Thrombomodulin Alfa for Acute Exacerbation of Idiopathic Pulmonary Fibrosis. A Randomized, Double-Blind Placebo-controlled Trial.

Rationale: Acute exacerbation during the course of idiopathic pulmonary fibrosis causes a poor prognosis. Coagulation abnormalities and endothelial damage are involved in its pathogenesis. Thrombomodulin alfa, a recombinant human soluble thrombomodulin, has anticoagulant and antiinflammatory effects. Several clinical studies have shown that thrombomodulin alfa may improve survival of acute exacerbation.Objectives: To determine the efficacy and safety of thrombomodulin alfa compared with placebo in acute exacerbation of idiopathic pulmonary fibrosis.Methods: This randomized, double-blind placebo-controlled phase 3 study conducted at 27 sites in Japan involved patients with an acute exacerbation of idiopathic pulmonary fibrosis. Subjects were randomized 1:1 to receive placebo or thrombomodulin alfa (380 U/kg/d for 14 d by intravenous drip infusion). All subjects were treated with high-dose corticosteroid therapy. The primary endpoint was the survival proportion on Day 90.Measurements and Main Results: Of the 82 randomized subjects, 77 completed the study and were included in the full analysis set (thrombomodulin alfa, n = 40; placebo, n = 37). The survival proportions on Day 90 were 72.5% (29 of 40) in the thrombomodulin alfa group and 89.2% (33 of 37) in the placebo group, a difference of -16.7 percentage points (95% confidence interval, -33.8 to 0.4%; P = 0.0863). In the safety population (n = 80), bleeding adverse events occurred in the thrombomodulin alfa group (10 of 42; 23.8%) and the placebo group (4 of 38; 10.5%).Conclusions: Thrombomodulin alfa did not improve the 90-day survival proportion. The present results suggest that the use of thrombomodulin alfa for the treatment of acute exacerbation of idiopathic pulmonary fibrosis not be recommended.Clinical trial registered with www.clinicaltrials.gov (NCT02739165).

Rab35, acting through ACAP2 switching off Arf6, negatively regulates oligodendrocyte differentiation and myelination.

Oligodendrocyte precursor cells differentiate to produce myelin sheaths that insulate axons to ensure fast propagation of action potentials. Many aspects of differentiation are regulated by multiple extracellular signals. However, their intracellular signalings remain elusive. We show that Rab35 and its effector, ACAP2, a GTPase-activating protein that switches off Arf6 activity, negatively regulate oligodendrocyte morphological differentiation. Knockdown of Rab35 or ACAP2 with their respective small interfering RNAs promotes differentiation. As differentiation initiates, the activities of Rab35 and ACAP2 are down-regulated. The activity of Arf6, in contrast, is up-regulated. Arf6 knockdown inhibits differentiation, indicating that Rab35 and ACAP2 negatively regulate differentiation by down-regulating Arf6. Importantly, as differentiation proceeds, the activity of cytohesin-2, a guanine nucleotide exchange factor that switches on Arf6 activity, is up-regulated. Pharmacological inhibition of cytohesin-2 inhibits differentiation, suggesting that cytohesin-2 promotes differentiation by activating Arf6. Furthermore, using oligodendrocyte-neuronal cocultures, we find that knockdown of Rab35 or ACAP2 promotes myelination, whereas inhibition of cytohesin-2 or knockdown of Arf6 inhibits myelination. Thus Rab35/ACAP2 and cytohesin-2 antagonistically control oligodendrocyte differentiation and myelination through Arf6 regulation, presenting a unique small GTPase on/off switching mechanism.

Akt and PP2A reciprocally regulate the guanine nucleotide exchange factor Dock6 to control axon growth of sensory neurons.

During neuronal development, axons navigate long distances, eventually forming precise connections with such targets as peripheral tissues. Dock6 is a guanine nucleotide exchange factor (GEF) that activates the Rho family guanosine triphosphatases Rac1 and Cdc42 to regulate the actin cytoskeleton. We found that phosphorylation of Ser(1194) in Dock6 inhibited its GEF activity and suppressed axonal growth of embryonic sensory neurons and axon regeneration of postnatal sensory neurons in vitro and in vivo. At early developmental stages, when axons are growing, the protein phosphatase PP2A interacted with and dephosphorylated Dock6, thereby increasing the activity of Dock6. At later developmental stages, the abundance of the kinase Akt increased, resulting in the binding of Akt to Dock6 and the phosphorylation of Dock6 at Ser(1194). In dorsal root ganglion neurons from mice lacking Dock6, reintroduction of Dock6 with a nonphosphorylatable S1194A mutation rescued axon extension but not branch number, whereas reintroduction of Dock6 with a phosphomimetic S1194E mutation resulted in premature branching. Thus, the phosphorylation status of Dock6 at Ser(1194) determines whether it promotes axon extension or branching in sensory neurons, revealing interplay between kinase and phosphatase action on a Rho-GEF during axon growth.

Paxillin is the target of c-Jun N-terminal kinase in Schwann cells and regulates migration.

During development of the peripheral nervous system (PNS), Schwann cells migrate along axons, wrapping individual axons to form a myelin sheath. This process is all mediated by the intercellular signaling between neurons and Schwann cells. As yet, little is known about the intracellular signaling mechanisms controlling these morphological changes including Schwann cell migration. We previously showed that c-Jun N-terminal kinase (JNK) plays a key role in Schwann cell migration before the initiation of myelination. Here we show that JNK, acting through phosphorylation of the cytoskeletal protein paxillin, regulates Schwann cell migration and that it mediates dorsal root ganglion (DRG) neuronal conditioned medium (CM). Phosphorylation of paxillin at the Ser-178 position, the JNK phosphorylation site, is observed following stimulation with neuronal CM. Phosphorylation is also detected as a result of stimulation with each of growth factors contained in neuronal CM. Knockdown of paxillin with the specific small interfering RNA (siRNA) inhibits migration. The reintroduction of paxillin reverses siRNA-mediated inhibition of migration, whereas paxillin harboring the Ser-178-to-Ala mutation fails to reverse it. In addition, while JNK binds to the N-terminal region (called LD1), the deletion of LD1 blocks migration. Together, JNK binds and phosphorylates paxillin to regulate Schwann cell migration, illustrating that paxillin provides one of the convergent points of intracellular signaling pathways controlling Schwann cell migration.