Clin Res Cardiol (2022).

Murine femoral arteries undergo vascular remodeling associated with accelerated stress-induced contractility and reactivity to nitric oxide
L. T. Lubomirov1, M. Jänsch2, S. Papadopoulos3, M. M. Schroeter3, O. Grisk1, J. Hescheler3, G. Pfitzer4, O. Ritter2
1Institut of Physiologie, Brandenburg Medical School Theodor Fontane, Brandenburg; 2Zentrum für Innere Medizin I, Städt. Klinikum Brandenburg, Brandenburg an der Havel; 3Institute of Neurophysiology, University of Cologne, Köln; 4Institut für Vegetative Physiologie, Universitätsklinikum Köln, Köln;
Femoral artery (FA) is a large conducting vessel, build at the first trimester of embryonal development. Together with its important role for adequate nutrient and oxygen supply of lower extremities, it is commonly used as percutaneous access in vascular surgery for both diagnostic and therapeutic cardiac procedures in aged patients. The recent shift from traditional open surgery to endovascular interventions gives rise to the question whether the safety of those diagnostic and surgical methods could be improved by matching them with the contractile state of common FA. Here we explored the mechanism of augmented stress-induced vascular reactivity of senescent murine femoral arteries (FAs).

The contractile activity of ring preparations from senescent (> 104 weeks) and young murine FAs (12-25 weeks) was measured by wire myography. Protein phosphorylation of the regulatory myosin light chain (MLC20) and targeting subunit of myosin-phosphatase, MYPT1 was studied by western blotting. Expression ratio of the Exon24 in/out splice isoforms of the regulatory subunit of myosin phosphatase, MYPT1 (MYPT1-Exon24 in/out), was determined by polymerase chain reaction (PCR).

While the length-tension relationship during initial normalization showed no alteration, in s-FAs the stretch-induced-tone slowly increased with time (4.6 ± 0.3 mN in y-FAs vs. 8.3 ± 0.9 mN in s-FA). Under basal conditions, phosphorylation of the regulatory light chain of myosin at S19 was 19.2 ± 5.8% in y-FA versus 49.2 ± 12.6% in s-FA. While the RhoA-kinase inhibitor Y27632 had no effect on MLC20-phosphorylation in y-FAs, in s-FAs, Y27632 reduced MLC20 phosphorylation to concentrations to those determined in y-FAs. Treatment with 3 µmol/L of the RhoA-kinase inhibitor Y27632 reduced this parameter to levels measured in young vessels while in y-FAs, treatment with Y27632 had no effect on MLC20-S19 phosphorylation.  Inhibition of endogenous NO release raised tone additionally to 10.4 ±1.2 mN in s-FA, whereas this treatment had a negligible effect in y-FAs (4.8 ± 0.3 mN). In s-FAs, in vessels pretreated with L-NAME, U46619 response dose curve was shifted leftward. The logEC50 value was significantly lower (-7.8±0.1 in s-FAs vs -7.5±0.09 in y-FAs), and the maximal force (Fmax) was higher as compared to those values measured in y-FAs (24.8 ± 1.2 mN in s-FAs vs. 20.2 ± 1.2 mN in y-FAs). In s-FAs, reactivity to NO donor was augmented (logEC50= -4.5 ± 0.3 in y-FA vs. -5.2 ± 0.1 in senescent). Accordingly, in s-FAs, MYPT1-Exon24-out-mRNA, which is responsible for expression of the more sensitive to protein-kinase G, leucine-zipper-positive MYPT1 isoform, was increased.

The present work provides evidence that senescent murine FAs undergo vascular remodeling associated with increased stretch-activated contractility and sensitivity towards the NO/cGMP/PKG system.  The data support the hypothesis that, without loss of contractile proteins, re-expression of MYPT1-LZ+ might act as molecular brake against pathological increase of mean blood pressure in ageing and senescence. Thus, re-expression of the more PKG-sensitive isoform of MYPT1 might increase the NO reserve of the vascular system, leading to dampening of hydrostatic pressure.