Marked elevation of myocardial trace elements in idiopathic dilated cardiomyopathy compared with secondary cardiac dysfunction

Molecular characterization of homo- and heterodimeric mercury(II)-bis-thiolates of some biologically relevant thiols by electrospray ionization and triple quadrupole tandem mass spectrometry

A series of 24 compounds of general formula R(1)S-Hg-SR(2), R(1) and R(2) being biologically relevant thiol-containing amino acids and peptides (cysteine, homo-cysteine, penicillamine, N-acetyl-cysteine, N-acetyl-penicillamine, cysteinyl-glycine, gamma-glutamyl-cysteine and glutathione) were prepared by direct reaction of mercury(II) ions and thiols in water at millimolar concentration. The obtained products were characterized by electrospray ionization and triple quadrupole tandem mass spectrometry. The source spectra of equimolar mixtures of two different thiols reacting with a stoichiometric amount of mercury(II) show the peak clusters of the three theoretically expected bis-thiolato-mercury(II) complexes with relative intensities close to the theoretically expected 1:2:1 ratio, thus pointing at lack of substantial discrimination between the different thiols, the only observed exception being homo-cysteine, which is less reactive than cysteine and penicillamine. The fragment spectra are structure-specific for the different ligands bound to the metal ion and allow a stand-alone discrimination of some constitutional isomer pairs. Among the peculiar fragmentation processes observed, loss of neutral ammonia from protonated symmetrical and unsymmetrical mercury(II)-bis-thiolates with free, protonizable amino groups leads to the formation of thiirane-carboxylic bound species; this process is suppressed when the protonated amino group is in the gamma-position with respect to the sulfur atom, as in the case of compounds with homo-cysteine. This unusual behavior may hint at unforeseen mechanisms for the interaction of mercury(II) with biological structures, ultimately leading to cellular and organ toxicity. Compounds with N-acetylated amino acids show distinctive fragment ions to which the connectivity of a protonated 2-methyl-oxazoline-5-carboxylic acid may be proposed on the basis of the loss of water and of the elements of formic acid. Finally, the adducts of mercury(II) with glutathione and gamma-glutamyl-cysteine feature a distinctive decomposition channel by loss of a pyroglutamic unit, much the same as protonated glutathione, glutathione disulfide, the S-glutathionyl adducts of biologically occurring electrophiles and other (pseudo)-peptides with gamma-glutamyl bonds.

Stress-induced activation of GATA-4 in cardiac muscle cells

GATA-4 regulates gene transcription in the heart. This study examined whether GATA-4 is influenced by stress-induced signaling events. Treatment of HL-1 cardiac muscle cells with mercury results in the induction of apoptosis that is blocked by overexpression of catalase. Similar to daunorubicin (DNR), mercury causes downregulation of GATA-4 mRNA expression. However, mercury is less effective in inducing apoptosis compared to DNR. Analyses of GATA-4 protein expression and activity reveal that mercury initially enhances the GATA-4 DNA-binding activity, before subsequent downregulation of GATA-4 expression. The mercury-induced GATA-4 activation is associated with a phosphorylation of GATA-4, which appears to occur via the MEK/ERK pathway. The level of phosphorylated GATA-4 is more slowly decreased by mercury or actinomycin D, compared to unphosphorylated GATA-4, suggesting that phosphorylated GATA-4 is more resistant to cellular degradation. Consistent with a previous finding that GATA-4 phosphorylation induces cell survival, mercury decreases cell death induced by DNR. These results suggest that cardiac muscle cells respond to mercury stress by eliciting MEK/ERK signaling to form phosphorylated GATA-4 that is more resistant to cellular degradation and induce cell survival.

Environmental exposure to mercury and its toxicopathologic implications for public health

Mercury is a toxic and hazardous metal that occurs naturally in the earth's crust. Natural phenomena such as erosion and volcanic eruptions, and anthropogenic activities like metal smelting and industrial production and use may lead to substantial contamination of the environment with mercury. Through consumption of mercury in food, the populations of many areas, particularly in the developing world, have been confronted with catastrophic outbreaks of mercury-induced diseases and mortality. Countries such as Japan, Iraq, Ghana, the Seychelles, and the Faroe Islands have faced such epidemics, which have unraveled the insidious and debilitating nature of mercury poisoning. Its creeping neurotoxicity is highly devastating, particularly in the central and peripheral nervous systems of children. Central nervous system defects and erethism as well as arrythmias, cardiomyopathies, and kidney damage have been associated with mercury exposure. Necrotizing bronchitis and pneumonitis arising from inhalation of mercury vapor can result in respiratory failure. Mercury is also considered a potent immunostimulant and -suppressant, depending on exposure dose and individual susceptibility, producing a number of pathologic sequelae including lymphoproliferation, hypergammaglobulinemia, and total systemic hyper- and hyporeactivities. In this review we discuss the sources of mercury and the potential for human exposure; its biogeochemical cycling in the environment; its systemic, immunotoxic, genotoxic/carcinogenic, and teratogenic health effects; and the dietary influences on its toxicity; as well as the important considerations in risk assessment and management of mercury poisoning.

Surviving heart failure: Robert L. Frye lecture

Heart failure is increasing in both incidence and prevalence and is associated with a high mortality. In patients with heart failure, coronary artery disease is the cause for about two thirds. Pathophysiologic changes have been linked to altered muscle function and hemodynamics, elevated neurohormones, and, more recently, cellular mechanisms, including apoptosis. Standard triple therapy for symptomatic heart failure consists of an angiotensin-converting enzyme (ACE) inhibitor, digoxin, and a diuretic. In patients with severe heart failure, spironolactone should be added. In large clinical trials, ACE inhibitors, spironolactone, and beta-blockers have reduced mortality. Other drugs may be helpful in the treatment of heart failure. Amiodarone is the antiarrhythmic drug of choice in patients with symptomatic arrhythmias and also has a role in the treatment of dilated cardiomyopathy. Angiotensin II receptor blockers are being compared with ACE inhibitors and appear promising. Newer agents being tested include antagonists to endothelin and tumor necrosis factor. Overall, it is clear that polypharmacy is the standard of care for patients with heart failure. A future challenge will be to prevent heart failure from occurring.