IAB Research Project Description
Collaborative Research: Redox balance in Antarctic notothenioid fishes: Do ice fishes have an advantage?
Antarctic channichthyid icefishes are stunning examples of the unique physiological traits that can arise during evolution in a constantly cold environment. Icefishes are the only vertebrates that as adults, lack the circulating oxygen-binding protein hemoglobin (Hb). Six of the 16 species within this family also lack the intracellular oxygen-binding protein myoglobin (Mb) in their heart ventricle. The loss of Hb and Mb has resulted in striking modifications in the cardiovascular system to ensure adequate tissue oxygenation, some of which are energetically costly. Recent results in our laboratories indicate there may be at least one benefit to not expressing these heme-centered proteins.
We have determined that levels of oxidized proteins and lipids are higher in red-blooded notothenioids compared to icefishes. Our proposed research will address the hypothesis that the loss of Hb and Mb reduces oxidative stress in icefishes compared to red-blooded notothenioid fishes, resulting in a lower rate of protein turnover and energetic cost savings.
This research will contribute to our understanding of iron-catalyzed oxidative stress, which is associated with the progression of Alzheimer’s, Parkinson’s and cardiovascular diseases. Moreover, studies proposed here will increase our understanding of factors related to iron metabolism and oxidative stress in notothenioid fishes that may have played key roles in the success of channichthyid icefishes.
Our research will address the following specific aims:
Characterize levels of oxidative stress in red- and white-blooded notothenioid fishes. Levels of oxidized proteins and lipids will be quantified in heart, oxidative skeletal muscle and liver of four species of notothenioid fishes differing in the expression of Hb and Mb. Levels of prooxidants, including Hb, Mb, and heme will be quantified, as well as antioxidants.
Determine if red- and white-blooded notothenioids differ in their regulation of iron. Iron is an important component of many biological molecules, yet also a potential oxidant. It remains unclear how icefishes, lacking a sink for Fe in the form of oxygen-binding proteins, sequester Fe in a non-toxic manner. We will quantify levels of non-heme Fe and Fe-and Hb-binding proteins (ferritin, transferrin, ceruloplasmin, haptoglobin) in fishes differing in the expression of Hb and Mb.
Determine if lower levels of oxidized proteins in icefishes result in lower rates of protein turnover and energetic cost savings. We anticipate that lower levels of oxidized proteins in icefishes will result in lower rates of protein degradation and synthesis compared to red-blooded species. Rates of protein degradation will be quantified in liver, heart and oxidative muscle of notothenioid fishes differing in the expression of Hb and Mb by measuring the activity of the 20S proteasome. Rates of protein synthesis will be determined by measuring the rate of incorporation of 3H phenylalanine into newly synthesized proteins. The energetic cost of protein synthesis will be determined by measuring the rate of oxygen consumption in isolated cardiomyocytes and hepatocytes in the presence and absence of cyclohexamide.
Determine if oxygen-binding proteins promote oxidative stress in-vivo and in-vitro. Redblooded notothenioids will be treated with iron-chelators, which bind Hb and Mb radical species and Fe. Levels of oxidized proteins and lipids will be quantified to determine if chelating Fe and protein radicals reduces levels of oxidized proteins and lipids. In-vitro experiments will be conducted by challenging tissue homogenates from red- and white-blooded notothenioids with an oxidant in the presence or absence of an iron chelator and antioxidant.
1 Sep 2011 – 31 Aug 2014
IAB Proposal #2010-121
UAF Grant #G7328
IAB Project #228
302A Irving I
University of Alaska Fairbanks
Fairbanks, AK 99775-7000