Statins for stroke prevention

Attenuation of experimental autoimmune neuritis with locally administered lovastatin-encapsulating poly(lactic-co-glycolic) acid nanoparticles

Acute inflammatory demyelinating polyneuropathy (AIDP) is an aggressive antibody- and T-cell-mediated variant of Guillain-Barré Syndrome (GBS), a prominent and debilitating autoimmune disorder of the peripheral nervous system. Despite advancements in clinical management, treatment of patients with AIDP/GBS and its chronic variant CIDP remains palliative and relies on the use of non-specific immunemodulating therapies. Our laboratory has previously reported that therapeutic administration of statins safely attenuates the clinical severity of experimental autoimmune neuritis (EAN), a well-characterized animal model of AIDP/GBS, by restricting the migration of autoreactive leukocytes across peripheral nerve microvascular endoneurial endothelial cells that form the blood-nerve barrier. Despite these advancements, the clinical application of systemically administered statins for the management of inflammatory disorders remains controversial as a result of disappointingly inconclusive phase trials. Here, poly(lactic-co-glycolic) acid (PLGA) nanoparticles were evaluated as an alternative strategy by which to locally administer statins for the management of EAN. When tested in vitro, lovastatin-encapsulating PLGA nanoparticles elicited a marked increase in RhoB mRNA content in peripheral nerve microvascular endoneurial endothelial cells, similar to cells treated with activated unencapsulated lovastatin. Unilateral peri-neural administration of lovastatin-encapsulating PLGA nanoparticles, but not empty nanoparticles, to naïve Lewis rats similarly enhanced RhoB mRNA content in adjacent nerve and muscle tissue. When administered in this manner, serum levels of lovastatin were below the level of detection. Bilateral peri-neural administration of lovastatin-encapsulating PLGA nanoparticles to EAN-induced Lewis rats significantly attenuated EAN clinical severity while protecting against EAN-induced peripheral nerve morphological and functional deficits. This study provides the first proof-of-concept approach for the application of a nanoparticle-based local drug delivery platform for the management of inflammatory demyelinating diseases, including AIDP/GBS.

Mechanisms regulating airway nucleotides

In the respiratory system, extracellular nucleotides and nucleosides serve as signaling molecules for a wide spectrum of biological functions regulating airway defenses against infection and toxic material. Their concentrations are controlled by a complex network of cell surface enzymes named ectonucleotidases. This highly integrated metabolic network combines the activities of three dephosphorylating ectonucleotidases, namely nucleoside triphosphate diphosphohydrolases (NTPDases), nucleotide pyrophosphatase/phosphodiesterases (NPPs) and alkaline phosphatases (APs). Extracellular nucleotides are also inter-converted by the transphosphorylating activities of ecto adenylate kinase (ectoAK) and nucleoside diphosphokinase (NDPK). Different cell types use specific combinations of ectonucleotidases to regulate local concentrations of P2 receptor agonists (ATP, UTP, ADP and UDP). In addition, they provide AMP for the activity of ecto 5'-nucleotidase (ecto 5'-NT; CD73), which produces the P1 receptor agonist: adenosine (ADO). Finally, mechanisms are in place to prevent the accumulation of airway ADO, namely adenosine deaminases and nucleoside transporters. This chapter reviews the properties of each enzyme and transporter, and the current knowledge on their distribution and regulation in the airways.

The effects of statins on prevention of stroke and dementia: a review

Stroke is the third leading cause of death in the United States and places a heavy toll on health care spending, especially in the elderly population. The prevalence of stroke increases with increasing age. Over the last 2 decades, there have been substantial data supporting the use of statins in the primary, as well as secondary, prevention of stroke. Although most of these studies were designed to evaluate cerebrovascular accidents (CVA) only as secondary endpoints, the data show a significant reduction in strokes associated with statin use. There have been numerous studies that have demonstrated the relationship between serum cholesterol levels, specifically low-density lipoprotein cholesterol, on CVA and the beneficial effects of statins in this setting. Furthermore, in addition to the lipid-lowering properties of statins, these drugs have also been shown to possess cholesterol-independent pleotropic properties that have been associated with neuroprotection. Finally, the role of statins for the prevention of dementia is still highly debatable. We examine the role of this class of drugs in the setting of dementia, particularly from vascular causes and stroke.

Lessons from the SYNTAX trial

Despite the fact that CABG is the standard of care for patients with multivessel coronary arteries and/or left main stem stenosis, PCI has become a rival to CABG in patients with multivessel coronary artery disease or left main disease. However, the need for repeat revascularization, in-stent stenosis and thrombosis remain the achilis heal of PCI. SYNTAX trial randomized patients with left main disease and/or three-vessel disease to PCI with TAXus stent or CABG with the concept that PCI is not inferior to CABG. At 1 and 2 years follow up, MACCE was significantly increased in PCI patients mainly attributed to increased rate of repeat revascularization; however, stroke was significantly more with CABG. The composite safety endpoint of death/stroke/MI was comparable between the 2 groups. Therefore the criterion for non-inferiority was not met. What we learn from SYNTAX is that multi disciplinary team approach should be the standard of care when recommending treatment in more complex coronary artery disease. SYNTAX makes interventionists and surgeons come together, it may set the benchmark for MVD revascularization. PCI and CABG should be considered complementary rather than competitive revascularization strategies. There is no substitute for sound clinical judgment that takes into account the patient's overall clinical profile, functionality, co-morbidities, as well as the patient's coronary anatomy. The SYNTAX Score should be utilized to decide on treatment of patients with LM/MVD. Patients with low and intermediate score can be treated with PCI or CABG with equal results. Those with high score do better with CABG. SYNTAX trial showed that 66% of patients with 3VD or LMD are still best treated with CABG. In the remaining 1/3 of patients with low syntax score, PCI may be considered as an alternative to surgery. Finally, medical treatment should be optimized in patients going for CABG.

Capillary injury in the ischemic brain of hyperlipidemic, apolipoprotein B-100 transgenic mice

AIMS

Apolipoprotein B-100 (apoB-100) has been implicated in hyperlipidemia, which contributes to the pathogenesis of vascular disorders. Our aim was to investigate whether the expression of human apoB-100 in transgenic mice and/or a high-cholesterol diet cause cerebral microvascular lesions, and whether these conditions augment ischemia-related capillary damage.

MAIN METHODS

Human apoB-100 overexpressing transgenic (Tg(apoB-100), n=23) and wild-type mice (C5/B6, Wt, n=26) were supplied with standard or 2% cholesterol-enriched diet for 17-19 weeks. Cerebral ischemia was induced by unilateral common carotid artery occlusion. Cortical samples were embedded for electron microscopy. Microvascular density (number of microvascular profiles/examined area), lumen diameter, the swelling of astrocytic endfeet, the occurrence of endothelial microvilli (affected capillaries expressed as ratio of all capillaries encountered), and the ratio of intact capillaries (devoid of all the above pathology) were calculated.

KEY FINDINGS

The expression of apoB-100 coincided with decreased cortical microvascular density (195+/-7 vs. 223+/-8 vessels/mm(2), vs. Wt; P<0.008) and increased capillary lumen diameter (3.16+/-0.5 vs. 2.88+/-0.6 microm, vs. Wt; P<0.001). Cerebral ischemia promoted the swelling of perivascular astrocytes (62.1+/-4.2 vs. 36.5+/-4.0%, vs. contralateral, Wt; P<0.001), and reduced the ratio of intact capillaries (32.1+/-5.6 vs. 65.2+/-3.7%, vs. contralateral, Wt; P<0.001). Hyperlipidemia did not exacerbate the injury.

SIGNIFICANCE

The overexpression of human apoB-100 alters the density of the microvascular network and the diameter of capillaries, which may compromise cerebrovascular reactivity during ischemia.