Renal transporter activation during angiotensin-II hypertension is blunted in interferon-γ-/- and interleukin-17A-/- mice

Abstract

Ample genetic and physiological evidence establishes that renal salt handling is a critical regulator of blood pressure. Studies also establish a role for the immune system, T-cell infiltration, and immune cytokines in hypertension. This study aimed to connect immune cytokines, specifically interferon-γ (IFN-γ) and interleukin-17A (IL-17A), to sodium transporter regulation in the kidney during angiotensin-II (Ang-II) hypertension. C57BL/6J (wild-type) mice responded to Ang-II infusion (490 ng/kg per minute, 2 weeks) with a rise in blood pressure (170 mm Hg) and a significant decrease in the rate of excretion of a saline challenge. In comparison, mice that lacked the ability to produce either IFN-γ (IFN-γ(-/-)) or IL-17A (IL-17A(-/-)) exhibited a blunted rise in blood pressure (<150 mm Hg), and both the genotypes maintained baseline diuretic and natriuretic responses to a saline challenge. Along the distal nephron, Ang-II infusion increased abundance of the phosphorylated forms of the Na-K-2Cl cotransporter, Na-Cl cotransporter, and Ste20/SPS-1-related proline-alanine-rich kinase, in both the wild-type and the IL-17A(-/-) but not in IFN-γ(-/-) mice; epithelial Na channel abundance increased similarly in all the 3 genotypes. In the proximal nephron, Ang-II infusion significantly decreased abundance of Na/H-exchanger isoform 3 and the motor myosin VI in IL-17A(-/-) and IFN-γ(-/-), but not in wild-type; the Na-phosphate cotransporter decreased in all the 3 genotypes. Our results suggest that during Ang-II hypertension both IFN-γ and IL-17A production interfere with the pressure natriuretic decrease in proximal tubule sodium transport and that IFN-γ production is necessary to activate distal sodium reabsorption.

Keywords: NHE3 protein; NKCC2 protein sodium chloride cotransporters; SPAK protein; angiotensin-II; cytokines; epithelial Na+ channel.

Figure 1. Physiologic responses to AngII infusion (490 ng/kg/min × 14 d) are blunted in IFN-γ^−/− and IL-17A ^−/− mice

At baseline (B), 2, 5, and 10 days of AngII infusion, WT, IFN-γ^−/− and IL-17A ^−/− mice were challenged with an i.p. bolus of warmed saline equivalent of 10% of their body weight and placed in metabolic cages for urine collection. Results are expressed as the fraction of the amount injected (the challenge) excreted over the 4 hr collection period. AngII infusion significantly reduced the natriuretic responses in WT, but not in the IFN-γ ^−/− or IL-17A ^−/− mice. Data are expressed as mean ± SEM, n= 4-7 per group. *P < 0.05 Diuretic responses are displayed in Figure S1.

Figure 2. Effects of IFN-γ and IL-17A on NKCC, NCC and ENaC abundance regulation during AngII infusion

Transporter abundance was analyzed in whole renal tissue homogenates from: A. wild-type (WT), B. IFN-γ ^−/−, and C. IL-17A ^−/− mice 2 weeks after sham or Ang II infusion. Immunoblots were performed with a constant amount of protein per lane and ½ amounts (not shown) to verify linearity of detection (details provided in Table S1). Relative abundance indicated as mean ± SEM. n = 5-6/group. *P < 0.05.

Figure 3. Effects of IFNγ and IL-17A on Ste20/SPS1-related Proline/Alanine-rich Kinase (SPAK) abundance and regulation during AngII infusion (490 ng/kg/min × 14 d)

SPAK and SPAK-P abundance (analyzed as described in Figure 2 and Table S1) from: A. wild-type (WT) , B. IFN-γ^−/− ,and C. IL-17A ^−/− mice 2 weeks after sham or Ang II infusion. SPAK 2 and kidney specific SPAK (SPAK KS) indicated but not quantified. Relative abundance indicated as mean ± SEM, n = 5-6/group. *P < 0.05.

Figure 4. Effects of IFNγ and IL-17A on NHE3, NaPi-2 and myosin VI abundance regulation during AngII infusion

Abundance (analyzed as described in Figure 2 and Table S1) from: A. wild-type (WT) , B. IFN-γ ^−/− , and C. IL-17A ^−/− mice 2 weeks after sham or Ang II infusion. Relative abundance values indicated as mean ± SEM. n = 5-6/group. *P < 0.05.

Figure 5. Renal transporter profiles of WT C57BL/6J, IFN-γ^−/− and IL-17A^−/− mice during AngII infusion

Data summarized from Figures 2-4 is displayed as relative abundance of AngII infused mice (490 ng/kg/min × 14 d) relative to abundance in control mice of the same genotype infused with saline, defined as abundance =1. *P<0.05 versus saline infused mice of the same genotype.