Antihypertensive medications for risk reduction of first and recurrent ischemic stroke

Activation of the ACE2/Ang-(1-7)/Mas pathway reduces oxygen-glucose deprivation-induced tissue swelling, ROS production, and cell death in mouse brain with angiotensin II overproduction

We previously demonstrated that mice which overexpress human renin and angiotensinogen (R+A+) show enhanced cerebral damage in both in vivo and in vitro experimental ischemia models. Angiotensin-converting enzyme 2 (ACE2) counteracts the effects of angiotensin (Ang-II) by transforming it into Ang-(1-7), thus reducing the ligand for the AT1 receptor and increasing stimulation of the Mas receptor. Triple transgenic mice, SARA, which specifically overexpress ACE2 in neurons of R+A+ mice were used to study the role of ACE2 in ischemic stroke using oxygen and glucose deprivation (OGD) of brain slices as an in vitro model. We examined tissue swelling, the production of reactive oxygen species (ROS), and cell death in the cerebral cortex (CX) and the hippocampal CA1 region during OGD. Expression levels of NADPH oxidase (Nox) isoforms, Nox2 and Nox4 were measured using western blots. Results show that SARA mice and R+A+ mice treated with the Mas receptor agonist Ang-(1-7) had less swelling, cell death, and ROS production in CX and CA1 areas compared to those in R+A+ animals. Treatment of slices from SARA mice with the Mas antagonist A779 eliminated this protection. Finally, western blots revealed less Nox2 and Nox4 expression in SARA mice compared with R+A+ mice both before and after OGD. We suggest that reduced brain swelling and cell death observed in SARA animals exposed to OGD result from diminished ROS production coupled with lower expression of Nox isoforms. Thus, the ACE2/Ang-(1-7)/Mas receptor pathway plays a protective role in brain ischemic damage by counteracting the detrimental effects of Ang-II-induced ROS production.

Characterization of ischemic events and use of prescription antiplatelet and anticoagulant agents after stroke or transient ischemic attack

Stroke patients are at risk for subsequent ischemic events; yet preventive therapy is often underused. An analysis was performed to determine the rate of secondary ischemic events and use of prescription antiplatelets or anticoagulants after ischemic stroke or transient ischemic attack (TIA). Patients age 25 years or older with a medical claim for stroke or TIA between July 1, 1998 and September 30, 1999 were identified from a managed care database. Patients sustaining a stroke or TIA within 6 months before the index event were excluded. Patients were categorized as hospitalized stroke, nonhospitalized stroke, or TIA and were followed for 24 months for a secondary stroke, TIA, or acute myocardial infarction (AMI). Use of prescription antiplatelet or anticoagulant agents was determined for each subgroup. Over 2 years, subsequent stroke occurred in 5.8% of patients, TIA occurred in 3.8%, and AMI occurred in 4.9%. Death occurred in 32.3% during follow-up. Hospitalized stroke patients were the subgroup at highest risk, with a 7.6% stroke rate and a 45.4% death rate within 2 years. Prescription antiplatelet or warfarin therapy was given in 45.7% of hospitalized stroke cases, 29.5% of nonhospitalized stroke cases, and 39.2% of TIA cases. Against the background of current treatment, patients who suffer a stroke or TIA are at high risk of death and a subsequent stroke within 2 years. These outcomes highlight the importance of effective secondary stroke prevention efforts for those suffering acute stroke, whether or not they are hospitalized.