Knockdown of corticotropin-releasing factor in the central amygdala reverses persistent viscerosomatic hyperalgesia

Gastrointestinal nociception is exacerbated by chronic stress through an unknown mechanism. The amygdala is a key nucleus involved in the autonomic and neuroendocrine responses to stress. The goal of this study was to test the hypothesis that prolonged exposure of the central amygdala (CeA) to stress or the stress hormone cortisol (or corticosterone in rats) induces nociceptive behaviors mediated by corticotropin-releasing factor (CRF) within the CeA. We selectively knocked down CRF in the CeA via antisense oligodeoxynucleotides (ASO) in animals with targeted, stereotaxically placed corticosterone (CORT) micropellets or following repeated water avoidance stress (WAS). CRF expression in the CeA was analyzed concurrently with the assessment of visceral hypersensitivity to colonic distension and mechanical somatic withdrawal threshold. The responses were characterized at 7 or 28 days post implantation of the CORT micropellet or following 7 days of WAS. Exposure of the CeA to elevated CORT or WAS increased CRF expression and heightened visceral and somatic sensitivity. Infusion of CRF ASO into the CeA decreased CRF expression and attenuated visceral and somatic hypersensitivity in both models. Our study provides important evidence for a CRF-mediated mechanism specifically within the CeA that regulates stress-induced visceral and somatic nociception.

In a non-human primate model, aging disrupts the neural control of intestinal smooth muscle contractility in a region-specific manner

BACKGROUND

Incidences of gastrointestinal (GI) motility disorders increase with age. However, there is a paucity of knowledge about the aging mechanisms leading to GI dysmotility. Motility in the GI tract is a function of smooth muscle contractility, which is modulated in part by the enteric nervous system (ENS). Evidence suggests that aging impairs the ENS, thus we tested the hypothesis that senescence in the GI tract precipitates abnormalities in smooth muscle and neurally mediated contractility in a region-specific manner.

METHODS

Jejunal and colonic circular muscle strips were isolated from young (4-10 years) and old (18+ years) baboons. Myogenic responses were investigated using potassium chloride (KCl) and carbachol (CCh). Neurally mediated contractile responses were evoked by electrical field stimulation (EFS) and were recorded in the absence and presence of atropine (1 μM) or NG-Nitro-l-arginine methyl ester (l-NAME; 100 μM).

KEY RESULTS

The myogenic responses to KCl in the jejunum and colon were unaffected by age. In the colon, but not the jejunum, CCh-induced contractile responses were reduced in aged animals. Compared to young baboons, there was enhanced EFS-induced contractility of old baboon jejunal smooth muscle in contrast to the reduced contractility in the colon. The effect of atropine on the EFS response was lower in aged colonic tissue, suggesting reduced participation of acetylcholine. In aged jejunal tissue, higher contractile responses to EFS were found to be due to reduced nitregic inhibition.

CONCLUSIONS & INFERENCES

These findings provide key evidence for the importance of intestinal smooth muscle and ENS senescence in age-associated GI motility disorders.

Depletion of serotonin in the basolateral amygdala elevates glutamate receptors and facilitates fear-potentiated startle

Our previous experiments demonstrated that systemic depletion of serotonin (5-hydroxytryptamine, 5-HT), similar to levels reported in patients with emotional disorders, enhanced glutamateric activity in the lateral nucleus of the amygdala (LA) and potentiated fear behaviors. However, the effects of isolated depletion of 5-HT in the LA, and the molecular mechanisms underlying enhanced glutamatergic activity are unknown. In the present study, we tested the hypothesis that depletion of 5-HT in the LA induces increased fear behavior, and concomitantly enhances glutamate receptor (GluR) expression. Bilateral infusions of 5,7-dihydroxytryptamine (4 μg per side) into the LA produced a regional reduction of serotonergic fibers, resulting in decreased 5-HT concentrations. The induction of low 5-HT in the LA elevated fear-potentiated startle, with a parallel increase in GluR1 mRNA and GluR1 protein expression. These findings suggest that low 5-HT concentrations in the LA may facilitate fear behavior through enhanced GluR-mediated mechanisms. Moreover, our data support a relationship between 5-HT and glutamate in psychopathologies.

Importance of epigenetic mechanisms in visceral pain induced by chronic water avoidance stress

Epigenetic molecular mechanisms, which include DNA methylation and histone deacetylation, are implicated in the dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis. Previously, we demonstrated that repeated water avoidance stress (WAS), a validated model of chronic psychological stress, induces heightened visceral pain behaviors in rodents that resemble irritable bowel syndrome (IBS) sequelae. However, the involvement of epigenetic molecular mechanisms in the pathophysiology of stress-induced visceral pain has not been explored. Our hypothesis is that epigenetic mechanisms within the central nervous system (CNS) are important to chronic stress-induced visceral hypersensitivity. Adult male F-344 rats with intracerebroventricular (i.c.v.) cannulae were exposed to 7 days of repeated WAS. Controls received a SHAM stress. Following the daily 1h stressor, trichostatin A (TSA; 100 ng/ml), a potent histone deacetylase inhibitor, or vehicle (VEH; 0.1% DMSO/saline,) as control was administered via the i.c.v. cannula. Visceral sensitivity was assessed 24h after the final WAS and quantified the visceromotor response (VMR) by recording the number of abdominal contractions in response to graded pressures (20-60 mmHg) of colorectal distensions (CRD). From a separate group of rats that were exposed to repeated WAS or SHAM stress, the amygdala was isolated to assess the methylation status of glucocorticoid receptor (GR) and corticotropin releasing-factor (CRF) genes via bisulfite sequencing and verified by pyrosequencing. GR and CRF gene expression was quantified via qRT-PCR. Stressed rats exhibited visceral hypersensitivity that was significantly attenuated by TSA. Compared to SHAM controls, methylation of the GR gene was increased following WAS while expression of the GR gene was decreased. Methylation of the CRF promoter was decreased with WAS with a concomitant increase in CRF expression. This study demonstrates the involvement of central epigenetic mechanisms in regulating stress-induced visceral hypersensitivity and provides a foundation for exploring the epigenetic mechanisms that may contribute to IBS-like symptomatology.

Lack of tumor uptake of 131-I labeled rituximab in a patient with a CD20 positive lymphoma lesion

Radioimmunotherapy has emerged as a treatment modality for patients with CD20 positive B-cell non-Hodgkin's lymphoma (NHL). Prior to administration of a therapeutic dose, confirmation of uptake of the radiolabeled compound in tumor locations and calculation of an appropriate dose can be performed using a diagnostic dose and subsequent imaging. We report the case of a 69-year-old male with a relapsed mantle cell lymphoma scheduled for radioimmunotherapy, where diagnostic imaging with 131-I labeled rituximab revealed unexpected new insights with implications for treatment. Persistence of the mantle cell lymphoma in a lymph node in the left arm was demonstrated by an 18-F fluorodeoxyglucose scan. However, a scan after a diagnostic dose of 131-I labeled rituximab did not show any uptake of the tracer, even though subsequent cytological analysis unequivocally confirmed a CD20 positive B-cell population in the lesion. The administration of a therapeutic dose of 131-I labeled rituximab was therefore cancelled. We here discuss the mechanisms that may explain lack of targeting in a proven CD20-positive lymphoma and provide recommendations for further studies.

Taste disorders in Australian Aboriginal and non-Aboriginal children

AIM

To assess the prevalence and type of taste disorders in Aboriginal and non-Aboriginal children matched for age, gender and living in the same general and educational environment.

METHODS

Taste function was assessed in 432 Aboriginal (n = 166) and non-Aboriginal (n = 266) children aged 8-12 years from six public schools in a rural township using a three-choice taste identification test and a cross-sectional design.

RESULTS

The prevalence of taste disorders was very high and significantly more common in Aboriginal (20/166; 12.0%) than in non-Aboriginal (21/266; 7.9%) children. Forty-one children had quality-specific disorders, of whom 27 (65.9%) had sweet disorders. Children often had more than one quality disorder.

CONCLUSION

The prevalence of taste disorders in children was high and exceeded the level (4%) designated by the World Health Organisation as requiring immediate action by health authorities. As the cause of the disorders is unknown, there is a need for a wider investigation of the causes and the consequences.

Reduced association of anti-apoptotic protein Mcl-1 with E3 ligase Mule increases the stability of Mcl-1 in breast cancer cells

Background:

Mechanisms that increase resistance to apoptosis help promote cellular transformation. Cancer cells have deregulated apoptotic pathways, where increased expression and stability of anti-apoptotic proteins Mcl-1 and Bcl-2 increases resistance to apoptosis. Pathways that increase the stability of proteins in cancer cells remain poorly understood.

Methods:

Using human mammary epithelial and established breast cancer cell lines, we assessed the mechanisms that increase the stability of anti-apoptotic proteins in breast cancer cells by caspase assay, western blot, small-inhibitory RNA treatment and immunoprecipitation.

Results:

While breast cancer cells were resistant to de novo inhibition of protein synthesis, a rapid proteosome-mediated degradation of Mcl-1 and Bcl-2 induced apoptosis in mammary epithelial cells. Although Mule, an E3 ligase that targets Mcl-1 for degradation was expressed in mammary epithelial and breast cancer cell lines, rapid increase of polyubiquitinated Mcl-1 and Bcl-2 was detected only in mammary epithelial cells. Only transient formation of the Mule–Mcl-1 complex was detected in breast cancer cells. Downregulation of pERK1/2 in breast cancer cells reduced Mcl-1 levels and increased Mcl-1/Mule complex.

Conclusion:

Our findings suggest that reduced Mule/Mcl-1 complex has a significant role in increasing the stability of Mcl-1 in breast cancer cells and increased resistance to apoptosis.

The pharmacokinetics of ¹³¹I-rituximab in a patient with CD20 positive non-Hodgkin Lymphoma: evaluation of the effect of radioiodination on the biological properties of rituximab

PURPOSE

To report the pharmacokinetics of ¹³¹I-rituximab a patient with a CD20 positive non-Hodgkin Lymphoma who has received ¹³¹I-rituximab as consolidation treatment after remission induction and to evaluate the effect of radioiodination on the biological properties of rituximab.

RESULTS

The patient was a 65-year-old male with a relapsed CD20 positive follicular non-Hodgkin Lymphoma. After induction therapy the patient was in partial remission. Following administration of a diagnostic dose of 185 MBq ¹³¹I-rituximab, remaining lesions were identified on the wholebody scans. The patient then received a therapeutic dose of 1000 MBq ¹³¹I-rituximab. The uptake by the tumor in the right axilla was 0.17-0.21% of the injected dose. The calculated biological half-life of ¹³¹I-rituximab was 684 hrs. This biological half-life corresponded well with the half-life of unlabeled rituximab which was approximately 720 hrs.

DISCUSSION AND CONCLUSION

Even though radioiodination of rituximab results in a reduced binding capacity, whole body scans demonstrated localization of ¹³¹I-rituximab in the tumor area. This observation supports the specific targeting of ¹³¹I-rituximab. The half-life of ¹³¹I-rituximab corresponded to the half-life of unlabeled rituximab. Hence, the pharmacokinetics of ¹³¹ I-rituximab was not relevantly affected by the radioiodination process.

CD20 antigen imaging with ¹²⁴I-rituximab PET/CT in patients with rheumatoid arthritis

INTRODUCTION

Visualization of the CD20-antigen expression could provide a tool to localize sites of inflammation and could be of additive value in the diagnosis, and subsequently, in the treatment follow-up of patients with rheumatoid arthritis. In this study, an anti-CD20 monoclonal antibody, rituximab (Mabthera®), was radiolabeled with ¹²⁴Iodine. We report the first results of I¹²⁴-rituximab PET/CT in patients with rheumatoid arthritis.

METHODS

Eligible patients received 50 MBq ¹²⁴I-rituximab. Wholebody PET/CT imaging was performed at 10 min, 24 h, 48 h and 72-96 h post injection. Images were evaluated primarily on a visual basis and were correlated with disease activity as determined by physical examination and clinical measures.

RESULTS

Joints with visually detectable targeting of ¹²⁴I-rituximab were observed in 4 out of 5 evaluable patients. Only the images at 24 h and later showed accumulation in joints, indicating that the visualized signal represented active targeting of rituximab to the CD20 antigen. Several images showed CD20 positive B-cell infiltration in joints which were clinically normal, while a few clinically diagnosed arthritis localizations were not visualized. This discrepancy suggests that infiltration of CD20 positive B-cells in synovium is a phenomenon that is at least partially independent of clinical inflammation. The level of uptake in joints was generally low, representing less than 0.5% of the injected dose.

CONCLUSION

We have shown the feasibility of CD20 antigen imaging using ¹²⁴I-rituximab in patients with rheumatoid arthritis. Further research is needed to elucidate the clinical significance of demonstrated B-cell infiltration in rheumatic joints.

The pharmacokinetics of ¹²⁴I-rituximab in patients with rheumatoid arthritis

Rheumatoid arthritis is a destructive inflammatory joint disorder. Pre- and mature B-cells, characterized by CD20 antigen expression, play an important role in the inflammatory process. Rituximab, a chimeric monoclonal antibody against the CD20 antigen, has been approved since 2006 for the treatment of patients with rheumatoid arthritis. However, not all patients benefit from this treatment. Persistent activity of the disease has been reported despite treatment with rituximab. Imaging of radiolabeled rituximab can be used to monitor the biodistribution of rituximab, and potentially to predict the efficacy of the treatment. In this study, rituximab was radiolabeled with ¹²⁴Iodine for positron emission tomography (PET) imaging. The aim of this study was to investigate the pharmacokinetics and biodistribution of ¹²⁴I-rituximab in patients with rheumatoid arthritis, to establish the optimal procedure for PET imaging. Eligible patients received 50 MBq ¹²⁴I-rituximab, corresponding to approximately 1.5 mg rituximab. Wholebody PET/CT imaging was performed at 10 min, 24 hrs, and 48 hrs post injection. The total body activity, radioactivity in whole blood, and rituximab serum levels were determined. ¹²⁴I-rituximab has favorable pharmacokinetics for targeting of (pathological) B cells and imaging over several days, but only after pre-treatment with unlabeled rituximab. In addition, protection of the thyroid is recommended to prevent uptake of released ¹²⁴I.