TRPM3 Is a Nociceptor Channel Involved in the Detection of Noxious Heat

SummaryTransient receptor potential melastatin-3 (TRPM3) is a broadly expressed Ca2+-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

Nanopartikel für neurodegenerative Erkrankungen : Transport eines potentiellen Medikaments gegen die Alzheimer Krankheit über ein in vitro Bluthirnschranken-Modell

The blood-brain barrier (BBB) rigorously shields off the central nervous system from the periphery thereby protecting the fragile brain homeostasis. Yet, it also causes many potentially effective brain drugs to fail in vivo - not because of a lack of potency, but for they cannot enter the brain parenchyma. Nanoparticles enable brain drug delivery by acting as Trojan Horses, masking the original physicochemical properties of a drug and allowing targeted transport to biostructures, thereby enlarging the pool of brain drug candidates, such as potential anti-Alzheimer’s disease (AD) drugs. Flurbiprofen (FBP) is a non-steroidal anti-inflammatory drug (NSAID) that lowers amyloid beta (Aβ) and AD prevalence in high dose long-term treatment. Still, an FBP enantiomer failed in clinical trials with AD patients, likely for its poor brain penetrating capacity. This study revisits FBP as an anti-AD drug by packing the drug into poly(lactic acid) nanoparticles (PLA-FBP NP). PLA-FBP NP crossed an advanced in vitro BBB model (consisting of primary porcine brain capillary endothelial cells (pBCEC) on Transwell® inserts to allow a blood and a brain compartment separation). Also, PLA-FBP NP reduced Aβ42 burden (generated by AD model cells) in the brain compartment – notably without destroying barrier integrity. These promising in vitro findings highlight the potential of nanotechnology-based approaches as a chance in BBB crossing for the prevention and treatment of neurodegenerative disorders.Die Blut-Hirn-Schranke (BHS) trennt Peripherie und Zentralnervensystem voneinander um die fragile Hirn-Homöostase zu schützen. Allerdings scheitern daher viele potentiell effektive Neurotherapeutika in vivo – sie können die BHS oft nicht überschreiten. Nanopartikel können den Transport ins Gehirn vermitteln indem sie als Trojanische Pferde die physikochemischen Eigenschaften der Substanzen maskieren und einen zielgerichteten Transport erlauben. Dies vergrößert die Anzahl potentieller Neuropharmaka, z.B. gegen die Alzheimer Krankheit (AD). Flurbiprofen (FBP) gehört zu den nichtsteroidalen Antirheumatika, die Amyloid beta (Aβ) und die AD-Prävalenz bei hoch dosierter Langzeitgabe verringern können. Dennoch verliefen klinische Studien mit AD Patienten enttäuschend, wahrscheinlich, weil FBP die BHS nur schlecht passiert. Diese Arbeit greift FBP wieder auf, indem die Substanz in Polymilchsäure-Nanopartikel (PLA-FBP NP) verpackt wird. PLA-FBP NP konnten ein in vitro BHS Modell (basierend auf primären porzinen Hirnkapillarendothel-Zellen (pBCEC) auf Transwell® Einsätzen zur Teilung in Blut- und Hirn-Kompartiment) überwinden. Darüber hinaus konnten die Nanopartikel Aβ42 im Hirn-Kompartiment (produziert von AD Modell-Zellen) reduzieren – ohne dabei die Barriere-Integrität zu zerstören. Diese vielversprechenden in vitro Daten unterstreichen das Potenzial Nanotechnologie-basierter Ansätze zur Überwindung der BHS für die Therapien und Prävention neurodegenerativer Erkrankungen

Transport of treosulfan and temozolomide across an in-vitro blood–brain barrier model

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

Tracking of magnetite labeled nanoparticles in the rat brain using MRI

This study was performed to explore the feasibility of tracing nanoparticles for drug transport in the healthy rat brain with a clinical MRI scanner. Phantom studies were performed to assess the R-1 (= 1/T-1) relaxivity of different magnetically labeled nanoparticle (MLNP) formulations that were based on biodegradable human serum albumin and that were labeled with magnetite of different size. In vivo MRI measurements in 26 rats were done at 3T to study the effect and dynamics of MLNP uptake in the rat brain and body. In the brain, MLNPs induced T-1 changes were quantitatively assessed by T-1 relaxation time mapping in vivo and compared to post-mortem results from fluorescence imaging. Following intravenous injection of MLNPs, a visible MLNP uptake was seen in the liver and spleen while no visual effect was seen in the brain. However a histogram analysis of T-1 changes in the brain demonstrated global and diffuse presence of MLNPs. The magnitude of these T-1 changes scaled with post-mortem fluorescence intensity. This study demonstrates the feasibility of tracking even small amounts of magnetite labeled NPs with a sensitive histogram technique in the brain of a living rodent

Uptake of MLNPs in the rat body.

<p>Two coronal MRI slices through the rat body are shown. Following MLNP injection, a significant and long lasting signal increase (arrows) was mostly observed in the liver L (row <b>A</b>) and in the spleen S (row <b>B</b>).</p

MLNP uptake corresponded to significant T₁ shortening and an increase in fluorescence signal intensity.

<p>GM T₁ values in rats treated with MLNPs were significantly decreased in comparison with control group after 26 minutes (<b>A</b>) and after 39 minutes (<b>B</b>). (<b>C</b>) The fluorescence signal in the hippocampus (HC) was significantly increased in the red channel after MLNP administration when compared to the control group (saline solution instead of MLNPs). * p<0.05; ** p<0.01.</p

Relationship between MLNP induced T₁ changes in white matter (WM) and gray matter (GM) and fluorescence signal in the red channel.

<p>The Pearson correlation coefficient is shown (* p<0.05; ** p<0.01). The subscripts 1 and 2 correspond to the post injection delay of 26 and 39 min, respectively.</p

T₁ histogram (dotted line) of a rat brain.

<p>Triple Gaussian fitting allowed for separation of white matter (circles), gray matter (diamonds) and cerebrospinal fluid (squares).</p