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Activation of Both the Calpain and Ubiquitin-Proteasome Systems Contributes to Septic Cardiomyopathy through Dystrophin Loss/Disruption and mTOR Inhibition

View Article: PubMed Central - PubMed

ABSTRACT

Cardiac dysfunction caused by the impairment of myocardial contractility has been recognized as an important factor contributing to the high mortality in sepsis. Calpain activation in the heart takes place in response to increased intracellular calcium influx resulting in proteolysis of structural and contractile proteins with subsequent myocardial dysfunction. The purpose of the present study was to test the hypothesis that increased levels of calpain in the septic heart leads to disruption of structural and contractile proteins and that administration of calpain inhibitor-1 (N-acetyl-leucinyl-leucinyl-norleucinal (ALLN)) after sepsis induced by cecal ligation and puncture prevents cardiac protein degradation. We also tested the hypothesis that calpain plays a role in the modulation of protein synthesis/degradation through the activation of proteasome-dependent proteolysis and inhibition of the mTOR pathway. Severe sepsis significantly increased heart calpain-1 levels and promoted ubiquitin and Pa28β over-expression with a reduction in the mTOR levels. In addition, sepsis reduced the expression of structural proteins dystrophin and β-dystroglycan as well as the contractile proteins actin and myosin. ALLN administration prevented sepsis-induced increases in calpain and ubiquitin levels in the heart, which resulted in decreased of structural and contractile proteins degradation and basal mTOR expression levels were re-established. Our results support the concept that increased calpain concentrations may be part of an important mechanism of sepsis-induced cardiac muscle proteolysis.

No MeSH data available.


Related in: MedlinePlus

(A) Western blot analysis of cardiac mTOR protein levels after CLP. Cardiac mTOR protein levels in the SHAM, SSI, SHAM+ALLN and SSI+ALLN groups were measured 24 h after surgery and were expressed in arbitrary units (AUs). GAPDH was used to determine equivalent loading conditions. (B) Analysis of cardiac dystrophin mRNA expression. Dystrophin mRNA expression was measured 24 h after the CLP procedure and expressed in arbitrary units (AUs). GAPDH gene expression was used as the internal control for gene expression normalization. The results (n = 6 per group) are representative of three different experiments.
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pone.0166839.g005: (A) Western blot analysis of cardiac mTOR protein levels after CLP. Cardiac mTOR protein levels in the SHAM, SSI, SHAM+ALLN and SSI+ALLN groups were measured 24 h after surgery and were expressed in arbitrary units (AUs). GAPDH was used to determine equivalent loading conditions. (B) Analysis of cardiac dystrophin mRNA expression. Dystrophin mRNA expression was measured 24 h after the CLP procedure and expressed in arbitrary units (AUs). GAPDH gene expression was used as the internal control for gene expression normalization. The results (n = 6 per group) are representative of three different experiments.

Mentions: We then verified mTOR protein levels and dystrophin gene expression. The cardiac levels of mTOR protein (Fig 5A) were reduced by approximately 40% in the SSI mice compared with the SHAM group (0.42 ± 0.05 vs. 0.69 ± 0.06). In contrast, SSI mice treated with ALLN (SSI+ALLN) significantly recovered the expression of mTOR protein levels compared with the SHAM or SHAM+ALLN hearts.


Activation of Both the Calpain and Ubiquitin-Proteasome Systems Contributes to Septic Cardiomyopathy through Dystrophin Loss/Disruption and mTOR Inhibition
(A) Western blot analysis of cardiac mTOR protein levels after CLP. Cardiac mTOR protein levels in the SHAM, SSI, SHAM+ALLN and SSI+ALLN groups were measured 24 h after surgery and were expressed in arbitrary units (AUs). GAPDH was used to determine equivalent loading conditions. (B) Analysis of cardiac dystrophin mRNA expression. Dystrophin mRNA expression was measured 24 h after the CLP procedure and expressed in arbitrary units (AUs). GAPDH gene expression was used as the internal control for gene expression normalization. The results (n = 6 per group) are representative of three different experiments.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5120800&req=5

pone.0166839.g005: (A) Western blot analysis of cardiac mTOR protein levels after CLP. Cardiac mTOR protein levels in the SHAM, SSI, SHAM+ALLN and SSI+ALLN groups were measured 24 h after surgery and were expressed in arbitrary units (AUs). GAPDH was used to determine equivalent loading conditions. (B) Analysis of cardiac dystrophin mRNA expression. Dystrophin mRNA expression was measured 24 h after the CLP procedure and expressed in arbitrary units (AUs). GAPDH gene expression was used as the internal control for gene expression normalization. The results (n = 6 per group) are representative of three different experiments.
Mentions: We then verified mTOR protein levels and dystrophin gene expression. The cardiac levels of mTOR protein (Fig 5A) were reduced by approximately 40% in the SSI mice compared with the SHAM group (0.42 ± 0.05 vs. 0.69 ± 0.06). In contrast, SSI mice treated with ALLN (SSI+ALLN) significantly recovered the expression of mTOR protein levels compared with the SHAM or SHAM+ALLN hearts.

View Article: PubMed Central - PubMed

ABSTRACT

Cardiac dysfunction caused by the impairment of myocardial contractility has been recognized as an important factor contributing to the high mortality in sepsis. Calpain activation in the heart takes place in response to increased intracellular calcium influx resulting in proteolysis of structural and contractile proteins with subsequent myocardial dysfunction. The purpose of the present study was to test the hypothesis that increased levels of calpain in the septic heart leads to disruption of structural and contractile proteins and that administration of calpain inhibitor-1 (N-acetyl-leucinyl-leucinyl-norleucinal (ALLN)) after sepsis induced by cecal ligation and puncture prevents cardiac protein degradation. We also tested the hypothesis that calpain plays a role in the modulation of protein synthesis/degradation through the activation of proteasome-dependent proteolysis and inhibition of the mTOR pathway. Severe sepsis significantly increased heart calpain-1 levels and promoted ubiquitin and Pa28β over-expression with a reduction in the mTOR levels. In addition, sepsis reduced the expression of structural proteins dystrophin and β-dystroglycan as well as the contractile proteins actin and myosin. ALLN administration prevented sepsis-induced increases in calpain and ubiquitin levels in the heart, which resulted in decreased of structural and contractile proteins degradation and basal mTOR expression levels were re-established. Our results support the concept that increased calpain concentrations may be part of an important mechanism of sepsis-induced cardiac muscle proteolysis.

No MeSH data available.


Related in: MedlinePlus