Wild type TDP-43 induces neuro-inflammation and alters APP metabolism in lentiviral gene transfer models

The transactivation DNA-binding protein (TDP-43) pathology is associated with fronto-temporal lobar dementia (FTLD) with ubiquitinated inclusions and some cases of Alzheimer's disease (AD). Proteolytic fragments of beta-amyloid precursor protein (beta APP) are detected in AD as well as the cerebrospinal fluid (CSF) from FTLD and Amyotrophic Lateral Sclerosis (ALS) patients, suggesting alteration in APP processing. Because of the overlap in TDP-43 pathology between FTLD and AD, we sought to determine whether there is a relationship between TDP-43 and APP metabolism. We generated gene transfer models using lentiviral delivery of human TDP-43 and A beta(1-42) into the rat primary motor cortex and examined their role 2 weeks post-injection. Expression of TDP-43 and/or A beta(1-42) increase pro-inflammatory markers, including Interleukin (IL)-6, tumor necrosis factor (TNF-alpha), glial neurofibrillary proteins (GFAP) and ionized calcium binding adaptor molecule 1 (IBA-1). Lentiviral A beta(1-42) up-regulates endogenous TDP-43 and promotes its phosphorylation, aggregation and cleavage into 35 kDa fragments. Inversely, lentiviral TDP-43 expression increases the levels and activity of beta-secretase (BACE), accelerating production of APP C-terminal fragments (C99) and A beta(1-40). Here we show that TDP-43 up-regulates APP metabolism and suggest a mechanistic link between TDP-43 and BACE. (C) 2012 Elsevier Inc. All rights reserved.