Cell damage following carbon monoxide releasing molecule exposure: implications for therapeutic applications.

The cytoprotective properties of carbon monoxide (CO) gas and CO-releasing molecules (CORMs) are well established. Despite promising pre-clinical results, little attention has been paid to the toxicological profile of CORMs. The effects of CORM-2 and its CO-depleted molecule (iCORM-2) (20-400 µM) were compared in primary rat cardiomyocytes and two cell lines [human embryonic kidney (HeK) and Madine-Darby canine kidney Cells (MDCK)]. Cells were assessed for cell viability, apoptosis, necrosis, cytology, mitochondrial energetics, oxidative stress and cell cycle arrest markers. In separate experiments, the anti-apoptotic effects of CORM-2 and i-CORM-2 treatment were compared against CO gas treatment in HeK and MDCK lines. H(2)O(2) -induced cellular damage, measured by lactate dehydrogenase (LDH) release from primary cardiomyocytes, was reduced by 20 µM CORM-2; LDH activity, however, was directly inhibited by 400 µM CORM-2. Both CORM-2/iCORM-2 and CO gas decreased cisplatin-induced caspase-3 activity in MDCK and HeK cells suggesting an anti-apoptotic effect. Conversely, both CORM-2 and iCORM-2 induced significant cellular toxicity in the form of decreased cell viability, abnormal cell cytology, increased apoptosis and necrosis, cell cycle arrest and reduced mitochondrial enzyme activity. Comparison of these markers after CO gas administration to MDCK cells found significantly less cellular toxicity than in 100 µM CORM-2/iCORM-2-treated cells. CO gas did not have an adverse effect on mitochondrial energetics and integrity. Release of CO by low concentrations of intact CORM-2 molecules provides cytoprotective effects. These results show, however, that the ruthenium-based CORM by-product, iCORM-2, is cytotoxic and suggest that the accumulation of iCORM-2 would seriously limit any clinical application of the ruthenium-based CORMs.

Tin protoporphyrin provides protection following cerebral hypoxia-ischemia: involvement of alternative pathways.

The contribution of heme oxygenase (HO)-linked pathways to neurodegeneration following cerebral hypoxia-ischemia (HI) remains unclear. We investigated whether HO modulators affected HI-induced brain damage and explored potential mechanisms involved. HI was induced in 26-day-old male Wistar rats by left common carotid artery ligation, followed by exposure to a humidified atmosphere of 8% oxygen for 1 hr. Tin protoporphyrin (SnPP; an HO inhibitor), ferriprotoporphyrin (FePP; an HO inducer), or saline was administered intraperitoneally once daily from 1 day prior to HI until sacrifice at 3 days post-HI. SnPP reduced (P < 0.05) infarct volume compared with saline-treated animals, but FePP had no effect on brain injury. SnPP did not significantly inhibit HO activity at 3 days post-HI, but SnPP increased (P < 0.001) total nitric oxide synthase (NOS) activity compared with HI + saline. Both inducible NOS and cyclooxygenase activities were attenuated (P < 0.05) by SnPP, whereas mitochondrial complex I and V activities were augmented (P < 0.05) by SnPP. SnPP had no effect on NMDA receptor currents. Overall, like other HO inhibitors, SnPP produced many nonselective effects, such as attenuation of inflammatory enzymes and increased mitochondrial respiratory function, which were associated with a protective response 3 days post-HI.

Domoic acid impairment of cardiac energetics.

Excitatory mediated neuronal injury has been shown to involve a complex cascade of events. However, the associated cardiac damage reported in humans and marine animals following exposure to excitotoxins has not been well characterized. We hypothesized that the excitotoxin domoic acid can traverse cardiac cell membranes and elicit a deleterious effect on cardiac mitochondrial energetics. Domoic acid (0.05-0.25 microM; 10 min) treatment of isolated rat cardiac mitochondria produced a marked decrease of both mitochondrial flavin adenine dinucleotide (FAD)- and nicotinamide adenine linked respiratory control indices (p < 0.001). Enzymatic assays of the mitochondrial electron transport chain (complexes I-V) and the mitochondrial matrix marker enzyme citrate synthase, showed marked concentration-dependent impairment in activity and integrity following exposure to domoic acid (p < 0.01). Similar mitochondrial effects were seen following exposure to the glutamic acid analog, kainic acid (0.5-2 microM). Domoic acid (0.05-10 microM; 40 min) was shown by competitive enzyme-linked immunosorbent assay to traverse the cellular membrane of H9c2 rat cardiac myoblasts. Exposure of intact H9c2 cells to domoic acid (10 microM; 24 h) impaired complex II-III activity but did not compromise cellular viability as assessed using cell quantification or lactate dehydrogenase leakage assays. Assessment of reactive oxygen species (superoxide and hydrogen peroxide) production in both isolated cardiac mitochondria and H9c2 cardiomyocytes failed to show any significant differences following exposure to domoic acid (0.05-5 microM). This is the first study to demonstrate a direct effect of domoic acid on cardiac mitochondrial energetics. However, the absence of substantial damage to intact cardiomyocytes raises questions regarding direct toxicological effects on cardiac energetics or viability under conditions of natural domoic acid exposure.

Expanding retrograde saphenous vein graft aneurysm treated with endovascular coiling.

Saphenous vein graft aneurysm is a potentially fatal complication of coronary artery bypass grafting and usually requires surgery. This report describes endovascular coiling of a saphenous vein graft aneurysm that developed after redo coronary artery bypass grafting. The aneurysm occurred in a proximally occluded saphenous vein graft after revascularization of the same target vessel. The procedure required a retrograde approach through a patent left internal mammary and left anterior descending artery to reach and successfully thrombose the aneurysm.