Atorvastatin increases myocardial indices of oxidative stress in a porcine model of hypercholesterolemia and chronic ischemia

Abstract

Background/aim: Atorvastatin has previously been shown to reduce the endogenous angiogenic response to chronic ischemia in a porcine model. One possible mechanism for this effect is reduced bioavailability of nitric oxide, a key mediator of angiogenesis, secondary to increased oxygen free radicals. We sought to determine if atorvastatin modulates oxidative stress in myocardial tissue.

Methods: Dietary induction of hypercholesterolemia was performed over 20 weeks in Yucatan swine with treated animals receiving atorvastatin 3 mg/kg/day. Chronic myocardial ischemia was induced via surgical placement of an ameroid constrictor ring around the proximal circumflex artery at age 20 weeks, followed by tissue harvest at age 27 weeks. Myocardial levels of protein, lipid, and DNA biomarkers of oxidative stress, serum levels of 8-isoprostane, nitric oxide (NO) dependent, and independent coronary microvascular reactivity, as well as isotope-labeled microsphere myocardial perfusion analysis and histologic analysis for endothelial cell density was performed.

Results: Atorvastatin treatment was associated with elevated levels of myocardial protein oxidation and lipid peroxidation. Conversely, serum oxidant stress biomarkers were not elevated. Atorvastatin treatment improved nitric oxide dependent and independent microvascular reactivity, and was associated with decreased perfusion in the ischemic myocardial territory.

Conclusion: Treatment with atorvastatin was associated with increased levels of myocardial tissue protein and lipid oxidative stress biomarkers and a reduced functional endogenous angiogenic response, but improved coronary microvascular reactivity. Increased oxidative stress in tissues may play a role in the reduced angiogenic response seen with atorvastatin treatment in other studies.

Figure 1

Myocardial levels of malondialdehyde (MDA), a reactive carbonyl compound produced during lipid peroxidation. Atorvastatin-treated animals demonstrated a 50.2% increase in tissue levels of MDA (p = 0.0049)*.

Figure 2

Myocardial levels of 2-4 DNPH-derivatized proteins. Atorvastatin-treated animals demonstrated a 33.9% increase in levels of 2-4 DNPH derivatized proteins (p = 0.043)*. DU = densitometry units.

Figure 3

Myocardial levels of 8-OHdG. No differences were observed for levels of DNA oxidation between control (HC) animals and animals receiving atorvastatin (HC + ATR).

Figure 4

Serum levels of 8-isoprostane. No significant difference was seen in serum levels of 8-isoprostane.

Figure 5

Myocardial perfusion in the ischemic circumflex territory (Cx). The atorvastatin (HC + AT) group demonstrates reduced perfusion by 42.9% during pacing conditions (p = 0.01)* relative to the control hypercholesterolemic group (HC). R = rest conditions, P = pacing conditions.

Figure 6

Endothelial cell density. CD31-positive endothelial cell density per high-power field (0.267 mm²) in the ischemic territory. (A) HC animals, (B) HC + ATR animals, (C) endothelial cell counts per highpower field. The HC animals had reduced endothelial cell density compared with HC + ATR animals (201 ± 26 vs 294 ± 24; p = 0.02*).

Figure 7

Microvascular relaxation in response to ADP 10^-7 mol/L, ADP 10^-6 mol/L, Sodium Nitroprusside (SNP) 10^-7 mol/L, and SNP 10^-6 mol/L in the left anterior descending (LAD) and Circumflex (Cx) territory. HC = hypercholesterolemic, HC A = hypercholesterolemic + atorvastatin. (*indicates p < 0.05.).