Thyroid hormones alter the adenine nucleotide hydrolysis in adult rat blood serum

The impacts of obesity in rheumatoid arthritis and insights into therapeutic purinergic modulation

Rheumatoid Arthritis (RA) is an autoimmune condition responsible for the impairment of synovia and joints, endangering the functionality of individuals and contributing to mortality. Currently, obesity is increasing worldwide, and recent studies have suggested an association between such condition and RA. In this sense, obese individuals present a lower capacity for achieving remission and present more intense symptoms of the disease, demonstrating a link between both disorders. Different studies aim to understand the possible connection between the conditions; however, few is known in this sense. Therefore, knowing that obesity can alter the activity of multiple body systems, this work's objective is to evaluate the main modifications caused by obesity, which can be linked to the pathophysiology of RA, highlighting as relevant topics obesity's negative impact triggering systemic inflammation, intestinal dysbiosis, endocrine disbalances. Furthermore, the relationship between oxidative stress and obesity also deserves to be highlighted, considering the influence of reactive oxygen species (ROS) accumulation in RA exacerbation. Additionally, many of those characteristics influenced by obesity, along with the classic peculiarities of RA pathophysiology, can also be associated with purinergic signaling. Hence, this work suggests possible connections between the purinergic system and RA, proposing potential therapeutic targets against RA to be studied.

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.

Post-thyroidectomy hypothyroidism increases the expression and activity of ectonucleotidases in platelets: Possible involvement of reactive oxygen species

Signaling mediated by purines is a widespread mechanism of cell-cell communication related to vasomotor responses and the control of platelet function in the vascular system. However, little is known about the involvement of this signaling as well as the role of reactive oxygen species (ROS) in the development of hypothyroidism. Therefore, the present study investigates changes in the purinergic system, including enzyme activities and expression in platelets, and oxidative profiles in patients with post-thyroidectomy hypothyroidism. The nucleoside triphosphate diphosphohydrolase 1 (NTPDase/CD39) expression in patients increased by 40%, and the adenosine triphosphate (ATP) or adenosine diphosphate (ADP) hydrolyzing activity increased by 82% and 70%, respectively. The activities of ecto-5´-nucleotidase and adenosine deaminase (ADA) also significantly enhanced (39% and 52%, respectively), which correlates with a 45% decrease in adenosine concentration. Furthermore, these patients demonstrated an increased production of ROS (42%), thiobarbituric acid reactive substances (TBARS) (115%), carbonyl protein (30%) and a decreased glutathione S-transferase (GST) activity (20%). This study demonstrates that hypothyroidism interferes with adenine nucleoside and nucleotide hydrolysis and this is correlated with oxidative stress, which might be responsible for the increase in ADA activity. This increase causes rapid adenosine deamination, which can generate a decrease in their concentration in the systemic circulation, which can be associated with the development of vascular complications.

Quercetin changes purinergic enzyme activities and oxidative profile in platelets of rats with hypothyroidism

Diseases related to thyroid hormones have been extensively studied because affect a large number of individuals, and these hormones participate in the regulation of the whole organism homeostasis. However, little is known about the involvement of purinergic signaling related to oxidative stress in hypothyroidism and possible therapeutic adjuncts for treatment of this disorder. Thus, the present study investigates the effects of quercetin on NTPDase, 5'-nucleotidase and adenosine deaminase activities, platelet aggregation and oxidative profile in platelets of rats with methimazole (MMI)-induced hypothyroidism. Methimazole at a concentration of 20mg/100mL was administered for 90days. From the second month the animals received quercetin 10 or 25mg/kg for 60days. Results showed that: Ecto-5'-nucleotidase activity decreased in methimazole/water group and the treatment with quercetin 25mg/kg decreased NTPDase, 5'-nucleotidase and adenosine deaminase activities. Moreover, platelet aggregation increased in methimazole/water group. Lipid peroxidation increased while superoxide dismutase and catalase activities decreased, but, interestingly, the treatment with quercetin reversed these changes. These results demonstrated that quercetin modulates adenine nucleotide hydrolysis decreasing the ADP formation and adenosine deamination. At the same time quercetin improves the oxidative profile, as well as reduces platelet aggregation, which together with the modulation in the nucleotides levels can contribute to the prevention of platelet 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.

The contribution of thyroid dysfunction on cardiovascular disease in patients with chronic kidney disease

Accelerated atherosclerosis and arterial stiffness are the two leading causes of increased cardiovascular disease in patients with chronic kidney disease. Dysfunctional thyroid hormone metabolism has been suggested to play a role in atherosclerosis and arterial stiffness. Changes in cardiac contractility and output, myocardial oxygen demand, systemic and peripheral vascular resistance, blood pressure and lipid profile, increased inflammatory burden and endothelial dysfunction may be responsible for thyroid hormone-related cardiovascular disease. This article focuses on the mechanistic insights of this association and provides a concise review of the current literature.