Dimethyl fumarate, an immune modulator and inducer of the antioxidant response, suppresses HIV replication and macrophage-mediated neurotoxicity: a novel candidate for HIV neuroprotection

Despite antiretroviral therapy (ART), HIV infection promotes cognitive dysfunction and neurodegeneration through persistent inflammation and neurotoxin release from infected and/or activated macrophages/microglia. Furthermore, inflammation and immune activation within both the CNS and periphery correlate with disease progression and morbidity in ART-treated individuals. Accordingly, drugs targeting these pathological processes in the CNS and systemic compartments are needed for effective, adjunctive therapy. Using our in vitro model of HIV-mediated neurotoxicity, in which HIV-infected monocyte-derived macrophages release excitatory neurotoxins, we show that HIV infection dysregulates the macrophage antioxidant response and reduces levels of heme oxygenase-1 (HO-1). Furthermore, restoration of HO-1 expression in HIV-infected monocyte-derived macrophages reduces neurotoxin release without altering HIV replication. Given these novel observations, we have identified dimethyl fumarate (DMF), used to treat psoriasis and showing promising results in clinical trials for multiple sclerosis, as a potential neuroprotectant and HIV disease-modifying agent. DMF, an immune modulator and inducer of the antioxidant response, suppresses HIV replication and neurotoxin release. Two distinct mechanisms are proposed: inhibition of NF-κB nuclear translocation and signaling, which could contribute to the suppression of HIV replication, and induction of HO-1, which is associated with decreased neurotoxin release. Finally, we found that DMF attenuates CCL2-induced monocyte chemotaxis, suggesting that DMF could decrease recruitment of activated monocytes to the CNS in response to inflammatory mediators. We propose that dysregulation of the antioxidant response during HIV infection drives macrophage-mediated neurotoxicity and that DMF could serve as an adjunctive neuroprotectant and HIV disease modifier in ART-treated individuals.     

P. falciparum enhances HIV replication in an experimental malaria challenge system

Co-infection with HIV and P. falciparum worsens the prognosis of both infections; however, the mechanisms driving this adverse interaction are not fully delineated. To evaluate this, we studied HIV-1 and P. falciparum interactions in vitro using peripheral blood mononuclear cells (PBMCs) from human malaria na?ve volunteers experimentally infected with P. falciparum in a malaria challenge trial. PBMCs collected before the malaria challenge and at several time points post-infection were infected with HIV-1 and co-cultured with either P. falciparum infected (iRBCs) or uninfected (uRBCs) red blood cells. HIV p24Ag and TNF-α, IFN-γ, IL-4, IL-6, IL-10, IL-17, and MIP-1α were quantified in the co-culture supernatants. In general, iRBCs stimulated more HIV p24Ag production by PBMCs than did uRBCs. HIV p24Ag production by PBMCs in the presence of iRBCs (but not uRBCs) further increased during convalescence (days 35, 56, and 90 post-challenge). In parallel, iRBCs induced higher secretion of pro-inflammatory cytokines (TNF-α, IFN-γ, and MIP-1α) than uRBCs, and production increased further during convalescence. Because the increase in p24Ag production occurred after parasitemia and generalized immune activation had resolved, our results suggest that enhanced HIV production is related to the development of anti-malaria immunity and may be mediated by pro-inflammatory cytokines.     

Tetrahydrocannabinol treatment suppresses growth restriction of Legionella pneumophila in murine macrophage cultures.

Legionella pneumophila is a facultative intracellular pathogen which readily grows in human and guinea pig macrophages and in peritoneal exudate macrophages from A/J mice. Macrophage cultures capable of supporting the growth of Legionella can be used to test the potency of biologically active substances suspected of modulating host mechanisms of resistance to infection. Accordingly, this model was used to evaluate the influence of delta-9-tetrahydro-cannabinol (THC) on macrophage resistance to infection with an intracellular pathogen. Pretreatment of the macrophages with THC in the concentration range of 2.5 micrograms/ml (8 microM) to 5.0 micrograms/ml (16 microM) had little if any effect on the ability of the macrophages to either ingest or support the replication of Legionella. However, THC treatment of cells following Legionella infection resulted in increased numbers of bacteria recoverable from the macrophage cultures. Stimulation of the macrophage cultures with the activating agent lipopolysaccharide (LPS) was effective in reducing the ability of Legionella to grow in the cells. However, treatment of the LPS activated macrophages with THC resulted in greater growth of the Legionella in the cultures, indicating that the drug abolished the LPS induced enhanced resistance. These results demonstrate that THC treatment of macrophages following infection rather than before infection with Legionella promotes the replication of the bacteria within the macrophages. In addition, drug treatment suppresses the growth restricting potential of macrophages activated by LPS.     

Benzylideneacetone suppresses both cellular and humoral immune responses of Spodoptera exigua and enhances fungal pathogenicity

An entomopathogenic fungus, Beauveria bassiana, had significant insecticidal activity against the beet armyworm, Spodoptera exigua. However, it took almost one week to cause significant mortality. This study used a mixture treatment with an immunosuppressant to enhance the fungal pathogenicity. A bacterial metabolite, benzylideneacetone (BZA), had a significant synergistic effect on the fungal pathogenicity against S. exigua, although it had little insecticidal activity by itself. The mixture treatment shortened median lethal time of B. bassiana by approximately 2 days. The synergistic activity of BZA on the pathogenicity of B. bassiana was induced by its immunosuppressive effects on both cellular and humoral antifungal responses of S. exigua. In response to B. bassiana, S. exigua larvae can form hemocytic nodules. Nodules were significantly suppressed by BZA treatment. Moreover, BZA inhibited expression of some antimicrobial peptide genes of S. exigua in response to fungal challenge. The immunosuppressive condition induced by BZA allowed B. bassiana to easily colonize and multiply in the hemocoel of treated larvae, which resulted in significant enhancement of the pathogenicity of B. bassiana.     

驱虫斑鸠菊对小鼠免疫分子的影响

探讨驱虫斑鸠菊对小鼠免疫功能的影响,揭示其免疫作用机理。利用[^3H]-TdR参入法测定驱虫斑鸠菊对小鼠体内免疫功能的影响,运用酶联免疫吸附实验测定驱虫斑鸠菊对小鼠B淋巴细胞分泌抗体功能的影响;采用流式细胞测定方法测定CD19B细胞亚类表达水平;采用[^3H]-TdR参入法利用CTLL－2细胞株测定T淋巴细胞分泌IL－2活性。结果驱虫斑鸠菊的低、中、高三个剂量对体内T、B淋巴细胞的增殖活性、血清总抗体和抗原特异性抗体含量、CD19B细胞亚类表达均有明显的抑制作用,对T淋巴细胞分泌IL－2活性也具有明显抑制作用。说明驱虫斑鸠菊对机体体液免疫和细胞免疫功能都具有明显抑制作用。     

Bovine serum albumin enhances nicotinic acetylcholine receptor function in mouse thalamic synaptosomes

Bovine serum albumin (BSA) enhances nicotinic agonist-induced (86)Rb+ efflux from synaptosomal fractions of the mouse thalamus, but how it does so is not understood. The experiments reported here indicated that BSA enhancement of nicotinic acetylcholine receptor function was rapid, reversible, depended on BSA concentration, and occurred at all points of the nicotinic agonist concentration-response curve. We hypothesized that BSA-extractable compounds, such as long-chain fatty acids, were responsible for inhibiting nicotinic responses in the absence of BSA. The hypothesis was tested by applying arachidonic, linolenic, or oleic acids in the absence of BSA after an initial prewash with BSA. All three fatty acids exhibited a rapid, concentration-dependent inhibition of nicotinic-agonist stimulated ion flux. Concentration-response curves produced after 30 s of pre-treatment with arachidonic acid were similar to those seen when BSA was completely absent. The effects of pre-treatment were reversed immediately by the introduction of BSA. Furthermore, no effects of fatty acids were observed when preparations were continuously exposed to BSA or when BSA was continuously absent. These results suggest that the removal of endogenous, inhibitory compounds is largely responsible for the rapid, potentiating action of BSA at nicotinic acetylcholine receptors expressed in the mouse thalamus.     

Polyomavirus small T antigen enhances replication of viral genomes in 3T6 mouse fibroblasts.

Transfection of 3T6 cells with a cloned polyomavirus genome encoding only large T antigen resulted in DNA replication with only about 1/10 the efficiency of wild-type viral DNA coding for all three T antigens. This replication defect was at least in part overcome by the simultaneous transfections of polyomavirus genomes which allowed the expression of small T antigen. We conclude that polyomavirus small T antigen has a (probably indirect) role in replication.     

Alcohol and HIV decrease proteasome and immunoproteasome function in macrophages: implications for impaired immune function during disease

Proteasomes (proteinase complexes, PR) and immunoproteasomes (IPR) degrade damaged proteins and affect protein processing required for antigen presentation by mononuclear phagocytes. These critical immune processes are attenuated during progressive HIV-1 infection and are affected by alcohol abuse. To investigate the mechanisms underlying these functional changes, we measured PR and CYP2E1 activities [an ethanol (EtOH) metabolizing enzyme] and reactive oxygen species (ROS) in human monocyte-derived macrophages (MDM) following HIV-1 infection and EtOH treatment. We observed progressive declines of PR activity and PR/IPR contents in HIV-1-infected MDM. PR activity and IPR expression increased after IFN-gamma stimulation but reduced after HIV-1 infection. EtOH inhibited both IFN-gamma-induced PR and IPR. Paradoxically, EtOH attenuated PR catalytic activity in infected MDM and suppressed viral replication. Elevated ROS followed EtOH exposure and paralleled decreased PR activity. The latter was restored by anti-oxidant. The data support the notion that HIV-1 infection and EtOH may work in concert to affect immune function including antigen presentation and thereby affect disease progression.     

Perillyl alcohol suppresses antigen-induced immune responses in the lung

Perillyl alcohol (POH) is an isoprenoid which inhibits farnesyl transferase and geranylgeranyl transferase, key enzymes that induce conformational and functional changes in small G proteins to conduct signal production for cell proliferation. Thus, it has been tried for the treatment of cancers. However, although it affects the proliferation of immunocytes, its influence on immune responses has been examined in only a few studies. Notably, its effect on antigen-induced immune responses has not been studied. In this study, we examined whether POH suppresses Ag-induced immune responses with a mouse model of allergic airway inflammation. POH treatment of sensitized mice suppressed proliferation and cytokine production in Ag-stimulated spleen cells or CD4⁺ T cells. Further, sensitized mice received aerosolized OVA to induce allergic airway inflammation, and some mice received POH treatment. POH significantly suppressed indicators of allergic airway inflammation such as airway eosinophilia. Cytokine production in thoracic lymph nodes was also significantly suppressed. These results demonstrate that POH suppresses antigen-induced immune responses in the lung. Considering that it exists naturally, POH could be a novel preventive or therapeutic option for immunologic lung disorders such as asthma with minimal side effects.     

FMRFamide suppresses kappa opiate induced feeding in the mouse

Intracerebroventricular administration of 0.01-1.0 micrograms of the peptide FMRFamide (Phe-Met-Arg-Phe-NH2) to mice suppressed feeding induced by the specific kappa opiate agonist, U-50, 488H. This suggests that FMRFamide, or FMRFamide-like neuropeptides, may have a role in the control of kappa opioid mediated feeding in the mouse.     

Injury enhances resistance to Escherichia coli infection by boosting innate immune system function

Major injury is widely thought to predispose the injured host to opportunistic infections. This idea is supported by animal studies showing that major injury causes reduced resistance to polymicrobial sepsis induced by cecal ligation and puncture. Although cecal ligation and puncture represents a clinically relevant sepsis model, we wanted to test whether injury might also lead to greater susceptibility to peritoneal infection caused by a single common pathogen, Escherichia coli. Contrary to our expectation, we show herein that the LD(50) for sham-injured mice was 10(3) CFU of E. coli, whereas the LD(50) for burn-injured mice was 50 x 10(3) CFU at 7 days postinjury. This injury-associated enhanced resistance was apparent as early as 1 day after injury, and maximal resistance was observed at days 7 and 14. We found that burn-injured mice had higher numbers of circulating neutrophils and monocytes than did sham mice before infection and that injured mice were able to recruit greater numbers of neutrophils to the site of infection. Moreover, the peritoneal neutrophils in burn-injured mice were more highly activated than neutrophils from sham mice as determined by Mac-1 expression, superoxide generation, and bactericidal activity. Our findings suggest that the enhanced innate immune response that develops following injury, although it is commonly accepted as the mediator of the detrimental systemic inflammatory response syndrome, may also, in some cases, benefit the injured host by boosting innate immune antimicrobial defenses.     

发酵灵芝菌粉抑制小鼠肿瘤及对正常小鼠免疫功能影响的研究

研究了发酵灵芝菌粉对接种S-180瘤细胞后的实验小鼠肿瘤的抑制作用、发酵灵芝菌粉对正常的实验小鼠腹腔巨噬细胞吞噬能力以及脾脏自然杀伤细胞活性的影响,结果表明发酵灵芝菌粉对小鼠移植性肿瘤的生长有明显的抑制作用,但对正常小鼠腹腔巨噬细胞吞噬能力以及脾脏自然杀伤细胞的活性无明显的免疫促进作用。     

Active hexose correlated compound enhances the immune function of mice in the hindlimb-unloading model of spaceflight conditions.

Hindlimb unloading is a ground-based model that simulates some of the aspects of spaceflight conditions, including lack of load bearing on hindlimbs and a fluid shift to the head. It has been shown that treatment with active hexose correlated compound (AHCC) restores resistance to infection in mice maintained under hindlimb-unloading conditions. The present study was designed to clarify the mechanisms by which AHCC enhances resistance to infection in this model. We hypothesized that oral administration of AHCC will enhance the function of the immune system, which could lead to the increased resistance to infection observed in this model. AHCC or the excipient was orally administered to mice, and the function of the immune system was assessed in spleen and peritoneal cells isolated from those groups. The results of the present study showed that administration of AHCC for 1 wk before and throughout the second day of the hindlimb-unloading period enhanced the function of the immune system assessed by spleen cell proliferation and cytokine production in spleens and nitric oxide and cytokine production in peritoneal cells. These findings suggest that AHCC can be used as a potent immunoenhancer, especially in cases in which the immune system is suppressed by any condition, including diseases such as human immunodeficiency virus infection and cancer.     

HU protein binding to the replication origin of the rolling-circle plasmid pKYM enhances DNA replication

The RepK protein, which is encoded by the rolling-circle plasmid pKYM, binds to the PR I site in the pKYM DNA replication origin. We have identified HU as a protein that binds to the PR II and PR III sites in the replication-enhancing region which is downstream of PR I. DNA footprinting assays show that HU binds to these two sites only when RepK is bound to PR I, and that HU also enhances the binding of RepK to PR I. In vivo, pKYM was unable to transform an HU null strain. Two mutant RepK proteins, RepKW179Y, which contains a Trp-to-Tyr exchange at position 179, and RepKD277L, which contains an Asp-to-Leu mutation at residue 277, initiate DNA replication in vivo in the absence of HU. In vitro, these mutant RepK proteins form more stable complexes with the pKYM origin region than does the wild-type RepK protein. These results indicate that HU plays a role in the formation of a stable RepK-origin complex, which is required for the initiation of pKYM DNA replication. Received: 24 July 1996 / Accepted: 30 December 1996