Activated human T lymphocytes express cyclooxygenase-2 and produce proadipogenic prostaglandins that drive human orbital fibroblast differentiation to adipocytes

Immune checkpoints: new insights into the pathogenesis of thyroid eye disease

Thyroid eye disease (TED) is a disfiguring autoimmune disease characterized by changes in the orbital tissues and is caused by abnormal thyroid function or thyroid-related antibodies. It is the ocular manifestation of Graves' disease. The expression of thyroid-stimulating hormone receptor (TSHR) and the insulin-like growth factor-1 receptor (IGF-1 R) on the cell membrane of orbital fibroblasts (OFs) is responsible for TED pathology. Excessive inflammation is caused when these receptors in the orbit are stimulated by autoantibodies. CD34+ fibrocytes, found in the peripheral blood and orbital tissues of patients with TED, express immune checkpoints (ICs) like MHC II, B7, and PD-L1, indicating their potential role in presenting antigens and regulating the immune response in TED pathogenesis. Immune checkpoint inhibitors (ICIs) have significantly transformed cancer treatment. However, it can also lead to the occurrence of TED in some instances, suggesting the abnormality of ICs in TED. This review will examine the overall pathogenic mechanism linked to the immune cells of TED and then discuss the latest research findings on the immunomodulatory role of ICs in the development and pathogenesis of TED. This will offer fresh perspectives on the study of pathogenesis and the identification of potential therapeutic targets.

Eicosapentaenoic Acid Influences the Lipid Profile of an In Vitro Psoriatic Skin Model Produced with T Cells

Psoriasis is a skin disease characterized by epidermal hyperplasia and an inappropriate activation of the adaptive immunity. A dysregulation of the skin's lipid mediators is reported in the disease with a predominance of the inflammatory cascade derived from n-6 polyunsaturated fatty acids (n-6 PUFAs). Bioactive lipid mediators derived from arachidonic acid (AA) are involved in the inflammatory functions of T cells in psoriasis, whereas n-3 PUFAs' derivatives are anti-inflammatory metabolites. Here, we sought to evaluate the influence of a supplementation of the culture media with eicosapentaenoic acid (EPA) on the lipid profile of a psoriatic skin model produced with polarized T cells. Healthy and psoriatic skin substitutes were produced following the auto-assembly technique. Psoriatic skin substitutes produced with or without T cells presented increased epidermal and dermal linolenic acid (LA) and AA levels. N-6 PUFA lipid mediators were strongly measured in psoriatic substitutes, namely, 13-hydroxyoctadecadienoic acid (13-HODE), prostaglandin E2 (PGE2) and 12-hydroxyeicosatetraenoic acid (12-HETE). The added EPA elevated the amounts of EPA, n-3 docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) in the epidermal and dermal phospholipids. The EPA supplementation balanced the production of epidermal lipid mediators, with an increase in prostaglandin E3 (PGE3), 12-hydroxyeicosapentaenoic acid (12-HEPE) and N-eicosapentaenoyl-ethanolamine (EPEA) levels. These findings show that EPA modulates the lipid composition of psoriatic skin substitutes by encouraging the return to a cutaneous homeostatic state.

Non-coding RNA-mediated epigenetic alterations in Grave's ophthalmopathy: A scoping systematic review

Background

It is becoming more and more apparent that Grave's Ophthalmopathy (GO) pathogenesis may be aided by epigenetic processes such as DNA methylation modifications, histone tail covalent modifications, and non-coding RNA (ncRNA)-based epigenetic processes. In the present study, we aimed to focus more on the miRNAs rather than lncRNAs due to lack of investigations on these non-coding RNAs and their role in GO's pathogenesis.

Methods

A six-stage methodology framework and the PRISMA recommendation were used to conduct this scoping review. A comprehensive search was conducted across seven databases to discover relevant papers published until February 2022. The data extraction separately, and quantitative and qualitative analyses were conducted.

Results

A total of 20 articles were found to meet inclusion criteria. According to the results, ncRNA were involved in the regulation of inflammation (miR-146a, LPAL2/miR-1287-5p axis, LINC01820:13/hsa miR-27b-3p axis, and ENST00000499452/hsa-miR-27a-3p axis), regulation of T cell functions (miR-146a/miR-183/miR-96), regulation of glycosaminoglycan aggregation and fibrosis (miR-146a/miR-21), glucocorticoid sensitivity (miR-224-5p), lipid accumulation and adipogenesis (miR-27a/miR-27b/miR-130a), oxidative stress and angiogenesis (miR-199a), and orbital fibroblast proliferation (miR-21/miR-146a/miR-155). Eleven miRNAs (miR-146a/miR-224-5p/miR-Let7d-5p/miR-96-5p/miR-301a-3p/miR-21-5p) were also indicated to have the capacity to be used as biomarkers.

Conclusions

Regardless of the fact that there is significant documentation of ncRNA-mediated epigenetic dysfunction in GO, additional study is needed to thoroughly comprehend the epigenetic connections concerned in disease pathogenesis, paving the way for novel diagnostic and prognostic tools for epigenetic therapies among the patients.

Integrated analysis of whole blood oxylipin and cytokine responses after bacterial, viral, and T cell stimulation reveals new immune networks

Oxylipins are major immunomodulating mediators, yet studies of inflammation focus mainly on cytokines. Here, using a standardized whole-blood stimulation system, we characterized the oxylipin-driven inflammatory responses to various stimuli and their relationships with cytokine responses. We performed a pilot study in 25 healthy individuals using 6 different stimuli: 2 bacterial stimuli (LPS and live BCG), 2 viral stimuli (vaccine-grade poly I:C and live H1N1 attenuated influenza), an enterotoxin superantigen and a Null control. All stimuli induced a strong production of oxylipins but most importantly, bacterial, viral, and T cell immune responses show distinct oxylipin signatures. Integration of the oxylipin and cytokine responses for each condition revealed new immune networks improving our understanding of inflammation regulation. Finally, the oxylipin responses and oxylipin-cytokine networks were compared in patients with active tuberculosis or with latent infection. This revealed different responses to BCG but not LPS stimulation highlighting new regulatory pathways for further investigations.

The biological actions of prostanoids in adipose tissue in physiological and pathophysiological conditions

Adipose tissue has been established as an endocrine organ that plays an important role in maintaining metabolic homeostasis. Adipose tissue releases several bioactive molecules called adipokines. Inflammation, dysregulation of adipokine synthesis, and secretion are observed in obesity and related diseases and cause adipose tissue dysfunction. Prostanoids, belonging to the eicosanoid family of lipid mediators, can be synthesized in adipose tissue and play a critical role in adipose tissue biology. In this review, we summarized the current knowledge regarding the interaction of prostanoids with adipokines, the expression of prostanoid receptors, and prostanoid synthase enzymes in adipose tissues in health and disease. Furthermore, the involvement of prostanoids in the physiological function or dysfunction of adipose tissue including inflammation, lipolysis, adipogenesis, thermogenesis, browning of adipocytes, and vascular tone regulation was also discussed by examining studies using pharmacological approaches or genetically modified animals for prostanoid receptors/synthase enzymes. Overall, the present review provides a perspective on the evidence from literature regarding the biological effects of prostanoids in adipose tissue. Among prostanoids, prostaglandin E2 (PGE₂) is prominent in regards to its substantial role in both adipose tissue physiology and pathophysiology. Targeting prostanoids may serve as a potential therapeutic strategy for preventing or treating obesity and related diseases.

Repurposing Lenvatinib as A Potential Therapeutic Agent against Thyroid Eye Disease by Suppressing Adipogenesis in Orbital Adipose Tissues

Thyroid eye disease (TED) is the most common orbital disease in adults. Targeting expanded orbital adipose tissue (OAT) removed by surgery has therapeutic potential. However, drugs targeting OAT are unavailable because of the lack of deciphering features of OAT. Here, we aimed to investigate the mechanism underlying OAT expansion and identify a drug targeting OAT in TED. We found an increasing number of adipocytes with smaller size in TED-derived OATs as compared with controls, indicating that hyperplasia rather than hypertrophy contributed to OAT enlargement in TED. Typically smaller-sized adipocytes in TED patient-derived OATs were noted to localize surrounding vessels. RNA sequencing revealed enriched vascular endothelial growth factor receptor (VEGFR) genes in adipocytes differentiated from preadipocytes of TED-derived stromal vascular fraction (SVF). Similarly, OATs in patients with TED also expressed a higher level of VEGFR-1 and -2. We induced adipogenesis in TED-derived SVF with or without Lenvatinib, an FDA-approved small-molecule VEGFR inhibitor. Lenvatinib significantly suppressed lipid accumulation in a dose-dependent manner. In conclusion, our study revealed the potential anti-adipogenic effect of Lenvatinib on the OAT of TED-affected patients. In addition to proposing a drug for TED treatment, this study shows the therapeutic potential of anti-adipogenesis drugs targeting the VEGF pathway.

Thinking inside the box: Current insights into targeting orbital tissue remodeling and inflammation in thyroid eye disease

Thyroid eye disease (TED) is an autoimmune disorder that manifests in the orbit. In TED, the connective tissue behind the eye becomes inflamed and remodels with increased fat accumulation and/or increased muscle and scar tissue. As orbital tissue expands, patients develop edema, exophthalmos, diplopia, and optic neuropathy. In severe cases vision loss may occur secondary to corneal scarring from exposure or optic nerve compression. Currently there is no cure for TED, and treatments are limited. A major breakthrough in TED therapy occurred with the FDA approval of teprotumumab, a monoclonal insulin-like growth factor 1 receptor (IGF1R) blocking antibody. Yet, teprotumumab therapy has limitations, including cost, infusion method of drug delivery, variable response, and relapse. We describe approaches to target orbital fibroblasts and the complex pathophysiology that underlies tissue remodeling and inflammation driving TED. Further advances in the elucidation of the mechanisms of TED may lead to prophylaxis based upon early biomarkers as well as lead to more convenient, less expensive therapies.

Alpha-Linolenic Acid Modulates T Cell Incorporation in a 3D Tissue-Engineered Psoriatic Skin Model

Psoriasis is an autoimmune skin disease with an increased number of leukocytes infiltrating the dermal and epidermal compartments compared with normal skin. N-3 polyunsaturated fatty acids (n-3 PUFAs) are frequently used in the clinic in order to attenuate the symptoms of psoriasis. For psoriatic patients, a supplementation of the diet with alpha-linolenic acid (ALA) reduces the activation of T cell signaling pathways, leading to a significant reduction in inflammatory cytokine secretion. However, the precise mechanism of action of n-3 PUFAs in psoriasis is still not understood. In the present study, we elucidated the bioaction of ALA on the adaptive immune component of psoriasis by using a psoriatic skin model produced with the addition of activated T cells. Healthy and psoriatic skin substitutes were produced according to the self-assembly method, using culture media supplemented with 10 μM of ALA. T cells were isolated from blood samples using a negative selection isolation method. ALA supplementation regulated the hyperproliferation and abnormal cell differentiation of psoriatic keratinocytes stimulated by T cells. Additionally, the exogenous ALA was correctly incorporated into the phospholipids of keratinocytes, which resulted in increased levels of ALA, eicosapentaenoic acid (EPA) and n-3 docosapentaenoic acid (n-3 DPA). The infiltration of T cells into the epidermis was reduced when ALA was added to the culture medium, and significant decreases in the levels of inflammatory cytokines and chemokines such as CXCL1, interleukin-6 (IL-6) and interleukin-8 (IL-8) were consequently measured in psoriatic substitutes supplemented with this n-3 PUFA. Altogether, our results showed that in this psoriatic skin model enriched with T cells, ALA exerted its beneficial effect by decreasing the quantities of inflammatory mediators released by T cells.

Upregulation of the PPAR signaling pathway and accumulation of lipids are related to the morphological and structural transformation of the dragon-eye goldfish eye

Goldfish comprise around 300 different strains with drastically altered and aesthetical morphologies making them suitable models for evolutionary developmental biology. The dragon-eye strain is characterized by protruding eyes (analogous to those of Chinese dragons). Although the strain has been selected for about 400 years, the mechanism of its eye development remains unclear. In this study, a stable dragon-eye goldfish strain with a clear genetic background was rapidly established and studied. We found that upregulation of the PPAR signaling pathway accompanied by an increase in lipid accumulation might trigger the morphological and structural transformation of the eye in dragon-eye goldfish. At the developmental stage of proptosis (eye protrusion), downregulation of the phototransduction pathway was consistent with the structural defects and myopia of the dragon-eye strain. With the impairment of retinal development, cytokine-induced inflammation was activated, especially after proptosis, similar to the pathologic symptoms of many human ocular diseases. In addition, differentially expressed transcription factors were significantly enriched in the PAX and homeobox families, two well-known transcription factor families involved in eye development. Therefore, our findings reveal the dynamic changes in key pathways during eye development in dragon-eye goldfish, and provide insights into the molecular mechanisms underlying drastically altered eyes in goldfish and human ocular disease.

MicroRNA-130a Is Elevated in Thyroid Eye Disease and Increases Lipid Accumulation in Fibroblasts Through the Suppression of AMPK

Purpose

Thyroid eye disease (TED) is a condition that causes the tissue behind the eye to become inflamed and can result in excessive fatty tissue accumulation in the orbit. Two subpopulations of fibroblasts reside in the orbit: those that highly express Thy1 (Thy1+) and those with little or no Thy1 (Thy1–). Thy1– orbital fibroblasts (OFs) are more prone to lipid accumulation than Thy1+ OFs. The purpose of this study was to investigate the mechanisms whereby Thy1– OFs more readily accumulate lipid.

Methods

We screened Thy1+ and Thy1– OFs for differences in microRNA (miRNA) expression. The effects of increasing miR-130a levels in OFs was investigated by measuring lipid accumulation and visualizing lipid deposits. To determine if adenosine monophosphate-activated protein kinase (AMPK) is important for lipid accumulation, we performed small interfering RNA (siRNA)-mediated knockdown of AMPKβ1. We measured AMPK expression and activity using immunoblotting for AMPK and AMPK target proteins.

Results

We determined that miR-130a was upregulated in Thy1– OFs and that miR-130a targets two subunits of AMPK. Increasing miR-130a levels enhanced lipid accumulation and reduced expression of AMPKα and AMPKβ in OFs. Depletion of AMPK also increased lipid accumulation. Activation of AMPK using AICAR attenuated lipid accumulation and increased phosphorylation of acetyl-CoA carboxylase (ACC) in OFs.

Conclusions

These data suggest that when Thy1– OFs accumulate in TED, miR-130a levels increase, leading to a decrease in AMPK activity. Decreased AMPK activity promotes lipid accumulation in TED OFs, leading to excessive fatty tissue accumulation in the orbit.

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.

Teprotumumab: a disease modifying treatment for graves' orbitopathy

BACKGROUND

On 21st January 2020, the FDA approved Tepezza (teprotumumab-trbw) for the treatment of active Graves' orbitopathy (GO) in adults. This approval was based on positive results from two multinational randomised double-blind placebo-controlled clinical trials.

DISCUSSION

This article discusses the outcomes of those trials and the potential role of teprotumumab in altering current treatment paradigms in Graves' orbitopathy. Future challenges are explored, including the need to confirm its disease-modifying effect, to establish its optimal position in the treatment pathway, and to define the appropriate subset of patients who would benefit from its use.

CONCLUSIONS

The results from these two large clinical trials have shown teprotumumab to have remarkable effects on multiple clinical outcomes in GO, particularly in its ability to reverse proptosis. It may herald a new era in the treatment of thyroid eye disease and could offer an alternative to surgery and its associated complications. Additional studies will continue to shape the treatment of GO and define the role of teprotumumab within the treatment paradigm.

TSHR Signaling Stimulates Proliferation Through PI3K/Akt and Induction of miR-146a and miR-155 in Thyroid Eye Disease Orbital Fibroblasts

Purpose

To investigate the molecular pathways that drive thyroid stimulating hormone receptor (TSHR)–induced cellular proliferation in orbital fibroblasts (OFs) from thyroid eye disease (TED) patients.

Methods

Orbital fibroblasts from TED and non-TED patients were treated with TSH and changes in gene expression and proliferation were measured. To determine the role of TSHR, TSHR-specific siRNA was used to deplete TSHR levels. Proliferation was measured by bromodeoxyuridine (BrdU) incorporation. PI3K/Akt activation was analyzed by Western blot. The PI3K inhibitor LY294002 was used to investigate PI3K/Akt signaling in OF proliferation. Expression of TSHR, inflammatory cytokines, proliferation related genes and miR-146a and miR-155 were measured by qPCR.

Results

Orbital fibroblasts from TED patients proliferate significantly more than non-TED OFs in response to TSH. TSH-induced proliferation was dependent upon TSHR expression and required the PI3K/Akt signaling cascade. TSHR activation stimulated miR-146a and miR-155 expression. TED OFs produced significantly more miR-146a and miR-155 than non-TED OFs. MiR-146a and miR-155 targets, ZNRF3 and PTEN, which both limit cell proliferation, were decreased in TSH treated OFs.

Conclusions

These data reveal that TSHR signaling in TED OFs stimulates proliferation directly through PI3K/Akt signaling and indirectly through induction of miR-146a and miR-155. MiR-146a and miR-155 enhance TED OF proliferation by reducing expression of target genes that normally block cell proliferation. TSHR-dependent expression of miR-146a and miR-155 may explain part of the fibroproliferative pathology observed in TED.

Immunological Aspects of Graves' Ophthalmopathy

The body's autoimmune process is involved in the development of Graves' disease (GD), which is manifested by an overactive thyroid gland. In some patients, autoreactive inflammatory reactions contribute to the development of symptoms such as thyroid ophthalmopathy, and the subsequent signs and symptoms are derived from the expansion of orbital adipose tissue and edema of extraocular muscles within the orbit. The autoimmune process, production of antibodies against self-antigens such as TSH receptor (TSHR) and IGF-1 receptor (IGF-1R), inflammatory infiltration, and accumulation of glycosaminoglycans (GAG) lead to edematous-infiltrative changes in periocular tissues. As a consequence, edema exophthalmos develops. Orbital fibroblasts seem to play a crucial role in orbital inflammation, tissue expansion, remodeling, and fibrosis because of their proliferative activity as well as their capacity to differentiate into adipocytes and myofibroblasts and production of GAG. In this paper, based on the available medical literature, the immunological mechanism of GO pathogenesis has been summarized. Particular attention was paid to the role of orbital fibroblasts and putative autoantigens. A deeper understanding of the pathomechanism of the disease and the involvement of immunological processes may give rise to the introduction of new, effective, and safe methods of treatment or monitoring of the disease activity.

The role of cell mediated immunopathogenesis in thyroid-associated ophthalmopathy

Currently, thyroid-associated ophthalmopathy (TAO) lacks effective treatment due to our lack of clarity in its immunopathogenesis. Orbital fibroblasts play a key role in altering inflammation and immune response in TAO, and are considered as the key target and effector cells in its pathogenesis. The orbit infiltrating CD34+ fibrocytes add on to the process by expressing high levels of autoantigens and inflammatory cytokines, while also differentiating into myofibroblasts or adipocytes. This review focuses on the role of orbital fibroblasts and CD34+ fibrocytes in the pathogenesis of TAO, highlighting the basis of emerging treatments.

CD40 Enhances Sphingolipids in Orbital Fibroblasts: Potential Role of Sphingosine-1-Phosphate in Inflammatory T-Cell Migration in Graves' Orbitopathy

Purpose

Graves' orbitopathy (GO) is an autoimmune orbital disorder associated with Graves' disease caused by thyrotropin receptor autoantibodies. Orbital fibroblasts (OFs) and CD40 play a key role in disease pathogenesis. The bioactive lipid sphingosine-1-phosphate (S1P) has been implicated in promoting adipogenesis, fibrosis, and inflammation in OFs. We investigated the role of CD40 signaling in inducing S1P activity in orbital inflammation.

Methods

OFs and T cells were derived from GO patients and healthy control (Ctl) persons. S1P abundance in orbital tissues was evaluated by immunofluorescence. OFs were stimulated with CD40 ligand and S1P levels were determined by ELISA. Further, activities of acid sphingomyelinase (ASM), acid ceramidase, and sphingosine kinase were measured by ultraperformance liquid chromatography. Sphingosine and ceramide contents were analyzed by mass spectrometry. Finally, the role for S1P in T-cell attraction was investigated by T-cell migration assays.

Results

GO orbital tissue showed elevated amounts of S1P as compared to control samples. Stimulation of CD40 induced S1P expression in GO-derived OFs, while Ctl-OFs remained unaffected. A significant increase of ASM and sphingosine kinase activities, as well as lipid formation, was observed in GO-derived OFs. Migration assay of T cells in the presence of SphK inhibitor revealed that S1P released by GO-OFs attracted T cells for migration.

Conclusions

The results demonstrated that CD40 ligand stimulates GO fibroblast to produce S1P, which is a driving force for T-cell migration. The results support the use of S1P receptor signaling modulators in GO management.

Anatomical, Physiological, and Functional Diversity of Adipose Tissue

Adipose tissue depots can exist in close association with other organs, where they assume diverse, often non-traditional functions. In stem cell-rich skin, bone marrow, and mammary glands, adipocytes signal to and modulate organ regeneration and remodeling. Skin adipocytes and their progenitors signal to hair follicles, promoting epithelial stem cell quiescence and activation, respectively. Hair follicles signal back to adipocyte progenitors, inducing their expansion and regeneration, as in skin scars. In mammary glands and heart, adipocytes supply lipids to neighboring cells for nutritional and metabolic functions, respectively. Adipose depots adjacent to skeletal structures function to absorb mechanical shock. Adipose tissue near the surface of skin and intestine senses and responds to bacterial invasion, contributing to the body's innate immune barrier. As the recognition of diverse adipose depot functions increases, novel therapeutic approaches centered on tissue-specific adipocytes are likely to emerge for a range of cancers and regenerative, infectious, and autoimmune disorders.

Activated human T lymphocytes inhibit TGFβ-induced fibroblast to myofibroblast differentiation via prostaglandins D2 and E2

In pulmonary fibrosis (PF), fibroblasts and myofibroblasts proliferate and deposit excessive extracellular matrix in the interstitium, impairing normal lung function. Because most forms of PF have a poor prognosis and limited treatment options, PF represents an urgent unmet need for novel, effective therapeutics. Although the role of immune cells in lung fibrosis is unclear, recent studies suggest that T lymphocyte (T cell) activation may be impaired in PF patients. Furthermore, we have previously shown that activated T cells can produce prostaglandins with anti-scarring potential. Here, we test the hypothesis that activated T cells directly inhibit myofibroblast differentiation using a coculture system. Coculture with activated primary blood-derived T cells, from both healthy human donors and PF patients, inhibited transforming growth factor β-induced myofibroblast differentiation in primary human lung fibroblasts isolated from either normal or PF lung tissue. Coculture supernatants contained anti-fibrotic prostaglandins D₂ and E₂, and the inhibitory effect of coculture on myofibroblast differentiation was largely reversed when prostaglandin production was abrogated either by resting the T cells before coculture or via specific pharmacological inhibitors. Moreover, coculture conditions induced COX-2 in HLFs but not in T cells, suggesting that T cells deliver an activating signal to HLFs, which in turn produce anti-fibrotic prostaglandins. We show for the first time that coculture with activated primary human T lymphocytes strongly inhibits myofibroblast differentiation, revealing a novel cell-to-cell communication network with therapeutic implications for fibrotic lung diseases.

Distinct inflammatory gene expression in extraocular muscle and fat from patients with Graves' orbitopathy

OBJECTIVE

This study sought to compare patients with thyroid eye disease (TED) and normal controls with respect to the expression of the NR3C1, CHUK, IKBKB, FOS, NFKB and HSD11B1 genes in orbital fat (OF) and extraocular muscle (EOM).

DESIGN AND METHODS

A prospective study design was used to evaluate 34 TED patients and 38 healthy controls. OF was harvested from 33 TED patients and 27 controls. EOM biopsies were obtained from 32 TED patients and 18 controls. Samples were examined by real-time PCR and evaluated using appropriate statistical analyses with a significance cut-off of P < 0.05.

RESULTS

NR3C1 mRNA levels were higher in TED EOM (median 213 (96-376)) than those in control EOM (78 (34-138)) (P < 0.001), and NFKB expression was elevated in TED muscle (223 (31-520)) relative to that in control muscle (8 (6-31)) (P < 0.001). HSD11B1 expression was higher in TED EOM (0.78 (0.47-2.01)) than that in control EOM (0.22 (0.09-0.51)) (P < 0.001). Levels of CHUK, IKBKB, and FOS were higher in TED EOM (115 (20-223), 111 (54-299) and 0.11 (0.03-0.19), respectively) than those in control EOM (5.8 (2-13), 21 (5-52) and 0.05 (0.001-0.03) respectively) (P < 0.001).

CONCLUSION

Tissues involved in GO exhibited different mRNA levels of NR3C1, CHUK, IKBKB, FOS, NFKB and HSD11B1. Gene expression in OF was similar for TED patients and controls. CHUK, IKBKB, FOS, NFKB, and HSD11B1 mRNA levels were higher in TED EOM than those in control EOM. NFKB was disproportionally elevated compared with NR3C1; this finding was indicative of a local proinflammatory profile.

Exercise effects on perivascular adipose tissue: endocrine and paracrine determinants of vascular function

Obesity is a global epidemic, accompanied by increased risk of type 2 diabetes and cardiovascular disease. Adipose tissue hypertrophy is associated with adipose tissue inflammation, which alters the secretion of adipose tissue-derived bioactive products, known as adipokines. Adipokines determine vessel wall properties such as smooth muscle tone and vessel wall inflammation. Exercise is a mainstay of prevention of chronic, non-communicable diseases, type 2 diabetes and cardiovascular disease in particular. Aside from reducing adipose tissue mass, exercise has been shown to reduce inflammatory activity in this tissue. Mechanistically, contracting muscles release bioactive molecules known as myokines, which alter the metabolic phenotype of adipose tissue. In adipose tissue, myokines induce browning, enhance fatty acid oxidation and improve insulin sensitivity. In the past years, the perivascular adipose tissue (PVAT) which surrounds the vasculature, has been shown to control vascular tone and inflammation through local release of adipokines. In obesity, an increase in mass and inflammation of PVAT culminate in dysregulation of adipokine secretion, which contributes to vascular dysfunction. This review describes our current understanding of the mechanisms by which active muscles interact with adipose tissue and improve vascular function. Aside from the exercise-dependent regulation of canonical adipose tissue function, we will focus on the interactions between skeletal muscle and PVAT and the role of novel myokines, such as IL-15, FGF21 and irisin, in these interactions.

LINKED ARTICLES

This article is part of a themed section on Molecular Mechanisms Regulating Perivascular Adipose Tissue - Potential Pharmacological Targets? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.20/issuetoc.

Differential Role of Adipose Tissues in Obesity and Related Metabolic and Vascular Complications

This review focuses on the contribution of white, brown, and perivascular adipose tissues to the pathophysiology of obesity and its associated metabolic and vascular complications. Weight gain in obesity generates excess of fat, usually visceral fat, and activates the inflammatory response in the adipocytes and then in other tissues such as liver. Therefore, low systemic inflammation responsible for insulin resistance contributes to atherosclerotic process. Furthermore, an inverse relationship between body mass index and brown adipose tissue activity has been described. For these reasons, in recent years, in order to combat obesity and its related complications, as a complement to conventional treatments, a new insight is focusing on the role of the thermogenic function of brown and perivascular adipose tissues as a promising therapy in humans. These lines of knowledge are focused on the design of new drugs, or other approaches, in order to increase the mass and/or activity of brown adipose tissue or the browning process of beige cells from white adipose tissue. These new treatments may contribute not only to reduce obesity but also to prevent highly prevalent complications such as type 2 diabetes and other vascular alterations, such as hypertension or atherosclerosis.

Current perspectives on the role of orbital fibroblasts in the pathogenesis of Graves' ophthalmopathy

Graves' ophthalmopathy (GO) is an extra-thyroidal complication of Graves' disease (GD; Graves' hyperthyroidism) characterized by orbital tissue inflammation, expansion, remodeling and fibrosis. Although the initiating trigger of GO is still indistinct, excessive orbital fibroblast activity is at the heart of its pathogenesis. Orbital fibroblasts are activated by cellular interactions with immune cells and the soluble factors they secrete. Orbital fibroblasts, especially from GO patients, express the thyrotropin receptor (TSH-receptor; TSHR), and activation of the orbital fibroblast population by stimulatory autoantibodies directed against the TSHR may provide an important link between GD and GO. Furthermore, stimulatory autoantibodies directed against the insulin-like growth factor-1 receptor have been proposed to contribute to orbital fibroblast activation in GO. Activated orbital fibroblasts produce inflammatory mediators thereby contributing to the orbital inflammatory process in GO. Moreover, orbital fibroblasts exhibit robust proliferative activity and extracellular matrix (especially hyaluronan) synthesizing capacity and can differentiate into adipocytes and myofibroblasts with disease progression, thereby contributing to tissue expansion/remodeling and fibrosis in GO. Orbital fibroblasts, especially those from GO patients, exhibit a hyper-responsive phenotype when compared to fibroblasts from other anatomical regions, which may further contribute to GO pathogenesis. Fibrocytes have been identified as additional source of orbital fibroblasts in GO, where they may contribute to orbital tissue inflammation, adipogenesis and remodeling/fibrosis. This review addresses our current view on the role that orbital fibroblasts fulfill in GO pathogenesis and both established as well as less established not fully crystallized concepts that need future studies will be discussed.

Role of bioactive lipid mediators in obese adipose tissue inflammation and endocrine dysfunction

White adipose tissue is recognized as an active endocrine organ implicated in the maintenance of metabolic homeostasis. However, adipose tissue function, which has a crucial role in the development of obesity-related comorbidities including insulin resistance and non-alcoholic fatty liver disease, is dysregulated in obese individuals. This review explores the physiological functions and molecular actions of bioactive lipids biosynthesized in adipose tissue including sphingolipids and phospholipids, and in particular fatty acids derived from phospholipids of the cell membrane. Special emphasis is given to polyunsaturated fatty acids of the omega-6 and omega-3 families and their conversion to bioactive lipid mediators through the cyclooxygenase and lipoxygenase pathways. The participation of omega-3-derived lipid autacoids in the resolution of adipose tissue inflammation and in the prevention of obesity-associated hepatic complications is also thoroughly discussed.

Breaking the mold: transcription factors in the anucleate platelet and platelet-derived microparticles

Platelets are small anucleate blood cells derived from megakaryocytes. In addition to their pivotal roles in hemostasis, platelets are the smallest, yet most abundant, immune cells and regulate inflammation, immunity, and disease progression. Although platelets lack DNA, and thus no functional transcriptional activities, they are nonetheless rich sources of RNAs, possess an intact spliceosome, and are thus capable of synthesizing proteins. Previously, it was thought that platelet RNAs and translational machinery were remnants from the megakaryocyte. We now know that the initial description of platelets as "cellular fragments" is an antiquated notion, as mounting evidence suggests otherwise. Therefore, it is reasonable to hypothesize that platelet transcription factors are not vestigial remnants from megakaryocytes, but have important, if only partly understood functions. Proteins play multiple cellular roles to minimize energy expenditure for maximum cellular function; thus, the same can be expected for transcription factors. In fact, numerous transcription factors have non-genomic roles, both in platelets and in nucleated cells. Our lab and others have discovered the presence and non-genomic roles of transcription factors in platelets, such as the nuclear factor kappa β (NFκB) family of proteins and peroxisome proliferator-activated receptor gamma (PPARγ). In addition to numerous roles in regulating platelet activation, functional transcription factors can be transferred to vascular and immune cells through platelet microparticles. This method of transcellular delivery of key immune molecules may be a vital mechanism by which platelet transcription factors regulate inflammation and immunity. At the very least, platelets are an ideal model cell to dissect out the non-genomic roles of transcription factors in nucleated cells. There is abundant evidence to suggest that transcription factors in platelets play key roles in regulating inflammatory and hemostatic functions.

The pathophysiology of thyroid eye disease

The pathophysiology of thyroid eye disease (TED) is complex and incompletely understood. Orbital fibroblasts (OFs) seem to be the key effector cells that are responsible for the characteristic soft tissue enlargement seen in TED. They express potentially pathogenic autoantigens, such as thyrotropin receptor and insulin-like growth factor-1 receptor. An intricate interplay between these autoantigens and the autoantibodies found in Graves disease may lead to the activation of OFs, which then leads to increased hyaluronan production, proinflammatory cytokine synthesis, and enhanced differentiation into either myofibroblasts or adipocytes. Some of the OFs in TED patients seem to be derived from infiltrating fibrocytes. These cells originate from the bone marrow and exhibit both fibroblast and myeloid phenotype. In the TED orbit, they may mediate the orbital expansion and inflammatory infiltration. Last, lymphocytes and cytokines are intimately involved in the initiation, amplification, and maintenance of the autoimmune process in TED.

Prostaglandin E2 signals white-to-brown adipogenic differentiation

The formation of new adipocytes from precursor cells is a crucial aspect of normal adipose tissue function. During the adipogenic process, adipocytes differentiated from mesenchymal stem cells give rise to two main types of fat: white adipose tissue (WAT) characterized by the presence of adipocytes containing large unilocular lipid droplets, and brown adipose tissue (BAT) composed by multilocular brown adipocytes packed with mitochondria. WAT is not only important for energy storage but also as an endocrine organ regulating whole body homeostasis by secreting adipokines and other mediators, which directly impact metabolic functions in obesity. By contrast, BAT is specialized in dissipating energy in form of heat and has salutary effects in combating obesity and associated disorders. Unfortunately, WAT is the predominant fat type, whereas BAT is scarce and located in discrete pockets in adult humans. Luckily, another type of brown adipocytes, called beige or brite (brown-in-white) adipocytes, with similar functions to those of "classical" brown adipocytes has recently been identified in WAT. In this review, a close look is given into the role of bioactive lipid mediators in the regulation of adipogenesis, with a special emphasis on the role of the microsomal prostaglandin E (PGE) synthase-1, a terminal enzyme in PGE2 biosynthesis, as a key regulator of white-to-brown adipogenesis in WAT.

Markers of inflammation and fibrosis in the orbital fat/connective tissue of patients with Graves' orbitopathy: clinical implications

Purpose. To assess FGF-β, TGF-β, and COX2 expression and immunocompetent cells in the orbital tissue of patients with severe and mild Graves' orbitopathy. Patients and Methods. Orbital tissue was taken from 27 patients with GO: (1) severe GO (n = 18), the mean clinical activity score (CAS) being 8.5 (SD 2.5); and (2) mild GO (n = 9), the mean CAS being 2.2 (SD 0.8), and from 10 individuals undergoing blepharoplasty. The expression of CD4+, CD8+, CD20+, and CD68 and FGF-β, TGF-β, and COX2 in the orbital tissue was evaluated by immunohistochemical methods. Results. We demonstrated predominant CD4+ T cells in severe GO. CD68 expression was observed in the fibrous connective area of mild GO and was robust in severe GO, while the prominent TGF-β expression was seen in all GO. Increased FGF-β expression was observed in the fibroblasts and adipocytes of severe GO. No expression of COX2 was found in patients with GO. Conclusions. Macrophages and CD4 T lymphocytes are both engaged in the active/severe and long stage of inflammation in the orbital tissue. FGF-β and TGF-β expression may contribute to tissue remodeling, fibrosis, and perpetuation of inflammation in the orbital tissue of GO especially in severe GO.

Skin fibroblasts from patients with type 1 diabetes (T1D) can be chemically transdifferentiated into insulin-expressing clusters: a transgene-free approach

The conversion of differentiated cells into insulin-producing cells is a promising approach for the autologous replacement of pancreatic cells in patients with type 1 diabetes (T1D). At present, cellular reprogramming strategies encompass ethical problems, epigenetic failure or teratoma formation, which has prompted the development of new approaches. Here, we report a novel technique for the conversion of skin fibroblasts from T1D patients into insulin-expressing clusters using only drug-based induction. Our results demonstrate that skin fibroblasts from diabetic patients have pancreatic differentiation capacities and avoid the necessity of using transgenic strategies, stem cell sources or global demethylation steps. These findings open new possibilities for studying diabetes mechanisms, drug screenings and ultimately autologous transgenic-free regenerative medicine therapies in patients with T1D.

Current concepts in the molecular pathogenesis of thyroid-associated ophthalmopathy

Graves' disease (GD) is a common autoimmune condition. At its core, stimulatory autoantibodies are directed at the thyroid-stimulating hormone receptor (TSHR), resulting in dysregulated thyroid gland activity and growth. Closely associated with GD is the ocular condition known as thyroid-associated ophthalmopathy (TAO). The pathogenesis of TAO remains enigmatic as do the connections between the thyroid and orbit. This review highlights the putative molecular mechanisms involved in TAO and suggests how these insights provide future directions for identifying therapeutic targets. Genetic, epigenetic, and environmental factors have been suggested as contributory to the development of GD and TAO. Thyroid-stimulating hormone receptor and insulin-like growth factor receptor (IGF-1R) are expressed at higher levels in the orbital connective tissue from individuals with TAO than in healthy tissues. Together, they form a functional complex and appear to promote signaling relevant to GD and TAO. Orbital fibroblasts display an array of cell surface receptors and generate a host of inflammatory molecules that may participate in T and B cell infiltration. Recently, a population of orbital fibroblasts has been putatively traced to bone marrow-derived progenitor cells, known as fibrocytes, as they express CD45, CD34, CXCR4, collagen I, functional TSHR, and thyroglobulin (Tg). Fibrocytes become more numerous in GD and we believe traffic to the orbit in TAO. Numerous attempts at developing complete animal models of GD have been largely unsuccessful, because they lack fidelity with the ocular manifestations seen in TAO. Better understanding of the pathogenesis of TAO and development of improved animal models should greatly accelerate the identification of medical therapy for this vexing medical problem.

Inhibitory effects of PPARγ ligands on TGF-β1-induced corneal myofibroblast transformation

Corneal scarring, whether caused by trauma, laser refractive surgery, or infection, remains a significant problem for humans. Certain ligands for peroxisome proliferator-activated receptor gamma (PPARγ) have shown promise as antiscarring agents in a variety of body tissues. In the cornea, their relative effectiveness and mechanisms of action are still poorly understood. Here, we contrasted the antifibrotic effects of three different PPARγ ligands (15-deoxy-Δ12,14-prostaglandin J2, troglitazone, and rosiglitazone) in cat corneal fibroblasts. Western blot analyses revealed that all three compounds reduced transforming growth factor (TGF)-β1-driven myofibroblast differentiation and up-regulation of α-smooth muscle actin, type I collagen, and fibronectin expression. Because these effects were independent of PPARγ, we ascertained whether they occurred by altering phosphorylation of Smads 2/3, p38 mitogen-activated protein kinase, stress-activated protein kinase, protein kinase B, extracellular signal-regulated kinase, and/or myosin light chain 2. Only p38 mitogen-activated protein kinase phosphorylation was significantly inhibited by all three PPARγ ligands. Finally, we tested the antifibrotic potential of troglitazone in a cat model of photorefractive keratectomy-induced corneal injury. Topical application of troglitazone significantly reduced α-smooth muscle actin expression and haze in the stromal ablation zone. Thus, the PPARγ ligands tested here showed great promise as antifibrotics, both in vitro and in vivo. Our results also provided new evidence for the signaling pathways that may underlie these antifibrotic actions in corneal fibroblasts.

Polyunsaturated Fatty Acid-derived lipid mediators and T cell function

Fatty acids are involved in T cell biology both as nutrients important for energy production as well as signaling molecules. In particular, polyunsaturated fatty acids are known to exhibit a range of immunomodulatory properties that progress through T cell mediated events, although the molecular mechanisms of these actions have not yet been fully elucidated. Some of these immune activities are linked to polyunsaturated fatty acid-induced alteration of the composition of cellular membranes and the consequent changes in signaling pathways linked to membrane raft-associated proteins. However, significant aspects of the polyunsaturated fatty acid bioactivities are mediated through their transformation to specific lipid mediators, products of cyclooxygenase, lipoxygenase, or cytochrome P450 enzymatic reactions. Resulting bioactive metabolites including prostaglandins, leukotrienes, and endocannabinoids are produced by and/or act upon T leukocytes through cell surface receptors and have been shown to alter T cell activation and differentiation, proliferation, cytokine production, motility, and homing events. Detailed appreciation of the mode of action of these lipids presents opportunities for the design and development of therapeutic strategies aimed at regulating T cell function.

Orbital fibroblasts from thyroid eye disease patients differ in proliferative and adipogenic responses depending on disease subtype

PURPOSE

Thyroid eye disease (TED) patients are classified as type I (predominantly fat compartment enlargement) or type II (predominantly extraocular muscle enlargement) based on orbital imaging. Orbital fibroblasts (OFs) can be driven to proliferate or differentiate into adipocytes in vitro. We tested the hypothesis that type I OFs undergo more adipogenesis than type II OFs, whereas type II OFs proliferate more than type I OFs. We also examined the effect of cyclooxygenase (COX) inhibitors on OF adipogenesis and proliferation.

METHODS

Type I, type II, and non-TED OFs were treated with transforming growth factor-beta (TGFβ) to induce proliferation and with 15-deoxy-Δ(-12,14)-prostaglandin J2 (15d-PGJ2) to induce adipogenesis. Proliferation was measured using the [(3)H]thymidine assay, and adipogenesis was measured using the AdipoRed assay, Oil Red O staining, and flow cytometry. The effect of COX inhibition on adipogenesis and proliferation was also studied.

RESULTS

Type II OFs incorporated 1.7-fold more [(3)H]thymidine than type I OFs (P < 0.05). Type I OFs accumulated 4.8-fold more lipid than type II OFs (P < 0.05) and 12.6-fold more lipid than non-TED OFs (P < 0.05). Oil Red O staining and flow cytometry also demonstrated increased adipogenesis in type I OFs compared to type II and non-TED OFs. Cyclooxygenase inhibition significantly decreased proliferation and adipogenesis in type II OFs, but not type I OFs.

CONCLUSIONS

We have demonstrated that OFs from TED patients have heterogeneous responses to proproliferative and proadipogenic stimulators in vitro in a manner that corresponds to their different clinical manifestations. Furthermore, we demonstrated a differential effect of COX inhibitors on type I and type II OF proliferation and adipogenesis.

Proinflammatory and immunoregulatory roles of eicosanoids in T cells

Eicosanoids are inflammatory mediators primarily generated by hydrolysis of membrane phospholipids by phospholipase A2 to ω-3 and ω-6 C20 fatty acids that next are converted to leukotrienes (LTs), prostaglandins (PGs), prostacyclins (PCs), and thromboxanes (TXAs). The rate-limiting and tightly regulated lipoxygenases control synthesis of LTs while the equally well-controlled cyclooxygenases 1 and 2 generate prostanoids, including PGs, PCs, and TXAs. While many of the classical signs of inflammation such as redness, swelling, pain, and heat are caused by eicosanoid species with vasoactive, pyretic, and pain-inducing effects locally, some eicosanoids also regulate T cell functions. Here, we will review eicosanoid production in T cell subsets and the inflammatory and immunoregulatory functions of LTs, PGs, PCs, and TXAs in T cells.

Endothelial dysfunction in (pre)diabetes: characteristics, causative mechanisms and pathogenic role in type 2 diabetes

Endothelial dysfunction associated with diabetes and cardiovascular disease is characterized by changes in vasoregulation, enhanced generation of reactive oxygen intermediates, inflammatory activation, and altered barrier function. These endothelial alterations contribute to excess cardiovascular disease in diabetes, but may also play a role in the pathogenesis of diabetes, especially type 2. The mechanisms underlying endothelial dysfunction in diabetes differ between type 1 (T1D) and type 2 diabetes (T2D): hyperglycemia contributes to endothelial dysfunction in all individuals with diabetes, whereas the causative mechanisms in T2D also include impaired insulin signaling in endothelial cells, dyslipidemia and altered secretion of bioactive substances (adipokines) by adipose tissue. The close association of so-called perivascular adipose tissue with arteries and arterioles facilitates the exposure of vascular endothelium to adipokines, particularly if inflammation activates the adipose tissue. Glucose and adipokines activate specific intracellular signaling pathways in endothelium, which in concert result in endothelial dysfunction in diabetes. Here, we review the characteristics of endothelial dysfunction in diabetes, the causative mechanisms involved and the role of endothelial dysfunction(s) in the pathogenesis of T2D. Finally, we will discuss the therapeutic potential of endothelial dysfunction in T2D.

Acute thyroid eye disease (TED): principles of medical and surgical management

The active inflammatory phase of thyroid eye disease (TED) is mediated by the innate immune system, and management is aimed at aborting this self-limited period of autoimmune activity. In most patients with TED, ocular and adnexal changes are mild and management involves controlling thyroid dysfunction, cessation of smoking, and addressing ocular surface inflammation and exposure. In patients with acute moderate disease, this being sufficient to impair orbital functions, immunosuppression reduces the long-term sequelae of acute inflammation, and adjunctive fractionated low-dose orbital radiotherapy is used as a steroid-sparing measure. Elective surgery is often required following moderate TED, be it for proptosis, diplopia, lid retraction, or to debulk the eyelid, and this should be delayed until the disease is quiescent, with the patient stable and weaned off all immunosuppression. Thus, surgical intervention during the active phase of moderate disease is rarely indicated, although clinical experience suggests that, where there is significant orbital congestion, early orbital decompression can limit progression to more severe disease. Acute severe TED poses a major risk of irreversible loss of vision due to marked exposure keratopathy, 'hydraulic' orbital congestion, or compressive optic neuropathy. If performed promptly, retractor recession with or without a suture tarsorrhaphy protects the ocular surface from severe exposure and, in patients not responding to high-dose corticosteroid treatment, decompression of the deep medial orbital wall and floor can rapidly relieve compressive optic neuropathy, as well as alleviate the inflammatory and congestive features of raised orbital pressure.

Quantitative MRI analysis of salivary glands in sickle cell disease

OBJECTIVES

The purpose of this prospective study was to characterize the MR relaxometric features of the major salivary glands in patients with sickle cell disease (SCD).

METHODS

15 patients with SCD (aged 19.8-43.6 years) and 12 controls were imaged with the mixed turbo-spin echo pulse sequence. The major salivary glands were manually segmented and T1, T2 and secular T2 relaxometry histograms were modelled with Gaussian functions.

RESULTS

Shortened T1 relaxation times were seen solely in the submandibular glands of patients with SCD (747.5±54.8 ms vs 807.1±38.3 ms, p<0.001). Slight T2 and secular T2 shortening were seen in the parotid gland; however, this difference was not significant (p=0.07). The sublingual gland showed no changes under MR relaxometry. There was no difference in glandular volumes, and no correlation was demonstrated between history of blood transfusion and salivary gland relaxometry.

CONCLUSIONS

Patients with SCD exhibited changes in quantitative MRI T1 relaxometry histograms of the submandibular glands.

[Role of brown and perivascular adipose tissue in vascular complications due to obesity]

The contribution of brown and perivascular adipose tissues to the pathophysiology of metabolic and vascular complications associated with obesity are analysed in this review. To combat obesity and prevent its highly prevalent metabolic and vascular complications, a new insight on our knowledge of the role of the thermogenic function of brown adipose tissue and its promising therapeutic potential in humans is needed in addition to conventional treatments. Owing to the impact of brown adipose tissue on energy expenditure related to lipid and glucose metabolism, as well as its potential resistance against inflammation along with perivascular adipose tissue, new perspectives in the treatment of obesity treatment could be focused on the design of new drugs, or different regimens or therapies, that increase the amount and activity of brown adipose tissue. These new treatments not only may contribute to combat obesity, but also prevent complications such as type 2 diabetes and other associated metabolic and vascular changes.

Concise review: the periosteum: tapping into a reservoir of clinically useful progenitor cells

Elucidation of the periosteum and its regenerative potential has become a hot topic in orthopedics. Yet few review articles address the unique features of periosteum-derived cells, particularly in light of translational therapies and engineering solutions inspired by the periosteum's remarkable regenerative capacity. This review strives to define periosteum-derived cells in light of cumulative research in the field; in addition, it addresses clinical translation of current insights, hurdles to advancement, and open questions in the field. First, we examine the periosteal niche and its inhabitant cells and the key characteristics of these cells in the context of mesenchymal stem cells and their relevance for clinical translation. We compare periosteum-derived cells with those derived from the marrow niche in in vivo studies, addressing commonalities as well as features unique to periosteum cells that make them potentially ideal candidates for clinical application. Thereafter, we review the differentiation and tissue-building properties of periosteum cells in vitro, evaluating their efficacy in comparison with marrow-derived cells. Finally, we address a new concept of banking periosteum and periosteum-derived cells as a novel alternative to currently available autogenic umbilical blood and perinatal tissue sources of stem cells for today's population of aging adults who were "born too early" to bank their own perinatal tissues. Elucidating similarities and differences inherent to multipotent cells from distinct tissue niches and their differentiation and tissue regeneration capacities will facilitate the use of such cells and their translation to regenerative medicine.

Different roles of mast cells in obesity and diabetes: lessons from experimental animals and humans

Mast cells (MCs) play an important role in allergic hyperresponsiveness and in defending microorganism infections. Recent studies of experimental animals and humans have suggested that MCs participate in obesity and diabetes. MC distribution and activities in adipose tissues may vary, depending on the locations of different adipose tissues. In addition to releasing inflammatory mediators to affect adipose tissue extracellular matrix remodeling and to promote inflammatory cell recruitment and proliferation, MCs directly and indirectly interact and activate adipose tissue cells, including adipocytes and recruited inflammatory cells. Plasma MC protease levels are significantly higher in obese patients than in lean subjects. Experimental obese animals lose body weight after MC inactivation. MC functions in diabetes are even more complicated, and depend on the type of diabetes and on different diabetic complications. Both plasma MC proteases and MC activation essential immunoglobulin E levels are significant risk factors for human pre-diabetes and diabetes mellitus. MC stabilization prevents diet-induced diabetes and improves pre-established diabetes in experimental animals. MC depletion or inactivation can improve diet-induced type 2 diabetes and some forms of type 1 diabetes, but also can worsen other forms of type 1 diabetes, at least in experimental animals. Observations from animal and human studies have suggested beneficial effects of treating diabetic patients with MC stabilizers. Some diabetic patients may benefit from enhancing MC survival and proliferation – hypotheses that merit detailed basic researches and clinical studies.

Electrophilic PPARγ ligands inhibit corneal fibroblast to myofibroblast differentiation in vitro: a potentially novel therapy for corneal scarring

A critical component of corneal scarring is the TGFβ-induced differentiation of corneal keratocytes into myofibroblasts. Inhibitors of this differentiation are potentially therapeutic for corneal scarring. In this study, we tested the relative effectiveness and mechanisms of action of two electrophilic peroxisome proliferator-activated receptor gamma (PPARγ) ligands: cyano-3,12-dioxolean-1,9-dien-28-oic acid-methyl ester (CDDO-Me) and 15-deoxy-Δ(-12,14)-prostaglandin J(2) (15d-PGJ(2)) for inhibiting TGFβ-induced myofibroblast differentiation in vitro. TGFβ was used to induce myofibroblast differentiation in cultured, primary human corneal fibroblasts. CDDO-Me and 15d-PGJ(2) were added to cultures to test their ability to inhibit this process. Myofibroblast differentiation was assessed by measuring the expression of myofibroblast-specific proteins (αSMA, collagen I, and fibronectin) and mRNA (αSMA and collagen III). The role of PPARγ in the inhibition of myofibroblast differentiation by these agents was tested in genetically and pharmacologically manipulated cells. Finally, we assayed the importance of electrophilicity in the actions of these agents on TGFβ-induced αSMA expression via Western blotting and immunofluorescence. Both electrophilic PPARγ ligands (CDDO-Me and 15d-PGJ(2)) potently inhibited TGFβ-induced myofibroblast differentiation, but PPARγ was only partially required for inhibition of myofibroblast differentiation by either agent. Electrophilic PPARγ ligands were able to inhibit myofibroblast differentiation more potently than non-electrophilic PPARγ ligands, suggesting an important role of electrophilicity in this process. CDDO-Me and 15d-PGJ(2) are strong inhibitors of TGFβ-induced corneal fibroblast to myofibroblast differentiation in vitro, suggesting this class of agents as potential novel therapies for corneal scarring warranting further study in pre-clinical animal models.

Quercetin inhibits IL-1β-induced inflammation, hyaluronan production and adipogenesis in orbital fibroblasts from Graves' orbitopathy

Management of Graves' orbitopathy (GO) is challenging, as no reliable, specific, and safe medical therapeutic agents have yet been developed. We investigated the effect of quercetin in primary cultured orbital fibroblasts from GO, targeting pathways of inflammation, aberrant accumulation of extracellular matrix macromolecules, and adipose tissue expansion. Quercetin significantly attenuated intercellular adhesion molecule-1 (ICAM-1), interleukin (IL) -6, IL-8, and cyclooxygenase (COX) -2 mRNA expression, and inhibited IL-1β-induced increases in ICAM-1, IL-6, and IL-8 mRNA. Increased hyaluronan production induced by IL-1β or tumor necrosis factor-α was suppressed by quercetin in a dose- and time-dependent manner. Treatment with noncytotoxic doses of quercetin inhibited accumulation of intracytoplasmic lipid droplets and resulted in a dose-dependent decrease in expression of peroxisome proliferator-activated receptor γ, CCAAT/enhancer-binding protein (C/EBP) α, and C/EBPβ proteins. In conclusion, inhibition of inflammation, hyaluronan production, and adipogenesis by the natural plant product quercetin in vitro provides the basis for further study of its potential use in the treatment of GO.

Δ12-prostaglandin J3, an omega-3 fatty acid-derived metabolite, selectively ablates leukemia stem cells in mice

Targeting cancer stem cells is of paramount importance in successfully preventing cancer relapse. Recently, in silico screening of public gene-expression datasets identified cyclooxygenase-derived cyclopentenone prostaglandins (CyPGs) as likely agents to target malignant stem cells. We show here that Δ(12)-PGJ(3), a novel and naturally produced CyPG from the dietary fish-oil ω-3 polyunsaturated fatty acid eicosapentaenoic acid (EPA; 20:5) alleviates the development of leukemia in 2 well-studied murine models of leukemia. IP administration of Δ(12)-PGJ(3) to mice infected with Friend erythroleukemia virus or those expressing the chronic myelogenous leukemia oncoprotein BCR-ABL in the hematopoietic stem cell pool completely restored normal hematologic parameters, splenic histology, and enhanced survival. More importantly, Δ(12)-PGJ(3) selectively targeted leukemia stem cells (LSCs) for apoptosis in the spleen and BM. This treatment completely eradicated LSCs in vivo, as demonstrated by the inability of donor cells from treated mice to cause leukemia in secondary transplantations. Given the potency of ω-3 polyunsaturated fatty acid-derived CyPGs and the well-known refractoriness of LSCs to currently used clinical agents, Δ(12)-PGJ(3) may represent a new chemotherapeutic for leukemia that targets LSCs.

Mast cells function as an alternative modulator of adipogenesis through 15-deoxy-delta-12, 14-prostaglandin J2

Mast cells are one of the major producers of prostaglandins (PGs). The final metabolite of PGs 15-deoxy-delta-12,14-PGJ(2) (15-deoxy-delta PGJ(2)) is the endogenous ligand of the peroxisome proliferator-activated receptor (PPAR) γ. PPARγ modulates adipocyte differentiation; therefore, we attempted to investigate whether PGs derived from mast cells influenced on adipogenesis. We found the increase of mast cell numbers in fat tissue of obese mice fed with a high-fat diet allowed us to speculate contributions of mast cells to adipogenesis. Mast cell-mediated induction of adipogenesis was evaluated by using 3T3 L1 cells. Supernatants obtained from mast cells stimulated with calcium ionophore or the high-glucose condition contained 15-deoxy-delta PGJ(2) and induced adipogenesis of 3T3 L1 cells. Agonistic activity of PGJ(2) from the supernatants on PPARγ was confirmed by a reporter gene assay. Culture medium collected from calcium ionophore-stimulated bone marrow-derived cultured mast cells (BMCMC) activated PPAR-responsive element in NIH3T3 fibroblasts, and the specific inhibitor of PPARγ canceled the activation. Contribution of mast cells to obesity was evaluated by using mast cell-deficient mice fed with a Western diet. Weight gain of mast cell-deficient mice during high-fat feeding was impaired compared with their littermate wild-type mice; on the other hand, transplantation of bone marrow-derived cultured mast cells to mast cell-deficient mice restored the weight gain by intake of a high-fat diet. In this study, we clearly demonstrated that mast cells produced PGs in response to the high-glucose condition and induced adipocyte differentiation and possibly obesity. This is the first study that provides evidence for a novel role of mast cells in adipogenesis via PPARγ activation.

Regulation of Lymphocyte Function by PPARgamma: Relevance to Thyroid Eye Disease-Related Inflammation

Thyroid eye disease (TED) is an autoimmune condition in which intense inflammation leads to orbital tissue remodeling, including the accumulation of extracellular macromolecules and fat. Disease progression depends upon interactions between lymphocytes and orbital fibroblasts. These cells engage in a cycle of reciprocal activation which produces the tissue characteristics of TED. Peroxisome proliferator-activated receptor-gamma (PPARgamma) may play divergent roles in this process, both attenuating and promoting disease progression. PPARgamma has anti-inflammatory activity, suggesting that it could interrupt intercellular communication. However, PPARgamma activation is also critical to adipogenesis, making it a potential culprit in the pathological fat accumulation associated with TED. This review explores the role of PPARgamma in TED, as it pertains to crosstalk between lymphocytes and fibroblasts and the development of therapeutics targeting cell-cell interactions mediated through this signaling pathway.

The Role of PPARs in Lung Fibrosis

Pulmonary fibrosis is a group of disorders characterized by accumulation of scar tissue in the lung interstitium, resulting in loss of alveolar function, destruction of normal lung architecture, and respiratory distress. Some types of fibrosis respond to corticosteroids, but for many there are no effective treatments. Prognosis varies but can be poor. For example, patients with idiopathic pulmonary fibrosis (IPF) have a median survival of only 2.9 years. Prognosis may be better in patients with some other types of pulmonary fibrosis, and there is variability in survival even among individuals with biopsy-proven IPF. Evidence is accumulating that the peroxisome proliferator-activated receptors (PPARs) play important roles in regulating processes related to fibrogenesis, including cellular differentiation, inflammation, and wound healing. PPARα agonists, including the hypolidipemic fibrate drugs, inhibit the production of collagen by hepatic stellate cells and inhibit liver, kidney, and cardiac fibrosis in animal models. In the mouse model of lung fibrosis induced by bleomycin, a PPARα agonist significantly inhibited the fibrotic response, while PPARα knockout mice developed more serious fibrosis. PPARβ/δ appears to play a critical role in regulating the transition from inflammation to wound healing. PPARβ/δ agonists inhibit lung fibroblast proliferation and enhance the antifibrotic properties of PPARγ agonists. PPARγ ligands oppose the profibrotic effect of TGF-β, which induces differentiation of fibroblasts to myofibroblasts, a critical effector cell in fibrosis. PPARγ ligands, including the thiazolidinedione class of antidiabetic drugs, effectively inhibit lung fibrosis in vitro and in animal models. The clinical availability of potent and selective PPARα and PPARγ agonists should facilitate rapid development of successful treatment strategies based on current and ongoing research.

Role of peroxisome proliferator-activated receptor gamma and its ligands in the treatment of hematological malignancies

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a multifunctional transcription factor with important regulatory roles in inflammation, cellular growth, differentiation, and apoptosis. PPARgamma is expressed in a variety of immune cells as well as in numerous leukemias and lymphomas. Here, we review recent studies that provide new insights into the mechanisms by which PPARgamma ligands influence hematological malignant cell growth, differentiation, and survival. Understanding the diverse properties of PPARgamma ligands is crucial for the development of new therapeutic approaches for hematological malignancies.

Electrophilic PPARγ Ligands Attenuate IL-1β and Silica-Induced Inflammatory Mediator Production in Human Lung Fibroblasts via a PPARγ-Independent Mechanism

Acute and chronic lung inflammation is associated with numerous important disease pathologies including asthma, chronic obstructive pulmonary disease and silicosis. Lung fibroblasts are a novel and important target of anti-inflammatory therapy, as they orchestrate, respond to, and amplify inflammatory cascades and are the key cell in the pathogenesis of lung fibrosis. Peroxisome proliferator-activated receptor gamma (PPARγ) ligands are small molecules that induce anti-inflammatory responses in a variety of tissues. Here, we report for the first time that PPARγ ligands have potent anti-inflammatory effects on human lung fibroblasts. 2-cyano-3, 12-dioxoolean-1, 9-dien-28-oic acid (CDDO) and 15-deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) inhibit production of the inflammatory mediators interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), COX-2, and prostaglandin (PG)E₂ in primary human lung fibroblasts stimulated with either IL-1β or silica. The anti-inflammatory properties of these molecules are not blocked by the PPARγ antagonist GW9662 and thus are largely PPARγ independent. However, they are dependent on the presence of an electrophilic carbon. CDDO and 15d-PGJ₂, but not rosiglitazone, inhibited NF-κB activity. These results demonstrate that CDDO and 15d-PGJ₂ are potent attenuators of proinflammatory responses in lung fibroblasts and suggest that these molecules should be explored as the basis for novel, targeted anti-inflammatory therapies in the lung and other organs.

Perivascular adipose tissue and its role in type 2 diabetes and cardiovascular disease

Obesity is associated with insulin resistance, hypertension, and cardiovascular disease, but the mechanisms underlying these associations are incompletely understood. Microvascular dysfunction may play an important role in the pathogenesis of both insulin resistance and hypertension in obesity. Adipose tissue-derived substances (adipokines) and especially inflammatory products of adipose tissue control insulin sensitivity and vascular function. In the past years, adipose tissue associated with the vasculature, or perivascular adipose tissue (PAT), has been shown to produce a variety of adipokines that contribute to regulation of vascular tone and local inflammation. This review describes our current understanding of the mechanisms linking perivascular adipose tissue to vascular function, inflammation, and insulin resistance. Furthermore, we will discuss mechanisms controlling the quantity and adipokines secretion by PAT.

Peroxisome proliferator-activated receptor gamma ligands inhibit transforming growth factor-beta-induced, hyaluronan-dependent, T cell adhesion to orbital fibroblasts

Thyroid eye disease is characterized by the infiltration of leukocytes and accumulation of hyaluronan (HA) in orbital tissue. Inflamed orbital tissue expands in size due to excessive HA and to the formation of scar tissue (fibrosis) and/or adipose accumulation. Transforming growth factor β (TGF-β) acts as a key inducer of fibrosis by enhancing extracellular matrix production. Treatment of primary human orbital fibroblasts with TGF-β led to significant increases in both HA synthesis and secretion. TGF-β also strongly induced hyaluronan synthase 1 (HAS1) and HAS2 mRNA levels, which increased 50- and 6-fold, respectively. Remarkably, the addition of the peroxisome proliferator-activated receptor (PPARγ) ligands pioglitazone (Pio) or rosiglitazone (Rosi) to TGF-β-treated orbital fibroblasts attenuated HA synthesis and reduced HAS1 and HAS2 mRNA levels. The attenuation of TGF-β function by Pio and Rosi was independent of PPARγ activity. Furthermore, Pio and Rosi treatment inhibited TGF-β-induced T cell adhesion to orbital fibroblasts. Our findings demonstrate that TGF-β plays an important role in HA synthesis and in the inflammatory response by enhancing or facilitating inflammatory cell infiltration and adhesion to orbital tissue. Pio and Rosi exhibit anti-fibrotic and anti-inflammatory activity and may be useful in treating thyroid eye disease.