Modulation by betaine of cellular responses to osmotic stress

Abstract

Various solutes were tested to see if they could modify the responses of SV-3T3 cells to hyperosmotic (0.5 osM) conditions, which cause an inhibition of general cell protein synthesis and of the rate of cell proliferation, coupled with an induction of amino acid transport activity. The added solutes were glycerol, proline, taurine, betaine, dimethylglycine and sarcosine. Of these, betaine produced the most dramatic and consistent effects. Addition of 10-25 mM-betaine to the hyperosmotic medium largely prevented the 90% inhibition of cell proliferation that occurred in its absence. Whether it was added initially or after the cells were exposed to hyperosmotic medium, 25 mM-betaine also converted a 50% recovery of the rate of protein synthesis into 100%. Similarly, the same concentrations of betaine prevented a 30% decrease in cell volume and decreased the induction of amino acid transport via system A by 73%. Lower concentrations of betaine produced smaller but still significant changes in these functional responses. With chick-embryo fibroblasts, under identical hyperosmotic conditions, 25 mM-betaine completely counteracted a 75% inhibition of the rate of protein synthesis. At present it is not clear how betaine modulates these effects of hyperosmolarity on cell functions.

Modulation of Hypertonicity-Induced Aquaporin-1 by Sodium Chloride, Urea, Betaine, and Heat Shock in Murine Renal Medullary Cells

“…Although the uptake and accumulation of betaine protects cells from severe hypertonicity, the addition of betaine under mild hypertonic conditions counteracts hypertonicity-induced AQP1 expression. Thus, the addition of betaine under severe hypertonic conditions restores its expression because betaine prevents hypertonicity-induced cell damage and apoptosis (35). Although the protective effect of betaine on hypertonicityinduced cell death after 48 h of incubation has been reported previously (36), our data showed that the adverse expression of AQP1 by the addition of betaine in N100 and N150 was not due to changes in cell viability.…”

Macromolecular Crowding Regulates Assembly of mRNA Stress Granules after Osmotic Stress

“…Altogether, these results indicate that compatible osmolytes play a key role in the disassembly of SGs and MT bundles. Interestingly, a high extracellular betaine concentration (in the millimolar range) was already shown to have a protective effect to hypertonicity (53,54).…”

Activation of heat-shock transcription factor 1 by hypertonic shock in 3T3 cells

“…Intracellular volumes were estimated by measurement of the equilibration of 3-O-methyl--[1-$H]glucose, as described previously [12] using the method of Kletzien et al [13]. Intracellular Na + and K + concentrations ([Na + ] i and [K + ] i respectively) were estimated using the procedure described by Owen and Villereal [14], with slight modifications [15].…”