Neuroendocrine-immune disturbances in animal models with spontaneous autoimmune diseases

Elevated Salivary Alpha-Amylase Level, Association Between Depression and Disease Activity, and Stress as a Predictor of Disease Flare in Systemic Lupus Erythematosus: A Prospective Case-Control Study

Psychological stress has been shown to trigger systemic lupus erythematosus (SLE). However, objective evidence of symptom aggravation due to mental stress is difficult to identify. We aimed to investigate the relationship between SLE disease activity and mental stress, and the usefulness of saliva as an assessment index for stress in patients with SLE.We prospectively assessed the salivary stress hormone and disease-related biomarkers, and questionnaire data regarding stress and depression in 100 patients with SLE and 49 sex- and age-matched normal controls (NCs).Patients with SLE had higher mean salivary α-amylase levels (5.7 ± 4.6 U/mL vs 2.7 ± 2.5 U/mL, P < 0.001), anti-chromatin antibody levels (25.3 ± 22.9 U/mL vs 15.9 ± 10.9 U/mL, P < 0.001), and Beck Depression Index (BDI) scores (11.1 ± 9.2 vs 5.3 ± 5.1, P < 0.001) than NCs. However, salivary cortisol levels and Perceived Stress Scale (PSS) scores did not differ between the groups. The BDI scores correlated with the SLE disease activity index (SLEDAI) scores (r = 0.253, P = 0.011) and erythrocyte sedimentation rates (r = 0.234, P = 0.019). SLE patients with the highest-quartile PSS scores had significantly increased SLEDAI scores compared to those with the lowest-quartile PSS scores after 4 to 5 months' follow-up. Moreover, SLE patients with elevated SLEDAI scores had higher baseline PSS scores.Patients with SLE showed uncoupling of the sympathetic nervous system and hypothalamic-pituitary-adrenal axis; higher salivary α-amylase and no different cortisol levels compared with NCs. Also, patients with SLE were more depressed, which correlated with disease activity. Furthermore, perceived stress was not correlated with disease activity; however, disease activity worsened several months later with elevated perceived stress levels.

Hepatic expression of metallothionein I/II, glycoprotein 96, IL-6, and TGF- β in rat strains with different susceptibilities to experimental autoimmune encephalomyelitis

In a search of peripheral factors that could be responsible for the discrepancy in susceptibility to EAE in Albino Oxford (AO) and Dark Agouti (DA) rats, we estimated the expression of metallothioneins I/II (MT), heat shock protein-gp96, interleukin (IL)-6, and transforming growth factor (TGF)-β in the livers of these animals. Rats were immunized with bovine brain homogenate (BBH) emulsified in complete Freund adjuvant (CFA) or only with CFA. Western blot and immunohistochemical analyses were done on day 12 after the immunization, as well as in intact rats. The data have shown that during the first attack of EAE only the EAE prone-DA rats markedly upregulated the hepatic MTs, gp96, IL-6, and TGF-β. In contrast, AO rats had a significantly higher expression of MT I/II, IL-6, and TGF-β in intact liver (P < 0,001), suggesting that the greater constitutive expression of these proteins contributed to the resistance of EAE. Besides, since previously we found that AO rats reacted on immunization by an early upregulation of TGF-β on several hepatic structures (vascular endothelium, Kupffer cells, and hepatocytes), the data suggest that the specific hepatic microenvironment might contribute also to the faster recovery of these rats from EAE.

Metallothioneins I/II expression in rat strains with genetically different susceptibility to experimental autoimmune encephalomyelitis

OBJECTIVES

Compared to the Dark Agouti (DA), the Albino Oxford (AO) rat strain exhibits lower susceptibility to the induction of experimental autoimmune encephalomyelitis (EAE). Here, we investigated the potential contribution of the heavy metal-binding proteins metallothioneins (MTs) I/II to these effects.

METHODS

Rats were immunized with bovine brain homogenate emulsified in complete Freund's adjuvant or only with complete Freund's adjuvant. The expression patterns of MTs mRNA and proteins and tissue concentrations of Zn2+ and Cu2+ were estimated in the brain and in the liver on days 7 and 12 after immunization, by real-time PCR, immunohistochemistry and inductively coupled plasma spectrometry, respectively. Additionally, the hepatic transforming growth factor beta and nuclear factor kappa B immunoreactivities were tested.

RESULTS

Clinical signs of EAE were not induced in AO rats, but they upregulated the expression of MT I/II proteins in the brain (hippocampus and cerebellum) and in the liver, similarly as DA rats. The transcriptional activation of MT-I occurred, however, only in DA rats, which accumulated also more zinc in the brain and in the liver. In contrast, intact AO rats had greater hepatic MT-I mRNA immunoreactivity and more Cu2+ in the hippocampus. Besides, in immunized AO rats a high upregulation of transforming growth factor beta and nuclear factor kappa B immunoreactivities was found in several hepatic structures (vascular endothelium, Kupffer cells and hepatocytes).

CONCLUSIONS

Our data show that AO and DA rats differ in constitutive and inductive MT-I gene expression in the brain and in the liver, as well as in the hepatic cytokine profile, suggesting that these mechanisms may contribute to the discrepancy in the susceptibility to EAE.

A hassle a day may keep the pathogens away: The fight-or-flight stress response and the augmentation of immune function

Stress is known to suppress or dysregulate immune function and increase susceptibility to disease. Paradoxically, the short-term fight-or-flight stress response is one of nature's fundamental defense mechanisms that galvanizes the neuroendocrine, cardiovascular, and musculoskeletal systems into action to enable survival. Therefore, it is unlikely that short-term stress would suppress immune function at a time when it may be critically required for survival (e.g., in response to wounding and infection by a predator or aggressor). In fact, studies have shown that stress can enhance immune function under certain conditions. Several factors influence the direction (enhancing versus suppressive) of the effects of stress on immune function: (1) DURATION: acute or short-term stress experienced at the time of activation of an immune response enhances innate and adaptive immune responses. Chronic or long-term stress can suppress or dysregulate immune function. (2) Leukocyte distribution: compartments (e.g., skin), that are enriched with immune cells during acute stress show immuno-enhancement, while those that are depleted of leukocytes (e.g., blood), show immuno-suppression. (3) The differential effects of physiologic versus pharmacologic stress hormones: Endogenous hormones in physiological concentrations can have immuno-enhancing effects. Endogenous hormones at pharmacologic concentrations, and synthetic hormones, are immuno-suppressive. (4) Timing: immuno-enhancement is observed when acute stress is experienced during the early stages of an immune response while immuno-suppression may be observed at late stages. The type of immune response (protective, regulatory/inhibitory, or pathological) that is affected determines whether the effects of stress are ultimately beneficial or harmful for the organism. Arguments based on conservation of energy have been invoked to explain potential adaptive benefits of stress-induced immuno-suppression, but generally do not hold true because most mechanisms for immuno-suppression expend, rather than conserve, energy. We propose that it is important to study, and if possible, to clinically harness, the immuno-enhancing effects of the acute stress response that evolution has finely sculpted as a survival mechanism, just as we study its maladaptive ramifications (chronic stress) that evolution has yet to resolve.

Aberrancies in Antigen-presenting Cells and T Cells in Autoimmune Thyroid Disease. A Role in Faulty Tolerance Induction

Various thyrocyte, monocyte, macrophage, DC and T cell abnormalities exist in the animal models of spontaneously developing autoimmune thyroiditis and in patients with autoimmune thyroid disease. An aberrant interaction between such abnormal thyrocytes, abnormal professional antigen-presenting cells (APC) and abnormal T cells forms the basis for the atypical autoimmune reaction targeting thyroid antigens. In the atypical interaction more than one gene and various environmental factors are involved. The genetic and environmental factors must act together to induce full-blown disease. Although there is a general blueprint for the development of destructive autoimmune thyroiditis, thyrocyte and immune cell abnormalities differ between the various animal models and the various forms of autoimmune thyroid disease (either associated with type 1 diabetes, associated with bipolar disorder or not associated). This tells us that there are different etio-pathogenic forms of destructive autoimmune thyroiditis. Whether such heterogeneity is also the case for the etio-pathogenesis of Graves' disease remains unknown. Animal models of spontaneously developing Graves' disease would be helpful in unraveling this question. If indeed there are various etio-pathogenic routes in different patients that lead to destructive autoimmune thyroiditis, then tailor-made therapeutic approaches need to be carried out in attempts to correct the underlying immune abnormalities in individual patients or to prevent the development of destructive autoimmune thyroiditis in individuals at risk. While in some forms of destructive autoimmune thyroiditis (f.i. those associated with bipolar disorder) immune suppression should be the first choice of intervention, other forms (f.i. those associated with type 1 diabetes) may benefit from immune stimulation in certain pre-stages of the disease (to restore f.i. the faulty APC function characteristic of this condition). Obviously a more precise determination of the spectrum of cell-mediated immune abnormalities is required in individual cases of destructive autoimmune thyroiditis, before therapies that aim at correcting the immune abnormalities can be tested successfully.

Enhancing versus suppressive effects of stress on immune function: implications for immunoprotection and immunopathology

Stress is known to suppress immune function and increase susceptibility to infections and cancer. Paradoxically, stress is also known to exacerbate asthma, and allergic, autoimmune and inflammatory diseases, although such diseases should be ameliorated by immunosuppression. Moreover, the short-term fight-or-flight stress response is one of nature's fundamental defense mechanisms that enables the cardiovascular and musculoskeletal systems to promote survival, and it is unlikely that this response would suppress immune function at a time when it is most required for survival (e.g. in response to wounding and infection by a predator or aggressor). These observations suggest that stress may suppress immune function under some conditions while enhancing it under others. The effects of stress are likely to be beneficial or harmful depending on the type (immunoprotective, immunoregulatory/inhibitory, or immunopathological) of immune response that is affected. Studies have shown that several critical factors influence the direction (enhancing vs. suppressive) of the effects of stress or stress hormones on immune function: (1) Duration (acute vs. chronic) of stress: Acute or short-term stress experienced at the time of immune activation can enhance innate and adaptive immune responses. Chronic or long-term stress can suppress immunity by decreasing immune cell numbers and function and/or increasing active immunosuppressive mechanisms (e.g. regulatory T cells). Chronic stress can also dysregulate immune function by promoting proinflammatory and type-2 cytokine-driven responses. (2) Effects of stress on leukocyte distribution: Compartments that are enriched with immune cells during acute stress show immunoenhancement, while those that are depleted of leukocytes, show immunosuppression. (3) The differential effects of physiologic versus pharmacologic concentrations of glucocorticoids, and the differential effects of endogenous versus synthetic glucocorticoids: Endogenous hormones in physiological concentrations can have immunoenhancing effects. Endogenous hormones at pharmacologic concentrations, and synthetic hormones, are immunosuppressive. (4) The timing of stressor or stress hormone exposure relative to the time of activation and time course of the immune response: Immunoenhancement is observed when acute stress is experienced at early stages of immune activation, while immunosuppression may be observed at late stages of the immune response. We propose that it is important to study and, if possible, to clinically harness the immunoenhancing effects of the acute stress response, that evolution has finely sculpted as a survival mechanism, just as we study its maladaptive ramifications (chronic stress) that evolution has yet to resolve. In view of the ubiquitous nature of stress and its significant effects on immunoprotection as well as immunopathology, it is important to further elucidate the mechanisms mediating stress-immune interactions and to meaningfully translate findings from bench to bedside.

Could single-nucleotide polymorphisms (SNPs) affecting the tumour necrosis factor promoter be considered as part of rheumatoid arthritis evolution?

Tumour necrosis factor (TNF), a cytokine mainly produced by macrophages, is associated with a broad spectrum of biological effects, mainly associated with the host defense against microbes. The TNF gene is located on chromosome six within the major histocompatibility complex (MHC). Rheumatoid arthritis (RA) is a systemic autoimmune disease where TNF plays a central role in its etiology and pathogenesis. Written medical evidence of RA can be traced at least as far back as the 17th century, while human paleopathological studies appear to show the presence of RA prior to this period. The fact that RA has experienced an increment both in severity and mortality could be explained by many causes, particularly the crucial role of the immune system. Single-nucleotide polymorphisms (SNPs) are the most common genetic variations and occur at a frequency of approximately 1 in 1000 bp throughout the genome. The -308 TNF SNP is a mutation that affects the promoter region of the TNF gene. It defines the TNF1 and TNF2 alleles, determining low and high levels of TNF expression, respectively. The presence of the TNF2 allele has also been linked to increased susceptibility to and severity in a variety of autoimmune and inflammatory disorders, including RA, systemic lupus erythematosus, and ankylosing spondylitis. Studies on the functional significance of -308 SNP have detected higher levels of TNF production by cells from TNF2-carrying individuals than cells from TNF1 individuals. This difference does not appear to be due to other genes lying within the MHC region. Since the presence of the TNF2 allele may increase the host's resistance to local infection, by increasing local production of TNF at the infection site, we may suggest that such a mutation has emerged as a selective advantage to carriers of the TNF2 allele. This hypothesis may prove itself by observing the high incidence of tuberculosis and other infectious processes in those patients treated with anti-TNF therapy. Since the human lifespan has increased, the persistence of the TNF2 allele at high frequency in the population now confers what appears to be a marked survival disadvantage. As a result of the disregulation of the immune system, the genetically-predisposed host expresses larger amounts of TNF, leading to chronic inflammatory processes and autoimmune diseases, currently more prevalent. We suggest that RA, a relatively new and increasingly frequent disease, is favored by the presence of the -308 TNF promoter polymorphism, responsible for increased TNF production.

Brain-immune interactions and disease susceptibility

Many studies have established the routes by which the immune and central nervous (CNS) systems communicate. This network of connections permits the CNS to regulate the immune system through both neuroendocrine and neuronal pathways. In turn, the immune system signals the CNS through neuronal and humoral routes, via immune mediators and cytokines. This regulatory system between the immune system and CNS plays an important role in susceptibility and resistance to autoimmune, inflammatory, infectious and allergic diseases. This review focuses on the regulation of the immune system via the neuroendocrine system, and underlines the link between neuroendocrine dysregulation and development of major depressive disorders, autoimmune diseases and osteoporosis.

Induction of experimental allergic encephalomyelitis in a low-susceptible Albino Oxford rat strain by somatostatin analogue SMS 201-995

OBJECTIVE

The effect of the somatostatin analogue SMS 201-995 (octreotide; OCT) on the course of experimental allergic encephalomyelitis (EAE) in the relatively resistant Albino Oxford (AO) strain of rats was studied.

METHODS

Animals were actively immunized with bovine brain homogenate in complete Freund's adjuvant. OCT was given subcutaneously in the hind legs on days 7, 8 and 9 after immunization, at a dose of 3 x 5 microg/kg/day. Rats in control groups were treated with saline or were left untreated. EAE was scored clinically and immunophenotypically, estimating by flow cytometry the changes in the popliteal lymph nodes (PLN) and spleen and monitoring immunohistologically the brain sections of rats recovered from disease.

RESULTS

In control AO rats, EAE was induced in only 2 of 22 rats (9%). In OCT-treated rats, however, EAE developed in 11 of 20 rats (55%), in comparison with 3 of 17 saline-treated animals (17%) (p <0.05). In PLN of OCT-treated rats during the clinical course of EAE, a decreased proportion of OX8+ cells was seen, followed by increases in OX39+ and W3/25+ cells on days 17 and 26. In spleen, OCT decreased the proportion of OX1+, OX39+ and OX8+ cells (on days 12 and/or 17), and increased the proportion of OX39+ cells on days 26 and 31. In the brain sections of saline-treated rats recovered from EAE, numerous Mac-1+, Mac-3+ and OX8+ cells were found. These cells were, however, absent in OCT-treated rats; instead, several W3/25+ cells were noticed.

CONCLUSIONS

These data imply that OCT increases the susceptibility of AO rats to EAE, interfering with specific and/or nonspecific defense mechanisms operating in both the initial and recovery phase of EAE.

Novel repression of the glucocorticoid receptor by anthrax lethal toxin

Death from anthrax has been reported to occur from systemic shock. The lethal toxin (LeTx) is the major effector of anthrax mortality. Although the mechanism of entry of this toxin into cells is well understood, its actions once inside the cell are not as well understood. LeTx is known to cleave and inactivate MAPKKs. We have recently shown that LeTx represses the glucocorticoid receptor (GR) both in vitro and in vivo. This repression is partial and specific, repressing the glucocorticoid, progesterone, and estrogen receptor alpha, but not the mineralocorticoid or estrogen receptor beta. This toxin does not affect GR ligand or DNA binding, and we have suggested that it may function by removing/inactivating one or more of the many cofactors involved in nuclear hormone receptor signaling. Although the precise involvement of this nuclear hormone receptor repression in LeTx toxicity is unknown, examples of blunted HPA axis and glucocorticoid signaling in numerous autoimmune/inflammatory diseases suggest that such repression of critically important receptors could have deleterious effects on health.

Neuroendocrine regulation of immunity

A reciprocal regulation exists between the central nervous and immune systems through which the CNS signals the immune system via hormonal and neuronal pathways and the immune system signals the CNS through cytokines. The primary hormonal pathway by which the CNS regulates the immune system is the hypothalamic-pituitary-adrenal axis, through the hormones of the neuroendocrine stress response. The sympathetic nervous system regulates the function of the immune system primarily via adrenergic neurotransmitters released through neuronal routes. Neuroendocrine regulation of immune function is essential for survival during stress or infection and to modulate immune responses in inflammatory disease. Glucocorticoids are the main effector end point of this neuroendocrine system and, through the glucocorticoid receptor, have multiple effects on immune cells and molecules. This review focuses on the regulation of the immune response via the neuroendocrine system. Particular details are presented on the effects of interruptions of this regulatory loop at multiple levels in predisposition and expression of immune diseases and on mechanisms of glucocorticoid effects on immune cells and molecules.

Association of familial and sporadic rheumatoid arthritis with a single corticotropin-releasing hormone genomic region (8q12.3) haplotype

OBJECTIVE

Rheumatoid arthritis (RA) is a common disabling autoimmune disease with a complex genetic component. We have previously described linkage of a region of chromosome 8q12.3 with RA and association of the microsatellite marker CRHRA1 with RA in 295 affected sibling-pair families. In the current study we aimed to physically link the RA-associated marker with the corticotropin-releasing hormone (CRH) candidate gene, and to examine the genomic region for additional short tandem repeat (STR) genetic markers in order to clarify the association with RA.

METHODS

We examined the association of 2 STR markers with disease in the original 295 multicase families and in a cohort of 131 simplex families to refine our understanding of this genetic region in disease susceptibility in sporadic and familial RA. Genomic library screening and sequencing were used to generate physical sequences in the CRH genomic region. Bioinformatic analysis of the sequence flanking the CRH structural gene was used to screen for additional STRs and other genetic features. Genotyping was carried out using a standard fluorescence approach. Estimations of haplotype frequencies were performed to assess linkage disequilibrium. The transmission disequilibrium test was performed using TRANSMIT.

RESULTS

Physical cloning and sequencing analyses identified the genomic region linking the CRHRA1 marker and the CRH structural locus. Moreover, we identified a further STR, CRHRA2, which was in strong linkage disequilibrium with CRHRA1 (P = 4.0 x 10(-14)). A haplotype, CRHRA1*10;CRHRA2*14, was preferentially carried by unaffected parents at a frequency of 8.6% compared with the expected frequency of 3.1%. This haplotype was overtransmitted in the multiply affected families (P = 0.0077) and, similarly, in the simplex families (P = 0.024). Combined analysis of both family cohorts confirmed significant evidence for linkage (P = 4.9 x 10(-4)) and association (P = 5.5 x 10(-3)) for this haplotype with RA.

CONCLUSION

In demonstrating significant linkage disequilibrium between these 2 markers, we have refined the disease-associated region to a single haplotype and confirmed the significance of this region in our understanding of the genetics of RA.

Glucocorticoids in T cell development and function*

Glucocorticoids are small lipophilic compounds that mediate their many biological effects by binding an intracellular receptor (GR) that, in turn, translocates to the nucleus and directly or indirectly regulates gene transcription. Perhaps the most recognized biologic effect of glucocorticoids on peripheral T cells is immunosuppression, which is due to inhibition of expression of a wide variety of activationinduced gene products. Glucocorticoids have also been implicated in Th lineage development (favoring the generation of Th2 cells) and, by virtue of their downregulation of fasL expression, the inhibition of activation-induced T cell apoptosis. Glucocorticoids are also potent inducers of apoptosis, and even glucocorticoid concentrations achieved during a stress response can cause the death of CD4(+)CD8(+ )thymocytes. Perhaps surprisingly, thymic epithelial cells produce glucocorticoids, and based upon in vitro and in vivo studies of T cell development it has been proposed that these locally produced glucocorticoids participate in antigen-specific thymocyte development by inhibiting activation-induced gene transcription and thus increasing the TCR signaling thresholds required to promote positive and negative selection. It is anticipated that studies in animals with tissue-specific GR-deficiency will further elucide how glucocorticoids affect T cell development and function.

Altered circadian rhythms of the stress hormone and melatonin response in lupus-prone MRL/MP-fas(Ipr) mice

The immune system interacts with the hypothalamo-pituitary-adrenal axis via so-called glucocorticoid increasing factors, which are produced by the immune system during immune reactions, causing an elevation of systemic glucocorticoid levels that contribute to preservation of the immune reactions specificities. Previous results from our laboratory had already shown an altered immuno-neuroendocrine dialogue via the hypothalamo-pituitary-adrenal axis in autoimmune disease-prone chicken and mouse strains. In the present study, we further investigated the altered glucocorticoid response via the hypothalamo-pituitary-adrenal axis in murine lupus. We established the circadian rhythms of corticosterone, dehydroepiandrosterone-sulfate, adrenocorticotropic hormone and melatonin, as well as the time response curves after injection of interleukin-1 of the first three parameters in normal SWISS and lupus-prone MRL/MP-fas(Ipr) mice. The results show that lupus-prone MRL/ MP-fas(Ipr) mice do not react appropriately to changes of the light/dark cycle, circadian melatonin rhythms seem to uncouple from the light/dark cycle, and plasma corticosterone levels are elevated during the resting phase. Diurnal changes of dehydroepiandrosterone-sulfate and adrenocorticotropic hormone were normal compared to healthy controls. These data indicate that MRL/ MP-fas(Ipr) mice not only show an altered glucocorticoid response mediated via the hypothalamo pituitary adrenal axis to IL-1, but are also affected by disturbances of corticosterone and melatonin circadian rhythms. Our findings may have implications for intrathymic T cell development and the emergence of autoimmune disease.

Animal models of neuroimmune interactions in inflammatory diseases

Animal models have been used successfully to study various aspects of neural-immune interactions. Although different approaches carry certain advantages and disadvantages, current high sensitivity screening and manipulation methods coupled with molecular and genetic approaches can be successfully used to tease out the neural pathways that regulate inflammatory disease and the effects of immune molecules, such as interleukins, on neuronal function and pathology. Newer methodologies that measure gene expression of thousands of genes will in the future add to the ability to evaluate complex systems interactions in whole animal models. This review addresses the advantages and disadvantages of some of these approaches in the context of application to neural-immune interactions.