Ageing and endothelium-mediated vascular dysfunction: the role of the NADPH oxidases.

The present study aimed to determine the isoform-specific role of the NADPH oxidases (NOX) in the endothelium-mediated vascular dysfunction associated with ageing. Endothelium-dependent [intraluminal flow- and acetylcholine (ACh)-induced] vasodilatation in human skeletal muscle feed arteries (SMFAs) of young (24 ± 1 years, n = 16), middle aged (45 ± 1 years, n = 18) and old (76 ± 2 years, n = 21) subjects was assessed in vitro with and without the inhibition of NOX1 (ML090), NOX2 (gp91) and NOX4 (plumbagin). To identify the role of nitric oxide (NO) bioavailability in these responses, NO synthase blockade (l-NG -monomethyl arginine citrate) was utilized. SMFA NOX1, NOX2 and NOX4 protein expression was determined by western blotting. Age related endothelium-dependent vasodilatory dysfunction was evident in response to flow (young: 69 ± 3; middle aged: 51 ± 3; old: 27 ± 3%, P < 0.05) and ACh (young: 89 ± 2; middle aged: 72 ± 3; old: 45 ± 4%, P < 0.05). NOX1 inhibition had no effect on SMFA vasodilatation, whereas NOX2 inhibition restored flow- and ACh-induced vasodilatation in the middle aged and the old SMFAs (middle aged + gp91: 69 ± 3; 86 ± 3, old + gp91: 65 ± 5; 83 ± 2%, P < 0.05) and NOX4 inhibition tended to restore these vasodilatory responses in these two groups, but neither achieved statistical significance (P ≈ 0.06). l-NG -monomethyl arginine citrate negated the restorative effects of NOX2 and NOX4 blockade. Only NOX2 and NOX4 protein expression was significantly greater in the two older groups and inversely related to vascular function (r = 0.48 to 0.93, P < 0.05). NOX2 and, to a lesser extent, NOX4 appear to play an important, probably NO-mediated, role in age-related endothelial dysfunction. KEY POINTS: The present study aimed to determine the isoform-specific role of the NADPH oxidases (NOX) in the endothelium-mediated vascular dysfunction associated with ageing. Age related endothelium-dependent vasodilatory dysfunction was evident in skeletal muscle feed arteries in response to both flow and acetylcholine. NOX2 inhibition (gp91) restored endothelium-dependent vasodilatation in the middle aged and the old skeletal muscle feed arteries, and NOX4 inhibition (plumbagin) tended to restore these vasodilatory responses in these two groups. Nitric oxide synthase inhibition negated the restorative effects of NOX2 and NOX4 blockade. NOX2 and NOX4 protein expression was significantly greater in the two older groups and inversely related to vascular function. NOX2 and, to a lesser extent, NOX4 appear to play an important, probably nitric oxide-mediated, role in age-related endothelial dysfunction and could be important therapeutic targets to maintain vascular health with ageing.

Quadriceps muscle atrophy after non-invasive anterior cruciate ligament injury: evidence linking to autophagy and mitophagy.

Introduction: Anterior cruciate ligament (ACL) injury is frequently accompanied by quadriceps muscle atrophy, a process closely linked to mitochondrial health and mitochondria-specific autophagy. However, the temporal progression of key quadricep atrophy-mediating events following ACL injury remains poorly understood. To advance our understanding, we conducted a longitudinal study to elucidate key parameters in quadriceps autophagy and mitophagy. Methods: Long-Evans rats were euthanized at 7, 14, 28, and 56 days after non-invasive ACL injury that was induced via tibial compression overload; controls were not injured. Vastus lateralis muscle was extracted, and subsequent immunoblotting analysis was conducted using primary antibodies targeting key proteins involved in autophagy and mitophagy cellular processes. Results: Our findings demonstrated dynamic changes in autophagy and mitophagy markers in the quadriceps muscle during the recovery period after ACL injury. The early response to the injury was characterized by the induction of autophagy at 14 days (Beclin1), indicating an initial cellular response to the injury. Subsequently, at 14 days we observed increase in the elongation of autophagosomes (Atg4B), suggesting a potential remodeling process. The autophagosome flux was also augmented between 14- and 28 days (LC3-II/LC3-I ratio and p62). Notably, at 56 days, markers associated with the elimination of damaged mitochondria were elevated (PINK1, Parkin, and VDAC1), indicating a possible ongoing cellular repair and restoration process. Conclusion: These data highlight the complexity of muscle recovery after ACL injury and underscore the overlooked but crucial role of autophagy and mitophagy in promoting the recovery process.

Skeletal muscle mitochondrial capacity in patients with statin-associated muscle symptoms (SAMS).

OBJECTIVE: The objective of this article is to evaluate near-infrared spectroscopy (NIRS), a non-invasive technique to assess tissue oxygenation and mitochondrial function, as a diagnostic tool for statin-associated muscle symptoms (SAMS). METHODS: We verified SAMS in 39 statin-treated patients (23 women) using a double-blind, placebo-controlled, cross-over protocol. Subjects with suspected SAMS were randomised to simvastatin 20 mg/day or placebo for 8 weeks, followed by a 4-week no treatment period and then assigned to the alternative treatment, either simvastatin or placebo. Tissue oxygenation was measured before and after each statin or placebo treatment using NIRS during handgrip exercise at increasing intensities of maximal voluntary contraction (MVC). RESULTS: 44% (n=17) of patients were confirmed as having SAMS (11 women) because they reported discomfort only during simvastatin treatment. There were no significant differences in percent change in tissue oxygenation in placebo versus statin at all % MVCs in all subjects. The percent change in tissue oxygenation also did not differ significantly between confirmed and unconfirmed SAMS subjects on statin (-2.4% vs -2.4%, respectively) or placebo treatment (-1.1% vs -9%, respectively). The percent change in tissue oxygenation was reduced after placebo therapy in unconfirmed SAMS subjects (-10.2%) (p≤0.01) suggesting potential measurement variability. CONCLUSIONS: NIRS in the forearm cannot differentiate between confirmed and unconfirmed SAMS, but further research is needed to assess the usability of NIRS as a diagnostic tool for SAMS. TRIAL REGISTRATION NUMBER: NCT03653663.