About the lab
Professor Ingrid Liu's laboratory is located at Tzu Chi University, Hualien, Taiwan. The Ingrid Liu lab has been focusing on researching the molecular mechanism underlying memory formation and brain disorders. Ingrid's lab uses several knockout/transgenic mouse models including the 3xTg Alzheimer's disease model, the Cav3.2 knockout model, and the peroxiredoxin 6 knockout model, to investigate key molecules involved in critical steps of memory information. The lab also use these mouse models to select for effective novel drugs and treatments for related diseases.
Featured research (6)
Fear dysregulation is one of the symptoms found in post-traumatic stress disorder (PTSD) patients. The functional abnormality of the hippocampus is known to be implicated in the development of such pathology. Peroxiredoxin 6 (PRDX6) belongs to the peroxiredoxin family. This antioxidant enzyme is expressed throughout the brain, including the hippocampus. Recent evidence reveals that PRDX6 plays an important role in redox regulation and the modulation of several signaling molecules involved in fear regulation. Thus, we hypothesized that PRDX6 plays a role in the regulation of fear memory. We subjected a systemic Prdx6 knockout ( Prdx6 −/− ) mice to trace fear conditioning and observed enhanced fear response after training. Intraventricular injection of lentivirus-carried mouse Prdx6 into the 3rd ventricle reduced the enhanced fear response in these knockout mice. Proteomic analysis followed by validation of western blot analysis revealed that several proteins in the MAPK pathway, such as NTRK2, AKT, and phospho-ERK1/2, cPLA2 were significantly upregulated in the hippocampus of Prdx6 −/− mice during the retrieval stage of contextual fear memory. The distribution of PRDX6 found in the astrocytes was also observed throughout the hippocampus. This study identifies PRDX6 as a participant in the regulation of fear response. It suggests that PRDX6 and related molecules may have important implications for understanding fear-dysregulation associated disorders like PTSD.
The triple transgenic Alzheimer’s disease (3xTg-AD) strain is a common mouse model used for studying the pathology and mechanism of Alzheimer’s disease (AD). The 3xTg-AD strain exhibits two hallmarks of AD, amyloid beta (Aβ) and neurofibrillary tangles. Several studies using different gender and age of 3xTg-AD mice to investigate their behavior phenotypes under the influence of various treatments have reported mixed results. Therefore, a comprehensive investigation on the optimal gender, age, and training paradigms used for behavioral studies of 3xTg-AD is necessary. In the present study, we investigated the behavioral phenotypes for the two genders of 3xTg-AD mice at 3, 6, 9, and 12 months old and compared the results with age-, gender-matched C57BL/6N control strain. All mice were subjected to tail flick, pinprick, open field, elevated plus maze, passive avoidance, and trace fear conditioning (TFC) tests to evaluate their sensory, locomotor, anxiety, and learning/memory functions. The results showed that TFC on male 3xTg-AD mice is optimal for studying the memory performance of AD. The sensory and locomotor functions of 3xTg-AD mice for two genders appear to be normal up to 6 months old, their fear memory starts to decline after that, and the difference between male control and 3xTg-AD mice in contextual and cued memories are robust, thus ideal for evaluating the effect of a treatment. Since it is time and cost consuming to obtain wildtype littermates as controls, C57BL/6N strain is suggested to be used as control mice for their baseline performance of sensorimotor functions similar to that of 3xTg-AD mice.
Alzheimer's disease (AD) is a neurodegenerative disease characterized by an excessive inflammatory response and impaired memory retrieval, including spatial memory, recognition memory, and emotional memory. Acquisition and retrieval of fear memory help one avoid dangers and natural threats. Thus, it is crucial for survival. AD patients with impaired retrieval of fear memory are vulnerable to dangerous conditions. Excessive expression of inflammatory markers is known to impede synaptic transmission and reduce the efficiency of memory retrieval. In wild-type mice, reducing inflammation response can improve fear memory retrieval; however, this effect of this approach is not yet investigated in 3xTg-AD model mice. To date, no satisfactory drug or treatment can attenuate the symptoms of AD despite numerous efforts. In the past few years, the direction of therapeutic drug development for AD has been shifted to natural compounds with anti-inflammatory effect. In the present study, we demonstrate that the compound 4-(phenylsulfanyl) butan-2-one (4-PSB-2) is effective in enhancing fear memory retrieval of wild-type and 3xTg-AD mice by reducing the expression of TNF-α, COX-2, and iNOS. We also found that 4-PSB-2 helps increase dendritic spine density, postsynaptic density protein-95 (PSD-95) expression, and long-term potentiation (LTP) in the hippocampus of 3xTg-AD mice. Our study indicates that 4-PSB-2 may be developed as a promising therapeutic compound for treating fear memory impairment of AD patients.
Age-related macular degeneration (AMD) is a progressive eye disease that causes irreversible impairment of central vision, and effective treatment is not yet available. Extracellular accumulation of amyloid-beta (Aβ) in drusen that lie under the retinal pigment epithelium (RPE) has been reported as one of the early signs of AMD and was found in more than 60% of Alzheimer’s disease (AD) patients. Extracellular deposition of Aβ can induce the expression of inflammatory cytokines such as IL-1β, TNF-α, COX-2, and iNOS in RPE cells. Thus, finding a compound that can effectively reduce the inflammatory response may help the treatment of AMD. In this research, we investigated the anti-inflammatory effect of the coral-derived compound 4-(phenylsulfanyl) butan-2-one (4-PSB-2) on Aβ1-42 oligomer (oAβ1-42) added to the human adult retinal pigment epithelial cell line (ARPE-19). Our results demonstrated that 4-PSB-2 can decrease the elevated expressions of TNF-α, COX-2, and iNOS via NF-κB signaling in ARPE-19 cells treated with oAβ1-42 without causing any cytotoxicity or notable side effects. This study suggests that 4-PSB-2 is a promising drug candidate for attenuation of AMD.
Peroxiredoxin 6 (PRDX6) is a multifunctional enzyme expressed in many organs including the brain. It is known to participate in many psychiatric functions, but its role in fear memory is unknown. The present study demonstrates that PRDX6 plays a critical role in the regulation of fear response. Using Prdx6 knockout (Prdx6-/-) mice, we identified that PRDX6 acts as a suppressor in fear memory formation. Lack of Prdx6 leads to the faster fear acquisition and enhanced contextual fear response. This phenomenon was confirmed by the fact that injection of lentivirus-carried human PRDX6-V5 into the hippocampus of Prdx6-/- mice restored the enhanced fear response to the wild-type level. In the hippocampus of Prdx6-/- mice, calcium-dependent PLA2 level was increased, which may compensate for the lack of aiPLA2 function to maintain normal synaptic membranes. On the other hand, reactive oxygen species (ROS) levels did not change, indicating loss of peroxidase function did not affect the regulation of fear response.
- Institute of Medical Sciences
About Ingrid Y Liu
- Research Overview 1. We use cytogenetic, molecular and genomic approaches to research patients with inherited or spontaneous brain disorders and screen for genes associated with these diseases. 2. We utilize mouse models to identify gene functions and molecular mechanisms underlying memory processing and formation. 3. We use mouse models to select promising drug candidates for treating Alzheimer's disease and PTSD.