β (CCL2) and α (CXCL10) chemokine modulations by cytokines and peroxisome proliferator-activated receptor-α agonists in Graves' ophthalmopathy

Redox mechanisms in autoimmune thyroid eye disease

Thyroid eye disease (TED) is an autoimmune condition affecting the orbit and the eye with its adnexa, often occurring as an extrathyroidal complication of Graves' disease (GD). Orbital inflammatory infiltration and the stimulation of orbital fibroblasts, triggering de novo adipogenesis, an overproduction of hyaluronan, myofibroblast differentiation, and eventual tissue fibrosis are hallmarks of the disease. Notably, several redox signaling pathways have been shown to intensify inflammation and to promote adipogenesis, myofibroblast differentiation, and fibrogenesis by upregulating potent cytokines, such as interleukin (IL)-1β, IL-6, and transforming growth factor (TGF)-β. While existing treatment options can manage symptoms and potentially halt disease progression, they come with drawbacks such as relapses, side effects, and chronic adverse effects on the optic nerve. Currently, several studies shed light on the pathogenetic contributions of emerging factors within immunological cascades and chronic oxidative stress. This review article provides an overview on the latest advancements in understanding the pathophysiology of TED, with a special focus of the interplay between oxidative stress, immunological mechanisms and environmental factors. Furthermore, cutting-edge therapeutic approaches targeting redox mechanisms will be presented and discussed.

CD169+ classical monocyte as an important participant in Graves' ophthalmopathy through CXCL12-CXCR4 axis

Patients with Graves' disease (GD) can develop Graves' ophthalmopathy (GO), but the underlying pathological mechanisms driving this development remain unclear. In our study, which included patients with GD and GO, we utilized single-cell RNA sequencing (scRNA-seq) and multiplatform analyses to investigate CD169+ classical monocytes, which secrete proinflammatory cytokines and are expanded through activated interferon signaling. We found that CD169+ clas_mono was clinically significant in predicting GO progression and prognosis, and differentiated into CD169+ macrophages that promote inflammation, adipogenesis, and fibrosis. Our murine model of early-stage GO showed that CD169+ classical monocytes accumulated in orbital tissue via the Cxcl12-Cxcr4 axis. Further studies are needed to investigate whether targeting circulating monocytes and the Cxcl12-Cxcr4 axis could alleviate GO progression.

Exercise-induced modulation of Interferon-signature: a therapeutic route toward management of Systemic Lupus Erythematosus

Systemic Lupus Erythematosus (SLE) is a multisystemic autoimmune disorder characterized by flares-ups/remissions with a complex clinical picture related to disease severity and organ/tissue injury, which, if left untreated, may result in permanent damage. Enhanced fatigue and pain perception, worsened quality of life (QoL) and outcome are constant, albeit symptoms may differ. An aberrant SLE immunoprofiling, note as "interferon (IFN)α-signature", is acknowledged to break immunotolerance. Recently, a deregulated "IFNγ-signature" is suggested to silently precede/trigger IFNα profile before clinical manifestations. IFNα- and IFNγ-over-signaling merge in cytokine/chemokine overexpression exacerbating autoimmunity. Remission achievement and QoL improvement are the main goals. The current therapy (i.e., corticosteroids, immunosuppressants) aims to downregulate immune over-response. Exercise could be a safe treatment due to its ever-emerging ability to shape and re-balance immune system without harmful side-effects; in addition, it improves cardiorespiratory capacity and musculoskeletal strength/power, usually impaired in SLE. Nevertheless, exercise is not yet included in SLE care plans. Furthermore, due to the fear to worsening pain/fatigue, SLE subjects experience kinesiophobia and sedentary lifestyle, worsening physical health. Training SLE patients to exercise is mandatory to fight inactive behavior and ameliorate health. This review aims to focus the attention on the role of exercise as a non-pharmacological therapy in SLE, considering its ability to mitigate IFN-signature and rebalance (auto)immune response. To this purpose, the significance of IFNα- and IFNγ-signaling in SLE etiopathogenesis will be addressed first and discussed thereafter as biotarget of exercise. Comments are addressed on the need to make aware all SLE care professional figures to promote exercise for health patients.

Chemokine Expression during Adipogenesis and Inflammation in Orbital Fibroblasts from Patients with Graves' Orbitopathy

Purpose

Chemokines are involved in the pathogenesis of various autoimmune diseases, including Graves' orbitopathy (GO), but comprehensive analyses of the dynamics of these cytokines and their receptors in such diseases remain lacking. In this study, we investigated the expressions of chemokines and their receptors during adipogenesis and inflammation in primary cultured orbital fibroblasts from patients with GO.

Methods

The messenger RNA (mRNA) expression levels of chemokines were compared between GO (n = 6) and non-GO (n = 5) orbital tissues by real-time polymerase chain reaction. After adipogenesis was induced in primary cultured orbital fibroblasts from patients with GO (n =5) and following stimulation with interleukin (IL)-1β and tumor necrosis factor (TNF)-α, the mRNA expression levels of chemokines and their receptors were analyzed.

Results

Chemokines were significantly downregulated in GO orbital tissues compared to non-GO orbital tissues (p < 0.05). Adipogenesis resulted in a strong increase in mRNA expression levels of chemokines and their receptors at an early stage (day 1); however, expression levels started to decrease thereafter and, eventually, decreased to below basal levels at the end of adipogenesis (day 10). Following stimulation with IL-1β and TNF-α, the mRNA expression levels of chemokines and their receptors increased, showing different responses to various proinflammatory cytokines.

Conclusions

Chemokines were strongly upregulated in the early phase of adipogenesis before decreasing continuously until the end of adipogenesis. Also, overt mature GO tissues showed reduced mRNA expression of chemokines compared to controls, which might indicate the existence of a shorter window for effective medical inflammatory treatment. The heightened levels of chemokines and their receptors observed after stimulation with IL-1β and TNF-α suggest a crucial role of proinflammatory cytokines in the pathogenesis of GO and, further, support the idea that chemokines could be used as biomarkers of GO activity.

CircRNA hsa_circ_0110102 inhibited macrophage activation and hepatocellular carcinoma progression via miR-580-5p/PPARα/CCL2 pathway

Circular RNAs (circRNAs) have critical regulatory roles in tumor biology. However, their contributions in hepatocellular carcinoma (HCC) still remain enigmatic. The present study aimed to investigate the molecular mechanisms underlying the involvement of hsa_circ_0110102 in the occurrence and development of HCC. The expression level of hsa_circ_0110102 was significantly downregulated in HCC cell lines and tissues, which was associated with poor prognosis. Knockdown hsa_circ_0110102 significantly promoted cell proliferation, migration, and invasion. Moreover, the interaction between hsa_circ_0110102 and miR-580-5p was predicted and verified by luciferase assay and RNA pull-down. The findings indicated that hsa_circ_0110102 functioned as a sponge for miR-580-5p. Moreover, miR-580-5p directly bound to the 3' UTR of PPARα, which decreased the production and release of C-C chemokine ligand 2 (CCL2) in HCC cells. CCL2 could activate the cyclooxygenase-2/prostaglandin E2 (COX-2/PGE2) pathway in macrophage via FoxO1 in a p38 MAPK-dependent manner. Furthermore, the Δ256 mutant of FoxO1 showed no activation effect. These results concluded that hsa_circ_0110102 acted as a sponge for miR-580-5p and inhibited CCL2 secretion into tumor microenvironment by decrease the expression of PPARα in HCC cells, then inhibited the pro-inflammatory cytokine release from macrophages by regulating the COX-2/PGE2 pathway. In conclusion, hsa_circ_0110102 served as a potential prognostic predictor or therapeutic target for HCC.

Mechanisms That Underly T Cell Immunity in Graves' Orbitopathy

Graves' orbitopathy (GO), also known as thyroid-associated ophthalmopathy, is the most common ocular abnormality of Graves' disease. It is a disfiguring, invalidating, and potentially blinding orbital disease mediated by an interlocking and complicated immune network. Self-reactive T cells directly against thyroid-stimulating hormone receptor-bearing orbital fibroblasts contribute to autoimmune inflammation and tissue remodeling in GO orbital connective tissues. To date, T helper (Th) 1 (cytotoxic leaning) and Th2 (antibody leaning) cell subsets and an emerging role of Th17 (fibrotic leaning) cells have been implicated in GO pathogenesis. The potential feedback loops between orbital native residential CD34^- fibroblasts, CD34⁺ infiltrating fibrocytes, and effector T cells may affect the T cell subset bias and the skewed pattern of cytokine production in the orbit, thereby determining the outcomes of GO autoimmune reactions. Characterization of the T cell subsets that drive GO and the cytokines they express may significantly advance our understanding of orbital autoimmunity and the development of promising therapeutic strategies against pathological T cells.

Polymorphisms of the genes CTLA4, PTPN22, CD40, and PPARG and their roles in Graves' disease: susceptibility and clinical features

PURPOSE

CTLA4, PTPN22, and CD40 are immune-regulatory genes strongly associated with GD, as well as PPARG, but their clinical significance in different populations is still uncertain.

METHODS

We genotyped 282 Brazilian GD patients (234 women and 48 men, 39.80 ± 11.69 years old), including 144 patients with GO, and 308 healthy control individuals (246 women and 62 men, 36.86 ± 12.95 years old).

RESULTS

A multivariate analysis demonstrated that the inheritance of the GG genotype rs3087243 of CTLA4 (OR = 2.593; 95% CI = 1.630-4.123; p < 0.0001) and the CC genotype of rs3789607 of PTPN22 (OR = 2.668; 95% CI = 1.399-5.086; p = 0.0029) consisted in factors independent of the susceptibility to GD. The inheritance of polymorphic genotypes of rs5742909 of CTLA4 was associated with older age at the time of diagnosis (42.90 ± 10.83 versus 38.84 ± 11.81 years old; p = 0.0105), with higher TRAb levels (148.17 ± 188.90 U/L versus 112.14 ± 208.54 U/L; p = 0.0229) and the need for higher therapeutic doses of radioiodine (64.23 ± 17.16 versus 50.22 ± 16.86; p = 0.0237). The inheritance of the CC genotype of rs1883832 CD40 gene was more frequent among women (69.65%) than men (52.00%; p = 0.0186). The polymorphic genotype of PPARG gene (rs1801282) was associated with TPOAb positivity (p = 0.0391), and the GG genotype of rs2476601 of PTPN22 gene was associated with positivity for both TgAb (p = 0.0360) and TPOAb (p < 0.0001). Both polymorphic genotypes rs2476601 and rs3789607 of the PTPN22 gene were more frequent among nonsmoking patients (p = 0.0102 and p = 0.0124, respectively).

CONCLUSIONS

Our data confirm the important role of CTLA4 polymorphisms in GD susceptibility; demonstrate the role of PTPN22 polymorphisms in patients' clinical features; and suggest these genes may influence the severity of the disease.

The potential markers involved in newly diagnosed graves' disease and the development of active graves' orbitopathy

BACKGROUND

Graves' disease (GD) patients experience two major issues: one is the severe hyperthyroidism associated with newly diagnosed GD, and the other involves the disfiguring and dysfunctional features of active Graves' orbitopathy (GO). Therefore, the aim of our study was to identify potential markers involved in the initial phase of GD dysfunction and the development of active GO.

METHODS

Seventy-eight subjects were recruited: 40 with newly diagnosed GD, 20 with inactive GO and 18 with active GO. GO activity was evaluated by the clinical activity score (CAS, active GO = CAS ≥ 3), and severity was assessed according to the NOSPECS classification. Plasma selenium concentrations were determined by dual channel hydride generation atomic fluorescence photometry. A liquid chip assay was used to measure plasma Th1 cytokines IFN-γ and TNF-α; Th2 cytokines IL4, IL5 and IL6; Th17 cytokine IL23; Treg cytokines IL10 and TGF-β; and two chemokines, CCL2 (Th2 chemokine) and CXCL10 (Th1 chemokine).

RESULTS

Among the three groups, newly diagnosed GD patients showed significantly elevated plasma levels of CXCL10 and IL-23 (all p < 0.05). Both CXCL10 and IL23 were significantly correlated with hyperthyroidism severity, specifically, increasing FT3 and FT4 and decreasing TSH. Notably, a very strong positive relationship between IL23 and CXCL10 was revealed (adjusted R square = 0.795; p < 0.001). Moreover, the selenium level was lower, while that of CCL2 was higher, in active GO than in inactive GO (p = 0.007, p < 0.001, respectively). Likewise, we also discovered that increasing CCL2 levels and decreasing selenium levels were associated with high CAS. Remarkably, after adjusting for potential confounding factors, selenium (OR, 0.919) and CCL2 (OR, 1.042) were still independent predictors for the diagnosis of active GO, and similar conclusions were drawn by receiver operating characteristic (ROC) curve analysis.

CONCLUSION

Pro-inflammatory cytokines, especially Th17-associated cytokines (e.g., IL23) and Th1 chemokines (e.g., CXCL10), appear to be involved in the initial phase of GD dysfunction. Moreover, we revealed for the first time that decreased plasma selenium levels and increased concentrations of Th2 chemokines (e.g., CCL2) may reflect GO disease activity, shedding light on the diagnosis and evaluation of active GO.

Differential modulation of CXCL8 versus CXCL10, by cytokines, PPAR-gamma, or PPAR-alpha agonists, in primary cells from Graves' disease and ophthalmopathy

BACKGROUND

Thyrocytes secrete CXC chemokines, particularly (C-X-C motif) ligand (CXCL)8 and CXCL10; its physiopathological significance remains unclear. This study investigates the modulation of the secretion of CXCL8 vs. CXCL10, in human primary cells cultures of thyroid follicular cells (TFC) in Graves' disease (GD), and fibroblasts (OF) or preadipocytes (OP) from Graves' ophthalmopathy (GO).

METHODS

Cells were initially incubated with different concentrations of tumor necrosis factor (TNF)α (1, 5, 10 ng/mL). Then, CXCL8 and CXCL10 were measured in the supernatants of TFC, OF or OP cells basally and after 24 h of treatment with interferon (IFN)γ (1000 IU/mL) and/or TNFα (10 ng/mL), in presence/absence of the peroxisome proliferator activated receptor (PPAR)γ agonist pioglitazone (0, 0.1, 1, 5, 10, 20 μM), or the PPARα agonist fenofibrate (5, 10, 50, 100 μM).

RESULTS

CXCL8, not CXCL10, was detected in basal conditions in TFC, OF and OP. CXCL8 secretion increased dose-dependently with increasing concentrations of TNFα. CXCL10 secretion was significantly stimulated by IFNγ (P < 0.01) and not by TNFα, whereas CXCL8 was induced by TNFα (P < 0.01), and inhibited by IFNγ (P < 0.01) in TFC, OF and OP. Combining TNFα and IFNγ, the IFNγ-induced CXCL10 secretion was synergistically increased (P < 0.01) while the TNFα-induced CXCL8 secretion (P < 0.01) was reversed in all cell types. Pioglitazone had no significant effect on the secretion of CXCL8 stimulated by TNFα, while inhibited CXCL10. Fenofibrate, in presence of IFNγ plus TNFα, dose-dependently inhibited both CXCL10 and CXCL8 release.

CONCLUSION

We first show that TFC, OF, and OP secrete CXCL8 and CXCL10 differentially, sustained by specific proinflammatory cytokines or their combination. This could reflect a different role of the two chemokines in the course of the disease, as CXCL10 could be associated with the initial phase of the disease when IFNγ is preponderant, while CXCL8 could be associated with a later chronic phase of the disease, when TNFα prevails.

A short field guide to fibroblast function in immunity

Fibroblasts in secondary lymphoid organs, or fibroblastic reticular cells (FRC), are gate-keepers of immune responses. Here, we frame how these cells regulate immune responses via a three-part scheme in which FRC can setup, support or suppress immune responses. We also review how fibroblasts from non-lymphoid tissues influence immunity and highlight how they resemble and differ from FRC. Overall, we aim to focus attention on the emerging roles of lymphoid tissue and non-lymphoid tissue fibroblasts in control of innate and adaptive immunity.

Acetaminophen-Induced Liver Injury Alters the Acyl Ethanolamine-Based Anti-Inflammatory Signaling System in Liver

Protective mechanisms against drug-induced liver injury are actively being searched to identify new therapeutic targets. Among them, the anti-inflammatory N-acyl ethanolamide (NAE)-peroxisome proliferators activated receptor alpha (PPARα) system has gained much interest after the identification of its protective role in steatohepatitis and liver fibrosis. An overdose of paracetamol (APAP), a commonly used analgesic/antipyretic drug, causes hepatotoxicity, and it is being used as a liver model. In the present study, we have analyzed the impact of APAP on the liver NAE-PPARα system. A dose-response (0.5-5-10-20 mM) and time-course (2-6-24 h) study in human HepG2 cells showed a biphasic response, with a decreased PPARα expression after 6-h APAP incubation followed by a generalized increase of NAE-PPARα system-related components (PPARα, NAPE-PLD, and FAAH), including the NAEs oleoyl ethanolamide (OEA) and docosahexaenoyl ethanolamide, after a 24-h exposure to APAP. These results were partially confirmed in a time-course study of mice exposed to an acute dose of APAP (750 mg/kg). The gene expression levels of Pparα and Faah were decreased after 6 h of treatment and, after 24 h, the gene expression levels of Nape-pld and Faah, as well as the liver levels of OEA and palmitoyl ethanolamide, were increased. Repeated APAP administration (750 mg/kg/day) up to 4 days also decreased the expression levels of PPARα and FAAH, and increased the liver levels of NAEs. A resting period of 15 days completely restored these impairments. Liver immunohistochemistry in a well-characterized human case of APAP hepatotoxicity confirmed PPARα and FAAH decrements. Histopathological and hepatic damage (Cyp2e1, Caspase3, αSma, Tnfα, and Mcp1)-related alterations observed after repeated APAP administration were aggravated in the liver of Pparα-deficient mice. Our results demonstrate that the anti-inflammatory NAE-PPARα signaling system is implicated in liver toxicity after exposure to APAP overdose, and may contribute to its recovery through a long-term time-dependent response.

Intersection of Chemokine and TSH Receptor Pathways in Human Fibrocytes: Emergence of CXCL-12/CXCR4 Cross Talk Potentially Relevant to Thyroid-Associated Ophthalmopathy

Fibrocytes are monocyte progenitor cells that have been implicated in normal and pathological tissue remodeling. Among the prominent chemokine receptors expressed by these cells is CXC motif receptor 4 (CXCR4), which, with its cognate ligand CXCL motif ligand 12 (CXCL-12), directs fibrocytes to sites of fibrosis. Fibrocytes have been implicated in the pathogenesis of thyroid-associated ophthalmopathy, the ocular manifestation of Graves' disease (GD), by virtue of their unique accumulation as CD34⁺ orbital fibroblasts (OFs). Fibrocytes also express high levels of functional TSH receptor (TSHR). Here, we determined CXCL-12 and CXCR4 expression in fibrocytes and GD-OF and whether that pathway interacts with TSHR. CXCL-12 is highly expressed in GD-OF, whereas CXCR4 levels are dramatically higher in fibrocytes. Levels of these proteins are differentially regulated by TSH in a cell type-specific manner. Further, CXCL-12 enhances the induction by TSH of IL-6 in fibrocytes but attenuates this induction in GD-OF. In contrast, in pure CD34⁺ OF, the interplay between TSH and CXCL-12 reverts to that observed in fibrocytes. Our results indicate that CXCL-12 enhances TSH actions in fibrocytes but inhibits them in GD-OF, a dichotomy imposed by factors emanating from CD34^- OF. They also suggest a potentially important modulatory role for CD34^- OF in determining the factors that influence pathological TSHR signaling in the TAO orbit.

TSH-receptor-expressing fibrocytes and thyroid-associated ophthalmopathy

Thyroid-associated ophthalmopathy (TAO) is a vexing and undertreated ocular component of Graves disease in which orbital tissues undergo extensive remodelling. My colleagues and I have introduced the concept that fibrocytes expressing the haematopoietic cell antigen CD34 (CD34(+) fibrocytes), which are precursor cells of bone-marrow-derived monocyte lineage, express the TSH receptor (TSHR). These cells also produce several other proteins whose expression was traditionally thought to be restricted to the thyroid gland. TSHR-expressing fibrocytes in which the receptor is activated by its ligand generate extremely high levels of several inflammatory cytokines. Acting in concert with TSHR, the insulin-like growth factor 1 receptor (IGF-1R) expressed by orbital fibroblasts and fibrocytes seems to be necessary for TSHR-dependent cytokine production, as anti-IGF-1R blocking antibodies attenuate these proinflammatory actions of TSH. Furthermore, circulating fibrocytes are highly abundant in patients with TAO and seem to infiltrate orbital connective tissues, where they might transition to CD34(+) fibroblasts. My research group has postulated that the infiltration of fibrocytes into the orbit, their unique biosynthetic repertoire and their proinflammatory and profibrotic phenotype account for the characteristic properties exhibited by orbital connective tissues that underlie susceptibility to TAO. These insights, which have emerged in the past few years, might be of use in therapeutically targeting pathogenic orbit-infiltrating fibrocytes selectively by utilizing novel biologic agents that interfere with TSHR and IGF-1R signalling.

Absence of CC chemokine receptors 2a and 2b from human adipose lineage cells

Previous results have suggested the existence of receptors for monocyte chemoattractant protein-1 (MCP-1), CC chemokine receptors 2 (CCR2), in human adipocytes and their involvement in mediating effects of MCP-1 on adipocyte functions. However, the presence of CCR2 present on non-adipose-lineage cells of adipose tissue has not been excluded. We have used human Simpson-Golabi-Behmel-Syndrome (SGBS) preadipocytes and in-vitro-differentiated mature adipocytes to investigate the expression of CCR2 in human (pre)adipocytes. We found that the cells are devoid of CCR2 receptor protein and mRNA expression and fail to respond to treatment with all known CCR2 chemokine agonists. CCR2 is also absent from (pre)adipocytes prepared in vitro from human multipotent adipose-derived stem cells, bone-marrow-derived mesenchymal stem cells, or from primary (pre)adipocytes. Conditions mimicking proinflammatory changes in adipose tissue did not induce CCR2 receptor expression. We conclude that CCR2 is absent from human adipose lineage cells. Functional effects previously described for MCP-1 in human adipose tissue may be mediated indirectly through paracrine effects on non-adipose-lineage cells or by a (pre)adipocyte receptor for MCP-1 distinct from CCR2.

PPARg2 Ala¹² variant protects against Graves' orbitopathy and modulates the course of the disease

Orbital fibroblast differentiation to adipocytes is a peroxisome proliferator-activated receptor g (PPARg)-dependent process essential for pathogenic tissue remodeling in Graves' orbitopathy (GO). PPARg2 Pro¹²Ala polymorphism modulates expression and/or function of the molecule encoded by this gene and is a promising locus of GO. Here, we analyzed associations of PPARg2 Pro¹²Ala with clinical manifestation of GO in 742 Polish Caucasians including 276 Graves' disease (GD) patients. In our study, the Ala¹² allele and Ala¹² variant (Ala¹²Ala and/or Pro¹²Ala genotype) decreased the risk of GO (p = 0.000012 and p = 0.00013). Moreover, Ala¹²Ala genotype was observed only in patients without GO (p = 0.002). GD patients with Ala¹² variant had less active and less severe eye symptoms. Female carriers of the Ala¹² allele rarely developed GO, but the marker was not related to symptoms of GO. The opposite finding was recorded in males, in whom the studied polymorphism was related to activity, but not to the development, of GO. In Ala¹² variant carriers without familial history of thyroid disease, risk of GO was lower than in persons with a familial background. The Ala¹² allele seemed to protect smokers from GO, but in nonsmokers, such a relation was not obvious. A multivariate analysis indicated the Pro¹²Ala marker as an independent risk factor of eye symptoms (p = 0.0001) and lack of Ala increases the risk of GO 3.24-fold. In conclusion, the gain-of-function Ala¹² variant protects against GO and modulates the course of the disease.