Chronic NF-{kappa}B blockade reduces cytosolic and mitochondrial oxidative stress and attenuates renal injury and hypertension in SHR

Abstract

Nuclear factor-kappaB (NF-kappaB) plays an important role in hypertensive renal injury; however, its roles in perpetuating mitochondrial oxidative stress and renal dysfunction remain unclear. In this study, we assessed the effects of chronic NF-kappaB blockade with pyrrolidine dithiocarbamate (PDTC) on renal dysfunction and mitochondrial redox status in spontaneously hypertensive rats (SHR). PDTC (150 mg.kg body wt(-1).day(-1)) or vehicle was administered orally to 8-wk-old SHR and their respective controls for 15 wk. Systolic blood pressure (SBP) was measured by tail-cuff plethysmography at the start of and at every third week throughout the study. After 15 wk of treatment, anesthetized rats underwent acute renal experiments to determine renal blood flow and glomerular filtration rate using PAH and inulin clearance techniques, respectively. Following renal experiments, kidneys were excised from killed rats, and cortical mitochondria were isolated for reactive oxygen species (ROS) measurements using electron paramagnetic resonance. Tissue mRNA and protein levels of NF-kappaB and oxidative stress genes were determined using real-time PCR and immunofluorescence or Western blotting, respectively. PDTC treatment partially attenuated the increase in SBP (196.4 +/- 9.76 vs. 151.4 +/- 2.12; P < 0.05) and normalized renal hemodynamic and excretory parameters and ATP production rates in SHR. PDTC treatment also attenuated the higher levels of cytosolic and mitochondrial ROS generation and tissue mRNA and protein expression levels of NF-kappaB and oxidative stress genes in SHR without any comparable responses in control rats. These findings suggest that NF-kappaB activation by ROS induces the cytosolic and mitochondrial oxidative stress and tissue injury that contribute to renal dysfunction observed in SHR.

Fig. 1.

Mitochondrial purity as determined by transmission electron microscopy (A) and Western blotting (B) for the mitochondrial marker voltage-dependent anion channel (VDAC). A representative electron micrograph is shown in A (×40,000).

Fig. 2.

Systolic blood pressure trends for each study group. WKY, Wistar-Kyoto; PDTC, pyrrolidine dithiocarbamate; SHR, spontaneously hypertensive rat. *P < 0.05 vs. SHR. †P < 0.05 vs. SHR+PDTC.

Fig. 3.

Immunofluorescence staining and luminometric analysis for glomerular desmin (A), NAD(P)H oxidase (NOX)2 (gp91^phox; B), and NOX4 (C). Scale bars = 50 μm. *P < 0.05 vs. SHR. †P < 0.05 vs. SHR+PDTC.

Fig. 4.

A: representative Western blots for NF-κB p65, p50, IκBα, and GAPDH (housekeeping) in cortical tissues. B: densitometric analysis of expression levels of proteins in Fig. 3A expressed as protein density/GAPDH density ratio. C: EMSA for NF-κB p65 DNA binding activity. *P < 0.05 vs. SHR; †P < 0.05 vs. SHR+PDTC.

Fig. 5.

A: mean plasma cytokine levels for all study groups. B: representative Western blots and densitometric analyses for IL-6 and IL-1β (expressed as protein density/GAPDH density ratio). C: immunofluorescence staining and luminometric analysis for glomerular TNF-α. Scale bars = 50 μm. *P < 0.05 vs. SHR. †P < 0.05 vs. SHR+PDTC.