Intracerebral HIV-1 glycoprotein 120 produces sickness behavior and pituitary-adrenal activation in rats: role of prostaglandins

Potential pharmacological approaches for the treatment of HIV-1 associated neurocognitive disorders

HIV associated neurocognitive disorders (HAND) are the spectrum of cognitive impairments present in patients infected with human immunodeficiency virus type 1 (HIV-1). The number of patients affected with HAND ranges from 30 to 50% of HIV infected individuals and although the development of combinational antiretroviral therapy (cART) has improved longevity, HAND continues to pose a significant clinical problem as the current standard of care does not alleviate or prevent HAND symptoms. At present, the pathological mechanisms contributing to HAND remain unclear, but evidence suggests that it stems from neuronal injury due to chronic release of neurotoxins, chemokines, viral proteins, and proinflammatory cytokines secreted by HIV-1 activated microglia, macrophages and astrocytes in the central nervous system (CNS). Furthermore, the blood-brain barrier (BBB) not only serves as a route for HIV-1 entry into the brain but also prevents cART therapy from reaching HIV-1 brain reservoirs, and therefore could play an important role in HAND. The goal of this review is to discuss the current data on the epidemiology, pathology and research models of HAND as well as address the potential pharmacological treatment approaches that are being investigated.

Impaired mental health and low-grade inflammation among fatigued bereaved individuals

BACKGROUND

Fatigue is a common symptom in stressed individuals. Bereavement is a major life event that has been associated with impaired mental health. Little research has investigated the prevalence of fatigue and its inflammatory correlates in bereaved individuals.

OBJECTIVES

To assess fatigue prevalence and its relationship with mental health outcomes and markers of inflammation, as indexed by C-reactive protein (CRP), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) in bereaved individuals.

METHODS

Seventy-eight-bereaved adults were examined for fatigue (SF-36 energy/vitality scale), perceived stress (PSS), depression (CES-D), sleep quality (PSQI), pain (SF-36 pain scale), and general health (SF-36 general), and their serum levels of CRP, IL-6 and TNF-α were measured. Group differences between fatigued versus non-fatigued individuals were estimated using analysis of covariance (ANCOVA), with adjustment for body mass index (BMI).

RESULTS

Fatigued bereaved individuals (33%; SF-36 energy/vitality score 0-45) had significantly higher CRP levels (p < .05) as compared to non-fatigued bereaved individuals and reported higher levels of pain (p < .001), greater stress (p < .001), depression (p < .001), and sleeping problems (p < .001), as well as poorer social functioning (p < .001) and general health (p < .001) than those in the non-fatigued group. No group differences were found for IL-6 and TNF-α.

CONCLUSIONS

Fatigued bereaved individuals showed elevated systemic inflammation as measured by CRP in comparison to non-fatigued bereaved individuals. They were also more likely to report mental health problems that co-occur with fatigue in the context of immune activation. Continued research is needed to help clarify the involvement of inflammatory markers in the development of fatigue in a larger sample of bereaved adults.

Depressive-like behavior, its sensitization, social buffering, and altered cytokine responses in rhesus macaques moved from outdoor social groups to indoor housing

Psychosocial stressors appear to promote the onset of depressive illness through activation and sensitization of inflammatory mechanisms. Here, adult male rhesus monkeys brought from large outdoor social groups to indoor housing for 8 days reliably exhibited a hunched, depressive-like posture. When rehoused indoors a second 8 days about 2 weeks later, monkeys housed alone, but not those with an affiliative partner, showed sensitization of the depressive-like hunched posture. Housing indoors also affected circulating pro-inflammatory cytokines: IL-1β showed increased responsiveness to immune challenge, and IL-1β and TNF-α showed reduced suppression by dexamethasone. Sensitivity of the anti-inflammatory cytokine IL-10 to immune challenge exhibited a relative increase from the first to the second round of indoor housing in animals housed in pairs, and a relative decrease in animals housed alone. Cytokine levels during indoor housing were positively correlated with duration of depressive-like behavior. Plasma cortisol levels increased but did not differentiate housing conditions or rounds. Results demonstrate a rapid induction and sensitization of depressive-like behavior to indoor individual housing, social buffering of sensitization, and associated inflammatory responses. This paradigm may provide a practical nonhuman primate model for examining inflammatory-mediated consequences of psychosocial stressors on depression and possible social buffering of these effects.

Depression as a microglial disease

Despite decades of intensive research, the biological mechanisms that causally underlie depression are still unclear, and therefore the development of novel effective antidepressant treatments is hindered. Recent studies indicate that impairment of the normal structure and function of microglia, caused by either intense inflammatory activation (e.g., following infections, trauma, stroke, short-term stress, autoimmune or neurodegenerative diseases) or by decline and senescence of these cells (e.g., during aging, Alzheimer's disease, or chronic unpredictable stress exposure), can lead to depression and associated impairments in neuroplasticity and neurogenesis. Accordingly, some forms of depression can be considered as a microglial disease (microgliopathy), which should be treated by a personalized medical approach using microglial inhibitors or stimulators depending on the microglial status of the depressed patient.

Impact of Depression and Inflammation on the Progression of HIV Disease

The human immunodeficiency virus type 1 (HIV-1) epidemic has negatively affected over 40 million people worldwide. Antiretroviral therapy (ART) has improved life expectancy and changed the outcome of HIV-1 infection, making it a chronic and manageable disease. However, AIDS and non-AIDS comorbid illnesses persist during the course of infection despite the use of ART. In addition, the development of neuropsychiatric comorbidities (including depression) by HIV-infected subjects significantly affects quality of life, medication adherence, and disease prognosis. The factors associated with depression during HIV-1 infection include altered immune response, the release of pro-inflammatory cytokines, and monoamine imbalance. Elevated plasma pro-inflammatory cytokine levels contribute to the development of depression and depressive-like behaviors in HIV⁺ subjects. In addition, comorbid depression influences the decline rates of CD4⁺ cell counts and increases plasma viral load. Depression can manifest in some subjects despite their adherence to ART. In addition, psychosocial factors related to stigma (negative attitudes, moral issues, and abuse of HIV⁺ subjects) are also associated with depression. Both neurobiological and psychosocial factors are important considerations for the effective clinical management of HIV and the prevention of HIV disease progression.

Social disruption alters pain and cognition in an animal model of multiple sclerosis

Although pain and cognitive deficits are widespread and debilitating symptoms of multiple sclerosis (MS), they remain poorly understood. Theiler's murine encephalomyelitis virus (TMEV) infection is an animal model of MS where disease course is exacerbated by prior stressors. Here chronic infection coupled with prior social stress increased pain behavior and impaired hippocampal-dependent memory consolidation during the demyelinating phase of disease in SJL mice. These results suggest that the TMEV model may be useful in investigating pain and cognitive impairments in MS. However, in contrast to prior Balb/cJ studies, stress failed to consistently alter behavioral and physiological indicators of disease course.

Electroacupuncture attenuates neuropathic pain after brachial plexus injury

Electroacupuncture has traditionally been used to treat pain, but its effect on pain following brachial plexus injury is still unknown. In this study, rat models of an avulsion injury to the left brachial plexus root (associated with upper-limb chronic neuropathic pain) were given electroacupuncture stimulation at bilateral Quchi (LI11), Hegu (LI04), Zusanli (ST36) and Yanglingquan (GB34). After electroacupuncture therapy, chronic neuropathic pain in the rats' upper limbs was significantly attenuated. Immunofluorescence staining showed that the expression of β-endorphins in the arcuate nucleus was significantly increased after therapy. Thus, experimental findings indicate that electroacupuncture can attenuate neuropathic pain after brachial plexus injury through upregulating β-endorphin expression.

Functional interaction between HIV-gp120 and opioid system in the preoptic anterior hypothalamus

BACKGROUND

Recently we found that fever (part of HIV-related wasting) is induced by the action of the human immunodeficiency virus-1 (HIV-1) envelope glycoprotein (gp120) in the preoptic anterior hypothalamus (POAH). As the opioid system plays a role in the pathogenesis of HIV-1, in the present study we sought to examine the capacity of the opioid system to regulate the febrile response induced by gp120.

METHODS

Stainless steel cannulas were stereotactically into the POAH, and a biotelemetry system was used to monitor the body temperature (Tb changes). We examined the in vivo effects of naloxone as well as highly opioid-selective receptor antagonists, on gp120-induced fever.

RESULTS

Pretreatment with naloxone or the mu-opioid receptor-selective antagonist, cyclic d-Phe-Cys-Tyr-d-Trp-Arg-Thr-Pen-Thr-NH(2) (CTAP), significantly delayed the febrile response induced by gp120. In contrast, naltriben (NTB), a selective antagonist for the delta-2 opioid receptor, did not cause any effect on gp120-induced fever.

CONCLUSION

These results (1) provide pharmacologic evidence of a functional in vivo interaction between the opioid system and this viral protein in the POAH and (2) show that mu-opioid receptors can regulate gp120-induced fever.

Intracerebroventricular administration of HIV-1 Tat induces brain cytokine and indoleamine 2,3-dioxygenase expression: a possible mechanism for AIDS comorbid depression

Human immunodeficiency virus (HIV) remains a major public health concern despite a large education effort during the past 25 years. A persistent problem with HIV infection is the high comorbity rate of clinical depression. We previously established that increasing proinflammatory cytokines within the brain of mice induces sickness that can culminate in depressive-like behavior. Here we investigated the role of the HIV transactivator of transcription (Tat) protein in activation of brain cytokine signaling and subsequent induction of depressive-like behavior in a murine model. Adult Balb/c mice were administered a single intracerebroventricular (ICV) injection of Tat (40 ng). Social investigation of a novel juvenile was measured at 2, 4, 8 and 24 h post-treatment. Mice treated with Tat did not display signs of sickness, as measured by either decreased social investigation or loss of body weight. At 24 h post-injection, mice were subjected to the forced swim test (FST). ICV administration of Tat to Balb/c mice increased immobility in the FST at 24 h post injection. A different strain of mice, C57BL/6J, responded similarly in the FST. Furthermore, adult C57BL/6J mice injected with Tat and tested in a two-bottle 1% sucrose preference test displayed reduced preference for sucrose during the 24 h post-injection period. Subsequently, brain tissues from Tat-treated and control C57BL/6J mice were collected at 4 and 24 h post injection. CNS tissue from Tat-treated mice had increased expression of IL-1β, TNF-α, IL-6, and IDO mRNAs at 4 h post injection. These data demonstrate that a single exposure to Tat in the brain is sufficient to induce brain cytokine signaling that culminates in depressive-like behavior. The results reveal a potential role for Tat in the development of comorbid depression in HIV-infected individuals.

HIV-1 Tat activates indoleamine 2,3 dioxygenase in murine organotypic hippocampal slice cultures in a p38 mitogen-activated protein kinase-dependent manner

Background

We have established that activation of the tryptophan degrading enzyme indoleamine 2,3 dioxygenase (IDO) mediates the switch from cytokine-induced sickness behavior to depressive-like behavior. Because human immunodeficiency virus type 1 (HIV-1) Tat protein causes depressive-like behavior in mice, we investigated its ability to activate IDO in organotypic hippocampal slice cultures (OHSCs) derived from neonatal C57BL/6 mice.

Methods

Depressive-like behavior in C57BL/6J mice was assessed by the forced swim test. Expression of cytokines and IDO mRNA in OHSCs was measured by real-time RT-PCR and cytokine protein was measured by enzyme-linked immunosorbent assays (ELISAs). p38 MAPK phosphorylation was analyzed by western blot.

Results

Intracerebroventricular (i.c.v.) administration of Tat (40 ng) induced depressive-like behavior in the absence of sickness. Addition of Tat (40 ng/slice) to the medium of OHSCs induced IDO steady-state mRNA that peaked at 6 h. This effect was potentiated by pretreatment with IFNγ. Tat also induced the synthesis and release of TNFα and IL-6 protein in the supernatant of the slices and increased expression of the inducible isoform of nitric oxide synthase (iNOS) and the serotonin transporter (SERT). Tat had no effect on endogenous synthesis of IFNγ. To explore the mechanisms of Tat-induced IDO expression, slices were pretreated with the p38 mitogen-activated protein kinase (MAPK) inhibitor SB 202190 for 30 min before Tat treatment. SB 202190 significantly decreased IDO expression induced by Tat, and this effect was accompanied by a reduction of Tat-induced expression of TNFα, IL-6, iNOS and SERT.

Conclusion

These data establish that Tat induces IDO expression via an IFNγ-independent mechanism that depends upon activation of p38 MAPK. Targeting IDO itself or the p38 MAPK signaling pathway could provide a novel therapy for comorbid depressive disorders in HIV-1-infected patients.

Intrahypothalamic injection of the HIV-1 envelope glycoprotein induces fever via interaction with the chemokine system

Wasting syndrome is a common complication of HIV infection and is marked by progressive weight loss and weakness, often associated with fever. The mechanisms involved in the pathogenesis of these syndromes are not well defined, and neither are the brain areas involved. The present study tests a new hypothesis: that the preoptic anterior hypothalamus (POAH), the main brain area for thermoregulation and fever, has a role in the pathogenesis of fever induced by glycoprotein 120 (gp120), the surface envelope protein used by the HIV to gain access into immune cells, and that the CXC chemokine receptors (CXCR4) that serve as a coreceptor for HIV entry mediate the effect. A sterilized stainless steel C313G cannula guide was implanted into the POAH, and a biotelemetry system was used to monitor the body temperature (Tb) changes. The administration of gp120 into the POAH induced fever in a dose-dependent manner. To demonstrate possible links between the gp120 and CXCR4 in generating the fever, we pretreated the rats with 1,1'-[1,4-phenylenebis(methylene)]bis[1,4,8,11-tetraazacyclotetradecane] octohydrobromide dihydrate (AMD 3100), an antagonist of stromal cell-derived growth factor (SDF)-1alpha/CXCL12, acting at its receptor, CXCR4, 30 min before administration of gp120. AMD 3100 significantly reduced the gp120-induced fever. The present studies show that the presence of HIV-1 envelope glycoprotein gp120 in the POAH provokes fever via interaction CXCR4 pathway.

Interleukin-1 (IL-1): a central regulator of stress responses

Ample evidence demonstrates that the pro-inflammatory cytokine interleukin-1 (IL-1), produced following exposure to immunological and psychological challenges, plays an important role in the neuroendocrine and behavioral stress responses. Specifically, production of brain IL-1 is an important link in stress-induced activation of the hypothalamus-pituitary-adrenal axis and secretion of glucocorticoids, which mediate the effects of stress on memory functioning and neural plasticity, exerting beneficial effects at low levels and detrimental effects at high levels. Furthermore, IL-1 signaling and the resultant glucocorticoid secretion mediate the development of depressive symptoms associated with exposure to acute and chronic stressors, at least partly via suppression of hippocampal neurogenesis. These findings indicate that whereas under some physiological conditions low levels of IL-1 promote the adaptive stress responses necessary for efficient coping, under severe and chronic stress conditions blockade of IL-1 signaling can be used as a preventive and therapeutic procedure for alleviating stress-associated neuropathology and psychopathology.

Interleukin-6 as a mechanism for the adverse effects of social stress on acute Theiler's virus infection

Prior exposure to social disruption stress (SDR) exacerbates both the acute and chronic phase of Theiler's murine encephalomyelitis virus infection (TMEV; [Johnson, R.R., Storts, R., Welsh, T.H., Jr., Welsh, C.J., Meagher, M.W., 2004. Social stress alters the severity of acute Theiler's virus infection. J. Neuroimmunol. 148, 74--85; Johnson, R.R., Prentice, T.W., Bridegam, P., Young, C.R., Steelman, A.J., Welsh, T.H., Welsh, C.J.R., Meagher, M.W., 2006. Social stress alters the severity and onset of the chronic phase of Theiler's virus infection. J. Neuroimmunol. 175, 39--51]). However, the neuroimmune mechanism(s) mediating this effect have not been determined. The present study examined whether stress-induced increases in the proinflammatory cytokine interleukin-6 (IL-6) contributes to the adverse effects of SDR on acute TMEV infection. Experiment 1 demonstrated that SDR increases central and peripheral levels of IL-6 and that this effect is reversed by intracerebral ventricular infusion of neutralizing antibody to IL-6 prior to each of six SDR sessions. Although SDR reduced the sensitivity of spleen cells to the anti-inflammatory effects of corticosterone, the neutralizing antibody to IL-6 did not alter this effect. To investigate whether stress-induced increases in IL-6 contribute to the exacerbation of acute TMEV infection, Experiment 2 examined whether intracerebral administration of neutralizing antibody to IL-6 during SDR would prevent the subsequent exacerbation of acute TMEV infection. Experiment 3 then replaced the social stress with intracerebral infusion of IL-6 to assess sufficiency. As expected, prior exposure to SDR subsequently increased infection-related sickness behaviors, motor impairment, CNS viral titers, and CNS inflammation. These deleterious effects of SDR were either prevented or significantly attenuated by intracerebral infusion of neutralizing antibody to IL-6 during the stress exposure period. However, infusion of IL-6 alone did not mimic the adverse effects of SDR. We conclude that IL-6 is necessary but not sufficient to exacerbate acute TMEV infection.

Spontaneous pain following spinal nerve injury in mice

Autotomy behavior is frequently observed in rats and mice in which the nerves of the hindlimb are severed, denervating the paw. This is the neuroma model of neuropathic pain. A large body of evidence suggests that this behavior reflects the presence of spontaneous dysesthesia and pain. In contrast, autotomy typically does not develop in partial nerve injury pain models, leading to the belief that these animals develop hypersensibility to applied stimuli (allodynia and hyperalgesia), but not spontaneous pain. We have modified the widely used Chung (spinal nerve ligation [SNL]) model of neuropathic pain in a way that retains the fundamental neural lesion, but eliminates nociceptive sensory cover of the paw. These animals performed autotomy. Moreover, the heritable across strains predisposition to spontaneous pain behavior in this new proximal denervation model (SNN) was highly correlated with pain phenotype in the neuroma model suggesting that the pain mechanism in the two models is the same. Relative reproducibility of strain predispositions across laboratories was verified. These data indicate that the neural substrate for spontaneous pain is present in the Chung-SNL model, and perhaps in the other partial nerve injury models as well, but that spontaneous pain is not expressed as autotomy in these models because there is protective nociceptive sensory cover.

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.

Aging sensitizes mice to behavioral deficits induced by central HIV-1 gp120

The number of older adults with HIV-1 disease is increasing but little is known about how age influences behavioral deficits associated with HIV-1 infection. The purpose of this study was to determine in a murine model if aging influenced sickness behavior following central injection of HIV-1 gp120. In initial studies, behavioral deficits induced by acute and repeated intracerebroventricular (ICV) injection of gp120 were greater in aged mice than in adults. Furthermore, repeated ICV injection of gp120 increased hippocampal levels of IL-1 beta and IL-6 mRNA in aged mice but not in adults. To determine if IL-6, which is elevated in aged brain, affects expression of the gp120-binding target, CCR5, microglia (BV-2 cell line) were incubated with increasing concentrations of IL-6. Cell surface expression of CCR5 was increased by IL-6 in a dose-dependent manner. Additionally, IL-6 increased gp120-dependent chemotaxis. These results suggest that aging increases the sensitivity of mice to behavioral deficits caused by ICV gp120, perhaps by increasing expression of CCR5 and augmenting production of cytokines.

Sex-dependent effects of chronic restraint stress during early Theiler's virus infection on the subsequent demyelinating disease in CBA mice

Chronic restraint stress, administered during early infection with Theiler's virus, was found to exacerbate the acute CNS viral infection in male and female mice. During the subsequent demyelinating phase of disease (a model of multiple sclerosis), the effect of stress on disease progression was sex-dependent. Previously stressed male mice had less severe behavioral signs of the chronic phase, better rotarod performance and decreased inflammatory lesions of the spinal cord, while the opposite pattern was observed in females. In addition, mice in all groups developed autoantibodies to MBP, PLP139-151 and MOG33-55.

RANTES, MDC and SDF-1α, prevent the HIVgp120-induced food and water intake decrease in rats

Human immunodeficiency virus (HIV)-wasting syndrome might be facilitated by the HIVgp120 affecting the immunological system. We studied the effect (subchronic administration: 5 days) of HIVgp120, and a few immune-response mediators: regulated upon activation normal T-cell expressed and presumably secreted (RANTES), stromal derived factor-1alpha (SDF-1alpha), macrophage-derived chemokine (MDC), and their combination, on food and water intake in rats, motor control and pain perception. Eighty male adult Wistar rats received an intracerebroventricular (icv) administration of: vehicle 5 microl/day or 0.92 nmol daily of HIVgp120IIIB, RANTES, SDF-1alpha, or MDC, and the combination of RANTES+HIVgp120IIIB, SDF-1alpha+HIVgp120IIIB, or MDC+HIVgp120IIIB. Food and water intake was measured every day during administration, and 24 and 48 h after the last administration. Rats were also weighed the first and the last day of experiment in order to detect the impact of these treatments in the body weight. HIVgp120IIIB significantly decreased food and water intake. These rats gain less weight than the control (vehicle) and chemokines-treated subjects with exception of those treated with SDF-1alpha that also gain less weight. In addition, HIVgp120 deteriorated motor control. HIVgp120IIIB effects on food and water intake, and motor control were prevented by these chemokines. HIVgp120+RANTES, HIVgp120+SDF-1alpha, and SDF-1alpha alone induced hyperalgesia. Results suggest an interaction between HIVgp120 and the chemokine system to generate the HIV-wasting syndrome, the motor abnormalities and changes in pain perception.

Rodent model systems for studies of HIV-1 associated dementia

Understanding of HIV-1 neuropathogenesis and development of rationale therapeutic approaches requires relevant animal models. The putative mechanisms of neuroinflammatory and neurotoxic events triggered by HIV-1 brain infection are reflected by a number of rodent models. These include transgenic animals (either expressing viral proteins or pro-inflammatory factors), infection with murine retroviruses, and severe combined immunodeficient (SCID) mice reconstituted with human lymphocytes and injected intracerebrally with HIV-1-infected human monocyte-derived macrophages. The potential importance and limitations of the models in reflecting human disease are discussed with emphasis on their utility for development of therapies to combat HIV-1-associated neurologic impairment.

Immune modulation of the hypothalamic-pituitary-adrenal (HPA) axis during viral infection

Compelling data has been amassed indicating that soluble factors, or cytokines, emanating from the immune system can have profound effects on the neuroendocrine system, in particular the hypothalamic- pituitary-adrenal (HPA) axis. HPA activation by cytokines (via the release of glucocorticoids), in turn, has been found to play a critical role in restraining and shaping immune responses. Thus, cytokine-HPA interactions represent a fundamental consideration regarding the maintenance of homeostasis and the development of disease during viral infection. Although reviews exist that focus on the bi-directional communication between the immune system and the HPA axis during viral infection (188,235), others have focused on the immunomodulatory effects of glucocorticoids during viral infection (14,225). This review, however, concentrates on the other side of the bi-directional loop of neuroendocrine-immune interactions, namely, the characterization of HPA axis activity during viral infection and the mechanisms employed by cytokines to stimulate glucocorticoid release.

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.

Chronic restraint stress during early Theiler's virus infection exacerbates the subsequent demyelinating disease in SJL mice

Chronic restraint stress, administered during early infection with Theiler's virus, was found to exacerbate the acute central nervous system (CNS) viral infection and the subsequent demyelinating phase of disease (an animal model of Multiple Sclerosis (MS)) in SJL male and female mice. During early infection, stressed mice displayed decreased body weights and spontaneous activity; while increased behavioral signs of illness and plasma corticosterone (CORT) levels. During the subsequent chronic demyelinating phase of disease, previously stressed mice had greater behavioral signs of the chronic phase, worsened rotarod performance, and increased inflammatory lesions of the spinal cord. In addition, mice developed autoantibodies to myelin basic protein (MBP), proteolipid protein peptide (PLP139-151), and myelin oligodendrocyte glycoprotein peptide (MOG33-55).

Endotoxin-induced changes in food consumption in healthy volunteers are associated with TNF-alpha and IL-6 secretion

This study examined the effects of endotoxin administration on food and water consumption in humans, and the associations between these changes and endotoxin-induced secretion of cytokines, cortisol, and fever. Twenty healthy male volunteers received an i.v. injection of Salmonella abortus equi endotoxin (0.8 ng/kg) or saline in two experimental sessions. Blood samples were collected hourly, and rectal temperature was monitored continuously. Food consumption was significantly reduced at 0-4 h and significantly elevated at 4-5 h after the endotoxin injection. Endotoxin administration had no significant effect on water consumption. Endotoxin-induced secretion of TNF-alpha and IL-6 was positively associated with the decrease in food consumption (r=0.61 and 0.68), and negatively associated with the rebound increase in food consumption (r=-0.53 and -0.45). Neither the febrile response, nor the secretion of cortisol was associated with the changes in food consumption. These results suggest that TNF-alpha and IL-6 are involved in endotoxin-induced anorexia in humans.

Involvement of brain cytokines in the neurobehavioral disturbances induced by HIV-1 glycoprotein120

Intracerebroventricular (i.c.v.) administration of HIV-1 glycoprotein 120 (gp120), the envelope protein used by the virus to gain access into immune cells, induces neurobehavioral alterations in rats. To examine the role of proinflammatory cytokines in mediating these effects, we measured the effects of gp120 on brain proinflammatory cytokine expression and the effects of anti-inflammatory agents, including interleukin-1 receptor antagonist (IL-1ra), pentoxifylline (a TNFalpha synthesis blocker) and IL-10, on gp120-induced sickness behavior. I.c.v. administration of gp120 induced the expression of IL-1beta, but not TNFalpha, mRNA in the hypothalamus, 3 h after the injection. Pretreatment of rats with IL-1ra, but not with pentoxifylline, significantly attenuated gp120-induced anorexia and loss in body weight, whereas both agents had no effect on gp120-induced reduction in locomotor activity in the open field. Pretreatment with either IL-1ra and pentoxifylline simultaneously, or with IL-10, produced effects that were similar to the effects of IL-1ra alone. Together, these findings indicate that IL-1, but not TNFalpha, mediates some of the behavioral effects of acute gp120 administration, suggesting that brain IL-1 may be involved in some of the neurobehavioral abnormalities evident in AIDS patients.