MAPKs Are Highly Abundant but Do Not Contribute to α1-Adrenergic Contraction of Rat Saphenous Arteries in the Early Postnatal Period

NADPH oxidase derived ROS promote arterial contraction in early postnatal rats by activation of L-type voltage-gated Ca2+ channels

Reactive oxygen species (ROS) produced by NADPH oxidase promote contraction of peripheral arteries, which is especially pronounced in early postnatal period in comparison to adulthood, but the mechanisms of such vasomotor influence are poorly understood. We tested the hypothesis that Rho-kinase and protein kinase C (PKC) mediate procontractile influence of NADPH oxidase derived ROS in peripheral artery of early postnatal rats. In addition, we evaluated the involvement Src-kinase and L-type voltage-gated Ca2+ channels (LTCC) into procontractile influence of ROS, produced by NADPH oxidase, because of their known interplay with Rho-kinase and PKC pathways. Saphenous arteries from 11- to 15-day-old male rats were studied using quantitative PCR, isometric myography and lucigenin-enhanced chemiluminescence. Arterial tissue of early postnatal rats contained Nox2, Nox4, Duox1 and Duox2 mRNAs, among which Nox2 mRNA was the most abundant. Pan-NADPH oxidase inhibitor VAS2870 (10 µM) significantly reduced arterial contractile responses to methoxamine. The inhibitors of Rho-kinase (Y27632, 3 µM), PKC (GF109203X, 10 µM) and Src-kinase (PP2, 10 µM), as well as LTCC blockers (nimodipine, 0.1 µM, and verapamil, 0.1 μM) also reduced methoxamine-induced contraction. Importantly, the effect of VAS2870 persisted in the presence of Rho-kinase, PKC or Src-kinase inhibitors, but not in the presence of LTCC blocker. Notably, the blockade of LTCC did not affect either basal or NADPH-induced O2•- production. Our data show that LTCC, but not Rho-kinase, PKC or Src-kinase are involved into procontractile effect of ROS, produced by NADPH oxidase, in saphenous artery of young rats. Сalcium influx through LTCC does not activate ROS production by NADPH oxidase.

Thyroxine Induces Acute Relaxation of Rat Skeletal Muscle Arteries via Integrin αvβ3, ERK1/2 and Integrin-Linked Kinase

Aim: Hyperthyroidism is associated with a decreased peripheral vascular resistance, which could be caused by the vasodilator genomic or non-genomic effects of thyroid hormones (TH). Non-genomic, or acute, effects develop within several minutes and involve a wide tissue-specific spectrum of molecular pathways poorly studied in vasculature. We aimed to investigate the mechanisms of acute effects of TH on rat skeletal muscle arteries.

Methods: Sural arteries from male Wistar rats were used for isometric force recording (wire myography) and phosphorylated protein content measurement (Western blotting).

Results: Both triiodothyronine (T3) and thyroxine (T4) reduced contractile response of sural arteries to α₁-adrenoceptor agonist methoxamine. The effect of T4 was more prominent than T3 and not affected by iopanoic acid, an inhibitor of deiodinase 2. Endothelium denudation abolished the effect of T3, but not T4. Integrin αvβ3 inhibitor tetrac abolished the effect of T4 in endothelium-denuded arteries. T4 weakened methoxamine-induced elevation of phospho-MLC2 (Ser19) content in arterial samples. The effect of T4 in endothelium-denuded arteries was abolished by inhibiting ERK1/2 activation with U0126 as well as by ILK inhibitor Cpd22 but persisted in the presence of Src- or Rho-kinase inhibitors (PP2 and Y27632, respectively).

Conclusion: Acute non-genomic relaxation of sural arteries induced by T3 is endothelium-dependent and that induced by T4 is endothelium-independent. The effect of T4 on α₁-adrenergic contraction is stronger compared to T3 and involves the suppression of extracellular matrix signaling via integrin αvβ3, ERK1/2 and ILK with subsequent decrease of MLC2 (Ser19) phosphorylation.