E-NTPDase 3 (ATP diphosphohydrolase) from cardiomyocytes, activity and expression are modulated by thyroid hormone

Purinergic signaling in thyroid disease

It is known that thyroid hormones play pivotal roles in a wide variety of pathological and physiological events. Thyroid diseases, mainly including hyperthyroidism, hypothyroidism, and thyroid cancer, are highly prevalent worldwide health problems and frequently associated with severe clinical manifestations. However, etiology of hyperthyroidism, hypothyroidism, and thyroid cancer is not fully understood. Purinergic signaling accounts for a complex network of receptors and extracellular enzymes responsible for the recognition and degradation of extracellular nucleotides and adenosine. It has been established that purinergic signaling modulates pathways in a wide range of physiopathological conditions including hypertension, diabetes, hepatic diseases, psychiatric and neurodegeneration, rheumatic immune diseases, and cancer. More recently, the purinergic system is found to exist in thyroid gland and play an important role in the pathophysiology of thyroid diseases. Therefore, throughout this review, we focus on elaborating the changes in purinergic receptors, extracellular enzymes, and extracellular nucleotides and adenosine in hyperthyroidism, hypothyroidism, and thyroid cancer. Profound understanding of the relationship between the purinergic signaling with thyroid diseases provides a promising research area for insights into the molecular basis of thyroid diseases and also develops new and exciting insights into the treatment of thyroid diseases, especially thyroid cancer.

Epidermal melanocytes metabolize extracellular nucleotides by purinergic enzymes

The human epidermal melanocyte (hEM) are melanin-producing cells that provide skin pigmentation and protection against ultraviolet radiation. Although purinergic signaling is involved in skin biology and pathology, the presence of NTPDase members, as well as the rate of nucleotides degradation by melanocytes were not described yet. Therefore, in this study, we analyzed the expression of ectonucleotidases in hEM derived from discarded foreskin of male patients. The expression of purinergic enzymes was confirmed by mRNA and flow cytometry. Among the ectonucleotidases, ectonucleoside triphosphate diphosphohydrolase1 (NTPDase1) and ecto-5´-nucleotidase were the ectoenzymes with higher expressions. The hydrolysis rate for ATP, ADP, and AMP was low in comparison to other primary cells already investigated. The amount of ATP in the culture medium was increased after a scratch wound and decreased to basal levels in 48 h, while the NTPDase1 and P2X7 expressions increased. Therefore, it is possible to suggest that after cell injury, the ATP released by hEM into the extracellular space will be hydrolyzed by ectonucleotidases as the NTPDase1 that will control the levels of nucleotides in the skin micro-environment.

Role of thyroid hormones in ventricular remodeling

Cardiac remodeling includes alterations in molecular, cellular, and interstitial systems contributing to changes in size, shape, and function of the heart. This may be the result of injury, alterations in hemodynamic load, neurohormonal effects, electrical abnormalities, metabolic changes, etc. Thyroid hormones (THs) serve as master regulators for diverse remodeling processes of the cardiovascular system-from the prenatal period to death. THs promote a beneficial cardiomyocyte shape and improve contractility, relaxation, and survival via reversal of molecular remodeling. THs reduce fibrosis by decreasing interstitial collagen and reduce the incidence and duration of arrhythmias via remodeling ion channel expression and function. THs restore metabolic function and also improve blood flow both by direct effects on the vessel architecture and decreasing atherosclerosis. Optimal levels of THs both in the circulation and in cardiac tissues are critical for normal homeostasis. This review highlights TH-based remodeling and clinically translatable strategies for diverse cardiovascular disorders.

Purinergic signalling in endocrine organs

There is widespread involvement of purinergic signalling in endocrine biology. Pituitary cells express P1, P2X and P2Y receptor subtypes to mediate hormone release. Adenosine 5'-triphosphate (ATP) regulates insulin release in the pancreas and is involved in the secretion of thyroid hormones. ATP plays a major role in the synthesis, storage and release of catecholamines from the adrenal gland. In the ovary purinoceptors mediate gonadotrophin-induced progesterone secretion, while in the testes, both Sertoli and Leydig cells express purinoceptors that mediate secretion of oestradiol and testosterone, respectively. ATP released as a cotransmitter with noradrenaline is involved in activities of the pineal gland and in the neuroendocrine control of the thymus. In the hypothalamus, ATP and adenosine stimulate or modulate the release of luteinising hormone-releasing hormone, as well as arginine-vasopressin and oxytocin. Functionally active P2X and P2Y receptors have been identified on human placental syncytiotrophoblast cells and on neuroendocrine cells in the lung, skin, prostate and intestine. Adipocytes have been recognised recently to have endocrine function involving purinoceptors.

New approaches to thyroid hormones and purinergic signaling

It is known that thyroid hormones influence a wide variety of events at the molecular, cellular, and functional levels. Thyroid hormones (TH) play pivotal roles in growth, cell proliferation, differentiation, apoptosis, development, and metabolic homeostasis via thyroid hormone receptors (TRs) by controlling the expression of TR target genes. Most of these effects result in pathological and physiological events and are already well described in the literature. Even so, many recent studies have been devoted to bringing new information on problems in controlling the synthesis and release of these hormones and to elucidating mechanisms of the action of these hormones unconventionally. The purinergic system was recently linked to thyroid diseases, including enzymes, receptors, and enzyme products related to neurotransmitter release, nociception, behavior, and other vascular systems. Thus, throughout this text we intend to relate the relationship between the TH in physiological and pathological situations with the purinergic signaling.

NTPDase family in zebrafish: Nucleotide hydrolysis, molecular identification and gene expression profiles in brain, liver and heart

The nucleoside triphosphate diphosphohydrolase (NTPDase) family cleaves tri- and diphosphonucleosides to monophosphonucleosides and is responsible for terminating purinergic transmission. Since the NTPDase family in zebrafish is poorly understood, here we evaluated the nucleotide hydrolysis in three tissues of adult zebrafish (brain, liver, and heart), confirmed the presence of distinct NTPDase members by a phylogenetic analysis and verified their relative gene expression profiles in the respective tissues. A different profile of ATP and ADP hydrolysis in the brain, liver, and heart as a function of time and protein concentration was observed. Sodium azide (20mM), ARL 67156 (300 microM) and Suramin (300 microM) differently altered the nucleotide hydrolysis in zebrafish tissues, suggesting the contribution of distinct NTPDase activities. Homology-based searches identified the presence of NTPDase1-6 and NTPDase8 orthologs and the phylogeny also grouped three NTPDase2 and two NTPDase5 paralogs. The deduced amino acid sequences share the apyrase conserved regions, conserved cysteine residues, putative N-glycosylation, phosphorylation, N-acetylation sites, and different numbers of transmembrane domains. RT-PCR experiments revealed the existence of a distinct relative entpd1-6 and entpd8 expression profile in brain, liver, and heart. Taken together, these results indicate that several NTPDase members might contribute to a tight regulation of nucleotide hydrolysis in zebrafish tissues.