Caveolae are plasma membrane invaginations that may play an important role in numerous cellular processes including transport, signaling, and tumor suppression. By targeted disruption of caveolin-1, the main protein component of caveolae, we generated mice that lacked caveolae. The absence of this organelle impaired nitric oxide and calcium signaling in the cardiovascular system, causing aberrations in endothelium-dependent relaxation, contractility, and maintenance of myogenic tone. In addition, the lungs of knockout animals displayed thickening of alveolar septa caused by uncontrolled endothelial cell proliferation and fibrosis, resulting in severe physical limitations in caveolin-1-disrupted mice. Thus, caveolin-1 and caveolae play a fundamental role in organizing multiple signaling pathways in the cell.

Activation of the transcription factor nuclear factor-B (NF-B) has been suggested to participate in chronic disorders, such as diabetes and its complications. In contrast to the short and transient activation of NF-B in vitro, we observed a long-lasting sustained activation of NF-B in the absence of decreased IB␣ in mononuclear cells from patients with type 1 diabetes. This was associated with increased transcription of NF-Bp65. A comparable increase in NF-Bp65 antigen and mRNA was also observed in vascular endothelial cells of diabetic rats. As a mechanism, we propose that binding of ligands such as advanced glycosylation end products (AGEs), members of the S100 family, or amyloid-␤ peptide ( T issue culture models of cellular activation provide easily accessible systems for detailed analysis of mechanisms potentially underlying the pathogenesis of human disease. However, the time course of such in vitro models is usually significantly abbreviated, limited to hours to days, compared with the pace of disorders under study in vivo. This indicates the importance of seeking out mechanisms in cell culture that might bridge the gap that accounts for the chronicity of cellular perturbation observed in the intact organism.The transcription factor nuclear factor-B (NF-B) has been proposed as a critical bridge between oxidant stress and gene expression (1-8). Exposure of cells to inflammatory, infectious, or other stressful stimuli results in rapid phosphorylation and degradation of IB␣ and the subsequent release and translocation of NF-B into the nucleus (1-11). This mechanism ensures quick and finely tuned cellular responses in the absence of de novo protein synthesis. Because transcription of IB␣ is positively autoregulated by NF-B (9 -11), activation of NF-B is usually self-terminated within minutes to hours (1-11). Such a scenario lends itself to analysis by short-term in vitro studies in which stimulus-induced responses are transient and the system returns to the baseline state over hours. Consequently, induction of NF-B and enhanced transcription of its target genes in vitro have been studied mainly in the setting of acute cellular responses.Reactive oxygen intermediates are generated by processes that occur over seconds. However, increasing evidence suggests a role for oxidative stress in chronic degenerative diseases such as atherosclerosis (1,6,12,13), diabetes (14 -16), and Alzheimer's disease (17)(18)(19). This indicates the relevance of signal transduction systems such as NF-B, which are capable of transforming the appearance and disappearance of short-lived oxygen free radicals into more sustained signals for cellular activation

Tissue factor, a member of the cytokine-receptor superfamily and high-affinity receptor and cofactor for plasma factor VII/VIIa (ref. 1), is the primary cellular initiator of blood coagulation. It is involved in thrombosis and inflammation associated with sepsis, atherosclerosis and cancer, and can participate in other cellular processes including intracellular signalling, metastasis, tumor-associated angiogenesis, and embryogenesis. Here we report that inactivation of the tissue factor gene (TF) results in abnormal circulation from yolk sac to embryo beyond embryonic day 8.5, leading to embryo wasting and death. Vitelline vessels from null mice were deficient in smooth-muscle alpha-actin-expressing mesenchymal cells, which participate in organization of the vessel wall. This implies that tissue factor has a role in blood vessel development.

While the initiation of the adaptive and innate immune response is well understood, less is known about cellular mechanisms propagating inflammation. The receptor for advanced glycation end products (RAGE), a transmembrane receptor of the immunoglobulin superfamily, leads to perpetuated cell activation. Using novel animal models with defective or tissue-specific RAGE expression, we show that in these animal models RAGE does not play a role in the adaptive immune response. However, deletion of RAGE provides protection from the lethal effects of septic shock caused by cecal ligation and puncture. Such protection is reversed by reconstitution of RAGE in endothelial and hematopoietic cells. These results indicate that the innate immune response is controlled by pattern-recognition receptors not only at the initiating steps but also at the phase of perpetuation. IntroductionThe adaptive and the innate immune systems are both capable of initiating inflammation. The two are interconnected at several levels, including the synthesis and action of cytokines, molecules regulating cell-cell interactions, and the activation of transcription factors (1-9). While the molecular events leading to activation of the immune response are well understood, less is known about factors that perpetuate inflammation. One mechanism considered central in the cross-talk between the innate and adaptive immune systems is the redox-dependent activation of the transcription factor NF-κB (1, 4, 9-13). Members of the NF-κB family control the initiation of inflammation by regulating expression of leukocyte adhesion molecules, cytokines, and other factors (10-13), but are also central in terminating inflammation (14)(15)(16)(17)(18). This leaves unanswered the question of the perpetuation of inflammation of the adaptive and innate immune responses.Recently, studies of the receptor for advanced glycation end products (RAGE) (19-23), a member of the immunoglobulin superfamily (23) whose gene is located in the vicinity of the MHC

While the initiation of the adaptive and innate immune response is well understood, less is known about cellular mechanisms propagating inflammation. The receptor for advanced glycation end products (RAGE), a transmembrane receptor of the immunoglobulin superfamily, leads to perpetuated cell activation. Using novel animal models with defective or tissue-specific RAGE expression, we show that in these animal models RAGE does not play a role in the adaptive immune response. However, deletion of RAGE provides protection from the lethal effects of septic shock caused by cecal ligation and puncture. Such protection is reversed by reconstitution of RAGE in endothelial and hematopoietic cells. These results indicate that the innate immune response is controlled by pattern-recognition receptors not only at the initiating steps but also at the phase of perpetuation. IntroductionThe adaptive and the innate immune systems are both capable of initiating inflammation. The two are interconnected at several levels, including the synthesis and action of cytokines, molecules regulating cell-cell interactions, and the activation of transcription factors (1-9). While the molecular events leading to activation of the immune response are well understood, less is known about factors that perpetuate inflammation. One mechanism considered central in the cross-talk between the innate and adaptive immune systems is the redox-dependent activation of the transcription factor NF-κB (1, 4, 9-13). Members of the NF-κB family control the initiation of inflammation by regulating expression of leukocyte adhesion molecules, cytokines, and other factors (10-13), but are also central in terminating inflammation (14)(15)(16)(17)(18). This leaves unanswered the question of the perpetuation of inflammation of the adaptive and innate immune responses.Recently, studies of the receptor for advanced glycation end products (RAGE) (19-23), a member of the immunoglobulin superfamily (23) whose gene is located in the vicinity of the MHC