Dendrimers-Novel Therapeutic Approaches for Alzheimer's Disease

Dendrimers are covalently bonded globular nanostructures that may be used in the treatment of Alzheimer's disease (AD). Nowadays, AD therapies are focused on improving cognitive functioning and not causal treatment. However, this may change with the use of dendrimers, which are being investigated as a drug-delivery system or as a drug per se. With their ability to inhibit amyloid formation and their anti-tau properties, they are a promising therapeutic option for AD patients. Studies have shown that dendrimers may inhibit amyloid formation in at least two ways: by blocking fibril growth and by breaking already existing fibrils. Neurofibrillary tangles (NFTs) are abnormal filaments built by tau proteins that can be accumulated in the cell, which leads to the loss of cytoskeletal microtubules and tubulin-associated proteins. Cationic phosphorus dendrimers, with their anti-tau properties, can induce the aggregation of tau into amorphous structures. Drug delivery to mitochondria is difficult due to poor transport across biological barriers, such as the inner mitochondrial membrane, which is highly negatively polarized. Dendrimers may be potential nanocarriers and increase mitochondria targeting. Another considered use of dendrimers in AD treatment is as a drug-delivery system, for example, carbamazepine (CBZ) or tacrine. They can also be used to transport siRNA into neuronal tissue and to carry antioxidants and anti-inflammatory drugs to act protectively on the nervous system.

Molecular regulation of neutrophil swarming in health and disease: Lessons from the phagocyte oxidase

Neutrophil swarming is a complex coordinated process in which neutrophils sensing pathogen or damage signals are rapidly recruited to sites of infections or injuries. This process involves cooperation between neutrophils where autocrine and paracrine positive-feedback loops, mediated by receptor/ligand pairs including lipid chemoattractants and chemokines, amplify localized recruitment of neutrophils. This review will provide an overview of key pathways involved in neutrophil swarming and then discuss the cell intrinsic and systemic mechanisms by which NADPH oxidase 2 (NOX2) regulates swarming, including modulation of calcium signaling, inflammatory mediators, and the mobilization and production of neutrophils. We will also discuss mechanisms by which altered neutrophil swarming in disease may contribute to deficient control of infections and/or exuberant inflammation. Deeper understanding of underlying mechanisms controlling neutrophil swarming and how neutrophil cooperative behavior can be perturbed in the setting of disease may help to guide development of tools for diagnosis and precision medicine.

Protein kinase C isoforms mediate the formation of neutrophil extracellular traps

Neutrophils release extracellular traps (NETs) in response to numerous pathogenic microbes as the last suicidal resource (NETosis) in the fight against infection. Apart from the host defense function, NETs play an essential role in the pathogenesis of various autoimmune, inflammatory and malignant diseases. Therefore, understanding the molecular mechanisms of NETosis is important for regulating the aberrant or excessive NET release. Protein kinase C (PKC) is a serine/threonine kinase which is involved in various neutrophil functions, however, little is known about its implication in NETosis activated by various physiological and pharmacological stimuli. Since there are conventional, novel and atypical PKC isoforms (α, βI, βII, δ, and ζ) found in human neutrophils, we investigated their impact in NETosis, oxidative burst and spreading applying pharmacological approach. Using specific inhibitors of PKC isoforms, we showed that PKCβ, PKCδ, and PKCζ are involved in the oxidative burst, spreading and NETosis activated by calcium ionophore A23187, while only PKCβ is implicated in these functions activated by phorbol 12-myristate 13-acetate (PMA). The data obtained in our study might help in the development of new drugs useful for the treatment of autoimmune and inflammatory diseases associated with NETs.

The Relationship of NADPH Oxidases and Heme Peroxidases: Fallin' in and Out

Peroxidase enzymes can oxidize a multitude of substrates in diverse biological processes. According to the latest phylogenetic analysis, there are four major heme peroxidase superfamilies. In this review, we focus on certain members of the cyclooxygenase-peroxidase superfamily (also labeled as animal heme peroxidases) and their connection to specific NADPH oxidase enzymes which provide H₂O₂ for the one- and two-electron oxidation of various peroxidase substrates. The family of NADPH oxidases is a group of enzymes dedicated to the production of superoxide and hydrogen peroxide. There is a handful of known and important physiological functions where one of the seven known human NADPH oxidases plays an essential role. In most of these functions NADPH oxidases provide H₂O₂ for specific heme peroxidases and the concerted action of the two enzymes is indispensable for the accomplishment of the biological function. We discuss human and other metazoan examples of such cooperation between oxidases and peroxidases and analyze the biological importance of their functional interaction. We also review those oxidases and peroxidases where this kind of partnership has not been identified yet.

The inducibility of TNF-alpha production is different in the granulocytic and monocytic differentiated forms of wild type and CGD-mutant PLB-985 cells

Chronic granulomatous disease is an inherited disorder associated with a defect in phagocytic cell oxidative metabolism resulting in ineffective microbicidal activity. Consequently, patients with chronic granulomatous disease suffer from recurrent infections. Published data show that besides the failure to produce superoxide and its derivatives, other functional problems can also be found in chronic granulomatous disease-mutant cells. Since in innate immune responses other mediators, such as cytokines, also play an important role, we hypothesized that there may be a disturbance in cytokine production by chronic granulomatous disease-mutant cells as well. To prove this hypothesis, the production of tumour necrosis factor-alpha, an important proinflammatory cytokine, was determined by enzyme-linked immunosorbent assay in wild-type and chronic granulomatous disease-mutant myelomonoblastic PLB-985 cells in their immature, granulocytic and monocytic/macrophage differentiated forms. Tumour necrosis factor-alpha production was induced with N-formyl-L-methionyl-L-leucyl-L-phenylalanine (100 nmol/L), lipopolysaccharide (10 micro g/mL), opsonized zymosan (100 micro g/mL) or phorbol 12-myristate 13-acetate (100 nmol/L) for 24 h. We could demonstrate that: (i) there were marked differences in tumour necrosis factor-alpha production only in the differentiated forms of both wild-type and chronic granulomatous disease-mutant cells, while there were no differences in the case of their immature counterparts; (ii) only chronic granulomatous disease-mutant cells retained sensitivity to phorbol 12-myristate 13-acetate both in their granulocytic and monocytic forms, although phorbol 12-myristate 13-acetate responsiveness was a characteristic of both types of immature cells; (iii) the granulocytic form of wild-type cells produced tumour necrosis factor-alpha after opsonized zymosan stimulation, but such a response was not observed in cells originating from the chronic granulomatous disease-mutant cell line; (iv) with the monocytic forms, significantly higher tumour necrosis factor-alpha production could be induced by lipopolysaccharide in the wild-type cells than in the chronic granulomatous disease-mutant cells, although there was no difference in their lipopolysaccharide receptor CD14 expression. In summary, these data show an altered inducibility of tumour necrosis factor-alpha production by chronic granulomatous disease-mutant cells. Our observations suggest a further defect in differentiated chronic granulomatous disease-mutant cells in addition to the known defect in reduced nicotinamide adenine dinucleotide phosphate oxidase, which may contribute to the development of susceptibility to infections in people with chronic granulomatous disease.

The arachidonic acid-binding protein S100A8/A9 promotes NADPH oxidase activation by interaction with p67phox and Rac-2

The Ca2+- and arachidonic acid-binding S100A8/A9 protein complex was recently identified by in vitro studies as a novel partner of the phagocyte NADPH oxidase. The present study demonstrated its functional relevance by the impaired oxidase activity in neutrophil-like NB4 cells, after specific blockage of S100A9 expression, and bone marrow polymorphonuclear neutrophils from S100A9-/- mice. The impaired oxidase activation could also be mimicked in a cell-free system by pretreatment of neutrophil cytosol with an S100A9-specific antibody. Further analyses gave insights into the molecular mechanisms by which S100A8/A9 promoted NADPH oxidase activation. In vitro analysis of oxidase activation as well as protein-protein interaction studies revealed that S100A8 is the privileged interaction partner for the NADPH oxidase complex since it bound to p67phox and Rac, whereas S100A9 did interact with neither p67phox nor p47phox. Moreover, S100A8/A9 transferred the cofactor arachidonic acid to NADPH oxidase as shown by the impotence of a mutant S100A8/A9 complex unable to bind arachidonic acid to enhance NADPH oxidase activity. It is concluded that S100A8/A9 plays an important role in phagocyte NADPH oxidase activation.

In vitro effects of aqueous seeds extract of Acacia cyanophylla on the opsonized zymosan-induced superoxide anions production by rat polymorphonuclear leukocytes

In vitro studies were carried out in rat pleural polymorphonuclear leukocytes (PMNs) activated by opsonized zymosan (OZ) to investigate the effects of aqueous extract from Acacia cyanophylla seeds on superoxide anions generation. PMNs were collected, after induction of an acute inflammatory reaction, by injection in the rat pleural cavity, of a suspension of calcium pyrophosphate (CaPP) crystals (pleurisy with CaPP) or serum (pleurisy with serum). The results obtained indicate that Acacia cyanophylla aqueous seeds extract had, in vitro, a significant stimulatory effect, in a dose dependent manner, on the PMN superoxide anions generation. It also corrected the diminution of superoxide anions production induced by diclofenac pre-treated PMNs. It could be concluded from the results of this study that the stimulatory properties of Acacia cyanophylla seeds aqueous extract may at least be due to the presence of polyphenols such tannins and/or lignins. Further investigations are needed to determine clearly the mechanisms mediating the generation of superoxide radicals in this phenomenon.