Effects of oxidative stress on the cardiac myocyte proteome: modifications to peroxiredoxins and small heat shock proteins.

Endogenous oxidative stress is a likely cause of cardiac myocyte death in vivo. We examined the early (0-2 h) changes in the proteome of isolated cardiac myocytes from neonatal rats exposed to H2O2 (0.1 mM), focussing on proteins with apparent molecular masses of between 20 and 30 kDa. Proteins were separated by two-dimensional gel electrophoresis (2DGE), located by silver-staining and identified by mass spectrometry. Incorporation of [35S]methionine or 32Pi was also studied. For selected proteins, transcript abundance was examined by reverse transcriptase-polymerase chain reaction. Of the 38 protein spots in the region, 23 were identified. Two families showed changes in 2DGE migration or abundance with H2O2 treatment: the peroxiredoxins and two small heat shock protein (Hsp) family members: heat shock 27 kDa protein 1 (Hsp25) and alphaB-crystallin. Peroxiredoxins shifted to lower pI values and this was probably attributable to 'over-oxidation' of active site Cys-residues. Hsp25 also shifted to lower pI values but this was attributable to phosphorylation. alphaB-crystallin migration was unchanged but its abundance decreased. Transcripts encoding peroxiredoxins 2 and 5 increased significantly. In addition, 10 further proteins were identified. For two (glutathione S-transferase pi, translationally-controlled tumour protein), we could not find any previous references indicating their occurrence in cardiac myocytes. We conclude that exposure of cardiac myocytes to oxidative stress causes post-translational modification in two protein families involved in cytoprotection. These changes may be potentially useful diagnostically. In the short term, oxidative stress causes few detectable changes in global protein abundance as assessed by silver-staining.

The ketogenic diet; fatty acids, fatty acid-activated receptors and neurological disorders.

This review outlines the molecular sensors that reprogram cellular metabolism in response to the ketogenic diet (KD). Special emphasis is placed on the fasting-, fatty acid- and drug-activated transcription factor, peroxisome proliferator-activated receptor alpha (PPARalpha). The KD causes a switch to ketogenesis that is coordinated with an array of changes in cellular lipid, amino acid, carbohydrate and inflammatory pathways. The role of both liver and brain PPARalpha in mediating such changes will be examined, with special reference to the anti-epileptic effects not only of the KD but a range of synthetic anti-epileptic drugs such as valproate. Finally, the implications of the KD and activated brain PPARalpha will be discussed in the context of their potential involvement in a range of disorders of neuro-degeneration and neuro-inflammation.

The ketogenic diet upregulates expression of the gene encoding the key ketogenic enzyme mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase in rat brain.

The ketogenic diet is a clinically and experimentally effective anti-epileptic treatment whose molecular mechanism(s) of action remain to be elucidated. As a first step in defining its effects on regulation of fatty acid oxidation and ketogenesis at the genetic level, we have administered to rats: (1) a calorie-restricted ketogenic diet (KCR); (2) a calorie-restricted normal diet (NCR); or (3) a normal diet ad libitum (NAL). We have used RNase protection to co-assay diet-induced changes in abundance of the mRNA encoding the critical enzyme of ketogenesis from acetyl-CoA namely mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (mHS) in liver and brain, together with mRNAs encoding three other key enzymes of fatty acid oxidation. We demonstrate that NCR-fed rats exhibit a significant 2-fold increase in liver mHS mRNA compared to NAL-fed rats, and that KCR-fed rats exhibit a significant 2-fold increase in both liver and brain mHS mRNA compared to NAL-fed rats. Our results demonstrate, for the first time, the effect of a ketogenic diet on gene expression in brain, and suggest possible anti-epileptic mechanisms for future investigation.

The peroxisome proliferator-activated receptor alpha-selective activator ciprofibrate upregulates expression of genes encoding fatty acid oxidation and ketogenesis enzymes in rat brain.

Activated peroxisome proliferator activated receptor alpha (PPAR alpha) protects against the cellular inflammatory response, and is central to fatty acid-mediated upregulation of the gene encoding the key ketogenic enzyme mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (mHS). We have previously demonstrated both PPAR alpha and mHS expression in brain, implying that brain-targeted PPAR alpha activators may likewise up-regulate mHS expression in brain. Thus, to attempt pharmacological activation of brain PPAR alpha in vivo, we have administered to rats two drugs with previously defined actions in rat brain, namely the PPAR alpha-selective activator ciprofibrate and the pan-PPAR activator valproate. Using the sensitive and discriminatory RNase protection co-assay, we demonstrate that both ciprofibrate and valproate induce mHS expression in liver, the archetypal PPAR alpha-expressing organ. Furthermore, ciprofibrate potently increases mHS mRNA abundance in rat brain, together with lesser increases in two other PPAR alpha-regulated mRNAs. Thus we demonstrate, for the first time, up-regulation of expression of PPAR alpha-dependent genes including mHS in brain, with implications in the increased elimination of neuro-inflammatory lipids and concomitant increased production of neuro-protective ketone bodies.