Sulfide metabolism and the mechanism of torpor

Effects of Hydrogen Sulfide at Normal Body Temperature and in the Cold on Isolated Tail and Carotid Arteries from Rats and TRPA1 Knockout and Wild-Type Mice

Background: Hydrogen sulfide (H2S) is a gasotransmitter that modulates vascular tone, causing either vasodilation or vasoconstriction depending on the vascular bed, species, and experimental conditions. The cold-sensitive transient receptor potential ankyrin-1 (TRPA1) channel mediates H2S-induced effects; however, its contribution to the vasomotor responses of different arteries at different temperatures has remained unclear. Here, we aimed to fill this gap by comparing the effects of sodium sulfide (Na2S), which is a fast-releasing H2S donor, on the isolated carotid and tail skin arteries of rats and mice at cold and normal body temperature with wire myography. Under the same circumstances, we also aimed to compare the effects of the canonical endothelium-dependent and -independent vasodilators, acetylcholine and sodium nitroprusside, respectively. Methods: We isolated the carotid and tail arteries from 32 adult Wistar rats and 64 TRPA1 knockout and wild-type mice, and then we studied their vasomotor responses to increasing doses (10-6-10-3 M) of Na2S as well as to acetylcholine and sodium nitroprusside (10-5 M for both) at 37 °C and in cold (17 or 20 °C). Results: In rat vessels, Na2S caused constriction of the carotids and relaxation of the tail arteries, which were not influenced by temperature. In mouse carotids, Na2S caused vasorelaxation, which was more pronounced in the cold at a lower dose (10-4 M). At a higher dose (10-3 M), the dilation was markedly attenuated in the absence of the TRPA1 channel. In the mouse tail arteries, Na2S caused vasorelaxation at 37 °C and vasocontraction in the cold. The genetic blockade of TRPA1 channels did not influence the vasomotor responses of the mouse tail arteries. Sodium nitroprusside-induced vasorelaxation was not influenced by any of the investigated factors, while acetylcholine-induced dilation decreased in the cold in all vessel types. Conclusions: Our results reveal the function of TRPA1 in the H2S-induced dilation of carotid arteries in mice. We also highlight interspecies differences in the vasomotor responses between rats and mice, as well as the importance of the effect of temperature on vascular responses. The implementation of the identified variables in future research can advance our understanding of cardiovascular physiology, especially in conditions with hypothermia (either accidental or therapeutic).

Cold resistance of mammalian hibernators ∼ a matter of ferroptosis?

Most mammals adapt thermal physiology around 37°C and large deviations from their range, as observed in severe hypothermia and hyperthermia, resulting in organ dysfunction and individual death. A prominent exception is mammalian hibernation. Mammalian hibernators resist the long-term duration of severe low body temperature that is lethal to non-hibernators, including humans and mice. This cold resistance is supported, at least in part, by intrinsic cellular properties, since primary or immortalized cells from several hibernator species can survive longer than those from non-hibernators when cultured at cold temperatures. Recent studies have suggested that cold-induced cell death fulfills the hallmarks of ferroptosis, a type of necrotic cell death that accompanies extensive lipid peroxidation by iron-ion-mediated reactions. In this review, we summarize the current knowledge of cold resistance of mammalian hibernators at the cellular and molecular levels to organ and systemic levels and discuss key pathways that confer cold resistance in mammals.

Whole-genome sequencing of the invasive golden apple snail Pomacea canaliculata from Asia reveals rapid expansion and adaptive evolution

Pomacea canaliculata, an invasive species native to South America, is recognized for its broad geographic distribution and adaptability to a variety of ecological conditions. The details concerning the evolution and adaptation of P. canaliculate remain unclear due to a lack of whole-genome resequencing data. We examined 173 P. canaliculata genomes representing 17 geographic populations in East and Southeast Asia. Interestingly, P. canaliculata showed a higher level of genetic diversity than other mollusks, and our analysis suggested that the dispersal of P. canaliculata could have been driven by climate changes and human activities. Notably, we identified a set of genes associated with low temperature adaptation, including Csde1, a cold shock protein coding gene. Further RNA sequencing analysis and reverse transcription quantitative polymerase chain reaction experiments demonstrated the gene's dynamic pattern and biological functions during cold exposure. Moreover, both positive selection and balancing selection are likely to have contributed to the rapid environmental adaptation of P. canaliculata populations. In particular, genes associated with energy metabolism and stress response were undergoing positive selection, while a large number of immune-related genes showed strong signatures of balancing selection. Our study has advanced our understanding of the evolution of P. canaliculata and has provided a valuable resource concerning an invasive species.

Mitochondrial Targeting against Alzheimer's Disease: Lessons from Hibernation

Alzheimer's disease (AD) is the most common cause of dementia worldwide and yet remains without effective therapy. Amongst the many proposed causes of AD, the mitochondrial cascade hypothesis is gaining attention. Accumulating evidence shows that mitochondrial dysfunction is a driving force behind synaptic dysfunction and cognitive decline in AD patients. However, therapies targeting the mitochondria in AD have proven unsuccessful so far, and out-of-the-box options, such as hibernation-derived mitochondrial mechanisms, may provide valuable new insights. Hibernators uniquely and rapidly alternate between suppression and re-activation of the mitochondria while maintaining a sufficient energy supply and without acquiring ROS damage. Here, we briefly give an overview of mitochondrial dysfunction in AD, how it affects synaptic function, and why mitochondrial targeting in AD has remained unsuccessful so far. We then discuss mitochondria in hibernation and daily torpor in mice, covering current advancements in hibernation-derived mitochondrial targeting strategies. We conclude with new ideas on how hibernation-derived dual mitochondrial targeting of both the ATP and ROS pathways may boost mitochondrial health and induce local synaptic protein translation to increase synaptic function and plasticity. Further exploration of these mechanisms may provide more effective treatment options for AD in the future.