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Research Interests

Proteostasis in Alzheimer’s disease (AD) and stroke, FOXOs in ischemic stroke, extracellular vesicles (exosomes) as a source for novel biomarkers and therapeutic agents for stroke and AD, stem cells, neuroinflammation, neurodegeneration, neuroprotection

My research focuses on the role of proteostasis in neuroinflammation and neuronal death in some chronic and acute neuropathological conditions, such as Alzheimer’s disease and ischemic stroke. Using cell culture models (including stem cells), genetically modified mice, patients derived tissues, as well as molecular, genetic, biochemical, physiological, behavioral, pharmacological, and computational approaches, we aim at (1) investigating the pathogenic mechanisms of the diseases, (2) identifying the targets that can be “druggable” for the disorders, and (3) screening and validating the therapeutic agents that can be used for treating these diseases.

Proteostasis and AD 

AD is a major health problem in our society, representing the most common cause of dementia in the elderly. Neuropathologically, AD is characterized by accumulation of insoluble protein aggregates in the forms of extracellular senile plaques (amyloid-β or Aβ plaques) and intraneuronal neurofibrillary tangles. Although it remains obscure why these proteins accumulate, growing evidence supports that impaired proteostasis, or loss of the dynamic regulation of a balanced and functional proteome, is likely causative to the disease.

Aging, the time-dependent deterioration of physiological functions, is the leading risk factor for AD. Among multiple molecular mechanistic alterations associated with aging, impaired proteasome is receiving increased attention, as emerging evidence suggests a strong link between proteasome activity and longevity. Conversely, proteasome functionality declines with age and impaired proteasome is also associated with AD. Using a ubiquitin-proteasome system (UPS) functionality reporter mouse, we previously showed that UPS functionality was reduced in the cortex and hippocampus in a familial AD mouse model. We have also reported that overexpression of a ubiquitin-like protein, ubiquilin1 (Ubqln1) that facilitates clearance of misfolded proteins, attenuates AD caused learning and memory deficits and neuropathology. Thus, modulation of UPS function likely modifies AD pathogenesis. However, how impaired UPS causes neuronal loss and whether proteasome activation is a therapeutic strategy remain to be defined. We are now utilizing both cell cultures, mouse models, and various methods to address these questions.

Selected References

1. Liu Y, Hettinger CL, Zhang D, Rezvani K, Wang X and Wang H (2014). The proteasome function reporter GFPu accumulates in young brains of the APPswe/PS1dE9 Alzheimer's disease mouse model. Cell Mol Neurobiol. 34(3):315-22.
2. Adegoke OO, Qiao F, Liu Y, Longley K, Feng S and Wang H (2017). Overexpression of ubiquilin-1 alleviates Alzheimer’s disease-caused cognitive and motor deficits and reduces β-amyloid accumulation in mice. J Alzheimer’s Dis. 59(2):575-590.
3. Wang X, Wang H (2020). Priming the proteasome to protect against proteotoxicity. Trends Mol Med. 2020 jul;26(7):639-648. doi:10.1016/j.molmed.2020.02.007. Epub 2020 Mar 26. PMID: 32589934
4. Huber CC, Callegari EA, Paez MD, Romanova S, and Wang H (2022). Heat shock-induced extracellular vesicles derived from neural stem cells confer marked neuroprotection against oxidative stress and amyloid-β caused neurotoxicity. Mol Neurobiol. 2022 Oct 3. doi:10.1007/s12035-022-03055-3. PMID: 36190693
5. Huber CC, Callegari EA, Paez MD, Li X, and Wang H (2024). Impaired 26S proteasome causes learning and memory deficiency and induces neuroinflammation mediated by NF-κB in mice. bioRxiv [Preprint]. 2024 Apr 7:2024.02.09.579699. doi: 10.1101/2024.02.09.579699

FOXOs in ischemic stroke

Cerebral ischemia/reperfusion (I/R) induces oxidative stress and neuroinflammation in the affected brain areas, eventually leading to neuronal death. We previously discovered that UPS influences neuronal death and brain function recovery following I/R. We recently extended our studies to the role of FOXOs, the forkhead box O (FOXO) transcription factors, in ischemic stroke induced brain injury. The FOXO transcription factors, consisting of four functionally related proteins, FOXO1, FOXO3, FOXO4 and FOXO6, are mammalian homologs of daf-16 in C. elegans and were previously identified as tumor suppressors, oxidative stress sensors, and cell survival modulators. FOXO activities are negatively regulated by phosphorylation via the phosphoinositide 3-kinase (PI3K)-Akt pathway, a well-known cell survival pathway: Akt phosphorylates FOXOs to inactivate their transcriptional activity by relocalizing FOXOs from the nucleus to the cytoplasm for degradation. However, under oxidative stress or absent the cellular survival drive of growth factors, FOXOs translocate to the nucleus and upregulate a series of target genes, thereby promoting cell growth arrest and cell death. Because FOXOs regulate cell survival and death in specific physio-pathological conditions, we are now determining whether they are therapeutic targets for ischemic stroke and whether suppression of their activities can be used to treat the disease. 

Selected References:

1.    Lü L and Wang H (2012). Transient focal cerebral ischemia upregulates immunoproteasomal subunits. Cell Mol Neurobiol. 32(6):965-70.
2.    Liu Y, Lü L, Hettinger CL, Dong G, Zhang D, Rezvani K, Wang X and Wang H (2014). Ubiquilin-1 protects cells from oxidative stress and ischemic stroke caused tissue injury in mice. J Neurosci. 34(8):2813-21. 
3.    Min J, Liu Y, Wang DL, Qaio F and Wang H (2018). The non-peptidic δ-opioid receptor agonist Tan-67 mediates neuroprotection post-ischemically and is associated with altered amyloid precursor protein expression, maturation and processing in mice. J Neurochem. 144(3):336-347.
4.    Liu Y, Min JW, Feng S, Subedi K, Qiao F, Mammenga E, Callegari E, Wang H (2020). Therapeutic role of a cysteine precursor, OTC, in ischemic stroke is mediated by improved proteostasis in mice. Transl Stroke Res. 2020 Feb;11(1):147-160. Epub 2019 May 2. doi:10.1007/s12975-019-00707-w. Epub 2019 May 2. PMID: 31049841
5.    Liu Y, Subedi K, Baride A, Romanova S, Callegari E, Huber CC, Wang X and Wang H (2021). Peripherally misfolded proteins exacerbate ischemic stroke-induced neuroinflammation and brain injury. J Neuroinflammation. 2021 Jan 20;18(1):29. doi: 10.1186/s12974-021-02081-7.

Extracellular vesicles (EVs) (exosomes) as disease biomarkers and therapeutic agents

EVs are membrane-bound small particles mediating intercellular traffic of nucleic acids, lipids, proteins, and metabolites. Exosomes are a subtype of EVs with a size range of 30 – 150 nanometers in diameter. Partly as drugs and partly as delivery devices, healthy (wild-type, WT) stem cells-derived EVs/exosomes have been considered as a potential therapeutic for AD, stroke, and many other diseases, whereas disease cells-derived EVs are a rich source of biomarkers for these diseases. We recently extended our studies from modeling Huntington’s disease with stem cells to AD by directly reprogramming AD somatic cells into neural stem cells (NSCs). With the cell models generated, we discovered that the EVs derived from the WT NSCs are able to efficiently repair the disrupted blood-brain barrier in an AD mouse model. In addition to developing effective therapeutics using WT stem cells-derived EVs, we are also interested in identifying the EV-derived biomarkers for AD.

Selected References:

1.    Liu Y, Qiao F, Leiferman PC, Ross A, Schlenker EH and Wang H (2017). FOXOs modulate proteasome activity in human induced pluripotent stem cells of Huntington’s disease and their derived neural cells. Hum Mol Genet. 26(22):4416-4428.
2.    Liu Y, Xue Y, Ridley S, Rezvani K, Zhang D, Fu XD and Wang H (2014). Direct reprogramming of Huntington’s disease patient fibroblasts into neuron-like cells leads to abnormal neurite outgrowth, increased cell death, and aggregate formation. PLOS One. 9(10):e109621. doi: 10.1371/journal.pone.0109621.
3.    Liu Y and Wang H (2020). Modeling sporadic Alzheimer’s disease by efficient direct reprogramming of the elderly derived disease dermal fibroblasts into neural stem cells. J Alzheimers Dis. 2020;73(3):919-933. doi:10.3233/JAD-190614. PMID: 31884463
4.    Liu Y, Huber CC, Wang H (2020). Disrupted blood-brain barrier in 5×FAD mouse model of Alzheimer's disease can be mimicked and repaired in vitro with neural stem cell-derived exosomes. Biochem Biophys Res Commun. 2020 Feb;18: S0006-291X(20)30342-9. doi:10.1016/j.bbrc.2020.02.074. PMID: 32081424
5.    Wang H, Huber CC, and Li X (2023). Mesenchymal and neural stem cell-derived exosomes in treating Alzheimer’s disease. Bioengineering. 10(2), 253; doi: 10.3390/bioengineering10020253

Complete List of Published Work in My Bibliography:

Funding

• NIH/NIA RF1 AG072510 – “Priming the Proteasome to Protect Against Aging and Alzheimer's Disease”, Role: MPI
• NIH/NINDS, R01 NS124846 - “FOXOs in Ischemic Stroke”, Role: PI