Mechanisms of I/R-Induced Endothelium-Dependent Vasodilator Dysfunction

Area of Science:

• Vascular Biology
• Physiology
• Immunology

Background:

• Ischemia/reperfusion (I/R) impairs endothelium-dependent dilation (EDD) in arterioles, critical for vascular resistance.
• Mechanisms of I/R-induced EDD dysfunction in arterioles are less understood than in conduit arteries.

Purpose of the Study:

• To investigate the causal link between leukocyte-endothelial cell adhesive interactions (LECA) in postcapillary venules and EDD dysfunction in upstream arterioles following I/R.
• To elucidate the signaling pathway connecting venular LECA to arteriolar EDD impairment.

Main Methods:

• Investigated I/R-induced changes in postcapillary venules and upstream arterioles.
• Examined the role of leukocyte emigration, interstitial signals, mast cells, and angiotensin II (Ang II) in EDD dysfunction.

Main Results:

• I/R-induced venular LECA causally linked to arteriolar EDD dysfunction, despite no leukocyte adhesion in arterioles.
• A mechanism involving interstitial signals, mast cell chymase, Ang II, and NAD(P)H oxidase activation identified.
• Oxidants generated inactivate nitric oxide (NO) and cause eNOS uncoupling, leading to EDD dysfunction.

Conclusions:

• Establishes a novel pathway where venular LECA triggers interstitial signals from emigrated leukocytes.
• This pathway involves mast cell degranulation and Ang II formation, ultimately impairing arteriolar EDD.
• Findings have significant implications for understanding blood flow dysregulation in I/R conditions.