Partial characterization of the RNA from LPS-stimulated macrophages that induces the release of chemotactic cytokines by resident macrophages

Ribeiro, Ronaldo A.; Flores, Carlos A.; Cunha, Fernando; Ferreira, Sérgio Henrique; Lucca, Fernando Luiz De

doi:10.1007/bf00928147

Cited by 12 publications

(4 citation statements)

References 24 publications

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“…It has previously been shown that the ability of fresh bacterial isolates (obtained from infected patients) to respond to proinflammatory cytokines is lost after several in vitro passages on a bacteriological medium without added cytokines (21). LPS activation of monocytes may also induce the expression of a variety of small mRNA molecules, which are thought to be converted into biologically active low-molecular-weight proteins (26). The low-molecular-weight mRNA molecules may code for proteins or small polypeptides that become growth factors for certain bacteria, or bacteria may acquire the ability to utilize those peptides under selective pressure.…”

Section: Discussionmentioning

confidence: 99%

Effects of Methylprednisolone on Intracellular Bacterial Growth

Meduri¹,

Kanangat²,

Bronze³

et al. 2001

Clin Diagn Lab Immunol

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Clinical studies have shown positive associations among sustained and intense inflammatory responses and the incidence of bacterial infections. Patients presenting with acute respiratory distress syndrome (ARDS) and high levels of proinflammatory cytokines, such as tumor necrosis factor alpha (TNF-␣), interleukin 1␤ (IL-1␤), and IL-6, have increased risk for developing nosocomial infections attributable to organisms such as Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter spp., compared to those patients with lower levels. Our previous in vitro studies have demonstrated that these bacterial strains exhibit enhanced growth extracellularly when supplemented with high concentrations of pure recombinant TNF-␣, IL-1␤, or IL-6. In addition, we have shown that the intracellular milieu of phagocytic cells that are exposed to supraoptimal concentrations of TNF-␣, IL-1␤, and IL-6 or lipopolysaccharide (LPS) favors survival and replication of ingested bacteria. Therefore, we hypothesized that under conditions of intense inflammation the host's micromilieu favors bacterial infections by exposing phagocytic cells to protracted high levels of inflammatory cytokines. Our clinical studies have shown that methylprednisolone is capable of reducing the levels of TNF-␣, IL-1␤, and IL-6 in ARDS patients. Hence, we designed a series of in vitro experiments to test whether human monocytic cells (U937 cells) that are activated with high concentrations of LPS, which upregulate the release of proinflammatory cytokines from these phagocytic cells, would effectively kill or restrict bacterial survival and replication after exposure to methylprednisolone. Fresh isolates of S. aureus, P. aeruginosa, and Acinetobacter were used in our studies. Our results indicate that, compared with the control, stimulation of U937 cells with 100-ng/ml, 1.0-g/ml, 5.0-g/ml, or 10.0-g/ml concentrations of LPS enhanced the intracellular survival and replication of all three species of bacteria significantly (for all, P ‫؍‬ 0.0001). Stimulation with <10.0 ng of LPS generally resulted in efficient killing of the ingested bacteria. Interestingly, when exposed to graded concentrations of methylprednisolone, U937 cells that had been stimulated with 10.0 g of LPS were able to suppress bacterial replication efficiently in a concentration-dependent manner. Significant reduction in numbers of CFU was observed at >150 g of methylprednisolone per ml (P values were 0.032, 0.008, and 0.009 for S. aureus, P. aeruginosa, and Acinetobacter, respectively). We have also shown that steady-state mRNA levels of TNF-␣, IL-1␤, and IL-6 in LPS-activated cells were reduced by treatment of such cells with methylprednisolone, in a concentration-dependent manner. The effective dose of methylprednisolone was 175 mg, a value that appeared to be independent of priming level of LPS and type of mRNA. We therefore postulate that a U-shaped relationship exists between the level of expression of TNF-␣, IL-1␤, and IL-6 within the phagocytic cells and their abilities to suppress act...

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Section: Discussionmentioning

confidence: 99%

Effects of Methylprednisolone on Intracellular Bacterial Growth

Meduri¹,

Kanangat²,

Bronze³

et al. 2001

Clin Diagn Lab Immunol

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“…The immunological effects observed in lymphocytes [27-29, 31, 101, 126, 127] and macrophages [8,30,106,107] treated with RNAs obtained from lymph nodes of immunized animals with different types of antigens including synthetic peptides of the human immunodeficiency virus type 1 (HIV-1) has been investigated. Recent results indicate that regulatory RNAs are involved in this phenomenon, which is due to the activation of the RNA-dependent protein kinase (PKR) by regulatory RNAs with subsequent activation of the transcription factor NF-κB [29 -31, 127].…”

Section: Introductionmentioning

confidence: 99%

Activation of the RNA-Dependent Protein Kinase (PKR) of Lymphocytes by Regulatory RNAs: Implications for Immunomodulation in HIV Infection

Watanabe

Souza²,

Murad³

et al. 2005

CHR

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It has been known for decades that exogenous RNAs are able to induce cytotoxic T lymphocytes (CTLs) and immunological reactivity to a wide variety of antigens. The molecular events responsible for these effects remain unclear for more than two decades. It has been decided to revisit this phenomenon in the light of new concepts that are just emerging in Molecular Biology, such as the regulation of gene expression by noncoding RNAs, named regulatory RNAs. The immunological effects observed in lymphocytes treated with RNAs obtained from lymph nodes of immunized animals with different types of antigens including synthetic peptides of the human immunodeficiency virus type 1 (HIV-1) have been investigated. Our recent results showed that regulatory RNAs are involved in this phenomenon, which is due to the activation of the RNA-dependent protein kinase (PKR) by regulatory RNAs with subsequent activation of the transcription factor NF-kappaB. The RNA-dependent protein kinase (PKR) is a serine/threonine kinase and contains two RNA-binding domains (RBD-I and RBD-II) within the N-terminal region. PKR is activated by viral double-stranded RNA (dsRNA) and highly structured single-stranded RNAs. This review will focus on the structure and functions of PKR including its role in HIV-1 infection. Special emphasis will be placed on a regulatory RNA, named p9-RNA, isolated from lymphocytes of animals immunized with the synthetic peptide p9 (pol: 476-484) of HIV-1. It was found that the regulatory p9-RNA induces CTLs and production of IFN-gamma. These findings showed for the first time that transcriptional control of gene expression by a regulatory RNA can be mediated by PKR through the activation of the transcription factor NF-kappaB. A model for the mechanism of action of the regulatory p9-RNA responsible for the production of IFN-gamma is proposed. Elucidating the molecular mechanism of p9-RNA may contribute to determining the rationale for the use of this regulatory RNA as an immunomodulator in HIV-infected patients.

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“…The presence of these cytokines in the supernatants of LPS-stimulated macrophages used to prepare MNF has been described. 15,16 The possibility that MNF activity results from the combination of these three cytokines was tested by injection of different concentrations of these cytokines alone or in combination into the abdominal cavity of mice. Although IL-1, IL-8 and TNF-a injected singly at high doses were unable to promote a signi cant nociception in mice, injection in combination reproduced the MNF-induced nociception.…”

Section: Discussionmentioning

confidence: 99%

Tumor necrosis factor, interleukin‐1 and interleukin‐8 mediate the nociceptive activity of the supernatant of LPS‐stimulated macrophages

Thomazzi

Ribeiro

Campos

et al. 1997

Mediators of Inflammation

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It has been suggested that the supernatant of LPSstimulated macrophages (macrophage nociceptive factor, MNF) promotes nociception in mice. Intraperitoneal administration of MNF induced dose-related writhing, which reached a plateau between 18 and 26 min after injection and decreased within 60 min. The release of MNF was inhibited by the pretreatment of the macrophages with cycloheximide, a protein synthesis inhibitor, or with the glucocorticoid dexamethasone. Cyclooxygenase inhibitors, such as indomethacin or paracetamol, had no effect. The MNF-induced nociception was inhibited in a dose-related manner by pretreatment of the animals with indomethacin, paracetamol or dexamethasone. Pretreatment of the animals with the sympatholytics guanethidine and atenolol partially reduced the MNF nociception, which was abolished by the combination of guanethidine or atenolol with indomethacin. The preincubation of MNF with antisera against TNF-α, IL-1 or IL-8 partially inhibited its nociceptive effect. Intraperitoneal injection of a mixture of the recombinants cytokines TNF-α, IL-1 and IL-8 mimicked MNF nociception. The individual injection of these cytokines was unable to induce the nociceptive effect. In conclusion, our data suggest that the nociceptive activity of the supernatant of LPSstimulated macrophages is explained by the presence of TNF-α, IL-1 and IL-8, the nociceptive activity of which (in mice) seems to be due to the release of cyclooxygenase and sympathetic metabolites.

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Partial characterization of the RNA from LPS-stimulated macrophages that induces the release of chemotactic cytokines by resident macrophages

Cited by 12 publications

References 24 publications

Effects of Methylprednisolone on Intracellular Bacterial Growth

Effects of Methylprednisolone on Intracellular Bacterial Growth

Activation of the RNA-Dependent Protein Kinase (PKR) of Lymphocytes by Regulatory RNAs: Implications for Immunomodulation in HIV Infection

Tumor necrosis factor, interleukin‐1 and interleukin‐8 mediate the nociceptive activity of the supernatant of LPS‐stimulated macrophages

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