Oligodendrocyte-selective deletion of the eIF2α kinase Perk/Eif2ak3 limits functional recovery after spinal cord injury.

After spinal cord injury (SCI), re-establishing cellular homeostasis is critical to optimize functional recovery. Central to that response is PERK signaling, which ultimately initiates a pro-apoptotic response if cellular homeostasis cannot be restored. Oligodendrocyte (OL) loss and white matter damage drive functional consequences and determine recovery potential after thoracic contusive SCI. We examined acute (<48 h post-SCI) and chronic (6 weeks post-SCI) effects of conditionally deleting Perk from OLs prior to SCI. While Perk transcript is expressed in many types of cells in the adult spinal cord, its levels are disproportionately high in OL lineage cells. Deletion of OL-Perk prior to SCI resulted in: (1) enhanced acute phosphorylation of eIF2α, a major PERK substrate and the critical mediator of the integrated stress response (ISR), (2) enhanced acute expression of the downstream ISR genes Atf4, Ddit3/Chop, and Tnfrsf10b/Dr5, (3) reduced acute OL lineage-specific Olig2 mRNA, but not neuronal or astrocytic mRNAs, (4) chronically decreased OL content in the spared white matter at the injury epicenter, (5) impaired hindlimb locomotor recovery, and (6) reduced chronic epicenter white matter sparing. Cultured primary OL precursor cells with reduced PERK expression and activated ER stress response showed: (1) unaffected phosphorylation of eIF2α, (2) enhanced ISR gene induction, and (3) increased cytotoxicity. Therefore, OL-Perk deficiency exacerbates ISR signaling and potentiates white matter damage after SCI. The latter effect is likely mediated by increased loss of Perk-/- OLs.

Limited changes in locomotor recovery and unaffected white matter sparing after spinal cord contusion at different times of day.

The circadian gene expression rhythmicity drives diurnal oscillations of physiological processes that may determine the injury response. While outcomes of various acute injuries are affected by the time of day at which the original insult occurred, such influences on recovery after spinal cord injury (SCI) are unknown. We report that mice receiving moderate, T9 contusive SCI at ZT0 (zeitgeber time 0, time of lights on) and ZT12 (time of lights off) showed similar hindlimb function recovery in the Basso mouse scale (BMS) over a 6 week post-injury period. In an independent study, no significant differences in BMS were observed after SCI at ZT18 vs. ZT6. However, the ladder walking test revealed modestly improved performance for ZT18 vs. ZT6 mice at week 6 after injury. Consistent with those minor effects on functional recovery, terminal histological analysis revealed no significant differences in white matter sparing at the injury epicenter. Likewise, blood-spinal cord barrier disruption and neuroinflammation appeared similar when analyzed at 1 week post injury at ZT6 or ZT18. Therefore, locomotor recovery after thoracic contusive SCI is not substantively modulated by the time of day at which the neurotrauma occurred.

Improved locomotor recovery after contusive spinal cord injury in Bmal1-/- mice is associated with protection of the blood spinal cord barrier.

The transcription factor BMAL1/ARNTL is a non-redundant component of the clock pathway that regulates circadian oscillations of gene expression. Loss of BMAL1 perturbs organismal homeostasis and usually exacerbates pathological responses to many types of insults by enhancing oxidative stress and inflammation. Surprisingly, we observed improved locomotor recovery and spinal cord white matter sparing in Bmal1-/- mice after T9 contusive spinal cord injury (SCI). While acute loss of neurons and oligodendrocytes was unaffected, Bmal1 deficiency reduced the chronic loss of oligodendrocytes at the injury epicenter 6 weeks post SCI. At 3 days post-injury (dpi), decreased expression of genes associated with cell proliferation, neuroinflammation and disruption of the blood spinal cord barrier (BSCB) was also observed. Moreover, intraspinal extravasation of fibrinogen and immunoglobulins was decreased acutely at dpi 1 and subacutely at dpi 7. Subacute decrease of hemoglobin deposition was also observed. Finally, subacutely reduced levels of the leukocyte marker CD45 and even greater reduction of the pro-inflammatory macrophage receptor CD36 suggest not only lower numbers of those cells but also their reduced inflammatory potential. These data indicate that Bmal1 deficiency improves SCI outcome, in part by reducing BSCB disruption and hemorrhage decreasing cytotoxic neuroinflammation and attenuating the chronic loss of oligodendrocytes.

Following spinal cord injury, PDE4B drives an acute, local inflammatory response and a chronic, systemic response exacerbated by gut dysbiosis and endotoxemia.

Emerging evidence links changes in the gut microbiome and intestinal barrier function to alterations in CNS function. We examined the role of endotoxin-responsive, cAMP-specific, Pde4 subfamily b (Pde4b) enzyme in gut dysbiosis induced neuro-inflammation and white matter loss following spinal cord injury (SCI). Using a thoracic contusion model in C57Bl/6 wild type female mice, SCI led to significant shifts in the gut bacterial community including an increase in the phylum Proteobacteria, which consists of endotoxin-harboring, gram-negative bacteria. This was accompanied by increased systemic inflammatory marker, soluble CD14, along with markers of the endoplasmic reticulum stress response (ERSR) and inflammation in the SCI epicenter. Deletion of Pde4b reduced epicenter expression of markers for the ERSR and inflammation, at both acute and chronic time points post-SCI. Correspondingly, expression of oligodendrocyte mRNAs increased. Within the injury penumbra, inflammatory protein markers of activated astrocytes (GFAP), macrophage/microglia (CD11b, Iba1), and the proinflammatory mediator Cox2, were decreased in Pde4b-/- mice. The absence of Pde4b improved white matter sparing and recovery of hindlimb locomotion following injury. Importantly, SCI-induced gut dysbiosis, bacterial overgrowth and endotoxemia were also prevented in Pde4b-/- mice. Taken together, these findings indicate that PDE4B plays an important role in the development of acute and chronic inflammatory response and consequent recovery following SCI.

Phosphodiesterase 4b expression plays a major role in alcohol-induced neuro-inflammation.

It is increasingly evident that alcohol-induced, gut-mediated peripheral endotoxemia plays a significant role in glial cell activation and neuro-inflammation. Using a mouse model of chronic alcohol feeding, we examined the causal role of endotoxin- and cytokine-responsive Pde4 subfamily b (Pde4b) expression in alcohol-induced neuro-inflammation. Both pharmacologic and genetic approaches were used to determine the regulatory role of Pde4b. In C57Bl/6 wild type (WT) alcohol fed (WT-AF) animals, alcohol significantly induced peripheral endotoxemia and Pde4b expression in brain tissue, accompanied by a decrease in cAMP levels. Further, along with Pde4b, there was a robust activation of astrocytes and microglia accompanied by significant increases in the inflammatory cytokines (Tnfα, Il-1ß, Mcp-1 and Il-17) and the generalized inflammatory marker Cox-2. At the cellular level, alcohol and inflammatory mediators, particularly LPS, Tnfα and Hmgb1 significantly activated microglial cells (Iba-1 expression) and selectively induced Pde4b expression with a minimal to no change in Pde4a and d isoforms. In comparison, the alcohol-induced decrease in brain cAMP levels was completely inhibited in WT mice treated with the Pde4 specific pharmacologic inhibitor rolipram and in Pde4b-/- mice. Moreover, all the observed markers of alcohol-induced brain inflammation were markedly attenuated. Importantly, glial cell activation induced by systemic endotoxemia (LPS administration) was also markedly decreased in Pde4b-/- mice. Taken together, these findings strongly support the notion that Pde4b plays a critical role in coordinating alcohol-induced, peripheral endotoxemia mediated neuro-inflammation and could serve as a significant therapeutic target.

Does the preclinical evidence for functional remyelination following myelinating cell engraftment into the injured spinal cord support progression to clinical trials?

This article reviews all historical literature in which rodent-derived myelinating cells have been engrafted into the contused adult rodent spinal cord. From 2500 initial PubMed citations identified, human cells grafts, bone mesenchymal stem cells, olfactory ensheathing cells, non-myelinating cell grafts, and rodent grafts into hemisection or transection models were excluded, resulting in the 67 studies encompassed in this review. Forty five of those involved central nervous system (CNS)-derived cells, including neural stem progenitor cells (NSPCs), neural restricted precursor cells (NRPs) or oligodendrocyte precursor cells (OPCs), and 22 studies involved Schwann cells (SC). Of the NSPC/NPC/OPC grafts, there was no consistency with respect to the types of cells grafted and/or the additional growth factors or cells co-grafted. Enhanced functional recovery was reported in 31/45 studies, but only 20 of those had appropriate controls making conclusive interpretation of the remaining studies impossible. Of those 20, 19 were properly powered and utilized appropriate statistical analyses. Ten of those 19 studies reported the presence of graft-derived myelin, 3 reported evidence of endogenous remyelination or myelin sparing, and 2 reported both. For the SC grafts, 16/21 reported functional improvement, with 11 having appropriate cellular controls and 9/11 using proper statistical analyses. Of those 9, increased myelin was reported in 6 studies. The lack of consistency and replication among these preclinical studies are discussed with respect to the progression of myelinating cell transplantation therapies into the clinic.

CD36 deletion improves recovery from spinal cord injury.

CD36 is a pleiotropic receptor involved in several pathophysiological conditions, including cerebral ischemia, neurovascular dysfunction and atherosclerosis, and recent reports implicate its involvement in the endoplasmic reticulum stress response (ERSR). We hypothesized that CD36 signaling contributes to the inflammation and microvascular dysfunction following spinal cord injury. Following contusive injury, CD36(-/-) mice demonstrated improved hindlimb functional recovery and greater white matter sparing than CD36(+/+) mice. CD36(-/-) mice exhibited a reduced macrophage, but not neutrophil, infiltration into the injury epicenter. Fewer infiltrating macrophages were either apoptotic or positive for the ERSR marker, phospho-ATF4. CD36(-/-) mice also exhibited significant improvements in injury heterodomain vascularity and function. These microvessels accumulated less of the oxidized lipid product 4-hydroxy-trans-2-nonenal (4HNE) and exhibited a reduced ERSR, as detected by vascular phospho-ATF4, CHOP and CHAC-1 expression. In cultured primary endothelial cells, deletion of CD36 diminished 4HNE-induced phospho-ATF4 and CHOP expression. A reduction in phospho-eIF2α and subsequent increase in KDEL-positive, ER-localized proteins suggest that 4HNE-CD36 signaling facilitates the detection of misfolded proteins upstream of eIF2α phosphorylation, ultimately leading to CHOP-induced apoptosis. We conclude that CD36 deletion modestly, but significantly, improves functional recovery from spinal cord injury by enhancing vascular function and reducing macrophage infiltration. These phenotypes may, in part, stem from reduced ER stress-induced cell death within endothelial and macrophage cells following injury.

Deletion of endoplasmic reticulum stress-induced CHOP protects microvasculature post-spinal cord injury.

Trauma introduces damaging stressors that compromise protein, lipid, and nucleic acid integrity. Aggregates of unfolded and misfolded proteins in the endoplasmic reticulum (ER) triggers the ER stress response (ERSR)/unfolded protein response (UPR) leading to activation of three signaling pathways mediated by PERK, ATF6, and IRE1. Initially, the ERSR/UPR is pro-homeostatic as it globally slows translation while increasing translation of chaperone proteins and inducing ER-associated degradation. If the cellular stress is not controlled, apoptosis is subsequently induced through several mechanisms, of which the most well-described is CHOP. Following spinal cord injury (SCI), mice deficient in CHOP signaling show increased spared white matter and enhanced locomotor recovery by 6 weeks. At 24 hours after SCI, ATF4 and CHOP are upregulated in under perfused microvessels. We observed vascular protection 3 days post-SCI and a significant decrease in macrophage infiltration by the end of the first week. These results suggest that modulating ER-stress signaling in endothelial cells and macrophages may protect against vascular injury and attenuate inflammation post-SCI.

Sildenafil improves epicenter vascular perfusion but not hindlimb functional recovery after contusive spinal cord injury in mice.

Nitric oxide (NO) is an important regulator of vasodilation and angiogenesis in the central nervous system (CNS). Signaling initiated by the membrane receptor CD47 antagonizes vasodilation and angiogenesis by inhibiting synthesis of cyclic guanosine monophosphate (cGMP). We recently found that deletion of CD47 led to significant functional locomotor improvements, enhanced angiogenesis, and increased epicenter microvascular perfusion in mice after moderate contusive spinal cord injury (SCI). We tested the hypothesis that improving NO/cGMP signaling within the spinal cord immediately after injury would increase microvascular perfusion, angiogenesis, and functional recovery, with an acute, 7-day administration of the cGMP phosphodiesterase 5 (PDE5) inhibitor sildenafil. PDE5 expression is localized within spinal cord microvascular endothelial cells and smooth muscle cells. While PDE5 antagonism has been shown to increase angiogenesis in a rat embolic stroke model, sildenafil had no significant effect on angiogenesis at 7 days post-injury after murine contusive SCI. Sildenafil treatment increased cGMP concentrations within the spinal cord and improved epicenter microvascular perfusion. Basso Mouse Scale (BMS) and Treadscan analyses revealed that sildenafil treatment had no functional consequence on hindlimb locomotor recovery. These data support the hypothesis that acutely improving microvascular perfusion within the injury epicenter by itself is an insufficient strategy for improving functional deficits following contusive SCI.

Activating Notch signaling post-SCI modulates angiogenesis in penumbral vascular beds but does not improve hindlimb locomotor recovery.

Manipulation of Notch signaling has led to significant tumor shrinkage as well as recovery from several traumatic and ischemic injury models indicating its potential clinical application. We have tested both an agonist and antagonist of Notch signaling to study the effects of Notch-mediated angiogenesis on spinal cord vascular pathology following traumatic injury. Initial neonatal retinal vascularization assays showed their respective bioactivities in vivo. Mice were treated with either the antagonist Jagged1-Fc chimera (Jag1-Fc) or agonist Notch1 antibody (N1 Ab) immediately following a mid-thoracic contusive injury through an initial jugular bolus and tail vein injections for 3 days post-injury. After 14 days, activating Notch signaling decreased the overall vascular density within the penumbral gray matter compared to controls while maintaining the density of perfused vessels. Inhibiting Notch signaling did not change the density or perfusion of microvessels within the lesion penumbra. Furthermore, neither activation nor inhibition of Notch signaling significantly altered inflammation, hypoxia, and lesion volume in the epicenter and penumbra. Importantly, neither treatment changed locomotor function. In postnatal retinal vascular assays, administration of Jag1-Fc and N1 Ab increased and decreased both tip cell numbers and branch points in each treatment, respectively. However, these agents did not modulate primary CNS EC proliferation in vitro in spite of sufficient Notch ligand expression. We conclude that Notch signaling, while an important part of developmental angiogenesis, may play a lesser role in mediating vascular recovery following traumatic injury to the CNS.

CD47 knockout mice exhibit improved recovery from spinal cord injury.

Recent data have implicated thrombospondin-1 (TSP-1) signaling in the acute neuropathological events that occur in microvascular endothelial cells (ECs) following spinal cord injury (SCI) (Benton et al., 2008b). We hypothesized that deletion of TSP-1 or its receptor CD47 would reduce these pathological events following SCI. CD47 is expressed in a variety of tissues, including vascular ECs and neutrophils. CD47 binds to TSP-1 and inhibits angiogenesis. CD47 also binds to the signal regulatory protein (SIRP)α and facilitates neutrophil diapedesis across ECs to sites of injury. After contusive SCI, TSP-1(-/-) mice did not show functional improvement compared to wildtype (WT) mice. CD47(-/-) mice, however, exhibited functional locomotor improvements and greater white matter sparing. Whereas targeted deletion of either CD47 or TSP-1 improved acute epicenter vascularity in contused mice, only CD47 deletion reduced neutrophil diapedesis and increased microvascular perfusion. An ex vivo model of the CNS microvasculature revealed that CD47(-/-)-derived microvessels (MVs) prominently exhibit adherent WT or CD47(-/-) neutrophils on the endothelial lumen, whereas WT-derived MVs do not. This implicates a defect in diapedesis mediated by the loss of CD47 expression on ECs. In vitro transmigration assays confirmed the role of SIRPα in neutrophil diapedesis through EC monolayers. We conclude that CD47 deletion modestly, but significantly, improves functional recovery from SCI via an increase in vascular patency and a reduction of SIRPα-mediated neutrophil diapedesis, rather than the abrogation of TSP-1-mediated anti-angiogenic signaling.

The relationship between students' self-reported aggressive communication and motives to communicate with their instructors.

Using a convenience sample, 172 college students' (M age = 20.2 yr., SD = 2.5) motives for communicating with their instructors and their own verbal aggressiveness and argumentativeness were studied using the Argumentativeness Scale, the Verbal Aggressiveness Scale, and the Student Motives to Communicate Scale. Significant negative relationships were obtained between students' self-reports of argumentativeness and the sycophantic motive and between students' self-reports of verbal aggressiveness and the functional motive, but generally, students' motives to communicate with their instructors generally were not associated with their self-reported aggressive communication behaviors.

Employees' communication attitudes and dislike for working in a group.

This study examined 128 working adults' attitudes of tolerance for disagreement, tolerance for ambiguity, and argumentativeness in relation to their dislike for working in a group. They completed the Revised Tolerance for Disagreement Scale, the Multiple Stimulus Types Ambiguity Tolerance Scale, the Argumentativeness Scale, and the Grouphate Scale. Dislike for working in a group correlated negatively with Tolerance for Disagreement (r = -.28, p < .01, r2 = .08), Tolerance for Ambiguity (r = -.21, p < .05, r2 = .04), and Argumentativeness (r = -.21, p < .05, r2 = .04). Although these correlations are in the expected directions, magnitudes are very weak; unaccounted for variance should be examined.

WASP-interacting protein is important for actin filament elongation and prompt pseudopod formation in response to a dynamic chemoattractant gradient.

The role of WASP-interacting protein (WIP) in the process of F-actin assembly during chemotaxis of Dictyostelium was examined. Mutations of the WH1 domain of WASP led to a reduction in binding to WIPa, a newly identified homolog of mammalian WIP, a reduction of F-actin polymerization at the leading edge, and a reduction in chemotactic efficiency. WIPa localizes to sites of new pseudopod protrusion and colocalizes with WASP at the leading edge. WIPa increases F-actin elongation in vivo and in vitro in a WASP-dependent manner. WIPa translocates to the cortical membrane upon uniform cAMP stimulation in a time course that parallels F-actin polymerization. WIPa-overexpressing cells exhibit multiple microspike formation and defects in chemotactic efficiency due to frequent changes of direction. Reduced expression of WIPa by expressing a hairpin WIPa (hp WIPa) construct resulted in more polarized cells that exhibit a delayed response to a new chemoattractant source due to delayed extension of pseudopod toward the new gradient. These results suggest that WIPa is required for new pseudopod protrusion and prompt reorientation of cells toward a new gradient by initiating localized bursts of actin polymerization and/or elongation.

Students' Machiavellianism and motives for communicating with instructors.

This study investigated the relationship between scores of college students (N=210, 114 women, 95 men, 1 unidentified; Mage=19.3 yr., SD=2.8) on Machiavellianism and their motives for communicating with their instructors in the classroom. Students' Machiavellianism scores were positively but weakly related to three motives of Functional (r=.22, p<.01), Excuse-making (r=.16, p<.05), and Sycophancy (r=.17, p<.05).

A study of grouphate in a course on small group communication.

This study explored the relationship between grouphate and cohesion, consensus, relational satisfaction, affective learning, and cognitive learning. Participants were 83 undergraduate students enrolled in an introductory course on small group communication. Participants completed the Grouphate scale, the Classroom Cohesion scale, the Consensus scale, the Relational Satisfaction scale, three subscales of the Instructional Affect Assessment Instrument, and the Cognitive Learning Loss measure. Mean grouphate significantly increased during the semester, and negative correlations were found between scores for grouphate and cohesion (-.50), consensus (-.45), relational satisfaction (-.58), attitude toward the behaviors recommended in the course (-.23), the likelihood of developing an appreciation for the course content (-.33), and cognitive learning (-.32). Results may imply that students' grouphate is not associated with prosocial outcomes of the group work in this course.

A Dictyostelium homologue of WASP is required for polarized F-actin assembly during chemotaxis.

The actin cytoskeleton controls the overall structure of cells and is highly polarized in chemotaxing cells, with F-actin assembled predominantly in the anterior leading edge and to a lesser degree in the cell's posterior. Wiskott-Aldrich syndrome protein (WASP) has emerged as a central player in controlling actin polymerization. We have investigated WASP function and its regulation in chemotaxing Dictyostelium cells and demonstrated the specific and essential role of WASP in organizing polarized F-actin assembly in chemotaxing cells. Cells expressing very low levels of WASP show reduced F-actin levels and significant defects in polarized F-actin assembly, resulting in an inability to establish axial polarity during chemotaxis. GFP-WASP preferentially localizes at the leading edge and uropod of chemotaxing cells and the B domain of WASP is required for the localization of WASP. We demonstrated that the B domain binds to PI(4,5)P2 and PI(3,4,5)P3 with similar affinities. The interaction between the B domain and PI(3,4,5)P3 plays an important role for the localization of WASP to the leading edge in chemotaxing cells. Our results suggest that the spatial and temporal control of WASP localization and activation is essential for the regulation of directional motility.

Scores on liking and solidarity in interpersonal relationships.

This study examined liking and solidarity in interpersonal relationships. Participants were 226 undergraduates (89 men, 137 women: M age=27.0) who identified (by initials) an individual with whom they had a recent interaction and referenced that interaction when completing Rubin's Liking Scale and Wheeless's Interpersonal Solidarity Scale. A correlation of .73 (p<.0001) was obtained between the scores on these scales, suggesting when individuals like one another, they report feelings of solidarity also.