Sebastian Peters

Dose-dependent effects of chronic central infusion of oxytocin on anxiety, oxytocin receptor binding and stress-related parameters in mice

Chronic psychosocial stress is a recognized risk factor for various affective and somatic disorders. In an established murine model of chronic psychosocial stress, exposure to chronic subordinate colony housing (CSC) results in an alteration of physiological, behavioral, neuroendocrine and immunological parameters, including a long-lasting increase in anxiety, adrenal hypertrophy and thymus atrophy. Based on the stress-protective and anxiolytic properties of oxytocin (OXT) after acute administration in rodents and humans, the major aims of our study were to assess whether chronic administration of OXT dose-dependently affects the behavior and physiology of male mice, as for therapeutic use in humans, mostly chronic treatment approaches will be used. Further, we studied, whether chronic administration during CSC prevents stress-induced consequences. Our results indicate that chronic intracerebroventricular (ICV) infusion of OXT (15 days) at high (10ng/h), but not at low (1ng/h) dose, induces an anxiogenic phenotype with a concomitant reduction of OXT receptor (OXTR) binding within the septum, the basolateral and medial amygdala, as well as the median raphe nucleus. Further, we demonstrate that chronic ICV infusion of OXT (1ng/h) during a 19-day CSC exposure prevents the hyper-anxiety, thymus atrophy, adrenal hypertrophy, and decreased in vitro adrenal ACTH sensitivity. Thus, given both negative, but also beneficial effects seen after chronic OXT treatment, which appear to be dose-dependent, a deeper understanding of long-lasting treatment effects is required before OXT can be considered for long-term therapeutic use for the treatment of psychopathologies such as autism, schizophrenia or anxiety-disorders.

Differential effects of baclofen and oxytocin on the increased ethanol consumption following chronic psychosocial stress in mice

Chronic stress is known to enhance the susceptibility for addiction disorders including alcoholism. While these findings have been recapitulated in animal models, the majority of these studies have utilized non‐social rather than social stress paradigms; the latter of which are believed to be more relevant to the human situation. Therefore, the major aim of this study was to investigate, if 14 days of chronic subordinate colony housing (CSC), a pre‐clinically validated psychosocial stress paradigm relevant for human psychiatric and somatic disorders, enhances ethanol (EtOH) consumption in male mice. To assess this, we employed the well‐established two‐bottle free‐choice paradigm where mice were given access to water and 2, 4, 6 and 8% EtOH solutions (with the concentrations increasing each fourth day) following termination of the stress procedure. After 14 days of CSC, stressed mice consumed significantly more EtOH at all concentrations tested and displayed increased EtOH preference at concentrations of 6 and 8%. This effect was not due to an altered taste preference in CSC mice as assessed by saccharine‐ and quinine‐preference tests, but was accompanied by increased anxiety‐related behavior. Systemic administration of baclofen (2.5 mg/kg) or oxytocin (OXT; 10 mg/kg) reduced the EtOH intake in single housed control (baclofen, OXT) and CSC (baclofen) mice, whereas intracerebroventricular OXT (0.5 μg/2 μl) was ineffective in both groups. Taken together, these results suggest that (i) chronic psychosocial stress enhances EtOH consumption, and (ii) baclofen and OXT differentially affect EtOH intake in mice.

Mucosal immunosuppression and epithelial barrier defects are key events in murine psychosocial stress-induced colitis.

Chronic psychosocial stress is a risk factor for many affective and somatic disorders, including inflammatory bowel diseases. In support chronic subordinate colony housing (CSC, 19 days), an established mouse model of chronic psychosocial stress, causes the development of spontaneous colitis. However, the mechanisms underlying the development of such stress-induced colitis are poorly understood. Assessing several functional levels of the colon during the initial stress phase, we show a pronounced adrenal hormone-mediated local immune suppression, paralleled by impaired intestinal barrier functions, resulting in enhanced bacterial load in stool and colonic tissue. Moreover, prolonged treatment with broad-spectrum antibiotics revealed the causal role of these early maladaptations in the development of stress-induced colitis. Together, we demonstrate that translocation of commensal bacteria is crucial in the initiation of stress-induced colonic inflammation. However, aggravation by the immune-modulatory effects of fluctuating levels of adrenal hormones is required to develop this into a full-blown colitis.

Oxytocin prevents ethanol actions at δ subunit-containing GABAA receptors and attenuates ethanol-induced motor impairment in rats

Significance Even moderate doses of alcohol can cause considerable motor impairment. This effect has been linked to ethanol-induced potentiation of GABA actions at δ subunit-containing GABAA receptors (δ-GABAARs). Here, we demonstrate that the neuropeptide oxytocin selectively attenuates ethanol-induced motor impairment in rats as well as ethanol-induced potentiation of GABAergic activity at δ-GABAARs. This effect of oxytocin is shown to be independent of the oxytocin receptor (OTR) and involves a direct action at δ-GABAARs. To our knowledge, this study provides the first evidence of oxytocin having a direct, non-OTR–mediated effect on GABA–ethanol interactions. Recent preclinical and clinical studies indicate that oxytocin may also attenuate alcohol consumption, craving, and withdrawal, and the present study shows a previously unidentified mechanism through which some of these effects may occur. Even moderate doses of alcohol cause considerable impairment of motor coordination, an effect that substantially involves potentiation of GABAergic activity at δ subunit-containing GABAA receptors (δ-GABAARs). Here, we demonstrate that oxytocin selectively attenuates ethanol-induced motor impairment and ethanol-induced increases in GABAergic activity at δ-GABAARs and that this effect does not involve the oxytocin receptor. Specifically, oxytocin (1 µg i.c.v.) given before ethanol (1.5 g/kg i.p.) attenuated the sedation and ataxia induced by ethanol in the open-field locomotor test, wire-hanging test, and righting-reflex test in male rats. Using two-electrode voltage-clamp electrophysiology in Xenopus oocytes, oxytocin was found to completely block ethanol-enhanced activity at α4β1δ and α4β3δ recombinant GABAARs. Conversely, ethanol had no effect when applied to α4β1 or α4β3 cells, demonstrating the critical presence of the δ subunit in this effect. Oxytocin had no effect on the motor impairment or in vitro effects induced by the δ-selective GABAAR agonist 4,5,6,7-tetrahydroisoxazolo(5,4-c)pyridin-3-ol, which binds at a different site on δ-GABAARs than ethanol. Vasopressin, which is a nonapeptide with substantial structural similarity to oxytocin, did not alter ethanol effects at δ-GABAARs. This pattern of results confirms the specificity of the interaction between oxytocin and ethanol at δ-GABAARs. Finally, our in vitro constructs did not express any oxytocin receptors, meaning that the observed interactions occur directly at δ-GABAARs. The profound and direct interaction observed between oxytocin and ethanol at the behavioral and cellular level may have relevance for the development of novel therapeutics for alcohol intoxication and dependence.

Oxytocin inhibits ethanol consumption and ethanol-induced dopamine release in the nucleus accumbens

Alcohol (EtOH) is one of the most widely abused recreational drugs and is arguably the most harmful. However, current treatment options for alcohol‐use disorders generally have limited efficacy and poor uptake in the community. In this context, the neuropeptide oxytocin (OXT) has emerged as a promising potential treatment option for a number of substance‐use disorders, including alcoholism. The utility of OXT in reducing consumption of and craving for a wide range of substances may lie in its ability to modulate drug‐induced neurochemical effects within the mesolimbic dopamine pathway. However, the impact of OXT on EtOH actions in this pathway has yet to be explored. Here, we reveal that an acute intracerebroventricular (icv) infusion of OXT (1 µg/5 µl) attenuated voluntary EtOH (20 percent) self‐administration after chronic intermittent access to EtOH for 59 days (28 drinking sessions) in male Wistar rats. Next, we demonstrated that an acute intraperitoneal (ip) injection of EtOH (1.5 g/kg, 15 percent w/v) increased dopamine release within the nucleus accumbens in both EtOH‐naive rats and rats that had received 10 daily ip injections of EtOH. Icv OXT completely blocked the EtOH‐induced dopamine release in both EtOH‐naive and chronically treated rats. The attenuation of EtOH‐induced dopamine release by OXT may help to explain the reduced EtOH self‐administration observed following icv OXT infusion.

Chronic psychosocial stress increases the risk for inflammation-related colon carcinogenesis in male mice

Patients with inflammatory bowel diseases (IBDs) have a higher risk of developing colorectal cancer (CRC) than the general population. Furthermore, chronic psychosocial stress increases the likelihood of developing IBD and multiple types of malignant neoplasms, including CRC. Here, for the first time, we investigate the effects of chronic psychosocial stress in male mice on an artificially induced CRC, by employing the chronic subordinate colony (CSC) housing paradigm in combination with the reliable azoxymethane (AOM)/dextran sodium sulfate (DSS) CRC model. Colonoscopy revealed that CSC mice showed accelerated macroscopic suspect lesions. In addition, more CSC mice developed low-grade dysplasia (LGD) and/or high-grade dysplasia (HGD) in the colonic tissue compared to the single-housed control mice (SHC). CSC mice showed an increased number of Ki67+ and a decreased number of terminal deoxynucleotidyl transferase dUTP nick end labeling epithelial cells in colonic tissue. Colonic liver receptor homolog-1 (LRH-1), cyclooxygenase II (COXII), tumor necrosis factor, forkhead box P3 (FoxP3) mRNA as well as colonic ß-catenin, COXII, and LRH-1 protein expression were also increased in CSC compared with SHC mice. Although the number of CD4+ Th cells was increased, a tendency toward a decreased colonic interferon-γ (IFN-γ) mRNA expression was observed. Furthermore, despite an increased percentage of CD3+ cells and CD3+/FoxP3+ double-positive cells within mesenteric lymph node cells of CSC mice, IFN-γ secretion from these cells was unaffected. Altogether, our results suggest that chronic psychosocial stress increases the risk for AOM/DSS-induced and, thus, inflammation-related CRC. Finally, assessment of additional time points may test whether the shift from tumor-protective Th1 cell to regulatory T-cell immunity represents a consequence of increased carcinogenesis or a causal factor involved in its development.

The Granulocyte-colony stimulating factor has a dual role in neuronal and vascular plasticity

Granulocyte-colony stimulating factor (G-CSF) is a growth factor that has originally been identified several decades ago as a hematopoietic factor required mainly for the generation of neutrophilic granulocytes, and is in clinical use for that. More recently, it has been discovered that G-CSF also plays a role in the brain as a growth factor for neurons and neural stem cells, and as a factor involved in the plasticity of the vasculature. We review and discuss these dual properties in view of the neuroregenerative potential of this growth factor.

The TGF-β System As a Potential Pathogenic Player in Disease Modulation of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) represents a fatal orphan disease with high unmet medical need, and a life time risk of approx. 1/400 persons per population. Based on increasing knowledge on pathophysiology including genetic and molecular changes, epigenetics, and immune dysfunction, inflammatory as well as fibrotic processes may contribute to the heterogeneity and dynamics of ALS. Animal and human studies indicate dysregulations of the TGF-β system as a common feature of neurodegenerative disorders in general and ALS in particular. The TGF-β system is involved in different essential developmental and physiological processes and regulates immunity and fibrosis, both affecting neurogenesis and neurodegeneration. Therefore, it has emerged as a potential therapeutic target for ALS: a persistent altered TGF-β system might promote disease progression by inducing an imbalance of neurogenesis and neurodegeneration. The current study assessed the activation state of the TGF-β system within the periphery/in life disease stage (serum samples) and a late stage of disease (central nervous system tissue samples), and a potential influence upon neuronal stem cell (NSC) activity, immune activation, and fibrosis. An upregulated TGF-β system was suggested with significantly increased TGF-β1 protein serum levels, enhanced TGF-β2 mRNA and protein levels, and a strong trend toward an increased TGF-β1 protein expression within the spinal cord (SC). Stem cell activity appeared diminished, reflected by reduced mRNA expression of NSC markers Musashi-1 and Nestin within SC—paralleled by enhanced protein contents of Musashi-1. Doublecortin mRNA and protein expression was reduced, suggesting an arrested neurogenesis at late stage ALS. Chemokine/cytokine analyses suggest a shift from a neuroprotective toward a more neurotoxic immune response: anti-inflammatory chemokines/cytokines were unchanged or reduced, expression of proinflammatory chemokines/cytokines were enhanced in ALS sera and SC postmortem tissue. Finally, we observed upregulated mRNA and protein expression for fibronectin in motor cortex of ALS patients which might suggest increased fibrotic changes. These data suggest that there is an upregulated TGF-β system in specific tissues in ALS that might lead to a “neurotoxic” immune response, promoting disease progression and neurodegeneration. The TGF-β system therefore may represent a promising target in treatment of ALS patients.

Fulminant Acute Ascending Hemorrhagic Myelitis Treated with Eculizumab

We describe an 18-year-old patient who developed back pain, rapidly ascending sensomotory deficits, bladder dysfunction, Lhermitte’s sign, absent abdominal reflexes of all three levels, brisk tendon reflexes, and positive Babinski’s sign. Magnetic resonance imaging of the spinal cord showed a long segment of cervical and thoracic intramedullary signal hyperintensity suggesting a longitudinally extensive transverse myelitis possibly within the course of a fast progressing ascending immune-mediated hemorrhagic myelopathy. Throughout his illness, the patient deteriorated with tetraplegia, cardiac arrest, and respiratory failure although he received, after exclusion of infective causes, therapy with steroids, immunoglobulins, plasmapheresis, and cyclophosphamide. Interestingly, treatment with the C5-inhibitor eculizumab to prevent complement-mediated spinal cord injury achieved an arrest of clinical deterioration. We propose eculizumab as treatment in fast progressive and potentially fatal immune-mediated spinal cord injury. Furthermore, this case raises awareness for the process of clinical decision-making in severe myelopathies.