Expression of apoptosis-related proteins in experimental coxsackievirus myocarditis.
OBJECTIVE
The extent to which apoptosis contributes to myocyte cell loss during acute carditic viral infection is unknown. To assess whether apoptosis occurs in acute viral myocarditis, and how it is modulated, we studied mice inoculated with coxsackievirus B3 (CVB3).


METHODS
Five CD1 and C3H.HeJ (C3H) mice/group were sacrificed as saline vehicle-injected controls, and at 1, 2, and 3 weeks post-inoculation (p.i.) with 5 x 10(6) pfu CVB3. Histopathological status and terminal transferase-mediated dUTP-biotin nick end-labeling (TUNEL) assays quantified inflammation, necrosis and apoptosis in myocardium. Apoptosis-related protein immunoreactivity defined presence and location of Bax, Fas, Fas Ligand (FasL), Bcl-2, interleukin-1 beta converting enzyme (ICE), inducible nitric oxide synthase (iNOS) and the proto-oncogene p53.


RESULTS
Both strains exhibited significant histopathology at all time points. Saline-injected control animals showed no signs of inflammation and no significant difference in apoptosis-related protein immunoreactivity was observed between strains. Myocardial TUNEL-positive cells were exceedingly rare though apoptosis was present in thymic medulla and spleen follicles. Pro-apoptotic proteins Bax, Fas, and FasL were present in all groups though no clear correlation with histopathology was apparent. By contrast, the anti-apoptotic protein Bcl-2 showed mild immunoreactivity in controls, which increased following infection and correlated well with histopathological scores in both strains. Myocardial iNOS immunoreactivity displayed a similar though weaker staining pattern to Bcl-2 over the 3 week study period in both strains. Neither ICE nor p53 immunoreactivity could be demonstrated in myocardium.


CONCLUSIONS
Thus, despite marked inflammatory activity, myocyte apoptosis is rare in acute CVB3 myocarditis in CD1 and C3H.HeJ mice.
Division of Cardiology, University of Texas Health Science Center at San Antonio, USA.
J T
JT
Colston
B
B
Chandrasekar
G L
GL
Freeman
D000818:Animals; D017209:Apoptosis; D003384:Coxsackievirus Infections / Q000378:metabolism*; D029822:Enterovirus B, Human; D053222:Fas Ligand Protein; D007150:Immunohistochemistry; D008297:Male; D008562:Membrane Glycoproteins / Q000032:analysis; D051379:Mice; D008809:Mice, Inbred C3H; D008815:Mice, Inbred Strains; D009205:Myocarditis / Q000378:metabolism* / Q000473:pathology / Q000821:virology; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D009336:Necrosis; D019001:Nitric Oxide Synthase / Q000032:analysis; D052247:Nitric Oxide Synthase Type II; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000032:analysis*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis; D013154:Spleen / Q000473:pathology; D013950:Thymus Gland / Q000473:pathology; D051028:bcl-2-Associated X Protein; D019014:fas Receptor / Q000032:analysis
C494827:Bax protein, mouse; C505661:FASLG protein, human; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; C000715470:MAS1 protein, human; D008562:Membrane Glycoproteins; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D019014:fas Receptor; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse