Necrosis and apoptosis have been initially identified as two exclusive pathways for cell death. In acute brain lesions, such as focal ischemia, this binary scheme is challenged by demonstrations of mixed morphological and biochemical characteristics of both apoptosis and necrosis in single cells. The resulting difficulty in defining the nature of cell death that is triggered by severe insults has dramatically impeded the development of therapeutic strategies. We show that in the early stages of cerebral infarction, neurons of the so-called "necrotic" core display a number of morphological, physiological, and biochemical features of early apoptosis, which include cytoplasmic and nuclear condensations and specific caspase activation cascades. Early activation cascades involve the death receptor pathway linked to caspase-8 and the caspase-1 pathway. They are not associated with alterations of mitochondrial respiration or activation of caspase-9. In contrast, pathways that are activated during the secondary expansion of the lesion in the penumbral area include caspase-9. In agreement with its downstream position in both mitochondria-dependent and -independent pathways, activation of caspase-3 displays a biphasic time course. We suggest that apoptosis is the first commitment to death after acute cerebral ischemia and that the final morphological features observed results from abortion of the process because of severe energy depletion in the core. In contrast, energy-dependent caspase activation cascades are observed in the penumbra in which apoptosis can fully develop because of residual blood supply.

The search for new molecules to fight Pseudomonas aeruginosa is of paramount importance. Carbon monoxide (CO) is known to act as an effective inhibitor of the respiratory chain in P. aeruginosa, but the practical use of this gas as an antibacterial molecule is hampered by its toxicity and difficulty to manipulate. Here, we show that a water-soluble CO releaser (CORM-3) possesses bactericidal properties against laboratory and antibiotic-resistant P. aeruginosa. CORM-3 reduced the bacterial count by 4 logs 180 min after in vitro treatment. CORM-3-treated bacteria had a lower O(2) consumption than vehicle-treated bacteria, and the decrease in O(2) consumption temporally preceded the bactericidal action of CORM-3. These results support the hypothesis that the antimicrobial effect of CORM-3 is mediated by an interaction of CO liberated by the carrier with the bacterial respiratory chain. The antibacterial effect occurred at concentrations of CORM-3 that are 50-fold lower than toxic concentrations for eukaryotic cells. CORM-3 treatment compared to vehicle treatment decreased bacterial counts in the spleen and increased survival in immunocompetent and immunosuppressed mice following P. aeruginosa bacteremia. Our results suggest that CORMs could form the basis for developing a new therapeutic strategy against P. aeruginosa-induced infection.

Background Cardiac overload, a major cause of heart failure, induces the expression of the heat shock protein H11 kinase/Hsp22 (Hsp22). Methods and Results To determine the specific function of Hsp22 in that context, a knockout (KO) mouse model of Hsp22 deletion was generated. Although comparable to wild type mice in basal conditions, KO mice exposed to pressure overload developed less hypertrophy, and showed ventricular dilation, impaired contractile function, increased myocyte length and accumulation of interstitial collagen, faster transition into heart failure and increased mortality. Microarrays revealed that hearts from KO mice failed to transactivate genes regulated by the transcription factor STAT3. Accordingly, nuclear STAT3 tyrosine phosphorylation was decreased in KO. Silencing and over-expression experiments in isolated neonatal rat cardiomyocytes showed that Hsp22 activates STAT3 via production of interleukin-6 by the transcription factor NF-κB. In addition to its transcriptional function, STAT3 also translocates to the mitochondria where it increases oxidative phosphorylation. Both mitochondrial STAT3 translocation and respiration were significantly decreased in KO mice as well. Conclusions Hsp22 represents a previously undescribed activator of both nuclear and mitochondrial functions of STAT3, and its deletion in a context of pressure overload in vivo accelerates the transition into heart failure and increases mortality.