Background and Purpose— Lymphocytes are important players in the pathophysiology of acute ischemic stroke. The interaction of lymphocytes with endothelial cells and platelets, termed thrombo-inflammation, fosters microvascular dysfunction and secondary infarct growth. FTY720, a sphingosine-1-phosphate receptor modulator, blocks the egress of lymphocytes from lymphoid organs and has been shown to reduce ischemic neurodegeneration; however, the underlying mechanisms are unclear. We investigated the mode of FTY720 action in models of cerebral ischemia. Methods— Transient middle cerebral artery occlusion (tMCAO) was induced in wild-type and lymphocyte-deficient Rag1 −/− mice treated with FTY720 (1 mg/kg) or vehicle immediately before reperfusion. Stroke outcome was assessed 24 hours later. Immune cells in the blood and brain were counted by flow cytometry. The integrity of the blood–brain barrier was analyzed using Evans Blue dye. Thrombus formation was determined by immunohistochemistry and Western blot, and was correlated with cerebral perfusion. Results— FTY720 significantly reduced stroke size and improved functional outcome in wild-type mice on day 1 and day 3 after transient middle cerebral artery occlusion. This protective effect was lost in lymphocyte-deficient Rag1 −/− mice and in cultured neurons subjected to hypoxia. Less lymphocytes were present in the cerebral vasculature of FTY720-treated wild-type mice, which in turn reduced thrombosis and increased cerebral perfusion. In contrast, FTY720 was unable to prevent blood–brain barrier breakdown and transendothelial immune cell trafficking after transient middle cerebral artery occlusion. Conclusions— Induction of lymphocytopenia and concomitant reduction of microvascular thrombosis are key modes of FTY720 action in stroke. In contrast, our findings in Rag1 −/− mice and cultured neurons argue against direct neuroprotective effects of FTY720.

BackgroundLINC complexes are nuclear envelope bridging protein structures formed by interaction of SUN and KASH proteins. They physically connect the nucleus with the peripheral cytoskeleton and are critically involved in a variety of dynamic processes, such as nuclear anchorage, movement and positioning and meiotic chromosome dynamics. Moreover, they are shown to be essential for maintaining nuclear shape.FindingsBased on detailed expression analysis and biochemical approaches, we show here that during mouse sperm development, a terminal cell differentiation process characterized by profound morphogenic restructuring, two novel distinctive LINC complexes are established. They consist either of spermiogenesis-specific Sun3 and Nesprin1 or Sun1η, a novel non-nuclear Sun1 isoform, and Nesprin3. We could find that these two LINC complexes specifically polarize to opposite spermatid poles likely linking to sperm-specific cytoskeletal structures. Although, as shown in co-transfection/immunoprecipitation experiments, SUN proteins appear to arbitrarily interact with various KASH partners, our study demonstrates that they actually are able to confine their binding to form distinct LINC complexes.ConclusionsFormation of the mammalian sperm head involves assembly and different polarization of two novel spermiogenesis-specific LINC complexes. Together, our findings suggest that theses LINC complexes connect the differentiating spermatid nucleus to surrounding cytoskeletal structures to enable its well-directed shaping and elongation, which in turn is a critical parameter for male fertility.

Thrombosis and inflammation are hallmarks of ischemic stroke still unamenable to therapeutic interventions. Highmolecular-weight kininogen (KNG) is a central constituent of the contact-kinin system which represents an interface between thrombotic and inflammatory circuits and is critically involved in stroke development. Kng Ϫ/Ϫ mice are protected from thrombosis after artificial vessel wall injury and lack the proinflammatory mediator bradykinin. We investigated the consequences of KNG deficiency in models of ischemic stroke. Kng Ϫ/Ϫ mice of either sex subjected to transient middle cerebral artery occlusion developed dramatically smaller brain infarctions and less severe neurologic deficits without an increase in infarct-associated hemorrhage. This protective effect was preserved at later stages of infarction as well as in elderly mice. Targeting KNG reduced thrombus formation in ischemic vessels and improved cerebral blood flow, and reconstitution of KNG-deficient mice with human KNG or bradykinin restored clot deposition and infarct susceptibility. Moreover, mice deficient in KNG showed less severe blood-brain barrier damage and edema formation, and the local inflammatory response was reduced compared with controls. Because KNG appears to be instrumental in pathologic thrombus formation and inflammation but dispensable for hemostasis, KNG inhibition may offer a selective and safe strategy for combating stroke and other thromboembolic diseases. (Blood. 2012;120(19): 4082-4092) IntroductionThe pathology of ischemic stroke is complex and involves a myriad of distinct molecular pathways and cellular interactions. Among these, progressive thrombus formation in the cerebral microvasculature is a key process that can cause secondary infarct growth despite successful recanalization of larger proximal brain vessels both under experimental conditions as well as in humans. 1,2 We recently identified the intrinsic coagulation cascade as a novel and safe antithrombotic target for the prevention and treatment of acute ischemic stroke. 3 Genetic depletion or pharmacologic blockade of coagulation factor XII (FXII), the origin of the intrinsic pathway, markedly reduced intracerebral thrombus formation and infarct growth in mice without increasing the risk of bleeding complications. 4,5 Clot formation was also significantly reduced in several in vitro models of thrombosis after FXII inhibition. 5 Current pathophysiologic concepts also emphasize the importance of inflammatory mechanisms in stroke. 6 The cerebral endothelium is activated early during the course of an ischemic event, leading to the up-regulation of cell adhesion molecules and successive trafficking of inflammatory cells (neutrophils, macrophages, T cells) from the blood stream into the brain parenchyma. Those cells attracted from the periphery in concert with resident cell populations (endothelial cells, microglia) secrete an array of soluble immune mediators such as cytokines and chemokines that perpetuate the inflammatory response to cause direct or indirect ti...

Telomeres fail to attach to the nuclear envelope and lose structural integrity in cells lacking SMC1β.