Indiana University-Purdue University Indianapolis (IUPUI) / Diabetes is a morbid metabolic disorder that affects almost 500 million people
worldwide. Although multiple factors contribute to diabetes pathogenesis, pancreatic islet
inflammation and dysfunction are shared characteristics of its major forms. 12-
lipoxygenase (12-LOX), an enzyme involved in lipid metabolism, has been implicated in
islet inflammation. 12-LOX generates reactive oxygen species (ROS) that activate
inflammation and serve as major contributors to islet dysfunction. Importantly, since ROS
are transient moieties, they are challenging to study in vivo. Hence, establishing better
animal models of ROS-mediated stress is critical to facilitate the discovery and preclinical
testing of novel diabetes therapeutics. Here, I have adapted a zebrafish model of conditional
β-cell injury, which is regulated by the administration of the prodrug metronidazole
(MTZ), to study responses to ROS in vivo. I demonstrate that with MTZ treatment, ROS
are generated within β-cells and subsequently exhibit recruitment of macrophages into the
islet and induction of β-cell death. I utilized this model to uncover roles for macrophages
and 12-LOX during islet injury. Excessive macrophage infiltration exacerbates islet
inflammation and dysfunction. Interestingly, on the depletion of macrophages in zebrafish,
I observed that β-cells recovered normal function upon cessation of prodrug treatment.
This suggests that infiltrating macrophages promote maladaptive inflammation and
premature removal of damaged β-cells. Thus, limiting the macrophage infiltration may be
a therapeutic approach to restoring β-cell function. Based on the established roles of 12-LOX in other contexts, I hypothesized that its inhibition would prevent the localized
infiltration of proinflammatory macrophages. To test this, I used both zebrafish and mouse
models and observed a significant reduction in macrophage migration upon loss of 12-
LOX activity. Furthermore, I found that expression of CXCR3, a crucial receptor
regulating migration, was significantly reduced in 12-LOX loss-of-function macrophages.
These data suggest a role for 12-LOX in macrophages, which is conserved across species.
Collectively, my study reveals novel roles for 12-LOX in macrophage function and
provides testable therapeutic targets for the resolution of inflammation-induced damage in
the pancreatic islets. / 2020-11-19
| Identifer | oai:union.ndltd.org:IUPUI/oai:scholarworks.iupui.edu:1805/22839 |
| Date | 05 1900 |
| Creators | Kulkarni, Abhishek Anant |
| Contributors | Harrington, Maureen, Mirmira, Raghavendra, Anderson, Ryan, Goebl, Mark, Mosley, Amber, Marrs, James |
| Source Sets | Indiana University-Purdue University Indianapolis |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation |
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