UP-REGULATION OF NEP-ACTIVITY OF SK-N-SH CELLS BY GREEN TEA EXTRACT AND ITS NATURAL PRODUCTS ON RISK OF ALZHEIMER

Abstract

Alzheimer's disease (AD) is the most common cause of dementia in the elderly AD is characterized pathologically by the accumulation of amyloid j3-peptide as senile plaques in the brain. Neutral endopeptidase (NEP) and angiotensin-converting enzyme (ACE) belong to the major AB-degrading enzymes. NEP and ACE are zinc-endopeptidases enzymes acting as ectoenzymes on the outer surface of different cells. In order to test the influence of green tea extract and some of its natural components (caffeine, theophylline, theanine, epicatechin and epigallocatechin), we used the neuroblastoma cell line SK-NSH then we studied the changes in the specific cellular NEP and ACE activity after longterm treatment with these substances. Despite the high similarity between both enzymes ACE and NEP green tea extract and the tested substances only influenced selectively the specific NEP activity without affecting the specific ACE activity We have also shown that dibutyryl-cAMp, forskolin and rolipram increase the level of intracellular cyclic adenosine monophosphate (cAMP) which results in an induction of the specific NEP activity without any effect on the specific ACE activity Green tea extract was also able to increase the level of intracellular cAMP in vitro. These results demonstrate that the enhancement effect of the specific NEP activity, by green tea extract and its natural products, was selective and correlated with an elevated level of cAMP.