Apelin-13 Regulates Vasopressin-Induced Aquaporin-2 Expression and Trafficking in Kidney Collecting Duct Cells.

BACKGROUND/AIMS: Apelin and its G protein-coupled receptor APJ (gene symbol Aplnr) are strongly expressed in magnocellular vasopressinergic neurons suggesting that the apelin/APJ system plays a key role at the central level in regulating salt and water balance by counteracting the antiduretic action of vasopressin (AVP). Likewise, recent studies revealed that apelin exerts opposite effects to those of vasopressin induced on water reabsorption via a direct action on the kidney collecting duct. However, the underlying mechanisms of the peripheral action of apelin are not clearly understood. Here, we thus investigated the role of the apelin/APJ system in the regulation of water balance in the kidney, and more specifically its involvement in modulating the function of aquaporin-2 (AQP2) in the collecting duct. METHODS: Mouse cortical collecting duct cells (mpkCCD) were incubated in the presence of dDAVP and treated with or without apelin-13. Changes in AQP2 expression and localization were determined by immunoblotting and confocal immunofluorescence staining. RESULTS: Herein, we showed that the APJ was present in mpkCCD cells. Treatment of mpkCCD with apelin-13 reduced the cAMP production and antagonized the AVP-induced increase in AQP2 mRNA and protein expressions. Immunofluorescent experiments also revealed that the AVP-induced apical cell surface expression of AQP2, and notably its phosphorylated isoform AQP2-pS269, was considerably reduced following apelin-13 application to mpkCCD cells. CONCLUSION: Our data reinforce the aquaretic role of the apelin/APJ system in the fine regulation of body fluid homeostasis at the kidney level and its physiological opposite action to the antiduretic activity of AVP.

Malignant solitary fibrous tumour of the kidney with an extensive thrombus: A case report and review of the literature.

Solitary fibrous tumours (SFTs) are neoplasms originating from mesenchymal cells, usually found in lung pleura. Extrapleuritic lesions are extremely rare, with about 60 cases of SFTs of the kidney available in the English literature. We report here the first case of a malignant SFT of the kidney presenting with an extensive vascular thrombus extending to the right atrium with associated pulmonary emboli. We describe management, pathological assessment, as well as radiological and clinical evolution. Our report provides a first therapeutic approach to a critical presentation of a rare pathology, which should help guide management of such disease in future cases.

[Subacute motor neuropathy induced by T3 hyperthyroidism]. / Neuropathie motrice subaiguë révélatrice d'une hyperthyroïdie à T3.

Subacute motor neuropathy involving bulbar nerves is an unusual complication of hyperthyroidism. Clinical and neurophysiologic follow-up of such patients has been rarely reported. We describe a 41-year-old Colombian patient who developed respiratory failure associated with motor neuropathy and severe weight loss. The major clinical features included diffuse amyotrophy, bilateral facial paresis, and fasciculations, suggesting motor neuropathy. Electromyography confirmed the presence of axonal neuropathy, with predominant motor involvement. Goiter with hypervascularization was noticed, associated with pure T3 hyperthyroidism (T3l=26 pg/ml; N<3.8). The patient was given carbimazole which induced a severe skin vasculitis 10 days later. Carbimazole was stopped and replaced by propylthiouracile, which also induced vasculitis with secondary cardiac failure. Total thyroidectomy was then performed. General status improved rapidly as well as motor deficit, amyotrophy and pyramidal syndrome. Electromyographic abnormalities improved significantly within 3 months. This observation demonstrates that hyperthyroidism can produce motor axonal neuropathy, curable with radical surgery.

[Peroneal nerve palsy induced by anterior tibialis pyomyositis]. / Pyomyosite du jambier antérieur: une cause inhabituelle de mononévrite du sciatique poplité externe.

A 16-year-old girl from Guadeloup developed paresis of the flexors of the right foot, associated with edema and acute pain located in the upper anterior tibialis muscle. Electromyography confirmed mononeuritis of the right peroneal nerve, with severe reduction of potential amplitude. Computed tomography of the right leg showed a heterogeneous mass involving the upper segment of the anterior tibialis muscle, close to the location of peroneal nerve. Muscle biopsy confirmed pyomyositis. Muscle culture was negative. Paresis improved soon after antibiotic therapy was started.