Macrophage-derived IL-6 contributes to ANG II-mediated angiotensinogen stimulation in renal proximal tubular cells

Abstract

The development of ANG II-dependent hypertension involves increased infiltration of macrophages (MΦ) and T cells into the kidney and the consequent elevation of intrarenal cytokines including IL-6, which facilitates the progression of hypertension and associated kidney injury. Intrarenal renin-angiotensin system (RAS) activation, including proximal tubular angiotensinogen (AGT) stimulation, has also been regarded as a cardinal mechanism contributing to these diseases. However, the interaction between immune cells and intrarenal RAS activation has not been fully delineated. Therefore, the present study investigated whether ANG II-treated MΦ induce AGT upregulation in renal proximal tubular cells (PTCs). MΦ were treated with 0-10(-6) M ANG II for up to 48 h. PTCs were incubated with the collected medium from MΦ. In ANG II-treated MΦ, IL-6 mRNA and protein levels were increased (1.86 ± 0.14, protein level, ratio to control); moreover, IL-6 levels were higher than TNF-α and IL-1β in culture medium isolated from ANG II-treated MΦ. Elevated AGT expression (1.69 ± 0.04, ratio to control) accompanied by phosphorylated STAT3 were observed in PTCs that received culture medium from ANG II-treated MΦ. The addition of a neutralizing IL-6 antibody to the collected medium attenuated phosphorylation of STAT3 and AGT augmentation in PTCs. Furthermore, a JAK2 inhibitor also suppressed STAT3 phosphorylation and AGT augmentation in PTCs. These results demonstrate that ANG II-induced IL-6 elevation in MΦ enhances activation of the JAK-STAT pathway and consequent AGT upregulation in PTCs, suggesting involvement of an immune response in driving intrarenal RAS activity.

Angiotensin II Signal Transduction: An Update on Mechanisms of Physiology and Pathophysiology

“…Stimulation of mouse macrophage cell line RAW264.7 cells by ANG II causes both NF-B and AP1 activation, ROS production, and secretion of inflammatory cytokines including TNF-␣, IL-1␤, IL-6, and IL-10 through AT 1 R (346). AT 1 R-dependent IL-6 production has been confirmed in rat lung macrophage-derived cell line, NR8383 (763). As mentioned in section IIIA1, macrophage depletion and C1qa gene deletion attenuated ANG II-induced ␤-catenin signaling and arterial remodeling (1010).…”

Aliskiren Attenuates the Inflammatory Response and Wound Healing Process in Diabetic Mice With Periodontal Disease

“…However, the gingival tissue also produces local AGT as observed in our study. Regulation of AGT expression by cytokines has been shown in multiple organs and isolated immune cells (Brasier et al, 1990; Corvol et al, 1997; O’Leary et al, 2016). If this result can be applied to this study, then it seems reasonable to assume that CXCL2, CCL8, or IL-1β could be stimulating AGT production from gingival tissue after PD in both normal and diabetic mice.…”

Canagliflozin Prevents Intrarenal Angiotensinogen Augmentation and Mitigates Kidney Injury and Hypertension in Mouse Model of Type 2 Diabetes Mellitus

“…The Western blots were performed as previously described [17,18]. Tissues were homogenized with 60 μL lysis buffer containing 1% Triton X-100, 150 mmol/L NaCl, 1 mmol/L EDTA, 1% Nonidet P-40, 1 mmol/L Na 3 VO 4 , and 0.25% Protease Inhibitor Cocktail (Sigma).…”