Proteomic Mechanisms of Cardioprotection during Mammalian Hibernation in Woodchucks, Marmota Monax

Abstract

Mammalian hibernation is a unique strategy for winter survival in response to limited food supply and harsh climate, which includes resistance to cardiac arrhythmias. We previously found that hibernating woodchucks (Marmota monax) exhibit natural resistance to Ca2+ overload-related cardiac dysfunction and nitric oxide (NO)-dependent vasodilation, which maintains myocardial blood flow during deep torpor (DT). Since, the cellular/molecular mechanisms mediating the protection are less clear, the goal of this study was to investigate dynamic seasonal changes in the heart proteome and reveal related signaling networks which are involved in establishing cardioprotection in woodchucks during hibernation. This was accomplished using isobaric tags for a relative and absolute quantification (iTRAQ) approach. The most significant seasonal changes observed were upregulation of the anti-oxidant, catalase, and inhibition of endoplasmic reticulum (ER) stress response by downregulation of GRP78, mechanisms which could be responsible for the adaptation and protection in hibernating animals. Furthermore, protein networks pertaining to NO signaling, acute phase response, CREB and NFAT transcriptional regulations, protein kinase A and α-adrenergic signaling were dramatically upregulated during hibernation. These adaptive mechanisms in hibernators may provide new directions to protect myocardium of non-hibernating animals, especially humans, from cardiac dysfunction induced by hypothermic stress and myocardial ischemia.

Myocardial ischemic protection in natural mammalian hibernation

“…Using a proteomic approach, from the network analysis, we found that CREB protein network was activated in the winter woodchuck hibernation [26]. In the present investigation, we found that CREB was activated in the hearts of woodchucks in winter at both room temperature and in the hibernaculum.…”

The Recovery of Hibernating Hearts Lies on a Spectrum: from Bears in Nature to Patients with Coronary Artery Disease

“…As a proton pump, UCP-2 decreases the inner membrane potential of mitochondria and, with mild depolarization, reduces the production of reactive oxygen species [23,24], suggesting that its greatest role in the heart would be as an antioxidant. More importantly, the antioxidant status of many tissues in animals that are in the hibernating state appears protected, as demonstrated by increased expression of additional proteins including catalase, superoxide dismutase [1,2], and glutathione peroxidase [25,26]. In fact, the activities of several antioxidant enzymes have been shown to be increased during hibernating states [27] and, in European ground squirrels, include enhanced activities of superoxide dismutase, ascorbate, and glutathione peroxidase [28].…”

The molecular mechanisms underlying sketetal and cardiac muscle remodeling in the hibernating thirteen-lined ground squirrel

“…Although metabolic rate depression in I. tridecemlineatus is characterized by a global suppression of most processes that cause ATP expenditure, including important functions such as transcription and translation, positive regulation of select genes and proteins still occur in order to ensure the animal's survival. As a matter of fact, various approaches of gene-and proteinscreening have identified various targets that are upregulated during hibernation (Li et al, 2013;Storey & Storey, 2010). These targets include transcription factors (TFs) that play an integral part in regulating gene transcription.…”

“…For instance, NFATc2-null mice have defective myoblast fusion and myogenesis, resulting in fibers with reduced size and delayed repair in response to injury (Horsley et al, 2001). In cardiomyocytes, NFATs regulate cardiomyocyte atrophy, apoptosis, development, and growth (Li et al, 2013;Lin et al, 2009;Liu, Wilkins, Lee, Ichijo, & Molkentin, 2006;Molkentin et al, 1998;Schubert et al, 2003). In fact, in another hibernating animal -the woodchuck (Mormota monax) - Li et al (2013) used iTRAQ technology and mass spectrometry to identify that there is an upregulation in the NFAT pathway during hibernation in the hearts of these animals.…”

“…In cardiomyocytes, NFATs regulate cardiomyocyte atrophy, apoptosis, development, and growth (Li et al, 2013;Lin et al, 2009;Liu, Wilkins, Lee, Ichijo, & Molkentin, 2006;Molkentin et al, 1998;Schubert et al, 2003). In fact, in another hibernating animal -the woodchuck (Mormota monax) - Li et al (2013) used iTRAQ technology and mass spectrometry to identify that there is an upregulation in the NFAT pathway during hibernation in the hearts of these animals. Inactive NFATs are located in the cytoplasm and are heavily phosphorylated, and NFATs are activated and nuclear localization occurs via dephosphorylation by calcineurin (Park et al, 2000), a calmodulin-stimulated protein phosphatase, allowing NFATs to translocate to the nucleus and bind to transcriptional complexes of their target genes (Rusnak & Mertz, 2000) (Figure 1.3).…”