[Cell death in inflammatory heart muscle diseases--apoptosis or necrosis?]

Myocardial apoptosis and SIDS

Apoptosis mediates cardiac damage in severe forms of myocarditis. In fatal myocarditis, large amounts of cardiomyocytes show apoptotic DNA fragmentation, while in human controls, few apoptotic cardiomyocytes are found. In the present study the frequency of apoptosis in 88 SIDS cases (category 1b according to the San Diego Classification) and 15 control cases was investigated. In every case myocardial samples from 8 standard locations were collected. Detection of apoptotic cardiomyocytes was performed by TUNEL method. Furthermore the myocardial tissue was stained with HE and immunohistochemical methods (LCA, CD68, CD45-R0). More than 90% of the slides did not contain apoptotic cardiomyocytes at all. The detection rate of apoptotic cardiomyocytes was almost equal in control group (26.7%) and SIDS group (23.86%). A quantification of apoptotic cardiomyocytes per mm(2) revealed no significant difference between both groups either. Altogether there is no evidence for a higher rate of apoptosis in SIDS.

Lung epithelial cell death induced by oil-dispersant mixtures

The dispersants used in oil spill disasters are claimed to be safe, but increased solubility of high-molecular-weight components in crude oil is of public health concern. The water-accommodated fractions (WAF) of crude oil mixed with dispersants may become airborne and cause lung epithelial damage when inhaled. This study was designed to examine the cell death and related death pathways of lung epithelial cells in response to WAF. Cultured A549 cells were treated for 2 or 24h with different concentrations of WAF. The WAF was prepared by mixing each of the dispersants (Corexit EC9527A, Corexit EC9500A and Corexit EC9580A) with crude oil for extraction with PBS. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide MTT assay, lactate dehydrogenase assay, morphology and cleaved caspase 9 protein, and microtubule-associated protein 1 light chain 3 were all used to measure cell viability, necrosis, apoptosis and autophagy quantitation, respectively. Results showed that the WAF of oil-dispersant mixtures caused cell death in the lung epithelial cells, in a dose-dependent manner, with the major cellular pathways of necrosis and apoptosis involved. Autophagy also occurred in cells exposed to WAF mixtures at lower concentrations before any detectable cell death, indicating greater sensitivity to WAF exposure. The three types of cell behavior, namely necrosis, apoptosis and autophagy, may play different roles in oil spill-related respiratory disorders.

Cyclical mechanical stretch-induced apoptosis in myocytes from young rats but necrosis in myocytes from old rats

Mechanical load as stimulus for apoptosis and necrosis could be responsible for the loss of cardiomyocytes. Ventricular myocytes from young (3 mo) and old (14-24 mo) rats underwent cyclical mechanical stretch (CMS; 5% elongation, 1 Hz) for 24 h. Spontaneous apoptosis was in myocytes from young rats 0.33 +/- 0.12% and from old rats 1.05 +/- 0.35% [Tdt-mediated dUTP nick-end labeling (TUNEL) assay]; associated with a decrease of Bcl-2. CMS increased the apoptosis to 0.58 +/- 0.18% in myocytes from young rats. Western blot analysis showed that CMS reduced Bcl-2 and increased p53 (young rats). Bax was not changed by CMS. These were confirmed by cytochrome c release (31 +/- 13%) and by the enrichment of cytosolic nucleosomes (11 +/- 8%). CMS did not influence the apoptosis in myocytes from old rats (TUNEL assay, Bcl-2, Bax, or p53). CMS did not cause necrosis in myocytes from young rats. CMS increased the number of necrotic cells by showing the cell membrane rupture in myocytes from old rats (50 +/- 13% 5-hexadecanoylaminofluorescein-positive and 38 +/- 6% propidium iodide-positive cells) as well as by measuring the lactate dehydrogenase release. The results suggest that CMS-induced apoptosis in myocytes of young rats but necrosis in myocytes from old rats, which could be attributed to more stress sensitivity of cells from old rats.

Apoptosis in myocarditis and dilated cardiomyopathy: does enterovirus genome persistence protect from apoptosis? An endomyocardial biopsy study

The purpose of this study was to examine the role of apoptosis in myocarditis and dilated cardiomyopathy. Apoptosis is an active energy-consuming mechanism of cell death in several cardiac diseases in different quality and quantity.

METHODS

Endomyocardial biopsies from 81 patients with active (1) and chronic myocarditis (10), dilated cardiomyopathy with inflammation (DCMi; 10) and without inflammation (DCM; 20), with borderline myocarditis and positive PCR for cytomegalovirus-DNA (6), adenovirus-DNA, or enterovirus-RNA (7), and controls (17) were analysed. Apoptosis was detected by using the TUNEL method. The highest rate of apoptotic cardiocytes was found in active and chronic myocarditis. One patient with severe active myocarditis demonstrated 6.15% of apoptotic cardiocytes. Mean percentage of apoptotic cardiocytes in chronic myocarditis was significantly increased (0.61+/-1.25%) when compared to controls (0.01+/-0.04%, P<.05). Particularly, patients with cytomegalovirus-DNA persistence in borderline myocarditis had an elevated rate of apoptosis (0.34+/-0.68%, P<.05). Increased rates of apoptosis were found in borderline myocarditis with adenovirus-DNA persistence (0.20+/-0.57%) and in DCM (0.06+/-0.15%). Only a nonsignificant increase of apoptotic cardiocytes was found in DCMi (0.03+/-0.08%). No apoptosis was found in patients with enteroviral genome persistence in borderline myocarditis.

CONCLUSIONS

Apoptosis of cardiac cells is increased in myocarditis and dilated cardiomyopathy, being highest in severe active myocarditis. Apoptosis thus contributes to cell death in active myocarditis and may play a role not to be neglected in dilated cardiomyopathy. Enteroviruses seem to have anti-apoptotic effects, because no apoptosis at all was found in the myocardium.