The roles of IL-1, IL-6, and TNFalpha in the feeding responses to endotoxin and influenza virus infection in mice

Biomolecules Triggering Altered Food Intake during Pathogenic Challenge in Chicks

Food intake is regulated by several complicated synergistic mechanisms that are affected by a variety of internal and external influences. Some of these factors include those that are released from pathogens such as bacteria, fungi, and viruses, and most of these factors are associated with suppression of the chick's food intake. Although chicks are well-known to decrease their food intake when they experience a pathogenic challenge, the mechanisms that mediate this type of satiety are poorly understood. One of the goals of our research group has been to better understand these mechanisms in chicks. We recently provided evidence that pathogen-associated molecular patterns, which are recognized by pattern-recognition receptors such as Toll-like receptors, likely contribute to satiety in chicks that are experiencing a pathogenic challenge. Additionally, we identified several inflammatory cytokines, including interleukin-1β, tumor necrosis factor-like cytokine 1A, prostaglandins, and nitric oxide, that likely contribute to satiety during a pathogenic challenge. This review summarizes the current knowledge on pathogen-induced satiety in chicks mainly accumulated through our recent research. The research will give good information to improve the loss of production during infection in poultry production in the future.

Polyphenols: Bioavailability, Microbiome Interactions and Cellular Effects on Health in Humans and Animals

Polyphenolic compounds have a variety of functions in plants including protecting them from a range of abiotic and biotic stresses such as pathogenic infections, ionising radiation and as signalling molecules. They are common constituents of human and animal diets, undergoing extensive metabolism by gut microbiota in many cases prior to entering circulation. They are linked to a range of positive health effects, including anti-oxidant, anti-inflammatory, antibiotic and disease-specific activities but the relationships between polyphenol bio-transformation products and their interactions in vivo are less well understood. Here we review the state of knowledge in this area, specifically what happens to dietary polyphenols after ingestion and how this is linked to health effects in humans and animals; paying particular attention to farm animals and pigs. We focus on the chemical transformation of polyphenols after ingestion, through microbial transformation, conjugation, absorption, entry into circulation and uptake by cells and tissues, focusing on recent findings in relation to bone. We review what is known about how these processes affect polyphenol bioactivity, highlighting gaps in knowledge. The implications of extending the use of polyphenols to treat specific pathogenic infections and other illnesses is explored.

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.

The Bone Marrow Niche in B-Cell Acute Lymphoblastic Leukemia: The Role of Microenvironment from Pre-Leukemia to Overt Leukemia

Genetic lesions predisposing to pediatric B-cell acute lymphoblastic leukemia (B-ALL) arise in utero, generating a clinically silent pre-leukemic phase. We here reviewed the role of the surrounding bone marrow (BM) microenvironment in the persistence and transformation of pre-leukemic clones into fully leukemic cells. In this context, inflammation has been highlighted as a crucial microenvironmental stimulus able to promote genetic instability, leading to the disease manifestation. Moreover, we focused on the cross-talk between the bulk of leukemic cells with the surrounding microenvironment, which creates a “corrupted” BM malignant niche, unfavorable for healthy hematopoietic precursors. In detail, several cell subsets, including stromal, endothelial cells, osteoblasts and immune cells, composing the peculiar leukemic niche, can actively interact with B-ALL blasts. Through deregulated molecular pathways they are able to influence leukemia development, survival, chemoresistance, migratory and invasive properties. The concept that the pre-leukemic and leukemic cell survival and evolution are strictly dependent both on genetic lesions and on the external signals coming from the microenvironment paves the way to a new idea of dual targeting therapeutic strategy.

Characterization of fever and sickness behavior regulated by cytokines during infection

In response to invasion of pathogens, hosts present fever and a series of behavioural changes including reduced grooming, reduction of foraging, decreased locomotion, withdrawing from social activities and reproductive process, which are collectively termed sickness behaviour. Fever as well as sickness behaviour are adaptive and benefit the host to reduce pathology caused by infections and opportunity costs for time away from foraging, reproduction and predator avoidance. Antipathogenic fever and sickness behaviour are mediated proximately by cytokines including pro- and anti-inflammatory cytokines. Pro-inflammation cytokines trigger these sickness responses, while anti-inflammatory cytokines constrain these responses and prevent damage to host from exaggerated responses. The present study reviews the characterization of fever and sickness behaviour regulated by cytokines during infection.

Understanding the Role of Interleukin-6 (IL-6) in the Joint and Beyond: A Comprehensive Review of IL-6 Inhibition for the Management of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic, debilitating autoimmune disorder involving inflammation and progressive destruction of the joints, affecting up to 1% of the population. The majority of patients with RA have one or more comorbid conditions, the most common being cardiovascular disease, osteoporosis, and depression, the presence of which are associated with poorer clinical outcomes and lower health-related quality of life. RA pathogenesis is driven by a complex network of proinflammatory cells and cytokines, and of these, interleukin-6 (IL-6) plays a key role in the chronic inflammation associated with RA. Through cell signaling that can be initiated by both membrane-bound and soluble forms of its receptor, IL-6 acts both locally to promote joint inflammation and destruction, and in the circulation to mediate extra-articular manifestations of RA, including pain, fatigue, morning stiffness, anemia, and weight loss. This narrative review describes the role of IL-6 in the pathogenesis of RA, its comorbidities, and extra-articular systemic manifestations, and examines the effects of the IL-6 receptor inhibitors sarilumab and tocilizumab on clinical endpoints of RA, patient-reported outcomes, and common comorbidities and extra-articular manifestations.

Maternal immune activation is associated with a lower number of dopamine receptor 3-expressing granulocytes with no alterations in cocaine reward, resistance to extinction or cue-induced reinstatement

There is evidence for increased rates of drug use among schizophrenic patients. However, the causality in this relationship remains unclear. In the present work, we use a maternal immune activation model to test whether animals at high risk of developing a schizophrenia-like condition are more prone to acquire cocaine self-administration, show enhanced sensitivity to the reinforcing actions of cocaine or if they are resistant to extinction or vulnerable to relapse. Also, given that D3 and CB2 receptor expression in immune cells is altered in patients with schizophrenia, we examined the populations of immune cells expressing these receptors. Pregnant rats were daily injected with lipopolysaccharide (LPS) (2 mg/kg s.c.) or saline during pregnancy, and we tested prepulse inhibition -PPI- in the offspring. After this, one group of rats was submitted to cocaine self-administration (0.5 mg/kg) under fixed and progressive ratio schedules, dose-response testing, extinction and cue-induced drug-seeking. Another group was sacrificed to study the immune blood cells by flow cytometry. While rats born to LPS-treated mothers showed impaired PPI, there were no differences in cocaine self-administration acquisition, responsiveness to dose shifts, extinction or cue-induced reinstatement. Finally, there were fewer D3R⁺ granulocytes in the LPS-offspring and an exciting trend for CB2R⁺ lymphocytes to be more abundant in LPS-exposed rats. Our results indicate that the higher prevalence of cocaine abuse among people with schizophrenia is not due to a pre-existing pathology and suggest that D3R⁺ granulocytes and possibly CB2R⁺ lymphocytes could be potential biomarkers of schizophrenia.

Pro-inflammatory cytokines favor the emergence of ETV6-RUNX1-positive pre-leukemic cells in a model of mesenchymal niche

ETV6-RUNX1 (E/R) fusion gene, arising in utero from translocation t(12;21)(p13:q22), is the most frequent alteration in childhood acute lymphoblastic leukemia (ALL). However, E/R is insufficient to cause overt leukemia since it generates a clinically silent pre-leukemic clone which persists in the bone marrow but fails to out-compete normal progenitors. Conversely, pre-leukemic cells show increased susceptibility to transformation following additional genetic insults. Infections/inflammation are the most accredited triggers for mutations accumulation and leukemic transformation in E/R⁺ pre-leukemic cells. However, precisely how E/R and inflammation interact in promoting leukemia is still poorly understood. Here we demonstrate that IL6/TNFα/ILβ pro-inflammatory cytokines cooperate with BM-MSC in promoting the emergence of E/R⁺ Ba/F3 over their normal counterparts by differentially affecting their proliferation and survival. Moreover, IL6/TNFα/ILβ-stimulated BM-MSC strongly attract E/R⁺ Ba/F3 in a CXCR2-dependent manner. Interestingly, E/R-expressing human CD34⁺ IL7R⁺ progenitors, a putative population for leukemia initiation during development, were preserved in the presence of BM-MSC and IL6/TNFα/ILβ compared to their normal counterparts. Finally, the extent of DNA damage increases within the inflamed niche in both control and E/R-expressing Ba/F3, potentially leading to transformation in the apoptosis-resistant pre-leukemic clone. Overall, our data provide new mechanistic insights into childhood ALL pathogenesis.

Interleukin-1 reduces food intake and body weight in rat by acting in the arcuate hypothalamus

A reduction in food intake is commonly observed after bacterial infection, a phenomenon that can be reproduced by peripheral administration of Gram-negative bacterial lipopolysaccharide (LPS) or interleukin-1beta (IL-1β), a pro-inflammatory cytokine released by LPS-activated macrophages. The arcuate nucleus of the hypothalamus (ARH) plays a major role in food intake regulation and expresses IL-1 type 1 receptor (IL-1R1) mRNA. In the present work, we tested the hypothesis that IL-1R1 expressing cells in the ARH mediate IL-1β and/or LPS-induced hypophagia in the rat. To do so, we developed an IL-1β-saporin conjugate, which eliminated IL-R1-expressing neurons in the hippocampus, and micro-injected it into the ARH prior to systemic IL-1β and LPS administration. ARH IL-1β-saporin injection resulted in loss of neuropeptide Y-containing cells and attenuated hypophagia and weight loss after intraperitoneal IL-1β, but not LPS, administration. In conclusion, the present study shows that ARH NPY-containing neurons express functional IL-1R1s that mediate peripheral IL-1β-, but not LPS-, induced hypophagia. Our present and previous findings indicate that the reduction of food intake after IL-1β and LPS are mediated by different neural pathways.

Association of dry matter intake and energy balance prepartum and postpartum with health disorders postpartum: Part II. Ketosis and clinical mastitis

The main objective of this study was to determine the association of dry matter intake as percentage of body weight (DMI%BW) and energy balance (EB) prepartum (-21 d relative to parturition) and postpartum (28 d) with ketosis (n = 189) and clinical mastitis (n = 79). For this, DMI%BW and EB were the independent variables and ketosis and clinical mastitis were the dependent variables. A secondary objective was to evaluate prepartum DMI%BW and EB as predictors of ketosis and clinical mastitis. For this, ketosis and clinical mastitis were the independent variables and DMI%BW and EB were the dependent variables. Data from 476 cows from 9 experiments were compiled. Clinical mastitis was diagnosed if milk from 1 or more quarters was abnormal in color, viscosity, or consistency, with or without accompanying heat, pain, redness, or swelling of the quarter or generalized illness, during the first 28 d postpartum. Ketosis was defined as the presence of acetoacetate in urine that resulted in any color change [5 mg/dL (trace) or higher] in the urine test strip (Ketostix, Bayer, Leverkusen, Germany). Cows that developed ketosis had lesser DMI%BW and lesser EB on d -5, -3, -2, and -1 than cows without ketosis. Each 0.1-percentage point decrease in the average DMI%BW and each 1-Mcal decrease in the average of EB in the last 3 d prepartum increased the odds of having ketosis by 8 and 5%, respectively. Cut-offs for DMI%BW and EB during the last 3 d prepartum to predict ketosis were established and were ≤1.5%/d and ≤1.1 Mcal/d, respectively. Cows that developed ketosis had lesser postpartum DMI%BW and EB and greater energy-corrected milk (ECM) than cows without ketosis. Cows that developed clinical mastitis had lesser DMI%BW but similar prepartum EB compared with cows without clinical mastitis. Each 0.1-percentage point decrease in the average DMI%BW and each 1-Mcal decrease in the average EB in the last 3 d prepartum increased the odds of having clinical mastitis by 10 and 8%, respectively. The average DMI%BW and EB during the last 3 d prepartum produced significant cut-offs to predict clinical mastitis postpartum, which were ≤1.2%/d and ≤1.0 Mcal/d, respectively. Cows that developed clinical mastitis had lesser postpartum DMI%BW from d 3 to 15 and on d 17; greater EB on d 18, from d 21 to 23, and on d 26; and lesser ECM. The main limitation in this study is that the time-order of disease relative to DMI%BW and ECM is inconsistent such that postpartum outcomes were measured before and after disease, which was diagnosed at variable intervals after calving. In summary, measures of prepartum DMI were associated with and were predictors of ketosis and clinical mastitis postpartum, although the effect sizes were small.

Hirsutanol A Attenuates Lipopolysaccharide-Mediated Matrix Metalloproteinase 9 Expression and Cytokines Production and Improves Endotoxemia-Induced Acute Sickness Behavior and Acute Lung Injury

Activated human monocytes/macrophages, which increase the levels of matrix metalloproteinases (MMPs) and pro-inflammatory cytokines, are the essential mechanisms for the progression of sepsis. In the present study, we determined the functions and mechanisms of hirsutanolA (HA), which is isolated from the red alga-derived marine fungus Chondrostereum sp. NTOU4196, on the production of pro-inflammatory mediators produced from lipopolysaccharide (LPS)-treated THP-1 cells. Our results showed that HA suppressed LPS-triggered MMP-9-mediated gelatinolysis and expression of protein and mRNA in a concentration-dependent manner without effects on TIMP-1 activity. Also, HA significantly attenuated the levels of TNF-α, IL-6, and IL-1β from LPS-treated THP-1 cells. Moreover, HA significantly inhibited LPS-mediated STAT3 (Tyr705) phosphorylation, IκBα degradation and ERK1/2 activation in THP-1 cells. In an LPS-induced endotoxemia mouse model, studies indicated that HA pretreatment improved endotoxemia-induced acute sickness behavior, including acute motor deficits and anxiety-like behavior. HA also attenuated LPS-induced phospho-STAT3 and pro-MMP-9 activity in the hippocampus. Notably, HA reduced pathologic lung injury features, including interstitial tissue edema, infiltration of inflammatory cells and alveolar collapse. Likewise, HA suppressed the induction of phospho-STAT3 and pro-MMP-9 in lung tissues. In conclusion, our results provide pharmacological evidence that HA could be a useful agent for treating inflammatory diseases, including sepsis.

Olive oil bioactives protect pigs against experimentally-induced chronic inflammation independently of alterations in gut microbiota

Subclinical chronic inflammation (SCI) is associated with impaired animal growth. Previous work has demonstrated that olive-derived plant bioactives exhibit anti-inflammatory properties that could possibly counteract the growth-depressing effects of SCI. To test this hypothesis and define the underlying mechanism, we conducted a 30-day study in which piglets fed an olive-oil bioactive extract (OBE) and their control counterparts (C+) were injected repeatedly during the last 10 days of the study with increasing doses of Escherichia coli lipopolysaccharides (LPS) to induce SCI. A third group of piglets remained untreated throughout the study and served as a negative control (C-). In C+ pigs, SCI increased the circulating concentration of interleukin 1 beta (p < 0.001) and decreased feed ingestion (p < 0.05) and weight gain (p < 0.05). These responses were not observed in OBE animals. Although intestinal inflammation and colonic microbial ecology was not altered by treatments, OBE enhanced ileal mRNA abundance of tight and adherens junctional proteins (p < 0.05) and plasma recovery of mannitol (p < 0.05) compared with C+ and C-. In line with these findings, OBE improved transepithelial electrical resistance (p < 0.01) in TNF-α-challenged Caco-2/TC-7 cells, and repressed the production of inflammatory cytokines (p < 0.05) in LPS-stimulated macrophages. In summary, this work demonstrates that OBE attenuates the suppressing effect of SCI on animal growth through a mechanism that appears to involve improvements in intestinal integrity unrelated to alterations in gut microbial ecology and function.

Activation of innate immune genes in caprine blood leukocytes after systemic endotoxin challenge

Background

Sepsis is a serious health problem associated with a range of infectious diseases in animals and humans. Early events of this syndrome can be mimicked by experimental administration of lipopolysaccharides (LPS). Compared with mice, small ruminants and humans are highly sensitive to LPS, making goats valuable in inflammatory models. We performed a longitudinal study in eight Norwegian dairy goats that received LPS (0.1 μg/kg, Escherichia coli O26:B6) intravenously. A control group of five goats received corresponding volumes of sterile saline. Clinical examinations were performed continuously, and blood samples were collected throughout the trial.

Results

Characteristic signs of acute sepsis, such as sickness behavior, fever, and leukopenia were observed within 1 h of LPS administration. A high-throughput longitudinal gene expression analysis of circulating leukocytes was performed, and genes associated with the acute phase response, type I interferon signaling, LPS cascade and apoptosis, in addition to cytokines and chemokines were targeted. Pro-inflammatory genes, such as IL1B, CCL3 and IL8, were significantly up-regulated. Interestingly, increased mRNA levels of seven interferon stimulated genes (ISGs) were observed peaking at 2 h, corroborating the increasing evidence that ISGs respond immediately to bacterial endotoxins. A slower response was manifested by four extrahepatic acute phase proteins (APP) (SAA3, HP, LF and LCN2) reaching maximum levels at 5 h.

Conclusions

We report an immediate induction of ISGs in leukocytes in response to LPS supporting a link between the interferon system and defense against bacterial infections. The extrahepatic expression of APPs suggests that leukocytes contribute to synthesis of these proteins at the beginning of a systemic inflammation. Taken together, these findings provide insights into the dynamic regulation of innate immune genes, as well as raising new questions regarding the importance of ISGs and extrahepatic APPs in leukocytes after systemic endotoxin challenge.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0870-x) contains supplementary material, which is available to authorized users.

Repeated exposure of male mice to low doses of lipopolysaccharide: dose and time dependent development of behavioral sensitization and tolerance in an automated light-dark anxiety test

Although lipopolysaccharide (LPS) is widely used to examine immune behavior relationships there has been little consideration of the effects of low doses and the roles of sensitization and, or tolerance. Here low doses of LPS (1.0, 5.0 and 25.0 μg/kg) were peripherally administered to male mice on Days 1, 4, 28 and 32 after a baseline recording of anxiety-like behaviors in an automated light-dark apparatus (total time in the light chamber, number of light-dark transitions, nose pokes into the light chamber). LPS at 1.0 μg/kg, while having no significant effects on anxiety-like behaviors in the light-dark test on Days 1 and 4, displayed sensitization with the mice exhibiting significantly enhanced anxiety-like responses on Days 28 and 32. LPS at 5.0 μg/kg had no consistent significant effects on anxiety-like behavior on Days 1 and 4, with sensitization and enhanced anxiety-like behaviors on Day 28 followed by tolerance on Day 32. LPS at 25 μg/kg significantly enhanced anxiety-like behaviors on Day 1, followed by tolerance on Day 4, which was not evident by Day 28 and re-emerged on Day 32. There was a similar overall pattern of sensitization and tolerance for LPS-induced decreases in locomotor activity in the safe dark chamber, without, however, any significant effects on activity in the riskier light chamber. This shows that low doses of LPS induce anxiety-like behavior and these effects are subject to sensitization and tolerance in a dose, context, and time related manner.

Chronic exposure to low dose bacterial lipopolysaccharide inhibits leptin signaling in vagal afferent neurons

Bacterially derived factors are implicated in the causation and persistence of obesity. Ingestion of a high fat diet in rodents and obesity in human subjects is associated with chronic elevation of low plasma levels of lipopolysaccharide (LPS), a breakdown product of Gram-negative bacteria. The terminals of vagal afferent neurons are positioned within the gut mucosa to convey information from the gut to the brain to regulate food intake and are responsive to LPS. We hypothesized that chronic elevation of LPS could alter vagal afferent signaling. We surgically implanted osmotic mini-pumps that delivered a constant, low-dose of LPS into the intraperitoneal cavity of rats (12.5 μg/kg/hr for 6 weeks). LPS-treated rats developed hyperphagia and showed marked changes in vagal afferent neuron function. Chronic LPS treatment reduced vagal afferent leptin signaling, characterized by a decrease in leptin-induced STAT3 phosphorylation. In addition, LPS treatment decreased cholecystokinin-induced satiety. There was no alteration in leptin signaling in the hypothalamus. These findings offer a mechanism by which a change in gut microflora can promote hyperphagia, possibly leading to obesity.

A systematic analysis of the peripheral and CNS effects of systemic LPS, IL-1β, [corrected] TNF-α and IL-6 challenges in C57BL/6 mice

It is increasingly clear that systemic inflammation has both adaptive and deleterious effects on the brain. However, detailed comparisons of brain effects of systemic challenges with different pro-inflammatory cytokines are lacking. In the present study, we challenged female C57BL/6 mice intraperitoneally with LPS (100 µg/kg), IL-1β (15 or 50 µg/kg), TNF-α (50 or 250 µg/kg) or IL-6 (50 or 125 µg/kg). We investigated effects on core body temperature, open field activity and plasma levels of inflammatory markers at 2 hours post injection. We also examined levels of hepatic, hypothalamic and hippocampal inflammatory cytokine transcripts. Hypothermia and locomotor hypoactivity were induced by LPS>IL-1β>TNF-α>>IL-6. Systemic LPS, IL-1β and TNF-α challenges induced robust and broadly similar systemic and central inflammation compared to IL-6, which showed limited effects, but did induce a hepatic acute phase response. Important exceptions included IFNβ, which could only be induced by LPS. Systemic IL-1β could not induce significant blood TNF-α, but induced CNS TNF-α mRNA, while systemic TNF-α could induce IL-1β in blood and brain. Differences between IL-1β and TNF-α-induced hippocampal profiles, specifically for IL-6 and CXCL1 prompted a temporal analysis of systemic and central responses at 1, 2, 4, 8 and 24 hours, which revealed that IL-1β and TNF-α both induced the chemokines CXCL1 and CCL2 but only IL-1β induced the pentraxin PTX3. Expression of COX-2, CXCL1 and CCL2, with nuclear localisation of the p65 subunit of NFκB, in the cerebrovasculature was demonstrated by immunohistochemistry. Furthermore, we used cFOS immunohistochemistry to show that LPS, IL-1β and to a lesser degree, TNF-α activated the central nucleus of the amygdala. Given the increasing attention in the clinical literautre on correlating specific systemic inflammatory mediators with neurological or neuropsychiatric conditions and complications, these data will provide a useful resource on the likely CNS inflammatory profiles resulting from systemic elevation of particular cytokines.

Genetic characterization of H1N2 swine influenza virus isolated in China and its pathogenesis and inflammatory responses in mice

In 2009, two H1N2 influenza viruses were isolated from trachea swabs of pigs in Hubei in China. We compared these sequences with the other 18 complete genome sequences of swine H1N2 isolates from China during 2004 to 2010 and undertook extensive analysis of their evolutionary patterns. Six different genotypes - two reassortants between triple reassortant (TR) H3N2 and classical swine (CS) H1N1 virus, three reassortants between TR H1N2, Eurasian avian-like H1N1 swine virus and H9N2 swine virus, and one reassortant between H1N1, H3N2 human virus and CS H1N1 virus - were observed in these 20 swine H1N2 isolates. The TR H1N2 swine virus is the predominant genotype, and the two Hubei H1N2 isolates were located in this cluster. We also used a mouse model to examine the pathogenesis and inflammatory responses of the two isolates. The isolates replicated efficiently in the lung, and exhibited a strong inflammatory response, serious pathological changes and mortality in infected mice. Given the role that swine can play as putative "genetic mixing vessels" and the observed transmission of TR H1N2 in ferrets, H1N2 influenza surveillance in pigs should be increased to minimize the potential threat to public health.

Prolonged restraint stress increases IL-6, reduces IL-10, and causes persistent depressive-like behavior that is reversed by recombinant IL-10

Altered inflammatory cytokine profiles are often observed in individuals suffering from major depression. Recent clinical work reports on elevated IL-6 and decreased IL-10 in depression. Elevated IL-6 has served as a consistent biomarker of depression and IL-10 is proposed to influence depressive behavior through its ability to counterbalance pro-inflammatory cytokine expression. Clinical and animal studies suggest a role for IL-10 in modifying depressive behavior. Murine restraint stress (RST) is regularly employed in the study of behavioral and biological symptoms associated with depressive disorders. While responses to acute RST exposure have been widely characterized, few studies have examined the ongoing and longitudinal effects of extended RST and fewer still have examined the lasting impact during the post-stress period. Consistent with clinical data, we report that a protocol of prolonged murine RST produced altered cytokine profiles similar to those observed in major depressive disorder. Parallel to these changes in circulating cytokines, IL-10 mRNA expression was diminished in the cortex and hippocampus throughout the stress period and following cessation of RST. Moreover, chronic RST promoted depressive-like behavior throughout the 28-day stress period and these depressive-like complications were maintained weeks after cessation of RST. Because of the correlation between IL-10 suppression and depressive behavior and because many successful antidepressant therapies yield increases in IL-10, we examined the effects of IL-10 treatment on RST-induced behavioral changes. Behavioral deficits induced by RST were reversed by exogenous administration of recombinant IL-10. This work provides one of the first reports describing the biological and behavioral impact following prolonged RST and, taken together, this study provides details on the correlation between responses to chronic RST and those seen in depressive disorders.

Inflammatory fatigue and sickness behaviour - lessons for the diagnosis and management of chronic fatigue syndrome

Persistent and severe fatigue is a common part of the presentation of a diverse range of disease processes. There is a growing body of evidence indicating a common inflammatory pathophysiology underlying many conditions where fatigue is a primary patient concern, including chronic fatigue syndrome. This review explores current models of how inflammatory mediators act on the central nervous system to produce fatigue and sickness behaviour, and the commonality of these processes in conditions as diverse as surgical trauma, infection, various cancers, inflammatory bowel disease, connective tissue diseases and autoimmune diseases. We also discuss evidence indicating chronic fatigue syndrome may have important pathophysiological similarities with cytokine mediated sickness behaviour, and what lessons can be applied from sickness behaviour to chronic fatigue syndrome with regards to the diagnosis and management.

Therapeutic efficacy of Hypericum perforatum L. extract for mice infected with an influenza A virus

Hypericum perforatum L., a plant used in Chinese herbal medicine, has been proven effective against many viral diseases. In the present study, the therapeutic efficacy of an extract of H. perforatum (HPE) against influenza A virus (IAV) was investigated in mice. Whether HPE would be a promising agent for influenza treatment was evaluated by measuring the protection rate, mean survival days, lung index, and viral titer, as well as the secretion of IL-6, interleukin-10 (IL-10), tumour necrosis factor-α (TNF-α), and interferon-gamma (IFN-γ) in lung tissue and serum on days 3 and 5 post-infection. The results showed that HPE could reduce the lung index and viral titer of mice infected with IAV, decrease mortality, and prolong the mean survival time. HPE decreased the concentration of IL-6 and TNF-α in lung tissue and serum on day 5 post-infection. In contrast, HPE enhanced the lung and serum levels of IL-10 and IFN-γ on the days 3 and 5 post-infection. Our study indicates that HPE has significant therapeutic efficacy for mice infected with IAV. The possible reasons for these results were concluded to be pertaining to up-regulating the expression of IL-10 and IFN-γ, and down-regulating the secretion of IL-6 and TNF-α in lung and serum.

Energy intake and response to infection with influenza

Influenza is a worldwide public health concern, particularly with emerging new strains of influenza to which vaccines are ineffective, limited, or unavailable. In addition, the relationship between adequate nutrition and immune function has been repeatedly demonstrated. Mouse models provide strong evidence that energy extremes, including energy restriction (ER) and diet-induced obesity (DIO), have deleterious effects on the immune response to influenza infection. Both ER and DIO mice demonstrate increased susceptibility and mortality to influenza infection. The effects of ER are more pronounced during innate responses to influenza infection, whereas the effects of DIO are evidenced during innate and adaptive responses to both primary and secondary infection. There are striking similarities between ER and DIO during influenza infection, including impaired natural killer cell function and altered inflammation. Future studies must develop effective nutritional paradigms to offset the effects of these energy extremes on the immune response to an acute infection.

Differences in the relative involvement of peripherally released interleukin (IL)-6, brain IL-1β and prostanoids in mediating lipopolysaccharide-induced fever and sickness behavior

Although peripherally released interleukin (IL)-6 is critical for fever, its role in sickness behaviors, in particular anorexia and lethargy, induced by lipopolysaccharide (LPS) administration appears to be less important. Using quantifiable measures of fever, anorexia and lethargy, that is, body temperature, food intake and voluntary wheel-running, we investigated whether the less-than-essential role for IL-6 in mediating sickness behaviors compared to fever implies important roles for other inflammatory mediators, particularly IL-1β and prostanoids, in these responses. Male Sprague-Dawley rats were randomly assigned to receive one of the following three injections before receiving a subcutaneous (SC) injection of LPS (250 μg/kg) or saline: (1) intraperitoneal injection of pre-immune serum or antiserum to IL-6 (IL-6AS), to reduce the biological activity of peripherally released IL-6; (2) intracerebroventricular injection of vehicle or a caspase-1 inhibitor, to inhibit the production of mature IL-1β; or (3) intraperitoneal injection of vehicle or one of the two doses (1 or 10 mg/kg) of diclofenac, a nonselective cyclooxygenase inhibitor shown to block the formation of prostanoids. LPS administration induced fever, anorexia and lethargy with an accompanying increase in IL-6 and IL-1β concentrations in the circulation and IL-1β in the brain. Rats pre-treated with: (1) IL-6AS had reduced plasma levels of bioactive IL-6, no fever and attenuated sickness behaviors; (2) the caspase-1 inhibitor had reduced concentrations of IL-1β in the pre-frontal cortex, hypothalamus and hippocampus, and attenuated fever and sickness behaviors; (3) diclofenac had a dose-dependent attenuation in fever and sickness behaviors. Doses of diclofenac which completely abolished fever however had lesser effects on anorexia and lethargy. Our results confirm a difference in the sensitivity of sickness responses to IL-6 antagonism and identify that it may be related to different levels of sensitivity or responsiveness in brain regions and/or mechanisms, to prostanoids, IL-1β, or IL-6 itself.

Inhibition of interleukin-6 trans-signaling in the brain facilitates recovery from lipopolysaccharide-induced sickness behavior

Background

Interleukin (IL)-6 is produced in the brain during peripheral infection and plays an important but poorly understood role in sickness behavior. Therefore, this study investigated the capacity of soluble gp130 (sgp130), a natural inhibitor of the IL-6 trans-signaling pathway to regulate IL-6 production in microglia and neurons in vitro and its effects on lipopolysaccharide (LPS)-induced sickness behavior in vivo.

Methods

A murine microglia (BV.2) and neuronal cell line (Neuro.2A) were used to study the effects of stimulating and inhibiting the IL-6 signaling pathway in vitro. In vivo, adult (3-6 mo) BALB/c mice received an intracerebroventricular (ICV) injection of sgp130 followed by an intraperitoneal (i.p.) injection of LPS, and sickness behavior and markers of neuroinflammation were measured.

Results

Soluble gp130 attenuated IL-6- and LPS-stimulated IL-6 receptor (IL-6R) activation along with IL-6 protein release in both microglial (BV.2) and neuronal (Neuro.2A) cell types in vitro. Moreover, in vivo experiments showed that sgp130 facilitated recovery from LPS-induced sickness, and this sgp130-associated recovery was paralleled by reduced IL-6 receptor signaling, mRNA, and protein levels of IL-6 in the hippocampus.

Conclusions

Taken together, the results show that sgp130 may exert an anti-inflammatory effect on microglia and neurons by inhibiting IL-6 binding. These data indicate that sgp130 inhibits the LPS-induced IL-6 trans-signal and show IL-6 and its receptor are involved in maintaining sickness behavior.

A new look on brain mechanisms of acute illness anorexia

Bacterial lipopolysaccharide (LPS) and other microbial substances trigger the organism's acute phase response and cause acute illness anorexia. Pro-inflammatory cytokines are major endogenous mediators of acute illness anorexia, but how LPS or cytokines stimulate the brain to inhibit eating is not fully resolved. One emerging mechanism involves the activation of the enzyme cyclooxygenase-2 (COX-2) in blood-brain barrier endothelial cells and the subsequent release of prostaglandin E2 (PGE2). Serotonin neurons in the midbrain raphe are targets of PGE2, and serotonergic projections from the midbrain raphe to the hypothalamus appear to be crucial for LPS anorexia. That is, raphe projections activate (1) the corticotrophin-releasing hormone neurons in the paraventricular nucleus which then elicit the stress response and (2) the pro-opiomelanocortin neurons in the arcuate nucleus which then release alphaMSH and elicit anorexia. Here we review available data to support a role for this brain mechanism in acute illness anorexia by center staging PGE2 signaling pathways that converge on central neural circuits that control normal eating. In addition, we review interactions between gonadal hormones and immune function that lead to sex differences in acute illness anorexia. The paper represents an invited review by a symposium, award winner or keynote speaker at the Society for the Study of Ingestive Behavior [SSIB] Annual Meeting in Portland, July 2009.

Modulation of cytokine production by 7-hydroxycoumarin in vitro and its efficacy against influenza infection in mice

We previously demonstrated that 7-hydroxycoumarin (7HC) was effective in reducing proinflammatory cytokine production in lipopolysaccharide-exposed macrophage-like P388D1 cells and fever production by suppressing the increase in interleukin (IL)-1alpha production in an influenza virus-intranasal infection model in mice. In this study, we assessed the effects of modulation of cytokine production by 7HC on influenza virus infection in relation to its efficacy in influenza virus-infected mice. 7HC was confirmed to suppress proinflammatory cytokine levels in P388D1 cells due to influenza virus infection. In the murine infection model, oral administration of 7HC (30 mg/kg) was significantly effective in reducing the weight loss of infected mice and virus titers in the bronchoalveolar lavage fluid (BALF) of lungs and in prolonging survival times without toxicity. The rise of proinflammatory and Th1 cytokine (IL-12 and interferon-gamma) production in the BALF from infected mice was significantly suppressed by 7HC at two and four days post-infection, respectively. This suppression correlated with the reduction of virus titers and diminution of lung consolidation. Because 7HC did not exhibit direct anti-influenza virus activity in vitro, 7HC was suggested to suppress pneumonia in influenza virus-infected mice through suppression of the cytokine production induced by infection.

Neonatal stress modulates sickness behavior

The quality of the early environment, especially during the neonatal period, influences the development of individual differences in resistance to stress and illness in adulthood. A previous study demonstrated that neonatal stress augmented proinflammatory cytokine expression and viral replication in influenza virus-infected adult mice. The goal of the following study was to examine the lifelong effects of neonatal stress on the behavioral response to an immune challenge. Neonatal stress consisted of separating mouse pups from their dams (maternal separation, MSP) at critical points of their development. In the first study, pups were separated from the dam daily for 6h between postnatal day 1 and 14. As adults, these mice were infected with influenza A/PR8 virus. In a second study, a similar paradigm of MSP was employed, and as adults mice were injected with lipopolysaccharide (LPS) (ip). In a third study pups were separated from the dam for 24h on postnatal day 4 or 9. As adults, these mice received ip injections of LPS. In all three studies, changes in body weight, food and sweet solution consumption were examined following immune challenge. As previously described, activation of the immune system using influenza virus infection or LPS administration resulted in sickness behavior that consisted of body weight loss, anorexia and reduced consumption of a sweet solution. Furthermore, neonatal stress induced more rapid kinetics of sickness behavior and augmented several aspects of these symptoms. Together with previous studies, these findings suggest that neonatal stress disrupted the regulation of innate resistance to an immune challenge resulting in enhanced immunological and behavioral responses to immune activation. Thus, long lasting effects of early stress events may be the basis for individual differences in health and susceptibility to disease.

Psychoneuroimmune implications of type 2 diabetes: redux

A sizable body of knowledge has arisen demonstrating that type 2 diabetes (T2D) is associated with alterations in the innate immune system. The resulting proinflammatory-leaning imbalance is implicated in the development of secondary disease complications and comorbidities, such as delayed wound healing, accelerated progress of atherosclerosis, and retinopathy, in people who have T2D. New experimental data and the results of recently published health-related quality-of-life surveys indicate that individuals who have T2D experience diminished feelings of happiness, well being, and satisfaction with life. These emotional and psychological consequences of T2D point to altered neuroimmunity as a previously unappreciated complication of T2D. This article discusses recent data detailing the impact of T2D on a person's PNI response.

Prostaglandins and sickness behavior: old story, new insights

Previous evidence has shown that prostaglandins play a key role in the development of sickness behavior observed during inflammatory states. In particular, prostaglandin E2 (PGE2) is produced in the brain by a variety of inflammatory signals such as endotoxins or cytokines. Its injection has been also shown to induce symptoms of sickness behavior. The role of cyclooxygenase enzymes (COX), the rate-limiting enzymes converting arachidonic acid into prostaglandins, in sickness behavior has been extensively studied, and it has been demonstrated that strategies aiming at inhibiting these enzymes limit anorexia, body weight loss and fever in animals with inflammatory diseases. However, inhibiting COX activity may lead to negative gastric or cardiovascular effects, since COX enzymes play a role in the synthesis of others prostanoids with various and sometimes contrasting properties. Recently, prostaglandin E synthases (PGES), which specifically catalyze the final step of PGE2 biosynthesis, were characterized. Among these enzymes, the microsomal prostaglandin E synthase-1 (mPGES-1) was of a particular interest since it was shown to be up-regulated by inflammatory signals in a variety of cell types. Moreover, mPGES-1 was shown to be crucial for correct immune-to-brain communication and induction of fever and anorexia by pro-inflammatory agents. This review takes stock of previous knowledge and recent advances in understanding the role of prostaglandins and of their specific synthesizing enzymes in the molecular mechanisms underlying sickness behavior. The review concludes with a short summary of key questions that remain to be addressed and points out therapeutic developments in this research field.

Central inhibition of interleukin-1beta ameliorates sickness behavior in aged mice

In elderly individuals high levels of interleukin-1beta (IL-1beta) in the brain have been implicated in infection-related behavioral pathologies but this has not been directly tested. Therefore, the current study investigated if sickness behavior in aged animals elicited by peripheral injection of lipopolysaccharide (LPS) is mediated through central IL-1beta. Adult and aged mice were injected intracerebroventricularly with either saline or IL-1ra (4mug) immediately prior to intraperitoneal administration of saline or LPS (10mug) and locomotor and social behaviors were assessed. As anticipated, LPS depressed locomotor activity and social behavior in both adult and aged mice but the behavioral deficits were markedly greater in the aged at 24h. Pretreatment with IL-1ra did not affect LPS-induced sickness behavior in adults; however, in aged mice IL-1ra attenuated LPS-induced sickness behavior, restoring it to the level exhibited by young adults. Twenty-four hours post-injection hippocampal and hypothalamic tissues were collected to determine IL-1beta mRNA expression. Neither LPS nor IL-1ra affected IL-1beta mRNA levels in adults, presumably because any effect of LPS had dissipated by 24h. In contrast, IL-1beta mRNA was markedly higher in aged mice 24h after LPS, and prior treatment with IL-1ra either blocked or attenuated this effect in the hippocampus and hypothalamus, respectively. Taken together these data provide the first direct evidence that central IL-1beta is responsible for the severe sickness behavior observed in aged animals after LPS treatment. Thus, inhibiting the central actions of IL-1beta may be useful for minimizing behavioral complications in older individuals with an infection.

Activation of the maternal immune system alters cerebellar development in the offspring

A common pathological finding in autism is a localized deficit in Purkinje cells (PCs). Cerebellar abnormalities have also been reported in schizophrenia. Using a mouse model that exploits a known risk factor for these disorders, maternal infection, we asked if the offspring of pregnant mice given a mid-gestation respiratory infection have cerebellar pathology resembling that seen in these disorders. We also tested the effects of maternal immune activation in the absence of virus by injection of the synthetic dsRNA, poly(I:C). We infected pregnant mice with influenza on embryonic day 9.5 (E9.5), or injected poly(I:C) i.p. on E12.5, and assessed the linear density of PCs in the cerebellum of adult or postnatal day 11 (P11) offspring. To study granule cell migration, we also injected BrdU on P11. Adult offspring of influenza- or poly(I:C)-exposed mice display a localized deficit in PCs in lobule VII of the cerebellum, as do P11 offspring. Coincident with this are heterotopic PCs, as well as delayed migration of granule cells in lobules VI and VII. The cerebellar pathology observed in the offspring of influenza- or poly(I:C)-exposed mice is strikingly similar to that observed in autism. The poly(I:C) findings indicate that deficits are likely caused by the activation of the maternal immune system. Finally, our data suggest that cerebellar abnormalities occur during embryonic development, and may be an early deficit in autism and schizophrenia.

Adrenalectomy enhances endotoxemia-induced hypophagia: higher activation of corticotrophin-releasing-factor and proopiomelanocortin hypothalamic neurons

Inflammatory and infectious processes evoke neuroendocrine and behavioral changes known as acute-phase response that includes activation of the hypothalamo-pituitary-adrenal (HPA) axis and reduction of food intake. Besides its action as the most important ACTH secretagogue, corticotrophin-releasing factor (CRF), synthesized in the paraventricular nucleus (PVN), is also involved in the control of food intake. Alpha-melanocyte stimulating hormone (alpha-MSH) in the arcuate nucleus also plays a role in the energy homeostasis, possessing anorexigenic effects. To investigate the participation of neuropeptides involved in the regulation of food intake during endotoxemia, we administrated lipopolysaccharide (LPS) in sham-operated and adrenalectomized (ADX) male Wistar rats to evaluate food intake, hormone responses and Fos-CRF and Fos-alpha-MSH immunoreactivity in the PVN and arcuate nucleus, as well as CRF and POMC mRNA expression in these hypothalamic nuclei. In sham-operated rats, treatment with LPS (100 microg/kg) showed lower food intake, higher plasma ACTH and corticosterone levels, as well as an increase in Fos-CRF double labeled neurons and CRF mRNA expression in the PVN, with no changes in Fos-alpha-MSH immunoreactivity and POMC mRNA expression in the arcuate nucleus, compared to saline treated rats. After LPS treatment, ADX rats showed further increase in plasma ACTH levels, marked decrease of food intake, higher Fos-CRF immunoreactive neurons in the PVN and CRF mRNA expression, as well as an increase in Fos-alpha-MSH immunoreactivity and POMC mRNA expression in the arcuate nucleus, compared to sham-operated rats treated with LPS. In conclusion, the present data indicate that the marked hypophagia during endotoxemia following ADX is associated with an increased activation of CRF and POMC neurons in the hypothalamus and an increased mRNA expression of these neuropeptides.

Signals generating anorexia during acute illness

Anorexia is part of the body's acute-phase response to illness. Microbial products such as lipopolysaccharides (LPS), which are also commonly used to model acute illness, trigger the acute-phase response and cause anorexia mainly through pro-inflammatory cytokines. LPS stimulate cytokine production through the cell-surface structural molecule CD14 and toll-like receptor-4. Cytokines ultimately change neural activity in brain areas controlling food intake and energy balance. The blood-brain barrier endothelial cells (BBB EC) are an important site of cytokine action in this context. BBB EC and perivascular cells (microglia and macrophages) form a complex regulatory interface that modulates neuronal activity by the release of messengers (e.g. PG, NO) in response to peripheral challenges. Serotonergic neurons originating in the raphe nuclei and glucagon-like peptide-1-expressing neurons in the hindbrain may be among the targets of these messengers, because serotonin (5-HT), acting through the 5-HT2C receptor, and glucagon-like peptide-1 have recently emerged as neurochemical mediators of LPS anorexia. The central melanocortin system, which is a downstream target of serotonergic neurons, also appears to be involved in mediation of LPS anorexia. Interestingly, LPS also reduce orexin expression and the activity of orexin neurons in the lateral hypothalamic area of fasted mice. As the eating-stimulatory properties of orexin are apparently related to arousal, the inhibitory effect of LPS on orexin neurons might be involved in LPS-induced inactivity and anorexia. In summary, the immune signalling pathways of LPS-induced, and presumably acute illness-induced, anorexia converge on central neural signalling systems that control food intake and energy balance in healthy individuals.

Endogenous glucocorticoids protect against TNF-alpha-induced increases in anxiety-like behavior in virally infected mice

Endogenous glucocorticoids restrain proinflammatory cytokine responses to immune challenges such as viral infection. In addition, proinflammatory cytokines induce behavioral alterations including changes in locomotor/exploratory activity. Accordingly, we examined proinflammatory cytokines and open-field behavior in virally infected mice rendered glucocorticoid deficient by adrenalectomy (ADX). Mice were infected with murine cytomegalovirus (MCMV), and open-field behavior (36 h post-infection) and plasma concentrations of tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 (42 h post-infection) were assessed. Compared to sham-ADX-MCMV-infected animals, ADX-MCMV-infected mice exhibited significant reductions in total distance moved, number of center entries, and time spent in center. These behavioral alterations were accompanied by significantly higher plasma concentrations of TNF-alpha and IL-6, both of which were correlated with degree of behavioral change. To examine the role of TNF-alpha in these behavioral alterations, open-field behavior was compared in wild-type (WT) and TNF-R1-knockout (KO), ADX-MCMV-infected mice. TNF-R1-KO mice exhibited significantly attenuated decreases in number of rearings, number of center entries and time spent in center, but not distance moved, which correlated with plasma IL-6. Given the potential role of brain cytokines in these findings, mRNA expression of TNF-alpha, IL-1 and IL-6 was assessed in various brain regions. Although MCMV induced increases in proinflammatory cytokine mRNA throughout the brain (especially in ADX animals), no remarkable differences were found between WT and TNF-R1-KO mice. These results demonstrate that endogenous glucocorticoids restrain proinflammatory cytokine responses to viral infection and their impact on locomotor/exploratory activity. Moreover, TNF-alpha appears to mediate cytokine-induced changes in open-field behaviors, especially those believed to reflect anxiety.

Twenty years of psychoneuroimmunology and viral infections in Brain, Behavior, and Immunity

For 20 years, Brain, Behavior, and Immunity has provided an important venue for the publication of studies in psychoneuroimmunology. During this time period, psychoneuroimmunology has matured into an important multidisciplinary science that has contributed significantly to our knowledge of mind, brain, and body interactions. This review will not only focus on the primary research papers dealing with psychoneuroimmunology, viral infections, and anti-viral vaccine responses in humans and animal models that have appeared on the pages of Brain, Behavior, and Immunity during the past 20 years, but will also outline a variety of strategies that could be used for expanding our understanding of the neuroimmune-viral pathogen relationship.

Interferon type I receptor-deficient mice have altered disease symptoms in response to influenza virus

The role of type I interferons (IFNs) in mediation of acute viral symptoms (fever, somnolence, anorexia, etc.) is unknown. To determine the role of type I IFN in selected symptom development, body temperature and sleep responses to a marginally lethal dose of X-31 influenza virus were examined in mice with a targeted mutation of the IFN receptor type I (IFN-RI knockouts) and compared to wild-type 129 SvEv control mice. Mice were monitored for 48 h to determine baseline temperature and sleep profiles prior to infection, and then for 9 days following infection. Hypothermic responses to virus were perceptible beginning at 64 h post-infection (PI) and were more marked in KO mice until 108 h, when hypothermia became more exaggerated in wild-type controls. Temperatures of wild-type mice continued to decline through day 9 while temperatures in IFN-RI KO mice stabilized. Time spent in non-rapid eye movement sleep (NREMS) increased in KO mice when hypothermia was marked and then returned to baseline levels, while NREMS continued to increase in wild-type mice through day 9. Other sleep parameters [time spent in rapid eye movement sleep (REMS), relative NREMS EEG slow wave activity, NREMS EEG power density] were all reduced in wild-type mice compared to KOs from days 3 to 8 while REMS low frequency EEG power density increased in wild-type relative to KOs. In conclusion, our results indicate that the presence of functional type I IFN slightly ameliorates disease symptoms early in the X-31 infection while exacerbating disease symptoms later in the infection.

Impaired immune responses in tuberculosis patients are related to weight loss that coexists with an immunoendocrine imbalance

The study's objective was to examine whether factors related to the host status may bear some relation with the profile of the immune response displayed by tuberculosis (TB) patients. The in vitro immune response (antigen-driven lymphoproliferation and cytokine production) and the presence of alcoholism or disease-related factors, like heart and respiratory rates, and weight loss (body mass index, BMI) were investigated in 31 males with active, untreated TB. Compared to 16 age-matched healthy males, TB patients presented depressed lymphoproliferation and increased IL-10 and TGF-beta production. Multivariate analysis indicated that most differences were no longer significant when controlling for the BMI. Immune and endocrine changes coexisting with weight loss, such as circulating levels of TNF-alpha, IFN-gamma, IL-6, cortisol, dehydroepiandrosterone and thyroid hormones, were also analyzed. While pairwise correlations between serum levels of IFN-gamma, T3 or T4 and BMI were not significant, BMI was negatively correlated with IL-6 levels (p < 0.025). In turn, levels of IL-6 correlated positively with cortisol concentrations (p <0.001). Stepwise regression analysis demonstrated that BMI was only associated with IL-6 (r = -0.423, R(2) = 0.18), with the difference remaining significant following adjustment for the other variables. As regards IL-6, BMI, cortisol and IFN-gamma could explain 74% of variability in IL-6 concentrations (R(2) = 0.74). No evidence for effect modification was shown when performing adjusted calculations. To conclude, the relation between weight loss and abnormal immune response of TB patients is partly associated with the immunoendocrine imbalance observed in parallel.

Regulation of food intake by inflammatory cytokines in the brain

A number of inflammatory cytokines are synthesized and released after activation of the immune system. In addition to other biological effects, these cytokines can potently inhibit food intake. Cytokine-mediated inhibition of food intake is of particular importance because excessive production of peripheral inflammatory cytokines is often associated with the cachexia-anorexia syndrome seen in some chronic diseases. The weight loss in cachexia is associated with an increase in morbidity and mortality. Understanding how cytokines regulate food intake may be crucial in enhancing quality of life and facilitating recovery in patients exhibiting cachexia. This review describes the main inflammatory cytokines that influence food intake and explores how peripheral cytokines communicate with hypothalamic nuclei to influence feeding.

Effects of cytokines and infections on brain neurochemistry

Administration of cytokines to animals can elicit many effects on the brain, particularly neuroendocrine and behavioral effects. Cytokine administration also alters neurotransmission, which may underlie these effects. The most well studied effect is the activation of the hypothalamo-pituitary-adrenocortical (HPA) axis, especially that by interleukin-1 (IL-1). Peripheral and central administration of IL-1 also induces norepinephrine (NE) release in the brain, most markedly in the hypothalamus. Small changes in brain dopamine (DA) are occasionally observed, but these effects are not regionally selective. IL-1 also increases brain concentrations of tryptophan, and the metabolism of serotonin (5-HT) throughout the brain in a regionally nonselective manner. Increases of tryptophan and 5-HT, but not NE, are also elicited by IL-6, which also activates the HPA axis, although it is much less potent in these respects than IL-1. IL-2 has modest effects on DA, NE and 5-HT. Like IL-6, tumor necrosis factor-α (TNFα) activates the HPA axis, but affects NE and tryptophan only at high doses. The interferons (IFN's) induce fever and HPA axis activation in man, but such effects are weak or absent in rodents. The reported effects of IFN's on brain catecholamines and serotonin have been very varied. However, interferon-γ, and to a lesser extent, interferon-α, have profound effects on the catabolism of tryptophan, effectively reducing its concentration in plasma, and may thus limit brain 5-HT synthesis.Administration of endotoxin (LPS) elicits responses similar to those of IL-1. Bacterial and viral infections induce HPA activation, and also increase brain NE and 5-HT metabolism and brain tryptophan. Typically, there is also behavioral depression. These effects are strikingly similar to those of IL-1, suggesting that IL-1 secretion, which accompanies many infections, may mediate these responses. Studies with IL-1 antagonists, support this possibility, although in most cases the antagonism is incomplete, suggesting the existence of multiple mechanisms. Because LPS is known to stimulate the secretion of IL-1, IL-6 and TNFα, it seems likely that these cytokines mediate at least some of the responses, but studies with antagonists indicate that there are multiple mechanisms. The neurochemical responses to cytokines are likely to underlie the endocrine and behavioral responses. The NE response to IL-1 appears to be instrumental in the HPA activation, but other mechanisms exist. Neither the noradrenergic nor the serotonergic systems appear to be involved in the major behavioral responses. The significance of the serotonin response is unknown.

Psychoneuroimmune Implications of Type 2 Diabetes

The idea that type 2 diabetes is associated with augmented innate immune function characterized by increased circulating levels of acute phase reactants and altered macrophage biology is fairly well established, even though the mechanisms involved in this complex interaction still are not entirely clear. To date, the majority of studies investigating innate immune function in type 2 diabetes are limited to the context of wound healing, atherosclerosis, stroke, and other commonly identified comorbidities. Several important recurring themes come out of these data. First, type 2 diabetes is associated with a state of chronic, subclinical inflammation. Second, in macrophages, type 2 diabetic conditions enhance proinflammatory reactions and impair anti-inflammatory responses. Third, after acute activation of the innate immune system in type 2 diabetes, recovery or resolution of inflammation is impaired. The consequences of type 2 diabetes-associated inflammatory alterations on PNI processes have been recognized only recently. Given the impact of diminished emotional well-being on the quality of life in patients who have type 2 diabetes, diabetes-induced exacerbation of PNI responses should be considered a serious complication of type 2 diabetes that warrants further clinical attention.

Feeding, exploratory, anxiety- and depression-related behaviors are not altered in interleukin-6-deficient male mice

Interleukin-6 (IL-6) has been implicated in behavioral responses associated with inflammation, sickness behavior and various nervous system disorders. We studied a range of different behaviors in IL-6-knockout (IL-6ko) and wild-type (WT) male mice. No significant differences were observed in ambulatory, exploratory, and stereotypic activities in home or novel cages, in an open field (OF), in the multicompartment chamber (MCC), or in the elevated plus-maze (EPM). IL-6ko mice shed fewer fecal boli than WT mice in the OF, in novel cages and in the MCC although this effect was not statistically significant in the OF. In novel cages, intraperitoneal (i.p.) injection of IL-6 (1 microg) depressed ambulatory activity slightly more in IL-6ko than in WT mice. Restraint and interleukin-1beta (IL-1beta, 100 ng i.p.) decreased exploration of mice in the MCC and EPM, but there was no indication of altered sensitivity in IL-6ko mice. No significant differences were detected in the tail suspension and the Porsolt forced swim tests. IL-1beta and lipopolysaccharide (LPS 1 microg i.p.) injection depressed sweetened milk and solid food intake similarly in IL-6ko and WT mice, but IL-6 had no effect, suggesting that IL-6 is not involved in these effects of IL-1 or LPS. However, IL-1beta and LPS depressed body weight more in WT than in IL-6ko mice. Plasma corticosterone and basal concentrations of catecholamines, indoleamines and their metabolites in several brain regions were similar. The responses in these measures to IL-1beta and LPS were also similar, except that there were no significant changes in tryptophan and serotonin metabolism in IL-6ko mice. This may reflect a role for IL-6 in the tryptophan and serotonin responses to IL-1 and LPS. It is concluded that the lack of IL-6 is not associated with substantial alterations in several different mouse behaviors, and in the responses to restraint, IL-1beta, IL-6 and LPS.

Sleep and body temperature responses in an acute viral infection model are altered in interferon type I receptor-deficient mice

Type I interferons (IFNs) include IFNalpha and IFNbeta, both of which are elevated in acute viral infections and both of which have been shown to induce symptoms such as fever and somnolence when administered in pharmacological doses. To investigate the role of type I IFNs in mediation of acute respiratory viral symptoms we examined sleep and body temperature responses in mice with a targeted mutation of the IFN receptor type I (IFN-RI knockouts). IFN-RI knockouts (KOs) or wild-type 129 SvEv controls were challenged intratracheally (IT) with combined poly[rI.rC] (synthetic double-stranded RNA) and IFNgamma, a model that simulates an acute viral infection with respect to body temperature and locomotor activity responses. Control mice of both strains were treated with IT IFNgamma alone. Hypothermic responses to IT poly[rI.rC]/IFNgamma were more exaggerated in the IFN-RI KO mice than in wild-type. The non-rapid eye movement sleep (NREMS) response to IT poly[rI.rC]/IFNgamma was increased earlier in the IFN-RI KO mice than in wild-type, though the total time spent in NREMS was reduced in the KOs compared to wild-type and the return to baseline NREMS was faster in the KOs. The quality of NREMS also was altered more extensively in the wild-type than in the KO mice. Spontaneous rapid eye movement sleep (REMS) was suppressed in IFN-RI KOs as previously reported, but was not substantially altered in either mouse strain by IT poly[rI.rC]/IFNgamma challenge. Our results implicate type I IFNs as inhibitors of the hypothermic response and enhancers of the NREMS response to IT poly[rI.rC]/IFNgamma, a model of acute viral infection.

Pathogenicity of influenza viruses with genes from the 1918 pandemic virus: functional roles of alveolar macrophages and neutrophils in limiting virus replication and mortality in mice

The Spanish influenza pandemic of 1918 to 1919 swept the globe and resulted in the deaths of at least 20 million people. The basis of the pulmonary damage and high lethality caused by the 1918 H1N1 influenza virus remains largely unknown. Recombinant influenza viruses bearing the 1918 influenza virus hemagglutinin (HA) and neuraminidase (NA) glycoproteins were rescued in the genetic background of the human A/Texas/36/91 (H1N1) (1918 HA/NA:Tx/91) virus. Pathogenesis experiments revealed that the 1918 HA/NA:Tx/91 virus was lethal for BALB/c mice without the prior adaptation that is usually required for human influenza A H1N1 viruses. The increased mortality of 1918 HA/NA:Tx/91-infected mice was accompanied by (i) increased (>200-fold) viral replication, (ii) greater influx of neutrophils into the lung, (iii) increased numbers of alveolar macrophages (AMs), and (iv) increased protein expression of cytokines and chemokines in lung tissues compared with the levels seen for control Tx/91 virus-infected mice. Because pathological changes in AMs and neutrophil migration correlated with lung inflammation, we assessed the role of these cells in the pathogenesis associated with 1918 HA/NA:Tx/91 virus infection. Neutrophil and/or AM depletion initiated 3 or 5 days after infection did not have a significant effect on the disease outcome following a lethal 1918 HA/NA:Tx/91 virus infection. By contrast, depletion of these cells before a sublethal infection with 1918 HA/NA:Tx/91 virus resulted in uncontrolled virus growth and mortality in mice. In addition, neutrophil and/or AM depletion was associated with decreased expression of cytokines and chemokines. These results indicate that a human influenza H1N1 virus possessing the 1918 HA and NA glycoproteins can induce severe lung inflammation consisting of AMs and neutrophils, which play a role in controlling the replication and spread of 1918 HA/NA:Tx/91 virus after intranasal infection of mice.

Differential Effects of Selective Cyclooxygenase (COX)-1 and COX-2 Inhibitors on Anorexic Response and Prostaglandin Generation in Various Tissues Induced by Zymosan

We have shown that anorexic response is induced by intraperitoneal injection of zymosan in mice, although the role of prostaglandins in this response is relatively unknown as compared with lipopolysaccharide (LPS)-induced anorexic response. Indomethacin (0.5 and 2.0 mg/kg), a non-selective cyclooxygenase (COX) inhibitor, as well as meloxicam (0.5 mg/kg), a selective COX-2 inhibitor, but not FR122047 (2.0 mg/kg), a selective COX-1 inhibitor, attenuated zymosan-induced anorexia. Zymosan injection elevated COX-2 expression in brain and liver but not in small intestine and colon. Meloxicam (0.5 mg/kg) and FR122047 treatment (2.0 mg/kg) similarly suppressed the generation of brain prostaglandin E(2) (PGE(2)) and peritoneal prostacyclin (PGI(2)) upon zymosan injection. PGE(2) generation in liver upon zymosan injection was suppressed by meloxicam (0.5 mg/kg) but not by FR122047 treatment (2.0 mg/kg). Our observations suggest that COX-2 plays an important role in zymosan-induced anorexia, which is a similar feature in LPS-induced anorexic response. However, non-selective inhibition by selective COX-1 and COX-2 inhibitors of brain PGE(2) generation upon zymosan injection does not support the role of COX-2 expressed in brain in zymosan-induced anorexic response. PGE(2) generation in liver may account for peripheral role of COX-2 in zymosan-induced anorexic response.

Cytokines as mediators of depression: what can we learn from animal studies?

It has recently been postulated that cytokines may cause depressive illness in man. This hypothesis is based on the following observations: 1. Treatment of patients with cytokines can produce symptoms of depression; 2. Activation of the immune system is observed in many depressed patients; 3. Depression occurs more frequently in those with medical disorders associated with immune dysfunction; 4. Activation of the immune system, and administration of endotoxin (LPS) or interleukin-1 (IL-1) to animals induces sickness behavior, which resembles depression, and chronic treatment with antidepressants has been shown to inhibit sickness behavior induced by LPS; 5. Several cytokines can activate the hypothalamo-pituitary-adrenocortical axis (HPAA), which is commonly activated in depressed patients; 6. Some cytokines activates cerebral noradrenergic systems, also commonly observed in depressed patients; 7. Some cytokines activate brain serotonergic systems, which have been implicated in major depressive illness and its treatment. The evidence for each of these tenets is reviewed and evaluated along with the effects of cytokines in classical animal tests of depression. Although certain sickness behaviors resemble the symptoms of depression, they are not identical and each has distinct features. Thus the value of sickness behavior as an animal model of major depressive disorder is limited, so that care should be taken in extrapolating results from the model to the human disorder. Nevertheless, the model may provide insight into the etiology and the mechanisms underlying some symptoms of major depressive disorder. It is concluded that immune activation and cytokines may be involved in depressive symptoms in some patients. However, cytokines do not appear to be essential mediators of depressive illness.

Behavioral responses during the forced swim test are not affected by anti-inflammatory agents or acute illness induced by lipopolysaccharide

Pro-inflammatory cytokines and other molecules traditionally associated with immune function have been implicated in mediating behavioral and physiological consequences of stressor exposure. There is also evidence that cytokines are aberrantly expressed in depressive populations, suggesting they may play an etiological role in the development of depression/despair-related processes. Thus, we conducted a series of experiments to determine whether agents known to suppress cytokine activity or inflammatory responses in the CNS would alter the normal progression of behavioral responses during the forced swim test (FST, an animal model of depression/behavioral despair). Adult male Sprague-Dawley rats were injected with indomethacin (1 or 10 mg/kg intraperitoneally (i.p.)), alpha-MSH (0.25 or 0.5 microg icv), or minocycline (20 or 40 mg/kg i.p.) prior to each day of the FST and behavioral assessments were performed. Injection of indomethacin, alpha-MSH, or minocycline had no effect on the development of the immobility response during the FST on either day of testing. In a second series of experiments, we examined whether behavioral responses during forced swim would be affected by acute illness induced by a single injection of lipopolysaccharide (LPS). Acute injection of LPS (10 or 100 microg/kg i.p.) had no effect on behavioral responding during the FST irrespective of when it was injected, despite pronounced reductions in social behavior following these same doses of LPS. From these studies, we conclude that (a) endogenous inflammatory mediators do not appear to be involved in the normal progression of behavioral responses during the FST, and (b) behavioral responses during the FST are not affected by acute systemic injection of LPS.