Angela B. Maffione

Biological Role of the N-Formyl Peptide Receptors

Ligation of N-formyl-methionyl-leucyl-phenylalanine (fMLP) to its specific cell surface receptors triggers different cascades of biochemical events, eventually leading to cellular activation. The formyl peptide receptors (FPRs) are members of the seven-transmembrane, G-protein coupled receptors superfamily, expressed at high levels on polymorphonuclear and mononuclear phagocytes. The main responses elicited upon ligation of formylated peptides, referred to as cellular activation, are those of morphological polarization, locomotion, production of reactive-oxygen species and release of proteolytic enzymes. FPRs have in recent years been shown to be expressed also in several non myelocytic populations, suggesting other unidentified functions for this receptor family, independent of the inflammatory response. Finally, a number of ligands acting as exogenous or host-derived agonists for FPRs, as well as ligands acting as FPRs antagonists, have been described, indicating that these receptors may be differentially modulated by distinct molecules.

Stress, Neuropsychiatric Disorders and Immunological Effects Exerted by Benzodiazepines

Psychoneuroimmunology is a growing scientific field which deals with the mutual interplay between nervous and immune systems. In this framework, many data have demonstrated that cytokines (CKs) derived from the periphery are able to cross the blood brain barrier and act upon the central nervous system (CNS) [e.g., the hypothalamic-pituitary-adrenal axis (HPAA)], thus regulating several physiological functions (thermoregulation, sleep, appetite) or damaging the nervous tissue, when released in exaggerated amounts. On the other hand, nervous cells, such as astrocytes and microglial cells also generate proinflammatory CKs which may be detrimental for the CNS. The neuromodulating CK network can be triggered by microorganisms and/or their products (i.e. bacterial endotoxins), but also stressful life events may activate the HPAA, thus affecting the immune system function. This review will place emphasis on some clinical conditions, such as phobia and migraine without aura (MWA), characterized by anxiety disorders. Patients affected by these neuropsychiatric alterations exhibit multiple functional deficits of phagocytes and T lymphocytes which allow penetration of various pathogens into the host. This is also supported by the detection of circulating bacterial endotoxins and the evidence of both spontaneous and induced exaggerated release of proinflammatory CKs in phobic and MWA patients. The possible iatrogenic effects of benzodiazepines (BDZ) on the immune system have been evaluated by in vitro and in vivo studies. In this respect, it emerges that diazepam exerts an inhibitory function on the immune system, while alprazolam behaves as an immunoenhancer. The presence of central and/or peripheral BDZ receptors on immune cells seems to be the key mechanism responsible for the immunomodulation exerted by these drugs.

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.

Triazolobenzodiazepines Exert Immunopotentiating Activities on Normal Human Peripheral Blood Lymphocytes

Previous studies have demonstrated that benzodiazepines (BDZ) (e.g. diazepam) inhibit immune responsiveness. Since these drugs are largely used in psychiatric patients it is of great importance to verify the existence of different types of BDZ, which are not suppressive for the immune system. In this framework, our results indicate that alprazolam and triazolam, two triazolo-BDZ, do not modify in vitro phagocytosis and killing exerted by normal human polimorphonuclear cells and monocytes. On the contrary, they significantly enhance T lymphocyte-dependent antibacterial activity in normal donors. These data support the concept that triazolo-BDZ and, in particular, alprazolam may represent more appropriate drugs for the treatment of psychiatric patients (e.g. patients with phobic disorders and/or migraine) who display immunodeficits.

In Vivo Effects of Alprazolam and Lorazepam on the Immune Response in Patients With Migraine Without Aura

Over the past few years, the immunomodulating role of benzodiazepines (BDZ) has been reported in literature. In particular, diazepam is an inhibitory BDZ with regard to its effects on the phagocytic and metabolic activities of polymorphonuclear cells (PMN) and monocytes, while triazolobenzodiazepines (alprazolam and triazolam) upregulate normal human peripheral blood T lymphocyte function. On these grounds, the administration of alprazolam (1 mg/per day for 1 month) in 13 patients with migraine without aura (MWA) and of lorazepam (2 mg/per day for 1 month) in 10 matched MWA subjects has been evaluated in terms of immune response. Results show that before administration of BDZ in both groups of patients phagocytosis and killing of PMN and monocytes were profoundly depressed and the same was true for the lymphocyte-dependent antibacterial activity. After one month treatment lorazepam further decreased lymphocyte function without modifying phagocytic capabilities. On the contrary, alprazolam increased PMN phagocytosis and killing and monocyte phagocytosis without modifying antibacterial activity values. Taken together, these results further support the existence of different classes of BDZ in terms of their immunomodulating capacities. Moreover, alprazolam seems to be a more appropriate BDZ for treating immunocompromised patients, even including MWA patients.

Chemokine CXC receptor 4: an evolutionary approach.

Selected segments of the nucleotide sequences of the human 18S rRNA and the human formyl peptide receptor 1 mRNA exhibit structural similarities that are unlikely to be due simply to chance. Herein we analyze the structural similarities between the human 18S rRNA gene and the vertebrate chemokine CXC receptor 4 (CXCR4) gene that encodes a class A (rhodopsin-like) seven-transmembrane G-protein coupled receptor belonging to the same superfamily of formyl peptide receptors. The method of study was based on the recording of the positions of the 7-or-more-base oligonucleotide identities encountered in the 18S and CXCR4 genes and the construction of scatter-plots (abscissa-18S; ordinate-CXCR4) displaying the identity points positions. Analysis of the distribution of distances between identity points (abscissa-ordinate in the scatter-plot) demonstrated distinct peaks of frequency around 1200. Series of identities arranged near diagonal lines at 45° in the scatter-plot (quasialignments) were evaluated for their probabilistic level of random occurrence. Results of this analysis demonstrated nonrandom quasialignments between (i) a 900-nt ca. section of the human CXCR4 intron that immediately precedes almost the whole of the coding sequence and the 18S gene from nt 125 to 1025 ca.; and (ii) a 425-nt ca. section of the CXCR4 vertebrate genes, corresponding to nt 137–560 of the coding sequence, and the 18S gene from nt 1300 to 1730 ca. In both instances significant quasialignments are evidenced when CXCR4 nt sequences are shifted to the right by about 1200 nt with respect to the 18S nt sequence, as confirmed by analysis of the abscissa - ordinate differences. Taken together, these results indicate that, at least in humans, a continuous nonrandom quasialignment extends for some 1600 nt, from the second part of the (single) intron to the first part of the coding sequence. We hypothesize that the relatively more recent CXCR4 vertebrate gene might be evolutionarily related to the more ancient and highly conserved 18S gene.

In Vivo Effects of Recombinant-Interferon-β1b Treatment on Polymorphonuclear Cell and Monocyte Functions and On T-Cell-Mediated Antibacterial Activity in Patients with Relapsing-Remitting Multiple Sclerosis

Abstract Treatment with Interferon (IFN)-β has been proposed as a therapeutic approach in multiple sclerosis (MS) patients, mostly in view of its immunomodulating actions. At the same time, evidence has been provided that MS patients exhibit polymorphonuclear cell (PMN) deficits, which can explain the increased susceptibility to infections in these subjects. Here, in 28 patients with relapsingremitting (RR) MS under treatment with recombinant (r)-IFN-β PMN polarization and PMN and monocyte (MO) phagocytosis and killing, as well as T-cell mediated antibacterial activity, were evaluated before treatment and over a period of nine months of treatment. Our results point out an enhanced rate of polarization (both “spontaneous” or N-formyl-methionyl-leucyl-phenylalanine-induced) in MS patients. After r-IFN-β1b treatment the polarization rate was further increased. On the contrary, PMN and MO phagocytosis and killing were depressed in comparison to controls and values were further reduced by r-IFN-β1b treatment. In patients T-cell mediated antibacterial activity was decreased at TO and dramatically dropped in the course of r-IFN-β1b therapy.

Structural Similarities Between mRNA for the Formyl Peptide Receptors and 18S rRNA

Formyl peptides released by some bacteria are powerful chemoattractants and activators of mammalian granulocytes and monocytes, acting through 7-transmembrane specific formyl peptide receptors (FPRs). Three distinct segments of the formyl peptide receptor 1 (FPR1) mRNA of Man share probabilistically significant homologies with segments of the 18S rRNA which are highly conserved from Drosophila to Man. Overall, the three segments cover ≈ 24% that of the 18S rRNA sequence and ≈ 36% of the FPR1 sequence. The three segments are, however, arranged in different orders in the 18S rRNAs and in the FPR1 mRNA, the segment appearing in the first location in the 18S rRNAs is located at the end of the FPR1 mRNA sequence. The hypothesis is advanced that the three “conserved” segments either derive from an ancestral gene that is the forerunner of both the ribosomal 18S genes and the FPR genes or that at some stage of evolution the FPR genes derived, at least in part, from the more ancient ribosomal 18S genes. The extant 18S rRNA sequences exhibit obvious signs of a number of breaks that occurred during evolution, especially in the transition from insects to vertebrates. Some of these events may have resulted in differential rearrangements of segments in the groups of FPR genes and ribosomal 18S genes.

The 18S rRNA is Basically Composed of Two Tandem Quasirepeats. Insights into the Evolution of Some Innate Immunity Receptors

The gene encoding the 18S rRNA is an ancient molecule and its basic structure has been highly conserved from fish to mammals. Recently, we compared the nucleotide sequences of the human 18S rRNA and the human formyl peptide receptor 1 mRNA and concluded that selected segments of the two sequences exhibit similarities that are unlikely to be due simply to chance. Other data suggest the existence of nonrandom similarities between the 18S rRNA and the chemokine CXC receptor 4 mRNA. Therefore we advance the hypothesis that some groups of genes encoding 7-transmembrane G-coupled receptors of immunological interest may be evolutionarily related to the 18S gene. In this article we analyze the base-sequence architecture of the human 18S rRNA in terms of similarities between selected segments within the molecule. The method of study was based on the recording of the positions of 7- to 11-base oligonucleotide repeats, followed by a probabilistic analysis of the random occurrence of the repeats. Herein we show that most of the 18S rRNA molecule appears to be composed of two long tandem quasirepeats. We hypothesize that an ancestral gene structure composed of a chain of about 850 nucleotides duplicated to form a two-unit tandem repeat. Then the two units diverged as a consequence of independent nucleotide mutations, deletions, and insertions, but still retaining recognizable homologies. In addition, further nonduplicated shorter segments were added to build up the complete sequence.