STEM I

In STEM I, taught by Dr. Crowthers, we learn to better read technical writing and work on improving our own technical writing. Starting over the summer and continuing into February, we brainstorm, research, experiment, and write about an independent research project of our choosing.

Investigating the Effects of Amyloid Plaques on Oxidative Stress throughout the Life Cycle of Caenorhabditis elegans

The prevalence of Alzheimer's is increasing, yet there is still no cure, accurate method of detection, or understanding of the root causes of Alzheimer's. This project investigates the relationship between age and two mechanisms of Alzheimer's, Amyloid plaques and oxidative stress.

Abstract

The prevalence of Alzheimer’s Disease (AD) is increasing, along with the average age of the population. There is no cure for AD due to a lack of knowledge on the underlying pathology of the disease. Amyloid plaques and oxidative stress are especially puzzling because there is conflicting evidence on which one appears first, and they both cause an increase in the amount of the other. Both Amyloid plaques and oxidative stress are found in both healthy and Alzheimer’s patients, which allows this research to also apply to the processes of general aging. In order to learn more about the mechanisms associated with the cognitive decline of Alzheimer's patients, we used Caenorhabditis elegans to test the effects of aging on the amounts of Amyloid plaque-induced oxidative stress. MO1, a novel strain of transgenic C. elegans, which continuously expresses GFP as a reporter for oxidative stress and expresses Amyloid beta when warmed was used. Amyloid plaques were induced at different stages in the life cycle of the worms, then the worms were dyed with Congo red to ensure the expression of amyloid plaques. We found that as the age of the C. elegans increases, the levels of ROS produced in response to amyloid plaques will decrease. This research will give us further insight on the pathology of Amyloid plaques and oxidative stress in Alzheimer’s, as well as in the process of aging. This relationship helps to explain the age-dependency and pathology of Alzheimer’s.

Keywords: Alzheimer’s Disease, Amyloid plaques, oxidative stress, Reactive Oxygen Species, aging

Graphical Abstract

Research Question

How does age affect the production of Reactive Oxygen Species in response to the expression of Amyloid Plaques?

Hypothesis

If the age of the Caenorhabtitis elegans increases, then the amount of Amyloid plaque-induced oxidative stress will also increase.

Infographic

Background

Graphical Methodology

Methodology

Figure 1

Figure 1. Both images show the same C. elegans. The image on the left shows the worm expressing GFP, while the image on the right shows the worm's Amyloid plaques stained with Congo red.

Figure 2

Figure 2. The pixel intensities of GFP in the heated MO1 worms, along with CL691 and MO1 control groups are shown for both the L4/Adult and the L1/L2 age groups. The pixel intensities of heated MO1 worms of the L4/Adult and L1/L2 groups were found to be s tatistically significant (p-value < 0.0001) to the pixel intensities of their respective CL691 and MO1 controls using one-tailed t-tests.

Figure 3

Figure 3. The pixel intensities of Congo red in the heated MO1 worms and MO1 control groups are shown for both the L4/Adult and the L1/L2 age groups. The pixel intensities of the heated MO1 worms of the L4/Adult and L1/L2 groups were found to be statistically significant (p-value < 0.0001) to the pixel intensities of their respective MO1 controls using one-tailed t-tests.

Figure 4

Figure 4. The above graph shows the amounts of GFP produced per unit of Pixel Intensity of Congo red (GFP pixel intensity/Congo Red pixel intensity), which was found using the average pixel intensities of GFP and Congo red calculated by Fiji. The amount of GFP per Pixel Intensity unit of Congo red for the L1/L2 group was found to be significantly greater than that of the L4/Adult (p-value < 0.0001). The pixel intensity of GFP per pixel intensity unit of Congo red in the L1/L2 age group was about 91.7% greater than that of the L4/Adult group.

Analysis

The CL691 and CL2355 worms crossbred which is shown by the same worm showing GFP and Congo red stain (Fig. 1). The pixel intensities of both GFP and Congo red in heated MO1 worms for both L4/adult and L1/L2 worms were significantly higher than in all controls (Fig. 2, Fig. 3). The pixel intensity of GFP per pixel intensity unit of Congo Red in younger worms was significantly greater than that in older worms (Fig. 4).

Discussion/Conclusion

References

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