microRNAs In Macrophages Research Articles

MicroRNA-25/93 induction by Vpu as a mechanism for counteracting MARCH1-restriction on HIV-1 infectivity in macrophages.

In order to efficiently produce infectious viral particles, HIV must counter several restrictions exerted by host cell antiviral proteins. MARCH1 is a member of the MARCH protein family that restricts HIV infection by limiting the incorporation of viral envelope glycoproteins into nascent virions. Here, we identified two regulatory RNAs, microRNAs-25 and -93, induced by the HIV-1 accessory protein Vpu, that downregulate MARCH1 mRNA. We also show that Vpu induces these cellular microRNAs in macrophages by hijacking the cellular β-catenin pathway. The notion that HIV-1 has evolved a mechanism to counteract MARCH1 restriction on viral infectivity underlines the importance of MARCH1 in the host antiviral response.

Long Noncoding RNA Metastasis-Associated Lung Adenocarcinoma Transcript 1 Promotes HIV-1 Replication through Modulating microRNAs in Macrophages.

Macrophages can serve as a reservoir for human immunodeficiency-1 (HIV-1) virus in host cells, constituting a barrier to eradication, even in patients who are receiving antiretroviral therapy. Although many noncoding RNAs have been characterized as regulators in HIV-1/AIDS-induced immune response and pathogenesis, only a few long noncoding RNAs (lncRNAs) have demonstrated a close association with HIV-1 replication, and the molecular mechanisms remain unknown. In this study, we investigated how lncRNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), related microRNAs, and key inflammatory genes alter HIV-1 replication in macrophages. Our data show that HIV-1 infection modulates the expression of miR-155 and miR-150-5p in a time-dependent manner, which is regulated by MALAT1. MALAT1 induced suppressor of cytokine signaling 1 (SOCS1) expression by sponging miR-150-5p in HIV-1-infected macrophages and stimulated inflammatory mediators triggering receptor expressed on myeloid cells/cold inducible RNA binding protein (TREM 1/CIRP) ligand/receptor. The RNA immunoprecipitation (RIP) assay validated the direct interaction within the MALAT1/miR-150-5p/SOCS1 axis. HIV-1 infection-mediated upregulation of MALAT1, SOCS1, and HIV-1 Gag was attenuated by SN50 (an NF-кB p50 inhibitor). MALAT1 antisense oligonucleotides (ASOs) suppressed HIV-1 p24 production and HIV-1 Gag gene expression and decreased expression of miR-155 and SOCS1, as well as the production of proinflammatory cytokines by HIV-1-infected macrophages. In conclusion, HIV-1 infection induces MALAT1, which attenuates miR-150-5p expression and increases SOCS1 expression, promoting HIV-1 replication and reactivation. These data provide new insights into how MALAT1 alters the macrophage microenvironment and subsequently promotes viral replication and suggest a potential role for targeting MALAT1 as a therapeutic approach to eliminate HIV-1 reservoirs. IMPORTANCE Viral reservoirs constitute an obstacle to curing HIV-1 diseases, despite antiretroviral therapy. Macrophages serve as viral reservoirs in HIV infection by promoting long-term replication and latency. Recent studies have shown that lncRNAs can modulate virus-host interactions, but the underlying mechanisms are not fully understood. In this study, we demonstrate how lncRNA MALAT1 contributes to HIV-1 replication through modulation of the miR-150/SOCS1 axis in human macrophages. Our findings have the potential to identify new therapies for eliminating HIV-1 reservoirs in immune cells.

Time-Series Transcriptome Analysis Reveals the miR-27a-5p-Ppm1l Axis as a New Pathway Regulating Macrophage Alternative Polarization After Myocardial Infarction.

Timely differentiation of monocytes into M2-like macrophages is important in the cardiac healing process after myocardial infarction (MI), but molecular mechanisms governing M2-like macrophage differentiation at the transcriptional level after MI have not been fully understood.Methods and Results:A time-series microarray analysis of mRNAs and microRNAs in macrophages isolated from the infarcted myocardium was performed to identify the microRNAs involved in regulating the process of differentiation to M2-like macrophages. Correlation analysis revealed 7 microRNAs showing negative correlations with the progression of polarity changes towards M2-like subsets. Next, correlation coefficients for the changes in expression of mRNAs and miRNAs over time were calculated for all combinations. As a result, miR-27a-5p was extracted as a possible regulator of the largest number of genes in the pathway for the M2-like polarization. By selecting mouse mRNAs and human mRNAs possessing target sequences of miR-27a-5p and showing expression patterns inversely correlated with that of miR-27a-5p, 8 potential targets of miR-27a-5p were identified, includingPpm1l. Using the mouse bone marrow-derived macrophages undergoing differentiation into M2-like subsets by interleukin 4 stimulation, we confirmed that miR-27a-5p suppressed M2-related genes by negatively regulatingPpm1lexpression. Ppm1land miR-27a-5p may be the key molecules regulating M2-like polarization, with miR-27a-5p inhibiting the M2-like polarization through downregulation ofPpm1lexpression.

Alcoholic and Non-Alcoholic Beer Modulate Plasma and Macrophage microRNAs Differently in a Pilot Intervention in Humans with Cardiovascular Risk

Beer is a popular beverage and some beneficial effects have been attributed to its moderate consumption. We carried out a pilot study to test if beer and non-alcoholic beer consumption modify the levels of a panel of 53 cardiometabolic microRNAs in plasma and macrophages. Seven non-smoker men aged 30–65 with high cardiovascular risk were recruited for a non-randomised cross-over intervention consisting of the ingestion of 500 mL/day of beer or non-alcoholic beer for 14 days with a 7-day washout period between interventions. Plasma and urine isoxanthohumol were measured to assess compliance with interventions. Monocytes were isolated and differentiated into macrophages, and plasma and macrophage microRNAs were analysed by quantitative real-time PCR. Anthropometric, biochemistry and dietary parameters were also measured. We found an increase in plasma miR-155-5p, miR-328-3p, and miR-92a-3p after beer and a decrease after non-alcoholic beer consumption. Plasma miR-320a-3p levels decreased with both beers. Circulating miR-320a-3p levels correlated with LDL-cholesterol. We found that miR-17-5p, miR-20a-5p, miR-145-5p, miR-26b-5p, and miR-223-3p macrophage levels increased after beer and decreased after non-alcoholic beer consumption. Functional analyses suggested that modulated microRNAs were involved in catabolism, nutrient sensing, Toll-like receptors signalling and inflammation. We concluded that beer and non-alcoholic beer intake modulated differentially plasma and macrophage microRNAs. Specifically, microRNAs related to inflammation increased after beer consumption and decreased after non-alcoholic beer consumption.

Morphine Withdrawal Enhances HIV Infection of Macrophages.

Opioid withdrawal recurs at high rates in opioid use disorder and compromises the immune system. In general, there are two types of opioid withdrawal: abrupt withdrawal (AW) and precipitated withdrawal (PW). In this study, we examined the effect of morphine AW or morphine PW on HIV infection of human blood monocyte-derived macrophages. We observed that both morphine AW and PW enhanced the susceptibility of macrophages to HIV infection. In addition, both AW and PW activated HIV replication in the latently infected myeloid cells (U1 and OM10.1). Investigation of mechanisms responsible for these observations showed that both AW and PW could inhibit the expression of multiple intracellular HIV inhibitory factors, including APOBE3G/F, SAMHD1, MX2, and HIV restriction microRNAs (miR-28, miR-125b, and miR-150) in macrophages. These findings provide additional evidence to support the notion that opioid use compromises the intracellular anti-HIV immunity and facilitates HIV infection and persistence in macrophages.

Dual mechanisms of posttranscriptional regulation of Tet2 by Let-7 microRNA in macrophages

Tet methylcytosine dioxygenase 2 (Tet2) is an epigenetic regulator that removes methyl groups from deoxycytosine residues in DNA. Tet2-deficient murine macrophages show increased lipopolysaccharide (LPS)-induced and spontaneous inflammation at least partially because Tet2 acts to restrain interleukin (IL)-1β and IL-6 expression in induced cells. MicroRNAs have emerged as critical regulatory noncoding RNAs that tune immune cell responses to physiological perturbations and play roles in pathological conditions in macrophages. To determine if a microRNA played any role in Tet2 activity, we examined the interrelationship of Tet2 action and the let-7 microRNA family, utilizing several let-7 microRNA engineered murine models. We first showed that Tet2, but not Tet3, is a direct target of the let-7a-1/let-7d/let-7f-1 (let-7adf) microRNAs in macrophages. We found that overexpression or deletion of the let-7adf gene cluster causes altered IL-6 induction both in tissue culture cells induced by LPS treatment in vitro as well as in a Salmonella infection mouse model in vivo. Mechanistically, let-7adf promotes IL-6 by directly repressing Tet2 levels and indirectly by enhancing a Tet2 suppressor, the key TCA cycle metabolite, succinate. We found that Let-7adf promotes succinate accumulation by regulating the Lin28a/Sdha axis. We thereby identify two pathways of let-7 control of Tet2 and, in turn, of the key inflammatory cytokine, IL-6, thus characterizing a regulatory pathway in which a microRNA acts as a feedback inhibitor of inflammatory processes.

A Review of Macrophage MicroRNAs' Role in Human Asthma.

There is an imbalance in asthma between classically activated macrophages (M1 cells) and alternatively activated macrophages (M2 cells) in favor of the latter. MicroRNAs (miRNAs) play a critical role in regulating macrophage proliferation and differentiation and control the balance of M1 and M2 macrophage polarization, thereby controlling immune responses. Here we review the current published data concerning miRNAs with known correlation to a specific human macrophage phenotype and polarization, and their association with adult asthma. MiRNA-targeted therapy is still in the initial stages, but clinical trials are under recruitment or currently running for some miRNAs in other diseases. Regulating miRNA expression via their upregulation or downregulation could show potential as a novel therapy for improving treatment efficacy in asthma.

Expression of ID4 protein in breast cancer cells induces reprogramming of tumour-associated macrophages

BackgroundAs crucial regulators of the immune response against pathogens, macrophages have been extensively shown also to be important players in several diseases, including cancer. Specifically, breast cancer macrophages tightly control the angiogenic switch and progression to malignancy. ID4, a member of the ID (inhibitors of differentiation) family of proteins, is associated with a stem-like phenotype and poor prognosis in basal-like breast cancer. Moreover, ID4 favours angiogenesis by enhancing the expression of pro-angiogenic cytokines interleukin-8, CXCL1 and vascular endothelial growth factor. In the present study, we investigated whether ID4 protein exerts its pro-angiogenic function while also modulating the activity of tumour-associated macrophages in breast cancer.MethodsWe performed IHC analysis of ID4 protein and macrophage marker CD68 in a triple-negative breast cancer series. Next, we used cell migration assays to evaluate the effect of ID4 expression modulation in breast cancer cells on the motility of co-cultured macrophages. The analysis of breast cancer gene expression data repositories allowed us to evaluate the ability of ID4 to predict survival in subsets of tumours showing high or low macrophage infiltration. By culturing macrophages in conditioned media obtained from breast cancer cells in which ID4 expression was modulated by overexpression or depletion, we identified changes in the expression of ID4-dependent angiogenesis-related transcripts and microRNAs (miRNAs, miRs) in macrophages by RT-qPCR.ResultsWe determined that ID4 and macrophage marker CD68 protein expression were significantly associated in a series of triple-negative breast tumours. Interestingly, ID4 messenger RNA (mRNA) levels robustly predicted survival, specifically in the subset of tumours showing high macrophage infiltration. In vitro and in vivo migration assays demonstrated that expression of ID4 in breast cancer cells stimulates macrophage motility. At the molecular level, ID4 protein expression in breast cancer cells controls, through paracrine signalling, the activation of an angiogenic programme in macrophages. This programme includes both the increase of angiogenesis-related mRNAs and the decrease of members of the anti-angiogenic miR-15b/107 group. Intriguingly, these miRNAs control the expression of the cytokine granulin, whose enhanced expression in macrophages confers increased angiogenic potential.ConclusionsThese results uncover a key role for ID4 in dictating the behaviour of tumour-associated macrophages in breast cancer.

Macrophage MicroRNAs as Therapeutic Targets for Atherosclerosis, Metabolic Syndrome, and Cancer.

Macrophages play a crucial role in the innate immune system and contribute to a broad spectrum of pathologies in chronic inflammatory diseases. MicroRNAs (miRNAs) have been demonstrated to play important roles in macrophage functions by regulating macrophage polarization, lipid metabolism and so on. Thus, miRNAs represent promising diagnostic and therapeutic targets in immune disorders. In this review, we will summarize the role of miRNAs in atherosclerosis, metabolic syndrome, and cancer by modulating macrophage phenotypes, which has been supported by in vivo evidence.

Brucella Downregulates Tumor Necrosis Factor-α to Promote Intracellular Survival via Omp25 Regulation of Different MicroRNAs in Porcine and Murine Macrophages.

Brucella spp. impedes the production of pro-inflammatory cytokines by its outer membrane protein Omp25 in order to promote survival and immune evasion. However, how Omp25 regulates tumor necrosis factor (TNF-α) expression in different mammalian macrophages remains unclear. In this study, we investigated the potential mechanisms by which Omp25 regulates TNF-α expression and found that Omp25-deficient mutant of B. suis exhibited an enhanced TNF-α expression compared with wild-type (WT) B. suis, whereas ectopic expression of Omp25 suppressed LPS-induced TNF-α production at both protein and mRNA levels in porcine alveolar macrophages (PAMs) and murine macrophage RAW264.7 cells. We observed that Omp25 protein as well as WT B. suis upregulated miR-146a, -181a, -181b, and -301a-3p and downregulated TRAF6 and IRAK1 in both PAMs and RAW264.7 cells, but separately upregulates miR-130a-3p in PAMs and miR-351-5p in RAW264.7. The upregulation of miR-146a or miR-351-5p attenuated TNF-α transcription by targeting TRAF6 and IRAK1 at the 3′ untranslated region (UTR), resulting in inhibition of NF-kB pathway, while upregulation of miR-130a-3p, -181a, or -301a-3p correlated temporally with decreased TNF-α by targeting its 3′UTR in PAMs or RAW264.7 cells. In contrast, inhibition of miR-130a-3p, -146a, -181a, and -301a-3p attenuated the inhibitory effects of Omp25 on LPS-induced TNF-α in PAMs, while inhibition of miR-146a, -181a, -301a-3p, and -351-5p attenuated the inhibitory effects of Omp25 in RAW264.7, resulting in an increased TNF-α production and decreased intracellular bacteria in both cells. Taken together, our results demonstrate that Brucella downregulates TNF-α to promote intracellular survival via Omp25 regulation of different microRNAs in porcine and murine macrophages.

Expression of MicroRNAs in Fibroblasts and Macrophages Is Regulated by Hypoxia-Induced Extracellular Acidosis.

Under pathological conditions like inflammation, ischemia or in solid tumors, parameters of the microenvironment like local oxygenation and extracellular pH show marked changes when compared to healthy tissue. The altered microenvironment affects cellular phenotype of omnipresent fibroblasts and immune cells. Recently, the impact of the microenvironment on the expression patterns of microRNAs, small non-coding RNAs that regulate gene expression on a post-transcriptional level, was discussed. Therefore, microRNAs might be the link between altered microenvironmental parameters and changes in cellular phenotype. In this study, the effect of hypoxia-induced extracellular acidosis (24h pH 6.6) on microRNA expression in fibroblasts and macrophages was analyzed. MicroRNAs in rat fibroblasts (NRK-49F) were examined with the miScript miRNA PCR Array and changes in the expression validated by TaqMan qPCR. Subsequently, the identified microRNAs were analyzed in RAW 264.7 mouse macrophages. Nine out of 84 tested microRNAs were found to be acidosis-regulated in fibroblasts by miRNA PCR array, most of them up-regulated. Of those, the pH dependency could be validated by TaqMan qPCR for five of these nine microRNAs. When comparing these microRNAs in terms of their expression in macrophages, profound differences were observed. Thus, acidosis-induced alterations in the expression of microRNAs seem to be cell-type specific. Only the up-regulation of the miR-133b by low pH was seen in all normal cells, but not in tumor cells. As the identified microRNAs are involved in the regulation of proliferation, cell death and migration (amongst others), acidosis-induced changes in their expression might affect cellular behavior of fibroblasts and macrophages under pathological conditions. For instance the proto-oncogene c-Jun, which is a target of the miR-133b, was shown to be acidosis-regulated. Acidosis could regulate the biological behavior via miRNA-133b and c-Jun.

Profile of microRNAs in human adipocytes and macrophages in inflammation

Profile of microRNAs in human adipocytes and macrophages in inflammation

Differential MicroRNA Expression in Human Macrophages with Mycobacterium tuberculosis Infection of Beijing/W and Non-Beijing/W Strain Types.

ObjectivesThe role of microRNAs in association with Mycobacterium tuberculosis (MTB) infection and the immunology regulated by microRNAs upon MTB infection have not been fully unravelled. We examined the microRNA profiles of THP-1 macrophages upon the MTB infection of Beijing/W and non-Beijing/W clinical strains. We also studied the microRNA profiles of the host macrophages by microarray in a small cohort with active MTB disease, latent infection (LTBI), and from healthy controls.ResultsThe results revealed that 14 microRNAs differentiated infections of Beijing/W from non-Beijing/W strains (P<0.05). A unique signature of 11 microRNAs in human macrophages was identified to differentiate active MTB disease from LTBI and healthy controls. Pathway analyses of these differentially expressed miRNAs suggest that the immune-regulatory interactions involving TGF-β signalling pathway take part in the dysregulation of critical TB processes in the macrophages, resulting in active expression of both cell communication and signalling transduction systems.ConclusionWe showed for the first time that the Beijing/W TB strains repressed a number of miRNAs expressions which may reflect their virulence characteristics in altering the host response. The unique signatures of 11 microRNAs may deserve further evaluation as candidates for biomarkers in the diagnosis of MTB and Beijing/W infections.

FP563MICRORNA REGULATION OF MACROPHAGE PHENOTYPE IN PERITONEAL FIBROSIS

Introduction and Aims: Peritoneal fibrosis is a major cause of treatment failure in peritoneal dialysis, which is linked to repeat episodes of infection-driven peritoneal inflammation. Macrophages are a heterogeneous population of immune cells essential for immune surveillance, response to infection and the resolution of inflammation. Distinct subpopulations of macrophages are implicated in tissue repair and fibrosis. Recent data from our group defines distinct origin, function and transcriptional control of discrete macrophage subsets within the peritoneal cavity, namely tissue resident (homeostatic) and inflammatory. microRNAs are post-transcriptional regulators of gene expression that play fundamental roles in regulation of cellular phenotype. However, the role of microRNAs has not been examined in this context. Aim: To investigate microRNA regulation of macrophage phenotype in the context of peritoneal fibrosis. Methods: An in vivo study of microRNA regulation of tissue resident and inflammatory macrophage phenotype in an established murine model of peritoneal fibrosis. Results: A single episode of acute peritoneal inflammation is self-limiting with restoration of tissue homeostasis, whereas repeat episodes initiate the development of fibrosis. In response to acute inflammation two distinct macrophage lineage branches are evident, M2-like tissue resident macrophages (F4/80highCD11bhighTIM4-/+) and bone marrow derived inflammatory macrophages (F4/80+CD11b+TIM4-). We have employed both hybridization arrays and next generation sequencing to identify differential expression of microRNAs in resident and inflammatory macrophages in response to single and repeat episodes of acute inflammation. Analysis of the microRNA expression data, together with in silico prediction of putative mRNA targets, has identified several microRNAs implicated in regulation of macrophage phenotype. In order to determine the precise functions of these microRNAs we are developing both constitutive and condition lentiviral vectors for 1) microRNA expression and 2) microRNA repression based on the Tough Decoy (TuD) principle. Conclusions: Macrophages are a heterogeneous population of cells tailored by their microenvironment and tissue-specific functions. Delineating the post-transcription regulation of macrophage heterogeneity has important therapeutic applications in peritoneal fibrosis.

Differential expression of microRNAs in Francisella tularensis-infected human macrophages: miR-155-dependent downregulation of MyD88 inhibits the inflammatory response.

Francisella tularensis is a Gram-negative, facultative intracellular pathogen that replicates in the cytosol of macrophages and is the causative agent of the potentially fatal disease tularemia. A characteristic feature of F. tularensis is its limited proinflammatory capacity, but the mechanisms that underlie the diminished host response to this organism are only partially defined. Recently, microRNAs have emerged as important regulators of immunity and inflammation. In the present study we investigated the microRNA response of primary human monocyte-derived macrophages (MDMs) to F. tularensis and identified 10 microRNAs that were significantly differentially expressed after infection with the live vaccine strain (LVS), as judged by Taqman Low Density Array profiling. Among the microRNAs identified, miR-155 is of particular interest as its established direct targets include components of the Toll-like receptor (TLR) pathway, which is essential for innate defense and proinflammatory cytokine production. Additional studies demonstrated that miR-155 acted by translational repression to downregulate the TLR adapter protein MyD88 and the inositol 5′-phosphatase SHIP-1 in MDMs infected with F. tularensis LVS or the fully virulent strain Schu S4. Kinetic analyses indicated that miR-155 increased progressively 3-18 hours after infection with LVS or Schu S4, and target proteins disappeared after 12–18 hours. Dynamic modulation of MyD88 and SHIP-1 was confirmed using specific pre-miRs and anti-miRs to increase and decrease miR-155 levels, respectively. Of note, miR-155 did not contribute to the attenuated cytokine response triggered by F. tularensis phagocytosis. Instead, this microRNA was required for the ability of LVS-infected cells to inhibit endotoxin-stimulated TNFα secretion 18–24 hours after infection. Thus, our data are consistent with the ability of miR-155 to act as a global negative regulator of the inflammatory response in F. tularensis-infected human macrophages.

Inflammation, Immunity, Vaccines for Helicobacter pylori infection

Over the last decades, it has become evident that chronic infection by Helicobacter pylori is achieved by colonizing an almost exclusive niche and hiding from many of the host's cellular immune defense mechanisms. Although recent years have seen progress in our understanding of the innate and adaptive immune response against H.pylori, it is still uncertain how to promote the development of immunity with the final goal of a successful vaccine. Research published in the last year revealed an intriguing mutual regulation of innate response mechanisms of mucosal epithelial cells by the host and H.pylori, respectively. A further focus was put on the interaction between H.pylori and dendritic cells, with some emphasis on the inflammasome and the resulting T-cell responses. Moreover, the function of microRNAs in macrophages and gastric MALT lymphoma development has been studied in more detail. Several novel antigens and adjuvants have been tested as vaccination strategies, primarily in mice. In this review, we present a concise summary of advances in the area of inflammation, immunity, and vaccines during the last twelve months.

Identifying Functional MicroRNAs in Macrophages with Polarized Phenotypes

Macrophages respond to external stimuli with rapid changes in expression of many genes. Different combinations of external stimuli lead to distinct polarized activation patterns, resulting in a spectrum of possible macrophage activation phenotypes. MicroRNAs (miRNAs) are small, noncoding RNAs that can repress the expression of many target genes. We hypothesized that miRNAs play a role in macrophage polarization. miRNA expression profiles were determined in monocyte-derived macrophages (MDMs) incubated in conditions causing activation toward M1, M2a, M2b, or M2c phenotypes. One miRNA guide strand and seven miRNA passenger strands were significantly altered. Changes were confirmed in MDMs from six separate donors. The amplitude of miRNA expression changes in MDMs was smaller than described studies of monocytes responding to inflammatory stimuli. Further investigation revealed this correlated with higher basal miRNA expression in MDMs compared with monocytes. The regulation of M1- and M2b-responsive miRNAs (miR-27a, miR-29b, miR-125a, miR-146a, miR-155, and miR-222) was similar in differentiated THP-1 cells and primary MDMs. Studies in this model revealed cross-talk between IFNγ- and LPS-associated pathways regulating miRNA expression. Furthermore, expression of M1-associated transcripts was increased in THP-1 cells transfected with mimics of miR-29b, miR-125a-5p, or miR-155. The apparent inflammatory property of miR-29b and miR-125a-5p can be at least partially explained by repression of TNFAIP3, a negative regulator of NF-κB signaling. Overall, these data suggest miRNAs can contribute to changes in macrophage gene expression that occur in different exogenous activating conditions.

Do Opioids Activate Latent HIV-1 by Down-Regulating Anti-HIV microRNAs?

Researchers have recently demonstrated the presence of anti-HIV-1 microRNAs (miR-28, miR-125b, miR-150, miR-223, and miR-382) in monocytes, macrophages, and CD4+ T cells, which are the primary targets of HIV infection. These miRNAs appear to regulate the level of infectivity of HIV-1 in the target cells, and thus have an impact on HIV-1 latency. The levels of these miRNAs are significantly higher in resting CD4+ T cells than those in active CD4+ T cells, whereas HIV-1 infectivity is greater in active than in resting CD4+ T cells. Similarly, the levels of these miRNAs are significantly higher in monocytes than in macrophages, whereas HIV-1 infectivity is greater in macrophages than in monocytes. Down-regulation or inhibition of the activity of these miRNAs can promote replication of latent HIV-1 in resting CD4+ T cells and in monocytes. Recently, morphine was shown to down regulate the expression of anti-HIV miRNAs (miRNA-28, 125b, 150, and 382) in cultured human monocytes and this effect of morphine was mediated via activation of mu opioid receptors (MOR). In addition, levels of these anti-HIV miRNAs were significantly lower in the peripheral blood mononuclear cells (PBMCs) isolated from heroin-dependent subjects than those from control subjects. These findings raise an important question: Does morphine have potential to activate latent HIV-1 in resting CD4+ T cells and macrophages, including microglia of human subjects maintained on highly active antiretroviral therapy (HAART)? Further research is required to answer this question.

Analysis of the host microRNA response toSalmonellauncovers the control of major cytokines by thelet-7family

MicroRNAs have well-established roles in eukaryotic host responses to viruses and extracellular bacterial pathogens. In contrast, microRNA responses to invasive bacteria have remained unknown. Here, we report cell type-dependent microRNA regulations upon infection of mammalian cells with the enteroinvasive pathogen, Salmonella Typhimurium. Murine macrophages strongly upregulate NF-κB associated microRNAs; strikingly, these regulations which are induced by bacterial lipopolysaccharide (LPS) occur and persist regardless of successful host invasion and/or replication, or whether an inflammatory response is mounted, suggesting that microRNAs belong to the first line of anti-bacterial defence. However, a suppression of the global immune regulator miR-155 in endotoxin-tolerant macrophages revealed that microRNA responses also depend on the status of infected cells. This study identifies the let-7 family as the common denominator of Salmonella-regulated microRNAs in macrophages and epithelial cells, and suggests that repression of let-7 relieves cytokine IL-6 and IL-10 mRNAs from negative post-transcriptional control. Our results establish a paradigm of microRNA-mediated feed-forward activation of inflammatory factors when mammalian cells are targeted by bacterial pathogens.