Activation of protease-activated receptor 2 mediates cutaneous vasodilatation but not sweating: roles of nitric oxide synthase and cyclo-oxygenase.

NEW FINDINGS: What is the central question of this study? Protease-activated receptor 2 (PAR2) is located in the endothelial cells of skin vessels and eccrine sweat glands. However, a functional role of PAR2 in the control of cutaneous blood flow and sweating remains to be assessed in humans in vivo. What is the main finding and its importance? Our results demonstrate that in normothermic resting humans in vivo, activation of PAR2 elicits cutaneous vasodilatation partly through nitric oxide synthase-dependent mechanisms, but does not mediate sweating. These results provide important new insights into the physiological significance of PAR2 in human skin. Protease-activated receptor 2 (PAR2) is present in human skin, including keratinocytes, endothelial cells of skin microvessels and eccrine sweat glands. However, whether PAR2 contributes functionally to the regulation of cutaneous blood flow and sweating remains entirely unclear in humans in vivo. We hypothesized that activation of PAR2 directly stimulates cutaneous vasodilatation and sweating via actions of nitric oxide synthase (NOS) and cyclo-oxygenase (COX). In 12 physically active young men (29 ± 5 years old), cutaneous vascular conductance (CVC) and sweat rate were measured at four intradermal microdialysis forearm skin sites that were treated with the following: (i) lactated Ringer's solution (control); (ii) 10 mm NG -nitro-l-arginine (NOS inhibitor); (iii) 10 mm ketorolac (COX inhibitor); or (iv) a combination of both inhibitors. At all sites, a PAR2 agonist (SLIGKV-NH2 ) was co-administered in a dose-dependent fashion (0.06, 0.18, 0.55, 1.66 and 5 mm, each for 25 min). The highest dose of SLIGKV-NH2 (5 mm) increased CVC from baseline at the control site (P ≤ 0.05). This increase in CVC associated with PAR2 activation was attenuated by NOS inhibition regardless of the presence or absence of simultaneous COX inhibition (both P ≤ 0.05). However, COX inhibition alone did not affect the PAR2-mediated increase in CVC (P > 0.05). No increase in sweat rate was measured at any administered dose of SLIGKV-NH2 (all P > 0.05). We show that in normothermic resting humans in vivo, PAR2 activation does not increase sweat rate, whereas it does modulate cutaneous vasodilatation through NOS-dependent mechanisms.

Coexistence of Autoimmune Hyper- and Hypothyroidism in a Kindred with Reduced Sensitivity to Thyroid Hormone.

INTRODUCTION: Resistance to thyroid hormone beta (RTHß) is a rare disease with an autosomal dominant transmission. Diagnosis may be challenging especially in patients with hyper- or hypothyroidism. CASE PRESENTATION: A 31-year-old male patient with suppressed thyroid-stimulating hormone (TSH), elevated free thyroxine and free triiodothyronine, along with high thyroid receptor antibodies was diagnosed with Graves' disease. Benzylthiouracil was started. One month later, reduced sensitivity to thyroid hormones was suspected because of persistently high thyroid hormone levels contrasting with high TSH level. Molecular analysis highlighted a 10c.1357C>T p.P453S mutation in the thyroid hormone receptor beta gene (THRB). RTHß was diagnosed. Several relatives also had RTHß (the mother, the young son, and 2 out of 3 siblings). Autoimmune hypothyroidism was present in the mother, whereas 2 out of 3 siblings had asymptomatic autoimmunity. DISCUSSION/CONCLUSION: Both Graves' disease and autoimmune hypothyroidism were described in patients with RTHß. We show here for the first time that autoimmune hypo- and hyperthyroidism may coexist in kindred with RTHß. Seven previously published cases of Graves' disease and RTHß were retrieved and analyzed. Treatments and thyroid hormone level targets are discussed as well as the possible link between RTHß and autoimmune thyroid diseases.