Contrasting pattern of cytokines in antigen- versus mitogen-stimulated splenocyte cultures from chemically denervated mice

Streptococcus pneumoniae fructose-1,6-bisphosphate aldolase, a protein vaccine candidate, elicits Th1/Th2/Th17-type cytokine responses in mice

Streptococcus pneumoniae (S. pneumoniae) is a major pathogen worldwide. The currently available polysaccharide-based vaccines significantly reduce morbidity and mortality. However, the inherent disadvantages of the currently available polysaccharide-based vaccines have motivated the search for other bacterial immunogens capable of eliciting a protective immune response against S. pneumoniae. Fructose-1,6-bisphosphate aldolase (FBA) is a glycolytic enzyme, which was found to localize to the bacterial surface, where it functions as an adhesin. Previously, immunizing mice with recombinant FBA (rFBA) in the presence of alum elicited a protective immune response against a lethal challenge with S. pneumoniae. Thus, the aim of the present study was to determine the cytokine responses that are indicative of protective immunity following immunization with rFBA. The protective effects against pneumococcal challenge in mice immunized with rFBA with complete Freund's adjuvant (CFA) in the initial immunization and with incomplete Freund's adjuvant (IFA) in booster immunizations surpassed the protective effects observed following immunization with either rFBA + alum or pVACfba. CD4+ T-cells obtained from the rFBA/CFA/IFA/IFA-immunized mice co-cultured with rFBA-pulsed antigen-presenting cells (APCs), exhibited a significantly greater proliferative ability than CD4+ T-cells obtained from the adjuvant-immunized mice co-cultured with rFBA‑pulsed APCs. The levels of the Th1-type cytokines, interferon (IFN)-γ, interleukin (IL)-2, tumor necrosis factor (TNF)-α and IL-12, the Th2-type cytokines, IL-4, IL-5 and IL-10, and the Th17-type cytokine, IL-17A, significantly increased within 72 h of the initiation of co-culture with CD4+ T-cells obtained from the rFBA‑immunized mice, in comparison with the co-cultures with CD4+ T-cells obtained from the adjuvant-immunized mice. Immunizing mice with rFBA resulted in an IgG1/IgG2 ratio of 41, indicating a Th2 response with substantial Th1 involvement. In addition, rabbit and mouse anti-rFBA antisera significantly protected the mice against a lethal S. pneumoniae challenge in comparison with preimmune sera. Our results emphasize the mixed involvement of the Th1, Th2 and Th17 arms of the immune system in response to immunization with pneumococcal rFBA, a potential vaccine candidate.

Role of the sympathetic nervous system in carbon tetrachloride-induced hepatotoxicity and systemic inflammation

Carbon tetrachloride (CCl₄) is widely used as an animal model of hepatotoxicity and the mechanisms have been arduously studied, however, the contribution of the sympathetic nervous system (SNS) in CCl₄-induced acute hepatotoxicity remains controversial. It is also known that either CCl₄ or SNS can affect systemic inflammatory responses. The aim of this study was to establish the effect of chemical sympathectomy with 6-hydroxydopamine (6-OHDA) in a mouse model of CCl₄-induced acute hepatotoxicity and systemic inflammatory response. Mice exposed to CCl₄ or vehicle were pretreated with 6-OHDA or saline. The serum levels of aminotransferases and alkaline phosphatase in the CCl₄-poisoning mice with sympathetic denervation were significantly lower than those without sympathetic denervation. With sympathetic denervation, hepatocellular necrosis and fat infiltration induced by CCl₄ were greatly decreased. Sympathetic denervation significantly attenuated CCl₄-induced lipid peroxidation in liver and serum. Acute CCl₄ intoxication showed increased expression of inflammatory cytokines/chemokines [eotaxin-2/CCL24, Fas ligand, interleukin (IL)-1α, IL-6, IL-12p40p70, monocyte chemoattractant protein-1 (MCP-1/CCL2), and tumor necrosis factor-α (TNF-α)], as well as decreased expression of granulocyte colony-stimulating factor and keratinocyte-derived chemokine. The overexpressed levels of IL-1α, IL-6, IL-12p40p70, MCP-1/CCL2, and TNF-α were attenuated by sympathetic denervation. Pretreatment with dexamethasone significantly reduced CCl₄-induced hepatic injury. Collectively, this study demonstrates that the SNS plays an important role in CCl₄-induced acute hepatotoxicity and systemic inflammation and the effect may be connected with chemical- or drug-induced hepatotoxicity and circulating immune response.

Neuroendocrine effects of stress on immunity in the elderly: implications for inflammatory disease

Age-related changes in immune function leave older adults at risk for a host of inflammatory diseases. Immune-mediated inflammatory processes are regulated by neuroendocrine hormones, including glucocorticoids, dehydroepiandrosterone, and the catecholamines, epinephrine, and norepinephrine. This regulation, however, becomes impaired in older adults in light of age-related changes in endocrine function. Chronic stress shows similarly harmful effects on neuroendocrine and immune function and may, therefore, combine with age to further increase disease risk in older adults. This article highlights evidence for the impact of age and stress on neuroendocrine regulation of inflammatory processes that may substantially increase risk for inflammatory disease at older ages.

Sympathetic nervous system control of anti-influenza CD8+ T cell responses

Despite the longstanding appreciation of communication between the nervous and the immune systems, the nature and significance of these interactions to immunity remain enigmatic. Here, we show that 6-hydroxydopamine-mediated ablation of the mouse peripheral sympathetic nervous system increases primary CD8(+) T cell responses to viral and cellular antigens presented by direct priming or cross-priming. The sympathetic nervous system also suppresses antiviral CD4(+) T cell responses, but this is not required for suppressing CD8(+) T cell responses. Adoptive transfer experiments indicate that enhanced CD8(+) responses do not result from permanent alterations in CD8(+) T cell function in sympathectomized mice. Rather, additional findings suggest that the sympathetic nervous system tempers the capacity of antigen-presenting cells to activate naïve CD8(+) T cells. We also show that antiviral CD8(+) T cell responses are enhanced by administration of a beta(2) (but not beta(1) or alpha) adrenergic antagonist. These findings demonstrate a critical role for the sympathetic nervous system in limiting CD8(+) T cell responses and indicate that CD8(+) T cell responses may be altered in patients using beta-blockers, one of the most widely prescribed classes of drugs.

Sympathetic modulation of immunity: relevance to disease

Optimal host defense against pathogens requires cross-talk between the nervous and immune systems. This paper reviews sympathetic-immune interaction, one major communication pathway, and its importance for health and disease. Sympathetic innervation of primary and secondary immune organs is described, as well as evidence for neurotransmission with cells of the immune system as targets. Most research thus far has focused on neural-immune modulation in secondary lymphoid organs, has revealed complex sympathetic modulation resulting in both potentiation and inhibition of immune functions. SNS-immune interaction may enhance immune readiness during disease- or injury-induced 'fight' responses. Research also indicate that dysregulation of the SNS can significantly affect the progression of immune-mediated diseases. However, a better understanding of neural-immune interactions is needed to develop strategies for treatment of immune-mediated diseases that are designed to return homeostasis and restore normal functioning neural-immune networks.

Role of adrenoceptor-coupled second messenger system in sympatho-adrenomedullary modulation of splenic macrophage functions in live fish Channa punctatus

In order to understand the role of sympatho-adrenomedullary (SAM) system in mediating stress effect on non-specific immune responses in fishes, the splenic macrophage phagocytic and respiratory burst activities of normal and chemically sympathectomized Channa punctatus under restraint stress were studied. Chemical sympathectomy abrogated the differential effects of acute stress on diverse functions of macrophages. The SAM regulation of macrophage activities was substantiated by in vitro experiments with catecholamines, the end product of SAM system. Further, for the first time in fishes, different adrenoceptors and their precise second messenger system regulating diverse functions of macrophages by catecholamines were demonstrated. Norepinephrine (NE)/epinephrine (E) decreased the phagocytosis through beta-adrenergic receptor as only propranolol, the beta-adrenergic receptor antagonist, blocked the suppressive effect of NE/E. However, dopamine (DA) regulates phagocytosis solely via the dopaminergic receptor. The DA effect was mimicked by DA receptor agonists, apomorphine and bromocryptine. Adenylate cyclase system linked to beta-adrenoceptor/dopaminergic receptor seems to be involved in mediating the effect of catecholamine on phagocytosis since db cAMP inhibited the phagocytosis in a dose-dependent manner. In case of superoxide production, only phenoxybenzamine, an alpha-adrenergic receptor antagonist, was seen effective in blocking the stimulatory effect of NE/E. Further, Ca2+ as second messenger system coupled to alpha1-adrenergic receptor was shown to mediate this effect since phospholipase C (PLC) inhibitor, U73122 and intracellular calcium chelating agent, BAPTA-AM downregulated the NE/E-induced superoxide production. The role of calcium in modulation of superoxide production was also emphasized using calcium ionophore A23187.

Cytokine- and interferon-modulating properties of Echinacea spp. root tinctures stored at -20 degrees C for 2 years

Echinacea spp. phytomedicines are popular for treating upper respiratory infections. The purpose of this investigation was to examine the immunomodulatory properties of Echinacea tinctures from seven species after being stored at -20 degrees C for 2 years. Two experimental techniques were employed using human peripheral blood mononuclear cells (PBMC). In the first set of experiments, PBMCs were stimulated in vitro with tinctures alone and assayed for proliferation and production of interleukin-10 (IL-10), IL-12, and tumor necrosis factor-alpha (TNF-alpha). In the second set of experiments, subjects were immunized with influenza vaccine. PBMCs from vaccinated individuals were stimulated in vitro with Echinacea tinctures and influenza virus; cytokine production (IL-2, IL-10, and interferon-gamma [IFN-gamma]) was compared prevaccination and postvaccination. In the first experiments, (1) tinctures from E. angustifolia, E. pallida, E. paradoxa, and E. tennesseensis stimulated proliferation and tended to increase IL-10, (2) E. sanguinea and E. simulata stimulated only proliferation, (3) E. purpurea stimulated only IL-10, and (4) none of the extracts influenced IL-12 or TNF-alpha. In the second experiments, (1) tinctures from E. pallida, E. paradoxa, E. sanguinea, and E. simulata diminished influenza-specific IL-2, and (2) none of the extracts influenced influenza-specific IL-10 or IFN-gamma. For in vitro models using Echinacea, immune response may vary based on stimulus (Echinacea alone vs. Echinacea + recall stimulation with virus).

Increased splenocyte mitogenesis following sympathetic denervation in Xenopus laevis

Studies in mammals reveal that ablation of the sympathetic nervous system (SNS) can alter in vivo and in vitro parameters of immunity. To shed some light on the phylogenetic history of the interactions between the SNS and the immune system, we studied the effects of chemical sympathectomy on the proliferative response of frog splenocytes to mitogens. Adult Xenopus laevis were injected with 6-hydroxydopamine 3 days before removal of spleen cells for culture with mitogens. Splenocytes from sympathectomized frogs exhibited an increased proliferative response to the T cell mitogens PHA and ConA and the B cell mitogen, LPS. That sympathectomy appears to effect a release from tonic inhibition by the SNS in Xenopus is consistent with comparable experiments in mice. It also reveals a phylogenetically ancient origin for SNS-immune system communications.

Ablation of peripheral dopaminergic nerves stimulates malignant tumor growth by inducing vascular permeability factor/vascular endothelial growth factor-mediated angiogenesis

Many important physiological and pathological processes are modulated by angiogenesis. It has been shown that initiation of this angiogenic process is an essential early step in the progression of malignant tumors. We report here that ablation of peripheral dopaminergic nerves markedly increased angiogenesis, microvessel density, microvascular permeability, and growth of malignant tumors in mice. Endogenous peripheral dopamine acted through D2 receptors as significantly more angiogenesis and tumor growth was observed in D2 dopamine receptor knockout mice in comparison with controls. The vascular endothelial growth factor receptor 2 phosphorylation, which is critical for promoting angiogenesis, was also significantly more in tumor endothelial cells collected from the dopamine-depleted and D2 dopamine receptor knockout animals. These results reveal that peripheral endogenous neurotransmitter dopamine might be an important physiological regulator of vascular endothelial growth factor-mediated tumor angiogenesis and growth and suggest a novel link between endogenous dopamine, angiogenesis, and tumor growth.

The induction of splenic suppressor T cells through an immune-privileged site requires an intact sympathetic nervous system

Antigen injection into the eye's anterior chamber (AC) induces the antigen-specific suppression of delayed-type hypersensitivity (DTH) that is mediated by NKT cells and splenic CD8+ suppressor T cells. Because the AC, uveal tissues, the thymus and spleen required to induce anterior chamber-associated immune deviation (ACAID) have dense sympathetic innervations, we examined the effects of chemical sympathectomy of mice by 6-hydroxydopamine (6-OHDA) on the induction of the suppression of contact sensitivity to trinitrophenol (TNP) induced by the injection of TNP-bovine serum albumin (BSA) into the anterior chamber. DTH measured as contact sensitivity to picrylchloride was not induced in mice that received 6-OHDA before immunization with TNP-BSA. Although spleen cells from 6-OHDA-treated TNP-BSA-immunized mice produced IFN-gamma when stimulated by TNP-BSA, the number of DTH-initiating hepatic NKT cells was reduced markedly in 6-OHDA-treated mice. Chemically denervated mice did not produce splenic suppressor T cells or thymic NKT cells that activate splenic suppressor T cells. We suggest that an intact sympathetic nervous system (SNS) is required to maintain cellular immunoregulation.

Cyclophosphamide induces dose- and time-dependent elevations in spleen norepinephrine levels of BALB/c mice

Chemotherapeutic drugs may not only kill rapidly dividing cells but may also alter the extracellular environment of surviving cells. We investigated the possibility that cyclophosphamide might alter the noradrenergic environment of the spleen. Male BALB/cByJ mice were administered a single injection of cyclophosphamide (0, 15, 50, or 100 mg/kg). Seventy-two hours after injection animals receiving 50 or 100 but not 15 mg/kg experienced elevated norepinephrine concentrations (pmol/mg) compared to animals given 0 mg/kg. The time course of changes in norepinephrine concentration was investigated 24-216 h after administration of 50 mg/kg cyclophosphamide; norepinephrine took 48 h to elevate, remained elevated for 48-96 h, and returned to vehicle-treated levels by 120 h. Cyclophosphamide in both experiments reduced spleen mass but did not alter total norepinephrine/spleen. These results suggest that low doses of cyclophosphamide can increase the norepinephrine available to influence cell-cell interactions in the spleen.