Date of Award

8-10-2021

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Hamed Laroui

Second Advisor

Donald Hamelberg

Third Advisor

Jun Yin

Fourth Advisor

Ning Fang

Abstract

CD98 is a glycoprotein with many important biological functions including amino acid transportation, endocytosis regulation, and activation of the integrin β signal pathway. Studies have shown the expression levels of CD98 are increased in the livers from fatty degeneration, although the role of CD98 in non-alcoholic fatty liver disease (NAFLD) is not clear. The inflammatory stress inside of the liver is considered one of the main driving forces for NAFLD development. It has been well-studied that the inhibition of CD98 protects mice from colitis (inflammation). To understand the role of CD98 in NAFLD, CD98 siRNA was loaded into the poly lactic acids (PLA) nanoparticles (NPs) to directly inhibit the CD98 expression level in the liver of the high-fat diet (HFD) mice. The decreased level of NAFLD-related markers and the improvements on the liver tissue conditions were observed in the HFD mice with the treatment of CD98 siRNA-loaded NPs. This study indicated that CD98 was important in the NAFLD progression, and downregulation of CD98 can be an effective way for NAFLD treatment.

The mechanism of how plant-derived nanovesicles uptaken by cells remains unknown. In this study, garlic-derived nanovesicles (GDVs) were isolated and digested with trypsin to remove all surface proteins. Digested GDVs showed less uptake compared to undigested GDVs, confirming the surface proteins played an important role in endocytosis. On the cell side (Hep G2 cells, HepG2), blocking CD98 receptors significantly reduced the uptake of GDVs. During the cellular internalization of GDVs, microcopy concluded that some surface proteins of GDVs were co-localized with CD98. A total lysate of the GDVs surface showed a high presence of a mannose-specific binding protein: II Lectin. Blocking II Lectin on surface of GDVs using mannose highly reduced the GDVs internalization which supports that direct interaction between II Lectin and CD98 plays an important role in internalization. The GDVs also exhibited in vitro anti-inflammatory effect by downregulating pro-inflammatory cytokines on HepG2 cells. This work contributes to understanding a part of the GDVs internalization process and the cellular anti-inflammatory effects of garlic. Since CD98 expression level is increased in many diseases including the NAFLD, the II Lectin-CD98 interaction can be utilized for the design of NPs for liver delivery.

In conclusion, this study indicates that CD98 can be used as the target for drug delivery, and decrease the expression of CD98 can protect mice from high-fat-diet-induced liver damages.

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