Increased Inflammatory Response Both In Brain And In Periphery In Presenilin-1/Presenilin-2 Conditional Double Knock-out Mice

Alzheimer's disease(AD) is the most common age-related neurodegenerative disease in the old group,which is characterized by reduced cortical thickness,significant elevation of Aβlevel in patients' brain,neurofibrillary tangles,formation of senile plaques and neuron loss.As a transmembrane aspartic protease,Presenilins(PS) play an important role in pathological process of AD.Conditional double knockout of presenilin-1 and presenilin-2 in forebrain of mice(dKO mice) exhibit symptoms most analogous to that of neurodegenerative diseases,especially Alzheimer's disease, including age-dependent memory impairment and forebrain degeneration.However, there is no deposition of extra Aβ₄₀ or Aβ₄₂ in dKO brain.1.Increased inflammatory response in brain in Presenilin-1/ Presenilin-2 conditional double knock-out miceIn the present study,we thoroughly measured the neuronal-inflammatory response, which is another global symptom in neurodegenerative diseases,in dKO mice at the ages of 3,6,9,and 12 months,respectively.Using methods of realtime PCR and western blotting,we found that glial cells(including microglia and astrocytes) were dramatically activated from early age(3-months) in dKO cortex and hippocampus, when compared with those in control mice.In addition,complement C1qαand C4, the key components in the classical complement pathway,were also stimulated in dKO mice brain in both mRNA and protein levels,as detected by methods of realtime PCR and ELISA.Antibody array was employed to screen inflammatory mediators whose expressions were significantly changed in dKO mice.Results revealed some mediators with changes in protein level.Moreover,ELISA analysis was used to detect expression levels of IL-1βin dKO and control cortex.These findings confirm that presenilins double knockout results in robust inflammatory response in brain,and suggest that dKO mice may be useful to further understand the effects of inflammation on the pathological processes of neurodegenerative diseases.2.Increased inflammatory response in periphery in Presenilin-1/ Presenilin-2 conditional double knock-out miceMoreover,the systemic inflammation level was thoroughly detected in conditional double knockout of presenilin-1 and presenilin-2 in forebrain of mice(dKO mice). Leukocytes in both dKO and control mice at the ages of 3,6,9,12 months were counted,and results showed that from the age of 6 months,leukocyte number in dKO mice blood were significantly higher than that in control mice blood.At the age of 3 months old,there was no significant difference in leukocyte number between dKO and control mice.Meanwhile,the level of high density lipoprotein(HDL) was detected in 6 and 12-month-old dKO and control mice plasma,using automatic analyzer.And results revealed a dramatic decrease in HDL level in 6 and 12-month-old dKO mice,as compared with that in age-matched control mice. Meanwhile,inflammatory cytokine array was employed to profile inflammatory mediators whose protein levels were significantly changed in 9-month-old dKO serum. Our results show that fourteen inflammatory molecules were found to be increased by＞2-fold and four mediators were decreased by＞2-fold in dKO mice as compared with those of control mice.Protein level of IL-1βwas further detected by ELISA in 6 and 12 month-old mice serum.In 6-month-old dKO serum,IL-1βwas significantly elevated when compared to the control.However,although dKO mice serum exhibited higher level of IL-1βthan control mice,there was no significant difference between them at 12 months.Above results indicate a delayed onset of systemic inflammation(beginning at the age of 6 months),as compared with neuroinflammation which appeared as early as 3 months.We speculate that severe inflammation occurs early in brain and then in periphery when PS1 and PS2 were double knocked out.Moreover,four cytokines were found to be significantly down-regulated in serum of dKO mice,including Eotaxin,I-TAC,Leptin and MIG,which support the point that proinflammatory and anti-proinflammatory signals would be balanced against each other for optimal outcome.