Autophagy is the constitutively active catabolic process regulating protein quality control and energy homeostasis. However, dysregulation of this process can have detrimental effects on cellular function. In particular, insufficient autophagy has been proposed as a mechanism of cellular aging, as this leads to the accumulation of damaged macromolecules and organelles. Hypertension is a condition of vascular aging. In fact, many factors that contribute to the deterioration of vascular function as we age are exacerbated in clinical and experimental hypertension. Nonetheless, whether high blood pressure per se is the cause or effect of diminished autophagy remains to be clarified. We hypothesized that mesenteric resistance arteries (MRA) from spontaneously hypertensive rats (SHR) would have decreased autophagic flux as measured by conversion of microtubule-associated protein light chain 3 (LC3-I to LC3-II) compared to normotensive Wistar Kyoto rats (WKY). We observed that MRA from male 12-15 week old SHR have decreased basal expression both cytosolic LC3 (LC3-I) and phosphatidylethanolamine conjugated LC3 (LC3-II), and expression of these proteins are similarly decreased in SHR chronically treated with hydrochlorothiazide and reserpine (SHR+HCTZ/Res) [Arbitrary units (AU), LC3-1: WKY: 1.4±0.1, SHR: 1.1±0.1*, and SHR+HCTZ/Res: 0.7±0.1*; LC3-II: WKY: 1.4±0.1, SHR: 1.1±0.1*, and SHR+HCTZ/Res: 0.7±0.1*, *p<0.05 vs. WKY]. To understand autophagic flux, some MRA were incubated with lysosomal inhibitor chloroquine (CQ; 30 μM) for 2 hours. CQ incubation significantly increased LC3-II expression to a similar magnitude in WKY, SHR, and SHR+HCTZ/Res MRA (all *p<0.05 vs. basal). However, the percent increase in LC3-II expression after CQ incubation was significantly less in SHR compared to WKY, and SHR+HCTZ/Res was not different from either WKY or SHR (% increase from basal LC3-II, WKY: 546±187, SHR: 156±38*, and SHR+HCTZ/Res: 273±106, *p<0.05 vs. WKY). Overall, these data suggest that SHR have impaired autophagosome-lysosomal fusion, and this is not solely attributable to high blood pressure. Therefore, reconstituting autophagic activity could be a novel prophylactic or therapeutic measure against vascular aging in hypertension.
Sustained Normalization of High Blood Pressure in Spontaneously Hypertensive Rats by Implanted Hemin Pump
