Gangliosides GT1b and GD3, components of keratinocyte membranes, inhibit keratinocyte adhesion to fibronectin. Although ganglioside sialylation is known to be important, the mechanism of inhibition is unknown. Using purified insect recombinant ␣ 5 and ␤ 1 proteins and ␣ 5 ␤ 1 integrin from lysed keratinocyte-derived SCC12 cells, we have shown that GT1b and GD3 inhibit the binding of ␣ 5 ␤ 1 to fibronectin. Co-immunoprecipitation of GT1b and ␣ 5 ␤ 1 from SCC12 cells and direct binding of GT1b and GD3 to affinity-purified ␣ 5 ␤ 1 from SCC12 cells and insect recombinant ␣ 5 ␤ 1 , particularly the ␣ 5 subunit, further suggest interaction between ganglioside and ␣ 5 ␤ 1 . The carbohydrate moieties of integrin appear to be critical since gangliosides are unable to bind deglycosylated forms of ␣ 5 ␤ 1 from SCC12 and insect cells or poorly glycosylated recombinant ␣ 5 ␤ 1 from Escherichia coli cells. The GT1b-␣ 5 ␤ 1 interaction is inhibited by concanavalin A, suggesting that GT1b binds to mannose structures in ␣ 5 ␤ 1 . The preferential binding of GT1b to high mannose rather than reduced mannose ovalbumin further implicates the binding of GT1b to mannose structures. These data provide evidence that highly sialylated gangliosides regulate ␣ 5 ␤ 1 -mediated adhesion of epithelial cells to fibronectin through carbohydrate-carbohydrate interactions between GT1b and the ␣ 5 subunit of ␣ 5 ␤ 1 integrin. Human keratinocyte motility on a fibronectin (FN)1 matrix is critical for the re-epithelialization of healing wounds, for the spread of cutaneous malignancy, and in cutaneous embryogenesis. Although the molecular events that influence this migration are poorly understood, the interaction between keratinocyte ␣ 5 ␤ 1 integrin and the arginine-glycine-aspartic acid (RGD) site of FN is known to be key (1). Increased expression of ␣ 5 ␤ 1 has been shown in keratinocytes at the migrating edge of wounds in vivo, in lesional skin of patients with psoriasis, and in cultured keratinocytes (2-4). Both receptor clustering on keratinocytes and ligand occupancy of ␣ 5 ␤ 1 are required to activate intracellular signal transduction components (5), including focal adhesion kinase, phosphatidylinositol 3-kinase, protein kinase C, and integrin-linked kinase, leading to cell adhesion to .Gangliosides are glycosphingolipids characterized by the presence of one or more sialic acid moieties in the oligosaccharide chain (9). The role of gangliosides, which are localized to the outer leaflet of the plasma membrane of eukaryotic cells, is largely unknown, but studies with cultured keratinocytes and keratinocyte-derived cells suggest that gangliosides are involved in regulating cellular proliferation, differentiation, and adhesion (10 -13). The discovery that gangliosides inhibit cell attachment and spreading on a FN matrix (14) led investigators to consider gangliosides to be the cell receptors for FN before integrin ␣ 5 ␤ 1 was identified (15,16). Although these early studies showed that the terminal sialic acid residues of gangliosides were critica...

Whereas previous investigations have shown that pharmacologic addition of gangliosides inhibits keratinocyte proliferation by downregulating epidermal growth factor receptor phosphorylation, the underlying biochemical basis and physiologic relevance are unknown. Using Scatchard and displacement plots, we have shown that supplemental purified gangliosides decrease the binding of (125)I-labeled epidermal growth factor to keratinocyte-derived SCC12 cells. Conversely, SCC12 cells transfected with sialidase and thus depleted of gangliosides show increased ligand binding to the epidermal growth factor receptor, which is consistent with their increased proliferation in response to epidermal growth factor and transforming growth factor-alpha, and increased phosphorylation of the epidermal growth factor receptor, and downstream signal transduction pathway components. The mechanism of the altered binding appears to involve primarily decreased numbers of available receptors within the intact membrane, but not altered receptor protein expression. These studies provide evidence that the effect of gangliosides on keratinocyte proliferation results, at least in part, from the direct binding of ganglioside to the receptor and disruption of the receptor-ligand interaction. Manipulation of membrane ganglioside content may be a powerful new means to alter epidermal growth factor receptor-dependent cell proliferation.

Our results suggest that venovenous extracorporeal membrane oxygenation can provide a safe and effective alternative to lung-protective mechanical ventilation in carefully selected patients. This approach facilitates participation in physical therapy and avoids complications associated with mechanical ventilation.

These data confirm that impaired CBF autoregulation is prevalent during CPB predisposing affected patients to brain hypoperfusion or hyperperfusion with low or high blood pressure, respectively. Small vessel, but not large vessel, cerebral vascular disease, male sex, and higher average body temperature during CPB appear to be associated with impaired autoregulation.

Purpose of Review: Central pulse pressure, a marker of vascular stiffness, is a novel indicator of risk for perioperative morbidity including ischemic stroke. Appreciation for the mechanism by which vascular stiffness leads to organ dysfunction along with understanding its clinical detection may lead to improved patient management. Recent Findings: Vascular stiffness is associated with increased mortality and neurologic, cardiac and renal injury in non-surgical and surgical patients. Left ventricular hypertrophy and diastolic dysfunction along with microcirculatory changes in the low vascular resistance, high blood flow cerebral and renal vasculature are seen in patients with vascular stiffness. Pulse wave velocity and the augmentation index have higher sensitivity for detecting of vascular stiffness than peripheral pulse pressure as the hemodynamic consequences of vascular stiffness are secondary to alterations in the central vasculature. Vascular stiffness alters cerebral autoregulation resulting in a high likelihood of having a lower limit of autoregulation > 65 mmHg during surgery. Vascular stiffness may predispose to cerebral hypoperfusion increasing vulnerability to ischemic stroke, postoperative delirium, and acute kidney injury. Summary: Vascular stiffness leads to alterations in cerebral, cardiac, and renal hemodynamics increasing the risk of perioperative ischemic stroke and neurologic, cardiac and renal dysfunction.