Thyrotropin receptor and membrane interactions in FRTL-5 thyroid cell strain in microgravity.

The aim of this work was to analyze the possible alteration of thyrotropin (TSH) receptors in microgravity, which could explain the absence of thyroid cell proliferation in the space environment. Several forms of the TSH receptor are localized on the plasma membrane associated with caveolae and lipid rafts. The TSH regulates the fluidity of the cell membrane and the presence of its receptors in microdomains that are rich in sphingomyelin and cholesterol. TSH also stimulates cyclic adenosine monophosphate (cAMP) accumulation and cell proliferation. Reported here are the results of an experiment in which the FRTL-5 thyroid cell line was exposed to microgravity during the Texus-44 mission (launched February 7, 2008, from Kiruna, Sweden). When the parabolic flight brought the sounding rocket to an altitude of 264 km, the culture media were injected with or without TSH in the different samples, and weightlessness prevailed on board for 6 minutes and 19 seconds. Control experiments were performed, in parallel, in an onboard 1g centrifuge and on the ground in Kiruna laboratory. Cell morphology and function were analyzed. Results show that in microgravity conditions the cells do not respond to TSH treatment and present an irregular shape with condensed chromatin, a modification of the cell membrane with shedding of the TSH receptor in the culture medium, and an increase of sphingomyelin-synthase and Bax proteins. It is possible that real microgravity induces a rearrangement of specific sections of the cell membrane, which act as platforms for molecular receptors, thus influencing thyroid cell function in astronauts during space missions.

Structural alterations in erythrocytes from patients with chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is characterized by inflammation of deep lung and pulmonary hypoxemia. In order to investigate if the clinical manifestations of this disease can be correlated to specific alterations in red blood cell (RBC) morphology, the erythrocytes from 12 COPD patients and 12 control subjects were obtained and examined by scanning electron microscopy (SEM), fluorescence microscopy and electron paramagnetic resonance (EPR) spectroscopy. The results demonstrate that the RBCs from COPD patients are greatly altered with respect to control erythrocytes. Specifically, SEM analysis revealed important shape changes while light fluorescence microscopy demonstrated microfilament network (actin and spectrin) redistribution. Finally, EPR spectroscopy, using the paramagnetic spin label 5-nitroxystearate, revealed an increase in membrane order (rigidity) in the erythrocytes of COPD patients with respect to controls. When taken together and when compared to the morphological variations present in the RBCs of other ill patients (i.e., diabetics), the data presented in this report seem to suggest that changes in erythrocyte shape and rheological properties play a key role in RBC dysfunction in the course of COPD.