Abstract P023: Toll-like Receptor 4 Deficiency Reduces Macrophage Mediated Renal Injury in Ang-II Induced Hypertension
Infiltration of macrophages has been amply demonstrated in the kidney of humans and experimental models of hypertension however, its role in tissue injury and repair remains unclear. Furthermore, recent studies implicate upregulation of toll-like receptor 4 (TLR4) and inflammation in hypertension and vascular remodeling. Previously, we observed that C3H/HeJ mice lacking functional TLR4 were hyporesponsive to Ang-II induced hypertension and renal damage. In this study, we hypothesized that TLR4 deficiency inhibits macrophage mediated inflammation and TGF-β-induced fibroblast accumulation to reduce renovascular injury and fibrosis. Male C3H/HeOuJ (functional TLR4) and C3H/HeJ mice (dysfunctional TLR4) aged 8-10 weeks underwent subcutaneous osmotic pump insertion for infusion of Angiotensin-II (Ang-II) at 1000 ng/kg/min or vehicle (0.9% saline) for 4 weeks. Blood pressure (BP) was measured twice weekly by non-invasive tail-cuff plethysmography. Ang-II treatment increased mean BP in both groups but to a greater degree in C3H/HeOuJ mice compared to C3H/HeJ (138.6± 6.3 vs. 103.4±7.2 mm/Hg). Plasma creatinine in saline treated C3H/HeOuJ and C3H/HeJ mice was normal (0.37±0.026 and 0.32±0.023 mg/dL respectively) in contrast to ang-II treated mice (1.34±0.075 vs. 0.78±0.052 mg/dL). Flow cytometry revealed increased F4/80+ and CD40+ cells indicating pro-inflammatory M1 macrophage in Ang-II treated C3H/HeOuJ compared to C3H/HeJ mice. Similarly, Ang-II increased the mRNA and protein expression of CD40, MCP-1, TNF-α and TGF-β in C3H/HeOuJ compared to C3H/HeJ mice. Immunostaining revealed increased colocalization of CD45 and procollagen-1 in renal sections of C3H/HeOuJ mice suggesting increased accumulation of myeloid fibroblasts than in C3H/HeJ mice. The expression of α-smooth muscle actin an indicator of myofibroblast and extracellular matrix proteins, collagen type I and fibronectin (Western blot and immunostaining) was increased in C3H/HeOuJ compared to C3H/HeJ mice. In conclusion, our data suggests that in C3H/HeJ mice, deficiency of functional TLR4 reduces macrophage activation and inflammation which in turn decreases TGF-β-induced renal fibrotic response in Ang-II induced hypertension.
Author Disclosures: S. Pushpakumar: None. M. Amin: None. U. Sen: None.
- © 2015 by American Heart Association, Inc.