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Alteration of multiple cell membrane functions in L-6 myoblasts by T-2 toxin: an important mechanism of action
1United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland 21701-5011.
Abstract:
Recent studies suggest that T-2 toxin interacts with cell membranes and alters membrane function. This study was done to assess the effect of T-2 toxin on a broad range of cell membrane functions in L-6 myoblasts. The following parameters were assessed after exposure to T-2 toxin for 10 min: (1) the uptake of calcium, rubidium, and glucose; (2) the uptake of leucine and tyrosine and incorporation into protein; (3) the uptake of thymidine and incorporation into DNA; and (4) residual cellular lactate dehydrogenase (LDH) as a measure of cell membrane integrity. The effects of T-2 toxin on these parameters were: (1) The minimal effective concentration (MEC) of T-2 toxin that caused a reduction in the uptake of calcium and glucose was 4 pg/ml. The uptake of rubidium was increased at 0.4 pg/ml and then reduced at 4 pg/ml and higher concentrations. (2) The MEC for reduction of the uptake of leucine and tyrosine and their incorporation into protein was 4 pg/ml. (3) Thymidine uptake and incorporation into DNA showed a biphasic response with an increase at 0.4 pg/ml and a reduction at 4 pg for uptake and 40 pg/ml for incorporation. (4) Intracellular LDH was reduced at 4 ng/ml. (5) Calcium efflux was reduced after 1-, 5-, and 15-min exposures to T-2 toxin in a concentration of 40 ng/ml. All of the changes noted, including protein synthesis inhibition, were present to a significant degree within 10 min of exposure to T-2 toxin. This time interval is too short to attribute all of these effects directly to protein synthesis inhibition since most short-lived proteins have half-lives measured in hours. In conclusion, T-2 toxin appears to have multiple effects on cell membrane function at very low concentrations (0.4 pg/ml to 4 ng/ml), which are independent of protein synthesis inhibition. These likely include effects either direct or indirect on amino acid, nucleotide, and glucose transporters, as well as calcium and potassium (rubidium) channel activities.
Insights
T-2 toxin significantly impacts cell membrane functions, including nutrient uptake and integrity, at very low concentrations. These effects occur rapidly and are independent of protein synthesis inhibition.
Area of Science:
- Cell Biology
- Toxicology
- Biochemistry
Background:
- T-2 toxin is known to interact with cell membranes, potentially altering their function.
- Understanding the precise mechanisms of T-2 toxin's cellular effects is crucial for assessing its toxicity.
Purpose of the Study:
- To investigate the effects of T-2 toxin on various cell membrane functions in L-6 myoblasts.
- To determine the minimal effective concentrations (MEC) and time course of T-2 toxin's impact on membrane transport and integrity.
Main Methods:
- L-6 myoblasts were exposed to varying concentrations of T-2 toxin for 10 minutes.
- Assessed were the uptake of calcium, rubidium, glucose, leucine, tyrosine, and thymidine.
- Evaluated were the incorporation of leucine, tyrosine, and thymidine into protein and DNA, respectively.
- Measured residual cellular lactate dehydrogenase (LDH) to assess membrane integrity.
- Calcium efflux was also monitored.
Main Results:
- T-2 toxin reduced calcium and glucose uptake at 4 pg/ml.
- Rubidium uptake showed an initial increase at 0.4 pg/ml, followed by a decrease at higher concentrations.
- Amino acid and nucleotide uptake/incorporation were affected at concentrations as low as 4 pg/ml.
- Cell membrane integrity was compromised at 4 ng/ml (LDH reduction).
- Calcium efflux was reduced after 1-15 minutes of exposure to 40 ng/ml T-2 toxin.
Conclusions:
- T-2 toxin exerts multiple effects on cell membrane functions at very low concentrations (0.4 pg/ml to 4 ng/ml).
- These observed effects are rapid (within 10 minutes) and independent of protein synthesis inhibition.
- T-2 toxin likely affects amino acid, nucleotide, and glucose transporters, as well as calcium and potassium channel activities.