Abstract 003: Role of Transient Receptor Potential Ankyrin 1 in Monocyte Activation and Hypertensive Kidney Injury

Abstract

It has been shown that monocyte activation and infiltration occur during the development of hypertensive kidney disease, a condition newly recognized as an inflammatory disorder. Indeed, monocytosis is linked to chronic kidney disease. Transient receptor potential ankyrin 1 (TRPA1), a Ca 2+ -permeable non-selective cation channel, has been shown to be an oxidative stress sensor that regulates neurogenic inflammation due to its abundant expression in sensory nerves. With the use of qPCR and immunostaining, we identified that the TRPA1 is also expressed in human and murine monocytes. The gene expression of TRPA1 is decreased in peripheral monocytes in hypertensive patients compared to normotensive subjects (-6-fold, p<0.05) and in kidney tissues in angiotensin II (1000ng/kg/min, s.c., 14 days)-induced hypertensive compared to control mice (-9-fold, p<0.01). The differentiation of human monocytic leukemia cells (THP-1) into macrophages induced by phorbol 12-myristate 13-acetate (PMA, 100nM, 48h) was accompanied with decreases in TRPA1 expression (-8-fold, p<0.05) and increases in pro-inflammatory cytokines, including interleukin (IL)-1β (+705-fold, p<0.01), monocyte chemotactic protein (MCP)-1 (+16-fold, p<0.01), and CD36 (+7-fold, p<0.01). Treatment with supercinnamaldehyde (SCA), a TRPA1 agonist, decreased the expression of IL-1β (-12-fold, p<0.01), MCP-1 (-3.5-fold, p<0.01), and CD36 (-2-fold, p<0.05) in THP-1-derived macrophages, whereas these effects were abolished by pre-treatment with the selective TRPA1 antagonist, HC-030031 (HC). Additionally, HC promoted the proliferation of THP-1 cells while SCA suppressed THP-1 cell growth and variability. SCA induced the apoptosis of THP-1 cells (Annexin V positive cells: 8.5±1.4% vs. 30.1±2.4%, p<0.01), which can be blocked by HC (30.1±2.4% vs. 15.6±1.9%, p<0.01). These results show that TRPA1 activation inhibits monocyte activation and differentiation, and that suppressed expression of TRPA1 occurs in monocytes and kidneys in hypertensive patients and animals, respectively. These findings indicate that impaired expression and function of TRPA1 may contribute to monocytosis and pro-inflammatory state during hypertension, leading to hypertension related kidney injury.