Activation of the classical pathway of inflammasome in vascular smooth muscle cells: effects of angiotensin II

Abstract

Angiotensin-II (Ang-II) plays an important role in the pathophysiology of systemic arterial hypertension (SAH). The binding of Ang-II to its AT1 receptor (AT1r) triggers a series of effects that raise blood pressure. Moreover, Ang-II plays a key role in the activation of inflammatory responses, and it is considered a peptide with powerful pro-inflammatory effects. Inflammation has also great importance in the pathophysiology of hypertension and recent studies suggest the involvement of components of the innate immunity in the vascular dysfunction associated with arterial hypertension. NOD-like receptors (NLRs), which recognize molecular patterns associated with tissue damage (DAMPs- damage-associated molecular patterns) and activate a multiprotein complex, called inflammasome, represent one of the components of innate immunity. The inflammasome is formed by the association of the NLR with adapter proteins ASC. This multiprotein complex activates caspase-1 and, consequently, the generation of pro-inflammatory cytokines, such as IL-1² and IL-18. Given the relationship between hypertension, Ang-II, and inflammation, and the central role of inflammasome activation in innate immune responses, it is possible that in hypertensive conditions the release of DAMPs activates the inflammasomes. This pro-inflammatory state, characteristic of hypertension, impairs vascular relaxation, leading to the worsening of vascular dysfunction. Therefore, the hypothesis of this study is that, in vascular smooth muscle cells (VSMC), Ang-II activates the inflammasome, which contributes to vascular inflammatory responses. To test our hypothesis, we will use macrophages (positive control) and VSMC to determine: 1) the presence of components of inflammasomes in VSMCs. 2) whether Ang-II stimulates the activation of the inflammasome pathway. Cultured VSMC and macrophages will be stimulated with Ang-II or lipopolysaccharide (LPS) and nigericin (positive controls for the activation of the inflammasome). We will determine if stimulation of VSMCs with Ang-II induces NLRs gene and protein expression as well as activation of caspase -1 and release of IL-1 ², markers of inflammasome activation. (AU)