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[Molecular mechanism underlying calcium handling in diastolic heart failure]
1Department of Senior Health Care, Qilu Hospital of Shandong University, Jinan 250012, China.
Insights
Diastolic heart failure (DHF) in rabbits shows reduced L-type calcium channel and SR Ca(2+)-ATPase expression. These molecular changes in calcium handling may contribute to the development of DHF.
Area of Science:
- Cardiology
- Molecular Biology
- Physiology
Background:
- Diastolic heart failure (DHF) is characterized by impaired cardiac relaxation and filling.
- Calcium handling is crucial for cardiomyocyte contraction and relaxation.
- The molecular mechanisms of calcium dysregulation in DHF require further elucidation.
Purpose of the Study:
- To investigate the molecular basis of altered calcium handling in a rabbit model of DHF.
- To examine the mRNA and protein expression of key calcium-handling proteins, including L-type calcium channel, sarcoplasmic reticulum (SR) Ca(2+)-ATPase, phospholamban, ryanodine receptor, and calsequestrin.
Main Methods:
- Diastolic heart failure (DHF) was induced in rabbits via abdominal aortic coarctation.
- mRNA levels of calcium-handling genes were quantified using RT-PCR.
- Protein expression of SR Ca(2+)-ATPase and phospholamban was assessed by Western blot analysis.
Main Results:
- Myocardial calcium content was elevated in DHF rabbits compared to sham-operated controls.
- SR Ca(2+)-ATPase activity and protein levels were significantly reduced in DHF rabbits.
- mRNA levels of L-type calcium channel and SR Ca(2+)-ATPase were significantly decreased in DHF.
- Downregulation of SR Ca(2+)-ATPase and L-type calcium channel mRNA correlated with impaired left ventricular relaxation and elevated end-diastolic pressure.
Conclusions:
- Downregulation of L-type calcium channel and SR Ca(2+)-ATPase occurs at both mRNA and protein levels in DHF.
- These molecular alterations in calcium handling proteins are implicated as contributing factors to the pathophysiology of diastolic heart failure.
Objective:
To elucidate the molecular mechanism underlying calcium handling in diastolic heart failure (DHF) from mRNA level and protein expression, including L-type calcium channel, sarcoplasmic reticulum (SR) Ca(2+)-ATPase, phospholamban, ryanodine receptor, calsequestrin.
Methods:
DHF was produced in rabbits by abdominal aortic coarctation. The mRNA amounts of these calcium-handling genes were measured by RT-PCR, while the protein levels of SR Ca(2+)-ATPase and phospholamban were analyzed by Western blot analysis.
Results:
The content of calcium was significantly increased in myocardium of rabbits with DHF than in the myocardium of sham-operated rabbits. The SR Ca(2+)-ATPase activity of DHF rabbits was significantly reduced compared with that in sham-operated rabbits (21.1 micromol.mg(-1).h(-1) +/- 5.7 micromol.mg(-1).h(-1) vs 10.5 micromol.mg(-1).h(-1) +/- 2.8 micromol.mg(-1).h(-1), P < 0.01). RT-PCR analyses showed that the steady-state level of mRNA encoding the L-type calcium channel and SR Ca2+-ATPase was decreased significantly in rabbits with DHF compared with that in the sham-operated rabbits (micromol.mg(-1).h(-1)): 0.75 +/- 0.11 vs 1.20 +/- 0.33; 0.76 +/- 0.12 vs 1.24 +/- 0.38, P < 0.05). The SR Ca(2+)-ATPase mRNA level correlated negatively well with left ventricular relaxation time constant and left ventricular end-diastolic pressure (r = -0.81, -0.64, respectively, P < 0.05 approximately 0.01); the mRNA level of L-type calcium channel correlated negatively with left ventricular end-diastolic pressure (r = -0.74, P < 0.05). The mRNA level of ryanodine receptor correlated negatively with the left ventricular relaxation time constant too (r = -0.71, P < 0.05). Protein level of SR Ca(2+)-ATPase was significantly lower in rabbits with DHF than in the sham-operated rabbits (0.76 +/- 0.6 vs 1.02 +/- 0.09, P < 0.05), whereas the protein level of phospholamban was unchanged.
Conclusion:
The L-type calcium channel and SR Ca(2+)-ATPase were down regulated in DHF. These changes may be a contributory factor for DHF.