Neuronal injury resulting from mechanical deformation is poorly characterized at the cellular level. The immediate structural consequences of the mechanical loading lead to a variety of inter-and intra-cellular signaling events that interact on multiple time and length scales. Thus, it is often difficult to establish cause-and-effect relationships such that appropriate treatment strategies can be devised. In this report, we showed that treating mechanically injured neuronal cells with an agent that promotes the resealing of disrupted plasma membranes rescues them from death at 24 h post-injury. A new in vitro model was developed to allow uniform mechanical loading conditions with precisely controlled magnitude and onset rate of loading. Injury severity increased monotonically with increasing peak shear stress and was strongly dependent on the rate of loading as assessed with the MTT cell viability assay, 24 h post-injury. Mechanical injury produced an immediate disruption of membrane integrity as indicated by a rapid and transient release of LDH. For the most severe injury, cell viability decreased approximately 40% with mechanical trauma compared to sham controls. Treatment of cells with Poloxamer 188 at 15 min post-injury restored long-term viability to control values. These data establish membrane integrity as a novel therapeutic target in the treatment of neuronal injury.

The mechanisms of cell death and the progressive degeneration of neural tissue following traumatic brain injury (TBI) have come under intense investigation. However, the complex interactions among the evolving pathologies in multiple cell types obscure the causal relationships between the initial effects of the mechanical trauma at the cellular level and the long-term dysfunction and neuronal death. We used an in vitro model of neuronal injury to study the mechanisms of cell death in response to a well-defined mechanical insult and found that the majority of dead cells were apoptotic. We have previously reported that promotion of membrane repair acutely with the non-ionic surfactant poloxamer 188 (P188) restored cell viability to control values at 24 h postinjury. Here, we showed that P188 significantly inhibits apoptosis and prevents necrosis. We also examined the role of mitogen-activated protein kinases (MAPKs) in cell death. There was a rapid, transient activation of extracellular signal-regulated kinases, c-Jun N-terminal kinase, and p38s after mechanical insult. Of these, activation of the proapoptotic p38 was the greatest. Treatment with P188 inhibited p38 activation; however, direct inhibition of p38 by SB203580, which selectively inhibits the activity of the p38 MAPK, provided only partial inhibition of apoptosis and had no effect on necrosis. These data suggest that multiple signaling pathways may be involved in the long-term response of neurons to mechanical injury. Furthermore, that the membrane resealing action of P188 provides such significant protection from both necrosis and apoptosis suggests that acute membrane damage due to trauma is a critical precipitating event that is upstream of the many signaling cascades contributing to the subsequent pathology.

To examine the time course and relative extent of proteolysis of neurofilament and tubulin proteins after traumatic axonal injury (TAI), anesthetized mice were subjected to optic nerve stretch injury. Immunohistochemistry confirmed neurofilament accumulation within axonal swellings at 4, 24, and 72 h postinjury (n = 4 injured and 2 sham per time point). Immunoblotting of optic nerve homogenates (n = 5 injured and 1 sham at 0.5, 4, 24 or 72 h) revealed calpain-mediated spectrin proteolytic fragments after injury. Protein levels for NF68 progressively decreased from 0.5 h to 24 h postinjury, while NF200 and alpha-tubulin levels decreased acutely (0.5-4 h), with a secondary decline at 72 h postinjury. These data demonstrate that diffusely distributed TAI is associated not only with a localized accumulation of neurofilament proteins, but also significant decreases in total cytoskeletal protein levels which may be mediated, in part, by calpains. Protection of the axonal cytoskeleton represents a potential therapeutic target for axonal damage associated with injury or neurodegenerative diseases.

Increases in cytosolic calcium ([Ca 2+ ] i ) following mechanical injury are often considered a major contributing factor to the cellular sequelae in traumatic brain injury (TBI). However, very little is known on how developmental changes may affect the calcium signaling in mechanically injured neurons. One key feature in the developing brain that may directly impact its sensitivity to stretch is the reduced inhibition which results in spontaneous [Ca 2+ ] i oscillations. In this study, we examined the mechanism of stretch-induced ] i response to stretch is initiated, and how reduced inhibition -a feature of the developing brain -may affect the sensitivity of the immature brain to trauma.

3003 Background: ECHO-204 is an ongoing, open-label, phase 1/2 (P1/2) study of epacadostat (E; potent and selective oral inhibitor of the immunosuppressive enzyme indoleamine 2,3-dioxygenase 1) plus PD-1 inhibitor nivolumab (N) in patients (pts) with advanced cancers (NSCLC, MEL, OVC, CRC, SCCHN, B-cell NHL [including DLBCL], GBM). Preliminary P1/2 safety and tolerability outcomes for the overall study population and P2 response for select tumor types (SCCHN, MEL, OVC, CRC) are reported. Methods: In P1 dose escalation, pts received E (25, 50, 100, 300 mg BID) + N (3 mg/kg Q2W); in P2 cohort expansion, pts received E (100 or 300 mg BID) + N (240 mg Q2W). Safety/tolerability was assessed in pts receiving ≥1 E + N dose. Response was assessed in RECIST v1.1 evaluable pts; for recently enrolled pt subgroups, only preliminary DCR (CR+PR+SD) is presented. Results: As of 29OCT2016,241 pts (P1, n = 36; P2, n = 205) were enrolled. No DLT was observed in P1. Most common TRAEs (≥15%) in pts treated with E 100 mg (n = 70) and E 300 mg (n = 135) were rash (33% and 22%, respectively), fatigue (26% and 31%), and nausea (24% and 19%). Rash was the most common grade ≥3 TRAE in E 100 mg and E 300 mg subgroups (10% and 12%). TRAEs led to discontinuation in 7% (E 100 mg) and 13% (E 300 mg) of pts. There were no TR-deaths. For the 23 recently enrolled, efficacy-evaluable SCCHN pts treated with E 300 mg, preliminary DCR was 70% (n = 16). Of 30 MEL pts, 8 were treated with E 100 mg and 22 were more recently enrolled and treated with E 300 mg. ORR (CR+PR) and DCR in MEL pts treated with E 100 mg were 75% (n = 6; all PR) and 100% (n = 8; 2 SD), respectively. Preliminary DCR in MEL pts treated with E 300 mg was 64% (n = 14). Of 29 OVC pts, 18 were treated with E 100 mg and 11 with E 300 mg.ORR and DCR for OVC pts treated with E 100 mg were 11% (n = 2; 2 PR) and 28% (n = 5; 3 SD); for 11 OVC pts treated with E 300 mg, ORR and DCR were 18% (n = 2; 2 PR) and 36% (n = 4; 2 SD).For 25 CRC pts (all E 100 mg), ORR and DCR were 4% (n = 1; PR) and 24% (n = 6; 5 SD).Safety/efficacy evaluations are ongoing for all cohorts. Conclusions: E + N was generally well tolerated up to the maximum E 300-mg dose. P2 ORR/DCR outcomes are promising, particularly in SCCHN and MEL pts. Updated data will be presented at the meeting. Clinical trial information: NCT02327078.