Effects Of Staphylococcal Alpha-toxin Research Articles

Interferon-γ Protects from Staphylococcal Alpha Toxin-Induced Keratinocyte Death through Apolipoprotein L1

Staphylococcus aureus is a bacterial pathogen that frequently infects the skin, causing lesions and cell destruction through its primary virulence factor, alpha-toxin. Here we show that interferon gamma (IFN-γ) protects human keratinocytes from cell death induced by staphylococcal alpha toxin. We find that IFN-γ prevents alpha toxin binding and reduces expression of the alpha toxin receptor, ADAM10. We determine that the mechanism for IFN-γ mediated resistance to alpha toxin involves the induction of autophagy, a process of cellular adaptation to sublethal damage. We find that IFN-γ potently stimulates activation of the primary autophagy effector, LC3. This process is dependent upon up-regulation of Apolipoprotein L1 (ApoL1). Depletion of ApoL1 by siRNA significantly increases alpha toxin induced lethality and inhibits activation of LC3. We conclude that IFN-γ plays a significant role to protect human keratinocytes from the lethal effects of staphylococcal alpha toxin through ApoL1 induced autophagy.

Effects of staphylococcal alpha-toxin on the ultrastructure of the rat hypothalamo-neurohypophyseal system

The influence of staphylococcal alpha-toxin on the ultrastructure of hypothalamo-neurohypophysical system in the brain (nucleus supraopticus, nucleus paraventricularis, neurohypophysis) was studied in the rat. In neurohypophysis, an area lacking blood-brain barrier, alpha-toxin damaged both neuronal endings and capillary vessels. On the other hand in hypothalamus, where blood-brain barrier is present structural alterations were much less pronounced. Reactive gliosis, accordant with cell damage, was observed in the entire neurosecretory system. Putative mechanisms leading to brain damage after systemic administration of alpha-toxin, including direct disruption of cell membrane and induction of nitric oxide synthesis, are discussed.

Effect of staphylococcal alpha-toxin on intracellular Ca2+ in polymorphonuclear leukocytes.

Staphylococcal alpha-toxin, a channel-forming protein, stimulates leukotriene B4 formation in rabbit polymorphonuclear leukocytes (PMN) (N. Suttorp, W. Seeger, J. Zucker-Reimann, L. Roka, and S. Bhakdi, Infect. Immun. 55:104-110, 1987). The concept was advanced that transmembrane toxin pores act as Ca2+ gates allowing passive Ca2+ influx into the cell, thus initiating stimulus response coupling. A critical step in this hypothesis is the demonstration of an increase in the cytosolic free Ca2+ concentration [( Ca2+]i). [Ca2+]i and membrane-associated Ca2+ were therefore monitored in quin-2- or chlorotetracycline-loaded PMN exposed to alpha-toxin. The effects of the Ca2+ ionophore ionomycin and the chemotactic tripeptide formylmethionyl-leucylphenylalanine (fMLP) were studied in parallel. All stimuli increased [Ca2+]i in dose- and time-dependent manner. In the presence of an EDTA excess there was a decrease of [Ca2+]i due to an efflux of Ca2+ in alpha-toxin- and ionomycin-treated cells, while addition of fMLP still induced an increase of [Ca2+]i. In the presence of verapamil, a Ca2+ channel blocker, [Ca2+]i was reduced after stimulation with fMLP but not with alpha-toxin or ionomycin. Addition of fMLP and ionomycin but not of alpha-toxin to PMN resulted in a rapid and substantial mobilization of membrane-associated Ca2+. The collective data demonstrate that exposure of PMN to staphylococcal alpha-toxin results in an increase in [Ca2+]i which is due to an influx of extracellular Ca2+ and not to a mobilization of intracellularly stored Ca2+. The concept of initiating stimulus response coupling by Ca2+ influx through transmembrane pores may be generally applicable to other channel-forming cytolysins.

Mechanism of leukotriene generation in polymorphonuclear leukocytes by staphylococcal alpha-toxin.

The effects of staphylococcal alpha-toxin on arachidonic acid metabolism in rabbit polymorphonuclear leukocytes (PMNs) were investigated and compared with those of the ionophore A23187 and the chemotactic tripeptide formylmethionyl-leucyl-phenylalanine (fMLP). Sublytic amounts of alpha-toxin stimulated the release of leukotriene B4 (LTB4) in PMNs in a dose-dependent manner. The toxin was several times more potent than fMLP but was not as effective as the ionophore. Preincubation of the toxin with neutralizing antibodies abolished the effect. Extracellular calcium was strictly required for eliciting LTB4 generation. Verapamil, a calcium channel blocker, inhibited fMLP-mediated LTB4 generation but had no effect on alpha-toxin- or A23187-exposed PMNs. Agents such as trifluoperazine and N-6(aminohexyl)-5-chloro-1-naphthalene sulfonamid that interfered with calmodulin activity, however, inhibited LTB4 generation in all cases. One minute after the addition of alpha-toxin, PMNs exhibited a severalfold enhancement in passive permeability to 45Ca2+. In addition, these cells became permeable to sucrose but not to inulin or dextran. The influx pattern was consistent with the previous observation that alpha-toxin creates discrete transmembrane channels in erythrocytes with an effective internal diameter of 2 to 3 nm. The results suggest that alpha-toxin triggers the arachidonic acid pathway in PMNs by facilitating calcium influx into the cells, possibly via transmembrane toxin pores that serve as calcium gates. Generation of arachidonic acid metabolites in PMNs by sublytic amounts of alpha-toxin may represent an important cellular reaction that generally occurs during infections with Staphylococcus aureus.

Effect of staphylococcal alpha-toxin on phagocytosis of staphylococci by human polymorphonuclear leukocytes

Evidence is presented which shows that alpha-toxin elaborated by Staphylococcus aureus can affect certain of the biological functions of human polymorphonuclear leukocytes (PMN). The pretreatment of PMNs with low doses (less than 10 hemolytic units) of purified toxin enhanced their ability to phagocytose and to kill serum-opsonized staphylococci. At higher doses (greater than or equal to 10 hemolytic units), a certain amount of cell damage was caused (detectable by trypan blue uptake), which resulted in a reduction of their phagocytic capacity. These effects were not seen either with heat-inactivated (60 degrees C, 30 min) or with antibody-neutralized toxin. It is thought that the toxin can bind onto the membrane of the PMN, either exposing additional receptor sites for opsonized bacteria or speeding up the transport of staphylococci across the membrane. Once ingested, the bacteria were more readily killed by the PMNs.

Effect of staphylococcal alpha-toxin on neutrophil migration and adhesiveness.

The effect of staphylococcal alpha-toxin on the chemotactic response of human polymorphonuclear leukocytes was studied by measuring the migration of alpha-toxin-treated cells either through membrane filters toward C5a or under agarose toward N-formyl-l-methionyl-l-phenylalanine. At doses of greater than or equal to 5 hemolytic units, alpha-toxin depressed chemotactic responsiveness in both best systems. Further studies revealed that alpha-toxin was also a potent granulocyte aggregant at doses similar to those necessary for depressed chemotactic capacity. It is proposed that the inhibitory effect of this membrane-active toxin on chemotactic function may be related to increased granulocyte adhesiveness and that the pathogenic properties of alpha-toxin may in part by explained by these effects.

The effect of staphylococcal alpha toxin on the superprecipitation and Ca 2+-uptake of isolated arterial smooth muscle preparations

The effects of Staphylococcal alpha toxin from culture filtrates of Staphylococcus aureus, strain Wood 46, on superprecipitation of actomyosin and Ca 2+-uptake of microsomes and fragments of plasma membrane from bovine carotid arteries were followed. It was found that alpha toxin inhibits the active Ca 2+-uptake by smooth muscle microsomes and fragments of plasma membrane and liberates bound calcium. The toxin causes in the absence of free Ca 2+ superprecipitation of actomyosin and activation of ATP-ase. The liberation of calcium from cellular structures and the inhibition of Ca 2+ transport into these structures by alpha toxin could be responsible for its spasmogenic action.

Effect of Staphylococcal alpha toxin on evoked potentials in the myenteric plexus-muscle preparation of the guinea pig taenia coli

Nerve and smooth muscle responses, of the electrically stimulated taenia coli of the guinea pig, were differentiated by means of tetrodotoxin, atropine and MnCl 2. The nerve action potential was resistant to the action of staphylococcal alpha toxin. However, the toxin caused a progressive decrease of first the indirectly and then the directly evoked action potential of this smooth muscle.

Analysis of staphylococcal alpha toxin action in the taenia coli of the guinea pig

The effects of staphylococcal alpha toxin were studied in taenia coli of the guinea pig by the sucrose gap method. The toxin evoked a dose-dependent depolarization, increase in action potential frequency and contraction during its contact time. Following removal of the toxin there was a block in responsiveness of the taenia toward 80 mM KCl or acetylcholine whereas the responsiveness toward histamine and BaCl 2 was only slightly reduced. Partial restoration of the excitability of the preparation was achieved by application of higher calcium concentrations. The effects of the toxin were similar to that of ouabain. On the depolarized preparation the toxin had no effect, the loosely bound fraction of membrane calcium being already released by depolarization. It is concluded that the toxin may release the loosely bound fraction of membrane calcium.

Effect of Staphylococcal alpha toxin on isolated rat mast cells: R. Nosál, M. Rýc, K. Mašek and H. Rašková, Toxicon, 10, 329. (Institute of Pharmacology, Czechoslovak Academy of Sciences, Institute of Hygiene and Epidemiology, Prague, Czechoslovakia)

Effect of Staphylococcal alpha toxin on isolated rat mast cells: R. Nosál, M. Rýc, K. Mašek and H. Rašková, Toxicon, 10, 329. (Institute of Pharmacology, Czechoslovak Academy of Sciences, Institute of Hygiene and Epidemiology, Prague, Czechoslovakia)

Effect of Staphylococcal alpha toxin on isolated rat mast cells

Staphylococcal alpha toxin releases histamine from rat mast cells. This is the result of marked cellular damage, as observed by electron microscopy.

Modification of drug absorption by bacterial toxins—II: The influence of staphylococcal alpha toxin and Shigella dysenteriae toxin on the penetration of sodium salicylate through the placental barrier

The effect of staphylococcal alpha toxin and Shigella dysenteriae toxin on the penetration of sodium salicylate through the placental barrier was investigated. Alpha toxin did not influence the penetration of sodium salicylate through the placental barrier, nor did it alter the histological appearance of the placenta. In contrast, Shigella dysenteriae toxin significantly increased the penetration of sodium salicylate through the placental barrier. The histological changes produced by the toxin help explain the observed effects on penetration.

Modification of drug absorption by bacterial toxins—I: The influence of staphylococcal alpha toxin and Shigella dysenteriae toxin on resorption of sodium salicylate

The effect of staphylococcal alpha toxin and Shigella dysenteriae toxin on intestinal absorption of sodium salicylate in rats was investigated. Shortly after intravenous (i.v.) administration, staphylococcal alpha toxin induced in the intestinal villi pathological changes which resulted in impaired absorption of orally administered sodium salicylate, lower levels being found in blood of intoxicated animals in comparison to control animals. When sodium salicylate was administered intraperitoneally (i.p.), the toxin did not induce any changes in the blood level of the drug. The effect of Shigella dysenteriae toxin reached its peak 72 hr after toxin injection, at which time the salicylate blood levels in intoxicated animals are significantly lower than in controls and the histological changes are most apparent.

Effects of staphylococcal alpha toxin on ion and water transports in isolated frog skin and bladder.

The action of staphylococcal alpha toxin (ST) on potential difference (PD) and short-circuit current (SCC) of the isolated frog skin was studied. Ringer solution bathed the corial side and 20 mM NaCl bathed the epidermal side. PD and SCC decreased to about half after the administration of ST to the corial side of the skin. Later, SCC raised considerably. The replacement of 20 mM NaCl by KCl on the epidermal side of the ST-pretreated skin did not cause any substantial decrease of PD, while in the untreated skin the same replacement caused a sharp drop of PD. No secondary increase of SCC was observed after ST administration when the Ringer solution bathing the corial side of the skin contained 1/2 S04− instead Cl−. In contrast to the normal skin, dilution from 120 to 2 mM of the NaCl solution on the epidermal side led to a PD increase in the toxin-treated skin.

Comparative study on the effect of staphylococcal alpha-toxin on erythrocytes and thrombocytes

The effect of staphylococcal alpha-toxin on the release of haemoglobin from rat erythrocytes, and serotonine from rat thrombocytes, has been measured and expressed in et 50 values. The Hb depletion is dose-dependent and appears after a latency period. Higher doses produce complete haemolysis. Diluted and full plasma decreases the toxin potency in this respect. 5-HT release from thrombocytes starts immediately after toxin administration and is dose-dependent. However, even after 60 min of incubation with plasma, high toxin doses release only about 50 per cent of 5-HT. Diluted plasma somewhat enhances the releasing effect.

The mechanism of staphylococcal alpha toxin action on smooth muscle

The mechanism of contraction of smooth muscles elicited by some bacterial toxins is still not clear. Within the past few years the attention of many investigators focused to the effect of Staphylococcal alpha toxin. The mechanism of contraction on various smooth muscle organs caused by this toxin has been studied and so far mainly the question of direct or mediated effect has been discussed (1–5). The purpose of this study was to try to contribute to the elucidation of the mechanism of contraction and loss of sensitivity of smooth muscles induced by Staphylococcal alpha toxin. The potential importance of phospholipase-like activity in the ffect of Staphylococcal products led us to complete some experiments with snake venom from Bitis gabonica (rich in phospholipase A) and with toxin from Clostridium perfringens (containing phospholipase C). Such assumed phospholipase activity could explain the direct effect of this toxin by liberation of pharmacologically active lipids.

Some effects of staphylococcal alpha-toxin on isolated mammalian smooth muscle preparations.

Some effects of staphylococcal alpha-toxin on isolated mammalian smooth muscle preparations.

The Effect of Staphylococcal Alpha Toxin and Preparations of Staphylococcal Antigens on Ciliated Respiratory Epithelium:A Study in Organ Cultures

This investigation was supported by grants from Alfred osterlund's Stiftelse, Malmo, Sweden, and the Medical Faculty, University of Lund, Lund, Sweden.Tracheal and nasal explants of mucous membrane from adult rabbits and human foetuses were used for the study of ciliary toxicity of culture filtrate, crude extract and five preparations of purified antigens from S. aureus, phage type 52, Cowan I, Oeding ab (ck)m; and, secondly, of culture filtrate from S. aureus, Wood 46. The Wood 46 filtrate was the only product that proved toxic to the cilia. The Wood 46 filtrate contained alpha hemolysin. The ciliary toxicity of the filtrate was neutralised by anti-alpha hemolysin in amounts equivalent to the alpha hemolysin. The ciliary action of the explants stopped before any sign of damage to the cells could be demonstrated by conventional histological methods. Prolonged exposure to the toxin destroyed the epithelial layer.