Thyroid hormone antagonizes tumor necrosis factor-alpha signaling in pituitary cells through the induction of dual specificity phosphatase 1

Dual-specificity phosphatase 1 inhibits Singapore grouper iridovirus replication via regulating apoptosis in Epinephelus coioides

The dual-specificity phosphatase (DUSP) family plays key roles in the maintenance of cellular homeostasis and apoptosis etc. In this study, the DUSP member DUSP1 of Epinephelus coioides was characterized: the length was 2371 bp including 281 bp 5' UTR, 911 bp 3' UTR, and a 1125 bp open reading frame encoding 374 amino acids. E. coioides DUSP1 has two conserved domains, a ROHD and DSPc along with a p38 MAPK phosphorylation site, localized at Ser308. E. coioides DUSP1 mRNA can be detected in all of the tissues examined, and the subcellular localization showed that DUSP1 was mainly distributed in the nucleus. Singapore grouper iridovirus (SGIV) infection could induce the differential expression of E. coioides DUSP1. Overexpression of DUSP1 could inhibit SGIV-induced cytopathic effect (CPE), the expressions of SGIV key genes, and the viral titers. Overexpression of DUSP1 could also regulate SGIV-induced apoptosis, and the expression of apoptosis-related factor caspase 3. The results would be helpful to further study the role of DUSP1 in viral infection.

Antiviral immunity of grouper MAP kinase phosphatase 1 to Singapore grouper iridovirus infection

Singapore grouper iridovirus (SGIV), with various mechanisms for evading and modulating host, has inflicted heavy economic losses in the grouper aquaculture. MAP kinase phosphatase 1 (MKP-1) regulates mitogen-activated protein kinases (MAPKs) to mediate the innate immune response. Here, we cloned EcMKP-1, an MKP-1 homolog from the orange-spotted grouper Epinephelus coioides, and investigated its role in the infection of SGIV. In juvenile grouper, EcMKP-1 was highly upregulated and peaked at different times after injection with lipopolysaccharide, polyriboinosinic polyribocytidylic acid and SGIV. EcMKP-1 expression in heterologous fathead minnow cells was able to suppress SGIV infection and replication. Furthermore, EcMKP-1 was a negative regulator of c-Jun N-terminal kinase (JNK) phosphorylation early in SGIV infection. EcMKP-1 decreased the apoptotic percentage and caspase-3 activity during the late stage of SGIV replication. Our results demonstrate critical functions of EcMKP-1 in antiviral immunity, JNK dephosphorylation and anti-apoptosis during SGIV infection.

Metformin alleviates the dysregulated testicular steroidogenesis and spermatogenesis induced by carbimazole in levothyroxine-primed rats

Most of the published experiments about carbimazole (CMZ)-induced testicular injury are constructed in normal healthy animals, which lakes the translational identification. Despite metformin (MET) having advantageous effects on injured testicles, its impact on thyroid function is arguable. In the current levothyroxine (LT4)/CMZ model, Wistar rats were primed by LT4 for sixty days. CMZ was then given individually or simultaneously with different doses of MET, 100, 200, and 400 mg, daily for thirty days. Serum was assessed for thyroid profile panel, sex hormones, and gonadotropin levels. Testicular tissues were examined for steroidogenesis, spermatogenesis, inflammation, and apoptosis. Histopathology of thyroid and testes were examined, besides thyroidal nuclear factor (NF)-kB expression. MET in a dose-response manner improved the LT4/CMZ-induced testicular toxicity by increasing the steroidogenic acute regulatory protein (StAR), and 17-β-hydroxysteroid dehydrogenase (17βHSD) activities, the proliferating cell nuclear antigen (PCNA), sperm count and motility, sex hormones, and gonadotropin levels. MET-400 mg markedly decreased the elevated NF-kB expressions, tumour necrosis factor (TNF)-α, caspase-3, and BAX, and increased BCL-2. LT4/CMZ could be used as translational animal modelling. MET displayed a dose-dependent ameliorative effect on the LT4/CMZ model without significant harmful effects on thyroid functions. MET-testicular protective roles in diabetics with thyroidal diseases should be explored.

Thyroid hormones act as modulators of inflammation through their nuclear receptors

Reciprocal crosstalk between endocrine and immune systems has been well-documented both in physiological and pathological conditions, although the connection between the immune system and thyroid hormones (THs) remains largely unclear. Inflammation and infection are two important processes modulated by the immune system, which have profound effects on both central and peripheral THs metabolism. Conversely, optimal levels of THs are necessary for the maintenance of immune function and response. Although some effects of THs are mediated by their binding to cell membrane integrin receptors, triggering a non-genomic response, most of the actions of these hormones involve their binding to specific nuclear thyroid receptors (TRs), which generate a genomic response by modulating the activity of a great variety of transcription factors. In this special review on THs role in health and disease, we highlight the relevance of these hormones in the molecular mechanisms linked to inflammation upon their binding to specific nuclear receptors. In particular, we focus on THs effects on different signaling pathways involved in the inflammation associated with various infectious and/or pathological processes, emphasizing those mediated by NF-kB, p38MAPK and JAK/STAT. The findings showed in this review suggest new opportunities to improve current therapeutic strategies for the treatment of inflammation associated with several infections and/or diseases, such as cancer, sepsis or Covid-19 infection.

Regulation of metabolic and transcriptional responses by the thyroid hormone in cellular models of murine macrophages

Oncogene-immortalized bone marrow-derived macrophages are considered to be a good model for the study of immune cell functions, but the factors required for their survival and proliferation are still unknown. Although the effect of the thyroid hormones on global metabolic and transcriptional responses in macrophages has not yet been examined, there is increasing evidence that they could modulate macrophage functions. We show here that the thyroid hormone T3 is an absolute requirement for the growth of immortal macrophages. The hormone regulates the activity of the main signaling pathways required for proliferation and anabolic processes, including the phosphorylation of ERK and p38 MAPKs, AKT, ribosomal S6 protein, AMPK and Sirtuin-1. T3 also alters the levels of metabolites controlling transcriptional and post-transcriptional actions in macrophages, and causes widespread transcriptomic changes, up-regulating genes needed for protein synthesis and cell proliferation, while down-regulating genes involved in immune responses and endocytosis, among others. This is not observed in primary bone marrow-derived macrophages, where only p38 and AMPK activation is regulated by T3 and in which the metabolic and transcriptomic effects of the hormone are much weaker. However, the response to IFN-γ is reduced by T3 similarly in immortalized macrophages and in the primary cells, confirming previous results showing that the thyroid hormones can antagonize JAK/STAT-mediated signaling. These results provide new perspectives on the relevant pathways involved in proliferation and survival of macrophage cell culture models and on the crosstalk between the thyroid hormones and the immune system.

Effects of Thyroid Hormones on Lipid Metabolism Pathologies in Non-Alcoholic Fatty Liver Disease

The typical modern lifestyle contributes to the development of many metabolic-related disorders, as exemplified by metabolic syndrome. How to prevent, resolve, or avoid subsequent deterioration of metabolic disturbances and the development of more serious diseases has become an important and much-discussed health issue. Thus, the question of the physiological and pathological roles of thyroid hormones (THs) in metabolism has never gone out of fashion. Although THs influence almost all organs, the liver is one of the most important targets as well as the hub of metabolic homeostasis. When this homeostasis is out of balance, diseases may result. In the current review, we summarize the common features and actions of THs, first focusing on their effects on lipid metabolism in the liver. In the second half of the review, we turn to a consideration of non-alcoholic fatty liver disease (NAFLD), a disease characterized by excessive accumulation of fat in the liver that is independent of heavy alcohol consumption. NAFLD is a growing health problem that currently affects ~25% of the world’s population. Unfortunately, there are currently no approved therapies specific for NAFLD, which, if left uncontrolled, may progress to more serious diseases, such as cirrhosis or liver cancer. This absence of effective treatment can also result in the development of non-alcoholic steatohepatitis (NASH), an aggressive form of NAFLD that is the leading cause of liver transplantation in the United States. Because THs play a clear role in hepatic fat metabolism, their potential application in the prevention and treatment of NAFLD has attracted considerable research attention. Studies that have investigated the use of TH-related compounds in the management of NAFLD are also summarized in the latter part of this review. An important take-home point of this review is that a comprehensive understanding of the physiological and pathological roles of THs in liver fat metabolism is possible, despite the complexities of this regulatory axis—an understanding that has clinical value for the specific management of NAFLD.

Downregulation of Snail by DUSP1 Impairs Cell Migration and Invasion through the Inactivation of JNK and ERK and Is Useful as a Predictive Factor in the Prognosis of Prostate Cancer

Dual specificity phosphatase 1 (DUSP1) is crucial in prostate cancer (PC), since its expression is downregulated in advanced carcinomas. Here, we investigated DUSP1 effects on the expression of mesenchymal marker Snail, cell migration and invasion, analyzing the underlying mechanisms mediated by mitogen-activated protein kinases (MAPKs) inhibition. To this purpose, we used different PC cells overexpressing or lacking DUSP1 or incubated with MAPKs inhibitors. Moreover, we addressed the correlation of DUSP1 expression with Snail and activated MAPKs levels in samples from patients diagnosed with benign hyperplasia or prostate carcinoma, studying its implication in tumor prognosis and survival. We found that DUSP1 downregulates Snail expression and impairs migration and invasion in PC cells. Similar results were obtained following the inhibition of c-Jun N-terminal kinase (JNK) and extracellular-signal-regulated kinase (ERK). In clinical samples, we evidenced an inverse correlation between DUSP1 expression and Snail levels, which are further associated with JNK and ERK activation. Consequently, the pattern DUSP1_high/activated JNK_low/activated ERK_low/Snail_low is associated with an overall extended survival of PC patients. In summary, the ratio between DUSP1 and Snail expression, with additional JNK and ERK activity measurement, may serve as a potential biomarker to predict the clinical outcome of PC patients. Furthermore, DUSP1 induction or inhibition of JNK and ERK pathways could be useful to treat PC.

Pyrimethamine Elicits Antitumor Effects on Prostate Cancer by Inhibiting the p38-NF-κB Pathway

Since incurable castration-resistant prostate cancer (CRPC) inevitably develops following treatment with androgen deprivation therapy, there is an urgent need to devise new therapeutic strategies to treat this cancer. Pyrimethamine, an FDA-approved antimalarial drug, is known to exert an antitumor activity in various types of human cancer cells. However, whether pyrimethamine can inhibit prostate cancer is not well established. Hence, the present study aimed to characterize the mechanism of action of pyrimethamine on prostate cancer. We investigated the potential effect of pyrimethamine on cell proliferation, cell cycle, and apoptosis in metastatic DU145 and PC3 prostate cancer cells. We found that pyrimethamine inhibited cell proliferation, induced cell cycle arrest in the S phase, and promoted cell apoptosis of prostate cells in vitro; it also suppressed tumor growth in xenograft models. In addition, we observed that pyrimethamine suppressed prostate cancer growth by inhibiting the p38-NF-κB axis in vitro and in vivo. Thus, this study demonstrates that pyrimethamine is a novel p38 inhibitor that can exert antiproliferative and proapoptotic effects in prostate cancer by affecting cell cycle and intrinsic apoptotic signaling, thereby providing a novel strategy for using pyrimethamine in CRPC treatment.

Thyroid Hormone Receptor β Inhibits Self-Renewal Capacity of Breast Cancer Stem Cells

Background: A subpopulation of cancer stem cells (CSCs) with capacity for self-renewal is believed to drive initiation, progression, and relapse of breast tumors. Methods: Since the thyroid hormone receptor β (TRβ) appears to suppress breast tumor growth and metastasis, we have analyzed the possibility that TRβ could affect the CSC population using MCF-7 cells grown under adherent conditions or as mammospheres, as well as inoculation into immunodeficient mice. Results: Treatment of TRβ-expressing MCF-7 cells (MCF7-TRβ cells) with the thyroid hormone triiodothyronine (T3) decreased significantly CD44⁺/CD24^- and ALDH⁺ cell subpopulations, the efficiency of mammosphere formation, the self-renewal capacity of CSCs in limiting dilution assays, the expression of the pluripotency factors in the mammospheres, and tumor initiating capacity in immunodeficient mice, indicating that the hormone reduces the CSC population present within the bulk MCF7-TRβ cultures. T3 also decreased migration and invasion, a hallmark of CSCs. Transcriptome analysis showed downregulation of the estrogen receptor alpha (ERα) and ER-responsive genes by T3. Furthermore, among the T3-repressed genes, there was an enrichment in genes containing binding sites for transcription factors that are key determinants of luminal-type breast cancers and are required for ER binding to chromatin. Conclusion: We demonstrate a novel role of TRβ in the biology of CSCs that may be related to its action as a tumor suppressor in breast cancer.

Resveratrol promotes apoptosis through the induction of dual specificity phosphatase 1 and sensitizes prostate cancer cells to cisplatin

Resveratrol is a polyphenol with chemopreventive properties against prostate cancer; however, the mechanisms underlying its actions are not completely understood. Previously, we demonstrated that DUSP1 induces apoptosis in prostate cancer cells; therefore in the present study we investigated the role of this phosphatase on resveratrol effects. Moreover, we analysed the efficiency of combined treatment of resveratrol and the chemotherapeutic drug cisplatin on cellular viability and apoptosis and its relation with DUSP1 in prostate cancer cells. We found that resveratrol up-regulates DUSP1 expression in androgen-independent prostate cancer cells, which in turn, is involved in the inhibition of the NF-κB pathway and Cox-2 expression. This phosphatase is required for the induction of apoptosis achieved by resveratrol, but does not regulate the effects of this compound on cell cycle. Furthermore, we show that resveratrol cooperates with cisplatin both in the up-regulation of DUSP1 levels and in the promotion of apoptosis, suggesting that DUSP1 is a major determinant of cisplatin sensitivity to apoptosis. These results reveal a novel molecular mechanism by which resveratrol induces apoptosis in prostate cancer cells, and highlight the importance of DUSP1 in future therapeutic approaches based in the use of this polyphenol and cisplatin.

Biofloc technology (BFT): An alternative aquaculture system for prevention of Cyprinid herpesvirus 2 infection in gibel carp (Carassius auratus gibelio)

Gibel carp (Carassius auratus gibelio), a major aquaculture species in China, has emerged in a seriously epizootic disease caused by Cyprinid herpesvirus 2 (CyHV-2). There are no effective methods to prevent or control this serious disease. Biofloc technology (BFT) can improve water quality, reduce pathogens introduction, enhance cultured species immunity and disease resistance. In this study, a 30-day experiment was conducted to investigate the effect of BFT on innate immune response and disease resistance of gibel carp against CyHV-2 infection. Gibel carp was cultured at different total suspended solid (TSS) concentrations of 10, 300, 600, 800 and 1000 mg L^-1, which were named as groups BF0, BF300, BF600, BF800 and BF1000. Results showed that fish in groups BF600/800 had significantly higher weight gain (WG) and specific growth rate (SGR) than them in control group (BF0). The transcriptional levels of seven immune-related genes in BF300/600/800 groups, including myeloid-specific- peroxidase (MPO), keratin 8 (KRT 8), dual specificity phosphatase 1 (DUSP 1), interleukin-11 (IL-11), intelectin (ITLN), purine nucleoside phosphorylase 5α (PNP 5α) and c-type lysozyme (c-lys), were up-regulated significantly compared to BF0 group. Furthermore, cumulative mortality of gibel carp in BF600 group after being challenged with CyHV-2 reduced significantly. In vivo viral replication in kidney demonstrated that CyHV-2 load at 168 h post injection in BF600 group was significantly higher than that in BF0 group. In conclusion, BFT could improve growth, immune response and disease resistance of gibel carp, and the effect was related with TSS concentration. The optimal TSS concentration of 600-800 mg L^-1 was recommended in the present study.

The ligand-bound thyroid hormone receptor in macrophages ameliorates kidney injury via inhibition of nuclear factor-κB activities

In chronic kidney disease (CKD) patients, inflammation plays a pivotal role in the progression of renal fibrosis. Hypothyroidism is associated with an increased occurrence of atherosclerosis and inflammation, suggesting protective roles of thyroid hormones and their receptors against inflammatory processes. The contribution of thyroid hormone receptors to macrophage differentiation has not been well documented. Here, we focused on the endogenous thyroid hormone receptor α (TRα) in macrophages and examined the role of ligand-bound TRα in macrophage polarization-mediated anti-inflammatory effects. TRα-deficient irradiated chimeric mice showed exacerbated tubulointerstitial injury in a unilateral ureteral obstruction model. Compared with wild-type macrophages, macrophages isolated from the obstructed kidneys of mice lacking TRα displayed increased expression of proinflammatory cytokines that was accompanied by enhanced nuclear translocation of p65. Comparison of TRα-deficient bone marrow-derived macrophages with wild-type macrophages confirmed the propensity of the former cells to produce excessive IL-1β levels. Co-culture of these macrophages with renal epithelial cells induced more severe damage to the epithelial cells via the IL-1 receptor. Our findings indicate that ligand-bound TRα on macrophages plays a protective role in kidney inflammation through the inhibition of NF-κB pathways, possibly by affecting the pro- and anti-inflammatory balance that controls the development of CKD.

The Thyroid Hormone Receptors Inhibit Hepatic Interleukin-6 Signaling During Endotoxemia

Decreased thyroidal hormone production is found during lipopolysaccharide (LPS)-induced endotoxic shock in animals as well as in critically ill patients. Here we studied the role of the thyroid hormone receptors (TRs) in activation of STAT3, NF-κB and ERK, which play a key role in the response to inflammatory cytokines during sepsis. TR knockout mice showed down-regulation of hepatic inflammatory mediators, including interleukin 6 (IL-6) in response to LPS. Paradoxically, STAT3 and ERK activity were higher, suggesting that TRs could act as endogenous repressors of these pathways. Furthermore, hyperthyroidism increased cytokine production and mortality in response to LPS, despite decreasing hepatic STAT3 and ERK activity. This suggested that TRs could directly repress the response of the cells to inflammatory mediators. Indeed, we found that the thyroid hormone T3 suppresses IL-6 signalling in macrophages and hepatocarcinoma cells, inhibiting STAT3 activation. Consequently, the hormone strongly antagonizes IL-6-stimulated gene transcription, reducing STAT3 recruitment and histone acetylation at IL-6 target promoters. In conclusion, TRs are potent regulators of inflammatory responses and immune homeostasis during sepsis. Reduced responses to IL-6 should serve as a negative feedback mechanism for preventing deleterious effects of excessive hormone signaling during infections.

Thyroid hormone reduces inflammatory cytokines improving glycaemia control in alloxan-induced diabetic wistar rats

AIM

This study aimed at evaluating whether thyroid hormone treatment could improve glycaemia and insulin response in alloxan-induced diabetic rats by altering cytokine expression in the skeletal muscle and epididymal white adipose tissue (eWAT) as well as altering inflammatory cell infiltration in eWAT.

METHODS

Diabetes mellitus (DM) was induced in male Wistar rats by alloxan injection, and a subset of the diabetic rats was treated with T3 (1.5 μg per 100 g body weight) for a 28-day period (DT3 ). Cytokines were measured in serum (MILIplex assay kit) as well as in soleus and EDL skeletal muscles and eWAT by Western blotting. Thyroid function was evaluated by morphological, molecular and biochemical parameters. Cardiac function was assessed by measuring heart rate, blood pressure, maximal rate of pressure development (dp/dtmax ) and decline (dp/dtmin ) as well as the contractility index (CI). Sixty rats were used in the study.

RESULTS

Diabetic rats exhibited decreased thyroid function and increased inflammatory cytokines in serum, soleus muscle and eWAT. T3 treatment decreased glycaemia and improved insulin sensitivity in diabetic animals. These alterations were accompanied by decreased TNF-alpha and IL-6 content in soleus muscle and eWAT, and inflammatory cell infiltration in eWAT. T3 treatment did not affect cardiac function of diabetic rats.

CONCLUSIONS

The present data provide evidence that T3 treatment reduces glycaemia and improves insulin sensitivity in diabetic rats, and that at least part of this effect could result from its negative modulation of inflammatory cytokine expression.

The thyroid hormone receptors as tumor suppressors

In addition to the well-known role of the thyroid hormone receptors (TRs) in growth, development and metabolism, there is increasing evidence that they have profound effects on cell proliferation and malignant transformation. TRs repress transcriptional induction of cyclin D1 by the ras oncogene and block transformation and tumor formation by Ras-transformed fibroblasts in nude mice. Mutant receptors that do not bind coactivators are able to display these actions, whereas receptors defective in corepressors binding are unable to antagonize the responses to the ras oncogene. Furthermore, expression of TRβ1 in hepatocarcinoma and breast cancer cells abolishes anchorage-independent growth and migration, blocks responses to growth factors and represses expression of prometastatic genes, reducing tumor growth and strongly inhibiting invasiveness, extravasation and metastasis formation in euthyroid mice. By contrast, when cells are inoculated into hypothyroid host, tumor growth is retarded, but tumors are more invasive and metastatic growth is enhanced. Increased aggressiveness and tumor growth retardation was also observed with parental cells that do not express TRs, showing that changes secondary to hypothyroidism can modulate tumor progression and metastatic growth independently of the presence of TRs on the tumor cells. Finally, increased malignancy of skin tumors is found in mice lacking TRs, further demonstrating the role of these receptors as inhibitors of tumor progression and suggesting that they represent a potential therapeutic target in cancer.

Deciphering the regulatory logic of an ancient, ultraconserved nuclear receptor enhancer module

Cooperative, synergistic gene regulation by nuclear hormone receptors can increase sensitivity and amplify cellular responses to hormones. We investigated thyroid hormone (TH) and glucocorticoid (GC) synergy on the Krüppel-like factor 9 (Klf9) gene, which codes for a zinc finger transcription factor involved in development and homeostasis of diverse tissues. We identified regions of the Xenopus and mouse Klf9 genes 5-6 kb upstream of the transcription start sites that supported synergistic transactivation by TH plus GC. Within these regions, we found an orthologous sequence of approximately 180 bp that is highly conserved among tetrapods, but absent in other chordates, and possesses chromatin marks characteristic of an enhancer element. The Xenopus and mouse approximately 180-bp DNA element conferred synergistic transactivation by hormones in transient transfection assays, so we designate this the Klf9 synergy module (KSM). We identified binding sites within the mouse KSM for TH receptor, GC receptor, and nuclear factor κB. TH strongly increased recruitment of liganded GC receptor and serine 5 phosphorylated (initiating) RNA polymerase II to chromatin at the KSM, suggesting a mechanism for transcriptional synergy. The KSM is transcribed to generate long noncoding RNAs, which are also synergistically induced by combined hormone treatment, and the KSM interacts with the Klf9 promoter and a far upstream region through chromosomal looping. Our findings support that the KSM plays a central role in hormone regulation of vertebrate Klf9 genes, it evolved in the tetrapod lineage, and has been maintained by strong stabilizing selection.

MAP kinase phosphatase DUSP1 is overexpressed in obese humans and modulated by physical exercise

Chronic low-grade inflammation and dysregulation of the stress defense system are cardinal features of obesity, a major risk factor for the development of insulin resistance and diabetes. Dual-specificity protein phosphatase 1 (DUSP1), known also as MAP kinase phosphatase 1 (MKP1), is implicated in metabolism and energy expenditure. Mice lacking DUSP1 are resistant to high-fat diet-induced obesity. However, the expression of DUSP1 has not been investigated in human obesity. In the current study, we compared the expression pattern of DUSP1 between lean and obese nondiabetic human subjects using subcutaneous adipose tissue (SAT) and peripheral blood mononuclear cells (PBMCs). The levels of DUSP1 mRNA and protein were significantly increased in obese subjects with concomitant decrease in the phosphorylation of p38 MAPK (p-p38 MAPK) and PGC-1α and an increase in the levels of phospho-JNK (p-JNK) and phospho-ERK (p-ERK). Moreover, obese subjects had higher levels of circulating DUSP1 protein that correlated positively with various obesity indicators, triglycerides, glucagon, insulin, leptin, and PAI-1 (P < 0.05) but negatively with V̇O(2max) and high-density lipoprotein (P < 0.05). The observation that DUSP1 was overexpressed in obese subjects prompted us to investigate whether physical exercise could reduce its expression. In this study, we report for the first time that physical exercise significantly attenuated the expression of DUSP1 in both the SAT and PBMCs, with a parallel increase in the expression of PGC-1α and a reduction in the levels of p-JNK and p-ERK along with attenuated inflammatory response. Collectively, our data suggest that DUSP1 upregulation is strongly linked to adiposity and that physical exercise modulates its expression. This gives further evidence that exercise might be useful as a strategy for managing obesity and preventing its associated complications.

Characterization of myeloid-specific peroxidase, keratin 8, and dual specificity phosphatase 1 as innate immune genes involved in the resistance of crucian carp (Carassius auratus gibelio) to Cyprinid herpesvirus 2 infection

Myeloid-specific peroxidase (MPO), keratin 8 (KRT-8), and dual specificity phosphatase 1 (DUSP-1) are believed to play essential roles in innate immunity. Through suppression subtractive hybridization (SSH) analysis, we previously identified MPO, KRT-8, and DUSP-1 as the three genes that were the most significantly upregulated in crucian carp (Carassius auratus gibelio) that survived Cyprinid herpesvirus 2 (CyHV-2) infection. Here, we have further characterized these three genes and their response to pathogen challenge. The open reading frames (ORF) of MPO, KRT-8, and DUSP-1 were cloned by RACE technique and sequenced. The full-length cDNAs of the three genes contained ORFs of 2289, 1575 and 1083 bp respectively. The polypeptides from each ORF were projected to contain 762 (MPO), 524 (KRT-8), and 360 (DUSP-1) amino acids. Phylogenetic analysis showed that the three genes were most closely related to zebrafish. We found that MPO, KRT-8, and DUSP-1 were expressed at low levels in all of the tissues examined in healthy crucian carp. Quantitative real-time RT-PCR analysis indicated that MPO, KRT-8, and DUSP-1 mRNA expression was significantly upregulated within 72 h of CyHV-2 infection compared to mock infected controls. Maximum expression of MPO was detected at 24 hpi (2.71-fold, P < 0.05). While, 12 hpi (3.80-fold, P < 0.01) and 6 hpi (8.70-fold, P < 0.01) were the highest expression time points for KRT-8 and DUSP-1, respectively. In contrast, after Aeromonas hydrophila challenge, the transcripts of these three genes remained unchanged or slightly down-regulated. For the fish survived from viral infection, expression levels of MPO and KRT-8 were 2.72 fold and 2.47 fold higher than those of fish died from acute infection, and similar level of DUSP-1 was observed in samples of survived fish. These data suggested MPO, KRT-8 and DUSP-1 might be involved in the antiviral, but not antibacterial innate immune response in crucian carp. These findings also support the use of MPO and KRT-8 as immunological markers for a response to viral infection in crucian carp.

Thyroid hormone signaling and adult neurogenesis in mammals

The vital roles of thyroid hormone in multiple aspects of perinatal brain development have been known for over a century. In the last decades, the molecular mechanisms underlying effects of thyroid hormone on proliferation, differentiation, migration, synaptogenesis, and myelination in the developing nervous system have been gradually dissected. However, recent data reveal that thyroid signaling influences neuronal development throughout life, from early embryogenesis to the neurogenesis in the adult brain. This review deals with the latter phase and analyses current knowledge on the role of T3, the active form of thyroid hormone, and its receptors in regulating neural stem cell function in the hippocampus and the subventricular zone, the two principal sites harboring neurogenesis in the adult mammalian brain. In particular, we discuss the critical roles of T3 and TRα1 in commitment to a neuronal phenotype, a process that entails the repression of a number of genes notably that encoding the pluripotency factor, Sox2. Furthermore, the question of the relevance of thyroid hormone control of adult neurogenesis is considered in the context of brain aging, cognitive decline, and neurodegenerative disease.

Involvement of the cellular phosphatase DUSP1 in vaccinia virus infection

Poxviruses encode a large variety of proteins that mimic, block or enhance host cell signaling pathways on their own benefit. It has been reported that mitogen-activated protein kinases (MAPKs) are specifically upregulated during vaccinia virus (VACV) infection. Here, we have evaluated the role of the MAPK negative regulator dual specificity phosphatase 1 (DUSP1) in the infection of VACV. We demonstrated that DUSP1 expression is enhanced upon infection with the replicative WR virus and with the attenuated VACV viruses MVA and NYVAC. This upregulation is dependent on early viral gene expression. In the absence of DUSP1 in cultured cells, there is an increased activation of its molecular targets JNK and ERK and an enhanced WR replication. Moreover, DUSP1 knock-out (KO) mice are more susceptible to WR infection as a result of enhanced virus replication in the lungs. Significantly, MVA, which is known to produce non-permissive infections in most mammalian cell lines, is able to grow in DUSP1 KO immortalized murine embryo fibroblasts (MEFs). By confocal and electron microscopy assays, we showed that in the absence of DUSP1 MVA morphogenesis is similar as in permissive cell lines and demonstrated that DUSP1 is involved at the stage of transition between IVN and MV in VACV morphogenesis. In addition, we have observed that the secretion of pro-inflammatory cytokines at early times post-infection in KO mice infected with MVA and NYVAC is increased and that the adaptive immune response is enhanced in comparison with WT-infected mice. Altogether, these findings reveal that DUSP1 is involved in the replication and host range of VACV and in the regulation of host immune responses through the modulation of MAPKs. Thus, in this study we demonstrate that DUSP1 is actively involved in the antiviral host defense mechanism against a poxvirus infection.

Phosphorylation is a post-translational modification that is highly conserved throughout the animal kingdom. Viruses have evolved to acquire their own kinases and phosphatases and to be able to modulate host phosphorylation mechanisms on their benefit. DUSP1 is an early induced gene that belongs to the superfamily of Dual-specificity phosphatases and provides an essential negative feedback regulation of MAPKs. DUSP1 is involved in innate and adaptive immune responses against different bacteria and parasites infections. The use of Knock-out technology has allowed us to understand the role of DUSP1 in the context of VACV infection both in cultured cells and in the in vivo mouse model. Here, we have showed that DUSP1 expression is upregulated during VACV infection and that DUSP1 plays an important role in VACV replication. Interestingly, we have demonstrated that the VACV attenuated virus MVA is able to grow in immortalized murine embryo fibroblasts in the absence of DUSP1. In vivo results showed that VACV replication-competent WR pathogenesis is enhanced in the absence of DUSP1. Furthermore, we have demonstrated that DUSP1 is involved in the host innate and adaptive responses against VACV. Altogether, we have presented a novel role for DUSP1 in VACV replication and anti-VACV host immune response.

Dual specificity phosphatase 1 expression inversely correlates with NF-κB activity and expression in prostate cancer and promotes apoptosis through a p38 MAPK dependent mechanism

Dual specificity phosphatase 1 (DUSP1) and the transcription factor NF-κB are implicated in prostate cancer since their expression levels are altered along this disease, although there are no evidences up to date demonstrating a crosstalk between them. In this report, we show for the first time that DUSP1 over-expression in DU145 cells promotes apoptosis and decreases NF-κB activity by blocking p65/NF-κB nuclear translocation. Moreover, although DUSP1 impairs TNF-α-induced p38 MAPK and JNK activation, only the specific inhibition of p38 MAPK exerts the same effects than DUSP1 over-expression on both apoptosis and NF-κB activity. Consistently, DUSP1 promotes apoptosis and decreases NF-κB activity in cells in which p38 MAPK is induced by TNF-α treatment. These results demonstrate that p38 MAPK is specifically involved in DUSP1-mediated effects on both apoptosis and NF-κB activity. Interestingly, we show an inverse correlation between DUSP1 expression and activation of both p65/NF-κB and p38 MAPK in human prostate tissue specimens. Thus, most of apparently normal glands, benign prostatic hyperplasia and low-grade prostatic intraepithelial neoplasia samples show high DUSP1 expression and low levels of both nuclear p65/NF-κB and activated p38 MAPK. By contrast, DUSP1 expression levels are low or even absent in high-grade prostatic intraepithelial neoplasia and prostatic adenocarcinoma samples, whereas nuclear p65/NF-κB and activated p38 MAPK are highly expressed in the same samples. Overall, our results provide evidence for a role of DUSP1 in the apoptosis of prostate cancer cells, through a mechanism involving the inhibition of p38 MAPK and NF-κB. Furthermore, our findings suggest that the ratio between DUSP1 and p65/NF-κB expression levels, rather than the individual expression of both molecules, is a better marker for diagnostic purposes in prostate cancer.

Thyroid hormone receptors, cell growth and differentiation

BACKGROUND

Tissue homeostasis depends on the balance between cell proliferation and differentiation. Thyroid hormones (THs), through binding to their nuclear receptors, can regulate the expression of many genes involved in cell cycle control and cellular differentiation. This can occur by direct transcriptional regulation or by modulation of the activity of different signaling pathways.

SCOPE OF REVIEW

In this review we will summarize the role of the different receptor isoforms in growth and maturation of selected tissues and organs. We will focus on mammalian tissues, and therefore we will not address the fundamental role of the THs during amphibian metamorphosis.

MAJOR CONCLUSIONS

The actions of THs are highly pleiotropic, affecting many tissues at different developmental stages. As a consequence, their effects on proliferation and differentiation are highly heterogeneous depending on the cell type, the cellular context, and the developmental or transformation status. Both during development and in the adult, stem cells are essential for proper organ formation, maintenance and regeneration. Recent evidence suggests that some of the actions of the thyroid hormone receptors could be secondary to regulation of stem/progenitor cell function. Here we will also include the latest knowledge on the role of these receptors in proliferation and differentiation of embryonic and adult stem cells.

GENERAL SIGNIFICANCE

The thyroid hormone receptors are potent regulators of proliferation and differentiation of many cell types. This can explain the important role of the thyroid hormones and their receptors in key processes such as growth, development, tissue homeostasis or cancer. This article is part of a Special Issue entitled Thyroid hormone signalling.

Inhibition of nuclear factor-kappa B sensitises anterior pituitary cells to tumour necrosis factor-α- and lipopolysaccharide-induced apoptosis

Nuclear factor-kappa B (NF-κB), an important pro-inflammatory factor, is a crucial regulator of cell survival. Both lipopolysaccharide (LPS) and tumour necrosis factor (TNF)-α activate NF-κB signalling. Oestrogens were shown to suppress NF-κB activation. Oestrogens exert a sensitising action to pro-apoptotic stimuli such as LPS and TNF-α in anterior pituitary cells. In the present study, we show by western blotting that 17β-oestradiol (E(2)) decreases TNF-α-induced NF-κB/p65 and p50 nuclear translocation in primary cultures of anterior pituitary cells from ovariectomised (OVX) rats. Also, the in vivo administration of E(2) decreases LPS-induced NF-κB/p65 and p50 nuclear translocation. To investigate whether the inhibition of NF-κB pathway sensitises anterior pituitary cells to pro-apoptotic stimuli, we used an inhibitor of NF-κB activity, BAY 11-7082 (BAY). BAY, at a concentration that fails to induce apoptosis, has permissive action on TNF-α-induced apoptosis of lactotrophs and somatotrophs from OVX rats, as assessed by terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL). Pharmacological inhibition of NF-κB signalling enhances E(2)-sensitising effect to TNF-α-induced apoptosis in lactotrophs but not in somatotrophs. In vivo administration of BAY allowed LPS-induced apoptosis in anterior pituitary cells from OVX rats (determined by fluorescence activated cell sorting). Furthermore, LPS-induced expression of Bcl-xL in pituitaries of OVX rats is decreased by E(2) administration. Our results show that inhibition of the NF-κB signalling pathway sensitises anterior pituitary cells to the pro-apoptotic action of LPS and TNF-α. Because E(2) inhibits LPS- and TNF-α-activated NF-κB nuclear translocation, the present study suggests that E(2) sensitises anterior pituitary cells to TNF-α- and LPS-induced apoptosis by inhibiting NF-κB activity.

The thyroid hormone receptors as modulators of skin proliferation and inflammation

We have analyzed the role of the thyroid hormone receptors (TRs) in epidermal homeostasis. Reduced keratinocyte proliferation is found in interfollicular epidermis of mice lacking the thyroid hormone binding isoforms TRα1 and TRβ (KO mice). Similar results were obtained in hypothyroid animals, showing the important role of the liganded TRs in epidermal proliferation. In addition, KO and hypothyroid animals display decreased hyperplasia in response to 12-O-tetradecanolyphorbol-13-acetate. Both receptor isoforms play overlapping functional roles in the skin because mice lacking individually TRα1 or TRβ also present a proliferative defect but not as marked as that found in double KO mice. Defective proliferation in KO mice is associated with reduction of cyclin D1 expression and up-regulation of the cyclin-dependent kinase inhibitors p19 and p27. Paradoxically, ERK and AKT activity and expression of downstream targets, such as AP-1 components, are increased in KO mice. Increased p65/NF-κB and STAT3 phosphorylation and, as a consequence, augmented expression of chemokines and proinflammatory cytokines is also found in these animals. These results show that thyroid hormones and their receptors are important mediators of skin proliferation and demonstrate that TRs act as endogenous inhibitors of skin inflammation, most likely due to interference with AP-1, NF-κB, and STAT3 activation.