Mammalian target of rapamycin inhibition in macrophages of asymptomatic HIV+ persons reverses the decrease in TLR-4-mediated TNF-α release through prolongation of MAPK pathway activation

Effect of TLR10 (2322A/G, 720A/C, and 992T/A) polymorphisms on the pathogenesis of Crimean Congo hemorrhagic fever disease

Crimean Congo hemorrhagic fever (CCHF) is a tick-borne disease caused by the Crimean Congo hemorrhagic fever virus (CCHFV). Toll-like receptors (TLRs) are type 1 transmembrane proteins of immune cells that play a critical role in innate and adaptive immunity. The present study first time aims to investigate the relation between TLR10 gene polymorphisms (720A/C, 992T/A, and 2322A/G), severity/non-severity, fatality/non-fatality, and CCFH disease by using PCR-RFLP assay in a Turkish population. TLR10 720A/C polymorphism was determined to be statistically significant both genotype and allele frequency (P = 0,011, P = 0.015, respectively). TLR10 992T/A polymorphism was found statistically significant relationships between patient and control (P = 0.026) and individual with AA genotype have approximately three times greater risk than TT genotype (OR = 2.93). There was not a significant difference in 2322A/G genotype distribution (P = 0.152). There were also statistically significant associations between both TLR10 992T/A and 2322A/G polymorphism and patient mortality (P = 0.001 and P = 0.008, respectively). We have not found statistically any linkage among TLR10 haplotype, but individual AAA and GAT haplotype have higher risk than individual AAT haplotype (OR = 3.22, OR = 1.93, respectively). Consequently, this study shows that pathogenesis of CCHF disease is associated with the TLR10 720A/C and 992T/A polymorphisms. There is a statistically significant association in fatal/non-fatal patients with TLR10 720A/C and 992T/A. The TLR10 992AA genotype might increase and TLR10 720CC genotype might decrease susceptibility to pathogenesis of CCHF disease. TLR 10 polymorphisms may be also an important biomarker for CCHF susceptibility and fatality rate.

HIV-1 enhances mTORC1 activity and repositions lysosomes to the periphery by co-opting Rag GTPases

HIV-1 co-opts several host machinery to generate a permissive environment for viral replication and transmission. In this work we reveal how HIV-1 impacts the host translation and intracellular vesicular trafficking machineries for protein synthesis and to impede the physiological late endosome/lysosome (LEL) trafficking in stressful conditions. First, HIV-1 enhances the activity of the master regulator of protein synthesis, the mammalian target of rapamycin (mTOR). Second, the virus commandeers mTOR-associated late endosome/lysosome (LEL) trafficking and counteracts metabolic and environmental stress-induced intracellular repositioning of LEL. We then show that the small Rag GTPases, RagA and RagB, are required for the HIV-1-mediated LEL repositioning that is likely mediated by interactions between the Rags and the viral proteins, Gag and Vif. siRNA-mediated depletion of RagA and RagB leads to a loss in mTOR association to LEL and to a blockade of viral particle assembly and release at the plasma membrane with a marked concomitant reduction in virus production. These results show that HIV-1 co-opts fundamental mechanisms that regulate LEL motility and positioning and support the notion that LEL positioning is critical for HIV-1 replication.

Expression of Iron Regulatory Protein 1 Is Regulated not only by HIF-1 but also pCREB under Hypoxia

The inconsistent of responses of IRP1 and HIF-1 alpha to hypoxia and the similar tendencies in the changes of IRP1 and pCREB contents led us to hypothesize that pCREB might be involved in the regulation of IRP1 under hypoxia. Here, we investigated the role of pCREB in IRP1 expression in HepG2 cells under hypoxia using quantitative PCR, western blot, immunofluorescence, electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP). We demonstrated that 1) Hypoxia increased pCREB levels inside of the nucleus; 2) Putative CREs were found in the IRP1 gene; 3) Nuclear extracts of HepG2 cells treated with hypoxia could bind to CRE1 and CRE3, and 100-fold competitor of putative CREs could abolish the binding activity to varying degrees; 4) pCREB was found in the CRE1 and CRE3 DNA-protein complexes of EMSA; 5) CRE1 and CRE3 binding activity of IRP1 depended on CREB activation but not on HIF-1; 6) Increased IRP1 expression under hypoxia could be prevented by LY294002; 7) ChIP assays demonstrated that pCREB binds to IRP1 promoter; and 8) HIF-1 and/or HIF-2 siRNA had no effect on the expression of pCREB and IRP1 proteins in cells treated with hypoxia for 8 hours. Our findings evidenced for the involvement of pCREB in IRP1 expression and revealed a dominant role of PI3K/Akt pathway in CREB activation under hypoxia and also suggested that dual-regulation of IRP1 expression by HIF-1 and pCERB or other transcription factor(s) under hypoxia might be a common mechanism in most if not all of hypoxia-inducible genes.

Rapid induction of REDD1 gene expression in macrophages in response to stress-related catecholamines

In the present study, we examined the effect of stress-related catecholamines adrenaline and noradrenaline on macrophage expression of a new host defense factor REDD1 using murine macrophage cell line RAW264.7 and murine peritoneal macrophages. Short-term adrenaline exposure (15-60 min) upregulated REDD1 mRNA expression and its protein synthesis in macrophages. This adrenaline-induced REDD1 expression was completely blocked by β2-adrenoceptor selective antagonist ICI 118,551, whereas β2-adrenoceptor specific agonist salmeterol markedly enhanced REDD1 expression. Moreover, noradrenaline increased REDD1 mRNA expression at doses higher than the effective doses of adrenaline. The effect of adrenaline on REDD1 mRNA expression was mimicked by treatment with membrane-permeable cAMP analog 8-Br-cAMP. Thus, increased intracellular cAMP level resulting from β2-adrenoceptor stimulation appeared to be responsible for adrenaline-induced REDD1 mRNA expression. However, inhibiting protein kinase A (PKA) activity had no significant effect on REDD1 mRNA expression after β2-adrenoceptor stimulation. In addition, exchange protein activated by cAMP (Epac) agonist 8-CPT-20-O-Me-cAMP had no effect on REDD1 mRNA expression. Thus, β2-adrenoceptor-mediated increase in cAMP levels seems to induce REDD1 mRNA expression in macrophages through a PKA- and Epac-independent pathway.

Immune responses of macrophages and dendritic cells regulated by mTOR signalling

The innate myeloid immune system is a complex network of cells that protect against disease by identifying and killing pathogens and tumour cells, but it is also implicated in homoeostatic mechanisms such as tissue remodelling and wound healing. Myeloid phagocytes such as monocytes, macrophages or dendritic cells are at the basis of controlling these immune responses in all tissues of the body. In the present review, we summarize recent studies demonstrating that mTOR [mammalian (or mechanistic) target of rapamycin] regulates innate immune reactions in macrophages and dendritic cells. The mTOR pathway serves as a decision maker to control the cellular response to pathogens and tumours by regulating the expression of inflammatory mediators such as cytokines, chemokines or interferons. In addition to various in vivo mouse models, kidney transplant patients under mTOR inhibitor therapy allowed the elucidation of important innate immune functions regulated by mTOR in humans. The role of the mTOR pathway in macrophages and dendritic cells enhances our understanding of the immune system and suggests new therapeutic avenues for the regulation of pro- versus anti-inflammatory mediators with potential relevance to cancer therapy, the design of novel adjuvants and the control of distinct infectious and autoimmune diseases.

Rapamycin increases pCREB, Bcl-2, and VEGF-A through ERK under normoxia

Rapamycin may serve as a new anti-osteosarcoma (OSA) agent due to its ability to inhibit the metastatic behavior of OSA. However, only limited benefit is observed in rodent studies and clinical trials using rapamycin as a single agent in the treatment of OSA. The target of rapamycin, mammalian target of rapamycin has multiple biological functions and may be linked with the kinases that mediate the phosphorylation of cyclic AMP-responsive element-binding (CREB) protein, an import factor in tumor progression. By employing an OSA cell line MG-63, we investigated how rapamycin regulates the phosphorylation of CREB (pCREB) at Ser133 and the expressions of two putative CREB targets, B-cell lymphoma 2 (Bcl-2) and vascular endothelial growth factor-A (VEGF-A). Under normoxia, we found that rapamycin (100 nM) induced an increase of pCREB that was prevented by mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK) inhibitor U0126 or cAMP-dependent protein kinase (PKA) inhibitor H89. However, H89 enhanced Akt phosphorylation and did not decrease the cell viability upon rapamycin treatment. In contrast, U0126 did not enhance Akt phosphorylation and decreased the cell viability upon rapamycin treatment. Moreover, U0126 prevented the rapamycin-induced increase of Bcl-2 and VEGF-A levels. Under hypoxia, rapamycin effectively prevented the hypoxia-induced increase of pCREB, Bcl-2, and VEGF-A. Our study demonstrated that rapamycin might be less effective in treating OSA cells under normoxia and provided the rationale for a combination of rapamycin and MEK/ERK inhibitor in the treatment of OSA.

Vitamin D rescues impaired Mycobacterium tuberculosis-mediated tumor necrosis factor release in macrophages of HIV-seropositive individuals through an enhanced Toll-like receptor signaling pathway in vitro

Mycobacterium tuberculosis disease represents an enormous global health problem, with exceptionally high morbidity and mortality in HIV-seropositive (HIV(+)) persons. Alveolar macrophages from HIV(+) persons demonstrate specific and targeted impairment of critical host cell responses, including impaired M. tuberculosis-mediated tumor necrosis factor (TNF) release and macrophage apoptosis. Vitamin D may promote anti-M. tuberculosis responses through upregulation of macrophage NO, NADPH oxidase, cathelicidin, and autophagy mechanisms, but whether vitamin D promotes anti-M. tuberculosis mechanisms in HIV(+) macrophages is not known. In the current study, human macrophages exposed to M. tuberculosis demonstrated robust release of TNF, IκB degradation, and NF-κB nuclear translocation, and these responses were independent of vitamin D pretreatment. In marked contrast, HIV(+) U1 human macrophages exposed to M. tuberculosis demonstrated very low TNF release and no significant IκB degradation or NF-κB nuclear translocation, whereas vitamin D pretreatment restored these critical responses. The vitamin D-mediated restored responses were dependent in part on macrophage CD14 expression. Importantly, similar response patterns were observed with clinically relevant human alveolar macrophages from healthy individuals and asymptomatic HIV(+) persons at high clinical risk of M. tuberculosis infection. Taken together with the observation that local bronchoalveolar lavage fluid (BALF) levels of vitamin D are severely deficient in HIV(+) persons, the data from this study demonstrate that exogenous vitamin D can selectively rescue impaired critical innate immune responses in vitro in alveolar macrophages from HIV(+) persons at risk for M. tuberculosis disease, supporting a potential role for exogenous vitamin D as a therapeutic adjuvant in M. tuberculosis infection in HIV(+) persons.

Associations of cytokines, sleep patterns, and neurocognitive function in youth with HIV infection

Youth infected with HIV at birth often have sleep disturbances, neurocognitive deficits, and abnormal psychosocial function which are associated with and possibly resulted from elevated blood cytokine levels that may lead to a decreased quality of life. To identify molecular pathways that might be associated with these disorders, we evaluated 38 HIV-infected and 35 uninfected subjects over 18-months for intracellular cytokine levels, sleep patterns and duration of sleep, and neurodevelopmental abilities. HIV infection was significantly associated with alterations of intracellular pro-inflammatory cytokines (TNF-α, IFN-γ, IL-12), sleep factors (total time asleep and daytime sleep patterns), and neurocognitive factors (parent and patient reported problems with socio-emotional, behavioral, and executive functions; working memory-mental fatigue; verbal memory; and sustained concentration and vigilance. By better defining the relationships between HIV infection, sleep disturbances, and poor psychosocial behavior and neurocognition, it may be possible to provide targeted pharmacologic and procedural interventions to improve these debilitating conditions.

Epigenetic regulation of tumor necrosis factor α (TNFα) release in human macrophages by HIV-1 single-stranded RNA (ssRNA) is dependent on TLR8 signaling

Human macrophages at mucosal sites are essential targets for acute HIV infection. During the chronic phase of infection, they are persistent reservoirs for the AIDS virus. HIV virions gain entry into macrophages following ligation of surface CD4-CCR5 co-receptors, which leads to the release of two copies of HIV ssRNA. These events lead to reverse transcription and viral replication initiation. Toll-like receptors TLR7 and TLR8 recognize specific intracellular viral ssRNA sequences, but in human alveolar macrophages, their individual roles in TLR-mediated HIV ssRNA recognition are unclear. In the current study, HIV-1 ssRNA induced TNFα release in a dose-dependent manner in adherent human macrophages expressing both intracellular TLR7 and TLR8. This response was reduced by inhibiting either endocytosis (50 μm dynasore) or endosomal acidification (1 μg/ml chloroquine). Either MYD88 or TLR8 gene knockdown with relevant siRNA reduced HIV-1 ssRNA-mediated TNFα release, but silencing TLR7 had no effect on this response. Furthermore, HIV-1 ssRNA induced histone 4 acetylation at the TNFα promoter as well as trimethylation of histone 3 at lysine 4, whereas TLR8 gene knockdown reduced these effects. Taken together in human macrophages, TLR8 binds and internalizes HIV ssRNA, leading to endosomal acidification, chromatin remodeling, and increases in TNFα release. Drugs targeting macrophage TLR8-linked signaling pathways may modulate the innate immune response to acute HIV infection by reducing viral replication.