Tumor necrosis factor-related apoptosis-inducing ligand inhibits experimental autoimmune thyroiditis by the expansion of CD4+CD25+ regulatory T cells

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

RAGE is a critical factor of sex-based differences in age-induced kidney damage

Introduction: Advanced glycation end products (AGEs) are a heterogeneous group of molecules with potential pathophysiological effects on the kidneys. Fibrosis together with the accumulation of AGEs has been investigated for its contribution to age-related decline in renal function. AGEs mediate their effects in large parts through their interactions with the receptor for AGEs (RAGE). RAGE is a transmembrane protein that belongs to the immunoglobulin superfamily and has the ability to interact with multiple pro-inflammatory/pro-oxidative ligands. The role of RAGE in aging kidneys has not been fully characterized, especially for sex-based differences.

Methods: Therefore, we analyzed constitutive RAGE knockout (KO) mice in an age- and sex-dependent manner. Paraffin-embedded kidney sections were used for histological analysis and protein expression of fibrosis and damage markers. RNA expression analysis from the kidney cortex was done by qPCR for AGE receptors, kidney damage, and early inflammation/fibrosis factors. FACS analysis was used for immune cell profiling of the kidneys.

Results: Histological analysis revealed enhanced infiltration of immune cells (positive for B220) in aged (>70 weeks old) KO mice in both sexes. FACS analysis revealed a similar pattern of enhanced B-1a cells in aged KO mice. There was an age-based increase in pro-fibrotic and pro-inflammatory markers (IL-6, TNF, TGF-β1, and SNAIL1) in KO male mice that presumably contributed to renal fibrosis and renal damage (glomerular and tubular). In fact, in KO mice, there was an age-dependent increase in renal damage (assessed by NGAL and KIM1) that was accompanied by increased fibrosis (assessed by CTGF). This effect was more pronounced in male KO mice than in the female KO mice. In contrast to the KO animals, no significant increase in damage markers was detectable in wild-type animals at the age examined (>70 weeks old). Moreover, there is an age-based increase in AGEs and scavenger receptor MSR-A2 in the kidneys.

Discussion: Our data suggest that the loss of the clearance receptor RAGE in male animals further accelerates age-dependent renal damage; this could be in part due to an increase in AGEs load during aging and the absence of protective female hormones. By contrast, in females, RAGE expression seems to play only a minor role when compared to tissue pathology.

Reduction in experimental autoimmune thyroiditis by IgG Fc fragments bearing regRF epitopes

Previously, we identified a new immunoregulatory factor, the production of which provides rats with resistance to certain experimental autoimmune diseases. It has been named regulatory rheumatoid factor (regRF). RegRF inhibits the expansion of CD4 T lymphocytes by killing activated cells. CD4 T cells are essential for antibody production against a majority of antigens and for the generation of cytotoxic T cells; therefore, regRF is an attractive therapeutic biotarget for T-cell and antibody-mediated autoimmune diseases. RegRF is anti-idiotypic antibodies that have a shared paratope in addition to an individual paratope. Epitopes specific to the shared regRF paratope (regRF epitopes) can be obtained on conformers of IgG Fc fragments. Immunization with Fc fragments carrying regRF epitopes reduces rat collagen-induced arthritis and diminishes experimental autoimmune encephalomyelitis. The aim of this study was to determine whether IgG Fc fragments bearing regRF epitopes suppress experimental autoimmune thyroiditis (EAT). Four weeks after EAT induction, rats were immunized with IgG Fc fragments exhibiting regRF epitopes. Histology studies of the thyroid were performed 4 weeks later. Thyroid function and other parameters were also evaluated. Treatment of rats with Fc fragments bearing regRF epitopes decreased the number of rats affected by EAT, significantly decreased the extent of thyroid damage, prevented thyroid metaplasia, and restored normal thyroid hormone production. Therefore, RegRF is a promising biotarget in autoimmune thyroiditis, and Fc fragments bearing regRF epitopes are a potential therapeutic agent for that condition.

Gender-Specific Impact of Metabolic Obesity Phenotypes on the Risk of Hashimoto’s Thyroiditis: A Retrospective Data Analysis Using a Health Check-Up Database

Background

Hashimoto’s thyroiditis (HT) is recognized as the most common autoimmune thyroid disease, often accompanied by the diffuse enlargement of thyroid with abundant blood flow and elevated level of thyroid autoantibodies. As obesity had a positive association with the risk of HT. Thus, this retrospective study was established to further explore the gender relationship between metabolic obesity phenotypes and the risk of Hashimoto’s thyroiditis (HT).

Materials and Methods

Data for 3697 subjects aged ≥18 years were randomly collected from a Health check-up database from April to December 2019. Obesity was defined by general obesity (GO; body mass index [BMI] ≥28 kg/m²) and abdominal obesity (AO; waist circumstance, male ≥90 cm, female ≥85 cm). Metabolic unhealthy was defined as having at least one metabolic syndrome component and a homeostasis model assessment of insulin resistance ≥2.5. Obesity phenotypes were divided into three groups: GO, AO, compound obesity (GO+AO). After adjustment for potential confounding factors, multivariate logistic regression was used to assess the association between metabolic obesity phenotypes and risk of HT by sex and explore the correlation between different obesity patterns and HT risk by metabolic health status.

Results

The incidence of HT was 23.5% and significantly higher among females than males with different metabolic phenotypes (26.2% vs 20.5%, p<0.05), except metabolically healthy AO. Compared with non-obese subjects, different metabolic obesity phenotypes were independent risk factors among males (p<0.05). Among females, unhealthy metabolic status with GO (adjusted odds ratio [OR]=2.62) or AO (adjusted OR=2.87) and metabolically healthy non-GO (adjusted OR=2.05) were risk factors of HT (p<0.05). Increasing BMI categories and waist circumstance quartiles were positively correlated with HT risk (p for trend <0.05). Subgroup analyses indicated that GO+AO (adjusted OR=2.52) or only AO (adjusted OR=2.41) were risk factors for HT for those with unhealthy metabolic status. Moreover, GO+AO (adjusted OR=2.37) was an independent risk factor for HT under healthy metabolic status.

Conclusion

GO+AO was associated with an increased risk of HT, identifying higher BMI/WC as a significant risk factor for HT. Males with unhealthy metabolic state or obesity and metabolically unhealthy females with obesity are high-risk group for HT. Additionally, only AO and GO+AO conferred increased risk of HT for individuals with metabolic abnormalities.

The multifaceted role of TRAIL signaling in cancer and immunity

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF superfamily that can lead to the induction of apoptosis in tumor or infected cells. However, activation of TRAIL signaling may also trigger nonapoptotic pathways in cancer and in nontransformed cells, that is, immune cells. Here, we review the current knowledge on noncanonical TRAIL signaling. The biological outcomes of TRAIL signaling in immune and malignant cells are presented and explained, with a focus on the role of TRAIL for natural killer (NK) cell function. Furthermore, we highlight the technical difficulties in dissecting the precise molecular mechanisms involved in the switch between apoptotic and nonapoptotic TRAIL signaling. Finally, we discuss the consequences thereof for a therapeutic manipulation of TRAIL in cancer and possible approaches to bypass these difficulties.

The immune system on the TRAIL of Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia, characterized by progressive degeneration and loss of neurons in specific regions of the central nervous system. Chronic activation of the immune cells resident in the brain, peripheral immune cell trafficking across the blood-brain barrier, and release of inflammatory and neurotoxic factors, appear critical contributors of the neuroinflammatory response that drives the progression of neurodegenerative processes in AD. As the neuro-immune network is impaired in course of AD, this review is aimed to point out the essential supportive role of innate and adaptive immune response either in normal brain as well as in brain recovery from injury. Since a fine-tuning of the immune response appears crucial to ensure proper nervous system functioning, we focused on the role of the TNF superfamily member, TNF-related apoptosis-inducing ligand (TRAIL), which modulates both the innate and adaptive immune response in the pathogenesis of several immunological disorders and, in particular, in AD-related neuroinflammation. We here summarized mounting evidence of potential involvement of TRAIL signaling in AD pathogenesis, with the aim to provide clearer insights about potential novel therapeutic approaches in AD.

Sex Differences in Diabetes- and TGF-β1-Induced Renal Damage

While females are less affected by non-diabetic kidney diseases compared to males, available data on sex differences in diabetic nephropathy (DN) are controversial. Although there is evidence for an imbalance of sex hormones in diabetes and hormone-dependent mechanisms in transforming growth factor β1 (TGF-β1) signaling, causes and consequences are still incompletely understood. Here we investigated the influence of sex hormones and sex-specific gene signatures in diabetes- and TGF-β1-induced renal damage using various complementary approaches (a db/db diabetes mouse model, ex vivo experiments on murine renal tissue, and experiments with a proximal tubular cell line TKPTS). Our results show that: (i) diabetes affects sex hormone concentrations and renal expression of their receptors in a sex-specific manner; (ii) sex, sex hormones and diabetic conditions influence differences in expression of TGF-β1, its receptor and bone morphogenetic protein 7 (BMP7); (iii) the sex and sex hormones, in combination with variable TGF-β1 doses, determine the net outcome in TGF-β1-induced expression of connective tissue growth factor (CTGF), a profibrotic cytokine. Altogether, these results suggest complex crosstalk between sex hormones, sex-dependent expression pattern and profibrotic signals for the precise course of DN development. Our data may help to better understand previous contradictory findings regarding sex differences in DN.

The Association of Obesity with Autoimmune Thyroiditis and Thyroid Function-Possible Mechanisms of Bilateral Interaction

A growing number of patients suffer from autoimmune diseases, including autoimmune thyroid disease. There has simultaneously been a significant increase in the prevalence of obesity worldwide. It is still an open question whether adiposity can directly influence activation of inflammatory processes affecting the thyroid in genetically predisposed individuals. Adipokines, biologically active substances derived from the adipocytes, belong to a heterogenic group of compounds involved in numerous physiological functions, including the maintenance of metabolism, hormonal balance, and immune response. Notably, the presence of obesity worsens the course of selected autoimmune diseases and impairs response to treatment. Moreover, the excess of body fat may result in the progression of autoimmune diseases. Nutritional status, body weight, and energy expenditure may influence thyroid hormone secretion. Interestingly, thyroid hormones might influence the activity of adipose tissue as metabolic alterations related to fat tissue are observed under pathological conditions in which there are deficits or overproduction of thyroid hormones. Functioning TSH receptors are expressed on adipocytes. Thermogenesis may presumably be stimulated by TSH binding to its receptor on brown adipocytes. There could be a bilateral interaction between the thyroid and adipose. Obesity may influence the onset and course of autoimmune disease.

Impact of Abdominal Obesity on Thyroid Auto-Antibody Positivity: Abdominal Obesity Can Enhance the Risk of Thyroid Autoimmunity in Men

BACKGROUND

The interrelation between obesity and autoimmune thyroid diseases is complex and has not been confirmed. The aim of the present study was to observe the relationship between thyroid autoimmunity and obesity, especially abdominal obesity, in a large population.

METHODS

A total of 2253 residents who had lived in Xinjiang for more than 3 years were enrolled. Serum thyroid hormone concentration, thyroid autoantibodies, lipid parameters, Weight, height, and waist and hip circumference were measured.

RESULTS

The prevalence of thyroid peroxidase antibody (TPOAb) and/or thyroglobulin antibody (TgAb) positive was 32.1% (21.2% in men and 37% in women, P < 0.01). Compared with women, men had significantly higher TG levels, waist circumference, and hip circumference levels (P < 0.01), while women showed higher TSH, TPOAb, and TgAb levels (P < 0.01). The prevalence of overweight and obesity was 71.1% in men and 63.5% in women. Men had a higher prevalence of abdominal obesity than women (56.6% in men and 47.6% in women, P < 0.01). TPOAb correlates positively with waist circumference (r = 0.100, P < 0.05) in men. Binary logistic analysis showed that TPOAb positivity had increased risks of abdominal obesity in men, and the OR was 1.1044 (95% CI 1.035, 1.151, P < 0.05).

CONCLUSION

Our results indicate that men had higher lipid levels, thicker waist circumference, and higher prevalence of overweight, obesity, and abdominal obesity. Abdominal obesity is a risk factor for TPOAb positivity in men, suggesting that abdominal obesity can enhance the risk of thyroid autoimmunity in men.

The Role of TRAIL/DRs in the Modulation of Immune Cells and Responses

Expression of TRAIL (tumor necrosis factor–related apoptosis–inducing ligand) by immune cells can lead to the induction of apoptosis in tumor cells. However, it becomes increasingly clear that the interaction of TRAIL and its death receptors (DRs) can also directly impact immune cells and influence immune responses. Here, we review what is known about the role of TRAIL/DRs in immune cells and immune responses in general and in the tumor microenvironment in particular.

Systematically understanding the immunity leading to CRPC progression

Prostate cancer (PCa) is the most commonly diagnosed malignancy and the second leading cause of cancer-related death in American men. Androgen deprivation therapy (ADT) has become a standard treatment strategy for advanced PCa. Although a majority of patients initially respond to ADT well, most of them will eventually develop castration-resistant PCa (CRPC). Previous studies suggest that ADT-induced changes in the immune microenvironment (mE) in PCa might be responsible for the failures of various therapies. However, the role of the immune system in CRPC development remains unclear. To systematically understand the immunity leading to CRPC progression and predict the optimal treatment strategy in silico, we developed a 3D Hybrid Multi-scale Model (HMSM), consisting of an ODE system and an agent-based model (ABM), to manipulate the tumor growth in a defined immune system. Based on our analysis, we revealed that the key factors (e.g. WNT5A, TRAIL, CSF1, etc.) mediated the activation of PC-Treg and PC-TAM interaction pathways, which induced the immunosuppression during CRPC progression. Our HMSM model also provided an optimal therapeutic strategy for improving the outcomes of PCa treatment.

Prostate cancer (PCa) is the second leading cause of cancer-related deaths in American men. Androgen deprivation therapy (ADT) is the first-line therapy for advanced PCa, yet a significant number of primary PCa patients treated with ADT eventually develop incurable castration-resistant prostate cancer (CRPC). Recent observations suggest that the immunosuppressive microenvironment of PCa might be responsible for the failures of various therapies. However, the role of immune system in CRPC progression is still unclear. To deeply understand the immunity leading to CRPC progression, we developed a unique systems biology approach (HMSM). Based on our analysis, we identified the key molecules (e.g. WNT5A, TRAIL, CSF1, etc.) mediating the communication of PCa and immune cells. Our HMSM system also revealed the optimal therapeutic strategy for PCa treatment. Collectively, our study provides a new insight to study tumor-related immune mechanisms and pave the way for the development of more effective treatments.

TRAIL and FasL Functions in Cancer and Autoimmune Diseases: Towards an Increasing Complexity

Tumor Necrosis Factor-Related Apoptosis Inducing Ligand (TRAIL/TNFSF10) and Fas Ligand (FasL/TNFSF6), two major cytokines of the TNF (Tumor Necrosis Factor) superfamily, exert their main functions from the immune system compartment. Mice model studies revealed that TRAIL and FasL-mediated signalling both control the homeostasis of the immune cells, mainly from the lymphoid lineage, and function on cytotoxic cells as effector proteins to eliminate the compromised cells. The first clues in the physiological functions of TRAIL arose from the analysis of TRAIL deficient mice, which, even though they are viable and fertile, are prone to cancer and autoimmune diseases development, revealing TRAIL as an important safeguard against autoimmunity and cancer. The naturally occurring gld (generalized lymphoproliferative disease) and lpr (lymphoproliferation) mutant mice develop lymphadenopathy and lupus-like autoimmune disease. The discovery that they are mutated in the fasl and the fas receptor gene, respectively, demonstrates the critical role of the FasL/Fas system in lymphocyte homeostasis and autoimmunity. This review summarizes the state of current knowledge regarding the key death and non-death immune functions that TRAIL and FasL play in the initiation and progression of cancer and autoimmune diseases.

Effect of vitamin E succinate on the expression of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor in gastric cancer cells and CD4(+) T cells

Gastric malignancy, which shows poor prognosis, is one of the most frequent causes of cancer-associated deaths. Vitamin E succinate (VES) inhibits cell proliferation and induces apoptosis in a concentration- and time-dependent manner. We explored the effect of VES on the expression of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor in gastric cancer cells and CD4(+) T cells. On one hand, VES dose-dependently regulated the expression of the TRAIL receptor in gastric cancer cells. Moreover, the activation of the TRAIL receptor, death receptor 4 (DR4), and death receptor 5 (DR5) in gastric cancer cells increased for up to 12 h. On the other hand, the expression of TRAIL protein in human CD4(+) T cells was obviously upregulated in the presence of VES. On the basis of these findings, we combined VES and human CD4(+) T cells to induce apoptosis of MKN28 human gastric cancer cells. The results showed that VES induced higher gastric cancer cell apoptosis when combined with human CD4(+) T cells than when applied alone. We conclude that VES can induce the expression of TRAIL receptor in gastric cancer cells, as well as the expression of TRAIL in CD4(+) T cells. Overall, our results provide a theoretical basis for future immunotherapy studies.

Effects of low-level laser therapy on the serum TGF-β1 concentrations in individuals with autoimmune thyroiditis

OBJECTIVE

The objective of this study was to evaluate the serum concentration of transforming growth factor-β1 (TGF-β1) after low-level laser therapy (LLLT) in patients with hypothyroidism resulting from chronic autoimmune thyroiditis (CAT).

BACKGROUND DATA

Certain data indicate that LLLT is effective in patients with hypothyroidism caused by CAT; however, the mechanisms of action of LLLT in thyroid tissue are unknown. Cytokines could play a role in the response to LLLT.

METHODS

A randomized, placebo-controlled trial included 43 patients with a history of levothyroxine therapy for CAT-induced hypothyroidism. The patients were randomly assigned to receive either 10 sessions of LLLT (830 nm, 50 mW output power, and 707 J/cm(2) fluence; L group, n=23) or 10 sessions of a placebo treatment (P group, n=20) twice a week. Levothyroxine was maintained at the same dose during the entire study period. TGF-β1 was measured both pre-intervention and 30 days post-intervention in both groups. The differences were calculated between the TGF-β1 values observed 30 days post-intervention and the pre-intervention TGF-β1 values for each group (intragroup).

RESULTS

Comparing the differences in TGF-β1 levels between the L group (874.9±541.7 pg/mL) and the P group (-128.4±832.8 pg/mL) revealed that there was a statistically significant increase in TGF-β1 levels 30 days post-intervention in group L compared with the placebo group (p=0.0379).

CONCLUSIONS

This finding suggested that the significant increase in serum TGF-β1 levels in patients with CAT-induced hypothyroidism was associated with the thyroid LLLT procedure. Future studies of the effect of LLLT on TGF-β1 gene expression in thyroid tissue are necessary to confirm these findings.

Pathogenesis of thyroid autoimmune disease: the role of cellular mechanisms

Hashimoto's thyroiditis (HT) and Graves' disease (GD) are two very common organ-specific autoimmune diseases which are characterized by circulating antibodies and lymphocyte infiltration. Although humoral and cellular mechanisms have been classically considered separately in the pathogenesis of autoimmune thyroid diseases (AITD), recent research suggests a close reciprocal relationship between these two immune pathways. Several B- and T-cell activation pathways through antigen-presenting cells (APCs) and cytokine production lead to specific differentiation of T helper (Th) and T regulatory (Treg) cells. This review will focus on the cellular mechanisms involved in the pathogenesis of AITD. Specifically, it will provide reasons for discarding the traditional simplistic dichotomous view of the T helper type 1 and 2 pathways (Th1/Th2) and will focus on the role of the recently characterized T cells, Treg and Th17 lymphocytes, as well as B lymphocytes and APCs, especially dendritic cells (DCs).

TRAIL modulates the immune system and protects against the development of diabetes

TRAIL or tumor necrosis factor (TNF) related apoptosis-inducing ligand is a member of the TNF superfamily of proteins, whose best characterized function is the induction of apoptosis in tumor, infected, or transformed cells through activation of specific receptors. In nontransformed cells, however, the actions of TRAIL are less well characterized. Recent studies suggest that TRAIL may be implicated in the development and progression of diabetes. Here we review TRAIL biological actions, its effects on the immune system, and how and to what extent it has been shown to protect against diabetes.

Tumor necrosis factor-related apoptosis-inducing ligand in vascular inflammation and atherosclerosis: a protector or culprit?

In addition to inducing tumor cell apoptosis, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) shows broad biological functions both in vitro and in vivo. TRAIL gene deletion enhanced atherogenesis in hyperlipidemic mice, supporting that endogenous TRAIL has protective actions in maintaining blood vessel homeostasis and repressing atherosclerosis. The mechanisms of this beneficial effect are not understood. It remains to be determined whether the athero-protective action of TRAIL is via direct impacts on residential vascular cells or indirectly by modulating systemic immune functions. However, in vitro experiments indicate that excessive TRAIL may stimulate endothelial cell apoptosis, smooth muscle proliferation and migration, and inflammatory responses. Moreover, TRAIL can stimulate lipid uptake and foam cell formation in cultured macrophages. Here we provide a critical review on the potential relationships between TRAIL and atherosclerosis. We propose that increased TRAIL production may also have potential detrimental effects on vascular inflammation and atherosclerosis. Further in vivo experiments are warranted to elucidate the effects of exogenous TRAIL on atherogenesis.

Mechanisms in endocrinology: the crosstalk between thyroid gland and adipose tissue: signal integration in health and disease

Obesity and thyroid diseases are common disorders in the general population and they frequently occur in single individuals. Alongside a chance association, a direct relationship between 'thyroid and obesity' has been hypothesized. Thyroid hormone is an important determinant of energy expenditure and contributes to appetite regulation, while hormones and cytokines from the adipose tissue act on the CNS to inform on the quantity of energy stores. A continuous interaction between the thyroid hormone and regulatory mechanisms localized in adipose tissue and brain is important for human body weight control and maintenance of optimal energy balance. Whether obesity has a pathogenic role in thyroid disease remains largely a matter of investigation. This review highlights the complexity in the identification of thyroid hormone deficiency in obese patients. Regardless of the importance of treating subclinical and overt hypothyroidism, at present there is no evidence to recommend pharmacological correction of the isolated hyperthyrotropinemia often encountered in obese patients. While thyroid hormones are not indicated as anti-obesity drugs, preclinical studies suggest that thyromimetic drugs, by targeting selected receptors, might be useful in the treatment of obesity and dyslipidemia.

TRAIL-receptor costimulation inhibits proximal TCR signaling and suppresses human T cell activation and proliferation

The TRAIL-receptor/TRAIL system originally described to induce apoptosis preferentially in malignant cells is also known to be involved in T cell homeostasis and the response to viral infections and autoimmune diseases. Whereas the expression of TRAIL on activated NK and T cells increases their cytotoxicity, induction of TRAIL on APCs can turn them into apoptosis inducers but might also change their immunostimulatory capacity. Therefore, we analyzed how TRAIL-receptor (TRAIL-R) costimulation is modulating TCR-mediated activation of human T cells. T cells triggered by rTRAIL in combination with anti-CD3 and -CD28 Abs exhibited a strong decrease in the expression of activation markers and Th1 and Th2 cytokines compared with CD3/CD28-activated T cells. Most importantly, proliferation of TRAIL-R costimulated T cells was strongly impaired, but no apoptosis was induced. Addition of exogenous IL-2 could not rescue T cells silenced by TRAIL-R costimulation, and TRAIL-mediated inhibition of T cell proliferation only prevented TCR-triggered proliferation but was ineffective if T cells were activated downstream of the TCR. Inhibition of T cell proliferation was associated with abrogation of proximal TCR signaling by inhibiting recruitment of TCR-associated signaling molecules to lipid rafts, followed by abrogation of protein tyrosine phosphorylation of ZAP70, phospholipase C-γ1, and protein kinase C-θ, and impaired nuclear translocation of NFAT, AP-1, and NF-κB. Most importantly, TRAIL-R costimulation efficiently inhibited alloantigen-induced T cell proliferation and CD3/28-induced activation and proliferation of autoreactive T cells derived from patients with Omenn syndrome, indicating that coactivation of TRAIL-R and TCR represents a mechanism to downmodulate T cell immune responses.

Overexpression of BID in thyroids of transgenic mice increases sensitivity to iodine-induced autoimmune thyroiditis

BACKGROUND

BID functions as a bridge molecule between death-receptor and mitochondrial related apoptotic pathways to amplify apoptotic signaling. Our previous studies have demonstrated a substantial increase in BID expression in primary normal thyroid epithelia cells treated with inflammatory cytokines, including the combination of IFNγ and IL-1β or IFNγ and TNFα. The aim of this study was to determine whether an increase in BID expression in thyroid can induce autoimmune thyroiditis.

METHODS

A transgenic mouse line that expresses human BID in thyroid cells was established by fusing a mouse thyroglobulin (Tg) promoter upstream of human BID (Tg-BID). We tested whether the increased expression of pro-apoptotic BID in thyroid would induce autoimmune thyroiditis, both in the presence and absence of 0.3% iodine water.

RESULTS

Our data show that Tg-BID mice in a CBA/J (H-2 k) background do not spontaneously develop autoimmune thyroiditis for over a year. However, upon ingestion of iodine in the drinking water, autoimmune thyroiditis does develop in Tg-BID transgenic mice, as shown by a significant increase in anti-Tg antibody and mononuclear cell infiltration in the thyroid glands in 30% of mice tested. Serum T4 levels, however, were similar between iodine-treated Tg-BID transgenic mice and the wild type mice.

CONCLUSIONS

Our data demonstrate that increased thyroid expression of BID facilitates the development of autoimmune thyroiditis induced by iodine uptake. However, the overexpression of BID itself is not sufficient to initiate thyroiditis in CBA/J (H-2 k) mice.

Mucopolysaccharide diseases: a complex interplay between neuroinflammation, microglial activation and adaptive immunity

Mucopolysaccharide (MPS) diseases are lysosomal storage disorders (LSDs) caused by deficiencies in enzymes required for glycosaminoglycan (GAG) catabolism. Mucopolysaccharidosis I (MPS I), MPS IIIA, MPS IIIB and MPS VII are deficient in the enzymes α-L-Iduronidase, Heparan-N-Sulphatase, N-Acetylglucosaminidase and Beta-Glucuronidase, respectively. Enzyme deficiency leads to the progressive multi-systemic build-up of heparan sulphate (HS) and dermatan sulphate (DS) within cellular lysosomes, followed by cell, tissue and organ damage and in particular neurodegeneration. Clinical manifestations of MPS are well established; however as lysosomes represent vital components of immune cells, it follows that lysosomal accumulation of GAGs could affect diverse immune functions and therefore influence disease pathogenesis. Theoretically, MPS neurodegeneration and GAGs could be substantiating a threat of danger and damage to alert the immune system for cellular clearance, which due to the progressive nature of MPS storage would propagate disease pathogenesis. Innate immunity appears to have a key role in MPS; however the extent of adaptive immune involvement remains to be elucidated. The current literature suggests a complex interplay between neuroinflammation, microglial activation and adaptive immunity in MPS disease.

Hyperthyroid monkeys: a nonhuman primate model of experimental Graves' disease

Graves' disease (GD) is a common organ-specific autoimmune disease with the prevalence between 0.5 and 2% in women. Several lines of evidence indicate that the shed A-subunit rather than the full-length thyrotropin receptor (TSHR) is the autoantigen that triggers autoimmunity and leads to hyperthyroidism. We have for the first time induced GD in female rhesus monkeys, which exhibit greater similarity to patients with GD than previous rodent models. After final immunization, the monkeys injected with adenovirus expressing the A-subunit of TSHR (A-sub-Ad) showed some characteristics of GD. When compared with controls, all the test monkeys had significantly higher TSHR antibody levels, half of them had increased total thyroxine (T₄) and free T₄, and 50% developed goiter. To better understand the underlying mechanisms, quantitative studies on subpopulations of CD4+T helper cells were carried out. The data indicated that this GD model involved a mixed Th1 and Th2 response. Declined Treg proportions and increased Th17:Treg ratio are also observed. Our rhesus monkey model successfully mimicked GD in humans in many aspects. It would be a useful tool for furthering our understanding of the pathogenesis of GD and would potentially shorten the distance toward the prevention and treatment of this disease in human.

TRAIL suppresses tumor growth in mice by inducing tumor-infiltrating CD4(+)CD25 (+) Treg apoptosis

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a promising and novel anticancer cytokine, specifically kills numerous tumor cells by apoptosis. However, some malignancies are resistant to TRAIL treatment in clinical trials, thus limiting its therapeutic potential. In the present study, the TRAIL-resistant murine hepatocellular carcinoma cell line Hepa1-6 was used to elucidate the physiological significance of TRAIL resistance, especially with respect to the immune regulatory function of TRAIL. Hepa1-6 cells were resistant to TRAIL-induced apoptosis in vitro; however, intratumoral injection of recombinant soluble TRAIL inhibited tumor growth and prolonged survival time in tumor-bearing mice. Local TRAIL treatment decreased the number of intratumoral CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) but did not affect CD4(+)CD25(+)Foxp3(+) Tregs in the draining lymph nodes and spleen. Further investigation showed that TRAIL induced apoptosis of tumor-activated CD4(+)CD25(+)Foxp3(+) Tregs, but not of CD4(+)CD25(-) T cells. Moreover, mouse TRAIL receptor DR5 expression was detected on the surface of the tumor-infiltrating CD4(+)CD25(+)Foxp3(+) Tregs, but not on naïve CD4(+)CD25(+)Foxp3(+) Tregs. Interestingly, intratumoral injection of TRAIL not only decreased the number of CD4(+)CD25(+)Foxp3(+) Tregs but also increased the number of tumor-specific CD8(+) CTL and augmented their cytotoxicity to the tumor cells. These data provide the novel evidence for an immune regulatory function of TRAIL and may shed light on the clinical application of TRAIL.

Targeted delivery of tumor necrosis factor-related apoptosis-inducing ligand to keratinocytes with a pemphigus mAb

We determined the feasibility of using an anti-desmoglein (Dsg) mAb, Px44, to deliver a biologically active protein to keratinocytes. Recombinantly produced Px44-green fluorescent protein (GFP) injected into mice and skin organ culture delivered GFP to the cell surface of keratinocytes. We replaced GFP with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) to produce Px44-TRAIL. We chose TRAIL as a biological model because it inhibits activated lymphocytes and causes apoptosis of hyperproliferative keratinocytes, features of various skin diseases. Px44-TRAIL formed a trimer, the biologically active form of TRAIL. Standard assays of TRAIL activity showed that Px44-TRAIL caused apoptosis of Jurkat cells and inhibited IFN-γ production by activated CD4+ T cells. Enzyme-linked immunoassay with Px44-TRAIL showed delivery of TRAIL to Dsg. Immunofluorescence with Px44-TRAIL incubated on skin sections and cultured keratinocytes or injected into mouse skin, human organ culture, or human xenografts detected TRAIL on keratinocytes. Px44-TRAIL caused apoptosis of the hyperproliferative, but not differentiating, cultured keratinocytes through binding to Dsg3. Foldon, a small trimerization domain, cloned into Px44-TRAIL maintained its stability and biological activity at 37° C for at least 48 hours. These data suggest that such targeted therapy is feasible and may be useful for hyperproliferative and inflamed skin diseases.

Role of Apo2L/TRAIL in immunity: Applications to rheumatoid arthritis

Rheumatoid arthritis (RA) is the most common inflammatory disease of the musculoskeletal system primarily affecting the joints. It is characterized by massive synovial hyperplasia and subsequent destruction of articular cartilage and bone. Although various aspects in the pathogenesis of RA remain unclear, genetic, environmental and of course immunological factors have been involved. Defects in apoptosis seem to play a role in both initiation and perpetuation of RA. Apo2 ligand/ tumor necrosis factor (TNF) related apoptosis-inducing ligand (Apo2L/TRAIL) is a cytokine that belongs to the TNF superfamily capable of inducing apoptosis on tumor cells through activation of the extrinsic pathway. Besides this function, like other members of the TNF superfamily, Apo2L/TRAIL has been shown to exert important functions in the regulation of the immune system. Concerning pathological conditions, the Apo2L/TRAIL signaling pathway plays an important role in the response to infections, in immune surveillance against tumors and in autoimmune diseases such as RA. Furthermore, its implication in suppression of autoimmunity suggests that Apo2L/TRAIL has potential as therapeutic agent not only in cancer but also in autoimmune diseases. In fact, Apo2L/TRAIL-based therapies have been shown effective in various animal models of RA. This review summarizes the current knowledge on the biology of Apo2L/TRAIL and its role in RA.

Induction of immune tolerance in mice with a novel mucosal nanoemulsion adjuvant and self-antigen

AIM

The aim of this study was to investigate the impact of a novel nanoemulsion (NE) adjuvant, a soybean oil emulsion, on autoimmune response. To this end, we used murine thyroglobulin (mTg)-induced experimental autoimmune thyroiditis in mice as a study model.

MATERIALS & METHODS

Mice received NE or NE + mTg by nasal delivery. At 1 week after the second nasal delivery of NE with or without mTg, all mice were immunized with mTg and lipopolysaccharides to induce experimental autoimmune thyroiditis.

RESULTS

Compared with controls, mTg-NE-treated mice had much more antigens accumulated in the nasal passage and thymus and developed a milder form of thyroiditis. This was accompanied by an increase in IL-10, IL-17 and reduced IFN-γ. The production of anti-mTg antibodies was significantly decreased in mTg-NE-treated mice. The percentage of Tregs in cervical lymph nodes was higher in mTg-NE-treated mice than NE-treated mice. Furthermore, Foxp3 and TGF-β levels were prominently enhanced in mTg-NE-treated mice.

CONCLUSION

This study indicates that a low dose of mTg in NE can significantly enhance antigen uptake and Tregs, resulting in inhibition of experimental autoimmune thyroiditis development.

TRAIL and DR5 promote thyroid follicular cell apoptosis in iodine excess-induced experimental autoimmune thyroiditis in NOD mice

Death receptor-mediated apoptosis has been implicated in target organ destruction in patients with chronic autoimmune thyroiditis. Several apoptosis signaling pathways, such as Fas ligand and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), have been shown to be active in thyroid cells and may be involved in destructive thyroiditis. Thyroid toxicity of iodide excess has been demonstrated in animals fed with an iodide-rich diet, but its pathogenic role remains unclear. The effects of excessive iodine on TRAIL and its death receptor expression in thyroid were investigated. Experimental autoimmune thyroiditis (EAT) was induced by excessive iodine and thyroglobulin (Tg) in non-obese diabetic mice. The expression of TRAIL and its death receptor DR5 was detected by immunofluorescence staining. Following administration of excessive iodine alone, Tg, and excessive iodine combined with Tg, TRAIL-positive cells appear not only in follicular cells but also in lymphocytes infiltrated in the thyroid, whereas DR5-positive cells appear only in follicular cells. Large numbers of CD3-positive cells and a few CD22-positive cells were detected in thyroid. A great amount of follicular cells were labeled specifically by terminal deoxynucleotide transferase-mediated deoxynucleotide triphosphate nick-end labeling assay. Taken together, our results suggest that excessive iodine could induce TRAIL and DR5 abnormal expression in thyroid. TRAIL band with DR5 to promote follicular cells apoptosis thus mediate thyroid destruction in EAT.

Role of cytokines in the pathogenesis and suppression of thyroid autoimmunity

Autoimmune thyroid diseases (AITD) are one of the most common organ-specific autoimmune disorders, of which Hashimoto's thyroiditis (HT) and Graves' disease (GD) are 2 of the most common clinical expressions. HT is characterized by hypothyroidism that results from the destruction of the thyroid by thyroglobulin-specific T cell-mediated autoimmune response. In contrast, GD is characterized by hyperthyroidism due to excessive production of thyroid hormone induced by thyrotropin receptor-specific stimulatory autoantibodies. Cytokines play a crucial role in modulating immune responses that affect the balance between maintenance of self-tolerance and initiation of autoimmunity. However, the role of cytokines is often confusing and is neither independent nor exclusive of other immune mediators. A regulatory cytokine may either favor induction of tolerance against thyroid autoimmune disease or favor activation and/or exacerbation of autoimmune responses. These apparently contradictory functions of a given cytokine are primarily influenced by the nature of co-signaling delivered by other cytokines. Consequently, a thorough understanding of the role of a particular cytokine in the context of a specific immune response is essential for the development of appropriate strategies to modulate cytokine responses to maintain or restore health. This review provides a summary of recent research pertaining to the role of cytokines in the pathogenesis of AITD with a particular emphasis on the therapeutic applications of cytokine modulation.

Impairment of regulatory capacity of CD4+CD25+ regulatory T cells mediated by dendritic cell polarization and hyperthyroidism in Graves' disease

Graves' disease (GD) is one of the most common autoimmune diseases. The immune dysfunction in GD involves the generation of thyroid-stimulating hormone receptor (TSHR) autoantibodies that presumably arise consequent to interactions among dendritic cells (DCs), T cells, and regulatory T (Treg) cells. However, the immunological mechanisms of interactions between them that lead to the induction and regulation of this autoimmune disease are poorly defined. In this study, we investigated whether DCs are the main cause of the defective activity of Treg cells in GD patients. We found a significant decrease in the percentage of circulating CD4(+)CD25(+)FOXP3(+) Treg cells in untreated GD patients (uGD), which was negatively correlated with the concentration of TSHR autoantibodies. uGD-derived DCs were polarized to increase the number of plasmacytoid DCs (pDCs) and conferred the ability to abrogate the suppressive function of Treg cells through inducing apoptosis of CD4(+)CD25(+) Treg cells in an IFN-α-dependent manner, and elevated thyroid hormones further exacerbated the effect. The nucleotide UDP, which inhibits IFN-α secretion of pDCs through P2Y6 receptor signaling, restored the suppressive function of CD4(+)CD25(+) Treg cells. Collectively, uGD-derived DCs through pDC polarization and elevated thyroid hormones act in concert to impair the regulatory capacity of Treg cells, facilitating the production of TSHR autoantibodies in the pathogenesis of GD.

HIV-1 impairs in vitro priming of naïve T cells and gives rise to contact-dependent suppressor T cells

Priming of T cells in lymphoid tissues of HIV-infected individuals occurs in the presence of HIV-1. DC in this milieu activate T cells and disseminate HIV-1 to newly activated T cells, the outcome of which may have serious implications in the development of optimal antiviral responses. We investigated the effects of HIV-1 on DC–naïve T-cell interactions using an allogeneic in vitro system. Our data demonstrate a dramatic decrease in the primary expansion of naïve T cells when cultured with HIV-1-exposed DC. CD4⁺ and CD8⁺ T cells showed enhanced expression of PD-1 and TRAIL, whereas CTLA-4 expression was observed on CD4⁺ T cells. It is worth noting that T cells primed in the presence of HIV-1 suppressed priming of other naïve T cells in a contact-dependent manner. We identified PD-1, CTLA-4, and TRAIL pathways as responsible for this suppresion, as blocking these negative molecules restored T-cell proliferation to a higher degree. In conclusion, the presence of HIV-1 during DC priming produced cells with inhibitory effects on T-cell activation and proliferation, i.e. suppressor T cells, a mechanism that could contribute to the enhancement of HIV-1 pathogenesis.

Investigations of thyroid hormones and antibodies in obesity: leptin levels are associated with thyroid autoimmunity independent of bioanthropometric, hormonal, and weight-related determinants

OBJECTIVES

Obesity can alter the thyroid hormone status as a result of a dysregulated endocrine loop between the hypothalamo-pituitary unit and adipose tissue. The adipocytokine leptin has been shown to promote autoimmunity; hence, we aimed to clarify whether leptin excess of obesity could increase the susceptibility to develop autoimmune thyroid disease (AITD).

STUDY DESIGN

This cross-sectional study was performed in a tertiary care center.

METHODS

Free thyroid hormones, TSH, thyroglobulin, and antithyroid antibodies levels were tested in 165 obese and 118 lean subjects. Results were plotted against variables related to body composition, leptin levels, glucose homeostasis, energy expenditure, and pattern of weight accrual.

RESULTS

Compared with controls, obese patients had lower free T3 levels and free T4 levels (P<0.01), greater prevalence of hypothyroidism (P<0.05), and higher commonness of antithyroid antibodies (P<0.05). As a marker of AITD, thyroid peroxidase antibodies were more frequent in the obese group (P<0.01). Correlation analysis showed that leptin levels were associated with AITD (P<0.01) independent of bioanthropometric variables. Multiple logistic regression analysis in pooled groups identified female sex and leptin as significant predictors of AITD.

CONCLUSIONS

Obesity increases the susceptibility to harbor AITD with an emerging role for leptin as a peripheral determinant, which needs to be confirmed in future investigations.

Selenium upregulates CD4(+)CD25(+) regulatory T cells in iodine-induced autoimmune thyroiditis model of NOD.H-2(h4) mice

Selenium (Se) is required for thyroid hormone synthesis and metabolism. Se treatment reduces serum thyroidspecific antibody titers in patients with autoimmune thyroiditis (AIT), but the exact mechanism is not clear. We investigated the effects of Se treatment on CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg) in a iodine-induced autoimmune thyroiditis model. NOD.H-2(h4) mice were randomly divided into control, AIT untreated, and AIT with Se treatment groups. Mice were fed with 0.005% sodium iodine (NaI) water for 8 weeks to induce AIT. Se-treated mice received 0.3 mg/L sodium selenite in drinking water. The AIT mice had fewer Treg cells and reduced Foxp3 mRNA expression in splenocytes compared with the controls (p < 0.01). The percentage of Treg cells and expression of Foxp3 mRNA were increased by Se treatment (as compared with untreated AIT mice, p < 0.05). Mice that received Se supplementation also had lower serum thyroglobulin antibody (TgAb) titers and reduced lymphocytic infiltration in thyroids than untreated AIT mice. These data suggest that CD4(+)CD25(+) T cells play an important role in the development of AIT. Se supplementation may restore normal levels of CD4(+)CD25(+) T cells by up-regulating the expression of Foxp3 mRNA in mice with AIT.

T regulatory cells: an overview and intervention techniques to modulate allergy outcome

Dysregulated immune response results in inflammatory symptoms in the respiratory mucosa leading to asthma and allergy in susceptible individuals. The T helper type 2 (Th2) subsets are primarily involved in this disease process. Nevertheless, there is growing evidence in support of T cells with regulatory potential that operates in non-allergic individuals. These regulatory T cells occur naturally are called natural T regulatory cells (nTregs) and express the transcription factor Foxp3. They are selected in the thymus and move to the periphery. The CD4 Th cells in the periphery can be induced to become regulatory T cells and hence called induced or adaptive T regulatory cells. These cells can make IL-10 or TGF-b or both, by which they attain most of their suppressive activity. This review gives an overview of the regulatory T cells, their role in allergic diseases and explores possible interventionist approaches to manipulate Tregs for achieving therapeutic goals.