ARHGEF10 knockout inhibits platelet aggregation and protects mice from thrombus formation.

Essentials ARHGEF10 single-nucleotide polymorphism provides risk of ischemic and atherothrombotic stroke. The role of ARHGEF10 in platelet function was examined using ARHGEF10 knockout mice. ARHGEF10 deficiency inhibits platelet function and arterial thrombus formation. ARHGEF10 knockout protects mice from stroke-induced infarction. SUMMARY: Background ARHGEF10, a member of the Rho guanine nucleotide exchange factor (GEF) family, stimulates Rho GTPases. Rho GTPases have been reported to regulate a variety of cellular behaviors, such as cell polarity, cytoskeletal organization, and gene transcription. ARHGEF10 single-nucleotide polymorphisms are linked to the risk of ischemic stroke. However, the role of ARHGEF10 in platelet function remains unknown. Objective To examine the role of ARHGEF10 in platelet function. Methods ARHGEF10-/- were generated. We examined the in vitro and in vivo effects of ARHGEF10 knockout on platelet function and arterial thrombosis formation. Results ARHGEF10-/- mice had normal platelet counts, but showed altered aggregation in response to thrombin, collagen, ADP, protease-activated receptor-4 peptide, and U46619 stimulation. ARHGEF10 knockout influenced platelet spreading on fibrinogen-coated surfaces, and caused the platelets to show less lamellipodia-like extension than wild-type platelets. ARHGEF10 knockout also inhibited platelet clot retraction induced by thrombin stimulation. ARHGEF10 knockout resulted in prolonged tail bleeding time and inhibited the stable thrombus formation induced by FeCl3 in the carotid artery. Conclusions ARHGEF10 serves as an important regulator in platelet shape change, spreading, and aggregation. Moreover, ARHGEF10 also plays an important role in arterial thrombosis formation.

Leukemia inhibitory factor (LIF) potentiates antinociception activity and inhibits tolerance induction of opioids.

BACKGROUND: The efficacy of opioids typically decreases after long-term use owing to the development of tolerance. Glial activation and the upregulation of proinflammatory cytokines are related to the induction of tolerance. We investigated the effect of leukemia inhibitory factor (LIF) on morphine analgesia and tolerance. METHODS: LIF concentrations in rat spinal cords were measured by polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) after morphine administration. LIF distribution was examined using confocal microscopy. To evaluate the effects of LIF on morphine analgesia and tolerance, LIF was intrathecally administered 30 min before morphine injection. The analgesic effect of morphine was evaluated by measuring tail-flick latency. Human LIF concentrations from the cerebrospinal fluid (CSF) of opioid tolerant patients were also determined by specific ELISA. RESULTS: Chronic morphine administration upregulated LIF concentrations in rat spinal cords. Intrathecal injection of LIF potentiated the analgesic action of morphine. Patch clamp recording of spinal cord slices showed that LIF enhanced DAMGO ([D-Ala2, N-MePhe4, Gly-ol]-enkephalin)-induced outward potassium current. The development of tolerance was markedly suppressed by exogenous LIF, whereas neutralizing the endogenously released LIF with anti-LIF antibodies accelerated the tolerance induction. Moreover, LIF concentrations in the CSF of opioid-tolerant patients were higher than those in the opioid-naive controls. CONCLUSIONS: Intrathecal administration of LIF potentiated morphine antinociceptive activity and attenuated the development of morphine tolerance. Upregulation of endogenously released LIF by long-term use of opioids might counterbalance the tolerance induction effects of other proinflammatory cytokines. LIF might be a novel drug candidate for inhibiting opioid tolerance induction.