TLR4/MD-2 is a receptor for extracellular nucleophosmin 1

Nucleophosmin: A Nucleolar Phosphoprotein Orchestrating Cellular Stress Responses

Nucleophosmin (NPM1) is a key nucleolar protein released from the nucleolus in response to stress stimuli. NPM1 functions as a stress regulator with nucleic acid and protein chaperone activities, rapidly shuttling between the nucleus and cytoplasm. NPM1 is ubiquitously expressed in tissues and can be found in the nucleolus, nucleoplasm, cytoplasm, and extracellular environment. It plays a central role in various biological processes such as ribosome biogenesis, cell cycle regulation, cell proliferation, DNA damage repair, and apoptosis. In addition, it is highly expressed in cancer cells and solid tumors, and its mutation is a major cause of acute myeloid leukemia (AML). This review focuses on NPM1's structural features, functional diversity, subcellular distribution, and role in stress modulation.

Ali S, Efferth T, Hegazy MEF. Salvimulticanol from Salvia multicaulis suppresses LPS-induced inflammation in RAW264.7 macrophages: in vitro and in silico studies

Sustained inflammatory responses can badly affect several vital organs and lead to chronic inflammation-related disorders, such as atherosclerosis, pneumonia, rheumatoid arthritis, obesity, diabetes, Alzheimer's disease, and cancers. Salvia multicaulis is one of the widely distributed plants that contains several biologically active phytochemicals and diterpenoids with anti-inflammatory effects. Therefore, finding alternative and safer natural plant-extracted compounds with good curative anti-inflammatory efficiencies is an urgent need for the clinical treatment of inflammation-related diseases. In the current study, S. multicaulis Vahl was used to extract and isolate two compounds identified as salvimulticanol and candesalvone B methyl ester to examine their effects against inflammation in murine macrophage RAW264.7 cells that were induced by lipopolysaccharide (LPS). Accordingly, after culturing RAW264.7 cells and induction of inflammation by LPS (100 ng/ml), cells were exposed to different concentrations (9, 18, 37.5, 75, and 150 µM) of each compound. Then, Griess assay for detection of nitric oxide (NO) levels and western blotting for the determination of inducible nitric oxide synthase (iNOS) expression were performed. Molecular docking and molecular dynamics (MD) simulation studies were employed to investigate the anti-inflammatory mechanism. Our obtained results validated that the level of NO was significantly decreased in the macrophage cell suspensions as a response to salvimulticanol treatment in a dose-dependent manner (IC50: 25.1 ± 1.2 µM) as compared to the methyl ester of candesalvone B which exerted a weaker inhibition (IC50: 69.2 ± 3.0 µM). This decline in NO percentage was comparable with a down-regulation of iNOS expression by western blotting. Salvimulticanol strongly interacted with both the Toll-like receptor 4 (TLR4)/myeloid differentiation factor 2 (MD-2) complex and the inhibitor of nuclear factor kappa-B (NF-κB) kinase subunit beta (IKKβ) to disrupt their inflammatory activation due to the significant hydrogen bonds and effective interactions with amino acid residues present in the target proteins' active sites. S.multicaulis is a rich natural source of the aromatic abietane diterpenoid, salvimulticanol, which exerted a strong anti-inflammatory effect through targeting iNOS and diminishing NO production in LPS-induced RAW264.7 cells in a mechanism that is dependent on the inhibition of TLR4-MD-2 and IKKβ as activators of the classical NF-κB-mediated inflammatory pathway.

FLT3 and IRAK4 Inhibitor Emavusertib in Combination with BH3-Mimetics in the Treatment of Acute Myeloid Leukemia

Targeting the FLT3 receptor and the IL-1R associated kinase 4 as well as the anti-apoptotic proteins MCL1 and BCL2 may be a promising novel approach in the treatment of acute myeloid leukemia (AML). The FLT3 and IRAK4 inhibitor emavusertib (CA4948), the MCL1 inhibitor S63845, the BCL2 inhibitor venetoclax, and the HSP90 inhibitor PU-H71 were assessed as single agents and in combination for their ability to induce apoptosis and cell death in leukemic cells in vitro. AML cells represented all major morphologic and molecular subtypes, including FLT3-ITD and NPM1 mutant AML cell lines and a variety of patient-derived AML cells. Emavusertib in combination with MCL1 inhibitor S63845 or BCL2 inhibitor venetoclax induced cell cycle arrest and apoptosis in MOLM-13 cells. In primary AML cells, the response to emavusertib was associated with the presence of the FLT3 gene mutation with an allelic ratio >0.5 and the presence of NPM1 gene mutations. S63845 was effective in all tested AML cell lines and primary AML samples. Blast cell percentage was positively associated with the response to CA4948, S63845, and venetoclax, with elevated susceptibility of primary AML with blast cell fraction >80%. Biomarkers of the response to venetoclax included the blast cell percentage and bone marrow infiltration rate, as well as the expression levels of CD11b, CD64, and CD117. Elevated susceptibility to CA4948 combination treatments with S63845 or PU-H71 was associated with FLT3-mutated AML and CD34 < 30%. The combination of CA4948 and BH3-mimetics may be effective in the treatment in FLT3-mutated AML with differential target specificity for MCL1 and BCL2 inhibitors. Moreover, the combination of CA4948 and PU-H71 may be a candidate combination treatment in FLT3-mutated AML.

PAMPs and DAMPs in Sepsis: A Review of Their Molecular Features and Potential Clinical Implications

Sepsis is a serious organ dysfunction caused by a dysregulated immune host reaction to a pathogen. The innate immunity is programmed to react immediately to conserved molecules, released by the pathogens (PAMPs), and the host (DAMPs). We aimed to review the molecular mechanisms of the early phases of sepsis, focusing on PAMPs, DAMPs, and their related pathways, to identify potential biomarkers. We included studies published in English and searched on PubMed® and Cochrane®. After a detailed discussion on the actual knowledge of PAMPs/DAMPs, we analyzed their role in the different organs affected by sepsis, trying to elucidate the molecular basis of some of the most-used prognostic scores for sepsis. Furthermore, we described a chronological trend for the release of PAMPs/DAMPs that may be useful to identify different subsets of septic patients, who may benefit from targeted therapies. These findings are preliminary since these pathways seem to be strongly influenced by the peculiar characteristics of different pathogens and host features. Due to these reasons, while initial findings are promising, additional studies are necessary to clarify the potential involvement of these molecular patterns in the natural evolution of sepsis and to facilitate their transition into the clinical setting.

Functional characterization of porcine nucleophosmin (NPM1) gene in promoting the replication of Japanese encephalitis virus and induction of inflammatory cytokines

Nucleophosmin (NPM1) is a multifunctional nucleolar protein that plays a role in cell cycle control, tumorigenesis, induction of the inflammatory cytokine, virus replication, as well as the cellular responses to a variety of stress stimuli. However, its physiological functions in pigs have not been well understood. Here, we cloned the porcine NPM1 (porNPM1) gene and analyzed the functions of the porNPM1 protein in pigs. The full-length porNPM1 gene encoded a 294-amino acid protein with 94.5%-99.3% sequence identity to its orthologues in mammals and was extensively expressed in various pig tissues at the mRNA level. The porNPM1 primarily localizes in the nucleus of ST cells, while it translocates from the nucleus to nucleoplasm upon UV irradiation or H2O2 treatment. Notably, JEV infection blocked the translocation of porNPM1 from the nucleolus to the nucleoplasm. Furthermore, porNPM1 interacted with the JEV C protein and facilitated JEV replication in ST cells. The overexpression and knockdown of porNPM1 respectively enhanced or impaired JEV replication, suggesting the important role of porNPM1 in JEV replication. Additionally, the purified ectodomain of porNPM1 induced the production of inflammatory cytokines (TNF-α, IL-6, and IL-8). Together, these data demonstrated that porNPM1 is involved in cellular stress stimuli, JEV replication, and induction of inflammatory cytokines.

Anti-Inflammatory Activity of Black Soldier Fly Oil Associated with Modulation of TLR Signaling: A Metabolomic Approach

Dietary intervention in the treatment of ulcerative colitis involves, among other things, modifications in fatty acid content and/or profile. For example, replacing saturated long chain fatty acids with medium chain fatty acids (MCFAs) has been reported to ameliorate inflammation. The Black Soldier Fly Larvae's (BSFL) oil is considered a sustainable dietary ingredient rich in the MCFA C12:0; however, its effect on inflammatory-related conditions has not been studied until now. Thus, the present study aimed to investigate the anti-inflammatory activity of BSFL oil in comparison to C12:0 using TLR4- or TLR2-activated THP-1 and J774A.1 cell lines and to assess its putative protective effect against dextran sulfate sodium (DSS)-induced acute colitis in mice. BSFL oil and C12:0 suppressed proinflammatory cytokines release in LPS-stimulated macrophages; however, only BSFL oil exerted anti-inflammatory activity in Pam3CSK4-stimulated macrophages. Transcriptome analysis provided insight into the possible role of BSFL oil in immunometabolism switch, involving mTOR signaling and an increase in PPAR target genes promoting fatty acid oxidation, exhibiting a discrepant mode of action compared to C12:0 treatment, which mainly affected cholesterol biosynthesis pathways. Additionally, we identified anti-inflammatory eicosanoids, oxylipins, and isoprenoids in the BSFL oil that may contribute to an orchestrated anti-inflammatory response. In vivo, a BSFL oil-enriched diet (20%) ameliorated the clinical signs of colitis, as indicated by improved body weight recovery, reduced colon shortening, reduced splenomegaly, and an earlier phase of secretory IgA response. These results indicate the novel beneficial use of BSFL oil as a modulator of inflammation.

Synthesis of small molecules targeting paclitaxel-induced MyD88 expression in triple-negative breast cancer cell lines

Acquired paclitaxel (PTX) chemoresistance in triple-negative breast cancer (TNBC) can be inferred from the overexpression of toll-like receptor 4 (TLR4) and myeloid differentiation primary response 88 (MyD88) proteins and the activation of the TLR4/MyD88 cascading signalling pathway. Finding a new inhibitor that can attenuate the activation of this pathway is a novel strategy for reducing PTX chemoresistance. In this study, a series of small molecule compounds were synthesised and tested in combination with PTX against TNBC cells. The trimethoxy-substituted compound significantly decreased MyD88 overexpression and improved PTX activity in MDA-MB-231^TLR4+ cells but not in HCC^TLR4- cells. On the contrary, the trifluoromethyl-substituted compound with PTX synergistically improved the growth inhibition in both TNBC subtypes. The fluorescence titrations indicated that both compounds could bind with MD2 with good and comparable binding affinities. This was further supported by docking analysis, in which both compounds fit perfectly well and form some critical binding interactions with MD2, an essential lipid-binding accessory to TLR4 involved in activating the TLR-4/MyD88-dependent pathway.

Doxorubicin induces an alarmin-like TLR4-dependent autocrine/paracrine action of Nucleophosmin in human cardiac mesenchymal progenitor cells

Background

Doxorubicin (Dox) is an anti-cancer anthracycline drug that causes double-stranded DNA breaks. It is highly effective against several types of tumours; however, it also has adverse effects on regenerative populations of normal cells, such as human cardiac mesenchymal progenitor cells (hCmPCs), and its clinical use is limited by cardiotoxicity. Another known effect of Dox is nucleolar disruption, which triggers the ubiquitously expressed nucleolar phosphoprotein Nucleophosmin (NPM) to be released from the nucleolus into the cell, where it participates in the orchestration of cellular stress responses. NPM has also been observed in the extracellular space in response to different stress stimuli; however, the mechanism behind this and its functional implications are as yet largely unexplored. The aim of this study was to establish whether Dox could elicit NPM secretion in the extracellular space and to elucidate the mechanism of secretion and the effect of extracellular NPM on hCmPCs.

Results

We found that following the double-strand break formation in hCmPCs caused by Dox, NPM was rapidly secreted in the extracellular space by an active mechanism, in the absence of either apoptosis or necrosis. Extracellular release of NPM was similarly seen in response to ultraviolet radiation (UV). Furthermore, we observed an increase of NPM levels in the plasma of Dox-treated mice; thus, NPM release also occurred in vivo. The treatment of hCmPCs with extracellular recombinant NPM induced a decrease of cell proliferation and a response mediated through the Toll-like receptor (TLR)4. We demonstrated that NPM binds to TLR4, and via TLR4, and nuclear factor kappa B (NFkB) activation/nuclear translocation, exerts proinflammatory functions by inducing IL-6 and COX-2 gene expression. Finally, we found that in hCmPCs, NPM secretion could be driven by an autophagy-dependent unconventional mechanism that requires TLR4, since TLR4 inhibition dramatically reduced Dox-induced secretion.

Conclusions

We hypothesise that the extracellular release of NPM could be a general response to DNA damage since it can be elicited by either a chemical agent such as Dox or a physical genotoxic stressor such as UV radiation. Following genotoxic stress, NPM acts similarly to an alarmin in hCmPCs, being rapidly secreted and promoting cell cycle arrest and a TLR4/NFκB-dependent inflammatory response.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01058-5.