Abstract P155: HSF-1 Deletion Induces MDR1 Gene in the Heart and Protects from Doxorubicin-Induced Cardiotoxicity

Heat shock factor 1 (HSF-1) has been found to be a frontline responder of different stresses in eukaryotic cells. Deletion of HSF-1 has been reported to develop defects in mice. In the present work we report that deletion of HSF-1 induced multidrug resistance 1 (MDR1) gene and P-glycoprotein (P-gp) expression. Both RT-PCR and western blotting, confirmed the higher level of MDR1 gene expression and P-gp protein in HSF-1 knock out mouse hearts. P-gp is well known ATP binding cassette, which extrudes intracellular drugs upon binding ATP. Hence the phenotype of the P-gp pump in HSF-1 −/− mice was studied in the form of Doxorubicin (Dox) extrusion in the heart. Cardiomyocytes isolated from HSF-1 −/− and HSF-1 +/− mice retained very less intracellular Dox, compared to wild type counterparts. Similarly, both HSF-1 +/− and HSF-1 −/− mice were less susceptible for Dox-induced cardiotoxicity, as seen from reduced cardiac dysfunction in these group against Dox (as confirmed by cardiac MRI and echocardiography). Further confirmatory studies revealed that deletion of HSF-1 enhances NF-B, which subsequently induces MDR1 gene. These results reveal that inactivation of HSF-1 in the heart will be a potential approach to prevent Dox-induced cardiotoxicity.

Role of DDAH-1 in lipid peroxidation product-mediated inhibition of endothelial NO generation

Altered nitric oxide (NO) biosynthesis is thought to play a role in the initiation and progression of atherosclerosis and may contribute to increased risk seen in other cardiovascular diseases. It is hypothesized that altered NO bioavailability may result from an increase in endogenous NO synthase (NOS) inhibitors, asymmetric dimethly araginine (ADMA), and N(G)-monomethyl arginine, which are normally metabolized by dimethyarginine dimethylamine hydrolase (DDAH). Lipid hydroperoxides and their degradation products are generated during inflammation and oxidative stress and have been implicated in the pathogenesis of cardiovascular disorders. Here, we show that the lipid hydroperoxide degradation product 4-hydroxy-2-nonenal (4-HNE) causes a dose-dependent decrease in NO generation from bovine aortic endothelial cells, accompanied by a decrease in DDAH enzyme activity. The inhibitory effects of 4-HNE (50 microM) on endothelial NO production were partially reversed with L-Arg supplementation (1 mM). Overexpression of human DDAH-1 along with antioxidant supplementation completely restored endothelial NO production following exposure to 4-HNE (50 microM). These results demonstrate a critical role for the endogenous methylarginines in the pathogenesis of endothelial dysfunction. Because lipid hydroperoxides and their degradation products are known to be involved in atherosclerosis, modulation of DDAH and methylarginines may serve as a novel therapeutic target in the treatment of cardiovascular disorders associated with oxidative stress.

Homozygosity mapping identifies an additional locus for Wolfram syndrome on chromosome 4q

Wolfram syndrome, which is sometimes referred to as "DIDMOAD" (diabetes insipidus, diabetes mellitus, optic atrophy, and deafness), is an autosomal recessive neurodegenerative disorder for which only insulin-dependent diabetes mellitus and optic atrophy are necessary to make the diagnosis. Researchers have mapped Wolfram syndrome to chromosome 4p16.1, and, recently, a gene encoding a putative transmembrane protein has been cloned and mutations have been identified in patients. To pursue the possibility of locus heterogeneity, 16 patients from four different families were recruited. These patients, who have the Wolfram syndrome phenotype, also have additional features that have not previously been reported. There is an absence of diabetes insipidus in all affected family members. In addition, several patients have profound upper gastrointestinal ulceration and bleeding. With the use of three microsatellite markers (D4S432, D4S3023, and D4S2366) reported to be linked to the chromosome 4p16.1 locus, we significantly excluded linkage in three of the four families. The two affected individuals in one family showed homozygosity for all three markers from the region of linkage on chromosome 4p16.1. For the other three families, genetic heterogeneity for Wolfram syndrome was verified by demonstration of linkage to chromosome 4q22-24. In conclusion, we report the unique clinical findings and linkage-analysis results of 16 patients with Wolfram syndrome and provide further evidence for the genetic heterogeneity of this disorder. We also provide data on a new locus that plays a role in the etiology of insulin-dependent diabetes mellitus.