Is interferon-alpha a neuromodulator?

Isolation and characterization of the mink interferon-epsilon gene and its antiviral activity

The interferon (IFN) response is the first line of defense against viral invasion and thus plays a central role in the regulation of the immune response. IFN-epsilon (IFN-ε) is a newly discovered type I IFN that does not require viral induction, unlike other type I IFNs. IFN-ε is constitutively expressed in epithelial cells and plays an important role in mucosal immunity. In this study, we evaluated the biological activity of the mink-IFN (MiIFN)-ε gene in prokaryotic cells. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to evaluate IFN-ε expression in different mink tissues. MiIFN-ε was highly expressed in brain, lung, tracheal, kidney, intestinal, bladder, ovarian, and testis tissues. There was no significant difference in MiIFN-ε expression between female and male minks, except in the reproductive system. Expression of the small ubiquitin-like modifier (SUMO3)-MiIFN-ε fusion gene was induced by isopropylβ-d-thiogalactoside, and MiIFN-ε was collected after SUMO-specific protease digestion. We tested the antiviral activity of MiIFN-ε against vesicular stomatitis virus (VSV) in epithelial cells of feline kidney 81 (F81). We used qRT-PCR to analyze the expression of several IFN-stimulated genes (ISGs), including ISG15, 2'-5' oligoadenylate synthetase (2'-5'OAS1), and myxovirus resistance protein 1 (Mx1). Recombinant IFN-ε induced high ISG expression in F81 cells. Compared with those in the cell control group, expressions of ISG15, Mx1, and 2'-5' OAS1 in the VSV-GFP control, IFN-ε, and MiIFN-ε-inhibited VSV-GFP groups were significantly increased. Compared with those in the VSV-GFP control group, expressions of ISG15 and 2'-5' OAS1 in the IFN-ε and MiIFN-ε-inhibited VSV-GFP groups were significantly increased, and the differences were highly significant (p < 0.0001). IFN-ε played an indirect antiviral role. These findings lay the foundation for detailed investigation of IFN-ε in the future.

The Swine IFN System in Viral Infections: Major Advances and Translational Prospects

Interferons (IFNs) are a family of cytokines that play a pivotal role in orchestrating the innate immune response during viral infections, thus representing the first line of defense in the host. After binding to their respective receptors, they are able to elicit a plethora of biological activities, by initiating signaling cascades which lead to the transcription of genes involved in antiviral, anti-inflammatory, immunomodulatory and antitumoral effector mechanisms. In hindsight, it is not surprising that viruses have evolved multiple IFN escape strategies toward efficient replication in the host. Hence, in order to achieve insight into preventive and treatment strategies, it is essential to explore the mechanisms underlying the IFN response to viral infections and the constraints thereof. Accordingly, this review is focused on three RNA and three DNA viruses of major importance in the swine farming sector, aiming to provide essential data as to how the IFN system modulates the antiviral immune response, and is affected by diverse, virus-driven, immune escape mechanisms.

Invited review: Mechanisms of hypophagia during disease

Suppression of appetite, or hypophagia, is among the most recognizable effects of disease in livestock, with the potential to impair growth, reproduction, and lactation. The continued evolution of the field of immunology has led to a greater understanding of the immune and endocrine signaling networks underlying this conserved response to disease. Inflammatory mediators, especially including the cytokines tumor necrosis factor-α and interleukin-1β, are likely pivotal to disease-induced hypophagia, based on findings in both rodents and cattle. However, the specific mechanisms linking a cytokine surge to decreased feeding behavior are more difficult to pin down and likely include direct effects on appetite centers in the brain, alteration of gastric motility, and modulation of other endocrine factors that influence appetite and satiety. These insights into the mechanisms for disease-induced hypophagia have great relevance for management of neonatal calves, mature cows transitioning to lactation, and cows experiencing mastitis; however, it is not necessarily the case that increasing feed intake by any means possible will improve health outcomes for diseased cattle. We explore conflicting effects of hypophagia on immune responses, which may be impaired by the lack of specific substrates, versus apparent benefits for controlling the growth of some pathogens. Anti-inflammatory strategies have shown promise for promoting recovery of feed intake following some conditions but not others. Finally, we explore the potential for early disease detection through automated monitoring of feeding behavior and consider which strategies may be implemented to respond to early hypophagia.

Type I Interferons in NeuroHIV

Infection with Human Immunodeficiency Virus (HIV)-1 continues to cause HIV-associated neurocognitive disorders despite combined antiretroviral therapy. Interferons (IFNs) are important for any antiviral immune response, but the lasting production of IFNα causes exhaustive activation leading eventually to progression to AIDS. Expression of IFNα in the HIV-exposed central nervous system has been linked to cognitive impairment and inflammatory neuropathology. In contrast, IFNβ exerts anti-inflammatory effects, appears to control, at least temporarily, lentiviral infection in the brain and provides neuroprotection. The dichotomy of type I IFN effects on HIV-1 infection and the associated brain injury will be discussed in this review, because the underlying mechanisms require further investigation to allow harnessing these innate immune factors for therapeutic purposes.

Interferon-induced sterile alpha motif and histidine/aspartic acid domain-containing protein 1 expression in astrocytes and microglia is mediated by microRNA-181a

OBJECTIVE

Sterile alpha motif and histidine/aspartic acid domain-containing protein 1 (SAMHD1), a newly discovered HIV-1 host restriction factor, has been found to be induced by interferons and to be regulated by microRNA-181a (miR-181a). However, the mechanism of interferons-induced SAMHD1 expression is unclear.

DESIGN

We hypothesized that interferons induce SAMHD1 expression through Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathways, which is mediated by miR-181a.

METHODS

We examined the effect of IFN-α and IFN-γ on SAMHD1 mRNA and protein expression, as well as the levels of phosphorylated SAMHD1 and miR-181a in astrocytes and microglia. To determine whether interferons-induced SAMHD1 expression was mediated by miR-181a, we overexpressed or inhibited miR-181a in these cells and exposed them to interferons. We also detected the effect of SAMHD1 and miR-181a on HIV-1 infection in astrocytes and microglia.

RESULTS

Both IFN-α and IFN-γ increased SAMHD1 mRNA and protein expression, and reduced miR-181a levels, particularly in microglia. Phosphorylated SAMHD1was not induced by interferons. Overexpression of miR-181a counteracted induction of SAMHD1 expression by interferons, and inhibition of miR-181a mimicked interferons treatment. Inhibition of JAK-STAT signaling pathways resulted in increased miR-181a levels and decreased SAMHD1 mRNA expression. Knock-down of SAMHD1 or overexpression of miR-181a enhanced HIV-1 infection, whereas inhibition of miR-181a reduced HIV-1 infection. However, inhibition of HIV-1 infection induced by IFN-α was not significantly affected by miR-181a and SAMHD1.

CONCLUSION

MiR-181a is an important mediator for interferons-induced SAMHD1 expression in astrocytes and microglia, but not for inhibition of HIV-1 infection induced by IFN-α.

Interferon-α induces neurotoxicity through activation of the type I receptor and the GluN2A subunit of the NMDA receptor

Elevated levels of interferon-alpha (IFNα) in the central nervous system (CNS) are linked to cognitive dysfunction in patients with inflammatory CNS diseases such as HIV-associated neurocognitive disorders (HAND). Increased CNS IFNα has also been found to be associated with cognitive dysfunction in a HAND mouse model. Here, we corroborate previous studies showing a dose-dependent decrease in dendritic branching and length caused by IFNα treatment and extend those studies. Because both direct and indirect mechanisms of IFNα-induced neurotoxicity are likely involved, the cell signaling pathway involving the IFNα receptor (IFNAR) was initially evaluated. Rat neuronal cultures exposed to IFNα demonstrate increased phosphorylation of STAT1 and increased interferon stimulating gene 15 (ISG15) expression, indicators of IFNAR engagement. However, specific blocking antibodies to the IFNAR were found to only partially protect neurons from IFNα-induced neurotoxicity. Additionally, inhibiting the GluN2A subunit of N-methyl-D-asparate receptor (NMDAR) was also found to be partially protective against IFNα-induced neurotoxicity compared with the GluN2B subunit. Neurotoxicity is evident in neurons extracted from IFNAR KO mice treated with IFNα as well, further indicating that IFNAR signaling is not required for IFNα neurotoxicity. The neurotoxic actions of IFNα are mediated through both the IFNAR as well as the GluN2A subunit of the NMDAR to reduce dendritic arborization in neurons. Complete protection from IFNα-induced neurotoxicity was demonstrated when both pathways were blocked. Blocking these pathways could lead to potential therapies for cognitive dysfunction during neuroinflammation and specifically lead to better treatments for HAND.

Evaluation of neuroimmunomodulatory activity of recombinant human interferon α

OBJECTIVE

Recombinant human interferon (rhIFN)-α is a potent immunoregulator having a wide range of therapeutic applications. In the present study, rhIFN-α was evaluated for its neuroimmunomodulatory activity.

METHOD

Dose-dependent gene expression of cytokines and chemokines in the brain of rhIFN-administered mice was studied using real-time SYBR green PCR.

RESULTS

Statistically significant increase in expression levels of tumor necrosis factor-α, interleukin (IL)-6, IL-1β and IFN-γ were observed.

CONCLUSION

The findings indicate that rhIFN-α may be used at an optimized dose to cause appropriate neuromodulation of cytokine/chemokine secretion that can aid in the development of therapeutic approaches for many infectious diseases of the central nervous system for which therapies are lacking.

Increased IFNα activity and differential antibody response in patients with a history of Lyme disease and persistent cognitive deficits

Following antibiotic treatment for Lyme disease, some patients report persistent or relapsing symptoms of pain, fatigue, and/or cognitive deficits. Factors other than active infection, including immune abnormalities, have been suggested, but few clues regarding mechanism have emerged. Furthermore, the effect of antibiotic treatment on immune response in affected individuals remains unknown. In this study, a longitudinal analysis of specific immune markers of interest was carried out in patients with a history of Lyme disease and persistent objective memory impairment, prior to and following treatment with either ceftriaxone or placebo. IFNα activity was measured by detection of serum-induced changes in specific target genes, using a functional cell-based assay and quantitative real-time PCR. Level and pattern of antibody reactivity to brain antigens and to Borrelia burgdorferi proteins were analyzed by ELISA and immunoblotting. Sera from the patient cohort induced significantly higher expression of IFIT1 and IFI44 target genes than those from healthy controls, indicating increased IFNα activity. Antibody reactivity to specific brain and borrelial proteins was significantly elevated in affected patients. IFNα activity and antibody profile did not change significantly in response to ceftriaxone. The heightened antibody response implies enhanced immune stimulation, possibly due to prolonged exposure to the organism prior to the initial diagnosis and antibiotic treatment of Lyme disease. The increase in IFNα activity is suggestive of a mechanism contributing to the ongoing neuropsychiatric symptoms.

Prefrontal dopaminergic and enkephalinergic synaptic accommodation in HIV-associated neurocognitive disorders and encephalitis

Changes in synapse structure occur in frontal neocortex with HIV encephalitis (HIVE) and may contribute to HIV-associated neurocognitive disorders (HAND). A postmortem survey was conducted to determine if mRNAs involved in synaptic transmission are perturbed in dorsolateral prefrontal cortex (DLPFC) in subjects with HIVE or HAND. Expression of the opioid neurotransmitter preproenkephalin mRNA (PENK) was significantly decreased in a sampling of 446 brain specimens from HIV-1 infected people compared to 67 HIV negative subjects. Decreased DLPFC PENK was most evident in subjects with HIVE and/or increased expression of interferon regulatory factor 1 mRNA (IRF1). Type 2 dopamine receptor mRNA (DRD2L) was decreased significantly, but not in the same set of subjects with PENK dysregulation. DRD2L downregulation occurred primarily in the subjects without HIVE or neurocognitive impairment. Subjects with neurocognitive impairment often failed to significantly downregulate DRD2L and had abnormally high IRF1 expression. Conclusion: Dysregulation of synaptic preproenkephalin and DRD2L in frontal neocortex can occur with and without neurocognitive impairment in HIV-infected people. Downregulation of DRD2L in the prefrontal cortex was associated with more favorable neuropsychological and neuropathological outcomes; the failure to downregulate DRD2L was significantly less favorable. PENK downregulation was related neuropathologically to HIVE, but was not related to neuropsychological outcome independently. Emulating endogenous synaptic plasticity pharmacodynamically could enhance synaptic accommodation and improve neuropsychological and neuropathological outcomes in HIV/AIDS.

Interferon-alpha enhances excitatory transmission in substantia gelatinosa neurons of rat spinal cord

OBJECTIVE

It has been shown that interferon-α (IFN-α) is synthesized and secreted by macrophages, monocytes, T lymphocytes, glial cells and neurons. IFN-α has been shown to have an antinociceptive effect at the supraspinal level in the nerve system. However, it is unclear how IFN-α is involved in the modulation of nociceptive transmission in the spinal cord.

METHODS

In the present study, IFN-α was used to test the potential functional roles in the nociceptive transmission. Using the whole-cell patch-clamp technique, we examined the effects of IFN-α on substantia gelatinosa (SG) neurons in the dorsal root-attached spinal cord slice prepared from adult rats.

RESULTS

We found that IFN-α increased glutamatergic excitatory postsynaptic currents evoked by the stimulation of either Aδ or C afferent fibers. Further studies showed that IFN-α treatment dose-dependently increased spontaneous excitatory postsynaptic current frequency in SG neurons, while not affecting the amplitude. Moreover, intrathecal antibody of IFN-α could reduce nociceptive responses in formalin test.

CONCLUSIONS

These results suggest that IFN-α presynaptically facilitates the excitatory synaptic transmission to SG neurons. The nociceptive responses could be inhibited by IFN-α antibody in the formalin test. Thus, IFN-α enhances the nociceptive transmission, which contributes to the behavioral nociceptive responses.

Interferon modulates central nervous system function

The interferons (IFNs) are an endogenous pleiotropic family of cytokines that perform fundamental physiological functions as well as protecting host organisms from disease and in maintaining homeostasis. This review covers the effects of endogenous IFN on the nervous system. It starts with the description of its receptors, followed how it modulate neuronal activity, mood, sleep, temperature, the endocrine system, the opioid system and how it regulate food consumption and the immune system. Similar to other multifunctional cytokines, an excessive or inappropriate activity of IFNs can cause toxicity and even death. Furthermore, IFNs are currently the major treatment modality for several malignant and non-malignant diseases such as chronic hepatitis C and B, multiple sclerosis, hematological malignancies, malignant melanoma, renal cell carcinoma, etc.

Interferon-alpha causes neuronal dysfunction in encephalitis

Interferon-alpha (IFNalpha) is a pleomorphic cytokine produced by nucleated cells in response to viral infection. In patients, treatment with IFNalpha has side effects including cognitive impairment resembling subcortical dementia, which is a hallmark of human immunodeficiency virus (HIV)-associated dementia (HAD). IFNalpha is increased in the CSF of HAD patients compared with HIV patients without dementia. In this study, blocking IFNalpha in a HIV encephalitis (HIVE) mouse model with intraperitoneal injections of IFNalpha neutralizing antibodies (NAbs) significantly improved cognitive function compared with untreated or control antibody-treated HIVE mice during water radial arm maze behavioral testing. Treatment with IFNalpha NAbs significantly decreased microgliosis and prevented loss of dendritic arborization in the brains of HIVE mice. Furthermore, treatment of primary neuron cultures with IFNalpha resulted in dose-dependent loss of dendritic arborization that was blocked with IFNalpha NAb treatment and partially blocked with NMDA antagonists [AP5 and MK801 (dizocilpine maleate)] indicating glutamate signaling is involved in IFNalpha-mediated neuronal damage. These results show that IFNalpha has a major role in the pathogenesis of HIVE in mice and is likely important in the development neurocognitive dysfunction in humans with HIV. Blocking IFNalpha could be important in improving cognitive and pathological developments in HAD patients and may be clinically important in other neuroinflammatory diseases as well.

Morphine suppresses intracellular interferon-alpha expression in neuronal cells

Interferon alpha (IFN-alpha) not only plays a key role in innate host immunity against infections but also is involved in the cellular functions of the central nervous system (CNS). In this study, we examined the impact of morphine on IFN-alpha expression in human neuronal cells (NT2-N). Similar to human immune cells, NT2-N cells also expressed IFN-alpha at both mRNA and protein levels. IFN-alpha expression in NT2-N cells, however, was inhibited by morphine. Naltrexone antagonized the inhibitory effect of morphine on IFN-alpha expression in NT2-N cells. The specific mu opioid receptor antagonist, Cys2, Tyr3, Arg5, Pen7-amide (CTAP), also blocked the morphine action on intracellular IFN-alpha expression. Investigation of the mechanisms involved in the morphine action showed that although morphine had little effect on the expression of key IFN regulatory factors (IRFs), morphine inhibited IFN-alpha promoter activation and suppressed the expression and phosphorylation of signal transducer and activator of transcription 1 (STAT1) in the neuronal cells. These findings provide direct in vitro evidence that opioids may impair neuronal cell-mediated innate protection in the CNS.

Cognitive dysfunction in HIV encephalitic SCID mice correlates with levels of Interferon-alpha in the brain

BACKGROUND

Interferon alpha (IFNalpha) is an antiviral cytokine produced in response to viral infection. IFNalpha also acts as a neuromodulatory molecule in the central nervous system (CNS). Elevated IFNalpha in the CNS causes cognitive deficits.

OBJECTIVE

To determine if elevated levels of IFNalpha in an HIV encephalitis mouse model correlate with cognitive deficits.

METHODS

C57BL/6J SCID mice were inoculated intracerebrally (i.c.) with HIV infected or uninfected (control) macrophages and cognitively tested in a water escape radial arm maze. After behavioral testing was completed, immunohistochemistry and ELISA were used to examine brain pathology and IFNalpha expression.

RESULTS

Mice injected i.c. with HIV infected macrophages exhibited significantly more working memory errors, particularly in trials with the highest memory load. Immunohistochemistry indicated increased mouse IFNalpha staining prevalent on neurons and glial cells in the brains of mice with HIV infected macrophages compared to mice with uninfected control macrophages. In addition, IFNalpha levels in the brain correlated directly with working memory errors for mice with HIV infected macrophages.

CONCLUSIONS

These data suggest that the cognitive deficit noted for the C57BL/6J SCID mice with HIV infected macrophages is mediated by the infection induced increase in IFNalpha.

Molecular networks of brain and immunity

Exciting complexity of natural phenomena can be based on rather simple biophysical principles. For example, the genetic code is based on a double-helix of DNA formed by planar geometry of weak hydrogen bounds. On the examples of cytokine networks, immune synapse, psychoneuroimmunology and systems biology, this review paper attempts to show how molecular networks both in brain and immunity can be studied using common principles of protein-protein interactions.

Purification of recombinant human interferon-ε and oligonucleotide microarray analysis of interferon-ε-regulated genes

Recently identified interferon-epsilon (IFN-epsilon) belongs to type I interferons. IFN-epsilon is highly and constitutively expressed in the brain, but its biochemical and biological characteristics are poorly understood. In this study, full-length IFN-epsilon cDNA was cloned from human peripheral blood lymphocyte by RT-PCR, and was expressed in Escherichia coli (E. coli). Reverse phase high pressure liquid chromatography was used to purify recombinant human IFN-epsilon (rhIFN-epsilon) and to facilitate refolding of the protein. About 0.8mg of highly purified rhIFN-epsilon protein was obtained from 100ml of E. coli culture. Functional study of rhIFN-epsilon demonstrated that the antiviral activity of rhIFN-epsilon was 6+/-0.5x10(5)IU/mg, which was lower than that of rhIFN-alpha-2b in the WISH-VSV (WISH cells infected with vesicular stomatitis virus) assay system. As for the activity to promote NK cytotoxicity and antiproliferation activities, rhIFN-epsilon was about 60 times less potent than rhIFN-alpha-2b. However, oligonucleotide microarray analyses revealed dramatic differences in gene expression profiles of cultured human cells treated with IFN-epsilon and IFN-alpha-2b. Particularly, differential regulation of genes related to central nervous system by rhIFN-epsilon suggests a role for IFN-epsilon in maintenance of the structure and function of brain.

Chronic administration of methylphenidate produces neurophysiological and behavioral sensitization

The electrophysiological properties of acute and chronic methylphenidate (MPD) on neurons of the prefrontal cortex (PFC) and caudate nucleus (CN) have not been studied in awake, freely behaving animals. The present study was designed to investigate the dose-response effects of MPD on sensory evoked potentials recorded from the PFC and CN in freely behaving rats previously implanted with permanent electrodes, as well as their behavioral (locomotor) activities. On experimental day 1, locomotor behavior of rats was recorded for 2 h post-saline injection, and sensory evoked field potentials were recorded before and after saline and 0.6, 2.5, and 10 mg/kg, i.p., MPD administration. Animals were injected for the next five days with daily 2.5 mg/kg MPD to elicit behavioral sensitization. Locomotor recording was resumed on experimental days 2 and 6 after the MPD maintenance dose followed by 3 days of washout. On experimental day 10, rats were connected again to the electrophysiological recording system and rechallenged with saline and the identical MPD doses as on experimental day 1. On experimental day 11, rat's locomotor recording was resumed before and after 2.5 mg/kg MPD administration. Behavioral results showed that repeated administration of MPD induced behavioral sensitization. Challenge doses (0.6, 2.5, and 10.0 mg/kg) of MPD on experimental day 1 elicited dose-response attenuation in the response amplitude of the average sensory evoked field potential components recorded from the PFC and CN. Chronic MPD administration resulted in attenuation of the PFC's baseline recorded on experimental day 10, while the same treatment did not modulate the baseline recorded from the CN. Treatment of MPD on experimental day 10 resulted in further decrease of the average sensory evoked response compared to that obtained on experimental day 1. This observation of further decrease in the electrophysiological responses after chronic administration of MPD suggests that the sensory evoked responses on experimental day 10 represent neurophysiological sensitization. Moreover, two different response patterns were obtained from PFC and CN following chronic methylphenidate administration. In PFC, the baseline and effect of methylphenidate expressed electrophysiological sensitization on experimental day 10, while recording from CN did not exhibit any electrophysiological sensitization.

The role of IFN-alpha as homeostatic agent in the inflammatory response: a balance between danger and response?

Interferon-alpha (IFN-alpha) is thought of by most immunologists as a fundamental component of the antiviral innate immune response, with other, accessory properties. Several lines of evidence point to a fundamental reappraisal of this conceptual framework because it may neglect other crucial functions of this cytokine under both health and disease conditions. Among these, a regulatory role in the inflammatory response is probably of paramount importance, as shown by in vivo and in vitro studies on humans, pets, and farm and laboratory animals. This role would not conflict with the main functions of IFN-alpha in the innate immune system and would complement these in line with major, evolution-based needs of the host. A hinge role of IFN-alpha between innate and adaptive immunity was recognized in the past on the basis of compelling evidence. This concept should now be widened; not only does IFN-alpha act to trigger, amplify, and sustain the different phases of the immune response, but it could also promote a substantial balance between danger and inflammatory response when an infectious challenge is either declining or completely over.

Chemiluminescent imaging analysis of interferon alpha in serum samples

Enzyme-linked immunosorbent assay (ELISA), horseradish peroxidase (HRP)-catalyzed fluorescent reaction, and oxalate chemiluminescence imaging analysis have been combined to develop a sensitive, simple, and rapid method for analysis of interferon alpha (alpha-IFN) in human serum samples. A typical "sandwich type" immunoassay was used. Reaction of o-phenylenediamine (OPD) with hydrogen peroxide (H(2)O(2)), catalyzed by HRP, produced 2,3-diaminophenazine (PDA), which was detected by chemiluminescence imaging analysis with the bis(2,4,6-trichlorophenyl)oxalate (TCPO)-H(2)O(2)-glyoxaline-PDA chemiluminescent system. The TCPO chemiluminescent imaging system is more sensitive and the chemiluminescence quantum yield is at least five times higher than for the luminol-H(2)O(2)-HRP-PIP (p-iodophenol) chemiluminescent imaging system. The results showed there was a very good linear correlation between response and amount of alpha-IFN in the range 1.3-156.0 pg mL(-1) (R = 0.9991) and the detection limit was 0.8 pg mL(-1) (S/N=3). The relative standard deviation (n = 9) was 4.7%. The proposed method has been used for successful analysis of the amount of alpha-IFN in human serum. The results obtained compared well with those obtained by conventional colorimetric ELISA and luminol chemiluminescent ELISA.

Altered central nervous system gene expression caused by congenitally acquired persistent infection with lymphocytic choriomeningitis virus

Neonatal infection of most mouse strains with lymphocytic choriomeningitis virus (LCMV) leads to a life-long persistent infection characterized by high virus loads in the central nervous system (CNS) in the absence of inflammation and tissue destruction. These mice, however, exhibit impaired learning and memory. The occurrence of cognitive defects in the absence of overt CNS pathology led us to the hypothesis that chronic virus infection may contribute to neuronal dysfunction by altering the host's gene expression profile. To test this hypothesis, we examined the impact of LCMV persistence on host gene expression in the CNS. To model the natural route of human congenital CNS infection observed with a variety of viruses, we established a persistently infected mouse colony where the virus was maintained via vertical transmission from infected mothers to offspring (LCMV-cgPi). LCMV-cgPi mice exhibited a lifelong persistent infection involving the CNS; the infection was associated with impaired spatial-temporal learning. Despite high viral loads in neurons of the brains of adult LCMV-cgPi mice, we detected changes in the host's CNS gene expression for only 75 genes, 56 and 19 being significantly induced and reduced, respectively. The majority of the genes induced in the brain of LCMV-cgPi mice were interferon (IFN)-stimulated genes (ISGs) and included the transcription factors STAT1 and IRF9, the ISG15 protease UBP43, and the glucocorticoid attenuated-response genes GARG16 and GARG49. Based on their crucial role in antiviral defense, these ISGs may play an important role in limiting viral spread and replication. However, since IFNs have also been implicated in adverse effects on neuronal function, the chronic induction of some ISGs may also contribute to the observed cognitive impairment.

Interferon and the central nervous system

Interferons (IFNs) were discovered as natural antiviral substances produced during viral infection and were initially characterized for their ability to "interfere" with viral replication, slow cell proliferation, and profound alteration of immunity. The IFNs are synthesized and secreted by monocytes, macrophages, T-lymphocytes, neurons, and glia cells. The different IFNs are classified into three classes: alpha, beta, and gamma. alpha-IFN produced in the brain exerts direct effects on the brain and endocrine system by activating the neurosecretory hypothalamic neurons and regulates the hypothalamic-pituitary-adrenocortical axis. IFNs modulate neurophysiological activities of many brain region involving in pain, temperature, and food intake regulation. alpha-IFN administration activates the sympathetic nerves innervating components of the immune system. IFNs may serve as regulatory mediators between the central nervous system, the immune system, and endocrine system. IFN is used as immunologic therapy to treat various hematologic malignancies and infectious ailments and autoimmune diseases.

Association of chronic fatigue syndrome with human leucocyte antigen class II alleles

BACKGROUND

A genetic component to the development of chronic fatigue syndrome (CFS) has been proposed, and a possible association between human leucocyte antigen (HLA) class II antigens and chronic fatigue immune dysfunction has been shown in some, but not all, studies.

AIMS

To investigate the role of HLA class II antigens in CFS.

METHODS

Forty nine patients with CFS were genotyped for the HLA-DRB1, HLA-DQA1, and HLA-DQB1 alleles and the frequency of these alleles was compared with a control group comprising 102 normal individuals from the UK. All patients and controls were from the same region of England and, apart from two patients, were white.

RESULTS

Analysis by 2 x 2 contingency tables revealed an increased frequency of HLA-DQA1*01 alleles in patients with CFS (51.0% v 35%; odds ratio (OR), 1.93; p = 0.008). HLA-DQB1*06 was also increased in the patients with CFS (30.2% v 20.0%; OR, 1.73, p = 0.052). Only the association between HLA-DQA1*01 and CFS was significant in logistic regression models containing HLA-DQA1*01 and HLA-DRQB1*06, and this was independent of HLA-DRB1 alleles. There was a decreased expression of HLA-DRB1*11 in CFS, although this association disappeared after correction for multiple comparisons.

CONCLUSIONS

CFS may be associated with HLA-DQA1*01, although a role for other genes in linkage disequilibrium cannot be ruled out.

Recombinant human interferon-alpha does not alter reward behavior, or neuroimmune and neuroendocrine activation in rats

Recombinant human interferon-alpha (IFN-alpha) induces depression, and neuroendocrine and neuroimmune activation, in a significant number of patients undergoing treatment for viral illnesses (e.g., hepatitis C), yet these effects have not been consistently reproduced in rodents. As such, we sought to determine the effects of acute or chronic IFN-alpha treatment on basic reward and immobility in the forced swim test (FST), neuroendocrine and neuroimmune activation, and monoamine turnover in brain. In the first experiment, male Wistar rats (N = 7/group) treated with human recombinant IFN-alpha (100,000 IU/kg, i.p.), as compared to saline, did not exhibit alterations to rate of sucrose pellet self-administration or total reinforcers obtained, corticosterone release, plasma IL-6 release, IL-1beta or IL-6 mRNA expression in hippocampus, or monoamine turnover in prefrontal cortex, striatum, nucleus accumbens, or amygdala. However, acute IFN-alpha decreased body weight and produced a trend toward reduced food consumption in the home cage 2 h after injection. In the second experiment, Wistar rats (N=4/group) were subjected to a chronic treatment regimen of saline or IFN-alpha (100,000 IU/kg, i.p.) once daily for 14 consecutive days. The data reveal that animals exposed to chronic IFN-alpha exhibited similar amounts of time immobile and similar latencies to primary immobility in the FST as compared to saline-treated controls. Chronic IFN-alpha did not induce corticosterone release, plasma TNF-alpha, or IL-6 release. Tissue monoamine analysis revealed that chronic IFN-alpha reduced DA levels in prefrontal cortex, and decreased 5-HT levels and increased 5-HT turnover in amygdala. In the third experiment, Wistar rats (N = 4/group) were exposed to either acute or chronic pegylated IFN-alpha (pegIFN-alpha: 3.25, 10 or 75 mg/kg, i.p.) at one of several time points from 1 h to 23 days. The data reveal that neither acute nor chronic pegIFN-alpha induced corticosterone release. Overall, the current report demonstrates that neither acute nor chronic IFN-alpha induced depressive-like behavior and neither IFN-alpha nor peg-IFN-alpha was capable of inducing neuroendocrine or neuroimmune activation. Despite the neurochemical alterations observed in the chronic treatment regimen, the data indicate that recombinant human IFN-alpha does not produce a robust model of depressive-like behavior in rodents.

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.

Restless legs syndrome due to interferon-alpha

A patient developed restless legs symptoms paralleling the course of interferon-alpha (IFN alpha) therapy for chronic hepatitis C. Symptoms began during a course of IFN alpha, resolved with its suspension, and recurred on rechallenge. Restless legs syndrome may thus be an adverse effect of IFN alpha treatment.

Association Between Apolipoprotein E ɛ4 and Neuropsychiatric Symptoms During Interferon α Treatment for Chronic Hepatitis C

Neuropsychiatric complications are common in patients with chronic hepatitis C undergoing treatment with interferon alpha. These side effects include alterations of mood, cognition, and neuroendocrine function and are unpredictable. In a number of neurological disorders characterized by neuropsychiatric symptoms and cognitive dysfunction, inheritance of an apolipoprotein E (APOE) epsilon4 allele is associated with adverse neuropsychiatric outcomes. The authors present evidence that the APOE genotype may influence a patient's neuropsychiatric response to interferon alpha treatment. The inheritance of APOE genotypes was examined in 110 patients with chronic hepatitis C treated with interferon alpha. A retrospective investigation was conducted by assessing the rates of psychiatric referral and neuropsychiatric symptoms experienced during treatment along with other complaints indicating psychological distress. A highly statistically significant association was seen between APOE genotypes and interferon-induced neuropsychiatric symptoms. Patients with an epsilon4 allele were more likely to be referred to a psychiatrist and had more neuropsychiatric symptoms during antiviral treatment than those without an epsilon4 allele. Additionally, patients with an epsilon4 allele were more likely to experience irritability or anger and anxiety or other mood symptoms. These data demonstrate that an individual's APOE genotype may influence the neuropsychiatric response to antiviral therapy with interferon alpha. Prospective studies evaluating the importance of APOE in susceptibility to interferon alpha-induced neuropsychiatric complications are needed. Moreover, pathways involving APOE should be considered in understanding the pathophysiology of interferon alpha-induced neuropsychiatric complications.

Chronic interferon-alpha potentiates latent inhibition in rats

Several recent reports based on microdialysis have shown that repeated injections of IFN-alpha induce reduced dopamine (DA) activity in the rodent brain, and specifically within the striatum. This mesolimbic DA system is thought to play a central role in controlling latent inhibition (LI), which refers to the phenomenon in which conditioning proceeds more slowly to an irrelevant pre-exposed (PE) stimulus. The purpose of the present experiment was to evaluate whether chronic treatment with IFN-alpha may induce similar effects on LI as other DA-depleting manipulations. Rats were injected daily, for 24 days either with 10(4)IU IFN-alpha or vehicle, while monitoring their locomotor activity in photocell cages. No changes in locomotor activity, either during the acute period after the first injection, or progressively over the chronic period were observed. LI was then evaluated in these rats with a Conditioned Taste Aversion (CTA) paradigm. Half of each group of rats were pre-exposed to the 5% sucrose Conditioned Stimulus (CS) for 30 min on three successive days before the conditioning session in which the 30 min access to the 5% sucrose solution was followed by a 0.15M injection of 127 mg/kg LiCl. Two test sessions, in which rats were given a choice between the 5% sucrose solution and water, were given 48 and 72 h after the conditioning session. The results showed moderate LI in the control group, which was considerably potentiated in the IFN-alpha group despite the absence of any change in locomotor activity. These results are interpreted as providing indirect support for the theory that suggests that LI depends on DA activity in the nucleus accumbens (NAcc).

Interferons: potential roles in affect

A review of the literature on interferons was conducted and possible roles in neuropsychiatric disorders with affective disturbances are assessed. Interferons and interferon receptors are present in the limbic system where they appear to exert physiological effects pertinent to affect, most potently when levels rise during CNS infections. Interferons interact closely with cytokines and nitric oxide, signaling molecules implicated in depression. Results from knock-out mice suggest a role for interferon-gamma in moderating fear and anxiety, while other lines of evidence point to a role in arousal and circadian rhythms. The interferon-alpha receptor deploys an arginine methyltransferase affecting RNA editing and splicing, which seem to be disrupted in schizophrenia and bipolar disorder. S-Adenosylmethionine (SAMe), an effective antidepressant, may owe its effects in the latter disorders in part to variations in the strength of interferon-alpha signaling impacting RNA processing. Antiviral effects of interferons are of interest in lieu of viral theories of affective disorders. Finally, the relative levels of interferons gamma and alpha might play important roles in neural, and glial, development, as well as the dialog between the CNS and the immune system.

Acute interferon-alpha administration modulates sucrose consumption in the rat

One of the two core symptoms of depression as defined by the Diagnostic and statistical manual of mental disorders (DSM-IV) (American Psychiatric Association) is anhedonia, or a loss of interest or pleasure. Sucrose consumption has been described as a valid measure of sensitivity to reward. In the present set of studies, changes in sucrose consumption (three-bottle test using 1, 8 and 32% sucrose) were taken as a measure of the anhedonic effect of interferon-alpha (IFN-alpha). Sucrose tests were carried out following the i.p. administration (20 min pre-treatment time) of Recombinant Human Interferon-alphaA (rHIFN-alpha), 10(1), 10(2), 10(4) units(U) and Rat Interferon alpha (rRIFN-alpha), 1,10 and 100 IRU. Both types of IFN-alpha produced a decrease in sucrose consumption and drinking rate (DR) at the highest doses, with the greatest inhibition being at the lowest sucrose concentration (1%). Longer pre-treatment times with rHIFN-alpha (40 and 80 min prior to commencement of 1 h drinking test) resulted in insignificant effects. Significant hypothermia relative to vehicle-injected rats was observed following interferon administration in the 20 min pre-treatment condition, but showed no significant difference when compared to vehicle at 40 or 80 min. Overall these results confirm a depression-like behavioural syndrome (anhedonia) following administration of IFN-alpha.

Analgesic domains of interferon-alpha

Interferon-alpha (IFNalpha) is not only an immunoregulatory factor, but is also an analgesic molecule. We ever reported that there exist distinct domains in IFNalpha molecule that mediate immune and analgesic effects respectively and inferred that the analgesic domain locates around the 122nd Tyr residue of IFNalpha molecule in the tertiary structure. After the 36th Phe residue, which was located closely to the 122nd Tyr residue in the tertiary structure, was mutated to Ser using site-directed mutagenesis, the analgesic activity of this mutant lost completely, but the antiviral activity of IFNalpha still maintained 40.5% of wild type IFNalpha. The results suggest that the 36th Phe residue is one of the constituent for the analgesic domain of IFNalpha and inferred that the analgesic domain of IFNalpha consists of the 122nd Tyr and the residues around the 122nd in the tertiary structure, which include the 36th Phe.

Interferon-alpha inhibits long-term potentiation and unmasks a long-term depression in the rat hippocampus

Interferons (IFN) appear to have various neuromodulatory actions. Here, we characterized the actions of IFN-alpha on the electrophysiological properties of CA1 hippocampal neurons using intracellular recordings. Superfusion of this cytokine did not alter the resting membrane potential, cell input resistance, action potentials, nor GABA-mediated fast synaptic potentials. IFN-alpha inhibited glutamate-mediated excitatory postsynaptic potentials (gEPSPs) and reversed or prevented long-term potentiation (LTP) induced by high-frequency tetanic stimulation. IFN-alpha reduced gEPSP amplitude far below its control value. Only a short-term potentiation (STP) was observed when either IFN-alpha or D-2-amino-5-phosphonovalerato (APV; NMDA receptor antagonist) were present during tetanic stimulation. After this STP in presence of APV, IFN-alpha had no effect on gEPSPs. APV had no effect on LTP when applied after tetanic stimulation and did also not prevent IFN-alpha effect on LTP. Genistein (a tyrosine kinase inhibitor) or heat inactivation prevented IFN-alpha effects. IFN-alpha also decreased the depolarization induced by local application of glutamate but did not modify those induced by NMDA. Similarly, IFN-alpha reversed the potentiation (induced by tetanic stimulation) of glutamate-induced depolarizations. IFN-alpha did not affect long-term depression (LTD) induced by low-frequency tetanic stimulation. In conclusion, IFN-alpha-induced inhibition of LTP is, at least in part, mediated by a postsynaptic effect, by tyrosine kinase activity, and by non-NMDA glutamate receptors. Inhibition of LTP by IFN-alpha unmasks LTD which is induced by the same high-frequency tetanic stimulation.

Distinct domains of IFNalpha mediate immune and analgesic effects respectively

Interferon-alpha (IFNalpha) is not only an immunoregulatory factor, but is also an analgesic molecule. The analgesic effect of IFNalpha was mediated by mu opioid receptor. After the 129th Tyr residue of human IFNalpha was mutated to Ser, the antiviral activity almost disappeared, but there still remained a strong analgesic activity that could be blocked by naloxone. These results indicate that there exist distinct domains in the IFNalpha molecule, which mediate immune and analgesic effects respectively, and suggest that there are different receptor mechanisms inducing immune and analgesic effects of IFNalpha. However, although the antiviral activity of IFNalpha decreased to 34.1% of wild type IFNalpha after the 122nd Tyr residue was changed to Ser, the analgesic activity of this mutant was lost completely. There were significant cross reactivities between INFalpha and anti-opioid sera. These studies show strong structural and functional similarities between INFalpha and opioid peptides, and inferred that the analgesic domain locates around the 122nd Tyr residue of IFNalpha molecule in tertiary structure.

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

1. We investigated the mechanism by which human interferon-alpha (IFN-alpha) increases the immobility time in a forced swimming test, an animal model of depression. 2. Central administration of IFN-alpha (0.05 - 50 IU per mouse, i.cist.) increased the immobility time in the forced swimming test in mice in a dose-dependent manner. 3. Neither IFN-beta nor -gamma possessed any effect under the same experimental conditions. 4. Pre-treatment with an opioid receptor antagonist, naloxone (1 mg kg(-1), s.c.) inhibited the prolonged immobility time induced by IFN-alpha (60 KIU kg(-1), i.v. or 50 IU per mouse. i.cist. ). 5. Peripheral administration of naloxone methiodide (1 mg kg(-1), s. c.), which does not pass the blood - brain barrier, failed to block the effect of IFN-alpha, while intracisternal administration of naloxone methiodide (1 nmol per mouse) completely blocked. 6. The effect of IFN-alpha was inhibited by a mu(1)-specific opioid receptor antagonist, naloxonazine (35 mg kg(-1), s.c.) and a mu(1)/mu(2) receptor antagonist, beta-FNA (40 mg kg(-1), s.c.). A selective delta-opioid receptor antagonist, naltrindole (3 mg kg(-1), s.c.) and a kappa-opioid receptor antagonist, nor-binaltorphimine (20 mg kg(-1), s.c.), both failed to inhibit the increasing effect of IFN-alpha. 7. These results suggest that the activator of the central opioid receptors of the mu(1)-subtype might be related to the prolonged immobility time of IFN-alpha, but delta and kappa-opioid receptors most likely are not involved.

Analgesic effect of interferon-alpha via mu opioid receptor in the rat

Using the tail-flick induced by electro-stimulation as a pain marker, it was found that pain threshold (PT) was significantly increased after injecting interferon-alpha (IFN alpha) into the lateral ventricle of rats. This effect was dosage-dependent and abolished by monoclonal antibody (McAb) to IFN alpha. Naloxone could inhibit the analgesic effect of IFN alpha, suggesting that the analgesic effect of IFN alpha be related to the opioid receptors. Beta-funaltrexamine (beta-FNA), the mu specific receptor antagonist could completely block the analgesic effect of IFN alpha. The selective delta-opioid receptor antagonist, ICI174,864 and the kappa-opioid receptor antagonist, nor-BNI both failed to prevent the analgesic effect of IFN alpha. IFN alpha could significantly inhibit the production of the cAMP stimulated by forskolin in SK-N-SH cells expressing the mu-opioid receptor, not in NG108-15 cells expressing the delta-opioid receptor uniformly. The results obtained provide further evidence for opioid activity of IFN alpha and suggest that this effect is mediated by central opioid receptors of the mu subtype. The evidence is consistent with the hypothesis that multiple actions of cytokines, such as immunoregulatory and neuroregulatory effects, might be mediated by distinct domains of cytokines interacting with different receptors.

Human interferon-alpha induces immobility in the mouse forced swimming test: involvement of the opioid system

In a previous study, we indicated that human interferon (IFN)-alpha (IFN-alpha, 6 x 10(4) IU/kg, i.v.), but not human IFN-beta or -gamma, prolonged the immobility time of the forced swimming test in mice. In this study, we investigated the mechanism of the effect of human IFN-alpha. None of the mouse IFNs tested (IFN-alpha/beta, IFN-beta, and IFN-gamma, 3 x 10(5) U/kg, i.v.) changed the immobility time or the spontaneous locomotor activity in mice. Indomethacin (10 mg/kg, s.c.), a cyclooxygenase inhibitor, did not affect the increase in the immobility time induced by human IFN-alpha (6 x 10(4) IU/kg, i.v.). However, naloxone (1 mg/kg, s.c.), an opioid receptor antagonist, blocked the increasing caused by human IFN-alpha in the forced swimming test. These results suggest that the increase in the immobility time caused by human IFN-alpha in the forced swimming test might be mediated through opioid receptors, but not mouse IFN receptors.

Endogenous opiates: 1998

This paper is the twenty-first installment of our annual review of research concerning the opiate system. It summarizes papers published during 1998 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; eating and drinking; alcohol; gastrointestinal, renal, and hepatic function; mental illness and mood; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurologic disorders; electrical-related activity; general activity and locomotion; sex, pregnancy, and development; immunologic responses; and other behaviors.

Structural and functional neuropathology in transgenic mice with CNS expression of IFN-alpha

Cytokines belonging to the type I interferon (e.g. interferon-alpha) family are important in the host response to infection and may have complex and broad ranging actions in the central nervous system (CNS) that may be beneficial or harmful. To better understand the impact of the CNS expression of the type I interferons (IFN), transgenic mice were developed that produce IFN-alpha(1) chronically from astrocytes. In two independent transgenic lines with moderate and low levels of astrocyte IFN-alpha mRNA expression respectively, a spectrum of transgene dose- and age-dependent structural and functional neurological alterations are induced. Structural changes include neurodegeneration with loss of cholinergic neurons, gliosis, angiopathy with mononuclear cell cuffing, progressive calcification affecting basal ganglia and cerebellum and the up-regulation of a number of IFN-alpha-regulated genes. At a functional level, in vivo and in vitro electrophysiological studies revealed impaired neuronal function and disturbed synaptic plasticity with pronounced hippocampal hyperexcitability. Severe behavioral alterations were also evident in higher expressor GFAP-IFNalpha mice which developed fatal seizures around 13 weeks of age precluding their further behavioral assessment. Modest impairments in discrimination learning were measured in lower expressor GFAP-IFNalpha mice at various ages (7-42 weeks). The behavioral and electrophysiological findings suggest regional changes in hippocampal excitability which may be linked to abnormal calcium metabolism and loss of cholinergic neurons in the GIFN mice. Thus, these transgenic mice provide a novel animal model in which to further evaluate the mechanisms that underlie the diverse actions of type I interferons in the intact CNS and to link specific structural changes with functional impairments.