Loss of GSTM1, a NRF2 target, is associated with accelerated progression of hypertensive kidney disease in the African American Study of Kidney Disease (AASK)

Abstract

Oxidative stress is acknowledged to play a role in kidney disease progression. Genetic variants that affect the capacity to handle oxidative stress may therefore influence the outcome of kidney disease. We examined whether genetic variants of the GSTM1 gene, a member of a superfamily of glutathione S-transferases, influence the course of kidney disease progression in participants of the African American Study of Kidney Disease (AASK) trial. Groups with and without the common GSTM1 null allele, GSTM1(0), differed significantly in the time to a glomerular filtration rate (GFR) event or dialysis (P = 0.04) and in the time to GFR event, dialysis, or death (P = 0.02). The hazard ratios (HR) for the time to a GFR event or dialysis in those with two or one null allele relative to those possessing none were 1.88 [95% confidence interval (CI), 1.07 to 3.30, P = 0.03] and 1.68 (95% CI, 1.00 to 2.84, P < 0.05), respectively. For the time to GFR event, dialysis, or death, the HR for two null alleles was 2.06 (95% CI, 1.20 to 3.55, P = 0.01) and for one null allele 1.70 (95% CI, 1.02 to 2.81, P = 0.04). We demonstrated that GSTM1 directly regulates intracellular levels of 4-hydroxynonenal (4-HNE) in vascular smooth muscle cells. Furthermore, we showed that renal 4-HNE levels and GSTM1 are both increased after reduction of renal mass (RRM) in the mouse. We conclude that GSTM1 is normally upregulated in chronic kidney disease (CKD) in a protective response to increased oxidative stress. A genetic variant that results in loss of GSTM1 activity may be deleterious in CKD.

Figures

Fig. 1.

Kaplan-Meier curve of composite outcome of glomerular filtration rate (GFR) event, dialysis, or death among genotype groups. A GFR event is defined as a 50% reduction or 25 ml·min−1·1.73 m−2 decline in measured GFR (iothalamate). The genotype groups are significantly different in the composite outcome of GFR event, dialysis, or death (log rank; P = 0.015).

Fig. 2.

Kaplan-Meier curve of composite outcome of GFR event or dialysis among genotype groups. GFR event is defined as in Fig. 1. The 3 genotype groups differed in time to a GFR event or dialysis (log-rank; P = 0.041).

Fig. 3.

A: effect of knockdown of glutathione S-transferase-μ1 (GSTM1) on intracellular levels of 4-hydroxynonenal (4-HNE) protein adducts in vascular smooth muscle cells (VSMCs) from the 129S6/SvEv (129) mouse strain. Knockdown of GSTM1 with Gstm1-small interfering (si) RNA results in significantly increased levels of 4-HNE protein adducts compared with control-siRNA (P = 0.0008 by densitometry). Bands at molecular weights of 140, 70, 50, and 37 kDa correspond to proteins that have been modified by 4-HNE. Each lane represents separate cell treatment conditions. B, left: successful overexpression of GSTM1 in C57BL/6 VSMCs by a Gstm1-expressing vector. Right: effect of overexpression of GSTM1 on intracellular levels of 4-HNE protein adducts in VSMCs from the B6 mouse strain. Overexpression of GSTM1 results in significantly decreased levels of 4-HNE protein adducts compared with untransfected and empty vector conditions (P = 0.0002 by densitometry). Each lane represents separate cell treatment conditions. C: effect of 4-HNE on expression of Nrf2 and GSTM1. Exposure to 4-HNE results in increased VSMC expression of Nrf2 and GSTM1 proteins in a dose-dependent manner. D: effect of GSTM1 on expression of NRF2. Knockdown of Gstm1 by siRNA results in increased expression of NRF2 in VSMCs.

Fig. 4.

A: comparison of renal 4-HNE protein adduct levels pre- and postnephrectomy. Reduction of renal mass (RRM) results in significantly higher levels of 4-HNE protein adducts in the remnant kidney compared with prenephrectomy state. Analysis was performed using kidney tissues from the same 3 mice, before and after RRM. B: effect of RRM on renal expression of nuclear factor-erythroid 2 (NRF2) and GSTM1 proteins. Induction of chronic kidney disease in the mouse results in significantly increased renal levels of Nrf2 and GSTM1 in the remnant kidney. Analysis was performed using kidney tissues from the same 3 mice, before and after RRM.