Chemokine Receptor Antagonists Prevent and Reverse Cofilin-Actin Rod Pathology and Protect Synapses in Cultured Rodent and Human iPSC-Derived Neurons.

Synapse loss is the principal cause of cognitive decline in Alzheimer's disease (AD) and related disorders (ADRD). Synapse development depends on the intricate dynamics of the neuronal cytoskeleton. Cofilin, the major protein regulating actin dynamics, can be sequestered into cofilactin rods, intra-neurite bundles of cofilin-saturated actin filaments that can disrupt vesicular trafficking and cause synaptic loss. Rods are a brain pathology in human AD and mouse models of AD and ADRD. Eliminating rods is the focus of this paper. One pathway for rod formation is triggered in ~20% of rodent hippocampal neurons by disease-related factors (e.g., soluble oligomers of Amyloid-ß (Aß)) and requires cellular prion protein (PrPC), active NADPH oxidase (NOX), and cytokine/chemokine receptors (CCRs). FDA-approved antagonists of CXCR4 and CCR5 inhibit Aß-induced rods in both rodent and human neurons with effective concentrations for 50% rod reduction (EC50) of 1-10 nM. Remarkably, two D-amino acid receptor-active peptides (RAP-103 and RAP-310) inhibit Aß-induced rods with an EC50 of ~1 pM in mouse neurons and ~0.1 pM in human neurons. These peptides are analogs of D-Ala-Peptide T-Amide (DAPTA) and share a pentapeptide sequence (TTNYT) antagonistic to several CCR-dependent responses. RAP-103 does not inhibit neuritogenesis or outgrowth even at 1 µM, >106-fold above its EC50. N-terminal methylation, or D-Thr to D-Ser substitution, decreases the rod-inhibiting potency of RAP-103 by 103-fold, suggesting high target specificity. Neither RAP peptide inhibits neuronal rod formation induced by excitotoxic glutamate, but both inhibit rods induced in human neurons by several PrPC/NOX pathway activators (Aß, HIV-gp120 protein, and IL-6). Significantly, RAP-103 completely protects against Aß-induced loss of mature and developing synapses and, at 0.1 nM, reverses rods in both rodent and human neurons (T½ ~ 3 h) even in the continuous presence of Aß. Thus, this orally available, brain-permeable peptide should be highly effective in reducing rod pathology in multifactorial neurological diseases with mixed proteinopathies acting through PrPC/NOX.

Short-term outcomes after pure bone marrow aspirate injection for severe knee osteoarthritis: a case series.

Background: Bone marrow aspiration (BMA) is among a group of autologous cell-based therapies currently being explored to treat osteoarthritis (OA). Materials & methods: This retrospective case study observed ten patients (13 knees) with severe knee OA who failed extensive conservative treatment and were treated with BMA injection using a novel, pure bone marrow aspiration (pBMA) technique. Results: No adverse events were reported. More than 50% reduction in the visual analog scale score for pain was observed at 2- and 12-weeks post-procedure, showing statistical significance. At 64 ± 26 weeks post-procedure, average knee pain remained significantly less than pre-procedure. Conclusion: Therefore, patients with severe knee OA may achieve significant relief after a BMA injection obtained using this pure bone marrow aspiration technique.

Surgical Outcomes of Os Trigonum Syndrome in Dancers: A Case Series.

BACKGROUND: Management of ankle pain in dancers can be challenging because of the repetitive stress and complex demands placed on this region. Despite the prevalence of ankle injuries in this population, literature on surgical outcomes and return to dance is limited. PURPOSE: To retrospectively evaluate the efficacy and functional outcomes after surgical excision of a symptomatic os trigonum in dancers. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Between June 2006 and June 2016, a total of 44 dancers underwent surgical excision of a symptomatic os trigonum at a single institution and by a single surgeon. All patients presented with symptoms of posterior ankle impingement syndrome and subsequently failed nonsurgical treatment. Clinical analysis was conducted using various pre- and postoperative patient-reported outcome questionnaires, including the Veterans RAND 12-Item Health Survey (VR-12), Foot Function Index-Revised (FFI-R), and visual analog scale (VAS) for pain, as well as subjective patient satisfaction. RESULTS: A total of 44 patients (54 ankles; mean age, 18.2 years) were retrospectively evaluated at a mean follow-up of 33.4 months. The VR-12 Physical Health score improved from a mean score of 37.8 ± 11.9 to 51.2 ± 10.5 (P < .001). The cumulative FFI-R score improved from 46.45 ± 13.8 to 31.2 ± 9.7 (P = .044), with the subcategory of "activity limitation" representing the highest-scoring FFI-R subcategory at 65.28 ± 13.4 preoperatively and improving to 34.47 ± 12.4 at follow-up (P < .001). The mean VAS score for subjective pain improved significantly from 5.39 ± 2.84 to 1.73 ± 2.10 (P < .00044). CONCLUSION: Overall, the findings of the present study demonstrate that dancers of varying style and level improved significantly according to various clinical measures. Patients included in this study reported that they returned to their previous level of dance upon completion of physical therapy and maintained thriving postoperative careers, which for several meant dancing at the professional level.

Cellular prion protein: A co-receptor mediating neuronal cofilin-actin rod formation induced by ß-amyloid and proinflammatory cytokines.

Increasing evidence suggests that proteins exhibiting "prion-like" behavior cause distinct neurodegenerative diseases, including inherited, sporadic and acquired types. The conversion of cellular prion protein (PrP(C)) to its infectious protease resistant counterpart (PrP(Res)) is the essential feature of prion diseases. However, PrP(C) also performs important functions in transmembrane signaling, especially in neurodegenerative processes. Beta-amyloid (Aß) synaptotoxicity and cognitive dysfunction in mouse models of Alzheimer disease are mediated by a PrP(C)-dependent pathway. Here we review how this pathway converges with proinflammatory cytokine signaling to activate membrane NADPH oxidase (NOX) and generate reactive oxygen species (ROS) leading to dynamic remodeling of the actin cytoskeleton. The NOX signaling pathway may also be integrated with those of other transmembrane receptors clustered in PrP(C)-enriched membrane domains. Such a signal convergence along the PrP(C)-NOX axis could explain the relevance of PrP(C) in a broad spectrum of neurodegenerative disorders, including neuroinflammatory-mediated alterations in synaptic function following traumatic brain injury. PrP(C) overexpression alone activates NOX and generates a local increase in ROS that initiates cofilin activation and formation of cofilin-saturated actin bundles (rods). Rods sequester cofilin from synaptic regions where it is required for plasticity associated with learning and memory. Rods can also interrupt vesicular transport by occluding the neurite within which they form. Through either or both mechanisms, rods may directly mediate the synaptic dysfunction that accompanies various neurodegenerative disorders.

Amyloid-ß and proinflammatory cytokines utilize a prion protein-dependent pathway to activate NADPH oxidase and induce cofilin-actin rods in hippocampal neurons.

Neurites of neurons under acute or chronic stress form bundles of filaments (rods) containing 1∶1 cofilin∶actin, which impair transport and synaptic function. Rods contain disulfide cross-linked cofilin and are induced by treatments resulting in oxidative stress. Rods form rapidly (5-30 min) in >80% of cultured hippocampal or cortical neurons treated with excitotoxic levels of glutamate or energy depleted (hypoxia/ischemia or mitochondrial inhibitors). In contrast, slow rod formation (50% of maximum response in ∼6 h) occurs in a subpopulation (∼20%) of hippocampal neurons upon exposure to soluble human amyloid-ß dimer/trimer (Aßd/t) at subnanomolar concentrations. Here we show that proinflammatory cytokines (TNFα, IL-1ß, IL-6) also induce rods at the same rate and within the same neuronal population as Aßd/t. Neurons from prion (PrP(C))-null mice form rods in response to glutamate or antimycin A, but not in response to proinflammatory cytokines or Aßd/t. Two pathways inducing rod formation were confirmed by demonstrating that NADPH-oxidase (NOX) activity is required for prion-dependent rod formation, but not for rods induced by glutamate or energy depletion. Surprisingly, overexpression of PrP(C) is by itself sufficient to induce rods in over 40% of hippocampal neurons through the NOX-dependent pathway. Persistence of PrP(C)-dependent rods requires the continuous activity of NOX. Removing inducers or inhibiting NOX activity in cells containing PrP(C)-dependent rods causes rod disappearance with a half-life of about 36 min. Cofilin-actin rods provide a mechanism for synapse loss bridging the amyloid and cytokine hypotheses for Alzheimer disease, and may explain how functionally diverse Aß-binding membrane proteins induce synaptic dysfunction.

A genetically encoded reporter for real-time imaging of cofilin-actin rods in living neurons.

Filament bundles (rods) of cofilin and actin (1:1) form in neurites of stressed neurons where they inhibit synaptic function. Live-cell imaging of rod formation is hampered by the fact that overexpression of a chimera of wild type cofilin with a fluorescent protein causes formation of spontaneous and persistent rods, which is exacerbated by the photostress of imaging. The study of rod induction in living cells calls for a rod reporter that does not cause spontaneous rods. From a study in which single cofilin surface residues were mutated, we identified a mutant, cofilinR21Q, which when fused with monomeric Red Fluorescent Protein (mRFP) and expressed several fold above endogenous cofilin, does not induce spontaneous rods even during the photostress of imaging. CofilinR21Q-mRFP only incorporates into rods when they form from endogenous proteins in stressed cells. In neurons, cofilinR21Q-mRFP reports on rods formed from endogenous cofilin and induced by all modes tested thus far. Rods have a half-life of 30-60 min upon removal of the inducer. Vesicle transport in neurites is arrested upon treatments that form rods and recovers as rods disappear. CofilinR21Q-mRFP is a genetically encoded rod reporter that is useful in live cell imaging studies of induced rod formation, including rod dynamics, and kinetics of rod elimination.