Oxygen metabolites induced by phorbol myristate acetate increase lateral diffusion of wheat germ agglutinin-labeled glycoconjugates in human polymorphonuclear leukocytes

Neutrophil priming in host defense: role of oxidants as priming agents

Neutrophils play an essential role in the body's innate immune response to infection. To protect the host, these phagocytic cells possess an impressive array of microbicidal weapons that can be brought to bear on an invading pathogen, including a variety of toxic oxygen radical species and proteolytic enzymes. Although the neutrophil response is designed to restrict the damage to the smallest possible region where the pathogen is located, some of the damaging agents inevitably leak into the surrounding areas where they have the capacity to inflict tissue damage at sites of inflammation. Thus, it is essential that the host defense response of these cells is finely tuned to result in the appropriate level of response to any given situation. One of the regulatory mechanisms implicated in controlling neutrophil responses is priming. Through the action of priming agents, the level of activation and subsequent responses of the cell can be regulated so that a continuum of activation states is achieved. In this review, we describe key features of the priming response in host defense and disease pathogenesis and focus on the unique role of reactive oxygen species as priming agents.

Mechanical manipulation of polymorphonuclear leukocyte plasma membranes with optical tweezers causes influx of extracellular calcium through membrane channels

Optical tweezers are used mechanically to manipulate the plasma membrane of polymophonuclear leukocytes attached to the bottom of a glass manipulation chamber. The laser trapping beam is dragged across the membrane of cells in calcium-containing and calcium-depleted extracellular medium. This treatment causes a significant rise in the intracellular calcium concentration compared with controls, in cells in calcium-containing medium (239.8 +/- 49.0% against 75.4 +/- 16.4%, respectively), but not in cells in calcium-depleted medium (69.1 +/- 9.6% against 83.4 +/- 18.5%, respectively), indicating that the calcium rise is caused by an influx of calcium from the environment. The rise in calcium concentration is blocked (23.5 +/- 7.1% against 17.1 +/- 4.1%, respectively) by the addition of lansoprazole, indicating that the influx is not due to unspecific membrane damage caused by the mechanical manipulation of the cell. It can therefore be concluded that mechanical manipulation of the neutrophil membrane, in the piconewton force range exerted by the optical tweezer, does not damage the plasma membrane but stimulates a mechanically inducible, membrane channel-mediated influx of extracellular calcium.

Lateral mobility of plasma membrane lipids in bull spermatozoa: heterogeneity between surface domains and rigidification following cell death

Compartmentalization of surface membrane antigens into discrete regions or domains is a characteristic feature of differentiated cells. In mammalian spermatozoa at least 5 surface domains are known, implying the presence of barriers or boundaries within the plasma membrane. Using the technique of fluorescence recovery after photobleaching (FRAP) to measure diffusibility of fluorescent lipid analogues 1,1′-dihexadecyl-3,3,3′3′-tetramethylindocarbocyanine (DiIC[16]) and 5-(N-octa-decanoyl) aminofluorescein (ODAF), we have investigated lipid topology and dynamics in the plasma membrane of ejaculated bull spermatozoa. Contrary to reports in the literature, we have found that DiIC(16) stains only dead or damaged spermatozoa whereas ODAF intercalates into the plasma membrane of both live and dead cells, each type showing a distinctive staining pattern. FRAP analysis with ODAF revealed that diffusion coefficients on live spermatozoa are significantly faster on the acrosome and postacrosome (29.3x10(−9) cm2/second) than on the midpiece and principal piece (11.8x10(−9) cm2/second). Recovery (R) is >90% in all domains. ODAF diffusion also shows regionalized temperature-sensitivity with a 4-fold increase over the sperm head and a 1.8-fold increase on the tail between 20 degrees C and 37 degrees C. Remarkably, dead or permeabilized spermatozoa rapidly develop a large immobile phase (R<25%) over the whole plasma membrane. This rigidification is temperature insensitive and irreversible suggesting major changes in the physical state of membrane lipids. It is concluded that lipid diffusion in the plasma membrane of live bull spermatozoa is rapid and varies significantly between surface domains. Following permeabilization or cell death, however, a large immobile phase develops indicating substantial changes in membrane lipid disposition.

The N-formyl methionyl peptide, formyl-methionyl-leucyl phenylalanine (fMLF) increases the lateral diffusion of complement receptor 1 (CR1/CD35) in human neutrophils; a causative role for oxidative metabolites?

The effects of the N-formyl methionyl peptide, formyl-methionyl-leucyl phenylalanine (fMLF) on the lateral mobility of the complement receptor type 1 (CR1/CD35) in glass-adherent human neutrophils were investigated, using fluorescence recovery after photobleaching (FRAP) and confocal microscopy (CSLM). It was found that addition of 0.1-1 microM fMLF increased the diffusion constant (D) of CR1/CD35 to 167-228% of controls. No effect was observed on the receptor distribution or the mobile fraction of receptors. The effect of fMLF on the lateral diffusion of CR1/CD35 could be totally inhibited by addition of pertussis toxon (PD, 250 ng/ml) or of the free radical scavenger enzymes superoxide dismutase (SOD, 2000 U/ml) and catalase (CAT, 200 U/ml), added together the results show that oxidative metabolites produced by neutrophils in response to fMLF can modulate CR1/CD35 diffusion, and indicate a regulatory role for oxygen radicals in phagocytosis.

UVB radiation affects the mobility of epidermal growth factor receptors in human keratinocytes and fibroblasts

Growth factor receptors transmit biological signals for the stimulation of cell growth in vitro and in vivo and their autocrine stimulation may be involved in tumorigenesis. It is therefore, of great value to understand receptor reactions in response to ultraviolet (UV) light which certain normal human cells are invaribly exposed to during their growth cycle. UV irradiation has recently been shown to deplete antioxidant enzymes in human skin. The aims of the present study were a) to compare the lateral mobility of epidermal growth factor receptors (EGF-R) in cultured human keratinocytes and human foreskin fibroblasts, b) to investigate effects of ultraviolet B radiation on the mobility of EGF-R in these cells, and c) study the response of EGF-R on addition of antioxidant enzymes. The epidermal growth factor receptors were labeled with rhodaminated EGF, the lateral diffusion was determined and the fraction of mobile EGF-R assessed with the fluorescence recovery after photobleaching (FRAP). We found that human keratinocytes display a higher basal level of EGF-R mobility than human skin fibroblasts, viz. with diffusion coefficients (D +/- standard error of the mean, SEM) of 4.2 +/- 0.2 x 10(-10) cm2/s, and 1.8 +/- 0.2 x 10(-10) cm2/s, respectively. UVB-irradiated fibroblasts showed an almost four-fold increase in the diffusion coefficient; D was 6.3 +/- 0.3 x 10(-10) cm2/s. The keratinocytes, however, displayed no significant increase in receptor diffusion after irradiation; D was 5.1 +/- 0.8 x 10(-10) cm2/s. In both cell types the percentage of EGF-R fluorescence recovery after photobleaching, i.e. the fraction of mobile receptors, was significantly increased after irradiation. In keratinocytes it increased from 69% before irradiation to 78% after irradiation. Analogous figures for fibroblasts were 61% and 73%. The effect of UVB on fibroblast receptors was abolished by prior addition of superoxide dismutase (SOD) and catalase (CAT). It is concluded that UVB radiation of fibroblasts and keratinocytes can affect their biophysical properties of EGF-R. The finding that addition of antioxidant enzymes prevented the UVB effect in fibroblasts may indicate the involvement of reactive oxygen metabolites.

In vitro effects of ethanol on polymorphonuclear leukocyte membrane receptor expression and mobility

The hampered inflammation and host defense seen in alcoholics may be due to impairment of functional responses of neutrophil polymorphonuclear leukocytes (PMN). We have shown that ethanol inhibits the oxidative metabolism of PMN induced by surface receptor dependent stimuli, such as N-formyl-methionyl-leucyl-phenylalanine (fMLP) and opsonized zymosan. Because the unresponsiveness might be due to reduced numbers of surface receptors, we assessed the expression of CR1, Fc-gamma, and fMLP receptors as well as membrane fluidity after treatment of PMN with ethanol in vitro. Ethanol impaired the induced expression of CR1 and fMLP receptors to 71% and 51% of control, respectively, but did not affect the resting level of CR1 nor Fc-gamma receptor expression. Furthermore, the mobility of cell membrane glycoconjugates was increased by ethanol. However, phagocytosis, a functional response dependent on membrane rheology, was unaffected. Because the results indicated an effect of ethanol on mobilization of receptors from intracellular stores, we assessed lactoferrin release, which was reduced to 59%. Thus, ethanol appeared to hamper the upregulation of PMN surface receptors or functional subsets of those stored in granules. Ethanol also increased the mobility of the cell membrane. These reactions were accompanied by reductions in the functional responses mediated by either class of receptors.

Antioxidants in peripheral nerve

Oxidative stress and antioxidants have been related in a wide variety of ways with nervous tissue. This review attempts to gather the most relevant information related to a) the antioxidant status in non pathologic nervous tissue; b) the hypothesis and evidence for oxidative stress (considered as the disequilibrium between prooxidants and antioxidants in the cell) as the responsible mechanism of diverse neurological diseases; and c) the correlation between antioxidant alterations and neural function, in different experimental neuropathies. Decreased antioxidant availability has been observed in different neurological disorders in the central nervous system, for example, Parkinson's disease, Alzheimer's disease, epilepsy, amyotrophic lateral sclerosis, cerebral ischaemia, etc. Moreover, the experimental manipulation of the antioxidant defense has led in some cases to interesting experimental models in which electrophysiological alterations are associated with the metabolic modifications induced. In view of the electrophysiological and biochemical effects of some protein kinase C inhibitors on different neural experimental models, special attention is dedicated to the role of this kinase in peripheral nervous tissue. The nervous tissue, central as well as peripheral, has two main special features that are certainly related to its antioxidant metabolism: the lipid-enriched membrane and myelin sheaths, and cellular excitability. The former explains the importance of the glutathione (GSH)-conjugating activity towards 4-hydroxy-nonenal, a biologically active product of lipid peroxidation, present in nervous tissue and in charge of its inactivation. The impairment of the latter by oxidative damage or experimental manipulation of antioxidant metabolism is discussed. Work on different experimental neuropathies from author's laboratory has been primarily used to provide information about the involvement of free radical damage and antioxidants in peripheral nerve metabolic and functional impairment.