Pasquale Annunziata

Norepinephrine and vasoactive intestinal peptide induce IL-6 secretion by astrocytes: Synergism with IL-1β and TNFα

Resident glial cells and invading inflammatory cells are responsible for cytokine production within the brain. Astrocytes are known to secrete a variety of cytokines upon stimulation with cytokines themselves, protein kinase C activators, bacterial or viral constituents. Astrocytes also have surface receptors for a wide number of neurotransmitters and neuropeptides and some of these substances affect astrocyte immune functions, such as major histocompatibility complex (MHC) class II antigen expression. To elucidate the activity of neuromediators on cytokine secretion by glial cells, we studied the secretion of interleukin-6 (IL-6) by cultured rat astrocytes after incubation with various neurotransmitters and neuropeptides. Norepinephrine (NE) and the β-adrenergic agonist isoproterenol (IPT) induced IL-6 secretion in a dose-dependent fashion. NE effect was predominantly mediated by β2-adrenergic receptors with a minor contribution of α1-adrenergic receptors. The induction of IL-6 release by dibutyryl-cAMP indicated that IL-6 secretion secondary to β2-adrenergic receptor activation probably occurs through cAMP signalling pathways. Vasoactive intestinal peptide (VIP) was the sole neuropeptide able to induce IL-6 secretion. NE and VIP promoted IL-6 mRNA synthesis and both substances synergized with interleukin-1β (IL-1β) and tumor necrosis factor α (TNFα) in inducing IL-6 release. Our findings provide further evidence that neurons modulate astrocyte cytokine production and thereby regulate central nervous system immune functions.

IL-6 detection in multiple sclerosis brain

By using a double-label immunohistochemistry technique, we demonstrated the presence of interleukin-6 (IL-6) in acute and chronic active plaques from the brain of six patients with multiple sclerosis (MS). IL-6 was mainly associated with astrocytes and rarely with macrophages or mononuclear infiltrating cells. The pattern of distribution for IL-6 immunoreactivity was similar to that of HLA-DR expression, but the two molecules almost never colocalized on the same cell. Our data indicate that in MS central nervous system IL-6 is predominantly located within resident glial cells which are concentrated at the sites of ongoing demyelination and immune activation. Although IL-6 exhibits several proinflammatory activities, indirect evidence suggests that the cytokine may also play an immunomodulatory role in inflammatory demyelinating disorders.

Relevance of cognitive deterioration in early relapsing-remitting MS: a 3-year follow-up study

Objective: To assess longitudinally cognitive functioning in relapsing—remitting multiple sclerosis (RRMS) patients and its relationship with clinical and MRI variables. Methods: Early RRMS patients and matched healthy controls were assessed in parallel in three testing sessions over 3 years, using the Rao’s Brief Repeatable Battery of Neuropsychological Tests. Patients also underwent an MRI analysis of T2-weighted lesion volume (T2LV), number of gadolinium-enhanced lesions and whole brain atrophy. Forty-nine RRMS patients (mean age 36.9 ± 8.9 years; mean disease duration 2.9 ± 1.7 years, mean Expanded Disability Status Scale, 1.7 ± 0.7) and 56 healthy controls were recruited. Results: At baseline, cognitive impairment was detected in 15 patients (30.6%). After 3 years, cognitive functioning worsened in the 29.3% of patients, whereas Expanded Disability Status Scale progression was observed in only three patients. The most sensitive test to detect cognitive deterioration over time was the Symbol Digit Modalities Test (SDMT). Only the presence of moderate cognitive impairment at baseline predicted further cognitive deterioration (p = 0.03). Among MRI variables, T2LV showed a weak to moderate relationship with some cognitive tasks. Conclusions: Over a 3-year period cognitive deterioration can be expected in approximately one-third of MS patients with relatively short disease duration. The SDMT is particularly suitable for longitudinal assessment of MS-related cognitive changes.

Blood-brain barrier changes during invasion of the central nervous system by HIV-1. Old and new insights into the mechanism.

Abstract.The mechanism underlying the early invasion of the central nervous system by HIV-1 is unclear. Here, we summarize old and new findings supporting blood-brain barrier changes during HIV and experimental simian immunodeficiency virus (SIV) infection. The effect of inflammatory and toxic molecules secreted by monocytes and microglia on the functional integrity of tight junctions of brain endothelium is highlighted. Furthermore, recent findings on a possible direct role of the envelope and regulatory HIV-1 proteins (gp120, Tat, Nef) in causing the blood-brain barrier changes are reviewed. The possibility that these proteins, as circulating molecules, may bind to microvessel endothelial cells and cause blood-brain changes with no direct participation of the virus is raised. Several issues deserve further investigation and answers to these questions may provide keys for new therapeutic strategies in HIV-1 infection of the central nervous system.

HIV-1 gp120 increases the permeability of rat brain endothelium cultures by a mechanism involving substance P.

Objective:To analyse whether an HIV-1 envelope protein might play a role in damaging the blood-brain barrier as a fundamental step in the early invasion of the central nervous system by HIV-1. Design:Analysis of permeability of rat brain endothelium cultures to albumin, to assess the functional integrity of the vascular component of the blood-brain barrier. Methods:Rat brain endothelium cultures prepared by cerebral microvessels were exposed to recombinant gp120IIIB on microporous membranes and passage of biotin-labelled albumin was analysed. Scanning electron microscopy was used to analyse cell culture morphology. Some cultures were preincubated with N-nitro-L-arginine methyl ester (L-NAME), a selective inhibitor of nitric oxide synthase, or with spantide, a selective substance P antagonist. Results:HIV-1 gp120 increased the permeability of rat brain endothelial cells to albumin in a dose-dependent manner. Scanning electron microscopy revealed profound gp120-induced alterations in cell morphology accounting for the increased permeability to macromolecules. These alterations were neutralized by anti-gp120 monoclonal antibody but not by isotype control antibody or L-NAME. By contrast, spantide and anti-substance P polyclonal antibody completely blocked the gp120-induced increase in albumin permeability. Control cultures exposed to measles virus nucleoprotein showed an increase in permeability that was not blocked by spantide. Brain endothelial cells, exposed to gp120, displayed cell surface immunoreactivity for substance P, suggesting that substance P is secreted by brain endothelium in response to gp120 stimulation and binds to brain endothelial cells through a receptor-mediated mechanism. Conclusions:These findings suggest a role for substance P in the gp120-induced increase in permeability of brain endothelium.

Serum and CSF anti-GM1 antibodies in patients with Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy.

High titers of antibodies directed against gangliosides, especially GM1, are found in the serum of patients with a variety of polyneuropathies, including those of the inflammatory type. We assayed anti-GM1 IgG and IgM levels in the serum and cerebrospinal fluid (CSF) of 23 patients with Guillain-Barré syndrome (GBS) and 10 with chronic inflammatory demyelinating polyneuropathy (CIDP) to investigate whether this immune response may also be localized within the intrathecal compartment and correlate with clinical parameters such as time interval since disease onset, disability score, preceding infectious episodes, and GM1 therapy. When compared to the control group, anti-GM1 IgG was increased in the serum of 39% of GBS and 10% of CIDP patients, whereas anti-GM1 IgM was elevated in 17% of GBS and none of the CIDP patients. In both patient groups, however, anti-GM1 antibody levels were more frequently elevated in CSF than paired sera: they belonged to the IgG class in 48% of GBS and 50% of CIDP patients, and to the IgM class in 48% of GBS and 55% of CIDP patients. In the GBS group, anti-GM1 IgM serum levels inversely correlated with time elapsed between sample collection and onset of disease (P < 0.05), whereas serum anti-GM1 IgG levels positively correlated with the loss of functional ability (P < 0.005). Increased anti-GM1 antibodies in GBS serum were not associated with clinical or serological evidence of infectious antecedents nor with previous GM1 treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukin-6 levels in the cerebrospinal fluid and serum of patients with Guillain-Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy

Clinical and experimental findings suggest that humoral factors, such as anti-peripheral nerve antibodies and cytokines, may be implicated in the immunopathogenesis of Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Interleukin-6 (IL-6) is a multifunctional cytokine that promotes immunoglobulin synthesis by B lymphocytes. Increased IL-6 release is associated with autoantibody production in a number of immune-mediated and neoplastic disorders. To investigate the possible involvement of abnormal IL-6 release in inflammatory polyneuropathies, we assayed IL-6 levels in the cerebrospinal fluid (CSF) and serum of 23 patients with acute GBS and seven with CIDP. We also studied 69 patients with other non-inflammatory neurological diseases (NIND), 25 with other inflammatory neurological diseases (IND), four with brain tumors (BT), and 15 normal donors (serum alone) as controls. We found detectable levels of IL-6 in the CSF of 57% of GBS, 43% of CIDP, 60% of IND, 75% of BT, and 4% of NIND. In GBS patients, no correlation was found between CSF IL-6 values and other laboratory or clinical parameters, such as CSF total protein, CSF albumin, CSF IgG, CSF/serum albumin ratio, functional disability score, and time elapsed from disease onset. Serum IL-6 levels were increased in six of 23 (26%) GBS, in one of 39 (3%) NIND, and in one of seven (14%) IND, but in none of the CIDP or BT patients. There was no correlation between serum and CSF IL-6 values, but cytokine levels in GBS sera correlated with time elapsed from clinical onset.(ABSTRACT TRUNCATED AT 250 WORDS)

Substance P antagonist blocks leakage and reduces activation of cytokine-stimulated rat brain endothelium.

We recently demonstrated that substance P mediates increased permeability of brain endothelium exposed to HIV-1 gp120. To test whether substance P is involved in immune processes at the blood-brain barrier (BBB), we stimulated rat brain endothelial cultures prepared from cerebral microvessels with Interferon-gamma (IFN-gamma) and Tumor necrosis factor-alpha (TNF-alpha), two proinflammatory cytokines that alter the BBB and measured permeability to albumin and expression of adhesion molecule ICAM-1 and MHC class II antigen in the presence and absence of spantide, a powerful substance P antagonist. In a dose-dependent manner, spantide completely neutralized increased permeability induced by TNF-alpha and IFN-gamma and expression of MHC class II molecule induced by IFN-gamma and prevented associated cell morphological changes as revealed by scanning electron microscope. Spantide also reduced expression of ICAM-1 induced by TNF-alpha and IFN-gamma by 35% and 30%, respectively. Substance P mRNA was found in unstimulated brain endothelial cells and was upregulated after stimulation with TNF-alpha and IFN-gamma. These in vitro findings demonstrate that substance P plays a major pathogenetic role in damaging and activating the BBB vascular component in the presence of proinflammatory cytokines.

High levels of C3c in the cerebrospinal fluid from amyotrophic lateral sclerosis patients

ABSTRACT – A study of several parameters of the humoral immunity in the serum and the cerebrospinal fluid (CSF) of thirtheen Amyotrophic Lateral Sclerosis (ALS) patients was carried out. A significant increase in CSF C3c was shown. This feature was found to be significantly correlated to the CSF albumin/serum albumin ratio (r = 0.70; p < 0.05) and to the total CSF proteins (r = 0.86; p < 0.01). The possible effect of the blood‐brain barrier breakdown on the CSF complement levels was evaluated. On the basis of the recently found biochemical changes in ALS cell membranes it is proposed that the high levels of the CSF C3c may also be due to a defective binding to the lymphocytes C3 receptors.

Circulating gp120 alters the blood-brain barrier permeability in HIV-1 gp120 transgenic mice.

The mechanism underlying invasion of the central nervous system by HIV-1 is unclear. We recently demonstrated blood-brain barrier changes in a model of HIV-1 gp120 transgenic mice. To test whether this alteration was intrinsic to the brain endothelium of transgenic mice or depended on circulating gp120, we used brain endothelial cultures from gp120 transgenic and non-transgenic mice and exposed them to serum from gp120 transgenic or non-transgenic mice. We measured permeability to albumin as a marker of functional endothelial integrity. A significant increase in permeability (up to 47%) was observed in transgenic and non-transgenic cultures exposed to serum samples from transgenic but not to those from non-transgenic mice. This permeability was neutralized after immunoabsorption of sera with anti-gp120 monoclonal antibody. These findings demonstrate that the blood-brain barrier alteration in HIV-1 gp120 transgenic mice is due to circulating gp120.