Involvement of central opioid systems in human interferon-alpha induced immobility in the mouse forced swimming test

Sheng Mai Yin shows anti-fatigue, anti-hypoxia and cardioprotective potential in an experimental joint model of fatigue and acute myocardial infarction

ETHNOPHARMACOLOGICAL RELEVANCE

Cardiovascular disease (CVD) and fatigue are two common diseases endangering human life and health that may interact and reinforce one another. Myocardial infarction survivors frequently experience fatigue, and acute myocardial infarction (AMI) is one of the most common cardiovascular diseases that cause fatigue-induced sudden death. Sheng Mai Yin (SMY), a Chinese medicine prescription, is traditionally used for the treatment of diabetes and cardiovascular disease, and has been demonstrated to reduce fatigue and safeguard cardiac function.

AIM OF THE STUDY

This study aims to investigate the effects and underlying mechanisms of SMY in treating fatigue and AMI.

MATERIALS AND METHODS

The pharmacological mechanisms of SMY in treating fatigue and AMI were predicted by bioinformatics and network pharmacology methods. After administering SMY at high, medium and low doses, the swimming time to exhaustion, hemoglobin level, serological parameters and hypoxia tolerance time were detected in C57BL/6N mice, and the left ventricular ejection fractions (LVEF), left ventricular fractional shortening (LVFS), grasp strength, cardiac histopathology, serological parameters and the expression of PINK1 and Parkin proteins were examined in Wistar rats.

RESULTS

371 core targets for SMY and 282 disease targets for fatigue and AMI were obtained using bioinformatics and network pharmacology methods. Enrichment analysis of target genes revealed that SMY might interfere with fatigue and AMI through biological processes such as mitochondrial autophagy, apoptosis, and oxidative stress. For in vivo experiments, SMY showed significant anti-fatigue and hypoxia tolerance effects in mice; It also improved the cardiac function and grasp strength, decreased their cardiac index, myocardial injury and fibrosis degree, and induced serological parameters levels and the expression of PTEN-induced putative kinase 1 (PINK1) and Parkin proteins in myocardium, suggesting that SMY may exert cardioprotective effects in a joint rat model of fatigue and AMI by inhibiting excessive mitochondrial autophagy.

CONCLUSION

This study revealed the anti-fatigue, anti-hypoxia and cardioprotective effects of SMY in a joint model of fatigue-AMI, and the pharmacological mechanism may be related to the inhibition of mitochondrial autophagy in cardiomyocytes through the PINK1/Parkin pathway. The discoveries may provide new ideas for the mechanism study of traditional Chinese medicine, especially complex prescriptions, in treating fatigue and AMI.

A new insight into mechanisms of interferon alpha neurotoxicity: Expression of GRIN3A subunit of NMDA receptors and NMDA-evoked exocytosis

Neurological and psychiatric side effects accompany the high-dose interferon-alpha (IFNA) therapy. The primary genes responsible for these complications are mostly unknown. Our genome-wide search in mouse and rat genomes for the conservative genes containing IFN-stimulated response elements (ISRE) in their promoters revealed a new potential target gene of IFNA, Grin3α, which encodes the 3A subunit of NMDA receptor. This study aimed to explore the impact of IFNA on the expression of Grin3α and Ifnα genes and neurotransmitters endo/exocytosis in the mouse brain. We administered recombinant human IFN-alpha 2b (rhIFN-α2b) intracranially, and 24 h later, we isolated six brain regions and used the samples for RT-qPCR and western blot analysis. Synaptosomes were isolated from the cortex to analyze endo/exocytosis with acridine orange and L-[14C]glutamate. IFNA induced an increase in Grin3α mRNA and GRIN3A protein, but a decrease in Ifnα mRNA and protein. IFNA did not affect the accumulation and distribution of L-[14C]glutamate and acridine orange between synaptosomes and the extra-synaptosomal space. It caused the more significant acridine orange release activated by NMDA or glutamate than from control mice's synaptosomes. In response to IFNA, the newly discovered association between elevated Grin3α expression and NMDA- and glutamate-evoked neurotransmitters release from synaptosomes implies a new molecular mechanism of IFNA neurotoxicity.

Paeoniflorin ameliorates interferon-alpha-induced neuroinflammation and depressive-like behaviors in mice

Long-term treatment with high-dose Interferon-alpha (IFN-α) has resulted in depression in 30-50% of the patients. Paeoniflorin may ameliorate the IFN-α-induced depression; however, the underlying mechanism is less studied. Here, we investigated the prophylactic antidepressant and anti-neuroinflammatory effects of paeoniflorin on the behaviors and specific emotion-related regions of the brain in mice with IFN-α-induced depression. A series of behavior assessments were conducted to identify the depressive state after subcutaneously IFN-α injections and with or without intragastrically paeoniflorin administration in C57BL/6J mice. Levels of many inflammatory-related cytokines in serum, mPFC, vHi and amygdala were determined by cytokine array analysis. Furthermore, microglia and astrocyte activation in these three regions were evaluated by immunohistochemistry. We found that the mice which were subcutaneously injected IFN-α 15×106 IU/kg for 4 successive weeks to mimic an IFN-α-induced depression model had distinct inflammatory changes in the amygdala. Interestingly, 4-week 20 mg/kg or 40 mg/kg paeoniflorin pretreatments reversed the depressive-like behaviors and the abnormal inflammatory cytokine levels in the serum, mPFC, vHi and amygdala. These cytokines were not limited to the commonly reported IL-6, IL-1β and TNF-α, but also IL-9, IL-10, IL-12, and MCP-1. Besides, the increased density of microglia in IFN-α-treated mice was reversed by paeoniflorin in these three brain areas. Taken together, our data suggest that paeoniflorin can reverse the long-term, high-dose IFN-α-induced depressive-like behaviors that were associated with local distinct neuroinflammation in the mPFC, vHi and particularly the amygdala. Paeoniflorin might have a preventive therapeutic potential in IFN-α-induced depression.

Kappa Opioids, Salvinorin A and Major Depressive Disorder

Opioids are traditionally associated with pain, analgesia and drug abuse. It is now clear, however, that the opioids are central players in mood. The implications for mood disorders, particularly clinical depression, suggest a paradigm shift from the monoamine neurotransmitters to the opioids either alone or in interaction with monoamine neurons. We have a special interest in dynorphin, the last of the major endogenous opioids to be isolated and identified. Dynorphin is derived from the Greek word for power, dynamis, which hints at the expectation that the neuropeptide held for its discoverers. Yet, dynorphin and its opioid receptor subtype, kappa, has always taken a backseat to the endogenous b-endorphin and the exogenous morphine that both bind the mu opioid receptor subtype. That may be changing as the dynorphin/ kappa system has been shown to have different, often opposite, neurophysiological and behavioral influences. This includes major depressive disorder (MDD). Here, we have undertaken a review of dynorphin/ kappa neurobiology as related to behaviors, especially MDD. Highlights include the unique features of dynorphin and kappa receptors and the special relation of a plant-based agonist of the kappa receptor salvinorin A. In addition to acting as a kappa opioid agonist, we conclude that salvinorin A has a complex pharmacologic profile, with potential additional mechanisms of action. Its unique neurophysiological effects make Salvinorina A an ideal candidate for MDD treatment research.

Inflammatory cytokine-associated depression

Inflammatory cytokines can sometimes trigger depression in humans, are often associated with depression, and can elicit some behaviors in animals that are homologous to major depression. Moreover, these cytokines can affect monoaminergic and glutamatergic systems, supporting an overlapping pathoetiology with major depression. This suggests that there could be a specific major depression subtype, inflammatory cytokine-associated depression (ICAD), which may require different therapeutic approaches. However, most people do not develop depression, even when exposed to sustained elevations in inflammatory cytokines. Thus several vulnerabilities and sources of resilience to inflammation-associated depression have been identified. These range from genetic differences in neurotrophic and serotonergic systems to sleep quality and omega-3 fatty acid levels. Replicating these sources of resilience as treatments could be one approach for preventing "ICAD". This article is part of a Special Issue entitled SI: Neuroimmunology in Health And Disease.

Mechanisms for interferon-α-induced depression and neural stem cell dysfunction

New neurons generated by the neural stem cells (NSCs) in the adult hippocampus play an important role in emotional regulation and respond to the action of antidepressants. Depression is a common and serious side effect of interferon-α (IFN-α), which limits its use as an antiviral and antitumor drug. However, the mechanism(s) underlying IFN-induced depression are largely unknown. Using a comprehensive battery of behavioral tests, we found that mice subjected to IFN-α treatment exhibited a depression-like phenotype. IFN-α directly suppressed NSC proliferation, resulting in the reduced generation of new neurons. Brain-specific mouse knockout of the IFN-α receptor prevented IFN-α-induced depressive behavioral phenotypes and the inhibition of neurogenesis, suggesting that IFN-α suppresses hippocampal neurogenesis and induces depression via its receptor in the brain. These findings provide insight for understanding the neuropathology underlying IFN-α-induced depression and for developing new strategies for the prevention and treatment of IFN-α-induced depressive effects.

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IFN-α-treated mice show a depression-like phenotype in a behavioral test battery

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IFN-α directly suppresses NSC proliferation in adult hippocampus

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IFN-α suppresses neurogenesis and induced depression via its receptor in the brain

Central administration of murine interferon-α induces depressive-like behavioral, brain cytokine and neurochemical alterations in mice: a mini-review and original experiments

A role for pro-inflammatory cytokines and their neuroinflammatory signaling cascades in depressive pathology has increasingly gained acceptance. In this regard, several lines of evidence suggested that interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) can provoke neurochemical and hormonal changes akin to those associated with psychological stressors, and that these cytokines also induce sickness behaviors that resemble some of the neurovegetative features of depression. Similarly, human depressed patients often display marked changes of pro-inflammatory cytokine levels and immune cell activity. Perhaps more germane in the analysis of the cytokine-depression connection, reports of humans undergoing interferon-α (IFN-α) treatment for certain cancers or viral infections have indicated that the pro-inflammatory cytokine caused signs of major depression in a substantial subset of those treated. In the present investigation, we demonstrated that acute or repeated infusion of IFN-α into the lateral ventricles provoked depressive-like behavior and concomitant changes in serotonin (5-HT) and mRNA expression of particular 5-HT receptors and pro-inflammatory cytokines. These actions were less evident following administration directly into the prefrontal cortex and not apparent at all when administered to the dorsal raphe nucleus. The data are discussed in relation to the induction of depression elicited by IFN-α, and are presented in the context of a mini-review that highlights potential mechanisms through which the cytokine might act to promote psychomotor and affective disturbances and interact with stressors.

Kappa-opioid receptors mediate the antidepressant-like activity of hesperidin in the mouse forced swimming test

The opioid system has been implicated as a contributing factor for major depression and is thought to play a role in the mechanism of action of antidepressants. This study investigated the involvement of the opioid system in the antidepressant-like effect of hesperidin in the mouse forced swimming test. Our results demonstrate that hesperidin (0.1, 0.3 and 1 mg/kg; intraperitoneal) decreased the immobility time in the forced swimming test without affecting locomotor activity in the open field test. The antidepressant-like effect of hesperidin (0.3 mg/kg) in the forced swimming test was prevented by pretreating mice with naloxone (1 mg/kg, a nonselective opioid receptor antagonist) and 2-(3,4-dichlorophenyl)-Nmethyl-N-[(1S)-1-(3-isothiocyanatophenyl)-2-(1-pyrrolidinyl)ethyl] acetamide (DIPPA (1 mg/kg), a selective κ-opioid receptor antagonist), but not with naloxone methiodide (1 mg/kg, a peripherally acting opioid receptor antagonist), naltrindole (3 mg/kg, a selective δ-opioid receptor antagonist), clocinnamox (1 mg/kg, a selective μ-opioid receptor antagonist) or caffeine (3 mg/kg, a nonselective adenosine receptor antagonist). In addition, a sub-effective dose of hesperidin (0.01 mg/kg) produced a synergistic antidepressant-like effect in the forced swimming test when combined with a sub-effective dose of morphine (1 mg/kg). The antidepressant-like effect of hesperidin in the forced swimming test on mice was dependent on its interaction with the κ-opioid receptor, but not with the δ-opioid, μ-opioid or adenosinergic receptors. Taken together, these results suggest that hesperidin possesses antidepressant-like properties and may be of interest as a therapeutic agent for the treatment of depressive disorders.

Effects of intracisternal administration of cannabidiol on the cardiovascular and behavioral responses to acute restraint stress

Systemic administration of cannabidiol (CBD), a non-psychotomimetic compound from Cannabis sativa, attenuates the cardiovascular and behavioral responses to restraint stress. Although the brain structures related to CBD effects are not entirely known, they could involve brainstem structures responsible for cardiovascular control. Therefore, to investigate this possibility the present study verified the effects of CBD (15, 30 and 60 nmol) injected into the cisterna magna on the autonomic and behavioral changes induced by acute restraint stress. During exposure to restraint stress (1h) there was a significant increase in mean arterial pressure (MAP) and heart rate (HR). Also, 24h later the animals showed a decreased percentage of entries onto the open arms of the elevated plus-maze. These effects were attenuated by CBD (30 nmol). The drug had no effect on MAP and HR baseline values. These results indicate that intracisternal administration of CBD can attenuate autonomic responses to stress. However, since CBD decreased the anxiogenic consequences of restraint stress, it is possible that the drug is also acting on forebrain structures.

Development of a murine animal model of depression for repeated dosing with human interferon alpha

BACKGROUND

Neuropsychiatric adverse effects of interferon (IFN) alpha are well known. There is little clinically relevant research on animal models of depression with recombinant human IFN alpha 2b (rhIFN-α2b).

AIM

To identify an appropriate dose and duration of administration of recombinant human interferon alpha-2b (rhIFN-α2b) to establish a convenient and clinically relevant murine model of chronic rhIFN-α2b-induced depression using the forced swim test (FST).

MATERIALS AND METHODS

Using a 4×3 factorial design, rhIFN-α2b was administered subcutaneously to mice (n=180) in the dose range of 400, 800, and 1600 IU/g/day for 5, 10, and 15 days; saline-treated mice formed the control groups. In each group, 1 day after the last dose, the mice were assessed for immobility in the FST. In another experiment, at these same doses and time points, the effect of rhIFN-α2b on murine motility was assessed in the small open field.

RESULTS

We found that rhIFN-α2b significantly increased immobility in the FST. The immobility was detectable by day 5 and did not increase with duration of IFN treatment. The immobility was apparent with the 400 IU/g/day dose and was not greater at higher IFN doses. At no dose or time point did rhIFN-α2b alter murine motility in the small open field.

CONCLUSION

We conclude that rhIFN-α2b-induced behavioral despair, represented by immobility in the FST, is not due to reduced basal motility. The FST may therefore be used as a convenient Swiss albino mouse model of chronic rhIFN-α2b-induced depression with a 400-1600 IU/g/day dose administered subcutaneously for 5-15 days. The most economical model is 400 IU/g/day administered for 5 days.

Pegylated human interferon alpha 2a does not induce depression-associated changes in mice

Interferon (IFN) alpha proteins are proinflammatory cytokines having immunomodulating and antiviral properties. States during which cytokine systems are activated (e.g., during viral infection or during treatment of chronic hepatitis C and various malignancies with IFN alpha, etc.) can be associated with depression-like syndromes or even full-blown depressive episodes. Therefore, the role of IFN alpha and other cytokines in the pathogenesis of depressive disorder ("cytokine hypothesis of depression") has been assessed for many years with contradictory results. We have investigated whether intraperitoneal administration of high doses (up to 600 µg/kg body weight) of pegylated, recombinant human IFN alpha 2a in mice induces changes known to be associated with depression using three different readouts: behavior in a model of despair (Porsolt swim test), presence of anhedonia (sucrose preference test), and sensitivity of the hypothalamic-pituitary-adrenal system (dexamethasone suppression test). We also assessed potential IFN-induced changes in gene expression in the liver. In none of the performed experiments, depression-associated effects could be found despite very high serum levels of IFN-induced antiviral activity compared to levels measured in hepatitis C virus (HCV) patients treated routinely with pegylated recombinant human IFN alpha 2a. The lack of such expected effects is probably due to the fact that pegylated human recombinant IFN alpha 2a does not activate the murine class I IFN receptor. Our results do not support the hypothesis that administration of recombinant pegylated human IFN alpha to mice produces a robust model of depression.

Major depression during interferon-alpha treatment: vulnerability and prevention

Major Depressive Disorder (MDD) during interferons (IFN-α) treatment can occur within a few months of therapy, and shares many homologies with other forms of MDD, Most patients are resilient to the side effect ofinterferon-induced depression (IFN-MDD), but 15% to 40% are vulnerable. Several studies have employed antidepressants to prevent the incidence of an IFN-MDD episode, and the results suggest that prophylactic antidepressants may be specifically useful in those with pre-existing subthreshold depressive symptoms andlor a history of prior MDD episodes. Several other potential markers of vulnerability for IFN-MDD have been implicated in assessments of nondepressed patients before they start IFN-α These include poor sleep quality, premorbid elevations in inflammatory cytokines, genetic polymorphisms in the serotonin system, personality, and social support. The interplay of these factors strongly predicts who is at risk for IFN-MDD, and indicates several potentially modifiable targets for the personalized prevention of IFN-MDD,

Psychiatric problems in patients infected with hepatitis C before and during antiviral treatment with interferon-alpha: a review

OBJECTIVE

Neuropsychiatric symptoms are common in patients with chronic hepatitis C (CHC) and can potentially be exacerbated by interferon-alpha treatment. Such symptoms can contribute to problems with treatment adherence, which can significantly compromise epidemiological virus control. This review summarizes current knowledge about the etiology, course, and management of neuropsychiatric symptoms in patients with CHC.

METHOD

Studies were identified using computerized searches, with further references obtained from the bibliographies of the reviewed articles.

RESULTS

Psychopathological syndromes that occur during interferon-alpha treatment frequently have atypical features that may complicate their recognition using standard diagnostic criteria. In addition, prospective studies in this area often exclude patients with psychiatric disorders and have methodological disparities that make it difficult to develop guidelines for management of psychiatric side effects induced by interferon-alpha. Despite the high prevalence of chronic hepatitis C virus (HCV) infection in patients with psychiatric and substance use disorders, neuropsychiatric concerns often lead to the exclusion of such patients from interferon-alpha treatment, inappropriately depriving them of the potential benefits of this therapy.

CONCLUSION

Consultation-liaison psychiatrists should become familiar with the clinical spectrum of presentations associated with HCV infection as well as with related neuropsychiatric symptoms in order to promote the creation of multidisciplinary teams who specialize in the care of patients with HCV infections. More studies are needed to define neuropsychiatric syndromes that can be induced by interferon-alpha and to clarify best assessment and treatment procedures for these syndromes. It is also important to create and evaluate psychoeducational programs for all patients with chronic HCV infections, even those with low risk of complications, in order to promote adherence to therapy and optimize patients' quality of life.

Evidence for the involvement of the opioid system in the antidepressant-like effect of folic acid in the mouse forced swimming test

The opioid system has been implicated in major depression and in the mechanism of action of antidepressants. This study investigated the involvement of the opioid system in the antidepressant-like effect of the water-soluble B-vitamin folic acid in the forced swimming test (FST). The effect of folic acid (10 nmol/site, i.c.v.) was prevented by the pretreatment of mice with naloxone (1 mg/kg, i.p., a nonselective opioid receptor antagonist), naltrindole (3 mg/kg, i.p., a selective delta-opioid receptor antagonist), naloxonazine (10 mg/kg, i.p., a selective mu(1)-opioid receptor antagonist, 24 h before), but not with naloxone methiodide (1 mg/kg, s.c., a peripherally acting opioid receptor antagonist). In addition, a sub-effective dose of folic acid (1 nmol/site, i.c.v.) produced a synergistic antidepressant-like effect in the FST with a sub-effective dose of morphine (1 mg/kg, s.c.). A further approach was designed to investigate the possible relationship between the opioid system and NMDA receptors in the mechanism of action of folic acid in the FST. Pretreatment of the animals with naloxone (1 mg/kg, i.p.) prevented the synergistic antidepressant-like effect of folic acid (1 nmol/site, i.c.v.) and MK-801 (0.001 mg/kg, i.p., a non-competitive NMDA receptor antagonist). Together the results firstly indicate that the anti-immobility effect of folic acid in the FST is mediated by an interaction with the opioid system (mu(1) and delta), likely dependent on the inhibition of NMDA receptors elicited by folic acid.

Systemic interferon-alpha regulates interferon-stimulated genes in the central nervous system

The prime anti-viral cytokine interferon-alpha (IFN-alpha) has been implicated in several central nervous system (CNS) disorders in addition to its beneficial effects. Systemic IFN-alpha treatment causes severe neuropsychiatric complications in humans, including depression, anxiety and cognitive impairments. While numerous neuromodulatory effects by IFN-alpha have been described, it remains unresolved whether or not systemic IFN-alpha acts directly on the brain to execute its CNS actions. In the present study, we have analyzed the genes directly regulated in post-IFN-alpha receptor signaling and found that intraperitoneal administration of mouse IFN-alpha, but not human IFN-alpha, activated expression of several prototypic IFN-stimulated genes (ISGs), in particular signal transducers and activators of transcription (STAT1), IFN-induced 15 kDa protein (ISG15), ubiquitin-specific proteinase 18 (USP18) and guanylate-binding protein 3 (GBP3) in the brain. A similar temporal profile for the regulated expression of these IFN-alpha-activated ISG genes was observed in the brain compared with the peripheral organs. Dual labeling in situ hybridization combined with immunocytochemical staining demonstrated a wide distribution of the key IFN-regulated gene STAT1 transcripts in the different parenchyma cells of the brain, particularly neurons. The overall response to IFN-alpha challenge was abolished in STAT1 knockout mice. Together, our results indicate a direct, STAT1-dependent action of systemic IFN-alpha in the CNS, which may provide the basis for a mechanism in humans for neurological/neuropsychiatric illnesses associated with IFN-alpha therapy.

Pharmacological evidence for the involvement of the opioid system in the antidepressant-like effect of adenosine in the mouse forced swimming test

This study investigated the involvement of the opioid system in the antidepressant-like effect of adenosine in the forced swimming test. The effect of adenosine (10 mg/kg, i.p.) was prevented by the pretreatment of mice with naloxone (1 mg/kg, i.p., a nonselective opioid receptor antagonist), naltrindole (3 mg/kg, i.p., a selective delta-opioid receptor antagonist), clocinnamox (1 mg/kg, i.p., an irreversible mu-opioid receptor antagonist), and 2-(3,4-dichlorophenyl)-Nmethyl-N-[(1S)-1-(3-isothiocyanatophenyl)-2-(1-pyrrolidinyl)ethyl]acetamide (DIPPA; 1 mg/kg, i.p., a selective kappa-opioid receptor antagonist), but not with naloxone methiodide (1 mg/kg, s.c., a nonselective opioid receptor antagonist that does not cross the blood-brain barrier). Naloxone also prevented the anti-immobility effect of cyclohexyladenosine (CHA, 0.1 mg/kg, i.p., a selective adenosine A(1) receptor agonist) and N6-[2-(3,5-dimethoxyphenyl)-2-(2-methylphenyl)ethyl]adenosine (DPMA, 1 mg/kg, i.p., a selective adenosine A(2A) receptor agonist). The administration of DIPPA (0.1 mg/kg, i.p.) or morphine (1 mg/kg, s.c., a nonselective opioid receptor agonist), but not naltrindole (0.3 mg/kg, i.p.) and clocinnamox (0.1 mg/kg, i.p.) potentiated the effect of a subeffective dose of adenosine (1 mg/kg, i.p.) in the forced swimming test, without affecting the locomotor activity. No additive effect in the immobility time was observed when mice were treated with morphine (5 mg/kg, s.c.) plus adenosine (10 mg/kg, i.p.). These results indicate that the anti-immobility effect of adenosine in the forced swimming test, via adenosine A(1) and A(2A) receptors, is mediated by an interaction with the opioid system, likely dependent on an activation of mu- and delta-opioid receptors and an inhibition of kappa-opioid receptors.

The endomorphin system and its evolving neurophysiological role

Endomorphin-1 (Tyr-Pro-Trp-Phe-NH2) and endomorphin-2 (Tyr-Pro-Phe-Phe-NH2) are two endogenous opioid peptides with high affinity and remarkable selectivity for the mu-opioid receptor. The neuroanatomical distribution of endomorphins reflects their potential endogenous role in many major physiological processes, which include perception of pain, responses related to stress, and complex functions such as reward, arousal, and vigilance, as well as autonomic, cognitive, neuroendocrine, and limbic homeostasis. In this review we discuss the biological effects of endomorphin-1 and endomorphin-2 in relation to their distribution in the central and peripheral nervous systems. We describe the relationship between these two mu-opioid receptor-selective peptides and endogenous neurohormones and neurotransmitters. We also evaluate the role of endomorphins from the physiological point of view and report selectively on the most important findings in their pharmacology.

Interferon-induced depression in chronic hepatitis C: a review of its prevalence, risk factors, biology, and treatment approaches

Hepatitis C viral infection is a global health problem that affects approximately 4 million people in the United States. Combination treatment with pegylated interferon (IFN)-alpha plus ribavirin has been shown to be most effective in treating patients with chronic hepatitis C (CHC). Despite its efficacy, one of the most common side effects of this regimen is depression. Whereas IFN-alpha has been found to induce depression in chronic myelogenous leukemia, melanoma, and renal cell carcinoma, CHC patients may be especially prone to develop IFN-induced depression. This review includes a summary of differences between IFN-alpha and IFN-beta and addresses whether pegylation of IFN (versus nonpegylated IFN) gives rise to a treatment with reduced potential to induce depressive symptoms. Consideration is also given to evidence showing that treatment with ribavirin may contribute to IFN-induced depression. Thyroid disorders and anemia (as well as other medical conditions) have also been associated with IFN exposure and may account for some incidences of depression in CHC patients. Evidence is reviewed indicating that prior psychiatric and mood disorders (especially previous episodes of major depressive disorder), just prior to IFN treatment, contribute to the propensity to develop depression during treatment. In addition, a brief description is provided of potential biological mechanisms of IFN-induced depression (ie, monoamines, hypothalamic-pituitary-adrenocortical [HPA] axis, proinflammatory cytokines, peptidases, intercellular adhesion molecule-1, and nitric oxide). Finally, a discussion is provided on the use of antidepressants as a preventative versus restorative treatment, including a commentary on risks of using antidepressants in this patient population.

Behavioral effects and ChE measures after acute and repeated administration of malathion in rats

Organophosphorus compounds such as malathion are environmental contaminants that may evoke neurobehavioral responses including anxiety and depression. In this study, after a functional observational battery, rats were tested in an open field and temperature test to better define doses used in subsequent experiments. Then, we investigated the effects of acute and repeated treatment with malathion on elevated plus-maze and forced-swim test, which are validated animal models to observe for anxiety- and depressive-related behaviors, respectively. We found that both acute and repeated malathion administration induced anxiogenic and depressive-like responses at doses that affected neither locomotion nor systemic temperature. Biochemical assays demonstrated inhibition of cholinesterase activity by these effective doses.

Electroacupuncture reduces rectal distension-induced blood pressure changes in conscious dogs

It has been shown that acupuncture relieves symptoms of abdominal pain and bloating in patients with irritable bowel syndrome (IBS). However, the mechanism of beneficial effects of acupuncture still remains unproven. The aim of the present study was to investigate the mechanisms of the antinociceptive effects of acupuncture in conscious dogs. We evaluated the increase in mean arterial blood pressure (MAP) caused by rectal distension as an index of visceral pain. Electroacupuncture (EA; 10 Hz) at ST-36 (lower leg), but not at BL-21 (back), significantly reduced the increase in MAP in response to rectal distension (30 and 40 cm3). The antinociceptive effect of EA at ST-36 was abolished by pretreatment with naloxone (a central and peripheral opioid receptor antagonist) but not by naloxone methiodide (a peripheral opioid receptor antagonist). These results suggest that EA at ST-36 may reduce visceral pain via central opioid pathway. Acupuncture may be useful to treat visceral hypersensitivity in IBS patients.

Effects of interferon-α on cloned opioid receptors expressed in Xenopus oocytes

Interferon-alpha (IFNalpha) affects the opioid system. However, the direct action of IFNalpha on cloned opioid receptors remains unknown. Taking advantage of the functional coupling of cloned opioid receptors to G protein-activated inwardly rectifying K+ (GIRK) channels in a Xenopus oocyte expression system, we investigated the effects of recombinant IFNalpha on cloned mu-, delta- and kappa-opioid receptors. In oocytes co-injected with mRNAs for either the delta- or kappa-opioid receptor and for GIRK channel subunits, IFNalpha at high concentrations induced small GIRK currents that were abolished by naloxone, an opioid-receptor antagonist, compared with the control responses to each selective opioid agonist. Additionally, IFNalpha induced no significant current response in oocytes injected with mRNA(s) for either opioid receptor alone or GIRK channels. In oocytes expressing the mu-opioid receptor and GIRK channels, IFNalpha had little or no effect. Moreover, in oocytes expressing each opioid receptor and GIRK channels, GIRK current responses to each selective opioid agonist were not affected by the presence of IFNalpha, indicating no significant antagonism of IFNalpha toward the opioid receptors. Furthermore, IFNalpha had little or no effect on the mu/delta-, delta/kappa- or mu/kappa-opioid receptors expressed together with GIRK channels in oocytes. Our results suggest that IFNalpha weakly activates the delta and kappa-opioid receptors. The direct activation of the delta- and kappa-opioid receptors by IFNalpha may partly contribute to some of the IFNalpha effects under its high-dose medication.

Neonatal impact of leukemia inhibitory factor on neurobehavioral development in rats

Cytokines have been implicated in the etiology or pathology of various psychiatric diseases of developmental origin such as autism and schizophrenia. Leukemia inhibitory factor (LIF) is induced by a variety of brain insults and known to have many influences on mature and immature nervous system. Here, we assessed the neurobehavioral and pathological consequences of peripheral administration of LIF in newborn rats. Subcutaneous LIF injection induced STAT3 phosphorylation in many brain regions and increased glial fibrillary acidic protein (GFAP) immunoreactivity in the neocortex, suggesting that LIF had direct effects in the central nervous system. The LIF-treated rats displayed decreased motor activity during juvenile stages, and developed abnormal prepulse inhibition in the acoustic startle test during and after adolescence. They displayed normal learning ability in active avoidance test, however. Brain neuronal structures and startle responses were grossly normal, except for the cortical astrogliosis during neonatal LIF administration. These results indicate that LIF induction in the periphery of the infant has a significant, but discrete impact on neurobehavioral development.

Dual effects of nitric oxide in the mouse forced swimming test: possible contribution of nitric oxide-mediated serotonin release and potassium channel modulation

Recent findings have indicated that nitric oxide (NO) may change the duration of immobility biphasically in the forced swimming test, which is a useful experimental model for screening antidepressant-like activity in rodents. In the present study, we have investigated the role of serotonin and of potassium (K(+)) channels in the dual effects of NO in the mouse forced swimming test (MFST). For this purpose, we tested the effects of l-arginine, an NO precursor, the NO synthase inhibitor N(G)-nitro-l-arginine methyl ester (l-NAME), and of K(+)-channel blockers tetraethylammonium (TEA) and 3,4-diaminopyridine (3,4-DAP). In addition, we used sertraline as a serotonin reuptake inhibitor and cyproheptadine as a serotonin antagonist. l-Arginine increased the duration of immobility in the MFST in low doses (25 mg/kg ip) but decreased it in higher doses (500 and 1000 mg/kg ip). Low doses of l-NAME (50 and 75 microg icv) decreased while higher dose of this drug (150 microg icv) increased the immobility time. TEA (5 microg icv) and 3,4-DAP (0.05 microg icv) significantly reduced the time, whereas K(+) channel opener pinacidil increased the duration of immobility. l-Arginine (100 mg/kg ip) significantly antagonised the effects of l-NAME (50 microg), 3,4-DAP and TEA. Higher dose of l-arginine (500 mg/kg ip) significantly potentiated the effects of 3,4-DAP and TEA, but reduced the effect of pinacidil. Low doses of l-arginine antagonized, but higher doses of l-arginine potentiated the antidepressant-like effect of sertraline. Sertraline potentiated the effects of 3,4-DAP and TEA, but reversed the effect of pinacidil. Cyproheptadine reduced the anti-immobility effect of l-arginine and 3,4-DAP. At the highest effective doses, drugs did not impair the motor functions. These data support the hypothesis that NO effects may involve the release of serotonin and/or modulation of K(+) channels.

Cardioprotection of Interleukin-2 Is Mediated via κ-Opioid Receptors

We examined whether interleukin-2 (IL-2) protects the myocardium against injury induced by ischemia and reperfusion via the kappa-opioid receptor (OR). The cardioprotective effect of IL-2 was evaluated by measuring infarct size and lactate dehydrogenase (LDH) release in response to ischemia and reperfusion in the isolated rat heart. IL-2 at an optimal dose of 50 U/ml mimicked the effect of ischemic preconditioning by reducing infarct size and LDH release. The infarct and LDH-reducing effects of IL-2 were blocked by nor-binaltorphimine (5 microM), a kappa-OR antagonist, but not naltrindole (5 microM), a delta-OR antagonist known to block the action of its stimulation. Moreover, blockade of the mitochondrial ATP-sensitive potassium (mito-K(ATP)) channel with a selective antagonist, 5-hydroxydecanoate (100 microM), or a nonselective antagonist of K(ATP) channels, glybenclamide (100 microM), or blockade of protein kinase C (PKC) with its inhibitors chelerythrine (5 microM) or GF 109203X (10 microM) [3-[1-[3-(dimethylaminopropyl]-1H-indol-3-yl]-4-(1H-indol-3-yl)-1H-pyrrole-2,5-dione monohydrochloride] abolished the protective effect of IL-2. Administration of free radical scavengers N-acetylcysteine (4 mM) or N-(2-mercaptopropionyl)-glycine (1 mM) also abolished the protective effects of IL-2 and U50,488H [(trans)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]benzeneacetamide], a selective kappa-OR agonist. This study provides the first evidence that IL-2 confers cardioprotection against injury induced by ischemia/reperfusion. The effect of IL-2 is mediated via kappa-OR as evidenced by kappa-OR antagonism and similar signaling mechanisms, mito-K(ATP), PKC, and reactive oxygen species involved in the cardioprotective effects of both IL-2 and kappa-OR stimulation.

The non-steroidal anti-inflammatory drug diclofenac sodium attenuates IFN-alpha induced alterations to monoamine turnover in prefrontal cortex and hippocampus

Interferon-alpha (IFN-alpha) administration induces major depression in a significant number of patients undergoing treatment for viral illnesses and other chronic diseases. Non-steroidal anti-inflammatory drugs (NSAIDs) are known to counteract a number of IFN-alpha-induced side effects, including pro-inflammatory cytokine activation and stress hormone release. To investigate this possibility further, we sought to determine the effect of the NSAID diclofenac sodium on monoamine turnover in brain induced by acute IFN-alpha exposure. Eleven male, Wistar rats (8 weeks old) were pretreated with diclofenac (20 mg/kg, s.c.) or saline, followed by intracerebroventricular (i.c.v.) infusion of IFN-alpha (1000 IU in 5 microl) or vehicle. The prefrontal cortex, striatum, and hippocampus were isolated and samples were assayed for monoamines and major metabolites by high-pressure liquid chromatography with electrochemical detection. The data show that acute IFN-alpha increased serotonin turnover in prefrontal cortex and increased dopamine turnover in hippocampus, while pre-treatment with diclofenac completely prevented these neurochemical responses. Importantly, these changes were recorded in two brain areas known to be important in depression and antidepressant action. These data offer support for a novel role of NSAIDs in modulating IFN-alpha-induced neurochemical alterations, and raise the possibility of the use of NSAIDs for the prevention of IFN-alpha-induced depression.

Endogenous opiates: 2000

This paper is the twenty-third installment of the annual review of research concerning the opiate system. It summarizes papers published during 2000 that studied the behavioral effects of the opiate peptides and antagonists, excluding the purely analgesic effects, although stress-induced analgesia is included. The specific topics covered this year include stress; tolerance and dependence; learning, memory, and reward; eating and drinking; alcohol and other drugs of abuse; sexual activity, pregnancy, and development; mental illness and mood; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; gastrointestinal, renal, and hepatic function; cardiovascular responses; respiration and thermoregulation; and immunological responses.