Onset and severity of inflammation in rats exposed to the learned helplessness paradigm

Modulatory role of prenatal alcohol exposure and adolescent stress on the response to arthritis challenge in adult female rats

Background

There are known environmental risk factors associated with rheumatoid arthritis; however, less is known regarding how the prenatal environment impacts later-life risk for rheumatoid arthritis. Based on preliminary clinical data suggesting that individuals with fetal alcohol spectrum disorder (FASD) are at higher risk for autoimmune disorders, this study investigated the modulatory impact of prenatal alcohol exposure (PAE) on the inflammatory disease profile in an adjuvant-induced arthritis rat model.

Methods

Pregnant rats received liquid ethanol or control diet throughout gestation. To model the increased exposure to stressors often experienced by individuals with FASD, adolescent offspring were exposed to chronic mild stress (CMS) or remained undisturbed. In adulthood, experimental arthritis was initiated and rats terminated either at the peak or following resolution from inflammation to assess endocrine, immune, and histopathological outcomes.

Findings

PAE rats had an increased incidence and severity of, and impaired recovery from, arthritis. Increased joint damage was observed in PAE animals, even in the face of apparent recovery from the clinical signs of arthritis, while it appeared that oestradiol may have a protective role. Moreover, with the combination of PAE and adolescent stress, increased macrophage density was detected in the synovium of PAE but not control rats.

Interpretation

These findings demonstrate that PAE alters the severity and course of arthritis, highlighting the potential immunomodulatory impact of adverse prenatal exposures. In particular, these data have implications for understanding preliminary data that suggest a heightened propensity for autoimmune disorders in individuals with FASD.

Oxidative stress and neuroinflammation in a rat model of co-morbid obesity and psychogenic stress

BACKGROUND

There is growing recognition for a reciprocal, bidirectional link between anxiety disorders and obesity. Although the mechanisms linking obesity and anxiety remain speculative, this bidirectionality suggests shared pathophysiological processes. Neuroinflammation and oxidative damage are implicated in both pathological anxiety and obesity. This study investigates the relative contribution of comorbid diet-induced obesity and stress-induced anxiety to neuroinflammation and oxidative stress.

METHODS

Thirty-six (36) male Lewis rats were divided into four groups based on diet type and stress exposure: 1) control diet unexposed (CDU) and 2) exposed (CDE), 3) Western-like high-saturated fat diet unexposed (WDU) and 4) exposed (WDE). Neurobehavioral tests were performed to assess anxiety-like behaviors. The catalytic concentrations of glutathione peroxidase and reductase were measured from plasma samples, and neuroinflammatory/oxidative stress biomarkers were measured from brain samples using Western blot. Correlations between behavioral phenotypes and biomarkers were assessed with Pearson's correlation procedures.

RESULTS

We found that WDE rats exhibited markedly increased levels of glial fibrillary acidic protein (185 %), catalase protein (215 %), and glutathione reductase (GSHR) enzymatic activity (418 %) relative to CDU rats. Interestingly, the brain protein levels of glutathione peroxidase (GPx) and catalase were positively associated with body weight and behavioral indices of anxiety.

CONCLUSIONS

Together, our results support a role for neuroinflammation and oxidative stress in heightened emotional reactivity to obesogenic environments and psychogenic stress. Uncovering adaptive responses to obesogenic environments characterized by high access to high-saturated fat/high-sugar diets and toxic stress has the potential to strongly impact how we treat psychiatric disorders in at-risk populations.

The Relevance of Operant Behavior in Conceptualizing the Psychological Well-Being of Captive Animals

The term "psychological well-being" is used in reference to husbandry with animals in human care settings such as research, agriculture, and zoos. This article seeks to clarify and conceptualize the term based upon two approaches that draw from several bodies of literature: the experimental analysis of behavior, experimental psychology, animal welfare and husbandry, farm animal behavior, zoo husbandry, and ethology. One approach focuses on the presence of problem behavior such as stereotypies, depressive-like behavior, and aggression, and emphasizes the conditions under which aberrant behavior in animals under human care occurs. The second approach examines what might be considered wellness by emphasizing opportunities to engage with its environment, or the absence of such opportunities, even if problematic behavior is not exhibited. Here, access to an interactive environment is relatively limited so opportunities for operant (voluntary) behavior could be considered. Designing for operant behavior provides opportunities for variability in both behavior and outcomes. Operant behavior also provides control over the environment, a characteristic that has been a core assumption of well-being. The importance of interactions with one's environment is especially evident in observations that animals prefer opportunities to work for items necessary for sustenance, such as food, over having them delivered freely. These considerations raise the importance of operant behavior to psychological well-being, especially as benefits to animals under human care.

Enhanced conditioning of adverse memories in the mouse modified swim test is associated with neuroinflammatory changes - Effects that are susceptible to antidepressants

Deficient learning and memory are well-established pathophysiologic features of depression, however, mechanisms of the enhanced learning of aversive experiences associated with this disorder are poorly understood. Currently, neurobiological mechanisms of enhanced retention of aversive memories during depression, and, in particular, their relation to neuroinflammation are unclear. As the association between major depressive disorder and inflammation has been recognized for some time, we aimed to address whether neuroinflammatory changes are involved in enhanced learning of adversity in a depressive state. To study this question, we used a recently described mouse model of enhanced contextual conditioning of aversive memories, the modified forced swim model (modFST). In this model, the classic two-day forced swim is followed by an additional delayed session on Day 5, where increased floating behaviour and upregulated glycogen synthase kinase-3 (GSK-3) are context-dependent. Here, increased time spent floating on Day 5, a parameter of enhanced learning of the adverse context, was accompanied by hypercorticosteronemia, increased gene expression of GSK-3α, GSK-3β, c-Fos, cyclooxygenase-1 (COX-1) and pro-inflammatory cytokines interleukin-1 beta (IL-1β), tumor necrosis factor (TNF), and elevated concentrations of protein carbonyl, a marker of oxidative stress, in the prefrontal cortex and hippocampus. There were significant correlations between cytokine levels and GSK-3β gene expression. Two-week administration of compounds with antidepressant properties, imipramine (7 mg/kg/day) or thiamine (vitamin B1; 200 mg/kg/day) ameliorated most of the modFST-induced changes. Thus, enhanced learning of adverse memories is associated with pro-inflammatory changes that should be considered for optimizing pharmacotherapy of depression associated with enhanced learning of aversive memories.

Genetic Disruption of Circadian Rhythms in the Suprachiasmatic Nucleus Causes Helplessness, Behavioral Despair, and Anxiety-like Behavior in Mice

BACKGROUND

Major depressive disorder is associated with disturbed circadian rhythms. To investigate the causal relationship between mood disorders and circadian clock disruption, previous studies in animal models have employed light/dark manipulations, global mutations of clock genes, or brain area lesions. However, light can impact mood by noncircadian mechanisms; clock genes have pleiotropic, clock-independent functions; and brain lesions not only disrupt cellular circadian rhythms but also destroy cells and eliminate important neuronal connections, including light reception pathways. Thus, a definitive causal role for functioning circadian clocks in mood regulation has not been established.

METHODS

We stereotactically injected viral vectors encoding short hairpin RNA to knock down expression of the essential clock gene Bmal1 into the brain's master circadian pacemaker, the suprachiasmatic nucleus (SCN).

RESULTS

In these SCN-specific Bmal1-knockdown (SCN-Bmal1-KD) mice, circadian rhythms were greatly attenuated in the SCN, while the mice were maintained in a standard light/dark cycle, SCN neurons remained intact, and neuronal connections were undisturbed, including photic inputs. In the learned helplessness paradigm, the SCN-Bmal1-KD mice were slower to escape, even before exposure to inescapable stress. They also spent more time immobile in the tail suspension test and less time in the lighted section of a light/dark box. The SCN-Bmal1-KD mice also showed greater weight gain, an abnormal circadian pattern of corticosterone, and an attenuated increase of corticosterone in response to stress.

CONCLUSIONS

Disrupting SCN circadian rhythms is sufficient to cause helplessness, behavioral despair, and anxiety-like behavior in mice, establishing SCN-Bmal1-KD mice as a new animal model of depression.

The role of the prolactin/vasoinhibin axis in rheumatoid arthritis: an integrative overview

Rheumatoid arthritis (RA) is a chronic, autoimmune, inflammatory disease destroying articular cartilage and bone. The female preponderance and the influence of reproductive states in RA have long linked this disease to sexually dimorphic, reproductive hormones such as prolactin (PRL). PRL has immune-enhancing properties and increases in the circulation of some patients with RA. However, PRL also suppresses the immune system, stimulates the formation and survival of joint tissues, acquires antiangiogenic properties upon its cleavage to vasoinhibins, and protects against joint destruction and inflammation in the adjuvant-induced model of RA. This review addresses risk factors for RA linked to PRL, the effects of PRL and vasoinhibins on joint tissues, blood vessels, and immune cells, and the clinical and experimental data associating PRL with RA. This information provides important insights into the pathophysiology of RA and highlights protective actions of the PRL/vasoinhibin axis that could lead to therapeutic benefits.

Endothelial dysfunction and negative emotions in adolescent girls

BACKGROUND

Endothelial dysfunction predicts adult cardiovascular disorder and may be associated with negative emotions in adolescents. This study was conducted to determine if hopelessness, hostility, and depressive, anxiety, or conduct disorders were associated with compromised endothelial function and whether those associations were mediated by health risk behaviors.

METHODS

Endothelial function, assessed through brachial artery reactive hyperemia, was measured in a psychopathology enriched sample of 60 15-18-year-old girls. The correlations between hopelessness, hostility, and depressive, anxiety, or conduct disorders and the percent change in forearm vascular resistance (PCFVR) were measured. Possible mediation effects of health risk behaviors were tested.

RESULTS

Hopelessness was negatively associated with PCFVR, controlling for race and body mass index. Conduct disorder without any anxiety disorder was associated with better endothelial function. The other negative emotions were not associated with PCFVR. Risky health behaviors were associated with conduct disorder and hopelessness, but not with PCFVR, so there was no evidence of mediation.

CONCLUSION

The main finding was that hopelessness in adolescent girls was associated with endothelial dysfunction. This may indicate that when present, hopelessness places a girl at risk for later cardiovascular disease, whether she has a psychiatric disorder or not. Possible mechanisms for this finding are examined and the surprising finding that conduct disorder is associated with better endothelial function is also discussed. Suggestions for future research are presented.

Individual differences in pre-carcinogen cytokine and corticosterone concentrations and depressive-like behavior predict tumor onset in rats exposed to a carcinogen

Individual variation in the susceptibility to chronic disease can be attributed to both genetic and environmental factors. Measures of the immune, nervous, and endocrine systems are predictive of survival outcomes after a chronic disease is diagnosed. However, determining biomarkers or "traits" that predict risk before chronic disease development remains elusive. In this study, natural individual variation in circulating cytokines, corticosterone, and depressive-like behaviors (using the Porsolt forced swim test) were measured in female rats before induction of mammary tumors using a chemical carcinogen (N-nitroso-N-methylurea). Early tumor onset was associated with relatively high (but within the physiologically typical range) circulating cytokine concentrations (IL-1α, IL-1β, TNFα) and depressive-like behavior and with relatively low corticosterone concentrations, all of which were assessed at baseline before carcinogen treatment. Multiple regression analyses indicated that IL-1β was primarily responsible for the variation in tumor onset when controlling for corticosterone concentration. These results suggest that the susceptibility to tumor initiation and/or growth may be related to individual differences in baseline immune and endocrine physiology and emotional tone present at the time of carcinogen exposure. Investigation of the mechanistic relevance of these individual differences may lead to prophylactic approaches to cancer treatment in the context of carcinogen exposure.

Differential effect of severe and moderate social stress on blood immune and endocrine measures and susceptibility to collagen type II arthritis in male rats

The effects of social stress on several blood immune measures and collagen-induced arthritis (CIA) were investigated in Wistar rats using the resident-intruder confrontation paradigm to induce stress of different intensity. Male intruders were exposed for one week to a dominant opponent either repeatedly for 4h daily (moderate stress) or continuously (severe stress). Arthritis was induced by intradermal injection of collagen type II (CII) into the tail skin at the end of day 3 of confrontation. Only severe stress was associated with decreased CD4 and CD8 T cells, and the increase in granulocyte numbers and body mass loss was more pronounced under these conditions. Only severe stress reduced the susceptibility to arthritis by about 50%. Severity scores did not differ in the first five days after disease onset between all groups. Subsequent experiments focused on severely stressed rats indicated that disease progressed until day 10 only in control animals, but not in severely stressed males. Stressor exposure resulted in increased blood monocyte numbers, but these males failed to accumulate macrophages into the skin at the site of CII injection. High numbers of attacks experienced by intruders correlated with delayed disease onset in severely stressed rats. We hypothesize that severe stress persisting after disease induction exhibits beneficial effects on the susceptibility of CIA and propose that the specific endocrine and immunological profile associated with severe stress is an important factor for disease outcome--a factor which probably explains many of the conflicting data of previous stress studies on CIA.

Prenatal alcohol exposure alters the course and severity of adjuvant-induced arthritis in female rats

Prenatal alcohol exposure (PAE) has adverse effects on the development of numerous physiological systems, including the hypothalamic-pituitary-adrenal (HPA) axis and the immune system. HPA hyper-responsiveness and impairments in immune competence have been demonstrated. The present study investigated immune function in PAE females utilizing an adjuvant-induced arthritis (AA) model, widely used as a model of human rheumatoid arthritis. Given the effects of PAE on HPA and immune function, and the known interaction between HPA and immune systems in arthritis, we hypothesized that PAE females would have heightened autoimmune responses, resulting in increased severity of arthritis, compared to controls, and that altered HPA activity might play a role in the immune system changes observed. The data demonstrate, for the first time, an adverse effect of PAE on the course and severity of AA in adulthood, indicating an important long-term alteration in functional immune status. Although overall, across prenatal treatments, adjuvant-injected animals gained less weight, and exhibited decreased thymus and increased adrenal weights, and increased basal levels of corticosterone and adrenocorticotropin, PAE females had a more prolonged course of disease and greater severity of inflammation compared to controls. In addition, PAE females exhibited blunted lymphocyte proliferative responses to concanavalin A and a greater increase in basal ACTH levels compared to controls during the induction phase, before any clinical signs of disease were apparent. These data suggest that prenatal alcohol exposure has both direct and indirect effects on inflammatory processes, altering both immune and HPA function, and likely, the normal interactions between these systems.

The determinants of susceptibility/resistance to adjuvant arthritis in rats

Adjuvant arthritis (AA) serves as an excellent model for human rheumatoid arthritis. AA is readily inducible in certain rat strains, but not in others. Susceptibility/resistance to AA is determined by multiple factors. Among the genetic factors, both MHC and non-MHC genes contribute to arthritis susceptibility, and specific quantitative trait loci show association with the severity of the disease. Differential T-cell proliferative and cytokine responses, as well as antibody responses, to heat-shock proteins are evident when comparing AA-susceptible and AA-resistant rats. In addition, neuroendocrine factors and the housing environment can further modulate arthritis susceptibility/severity in particular rat strains.

Stress exacerbates neuropathic pain via glucocorticoid and NMDA receptor activation

There is growing recognition that psychological stress influences pain. Hormones that comprise the physiological response to stress (e.g., corticosterone; CORT) may interact with effectors of neuropathic pain. To test this hypothesis, mice received a spared nerve injury (SNI) after exposure to 60 min restraint stress. In stressed mice, allodynia was consistently increased. The mechanism(s) underlying the exacerbated pain response involves CORT acting via glucocorticoid receptors (GRs); RU486, a GR antagonist, prevented the stress-induced increase in allodynia whereas exogenous administration of CORT to non-stressed mice reproduced the allodynic response caused by stress. Since nerve injury-induced microglial activation has been implicated in the onset and propagation of neuropathic pain, we evaluated cellular and molecular indices of microglial activation in the context of stress. Activation of dorsal horn microglia was accelerated by stress; however, this effect was transient and was not associated with the onset or maintenance of a pro-inflammatory phenotype. Stress-enhanced allodynia was associated with increased dorsal horn extracellular signal-regulated kinase phosphorylation (pERK). ERK activation could indicate a stress-mediated increase in glutamatergic signaling, therefore mice were treated prior to SNI and stress with memantine, an N-methyl-D-aspartate receptor (NMDAR) antagonist. Memantine prevented stress-induced enhancement of allodynia after SNI. These data suggest that the hormonal responses elicited by stress exacerbate neuropathic pain through enhanced central sensitization. Moreover, drugs that inhibit glucocorticoids (GCs) and/or NMDAR signaling could ameliorate pain syndromes caused by stress.

Stress activation of cellular markers of inflammation in rheumatoid arthritis: protective effects of tumor necrosis factor alpha antagonists

OBJECTIVE

Psychological stress is thought to aggravate disease activity in rheumatoid arthritis (RA), although the physiologic mechanisms are unclear. Tumor necrosis factor alpha (TNFalpha) is an inflammatory cytokine involved in the exacerbation of RA, and TNFalpha antagonists have emerged as efficacious treatments. The purpose of this study was to determine whether RA patients show increased monocyte production of TNFalpha following acute psychological stress and whether such responses are abrogated in RA patients taking TNFalpha antagonists.

METHODS

A standardized stress task was administered to 3 groups of subjects: RA patients taking TNFalpha antagonists, RA patients not taking such medications, and healthy controls. Lipopolysaccharide-stimulated monocyte production of inflammatory cytokines was repeatedly measured using intracellular staining and flow cytometry. Subjective stress, cardiovascular responses, adrenocorticotropic hormone (ACTH) levels, and cortisol levels were also measured.

RESULTS

The stress task induced increases in subjective stress, cardiovascular activity, and levels of ACTH and cortisol, with similar responses in the 3 groups. In addition, the stress task induced a significant increase (P < 0.001) in monocyte production of TNFalpha among RA patients who were not taking TNFalpha antagonists. However, monocyte production of TNFalpha did not change following psychological stress in RA patients taking TNFalpha antagonists or in healthy controls.

CONCLUSION

Brief psychological stress can trigger increased stimulated monocyte production of TNFalpha in RA patients. The use of TNFalpha antagonists protects against stress activation of cellular markers of inflammation in RA patients.

Effects of stress and neuropeptides on airway responses in ovalbumin-sensitized rats

OBJECTIVE

The aim of this study was to investigate the influence of stress and neuropeptides on airway responses in ovalbumin (OVA)-sensitized rats.

METHODS

Three experimental conditions were employed: neonatal capsaicin treatment, foot shock stress and OVA sensitization. For neuropeptide depletion, male Wistar rats were neonatally treated with capsaicin (50 mg/kg) or with control solution 2 days after birth. Ninety days later, they were injected with OVA and aluminum hydroxide (ED0) or no injection. Thereafter, rats of the stressed groups were individually placed in a shuttle box where they received 50 mild escapable foot shocks/day; the stressful stimuli were repeated until ED14, when the animals received OVA aerosol. Pulmonary mechanic function was measured before and after OVA challenge in anesthetized and mechanically ventilated rats.

RESULTS

Data on ultrasonic vocalizations and corticosterone showed high levels of anxiety in stressed animals. As expected, a significant increment in airway elastance and resistance after the OVA challenge was found in sensitized rats compared to non-sensitized ones. Capsaicin treatment decreased the values of elastance in sensitized and non-stressed rats; however, after the OVA challenge, elastance was increased in stressed animals. No differences were found in the levels of resistance among sensitized and non-stressed rats; however, a reduced increment in resistance was verified in capsaicin-treated, stressed animals.

CONCLUSIONS

Our results suggest that neurokinin depletion and stress may affect smooth muscle tonus around the airways during an anaphylactic reaction. These data suggest that stress and neuropeptides play a significant role in pulmonary function in OVA-sensitized rats.

Protective effects of endotoxin in a rat model of chronic inflammation are accompanied by suppressed secretion of pro-inflammatory cytokines and biphasic alteration in hypothalamo-pituitary-adrenal axis activity

We have previously demonstrated that Gram-negative bacterial endotoxin can exert long-term protective effects against the chronic inflammatory disease adjuvant arthritis in rats. The present study was designed to investigate the mechanisms and time-course of hypothalamo-pituitary-adrenocortical (HPA) axis activity and cytokine secretion underlying this phenomenon. Rats were injected with endotoxin (lipopolysaccharide) and blood was collected either 7 or 21 days later. Priming with endotoxin induced a biphasic alteration in secretion of adrenocorticotrophic hormone and corticosterone in response to a second injection of endotoxin, with decreased secretion observed after 7 days whereas robust secretion was observed at 21 days. Seven days following priming with endotoxin, plasma concentrations of pro-inflammatory cytokines interleukin (IL)-6 and interferon (IFN)-gamma were reduced by 90%, and tumour necrosis factor (TNF)-alpha by 70%, compared to saline-treated rats, whereas robust secretion of the anti-inflammatory cytokine IL-10 was maintained in both groups. A similar net change favouring an anti-inflammatory cytokine secretory milieu was also observed 21 days following priming with endotoxin. This study provides evidence that the long-term protective effects of endotoxin on inflammation are associated with a sustained reduction in secretion of pro-inflammatory cytokines. HPA axis hypoactivity at 7 days suggests that corticosterone is not involved in suppressing IL-6, IFN-gamma and TNF-alpha at this time point. Conversely, hypersecretion of corticosterone at 21 days may underlie synchronous suppression of IL-6 and IFN-gamma. These data provide novel insight into interactions between HPA axis activity and cytokine secretion following endotoxin priming prior to induction of inflammatory disease.

Endocrine and immunological correlates of behaviorally identified swim stress resilient and vulnerable rats

Animal models of stress-induced depression have identified a bimodal reactivity to stress, namely 'resilience' and 'vulnerability.' Possible corresponding differences in endocrine and immunological responses between these groups have not been delineated. Male Sprague-Dawley rats were divided into three groups: stress (n=25), confined controls (n=7), and home cage controls (n=7). Stress rats were exposed to 80, 5-s inescapable cold water swim trials (15 degrees C). Twenty-four hours later, the stress rats were tested on an instrumental swim escape test (SET) but now they had access to an omnidirectional lever that terminated the stress. Immediately after the SET, trunk blood was collected to assay for serum corticosterone (CORT), and spleens were removed and natural killer cell activity (NKCA) and concanavalin A (CON-A) induced lymphocyte proliferation determined. Subjects in the stress treatment group were divided into distinct 'resilient' and 'vulnerable' categories by a median split for average escape latencies across the last 25 trials of the SET. Stress rats secreted more CORT than controls and vulnerable rats secreted greater levels than resilient rats. NKCA was greatest in control rats, and was decreased in the stress rats although the resilient and the vulnerable groups did not differ. Conversely, CON-A-induced lymphocyte proliferation was greatest in stress rats, vulnerable rats exhibiting more proliferation than resilient rats, but both were greater than both control groups. Stress animals were hypothermic throughout the swim stress procedures but exhibited a stress-induced fever following the initial swim trials. The observed differences may have important predictive and theoretical utility for vulnerable and resilient profiles.

Inflammation-Susceptible Lewis Rats Show Less Sensitivity Than Resistant Fischer Rats in the Formalin Inflammatory Pain Test and With Repeated Thermal Testing

Comparisons between Lewis and Fischer inbred strains of rats are used frequently to study the effect of inherent differences in function of the hypothalamic-pituitary-adrenal axis on pain-relevant traits, including differential susceptibility to chronic inflammatory disease and differential responsiveness to analgesic drugs. Increasing use of genetic models including transgenic knockout mice and inbred strains of rodents has raised our awareness of, and the importance of, thorough characterization (or phenotyping) of the strains of rodents being compared. Furthermore, genetic variability in analgesic sensitivity is correlated with, and may be caused by, genetically determined baseline sensitivity. Thus in this study, baseline inflammatory and thermal nociceptive sensitivities were measured in awake male and female Lewis and Fischer rats to examine whether the results could explain relevant strain differences reported in the literature. The effect of maternal separation was also examined and no effect was found on nociceptive sensitivity, corticosterone responses, or the development of adjuvant-induced arthritis, a model of rheumatoid arthritis. Lewis rats and female rats were more sensitive to thermal nociception in the tail withdrawal test (mean of 3 trials) than Fischer rats and male rats, respectively. Unexpectedly, the more inflammation-susceptible Lewis rats were less sensitive in the formalin inflammatory nociception test, and showed a significant decrease in sensitivity with repeated thermal nociceptive testing, whereas Fischer rats did not. These results affect the interpretation of previously observed results. Further study of the underlying mechanisms and the relevance to differential susceptibility to chronic inflammation is warranted.

Social isolation and the inflammatory response: sex differences in the enduring effects of a prior stressor

Numerous epidemiological studies have demonstrated an association between persistent social isolation and “all-cause” morbidity and mortality. To date, no causal mechanism for these findings has been established. Whereas animal studies have often reported short-term effects of social isolation on biological systems, the long-term effects of this adverse psychological state have been understudied. This is the first animal study to examine the effects of long-term social isolation from weaning through young adulthood on an innate inflammatory response linked to numerous disease processes. Results presented here offer a plausible link between vulnerability to disease and social neglect. For socially isolated male and female Sprague-Dawley rats, a naturally gregarious species, formation of a granuloma in response to a subcutaneous injection of carrageenin (seaweed) was significantly delayed compared with the response of animals housed in single-sex groups of five. Significant sex differences, however, emerged when an acute prior stressor was superimposed on the experience of chronic social isolation. In this context, isolated females produced a more robust inflammatory response than isolated males. This sexual dimorphism at the nexus of chronic social isolation, acute stress, and inflammatory processes may account for the observation in humans that men with low levels of social integration are more vulnerable to disease and death than women.

The Neuroendocrine–Immune Interactions in Systemic Lupus Erythematosus: A Basis for Understanding Disease Pathogenesis and Complexity

Much progress has been made in the understanding of the impact of the neuroendocrine immune interactions and the pathogenic role in systemic lupus erythematosus, clinically and at the molecular level. This article focuses on the intertwining networks that involve the hypothalamic-pituitary-adrenal axis, cytokines within the central nervous system, and the sympathetic system. Hormones (estrogen, prolactin, gonadotropin-releasing hormone, and leptin) play an important role as immunomodulatory agents.

Pain, stiffness, and fatigue in juvenile polyarticular arthritis: Contemporaneous stressful events and mood as predictors

OBJECTIVE

To analyze patterns of stress, mood, disease symptoms, and activity reduction in children with polyarticular arthritis, using a prospective daily diary method.

METHODS

For a 2-month period, 51 children with polyarticular arthritis (mean age 12.4 years, 65% female) completed daily diaries that included measures of symptoms of pain, stiffness, and fatigue, as well as stress, mood, and activity reduction. Functional status and disease activity were assessed at the initial and followup evaluations with use of the Childhood Health Assessment Questionnaire, physician global assessment, joint count, and laboratory testing.

RESULTS

Children reported having pain, stiffness, and fatigue on >70% of days, with significant variability in symptom levels. Results revealed significant same-day relationships between stress, mood, and disease symptoms, after controlling for covariates. Specifically, daily fluctuations in both stress and mood were predictive of increased pain, stiffness, and fatigue. Increases in daily stress, mood, and disease symptoms were also significantly related to decreased participation in social activities on a day-to-day basis. Only mood and stiffness were predictors of a cutback in school attendance.

CONCLUSION

Stress and mood are important predictors of daily disease symptoms in children with polyarticular arthritis. Moreover, daily fluctuations in stress, mood, and disease symptoms are predictive of aspects of daily function, including participation in school and social activities. Thus, health care providers should solicit daily symptom reports when making decisions regarding clinical management. Nonpharmacologic interventions such as cognitive-behavioral therapy and stress management may be useful adjuvant therapy when treating the disease symptoms of children with polyarticular arthritis.

Effects of stress on inflammatory autoimmune disease: destructive or protective?

We have summarised evidence in the literature for modulatory effects of stress on inflammatory autoimmune disease. We find that overall there is strong evidence for such an interrelationship. Apparent discrepancies between groups and studies are probably due to differences in experimental design, whether longitudinal or retrospective. Other important variables are the specific effects of different types of stress and the intensity and timing of the stressor relative to onset of inflammation. We conclude that there is much of benefit to be learned from scientific study of stress, such as harnessing and rationalising of stressful experiences through self-expression in patients, or the identification of novel anti-inflammatory compounds activated by stress.

Individual differences in behavior of inbred Lewis rats are associated with severity of joint destruction in adjuvant-induced arthritis

The aim of our study was to test the hypothesis that differences in behavioral characteristics are linked to severity of arthritis in association with neuro-endocrine and immune reactivity in an inbred strain of rats. Lewis rats were selected as high-active (HA) and low-active (LA) animals based on their exploratory activity in the open field. Subsequently, adjuvant-arthritis (AA) was induced in both groups. We observed no differences in the severity of inflammation as determined by paw swelling and redness. However, LA and HA animals differed in the severity of bone destruction as determined on radiographs taken on day 30 after induction of AA. LA rats had more osteoporosis, periostal new bone formation, and bone destruction than HA rats. There were no differences between HA and LA rats in corticosterone response after acute or chronic immune challenge. Splenocytes of LA rats had a lower mitogen-induced IL-10 and IFNgamma production during AA. Histological examination revealed more intense factor VIII staining in arthritic joints of LA animals, indicating more pronounced synovial angiogenesis. In addition, LA rats had higher plasma VEGF, an important angiogenic factor. Expression of RANKL, a crucial factor promoting bone resorption, was also higher in joints of LA animals. Our data demonstrate that activity in the open field, a behavioral trait, is associated with the severity of bone destruction in AA. Lower production of bone-protective cytokines and a higher rate of angiogenesis leading to more synovial proliferation may be responsible for the more severe joint destruction in LA animals.

Involvement and role of the hypothalamo-pituitary-adrenal (HPA) stress axis in animal models of chronic pain and inflammation

Hypothalamo-pituitary-adrenal (HPA) axis changes have been reported in several disease states, including major depressive disorder, rheumatoid arthritis, multiple sclerosis and various other conditions associated with chronic pain. These observations suggest that stress and the HPA axis may play important roles in the pathology of these diseases. In order to contribute to a better understanding of the role that chronic stress may play in human pathology, this review article explores the involvement of the HPA axis in those animal models of chronic pain and inflammation that entail persistent rather than intermittent stress.

Non-opioid-dependent anti-inflammatory effects of low frequency electroacupuncture

Low frequency electroacupuncture, which is commonly used in pain relief, is known to induce opioid-mediated analgesia. This study examined the contribution of the opioid system in mediating the anti-inflammatory effects of low frequency EA in a standard model of acute inflammation, the carrageenan-induced edema model. Carrageenan was injected in the hind paw of anesthetized rats and low frequency electroacupuncture was applied to acupoints equivalent to Zusanli (St 36) and Sanyinjiao (Sp 6) in humans just prior to the induction of inflammation in the ipsilateral leg. Induction of Fos protein, reflecting neuronal activation, was investigated in the spinal cord with immunohistochemistry. It was found that electroacupuncture strongly inhibited the carrageenan-induced edema by over 60%, and suppressed the associated Fos expression in the superficial laminae (I-II) of the ipsilateral dorsal horn by 50%. Neither the anti-edematous effect nor the suppression of Fos expression in the superficial spinal laminae was affected by intraperitoneal injection of the opioid antagonist naloxone. These results demonstrate that low frequency electroacupuncture is capable of inhibiting peripheral inflammation and the associated central neuronal activity via a non-opioid-dependent mechanism.

Hypothalamo-pituitary-adrenal axis and chronic immune activation

Corticosteroids have potent immunosuppressive and anti-inflammatory effects. Although corticosteroids are an important weapon in the clinical arsenal for treating inflammatory episodes, the mechanisms underlying the actions and regulation of endogenous corticosteroids remain obscure. In the late 1980s and early 1990s, a hypothesis was proposed that suggested that susceptibility to autoimmune disease was linked to a hypoactive hypothalamo-pituitary-adrenal (HPA) axis. It was further suggested that this defect in regulation of the HPA axis was situated at the level of the hypothalamus. This compelling hypothesis directly linked control of the HPA axis with susceptibility to disease rather than just severity of inflammation. The initial findings acted as a stimulus to further research, and over the next decade the hypothesis was tested. Recent studies suggest that the original hypothesis is in need of modification and that susceptibility is more complex and requires the involvement of more than a single parameter. These data are discussed together with recent developments concerning regulation of the HPA in disease in preclinical models and patients with rheumatoid arthritis. The latter studies in patients with rheumatoid arthritis provide evidence for the existence of a subpopulation of these patients with altered negative feedback regulation of the HPA axis.

Neuroendocrinology of autoimmunity

The HPA axis is fundamental for long-term survival and protection from the ravages of autoimmune disease. Continuing investigations suggest that the hypothesis linking susceptibility to autoimmune disease and a hyporesponsive HPA axis is somewhat simplistic. Instead, data from a number of different human diseases and from preclinical studies in a variety of models have suggested a more complicated picture. Alterations in the diurnal rhythms of ACTH, cortisol, and immune parameters appear to be linked to severity of disease. The use of low doses of steroids timed to target disrupted diurnal immune system changes in patients with RA may reduce the unfortunate side effects of long-term steroid use. Studies in cancer patients have related alterations in diurnal cortisol to survival. Whether differences in individual cortisol profiles are predictive of a deterioration in symptoms of autoimmune disease remains to be established. Responsiveness of the HPA axis to subtle challenges such as the dexamethasone suppression test and the related dexamethasone-CRF test suggest that there are different sub-populations of patients with RA and MS and these may have confounded earlier, apparently contradictory, studies. These different responses may be related to the severity of the disease. That these HPA axis differences can be altered beneficially through the use of antidepressants, as has been shown in MS, may impact on future health care strategies. However, reports of negative developments in arthritis associated with SSRI use suggest that the SSRIs may be unsuitable under some circumstances. The link of behavioral differences to alterations in neurotransmitter changes associated with disease is intriguing and opens new avenues of research. These future studies will require input from neuroscientists, neuroendocrinologists, psychologists, and immunologists working with the clinical specialties already involved in treating patients with autoimmune disease. These multidisciplinary studies reflecting the increased importance of hormonal and neurotransmitter involvement with the immune system hold great promise for the future.

Effects of chronic food restriction stress and chronic psychological stress on the development of adjuvant arthritis in male long evans rats

The aim of the present experiments was to study the effect of stress of chronic food restriction (FR) and of repeated psychological challenge (PS) on the development of adjuvant arthritis in the Long Evans male rats. In the FR series, four groups of animals were compared: non-treated control (C) and arthritic (AA) rats, both with free access to food and water, and two analogous groups with a 40% food restriction-FR and AA-FR. All animals were killed 22 days after injection of cFA. In the PS series, stress was induced by random daily exposures of the rats to isolation, over-crowding, food/water deprivation, foot shock, tilting, fear for 14 days before cFA injection and 12 days thereafter (groups: C, AA, PS, and AA-PS). Arthritis causes swelling of the hindpaw, which was prevented in the AA-FR group. PS causes more severe disease symptoms: AA-PS rats had more severe hindpaw swelling than AA rats. Forty percent food restriction associated with elevated CORT levels mitigated inflammatory parameters activated during AA. PS worsened the disease. These results suggested that activated CORT is not the only cause of disease suppression, but some metabolic changes during FR play a role.

CRH in chronic inflammatory stress

Corticotropin-releasing hormone (CRH) is an important regulator of inflammation at the central level through hypothalamo-pituitary-adrenal (HPA) axis control of glucocorticoid secretion. Integrity of the HPA axis during autoimmune disease is critical in controlling the severity of inflammation, but the evidence for an HPA axis defect in the etiology of autoimmune diseases is not compelling. CRH secreted from leukocytes and neuronal terminals in peripheral tissues also plays a role in mediating inflammation. Elucidating the pathways underlying the expression of CRH, both central and peripheral, and interactions of CRH with other inflammatory mediators such as substance P, confers great potential for the development of a new generation of anti-inflammatory agents.

The effect of stress on inflammation

Stress can either enhance or suppress aspects of the immune response, depending on the nature, duration, timing and intensity of the stressor. This paper focuses on the effects on inflammation of two behavioural stress paradigms: learned helplessness (La) and the open-field test (OF), and of the immunological stressor lipopolysaccharide (LPS). We have observed that the onset and severity of inflammation in adjuvant-induced arthritis (AA) in the rat can be altered by experience of the LH paradigm, or by priming with LPS, but not by OF.In the LH test, some rats escape (LH(-)) and others do not (LH(+)). Despite the LH(-) group demonstrating a greater corticosterone response to the LH stressor compared to the LH(+)rats, they exhibited earlier onset and greater seventy of AA. In contrast, intraperitoneal injection of LPS several weeks prior to induction of AA protected against inflammation. These results provide further evidence that environmental factors influence the etiology of at least one type of inflammation. The modulation of inflammation by a defined stressor suggests that understanding of the underlying mechanisms may provide a potential for novel therapies.