Neuroprotective effects of a new synthetic peptide, CMX-9236, in in vitro and in vivo models of cerebral ischemia

NGF (nerve growth factor) and BDNF (brain-derived neurotrophic factor) are protein molecules (MW 26 and 13.6 kDa, respectively) that are neuroprotective in the middle cerebral artery occlusion (MCAO) rat stroke model. Their mechanism of action involves the activation of transcription factor AP-1 that turns on neuronal growth genes. In our ongoing studies we are designing short peptides that mimic some of the properties of full-length neurotrophic factors. We have synthesized a neuroprotective 14-amino acid peptide (CMX-9236) with an N-terminal docosahexaenoic acid (DHA). DHA enhances entry through the blood-brain barrier. Using primary rat brain cortical cultures and a fluorescent assay we found that CMX-9236 can counteract the excitotoxic effects of glutamate or kainate, reversing the intracellular accumulation of Ca(2+) to normal levels. Administration (i.v.) of CMX-9236 post initiation of ischemia reduced the lesion volumes from 178+/-50 to 117+/-55 mm(3) in the temporary rat MCAO model (90 min), and from 216+/-58 to 127+/-57 mm(3) in the permanent (24 h) model for stroke, corresponding to 34+/-28% (P=0.01) and 41+/-19% (P=0.038) reductions of the infarct volumes. Neurological behavior scores showed 57 and 47% improvements for treated temporary and permanent models, respectively. Dose-response studies indicated a 60-fold activation of AP-1 transcription factor in cells treated with 100 ng/ml of the peptide. These studies illustrate that a small peptide can function as a neuroprotective agent and an activator of a beneficial signal transduction pathway

Proteoglycan abnormalities in olfactory epithelium tissue from subjects diagnosed with schizophrenia

Emerging evidence points to proteoglycans abnormalities in the pathophysiology of schizophrenia (SZ). In particular, markedly abnormal expression of chondroitin sulfate proteoglycans (CSPGs), key components of the extracellular matrix, was observed in the medial temporal lobe. CSPG functions, including regulation of neuronal differentiation and migration, are highly relevant to the pathophysiology of SZ. CSPGs may exert similar functions in the olfactory epithelium (OE), a continuously regenerating neural tissue that shows cell and molecular abnormalities in SZ. We tested the hypothesis that CSPG expression in OE may be altered in SZ. CSPG-positive cells in postmortem OE from nonpsychiatric control (n=9) and SZ (n=10) subjects were counted using computer-assisted light microscopy. ‘Cytoplasmic’ CSPG (c-CSPG) labeling was detected in sustentacular cells and some olfactory receptor neurons (c-CSPG+ORNs), while ‘pericellular’ CSPG (p-CSPG) labeling was found in basal cells and some ORNs (p-CSPG+ORNs). Dual labeling for CSPG and markers for mature and immature ORNs suggests that c-CSPG+ORNs correspond to mature ORNs, and p-CSPG+ORNs to immature ORNs. Previous studies in the same cohort demonstrated that densities of mature ORNs were unaltered (Arnold et al, 2001). In the present study, numerical densities of c-CSPG+ORNs were significantly decreased in SZ (p <0.025; 99.32% decrease), suggesting a reduction of CSPG expression in mature ORNs. Previous studies showed a striking increase in the ratios of immature neurons with respect to basal cells. In this study, we find that the ratio of p-CSPG+ORNs/ CSPG+ basal cells was significantly increased (p=0.03) in SZ, while numerical density changes of p-CSPG+ORNs (110.71% increase) or CSPG+ basal cells (53.71% decrease), did not reach statistical significance. Together, these results indicate that CSPG abnormalities are present in the OE of SZ and specifically point to a reduction of CSPGs expression in mature ORNs in SZ. Given the role CSPG play in OE cell differentiation and axon guidance, we suggest that altered CSPG expression may contribute to ORN lineage dysregulation, and olfactory identification abnormalities, observed in SZ

Down Syndrome Fibroblast Model of Alzheimer-Related Endosome Pathology : Accelerated Endocytosis Promotes Late Endocytic Defects

Endocytic dysfunction is an early pathological change in Alzheimer’s disease (AD) and Down’s syndrome (DS). Using primary fibroblasts from DS individuals, we explored the interactions among endocytic compartments that are altered in AD and assessed their functional consequences in AD pathogenesis. We found that, like neurons in both AD and DS brains, DS fibroblasts exhibit increased endocytic uptake, fusion, and recycling, and trafficking of lysosomal hydrolases to rab5-positive early endosomes. Moreover, late endosomes identified using antibodies to rab7 and lysobisphosphatidic acid increased in number and appeared as enlarged, perinuclear vacuoles, resembling those in neurons of both AD and DS brains. In control fibroblasts, similar enlargement of rab5-, rab7-, and lysobisphosphatidic acid-positive endosomes was induced when endocytosis and endosomal fusion were increased by expression of either a rab5 or an active rab5 mutant, suggesting that persistent endocytic activation results in late endocytic dysfunction. Conversely, expression of a rab5 mutant that inhibits endocytic uptake reversed early and late endosomal abnormalities in DS fibroblasts. Our results indicate that DS fibroblasts recapitulate the neuronal endocytic dysfunction of AD and DS, suggesting that increased trafficking from early endosomes can account, in part, for downstream endocytic perturbations that occur in neurons in both AD and DS brains