TLJN is a modern Chinese formula that has recently been applied in phase II clinical trial in patients with cerebral ischemic stroke and vascular dementia 
. However, the roles of TLJN in AD still need to be tested in rigorous clinical trials. In the present study, we are the first to examine the effects of an anti-stroke herbal medicine TLJN on amyloid-related pathology in APP23 transgenic mice. Following TLJN chronic administration, we found in the brain tissues of APP23 mice that (1) Aβ levels and deposition were significantly decreased; (2) BACE1 protein levels as well as activity were significantly down-regulated; (3) the levels of γ-secretase components PS1, APH1 and nicastrin but not PEN2 were decreased; (4) there were not significant changes in the levels of the degrading enzymes NEP and IDE. Our finding of TLJN-decreased Aβ levels induced by TLJN is consistent with previous observations of Ginsenoside-induced Aβ level decrease 
. Therefore, Ginsenoside in TLJN might be the main active ingredients responsible for decreasing Aβ levels. In addition to Aβ reduction, we also found a significant decrease in the number of insoluble Aβ plaques in the chronic presence of TLJN. The number decrease may be associated with total reduction of Aβ levels. Meanwhile, there is another possibility that Ginsenoside in TLJN inhibits transforming of soluble Aβ to insoluble or directly blocks the aggregation of insoluble Aβ.
It has been reported that BACE1 is a stress-response protein 
, which means that its protein levels and/or activities might be modulated 
. Here, we observed BACE1 level reduction in the brain treated with TLJN. In addition to TJLN-induced BACE1 protein level decrease, we also found that long-term TLJN treatment inhibited BACE1 activity in brains, consistent with the observation in vitro
of BACE1 activity inhibition by the treatment of Ginsenoside Rg1 
. The mechanism involved in BACE1 down-regulation by TLJN remains to be confirmed. It has been found that glucose reduction could possibly be involved in the early events of AD pathogenesis 
. It has been evidenced that glucose reduction as well as energy inhibition elevates BACE1 levels and activity in APP transgenic mice 
. In contrast, Ginsenoside stimulates glucose uptake 
. Therefore, the capability of Ginsenoside to improve glucose uptake could be a cause of the regulation of BACE1 level and activity by TLJN in the brain of APP23 mice. Ginsenoside has also been implicated in down-regulating NF-κB signaling, resulting in anti-inflammatory consequences 
. Combining our previous finding that genetic inactivation of tumor necrosis factor receptor-mediated NF-κB signal transduction pathway results in the decrease of BACE1 levels, ultimately leads to Aβ reduction 
, hence we postulate that TLJN-containing Ginsenoside down-regulates NF-κB signaling, resulting BACE1 inhibition. Recently, Ginsenoside has been found to enhance the binding of peroxisome proliferator-activated receptor γ (PPARγ) to BACE1 promoter, which in turn inhibits the transcription and translation of BACE1 and thus suppress BACE1 activity 
Another finding is that TLJN can partially decrease γ-secretase activity by reducing PS1, APH1 and nicastrin levels, which are components of γ-secretase enzyme complex. A number of small molecule γ-secretase inhibitors have been identified to block Aβ generation with high potency in cultured cells and in APP transgenic mouse models of AD 
. However, It is noticed that γ-secretase also cleaves a number of additional substrates besides APP, such as Notch 
and ErbB-4 
, and thus γ-secretase inhibitors can suppress Notch processing 
. Consequently, γ-secretase inhibition can result in serious adverse effects. Therefore, further elucidation of the mechanism of TLJN’s action is highly desirable for pharmacological intervention in AD.
One recent report suggested that TLJN improves Aβ clearance enzyme IDE and NEP expression 
. It has further been demonstrated that Geniposide has the capability to up-regulate IDE expression in cultured cortical neurons 
. However, we did not find a significant elevation of either IDE or NEP levels in the brain chronically treated with TLJN. The previous observation of elevating IDE and NEP levels is based on a rat AD model induced by bilateral intra-hippocampal injection of Aβ peptide 25–35. The discrepancy of these results may be due to different AD models used.
Neuron injury and loss is an important cause of dementia in AD patients. Another compound in TLJN is Geniposide, which has biological activities of neuroprotection and anti-oxidative stress. Lines of evidence have shown that Geniposide promotes nuclear translocation of nuclear factor-E2-related factor 2 (Nrf2) 
. Binding of Nrf2 to the antioxidant response element induces a battery of gene transcriptions that can coordinate a protective response against oxidative stressors 
. Geniposide also up-regulates the expression of heme oxygenase-1 (HO-1) 
. HO-1 is an enzyme which is responsible for degrading heme to carbon monoxide, free iron, and biliverdin and for the cell defense against oxidative stress 
. There has been evidenced that Geniposide could enhance insulin secretion 
, which prevents oxidative stress-induced damage in AD 
. Recently, it has been found that Geniposide could inhibit Aβ42-mediated cytotoxicity in neurons 
. Therefore, the roles of Geniposide in neuroprotection might be one of the beneficial actions of TLJN.
In summary, besides the application in the patients with cerebral ischemic stroke 
, we have identified anti-stroke herbal medicine TLJN as a modulator of BACE1 and γ-secretase complex, which provides a mechanistic clue for the application in neurodegenerative diseases such as AD.