The Effect Of Curcumin Monomer On Aβ Production In SwAPP HEK293 Cells

Background and Purpose Alzheimer’s disease(AD)is the most common type of dementia.The major pathological characteristics of AD are deposition of β-amyloid(Aβ)in senile plaques,neurofibrillary tangles(NFTs),the deficiency of synaptic contact between cerebral cortex and hippocampus and so on.Aβ is generated from the amyloid precursor protein(APP)through the proteolysis of β-site APP cleaving enzyme and γ-secretase enzyme.Aβ is easy to form aggregation,fibrosis,deposition of plaque,which will cause damage to neurons,therefore,inhibition of Aβ generation is the key to the treatment of AD.Currently clinical treatment of AD mainly had cholinesterase inhibitors,NMDA receptor antagonists and others drugs to improve symptoms,there still had no specific drugs for the cause,prevention and progression blocking of the disease.Curcumin is extracted from the ginger rhizome plants like turmeric yellow pigment,has the effects of anti-amyloid,anti-inflammatory,anti-oxidation,anticholinesterase activity and so on.It has confirmed that curcumin insignificantly reduced the amount of Aβ and inhibited the aggregation and fibrosis of Aβ in vitro and in vivo.However,the current AD studies mostly use curcumin complex,which contain three monomers:Curcumin(Cur),Demethoxy curcumin(DMC)and Bis-demethoxy-curcumin(BDMC).In addition,it’s suggested that the inhibition of curcumin monomer Cur on Aβ production is stronger than that of curcumin complex and other monomers,but the mechanism of curcumin monomer Cur inhibiting Aβ still remain uncertain.micro RNAs are endogenous small non-coding RNA molecule,which combines with the their target gene m RNA and hinder its translation and degradation by base pairing.It’s reported that mi RNAs were involved in the pathological process of neurodegenerative diseases and can target at the 3’ untranslated region(3’ UTR)of the AD-related genes to inhibit the expression of their translated production.However,there had no reports that Cur,the curcumin monomer,affected the expression of target gene productions through regulating the expression of APP gene specific mi RNAs in the AD study.Therefore,the present study was conducted to examine the effects and preliminary mechanisms of curcumin monomer on Aβ production,aimed to provide experimental basic for the further application of curcumin monomer.Methods The sw APP HEK293 cells were treating by different concentration(2,5,10,20,40 μM)and different time points(6,12,24 h)of Cur.MTT assay was used to detect cell viability,Enzyme-linked immunosorbent assay(ELISA)was carried to test Aβ40 and Aβ42 production,then selected out the best concentration and time point of Cur for following experiments:RT-PCR(polymerase chain reaction)was used to detect APP m RNA expression,Western blot(Polyacrylamide gel electrophoresis)was used to analyze APP protein expression,q RT-PCR(quantitative real-time polymerase chain reaction)was used to detect mi RNA level.Results1.Compared with the control group,concentration ≤ 5 μM of Cur had no effects on cell viability,while ≥ 10 μM of Cur had significantly cytotoxic effects.2.It obviously inhibited Aβ40 and Aβ42 production when cells were treated with ≤ 5 μM of Cur for 24 h,the differences were significantly different compared with the controls.3.Cur had no obviously effects on APP m RNA expression,but inhibited APP protein expression at the post-transcriptional level,the difference was significantly different from the controls.4.Cur could significantly increase mi R-153 level,decrease mi R-101 level,it had significant differences when compared with the controls,but not significantly affected mi R-195 level.5.mi R-153 had no obviously effects on APP m RNA expression,but negatively regulated APP protein expression at the post-transcriptional level,the difference was significantly different from the controls.Conclusion1.The most significant suppression of Cur on Aβ production presented at the concentration and time point of 5 μM,24 h.2.Cur regulated the APP protein expression instead of APP m RNA at the post-transcriptional level,thus inhibiting Aβ40 and Aβ42 production.3.Cur may inhibit APP protein expression at the post-transcriptional level through up-regulating mi R-153,thereby suppressing Aβ40 and Aβ42 production.