(-)-Phenserine and the prevention of pre-programmed cell death and neuroinflammation in mild traumatic brain injury and Alzheimer's disease challenged mice

Abstract

Mild traumatic brain injury (mTBI) is a risk factor for neurodegenerative disorders, such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). TBI-derived neuropathologies are promoted by inflammatory processes: chronic microgliosis and release of pro-inflammatory cytokines that further promote neuronal dysfunction and loss. Herein, we evaluated the effect on pre-programmed cell death/neuroinflammation/synaptic integrity and function of (−)-Phenserine tartrate (Phen), an agent originally developed for AD. This was studied at two clinically translatable doses (2.5 and 5.0 mg/kg, BID), in a weight drop (concussive) mTBI model in wild type (WT) and AD APP/PSEN1 transgenic mice. Phen mitigated mTBI-induced cognitive impairment, assessed by Novel Object Recognition and Y-maze behavioral paradigms, in WT mice. Phen fully abated mTBI-induced neurodegeneration, evaluated by counting Fluoro-Jade C-positive (FJC+) cells, in hippocampus and cortex of WT mice. In APP/PSEN1 mice, degenerating cell counts were consistently greater across all experimental groups vs. WT mice. mTBI elevated FJC+ cell counts vs. the APP/PSEN1 control (sham) group, and Phen similarly mitigated this. Anti-inflammatory effects on microglial activation (IBA1-immunoreactivity (IR)) and the pro-inflammatory cytokine TNF-α were evaluated. mTBI increased IBA1-IR and TNF-α/IBA1 colocalization vs. sham, both in WT and APP/PSEN1 mice. Phen decreased IBA1-IR throughout hippocampi and cortices of WT mice, and in cortices of AD mice. Phen, likewise, reduced levels of IBA1/TNF-α-IR colocalization volume across all areas in WT animals, with a similar trend in APP/PSEN1 mice. Actions on astrocyte activation by mTBI were followed by evaluating GFAP, and were similarly mitigated by Phen. Synaptic density was evaluated by quantifying PSD-95+ dendritic spines and Synaptophysin (Syn)-IR. Both were significantly reduced in mTBI vs. sham in both WT and APP/PSEN1 mice. Phen fully reversed the PSD-95+ spine loss in WT and Syn-IR decrease in both WT and APP/PSEN1 mice. To associate immunohistochemical changes in synaptic markers with function, hippocampal long term potentiation (LTP) was induced in WT mice. LTP was impaired by mTBI, and this impairment was mitigated by Phen. In synopsis, clinically translatable doses of Phen ameliorated mTBI-mediated pre-programmed cell death/neuroinflammation/synaptic dysfunction in WT mice, consistent with fully mitigating mTBI-induced cognitive impairments. Phen additionally demonstrated positive actions in the more pathologic brain microenvironment of AD mice, further supporting consideration of its repurposing as a treatment for mTBI.

(−)‐Phenserine tartrate (PhenT) as a treatment for traumatic brain injury

“…Notably, the background number of activated (IBA1+) microglia was greater than in WT mice across brain regions, in those with and without mTBI. mTBI further elevated this, and a similar treatment effect was achieved with PhenT (5 mg/kg BID) . Not shown, but clearly apparent, PhenT also significantly mitigated TBI‐induced astrocytosis as evaluated glial fibrillary protein (GFP) immunohistochemistry (see data and figures within Ref …”

“…Detailed below are our latest PhenT preclinical studies demonstrating inhibition of PNCD and neuroinflammation in mice challenged with mTBI; notably, this was cross‐validated in both AD transgenic (APP + PS1) mice subjected to mTBI and in controlled cortical impact (CCI) injury challenged mice, which is a well‐characterized animal model of modTBI.…”

“…To evaluate the basis of the PhenT mediated mitigation of mTBI‐induced cognitive impairments, the antiapoptotic potential of PhenT was appraised in the brains of separate cohorts of mice. Using immunohistochemical techniques detailed previously, PNCD was evaluated at 72 hours following head injury by Fluoro‐Jade C (FJC) staining and counting of degenerating cells within the parietal cortex and the CA1, CA3, and dentate gyrus regions of the hippocampus in sham (uninjured)‐, mTBI (vehicle treated)‐, and mTBI + PhenT (2.5 and 5 mg/kg, BID)‐treated animals. As illustrated in Figure A, the mTBI‐induced PNCD was dose‐dependently mitigated by PhenT across all evaluated brain areas .…”

“…Using immunohistochemical techniques detailed previously, PNCD was evaluated at 72 hours following head injury by Fluoro‐Jade C (FJC) staining and counting of degenerating cells within the parietal cortex and the CA1, CA3, and dentate gyrus regions of the hippocampus in sham (uninjured)‐, mTBI (vehicle treated)‐, and mTBI + PhenT (2.5 and 5 mg/kg, BID)‐treated animals. As illustrated in Figure A, the mTBI‐induced PNCD was dose‐dependently mitigated by PhenT across all evaluated brain areas . To cross‐validate this in a more complex model in which neuronal cell dysfunction and death, together with neuroinflammation, were already occurring, aged (10‐12 months old) APP + PS1 AD transgenic (Tg) male mice were challenged with mTBI (a similar concussive 30 g weight drop), followed by identical PhenT or vehicle posttreatment.…”

“…# P < .05 ## P < .01 vs CTRL by Mann‐Whitney rank test; @ P < .05 vs mTBI by Mann‐Whitney rank test . Data shown as mean ± SEM Scale bar = 30 μm…”