Natural thermal adaptation increases heat shock protein levels and decreases oxidative stress

Abstract

Heat shock proteins (HSPs), originally identified as heat-inducible gene products, are a family of highly conserved proteins that respond to a wide variety of stress including oxidative stress. Although both acute and chronic oxidative stress have been well demonstrated to induce HSP responses, little evidence is available whether increased HSP levels provide enhanced protection against oxidative stress under elevated yet sublethal temperatures. We studied relationships between oxidative stress and HSPs in a physiological model by using Garra rufa (doctor fish), a fish species naturally acclimatized to different thermal conditions. We compared fish naturally living in a hot spring with relatively high water temperature (34.4±0.6 °C) to those living in normal river water temperature (25.4±4.7 °C), and found that levels of all the studied HSPs (HSP70, HSP60, HSP90, HSC70 and GRP75) were higher in fish living in elevated water temperature compared with normal river water temperature. In contrast, indicators of oxidative stress, including protein carbonyls and lipid hydroperoxides, were decreased in fish living in the elevated temperature, indicating that HSP levels are inversely associated with oxidative stress. The present results provide evidence that physiologically increased HSP levels provide protection against oxidative stress and enhance cytoprotection.

Comparative proteomics of stenotopic caddisfly Crunoecia irrorata identifies acclimation strategies to warming

“…Upon exposure of insects to various environmental stressors, synthesis of most proteins declines, but hsp expression usually increases (King & MacRae, ). Some species with a local adaptation history to cold environmental conditions show attenuated hsp levels or even lost this essential protective mechanism in response to elevated temperatures (Clark, Fraser, & Peck, ; Detrich, Buckley, Doolittle, Jones, & Lockhart, ; Oksala et al, ). Most hsps identified in all treatments showed no significant norm of reaction variability between temperature treatments, but generally high abundances at all three temperatures could be observed (Figure ).…”

Heat Shock Proteins in the “Hot” Mitochondrion: Identity and Putative Roles

“…Since elevated temperatures accelerate the production of ROS, we expect that mitochondrial ROS production is higher at 50 °C than at 37 °C, an observation that could be a contributing cause for a possibly higher level of damage in the mitochondrion relative to the cytosol. Hsps, on the other hand, could mitigate thermally induced oxidative damage by ROS . For example, mt‐Hsp60 has been shown to reduce the levels of ROS and protect mitochondrial enzymes from oxidative damage .…”

“…If mitochondria are, as is widely assumed, the site of net ROS production, then this production is known to be accelerated at higher temperatures in part due to the impairment of the antioxidant enzyme systems . Since ROS production is accelerated in a hotter environment, and since Hsps afford protection against oxidative damage caused by ROS, it is quite plausible that Hsps may play an important role in protecting mitochondrial proteins and DNA against thermal lability and the endogenous thermally increased oxidative stress. Herein, we hypothesize that, in addition to their role in unfolding and refolding proteins transported to and from the mitochondrion, Hsps also function to protect macromolecules from heat denaturation and from the increased levels of ROS in the hot mitochondrial environment and may also contribute to its putative role as a sink for free radicals (Figure ).…”

Mechanisms of oxidative stress resistance in the brain: Lessons learned from hypoxia tolerant extremophilic vertebrates

“…Molecular chaperones protect proteins from unfolding stressors and also help traffic damaged proteins, preventing them from aggregating or damaging other molecules. The induction of the heat shock protein family of chaperones may be triggered by both oxidative stress and temperature changes [94, 95]. Hibernating ground squirrels show increased levels of heat shock protein (HSP) HSP70 family protein GRP78, and its transcription factor ATF4 [96, 97] (Table 2).…”