Cardiac oxidative stress in a mouse model of neutral lipid storage disease.
Bottom Line: Systemic deletion of the gene encoding adipose triglyceride lipase (ATGL), the enzyme that catalyzes the rate-limiting step of triglyceride lipolysis, results in a phenotype characterized by severe steatotic cardiac dysfunction.Investigating the effect of oxidative and inflammatory stress on nitric oxide/cGMP signal transduction we observed a ~2.5-fold upregulation of soluble guanylate cyclase activity and a ~2-fold increase in cardiac tetrahydrobiopterin levels.Upregulation of soluble guanylate cyclase and cardiac tetrahydrobiopterin might be regarded as counterregulatory mechanisms in cardiac ATGL deficiency.
Affiliation: Department of Pharmacology and Toxicology, Institute of Pharmaceutical Sciences, University of Graz, Universitätsplatz 2, 8010 Graz, Austria. Electronic address: email@example.com.Show MeSH
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Mentions: The potential consequences of oxidative stress for cardiac NO/cGMP signaling in ATGL deficiency were studied by measuring various parameters characteristic for different steps of the signaling cascade. As shown in Fig. 4A, cardiac NOS activity determined as conversion of l-arginine to l-citrulline was not affected by any genetic manipulation. Ca2 +-independent activity was not detectable (data not shown), arguing against significant iNOS expression in any experimental group. Protein expression of eNOS and nNOS was not affected (data not shown). However, activity of sGC, the major downstream target of NOS-derived NO, was significantly increased in ATGL(−/−) hearts (Fig. 4B). Basal cGMP formation measured in the presence of Mn2 + was increased from 0.023 ± 0.002 to 0.077 ± 0.011 nmol × mg− 1 × min− 1 (Fig. 4B; inset). Upon stimulation with the NO donor DEA/NO or co-stimulation with the NO-sensitizing drug YC-1 , the rates of cGMP formation were enhanced ~ 2.6- and ~ 2.4-fold, respectively. Thus, sGC activity was significantly increased at different activation states of the enzyme. Cardiac-specific overexpression of ATGL resulted in sGC activities identical to that of WT animals (Fig. 4B). Quantification of cardiac cGMP by radioimmunoassay showed that, despite the significantly higher sGC activity in ATGL(−/−) hearts, cGMP levels were virtually identical in all experimental groups (Fig. 4C). Similarly, cGMP-dependent phosphorylation of vasodilator-stimulated phosphoprotein (VASP) at serine 239, which represents a reliable biochemical marker of the NO/cGMP pathway , was not affected (Fig. 4D).
Affiliation: Department of Pharmacology and Toxicology, Institute of Pharmaceutical Sciences, University of Graz, Universitätsplatz 2, 8010 Graz, Austria. Electronic address: firstname.lastname@example.org.