Involvement of transglutaminase 2 and voltage‐gated potassium channels in cystamine vasodilatation in rat mesenteric small arteries

Background and Purpose

Vasodilatation may contribute to the neuroprotective and vascular anti‐remodelling effect of the tissue transglutaminase 2 (TG2) inhibitor cystamine. Here, we hypothesized that inhibition of TG2 followed by blockade of smooth muscle calcium entry and/or inhibition of Rho kinase underlies cystamine vasodilatation.

Experimental Approach

We used rat mesenteric small arteries and RT‐PCR, immunoblotting, and measurements of isometric wall tension, intracellular Ca²⁺ ([Ca²⁺]_i), K⁺ currents (patch clamp), and phosphorylation of myosin phosphatase targeting subunit 1 (MYPT1) and myosin regulatory light chain, in our experiments.

Key Results

RT‐PCR and immunoblotting revealed expression of TG2 in mesenteric small arteries. Cystamine concentration‐dependently inhibited responses to phenylephrine, 5‐HT and U46619 and for extracellular potassium. Selective inhibitors of TG2, LDN 27129 and T101, also inhibited phenylephrine contraction. An inhibitor of PLC suppressed cystamine relaxation. Cystamine relaxed and reduced [Ca²⁺]_i in phenylephrine‐contracted arteries. In potassium‐contracted arteries, cystamine induced less relaxation without changing [Ca²⁺]_i, and these relaxations were blocked by mitochondrial complex inhibitors. Blockers of K_v7 channels, XE991 and linopirdine, inhibited cystamine relaxation and increases in voltage‐dependent smooth muscle currents. Cystamine and the Rho kinase inhibitor Y27632 reduced basal MYPT1‐Thr⁸⁵⁵ phosphorylation, but only Y27632 reduced phenylephrine‐induced increases in MYPT1‐Thr⁸⁵⁵ and myosin regulatory light chain phosphorylation.

Conclusions and Implications

Cystamine induced vasodilatation by inhibition of receptor‐coupled TG2, leading to opening of K_v channels and reduction of intracellular calcium, and by activation of a pathway sensitive to inhibitors of the mitochondrial complexes I and III. Both pathways may contribute to the antihypertensive and neuroprotective effect of cystamine.

DOI: 10.1111/bph.13393

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