Peripheral Endothelial Cells Research Articles

Oxygen Delivery and Uptake by Peripheral Tissues: Physiology and Pathophysiology

When oxygen availability to tissues becomes limited, several mechanisms interact to maintain a supply-independent O2 uptake by tissues. Among tissues, adrenergic vasoconstriction prevents a vascular steal of a limited O2 supply by tissues with low metabolic demands. Within tissues, increases in perfused capillary density facilitate an increase in the extraction ratio for oxygen ([CaO2-CvO2]/CaO2). Factors that disrupt the physiologic balance between sympathetic-mediated vasoconstriction and local metabolic vasodilation may impair the ability of the organism to adjust the regional extraction of oxygen in response to changes in O2 delivery, resulting in a pathologic dependence of O2 uptake on supply. Patients with ARDS have demonstrated such an O2 extraction defect, although the mechanism is not fully understood. Although a tissue mitochondrial abnormality could explain these findings, experimental studies of endotoxemia and bacteremia demonstrate a peripheral O2 extraction defect similar to that seen in patients. This defect has been found at the whole body level and within intestine, but not within skeletal muscle. Evidence points to a defect in microvascular control as the mechanism responsible for the defect. Other evidence suggests that damaged peripheral endothelial cells may mediate the loss of vascular control. Hence, in patients with ARDS a damaged endothelium in the pulmonary circulation contributes to the lung edemagenesis, and damaged peripheral endothelium may mediate the defect in microvascular control, leading to the pathologic dependence of oxygen uptake on delivery.

Differential regulation of lipopolysaccharide-induced interleukin 1 and tumor necrosis factor synthesis: effects of endogenous and exogenous glucocorticoids and the role of the pituitary-adrenal axis.

Intraperitoneal injection of a sublethal dose of lipopolysaccharide (LPS) into mice resulted in the appearance of tumor necrosis factor (TNF) in the serum within 45 min. Maximal serum TNF was detected by 1 h, and by 3-4 h TNF levels were no longer significantly above baseline. Injection of mice with an additional dose of LPS at 4 h resulted in no further increase in serum TNF. The in vivo kinetics of TNF appearance correlated with in vitro studies in which TNF mRNA was detected in murine peritoneal macrophages 30 min after LPS stimulation. The increase in serum TNF was not detected in mice treated with dexamethasone, 3 mg/kg, prior to LPS stimulation. The decrease in TNF correlated with the appearance of significant amounts of endogenous serum corticosterone which were maximal by 3 h. Further evidence for the role of endogenous steroids in the modulation of serum TNF levels was obtained in studies with adrenalectomized or hypophysectomized mice. Compared to sham-operated animals, serum TNF levels remain elevated 5 h post LPS stimulation in adrenalectomized or hypophysectomized mice. In contrast with the transient increase in TNF, serum IL 1 was maximal 4 h post LPS injection and remained elevated at 24 h. In vitro studies with primary cultures of human peripheral blood monocytes and human umbilical cord vein endothelial cells demonstrated that LPS-induced monocyte IL 1 levels were reduced approximately 5-fold by 10(-7) M dexamethasone while dexamethasone had only minimal effects on endothelial cell IL 1. Therefore, the in vitro data would suggest that the maintenance of elevated IL 1 levels coincident with the appearance of endogenous corticosteroids during LPS shock is related to the synthesis of IL 1 by both monocyte-macrophages and non-myeloid cell populations including endothelial cells.

The role of interstitial collagens in cleft formation of mouse embryonic submandibular gland during initial branching.

An interstitial collagenase was purified from the explant medium of bovine dental pulp and was shown to degrade collagens I and III but not IV and V. The enzyme halted cleft initiation in the epithelium of 12-day mouse embryonic submandibular glands in vitro, indicating the active involvement of interstitial collagens in the branching morphogenesis. Transmission electron microscopic observation of the intact 12-day gland without any clefts showed the scattered localization of a few collagen fibrils at the epithelial-mesenchymal interface of the bulb and also revealed the presence of numerous microfibrils around the stalk. Collagen bundles were regularly seen close to the wavy basal lamina at the bottom of clefts of the intact 13-day gland and 12-day gland cultured for 17 h under normal conditions. Mesenchymal cells were found in the clefts together with the frequent localization of peripheral nerve fibres and capillary endothelial cells. The collagen bundles were more often observed in the 12-day gland cultured in the presence of bovine dental pulp collagenase inhibitor, which had been shown to enhance cleft formation. In contrast, collagen fibrils were rarely found at the epithelial-mesenchymal interface of the 12-day gland cultured in the presence of Clostridial or bovine dental pulp collagenase. The findings indicated that the formation of interstitial collagen bundles is essential to form clefts in the epithelium both in vivo and in vitro.

Characterization and use of polyclonal antibody to Na+,K+-ATPase: immunocytochemical localization in salt glands of the duck.

The amount of Na+,K+-ATPase of the avian salt gland increased concomitantly with plasma membrane surface area during salt feeding of ducklings (adaptation), and both enzyme content and membrane surface area decreased upon return to fresh water (deadaptation). In a further study of the enzyme, a marker for plasma membrane biogenesis, polyvalent antibodies were raised to the denatured alpha-subunit of the purified ATPase. Antisera did not inhibit enzymatic activity but immunoprecipitated the phosphorylated intermediate of the alpha-subunit. Furthermore, the alpha-subunit, which was not glycosylated, was immunoprecipitated from homogenates of tissue slices metabolically labelled with [35S]-methionine, using antisera raised against either duck salt gland or dog kidney alpha-subunit. The former antisera also recognized the alpha-subunit in the brain, heart, kidney, liver, intestine and skeletal muscle of the duck. Immunocytochemistry with the antisera raised to the duck salt gland alpha-subunit revealed reaction at basolateral as well as apical plasma membrane in the duck salt gland principal cells, with essentially no deposits on peripheral cells, fibroblasts, erythrocytes, endothelial cells and neural elements. Within the principal cells, immunolabelling was also detected on small vesicles, multivesicular bodies and lysosomes; deposits on extracellular debris and vesicles in the lateral and lumenal spaces were also apparent. The labelling patterns were qualitatively but not quantitatively similar in salt glands of control, adapted and deadapted ducklings, and are discussed in the context of a model for plasma membrane biogenesis and turnover in which degradative events may play a major role.

Meta-vinculin distribution in adult human tissues and cultured cells

Meta-vinculin distribution in adult human tissue was studied by immunoblotting technique. Meta-vinculin was found in smooth (aorta wall and myometrium) and cardiac muscle, rather than in skeletal muscle, liver, kidney and cultured cells - macrophages, foreskin fibroblasts, peripheral blood lymphocytes and vascular endothelial cells. In the primary culture of smooth muscle cells from human aorta the meta-vinculin/vinculin ratio was reduced, and on the onset of cell division meta-vinculin could hardly be detected. Subcultured smooth muscle cells from human aorta did not contain meta-vinculin. The data show that the presence of meta-vinculin is characteristic of'contractile' smooth muscle cells rather than of proliferating in vitro.

Changes of serum angiotensin-converting enzyme activity during treatment of patients with Graves' disease.

Serum angiotensin-converting enzyme activity was measured spectrophotometrically, and serum thyrotropin-binding-inhibitory immunoglobulin (TBII) activity was measured by radioreceptor assay in normal subjects and in patients with Graves’ disease serially before and during treatment, and these activities were compared with each other and with thyroid hormone levels in various thyroid functional status. Correlation between serum angiotensin-converting enzyme activity and serum thyroid hormone level was pursued with relation to the changes of thyroid functional status in patients with Graves’ disease during treatment.Serum angiotensin-converting enzyme activity was significantly elevated in patients with hyperthyroid Graves’ disease before the start of treatment (35 ± 13 nmol/min/ml, n=50), and not in patients with Graves’ disease, euthyroid state during treatment with antithyroid drugs or radioactive iodine (23 ± 9 nmol/min/ml, n=12), but decreased significantly in patients with Graves’ disease, hypothyroid state transiently during treatment (15 ± 4 nmol/min/ml, n=12), respectively in comparison with normal control subjects. Serum angiotensin-converting enzyme activity was positively correlated with the log value of serum T3 concentration (r=0.62, p<0.001, n=95), and with the log value of free thyroxine index (r=0.66, p<0.001, n=91) but not statistically significantly with serum TBII activity. Serum angiotensin-converting enzyme activity was followed in 11 patients with initially increased activity and the activity decreased in proportion to serum thyroid hormone level during treatment, irrespective of treatment modality. It is suggested that thyroid hormones play a role in the increase and decrease of serum angiotensin-converting enzyme activity directly or indirectly influencing the peripheral tissues (probably reticuloendothelial cells or peripheral endothelial cells) in patients with Graves’ disease.

Lymphocyte Traffic and the Skin

Lymphocyte migration patterns into and within lymphoid organs and nonlymphoid organs such as the skin as highly regulated and controlled by a variety of factors, some of which we are beginning to understand at a basic cellular and molecular level. In the case of lymphocyte migration into lymphoid organs, recirculatory patterns and preferences appear to be mediated by selective recognition via lymphocyte membrane receptors of distinctive determinants expressed by specialized endothelial cells in different organ sites. A similar model in which endothelial cells in the skin share common determinants with endothelial cells in peripheral lymph nodes can be developed to explain the migration patterns of lymphocytes from the blood into the skin. Cells that have undergone blast transformation in the microenvironment of the skin or peripheral lymph nodes, or both, appear to recirculate selectively within this particular sphere of immunologic influence, whereas other cells that undergo this transformation in the microenvironment of the gastrointestinal tract and its draining mesenteric lymph nodes selectively recirculate within that sphere of immunologic influence. This preferential recirculation increases the probability that the immunologic defense needs of a given region or tissue such as the skin will be met efficiently and appropriately. Finally, some of the phenotypic characteristics favoring the movement of lymphocytes from the bloodstream into the dermis (such as recent stimulation and the presence of T-cell surface markers) also seem to favor lymphocyte migration into or retention in the epidermis. However, under appropriate circumstances, epidermotropism can be exhibited by both major subsets of T cells as well as a variety of non-T cells.

Cell surface glycosaminoglycans in normal and leukemic leukocytes

The intracellular and extracellular glycosaminoglycans (GAGs) of peripheral leukocytes in normal subjects and leukemic patients were characterised by electrophoresis and enzyme sensitivity. Normal peripheral granulocytes (PMN) are very rich in trypsin removable surface GAGs, while none are present on the surface of leukemic cells in acute myeloid leukemia. The intracellular and extracellular GAGs have also been analysed in the pig and compared to normal pig bone marrow haematopoietic cells. Mesenchymal cells cultured in vitro from marrow matrix and peripheral endothelial cells have also been studied. The results suggest that the exposure of cell surface chondroitin sulphate A is an important step involved in the peripheralisation of PMN.

HLA-D region products are expressed in endothelial cells.

The mixed lymphocyte endothelial cell culture was studied by the primed lymphocyte typing (PLT) technique. By comparing the HLA-D/DR specificity of the secondary response when using either peripheral blood mononuclear cells (PBM) or endothelial cells from umbilical cords for priming or restimulation of lymphocytes, it was found that PBM from newborn would induce a clear-cut specificity for HLA-D/DR when used for priming a well a for restimulation. No HLA-D/DR specificity was seen, however, when endothelial cells were used for restimulation of lymphocytes primed to HLA-D/DR on PBM. On the other hand, lymphocytes primed to endothelial cells showed significant, albeit not very strong specificity for HLA-D/DR when restimulated with PBM. Our experiments suggest that HLA-D region products are present on endotheial cells, and thus confirm and extend serological studies using anti DR antisera.