Myocardial stunning: association with altered gene expression

Acute and chronic effects of alcohol exposure on skeletal muscle c-myc, p53, and Bcl-2 mRNA expression

Skeletal muscle atrophy is a common feature in alcoholism that affects up to two-thirds of alcohol misusers, and women appear to be particularly susceptible. There is also some evidence to suggest that malnutrition exacerbates the effects of alcohol on muscle. However, the mechanisms responsible for the myopathy remain elusive, and some studies suggest that acetaldehyde, rather than alcohol, is the principal pathogenic perturbant. Previous reports on rats dosed acutely with ethanol (<24 h) have suggested that increased proto-oncogene expression (i.e., c-myc) may be a causative process, possibly via activating preapoptotic or transcriptional pathways. We hypothesized that 1) increases in c-myc mRNA levels also occur in muscle exposed chronically to alcohol, 2) muscle of female rats is more sensitive than that from male rats, 3) raising acetaldehyde will also increase c-myc, 4) prior starvation will cause further increases in c-myc mRNA expression in response to ethanol, and 5) other genes involved in apoptosis (i.e., p53 and Bcl-2) would also be affected by alcohol. To test this, we measured c-myc mRNA levels in skeletal muscle of rats dosed either chronically (6-7 wk; ethanol as 35% of total dietary energy) or acutely (2.5 h; ethanol as 75 mmol/kg body wt ip) with ethanol. All experiments were carried out in male Wistar rats (approximately 0.1-0.15 kg body wt) except the study that examined gender susceptibility in male and female rats. At the end of the studies, rats were killed, and c-myc, p53, and Bcl-2 mRNA was analyzed in skeletal muscle by RT-PCR with an endogenous internal standard, GAPDH. The results showed that 1) in male rats fed ethanol chronically, there were no increases in c-myc mRNA; 2) increases, however, occurred in c-myc mRNA in muscle from female rats fed ethanol chronically; 3) raising endogenous acetaldehyde with cyanamide increased c-myc mRNA in acute studies; 4) starvation per se increased c-myc mRNA levels and at 1 day potentiated the acute effects of ethanol, indicative of a sensitization response; 5) the only effect seen with p53 mRNA levels was a decrease in muscle of rats starved for 1 day compared with fed rats, and there was no statistically significant effect on Bcl-2 mRNA in any of the experimental conditions. The increases in c-myc may well represent a preapoptotic effect, or even a nonspecific cellular stress response to alcohol and/or acetaldehyde. These data are important in our understanding of a common muscle pathology induced by alcohol.

Reversible myocardial dysfunction in critically ill, noncardiac patients: a review

OBJECTIVE

To review reversible myocardial dysfunction affecting critically ill patients without cardiac pathology.

DATA SOURCES

The bibliography for the study was compiled through a search of different databases for the period 1966-2001. References cited in the selected articles also were reviewed.

STUDY SELECTION

The selection criteria included all articles published on reversible myocardial dysfunction in critically ill patients.

CONCLUSIONS

Reversible myocardial dysfunction may develop in a situation of critical pathology, but the etiology of reversible myocardial dysfunction is not fully understood. This dysfunction may be accompanied by increases in enzyme concentrations and electrocardiographic changes. Reversible myocardial dysfunction probably is underdiagnosed, although its presence is associated with a worsening of the prognosis and with more specific therapeutic options. Further studies are necessary to define its true incidence and clinical implications.

Apoptosis in myocardial ischemia, infarction, and altered myocardial states

The work ahead necessary to develop and refine clinically useful antiapoptotic therapy in ischemic-reperfusion injury is daunting. There are many unanswered questions. What is the best method of detecting apoptosis in the cardiac myocytes? What will be the most practical method to deliver this therapy to the cardiac myocyte? Will antiapoptotic agents act selectively on affected myocytes to provide clinical efficacy? Will antiapoptotic agents be effective, or will they be limited by dose heterogeneity? If antiapoptotic is proven to have long lasting efficacy, should it be used for all patients with myocardial infarction or confined only to patients with left ventricular dysfunction. Will antiapoptotic therapy be so effective that it replaces ACE inhibitors and betablockers, or will it always be used as an adjunct to an ACE inhibitor or a betablocker? These questions lay the foundation for investigation for the next decade.

Alteration of gene expression for glycolytic enzymes in aerobic and ischemic myocardium

The purpose of this report was to describe mRNA abundance for the glycolytic enzymes glyceraldehyde-3-phosphate dehydrogenase (GAPDH), pyruvate kinase, and pyruvate dehydrogenase in ischemic and adjacent aerobic myocardium. Mechanical, metabolic, and mRNA data were acquired in a pig model of regulated coronary flow using extracorporeal perfusion. Trials of coronary hypoperfusion included sustained and intermittent exposures of acute ischemia with or without reperfusion. These were compared with a chronic 4-day model of partial coronary stenosis. In ischemic tissues, levels of mRNA, normalized by mRNA for beta-actin, were increased over control values for GAPDH (range 2.7- to 4.6-fold), pyruvate kinase (2.9-fold), and pyruvate dehydrogenase (2.1-fold). It is of interest that increases in mRNA levels over control values were also observed in adjacent aerobic heart muscle from intervention hearts, including 3.6- to 4.5-fold elevations in message for GAPDH and a 2.1-fold increase in signal for pyruvate dehydrogenase. Augmentation in mRNA abundance occurred in as short a time as 40 min of ischemia and was maintained for as long as 4 days in partial coronary stenosis. Whether the former time was of an interval sufficient to affect protein production is problematic, but the latter time was ample to influence enzyme concentration, which may in turn have regulated glycolysis in this condition.