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Published on: June 14, 2020
Mechanism of polyamine toxicity in cultured cardiac myocytes
1Department of Pathology, The University of Texas Medical Branch, Galveston, TX 77555-0609, USA.
Abstract:
The goal of this study was to investigate the mechanism of polyamine-mediated injury to the cardiac myocytes isolated from neonatal rat hearts. The myocytes, cultured in Dulbecco's minimal essential medium-1% foetal calf serum (FBS), were exposed to spermidine or spermine. The toxicity to myocytes was determined by (a) increased release of creatine kinase (CPK) into the media and (b) decline in cell viability or functional activity. Spermidine, above 10 mum, increased the release of CPK into media, decreased cell viability and decreased the functional activity of the myocytes. The FBS exhibited polyamine oxidase activity and semicarbazide-sensitive amine oxidase activity. Aminoguanidine, MDL72,527 or semicarbazide, are the inhibitors of amine oxidases, polyamine oxidase (PAO) and semicarbazide-sensitive amine oxidase (SSAO), respectively. The addition of these inhibitors to the medium protected the myocytes from spermidine toxicity. To determine whether myocyte PAO is involved in polyamine toxicity, we used horse serum that contained high SSAO activity and negligible PAO activity. The myocyte extracts had negligible SSAO activity but high PAO activity. When myocytes were cultured in horse serum in lieu of FBS, spermine caused toxicity at above 100 mum. In horse serum, MDL72,527 and semicarbazide protected the myocytes from spermine toxicity. These observations show that extracellular amine oxidases and myocyte PAO are significant in mediation of polyamine toxicity.
Insights
Polyamines like spermidine can harm cardiac cells. Inhibiting specific enzymes, polyamine oxidase (PAO) and semicarbazide-sensitive amine oxidase (SSAO), protects these heart cells from polyamine toxicity.
Area of Science:
- Cardiovascular Biology
- Cellular Toxicology
- Biochemistry
Background:
- Polyamines are essential for cell growth but can be toxic at high concentrations.
- Cardiac myocytes are susceptible to cellular injury, and the mechanisms of polyamine toxicity are not fully understood.
- Extracellular and intracellular enzymes, including polyamine oxidase (PAO) and semicarbazide-sensitive amine oxidase (SSAO), may play a role in polyamine metabolism and toxicity.
Purpose of the Study:
- To investigate the mechanism of polyamine-induced injury in neonatal rat cardiac myocytes.
- To determine the role of extracellular and intracellular amine oxidases in mediating polyamine toxicity.
- To evaluate the protective effects of specific enzyme inhibitors against polyamine toxicity.
Main Methods:
- Neonatal rat cardiac myocytes were cultured and exposed to spermidine or spermine.
- Myocyte toxicity was assessed by measuring creatine kinase (CPK) release and cell viability.
- Experiments involved using different culture media (FBS, horse serum) and adding inhibitors of PAO and SSAO (aminoguanidine, MDL72,527, semicarbazide).
Main Results:
- Spermidine induced toxicity in myocytes at concentrations above 10 µM, evidenced by increased CPK release and decreased cell viability.
- Foetal calf serum (FBS) contained both PAO and SSAO activity, and inhibitors protected myocytes from spermidine toxicity.
- When myocytes were cultured in horse serum (high SSAO, low PAO), spermine toxicity was observed at higher concentrations, and inhibitors still provided protection, indicating both extracellular and intracellular enzyme involvement.
Conclusions:
- Extracellular amine oxidases and myocyte-associated PAO are significant contributors to polyamine toxicity in cardiac myocytes.
- Inhibiting these enzymes offers a protective strategy against polyamine-induced cardiac cell injury.
- Understanding these mechanisms is crucial for developing therapeutic interventions for conditions involving polyamine dysregulation.
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