Anoxic injury accelerates phosphatidylcholine degradation in cultured cardiac myocytes by phospholipase C

MALDI-Mass Spectrometric Imaging Revealing Hypoxia-Driven Lipids and Proteins in a Breast Tumor Model

Hypoxic areas are a common feature of rapidly growing malignant tumors and their metastases and are typically spatially heterogeneous. Hypoxia has a strong impact on tumor cell biology and contributes to tumor progression in multiple ways. To date, only a few molecular key players in tumor hypoxia, such as hypoxia-inducible factor-1 (HIF-1), have been discovered. The distribution of biomolecules is frequently heterogeneous in the tumor volume and may be driven by hypoxia and HIF-1α. Understanding the spatially heterogeneous hypoxic response of tumors is critical. Mass spectrometric imaging (MSI) provides a unique way of imaging biomolecular distributions in tissue sections with high spectral and spatial resolution. In this paper, breast tumor xenografts grown from MDA-MB-231-HRE-tdTomato cells, with a red fluorescent tdTomato protein construct under the control of a hypoxia response element (HRE)-containing promoter driven by HIF-1α, were used to detect the spatial distribution of hypoxic regions. We elucidated the 3D spatial relationship between hypoxic regions and the localization of lipids and proteins by using principal component analysis-linear discriminant analysis (PCA-LDA) on 3D rendered MSI volume data from MDA-MB-231-HRE-tdTomato breast tumor xenografts. In this study, we identified hypoxia-regulated proteins active in several distinct pathways such as glucose metabolism, regulation of actin cytoskeleton, protein folding, translation/ribosome, splicesome, the PI3K-Akt signaling pathway, hemoglobin chaperone, protein processing in endoplasmic reticulum, detoxification of reactive oxygen species, aurora B signaling/apoptotic execution phase, the RAS signaling pathway, the FAS signaling pathway/caspase cascade in apoptosis, and telomere stress induced senescence. In parallel, we also identified colocalization of hypoxic regions and various lipid species such as PC(16:0/18:0), PC(16:0/18:1), PC(16:0/18:2), PC(16:1/18:4), PC(18:0/18:1), and PC(18:1/18:1), among others. Our findings shed light on the biomolecular composition of hypoxic tumor regions, which may be responsible for a given tumor's resistance to radiation or chemotherapy.

Maintenance of ischemic β cell viability through delivery of lipids and ATP by targeted liposomes

Islet transplantation is a promising treatment for type 1 diabetes, but despite the successes, existing challenges prevent widespread application. Ischemia, occurring during pancreas preservation and isolation, as well as after islet transplantation, decreases islet viability and function. We hypothesized that the liposomal delivery of adenosine triphosphate (ATP) could prevent the loss of cell viability during an ischemic insult. In this work we use a model β cell line, INS-1 to probe the liposome/cell interactions and examined the ability of liposomes functionalized with the fibronectin-mimetic peptide PR_b to facilitate the delivery of ATP to ischemic β cells. We demonstrate that PR_b increases the binding and internalization of liposomes to the β cells. Unexpectedly, when comparing the ability of PR_b liposomes with and without ATP to protect INS-1 cells from ischemia we found that both formulations increased cell survival. By probing the functional activity of ischemic cells treated with PR_b functionalized liposomes with and without ATP we find that both lipids and ATP play a role in maintaining cell metabolic activity after an ischemic insult and preventing cell necrosis. This approach may be beneficial for preventing ischemia related damage to islet cells, especially in the organ preservation stage.

General toxicity of Pinellia ternata (Thunb.) Berit. in rat: a metabonomic method for profiling of serum metabolic changes

ETHNOPHARMACOLOGICAL RELEVANCE

BX is a traditional Chinese medicine (TCM) from the plant Pinellia ternata(Thunb.) Berit. It has been traditionally used to treat cough, vomiting, infection and inflammation. Despite of its potentially clinical utility, it also has many side effects and toxicity.

AIM OF THE STUDY

We propose here an ultra performance liquid chromatography coupled with quadrupole time-of-fight mass spectrometry (UPLC Q-TOF/MS) metabonomics approach to elucidate the toxicity in rats induced by orally administered BX in multiple organs including the kidney, liver, and heart.

MATERIALS AND METHODS

Serum samples were collected from Sprague-Dawley male rats exposed to BX (6g/kg/day, n=10) and healthy controls (n=10) at the 48 h, 144 h, 240 h, and 336 h postdose for LC/MS analyses. Through principal component analysis and orthogonal partial least squares-discriminant analysis of the integrated serum MS data, we distinguished the BX group from the healthy control group and identified the differential metabolites and pertinent altered biological pathways in response to the herbal toxin. The liver, kidney, heart were assessed using conventional histopathological examinations at the end point of the experiment. The serum samples at the 336 h postdose were assessed using biochemistry test.

RESULTS

Significant differences in the serum levels of phospholipids, amino acids, L-carnitine and L-acetylcarnitine were observed in BX-induced rats, indicating the perturbations of phospholipid metabolism, amino acid metabolism and carnitine metabolism in BX-induced rats.

CONCLUSIONS

In the paper, we used metabonomics approach to study the toxicity of BX for the first time. With blood biochemistry, histopathological examinations and metabonomics methods, we validated that oral administration of crude BX caused no obvious liver and kidney toxicity in SD rats. BX may possess certain cardio toxicity in SD rats. The metabolism changes suggested that metabonomic approach was a promising tool to study and diagnose TCM-induced toxicity.

Oxygen deprivation and reoxygenation augment prostacyclin synthesis in cultured ventricular myocytes

Prostacyclin production in cultured cardiomyocytes is not induced by cellular ATP depletion per se, suggesting that the mechanism of ischemic injury is more complex. In the present study we subjected cultured ventricular myocytes to 'simulated ischemia' followed by reoxygenation. A slight increase in 6-keto-PGF(1 alpha) (the stable metabolite of PGI(2)) was found during 'ischemia', which continued to increase markedly during reoxygenation. PGE(2) levels were pronouncedly enhanced during ischemia but decreased during reoxygenation, and TXB(2) levels remained undetectable throughout. These findings reflect a cardiomyocyte response to anoxic injury, suggesting that they act to protect against cardiac injury by producing the potent vasodilators PGI(2) and PGE(2) during ischemia and reoxygenation.

Indenoindole depresses lipofuscin formation in cultured neonatal rat myocardial cells

Lipofuscin accumulation in cultured rat myocardial cells is considered an index of intra-lysosomal oxidative reactions and was registered by autofluorescence measurements. Lipofuscinogenesis in secondary lysosomes is thought to be a consequence of Fenton reactions, and is much enhanced by oxidative stress obtained by culturing the cells in an atmosphere containing 40% oxygen. The influence of the synthetic antioxidant indenoindole (DHII), as compared to control cells, was a dose-responsive depression of lipofuscinogenesis to a degree of 19% and 17% with 20 microM DHII and to 25% and 23% with 40 microM DHII after 7 and 14 days in culture, respectively. This demonstrates a significant quenching of oxidative stress and suggests the therapeutic value of DHII and related antioxidants in protecting against oxygen radical-related diseases. It is also suggested that neonatal cardiac myocytes in culture are a suitable model system for the evaluation of oxygen radical-induced myocardial damage.

High oligomycin concentrations augment 6-keto-PGF1 alpha production in ventricular cardiomyocytes

Incubation of cultured ventricular cardiomyocytes with high oligomycin concentrations (100 micrograms/ml), either alone or combined with 2-deoxyglucose (20 mM), led to the rapid depletion of cellular ATP. Inositol (poly)phosphate production decreased, and 6-keto PGF1 alpha production was increased. In cells depleted of ATP, either by low oligomycin concentrations or by sodium azide, 6-keto PGF1 alpha was not appreciably increased. There was a 25% rise in the release of fatty acids from the sn-2 position in glycerophospholipids. We suggest that oligomycin at high concentrations causes the release of free arachidonic acid from phospholipids either by non-PIP2-specific PLC and DG lipase or by phospholipase D, phosphatidic acid phosphatase and DG lipase. The effect is unrelated to decreased cellular ATP content.

Phospholipid loss in dying platelets

The death of a cell results in a large amount of membrane lipid, predominantly phospholipids and cholesterol, that must be eliminated. In this study, we have examined what happens to phospholipids in dying rat platelets. Rat platelets were incubated for up to three days following their activation with thrombin. Platelet death occurred during the first day of incubation. This was indicated by a complete loss of platelet lactate dehydrogenase into the incubation medium. The platelets progressively lost over one-half of their phospholipid content during the three days of incubation. Cholesterol and sphingomyelin (the phospholipid with the highest affinity for cholesterol) were not lost during the same period. Our findings suggest that significant degradation of cellular non-sphingomyelin phospholipid can be triggered by cell death. The preservation of sphingomyelin in dying platelets, may be an adaptive response to maintain cholesterol in a solubilized state within dying cells.