Stroke: a double-edged sword for cleaving clots?

Plasminogen Activator Inhibitor-1 Activity in Type 2 Diabetes

Background— Plasminogen activator inhibitor (PAI)-1, a key regulator of fibrinolysis, is associated with increased risk of coronary heart disease (CHD) and is a potential therapeutic target for CHD. However, the relationship between PAI-1 and the most common diabetic microvascular complication, retinopathy, is unclear. The purpose of this study was to assess the relationship between PAI-1 activity and both retinopathy and CHD in type 2 diabetes.

Methods and Results— We determined PAI-1 activity and both retinopathy (assessed by masked grading of 3-field retinal photographs) and CHD status (assessed by ECG and standard questionnaires) in 147 men and women with type 2 diabetes, mean age (SD) 64 (7) years, in a cross-sectional setting. Plasma PAI-1 activity was inversely associated with prevalent retinopathy ( P =0.006) and severity of retinopathy ( P =0.022), and was associated with lower risk of diabetic retinopathy, independent of major retinopathy risk factors (duration of diabetes and HbA1c) and determinants of PAI-1 (obesity and triglyceride level) (OR 0.74 [0.60 to 0.92], P =0.006). Conversely, higher plasma PAI-1 activity was independently associated with greater risk of CHD, after adjusting for the major CHD risk factors and determinants of PAI-1 (OR 1.31 [1.06 to 1.62], P =0.001).

Conclusion— These data support mounting evidence that a higher PAI-1 plasma level is independently associated with a lower risk of retinopathy but a higher risk of CHD in type 2 diabetes.

Reduction of excitotoxicity and associated leukocyte recruitment by a broad‐spectrum matrix metalloproteinase inhibitor

An important step in the cascade leading to neuronal cell death is degradation of laminin and other components of the brain extracellular matrix by microglia-derived proteases. Excitotoxic cell death of murine hippocampal neurones in vivo can be prevented by inhibitors of tissue plasminogen activator (tPA) or by inhibitors of plasmin. Plasmin is a potent activator of the matrix metalloproteinases (MMPs), which are made by resident and recruited leukocytes following CNS injury. In this study, we show, using Taqman RT-PCR, that MMP mRNAs, but not other calcium-dependent proteases such as calpain mRNAs, are acutely up-regulated after an excitotoxic challenge in vivo. alpha(2)-antiplasmin or BB-3103, a broad-spectrum inhibitor of the MMPs, co-injected with kainic acid into the striatum, inhibits excitotoxic cell death in the rat striatum, and reduces both the number of recruited macrophages and the size of the lesion. We also show that leukocyte populations differentially express MMPs, which may account, in part, for the expression profile we observe in the challenged brain. Our results show that inhibition of the MMPs in the rat will prevent kainic acid-induced cell death in the brain. These studies suggest that MMP inhibitors have therapeutic potential for use in stroke, and support the increasing evidence that microglial activation may contribute to neuronal cell death.

Changes in spinal cord regenerative ability through phylogenesis and development: lessons to be learnt

Lower vertebrates, such as fish and amphibians, and developing higher vertebrates can regenerate complex body structures, including significant portions of their central nervous system. It is still poorly understood why this potential is lost with evolution and development and becomes very limited in adult mammals. In this review, we will discuss the current knowledge on the cellular and molecular changes after spinal cord injury in adult tailed amphibians, where regeneration does take place, and in developing chick and mammalian embryos at different developmental stages. We will focus on the recruitment of progenitor cells to repair the damage and discuss possible roles of changes in early response to injury, such as cell death by apoptosis, and of myelin-associated proteins, such as Nogo, in the transition between regeneration-competent and regeneration-incompetent stages of development. A better understanding of the mechanisms underlying spontaneous regeneration of the spinal cord in vivo in amphibians and in the chick embryo will help to devise strategies for restoring function to damaged or diseased nervous tissues in mammals.

Molecular mechanisms of ischemic neuronal injury

Brain ischemia triggers a complex cascade of molecular events that unfolds over hours to days. Identified mechanisms of postischemic neuronal injury include altered Ca(2+) homeostasis, free radical formation, mitochondrial dysfunction, protease activation, altered gene expression, and inflammation. Although many of these events are well characterized, our understanding of how they are integrated into the causal pathways of postischemic neuronal death remains incomplete. The primary goal of this review is to provide an overview of molecular injury mechanisms currently believed to be involved in postischemic neuronal death specifically highlighting their time course and potential interactions.