An indirect bioluminescence method for the quantitative measurement of polymorphonuclear cell chemotaxis

β2-Integrins – Regulatory and Executive Bridges in the Signaling Network Controlling Leukocyte Trafficking and Migration

Leukocyte trafficking is an essential process of immunity, occurring as leukocytes travel within the bloodstream and as leukocyte migration within tissues. While it is now established that leukocytes can utilize the mesenchymal migration mode or amoeboid migration mode, differences in the migratory behavior of leukocyte subclasses and how these are realized on a molecular level in each subclass is not fully understood. To outline these differences, first migration modes and their dependence on parameters of the extracellular environments will be explained, as well as the intracellular molecular machinery that powers migration in general. Extracellular parameters are detected by adhesion receptors such as integrins. β2-integrins are surface receptors exclusively expressed on leukocytes and are essential for leukocytes exiting the bloodstream, as well as in mesenchymal migration modes, however, integrins are dispensable for the amoeboid migration mode. Additionally, the balance of different RhoGTPases – which are downstream of surface receptor signaling, including integrins – mediate formation of membrane structures as well as actin dynamics. Individual leukocyte subpopulations have been shown to express distinct RhoGTPase profiles along with their differences in migration behavior, which will be outlined. Emerging aspects of leukocyte migration include signal transduction from integrins via actin to the nucleus that regulates DNA status, gene expression profiles and ultimately leukocyte migratory phenotypes, as well as altered leukocyte migration in tumors, which will be touched upon.

Transmigration and phagocytosis of macrophages in an airway infection model using four-dimensional techniques

During infection, recruited phagocytes transmigrate across the epithelium to remove the pathogens deposited on the airway surface. However, it is difficult to directly observe cellular behaviors (e.g., transmigration) in single-cell layer cultures or in live animals. Combining a three-dimensional (3D) cell coculture model mimicking airway infection with time-lapse confocal imaging as a four-dimensional technique allowed us to image the behaviors of macrophages in 3D over time. The airway infection model was moved to a glass-bottomed dish for live-cell imaging by confocal laser scanning microscopy. Using time-lapse confocal imaging, we recorded macrophages transmigrating across the polyethylene terephthalate (PET) membrane of the inserts through the 5-μm pores in the PET membrane. Macrophages on the apical side of the insert exhibited essentially three types of movements, one of which was transmigrating across the epithelial cell monolayer and arriving at the surface of monolayer. We found that adding Staphylococcus aureus to the model increased the transmigration index but not the transmigration time of the macrophages. Only in the presence of S. aureus were the macrophages able to transmigrate across the epithelial cell monolayer. Apical-to-basal transmigration of macrophages was visualized dynamically. We also imaged the macrophages phagocytizing S. aureus deposited on the surface of the monolayer in the airway infection model. This work provides a useful tool to study the cellular behaviors of immune cells spatially and temporally during infection.

Sensitive determination of cell number using the CyQUANT cell proliferation assay

We describe here the development and characterization of the CyQUANT cell proliferation assay, a highly sensitive, fluorescence-based microplate assay for determining numbers of cultured cells. The assay employs CyQUANT GR dye, which produces a large fluorescence enhancement upon binding to cellular nucleic acids that can be measured using standard fluorescein excitation and emission wavelengths. The fluorescence emission of the dye-nucleic acid complexes correlated linearly with cell number over a large range using a wide variety of cell types. Under the recommended assay conditions, standard curves were linear (r(2)>0.995), detecting as few as 10-50 cells and as many as 25,000-50,000 cells with a single dye concentration, depending on cell type. Increasing the dye concentration extended the linear range of the assay to 100,000-250,000 cells. Results of cell proliferation and growth inhibition studies with the assay were similar to those obtained in published studies using other standard assays. CyQUANT assay measurements of serum-stimulated cell proliferation correlated well with measurements made using [3H]-thymidine. Also, the assay was used to analyze cellular DNA or RNA content, with the addition of a nuclease digestion step to the protocol. The assay procedure is simple and convenient, with no wash steps, and is readily amenable to automation.

The effect of cefodizime on phagocyte function in non-patient volunteers and patients with chronic renal failure. In vitro and ex vivo studies

Cefodizime has previously been shown to possess a number of immunomodulating properties in vivo and in vitro using several different test systems. Since most in vitro studies have been performed with cells from normal individuals, we first investigated whether cells from chronic renal failure patients would respond in vitro to cefodizime in the same way as healthy subjects. Subsequently, we investigated the effect of cefodizime (10 g over 10 days in 2-g doses) on phagocyte function ex vivo in an open study of 26 chronic renal failure patients and 16 healthy subjects. Polymorphonuclear leukocytes were tested for their ability to polarize in response to cefodizime and/or f-met-leu-phe peptide. Polymorphonuclear leukocytes and monocytes were tested for their ability to produce chemiluminescence on stimulation with either phagocytic (zymosan) or soluble phorbol myristate acetate stimuli. Phagocyte and lymphocyte membrane receptor expression was compared after exposure to cefodizime. Exposure to cefodizime in vitro causes a significant increase in polarization of polymorphonuclear leukocytes from both normal individuals and renal failure patients (both P < 0.001). It also caused increased chemotaxis and chemokinesis in a modified Boyden chamber assay. Cefodizime did not affect lucigenin-enhanced chemiluminescence and there were only minor effects on cell membrane antigen levels. In the ex vivo study there was a significant increase in polymorphonuclear leukocyte polarization (P < 0.001) attributable to cefodizime, but other investigations showed no significant differences. The results suggest that cefodizime may act as a mild priming agent for some functions, particularly chemotaxis.

Auranofin and its combination with LTB4 influences ATP level and migration of human polymorphonuclear cells in vitro

Auranofin (AF), an orally administered antirheumatic drug, reduces the ATP level of PMN cells in vitro in a dose-dependent manner and provokes various effects on PMN migration. Under the experimental conditions, AF in concentrations between 10(-8) M and 10(-3) M produced a statistically significant (P < 0.05) dose-related reduction in ATP level, which ranged from 89% of the control value with 10(-8) M AF to 46.8% of the control with 10(-3) M AF. On the other hand, the combination of AF and the chemoattractant LTB4 (1 ng/ml) shows agonistic effects on the intracellular ATP level. AF at 10(-5) M significantly increases the ATP (33%; P < 0.03). In general migration of PMN cells is stimulated by 10(-7) M AF [chemotactic index (CI) = 1.26], but inhibited by 10(-5) M (CI = 0.65), 10(-4) M (CI = 0.09) and 10(-3) M AF (CI = 0.01). These effects were statistically significant at P < 0.05. In the presence of LTB4 (1 ng/ml), which resulted in an average CI of 2.9, AF also inhibits the chemotactic effect of the chemoattractant, with the CI being significantly reduced at 10(-6) M AF (CI = 2.3) and 10(-4) M AF (CI = 0.05). In the latter case the effect was also confirmed by the leading-front technique. AF at 10(-6) M is a level that could be reached in the blood after continuous therapy regimens, and these results are therefore of practical interest. They expand our knowledge of the effects of AF on PMN cells, whereby reducing effects on intracellular ATP were observed with AF alone and stimulating effects in combination with LTB4. With low AF concentrations, the reduction of the ATP level is only a part of its action that seems to be independent of its effect on cell migration and chemotaxis.

A simple fluorometric assay for the determination of cell numbers

A sensitive fluorometric assay was developed for the enumeration of cells in microtiter plates. This assay is based on the fluorescence enhancement of propidium iodide (PI) upon binding with double-stranded nucleic acids. This fluorochrome is compatible with a wide range of reagents commonly used in the laboratory, thus washing the cells before staining is not necessary. PI, together with Triton-X 100 and EDTA, was added directly to the cell culture. After 16-18 h incubation at room temperature, intensity of fluorescence was determined with a micro-plate fluorometer. This quick and simple method is sensitive for as little as 1.95 x 10(3) mononuclear leukocytes, and provides a linear correlation (r = 0.999) between cell number and fluorescence up to 1 x 10(6) cells. Since PI has a large Stokes shift with excitation wavelength at common visible range and emission wavelength far out in the red region of the spectrum, it allows simultaneous detection of DNA and other fluorescent compounds such as calcein and fluorescein. This assay may prove to be a valuable alternative for cell number determination.

Measurement of cell migration stimulated by interleukin 8: use of ATP chemiluminescence

The reliability of methods for the measurement of chemotaxis is a problem which many previous studies have attempted to solve. However, it has recently been shown that the number of cells migrating through a filter can be measured by determining their ATP content by chemiluminescence. We have adapted this method to use microplates with a 24-well format. This allows cells traversing the membranes to be harvested by centrifugation. The modified method has been used to measure the chemotactic activity of interleukin 8 (IL-8) for human polymorphonuclear leukocytes (PMNL). There was a dose response to IL-8, with an optimal concentration of 10(-8) micrograms/ml. The main advantages of this ATP-based cell migration assay were found to be its speed, reproducibility and ease of use.

Capsaicin stimulates the migration of human polymorphonuclear cells (PMN) in vitro

Capsaicin, a homovanillic acid derivative in plants, has distinct pharmacological effects in vivo, e.g. it depletes primary afferent neurons of substance P and other tachykinins. The effect of capsaicin on the migration of human neutrophils was tested in concentrations ranging from 10(-8) M to 10(-3) M. In comparison to the control 10(-8) M capsaicin significantly enhanced the migration of PMN cells (CI 1.29; 2P < 0.009) and a peak migration activity was detected with 10(-6) M (CI 1.32; 2P < 0.01). With higher concentrations of capsaicin the CI was not significantly changed. These results show that capsaicin, a plant derived neurotoxin, exhibits a migration modifying activity on human neutrophils through a direct mechanism not mediated by neuropeptides. In addition capsaicin (10(-7) and 10(-5) M) did not affect the luminol-dependent chemiluminescence and therefore does not contribute to a superoxide anion generation in human PMN.

Effect of substance P and somatostatin on migration of polymorphonuclear (PMN) cells in vitro

The effects of the two neuropeptides, substance P (SP) and somatostatin (SOM), on the migration of polymorphonuclear cells derived from 13 volunteers were investigated. The neuropeptides were applied in concentrations between 10(-12) and 10(-6) M. Only at a concentration of 10(-6) M SP did the chemotaxis of PMN cells increase slightly but statistically significantly. In contrast to SP, SOM showed a significant dose-dependent stimulation of chemotaxis, which was first traceable at 10(-10) M and increased up to 10(-6) M. Although it is uncertain whether in vivo SP and SOM contribute directly to the invasion of PMN cells into the joint cavity, the influence of these neuropeptides on PMN migration in vitro is a further indication of the neuropeptide involvement in the genesis of inflammation.