Decreased expression of retinoid nuclear receptor (RARα and RARγ) mRNA determined by real-time quantitative RT-PCR in peripheral blood mononuclear cells of hypothyroid patients

Abstract

In vivo assessment of the cellular impact of thyroid hormones on target tissues might be of help for physiological studies and to evaluate the consequences of various diseases of the thyroid gland in humans. Given the tenuous relationship between retinoid and tri-iodothyronine (T 3 ) status and that retinoids have also intracellular roles, the aim of this study was to determine the effect of hypothyroidism on the expression of T 3 nuclear receptors (TR) and retinoic acid nuclear receptors (RAR, RXR) in human peripheral blood mononuclear cells (PBMC). Using real time RT-PCR, we quantified the relative amount of mRNA of the thyroid (TR and TR ) and retinoid (RAR , RAR , and RXR ) nuclear receptors in PBMC of euthyroid (n=22) compared with hypothyroid (n=22) subjects. Classical plasma parameters (free T 3 (FT 3 ), free thyroxine (T 4 ) (FT 4 ), thyroid-stimulating hormone (TSH), retinol (ROH), retinol-binding protein (RBP) and transthyretin (TTR)) were also measured. In hypothyroid subjects, the concentration of TSH was elevated, and dramatically low T 3 and T 4 concentrations were associated with a decrease in the expression of TR . Expression of RAR and RAR significantly decreased in hypothyroid versus control subjects, while an increased concentration of ROH was emphasised by hypothyroidism. These results first indicated that primary hypothyroidism induces hypoactivation of the retinoid nuclear pathway in PBMC, which was not predicted by the plasma ROH level. Further investigations will be necessary to evaluate these parameters in very small changes in thyroid hormone production such as mild (subclinical) hypothyroidism.

Clinical relevance of thyroid dysfunction in human haematopoiesis: biochemical and molecular studies

“…Previous observations by Meier-Heusler that suggested a non-significant trend towards a down-regulation of TRb-1 mRNA levels in PB MNCs of hyperthyroid patients support this notion (23). Similarly, Féart et al documented that in hypothyroid subjects, dramatically low T 3 and T 4 concentrations were associated with a decrease in the expression of TRb-1 in PB MNCs (24). These data suggest that TR expression in HPCs is sensitive to the pathological conditions related to hypo-and hyperthyroidism.…”

RARγ and TRβ expressions are decreased in PBMC and SWAT of obese subjects in weight gain

“…Preparation of PBMC Isolation of human blood mononuclear cells was performed by density gradient centrifugation using Ficoll-Plaque Plus solution (Amersham Biosciences, F-91898 Orsay France) as previously described [7,8]. The PBMC were then suspended in TRIZOL® Reagent (Invitrogen, Cergy Pontoise, France) and stored at -80°C before RNA extraction.…”

“…Real-time polymerase chain reaction Real-time quantitative PCR involving LightCycler TM technology (Roche Diagnostics, Mannheim, Germany) was performed according to a modification of the protocol recommended by the manufacturer, as previously described [8]. In brief, the principle of real-time quantification is based on the quantification of the PCR product during the linear phase of the amplification process.…”

“…Various studies showed disease-characteristic gene expression patterns in PBMC, in particular, some studies previously performed in our laboratory, which have shown that hypothyroid and aged subjects present hypoactivation of the retinoid nuclear pathway in PBMC [7,8], suggesting that alterations in the messenger RNA (mRNA) levels of these nuclear receptors are manifested at this peripheral level.…”

“…In humans, access to tissue depots as subcutaneous adipose tissue is limited, but the blood compartment is easy to sample and members of the superfamily of nuclear receptors such as PPARγ, RARα and RARγ, RXRα, TRα, and TRβ [8,31] are expressed in peripheral blood mononuclear cells (PBMC), which are the only readily available cells in healthy humans. Various studies showed disease-characteristic gene expression patterns in PBMC, in particular, some studies previously performed in our laboratory, which have shown that hypothyroid and aged subjects present hypoactivation of the retinoid nuclear pathway in PBMC [7,8], suggesting that alterations in the messenger RNA (mRNA) levels of these nuclear receptors are manifested at this peripheral level.…”