate (L-AA) and c-Fos antisense oligodeoxy nucleotides (ASO) both decreased RWIS-induced gastric mucosal damage. Results of immunohistochemistry assay revealed that both L-AA and ASO decreased the activation of astrocytes and neurons in the hypothalamus by RWIS. These results showed that hypothalamus neuron-astrocyte “network” involved in gastric mucosal damage induced by RWIS. This study may offer theoretical basis for some novel therapeutic strategies for RWIS-induced gastric ulcers.