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Effect of glutamine on heat-shock-induced mRNA and stress proteins
1Department of Pediatrics, Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine 19104.
Abstract:
Our aim was to delineate the effect of glutamine on the level of heat shock-inducible mRNA and synthesis of stress protein(s) in cultured kidney cells. Experiments were carried out using opossum kidney (OK) cells. The induction of HSP70 mRNA as well as the synthesis of 72,73 kDa stress proteins was evaluated in cell monolayers exposed to 45 degrees C for 15 minutes followed by a recovery period at 37 degrees C for 3 hours. Incubations were performed in Krebs buffer supplemented with 0, 2, 5, or 10 mM glutamine. A separate series of experiments was performed in the presence of glutamine metabolites, such as NH4Cl, glutamate, or aspartate. Glutamine without preincubation at 37 degrees C remarkably increased the steady-state level of HSP70 mRNA as well as the production of 72,73 kDa stress proteins in a dose-dependent manner. The production of stress protein(s) in the presence of glutamine was associated with decreased percent LDH efflux, suggesting cytoprotective action of glutamine in cultured kidney cells. However, when OK cells were preincubated for 1 hour at 37 degrees C with 10 mM glutamine, there was an approximately fourfold decline in level of HSP70 mRNA compared with experiments in the presence of 10 mM glutamine without preincubation. In addition, metabolites of glutamine, i.e., ammonia and glutamate decreased the level of heat-inducible HSP70 mRNA. Furthermore, aspartate or NH4Cl had little effect on LDH release compared with heat shock experiments, without addition of amino acids. These observations suggest that metabolites of glutamine may blunt the steady-state level of glutamate or HSP70 mRNA. The decreased level of HSP70 mRNA in the presence of NH4Cl may explain the role of ammonia in renal injury and brain toxicity, as well as glutamate excitotoxicity.
Insights
Glutamine boosts heat shock protein production in kidney cells, offering protection. However, glutamine metabolites like ammonia may reduce these protective effects and contribute to cellular damage.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Heat shock proteins (HSPs) are crucial for cellular protection against stress.
- Glutamine is an important amino acid with potential roles in cellular metabolism and stress response.
- Kidney cells are susceptible to various forms of cellular stress.
Purpose of the Study:
- To investigate the impact of glutamine on heat shock-inducible mRNA and stress protein synthesis in cultured kidney cells.
- To explore the cytoprotective effects of glutamine and its metabolites under heat stress conditions.
Main Methods:
- Opossum kidney (OK) cells were exposed to heat shock (45°C for 15 minutes).
- Cells were incubated with varying concentrations of glutamine (0-10 mM) or its metabolites (NH4Cl, glutamate, aspartate).
- Levels of HSP70 mRNA and 72,73 kDa stress proteins were quantified; lactate dehydrogenase (LDH) efflux was measured.
Main Results:
- Glutamine significantly increased HSP70 mRNA and stress protein production in a dose-dependent manner without preincubation.
- Glutamine administration reduced LDH efflux, indicating a cytoprotective effect.
- Preincubation with glutamine or the presence of glutamine metabolites (ammonia, glutamate) decreased HSP70 mRNA levels.
Conclusions:
- Glutamine itself exhibits cytoprotective properties in kidney cells by upregulating heat shock response.
- Glutamine metabolites, particularly ammonia and glutamate, can attenuate the heat shock response, potentially contributing to cellular injury.
- These findings shed light on the complex role of glutamine and its metabolites in cellular stress and toxicity, with implications for conditions like renal injury and neurotoxicity.