Different approaches to understanding autoimmune rheumatic diseases: the neuroimmunoendocrine system

Do Early-Life Social, Behavioral, and Health Exposures Increase Later-Life Arthritis Incidence?

OBJECTIVES

This study investigates direct and indirect influences of childhood social, behavioral, and health exposures on later-life osteoarthritis and rheumatoid arthritis development.

METHODS

Drawing from cumulative inequality theory and six waves of the Health and Retirement Study (2004-2014), we estimate structural equation modeling-based discrete-time survival analysis of the association between six childhood exposure domains and both osteoarthritis and rheumatoid arthritis incidence for men (n = 2720) and women (n = 2974). Using the delta method to test for mediation, we examine indirect effects via selected health-related risks and resources.

RESULTS

Risky adolescent behavior is associated with rheumatoid arthritis incidence for women (h.O.R. = 1.883, 95% C.I. [1.016, 3.490]), whereas several types of childhood exposures are associated with later-life osteoarthritis development for both men and women. Experiencing two or more childhood socioeconomic disadvantages is indirectly associated with osteoarthritis (men: coef. = 0.024, 95% C.I. [0.003, 0.045]; women: coef. = 0.111, 95% C.I. [0.071, 0.150]) and rheumatoid arthritis (men: coef. = 0.037, 95% C.I. [0.000, 0.074]; women: coef. = 0.097, 95% C.I. [0.035, 0.159]) development through adult body mass index.

DISCUSSION

Findings highlight the importance of childhood contexts in understanding the development of later-life osteoarthritis and rheumatoid arthritis.

Gender-specific association between childhood trauma and rheumatoid arthritis: a case-control study

OBJECTIVE

Rheumatoid arthritis (RA) has been associated with a variety of emotional stressors, but findings remain inconclusive if RA is related to childhood trauma, which is known to have long-lasting negative consequences for physical health decades into adulthood. We investigated the association between childhood trauma and RA by comparing histories of child abuse and neglect between RA patients and adults from the general population in a cross-sectional case-control study.

METHODS

331 patients with definite RA and 662 gender- and age-matched adults from the general population were administered the self-report Childhood Trauma Questionnaire (CTQ) for the assessment of emotional, physical and sexual abuse as well as emotional and physical neglect.

RESULTS

Adjusting for gender and current depression, RA patients scored significantly higher in all CTQ subscales apart from sexual abuse and physical neglect than the controls. Adjusted odds ratios for these types of childhood trauma were higher in the RA group than in controls ranging from 2.0 for emotional neglect (95% confidence interval [CI]: 1.4-3.0) to 2.6 for emotional abuse (95% CI: 1.4-4.7). Gender-specific analyses revealed basically the same pattern for women, but not for men.

CONCLUSION

Our findings suggest an association between childhood trauma and development of RA, particularly in women. This relationship may be mediated by dysregulations of neuro-endocrine-immune networks, but larger prospective studies are needed to clarify the association between early life stress and the risk for RA in genetically susceptible individuals.

Stress-induced redistribution of immune cells--from barracks to boulevards to battlefields: a tale of three hormones--Curt Richter Award winner

BACKGROUND

The surveillance and effector functions of the immune system are critically dependent on the appropriate distribution of immune cells in the body. An acute or short-term stress response induces a rapid and significant redistribution of immune cells among different body compartments. Stress-induced leukocyte redistribution may be a fundamental survival response that directs leukocyte subpopulations to specific target organs during stress, and significantly enhances the speed, efficacy and regulation of an immune response. Immune responses are generally enhanced in compartments (e.g., skin) that are enriched with leukocytes, and suppressed in compartments that are depleted of leukocytes during/following stress. The experiments described here were designed to elucidate the: (1) Time-course, trajectory, and subpopulation-specificity of stress-induced mobilization and trafficking of blood leukocytes. (2) Individual and combined actions of the principal stress hormones, norepinephrine (NE), epinephrine (EPI), and corticosterone (CORT), in mediating mobilization or trafficking of specific leukocyte subpopulations. (3) Effects of stress/stress hormones on adhesion molecule, L-selectin (CD62L), expression by each subpopulation to assess its adhesion/functional/maturation status.

METHODS

Male Sprague Dawley rats were stressed (short-term restraint, 2-120 min), or adrenalectomized and injected with vehicle (VEH), NE, EPI, CORT, or their combinations, and blood was collected for measurement of hormones and flow cytometric quantification of leukocyte subpopulations.

RESULTS

Acute stress induced an early increase/mobilization of neutrophils, lymphocytes, helper T cells (Th), cytolytic T cells (CTL), and B cells into the blood, followed by a decrease/trafficking of all cell types out of the blood, except neutrophil numbers that continued to increase. CD62L expression was increased on neutrophils, decreased on Th, CTL, and natural killer (NK) cells, and showed a biphasic decrease on monocytes & B cells, suggesting that CD62L is involved in mediating the redistribution effects of stress. Additionally, we observed significant differences in the direction, magnitude, and subpopulation specificity of the effects of each hormone: NE increased leukocyte numbers, most notably CD62L⁻/⁺ neutrophils and CD62L⁻ B cells. EPI increased monocyte and neutrophil numbers, most notably CD62L⁻/⁺ neutrophils and CD62L⁻ monocytes, but decreased lymphocyte numbers with CD62L⁻/⁺ CTL and CD62L⁺ B cells being especially sensitive. CORT decreased monocyte, lymphocyte, Th, CTL, and B cell numbers with CD62L⁻ and CD62L⁺ cells being equally affected. Thus, naïve (CD62L⁺) vs. memory (CD62L⁻) T cells, classical (CD62L⁺) vs. non-classical (CD62L⁻) monocytes, and similarly distinct functional subsets of other leukocyte populations are differentially mobilized into the blood and trafficked to tissues by stress hormones.

CONCLUSION

Stress hormones orchestrate a large-scale redistribution of immune cells in the body. NE and EPI mobilize immune cells into the bloodstream, and EPI and CORT induce traffic out of the blood possibly to tissue surveillance pathways, lymphoid tissues, and sites of ongoing or de novo immune activation. Immune cell subpopulations appear to show differential sensitivities and redistribution responses to each hormone depending on the type of leukocyte (neutrophil, monocyte or lymphocyte) and its maturation/functional characteristics (e.g., non-classical/resident or classical/inflammatory monocyte, naïve or central/effector memory T cell). Thus, stress hormones could be administered simultaneously or sequentially to induce specific leukocyte subpopulations to be mobilized into the blood, or to traffic from blood to tissues. Stress- or stress hormone-mediated changes in immune cell distribution could be clinically harnessed to: (1) Direct leukocytes to sites of vaccination, wound healing, infection, or cancer and thereby enhance protective immunity. (2) Reduce leukocyte traffic to sites of inflammatory/autoimmune reactions. (3) Sequester immune cells in relatively protected compartments to minimize exposure to cytotoxic treatments like radiation or localized chemotherapy. (4) Measure biological resistance/sensitivity to stress hormones in vivo. In keeping with the guidelines for Richter Award manuscripts, in addition to original data we also present a model and synthesis of findings in the context of the literature on the effects of short-term stress on immune cell distribution and function.

The nongenomic effects of progesterone in repressing iNOS activation through P38MAPK pathways in gonococci-infected polymorphonuclear leukocytes and the clinical significance

Progesterone has nongenomic effects on inducible nitric oxide synthase (iNOS), which is mediated by mitogen activated protein kinase (MAPK) pathways. This effect is supposed to have some potential association with asymptomatic gonococcal infections in women by immunological depression. In this study, polymorphonuclear leukocytes (PMNs) challenged by gonococci were used to study the nongenomic effects of progesterone. The activation of iNOS was assessed by measuring [(3)H] L-arginine converses to [(3)H] L-citrulline, and the activity of MAPK was detected by Western blot. It was found that the activity of iNOS and the yields of NO were enhanced significantly in gonococci-challenged PMNs compared with the controls (P<0.01). Progesterone could repress the activation of iNOS through P38MAPK pathway within PMNs (P<0.05), which could be blocked by SB203580 (P<0.01), but not by actinomycin D (P>0.05). It was also found subsequently that in the serum specimens collected from gonococci-infected but asymptomatic women, the progesterone level was higher than that in women with severe symptoms (P<0.01). Moreover, the yield of NO had an inverse correlation with progesterone. With these results it suggested that the rapid nongenomic effects of progesterone may inhibit iNOS activation and NO yields mediated by P38MAPK pathways, which were supposed to be concerned with asymptomatic women infected with gonococci.

Characterization and pharmacological evaluation of febrile response on zymosan-induced arthritis in rats

The present study investigated the febrile response in zymosan-induced arthritis, as well as the increase in PGE2concentration in the cerebrospinal fluid (CSF), along with the effects of antipyretic drugs on these responses in rats. Zymosan intra-articularly injected at the dose of 0.5 mg did not affect the body core temperature (Tc) compared with saline (control), whereas at doses of 1 and 2 mg, zymosan promoted a flattened increase in Tc and declined thereafter. The dose of 4 mg of zymosan was selected for further experiments because it elicited a marked and long-lasting Tc elevation starting at 3 1/2 h, peaking at 5 1/2 h, and remaining until 10 h. This temperature increase was preceded by a decrease in the tail skin temperature, as well as hyperalgesia and edema in the knee joint. No febrile response was observed in the following days. In addition, zymosan-induced fever was not modified by the sciatic nerve excision. Zymosan increased PGE2concentration in the CSF but not in the plasma. Oral pretreatment with ibuprofen (5–20 mg/kg), celecoxib (1–10 mg/kg), dipyrone (60–240 mg/kg), and paracetamol (100–200 mg/kg) or subcutaneous injection of dexamethasone (0.25–1.0 mg/kg) dose-dependently reduced or prevented the fever during the zymosan-induced arthritis. Celecoxib (5 mg/kg), paracetamol (150 mg/kg), and dipyrone (120 mg/kg) decreased CSF PGE2concentration and fever during zymosan-induced arthritis, suggesting the involvement of PGE2in this response.

Inhibitory effects of progesterone differ in dendritic cells from female and male rodents

BACKGROUND

Steroid hormones, such as progesterone, are known to have immunomodulatory effects. Our research group previously reported direct effects of progesterone on dendritic cells (DCs) from female rodents. Primarily affecting mature DC function, progesterone effects included inhibition of proinflammatory cytokine secretion, downregulation of cell surface marker (major histocompatibility complex class II, CD80) expression, and decreased T-cell proliferative capacity, and were likely mediated through progesterone receptor (PR) because the PR antagonist RU486 reversed these effects.

OBJECTIVE

The goal of this study was to assess differences in response to progesterone by DCs from female and male rodents.

METHODS

Using real-time reverse-transcriptase polymerase chain reaction, transcriptional expression of steroid hormone receptors was measured in immature bone marrow-derived DCs (BMDCs) from male and female rats. Expression of steroid hormone receptor protein was also assessed in these cells using flow cytometry and fluorescence microscopy. To evaluate functional differences between BMDCs from female and male rats in response to the steroid hormone progesterone, levels of secreted cytokines were measured using enzyme-linked immunosorbent assay.

RESULTS

Higher numbers of immature BMDCs from males expressed glucocorticoid receptor (GR) and androgen receptor (AR) proteins compared with females (males vs females, mean [SD]: GR = 68.75 [7.27] vs 43.61 [13.97], P = NS; AR = 75.99 [15.38] vs 8.25 [1.88], P = 0.002), whereas higher numbers of immature BMDCs from females expressed PR protein compared with males (females vs males: PR = 74.19 [12.11] vs 14.14 [4.55], P = 0.043). These differences were not found at the level of transcription (females vs males: GR = 0.088 vs 0.073, P = NS; AR = 0.076 vs 0.069, P = NS; PR = 0.075 vs 0.065, P = NS). Compared with those from females, mature BMDCs from males produced higher quantities of cytokines (tumor necrosis factor-alpha [TNF-alpha], interleukin [IL]-1beta, IL-10) (females vs males: TNF-alpha = 920.0 [79.25] vs 1100.61 [107.97], P = NS; IL-1beta = 146.60 [38.04] vs 191.10 [10.47], P = NS; IL-10 = 167.25 [4.50] vs 206.15 [23.48], P = NS). Conversely, BMDCs from females were more sensitive to progesterone, as indicated by a more dramatic reduction in proinflammatory cytokine secretion (females vs males, highest concentration of progesterone: TNF-alpha = 268.94 [28.59] vs 589.91 [100.98], P = 0.04; IL-1beta = 119.50 [10.32] vs 154.35 [6.22], P = NS).

CONCLUSIONS

These findings suggest that progesterone effects on DCs in rodents may be more pronounced in females than in males, and this is likely due to differences in PR protein expression. Our observations may help elucidate disparities in the incidence and severity of autoimmune disorders between females and males, and the role specific steroid hormones play in regulating immune responses.

Neuroendocrine factors alter host defense by modulating immune function

An increasing body of evidence demonstrates that there is bidirectional communication between the neuroendocrine and immune systems. Interaction between these systems results in a variety of outcomes, including the well documented "sickness behavior" elicited by cytokines of the immune system that can enter the brain and activate second messengers that modify neuronal activity. Crosstalk between the neuroendocrine and immune systems can also result in production of factors by the nervous and endocrine systems that alter immune cell function and subsequent modulation of immune responses against infectious agents and other pathogens. Continued exposure to molecules produced by the neuroendocrine system has also been known to increase susceptibility and/or severity of disease. Furthermore, neuroendocrine factors are thought to play a major role in gender-specific differences in development of certain disorders, including autoimmune/inflammatory diseases that have a two to tenfold higher incidence in females compared to males. Neuroendocrine factors can affect immune cells at the level of gene transcription but have also been shown to modify immune cell activity by interacting with intracellular molecules, resulting in modified ability of these cells to mount a potent immune response. In this review, we will consider various effects of the neuroendocrine system and its proteins on specific populations of immune cells and associated responses in host immunity against pathogens. We will further discuss how this modification of immune cell activity by the neuroendocrine system can contribute to susceptibility/severity of disease development.

Evaluation of steroid hormone receptor protein expression in intact cells using flow cytometry

Several methods are currently employed to evaluate expression of steroid hormone receptors in tissues and cells, including real-time reverse-transcriptase polymerase chain reaction (real-time RT-PCR) and western blot assays. These methods require homogenization of cells, thereby preventing evaluation of individual cells or specific cell types in a given tissue sample. In addition, methods such as real-time RT-PCR assess mRNA levels, which may be subject to posttranslational modifications that prevent subsequent production of functional proteins. Flow cytometry is a fluorescence-based technique commonly used to evaluate expression of cell surface and intracellular proteins. This method is especially useful as it allows for single-cell analysis and can be utilized to determine the amount of receptor expressed by individual cells. Flow cytometry is commonly used to analyze immune cell activity and determine functionality based on changes in expression of cell surface molecules, as well as intracellular proteins (such as cytokines). Here, we describe a method to identify protein expression of steroid hormone receptors by rat leukocytes from different organs (spleen, liver and thymus) using flow cytometry. We examined expression of glucocorticoid receptor (GR), androgen receptor (AR) and progesterone receptor (PR) by cells at these sites and were able to demonstrate expression of receptors, as well as the intensity of expression of each receptor. This method is useful for rapid, high throughput measurement of steroid hormone receptors at the protein level in single, intact cells and would be valuable to determine which cells are more likely to respond to steroid hormone treatment.

An interaction between genetic factors and gender determines the magnitude of the inflammatory response in the mouse air pouch model of acute inflammation

The widely used mouse air pouch model of acute inflammation is inducible in a variety of inbred strains, but the potential influence of genetic background and gender on inflammation severity has never been examined. We directly compared the degree of inflammation induced in the air pouch model across four commonly utilized inbred strains in both male and female mice. We then applied an in silico mapping method to identify loci potentially associated with determining inflammation severity for each gender. Air pouches were induced by subcutaneous injection 3 (3 cc) and 5 (1.5 cc) days prior to the experiment. 4h after carrageenan injection, exudates were retrieved and leukocyte concentration quantified using a hemocytometer. The in silico mapping method was applied as described below. The strain order for mean leukocyte count/mL in inflamed exudates differed between genders. In males, the order was C57BL/6J > BALB/cByJ > DBA/2J > DBA/1J, while in females the order was BALB/cByJ > DBA/2J > C57BL/6J > DBA/1J. The difference in inflammation severity between genders reached significance only in C57BL/6J mice. Independent in silico analysis based on phenotypic data from male versus female mice identified distinct sets of loci as potentially associated with the exudate count reached. We conclude that the degree of inflammation induced in the mouse air pouch model of inflammation is strain-specific and, therefore, genetically based, and the pattern of interstrain differences is altered in male relative to female mice. The loci identified by in silico mapping likely contain genes with differential roles in determining this phenotype between genders.