Lipid signalling in cardiovascular pathophysiology

Metabolomics reveals the toxicological effects of polar compounds from frying palm oil

Polar compounds from frying oils have been found to be harmful to health. However, the mechanisms underlying this phenomenon have largely remained elusive. In this study, mass spectrometry-based metabolomics was used to investigate the toxicological effects of polar compounds. The serum and hepatic metabolites from polar compound-treated mice were measured using liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry. Multi-variate statistical analysis showed that a total of 36 serum metabolites and 18 hepatic metabolites were altered in the polar compound-treated mice as compared with that for normal diet-fed animals. These metabolic changes suggested novel alterations in lipid metabolism with the increase in phospholipids, fatty acids, and cholesterol and the decrease in choline, betaine and l-acetylcarnitine. The TCA cycle and carbohydrate, amino acid and purine metabolism were also impaired, with a significant elevation of d-glucose, d-maltose, β-mannobiose, branched chain amino acids, aromatic amino acids, and uric acid and a decline in succinate, serine, aspartate, arginine and ornithine. Pearson correlation analysis demonstrated the strong correlations between specific metabolic alterations and the redox index. Our overall findings reveal that polar compounds may progressively cause lipid deposition, impaired energy metabolism and oxidative stress, resulting in toxicological effects on the mammalian health.

FTY720 postconditions isolated perfused heart by a mechanism independent of sphingosine kinase 2 and different from S1P or ischemic postconditioning

Background

We investigated the hypothesis that postconditioning by FTY720 (FTY) in isolated perfused mouse hearts is independent of the sphingosine 1-phosphate (S1P) pathway.

Material/Methods

Ex vivo hearts were exposed to postconditioning (POST) by either ischemia or FTY720. Protection against ischemia/reperfusion (IR) injury was measured by recovery of left ventricular developed pressure (LVDP) and infarct size.

Results

FTY effectively postconditioned (POST) ex vivo hearts against ischemia/reperfusion (IR) injury as measured by recovery of LVDP and a low infarct size. FTY protection, unlike S1P but like sphingosine (Sph), was insensitive to inhibition of S1P G-Protein Coupled Receptors (GPCRs) or inhibition of PI3 kinase. Protection by FTY and Sph was however blocked by inhibitors of PKA and PKG. Thus, FTY follows the same cardioprotective pathway as Sph. This was further supported by studies of FTY POST in knockout (KO) mice lacking the SphK2 form of Sph kinase that is needed for phosphorylation of FTY to an S1P analog. In the absence of SphK2, FTY (and Sph) POST was still cardioprotective. This differed from the effect of SphK2 KO on protection by ischemic POST (IPOST). IPOST was not effective in KO hearts. To see if the GPCR signaling pathway to protection is normal in KO hearts, we looked at POST by GPCR agonists S1P and adenosine. Both provided effective protection even in KO hearts suggesting that the problem with IPOST in KO hearts is a low level of S1P available for release during IPOST. Thus, pharmacologic POST with FTY or Sph, like adenosine and S1P, is unaffected in the KO.

Conclusions

FTY720 administered in vivo might behave in a dual manner showing both S1P-like effects and sphingosine-like effects. It appears that the latter may have been overlooked and may be the more important in aging hearts.

Lysophospholipid receptor activation of RhoA and lipid signaling pathways

The lysophospholipids sphingosine 1-phosphate (S1P) and lysophosphatidic acid (LPA) signal through G-protein coupled receptors (GPCRs) which couple to multiple G-proteins and their effectors. These GPCRs are quite efficacious in coupling to the Gα(12/13) family of G-proteins, which stimulate guanine nucleotide exchange factors (GEFs) for RhoA. Activated RhoA subsequently regulates downstream enzymes that transduce signals which affect the actin cytoskeleton, gene expression, cell proliferation and cell survival. Remarkably many of the enzymes regulated downstream of RhoA either use phospholipids as substrates (e.g. phospholipase D, phospholipase C-epsilon, PTEN, PI3 kinase) or are regulated by phospholipid products (e.g. protein kinase D, Akt). Thus lysophospholipids signal from outside of the cell and control phospholipid signaling processes within the cell that they target. Here we review evidence suggesting an integrative role for RhoA in responding to lysophospholipids upregulated in the pathophysiological environment, and in transducing this signal to cellular responses through effects on phospholipid regulatory or phospholipid regulated enzymes. This article is part of a Special Issue entitled Advances in Lysophospholipid Research.

A sphingosine kinase form 2 knockout sensitizes mouse myocardium to ischemia/reoxygenation injury and diminishes responsiveness to ischemic preconditioning. Oxid Med Cell Longev. 2011;2011:961059. [PMID: 21904650 PMCID: PMC3166792 DOI: 10.1155/2011/961059]

Sphingosine kinase (SphK) exhibits two isoforms, SphK1 and SphK2. Both forms catalyze the synthesis of sphingosine 1-phosphate (S1P), a sphingolipid involved in ischemic preconditioning (IPC). Since the ratio of SphK1:SphK2 changes dramatically with aging, it is important to assess the role of SphK2 in IR injury and IPC. Langendorff mouse hearts were subjected to IR (30 min equilibration, 50 min global ischemia, and 40 min reperfusion). IPC consisted of 2 min of ischemia and 2 min of reperfusion for two cycles. At baseline, there were no differences in left ventricular developed pressure (LVDP), ± dP/dtmax, and heart rate between SphK2 null (KO) and wild-type (WT) hearts. In KO hearts, SphK2 activity was undetectable, and SphK1 activity was unchanged compared to WT. Total SphK activity was reduced by 53%. SphK2 KO hearts subjected to IR exhibited significantly more cardiac damage (37 ± 1% infarct size) compared with WT (28 ± 1% infarct size); postischemic recovery of LVDP was lower in KO hearts. IPC exerted cardioprotection in WT hearts. The protective effect of IPC against IR was diminished in KO hearts which had much higher infarction sizes (35 ± 2%) compared to the IPC/IR group in control hearts (12 ± 1%). Western analysis revealed that KO hearts had substantial levels of phosphorylated p38 which could predispose the heart to IR injury. Thus, deletion of the SphK2 gene sensitizes the myocardium to IR injury and diminishes the protective effect of IPC.