Effect of peroxisome proliferator-activated receptor-alpha siRNA on hypertension and renal injury in the rat following nitric oxide withdrawal and high salt diet.
BACKGROUND
Peroxisome proliferator-activated receptor (PPAR)-alpha has been implicated in the regulation of normal and pathological cellular functions, but the effect of specific gene silencing on PPARalpha-mediated function is not fully defined.


OBJECTIVE
This study evaluated the role of PPARalpha in hypertensive renal injury induced by nitric oxide withdrawal and high salt (4% NaCl) diet [high salt/N(omega)-nitro-L-arginine (L-NNA)].


METHODS
Three PPARalpha siRNA clones, siRNA(790-811), siRNA(974-995) or siRNA(1410-1431), directed at the DNA or ligand binding domain of PPARalpha mRNA or scrambled siRNA was cloned into plasmid expression vector and was injected (10 microg intravenously) in hypertensive rats. Twenty-four-hour readings of blood pressure and heart rate were taken in conscious rats using radiotelemetry. Kidney injury was evaluated by determining N-acetyl-beta-glucosaminidase excretion, expression of kidney injury molecule-1 and histopathology. PPARalpha mRNA and protein expression were also determined.


RESULTS
High salt/L-NNA increased PPARalpha mRNA expression three-fold, and this was abolished in rats treated with PPARalpha siRNA(790-811), siRNA(974-995) or siRNA(1410-1431). High salt/L-NNA also increased blood pressure but reduced heart rate without affecting pulse pressure. However, blood pressure was further increased in rats treated with PPARalpha siRNA(790-811) (37 +/- 3%, P < 0.05). High salt/L-NNA also increased N-acetyl-beta-glucosaminidase excretion and expression of kidney injury molecule-1. However, PPARalpha siRNA(790-811) did not affect N-acetyl-beta-glucosaminidase excretion but reduced kidney injury molecule-1 expression. Histopathology of kidney tissues in high salt/L-NNA-treated rats revealed global, fibrinoid and tubular interstitial necrosis that was blunted by PPARalpha siRNA(790-811).


CONCLUSIONS
These data suggest that increased PPARalpha expression is a protective mechanism in hypertensive renal injury induced by nitric oxide withdrawal/high salt diet and that siRNAs targeting the DNA-binding domain of PPARalpha gene elicited differential effects on hypertension and kidney injury.
Newaz
Mohammad
M
Center for Cardiovascular Diseases, College of Pharmacy and Health Sciences, Texas Southern University, USA.
Ranganna
Katsuri
K
Truong
Luan D
LD
Oyekan
Adebayo
A
D000818:Animals; D001483:Base Sequence; D001794:Blood Pressure; D006973:Hypertension / Q000473:pathology / Q000503:physiopathology*; D007668:Kidney / Q000473:pathology / Q000503:physiopathology*; D008969:Molecular Sequence Data; D009569:Nitric Oxide / Q000378:metabolism*; D047493:PPAR alpha / Q000235:genetics*; D010957:Plasmids; D016133:Polymerase Chain Reaction; D034741:RNA, Small Interfering / Q000235:genetics*; D051381:Rats; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage*
D047493:PPAR alpha; D034741:RNA, Small Interfering; D017673:Sodium Chloride, Dietary; D009569:Nitric Oxide