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In vitro, treosulfan (TREO) has shown high effectiveness against malignant gliomas. However, a first clinical trial for newly diagnosed glioblastoma did not show any positive effect. Even though dosing and timing might have been the reasons for this failure, it might also be that TREO does not reach the brain in sufficient amount. Surprisingly, there are no published data on TREO uptake into the brain of patients, despite extensive research on this compound. An in-vitro blood-brain barrier (BBB) model consisting of primary porcine brain capillary endothelial cells was used to determine the transport of TREO across the cell monolayer. Temozolomide (TMZ), the most widely used cytotoxic drug for malignant gliomas, served as a reference. An HPLC-ESI-MS/MS procedure was developed to detect TREO and TMZ in cell culture medium. Parallel to the experimental approach, the permeability of TREO and the reference substance across the in-vitro BBB was estimated on the basis of their physicochemical properties. The detection limit was 30 nmol/l for TREO and 10 nmol/l for TMZ. Drug transport was measured in two directions: influx, apical-to-basolateral (A-to-B), and efflux, basolateral-to-apical (B-to-A). For TREO, the A-to-B permeability was lower (1.6%) than the B-to-A permeability (3.0%). This was in contrast to TMZ, which had higher A-to-B (13.1%) than B-to-A (7.2%) permeability values. The in-vitro BBB model applied simulated the human BBB properly for TMZ. It is, therefore, reasonable to assume that the values for TREO are also meaningful. Considering the lack of noninvasive, significant alternative methods to study transport across the BBB, the porcine brain capillary endothelial cell model was efficient to collect first data for TREO that explain the disappointing clinical results for this drug against cerebral tumors.

Opioids, agonists of µ-opioid receptors (µORs), are the strongest pain killers clinically available. Their action includes a strong central component, which also causes important adverse effects. However, µORs are also found on the peripheral endings of nociceptors and their activation there produces meaningful analgesia. The cellular mechanisms downstream of peripheral µORs are not well understood. Here, we show in neurons of murine dorsal root ganglia that pro-nociceptive TRPM3 channels, present in the peripheral parts of nociceptors, are strongly inhibited by µOR activation, much more than other TRP channels in the same compartment, like TRPV1 and TRPA1. Inhibition of TRPM3 channels occurs via a short signaling cascade involving Gβγ proteins, which form a complex with TRPM3. Accordingly, activation of peripheral µORs in vivo strongly attenuates TRPM3-dependent pain. Our data establish TRPM3 inhibition as important consequence of peripheral µOR activation indicating that pharmacologically antagonizing TRPM3 may be a useful analgesic strategy., eLife digest There are very few treatments available for people suffering from strong or long-lasting pain. Currently, substances called opioids – which include the well-known drug morphine – are the strongest painkillers. However, these drugs also cause harmful side effects, which makes them less useful. Like all drugs, opioids mediate their effects by interacting with molecules in the body. In the case of opioids, these interacting molecules belong to a group of receptor proteins called G-protein coupled receptors (or GPCRs for short). These opioid receptors are widely distributed in the nerve cells and brain regions that detect and transmit pain signals. It was poorly understood how activation of opioid receptors reduces the activity of pain-sensing nerve cells, however several lines of evidence had suggested that a protein called TRPM3 might be involved. TRPM3 is a channel protein that allows sodium and calcium ions to enter into nerve cells by forming pores in cell membranes, and mice that lack this protein are less sensitive to certain kinds of pain. Dembla, Behrendt et al. now show that activating opioid receptors on nerve cells from mice, with morphine and a similar substance, rapidly reduces the flow of calcium ions through TRPM3 channels. Further experiments confirmed that activating opioid receptors in a mouse’s paw also reduced the pain caused when TRPM3 proteins are activated. GPCRs interact with a group of small proteins called G-proteins that, when activated by the receptor, split into two subunits. Based on studies with human kidney cells, Dembla, Behrendt et al. found the so-called G-beta-gamma subunit then carries the signal from the opioid receptor to TRPM3. Two independent studies by Quallo et al. and Badheka, Yudin et al. also report similar findings. These new findings show that drugs already used in the treatment of pain can indirectly alter how TRPM3 works in a dramatic way. These results might help scientists to find drugs that work in a more direct way to dial down the activity of TRPM3 and to combat pain with fewer side effects. Though first it will be important to confirm these new findings in human nerve cells.

The overall objective of this study was to develop a HDL-based multifunctional platform for transport and delivery of highly hydrophobic gold nanoparticles (AuNP) bearing photothermic properties across the blood brain barrier (BBB). We exploited the ability of apolipoprotein E3 (apoE3) to act as a high affinity ligand for the low-density lipoprotein receptor to gain entry into endothelial and glioblastoma cells. The issue of poor aqueous solubility of AuNP of varying diameters (3, 10, or 10 nm) was overcome by integrating them with phospholipids and apoE3, yielding reconstituted rHDL bearing AuNP (rHDL-AuNP). Transmission electron microscopy (TEM) revealed the presence of AuNP embedded in spherical particles. Incubation of human brain microvasculature endothelial cells or glioblastoma cells with rHDL-AuNP bearing unlabeled or FITC-labeled apoE3 revealed robust uptake of particles that were localized in endocytic/lysosomal vesicles. The transport of rHDL-AuNP across an in vitro BBB model developed from primary porcine endothelial cells was examined. The addition of rHDL-AuNP to the luminal side of the cells did not affect the integrity of the BBB as assessed by the localization of key tight junction markers such as occludin, claudins and ZO-1 by immunofluorescence, and, by continual measurement of the transepithelial electrical resistance by impedance spectroscopy under physiological conditions. Lastly, the appearance of fluorescein fluorescence and AuNP in the abluminal side suggested transport of rHDL-AuNP across the neurovascular junction. These findings demonstrate that rHDL bearing apoE3 acts as a detergent in solubilizing and dramatically improving the aqueous solubility of AuNP, facilitates cellular uptake and transcellular transport of rHDL-AuNP across endothelial cells. They are significant since they present rHDL bearing apoE3 as an effective platform for delivering AuNP across the BBB.

Elevated amyloid-β42 (Aβ42) in the brain is expected to cause Alzheimer’s Disease (AD). Reducing Aβ42 is therefore a cornerstone in causal drug development. Nevertheless, many promising substances failed in clinical trials, because reaching the target organ in vivo is difficult. The brain is protected by the Blood-Brain Barrier (BBB) that shields off most molecules to maintain the brain homeostasis. Brain-targeted nanoparticles are one successful tool to bypass this problem: by acting as Trojan horses they carry embedded drugs across the BBB for brain disorder treatment. Here, flurbiprofen, a γ-secretase modulator, was embedded in Poly(Lactic Acid) (PLA) nanoparticles. We tested if the drug-loaded nanoparticles affected the integrity of our advanced in vitro BBB model in transendothelial electrical resistance measurements and permeability assays, and investigated the nanoparticle-cell interaction in flow cytometry and confocal laser scanning microscopy. Furthermore, we assessed the drug transport capacity by highperformance liquid chromatography and the biological efficacy of the embedded drug in an Aβ42-detecing ELISA. We also verified the viability of the AD model cells by a cellular viability assay. After adding flurbiprofen-loaded nanoparticles to the blood compartment of a Transwell® model, the drug was detectable in the brain compartment, where it induced an Aβ42 lowering effect. Flurbiprofen from nanoparticles crossed the BBB without impairing barrier integrity, whereas the free drug was highly cytotoxic and destroyed the barrier. Ligand coupling of apolipoprotein E3 to the nanoparticles increased cellular uptake. Hence, we expect an even more pronounced Aβ42 reducing effect for apolipoprotein-modified, flurbiprofen-loaded nanoparticles. In conclusion, we enabled transport of a hardly permeable drug across an advanced in vitro BBB model, opening opportunities in the treatment and prevention of AD and other brain disorders. Using a primary porcine BBB model that displays excellent barrier characteristics, we show that flurbiprofen-loaded nanoparticles reduce Aβ42 burden without impairing barrier function.

Summary Transient receptor potential melastatin-3 (TRPM3) is a broadly expressed Ca 2+ -permeable nonselective cation channel. Previous work has demonstrated robust activation of TRPM3 by the neuroactive steroid pregnenolone sulfate (PS), but its in vivo gating mechanisms and functions remained poorly understood. Here, we provide evidence that TRPM3 functions as a chemo- and thermosensor in the somatosensory system. TRPM3 is molecularly and functionally expressed in a large subset of small-diameter sensory neurons from dorsal root and trigeminal ganglia, and mediates the aversive and nocifensive behavioral responses to PS. Moreover, we demonstrate that TRPM3 is steeply activated by heating and underlies heat sensitivity in a subset of sensory neurons. TRPM3-deficient mice exhibited clear deficits in their avoidance responses to noxious heat and in the development of inflammatory heat hyperalgesia. These experiments reveal an unanticipated role for TRPM3 as a thermosensitive nociceptor channel implicated in the detection of noxious heat.