Decreased myocardial expression of dystrophin and titin mRNA and protein in dilated cardiomyopathy: possibly an adverse effect of TNF-alpha.
OBJECTIVE
While the molecular basis of dilated cardiomyopathy (DCM) remains uncertain, concrete evidence is emerging that sarcomeric and cytoskeleton gene expression of myocardium isolated from failing versus non-failing patients differ dramatically. The central aim to this work was to find out the possible role of dystrophin and titin along with the TNF-alpha in the pathogenesis of cardiomyopathy.


METHODS
mRNA levels and protein expression of a cytoskeletal protein, dystrophin and a sarcomeric protein, titin in endomyocardial biopsies of DCM patients were examined using RT-PCR and immunohistochemistry, respectively. Further, we examined the effect of TNF-alpha on myocardial expression of titin and dystrophin in vitro in rat cardiac myoblast cell line (H9c2).


RESULTS
We observed significantly decreased mRNA and protein levels of dystrophin and titin in endomyocardial biopsy of DCM patients as compared to control group. The decreased levels of these proteins correlated with the severity of the disease. Plasma levels of both TNF-alpha and its soluble receptors TNFR1 and TNFR2 were found to be significantly higher in patients as compared to control group. Treatment of H9c2 cells with TNF-alpha resulted in a dose- and time-dependent decrease in mRNA levels of dystrophin and titin. Pretreatment of these cells with MG132, an inhibitor of nuclear factor kappa B (NF-kappaB) pathway, abolished TNF-alpha-induced reduction in mRNA levels of dystrophin and titin.


CONCLUSIONS
Our results suggest that reduced expression of dystrophin and titin is associated with the pathophysiology of DCM, and TNF-alpha may modulate the expression of these proteins via NF-kappaB pathway.
Ahmad
Shamim
S
Department of Cardiology, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
Rai
Taranjit Singh
TS
Khullar
Madhu
M
Bahl
Ajay
A
Saikia
Uma Nahar
UN
Thungapathra
M
M
Kumar
Rohit Manoj
RM
Mahajan
Rajiv
R
Talwar
Kewal K
KK
D000818:Animals; D002311:Cardiomyopathy, Dilated / Q000235:genetics / Q000378:metabolism*; D016022:Case-Control Studies; D002460:Cell Line; D064211:Connectin; D004305:Dose-Response Relationship, Drug; D016189:Dystrophin / Q000032:analysis* / Q000235:genetics; D006801:Humans; D009124:Muscle Proteins / Q000032:analysis* / Q000235:genetics; D009206:Myocardium / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D011494:Protein Kinases / Q000032:analysis* / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D064211:Connectin; D016189:Dystrophin; D009124:Muscle Proteins; D016328:NF-kappa B; D012333:RNA, Messenger; C577285:TTN protein, human; D014409:Tumor Necrosis Factor-alpha; D011494:Protein Kinases