Hormonal and immunologic risk factors for the development of rheumatoid arthritis: an integrative physiopathogenetic perspective

Unveiling the Nexus: Cellular Metabolomics Unravels the Impact of Estrogen on Nicotinamide Metabolism in Mitigating Rheumatoid Arthritis Pathogenesis

Rheumatoid arthritis (RA) is a metabolic joint disorder influenced by hormonal regulation, notably estrogen, which plays a cytoprotective role against inflammation. While estrogen's impact on RA pathogenesis has been studied, the altered metabolite expression under estrogen's influence remains unexplored. This study investigated the changes in the metabolome of synovial fibroblasts isolated from RA patients under 17β-estradiol (E2) using the liquid chromatography with tandem mass spectrometry (LC-MS/MS) approach followed by multivariate and biological pathway analysis along with in vitro validation. Results identified 3624 m/z, among which eight metabolites were significant (p < 0.05). Nicotinate and nicotinamide metabolism was found to be highly correlated with the treatment of E2, with metabolites NAD+ and 1-methynicotinamide (1-MNA) upregulated by E2 induction in RA-FLS. PharmMapper analysis identified potential gene targets of 1-MNA, which were further matched with RA gene targets, and thus, STAT1, MAPK14, MMP3, and MMP9 were concluded to be the common targets. E2 treatment affected the expression of these gene targets and ameliorated the development of oxidative stress associated with RA inflammation, which can be attributed to increased concentration of 1-MNA. Thus, an LC-MS/MS-based metabolomics study revealed the prominent role of estrogen in preventing inflammatory progression in RA by altering metabolite concentration, which can support its therapeutic capacity in remitting RA.

Why are women predisposed to autoimmune rheumatic diseases?

The majority of autoimmune diseases predominate in females. In searching for an explanation for this female excess, most attention has focused on hormonal changes - both exogenous changes (for example, oral contraceptive pill) and fluctuations in endogenous hormone levels particularly related to menstruation and pregnancy history. Other reasons include genetic differences, both direct (influence of genes on sex chromosomes) and indirect (such as microchimerism), as well as gender differences in lifestyle factors. These will all be reviewed, focusing on the major autoimmune connective tissue disorders: rheumatoid arthritis, systemic lupus erythematosus and scleroderma.

Estrogen receptor-beta is the predominant estrogen receptor subtype in normal human synovia

OBJECTIVE

Joint pain increases after menopause with more than 50% of woman suffering from arthralgies. Since pain and inflammation of joints originate from synovial tissue, we aimed to discover whether estrogen receptors are present in the human synovia.

METHODS

This in vitro study was performed on samples of human synovial tissue, obtained from pre- (n = 8) and postmenopausal woman (n = 11) and men (n = 5) following surgery due to traumatic lesions. Fresh synovial tissue specimens were assessed for the localization as well as the presence of estrogen receptor-alpha (ER alpha) and estrogen receptor-beta (ER beta) by means of immunohistochemistry, as well as Western blot and reverse transcriptase-polymerase chain reaction (RT-PCR), respectively.

RESULTS

ER beta protein and mRNA were found to be equally and highly expressed in synovial stroma and lining cells of all explants independent of sex or menopausal status. In contrast, weak ER alpha staining was localized in the synovial lining cells in only three of 24 explants. ER alpha protein was found to be weakly expressed in three of ten explants. ER alpha mRNA was found with highly variable amounts in seven of ten explants.

CONCLUSION

In view of our observation that ER beta but not ER alpha is expressed regularly in normal human synovia in high amounts, we propose that estrogen could play a significant role in synovial membrane function in women and men, operating preferably via the ER beta isoform.

Sex Hormones and Risks of Rheumatoid Arthritis and Developmental or Environmental Influences

Sex hormone relationships for onset risks of rheumatoid arthritis (RA) were analyzed in a nested case-control study, derived from a large community-based prospective cohort. A self-reported history of RA in a first-degree relative, heavy cigarette smoking, and positive rheumatoid factor (RF) were confirmed predictors of subsequent RA onset in this data set. In the 11 premenopausal onset cases, lower serum dehydroepiandrosterone sulfate levels were observed as was an imbalance in serum IL-1beta to IL-1ra levels; the latter was not observed in the 43 controls (CNs). In the 18 male cases, significantly higher serum cortisol was observed in the six cases with positive family history versus the 12 with a negative history. To the contrary, a small minority of the male cases had combined low serum cortisol and testosterone, which was not observed in the 72 CNs. Significant gender dimorphism was observed between the sex hormones and serum log RF titers as well as in the correlations of serum log testosterone and estradiol. Principal component analysis of multiply-imputed data sets extracted four uncorrelated components, which provided concordant neuroendocrine immune relationships to the previously investigated univariate and multivariate analyses. The literature on developmental and environmental influences on sex hormones and risks of RA was reviewed.

Integrated neuroendocrine immune risk factors in relation to rheumatoid arthritis: should rheumatologists now adopt a model of a multiyear, presymptomatic phase?

An integrative perspective of neuroendocrine immune (NEI) and related risk factors for the onset of rheumatoid arthritis (RA) is presented, based upon studies of the long-term presymptomatic phase. Besides the recognized genetic markers and familial predisposition, multiple immunological precursors of RA have been identified many years before the clinical onset of inflammatory manifestations. Rheumatoid factors and related antibodies occur in approximately one-half of presymptomatic susceptibles. Cigarette smoking in sufficient amount and duration is a major risk factor for RA, particularly for postmenopausal-onset women and for men. In premenopausal-onset RA, subtle insufficiency of adrenal cortical function is less well recognized. In such women, cytokine imbalance may also precede inflammatory onset of RA. In males alone, multiple hormonal and cytokine correlations were found many years before the onset of RA, implying long-term activation or perturbation of this NEI system. The proposed physiopathogenetic model of RA requires further controlled, prospective studies for validation of the multiyear presymptomatic phase of RA. Such studies promise to clarify the currently unknown causal and sequential chains in this enigmatic disease.

Rheumatoid Arthritis: Neuroendocrine Immune Integrated Physiopathogenetic Perspectives and Therapy

Current concepts of neuroendocrine immune (NEI) aspects of rheumatoid arthritis (RA) are reviewed and recent clinical trials of glucocorticoids and sex steroids are summarized. A novel physiopathogenetic perspective is presented. Data are provided of amplified NEI interactions and dysregulation, many years before symptomatic onset of RA. Chronic imbalances between the NEI, vascular endothelial, neural, and other vital counterregulatory intertwined networks are proposed to cause RA and influence its disease activity. Future research may reveal means of diminishing the onset risk as well as disease activity of RA by controlling these imbalances of NEI and other vital networks.

Tumor necrosis factor inhibits conversion of dehydroepiandrosterone sulfate (DHEAS) to DHEA in rheumatoid arthritis synovial cells: A prerequisite for local androgen deficiency

OBJECTIVE

Use of anti-tumor necrosis factor (anti-TNF) antibody therapy in rheumatoid arthritis (RA) has expanded our understanding of possible mechanisms by which this treatment reduces inflammation. Beyond its effects on local immune responses, anti-TNF treatment may also modulate the local hormone supply. Because androgens are thought to inhibit immune responses, their presence in inflamed tissue is an additional important antiinflammatory factor.

METHODS

We investigated conversion of the ubiquitous dehydroepiandrosterone sulfate (DHEAS), the biologically inactive precursor of DHEA, to the androgen DHEA in mixed synovial cells from patients with RA and patients with osteoarthritis (OA), making use of thin-layer chromatography and phosphorimaging. Using immunohistochemical analysis, we detected the key enzyme, steroid sulfatase.

RESULTS

DHEAS-to-DHEA conversion in synovial cells from patients with RA was significantly lower than that in synovial cells from patients with OA (mean +/- SEM 3.3 +/- 0.5% versus 6.0 +/- 0.9% of applied (3)H-DHEAS per 10(6) synovial cells; P = 0.042). In RA, but not in OA, the level of converted (3)H-DHEA was inversely correlated with the density of synovial macrophages (for RA, R(rank) = -0.725, P = 0.005; for OA, R(rank) = 0.069, P not significant [NS]) and T cells (for RA, R(rank) = -0.621, P = 0.024; for OA, R(rank) = 0.247, P NS). Double immunohistochemistry analysis revealed that steroid sulfatase was located mainly in synovial macrophages but was also observed in fibroblasts. Neutralization of TNF largely up-regulated the conversion of DHEAS to DHEA in RA, but not in OA. A similar neutralizing effect was observed with polyclonal human immunoglobulins; this effect is most probably mediated via TNF neutralization at low TNF concentrations.

CONCLUSION

These data indicate that TNF inhibits the conversion of DHEAS to DHEA in RA synovial cells. Because androgens are antiinflammatory mediators, TNF-induced inhibition of the local androgen supply is a supplementary proinflammatory factor. Consequently, anti-TNF strategies may also exert their positive effects by increasing tissue androgens.

Advances in understanding the genetic basis of rheumatoid arthritis and osteoarthritis: implications for therapy

Rheumatoid arthritis (RA) and osteoarthritis (OA) are polygenic diseases. Polymorphisms in candidate genes have been studied for possible association with susceptibility to disease development. Aside from HLA polymorphisms, of particular interest are those in genes encoding cytokines, signaling molecules, and enzymes involved in the production and catabolism of oxygen and nitrogen radicals. Cytokines are involved in the modulation of the pathological process and have been the target for novel therapeutic interventions. Evidence for their involvement in RA and OA has been provided from genetic analyses in patient populations as well as from animal models of disease. Intracellular signaling cascades control cellular responses and thus regulate many aspects of the pathology manifested in rheumatic diseases. Deciphering the organization and activity of such signaling pathways in disease is underway. Polymorphisms have been identified in gene promoter regions regulating efficient binding of transcription factors, and in coding regions of genes whose products are involved in signal cascades relevant to RA. Among these are the NF-kappaB pathway, steroid receptors and the p53 tumor suppressor gene. Both reactive oxygen species (ROS) and reactive nitrogen species (RNS) have also been implicated in rheumatic diseases. It is thought that excess, damaging, ROS/RNS may arise from an imbalance between the production and removal of these chemical species. Polymorphisms in genes that encode enzymes involved in either generating or degrading ROS/RNS may contribute to such an imbalance. In the last few years, polymorphisms in such genes have indeed been identified as risk factors for rheumatic diseases.

Perspectives on the relationship of adrenal steroids to rheumatoid arthritis

An expanded model of RA is presented that incorporates cumulative multifactorial processes operating over a prolonged physiological phase prior to initial clinical manifestations. During this phase, progressive imbalances in the homeostasis of core neuroendocrine, immunological, and microvascular systems are believed to occur. Normal adrenal function plays an essential role in helping to maintain homeostasis of core systems in health. In RA, chronic adrenal hypocompetence is suspected to occur in a minority subset of females who have younger clinical onset and males who have associated low serum testosterone levels. Chronic, relative glucocorticoid insufficiency is believed to contribute to development of inflammatory manifestations in RA patients. Androgenic deficiencies, particularly of gonadal origin in males, may also contribute to RA, particularly its decreased anabolic features. Precise influences of hypocompetent adrenal steroid function on long-term modeling of the immunological compartment and control of microvascular activation processes are not well understood. These complex mechanisms need to be elucidated for better understanding of the physiopathogenesis of RA. Nevertheless, at a clinical level, sufficient data are currently available to endorse further controlled studies of early clinical onset patients and prospective investigations to determine more definitively the roles of adrenal (and gonadal) steroids in subsets of RA patients and unaffected susceptible persons in the population.

Relationships between glucocorticoids and gonadal steroids in rheumatoid arthritis

Gender and sex hormones are strongly related to the incidence and progression of autoimmune rheumatic diseases. Although sex steroids have been shown to have direct effects on the immune system, their influence in vivo may be mediated via interactions with third party systems including the hypothalamic-pituitary-adrenal axis. Such interactions are well demonstrated in experimental animals. In humans, there is increasing, although indirect, evidence that these interactions also occur. Possible interactions at the cell and gene level, with mutual antagonism or synergy between cortico- and gonadal steroids, open new exciting hypotheses that await clarification.

Somatotropic, lactotropic and adrenocortical responses to insulin-induced hypoglycemia in patients with rheumatoid arthritis

Neuroendocrine mechanisms have been suggested to play an important role in the onset and progression of rheumatoid arthritis (RA). The aim of this study was to evaluate hypothalamic-pituitary functions in RA patients by measurement of hormone responses to insulin-induced hypoglycemia. Insulin-hypoglycemia (Actrapid HM 0.1 IU/kg, i.v. as a bolus) was induced in 17 male patients and in 11 age-, gender-, and weight-matched healthy subjects. Concentrations of growth hormone (GH), prolactin (PRL) and cortisol were analyzed in plasma. PRL release after thyreoliberin stimulation (TRH, 200 g, i.v.) was determined in 21 patients with active forms of RA and in 12 control subjects to evaluate pituitary lactotropic response. In RA patients, basal concentrations of glucose, GH, PRL, and cortisol were in the normal range and they were comparable to those in the control group. Stress of hypoglycemia induced significant elevation of GH, PRL, and cortisol concentrations in all groups. Cortisol responses to hypoglycemia were comparable in patients and in control subjects. GH release during hypoglycemia was increased (p < 0.05) and PRL response was attenuated (p < 0.05) in RA patients versus control subjects. After TRH administration, PRL response was the same in patients as in healthy subjects. In conclusion, the present study revealed an altered hypothalamic-pituitary function in patients with RA, namely, an enhanced somatotropic and reduced lactotropic activation in response to insulin-induced hypoglycemia. Basal hormone levels and cortisol release during hypoglycemia were similar to those in healthy subjects.

The hypothalamic-pituitary-adrenal axis in the pathogenesis of rheumatic diseases

Many studies have demonstrated altered HPA axis activity in patients with rheumatic diseases. In the case of autoimmune inflammatory diseases, circumstantial evidence suggests that failure of the neuroendocrine-immune regulatory loop may lead to insufficient production of endogenous glucocorticoid. Nevertheless, in human autoimmune disease, it is not possible to determine if altered HPA axis activity predates the onset of chronic inflammation. Animal studies and some early genetic studies in RA patients lend credibility to the argument that insufficient HPA axis response to inflammatory stimuli may increase susceptibility to, or severity of, these diseases. Most patients with rheumatic diseases complain of musculoskeletal pain. There is evidence of HPA axis involvement in acute and chronic pain. In the case of FM, pain cannot be explained on the basis of inflammation or altered musculoskeletal anatomy. This has led to the hypothesis that central nervous system mechanisms contribute to the symptom of somatic pain. Again, it is unclear if the observed HPA axis abnormalities reflect pre-existing vulnerability to the FM spectrum of disease, or whether chronic somatic symptoms alter HPA axis activity. Availability of technology to study better central components of the HPA axis may shed further light on its role in the pathogenesis of inflammatory autoimmune rheumatic diseases and musculoskeletal pain syndromes.

Neuroendocrine immune mechanisms in rheumatic diseases. An overview and future implications

A new physiopathogenetic paradigm may be proposed for RA and possibly its related systemic rheumatic diseases (i.e., mechanisms whereby multiple risk factors initially perturb the homeostasis of core physiologic components over an extended premorbid phase, which may progress to clinical disease in later decompensated stages). These complex interactive processes are likely to be individualized according to genetic, nongenomic somatic, developmental, behavioral, and environmental influences. Future research promises to further elucidate the roles of neuroendocrine mechanisms in the rheumatic diseases and offers promise for enhanced therapies and possible avenues for disease modification if not eventual prevention.

Different roles for androgens and estrogens in the susceptibility to autoimmune rheumatic diseases

It is now documented that androgens and estrogens modulate susceptibility and progression to autoimmune rheumatic diseases. At any concentration, androgens seem to be primarily suppressive on cellular and humoral immunity, whereas at physiologic concentrations, estrogens seem to enhance humoral immunity. Further research should focus on the different and frequently opposite effects exerted by physiologic and pharmacologic doses of estrogens (dose-related effects). In addition to the influence of endogenous estrogen fluctuations (i.e., during pregnancy, postpartum, menstrual periods, menopause), estrogen replacement therapy, and the use of oral contraceptives, the susceptibility to autoimmunity might be increased by the environmental estrogens (xenobiotics). Further studies must be directed to the inflammatory mediators (i.e., cytokines) that seem to alter the peripheral metabolism of sex hormones and complicate the effects of sex hormones on susceptibility to autoimmunity. Finally, genetic factors might further interfere with the roles of androgens and estrogens in selected individuals.