Department of Ophthalmology and Visual Sciences

University of Illinois at Chicago

Chicago, Illinois

BASIC RESEARCH PROJECT

Hyperglycemia-induced mitochondrial adaptation

Research Interests

The long delay between the onset of diabetes mellitus (DM) to the development of retinopathy suggests the existence of processes that prevent retinal pathogenesis. Dr. Kazlauskas recently discovered that prolonged hyperglycemia (HG) induces adaptation of retinal blood vessels cells. Furthermore, such adaptation appears to be beneficial: it protects the cells from death and inflammation. He will test the hypothesis that soon after the onset of DM, retinal vessels undergo adaption, which protects them from succumbing to retinopathy that occurs only after loss of such adaption.

The long-term goal of this proposal is to overcome existing roadblocks that prevent us from developing approaches to prevent and /or delay diabetic retinopathy (DR). To accomplish this, he will conduct research to learn the mechanism by which HG induces adaptation, i.e. protection from progression to DR. This information will birth a new therapeutic strategy, namely enforcing and/or restoring mitochondrial adaptation as an approach to prevent patients with DM from developing DR.

Plans for 2023

In the coming year, Dr. Kazlauskas and his team will determine which retinal cells types in a mouse retina are protected from the deleterious effects of DM during the pre-DR period. Their working hypothesis is that those cells types that perish as DR develops are the ones that are protected during the pre-DR phase of DM. Findings from 2022 indicate that the blood vessels were protected; whether the two vascular cell types are equally protected remains an open question.

Specific Aims 1. Identify cell types in the mouse retina that undergo protection during the pre-DR phase of DM. We will develop assays to induce and quantify death of multiple retinal cells types in healthy, non-DM mice. Death will be induced by intravitreal injection of DM-related insults such as cytokines. A FACS (fluorescence activated cell sorting)-based approach will be used to quantify the extent of death in the following four retinal cell types: pericytes, endothelial cells, retinal ganglion cells and glial cells. After optimizing the approach with non-DM mice, we will apply it to mice that have endured increasing durations of DM. Observation of protection in at least one of the vascular cell types during the preDR phase of DM will confirm our existing results using a distinct experimental approach. This series of experiments will also reveal whether other cell types are protected during the pre-DR phase of DM.

Progress in 2022

Dr. Kazlauskas proposed to investigate the mechanism by which HG induces mitophagy (Aim 1), and to test if all cells respond to HG by undergoing HIMA, or is this response unique to HRECs (Aim 2).

Dr. Kazlauskas made excellent progress in 2022. In the tissue culture experimental setting, his lab discovered that hyperglycemia-induced mitochondrial adaptation (HIMA) was associated with elevated glycolysis, which was in part required for cells to retain HIMA. They also determined that primary human glomerular endothelial cells and pericytes did not undergo HIMA as did primary human retinal endothelial cells. A first publication on this project will appear in December 2022. Serikbaeva, A, Li Y, Ganesh B, Zelkha R, Kazlauskas A. Hyperglycemia promotes mitophagy and thereby mitigates hyperglycemia-induced damage. Am J Pathol. 2022; In press.

In addition, Dr. Kazlauskas considered if a key component of HIMA (HG-induced protection) exists in vivo. Indeed, it appears that is does. As in humans, development of diabetic retinopathy (DR) in experimental animals is delayed from the onset of DM. The team found that retinal blood vessels of DM mice were protected from DM-related insult-induced death during the period of DM that precedes DR. Furthermore, protection waned and then vulnerability to death increased as the duration of DM was prolonged and began to approach the duration that causes DR.

Specific Aims:

Aim 1. Investigating the mechanism by which HG induces mitophagy. In 2021, the Kazlauskas lab screened a number of agents that promote mitophagy and learned that not all of them induced adaptation.  They will compare the effect of this panel of agents on mitochondrial functionality using an oximetry-based approach (also called Seahorse).  These results will identify the specific changes in mitochondrial functionality that are associated with adaption.  In parallel, they will subject HG-treated cells to the same type of in-depth analysis.  The results will identify those changes that are most likely to be required for adaptation.  Subsequent experimentation will determine which of these changes are necessary and/or sufficient for HG to promote mitophagy and thereby induce HIMA.

Aim 2. Test if HIMA is unique to HRECs. The lab team will subject other retinal cell types (vascular -pericytes; neuronal – glial cells) and endothelial cells from other organs (kidney/glomerulus) to the same type of analysis that was done on HRECs. These results will determine whether HIMA is or is not a universal response of cells to HG.

Progress in 2021

Dr. Kazlauskus made excellent progress in 2021. He tested the hypothesis that HG improves mitochondrial functionality by activating mitophagy, a process that clears dysfunctional mitochondria, and learned that this was indeed the case.  Dr. Kazlauskus established an approach to monitor mitophagy and used it to learn that mitophagy was elevated in cells that had undergone HIMA.  Furthermore, his laboratory team discovered that mitophagy was required for cells to maintain HIMA.  Finally, boosting mitophagy was sufficient to induce adaption in normal glucose cells. These observations provide an explanation for how HG improves the functionality of the mitochondria, i.e. by culling those mitochondria that have become dysfunctional.