In this study, we present a strategy for the synthesis of catecholamine functionalised gold nanoparticles and investigated their multivalent interactions with adrenergic receptors in different biological systems. The catecholamines adrenaline...

Gold nanoparticles have a high potential to be a treatment of diseases by their specific drug delivery properties and multivalent receptor stimulation. For the present project, spherical gold nanoparticles were synthesized and functionalized with the muscarinic receptor antagonist atropine (Au-MUDA-AT NPs). The diameter of the gold core could precisely be controlled by using different synthetic methods and reducing agents resulting in functionalized gold nanoparticles with diameters ranging from 8 to 16 nm. The ability to interact with intestinal muscarinic receptors is size-dependent. When using intestinal chloride secretion induced by the stable acetylcholine derivative, carbachol, as read-out, the strongest inhibition, i.e. the most efficient blockade of muscarinic receptors, was observed with 13 nm sized Au-MUDA-AT NPs. Functional experiments indicate that Au-MUDA-AT NPs with a diameter of 14 nm are able to pass the intestinal mucosa in a time-dependent manner after administration to the intestinal lumen. For example, luminally administered Au-MUDA-AT NPs inhibited contractions of the small intestinal longitudinal muscle layer induced by electrical stimulation of myenteric neurons. A similar inhibition of basolateral epithelial receptors was observed after luminal administration of Au-MUDA-AT NPs when using carbachol-induced chloride secretion across the intestinal epithelium as a test system. Thus, Au-MUDA-AT NPs might be a therapeutic tool for the modulation of intestinal secretion and motility after oral application in the future.

Inflammatory processes within the peripheral nervous system (PNS) are associated with symptoms of hyperalgesia and allodynia. Pro-inflammatory mediators, such as cytokines or prostaglandins, modulate the excitability of nociceptive neurons, called peripheral sensitization. Here, we aimed to examine if previously reported effects of in vitro stimulation with lipopolysaccharide (LPS) on primary cell cultures of dorsal root ganglia (DRG) reflect changes in a model of LPS-induced systemic inflammation in vivo. Male rats were intraperitoneally injected with LPS (100 µg/kg) or saline. Effects of systemic inflammation on expression of inflammatory mediators, neuronal Ca2+ responses, and activation of inflammatory transcription factors in DRG were assessed. Systemic inflammation was accompanied by an enhanced expression of pro-inflammatory cytokines and cyclooxygenase-2 in lumbar DRG. In DRG primary cultures obtained from LPS-treated rats enhanced neuronal capsaicin-responses were detectable. Moreover, we found an increased activation of inflammatory transcription factors in cultured macrophages and neurons after an in vivo LPS challenge compared to saline controls. Overall, our study emphasizes the role of inflammatory processes in the PNS that may be involved in sickness-behavior-associated hyperalgesia induced by systemic LPS treatment. Moreover, we present DRG primary cultures as tools to study inflammatory processes on a cellular level, not only in vitro but also ex vivo.

Background and purpose: ATP plays an important role as an extracellular messenger acting via different types of purinoceptors. Whereas most of the actions of ATP at intestinal epithelia are thought to be mediated by metabotropic P2Y receptors, the role of ionotropic P2X receptors remains unclear. Consequently, we investigated the role of P2X4 and P2X7 receptors on ion transport across rat colonic epithelia by using BzATP, a potent agonist at P2X7 (and weak agonist at P2X4).Experimental approach: Ussing chamber and Ca 2+ imaging experiments were performed on rat colonic epithelia, combined with P2X receptor expression studies.Key results: Ussing chamber experiments revealed that serosal BzATP induced a neuronally mediated increase in short-circuit current caused by Cl À secretion. In contrast, the effect of mucosal BzATP was smaller, insensitive to tetrodotoxin and Cl À -independent. When epithelia were basolaterally depolarized to measure currents across the apical membrane, BzATP stimulated a cation current consistent with the activation of apical nonselective cation channels. Experiments with isolated colonic crypts revealed a BzATP-induced increase in the cytosolic Ca 2+ concentration. Sensitivity to antagonists indicates stimulation of P2X4 and P2X7 receptors by serosal BzATP and of P2X7 receptors by mucosal BzATP. A similar pattern was observed with native ATP, which induced larger transepithelial currents in comparison to BzATP. RT-PCR and immunohistochemistry experiments confirmed the expression of P2X4 and P2X7 receptors in the colon localized in the epithelium and in submucosal ganglia. Conclusions and implications: Epithelial and neuronal ionotropic P2X receptors are involved in the regulation of intestinal ion transport.