We have developed a versatile new class of genetically encoded fluorescent biosensor based on reversible exchange of the heterodimeric partners of green and red dimerization dependent fluorescent proteins (ddFPs). This strategy has been used to construct both intermolecular and intramolecular ratiometric biosensors for qualitative imaging of caspase activity, Ca2+ concentration dynamics, and other second messenger signaling activities.

The overall findings indicate that BNNTs can function as nanocarriers of biologically relevant probes/drugs allowing one to examine/control their local intracellular localization and biochemical effects, leading the way to applications as intracellular nanosensors.

Dendritic polyglycerols (dPG), particularly dendritic polyglycerol sulfates (dPGS), have been intensively studied due to their intrinsic anti-inflammatory activity. As related to brain pathologies involving neuroinflammation, the current study examined if dPG and dPGS can (i) regulate neuroglial activation, and (ii) normalize the morphology and function of excitatory postsynaptic dendritic spines adversely affected by the neurotoxic 42 amino acid amyloid-β (Aβ) peptide of Alzheimer disease (AD). The exact role of neuroglia, such as microglia and astrocytes, remains controversial especially their positive and negative impact on inflammatory processes in AD. To test dPGS effectiveness in AD models we used primary neuroglia and organotypic hippocampal slice cultures exposed to Aβ peptide. Overall, our data indicate that dPGS is taken up by both microglia and astrocytes in a concentration- and time-dependent manner. The mechanism of action of dPGS involves binding to Aβ, i.e., a direct interaction between dPGS and Aβ species interfered with Aβ fibril formation and reduced the production of the neuroinflammagen lipocalin-2 (LCN2) mainly in astrocytes. Moreover, dPGS normalized the impairment of neuroglia and prevented the loss of dendritic spines at excitatory synapses in the hippocampus. In summary, dPGS has desirable therapeutic properties that may help reduce amyloid-induced neuroinflammation and neurotoxicity in AD.

Glioblastoma multiforme is one of the most aggressive brain tumors and current therapies with temozolomide or suberoylanilide hydroxamic acid (SAHA, vorinostat) show considerable limitations. SAHA is a histone deacetylase (HDAC) inhibitor that can cause undesirable side effects due to the lack of selectivity. We show here properties of a novel hybrid molecule, sahaquine, which selectively inhibits cytoplasmic HDAC6 at nanomolar concentrations without markedly suppressing class I HDACs. Inhibition of HDAC6 leads to significant α-tubulin acetylation, thereby impairing cytoskeletal organization in glioblastoma cells. The primaquine moiety of sahaquine reduced the activity of P-glycoprotein, which contributes to glioblastoma multiforme drug resistance. We propose the mechanism of action of sahaquine to implicate HDAC6 inhibition together with suppression of epidermal growth factor receptor and downstream kinase activity, which are prominent therapeutic targets in glioblastoma multiforme. Sahaquine significantly reduces the viability and invasiveness of glioblastoma tumoroids, as well as brain tumor stem cells, which are key to tumor survival and recurrence. These effects are augmented with the combination of sahaquine with temozolomide, the natural compound quercetin or buthionine sulfoximine, an inhibitor of glutathione biosynthesis. Thus, a combination of agents disrupting glioblastoma and brain tumor stem cell homeostasis provides an effective anti–cancer intervention.

BackgroundOrganelle remodeling processes are evolutionarily conserved and involved in cell functions during development, aging, and cell death. Some endogenous and exogenous molecules can modulate these processes. Docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid, has mainly been considered as a modulator of plasma membrane fluidity in brain development and aging, while DHA’s role in organelle remodeling in specific neural cell types at the ultrastructural level remains largely unexplored. DHA is notably incorporated into dynamic organelles named lipid bodies (LBs). We hypothesized that DHA could attenuate the inflammatory response in lipopolysaccharide (LPS)-activated microglia by remodeling LBs and altering their functional interplay with mitochondria and other associated organelles.ResultsWe used electron microscopy to analyze at high spatial resolution organelle changes in N9 microglial cells exposed to the proinflammogen LPS, with or without DHA supplementation. Our results revealed that DHA reverses several effects of LPS in organelles. In particular, a large number of very small and grouped LBs was exclusively found in microglial cells exposed to DHA. In contrast, LBs in LPS-stimulated cells in the absence of DHA were sparse and large. LBs formed in the presence of DHA were generally electron-dense, suggesting DHA incorporation into these organelles. The accumulation of LBs in microglial cells from mouse and human was confirmed in situ. In addition, DHA induced numerous contacts between LBs and mitochondria and reversed the frequent disruption of mitochondrial integrity observed upon LPS stimulation. Dilation of the endoplasmic reticulum lumen was also infrequent following DHA treatment, suggesting that DHA reduces oxidative stress and protein misfolding. Lipidomic analysis in N9 microglial cells treated with DHA revealed an increase in phosphatidylserine, indicating the role of this phospholipid in normalization and maintenance of physiological membrane functions. This finding was supported by a marked reduction of microglial filopodia and endosome number and significant reduction of LPS-induced phagocytosis.ConclusionsDHA attenuates the inflammatory response in LPS-stimulated microglial cells by remodeling LBs and altering their interplay with mitochondria and other associated organelles. Our findings point towards a mechanism by which omega-3 DHA participates in organelle reorganization and contributes to the maintenance of neural cell homeostasis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0580-0) contains supplementary material, which is available to authorized users.