Poly(lipoic acid)-based nanoparticles as a new therapeutic tool for delivering active molecules.

Pluronic-coated polylipoic acid-based nanoparticles (F127@PLA-NPs) have great potential as biodegradable nanovectors for delivering active molecules to different organs in complex diseases. In this study we describe the in vivo biodistribution, safety and ability to deliver molecules of F127@PLA-NPs in healthy rats following intravenous administration. Adult rats were injected with 10 mg/kg of rhodamine B-labeled F127@PLA-NPs, and NPs fluorescence and MFI rate were measured by confocal microscopy in whole collected organs. The NPs accumulation rate was maximal in the heart, compared to the other organs. At the cellular level, myocytes and kidney tubular cells showed the highest NPs uptake. Neither histopathological lesion nor thrombogenicity were observed after NPs injection. Finally, F127@PLA-NPs were tested in vitro as miRNAs delivery nanosystem, and they showed good ability in targeting cardiomyocytes. These results demonstrated that our F127@PLA-NPs constitute a biological, minimally invasive and safe delivery tool targeting organs and cells, such as heart and kidney.

Poly(lipoic acid)-Based Nanoparticles as Self-Organized, Biocompatible, and Corona-Free Nanovectors.

Herein we present an innovative approach to produce biocompatible, degradable, and stealth polymeric nanoparticles based on poly(lipoic acid), stabilized by a PEG-ended surfactant. Taking advantage of the well-known thiol-induced polymerization of lipoic acid, a universal and nontoxic nanovector consisted of a solid cross-linked polymeric matrix of lipoic acid monomers was prepared and loaded with active species with a one-step protocol. The biological studies demonstrated a high stability in biological media, the virtual absence of "protein" corona in biological fluids, the absence of acute toxicity in vitro and in vivo, complete clearance from the organism, and a relevant preference for short-term accumulation in the heart. All these features make these nanoparticles candidates as a promising tool for nanomedicine.

The peculiar N- and (-termini of trichogin GA IV are needed for membrane interaction and human cell death induction at doses lacking antibiotic activity.

Peptaibiotics, non-ribosomally synthetized peptides from various ascomycetes, are uniquely characterized by dialkylated a-amino acids, a rigid heli cal conformation, and membrane permeation properties. Although generally considered as antimicrobial peptides, peptaibiotics may display other toxicological properties, and their function is in many cases unknown. With the goal to define the biological activity and selectivity of the peptaibiotictrichogin GA IV from the human opportunist Trichodenna longibrachiatum we analyzed its membrane interaction,cytotoxic activity and antibacterial effect. Trichogin GA IV effectively killed several types of healthy and neoplastic human cells at doses (EC 50%= 4-6 ~) lacking antibiotic effects on both Gram- and Gram+ bacteria(MIC > 64 ~ ). The peptaibiotic distinctive (-terminal primary alcohol was found to cooperate with theN-terminal n-octanoyl group to permeate the membrane phospholipid bilayer and to mediate effective binding and active endocytosis of trichogin GA IV in eukaryotic cells, two steps essential for cell death induction.Replacement of one Gly with Lys plus the simultaneous esterification of the (-terminus, strongly increased trichogin GA IV anti-Gram+ activity (MIC 1-4 ~ ). but further mitigated its cytotoxicity on human cells.

Nanotechnological Approaches to Enhance the Potential of α-Lipoic Acid for Application in the Clinic.

α-lipoic acid is a naturally occurring compound with potent antioxidant properties that helps protect cells and tissues from oxidative stress. Its incorporation into nanoplatforms can affect factors like bioavailability, stability, reactivity, and targeted delivery. Nanoformulations of α-lipoic acid can significantly enhance its solubility and absorption, making it more bioavailable. While α-lipoic acid can be prone to degradation in its free form, encapsulation within nanoparticles ensures its stability over time, and its release in a controlled and sustained manner to the targeted tissues and cells. In addition, α-lipoic acid can be combined with other compounds, such as other antioxidants, drugs, or nanomaterials, to create synergistic effects that enhance their overall therapeutic benefits or hinder their potential cytotoxicity. This review outlines the advantages and drawbacks associated with the use of α-lipoic acid, as well as various nanotechnological approaches employed to enhance its therapeutic effectiveness, whether alone or in combination with other bioactive agents. Furthermore, it describes the engineering of α-lipoic acid to produce poly(α-lipoic acid) nanoparticles, which hold promise as an effective drug delivery system.

CD28 interaction with filamin-A controls lipid raft accumulation at the T-cell immunological synapse.

During physiological T-cell stimulation by antigen presenting cells (APCs), a major T-cell membrane rearrangement is known to occur leading to the organization of 'supramolecular activation clusters' at the immunological synapse. A possible role for the synapse is the generation of membrane compartments where signalling may be organized and propagated. Thus, engagement of the costimulatory molecule CD28 at the immunological synapse promotes the organization of a signalling compartment by inducing cytoskeletal changes and lipid raft accumulation. We identified the actin-binding protein Filamin-A (FLNa) as a novel molecular partner of CD28. We found that, after physiological stimulation, CD28 associated with and recruited FLNa into the immunological synapse, where FLNa organized CD28 signalling. FLNa knockdown by short interfering RNA (siRNA) inhibited CD28-mediated raft accumulation at the immunological synapse and T-cell costimulation. Together, our data indicate that CD28 binding to FLNa is required to induce the T-cell cytoskeletal rearrangements leading to recruitment of lipid microdomains and signalling mediators into the immunological synapse.

Nanoparticles Based on Cross-Linked Poly(Lipoic Acid) Protect Macrophages and Cardiomyocytes from Oxidative Stress and Ischemia Reperfusion Injury.

The control of radical damage and oxidative stress, phenomena involved in a large number of human pathologies, is a major pharmaceutical and medical goal. We here show that two biocompatible formulations of Pluronic-stabilized, poly (lipoic acid)-based nanoparticles (NP) effectively antagonized the formation of radicals and reactive oxygen species (ROS). These NPs, not only intrinsically scavenged radicals in a-cellular DPPH/ABTS assays, but also inhibited the overproduction of ROS induced by tert-Butyl hydroperoxide (t-BHP) in tumor cells (HeLa), human macrophages and neonatal rat ventricular myocytes (NRVMs). NPs were captured by macrophages and cardiomyocytes much more effectively as compared to HeLa cells and non-phagocytic leukocytes, eventually undergoing intracellular disassembly. Notably, NPs decreased the mitochondrial ROS generation induced by simulated Ischemia/Reperfusion Injury (IRI) in isolated cardiomyocytes. NPs also prevented IRI-triggered cardiomyocyte necrosis, mitochondrial dysfunction, and alterations of contraction-related intracellular Ca2+ waves. Hence, NPs appear to be an effective and cardiomyocyte-selective drug to protect against damages induced by post-ischemic reperfusion.

Mapping of the Neisseria meningitidis NadA cell-binding site: relevance of predicted {alpha}-helices in the NH2-terminal and dimeric coiled-coil regions.

NadA is a trimeric autotransporter protein of Neisseria meningitidis belonging to the group of oligomeric coiled-coil adhesins. It is implicated in the colonization of the human upper respiratory tract by hypervirulent serogroup B N. meningitidis strains and is part of a multiantigen anti-serogroup B vaccine. Structure prediction indicates that NadA is made by a COOH-terminal membrane anchor (also necessary for autotranslocation to the bacterial surface), an intermediate elongated coiled-coil-rich stalk, and an NH(2)-terminal region involved in cell interaction. Electron microscopy analysis and structure prediction suggest that the apical region of NadA forms a compact and globular domain. Deletion studies proved that the NH(2)-terminal sequence (residues 24 to 87) is necessary for cell adhesion. In this study, to better define the NadA cell binding site, we exploited (i) a panel of NadA mutants lacking sequences along the coiled-coil stalk and (ii) several oligoclonal rabbit antibodies, and their relative Fab fragments, directed to linear epitopes distributed along the NadA ectodomain. We identified two critical regions for the NadA-cell receptor interaction with Chang cells: the NH(2) globular head domain and the NH(2) dimeric intrachain coiled-coil α-helices stemming from the stalk. This raises the importance of different modules within the predicted NadA structure. The identification of linear epitopes involved in receptor binding that are able to induce interfering antibodies reinforces the importance of NadA as a vaccine antigen.

Water-soluble peptide-coated nanoparticles: control of the helix structure and enhanced differential binding to immune cells.

The stabilizing action of C(α)-tetrasubstituted α-amino acids inserted into a sequence of short peptides allowed for the first time the preparation of water-soluble nanoparticles of different materials coated with a helix-structured undecapeptide. This peptide coating strongly favors nanoparticle uptake by human immune system cells.

Opsonins and Dysopsonins of Nanoparticles: Facts, Concepts, and Methodological Guidelines.

Understanding the effects mediated by a set of nanoparticle (NP)-bound host biomolecules, often indicated with the umbrella term of NP corona, is essential in nanomedicine, nanopharmacology, and nanotoxicology. Among the NP-adsorbed proteome, some factors mediate cell binding, endocytosis, and clearing by macrophages and other phagocytes (opsonins), while some others display few affinities for the cell surface (dysopsonins). The functional mapping of opsonins and dysopsonins is instrumental to design long-circulating and nanotoxicologically safe next-generation nanotheranostics. In this review, we critically analyze functional data identifying specific proteins with opsonin or dysopsonin properties. Special attention is dedicated to the following: (1) the simplicity or complexity of the NP proteome and its modulation, (2) the role of specific host proteins in mediating the stealth properties of uncoated or polymer-coated NPs, and (3) the ability of the innate immune system, and, in particular, of the complement proteins, to mediate NP clearance by phagocytes. Emerging species-specific peculiarities, differentiating humans from preclinical animal models (the murine especially), are highlighted throughout this overview. The operative definition of opsonin and dysopsonin and the measurement schemes to assess their in vitro efficacy is critically re-examined. This provides a shared and unbiased approach useful for NP opsonin and dysopsonin systematic identification.

Human monocytes/macrophages are a target of Neisseria meningitidis Adhesin A (NadA).

Specific surface proteins of Neisseria meningitidis have been proposed to stimulate leukocytes during tissue invasion and septic shock. In this study, we demonstrate that the adhesin N. meningitidis Adhesin A (NadA) involved in the colonization of the respiratory epithelium by hypervirulent N. meningitidis B strains also binds to and activates human monocytes/macrophages. Expression of NadA on the surface on Escherichia coli does not increase bacterial-monocyte association, but a NadA-positive strain induced a significantly higher amount of TNF-alpha and IL-8 compared with the parental NadA-negative strain, suggesting that NadA has an intrinsic stimulatory action on these cells. Consistently, highly pure, soluble NadA(Delta351-405), a proposed component of an antimeningococcal vaccine, efficiently stimulates monocytes/macrophages to secrete a selected pattern of cytokines and chemotactic factors characterized by high levels of IL-8, IL-6, MCP-1, and MIP-1alpha and low levels of the main vasoactive mediators TNF-alpha and IL-1. NadA(Delta351-405) also inhibited monocyte apoptosis and determined its differentiation into a macrophage-like phenotype.

Self-Assembled Biocompatible Fluorescent Nanoparticles for Bioimaging.

Fluorescence is a powerful tool for mapping biological events in real-time with high spatial resolution. Ultra-bright probes are needed in order to achieve high sensitivity: these probes are typically obtained by gathering a huge number of fluorophores in a single nanoparticle (NP). Unfortunately this assembly produces quenching of the fluorescence because of short-range intermolecular interactions. Here we demonstrate that rational structural modification of a well-known molecular fluorophore N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) (NBD) produces fluorophores that self-assemble in nanoparticles in the biocompatible environment without any dramatic decrease of the fluorescence quantum yield. Most importantly, the resulting NP show, in an aqueous environment, a brightness which is more than six orders of magnitude higher than the molecular component in the organic solvent. Moreover, the NP are prepared by nanoprecipitation and they are stabilized only via non-covalent interaction, they are surprisingly stable and can be observed as individual bright spots freely diffusing in solution at a concentration as low as 1 nM. The suitability of the NP as biocompatible fluorescent probes was demonstrated in the case of HeLa cells by fluorescence confocal microscopy and MTS assays.

Stem cells transplantation positively modulates the heart-kidney cross talk in cardiorenal syndrome type II.

INTRODUCTION: We investigated the effects of human amniotic fluid stem cells (hAFS) and rat adipose tissue stromal vascular fraction GFP-positive cells (rSVC-GFP) in a model of cardio-renal syndrome type II (CRSII). METHODS AND RESULTS: RHF was induced by monocrotaline (MCT) in 28 Sprague-Dawley rats. Three weeks later, four million hAFS or rSVC-GFP cells were injected via tail vein. BNP, sCreatinine, kidney and heart NGAL and MMP9, sCytokines, kidney and heart apoptosis and cells (Cs) engraftment were evaluated. Cell-treated rats showed a significant reduction of serum NGAL and Creatinine compared to CRSII. In both hAFS and rSVC-GFP group, kidney protein expression of NGAL was significantly lower than in CRSII (hAFS p = 0.036 and rSVC-GFP p < 0.0001) and similar to that of controls. In both hAFS and rSVC-GFP treated rats, we observed cell engraftment in the medulla and differentiation into tubular, endothelial and SMCs cells. Apoptosis was significantly decreased in cell-treated rats (hAFS 14.07 ±â€¯1.38 and rSVC-GFP 12.67 ±â€¯2.96 cells/mm2) and similar to controls (9.85 ±â€¯2.1 cell/mm2). TUNEL-positive cells were mainly located in the kidney medulla. Pro-inflammatory cytokines were down regulated in cell-treated groups and similar to controls. In cell-treated rats, kidney and heart tissue NGAL was not complexed with MMP9 as in CRSII group, suggesting inhibition of MMPs activity. CONCLUSION: Cell therapy produced improvement in kidney function in rats with CRSII. This was the result of interstitial, vessel and tubular cell engraftment leading to tubular and vessel regeneration, decreased tubular cells apoptosis and mitigated pro-inflammatory milieu. Reduction of NGLA-MMP9 complexes mainly due to decrease MMPs activity prevented further negative heart remodeling.

Tumor-facing hepatocytes significantly contribute to mild hyperthermia-induced targeting of rat liver metastasis by PLGA-NPs.

The effect of mild hyperthermia (MHT) on nanoparticle (NP) accumulation in rat model liver metastasis and the contribution of neoplastic and non-neoplastic cells were characterized. CdSe/ZnS QD-doped poly(lactic-co-glycolic acid) (PLGA) NPs (155 ±â€¯10 nm) were delivered via the ileocolic vein to metastatic livers 15 min after localized MW irradiation (1 min, 41 °C) or in normothermia (37 °C, NT). Quantitative analysis of tissue sections by confocal fluorescence microscopy 1 h after NP injection showed no NP tumor accumulation in NT. On the contrary, MHT increased NP association with tumor, compared to normal tissue. Counterstaining of specific markers showed that the MHT effect is due to an increased NP endocytosis not only by tumor cells, but also by hepatocytes at the growing tumor edge and, to a minor extent, by tumor-associated macrophages. High-NP capturing hepatocytes, close to the tumor, may be a relevant phenomenon in MHT-induced increased targeting of NPs to liver metastasis, influencing their therapeutic efficacy.

Data on the stem cells paracrine effects on apoptosis and cytokine milieu in an experimental model of cardiorenal syndrome type II.

The data reported in this article are related to the paper entitle "Stem cells transplantation positively modulates the heart-kidney cross talk in Cardiorenal Syndrome Type II" (Vescovo et al., 2019), which analyzed the impact of stem cells injection in cardiorenal syndrome type II. The dataset contains detailed information on apoptosis and cytokines milieu modification after injection of c-Kit-selected human amniotic fluid stem cells (hAFS) or rats vascular progenitor cells (rSVC-GFP group) in an experimental model of CRSII. The data can be useful for clarifying the paracrine effects exerted by the injected cells.

Biofabrication of a novel leukocyte-fibrin-platelet membrane as a cells and growth factors delivery platform for tissue engineering applications.

Autologous platelet-rich hemocomponents have emerged as potential biologic tools for regenerative purpose, but their therapeutic efficacy still remains controversial. This work represents the characterization study of an innovative autologous leukocyte-fibrin-platelet membrane (LFPm), which we prepared according to a novel protocol involving multiple cycles of apheresis. The high content in fibrinogen gave to our hemocomponent the appearance of a manipulable and suturable membrane with high elasticity and deformation capacity. Moreover, being highly enriched with platelets, leukocytes, and monocytes/macrophages, the LFPm sustained the local release of bioactive molecules (platelet derived growth factor, vascular endothelial growth factor, interleukin-10, and tumour necrosis factor alpha). In parallel, the evaluation of stemness potential highlighted also that the LFPm contained cells expressing pluripotency and multipotency markers both at the messenger ribonucleic acid (NANOG, SOX2, THY1, NT5E, and ENG) and surface-protein level (CD44high /CD73+ /CD34+ /CD117+ /CD31+ ). Finally, biodegradation analysis interestingly showed a good stability of the membrane for at least 3 weeks in vitro and 1 week in vivo. In both cases, biodegradation was associated with progressive exposure of fibrin scaffold, loss/migration of cellular elements, and release of growth factors. Overall, collected evidence could shed some light on the regenerative effect that LFPms may exert after the autologous implant on a defect site.

C1q-Mediated Complement Activation and C3 Opsonization Trigger Recognition of Stealth Poly(2-methyl-2-oxazoline)-Coated Silica Nanoparticles by Human Phagocytes.

Poly(2-methyl-2-oxazoline) (PMOXA) is an alternative promising polymer to poly(ethylene glycol) (PEG) for design and engineering of macrophage-evading nanoparticles (NPs). Although PMOXA-engineered NPs have shown comparable pharmacokinetics and in vivo performance to PEGylated stealth NPs in the murine model, its interaction with elements of the human innate immune system has not been studied. From a translational angle, we studied the interaction of fully characterized PMOXA-coated vinyltriethoxysilane-derived organically modified silica NPs (PMOXA-coated NPs) of approximately 100 nm in diameter with human complement system, blood leukocytes, and macrophages and compared their performance with PEGylated and uncoated NP counterparts. Through detailed immunological and proteomic profiling, we show that PMOXA-coated NPs extensively trigger complement activation in human sera exclusively through the classical pathway. Complement activation is initiated by the sensing molecule C1q, where C1q binds with high affinity ( Kd = 11 ± 1 nM) to NP surfaces independent of immunoglobulin binding. C1q-mediated complement activation accelerates PMOXA opsonization with the third complement protein (C3) through the amplification loop of the alternative pathway. This promoted NP recognition by human blood leukocytes and monocyte-derived macrophages. The macrophage capture of PMOXA-coated NPs correlates with sera donor variability in complement activation and opsonization but not with other major corona proteins, including clusterin and a wide range of apolipoproteins. In contrast to these observations, PMOXA-coated NPs poorly activated the murine complement system and were marginally recognized by mouse macrophages. These studies provide important insights into compatibility of engineered NPs with elements of the human innate immune system for translational steps.

Combined Action of Human Commensal Bacteria and Amorphous Silica Nanoparticles on the Viability and Immune Responses of Dendritic Cells.

Dendritic cells (DCs) regulate the host-microbe balance in the gut and skin, tissues likely exposed to nanoparticles (NPs) present in drugs, food, and cosmetics. We analyzed the viability and the activation of DCs incubated with extracellular media (EMs) obtained from cultures of commensal bacteria (Escherichia coli, Staphylococcus epidermidis) or pathogenic bacteria (Pseudomonas aeruginosa, Staphylococcus aureus) in the presence of amorphous silica nanoparticles (SiO2 NPs). EMs and NPs synergistically increased the levels of cytotoxicity and cytokine production, with different nanoparticle dose-response characteristics being found, depending on the bacterial species. E. coli and S. epidermidis EMs plus NPs at nontoxic doses stimulated the secretion of interleukin-1ß (IL-1ß), IL-12, IL-10, and IL-6, while E. coli and S. epidermidis EMs plus NPs at toxic doses stimulated the secretion of gamma interferon (IFN-γ), tumor necrosis factor alpha (TNF-α), IL-4, and IL-5. On the contrary, S. aureus and P. aeruginosa EMs induced cytokines only when they were combined with NPs at toxic concentrations. The induction of maturation markers (CD86, CD80, CD83, intercellular adhesion molecule 1, and major histocompatibility complex class II) by commensal bacteria but not by pathogenic ones was improved in the presence of noncytotoxic SiO2 NP doses. DCs consistently supported the proliferation and differentiation of CD4+ and CD8+ T cells secreting IFN-γ and IL-17A. The synergistic induction of CD86 was due to nonprotein molecules present in the EMs from all bacteria tested. At variance with this finding, the synergistic induction of IL-1ß was prevalently mediated by proteins in the case of E. coli EMs and by nonproteins in the case of S. epidermidis EMs. A bacterial costimulus did not act on DCs after adsorption on SiO2 NPs but rather acted as an independent agonist. The inflammatory and immune actions of DCs stimulated by commensal bacterial agonists might be altered by the simultaneous exposure to engineered or environmental NPs.

Form Matters: Stable Helical Foldamers Preferentially Target Human Monocytes and Granulocytes.

Some hybrid foldamers of various length, all containing the (4R,5S)-4-carboxy-5-methyloxazolidin-2-one (d-Oxd) moiety alternating with an l-amino acid (l-Val, l-Lys, or l-Ala), were prepared in order to study their preferred conformations and to evaluate their biological activity. Surprisingly, only the longer oligomers containing l-Ala fold into well-established helices, whereas all the other oligomers give partially unfolded turn structures. Nevertheless, they all show good biocompatibility, with no detrimental effects up to 64 µm. After equipping some selected foldamers with the fluorescent tag rhodamine B, a quantitative analysis was performed by dose- and time-response fluorescence-activated cell sorting (FACS) assays with human HeLa cells and primary blood lymphocytes, granulocytes, and monocytes. Among the cell types analyzed, the oligomers associated with monocytes and granulocytes with greatest efficacy, still visible after 24 h incubation. This effect is even more pronounced for foldamers that are able to form stable helices.

Comparison of bactericidal and cytotoxic activities of trichogin analogs.

Peptaibiotics are a group of membrane active peptides of fungal origin. They typically contain α-aminoisobutyric acid (Aib; 1-letter code, U) and other non-coded residues (Toniolo and Brückner, 2009; Neumann et al., 2015; Benedett et al., 1982) [1], [2], [3] stabilizing their helical structure. Peptaibols are peptaibiotics carrying a 1, 2-aminoalcohol at the C-terminus. When a fatty acid chain (of 8-10 carbon atoms) is present at their N-terminus, they are called lipopeptaibols (Toniolo et al., 2001; Degenkolb et al., 2003) [4], [5]. We found (Tavano et al., 2015) [6] that the lipopeptaibol trichogin displays no antibacterial effects up to 64 µM, against both Gram(-) and Gram(+) bacteria, but kills tumor and healthy human cells via a mechanism requiring both the C-terminal primary alcohol group and the N-terminal n-octanoyl moiety, with EC50s around 4-5 µM. However, the substitution of single Gly residues with Lys strongly improves anti-Gram(+) activity (Tavano et al., 2015; De Zotti, Biondi, Park et al., 2012; De Zotti, Biondi, Peggion et al., 2012) [6], [7], [8]. To further characterize the activity of trichogin analogs as antibiotics and cytotoxic agents, we here manipulated the peptide helix amphipathicity by means of two different substitutions: (i) Aib to Leu (De Zotti et al., 2012) [7] or (ii) multiple Gly to Lys changes (Tavano et al., 2015; De Zotti, Biondi, Park et al., 2012; De Zotti, Biondi, Peggion, Formaggio et al., 2012; De Zotti, Biondi, Peggion, De Poli et al., 2012) [6], [7], [8], [9]. The antibacterial activity against four commensal or opportunistic bacterial species and the cytotoxicity against a panel of 9 healthy and tumor-derived eukaryotic cell types (including erythrocytes) are reported as MIC and EC50 (MTS - [3-(4, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)]-2H-tetrazolium- reduction and LDH - lactate dehydrogenase - release assay).

Formyl-Peptide Receptor Agonists and Amorphous SiO2-NPs Synergistically and Selectively Increase the Inflammatory Responses of Human Monocytes and PMNs.

We tested whether amorphous SiO2-NPs and formylpeptide receptor (FPRs) agonists synergistically activate human monocytes and neutrophil polymorphonuclear granulocytes (PMNs). Peptide ligands specifically binding to FPR1 (f-MLP) and to FPR2 (MMK-1, WKYMVM and WKYMVm) human isoforms did not modify the association of SiO2-NPs to both cell types or their cytotoxic effects. Similarly, the extent of CD80, CD86, CD83, ICAM-1 and MHCII expression in monocytes treated with SiO2-NPs was not significantly altered by any FPRs agonist. However, FPR1 stimulation with f-MLP strongly increased the secretion of IL-1ß, IL-6 and IL-8 by human monocytes, and of IL-8 by PMNs in the presence of SiO2-NPs, due to the synergic stimulation of gene transcription. FPR2 agonists also up-modulated the production of IL-1ß induced by monocytes treated with SiO2-NPs. In turn, SiO2-NPs increased the chemotaxis of PMNs toward FPR1-specific ligands, but not toward FPR2-specific ones. Conversely, the chemotaxis of monocytes toward FPR2-specific peptides was inhibited by SiO2-NPs. NADPH-oxidase activation triggered by FPR1- and FPR2-specific ligands in both cell types was not altered by SiO2-NPs. Microbial and tissue danger signals sensed by FPRs selectively amplified the functional responses of monocytes and PMNS to SiO2-NPs, and should be carefully considered in the assessment of the risk associated with nanoparticle exposure.