Salvatore Pece

Spontaneous and Fas-induced apoptotic cell death in aged neutrophils.

On the basis of the strict analogies between polymorphonuclear cell (PMN) alterations in the aging and depressed functional capacities displayed by apoptotic PMN, we investigated the possible occurrence of age-associated changes in neutrophil apoptosis, either spontaneous or induced by Fas antigen (CD95) activation. In both cases, old subjects exhibited a time course kinetics of neutrophil apoptosis, as assessed by morphologic and quantitative DNA fragmentation analysis, which overlapped that observed in the young. These findings were confirmed by DNA ladder analysis, showing a progressive increase in DNA cleavage products in cells cultured in medium alone or added with agonistic anti-Fas IgM (CH-11) monoclonal antibodies (mAbs), after 12 and 6 hr of incubation, respectively. Aged purified neutrophils constitutively expressed CD95, at levels similar to those observed in the young. Moreover, although we failed to detect Fas ligand expression on PMN surface, treatment of cell cultures with antagonistic anti-Fas IgG1 (ZB4) mAbs determined a significant inhibition of spontaneous apoptosis in neutrophils from both groups of subjects, thus suggesting that the Fas/Fas ligand system is in fact involved in such an event. The results indicate that the overall intrinsic mechanisms regulating neutrophil cell death are not affected by age. Yet aged neutrophils showed a diminished capacity to be rescued by proinflammatory mediators, such as granulocyte–monocyte colony-stimulating factor, granulocyte colony-stimulating factor, and bacterial lipopolysaccharide, following Fas activation. This may hamper the accumulation of functionally active cells in inflammatory areas in vivo, thus contributing to the increased susceptibility of elderly individuals to life-threatening infections.

Hyporeactivity of mesenteric vascular bed in endotoxin-treated rats

Vascular reactivity and activation of the nitric oxide (NO) pathway were investigated in perfused mesenteric vascular bed removed from rats 5 h after i.p. injection of bacterial lipopolysaccharide (E. coli lipopolysaccharide, 30 mg kg -1). Lipopolysaccharide treatment induced hyporesponsiveness to noradrenaline. Maximal noradrenaline-induced vasoconstriction was significantly reduced in lipopolysaccharide-treated vs. untreated preparations. Continuous infusion of L-arginine (L-Arg) (0.2 mM) enhanced noradrenaline hyporeactivity of lipopolysaccharide-treated rats. N omega-Nitro-L-arginine methyl ester (L-NAME) (0.2 mM), a non-selective inhibitor of NO synthase, failed to completely restore the noradrenaline hyporeactivity of lipopolysaccharide-treated + L-Arg-infused mesenteric vascular bed. After L-NAME treatment. Methylene blue (10 microM), a guanylate cyclase inhibitor, produced no additional increase of noradrenaline vasoconstriction in lipopolysaccharide-treated + L-Arg-infused mesenteric vascular bed, suggesting that an NO-independent activation of guanylate cyclase may be excluded. In lipopolysaccharide-treated preparations, L-Arg (0.2 mM) elicited a significant increase in nitrite production, which was antagonized by L-NAME. In conclusion, lipopolysaccharide-induced noradrenaline hyporesponsiveness of rat resistance vessels can only be partially explained by NO overproduction. Other mechanisms, probably related to vasoconstriction, may be involved.

Downregulation of Human Polymorphonuclear Cell Activities Exerted by Microorganisms Belonging to the α-2 Subgroup of Proteobacteria (Afipia Fs and Rochallmaea Henselae)

Intracellular pathogens have evolved effective mechanisms in order to survive in an intracellular environment, thus avoiding destruction by phagocytic cells. In this regard, a correlation between resistance to phagocytic killing and expression of pathogenic potency has been established. In this report, we have studied the interaction between human polymorphonuclear cells (PMN) and two gram-negative microorganisms, Afipia felis and Rochalimaea henselae, which belong to the alpha-2 subgroup of the class Proteobacteria. A. falis has been previously proposed as the causative agent of Cat Scratch Disease (CSD), but several recent lines of evidence attribute a major role to R. henselae. Of note, CSD is a syndrome characterized by a chronic lymphoadenopathy, involving macrophages and endothelial cells with a progression towards a granulomatous process and/or angiogenesis. Since members of the alpha-2 subgroup of Proteobacteria have the property to survive intracellularly, we have evaluated the effects exerted by A. felis and R. henselae on human PMN in terms of chemotaxis locomotion, degranulation and oxidative metabolism. Results will show an impairment of PMN activities as a consequence of the challenge with both microrganisms. In particular, inhibition of PMN oxidative function occurred either as result of a direct exposure to both A. felis and R. henselae or when PMN were primed by bacteria for the N-formyl-methionyl-leucyl-phenylalanine enhancement of the oxidative burst. These findings may account for the ability of A. felis and R. henselae to survive within PMN as expression of a further mechanism of pathogenic potency, influencing also the nature and the evolution of inflammatory response in the lesion sites.

HELICOBACTER PYLORI INFECTION AND HOST CELL RESPONSES

It is well known that Helicobacter pylori is able to colonize the gastric mucosa, causing a chronic and persistent infection with complications, such as peptic ulcer and gastric cancer. This review places emphasis on some epidemiological aspects of Helicobacter pylori infection and its mode of transmission. At the same time, invasive and non-invasive methods of diagnosis of Helicobacter pylori infection are illustrated. More space is devoted to the host response following invasion of the stomach. In this respect, the role played by different growth factors and polyamines in the course of Helicobacter pylori disease is discussed also in relation to the result of eradicating treatment. On the other hand, an accurate description of the host immune responses against Helicobacter pylori organism and/or their components (e.g. lipopolysaccharides) is reported. Finally, since Helicobacter pylori has been classified as a class I carcinogen, current researches are focussed on the Helicobacter pylori-induced carcinogenesis.

Endotoxins, cytokines, and neuroimmune networks with special reference to HIV infection.

The mutual interplay between the nervous system and the immune system has been the object of extensive studies in either conditions of stress or human diseases such as multiple sclerosis, psychiatric disorders, and migraine.’” Initial studies by Selye4 demonstrated activation of the hypothalamus-pituitary-adrenal axis in normal animals in response to stressful events; these effects were similar to the wasting syndrome that follows the experimental administration of bacterial endotoxins or lipopolysaccharides

Pathogenetic role of phagocytic abnormalities in human virus immunodeficiency infection: possible therapeutical approaches. A review.

Polymorphonuclear cells (PMN) and monocytes/macrophages (M/M) represent the first defence line against invading microorganisms. Both phagocytic cell functions are precociously compromised in human immunodeficiency virus (HIV)-infected subjects, thus leading to infectious and neurological complications in the late stages of disease. Among intracellular pathogens, emerging bacteria such as Bartonella henselae and Rhodococcus equi can cause peculiar clinical pictures, i.e. the bacillary parenchimal angiomatosis and a classical pyogranulomatous broncopneumonia, respectively. On the other hand, overproduction of proinflammatory cytokines (CKs) and, in particular, tumor necrosis factor-alpha under HIV or lipopolysaccharide stimulation may cause neural damage in terms of demyelination and subsequent development of acquired immunodeficiency syndrome (AIDS) dementia complex. Some therapeutical attempts have been made with colony stimulating factors in order to increase the number and potentiate the function of PMN and M/M. On the other hand, the use of drugs able to reduce exaggerated release of CKs by M/M is suggested in AIDS patients in order to prevent a further aggravation of the clinical condition.

In vitro production of tumor necrosis factor-α, interleukin-6 and interleukin-8 from normal human peripheral blood mononuclear cells stimulated by Rhodococcus equi

The capability of heat-killed Rhodococcus equi organisms to induce in vitro release of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6 and IL-8 from normal human mononuclear cells as well as the secretion kinetics of these inflammatory cytokines over a 48 h period were evaluated. Results show that normal human mononuclear cells are efficiently triggered to secrete TNF-alpha, IL-6 and IL-8 following R. equi stimulation according to a different kinetics. In particular, release of IL-B was already maximally expressed after 2 h of stimulation, while TNF-alpha amounts progressively increased in a time-dependent fashion. Finally, IL-6 secretion reached peak levels as soon as 18 h of incubation. Taken together, these data point out that monocyte-derived cytokines may play an important role in the immunological control of R. equi infection in immunocompetent people.