Combined ampakine and BDNF treatments enhance poststroke functional recovery in aged mice via AKT-CREB signaling

Nano-particle delivery of brain derived neurotrophic factor after focal cerebral ischemia reduces tissue injury and enhances behavioral recovery

BACKGROUND

Low levels of brain-derived neurotrophic factor (BDNF) are linked to delayed neurological recovery, depression, and cognitive impairment following stroke. Supplementation with BDNF reverses these effects. Unfortunately, systemically administered BDNF in its native form has minimal therapeutic value due to its poor blood brain barrier permeability and short serum half-life. In this study, a novel nano-particle polyion complex formulation of BDNF (nano-BDNF) was administered to mice after experimental ischemic stroke.

METHODS

Male C57BL/6J (8-10weeks) mice were randomly assigned to receive nano-BDNF, native-BDNF, or saline treatment after being subjected to 60min of reversible middle cerebral artery occlusion (MCAo). Mice received the first dose at 3 (early treatment), 6 (intermediate treatment), or 12h (delayed treatment) following stroke onset; a second dose was given in all cohorts at 24h after stroke onset. Post-stroke outcome was evaluated by behavioral, histological, and molecular analysis for 15days after stroke.

RESULTS

Early and intermediate nano-BDNF treatment led to a significant reduction in cerebral tissue loss. Delayed treatment led to improved memory/cognition, reduced post-stroke depressive phenotypes, and maintained myelin basic protein and brain BDNF levels, but had no effect on tissue atrophy.

CONCLUSIONS

The results indicate that administration of a novel nano-particle formulation of BDNF leads to both neuroprotective and neuro-restorative effects after stroke.

Reversal of the Detrimental Effects of Post-Stroke Social Isolation by Pair-Housing is Mediated by Activation of BDNF-MAPK/ERK in Aged Mice

Social isolation (SI) increases stroke-related mortality and morbidity in clinical populations. The detrimental effects of SI have been successfully modeled in the laboratory using young animals. Mechanistically, the negative effects of SI in young animals are primarily mediated by an enhanced inflammatory response to injury and a reduction in neurotrophic factors. However, the response to brain injury differs considerably in the aged. Given that SI is more prevalent in aged populations, we hypothesized that isolation, even when initiated after stroke, would delay recovery in aged mice. We found that aged isolated male mice had significantly increased infarct volume, neurological deficits, and serum IL-6 levels three days after stroke compared to pair housed (PH) mice. Using RT² Profiler PCR Array and real-time quantitative PCR we found several important synaptic plasticity genes were differentially expressed in post-stroke SI mice. Furthermore, paired mice showed improved memory and neurobehavioral recovery four weeks after injury. Mechanistic and histological studies showed that the beneficial effects of pair housing are partially mediated by BDNF via downstream MAPK/ERK signaling and restoration of axonal basic myelin protein levels.