title: Altered expression of the natriuretic peptide system in genetically modified heme oxygenase-1 mice treated with high dietary salt.
abstract: Heme oxygenase-1 (HO-1) has been well established as a cytoprotective molecule, and has been shown to exert cardioprotective effects in both hypertension and cardiac hypertrophy. However, the precise mechanism of the cardioprotective effect of HO-1 has yet to be fully elucidated. With the natriuretic peptide system (NPS) as a key player in cardiovascular homeostasis and tissue dynamics, we sought to examine the effect of high dietary salt treatment in genetic models of HO-1 expression, and assessed the expression of the NPS in the left ventricle (LV), to determine if the effects of altered HO-1 expression may be due to modified levels of the NPS. Age-matched 12-week old male HO-1 knockout (HO-1(-/-)) and HO-1 cardiomyocyte-specific transgenic overexpressing (HO-1(Tg)) mice were treated with either normal salt (NS; 0.8%) or high salt (HS; 8.0%) chow for 5 weeks. LV mRNA expression was determined using quantitative real-time PCR. ANP peptide level was measured in the LV and plasma using radioimmunoassay, and LV cyclic 3'-5' guanosine monophosphate level was measured using an enzyme immunoassay kit. HO-1(-/-) fed HS diet had significantly higher left ventricle-to-body weight ratio (LV/BW) compared to HO-1(+/+) mice fed NS diet. HO-1(-/-) mice had significantly reduced expression of the NPS compared to controls, and these mice did not exhibit a salt-induced increase in ANP expression. HS treatment had no noticeable effect on LV/BW in HO-1(Tg) mice compared to controls. HO-1(Tg) mice had significantly higher ANP and BNP expression compared to controls. There were no differences in LV cGMP levels among all genotypes and dietary treatments. HO-1 ablation resulted in significantly lower mRNA expression of the NPS, whereas HO-1 overexpression resulted in higher mRNA expression of the NPS. Both were substantiated by peptide levels as measured by RIA. These data indicate that the detrimental effect of reduced HO-1 expression and the cardioprotective effect of increased HO-1 expression may be due, in part, to altered expression of the NPS.
authors.affiliation: Department of Anatomy and Cell Biology, Queen's University, Room 850 Botterell Hall, Kingston, ON, K7L 3N6, Canada.
authors.forename: David W J
authors.initials: DW
authors.lastname: Armstrong
authors.forename: M Yat
authors.initials: MY
authors.lastname: Tse
authors.forename: Luis G
authors.initials: LG
authors.lastname: Melo
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Pang
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D017931:DNA Primers; D005260:Female; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D020097:Natriuretic Peptide, Brain / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D011863:Radioimmunoassay; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage*
chemical_list: D017931:DNA Primers; D012333:RNA, Messenger; D017673:Sodium Chloride, Dietary; D020097:Natriuretic Peptide, Brain; D009320:Atrial Natriuretic Factor; D006419:Heme Oxygenase (Decyclizing)