ABSTRACT
Evidence is emerging that disruption of the endothelial glycocalyx might contribute importantly to arterial dysfunction in the context of diabetes. One approach to assess the integrity of the endothelium and the vascular smooth muscle cell layer, in the absence of neural, humoral, and mechanical influences, is by measuring arterial vasomotion ex vivo. Here we describe a procedure to assess non-receptor-mediated vasoconstriction, receptor-mediated vasoconstriction, and endothelium-dependent and -independent vasodilation, in resistance and conductance arteries pressurized to 60 mmHg. In addition to evaluating vasoreactivity using isobaric approaches, the same experimental set-up can be used to initiate a pressure gradient across the artery such that intraluminal, flow-mediated vasodilation can be measured. After recording endothelium-dependent vasodilation using isobaric or flow-mediated approaches, identical interventions can be completed in the presence of enzymes that cleave biologically active heparan sulfates into inactive disaccharide and oligosaccharide fragments to assess the contribution from: (a) endothelial-derived substances (e.g., nitric oxide via nitric oxide synthase inhibition); or (b) important components of the glycocalyx (e.g., removal of heparan sulfate via heparitinase III treatment). Here, we show that acute disruption of a predominant glycosaminoglycan i.e., heparan sulfate impairs intraluminal flow-mediated vasodilation in murine resistance arteries.
Subject(s)
Arteries , Animals , Endothelium, Vascular , Glycocalyx , Heparitin Sulfate , Mice , Nitric Oxide , Vasoconstriction , VasodilationABSTRACT
Protein quality control mechanisms decline during the process of cardiac aging. This enables the accumulation of protein aggregates and damaged organelles that contribute to age-associated cardiac dysfunction. Macroautophagy is the process by which post-mitotic cells such as cardiomyocytes clear defective proteins and organelles. We hypothesized that late-in-life exercise training improves autophagy, protein aggregate clearance, and function that is otherwise dysregulated in hearts from old vs. adult mice. As expected, 24-month-old male C57BL/6J mice (old) exhibited repressed autophagosome formation and protein aggregate accumulation in the heart, systolic and diastolic dysfunction, and reduced exercise capacity vs. 8-month-old (adult) mice (all p < 0.05). To investigate the influence of late-in-life exercise training, additional cohorts of 21-month-old mice did (old-ETR) or did not (old-SED) complete a 3-month progressive resistance treadmill running program. Body composition, exercise capacity, and soleus muscle citrate synthase activity improved in old-ETR vs. old-SED mice at 24 months (all p < 0.05). Importantly, protein expression of autophagy markers indicate trafficking of the autophagosome to the lysosome increased, protein aggregate clearance improved, and overall function was enhanced (all p < 0.05) in hearts from old-ETR vs. old-SED mice. These data provide the first evidence that a physiological intervention initiated late-in-life improves autophagic flux, protein aggregate clearance, and contractile performance in mouse hearts.
