Abstract 19525: Role of Nitric Oxide in Sonoreperfusion Therapy for Microvascular Obstruction
Introduction: Microembolization during PCI for acute myocardial infarction causes microvascular[FY1] obstruction (MVO). We have shown that ultrasound (US) and microbubble (MB) therapy restores perfusion during MVO (termed “sonoreperfusion” or “SRP”) and that this response is blunted during blockade of nitric oxide (NO) with LNAME. Now, we further investigate the role of NO by quantifying both intramuscular NO and phosphorylated eNOS during US and MB therapy.
Methods: A membrane catheter probe was placed intramuscularly in the left hindlimb of anesthetized rats to monitor NO concentration variations (Δ[NO]). Hindlimb MVO was created by injecting microthrombi into the femoral artery 5 min after i.v. bolus of LNAME (10 mg/kg) or saline. Therapeutic US (1 MHz, 1.5 MPa, 5000 cycles, PRF 0.33 Hz) was delivered to the muscle for two 10-minute sessions during intra-femoral arterial infusion of lipid-encapsulated MBs (n=3 rats/group). In separate experiments, HUVECs were grown to confluence and sonicated in the presence or absence of MBs (1 MHz, 100kPa, 5000 cycles, PRF 100 Hz, 2 min). Phosphorylated/Total eNOS ratio was quantified using Western blotting following MB+US exposure (n=3). Cell viability and metabolic activity were assessed with trypan blue exclusion and Alamar blue assays. Statistical analysis was performed using ANOVA and Student’s t-test.
Results: Ten minutes after microthrombi injection (MVO stage), intramuscular [NO] decreased by 35.2±11.2 and 29.2±8.2 nM in the LNAME+MB+US and MB+US groups, respectively. This decrease was significant with respect to baseline [NO] (p<0.05) but was similar between the groups. [NO] increased during SRP therapy in the group with intact NO, but not in the LNAME group. At the end of treatment 2, Δ[NO] reached baseline values in the group with intact NO (Δ[NO]=1.1±6.0 nM), which was higher than at MVO stage (p<0.05) and compared to the LNAME group post treatment 2 (p<0.05). In the cell culture, phosphorylated eNOS increased by 6-fold following MB+US but remained unchanged with US alone (no MB); cell viability and metabolic activity remained intact.
Conclusions: These data demonstrate that NO plays a significant role in SRP efficacy. This could inform strategies to tune SRP US regimes for optimal reperfusion of MVO.
Author Disclosures: F.T. Yu: None. X. Chen: None. F.S. Villanueva: None. J.J. Pacella: None.
- © 2016 by American Heart Association, Inc.