Therapeutic efficacy of matrix metalloproteinase-12 suppression on neurological recovery after ischemic stroke: Optimal treatment timing and duration.

We recently showed that the post-ischemic induction of matrix metalloproteinase-12 (MMP-12) in the brain degrades tight junction proteins, increases MMP-9 and TNFα expression, and contributes to the blood-brain barrier (BBB) disruption, apoptosis, demyelination, and infarct volume development. The objectives of this study were to (1) determine the effect of MMP-12 suppression by shRNA-mediated gene silencing on neurological/functional recovery, (2) establish the optimal timing of MMP-12shRNA treatment that provides maximum therapeutic benefit, (3) compare the effectiveness of acute versus chronic MMP-12 suppression, and (4) evaluate potential sex-related differences in treatment outcomes. Young male and female Sprague-Dawley rats were subjected to transient middle cerebral artery occlusion and reperfusion. Cohorts of rats were administered either MMP-12shRNA or scrambled shRNA sequence (control) expressing plasmids (1 mg/kg; i.v.) formulated as nanoparticles. At designated time points after reperfusion, rats from various groups were subjected to a battery of neurological tests to assess their reflex, balance, sensory, and motor functions. Suppression of MMP-12 promoted the neurological recovery of stroke-induced male and female rats, although the effect was less apparent in females. Immediate treatment after reperfusion resulted in a better recovery of sensory and motor function than delayed treatments. Chronic MMP-12 suppression neither enhanced nor diminished the therapeutic effects of acute MMP-12 suppression, indicating that a single dose of plasmid may be sufficient. We conclude that suppressing MMP-12 after an ischemic stroke is a promising therapeutic strategy for promoting the recovery of neurological function.

Effect of convergence on the horizontal VOR in normal subjects and patients with peripheral and central vestibulopathy.

BACKGROUND: Vestibular compensatory eye movements provide visual fixation stabilization during head movement. The anatomic pathways mediating a normal horizontal vestibulo-ocular reflex (h-VOR), when lesioned, cause spontaneous nystagmus. While previous reports address the effect of convergence on different spontaneous nystagmus types, to our knowledge, a study of acute vestibular nystagmus suppression viewing near targets comparing patients with peripheral or central vestibular lesions has not been previously reported. METHODS: We attempt to clarify potential vestibular and near-reflex interaction by comparing near and far h-VOR gain in 19 healthy controls, six patients with acute/subacute peripheral vestibular lesion (PVL), and one patient with unilateral vestibular nuclear lesion (VNL) in the pontine tegmentum. RESULTS: The horizontal (h)-VOR in normal subjects increased with convergence in both eyes (P = 0.027, P < 0.001). In unilateral PVL patients, gain failed to increase in either direction (P = 0.25, P = 0.47). In contrast, when fixating at 15 cm, the h-aVOR in the VNL lesion, gain did not increase, and a right h-nystagmus developed. Even though we found inability to increase gain in PVL with near target fixation, this did not interfere with h-nystagmus suppression upon converging. Our VNL patient had normal h-nystagmus suppression viewing far distance targets and lacked near target h-nystagmus suppression. CONCLUSION: We hypothesize that normal IO/flocculus pathway suppressed spontaneous nystagmus in PVL. Impaired h-VOR near adaptation in the medial vestibular nucleus was responsible for h-nystagmus direction with fixation block. Additionally, impaired viewing distance estimate contributed to near h-nystagmus suppression failure.

A Single Test to Study Social Behavior and Repetitive Self-grooming in Mice.

The ability to recognize and interact with members of the same species is essential for social communication. Investigating the neural substrates of social interest and recognition may offer insights into the behavioral differences present in disorders affecting social behavior. Assays used to study social interest in rodents include the 3-chamber test, a partition test, and a social interaction test. Here, we present a single protocol that can be used to quantify the level of social interest displayed by mice, the ability to distinguish between different individual mice (social recognition), and the level of repetitive self-grooming displayed. In the first part of the protocol, a social habituation/dishabituation test, the time spent by a test mouse sniffing a stimulus mouse is quantified over 9 trials. In the first 8 interactions, the same stimulus mouse is used repeatedly; on the ninth trial, a novel stimulus mouse is presented. Intact social recognition is indicated by a progressive decrease in the investigation time over trials 1-8, and an increase in trial 9. The interval between each social trial is used to quantify self-grooming, a stereotyped repetitive behavior in mice. We also present a method for randomized, blinded analysis of these behaviors to increase rigor and reproducibility of results. Therefore, this single behavioral test enables ready assessment of phenotypes of both social and repetitive behaviors in an integrated manner in the same animals. This feature can be advantageous in understanding interactions between these behaviors and phenotypes in mouse models with genetic variants associated with autism and other neurodevelopmental or neuropsychiatric disorders, which are often characterized by these behavioral differences.

Differential impacts on multiple forms of spatial and contextual memory in diazepam binding inhibitor knockout mice.

Learning and memory are fundamental processes that are disrupted in many neurological disorders including Alzheimer's disease and epilepsy. The hippocampus plays an integral role in these functions, and modulation of synaptic transmission mediated by γ-aminobutyric acid (GABA) type-A receptors (GABAA Rs) impacts hippocampus-dependent learning and memory. The protein diazepam binding inhibitor (DBI) differentially modulates GABAA Rs in various brain regions, including hippocampus, and changes in DBI levels may be linked to altered learning and memory. The effects of genetic loss of DBI signaling on these processes, however, have not been determined. In these studies, we examined male and female constitutive DBI knockout mice and wild-type littermates to investigate the role of DBI signaling in modulating multiple forms of hippocampus-dependent spatial learning and memory. DBI knockout mice did not show impaired discrimination of objects in familiar and novel locations in an object location memory test, but did exhibit reduced time spent exploring the objects. Multiple parameters of Barnes maze performance, testing the capability to utilize spatial reference cues, were disrupted in DBI knockout mice. Furthermore, whereas most wild-type mice adopted a direct search strategy upon learning the location of the target hole, knockout mice showed higher rates of using an inefficient random strategy. In addition, DBI knockout mice displayed typical levels of contextual fear conditioning, but lacked a sex difference observed in wild-type mice. Together, these data suggest that DBI selectively influences certain forms of spatial learning and memory, indicating novel roles for DBI signaling in modulating hippocampus-dependent behavior in a task-specific manner.