Lysophosphatidic acid LPA1 and LPA3 receptors play roles in the maintenance of late tissue plasminogen activator-induced central poststroke pain in mice

We developed a mouse model for central post-stroke pain (CPSP), a centrally-originated neuropathic pain (NeuP). In this mode, mice were first injected with Rose Bengal, followed by photo-irradiation of left middlecerebral artery (MCA) to generate thrombosis. Although the MCA thrombosis was soon dissolved, the reducedblood flow remained for more than 24 h due to subsequent occlusion of microvessels. This photochemicallyinduced thrombosis (PIT) model showed a hypersensitivity to the electrical stimulation of both sides of paw, butdid not show any abnormal pain in popular thermal or mechanical nociception tests. When tissue-type plas-minogen activator (tPA) was injected 6h after the PIT stress, tPA-dependent hypersensitivity to the electricalpaw stimulation and stable thermal and mechanical hyperalgesia on both sides for more than 17 or 18 days afterthe PIT treatment. These hyperalgesic effects were abolished in lysophosphatidic acid receptor 1 (LPA1)- andlysophosphatidic acid receptor 3 (LPA3)-deficient mice. When Ki-16425, an LPA1and LPA3antagonist wastreated twice daily for 6days consecutively, the thermal and mechanical hyperalgesia at day 17 and 18 weresignificantly reversed. The liquid chromatography?mass spectrometry (LC?MS/MS) analysis revealed that thereis a significant increase in several species of LPA molecules in somatosensory S-I and medial dorsal thalamus (MD), but not in striatum or ventroposterior thalamus. All these results suggest that LPA1and LPA3signalingplay key roles in the development and maintenance of CPSP

Morphologically homogeneous red blood cells present a heterogeneous response to hormonal stimulation

Red blood cells (RBCs) are among the most intensively studied cells in natural history, elucidating numerous principles and ground-breaking knowledge in cell biology. Morphologically, RBCs are largely homogeneous, and most of the functional studies have been performed on large populations of cells, masking putative cellular variations. We studied human and mouse RBCs by live-cell video imaging, which allowed single cells to be followed over time. In particular we analysed functional responses to hormonal stimulation with lysophosphatidic acid (LPA), a signalling molecule occurring in blood plasma, with the Ca(2+) sensor Fluo-4. Additionally, we developed an approach for analysing the Ca(2+) responses of RBCs that allowed the quantitative characterization of single-cell signals. In RBCs, the LPA-induced Ca(2+) influx showed substantial diversity in both kinetics and amplitude. Also the age-classification was determined for each particular RBC and consecutively analysed. While reticulocytes lack a Ca(2+) response to LPA stimulation, old RBCs approaching clearance generated robust LPA-induced signals, which still displayed broad heterogeneity. Observing phospatidylserine exposure as an effector mechanism of intracellular Ca(2+) revealed an even increased heterogeneity of RBC responses. The functional diversity of RBCs needs to be taken into account in future studies, which will increasingly require single-cell analysis approaches. The identified heterogeneity in RBC responses is important for the basic understanding of RBC signalling and their contribution to numerous diseases, especially with respect to Ca(2+) influx and the associated pro-thrombotic activity