Biomedical subjects

Doina Ganea

Publications and source records attributed to Doina Ganea.

At least 37 records · Page 2Linked to original sources

PubMed2004

VIP/PACAP oppositely affects immature and mature dendritic cell expression of CD80/CD86 and the stimulatory activity for CD4(+) T cells.

The neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) released within lymphoid organs from nerve terminals and/or immune cells play a significant, anti-inflammatory role by inhibiting macrophage-induced inflammatory reactions and promoting T helper cell type 2 (Th2) responses. However, dendritic cells (DC) and not macrophages often are the major antigen-presenting cells and link between innate and adaptive immunity. The role of VIP/PACAP in DC development and function is mostly unknown. Here, we report that bone marrow-derived DC express VIP/PACAP receptors and that VIP and PACAP exert a differential effect on immature DC (iDC) and lipopolysaccharide (LPS)-treated DC. In iDC, VIP/PACAP up-regulates CD86 expression and enables them to stimulate T cell proliferation and differentiation into Th2 effectors in vivo and in vitro. In contrast, VIP/PACAP down-regulates CD80/CD86 expression in LPS-stimulated DC and strongly reduces their capacity to stimulate T cell proliferation and secretion of Th1 and Th2 cytokines. The VIP/PACAP effects on iDC and LPS-stimulated DC are mediated primarily through the VIP receptor 1. These results indicate that neuropeptides such as VIP and PACAP can differentially affect the function of iDC and mature DC. In the absence of an ongoing immune response, VIP/PACAP contributes to the initiation of Th2-type immunity, whereas in the presence of a full-blown, inflammatory reaction, VIP/PACAP act as anti-inflammatory agents.

Animals↗

PubMed2004

The significance of vasoactive intestinal peptide in immunomodulation.

First identified by Said and Mutt some 30 years ago, the vasoactive intestinal peptide (VIP) was originally isolated as a vasodilator peptide. Subsequently, its biochemistry was elucidated, and within the 1st decade, their signature features as a neuropeptide became consolidated. It did not take long for these insights to permeate the field of immunology, out of which surprising new attributes for VIP were found in the last years. VIP is rapidly transforming into something more than a mere hormone. In evolving scientifically from a hormone to a novel agent for modifying immune function and possibly a cytokine-like molecule, VIP research has engaged many physiologists, molecular biologists, biochemists, endocrinologists, and pharmacologists and it is a paradigm to explore mutual interactions between neural and neuroendocrine links in health and disease. The aim of this review is firstly to update our knowledge of the cellular and molecular events relevant to VIP function on the immune system and secondly to gather together recent data that support its role as a type 2 cytokine. Recognition of the central functions VIP plays in cellular processes is focusing our attention on this "very important peptide" as exciting new candidates for therapeutic intervention and drug development.

Adaptation, Physiological↗

PubMed2003

Vasoactive intestinal peptide prevents activated microglia-induced neurodegeneration under inflammatory conditions: potential therapeutic role in brain trauma.

In most neurodegenerative disorders, including multiple sclerosis, Parkinson's disease, and Alzheimer's disease, a massive neuronal cell death occurs as a consequence of an uncontrolled inflammatory response, where activated microglia and its cytotoxic agents play a crucial pathologic role. Because current treatments for these diseases are not effective, several regulatory molecules termed "microglia-deactivating factors" recently have been the focus of considerable research. Vasoactive intestinal peptide (VIP) is a neuropeptide with a potent anti-inflammatory effect, which has been found to protect from other inflammatory disorders, such as endotoxic shock and rheumatoid arthritis. In the present study, we investigate the effect of VIP on inflammation-mediated neurodegeneration in vitro and in vivo as well as on the putative neuroprotective effect of VIP on experimental pathological conditions in which central nervous system (CNS) inflammation is involved, such as brain trauma. The involvement of activated microglia and their derived cytotoxic products is also studied. VIP has a clear neuroprotective effect on inflammatory conditions by inhibiting the production of microglia-derived proinflammatory factors (tumor necrosis factor alpha, interleukin-1beta, nitric oxide). In this sense, VIP prevents neuronal cell death following brain trauma by reducing the inflammatory response of neighboring microglia. Therefore, VIP emerges as a valuable neuroprotective agent for the treatment of pathologic conditions of the CNS where inflammation-induced neurodegeneration occurs.

Animals↗

PubMed2003

Prostaglandin E2 inhibits production of the inflammatory chemokines CCL3 and CCL4 in dendritic cells.

Dendritic cells bridge innate and adaptive immunity and participate in both responses. Upon capture of pathogens, dendritic cells release inflammatory cytokines and chemokines, attracting other immune cells to the infection site. Anti-inflammatory cytokines, glucocorticoids, anti-inflammatory neuropeptides, and lipid mediators such as prostaglandin E2 (PGE2) limit and control the inflammatory response. In this study we report that exogenous PGE2 inhibits CCL3 (MIP-1alpha) and CCL4 (MIP-1beta) expression and release from dendritic cells stimulated with either lipopolysaccharide (LPS), a TLR4 ligand, or peptidoglycan, a TLR2 ligand. The inhibition is dose-dependent and occurs at both the mRNA and protein levels. The inhibitory effect is mediated through EP2 and EP4 receptors and requires the presence of PGE2 at the time of LPS stimulation. Intraperitoneal administration of PGE2 together with LPS results in a reduction in the levels of CCL3 and CCL4 released in the peritoneal fluid, a reduction in the number of dendritic cells accumulating in the peritoneal cavity, and a reduction in CCL3 amount per cell in the peritoneal cell population. These results suggest that one of the mechanisms by which endogenous PGE2 acts as an anti-inflammatory agent, is the inhibition of inflammatory chemokine release from activated dendritic cells, preventing the excess accumulation of activated immune cells.

Animals↗

PubMed2003

Vasoactive intestinal peptide inhibits IL-8 production in human monocytes by downregulating nuclear factor kappaB-dependent transcriptional activity.

Although interleukin-8 (IL-8) is a chemokine that plays a beneficial and central role in the inflammatory response, hematopoiesis, and angiogenesis, excessive IL-8 production can be deleterious to the host, and its selective inhibition represents an important therapeutic goal. Vasoactive intestinal peptide (VIP) is a neuropeptide that acts as a potent anti-inflammatory agent inhibiting the function of activated macrophages/monocytes. The present study reports the effect of VIP on IL-8 production by stimulated human THP1 monocytes. VIP inhibits IL-8 production in a dose- and time-dependent manner at the mRNA level. VIP seems to act by inhibiting the NF-kappaB-dependent IL-8 gene activation. The specific VPAC1 receptor mediates the inhibitory effect of VIP. Two transduction pathways appear to be involved, a major cAMP-independent pathway that preferentially blocks nuclear translocation of NF-kappaB and its binding to the kappaB site of the IL-8 promoter, and a cAMP-dependent pathway that inhibits the activation and binding to the IL-8 promoter of both CREB-binding protein (CBP) and TATA box-binding protein (TBP), two transcriptional cofactors strictly required for the transactivating activity of NF-kappaB. These findings support the proposed role of VIP as a key endogenous anti-inflammatory agent and describe a novel mechanism, i.e., the inhibition of the production of monocyte-derived IL-8, and are of obvious physiological significance, because VIP, through the inhibition of IL-8 production, could reduce the monocyte-induced neutrophil chemotaxis/infiltration, an important event in the pathogenesis of several inflammatory and autoimmune disorders.

Down-Regulation↗

PubMed2003

Neuroprotective effect of vasoactive intestinal peptide (VIP) in a mouse model of Parkinson's disease by blocking microglial activation.

Parkinson's disease (PD) is a common neurodegenerative disorder with no effective protective treatment, characterized by a massive degeneration of dopaminergic neurons in the substantia nigra (SNpc) and the subsequent loss of their projecting nerve fibers in the striatum. To elucidate PD pathogenic factors, and thus to develop therapeutic strategies, a murine PD model based on the administration of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) has been used extensively. It has been demonstrated that activated microglia cells actively participate in the pathogenesis of MPTP-induced PD through the release of cytotoxic factors. Because current treatments for PD are not effective, considerable research focused lately on a number of regulatory molecules termed microglia-deactivating factors. Vasoactive intestinal peptide (VIP), a neuropeptide with a potent anti-inflammatory effect, has been found to be protective in several inflammatory disorders. This study investigates the putative protective effect of VIP in the MPTP model for PD. VIP treatment significantly decreases MPTP-induced dopaminergic neuronal loss in SNpc and nigrostriatal nerve-fiber loss. VIP prevents MPTP-induced activation of microglia in SNpc and striatum and the expression of the cytotoxic mediators, iNOS, interleukin 1beta, and numor necrosis factor alpha. VIP emerges as a potential valuable neuroprotective agent for the treatment of pathologic conditions in the central nervous system, such as PD, where inflammation-induced neurodegeneration occurs.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed2003

Vasoactive intestinal peptide inhibits IL-8 production in human monocytes.

Vasoactive intestinal peptide (VIP), a neuropeptide present in the lymphoid microenvironment, acts as a potent anti-inflammatory agent that inhibits the function of activated macrophages. VIP was shown to inhibit IL-6, TNFalpha, IL-12, chemokine, and nitric oxide production in endotoxin-activated macrophages. The present study reports the effect of VIP on IL-8 production by stimulated human monocytes. VIP inhibits IL-8 production in a dose- and time-dependent manner at the mRNA level. The specific VPAC1 receptor mediates the inhibitory effect of VIP. Two transduction pathways appear to be involved, a major cAMP-independent pathway and a secondary cAMP-dependent pathway. Of obvious physiological significance is the fact that VIP, presumably through the inhibition of IL-8 production, dramatically reduces the monocyte-induced neutrophil chemotaxis, an important event in the pathogenesis of several inflammatory and autoimmune disorders. These findings support the proposed role of VIP as a key endogenous anti-inflammatory agent and describe a novel mechanism, i.e., the inhibition of the production of monocyte-derived IL-8.

Anti-Inflammatory Agents↗

PubMed2003

Prostaglandin E2 inhibits TNF production in murine bone marrow-derived dendritic cells.

Exposure to pathogens induces dendritic cells to release inflammatory cytokines and chemokines. The inflammatory response is controlled by endogenous agents such as anti-inflammatory cytokines, glucocorticoids, anti-inflammatory neuropeptides, and lipid mediators. This study is the first report on the inhibition by prostaglandin E2 (PGE2) of TNF release from bone marrow-derived dendritic cells stimulated with lipopolysaccharide (LPS), a TLR4 ligand, or peptidoglycan, a TLR2 ligand. The inhibition of TNF occurs at both mRNA and protein level. The inhibitory effect of PGE2 is mediated by the EP2 and EP4 receptors, and involves both PKA signaling and mediation by DC-derived IL-10. Intraperitoneal administration of PGE2 together with LPS results in a reduction in serum TNF and intracellular TNF in peritoneal exudate cells, compared to LPS alone. In addition, administration of PGE2 in vivo reduces the numbers of CD11c+ DCc that accumulate in the peritoneal cavity in response to LPS. The various implications of the PGE2-induced reduction in TNF are discussed.

Animals↗

PubMed2003

Galanin down-regulates microglial tumor necrosis factor-alpha production by a post-transcriptional mechanism.

The neuropeptide galanin (GAL) is up-regulated following neuronal axotomy or inflammation. Since other neuropeptides act as immunomodulatory agents, we sought to determine whether GAL might affect the murine microglial cell line BV2, which expresses the GAL2 receptor. Even at very low concentrations, GAL inhibited tumor necrosis factor-alpha (TNF alpha) release but not TNF alpha mRNA levels in LPS-stimulated BV2 cells. Northern blot analysis showed that GAL inhibited the addition of a poly(A) tail, and stability assays showed that it also destabilized TNF alpha mRNA. Thus, GAL inhibits TNF alpha production by a post-transcriptional mechanism that both prevents the efficient addition of the poly(A) tail and accelerates TNF alpha mRNA degradation.

Alzheimer Disease↗

PubMed2003

Acute down-regulation of antibody production following spinal cord injury: role of systemic catecholamines.

We investigated whether antibody production to antigens arising in the subarachnoid space is depressed acutely after spinal cord injury (SCI), and whether such depression is due to abnormal catecholamine levels. To assess antibody responses, ovalbumin (OVA) was injected into the spinal subarachnoid space (i.t.) of rats via an indwelling catheter after SCI at T4 or laminectomy (LAM). Antibody responses tested at days 0, 7, and 14 (d0, d7, d14) postinjury revealed that SCI animals exhibited an antibody response significantly lower than LAM animals on d7, but one that reached control levels by d14. ELISPOT assays indicated that the cervical lymph nodes, known to be innervated by superior cervical ganglia (SCG), processed i.t. OVA. The reduction in antibody production after SCI could not be mimicked with surgical deafferentation of the SCG. However, blockade of beta-adrenergic receptors prior to SCI did reverse the decrease, suggesting an adverse effect of the surge of catecholamines that accompanies the injury. Surgical removal of sympathetic inputs to the cervical lymph nodes prior to SCI failed to reverse the effect on antibody production, suggesting a systemic source of catecholamines. We conclude that antibody responses against i.t. antigens are attenuated acutely after SCI due to the massive release of systemic catecholamines that accompanies SCI.

Adrenergic beta-Antagonists↗

PubMed2003

PACAP in immunity and inflammation.

The pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide belonging to the VIP/secretin/glucagon family of peptides, produced by the lymphoid cells, which exerts a wide spectrum of immunological functions controlling the homeostasis of immune system through different receptors expressed in various immunocompetent cells. In the last decade, PACAP has been clearly identified as a potent anti-inflammatory factor that exerts its function by regulating the production of both anti- and proinflammatory mediators. In this sense, PACAP prevents death by septic shock, an acute inflammatory disease with a high mortality. In addition, PACAP regulates the expression of costimulatory molecules, inasmuch as this related to the modulation in the shift from Th1 towards Th2 differentiation. We recently reported that PACAP prevents the deleterious effects of arthritis by downregulating both inflammatory and autoimmune components of the disease. Therefore, PACAP and analogs have been proposed as very promising candidates, alternative to other existing treatments, for treating acute and chronic inflammatory and autoimmune diseases, such as septic shock, arthritis, multiple sclerosis, Crohn's disease, or autoimmune diabetes.

Animals↗

PubMed2003

Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit the production of inflammatory mediators by activated microglia.

Microglia play a central role in the regulation of immune and inflammatory activities, as well as tissue remodeling in the central nervous system. However, activation of microglia is a histopathological hallmark of several neurodegenerative diseases. Pathological microglial activation is believed to contribute to progressive damage in neurodegenerative diseases through the release of proinflammatory and/or cytotoxic factors, including tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-1beta, IL-6, IL-12, and nitric oxide (NO). Hence, it is important to unravel mechanisms regulating microglia activation of inflamed brain parenchyma to provide insights into efficient therapeutic intervention. This study examines the role of two anti-inflammatory neuropeptides, the vasoactive intestinal peptide (VIP) and the pituitary adenylate cyclase-activating polypeptide (PACAP) on the production of various proinflammatory factors by endotoxin-stimulated microglia. VIP and PACAP inhibit TNF-alpha, IL-1beta, IL-6, and NO production by lipopolysaccharide (LPS)-activated microglia. The specific type 1 VIP receptor mediates the inhibitory effect of VIP/PACAP, and cyclic adenosine monophosphate is the major, second messenger involved. VIP and PACAP regulate the production of these proinflammatory factors at a transcriptional level by inhibiting p65 nuclear translocation and nuclear factor-kappaB-DNA binding. This effect is mediated, as neuropeptides stabilize the inhibitor IkappaB by inhibiting LPS-induced IkappaB-kinase activity. Therefore, the inhibitory effects on the production of proinflammatory mediators define VIP and PACAP as "microglia-deactivating factors" with significant, therapeutical potential for inflammatory/degenerative brain disorders.

Animals↗

PubMed2003

The neuropeptides VIP/PACAP and T cells: inhibitors or activators?

The structurally related neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating polypeptide (PACAP) are released within the lymphoid organs following antigenic stimulation, and modulate the function of inflammatory cells through specific receptors. In activated macrophages, VIP and PACAP inhibit the expression at both mRNA and protein level of pro-inflammatory cytokines and chemokines, through effects on de novo expression or nuclear translocation of a number of transcription factors, i.e. NFkB, CREB, c-Jun, JunB, and IRF-1. In addition, VIP and PACAP promote Th2-type, and inhibit Th1-type responses in vivo and in vitro, through several mechanisms, including preferential survival of Th2 effectors and subsequent generation of Th2 memory cells. The function of VIP/PACAP as "macrophage deactivating factors" appears to be responsible for their protective effect in vivo in models of septic shock. Both deactivation of macrophages and inhibition of Th1-type responses appear to be responsible for the beneficial effect of VIP/PACAP in models of Th1-type autoimmune diseases such as rheumatoid arthritis.

Animals↗

PubMed2002

Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide promote in vivo generation of memory Th2 cells.

Functionally active effector T cells are generated through clonal expansion. Most effector T cells are later eliminated, whereas a small number survive and differentiate into memory T cells. The mechanisms by which some effector T cells escape apoptosis and become memory T cells are not understood. Neuropeptides such as the vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) inhibit antigen-induced apoptosis of CD4 T cells. By using an in vivo long-term experimental model, in which CD4 T cells from TRC-transgenic mice were transferred into hosts, we demonstrate that VIP and PACAP induce the survival and/or generation of antigen-specific CD4 T cells with a memory Th2 phenotype. This was confirmed by the fact that transgenic CD4 T cells were recovered only from mice that received Th2, but not Th1 effector cells, in the presence of VIP or PACAP. In vitro, VIP/PACAP support the survival of Th2, but not Th1, cell lines through an inhibition of antigen-induced apoptosis. The role of neuropeptides in the biased development of Th2 memory cells is particularly relevant in view of the immune deviation existing in immune-privileged sites such as the brain and eye, where Th2, but not Th1, responses occur in nonpathological conditions.

Animals↗

PubMed2002

Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit chemokine production in activated microglia.

Microglia react to even minor disturbances in CNS homeostasis and function as critical regulators of CNS inflammation. Activated microglia secrete inflammatory mediators such as cytokines and chemokines, which contribute to the pathophysiological changes associated with several neuroimmunologic disorders. Microglia-derived inflammatory chemokines recruit various populations of immune cells, which initiate and maintain the inflammatory response against foreign antigens. Entry and retention of activated immune cells in the CNS is a common denominator in a variety of traumatic, ischemic, and degenerative diseases. Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are two structurally related neuropeptides that function as potent anti-inflammatory factors in the periphery. Here we investigated the effects of VIP and PACAP on chemokine production by activated microglia. VIP and PACAP inhibit the expression of the microglia-derived CXC chemokines MIP-2 and KC, and of the CC chemokines MIP-1alpha, -1beta, MCP-1, and RANTES. The inhibition of chemokine gene expression correlates with an inhibitory effect of VIP/PACAP on NFkB binding. The VIP/PACAP inhibition of both chemokine production and of NFkB binding is mediated through the specific receptor VPAC1 and involves a cAMP-dependent intracellular pathway. Of biological significance is the fact that the inhibition of chemokine production by VIP/PACAP leads to a significant reduction in the chemotactic activity generated by activated microglia for peripheral leukocytes, i.e., neutrophils, macrophages, and lymphocytes. Because reduction in the number and activation of infiltrating leukocytes represents an important factor in the control of inflammation in the CNS, VIP and/or PACAP released by neurons during an inflammatory response could serve as neuronal survival factors by limiting the inflammatory process.

Animals↗

PubMed2002

Inhibition of microglial CD40 expression by pituitary adenylate cyclase-activating polypeptide is mediated by interleukin-10.

Microglia are intrinsic mediators of the central nervous system (CNS) immune response induced by a variety of insults. Activated microglia express costimulatory molecules CD40 and B7 that are important equally for T-cell activation and further activation of microglia. In this study, we sought to investigate the regulation of costimulatory molecule expression on primary microglia and microglial cell line, BV-2, by pituitary adenylyl cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP), potent anti-inflammatory neuropeptides. The neuropeptides inhibited CD40 and B7-2 mRNA expression in activated microglia. PACAP decreased surface expression of CD40 and B7-2 on activated microglia. The inclusion of an anti-IL-10 antibody completely abrogated PACAP inhibition of lipopolysaccharide (LPS)-induced CD40 expression, suggesting that PACAP inhibition is at least in part mediated by IL-10. Indeed, PACAP enhanced LPS-induced IL-10 mRNA and protein levels in microglia. These data indicate that PACAP, through an increase in IL-10 protein, can down-regulate important costimulatory molecule expression on microglia, thereby possibly affecting CNS immunity.

Animals↗

PubMed2002

VIP and PACAP down-regulate CXCL10 (IP-10) and up-regulate CCL22 (MDC) in spleen cells.

The immunoregulatory neuropeptides VIP and PACAP favor Th2-type immune responses. Antigen-stimulated Th2 cells produce VIP, VIP/PACAP induce Th2 cytokine responses, and promote the preferential survival of Th2 effectors. In this study, we investigate the effects of VIP/PACAP on two chemokines, i.e. CXCL10 (IP-10) acting on CXCR3 expressed on activated Th1 cells, and CCL22 (MDC) acting on CCR4 and 8 expressed on activated Th2 cells. VIP and PACAP down-regulate CXCL10, and up-regulate CCL22 in vivo and in vitro. The effects on the two chemokines appear to be different in mechanistic terms. The fact that VIP/PACAP might promote the directed migration of Th2 cells adds a new dimension to their participation in the Th2 auto-regulatory loop.

Animals↗

PubMed2002

Vasoactive intestinal peptide (VIP) inhibits the proliferation of bone marrow progenitors through the VPAC1 receptor.

OBJECTIVE: The cellular and molecular mechanisms of hematopoietic stimulation have been studied. However, an understanding of negative effects in the hematopoietic system remains elusive. To this end, we studied the effects of vasoactive intestinal peptide (VIP) on bone marrow (BM) progenitors. MATERIALS AND METHODS: Different BM cell subsets were used to perform clonogenic assay for granulocytic (CFU-GM) or erythroid (BFU-E and CFU-E) progenitors with 10(-7)-10(-13) M VIP. The relevant receptor was verified with specific antagonists, or agonists, semi-quantitative RT-PCR, and chemical cross-linking studies with stromal membranes. RESULTS: Assays performed with unfractionated mononuclear cells and enriched CD34(+) cells showed dose-dependent inhibition on BM progenitors with significant inhibition up to 10(-10) M. Nylon wool separated cells, which depleted stroma, reversed the inhibitory effects of VIP between 10 and 20%. Combined experimental evaluation indicated that the effects of VIP on BM functions are mediated through the type 1 receptor (VPAC1). VIP induced the production of TGF-beta and TNF-alpha in BM mononuclear cells and stroma. These cytokines are partly involved in reversing the suppressive effects of VIP on CFU-GM. CONCLUSIONS: The effect of VIP on BM progenitors could be mediated through direct and indirect mechanism. Direct effects were evident by the suppressive effects of VIP on clonogenic assays with highly purified CD34(+) cells. Indirect effects were mediated through putative functions of the stromal cells and the production of TGF-beta and TNF-alpha.

Adult↗