Immunocytochemical characterization of rat brainstem neurons with vagal afferent input from the stomach challenged by acid or ammonia

Impact of infection on risk of Parkinson's disease: a quantitative assessment of case-control and cohort studies

Identifying modifiable risk factors for Parkinson's disease (PD) to help prevent this disease has attracted increasing interest in recent years for the limited effective drugs at present. Despite many studies indicated that infection acts as a risk factor for PD, there is no quantitative assessment of the impact of viral and bacterial infections on the risk of developing PD. The present study performed a meta-analysis on the basis of 38 datasets from 13 studies covering 287,773 PD cases and 7,102,901 controls to ascertain the association between PD and infection and the differences in the strength of the viral and bacterial infections. The overall meta-analytic results indicated that individuals with infection had a 20% increased risk of PD compared with controls (OR 1.20, 95%CI 1.07-1.32). The subgroup analysis according to the type of infection found that bacterial infection had a significant impact on increased risk of PD (OR 1.40, 95%CI 1.32-1.48). The present analysis indicated that infection could increase the risk of developing PD, and physician should be aware of the risk of developing PD in subjects with infection.

Helicobacter pylori infection is associated with an increased risk of Parkinson's disease: A population-based retrospective cohort study

BACKGROUND

Several studies have evaluated the association of Parkinson's disease with Helicobacter pylori (HP) infection, although no cohort studies have evaluated this association among the general population.

OBJECTIVE

This study aimed to investigate the risk of Parkinson's disease after HP infection in the general Taiwanese population.

METHODS

This study of Taiwanese health insurance data (2000-2012) evaluated 9105 cases of HP infection and 9105 controls matched with propensity scoring. Univariate and multivariate Cox proportional hazards regression models were used to assess the risk of subsequent Parkinson's disease.

RESULTS

We observed 64 cases of Parkinson's disease in the HP infection group (1.7/1000 person-years), and 25 cases in the control group (0.7/1000 person-years). Overall, there was a significantly higher risk of Parkinson's disease in the HP infection group (adjusted hazard ratio [aHR]: 2.29, 95% confidence interval [CI]: 1.44-3.66). HP infection was significantly associated with an increased risk of Parkinson's disease among individuals who were ≥60 years old (aHR: 2.53, 95% CI: 1.47-4.35), but not among those <60 years old (aHR: 1.86, 95% CI: 0.69-4.98). Furthermore, HP infection was associated with an increased risk of Parkinson's disease among both men (aHR: 2.14, 95% CI: 1.15-3.96) and women (aHR: 2.84, 95% CI: 1.37-5.89). Nonetheless, eradication therapy was not significantly associated with the risk of Parkinson's disease (aHR: 1.07, 95% CI: 0.63-1.82).

CONCLUSION

Although HP infection was associated with an increased risk of Parkinson's disease, eradication therapy did not ameliorate this association. Further research is needed to explore the underlying biological mechanisms.

Meta-analysis: Association of Helicobacter pylori infection with Parkinson's diseases

BACKGROUND

The results from observational studies on the relationship between helicobacter pylori (H. pylori) infection and Parkinson's disease remain controversial. A meta-analysis was conducted to evaluate the association between helicobacter pylori infection and Parkinson's disease.

METHODS

A comprehensive literature search was performed on relevant studies published from January 1983 to January 2017 in PubMed, Web of Science and EMBASE databases. The fixed or random effects model was used to pool the odds ratio with 95% confidence interval from individual studies. Publication bias was estimated by Egger's test and the funnel plot.

RESULTS

Eight eligible studies involving 33 125 participants were included in this meta-analysis. Compared with the no helicobacter pylori infected person, the pooled odds ratio of Parkinson's disease in helicobacter pylori infected person was 1.59 (95% confidence interval: 1.37-1.85). In subgroup analyzes, the combined odds ratios were 1.96 (1.23-3.12) in Asia, 1.55 (1.32-1.82) in Europe, 1.59 (1.35-1.88) in case-control studies, 1.56 (1.01-2.39) in cross-sectional studies, 1.56 (1.32-1.85) in studies with confounders adjusted, and 1.71 (1.21-2.43) in studies with no confounder adjusted, respectively.

CONCLUSIONS

This meta-analysis indicated that H. pylori infection might be associated with the risk of Parkinson's disease.

Treatment for Helicobacter pylori infection and risk of Parkinson's disease in Denmark

BACKGROUND AND PURPOSE

It has been speculated that gastrointestinal infection with Helicobacter pylori (HP) contributes to the development of Parkinson's disease (PD). We used nationwide Danish registers to investigate this hypothesis.

METHODS

 We identified 4484 patients with a first time PD diagnosis between 2001 and 2008 from the Danish National Patient Register (DNPR) and 22, 416 population controls from the Danish Civil Registration System (CRS). Information on drug use was obtained from the National Prescription Registry (NPR). We used logistic regression to compute odds ratios (OR) for the association between treatment for HP and risk of PD.

RESULTS

Prescriptions for HP-eradication drugs and proton pump inhibitors (PPI) 5 or more years prior to the diagnosis of PD were associated with a 45% and 23% increase in PD risk, respectively. Hospitalizations and outpatient visits for gastritis and peptic/duodenal ulcers, however, were not associated with PD.

CONCLUSIONS

  Our population-based study suggests that chronic HP infections and/or gastritis contribute to PD or that these are PD-related pathologies that precede motor symptoms.

Acute oxycodone induces the pro-emetic pica response in rats

Oxycodone, a semisynthetic opioid analgesic, is frequently prescribed for the management of pain. Side effects of nausea and emesis affect patient compliance and limit its therapeutic use. The present study established that an antinociceptive dose of oxycodone (15 mg/kg; oral) induces the pica response. We found sex differences in the temporal course of pica, with females having a longer duration. Opioid receptors mediated the pica response, as 1.0 mg/kg naloxone transiently attenuated and 2.0 mg/kg naloxone blocked pica. A κ-selective antagonist failed to block the response, suggesting mediation by μ opioid receptor. For further validation, we used the well established kaolin intake model to assess pica with the chemotherapeutic drug cisplatin as a positive control. Oxycodone and cisplatin significantly increased kaolin intake 4- to 7-fold, and the wet weight of stomach was elevated 2- to 3-fold. To examine the underlying neural circuitry, we investigated c-fos activation in the area postrema and nucleus of solitary tract (NTS). Oxycodone treatment significantly increased the number of c-fos-positive neurons in the area postrema and NTS compared with water controls. As expected, cisplatin also increased the number of c-fos-positive cells in these regions. In the area postrema, the oxycodone effect was greater than cisplatin, especially at 2 h. These results indicate that an antinociceptive dose of oxycodone is associated with the expression of pica, a pro-emetic response.

Association of cathepsin E deficiency with the increased territorial aggressive response of mice

Cathepsin E is an endolysosomal aspartic proteinase predominantly expressed in cells of the immune system, but physiological functions of this protein in the brain remains unclear. In this study, we investigate the behavioral effect of disrupting the gene encoding cathepsin E in mice. We found that the cathepsin E-deficient (CatE-/-) mice were behaviorally normal when housed communally, but they became more aggressive compared with the wild-type littermates when housed individually in a single cage. The increased aggressive response of CatE-/- mice was reduced to the level comparable to that seen for CatE+/+ mice by pretreatment with an NK-1-specific antagonist. Consistent with this, the neurotransmitter substance P (SP) level in affective brain areas including amygdala, hypothalamus, and periaqueductal gray was significantly increased in CatE-/- mice compared with CatE+/+ mice, indicating that the increased aggressive behavior of CatE-/- mice by isolation housing followed by territorial challenge is mainly because of the enhanced SP/NK-1 receptor signaling system. Double immunofluorescence microscopy also revealed the co-localization of SP with synaptophysin but not with microtubule-associated protein-2. Our data thus indicate that cathepsin E is associated with the SP/NK-1 receptor signaling system and thereby regulates the aggressive response of the animals to stressors such as territorial challenge.

Effect of reflux-induced inflammation on transient receptor potential vanilloid one (TRPV1) expression in primary sensory neurons innervating the oesophagus of rats

A possible mechanism of oesophageal hypersensitivity is the acid-induced activation of transient receptor potential vanilloid receptor 1 (TRPV1) in the primary sensory neurons. We investigated TRPV1 expression and its colocalization with substance P (SP) and isolectin B4 (IB4)-positive cells in the thoracic dorsal root ganglia (DRGs) and nodose ganglia (NGs) of rats with reflux-induced oesophagitis (RO). RO was developed by fundus ligation and partial obstruction of the pylorus of Sprague-Dawley rats. Four groups of rats were used; fundus ligated acute (RO 48 h), chronic 7 days (RO 7D), RO 7D + omeprazole (7D + Omz, 40 mg kg(-1), i.p.) and sham-operated controls. Immunohistochemical analysis of TRPV1, SP and IB4 expression were carried out in spinal cord (SC), DRGs and NGs. RO rats exhibited significant inflammation and increase in TRPV1-ir and SP-ir expressions in the SC, DRGs and NGs. The maximum colocalization of TRPV1 and SP was observed in RO 7D rats, but Omz prevented inflammation and over expression of TRPV1 and SP. TRPV1-ir significantly increased in IB4-positive cells in DRGs and SC, but not in the NGs. Results document that acid-induced oesophagitis increases TRPV1 expression in both SP- and IB4-positive sensory neurons. The over expression of TRPV1 may contribute to oesophageal hypersensitivity observed in gastro-oesophageal reflux disease (GORD).

Significant increase in the aggressive behavior of transgenic mice overexpressing peripheral progastrin peptides: associated changes in CCK2 and serotonin receptors in the CNS

The gastrin precursor peptide, progastrin (PG), is secreted from enteroendocrine cells in the intestine and increased in patients with hypergastrinemia and colorectal cancers. In recent years, we and others have demonstrated an important role of PG peptides in colorectal carcinogenesis, and were surprised to note significant changes in the behaviors of transgenic mice overexpressing PGs. In the present studies, we examined emotional behaviors of transgenic mice overexpressing PG in the intestinal and peripheral circulation. Aggression, locomotor activity and anxiety-like behaviors of the homozygous transgenic (Tg/Tg) mice and the wild-type (WT) littermates were examined by intruder/resident test, open field and elevated plus maze, respectively. A significant increase in the aggression, locomotor activity, and anxiety-like behaviors was detected in the Tg/Tg vs WT mice. As CCK, CCK(2) receptors (CCK(2)R), and 5-HT(1A) receptors (5-HT(1A)R) in the CNS play an important role in these behaviors, possible changes in the expression of CCK and CCK(2)R and the density of CCK(2)R and 5-HT(1A)R were determined by either real-time RT-PCR or autoradiography of ligand binding assays. The results suggest that the expressions of CCK and CCK(2)R were increased in the hypothalamus, and the density of CCK(2)R were increased in the hypothalamus and amygdala of Tg/Tg vs WT mice. Similarly, the density of 5-HT(1A)R was increased in the hypothalamus. Our results suggest that an upregulation of the CCK response system and 5-HT(1A)R in the hypothalamus of Tg/Tg mice may mediate the alterations in the observed behaviors of these mice.

Innervation of the mammalian esophagus

Understanding the innervation of the esophagus is a prerequisite for successful treatment of a variety of disorders, e.g., dysphagia, achalasia, gastroesophageal reflux disease (GERD) and non-cardiac chest pain. Although, at first glance, functions of the esophagus are relatively simple, their neuronal control is considerably complex. Vagal motor neurons of the nucleus ambiguus and preganglionic neurons of the dorsal motor nucleus innervate striated and smooth muscle, respectively. Myenteric neurons represent the interface between the dorsal motor nucleus and smooth muscle but they are also involved in striated muscle innervation. Intraganglionic laminar endings (IGLEs) represent mechanosensory vagal afferent terminals. They also establish intricate connections with enteric neurons. Afferent information is implemented by the swallowing central pattern generator in the brainstem, which generates and coordinates deglutitive activity in both striated and smooth esophageal muscle and orchestrates esophageal sphincters as well as gastric adaptive relaxation. Disturbed excitation/inhibition balance in the lower esophageal sphincter results in motility disorders, e.g., achalasia and GERD. Loss of mechanosensory afferents disrupts adaptation of deglutitive motor programs to bolus variables, eventually leading to megaesophagus. Both spinal and vagal afferents appear to contribute to painful sensations, e.g., non-cardiac chest pain. Extrinsic and intrinsic neurons may be involved in intramural reflexes using acetylcholine, nitric oxide, substance P, CGRP and glutamate as main transmitters. In addition, other molecules, e.g., ATP, GABA and probably also inflammatory cytokines, may modulate these neuronal functions.

Endogenous neuropeptide Y depresses the afferent signaling of gastric acid challenge to the mouse brainstem via neuropeptide Y type Y2 and Y4 receptors

Vagal afferents signal gastric acid challenge to the nucleus tractus solitarii of the rat brainstem. This study investigated whether nucleus tractus solitarii neurons in the mouse also respond to gastric acid challenge and whether this chemonociceptive input is modified by neuropeptide Y acting via neuropeptide Y receptors of type Y2 or Y4. The gastric mucosa of female mice was exposed to different concentrations of HCl or saline, excitation of neurons in the nucleus tractus solitarii visualized by c-Fos immunohistochemistry, gastric emptying deduced from the gastric volume recovery, and gastric lesion formation evaluated by planimetry. Relative to saline, intragastric HCl (0.15-0.35 M) increased the number of c-Fos-expressing cells in the nucleus tractus solitarii in a concentration-dependent manner, inhibited gastric emptying but failed to cause significant hemorrhagic injury in the stomach. Mice in which the Y2 or Y4 receptor gene had been deleted responded to gastric acid challenge with a significantly higher expression of c-Fos in the nucleus tractus solitarii, the increases amounting to 39 and 31%, respectively. The HCl-induced inhibition of gastric emptying was not altered by deletion of the Y2 or Y4 receptor gene. BIIE0246 ((S)-N2-[[1-[2-[4-[(R,S)-5,11-dihydro-6(6H)-oxodibenz[b,e] azepin-11-yl]-1-piperazinyl]-2-oxoethyl]cyclopentyl] acetyl]-N-[2-[1,2-dihydro-3,5 (4H)-dioxo-1,2-diphenyl-3H-1,2,4-triazol-4-yl]ethyl]-argininamide; 0.03 mmol/kg s.c.), a Y2 receptor antagonist which does not cross the blood-brain barrier, did not modify the c-Fos response to gastric acid challenge. The Y2 receptor agonist peptide YY-(3-36) (0.1 mg/kg intraperitoneally) likewise failed to alter the gastric HCl-evoked expression of c-Fos in the nucleus tractus solitarii. BIIE0246, however, prevented the effect of peptide YY-(3-36) to inhibit gastric acid secretion as deduced from measurement of intragastric pH. The current data indicate that gastric challenge with acid concentrations that do not induce overt injury but inhibit gastric emptying is signaled to the mouse nucleus tractus solitarii. Endogenous neuropeptide Y acting via Y2 and Y4 receptors depresses the afferent input to the nucleus tractus solitarii by a presumably central site of action.

Differential effects of intragastric acid and capsaicin on gastric emptying and afferent input to the rat spinal cord and brainstem

Background

Hydrochloric acid (HCl) is a potential threat to the integrity of the gastric mucosa and is known to contribute to upper abdominal pain. We have previously found that gastric mucosal challenge with excess HCl is signalled to the rat brainstem, but not spinal cord, as visualized by expression of c-fos messenger ribonucleic acid (mRNA), a surrogate marker of neuronal excitation. This study examined whether gastric mucosal exposure to capsaicin, a stimulant of nociceptive afferents that does not damage the gastric mucosa, is signalled to both brainstem and spinal cord and whether differences in the afferent signalling of gastric HCl and capsaicin challenge are related to different effects on gastric emptying.

Results

Rats were treated intragastrically with vehicle, HCl or capsaicin, activation of neurons in the brainstem and spinal cord was visualized by in situ hybridization autoradiography for c-fos mRNA, and gastric emptying deduced from the retention of intragastrically administered fluid. Relative to vehicle, HCl (0.5 M) and capsaicin (3.2 mM) increased c-fos transcription in the nucleus tractus solitarii by factors of 7.0 and 2.1, respectively. Capsaicin also caused a 5.2-fold rise of c-fos mRNA expression in lamina I of the caudal thoracic spinal cord, although the number of c-fos mRNA-positive cells in this lamina was very small. Thus, on average only 0.13 and 0.68 c-fos mRNA-positive cells were counted in 0.01 mm sections of the unilateral lamina I following intragastric administration of vehicle and capsaicin, respectively. In contrast, intragastric HCl failed to induce c-fos mRNA in the spinal cord. Measurement of gastric fluid retention revealed that HCl suppressed gastric emptying while capsaicin did not.

Conclusion

The findings of this study show that gastric mucosal exposure to HCl and capsaicin is differentially transmitted to the brainstem and spinal cord. Since only HCl blocks gastric emptying, it is hypothesized that the two stimuli are transduced by different afferent pathways. We infer that HCl is exclusively signalled by gastric vagal afferents whereas capsaicin is processed both by gastric vagal and intestinal spinal afferents.

Nociceptive transmitter release in the dorsal spinal cord by capsaicin-sensitive fibers after noxious gastric stimulation

Little is known about transmitters that encode noxious gastric stimuli in the spinal cord. The release of glutamate, substance P, and CGRP from the spinal cord was therefore investigated in response to acid injury of the gastric mucosa. Dorsal halves of the caudal thoracic spinal cord (T7-T13) were removed 6 h after oral application of 0.5 M HCl or saline, transferred to a superfusion chamber, and the basal and capsaicin-stimulated (3.3 microM) transmitter release was determined. After acid injury, basal glutamate release increased 134% as compared to saline-treated animals. Capsaicin-stimulated release of CGRP and SP was 48% and 58% lower in acid- than in saline-treated animals, indicating that capsaicin-sensitive fibers in the dorsal spinal cord were already partially depleted by acid treatment. Capsaicin denervation reduced basal glutamate release by 33% after acid injury as compared to non-denervated acid-treated animals. Gastric origin and capsaicin sensitivity of glutamatergic, CGRP- and SP-containing primary afferents in thoracic dorsal root ganglia were then determined by retrograde tracing with True Blue and immunohistochemical labeling with the vanilloid receptor TRPV1. About 65% of True Blue-labeled cells were glutamatergic and more than 73% of this population expressed the TRPV1 receptor. Nearly all True Blue/CGRP (85%)- and True Blue/SP-positive cells (97%) coexpressed TRPV1. We conclude that noxious gastric stimulation with acid induces release of glutamate, SP, and CGRP from capsaicin-sensitive sensory afferents in the dorsal horn of the spinal cord where they may play an important role in gastric nociception and hyperalgesia.

Extracellular signal-regulated kinase-1 and -2 are activated by gastric luminal injury in dorsal root ganglion neurons via n-methyl-d-aspartate receptors

Mitogen activated protein kinases such as phosphorylated extracellular signal-regulated kinase-1 and -2 (pERK 1/2) have been recently demonstrated to play an important role in somatic nociception and hyperalgesia. In the present study we examined whether pERK 1/2 is involved in the response of sensory neurons to a noxious visceral stimulation, in particular, of the gastric mucosa. After induction of gastric injury by oral administration of 0.5M HCl pERK 1/2 expression was determined by Western blotting of caudal thoracic dorsal root ganglia and by immunohistochemistry in stomach-innervating dorsal root ganglion neurons which were retrogradely labeled with True Blue. The content of pERK 1/2 remained unchanged in dorsal root ganglia until 2 h post-HCl, however, was found elevated 4 (approximately 80%) and 6 h (approximately 100%) after HCl administration. True Blue-labeled pERK 1/2-immunoreactive neurons were likewise increased 6 h post-HCl (204%) and were mainly of small size (20-40 microm) and negative for neurofilament 200 (approximately 76%). The majority of these cells also expressed the nociceptive transient receptor potential vanilloid receptor 1 (approximately 70%). The gastric mucosa was simultaneously examined for lesion formation showing highest percentage of damage 6 h post-HCl. Application of a N-methyl-D-aspartate receptor antagonist (MK-801; 100 microg/kg s.c.) significantly reduced HCl-induced pERK 1/2 expression and mucosal lesions 6 h post-HCl. Activation of the extracellular signal-regulated kinase-1 and -2 signaling cascade indicates that visceral primary afferents may sensitize after gastric noxious stimulation involving N-methyl-D-aspartate receptors. The extracellular signal-regulated kinase-1 and -2 pathway therefore may not only be of importance for somatic but also for visceral nociception.

Vagal afferent input from the acid-challenged rat stomach to the brainstem: Enhancement by interleukin-1β

Exposure of the gastric mucosa to back-diffusing concentrations of HCl (0.25 M, pH 0.51) stimulates vagal afferent input to the brainstem. Here we have examined whether pretreatment of rats with the proinflammatory cytokines interleukin-1beta and tumor necrosis factor-alpha causes sensitization of vagal afferent pathways to HCl. Rats were pretreated i.p. with interleukin-1beta, tumor necrosis factor-alpha (10 microg/kg) or their vehicle (sterile saline) 24, 48 and 96 h before intragastric administration of HCl (0.25 M, 1 ml/100 g). Activation of neurons in the nucleus tractus solitarii was visualized by c-Fos immunohistochemistry 2 h after the HCl challenge. I.p. administration of interleukin-1beta and tumor necrosis factor-alpha alone induced c-Fos in the brainstem, an effect that was gone after 24 h. At this time, however, the effect of HCl to cause expression of c-Fos in the nucleus tractus solitarii was significantly enhanced by pretreatment with interleukin-1beta and tumor necrosis factor-alpha. The sensitizing effect of i.p.-administered interleukin-1beta was sustained for more than 48 h and prevented by the interleukin-1 receptor antagonist anakinra. Intracisternal administration of interleukin-1beta and tumor necrosis factor-alpha (100 ng) failed to amplify the HCl-evoked expression of c-Fos in the brainstem. These results show that peripheral administration of the proinflammatory cytokines interleukin-1beta and tumor necrosis factor-alpha induces prolonged sensitization of vagal afferent pathways to gastric HCl challenge. This effect seems to arise from a peripheral action on vagal afferents and may be of relevance to gastric chemonociception.