Survival response to increased ceramide involves metabolic adaptation through novel regulators of glycolysis and lipolysis.

The sphingolipid ceramide elicits several stress responses, however, organisms survive despite increased ceramide but how they do so is poorly understood. We demonstrate here that the AKT/FOXO pathway regulates survival in increased ceramide environment by metabolic adaptation involving changes in glycolysis and lipolysis through novel downstream targets. We show that ceramide kinase mutants accumulate ceramide and this leads to reduction in energy levels due to compromised oxidative phosphorylation. Mutants show increased activation of Akt and a consequent decrease in FOXO levels. These changes lead to enhanced glycolysis by upregulating the activity of phosphoglyceromutase, enolase, pyruvate kinase, and lactate dehydrogenase to provide energy. A second major consequence of AKT/FOXO reprogramming in the mutants is the increased mobilization of lipid from the gut through novel lipase targets, CG8093 and CG6277 for energy contribution. Ubiquitous reduction of these targets by knockdown experiments results in semi or total lethality of the mutants, demonstrating the importance of activating them. The efficiency of these adaptive mechanisms decreases with age and leads to reduction in adult life span of the mutants. In particular, mutants develop cardiac dysfunction with age, likely reflecting the high energy requirement of a well-functioning heart. The lipases also regulate physiological triacylglycerol homeostasis and are important for energy metabolism since midgut specific reduction of them in wild type flies results in increased sensitivity to starvation and accumulation of triglycerides leading to cardiac defects. The central findings of increased AKT activation, decreased FOXO level and activation of phosphoglyceromutase and pyruvate kinase are also observed in mice heterozygous for ceramide transfer protein suggesting a conserved role of this pathway in mammals. These data reveal novel glycolytic and non-autonomous lipolytic pathways in response to increased ceramide for sustenance of high energy demanding organ functions like the heart.

Marrow transplantation for acute nonlymphocytic leukemia following therapy for Hodgkin's disease.

Seven patients with acute nonlymphocytic leukemia (ANL) following therapy for Hodgkin's disease (HD) were treated with cyclophosphamide (Cy) alone or combined with 10.00 to 15.75 Gy total body irradiation (TBI) and marrow transplantation. Five patients were transplanted without an attempt at prior remission induction, one patient following failure of remission induction and one patient in first remission following successful induction. Four patients died of multiorgan failure, 15 to 70 days after transplant. Three patients died of progressive or recurrent leukemia 56, 120, and 280 days after transplant. These results illustrate the difficulty of treating patients for secondary leukemia with marrow transplantation and suggest that transplantation in the preleukemic phase should be studied.

Dose effects of alfentanil in human analgesia.

Alfentanil, a rapidly acting opioid, was given in subanesthetic doses to 10 subjects in a laboratory setting. Analgesia was assessed from the subjects' responses to painful dental stimulation. A subjective pain report (PR) and brain evoked potential (EP) amplitude were obtained repeatedly before and after injection on each of 4 testing days, on which the following intravenous doses were administered: 0 (saline solution), 5, 10, and 15 micrograms/kg. Significant dose effects were observed for EP amplitude during but not beyond the distributional t1/2 of the drug, but significant effects on the PR extended beyond this time point. Mean volume of distribution, total body clearance, and distribution t1/2 did not differ significantly across the doses of alfentanil. Strong correlations between each effect measure and plasma drug concentration were observed at all doses and were significant at P less than 0.01. The EP scores tracked the distribution of alfentanil very closely, but the correlation between EP amplitude and plasma alfentanil concentration was lower during the elimination phase. In contrast, the PR effects closely tracked the elimination of alfentanil but not its distribution. These findings suggest that EP amplitude and the PR represent two different central effects in opioid analgesia.

Hypnosis effect on carbon dioxide chemosensitivity.

Hypnosis is an induced state of heightened suggestibility during which certain physiologic variables can be altered. To investigate if carbon dioxide (CO2) chemosensitivity could be blunted during this suggestible state, we measured hypercapnic ventilatory response (HCVR, delta VE/delta PaCO2), oxygen consumption (VO2), breathing pattern (VT and f), inspiratory flow rate (VT/Ti), and inspiratory timing (Ti/Ttot) in 20 healthy subjects. Mouth occlusion pressures (P0.1) were measured in the last nine subjects. Resting oxygen consumption and minute ventilation were measured during awake and hypnotic control states. The HCVR was measured spontaneously and with the suggestion to maintain normal ventilation during both awake and hypnotic conditions. It was found that without a change in metabolism, ventilatory responses to CO2 could be blunted both voluntarily, and to a greater degree, with hypnotic suggestion. These findings may have important implications in clinical settings in which patients suffer from marked dyspnea secondary to increased ventilatory chemosensitivity.

Acute acquired demyelinating polyneuropathy with respiratory failure following high-dose systemic cytosine arabinoside and marrow transplantation.

Reversible ventilatory failure secondary to acute, acquired polyneuropathy developed in a patient undergoing marrow transplantation for chronic myelogenous leukemia. The onset of the neuropathy was temporally related to the conditioning regimen of high-dose, systemic cytosine arabinoside (Ara-C). The clinical features and course were consistent with the Guillain-Barré syndrome and no other conditions causally associated with the syndrome were noted. Although central nervous system toxicity is a well recognized complication of high-dose Ara-C, peripheral neuropathy is infrequently reported. Possible mechanisms of peripheral polyneuropathy in this marrow transplant recipient are discussed.

Ceramide transfer protein deficiency compromises organelle function and leads to senescence in primary cells.

Ceramide transfer protein (CERT) transfers ceramide from the endoplasmic reticulum (ER) to the Golgi complex. Its deficiency in mouse leads to embryonic death at E11.5. CERT deficient embryos die from cardiac failure due to defective organogenesis, but not due to ceramide induced apoptotic or necrotic cell death. In the current study we examined the effect of CERT deficiency in a primary cell line, namely, mouse embryonic fibroblasts (MEFs). We show that in MEFs, unlike in mutant embryos, lack of CERT does not lead to increased ceramide but causes an accumulation of hexosylceramides. Nevertheless, the defects due to defective sphingolipid metabolism that ensue, when ceramide fails to be trafficked from ER to the Golgi complex, compromise the viability of the cell. Therefore, MEFs display an incipient ER stress. While we observe that ceramide trafficking from ER to the Golgi complex is compromised, the forward transport of VSVG-GFP protein is unhindered from ER to Golgi complex to the plasma membrane. However, retrograde trafficking of the plasma membrane-associated cholera toxin B to the Golgi complex is reduced. The dysregulated sphingolipid metabolism also leads to increased mitochondrial hexosylceramide. The mitochondrial functions are also compromised in mutant MEFs since they have reduced ATP levels, have increased reactive oxygen species, and show increased glutathione reductase activity. Live-cell imaging shows that the mutant mitochondria exhibit reduced fission and fusion events. The mitochondrial dysfunction leads to an increased mitophagy in the CERT mutant MEFs. The compromised organelle function compromise cell viability and results in premature senescence of these MEFs.