Chemoattractant Substances Research Articles

Laminin promotes the oxidative burst in human neutrophils via increased chemoattractant receptor expression.

The extracellular matrix component, laminin, enhances the chemotactic responsiveness of polymorphonuclear leukocytes (PMN) in vitro, and low doses of chemoattractant substances augment the expression of PMN cell surface receptors for laminin. This study determined whether laminin acts in concert with chemoattractants to activate PMN. Laminin (5 to 100 micrograms/ml) stimulated lysozyme release and superoxide production in response to the chemoattractant, FMLP by as much as 69%. These results could be explained by changes in cell surface chemoattractant receptor expression in that incubation of normal PMN with laminin (5 to 75 micrograms/ml) increased the binding of 19 nM FML[3H]P by 35 to 80%. This corresponded to as much as a 2.5-fold increase in the number of chemoattractant receptors/cells which had a lower average affinity. Laminin did not change the number or affinity of FML[3H]P receptors present on organelle-depleted PMN cytoplasts, and the laminin-induced increase in FML[3H]P receptors expressed on PMN from a patient with a specific granule deficiency was only 11 to 21% of that seen in normal PMN. These findings suggest that chemoattractants augment the expression of laminin receptors which mediate PMN attachment to basement membranes, followed by laminin-induced increases in the expression of cryptic chemoattractant receptors contained in intracellular granules, with resultant augmentation of the oxidative burst.

Bovine uterine defense mechanisms: a review.

Bovine uterine defense mechanisms during physiological and pathological conditions have been reviewed in this article. The initial uterine defense against bacterial infection is phagocytosis by uterine leucocytes (mainly neutrophils). The reported literature showed that very little work has been done on immunoglobulins and their role in the bovine uterine defense mechanisms; however, some investigators have found a positive correlation between gamma-globulin and the development of uterine infection after calving. Many explanations exist for the difference in susceptibility of the uterus to infection during the different phases of estrous cycle; however, most of the reports agreed that the uterine defense mechanism is inadequate during diestrus. The abnormal puerperium effects uterine defense mechanisms adversely and prolongs the time to complete uterine involution. Future treatment may utilise natural antimicrobial substances such as proteins or peptides derived from PMN, chemoattractant substances such as E. coli lipopolysaccharide or a bacteria-free filtrate of streptococci. Specific hyperimmunserum could also be used as opsonin for refractory cases of uterine bacterial infections.

Ultrastructural evidence of directed cell migration during initial cementoblast differentiation in root formation.

Root formation in 14‐day‐old Sprague‐Dawley rats was studied by light and electron microscopy. Special attention was focused on initial cementoblast differentiation. Disruption of the epithelial root sheath appears to be a consequence of directed cell migration by cells of the dental follicle proper which undergo differentiation into precementoblasts. Precementoblasts rapidly develop polarity towards the dentin, exhibiting major cytoplasmic processes rich in cytoplasmic filaments. These processes grow toward and eventually contact the dentin matrix. It is suggested that the cells of the dental follicle proper are cementoblast precursors which respond to chemoattractant substances released from newly deposited dentin matrix‐ and/or basal lamina‐associated material of root sheath origin.

Chemotactic peptides. Mechanisms, functions, and possible role in inflammatory bowel disease.

An important component of host defenses is the ability of inflammatory cells to detect and respond to minute concentrations of chemoattractant substances. Chemotactic peptides elaborated by both bacteria and leukocytes are the focus of this review. These peptides induce directed migration of inflammatory cells towards their targets, and stimulate biological functions including degranulation, release of oxygen radicals, phagocytosis, and eicosanoid production. Among the released eicosanoids, leukotriene B4 potentiates the leukocyte response. As with other chemotactic factors, these functions are regulated partially through differential coupling to high- and low-affinity receptors and via calcium as the second messenger. Some chemotactic peptides are elaborated by normal colonic luminal bacteria. Recent evidence demonstrates that these peptides can produce mucosal inflammation in vivo. A possible mechanism for this effect involves abnormal colonic permeability in susceptible individuals that allows bacterial chemotactic peptides access to the mucosa where they may induce inflammation. Remaining questions include the mechanism by which the mucosal barrier is breached and the role of leukotrienes in the potentiation of colonic inflammation.

Chemotactic response of a gliding mycoplasma

Mycoplasma sp. nov. strain 163K, the gliding microorganism isolated from the gills of a tench (Tinca tinca L.), is capable of chemotaxis, being attracted to sugars, amino acids, and mucus. The chemotactic behavior of the organisms was microscopically investigated and documented by long-time exposure photomicrographs providing motility tracks. In diffusion-generated concentration gradients of chemoattractive substances, the random motion of the mycoplasmas was strongly biased in the direction of increasing attractant concentrations.

Macrophage-like tumor cells as tools to study chemoattractive activity.

Macrophage-like tumor cells can be obtained in large quantities as rather homogeneous populations, making these cells useful for chemotaxis assays. Therefore, macrophage-like cells J774A, WEHI-3, P388D1, IC-21, and NCTC 1469, all of murine origin, and U937 of human origin, were tested for chemotactic activity to a number of chemoattractive agents, such as casein, an N-formyl tetrapeptide (N-formyl-L-norleucyl-L-leucyl-L-phenylalanyl-L-tyrosine), and culture supernatants of murine SL2 lymphoma cells. J774A and WEHI-3 macrophage-like cells of murine (BALB/c) origin expressed the strongest chemotactic activity to casein and N-formyl tetrapeptide, respectively. The results show that: very standardized chemotaxis assays can be performed using these cell lines; these assays require appropriate cell line-stimulus combinations; there are substantial differences among cell lines as to sensitivity to various chemoattractive substances; macrophage cell lines and functional mutants may be helpful for the study of receptors for chemotaxins and the study of transducer signals for chemotaxis.

Bovine and human endothelial cell production of neutrophil chemoattractant activity in response to components of the angiotensin system.

Although there is growing evidence that angiotensin II affects macrophage-mediated inflammatory responses, it is unclear whether it can affect neutrophil-mediated inflammatory responses. Because vascular endothelial cells are capable of releasing neutrophil chemoattractant activity, we attempted to determine whether components of the angiotensin system could affect neutrophil-mediated responses indirectly by stimulating endothelial cells to release neutrophil chemoattractant substances. Cultured bovine and human endothelial cells incubated with angiotensin II released neutrophil chemoattractant activity. This activity appeared within 1 minute of exposure to angiotensin II, and was blocked by saralasin, an angiotensin II antagonist. Angiotensin I also caused release of neutrophil chemoattractant activity, but its effect required conversion to angiotensin II. Bradykinin, another substrate for angiotensin-converting enzyme, did not stimulate appearance of chemoattractant. Chemoattractant generation was not inhibited by indomethacin but was blocked by diethylcarbamazine and 5,8,11,14-eicosatetraynoic acid. This study demonstrates that angiotensin II may influence neutrophil accumulation, via production of neutrophil chemoattractant activity by vascular endothelial cells.

Importance of fibroblast chemotaxis in wound healing and tumor cell evasion

Fibroblast are responsible for the synthesis of the structural proteins of the connective tissue. A further property of these cells, their migratory ability, could be analyzed in the last years. A special form of migration is chemotaxis, which can be quantitatively measured in a modified Boyden chamber in-vitro. Using this method chemoattractive substances could be characterized, which are able to stimulate fibroblasts and tumorcells to chemotactic migration. Furthermore it could be proved, that benign and transformed cell lines react in a different manner towards these chemoattractive substances. The in-vitro results allow some hypotheses about both fibroblast migration in wound healing or chronic inflammation, and the mechanisms of tumor cell evasion in the tumor surrounding tissue or the metastasizing process in other organs.

In vivo evidence for the chemotactic activity of cyclooxygenase- and lipoxygenase-dependent compounds using a corneal implantation technique.

Cyclooxygenase- and lipoxygenase-dependent compounds of arachidonic acid were studied in a corneal implantation technique concerning their chemotactic activity for polymorphonuclear leukocytes. Arachidonic acid, prostaglandins A1, A2, B2, I2, thromboxane A2 and leukotriene D4 showed no activity, whereas leukotriene B4 was the most potent chemoattractant substance for polymorphonuclear leukocytes, followed by 5-HETE, prostaglandins E2 and E1. This gives evidence for the decisive role of some prostaglandins and leukotrienes in inflammation in general, and in corneal inflammatory processes in special.